Method and system for variable optical thickness waveguides in augmented reality devices - Patents.com

Abstract

An augmented reality device includes a projector, projector optics optically coupled to the projector, and an eyepiece optically coupled to the projector optics, the eyepiece including an eyepiece waveguide characterized by lateral dimensions and an optical path length difference as a function of one or more of the lateral dimensions.

Description

[Technical field]

[0001]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. patent application Ser. No. 17 / 705,202, filed March 25, 2022, entitled "METHOD AND SYSTEM FOR VARIABLE OPTICAL THICKNESS WAVEGUIDES FOR AUGMENTED REALITY DEVICES," which issued on November 1, 2022, and U.S. patent application Ser. No. 17 / 308,407, filed May 5, 2021, entitled "BIASED TOTAL THICKNESS VARIATIONS IN WAVEGUIDE DISPLAY," now U.S. Patent No. 11,487,061. No. 16 / 792,083, filed February 14, 2020, now U.S. Patent No. 11,022,753, issued June 6, 2021, which claims priority to U.S. Provisional Patent Application No. 62 / 820,769, filed March 19, 2019, and U.S. Provisional Patent Application No. 62 / 805,832, filed February 14, 2019, the disclosures of which are incorporated herein by reference in their entireties for all purposes. [Background technology]

[0002]

[0002] Modern computing and display technologies have facilitated the development of systems for so-called "virtual reality" or "augmented reality" experiences, in which digitally reproduced images or portions thereof are presented to a viewer in such a way that they appear to be, or can be perceived as, real. Virtual reality, or "VR", scenarios typically involve the presentation of digital or virtual image information without transparency to other actual real-world visual inputs, while augmented reality, or "AR", scenarios typically involve the presentation of digital or virtual image information as an extension to a visualization of the real world around the viewer.

[0003]

[0003] Referring to FIG. 1, an augmented reality scene 10 is depicted. A user of the AR technology sees a real-world park-like setting 20 featuring people, trees, buildings, and a concrete platform 30 in the background. The user also perceives that they are "seeing" "virtual content," such as a robotic figure 40 standing on the real-world platform 30, and a flying cartoon-like avatar character 50 that appears to be an anthropomorphic version of a bumblebee. These elements 50, 40 are "virtual" in that they do not exist in the real world. Because of the complexity of the human visual system, it is difficult to create AR technology that facilitates a comfortable, natural-feeling rich presentation of virtual image elements surrounded by other virtual or real-world image elements.

[0004]

[0004] Despite these advances in display technology, there remains a need in the art for improved methods and systems relating to augmented reality systems, and particularly to display systems. Summary of the Invention

[0005]

[0005] The present invention generally relates to methods and systems relating to projection display systems, including wearable displays. More specifically, embodiments of the present invention provide methods and systems including an eyepiece waveguide layer having a variable optical thickness that is utilized to perform optical imaging in an augmented reality system. The present invention is applicable to a variety of applications in computer vision and image display systems.

[0006] According to one embodiment of the present invention, an augmented reality device is provided. The augmented reality device includes a projector, projector optics optically coupled to the projector, and an eyepiece optically coupled to the projector optics. The eyepiece comprises an eyepiece waveguide characterized by a lateral dimension and an optical path length difference as a function of one or more of the lateral dimensions. The eyepiece may further include a second eyepiece waveguide characterized by a second lateral dimension and a second optical path length difference as a function of one or more of the second lateral dimensions, and a third eyepiece waveguide characterized by a third lateral dimension and a third optical path length difference as a function of one or more of the third lateral dimensions. The eyepiece waveguide, the second eyepiece waveguide, and the third eyepiece waveguide may form the eyepiece. The eyepiece can be a stacked structure including an eyepiece waveguide, a second eyepiece waveguide, and a third eyepiece waveguide. The augmented reality device can also include a second projector, a second projector optics optically coupled to the projector, and a second eyepiece optically coupled to the second projector optics. The second eyepiece can include a fourth eyepiece waveguide characterized by a fourth lateral dimension and a fourth optical path length difference as a function of one or more of the fourth lateral dimensions. The second eyepiece can further include a fifth eyepiece waveguide characterized by a fifth lateral dimension and a fifth optical path length difference as a function of one or more of the fifth lateral dimensions, and a sixth eyepiece waveguide characterized by a sixth lateral dimension and a sixth optical path length difference as a function of one or more of the sixth lateral dimensions. The projector, projector optics, and eyepiece can be mounted within an augmented reality headset.

[0007] In one embodiment, the eyepiece waveguide may include a combined pupil expander, the second eyepiece waveguide comprises a second combined pupil expander, and the third eyepiece waveguide comprises a third combined pupil expander. The thickness of the eyepiece waveguide varies across the combined pupil expander, the thickness of the second eyepiece waveguide varies across the second combined pupil expander, and the thickness of the third eyepiece waveguide varies across the third combined pupil expander. The eyepiece waveguide may be characterized by a thickness variation as a function of one or more lateral dimensions. The eyepiece waveguide may be characterized by a refractive index change as a function of one or more lateral dimensions. The eyepiece may include three eyepiece waveguides. The optical path length difference can vary from a first value in a first region of each of the three eyepiece waveguides to a second value in a second region of each of the three eyepiece waveguides. The first region can correspond to an input coupling grating and the second region can correspond to a combined pupil expander, and the optical path length difference can decrease from a first value to a second value. The optical path length difference of each of the three eyepiece waveguides can extend along a common direction. The optical path length difference of each of the three eyepiece waveguides can decrease along a lateral dimension of each of the three eyepiece waveguides, and the lateral dimensions of each of the three eyepiece waveguides are parallel.

[0008] According to another embodiment of the present invention, an augmented reality device is provided. The augmented reality device includes a projector, projector optics optically coupled to the projector, and an eyepiece optically coupled to the projector optics. The eyepiece includes a first eyepiece waveguide characterized by a lateral dimension and a first optical path length difference gradient, and a second eyepiece waveguide characterized by a lateral dimension and a second optical path length difference gradient aligned with the first optical path length difference gradient. The eyepiece can further include a third eyepiece waveguide characterized by a lateral dimension and a third optical path length difference gradient aligned with the first optical path length difference gradient and the third optical path length difference gradient. The first eyepiece waveguide, the second eyepiece waveguide, and the third eyepiece waveguide can be stacked together. The projector, the projector optics, and the eyepiece can be mounted within an augmented reality headset. The first eyepiece waveguide may include a first combined pupil expander, the thickness of the first eyepiece waveguide varying from a first portion of the first combined pupil expander to a second portion of the first combined pupil expander. The second eyepiece waveguide may include a second combined pupil expander, the thickness of the second eyepiece waveguide varying from a first portion of the second combined pupil expander to a second portion of the second combined pupil expander. The first optical path length difference gradient may be aligned with the second optical path length difference gradient. The first optical path length difference gradient may correspond to a direction, the second optical path length difference gradient corresponds to the direction.

[0009]

[0009] According to certain embodiments of the present invention, an augmented reality device is provided. The augmented reality device includes a projector, projector optics optically coupled to the projector, and an eyepiece optically coupled to the projector optics. The eyepiece comprises an eyepiece waveguide characterized by a lateral dimension and one or more layers. At least one of the one or more layers is characterized by an optical path length difference as a function of one or more of the lateral dimensions. The eyepiece may include a substrate and a layer of variable thickness coupled to the substrate. The refractive index of the substrate may be substantially equal to the refractive index of the layer of variable thickness. The eyepiece may further include a second eyepiece waveguide characterized by a second lateral dimension and one or more second layers, and a third eyepiece waveguide characterized by a third lateral dimension and one or more third layers. At least one of the one or more second layers is characterized by a second optical path length difference as a function of one or more of the lateral dimensions, and at least one of the one or more third layers is characterized by a third optical path length difference as a function of one or more of the lateral dimensions. The eyepiece waveguide, the second eyepiece waveguide, and the third eyepiece waveguide can form an eyepiece. The eyepiece can be a laminated structure including the eyepiece waveguide, the second eyepiece waveguide, and the third eyepiece waveguide. The one or more layers, the one or more second layers, and the one or more third layers can be characterized by a thickness variation as a function of one or more lateral dimensions, and the thickness variation of each of the one or more layers, the one or more second layers, and the one or more third layers can be reduced along a lateral dimension of each of the three eyepiece waveguides, and the lateral dimensions of each of the three eyepiece waveguides are parallel. The augmented reality device may further include a second projector, second projector optics optically coupled to the projector, and a second eyepiece optically coupled to the projector optics.The second eyepiece comprises a fourth eyepiece waveguide characterized by a fourth lateral dimension and one or more fourth layers, at least one of the one or more fourth layers characterized by a fourth optical path length difference as a function of one or more of the fourth lateral dimensions. The second eyepiece may further include a fifth eyepiece waveguide characterized by a fifth lateral dimension and one or more fifth layers, at least one of the one or more fifth layers characterized by a fifth optical path length difference as a function of one or more of the fifth lateral dimensions, and a sixth eyepiece waveguide characterized by a sixth lateral dimension and one or more sixth layers, at least one of the one or more sixth layers characterized by a sixth optical path length difference as a function of one or more of the sixth lateral dimensions.

[0010] In one embodiment, the projector, projector optics, and eyepiece are mounted in an augmented reality headset. The eyepiece waveguide can include a combined pupil expander, the second eyepiece waveguide can include a second combined pupil expander, and the third eyepiece waveguide can include a third combined pupil expander, where the one or more layers are characterized by a thickness that varies across the combined pupil expander, the one or more second layers are characterized by a thickness that varies across the second combined pupil expander, and the one or more third layers are characterized by a thickness that varies across the third combined pupil expander. The one or more layers can be characterized by a thickness variation as a function of one or more of the lateral dimensions. The thickness variation can vary from a first value in a first region of the eyepiece waveguide to a second value in a second region of the eyepiece waveguide. The first region can correspond to an input coupling grating and the second region can correspond to a combined pupil expander, and the thickness variation can be reduced from a first value to a second value. The one or more layers can be characterized by a refractive index change as a function of one or more of the lateral dimensions. The eyepiece waveguide can include a nanopattern. The nanopattern can include a polymer grating having a polymer refractive index less than the refractive index of the eyepiece. The one or more layers can have a thickness of less than 50 nm, less than 30 nm, or less than 10 nm. The nanopattern can include a conformal or directional deposition structure formed in the one or more layers or eyepiece. The nanopattern can include a polymer grating having a polymer refractive index greater than the refractive index of the eyepiece. The one or more layers can have a thickness of less than 100 nm and include at least one of ZrO2 or TiO2. The nanopattern can include an etched structure formed in the one or more layers or eyepiece. The nanopattern can include a binary grating, a blazed sawtooth grating, a blazed multi-step grating, a blazed tilted grating, holes, or pillars.

[0011]

[0011] According to another particular embodiment of the present invention, an augmented reality device includes a projector, projector optics optically coupled to the projector, and a substrate structure including a substrate having an entrance surface and an opposite exit surface, and a first variable thickness film coupled to the entrance surface. The substrate structure may further include a first combined pupil expander coupled to the first variable thickness film, a second variable thickness film coupled to the exit surface, an internal coupling grating coupled to the exit surface, and a second combined pupil expander coupled to the exit surface. The second variable thickness film may be thicker adjacent to the internal coupling grating than adjacent to the second combined pupil expander. The thickness variation of the substrate may be less than the thickness variation of the first variable thickness film or the second variable thickness film. The augmented reality device may further include a first intermediate film disposed between the substrate and the first variable thickness film, and a second intermediate film disposed between the substrate and the second variable thickness film. The first intermediate film may have a refractive index less than the refractive index of the substrate and the refractive index of the first variable thickness film, and the second intermediate film may have a refractive index less than the refractive index of the substrate and the refractive index of the second variable thickness film.

[0012]

[0012] According to a particular embodiment of the present invention, an augmented reality device includes a projector, projector optics optically coupled to the projector, and an eyepiece optically coupled to the projector optics. The eyepiece includes a first eyepiece waveguide characterized by a lateral dimension and a first variable thickness film having a first thickness gradient, and a second eyepiece waveguide characterized by a lateral dimension and a second variable thickness film having a second thickness gradient aligned with the first thickness gradient. The eyepiece can further include a third eyepiece waveguide characterized by a lateral dimension and a third variable thickness film having a third thickness gradient aligned with the first thickness gradient and the third thickness gradient. The first eyepiece waveguide, the second eyepiece waveguide, and the third eyepiece waveguide can be stacked together. The projector, the projector optics, and the eyepiece can be mounted within an augmented reality headset. The first eyepiece waveguide can include a first combined pupil expander, where the thickness of the first variable thickness film varies from a first portion of the first combined pupil expander to a second portion of the first combined pupil expander, and the second eyepiece waveguide can include a second combined pupil expander, where the thickness of the second variable thickness film varies from a first portion of the second combined pupil expander to a second portion of the second combined pupil expander. The first thickness gradient can be aligned with the second thickness gradient. The first thickness gradient can correspond to a direction and the second thickness gradient can correspond to the direction.

[0013]

[0013] Many advantages are achieved by the present invention over conventional techniques. For example, embodiments of the present invention provide methods and systems that can improve the quality of virtual content, including image sharpness. These and other embodiments of the present invention, along with many of its advantages and features, are described in more detail in conjunction with the following text and accompanying drawings. [Brief description of the drawings]

[0014] [Figure 1]FIG. 1 illustrates a user's view of an augmented reality (AR) device. [Diagram 2] FIG. 1 illustrates a conventional display system for simulating a three-dimensional image for a user. [Figure 3A] FIG. 13 is a diagram showing the relationship between the radius of curvature and the radius of the focal point. [Figure 3B] FIG. 13 is a diagram showing the relationship between the radius of curvature and the radius of the focal point. [Figure 3C] FIG. 13 is a diagram showing the relationship between the radius of curvature and the radius of the focal point. [Figure 4A] FIG. 1 illustrates a representation of the accommodation-vergence response of the human visual system. [Figure 4B] 1A-1C are diagrams illustrating examples of different accommodation and convergence states of a pair of eyes of a user. [Figure 4C] FIG. 2 illustrates an example of a representation of a top view of a user viewing content through a display system. [Figure 4D] FIG. 2 illustrates another example of a top-view representation of a user viewing content through a display system. [Diagram 5] 1A-1C illustrate aspects of a technique for simulating a three-dimensional image by modifying wavefront divergence. [Figure 6] FIG. 1 illustrates an example of a waveguide stack for outputting image information to a user. [Figure 7] FIG. 2 illustrates an example of an emitted beam output by a waveguide. [Figure 8] FIG. 1 illustrates an example of a stacked waveguide assembly where each depth plane contains an image formed using multiple different component colors. [Figure 9A] FIG. 2 is a cross-sectional side view of an example set of stacked waveguides, each including an incoupling optical element. [Figure 9B] FIG. 9B is a perspective view of one example of one or more stacked waveguides of FIG. 9A. [Figure 9C] FIG. 9C is a top view of one example of the stacked waveguides of FIG. 9A and FIG. 9B. [Figure 9D]FIG. 1 illustrates an example of a wearable display system. [Figure 10] FIG. 1 is a side view of a projector assembly including a polarizing beam splitter having a light source that injects light onto one side of the beam splitter and projection optics that receive light from another side of the beam splitter. [Figure 11A] FIG. 1 is a side view of an augmented reality display system including a light source, a spatial light modulator, an optical system for illuminating the spatial light modulator and projecting an image of the spatial light modulator (SLM), and a waveguide for outputting image information to a user. The system includes in-coupling optics for coupling light from the optical system into the waveguide, and out-coupling optics for coupling light from the waveguide to the eye. [Figure 11B] 11B is a top view of the augmented reality display system shown in FIG. 11A showing a waveguide with in-coupling and out-coupling optics and a light source disposed thereon. The top view also shows an orthogonal pupil expander. [Figure 11C] FIG. 11B is a side view of the augmented reality display system of FIG. 11A having a common polarizer / analyzer and a polarization-based spatial light modulator (e.g., liquid crystal on silicon SLM). [Figure 11D] FIG. 2 illustrates an example of a waveguide having a combined OPE / EPE, according to one embodiment of the present invention. [Figure 12A] FIG. 1 is a side view of an augmented reality display system including a multi-color light source (e.g., a time-multiplexed RGB LED or laser diode), a spatial light modulator, an optical system for illuminating the spatial light modulator and projecting an image of the spatial light modulator to the eye, and a stack of waveguides, where different waveguides include different color-selective in-coupling and out-coupling optical elements. [Figure 12B] FIG. 12B is a side view of the augmented reality display system of FIG. 12A further including a MEMS (micro-electromechanical) based SLM such as an array of moveable mirrors (e.g., Digital Light Processing (DLP™) technology) and a light dump. [Figure 12C]FIG. 12C is a top view of a portion of the augmented reality display system of FIG. 12B, illustrating generally one of the internal coupling optical elements and the lateral arrangement of the light dump and light source. [Figure 13A] 1 is a perspective view of an augmented reality display system including a stack of waveguides, different waveguides including different incoupling optical elements, the incoupling optical elements being laterally displaced with respect to one another, and one or more light sources, also laterally displaced with respect to one another, arranged to direct light to each of the incoupling optical elements by passing the light through an optical system, reflecting the light off a spatial light modulator, and passing the reflected light back through the optical system. [Figure 13B] FIG. 13B is a side view of the example shown in FIG. 13A showing the laterally displaced incoupling optics and light source, as well as the optical system and spatial light modulator. [Figure 13C] A top view of the augmented reality display system shown in Figures 13A and 13B, showing one or more laterally displaced internal coupling optical elements and associated one or more laterally displaced light sources. [Figure 14A] FIG. 1 is a side view of an augmented reality display system including a waveguide stack, where different waveguides include different internal coupling optical elements that are laterally displaced relative to each other (in this example the lateral displacement occurs in the z direction). [Figure 14B] FIG. 14B is a top view of the display system shown in FIG. 14A showing laterally displaced incoupling optics and light sources. [Figure 14C] FIG. 14C is an orthogonal side view of the display system shown in FIGS. 14A and 14B. [Figure 15] 14A-14C are top views of an augmented reality display system including a set of stacked waveguides, different waveguides including different incoupling optical elements, the light sources and incoupling optical elements being arranged in alternative configurations to those shown in FIGS. [Figure 16A] FIG. 1 is a side view of an augmented reality display system including groups of inter-coupling optical elements laterally displaced relative to one another, each group including one or more color-selective inter-coupling optical elements. [Figure 16B] FIG. 16B is a top view of the display system of FIG. 16A. [Figure 17] 1 is a side view of an augmented reality display system including a waveguide split with a reflective surface that can couple light guided from that portion of the waveguide into an optics system toward a spatial light modulator in a portion of the waveguide proximate a light source, in this example the optics system and light source are shown disposed on the same side of the waveguide. [Figure 18] FIG. 1 is a side view of an augmented reality display system including a waveguide for receiving light from a light source and directing light guided in the waveguide into an optical system and towards a spatial light modulator. The display system additionally includes a waveguide for receiving light from the spatial light modulator that passes back through the optical system. The waveguide includes reflective surfaces for out-coupling light. The waveguide also includes reflective surfaces for in-coupling light therein. In this example, the optical system and the light source are shown disposed on the same side of the waveguide. [Figure 19] FIG. 1 is a side view of an augmented reality display system including adaptive or variable focus optics. A first variable optical element between the stack of waveguides and the eye can vary the divergence and collimation of light coupled out of the waveguides and directed to the eye to vary the depth at which an object appears to be located. A second variable optical element on the other side of the stack of waveguides can compensate for the effect of the first optical element on light received from the augmented reality display system and the environment in front of the user. The augmented reality display system further includes prescription lenses to provide ophthalmic corrections, such as refractive corrections, for users with myopia, hyperopia, astigmatism, and the like. [Figure 20A] 1 is a side view of an augmented reality display system including a color filter array, where one or more laterally displaced in-coupling optical elements are positioned on different waveguides, and a laterally displaced color filter is aligned with each in-coupling optical element. [Figure 20B] FIG. 20B illustrates the augmented reality display system of FIG. 20A, in which an analyzer is positioned between the optical system and the spatial light modulator. [Figure 20C] FIG. 24 illustrates an augmented reality display system similar to that shown in FIGS. 20A and 20B, but using a deflection-based spatial light modulator, such as a movable micromirror-based spatial light modulator. [Figure 20D] FIG. 20D is a top view of a portion of the augmented reality display system as shown in FIG. 20C, illustrating generally laterally displaced light sources and corresponding laterally displaced incoupling optics above a color filter array. [Figure 20E] A diagram showing how a deflection-based spatial light modulator directs light from a corresponding internal coupling optical element onto a mask that surrounds the filters in the filter array of the augmented reality display system of Figure 20D. [Figure 20F] FIG. 1 is a side view of an augmented reality display system including a cover glass disposed on the user side of the waveguide stack and a light source disposed on the world side of the cover glass. [Figure 20G] FIG. 1 is a side view of an augmented reality display system including a cover glass disposed on the world side of a stack of waveguides and a light source disposed on the world side of the cover glass. [Figure 21] FIG. 1 is a side view of an augmented reality display system including a light source with a light recycler configured to recycle light, such as light of one polarization. [Figure 22] 1 is a side view of one or more light sources propagating light through one or more apertures and corresponding collection optics. The light may also propagate through a diffuser positioned proximate to the one or more apertures. [Figure 23A] FIG. 1 is a side view of a portion of an augmented reality display system including a light source, an optical system having refractive power, and a waveguide for receiving and outputting image information to a user's eye, the system further including one or more retarders and polarizers configured to reduce reflections from optical surfaces that may be input to the waveguide as ghost images. [Figure 23B]FIG. 23B is a side view of a portion of an augmented reality display system as shown in FIG. 23A having an additional retarder and polarizer configured to reduce reflections that can produce ghost images. [Figure 23C] A side view of a portion of the augmented reality display system as shown in Figures 23A and 23B with reduced retarders and polarizers configured to reduce reflections that can create ghost images. [Figure 24] FIG. 1 is a side view of an augmented reality display system that utilizes an inclined surface, such as an inclined surface on a cover glass, to direct reflections away from the user's eyes, potentially reducing ghost reflections. [Diagram 25] FIG. 25 illustrates an embodiment of the system of FIG. 24 in which an angled surface on the cover glass is configured to direct the reflection towards a light dump that absorbs the light. [Figure 26A] FIG. 1 depicts a sample waveguide display substrate having a waveguide area. [Figure 26B] 4 is a plot showing thickness of a waveguide display substrate as a function of position, according to one embodiment of the present invention. [Figure 26C] 4 is a plot showing thickness of a waveguide display substrate as a function of position, according to one embodiment of the present invention. [Figure 26D] 1 depicts a waveguide display substrate having a linear arrangement of waveguides, according to one embodiment of the present invention. [Figure 26E] FIG. 2 is a simplified schematic diagram illustrating thickness variation of a waveguide display substrate having a linear layout, according to one embodiment of the present invention. [Figure 26F] 1 is a simplified schematic diagram illustrating a rectangular waveguide display substrate having a linear arrangement of waveguides, according to one embodiment of the present invention. [Figure 26G] FIG. 2 is a simplified schematic diagram illustrating a waveguide display substrate having localized TTV, according to one embodiment of the present invention. [Figure 27A] FIG. 1 depicts a polished flat waveguide display substrate. [Figure 27B] FIG. 1 depicts a polished convex waveguide display substrate. [Figure 27C] FIG. 1 depicts a polished concave waveguide display substrate. [Figure 27D] FIG. 2 depicts a polished meniscus waveguide display substrate having one convex surface and one concave surface. [Figure 27E] FIG. 1 depicts a polished biconvex waveguide display substrate. [Figure 27F] FIG. 1 depicts a polished biconcave waveguide display substrate. [Figure 28A] FIG. 1 depicts a comparison of total thickness variation (TTV) of waveguide display substrates. [Figure 28B] FIG. 1 depicts a comparison of total thickness variation (TTV) of waveguide display substrates. [Figure 28C] FIG. 1 depicts the TTV of a set of eyepiece waveguides according to one embodiment of the present invention. [Figure 28D] 1 is a simplified schematic diagram illustrating an augmented reality system, according to one embodiment of the present invention. [Figure 29] FIG. 1 depicts the TTV of a polished waveguide display substrate having a convex surface. [Diagram 30] FIG. 1 shows a cross section of a waveguide display substrate with a biased TTV having a linear (wedge) and a nonlinear (dome) component. [Figure 31A] FIG. 13 shows waveguide display substrate yield versus TTV, dome height, and wedge height for ultra-low TTV waveguide display substrates. [Figure 31B] FIG. 13 shows waveguide display substrate yield versus TTV, dome height, and wedge height for ultra-low TTV waveguide display substrates. [Figure 31C] FIG. 13 shows waveguide display substrate yield versus TTV, dome height, and wedge height for ultra-low TTV waveguide display substrates. [Figure 31D]FIG. 13 shows waveguide display substrate yield versus TTV, dome height, and wedge height for biased TTV waveguide display substrates. [Figure 31E] FIG. 13 shows waveguide display substrate yield versus TTV, dome height, and wedge height for biased TTV waveguide display substrates. [Fig. 31F] FIG. 13 shows waveguide display substrate yield versus TTV, dome height, and wedge height for biased TTV waveguide display substrates. [Figure 32A] FIG. 13 shows the waveguide eyebox efficiency versus the “dome” TTV (nm) of a spherical waveguide display substrate geometry on a 6-inch wafer for a typical diffractive waveguide display with an average thickness of 300 μm and a “wedge” TTV of 0 nm. [Figure 32B] FIG. 13 shows the waveguide eyebox efficiency versus "dome" TTV (μm) of a spherical waveguide display substrate geometry on a 6-inch wafer for a typical diffractive waveguide display with an average thickness of 300 μm. [Figure 32C] FIG. 13 shows the waveguide eyebox efficiency versus "dome" TTV (μm) of a spherical waveguide display substrate geometry on a 6-inch wafer for another diffractive waveguide display having an average thickness of 300 μm. [Diagram 33] 1 is a simplified schematic diagram illustrating the process flow used in forming an inverted dome thickness variation in accordance with one embodiment of the present invention. [Diagram 34] 1 is a simplified schematic diagram illustrating the process flow used in forming an inverted dome thickness variation in accordance with one embodiment of the present invention. [Figure 35A] 1A-1D are simplified cross-sectional views illustrating showerhead designs according to various embodiments of the present invention. [Figure 35B] 1A-1D are simplified cross-sectional views illustrating showerhead designs according to various embodiments of the present invention. [Figure 35C] FIG. 2 is a simplified schematic diagram illustrating an etching mask, according to one embodiment of the present invention. [Figure 36A]2 is a simplified plan view of a substrate illustrating thickness variations, according to one embodiment of the present invention; [Figure 36B] FIG. 2 is a simplified cross-sectional view illustrating thickness variation on one side according to one embodiment of the present invention. [Figure 36C] 1 is a simplified cross-sectional view illustrating thickness variations on both sides according to one embodiment of the present invention. [Figure 36D] FIG. 2 is a simplified schematic diagram illustrating nano-features of various heights, according to one embodiment of the present invention. [Figure 36E] FIG. 2 is a simplified schematic diagram illustrating a single height nano-feature, in accordance with one embodiment of the present invention. [Figure 36F] FIG. 2 is a simplified plan view of a substrate illustrating thickness variations according to another embodiment of the present invention. [Figure 36G] FIG. 2 is a simplified cross-sectional view illustrating thickness variation on one side according to one embodiment of the present invention. [Fig. 36H] 1 is a simplified cross-sectional view illustrating thickness variations on both sides according to one embodiment of the present invention. [Figure 37A] 2 is a simplified plan view of a substrate illustrating thickness variations, according to one embodiment of the present invention; [Figure 37B] FIG. 2 is a simplified schematic diagram illustrating thickness variation on one side, according to one embodiment of the present invention. [Figure 37C] FIG. 2 is a simplified schematic diagram illustrating thickness variations on both sides according to one embodiment of the present invention. [Figure 37D] FIG. 2 is a simplified plan view of a substrate illustrating thickness variations according to another embodiment of the present invention. [Figure 37E] FIG. 2 is a simplified schematic diagram illustrating thickness variation on one side, according to one embodiment of the present invention. [Figure 37F] FIG. 2 is a simplified schematic diagram illustrating thickness variations on both sides according to one embodiment of the present invention. [Figure 38A] FIG. 1 is a simplified cross-sectional view showing an eyepiece waveguide with total thickness variation on one side, according to one embodiment of the present invention. [Figure 38B]A simplified cross-sectional view showing an eyepiece waveguide with total thickness variation on both sides, according to one embodiment of the present invention. [Figure 38C] A simplified cross-sectional view showing an eyepiece waveguide with total thickness variation on both sides according to another embodiment of the present invention. [Figure 38D] A simplified cross-sectional view showing an eyepiece waveguide with total thickness variation on both sides according to yet another embodiment of the present invention. [Figure 38E] A simplified cross-sectional view showing an eyepiece waveguide with total thickness variation on both sides according to an alternative embodiment of the present invention. [Figure 38F] FIG. 2 is a simplified cross-sectional view showing an eyepiece waveguide with total thickness variation and an overcoat on both sides, according to one embodiment of the present invention. [Figure 39A] FIG. 1 is a simplified cross-sectional view showing an eyepiece waveguide with total thickness variation on one side, according to one embodiment of the present invention. [Figure 39B] A simplified cross-sectional view showing an eyepiece waveguide with total thickness variation on both sides, according to one embodiment of the present invention. [Figure 39C] A simplified cross-sectional view showing an eyepiece waveguide with total thickness variation on both sides according to another embodiment of the present invention. [Figure 39D] A simplified cross-sectional view showing an eyepiece waveguide with total thickness variation on both sides according to yet another embodiment of the present invention. [Figure 39E] A simplified cross-sectional view showing an eyepiece waveguide with total thickness variation on both sides according to an alternative embodiment of the present invention. [Figure 39F] FIG. 2 is a simplified cross-sectional view showing an eyepiece waveguide with total thickness variation and an overcoat on both sides, according to one embodiment of the present invention. [Figure 40A] FIG. 1 is a simplified cross-sectional view showing an eyepiece waveguide with a total thickness variation and low refractive index film on one side, according to one embodiment of the present invention. [Figure 40B] FIG. 1 is a simplified cross-sectional view showing an eyepiece waveguide with a total thickness variation and low refractive index film on both sides, according to one embodiment of the present invention. [Figure 40C] A simplified cross-sectional view showing an eyepiece waveguide with a total thickness variation and low refractive index films on both sides according to another embodiment of the present invention. [Figure 40D] A simplified cross-sectional view showing an eyepiece waveguide with a total thickness variation and low refractive index films on both sides according to yet another embodiment of the present invention. [Figure 40E] A simplified cross-sectional view showing an eyepiece waveguide with a total thickness variation and low refractive index film on both sides according to an alternative embodiment of the present invention. [Diagram 40F] A simplified cross-sectional view showing an eyepiece waveguide with total thickness variation and low refractive index films and overcoats on both sides in accordance with one embodiment of the present invention. [Figure 41A] FIG. 1 is a simplified cross-sectional view showing an eyepiece waveguide with a total thickness variation and low refractive index film on one side, according to one embodiment of the present invention. [Figure 41B] FIG. 1 is a simplified cross-sectional view showing an eyepiece waveguide with a total thickness variation and low refractive index film on both sides, according to one embodiment of the present invention. [Figure 41C] A simplified cross-sectional view showing an eyepiece waveguide with a total thickness variation and low refractive index films on both sides according to another embodiment of the present invention. [Figure 41D] A simplified cross-sectional view showing an eyepiece waveguide with a total thickness variation and low refractive index films on both sides according to yet another embodiment of the present invention. [Figure 41E] A simplified cross-sectional view showing an eyepiece waveguide with a total thickness variation and low refractive index film on both sides according to an alternative embodiment of the present invention. [Fig.41F] A simplified cross-sectional view showing an eyepiece waveguide with total thickness variation and low refractive index films and overcoats on both sides in accordance with one embodiment of the present invention. [Figure 42A] A simplified cross-sectional view showing an eyepiece waveguide with total thickness variation on both sides, according to one embodiment of the present invention. [Figure 42B]A simplified cross-sectional view showing an eyepiece waveguide with a total thickness variation on both sides and a first flattening level in accordance with one embodiment of the present invention. [Figure 42C] A simplified cross-sectional view showing an eyepiece waveguide with a total thickness variation on both sides and a second flattening level in accordance with one embodiment of the present invention. [Figure 43A] FIG. 2 is a simplified cross-sectional view showing an eyepiece waveguide with total thickness variation and an overcoat on both sides, according to one embodiment of the present invention. [Figure 43B] A simplified cross-sectional view showing an eyepiece lens waveguide with a total thickness variation on both sides, an overcoat and a first planarization level in accordance with one embodiment of the present invention. [Figure 43C] A simplified cross-sectional view showing an eyepiece waveguide with a total thickness variation on both sides, an overcoat and a second planarization level in accordance with one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015]

[0133] Reference will now be made to the drawings, in which like reference numerals refer to like parts throughout. Unless otherwise indicated, the drawings are schematic representations and are not necessarily drawn to scale.

[0016]

[0134] FIG. 2 illustrates a conventional display system for simulating a three-dimensional image of a user. It will be appreciated that the user's eyes are spaced apart and when viewing a real object in space, each eye may have a slightly different view of the object and form an image of the object at a different location on each eye's retina. This is sometimes referred to as binocular disparity and can be exploited by the human visual system to provide the perception of depth. Conventional display systems simulate binocular disparity by presenting two separate images 190, 200, one for each eye 210a, 210b, with slightly different views of the same virtual object, corresponding to the view of the virtual object as seen by each eye as if the virtual object at the desired depth were a real object. These images provide binocular cues that the user's visual system can interpret to derive the perception of depth.

[0017]

[0135] 2, the images 190, 200 are spaced a distance 230 along the z-axis from the eyes 210a, 210b. The z-axis is parallel to the viewer's optical axis, and the viewer's eyes are fixated on an object at optical infinity just in front of the viewer. The images 190, 200 are flat and at a fixed distance from the eyes 210a, 210b, based on slightly different views of the virtual object in the images presented to the eyes 210a, 210b, respectively.

[0018]

[0136] To maintain single binocular vision, the eyes can naturally rotate so that the image of the object is located at a corresponding point on each eye's retina. This rotation can cause the line of sight of each of the eyes 210a, 210b to converge to a point in space where the virtual object is perceived to reside. As a result, providing a three-dimensional image traditionally involves manipulating the convergence of the eyes 210a, 210b and providing binocular cues that the human visual system interprets to provide the perception of depth.

[0019]

[0137] However, it is difficult to generate a realistic and comfortable depth perception. It will be appreciated that light from objects at different distances from the eye has wavefronts with different amounts of divergence. Figures 3A-3C show the relationship between distance and divergence of light rays. The distances between the object and the eye 210 are represented by R1, R2 and R3 in order of decreasing distance. As shown in Figures 3A-3C, the light rays become more divergent as the distance to the object decreases. Conversely, as the distance increases, the light rays become more collimated. In other words, it can be said that the light field generated by a point (object or part of an object) has a spherical wavefront curvature, which is a function of how far the point is from the user's eye. The curvature increases as the distance between the object and the eye 210 decreases. In Figures 3A-3C and other figures herein, only a single eye 210 is shown for clarity of illustration, but the discussion of the eye 210 may apply to both eyes 210a and 210b.

[0020]

[0138] 3A-3C, light from an object on which a viewer's eye is fixed may have different degrees of wavefront divergence. Due to the different amounts of wavefront divergence, the light may be focused differently by the eye's lens, which may require the lens to assume a different shape to form a focused image on the eye's retina. If a focused image is not formed on the retina, the resulting retinal blur acts as an accommodation cue that causes the eye's lens to change shape until a focused image is formed on the retina. For example, the accommodation cue may trigger the ciliary muscles surrounding the eye's lens to relax or contract, thereby adjusting the force applied to the suspensory ligaments that hold the lens, thereby changing the shape of the eye's lens, thereby forming a focused image of the gazed upon object on the eye's retina (e.g., fovea) until retinal blur of the gazed upon object is eliminated or minimized. The process by which the eye lens changes shape may be referred to as accommodation, and the shape of the eye lens required to form a focused image of a gazed upon object on the eye's retina (e.g., the fovea) may be referred to as the state of accommodation.

[0021]

[0139] Now referring to FIG. 4A, a representation of the accommodation-vergence response of the human visual system is shown. Eye movements to gaze at an object cause the eyes to receive light from the object, which forms an image on each retina of the eye. The presence of retinal blur in the image formed on the retina can provide a cue to accommodation, and the relative position of the image on the retina can provide a cue to convergence. The accommodation cue causes accommodation, such that the lenses of the eyes each assume a particular accommodation state that forms a focused image of the object on the retina of the eye (e.g., the fovea). Convergence cues, on the other hand, cause convergence movements (eye rotation) such that the images formed on each retina of each eye are at corresponding retinal points that maintain single binocular vision. In these positions, the eyes can be said to assume a particular convergence state. With continued reference to FIG. 4A, accommodation can be understood as the process by which the eyes achieve a particular accommodation state, and convergence can be understood as the process by which the eyes achieve a particular convergence state. As depicted in FIG. 4A, the accommodation and convergence states of the eyes can change when a user gazes at another object. For example, the accommodation state may change if the user gazes at a new object at a different depth on the z-axis.

[0022]

[0140] Without being limited by theory, it is believed that a viewer of an object may perceive the object as "three-dimensional" through a combination of vergence and accommodation. As described above, the vergence movement of the two eyes relative to one another (e.g., rotating the eyes so that the pupils move toward or away from one another to converge the line of sight of the eyes to gaze at an object) is closely linked to accommodation of the eye's lenses. Under normal conditions, changing the shape of the eye's lenses to change focus from one object to another at different distances automatically produces a corresponding change in vergence to the same distance, under a relationship known as the "accommodation-vergence reflex." Similarly, a change in vergence causes a corresponding change in lens shape under normal conditions.

[0023]

[0141] 4B, examples of different accommodation and convergence states of the eyes are shown. The pair of eyes 222a gazes at an object at optical infinity, and the pair of eyes 222b gazes at an object 221 at less than optical infinity. Note that the convergence states of each pair of eyes are different when the pair of eyes 222a is looking straight ahead and when the pair of eyes 222 converge to the object 221. Also, the accommodation states of the eyes forming each pair of eyes 222a and 222b are different, as represented by the different shapes of the lenses 220a and 220b.

[0024]

[0142] Unfortunately, many users of conventional "3-D" display systems may find such conventional systems uncomfortable or may not perceive any depth sensation at all due to the mismatch between accommodation and vergence states in these displays. As discussed above, many stereoscopic or "3-D" display systems display a scene by providing a slightly different image to each eye. Such systems are uncomfortable for many viewers because, among other things, they simply provide a different presentation of the scene, causing a change in the vergence state of the eyes, but without a corresponding change in the accommodation state of those eyes. Rather, the image is shown by a display at a fixed distance from the eyes, such that the eyes see all the image information in a single state of accommodation. Such an arrangement counters the "accommodation-vergence reflex" by causing a change in vergence state without a corresponding change in accommodation state. This mismatch is believed to cause discomfort to the viewer. A display system that provides a better match between accommodation and vergence can form a more realistic and comfortable simulation of a three-dimensional image.

[0025]

[0143] Without being limited by theory, it is believed that the human eye is typically capable of interpreting a finite number of depth planes to provide depth perception. As a result, a highly realistic simulation of perceived depth can be achieved by providing the eye with different presentations of images corresponding to each of these limited number of depth planes. In some embodiments, the different presentations can provide both a cue to convergence and a matching cue to accommodation, thereby providing a physiologically correct accommodation-vergence match.

[0026]

[0144] 4B, two depth planes 240 are shown corresponding to different distances in space from the eyes 210a, 210b. For a given depth plane 240, convergence cues can be provided by displaying appropriately different perspective images for each eye 210a, 210b. In addition, for a given depth plane 240, the light forming the image provided to each eye 210a, 210b can have a wavefront divergence corresponding to the light field generated by points at the distance of that depth plane 240.

[0027]

[0145] In the illustrated embodiment, the distance along the z-axis of the depth plane 240 that includes the point 221 is 1 m. As used herein, the distance or depth along the z-axis may be measured at a zero point located at the exit pupil of the user's eye. Thus, the depth plane 240 located at a depth of 1 m corresponds to a distance of 1 m away from the exit pupil of the user's eye on the optical axis of those eyes where the eyes are oriented at optical infinity. As an approximation, the depth or distance along the z-axis may be measured from the display in front of the user's eye (e.g., from the surface of the waveguide) plus the value of the distance between the device and the exit pupil of the user's eye. That value may be referred to as the pupil distance and corresponds to the distance between the exit pupil of the user's eye and the display worn by the user in front of the eye. In practice, the pupil distance value may be a normalized value that is universally used for all viewers. For example, the pupil distance may be assumed to be 20 mm, and a depth plane at a depth of 1 m may be at a distance of 980 mm in front of the display.

[0028]

[0146] Now, referring to FIG. 4C and FIG. 4D, examples of matched accommodation-vergence distance and mismatched accommodation-vergence distance are shown, respectively. As shown in FIG. 4C, the display system can provide an image of a virtual object to each eye 210a, 210b. The image can cause the eyes 210a, 210b to assume a convergence state in which the eyes converge to a point 15 on the depth plane 240. In addition, the image may be formed by light having a wavefront curvature corresponding to the real object in that depth plane 240. As a result, both eyes 210a, 210b assume an accommodation state in which the image is focused on the retinas of both eyes. Thus, the user can perceive the virtual object to be at a point 15 on the depth plane 240.

[0029]

[0147] It will be appreciated that each of the accommodation and convergence states of the eyes 210a, 210b is associated with a particular distance on the z-axis. For example, an object at a particular distance from the eyes 210a, 210b will cause the eyes to assume a particular accommodation state based on the distance of the object. The distance associated with a particular accommodation state can be referred to as the accommodation distance Ad. Similarly, there is a particular convergence distance Vd associated with the eyes in a particular convergence state, or position relative to each other. When the accommodation distance and the convergence distance match, the relationship between accommodation and convergence is said to be physiologically correct. This is believed to be the most comfortable scenario for the viewer.

[0030]

[0148] However, in a stereoscopic display, the accommodation distance and the vergence distance may not necessarily coincide. For example, as shown in FIG. 4D, the images displayed to the eyes 210a, 210b may be displayed with a wavefront divergence corresponding to the depth plane 240, and the eyes 210a, 210b may assume a certain accommodation state in which the eyes 210a, 210b are focused on points 15a, 15b on the depth plane. However, the images displayed to the eyes 210a, 210b may provide a convergence cue that causes the eyes 210a, 210b to converge to a point 15 that is not located on the depth plane 240. As a result, in some embodiments, the accommodation distance corresponds to the distance from the exit pupils of the eyes 210a, 210b to the depth plane 240, and the vergence distance corresponds to a larger distance from the exit pupils of the eyes 210a, 210b to the point 15. The accommodation distance is different from the vergence distance. As a result, there is an accommodation-vergence mismatch. Such a mismatch may be considered undesirable and may cause discomfort to the user. It will be appreciated that the discrepancy corresponds to a distance (eg, VaAd) and can be characterized using diopters.

[0031]

[0149] It will be appreciated that in some embodiments, a reference point other than the exit pupil of the eye 210a, 210b may be utilized to determine the distance for determining accommodation-vergence mismatch, so long as the same reference point is utilized for accommodation distance and convergence distance. For example, distances can be measured from the cornea to the depth plane, from the retina to the depth plane, from the eyepiece (e.g., a waveguide in a display device) to the depth plane, etc.

[0032]

[0150] Without being limited by theory, it is believed that a user may still perceive an accommodation-vergence mismatch of up to about 0.25 diopters, up to about 0.33 diopters, and up to about 0.5 diopters as physiologically correct, and the mismatch itself does not cause significant discomfort. In some embodiments, a display system disclosed herein (e.g., display system 250 of FIG. 6) presents an image to a viewer having an accommodation-vergence mismatch of about 0.5 diopters or less. In some other embodiments, the accommodation-vergence mismatch of an image provided by the display system is about 0.33 diopters or less. In still other embodiments, the accommodation-vergence mismatch of an image provided by the display system is about 0.25 diopters or less, including about 0.1 diopters or less.

[0033]

[0151] FIG. 5 illustrates aspects of an approach for simulating a three-dimensional image by modifying the wavefront divergence. The display system includes a waveguide 270 configured to receive light 770 encoded with image information and output the light to a user's eye 210. The waveguide 270 can output light 650 with a prescribed amount of wavefront divergence that corresponds to the wavefront divergence of the light field generated by a point on a desired depth plane 240. In some embodiments, the same amount of wavefront divergence is provided for all objects presented on that depth plane. In addition, it is shown that the other eye of the user can be provided with image information from a similar waveguide.

[0034]

[0152] In some embodiments, a single waveguide may be configured to output light with a set amount of wavefront divergence corresponding to a single or limited number of depth planes, and / or the waveguide may be configured to output light in a limited wavelength range. As a result, in some embodiments, a stack of waveguides may be utilized to provide different amounts of wavefront divergence for different depth planes and / or output light in different wavelength ranges. As used herein, it will be appreciated that a depth plane may follow the contour of a flat or curved surface. In some embodiments, advantageously for simplicity, a depth plane may follow the contour of a flat surface.

[0035]

[0153] 6 shows an example of a waveguide stack for outputting image information to a user. Display system 250 includes a stack of waveguides or stacked waveguide assembly 260 that can be utilized to provide three-dimensional perception to the eye / brain using waveguides 270, 280, 290, 300, 310. It will be appreciated that in some embodiments, display system 250 can be considered a light field display. Additionally, waveguide assembly 260 can also be referred to as an eyepiece.

[0036]

[0154] In some embodiments, the display system 250 may be configured to provide a substantially continuous vergence cue and to provide multiple discrete accommodation cues. The vergence cues may be provided by displaying different images to each eye of the user, and the accommodation cues may be provided by outputting light forming images with selectable discrete amounts of wavefront divergence. Stated differently, the display system 250 may be configured to output light with variable levels of wavefront divergence. In some embodiments, each discrete level of wavefront divergence corresponds to a particular depth plane and may be provided by a particular one of the waveguides 270, 280, 290, 300, 310.

[0037]

[0155] 6, the waveguide assembly 260 may also include features 320, 330, 340, 350 between the waveguides. In some embodiments, the features 320, 330, 340, 350 may be one or more lenses. The waveguides 270, 280, 290, 300, 310 and / or features (e.g., lenses) 320, 330, 340, 350 may be configured to transmit image information to the eye at various levels of wavefront curvature or light beam divergence. Each waveguide level may be associated with a particular depth plane and may be configured to output image information corresponding to that depth plane. Image input devices 360, 370, 380, 390, 400 may act as light sources for the waveguides and may be utilized to input image information into the waveguides 270, 280, 290, 300, 310, each of which may be configured to distribute incident light across each respective waveguide for output towards the eye 210, as described herein. The light exits output surfaces 410, 420, 430, 440, 450 of the image input devices 360, 370, 380, 390, 400 and is input to corresponding input surfaces 460, 470, 480, 490, 500 of the waveguides 270, 280, 290, 300, 310. In some embodiments, each of the input surfaces 460, 470, 480, 490, 500 may be an edge of the corresponding waveguide or may be a portion of the main surface of the corresponding waveguide (i.e., one of the waveguide surfaces that directly faces the world 510 or the viewer's eye 210). In some embodiments, a single light beam (e.g., a collimated beam) may be launched into each waveguide to output a full field of cloned collimated beams that are directed towards the eye 210 at a particular angle (and amount of divergence) corresponding to the depth plane associated with the particular waveguide. In some embodiments, a single one of the image launch devices 360, 370, 380, 390, 400 may be associated with and launch light into one or more (e.g., three) of the waveguides 270, 280, 290, 300, 310.

[0038]

[0156] In some embodiments, the image input devices 360, 370, 380, 390, 400 are individual displays that each generate image information for input to the corresponding waveguides 270, 280, 290, 300, 310, respectively. In some other embodiments, the image input devices 360, 370, 380, 390, 400 are output ends of a single multiplexed display that can, for example, send image information via one or more optical conduits (such as fiber optic cables) to each of the image input devices 360, 370, 380, 390, 400. It will be appreciated that the image information provided by the image input devices 360, 370, 380, 390, 400 may include light of different wavelengths or colors (e.g., different component colors as discussed herein).

[0039]

[0157] In some embodiments, the light injected into the waveguides 270, 280, 290, 300, 310 is provided by a light projector system 520 that includes a light module 530 that may include a light emitter such as a light emitting diode (LED). Light from the light module 530 may be directed through a beam splitter 550 to and altered by a light modulator 540, such as a spatial light modulator. The light modulator 540 may be configured to vary the perceived intensity of the light injected into the waveguides 270, 280, 290, 300, 310 to encode the light with image information. Examples of spatial light modulators include liquid crystal displays (LCDs), including liquid crystal on silicon (LCoS) displays. It will be appreciated that image injection devices 360, 370, 380, 390, 400 are shown diagrammatically and in some embodiments these image injection devices may represent different light paths and positions within a common projection system configured to output light to an associated one of the waveguides 270, 280, 290, 300, 310. In some embodiments, the waveguides of the waveguide assembly 260 may act as ideal lenses while relaying light injected into the waveguides to the user's eye. In this concept, the object may be a spatial light modulator 540 and the image may be an image on a depth plane.

[0040]

[0158] In some embodiments, the display system 250 may be a scanning fiber display including one or more scanning fibers configured to project light in various patterns (e.g., raster scan, spiral scan, Lissajous pattern, etc.) into one or more waveguides 270, 280, 290, 300, 310 and ultimately to the viewer's eye 210. In some embodiments, the illustrated image injection devices 360, 370, 380, 390, 400 may generally represent a single scanning fiber or a bundle of scanning fibers configured to inject light into one or more of the waveguides 270, 280, 290, 300, 310. In some other embodiments, the illustrated image injection devices 360, 370, 380, 390, 400 may generally represent one or more scanning fibers or one or more bundles of scanning fibers, each configured to inject light into an associated one of the waveguides 270, 280, 290, 300, 310. It will be appreciated that the one or more optical fibers may be configured to transmit light from the optical module 530 to one or more of the waveguides 270, 280, 290, 300, 310. It will be appreciated that one or more intervening optical structures may be provided between the scanning fiber or fibers and the one or more of the waveguides 270, 280, 290, 300, 310, for example, to redirect light exiting the scanning fiber to the one or more of the waveguides 270, 280, 290, 300, 310.

[0041]

[0159] A controller 560 controls the operation of one or more of the stacked waveguide assemblies 260, including the operation of the image input devices 360, 370, 380, 390, 400, the light source 530, and the light modulator 540. In some embodiments, the controller 560 is part of the local data processing module 140. The controller 560 includes programming (e.g., instructions in a non-transitory medium) that coordinates the timing and provision of image information to the waveguides 270, 280, 290, 300, 310, for example, according to any of the various schemes disclosed herein. In some embodiments, the controller may be a single integrated device or a distributed system connected by wired or wireless communication channels. In some embodiments, the controller 560 may be part of the processing module 140 or 150 (FIG. 9D).

[0042]

[0160] Continuing with reference to FIG. 6, the waveguides 270, 280, 290, 300, 310 may be configured to propagate light within each respective waveguide by total internal reflection (TIR). The waveguides 270, 280, 290, 300, 310 may each be planar or have another shape (e.g., curved) and have major top and bottom surfaces and edges extending between their major top and bottom surfaces. In the illustrated configuration, the waveguides 270, 280, 290, 300, 310 may each include outcoupling optics 570, 580, 590, 600, 610 configured to extract light from the waveguide by redirecting light propagating within each respective waveguide out of the waveguide to output image information to the eye 210. Although referred to throughout this specification as "outcoupling optics," the outcoupling optics need not be optical and may be non-optical. The extracted light may also be referred to as outcoupling light, and the outcoupling optics may also be referred to as light extraction optics. The extracted light beam may be output by the waveguide where the light propagating in the waveguide strikes the light extraction optic. The outcoupling optics 570, 580, 590, 600, 610 may be, for example, a grating including diffractive optical features, as discussed further herein. While shown disposed on the bottom major surface of the waveguides 270, 280, 290, 300, 310 for ease of explanation and clarity of the drawings, in some embodiments the outcoupling optical elements 570, 580, 590, 600, 610 may be disposed on the top and / or bottom major surfaces and / or directly within the volume of the waveguides 270, 280, 290, 300, 310, as discussed further herein. In some embodiments the outcoupling optical elements 570, 580, 590, 600, 610 may be formed in a layer of material attached to a transparent substrate to form the waveguides 270, 280, 290, 300, 310. In some other embodiments, the waveguides 270, 280, 290, 300, 310 may be a monolithic piece of material and the outcoupling optical elements 570, 580, 590, 600, 610 may be formed on and / or within that piece of material.

[0043]

[0161] Continuing with reference to FIG. 6, as discussed herein, each waveguide 270, 280, 290, 300, 310 is configured to output light to form an image corresponding to a particular depth plane. For example, the waveguide 270 closest to the eye may be configured to deliver collimated light (injected into such waveguide 270) to the eye 210. The collimated light may represent an optical infinity focal plane. The next waveguide 280 may be configured to send collimated light that passes through a first lens 350 (e.g., a negative lens) before it can reach the eye 210. Such a first lens 350 may be configured to create a slightly convex wavefront curvature such that the eye / brain interprets the light coming from that next waveguide 280 as coming from a first focal plane closer inward from optical infinity toward the eye 210. Similarly, the third waveguide 290 passes its output light through both the first lens 350 and the second lens 340 before reaching the eye 210. The combined refractive power of the first lens 350 and the second lens 340 may be configured to create another incremental amount of wavefront curvature such that the eye / brain interprets the light coming from the third waveguide 290 as coming from a second focal plane that is closer to optical infinity and further inward towards the person than the light from the next waveguide 280.

[0044]

[0162] The other waveguide layers 300, 310 and lenses 330, 320 are similarly configured, with the highest waveguide 310 in the stack sending its output through all lenses between the eyes for a total focal power that represents the focal plane closest to the person. To compensate the stack of lenses 320, 330, 340, 350 when viewing / interpreting light coming from the world 510 on the other side of the stacked waveguide assembly 260, a compensation lens layer 620 can be disposed on top of the stack to compensate for the total magnification of the lens stack 320, 330, 340, 350 below. Such a configuration provides as many perceived focal planes as there are waveguide / lens pairings available. Both the outcoupling optics of the waveguides and the focusing aspects of the lenses may be static (i.e., not dynamic or electrically active). In some alternative embodiments, either or both may be dynamic using electrically active features.

[0045]

[0163] In some embodiments, two or more of the waveguides 270, 280, 290, 300, 310 can have the same associated depth plane. For example, multiple waveguides 270, 280, 290, 300, 310 may be configured to output images set at the same depth plane, or multiple subsets of the waveguides 270, 280, 290, 300, 310 may be configured to output images set at the same one or more depth planes, one set for each depth plane. This can provide advantages for forming tiled images to provide an extended field of view at those depth planes.

[0046]

[0164] Continuing with reference to FIG. 6, the outcoupling optics 570, 580, 590, 600, 610 can be configured to redirect light from their respective waveguides and output this light with the appropriate amount of divergence or collimation for the particular depth plane associated with the waveguide. As a result, waveguides with different associated depth planes can have different configurations of outcoupling optics 570, 580, 590, 600, 610 that output light with different amounts of divergence depending on the associated depth plane. In some embodiments, the light extraction optics 570, 580, 590, 600, 610 can be volume or surface features that can be configured to output light at a particular angle. For example, the light extraction optics 570, 580, 590, 600, 610 can be volume holograms, surface holograms, and / or diffraction gratings. In some embodiments, the features 320, 330, 340, 350 do not have to be lenses. Rather, they may simply be spacers (eg, cladding layers and / or structures for forming air gaps).

[0047]

[0165] In some embodiments, the outcoupling optics 570, 580, 590, 600, 610 are diffractive features, or "diffractive optical elements" (also referred to herein as "DOEs"), that form a diffraction pattern. Preferably, the DOEs have a sufficiently low diffraction efficiency so that only a portion of the light in the beam is deflected towards the eye 210 at each intersection of the DOE, while the remainder continues to travel through the waveguide via TIR. Thus, the light carrying the image information is split into several related exit beams that exit the waveguide at multiple locations, resulting in a fairly uniform pattern of exit emissions towards the eye 210 for this particular collimated beam bouncing within the waveguide.

[0048]

[0166] In some embodiments, one or more DOEs may be switchable between an "on" state in which they actively diffract and an "off" state in which they do not significantly diffract. For example, a switchable DOE may include a layer of polymer dispersed liquid crystal, where microdroplets contain a diffractive pattern in a host medium, and the refractive index of the microdroplets may be switched to substantially match the refractive index of the host material (in which case the pattern does not appreciably diffract incident light), or the microdroplets may be switched to a refractive index that does not match the refractive index of the host medium (in which case the pattern actively diffracts incident light).

[0049]

[0167] In some embodiments, a camera assembly 630 (e.g., a digital camera including a visible light and infrared light camera) may be provided to capture images of the eye 210 and / or tissue surrounding the eye 210, for example, to detect user input and / or to monitor a physiological condition of the user. As used herein, a camera may be any image capture device. In some embodiments, the camera assembly 630 may include an image capture device and a light source for projecting light (e.g., infrared light) onto the eye, which may then be reflected by the eye and detected by the image capture device. In some embodiments, the camera assembly 630 may be mounted on the frame 80 (FIG. 9D) and may be in electrical communication with the processing modules 140 and / or 150 that may process image information from the camera assembly 630. In some embodiments, one camera assembly 630 may be utilized for each eye to monitor each eye separately.

[0050]

[0168] 7, an example of an exit beam output by a waveguide is shown. Although one waveguide is shown, it will be appreciated that other waveguides in the waveguide assembly 260 (FIG. 6) may function similarly if the waveguide assembly 260 includes multiple waveguides. Light 640 is launched into the waveguide 270 at the input surface 460 of the waveguide 270 and propagates within the waveguide 270 by TIR. At the point where the light 640 impinges on the DOE 570, a portion of the light exits the waveguide as an exit beam 650. The exit beam 650 is shown as being substantially parallel, but may be redirected to propagate to the eye 210 at an angle (e.g., forming a diverging exit beam) depending on the depth plane associated with the waveguide 270, as discussed herein. It will be appreciated that a substantially parallel exit beam may refer to a waveguide with outcoupling optics that outcouples light to form an image that appears to be set on a depth plane at a large distance (e.g., optical infinity) from the eye 210. Other waveguides or other sets of outcoupling optics may output a more diverging exit beam pattern, which requires the eye 210 to adjust to a closer distance to focus on the retina, and is interpreted by the brain as light from a distance closer to the eye 210 than optical infinity.

[0051]

[0169] In some embodiments, a full color image can be formed at each depth plane by overlaying images of each component color, for example three or more component colors.

[0052]

[0170] FIG. 8 illustrates an example of a stacked waveguide assembly where each depth plane includes an image formed using multiple different component colors. The illustrated embodiment shows depth planes 240a-240f, however more or less depths are contemplated. Each depth plane can have three or more component color images associated with it, including a first image of a first color G, a second image of a second color R, and a third image of a third color B. The different depth planes are indicated in the figure by different numbers in diopters (dpt) following the letters G, R, and B. By way of example only, the numbers following each of these letters indicate the diopter (1 / m), or inverse distance of the depth plane from the viewer, and each box in the figure represents an individual component color image. In some embodiments, the exact placement of the depth planes for the different component colors may vary to account for differences in the eye's focusing of different wavelengths of light. For example, the component color images for a given depth plane may be positioned on depth planes that correspond to different distances from the user. Such an arrangement may improve vision and user comfort and / or reduce chromatic aberration.

[0053]

[0171] In some embodiments, the light of each component color may be output by a single dedicated waveguide, such that each depth plane may have multiple waveguides associated with it. In such embodiments, each box in the diagram containing the letter G, R, or B may be understood to represent an individual waveguide, and three waveguides may be provided per depth plane, providing three component color images per depth plane. Although the waveguides associated with each depth plane are shown adjacent to each other in this diagram for ease of illustration, it will be recognized that in a physical device, the waveguides may all be arranged in a stack with one waveguide per level. In some other embodiments, multiple component colors may be output by the same waveguide, such that, for example, only a single waveguide may be provided per depth plane.

[0054]

[0172] 8, in some embodiments, G is green, R is red, and B is blue. In some other embodiments, other colors associated with other wavelengths of light, including magenta and cyan, may be used or may be substituted in addition to one or more of red, green, or blue.

[0055]

[0173] It will be appreciated that throughout this disclosure, reference to light of a given color is understood to encompass light of one or more wavelengths within the wavelength range of light perceived by a viewer to be of that given color. For example, red light may include one or more wavelengths of light in the range of about 620-780 nm, green light may include one or more wavelengths of light in the range of about 492-577 nm, and blue light may include one or more wavelengths of light in the range of about 435-493 nm.

[0056]

[0174] In some embodiments, the light source 530 (FIG. 6) may be configured to emit light at one or more wavelengths outside the visual range of a viewer, such as infrared and / or ultraviolet wavelengths. Additionally, the in-coupling, out-coupling, and other light redirecting structures of the display 250 may be configured to direct and emit this light from the display toward the eye 210, for example, for imaging and / or user stimulation applications.

[0057]

[0175] Referring now to FIG. 9A, in some embodiments, light impinging on a waveguide may need to be redirected to incouple the light into the waveguide. Incoupling optical elements may be used to redirect and incoupling the light into its corresponding waveguide. Although referred to throughout this specification as "incoupling optical elements," incoupling optical elements need not be optical elements, but may be non-optical elements. FIG. 9A shows a cross-sectional side view of one example of a set 660 of stacked waveguides, each including an incoupling optical element. The waveguides may each be configured to output light of one or more different wavelengths, or one or more different wavelength ranges. It will be appreciated that stack 660 may correspond to stack 260 (FIG. 6), except that light from one or more of image injection devices 360, 370, 380, 390, 400 is injected into the waveguide from a location where the light requires redirection for internal coupling, and the illustrated waveguides of stack 660 may correspond to portions of waveguides 270, 280, 290, 300, 310.

[0058]

[0176] The illustrated stacked waveguide set 660 includes waveguides 670, 680, and 690. Each waveguide includes an associated incoupling optical element (which may also be referred to as a light input area on a waveguide), for example having an incoupling optical element 700 disposed on a major surface (e.g., the top major surface) of waveguide 670, an incoupling optical element 710 disposed on a major surface (e.g., the top major surface) of waveguide 680, and an incoupling optical element 720 disposed on a major surface (e.g., the top major surface) of waveguide 690. In some embodiments, one or more of the incoupling optical elements 700, 710, 720 may be disposed on a bottom major surface of the respective waveguide 670, 680, 690 (particularly when one or more of the incoupling optical elements are reflective turning optical elements). As shown, the incoupling optical elements 700, 710, 720 may be disposed on the top major surface of their respective waveguides 670, 680, 690 (or on top of the next lower waveguide), especially if the incoupling optical elements are transmissive deflecting optical elements. In some embodiments, the incoupling optical elements 700, 710, 720 may be disposed within the body of the respective waveguides 670, 680, 690. In some embodiments, as discussed herein, the incoupling optical elements 700, 710, 720 are wavelength selective, such that they selectively redirect light of one or more wavelengths while transmitting light of other wavelengths. It will be appreciated that while the incoupling optical elements 700, 710, 720 are shown on one side or corner of their respective waveguides 670, 680, 690, in some embodiments, they may be disposed in other areas of their respective waveguides 670, 680, 690.

[0059]

[0177] As shown, the in-coupling optical elements 700, 710, 720 may be laterally offset from one another. In some embodiments, each in-coupling optical element may be offset to receive light without the light passing through another in-coupling optical element. For example, each in-coupling optical element 700, 710, 720 may be configured to receive light from different image input devices 360, 370, 380, 390, and 400 as shown in FIG. 6, and may be separated (e.g., laterally spaced) from the other in-coupling optical elements 700, 710, 720 such that it does not receive substantially any light from the other in-coupling optical elements 700, 710, 720.

[0060]

[0178] Each waveguide also includes an associated light distribution element, having, for example, a light distribution element 730 disposed on a major surface (e.g., a top major surface) of the waveguide 670, a light distribution element 740 disposed on a major surface (e.g., a top major surface) of the waveguide 680, and a light distribution element 750 disposed on a major surface (e.g., a top major surface) of the waveguide 690. In some other embodiments, the light distribution elements 730, 740, 750 may be disposed on the bottom major surface of the associated waveguide 670, 680, 690, respectively. In some other embodiments, the light distribution elements 730, 740, 750 may be disposed on both the top and bottom major surfaces of the associated waveguide 670, 680, 690, respectively. Alternatively, the light distribution elements 730, 740, 750 may be disposed on different top and bottom major surfaces of different associated waveguides 670, 680, 690, respectively.

[0061]

[0179] The waveguides 670, 680, 690 may be spaced apart and separated by, for example, gas, liquid, and / or solid material layers. For example, as shown, layer 760a may separate the waveguides 670 and 680, and layer 760b may separate the waveguides 680 and 690. In some embodiments, layers 760a and 760b are formed from a low refractive index material (i.e., a material having a lower refractive index than the material forming the immediately adjacent ones of the waveguides 670, 680, 690). Preferably, the refractive index of the material forming layers 760a, 760b is greater than or equal to 0.05 or less than 0.10 less than the refractive index of the material forming the waveguides 670, 680, 690. Advantageously, the lower refractive index layers 760a, 760b can function as cladding layers to facilitate total internal reflection (TIR) ​​of light through the waveguides 670, 680, 690 (e.g., TIR between the top and bottom major surfaces of each waveguide). In some embodiments, the layers 760a, 760b are formed from air. Although not shown, it will be appreciated that the top and bottom of the illustrated set of waveguides 660 may include immediately adjacent cladding layers.

[0062]

[0180] Preferably, for ease of manufacture and other considerations, the materials forming the waveguides 670, 680, 690 are similar or identical, and the materials forming the layers 760a, 760b are similar or identical. In some embodiments, the materials forming the waveguides 670, 680, 690 may differ between one or more of the waveguides, and / or the materials forming the layers 760a, 760b may differ while still maintaining the various refractive index relationships described above. A variety of materials may be utilized to form the waveguides. Glass is one material that may be utilized to fabricate the waveguides, but other materials may be utilized, including LiNbO3, SiC, ZnS, and the like. These materials may be in the form of optical quality single crystal materials or optical quality but not single crystal materials. Additionally, multi-grain ceramics of similar composition may be utilized to form the waveguides. As an example, nanocrystalline materials may be utilized in the fabrication of the waveguides.

[0063]

[0181] 9A, light rays 770, 780, 790 are incident on the set of waveguides 660. It will be appreciated that light rays 770, 780, 790 may be injected into the waveguides 670, 680, 690 by one or more image injection devices 360, 370, 380, 390, 400 (FIG. 6).

[0064]

[0182] In some embodiments, the light beams 770, 780, 790 have different characteristics, e.g., different wavelengths or different ranges of wavelengths, which may correspond to different colors. Each incoupling optical element 700, 710, 720 deflects the incident light such that the light propagates by TIR through each of the waveguides 670, 680, 690. In some embodiments, the incoupling optical elements 700, 710, 720 each selectively deflect one or more particular wavelengths of light while transmitting other wavelengths to the underlying waveguide and associated incoupling optical element.

[0065]

[0183] For example, incoupling optics 700 may be configured to deflect light beam 770 having a first wavelength or range of wavelengths and transmit light beams 780 and 790 having different second and third wavelengths or ranges of wavelengths, respectively. The transmitted light beam 780 impinges on and is deflected by incoupling optics 710 configured to deflect light of the second wavelength or range of wavelengths. Light beam 790 is deflected by incoupling optics 720 configured to selectively deflect light of the third wavelength or range of wavelengths.

[0066]

[0184] 9A, the deflected light rays 770, 780, 790 are deflected such that they propagate through their corresponding waveguides 670, 680, 690. That is, the incoupling optical element 700, 710, 720 of each waveguide deflects the light into its corresponding waveguide 670, 680, 690 to incoupling the light into its corresponding waveguide. The light rays 770, 780, 790 are deflected at an angle that causes the light to propagate through the respective waveguide 670, 680, 690 by TIR. The light rays 770, 780, 790 propagate through the respective waveguide 670, 680, 690 by TIR until they impinge on the corresponding light distribution element 730, 740, 750 of the waveguide.

[0067]

[0185]

[0046] Referring now to Figure 9B, a perspective view of one example of the stacked waveguide of Figure 9A is shown. As described above, the in-coupled light rays 770, 780, 790 propagate by TIR in the waveguides 670, 680, 690, respectively, after being deflected by the in-coupling optical elements 700, 710, 720, respectively. The light rays 770, 780, 790 then impinge on the light distribution elements 730, 740, 750, respectively. The light distribution elements 730, 740, 750 deflect the light rays 770, 780, 790 to propagate towards the out-coupling optical elements 800, 810, 820, respectively.

[0068]

[0186] In some embodiments, the light distribution elements 730, 740, 750 are orthogonal pupil expanders (OPEs). In some embodiments, the OPEs deflect or distribute the light to the out-coupling optics 800, 810, 820, and in some embodiments, can also increase the beam or spot size of this light as it propagates to the out-coupling optics. In some embodiments, the light distribution elements 730, 740, 750 may be omitted and the in-coupling optics 700, 710, 720 may be configured to deflect the light directly to the out-coupling optics 800, 810, 820. For example, referring to FIG. 9A, the light distribution elements 730, 740, 750 may be replaced by the out-coupling optics 800, 810, 820, respectively. In some embodiments, the out-coupling optics 800, 810, 820 are exit pupils (EPs) or exit pupil expanders (EPEs) that direct the light into the eye 210 (FIG. 7). It will be appreciated that an OPE may be configured to increase a dimension of the eyebox in at least one axis, and an EPE may increase the eyebox in an axis that intersects, e.g., orthogonal to, the axis of the OPE. For example, each OPE may be configured to redirect a portion of the light that strikes it to an EPE of the same waveguide, while allowing the remaining portion of the light to continue propagating down the waveguide. Upon striking the OPE again, another portion of the remaining light is redirected to the EPE, which continues to propagate further down the waveguide, and so on. Similarly, upon striking an EPE, a portion of the impinging light is directed out of the waveguide toward the user, and the remaining portion of that light continues to propagate through the waveguide until it strikes an EPE again, at which point another portion of the impinging light is directed out of the waveguide, and so on. As a result, as shown in FIG. 6, a single beam of internally coupled light may be "replicated" each time a portion of that light is redirected by an OPE or EPE, thereby forming a field of cloned light beams. In some embodiments, the OPE and / or the EPE may be configured to modify the size of the light beam.

[0069]

[0187] Thus, referring to Figures 9A and 9B, in some embodiments, a set of waveguides 660 includes a waveguide 670, 680, 690 for each component color, an in-coupling optical element 700, 710, 720, a light distribution element (e.g., OPE) 730, 740, 750, and an out-coupling optical element (e.g., EP) 800, 810, 820. The waveguides 670, 680, 690 may be stacked with an air gap / cladding layer between each. The in-coupling optical element 700, 710, 720 redirects or deflects the incoming light into its waveguide (by different in-coupling optical elements receiving different wavelengths of light). The light then propagates at an angle that results in TIR in the respective waveguide 670, 680, 690. In the illustrated example, light ray 770 (e.g., blue light) is deflected by the first incoupling optical element 700 and then continues bouncing around the waveguide, interacting with the light distribution element (e.g., OPE) 730 and then the outcoupling optical element (e.g., EP) 800 in the manner previously described. Light rays 780 and 790 (e.g., green and red light, respectively) pass through the waveguide 670, with light ray 780 hitting the incoupling optical element 710 and getting deflected. Light ray 780 then bounces through the waveguide 680 via TIR and continues to its light distribution element (e.g., OPE) 740 and then to the outcoupling optical element (e.g., EP) 810. Finally, light ray 790 (e.g., red light) passes through the waveguide 690 and hits the light incoupling optical element 720 of the waveguide 690. The light in-coupling optical element 720 deflects the light beam 790 so that it propagates by TIR to the light distribution element (e.g., OPE) 750 and then by TIR to the out-coupling optical element (e.g., EP) 820. The out-coupling optical element 820 then finally out-couples the light beam 790 to a viewer, who also receives the out-coupled light from the other waveguides 670, 680.

[0070]

[0188] FIG. 9C is a top view of one example of the stacked waveguides of FIGS. 9A and 9B. As shown, the waveguides 670, 680, 690 may be vertically aligned along with each waveguide's associated light distribution elements 730, 740, 750 and associated outcoupling optics 800, 810, 820. However, as discussed herein, the incoupling optics 700, 710, 720 are not vertically aligned. Rather, the incoupling optics are preferably non-overlapping (e.g., laterally spaced apart as seen in the top view). As discussed further herein, this non-overlapping spatial arrangement facilitates one-to-one injection of light from different sources into different waveguides, thereby allowing a particular light source to be uniquely coupled to a particular waveguide. In some embodiments, arrangements including non-overlapping, spatially separated incoupling optics may be referred to as shifted pupil systems, and the incoupling optics in these arrangements may correspond to sub-pupils.

[0071]

[0189] 9D shows an example of a wearable display system 60 into which the various waveguide and associated systems disclosed herein may be integrated. In some embodiments, the display system 60 is the system 250 of FIG. 6, which shows several portions of the system 60 in more detail. For example, the waveguide assembly 260 of FIG. 6 may be part of the display 70.

[0072]

[0190] 9D, the display system 60 includes a display 70 and various mechanical and electronic modules and systems to support the functionality of the display 70. The display 70 can be coupled to a frame 80 that is wearable by a user or viewer 90 of the display system and configured to position the display 70 in front of the eye of the user 90. The display 70 can be considered eyewear in some embodiments. In some embodiments, a speaker 100 is coupled to the frame 80 and configured to be positioned adjacent to the ear canal of the user 90 (in some embodiments, another speaker, not shown, can be optionally positioned adjacent the other ear canal of the user to provide stereo / shapeable sound control). The display system 60 can also include one or more microphones 110 or other devices to detect sound. In some embodiments, the microphones are configured to enable the user to provide input or commands to the system 60 (e.g., voice menu command selections, natural language questions, etc.) and / or enable voice communication with others (e.g., with other users of similar display systems). The microphone may further be configured as an ambient sensor to collect audio data (e.g., sounds from the user and / or the environment). In some embodiments, the display system 60 may further include one or more outwardly oriented environmental sensors 112 configured to detect objects, stimuli, people, animals, places, or other aspects of the world around the user. For example, the environmental sensors 112 may include one or more cameras, which may be positioned, for example, outwardly, to capture images similar to at least a portion of the user 90's normal field of view. In some embodiments, the display system may also include ambient sensors 120a, which may be separate from the frame 80 and attached to the body of the user 90 (e.g., the head, torso, limbs, etc. of the user 90). The ambient sensors 120a, in some embodiments, may be configured to acquire data characterizing a physiological state of the user 90.For example, the sensor 120a may be an electrode.

[0073]

[0191] 9D, the display 70 is operably coupled to a local data processing module 140 by a communication link 130, such as a wired lead or a wireless connection, which can be worn in a variety of configurations, such as fixedly attached to the frame 80, fixedly attached to a helmet or hat worn by the user, embedded in headphones, or otherwise removably attached to the user 90 (e.g., in a backpack configuration, in a belt-connected configuration). Similarly, the sensor 120a can be operably coupled to the local processor and data module 140 by a communication link 120b, such as a wired lead or a wireless connection. The local processing and data module 140 can comprise a hardware processor and digital memory, such as non-volatile memory (e.g., flash memory or hard disk drive), both of which can be utilized to assist in processing, caching, and storing data. Optionally, the local processor and data module 140 can include one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, and the like. The data may include a) data captured from sensors (which may be operatively coupled to the frame 80 or otherwise attached to the user 90), such as image capture devices (such as cameras), microphones, inertial measurement units, accelerometers, compasses, GPS units, wireless devices, gyros, and / or other sensors disclosed herein, and / or b) data obtained and / or processed using the remote processing module 150 and / or remote data repository 160 (including data related to the virtual content), possibly for passage to the display 70 after such processing or retrieval.The local processing and data module 140 may be operatively coupled to a remote processing module 150 and a remote data repository 160 by communication links 170, 180, e.g., via wired or wireless communication links, such that the remote modules 150, 160 are operatively coupled to one another and available as resources to the local processing and data module 140. In some embodiments, the local processing and data module 140 may include one or more of an image capture device, a microphone, an inertial measurement unit, an accelerometer, a compass, a GPS unit, a wireless device, and / or a gyro. In some other embodiments, one or more of these sensors may be mounted to the frame 80 or may be a stand-alone structure that communicates with the local processing and data module 140 by a wired or wireless communication path.

[0074]

[0192] 9D , in some embodiments, the remote processing module 150 can include one or more processors configured to analyze and process the data and / or image information, including, for example, one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, etc. In some embodiments, the remote data repository 160 can include a digital data storage facility that can be available over the Internet or other networking configurations in a “cloud” resource configuration. In some embodiments, the remote data repository 160 can include one or more remote servers that provide information, for example, information for generating augmented reality content, to the local processing and data module 140 and / or the remote processing module 150. In some embodiments, all data is stored and all calculations are performed in the local processing and data module, allowing for fully autonomous use from the remote module. Optionally, an external system (e.g., one or more processors, one or more computer systems), including a CPU, GPU, etc., can perform at least a portion of the processing (e.g., generating image information, processing data) and provide and receive information from the modules 140, 150, 160, for example, via wireless or wired connections.

[0075]

[0193] FIG. 10 is a schematic diagram illustrating a projector assembly 1000 that utilizes a polarizing beam splitter (PBS) 1020 to illuminate a spatial light modulator (SLM) 1030 and redirect light from the SLM 1030 through projection optics 1040 to an eyepiece (not shown). The projector assembly 1000 includes an illumination source 1010, which may include, for example, a light emitting diode (LED), a laser (e.g., a laser diode), or other types of light sources. The light may be collimated by a collimating optic. The illumination source 1010 may emit polarized light, unpolarized light, or partially polarized light. In the illustrated design, the illumination source 1010 may emit polarized light 1012 having p-polarization. A first optical element 1015 (e.g., a pre-polarizer) is aligned to pass light having a first polarization (e.g., p-polarization).

[0076]

[0194] The light is directed to a polarizing beam splitter 1020. Initially, the light passes through an interface 1022 (e.g., a polarizing interface) of the PBS 1020 configured to transmit light of a first polarization (e.g., p-polarized). Thus, the light continues to be incident on the spatial light modulator 1030. As shown, the SLM 1030 is a reflective SLM configured to retroreflect the light incident thereon and selectively modulate the light. The SLM 1030 includes, for example, one or more pixels that can have different states. The light incident on each pixel may be modulated based on the state of the pixel. Thus, the SLM 1030 may be driven to modulate the light to provide an image. In this example, the SLM 1030 may be a polarization-based SLM that modulates the polarization of the light incident thereon. For example, in an on state, a pixel of the SLM 1030 changes the input light from a first polarization state (e.g., p-polarized state) to a second polarization state (e.g., s-polarized state) to indicate a bright state (e.g., a white pixel). The second polarization state may be the first polarization state modulated (e.g., rotated) by 90°. In the on state, light having the second polarization state is reflected by the interface 1022 and propagates downstream to the projector optics 1040. In the off state, the SLM 1030 does not change the polarization state of the light incident thereon, e.g., does not rotate the input light from the first polarization state, and thus a dark state (e.g., black pixel) is indicated. In the off state, light having the first polarization state is transmitted through the interface 1022 and propagates upstream back to the illumination source 1010 and does not reach the user's eye.

[0077]

[0195] After reflection from the SLM 1030, a portion of the light 1014 (e.g., the modulated light) is reflected from the interface 1022 and exits the PBS 1020 and is directed to the user's eye. The emitted light passes through the projector optics 1040 and is imaged onto an internal coupling grating (ICG) 1050 in the eyepiece (not shown).

[0078]

[0196] 11A shows a system (e.g., an augmented reality display system) 1100A for presenting an image to a user's eye 210 and viewing the world 510, having an alternative configuration to that shown in FIG. 10. The system 1100 includes a light source 1110, a spatial light modulator (SLM) 1140, and a waveguide 1120, also referred to as an eyepiece waveguide, arranged such that light from the light source 1110 illuminates the SLM 1140 and is coupled into the waveguide 1120 such that light reflected from the SLM 1140 is directed to the eye 210. The system 1100A includes an optical system 1130 arranged to illuminate the SLM 1140 and to project an image of the SLM 1140. Light from the light source 1110 propagates, for example, through the optical system 1130 in a first direction onto the SLM 1140, thereby illuminating the SLM 1140. Light reflected from SLM 1140 re-propagates through optics 1130 in a second direction opposite to the first direction and is directed to and coupled into waveguide 1120.

[0079]

[0197] The light source 1110 may include a light emitting diode (LED), a laser (e.g., a laser diode), or other types of light sources. The light source 1110 may be a polarized light source, but the light source 1110 need not be so limited. In some implementations, a polarizer 1115 may be positioned between the light source 1110 and the SLM 1140. As shown, the polarizer 1115 is between the light source 1110 and the waveguide 1120. This polarizer 1115 may also be a light recycler that transmits light of a first polarization and reflects light of a second polarization back to the light source 1110. Such a polarizer 1115 may be, for example, a wire grid polarizer. A coupling optic 1105, such as a non-imaging optical element (e.g., a cone, a compound parabolic concentrator (CPC, lens)), may be disposed with respect to the light source 1110 to receive the light output from the light source 1110. The coupling optics 1105 can collect light from the light source 1110 and, in some cases, reduce the divergence of the light emitted from the light source 1110. The coupling optics 1105 can, for example, collimate the light output from the light source 1110. The coupling optics 1105 can collect light that matches the angular spectrum field of view of the system 1100A. Thus, the coupling optics 1105 can match the angular spectrum of the light output by the light source 1110 to the field of view of the system 1100A. The coupling optics 1105 can have an asymmetric profile that operates asymmetrically on the light emitted from the light source 1110. For example, the coupling optics 1105 can reduce the divergence by different amounts in orthogonal directions (e.g., x and z directions). Such asymmetry in the coupling optics 1105 can address the asymmetry of the light emitted from the light source 1110, which can, for example, include a laser diode that emits light at a wider range of angles in one direction (e.g., x or z) as opposed to an orthogonal direction (e.g., z or x, respectively).

[0080]

[0198] As discussed above, the system 1100A includes an optical system 1130 disposed in an optical path between the light source 1110 and the SLM 1140 and configured to illuminate the SLM 1140. The optical system 1130 may include a transmission optical system that transmits light from the light source 1110 to the SLM 1140. The optical system 1130 may also be configured to project an image of or formed by the SLM 1140 into the waveguide 1120. The image may be projected into the eye of the eye 210. In some designs, the optical system 1130 may include one or more lenses or optical elements having refractive power. The optical system 1130 may have, for example, a positive optical power. The optical system 1130 may include one or more refractive optical elements, such as a refractive lens. Other types of optical elements may also be used.

[0081]

[0199] The SLM 1140 can reflect, modulate, and reflect light therefrom. The SLM 1140 may be a polarization-based SLM configured to modulate polarization. The SLM 1140 can include, for example, a liquid crystal (LC) SLM (e.g., a liquid crystal on silicon (LCoS) SLM). The LC SLM can include, for example, a twisted nematic (TN) liquid crystal. The SLM 1140 can be substantially similar to the SLM 1030 with reference to FIG. 10. The SLM 1140 can include one or more pixels configured to selectively modulate light incident on the pixel depending on the state of the pixel. For some types of SLM 1140, the pixel can modulate a beam incident thereon by changing the polarization state, for example, by rotating the polarization (e.g., rotating the orientation of linearly polarized light).

[0082]

[0200] As discussed above, the SLM 1140 may be an LCoS SLM 1140. In a crossed polarizer configuration, the LCoS SLM 1140 may be nominally white. A pixel has a bright state when it is off (e.g., 0 voltage) and a pixel has a dark state when it is on (e.g., a voltage above a threshold turn on voltage). In this crossed polarizer configuration, leakage is minimized when the pixel is on and has a dark state.

[0083]

[0201] In the parallel polarizer configuration, the LCoS SLM 1140 is nominally black. The pixel has a dark state if it is off (e.g., 0 voltage) and the pixel has a bright state if it is on (e.g., voltage above a threshold turns on voltage). In this parallel polarizer configuration, leakage is minimized when the pixel is off and has a dark state. The dark state can be (re)optimized using the friction direction and the compensator angle. The compensator angle can refer to the angle of the compensator, which can be between the optical system 1130 and the SLM 1140, for example, as shown in FIG. 20B.

[0084]

[0202] The dynamic range and throughput of the parallel polarizer configuration may be different from that of the crossed polarizer configuration. Additionally, the parallel polarizer configuration may be optimized for different contrast than the crossed polarizer configuration.

[0085]

[0203] The system 1100A includes a waveguide 1120 for outputting image information to the eye 210. The waveguide 1120 may be substantially similar to the waveguides 270, 280, 290, 300, 310, 670, 680, and 690 discussed above. The waveguide 1120 may include a substantially transparent material having a sufficient refractive index to guide light therein. As shown, the waveguide 1120 may include a first side 1121, a second side 1123 opposite the first side 1121, and corresponding top and bottom major surfaces and edges therearound. The first and second major 1121, 1123 surfaces may be sufficiently flat such that image information may be preserved during propagation of light from the SLM 1140 to the eye 210 such that an image formed by the SLM 1140 may be projected into the eye. The optics 1130 and the SLM 1140 may be positioned on a first side 1121 of the waveguide 1120. The light source 1110 may be disposed on the second side 1123 such that light from the light source 1110 is incident on the second side 1123 before passing through the waveguide 1120 and the optics 1130 to the SLM 1140. Thus, the waveguide 1120 may be disposed between the light source 1110 and the optics 1130. Additionally, at least a portion of the waveguide 1120 may extend between the light source 1110 and the optics 1130 such that light travels through a portion of the waveguide 1120 to the optics 1130. Thus, light emitted from the light source 1110 may be directed through the waveguide 1120 into and through the optics 1130 and incident on the SLM 1140. The SLM 1140 reflects the light back through the optics 1130 into the waveguide 1120 .

[0086]

[0204] The system 1100A also includes an incoupling optical element 1160 for coupling light from the optical system 1130 into the waveguide 1120. The incoupling optical element 1160 may be disposed on a major surface (e.g., the top major surface 1123) of the waveguide 1120. In some designs, the incoupling optical element 1160 may be disposed on the bottom major surface 1121 of the waveguide 1120. In some designs, the incoupling optical element 1160 may be disposed within the body of the waveguide 1120. The incoupling optical element 1160 is shown on one side or corner of the waveguide 1120, but may be disposed in / on other areas of the waveguide 1120. The incoupling optical element 1160 may be substantially similar to the incoupling optical elements 700, 710, 720 described above with reference to FIGS. 9A, 9B, and 9C. The incoupling optical element 1160 may be a diffractive optical element or a reflector. Other structures may be used as the incoupling optical element 1160. The incoupling optical element 1160 may be configured to direct light incident thereon into the waveguide 1120 at a sufficiently large grazing angle (e.g., greater than the critical angle) with respect to the top 1123 and bottom 1121 major surfaces of the waveguide 1120 to guide the light therein by total internal reflection. Furthermore, the incoupling optical element 1160 may operate over a wide range of wavelengths and thus may be configured to couple multiple colors of light into the waveguide 1120. For example, the incoupling optical element 1160 may be configured to couple red, green, and blue light into the waveguide 1120. The light source 1110 may emit red, green, and blue light at different times.

[0087]

[0205] The system 1100A includes a light distribution element 1170 disposed on or in the waveguide 1120. The light distribution element 1170 may be substantially similar to the light distribution elements 730, 740, and 750 described above with respect to FIG. 9B. For example, the light distribution element 1170 may be an orthogonal pupil expander (OPE). The light distribution element 1170 may be configured to spread the light in the waveguide 1120 by directing light propagating in the x-direction, for example, in the z-direction shown in the top view of FIG. 11B. Thus, the light distribution element 1170 may be configured to increase the dimension of the eyebox along the z-axis. See FIG. 11B. The light distribution element 1170 may include, for example, one or more diffractive optical elements configured to diffract light propagating in the waveguide 1120 that is incident on the diffractive optical element to redirect the light, for example, in a substantially orthogonal direction. Other configurations are possible.

[0088]

[0206] 11B, the system 1100 may also include an outcoupling optical element 1180 for coupling light from the waveguide 1120 to the eye 210. The outcoupling optical element 1180 may be configured to redirect light propagating in the waveguide 1120 by total internal reflection (TIR) ​​at an angle more perpendicular to the top major surface 1123 and / or the bottom major surface 1121 of the waveguide 1120 so that the light is not guided in the waveguide 1120. Instead, the light is directed out of the waveguide 1120, for example, through the bottom major surface 1121. The outcoupling optical element 1180 may include, for example, one or more diffractive optical elements configured to diffract light propagating in the waveguide 1120 that is incident on the diffractive optical element to redirect the light, for example, out of the waveguide 1120. Other configurations are possible.

[0089]

[0207] 11B also shows the position of the in-coupling optic 1160 disposed laterally relative to the light distribution optic (e.g., orthogonal pupil expander) 1170 and the out-coupling optic 1180. FIG. 11B also shows the position of the light source 1110 disposed laterally relative to the in-coupling optic 1160, the light distribution optic (e.g., orthogonal pupil expander) 1170 and the out-coupling optic 1180.

[0090]

[0208] In operation, the light source 1110 of the system 1100A emits light into the coupling optics 1105 and through the polarizer 1115. This light may therefore be polarized, e.g., linearly polarized in a first direction. This polarization may be transmitted through the waveguide 1120, enter the second major surface of the waveguide 1120, and exit the first major surface of the waveguide 1120. This light may propagate through the optics 1130 to the SLM 1140. The optics 1130 quasi-collimates and / or selects the light from the light source 1110, thereby illuminating the SLM 1140, which may include a polarization-based modulator that modulates the polarization of the light incident thereon, such as by selectively rotating the orientation of the modulator for each pixel depending on the state of the pixel. For example, a first pixel may be in a first state and rotate the polarization, and a second pixel may be in a second state and not rotate the polarization. The light between the coupling optics 1105 and the optics 1130 can illuminate the SLM 1140 fairly uniformly. After entering the SLM 1140, the light is reflected back through the optics 1130. The optics 1130 can be configured to project an image from the SLM 1140 into the waveguide 1120 and ultimately to the eye 210 so that the image is visible to the eye 210. In some designs, the retina of the eye 210 is optically conjugated with the SLM 1140 and / or an image formed by and / or on the SLM 1140. The output of the optics 1130 can facilitate the projection of the image on the SLM 1140 into the eye 210 and onto the retina of the eye 210. In some implementations, for example, optical power provided by the outcoupling optics 1180 can assist and / or affect the image ultimately formed in the eye 210. The optical system 1130 acts as a projection lens as light reflected from the SLM 1140 travels through the optical system towards the waveguide 1120. The optical system can function approximately as a Fourier transform of the image on the SLM 1140 onto a plane within the waveguide 1120 near the incoupling optic 1160.Together, both passing through the optical system 1130 (the first from the light source 1110 to the SLM 1140, and the second from the SLM 1140 to the waveguide 1120) can act to roughly image the pupil of the coupling optical system 1105. The alignment and orientation of the light source 1110 (and possibly also the coupling optical system 1105 and / or the polarizer 1115), the optical system 1130, and the SLM 1140 are such that the light from the light source 1110 reflected from the SLM 1140 is directed onto the incoupling optical element 1160. The pupil associated with the coupling optical system 1105 may be aligned with the incoupling optical element 1160. The light can pass through an analyzer 1150 (e.g., a polarizer) in the optical path between the SLM 1140 and the eye 210. As depicted in FIG. 11A, an analyzer (e.g., polarizer) 1150 may be disposed in the optical path between the optical system 1130 and the incoupling optical element 1160. The analyzer 1150 may be, for example, a linear polarizer with an orientation that transmits light of a first polarization (p-polarized) and blocks light of a second polarization (s-polarized), or vice versa. The analyzer 1150 may be a clean-up polarizer and may further block light of a polarization blocked by another polarizer between the SLM 1140 and the analyzer 1150 or within the SLM 1140. The analyzer 1150 may be, for example, a circular polarizer that acts as an isolator to mitigate reflections back from the waveguide 1120, specifically the incoupling optical element 1160, towards the SLM 1140. The analyzer 1150 may include a wire grid polarizer, such as an absorptive wire grid polarizer, as any of the polarizers disclosed herein. Such polarizers may result in significant absorption of undesired light and thus increased contrast. Some such polarizers can be fabricated to include one or more dielectric layers over the wires and / or multilayers. In some implementations, the SLM 1140 may be a liquid crystal on silicon (LCoS) SLM and may include an LC cell and a retarder (e.g., a compensator). In some implementations, the analyzer 1150 may be a compensator intended to provide a more consistent polarization rotation (e.g., 90°) of the SLM 1140 for different angles of incidence and different wavelengths.The compensator can be used to improve the contrast of the display by improving the circular polarization of the incident light beam over a spread of angles and wavelengths. The SLM 1140 may, for example, include a TN LCoS configured to rotate incident light of a first polarization (e.g., s-polarized) to a second polarization (e.g., p-polarized) for a first pixel to generate a bright pixel state when the light passes through the analyzer 1150. Conversely, the SLM 1140 may be configured to not rotate incident light of a first polarization (e.g., s-polarized) to a second polarization (e.g., p-polarized) for a second pixel such that the reflected light remains of the first polarization and generates a dark pixel state when the light is attenuated or blocked by the analyzer 1150. In such a configuration, the polarizer 1115 closer along the optical path to the light source 1110 may be oriented differently (e.g., orthogonally) with respect to the analyzer 1150 further along the optical path from the light source 1110. Other, e.g., opposite, configurations are also possible.

[0091]

[0209] The light is then deflected, e.g., rotated, by the in-coupling optics 1160 so that it is guided into the waveguide 1120 and propagates there by TIR. The light then impinges on the light distribution element 1170, which rotates the light in another direction (e.g., more towards the z-direction), increasing the size of the eyebox along the direction of the z-axis as shown in FIG. 11B. Thus, the light is deflected towards the out-coupling optics 1180, which directs the light from the waveguide 1120 towards the eye 210 (e.g., the eye of the user as shown). The light out-coupled along the z-direction by different portions of the out-coupling optics 1180 increases the size of the eyebox along at least a direction parallel to the z-axis as defined in FIG. 11B. Notably, in this configuration, the optical system 1130 is used to illuminate the SLM 1140 as well as to project an image onto the in-coupling optics 1160. Thus, the optical system 1130 can act as projection optics to distribute (e.g., uniformly) the light from the light source 1110, as well as imaging optics to provide an image of the SLM 1140 and / or an image formed in the eye by the SLM 1140. The system 1100A of FIG. 11A / B may be more compact than the system 1000 of FIG. 10 in some examples. In some cases, not employing the PBS 1020 shown in FIG. 10 could potentially reduce the cost and / or size of the system. Additionally, without the PBS 1020, the system may be more symmetrical and easier to design by shortening the back focal length of the optical system 1130.

[0092]

[0210] As mentioned above, alternative configurations are possible. With reference to FIG. 11C, for example, in some designs, the system 1100C may be configured to pass light having a polarization that is not rotated by the SLM 1140. In one implementation, for example, the SLM 1140 is a liquid crystal (LC) based SLM and may include a vertically aligned (VA) LC on silicon (LCoS). The SLM 1140 may have a first pixel in a first state that does not rotate the polarization and a second pixel in a second state that rotates the polarization. In the configuration shown in FIG. 11C, a single common analyzer / polarizer 1155 is utilized. This analyzer 1155 may transmit light of a first polarization (e.g., s-polarized) and attenuate or reduce the transmission of a second polarization (e.g., p-polarized). Thus, light incident on a first pixel in a first state that does not rotate the polarization orientation (e.g., s-polarized light) is reflected from the SLM 1140 and passes through the analyzer 1155 to the waveguide 1120. Conversely, light incident on a second pixel in a second state that rotates the polarization orientation (e.g., s-polarized light) is reflected from the SLM 1140 and attenuated, reduced, or not passed through the analyzer 1155 to the waveguide 1120. This configuration thereby allows the polarizer 1115 and the analyzer 1150 shown in FIG. 11A to be incorporated into a common optical element, the analyzer 1155 shown in FIG. 11C, thereby simplifying the system 1100 of FIG. 11A / B by potentially reducing the number of optical components. The analyzer 1155 may be disposed between the waveguide 1120 and the optical system 1130. In other implementations, separate analyzer / polarizers and analyzers / polarizers may be used, as shown in the system 1100 of Figures 11A / B. Figures 11A and 11B show a polarizer 1115 between the light source 1110 and the waveguide 1120, and an analyzer 1140 between the optical system 1130 and the waveguide 1120.

[0093]

[0211] FIG. 11D illustrates an example of a waveguide with a combined OPE / EPE, according to an embodiment of the present invention. Referring to FIG. 11D, a waveguide 1190 with a combined OPE / EPE region 1191 includes gratings corresponding to both the OPE and the EPE that are spatially overlapped in the x and y directions. In some embodiments, the gratings corresponding to both the OPE and the EPE are located on the same side of the substrate, such that the OPE grating is overlaid on the EPE grating, or the EPE grating is overlaid on the OPE grating (or both). In other embodiments, the OPE grating is located on the opposite side of the substrate from the EPE grating, such that the gratings are spatially overlapped in the x and y directions but separated from each other in the z direction (i.e., in different planes). Thus, the combined OPE / EPE region 1191 can be implemented in either a single-sided or double-sided configuration.

[0094]

[0212] The light path in the eyepiece waveguide 1190 includes incident light 1194 that is coupled into the eyepiece waveguide 1190 at ICG 1193. The internally coupled light propagates through the substrate 1192 towards the combined OPE / EPE 1191 by total internal reflection. When these light rays encounter the combined OPE / EPE 1191, also referred to as the combined pupil expander (CPE), the light is diffracted in the +y direction and then diffracted in the -z direction along light path 1195 out of the waveguide towards the user's eye. Similarly, the internally coupled light may alternatively encounter the combined OPE / EPE 1191 and be diffracted in the -y direction and then diffracted out of the waveguide along light path 1195 towards the user's eye.

[0095]

[0213] As described more fully herein, embodiments of the invention utilize eyepiece waveguides having optical path length differences, e.g., the thickness of the eyepiece waveguide as a function of lateral position, i.e., position in the xy plane. In some embodiments, the portion of the eyepiece waveguide in which the ICG is formed is thicker than the portion of the eyepiece waveguide in which the CPE is formed. Additionally, in some embodiments, the thickness of the CPE varies, with the portion adjacent the ICG being thicker than the portion distal to the ICG. In other embodiments, the physical thickness is uniform, but the refractive index varies as a function of lateral position, resulting in an optical path length difference that characterizes the eyepiece waveguide as a function of lateral position.

[0096]

[0214] A wide variety of other configurations can be employed that utilize optical system 1130 for both illuminating SLM 1140 and imaging the image formed by SLM 1140. For example, while Figures 11A-11D show a single waveguide 1120, more than one waveguide may be used, such as a stack of waveguides (possibly different waveguides for different colors of light).

[0097]

[0215] For example, Figure 12A shows a cross-sectional side view of an exemplary system 1200A including a stack 1205 including waveguides 1120, 1122, 1124, each including an internal coupling optical element 1260, 1262, 1264. The waveguides 1120, 1122, 1124 may each be configured to output light at one or more different wavelengths or one or more different wavelength ranges. The stack 1205 may be substantially similar to stacks 260 and 660 (Figures 6 and 9A), and the illustrated waveguides 1120, 1122, 1124 of the stack 1205 may correspond to portions of the waveguides 670, 680, 690, although the stack 1205 and the waveguides 1120, 1122, 1124 need not be so limited. As shown in FIG. 12A, the incoupling optical elements 1260, 1262, 1264 may be associated with or included within or on the waveguides 1120, 1122, 1124, for example. The incoupling optical elements 1260, 1262, 1264 may be color selective and may primarily redirect or redirect specific wavelengths to be guided into the corresponding waveguides 1120, 1122, 1124. As shown, because the incoupling optical elements 1260, 1262, 1264 are color selective, the incoupling optical elements 1260, 1262, 1264 do not need to be laterally displaced and may be stacked on top of one another. Wavelength multiplexing may be employed to couple specific colors into the corresponding waveguides. For example, a red incoupling optical element may incoupling red light into a waveguide designated to propagate red light, but not incoupling blue or green light, which are instead coupled into other waveguides by other blue and green selective waveguides, respectively.

[0098]

[0216] In some implementations, the light source 1110 may be a multi-color light source capable of emitting different colors of light at different times. For example, the light source 1110 may emit red, green, and blue (RGB) light and may be configured to emit red and negligible amounts of green and blue during a first period, green and negligible amounts of red and blue during a second period, and blue and negligible amounts of red and green during a third period. These cycles may be repeated and the SLM 1140 may generate a pattern of pixel states appropriate for a particular color (red, green, or blue) to provide the appropriate image color components for a given image frame. The different waveguides 1120, 1122, 1124 of the stack 1205 may each be configured to output light of a different respective color. For example, as depicted in FIG. 12A, the waveguides 1120, 1122, 1124 may be configured to output blue, green, and red light, respectively. Of course, other colors are possible, for example, the light source 1110 may emit other colors, and the color-selective incoupling optics 1260, 1262, 1264, outcoupling optics, etc., may be configured for such other colors. Additionally, individual red, green, and blue emitters may be positioned close enough together to effectively function as a single pupil light source. The red, green, and blue emitters may be combined with lenses and dichroic splitters to form a single red, green, and blue pupil source. Single pupil multiplexing may be extended beyond or in addition to color selectivity and may include the use of polarization-sensitive gratings and polarization switching. These color or polarization gratings may also be used in combination with multiple display pupils to increase the number of layers that can be addressed.

[0099]

[0217] The different incoupling optical elements 1260, 1262, 1264 in the different waveguides 1120, 1122, 1124 may be disposed above and / or below one another and aligned laterally (e.g., in the x and z directions shown in FIG. 12A ), as opposed to being laterally displaced and unaligned with one another. Thus, in some implementations, for example, the different incoupling optical elements 1260, 1262, 1264 may be configured such that light of a first color can be coupled and guided into the waveguide 1120 by the incoupling optical element 1260, and light of a second color, different from the first color, can pass through the incoupling optical element 1260 to the next incoupling optical element 1262 and can be coupled and guided into the waveguide 1122 by the incoupling optical element 1262. Light of a third color, different from the first and second colors, can pass through the incoupling optical elements 1260 and 1262 to the incoupling optical element 1264 and can be coupled into and guided within the waveguide 1124. Additionally, the incoupling optical elements 1260, 1262, 1264 may be polarization selective. For example, the different incoupling optical elements 1260, 1262, 1264 can be configured such that light of a particular polarization is coupled into the waveguide by the corresponding polarization selective incoupling optical element 1260, 1262, 1264 or passes through the incoupling optical element 1260, 1262, 1264.

[0100]

[0218] Depending on the configuration, the SLM 1140 may include a polarization-based SLM that modulates the polarization. The system 1200A may include, for example, a polarizer and / or analyzer to modulate the light injected into the stack 1205 for each pixel depending on the state of the respective pixel (e.g., whether the pixel rotates the polarization orientation or not). Various aspects of such systems employing polarization-based SLMs are discussed above, and any one of such features may be employed in combination with any other features described herein. However, other designs remain possible.

[0101]

[0219] For example, a deflection-based SLM 1140 may be employed. For example, the SLM 1140 may include one or more movable optical elements, such as movable mirrors, that can reflect and / or deflect light along different directions depending on the state of the optical elements. The SLM 1140 may include one or more pixels that include optical elements, such as, for example, micromirrors or reflectors. The SLM 1140 may incorporate digital light processing (DLP™) technology, for example, using a digital micromirror device (DMD). An example of a system 1200B using such a deflection-based SLM 1140 is shown in FIG. 12B. The system 1200B includes a deflection-based SLM 1140 and a light dump 1250. The light dump 1250 may include an absorbing material or structure configured to absorb light. The deflection-based SLM 1140 may include one or more micro movable mirrors that can be selectively tilted to deflect light in different directions. For example, the deflection-based SLM 1140 may be configured to deflect light from the light source 1110 incident thereon to the incoupling optics 1260, 1262, 1264 when a given pixel is in a bright state. Thus, as discussed above, this light is coupled by one of the incoupling optics 1260, 1262, 1264 into one of the respective waveguides 1120, 1122, 1124, depending on, for example, the color of the light, and directed to the eye 210. Conversely, when a given pixel is in a dark state, the light from the light source 1110 may be deflected to the light dump 1250, such that the light is not coupled by one of the incoupling optics 1260, 1262, 1264 into one of the respective waveguides 1120, 1122, 1124, and directed to the eye 210. Alternatively, the light may be absorbed by an absorbing material that constitutes the light dump 1250. In some implementations, the analyzer 1150 may be a polarizer (e.g., a "clean-up" polarizer) used to eliminate unwanted reflections from the incoupling optical elements 1260, 1262, 1264. This polarizer may be useful because the optical system 1130 may include plastic optical elements that are birefringent and can change the polarization of light.The "clean-up" polarizer can attenuate or eliminate light having undesired polarization (e.g., reflections) from being directed into the waveguides 1120, 1122, 1124. Other types of light conditioning elements may be disposed between the SLM 1140 and the waveguides 1120, 1122, 1124, such as between the optics 1130 and the waveguides 1120, 1122, 1124. For example, such light conditioning elements may also include a circular polarizer (i.e., a linear polarizer and a retarder such as a quarter wave plate). The circular polarizer can reduce the amount of reflections from the waveguides 1120, 1122, 1124 or the in-coupling optical elements 1260, 1262, 1264 that re-enter and are coupled into the waveguides 1120, 1122, 1124. The reflected light may be circularly polarized or may have the opposite circular polarization to that of the incident light (e.g., right-handed circular polarizer light is converted to left-handed circular polarized light upon reflection, or vice versa). A retarder in a circular polarizer can convert the circularly polarized light to linearly polarized light, such as the polarizer's orthogonal polarization, which is attenuated, e.g., absorbed, by the linear polarizer in the circular polarizer. Clean-up polarizers can be used with polarization independent modulators, such as DMDs. As mentioned above, clean-up polarizers can be useful to suppress reflections and / or improve the coupling of light into the internally coupled optical elements 1260, 1262, 1264 in an optimal polarization state.

[0102]

[0220] 12B shows a side or cross-sectional view of such a system 1200B, and FIG. 12C shows a top view of the lateral arrangement of the incoupling optics 1264, the light dump 1250, and the light source 1110. The SLM 1140 is configured to reflect, deflect, and / or direct light from the light source 1110 either to the lateral position of the incoupling optics 1264 (and other incoupling optics 1260, 1262) or to the light dump 1250, depending on the state of a particular pixel.

[0103]

[0221] In a particular design, the light dump 1250 may include an energy harvesting system. The light dump 1250 may include, for example, a light energy conversion element configured to convert light energy into electrical energy. The light energy conversion element may include, for example, a solar cell. The light energy conversion element may include, for example, a photovoltaic detector that generates an electrical output when light is incident on it. The light energy conversion element may be electrically connected to an electrical component, for example, a conductive wire, to direct the electrical output to power the system 1200B and / or possibly charge one or more batteries.

[0104]

[0222] In certain designs, laterally displaced, non-color-selective, or broadband, or polychromatic incoupling optical elements can be used. FIG. 13A is a perspective view of a system 1300 including, for example, a stack 1305 including waveguides. The stack 1305 may be substantially similar to the stack 1205 with reference to FIG. 12A. Each waveguide in the stack 1305 may include an incoupling optical element 1360, 1362, 1364, but in contrast to the design shown in FIG. 12A, the incoupling optical elements 1360, 1362, 1364 are laterally displaced with respect to each other. As shown in Figures 13A, 13B, and 13C, the light sources 1110, 1112, 1114 may also be laterally displaced with respect to one another and arranged to direct light to respective incoupling optical elements 1360, 1362, 1364 by passing the light through optics 1130, reflecting the light off the SLM 1140, and passing the reflected light back through optics 1130. The system 1300 in Figure 13B is depicted with the light source 1114 located behind the light source 1110 and therefore is not shown in Figure 13B. The light sources 1110, 1112, 1114 may correspond to the incoupling optical elements 1360, 1362, 1634, respectively. In one design, for example, the light sources 1110, 1112, 1114 and the corresponding incoupling optics 1360, 1362, 1364 are disposed approximately equidistant from (symmetrically about) the center of the optical system 1130 along a common (optical) axis. The common (optical) axis may intersect the center of the optical system 1130. In one design, for example, the light sources 1110, 1112, 1114 and the corresponding incoupling optics 1360, 1362, 1364 are not disposed equidistant from (symmetrically about) the center of the optical system 1130 along the common (optical) axis.

[0105]

[0223] The incoupling optical elements 1360, 1362, 1364 may be configured to couple multiple colors of light into their respective waveguides. Accordingly, these incoupling optical elements 1360, 1362, 1364 may be referred to herein as broadband, polychromatic, or non-color-selective incoupling optical elements 1360, 1362, 1364. For example, in some cases, these incoupling optical elements 1360, 1362, 1364 are configured to incoupling red light, green light, and blue light into the associated waveguide in which the incoupling optical element 1360, 1362, 1364 is included, such that light of such colors is guided into the waveguide by TIR. Such broadband incoupling optical elements 1360, 1362, 1364 may operate, for example, over a wide range of wavelengths, for example within the visible range, or over a selected wavelength or wavelength range, for example spanning across the visible range. Thus, such broadband or polychromatic or non-color selective incoupling optics 1360, 1362, 1364 may be configured to direct a variety of different colors (e.g., red, green, and blue) of light into the waveguide and guide it therein by TIR. Although red, green, and blue (RGB) are referred to herein in connection with light sources, incoupling optics, waveguides, etc., other colors or color systems may additionally or alternatively be used, such as, for example, but not limited to, magenta, cyan, yellow (CMY).

[0106]

[0224] As shown in FIG. 13A, the light sources 1110, 1112, 1114 are shown above the top waveguide and displaced relative to each other (e.g., in the x and z directions). Similarly, three internal coupling optical elements 1360, 1362, 1364 are shown on the three respective waveguides and displaced relative to each other (e.g., in the x, y, and z directions). FIG. 13B is a side view of the system 1300 shown in FIG. 13A, showing the internal coupling optical elements 1360, 1362, 1364 spatially displaced laterally relative to each other (e.g., in the x and z directions), as well as some of the light sources 1110, 1112, 1114 laterally displaced relative to each other (e.g., in the x and z directions). FIG. 13B also shows the optical system 1130 and the SLM 1140.

[0107]

[0225] 13C is a top view of the augmented reality display system shown in FIG. 13A and FIG. 13B showing the incoupling optical elements 1360, 1362, 1364 and associated light sources 1110, 1112, 1114. In this design, the incoupling optical elements 1360, 1362, 1364 and associated light sources 1110, 1112, 1114 are arranged in a ring-like pattern around a center point of a common (optical) axis. As shown, the light sources 1110, 1112, 1114 and corresponding incoupling optical elements 1360, 1362, 1364 are arranged approximately equidistant around the center point of the common (optical) axis, although this should be the case. In some designs, this center point may correspond to the center of the optical system 1130 and / or the center of the optical system 1130 along the common (optical) axis that intersects with the position of the optical system 1130 along the optical axis. Also as a result, the non-color-selective incoupling optical elements 1360, 1362, 1364 and the light sources 1110, 1112, 1114 are laterally displaced (eg, in the x and z directions) relative to one another.

[0108]

[0226] Other configurations of the lateral arrangement are possible. Figures 14A-14C show alternative configurations of a system 1400 including a stack 1405 in which the incoupling optical elements 1360, 1362, 1364 and the light sources 1110, 1112, 1114 include waveguides that are laterally displaced with respect to one another. Figure 14A is a side view and Figure 14B is a top view of the system 1400 shown in Figure 14A showing the incoupling optical elements 1360, 1362, 1364 and the light sources 1110, 1112, 1114 laterally displaced. Figure 14C is an orthogonal side view of the system 1400 shown in Figures 14A and 14B.

[0109]

[0227] The side views of Figures 14A and 14C show how the incoupling optical elements 1360, 1362, 1364 are disposed on separate waveguides in the stack 1405 such that light can be coupled into a corresponding waveguide by each laterally displaced incoupling optical element 1360, 1362, 1364. The incoupling optical elements 1360, 1362, 1364 are shown disposed on the top major surfaces of the waveguides in Figures 14A and 14C. However, the incoupling optical elements 1360, 1362, 1364 may alternatively be disposed on the bottom major surfaces of the respective waveguides or in the bulk of the waveguides. A wide variety of configurations are possible.

[0110]

[0228] 14B, the incoupling optical elements 1360, 1362, 1364 are arranged in a row that is laterally displaced relative to one another along the z-direction, but not displaced along the x-direction. Similarly, the light sources 1110, 1112, 1114 are arranged in a row that is also laterally displaced relative to one another along the z-direction, but not displaced along the x-direction. The incoupling optical elements 1360, 1362, 1364 are laterally displaced in the x-direction relative to the light sources 1110, 1112, 1114.

[0111]

[0229] Still other configurations are possible. Figure 15 is a top view of a system 1500 showing an alternative configuration of the light sources 1110, 1112, 1114 and the incoupling optical elements 1360, 1362, 1364. In contrast to Figure 13C, where all of the light sources 1110, 1112, 1114 are generally on one side (e.g., of a ring-like pattern) and all of the incoupling optical elements 1360, 1362, 1364 are generally on one side (i.e., the opposite side), the light sources 1110, 1112, 1114 and the incoupling optical elements 1360, 1362, 1364 are interspersed or alternating around the circumference of the ring-like pattern.

[0112]

[0230] However, in some implementations, the incoupling optical elements 1360, 1362, 1364 and associated one or more light sources 1110, 1112, 1114 are also arranged in a ring-like pattern around a center point. As a result, the light sources 1110, 1112, 1114 and corresponding incoupling optical elements 1360, 1362, 1364 may be arranged approximately equidistant from the center. In some designs, this center may correspond to the center of the optical system 1130 along a common central axis that intersects with the center of the optical system 1130 and / or a position along the optical axis of the optical system. Thus, light from the first light source 1110 (as can be seen from the top view of FIG. 15 ) may be coupled through the optical system 1130 to the incoupling optical element 1360 across the center or central axis or optical axis of the optical system 1130. Similarly, light from the second light source 1112 may be coupled through the optical system 1130 to the incoupling optical element 1362 across the center or central axis or optical axis of the optical system 1130. Similarly, light from the third light source 1114 may be coupled through the optical system 1130 to the incoupling optical element 1364 across the center or central axis or optical axis of the optical system 1130. Also, as a result, the non-color-selective incoupling optical elements 1360, 1362, 1364 and the light sources 1110, 1112, 1114 are displaced laterally (e.g., in the x and z directions) relative to one another. The optical system 1130 may be designed to be more focused within the stack 1405 such that the sub-pupil and the incoupling optical elements 1360, 1362, 1364 are closer together in the y direction. In this configuration, the incoupling optics 1360, 1362, 1364 can be smaller because they are closer to the focal point of the optical system 1130. The light source 1110 may be on the user side of the stack 1405 (e.g., similar to FIGS. 17 and 18), thus reducing the distance or optical path between the light source 1110 and the optical system 1130.

[0113]

[0231] In various implementations as shown in FIGS. 12A-15 above, stacks (e.g., stacks 1205, 1305, 1405) including multiple waveguides (e.g., stack 1205 including waveguides 1120, 1122, 1124, stack 1305 including a waveguide (not labeled), and stack 1405 including a waveguide (not labeled)) may be included to address different colors (e.g., red, green, and blue). Different waveguides may be for different colors. Similarly, multiple stacks may be included to provide different optical properties to the light outcoupled from each stack. For example, the waveguides 1120, 1122, 1124 of stack 1205 in FIGS. 12A-12B may be configured to output light with optical properties (e.g., refractive power to provide a particular wavefront shape) that are possibly related to the apparent depth from which the light appears to emanate. For example, wavefronts with different amounts of divergence, convergence, or collimation may appear as if projected from different distances from the eye 210. Thus, multiple stacks may be included, with different stacks configured such that the light outcoupled by the outcoupling optics has different amounts of convergence, divergence, or collimation and thus appears to originate from different depths. In some designs, the different stacks may include different lenses, such as diffractive lenses or other diffractive optical elements, to provide different amounts of refractive power to the different stacks. As a result, the different stacks produce different amounts of convergence, divergence, or collimation, and thus the light from the different stacks appears as if it is associated with different depth planes or objects that are at different distances from the eye 210.

[0114]

[0232] FIG. 16A is a side view of a system 1600 including stacks 1605, 1610, 1620. As shown in FIG. 16A, the system 1600 includes three stacks 1605, 1610, 1620, but this need not be the case. The system may be conceived with fewer or more stacks. Each of the stacks 1605, 1610, and 1620 includes one or more (e.g., three) waveguides. FIG. 16A also shows groups 1630, 1640, 1650 of internally coupled optical elements. A first group 1630 is associated with the first stack 1605, a second group 1640 is associated with the second stack 1610, and a third group 1650 is associated with the third stack 1620. The groups 1630, 1640, 1650 are laterally displaced with respect to each other. Each of the groups 1630, 1640, 1650 includes a color-selective incoupling optical element configured to incoupling different respective colors, substantially similar to the incoupling optical elements 1260, 1262, 1264 of FIG. 12A. As shown in FIG. 16A, the incoupling optical elements in each group 1630, 1640, 1650 are not laterally displaced relative to one another, but this need not be the case. Systems can be devised in which the incoupling optical elements in a group are laterally displaced relative to one another. The system 1600 can be configured such that the light outcoupled from each of the stacks 1605, 1610, 1620 has a different amount of refractive power. For example, the waveguides in the stacks can have outcoupling optical elements or diffractive lenses with a given refractive power. The refractive power of the different stacks 1605, 1610, 1615 can be different such that light from one stack appears to originate at a different depth than light from another stack. For example, the refractive power of one stack may collimate the light from that stack, while the refractive power of another stack may diverge the light from that stack. The divergent light may appear to originate from an object that is a close distance from the eye 210, while the collimated light may appear to originate from an object that is a far distance away.Thus, the light outcoupled from the first stack 1605, the second stack 1610, and the third stack 1620 may have different amounts of convergence, divergence, and / or collimation and therefore appear to originate from different depths. In some implementations, the light outcoupled from one of the stacks may be collimated, while the light outcoupled by the different stack may diverge. The light outcoupled from one of the other stacks may also diverge, but by a different amount.

[0115]

[0233] As shown in FIG. 16A, the light source 1110 may be disposed relative to the optics 1130 and the SLM 1140 to direct light to the group 1630 of incoupling optical elements, the light source 1112 may be disposed relative to the optics 1130 and the SLM 1140 to direct light to the group 1640 of incoupling optical elements, and the light source 1114 may be disposed relative to the optics 1130 and the SLM 1140 to direct light to the group 1650 of incoupling optical elements. The light sources 1110, 1112, 1114 may be configured to emit different colors of light at different times. Similarly, the different respective colors of light may be coupled into different waveguides in the stack as a result of the color-selective incoupling optical elements in the manner described above. For example, if blue light is emitted from the second light source 1112, the optics 1130 and the SLM 1140 direct the blue light to the second group 1640 of incoupling optical elements. The light may pass through a first red incoupling optical element and a second green incoupling optical element in the second group 1640 and be directed by a third blue incoupling optical element in the second group 1640 to a third waveguide in the second stack 1610. The waveguide in the second stack 1610 may include an outcoupling optical element or other optical element with refractive power (e.g., a diffractive lens) to provide a beam to the eye 210 associated with a particular depth plane or object distance associated with the second stack 1610.

[0116]

[0234] Figure 16B is a top view of the system 1600 of Figure 16A. Different groups of incoupling optical elements 1630, 1640, 1650 are shown laterally displaced (e.g., in the x-direction) relative to one another. Similarly, light sources 1110, 1112, 1114 are shown laterally displaced (e.g., in the x-direction) relative to one another.

[0117]

[0235] A wide variety of different variations in the aforementioned system are possible. For example, the location of the light source 1110 relative to the waveguide(s) and the optical system 1130 may be different. FIG. 17, for example, is a side view of a system 1700 having the light source 1110 at a different location relative to the waveguide 1720 and the optical system 1130 than shown in FIGS. 11-16B. Additionally, FIG. 17 shows a design in which the waveguide 1720 is split into a first portion 1720a and a second portion 1720b. The waveguide 1720 may further include a reflector 1730 configured to couple light guided from the first portion 1720a into the optical system 1130 towards the SLM 1140 within the first portion 1720a proximal to the light source 1110. Additionally or alternatively, the system 1700 may include a diffractive outcoupling optical element for outcoupling light in the first portion 1720a of the waveguide 1720 into the optical system 1130 towards the SLM 1140. The reflector 1730 may be opaque and may include an isolator to reduce crosstalk between the first portion 1720a and the second portion 1720b. The waveguide 1720 has a first side 1721 and a second side 1723 opposite the first side 1721, and the optical system 1130 and the SLM 1140 are disposed on the first side 1721 such that light from the SLM 1140 is directed towards the first side 1721. In this example, the light source 1110 may be disposed on a first side 1721 of the waveguide 1720 such that light from the light source 1110 is incident on the first side 1721 before passing through the optics 1130 to the SLM 1140. The system 1700 may further include an incoupling optical element 1710 disposed on or in the first portion 1720a. The incoupling optical element 1710 may be configured to receive light from the light source 1110 and couple the light into the first portion 1720a. The incoupling optical element 1710 may include a diffractive optical element or a reflector configured to direct light incident thereon into the first portion 1720a at an angle induced therein by TIR.

[0118]

[0236] The reflector 1730 may be configured to direct light guided into the first portion 1720a from the first portion 1720a towards the optics 1130 and the SLM 1140. (As discussed above, in some implementations, a diffractive optical element may be used in addition or as an alternative to direct light in the first portion 1720a from the first portion 1720a towards the optics 1130 and the SLM 1140.) Thus, the reflector 1730 may be a mirror, a reflective grating, one or more coatings that reflect light of the waveguide 1720 towards the SLM 1140. Light emitted from the first portion 1720a by the reflector 1730 passes through the optics 1130 to enter the SLM 1140 and passes through the optics 1130 again to enter the second portion 1720b. As explained above, light reflected from the SLM 1140 that is transmitted through the optical system 1130 may be incident on the in-coupling optics 1160, which may direct the light to be guided within the second portion 1720b. The light guided within the second portion 1720b may be out-coupled therefrom by the out-coupling optics 1180 (not shown) and directed to the eye 210.

[0119]

[0237] As discussed above, the reflector 1730 may be an isolator that reduces crosstalk between the first portion 1720a and the second portion 1720b. The reflector 1730 may include an opaque and / or reflective surface. The reflector 1730 may be disposed within the waveguide 1720 and, in some cases, may define sides of the first portion 1720a and the second portion 1720b.

[0120]

[0238] Instead of having a first portion 1720a and a second portion 1720b of the waveguide 1720, separate waveguides may be used. FIG. 18 is a side view of a system 1800 including a first waveguide 1822 for receiving light from the light source 1110 and directing the light guided therein to the optical system 1130 and towards the SLM 1140. The system 1800 additionally includes a second waveguide 1820 that receives light from the SLM 1140 after the light passes through the optical system 1130 again. The first waveguide 1822 includes an in-coupling optical element 1730a and an out-coupling optical element 1730b, respectively. These in-coupling optical element 1730a and out-coupling optical element 1730b may include reflective surfaces oriented to in-couple and out-couple light into and out of the waveguide 1822. The in-coupling optical element 1730a may, for example, be disposed to receive light from the light source 1110 and may include a reflective surface oriented (e.g., tilted) to direct the light into the waveguide 1822 at an angle such that it is guided therein by TIR. The out-coupling optical element 1730b may, for example, include a reflective surface oriented (e.g., tilted) to direct the light guided in the waveguide 1822 at an angle such that it is emitted from the waveguide 1822. The out-coupling optical element 1730b may be positioned such that light directed from the waveguide 1822 is directed into the optical system 1130, reflected off the SLM 1140, passed back through the optical system 1130, and incident on the in-coupling optical element 1730c of the second waveguide 1820.

[0121]

[0239] The internal coupling optical element 1730c in the second waveguide 1820 may include a reflective surface that may be positioned and oriented (e.g., tilted) to receive light from the SLM 1140 and direct the light incident thereon to be guided by TIR in the second waveguide 1820. FIG. 18 shows the optical system 1130 and the light source 1110 disposed on the same side of the waveguides 1820, 1822. The system 1800 may further include an isolator to reduce crosstalk between the waveguide 1822 and the waveguide 1820. The isolator may include an opaque and / or reflective surface. The isolator may be disposed in or on at least one of the waveguides 1820, 1822.

[0122]

[0240] Various designs, such as those discussed above, can include additional features or components. FIG. 19, for example, shows a side view of a system 1900 including variable focus optics (or adaptive optics) 1910, 1920. The variable focus optics 1910, 1920 can include optical elements configured to be altered to provide variable refractive power. The variable focus optics 1910, 1920 can include multiple states, such as a first state and a second state, where in the first state, the variable focus optics 1910, 1920 have a different refractive power than when in the second state. For example, the variable focus optics 1910, 1920 can have a negative refractive power in the first state and a zero refractive power in the second state. In some implementations, the variable focus optics 1910, 1920 have a positive refractive power in the first state and a zero refractive power in the second state. In some implementations, the variable-focus optic 1910, 1920 has a first negative or positive refractive power in a first state and a second different negative or positive refractive power in a second state. Some adaptive optics or variable-focus optics 1910, 1920 can have more than two states, possibly providing a continuous distribution of refractive powers.

[0123]

[0241] The variable focus optics 1910, 1920 may include lenses (e.g., variable lenses) and may be transmissive. Transmissive or transparent adaptive or variable focus optics 1910, 1920 are shown in FIG. 7. The variable focus optics 1910, 1920 may include liquid lenses (e.g., movable membranes and / or electrowetting). The variable focus lenses may also include liquid crystal lenses, such as switchable liquid crystal lenses, such as switchable liquid crystal polarizing lenses, which may include diffractive lenses. Alverez lenses may also be used. Other types of variable focus optics 1910, 1920 may be employed in some cases. Examples of variable focus optics may be found in U.S. Patent Application No. 62 / 518,539, entitled "AUGMENTED REALITY DISPLAY HAVING MULTI-ELEMENT ADAPTIVE LENS FOR CHANGING DEPTH PLANES," filed June 12, 2017, which is incorporated herein by reference in its entirety. The variable focus optics 1910, 1920 can have electrical inputs that receive electrical signals that control the amount of refractive power exhibited by the variable focus optics 1910, 1920. The variable focus optics 1910, 1920 can have positive and / or negative refractive power. In addition to variable focus elements (e.g., polarization switches, geometric phase (GP) lenses, fluid lenses, etc.), the variable focus elements 1910, 1920 can include fixed lenses (e.g., diffractive lenses, refractive lenses, etc.) to generate a desired depth plane in the light field.

[0124]

[0242] The first variable focus optical element 1910 may be disposed between the stack 1905 and the eye 210. The stack 1905 may include different waveguides for different colors, as discussed above. The first variable optical element 1910 may be configured to introduce different amounts of refractive power, negative and / or positive refractive power. The variable refractive power may be used to vary the divergence and / or collimation of the light outcoupled from the stack 1905 to vary the depth at which a virtual object projected by the system 1900 into the eye 210 appears to be located. Thus, a four-dimensional (4D) light field may be created.

[0125]

[0243] The second variable focus optical element 1920 is on the opposite side of the stack 1905 from the first variable focus optical element 1920. The second variable focus optical element 1920 can thus compensate for the effect of the first optical element 1910 on light received from the world 510 in front of the system 1900 and the eye 210. Thus, the view of the world can effectively be unaltered or altered as desired.

[0126]

[0244] The system 1900 may further include a static or variable prescription or corrective lens 1930. Such a lens 1930 may provide refractive correction for the eye 210. Additionally, the prescription lens 1930, if a variable lens, may provide different refractive corrections for multiple users. Variable focus lenses are discussed above. The eye 210 may have, for example, myopia, hyperopia, and / or astigmatism. The lens 1930 may have a prescription (e.g., refractive power) to reduce refractive errors of the eye 210. The lens 1930 may be spherical and / or cylindrical, and may be positive or negative. The lens 1930 may be disposed between the stack 1905 and the eye 210 such that light from both the world 510 and the stack 1905 receives the correction provided by the lens 1930. In some implementations, the lens 1930 may be disposed between the eye 210 and the first variable focus optical element 1910. Other positions of the lens 1930 are possible. In some embodiments, the prescription lenses may be variable, allowing multiple user prescriptions to be implemented.

[0127]

[0245] In some designs, the system 1900 may include an adjustable dimmer 1940. In some implementations, the adjustable dimmer 1940 may be disposed on a side of the stack of waveguides 1900 opposite the eye 210 (e.g., the world side). Thus, the adjustable dimmer 1940 may be disposed between the stack of waveguides 1900 and the world 510. The adjustable dimmer 1940 may include an optical element that provides variable attenuation of light transmitted therethrough. The adjustable dimmer 1940 may include an electrical input for controlling the level of attenuation. In some cases, the adjustable dimmer 1940 is configured to increase the attenuation when the eye 210 is exposed to bright light, such as when the user goes outdoors. Thus, the system 1900 may include a light sensor that senses the brightness of the ambient light and control electronics for driving the adjustable dimmer 1940 to vary the attenuation based on the light level sensed by the light sensor.

[0128]

[0246] Different types of adjustable dimmers 1940 can be employed. Such adjustable dimmers 1940 can include variable liquid crystal switches with polarizers, electrochromic materials, photochromic materials, and the like. The adjustable dimmers 1940 may be configured to adjust the amount of light incident and / or transmitted from the world 510 to the stack 1905. The adjustable dimmers 1940 can be used in some cases to reduce the amount of light from the surroundings passing through the waveguide stack 1900 to the eye 210, which may otherwise provide glare and reduce the user's ability to perceive virtual objects / images projected from the stack 1905 into the eye 210. Such adjustable dimmers 1940 can reduce the incidence of bright ambient light blurring the image projected into the eye 210. Thus, the contrast of the virtual object / image presented to the eye 210 can be increased by the adjustable dimmers 1940. In contrast, when the ambient light is low, the adjustable dimmer 1940 may be adjusted to reduce attenuation so that the eye 210 can more easily see objects in the world 510 in front of the user. The dimming or attenuation may be system-wide or localized to one or more portions of the system. For example, multiple localized portions may be dimmed or set to attenuate light from the world 510 in front of the user 210. These localized portions may be separated from each other by portions without such dimming or increased attenuation. In some cases, only one portion is dimmed or made to provide increased attenuation relative to other portions of the eyepiece. Other components may be added in different designs. Also, the arrangement of the components may be different. Similarly, one or more components may be excluded from the system.

[0129]

[0247] An example of another configuration is shown in FIG. 20A. FIG. 20A shows a side view of a system 2000 including laterally displaced incoupling optical elements 1360, 1362, 1364 on different waveguides and a color filter array 2030 including laterally displaced color filters 2040, 2042, 2044 aligned with the respective incoupling optical elements 1360, 1362, 1364. The color filter array 2030 may be disposed on the side of the stack 2005 in proximity to the eye 210 and the optics 1130. The color filter array 2030 may be between the stack 2005 and the optics 1130. The color filter array 2030 may be disposed in or on a cover glass 2050 located between the stack 2005 and the optics 1130. The color filter array 2030 can include one or more different color filters 2040, 2042, 2044, such as red, green, and blue color filters, disposed laterally relative to one another. The system 2000 includes light sources 1110, 1112, 1114 laterally displaced relative to one another. These light sources 1110, 1112, 1114 can include light sources of different colors, such as red, green, and blue light sources. The color filters 2040, 2042, 2044 can be transmissive or transparent filters. In some implementations, the color filters 2040, 2042, 2044 include absorptive filters, but the color filters 2040, 2042, 2044 can also include reflective filters. The color filters 2040, 2042, 2044 in the color filter array 2030 can be separated and / or surrounded by masks, such as opaque masks, that reduce the propagation of stray light. The filters in the color filter array 2030 may be used to reduce or eliminate undesirable reflections in the system, such as from the waveguides and / or internal coupling optical elements 1360, 1362, 1364, from re-entering the waveguides used for the different colors through the internal coupling optical elements 1360, 1362, 1364 for different colors.Examples of color filter arrays can be found in U.S. Patent Application No. 15 / 683,412, entitled "PROJECTOR ARCHITECTURE INCORPORATING ARTIFACT MITIGATION," filed August 22, 2017, which is incorporated herein by reference in its entirety, and U.S. Patent Application No. 62 / 592,607, entitled "PROJECTOR ARCHITECTURE INCORPORATING ARTIFACT MITIGATION," filed November 30, 2017, which is incorporated herein by reference in its entirety. The mask may be a black mask and may include an absorbing material to reduce stray light propagation and reflection. The light sources 1110, 1112, 1114 may be arranged to internally couple light to corresponding color filters 2040, 2042, 2044 in the color filter array 2030 relative to the optical system 1130 and the SLM 1140. For example, the color filter array 2030 may include first, second, and third (e.g., red, green, and blue) color filters 2040, 2042, 2044 arranged to receive light from the first, second, and third light sources 1110, 1112, 1114, respectively. The first, second, and third (e.g., red, green, and blue) color filters 2040, 2042, 2044 may be aligned (e.g., in the x and z directions) with the respective incoupling optical elements 1360, 1362, 1364. Thus, light from the first light source 1110 is directed through the first color filter 2040 to the first incoupling optical element 1360, light from the second light source 1112 is directed through the second color filter 2042 to the second incoupling optical element 1362, and light from the third light source 1114 is directed through the third color filter 2044 to the third incoupling optical element 1364. In some implementations, the incoupling optical elements 1360, 1362, 1364 may be color specific. For example, the first and second incoupling optical elements 1360, 1362 may be configured to couple light of respective first and second colors into the first and second waveguides, respectively.Similarly, the first, second, and third incoupling optical elements 1360, 1362, 1364 may be configured to couple light of the respective first, second, and third colors into the first, second, and third waveguides, respectively. The first incoupling optical element 1360 may be configured to couple more of the first color of light into the first waveguide than the second color (or third color). The second incoupling optical element 1362 may be configured to couple more of the second color of light into the second waveguide than the first color (or third color). The third incoupling optical element 1364 may be configured to couple more of the third color of light into the second waveguide than the first color or the second color. In other configurations, the incoupling optical elements 1360, 1362, 1364 may be broadband. For example, the first incoupling optical element 1360 may be configured to couple light of the first, second, and third colors into the first waveguide. The second in-coupling optical element 1362 may be configured to couple the first, second and third color light into the second waveguide. The third in-coupling optical element 1364 may be configured to couple the first, second and third color light into the third waveguide. However, the multiple color filters 2040, 2042, 2044 may be color-specific, selectively transmitting light of a particular color. For example, the first color filter 2040 may transmit more of the first color than the second color (and the third color). The second color filter 2042 may transmit more of the second color than the first color (and the third color). The third color filter 2044 may transmit more of the third color than the first color and the second color. Similarly, the first, second and third color filters 2040, 2042, 2044 may be color filters selectively transmitting the first, second and third colors, respectively. Thus, the first, second, and third color filters 2040, 2042, 2044 may be bandpass filters that selectively pass the first, second, and third colors, respectively. In some implementations, the first, second, and third light sources 1110, 1112, 1114 may selectively emit the first, second, and third colors, respectively. For example, the first light source 1110 may emit more of the first color than the second color (and the third color).The second light source 2042 may emit more of the second color than the first color (and the third color). The third light source 2044 may transmit more of the third color than the first and second colors. The color filters 2040, 2042, 2044 may reduce the amount of stray light inadvertently directed to a particular internal coupling optical element. In other implementations, one or more of the light sources 1110, 1112, 1114 are broadband light sources. For example, the first light source 1110 may emit a first and second (and possibly a third) color. The second light source 1112 may also emit a first and second (and possibly a third) color. The third light source 1114 may also emit a first and second (and possibly a third) color. Although three filters are shown in Figures 20A-20G, more or fewer filters may be included. For example, in some implementations, two filters (rather than three) may be used. Thus, two colors corresponding to the two color filters may be selectively transmitted by the filters. In some such implementations, two corresponding in-coupling optical elements may be used and aligned with the two filters. In some implementations, the two in-coupling optical elements each selectively couple the two colors into two respective waveguides. In some implementations, two light sources may be used instead of three. Other variations and other numbers of components may be used. Also, the color filters 2040, 2042, 2044 may or may not be integrated together into a single array.

[0130]

[0248] As discussed above, the components and their positions and arrangements may vary. For example, while FIG. 20A shows the analyzer 1150 disposed between the optical system 1130 and the stack 1905, the analyzer 1150 may be positioned in a different location. FIG. 20B shows the analyzer 1150 positioned between the optical system 1130 and the SLM 1140. In some designs, the analyzer (e.g., polarizer) 1150 may be directly attached to the SLM 1140. For example, the analyzer 1150 may be bonded or mechanically coupled to the SLM 1140. For example, the analyzer 1150 may be glued or fixed to the SLM 1140 (e.g., an SLM window) using an adhesive. Thus, while FIG. 20B shows a gap between the analyzer 1150 and the SLM 1140, in some designs, there is no gap between the analyzer 1150 and the SLM 1140. The analyzer 1150 may be mechanically affixed to the SLM 1140 (e.g., using a mechanical fastener), in which case it may or may not include a gap between the analyzer 1150 and the SLM 1140. Birefringence from the optical system 1130 may be cleaned up by positioning a polarizer directly on the SLM 1140 as described above. In some implementations, an analyzer 1150 disposed between the optical system 1130 and the incoupling optics 1360, 1362, 1364 may also be included to clean up the polarization of light outward from the optical system 1130 (e.g., as shown by the dashed lines in FIG. 20B). Additionally, a retarder (not shown), such as a quarter wave plate, may be included proximate the SLM 1140, e.g., between the optical system 1130 and the SLM 1140. As used herein, a quarter wave plate can refer to a quarter wave retarder, regardless of whether the quarter wave retarder includes a plate, film, or other structure for providing a quarter wave retardation. In FIG. 20B, for example, a retarder (e.g., a quarter wave plate) can be disposed between the analyzer 1150 and the SLM 1140. The retarder (e.g., a quarter wave plate) can be used for skew ray management. For example, the retarder (e.g., a quarter wave plate) can compensate for variations caused by differences in wavelength and angle of incidence to the SLM 1140, for example.As discussed above, a compensator may be included to provide a more consistent polarization rotation (e.g., 90°) of the SLM 1140 for different angles of incidence and different wavelengths. The compensator may be used to increase the contrast of the display by providing a more consistent orthogonal rotation. The compensator may be attached or affixed to the SLM 1140 as described above. For example, glue, cement or other adhesives may be used. The compensator may also be attached to the SLM 1140 using mechanical fasteners. A gap may or may not be included between the compensator or the SLM 1140. Other light conditioning optics may additionally or alternatively be included and may be affixed to the SLM 1140 as described above with respect to the analyzer 1150 and / or the compensator.

[0131]

[0249] In some embodiments, a large angular spread (e.g., -70 degrees) can be used. The angular spread can refer to, for example, the angle of light entering the optical system 1130 from the light sources 1110, 1112, 1114 and / or the angle of light leaving the optical system 1130 and entering the incoupling optics 1360, 1362, 1364. In these embodiments, a thinner SLM 1140 can be used. For example, if the SLM 1140 is a liquid crystal (LC) SLM (e.g., a liquid crystal on silicon (LCoS) SLM), the LC layer can be made thinner to accommodate the large angular spread.

[0132]

[0250] The double pass phase difference through the polarizer and analyzer 1150 may need to be a half wave. The polarizer may be between the optical system 1130 and the analyzer 1150. The double pass phase difference may be a function of the ratio of the refractive index of the LCoS SLM 1140 to the thickness of the LCoS SLM 1140. For a given refractive index of the LCoS SLM 1140 and a given thickness of the LCoS SLM 1140, entering and exiting the LCoS SLM 1140 at a large angle will result in a longer path length for the light than entering and exiting the LCoS SLM 1140 at a small angle. The path length is related to the thickness of the LCoS SLM 1140. In one example, the LCoS SLM may have a first refractive index and a first thickness. For small angles, the double pass phase difference of an LCoS SLM with a first refractive index and a first thickness may be a half wave. For larger angles, the double pass phase difference of an LCoS SLM having a first refractive index and a first thickness may not be a half wave (e.g., may be greater than a half wave). The thickness of the LCoS SLM may change from a first thickness to a second thickness, the second thickness being less than the first thickness. For smaller angles, the double pass phase difference of an LCoS SLM having a first refractive index and a second thickness may not be a half wave (e.g., may be less than a half wave). For larger angles, the double pass phase difference of an LCoS SLM having a first refractive index and a second thickness may be a half wave.

[0133]

[0251] Also, while Figures 20A and 20B show the use of a deflection-based SLM 1140, other types of SLMs may be utilized. Figure 20C shows the use of a deflection-based SLM 1140, such as, for example, a movable micromirror-based SLM. As discussed above, such an SLM 1140 may include digital light processing (DLP™) and digital micromirror device (DMD) technology. As discussed above, the deflection-based SLM 1140 may couple light from one of the light sources 1110, 1112, 1114 into a respective incoupling optical element 1360, 1362, 1364 depending on the state of the pixels of the SLM 1140. In one state, the light from the light sources 1110, 1112, 1114 is directed to the respective incoupling optical element 1360, 1362, 1364, as shown in Figure 20D. In another state, the light from the light sources 1110, 1112, 1114 is directed away from the incoupling optical elements 1360, 1362, 1364, as shown in FIG. 20E. In some implementations, while in the off state, a black absorbing mask between the color filters 2040, 2042, 2044 in the color filter array 2030 can act as a light dump. As explained above, the color filters 2040, 2042, 2044 may be surrounded and / or separated by a mask, such as an absorbing mask (e.g., a black mask). The mask may include an absorbing material such that more incident light is absorbed than is reflected therefrom. The mask may be opaque.

[0134]

[0252] Other variations are possible. Although the light sources are shown as emitters 1110, 1112, 1114 (e.g., LEDs, laser diodes) coupled to a coupling optic 1105, such as a non-imaging optical coupling element (e.g., a compound parabolic concentrator (CPC) or cone), other configurations are possible. For example, the coupling optic 1105 (e.g., a CPC) may be tilted relative to the stack of waveguides. In some cases, the projector (i.e., the optic 1130 and the SLM 1140) may be tilted relative to the eyepiece (e.g., the stack of waveguides). In some implementations, the lens optic 1130 is tilted relative to the SLM 1140 to reduce distortions such as keystone distortion. To reduce such distortions, a Scheimpflug configuration can be employed. Components can be tilted as needed (e.g., the optic 1130 and / or the spatial light modulator 1140), for example, to fit more conformally around the head and / or face. As explained above, the light emitter(s) and / or the coupling optics 1105 may be tilted. In some configurations, the assembly including the waveguides may be tilted with the side closer to the side (e.g., temporal) of the eye 210 closer to the eye 210 to increase the perceived field of view of the entire binocular system (at the expense of eye overlap).

[0135]

[0253] As discussed above, the components and their positions and arrangements may vary. For example, FIG. 20F is a side view of a system 2000F including a cover glass 2050 disposed between the stack 2005 and the optical system 1130. In some designs, the light sources 1110, 1112, 1114 may be disposed on the world side of the cover glass 2050 and configured to propagate light through the cover glass 2050 to the optical system 1130 and the SLM 1140. As shown, the cover glass 2050 may extend laterally (e.g., parallel to the x-axis) beyond the stack 2005 such that light emitted by the light sources 1110, 1112, 1114 enters the optical system 1130 without passing through a waveguide in the stack 2005. Although the system 2000F depicts a deflection-based SLM 1140, a similar configuration of light sources may also be used with a non-deflection-based SLM or with any other configuration or feature disclosed herein.

[0136]

[0254] FIG. 20G is a side view of system 2000G including a cover glass 2060 disposed on the world side of stack 2005 (i.e., opposite the side of stack 2005 proximate optics 1130). In some designs, light sources 1110, 1112, 1114 may be disposed on the world side of cover glass 2050 and configured to propagate light through cover glass 2050 to optics 1130 and SLM 1140. As shown, cover glass 2060 may extend laterally (e.g., parallel to the x-axis) beyond stack 2005 such that light emitted by light sources 1110, 1112, 1114 enters optics 1130 without passing through a waveguide in stack 2005. Although system 2000G depicts a deflection-based SLM 1140, a similar configuration of light sources may be used with non-deflection-based SLMs or with any other configurations or features disclosed herein.

[0137]

[0255] Additionally, configurations that facilitate light recycling may be employed, as discussed above. FIG. 21 is a partial side view of a system 2100 with a configuration that provides light recycling of light from, for example, a light source 1110. The light source 1110 may be disposed relative to a polarizer 1115 configured to recycle light having an undesired polarization. The polarizer 1115 may, for example, include a wire grid polarizer that transmits light of a first polarization and retroreflects light of a second, opposite polarization. Thus, light 2110 may be emitted from the light source 1110 and impinge on the polarizer 1115. The polarizer 1115 may transmit light of a first polarization that is configured for use by a projector (not shown). For example, an SLM may operate appropriately with light of this first polarization. Light of the second polarization 2120 may be reflected back towards the light source 1110 and recycled. The polarization of the light 2120 can be changed due to polarization rotation after reflecting off a portion (e.g., a side wall) of a combining optic (not shown), such as a non-imaging optic like a compound parabolic concentrator (CPC) at various angles. Some light with the appropriate polarization (e.g., polarization orientation) can be generated that can pass through the polarizer 1115. Multiple reflections can change the polarization of the light and emit light with the desired polarization. This recycled light 2130 is then emitted back toward the polarizer 1115. Such a configuration can improve efficiency, e.g., energy efficiency, as more of the desired polarization is generated. Also, in addition or alternatively, a retarder can be used to change the reflected polarization state and regenerate the light.

[0138]

[0256] FIG. 22 shows another configuration including light sources 1110, 1112, 1114 and corresponding collection optics 2210, 2212, 2214. The collection optics 2210, 2212, 2214 can include lenses or other optics for collecting light from the light sources 1110, 1112, 1114. The light sources 1110, 1112, 1114 can be laser diodes or other emitters that emit light over a wide range of angles. The collection optics 2210, 2212, 2214 can be used to collect most of that light. The light sources 1110, 1112, 1114 can emit light asymmetrically. For example, light can be emitted at a wider range of angles in one direction (e.g., x or z direction) than in an orthogonal direction (e.g., z or x direction). Thus, the collection optics 2210, 2212, 2214 can be asymmetric. For example, the collection optics 2210, 2212, 2214 can have different refractive powers in different possible orthogonal directions. The collection optics 2210, 2212, 2214 can include lenses, such as, for example, anamorphic lenses. The collection optics 2210, 2212, 2214 may also include non-imaging optics in some cases. Apertures 2220, 2222, 2224 may also be included. For example, in the case of a laser light source 1110, 1112, 1114, such as a laser diode, a diffuser 2230 may also be included proximate the apertures 2220, 2222, 2224. If the diffuser is proximate the apertures 2220, 2222, 2224, the apertures may appear to be laterally displaced light source positions. The apertures 2220, 2222, 2224 can be matched with incoupling optical elements on the waveguide(s) via the optics and SLM, as discussed above. For example, each aperture 2220, 2222, 2224 may be matched with a respective incoupling optical element. Similarly, in a particular implementation such as that shown in FIG. 16A, each aperture 2220, 2222, 2224 may be matched with a respective group of (e.g., color-selective) incoupling optical elements.

[0139]

[0257] A wide range of system variations and configurations are possible. For example, although linearly polarized light has been described as propagating through the optics 1130 to the SLM 1140 and back through the optics to the waveguide stack, in some designs circular polarization may be used instead. For example, circularly polarized light may be directed to the optics 1130. A retarder, such as a quarter wave plate, may be disposed so that this light passes through the retarder before entering the SLM. The retarder (e.g., a quarter wave plate) may be disposed between the optics 1130 and the SLM 1140. In some cases, as described above, the retarder (e.g., a quarter wave plate) may be affixed to the SLM 1140, for example using an adhesive or mechanical fasteners. The retarder (e.g., a quarter wave plate) may convert linearly polarized light to circularly polarized light after reflection from the SLM 1140. Thus, in some implementations, the circularly polarized light may pass through the optics 1130 again towards the stack. For example, another retarder (e.g., a quarter wave plate) proximal to the analyzer 1150 can convert the circularly polarized light to linearly polarized light that may or may not pass through the analyzer depending on the linear polarization (e.g., orientation). The pixels of the SLM 1140 can have states that can be changed to rotate or not rotate the polarization. Still other configurations are possible.

[0140]

[0258] 23A is a side view of an augmented reality display system 2300 including a light source 2305, a polarization rotator 2307, an optical system (e.g., a lens) 2320 having refractive power, a polarizer 2312, 2335 such as a linear polarizer (e.g., a horizontal polarizer or a vertical polarizer), a retarder 2315, 2330, 2340 such as a quarter wave retarder (e.g., a quarter wave plate), and at least one waveguide 2348 for outputting image information to a user. Such a configuration can be used to illuminate a reflective spatial light modulator (not shown) such that light emitted from the light source 2305 is reflected from the spatial light modulator and coupled into at least one waveguide 2348 for directing to the user's eye. The configuration and arrangement of these elements, particularly the polarizer and retarder, can reduce or eliminate reflections from optical surfaces in the system, such as surfaces from the optical system 2320, which could otherwise cause ghost images to be visible to the user. For example, polarization selective and / or retarder optical elements (e.g., polarizers 2312, 2335 and retarders 2315, 2330, 2340) can be arranged and configured to convert linearly polarized light into circularly polarized light that changes from left-handed to right-handed or right-handed to left-handed upon reflection from an optical surface. Similarly, such polarization selective and / or retarder optical elements (e.g., polarizers 2312, 2335 and retarders 2315, 2330, 2340) can be arranged and configured to convert circularly polarized light into linearly polarized light that can be attenuated or filtered out by a polarizer (e.g., a linear polarizer). A circular polarizer that converts linearly polarized light into circularly polarized light and vice versa can be fabricated using such polarization selective and retarder optical elements (e.g., polarizers 2312, 2335 and retarders 2315, 2330, 2340). For example, a circular polarizer may include a linear polarizer and a quarter-wave retarder. A circular polarizer can be used to convert linearly polarized light into circularly polarized light having a first state (e.g., handedness) and filter out circularly polarized light having a second state (e.g., handedness) that is different from the first state.For example, a circular polarizer can be used to convert linearly polarized light with a certain orientation into left-handed circularly polarized light and filter out right-handed circularly polarized light. A circular polarizer can be used to convert linearly polarized light with a certain orientation into right-handed circularly polarized light and filter out left-handed circularly polarized light. Circular polarizers, or other configurations of optical elements that can be used to convert linearly polarized light back into circularly polarized light and that include phase differences that can selectively filter linearly polarized light, can be used to reduce back reflections from optical surfaces, as discussed below in connection with Figures 23A and 23B.

[0141]

[0259] Note that in Figures 23A and 23B, left-handed and right-handed circularly polarized light are indicated by clockwise and counterclockwise arrows, respectively. Additionally, horizontal and vertical linear polarizations are depicted using horizontal arrows and circular dots, respectively.

[0142]

[0260] As discussed above, FIG. 23A illustrates a configuration of an augmented reality display system 2300 in which polarizers 2312, 2335, such as linear polarizers (e.g., horizontal polarizers), and retarders 2315, 2330, 2340, such as quarter-wave retarders (e.g., quarter-wave retarders), are arranged to reduce back reflections from optical surfaces, such as surfaces of an optical system 2320, in the path of light illuminating and reflecting off a spatial light modulator (not shown). The first polarizer 2312 and the first retarder 2315 are disposed between the light source 2305 and the optical system 2320. The first polarizer 2312 is disposed between the light source 2305 and the first retarder 2315. Similarly, the first retarder 2315 is disposed between the first polarizer 2312 and the optical system 2320.

[0143]

[0261] As shown, the light source 2305 emits light, as represented by light ray 2310. In some implementations, the light ray 2310 can pass through a polarization rotator 2307. The rotator 2307 is optional and can be used to rotate the polarization of the light from the light source 2305, such as the light ray 2310. In various implementations, the rotator 2307 can rotate the angle of the polarization (e.g., of the linear polarization). For example, the rotator 2307 can rotate the linear polarization of the light ray 2310 to an orientation aligned with the first polarizer 2312 and transmit it therethrough. In some implementations, the polarization rotation 2307 can include a retarder, such as a half-wave retarder in some cases. The optical axis of the half-wave retarder can be oriented to rotate the polarization of the light from the light source 2305 from vertical to horizontal or vice versa. Alternatively, the polarization rotator 2307 may be configured to rotate the polarization angle of the linearly polarized light emitted from the light source 2305 by a different amount. The polarization rotator 2307 may not be included in the system. For example, in an implementation in which the light source 2305 emits light having the same polarization as the first polarizer 2312, the polarization rotator 2307 may be omitted. As shown, light, e.g., light ray 2310, passes through the polarizer 2312, shown here as a horizontal polarizer. If the light from the light source 2305 is unpolarized, the light transmitted through the horizontal polarizer 2312, shown as light ray 2310, will be linearly polarized (e.g., horizontally polarized) after passing through the polarizer 2312. Although a horizontal linear polarizer is used in this example, it will be understood that the principles taught can be applied using a vertical linear polarizer. Alternatively, linear polarizers with different orientations other than vertical or linear may be used.

[0144]

[0262] The horizontally polarized light beam 2310 travels through a retarder 2315, shown here as a quarter-wave retarder. This retarder 2315 can contain sufficient phase difference to convert linearly polarized light to circularly polarized light. For example, horizontally polarized light may be converted to left-handed circularly polarized light, as indicated by the curved (e.g., clockwise) arrow. In this example, the combination of the polarizer 2312 and the retarder 2315 (e.g., quarter-wave) forms a circular polarizer, referred to herein as a first circular polarizer, that can convert light of a particular linear polarization (e.g., horizontal or vertical polarization) to a particular circular polarization (e.g., left-handed or right-handed, or vice versa). The circular polarizer can also block light of a particular circular polarization (e.g., right-handed or left-handed) depending on the configuration.

[0145]

[0263] In some implementations, the various optical elements have birefringence. In certain such cases, the retarder 2315 can include a sufficient amount of retardation to convert linearly polarized light to circularly polarized light and need not be a quarter wave plate. Retardation more or less than a quarter wave may be included in the retarder 2315, since retardation may be contributed by other optical elements. Similarly, retardation may be distributed among several optical elements. As another example, multiple retarders may be employed to provide the appropriate amount of retardation.

[0146]

[0264] The circularly polarized light beam 2310 (here left-handed circularly polarized) then passes through the optical system 2320. Unwanted reflections can occur at any interface in the system with media having different refractive indices, such as an air-material interface. These reflections can be problematic if allowed to enter the at least one waveguide 2348, as this reflected light can be directed to the user's eye and form a "ghost" image visible to the user's eye. For example, if the display uses the at least one waveguide 2348 to project a first image to the viewer's eye, a second, faint replica image displaced (e.g., laterally displaced) relative to the first image may also be visible to the user. Such "ghost" images formed by reflections from optical surfaces directed to the user's eye can confuse or otherwise degrade the viewing experience. For example, as shown in FIG. 23A, light such as the reflected light beam 2325 can be reflected from a lens in the optical system 2320. This light may be directed towards at least one waveguide 2348 configured to direct the light there to present an image to the user's eye. In this case, however, the circularly polarized light reverses its handedness. For example, upon reflection from a lens, the direction of the circularly polarized light changes (e.g., from left-handed to right-handed). The right-handed reflected light beam 2325 then travels through the retarder 2315 and is converted to linearly polarized light having a different (e.g., orthogonal) linear polarization than that transmitted by the polarizer 2312. In this case, for example, the light reflected from the optical surface of the lens is converted by the retarder 2315 to vertically linearly polarized light that is orthogonal to the polarization transmitted by the horizontal linear polarizer 2312. The horizontal linear polarizer 2312 selectively passes horizontally polarized light and filters out vertically polarized light. Thus, the reflected light rays 2325 are attenuated and / or not transmitted by the horizontal linear polarizer 2312 and prevented from reaching the at least one waveguide 2348, or at least a reduced amount of such reflected light reaches the at least one waveguide 2348 or is coupled therein, for example through an internal coupling optical element (e.g., one or more internal coupling gratings).The results are similar for left-handed circularly polarized light reflected from a different optical surface of optical system 2320 or from other optical surfaces on different optical elements.

[0147]

[0265] As shown, the display system 2300 further includes a second retarder 2330 (e.g., a quarter-wave retarder or a quarter-wave plate) and a second polarizer 2335 (e.g., a linear polarizer) disposed between the optical system 2320 and a spatial light modulator (not shown). The second retarder 2330 and the second linear polarizer 2335 may form a second circular polarizer in certain implementations. The second retarder 2330 is disposed between the optical system 2320 and the second polarizer 2335. Similarly, the second polarizer 2335 is disposed between the second retarder 2330 and the spatial light modulator. Thus, after passing through the optical system 2320, the light beam 2310 can pass through the second retarder 2330 (e.g., a quarter-wave retarder). The second retarder 2330 is configured (e.g., with the optical axis appropriately oriented) such that the light beam 2310 is converted from left-handed circular polarization to horizontal linear polarization. Similarly, the second retarder 2330 converts the circularly polarized light back to the original linear polarization state output by the first polarizer 2312. As discussed below, this second retarder 2330 and second polarizer 2312 can be useful to reduce "ghost" images caused by light reflected from the spatial light modulator passing through an optical surface (e.g., on the powered optics or lens 2320) as the light travels to the at least one light guide 2348.

[0148]

[0266] A third retarder 2340 (e.g., a quarter wave retarder or a quarter wavelength plate) is disposed between the second polarizer 2335 and the spatial light modulator. Thus, the third retarder 2340 is disposed between the second retarder 2330 and the spatial light modulator. Also, in various implementations as shown, the second polarizer 2335 is between the second retarder 2330 and the third retarder 2340. As shown, the light beam 2310 becomes linearly polarized when it passes through the second polarizer 2335, and in some implementations, the second retarder 2330 / second polarizer 2335 may convert the light back to the original linear polarization of the first polarizer 2312 (e.g., horizontally polarized). This linear polarization is incident on the third retarder 2340. The third retarder 2340 is configured to convert the light back into circular polarization, and in some implementations, into the same polarization as that output by the first retarder 2315 (e.g., left-handed circular polarization in this example). In certain implementations, the spatial light modulator is configured to operate on circularly polarized light. In some implementations, the spatial light modulator is a reflective spatial light modulator that reflects the incident circularly polarized light back as circularly polarized light. In some embodiments, the circularly polarized light reflected from the spatial light modulator can have the same handedness as that incident thereon (e.g., left-handed circular polarization), possibly depending on whether the spatial light modulator pixel is in an "on" or "off" state. In some embodiments, the spatial light modulator can reflect circularly polarized light of a different handedness than that incident thereon (e.g., right-handed circular polarization), possibly depending on whether the spatial light modulator pixel is in an "on" or "off" state. However, other types of spatial light modulators may be used.

[0149]

[0267] FIG. 23A shows light reflected from the spatial light modulator and traveling towards the waveguide 2385, shown as ray 2342. The reflected ray 2342 is depicted as left-handed circularly polarized light. The ray 2342 passes through the third retarder 2340, which converts the circularly polarized light to linearly polarized light. In this example, the left-handed circularly polarized light is converted to horizontally polarized light. The linearly polarized light is transmitted through the second polarizer 2335. In this example, the horizontally polarized light is transmitted through the second polarizer 2335. The linearly polarized light enters the second retarder 2330 and is converted to circularly polarized light. In this example, the horizontally polarized light is converted to left-handed polarization and transmitted to the optical system 2320. Again, reflections from optical surfaces, such as surfaces of the optical system 2320 having refractive power, can create ghost images by reflecting back from the spatial light modulator to at least one waveguide 2348 and the user's eye. As explained above, unwanted reflections can occur at any interface with media having different refractive indices, such as an air-material interface. As mentioned above, the inclusion of the second retarder 2330 and polarizer 2335 can attenuate these reflections and reduce the possibility of ghost reflections. FIG. 23A depicts light reflected from an optical surface of the optical system 2320, for example, shown as ray 2346. The action of reflecting from the surface results in a reflected ray 2346 that becomes circularly polarized and switches handedness, in this example from left-handed to right-handed. The switched circular polarization is attenuated by the second circular polarizer formed by the second retarder 2330 and polarizer 2335. As shown in FIG. 23A, for example, the reflected circularly polarized light 2346 enters the second retarder 2330 and is converted by the second retarder to linearly polarized light having a different, e.g., orthogonal, linear polarization from the linear polarization selectively transmitted by the second linear polarizer 2335. In this case, for example, right-handed circularly polarized light reflected from an optical surface of optical system 2320 is converted by retarder 2330 to vertical linearly polarized light that is orthogonal to the polarization selectively transmitted by polarizer 2335. Second polarizer 2335 attenuates or prevents transmission of this linearly polarized light. In this example, light 2346 is vertically polarized and second polarizer 2335 is a horizontal polarizer that selectively passes horizontally polarized light and filters out vertically polarized light.

[0150]

[0268] In contrast, light 2342 passing through the optical system 2320 and entering the first retarder 2315 is circularly polarized and has a different handedness than the light reflected from the optical surfaces of the optical system 2320. This light 2342 directed towards the at least one waveguide 2348 has a polarization (e.g., left-handed polarization) that is converted by the first retarder 2315 to a linear polarization (e.g., horizontal linear polarization) that the first polarizer 2312 selectively transmits. In this way, the light 2342 reaches the at least one waveguide 2348 and can be coupled therein and directed towards the user's eye.

[0151]

[0269] In the example shown in FIG. 23A, a first circular polarizer formed by a first polarizer 2312 and a first retarder 2315, and a second circular polarizer formed by a second retarder 2330 and a second polarizer 2335 are used on both sides of the optical system 2320, one closer to the light source 2305 and one closer to the spatial light modulator, to reduce reflections that may result in "ghost images". An additional retarder 2340 is included between the second circular polarizer (e.g., the second polarizer 2335) and the spatial light modulator to convert the light to circularly polarized light. However, a wide range of variations are possible. For example, there may be only one circular polarizer. Alternatively, additional circular polarizers or other types of polarizing optics may be included.

[0152]

[0270] FIG 23B illustrates a third circular polarizer that can be added to the augmented reality system 2300 as shown in FIG 23A. In particular, FIG 23B illustrates a second circular polarizer including the second polarizer 2335 and second retarder 2330 introduced above, as well as a third retarder 2340, and further illustrates a spatial light modulator 2375. This spatial light modulator (SLM) 2375 can include a liquid crystal spatial light modulator (e.g., liquid crystal on silicon or LCoS). In some implementations, the SLM 2375 can be covered with a cover glass 2370.

[0153]

[0271] 23B also shows a third circular polarizer including a fourth retarder 2345, such as a quarter wave retarder (e.g., a quarter wave plate), and a third polarizer 2355, such as a linear polarizer, disposed between the second circular polarizer including the second polarizer 2335 and the second retarder 2330 and the spatial light modulator 2375. The third polarizer 2355 is between the fourth retarder 2345 and the spatial light modulator 2375. An additional fifth retarder 2360, such as a quarter wave retarder (e.g., a quarter wave plate), and a compensator 2365 are disposed between the third circular polarizer including the fourth retarder 2345 and the third polarizer 2355 and the spatial light module 2375, or more specifically the cover glass 2370 shown in FIG. 23B. The fifth retarder 2360 is between the third polarizer 2355 and the compensator 2365. The compensator 2365 is between the fifth retarder 2360 and the spatial light modulator 2375, or specifically the cover glass 2370.

[0154]

[0272] FIG. 23B illustrates how light from a light source 2305 (shown in FIG. 23A), for example, light ray 2310, may propagate through a second circular polarizer including a retarder 2330 and a second polarizer 2335, as well as a third retarder 2340, to a third circular polarizer including a fourth retarder 2345 and a third polarizer 2355. After passing through the second circular polarizer including the second retarder 2330 and the second polarizer 2335, the light ray 2310 from the light source 2305 enters the third circular polarizer, specifically the fourth retarder 2345. The fourth retarder 2345 may convert the circular polarizer light of the light ray 2310 into linearly polarized light. In the example shown in FIG. 23B, the light beam 2310 is circularly polarized (e.g., left-handed circularly polarized) and converted to linearly polarized (e.g., horizontally polarized) by the fourth retarder 2345. This linearly polarized light travels through the third polarizer 2355, which in FIG. 23B includes a horizontal polarizer that selectively transmits horizontally polarized light. This linearly polarized light propagates through the fifth retarder 2360, which may include a quarter-wave retarder that converts the linearly polarized light to circularly polarized light. In the example shown in FIG. 23B, the horizontally polarized light 2310 incident on the fifth retarder 2360 is converted to left-handed circularly polarized light. This circularly polarized light enters and passes through the compensator 2365. The compensator 2365 may include a polarizing element that adjusts the polarization to a desired polarization. The compensator 2365 may be used to offset the birefringence of various optical elements in the system. For example, the light may be slightly elliptically polarized due to the retardation contribution of one or more optical elements. In various implementations, the light output from the compensator 2365 is circularly polarized. In the example shown in FIG. 23B, the light output from the compensator 2365 is left-handed circularly polarized. In various implementations, the compensator 2365 can be used to cancel out residual retardation in an SLM, which may include, for example, a liquid crystal (e.g., LCoS) SLM cell. The compensator can introduce an in-plane retardation and / or an out-of-plane retardation. In some implementations, the compensator 2365 can include a combination of optical retarders that, when combined, generate a retardation that can potentially cancel out residual retardation from an SLM (e.g., an LCoS panel).

[0155]

[0273] In FIG. 23B, the light is incident on the cover glass 2370 and the SLM 2375 after passing through the compensator 2365. This light incident on the cover glass 2370 and the SLM 2375 is depicted as left-handed circularly polarized light. Depending on the type and state of the spatial modulator, the SLM 2375 may reflect circularly polarized light of the same handedness. For example, when a pixel of the SLM 2375 is in the "on" state (which may be an undriven state in some implementations), the SLM 2375 may introduce a phase difference of 1 / 4 wave each time it passes through the SLM 2375. Thus, upon reflection, the incident circularly polarized light may remain circularly polarized upon reflection. In various configurations, the handedness may also remain the same. For example, as shown in FIG. 23B, the incident left-handed circularly polarized light may remain left-handed circularly polarized upon reflection. This circularly polarized light reflected from the SLM 2375, represented by ray 2342, may pass through the cover glass 2370 and the compensator 2365 and enter the fifth retarder 2360, which converts the circularly polarized light to linearly polarized light. In the example shown in FIG. 23B, the circularly polarized light entering the fifth retarder 2360 is left-handed, and the fifth retarder 2360 converts the circularly polarized light to horizontally polarized light. The third polarizer 2355 may be configured to selectively transmit the polarization of the light output by the fifth retarder 2360. Thus, in the example shown in FIG. 23B, where the light output from the fifth retarder 2360 is horizontally polarized, the third polarizer 2355 selectively transmits horizontally polarized light. This linearly polarized light transmitted by the polarizer 2355 enters the fourth retarder 2345 and is converted to circularly polarized light. In the example shown in FIG. 23B, the circularly polarized light is left-handed. This light can pass through a second circular polarizer including a second retarder 2330 and a second polarizer 2335, the optical system 2320, and a first circular polarizer including a first polarizer 2312 and a first retarder 2315, as discussed above in connection with FIG. 23A, onto at least one waveguide 2348 and into the user's eye.

[0156]

[0274] However, light reflected from the optical surface may be attenuated by the third circular polarizer, thereby reducing the possibility of such reflection reaching at least one waveguide 2348 and being directed to the user's eye to produce a ghost image. For illustration, FIG. 23B shows an exemplary light ray 2343 reflected from an optical surface of the third retarder 2340, e.g., from an interface between air and the third retarder 2340. As discussed above, reflection may occur at any interface between media with different refractive indices, such as an air-material interface or an interface between different dielectric layers. However, the circularly polarized light reverses its handedness upon reflection. For example, upon reflection from the surface of the third retarder 2340, the direction of the circularly polarized light changes (e.g., from left-handed to right-handed). The right-handed reflected light ray 2343 then travels through the fourth retarder 2345 and is converted to linearly polarized light having a different, e.g., orthogonal, linear polarization from the linear polarization selectively transmitted by the third polarizer 2355. In this case, for example, light reflected from an optical surface of the third retarder 2340 is converted by the fourth retarder 2345 to vertical linear polarization orthogonal to the polarization selectively transmitted by the third polarizer 2355. The third polarizer 2355 selectively passes horizontally polarized light and filters out vertically polarized light. Thus, the reflected light beam 2343 is attenuated and / or not transmitted by the third polarizer 2355 and is prevented from reaching the at least one waveguide 2348 (e.g., by reflecting off another surface), or at least a reduced amount of such reflected light reaches or is coupled into the at least one waveguide 2348.

[0157]

[0275] The results may be similar for circularly polarized light reflected from different optical surfaces. FIG. 23B, for example, shows the reflection of incident light ray 2310 from the optical surface of the fourth retarder 2345. The reflection 2350 from the fourth retarder 2345 switches the handedness of the polarization. For example, the incident light ray 2310 depicted as left-handed circularly polarized light is converted upon reflection to light ray 2350 depicted as having right-handed circular polarization. The reflected light ray 2350 passes through the third retarder 2340 and is converted to vertically polarized light. This vertically polarized light is selectively attenuated or filtered out by the second polarizer 2335.

[0158]

[0276] As explained above, a pixel of the SLM2375 may be in, for example, an "on" state (although in some implementations it is an undriven state) in which light incident on that pixel of the SLM2375 is reflected therefrom and coupled to at least one waveguide 2348 and directed to the user's eye. However, a pixel of the SLM2375 may be in an "off" state (which may be a driven state in some implementations) in which light incident on the pixel of the SLM2375 is not coupled to at least one waveguide 2348 and is not coupled to the user's eye. In this "off" state, for example, various implementations of the SLM2375 may not introduce a phase difference upon reflection therefrom. Thus, in the example shown in FIG. 23B, circularly polarized light incident on the SLM2375 may remain circularly polarized upon reflection from the SLM2375. However, the handedness of this circularly polarized light may change upon reflection from the SLM2375. For example, the light ray 2310 shown in FIG. 23B, which is left-handed circularly polarized light incident on the SLM 2375, may be converted to right-handed circularly polarized light upon reflection from the SLM 2375. However, this reflected light may be selectively attenuated by the third polarizer 2355. For example, the right-handed circularly polarized light reflected from the SLM 2375 may pass through the cover glass 2370, the compensator 2365, and the fifth retarder 2360. The fifth retarder 2360 may convert the right-handed circularly polarized light to vertically polarized light, which is selectively attenuated by the third polarizer 2355, which may include a horizontal polarizer. Thus, in various implementations, the fifth retarder 2360 may convert light reflected from the pixels of the SLM when the pixels of the SLM 2375 are in the “off” state into linearly polarized light that is orthogonal to the linearly polarized light selectively transmitted by the third polarizer 2355. This third polarizer 2355 can therefore selectively attenuate this linearly polarized light, thereby reducing or blocking light from that pixel of the SLM 2375 from reaching at least one waveguide 2348 and being directed into the eye.

[0159]

[0277] Variations in the configuration are possible, such as variations in the polarizing optics. For example, more or fewer circular polarizers may be included.

[0160]

[0278] In various implementations, the third circular polarizer, including the fourth retarder 2345 and the third polarizer 2355, is excluded, for example, as shown in FIG. 23C. In this particular implementation, the fourth retarder 2345, the third polarizer 2355, and the fifth retarder 2360 are not included in the system. FIG. 23C shows a design of an augmented reality system 2300 including the components shown in FIG. 23A and FIG. 23B, except for the fourth retarder 2345, the third polarizer 2355, and the fifth retarder 2360. Nevertheless, despite the exclusion of the third circular polarizer, the augmented reality display system is still configured to reduce ghost images. The second circular polarizer, for example, reduces reflections that would otherwise contribute to ghost images. For illustrative purposes, FIG. 23C depicts light reflected from the third retarder 2340, shown as light ray 2380. The reflected light ray 2380, which is circularly polarized, switches handedness due to the effect of being reflected from the surface of the third retarder 2340. In this example, the polarization is switched from left-handed to right-handed circular polarization. The switched circularly polarized light 2380 then passes through the compensator 2365 and is incident on the cover glass 2370 and the SLM 2375. As discussed above, the SLM 2375 can reflect circularly polarized light of the same handedness. Thus, the incident right-handed circularly polarized light can remain right-handed upon reflection. This circularly polarized light reflected from the SLM 2375, represented by light ray 2382, can then pass through the cover glass 2370 and the compensator 2365 and be incident on the third retarder 2340. The switched circularly polarized light 2382 is attenuated by the second circular polarizer, particularly by the third retarder 2340 and the polarizer 2335. 23C, for example, circularly polarized light 2382 reflected from SLM 2375 enters third retarder 2340 and is converted by third retarder 2340 to linearly polarized light having a different, e.g., orthogonal, linear polarization than the linear polarization selectively transmitted by second linear polarizer 2335. In this case, for example, right-handed circularly polarized light 2382 is converted by third retarder 2340 to vertical linear polarization orthogonal to the polarization selectively transmitted by second polarizer 2335. Second polarizer 2335 attenuates or prevents transmission of this linear polarization.

[0161]

[0279] Reflections that may contribute to ghost reflections can also potentially be reduced by tilting optical surfaces in the system. FIG. 24 shows an example configuration with tilted optical surfaces to reduce reflections that may generate ghost reflections. FIG. 24 shows an augmented reality display system 2400 including a light source 2305 that emits light represented by a light beam 2310 that passes through any number of polarizers, retarders, lenses, and / or other optical components as the light travels toward a spatial light modulator (SLM) 2375. A first polarizer 2312 and a first retarder 2315 that may form a first circular polarizer, as well as a lens 2320, are shown in FIG. 24 for illustrative purposes. However, additional components may be included, or components may be omitted or arranged or configured differently. In the illustrated example, the SLM 2375 includes a cover glass 2370 together. The cover glass 2370 may contribute to reflections that generate ghost images. Thus, in some implementations, the cover glass 2370 can be shaped to direct reflections that may result in ghost images away from the user's eyes. As shown, the cover glass 2370 has surfaces that can be tilted such that the surfaces are not parallel to other components or optical surfaces of the system (e.g., the SLM 2375, the first retarder 2315, the first polarizer 2312, the at least one waveguide 2348, etc., or their optical surfaces). The major surfaces of the cover glass 2370 can have normals that are tilted such that they are not aligned or parallel to the optical components therein, such as the optical axis or optics 2320 of the augmented reality display system 2400, for example. By being tilted, reflections from the optical surfaces of the cover glass 2370 can be directed away from the at least one waveguide 2348 or an incoupling optical element (e.g., an incoupling grating or diffractive optical element) for incoupling light into the at least one waveguide 2348, reducing the likelihood of reflections from the cover glass 2370 entering the at least one waveguide 2348. As depicted, the reflected light 2405 is directed back towards the light source 2305 and is directed away from the at least one waveguide 2348 where such light may ultimately reach the user's eye.In some implementations, the reflected light 2405 can be directed back to the light source and at least partially recycled at the light source 2305.

[0162]

[0280] Although FIG. 24 depicts a cover glass 2370 with a sloped surface, any component in the system in which undesired reflections are possible may include a sloped optical surface to deflect reflections from being coupled into the at least one waveguide 2348. Thus, optical surfaces on other components such as polarizers, retarders, etc. may be sloped to reduce reflections that are coupled into the at least one waveguide 2348 and the user's eye. Variations in the shape and size of the cover glass 2370 or other optical components are possible. The cover glass 2370 or other optical components may be thinner, for example. Similarly, the cover glass 2370 or other optical components may have an aspect ratio (length vs. thickness) different from that shown in FIG. 24. In some implementations, the cover glass 2370 or other optical components are wedge-shaped. However, other shapes are possible.

[0163]

[0281] Further other configurations are possible. Figure 25 shows, for example, an implementation of an augmented reality display system 2500 similar to the system 2400 shown in Figure 24, but further including a light dump 2505 to absorb light directed thereto. The system 2500 includes a tilted cover glass 2370 to direct reflections 2510 from the cover glass 2370 to the light dump 2505 instead of directing them back to the light source 2305. The light dump 2505 can include an absorbing material or structure configured to absorb light. The position of the light dump 2505 can vary depending on the implementation, for example, depending on the angle of the tilted cover glass 2370. As discussed above, this approach can be applied to other optical surfaces in the system. In addition, the shapes and sizes of the optical elements may be different.

[0164]

[0282] A wide range of variations of the augmented reality display are possible. Variations of the polarizing optical elements are possible. For example, a horizontal polarizer is used, but in some implementations, a vertical polarizer or a combination of horizontal and vertical polarizers are employed. Additionally, polarizers featuring polarizations other than vertical or horizontal may be used. Similarly, the light shown in the figures need not be horizontally polarized, but may be vertically polarized. Similarly, light shown as vertically polarized may be horizontally polarized in different implementations, or vice versa. Also, linearly polarized light with polarizations other than vertical or horizontal may be used.

[0165]

[0283] Additionally, the retarders may be configured differently. For example, the polarization in the figures need not be left-handed circular polarization, but may be right-handed circular polarization, and / or the right-handed polarization may be left-handed circular polarization. Further other variations are possible. Different retarder configurations can be employed to generate different combinations of left-handed and / or right-handed polarization than those shown. Also, in some implementations, elliptical polarization can potentially be used instead of circular polarization. For example, retarders may be employed to convert elliptical polarization to linear polarization and vice versa. Linear polarizers can be used to filter light and can be used to reduce ghost reflections as described herein.

[0166]

[0284] In some implementations, other types of polarizing elements and configurations thereof are employed. For example, the retarders are not limited to quarter-wave retarders or quarter-wave plates. For example, in some implementations, various optical elements have birefringence. In certain such cases, any one or more of the retarders 2315, 2330, 2340 can include a sufficient amount of retardation to convert linearly polarized light to circularly polarized light and need not be quarter-wave retarders. Retardation more or less than a quarter wave may be included in any one or more of the retarders 2315, 2330, 2340, since retardation may be contributed by other optical elements. Similarly, retardation may be distributed among several optical elements. As another example, multiple retarders may be employed to provide the appropriate amount of retardation. Also, as explained above, in some implementations, elliptical polarization may be used instead of circular polarization in some cases. For example, retarders may be employed to convert elliptical polarization to linear polarization and vice versa. Linear polarizers can be used to filter light and can be used to reduce ghost reflections as described herein.

[0167]

[0285] Additionally, the optical components may be in the form of optical layers, sheets and / or films, as well as stacks or one or more layers, sheets and / or films. Thus, different amounts, positions and arrangements of different polarizing elements may be used. For example, one or more of the retarders and / or polarizers may include a film.

[0168]

[0286] In some implementations, the spatial light modulator may operate differently, for example, the spatial light modulator may operate on and / or output light other than circularly polarized.

[0169]

[0287] Diffractive waveguide image combiners are an attractive approach for conveying computer-generated images to a user in AR applications. These waveguides work through repeated splitting and out-coupling of image-bearing light beams, spreading the in-coupled light to fill the far-field viewing area and acting as a pupil expander. The inventors have found that the splitting process inherently results in recombination of the beams, and when this occurs, there is an opportunity for the beams to interfere with each other. This interference effect results in intensity non-uniformities that are addressed by embodiments of the present invention. As described herein, small differences in the path lengths of the interfering beams, as introduced through small variations in the thickness of the waveguide, lead to random occurrences of these non-uniformities. The addition of an intentionally controlled bias to the path length difference has been shown to result in improved and more repeatable brightness uniformity. This bias can be in the form of a controlled variation in the waveguide thickness oriented along a certain direction relative to the main propagation path in the waveguide. Examples of this include a wedge-shaped taper in optical or physical thickness, a parabolic variation in optical or physical thickness, and the like. As described herein, embodiments of the present invention provide improvements in various performance characteristics, particularly modulation transfer function (MTF), image sharpness, and the like.

[0170]

[0288] Total thickness variation (TTV) is one metric for improving the performance of light guides. As used herein, TTV generally refers to the difference between the maximum and minimum thickness of the waveguide or the waveguide display substrate on which the waveguide is formed. As light travels through the light guide, typically by total internal reflection, the thickness variation changes the light propagation path(s). The angular difference in the light propagation path(s) can affect image quality by distorting the field of view, blurring the image, and losing sharpness.

[0171]

[0289] In some embodiments described herein, TTV is achieved by the physical thickness variation of the optical waveguide. However, embodiments of the present invention are not limited to the physical thickness variation and optical thickness variation of the substrate, and a combination of physical thickness variation and refractive index variation is included within the scope of the present invention. As will be apparent to those skilled in the art, the optical path length can be expressed by optical thickness variation = physical thickness variation + refractive index variation. In applications that utilize the splitting and combining behavior of beamlets to control interference and brightness uniformity, optical thickness variation is implemented. For most high quality optical glasses, the refractive index variation is usually small (ISO NV ± 2 × 10 -5 ~±30×10 -5 ). However, other materials, including polymers and ceramics, do not have such small refractive index variations. Additionally, materials having graded refractive index materials can be used to fabricate optical waveguides to achieve optical thickness variations instead of any physical thickness variations. Thus, the discussion of TTV provided herein is understood to include a broader class of optical thickness variations that can include physical thickness variations with a uniform refractive index, uniform thickness with a varying (i.e., stepped) refractive index, or a combination of physical thickness variations and varying refractive index.

[0172]

[0290] Waveguide preparation and processing is typically performed by placing several waveguides in a designated area on a waveguide display substrate (e.g., a wafer). Figure 26A depicts a waveguide display substrate 2600 having a radial arrangement of waveguides 2602.

[0173]

[0291] FIG. 26B is a plot showing the thickness of a waveguide display substrate as a function of position, according to one embodiment of the present invention. In FIG. 26B, the thickness of the waveguide display substrate corresponds to the cross section A-A' shown in FIG. 26A. As shown in FIG. 26B, the thickness is characterized by a dome shape, with half of the dome shown in the figure. The thickness is approximately constant from 0 mm, which corresponds to the center of the waveguide display substrate, to about 30 mm. The thickness is characterized by a decrease in thickness from about 30 mm to 70 mm, with the thickness variation from the center to the edge of the waveguide display substrate being approximately 0.7 μm=700 nm. From about 30 mm to 70 mm, the thickness variation decreases as a function of the direction aligned with the cross section A-A'. This thickness variation can be defined as a thickness difference gradient, where the gradient is measured along the direction aligned with the cross section A-A'. A similar description applies to the gradient of the optical path length difference when considering the optical path length.

[0174]

[0292] Figure 26C is a plot showing the thickness of a waveguide display substrate as a function of position, according to one embodiment of the present invention. In Figure 26C, the thickness of the waveguide display substrate corresponds to cross section B-B' shown in Figure 26A. As shown in Figure 26C, the thickness is substantially uniform as a function of position, with a slight increase in thickness observed at the center of the waveguide compared to the sides of the waveguide.

[0175]

[0293] In addition to the radial arrangement of waveguides 2602 as shown in Figure 26A, some embodiments utilize a linear arrangement. Figure 26D depicts a waveguide display substrate 2610 having a linear arrangement of waveguides 2612, 2614, etc. Thus, embodiments include waveguide layouts with rotational symmetry with four waveguides, six waveguides, or another number of waveguides as shown in Figure 26A, as well as linear layouts typically utilized in semiconductor manufacturing processes.

[0176]

[0294] The linear layout shown in FIG. 26D offers several advantages with respect to optical TTV bias that may not be available using a rotationally symmetric layout. FIG. 26E is a simplified schematic diagram illustrating thickness variation of a waveguide display substrate having a linear layout, according to an embodiment of the present invention. As an example, in a linear layout, a unidirectional wedge shape can be implemented with a thickness that varies linearly from a first thickness t1 at a first side (i.e., position A) of the waveguide display substrate and a second thickness t2 at a second side (i.e., position A') of the waveguide display substrate. FIG. 26E illustrates the thickness variation in the case of linear variation by curve 2620. Thus, both the waveguide 2612 and the waveguide 2614 have a thickness that decreases as the position moves along the line A-A'. Although waveguide 2612 has a larger nominal thickness than waveguide 2614, the variation in thickness of the waveguide display substrate (e.g., on the order of less than one micron) is small enough compared to the overall thickness of the waveguide (i.e., on the order of several hundred microns) that this difference in nominal thickness is acceptable for various applications.

[0177]

[0295] In addition to linear variations, other variations in thickness can be implemented, including quadratic variations, other smoothly varying TTVs, etc. These embodiments can be utilized to align the direction of light propagation to the TTV variations. FIG. 26C illustrates thickness variations for smooth variations by curve 2622. Thus, in some embodiments, a section of a sphere is utilized to provide the thickness variation, while in other embodiments, linear variations, quadratic variations, or other suitable variations are utilized to implement the TTV, resulting in a bias in thickness across the waveguide.

[0178]

[0296] FIG. 26F is a simplified schematic diagram showing a rectangular waveguide display substrate 2630 with linearly arranged waveguides 2632. In this exemplary embodiment, a non-circular configuration is implemented to take advantage of tapered waveguide architecture and bias thickness variations that can be characterized by thickness variations that can depend on the layout and directionality of the waveguide fields. As shown in FIG. 26F, the TTV increases linearly from side 2634 to side 2636 as shown by the plot included in the figure, as is typical of wedge-shaped thickness variations across the substrate 2630. Thus, each waveguide 2632 is characterized by the TTV as measured along the length of the waveguide (i.e., along the y-axis). Although a rectangular geometric shape is shown in FIG. 26F, other non-circular shapes can be utilized, including square shapes. Additionally, although a linear variation in thickness is shown in FIG. 26F, a smoothly varying function can be used to define the TTV. Additionally, while a uniform thickness as a function of waveguide width (i.e., along the x-axis) is shown in FIG. 26F, in other embodiments, variations in thickness along both the length and width are utilized.

[0179]

[0297] FIG. 26G is a simplified schematic diagram showing a waveguide display substrate with localized TTV according to an embodiment of the present invention. In addition to the overall substrate TTV provided by embodiments of the present invention, other embodiments utilize localized TTV for specific waveguides, as shown, for example, in FIG. 26F. As an example, localized wedge or tapered morphology specific to individual waveguides can be implemented by a deterministic polishing process that forms sections in the substrate with sloping bottom features. Thus, FIG. 26G shows a substrate with specific "cavities" corresponding to specific waveguides. Thus, this embodiment decouples the thickness profile of the waveguide from the thickness of the waveguide display substrate.

[0180]

[0298] Referring to FIG. 26G, a rectangular waveguide display substrate 2640 includes a linear arrangement of waveguides 2642. The thickness of the waveguides 2642 is uniform as measured in the y direction. However, as measured in the x direction, the thickness of each waveguide varies, decreasing linearly from side 2634 to side 2636. This wedge shape is unique to each waveguide. Thus, using a waveguide display substrate 2640 with an overall flat-flat thickness profile, multiple waveguides 2642 are provided, each with a local TTV having a wedge shape. Although a linear thickness variation from waveguide to waveguide is shown in FIG. 26G, this is not required and other shapes can be utilized, including smoothly varying functions.

[0181]

[0299] In addition to the deterministic polishing to form the localized TTV described in connection with Figure 26G, other methods of implementing the localized TTV are included within the scope of the present invention, including molding processes, etc. Other methods of creating the localized TTV include patterned (masked) film deposition (organic, inorganic, gas phase vacuum, atmospheric, or nanoimprint), patterned (masked) etching into the substrate, spatially varying ion implantation or ion diffusion to create changes in the refractive index and thus the optical TTV, creating a mold with an inverse TTV pattern and molding a polymer or glass with it, creating localized areas of desired TTV bias.

[0182]

[0300] TTV can be reduced by manufacturing a flat waveguide display substrate (i.e., a waveguide display substrate with zero TTV), for example, by polishing a substrate (such as a metal, glass, or silicon substrate), or by initially shaping a substrate (such as a polymer substrate) with high precision. However, polishing can generate a certain amount of curvature on the waveguide display substrate and the resulting waveguides formed thereon. FIG. 27A depicts a polished flat waveguide display substrate 2700. FIGS. 27B and 27C depict a polished convex waveguide display substrate 2702 and a polished concave waveguide display substrate 2704, respectively. Polishing can result in a convex or concave curvature, but the embodiments described herein are described with reference to a convex curvature as depicted in FIG. 27B.

[0183]

[0301] Fully flat polishing or shaping, as depicted in FIG. 27A, typically requires extensive and costly processing to achieve, so some degree of TTV is typically tolerated. In most low-TTV processes for waveguide display substrates (e.g., 20 nm < TTV < 2 μm), there are thickness shapes or profiles of the substrate that vary from portion to portion (e.g., randomly). Here, "thickness shape" generally refers to a 3D mapping of the height difference between the top and bottom surfaces of the substrate. In one example, a typical plano-convex lens has a thickness shape that is a convex spherical surface or a positive "dome". In another example, a meniscus lens (e.g., non-prescription sunglasses) having the same radius of curvature on each surface has a TTV thickness shape that is nearly flat to zero, but each surface itself is not flat. When waveguides are stacked to form a multi-layer multi-color waveguide display, due to differences in the random thickness shapes, each of the red, green, and blue color channels can have different luminance uniformity patterns. Due to the differences in the luminance uniformity patterns, when the waveguide stack is illuminated with a uniform white light image, it may cause color variations across the field of view. These color non-uniformities can potentially degrade the image quality.

[0184]

[0302] It should be noted that while Figures 27A-C show a waveguide display substrate having at least one planar surface, embodiments of the present invention are not limited to plano-convex or plano-concave geometries. Figure 27D depicts a polished meniscus waveguide display substrate 2706 having one convex and one concave surface. The embodiment shown in Figure 27D is a positive lens, but changing the curvature of the convex and concave surfaces can result in a negative lens. Figure 27E depicts a polished biconvex waveguide display substrate 2708. Figure 27F depicts a polished biconcave waveguide display substrate 2710. Thus, a variety of waveguide display substrates, including those including planar surfaces, can be utilized to implement controlled changes in path length during beamlet splitting and combining. However, as shown in Figures 27D-27F, physical thickness changes, refractive index changes, or a combination of both (i.e., optical thickness changes) can be achieved using waveguide display structures in which planar surfaces are not utilized.

[0185]

[0303] Referring to Figure 28A, a polished waveguide display substrate 300 is shown having a TTV measured from the highest point to the lowest point of the curved portion of the polished waveguide display substrate. Note that a polished waveguide display substrate need not have a planar surface, and both surfaces can exhibit curvature. A perfectly flat waveguide display substrate 302, depicted in Figure 28B, has zero TTV.

[0186]

[0304] FIG. 28C illustrates the TTV of a set of eyepiece waveguides, according to one embodiment of the present invention. Referring to FIG. 28C, an eyepiece 2810 includes a set of three eyepiece waveguides, namely, an eyepiece waveguide 2820, a second eyepiece waveguide 2830, and a third eyepiece waveguide 2840. In some embodiments, the three eyepiece waveguides are designed to in-couple, propagate, and out-couple light of red, green, and blue wavelengths, respectively. The eyepiece waveguide 2820 includes an internal coupling grating 2822 and a combined pupil expander 2824 that out-couples light toward a user. The second eyepiece waveguide 2830 includes a second internal coupling grating 2832 and a second combined pupil expander 2834 that out-couples light toward a user. The third eyepiece waveguide 2840 includes a third internal coupling grating 2842 and a third combined pupil expander 2844 that outcouples light towards the user. In some embodiments, the eyepiece waveguide 2820, the second eyepiece waveguide 2830, and the third eyepiece waveguide 2840 are stacked together into a single structure to form the eyepiece 2810. A spacer (not shown) between each eyepiece waveguide may be utilized to maintain a fixed relationship between each eyepiece waveguide.

[0187]

[0305] As shown in FIG. 28C, the thickness, and therefore the optical path length, measured along the longitudinal axis (i.e., z-axis) varies as a function of the lateral dimensions (i.e., x- and y-directions). In the illustrated embodiment, the variation in optical path length of each eyepiece waveguide occurs along the x-direction, but this is not required by the present invention. Thus, as shown in FIG. 28C, the varying optical path length difference varies from a first value in a first region of each of the three eyepiece waveguides (e.g., the internal coupling grating regions adjacent to internal coupling grating 2822, internal coupling grating 2832, and internal coupling grating 2842) to a second value in a second region of each of the three eyepiece waveguides (e.g., the combined pupil expander regions adjacent to combined pupil expander 2824, second combined pupil expander 2834, and third combined pupil expander 2844).

[0188]

[0306] The change in optical path length of each eyepiece waveguide within the eyepiece can be aligned such that the change in each eyepiece waveguide changes (e.g., decreases) along a single direction, which can be common to all eyepiece waveguides within the eyepiece. As shown in FIG. 28C, each eyepiece waveguide decreases in thickness as a function of a lateral direction aligned with the x-axis. That is, the thickness decreases as measurements are made at various points along the x-axis. As a result, the x-axis can be considered the direction corresponding to the change. In FIG. 28C, the direction corresponding to the change among each of the three eyepiece waveguides is common, i.e., a common direction (i.e., the x-axis), and the direction corresponding to the change in each eyepiece waveguide is aligned with the direction corresponding to the change in each eyepiece waveguide that is parallel to the direction corresponding to the change in each of the other eyepiece waveguides. Thus, the combined decrease in optical path length corresponding to the eyepiece 2810 is the sum of the decrease in optical path length corresponding to each eyepiece waveguide.

[0189]

[0307] Referring to FIG. 28C, the portion of each eyepiece waveguide adjacent to the internal coupling grating is thicker than the portion of each eyepiece waveguide adjacent to the combined pupil expander. Thus, the varying optical path length difference decreases from a first value in a first region of each of the three eyepiece waveguides (i.e., corresponding to the input coupling grating) to a second value in a second region of each of the three eyepiece waveguides (i.e., corresponding to the combined pupil expander). In some implementations, the internal coupling grating is disposed near the peripheral region of the eyepiece, and the combined pupil expander is disposed near the nose region of the eyepiece. Thus, in these implementations, the thickness of the eyepiece is thicker near the peripheral region and thinner near the nose region.

[0190]

[0308] In other embodiments, the optical path length difference is reduced in other ways, for example, thicker near the nose region and thinner near the peripheral region, thicker in the region of the combined pupil expander and thinner in the region of the internal coupling grating, combinations thereof, etc. Thus, various structures having gradients in their optical path length difference are within the scope of the present invention, and the examples discussed herein are merely illustrative. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

[0191]

[0309] In a binocular application, the eyepiece associated with the right eye may utilize a change in optical path length as shown in Figure 28C, for example, where the optical path length decreases as a function of position relative to the nose region of the eyepiece, i.e., the optical path length is shorter at the periphery than near the nose region. The eyepiece associated with the left eye may utilize a mirror image configuration, where the optical path length also decreases as a function of position relative to the nose region of the eyepiece for the left eye but not for the right eye.

[0192]

[0310] FIG. 28D is a simplified schematic diagram illustrating an augmented reality system according to an embodiment of the present invention. The augmented reality system 2850 can be implemented as an augmented reality headset suitable for a user. The augmented reality system 2850 includes a controller, a first set of elements corresponding to the user's left eye, and a second set of elements corresponding to the user's right eye. In the embodiment shown in FIG. 28D, the first set of elements includes a left projector 2852, left projector optics 2854, and one or more left eyepiece waveguides 2856. The second set of elements includes a right projector 2852, right projector optics 2854, and one or more right eyepiece waveguides 2856. For each eye, light from the projector is focused using the projector optics onto an eyepiece lens that includes an eyepiece waveguide, for example, onto an internal coupling grating of the eyepiece waveguide. As described herein, due to the optical path length changes associated with the eyepiece, the image quality provided by the augmented reality system 2850 is higher than that available using conventional approaches.

[0193]

[0311] The augmented reality system can operate to provide virtual content to a user. Accordingly, methods of operating the augmented reality systems described herein, including the augmented reality system 2850 shown in FIG. 28D, are included within the scope of the present invention. These methods can utilize the eyepieces and eyepiece waveguides described herein, characterized by optical path length differences measured across their lateral dimensions, to improve the user experience compared to conventional techniques.

[0194]

[0312] FIG. 29 depicts a waveguide display substrate 400 having a minimum thickness X. That is, no part of the waveguide display substrate is thinner than X, and any thickness variation is measured as X plus thickness. The maximum thickness is h, and the TTV is mathematically Y, where Y=hX. The TTV specification is usually stated as the maximum allowable TTV (TTV max ) and product specifications are expressed as TTV max Aim for a TTV(Y) less than 0 (i.e., 0≦Y <TTV max ). Here, an "ultra-low TTV" waveguide display substrate refers to a waveguide display substrate with a target TTV of zero (or as close to zero as practical). Note that a polished waveguide display substrate need not have planar surfaces; both surfaces can exhibit curvature.

[0195]

[0313] In optical products, image quality and uniformity can be sensitive to the particular shape or profile of the polished waveguide display substrate as the TTV approaches zero. In one example, the comparative difference in image quality (measured by uniformity) of a waveguide fabricated on a 20 nm TTV and a 40 nm TTV waveguide display substrate can be much higher than the comparative quality of a waveguide fabricated on a 100 nm TTV substrate and a 120 nm waveguide display substrate, even though both pairs differ by only 20 nm. In other words, a 100 nm TTV waveguide and a 120 nm waveguide can yield a similarly uniform image than a 20 nm TTV waveguide and a 40 nm TTV waveguide (the former pair is more dome-shaped compared to the latter pair). Thus, a 100 nm TTV waveguide and a 120 nm TTV waveguide can produce lower image variation and more consistent image uniformity across a product line.

[0196]

[0314] The path length difference of the light propagation path(s) in a waveguide fabricated on a non-flat waveguide display substrate can also affect image quality with luminance pattern non-uniformity and color non-uniformity. Sources of luminance pattern non-uniformity include electromagnetic interference patterns generated by the multiple paths through the pupil replica waveguide display substrate. A typical pupil replica waveguide unit cell resembles a Mach-Zehnder interferometer, where there are two paths per unit cell from the input to the output replica pupil location. The path length difference between the two paths is affected by the path length through the thickness of the waveguide display substrate, defined by the TTV metric and thickness profile (whether the thickness varies linearly or quadratically, and at an angle relative to the light in total internal reflection within the waveguide display). If the path lengths have equal or opposite phase, constructive or destructive interference can exist, respectively. Thus, the thickness profile can affect the magnitude of the pupil replica copy and, ultimately, the output image that is outcoupled by the waveguide display.

[0197]

[0315] Therefore, it may be advantageous to minimize thickness profile variation and TTV. Certain manufacturing distributions may occur because perfect replication may not be achieved in the polishing or shaping process. In the virtual distribution model, a standard set of shape basis functions can be defined using circular substrate shapes defined by Zernike polynomials. Even and odd Zernike polynomials exist. The even ones are defined as follows: Z n m (ρ,ψ)=R n m (ρ)cos(mψ) The odd ones are defined as follows: Z n -m (ρ,ψ)=R n m (ρ)sin(mψ), where m and n are non-negative integers with n≧m, ψ is the azimuth angle, ρ is the radial distance, and R m n is a radial polynomial defined as follows. Zernike polynomials have the property that they are limited to the range of -1 to +1. That is, the radial polynomial R m n is defined as follows when nm is even:

number

[0198]

[0316] Image quality, especially brightness uniformity, is nonlinearly sensitive to thickness shape as TTV approaches zero. In other words, as TTV decreases below a certain threshold, image quality becomes increasingly variable between waveguides that exhibit even slight changes in thickness shape. To compensate for this anomaly, a biased TTV with a consistent thickness shape can be incorporated into the substrate processing. As used herein, a "biased" TTV generally refers to a TTV with a non-zero target. More specifically, a "biased" TTV generally refers to a substrate thickness shape with one or more coefficients of a Zernike-matched polynomial with a non-zero target, and all remaining coefficients of the Zernike-matched polynomial with a zero target. Consistency of thickness shape within a multiple waveguide display substrate generally refers to multiple waveguide display substrates with small changes in the coefficients of the Zernike-matched polynomial. For "biased" TTV, thickness profile consistency refers to (i) all non-zero target Zernike coefficients that have minimal variation from their target magnitudes, e.g., the coefficients of all waveguide display substrate non-zero targets are about 70% to about 130% of their target magnitudes, and (ii) all zero target Zernike coefficients that have a substantially smaller absolute magnitude than the non-zero target Zernike coefficients, e.g., the zero target coefficients are 0 to about 30% of the non-zero target coefficients.

[0199]

[0317] An example of biased TTV and consistent substrate thickness profile is a substrate that is polished (or shaped) substantially into a spherical shape with a TTV many times greater than the typical minimum TTV range of the substrate polishing (or shaping) process. This substrate shape can be described as having a wedge-shaped (linear change in thickness) and a dome-shaped (quadratic change in thickness) component. FIG. 30 depicts a waveguide display substrate 3000 having a wedge-shaped component 3002 with height W, a dome-shaped component 504 with height D, and a cylindrical component 3006 with a flat surface 3008 and thickness t and diameter d. Using Zernike fitted polynomials, the average thickness of the waveguide display substrate is Z0 0 and the height of the "wedge" component of the TTV is sqrt(Z1 -1 +Z1 1) and the height of the convex "dome-shaped" component of the TTV can be defined as -2 × Z2 0 The average thickness of a waveguide display substrate is typically between 200 μm and 2000 μm. In a substrate polishing or shaping process that produces a "dome-shaped" bias TTV, the waveguide display substrate is typically 10 times the substrate diameter. -7 ~10 -6 Target "dome" height D within the range t and each substrate can have a "dome" height of less than 30% of the target "dome" height and a "wedge" height of less than 30% of the target "dome" height. In one example, the diameter is 150 nm and the average "dome" (D mean ) height is 1000 nm, and the range of "dome" heights (D min ~D max ) is 700nm to 1300nm, and the maximum "wedge" height (W max Waveguide display substrates with a TTV of less than 300 nm have improved efficiency, brightness uniformity and color uniformity, and reduced part-to-part variation in efficiency, brightness uniformity and color uniformity, compared to waveguide display substrates with near-zero target TTVs with "dome" and "wedge" heights in the range of 0-300 nm. In the radial display layout of FIG. 26 and the radially symmetric substrate thickness profile of a consistent shape biased to a dome shape, consistent thickness variation from the waveguide display input coupler to the output coupler can be achieved on a single substrate as well as among multiple components arranged from substrate to substrate. Such an arrangement of consistent thickness shapes shows improved color uniformity and image quality, compared to the typical ultra-low TTVs with random thickness shapes used in conventional waveguide displays.

[0200]

[0318] A biased TTV with a consistent shape can be applied to a waveguide display substrate in a number of ways. For glass or crystalline substrates, this can be applied by polishing into the biased shape, or by applying a coating with a non-uniform thickness (of consistent shape and size) to an ultra-low TTV waveguide display substrate with small but random thickness shape variations. For moldable polymeric materials, the biased thickness profile can be designed into the mold that produces the waveguide display substrate.

[0201]

[0319] 31A-31C show the waveguide display substrate yield versus TTV, dome height, and wedge height for ultra-low TTV waveguide display substrates. For these ultra-low TTV waveguide display substrates, the magnitudes of the dome height and wedge height are typically similar to each other. Also, the range of dome height variation is similar in magnitude to the average dome height. FIG. 31D-31F show the waveguide display substrate yield versus TTV, dome height, and wedge height for biased TTV waveguide display substrates. For these biased TTV waveguide display substrates, the magnitude of the dome height is greater than the magnitude of the wedge height, and the dome height variation is less than the average dome height. FIG. 31D-31F represent the biased relationships without reference to specific values. The biased TTV tolerance specification can be expressed as follows: W max / D mean <X (D mean -D min ) / D mean <Y (D max -D mean ) / D mean <Z

[0202]

[0320] For these relationships, X, Y, and Z typically range from 0 to 10 between different substrate polishing or shaping processes. Figures 31A-31C show a set of waveguide display substrates that yield higher values ​​of X, Y, and Z than the set of waveguide display substrates shown in Figures 31D-31F. As X, Y, and Z approach zero, the overall efficiency of multiple waveguides fabricated on multiple subsections of multiple waveguide display substrates increases and varies less, as opposed to the TTV itself approaching zero. Also, as X, Y, and Z approach zero, the resulting luminance and color uniformity between waveguides also increases and varies less. In a typical substrate polishing or shaping process, the target TTV max As approaches zero, X, Y, and Z increase. Ultra-low TTV waveguide display substrates typically have X, Y, and Z in the range of 1 to 10, and biased TTV waveguide display substrates have X, Y, and Z in the range of 0 to 0.3, so biased (or non-zero target) TTV can contribute to improving waveguide display image quality.

[0203]

[0321] FIG. 32A shows the waveguide eyebox efficiency versus the "dome" TTV (nm) of a spherical waveguide display substrate geometry on a 6-inch wafer for a typical diffractive waveguide display with an average thickness of 300 μm and a "wedge" TTV of 0 nm. As can be seen in FIG. 32A, the eyebox efficiency is maximum between a TTV of 400 nm and a TTV of 600 nm. Here, the waveguide eyebox efficiency is the sum of the light incident on the input coupling grating of the waveguide display relative to the light incident on the input coupling grating 15 mm from the eye side of the output grating of the diffractive waveguide display, as calculated by a typical diffractive waveguide simulation. 2 15×20mm apart 2 It refers to the sum of the light incident on a rectangular area.

[0204]

[0322] FIG. 32B shows the waveguide eyebox efficiency versus the "dome" TTV (μm) of a spherical waveguide display substrate geometry on a 6-inch wafer for a typical diffractive waveguide display with an average thickness of 300 μm. The TTV is measured from the center of the wafer to the edge of the wafer. In FIG. 32B, the pupil efficiency increases as the TTV increases from 0 μm to about 0.6 μm. Thus, the waveguide, if flat, has a pupil efficiency of about 0.0023, which corresponds to a TTV of 0 μm. Thus, at a TTV of about 0.6 μm, the pupil efficiency is at a maximum. As shown in FIG. 32B, the range in which the pupil efficiency is acceptable (e.g., greater than 0.003) is a function of the design of the eyepiece waveguide. Thus, a wide range of TTV values ​​can be utilized according to embodiments of the present invention.

[0205]

[0323] FIG. 32C shows the waveguide eyebox efficiency versus "dome" TTV (μm) of a spherical waveguide display substrate geometry on a 6-inch wafer for another diffractive waveguide display having an average thickness of 300 μm. In FIG. 32C, the diffractive waveguide display utilizes a two-dimensional grating design. In this case, the pupil efficiency increases to about 0.001 at a TTV of about 0.4 μm and remains at this efficiency over a wide range of TTV values. Thus, the desired TTV value can be a function of the grating design, and embodiments of the present invention provide a range of acceptable values ​​of TTV.

[0206]

[0324] The inventors have found that the color uniformity of an eyepiece stack made from multiple eyepiece waveguide layers (e.g., three separate layers) can be improved if the multiple (e.g., three) layers have similar TTV profiles. Similar to that shown in Figures 32A-32C, the pupil efficiency increases as the TTV increases, and the color uniformity also improves as the TTV variance increases up to a certain value. Without limiting the scope of the invention, the inventors believe that this improvement in color uniformity is because the more similar the uniformity patterns of each layer are in each other layer, the more similar the color of the combined image made from all three layers will be. The inventors have demonstrated that the color uniformity RMS error, when plotted as a function of the spherical component of the TTV of the wafer used to fabricate the eyepiece, decreases as the TTV increases. This improvement in color uniformity is likely due to the similar emission uniformity patterns of each eyepiece waveguide layer. Thus, as the TTV increases and matches between the multiple eyepiece waveguide layers, the color uniformity error is reduced.

[0207]

[0325] Additionally, the inventors have also found that in addition to color uniformity, the use of TTV can improve image uniformity. Using a measure of low spatial frequency variation in image intensity, the inventors have found that the introduction of TTV results in a significant reduction in low spatial frequency variation compared to a flat eyepiece waveguide layer. This reduction in variation improves image uniformity. Thus, eyepiece waveguides with low values ​​of TTV were characterized by higher pixel-to-pixel uniformity compared to eyepiece waveguides with higher values ​​of TTV (e.g., TTV in the 0.5 μm range).

[0208]

[0326] According to an embodiment of the present invention, methods and systems are provided for eyepiece waveguides with optical thickness variations. Total thickness variations can result from refractive index changes and / or physical thickness variations and can be implemented as total thickness variations (TTV) across the substrate or as local thickness variations (LTV) in areas within the substrate. As described herein, either TTV or LTV, which can improve image and color uniformity of the eyepiece waveguide, can be implemented by using at least one or more thin film coatings, which can be disposed on at least one or both sides of the substrate. The thin film coatings, referred to herein as films, are applied to the substrate, e.g., silicon oxynitride (Si 2 O 3 ) having a refractive index ranging from about 1.42 to about 2.0. x O y N z) can have a refractive index similar to that of TiO2. Additionally, films of ZnO, ZrO2, TiO2, SiC, etc. can be utilized to achieve refractive index values ​​ranging from about 2.0 to about 2.7. Such inorganic films can be deposited using physical vapor deposition (PVD) techniques such as evaporation, sputtering, and / or chemical vapor deposition (CVD) techniques such as low pressure plasma enhanced CVD (LPPECVD), atmospheric pressure plasma enhanced CVD (APPECVD), atomic layer deposition (ALD), etc. The thin film coating can also be comprised of organic polymers, which may contain higher refractive index inorganic nanoparticles (ZrO2, TiO2) that can modify the refractive index of this polymer-based film to a range of refractive index from 1.7 to 2.0. In some implementations, the base polymer material can include a resin material such as an epoxy vinyl ester. The resin can include vinyl monomers (e.g., methyl methacrylate) and / or di- or tri-functional vinyl monomers (e.g., diacrylates, triacrylates, dimethacrylates, etc.) with or without aromatic molecules in the monomer in addition to sulfur. In some implementations, the base polymer material can have a refractive index in the range of approximately 1.5 to 1.75. In some implementations, the base material can include a cycloaliphatic epoxy-containing resin that can be cured using ultraviolet light and / or heat. Additionally, the base polymer material can include an ultraviolet cationic photoinitiator and a co-reactant to facilitate efficient ultraviolet curing at ambient conditions. The prepolymer composite resin can have nanoparticles (e.g., ZrO2, TiO2) with functional surfaces to prevent particle agglomeration and maintain uniform particle dispersion in the composite resin solution, which, once coated and cured, helps improve scattering losses of light undergoing total internal reflection within the now modified TTV of the base substrate. These polymer resins can be deposited using inkjet dispensing, spin coating, slot die coating, gravure coating, and the like.These thin films can be used with substrates made from SiO2 (n=1.42), barium flint (e.g., BaF) (n=1.58), lanthanum flint (e.g., LaF) (n=1.75), tantalum flint (e.g., TaF) (n=1.77), dense tantalum flint (e.g., TAFD55) (n=2.0), LiNbO3 (n=2.25), or SiC (n=2.65). In some embodiments, the films can be shaped in a manner similar to that shown in FIG. 33 using dry etching methods such as, for example, reactive ion etching (RIE), inductively coupled plasma enhanced RIE (RIE-ICP), or ion beam etching (IBE).

[0209]

[0327] Figure 33 is a simplified schematic diagram illustrating the process flow used in forming an inverted dome thickness variation according to one embodiment of the present invention. In addition to the method of forming an inverted dome thickness variation by polishing, Figure 33 illustrates a set of methods that utilize at least one thin film coating that can be formed by various methods described herein on at least one side of a similar refractive index waveguide substrate to enhance light propagation internally so that the virtual image that is outcoupled toward the user's eye is more uniform and fills the intended field of view, and is characterized by improved color uniformity.

[0210]

[0328] Referring to FIG. 33, a substrate 3305, for example a glass substrate having a refractive index of 1.9, is coated with a thin film 3307, typically a deposited film of silicon nitride (Si3N4), having a refractive index that substantially matches the refractive index of the substrate 3305. In this example, the thin film 3307 and the substrate 3305, both having a uniform thickness profile, thus form a substrate structure 3311 having a uniform thickness profile. The substrate structure 3311 can be etched using selective etching to form a variable thickness film 3308, resulting in a substrate structure 3313 with a TTV. The substrate structure 3313 has an inverted dome profile that is thicker at the periphery than at the center of the substrate structure. In an embodiment where the thin film is index matched to the substrate, the substrate structure is optically equivalent to a substrate with a TTV. In a typical implementation, the substrate 3305 has a thickness of around 350 μm, the variable thickness film 3308 has a thickness of around 1 μm, and the TTV is in the range of 300 nm to 600 nm.

[0211]

[0329] In optional process 3330, substrate structure 3313 can have second side 3315 processed to form a double-sided structure, e.g., the TTV is defined by the TTV of variable thickness film 3308 combined with the TTV of additional variable thickness films (not shown) that are fabricated on second side 3315. After optional double-sided processing in optional process 3330, process 3332 can be utilized to imprint a diffraction pattern into variable thickness film 3308, second side 3315, and / or additional variable thickness films (not shown) that may be fabricated on second side 3315. Either contact printing or photolithography processes can be utilized. After imprinting, etching and / or deposition processes can be utilized to generate thickness gradations defined by the imprint, residual thickness (RLT), combinations thereof, etc.

[0212]

[0330] Alternatively, a variable thickness film 3320 can be deposited on substrate 3305 to produce substrate structure 3322 with TTV. Variable thickness film 3320 can be uniformly etched to produce variable thickness film 3308 or proceed to optional double sided processing in optional process 3330. Thus, embodiments utilizing an etching process to form a variable thickness film, e.g., as illustrated by variable thickness film 3308, and embodiments utilizing a deposition process to form a variable thickness film, e.g., as illustrated by variable thickness film 3320, are within the scope of the present invention.

[0213]

[0331] The inventors have found that the inverted dome profile shown in FIG. 33 is difficult to achieve using wafer polishing. Thus, embodiments of the present invention allow for the use of thin film deposition / etching to produce structures that are not easily achieved using conventional wafer polishing techniques. Note that while substrate 3305 is shown as having a uniform thickness, a substrate having a first TTV can be utilized with a film having a second TTV to produce a coated substrate having a combined TTV equal to a predetermined thickness profile. Thus, embodiments of the present invention are not limited to substrates having a predetermined TTV, but rather extend the concept of TTV to the use of films having TTV, thereby allowing implementation independent of wafer polishing techniques.

[0214]

[0332] Figure 34 is a simplified schematic diagram illustrating a process flow used in forming an inverted dome thickness variation, according to one embodiment of the present invention. The process and structure illustrated in Figure 34 share common elements with the process and structure illustrated in Figure 33, but produces a dome thickness variation rather than the inverted dome thickness variation illustrated in Figure 33.

[0215]

[0333] Referring to FIG. 34, a substrate 3405, for example a glass substrate having a refractive index of 1.9, is coated with a thin film 3407, typically a deposited film of silicon nitride (Si3N4), having a refractive index that substantially matches the refractive index of the substrate 3405. In this example, the thin film 3407 and the substrate 3405, both having a uniform thickness profile, thus form a substrate structure 3411 having a uniform thickness profile. The substrate structure 3411 can be etched using selective etching to form a variable thickness film 3408, resulting in a substrate structure 3413 with a TTV. The substrate structure 3413 has a dome profile that is thicker at the center than the periphery of the substrate structure. In an embodiment where the thin film is index matched to the substrate, the substrate structure is optically equivalent to a substrate with a TTV. In a typical implementation, the substrate 3405 has a thickness of around 350 μm, the variable thickness film 3408 has a thickness of around 1 μm, and the TTV is in the range of 300 nm to 600 nm.

[0216]

[0334] In optional process 3430, the substrate structure 3413 can have a second side 3415 processed to form a double-sided structure, e.g., the TTV is defined by the TTV of the variable thickness film 3408 combined with the TTV of an additional variable thickness film (not shown) that is fabricated on the second side 3415. After the optional double-sided processing in optional process 3430, process 3432 can be utilized to imprint a diffraction pattern into the variable thickness film 3408, the second side 3415, and / or the additional variable thickness film (not shown) that may be fabricated on the second side 3415. Either contact printing or photolithography processes can be utilized. After imprinting, etching and / or deposition processes can be utilized to generate thickness gradations defined by the imprint, residual thickness (RLT), combinations thereof, etc.

[0217]

[0335] Alternatively, a variable thickness film 3420 can be deposited on substrate 3405 to produce substrate structure 3422 with TTV. The variable thickness film 3420 can be uniformly etched to produce variable thickness film 3408 or proceed to optional double sided processing in optional process 3430. Thus, embodiments utilizing an etching process to form a variable thickness film, e.g., as illustrated by variable thickness film 3408, and embodiments utilizing a deposition process to form a variable thickness film, e.g., as illustrated by variable thickness film 3420, are within the scope of the present invention.

[0218]

[0336] The LTV and TTV discussed herein can be implemented using a stencil to control plasma density during deposition or etching. Plasma-enhanced deposition techniques such as plasma-enhanced chemical vapor deposition (PECVD) can be used to fabricate films with TTV. Additionally, uniform film coating techniques relying on deposition, sputtering, etc. (e.g., using physical vapor deposition (PVD), chemical vapor deposition (CVD), PECVD, etc.) can be utilized to form uniform films, followed by an optional stencil-controlled etching process, e.g., plasma etching, that defines a specific etching pattern and results in a desired LTV / TTV profile on the substrate. The coating or etched profile can then be patterned using imprint lithography or photolithography to form a diffraction pattern, which may or may not be followed by an etching or deposition step that defines the diffraction pattern in the coating, additional coating, or coating under the pattern.

[0219]

[0337] 35A-35B are simplified cross-sectional views illustrating showerhead designs according to various embodiments of the present invention. Referring to FIG. 35A, a showerhead 3510 is provided having a plurality of apertures 3512 that can be utilized during a deposition process. The plurality of apertures 3512 are disposed adjacent the periphery of the showerhead 3510, but are not disposed at the center of the showerhead 3510. The spacing of the plurality of apertures 3512 can vary as a function of lateral position. Using a showerhead as shown in FIG. 35A, which reduces the plasma density and resulting deposition rate near the center of the showerhead compared to the deposition rate near the periphery, an inverted dome profile can be achieved, similar to the profile associated with the films 3320 of various thicknesses shown in FIG. 33.

[0220]

[0338] 35B, a showerhead 3520 is provided having a number of apertures 3522 that can be utilized during a deposition process. The number of apertures 3522 are disposed adjacent to the center of the showerhead 3520, but not at the periphery of the showerhead 3520. The spacing of the number of apertures 3522 can vary as a function of lateral position. Using a showerhead as shown in FIG. 35B, which reduces the plasma density and resulting deposition rate near the periphery of the showerhead compared to the deposition rate near the center, a dome profile can be achieved similar to the profile associated with the variable thickness film 3420 shown in FIG.

[0221]

[0339] FIG. 35C is a simplified schematic diagram illustrating an etch mask, according to one embodiment of the present invention. Referring to FIG. 35C, an etch mask 3530 is provided having a plurality of apertures 3532 having various sizes that can be utilized during an etching process. The plurality of apertures 3532 are disposed across a face of the etch mask 3530, and the size of the apertures varies from a small dimension adjacent the periphery of the etch mask 3530 to a large dimension adjacent the center of the etch mask 3530. The spacing of the plurality of apertures 3532 can also vary as a function of lateral position. Using an etch mask as shown in FIG. 35C that reduces the etch rate near the periphery of the etch mask compared to the etch rate near the center, an inverted dome profile can be achieved, similar to the profile associated with the membrane 3320 of various thicknesses shown in FIG. 33. In some embodiments, portions of the etch mask are free of apertures, reducing the etch rate of these portions, for example to zero. Additional description of shadow masks and variable density plasma deposition and etching is provided in U.S. Pat. No. 10,527,865, issued Jan. 7, 2020, the disclosure of which is incorporated by reference in its entirety for all purposes.

[0222]

[0340] Thus, embodiments of the invention can be used to deposit one or more thin films, for example, using PECVD and modified plasma showerheads to increase the density of reactions and reactive species in a particular zone, or to decrease the density of reactions / reactive species. Thus, the ability to fabricate thin films (e.g., Si3N4 films) on a substrate having a dome or inverted dome shape is provided by embodiments of the invention. During the deposition process, precursors can be selected to form a film of a predetermined refractive index. As an example, silicon oxynitride can be grown with a refractive index ranging from 1.45 (i.e., SiO2) to about 2.0 (Si3N4) by varying the oxygen content.

[0223]

[0341] FIG. 36A is a simplified plan view of a substrate showing thickness variations, according to one embodiment of the present invention. As shown in FIG. 36A, the deposition and / or etching process is controlled to produce a TTV that covers the entire substrate area. As will be discussed more fully in connection with FIG. 36F, the thickness variations can cover only portions or areas of the substrate, resulting in an LTV that can be repeated multiple times in a particular area of ​​the substrate. With reference to FIG. 36A, the thickness variations across the substrate 3610 are shown by legend, which shows a thickness variation ranging from about 0 nm near the periphery of the substrate to about 500 nm at the center of the substrate. Thus, in this figure, a dome-shaped profile is shown.

[0224]

[0342] Figure 36B is a simplified cross-sectional view showing single-sided thickness variation according to one embodiment of the present invention, which can be implemented to achieve the dome-shaped profile shown in Figure 36A, with a variation of about 500 nm from periphery to center. In Figure 36B, substrate 3620 is a substrate of uniform thickness, and film 3622 varies in thickness as a function of lateral position.

[0225]

[0343] FIG. 36C is a simplified cross-sectional view showing thickness variation on both sides according to an embodiment of the present invention. This thickness variation on both sides can be implemented to achieve the dome-shaped profile shown in FIG. 36A, with a variation of about 250 nm from periphery to center on a first side of the substrate and a variation of about 250 nm from periphery to center on a second side of the substrate. In FIG. 36C, substrate 3630 is a substrate of uniform thickness, and membranes 3632 and 3634 vary in thickness as a function of lateral position. Although membranes 3632 and 3634 are shown as coincident in FIG. 36C, this is not required and they can have different thickness profiles, for example, membrane 3632 varies about 100 nm from periphery to center and membrane 3634 varies about 400 nm from periphery to center. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0226]

[0344] FIG. 36D is a simplified schematic diagram illustrating nanofeatures of varying heights, according to one embodiment of the present invention. As shown in FIG. 36D, the thickness of the film 3622 varies as a function of lateral dimension. As discussed in connection with FIG. 36A and FIG. 36B, the thickness variation can be as much as 350 nm. With reference to FIG. 36D, the height of the nanofeatures 3640 formed in the film 3622 can vary as a function of lateral dimension, for example, from as little as 100 nm (i.e., as shown by the nanofeature on the left) to about 0 nm (i.e., as shown by the nanofeature on the right) across a film or substrate of varying heights. These nanofeatures of varying heights can be imprinted, for example, using contact printing, formed using photolithography, etched, or otherwise formed in the film 3622 with similar varying heights as discussed above.

[0227]

[0345] Figure 36E is a simplified schematic diagram showing nanofeatures of a single height, according to one embodiment of the present invention. In the embodiment shown in Figure 36F, the membrane 3622 includes nanofeatures 3650 having uniform height as a function of lateral position. These uniform height nanofeatures can be imprinted, etched, or otherwise formed in the membrane 3622 with varying heights as discussed above.

[0228]

[0346] FIG. 36F is a simplified plan view of a substrate exhibiting thickness variations according to another embodiment of the present invention. In FIG. 36F, six regions 3661, 3662, 3663, 3664, 3665, and 3666 of substrate 3660 are characterized by local thickness variations (LTV). Rather than a single height variation across the substrate, each of the six regions is characterized by the height variation characteristic of substrate 3610 shown in FIG. 36A. A stencil or other masking pattern can be used to define six regions, each of which can correspond to an ocular lens element. This allows adjustment of the height variations to be implemented, as shown in FIG. 36F. Although six regions with LTV are shown, it will be recognized that fewer or more regions can be utilized. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0229]

[0347] Figure 36G is a simplified cross-sectional view showing single-sided thickness variation according to one embodiment of the present invention. Figure 36G, showing a cross-section corresponding to cross-section A-A' of Figure 36F, shows regions 3662 and 3665, which are characterized by single-sided thickness variation implemented to achieve a tapered profile with a variation of about 500 nm from the outer edge to the inner edge of each region. In Figure 36G, substrate 3660 is a substrate of uniform thickness, and films 3668 and 3669 vary in thickness as a function of lateral position.

[0230]

[0348] Figure 36H is a simplified cross-sectional view showing double-sided thickness variations according to one embodiment of the present invention. Similarly, Figure 36H, which shows a cross-section corresponding to cross-section A-A' of Figure 36F, shows regions 3662 and 3665, which are characterized by double-sided thickness variations implemented to achieve a tapered profile, here with a linear variation of about 250 nm from the outer edge to the inner edge of each region on each side of the substrate.

[0231]

[0349] FIG. 37A is a simplified plan view of a substrate showing thickness variations, according to one embodiment of the present invention. In FIG. 37A, substrate 3710 is rectangular in form, rather than circular, as shown for substrate 3610. Referring to FIG. 37A, the thickness variations across substrate 3710 are defined into four regions 3711, 3712, 3713, and 3714, each having a thickness variation ranging from about 0 nm near the left side of the periphery of each region of the substrate to about 500 nm at the right edge of the region. Thus, in this view, a series of tapered profiles are shown that increase in height linearly across the region. In addition to circular and rectangular substrates, other substrate form factors can be utilized, including square substrates or substrates in the form of a web.

[0232]

[0350] Figure 37B is a simplified schematic diagram showing single-sided thickness variations that can be implemented to achieve the set of linear tapered profiles shown in Figure 37A, with approximately 500 nm variation across each region, according to one embodiment of the present invention.

[0233]

[0351] Figure 37C is a simplified schematic diagram illustrating a double-sided thickness variation that can be implemented to achieve the linear tapered profile shown in Figure 37A, with a variation of about 250 nm from one edge of each region to the opposite edge of each region, and a corresponding variation of about 250 nm from edge to edge on the second side of the substrate, according to one embodiment of the invention.

[0234]

[0352] FIG. 37D is a simplified plan view of a substrate showing thickness variations according to another embodiment of the present invention. In FIG. 37D, nine regions 3721, 3722, 3723, 3724, 3725, 3726, 3727, 3728, and 3729 of a substrate 3720 are characterized by LTV, similar to that discussed in connection with FIG. 37A. Rather than a single height variation across the substrate, each of the nine regions is characterized by the height variation characteristics of the four regions shown in FIG. 37A. A stencil or other masking pattern can be used to define the nine regions, each of which can correspond to an eyepiece element. In the example shown in FIG. 37D, a rectangular substrate is utilized, with the thickness varying along the length of the rectangle, providing an alternative to the polar coordinate-based layout shown in FIG. 36F. In other embodiments, rather than increasing thickness variation in the same direction for all eyepiece waveguides, the thickness variation can be reversed for some eyepiece waveguides, i.e. decreasing along the length, increasing / decreasing along the width, etc. Thus, embodiments of the present invention can be implemented in a variety of substrate geometries and a variety of eyepiece waveguide geometries.

[0235]

[0353] Figure 37E is a simplified schematic diagram illustrating single-sided thickness variation according to one embodiment of the present invention. Figure 37E, showing a cross section corresponding to cross section B-B' of Figure 37D, shows regions 3727, 3728, and 3729, which are characterized by single-sided thickness variation implemented to achieve a tapered profile with a linear variation of about 500 nm from the left edge to the right edge of each region.

[0236]

[0354] Figure 37F is a simplified schematic diagram illustrating a double-sided thickness variation that can be implemented to achieve the linear tapered profile shown in Figure 37D, with a variation of about 250 nm from one edge of each region to the opposite edge of each region, and a corresponding variation of about 250 nm from edge to edge on the second side of the substrate, according to one embodiment of the invention.

[0237]

[0355] 38A-41F are simplified cross-sectional views illustrating eyepiece waveguides with various thickness variations based on thin film TTV. As will be described more fully below, in the examples discussed in connection with FIGS. 38A-38F, the thin film thickness decreases from a region corresponding to an internal coupling grating to a region corresponding to a combined pupil expander. The examples described in connection with FIGS. 38A-41F are merely illustrative and are not intended to limit the scope of the invention or the architectures that may be utilized in accordance with embodiments of the invention. With reference to FIG. 28C, the eyepiece waveguides shown in FIGS. 38A-41F may be utilized in place of eyepiece waveguide 2820, second eyepiece waveguide 2830, and third eyepiece waveguide 2840 as elements of an eyepiece. Thus, embodiments in which the substrate varies in optical path length (e.g., thickness) and embodiments in which the substrate structure varies in optical path length (e.g., thickness) are interchangeable in the systems described herein.

[0238]

[0356] FIG. 38A is a simplified cross-sectional view showing an eyepiece waveguide with a total thickness variation on one side, according to an embodiment of the present invention. As shown in FIG. 38A, a variable thickness film 3812 is formed, for example by vapor deposition, on a substrate 3810 characterized by a uniform thickness. Although the substrate 3810 is shown as having a uniform thickness, and the thickness variation of the substrate structure 3813 including the variable thickness film 3812 and the substrate 3810 is due only to the thickness variation of the variable thickness film 3812, it will be appreciated that the substrate 3810 can also be characterized by some thickness variation that can be taken into account during deposition of the variable thickness film 3812 to produce a substrate structure 3813 with a desired total thickness variation.

[0239]

[0357] A diffractive structure is formed on the variable thickness film 3812, including an internal coupling grating 3814 and a combined pupil expander 3816, which in this embodiment includes nanofeatures of variable height. As will be apparent to one of ordinary skill in the art, the representation of the internal coupling grating 3814 and combined pupil expander 3816 is for illustrative purposes only. In the eyepiece waveguide shown in FIG. 38A , incident light is received below the internal coupling grating 3814, propagates through the anti-reflective coating 3818 and substrate 3810, is coupled by the internal coupling grating 3814 to the variable thickness film 3812 and substrate 3810, and propagates through the substrate 3810 and variable thickness film 3812 before being outcoupled by the combined pupil expander 3816. Thus, the eyepiece waveguide decreases in thickness as light propagates from the internal coupling grating 3814 to the combined pupil expander 3816. In an alternative embodiment of a single-sided eyepiece waveguide, an internal coupling grating 3814 and combined pupil expander 3816 are fabricated on a substrate 3810, and a variable thickness membrane 3812 is positioned between an anti-reflective coating 3818 and the substrate 3810.

[0240]

[0358] FIG. 38B is a simplified cross-sectional view showing an eyepiece waveguide with double-sided total thickness variation, according to an embodiment of the present invention. The eyepiece waveguide shown in FIG. 38B shares common elements with the eyepiece waveguide shown in FIG. 38A with the addition of a second variable thickness film 3820 and a second combined pupil expander 3826. Thus, the substrate structure 3823 includes the variable thickness film 3812, the substrate 3810, and the second variable thickness film 3820, and is characterized by a total variable thickness resulting from the thicknesses of these elements varying in the lateral dimensions. Although a double-sided structure is shown in FIG. 38B, an alternative embodiment removes the second variable thickness film 3820 and defines a second combined pupil expander 3826 on the substrate 3810. Thus, in this and other embodiments, double-sided patterning for diffractive structures can be implemented in the context of a single-sided variable thickness film.

[0241]

[0359] Figure 38C is a simplified cross-sectional view showing an eyepiece waveguide with total thickness variation on both sides according to another embodiment of the invention. The eyepiece waveguide shown in Figure 38C shares common elements with the eyepiece waveguide shown in Figure 38B, with the interconnect layer between the diffractive nanofeatures removed.

[0242]

[0360] Figure 38D is a simplified cross-sectional view showing an eyepiece waveguide with total thickness variation on both sides, according to yet another embodiment of the invention. The eyepiece waveguide shown in Figure 38D shares common elements with the eyepiece waveguide shown in Figure 38C, with the addition of etching of portions of variable thickness film 3812 and second variable thickness film 3820 to increase the diffraction efficiency of the diffractive structure defined by internal coupling grating 3814 and combined pupil expander 3816 with the remaining portions of variable thickness film 3812, and by second combined pupil expander 3826 with the remaining portions of variable thickness film 3820.

[0243]

[0361] FIG. 38E is a simplified cross-sectional view showing an eyepiece waveguide with total thickness variation on both sides, according to an alternative embodiment of the present invention. The eyepiece waveguide shown in FIG. 38E shares common elements with the eyepiece waveguide shown in FIG. 38D, with the combined pupil expander 3816 and the second combined pupil expander 3826 removed. In this embodiment, the diffractive properties associated with the combined pupil expander 3816 and the second combined pupil expander 3826 are implemented through the remaining portions of the variable thickness film 3812 and the remaining portions of the second variable thickness film 3820. In some embodiments, the internal coupling grating 3814 is also partially or completely removed in favor of diffractive structures etched or otherwise formed in the variable thickness film 3812.

[0244]

[0362] FIG. 38F is a simplified cross-sectional view showing an eyepiece waveguide with total thickness variation and an overcoat on both sides, according to one embodiment of the present invention. The eyepiece waveguide shown in FIG. 38F shares common elements with the eyepiece waveguide shown in FIG. 38B, with the addition of an overcoat 3830. The overcoat 3830 may be a material with a high refractive index compared to the refractive index of the variable thickness film 3812 and the second variable thickness film 3820. The overcoat 3830 may be deposited in a desired pattern, or deposited and then etched to form the desired pattern.

[0245]

[0363] The eyepiece waveguides shown in Figures 38A-38F can be utilized in an augmented reality device that includes a projector, projector optics optically coupled to the projector, and an eyepiece optically coupled to the projector optics and including one or more eyepiece waveguides. As shown in Figures 38A-38F, each eyepiece waveguide can implement a substrate structure characterized by a lateral dimension and one or more layers, at least one of which is characterized by an optical path length difference (e.g., thickness variation) as one or more functions of the lateral dimension. As shown in Figure 38A, the substrate structure can include a substrate and a layer of variable thickness coupled to the substrate, where the refractive indices of the substrate and the layer of variable thickness match or are within a given value. Multiple eyepiece waveguides can be stacked with the gradient of thickness variation of each eyepiece waveguide aligned to form an eyepiece. Thus, in some embodiments using three eyepiece waveguides, the variable thickness layers of each eyepiece waveguide are aligned such that the thickness of each of the variable thickness layers decreases along the same direction. Thus, in an eyepiece using three eyepiece waveguides similar to the one shown in FIG. 38A, the thickness of each variable thickness layer (i.e., variable thickness film 3812 in FIG. 38A) decreases along a direction from the internal coupling grating toward the combined pupil expander. Thus, the gradient of each of the variable thickness layers is aligned from the internal coupling grating of each eyepiece waveguide toward the combined pupil expander of each eyepiece waveguide.

[0246]

[0364] Figures 39A-F are simplified cross-sectional diagrams showing eyepiece waveguides with various thickness variations based on thin film TTV. These examples correspond to those discussed in connection with Figures 38A-F, but the thin film thickness increases from the region corresponding to the internal coupling grating to the region corresponding to the associated pupil expander. [02...

Claims

1. It is an augmented reality device, Projector and A projector optical system optically coupled to the aforementioned projector, An eyepiece optically coupled to the projector optical system, the eyepiece having an eyepiece waveguide including a portion of uniform thickness, a tapered portion, a thin portion, a diffraction internal coupling element, and a diffraction external coupling element, the eyepiece being characterized by a lateral dimension and an optical thickness of the eyepiece waveguide decreasing from the portion of uniform thickness to the thin portion of the eyepiece waveguide as a function of one or more of the lateral dimensions, the diffraction internal coupling element being positioned in close proximity to the portion of uniform thickness of the eyepiece waveguide, and the diffraction external coupling element being positioned in close proximity to the thin portion of the eyepiece waveguide, An augmented reality device equipped with [these features].

2. The aforementioned eyepiece lens, A second eyepiece waveguide characterized by a second lateral dimension and the optical thickness of the second eyepiece waveguide as a function of one or more of the second lateral dimensions, A third eyepiece waveguide characterized by a third lateral dimension and the optical thickness of the third eyepiece waveguide as a function of one or more of the third lateral dimensions, The augmented reality device according to claim 1, further comprising:

3. The augmented reality device according to claim 2, wherein the eyepiece waveguide, the second eyepiece waveguide, and the third eyepiece waveguide form the eyepiece.

4. The augmented reality device according to claim 3, wherein the eyepiece is a stacked structure including the eyepiece waveguide, the second eyepiece waveguide, and the third eyepiece waveguide.

5. The second projector, A second projector optical system optically coupled to the second projector, A second eyepiece optically coupled to the second projector optical system, comprising a fourth eyepiece waveguide characterized by a fourth lateral dimension and the optical thickness of the fourth eyepiece waveguide as a function of one or more of the fourth lateral dimensions, The augmented reality device according to claim 2, further comprising:

6. The second eyepiece, A fifth eyepiece waveguide characterized by a fifth lateral dimension and the optical thickness of the fifth eyepiece waveguide as a function of one or more of the fifth lateral dimensions, A sixth eyepiece waveguide characterized by a sixth lateral dimension and the optical thickness of the sixth eyepiece waveguide as a function of one or more of the sixth lateral dimensions, The augmented reality device according to claim 5, further comprising:

7. The diffraction external coupling element of the eyepiece waveguide comprises a combined pupil expander, The second eyepiece waveguide comprises a second combined pupil expander, The augmented reality device according to claim 2, wherein the third eyepiece waveguide comprises a third combined pupil expander, the thickness of the eyepiece waveguide varies across the combined pupil expander, the thickness of the second eyepiece waveguide varies across the second combined pupil expander, and the thickness of the third eyepiece waveguide varies across the third combined pupil expander.

8. The augmented reality device according to claim 1, wherein the projector, the projector optical system, and the eyepiece are mounted inside an augmented reality headset.

9. The augmented reality device according to claim 1, wherein the eyepiece waveguide is characterized by a change in refractive index as a function of one or more of the lateral dimensions.

10. The augmented reality device according to claim 1, wherein the eyepiece includes three eyepiece waveguides.

11. The augmented reality device according to claim 10, wherein the optical thickness of the eyepiece waveguide varies from a first value in a first region of each of the three eyepiece waveguides to a second value in a second region of each of the three eyepiece waveguides.

12. The augmented reality device according to claim 11, wherein the first region corresponds to an input coupling grid, the second region corresponds to a combined pupil expander, and the optical thickness of the eyepiece waveguide decreases from the first value to the second value.

13. The augmented reality device according to claim 10, wherein the optical thickness of each of the three eyepiece waveguides extends along a common direction.

14. The augmented reality device according to claim 10, wherein the optical thickness of each of the three eyepiece waveguides decreases along the lateral dimension of each of the three eyepiece waveguides, and the lateral dimensions of each of the three eyepiece waveguides are parallel.

15. It is an augmented reality device, Projector and A projector optical system optically coupled to the aforementioned projector, An eyepiece optically coupled to the aforementioned projector optical system, A first eyepiece waveguide characterized by its lateral dimension and first optical path length difference gradient, A second eyepiece waveguide characterized by the aforementioned lateral dimension and a second optical path length difference gradient aligned with the first optical path length difference gradient, An eyepiece equipped with, An augmented reality device equipped with [these features].

16. The augmented reality device according to claim 15, wherein the eyepiece further comprises a third eyepiece waveguide characterized by the lateral dimension and a third optical path length difference gradient aligned with the first optical path length difference gradient and the third optical path length difference gradient.

17. The augmented reality device according to claim 16, wherein the first eyepiece waveguide, the second eyepiece waveguide, and the third eyepiece waveguide are stacked together.

18. The augmented reality device according to claim 15, wherein the projector, the projector optical system, and the eyepiece are mounted inside an augmented reality headset.

19. The first eyepiece waveguide comprises a first combined pupil expander, and the thickness of the first eyepiece waveguide changes from a first portion of the first combined pupil expander to a second portion of the first combined pupil expander. The augmented reality device according to claim 15, wherein the second eyepiece waveguide comprises a second combined pupil expander, and the thickness of the second eyepiece waveguide varies from a first portion of the second combined pupil expander to a second portion of the second combined pupil expander.

20. The augmented reality device according to claim 15, wherein the first optical path length difference gradient is aligned with the second optical path length difference gradient.

21. The augmented reality device according to claim 15, wherein the first optical path length difference gradient corresponds to a certain direction, and the second optical path length difference gradient corresponds to the aforementioned direction.

22. It is an augmented reality device, Projector and A projector optical system optically coupled to the aforementioned projector, An eyepiece optically coupled to the projector optical system, comprising an eyepiece waveguide characterized by a lateral dimension and one or more layers, wherein at least one of the one or more layers includes a portion of uniform thickness, a tapered portion, a thin portion, a diffraction internal coupling element, and a diffraction external coupling element, the eyepiece waveguide being characterized by the lateral dimension and the optical thickness of the eyepiece waveguide decreasing from the portion of uniform thickness to the thin portion of the eyepiece waveguide as a function of one or more of the lateral dimensions, the diffraction internal coupling element being positioned in close proximity to the portion of uniform thickness of the eyepiece waveguide, and the diffraction external coupling element being positioned in close proximity to the thin portion of the eyepiece waveguide, An augmented reality device equipped with [these features].

23. The aforementioned eyepiece lens, circuit board and A layer of variable thickness bonded to the substrate, The augmented reality device according to claim 22, comprising:

24. The augmented reality device according to claim 23, wherein the refractive index of the substrate is substantially equal to the refractive index of the variable-thickness layer.

25. The aforementioned eyepiece lens, A second eyepiece waveguide characterized by a second lateral dimension and one or more second layers, wherein at least one of the one or more second layers is characterized by the optical thickness of the second eyepiece waveguide as a function of one or more of the second lateral dimensions, A third eyepiece waveguide characterized by a third lateral dimension and one or more third layers, wherein at least one of the one or more third layers is characterized by the optical thickness of the third eyepiece waveguide as a function of one or more of the third lateral dimensions, The augmented reality device according to claim 22, further comprising:

26. The augmented reality device according to claim 25, wherein the eyepiece waveguide, the second eyepiece waveguide, and the third eyepiece waveguide form the eyepiece.

27. The augmented reality device according to claim 26, wherein the eyepiece is a stacked structure including the eyepiece waveguide, the second eyepiece waveguide, and the third eyepiece waveguide.

28. The one or more layers, the one or more second layers, and the one or more third layers are characterized by thickness variations as a function of the one or more lateral dimensions. The augmented reality device according to claim 25, wherein the thickness variation of each of the one or more layers, the one or more second layers, and the one or more third layers decreases along the lateral dimensions of each of the eyepiece waveguide, the second eyepiece waveguide, and the third eyepiece waveguide, and the lateral dimensions are parallel.

29. The second projector, A second projector optical system optically coupled to the second projector, A second eyepiece optically coupled to the projector optical system, comprising a fourth eyepiece waveguide characterized by a fourth lateral dimension and one or more fourth layers, wherein at least one of the one or more fourth layers is characterized by the optical thickness of the fourth eyepiece waveguide as a function of one or more of the fourth lateral dimensions, The augmented reality device according to claim 25, further comprising:

30. The second eyepiece, A fifth eyepiece waveguide characterized by a fifth lateral dimension and one or more fifth layers, wherein at least one of the one or more fifth layers is characterized by the optical thickness of the fifth eyepiece waveguide as a function of one or more of the fifth lateral dimensions, A sixth eyepiece waveguide characterized by a sixth lateral dimension and one or more sixth layers, wherein at least one of the one or more sixth layers is characterized by the optical thickness of the sixth eyepiece waveguide as a function of one or more of the sixth lateral dimensions, The augmented reality device according to claim 29, further comprising:

31. The augmented reality device according to claim 22, wherein the projector, the projector optical system, and the eyepiece are mounted inside an augmented reality headset.

32. The eyepiece waveguide is equipped with a combined pupil expander, The second eyepiece waveguide comprises a second combined pupil expander, The augmented reality device according to claim 25, wherein the third eyepiece waveguide comprises a third combined pupil expander, one or more layers characterized by a thickness that varies across the combined pupil expander, one or more second layers characterized by a thickness that varies across the second combined pupil expander, and one or more third layers characterized by a thickness that varies across the third combined pupil expander.

33. The augmented reality device according to claim 22, wherein one or more layers are characterized by thickness variation as a function of one or more of the lateral dimensions.

34. The augmented reality device according to claim 33, wherein the thickness variation varies from a first value in a first region of the eyepiece waveguide to a second value in a second region of the eyepiece waveguide.

35. The augmented reality device according to claim 34, wherein the first region corresponds to an input coupling grid, the second region corresponds to a combined pupil expander, and the thickness variation decreases from the first value to the second value.

36. The augmented reality device according to claim 22, wherein one or more layers are characterized by a change in refractive index as a function of one or more of the lateral dimensions.

37. The augmented reality device according to claim 22, wherein the eyepiece waveguide includes a nanopattern.

38. The augmented reality device according to claim 37, wherein the nanopattern includes a polymer grid having a polymer refractive index smaller than the refractive index of the eyepiece.

39. The augmented reality device according to claim 38, wherein one or more layers have a thickness of less than 50 nm, less than 30 nm, or less than 10 nm.

40. The augmented reality device according to claim 38, wherein the nanopattern includes conformal or directional deposited structures formed on one or more layers or the eyepiece.

41. The augmented reality device according to claim 37, wherein the nanopattern includes a polymer grid having a polymer refractive index higher than the refractive index of the eyepiece.

42. The augmented reality device according to claim 41, wherein one or more layers have a thickness of less than 100 nm and contain at least one of ZrO2 or TiO2.

43. The augmented reality device according to claim 41, wherein the nanopattern includes an etched structure formed on one or more layers or the eyepiece.

44. The augmented reality device according to claim 37, wherein the nanopattern includes a binary grid, a blazed sawtooth grid, a blazed multi-stage grid, a blazed inclined grid, holes, or pillars.

45. It is an augmented reality device, Projector and A projector optical system optically coupled to the aforementioned projector, A substrate structure, A substrate having an incident surface and an injection surface on the opposite side, A first variable-thickness film bonded to the incident surface, A substrate structure including, An augmented reality device equipped with [these features].

46. The aforementioned substrate structure is A first combined pupil expander bonded to the first variable-thickness film, A second variable-thickness film bonded to the injection surface on the opposite side, An internal bonding grid bonded to the injection surface on the opposite side, A second combined pupil expander coupled to the opposite exit surface, The augmented reality device according to claim 45, further comprising:

47. The augmented reality device according to claim 46, wherein the second variable-thickness film is thicker adjacent to the internal bonding grid than adjacent to the second combined pupil expander.

48. The augmented reality device according to claim 46, wherein the variation in the thickness of the substrate is smaller than the variation in the thickness of the first variable-thickness film or the second variable-thickness film.

49. A first interlayer film disposed between the substrate and the first variable-thickness film, A second interlayer film is disposed between the substrate and the second variable-thickness film, The augmented reality device according to claim 46, further comprising:

50. The first interlayer has a refractive index smaller than the refractive index of the substrate and the refractive index of the first variable-thickness film. The augmented reality device according to claim 49, wherein the second interlayer has a refractive index smaller than the refractive index of the substrate and the refractive index of the second variable-thickness film.

51. It is an augmented reality device, Projector and A projector optical system optically coupled to the aforementioned projector, An eyepiece optically coupled to the aforementioned projector optical system, A first eyepiece waveguide characterized by a lateral dimension and a first variable-thickness film having a first thickness gradient, A second eyepiece waveguide characterized by the aforementioned lateral dimension and a second variable-thickness film having a second thickness gradient aligned with the first thickness gradient, An eyepiece equipped with, An augmented reality device equipped with [these features].

52. The augmented reality device according to claim 51, further comprising a third eyepiece waveguide characterized by the lateral dimension and a third variable-thickness film having a third thickness gradient aligned with the first and second thickness gradients.

53. The augmented reality device according to claim 52, wherein the first eyepiece waveguide, the second eyepiece waveguide, and the third eyepiece waveguide are stacked together.

54. The augmented reality device according to claim 51, wherein the projector, the projector optical system, and the eyepiece are mounted inside an augmented reality headset.

55. The first eyepiece waveguide comprises a first combined pupil expander, wherein the thickness of the first variable-thickness film varies from a first portion of the first combined pupil expander to a second portion of the first combined pupil expander. The augmented reality device according to claim 51, wherein the second eyepiece waveguide comprises a second combined pupil expander, and the thickness of the second variable-thickness film varies from a first portion of the second combined pupil expander to a second portion of the second combined pupil expander.

56. The augmented reality device according to claim 51, wherein the first thickness gradient is aligned with the second thickness gradient.

57. The augmented reality device according to claim 51, wherein the first thickness gradient corresponds to a certain direction, and the second thickness gradient corresponds to the aforementioned direction.

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