Methods and systems for hybrid surface relief waveguide structures for augmented reality devices

Abstract

An augmented reality system includes a projector and projection optics coupled with the projector. The augmented reality system also includes an eyepiece waveguide including a mixed diffractive structure including: 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.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 418,371, filed on October 21, 2022, and U.S. Provisional Patent Application No. 63 / 425,866, filed on November 16, 2022, the disclosures of which are hereby incorporated by reference in their entireties for all purposes. Background Art

[0003] Modern computing and display technologies have facilitated the development of systems for so - called "virtual reality" or "augmented reality" experiences, in which digitally reproduced images or portions thereof are presented to a viewer in a way that they appear real or are perceivable as real. Virtual reality or "VR" scenarios typically involve the presentation of digital or virtual image information without transparency to other actual real - world visual inputs; augmented reality or "AR" scenarios generally involve presenting digital or virtual image information as an enhancement to the visualization of the actual world surrounding the viewer.

[0004] Reference Figure 1 , describes augmented reality scenario 10. A user of AR technology sees a real - world park - like setting 20 featuring people, trees, buildings in the background, and a concrete platform 30. The user also perceives that he / she "sees" "virtual content", such as a robotic figure 40 standing on the real - world platform 30, and a cartoon - like avatar character 50 flying by, which appears to be an anthropomorphized bumblebee. These elements 50, 40 are "virtual" because they do not exist in the real world. Because the human visual perception system is complex, it is challenging to produce AR technologies that facilitate a comfortable, natural - feeling, rich presentation of virtual image elements with other virtual or real - world image elements.

[0005] Despite the progress of these display technologies, there remains a need in the art for improved methods and systems related to augmented reality systems, particularly display systems. Summary of the Invention

[0006] The present invention generally relates to methods and systems related to projection display systems including wearable displays. More specifically, embodiments of the present invention provide methods and systems including an eyepiece waveguide layer having a hybrid diffraction structure. The present invention is applicable to various applications in computer vision and image display systems.

[0007] Using a single input coupler pupil located on one side of the active waveguide layer to couple blue and red light into a single active waveguide layer over a small or large field of view presents challenges in diffusing and emitting light of all wavelengths (e.g., blue at 455 nm and red at 630 nm) from the combined output coupler with the desired uniformity and efficiency. If the diffraction features become efficient (height, refractive index, tilt angle), more light can be coupled out compared to the initial diffusion. Conversely, if the coupling-out efficiency of the diffraction features is low, the light output coupling towards the user may be reduced despite improved light diffusion and uniformity in the combiner.

[0008] Embodiments of the present invention relate to a unique architecture layout that uses low and high refractive index gratings in different regions of the waveguide, related to the optical path and optical waveguide from the input diffraction structure to the output diffraction structure. This architecture can be a combined pupil expander, implementing the functions of an orthogonal pupil expander and an exit pupil expander. Such an architecture can be implemented using imprinting or lithography, as well as deposition and / or etching processes. The methods and systems described herein provide a competitive advantage in creating such a hybrid diffraction structure in a simple process and are easy to vary the refractive index gradient on a large surface when combined with etching (RIE, ICP) and / or deposition (evaporation / sputtering) processes.

[0009] Compared with the prior art, many benefits are achieved by the means of the present invention. 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, as well as many of their advantages and features, are described in more detail in conjunction with the following text and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 Shows a user's view of AR through an augmented reality (AR) device.

[0011] Figure 2 Shows a conventional display system for simulating three-dimensional images for a user.

[0012] Figures 3A - 3C Shows the relationship between the radius of curvature and the radius of focus.

[0013] Figure 4A Shows a representation of the accommodation-vergence response of the human visual system.

[0014] Figure 4B Shows examples of different accommodation states and vergence states of a user's pair of eyes.

[0015] Figure 4C Shows an example of a representation of a top view of a user viewing content via a display system.

[0016] Figure 4D Another example of a representation showing a top view of a user viewing content via a display system.

[0017] Figure 5 Aspects of a method for simulating a three-dimensional image by modifying wavefront divergence are shown.

[0018] Figure 6 An example of a waveguide stack for outputting image information to a user is shown.

[0019] Figure 7 An example of an output beam output from a waveguide is shown.

[0020] Figure 8 An example of a stacked waveguide assembly is shown, where each depth plane includes an image formed using a plurality of different component colors.

[0021] Figure 9A A cross-sectional side view of an example of a set of stacked waveguides is shown, where each waveguide includes an optical element coupled in.

[0022] Figure 9B Shows Figure 9A A perspective view of an example of one or more stacked waveguides of.

[0023] Figure 9C Shows Figure 9A And 9B A top plan view of an example of one or more stacked waveguides of.

[0024] Figure 9D An example of a wearable display system is shown.

[0025] Figure 10 Is a side view of a projector assembly that includes a polarization beam splitter, where a light source injects light into one side of the beam splitter and projection optics receive light from the other side of the beam splitter.

[0026] Figure 11A Is a side view of an augmented reality display system that includes a light source, a spatial light modulator, optics 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 optical element coupled in for coupling light from the optics into the waveguide and an optical element coupled out for coupling light out of the waveguide to the eye.

[0027] Figure 11B Is Figure 11A A top view of the augmented reality display system shown in, which shows a waveguide having an optical element coupled in and an optical element coupled out and a light source disposed thereon. The top view also shows an orthogonal pupil expander.

[0028] Figure 11C Is Figure 11A A side view of an augmented reality display system having a shared polarizer / analyzer and a polarization-based spatial light modulator (e.g., a liquid crystal on silicon SLM).

[0029] Figure 11D Shows an example of a waveguide having a combined OPE / EPE according to an embodiment of the present invention.

[0030] Figure 12A Is a side view of an augmented reality display system that includes a multi-color light source (e.g., a time-multiplexed RGB LED or a laser diode), a spatial light modulator, optics for illuminating the spatial light modulator and projecting an image of the spatial light modulator onto the eye, and a waveguide stack, where different waveguides include different color-selective coupling-in optical elements as well as coupling-out optical elements.

[0031] Figure 12B Is Figure 12A A side view of an augmented reality display system thereof, which further includes a MEMS (microelectromechanical)-based SLM, such as a movable mirror array (e.g., digital light processing (DLP TM ) technology) and a light dump.

[0032] Figure 12C Is Figure 12B A top view of a part of an augmented reality display system thereof, which schematically shows a lateral arrangement of one of the coupling-in optical elements and the light dump and the light source.

[0033] Figure 13A Is a perspective view of an augmented reality display system including a waveguide stack, where different waveguides include different coupling-in optical elements, and where the coupling-in optical elements are laterally shifted relative to each other. One or more light sources that are also laterally shifted relative to each other are arranged to direct light to corresponding coupling-in optical elements by passing the light through the optics, reflecting the light off the spatial light modulator, and passing the reflected light through the optics again.

[0034] Figure 13B Is Figure 13A A side view of the example shown in, which shows the laterally shifted coupling-in optical elements and light sources and the optics and the spatial light modulator.

[0035] Figure 13C Is Figure 13A And 13B A top view of the augmented reality display system shown in, which shows one or more laterally shifted coupling-in optical elements and associated one or more laterally shifted light sources.

[0036] Figure 14AIs a side view of an augmented reality display system including a waveguide stack, where different waveguides include different light-coupling-in optical elements, and the light-coupling-in optical elements are laterally displaced relative to each other (in this example, the lateral displacement occurs in the z direction).

[0037] Figure 14B Is Figure 14A A top view of the display system shown in, which shows the laterally displaced light-coupling-in optical elements and the light source.

[0038] Figure 14C Is Figure 14A And 14B An orthogonal side view of the display system shown in.

[0039] Figure 15 Is a top view of an augmented reality display system including a set of stacked waveguides, where different waveguides include different light-coupling-in optical elements. The light source and the light-coupling-in optical elements are arranged in a configuration different from the configuration shown in Figures 14A - 14C .

[0040] Figure 16A Is a side view of an augmented reality display system that includes groups of light-coupling-in optical elements that are laterally displaced relative to each other, and each group includes one or more color-selective light-coupling-in optical elements.

[0041] Figure 16B Is Figure 16A A top view of the display system in.

[0042] Figure 17 Is a side view of an augmented reality display system including a waveguide that is segmented by a reflective surface, and the reflective surface can couple out light guided in a portion of the waveguide near the light source and direct it into an optical device towards a spatial light modulator. In this example, the optical device and the light source are shown on the same side of the waveguide.

[0043] Figure 18 Is a side view of an augmented reality display system including a waveguide that is configured to receive light from a light source and direct the light guided in the waveguide into an optical device and towards a spatial light modulator. The display system further includes a waveguide that receives light that has passed through the optical device again from the spatial light modulator. The waveguide includes a reflective surface to couple out light. The waveguide also includes a reflective surface to couple light into it. In this example, the optical device and the light source are shown on the same side of the waveguide.

[0044] Figure 19A side view of an augmented reality display system including an adaptive optics element or a variable focus optics element. A first variable optical element between the waveguide stack and the eye can change the divergence and collimation of light coupled out of the waveguide and directed towards the eye to change the depth at which an object appears to be located. A second variable optical element on the opposite side of the waveguide stack 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.

[0045] Figure 20A A side view of an augmented reality display system including a color filter array. One or more laterally shifted light-coupling optical elements are located on different waveguides, and the laterally shifted color filters are aligned with the corresponding light-coupling optical elements.

[0046] Figure 20B Shows Figure 20A an augmented reality display system in which an analyzer is located between the optical device and the spatial light modulator.

[0047] Figure 20C Shows an augmented reality display system similar to the augmented reality display system shown in Figure 20A and 20B but using a deflection-based spatial light modulator, such as a spatial light modulator based on movable micromirrors.

[0048] Figure 20D Is part of an augmented reality display system such as Figure 20C shown in, which schematically shows a laterally shifted light source above the color filter array and corresponding laterally shifted light-coupling optical elements.

[0049] Figure 20E Shows how a deflection-based spatial light modulator directs light away from a corresponding light-coupling optical element and onto a mask surrounding a filter in the Figure 20D filter array of the augmented reality display system.

[0050] Figure 20F A side view of an augmented reality display system that includes a cover glass disposed on the user side of a waveguide stack and a light source disposed on the world side of the cover glass.

[0051] Figure 20G A side view of an augmented reality display system that includes a cover glass disposed on the world side of a waveguide stack and a light source disposed on the world side of the cover glass.

[0052] Figure 21A side view of an augmented reality display system that includes a light source equipped with a light recycler configured to recycle light, such as light of a particular polarization.

[0053] Figure 22 A side view of one or more light sources that propagate light through corresponding light collection optics and one or more apertures. The light may also propagate through a diffuser located near the one or more apertures.

[0054] Figure 23A A side view of a portion of an augmented reality display system that includes a light source, an optical device with a focal power, and a waveguide configured to receive image information and output the image information to a user's eye. The system further includes one or more retarders and polarizers configured to reduce reflections from optical surfaces that may enter the waveguide as ghost images.

[0055] Figure 23B Such as Figure 23A A side view of a portion of an augmented reality display system as shown in

[0056] Figure 23C Such as Figure 23A And 23B A side view of an augmented reality display system as shown in

[0057] Figure 24 A side view of an augmented reality display system that utilizes an inclined surface (such as an inclined surface on a cover glass) to deflect reflections away from entering a user's eye, thereby potentially reducing ghost reflections.

[0058] Figure 25 Is Figure 24 An embodiment of a system where an inclined surface on a cover glass is configured to deflect reflections towards a light dump that absorbs light.

[0059] Figure 26A A simplified cross-sectional view of an eyepiece waveguide showing an embodiment according to the present invention.

[0060] Figure 26B Shows Figure 26A A simplified k-space diagram of the field of view, ICG, and CPE grating vectors of the eyepiece waveguide as shown in

[0061] Figure 26C Is Figure 26A A simplified plan view of the user side of the eyepiece waveguide as shown in

[0062] Figure 26DYes Figure 26A A simplified plan view of the world side of the eyepiece waveguide shown in

[0063] Figure 27A A simplified schematic diagram showing an example of an eyepiece waveguide including a hybrid individual diffraction structure according to an embodiment of the present invention.

[0064] Figure 27B A simplified schematic diagram showing the process of forming a hybrid individual diffraction structure according to an embodiment of the present invention.

[0065] Figure 27C A simplified schematic diagram showing the variation of grating parameters over the entire eyepiece waveguide according to an embodiment of the present invention.

[0066] Figure 27D A simplified cross-sectional view showing a hybrid individual diffraction structure according to an embodiment of the present invention.

[0067] Figure 27E Is using Figure 27D The eyebox efficiency diagram of the eyepiece with the hybrid individual diffraction structure shown in

[0068] Figure 27F A simplified cross-sectional view showing a hybrid individual diffraction structure formed on a low refractive index coating according to an embodiment of the present invention.

[0069] Figure 27G Is using Figure 27F The eyebox efficiency diagram of the eyepiece with the hybrid individual diffraction structure shown in

[0070] Figure 28A A simplified cross-sectional view showing an eyepiece waveguide according to an embodiment of the present invention.

[0071] Figure 28B Is showing Figure 28A A diagram of the refractive index region of the eyepiece waveguide shown in

[0072] Figures 28C - 28E Yes Figure 28A The eyebox efficiency diagram of the eyepiece shown in

[0073] Figure 29A A simplified cross-sectional view showing an eyepiece waveguide according to another embodiment of the present invention.

[0074] Figure 29B Is showing Figure 29A A diagram of the refractive index region of the eyepiece waveguide shown in

[0075] Figures 29C - 29E Yes Figure 29A The eyebox efficiency diagram of the eyepiece shown in

[0076] Figure 30A is a simplified cross-sectional view showing an eyepiece waveguide including a hybrid CPE according to an embodiment of the present invention.

[0077] Figure 30B is showing Figure 30A a diagram of the refractive index region of the eyepiece waveguide shown in

[0078] Figures 30C - 30E is Figure 30A an eye box efficiency diagram of the eyepiece shown in

[0079] Figure 31A is a simplified cross-sectional view showing an eyepiece waveguide according to an embodiment of the present invention.

[0080] Figures 31B - 31D is Figure 31A an eye box efficiency diagram of the eyepiece shown in

[0081] Figure 32A is a simplified cross-sectional view showing an eyepiece waveguide according to an embodiment of the present invention.

[0082] Figures 32B - 32D is Figure 32A an eye box efficiency diagram of the eyepiece shown in

[0083] Figure 33A is a simplified cross-sectional view showing a manufacturing process of an eyepiece waveguide using a shadow mask according to an embodiment of the present invention.

[0084] Figure 33B is a simplified cross-sectional view showing a manufacturing process of an eyepiece waveguide using an etching process according to an embodiment of the present invention.

[0085] Figure 33C is a simplified cross-sectional view showing another manufacturing process of an eyepiece waveguide using an etching process according to an embodiment of the present invention.

[0086] Figure 33D is a simplified cross-sectional view showing a manufacturing process of an eyepiece waveguide using an etching process and a tapered substrate according to an embodiment of the present invention.

[0087] Figure 34A is a simplified cross-sectional view showing a manufacturing process of a bilateral eyepiece waveguide using a shadow mask according to an embodiment of the present invention.

[0088] Figure 34B is a simplified cross-sectional view showing a manufacturing process of a bilateral eyepiece waveguide using an etching process according to an embodiment of the present invention.

[0089] Figure 34CIs a simplified cross-sectional view showing a bilateral eyepiece waveguide manufacturing process using an etching process and a tapered substrate according to an embodiment of the present invention.

[0090] Figure 35A Is a simplified cross-sectional view showing an eyepiece waveguide manufacturing process for forming a blazed grating according to an embodiment of the present invention.

[0091] Figure 35B Is a simplified cross-sectional view showing an eyepiece waveguide manufacturing process for a coated substrate according to an embodiment of the present invention.

[0092] Figure 35C Is a simplified cross-sectional view showing an eyepiece waveguide manufacturing process for a coated substrate according to another embodiment of the present invention.

[0093] Figure 35D Is a simplified cross-sectional view showing an eyepiece waveguide manufacturing process for a multi-layer coated substrate according to an embodiment of the present invention.

[0094] Figure 35E Is a simplified cross-sectional view showing an eyepiece waveguide manufacturing process for forming a hybrid individual diffraction structure according to an embodiment of the present invention.

[0095] Figure 36A Is a simplified cross-sectional view showing an eyepiece waveguide manufacturing process using a shadow mask according to an embodiment of the present invention.

[0096] Figure 36B Is a simplified cross-sectional view showing an eyepiece waveguide manufacturing process using a shadow mask according to another embodiment of the present invention.

[0097] Figure 37A Is a simplified cross-sectional view showing an eyepiece waveguide including a planarization layer according to an embodiment of the present invention.

[0098] Figure 37B Is a simplified cross-sectional view showing an eyepiece waveguide including a planarization layer according to another embodiment of the present invention.

[0099] Figure 37C Is a simplified cross-sectional view showing an eyepiece waveguide including a packaging layer according to another embodiment of the present invention.

[0100] Figure 38 Is a cross-sectional view showing a hybrid multi-refractive index architecture of diffraction structures with different shapes composed of individual refractive indices / materials according to an embodiment of the present invention.

[0101] Figure 39A Shows a cross-sectional view of a bilateral eyepiece waveguide according to an embodiment of the present invention.

[0102] Figure 39B A cross-sectional view of a bilateral eyepiece waveguide having a hybrid individual diffraction structure according to an embodiment of the present invention is shown.

[0103] Figure 39C A cross-sectional view of a bilateral eyepiece waveguide having a hybrid individual diffraction structure according to another embodiment of the present invention is shown. Detailed Description

[0104] Reference will now be made to the accompanying drawings, in which like reference numerals always refer to like parts. Unless otherwise noted, the drawings are schematic and not necessarily drawn to scale.

[0105] Figure 2 A conventional display system for simulating three-dimensional images for a user is shown. It will be understood that the user's eyes are separated, and when viewing a real object in space, each eye will have a slightly different view of the object, and an image of the object can be formed at different positions on the retina of each eye. This can be referred to as binocular parallax and can be utilized by the human visual system to provide depth perception. The conventional display system simulates binocular parallax by presenting two different images 190, 200 having slightly different views of the same virtual object (one for each eye 210a, 210b), the different views corresponding to the views of the virtual object that each eye would see, the virtual object being a virtual object of a real object located at a desired depth. These images provide binocular cues, where the user's visual system can interpret the binocular cues to obtain depth perception.

[0106] Continuing to refer Figure 2 , the images 190, 200 are separated from the eyes 210a, 210b by a distance 230 along the z-axis. In the case where their eyes are focused on an object at optical infinity directly in front of the viewer, the z-axis is parallel to the viewer's optical axis. The images 190, 200 are flat and at a fixed distance from the eyes 210a, 210b. Based on the slightly different views of the virtual object in the images presented to the eyes 210a, 210b respectively, the eyes can naturally rotate such that the images of the object fall on corresponding points on the retina of each eye to maintain single binocular vision. This rotation can cause the lines of sight of each eye 210a, 210b to converge to a point in the space where the virtual object is perceived to exist. As a result, providing a three-dimensional image typically involves providing binocular cues that can manipulate the convergence of the user's eyes 210a, 210b, and the human visual system interprets the binocular cues to provide depth perception.

[0107] However, generating a realistic and comfortable depth perception is challenging. It will be understood that light from objects at different distances from the eyes has wavefronts with different amounts of divergence. Figures 3A - 3CShows the relationship between distance and the divergence of light. The distances between the object and the eye 210 are represented by R1, R2, and R3 in decreasing order of distance. As shown in Figures 3A - 3C , as the distance to the object decreases, the light becomes more divergent. Conversely, as the distance increases, the light becomes more collimated. In other words, it can be said that the light field generated by a point (the object or a part of the object) has a spherical wavefront curvature that is a function of the distance of that point from the user's eye. The curvature increases as the distance between the object and the eye 210 decreases. Although only a single eye 210 is shown in Figures 3A - 3C and the other figures in this document for clarity of illustration, the discussion regarding the eye 210 can be applied to both eyes 210a and 210b.

[0108] Continuing to refer to Figures 3A - 3C , the light from an object that a viewer's eyes are fixated on can have different degrees of wavefront divergence. Due to the different amounts of wavefront divergence, the light can be focused differently by the lens of the eye, which in turn may require the lens to assume different shapes to form a focused image on the retina of the eye. In the case where a focused image is not formed on the retina, the resulting retinal blur serves as an accommodation cue that causes a change in the shape of the lens of the eye until a focused image is formed on the retina. For example, the accommodation cue can trigger the relaxation or contraction of the ciliary muscles surrounding the eye lens, thereby adjusting the force applied to the zonular ligaments that hold the lens, thus causing the shape of the eye lens to change until the retinal blur of the fixated object is eliminated or minimized, thereby forming a focused image of the fixated object on the retina of the eye (e.g., the fovea). The process by which the lens of the eye changes shape can be referred to as accommodation, and the shape of the lens of the eye required to form a focused image of the fixated object on the retina of the eye (e.g., the fovea) can be referred to as the accommodative state.

[0109] Now referring to Figure 4A , a representation of the accommodation-convergence response of the human visual system is shown. Eye movements are made to fixate on an object such that the eyes receive light from the object, where the light forms an image on each retina of the eyes. The presence of retinal blur in the images formed on the retinas can provide an accommodation cue, and the relative positions of the images on the retinas can provide a convergence cue. The accommodation cue causes accommodation to occur, resulting in each lens of the eyes assuming a specific accommodative state that forms a focused image of the object on the retina of the eyes (e.g., the fovea). On the other hand, the convergence cue causes a convergence movement (rotation of the eyes) to occur such that the images formed on each retina of each eye are at corresponding retinal points that maintain single binocular vision. At these positions, it can be said that the eyes are in a specific convergence state. Continuing to refer to Figure 4A, accommodation can be understood as the process by which the eyes achieve a specific accommodative state, and convergence can be understood as the process by which the eyes achieve a specific convergent state. As Figure 4A shown in

[0110] Without being limited by theory, it is believed that a viewer of an object can perceive the object as "three-dimensional" due to the combination of convergence and accommodation. As described above, the convergent movement of the two eyes relative to each other (e.g., the rotation of the eyes such that the pupils move towards or away from each other to converge the lines of sight of the eyes to fixate on an object) is closely related to the accommodation of the lenses of the eyes. Under normal circumstances, changing the shape of the lens of the eye to change the focus from one object to another object located at a different distance will automatically cause a matching change in the convergence to the same distance under a relationship called the "accommodation-convergence reflex". Similarly, under normal circumstances, a change in convergence will trigger a matching change in the shape of the lens.

[0111] Now referring to Figure 4B , an example of different accommodative and convergent states of the eyes is shown. The eye pair 222a is fixated on an object at optical infinity, while the eye pair 222b is fixated on an object 221 that is less than optically infinite. It is worth noting that the convergent states of each eye pair are different, where the eye pair 222a is directed straight ahead, while the eye pair 222 converges on the object 221. The accommodative states of the eyes forming each eye pair 222a and 222b are also different, as indicated by the different shapes of the lenses 220a, 220b.

[0112] Unfortunately, many users of traditional "3-D" display systems find these traditional systems uncomfortable or do not perceive a sense of depth at all due to the mismatch between the accommodative and convergent states in these displays. As described 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 they merely provide different renderings of the scene among other things and cause a change in the convergent state of the eyes, but without a corresponding change in the accommodative state of those eyes. Instead, the images are shown by a display at a fixed distance from the eyes such that the eyes view all the image information in a single accommodative state. This arrangement violates the "accommodation-convergence reflex" by causing a change in the convergent state without a matching change in the accommodative state. This mismatch is thought to cause discomfort to the viewer. A display system that provides a better match between accommodation and convergence can form a more realistic and comfortable three-dimensional image simulation.

[0113] Without being bound by theory, it is believed that the human eye can typically interpret a limited number of depth planes to provide depth perception. Thus, by providing the eye with different renditions of images corresponding to each of these limited number of depth planes, a highly believable simulation of perceived depth can be achieved. In some embodiments, the different renditions can provide vergence cues and matching accommodation cues, thereby providing a physiologically correct accommodation-vergence match.

[0114] Continuing reference Figure 4B is made to, which shows two depth planes 240 corresponding to different distances from the eyes 210a, 210b in space. For a given depth plane 240, a vergence cue can be provided by displaying images of appropriately different perspectives for each eye 210a, 210b. Additionally, for a given depth plane 240, the light forming the images provided to each eye 210a, 210b can have a wavefront divergence corresponding to the light field generated by points at the distance of that depth plane 240.

[0115] In the illustrated embodiment, the depth plane 240 containing the point 221 is at a distance of 1 m along the z-axis. As used herein, the distance or depth along the z-axis can be measured by a zero point located at the exit pupil of the user's eye. Thus, the depth plane 240 at a depth of 1 m corresponds to a distance of 1 m from the exit pupil of the user's eye on the optical axis of those eyes when the eyes are pointed at optical infinity. As an approximation, the depth or distance along the z-axis can be measured from a display in front of the user's eyes (e.g., from the surface of a waveguide), plus the value of the distance between the device and the exit pupil of the user's eye. This value can be referred to as the eye relief and corresponds to the distance between the exit pupil of the user's eye and the display worn by the user in front of the eyes. In practice, the value of the eye relief can be a standardized value typically used for all viewers. For example, it can be assumed that the eye relief is 20 mm, and the depth plane at a depth of 1 m can be at a distance of 980 mm in front of the display.

[0116] Now reference Figure 4C and 4D are made to, which show examples of a matched accommodation-vergence distance and a mismatched accommodation-vergence distance, respectively. As Figure 4C shown, the display system can provide images of a virtual object to each eye 210a, 210b. The images can cause the eyes 210a, 210b to assume a vergence state in which the eyes converge on a point 15 on the depth plane 240. Additionally, the images can be formed by light having a wavefront curvature corresponding to a real object at that depth plane 240. As a result, the eyes 210a, 210b assume an accommodation state in which the images are in focus on the retinas of those eyes. Thus, the user can perceive the virtual object at the point 15 on the depth plane 240.

[0117] It will be understood that each of the accommodation and vergence states of eyes 210a, 210b is associated with a specific distance on the z-axis. For example, an object at a specific distance from eyes 210a, 210b causes those eyes to assume a specific accommodation state based on the distance of the object. The distance associated with a specific accommodation state may be referred to as the accommodation distance Ad. Similarly, there is a specific vergence distance Vd associated with the eyes in a specific vergence state or their positions relative to each other. When the accommodation distance and the vergence distance match, it can be said that the relationship between accommodation and vergence is physiologically correct. This is considered the most comfortable scenario for the viewer.

[0118] However, in a stereoscopic display, the accommodation distance and the vergence distance may not always match. For example, as Figure 4D shown, the images presented to eyes 210a, 210b may be presented with a wavefront divergence corresponding to depth plane 240, and eyes 210a, 210b may assume a specific accommodation state in which points 15a, 15b on that depth plane are in focus. However, the images presented to eyes 210a, 210b may provide vergence cues that cause eyes 210a, 210b to converge at a point 15 that does not lie on depth plane 240. As a result, in some embodiments, the accommodation distance corresponds to the distance from the exit pupils of eyes 210a, 210b to depth plane 240, while the vergence distance corresponds to a greater distance from the exit pupils of eyes 210a, 210b to point 15. The accommodation distance is different from the vergence distance. Thus, there is an accommodation-vergence mismatch. This mismatch is considered undesirable and may cause discomfort to the user. It will be understood that this mismatch corresponds to a distance (e.g., VaAd) and can be characterized using diopters.

[0119] In some embodiments, it will be understood that reference points other than the exit pupils of eyes 210a, 210b may be used to determine the distances for determining the accommodation-vergence mismatch, provided that the same reference point is used for both the accommodation distance and the vergence distance. For example, the distance from the cornea to the depth plane, from the retina to the depth plane, from the eyepiece (e.g., the waveguide of the display device) to the depth plane, etc. may be measured.

[0120] Without being limited by theory, it is believed that a user can 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 being physiologically correct without significant discomfort caused by the mismatch itself. In some embodiments, the display systems disclosed herein (e.g., Figure 6The display system 250) presents an image to the viewer with an accommodation-convergence mismatch of about 0.5 diopters or less. In some other embodiments, the accommodation-convergence mismatch of the image provided by the display system is about 0.33 diopters or less. In still some other embodiments, the accommodation-convergence mismatch of the image provided by the display system is about 0.25 diopters or less, including about 0.1 diopters or less.

[0121] Figure 5 Aspects of a method of simulating a three-dimensional image by modifying wavefront divergence are shown. 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 having a limited amount of wavefront divergence corresponding to the wavefront divergence of the light field generated by points on a desired depth plane 240. In some embodiments, the same amount of wavefront divergence is provided for all objects presented on the depth plane. Additionally, it will be described that image information from a similar waveguide may be provided to the user's other eye.

[0122] 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. Thus, in some embodiments, a waveguide stack may be utilized to provide different amounts of wavefront divergence for different depth planes and / or output light having different wavelength ranges. As used herein, it will be understood that at the depth plane, the contour of a flat or curved surface may be followed. In some embodiments, for simplicity, the depth plane may advantageously follow the contour of a flat surface.

[0123] Figure 6 An example of a waveguide stack for outputting image information to a user is shown. The display system 250 includes a stack of waveguides or a stacked waveguide assembly 260 that may be used to provide a three-dimensional perception to the eye / brain using waveguides 270, 280, 290, 300, 310. It will be understood that in some embodiments, the display system 250 may be considered a light field display. Additionally, the waveguide assembly 260 may also be referred to as an eyepiece.

[0124] In some embodiments, the display system 250 can be configured to provide substantially continuous vergence cues and a plurality of discrete accommodation cues. Vergence cues can be provided by displaying different images to each eye of the user, and accommodation cues can be provided by forming the light of the image with a selectable discrete amount of wavefront divergence. In other words, the display system 250 can be configured to output light with a variable level of wavefront divergence. In some embodiments, each discrete level of wavefront divergence corresponds to a particular depth plane and can be provided by a particular one of waveguides 270, 280, 290, 300, 310.

[0125] Continuing reference Figure 6 to, the waveguide assembly 260 can also include features 320, 330, 340, 350 between waveguides. In some embodiments, the features 320, 330, 340, 350 can be one or more lenses. Waveguides 270, 280, 290, 300, 310 and / or features (e.g., lenses) 320, 330, 340, 350 can be configured to send image information to the eyes with various levels of wavefront curvature or ray divergence. Each waveguide level can be associated with a particular depth plane and can be configured to output image information corresponding to that depth plane. Image injection devices 360, 370, 380, 390, 400 can serve as light sources for the waveguides and can be used to inject image information into waveguides 270, 280, 290, 300, 310, as described herein, each waveguide can be configured to distribute incident light across each corresponding waveguide for output toward the eye 210. Light leaves the output surfaces 410, 420, 430, 440, 450 of the image injection devices 360, 370, 380, 390, 400 and is injected into the corresponding input surfaces 460, 470, 480, 490, 500 of waveguides 270, 280, 290, 300, 310. In some embodiments, each of the input surfaces 460, 470, 480, 490, 500 can be an edge of the corresponding waveguide, or can be a part of the major surface of the corresponding waveguide (i.e., a surface of the waveguide that directly faces the world 510 or the viewer's eye 210). In some embodiments, a single light beam (e.g., a collimated beam) can be injected into each waveguide to output an entire field of cloned collimated beams that are 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 can be associated with one or more (e.g., three) waveguides 270, 280, 290, 300, 310 and inject light into one or more (e.g., three) waveguides 270, 280, 290, 300, 310.

[0126] In some embodiments, the image injection devices 360, 370, 380, 390, 400 are discrete displays, each of which generates image information for injection into the corresponding waveguides 270, 280, 290, 300, 310, respectively. In some other embodiments, the image injection devices 360, 370, 380, 390, 400 are output terminals of a single multiplexed display, and the output terminals of the single multiplexed display can deliver image information to each of the image injection devices 360, 370, 380, 390, 400 via, for example, one or more optical conduits such as fiber optic cables. It will be understood that the image information provided by the image injection devices 360, 370, 380, 390, 400 can include light of different wavelengths or colors (e.g., different component colors as discussed herein).

[0127] In some embodiments, the light injected into the waveguides 270, 280, 290, 300, 310 is provided by a light projector system 520, which includes a light module 530 that can include a light emitter such as a light-emitting diode (LED). The light from the light module 530 can be guided to a light modulator 540 (e.g., a spatial light modulator) via a beam splitter 550 and modified by the light modulator 540. The light modulator 540 can 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) that include liquid crystal on silicon (LCOS) displays. It will be understood that the image injection devices 360, 370, 380, 390, 400 are schematically shown, and in some embodiments, these image injection devices can represent different optical paths and positions in a common projection system configured to output light into the associated waveguides among the waveguides 270, 280, 290, 300, 310. In some embodiments, the waveguides of the waveguide assembly 260 can act as ideal lenses while relaying the light injected into the waveguides out to the user's eyes. In this concept, the object can be the spatial light modulator 540, and the image can be an image on a depth plane.

[0128] In some embodiments, the display system 250 can be a scanned fiber optic display that includes one or more scanned optical fibers configured to project light into one or more waveguides 270, 280, 290, 300, 310 and ultimately to the viewer's eye 310 in various patterns (e.g., raster scan, helical scan, Lissajous pattern, etc.). In some embodiments, the illustrated image injection devices 360, 370, 380, 390, 400 can schematically represent a single scanned optical fiber or a bundle of scanned optical 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 can schematically represent one or more scanned optical fibers or one or more bundles of scanned optical fibers, each of which is configured to inject light into an associated one of the waveguides 270, 280, 290, 300, 310. It will be understood that one or more optical fibers can be configured to transmit light from the optical module 530 to one or more of the waveguides 270, 280, 290, 300, 310. It will be understood that one or more intermediate optical structures can be provided between the scanned optical fiber or fibers and one or more of the waveguides 270, 280, 290, 300, 310 to, for example, redirect the light exiting the scanned optical fiber into one or more of the waveguides 270, 280, 290, 300, 310.

[0129] The controller 560 controls the operation of one or more of the stacked waveguide assemblies 260, including the operation of the image injection devices 360, 370, 380, 390, 400, the light source 530, and the light modulator 540. In some embodiments, the controller 560 is part of the local data processing module 140. The controller 560 includes programming (e.g., instructions in a non-transitory medium) that regulates the timing and provision of image information to the waveguides 270, 280, 290, 300, 310 according to any of the various schemes disclosed herein, for example. In some embodiments, the controller can be a single integral device, or a distributed system connected by wired or wireless communication channels. In some embodiments, the controller 560 can be part of the processing module 140 or 150 ( Figure 9D ).

[0130] Continuing to refer Figure 6, waveguides 270, 280, 290, 300, 310 can be configured to enable light to propagate within each respective waveguide by total internal reflection (TIR). Waveguides 270, 280, 290, 300, 310 can each be planar or have an alternative shape (e.g., curved), having a major top surface and a major bottom surface and edges extending between those major top and bottom surfaces. In the illustrated configuration, waveguides 270, 280, 290, 300, 310 can each include outcoupling optical elements 570, 580, 590, 600, 610, which are configured to extract light from the waveguide by redirecting the light propagating within each respective waveguide out of the waveguide for outputting image information to the eye 210. Although referred to throughout the specification as "outcoupling optical elements", the outcoupling optical elements are not necessarily optical elements and can be non-optical elements. The extracted light can also be referred to as outcoupled light, and the outcoupling optical element light can also be referred to as a light extraction optical element. The extracted light beam can be output by the waveguide at the location where the light propagating in the waveguide impinges on the light extraction optical element. The outcoupling optical elements 570, 580, 590, 600, 610 can be, for example, gratings including diffractive optical features, as further discussed herein. Although illustrated as being disposed at the bottom major surface of waveguides 270, 280, 290, 300, 310 for ease of description and clarity of the drawings, in some embodiments, the outcoupling optical elements 570, 580, 590, 600, 610 can be disposed at the top and / or bottom major surfaces, and / or can be disposed directly within the volume of waveguides 270, 280, 290, 300, 310, as further discussed herein. In some embodiments, the outcoupling optical elements 570, 580, 590, 600, 610 can be formed in a material layer attached to a transparent substrate to form waveguides 270, 280, 290, 300, 310. In some other embodiments, waveguides 270, 280, 290, 300, 310 can be a single-piece material, and the outcoupling optical elements 570, 580, 590, 600, 610 can be formed on and / or within the surface of the piece of material.

[0131] Continue to refer to Figure 6, as discussed herein, each waveguide 270, 280, 290, 300, 310 is configured to output light to form an image corresponding to a particular depth plane. For example, the waveguide 270 closest to the eye can be configured to deliver collimated light (which is injected into such waveguide 270) to the eye 210. The collimated light can represent an optically infinite focal plane. The next upper waveguide 280 can be configured to send out collimated light that passes through a first lens 350 (e.g., a negative lens) before it can reach the eye 210; such first lens 350 can be configured to produce a slightly convex wavefront curvature such that the eye / brain interprets the light from this next upper waveguide 280 as coming from a first focal plane that is closer inward from the optically infinite towards the eye 210. Similarly, the third upper waveguide 290 has its output light pass through the first lens 350 and the second lens 340 before reaching the eye 210; the combined optical power of the first lens 350 and the second lens 340 can be configured to produce another increment of wavefront curvature such that the eye / brain interprets the light from the third waveguide 290 as coming from a second focal plane that is closer inward from the optically infinite towards the person than the light from the next upper waveguide 280.

[0132] The other waveguide layers 300, 310 and lenses 330, 320 are configured similarly, where the highest waveguide 310 in the stack sends its output through all the lenses between it and the eye, for representing the total optical power of the focal plane closest to the person. To compensate for the stack of lenses 320, 330, 340, 350 when viewing / interpreting light from the world 510 on the other side of the stacked waveguide assembly 260, a compensation lens layer 620 can be provided on top of the stack to compensate for the total optical power of the underlying lens stack 320, 330, 340, 350. Such a configuration provides as many focal planes as there are available waveguide / lens pairings. Both the outcoupling optical elements of the waveguides and the focusing aspects of the lenses can be static (i.e., non-dynamic or electroactive). In some alternative embodiments, one or both of them can be dynamic using electroactive features.

[0133] In some embodiments, two or more of the waveguides 270, 280, 290, 300, 310 can have the same associated depth plane. For example, multiple waveguides 270, 280, 290, 300, 310 can be configured to output a set of images to the same depth plane, or multiple subsets of the waveguides 270, 280, 290, 300, 310 can be configured to output a set of images to the same one or more depth planes, where there is one set of images for each depth plane. This can provide the advantage of forming a stitched image to provide an extended field of view at those depth planes.

[0134] Continuing to refer to Figure 6, the out-coupling optical elements 570, 580, 590, 600, 610 can be configured to redirect light out of their respective waveguides and output the light with an appropriate amount of divergence or collimation for a particular depth plane associated with the waveguide. Thus, waveguides with different associated depth planes can have different configurations of the out-coupling optical elements 570, 580, 590, 600, 610, which depend on the associated depth plane to output light with different amounts of divergence. In some embodiments, the light extraction optical elements 570, 580, 590, 600, 610 can be volume or surface features that can be configured to output light at a specific angle. For example, the light extraction optical elements 570, 580, 590, 600, 610 can be volume holograms, surface holograms, and / or diffraction gratings. In some embodiments, the features 320, 330, 340, 350 can not be lenses; instead, they can simply be spacers (e.g., cladding and / or structures for forming voids).

[0135] In some embodiments, the out-coupling optical elements 570, 580, 590, 600, 610 are diffraction features that form a diffraction pattern, or "diffractive optical elements" (also referred to herein as "DOEs"). Preferably, the DOE has a low enough diffraction efficiency such that only a portion of the light beam is deflected away from the waveguide towards the eye 210 at each intersection of the DOE, while the remaining portion continues to travel through the waveguide via TIR. The light carrying the image information is thus split into many associated outgoing beams that leave the waveguide at many locations, and the result is a reasonably uniform pattern of outgoing emission towards the eye 210 for that particular collimated beam that bounces around inside the waveguide.

[0136] In some embodiments, one or more DOEs can be switched 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 can include a polymer dispersed liquid crystal layer, where the microdroplets include a diffraction pattern in a host medium, and the refractive index of the microdroplets can be switched to substantially match the refractive index of the host material (in which case the pattern does not significantly diffract the incident light) or the microdroplets can be switched to a refractive index that does not match the refractive index of the host medium (in which case the pattern actively diffracts the incident light).

[0137] In some embodiments, a camera component 630 (e.g., a digital camera, including visible and infrared cameras) may be provided to capture images of the eye 210 and / or tissue around the eye 210 to, for example, detect user input and / or monitor the user's physiological state. As used herein, a camera may be any image capture device. In some embodiments, the camera component 630 may include an image capture device and a light source that projects light (e.g., infrared light) toward the eye, which may then be reflected by the eye and detected by the image capture device. In some embodiments, the camera component 630 may be attached to the frame 80( Figure 9D ) and may be in electrical communication with the processing module 140 and / or 150, which may process image information from the camera component 630. In some embodiments, one camera component 630 may be utilized for each eye to monitor each eye separately.

[0138] Now referring to Figure 7 , an example of an output beam exiting a waveguide is shown. One waveguide is shown, but it will be understood that in cases where the waveguide assembly 260 includes multiple waveguides, the other waveguides in the waveguide assembly 260( Figure 6 ) may operate similarly. Light 640 is injected into the waveguide 270 at the input surface 460 of the waveguide 270 and propagates within the waveguide 270 by TIR. At the point where the light 640 is incident on the DOE 570, a portion of the light exits the waveguide as an output beam 650. The output beam 650 is illustrated as being substantially parallel, but as discussed herein, it may also be redirected to propagate at an angle to the eye 210 (e.g., form a diverging output beam), depending on the depth plane associated with the waveguide 270. It will be understood that a substantially parallel output beam may indicate that the waveguide has an outcoupling optical element that outcouples light to form an image that appears to be set on a depth plane at a large distance (e.g., optically infinite) from the eye 210. Other waveguides or other sets of outcoupling optical elements may output a more diverging output beam pattern, which will require the eye 210 to accommodate to a closer distance to focus on the retina and will be interpreted by the brain as light from a distance closer to the eye 210 than optically infinite.

[0139] In some embodiments, a full-color image may be formed at each depth plane by overlapping images of each component color (e.g., three or more component colors).

[0140] Figure 8An example of a stacked waveguide assembly is shown, where each depth plane includes an image formed using a plurality of different component colors. The illustrated embodiment shows depth planes 240a–240f, although more or fewer depths are also contemplated. Each depth plane may have three or more component color images associated therewith, including: a first image in a first color G; a second image in a second color R; and a third image in a third color B. Different depth planes are indicated in the figures by different numbers for diopters (dpt) following the letters G, R, and B. By way of example only, the numbers following each of these letters indicate the diopter (1 / m), or the inverse distance of the depth plane from the viewer, and each box in the figures represents a single component color image. In some embodiments, to account for differences in the focusing of light of different wavelengths by the eye, the exact placement of the depth planes for different component colors may vary. For example, the different component color images for a given depth plane may be placed on depth planes corresponding to different distances from the user. Such an arrangement may increase visual sensitivity and user comfort and / or may reduce chromatic aberration.

[0141] In some embodiments, light of each component color may be output by a single dedicated waveguide, and thus, each depth plane may have a plurality of waveguides associated therewith. In such embodiments, each box in the figures that includes the letters G, R, or B may be understood to represent a separate waveguide, and three waveguides may be provided per depth plane, where three component color images are provided per depth plane. While the waveguides associated with each depth plane are shown in the figures as being adjacent to each other, it will be understood that in a physical device, the waveguides may all be arranged in a stack, with one waveguide per layer. 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.

[0142] Continuing to refer Figure 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 additionally be used or may replace one or more of red, green, or blue.

[0143] It will be understood that references throughout this disclosure to a given light color will be understood to encompass light having one or more wavelengths within the range of wavelengths of light that are perceived by a viewer as having that given color. For example, red light may include light having one or more wavelengths in the range of approximately 620–780 nm, green light may include light having one or more wavelengths in the range of approximately 492–577 nm, and blue light may include light having one or more wavelengths in the range of approximately 435–493 nm.

[0144] In some embodiments, light source 530 (Figure 6 ) can be configured to emit light at one or more wavelengths outside the viewer's visual perception range, e.g., infrared and / or ultraviolet wavelengths. Additionally, the input, output, and other light redirecting structures of the waveguide of the display 250 can be configured to direct and emit the light towards the eye 210 and out of the display, e.g., for imaging and / or user stimulation applications.

[0145] Now referring to Figure 9A , in some embodiments, light incident on the waveguide may need to be redirected to couple the light into the waveguide. An input optical element can be used to redirect and couple the light into its corresponding waveguide. Although referred to throughout the specification as an "input optical element", the input optical element is not necessarily an optical element and can be a non-optical element. Figure 9A FIG. shows a cross-sectional side view of an example of a stack of waveguides 660, where each waveguide includes an input optical element. The waveguides can each be configured to output light at one or more different wavelengths or one or more different wavelength ranges. It will be understood that the stack 660 can correspond to the stack 260 ( Figure 6 ), and the waveguides of the illustrated stack 660 can correspond to a portion of the waveguides 270, 280, 290, 300, 310, except that light from one or more of the image injection devices 360, 370, 380, 390, 400 is injected into the waveguide from a location where the desired light redirection for coupling is to occur.

[0146] The illustrated set of stacked waveguides 660 includes waveguides 670, 680, and 690. Each waveguide includes an associated optical input element (which may also be referred to as an optical input region on the waveguide), for example, an optical input element 700 disposed on the main surface (e.g., the upper main surface) of waveguide 670, an optical input element 710 disposed on the main surface (e.g., the upper main surface) of waveguide 680, and an optical input element 720 disposed on the main surface (e.g., the upper main surface) of waveguide 690. In some embodiments, one or more of the optical input elements 700, 710, 720 may be disposed on the bottom main surface of the respective waveguides 670, 680, 690 (specifically, where one or more of the optical input elements are reflective deflecting optical elements). As illustrated, the optical input elements 700, 710, 720 may be disposed on the upper main surface of their respective waveguides 670, 680, 690 (or on top of the next lower waveguide), specifically, where those optical input elements are transmissive deflecting optical elements. In some embodiments, the optical input elements 700, 710, 720 may be disposed within the body of the respective waveguides 670, 680, 690. In some embodiments, as discussed herein, the optical input elements 700, 710, 720 are wavelength selective such that they selectively redirect one or more wavelengths of light while transmitting other wavelengths of light. Although illustrated at one side or corner of their respective waveguides 670, 680, 690, it will be understood that in some embodiments, the optical input elements 700, 710, 720 may be disposed in other regions of their respective waveguides 670, 680, 690.

[0147] As illustrated, the optical input elements 700, 710, 720 may be laterally offset from each other. In some embodiments, each optical input element may be offset such that it receives light without the light passing through another optical input element. For example, each of the optical input elements 700, 710, 720 may be configured to receive light from different image injection devices 360, 370, 380, 390, and 400 as shown in Figure 6 and may be separated (e.g., laterally spaced apart) from the other optical input elements 700, 710, 720 such that it substantially does not receive light from the other optical input elements among the optical input elements 700, 710, 720.

[0148] Each waveguide also includes an associated light distribution element, e.g., a light distribution element 730 disposed on the main surface (e.g., the top main surface) of waveguide 670, a light distribution element 740 disposed on the main surface (e.g., the top main surface) of waveguide 680, and a light distribution element 750 disposed on the main surface (e.g., the top main surface) of waveguide 690. In some other embodiments, the light distribution elements 730, 740, 750 may be respectively disposed on the bottom main surfaces of the associated waveguides 670, 680, 690. In some other embodiments, the light distribution elements 730, 740, 750 may be respectively disposed on the top main surface and the bottom main surface of the associated waveguides 670, 680, 690; or the light distribution elements 730, 740, 750 may be respectively disposed on different main surfaces of the top main surface and the bottom main surface in different associated waveguides 670, 680, 690.

[0149] Waveguides 670, 680, 690 may be separated and isolated by, e.g., a layer of gas, liquid, and / or solid material. For example, as illustrated, 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 of a low refractive index material (i.e., a material having a lower refractive index than the material of the directly adjacent waveguides among waveguides 670, 680, 690). Preferably, the refractive index of the material forming layers 760a, 760b is less than the refractive index of the material forming waveguides 670, 680, 690 by 0.05 or more, or 0.10 or less. Advantageously, the lower refractive index layers 760a, 760b may serve as claddings that facilitate total internal reflection (TIR) of light through waveguides 670, 680, 690 (e.g., TIR between the top main surface and the bottom main surface of each waveguide). In some embodiments, layers 760a, 760b are formed of air. Although not illustrated, it will be understood that the top and bottom of the illustrated waveguide group 660 may include directly adjacent claddings.

[0150] Preferably, for ease of manufacturing and other considerations, the materials forming waveguides 670, 680, 690 are similar or the same, and the materials forming layers 760a, 760b are similar or the same. In some embodiments, the materials forming waveguides 670, 680, 690 may be different between one or more waveguides, and / or the materials forming layers 760a, 760b may be different, while still maintaining the various refractive index relationships noted above. A variety of materials may be used to form the waveguides. Although glass is a material that can be used to fabricate waveguides, other materials may also be used, including LiNbO 3, SiC, ZnS, or similar materials. These materials can be in the form of optically quality single crystal materials, or materials with optical quality but not single crystal. Additionally, polycrystalline ceramics of similar composition can also be used to form waveguides. As an example, nanocrystalline materials can be used in the manufacture of waveguides.

[0151] Continuing to refer to Figure 9A , light rays 770, 780, 790 are incident on waveguide group 660. It will be understood that light rays 770, 780, 790 can be injected into waveguides 670, 680, 690 through one or more image injection devices 360, 370, 380, 390, 400 ( Figure 6 ).

[0152] In some embodiments, light rays 770, 780, 790 have different characteristics, e.g., different wavelengths or different wavelength ranges corresponding to different colors. Each of the coupling optical elements 700, 710, 720 deflects the incident light such that the light propagates through the corresponding waveguide in the waveguides 670, 680, 690 by TIR. In some embodiments, each of the coupling optical elements 700, 710, 720 selectively deflects one or more specific wavelengths of light while transmitting other wavelengths to the underlying waveguide and the associated coupling optical element.

[0153] For example, the coupling optical element 700 can be configured to deflect the light ray 770 having a first wavelength or wavelength range while transmitting the light rays 780 and 790 having different second and third wavelengths or wavelength ranges respectively. The transmitted light ray 780 is incident on the coupling optical element 710 and is deflected by the coupling optical element 710 which is configured to deflect the light of the second wavelength or wavelength range. The light ray 790 is deflected by the coupling optical element 720 which is configured to selectively deflect the light of the third wavelength or wavelength range.

[0154] Continuing to refer to Figure 9A , the deflected light rays 770, 780, 790 are deflected such that they propagate through the corresponding waveguides 670, 680, 690; that is, the coupling optical elements 700, 710, 720 of each waveguide deflect the light into the corresponding waveguide 670, 680, 690 to couple the light into the corresponding waveguide. The light rays 770, 780, 790 are deflected at an angle such that the light propagates through the corresponding waveguides 670, 680, 690 by TIR. The light rays 770, 780, 790 propagate through the corresponding waveguides 670, 680, 690 by TIR until they are incident on the corresponding light distribution elements 730, 740, 750 of the waveguide.

[0155] Now referring to Figure 9B , there is shown Figure 9APerspective view of an example of a stacked waveguide. As described above, the input light rays 770, 780, 790 are deflected by the input optical elements 700, 710, 720 respectively, and then propagate in the waveguides 670, 680, 690 respectively by TIR. The light rays 770, 780, 790 then impinge on the light distribution elements 730, 740, 750 respectively. The light distribution elements 730, 740, 750 deflect the light rays 770, 780, 790 such that they propagate towards the output optical elements 800, 810, 820 respectively.

[0156] In some embodiments, the light distribution elements 730, 740, 750 are orthogonal pupil expanders (OPEs). In some embodiments, the OPE deflects or distributes light to the output optical elements 800, 810, 820, and in some embodiments may also increase the beam size or spot size of the light as the light propagates to the output optical elements. In some embodiments, the light distribution elements 730, 740, 750 may be omitted and the input optical elements 700, 710, 720 may be configured to deflect light directly to the output optical elements 800, 810, 820. For example, referring to Figure 9A , the light distribution elements 730, 740, 750 may be replaced by the output optical elements 800, 810, 820 respectively. In some embodiments, the output optical elements 800, 810, 820 are exit pupils (EPs) or exit pupil expanders (EPEs) that direct light to the viewer's eye 210 ( Figure 7 ). It will be understood that the OPE may be configured to increase the size of the eye box on at least one axis, and the EPE may increase the eye box on an axis that intersects (e.g., is orthogonal to) the axis of the OPE. For example, each OPE may be configured to redirect a portion of the light impinging on the OPE to the EPE of the same waveguide while allowing the remaining portion of the light to continue propagating down the waveguide. When the remaining light impinges on the OPE again, another portion of the remaining light is redirected to the EPE, and the remaining portion of that portion continues to propagate further down the waveguide, and so on. Similarly, when impinging on the EPE, a portion of the incident light is directed out of the waveguide towards the user, and the remaining portion of the light continues to propagate through the waveguide until it impinges on the EP again, at which time another portion of the incident light is directed out of the waveguide, and so on. Thus, a single beam of input light can be "copied" each time a portion of the light is redirected by the OPE or EPE, thereby forming a field of cloned beams, as shown in Figure 6 . In some embodiments, the OPE and / or EPE may be configured to modify the size of the beam.

[0157] Thus, referring to Figure 9A and 9B, in some embodiments, the set of waveguides 660 includes waveguides 670, 680, 690 for each component color; input optical elements 700, 710, 720; light distribution elements (e.g., OPE) 730, 740, 750; and output optical elements (e.g., EPE) 800, 810, 820. The waveguides 670, 680, 690 may be stacked with a gap / cladding between each one. The input optical elements 700, 710, 720 redirect or deflect incident light (where different input optical elements receive light of different wavelengths) into their respective waveguides. The light then propagates at an angle that will result in TIR within the respective waveguides 670, 680, 690. In the illustrated example, the light ray 770 (e.g., blue light) is deflected by the first input optical element 700 in the manner previously described and then continues to bounce down the waveguide, interacting with the light distribution element (e.g., OPE) 730 and then the output optical element (e.g., EP) 800. The light rays 780 and 790 (e.g., green and red light, respectively) will pass through the waveguide 670, where the light ray 780 is incident on the input optical element 710 and is deflected by the input optical element 710. The light ray 780 then bounces down the waveguide 680 via TIR, continues to its light distribution element (e.g., OPE) 740 and then to the output optical element (e.g., EP) 810. Finally, the light ray 790 (e.g., red light) passes through the waveguide 690 to be incident on the light input optical element 720 of the waveguide 690. The light input optical element 720 deflects the light ray 790 such that the light ray propagates to the light distribution element (e.g., OPE) 750 via TIR and then to the output optical element (e.g., EP) 820 via TIR. Then, the output optical element 820 finally couples out the light ray 790 to the viewer, who also receives the output light from the other waveguides 670, 680.

[0158] Figure 9C Shows Figure 9A And Figure 9B A top plan view of an example of a stacked waveguide. As illustrated, the waveguides 670, 680, 690 together with the associated light distribution elements 730, 740, 750 and the associated output optical elements 800, 810, 820 of each waveguide may be vertically aligned. However, as discussed herein, the input optical elements 700, 710, 720 are not vertically aligned; rather, the input optical elements are preferably non-overlapping (e.g., laterally separated, as seen in the top view). As further discussed herein, this non-overlapping spatial arrangement facilitates injecting light from different sources into different waveguides on a one-to-one basis, thereby allowing a particular light source to be uniquely coupled to a particular waveguide. In some embodiments, an arrangement including non-overlapping spatially separated input optical elements may be referred to as an offset pupil system, and the input optical elements within these arrangements may correspond to sub-pupils.

[0159] Figure 9D illustrates an example of a wearable display system 60 into which various waveguides and related systems disclosed herein can be integrated. In some embodiments, the display system 60 is Figure 6 system 250, where Figure 6 some components of the system 60 are shown schematically in more detail. For example, Figure 6 the waveguide assembly 260 can be part of the display 70.

[0160] Continuing to refer to Figure 9D , the display system 60 includes a display 70 and various mechanical and electronic modules and systems that support the functions of the display 70. The display 70 can be coupled to a frame 80 that can be worn by a user or viewer 90 of the display system and is configured to position the display 70 in front of the eyes of the user 90. In some embodiments, the display 70 can be considered glasses. In some embodiments, a speaker 100 is coupled to the frame 80 and is configured to be located near the ear canal of the user 90 (in some embodiments, another speaker, not shown, can optionally be located near the other ear canal of the user to provide stereo / plastic sound control). The display system 60 can also include one or more microphones 110 or other devices to detect sound. In some embodiments, the microphone is configured to allow the user to provide input or commands to the system 60 (e.g., selection of voice menu commands, natural language questions, etc.) and / or can allow audio communication with other people (e.g., other users of a similar display system. The microphone can also be configured as a peripheral sensor to collect audio data (e.g., sounds from the user and / or the environment). In some embodiments, the display system 60 can also include one or more outwardly directed environmental sensors 112 that are configured to detect objects, stimuli, people, animals, locations, or other aspects of the world around the user. For example, the environmental sensors 112 can include one or more cameras that can be positioned, for example, facing outward to capture images similar to at least a portion of the normal field of view of the user 90. In some embodiments, the display system can also include a peripheral sensor 120a that can be separated from the frame 80 and attached to the body of the user 90 (e.g., on the head, torso, limb, etc. of the user 90). In some embodiments, the peripheral sensor 120a can be configured to capture data characterizing the physiological state of the user 90. For example, the sensor 120a can be an electrode.

[0161] Continuing to refer to Figure 9D, the display 70 is operatively coupled to the local data processing module 140 via a communication link 130 (such as via a wired lead or a wireless connection). The local data processing module 140 can be installed in various configurations, such as fixedly attached to the frame 80, fixedly attached to a helmet or hat worn by the user, embedded within a headset, or removably attached to the user 90 (e.g., in a backpack configuration, in a belt-coupled configuration). Similarly, the sensor 120a can be operatively coupled to the local processor and data module 140 via a communication link 120b (e.g., a wired lead or a wireless connection). The local processing and data module 140 can include a hardware processor and a digital memory such as a non-volatile memory (e.g., flash memory or a hard disk drive), both of which can be used to assist in processing, caching, and storing data. Optionally, the local processor and data module 140 can include one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, etc. The data can include: a) data captured from sensors (e.g., the sensor can be operatively coupled to the frame 80 or otherwise attached to the user 90), such as an image capture device (such as a camera), a microphone, an inertial measurement unit, an accelerometer, a compass, a GPS unit, a radio device, a gyroscope, and / or other sensors disclosed herein; and / or b) data obtained and / or processed using the remote processing module 150 and / or the remote data repository 160 (including data related to virtual content), which can be transmitted to the display 70 after such processing or retrieval. The local processing and data module 140 can be operatively coupled to the remote processing module 150 and the remote data repository 160 via communication links 170, 180 (such as via wired or wireless communication links), such that these remote modules 150, 160 are operatively coupled to each other and can be used as resources for the local processing and data module 140. In some embodiments, the local processing and data module 140 can include one or more of an image capture device, a microphone, an inertial measurement unit, an accelerometer, a compass, a GPS unit, a radio device, and / or a gyroscope. In some other embodiments, one or more of these sensors can be attached to the frame 80, or can be a separate structure that communicates with the local processing and data module 140 via a wired or wireless communication path.

[0162] Continuing to refer to Figure 9D, in some embodiments, the remote processing module 150 may include one or more processors configured to analyze and process data and / or image information, such as one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, etc. In some embodiments, the remote data repository 160 may include a digital data storage facility that may be available via the Internet or other network configurations in a "cloud" resource configuration. In some embodiments, the remote data repository 160 may include one or more remote servers that provide information to the local processing and data module 140 and / or the remote processing module 150, such as information for generating augmented reality content. 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. Alternatively, an external system including a CPU, GPU, etc. (e.g., a system with one or more processors, one or more computers) 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.

[0163] Figure 10 is a schematic diagram showing a projector assembly 1000 that uses a polarization beam splitter (PBS) 1020 to illuminate a spatial light modulator (SLM) 1030 and redirect light from the SLM 1030 through projection optics 1040 to an eyepiece (not shown). The projector assembly 1000 includes an illumination source 1010, which may include, for example, a light emitting diode (LED), a laser (e.g., a laser diode), or other types of light sources. The light may be collimated by collimation optics. The illumination source 1010 may emit polarized, unpolarized, 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 allow light having a first polarization (e.g., p-polarization) to pass through.

[0164] The light is directed to a polarization beam splitter 1020. Initially, the light passes through an interface 1022 (e.g., a polarization interface) of the PBS 1020, which is configured to transmit light of a first polarization (e.g., p-polarization). Thus, the light advances to and impinges on a spatial light modulator 1030. As illustrated, the SLM 1030 is a reflective SLM, which is configured to retroreflect the incident light and selectively modulate the light. For example, the SLM 1030 includes one or more pixels that can have different states. The light impinging on a corresponding pixel can 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 can be a polarization-based SLM, which modulates the polarization of the light impinging on it. For example, in the on state, the pixels of the SLM 1030 change the input light from a first polarization state (e.g., p-polarization state) to a second polarization state (e.g., s-polarization state), such that a bright state (e.g., a white pixel) is displayed. The second polarization state can be the first polarization state modulated (e.g., rotated) by 90°. In the on state, the light having the second polarization state is reflected by the interface 1022 and propagates downstream to the projector optics 1040. In the off state, the SLM 1030 does not change the polarization state of the light impinging on it, e.g., does not rotate the input light from the first polarization state, and thus a dark state (e.g., a black pixel) is displayed. In the off state, the light having the first polarization state is transmitted through the interface 1022 and propagates upstream back to the illumination source 1010, rather than to the user's eye.

[0165] After reflection from the SLM 1030, a portion of the light 1014 (e.g., the modulated light) is reflected from the interface 1022 and exits the PBS 1020 to be directed to the user's eye. The emitted light passes through the projector optics 1040 and is imaged onto an input coupling grating (ICG) 1050 of an eyepiece (not shown).

[0166] Figure 11A Shown is a system (e.g., an augmented reality display system) 1100A for presenting an image to a user's eye 210 and for viewing the world 510, which has an Figure 10Configurations different from those shown in the figure. System 1100 includes a light source 1110, a spatial light modulator (SLM) 1140, and a waveguide 1120 (also referred to as an eyepiece waveguide), which are arranged such that light from the light source 1110 irradiates the SLM 1140, and the light reflected from the SLM 1140 is coupled into the waveguide 1120 to be guided to the eye 210. System 1100A includes an optical device 1130, which is configured to both irradiate the SLM 1140 and project an image of the SLM 1140. Light from the light source 1110 propagates through the optical device 1130 in a first direction, for example, and impinges on the SLM 1140, thereby irradiating the SLM 1140. The light reflected from the SLM 1140 propagates through the optical device 1130 again in a second direction opposite to the first direction and is guided to the waveguide 1120 and coupled therein.

[0167] 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, although the light source 1110 need not be so limited. In some embodiments, a polarizer 1115 may be positioned between the light source 1110 and the SLM 1140. As illustrated, the polarizer 1115 is located between the light source 1110 and the waveguide 1120. This polarizer 1115 may also be a light recycler, transmitting light of a first polarization and reflecting 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 optical device 1105 (such as a non-imaging optical element (e.g., a cone, a compound parabolic concentrator (CPC), a lens)) may be disposed relative to the light source 1110 to receive the light output from the light source 1110. The coupling optical device 1105 may collect light from the light source 1110 and, in some cases, reduce the divergence of the light emitted from the light source 1110. The coupling optical device 1105 may, for example, collimate the light output from the light source 1110. The coupling optical device 1105 may collect light that matches the angular spectrum field of view of the system 1100A. Thus, the coupling optical device 1105 may match the angular spectrum of the light output by the light source 1110 to the field of view of the system 1100A. The coupling optical device 1105 may have an asymmetric profile to operate on the light emitted from the light source 1110 asymmetrically. For example, the coupling optical device 1105 may reduce the divergence to different amounts in orthogonal directions (e.g., the x and z directions). Such an asymmetry in the coupling optical device 1105 may address the asymmetry of the light emitted from the light source 1110, which may include, for example, a laser diode that emits a wider range of light angles in one direction (e.g., x or z) than in the orthogonal direction (e.g., z or x, respectively).

[0168] As discussed above, system 1100A includes optics 1130 configured to illuminate SLM 1140, and the optics 1130 is disposed in the optical path between light source 1110 and SLM 1140. The optics 1130 may include transmissive optics that transmits light from the light source 1110 to the SLM 1140. The optics 1130 may also be configured to project an image of the SLM 1140 or an image formed by the SLM 1140 into waveguide 1120. The image may be projected into the eye of eye 210. In some designs, the optics 1130 may include one or more lenses or optical elements having a focal power. The optics 1130 may, for example, have a positive focal power. The optics 1130 may include one or more refractive optical elements, such as refractive lenses. Other types of optical elements may also be used.

[0169] The SLM 1140 may be reflective, modulating, and reflecting light therefrom. The SLM 1140 may be a polarization-based SLM configured to modulate polarization. The SLM 1140 may, for example, include a liquid crystal (LC) SLM (e.g., a liquid crystal on silicon (LCoS) SLM). The LC SLM may, for example, include twisted nematic (TN) liquid crystal. The SLM 1140 may be substantially similar to the SLM 1030 of the reference Figure 10 . The SLM 1140 may, for example, include one or more pixels configured to selectively modulate light incident on the pixel depending on the state of the pixel. For some types of SLM 1140, the pixel may modulate the light beam incident thereon, for example, by changing the polarization state (such as rotating the polarization (e.g., rotating the orientation of linearly polarized light)).

[0170] As discussed above, the SLM 1140 may be an LCoS SLM 1140. In a cross-polarizer configuration, the LCoS SLM 1140 may be nominally white. When the pixel is off (e.g., 0 volts), it has a bright state, and when the pixel is on (e.g., a voltage higher than the threshold turn-on voltage), it has a dark state. In this cross-polarization configuration, leakage is minimized when the pixel is on and has a dark state.

[0171] In a parallel-polarizer configuration, the LCoS SLM 1140 is nominally black. When the pixel is off (e.g., 0 volts), it has a dark state, and when the pixel is on (e.g., a voltage higher than the threshold turn-on voltage), it has a bright state. In this parallel-polarizer configuration, leakage is minimized when the pixel is off and has a dark state. The rubbing direction and compensator angle may be used to (re)optimize the dark state. The compensator angle may refer to the angle of a compensator that may be located between the optics 1130 and the SLM 1140, for example, as shown in Figure 20B .

[0172] The dynamic range and throughput of a parallel polarizer configuration can be different from those of a crossed polarizer configuration. Additionally, the parallel polarizer configuration can be optimized differently for contrast than the crossed polarizer configuration.

[0173] System 1100A includes a waveguide 1120 for outputting image information to an eye 210. The waveguide 1120 can be substantially similar to the waveguides 270, 280, 290, 300, 310, 670, 680, and 690 discussed above. The waveguide 1120 can include a substantially transparent material having a refractive index sufficient to guide light therein. As illustrated, the waveguide 1120 can include a first side 1121 and a second side 1123 opposite the first side 1121, as well as corresponding upper and lower major surfaces and surrounding edges. The first major surface 1121 and the second major surface 1123 can be sufficiently flat such that image information can be retained as light propagates from the SLM 1140 to the eye 210, such that the image formed by the SLM 1140 can be injected into the eye. The optical device 1130 and the SLM 1140 can be positioned on the first side 1121 of the waveguide 1120. The light source 1110 can be disposed on the second side 1123 such that light from the light source 1110 is incident on the second side 1123 before passing through the waveguide 1120 and through the optical device 1130 to reach the SLM 1140. Thus, the waveguide 1120 can be disposed between the light source 1110 and the optical device 1130. Additionally, at least a portion of the waveguide 1120 can extend between the light source 1110 and the optical device 1130 such that light passes through this portion of the waveguide 1120 to reach the optical device 1130. Thus, light emitted from the light source 1110 can be guided through the waveguide 1120, into the optical device 1130 and through the optical device 1130, and incident on the SLM 1140. The SLM 1140 reflects the light back through the optical device 1130 and to the waveguide 1120.

[0174] System 1100A further includes an input optical element 1160 for coupling light from the optical device 1130 into the waveguide 1120. The input optical element 1160 can be disposed on a major surface (e.g., the upper major surface 1123) of the waveguide 1120. In some designs, the input optical element 1160 can be disposed on the lower major surface 1121 of the waveguide 1120. In some designs, the input optical element 1160 can be disposed within the body of the waveguide 1120. Although the input optical element 1160 is shown on one side or a corner of the waveguide 1120, the input optical element 1160 can be disposed in / on other regions of the waveguide 1120. The input optical element 1160 can be similar to that referenced above Figure 9A 、 9BThe coupling optical elements 700, 710, and 720 described in 9C are substantially similar. The coupling optical element 1160 can be a diffractive optical element or a reflector. Other structures can be used as the coupling optical element 1160. The coupling optical element 1160 can be configured to guide light incident thereon into the waveguide 1120 at a grazing angle (e.g., greater than the critical angle) relative to the upper major surface 1123 and the lower major surface 1121 of the waveguide 1120 large enough to be guided in the waveguide 1120 by total internal reflection. In addition, the coupling optical element 1160 can operate over a wide wavelength range and can thus be configured to couple light of multiple colors into the waveguide 1120. For example, the coupling optical element 1160 can be configured to couple red, green, and blue light into the waveguide 1120. The light source 1110 can emit red, green, and blue light at different times.

[0175] The system 1100A includes a light distribution element 1170 disposed on or in the waveguide 1120. The light distribution element 1170 can be substantially similar to the light distribution elements 730, 740, and 750 described above with respect to Figure 9B . For example, the light distribution element 1170 can be an orthogonal pupil expander (OPE). The light distribution element 1170 can be configured to spread light within the waveguide 1120 by turning light propagating in the x direction, for example, toward the z direction as shown in the top view Figure 11B . Thus, the light distribution element 1170 can be configured to increase the size of the eye box along the z axis; see Figure 11B . For example, the light distribution element 1170 can include one or more diffractive optical elements configured to diffract light incident on the diffractive optical element propagating within the waveguide 1120 so as to redirect the light in a direction that is, for example, substantially orthogonal. Other configurations are possible.

[0176] As Figure 11B shown, the system 1100 can also include a coupling-out optical element 1180 for coupling light from the waveguide 1120 to the eye 210. The coupling-out optical element 1180 can be configured to redirect light propagating within the waveguide 1120 by total internal reflection (TIR) to an angle that is more perpendicular to the upper major surface 1123 and / or the lower major surface 1121 of the waveguide 1120 such that the light is not guided within the waveguide 1120. Instead, the light is guided out of the waveguide 1120 through, for example, the lower major surface 1121. The coupling-out optical element 1180 can include, for example, one or more diffractive optical elements configured to diffract light incident on the diffractive optical element propagating within the waveguide 1120 so as to, for example, redirect the light out of the waveguide 1120. Other configurations are possible.

[0177] Figure 11BThe position of the light-incoupling optical element 1160, which is disposed laterally with respect to the light distribution optical element (e.g., an orthogonal pupil expander) 1170 and the light-extracting optical element 1180, is also shown. Figure 11B The position of the light source 1110, which is disposed laterally with respect to the light-incoupling optical element 1160, the light distribution optical element (e.g., an orthogonal pupil expander) 1170, and the light-extracting optical element 1180, is also shown.

[0178] In operation, the light source 1110 of system 1100A emits light into the coupling optics 1105 and through the polarizer 1115. Thus, the light can be polarized, for example, linearly polarized in a first direction. The polarized light can pass through the waveguide 1120, enter the second major surface of the waveguide 1120, and exit from the first major surface of the waveguide 1120. The light can propagate through the optics 1130 to reach the SLM 1140. The optics 1130 collimates and / or selects the light from the light source 1110 so as to illuminate the SLM 1140, which may include a polarization-based modulator that modulates the polarization of the light incident thereon, such as by selectively rotating the orientation of the modulator 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 but not rotate the polarization. The light between the coupling optics 1105 and the optics 1130 can illuminate the SLM 1140 rather uniformly. After being incident on the SLM 1140, the light is reflected back through the optics 1130. The optics 1130 can be configured to project the image from the SLM 1140 into the waveguide 1120 and ultimately into the eye 210 such that the image is visible to the eye 210. In some designs, the retina of the eye 210 is the optical conjugate of the SLM 1140 and / or the image formed by and / or on the SLM 1140. The power of the optics 1130 can facilitate projecting the image on the SLM 1140 into the eye 210 and onto the retina of the eye 210. In some embodiments, the optical power provided, for example, by the decoupling optical element 1180 can contribute to and / or affect the image ultimately formed in the eye 210. When the light reflected from the SLM 1140 travels through the optics towards the waveguide 1120, the optics 1130 acts as a projection lens. The optics can be roughly used as a Fourier transform of the image on the SLM 1140 to a plane in the waveguide 1120 near the coupling optical element 1160. Passing through the optics 1130 a total of two times (the first time from the light source 1110 to the SLM 1140 and the second time from the SLM 1140 to the waveguide 1120) can together roughly image the pupil of the coupling optics 1105. The alignment and orientation of the light source 1110 (and possibly also the coupling optics 1105 and / or the polarizer 1115), the optics 1130, and the SLM 1140 are such that the light from the light source 1110 reflected from the SLM 1140 is directed onto the coupling optical element 1160. The pupil associated with the coupling optics 1105 can be aligned with the coupling optical element 1160. The light can pass through an analyzer 1150 (e.g., a polarizer) in the optical path between the SLM 1140 and the eye 210. As Figure 11AAs shown, analyzer (e.g., polarizer) 1150 can be disposed in the optical path between optical device 1130 and input-coupling optical element 1160. Analyzer 1150 can be, for example, a linear polarizer having an orientation that transmits light of a first polarization (p-polarization) and blocks light of a second polarization (s-polarization), and vice versa. Analyzer 1150 can be a clean-up polarizer and further block polarized light blocked by another polarizer between SLM 1140 and analyzer 1150 or within SLM 1140. Analyzer 1150 can be, for example, a circular polarizer that acts as an isolator to mitigate reflections reflected back from waveguide 1120 (specifically input-coupling optical element 1160) to SLM 1140. Like any polarizer disclosed herein, analyzer 1150 can include a wire-grid polarizer, such as an absorptive wire-grid polarizer. Such polarizers can significantly absorb unwanted light and thereby increase contrast. Some such polarizers can be made to include one or more dielectric layers on top of the wires and / or multilayer films. In some embodiments, SLM 1140 can be a liquid crystal on silicon (LCoS) SLM and can include LC cells and retarders (e.g., compensators). In some embodiments, analyzer 1150 can be a compensator that is designed to provide more consistent polarization rotation (e.g., 90°) of SLM 1140 for different angles of incidence and different wavelengths. The compensator can be used to improve the contrast of the display by improving the rotational polarization of light incident across the angular and wavelength ranges. SLM 1140 can include, for example, TN LCoS that is configured to rotate incident light of a first polarization (e.g., s-polarization) to a second polarization (e.g., p-polarization) for a first pixel to create a bright pixel state when the light will pass through analyzer 1150. Conversely, SLM 1140 can be configured not to rotate incident light of a first polarization (e.g., s-polarization) to a second polarization (e.g., p-polarization) for a second pixel such that the reflected light maintains the first polarization to create a dark pixel state when the light will be attenuated or blocked by analyzer 1150. In such a configuration, polarizer 1115 closer to light source 1110 along the optical path can be oriented differently (e.g., orthogonally) from analyzer 1150 farther from light source 1110 along the optical path. Other (e.g., opposite) configurations are possible.

[0179] Then, the light is deflected, e.g., steered by input-coupling optical element 1160, so as to be guided in waveguide 1120, where the light propagates by TIR. Then, the light impinges on light distribution element 1170, steering the light in another direction (e.g., more toward the z-direction), resulting in an increase in the size of the eye box along the z-axis direction, as Figure 11B shown. Thus, the light is deflected toward output-coupling optical element 1180, which causes the light to be directed out of waveguide 1120 toward eye 210 (e.g., the user's eye as shown). The light is output-coupled along the z-direction by different portions of output-coupling optical element 1180, resulting in an eye box size along at least theFigure 11B increases in a direction parallel to the z-axis defined in . It is noted that in this configuration, the optical device 1130 is used both to illuminate the SLM 1140 and to project an image onto the coupled-in optical element 1160. Thus, the optical device 1130 can act as a projection optical device to distribute the light from the light source 1110 (e.g., uniformly), and act as an imaging optical device to provide the image of the SLM 1140 and / or the image formed by the SLM 1140 into the eye. Figure 11A The system 1100A in / B may be more compact than Figure 10 the system 1000 in . In some cases, not using Figure 10 the PBS 1020 shown in may reduce the cost and / or size of the system. Additionally, in the absence of the PBS 1020, the system can be more symmetric and easier to design by shortening the back focal length of the optical device 1130.

[0180] As described above, alternative configurations are possible. Referring to Figure 11C , for example, in some designs, the system 1100C can be configured to allow light with a polarization that is not rotated by the SLM 1140 to pass through. In one embodiment, for example, the SLM 1140 is a liquid crystal (LC)-based SLM and may include vertically aligned (VA) liquid crystal on silicon (LCoS). The SLM 1140 can have a first pixel in a first state that does not rotate polarization and a second pixel in a second state that rotates polarization. In Figure 11C the configuration shown in , a single shared analyzer / polarizer 1155 is utilized. This analyzer 1155 can transmit light of a first polarization (e.g., s-polarization) and attenuate or reduce the transmission of a second polarization (e.g., p-polarization). Thus, light (e.g., s-polarized light) incident on the first pixel in the first state that does not rotate the polarization orientation is reflected from the SLM 1140 and passes through the analyzer 1155 to reach the waveguide 1120. In contrast, light (e.g., s-polarized light) incident on the second pixel in the second state that rotates the polarization orientation is reflected from the SLM 1140 and is attenuated, reduced, or does not pass through the analyzer 1155 to reach the waveguide 1120. This configuration can thus allow Figure 11A the polarizer 1115 and the analyzer 1150 shown in to be combined into a shared optical element ( Figure 11C the analyzer 1155 shown in ), thereby potentially simplifying Figure 11A the system 1100 in / B by reducing the number of optical components. The analyzer 1155 can be disposed between the waveguide 1120 and the optical device 1130. In other embodiments, separate analyzer / polarizers and analyzer / polarizers can be used, such as Figure 11A shown in the system 1100 in / B. Figure 11A and 11BA polarizer 1115 is shown between the light source 1110 and the waveguide 1120, and an analyzer 1140 is shown between the optical device 1130 and the waveguide 1120.

[0181] Figure 11D An example of a waveguide with a combined OPE / EPE according to an embodiment of the present invention is shown. Referring to Figure 11D , the waveguide 1190 having a combined OPE / EPE region 1191 includes gratings corresponding to OPE and EPE that are spatially overlapped in the x and y directions. In some embodiments, the gratings corresponding to OPE and EPE are located on the same side of the substrate such that the OPE grating is superimposed on the EPE grating, or the EPE grating is superimposed on the OPE grating (or both). In other embodiments, the OPE grating is located on the opposite side of the substrate from the EPE grating such that the gratings are spatially overlapped in the x and y directions but are separated from each other in the z direction (i.e., in different planes). Thus, the combined OPE / EPE region 1191 can be implemented in a single-sided configuration or a double-sided configuration.

[0182] The optical path within the eyepiece waveguide 1190 includes incident light 1194 that is coupled into the eyepiece waveguide 1190 at the ICG 1193. The incident light propagates through total internal reflection in the substrate 1192 towards the combined OPE / EPE 1191. When these light rays encounter the combined OPE / EPE 1191 (also referred to as a combined pupil expander (CPE)), the light diffracts in the +y direction and then diffracts out of the waveguide in the -z direction along the optical path 1195 towards the user's eye. Similarly, the coupled-in light alternatively encounters the combined OPE / EPE 1191 and diffracts in the -y direction and then diffracts out of the waveguide along the optical path 1195 towards the user's eye.

[0183] As described in more detail herein, embodiments of the present invention utilize an eyepiece waveguide having a difference in optical path length, e.g., the thickness of the eyepiece waveguide varies according to the lateral position (i.e., the position in the x-y plane). In some embodiments, the portion of the eyepiece waveguide that forms the ICG is thicker than the portion of the eyepiece waveguide that forms the CPE. Additionally, in some embodiments, the thickness of the CPE is different, with the portion adjacent to the ICG being thicker than the portion farther from the ICG. In other embodiments, the physical thickness is uniform, but the refractive index varies according to the lateral position, resulting in a difference in the optical path length characterizing the eyepiece waveguide that varies according to the lateral position.

[0184] Various other configurations can be employed that utilize the optical device 1130 to illuminate the SLM 1140 and image the image formed by the SLM 1140. For example, although Figures 11A - 11DA single waveguide 1120 is shown, but one or more waveguides may be used, such as a waveguide stack (possibly using different waveguides for different colors of light).

[0185] For example, Figure 12A FIG. 12 shows a cross-sectional side view of an example system 1200A that includes a stack 1205. The stack 1205 includes waveguides 1120, 1122, 1124, and each waveguide includes an optical coupling element 1260, 1262, 1264. The waveguides 1120, 1122, 1124 may each be configured to output one or more different wavelengths of light, or one or more different wavelength ranges of light. The stack 1205 may be substantially similar to stacks 260 and 660 ( Figure 6 and 9A ), and the illustrated waveguides 1120, 1122, 1124 of the stack 1205 may correspond to a portion of waveguides 670, 680, 690. However, the stack 1205 and the waveguides 1120, 1122, 1124 are not necessarily so limited. As Figure 12A shown, the optical coupling elements 1260, 1262, 1264 may, for example, be associated with, included in, or on the waveguides 1120, 1122, 1124, respectively. The optical coupling elements 1260, 1262, 1264 may be color selective and may primarily transfer or redirect certain wavelengths into the corresponding waveguides 1120, 1122, 1124 for guiding therein. As shown, since the optical coupling elements 1260, 1262, 1264 are color selective, the optical coupling elements 1260, 1262, 1264 do not need to be laterally displaced and may be stacked on top of each other. Wavelength multiplexing may be employed to couple a particular color into the corresponding waveguide. For example, a red optical coupling element may couple red light into a waveguide designated for propagating red light without coupling blue or green light, which is coupled into other waveguides by other blue and green selective waveguides, respectively.

[0186] In some embodiments, the light source 1110 can be a multi-color light source capable of emitting different colors of light at different times. For example, the light source 1110 can emit red, green, and blue (RGB) light and can be configured to emit red light and no more than a negligible amount of green and blue light during a first time period, green light and no more than a negligible amount of red and blue light during a second time period, and blue light and no more than a negligible amount of red and green light during a third time period. These cycles can repeat, and the SLM 1140 can be coordinated to generate a suitable pixel state pattern for a particular color (red, green, or blue) to provide an appropriate image color component for a given image frame. The different waveguides 1120, 1122, 1124 of the stack 1205 can each be configured to output light having a different corresponding color. For example, as Figure 12A shown, the waveguides 1120, 1122, 1124 can be configured to output blue, green, and red light, respectively. Of course, other colors are possible. For example, the light source 1110 can emit other colors, and the color-selective coupling-in optical elements 1260, 1262, 1264, the coupling-out optical elements, etc. can be configured for such other colors. In addition, separate red, green, and blue emitters can be positioned close enough to effectively act as a single-pupil light source. The red, green, and blue emitters can be combined with lenses and dichroic beam splitters to form a single red, green, and blue pupil source. The multiplexing of a single pupil can extend beyond or be supplementary to color selectivity and can include the use of polarization-sensitive gratings and polarization switches. These color or polarization gratings can also be used in combination with multiple display pupils to increase the number of addressable layers.

[0187] The different coupling-in optical elements 1260, 1262, 1264 in the different waveguides 1120, 1122, 1124 can be disposed above and / or below one another and laterally aligned with respect to one another (e.g., in Figure 12Ain the x and z directions shown), rather than being laterally shifted relative to each other and misaligned. Thus, in some embodiments, for example, the different input optical elements 1260, 1262, 1264 may be configured such that light of a first color may be coupled into waveguide 1120 by input optical element 1260 for guiding therein, while light of a second color different from the first color may pass through input optical element 1260 to the next input optical element 1262 and may be coupled into waveguide 1122 by input optical element 1262 for guiding therein. Light of a third color different from the first and second colors may pass through input optical elements 1260 and 1262 to input optical element 1264 and may be coupled into waveguide 1124 for guiding therein. Additionally, input optical elements 1260, 1262, 1264 may be polarization selective. For example, the different input optical elements 1260, 1262, 1264 may be configured such that light of a particular polarization is either coupled into the waveguide by the corresponding polarization selective input optical element 1260, 1262, 1264 or passes through input optical elements 1260, 1262, 1264.

[0188] Depending on the configuration, SLM 1140 may include a polarization-based SLM that modulates polarization. System 1200A may include a polarizer and / or an analyzer to modulate the light injected into stack 1205 pixel-by-pixel, for example depending on the state of the respective pixel (e.g., whether the pixel rotates the polarization orientation). Various aspects of such systems employing a polarization-based SLM have been discussed above, and any one of such features may be used in combination with any other features described herein. However, other designs are still possible.

[0189] For example, a deflection-based SLM 1140 may be employed. For example, SLM 1140 may include one or more movable optical elements, such as movable mirrors, that may reflect and / or deflect light in different directions depending on the state of the optical element. SLM 1140 may include, for example, one or more pixels that include optical elements such as micromirrors or reflectors. SLM 1140 may incorporate, for example, digital light processing (DLP TM ) technology using a digital micromirror device (DMD). Figure 12BAn example of a system 1200B using such a deflection-based SLM 1140 is shown. The system 1200B includes a deflection-based SLM 1140 and a light dump 1250. The light dump 1250 may include an absorbing material or structure configured to absorb light. The deflection-based SLM 1140 may include one or more micro-movable mirrors that can be selectively tilted to deflect light in different directions. For example, the deflection-based SLM 1140 can be configured to deflect light from the light source 1110 incident thereon to the coupling optical elements 1260, 1262, 1264 when a given pixel is in the bright state. As discussed above, depending on the color of the light, for example, the light will thus be coupled by one of the coupling optical elements 1260, 1262, 1264 into one of the corresponding waveguides 1120, 1122, 1124 and guided to the eye 210. Conversely, when a given pixel is in the dark state, the light from the light source 1110 can be deflected to the light dump 1250, and the light will not be coupled by one of the coupling optical elements 1260, 1262, 1264 into one of the corresponding waveguides 1120, 1122, 1124 and guided to the eye 210. Instead, the light may be absorbed by the absorbing material including the light dump 1250. In some embodiments, the analyzer 1150 can be a polarizer (e.g., a "cleaning" polarizer) that is used to eliminate unwanted reflections from the coupling optical elements 1260, 1262, 1264. Since the optical device 1130 may include plastic optical elements having birefringence and capable of changing polarization, this polarizer may be useful. The "cleaning" polarizer can attenuate or remove light (e.g., reflections) having unwanted polarization so that it is not guided onto the waveguides 1120, 1122, 1124. Other types of light conditioning elements can be disposed between the SLM 1140 and the waveguides 1120, 1122, 1124, such as between the optical device 1130 and the waveguides 1120, 1122, 1124. For example, such light conditioning elements can also include circular polarizers (i.e., linear polarizers and retarders, such as quarter-wave plates). The circular polarizer can reduce the amount of reflection from the waveguides 1120, 1122, 1124 or the coupling optical elements 1260, 1262, 1264 that is incident again onto the waveguides 1120, 1122, 1124 and coupled therein. The reflected light can be circularly polarized and can have a circular polarization opposite to that of the incident light (e.g., right-handed circularly polarized light is converted to left-handed circularly polarized light upon reflection and vice versa). The retarder in the circular polarizer can convert the circularly polarized light into linearly polarized light, such as linearly polarized light orthogonal to the polarization of the polarizer, which is attenuated (e.g., absorbed) by the linear polarizer in the circular polarizer. The cleaning polarizer can be used with polarization-independent modulators such as DMDs.As described above, the cleaning polarizer can be used to suppress reflections and / or improve the coupling of light into the coupling optical elements 1260, 1262, 1264 in an optimal polarization state.

[0190] Figure 12B A side view or cross-sectional view of the system 1200B is shown, while Figure 12C A top view showing the lateral arrangement of the coupling optical element 1264, the light dump 1250, and the light source 1110 is shown. The SLM 1140 will be configured to reflect, deflect, and / or direct light from the light source 1110 to the lateral position of the coupling optical element 1264 (and other coupling optical elements 1260, 1262) or the light dump 1250 depending on the state of a particular pixel.

[0191] In some designs, the light dump 1250 can include an energy harvesting system. The light dump 1250 can include, for example, a light energy conversion element configured to convert light energy into electrical energy. The light energy conversion element can include, for example, a solar cell. The light energy conversion element can include, for example, a photovoltaic detector that generates an electrical output when light is incident thereon. The light energy conversion element can be electrically connected to an electrical component, such as a conductive wire, to guide the electrical output to provide power for the system 1200B and / or possibly charge one or more batteries.

[0192] In some designs, laterally shifted, non-color selective, or broadband or multi-color coupling optical elements can be used. For example, Figure 13A is a perspective view of a system 1300 including a stack 1305 containing waveguides. The stack 1305 can be substantially similar to the stack 1205 with reference to Figure 12A Each waveguide in the stack 1305 can include coupling optical elements 1360, 1362, 1364. However, contrary to the design shown in Figure 12A , the coupling optical elements 1360, 1362, 1364 are laterally shifted relative to each other. As shown in Figure 13A , 13B and 13C, the light sources 1110, 1112, 1114 are also laterally shifted relative to each other and can be arranged to direct light to the corresponding coupling optical elements 1360, 1362, 1364 by passing the light through the optical device 1130, reflecting the light away from the SLM 1140, and passing the reflected light through the optical device 1130 again. Figure 13B The system 1300 of Figure 13BShown in. Light sources 1110, 1112, 1114 may respectively correspond to the coupled-in optical elements 1360, 1362, 1634. For example, in one design, the light sources 1110, 1112, 1114 and the corresponding coupled-in optical elements 1360, 1362, 1364 are disposed substantially equidistantly (symmetrically) along a common (optical) axis from the center of the optical device 1130. The common (optical) axis may intersect the center of the optical device 1130. For example, in one design, the light sources 1110, 1112, 1114 and the corresponding coupled-in optical elements 1360, 1362, 1364 are disposed non-equidistantly (asymmetrically) along a common (optical) axis from the center of the optical device 1130.

[0193] The coupled-in optical elements 1360, 1362, 1364 may be configured to couple light of multiple colors into their respective waveguides. Thus, these coupled-in optical elements 1360, 1362, 1364 may herein be referred to as broadband, multi-color, or non-color-selective coupled-in optical elements 1360, 1362, 1364. For example, in some cases, each of these coupled-in optical elements 1360, 1362, 1364 is configured to couple red, green, and blue light into the associated waveguide containing that coupled-in optical element 1360, 1362, 1364 such that such colored light is guided within the waveguide by TIR. For example, such broadband coupled-in optical elements 1360, 1362, 1364 may operate across a wide wavelength range, e.g., within the visible light range, or may select wavelengths or wavelength regions across, e.g., the visible light range. Thus, such broadband or multi-color or non-color-selective coupled-in optical elements 1360, 1362, 1364 may be configured to direct light of various different colors (e.g., red, green, and blue) into the waveguide to be guided therein by TIR. Although red, green, blue (RGB) is mentioned herein, such as in relation to light sources, coupled-in optical elements, waveguides, etc., other colors or color systems may be used additionally or alternatively, such as, for example but not limited to, magenta, cyan, yellow (CMY).

[0194] As Figure 13A shown, the light sources 1110, 1112, 1114 are shown above the uppermost waveguide and are displaced relative to each other (e.g., in the x and z directions). Similarly, the three coupled-in optical elements 1360, 1362, 1364 are shown on three respective waveguides and are displaced relative to each other (e.g., in the x, y, and z directions). Figure 13B is Figure 13A a side view of the system 1300 shown in, which shows the coupled-in optical elements 1360, 1362, 1364 that are laterally spatially displaced relative to each other (e.g., in the x and z directions), and some of the light sources 1110, 1112, 1114 that are laterally displaced relative to each other (e.g., in the x and z directions).Figure 13B Optical device 1130 and SLM 1140 are also shown.

[0195] Figure 13C is Figure 13A and 13B is a top view of the augmented reality display system shown in, which shows the coupled-in optical elements 1360, 1362, 1364 and the associated light sources 1110, 1112, 1114. In this design, the coupled-in optical elements 1360, 1362, 1364 and the associated light sources 1110, 1112, 1114 are arranged in an annular pattern around the center point of the common (optical) axis. As shown, the light sources 1110, 1112, 1114 and the corresponding coupled-in optical elements 1360, 1362, 1364 are arranged approximately equidistantly around the center point of the common (optical) axis. However, this must be the case. In some designs, this center point can correspond to the center along the common (optical) axis that intersects the center of the optical device 1130 and / or the position along the optical axis of the optical device 1130. Similarly, as a result, the non-color-selective coupled-in optical elements 1360, 1362, 1364 and the light sources 1110, 1112, 1114 are laterally displaced relative to each other (e.g., in the x and z directions).

[0196] Other arrangements placed laterally are also possible. Figures 14A - 14C shows an alternative configuration of system 1400, which includes a stack 1405 that includes waveguides, where the coupled-in optical elements 1360, 1362, 1364 and the light sources 1110, 1112, 1114 are laterally displaced relative to each other. Figure 14A is a side view, while Figure 14B is Figure 14A is a top view of the system 1400 shown in, which shows the laterally displaced coupled-in optical elements 1360, 1362, 1364 and the light sources 1110, 1112, 1114. Figure 14C is Figure 14A and 14B are orthogonal side views of the system 1400 shown in.

[0197] Figure 14A and 14C The side views of show how the coupled-in optical elements 1360, 1362, 1364 are arranged on individual waveguides within the stack 1405 such that light can be coupled into the corresponding waveguides through the respective laterally displaced coupled-in optical elements 1360, 1362, 1364. Figure 14A and 14CThe input optical elements 1360, 1362, 1364 are shown as being disposed in the upper major surface of the waveguide. However, the input optical elements 1360, 1362, 1364 may alternatively be disposed on the lower major surface of the respective waveguide or in the body of the waveguide. A variety of configurations are possible.

[0198] As Figure 14B shown in the top view of, the input optical elements 1360, 1362, 1364 are arranged in a column, laterally shifted relative to each other in the z direction, but not shifted in the x direction. Similarly, the light sources 1110, 1112, 1114 are arranged in a column, also laterally shifted relative to each other in the z direction, but not shifted in the x direction. The input optical elements 1360, 1362, 1364 are laterally shifted relative to the light sources 1110, 1112, 1114 in the x direction.

[0199] Other configurations are still possible. Figure 15 is a top view of the system 1500, showing an alternative configuration of the light sources 1110, 1112, 1114 and the input optical elements 1360, 1362, 1364. Compared with Figure 13C where all the light sources 1110, 1112, 1114 are located substantially on one side (e.g., in an annular pattern) and all the input optical elements 1360, 1362, 1364 are located substantially on one side (i.e., the opposite side), the light sources 1110, 1112, 1114 and the input optical elements 1360, 1362, 1364 are interspersed or alternated along the circumference of the annular pattern.

[0200] However, in some embodiments, the input optical elements 1360, 1362, 1364 and one or more associated light sources 1110, 1112, 1114 are also arranged in an annular pattern around a central point. Thus, the light sources 1110, 1112, 1114 and the corresponding input optical elements 1360, 1362, 1364 can be arranged substantially equidistant from the center. In some designs, this center may correspond to the center of the optical device 1130 along a common central axis intersecting the center of the optical device 1130 and / or the position along the optical axis of the optical device. Thus, light from the first light source 1110 can be coupled into the input optical element 1360 via the optical device 1130 across the center or central axis or optical axis of the optical device 1130 (as from Figure 15as seen in the top view). Similarly, light from the second light source 1112 can be coupled into the light-incoupling optical element 1362 via the optical device 1130 across the center or central axis or optical axis of the optical device 1130. Likewise, light from the third light source 1114 can be coupled into the light-incoupling optical element 1364 via the optical device 1130 across the center or central axis or optical axis of the optical device 1130. As a result, the non-color-selective light-incoupling optical elements 1360, 1362, 1364 and the light sources 1110, 1112, 1114 are laterally displaced relative to each other (e.g., in the x and z directions). The optical device 1130 can be designed such that the focus is more into the stack 1405, such that the positions of the sub-pupils and the light-incoupling optical elements 1360, 1362, 1364 are closer in their directions. In this configuration, the light-incoupling optical elements 1360, 1362, 1364 can be smaller because they are closer to the focus of the optical device 1130. The light source 1110 can be located on the user side of the stack 1405 (e.g., similar to Figure 17 and 18 ), and thereby reduce the distance or optical path between the light source 1110 and the optical device 1130.

[0201] In the various embodiments described above, such as Figures 12A - 15 as shown in, stacks including a plurality of waveguides (e.g., stacks 1205, 1305, 1405) (e.g., stack 1205 includes waveguides 1120, 1122, 1124, stack 1305 includes waveguides (not labeled), and stack 1405 includes waveguides (not labeled)) can be included to process different colors (e.g., red, green, and blue). Different waveguides can be used for different colors. Similarly, a plurality of stacks can be included to provide different optical characteristics to the light coupled out from the respective stacks. For example, Figures 12A - 12B the waveguides 1120, 1122, 1124 of the stack 1205 of

[0202] Figure 16A Figures 12A - 12B can be configured to output light having optical characteristics (e.g., providing a light power of a specific wavefront shape) that may be associated with an apparent depth from which the light appears to emanate. For example, wavefronts having different amounts of divergence, convergence, or collimation may appear as if projected from different distances from the eye 210. Thus, a plurality of stacks can be included, where different stacks are configured such that the light coupled out by the light-outcoupling optical elements has different amounts of convergence, divergence, or collimation, and thus appears to originate from different depths. In some designs, different stacks can include different lenses, such as diffractive lenses or other diffractive optical elements, to provide different amounts of light power to different stacks. Thus, different stacks will produce different amounts of convergence, divergence, or collimation, and thus the light from different stacks will appear as if associated with different depth planes or objects at different distances from the eye 210.is a side view of a system 1600 including stacks 1605, 1610, 1620. As Figure 16A shown, system 1600 includes three stacks 1605, 1610, 1620; however, this need not be the case. The system can be designed to have fewer or more stacks. Each of stacks 1605, 1610, and 1620 includes one or more (e.g., three) waveguides. Figure 16A Also shown are groups 1630, 1640, 1650 of optical elements coupled in. A first group 1630 is associated with a first stack 1605, a second group 1640 is associated with a second stack 1610, and a third group 1650 is associated with a third stack 1620. Groups 1630, 1640, 1650 are laterally offset relative to each other. Each of groups 1630, 1640, 1650 includes color-selective optical elements coupled in, which are configured to couple in different respective colors substantially similarly to Figure 12A the optical elements 1260, 1262, 1264 coupled in. As Figure 16A shown, the optical elements coupled in within each of groups 1630, 1640, 1650 are not laterally displaced relative to each other; however, this need not be the case. A system can be designed in which the optical elements coupled in within a group are laterally displaced relative to each other. System 1600 can be configured such that the light coupled out from each of stacks 1605, 1610, 1620 has a different optical power. For example, the waveguides in a stack can contain an optical element coupled out or a diffractive lens having a given optical power. The optical powers of different stacks 1605, 1610, 1615 can be different such that the light from one stack may appear to originate from a different depth than the light from another stack. For example, the optical power of one stack can cause the light from that stack to be collimated, while the optical power of another stack can cause the light from that stack to diverge. The diverging light can appear to originate from an object at a relatively close distance from the eye 210, while the collimated light can appear to originate from an object at a relatively far distance. Thus, the light coupled out from a first stack 1605, a second stack 1610, and a third stack 1620 can have at least one of different amounts of convergence, divergence, and collimation, and thus can appear to originate from different depths. In some embodiments, the light coupled out from one of the stacks can be collimated, while the light coupled out from a different stack can diverge. The light coupled out from one of the other stacks can also diverge, but by a different amount.

[0203] As Figure 16AAs shown, light source 1110 can be arranged relative to optical device 1130 and SLM 1140 to direct light into the optical element group 1630, light source 1112 can be arranged relative to optical device 1130 and SLM 1140 to direct light into the optical element group 1640, and light source 1114 can be arranged relative to optical device 1130 and SLM 1140 to direct light into the optical element group 1650. Light sources 1110, 1112, 1114 can be configured to emit light of different colors at different times. Similarly, light of different corresponding colors can be coupled into different waveguides within the stack in the manner described above due to color-selective coupling into the optical elements. For example, if blue light is emitted from the second light source 1112, the optical device 1130 and SLM 1140 will direct the blue light to the second group 1640 of coupled optical elements. This light can pass through the first red-coupled optical element and the second green-coupled optical element in the second group 1640 and be redirected by the third blue-coupled optical element in the second group 1640 into the third waveguide in the second stack 1610. The waveguides in the second stack 1610 can include output optical elements or other optical elements with optical power (e.g., diffractive lenses) to provide a light beam associated with a specific depth plane or object distance associated with the second stack 1610 to the eye 210.

[0204] Figure 16B is Figure 16A A top view of the system 1600 in. The coupled optical elements of the different groups 1630, 1640, 1650 are shown shifted laterally relative to each other (e.g., in the x direction). Similarly, the light sources 1110, 1112, 1114 are shown shifted laterally relative to each other (e.g., in the x direction).

[0205] Various different variations in the above system are possible. For example, the position of the light source 1110 relative to the waveguide and the optical device 1130 may be different. For example, Figure 17 is a side view of the system 1700, which has a light source 1110 in a position different from that shown in FIGS. 11-16B relative to the waveguide 1720 and the optical device 1130. In addition, Figure 17A design is shown in which the waveguide 1720 is divided into a first portion 1720a and a second portion 1720b. The waveguide 1720 may further include a reflector 1730 configured to couple out light guided in the first portion 1720a near the light source 1110 from the first portion 1720a and direct it into the optical device 1130 towards the SLM 1140. Additionally or alternatively, the system 1700 may include a diffractive coupling-out optical element to couple out light in the first portion 1720a of the waveguide 1720 and direct it into the optical device 1130 towards the SLM 1140. The reflector 1730 may be opaque and include an isolator that reduces crosstalk between the first portion 1720a and the second portion 1720b. The waveguide 1720 has a first side 1721 and a second side 1723 opposite the first side 1721, and the optical device 1130 and the SLM 1140 are disposed on the first side 1721 such that light from the SLM 1140 is directed onto the first side 1721. In this example, the light source 1110 is disposed 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 optical device 1130 and reaching the SLM 1140. The system 1700 may further include a coupling-in optical element 1710 disposed on or in the first portion 1720a. The coupling-in optical element 1710 may be configured to receive light from the light source 1110 and couple the light into the first portion 1720a. The coupling-in optical element 1710 may include a diffractive optical element or a reflector configured to turn light incident thereon at an angle into the first portion 1720a for guiding therein by TIR.

[0206] The reflector 1730 may be configured to couple out light guided in the first portion 1720a from the first portion 1720a and direct it towards the optical device 1130 and the SLM 1140 (as discussed above, in some embodiments, a diffractive optical element may additionally or alternatively be used to couple out light in the first portion 1720a from the first portion 1720a and direct it towards the optical device 1130 and the SLM 1140). Thus, the reflector 1730 may be a mirror, a reflective grating, one or more coatings that reflect light from the waveguide 1720 towards the SLM 1140. The light emitted from the first portion 1720a by the reflector 1730 passes through the optical device 1130, is incident on the SLM 1140, passes through the optical device 1130 again, and is incident on the second portion 1720b. As described above, the light reflected from the SLM 1140 and transmitted through the optical device 1130 may be incident on the coupling-in optical element 1160 and turn the light for guiding in the second portion 1720b. The light guided in the second portion 1720b may be coupled out therefrom by a coupling-out optical element 1180 (not shown) and directed to the eye 210.

[0207] As discussed above, the reflector 1730 can be an isolator that reduces crosstalk between the first portion 1720a and the second portion 1720b. The reflector 1730 can include an opaque and / or reflective surface. The reflector 1730 can be disposed within the waveguide 1720 and, in some cases, can define the sides of the first portion 1720a and the second portion 1720b.

[0208] Separate waveguides can be used instead of the first and second portions 1720a, 1720b of the waveguide 1720. Figure 18 is a side view of the system 1800, which includes a first waveguide 1822 for receiving light from the light source 1110 and guiding the light therein to the optical device 1130 and towards the SLM 1140. The system 1800 further includes a second waveguide 1820 that receives light from the SLM 1140 after the light passes through the optical device 1130 again. The first waveguide 1822 includes coupling-in and coupling-out optical elements 1730a, 1730b, respectively. These coupling-in and coupling-out optical elements 1730a, 1730b can include reflective surfaces that are oriented to couple light into and out of the waveguide 1822. The coupling-in optical element 1730a can include, for example, a reflective surface that is arranged to receive light from the light source 1110 and is oriented (e.g., tilted) to guide the light into the waveguide 1822 at an angle so as to be guided therein by TIR. The coupling-out optical element 1730b can include, for example, a reflective surface that is oriented (e.g., tilted) to guide the light guided within the waveguide 1822 at an angle so as to exit the waveguide 1822. The coupling-out optical element 1730b can be positioned such that the light exiting the waveguide 1822 is guided into the optical device 1130, reflected from the SLM 1140, passes through the optical device 1130 again, and is incident on the coupling-in optical element 1730c of the second waveguide 1820.

[0209] The coupling-in optical element 1730c in the second waveguide 1820 can include a reflective surface that can be positioned and oriented (e.g., tilted) so as to receive and redirect the light incident thereon from the SLM 1140 to be guided in the second waveguide 1820 by TIR. Figure 18 Shows the optical device 1130 and the light source 1110 disposed on the same side of the waveguides 1820, 1822. The system 1800 can further include an isolator to reduce crosstalk between the waveguide 1822 and the waveguide 1820. The isolator can include an opaque and / or reflective surface. The isolator can be disposed in or on at least one of the waveguides 1820, 1822.

[0210] Various designs (such as the designs discussed above) can include additional features or components. For example,Figure 19 A side view of a system 1900 including variable-focus optical elements (or adaptive optical elements) 1910, 1920 is shown. The variable-focus optical elements 1910, 1920 may include optical elements configured to be changeable 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, wherein in the first state, the variable-focus optical elements 1910, 1920 have an optical power different from that in the second state. For example, the variable-focus optical elements 1910, 1920 may have a negative optical power in the first state and a zero optical power in the second state. In some embodiments, the variable-focus optical elements 1910, 1920 have a positive optical power in the first state and a zero optical power in the second state. In some embodiments, the variable-focus optical elements 1910, 1920 have a first negative or positive optical power in the first state and a second different negative or positive optical power in the second state. Some adaptive optical elements or variable-focus optical elements 1910, 1920 may have more than two states and may provide a continuous distribution of optical power.

[0211] The variable-focus optical elements 1910, 1920 may include lenses (e.g., variable-focus lenses) and are transmissive. Figure 7 Transmissive or transparent adaptive optical elements or variable-focus optical elements 1910, 1920 are shown. 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, such as switchable liquid crystal polarization lenses, which may include diffractive lenses, for example. 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. Application No. 62 / 518,539, filed on June 12, 2017, entitled “AUGMENTED REALITY DISPLAY HAVING MULTI-ELEMENT ADAPTIVE LENS FOR CHANGING DEPTH PLANES”, the entire content of which is incorporated herein by reference. The variable-focus optical elements 1910, 1920 may have an electrical input that receives an electrical signal controlling the amount of optical power presented by the variable-focus optical elements 1910, 1920. The variable-focus optical elements 1910, 1920 may have positive and / or negative optical power. In addition to the variable-focus elements (e.g., polarization switches, geometric phase (GP) lenses, fluid lenses, etc.), the variable-focus elements 1910, 1920 may also include fixed lenses (e.g., diffractive lenses, refractive lenses, etc.) to generate the desired depth planes in the light field.

[0212] The first variable-focus optical element 1910 may be disposed between the stack 1905 and the eye 210. As discussed above, the stack 1905 may include different waveguides of different colors. The first variable optical element 1910 may be configured to introduce different amounts of optical power, negative and / or positive optical power. The variable optical power may be used to change the divergence and / or collimation of the light coupled out from the stack 1905 to change the depth at which the virtual object projected by the system 1900 into the eye 210 is located. Thus, a 4-dimensional (4D) light field may be created.

[0213] The second variable-focus optical element 1920 is located on the side of the stack 1905 opposite the first variable-focus optical element 1920. Thus, the second variable-focus optical element 1920 may compensate for the effect of the first optical element 1910 on the light received from the world 510 in front of the system 1900 and the eye 210. Thus, the world view may effectively remain unchanged or be changed as desired.

[0214] The system 1900 may further include a static or variable prescription or corrective lens 1930. Such a lens 1930 may provide refractive correction for the eye 210. Additionally, if the prescription lens 1930 is a variable lens, it may provide different refractive corrections for multiple users. Variable-focus lenses were discussed above. The eye 210 may, for example, suffer from myopia, hyperopia, and / or astigmatism. The lens 1930 may have a prescription (e.g., optical power) to reduce the refractive error of the eye 210. The lens 1930 may be spherical and / or cylindrical and may be positive or negative. The lens 1930 may be disposed between the stack 1905 and the eye 210 such that light from both the world 510 and the stack 1905 undergoes the correction provided by the lens 1930. In some embodiments, the lens 1930 may be disposed between the eye 210 and the first variable-focus optical element 1910. Other positions of the lens 1930 are possible. In some embodiments, the prescription lens may be variable and allow for multiple user prescriptions to be implemented.

[0215] In some designs, system 1900 can include an adjustable dimming device 1940. In some embodiments, the adjustable dimming device 1940 can be disposed on the side of the waveguide 1900 stack opposite to the eye 210 (e.g., the world side). Thus, the adjustable dimming device 1940 can be disposed between the stack of waveguides 1900 and the world 510. The adjustable dimming device 1940 can include an optical element that provides variable attenuation of the light transmitted therethrough. The adjustable dimming device 1940 can include an electrical input to control the attenuation level. In some cases, the adjustable dimming device 1940 is configured to increase attenuation when the eye 210 is exposed to bright light (such as when the user walks outdoors). Thus, system 1900 can include a light sensor to sense the brightness of the ambient light and control electronics to drive the adjustable dimming device 1940 to change the attenuation based on the light level sensed by the light sensor.

[0216] Different types of adjustable dimming devices 1940 can be employed. Such adjustable dimming devices 1940 can include variable liquid crystal switches having polarizers, electrochromic materials, photochromic materials, etc. The adjustable dimming device 1940 can be configured to adjust the amount of light entering and / or transmitted through the stack 1905 from the world 510. In some cases, the adjustable dimming device 1940 can be used to reduce the amount of ambient light passing through the waveguide stack 1900 to the eye 210, which otherwise might provide glare and reduce the user's ability to perceive virtual objects / images injected into the eye 210 from the stack 1905. Such adjustable dimming devices 1940 can reduce the incident bright ambient light so as not to wash out the image projected onto the eye 210. Thus, employing the adjustable dimming device 1940 can increase the contrast of the virtual objects / images presented to the eye 210. Conversely, if the ambient light is low, the adjustable dimming device 1940 can be adjusted to reduce the attenuation so that the eye 210 can more easily see the objects in the world 510 in front of the user. The dimming or attenuation can be across the system or local to one or more parts of the system. For example, multiple local parts can be dimmed or set to attenuate the light from the world 510 in front of the user 210. These local parts can be separated from each other by parts without such increased dimming or attenuation. In some cases, only one part is dimmed or causes increased attenuation relative to other parts of the eyepiece. Other components can be added in different designs. The arrangement of the components can also be different. Similarly, one or more components can be excluded from the system.

[0217] Figure 20A An example of another configuration is shown. Figure 20AShows a side view of system 2000, which includes laterally shifted optical coupling elements 1360, 1362, 1364 located on different waveguides and a color filter array 2030, which includes laterally shifted color filters 2040, 2042, 2044 aligned with the corresponding optical coupling elements 1360, 1362, 1364. The color filter array 2030 may be disposed on a side of stack 2005 closer to the eye 210 and the optical device 1130. The color filter array 2030 may be located between the stack 2005 and the optical device 1130. The color filter array 2030 may be disposed in or on a cover glass 2050 located between the stack 2005 and the optical device 1130. The color filter array 2030 may include one or more different color filters 2040, 2042, 2044 that are laterally disposed relative to each other, such as a red color filter, a green color filter, and a blue color filter. The system 2000 includes light sources 1110, 1112, 1114 that are laterally shifted relative to each other. These light sources 1110, 1112, 1114 may include light sources of different colors, such as a red light source, a green light source, and a blue light source. The color filters 2040, 2042, 2044 may be transmissive or transparent filters. In some embodiments, the color filters 2040, 2042, 2044 include absorption filters, however, 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 a mask (such as an opaque mask) that will reduce the propagation of stray light. The color 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 the optical coupling elements 1360, 1362, 1364, to prevent them from re-entering the waveguides for different colors through the optical coupling elements 1360, 1362, 1364 for different colors. Examples of color filter arrays can be found in U.S. Application Serial No. 15 / 683,412, filed August 22, 2017, entitled "PROJECTOR ARCHITECTURE INCORPORATING ARTIFACT MITIGATION", the entire content of which is incorporated herein by reference; and U.S. Application No. 62 / 592,607, filed November 30, 2017, entitled "PROJECTOR ARCHITECTURE INCORPORATING ARTIFACT MITIGATION", the entire content of which is incorporated herein by reference. The mask may be a black mask and may include an absorbing material to reduce the propagation and reflection of stray light. The light sources 1110, 1112, 1114 may be disposed relative to the optical device 1130 and the SLM 1140 to couple light into the corresponding color filters 2040, 2042, 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 that are arranged to receive light from 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 corresponding light-coupling optical elements 1360, 1362, 1364. Thus, the light from the first light source 1110 will be guided through the first color filter 2040 and reach the first light-coupling optical element 1360, the light from the second light source 1112 will be guided through the second color filter 2042 and reach the second light-coupling optical element 1362, and the light from the third light source 1114 will be guided through the third color filter 2044 and reach the third light-coupling optical element 1364. In some embodiments, the light-coupling optical elements 1360, 1362, 1364 may be color-specific. For example, the first and second light-coupling optical elements 1360, 1362 may be configured to couple light of corresponding first and second colors into first and second waveguides, respectively. Similarly, the first, second, and third light-coupling optical elements 1360, 1362, 1364 may be configured to couple light of corresponding first, second, and third colors into first, second, and third waveguides, respectively. The first light-coupling optical element 1360 may be configured to couple more light of the first color than the second color (or the third color) into the first waveguide. The second light-coupling optical element 1362 may be configured to couple more light of the second color than the first color (or the third color) into the second waveguide. The third light-coupling 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 light-coupling optical elements 1360, 1362, 1364 may be broadband. For example, the first light-coupling optical element 1360 may be configured to couple light of the first, second, and third colors into the first waveguide. The second light-coupling optical element 1362 may be configured to couple light of the first, second, and third colors into the second waveguide. The third light-coupling optical element 1364 may be configured to couple light of the first, second, and third colors into the third waveguide. However, the plurality of color filters 2040, 2042, 2044 may be color-specific, selectively transmitting light of a specific color. For example, the first color filter 2040 may transmit more light of the first color than the second color (and the third color). The second color filter 2042 may transmit more light of the second color than the first color (and the third color). The third color filter 2044 may transmit more light 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.Accordingly, the first, second, and third color filters 2040, 2042, 2044 can be band-pass filters that selectively transmit the first, second, and third colors, respectively. In some embodiments, the first, second, and third light sources 1110, 1112, 1114 can selectively emit the first, second, and third colors, respectively. For example, the first light source 1110 can emit more of the first color than the second color (and the third color). The second light source 2042 can emit more of the second color than the first color (and the third color). The third light source 2044 can transmit more of the third color than the first and second colors. The color filters 2040, 2042, 2044 can reduce the amount of stray light inadvertently guided to a particular coupling optical element. In other embodiments, 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 the third) colors. The second light source 1112 may also emit the first and second (and possibly the third) colors. The third light source 1114 may also emit the first and second (and possibly the third) colors. Although. Figures 20A - 20G Three filters are shown, but more or fewer filters can be included. For example, in some embodiments, two filters (instead of three) can be used. Accordingly, two colors corresponding to the two color filters can be selectively transmitted by the filters. In some such embodiments, two corresponding coupling optical elements can be used and aligned with the two filters. In some embodiments, the two coupling optical elements selectively couple the two colors into two respective waveguides. In some embodiments, two light sources can be used instead of three light sources. Other variations and other numbers of components can be used. Additionally, the color filters 2040, 2042, 2044 can or can not be integrated in a single array.

[0218] As discussed above, the components and their locations and arrangements can vary. For example, although Figure 20A the analyzer 1150 is shown disposed between the optical device 1130 and the stack 1905, the analyzer 1150 can be located at different positions. Figure 20B the analyzer 1150 is shown located between the optical device 1130 and the SLM 1140. In some designs, the analyzer (e.g., polarizer) 1150 can be directly attached to the SLM 1140. For example, the analyzer 1150 can be adhered to or mechanically coupled to the SLM 1140. For example, the analyzer 1150 can be glued, bonded to the SLM 1140 (e.g., to the SLM window) using an adhesive. Accordingly, although Figure 20BThe gap between the analyzer 1150 and the SLM 1140 is shown, but in some designs, there is no gap between the analyzer 1150 and the SLM 1140. The analyzer 1150 can be mechanically fixed (e.g., using mechanical fixtures) to the SLM 1140, and in such cases, there may or may not be a gap between the analyzer 1150 and the SLM 1140. As described above, the birefringence from the optical device 1130 can be removed by positioning the polarizer directly on the SLM 1140. In some embodiments, an analyzer 1150 may also be included between the optical device 1130 and the coupled-in optical elements 1360, 1362, 1364 to remove the polarization of the light exiting the optical device 1130 (e.g., as shown by the dashed line in Figure 20B ). In addition, a retarder (not shown), such as a quarter-wave plate, may be included near the SLM 1140, e.g., between the optical device 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 includes a plate, film, or other structure for providing a quarter-wave delay. For example, in Figure 20B , 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) can be used for skew ray management. For example, the retarder (e.g., a quarter-wave plate) can compensate for variations caused by wavelength and angle-of-incidence differences onto the SLM 1140. As discussed above, a compensator may be included and can provide more consistent polarization rotation (e.g., 90°) of the SLM 1140 for different angles of incidence and different wavelengths. The compensator can be used to increase the contrast of the display by providing more consistent orthogonal rotation. The compensator can be attached or fixed to the SLM 1140 as described above. For example, glue, adhesive, or other adhesives can be used. The compensator can also be attached to the SLM 1140 using mechanical fixtures. There may or may not be a gap between the compensator and the SLM 1140. Other light-adjusting optical devices may also be included additionally or alternatively and can be fixed to the SLM 1140, such as those described above with respect to the analyzer 1150 and / or the compensator.

[0219] In some embodiments, a large angle spread (e.g., -70 degrees) can be used. The angle spread can refer to, for example, the angle of the light entering the optical device 1130 from the light sources 1110, 1112, 1114, and / or the angle of the light exiting the optical device 1130 and entering the coupled-in optical elements 1360, 1362, 1364. In these embodiments, a thinner SLM 1140 can be used. For example, if the SLM 1140 is a liquid crystal (LC) SLM (e.g., a liquid crystal on silicon (LCoS) SLM), the LC layer can be made thinner to accommodate the large angle spread.

[0220] The double-pass delay through the polarizer and analyzer 1150 may need to be a half-wave. The polarizer may be located between the optical device 1130 and the analyzer 1150. The double-pass delay 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, light entering and exiting the LCoS SLM 1140 at a large angle results in a longer optical path length than light entering and exiting the LCoS SLM 1140 at a small angle. The path length is related to the thickness of the LCoS SLM 1140. In one example, the LCoS SLM may have a first refractive index and a first thickness. For a small angle, the double-pass delay of the LCoS SLM with the first refractive index and the first thickness may be a half-wave. For a large angle, the double-pass delay of the LCoS SLM with the first refractive index and the first thickness may not be a half-wave (e.g., may be greater than a half-wave). The thickness of the LCoS SLM may be changed from the first thickness to a second thickness, where the second thickness is less than the first thickness. For a small angle, the double-pass delay of the LCoS SLM with the first refractive index and the second thickness may not be a half-wave (e.g., may be less than a half-wave). For a large angle, the double-pass delay of the LCoS SLM with the first refractive index and the second thickness may be a half-wave.

[0221] In addition, although Figure 20A and 20B illustrate the use of a polarization-based SLM 1140, other types of SLMs may also be employed. For example, Figure 20C illustrates the use of a deflection-based SLM 1140, such as an SLM based on a movable micromirror. As discussed above, such an SLM 1140 may include digital light processing and digital micromirror device (DMD) technology. As discussed above, the deflection-based SLM 1140 may couple light from one of the light sources 1110, 1112, 1114 to the corresponding input optical elements 1360, 1362, 1364 depending on the pixel state of the SLM 1140. In one state, as Figure 20D shown, light from the light sources 1110, 1112, 1114 will be directed to the corresponding input optical elements 1360, 1362, 1364. In another state, as [[IDAs shown, the light from light sources 1110, 1112, 1114 will be guided away from the coupling optical elements 1360, 1362, 1364. In some embodiments, when in the off state, the black absorption mask between the color filters 2040, 2042, 2044 in the color filter array 2030 can be used as a light dump. As described above, the color filters 2040, 2042, 2044 can be surrounded and / or separated by a mask (such as an absorption mask (e.g., a black mask)). The mask can include an absorbing material such that more incident light is absorbed compared to the light reflected therefrom. The mask can also be opaque.

[0222] Other variations are possible. Although the light sources are shown as emitters 1110, 1112, 1114 (such as LEDs, laser diodes) coupled to a coupling optical device 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 optical device 1105 (e.g., a CPC) can be tilted with respect to the waveguide stack. In some cases, the projector (i.e., the optical device 1130 and the SLM 1140) can be tilted with respect to the eyepiece (e.g., the waveguide stack). In some embodiments, the lens optical device 1130 is tilted with respect to the SLM 1140 to reduce distortion, such as trapezoidal distortion. A Scheimplug configuration can be employed to reduce such distortion. The components (e.g., the optical device 1130 and / or the spatial light modulator 1140) can be tilted as needed, for example, to more conformally fit the head and / or face. As described above, the light emitter and / or the coupling optical device 1105 can be tilted. In some configurations, the components including the waveguide can be tilted such that the side closer to the eye 210 (e.g., the temporal side) is closer to the eye 210 to increase the perceived field of view of the entire binocular system (at the expense of binocular overlap).

[0223] As discussed above, the components and their positions and arrangements can vary. For example, Figure 20F is a side view of the system 2000F, which includes a cover glass 2050 disposed between the stack 2005 and the optical device 1130. In some designs, the light sources 1110, 1112, 1114 can be disposed on the world side of the cover glass 2050 and configured to cause light to propagate through the cover glass 2050 to the optical device 1130 and the SLM 1140. As illustrated, the cover glass 2050 can extend laterally (e.g., parallel to the x-axis) beyond the stack 2005 such that the light emitted by the light sources 1110, 1112, 1114 enters the optical device 1130 without passing through the waveguides in the stack 2005. Although the system 2000F depicts a deflection-based SLM 1140, a similar configuration of the light source can also be used with a non-deflection-based SLM, or with any other configuration or feature disclosed herein.

[0224] Figure 20G It is a side view of system 2000G, which includes a cover glass 2060 disposed on the world side of stack 2005 (i.e., opposite to the side of stack 2005 near optical device 1130). In some designs, light sources 1110, 1112, 1114 may be disposed on the world side of cover glass 2050 and are configured to cause light to propagate through cover glass 2050 to optical device 1130 and SLM 1140. As illustrated, cover glass 2060 may extend laterally (e.g., parallel to the x-axis) beyond stack 2005 such that light emitted by light sources 1110, 1112, 1114 enters optical device 1130 without passing through the waveguides in stack 2005. Although system 2000G depicts a deflection-based SLM 1140, a similar configuration of light sources may also be used with non-deflection-based SLMs or with any other configuration or feature disclosed herein.

[0225] In addition, as discussed above, configurations facilitating light recycling may be employed. For example, Figure 21 It is a partial side view of system 2100 equipped with a configuration providing light recycling of light from light source 1110. Light source 1110 may be disposed relative to polarizer 1115, which is configured to recycle light having an unwanted polarization. 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 light source 1110 and impinge on polarizer 1115. Polarizer 1115 may transmit light of the first polarization, and a projector (not shown) is configured to use the light of the first polarization. For example, the SLM may operate correctly using the light of the first polarization. Light of the second polarization 2120 is reflected back to light source 1110 and may be recycled. After reflecting off a portion (e.g., sidewall) of a coupling optical device (not shown) (such as a non-imaging optical device like a compound parabolic concentrator (CPC)) at various angles, the polarization of light 2120 may be changed for polarization rotation. Some light having an appropriate polarization (e.g., polarization orientation) may be generated, and this light may pass through polarizer 1115. Multiple reflections may change the polarization of the light and may cause the light to exit with the desired polarization. Then, this recycled light 2130 is emitted back to polarizer 1115. Such configurations may improve efficiency, such as energy efficiency, because more of the desired polarization is generated. In addition, as a supplement or alternative, retarders may be used to change the polarization state of the reflected light and recycle the light.

[0226] Figure 22Shows another configuration that includes light sources 1110, 1112, 1114 and corresponding light collection optics 2210, 2212, 2214. The light collection optics 2210, 2212, 2214 may include lenses or other optics to collect 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 angular range. The light collection optics 2210, 2212, 2214 can be used to collect most of the light. The light sources 1110, 1112, 1114 may emit light asymmetrically. For example, the light may be emitted over a wider angular range in one direction (e.g., the x or z direction) than in the orthogonal direction (e.g., the z or x direction). Thus, the light collection optics 2210, 2212, 2214 may be asymmetric. For example, the light collection optics 2210, 2212, 2214 may have different optical powers in different possible orthogonal directions. The light collection optics 2210, 2212, 2214 may include, for example, lenses such as anamorphic lenses. The light collection optics 2210, 2212, 2214 may also include non-imaging optics. Apertures 2220, 2222, 2224 may be included. For example, when the light sources 1110, 1112, 1114 are lasers such as laser diodes, diffusers 2230 may also be included near the apertures 2220, 2222, 2224. Through the diffusers near the apertures 2220, 2222, 2224, the apertures may appear to be located at the position of the laterally shifted light sources. As discussed above, the apertures 2220, 2222, 2224 may be matched to the coupling optical elements on one waveguide or multiple waveguides via the optics and the SLM. For example, each aperture 2220, 2222, 2224 may be matched to a corresponding coupling optical element. Similarly, in some embodiments, such as Figure 16A as shown in, each aperture 2220, 2222, 2224 may be matched to a corresponding set (e.g., color-selective) of coupling optical elements.

[0227] Multiple system variations and configurations are possible. For example, although linearly polarized light has been described as propagating through the optical device 1130 to the SLM 1140 and back through the optical device to the waveguide stack, in some designs, circularly polarized light may be used instead. For example, circularly polarized light may be directed into the optical device 1130. A retarder (such as a quarter-wave plate) may be set such that the light passes through the retarder before being incident on the SLM. The retarder (e.g., a quarter-wave plate) may be set between the optical device 1130 and the SLM 1140. In some cases, such as the above, the retarder (e.g., a quarter-wave plate) may be fixed to the SLM 1140, such as using an adhesive or a mechanical clamp, for example. The retarder (e.g., a quarter-wave plate) may convert the linearly polarized light into circularly polarized light after being reflected from the SLM 1140. Thus, in some embodiments, the circularly polarized light may pass through the optical device 1130 again towards the stack. For example, another retarder (e.g., a quarter-wave plate) near the analyzer 1150 may convert the circularly polarized light into linearly polarized light, which may or may not pass through the analyzer depending on the linear polarization (e.g., orientation). The pixels of the SLM 1140 may have variable states to rotate or not rotate the polarization. Other configurations are possible.

[0228] Figure 23Ais a side view of an augmented reality display system 2300 that includes a light source 2305, a polarization rotator 2307, an optical device (such as a lens) 2320 having a focal 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 to be directed to the user's eye. The configuration and placement of these elements (especially polarizers and retarders) can reduce or eliminate reflections from optical surfaces within the system (such as from the surface of the optical device 2320), which otherwise might cause the user to see ghost images. For example, polarization-selective and / or retardance-based optical elements (such as polarizers 2312, 2335 and retarders 2315, 2330, 2340) can be arranged and configured to convert linearly polarized light into circularly polarized light that changes from left-handed to right-handed or from right-handed to left-handed when reflected from an optical surface. Similarly, such polarization-selective and / or retardance-based optical elements (such as polarizers 2312, 2335 and retarders 2315, 2330, 2340) can be arranged and configured to convert circularly polarized light into linearly polarized light that can be attenuated or filtered by a polarizer (such as a linear polarizer). Polarization-selective and retardance-based such optical elements (such as polarizers 2312, 2335 and retarders 2315, 2330, 2340) can be used to fabricate a circular polarizer that converts linearly polarized light into circularly polarized light and vice versa. For example, a circular polarizer can include a linear polarizer and a quarter-wave retarder. A circular polarizer can be used to convert linearly polarized light into circularly polarized light having a first state (e.g., handedness) and filter out circularly polarized light having a second state (e.g., handedness) different from the first state. For example, a circular polarizer can be used to convert linearly polarized light having a specific orientation into left-handed circularly polarized light and filter out right-handed circularly polarized light. A circular polarizer can also be used to convert linearly polarized light having a specific orientation into right-handed circularly polarized light and filter out left-handed circularly polarized light. As described below in connection with Figure 23A and 23B a circular polarizer or other configurations of optical elements that include retardation and can selectively filter linearly polarized light can be used to reduce back reflections from optical surfaces, and the retardation can be used to convert linearly polarized light into circularly polarized light and vice versa.

[0229] It is noted that in Figure 23A and 23BIn it, left-handed and right-handed circular polarizations are respectively represented by clockwise and counterclockwise arrows. In addition, horizontal and vertical linear polarizations are respectively represented by horizontal arrows and dots.

[0230] As discussed above, Figure 23A FIG. shows the 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 arranged to reduce back-reflection from an optical surface (such as the surface of an optical device 2320 in the path of light that irradiates a spatial light modulator (not shown) and is reflected from the spatial light modulator). A first polarizer 2312 and a first retarder 2315 are disposed between a light source 2305 and the optical device 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 device 2320.

[0231] As illustrated, the light source 2305 emits light represented by light rays 2310. In some embodiments, the light rays 2310 may pass through a polarization rotator 2307. The rotator 2307 is optional and can be used to rotate the polarization of light (such as light rays 2310) from the light source 2305. In various embodiments, the rotator 2307 can rotate the angle of polarization (such as linear polarization). For example, the rotator 2307 can rotate the linear polarization of the light rays 2310 to an orientation aligned with the first polarizer 2312 so as to pass through and be transmitted therefrom. In some embodiments, the polarization rotation 2307 may include a retarder, for example, in some cases a half-wave retarder. The optical axis of the half-wave retarder can be oriented to rotate the polarization of light from the light source 2305 from vertical to horizontal or vice versa. Alternatively, the polarization rotator 2307 can be configured to rotate the polarization angle of linearly polarized light emitted from the light source 2305 by a different amount. The polarization rotator 2307 does not need to be included in the system. For example, in embodiments where the light source 2305 emits light having the same polarization as the first polarizer 2312, the polarization rotator 2307 can be excluded. As illustrated, the light (such as light rays 2310) passes through the polarizer 2312 (shown here as a horizontal polarizer). In the case where the light from the light source 2305 is unpolarized, the light (shown as light rays 2310) transmitted through the horizontal polarizer 2312 is linearly polarized (e.g., horizontally polarized) after passing through the polarizer 2312. Although a horizontal linear polarizer is used in this example, it can be understood that the principles taught are applicable to vertical linear polarizers. Alternatively, linear polarizers with different orientations other than vertical or linear can also be used.

[0232] The horizontally polarized light ray 2310 travels through a retarder 2315, shown here as a quarter-wave retarder. The retarder 2315 may include sufficient retardation to convert linearly polarized light into circularly polarized light. For example, horizontally polarized light may be converted into left-handed circularly polarized light, as indicated by the curved (e.g., clockwise) arrow. In this example, the combination of the polarizer 2312 and the retarder 2315 (e.g., quarter-wave) forms a circular polarizer, herein referred to as the first circular polarizer, which may convert light of a particular linear polarization (e.g., horizontal or vertical polarization) into a particular circular polarization (e.g., left-handed or right-handed circular polarization or vice versa). The circular polarizer may also block light of a particular circular polarization (e.g., right-handed or left-handed circular polarization) depending on the configuration.

[0233] In some embodiments, various optical elements have birefringence. In some such cases, the retarder 2315 may include a retardation sufficient to convert linearly polarized light into circularly polarized light and need not be a quarter-wave plate. The retarder 2315 may include more or less than a quarter-wave of retardation because the retardation may be contributed by other optical elements. Similarly, the retardation may be distributed among multiple optical elements. As another example, multiple retarders may be employed to provide an appropriate amount of retardation.

[0234] The circularly polarized light ray 2310 (here, left-handed circularly polarized) then passes through the optical device 2320. Unwanted reflections may occur at any interface in the system between media having different refractive indices, such as, for example, an air-to-material interface. If these reflections are allowed to enter at least one waveguide 2348, they may be problematic because the reflected light may be directed into the user's eye and form a "ghost" image visible in the user's eye. For example, in a case where a display uses at least one waveguide 2348 to project a first image onto a viewer's eye, the user may also see a second blurred and repeated image that is shifted (e.g., laterally) relative to the first image. Such "ghost" images formed by reflections from optical surfaces that are directed into the user's eye may be distracting or otherwise degrade the viewing experience. For example, as Figure 23AAs shown, light such as reflected light 2325 can be reflected from a lens within the optical device 2320. This light can be directed towards at least one waveguide 2348, which is configured to direct the light to the user's eye to present an image thereto. However, in this case, the circularly polarized light will reverse its handedness. For example, after reflection from the lens, the direction of circular polarization will change (e.g., from left-handed to right-handed). Then, the right-handed reflected light ray 2325 travels through the retarder 2315 and is converted into linearly polarized light that has a different (e.g., orthogonal) linear polarization from the linear polarization transmitted by the polarizer 2312. In this case, for example, light reflected from the optical surface of the lens is converted by the retarder 2315 into vertically linearly polarized light that is orthogonal to the polarization transmitted by the horizontally linear polarizer 2312. The horizontally linear polarizer 2312 selectively allows horizontally polarized light to pass through and filters out vertically polarized light. Thus, the reflected light ray 2325 is attenuated and / or not transmitted by the horizontally linear polarizer 2312 and is prevented from reaching at least one waveguide 2348, or at least a reduced amount of such reflected light reaches and / or couples into at least one waveguide 2348, e.g., by coupling into an optical element (e.g., one or more coupling gratings). The result will be similar for left-handed circularly polarized light rays reflected from different optical surfaces of the optical device 2320 or other optical surfaces on different optical elements.

[0235] As illustrated, the display system 2300 further includes a second retarder 2330 (e.g., a quarter-wave retarder or quarter-wave plate) and a second polarizer 2335 (e.g., a linear polarizer) disposed between the optical device 2320 and a spatial light modulator (not shown). In some embodiments, the second retarder 2330 and the second linear polarizer 2335 can form a second circular polarizer. The second retarder 2330 is disposed between the optical device 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 device 2320, the light ray 2310 can 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) such that the light ray 2310 is converted from left-handed circular polarization to horizontally linear polarization. Similarly, the second retarder 2330 converts the circularly polarized light back to the original linearly polarized state output by the first polarizer 2312. As will be discussed below, the second retarder 2330 and the second polarizer 2312 can be used to reduce "ghost" images caused by light reflected from the spatial light modulator that passes through an optical surface (e.g., on the active optical device or lens 2320) as it travels to at least one light guide 2348.

[0236] 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. Additionally, in various embodiments such as illustrated, the second polarizer 2335 is located between the second and third retarders 2330, 2340. As illustrated, the light ray 2310 is linearly polarized when passing through the second polarizer 2335, and in some embodiments, the second retarder 2330 / second polarizer 2335 may convert the light into the original linear polarization (e.g., horizontal polarization) of the first polarizer 2312. This linearly polarized light is incident on the third retarder 2340. The third retarder 2340 is configured such that the light ray is converted back into circularly polarized light and in some embodiments is converted back into the same polarization as that output by the first retarder 2315 (e.g., left-handed circularly polarized light in this example). In certain embodiments, the spatial light modulator is configured to operate on the circularly polarized light. In some embodiments, the spatial light modulator is a reflective spatial light modulator that reflects the incident circularly polarized light back as circularly polarized light. In some embodiments, the circularly polarized light reflected from the spatial light modulator may have the same handedness (e.g., left-handed circular polarization) as the circularly polarized light incident thereon, which may depend on whether the spatial light modulator pixels are in the "on" or "off" state. In some embodiments, the spatial light modulator may reflect circularly polarized light of a different handedness (e.g., right-handed circular polarization) incident thereon, which may depend on whether the spatial light modulator pixels are in the "on" or "off" state. However, other types of spatial light modulators may also be used.

[0237] Figure 23A The light reflected from the spatial light modulator and traveling toward the waveguide 2385 is shown as the light ray 2342. The reflected light ray 2342 is depicted as left-handed circularly polarized light. The light ray 2342 passes through the third retarder 2340. The third retarder 2340 converts the circularly polarized light into linearly polarized light. In this example, the left-handed circularly polarized light is converted into horizontally polarized light. The linearly polarized light is transmitted through the second polarizer 2335. In this example, the horizontally polarized light passes through the second polarizer 2335. The linearly polarized light is incident on the second retarder 2330 and is converted into circularly polarized light. In this example, the horizontally polarized light is converted into left-handed polarized light and is transmitted to the optical device 2320. Similarly, reflections from optical surfaces (such as the surface of the optical device 2320 having a focal power) can produce ghost images by reflecting back from the spatial light modulator to at least one waveguide 2348 and to the user's eye. As described above, unwanted reflections can occur at any interface between media having different refractive indices, such as an air-to-material interface. As described above, the addition of the second retarder and polarizers 2330, 2335 can attenuate these reflections and reduce the likelihood of ghost reflections. For exampleFigure 23A depicts light reflected from the optical surface of the optical device 2320, illustrated as ray 2346. The act of reflection from the surface causes the circularly polarized reflected ray 2346 to switch its handedness, in this example, from left-handed circular polarization to right-handed circular polarization. The second circular polarizer formed by the second retarder and polarizers 2330, 2335 attenuates this switched circularly polarized light. For example, as Figure 23A shown, the reflected circularly polarized light 2346 is incident on the second retarder 2330 and is converted by the second retarder into linearly polarized light that has a different (e.g., orthogonal) linear polarization from the polarization selectively transmitted by the second linear polarizer 2335. In this case, for example, the right-handed circularly polarized light reflected from the optical surface of the optical device 2320 is converted by the retarder 2330 into vertically linearly polarized light that is orthogonal to the polarization selectively transmitted by the polarizer 2335. The second polarizer 2335 attenuates or blocks the transmission of this linearly polarized light. In this example, the light 2346 is vertically polarized, while the second polarizer 2335 is a horizontal polarizer that selectively passes horizontally polarized light and filters out vertically polarized light.

[0238] Conversely, the light 2342 that passes through the optical device 2320 and is incident on the first retarder 2315 is circularly polarized and has a handedness different from that of the light reflected from the optical surface of the optical device 2320. This light 2342 that is directed towards at least one waveguide 2348 has a polarization (e.g., left-handed polarization) that is converted by the first retarder 2315 into linearly polarized (e.g., horizontally linearly polarized light) that is selectively transmitted by the first polarizer 2312. In this way, the light 2342 can reach and be coupled into at least one waveguide 2348 and be directed to the user's eye.

[0239] In Figure 23A the example shown, the first circular polarizer formed by the first polarizer 2312 and the first retarder 2315 and the second circular polarizer formed by the second retarder 2330 and the second polarizer 2335 are located on opposite sides of the optical device 2320, one closer to the light source 2305 and one closer to the spatial light modulator, to reduce reflections that may cause "ghost images". An additional retarder 2340 is included between the second circular polarizer (e.g., the second polarizer 2335) and the spatial light modulator to convert the light into 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 optical devices may be included.

[0240] Figure 23B shows a third circular polarizer that can be added to an augmented reality system 2300 such as Figure 23A shown. In particular, Figure 23BDepicts a second circular polarizer including a second polarizer 2335 and a second retarder 2330, and a third retarder 2340 as described above, and further depicts a spatial light modulator 2375. The spatial light modulator (SLM) 2375 may include a liquid crystal spatial light modulator (e.g., liquid crystal on silicon or LCoS). In some embodiments, the SLM 2375 may be covered with a cover glass 2370.

[0241] Figure 23B Also shown is a third circular polarizer, which includes 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), which is disposed between the second circular polarizer including the second polarizer 2335 and the second retarder 2330 and the spatial light modulator 2375. The third polarizer 2355 is located between the fourth retarder 2345 and the spatial light modulator 2375. An additional fifth retarder 2360 (such as a quarter-wave retarder (e.g., a quarter-wave plate)) and a compensator 2365 are disposed between the third circular polarizer including the fourth retarder 2345 and the third polarizer 2355 and the spatial light modulator 2375 or more specifically between the third circular polarizer including the fourth retarder 2345 and the third polarizer 2355 and the cover glass 2370 shown in Figure 23B The fifth retarder 2360 is located between the third polarizer 2355 and the compensator 2365. The compensator 2365 is located between the fifth retarder 2360 and the spatial light modulator 2375 or specifically the cover glass 2370.

[0242] Figure 23B Shows how light (e.g., light ray 2310) from a light source 2305 (shown in Figure 23A propagates through the second circular polarizer including the retarder 2330 and the second polarizer 2335 and the third retarder 2340 to reach the third circular polarizer including the fourth retarder 2345 and the third polarizer 2355. The light ray 2310 from the light source 2305 is incident on the third circular polarizer after passing through the second circular polarizer including the second retarder 2330 and the second polarizer 2335, and in particular is incident on the fourth retarder 2345. The fourth retarder 2345 may convert the circularly polarized light of the light ray 2310 into linearly polarized light. In the example shown in Figure 23B the light ray 2310 is circularly polarized (e.g., left-handed circularly polarized) and is converted into linearly polarized light (e.g., horizontally polarized light) by the fourth retarder 2345. This linearly polarized light passes through the third polarizer 2355, in Figure 23B which the third polarizer 2355 includes a horizontal polarizer that selectively transmits horizontally polarized light. This linearly polarized light propagates through the fifth retarder 2360, which may include a quarter-wave retarder that converts the linearly polarized light into circularly polarized light. In Figure 23BIn the example shown, the horizontally linearly polarized light 2310 incident on the fifth retarder 2360 is converted into left-handed circularly polarized light. This circularly polarized light is incident on the compensator 2365 and passes through the compensator 2365. The compensator 2365 may include polarization elements that adjust the polarization to the desired polarization. The compensator 2365 can be used to cancel the birefringence of various optical elements in the system. For example, due to the retardation contributions of one or more optical elements, the light may be slightly elliptically polarized. In various embodiments, the light output from the compensator 2365 is circularly polarized light. In Figure 23B In the example shown, the light output from the compensator 2365 is left-handed circularly polarized light. In various embodiments, the compensator 2365 can be used to cancel the residual retardation within the SLM, which may include, for example, a liquid crystal (e.g., LCoS) SLM cell. The compensator can introduce in-plane retardation and / or out-of-plane retardation. In some embodiments, the compensator 2365 may include a combination of optical retarders that, when combined, produce a retardation that can potentially cancel the residual retardation from the SLM (e.g., an LCoS panel).

[0243] In Figure 23B , the light is incident on the cover glass 2370 and the SLM 2375 after passing through the compensator 2365. The light incident on the cover glass 2370 and the SLM 2375 is depicted as left-handed circularly polarized light. Depending on the type and state of the spatial modulator, the SLM 2375 can reflect circularly polarized light with the same handedness. For example, when the pixels of the SLM 2375 are in the "on" state (although in some embodiments this state may be the undriven state), the SLM 2375 can introduce a quarter-wave retardation each time the light passes through the SLM 2375. Thus, upon reflection, the incident circularly polarized light can remain circularly polarized. In various configurations, the handedness can also remain unchanged. For example, as Figure 23B shown, the incident left-handed circularly polarized light can remain left-handed circularly polarized upon reflection. This circularly polarized light reflected from the SLM 2375 (represented by the ray 2342) can pass through the cover glass 2370 and the compensator 2365 and be incident on the fifth retarder 2360, which converts the circularly polarized light into linearly polarized light. In Figure 23B In the example shown, the circularly polarized light incident on the fifth retarder 2360 is left-handed, and the fifth retarder 2360 converts this circularly polarized light into horizontally polarized light. The third polarizer 2355 can be configured to selectively transmit the polarization of the light output from the fifth retarder 2360. Thus, in Figure 23B In the example where the light output from the fifth retarder 2360 is horizontally polarized as shown, the third polarizer 2355 selectively transmits the horizontally polarized light. This linearly polarized light transmitted by the polarizer 2355 is incident on the fourth retarder 2345 and is converted into circularly polarized light. In Figure 23BIn the example shown, the circularly polarized light is left-handed circularly polarized light. This light can travel through a second circular polarizer including a second retarder 2330 and a second polarizer 2335, an optical device 2320, and a first circular polarizer including a first polarizer 2312 and a first retarder 2315, reach at least one waveguide 2348 and enter the user's eye, as discussed above in connection with Figure 23A discussed.

[0244] However, the light reflected from the optical surface can be attenuated by a third circular polarizer, thereby reducing the likelihood that such reflections will reach at least one waveguide 2348 and be guided to the user's eye to produce ghost images. For illustration, Figure 23B an example ray 2343 reflected from the optical surface of the third retarder 2340 (e.g., from the interface between air and the third retarder 2340) is shown. As discussed above, reflection can occur at any interface between media having different refractive indices, such as an air-material interface or an interface between different dielectric layers. However, the circularly polarized light will reverse its handedness upon reflection. For example, when reflected from the surface of the third retarder 2340, the direction of circular polarization changes (e.g., from left-handed to right-handed). The right-handed reflected ray 2343 then travels through the fourth retarder 2345 and is converted into linearly polarized light that has a different (e.g., orthogonal) linear polarization from the polarization selectively transmitted by the third polarizer 2355. In this case, for example, the light reflected from the optical surface of the third retarder 2340 is converted by the fourth retarder 2345 into vertically linearly polarized light that is orthogonal to the polarization selectively transmitted by the third polarizer 2355. The third polarizer 2355 selectively passes horizontally polarized light and filters out vertically polarized light. Thus, the reflected ray 2343 is attenuated and / or not transmitted by the third polarizer 2355 and is prevented from reaching at least one waveguide 2348 (e.g., by reflecting off another surface) or at least a reduced amount of such reflected light reaches at least one waveguide 2348 or is coupled therein.

[0245] For circularly polarized light rays reflected from different optical surfaces, the results may be similar. For example, Figure 23B an incident ray 2310 reflected from the optical surface of the fourth retarder 2345 is shown. Reflection 2350 from the fourth retarder 2345 switches the handedness of the polarization. For example, the incident ray 2310 depicted as left-handed circularly polarized is converted into a ray 2350 shown as having right-handed circular polarization upon reflection. The reflected ray 2350 passes through the third retarder 2340 and is converted into vertically polarized light. This vertically polarized light is selectively attenuated or filtered out by the second polarizer 2335.

[0246] As described above, the pixels of the SLM 2375 can be, for example, in an "on" state (although undriven in some embodiments), where light incident on the pixel of the SLM 2375 is reflected therefrom and coupled into at least one waveguide 2348 and directed to the user's eye. However, the pixels of the SLM 2375 can be in an "off" state (which can be a driven state in some embodiments), where light incident on the pixel of the SLM 2375 is not coupled into at least one waveguide 2348 and not coupled into the user's eye. For example, in this "off" state, various embodiments of the SLM 2375 do not introduce a delay when reflecting therefrom. Thus, in Figure 23B In the example shown, the circularly polarized light incident on the SLM 2375 can remain circularly polarized when reflected from the SLM 2375. However, the handedness of the circularly polarized light can change when reflected from the SLM 2375. For example, Figure 23B The ray 2310 of left-handed circularly polarized light incident on the SLM 2375 shown in can be converted to right-handed circularly polarized light when reflected from the SLM 2375. However, this reflected light can be selectively attenuated by the third polarizer 2355. For example, the right-handed circularly polarized light reflected from the SLM 2375 can pass through the cover glass 2370, the compensator 2365, and the fifth retarder 2360. The fifth retarder 2360 can convert the right-handed circularly polarized light to vertically polarized light, which is selectively attenuated by the third polarizer 2355 that can include a horizontal polarizer. Thus, in various embodiments, when the pixel of the SLM is in the "off" state, the fifth retarder 2360 can convert the light reflected from the pixel of the SLM 2375 to a linear polarization orthogonal to the linear polarization selectively transmitted by the third polarizer 2355. Thus, the third polarizer 2355 can selectively attenuate this linearly polarized light, thereby reducing or preventing light from the pixel of the SLM 2375 from reaching at least one waveguide 2348 and being directed to the eye.

[0247] Changes in configuration, such as changes in polarization optics, are possible. For example, more or fewer circular polarizers can be included.

[0248] In various embodiments, for example, such as Figure 23C As shown, the third circular polarizer including the fourth retarder 2345 and the third polarizer 2355 is excluded. In this particular embodiment, the fourth retarder 2345, the third polarizer 2355, and the fifth retarder 2360 are not included in the system. Figure 23C Shows a design of the augmented reality system 2300, which includes Figure 23A and 23Bthe components shown in, but excluding the fourth retarder 2345, the third polarizer 2355, and the fifth retarder 2360. Nevertheless, even though the third circular polarizer is excluded, the augmented reality display system is still configured to reduce ghost images. For example, the second circular polarizer reduces reflections that would otherwise cause ghost images. For illustration, Figure 23C depicts light reflected from the third retarder 2340, illustrated as light ray 2380. The act of reflection from the surface of the third retarder 2340 causes the reflected light ray 2380 (which is circularly polarized) to switch its handedness. In this example, the polarization switches from left-handed circular polarization to right-handed circular polarization. The switched circularly polarized light 2380 then passes through the compensator 2365 and impinges on the cover glass 2370 and the SLM 2375. As discussed above, the SLM 2375 can reflect circularly polarized light with the same handedness. Thus, the incident right-handed circularly polarized light can remain right-handed circularly polarized upon reflection. Then, this circularly polarized light reflected from the SLM 2375 (represented by light ray 2382) can pass through the cover glass 2370 and the compensator 2365 and impinge on the third retarder 2340. The switched circularly polarized light 2382 is attenuated by the second circular polarizer, and in particular, by the third retarder 2340 and the polarizer 2335. As Figure 23C shown in, for example, the circularly polarized light 2382 reflected from the SLM 2375 impinges on the third retarder 2340 and is converted by the third retarder 2340 into a linearly polarized light with a polarization different from (e.g., orthogonal to) the polarization selectively transmitted by the second linear polarizer 2335. In this case, for example, the right-handed circularly polarized light 2382 is converted by the third retarder 2340 into a vertical linearly polarized light orthogonal to the polarization selectively transmitted by the second polarizer 2335. The second polarizer 2335 attenuates or blocks the transmission of this linearly polarized light.

[0249] Reflections that can contribute to ghost reflections can also potentially be reduced by tilting the optical surfaces in the system. Figure 24 Shows an example configuration with tilted optical surfaces for reducing reflections that can produce ghost reflections. Figure 24 Shows an augmented reality display system 2400 that includes a light source 2305 that emits light represented by light ray 2310, which passes through any number of polarizers, retarders, lenses, and / or other optical elements as it travels towards the spatial light modulator (SLM) 2375. For illustrative purposes, Figure 24Shown therein are a first polarizer 2312, a first retarder 2315, and a lens 2320 that may form a first circular polarizer. However, additional components may be included, or components may be excluded or arranged or configured in a different manner. In the illustrated example, the SLM 2375 includes a cover glass 2370 therewith. The cover glass 2370 can contribute to reflections that produce ghost images. Thus, in some embodiments, the cover glass 2370 can be shaped to direct reflections that may produce ghost images away from the user's eyes. As illustrated, the cover glass 2370 has a surface that is tiltable such 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, at least one waveguide 2348, etc., or their optical surfaces). The major surface of the cover glass 2370 can, for example, have a tilted normal so as not to be aligned or parallel with the optical axis of the augmented reality display system 2400 or optical components therein (such as the optics 2320). By tilting, reflections from the optical surface of the cover glass 2370 can be directed away from at least one waveguide 2348 or an optical coupling element (e.g., a coupling grating or diffractive optical element) for coupling light into at least one waveguide 2348, and the likelihood of reflection from the cover glass 2370 entering at least one waveguide 2348 is reduced. As illustrated, the reflected light 2405 is directed back to the light source 2305 and away from at least one waveguide 2348, where such light may ultimately reach the user's eyes. In some embodiments, the reflected light 2405 can be directed back to the light source and at least a portion thereof can be recycled at the light source 2305.

[0250] Although Figure 24 a cover glass 2370 with a tilted surface is depicted, an inclined optical surface can be included on any component in the system where unwanted reflections may occur so that the reflections are not coupled into at least one waveguide 2348. Thus, the optical surfaces on other components (such as polarizers, retarders, etc.) can be tilted to reduce reflections that are coupled into at least one waveguide 2348 and the user's eyes. Variations in the shape and size of the cover glass 2370 or other optical components are possible. For example, the cover glass 2370 or other optical components can be thinner. Similarly, the cover glass 2370 or other optical components can have an aspect ratio (ratio of length to thickness) different from that Figure 24 shown. In some embodiments, the cover glass 2370 or other optical components are wedge-shaped. However, other shapes are possible.

[0251] Other arrangements are possible. For example, Figure 25 an embodiment of an augmented reality display system 2500 is shown, which is similar to Figure 24The system 2400 shown in [description], but further includes a light dump 2505 for absorbing the light directed thereto. The system 2500 includes an angled cover glass 2370 to direct the reflection 2510 from the cover glass 2370 to the light dump 2505 rather than back to the light source 2305. The light dump 2505 may include an absorbing material or structure configured to absorb light. The position of the light dump 2505 may vary depending on the implementation, e.g., depending on the angle of the angled cover glass 2370. As discussed above, the method may be applied to other optical surfaces in the system. Additionally, the shape and size of the optical elements may vary.

[0252] A wide range of variations in the augmented reality display are possible. Variations in the polarization optical elements are possible. For example, although a horizontal polarizer is used, in some implementations, a vertical polarizer or a combination of horizontal and vertical polarizers may be employed. Additionally, polarizers characterized by polarizations other than vertical or horizontal may be used. Similarly, the light shown in the figures need not be horizontally polarized and may be vertically polarized. Likewise, in different implementations, light shown as vertically polarized may be horizontally polarized or vice versa. Linearly polarized light having a polarization other than vertical or horizontal may also be used.

[0253] Furthermore, the retarders may be configured differently. For example, the polarized light in the figures need not be left-handed circularly polarized light and may be right-handed circularly polarized light and / or right-handed polarized light may be left-handed circularly polarized light. Other variations are possible. Different retarder configurations may be employed to produce different combinations of left-handed and / or right-handed polarized light than those shown. Additionally, 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 and vice versa. Linear polarizers may be used to filter light and may be used to reduce ghost reflections as described herein.

[0254] In some embodiments, other types of polarization elements and their configurations are employed. For example, retarders are not limited to quarter-wave retarders or quarter-wave plates. For instance, in some embodiments, various optical elements are birefringent. In some such cases, any one or more of retarders 2315, 2330, 2340 can include a retardation amount sufficient to convert linearly polarized light into circularly polarized light and need not be a quarter-wave retarder. Any one or more of retarders 2315, 2330, 2340 can include more or less than a quarter-wave of retardation since the retardation can be contributed by other optical elements. Similarly, the retardation can be distributed among multiple optical elements. As another example, multiple retarders can be employed to provide an appropriate amount of retardation. Additionally, as described above, in some embodiments, elliptically polarized light may be used instead of circularly polarized light. For example, a retarder can be employed to convert elliptically polarized light into linearly polarized light and vice versa. Linear polarizers can be used to filter light and can be used to reduce ghost reflections as described herein.

[0255] Furthermore, the optical component can be in the form of an optical layer, sheet, and / or film and a stack or one or more layers, sheets, and / or films. Thus, different polarization elements with different amounts, positions, and arrangements can be used. For example, one or more retarders and / or polarizers can include a film.

[0256] In some embodiments, the spatial light modulator can operate differently. For example, the spatial light modulator can operate on light other than circularly polarized light and / or can output light other than circularly polarized light.

[0257] Embodiments of the present invention relate to the use of a hybrid surface relief structure in which refractive index modulation or variation exists along a separate diffraction structure (e.g., perpendicular to the substrate normal direction), also referred to as a hybrid diffractive nanofeature. In these hybrid diffractive structures, a material with a higher refractive index is adjacent to the substrate, the refractive index of which can be greater than n = 1.8, and a material with a lower refractive index is adjacent to the surrounding environment (e.g., air).

[0258] The hybrid eyepiece waveguide design can also embody the use of diffractive features with different refractive indices that are placed at different positions in a patterned waveguide such that when light propagates from one side of the CPE to the other, it can propagate through diffractive structures having at least two different refractive indices. In some of the examples discussed herein, the initial pattern is created lithographically using MagicLeap's J-FIL nanoimprint lithography technique; however, embodiments of the present invention are not limited to this particular lithography technique. Thus, other lithography processes can be used to create the pattern, and even optical lithography can be utilized in some cases. As described herein, embodiments of the present invention provide hybrid structures formed in an eyepiece waveguide for projecting bright, uniform color images to a user.

[0259] To demonstrate some of the advantages of using a hybrid grating, regarding Figures 26A - 26D the basic functionality of a single-layer eyepiece design using a micro-LED display engine is discussed, which uses a single input coupling grating (ICG) to emit light into a waveguide.

[0260] Figure 26A is a simplified cross-sectional view of an eyepiece waveguide according to an embodiment of the present invention. Figure 26A A single-layer eyepiece waveguide design with gradation is shown, i.e., in this example, when light propagates into the CPE, the grating intensity / efficiency varies according to position. The eyepiece waveguide 2600 includes an ICG 2610 and a CPE 2612 on one side (i.e., the user side) of the eyepiece waveguide 2600. In this example, the eyepiece waveguide 2600 is fabricated using a substrate 2605, which supports total internal reflection (TIR) of the coupled-in light and has a refractive index n = 2.0, although substrates with other refractive indices can be used.

[0261] In these single-layer eyepiece waveguide designs, light of multiple colors (e.g., red, green, and blue (RGB)) is coupled in by a single ICG, propagates in the eyepiece waveguide through TIR, and is coupled out by the CPE. Thus, the eyepiece waveguide supports all colors simultaneously, which is different from a design that uses one eyepiece waveguide for each color (i.e., a red eyepiece waveguide for the red wavelength, a green eyepiece waveguide for the green wavelength, and a blue eyepiece waveguide for the blue wavelength).

[0262] Although Figure 26A a single-layer eyepiece waveguide design is shown, other embodiments of the present invention utilize a waveguide stack including multiple waveguide layers. Thus, embodiments of the present invention can display multiple colors through each waveguide layer, or display a single color through each waveguide layer.

[0263] Figure 26B is a simplified k-space diagram showing Figure 26A the field of view, ICG, and CPE grating vectors of the eyepiece waveguide shown in Figure 26B In Figure 26A the light coupled in by the ICG 2610 shown in ICG is shown by the grating vector k 1 and k 2 show the light propagating in the eyepiece waveguide, and the light coupled out by the CPE 2612 shown in Figure 26A is shown by the dashed grating vectors k 2 and k 1 show. The grating vector k recA grating corresponding to "recycling" light in the eyepiece waveguide, thereby improving efficiency. The field of view considered is 26°(H) x 26°(V), and all three R, G, B wavelengths can be emitted into the eyepiece waveguide using an ICG 2610, where the input light is provided, for example, by a microLED illuminated projector.

[0264] Figure 26C is Figure 26A a simplified plan view of the user side of the eyepiece waveguide shown in Figure 26D is Figure 26A a simplified plan view of the world side of the eyepiece waveguide shown in. As Figure 26C shown, Figure 26A the ICG 2610 shown in 1 forms on or in the user side of the substrate 2605 together with a grating corresponding to the grating vector k Figure 26D shown, a grating corresponding to the grating vectors k 2 and k rec forms on or in the world side of the substrate 2605. Additional descriptions related to the k-space diagram are provided in International Patent Application No. PCT / US2022 / 043721 filed on September 15, 2022, the disclosure of which is hereby incorporated by reference in its entirety for all purposes.

[0265] Referring again to Figure 26A , the ICG 2610 is used to couple light from a projector (not shown) into the substrate 2605, which can be high refractive index glass (e.g., n = 2.0). Figure 26B shows the flow of light using momentum space representation. As Figure 26B shown, the inner circle with a radius = 1 represents the momentum of light at all physically possible angles of incidence (i.e., refractive index n = 1) in free space or vacuum. The outer circle with a radius = the refractive index of the substrate (in this case, n = 2.0) represents all physically possible angles of incidence inside the substrate. The three lines in the outer circle represent the corresponding refractive index values at the red, green, and blue wavelengths. The field of view is described by the range of the barrel-shaped R, G, B frames 2622, 2624, and 2626 shown in Figure 26B . Thus, the light coupled or emitted into the substrate has momentum located in the annular region in momentum space (i.e., between the inner and outer circles for each wavelength), and it will not escape unless it interacts with a diffraction grating that changes the momentum.

[0266] The CPE 2612 in this example has k Figure 26B from 1 and k 2A 1D binary square-ridge grating defined by momentum translation. The diffraction of the emitted light by these diffraction gratings allows the emitted light to be spread over a larger area (i.e., for pupil expansion). At the same time, these gratings also couple out the spread light, which corresponds to Figure 26B the dashed grating vector k 2 and k 1 shown in the momentum translation. The user's eye can see this coupled-out light and subsequently observe the digital content. Since the eyepiece has two sides (i.e., the user side facing the user and the world side facing the outside world), a 2D grating defined by the momentum translations k 1 and k 2 can be used, or 1D gratings on both sides of the eyepiece can be used. Those of ordinary skill in the art will recognize many variations, modifications, and alternatives.

[0267] Figure 27A is a simplified schematic diagram showing an example of an eyepiece waveguide including a hybrid individual diffraction structure according to an embodiment of the present invention. As shown in the plan view shown in Figure 27A , the eyepiece waveguide 2700 includes an ICG 2710 and a CPE 2712, which include individual diffraction structures that can have multiple refractive index materials, i.e., hybrid individual diffraction structures. In Figure 27A , four regions are shown, where the first region 2720 includes a first individual diffraction structure 2722, the second region 2730 includes a second individual diffraction structure 2732, the third region 2740 includes a hybrid individual diffraction structure 2742, and the fourth region 2750 includes a fourth individual diffraction structure 2752. Although in this example only the hybrid individual diffraction structure 2742 includes multiple refractive index materials, this is not necessary, and other diffraction structures can be hybrid individual diffraction structures.

[0268] As shown in Figure 27A , the individual diffraction structure 2722 includes a low refractive index material (e.g., a material with a refractive index between 1.6 and 1.8) having a first height H 1 formed on a substrate 2715 (e.g., a material with a refractive index between 2.0 and 2.65), the second individual diffraction structure 2732 includes a low refractive index material formed on the substrate 2715 and having a second height H 1 greater than the first height H 2 , the hybrid individual diffraction structure 2742 includes a first part formed of the substrate material, i.e., a high refractive index material having a third height H 3 and a low refractive index material having a fourth height H 4 , and the fourth individual diffraction structure 2752 includes a high refractive index material having a fifth height H 5 .

[0269] Thus, the CPE can be called a hybrid grating structure on two levels. On the first level, the CPE can be called a hybrid CPE because separate diffraction structures can be formed using two materials with different refractive indices, i.e., a hybrid separate diffraction structure. This first level is shown by the hybrid separate diffraction structure 2742, which includes a first portion 2744 formed of a substrate material, i.e., the substrate has been etched such that the first portion 2744 extends from the substrate to a third height H 3 , and a low refractive index material 2746 deposited on the first portion 2744 having a fourth height H 4 . Thus, by including separate diffraction structures made of different materials, the CPE can be called a hybrid CPE.

[0270] The second level is shown by the CPE, which includes separate diffraction structures (i.e., nano-features) having different properties (including different materials). For example, referring to Figure 27A , the first separate diffraction structure 2722 is made of a low refractive index material and the fourth separate diffraction structure 2752 is made of a high refractive index material. Thus, the grating parameters of the gratings formed in these different regions of the CPE vary across the entire CPE, with some regions using diffraction structures with a lower refractive index and other regions using diffraction structures with a higher refractive index. For example, the region near the ICG has a diffraction structure with a low refractive index, while the region far from the ICG has a diffraction structure with a high refractive index. Thus, in this example, since the nano-features are formed of different materials, the grating intensity / efficiency increases as light propagates from the ICG 2710 to the CPE 2712. Thus, this second level can include nano-features (e.g., the first separate diffraction structure 2722) formed of a first material deposited on a substrate, nano-features formed by etching the substrate to form a substrate portion extending from the substrate, where the first material is deposited on the substrate portion extending from the substrate (e.g., the hybrid separate diffraction structure 2742), and / or nano-features formed of a substrate portion extending from the substrate (e.g., the fourth separate diffraction structure 2752). Thus, the combination of these different nano-features results in a hybrid CPE. As discussed more fully with respect to Figure 36A and 36B , embodiments of the present invention are not limited to etching structures to provide high refractive index nano-features and can also include depositing high refractive index materials to form nano-features.

[0271] In Figure 27AIn the example shown, four discrete regions, namely a first region 2720, a second region 2730, a third region 2740, and a fourth region 2750, each have uniform grating characteristics, with a discontinuous step from one region to the next. This discontinuity can lead to phase tearing, thereby reducing the modulation transfer function (MTF) of the display. However, embodiments of the present invention are not limited to this exemplary design, which is provided by way of illustration only. Instead, a transition region with different grating characteristics can be provided between each discrete region, thereby providing a smooth transition of the grating characteristics as light propagates through the CPE. For example, the inventors have determined that if the width of the ICG 2710 measured along the x-axis is d i , then the transition region between adjacent regions with a width d f ≥d i results in a significant improvement in the MTF.

[0272] Although Figure 27A shows four discrete regions, namely a first region 2720, a second region 2730, a third region 2740, and a fourth region 2750, it should be understood that this design is only exemplary, and a more continuous variation of the diffraction structure can be utilized. For example, a larger number of regions can be used, or a continuously varying material composition / height / shape / etc. as a function of position can be used. Those of ordinary skill in the art will recognize many variations, modifications, and alternatives.

[0273] Figure 27B is a simplified schematic diagram showing a process of forming a hybrid individual diffraction structure according to an embodiment of the present invention. In Figure 27B , an imprint pattern with a thick residual layer thickness is formed using a low refractive index imprint material 2780. The imprint pattern can be transferred into a high refractive index substrate using an etching process to form an individual diffraction structure 2782. Alternatively, if the etching process is terminated before all the imprint layers are removed, a hybrid individual diffraction structure 2784 is formed, which includes a lower part (including the high refractive index substrate material) and an upper part (including the low refractive index imprint material 2780). The presence of the low refractive index imprint material 2780 reduces the reflectivity of the diffraction structure, thereby increasing the transmittance through the hybrid individual diffraction structure.

[0274] Patterns can be etched into the underlying low - refractive - index layer or high - refractive - index layer above a high - refractive - index substrate by reactive ion etching (RIE), ion beam etching / milling (IBE / M), RIE - inductively coupled plasma (RIE - ICP), etc. They can also be etched directly into the high - refractive - index substrate. The pattern can also be a hierarchical pattern obtained by depositing on an initial polymer pattern using physical vapor deposition (PVD) or chemical vapor deposition (CVD) processes such as evaporation, sputtering, plasma - enhanced CVD (PECVD), atomic layer deposition (ALD), etc. The waveguide diffraction structure can be of any shape in 1D: square ridge, sawtooth, tilted, multi - stepped, or of any shape in 2D: pillars, holes, tilted or blazed pillars, meta - structures, or of any shape in 3D: double - sided blazed pillars or holes, etc. A single - depth initial imprint pattern with different residual layer thicknesses can be used to achieve graded height / depth etching or deposition profiles, which can be used as an etching mask or a graded initial pattern, where etching and deposition maintain a similar graded profile. These embodiments are shown in Figures 33A - 34C The graded height, depth, duty cycle, etc. are key factors for effectively and uniformly guiding light waves from the projector waveguide interfacing with the ICG, guiding them through the substrate by TIR, and coupling them out to the user through the combined pupil expander (CPE), which combines the functions of the orthogonal pupil expander (OPE) and the exit pupil expander (EPE).

[0275] Figure 27C is a simplified schematic diagram showing the variation of grating parameters according to an embodiment of the present invention across the entire eyepiece waveguide 2760. In Figure 27C the grating intensity / efficiency of the ICG 2762 increases until position A, at which it decreases in the direction towards the CPE 2764. Similarly, the grating intensity / efficiency of the CPE 2764 increases in the direction away from the ICG 2762. In this example, the grating characteristics vary continuously across the entire eyepiece waveguide 2760 without discontinuities. The method of manufacturing such a continuously varying structure will be discussed in more detail below in conjunction with Figure 33A 、 36A and 36B.

[0276] Figure 27D -G shows how to fabricate a hybrid individual diffraction structure on top of a low - refractive - index coated substrate / waveguide to achieve better uniformity over a larger field of view, as demonstrated by the corresponding eye - box efficiency plots.

[0277] Figure 27D is a simplified cross - sectional view showing a hybrid individual diffraction structure according to an embodiment of the present invention. As Figure 27D shown, the substrate 2770 supports a high - refractive - index material 2772 (e.g., TiO with a refractive index of 2.45 2) and a low refractive index material 2774 (e.g., a photoresist with a refractive index of 1.65) supported by a high refractive index material 2772. Using this hybrid individual diffraction structure in a CPE results in Figure 27E the figure shown.

[0278] Figure 27E is the eye box efficiency map over the entire field of view of the entire eyepiece using the hybrid individual diffraction structure shown in Figure 27D . As shown in Figure 27E , the user eye box efficiency (U EBE ) is 6.93%, and the world eye box efficiency (W EBE ) is 3.13%. The uniformity is characterized by using the 80 / 20 percentile fraction (i.e., the figure of merit (FoM)), which is the ratio of the difference between the 80th percentile and the 20th percentile to the 50th percentile. The uniformity FoM (U FOV ) measured over the entire field of view is 5.615, and the uniformity FoM (U inner80 ) measured over the inner 80% of the field of view is 3.536, with lower values indicating better uniformity.

[0279] Figure 27F is a simplified cross-sectional view showing a hybrid individual diffraction structure formed on a low refractive index coating according to an 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 refractive index material, i.e., the substrate 2770 supports a low refractive index film 2790 (e.g., SiO with a refractive index of approximately 1.45 at 545 nm 2 ), which supports a high refractive index material 2772 (e.g., TiO with a refractive index of 2.45 2 ) and a low refractive index material 2774 (e.g., a photoresist with a refractive index of 1.65) supported by the high refractive index material 2772. This embodiment is applicable to large field of view, single layer, single wavelength AR displays. Using this hybrid individual diffraction structure in a CPE results in the figure shown in Figure 27G .

[0280] Figure 27G is the eye box efficiency map over the entire field of view of the eyepiece using the hybrid individual diffraction structure shown in Figure 27F . This figure shows the efficiency distribution of the eyepiece waveguide design using a 2.0 refractive index waveguide over a large field of view range of 55° (H) x 55° (V). As shown in Figure 27G , the user eye box efficiency (U EBE ) is 5.20%, the world eye box efficiency (W EBE ) is 1.98%, the uniformity FoM (U FOV ) over the entire field of view is 2.546, and the uniformity FoM (U inner80) is 1.394. High refractive index TiO 2 Although the grating is covered with a low refractive index layer on top, it still has a higher diffraction efficiency than a low refractive index grating. This results in higher efficiency but lower uniformity, as shown in the comparison with Figure 27E . One way to reduce the diffraction efficiency of such a hybrid grating is to use a low refractive index material layer between the grating structure and the substrate. As Figure 27G shows, such a hybrid structure on top of a low refractive index coated waveguide enables better uniformity.

[0281] To more fully explain and understand the benefits provided by an eyepiece waveguide utilizing the hybrid individual diffraction structures discussed herein, Figures 28A - 20E shows the impact of using different grating types with the same eyepiece layout and the same grating vector but with different grating height taper patterns for a single eyepiece waveguide design. To demonstrate the performance of the various designs, luminance efficiency profiles (normalized with respect to maximum luminance) and useful optical performance metrics for a 26° x 26° field of view at RGB wavelengths are provided.

[0282] In particular, for the Figure 26A eyepiece design shown, three different grating types are considered, as shown in Figure 28A , 29A and as shown in 30A. In all cases, a square-ridge grating shape with a 50% duty cycle is used, but the individual diffraction structures can be made of different materials and fabricated using different material-related fabrication processes described herein.

[0283] Figure 28A is a simplified cross-sectional view of an eyepiece waveguide according to an embodiment of the present invention. In this example, the eyepiece waveguide 2800 includes a CPE having an imprinted grating (i.e., a square-ridge grating) with a refractive index of 1.65 formed on a substrate (e.g., glass with a refractive index of 2.0). The imprinted grating is formed in 12 regions, as discussed with respect to Figure 28B . As Figure 28A shows, the imprinted thickness increases with the distance from the ICG.

[0284] Figure 28B is a diagram showing the refractive index regions of the Figure 28A eyepiece waveguide 2800 shown. The thickness of the imprinted grating in the 12 shown refractive index regions is shown, increasing from 10 nm in the portion of the CPE close to the ICG to 110 nm in the portion of the CPE far from the ICG.

[0285] Figures 28C - 28E is the Figure 28A eye box efficiency diagram of the eyepiece shown over the entire field of view. Figure 28C is a diagram for the red wavelength, Figure 28Dis a graph for the green wavelength, and Figure 28E is a graph for the blue wavelength. The performance metrics analyzed include the user-side eye box efficiency (U EBE ) and the world-side eye box efficiency (W EBE ), which represent the percentage of the total incident power from the projector that ultimately reaches the eye box plane at the nominal distance of the waveguide on both sides of the eye and the eyepiece. The uniformity of the display is captured by the 80 - 20 percentile score of the inner 80% of the field of view (denoted by U inner80 ), which is the ratio of the difference between the 80th percentile and the 20th percentile to the 50th percentile (median). A lower value of U inner80 indicates better uniformity. In addition, the central peak ratio CP (i.e., the efficiency at the center divided by the peak efficiency, with an ideal value of CP = 1) represents the centrality of the efficiency distribution across the entire f.

[0286] For these graphs, the light injection is from the upper right side of the field of view. The efficiency distribution is non-uniform because the light rays corresponding to different incident angles spread within the waveguide and interact with the grating in different ways. As shown in these graphs, although the uniformity for the blue and green wavelengths is relatively high, the red wavelength experiences reduced coupling out in the temple region, resulting in Figure 28C the dark area in the upper right corner of the field of view shown. From Figures 28C - 28E the optical efficiency distribution, it can be seen that the red efficiency is very small compared to green and blue because of the smaller diffraction efficiency associated with the low refractive index grating.

[0287] Figure 29A is a simplified cross-sectional view showing the eyepiece waveguide 2900 according to another embodiment of the present invention. In this example, the substrate (e.g., a glass substrate with a TiO 2 layer having a refractive index of 2.45 deposited on the glass) has been etched to produce a grating (i.e., a square-ridge grating) with a refractive index of 2.45. The grating is formed in 12 regions, as discussed with respect to Figure 29B . As Figure 29A shown, the grating thickness increases with the distance from the ICG.

[0288] Figure 29B is a graph showing Figure 29A the refractive index regions of the eyepiece waveguide 2900 shown in

[0289] Figures 29C - 29E . The thickness of the imprinted grating in the 12 shown refractive index regions is shown, increasing from 10 nm in the part of the CPE close to the ICG to 75 nm in the part of the CPE far from the ICG. Figure 29A is a graph of the eye box efficiency across the entire field of view of the eyepiece shown in Figure 29C is a graph for the red wavelength, Figure 29Dis a diagram of the green wavelength, and Figure 29E is a diagram of the blue wavelength. As shown in these diagrams, using a high refractive index grating results in a reduction in uniformity for the blue and green wavelengths, with significant coupling out of these wavelengths in the temple region (i.e., the upper right part of the field of view) and the dark nose region (i.e., the lower left part of the field of view). Using Figure 29A the high refractive index grating shown in results in an increase in efficiency but a reduction in uniformity. This difference stems from the difference in diffraction efficiency (i.e., the diffusion and coupling of the emitted light) between the low refractive index grating and the high refractive index grating.

[0290] Figure 30A is a simplified cross-sectional view showing an eyepiece waveguide 3000 including a hybrid CPE according to an embodiment of the present invention. Compared with Figure 28A and 29A the diffraction structures shown in, the diffraction structure is fabricated to include an imprinted grating with a refractive index of 1.65 formed on a substrate in a portion of the CPE near the ICG and a hybrid individual diffraction structure in a portion of the CPE far from the ICG. These hybrid individual diffraction structures include a substrate portion near the substrate made of the substrate material (i.e., the TiO 2 layer with a refractive index of 2.45) and an imprinted portion far from the substrate made of the imprinted layer (i.e., with a refractive index of 1.65). The grating is formed in 12 regions, as described with respect to Figure 30B As Figure 30A shown, the thickness of the nano-features (i.e., the imprinted grating and the hybrid individual diffraction structure) increases with the distance from the ICG.

[0291] Figure 30B is a diagram showing Figure 30A the refractive index regions of the eyepiece waveguide shown in. The thickness of the imprinted grating starts from 15 nm in the portion of the CPE near the ICG and increases to 45 nm in region 7. The thickness of the hybrid individual diffraction structure is constant in regions 8 - 12, but the thickness of the portion made of the substrate material increases from 15 nm in region 8 to 35 nm in region 12. Thus, the refractive index of each hybrid individual diffraction structure increases with the distance from the ICG.

[0292] Figures 30C - 30E is Figure 30A the eye box efficiency diagram within the field of view of the eyepiece shown in. Figure 30C is a diagram of the red wavelength, Figure 30D is a diagram of the green wavelength, and Figure 30E is a diagram of the blue wavelength. By using an imprinted grating with a varying height and a hybrid individual diffraction structure with an increasing refractive index, the eyepiece waveguide fabricated only using an imprinted grating (as discussed with respect to Figure 28A ) and the eyepiece waveguide fabricated only using an etched substrate grating (as discussed with respect to Figure 29AThe uniformity of (discussed).

[0293] As Figures 30C - 30E shown, the coupling out of the red wavelength in the temple region is reduced, while the uniformity of the field of view for the blue and green wavelengths is also improved. In addition to the uniformity improvement, using the Figure 30A shown hybrid CPE design can also significantly improve the user eye box efficiency. As shown by comparing Figures 28C - 28E and 29C-29E with Figures 30C - 30E , when using the hybrid separate diffraction structure instead of the imprinted grating, the user eye box efficiency (U EBE ) increases from 0.74% to 4.01% for the red wavelength, from 2.82% to 6.21% for the green wavelength, and from 3.59% to 4.28% for the blue wavelength; when using the hybrid separate diffraction structure instead of the grating made of the substrate material, it increases from 3.53% to 6.21% for the green wavelength and from 1.98% to 4.28% for the blue wavelength. Similarly, as shown in the figure, an improvement in the world eye box efficiency and an increase in the 80-20 percentile fraction of 80% within the field of view are also achieved. In addition, the center-to-peak ratio CP represents the centrality of the efficiency distribution across the entire field of view. Although the efficiency distribution is not uniform, the color correction algorithm adjusts the weights corresponding to different incident angles within the field of view, enabling the AR display to achieve good color (white) uniformity.

[0294] Therefore, Figure 30A the eyepiece waveguide shown in

[0295] including the hybrid separate diffraction structure provides a structure for achieving high red efficiency by combining the low diffraction efficiency of the low refractive index grating with the high coupling out diffraction efficiency of the high refractive index grating, while also maintaining good uniformity for all three colors. It should be noted that in a display system using a μLED-based projector, since the LED has low efficiency in generating these red wavelengths, it is desirable to achieve high efficiency for the red wavelength. Therefore, embodiments of the present invention utilizing the hybrid separate diffraction structure can provide very important optimization options to meet the efficiency and uniformity goals of a single-layer eyepiece waveguide AR display. Figure 30A In addition, since the hybrid separate diffraction structure shown in

[0296] has an imprinted material on the user side, the reflection from the CPE is reduced even in the absence of a planarization or encapsulation layer. Those of ordinary skill in the art will recognize many variations, modifications, and alternatives. Figures 31A - 31DExamples of how variations in the refractive index regions in the CPE of a waveguide eyepiece can utilize additional architectures to improve the brightness of the projected virtual image (e.g., percentage of eye box efficiency) are described and discussed in 32A - 32D, where most of the diffractive structures in the middle and end regions of the CPE are composed of materials with more than one refractive index.

[0297] In particular, Figure 31A and 31B illustrate examples of an eyepiece waveguide that can be used to project RGB light into a single - active - layer eyepiece waveguide using a single or multiple ICG pupils. By incorporating low - refractive - index feature regions to compensate for the initially diffused and coupled - out blue light, efficiency is increased while maintaining the same uniformity.

[0298] Figure 31A is a simplified cross - sectional view of an eyepiece waveguide according to an embodiment of the present invention. The eyepiece waveguide 3100 is formed using a substrate 3105 (e.g., a substrate with 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 gradient in the refractive index height of a single material, a gradient in the absolute height (i.e., combined material multi - refractive index), or a gradient in the duty cycle. The diffractive structures can include different types of structures in different regions. For example, square ridges with a specific duty cycle and height of a material with 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 of a second material with a different refractive index, and so on. In some implementations, the diffractive structures can include an interconnect material with a residual layer thickness of less than about 50 nm.

[0299] In this embodiment, an anti - reflection pattern 3107 is formed opposite the ICG 3110. The anti - reflection structure can be located at positions on the substrate that do not overlap with the coupled - out diffractive structures. Additionally, the anti - reflection structure can be present in any region of the hybrid surface relief waveguide that does not have diffractive structures. Including on the other side of the waveguide substrate opposite the input coupler or in regions outside the combined expander - output coupler (CPE). The anti - reflection structure can include multi - materials or a single material with single or multi - refractive indices, respectively.

[0300] Furthermore, a reflective layer 3111 (e.g., an aluminum layer) is deposited on the ICG 3110 to improve the ICG coupling - in efficiency. For example, an imprinted grating using a material with a refractive index of n = 1.65 is used to form the ICG and the CPE.

[0301] In this embodiment, the substrate 3105 is etched in the CPE region to reduce the thickness of the substrate. Additionally, the portion of the substrate near the ICG (which can be part of the CPE) is not etched, and a diffraction structure is formed by depositing and patterning a low refractive index material to form single or multi-level nano-features. As described below, this diffraction structure reduces the initial out-coupling and increases the spread of shorter wavelengths, while increasing the initial out-coupling of longer wavelengths. Thus, the eyepiece waveguide includes a variable thickness substrate, where the substrate thickness is higher at the ICG and the portion of the substrate near the ICG in this embodiment, and lower at the portion of the substrate away from the ICG. Additionally, the substrate thickness can be uniform or vary with position in the CPE. Further, as previously discussed with respect to Figure 27A Etching the substrate can produce nano-features that include a base portion formed from the substrate material and extending from the substrate.

[0302] Figures 31B - 31D is Figure 31A The eye box efficiency plot of the eyepiece shown in the entire field of view. For these plots, the ICG is located in the upper right of the field of view, injecting light downward and to the left. Figure 31B Shows the eye box efficiency at a blue wavelength (e.g., 455 nm), Figure 31C Shows the eye box efficiency at a green wavelength (e.g., 530 nm), and Figure 31D Shows the eye box efficiency at a red wavelength (e.g., 630 nm). For a grating designed to operate at a green wavelength (e.g., 530 nm), injecting light of a shorter wavelength (e.g., blue wavelength) will result in rapid out-coupling, as shown by the bright blue light in the temporal region of the field of view. Conversely, injecting light of a longer wavelength (e.g., red wavelength) will result in reduced initial out-coupling, as shown by the bright red light in the nasal region of the field of view. Using an embodiment of the present invention related to Figures 32A - 32D Shorter wavelengths experience reduced initial out-coupling and increased diffusion in the CPE, while longer wavelengths experience increased initial out-coupling while maintaining the desired diffusion, thereby improving uniformity.

[0303] Figure 32A Is a simplified cross-sectional view of an eyepiece waveguide according to an embodiment of the present invention. The eyepiece waveguide 3200 is formed using a substrate 3205 (e.g., a substrate with a refractive index of n = 2.25), and includes an ICG 3210 and a CPE 3212. Similar to the eyepiece waveguide 3100 discussed with respect to Figure 31A An anti-reflection pattern 3207 is formed opposite the ICG 3210. Additionally, a reflective layer 3211 (e.g., an aluminum layer) is deposited on the ICG 3210 to increase the ICG in-coupling efficiency. For example, an imprinted grating using a material with a refractive index of n = 1.65 is used to form the ICG and the CPE.

[0304] Compared to the eyepiece waveguide 3100, the CPE 3212 includes an initial region 3213 where an imprinted grating (e.g., refractive index 1.6 < n < 1.8) is formed to increase the diffusion of light of blue wavelengths in the CPE. Additionally, the substrate 3200 is etched in a second region 3215 to reduce the thickness of the substrate.

[0305] Figures 32B - 32D is Figure 32A The eye box efficiency diagram of the eyepiece shown in the entire field of view. As Figures 32B - 32D shown, using embodiments of the present invention, the efficiency and uniformity of the eyepiece waveguide are improved compared to the prior art. Specifically, for blue wavelengths, the eye box efficiency increases from 1.1% to 2.7%, for green wavelengths, the eye box efficiency increases from 3.6% to 6.1%, and for red wavelengths, the eye box efficiency increases from 3.5% to 4.8%.

[0306] Figure 33A is a simplified cross-sectional view showing the manufacturing process of an eyepiece waveguide using a shadow mask according to an embodiment of the present invention. In Figure 33A it shows a single-sided eyepiece waveguide, i.e., a diffraction structure is formed on one side of the eyepiece waveguide. As described in more detail below with respect to Figures 34A - 34C the embodiments of the present invention also include a double-sided eyepiece waveguide design where the diffraction structure is formed on both sides of the eyepiece waveguide.

[0307] As Figure 33A shown, a photoresist pattern 3315 is coated on the substrate 3310 to define the ICG 3312 and the CPE 3314. The photoresist thickness in the ICG region and the CPE region varies with position as shown to produce a diffraction structure that varies with position. In this embodiment, the diffraction structure in the portion of the CPE 3314 remote from the ICG 3312 is used to reduce the outcoupling and increase the diffusion of light of shorter wavelengths. The photoresist thickness also increases with the distance from the CPE 3314. Additionally, the shadow mask 3311 is used for a position-varying etching process. As an example, the plasma density in a plasma etching process can vary, as more detailedly explained in U.S. Patent No. 10,527,865, the disclosure of which is hereby incorporated herein by reference in its entirety. Thus, as Figure 33A shown, the etching depth increases with the distance from the ICG 3312, thereby producing a transition of grating characteristics (e.g., as a result of higher intensity plasma as a function of the distance from the ICG), such that as light propagates through the CPE 3314, the grating intensity also increases.

[0308] Figure 33Bis a simplified cross-sectional view showing an eyepiece waveguide manufacturing process using an etching process according to an embodiment of the present invention. In this example, instead of using a shadow mask, a lithographic pattern is combined with the etching process, such that the substrate is etched to produce features etched into the underlying substrate, where the etching depth varies with position, and the thickness of the first material coupled to the remaining substrate portion after etching also varies. Thus, the height of portion 3342 is greater than that of portion 3344, and the thickness of the remaining first material 3346 is greater than the remaining first material near the ICG.

[0309] Figure 33C is a simplified cross-sectional view showing another eyepiece waveguide manufacturing process using an etching process according to an embodiment of the present invention. In this example, the etching process results in the first material coupled to the remaining substrate portion after etching having different thicknesses. Thus, the thickness of the remaining first material 3352 is greater than that of the remaining first material 3354, thereby providing a variation in the nano-feature material with position.

[0310] Figure 33D is a simplified cross-sectional view showing an eyepiece waveguide manufacturing process using an etching process and a tapered substrate according to an embodiment of the present invention. This process is similar to the process shown in Figure 33B and utilizes a substrate with a varying thickness and a lithographic pattern with a varying thickness to produce an eyepiece waveguide whose thickness varies due to thickness variations caused by etching on the user side of the eyepiece waveguide and variations due to the substrate thickness on the world side of the eyepiece waveguide.

[0311] Although Figures 33A - 33D shows an example of a hybrid hierarchical etching structure where nano-features are etched into the 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, deposition structures rather than etching structures, etc. are all included within the scope of the present invention.

[0312] Figure 34A is a simplified cross-sectional view showing a bilateral eyepiece waveguide manufacturing process using a shadow mask as shown in Figure 33A As an extension of the process shown in Figure 33A diffraction structures are formed on both the user side and the world side of the eyepiece waveguide.

[0313] Figure 34B is a simplified cross-sectional view showing a bilateral eyepiece waveguide manufacturing process using an etching process according to an embodiment of the present invention. As Figure 33BAn extension of the process shown in forms diffraction structures on both the user side and the world side of the eyepiece waveguide. In this example, etching of the substrate is performed on both sides of the substrate to form different etching depths that vary with position. Thus, the height of portion 3410 is greater than that of portion 3412 on the user side of the eyepiece waveguide, and the height of portion 3420 is greater than that of portion 3422 on the world side of the eyepiece waveguide.

[0314] Figure 34C is a simplified cross-sectional view showing a bilateral eyepiece waveguide manufacturing process using an etching process according to an embodiment of the present invention. As Figure 33C an extension of the process shown in, diffraction structures are formed on both the user side and the world side of the eyepiece waveguide. The etching process causes the substrate to taper to reduce the substrate thickness away from the ICG. Thus, the remaining first material 3430 has a greater thickness than the remaining first material 3432 to provide a variation in the nanoscale feature material as a function of position on the user side of the eyepiece waveguide, and the remaining first material 3440 has a greater thickness than the remaining first material 3442 on the world side of the eyepiece waveguide.

[0315] Figure 35A is a simplified cross-sectional view showing an eyepiece waveguide manufacturing process according to an embodiment of the present invention to form a blazed grating. The process shows that a hybrid graded etching structure can be formed, where a sawtooth blaze is etched into an underlying imprint layer 3512 of a 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 the substrate material and the imprint material.

[0316] Figure 35B is a simplified cross-sectional view showing an eyepiece waveguide manufacturing process for a coated substrate according to an 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 diffraction structure is formed that includes a portion of the high refractive index coating and a portion that includes the imprint layer. Compared with Figure 35A the process shown in, the substrate is not etched in this embodiment. Additionally, although Figure 35B shows square ridge nanoscale features, this particular grating shape is not required and other shapes can be used. In some embodiments, the high refractive index coating 3520 or other films discussed herein are etched to form a patterned film. Those of ordinary skill in the art will recognize many variations, modifications, and alternatives.

[0317] Figure 35C is a simplified cross-sectional view showing an eyepiece waveguide manufacturing process for a coated substrate according to another embodiment of the present invention. Compared with Figure 35BThe process shown is similar, where etching is used to form a hybrid diffractive structure that includes a portion of the high refractive index coating and a portion of the imprint layer. Additionally, in this embodiment, the thickness of the high refractive index coating 3520 decreases during the etching process.

[0318] Figure 35D is a simplified cross-sectional view showing an eyepiece waveguide manufacturing process for a multi-level coated substrate according to an embodiment of the present invention. In this example process, before forming the imprint layer 3534, the substrate 3510 is coated with a high refractive index coating 3530 and a low refractive index coating 3532 in the CPE region. The imprint layer varies according to position. After etching, a hybrid diffractive structure is formed that includes a portion of the high refractive index coating and a portion of the low refractive index coating.

[0319] Figure 35E is a simplified cross-sectional view showing an eyepiece waveguide manufacturing process to form a hybrid individual diffractive structure according to an embodiment of the present invention. Similar to the process shown in Figure 35C etched to form a hybrid diffractive structure that includes a portion of the high refractive index coating and a portion of the imprint layer. Additionally, in this embodiment, the high refractive index coating is removed from the gaps between the nano-features. These gaps can then be filled with a planarizing material, as described with respect to Figure 37A or the gaps can be encapsulated, as described with respect to Figure 37B as described.

[0320] Figures 36A - 36B shows an example of a hybrid graded structure with two or more coating materials in different portions of an eyepiece waveguide according to an embodiment of the present invention.

[0321] As discussed with respect to Figure 33A a shadow mask can be used to vary the deposition process according to position. As an example, the plasma density during a plasma deposition process can be more specifically explained as described in U.S. Patent No. 10,527,865, which is previously incorporated herein by reference.

[0322] Figure 36A is a simplified cross-sectional view showing an eyepiece waveguide manufacturing process using a shadow mask according to an embodiment of the present invention. The low refractive index material 3611 is patterned to define the ICG 3612 and the CPE 3614. In Figure 36A a shadow mask 3605 is used during the deposition process, which forms a deposition thickness that varies according to position. Thus, as shown in Figure 36A the deposition thickness increases with the distance from the ICG 3612, resulting in a transition of grating characteristics (e.g., as a result of higher intensity plasma as a function of the distance from the ICG), thereby increasing the grating intensity as light propagates through the CPE 3614.

[0323] Figure 36B is a simplified cross-sectional view showing the manufacturing process of an eyepiece waveguide using a shadow mask according to another embodiment of the present invention. In Figure 36B the process shown, the process has common features with Figure 36A the process shown, and a two-level deposition process is implemented using a shadow mask 3625 to form a separate diffraction structure with two deposition materials (i.e., a low refractive index coating 3632 and a high refractive index coating 3634) on the low refractive index material 3611 in the CPE 3613. The thickness of the coatings can be different and can be selected according to specific applications. Additionally, although the transition from the deposited to the non-deposited area is shown as abrupt, it can be understood that due to the use of a shadow mask, this transition can be gradual.

[0324] The processes included within the scope of the present invention are not limited to forming the transition region using etching and deposition, but also include spin coating, spraying, inkjet dispensing, etc.

[0325] Figures 37A - 37C is a cross-sectional view showing an architecture including additional materials according to an embodiment of the present invention. As Figures 37A - 37C shown, one or more additional materials can be used, such as third / fourth materials, where the refractive index can be lower or between the low refractive index and the high refractive index, as shown by the planarization or encapsulation materials discussed below. As an example, these materials can fill the gaps between adjacent high refractive index materials with a low refractive index upper part or cover. This type of architecture can provide the benefits shown by the hybrid structure, but also helps to reduce rainbow artifacts. Rainbow artifacts are generally external light artifacts, which can interact with the exposed surface relief grating and may cause visual artifacts to be replicated and projected into the user's field of view. These are mainly caused by world light hitting the grating at a specific angle. Although the figure only shows a square ridge hybrid structure, this concept can be applied to blazed sawteeth, multi-step hybrid structures, etc.

[0326] Figure 37A is a simplified cross-sectional view showing an eyepiece waveguide including a planarization layer according to an embodiment of the present invention. In Figure 37A it, the eyepiece waveguide 3700 includes a substrate 3705, an ICG 3710, and a CPE 3712 as described above. Additionally, additional materials are incorporated into the eyepiece waveguide design, as shown by the planarization layer 3715, including a planarization material 3718 formed on the substrate 3705 between separate diffraction structures.

[0327] 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 37BIn [description], the planarizing material 3730 not only fills the gaps in the substrate between adjacent individual diffraction structures, but also forms at a level above the substrate surface, thereby partially filling the gaps between adjacent individual diffraction structures. The refractive index of the planarizing material can be in the range of 1.1 to 1.4. This design can be referred to as an "immersion" design.

[0328] Figure 37C is a simplified cross-sectional view of an eyepiece waveguide including a packaging layer according to another embodiment of the present invention. In Figure 37C In [description], the thickness of the planarizing material 3740 not only fills the gaps in the substrate between adjacent individual diffraction structures, but also forms at a level above the individual diffraction structures, thereby encapsulating the individual diffraction structures and hybridizing the individual diffraction structures. Due to the presence of a low refractive index material that encapsulates the diffraction structures of the eyepiece waveguide, this immersion design provides a reduced reflectivity compared to other designs.

[0329] Material considerations for the eyepiece waveguide

[0330] The waveguide substrate for manufacturing the eyepiece can consist of a series of refractive indices, such as high refractive index glass, such as 1.7 SCHOTT SF5, 1.8 SF6, HOYA dense tantalum flint glass TAFD55 (2.01), TAFD65 (2.06), etc., to crystal substrates, such as lithium tantalate LiTaO 3 、lithium niobate LiNbO 3 (2.25), silicon carbide (2.65), fused quartz (1.45), or glass containing La, Na, TiO 2 、ZrO 2 、Li or Nb. The high refractive index coating can consist of SiC with a refractive index of 2.5 - 2.6, TiO 2 with a refractive index of 2.2 - 2.5, ZrO 2 with a refractive index of 2.1, Si 3 N 4 and silicon oxynitride, 1.45 m of SiO 2 and MgF with a refractive index of 1.38 2 etc. Physical vapor deposition (PVD) (such as evaporation or sputtering with or without ion assistance (such as Ar / O 2 )) or chemical vapor deposition (CVD) (such as low-pressure PECVD, atmospheric PECVD, ALD, etc.) can be used on blank or patterned surfaces to obtain thin film coatings.

[0331] The patterned embossable prepolymer material may include a resin material such as epoxy vinyl ester. The resin may include vinyl monomers (such as methyl methacrylate) and / or difunctional or trifunctional vinyl monomers (such as diacrylate, triacrylate, dimethacrylate, etc.), and the monomers may or may not contain aromatic molecules. The prepolymer material may include monomers having one or more functional groups (such as alkyl, carboxyl, carbonyl, hydroxyl, and / or alkoxy). Both sulfur atoms and aromatic groups have relatively high polarizabilities and can be incorporated into these acrylate components to increase the refractive index of the formulation, and generally have a refractive index in the range of 1.5 to 1.75. In some embodiments, the prepolymer material may include a resin containing cycloaliphatic epoxy resin and can be cured using ultraviolet light and / or heat. Additionally, the prepolymer material may include an ultraviolet cationic photoinitiator and a co-reactant to facilitate effective ultraviolet curing under ambient conditions.

[0332] Incorporating inorganic nanoparticles (NP) (such as ZrO 2 and TiO 2 ) into such embossable resin polymers can significantly increase the refractive index, up to 2.1. Pure ZrO 2 and TiO 2 crystals can reach refractive indices of 2.2 and 2.4 - 2.6 respectively at 532 nm. For the preparation of optical nanocomposites of acrylate monomers and inorganic nanoparticles, the particle size is less than 10 nm to avoid excessive Rayleigh scattering. Due to its high specific surface area, high polarity, and incompatibility with the crosslinked polymer matrix, ZrO 2 NP tends to aggregate in the polymer matrix. Surface modification of the NP can be used to overcome this problem. In this technique, the hydrophilic surface of ZrO 2 is modified to be compatible with organic matter, enabling the NP to be uniformly mixed with the polymer. This modification can be accomplished using capping agents containing silane and carboxylic acid. One end of the capping agent binds to the ZrO 2 surface; the other end of the capping agent either contains a functional group that can participate in acrylate crosslinking or a non-functional organic moiety. Examples of surface-modified sub-10 nm ZrO 2 particles include those provided by Pixelligent Technologies TM and Cerion Advanced Materials TM . These functionalized nanoparticles are typically sold as a homogeneous suspension in a solvent in the form of a uniform mixture and can be combined with other base materials to produce a resist formulation with a jetable viscosity and an increased refractive index.

[0333] For crosslinking and patterning, the prepolymer having a diffraction pattern is contacted with a template (such as in the case of imprint lithography, such as J-FILTM , wherein the prepolymer material is dispensed by inkjet) includes exposing the prepolymer to actinic radiation having a wavelength between 310 nm and 410 nm and an intensity between 0.1 J / cm 2 and 100 J / cm 2 . The method may further include heating the prepolymer to a temperature between 40 °C and 120 °C while exposing the prepolymer to actinic radiation. Such prepolymer resin can be dispensed onto the desired surface to be patterned using an on-demand inkjet drop or continuous jetting system, slot die coating, spin coating, knife coating, microgravure coating, screen printing, spraying or atomization, etc. before patterning using a template / mold having inverse tone features.

[0334] To improve adhesion, a crosslinking silane coupling agent is used between post-patterning (template / mold release) of the prepolymer material and curing on the desired surface or substrate. These consist of an organic functional group at one end and a hydrolyzable group at the other end, and they form a durable bond with different types of organic and inorganic materials. Examples of organic functional groups can be acryloyl groups, which can crosslink into a patternable polymer material to form the desired optical pattern / shape. Conversely, the template or mold can be coated with a similar coating where the acryloyl end is replaced by a fluorinated chain, which can reduce the surface energy and thus act as a non-bonding but releasing site. Chemical vapor deposition is carried out at low pressure, where the coupling agent is delivered in vapor form, with or without an inert gas (e.g., N 2 ), e.g., in the presence of reactive -O and / or -OH groups on the surface of the material to be coated. A monolayer film as thin as 0.5 nm - 0.7 nm can be deposited using a chemical vapor coating process, or a thicker film can also be deposited.

[0335] Figure 38 is a cross-sectional view of a hybrid multi-refractive index architecture having diffractive structures of different shapes composed of individual refractive indices / materials according to an embodiment of the present invention. As Figure 38 shown, the hybrid multi-refractive index architecture can include diffractive structures of different shapes composed of individual refractive indices / materials. As an example, Figure 38 shows a blazed sawtooth structure, where a large bottom blazed portion is etched into a high refractive index material, leaving a low refractive index top cap. In this example, the low refractive index top cap is substantially a square ridge. Similarly, as previously described, the hybrid structure can be multi-step, and an example of a multi-step structure etched with two different refractive index materials is shown (e.g., the low refractive index is at the top and the high refractive index is etched below).

[0336] Figure 39A -C shows a cross-sectional view of an architecture having a hybrid individual diffractive structure, which includes a multi-refractive index material on one side of the substrate and a single refractive index material on the opposite side of the substrate.

[0337] Figure 39A Shows a cross-sectional view of a bilateral eyepiece waveguide according to an embodiment of the present invention. In Figure 39A it, 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 the substrate 3905, while an imprinted grating 3914 is formed on the other side of the substrate.

[0338] Figure 39B Shows a cross-sectional view of a bilateral eyepiece waveguide having a hybrid individual diffraction structure according to an embodiment of the present invention. In Figure 39B it, an ICG 3910 and a hybrid individual diffraction structure 3920 (i.e., a grating formed partly by etching the high refractive index material of the substrate and partly using an imprinted material) are formed on one side of the substrate 3905, while an imprinted grating 3914 is formed on the other side of the substrate.

[0339] Figure 39C Shows a cross-sectional view of a bilateral eyepiece waveguide having a hybrid individual diffraction structure according to another embodiment of the present invention. In Figure 39C it, an ICG 3910 and a hybrid individual diffraction structure 3930 (i.e., a grating formed partly by etching the high refractive index material of the substrate and partly using a low refractive index imprinted material different from the material used for manufacturing the imprinted grating 3914) are formed on one side of the substrate 3905, while an imprinted grating 3914 is formed on the other side of the substrate. Thus, two different imprinted materials having different refractive indices are utilized in this embodiment.

[0340] As Figures 39A - 39C shown, the hybrid multi-refractive index structure can be located on one or both sides of the substrate, while a single refractive index grating can be used on the other side to form a bilateral waveguide architecture. Such an architecture having a hybrid refractive index grating on either side can help improve the user-side virtual image brightness, especially in embodiments having a single active layer, where multiple colors (e.g., two or more of RGB) are waveguided in the eyepiece waveguide. The examples shown are for single-sided or double-sided imprinting of the multi-refractive index features within the structure or different patterned regions of the material refractive index on one side of the eyepiece waveguide, but these examples can be applied to the bilateral architecture as Figures 39A - 39C shown. Additionally, since a diffraction structure having etched nano-features (as the etched substrate grating 3912 or the hybrid individual diffraction structure 3920) is combined with imprinted nano-features, the different diffraction attributes of these structures can be utilized to improve system performance. By way of example only, since the etched and imprinted gratings can have different diffraction efficiencies, diffracted light can be preferentially directed to the user to increase the brightness of the virtual. Those of ordinary skill in the art will recognize many variations, modifications, and alternatives.

[0341] The eyepiece waveguide design described herein can be used in augmented reality display systems, such as those Figures 1 - 25 associated with. Thus, for example, Figure 11A the waveguide 1120 in and other waveguides implemented as components of an augmented reality display system can be implemented using one or more embodiments described herein.

[0342] Example 1 is an augmented reality system, comprising: a projector; projection optics coupled to the projector; and an eyepiece waveguide including a hybrid diffraction structure, comprising: one or more first nano-features having a first material with a first refractive index; and one or more second nano-features having a second material with a second refractive index.

[0343] Example 2 is the augmented reality system according to Example 1, wherein the eyepiece waveguide further comprises: a substrate and an input coupling diffraction structure coupled to the substrate.

[0344] Example 3 is the eyepiece waveguide according to Examples 1-2, wherein the eyepiece waveguide further comprises an output coupling diffraction structure, and the hybrid diffraction structure is part of the output coupling diffraction structure.

[0345] Example 4 is the eyepiece waveguide according to Examples 1-3, wherein the substrate comprises the second material.

[0346] Example 5 is the eyepiece waveguide according to Examples 1-4, wherein the first refractive index is less than the second refractive index.

[0347] Example 6 is the eyepiece waveguide of claim Examples 1-5, wherein the eyepiece waveguide further comprises a substrate, wherein the one or more first nano-features comprise the first material coupled to the substrate; and the one or more second nano-features comprise a portion of the substrate extending from the substrate.

[0348] Example 7 is the eyepiece waveguide according to Examples 1-6, wherein the one or more second nano-features further comprise the first material coupled to the portion of the substrate.

[0349] Example 8 is the eyepiece waveguide according to Examples 1-7, wherein the eyepiece waveguide further comprises a substrate, and the one or more first nano-features are close to the input coupling diffraction structure coupled to the substrate, and the one or more second nano-features are away from the input coupling diffraction structure.

[0350] Example 9 is the eyepiece waveguide according to Examples 1-8, wherein the one or more first nano-features or the one or more second nano-features are separated by gaps between adjacent nano-features, and the eyepiece waveguide further comprises a planarizing material filling the gaps.

[0351] Example 10 is the eyepiece waveguide described in Examples 1-9, wherein the planarizing material encapsulates the one or more first nano-features or the one or more second nano-features.

[0352] Example 11 is an eyepiece waveguide, comprising: a substrate operable to support the propagation of light; an input diffraction structure coupled to the substrate; and an output diffraction structure coupled to the substrate, wherein the output diffraction structure comprises one or more first nano-features having a first material with a first refractive index and one or more second nano-features having a second material with a second refractive index.

[0353] Example 12 is the eyepiece waveguide described in Example 11, wherein the substrate comprises the second material.

[0354] Example 13 is the eyepiece waveguide described in Examples 11-12, wherein the first refractive index is less than the second refractive index.

[0355] Example 14 is the eyepiece waveguide described in Examples 11-13, wherein the one or more first nano-features comprise a first material coupled to the substrate; and the one or more second nano-features comprise a portion of the substrate extending from the substrate.

[0356] Example 15 is the eyepiece waveguide described in Examples 11-14, wherein the one or more second nano-features further comprise the first material coupled to the portion of the substrate.

[0357] Example 16 is the eyepiece waveguide described in Examples 11-15, wherein the one or more first nano-features are close to the input diffraction structure, and the one or more second nano-features are away from the input diffraction structure.

[0358] Example 17 is the eyepiece waveguide described in Examples 11-16, wherein the one or more first nano-features are located in a first region close to the input diffraction structure; the one or more second nano-features are located in a second region away from the input diffraction structure; and the eyepiece waveguide further comprises a transition region disposed between the first region and the second region.

[0359] Example 18 is the eyepiece waveguide described in Examples 11-17, wherein the transition region comprises transition nano-features having a transition material with a refractive index between the first refractive index and the second refractive index.

[0360] Example 19 is the eyepiece waveguide described in Examples 11-18, wherein the input diffraction structure has a first width measured parallel to the substrate, and the transition region has a second width measured parallel to the substrate and greater than the first width.

[0361] Example 20 is the eyepiece waveguide described in Examples 11-19, wherein the one or more first nano-features or the one or more second nano-features are separated by gaps between adjacent nano-features, and the eyepiece waveguide further includes a planarizing material filling the gaps.

[0362] Example 21 is the eyepiece waveguide described in Examples 11-20, wherein the planarizing material encapsulates the outcoupling diffraction structure.

[0363] Example 22 is a hybrid surface relief waveguide structure, including: a substrate; and a diffraction structure coupled to the substrate and including a plurality of diffraction nano-features, wherein each of the plurality of diffraction nano-features is characterized by a change in refractive index.

[0364] Example 23 is the hybrid surface relief waveguide structure described in Example 22, wherein the normal vector is orthogonal to the substrate and the change in refractive index varies along the normal vector.

[0365] Example 24 is the hybrid surface relief waveguide structure described in Examples 22-23, wherein the change in refractive index includes a first material having a first refractive index close to the substrate and a second material having a second refractive index less than the first refractive index away from the substrate.

[0366] Example 25 is the hybrid surface relief waveguide structure described in Examples 22-24, wherein the diffraction structure includes a first nano-feature, and the first nano-feature includes a first material coupled to the substrate.

[0367] Example 26 is the hybrid surface relief waveguide structure described in Examples 22-25, wherein the diffraction structure includes a portion of the substrate and the first material is coupled to the portion of the substrate.

[0368] Example 27 is the hybrid surface relief waveguide structure described in Examples 22-26, wherein the diffraction structure includes an outcoupling diffraction structure, and the outcoupling diffraction structure includes a third nano-feature formed by a second portion of the substrate.

[0369] Example 28 is the hybrid surface relief waveguide structure described in Examples 22-27, wherein the portion of the substrate and the second portion of the substrate extend different distances from the substrate.

[0370] Example 29 is the hybrid surface relief waveguide structure described in Examples 22-28, wherein the first nano-feature is composed of the first material, and the third nano-feature is composed of the second material.

[0371] Example 30 is the hybrid surface relief waveguide structure described in Examples 22-29, further comprising: a film disposed between the substrate and the diffraction structure.

[0372] Example 31 is the hybrid surface relief waveguide structure described in Examples 22-30, wherein the substrate includes a pattern, and the film is coupled to the pattern.

[0373] Example 32 is an eyepiece waveguide, comprising: a substrate operable to support the propagation of light; an input diffraction structure coupled to the substrate; and an output diffraction structure coupled to the substrate, wherein the output diffraction structure includes a first nano feature and a second nano feature, the first nano feature includes a first material having a first refractive index, and the second nano feature includes the first material and a second material having a second refractive index.

[0374] Example 33 is the eyepiece waveguide described in Example 32, wherein the first nano feature includes the first material coupled to the substrate.

[0375] Example 34 is the eyepiece waveguide described in Examples 32-33, wherein the second material includes a portion of the substrate, and the first material is coupled to the portion of the substrate.

[0376] Example 35 is the eyepiece waveguide described in Examples 32-34, wherein the output diffraction structure further includes a third nano feature formed from a second portion of the substrate.

[0377] Example 36 is the eyepiece waveguide described in Examples 32-35, wherein the portion of the substrate and the second portion of the substrate extend different distances from the substrate.

[0378] Example 37 is the eyepiece waveguide described in Examples 32-36, wherein the first nano feature consists of the first material, and the third nano feature consists of the second material.

[0379] Example 38 is the eyepiece waveguide described in Examples 32-37, wherein the eyepiece waveguide includes a film disposed between the substrate and the output diffraction structure.

[0380] Example 39 is the eyepiece waveguide described in Examples 32-38, wherein the substrate includes a pattern, and the film is coupled to the pattern.

[0381] Example 40 is the eyepiece waveguide described in Examples 32-39, wherein the film includes a pattern.

[0382] Example 41 is the eyepiece waveguide described in Examples 32-40, wherein at least one of the first nano feature or the second nano feature includes: a square ridge, a blazed grating, serrations, a tilt, or a multi-step structure.

[0383] Example 42 is the eyepiece waveguide described in Examples 32-41, wherein at least one of the first nano feature or the second nano feature is an element of a one-dimensional grating structure.

[0384] Example 43 is the eyepiece waveguide described in Examples 32-42, wherein at least one of the first nano feature or the second nano feature is an element of a two-dimensional grating structure.

[0385] Example 44 is the eyepiece waveguide described in Examples 32-43, wherein at least one of the first nano feature or the second nano feature is an element of a three-dimensional grating structure.

[0386] Example 45 is the eyepiece waveguide described in Examples 32-44, wherein the substrate has a refractive index between 1.45 and 2.65.

[0387] Example 46 is the eyepiece waveguide described in Examples 32-45, wherein the substrate comprises a glass or fused silica containing La, Na, TiO 2 , ZrO 2 , Li or Nb.

[0388] Example 47 is the eyepiece waveguide described in Examples 32-46, wherein the substrate comprises LiTaO 3 , LiNbO 3 , or SiC.

[0389] Example 48 is the eyepiece waveguide described in Examples 32-47, wherein the substrate is a crystal.

[0390] Example 49 is the eyepiece waveguide described in Examples 32-48, wherein the first material has a refractive index between 1.31 and 2.65.

[0391] Example 50 is the eyepiece waveguide described in Examples 32-49, further comprising an anti-reflection structure coupled to the substrate, wherein the anti-reflection structure has a refractive index between 1.31 and 1.75.

[0392] Example 51 is the eyepiece waveguide described in Examples 32-50, wherein the anti-reflection structure comprises a sub-wavelength diffraction structure.

[0393] Example 52 is the eyepiece waveguide described in Examples 32-51, wherein the anti-reflection structure is located on the substrate opposite the input diffraction structure.

[0394] Example 53 is the eyepiece waveguide described in Examples 32 - 52, wherein the antireflection structure is located on the substrate at a position that does not overlap with the output diffraction structure.

[0395] Example 54 is the eyepiece waveguide described in Examples 32 - 53, wherein the substrate has a thickness variation of less than approximately 800 nm.

[0396] Example 55 is an eyepiece waveguide, comprising: a substrate operable to support the propagation of light; an input diffraction structure coupled to the substrate; and an output diffraction structure coupled to the substrate, wherein at least one of the input diffraction structure or the output diffraction structure comprises one or more first nano - features having a first material with a first refractive index and one or more second nano - features having a second material with a second refractive index.

[0397] In the foregoing specification, it has been described with reference to specific embodiments of the present disclosure. However, it will be apparent that various modifications and changes can be made thereto without departing from the broader spirit and scope of the present disclosure. Accordingly, the specification and drawings are to be regarded as illustrative rather than restrictive.

[0398] In fact, it will be understood that the systems and methods of the present disclosure each have several innovative aspects, none of which is the sole responsibility or requirement for the desired attributes disclosed herein. The various features and processes described above can be used independently of one another or can be combined in various ways. All possible combinations and sub - combinations are intended to fall within the scope of the present disclosure.

[0399] Certain features that are described in the context of separate embodiments in this specification can also be implemented in combination in a single embodiment. Conversely, the various features that are described in the context of a single embodiment can also be implemented separately or in any suitable sub - combination in multiple embodiments. Additionally, although features may have been described above as acting in certain combinations and even initially claimed as such, in some cases, one or more features in the claimed combination can be excluded from the combination, and the claimed combination can be directed to a sub - combination or a variation of a sub - combination. No single feature or group of features is necessary or indispensable for each embodiment.

[0400] It will be understood that, unless otherwise expressly stated or otherwise understood in context, conditional language used herein, such as "can", "might", "may", "for example", etc., generally is intended to convey that certain embodiments include certain features, elements, and / or steps, while other embodiments do not include such features, elements, and / or steps. Thus, such conditional language generally is not intended to imply that the features, elements, and / or steps are necessary to one or more embodiments in any way, or that one or more embodiments necessarily include logic for determining whether such features, elements, and / or steps are included or are to be performed in any particular embodiment (whether the author inputs or suggests such). The terms "comprising", "including", "having", etc. are synonyms and are used inclusively in an open-ended manner and do not exclude additional elements, features, acts, operations, etc. Further, the term "or" is used in an inclusive sense (and not an exclusive sense), so that when, for example, used to connect a list of elements, the term "or" means one, some, or all of the elements in the list. Additionally, unless otherwise specified, 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". Similarly, although operations may be depicted in a particular order in the figures, it should be recognized that such operations need not be performed in the particular order shown or sequentially, and all the illustrated operations need not be performed to achieve the desired result. Further, the figures may schematically depict one or more example processes in the form of a flowchart. However, other operations not depicted may be incorporated into the example methods and processes schematically shown. For example, one or more additional operations may be performed before, after, simultaneously with, or between any of the illustrated operations. Additionally, in other embodiments, the operations may be rearranged or reordered. In some cases, multitasking and parallel processing may be advantageous. Further, the separation of various system components in the above embodiments should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems generally may be integrated together in a single software product or packaged into multiple software products. Additionally, other embodiments are within the scope of the following claims. In some cases, the acts recited in the claims may be performed in a different order and still achieve the desired result.

[0401] Although the present disclosure contains many specific example details, these details should not be construed as limitations on the scope of the subject matter or the scope of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments. Certain features described in the context of separate embodiments in the present disclosure may also be implemented in combination in a single embodiment. Conversely, the various features described in the context of a single embodiment may also be implemented separately in multiple embodiments, or in any suitable sub-combination. Additionally, although the previously described features may be described as acting in certain combinations and even initially claimed as such, in some cases, one or more features from the claimed combination may be excluded from the combination, and the claimed combination may be directed to a sub-combination or a variation of a sub-combination.

[0402] Specific embodiments of the subject matter have been described. It will be apparent to those skilled in the art that other embodiments, changes, and permutations of the described embodiments are within the scope of the following claims. Although the operations are described in a specific order in the figures or the claims, this should not be construed as requiring that the operations be performed in the specific order or sequence shown, or that all illustrated operations (some operations may be regarded as optional) be performed, to achieve the desired result.

[0403] Accordingly, the example embodiments described above do not define or limit the present disclosure. Other changes, substitutions, and alterations can be made without departing from the spirit and scope of the present disclosure.

[0404] Accordingly, the claims are not intended to be limited to the embodiments shown herein, but rather to the broadest scope consistent with the present disclosure, the principles disclosed herein, and the novel features.

[0405] The examples and embodiments described herein are for illustrative purposes only. It will be clear to those skilled in the art to make various modifications or changes therefrom. Such modifications or changes should be included within the spirit and scope of this application and the scope of the appended claims that follow.

Claims

1. An augmented reality system, comprising: a projector; projection optics coupled to the projector; and an eyepiece waveguide including a hybrid diffraction structure, comprising: one or more first nano-features having a first material with a first refractive index; and one or more second nano-features having a second material with a second refractive index.

2. The augmented reality system according to claim 1, wherein the eyepiece waveguide further comprises: a substrate and an input coupling diffraction structure coupled to the substrate.

3. The eyepiece waveguide according to claim 2, wherein the eyepiece waveguide further comprises an output coupling diffraction structure, and the hybrid diffraction structure is part of the output coupling diffraction structure.

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

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

6. The eyepiece waveguide according to claim 1, wherein the eyepiece waveguide further comprises a substrate, wherein the one or more first nano-features comprise the first material coupled to the substrate; and the one or more second nano-features comprise a portion of the substrate extending from the substrate.

7. The eyepiece waveguide according to claim 6, wherein the one or more second nano-features further comprise the first material coupled to the portion of the substrate.

8. The eyepiece waveguide according to claim 1, wherein the eyepiece waveguide further comprises a substrate, and the one or more first nano-features are close to the input coupling diffraction structure coupled to the substrate, and the one or more second nano-features are far from the input coupling diffraction structure.

9. The eyepiece waveguide according to claim 1, wherein the one or more first nano-features or the one or more second nano-features are separated by gaps between adjacent nano-features, and the eyepiece waveguide further comprises a planarizing material filling the gaps.

10. The eyepiece waveguide according to claim 9, wherein the planarizing material encapsulates the one or more first nano-features or the one or more second nano-features.

11. An eyepiece waveguide, comprising: a substrate operable to support the propagation of light; an input coupling diffraction structure coupled to the substrate; and an output coupling diffraction structure coupled to the substrate, wherein the output coupling diffraction structure comprises one or more first nano-features having a first material with a first refractive index and one or more second nano-features having a second material with a second refractive index.

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

13. The eyepiece waveguide according to claim 12, wherein the first refractive index is less than the second refractive index.

14. The eyepiece waveguide according to claim 12, wherein the one or more first nano-features comprise the first material coupled to the substrate; and the one or more second nano-features comprise a portion of the substrate extending from the substrate.

15. The eyepiece waveguide according to claim 14, wherein The one or more second nano-features also include the first material coupled to the portion of the substrate.

16. The eyepiece waveguide according to claim 11, wherein, the one or more first nano-features are close to the light-coupling diffraction structure, and the one or more second nano-features are away from the light-coupling diffraction structure.

17. The eyepiece waveguide according to claim 11, wherein, the one or more first nano-features are located in a first region close to the light-coupling diffraction structure; the one or more second nano-features are located in a second region away from the light-coupling diffraction structure; and the eyepiece waveguide further includes a transition region disposed between the first region and the second region.

18. The eyepiece waveguide according to claim 17, wherein, the transition region includes transition nano-features having a transition material with a refractive index between the first refractive index and the second refractive index.

19. The eyepiece waveguide according to claim 17, wherein, the light-coupling diffraction structure has a first width measured parallel to the substrate, and the transition region has a second width measured parallel to the substrate and greater than the first width.

20. The eyepiece waveguide according to claim 11, wherein, the one or more first nano-features or the one or more second nano-features are separated by gaps between adjacent nano-features, and the eyepiece waveguide further includes a planarizing material filling the gaps.

21. The eyepiece waveguide according to claim 20, wherein, the planarizing material encapsulates the light-extracting diffraction structure.

22. A hybrid surface-relief waveguide structure, comprising: a substrate; and a diffraction structure coupled to the substrate and including a plurality of diffraction nano-features, wherein each of the plurality of diffraction nano-features is characterized by a change in refractive index.

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

24. The hybrid surface-relief waveguide structure according to claim 22, wherein, the change in refractive index includes a first material having a first refractive index close to the substrate and a second material having a second refractive index less than the first refractive index away from the substrate.

25. The hybrid surface-relief waveguide structure according to claim 22, wherein, the diffraction structure includes first nano-features, and the first nano-features include a first material coupled to the substrate.

26. The hybrid surface-relief waveguide structure according to claim 25, wherein, the diffraction structure includes a portion of the substrate and the first material is coupled to the portion of the substrate.

27. The hybrid surface-relief waveguide structure according to claim 26, wherein, the diffraction structure includes a light-extracting diffraction structure, and the light-extracting diffraction structure includes third nano-features formed by a second portion of the substrate.

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

29. The hybrid surface relief waveguide structure according to claim 27, wherein, the first nano feature is composed of the first material, and the third nano feature is composed of the second material.

30. The hybrid surface relief waveguide structure according to claim 22, further comprising: a film disposed between the substrate and the diffraction structure.

31. The hybrid surface relief waveguide structure according to claim 30, wherein, the substrate includes a pattern, and the film is coupled to the pattern.

32. An eyepiece waveguide, comprising: a substrate operable to support the propagation of light; an input diffraction structure coupled to the substrate; and an output diffraction structure coupled to the substrate, wherein the output diffraction structure includes a first nano feature and a second nano feature, the first nano feature includes a first material having a first refractive index, and the second nano feature includes the first material and a second material having a second refractive index.

33. The eyepiece waveguide according to claim 32, wherein, the first nano feature includes the first material coupled to the substrate.

34. The eyepiece waveguide according to claim 32, wherein, the second material includes a portion of the substrate, and the first material is coupled to the portion of the substrate.

35. The eyepiece waveguide according to claim 34, wherein, the output diffraction structure further includes a third nano feature formed from a second portion of the substrate.

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

37. The eyepiece waveguide according to claim 35, wherein, the first nano feature is composed of the first material, and the third nano feature is composed of the second material.

38. The eyepiece waveguide according to claim 32, wherein, the eyepiece waveguide includes a film disposed between the substrate and the output diffraction structure.

39. The eyepiece waveguide according to claim 38, wherein, the substrate includes a pattern, and the film is coupled to the pattern.

40. The eyepiece waveguide according to claim 38, wherein, the film includes a pattern.

41. The eyepiece waveguide according to claim 32, wherein, at least one of the first nano feature or the second nano feature includes: a square ridge, a blazed, a sawtooth, a tilt, or a multi-step structure.

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

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

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

45. The eyepiece waveguide according to claim 32, Among them, the substrate has a refractive index between 1.45 and 2.

65.

46. The eyepiece waveguide according to claim 45, wherein, The substrate includes glass or fused quartz containing La, Na, TiO 2 , ZrO 2 , Li or Nb.

47. The eyepiece waveguide according to claim 45, wherein, The substrate includes LiTaO 3 , LiNbO 3 , or SiC.

48. The eyepiece waveguide according to claim 47, wherein, the substrate is a crystal.

49. The eyepiece waveguide according to claim 32, wherein, the first material has a refractive index between 1.31 and 2.

65.

50. The eyepiece waveguide according to claim 32, further comprising an antireflection structure coupled to the substrate, wherein, the antireflection structure has a refractive index between 1.31 and 1.

75.

51. The eyepiece waveguide according to claim 50, wherein, the antireflection structure includes a sub-wavelength diffraction structure.

52. The eyepiece waveguide according to claim 50, wherein, the antireflection structure is located on the substrate opposite to the input diffraction structure.

53. The eyepiece waveguide according to claim 50, wherein, the antireflection structure is located on the substrate at a position not overlapping with the output diffraction structure.

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

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