Method and system for hybrid surface-relief waveguide structures for augmented reality devices

Abstract

The augmented reality system includes a projector and projection optics coupled to the projector. The augmented reality system also includes an eyepiece waveguide including a hybrid diffractive structure including one or more first nanofeatures having a first material with a first refractive index and one or more second nanofeatures having a second material with a second refractive index.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 418,371, filed October 21, 2022, and U.S. Provisional Patent Application No. 63 / 425,866, filed November 16, 2022, the disclosures of which are incorporated herein by reference in their entireties for all purposes. [Background technology]

[0002]

[0002] Modern computer and display technology has 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 a manner that makes them appear or 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 input, while AR scenarios typically involve the presentation of digital or virtual image information as an extension to the visualization of the real world around the viewer.

[0003] Referring to FIG. 1, an augmented reality scene 10 is shown. A user of AR technology views 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 "see" "virtual content," such as a robotic figure 40 standing on the real-world platform 30 and a flying, cartoonish avatar character 50 that appears to be an anthropomorphic bumblebee. These elements 50, 40 are "virtual" in that they do not exist in the real world. Due to the complexity of the human visual perception system, it is challenging to create AR technology that facilitates a comfortable, natural-feeling, and rich presentation of virtual image elements among 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 [Problem to be solved by the invention]

[0005]

[0005] The present invention generally relates to methods and systems for projection display systems, including wearable displays. More particularly, embodiments of the present invention provide methods and systems that include an eyepiece waveguide layer with a hybrid diffractive structure. The present invention is applicable to a variety of applications in computer vision and image display systems.

[0006]

[0006] Guiding blue and red into a single active waveguide layer over a small or large field of view using a single input coupler pupil on one side of the active waveguide layer presents the challenge of diffusing all wavelengths of light (e.g., blue at 455 nm and red at 630 nm) with the desired uniformity and efficiency and exiting the combined output coupler. If the diffractive features are efficient (height, refractive index, tilt angle), more light may be outcoupled relative to the initial diffusion. Conversely, if the diffractive features become less efficient for outcoupling, the diffusion and uniformity of light at the combiner is improved, but the light output coupling towards the user may be reduced. [Means for solving the problem]

[0007]

[0007] Embodiments of the present invention relate to a unique structural layout that uses low and high refractive index gratings in different areas of the waveguide relative to the light path and light guide from the incoupling diffractive structure to the output diffractive structure, which may be a composite pupil dilator that implements orthogonal pupil dilator and exit pupil dilator functions. Such architectures are possible using imprint or photolithography in conjunction with deposition and / or etching processes. The methods and systems described herein offer the competitive advantage of a simple process for creating such hybrid diffractive structures, as well as the ease of varying refractive index gradations over large surfaces when combined with etching (RIE, ICP) and / or deposition (evaporation / sputtering) processes.

[0008]

[0008] The present invention provides many advantages over conventional techniques. For example, embodiments of the present invention provide methods and systems that can improve the quality of virtual content, including image clarity. These and other embodiments of the present invention, along with many of their advantages and features, are described in detail below in conjunction with the text and corresponding figures. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 illustrates a user's view of an augmented reality (AR) device. [Figure 2] FIG. 1 illustrates a conventional display system for simulating a three-dimensional image of a user. [Figure 3A] FIG. 1 illustrates the relationship between the radius of curvature and the focal radius. [Figure 3B] FIG. 1 illustrates the relationship between the radius of curvature and the focal radius. [Figure 3C] FIG. 1 illustrates the relationship between the radius of curvature and the focal radius. [Figure 4A] FIG. 1 illustrates a representation of the accommodation-vergence response of the human visual system. [Figure 4B] 1A-1C illustrate 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. 10 illustrates another example of a top-view representation of a user viewing content through a display system. [Figure 5] 1A-1C illustrate aspects of a technique for simulating three-dimensional images by modifying wavefront divergence. [Figure 6] FIG. 1 illustrates one embodiment of a waveguide stack for outputting image information to a user. [Figure 7] FIG. 10 illustrates an example of an emitted beam output by a waveguide. [Figure 8] FIG. 1 illustrates an example of a stacked waveguide assembly in which each depth plane contains an image formed using multiple different component colors. [Figure 9A] FIG. 1 is a cross-sectional side view of one embodiment of a set of stacked waveguides, each including an incoupling optical element. [Figure 9B] FIG. 9B is a perspective view of one embodiment of one or more stacked waveguides of FIG. 9A. [Figure 9C] FIG. 9C is a top view of one embodiment of one or more stacked waveguides of FIGS. 9A and 9B. [Figure 9D] FIG. 1 illustrates an example of a wearable display system. [Figure 10] 1 is a side view of a projector assembly including a polarizing beam splitter with a light source injecting light onto one side of the beam splitter and projection optics receiving light from another side of the beam splitter. [Figure 11A] 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 an in-coupling optical element for coupling light from the optical system into the waveguide, and an out-coupling optical element 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 incoupling and outcoupling optical elements and a light source disposed thereon. The top view also shows an orthogonal pupil dilator. [Figure 11C] FIG. 11B is a side view of the augmented reality display system of FIG. 11A with a shared polarizer / analyzer and a polarization-based spatial light modulator (e.g., liquid crystal on silicon SLM). [Figure 11D] FIG. 1 illustrates an example of a waveguide having a composite 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 multicolor 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 the image of the spatial light modulator into the eye, and a stack of waveguides, where different waveguides include different color-selective incoupling optical elements as well as outcoupling optical elements. [Figure 12B] 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 movable mirrors (e.g., Digital Light Processing (DLP™) technology) and a light dump. [Figure 12C] 12C is a top view of a portion of the augmented reality display system of FIG. 12B, showing a schematic lateral arrangement of one of the incoupling optical elements and light dumps, and the 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 being laterally displaced with respect to one another, arranged to direct light to each incoupling optical element 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 embodiment shown in FIG. 13A showing the laterally displaced incoupling optical element and light source, as well as the optical system and spatial light modulator. [Figure 13C] FIG. 13C is a top view of the augmented reality display system shown in FIGS. 13A and 13B, showing one or more laterally displaced incoupling 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 incoupling optical elements, and the incoupling optical elements are laterally displaced relative to each other (in this example the lateral displacement occurs in the z-direction). [Figure 14B] 14B is a top view of the display system shown in FIG. 14A showing laterally displaced incoupling optical elements and light sources. [Figure 14C] 14C is an orthogonal side view of the display system shown in FIGS. 14A and 14B. FIG. [Figure 15] 14A-14C are top views of an augmented reality display system including a set of stacked waveguides, where different waveguides include different incoupling optical elements, where the light sources and incoupling optical elements are arranged in a different configuration than that shown in FIGS. [Figure 16A] FIG. 1 is a side view of an augmented reality display system including groups of incoupling optical elements that are laterally displaced relative to one another, each group including one or more color-selective incoupling 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 by a reflective surface that can couple light guided in a portion of the waveguide from a portion of the waveguide closer to the light source to an optics system toward a spatial light modulator, in this example the optics system and the light source are shown located on the same side of the waveguide. [Figure 18]1 is a side view of an augmented reality display system including a waveguide for receiving light from a light source and directing the light guided in the waveguide to an optical system and toward a spatial light modulator. The display system further includes a waveguide for receiving light from the spatial light modulator where it passes back through the optical system. The waveguide includes a reflective surface for outcoupling light. The waveguide also includes a reflective surface for incoupling light therein. In this example, the optical system and the light source are shown located on the same side of the waveguide. [Figure 19] 1 is a side view of an augmented reality display system including an adaptive optical element and a variable-focus optical element. A first variable optical element between the stack of waveguides and the eye can vary the divergence and collimation of light coupled from the waveguides and directed to the eye to change 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 correction, such as refractive correction, for users with myopia, hyperopia, astigmatism, etc. [Figure 20A] 1 is a side view of an augmented reality display system including a color filter array, where one or more laterally displaced incoupling optical elements are positioned on different waveguides, and laterally displaced color filters are aligned with each incoupling optical element. [Figure 20B] FIG. 20B illustrates the augmented reality display system of FIG. 20A with an analyzer positioned between the optical system and the spatial light modulator. [Figure 20C] FIG. 26 shows 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, showing a schematic diagram of a laterally displaced light source above a color filter array and a corresponding laterally displaced incoupling optical element. [Figure 20E] FIG. 26B illustrates how a deflection-based spatial light modulator directs light from corresponding incoupling optical elements onto a mask surrounding the filters in the filter array of the augmented reality display system of FIG. 20D. [Figure 20F] FIG. 1 is a side view of an augmented reality display system including a cover glass positioned on the user side of a stack of waveguides and a light source positioned 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 positioned on the world side of a stack of waveguides and a light source positioned 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 equipped with a light recycler configured to recycle light, such as light of any 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 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 with additional retarders and polarizers configured to reduce reflections that can produce ghost images. [Figure 23C] FIG. 23C is a side view of an augmented reality display system as shown in FIGS. 23A and 23B having a retarder and polarizer configured to reduce reflections that can produce ghost images. [Figure 24] FIG. 1 is a side view of an augmented reality display system that utilizes an angled surface, such as an angled surface on a cover glass, to direct reflections away from the user's eyes, potentially reducing ghost reflections. [Figure 25] FIG. 25 illustrates an embodiment of the system of FIG. 24 in which a beveled surface on the cover glass is configured to direct reflections toward a light dump that absorbs the light. [Figure 26A] FIG. 2 is a simplified cross-sectional view illustrating an eyepiece waveguide, according to one embodiment of the present invention. [Figure 26B] FIG. 26B is a simplified k-space diagram showing the field of view, ICG, and CPE grating vectors of the eyepiece waveguide shown in FIG. 26A. [Figure 26C] FIG. 26B is a simplified plan view of the user side of the eyepiece waveguide shown in FIG. 26A. [Figure 26D] FIG. 26B is a simplified plan view of the world side of the eyepiece waveguide shown in FIG. 26A. [Figure 27A] FIG. 1 is a simplified schematic diagram illustrating an example of an eyepiece waveguide including a hybrid discrete diffractive structure, according to an embodiment of the present invention. [Figure 27B] 1A-1C are simplified schematic diagrams illustrating a process for forming hybrid discrete diffractive structures according to one embodiment of the present invention. [Figure 27C] FIG. 1 is a simplified schematic diagram illustrating the variation of grating parameters across an eyepiece waveguide, according to one embodiment of the present invention. [Figure 27D] 1 is a simplified cross-sectional view illustrating a hybrid discrete diffractive structure according to one embodiment of the present invention. [Figure 27E] FIG. 27D is a plot of eyebox efficiency across the field of view for an eyepiece using the hybrid discrete diffractive structure shown in FIG. 27D. [Figure 27F] 2 is a simplified cross-sectional view illustrating a hybrid discrete diffractive structure formed on a low refractive index coating according to one embodiment of the present invention. [Figure 27G] FIG. 27F is a plot of eyebox efficiency across the field of view for an eyepiece using the hybrid discrete diffractive structure shown in FIG. 27F. [Figure 28A] FIG. 2 is a simplified cross-sectional view illustrating an eyepiece waveguide, according to one embodiment of the present invention. [Figure 28B] 28B is a plot showing the refractive index zones of the eyepiece waveguide shown in FIG. 28A. [Figure 28C] FIG. 28B is a plot of eyebox efficiency across the field of view for the eyepiece shown in FIG. 28A. [Figure 28D] FIG. 28B is a plot of eyebox efficiency across the field of view for the eyepiece shown in FIG. 28A. [Figure 28E] FIG. 28B is a plot of eyebox efficiency across the field of view for the eyepiece shown in FIG. 28A. [Figure 29A] FIG. 10 is a simplified cross-sectional view illustrating an eyepiece waveguide according to another embodiment of the present invention. [Figure 29B] 29B is a plot showing the refractive index zones of the eyepiece waveguide shown in FIG. 29A. [Figure 29C] 29B is a plot of eyebox efficiency across the field of view for the eyepiece shown in FIG. 29A. [Figure 29D] 29B is a plot of eyebox efficiency across the field of view for the eyepiece shown in FIG. 29A. [Figure 29E] 29B is a plot of eyebox efficiency across the field of view for the eyepiece shown in FIG. 29A. [Figure 30A] FIG. 2 is a simplified cross-sectional view illustrating an eyepiece waveguide including a hybrid CPE, according to one embodiment of the present invention. [Figure 30B] 30B is a plot showing the refractive index of the zones of the eyepiece waveguide shown in FIG. 30A. [Figure 30C] FIG. 30B is a plot of eyebox efficiency across the field of view for the eyepiece shown in FIG. 30A. [Figure 30D] FIG. 30B is a plot of eyebox efficiency across the field of view for the eyepiece shown in FIG. 30A. [Figure 30E] FIG. 30B is a plot of eyebox efficiency across the field of view for the eyepiece shown in FIG. 30A. [Figure 31A] FIG. 2 is a simplified cross-sectional view illustrating an eyepiece waveguide, according to one embodiment of the present invention. [Figure 31B] FIG. 31B is a plot of eyebox efficiency across the field of view for the eyepiece shown in FIG. 31A. [Figure 31C] FIG. 31B is a plot of eyebox efficiency across the field of view for the eyepiece shown in FIG. 31A. [Figure 31D] FIG. 31B is a plot of eyebox efficiency across the field of view for the eyepiece shown in FIG. 31A. [Figure 32A] FIG. 2 is a simplified cross-sectional view illustrating an eyepiece waveguide, according to one embodiment of the present invention. [Figure 32B] FIG. 32B is a plot of eyebox efficiency across the field of view for the eyepiece shown in FIG. 32A. [Figure 32C] FIG. 32B is a plot of eyebox efficiency across the field of view for the eyepiece shown in FIG. 32A. [Figure 32D] FIG. 32B is a plot of eyebox efficiency across the field of view for the eyepiece shown in FIG. 32A. [Figure 33A] 1A-1C are simplified cross-sectional views illustrating an eyepiece waveguide fabrication process using a shadow mask, according to one embodiment of the present invention. [Figure 33B] 1A-1C are simplified cross-sectional views illustrating an eyepiece waveguide fabrication process using an etching process, according to one embodiment of the present invention. [Figure 33C] 10A-10C are simplified cross-sectional views illustrating another eyepiece waveguide fabrication process using an etching process, in accordance with an embodiment of the present invention. [Figure 33D] 1A-1C are simplified cross-sectional views illustrating an eyepiece waveguide fabrication process using an etching process and a tapered substrate, according to one embodiment of the present invention. [Figure 34A] 1A-1C are simplified cross-sectional views illustrating a double-sided eyepiece waveguide fabrication process using a shadow mask, according to one embodiment of the present invention. [Figure 34B] 1A-1C are simplified cross-sectional views illustrating a double-sided eyepiece waveguide fabrication process using an etching process, according to one embodiment of the present invention. [Figure 34C] 1A-1C are simplified cross-sectional views illustrating a double-sided eyepiece waveguide fabrication process using an etching process and a tapered substrate, according to one embodiment of the present invention. [Figure 35A] 1A-1C are simplified cross-sectional views illustrating an eyepiece waveguide fabrication process to form a blazed grating, according to one embodiment of the present invention. [Figure 35B]1A-1D are simplified cross-sectional views illustrating an eyepiece waveguide fabrication process for a coated substrate according to one embodiment of the present invention. [Figure 35C] 10A-10C are simplified cross-sectional diagrams illustrating an eyepiece waveguide manufacturing process for a coated substrate according to another embodiment of the present invention. [Figure 35D] 1A-1D are simplified cross-sectional views illustrating an eyepiece waveguide fabrication process for a multi-layer coated substrate according to one embodiment of the present invention. [Figure 35E] 1A-1C are simplified cross-sectional views illustrating an eyepiece waveguide fabrication process for forming hybrid discrete diffractive structures according to one embodiment of the present invention. [Figure 36A] 1A-1C are simplified cross-sectional views illustrating an eyepiece waveguide fabrication process using a shadow mask, according to one embodiment of the present invention. [Figure 36B] 10A-10C are simplified cross-sectional diagrams illustrating an eyepiece waveguide fabrication process using a shadow mask according to another embodiment of the present invention. [Figure 37A] FIG. 2 is a simplified cross-sectional view illustrating an eyepiece waveguide including a planarization layer, according to one embodiment of the present invention. [Figure 37B] FIG. 10 is a simplified cross-sectional view illustrating an eyepiece waveguide including a planarization layer according to another embodiment of the present invention. [Figure 37C] FIG. 10 is a simplified cross-sectional view illustrating an eyepiece waveguide including an encapsulation layer according to another embodiment of the present invention. [Figure 38] 1 is a cross-sectional view illustrating a hybrid, multi-index architecture having differently shaped diffractive structures made of distinct refractive indices / materials according to one embodiment of the present invention. [Figure 39A] FIG. 1 is a cross-sectional view of a double-sided eyepiece waveguide, according to one embodiment of the present invention. [Figure 39B] FIG. 1 is a cross-sectional view of a double-sided eyepiece waveguide with a hybrid discrete diffractive structure, according to one embodiment of the present invention. [Figure 39C] FIG. 10 is a cross-sectional view of a double-sided eyepiece waveguide having a hybrid discrete diffractive structure according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010]

[0103] 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.

[0011]

[0104] FIG. 2 illustrates a conventional display system for simulating a three-dimensional image for a user. It will be appreciated that a 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, forming an image of the object at a different location on each eye's retina. This is sometimes referred to as binocular disparity and may be exploited by the human visual system to provide depth perception. Conventional display systems simulate binocular disparity by displaying two different images 190, 200, each with a slightly different view of the same virtual object, for each eye 210a, 210b, which correspond to the view of the virtual object that each eye would see if the virtual object were a real object at a desired depth. These images provide binocular cues that the user's visual system may interpret to derive depth perception.

[0012]

[0105] Continuing with reference to FIG. 2 , the images 190 and 200 are spaced a distance 230 along the z-axis from the eyes 210a and 210b. The z-axis is parallel to the viewer's optical axis for a viewer's eyes fixed on an object at optical infinity directly in front of the viewer. The images 190 and 200 are flat and at a fixed distance from the eyes 210a and 210b. Based on slightly different views of the virtual object in the images presented to the eyes 210a and 210b, the eyes may naturally rotate to maintain single binocular vision so that the image of the object falls on a corresponding point on each eye's retina. This rotation may cause the line of sight of each eye 210a and 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 and 210b and providing binocular cues that the human visual system interprets to provide depth perception.

[0013]

[0106] However, creating a realistic and comfortable depth perception is difficult. It is understood that light from objects at different distances from the eye has wavefronts with different amounts of divergence. Figures 3A-3C illustrate the relationship between distance and divergence of a light ray. The distances between the object and the eye 210 are denoted R1, R2, and R3, in order of decreasing distance. As shown in Figures 3A-3C, 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, the light field generated by a point (an object or portion 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. While Figures 3A-3C and other figures herein show only a single eye 210 for clarity, discussions regarding the eye 210 may apply to both eyes 210a and 210b.

[0014]

[0107] Continuing with reference to FIGS. 3A-3C , light from an object that a viewer's eyes are viewing 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 accommodative cue, causing the eye's lens to change shape until a focused image is formed on the retina. For example, the accommodative cue may pull 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, thus changing the shape of the eye's lens until retinal blur of the viewed object is eliminated or minimized, thereby forming a focused image of the viewed object on the eye's retina (e.g., the fovea). The process by which the eye's lens changes shape is sometimes called accommodation, and the shape of the eye's lens required to form a focused image of the viewed object on the eye's retina (e.g., fovea) is sometimes called the state of accommodation.

[0015]

[0108] Referring now to FIG. 4A, a representation of the accommodation-vergence response of the human visual system is shown. Eye movement while gazing at an object causes the eye to receive light from the object, which forms an image on each of the eye's retinas. The presence of retinal blur in the image formed on the retina may provide a cue for accommodation, and the relative position of the image on the retina may provide a cue for convergence. The accommodation cue causes accommodation, resulting in each of the eye's lenses adopting a specific accommodation state that forms a focused image of the object on the eye's retina (e.g., the fovea). Meanwhile, the convergence cue causes vergence movement (eye rotation) so that the images formed on each retina of each eye are at corresponding retinal points that maintain single binocular vision. At these positions, the eyes may be said to have adopted a specific convergence state. Continuing to refer to FIG. 4A, accommodation may be understood as the process by which the eye achieves a specific accommodation state, and convergence may be understood as the process by which the eye achieves a specific convergence state. As shown in FIG. 4A, when a user gazes at a different object, the accommodation and convergence states of the eyes may change. For example, accommodation state may change when the user gazes at a new object at a different depth on the z-axis.

[0016]

[0109] 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 convergence and accommodation. As described above, the convergence movement of the two eyes relative to each other (e.g., rotating the eyes so that the pupils move toward or away from each other and converge the lines of sight to gaze at an object) is closely related to the 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 a different distance automatically results in a corresponding change in convergence for the same distance, under a relationship known as the "accommodation-vergence reflex." Similarly, changes in convergence induce a corresponding change in lens shape under normal conditions.

[0017]

[0110] 4B, an example of different accommodation and convergence states of the eyes is shown. The pair of eyes 222a gazes at an object at optical infinity, while the pair of eyes 222b gazes at an object 221 at a distance 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 on the object 221. Furthermore, as exemplified by the different shapes of the lenses 220a and 220b, the accommodation states of the pair of eyes 222a and 222b are also different.

[0018]

[0111] Unfortunately, many users of conventional "3-D" display systems find such systems uncomfortable or may not perceive depth at all due to the mismatch between accommodation and convergence in these displays. As discussed above, many stereoscopic or "3-D" display systems display a scene by providing slightly different images to each eye. Such systems are uncomfortable for many viewers because, among other things, they simply provide different presentations of the scene, causing changes in the eyes' convergence state without a corresponding change in the eyes' accommodation state. Rather, images are presented by displays at a fixed distance from the eyes so that the eyes view all image information in a single accommodation state. This arrangement acts to counter the "accommodation-vergence reflex" by causing changes in convergence state without a corresponding change in accommodation state. This mismatch is thought to cause discomfort to the viewer. Display systems that provide good match between accommodation and convergence can create realistic and comfortable simulations of three-dimensional images.

[0019]

[0112] Without being limited by theory, it is believed that the human eye can typically interpret a finite number of depth planes to provide depth perception. As a result, 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 may provide both vergence cues and accommodation matching cues, thereby providing physiologically correct accommodation-vergence matching.

[0020]

[0113] 4B, two depth planes 240 corresponding to different distances in space from the eyes 210a, 210b are shown. For a given depth plane 240, convergence cues may be provided by displaying images from different perspectives for each eye 210a, 210b, as appropriate. Furthermore, for a given depth plane 240, the light forming the image provided to each eye 210a, 210b may have a wavefront divergence corresponding to the light field generated by points at that depth plane 240.

[0021]

[0114] In the illustrated embodiment, the distance along the z-axis of depth plane 240 containing point 221 is 1 m. As used herein, 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, a depth plane 240 located at a depth of 1 m corresponds to a distance of 1 m from the exit pupil of the user's eye on the eye's optical axis, where the eye is directed toward optical infinity. As an approximation, the depth or distance along the z-axis may be measured by adding the value of the distance between the device and the exit pupil of the user's eye to the display (e.g., the surface of the waveguide) in front of the user's eye. That value may be referred to as eye relief and corresponds to the distance between the exit pupil of the user's eye and the display in front of the eye worn by the user. In practice, the eye relief value may be a normalized value commonly used for all viewers. For example, the eye relief 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.

[0022]

[0115] 4C and 4D, examples of matched and mismatched accommodation-vergence distances 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 point 15 on the depth plane 240. In addition, the image can be formed by light having a wavefront curvature corresponding to the real object in the depth plane 240. This causes the eyes 210a, 210b to assume an accommodation state in which the image is focused on the retinas of the eyes. Thus, the user can perceive the virtual object as being at point 15 on the depth plane 240.

[0023]

[0116] It will be appreciated that each of the accommodation and convergence states of the eyes 210 a, 210 b is associated with a particular distance on the z-axis. For example, an object at a particular distance from the eyes 210 a, 210 b will cause the eyes to assume a particular accommodation state based on the object's distance. The distance associated with a particular accommodation state may be referred to as the accommodation distance Ad. Similarly, there is a particular convergence distance Vd, i.e., position relative to one another, associated with the eyes in a particular convergence state. When the accommodation distance and the convergence distance match, the relationship between accommodation and convergence may be said to be physiologically correct. This is believed to be the most comfortable scenario for the viewer.

[0024]

[0117] However, in a stereoscopic display, the accommodation distance and the convergence 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 particular accommodation state focused on points 15a, 15b on that depth plane. However, the images displayed to the eyes 210a, 210b may provide convergence cues that cause the eyes 210a, 210b to converge to points 15 that cannot be 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, while the convergence distance corresponds to a large distance from the exit pupils of the eyes 210a, 210b to point 15. The accommodation distance is different from the convergence distance. As a result, an accommodation-vergence mismatch exists. 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 may be characterized using diopters.

[0025]

[0118] It will be appreciated that in some embodiments, a reference point other than the exit pupil of the eye 210 a, 210 b may be used to determine the distance for determining accommodation-vergence discrepancy, so long as the same reference point is used 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.

[0026]

[0119] 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 images to a viewer with an accommodation-vergence mismatch of about 0.5 diopters or less. In some other embodiments, the accommodation-vergence mismatch of images provided by the display system is about 0.33 diopters or less. In still other embodiments, the accommodation-vergence mismatch of images provided by the display system is about 0.25 diopters or less, including about 0.1 diopters or less.

[0027]

[0120] FIG. 5 illustrates aspects of an approach for simulating a three-dimensional image by modifying 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 may output light 650 with a prescribed amount of wavefront divergence corresponding 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. Additionally, it is shown that the user's other eye may be provided with image information from a similar waveguide.

[0028]

[0121] In some embodiments, a single waveguide may be configured to output light having 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 to output light in different wavelength ranges. As used herein, it will be understood that a depth plane may follow the contour of a flat or curved surface. In some embodiments, for advantageous simplicity, a depth plane may follow the contour of a flat surface.

[0029]

[0122] 6 shows an example of a waveguide stack for outputting image information to a user. Display system 250 includes a stack of waveguides, or stack waveguide assembly 260, that can be utilized to provide three-dimensional perception to the eye / brain using waveguides 270, 280, 290, 300, and 310. It will be appreciated that in some embodiments, display system 250 can be considered a light field display. Waveguide assembly 260 can also be referred to as an eyepiece.

[0030]

[0123] In some embodiments, display system 250 may be configured to provide a substantially continuous cue for vergence and multiple discrete cues for accommodation. Vergence cues may be provided by displaying different images to each of the user's eyes, and accommodation cues may be provided by outputting light forming images with selectable discrete amounts of wavefront divergence. Stated another way, display system 250 may be configured to output light having 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 waveguides 270, 280, 290, 300, 310.

[0031]

[0124] Continuing with reference to FIG. 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 ray divergence. Each waveguide level may be associated with a particular depth plane and configured to output image information corresponding to that depth plane. The image injection devices 360, 370, 380, 390, 400 may act as light sources for the waveguides and may be utilized to inject 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 toward the eye 210, as described herein. Light is emitted from output faces 410, 420, 430, 440, 450 of the image injection devices 360, 370, 380, 390, 400 and injected into corresponding input faces 460, 470, 480, 490, 500 of the waveguides 270, 280, 290, 300, 310. In some embodiments, each of the input faces 460, 470, 480, 490, 500 may be an edge of the corresponding waveguide or may be a portion of a major 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 injected into each waveguide to output a full field of cloned collimated beams directed toward 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 injection devices 360, 370, 380, 390, 400 may be associated with one or more (e.g., three) of the waveguides 270, 280, 290, 300, 310 to inject light.

[0032]

[0125] In some embodiments, image injection devices 360, 370, 380, 390, 400 are individual displays that each generate image information for injection into a respective waveguide 270, 280, 290, 300, 310. In some other embodiments, image injection devices 360, 370, 380, 390, 400 are the output of a single multiplexed display that may, for example, pass image information via one or more optical conduits (such as fiber optic cables) to each of image injection devices 360, 370, 380, 390, 400. It is understood that the image information provided by image injection devices 360, 370, 380, 390, 400 may include light of different wavelengths or colors (e.g., different component colors, as described herein).

[0033]

[0126] In some embodiments, light injected into the waveguides 270, 280, 290, 300, 310 is provided by a light projector system 520 that includes a light module 530, which may include light emitters such as light emitting diodes (LEDs). Light from the light module 530 may be directed via a beam splitter 550 to and modified by a light modulator 540, such as, for example, a spatial light modulator. The light modulator 540 may be configured to change 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 understood that image injection devices 360, 370, 380, 390, 400 are shown schematically, 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 associated ones of waveguides 270, 280, 290, 300, 310. In some embodiments, the waveguides of waveguide assembly 260 may act as ideal lenses, 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.

[0034]

[0127] In some embodiments, the display system 250 may be a scanning fiber display comprising 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 into 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 waveguides 270, 280, 290, 300, 310, for example, to redirect light exiting the scanning fiber into the one or more waveguides 270, 280, 290, 300, 310.

[0035]

[0128] Controller 560 controls the operation of one or more of stacked waveguide assembly 260, including the operation of image injection devices 360, 370, 380, 390, 400, light source 530, and light modulator 540. In some embodiments, controller 560 is part of local data processing module 140. Controller 560 includes programming (e.g., instructions in a non-transitory medium) that coordinates the timing and provision of image information to 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 distribution system connected by a wired or wireless communication channel. In some embodiments, controller 560 may be part of processing module 140 or 150 (FIG. 9D).

[0036]

[0129] Continuing with reference to FIG. 6 , the waveguides 270, 280, 290, 300, and 310 may be configured to propagate light within each respective waveguide by total internal reflection (TIR). The waveguides 270, 280, 290, 300, and 310 may each be planar or have another (e.g., curved) shape, with top and bottom major surfaces and edges extending between the top and bottom major surfaces. In the illustrated configuration, the waveguides 270, 280, 290, 300, and 310 may each include outcoupling optical elements 570, 580, 590, 600, and 610 configured to extract light from the respective waveguide by redirecting light propagating within the waveguide from the waveguide to output image information to the eye 210. While referred to throughout this specification as an “outcoupling optical element,” the outcoupling optical element need not be an optical element and may be a non-optical element. The extracted light may also be referred to as outcoupling light, and the outcoupling optical element may also be referred to as a light extraction optical element. The extracted light beam may be output by the waveguide where light propagating within the waveguide strikes the light extraction optical element. The outcoupling optical elements 570, 580, 590, 600, 610 may be, for example, gratings including diffractive optical features, as described 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 illustration, 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 described 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.

[0037]

[0130] Continuing with reference to FIG. 6 , as described 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 upper waveguide 280 may be configured to deliver collimated light that passes through a first lens 350 (e.g., a negative lens) before reaching the eye 210, and such first lens 350 may be configured to create a slightly convex wavefront curvature such that the eye / brain interprets light coming from the next upper waveguide 280 as coming from a first focal plane closer inward from optical infinity toward the eye 210. Similarly, the third upper waveguide 290 may have its output light pass through both the first lens 350 and the second lens 340 before reaching the eye 210, and 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 so 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 upper waveguide 280.

[0038]

[0131] 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 it and the eye for a total focal power representing the focal plane closest to the person. To compensate for the stack of lenses 320, 330, 340, 350 when viewing / interpreting light coming from the world 510 on the other side of the stack waveguide assembly 260, a compensating lens layer 620 may be placed on top of the stack to compensate for the total refractive power of the lens stacks 320, 330, 340, 350 below. Such a configuration provides as many perceived focal planes as there are available waveguide / lens pairings. Both the outcoupling optical elements 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.

[0039]

[0132] In some embodiments, two or more of the waveguides 270, 280, 290, 300, 310 may 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, one set per depth plane, to output images set at the same one or more depth planes. This may provide advantages for forming tiled images to provide an extended field of view at those depth planes.

[0040]

[0133] Continuing with reference to FIG. 6 , outcoupling optical elements 570, 580, 590, 600, 610 may be configured to both redirect light from their respective waveguides and output this light with an appropriate amount of divergence or collimation for a particular depth plane associated with the waveguide. As a result, waveguides with different associated depth planes may have different configurations of outcoupling optical elements 570, 580, 590, 600, 610 that output light with different amounts of divergence depending on the associated depth plane. In some embodiments, light extraction optical elements 570, 580, 590, 600, 610 may be volume or surface features that can be configured to output light at a particular angle. For example, light extraction optical elements 570, 580, 590, 600, 610 may be volume holograms, surface holograms, and / or diffraction gratings. In some embodiments, features 320, 330, 340, 350 may not be lenses; rather, they may simply be spacers (eg, cladding layers and / or structures for forming air gaps).

[0041]

[0134] In some embodiments, the outcoupling optical elements 570, 580, 590, 600, 610 are diffractive features that form a diffraction pattern or "diffractive optical element" (also referred to herein as a "DOE"). Preferably, the DOE has a sufficiently low diffraction efficiency so that only a portion of the light in the beam is deflected toward the eye 210 at each intersection of the DOE, while the remainder continues traveling 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 radiation toward the eye 210 due to the bouncing of this particular collimated beam within the waveguide.

[0042]

[0135] 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 comprise a layer of polymer-dispersed liquid crystal, in which microdroplets comprise 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).

[0043]

[0136] 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 the tissue surrounding the eye 210, for example, to detect user input and / or monitor the 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 processing modules 140 and / or 150, which may process image information from the camera assembly 630. In some embodiments, one camera assembly 630 may be utilized per eye to monitor the eyes separately.

[0044]

[0137] Referring now to FIG. 7 , an example of an exit beam output by a waveguide is shown. While one waveguide is shown, it will be understood that if the waveguide assembly 260 includes multiple waveguides, the other waveguides in the waveguide assembly 260 ( FIG. 6 ) may function similarly. Light 640 is injected into the waveguide 270 at the input face 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 exit beam 650. While the exit beams 650 are shown as substantially parallel, they may also be redirected to propagate to the eye 210 at any angle (e.g., to form a diverging exit beam), depending on the depth plane associated with the waveguide 270, as described herein. It will be understood that a substantially parallel exit beam may refer to a waveguide having 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 divergent exit beam pattern, which requires the eye 210 to adjust to closer distances to focus on the retina, and which the brain will interpret as light from a distance closer to the eye 210 than optical infinity.

[0045]

[0138] In some embodiments, a full color image may be formed at each depth plane by overlaying images of each of the component colors, for example, three or more component colors.

[0046]

[0139] FIG. 8 illustrates an example of a stacked waveguide assembly in which each depth plane includes an image formed using multiple different component colors. The illustrated embodiment shows depth planes 240a-240f, although more or fewer depth planes are contemplated. Each depth plane may 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 illustration shows different depth planes with different numbers of diopters (dpt) following the letters G, R, and B. By way of example, the number following each of these letters indicates a diopter (1 / m), i.e., the reciprocal of the distance of the depth plane from the viewer, and each box in the illustration represents a separate component color image. In some embodiments, the exact placement of the different component color depth planes may vary to account for differences in the eye's focusing of different wavelengths of light. For example, different component color images for a given depth plane may be positioned on depth planes corresponding to different distances from the user. Such an arrangement may improve visual acuity and user comfort and / or may reduce chromatic aberration.

[0047]

[0140] In some embodiments, light for 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 a separate waveguide, and three waveguides may be provided per depth plane, with three component color images provided per depth plane. While the waveguides associated with each depth plane are shown adjacent to each other in this diagram for ease of illustration, it will be understood 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.

[0048]

[0141] 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 in addition to or replace one or more of red, green, or blue.

[0049]

[0142] It will be understood that throughout this disclosure, references to a given color of light are understood to encompass light of one or more wavelengths within the wavelength range of light perceived by a viewer as being 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.

[0050]

[0143] In some embodiments, light source 530 (FIG. 6) may be configured to emit light at one or more wavelengths outside the range of a viewer's visual perception, such as infrared and / or ultraviolet wavelengths. Additionally, waveguide incoupling, outcoupling, and other light redirecting structures of display 250 may be configured to direct and emit this light from the display toward eye 210, for example, for imaging and / or user stimulation applications.

[0051]

[0144] 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 incouple the light into its corresponding waveguide. Although referred to herein as “incoupling optical elements,” incoupling optical elements need not be optical elements and 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 at one or more different wavelengths or in one or more different wavelength ranges. It will be appreciated that stack 660 may correspond to stack 260 (FIG. 6), and the illustrated waveguides of stack 660 may correspond to portions of waveguides 270, 280, 290, 300, 310, except that light from one or more of image injection devices 360, 370, 380, 390, 400 is injected into the waveguides from locations where it needs to be redirected for incoupling.

[0052]

[0145] 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 the waveguide), having, for example, 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 if one or more incoupling optical elements are reflective turning optical elements). As shown, the incoupling optical elements 700, 710, 720 may be disposed on the upper major surfaces of their respective waveguides 670, 680, 690 (or on top of the next lower waveguide), particularly 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 described herein, the incoupling optical elements 700, 710, 720 are wavelength selective so as to selectively redirect one or more wavelengths of light while transmitting other wavelengths of light. While shown on one side or corner of their respective waveguides 670, 680, 690, it will be understood that in some embodiments, the incoupling optical elements 700, 710, 720 may be disposed in other areas of their respective waveguides 670, 680, 690.

[0053]

[0146] As shown, the incoupling optical elements 700, 710, 720 may be laterally offset from one another. In some embodiments, each incoupling optical element may be offset to receive light without the light passing through another incoupling optical element. For example, each incoupling optical element 700, 710, 720 may be configured to receive light from a different image injection device 360, 370, 380, 390, and 400, as shown in FIG. 6 , and may be separated (e.g., laterally spaced) from the other incoupling optical elements 700, 710, 720 so as to substantially not receive light from others of the incoupling optical elements 700, 710, 720.

[0054]

[0147] Each waveguide also includes an associated light distribution element, e.g., a light distribution element 730 disposed on a major surface (e.g., the top major surface) of waveguide 670, a light distribution element 740 disposed on a major surface (e.g., the top major surface) of waveguide 680, and a light distribution element 750 disposed on a major surface (e.g., the top major surface) of waveguide 690. In some other embodiments, light distribution elements 730, 740, 750 may be disposed on the bottom major surface of each associated waveguide 670, 680, 690. In some other embodiments, light distribution elements 730, 740, 750 may be disposed on both the top and bottom major surfaces of each associated waveguide 670, 680, 690, or distribution elements 730, 740, 750 may be disposed on different top and bottom major surfaces of each different associated waveguides 670, 680, 690.

[0055]

[0148] The waveguides 670, 680, 690 may be spaced apart or separated by, for example, a gas, liquid, and / or a solid layer of material. For example, as shown, layer 760a may separate waveguides 670 and 680, and layer 760b may separate 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 and 760b is 0.05 or more, or 0.10 or less, than the refractive index of the material forming waveguides 670, 680, 690. Advantageously, the low refractive index layers 760a, 760b may 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 understood that the top and bottom of the illustrated set of waveguides 660 may include immediately adjacent cladding layers.

[0056]

[0149] Preferably, for ease of fabrication and other considerations, the materials forming waveguides 670, 680, and 690 are similar or identical, and the materials forming layers 760a and 760b are similar or identical. In some embodiments, the materials forming waveguides 670, 680, and 690 may vary between one or more waveguides, and / or the materials forming layers 760a and 760b may be different while still maintaining the various refractive index relationships described above. A variety of materials can be used to form the waveguides. Glass is one material that can be used to fabricate waveguides, but other materials can be used, including LiNbO, SiC, ZnS, and the like. These materials can be in the form of optical-quality single-crystal materials or optical-quality, but not single-crystal, materials. Additionally, polycrystalline ceramics of similar composition can be used to form waveguides. As an example, nanocrystalline materials can be used to fabricate waveguides.

[0057]

[0150] 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).

[0058]

[0151] In some embodiments, light rays 770, 780, 790 have different characteristics, such as different wavelengths or different ranges of wavelengths, which may correspond to different colors. Incoupling optical elements 700, 710, 720 each deflect incident light so that the light propagates through a respective one of waveguides 670, 680, 690 by TIR. In some embodiments, 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.

[0059]

[0152] For example, incoupling optical element 700 may be configured to deflect light ray 770 having a first wavelength or wavelength range, while transmitting light rays 780 and 790 having different second and third wavelengths or wavelength ranges, respectively. Transmitted light ray 780 impinges on and is deflected by incoupling optical element 710, which is configured to deflect light of the second wavelength or wavelength range. Light ray 790 is deflected by incoupling optical element 720, which is configured to selectively deflect light of the third wavelength or wavelength range.

[0060]

[0153] 9A , the deflected light rays 770, 780, 790 are deflected such that they propagate through their corresponding waveguides 670, 680, 690; i.e., the incoupling optical element 700, 710, 720 of each waveguide deflects the light into its corresponding waveguide 670, 680, 690, 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 their respective waveguides 670, 680, 690 by TIR. The light rays 770, 780, 790 propagate through their respective waveguides 670, 680, 690 by TIR until they impinge on the waveguide's corresponding distributing element 730, 740, 750.

[0061]

[0154] Referring now to Figure 9B, a perspective view of one embodiment of the stacked waveguide of Figure 9A is shown. As described above, incoupling light rays 770, 780, and 790 propagate by TIR within waveguides 670, 680, and 690, respectively, after being deflected by incoupling optical elements 700, 710, and 720, respectively. Light rays 770, 780, and 790 then impinge upon distribution elements 730, 740, and 750, respectively. Light distribution elements 730, 740, and 750 deflect light rays 770, 780, and 790 to propagate toward outcoupling optical elements 800, 810, and 820, respectively.

[0062]

[0155] In some embodiments, the light distribution elements 730, 740, 750 are orthogonal pupil dilators (OPEs). In some embodiments, the OPEs deflect or distribute light to the outcoupling optical elements 800, 810, 820, and in some embodiments, may increase the beam or spot size of this light as it propagates to the outcoupling optical elements. In some embodiments, the light distribution elements 730, 740, 750 may be omitted, and the incoupling optical elements 700, 710, 720 may be configured to deflect light directly to the outcoupling optical elements 800, 810, 820. For example, with reference to FIG. 9A , the light distribution elements 730, 740, 750 may be replaced by the outcoupling optical elements 800, 810, 820, respectively. In some embodiments, the outcoupling optical elements 800, 810, 820 are exit pupils (EPs) or exit pupil dilators (EPEs) that direct light into the eye 210 ( FIG. 7 ). It will be appreciated that an OPE may be configured to increase the dimension of the eyebox in at least one axis, and an EPE may increase the eyebox in an axis that intersects the axis of the OPE, e.g., orthogonal to the axis of the OPE. For example, each OPE may be configured to redirect a portion of the light striking 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 redirected out of the waveguide toward the user, and the remaining portion of that light continues to propagate through the waveguide until it again strikes an EPE, at which point another portion of the impinging light is redirected out of the waveguide, and so on. As a result, as shown in FIG. 6 , a single beam of incoupled light is “replicated” each time a portion of that light is redirected by the OPE or EPE, thereby forming a field of cloned light beams. In some embodiments, the OPE and / or EPE may be configured to modify the size of the light beam.

[0063]

[0156] 9A and 9B, in some embodiments, a waveguide set 660 includes waveguides 670, 680, 690, incoupling optical elements 700, 710, 720, light distribution elements (e.g., OPEs) 730, 740, 750, and outcoupling optical elements (e.g., EPs) 800, 810, 820 for each component color. The waveguides 670, 680, 690 may be stacked with an air gap / cladding layer between them. The incoupling optical elements 700, 710, 720 redirect or deflect incident light into their respective waveguides (with different incoupling optical elements receiving light of different wavelengths). The light then propagates within each waveguide 670, 680, 690 at an angle that results in TIR. In the illustrated embodiment, light ray 770 (e.g., blue light) is deflected by the first incoupling optical element 700 and then continues bouncing down 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 described above. Light rays 780 and 790 (e.g., green and red light, respectively) pass through the waveguide 670, where light ray 780 strikes the incoupling optical element 710 and is deflected thereby. Light ray 780 then bounces down the waveguide 680 via TIR, traveling 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 strikes the incoupling optical element 720 of the waveguide 690. After the light ray propagates by TIR to the light distribution element (e.g., OPE) 750, the incoupling optical element 720 deflects the light ray 790 so that it propagates by TIR to the light outcoupling optical element (e.g., EP) 820. The outcoupling optical element 820 then finally outcouples the light ray 790 to a viewer, who also receives outcoupled light from the other waveguides 670, 680.

[0064]

[0157] FIG. 9C shows a top view of one embodiment of the stacked waveguides of FIGS. 9A and 9B. As shown, the waveguides 670, 680, and 690 may be vertically aligned, along with each waveguide's associated light distribution elements 730, 740, and 750 and associated outcoupling optical elements 800, 810, and 820. However, as described herein, the incoupling optical elements 700, 710, and 720 are not vertically aligned; rather, the incoupling optical elements are preferably non-overlapping (e.g., laterally spaced apart, as seen in the top view). As further described herein, this non-overlapping spatial arrangement facilitates one-to-one injection of light from different sources into different waveguides, thereby enabling unique coupling of a particular light source to a particular waveguide. In some embodiments, arrangements including non-overlapping, spatially separated incoupling optical elements may be referred to as shifted pupil systems, and the incoupling optical elements in these arrangements may correspond to sub-pupils.

[0065]

[0158] 9D shows an example of a wearable display system 60 that may incorporate various waveguides and associated systems disclosed herein. In some embodiments, the display system 60 is the system 250 of FIG. 6, which schematically illustrates several portions of the system 60 in greater detail. For example, the waveguide assembly 260 of FIG. 6 may be part of the display 70.

[0066]

[0159] 9D , display system 60 includes display 70 and various mechanical and electronic modules and systems to support the functionality of display 70. Display 70 may be coupled to a frame 80 that is wearable by a user or viewer 90 of the display system and configured to position display 70 in front of the user's 90 eyes. Display 70 may be considered eyewear in some embodiments. In some embodiments, speakers 100 are coupled to frame 80 and configured to be positioned adjacent to the user's 90 ear canals (in some embodiments, additional speakers, not shown, may optionally be positioned adjacent the user's other ear canals to provide stereo / shapeable sound control). Display system 60 may also include one or more microphones 110 or other devices for detecting sound. In some embodiments, the microphones are configured to allow a user to provide input or commands to system 60 (e.g., select voice menu commands, natural language questions, etc.) and / or enable audio communication with others (e.g., other users of similar display systems). The microphone may further be configured as an ambient sensor for collecting 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 outward-facing 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 that may be positioned, for example, facing outward, to capture images similar to at least a portion of the user's 90's normal field of view. In some embodiments, the display system may also include ambient sensors 120a that are separate from the frame 80 and may be attached to the user's 90's body (e.g., the user's 90's head, torso, limbs, etc.). The ambient sensors 120a may, in some embodiments, be configured to acquire data characterizing the user's 90's physiological state. For example, the sensors 120a may be electrodes.

[0067]

[0160] 9D , display 70 is operably coupled to local data processing module 140 by a communication link 130, such as a wired lead or a wireless connection, which may be mounted in a variety of configurations, such as fixedly attached to frame 80, fixedly attached to a helmet or hat worn by a user, embedded in headphones, or typically removably attached to user 90 (e.g., in a backpack-type configuration, in a belt-type configuration). Similarly, sensor 120a may be operably coupled to local processor and data module 140 by a communication link 120b, such as a wired lead or a wireless connection. Local processing and data module 140 may comprise a hardware processor and digital memory, such as non-volatile memory (e.g., flash memory or a hard disk drive), both of which may be utilized to assist in processing, caching, and storing data. Optionally, local processor and data module 140 may include one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, etc. The data may include a) 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 a remote processing module 150 and / or a 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 the remote processing module 150 and the remote data repository 160 by communication links 170, 180, e.g., via wired or wireless communication links, such that these remote modules 150, 160 are operatively coupled to each other and available as resources to the local processing and data module 140.In some embodiments, 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 frame 80 or may be a stand-alone structure that communicates with local processing and data module 140 by a wired or wireless communication path.

[0068]

[0161] 9D , in some embodiments, remote processing module 150 may comprise one or more processors configured to analyze and process 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, remote data repository 160 may comprise a digital data storage facility that may be available over the Internet or other networking configuration in a “cloud” resource configuration. In some embodiments, remote data repository 160 may include one or more remote servers that provide information, e.g., information for generating augmented reality content, to local processing and data module 140 and / or to remote processing module 150. In some embodiments, all data is stored and all computations are performed in the local processing and data module, allowing for fully autonomous use from the remote module. Optionally, an external system (e.g., a system of one or more processors, one or more computers) including a CPU, GPU, etc. may perform at least a portion of the processing (e.g., generating image information, processing data) and provide information to and receive information from modules 140, 150, 160, e.g., via a wireless or wired connection.

[0069]

[0162] 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 type of light source. This light may be collimated by collimating optics. The illumination source 1010 can 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).

[0070]

[0163] This light is directed to the 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 light). This allows the light to continue incident on the spatial light modulator 1030. As shown, the SLM 1030 is a reflective SLM configured to retroreflect and selectively modulate the incident light. The SLM 1030 includes, for example, one or more pixels that can have different states. Light incident on each pixel may be modulated based on the state of the pixel. Thus, the SLM 1030 can 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 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 interface 1022 and propagates downstream to projector optics 1040. In the off state, SLM 1030 does not change the polarization state of light incident thereon, e.g., does not rotate the input light from the first polarization state, and thus exhibits a dark state (e.g., a black pixel). In the off state, light having the first polarization state is transmitted through interface 1022 and propagates upstream back to illumination source 1010, not to the user's eyes.

[0071]

[0164] After reflecting from the SLM 1030, a portion of the light 1014 (e.g., modulated light) is reflected from interface 1022 and exits the PBS 1020 toward the user's eye. The emitted light passes through projector optics 1040 and is imaged onto an incoupling grating (ICG) 1050 in an eyepiece (not shown).

[0072]

[0165] 11A shows a system (e.g., an augmented reality display system) 1100A for presenting an image to a user's eye 210 and viewing a world 510, having an alternative configuration to that shown in FIG. 10 . 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 light source 1110 illuminates SLM 1140 and light reflected from SLM 1140 is directed to eye 210. System 1100A includes an optical system 1130 arranged to both illuminate SLM 1140 and project an image of SLM 1140. Light from light source 1110 propagates, for example, through optical system 1130 in a first direction onto SLM 1140, thereby illuminating SLM 1140. Light reflected from SLM 1140 propagates again through optics 1130 in a second direction opposite to the first direction and is directed into waveguide 1120 where it is coupled.

[0073]

[0166] 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 disposed 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 relative to the light source 1110 to receive the light output from the light source 1110. The coupling optics 1105 may collect light from the light source 1110 and, in some cases, may reduce the divergence of the light emitted from the light source 1110. The coupling optics 1105 may, for example, collimate the light output from the light source 1110. The coupling optics 1105 may collect light that matches the angular spectral field of view of the system 1100A. Thus, the coupling optics 1105 may cause the angular spectrum of the light output by the light source 1110 to match the field of view of the system 1100A. The coupling optics 1105 may have an asymmetric profile that operates asymmetrically on the light emitted from the light source 1110. For example, the coupling optics 1105 may reduce the divergence by different amounts in orthogonal directions (e.g., the x and z directions). Such asymmetry in the coupling optics 1105 can address asymmetry in the light emitted from the light source 1110, which may include, for example, a laser diode that emits a wide range of angles of light in one direction (e.g., x or z) as opposed to an orthogonal direction (e.g., z or x, respectively).

[0074]

[0167] As described above, the system 1100A includes an optical system 1130 configured to illuminate the SLM 1140 and disposed in the optical path between the light source 1110 and 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 the SLM 1140, or the image may be formed by the SLM 1140 onto the waveguide 1120. The image may be projected intraocularly into 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, positive refractive 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.

[0075]

[0168] The SLM 1140 may reflect, modulate, and reflect light therefrom. The SLM 1140 may be a polarization-based SLM configured to modulate polarization. The SLM 1140 may include, for example, a liquid crystal (LC) SLM (e.g., a liquid crystal on silicon (LCoS) SLM). The LC SLM may include, for example, a twisted nematic (TN) liquid crystal. The SLM 1140 may be substantially similar to the SLM 1030 with reference to FIG. 10 . The SLM 1140 may include one or more pixels configured to selectively modulate light incident thereon, for example, depending on the state of the pixel. For some types of SLM 1140, the pixel may modulate a beam incident thereon by changing the polarization state, for example, by rotating the polarization (e.g., rotating the direction of linearly polarized light).

[0076]

[0169] As mentioned above, the SLM 1140 may be an LCoS SLM 1140. In a crossed polarizer configuration, the LCoS SLM 1140 may be nominally white. When the pixel is off (e.g., 0 voltage), it is in a bright state, and when the pixel is on (e.g., a voltage above a threshold turns on voltage), it is in a dark state. In this crossed polarizer configuration, leakage is minimized when the pixel is on and in a dark state.

[0077]

[0170] In a parallel polarizer configuration, the LCoS SLM 1140 is nominally black. When the pixel is off (e.g., 0 voltage), it is in a dark state, and when the pixel is on (e.g., a voltage above the threshold turns on the voltage), it is in a bright state. In this parallel polarizer configuration, leakage is minimized when the pixel is off and in the dark state. The dark state may be (re)optimized using the friction direction and compensator angle. The compensator angle may refer to the angle of the compensator, which may be between the optical system 1130 and the SLM 1140, for example, as shown in FIG. 20B.

[0078]

[0171] The dynamic range and throughput of the parallel polarizer configuration may be different from the dynamic range and throughput of the crossed polarizer configuration. Additionally, the parallel polarizer configuration may be optimized for different contrast than the crossed polarizer configuration.

[0079]

[0172] 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 described above. The waveguide 1120 may include a substantially transparent material having a refractive index sufficient to guide light therethrough. As shown, the waveguide 1120 may include a first side 1121, a second side 1123 opposite the first side 1121, corresponding upper and lower major surfaces and edges therearound. The first and second major surfaces 1121, 1123 may be sufficiently flat so that image information can be preserved during propagation of light from the SLM 1140 to the eye 210, such that an image formed by the SLM 1140 can be injected into the eye. The optical system 1130 and the SLM 1140 may be disposed on a first side 1121 of the waveguide 1120. The light source 1110 may be disposed on a second side 1123 such that light from the light source 1110 passes through the waveguide 1120 and enters the second side 1123 before passing through the optical system 1130 and entering the SLM 1140. Thus, the waveguide 1120 may be disposed between the light source 1110 and the optical system 1130. Furthermore, at least a portion of the waveguide 1120 may extend between the light source 1110 and the optical system 1130, such that light passes through a portion of the waveguide 1120 and enters the optical system 1130. Thus, light emitted from the light source 1110 can be directed through the waveguide 1120 into the optical system 1130 and through the optical elements to enter the SLM 1140. SLM 1140 reflects the light back through optics 1130 into waveguide 1120 .

[0080]

[0173] 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 upper major surface 1123) of the waveguide 1120. In some designs, the incoupling optical element 1160 may be disposed on the lower 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. Although shown on one side or corner of the waveguide 1120, the incoupling optical element 1160 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. It should be noted that other structures may be used for 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) relative to the upper and lower major surfaces 1123, 1121 of the waveguide 1120, and guide the light therein by total internal reflection. Furthermore, the incoupling optical element 1160 may be configured to operate over a wide wavelength range and thus couple light of multiple colors 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.

[0081]

[0174] The system 1100A includes a light distribution element 1170 disposed on or within the waveguide 1120. The light distribution element 1170 may be substantially similar to the light distribution elements 730, 740, and 750 described above with reference to FIG. 9B . For example, the light distribution element 1170 may be an orthogonal pupil dilator (OPE). The light distribution element 1170 may be configured to diffuse light within the waveguide 1120 by redirecting light propagating in the x-direction, e.g., 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 within the waveguide 1120 that enters the diffractive optical element and redirect the light, e.g., in a substantially orthogonal direction. Other configurations are possible.

[0082]

[0175] 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 within the waveguide 1120 by total internal reflection (TIR) ​​at an angle more perpendicular to the upper major surface 1123 and / or the lower major surface 1121 of the waveguide 1120 so that the light is not guided within the waveguide 1120. Instead, the light is directed out of the waveguide 1120, for example, through the lower major surface 1121. The outcoupling optical element 1180 may include, for example, one or more diffractive optical elements configured to diffract light propagating within 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.

[0083]

[0176] 11B also shows the position of the incoupling optical element 1160 disposed laterally relative to the light distribution optical element (e.g., orthogonal pupil dilator) 1170 and the outcoupling optical element 1180. FIG. 11B also shows the position of the light source 1110 disposed laterally relative to the incoupling optical element 1160, the light distribution optical element (e.g., orthogonal pupil dilator) 1170 and the outcoupling optical element 1180.

[0084]

[0177] During operation, the light source 1110 of the system 1100A emits light through the polarizer 1115 and into the coupling optics 1105. This light may therefore be polarized, for example, 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 light incident thereon, such as by selectively rotating the orientation of the modulator pixel by pixel depending on the state of the pixel. For example, a first pixel may be in a first state and rotate the polarization, while a second pixel may be in a second state and not rotate the polarization. Light between the coupling optics 1105 and the optics 1130 may illuminate the SLM 1140 fairly uniformly. After entering the SLM 1140, the light is reflected through the optics 1130. The optics 1130 may be configured to project an image from the SLM 1140 to 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 conjugate with the SLM 1140 and / or the image formed by and / or on the SLM 1140. The output of the optics 1130 may 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 may assist and / or influence the image ultimately formed in the eye 210. Optical system 1130 acts as a projection lens as light reflected from SLM 1140 travels through the optics towards waveguide 1120. The optics may function approximately as a Fourier transform of the image on SLM 1140 to a plane at waveguide 1120 near incoupling optic 1160. Both passes through optics 1130 (first from light source 1110 to SLM 1140, and second from SLM 1140 to waveguide 1120) may together act to roughly image the pupil of coupling optics 1105.The alignment and orientation of the light source 1110 (and possibly the coupling optic 1105 and / or polarizer 1115), the optics 1130, and the SLM 1140 are such that light from the light source 1110 reflected from the SLM 1140 is directed onto the incoupling optic 1160. The pupil associated with the coupling optic 1105 may be aligned with the incoupling optic 1160. The light may pass through an analyzer 1150 (e.g., a polarizer) in the optical path between the SLM 1140 and the eye 210. As shown in FIG. 11A , the analyzer (e.g., polarizer) 1150 may be positioned in the optical path between the optics 1130 and the incoupling optic 1160. The analyzer 1150 may be, for example, a linear polarizer that orients light to transmit light of a first polarization (p-polarization) and block light of a second polarization (s-polarization), 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 from the waveguide 1120, specifically the incoupling optical element 1160, back toward 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 provide significant absorption of undesired light and thus increased contrast. Some such polarizers can be fabricated to include one or more dielectric layers on top of the wires and / or multilayer film. 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 consistent polarization rotation (e.g., 90°) of the SLM 1140 for different angles of incidence and different wavelengths. The compensator may 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 not to rotate incident light of a first polarization (e.g., s-polarized) to a second polarization (e.g., p-polarized) for a second pixel so that when the light is attenuated or blocked by the analyzer 1150, the reflected light remains at the first polarization to generate a dark pixel state. In such a configuration, the polarizer 1115 closer along the optical path to the light source 1110 may be oriented differently (e.g., orthogonal) relative to the analyzer 1150 further along the optical path from the light source 1110. Other, e.g., opposite, configurations are also possible.

[0085]

[0178] The light is then deflected and redirected, for example, by the incoupling optical element 1160, to be guided within the waveguide 1120 where it propagates by TIR. The light then strikes the light distribution element 1170, which redirects the light in another direction (e.g., further toward the z-direction), increasing the size of the eyebox along the z-axis, as shown in FIG. 11B. The light is thus deflected toward the outcoupling optical element 1180, which directs the light from the waveguide 1120 toward the eye 210 (e.g., the user's eye as shown). The light coupled along the z-direction by different portions of the outcoupling optical element 1180 increases the size of the eyebox at least along a direction parallel to the z-axis, as defined in FIG. 11B. Notably, in this configuration, the optical system 1130 is used both to illuminate the SLM 1140 and to project an image onto the incoupling optical element 1160. Thus, optical system 1130 may act as projection optics, distributing (e.g., uniform) light from light source 1110, and as imaging optics, providing an image of SLM 1140 and / or an image formed in the eye by SLM 1140. System 1100A of Figures 11A / B may, in some cases, be more compact than system 1000 of Figure 10. In some cases, not employing PBS 1020 shown in Figure 10 may potentially reduce the cost and / or size of the system. Furthermore, without PBS 1020, the system may be more symmetrical, making it easier to design by shortening the back focal length of optical system 1130.

[0086]

[0179] As mentioned above, alternative configurations are possible. Referring to FIG. 11C , for example, in some designs, system 1100C may be configured to pass light having a polarization that is not rotated by SLM 1140. In one implementation, for example, SLM 1140 is a liquid crystal (LC)-based SLM and may include a vertically aligned (VA) LC-on-silicon (LCoS) SLM. 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. The configuration shown in FIG. 11C utilizes a single shared analyzer / polarizer 1155. This analyzer 1155 may transmit light of a first polarization (e.g., s-polarized) and attenuate or reduce transmission of light of a second polarization (e.g., p-polarized). As a result, light (e.g., s-polarized light) incident on the first pixel in a first state that does not rotate the polarization direction is reflected from the SLM 1140 and transmitted through the analyzer 1155 to the waveguide 1120. Conversely, light (e.g., s-polarized light) incident on the second pixel in a second state that rotates the polarization direction is reflected from the SLM 1140 and attenuated, reduced, or not transmitted through the analyzer 1155 to the waveguide 1120. This configuration allows the polarizer 1115 and analyzer 1150 shown in FIG. 11A to be combined into a common optical element, the analyzer 1155 shown in FIG. 11C, thereby simplifying the system 1100 of FIGS. 11A / B by 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 analyzer / polarizers may be used, as shown in 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 optics 1130 and the waveguide 1120.

[0087]

[0180] FIG. 11D illustrates an example of a waveguide having a composite OPE / EPE according to one embodiment of the present invention. Referring to FIG. 11D , a waveguide 1190 having a composite OPE / EPE region 1191 includes gratings corresponding to both the OPE and the EPE, which spatially overlap in the x and y directions. In some embodiments, the gratings corresponding to both the OPE and the EPE are positioned 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 positioned on the opposite side of the substrate from the EPE grating, such that the gratings spatially overlap in the x and y directions but are separated from each other in the z direction (i.e., in different planes). Thus, the composite OPE / EPE region 1191 can be implemented in either a single-sided or double-sided configuration.

[0088]

[0181] The optical path within eyepiece waveguide 1190 includes incident light 1194 that is coupled into eyepiece waveguide 1190 at ICG 1193. The incoupled light propagates within substrate 1192 toward composite OPE / EPE 1191 by total internal reflection. When these light rays encounter composite OPE / EPE 1191, also referred to as a synthetic pupil dilator (CPE), the light is diffracted in the +y direction and then in the -z direction along optical path 1195 out of the waveguide toward the user's eye. Similarly, the incoupled light may alternatively encounter composite OPE / EPE 1191, be diffracted in the -y direction, and then in the -z direction out of the waveguide toward the user's eye along optical path 1195.

[0089]

[0182] As described more fully herein, embodiments of the present invention utilize eyepiece waveguides that have optical path length differences, e.g., eyepiece waveguide thicknesses that vary with lateral position, i.e., position in the x-y 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. Furthermore, in some embodiments, the CPE thickness varies, with the portion adjacent to the ICG being thicker than the portion distal to the ICG. In other embodiments, the physical thickness is uniform, but the refractive index varies with lateral position, resulting in optical path length differences that characterize the eyepiece waveguide as a function of lateral position.

[0090]

[0183] A wide variety of other configurations may 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, one or more waveguides, such as a stack of waveguides (possibly different waveguides for different colors of light), may also be used.

[0091]

[0184] For example, Figure 12A shows a cross-sectional side view of an exemplary system 1200A including a stack 1205 including waveguides 1120, 1122, and 1124, each including an incoupling optical element 1260, 1262, and 1264. The waveguides 1120, 1122, and 1124 may each be configured to output light at one or more different wavelengths or in 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, and 1124 of the stack 1205 may correspond to portions of the waveguides 670, 680, and 690, although the stack 1205 and the waveguides 1120, 1122, and 1124 need not be so limited. As shown in FIG. 12A , incoupling optical elements 1260, 1262, 1264 may be associated with, included in, or located on each of 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 need not be laterally displaced but may be stacked on top of one another. Wavelength multiplexing may be employed to couple specific colors into corresponding waveguides. For example, a red incoupling optical element may incoupling red light into a waveguide designated to propagate red light, while not incoupling blue or green light, which is instead coupled into other waveguides by other blue and green selective waveguides, respectively.

[0092]

[0185] In some implementations, the light source 1110 may be a multicolor light source that can emit 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 time period, green and negligible amounts of red and blue during a second time period, and blue and negligible amounts of red and green during a third time period. These cycles can be repeated, and the SLM 1140 can be adjusted to generate a suitable pattern of pixel states for a particular color (red, green, or blue) to provide the appropriate image color components for a given image frame. Different waveguides 1120, 1122, and 1124 of the stack 1205 may each be configured to output light of a different respective color. For example, as shown in FIG. 12A , the waveguides 1120, 1122, and 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. Furthermore, separate 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 selection 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.

[0093]

[0186] 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 laterally aligned (e.g., in the x and z directions shown in FIG. 12A ) as opposed to being laterally displaced and unaligned from one another. Thus, in some implementations, the different incoupling optical elements 1260, 1262, 1264 can be configured such that, for example, light of a first color can be coupled into 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 be coupled into 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 incoupling optical elements 1260 and 1262 to incoupling optical element 1264 and be coupled to and guided into waveguide 1124. Furthermore, incoupling optical elements 1260, 1262, 1264 may be polarization-selective. For example, different incoupling optical elements 1260, 1262, 1264 can be configured such that light of a particular polarization is either 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.

[0094]

[0187] Depending on the configuration, SLM 1140 may include a polarization-based SLM that modulates polarization. System 1200A may include, for example, a polarizer and / or analyzer to modulate the light injected into stack 1205 for each pixel depending on the state of the respective pixel (e.g., whether the pixel rotates the polarization direction or not). Various aspects of such systems employing polarization-based SLMs are described above, and any one of such features may be employed in combination with any other feature described herein. However, other designs are still possible.

[0095]

[0188] 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 micromirrors or reflectors. The SLM 1140 may incorporate digital light processing (DLP™) technology, for example, using a digital micromirror device (DMD). One example of a system 1200B using such a deflection-based SLM 1140 is shown in FIG. 12B. The system 1200B includes the deflection-based SLM 1140 and a light dump 1250. The light dump 1250 may include an absorptive 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 optical elements 1260, 1262, 1264 when a given pixel is in a bright state. Thus, as described above, this light is coupled by one of the incoupling optical elements 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, light from the light source 1110 may be deflected to the light dump 1250, and the light is not coupled by one of the incoupling optical elements 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 comprising the light dump 1250. In some implementations, the analyzer 1150 may be a polarizer (e.g., a "clean-up" polarizer) used to remove 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 have birefringence and may change polarization.The "clean-up" polarizer may attenuate or eliminate light with undesired polarizations (e.g., reflections) from being guided 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 optical system 1130 and the waveguides 1120, 1122, 1124. For example, such light conditioning elements may also include circular polarizers (i.e., linear polarizers and retarders such as quarter-wave plates). The circular polarizers may reduce the amount of reflections from the waveguides 1120, 1122, 1124 or from incoupling optical elements 1260, 1262, 1264 that re-enter and couple 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 circularly polarized light is converted to left-handed circularly polarized light upon reflection, or vice versa). A retarder in the circular polarizer may convert circularly polarized light to linearly polarized light, such as the polarizer's orthogonal polarization, which is attenuated, e.g., absorbed, by the circular polarizer's linear polarizer. Clean-up polarizers may also be used with polarization-independent modulators, such as DMDs. As mentioned above, clean-up polarizers can be useful for suppressing reflections and / or improving the coupling of light into the incoupling optical elements 1260, 1262, 1264 with optimal polarization states.

[0096]

[0189] 12B shows a side or cross-sectional view of such a system 1200B, while FIG. 12C shows a top view of the lateral arrangement of the incoupling optical element 1264, light dump 1250, and light source 1110. The SLM 1140 is configured to reflect, deflect, and / or direct light from the light source 1110 either to a position lateral to the incoupling optical element 1264 (as well as the other incoupling optical elements 1260, 1262) or to the light dump 1250, depending on the state of the particular pixel.

[0097]

[0190] In certain designs, 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 electrical components, for example, conductive wires, to direct the electrical output to power the system 1200B and / or possibly charge one or more batteries.

[0098]

[0191] Certain designs may use laterally displaced, non-color-selective, broadband, or multicolor incoupling optical elements. Figure 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 stack 1205, with reference to Figure 12A. Each waveguide in the stack 1305 may include an incoupling optical element 1360, 1362, 1364, but in contrast to the design shown in Figure 12A, the incoupling optical elements 1360, 1362, 1364 are laterally displaced relative to one another. 13A, 13B, and 13C, the light sources 1110, 1112, 1114 may also be laterally displaced relative to one another and positioned 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 FIG. 13B shows the light source 1114 as being positioned behind the light source 1110 and therefore not shown in FIG. 13B. The light sources 1110, 1112, 1114 may correspond to the incoupling optical elements 1360, 1362, 1364, respectively. In one design, for example, the light sources 1110, 1112, 1114 and corresponding incoupling optical elements 1360, 1362, 1364 are positioned approximately equidistant (symmetrically) from 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 corresponding incoupling optical elements 1360, 1362, 1364 are not positioned equidistant (symmetrically) from the center of the optical system 1130 along the common (optical) axis.

[0099]

[0192] The incoupling optical elements 1360, 1362, 1364 may be configured to couple light of multiple colors into their respective waveguides. Accordingly, these incoupling optical elements 1360, 1362, 1364 may be referred to herein as broadband, multicolor, or non-color-selective incoupling optical elements 1360, 1362, 1364. For example, in some cases, these incoupling optical elements 1360, 1362, 1364 are each configured to incouple red light, green light, and blue light into an associated waveguide that includes the incoupling optical element 1360, 1362, 1364 such that TIR guides such colored light into the waveguide. Such broadband incoupling optical elements 1360, 1362, 1364 may operate over a wide wavelength range, for example, within the visible range, or may select wavelengths or wavelength regions that are spread across the visible range, for example. Thus, such broadband or multicolor or non-color-selective incoupling optical elements 1360, 1362, 1364 may be configured to redirect light of a variety of different colors (e.g., red, green, and blue) into the TIR-guided waveguide. Although reference is made herein to red, green, and blue (RGB) in connection with light sources, incoupling optical elements, waveguides, etc., other colors or color systems, such as, for example, without limitation, magenta, cyan, and yellow (CMY), may additionally or alternatively be used.

[0100]

[0193] As shown in FIG. 13A, light sources 1110, 1112, and 1114 are shown above the top waveguide and are displaced relative to each other (e.g., in the x and z directions). Similarly, three incoupling optical elements 1360, 1362, and 1364 are shown above three respective waveguides and are 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 incoupling optical elements 1360, 1362, and 1364 spatially displaced laterally (e.g., in the x and z directions) relative to each other, as well as some of the light sources 1110, 1112, and 1114 displaced laterally (e.g., in the x and z directions) relative to each other. FIG. 13B also shows the optical system 1130 and the SLM 1140.

[0101]

[0194] 13A and 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, but need not be, spaced approximately equidistantly around the center point of the common (optical) axis. In some designs, this center point may correspond to the center of the optical system 1130 and / or a position along the optical axis of the optical system 1130 that intersects the center 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 (eg, in the x and z directions) relative to one another.

[0102]

[0195] Other arrangements of lateral placement are possible. Figures 14A-14C show alternative configurations of a system 1400 including a stack 1405 including waveguides in which incoupling optical elements 1360, 1362, 1364 and light sources 1110, 1112, 1114 are laterally displaced relative to one another. Figure 14A is a side view, while Figure 14B is a top view of the system 1400 shown in Figure 14A, showing the incoupling optical elements 1360, 1362, 1364 and light sources 1110, 1112, 1114 laterally displaced. Figure 14C is an orthogonal side view of the system 1400 shown in Figures 14A and 14B.

[0103]

[0196] The side views of Figures 14A and 14C show how incoupling optical elements 1360, 1362, 1364 are positioned on separate waveguides within stack 1405 such that light can be coupled into corresponding waveguides by each laterally displaced incoupling optical element 1360, 1362, 1364. The incoupling optical elements 1360, 1362, 1364 are shown positioned on the upper major surfaces of the waveguides in Figures 14A and 14C. However, the incoupling optical elements 1360, 1362, 1364 can alternatively be positioned on the lower major surfaces of the respective waveguides or within the bulk of the waveguides. Various configurations are possible.

[0104]

[0197] 14B, the incoupling optical elements 1360, 1362, 1364 are vertically disposed and laterally displaced relative to one another along the z-direction, but not displaced relative to one another along the x-direction. Similarly, the light sources 1110, 1112, 1114 are vertically disposed and laterally displaced relative to one another also along the z-direction, but not displaced relative to one another along the x-direction. The incoupling optical elements 1360, 1362, 1364 are laterally displaced relative to the light sources 1110, 1112, 1114 in the x-direction.

[0105]

[0198] Still other configurations are possible. Figure 15 is a top view of a system 1500 illustrating an alternative configuration of light sources 1110, 1112, 1114 and incoupling optical elements 1360, 1362, 1364. In contrast to Figure 13C, in which all of the light sources 1110, 1112, 1114 are generally on one side (e.g., of the ring-shaped 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 incoupling optical elements 1360, 1362, 1364 are interspersed or alternating around the circumference of the ring-shaped pattern.

[0106]

[0199] However, in some implementations, the incoupling optical elements 1360, 1362, 1364 and associated light source(s) 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 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 (as can be seen in the top view of FIG. 15 ). Similarly, light from the second light source 1112 may be coupled via 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 via 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 such that the focal point is within the stack 1405, thereby causing the positions of the sub-pupil and the incoupling optical elements 1360, 1362, 1364 to be close in the y direction. In this configuration, the incoupling optical elements 1360, 1362, 1364 may be small 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.

[0107]

[0200] In various implementations described above, such as those shown in FIGS. 12A-15 , 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 handle 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 light outcoupled from each stack. For example, 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) perhaps related to the apparent depth from which the light appears to diverge. For example, wavefronts with different amounts of divergence, convergence, or collimation may appear to be projected at different distances from the eye 210. Thus, multiple stacks may be included, with different stacks configured so that light outcoupled by the outcoupling optical element has different amounts of convergence, divergence, or collimation and therefore 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 therefore, the light from the different stacks appears to be associated with different depth planes or objects that are different distances from the eye 210.

[0108]

[0201] FIG. 16A is a side view of a system 1600 including stacks 1605, 1610, and 1620. As shown in FIG. 16A, the system 1600 includes three stacks 1605, 1610, and 1620, but this need not be the case. Systems 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, and 1650 of incoupling optical elements. The first group 1630 is associated with the first stack 1605, the second group 1640 is associated with the second stack 1610, and the third group 1650 is associated with the third stack 1620. The groups 1630, 1640, and 1650 are laterally displaced relative to each other. Each of the groups 1630, 1640, and 1650 includes a color-selective incoupling optical element configured to incouple a different respective color, substantially similar to the incoupling optical elements 1260, 1262, and 1264 of FIG. 12A . As shown in FIG. 16A , the incoupling optical elements within each of the groups 1630, 1640, and 1650 are not laterally displaced relative to one another, but this need not be the case. Systems may be devised in which the incoupling optical elements within a group are laterally displaced relative to one another. The system 1600 may be configured so that light outcoupled from each of the stacks 1605, 1610, and 1620 has a different amount of refractive power. For example, the waveguides within the stacks may have an outcoupling optical element or diffractive lens with a given refractive power. The refractive power for the different stacks 1605, 1610, and 1615 may be different so that light from any stack appears to originate at a different depth than light from another stack. For example, the refractive power of any stack may collimate the light from that stack, while the refractive power of another stack may diverge the light from that stack. Diverging light may appear to emanate from an object that is a close distance from the eye 210, while collimated light may appear to emanate from an object that is a far distance.Thus, 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 thus appear to originate from different depths. In some implementations, light outcoupled from one of the stacks may be collimated, while light outcoupled by a different stack may diverge. Light outcoupled from one of the other stacks may also diverge, but by a different amount.

[0109]

[0202] 16A , light source 1110 may be positioned relative to optics 1130 and SLM 1140 to direct light to group 1630 of incoupling optical elements, light source 1112 may be positioned relative to optics 1130 and SLM 1140 to direct light to group 1640 of incoupling optical elements, and light source 1114 may be positioned relative to optics 1130 and SLM 1140 to direct light to group 1650 of incoupling optical elements. Light sources 1110, 1112, and 1114 may be configured to emit light of different colors at different times. Similarly, light of different respective colors may be coupled into different waveguides within the stack as a result of color-selective incoupling optical elements in the manner described above. For example, if blue light is emitted from second light source 1112, optics 1130 and SLM 1140 direct the blue light to 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 redirected 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.

[0110]

[0203] Figure 16B is a top view of the system 1600 of Figure 16A. Different groups of incoupling optical elements 1630, 1640, 1650 are shown as being laterally displaced (e.g., in the x-direction) relative to one another. Similarly, light sources 1110, 1112, 1114 are shown as being laterally displaced (e.g., in the x-direction) relative to one another.

[0111]

[0204] A wide variety of different variations on the above-described systems are possible. For example, the location of the light source 1110 relative to the waveguide and optics 1130 may be different. FIG. 17, for example, is a side view of a system 1700 having a light source 1110 in a different location relative to the waveguide 1720 and optics 1130 than shown in FIGS. 11-16B . Additionally, FIG. 17 illustrates a design in which the waveguide 1720 is split into a first portion 1720 a and a second portion 1720 b. The waveguide 1720 may further include a reflector 1730 configured within the first portion 1720 a proximal to the light source 1110 to couple light guided into the optics 1130 from the first portion 1720 a toward the SLM 1140. Additionally or alternatively, system 1700 may include a diffractive outcoupling optical element for outcoupling light in first portion 1720a of waveguide 1720 to optics 1130 toward SLM 1140. This reflector 1730 may be opaque and may include an isolator to reduce crosstalk between first portion 1720a and second portion 1720b. Waveguide 1720 has a first side 1721 and a second side 1723 opposite first side 1721, and optics 1130 and SLM 1140 are disposed on first side 1721 such that light from SLM 1140 is directed to first side 1721. In this embodiment, the light source 1110 is positioned on the 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 and entering the SLM 1140. The system 1700 may further include an incoupling optical element 1710 positioned on or within 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 redirect incident light into the first portion 1720a at an angle that is guided into the first portion 1720a by TIR.

[0112]

[0205] The reflector 1730 may be configured to direct light guided into the first portion 1720a from the first portion 1720a toward the optical system 1130 and the SLM 1140. (As mentioned above, in some implementations, a diffractive optical element may additionally or alternatively be used to direct light in the first portion 1720a from the first portion 1720a toward the optical system 1130 and the SLM 1140.) Thus, the reflector 1730 may be a mirror, a reflective grating, or one or more coatings that reflect light from the waveguide 1720 toward the SLM 1140. Light emitted from the first portion 1720a by the reflector 1730 passes through the optical system 1130, enters the SLM 1140, and passes through the optical system 1130 again to enter the second portion 1720b. As described above, light reflected from SLM 1140 that has passed through optical system 1130 may be incident on incoupling optical element 1160, which may redirect the light to be directed into second portion 1720b. Light directed into second portion 1720b may be outcoupled therefrom by outcoupling optical element 1180 (not shown) and directed to eye 210.

[0113]

[0206] As described above, the reflector 1730 may be an isolator that reduces crosstalk between the first portion 1720 a and the second portion 1720 b. 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 1720 a and the second portion 1720 b.

[0114]

[0207] Instead of having first and second portions 1720a, 1720b of 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 light source 1110 and directing the light guided therein to optical system 1130 and toward SLM 1140. System 1800 further includes a second waveguide 1820 for receiving light from SLM 1140 after the light has passed through optical system 1130 again. First waveguide 1822 includes incoupling and outcoupling optical elements 1730a, 1730b, respectively. These incoupling and outcoupling optical elements 1730a, 1730b may include reflective surfaces oriented to incoupling and outcoupling light into and out of waveguide 1822. The incoupling optical element 1730a may, for example, be positioned 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 into the waveguide 1822 by TIR. The outcoupling 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 outcoupling optical element 1730b may be positioned such that redirected light emerging from the waveguide 1822 is directed into the optical system 1130, reflected from the SLM 1140, and passed through the optical system 1130 again to be incident on the incoupling optical element 1730c of the second waveguide 1820.

[0115]

[0208] The incoupling optical element 1730c in the second waveguide 1820 may include a reflective surface that may be positioned and oriented (e.g., tilted) to receive and redirect light incident from the SLM 1140 and guided into the second waveguide 1820 by TIR. 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.

[0116]

[0209] Various designs, such as those described above, can include additional features or components. FIG. 19, for example, shows a side view of a system 1900 including variable-focus optical elements (or adaptive optical elements) 1910, 1920. The variable-focus optical elements 1910, 1920 may include optical elements configured to be changed to provide variable optical power. The variable-focus optical elements 1910, 1920 may include multiple states, such as a first state and a second state, where in the first state, the variable-focus optical elements 1910, 1920 have a different optical power than in the second state. For example, the variable-focus optical elements 1910, 1920 may have a negative optical power in the first state and zero optical power in the second state. In some implementations, the variable-focus optical elements 1910, 1920 have a positive optical power in the first state and zero optical power in the second state. In some implementations, the variable-focus optic 1910, 1920 has a first negative or positive optical power in a first state and a second, different negative or positive optical power in a second state. Some adaptive or variable-focus optics 1910, 1920 may have more than two states, potentially providing a continuous distribution of optical powers.

[0117]

[0210] The variable-focus optical elements 1910, 1920 may include lenses (e.g., variable lenses) and may be transmissive. Transmissive or transparent adaptive or variable-focus optical elements 1910, 1920 are shown in FIG. 7 . The variable-focus optical elements 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, e.g., switchable liquid crystal polarized lenses, which may comprise diffractive lenses. Alverez lenses may also be used. Other types of variable-focus optical elements 1910, 1920 may be employed. Examples of variable-focus optical elements can be found in U.S. Patent Application No. 62 / 518,539, filed June 12, 2017, entitled "AUGMENTED REALITY DISPLAY HAVING MULTI-ELEMENT ADAPTIVE LENS FOR CHANGING DEPTH PLANES," which is incorporated herein by reference in its entirety. The variable-focus optical elements 1910, 1920 may have electrical inputs that receive electrical signals that control the amount of refractive power exhibited by the variable-focus optical elements 1910, 1920. The variable-focus optical elements 1910, 1920 may 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 may include fixed lenses (e.g., diffractive lenses, refractive lenses, etc.) to generate desired depth planes in the light field.

[0118]

[0211] A 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 described above. The first variable-focus 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 coupled out of 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.

[0119]

[0212] The second variable-focus optical element 1920 is on the opposite side of the stack 1905 from the first variable-focus optical element 1910. 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 world view may effectively be unchanged or may be altered, as desired.

[0120]

[0213] 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. Furthermore, if the prescription lens 1930 is a variable lens, it may provide different refractive corrections for multiple users. Variable focus lenses are described 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 positioned 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 positioned between the eye 210 and the first variable focus optical element 1910. Other positions of the lens 1930 are also possible. In some embodiments, the prescription lenses may be variable, allowing multiple user prescriptions to be implemented.

[0121]

[0214] In some designs, the system 1900 may include an adjustable dimmer 1940. In some implementations, this adjustable dimmer 1940 may be located on the opposite side (e.g., the world side) of the stack of waveguides 1900 from the eye 210. Thus, this adjustable dimmer 1940 may be located 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 ambient light and control electronics that drive the adjustable dimmer 1940 to vary the attenuation based on the light level sensed by the light sensor.

[0122]

[0215] Different types of adjustable dimmer 1940 may be employed. Such adjustable dimmer 1940 may include a variable liquid crystal switch with a polarizer, an electrochromic material, a photochromic material, or the like. The adjustable dimmer 1940 may be configured to adjust the amount of light entering the stack 1905 from the world 510 and / or transmitted through the stack 1905. The adjustable dimmer 1940 may, in some cases, be used to reduce the amount of ambient light 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 injected into the eye 210 from the stack 1905. Such an adjustable dimmer 1940 may reduce washout of the image projected into the eye 210 due to incoming bright ambient light. Thus, the contrast of the virtual object / image presented to the eye 210 may be increased by the adjustable dimmer 1940. In contrast, when ambient light is low, the adjustable dimmer 1940 may be adjusted to reduce attenuation, allowing the eye 210 to 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 local portions may be dimmed or set to attenuate light from the world 510 in front of the user 210. These local portions may be separated from each other by portions without such increased dimming or 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 with different designs. Also, the placement of components may be different. Similarly, one or more components may be excluded from the system.

[0123]

[0216] An example of another configuration is shown in Figure 20A, which 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 located on a side of the stack 2005 proximate 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 located in or on a cover glass 2050 positioned between the stack 2005 and the optics 1130. The color filter array 2030 may include one or more different color filters 2040, 2042, 2044, such as red, green, and blue color filters, arranged laterally relative to one another. The system 2000 includes light sources 1110, 1112, 1114 that are laterally displaced relative to one another. These light sources 1110, 1112, 1114 may include light sources of different colors, such as red, green, and blue light sources. The color filters 2040, 2042, 2044 may be transmissive or transparent filters. In some implementations, the color filters 2040, 2042, 2044 include absorptive filters, although the color filters 2040, 2042, 2044 may also include reflective filters. The color filters 2040, 2042, 2044 in the color filter array 2030 may 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 unwanted reflections within the system, such as from the waveguides and / or incoupling optical elements 1360, 1362, 1364, from re-entering the waveguides used for the different colors through the incoupling optical elements 1360, 1362, 1364 for the different colors.Examples of color filter arrays can be found in U.S. patent application Ser. No. 15 / 683,412, entitled "PROJECTOR ARCHITECTURE INCORPORATING ARTIFACT MITIGATION," filed Aug. 22, 2017, and U.S. patent application Ser. No. 62 / 592,607, entitled "PROJECTOR ARCHITECTURE INCORPORATING ARTIFACT MITIGATION," filed Nov. 30, 2017, and incorporated herein by reference in their entireties. The mask may be a black mask or may include an absorbing material to reduce the propagation and reflection of stray light. The light sources 1110, 1112, and 1114 may be positioned relative to the optical system 1130 and the SLM 1140 to couple light to corresponding color filters 2040, 2042, and 2044 in the color filter array 2030. 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 first, second, and third colors, respectively, into the first, second, and third waveguides. The first incoupling optical element 1360 may be configured to couple more light of the first color than the second color (or third color) into the first waveguide. The second incoupling optical element 1362 may be configured to couple more light of the second color than the first color (or third color) into the second waveguide. The third incoupling optical element 1364 may be configured to couple more light of the third color than the first color or the second color into the second waveguide. 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 incoupling optical element 1362 may be configured to couple light of the first, second, and third colors into the second waveguide. The third incoupling optical element 1364 may be configured to couple light of the first, second, and third colors 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 that selectively transmit 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 third color). The second light source 2042 may emit more of the second color than the first color (and third color). The third light source 2044 may transmit more of the third color than the first color and second color. The color filters 2040, 2042, 2044 may reduce the amount of stray light inadvertently introduced into a particular incoupling 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 the first and second (and possibly third) colors. The second light source 1112 may also emit the first and second (and possibly third) colors. The third light source 1114 may also emit the first and second (and possibly third) colors. Although three filters are shown in FIGS. 20A-20G, more or fewer filters may be included. For example, in some implementations, two filters (rather than three) may be used. Thus, a filter may selectively transmit two colors corresponding to the two color filters. In some such implementations, two corresponding incoupling optical elements may be used and aligned with the two filters. In some implementations, the two incoupling optical elements each selectively couple two colors into two respective waveguides. In some implementations, two light sources may be used instead of three. Other variations and numbers of components may be used. Also, the color filters 2040, 2042, 2044 may or may not be integrated together into a single array.

[0124]

[0217] As noted above, the components and their positions and arrangements may vary. For example, while FIG. 20A shows the analyzer 1150 positioned 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 glued or mechanically coupled to the SLM 1140. For example, the analyzer 1150 may be glued or bonded to the SLM 1140 (e.g., to 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 fixed to the SLM 1140 (e.g., using a mechanical fixture), in which case there may or may not be a gap between the analyzer 1150 and the SLM 1140. Birefringence from the optical system 1130 may be cleaned up by placing a polarizer directly on the SLM 1140, as described above. In some implementations, the analyzer 1150 positioned between the optical system 1130 and the incoupling optical elements 1360, 1362, 1364 may also be included (e.g., as shown by the dashed lines in FIG. 20B ) to clean up the polarization of light outgoing from the optical system 1130. 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 may refer to a quarter-wave retarder, regardless of whether the quarter-wave retarder comprises a plate, a film, or other structure for providing quarter-wave retardation characteristics. In FIG. 20B , for example, a retarder (e.g., a quarter-wave plate) may be disposed between the analyzer 1150 and the SLM 1140. The retarder (e.g., a quarter-wave plate) may be used for skew ray management. For example, the retarder (e.g., a quarter-wave plate) may compensate for variations caused by differences in wavelength and angle of incidence on the SLM 1140.As described above, a compensator may be included to provide 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 consistent orthogonal rotation. The compensator may be attached or fixed 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 also be included, additionally or alternatively, and attached to the SLM 1140 as described above with respect to the analyzer 1150 and / or compensator.

[0125]

[0218] In some embodiments, a large angular spread (e.g., -70 degrees) may be used. Angular spread may refer, for example, to the angle of light entering the optical system 1130 from the light sources 1110, 1112, 1114 and / or the angle of light exiting the optical system 1130 to the incoupling optical elements 1360, 1362, 1364. In these embodiments, a thin SLM 1140 may 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 may be thinned to accommodate the large angular spread.

[0126]

[0219] The double-pass retardance through the polarizer and analyzer 1150 may need to be half-wave. A polarizer may be between the optical system 1130 and the analyzer 1150. The double-pass retardance 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 results in a longer path length for 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 embodiment, the LCoS SLM may have a first refractive index and a first thickness. For small angles, the double-pass retardance of an LCoS SLM having a first refractive index and a first thickness may be half-wave. For large angles, the double-pass retardation characteristic of an LCoS SLM having a first refractive index and a first thickness may not be half-wave (e.g., may be greater than half-wave). The thickness of the LCoS SLM may be changed from a first thickness to a second thickness, the second thickness being smaller than the first thickness. For small angles, the double-pass retardation characteristic of an LCoS SLM having a first refractive index and a second thickness may not be half-wave (e.g., may be less than half-wave). For large angles, the double-pass retardation characteristic of an LCoS SLM having a first refractive index and a second thickness may be half-wave.

[0127]

[0220] Also, while Figures 20A and 20B illustrate the use of a polarization-based SLM 1140, other types of SLMs may be utilized. Figure 20C illustrates the use of a deflection-based SLM 1140, such as 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 can couple light from one of the light sources 1110, 1112, and 1114 into a respective incoupling optical element 1360, 1362, and 1364 depending on the state of the pixels of the SLM 1140. In one state, light from the light sources 1110, 1112, and 1114 is directed to a respective incoupling optical element 1360, 1362, and 1364, as shown in Figure 20D. In another state, 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 may act as a light dump. As described 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 so that more incident light is absorbed than is reflected. The mask may be opaque.

[0128]

[0221] Other variations are possible. While the light sources are shown as emitters 1110, 1112, 1114 (e.g., LEDs, laser diodes) coupled to coupling optics 1105, such as a non-imaging optical coupling element (e.g., a compound parabolic concentrator (CPC) or a cone), other configurations are possible. For example, the coupling optics 1105 (e.g., a CPC) may be tilted with respect to the waveguide stack. In some cases, the projector (i.e., the optics 1130 and the SLM 1140) may be tilted with respect to the eyepiece (e.g., the waveguide stack). In some implementations, the lens optics 1130 is tilted with respect to the SLM 1140 to reduce distortions such as keystone distortion. A Scheinplug configuration may be employed to reduce such distortions. Components may be tilted as needed (e.g., the optics 1130 and / or the spatial light modulator 1140), for example, to conformally fit around the head and / or face. As mentioned above, the light emitter and / or coupling optics 1105 may be tilted. In some configurations, the assembly including the waveguide may be tilted with the side closer to the eye 210 (e.g., the temporal side) closer to the eye 210 to increase the perceived field of view of the entire binocular system (at the expense of overlap of the eyes).

[0129]

[0222] As noted above, the components and their positions and arrangements may vary. For example, FIG. 20F is a side view of system 2000F including a cover glass 2050 disposed between stack 2005 and 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 2050 may extend laterally (e.g., parallel to the x-axis) beyond stack 2005 so that light emitted by light sources 1110, 1112, 1114 enters optics 1130 without passing through a waveguide within stack 2005. While system 2000F shows a deflection-based SLM 1140, similar configurations of light sources may also be used with non-deflection-based SLMs or with any other configurations or features disclosed herein.

[0130]

[0223] FIG. 20G is a side view of system 2000G including a cover glass 2060 positioned 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 positioned 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 so that light emitted by light sources 1110, 1112, 1114 enters optics 1130 without passing through a waveguide within stack 2005. While system 2000G shows a deflection-based SLM 1140, similar configurations of light sources may also be used with non-deflection-based SLMs, or in or with any other configurations or features disclosed herein.

[0131]

[0224] Additionally, as described above, configurations that facilitate light recycling may be employed. FIG. 21 illustrates, for example, a partial side view of a system 2100 with a configuration that provides light recycling of light from a light source 1110. The light source 1110 may be positioned relative to a polarizer 1115 configured to recycle light having an undesired polarization. The polarizer 1115 may include, for example, 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 configured for use by a projector (not shown). For example, an SLM may operate appropriately with light of this first polarization. Light of a second polarization 2120 may be reflected back toward the light source 1110 and recycled. The polarization of light 2120 may be altered due to polarization rotation after reflecting off portions (e.g., sidewalls) of a coupling optic (not shown), such as a non-imaging optic like a compound parabolic concentrator (CPC) at various angles. Some light may be generated with the appropriate polarization (e.g., polarization direction) that may pass through the polarizer 1115. Multiple reflections may change the polarization of the light, causing it to exit with the desired polarization. This recycled light 2130 is then emitted back toward the polarizer 1115. Such a configuration may improve efficiency, e.g., energy efficiency, as more of the desired polarization is produced. Additionally or alternatively, a retarder may be used to change the reflected polarization state and recapture the light.

[0132]

[0225] FIG. 22 shows another configuration including light sources 1110, 1112, 1114 and corresponding collection optics 2210, 2212, 2214. The collection optics 2210, 2212, 2214 may include lenses or other optics for collecting light from the light sources 1110, 1112, 1114. The light sources 1110, 1112, 1114 may be laser diodes or other emitters that emit light over a wide range of angles. The collection optics 2210, 2212, 2214 may be used to collect most of that light. The light sources 1110, 1112, 1114 may emit light asymmetrically. For example, light may be emitted over a wider range of angles in one direction (e.g., the x or z direction) than in an orthogonal direction (e.g., the z or x direction). Thus, the collection optics 2210, 2212, 2214 may be asymmetric. For example, the collection optics 2210, 2212, 2214 may have different refractive powers in different possible orthogonal directions. The collection optics 2210, 2212, 2214 may include lenses, such as anamorphic lenses. The collection optics 2210, 2212, 2214 may also include non-imaging optics in some cases. Apertures 2220, 2222, 2224 may be included. For example, a diffuser 2230 may be included proximate the apertures 2220, 2222, 2224 when the light sources 1110, 1112, 1114 are lasers, such as laser diodes. When the diffuser is proximate the apertures 2220, 2222, 2224, the apertures may appear to be the location of laterally displaced light sources. The openings 2220, 2222, 2224 may coincide with incoupling optical elements on one or more waveguides via the optics and SLM, as described above. For example, each opening 2220, 2222, 2224 may coincide with a respective incoupling optical element. Similarly, in certain implementations such as that shown in FIG. 16A, each opening 2220, 2222, 2224 may coincide with a respective group of (e.g., color-selective) incoupling optical elements.

[0133]

[0226] A wide range of system variations and configurations are possible. For example, while linearly polarized light is described as propagating through optics 1130 to SLM 1140 and then back through the optics to the waveguide stack, some designs may use circularly polarized light instead. For example, circularly polarized light may be directed into optics 1130. A retarder, such as a quarter-wave plate, may be positioned so that this light passes through the retarder before entering the SLM. The retarder (e.g., a quarter-wave plate) may be positioned between optics 1130 and SLM 1140. In some cases, as described above, the retarder (e.g., a quarter-wave plate) may be affixed to SLM 1140 using, for example, adhesive or mechanical fasteners. The retarder (e.g., a quarter-wave plate) may convert linearly polarized light to circularly polarized light after reflection from SLM 1140. Thus, in some implementations, the circularly polarized light may pass through optics 1130 again toward the stack. For example, another retarder (e.g., a quarter-wave plate) proximal to the analyzer 1150 may convert circularly polarized light to linearly polarized light, which may or may not pass through the analyzer depending on the linear polarization (e.g., direction). The pixels of the SLM 1140 may have states that can be changed to rotate or not rotate the polarization. Still other configurations are possible.

[0134]

[0227] 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, polarizers 2312, 2335 such as linear polarizers (e.g., horizontal or vertical polarizers), retarders 2315, 2330, 2340 such as quarter-wave retarders (e.g., quarter-wave plates), 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 the 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, that might otherwise cause ghost images to be visible to the user. For example, polarization-selective and / or retarding optical elements (e.g., polarizers 2312, 2335 and retarders 2315, 2330, 2340) can be positioned 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, polarization-selective and / or retarding optical elements (e.g., polarizers 2312, 2335 and retarders 2315, 2330, 2340) can be positioned and configured to convert circularly polarized light into linearly polarized light that can be attenuated or eliminated by a polarizer (e.g., a linear polarizer). Circular polarizers that convert linearly polarized light into circularly polarized light, and vice versa, can be fabricated using polarization-selective and retarding 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 to remove 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 in a particular direction into left-handed circularly polarized light and to remove right-handed circularly polarized light.Circular polarizers can also be used to convert linearly polarized light of a particular orientation into right-handed circularly polarized light and to filter out left-handed circularly polarized light. Circular polarizers, or other configurations of optical elements used to convert linearly polarized light back into circularly polarized light and containing retardation properties that can selectively filter linearly polarized light, can be used to reduce back reflections from optical surfaces, as described below in connection with Figures 23A and 23B.

[0135]

[0228] Note that in Figures 23A and 23B, left- and right-handed circular polarizations are indicated by clockwise and counterclockwise arrows, respectively, and horizontal and vertical linear polarizations are indicated using horizontal arrows and circular dots, respectively.

[0136]

[0229] As mentioned above, Figure 23A shows 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 plates), are disposed to reduce back reflections from optical surfaces, such as surfaces of an optical system 2320, in the path of light illuminating and reflecting 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.

[0137]

[0230] As shown, light source 2305 emits light, as represented by light ray 2310. In some implementations, light ray 2310 can pass through polarization rotator 2307. Rotator 2307 is optional and can be used to rotate the polarization of the light from light source 2305, for example, light ray 2310. In various implementations, rotator 2307 can rotate the angle of polarization (e.g., linear polarization). For example, rotator 2307 can rotate the linear polarization of light ray 2310 to a direction aligned with and transmitted through first polarizer 2312. In some implementations, polarization rotator 2307 can comprise a retarder, for example, possibly a half-wave retarder. The optical axis of the half-wave retarder can be oriented to rotate the polarization of the light from light source 2305 from vertical to horizontal, or vice versa. Alternatively, polarization rotator 2307 may be configured to rotate the angle of polarization of linearly polarized light emitted from light source 2305 by a different amount. Polarization rotator 2307 need not be included in the system. For example, in implementations in which light source 2305 emits light having the same polarization as first polarizer 2312, polarization rotator 2307 may be omitted. As shown, light, e.g., light ray 2310, passes through polarizer 2312, shown here as a horizontal polarizer. If the light from light source 2305 is unpolarized, light transmitted through horizontal polarizer 2312, shown as light ray 2310, will be linearly polarized (e.g., horizontally polarized) after passing through polarizer 2312. While a horizontal linear polarizer is used in this example, it will be understood that the principles taught can also be applied using a vertical linear polarizer. Linear polarizers with different orientations other than vertical, linear, may also be used.

[0138]

[0231] Horizontally polarized light ray 2310 travels through retarder 2315, shown here as a quarter-wave retarder. This retarder 2315 may contain sufficient retardation to convert linearly polarized light to circularly polarized light. For example, horizontally polarized light may be converted to left-handed circular polarization, as indicated by the curved (e.g., clockwise) arrow. In this example, the combination of polarizer 2312 and 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., horizontally or vertically polarized) to a particular circular polarization (e.g., left-handed or right-handed circular polarization, or vice versa). Depending on the configuration, the circular polarizer may also block light of a particular circular polarization (e.g., right-handed or left-handed circular polarization).

[0139]

[0232] In some implementations, various optical elements have birefringence. In certain such cases, retarder 2315 may include an amount of retardation sufficient to convert linearly polarized light to circularly polarized light and need not be a quarter-wave plate. Because retardation may be contributed by other optical elements, more or less than a quarter-wave retardation may be included in retarder 2315. Similarly, retardation may be distributed among several optical elements. As another example, multiple retarders may be employed to provide the appropriate amount of retardation.

[0140]

[0233] Circularly polarized light ray 2310 (here left-hand circularly polarized) then passes through 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. This reflected light can be problematic when incident on at least one waveguide 2348 because these reflections can be directed toward a user's eye and form a "ghost" image visible to the user. For example, if a display uses at least one waveguide 2348 to project a first image into a viewer's eye, the user may also see a second, slightly duplicate image that is displaced (e.g., laterally displaced) relative to the first image. Such "ghost" images formed by reflections from optical surfaces that are directed toward the user's eye can disrupt or otherwise degrade the viewing experience. For example, as shown in FIG. 23A, light such as reflected light ray 2325 can reflect off a lens in optical system 2320. This light may be directed towards at least one waveguide 2348 configured to direct the light to the user's eye to present an image. However, in this case, the circularly polarized light reverses its handedness. For example, upon reflection from the lens, the direction of the circularly polarized light changes (e.g., from left-handed to right-handed). The right-handed reflected light ray 2325 then travels through the retarder 2315 and is converted to a linear polarization different from (e.g., orthogonal to) the linear polarization 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 vertical linear polarization, orthogonal to the polarization transmitted by the horizontal linear polarizer 2312. The horizontal linear polarizer 2312 selectively passes horizontally polarized light and removes vertically polarized light. Thus, reflected light ray 2325 is attenuated and / or not transmitted by horizontal linear polarizer 2312 and prevented from reaching at least one waveguide 2348, or at least a reduced amount of such reflected light reaches at least one waveguide 2348 or is coupled into it, for example, through an incoupling optical element (e.g., one or more incoupling gratings). The result is similar for left-handed circularly polarized light rays reflected from a different optical surface of optical system 2320, or from other optical surfaces on a different optical element.

[0141]

[0234] 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 the 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 ray 2310 may pass through the second retarder 2330 (e.g., a quarter-wave retarder). The second retarder 2330 is configured (e.g., the optical axis is appropriately oriented) so that the light beam 2310 is converted from left-handed circularly polarized light to horizontally linearly polarized light. Similarly, the second retarder 2330 converts the circularly polarized light back to the original linear polarization state output by the first polarizer 2312. As will be described below, this second retarder 2330 and second polarizer 2312 can be useful in reducing "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) when the light travels through at least one light guide 2348.

[0142]

[0235] A third retarder 2340 (e.g., a quarter-wave retarder or a quarter-wave 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 and third retarders 2330, 2340. As shown, the light ray 2310 becomes linearly polarized upon passing through the second polarizer 2335; 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 linearly polarized light is incident on the third retarder 2340. The third retarder 2340 is configured so that the light is converted back to circularly polarized light, and in some implementations, converted to 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 with circularly polarized light. In some implementations, the spatial light modulator is a reflective spatial light modulator that reflects incident circularly polarized light back as circularly polarized light. In some embodiments, the circularly polarized light reflected from the spatial light modulator may have the same handedness as that incident (e.g., left-handed circular polarization) depending on whether the spatial light modulator pixel is in an "on" or "off" state. In some embodiments, the spatial light modulator may reflect circularly polarized light of a different handedness than that incident (e.g., right-handed circular polarization) 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.

[0143]

[0236] FIG. 23A shows light, shown as ray 2342, reflected from the spatial light modulator and traveling toward waveguide 2385. Reflected ray 2342 is shown as left-handed circularly polarized light. Ray 2342 passes through 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 second polarizer 2335. In this example, horizontally polarized light is transmitted through second polarizer 2335. The linearly polarized light enters 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 optical system 2320. Again, reflections from optical surfaces, such as surfaces of 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 mentioned above, unwanted reflections can occur at any interface between media with different refractive indices, such as an air-material interface. As mentioned above, the inclusion of a second retarder and polarizer 2330, 2335 can attenuate these reflections and reduce the likelihood of ghost reflections. FIG. 23A shows light, shown as ray 2346, reflected from an optical surface of optical system 2320. Upon reflection from the surface, reflected ray 2346, which is circularly polarized and switches handedness, switches from left-handed to right-handed circular polarization in this example. The switched circular polarization is attenuated by the second circular polarizer formed by the second retarder and polarizer 2330, 2335. 23A , for example, reflected circularly polarized light 2346 enters second retarder 2330 and is converted by the second retarder to linearly polarized light having a different, e.g., orthogonal, linear polarization than that selectively transmitted by 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 vertically linearly polarized light, 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, while second polarizer 2335 is a horizontal polarizer that selectively passes horizontally polarized light and removes vertically polarized light.

[0144]

[0237] In contrast, light 2342 passing through optical system 2320 and incident on first retarder 2315 is circularly polarized and has a different handedness than light reflected from the optical surfaces of optical system 2320. This light 2342 directed towards at least one waveguide 2348 has a polarization (e.g., left-handed polarization) that is converted by first retarder 2315 to a linear polarization (e.g., horizontal linear polarization) that is selectively transmitted by first polarizer 2312. In this way, light 2342 reaches at least one waveguide 2348, where it can be coupled and directed towards the user's eye.

[0145]

[0238] In the embodiment shown in Figure 23A, a first circular polarizer formed by a first polarizer 2312 and a first retarder 2315, closer to the light source 2305, and a second circular polarizer formed by a second retarder 2330 and a second polarizer 2335, closer to the spatial light modulator, on either side of the optical system 2320, are used to reduce reflections that can result in "ghost images." An additional retarder 2340 is included between the second circular polarizer (e.g., second polarizer 2335) and the spatial light modulator to convert the light to circularly polarized light. However, a wide range of variations is possible. For example, only one circular polarizer may be included. Alternatively, additional circular polarizers or other types of polarization optics may be included.

[0146]

[0239] Figure 23B illustrates a third circular polarizer that can be added to the augmented reality system 2300 as shown in Figure 23A. In particular, Figure 23B illustrates a second circular polarizer including the second polarizer 2335 and second retarder 2330 introduced above, and a third retarder 2340, and further illustrates a spatial light modulator 2375. This spatial light modulator (SLM) 2375 may 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.

[0147]

[0240] 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 a second circular polarizer including second polarizer 2335 and second retarder 2330 and a 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 fourth retarder 2345 and third polarizer 2355 and the spatial light module 2375, or specifically, in the cover glass 2370 shown in FIG. 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, specifically at the cover glass 2370.

[0148]

[0241] FIG. 23B illustrates how light from light source 2305 (shown in FIG. 23A), e.g., light ray 2310, may propagate through a second circular polarizer including retarder 2330 and second polarizer 2335, and through third retarder 2340, to a third circular polarizer including fourth retarder 2345 and third polarizer 2355. After passing through the second circular polarizer including second retarder 2330 and second polarizer 2335, light ray 2310 from light source 2305 is incident on a third circular polarizer, specifically fourth retarder 2345. Fourth retarder 2345 may convert the circular polarization of light ray 2310 to linear polarization. In the example illustrated in FIG. 23B, light ray 2310 is circularly polarized (e.g., left-handed circularly polarized) and is converted to linear polarization (e.g., horizontally polarized) by fourth retarder 2345. This linearly polarized light travels through a third polarizer 2355, which in FIG. 23B includes a horizontal polarizer that selectively transmits horizontally polarized light. The linearly polarized light then propagates through a 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 then enters and passes through a 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 light. In various implementations, the compensator 2365 may be used to offset residual retardance within an SLM, which may comprise, for example, liquid crystal (e.g., LCoS) SLM cells. The compensator may introduce in-plane retardance and / or out-of-plane retardance. In some implementations, the compensator 2365 may include a combination of optical retarders that, when combined, produce a retardance that can potentially offset the residual retardance from the SLM (e.g., an LCoS panel).

[0149]

[0242] In FIG. 23B, the light after passing through the compensator 2365 is incident on the cover glass 2370 and the SLM 2375. This light incident on the cover glass 2370 and the SLM 2375 is shown 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 the pixels of the SLM 2375 are in the "on" state (which may be an undriven state in some implementations), the SLM 2375 may introduce a quarter-wave retardation characteristic for each pass 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 SLM 2375, represented by ray 2342, may pass through cover glass 2370 and compensator 2365 and be incident on fifth retarder 2360, which converts the circularly polarized light to linearly polarized light. In the example shown in FIG. 23B, the circularly polarized light incident on fifth retarder 2360 is left-handed, and fifth retarder 2360 converts the circularly polarized light to horizontally polarized light. Third polarizer 2355 may be configured to selectively transmit the polarization of the light output by fifth retarder 2360. Thus, in the example shown in FIG. 23B, where the light output from fifth retarder 2360 is horizontally polarized, third polarizer 2355 selectively transmits horizontally polarized light. This linearly polarized light transmitted by polarizer 2355 is incident on fourth retarder 2345 and 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 comprising a second retarder 2330 and a second polarizer 2335, the optical system 2320, and a first circular polarizer comprising a first polarizer 2312 and a first retarder 2315, as described above in connection with Figure 23A, onto at least one waveguide 2348 and into the user's eye.

[0150]

[0243] However, light reflected from the optical surface may be attenuated by the third circular polarizer, thereby reducing the likelihood that such reflections will reach at least one waveguide 2348 and be directed toward a user's eye, creating a ghost image. For illustrative purposes, FIG. 23B shows an example of a light ray 2343 being reflected from an optical surface of the third retarder 2340, e.g., from the interface between air and the third retarder 2340. As discussed above, reflections can occur at any interface between media with different refractive indices, such as between air and a material interface or interface between different dielectric layers. However, circularly polarized light reverses its handedness upon reflection. For example, reflection from the surface of the third retarder 2340 changes the direction of the circular polarization (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 than that selectively transmitted by the third polarizer 2355. In this case, for example, light reflected by the 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 removes vertically polarized light. Thus, the reflected light ray 2343 is attenuated and / or not transmitted by the third polarizer 2355 and 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.

[0151]

[0244] The results can be similar for circularly polarized light reflected from different optical surfaces. Figure 23B, for example, shows the reflection of incident light ray 2310 from the optical surface of fourth retarder 2345. Reflection 2350 off of fourth retarder 2345 switches the handedness of the polarization. For example, incident light ray 2310, shown as left-handed circularly polarized, is converted upon reflection to light ray 2350, shown as having right-handed circular polarization. Reflected light ray 2350 passes through third retarder 2340 and is converted to vertically polarized light. This vertically polarized light is selectively attenuated or eliminated by second polarizer 2335.

[0152]

[0245] As described above, a pixel of SLM2375 may be in an “on” state (although unactuated in some implementations) in which, for example, light incident on that pixel of SLM2375 is reflected therefrom and coupled into at least one waveguide 2348 and directed to a user's eye. However, a pixel of SLM2375 may be in an “off” state (which may be actuated in some implementations) in which light incident on that pixel of SLM2375 is not coupled into at least one waveguide 2348 and directed to a user's eye. In this “off” state, for example, various implementations of SLM2375 may not introduce a retardation characteristic upon reflection therefrom. Thus, in the example shown in FIG. 23B , circularly polarized light incident on SLM2375 may remain circularly polarized upon reflection from SLM2375. However, the handedness of this circular polarization may change upon reflection from SLM2375. For example, light ray 2310 shown in FIG. 23B , which is left-handed circularly polarized light incident on SLM 2375, may be converted to right-handed circularly polarized light upon reflection from SLM 2375. However, this reflected light may be selectively attenuated by third polarizer 2355. For example, right-handed circularly polarized light reflected from SLM 2375 may pass through cover glass 2370, compensator 2365, and fifth retarder 2360. Fifth retarder 2360 may convert the right-handed circularly polarized light to vertically polarized light, which is selectively attenuated by third polarizer 2355, which may include a horizontal polarizer. Thus, in various implementations, fifth retarder 2360 may convert light reflected from pixels of SLM 2375 to linearly polarized light that is orthogonal to the linearly polarized light selectively transmitted by third polarizer 2355 when the pixels of the SLM are in the “off” state. This third polarizer 2355 may 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 guided into the eye.

[0153]

[0246] Modifications to the configuration are possible, such as changing the polarizing optical elements, for example, including more or fewer circular polarizers.

[0154]

[0247] In various implementations, the third circular polarizer, including the fourth retarder 2345 and the third polarizer 2355, is omitted, as shown, for example, 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 illustrates a design of an augmented reality system 2300 including the components shown in FIGS. 23A and 23B , except for the fourth retarder 2345, the third polarizer 2355, and the fifth retarder 2360. Nevertheless, despite the omission 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 illustrates light reflected from the third retarder 2340 as ray 2380. Upon reflection from the surface of third retarder 2340, reflected ray 2380, which is circularly polarized, switches handedness. In this example, it is switched from left-handed circularly polarized light to right-handed circularly polarized light. Switched circularly polarized light 2380 then passes through compensator 2365 and is incident on cover glass 2370 and SLM 2375. As described above, SLM 2375 may reflect circularly polarized light of the same handedness. Thus, incident right-handed circularly polarized light may remain right-handed circularly polarized upon reflection. This circularly polarized light reflected from SLM 2375, represented by ray 2382, may then pass through cover glass 2370 and compensator 2365 and be incident on third retarder 2340. Switched circularly polarized light 2382 is attenuated by the second circular polarizer, particularly by third retarder 2340 and polarizer 2335. 23C , for example, circularly polarized light 2382 reflected from SLM 2375 is incident on third retarder 2340 and converted by third retarder 2340 into linearly polarized light having a different, e.g., orthogonal, linear polarization than that selectively transmitted by second linear polarizer 2335. In this case, for example, right-handed circularly polarized light 2382 is converted by third retarder 2340 into vertically linearly polarized light that is orthogonal to the polarization selectively transmitted by second polarizer 2335. Second polarizer 2335 attenuates or prevents transmission of this linearly polarized light.

[0155]

[0248] Reflections that may contribute to ghost reflections may also potentially be reduced by tilting optical surfaces within the system. FIG. 24 illustrates an exemplary configuration with tilted optical surfaces to reduce reflections that may produce ghost reflections. FIG. 24 illustrates an augmented reality display system 2400 including a light source 2305 that emits light represented by light rays 2310 that pass 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, which may form a first circular polarizer, and a lens 2320 are shown in FIG. 24 for illustrative purposes. However, additional components may be included, or components may be excluded, or may be positioned or configured differently. In the illustrated embodiment, the SLM 2375 includes a cover glass 2370. The cover glass 2370 may contribute to reflections that produce ghost images. Thus, in some implementations, the cover glass 2370 can be shaped to direct reflections that may prevent ghost images from being directed to the user's eyes. As shown, the cover glass 2370 has a surface that can be tilted so that the surface is 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). A major surface of the cover glass 2370 may have a normal that is tilted so that it is not aligned or parallel to the optical axis of the augmented reality display system 2400 or the optical system 2320 of the optical components therein. 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 a diffractive optical element) to incouple light into the at least one waveguide 2348, reducing the likelihood that reflections from the cover glass 2370 will enter the at least one waveguide 2348. As shown, reflected light 2405 returns 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, where it is at least partially recycled by the light source 2305 .

[0156]

[0249] Although FIG. 24 shows the cover glass 2370 with a sloped surface, any component in the system where unwanted reflections may occur can include a sloped optical surface to deflect reflections and prevent them from coupling into the at least one waveguide 2348. Accordingly, optical surfaces on other components, such as polarizers, retarders, etc., may be sloped to reduce reflections from coupling into the at least one waveguide 2348 and the user's eye. Various variations in the shape and size of the cover glass 2370 or other optical components are possible. The cover glass 2370 or other optical component may be thin, for example. Similarly, the cover glass 2370 or other optical component may have an aspect ratio (length to thickness) different from that shown in FIG. 24 . In some implementations, the cover glass 2370 or other optical component is wedge-shaped. However, other shapes are possible.

[0157]

[0250] Still other arrangements are possible. For example, FIG. 25 illustrates an implementation of an augmented reality display system 2500 similar to system 2400 shown in FIG. 24 , but further including a light dump 2505 to absorb light directed thereto. System 2500 includes a sloped 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 may include an absorbing material or structure configured to absorb light. The location of the light dump 2505 can vary depending on the implementation, for example, depending on the angle of the sloped cover glass 2370. As mentioned above, this approach can be applied to other optical surfaces in the system. Also, the shapes and sizes of the optical elements may be different.

[0158]

[0251] A wide range of variations in augmented reality displays are possible. Variations in polarization optical elements are possible. For example, while horizontal polarizers are used, in some implementations vertical polarizers or a combination of horizontal and vertical polarizers are employed. Furthermore, polarizers featuring polarizations other than vertical or horizontal may be used. Similarly, 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.

[0159]

[0252] Additionally, 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 circular polarization may be left-handed circular polarization. Still other variations are possible. Different retarder configurations can be employed to generate different combinations of left-handed and / or right-handed polarization other than those shown. Also, some implementations may use elliptically polarized light instead of circularly polarized light. For example, retarders may be employed to convert elliptically polarized light to linearly polarized light and vice versa. Linear polarizers can be used to filter light and may be used to reduce ghost reflections as described herein.

[0160]

[0253] In some implementations, other types and configurations of polarizing elements 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 may include a sufficient amount of retardation to convert linearly polarized light to circularly polarized light and need not be a quarter-wave retarder. Because retardation can be contributed by other optical elements, retardation greater or less than a quarter wave may be included in any one or more of the retarders 2315, 2330, 2340. Similarly, retardation can be distributed among several optical elements. As another example, multiple retarders may be employed to provide the appropriate amount of retardation. Also, as mentioned above, in some implementations, elliptically polarized light may be used instead of circularly polarized light. For example, a retarder may be employed to convert elliptically polarized light to linearly polarized light, or vice versa. Linear polarizers can be used to filter light and may be used to reduce ghost reflections as described herein.

[0161]

[0254] Furthermore, 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 polarizing elements may be used in different amounts, positions, and arrangements. For example, one or more of the retarders and / or polarizers may comprise a film.

[0162]

[0255] In some implementations, the spatial light modulator may operate differently, for example, the spatial light modulator may operate with and / or output light other than circularly polarized light.

[0163]

[0256] Embodiments of the present invention relate to the use of hybrid surface relief structures, also referred to as hybrid diffractive nanofeatures, in which there is a refractive index modulation or variation (e.g., perpendicular to the direction normal to the substrate) along a single diffractive structure. In these hybrid diffractive structures, a high refractive index material is adjacent to a substrate, which may have a refractive index greater than n=1.8, and a low refractive index material is adjacent to the surrounding environment, e.g., air.

[0164]

[0257] Hybrid eyepiece waveguide designs can also incorporate the use of diffractive features with different refractive indices located at different locations in the patterned waveguide, such that light can propagate through diffractive structures with at least two different refractive indices as it propagates from one side of the CPE to the other. In some examples discussed herein, the initial pattern is lithographically created using Magic Leap's J-FIL nanoimprint lithography technology, but embodiments of the present invention are not limited to this particular lithography technique. Thus, patterns can be created using other lithography processes, and in some cases, can even utilize optical lithography. As described herein, embodiments of the present invention provide hybrid structures formed in eyepiece waveguides to project a bright, uniform color image toward a user.

[0165]

[0258] To demonstrate some of the advantages of utilizing a hybrid grating, the basic functionality of a single-layer eyepiece design utilizing a micro-LED display engine that uses a single input coupling grating (ICG) to launch light into a waveguide will be described in connection with Figures 26A-26D.

[0166]

[0259] Figure 26A is a simplified cross-sectional view of an eyepiece waveguide according to one embodiment of the present invention. Figure 26A shows a single-layer eyepiece waveguide design with gradation, i.e., the grating strength / efficiency varies with position as light propagates within the CPE in this example. Eyepiece waveguide 2600 includes an ICG 2610 and a CPE 2612 on one side of eyepiece waveguide 2600, the user side. In this example, eyepiece waveguide 2600 is fabricated using substrate 2605, which supports total internal reflection (TIR) ​​of the incoupled light and has a refractive index of n=2.0, although substrates with other refractive indices can be used.

[0167]

[0260] In these single-layer eyepiece waveguide designs, multiple colors of light, such as red, green, and blue (RGB), are incoupled by a single ICG, propagate by TIR within the eyepiece waveguide, and outcoupled by a CPE. Thus, the eyepiece waveguide supports all colors simultaneously, as opposed to designs that utilize one eyepiece waveguide per color, i.e., a red eyepiece waveguide for red wavelengths, a green eyepiece waveguide for green wavelengths, and a blue eyepiece waveguide for blue wavelengths.

[0168]

[0261] While a single-layer eyepiece waveguide design is shown in Figure 26A, other embodiments of the present invention utilize waveguide stacks that include multiple waveguide layers. Thus, embodiments of the present invention can display multiple colors through each waveguide layer, or a single color through each waveguide layer.

[0169]

[0262] Figure 26B is a simplified k-space diagram showing the field of view, ICG, and CPE grating vectors of the eyepiece waveguide shown in Figure 26A. In Figure 26B, the ICG 2610 shown in Figure 26A couples light into the grating vector k ICG The light propagating in the eyepiece waveguide is represented by the solid grating vectors k1 and k2, and the light outcoupled by the CPE 2612 shown in FIG. 26A is represented by the dashed grating vectors k2 and k1. reccorresponds to a grating that "recycles" light within the eyepiece waveguide, thereby improving efficiency. The field of view under consideration is 26° (H) x 26° (V), and all three R, G, and B wavelengths can be launched into the eyepiece waveguide using the ICG2610, with input light provided by, for example, a micro-LED lighting projector.

[0170]

[0263] FIG. 26C is a simplified plan view of the user side of the eyepiece waveguide shown in FIG. 26A. FIG. 26D is a simplified plan view of the world side of the eyepiece waveguide shown in FIG. 26A. As shown in FIG. 26C, the ICG 2610 shown in FIG. 26A is formed on or on the user side of substrate 2605 with a grating corresponding to grating vector k1. In addition, as shown in FIG. 26D, grating vectors k2 and k rec is formed on or within the world side of substrate 2605. Additional description regarding k-space diagrams is provided in International Patent Application No. PCT / US2022 / 043721, filed September 15, 2022, the disclosure of which is incorporated herein by reference in its entirety for all purposes.

[0171]

[0264] Referring again to FIG. 26A, ICG 2610 is used to couple light from a projector (not shown) into substrate 2605, which can be high-index glass (e.g., n=2.0). The flow of light is illustrated using a momentum space representation in FIG. 26B. As shown in FIG. 26B, the inner circle with radius = 1 represents the momentum of light at all physically possible angles of incidence in free space or vacuum (i.e., refractive index n=1). The outer circle with radius = refractive index of the substrate (in this case, n=2.0) represents all physically possible angles of incidence inside the substrate. The three lines on the outer circle represent refractive index values ​​at red, green, and blue wavelengths, respectively. The field of view is described by the ranges of barrel-shaped R, G, and B boxes 2622, 2624, and 2626 shown in FIG. 26B. Thus, light coupled into or launched into the substrate has momentum that lies in an annular region in momentum space (i.e., between the inner and outer circles at each wavelength) and does not escape unless and until it interacts with a diffraction grating, which changes the momentum.

[0172]

[0265] The CPE 2612 in this example has a 1D binary sail-shaped grating defined by the momentum translations k1 and k2 in FIG. 26B. Diffraction of the emitted light by these gratings allows the emitted light to be spread over a large area (i.e., due to pupil dilation). At the same time, these gratings also outcouple diffused light, which corresponds to the momentum transfer indicated by the dashed grating vectors k2 and k1 in FIG. 26B. This outcoupled light is seen by the user's eye, and digital content can then be viewed. Because the eyepiece has two sides (i.e., a user side facing the user and a world side facing the outside world), either a 2D grating defined by momentum translations k1 and k2 or a 1D grating on two sides of the eyepiece can be used. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0173]

[0266] Figure 27A is a simplified schematic diagram illustrating an example of an eyepiece waveguide including a hybrid individual diffractive structure, according to an embodiment of the present invention. As shown in the plan view of Figure 27A, eyepiece waveguide 2700 includes an ICG 2710 and a CPE 2712 including an individual diffractive structure that may have multiple refractive index materials, i.e., a hybrid individual diffractive structure. Figure 27A shows four zones: first zone 2720 includes first individual diffractive structure 2722; second zone 2730 includes second individual diffractive structure 2732; third zone 2740 includes hybrid individual diffractive structure 2742; and fourth zone 2750 includes fourth individual diffractive structure 2752. In this example, only hybrid individual diffractive structure 2742 includes multiple refractive index materials, but this is not required; the other diffractive structures can be hybrid individual diffractive structures.

[0174]

[0267] As shown in FIG. 27A, the individual diffractive structure 2722 includes a low refractive index material (e.g., a material having a refractive index between 1.6 and 1.8) having a first height H1 formed on a substrate 2715 (e.g., a material having a refractive index between 2.0 and 2.65), the second individual diffractive structure 2732 includes a low refractive index material formed on the substrate 2715 and having a second height H2 higher than the first height H1, the hybrid individual diffractive structure 2742 includes a first portion formed from the substrate material, i.e., a high refractive index material having a third height H3 and a low refractive index material having a fourth height H4, and the fourth individual diffractive structure 2752 includes a high refractive index material having a fifth height H5.

[0175]

[0268] Therefore, the CPE can be referred to as a two-level hybrid grating structure. In the first level, the individual diffractive structures can be formed using materials with two different refractive indices, i.e., a hybrid individual diffractive structure, and thus the CPE can be referred to as a hybrid CPE. This first level is illustrated by a hybrid individual diffractive structure 2742 including a first portion 2744 formed from a substrate material that has been etched so that the first portion 2744 extends from the substrate to a third height H3, and a low refractive index material 2746 having a fourth height H4 deposited on the first portion 2744. Therefore, by including individual diffractive structures fabricated using different materials, the CPE can be referred to as a hybrid CPE.

[0176]

[0269] The second level is illustrated by a CPE including individual diffractive structures, i.e., nanofeatures, with different properties, comprising different materials. Referring to FIG. 27A , for example, first individual diffractive structure 2722 is fabricated using a low-index material, while fourth individual diffractive structure 2752 is fabricated using a high-index material. As a result, the grating parameters of the gratings formed in these different zones of the CPE vary across the CPE, with some zones using low-index diffractive structures and other zones using high-index diffractive structures. For example, some zones are closer to the ICG with the low-index diffractive structure, while other zones are farther from the ICG with the high-index diffractive structure. Thus, in this example, as a result of the nanofeatures being fabricated from different materials, the grating strength / efficiency increases as light propagates from ICG 2710 to CPE 2712. Thus, this second level can include nanofeatures formed from a first material deposited on the substrate (e.g., first individual diffractive structure 2722), nanofeatures formed by etching the substrate to form portions of the substrate extending from the substrate, the first material deposited on the portions of the substrate extending from the substrate (e.g., hybrid individual diffractive structure 2742), and / or nanofeatures formed from portions of the substrate extending from the substrate (e.g., fourth individual diffractive structure 2752). Thus, the combination of these different nanofeatures produces a hybrid CPE. As more fully described in connection with Figures 36A and 36B, embodiments of the present invention are not limited to etching structures to provide high refractive index nanofeatures, but can also include deposition of high refractive index materials to form the nanofeatures.

[0177]

[0270] In the example shown in FIG. 27A , the four discrete zones, first zone 2720, second zone 2730, third zone 2740, and fourth zone 2750, all have uniform grating characteristics with step discontinuities from one zone to the next. This discontinuity can introduce a phase shift that reduces the modulation transfer function (MTF) of the display. However, embodiments of the present invention are not limited to this exemplary design, which is provided merely as an illustration. Rather, transition zones having different grating characteristics can be provided between each of the discrete zones, thereby providing a smooth transition in grating characteristics as light propagates through the CPE. The inventors have found that, for example, the width of ICG 2710 measured along the x-axis is d i If the width d f ≧d i It was determined that a transition region between adjacent zones with

[0178]

[0271] Although four distinct regions, i.e., first zone 2720, second zone 2730, third zone 2740, and fourth zone 2750, are shown in Figure 27A, it will be understood that this design is merely exemplary and that continuous variations in diffractive structure may be utilized, for example, multiple zones may be used, or continuously varying material composition / height / shape with position, etc. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0179]

[0272] Figure 27B is a simplified schematic diagram illustrating a process for forming hybrid individual diffractive structures according to one embodiment of the present invention. In Figure 27B, a low refractive index imprint material 2780 is used to form an imprint pattern with a large residual layer thickness. An etching process can be used to transfer this imprint pattern to a high refractive index substrate to form individual diffractive structures 2782. Alternatively, if the etching process is terminated before all of the imprint layer is removed, a hybrid individual diffractive structure 2784 is formed that includes a lower portion comprising a high refractive index substrate material and an upper portion comprising a low refractive index imprint material 2780. The presence of the low refractive index imprint material 2780 reduces the reflectivity of the diffractive structure, thereby improving transmission through the hybrid individual diffractive structure.

[0180]

[0273] The pattern can be etched into an underlying low- or high-index layer on a high-index substrate via reactive ion etching (RIE), ion beam etching / milling (IBE / M), RIE-inductively coupled plasma (RIE-ICP), etc. It can also be etched directly into the high-index substrate. The pattern can also be a layered pattern realized using a physical vapor deposition (PVD) process or deposition on an initial polymer pattern using a chemical vapor deposition (CVD) process, such as evaporation, sputtering, plasma-enhanced CVD (PECVD), or atomic layer deposition (ALD). The waveguide diffraction structure can be any shape, such as 1D: sail-shaped, sawtooth, sloped, multi-step, or 2D: pillar, hole, sloped or blazed pillar, metastructure, or 3D: double-sided blazed pillar or hole. A graded height / depth etching or deposition profile can be achieved using a single-depth initial imprint pattern with varying residual layer thickness, which can act as an etching mask or a graded initial pattern where etching and deposition maintain a similar gradient profile. These embodiments are shown in Figures 33A-34C. The step height, depth, duty cycle, etc. are key factors that allow the light from the projector interfacing with the ICG to be efficiently and uniformly guided, guided through the substrate with TIR, and outcoupled towards the user through a composite pupil dilator (CPE) that combines the functions of an orthogonal pupil dilator (OPE) and an exit pupil dilator (EPE).

[0181]

[0274] FIG. 27C is a simplified schematic diagram illustrating the variation of grating parameters across eyepiece waveguide 2760, according to one embodiment of the present invention. In FIG. 27C, ICG 2762 increases in grating strength / efficiency up to position A, where it decreases in the direction toward CPE 2764. Similarly, CPE 2764 increases in grating strength / efficiency away from ICG 2762. In this example, the grating characteristics vary continuously across eyepiece waveguide 2760, rather than discontinuously. Methods for fabricating such continuously varying structures are described in detail with respect to FIGS. 33A, 36A, and 36B below.

[0182]

[0275] Figures 27D-27G show how hybrid discrete diffractive structures can be fabricated on top of a low index coated substrate / waveguide to achieve improved uniformity over a large field of view, as evidenced by the corresponding plots of eyebox efficiency.

[0183]

[0276] Figure 27D is a simplified cross-sectional diagram illustrating a hybrid discrete diffractive structure according to one embodiment of the present invention. As shown in Figure 27D, a substrate 2770 supports a high refractive index material 2772 (e.g., TiO2, having a refractive index of 2.45) and a low refractive index material 2774 (e.g., photoresist, having a refractive index of 1.65) supported by the high refractive index material 2772. This hybrid discrete diffractive structure is used in a CPE to generate the plot shown in Figure 27E.

[0184]

[0277] FIG. 27E is a plot of the eyebox efficiency across the field of view for an eyepiece using the hybrid discrete diffractive structure shown in FIG. 27D. As shown in FIG. 27E, the user eyebox efficiency (U EBE ) is 6.93%, and the world eyebox efficiency (W EBE ) is 3.13%. Uniformity is characterized using the 80 / 20 percentile score (i.e., figure of merit (FoM)), which is the ratio of the difference between the 80th and 20th percentiles to the 50th percentile. FOV ), the uniformity of this FoM measured over the inner 80% of the field of view (U inner80 ), the uniformity FoM measured over the entire surface is 3.536, with a low value characterizing good uniformity.

[0185]

[0278] Figure 27F is a simplified cross-sectional view illustrating a hybrid individual diffractive structure formed on a low-index coating according to one embodiment of the present invention. As shown in Figure 27F, the hybrid structure can be fabricated on top of a substrate coated with a low-index material, i.e., substrate 2770 supports a low-index film 2790 (e.g., SiO2, having a refractive index of approximately 1.45 at 545 nm) that supports a high-index material 2772 (e.g., TiO2, having a refractive index of 2.45), and a low-index material 2774 (e.g., photoresist, having a refractive index of 1.65) supported by the high-index material 2772. Such an embodiment is relevant for wide-field, single-layer, single-wavelength AR displays. This hybrid individual diffractive structure is used in a CPE to generate the plot shown in Figure 27G.

[0186]

[0279] Figure 27G is a plot of the eyebox efficiency across the field of view for an eyepiece using the hybrid discrete diffractive structure shown in Figure 27F. This plot shows the efficiency distribution across a wide field of view of 55° (H) x 55° (V) for an eyepiece waveguide design using a 2.0 index waveguide. As shown in Figure 27G, the user eyebox efficiency (U EBE ) is 5.20%, and the world eyebox efficiency (W EBE ) is 1.98%, and the total field of view (U FOV ) is 2.546, and the inner 80% (U inner80 The uniformity FoM over the entire waveguide is 1.394. The high-index TiO2 grating is capped on top with a low-index layer, but still provides higher diffraction efficiency than the low-index grating. This provides high efficiency but reduces uniformity, as shown by comparison with Figure 27E. One approach to the reduced diffraction efficiency of such hybrid gratings is the use of a low-index material layer between the grating structure and the substrate. Such a hybrid structure on top of a low-index coated waveguide provides good uniformity, as shown in Figure 27G.

[0187]

[0280] To fully illustrate and understand the benefits offered by eyepiece waveguides utilizing the hybrid discrete diffractive structures described herein, Figures 28A-20E show the effect of using a single eyepiece waveguide design and the same eyepiece layout for the same grating vector, but different grating types with different grating height gradient patterns. To demonstrate the performance of the various designs, luminance efficiency distribution plots normalized to maximum luminance are provided along with useful optical performance metrics for a 26° × 26° field of view for RGB wavelengths.

[0188]

[0281] In particular, the eyepiece design shown in Figure 26A considers three different grating types, as shown in Figures 28A, 29A, and 30A. In all cases, a sail-shaped grating shape with a 50% duty cycle was used, but the individual diffractive structures can be made from different materials and fabricated using the different material-dependent manufacturing processes described herein.

[0189]

[0282] Figure 28A is a simplified cross-sectional view of an eyepiece waveguide according to one embodiment of the present invention. In this example, eyepiece waveguide 2800 includes a CPE with an imprinted grating (i.e., a sail grating) having a refractive index of 1.65 formed on a substrate (e.g., glass having a refractive index of 2.0). The imprinted grating is formed in 12 regions as described in connection with Figure 28B. As shown in Figure 28A, the imprint thickness increases with distance from the ICG.

[0190]

[0283] Figure 28B is a plot showing the refractive index zones of the eyepiece waveguide 2800 shown in Figure 28A. It shows the thickness of the imprinted grating in the 12 illustrated refractive index zones, increasing from 10 nm in the portion of the CPE proximal to the ICG to 110 nm in the portion of the CPE distal to the ICG.

[0191]

[0284] 28C-28E are plots of eyebox efficiency across the field of view for the eyepiece shown in FIG. 28A. FIG. 28C is a plot for red wavelengths, FIG. 28D is a plot for green wavelengths, and FIG. 28E is a plot for blue wavelengths. The performance metric analyzed is user eyebox efficiency (U EBE ) and world-side eyebox efficiency (W EBE ) and , which indicate the fraction of the total incident power from the projector that ultimately reaches the eyebox plane at the nominal eye distance from the waveguides on either side of the eyepiece. The uniformity of the display is measured by U inner80 The 80-20th percentile score over the inner 80% of the visual field is captured by the 80-20th percentile score, which is the ratio (median) of the difference between the 80th and 20th percentiles to the 50th percentile. inner80 Lower values ​​of σ indicate better uniformity. Furthermore, the center-to-peak ratio CP (i.e., the efficiency at the center divided by the peak efficiency, with an ideal value = 1) indicates the centrality of the efficiency distribution across the field of view.

[0192]

[0285] In these plots, light injection is from the top right of the field of view. The efficiency distribution is non-uniform because light rays corresponding to different incident angles diffuse inside the waveguide and interact differently with the grating. As shown in these figures, the uniformity for blue and green wavelengths is relatively high, while the red wavelength has reduced outcoupling in the temple region, resulting in a dark region in the top right corner of the field of view shown in Figure 28C. As is evident from the optical efficiency distributions in Figures 28C-28E, the red efficiency is significantly smaller than that of green and blue due to the small diffraction efficiency associated with the low-index grating.

[0193]

[0286] Figure 29A is a simplified cross-sectional view of an eyepiece waveguide 2900, according to one embodiment of the present invention. In this example, a substrate, e.g., a glass substrate having a TiO layer with a refractive index of 2.45 deposited thereon, is etched to produce a grating (i.e., a sail grating) with a refractive index of 2.45. The grating is formed into 12 regions as described in connection with Figure 29B. As shown in Figure 29A, the thickness of the grating increases with distance from the ICG.

[0194]

[0287] Figure 29B is a plot showing the refractive index zones of the eyepiece waveguide 2900 shown in Figure 29A. It shows the thickness of the imprinted grating in the 12 illustrated refractive index zones, increasing from 10 nm in the portion of the CPE proximal to the ICG to 75 nm in the portion of the CPE distal to the ICG.

[0195]

[0288] Figures 29C-29E are plots of eyebox efficiency across the field of view for the eyepiece shown in Figure 29A. Figure 29C is a plot for red wavelengths, Figure 29D is a plot for green wavelengths, and Figure 29E is a plot for blue wavelengths. As shown in these figures, using a high index grating reduces the uniformity of blue and green wavelengths, resulting in significant outcoupling of these wavelengths in the temple region (i.e., the upper right portion of the field) and the dark nose region (i.e., the lower left portion of the field). Utilizing the high index grating shown in Figure 29A improves efficiency but reduces uniformity. This difference arises from the difference in diffraction efficiency (i.e., the diffusion and outcoupling of the emitted light) between the low index grating and the high index grating.

[0196]

[0289] FIG. 30A is a simplified cross-sectional view of an eyepiece waveguide including a hybrid ICG according to one embodiment of the present invention. In contrast to the diffractive structures shown in FIGS. 28A and 29A, the diffractive structure is fabricated to include an imprinted grating having a refractive index of 1.65 formed on a substrate in a portion of the CPE proximal to the ICG and a hybrid individual diffractive structure in a portion of the CPE distal to the ICG. These hybrid individual diffractive structures include a substrate portion adjacent to the substrate fabricated from the substrate material (i.e., a refractive index of 2.45 of a TiO layer deposited on glass) and an imprint portion distal to the substrate fabricated from an imprint layer (i.e., a refractive index of 1.65). The grating is formed into 12 regions as described in connection with FIG. 30B. As shown in FIG. 30A, the thickness of the nanofeatures (i.e., both the imprinted grating and the hybrid individual diffractive structure) increases with distance from the ICG.

[0197]

[0290] Figure 30B is a plot showing the refractive index zones of the eyepiece waveguide shown in Figure 30A. The thickness of the imprinted grating begins at 15 nm in the portion of the CPE proximal to the ICG and increases to 45 nm in zone 7. The thickness of the hybrid individual diffractive structures is constant in zones 8-12, while the thickness of the portion fabricated from the substrate material increases from 15 nm in zone 8 to 35 nm in zone 12. As a result, the refractive index of each of the hybrid individual diffractive structures increases with distance from the ICG.

[0198]

[0291] Figures 30C-30E are plots of eyebox efficiency across the field of view for the eyepiece shown in Figure 30A. Figure 30C is a plot for red wavelengths, Figure 30D is a plot for green wavelengths, and Figure 30E is a plot for blue wavelengths. The use of hybrid discrete diffractive structures of varying height imprinted gratings and increasing refractive index results in improved uniformity for both the eyepiece fabricated using only imprinted gratings as described in connection with Figure 28A and the eyepiece waveguide fabricated using only etched substrate gratings as described in connection with Figure 29A.

[0199]

[0292] As shown in Figures 30C-30E, outcoupling of red wavelengths in the temple region is reduced, while the uniformity of the field of view for blue and green wavelengths is also improved. In addition to improved uniformity, a significant improvement in user eyebox efficiency is realized using the hybrid CPE design shown in Figure 30A. As shown by comparing Figures 28C-28E and 29C-29E with Figures 30C-30E, the user eyebox efficiency (U EBE ) increases from 0.74% to 4.01% for red wavelengths, from 2.82% to 6.21% for green wavelengths, and from 3.59% to 4.28% for blue wavelengths when hybrid discrete diffractive structures are used instead of imprinted gratings. It also increases from 3.53% to 6.21% for green wavelengths and from 1.98% to 4.28% for blue wavelengths when hybrid discrete diffractive structures are used instead of gratings fabricated from the substrate material. Similarly, as shown in the figure, improvements in world eyebox efficiency beyond 80% inside the field of view and in the 80-20th percentile score are also achieved. Furthermore, the center-to-peak ratio (CP) indicates the centrality of the efficiency distribution across the field of view. Although the efficiency distribution is nonuniform, the color correction algorithm adjusts the weights corresponding to different incident angles within the field of view to obtain good color (white) uniformity for the AR display.

[0200]

[0293] Thus, the eyepiece waveguide shown in FIG. 30A , which includes a hybrid discrete diffractive structure, provides a structure that achieves high red efficiency while also maintaining good uniformity for all three colors by combining the low diffuse diffraction efficiency of a low-index grating with the high outcoupling diffraction efficiency of a high-index grating. Note that in display systems using μLED-based projectors, achieving high efficiency for red wavelengths is desirable due to the low LED efficiency in producing these wavelengths. Thus, embodiments of the present invention utilizing hybrid discrete diffractive structures can provide a crucial optimization option for meeting both efficiency and uniformity goals for single-layer eyepiece waveguide AR displays.

[0201]

[0294] Furthermore, because the hybrid discrete diffractive structure shown in Figure 30A has the imprint material facing the user side, reflections from the CPE are reduced even in the absence of a planarization or encapsulation layer. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0202]

[0295] Examples of how various refractive index regions within the CPE of a waveguide eyepiece improve the brightness (e.g., eyebox efficiency percentage) of a projected virtual image using additional architectures in which the majority of the diffractive structures in the intermediate and end zones of the CPE are composed of two or more refractive index materials are shown and described in connection with Figures 31A-31D and 32A-32D.

[0203]

[0296] In particular, Figures 31A and 31B show examples of eyepiece waveguides useful for projecting RGB light into a single active layer eyepiece waveguide using single or multiple ICG pupils with improved efficiency while maintaining the same uniformity by incorporating regions of low refractive index features to compensate for the blue light that is initially diffusely outcoupled.

[0204]

[0297] FIG. 31A is a simplified cross-sectional view of an eyepiece waveguide according to one embodiment of the present invention. The eyepiece waveguide 3100 is formed using a substrate 3105 (e.g., a substrate having a refractive index of n=2.25) and includes an ICG 3110 and a CPE 3112. In some embodiments described herein, the substrate has a discrete material refractive index height gradient, an absolute (i.e., composite material multi-index) height gradient, or a duty cycle gradient. The diffractive structure can include different types of structures in different regions; for example, a sail shape of a particular duty cycle and height of a material having a first refractive index can be present in one region of the CPE, while another region of the CPE (or ICG) can have a blazed sawtooth structure with a second material of a different refractive index. In some implementations, the diffractive structure can include an interconnect material with a residual layer thickness of less than about 50 nm.

[0205]

[0298] In this embodiment, an anti-reflection pattern 3107 is formed on the opposite side of the ICG 3110. The anti-reflection structure can be disposed on the substrate at a position that does not overlap with the outcoupling diffractive structure. Furthermore, the anti-reflection structure can be present in any area of ​​the hybrid surface relief waveguide that does not have a diffractive structure, including the other side of the waveguide substrate opposite the input coupler or the area outside the composite extender output coupler (CPE). The anti-reflection structure can include a single material or multiple materials, each with a single or multiple refractive index.

[0206]

[0299] Furthermore, a reflective layer 3111 (e.g., an aluminum layer) is deposited on the ICG 3110 to enhance the ICG in-coupling efficiency. For example, an imprinted grating using a material with a refractive index n=1.65 is utilized to form the ICG and CPE.

[0207]

[0300] In this embodiment, the substrate 3105 is etched in the CPE region to reduce the substrate thickness. Furthermore, portions of the substrate proximal to the ICG, which may be part of the CPE, are not etched, and a diffractive structure is formed by depositing and patterning a low-index material to form single-level or multi-level nanofeatures. As described below, this diffractive structure reduces initial outcoupling and increases diffusion at shorter wavelengths, while increasing initial outcoupling at longer wavelengths. Therefore, the eyepiece waveguide includes a substrate with a variable thickness; in this embodiment, the substrate thickness is higher at the ICG and portions of the substrate proximal to the ICG and lower at portions of the substrate distal to the ICG. Furthermore, the substrate thickness can be uniform or vary depending on the position within the CPE. Furthermore, as described above in connection with FIG. 27A , etching the substrate can produce nanofeatures that include base portions formed from the substrate material and extending from the substrate.

[0208]

[0301] Figures 31B-31D are plots of eyebox efficiency across the field of view for the eyepiece shown in Figure 31A. In these figures, the ICG is located above and to the right of the field of view, injecting light below and to the left. The eyebox efficiency for blue wavelengths (e.g., 455 nm) is shown in Figure 31B, the eyebox efficiency for green wavelengths (e.g., 530 nm) is shown in Figure 31C, and the eyebox efficiency for red wavelengths (e.g., 630 nm) is shown in Figure 31D. For a grating designed to operate at green wavelengths (e.g., 530 nm), injection of light at short wavelengths, e.g., blue wavelengths, results in rapid outcoupling, as indicated by the bright blue light in the temple region of the field. In contrast, injection of light at longer wavelengths, e.g., red wavelengths, results in reduced initial outcoupling, as indicated by the bright red light in the nasal region of the field. Utilizing embodiments of the present invention such as those described in connection with Figures 32A-32D, at shorter wavelengths, initial outcoupling is reduced and diffusion within the CPE is increased, while at longer wavelengths, initial outcoupling is increased while maintaining the desired diffusion, thereby improving uniformity.

[0209]

[0302] Figure 32A is a simplified cross-sectional view of an eyepiece waveguide according to one embodiment of the present invention. Eyepiece waveguide 3200 is formed using substrate 3205 (e.g., a substrate having a refractive index of n = 2.25) and includes ICG 3210 and CPE 3212. Similar to eyepiece waveguide 3100 described in connection with Figure 31A, anti-reflection pattern 3207 is formed on the opposite side of ICG 3210. Additionally, reflective layer 3211 (e.g., an aluminum layer) is deposited on ICG 3210 to enhance ICG incoupling efficiency. For example, an imprinted grating using a material having a refractive index of n = 1.65 is utilized to form the ICG and CPE.

[0210]

[0303] In contrast to the eyepiece waveguide 3100, the CPE 3212 includes an initial zone 3213 in which an imprinted grating (e.g., having a refractive index of 1.6 < n < 1.8) is formed to increase the diffusion of light within the CPE at the blue wavelength. Further, the substrate 3200 is etched in a second zone 3215 to reduce the thickness of the substrate.

[0211]

[0304] Figs. 32B to 32D are plots of the eye box efficiency across the field of view of the eyepiece shown in Fig. 32A. As shown in Figs. 32B to 32D, using embodiments of the present invention, the efficiency and uniformity of the eyepiece waveguide are improved over the prior art. In particular, the eye box efficiency increased from 1.1% to 2.7% at the blue wavelength, from 3.6% to 6.1% at the green wavelength, and from 3.5% to 4.8% at the red wavelength.

[0212]

[0305] Fig. 33A is a simplified cross-sectional view showing an eyepiece waveguide manufacturing process using a shadow mask according to an embodiment of the present invention. In Fig. 33A, an eyepiece waveguide on one side is shown, i.e., the diffraction structure is formed on one side of the eyepiece waveguide. As will be described in detail in connection with Figs. 34A to 34C below, embodiments of the present invention also include a double-sided eyepiece waveguide design in which the diffraction structure is formed on both sides of the eyepiece waveguide.

[0213]

[0306] As shown in FIG. 33A, a substrate 3310 is coated with a photoresist pattern 3315 to define an ICG 3312 and a CPE 3314. The photoresist thickness in both the ICG and CPE regions varies with position as shown to create a diffraction structure that varies with position. In this embodiment, the diffraction structure in the portion of the CPE 3314 distal to the ICG 3312 helps reduce outcoupling of light at shorter wavelengths and increase diffusion. The photoresist thickness also increases with distance from the CPE 3314. Additionally, a shadow mask 3311 is utilized to vary the etching process with position. As an example, the plasma density during a plasma-based etching process can be varied as more fully described in U.S. Pat. No. 10,527,865, the disclosure of which is incorporated herein by reference in its entirety for all purposes. Thus, as shown in Figure 33A, the etch depth increases with distance from the ICG 3312, creating a transition in the lattice properties (e.g., as a result of a higher intensity plasma depending on the distance from the ICG), thereby increasing the lattice strength as light propagates through the CPE 3314.

[0214]

[0307] Figure 33B is a simplified cross-sectional view illustrating an eyepiece waveguide fabrication process using an etching process, according to one embodiment of the present invention. In this example, rather than using a shadow mask, a lithographic pattern combined with an etching process etches the substrate to create features etched into the underlying substrate at different etch depths depending on the location and different thicknesses of the first material bonded to the portions of the substrate that remain after etching. Thus, portion 3342 has a greater height than portion 3344, and remaining first material 3346 has a greater thickness than the remaining first material proximal to the ICG.

[0215]

[0308] 33C is a simplified cross-sectional view illustrating another eyepiece waveguide fabrication process using an etching process, according to one embodiment of the present invention. In this example, the etching process results in different thicknesses of first material that are bonded to the portions of the substrate that remain after etching. Thus, remaining first material 3352 has a greater thickness than remaining first material 3354 to result in variations in the nanofeature material depending on location.

[0216]

[0309] Figure 33D is a simplified cross-sectional view showing an eyepiece waveguide fabrication process using an etching process and a tapered substrate according to one embodiment of the present invention. Similar to the process shown in Figure 33B, this process utilizes a variable-thickness substrate and a variable-thickness lithography pattern to produce an eyepiece waveguide with varying thickness due to etching-induced thickness variations on the user side of the eyepiece waveguide and substrate thickness variations on the world side of the eyepiece waveguide.

[0217]

[0310] While Figures 33A-33D show examples of hybrid step-etched structures having nanofeatures etched into an underlying substrate and coated with a low refractive index material, embodiments of the present invention are not limited to this particular implementation, and coatings using high refractive index materials, deposited structures that are not etched structures, etc. are within the scope of the present invention.

[0218]

[0311] Figure 34A is a simplified cross-sectional view showing a double-sided eyepiece waveguide fabrication process using a shadow mask as shown in Figure 33 A, according to one embodiment of the present invention. As an extension of the process shown in Figure 33A, diffractive structures are formed on both the user side and the world side of the eyepiece waveguide.

[0219]

[0312] Figure 34B is a simplified cross-sectional view illustrating a double-sided eyepiece waveguide fabrication process using an etching process, according to one embodiment of the present invention. As an extension of the process shown in Figure 33B, diffractive structures are formed on both the user side and the world side of the eyepiece waveguide. In this example, etching of the substrate to form positionally varying etch depths is performed on both sides of the substrate. Thus, portion 3410 has a greater height than portion 3412 on the user side of the eyepiece waveguide, and portion 3420 has a greater height than portion 3422 on the world side of the eyepiece waveguide.

[0220]

[0313] Figure 34C is a simplified cross-sectional view illustrating a double-sided eyepiece waveguide fabrication process using an etching process, according to one embodiment of the present invention. As an extension of the process shown in Figure 33C, diffractive structures are formed on both the user side and the world side of the eyepiece waveguide. The etching process tapers the substrate to reduce the substrate thickness distal to the ICG. As a result, remaining first material 3430 has a greater thickness than remaining first material 3432 to provide a change in nanofeature material depending on the position on the user side of the eyepiece waveguide, and remaining first material 3440 has a greater thickness than remaining first material 3442 on the world side of the eyepiece waveguide.

[0221]

[0314] Figure 35A is a simplified cross-sectional view showing an eyepiece waveguide fabrication process for forming a blazed grating, according to one embodiment of the present invention. This process demonstrates that a hybrid stepped etch structure can be formed using a sawtooth blaze etched into an underlying imprint layer 3512 of low refractive index material coated on a substrate 3510. The leftmost blazed grating 3514 includes only the substrate material, while the rightmost blazed grating 3516 includes both the substrate material and the imprint material.

[0222]

[0315] Figure 35B is a simplified cross-sectional view illustrating an eyepiece waveguide fabrication process for a coated substrate according to one embodiment of the present invention. In this process, a high refractive index coating 3520 is deposited on a substrate 3510 before forming an imprint layer 3522. After etching, a hybrid diffractive structure is formed, including portions of the high refractive index coating and portions including the imprint layer. Compared to the process shown in Figure 35A, the substrate is not etched in this embodiment. Furthermore, while Figure 35B illustrates sail-shaped nanofeatures, this particular grating shape is not required; other shapes can be utilized. In some embodiments, the high refractive index coating 3520, or other films described herein, is etched to form a patterned film. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0223]

[0316] Figure 35C is a simplified cross-sectional view showing an eyepiece waveguide fabrication process for a coated substrate according to another embodiment of the invention. Similar to the process shown in Figure 35B, etching is used to form a hybrid diffractive structure that includes a portion of the high refractive index coating and a portion that includes the imprint layer. Furthermore, in this embodiment, the thickness of the high refractive index coating 3520 is reduced during the etching process.

[0224]

[0317] Figure 35D is a simplified cross-sectional view showing an eyepiece waveguide fabrication process for a multi-layer coated substrate according to one embodiment of the present invention. In this exemplary process, substrate 3510 is coated in the CPE region with a high refractive index coating 3530 and a low refractive index coating 3532 before forming imprint layer 3534. The imprint layer varies depending on position. After etching, a hybrid diffractive structure is formed, including portions of the high refractive index coating and portions of the low refractive index coating.

[0225]

[0318] Figure 35E is a simplified cross-sectional view illustrating an eyepiece waveguide fabrication process for forming a hybrid discrete diffractive structure according to one embodiment of the present invention. Similar to the process shown in Figure 35C, etching is used to form a hybrid diffractive structure that includes a portion with a high refractive index coating and a portion with an imprint layer. Additionally, in this embodiment, the high refractive index coating is removed in the gaps between the nanofeatures. These gaps can then be filled with a planarizing material as described in connection with Figure 37A or encapsulated as described in connection with Figure 37B.

[0226]

[0319] 36A-36B show examples of hybrid graded structures with two or more coated materials on different portions of the eyepiece waveguide according to embodiments of the present invention.

[0227]

[0320] Shadow masks can be utilized to vary the deposition process depending on location, as described in connection with Figure 33A. As an example, plasma density during a plasma-based deposition process can be varied as more fully described in U.S. Patent No. 10,527,865, previously incorporated by reference.

[0228]

[0321] Figure 36A is a simplified cross-sectional view illustrating an eyepiece waveguide fabrication process using a shadow mask, according to one embodiment of the present invention. Low-index material 3611 is patterned to define ICG 3612 and CPE 3614. In Figure 36A, a shadow mask 3605 is utilized during the deposition process to create a deposition thickness that varies with position. Thus, as shown in Figure 36A, the deposition thickness increases with distance from ICG 3612, creating a transition in the grating characteristics (e.g., as a result of a plasma with higher intensity with distance from the ICG), thereby increasing the grating strength as light propagates through CPE 3614.

[0229]

[0322] Figure 36B is a simplified cross-sectional view illustrating an eyepiece waveguide fabrication process using a shadow mask according to another embodiment of the present invention. In the process illustrated in Figure 36B, which shares common features with the process illustrated in Figure 36A, a two-step deposition process is implemented using a shadow mask 3625 to form individual diffractive structures having two deposited materials (i.e., a low refractive index coating 3632 and a high refractive index coating 3634) on a low refractive index material 3611 within CPE 3613. The thicknesses of the coating layers may vary and may be selected appropriately for a particular application. Furthermore, while the transition from deposited to undeposited regions is shown as abrupt, it will be understood that this transition may be gradual due to the use of a shadow mask.

[0230]

[0323] Processes included within the scope of the present invention are not limited to forming the transition zone using etching and deposition, but also include spin coating, spray coating, inkjet dispensing, and the like.

[0231]

[0324] 37A-37C are cross-sectional views illustrating architectures incorporating additional materials according to embodiments of the present invention. As shown in FIGS. 37A-37C, one or more additional materials, e.g., third / fourth materials, can be utilized to lower the refractive index or to create a refractive index between low and high, as illustrated by the planarization or encapsulation materials described below. As an example, these materials can fill gaps between adjacent high-index materials with a low-index top or cap. This type of architecture can provide benefits as illustrated for hybrid structures, but also helps reduce rainbow artifacts. Rainbow artifacts are generalized as extraneous light artifacts that can interact with exposed surface-relief gratings, causing visual artifacts that replicate and project toward the user's field of view. They are primarily caused by world light striking the grating at a specific angle. While the illustrations show only square-sail hybrid structures, this concept can be applied to blazed sawtooth structures, multi-stage hybrid structures, and more.

[0232]

[0325] Figure 37A is a simplified cross-sectional view showing an eyepiece waveguide including a planarization layer, according to one embodiment of the present invention. In Figure 37A, eyepiece waveguide 3700 includes substrate 3705, ICG 3710, and CPE 3712, as described above. Additionally, additional material is incorporated into the eyepiece waveguide design, as indicated by planarization layer 3715, which includes planarization material 3718 formed on substrate 3705 between individual diffractive structures.

[0233]

[0326] Figure 37B is a simplified cross-sectional view showing an eyepiece waveguide including a planarization layer according to another embodiment of the present invention. In Figure 37B, the planarization material 3730 not only fills the gaps in the substrate between adjacent individual diffractive structures, but is also formed at a level above the substrate surface, thereby partially filling the gaps between adjacent individual diffractive structures. The planarization material can have a refractive index in the range of 1.1 to 1.4. This design can be referred to as an "immersion" design.

[0234]

[0327] Figure 37C is a simplified cross-sectional view showing an eyepiece waveguide including an encapsulation layer according to another embodiment of the invention. In Figure 37C, the thickness of the planarization material 3740 not only fills the gaps in the substrate between adjacent individual diffractive structures, but is also formed at a level above the individual diffractive structures, thereby encapsulating the individual and hybrid individual diffractive structures. This immersion design provides reduced reflectivity compared to other designs due to the presence of a low-index material encapsulating the diffractive structures of the eyepiece waveguide.

[0235]

[0328] Eyepiece waveguide material considerations

[0236]

[0329] Waveguide substrates used to make eyepieces can range in refractive index from high-index glasses such as SCHOTT SF5 at 1.7, SF6 at 1.8, HOYA Dense Tantalum Flint glass TAFD55 at 2.01, and TAFD65 at 2.06, to crystalline substrates such as lithium tantalate LiTaO3 at 2.25, lithium niobate LiNbO3 at 2.25, silicon carbide at 2.65, fused silica at 1.45, or glasses containing La, Na, TiO2, ZrO2, Li, or Nb. High-index coatings can be made of SiC at 2.5-2.6, TiO2 at 2.2-2.5, ZrO2 at 2.1, Si3N4 and silicon oxynitride, whose refractive indices can be 1.8-2.0, SiO2 at 1.45m, MgF2 at 1.38, etc. Thin film coatings can be achieved on blank or patterned surfaces using physical vapor deposition (PVD) such as evaporation or sputtering, with or without ion assistance (e.g., Ar / O) or chemical vapor deposition (CVD) such as low-pressure PECVD, atmospheric pressure PECVD, ALD.

[0237]

[0330] The patterned imprintable prepolymer 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. The prepolymer material can include monomers with one or more functional groups, such as alkyl, carboxyl, carbonyl, hydroxyl, and / or alkoxy. Both sulfur atoms with high polarizability and aromatic groups can be incorporated into these acrylate components to increase the refractive index of the formulation, typically in the range of 1.5 to 1.75. In some implementations, the prepolymer material can include a cycloaliphatic epoxy containing resin that can be cured using ultraviolet light and / or heat. Additionally, the prepolymer material can include an ultraviolet cationic photoinitiator and a co-reactant to promote efficient ultraviolet curing under ambient conditions.

[0238]

[0331] Incorporating inorganic nanoparticles (NPs) such as ZrO2 and TiO2 into such imprintable resin polymers can significantly increase the refractive index, even to 2.1. Pure ZrO2 and TiO2 crystals can reach refractive indices of 2.2 and 2.4–2.6 at 532 nm, respectively. To prepare optical nanocomposites of acrylate monomers and inorganic nanoparticles, the particle size is generally less than 10 nm to avoid excessive Rayleigh scattering. Due to their high specific surface area, high polarity, and incompatibility with crosslinked polymer matrices, ZrO2 NPs tend to aggregate in the polymer matrix. To overcome this problem, surface modification of NPs can be used. In this technique, the hydrophilic surface of ZrO2 is modified to be compatible with organics, thus allowing the NPs to be uniformly mixed with the polymer. Such modification can be carried out using silane and carboxylic acid-containing capping agents. One end of the capping agent binds to the ZrO2 surface, and the other end contains either a functional group capable of participating in acrylate crosslinking or a non-functional organic moiety. Examples of surface-modified sub-10 nm ZrO2 particles are those supplied by Pixelligent Technologies™ and Cerion Advanced Materials™. These functionalized nanoparticles are typically sold as homogeneous blends suspended in solvents and can be combined with other bases to yield resist formulations with jettable viscosities and increased refractive indices.

[0239]

[0332] Crosslinking and patterning using diffraction patterns involves contacting a prepolymer with a template (e.g., in the case of imprint lithography, e.g., J-FIL™, where the prepolymer material is dispensed using an inkjet), and applying a light source at a wavelength between 310 nm and 410 nm and 0.1 J / cm. 2 ~100J / cm 2The method can further include exposing the prepolymer to actinic radiation having an intensity between 40° C. and 120° C. while exposing the prepolymer to actinic radiation. Such prepolymer resins prior to patterning using a template / mold with inverse color features can be dispensed onto the desired surface to be patterned using on-demand inkjet drop or continuous jetting systems, slot die coating, spin coating, doctor blade coating, microgravure coating, screen printing, spraying or atomization, or the like.

[0240]

[0333] To promote adhesion, crosslinking silane coupling agents are used between the prepolymer material after patterning (template / mold demolding) and curing on the desired surface or substrate. These have an organic functional group at one end and a hydrolyzable group at the other, forming durable bonds between different types of organic and inorganic materials. An example of an organic functional group is acryloyl, which can crosslink to the patternable polymer material to form the desired optical pattern / shape. Conversely, templates or molds can be coated with similar coatings in which the acryloyl termini are substituted with fluorinated chains, which reduce surface energy and therefore act as release sites while remaining non-bonding. Vapor deposition is performed at low pressure, with or without an inert gas such as N2, in which the coupling agent is delivered in vapor form in the presence of activated -O and / or -OH groups present on the surface of the material to be coated. The vapor coating process can deposit monolayer films as thin as 0.5 nm to 0.7 nm, and can be thicker.

[0241]

[0334] FIG. 38 is a cross-sectional view illustrating a hybrid, multi-index architecture having differently shaped diffractive structures composed of distinct refractive indexes / materials, according to one embodiment of the present invention. As shown in FIG. 38, the hybrid multi-index architecture can include differently shaped diffractive structures that may be composed of distinct refractive indexes / materials. As an example, FIG. 38 shows a blazed sawtooth structure in which a large bottom blaze section is etched into a high-index material, leaving a low-index top hat. In this example, the low-index top hat is substantially square-sail shaped. Similarly, as previously mentioned, hybrid structures can be multi-stepped; one example shows a multi-stepped structure etched with two different refractive index materials (e.g., a low-index material seated on top and a high-index material etched at the bottom).

[0242]

[0335] 39A-39C show cross-sectional views of architectures with hybrid discrete diffractive structures that include a multi-index material on one side of a substrate and a single index material on the opposite side of the substrate.

[0243]

[0336] Figure 39A shows a cross-sectional view of a double-sided eyepiece waveguide according to one embodiment of the present invention, in which an ICG 3910 and an etched substrate grating 3912 (i.e., a grating formed by etching the high refractive index material of the substrate) are formed on one side of a substrate 3905, and an imprinted grating 3914 is formed on the other side of the substrate.

[0244]

[0337] Figure 39B shows a cross-sectional view of a double-sided eyepiece waveguide with a hybrid discrete diffractive structure, according to one embodiment of the present invention, in which an ICG 3910 and a hybrid discrete diffractive structure 3920 (i.e., a grating having a portion formed by etching the high refractive index material of the substrate and a portion formed using an imprinted material) are formed on one side of a substrate 3905, and an imprinted grating 3914 is formed on the other side of the substrate.

[0245]

[0338] Figure 39C shows a cross-sectional view of a double-sided eyepiece waveguide with a hybrid discrete diffractive structure according to another embodiment of the invention. In Figure 39C, an ICG 3910 and a hybrid discrete diffractive structure 3930 (i.e., a grating having a portion formed by etching a high refractive index material of the substrate and a portion formed using a low refractive index imprint material different from the material used to create the imprinted grating 3914) are formed on one side of a substrate 3905, and the imprinted grating 3914 is formed on the other side of the substrate. Thus, in this embodiment, two different imprint materials with different refractive indices are utilized.

[0246]

[0339] As shown in Figures 39A-39C, hybrid multi-refractive index structures can be on either one or both sides of the substrate, while a single refractive index grating can be used on the other side to form a double-sided waveguide architecture. This architecture with mixed refractive index gratings on both sides can help improve user-side virtual image brightness, especially in embodiments with a single active layer where multiple colors (e.g., two or more RGB) are guided within the eyepiece waveguide. While the illustrated examples are for single- or double-sided imprinting of multi-refractive index features within patterned regions of different structure or material refractive index on one side of the eyepiece waveguide, these examples can also be applied to double-sided architectures such as those shown in Figures 39A-39C. Furthermore, because diffractive structures with etched nanofeatures, either as etched substrate grating 3912 or hybrid discrete diffractive structures 3920, are combined with imprinted nanofeatures, the different diffractive properties of these structures can be utilized to improve system performance. By way of example only, etched and imprinted gratings can have different diffraction efficiencies, allowing diffracted light to be preferentially directed toward the user to improve virtual brightness. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

[0247]

[0340] The eyepiece waveguide designs described herein can be utilized in augmented reality display systems such as those described in connection with Figures 1-25. Thus, for example, waveguide 1120 of Figure 11A, as well as other waveguides implemented as components of an augmented reality display system, can be implemented using one or more of the embodiments described herein.

[0248]

[0341] Example 1 is an augmented reality system including a projector, projection optics coupled to the projector, and an eyepiece waveguide including a hybrid diffractive structure including one or more first nanofeatures having a first material with a first refractive index and one or more second nanofeatures having a second material with a second refractive index.

[0249]

[0342] Example 2 is the augmented reality system of example 1, in which the eyepiece waveguide further comprises a substrate and an incoupling diffractive structure coupled to the substrate.

[0250]

[0343] Example 3 is the eyepiece waveguide of Examples 1 and 2, in which the eyepiece waveguide further includes an outcoupling diffractive structure, and the hybrid diffractive structure is a component of the outcoupling diffractive structure.

[0251]

[0344] Example 4 is the eyepiece waveguide of Examples 1 to 3, wherein the substrate comprises a second material.

[0252]

[0345] Example 5 is the eyepiece waveguide of Examples 1 to 4, and the first refractive index is smaller than the second refractive index.

[0253]

[0346] Example 6 is the eyepiece waveguide of Examples 1-5, wherein the eyepiece waveguide further comprises a substrate, the one or more first nanofeatures comprise a first material bonded to the substrate, and the one or more second nanofeatures comprise a portion of the substrate extending from the substrate.

[0254]

[0347] Example 7 is the eyepiece waveguide of Examples 1-6, wherein the one or more second nanofeatures further comprise a first material bonded to a portion of the substrate.

[0255]

[0348] Example 8 is the eyepiece waveguide of Examples 1-7, wherein the eyepiece waveguide further comprises a substrate, wherein the one or more first nanofeatures are proximal to an incoupling diffractive structure coupled to the substrate, and the one or more second nanofeatures are distal from the incoupling diffractive structure.

[0256]

[0349] Example 9 is the eyepiece waveguide of Examples 1-8, wherein the one or more first nanofeatures or the one or more second nanofeatures are separated by gaps between adjacent nanofeatures, and the eyepiece waveguide further comprises a planarizing material filling the gaps.

[0257]

[0350] Example 10 is the eyepiece waveguide of Examples 1-9, wherein the planarizing material encapsulates the one or more first nanofeatures or the one or more second nanofeatures.

[0258]

[0351] Example 11 is an eyepiece waveguide comprising: a substrate operable to support the propagation of light; an incoupling diffractive structure coupled to the substrate; and an outcoupling diffractive structure coupled to the substrate, the outcoupling diffractive structure including one or more first nanofeatures having a first material with a first refractive index and one or more second nanofeatures having a second material with a second refractive index.

[0259]

[0352] Example 12 is the eyepiece waveguide of Example 11, wherein the substrate comprises a second material.

[0260]

[0353] Example 13 is the eyepiece waveguide of Examples 11 and 12, and the first refractive index is smaller than the second refractive index.

[0261]

[0354] Example 14 is the eyepiece waveguide of Examples 11-13, wherein the one or more first nanofeatures comprise a first material coupled to the substrate, and the one or more second nanofeatures comprise a portion of the substrate extending from the substrate.

[0262]

[0355] Example 15 is the eyepiece waveguide of Examples 11-14, wherein the one or more second nanofeatures further comprise a first material bonded to a portion of the substrate.

[0263]

[0356] Example 16 is the eyepiece waveguide of Examples 11-15, wherein the one or more first nanofeatures are proximal to the incoupling diffractive structure and the one or more second nanofeatures are distal from the incoupling diffractive structure.

[0264]

[0357] Example 17 is the eyepiece waveguide of Examples 11-16, wherein the one or more first nanofeatures are disposed in a first zone proximal to the incoupling diffractive structure and the one or more second nanofeatures are disposed in a second zone distal from the incoupling diffractive structure, and the eyepiece waveguide further comprises a transition zone disposed between the first zone and the second zone.

[0265]

[0358] Example 18 is the eyepiece waveguide of Examples 11-17, wherein the transition zone comprises transition nanofeatures having a transition material with a refractive index between the first refractive index and the second refractive index.

[0266]

[0359] Example 19 is the eyepiece waveguide of Examples 11 to 18, wherein the incoupling diffractive structure has a first width measured parallel to the substrate, and the transition zone has a second width measured parallel to the substrate that is wider than the first width.

[0267]

[0360] Example 20 is the eyepiece waveguide of Examples 11-19, wherein the one or more first nanofeatures or the one or more second nanofeatures are separated by gaps between adjacent nanofeatures, and the eyepiece waveguide further comprises a planarizing material filling the gaps.

[0268]

[0361] Example 21 is the eyepiece waveguide of Examples 11-20, wherein the planarizing material encapsulates the outcoupling diffractive structure.

[0269]

[0362] Example 22 is a hybrid surface relief waveguide structure comprising a substrate and a diffractive structure bonded to the substrate and including a plurality of diffractive nanofeatures, each of the plurality of diffractive nanofeatures characterized by a change in refractive index.

[0270]

[0363] Example 23 is the hybrid surface relief waveguide structure of Example 22, where the normal vector is perpendicular to the substrate and the refractive index variation varies along the normal vector.

[0271]

[0364] Example 24 is the hybrid surface relief waveguide structure of Examples 22-23, wherein the refractive index change comprises a first material having a first refractive index proximal to the substrate and a second material having a second refractive index less than the first refractive index distal to the substrate.

[0272]

[0365] Example 25 is the hybrid surface relief waveguide structure of Examples 22-24, wherein the diffractive structure comprises first nanofeatures comprising a first material bonded to the substrate.

[0273]

[0366] Example 26 is the hybrid surface relief waveguide structure of Examples 22-25, wherein the diffractive structure comprises a portion of the substrate, and the first material is bonded to the portion of the substrate.

[0274]

[0367] Example 27 is the hybrid surface relief waveguide structure of Examples 22-26, wherein the diffractive structure comprises an outcoupling diffractive structure including third nanofeatures formed from the second portion of the substrate.

[0275]

[0368] Example 28 is a hybrid surface relief waveguide structure of Examples 22-27, wherein the portion of the substrate and the second portion of the substrate extend different distances from the substrate.

[0276]

[0369] Example 29 is the hybrid surface relief waveguide structure of Examples 22-28, wherein the first nanofeature is comprised of a first material and the third nanofeature is comprised of a second material.

[0277]

[0370] Example 30 is the hybrid surface relief waveguide structure of Examples 22-29, further comprising a film disposed between the substrate and the diffractive structure.

[0278]

[0371] Example 31 is a hybrid surface relief waveguide structure of Examples 22-30, in which the substrate is provided with a pattern and the film is bonded to the pattern.

[0279]

[0372] Example 32 is an eyepiece waveguide comprising: a substrate operable to support the propagation of light; an incoupling diffractive structure coupled to the substrate; and an outcoupling diffractive structure coupled to the substrate, the outcoupling diffractive structure including first nanofeatures comprising a first material having a first refractive index, and second nanofeatures comprising the first material and a second material having a second refractive index.

[0280]

[0373] Example 33 is the eyepiece waveguide of example 32, wherein the first nanofeatures comprise a first material bonded to the substrate.

[0281]

[0374] Example 34 is the eyepiece waveguide of Examples 32-33, wherein the second material comprises a portion of the substrate, and the first material is bonded to the portion of the substrate.

[0282]

[0375] Example 35 is the eyepiece waveguide of Examples 32-34, wherein the outcoupling diffractive structure further comprises third nanofeatures formed from the second portion of the substrate.

[0283]

[0376] Example 36 is the eyepiece waveguide of Examples 32-35, wherein the portion of the substrate and the second portion of the substrate extend different distances from the substrate.

[0284]

[0377] Example 37 is the eyepiece waveguide of Examples 32-36, wherein the first nanofeature is comprised of a first material and the third nanofeature is comprised of a second material.

[0285]

[0378] Example 38 is the eyepiece waveguide of Examples 32 to 37, wherein the eyepiece waveguide includes a film disposed between the substrate and the outcoupling diffractive structure.

[0286]

[0379] Example 39 is the eyepiece waveguide of Examples 32 to 38, wherein the substrate includes a pattern and the film is bonded to the pattern.

[0287]

[0380] Example 40 is the eyepiece waveguide of Examples 32 to 39, wherein the film is provided with a pattern.

[0288]

[0381] Example 41 is the eyepiece waveguide of Examples 32-40, wherein at least one of the first nanofeatures or the second nanofeatures comprises a sail-shaped, blazed, sawtooth, tapered, or multi-step structure.

[0289]

[0382] Example 42 is the eyepiece waveguide of Examples 32-41, wherein at least one of the first nanofeatures or the second nanofeatures is an element of a one-dimensional grating structure.

[0290]

[0383] Example 43 is the eyepiece waveguide of Examples 32-42, wherein at least one of the first nanofeatures or the second nanofeatures is an element of a two-dimensional grating structure.

[0291]

[0384] Example 44 is the eyepiece waveguide of Examples 32-43, wherein at least one of the first nanofeatures or the second nanofeatures is an element of a three-dimensional grating structure.

[0292]

[0385] Example 45 is the eyepiece waveguide of Examples 32 to 44, wherein the substrate has a refractive index between 1.45 and 2.65.

[0293]

[0386] Example 46 is the eyepiece waveguide of Examples 32 to 45, wherein the substrate comprises fused silica or glass containing La, Na, TiO 2 , ZrO 2 , Li, or Nb.

[0294]

[0387] Example 47 is the eyepiece waveguide of Examples 32 to 46, wherein the substrate includes LiTaO3, LiNbO3, or SiC.

[0295]

[0388] Example 48 is the eyepiece waveguide of Examples 32 to 47, and the substrate is crystalline.

[0296]

[0389] Example 49 is the eyepiece waveguide of Examples 32 to 48, wherein the first material has a refractive index between 1.31 and 2.65.

[0297]

[0390] Example 50 is the eyepiece waveguide of Examples 32 to 49, further comprising an anti-reflection structure coupled to the substrate, the anti-reflection structure having a refractive index between 1.31 and 1.75.

[0298]

[0391] Example 51 is the eyepiece waveguide of Examples 32 to 50, wherein the anti-reflection structure includes a sub-wavelength diffractive structure.

[0299]

[0392] Example 52 is the eyepiece waveguide of Examples 32 to 51, in which the anti-reflection structure is disposed on the substrate opposite the incoupling diffraction structure.

[0300]

[0393] Example 53 is the eyepiece waveguide of Examples 32 to 52, in which the antireflection structure is disposed on the substrate at a position that does not overlap with the outcoupling diffraction structure.

[0301]

[0394] Example 54 is the eyepiece waveguide of Examples 32-53, wherein the substrate has a thickness variation of less than about 800 nm.

[0302]

[0395] Example 55 is an eyepiece waveguide comprising: a substrate operable to support the propagation of light; an incoupling diffraction structure coupled to the substrate; and an outcoupling diffraction structure coupled to the substrate, wherein at least one of the incoupling diffraction structure or the outcoupling diffraction structure includes one or more first nanofeatures having a first material with a first refractive index and one or more second nanofeatures having a second material with a second refractive index.

[0303]

[0396] In the foregoing specification, the present disclosure has been described with reference to specific embodiments thereof. It will, however, be apparent that various modifications and changes may be made thereto without departing from the broader spirit and scope of the present disclosure. The specification and drawings are, therefore, to be regarded in an illustrative rather than a restrictive sense.

[0304]

[0397] Indeed, it will be understood that the systems and methods of the present disclosure each have several innovative aspects, no single one of which is solely responsible for or required for the desirable attributes disclosed herein. The various features and processes described above may be used independently of one another or may be combined in various ways. All possible combinations and subcombinations are intended to fall within the scope of the present disclosure.

[0305]

[0398] Certain features that are described in this specification in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, while features may be described above as working in a particular combination and initially claimed as such, one or more features from a claimed combination may, in some cases, be deleted from the combination, and the claimed combination may be directed to a subcombination or a variation of a subcombination. No single feature or group of features is required or essential to every embodiment.

[0306]

[0399] It will be understood that conditional language used herein, such as "can," "could," "may," "for example," and the like, in particular, is generally intended to convey that certain embodiments include certain features, elements, and / or steps, while other embodiments do not, unless otherwise specified or understood otherwise within the context of use. Thus, such conditional language is not generally intended to imply that features, elements, and / or steps are somehow required for one or more embodiments, or that one or more embodiments necessarily include logic for determining whether those features, elements, and / or steps are included in or should be performed in any particular embodiment, with or without authorial input or prompting. Terms such as "comprising," "including," and "having" are synonymous and are used in an inclusive, open-ended manner and do not exclude additional elements, features, acts, operations, etc. Additionally, the term "or" is used in an inclusive (rather than exclusive) sense; for example, when used to connect a list of elements, the term "or" may mean one, some, or all of the elements in the list. Furthermore, the articles "a," "an," and "the," as used in this application and the appended claims, should be construed to mean "one or more" or "at least one," unless otherwise specified. Similarly, while operations are shown in the figures in a particular order, it should be recognized that such operations need not be performed in the particular order shown, or in any sequential order, to achieve desirable results, or that all of the operations shown be performed. Furthermore, the figures may generally depict additional exemplary processes in flow chart form. However, other operations not shown may be incorporated into the generally depicted exemplary methods and processes. For example, one or more additional operations may be performed before, after, simultaneously with, or during any of the depicted operations. Furthermore, operations may be rearranged or reordered in other embodiments. Multitasking and parallel processing may be advantageous in certain situations.Furthermore, the separation of various system components in the above-described embodiments should not be understood to require such separation in all embodiments, and it should be understood that the described program components and systems may generally be integrated together in a single software product or packaged in multiple software products. Moreover, other embodiments are within the scope of the following claims. In some cases, the actions recited in the claims may be performed in a different order and still achieve desirable results.

[0307]

[0400] While the present disclosure includes details of many specific embodiments, these should not be construed as limitations on the scope of the subject matter or the scope that may be claimed, but rather as descriptions of features that may be unique to particular embodiments. Certain features that are described in this disclosure in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, while the foregoing features may be described as working in particular combinations and initially claimed as such, one or more features from a claimed combination can, in some cases, be deleted from the combination, and the claimed combination may be directed to subcombinations or variations of subcombinations.

[0308]

[0401] Specific embodiments of the subject matter have been described. Other embodiments, modifications, and permutations of the described embodiments, as will be apparent to those skilled in the art, are within the scope of the following claims. Although operations are shown in the drawings or in the claims in a particular order, this should not be understood as requiring such operations to be performed in the particular order shown, or in any sequential order, or that all illustrated operations be performed (although some operations may be considered optional), to achieve desirable results.

[0309]

[0402] Accordingly, the foregoing exemplary embodiments do not define or limit the present disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of the present disclosure.

[0310]

[0403] Thus, the scope of the claims is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the present disclosure and the principles and novel features disclosed herein.

[0311]

[0404] The examples and embodiments described herein are for illustrative purposes only. Various modifications or changes will be apparent to those skilled in the art in light thereof. These are to be included within the spirit and scope of this application and the appended claims.

Claims

1. A projector and a projection optical system coupled to the projector; one or more first nanofeatures having a first material having a first refractive index; and one or more second nanofeatures having a second material having a second refractive index; an eyepiece waveguide including a hybrid diffractive structure; augmented reality systems, including

2. The augmented reality system of claim 1 , wherein the eyepiece waveguide further comprises a substrate and an incoupling diffractive structure coupled to the substrate.

3. 3. The eyepiece waveguide of claim 2, further comprising an outcoupling diffractive structure, the hybrid diffractive structure being a component of the outcoupling diffractive structure.

4. The eyepiece waveguide of claim 2 , wherein the substrate comprises the second material.

5. 2. The eyepiece waveguide of claim 1, wherein the first refractive index is less than the second refractive index.

6. the eyepiece waveguide further comprising a substrate; the one or more first nanofeatures comprise the first material bonded to the substrate; The eyepiece waveguide of claim 1 , wherein the one or more second nanofeatures comprise a portion of the substrate extending from the substrate.

7. The eyepiece waveguide of claim 6 , wherein the one or more second nanofeatures further comprise the first material bonded to the portion of the substrate.

8. 10. The eyepiece waveguide of claim 1, further comprising a substrate, the one or more first nanofeatures being proximal to an incoupling diffractive structure coupled to the substrate, and the one or more second nanofeatures being distal to the incoupling diffractive structure.

9. 10. The eyepiece waveguide of claim 1, wherein the one or more first nanofeatures or the one or more second nanofeatures are separated by gaps between adjacent nanofeatures, the eyepiece waveguide further comprising a planarizing material filling the gaps.

10. The eyepiece waveguide of claim 9 , wherein the planarizing material encapsulates the one or more first nanofeatures or the one or more second nanofeatures.

11. a substrate operable to support the propagation of light; an incoupling diffractive structure bonded to the substrate; an outcoupling diffractive structure coupled to the substrate, the outcoupling diffractive structure including one or more first nanofeatures having a first material with a first refractive index and one or more second nanofeatures having a second material with a second refractive index; and 1. An eyepiece waveguide comprising:

12. 12. The eyepiece waveguide of claim 11, wherein the substrate comprises the second material.

13. 13. An eyepiece waveguide as claimed in claim 12, wherein the first refractive index is less than the second refractive index.

14. the one or more first nanofeatures comprise the first material bonded to the substrate; The eyepiece waveguide of claim 12 , wherein the one or more second nanofeatures comprise a portion of the substrate extending from the substrate.

15. The eyepiece waveguide of claim 14 , wherein the one or more second nanofeatures further comprise the first material bonded to the portion of the substrate.

16. 12. The eyepiece waveguide of claim 11 , wherein the one or more first nanofeatures are proximal to the incoupling diffractive structure and the one or more second nanofeatures are distal from the incoupling diffractive structure.

17. the one or more first nanofeatures are disposed in a first zone proximate to the incoupling diffractive structure; the one or more second nanofeatures are disposed in a second zone distal to the incoupling diffractive structure; the eyepiece waveguide further comprising a transition zone disposed between the first zone and the second zone.

12. An eyepiece waveguide according to claim 11.

18. 18. The eyepiece waveguide of claim 17, wherein the transition zone comprises transition nanofeatures having a transition material with a refractive index between the first refractive index and the second refractive index.

19. 18. The eyepiece waveguide of claim 17, wherein the incoupling diffractive structure has a first width measured parallel to the substrate, and the transition zone has a second width measured parallel to the substrate that is wider than the first width.

20. 12. The eyepiece waveguide of claim 11 , wherein the one or more first nanofeatures or the one or more second nanofeatures are separated by gaps between adjacent nanofeatures, and the eyepiece waveguide further comprises a planarizing material filling the gaps.

21. 21. An eyepiece waveguide as claimed in claim 20, wherein the planarizing material encapsulates the outcoupling diffractive structure.

22. A substrate; a diffractive structure coupled to the substrate and comprising a plurality of diffractive nanofeatures, each of the plurality of diffractive nanofeatures characterized by a change in refractive index; A hybrid surface relief waveguide structure comprising:

23. 23. The hybrid surface relief waveguide structure of claim 22, wherein a normal vector is orthogonal to the substrate and the refractive index variation varies along the normal vector.

24. 23. The hybrid surface relief waveguide structure of claim 22, wherein the refractive index change comprises a first material having a first refractive index proximal to the substrate and a second material having a second refractive index less than the first refractive index distal to the substrate.

25. 23. The hybrid surface relief waveguide structure of claim 22, wherein the diffractive structure comprises first nanofeatures comprising a first material bonded to the substrate.

26. 26. The hybrid surface relief waveguide structure of claim 25, wherein the diffractive structure comprises a portion of the substrate, and the first material is bonded to the portion of the substrate.

27. 27. The hybrid surface relief waveguide structure of claim 26, wherein the diffractive structure comprises an outcoupling diffractive structure including third nanofeatures formed from a second portion of the substrate.

28. 28. The hybrid surface relief waveguide structure of claim 27, wherein the portion of the substrate and the second portion of the substrate extend different distances from the substrate.

29. 28. The hybrid surface relief waveguide structure of claim 27, wherein the first nanofeatures are comprised of the first material and the third nanofeatures are comprised of the second material.

30. 23. The hybrid surface relief waveguide structure of claim 22, further comprising a film disposed between the substrate and the diffractive structure.

31. 31. The hybrid surface relief waveguide structure of claim 30, wherein the substrate comprises a pattern and the film is bonded to the pattern.

32. a substrate operable to support the propagation of light; an incoupling diffractive structure bonded to the substrate; an outcoupling diffractive structure coupled to the substrate, the outcoupling diffractive structure including first nanofeatures comprising a first material having a first refractive index, and second nanofeatures comprising the first material and a second material having a second refractive index; and 1. An eyepiece waveguide comprising:

33. 33. The eyepiece waveguide of claim 32, wherein the first nanofeatures comprise the first material bonded to the substrate.

34. 33. An eyepiece waveguide as defined in claim 32, wherein the second material comprises a portion of the substrate, and the first material is bonded to the portion of the substrate.

35. 35. The eyepiece waveguide of claim 34, wherein the outcoupling diffractive structure further comprises third nanofeatures formed from a second portion of the substrate.

36. 36. The eyepiece waveguide of claim 35, wherein the portion of the substrate and the second portion of the substrate extend different distances from the substrate.

37. 36. The eyepiece waveguide of claim 35, wherein the first nanofeatures are comprised of the first material and the third nanofeatures are comprised of the second material.

38. 33. The eyepiece waveguide of claim 32, wherein the eyepiece waveguide includes a film disposed between the substrate and the outcoupling diffractive structure.

39. 39. The eyepiece waveguide of claim 38, wherein the substrate comprises a pattern and the film is bonded to the pattern.

40. 39. The eyepiece waveguide of claim 38, wherein the film comprises a pattern.

41. 33. The eyepiece waveguide of claim 32, wherein at least one of the first nanofeatures or the second nanofeatures comprises a sail-shaped, blazed, sawtooth, tapered, or multi-step structure.

42. 33. The eyepiece waveguide of claim 32, wherein at least one of the first nanofeatures or the second nanofeatures is an element of a one-dimensional grating structure.

43. 33. The eyepiece waveguide of claim 32, wherein at least one of the first nanofeatures or the second nanofeatures is an element of a two-dimensional grating structure.

44. 33. The eyepiece waveguide of claim 32, wherein at least one of the first nanofeatures or the second nanofeatures is an element of a three-dimensional grating structure.

45. 33. An eyepiece waveguide as claimed in claim 32, wherein the substrate has a refractive index between 1.45 and 2.

65.

46. The substrate is made of La, Na, TiO ２ , ZrO ２ 46. ​​An eyepiece waveguide as claimed in claim 45 comprising fused silica or glass containing Li, Li, or Nb.

47. The substrate is LiTaO ３ , LiNbO ３ 46. ​​An eyepiece waveguide as claimed in claim 45, comprising:

48. 48. An eyepiece waveguide as defined in claim 47, wherein the substrate is crystalline.

49. 33. An eyepiece waveguide as claimed in claim 32, wherein the first material has a refractive index between 1.31 and 2.

65.

50. 33. The eyepiece waveguide of claim 32, further comprising an anti-reflective structure bonded to the substrate, the anti-reflective structure having a refractive index between 1.31 and 1.

75.

51. 51. The eyepiece waveguide of claim 50, wherein the anti-reflective structure comprises a sub-wavelength diffractive structure.

52. 51. The eyepiece waveguide of claim 50, wherein the anti-reflection structure is disposed on the substrate opposite the incoupling diffractive structure.

53. 51. The eyepiece waveguide of claim 50, wherein the anti-reflection structure is disposed on the substrate in a position that does not overlap the outcoupling diffractive structure.

54. 51. The eyepiece waveguide of claim 50, wherein the substrate has a thickness variation of less than about 800 nm.

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