Display device with diffraction grating having reduced polarization sensitivity

Abstract

To provide a display device with a diffraction grating having reduced polarization sensitivity. [Solution] The diffraction grating provides an optical element within a head-mounted display system for, for example, internally coupling light into a waveguide or externally coupling light out of it. These diffraction gratings may be configured to have reduced polarization sensitivity. Such gratings can internally or externally couple light of different polarizations with similar levels of efficiency. The diffraction grating and waveguide may include a transmissive layer and a metallic layer. The diffraction grating may include a blazed grating.

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This application claims the benefit of priority under 35 U.S.C. § 119(e) (Title 35, United States Code, Section 119(e)) to U.S. Provisional Application No. 62 / 899,063, filed on September 11, 2019, entitled "DISPLAY DEVICE WITH DIFFRACTION GRATING HAVING REDUCED POLARIZATION SENSITIVITY"; U.S. Provisional Application No. 62 / 899,673, filed on September 12, 2019, entitled "DISPLAY DEVICE WITH DIFFRACTION GRATING HAVING REDUCED POLARIZATION SENSITIVITY"; and U.S. Provisional Application No. 62 / 902,295, filed on September 18, 2019, entitled "DISPLAY DEVICE WITH DIFFRACTION GRATING HAVING REDUCED POLARIZATION SENSITIVITY", each of which is incorporated herein by reference in its entirety.

[0002] (Field) The present disclosure relates to display systems, and more particularly to augmented and virtual reality display systems.

Background Art

[0003] (Background) (Description of Related Art) Modern computing and display technologies are driving the development of systems for so-called "virtual reality" or "augmented reality" experiences, where digitally reproduced images or parts thereof are presented to the user in a manner that appears, or can be perceived, as real. Virtual reality, or "VR," scenarios typically involve the presentation of digital or virtual imagery without transparency to other real-world visual inputs, while augmented reality, or "AR," scenarios typically involve the presentation of digital or virtual imagery as an extension of the user's visualization of the real world around them. Mixed reality, or "MR," scenarios, are a type of AR scenario that typically involves virtual objects integrated into and responding to the natural world. For example, in an MR scenario, AR imagery may be perceived as being obscured by, or interacting with, objects in the real world in a different way.

[0004] Referring to Figure 1, an augmented reality scene 10 is depicted, and the user of AR technology sees a real-world park-like setting 20 featuring people, trees, buildings in the background, and a concrete platform 30. In addition to these items, the user of AR technology also perceives "virtual content" such as a robot figure 40 standing on the real-world platform 30 and a flying cartoon-like avatar character 50 that looks like an anthropomorphic bumblebee, although these elements 40 and 50 do not exist in the real world. The human visual perception system is complex, and it is difficult to produce AR technology that facilitates a comfortable, natural, and rich presentation of virtual image elements among other virtual or real-world image elements.

[0005] The systems and methods disclosed herein address various challenges related to AR and VR technologies. [Overview of the project] [Means for solving the problem]

[0006] (summary) For the purpose of summarizing this disclosure, certain aspects, advantages, and novel features are described herein. It should be understood that not all such advantages can necessarily be achieved according to any particular embodiment disclosed herein. Thus, embodiments disclosed herein can be embodied or practiced in a manner that achieves or optimizes one advantage or group of advantages taught or proposed herein without necessarily achieving others.

[0007] Disclosed herein are head-mounted display systems. In one configuration, the head-mounted display system may include a head-mountable frame, a light projection system, a waveguide supported by the frame, a diffraction grating, a first layer extending over the diffraction grating, and a second layer, including a metal, positioned over the first layer. The light projection system may be configured to emit light and provide image content. The waveguide may include a substrate configured to guide at least a portion of the light from the light projection system into the waveguide. The diffraction grating may include a different material from the substrate extending over the substrate. The diffraction grating may have a first diffraction efficiency for a first polarization over a range of angles of light incident thereon, and may also have a second diffraction efficiency for a second polarization over that range of angles of light incident thereon, where the first diffraction efficiency is 1 to 2 times that of the second diffraction efficiency.

[0008] In an alternative configuration, a head-mounted display system may include a head-mountable frame, a light projection system, a waveguide supported by the frame, a diffraction grating formed in a substrate, a first layer positioned across the diffraction grating formed in the substrate, and a second layer, including a metal, positioned across the diffraction grating formed in the substrate. The light projection system may be configured to emit light and provide image content. The waveguide may include a substrate. The substrate may be made of an optically transparent material. The substrate may be configured to guide at least a portion of the light from the light projection system into the waveguide via the diffraction grating. The diffraction grating may have a first diffraction efficiency for a first polarization over a range of angles of light incident on it, and may also have a second diffraction efficiency for a second polarization over that range of angles of light incident on it, where the first diffraction efficiency is 1 to 2 times that of the second diffraction efficiency.

[0009] In some configurations, a head-mounted display system may include a head-mountable frame, a light projection system configured to emit light and provide image content, a waveguide supported by the frame, which may include a substrate configured to guide at least a portion of the light from the light projection system into the waveguide, a first diffraction grating extending across the substrate, which may include a material different from the substrate, a first layer positioned across the first diffraction grating, and a second layer positioned across the first diffraction grating, which may include a metal, such that the diffraction grating has a first diffraction efficiency for a first polarization over a range of angles of light incident thereon, and a second diffraction efficiency for a second polarization over the same range of angles of light incident thereon, with the first diffraction efficiency being 1 to 2 times that of the second diffraction efficiency.

[0010] In some configurations, a head-mounted display system may include a head-mountable frame, a light projection system configured to emit light and provide image content, and a waveguide supported by the frame, the waveguide may include a substrate which may contain an optically transparent material and a first diffraction grating formed within the substrate, the substrate having a first layer positioned over the first diffraction grating formed within the substrate, and a second layer which may contain a metal, positioned over the first diffraction grating formed within the substrate, such that the first diffraction grating has a first diffraction efficiency for a first polarization over a range of angles of light incident thereon and a second diffraction efficiency for a second polarization over that range of angles of light incident thereon, and the first diffraction efficiency is 1 to 2 times that of the second diffraction efficiency.

[0011] In some configurations, a head-mounted display system includes a head-mountable frame, a light projection system configured to emit light and provide image content, a waveguide supported by the frame, which may include a substrate configured to guide at least a portion of the light from the light projection system into the waveguide, a first diffraction grating which may include a material different from the substrate, and the first diffraction grating having a first diffraction efficiency for a first polarization over a range of angles of light incident on it, which exceeds a second diffraction efficiency for a second polarization over a range of angles of light incident on it. The diffraction grating may include a first layer and a second layer positioned across the first diffraction grating such that the first diffraction grating has a third diffraction efficiency for a second polarization of light incident on it over a range of angles, exceeding a fourth diffraction efficiency for a first polarization over a range of angles of light incident on it, and the combined diffraction efficiency of the first diffraction grating and the first and second layers is configured to provide a fifth diffraction efficiency for a first polarization over that range of angles of light incident on it, and a sixth diffraction efficiency for a second polarization over that range of angles of light incident on it, where the fifth diffraction efficiency is 1 to 2 times that of the sixth diffraction efficiency.

[0012] In some configurations, a head-mounted display system comprises a head-mountable frame, a light projection system configured to emit light and provide image content, and a waveguide supported by the frame, the waveguide may include a substrate which may contain an optically transparent material, and a first diffraction grating formed within the substrate, the substrate which is configured to guide at least a portion of the light from the light projection system into the waveguide, and a first layer positioned over the first diffraction grating formed within the substrate which, together with the first diffraction grating, exceeds a second diffraction efficiency for a second polarization over a range of angles of light incident on it. The first diffraction grating may include a first layer configured to provide a first diffraction efficiency, and a second layer positioned across the first diffraction grating formed within the substrate, configured to provide a third diffraction efficiency for a second polarization of light incident on it, exceeding a fourth diffraction efficiency for a first polarization over a range of angles of light incident on it, together with the first diffraction grating, wherein the first diffraction grating, together with the first and second layers, is configured to provide a fifth diffraction efficiency for a first polarization over a range of angles of light incident on it, and a sixth diffraction efficiency for a second polarization over that range of angles of light incident on it, the fifth diffraction efficiency being 1 to 2 times that of the sixth diffraction efficiency.

[0013] In some configurations, a head-mounted display system may include a head-mountable frame, a light projection system configured to emit light and provide image content, a waveguide supported by the frame, which may include a substrate configured to guide at least a portion of the light from the light projection system into the waveguide, a first diffraction grating extending across the substrate, which may include a material different from the substrate, and a first layer, which may include a multilayer coating, disposed across the first diffraction grating, wherein the first diffraction grating, together with the first layer, has a first diffraction efficiency for a first polarization over a range of angles of light incident thereon that exceeds a second diffraction efficiency for a second polarization over a range of angles of light incident thereon.

[0014] In some configurations, a head-mounted display system may include a head-mountable frame, a light projection system configured to emit light and provide image content, a waveguide supported by the frame, which may include a substrate configured to guide at least a portion of the light from the light projection system into the waveguide, and a first diffraction grating configured to have a first diffraction efficiency for a first polarization over a range of angles of light incident thereon, which is greater than a second diffraction efficiency for a second polarization over a range of angles of light incident thereon.

[0015] In some configurations, a head-mounted display system may include a head-mountable frame, a light projection system configured to emit light and provide image content, a waveguide supported by the frame, which may include a substrate configured to guide at least a portion of the light from the light projection system into the waveguide, and a first diffraction grating extending across the substrate, which may include a material different from the substrate, the substrate may include a material having a first refractive index, a first layer distributed across the first diffraction grating, which may include a material having a second refractive index, and a material distributed across the first layer having a third refractive index between the second refractive index and the refractive index of air, the first diffraction grating being configured, together with the first layer and the material extending across the first layer, to have a first diffraction efficiency for a first polarization over a range of angles of light incident thereon, which exceeds a second diffraction efficiency for a second polarization over a range of angles of light incident thereon.

[0016] In some configurations, a head-mounted display system may include a head-mountable frame, a light projection system configured to emit light and provide image content, a waveguide supported by the frame, which may include a substrate configured to guide at least a portion of the light from the light projection system into the waveguide, a first diffraction grating, and a first layer arranged across the first diffraction grating such that the diffraction grating has a first diffraction efficiency for a first polarization over a range of angles, which is 1 to 2 times a second diffraction efficiency for a second polarization over a range of angles of light incident thereon.

[0017] A method for fabricating a diffraction grating with reduced polarization sensitivity, the method comprising the steps of: forming one or more diffraction features in or on a substrate, configured to guide at least a portion of light from a light projection system into the substrate; depositing a first layer over the one or more diffraction features; and depositing a second layer over the one or more diffraction features such that the one or more diffraction features have a first diffraction efficiency for a first polarization over a range of angles of light incident thereon, and a second diffraction efficiency for a second polarization over the same range of angles of light incident thereon, and the first diffraction efficiency is 1 to 2 times that of the second diffraction efficiency.

[0018] In some configurations, a head-mounted display system may include a head-mountable frame, a light projection system configured to emit light and provide image content, a waveguide supported by the frame, which may include a substrate configured to guide at least a portion of the light from the light projection system into the waveguide, and a first diffraction grating configured to have a first diffraction efficiency for a first polarization over a range of angles of light incident thereon, which is 1 to 2 times a second diffraction efficiency for a second polarization over a range of angles of light incident thereon.

[0019] In some configurations, a head-mounted display system may include a head-mountable frame, a light projection system configured to emit light and provide image content, and a waveguide supported by the frame, the waveguide may include a substrate configured to guide at least a portion of the light from the light projection system into the waveguide, the substrate having a refractive index of less than 1.9, and a first diffraction grating configured to have a first diffraction efficiency for a first polarization over a range of angles of light incident thereon, which is 1 to 2 times a second diffraction efficiency for a second polarization over a range of angles of light incident thereon. The present invention provides, for example, the following. (Item 1) A head-mounted display system comprising: A head-mountable frame; An optical projection system configured to output light and provide image content; An optical waveguide supported by the frame, the optical waveguide comprising a substrate configured to guide at least a portion of the light from the optical projection system to be coupled into the optical waveguide; A first diffraction grating including a material different from the substrate across the substrate; A first layer disposed across the first diffraction grating; A second layer, the second layer being such that the diffraction grating has a first diffraction efficiency for a first polarization over a certain range of angles of light incident thereon, and has a second diffraction efficiency for a second polarization over the certain range of angles of light incident thereon, and the first diffraction efficiency is 1 to 2 times the second diffraction efficiency, the second layer including a metal disposed across the first diffraction grating; A head-mounted display system comprising the above. (Item 2) The head-mounted display system according to item 1, wherein the substrate includes a material having a refractive index of at least 1.9. (Item 3) The head-mounted display system according to item 1, wherein the first diffraction grating material includes a polymer. (Item 4) The head-mounted display system according to item 1, wherein the first diffraction grating material includes an imprintable material. (Item 5) The head-mounted display system according to item 1, wherein the first diffraction grating material has a refractive index of 1.4 to 1.95. (Item 6) The head-mounted display system according to item 1, wherein the first diffraction grating material has a refractive index lower than that of the substrate. (Item 7) The head-mounted display system according to item 1, wherein the first diffraction grating comprises a blazed diffraction grating. (Item 8) The head-mounted display system according to item 1, wherein the first layer comprises titanium dioxide (TiO2), zirconium dioxide (ZrO2), or silicon carbide (SiC). (Item 9) The head-mounted display system according to item 1, wherein the first and second polarizations each comprise transverse magnetic and transverse electropolarization, respectively. (Item 10) The head-mounted display system according to item 1, wherein the first and second polarizations each comprise transverse electric and transverse magnetic polarizations, respectively. (Item 11) The head-mounted display system according to item 1, wherein the first diffraction efficiency is 1 to 1.5 times that of the second diffraction efficiency. (Item 12) The head-mounted display system according to item 11, wherein the first diffraction efficiency is 1 to 1.3 times that of the second diffraction efficiency. (Item 13) The head-mounted display system according to item 12, wherein the first diffraction efficiency is 1 to 1.2 times the second diffraction efficiency. (Item 14) The head-mounted display system according to item 1, wherein the range of the angle is at least 12 degrees. (Item 15) The head-mounted display system according to item 14, wherein the range of the angle is at least 22 degrees. (Item 16) The head-mounted display system according to item 1, wherein the range of the angle is between ±6 degrees with respect to the plane of the substrate. (Item 17) The head-mounted display system according to item 16, wherein the range of the angle is between ±11 degrees with respect to the plane of the substrate. (Item 18) The head-mounted display system according to item 1, wherein the waveguide is contained within an eyepiece configured to direct light towards the eye of a user wearing the head-mounted display. (Item 19) A head-mounted display system, A frame that can be mounted on the head, A light projection system configured to output light and provide image content, A waveguide supported by the frame, wherein the waveguide comprises a substrate configured to guide at least a portion of the light from the light projection system into the waveguide, The first diffraction grating and A first layer, the first layer being arranged across the first diffraction grating such that the diffraction grating has a first diffraction efficiency for the first polarization of light incident on it, which is 1 to 2 times the second diffraction efficiency for the second polarization over a certain range of angles of light incident on it. A head-mounted display system equipped with the following features. (Item 20) The head-mounted display system according to item 19, wherein the first diffraction grating on which the first layer is formed comprises a transmissive diffraction grating. [Brief explanation of the drawing]

[0020] Throughout the drawings, reference numbers are reused to indicate correspondences between referenced elements. The drawings are provided to illustrate, and not limit, embodiments of the features described herein.

[0021] [Figure 1] Figure 1 illustrates the user's view of augmented reality (AR) through an AR device.

[0022] [Figure 2] Figure 2 illustrates a conventional display system for simulating a three-dimensional image for the user.

[0023] [Figure 3] Figures 3A-3C illustrate the relationship between the radius of curvature and the radius of focus.

[0024] [Figure 4A] Figure 4A illustrates the representation of the accommodation-convergence-divergence motion response of the human visual system.

[0025] [Figure 4B] Figure 4B illustrates examples of different near and far accommodative states and convergence / divergence motion states of a user's pair of eyes.

[0026] [Figure 4C] Figure 4C illustrates an example of how the upper and lower figures represent a user viewing content through a display system.

[0027] [Figure 4D] Figure 4D illustrates another embodiment of the representation of the upper and lower figures of a user viewing content through a display system.

[0028] [Figure 5] Figure 5 illustrates aspects of an approach to simulating a 3D image by correcting wavefront divergence.

[0029] [Figure 6] Figure 6 illustrates an example of a waveguide stack for outputting image information to the user.

[0030] [Figure 7] Figure 7 illustrates an example of an output beam produced by a waveguide.

[0031] [Figure 8] Figure 8 illustrates an embodiment of a stacked waveguide assembly in which each depth plane includes an image formed using multiple different primary colors.

[0032] [Figure 9A] Figure 9A shows a cross-sectional side view of an embodiment of a stacked waveguide set, each including an internally coupled optical element.

[0033] [Figure 9B] Figure 9B shows a perspective view of an embodiment of the multiple stacked waveguides shown in Figure 9A.

[0034] [Figure 9C] Figure 9C shows top and bottom plan views of the embodiment of the multiple stacked waveguides shown in Figures 9A and 9B.

[0035] [Figure 9D] Figure 9D illustrates an embodiment of a wearable display system.

[0036] [Figure 10] Figures 10A and 10B illustrate the polarization dependence of two exemplary diffraction gratings.

[0037] [Figure 11A] Figure 11A illustrates an exemplary lattice with a single coating, which may have high efficiency for single polarization.

[0038] [Figure 11B] Figure 11B illustrates an exemplary lattice with multiple coatings, which may have high efficiency for more than one polarization.

[0039] [Figure 12A] Figure 12A schematically illustrates a cross-sectional view of a portion of a waveguide, for example, which has a diffraction grating placed on it for internal coupling of light into the waveguide.

[0040] [Figure 12B] Figure 12B shows a cross-sectional view of a waveguide with a blazed diffraction grating positioned above it, indicating the waveguide's field of view (FOV) Δα.

[0041] [Figure 13A] Figure 13A illustrates different exemplary geometric shapes for diffraction features that may be used to form diffraction gratings.

[0042] [Figure 13B] Figures 13B-1 and 13B-2 illustrate a one-dimensional (1D) grid.

[0043] [Figure 13C] Figure 13C illustrates an exemplary device having a two-dimensional (2D) array of diffraction features.

[0044] [Figure 13D] Figures 13D-1 and 13D-2 show a cross-sectional side view and a top view of an exemplary 2D array of symmetric diffraction features, respectively.

[0045] [Figure 13E] Figure 13E shows another exemplary device having a 2D array of diffractive features that are blazed.

[0046] [Figure 13F] Figures 13F-1 and 13F-2 show a cross-sectional side view and a top view of an exemplary array of asymmetric diffraction features, respectively.

[0047] [Figure 13G-1] Figure 13G-1 shows an exemplary device having a 2D array of diffraction features formed in or on a substrate and blazed in two directions.

[0048] [Figure 13G-2] Figure 13G-2 shows exemplary diffraction features that direct more light in two specific directions.

[0049] [Figure 13H] Figure 13H shows an exemplary method for forming a blazed grid.

[0050] [Figure 13I] Figure 13I shows another exemplary method for forming a blazed lattice.

[0051] [Figure 13J] Figure 13J shows another exemplary method for forming a blazed lattice.

[0052] [Figure 14] Figure 14 illustrates an exemplary method for depositing a layer of material onto the diffraction features of a diffractive optical element. This layer may be an optically transparent layer in various implementations.

[0053] [Figure 15] Figure 15 illustrates exemplary diffraction features within a transmissive layer comprising multiple sublayers, and the corresponding graphs of reflections from the surface of diffractive optical elements formed from such exemplary diffraction features.

[0054] [Figure 16] Figure 16 illustrates an exemplary method for depositing layers of materials such as dielectric and metal layers onto multiple diffraction features that form diffractive optical elements such as diffraction gratings.

[0055] [Figure 17A] Figure 17A illustrates an exemplary waveguide that includes multiple diffractive optical elements, such as diffraction gratings, that form an internal coupling optical element and an external coupling optical element. At least one of the diffractive optical elements, for example, the internal coupling optical element, may include a reduced polarization sensitivity diffraction grating.

[0056] [Figure 17B] Figure 17B illustrates another exemplary waveguide, which includes multiple diffractive optical elements, such as diffraction gratings, that form an internal coupling optical element and / or an external coupling optical element. The diffractive optical elements, for example, the internal coupling optical element, may include a diffraction grating that couples more TE-polarized light into the waveguide than TM-polarized light, and a diffraction grating that couples more TM-polarized light into the waveguide than TE-polarized light.

[0057] [Figure 17C] Figure 17C illustrates another exemplary waveguide that includes diffractive optical elements, such as a diffraction grating, which form an internal coupling optical element that couples both the TE and TM within the waveguide with high efficiency.

[0058] [Figure 17D] Figures 17D-1-17D-4 illustrate different diffractive optical element designs that can be used as internally coupled optical elements, for example, as shown in Figure 17C, along with TM and TE efficiency profiles for each individual different diffractive optical element.

[0059] [Figure 18] Figure 18 illustrates exemplary diffraction features that can reduce reflection loss. [Modes for carrying out the invention]

[0060] (Detailed explanation) While some preferred embodiments and examples are disclosed below, the subject matter of the present invention extends beyond the specifically disclosed embodiments to other alternative embodiments and / or uses and modifications and equivalents of the present invention. Therefore, the scope of the present invention disclosed herein is not limited to any of the specific embodiments described below. For example, in any method or process disclosed herein, the actions or operations of the method or process may be carried out in any preferred sequence, and are not necessarily limited to any specific disclosed sequence. For the purpose of comparing various embodiments with the prior art, certain aspects and advantages of these embodiments are described. Not all such aspects or advantages are necessarily achieved by any specific embodiment. Therefore, for example, various embodiments may be carried out in a manner that achieves or optimizes one advantage or group of advantages taught herein, without necessarily achieving other aspects or advantages that may similarly be taught or proposed herein.

[0061] AR systems can still display virtual content to a user or viewer while allowing the user to see the world around them. Preferably, this content is displayed on a head-mounted display, for example, as part of eyewear that projects image information onto the user's eyes. In addition, the display may also transmit light from the surrounding environment to the user's eyes, enabling a view of that environment. As used herein, “head-mounted” or “head-mountable” display should be understood as a display that can be mounted on the head of a viewer or user.

[0062] In some AR systems, virtual / enhanced / composite displays with a relatively wide field of view (FOV) can improve the viewing experience. The FOV of a display depends on the angle of light output by the eyepiece waveguide through which the viewer sees the projected image in their eyes. For example, a waveguide with a relatively high refractive index of 2.0 or above can provide a relatively high FOV. However, in order to efficiently couple light into the high refractive index waveguide, the diffractive optical coupling element should also have a correspondingly high refractive index. Among the advantages, to achieve this goal, some displays for AR systems according to embodiments described herein include waveguides made of a relatively high refractive index (e.g., above or equal to 2.0) material, having a separate diffraction grating formed thereon, with a correspondingly high refractive index, such as a Li-based oxide. For example, the diffraction grating may be formed directly on a Li-based oxide waveguide by patterning a surface portion of the waveguide formed from the Li-based oxide.

[0063] Some high refractive index diffractive optical coupling elements, such as internal or external coupling optical elements, exhibit strong polarization dependence. For example, an internal coupling grating (ICG) for internally coupling light into a waveguide, in which the diffractive optical coupling element contains a high refractive index material, can accept significantly more light of a given polarization than light of another polarization. Such an element can internally couple light with TM polarization into a waveguide, for example, with about three times the rate of light with TE polarization. Diffractive optical coupling elements with this type of polarization dependence may have reduced efficiency (due to poor efficiency and general blocking of one polarization) and may create coherent artifacts, reducing the uniformity of the far-field image formed by light coupled out of the waveguide. To obtain a diffractive optical coupling element that is insensitive to polarization, or at least has reduced polarization sensitivity (e.g., coupling light with some efficiency relatively independent of polarization), some displays for AR systems in various implementations described herein include a waveguide with a diffraction grating formed using a blazed geometric shape. Diffraction gratings may also be formed directly within a waveguide, which may contain high refractive index materials (e.g., having refractive indices of at least 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, or up to 2.7 or any range between these values). Diffraction gratings may also be formed within high refractive index materials such as lithium niobate (LiNbO3) or lithium tantalate (LiTaO3), or high refractive index materials such as zirconium oxide (ZrO2), titanium dioxide (TiO2), or silicon carbide (SiC), for example, by patterning the high refractive index material using blazed geometry.

[0064] Here, similar reference numbers will refer to the same parts throughout the document. Unless otherwise indicated, the drawings are schematic and not necessarily drawn to exact scale.

[0065] Figure 2 illustrates a conventional display system for simulating a three-dimensional image for a user. It should be understood that when a user's eyes are spaced apart and viewing a real object in space, each eye may have a slightly different view of the object and may form an image of the object in different locations on the retina of each eye. This may be called binocular parallax and can be used by the human visual system to provide a sense of depth. Conventional display systems simulate binocular parallax by presenting two distinctly different images 190, 200, one for each eye 210, 220, with slightly different views of the same virtual object, corresponding to the view of the virtual object that each eye would see as a real object at a desired depth. These images provide binocular cues that the user's visual system can interpret to derive a sense of depth.

[0066] Continuing with Figure 2, images 190 and 200 are spaced 230 units away from eyes 210 and 220 on the z-axis. The z-axis is parallel to the viewer's optical axis when the eye is fixated on an object at optical infinity directly in front of the viewer. Images 190 and 200 are flat and at a fixed distance from eyes 210 and 220. Based on slightly different views of the virtual object in the images presented to eyes 210 and 220, the eyes may necessarily rotate so that the image of the object comes to the corresponding point on the respective retina of the eye, maintaining monobiocular vision. This rotation can converge the lines of sight of eyes 210 and 220 to a point in space where the virtual object is perceived to exist. As a result, the provision of three-dimensional images involves providing binocular cues that can conventionally manipulate the convergence and divergence movements of the user's eyes 210 and 220, which the human visual system interprets to provide depth perception.

[0067] However, generating a realistic and comfortable perception of depth is difficult. It should be understood that light from an object at different distances from the eye has wavefronts with different amounts of divergence. Figures 3A-3C illustrate the relationship between distance and ray divergence. The distances between the object and the eye 210 are expressed in the order of decreasing distances R1, R2, and R3. As shown in Figures 3A-3C, the rays diverge more as the distance to the object decreases. Conversely, as the distance increases, the rays become more collimated. In other words, the light field generated by a point (object or part of an object) can be said to have a spherical wavefront curvature, which is a function of the distance the point is from the user's eye. The curvature increases with decreasing distance between the object and the eye 210. Only a monocular eye 210 is illustrated in Figures 3A-3C and other figures herein for the sake of clarity in the illustration, but the discussion with respect to eye 210 can be applied to both eyes 210 and 220 of a viewer.

[0068] Continuing to refer to Figures 3A-3C, light from an object that the viewer's eye is fixated on may have different wavefront divergences. Due to the different wavefront divergences, the light may be focused differently by the eye's lens, which may require the lens to take on different shapes and form a focused image on the retina. If a focused image is not formed on the retina, the resulting retinal blur acts as a cue for accommodation, causing a change in the shape of the eye's lens until a focused image is formed on the retina. For example, the cue for accommodation induces relaxation or contraction of the ciliary muscle surrounding the eye's lens, thereby modulating the force applied to the suspensory ligament that holds the lens, and thus changing the shape of the eye's lens until the retinal blur of the fixed object is eliminated or minimized, thereby forming a focused image of the fixed object on the retina (e.g., the fovea). The process by which the lens of the eye changes shape can be called accommodation, and the shape of the lens required to form a focused image of the object being fixed on onto the retina of the eye (e.g., the fovea) can be called the accommodative state.

[0069] Referring here to Figure 4A, the representation of the accommodation-convergence-divergence response of the human visual system is illustrated. Eye movement to fixate on an object causes the eye to receive light from the object, and the light forms an image on each of the eye's retinas. The presence of retinal blur in the image formed on the retina can provide a cue for accommodation, and the relative location of the image on the retina can provide a cue for convergence-divergence movement. The cue for accommodation causes accommodation, prompting the lens of the eye to assume a specific accommodative state in which a focused image of the object is formed on the eye's retina (e.g., the fovea). On the other hand, the cue for convergence-divergence movement causes convergence-divergence movement (rotation of the eye) so that the image formed on each retina of each eye is at the corresponding retinal point that maintains monobiocular vision. At these positions, the eye can be said to be in a specific convergence-divergence state. Continuing to refer to Figure 4A, accommodation can be understood as the process by which the eye achieves a specific state of accommodation, and convergence / divergence can be understood as the process by which the eye achieves a specific state of convergence / divergence. As shown in Figure 4A, the state of accommodation and convergence / divergence of the eye can change when the user fixates on a different object. For example, the accommodated state can change when the user fixates on a new object at a different depth on the z-axis.

[0070] While not limited by theory, it is thought that viewers of objects may perceive them as "three-dimensional" due to a combination of convergence / divergence movements and accommodation. As described above, the convergence / divergence movements of two eyes relative to each other (for example, eye rotations such as pupils moving toward or away from each other, converging the lines of sight and fixing on an object) are closely related to the accommodation of the eye's lens. Under normal conditions, a change in the shape of the eye's lens to shift focus from one object to another at a different distance will automatically produce a corresponding change in convergence / divergence movements to the same distance, under a relationship known as the "accommodation-convergence / divergence reflex." Similarly, a change in convergence / divergence movements will, under normal conditions, induce a corresponding change in the shape of the lens.

[0071] Referring now to Figure 4B, embodiments of different accommodation and convergence / divergence states of the eyes are illustrated. A pair of eyes 222a fixate on an object at optical infinity, while a pair of eyes 222b fixate on an object 221 below optical infinity. It is noteworthy that the convergence / divergence states of each pair of eyes are different, with the pair of eyes 222a pointing straight ahead, while the pair of eyes 222 converges on the object 221. The accommodation states of the eyes forming each pair of eyes 222a and 222b are also different, as represented by the different shapes of the lenses 210a and 220a.

[0072] Unfortunately, many users of conventional "3-D" display systems find such systems uncomfortable or completely fail to perceive depth due to the mismatch between the accommodation and convergence / divergence states in these displays. As mentioned above, many stereoscopic or "3-D" display systems display scenes by providing slightly different images to each eye. Such systems are uncomfortable for many viewers because they, above all, simply provide different presentations of scenes and cause changes in the convergence / divergence states of the eyes, but without corresponding changes in the accommodation states of those eyes. Rather, the images are presented by the display at a fixed distance from the eyes so that the eyes perceive all image information in a single accommodation state. Such arrangements go against the "accommodation-convergence / divergence reflex" by causing changes in the convergence / divergence state without corresponding changes in the accommodation state. This mismatch is thought to cause discomfort to the viewer. A display system that provides a better match between distance accommodation and convergence / divergence motion can create a more realistic and comfortable simulation of three-dimensional images.

[0073] While not limited by theory, the human eye is typically thought to be capable of interpreting a finite number of depth planes and providing depth perception. Consequently, a highly realistic simulation of perceived depth can be achieved by providing the eye with different presentations of images corresponding to each of these limited number of depth planes. In some embodiments, the different presentations may provide both cues for convergence-divergence movements and matching cues for accommodation, thereby providing a physiologically correct accommodation-convergence-divergence movement match.

[0074] Continuing with Figure 4B, two depth planes 240 are illustrated, corresponding to different spatial distances from eyes 210 and 220. With respect to a given depth plane 240, convergence and divergence motion cues may be provided by displaying appropriately different viewpoint images for each eye 210 and 220. In addition, with respect to a given depth plane 240, the light forming the image provided to each eye 210 and 220 may have wavefront divergence corresponding to a light field generated by a point at a distance in that depth plane 240.

[0075] In the illustrated embodiment, the distance along the z-axis of the depth plane 240 containing point 221 is 1 m. As used herein, the distance along the z-axis, or depth, may be measured using a zero point located at the exit pupil of the user's eye. Thus, the depth plane 240 located at a depth of 1 m corresponds to a distance of 1 m from the exit pupil of the user's eye on the optical axis of those eyes, with the eyes pointed toward optical infinity. As an approximation, the depth or distance along the z-axis may be measured from the display in front of the user's eye (e.g., from the surface of the waveguide) and a value relating to the distance between the device and the exit pupil of the user's eye may be added. This value may be called the pupil distance and corresponds to the distance between the exit pupil of the user's eye and the user-worn display in front of the eye. In practice, the value relating to the pupil distance may generally be a normalized value used for all viewers. For example, the pupil distance may be assumed to be 20 mm, and the depth plane at a depth of 1 m may be at a distance of 980 mm from the front of the display.

[0076] Referring here to Figures 4C and 4D, embodiments of coincident accommodation-convergence-divergence distance and mismatched accommodation-convergence-divergence distance are illustrated, respectively. As shown in Figure 4C, the display system may provide images of virtual objects to each eye 210, 220. The images can cause the eyes 210, 220 to assume a convergence-divergence state in which the eyes converge on point 15 on the depth plane 240. In addition, the images may be formed by light having a wavefront curvature corresponding to the real object in its depth plane 240. As a result, the eyes 210, 220 assume an accommodation state in which the images are in focus on the retinas of their eyes. Thus, the user can perceive the virtual object as being at point 15 on the depth plane 240.

[0077] It should be understood that the accommodation and convergence / divergence movements of eyes 210 and 220 are each associated with a specific distance on the z-axis. For example, an object at a specific distance from eyes 210 and 220 will cause those eyes to adopt a specific accommodation state based on the distance of the object. The distance associated with a specific accommodation state is the accommodation distance A. d It can be called a specific convergence-divergence distance V associated with the eyes in a specific convergence-divergence movement state or relative position. d However, such a scenario exists. When the accommodation distance and the convergence / divergence distance match, the relationship between accommodation and convergence / divergence can be said to be physiologically correct. This is considered the most comfortable scenario for the viewer.

[0078] However, in stereoscopic displays, the accommodation distance and the convergence / divergence distance do not always coincide. For example, as illustrated in Figure 4D, the images displayed to eyes 210 and 220 may be displayed with wavefront divergence corresponding to the depth plane 240, and eyes 210 and 220 may take on a specific accommodation state in which points 15a and 15b on their depth plane are in focus. However, the images displayed to eyes 210 and 220 may provide cues for convergence / divergence movements that cause eyes 210 and 220 to converge on point 15, which is not located on the depth plane 240. As a result, in some embodiments, the accommodation distance corresponds to the distance from the exit pupils of eyes 210 and 220 to the depth plane 240, while the convergence / divergence distance corresponds to a larger distance from the exit pupils of eyes 210 and 220 to point 15. The accommodation distance is different from the convergence / divergence distance. As a result, there is a mismatch in accommodation-convergence / divergence motion. Such a mismatch is considered undesirable and can cause discomfort to the user. The mismatch is due to distance (e.g., V d -A d Please understand that this corresponds to and can be characterized using diopters.

[0079] It should be understood that in some embodiments, reference points other than the exit pupils of eyes 210, 220 may also be used to determine distances for determining the mismatch between accommodative and convergence / divergence movements, insofar as the same reference points are used for accommodative distance and convergence / divergence distance. For example, distances may be measured from the cornea to the depth plane, from the retina to the depth plane, from the eyepiece (e.g., the waveguide of a display device) to the depth plane, etc.

[0080] While not limited by theory, it is conceivable that users may still perceive physiologically correct accommodation-convergence / divergence mismatches of up to approximately 0.25 diopters, up to approximately 0.33 diopters, and up to approximately 0.5 diopters, without the mismatch itself causing significant discomfort. In some embodiments, the display systems disclosed herein (e.g., display system 250, Figure 6) present images to the viewer having accommodation-convergence / divergence mismatches of about 0.5 diopters or less. In some other embodiments, the accommodation-convergence / divergence mismatch of the images provided by the display system is about 0.33 diopters or less. In yet more embodiments, the accommodation-convergence / divergence mismatch of the images provided by the display system is about 0.25 diopters or less, including about 0.1 diopters or less.

[0081] Figure 5 illustrates an aspect of an approach to simulating a three-dimensional image by correcting wavefront divergence. The display system includes a waveguide 270 configured to receive light 770 encoded with image information and output that light to the user's eye 210. The waveguide 270 may output light 650 with a defined amount of wavefront divergence corresponding to the wavefront divergence of the light field generated by a point on a desired depth plane 240. In some embodiments, the same amount of wavefront divergence is provided for all objects presented on that depth plane. In addition, it will be illustrated that the user's other eye may be provided with image information from a similar waveguide.

[0082] In some embodiments, a single waveguide may be configured to output light with a set wavefront divergence corresponding to a single or limited number of depth planes, and / or the waveguide may be configured to output light with a limited range of wavelengths. As a result, in some embodiments, multiple or stacked waveguides may be used to provide different wavefront divergences for different depth planes, and / or to output light with different ranges of wavelengths. It should be understood that, as used herein, depth planes can follow the contours of flat or curved surfaces.

[0083] Figure 6 illustrates an embodiment of a waveguide stack for outputting image information to a user. The display system 250 includes a waveguide stack or stacked waveguide assembly 260, which may be used to provide three-dimensional perception to the eye / brain using a plurality of waveguides 270, 280, 290, 300, 310. It should be understood that the display system 250 may be considered a light field display in some embodiments. In addition, the waveguide assembly 260 may also be referred to as an eyepiece.

[0084] In some embodiments, the display system 250 may be configured to provide substantially continuous cues for convergence-divergence motion and a plurality of discrete cues for near accommodation. The cues for convergence-divergence motion may be provided by displaying different images to each of the user's eyes, and the cues for near accommodation may be provided by outputting light that forms an image with a selectable discrete amount of wavefront divergence. In other words, the display system 250 may be configured to output light with a variable level of wavefront divergence. In some embodiments, each discrete level of wavefront divergence may correspond to a specific depth plane and be provided by a specific waveguide among 270, 280, 290, 300, and 310.

[0085] Continuing with Figure 6, the waveguide assembly 260 may also include several features 320, 330, 340, and 350 between the waveguides. In some embodiments, features 320, 330, 340, and 350 may be one or more lenses. Waveguides 270, 280, 290, 300, and 310, and / or multiple lenses 320, 330, 340, and 350 may be configured to transmit image information to the eye using varying levels of wavefront curvature or ray divergence. Each waveguide level may be associated with a specific depth plane and may be configured to output image information corresponding to that depth plane. Image input devices 360, 370, 380, 390, and 400 may also function as light sources for the waveguides and may be used to input image information into waveguides 270, 280, 290, 300, and 310, each of which may be configured to disperse incident light across each individual waveguide for output toward the eye 210, as described herein. The light exits from the output surfaces 410, 420, 430, 440, and 450 of the image input devices 360, 370, 380, 390, and 400 and is input into the corresponding input surfaces 460, 470, 480, 490, and 500 of waveguides 270, 280, 290, 300, and 310. In some embodiments, the input surfaces 460, 470, 480, 490, and 500 may each be the edge of the corresponding waveguide or a portion of the main surface of the corresponding waveguide (i.e., one of the waveguide surfaces that directly faces the world 510 or the viewer's eye 210). In some embodiments, a single beam of light (e.g., a collimated beam) may be injected into each waveguide and output the entire field of cloned collimated beams that is directed toward the eye 210 at a specific angle (and divergence) corresponding to the depth plane associated with the particular waveguide. In some embodiments, one of the image input devices 360, 370, 380, 390, and 400 may be associated with a plurality (e.g., three) of waveguides 270, 280, 290, 300, and 310 and injected into them.

[0086] In some embodiments, the image input devices 360, 370, 380, 390, and 400 are discrete displays, each generating image information for input into the corresponding waveguides 270, 280, 290, 300, and 310, respectively. In some other embodiments, the image input devices 360, 370, 380, 390, and 400 are output terminals of a single multiplexed display, which can send image information to each of the image input devices 360, 370, 380, 390, and 400, for example, via one or more optical conduits (such as fiber optic cables). It should be understood that the image information provided by the image input devices 360, 370, 380, 390, and 400 may include light of different wavelengths or colors (e.g., different primary colors, as discussed herein).

[0087] In some embodiments, the light introduced into waveguides 270, 280, 290, 300, and 310 is provided by an optical projector system 520 comprising an optical module 530, which may include an optical emitter such as a light-emitting diode (LED). The light from the optical module 530 may be directed and modified via a beam splitter 550 to an optical modulator 540, for example, a spatial light modulator. The optical modulator 540 may be configured to change the perceived intensity of the light introduced into waveguides 270, 280, 290, 300, and 310, thereby encoding the light with image information. Embodiments of the spatial light modulator include liquid crystal displays (LCDs), including liquid crystal on silicon (LCOS) displays. Image input devices 360, 370, 380, 390, and 400 are graphically illustrated, and it should be understood that in some embodiments, these image input devices may represent different optical paths and locations within a common projection system, configured to output light into associated waveguides 270, 280, 290, 300, and 310. In some embodiments, the waveguides of waveguide assembly 260 may function as ideal lenses, relaying the light input into the waveguides to the user's eye. In this concept, the object may be a spatial light modulator 540, and the image may be an image on the depth plane.

[0088] In some embodiments, the display system 250 may be a scanning fiber display comprising one or more scanning fibers configured to project light in various patterns (e.g., raster scanning, helical scanning, Lissajous patterns, etc.) into one or more waveguides 270, 280, 290, 300, 310, ultimately to the viewer's eye 210. In some embodiments, the illustrated image input devices 360, 370, 380, 390, 400 may schematically represent a single scanning fiber or a bundle of scanning fibers configured to input light into one or more waveguides 270, 280, 290, 300, 310. In some other embodiments, the illustrated image input devices 360, 370, 380, 390, 400 may schematically represent multiple scanning fibers or multiple bundles of scanning fibers, each configured to input light into the associated waveguides 270, 280, 290, 300, 310. It should be understood that one or more optical fibers may be configured to transmit light from the optical module 530 to one or more waveguides 270, 280, 290, 300, and 310. It should be understood that one or more intervening optical structures may be provided between the scanning fiber or multiple fibers and one or more waveguides 270, 280, 290, 300, and 310 to, for example, redirect light emanating from the scanning fiber into one or more waveguides 270, 280, 290, 300, and 310.

[0089] The controller 560 controls the operation of one or more of the stacked waveguide assemblies 260, including the operation of the image input devices 360, 370, 380, 390, 400, the light source 530, and the optical 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-transient medium) to coordinate the timing and delivery of image information to the waveguides 270, 280, 290, 300, 310, for example, according to any of the various schemes disclosed herein. In some embodiments, the controller may be a single integrated device or a distributed system connected by wired or wireless communication channels. In some embodiments, the controller 560 may be part of the processing module 140 or 150 (Figure 9D).

[0090] Continuing with Figure 6, waveguides 270, 280, 290, 300, and 310 may be configured to propagate light within each individual waveguide by total internal reflection (TIR). Waveguides 270, 280, 290, 300, and 310 may each be planar or have another shape (e.g., curved), with major upper and lower surfaces and edges extending between their major upper and lower surfaces. In the illustrated configuration, waveguides 270, 280, 290, 300, and 310 may each include external coupling optical elements 570, 580, 590, 600, and 610, respectively, configured to extract light from the waveguide by redirecting the light propagating within each individual waveguide out of the waveguide and outputting image information to the eye 210. The extracted light may also be referred to as externally coupled light, and the external coupling optical elements may also be referred to as light extraction optical elements. The extracted beam of light can be output by the waveguide at the point where light propagating within the waveguide strikes the light extraction optical element. The external coupling optical elements 570, 580, 590, 600, 610 may be gratings, for example, including diffractive optical features as further discussed herein. For the sake of clarity and to facilitate the explanation, they are shown positioned on the bottom main surfaces of the waveguides 270, 280, 290, 300, 310, but in some embodiments, the external coupling optical elements 570, 580, 590, 600, 610 may be positioned on the top and / or bottom main surfaces, and / or directly within the volume of the waveguides 270, 280, 290, 300, 310, as further discussed herein. In some embodiments, the external coupling optical elements 570, 580, 590, 600, 610 may be mounted on a transparent substrate and formed within a layer of material that forms the waveguides 270, 280, 290, 300, 310. In some other embodiments, the waveguides 270, 280, 290, 300, 310 may be a monolithic piece of material, and the external coupling optical elements 570, 580, 590, 600, 610 may be formed on and / or inside the material piece.

[0091] Continuing with reference to Figure 6, as discussed herein, each waveguide 270, 280, 290, 300, 310 is configured to emit light and form an image corresponding to a particular depth plane. For example, the waveguide 270 closest to the eye may be configured to deliver collimated light (injected into such waveguide 270) to the eye 210. The collimated light may represent the optical infinity focal plane. The next upper waveguide 280 may be configured to emit collimated light that passes through a first lens 350 (e.g., a negative lens) before reaching the eye 210. Such a first lens 350 may be configured to generate some convex wavefront curvature so that the eye / brain interprets the light originating from the next upper waveguide 280 as originating from a first focal plane closer inward from optical infinity toward the eye 210. Similarly, the third upper waveguide 290 passes its output light through both the first lens 350 and the second lens 340 before reaching the eye 210. The combined refractive power of the first 350 and the second 340 lenses may be configured to produce a different, gradually increasing wavefront curvature so that the eye / brain interprets the light originating from the third upper waveguide 290 as originating from a second focal plane that is closer inward toward the person from optical infinity than the light originating from the next upper waveguide 280.

[0092] Other waveguide layers 300, 310 and lenses 330, 320 are configured similarly, with the highest waveguide 310 in the stack emitting its output through all the lenses between it and the eye for a convergent focusing force representing the focal plane closest to the person. When viewing / interpreting light originating from the other side world 510 of the stacked waveguide assembly 260, a compensating lens layer 620 may be positioned on top of the stack to compensate for the convergent forces of the lower lens stacks 320, 330, 340, 350 to compensate for the stack of lenses 320, 330, 340, 350. Such a configuration provides the same number of perceived focal planes as there are available waveguide / lens pairs. Both the external coupling optical elements of the waveguides and the focusing sides of the lenses may be static (i.e., not dynamic or electroactive). In some alternative embodiments, one or both may be dynamic using electroactive features.

[0093] In some embodiments, two or more of the waveguides 270, 280, 290, 300, and 310 may have the same associated depth plane. For example, multiple waveguides 270, 280, 290, 300, and 310 may be configured to output images set on the same depth plane, or multiple subsets of waveguides 270, 280, 290, 300, and 310 may be configured to output images set on the same multiple depth planes, using one set per depth plane. This may offer the advantage of forming tiled images that provide an extended field of view in those depth planes.

[0094] Continuing with Figure 6, the external coupling optical elements 570, 580, 590, 600, and 610 may be configured to redirect light outward from their individual waveguides for specific depth planes associated with the waveguides, and to output the light with an appropriate amount of divergence or collimation. As a result, waveguides having different associated depth planes may have different configurations of the external coupling optical elements 570, 580, 590, 600, and 610, which output light with different amounts of divergence depending on the associated depth plane. In some embodiments, the light extraction optical elements 570, 580, 590, 600, and 610 may be three-dimensional or surface features that can be configured to output light at specific angles. For example, the light extraction optical elements 570, 580, 590, 600, and 610 may be three-dimensional holograms, surface holograms, and / or diffraction gratings. In some embodiments, features 320, 330, 340, and 350 may not be lenses. Rather, they may simply be spacers (e.g., cladding layers and / or structures for forming voids).

[0095] In some embodiments, the external coupling optical elements 570, 580, 590, 600, and 610 are diffraction features or “diffractive optical elements” (also referred to herein as “DOEs”) that form a diffraction pattern. Preferably, the DOEs have sufficiently low diffraction efficiency such that only a portion of the beam light is deflected toward the eye 210 at each intersection of the DOEs, while the remainder continues to travel through the waveguide via TIR. The light carrying the image information is therefore split into several associated emission beams that exit the waveguide at multiple locations, resulting in a very uniform pattern of emission toward the eye 210 with respect to this particular collimated beam bouncing within the waveguide.

[0096] In some embodiments, one or more DOEs may be switchable between an "on" state in which they actively diffract and an "off" state in which they do not significantly diffract. For example, a switchable DOE may comprise a layer of polymer-dispersed liquid crystals in which microdroplets have a diffraction pattern within the host medium, and the refractive index of the microdroplets may be switched to substantially match the refractive index of the host material (in which case the pattern does not significantly diffract incident light), or the microdroplets may be switched to a refractive index that does not match that of the host medium (in which case the pattern actively diffracts incident light).

[0097] In some embodiments, a camera assembly 630 (e.g., a digital camera including visible light and infrared light cameras) may be provided to capture images of the eye 210 and / or the surrounding tissues, for example, to detect user input and / or monitor the user's physiological state. As used herein, the camera may be any image-capturing device. In some embodiments, the camera assembly 630 may include the image-capturing device and a light source that projects light (e.g., infrared light) onto the eye, which is then reflected by the eye and can be detected by the image-capturing device. In some embodiments, the camera assembly 630 may be mounted on a frame 80 (Figure 9D) and may communicate with processing modules 140 and / or 150 that can process image information from the camera assembly 630. In some embodiments, one camera assembly 630 may be used per eye to monitor each eye separately.

[0098] Referring here to Figure 7, an embodiment of an outgoing beam output by a waveguide is shown. Although one waveguide is illustrated, other waveguides within the waveguide assembly 260 (Figure 6) may function similarly, and it should be understood that the waveguide assembly 260 includes multiple waveguides. Light 640 is introduced into the waveguide 270 at the input surface 460 of the waveguide 270 and propagates through the waveguide 270 by TIR. At the point where the light 640 collides on the DOE 570, a portion of the light exits the waveguide as an outgoing beam 650. The outgoing beams 650 are illustrated as substantially parallel, but as discussed herein, they may also be redirected to propagate towards the eye 210 at a certain angle (e.g., forming a divergent outgoing beam), depending on the depth plane associated with the waveguide 270. It should be understood that a nearly parallel emitted beam may represent a waveguide with an externally coupled optical element that externally couples the light to form an image that appears to be set on the depth plane at a distance from the eye 210 (e.g., optical infinity). Other waveguides or other sets of externally coupled optical elements may output a more divergent emitted beam pattern, which would require the eye 210 to adjust to a closer distance and focus onto the retina, and would be interpreted by the brain as light from a distance closer to the eye 210 than optical infinity.

[0099] In some embodiments, a full-color image may be formed in each depth plane by overlaying an image onto each of the primary colors, for example, three or more primary colors. Figure 8 illustrates an embodiment of a stacked waveguide assembly in which each depth plane includes an image formed using multiple different primary colors. The illustrated embodiment shows depth planes 240a–240f, but more or fewer depths may also be considered. Each depth plane may have three or more primary color images associated with it, including a first image of a first color G, a second image of a second color R, and a third image of a third color B. Different depth planes are indicated in the figure by different numbers relating to diopters (dpt) following the letters G, R, and B. As merely an embodiment, the numbers following each of these letters indicate diopters (1 / m), i.e., the inverse distance of the depth plane from the viewer, and each box in the figure represents an individual primary color image. In some embodiments, the precise placement of depth planes for different primary colors may vary to account for differences in the focusing of light of different wavelengths in the eye. For example, different primary color images for a given depth plane may be placed on depth planes corresponding to different distances from the user. Such arrangements may increase visual acuity and user comfort and / or reduce chromatic aberration.

[0100] In some embodiments, each primary color light may be output by a single dedicated waveguide, and as a result, each depth plane may have multiple waveguides associated with it. In such embodiments, each box in the figure, including the letters G, R, or B, can be understood to represent an individual waveguide, and three waveguides may be provided for each depth plane, with three primary color images provided for each depth plane. The waveguides associated with each depth plane are shown adjacent to each other in this drawing for ease of explanation, but it should be understood that in a physical device, all waveguides may be arranged in a stack with one waveguide per level. In some other embodiments, multiple primary colors may be output by the same waveguide, for example, so that only a single waveguide may be provided for each depth plane.

[0101] Continuing to refer to 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 be used in addition to or replace one or more of red, green, or blue.

[0102] It should be understood that any reference to a given color of light throughout this disclosure will be understood to encompass light of one or more wavelengths within the range of wavelengths of light that is perceived by the viewer as that given color. For example, red light may include light of one or more wavelengths within the range of approximately 620–780 nm, green light may include light of one or more wavelengths within the range of approximately 492–577 nm, and blue light may include light of one or more wavelengths within the range of approximately 435–493 nm.

[0103] In some embodiments, the light source 530 (Figure 6) may be configured to emit light of one or more wavelengths outside the viewer's visual perception range, such as infrared and / or ultraviolet wavelengths. In addition, internal coupling, external coupling, and other light redirection structures of the waveguide of the display 250 may be configured to direct and emit this light from the display towards the user's eye 210, for example, for imaging and / or user stimulation applications.

[0104] Referring here to Figure 9A, in some embodiments, light impacting a waveguide may need to be redirected to internally couple that light into the waveguide. Internal coupling optical elements may be used to redirect and internally couple the light into its corresponding waveguide. Figure 9A illustrates cross-sectional side views of embodiments of multiple or set 660 stacked waveguides, each including an internal coupling optical element. Each waveguide may be configured to output light of one or more different wavelengths or one or more different wavelength ranges. It should be understood that a stack 660 may correspond to a stack 260 (Figure 6), and the illustrated waveguides of a stack 660 may correspond to a portion of multiple waveguides 270, 280, 290, 300, 310, except that light from one or more of the image input devices 360, 370, 380, 390, 400 is input into the waveguide from a position requiring the light to be redirected for internal coupling.

[0105] The illustrated set of stacked waveguides 660 includes waveguides 670, 680, and 690. Each waveguide includes associated internal coupling optical elements (which may also be referred to as optical input areas on the waveguide), for example, internal coupling optical element 700 is located on the main surface of waveguide 670 (e.g., the upper main surface), internal coupling optical element 710 is located on the main surface of waveguide 680 (e.g., the upper main surface), and internal coupling optical element 720 is located on the main surface of waveguide 690 (e.g., the upper main surface). In some embodiments, one or more of the internal coupling optical elements 700, 710, and 720 may be located on the bottom main surfaces of the individual waveguides 670, 680, and 690 (in particular when one or more of the internal coupling optical elements are reflective deflection optical elements). As illustrated, the internal coupling optical elements 700, 710, and 720 may be located on the upper main surface of their individual waveguides 670, 680, and 690 (or on the upper part of the following lower waveguide), in particular when their internal coupling optical elements are transmissive deflection optical elements. In some embodiments, the internal coupling optical elements 700, 710, and 720 may be located within the body of the individual waveguides 670, 680, and 690. In some embodiments, as discussed herein, the internal coupling optical elements 700, 710, and 720 are wavelength-selective, selectively redirecting one or more wavelengths of light while transmitting other wavelengths of light. Although illustrated on one side or corner of their individual waveguides 670, 680, and 690, it should be understood that in some embodiments, the internal coupling optical elements 700, 710, and 720 may be located within other areas of their individual waveguides 670, 680, and 690.

[0106] As illustrated, the internally coupled optical elements 700, 710, and 720 may be offset laterally from one another. In some embodiments, each internally coupled optical element may be offset so that it receives light without its light passing through another internally coupled optical element. For example, each internally coupled optical element 700, 710, and 720 may be configured to receive light from different image input devices 360, 370, 380, 390, and 400, as shown in Figure 6, and may be separated from other internally coupled optical elements 700, 710, and 720 (e.g., separated laterally) so that it substantially does not receive light from the other internally coupled optical elements 700, 710, and 720.

[0107] Each waveguide also includes associated optical dispersion elements, for example, optical dispersion element 730 is located on the main surface (e.g., upper main surface) of waveguide 670, optical dispersion element 740 is located on the main surface (e.g., upper main surface) of waveguide 680, and optical dispersion element 750 is located on the main surface (e.g., upper main surface) of waveguide 690. In some other embodiments, optical dispersion elements 730, 740, and 750 may be located on the bottom main surfaces of the associated waveguides 670, 680, and 690, respectively. In some other embodiments, optical dispersion elements 730, 740, and 750 may be located on both the top and bottom main surfaces of the associated waveguides 670, 680, and 690, respectively, or optical dispersion elements 730, 740, and 750 may be located on different top and bottom main surfaces within different associated waveguides 670, 680, and 690.

[0108] Waveguides 670, 680, and 690 may be separated and isolated by, for example, gaseous, liquid, and / or solid layers of material. For example, as shown, layer 760a may separate waveguides 670 and 680, and layer 760b may separate waveguides 680 and 690. In some embodiments, layers 760a and 760b are formed from a low refractive index material (i.e., a material having a lower refractive index than the material forming the directly adjacent waveguides 670, 680, and 690). Preferably, the refractive index of the material forming layers 760a and 760b is 0.05 or 0.10 or less than the refractive index of the material forming waveguides 670, 680, and 690. Advantageously, the lower refractive index layers 760a, 760b may function as cladding layers that promote total internal reflection (TIR) ​​of light through the waveguides 670, 680, 690 (e.g., TIR between the upper and lower main surfaces of each waveguide). In some embodiments, layers 760a, 760b are formed from air. It should be understood that the upper and lower parts of the illustrated set of waveguides 660 may include the immediate cladding layer, although not shown.

[0109] Preferably, to facilitate manufacturing and other considerations, the materials forming waveguides 670, 680, and 690 are similar or identical, and the materials forming layers 760a and 760b are similar or identical. In some embodiments, the materials forming waveguides 670, 680, and 690 may differ between one or more waveguides, and / or the materials forming layers 760a and 760b may still differ while maintaining the various refractive index relationships described above.

[0110] Continuing to refer to Figure 9A, rays 770, 780, and 790 are incident on set of waveguides 660. It should be understood that rays 770, 780, and 790 may also be injected into waveguides 670, 680, and 690 by one or more imaging devices 360, 370, 380, 390, and 400 (Figure 6).

[0111] In some embodiments, the rays 770, 780, and 790 may have different properties, such as different wavelengths or different wavelength ranges, which may correspond to different colors. The internal coupling optical elements 700, 710, and 720 each deflect the incident light so that the light propagates through one of the waveguides 670, 680, and 690 by TIR. In some embodiments, the internal coupling optical elements 700, 710, and 720 each selectively deflect one or more specific wavelengths of light while allowing other wavelengths to pass through the lower waveguide and associated internal coupling optical elements.

[0112] For example, the internally coupled optical element 700 may be configured to transmit rays 780 and 790 having different second and third wavelengths or wavelength ranges, while deflecting a ray 770 having a first wavelength or wavelength range. The transmitted ray 780 collides with an internally coupled optical element 710 configured to deflect light of the second wavelength or wavelength range, and is thereby deflected. The ray 790 is deflected by an internally coupled optical element 720 configured to selectively deflect light of a third wavelength or wavelength range.

[0113] Continuing with Figure 9A, the deflected rays 770, 780, and 790 are deflected so that they propagate through the corresponding waveguides 670, 680, and 690. That is, the internal coupling optical elements 700, 710, and 720 of each waveguide deflect the light into its corresponding waveguide 670, 680, and 690, and internally couple the light into the corresponding waveguide. The rays 770, 780, and 790 are deflected at an angle that causes the light to propagate through the individual waveguides 670, 680, and 690 by TIR. The rays 770, 780, and 790 propagate through the individual waveguides 670, 680, and 690 by TIR until they collide with the corresponding optical dispersion elements 730, 740, and 750 of the waveguide.

[0114] Referring now to Figure 9B, a perspective view of an embodiment of the multiple stacked waveguides shown in Figure 9A is illustrated. As described above, the internally coupled rays 770, 780, and 790 are deflected by the internally coupled optical elements 700, 710, and 720, respectively, and then propagate by TIR within waveguides 670, 680, and 690, respectively. The rays 770, 780, and 790 then collide with the optical dispersion elements 730, 740, and 750, respectively. The optical dispersion elements 730, 740, and 750 deflect the rays 770, 780, and 790 so that they propagate toward the externally coupled optical elements 800, 810, and 820, respectively.

[0115] In some embodiments, the light dispersion elements 730, 740, and 750 are orthogonal pupil expanders (OPEs). In some embodiments, the OPEs deflect or disperse light to the external coupling optical elements 800, 810, and 820, and in some embodiments, they can also increase the beam or spot size of the light as it propagates to the external coupling optical elements. In some embodiments, the light dispersion elements 730, 740, and 750 may be omitted, and the internal coupling optical elements 700, 710, and 720 may be configured to deflect light directly to the external coupling optical elements 800, 810, and 820. For example, referring to Figure 9A, the light dispersion elements 730, 740, and 750 may be replaced by the external coupling optical elements 800, 810, and 820, respectively. In some embodiments, the external coupling optical elements 800, 810, 820 are exit pupils (EPs) or exit pupil expanders (EPEs) that direct light into the viewer's eye 210 (Figure 7). It should be understood that the OPEs may be configured to increase the dimensions of the eyebox along at least one axis, and the EPEs may increase the eyebox along an axis intersecting, for example, orthogonal to the axis of the OPE. For example, each OPE may be configured to redirect a portion of the light impacting the OPE to an EPE in the same waveguide, while allowing the rest of the light to continue propagating along the waveguide. Again, in response to the impact on the OPE, another portion of the remaining light is redirected to the EPE, and the rest of that portion continues to propagate further along the waveguide, etc. Similarly, in response to the impact on the EPE, a portion of the impacting light is directed out of the waveguide toward the user, and the rest of that light continues to propagate through the waveguide until it impacts the EP again, at which point another portion of the impacting light is directed out of the waveguide, and so on. As a result, a single beam of internally coupled light is "duplicated" each time a portion of its light is redirected by the OPE or EPE, thereby forming a cloned beam field of light, as shown in Figure 6. In some embodiments, the OPE and / or EPE may be configured to modify the size of the light beam.

[0116] Therefore, referring to Figures 9A and 9B, in some embodiments, the set of waveguides 660 includes, for each primary color, waveguides 670, 680, 690, internally coupled optical elements 700, 710, 720, optical dispersion elements (e.g., OPE) 730, 740, 750, and externally coupled optical elements (e.g., EP) 800, 810, 820. Waveguides 670, 680, 690 may be stacked with air gaps / cladding layers between each one. The internally coupled optical elements 700, 710, 720 redirect or deflect the incident light into their waveguides (using different internally coupled optical elements that receive light of different wavelengths). The light then propagates within the individual waveguides 670, 680, 690 at angles that will result in a TIR. In the embodiment shown, a ray 770 (e.g., blue light) is polarized by the first internal coupling optical element 700 in the manner described above, and then continues to bounce along the waveguide, interacting with the optical dispersion element (e.g., OPE) 730 and then the external coupling optical element (e.g., EP) 800. Rays 780 and 790 (e.g., green and red light, respectively) pass through waveguide 670, with ray 780 colliding with the internal coupling optical element 710, thereby being deflected. Ray 780 then bounces along waveguide 680 via TIR, proceeding to its optical dispersion element (e.g., OPE) 740 and then the external coupling optical element (e.g., EP) 810. Finally, ray 790 (e.g., red light) passes through waveguide 690 and colliding with the optical internal coupling optical element 720 of waveguide 690. The internal optical coupling element 720 deflects the ray 790 so that it propagates by TIR to the optical dispersion element (e.g., OPE) 750, and then by TIR to the external coupling optical element (e.g., EP) 820. The external coupling optical element 820 then finally externally couples the ray 790 to the viewer, who also receives externally coupled light from other waveguides 670, 680.

[0117] Figure 9C illustrates upper and lower plan views of embodiments of the multiple stacked waveguides shown in Figures 9A and 9B. As shown, waveguides 670, 680, and 690 may be vertically aligned with the associated optical dispersion elements 730, 740, and 750 and associated external coupling optical elements 800, 810, and 820 of each waveguide. However, as discussed herein, the internal coupling optical elements 700, 710, and 720 are not vertically aligned. Rather, the internal coupling optical elements are preferably non-overlapping (e.g., laterally spaced, as seen in the upper and lower figures). As further discussed herein, this non-overlapping spatial arrangement facilitates the ingress of light from different resources into different waveguides on a one-to-one basis, thereby enabling a specific light source to be uniquely coupled to a specific waveguide. In some embodiments, arrangements including non-overlapping, spatially separated internal coupling optical elements may be referred to as pupil-shifting systems, where the internal coupling optical elements in these arrangements may correspond to subpupils.

[0118] Figure 9D illustrates an embodiment of a wearable display system 60 in which various waveguides and associated systems disclosed herein may be integrated. In some embodiments, the display system 60 is the system 250 of Figure 6, which graphically illustrates some parts of the system 60 in more detail. For example, the waveguide assembly 260 of Figure 6 may be part of the display 70.

[0119] Continuing with reference to Figure 9D, the display system 60 includes a display 70 and various mechanical and electronic modules and systems to support the functionality of the display 70. The display 70 may be attached to a frame 80, which is wearable by a display system user or viewer 90 and configured to position the display 70 in front of the user 90's eyes. In some embodiments, the display 70 may be considered an eyepiece. In some embodiments, a speaker 100 is attached to the frame 80 and configured to be positioned adjacent to the user 90's ear canal (in some embodiments, another speaker, not shown, may optionally be positioned adjacent to the user's other ear canal to provide stereo / shapeable sound control). The display system 60 also includes one or more microphones 110 or other devices to detect sound. In some embodiments, the microphones may be configured to allow the user to provide input or commands (e.g., selection of voice menu commands, natural language questions, etc.) to the system 60 and / or to enable audio communication with other persons (e.g., other users of a similar display system). The microphone may 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 may also include a peripheral sensor 120a, separate from the frame 80, which can be attached to the user 90's body (e.g., on the user 90's head, torso, limbs, etc.). In some embodiments, the peripheral sensor 120a may be configured to obtain data characterizing the user 90's physiological state. For example, the sensor 120a may be an electrode.

[0120] Continuing with Figure 9D, the display 70 is operably coupled to the local data processing module 140 by a communication link 130, such as a wired connection or wireless connectivity, which may be mounted in various configurations, such as being fixedly attached to the frame 80, fixedly attached to a helmet or hat worn by the user, built into headphones, or otherwise detachably attached to the user 90 (e.g., in a backpack configuration, in a belt-mounted configuration). Similarly, the sensor 120a may be operably coupled to the local processor and data module 140 by a communication link 120b, such as a wired connection or wireless connectivity. The local processing and data module 140 may include a hardware processor and digital memory such as non-volatile memory (e.g., flash memory or a hard disk drive), both of which may be used to assist in data processing, caching, and storage. Optionally, the local processor and data module 140 may include one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, etc. The data may include (a) data captured from sensors such as image acquisition devices (cameras, etc.), microphones, inertial measurement units, accelerometers, compasses, GPS units, wireless devices, gyroscopes, and / or other sensors disclosed herein (for example, operably coupled to frame 80 or otherwise attached to user 90), and / or (b) possibly data obtained and / or processed using the remote processing module 150 and / or remote data repository 160 (including data related to virtual content) for passage to display 70 after processing or reading. The local processing and data module 140 may be operably coupled to the remote processing module 150 and the remote data repository 160 by communication links 170, 180 via wired or wireless communication links, etc., so that these remote modules 150, 160 are operably coupled to each other and available as resources to the local processing and data module 140.In some embodiments, the local processing and data module 140 may include one or more of the following: an image acquisition device, a microphone, an inertial measurement unit, an accelerometer, a compass, a GPS unit, a wireless device, and / or a gyroscope. In some other embodiments, one or more of these sensors may be mounted on the frame 80 or may be a standalone structure communicating with the local processing and data module 140 via a wired or wireless communication path.

[0121] Continuing to refer to Figure 9D, in some embodiments, the remote processing module 150 may comprise one or more processors configured to analyze and process data and / or image information, including, for example, one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, etc. In some embodiments, the remote data repository 160 may comprise digital data storage facilities, which may be available through the Internet or other networking configurations in a “cloud” resource configuration. In some embodiments, the remote data repository 160 may comprise one or more remote servers that provide information, for example, augmented reality content, for generating data for the local processing and data modules 140 and / or the remote processing module 150. In some embodiments, all data is stored, and all calculations are performed in the local processing and data modules, enabling fully autonomous use from the remote modules. Optionally, an external system (e.g., one or more processors, one or more computer systems) including a CPU, GPU, etc., may perform at least part of the processing (e.g., generating image information, processing data) and provide information to and receive information from modules 140, 150, and 160, for example, via a wireless or wired connection.

[0122] A. Diffraction grating with reduced polarization sensitivity Providing users of waveguide-based display systems, such as various display systems configured for the virtual / enhanced / composite display applications described above, can depend, in particular, on various properties of optical coupling in and / or out of the waveguide within the eyepiece of the display system. For example, virtual / enhanced / composite displays with high optical internal and external coupling efficiencies can improve the viewing experience by increasing the brightness of the light directed to the user's eye. As discussed above, internal coupling optical elements, such as internal coupling diffraction gratings, may be employed to couple light into the waveguide so that it is induced therein by total internal reflection. Similarly, external coupling optical elements, such as external coupling diffraction gratings, may be employed to couple light induced in the waveguide by total internal reflection out of the waveguide.

[0123] For example, as described above with reference to Figures 6 and 7, the display systems in various implementations described herein may include optical elements, such as internally coupled optical elements, externally coupled optical elements, and optical dispersion elements, which may include diffraction gratings. For example, as described above with reference to Figure 7, light 640, which is introduced into the waveguide 270 at the input surface 460 of the waveguide 270, propagates within the waveguide 270 and is induced by total internal reflection (TIR). In various implementations, at the point where the light 640 collides with the externally coupled optical element 570, a portion of the light induced within the waveguide may exit the waveguide as a beamlet 650. In some implementations, for example, any of the optical elements 570, 580, 590, 600, and 610 in Figure 6 can be configured as a diffraction grating.

[0124] To achieve desirable characteristics of the internal coupling of light into (or external coupling of light from) the waveguides 270, 280, 290, 300, and 310, the optical elements 570, 580, 590, 600, and 610, configured as diffraction gratings, are formed from suitable materials and can have suitable structures for controlling various optical properties, including diffraction properties such as diffraction efficiency as a function of polarization. Possible desirable diffraction properties may include, among other things, any one or more of the following: spectral selectivity, angular selectivity, polarization selectivity (or non-selectivity), high spectral bandwidth, high diffraction efficiency, or wide field of view (FOV).

[0125] Some diffraction gratings have a strong polarization dependence and therefore may have a relatively reduced overall efficiency (due to the blocking of one polarization). In some cases, such diffraction gratings may also create coherent artifacts and reduce the uniformity of far-field images. For example, diffraction gratings can be formed by imprinting a layer of patternable material and metallizing the patterned layer (e.g., of a resist) to form multiple diffraction features. Some grating designs formed in this way can diffract more light to a given order of diffraction. Such diffraction gratings may be highly efficient with respect to one polarization (e.g., TM or P-polarization) but inefficient with respect to unpolarized light.

[0126] Figures 10A and 10B illustrate the polarization dependence of two exemplary diffraction gratings (1102, 1122). For example, Figure 10A illustrates the diffraction efficiency as a function of the incident angle in degrees with respect to diffraction grating 1102. Diffraction grating 1102 may include a metallic coating 1104 deposited on an internally coupled grating (ICG) pattern 1106 comprising a patterned photoresist. Diffraction grating 1102 may be a blazed grating or another grating having asymmetric diffraction features, including, but not limited to, an asymmetric morphology with at least one straight sidewall, a tilted sidewall, a concave angle (e.g., a sidewall with an acute concave angle relative to the base surface) or a concave sidewall, a multi-stage sidewall, other types of sidewalls, or some combination thereof. The resulting diffraction efficiency 1108 can be high with respect to P-polarization (e.g., approximately 70% on average over an incident angle range of -20 to 20 degrees). However, the diffraction grating 1102 may not be very efficient with respect to S-polarization (e.g., over the range of incidence angles of -20 and 20 degrees, for example, on average about 20% or 30%). Therefore, the diffraction grating 1102 may result in an overall lower efficiency with respect to unpolarized light (e.g., over the range of incidence angles of -20 and 20 degrees, for example, on average about 40% or 45%). Other efficiency values ​​within and outside the enumerated range of incidence angles are also possible.

[0127] In another embodiment, Figure 10B illustrates the diffraction efficiency as a function of the angle of incidence in degrees for different diffraction gratings 1122. The diffraction grating 1122 may include a blazed grating or another grating having asymmetric diffraction features, including, but not limited to, an asymmetric morphology with at least one straight sidewall, a tilted sidewall, a concave sidewall (e.g., a sidewall with an acute concave angle relative to the base surface) or a concave sidewall, a multi-stage sidewall, other types of sidewalls, or some combination thereof. The diffraction grating 1122 shown in Figure 10B may have a nonmetallic permeable coating 1124 such as ZrO2, TiO2, or SiC deposited on an ICG pattern 1106, for example, a patterned photoresist. The resulting diffraction efficiency 1128 for S-polarization may be higher than the diffraction efficiency 1126 for P-polarization. For example, S-polarization may have an average efficiency 1128 for 80%, 60%, or 40% of S-polarization over an incident angle range of approximately -20 to 20 degrees. In another embodiment, P-polarization may have an average efficiency 1126 for 10%, 15%, or 20% of P-polarization over an incident angle range of approximately -20 to 20 degrees. Other efficiency values ​​within and outside the enumerated range of incident angles are also possible.

[0128] To provide a diffraction grating having reduced polarization sensitivity (e.g., coupling light with efficiency relatively independent of polarization), some displays for AR systems according to the implementations described herein include a waveguide in which a diffraction grating is formed having multiple coatings. For example, the diffraction grating may include a patterned dielectric (e.g., a patterned photoresist) having a first transparent layer formed thereon, possibly a non-metallic (e.g., dielectric or semiconductor) coating, and a second layer containing a metal extending over the first transparent layer. In some implementations, the coated diffraction grating may achieve improved grating diffraction efficiency for a given order of diffraction, while the diffraction efficiency for other orders is reduced or minimized. As a result, more light may be directed to a particular given order of diffraction, in contrast to any of the other orders, in some implementations.

[0129] Figures 11A and 11B illustrate, respectively, an exemplary grid with a single coating that may exhibit high efficiency in single polarization (e.g., TE or S-polarization) and an exemplary grid with multiple coatings, as disclosed herein, which exhibit high efficiency in both TE and TM polarization.

[0130] For example, as shown in Figure 11A, the diffraction grating 1201 may include an ICG pattern 1202 and a transparent layer 1204. The ICG pattern 1202 can be any suitable grating pattern, such as a sawtooth pattern. These diffraction features may comprise a patterned polymer, such as a patterned resist (e.g., photoresist), or may be formed by imprinting, such as nanoimprinting. The transparent layer 1204 may include a nonmetallic material, such as a dielectric or semiconductor material like ZrO2, TiO2, or SiC. Image 1200 shows an exemplary scanning electron microscope image of a diffraction grating, such as a diffraction grating 1201, which may have a sawtooth pattern ICG 1202 and a TiO2 coating 1204. The transparent layer 1204 (e.g., TiO2 coating) was deposited using glissando deposition (GLAD). Therefore, as shown, much of the transparent layer lies on one side of the diffraction features rather than the other side. Table 1 shows exemplary efficiencies associated with different types of light, including TE-polarized, TM-polarized, and unpolarized light, incident on the diffraction grating 1201. As shown in Table 1, the grating 1201 exhibits increased efficiency in TE-polarized light compared to TM-polarized and unpolarized light. As discussed above, such polarization-dependent efficiency may not be desirable. [Table 1]

[0131] As shown in Figure 11B, the diffraction grating 1205 may include an ICG pattern 1202, a transparent layer 1204 formed thereon, and a metal layer 1206 formed on the transparent layer. The ICG pattern 1202 may be any suitable grating pattern, such as a blazed grating pattern, such as the sawtooth pattern shown. These diffraction features may comprise a patterned polymer, such as a patterned resist (e.g., photoresist), and may be formed by imprinting, such as nanoimprinting. The transparent layer 1204 may include a nonmetallic material such as a dielectric such as ZrO2 or TiO2, or other high-n, low-k materials such as SiC. The transparent layer 1204 (e.g., TiO2 coating) was deposited using glissando deposition (GLAD). Therefore, as shown, much of the transparent layer is on one side of the diffraction features rather than the other side. The metal layer 1206 may include any suitable metal such as Al, Ag, or AlSi. This metal layer may be a conformal metal layer. Figure 1203 shows an example of a method in which the metal layer 1206 may be arranged across a transparent layer formed across the diffraction grating. Table 2 shows exemplary efficiencies associated with different types of light, including TE-polarized, TM-polarized, and unpolarized light, incident on the diffraction grating 1205.

[0132] As shown in Table 2, the grating 1205 illustrated in Figure 11B exhibits improved efficiency in unpolarized light compared to the grating 1201 illustrated in Figure 11A. The grating 1205 illustrated in Figure 11B yields similar efficiencies in TE-polarized, TM-polarized, and unpolarized light. Therefore, advantageously, the grating 1205 has reduced polarization sensitivity. This polarization insensitivity is achieved by using both a transmissive non-metallic layer 1204 that improves TE diffraction efficiency and a metallic layer 1206 that improves TM diffraction efficiency. By providing a first layer on the ICG pattern 1202 that improves TE-polarized efficiency and a second layer that improves TM-polarized efficiency, the effects of both layers can help reduce the polarization sensitivity of the grating 1205. In some implementations, increased uniformity and brighter images can be achieved thereby. [Table 2-1] [Table 2-2]

[0133] 1. Exemplary grid patterns Figures 12A and 12B illustrate exemplary cross-sectional views of a portion of a diffraction grating 1008 formed on a substrate, which is a waveguide 1004. In the shown implementation, the blazed diffraction grating 1008 is formed within the substrate / waveguide 1004 (which is planar in this embodiment). The surface of the substrate or waveguide 1004 has a surface topography with diffraction features that together form the diffraction grating 1008. The blazed diffraction grating 1008 is configured to diffract light having wavelengths in the visible spectrum so that light incident on it is guided within the waveguide 1004 by TIR. The waveguide 1004 may be transparent and may form a portion of an eyepiece that can be seen through it by the user. Such a waveguide 1004 and eyepiece may be incorporated within a head-mounted display, such as an augmented reality display. Waveguide 1004 may correspond to, for example, one of waveguides 670, 680, and 690, as described above with respect to Figures 9A-9C. Blazed diffraction grating 1008 may correspond to, for example, one of internally coupled optical elements 700, 710, and 720, as described above with respect to Figures 9A-9C. Blazed diffraction grating 1008, configured to internally couple light into waveguide 1004, may be referred to herein as an internally coupled grating (ICG). Display device 1000 may also include optical element 1012, which may correspond to, for example, an optical dispersion element (for example, one of optical dispersion elements 730, 740, and 750 shown in Figures 9A-9C) or an externally coupled optical element (for example, one of externally coupled optical elements 800, 810, and 820 shown in Figures 9A-9C).

[0134] When an incident light beam 1016, such as visible light, from a light projection system providing image content during operation is incident on the blazed diffraction grating 1008 at an incident angle α measured with respect to a surface normal 1002 that is normal to or perpendicular to the main surface of the waveguide (shown in Figure 12A as extending parallel to the yx plane) and / or the surface 1004S of the waveguide 1004, such as the main surface of the waveguide (shown in Figure 12A as extending parallel to the yx plane) on which the grating is formed, the blazed diffraction grating diffracts the incident light beam 1016 as a diffracted light beam 1024 at a diffraction angle θ measured with respect to the surface normal 1002, at least partially. The diffracted light beam 1024 reaches a critical angle θ for the occurrence of total internal reflection within the waveguide 1004. TIR When diffracted at a diffraction angle θ exceeding θ, the diffracted light beam 1024 propagates within the waveguide 1004 and is generally guided via total internal reflection (TIR) ​​along the direction parallel to the x-axis and along the length of the waveguide. A portion of this light guided within the waveguide 1004 reaches one of the optical dispersion elements 730, 740, 750 or one of the external coupling optical elements (800, 810, 820, Figures 9A-9C) and may be diffracted again, for example.

[0135] As described herein, in the illustrated implementation, a light beam incident at an angle clockwise with respect to the surface normal 1002 (i.e., to the right of the surface normal 1002) is said to have a negative α (α < 0), while a light beam incident at an angle counterclockwise with respect to the surface normal 1012 (i.e., to the left of the surface normal) is said to have a positive α (α > 0).

[0136] A suitable combination of high refractive index material and / or structure of the diffraction grating 1008 may result in a specific range (Δα) of the incident angle α, which is referred herein to as the range of the receiving angle or field of view (FOV). One range Δα may be described by a range of angles that spans negative and / or positive values, outside of which the diffraction efficiency drops by 10%, greater than 25%, greater than 50%, or greater than 75%, 80%, 90%, 95%, or any range between these values, relative to the diffraction efficiency at α=0 or in some other direction. In some implementations, it may be desirable to have a range Δα within which the diffraction efficiency is relatively high and constant, for example, if uniform intensity of diffracted light is desired within Δα. Therefore, in some implementations, Δα is associated with the angular bandwidth of the diffraction grating 1008 such that the incident light beam 1016 in Δα is efficiently diffracted by the diffraction grating 1008 at a diffraction angle θ with respect to the surface normal 1002 (e.g., parallel to the yz plane), and θ is associated with the angular bandwidth of the diffraction grating 1008 such that the diffracted light is guided within the waveguide 1004 under total internal reflection (TIR). TIR This exceeds [a certain value]. In some implementations, this angle Δα range may affect the field of view seen by the user. Note that in various implementations, light can be directed onto an internally coupled grating (ICG) from both sides. For example, light can be directed to enter a reflective internally coupled grating (ICG) 1008, such as the one shown in Figure 12A, through the substrate or waveguide 1004. The light can be coupled into the substrate or waveguide 1004 by the internally coupled grating 1008 so that, for example, the light is guided into the substrate or waveguide by total internal reflection, subject to the same effect. The range of incident angle α (Δα), referred herein to as the range of the receiving angle or field of view (FOV), may be influenced by the refractive index of the substrate or waveguide material. In Figure 12A, for example, the reduced angle range (Δα') shows the effect of refraction by a high refractive index material on light incident on the internally coupled grating (ICG). However, the angle (Δα) or FOV range is larger.

[0137] Figure 12B illustrates a cross-sectional view of an exemplary blazed diffraction grating 1008. The grating 1008 consists of grating features having peaks 1003 and grooves 1005. The blazed transmission grating 1008 has a surface corresponding to the substrate or waveguide surface 1004S having a “sawtooth” shaped pattern, as can be seen from the shown cross-section. The patterned “sawtooth” is first formed by tilting a portion 1007 of the surface 1004S. In the embodiment shown in Figure 12B, the grating 1008 also includes a second (steeper) tilted portion 1009. In the embodiment shown, the first tilted portion 1007 has a shallower tilt than the second tilted portion 1009, which has a steeper tilt. The first tilted portion 1007 is also wider than the second tilted portion 1009 in this embodiment.

[0138] Peak 1003 has a height H corresponding to the distance from the bottom of groove 1005 to the top of peak 1003. Thus, this value may be referred to herein as peak height and / or groove depth and grating height or grating depth or height of the diffraction feature of the diffraction grating. In the embodiment shown in Figure 12B, the bottom of groove 1005 is formed by the intersection of first and second inclined portions 1007, 1009 of two adjacent peaks 1003. The first inclined portion 1007 lies on one of the adjacent peaks 1003, and the second inclined portion 1009 lies on the other adjacent peak. Similarly, the top of peak 1003 is formed by the intersection of the first and second inclined portions 1007, 1009 at the top of peak 1003. However, other configurations are also possible. For example, the first and second inclined portions do not necessarily intersect if, for example, the bottom of groove 1005 has a flat base, or the top of peak 1003 includes a flat region, as discussed below. The blazed diffraction grating 1008 has a line spacing or pitch d, which may be constant in some implementations. This line spacing or pitch d may be a measure of the separation of the vertices of peak 1003 in the grating 1008, having a shape similar to, for example, that shown in Figure 12B. Similarly, the line spacing or pitch d may be a measure of the separation at the deepest locations of adjacent grooves 1005. The line spacing or pitch d may be measured from other locations on the grating features.

[0139] The inclination can be tilted at an angle δ with respect to a plane parallel to the grid 1008 or the surface of the waveguide (for example, the surface 1004S of the waveguide which may extend beyond the grid or surface 1004S' of the waveguide opposite the grid in Figure 12A). This angle δ of the first (shallower) inclined portion 1007 may be referred to herein as the blaze angle.

[0140] As illustrated in Figure 12B, the blazed diffraction grating 1008 may include grating lines or features having an asymmetrical shape, for example, comprising asymmetrically shaped peaks 1003 and / or grooves 1005. For example, in the diffraction grating shown in Figure 12B, the diffraction features comprise peaks 1003 and / or grooves 1005 having an asymmetrical triangular cross-sectional shape. As discussed above, this asymmetrical shape results in different inclinations and / or widths of the first and second inclined portions 1007, 1009. However, other shapes are also possible.

[0141] In designs where the diffraction features are asymmetric, for example, where the slope of the first inclined portion is shallower and the slope of the second inclined portion is steeper, the diffraction features can be considered to be formed from repeating inclinations and steps. Such a structure may be referred to herein as an inclined step structure. In some implementations, the second portion may not be as steep as the inclination. For example, the second portion may be parallel to the normal 1002.

[0142] In other implementations, the “sawtooth” pattern, for example, the peak 1003 and / or groove 1005, may be symmetrical. For example, the first and second inclined portions 1007 and 1009 may have the same inclination and the same width.

[0143] The cross-sectional pattern shown in Figure 12B may be referred to herein as a single-stage geometric shape in comparison to the multi-stage structure discussed below. The multi-stage structure is shown, for example, in Figure 11D.

[0144] Regardless of whether the diffraction features are asymmetric or symmetric, in some implementations, the flat region or flat portion may be located above peak 1003, as discussed below. A diffraction grating 1008 having diffraction features with a flat region or flat portion above peak 1003 is shown, for example, in Figures 10B and 11D.

[0145] Figure 12B shows an incident light beam 1016 incident on the grating 1008 at an angle α with respect to the normal direction 1002. (As discussed above with respect to Figure 12A, in other embodiments, the light can pass through the substrate or waveguide 1004 and be incident on the diffraction grating 1008 from the other side.) As discussed above, the normal 1002 is normal to or perpendicular to the plane of the grating or waveguide and / or the surface 1004S of the waveguide 1004, for example, the main surface or opposing plane surface 1004S' of the waveguide on which the grating is formed. In Figure 12B, the light 1016 incident on the diffraction grating 1008 is shown as being diffracted at an angle β with respect to the normal direction 1002.

[0146] According to various embodiments, when configured as an internally coupled optical element or an internally coupled diffraction grating, the diffraction grating 1008 can diffract and couple light incident on the substrate 1004, which may be a waveguide, as described above. The diffraction grating 1008 may optionally be configured as an externally coupled optical element, in which case it can diffract and couple light from the substrate 1004, which may be a waveguide, as similarly described above.

[0147] Referring to Figures 12A and 12B, in some implementations, the substrate 1004 contains a polymer. For example, the polymer may contain a polymerizable composition of one or more materials such as high-viscosity polyfunctional components, low-viscosity mono- or polyfunctional components, photoinitiators, photostabilizers, antioxidants, surfactants, inorganic nanoparticles or molecular-level clusters, or any combination thereof, or other materials. The substrate may contain a polymer and have a low refractive index (e.g., 1.6 or less) or a high refractive index (e.g., greater than 1.6). The substrate 1004 may contain, for example, an organic polymer consisting of a low refractive index (e.g., less than 1.6) or a high refractive index organic resin (e.g., greater than 1.6). Low refractive index organic polymers such as PC, PMMA, PVA, etc., or resin-containing acrylates that can be crosslinked in response to UV and / or thermocuring may have a refractive index of 1.5 to 1.6. Some high refractive index organic polymers may have sulfur and / or aromatic groups in the acrylate crosslinking molecule.

[0148] The polymer may be patterned, for example, etched, to create a lattice structure. The diffraction features of the diffraction gratings 1008, 1010, such as lines, are formed within the substrate 1004, such as within the surface of the substrate. The diffraction features may be etched, for example, on one or both sides of the substrate, within the polymer-containing substrate 1004. The substrate may, for example, contain a polymer, and the diffraction grating may be formed within the polymer substrate by etching or patterning the surface of the substrate.

[0149] Therefore, in some implementations, the substrate and / or waveguide may include a material having a refractive index of 1.4 to 2.7, for example, depending on the material. For example, the substrate may be an inorganic material such as SiO2, LiNbO3, LiTaO3, SiC, or other inorganic materials, or a glass substrate with, but not limited to, the following materials, namely SiO2, TiO2, B2O3, Li2O, La2O3, ZrO2, ZnO, Si3N4, or other glass materials. The substrate may, therefore, have different refractive indices depending on the design. In some implementations, the substrate may include a polymer that may have a low refractive index (e.g., 1.6 or less) or a high refractive index (e.g., greater than 1.6). For example, the substrate and / or waveguide may include an organic polymer such as a low refractive index (less than 1.6, etc.) or a high refractive index organic resin (greater than 1.6). Low refractive index organic polymers having a refractive index of 1.5 to 1.6, such as PC, PMMA, and PVA, may be used, for example, or acrylates containing resins that can be crosslinked in response to UV and / or thermosetting may be employed. Some exemplary high refractive index organic polymers may have sulfur and / or aromatic groups within the acrylate crosslinking molecule.

[0150] Therefore, as described above, in the various implementations described herein, both the diffraction grating 1008 and the substrate 1004 or waveguide contain the same material, for example, a polymer. In some implementations, the diffraction grating 1008 is patterned directly into the substrate 1004 such that the diffraction grating 1008 and the substrate 1004 form a single piece or monolithic structure. For example, the substrate 1004 may comprise a waveguide having a diffraction grating 1008 formed directly within the waveguide or the surface of the substrate. In these implementations, a bulk polymer material may be patterned on the surface 1004S to form the diffraction grating 1008, while the polymer material beneath the diffraction grating 1008 may form the waveguide. Other materials may also be used as substrates, as discussed above, and may be patterned to form diffraction features therein. First and second layers of material, such as a first layer that increases the diffraction efficiency for a first polarization and a second layer that increases the diffraction efficiency for a second polarization different from the first polarization, may be deposited across the diffraction grating (e.g., across the diffraction features). As discussed above, the first layer may include an optically transparent or transparent material, and in some implementations, a nonmetallic material such as a dielectric or semiconductor. The second layer may include a metal. Such combinations of layers can increase the diffraction efficiency for both the first and second polarizations, and therefore increase the diffraction efficiency for unpolarized light.

[0151] However, in some other implementations, the diffraction features, such as lines, that form the diffraction gratings 1008 and 1010 may include materials that are different from those of the substrate. The bulk or substrate 1004 and surface 1004S patterned to form the diffraction grating 1008 may therefore include different materials. For example, a polymer may be patterned in a surface region to form the diffraction grating 1008, while a higher refractive index material may be located below the diffraction grating 1008, forming the substrate 1004. In some implementations, the patternable material from which the base pattern is formed includes a polymer having a refractive index in the range of 1.4 to 1.95. In some implementations, the substrate includes a high refractive index material having a refractive index of at least 1.9. The refractive index can be, for example, at least 2.0, at least 2.1, at least 2.2, or at least 2.3, and may be 2.4, 2.5, 2.6, 2.7, 2.8 or less, or may be within any range formed by any of these values, or may be outside these ranges. In some implementations, the substrate may include, for example, a Li-based oxide such as lithium niobate. Other materials with high refractive indices may also be used. In some implementations, the substrate may include, for example, silicon carbide (SiC). The substrate may include crystalline, cryptocrystalline, or amorphous substrates, for example, potentially containing Ti, Z, Hf, La, Ba, Ca, Si, or O2. The substrate may include a high refractive index material such as, for example, a Li-based oxide (e.g., lithium niobate, LiNbO3), while the diffraction features may be formed from different materials such as polymers formed on the high refractive index substrate. In some implementations, the other material formed on the substrate may have a lower refractive index than the substrate.

[0152] First and second layers of material, such as a first layer that increases the diffraction efficiency for a first polarization and a second layer that increases the diffraction efficiency for a second polarization different from the first polarization, may be deposited across the diffraction grating. As discussed above, the first layer may include an optically transparent or transparent material, or a nonmetallic material such as a dielectric or semiconductor. The second layer may include a metal. Such combinations of layers can increase the diffraction efficiency for both the first and second polarizations, and therefore increase the diffraction efficiency for unpolarized light.

[0153] Referring to Figures 12A and 12B, according to various embodiments, the diffraction grating 1008 may have various dimensions. For example, the diffraction features of the diffraction grating 1008 may have heights (H) of 10 nm to 150 nm, 100 nm to 200 nm, 150 nm to 300 nm, or 300 nm to 500 nm, or within a range defined by any of these values ​​(e.g., 100 nm to 600 nm), depending on the design. In some implementations, this height may correspond to the height of the peak 1003 and / or the depth of the groove 1005 or region (e.g., gap) between the peaks. However, other heights may also be considered as possibilities.

[0154] The diffraction grating 1008 may, according to various embodiments, have a pitch of 200 nm to 300 nm, or 300 nm to 400 nm, 400 nm to 550 nm, or any range defined by any of these values. Other pitches are also possible.

[0155] The diffraction grating 1008 may have a blaze angle of approximately 20 to 70 degrees (shallow size) or 20 to 85 degrees and an inverse blaze angle of 70 to 150 degrees (steep side), or any value within the range defined by these values ​​measured in the same angular direction.

[0156] Values ​​outside of these ranges are also possible.

[0157] Figure 13A illustrates exemplary geometric forms 1302 for diffraction features within a diffraction grating 1008, such as those described above with reference to Figures 12A and 12B. For example, the geometric forms can be symmetrical, with straight sidewalls (e.g., the first column in the top row of Figure 13A), angled sidewalls (e.g., the second column in the top row, a serrated embodiment), concave or concave sidewalls, multi-stage sidewalls (e.g., the third column in the first row), other types of sidewalls, or any combination thereof. In another embodiment, the geometric form can be asymmetrical, with at least one straight sidewall, an inclined sidewall (e.g., the first and third columns of the second row in Figure 13A), a concave sidewall (e.g., a sidewall with an acute concave angle relative to the base surface, as shown in the third column of the second row, also referred to as a shark's tail), a multi-stage sidewall (e.g., the second column of the second row), other types of sidewalls, or some combination thereof. Regardless of whether the diffraction feature is asymmetric or symmetric, in some implementations, a flat region or flat portion may be located at the top of the feature (e.g., a peak).

[0158] In some embodiments, the asymmetric geometric form may include a profile in which the first sidewall forms an angle of 20–85 degrees with the substrate. In some embodiments, the second sidewall forms a different angle from the first sidewall. In some embodiments, it may be advantageous for the second sidewall to form an angle of 90 degrees or greater with the substrate to provide a biased deposition in which the coating is included on the first sidewall but not on the second sidewall, or may include less coating on the second sidewall (e.g., a thinner or lesser coating on the second sidewall) during substantially linear deposition onto the grid (as shown in Figure 14). In some embodiments, the height of the grid features can be 100 nm–600 nm. In some embodiments, the pitch of the grid features can be 290 nm–690 nm. Other values ​​outside these ranges are also possible.

[0159] A diffraction grating may be a one-dimensional (1D) or two-dimensional (2D) grating. For example, as shown in Figures 13B-1 and 13B-2, a diffraction grating may comprise a 1D array of grating features such as an array of lines or grooves (e.g., straight lines or grooves). Such a 1D grating may be, for example, undulating, repeating, or periodic or quasi-periodic in one direction. In some cases, the 1D array may comprise multiple parallel linear features such as linear ridges and / or linear ridges. For example, Figure 13B-1 shows a cross-sectional side view of an exemplary device 3300 having a series of diffraction features 3303 arranged laterally in one direction (e.g., the horizontal direction in Figure 13B-2). The diffraction features 3303 undulate in one direction (e.g., the horizontal direction in Figure 13B-2) and are therefore referred to as 1D. Figure 13B-2 shows a top view of the exemplary device 3300. The diffraction features 3303 can form a series of elongated longitudinal features, such as lines, extending in one direction (e.g., the vertical direction in Figure 13B-2). The elongated longitudinal features are arranged along one direction (e.g., the horizontal direction in Figure 13B-2) and repeated in that direction.

[0160] In another embodiment, the diffraction grating may include projections or high points or regions and a 2D array of grating features such as holes, gaps, or low-area 2D arrays between high points, regions, or projections. The 2D array may, for example, in some cases be like a grid pattern. Any 1D array of structures described herein can also be arranged in two directions to form a 2D array of diffraction features. The 2D array of diffraction features may include multiple reliefs in two directions. In some instances, the reliefs may be periodic, while in other instances, the pitch of the reliefs may vary. Figure 13C shows an exemplary device 3400 having a 2D array of diffraction features 3403 (e.g., diffraction features 3403 arranged laterally in two dimensions or directions). In this embodiment, the array is analogous to a grid pattern. These features may be referred to as projections, or in this case, columns. In this embodiment, the diffraction features 3403 are symmetric with side walls substantially perpendicular to the horizontal axis. In other embodiments, diffraction features, such as projections, can be symmetrical with angled or inclined sidewalls. For example, Figures 13D-1 and 13D-2 show a cross-sectional side view and a top view, respectively, of an exemplary array of symmetric diffraction features. Both the left and right sidewalls are inclined inward such that the diffraction features become tapered or their width decreases with increasing height. Thus, in this embodiment, the first sidewall is inclined in one direction, and the second sidewall is inclined in a second opposing direction. In this embodiment, the sidewall inclination angle is approximately 30 degrees with respect to the horizontal axis and is symmetrical on both sides. In some implementations, the 2D array can include lattice features formed by orthogonal covering of two 1D lattice structures. For example, the 2D array can include orthogonal covering of two blaze lattice structures, as described with reference to Figures 12A and 12B. Other configurations of 1D and 2D lattices are also possible. The geometric form 1302 shown in Figure 13A may correspond to a cross-section of a diffraction feature of either a 1D or 2D grating. Such diffraction features may be arranged, for example, in a 1D or 2D array.

[0161] Figure 13E shows another exemplary device 3600 having a 2D array of diffraction features 3603. In this embodiment, the diffraction features are asymmetric. Figures 13F-1 and 13F-2 show a cross-sectional side view and a top view, respectively, of an exemplary array of asymmetric diffraction features. This 2D diffraction grating comprises a blazed diffraction grating. The diffraction features may be tapered, for example, in width or thickness with respect to height. In the embodiment shown in Figure 13E, the diffraction features have two inclined sidewalls or facets, one of which is inclined more than the other, whereas in the embodiments shown in Figures 13F-1 and 13F-2, one sidewall is inclined, but the other opposing sidewall is not inclined, or any inclination on the second sidewall is negligible. In both cases, the inclination of one sidewall is greater than that of the other (where applicable) so that the diffraction features are asymmetric and blazed. As a result, diffraction features preferentially diffract light in one direction over others. Such diffraction gratings can be useful, for example, as internal coupling optics configured to diffract light received from a projector toward a light distribution element, an external coupling optics element, or a combination of a light distribution element and an external coupling optics element, such as a CPE or a combined pupil expander-extractor. Such diffraction gratings can also be useful for externally coupling light to the eye, as opposed to the direction facing the environment or world in front of the user and head-mounted display. The sidewall inclination angle is less than 30 degrees with respect to the horizontal axis on one side and greater than 80 degrees (possibly 90 degrees) on the other side in some implementations. However, other inclinations and inclination angles are also possible. In some instances, diffraction features can form a 2D array of sawtooth structures, such as sawtooth nanostructures.

[0162] Therefore, in various implementations, a 2D array of symmetric or asymmetric diffraction features can provide a blazed diffraction grating. As discussed above, the shape of the diffraction features (e.g., the tilt angle of the sidewalls) can determine the direction in which the grating directs, or preferentially directs, light. For example, the grating may direct more light towards other gratings (e.g., EPE, OPE, or CPE) and / or towards the viewer. In some instances, the diffraction features can be faceted (e.g., blazed in multiple directions) to bias the propagation of light in two or more directions. For example, Figure 13G-1 shows an exemplary device 3700 having a 2D array of diffraction features 3703 formed in or on a substrate 3701. The diffraction feature 3703 has a tilted first sidewall or facet 3703b-1 and a second sidewall or facet 3703b-2. Therefore, the diffraction features are tapered with height, for example, in thickness or width. The diffraction features 3703 can be configured to preferentially direct light in directions based on the inclination angles of the first and second sidewalls or facets 3703b-1, 3703b-2. Figure 13G-2 shows an exemplary diffraction feature that directs more light in two specific directions (as illustrated by two thick solid arrows pointing upwards to the right and downwards to the left). Other embodiments are also possible.

[0163] Therefore, any of the structures or devices described herein, such as lattice structures, may comprise a 1D lattice. Similarly, any of the structures or devices described herein, such as lattice structures, may comprise a 2D lattice. Such a 2D lattice can diffuse light. These lattices may also comprise a blazed lattice. Such a blazed lattice can preferentially direct light in a particular direction. In some implementations, a 2D lattice (e.g., having one tilted facet on the diffraction feature) preferentially directs light in one direction, while in other implementations, a 2D lattice (e.g., having two differently tilted facets on the diffraction feature) preferentially directs light in multiple directions. Similarly, any of the methods or processes described herein can be used for a 1D lattice. Similarly, any of the methods or processes described herein can be used for a 2D lattice. These lattices, being 1D or 2D, may be incorporated on a substrate and / or waveguide, incorporated within an eyepiece, and possibly integrated into a head-mounted display as disclosed herein. These gratings may be used, for example, as input gratings (e.g., ICG), output gratings (EPE), distribution gratings (OPE), or combined distribution gratings / output gratings (e.g., CPE).

[0164] The diffraction grating pattern may be formed within a substrate that may include waveguides. In some implementations, the patternable material includes polymers. The pattern may be formed using photolithography, in which the patternable material, such as photoresist, may be deposited on a substrate that may include waveguides. The patternable material / photoresist may be patterned to have a geometric form as illustrated in Figure 13A. Imprinting, such as nanoimprinting, may be used to pattern the patternable material. Forming a patterned geometric shape within the patternable material may, in some implementations, involve imprinting a pattern, such as a single-step "sawtooth" pattern, into the photoresist (e.g., depositing the photoresist on a substrate and then imprinting a blazed geometric shape). The patterned material, such as photoresist, may form a mask, such as a rigid mask, after patterning.

[0165] Patternable materials, such as polymers and photoresists, can be imprinted with or without a residual interconnection layer (RLT), or the polymer or resist pattern may be a photolithographic pattern with or without an RLT. A monolithic polymer substrate may have a surface relief pattern defined on one or both sides of the waveguide. The pattern (e.g., multiple diffraction features) can be etched into the substrate (e.g., having a refractive index of 1.45 to 2.0) once the pattern has been imprinted or otherwise formed on the substrate.

[0166] In various implementations, the patterned material (e.g., polymer or photoresist) and the substrate may be etched to form patterns within the substrate, such as those described with reference to Figure 13A. Etching the photoresist and substrate may involve, for example, dry plasma or chemical etching and / or wet chemical etching. In some implementations, etching may be performed at a relatively constant rate such that areas where the patterned photoresist is thickest result in negligible or no removal of material from the substrate, while areas where the patterned photoresist is thinnest (or absent) result in the deepest etching within the substrate.

[0167] In some other implementations, the patternable material is etched to form diffraction features of the patternable material. In such implementations, the diffraction features of the patternable material remain on the substrate and do not need to be patterned.

[0168] Figure 13H shows an exemplary method 3800 for forming a blazed lattice. Method 3800 provides a template or master 3810. If the diffraction features are to be angled, tilted, or inclined, the template 3810 can be patterned to form an angled structure. Various processes, such as etching processes, may be directional and angled to form such an angled structure. Some embodiments of angled processes, such as angled etching processes, include ion beam milling, angled dry etching, ion etching, GLAD etching, tilted etching, Faraday cage etching, etc. In some implementations, the choice of material employed for the template 3810 may help produce an angled structure having angled sidewalls within the template. In this embodiment, the angled structure comprises angled extensions (e.g., for a 1D lattice) or angled columns (e.g., for a 2D lattice). These angled extensions or angled columns may have sidewalls that are inclined in the same direction and, in some cases, may be substantially parallel. Once the template 3810 is fabricated, a layer of patternable material (e.g., polymer, resist, photoresist, etc.) can be deposited on the substrate 3801, and this layer can be imprinted using the imprint template 3810. The template 3810 can be imprinted into the patternable material (e.g., resist material) 3805 on the substrate 3801 to form a mask 3805 for the substrate. In other implementations, the patternable material can be deposited on the template, and the substrate can be brought into contact with the template, which accompanies the patternable material. The template can be removed, and the resist material 3805 and the underlying substrate 3801 can be dry-etched to form diffraction features 3803 within the substrate 3801 (or within the layer of material placed on the substrate 3801). In various implementations, dry etching is employed as shown. The etching may be directional. In the shown embodiment, the etching process is not angled.The resulting diffraction features 3803, formed within the substrate 3801 (or within a layer of material placed on the substrate 3801), may have a certain shape, for example, they may be blazed as a result of angled features within the mask 3805. In the shown embodiments, the cross-section of the diffraction features has a trapezoidal or substantially triangular shape with two sloping sides. The sides are sloping in opposite directions. In the shown embodiments, one side is sloping more than the other side, creating an asymmetrical or blazed structure. This process may be used to form a 1D or 2D array of diffraction features.

[0169] Figure 13I shows another exemplary method 3850 for forming blazed diffraction features. The mask 3855 and the underlying substrate 3851 (or a layer of material placed on the substrate 3851) can be etched at an angle (e.g., dry etching) to form diffraction features 3853 within the substrate 3851 (or within a layer of material placed on the substrate 3851). Some embodiments of angled directional etching processes (e.g., angled etching) include ion beam milling, angled dry etching, ion etching, GLAD etching, tilted etching, Faraday cage etching, etc. The template may comprise elongated projections (e.g., for a 1D grid) or tapered columns (e.g., for a 2D grid) having a trapezoidal or substantially triangular cross-section. These elongated projections or tapered columns may have sidewalls tilted in opposite directions. One sidewall may be tilted more than the other sidewall. Applying an angled etching process to these extensional projections or tapered columns can produce a blazed grid within the underlying material of the extensional projections or tapered columns, such as a substrate or a layer of material placed on the substrate. Blazed diffraction features having edges tilted in the same direction may be produced. In various implementations, one edge is tilted more than the other. This process may be used to form a 1D or 2D array of diffraction features.

[0170] In various implementations, the resulting diffraction features may be blazed in two or more directions (e.g., as shown in Figure 13G-1) as a result of angled features in the mask (e.g., as shown in Figure 13H) and / or as a result of using an angled process (e.g., as shown in Figure 13I). The diffraction features or gratings blazed in two or more directions may be produced by etching twice. In some implementations, for example, the diffraction features or gratings blazed in two or more directions may be produced by etching with a first mask and then etching again with a second different mask. In some instances, as shown in Figure 13J, the mask 3905 and substrate 3901 may be etched to form a first sidewall of the diffraction feature 3903 within the substrate 3901. In addition, patterning may be provided to form a second sidewall. In various implementations, a second mask having a different orientation and / or shape may be used to form the second sidewall. A second mask (e.g., at a certain angle and / or orientation relative to the first sidewall) may be etched, for example, to form a second sidewall. In some implementations, after the first sidewall of the diffraction feature 3903 is formed, a planaring layer 3907 may be added to the intermediate diffraction feature 3903 and the substrate 3901. The planaring layer 3907, the intermediate diffraction feature 3903, and / or the substrate 3901 may be patterned and etched (e.g., at a certain angle relative to the first sidewall) to form a second sidewall. The above embodiments are discussed in the context of patterning a substrate, but in some implementations, the process described above may be employed to pattern layers formed on the substrate and not to pattern the substrate. Alternatively, in some implementations, the process described above may be employed to pattern layers formed on the substrate and the substrate.

[0171] In addition, while exemplary methods 3800, 3850, and 3900 are illustrated for forming a 2D array of asymmetric diffraction features, the methods can also be used to form a 2D array of symmetric diffraction features (with or without angled sidewalls). The methods can also be used to form a 1D array of diffraction features. In some instances, the diffraction features in the 1D array can be symmetric, with or without angled sidewalls. In some instances, the diffraction features in the 1D array can be asymmetric, for example, with angled sidewalls. Thus, in some cases, blazed diffraction features may be formed.

[0172] 2. Exemplary Layer One or more permeable layers may be laid on the base pattern. For example, as shown in Figure 14, the deposition of one or more permeable layers on the base pattern can be carried out conformally (1402A, 1402B, 1402C) or directionally (1404A, 1404B, 1404C, 1406A, 1406B, 1406C).

[0173] Conformal deposition (1402A, 1402B, 1402C) may include various deposition techniques for depositing material 1412, resulting in a material layer that covers various surfaces of the underlying features. The deposited layer may potentially be substantially equal in thickness across the base pattern geometry 1410. In some embodiments, directional deposition may include linear deposition (1404A, 1404B, 1404C) such that the material 1412 to be deposited is incident on the base pattern 1410 at an angle approximately perpendicular to the plane or horizontal or planar main surface of the substrate. In other embodiments, directional deposition may include angled deposition (1406A, 1406B, 1406C) such that the material 1412 to be deposited is incident on the base pattern 1410 at an angle 1414 with respect to the plane or horizontal or planar main surface of the substrate. For example, the angle 1414 may be selected based on the pattern geometry. For example, the diffraction grating may be a blazed diffraction grating having a sawtooth structure. The angle 1414 may be substantially perpendicular to the surface of the sawtooth structure so that the material to be deposited 1412 is substantially deposited more on a portion (or specific sidewall) of the sawtooth structure, as shown in 1406A, 1406B, and 1406C.

[0174] The deposition type and base pattern geometry can influence the thickness and placement of the layer of material 1412 to be deposited. Advantageously, controlling the thickness and placement of the layer of material 1412 to be deposited and generating a biased or angled deposition profile can allow for better control of the direction in which light is emitted from the ICG. As illustrated in Figures 13 and 14, the pattern geometry may be asymmetric, having one or more straight sidewalls, inclined sidewalls, concave or concave sidewalls, multi-stage sidewalls, other sidewalls, or some combination thereof. For example, the pattern geometry may be serrated, with two asymmetric inclined sidewalls, as shown in 1402A, 1404A, and 1406A. In another embodiment, the pattern geometry may have straight sidewalls and multi-stage sidewalls, as shown in 1402B, 1404B, and 1406B. In another embodiment, the pattern geometry may have concave sidewalls and inclined sidewalls, as shown in 1402C, 1404C, and 1406C. In conformal deposition, layer 1412 may cover the top and sides of the diffraction features. In some cases, the thickness of layer 1412 may be substantially equal across different types of pattern geometry (or most of the pattern geometry). In directional deposition, with respect to some cases of linear or angled deposition, the amounts deposited on the top and one or more sides may differ (see, e.g., 1404B, 1406B) or the amounts deposited on two different sides (e.g., opposing sides) may differ (see, e.g., 1404A, 1404B, 1404C, 1406A, 1406B, 1406C). In some cases, one or more sides may have a small amount of material exposed and deposited on it, as in 1406A, 1406B, and 1406C and 1404B and 1404C. In addition, in the case of directional deposition, the thickness of the layer 1412 traversing different types of pattern geometry may depend more strongly on the pattern geometry. For example, in the case of sawtooth geometry 1404A, linear directional deposition may substantially deposit more on the sawtooth portions 1416 with lower inclines than on the sawtooth portions 1418 with higher inclines.In another embodiment, in the case of a sawtooth geometric shape 1406A, a deposition angled approximately perpendicular to the substrate surface 1420 at an angle 1414 θ of 45°~135°, 60°~120°, or 80°~100° would likely deposit more material on such a surface 1420 than an angled deposition where the surface 1422 is parallel to the deposition direction (e.g., having a small angle θ of less than 20° or 10° with respect to the surface).

[0175] The optically transparent or transparent layer may include an optically transparent material that can improve diffraction efficiency for polarization such as S-polarized or TE-polarized light. In some implementations, the transparent layer is not metallic. In some implementations, the transparent layer is a dielectric or semiconductor, for example. In some embodiments, the transparent layer may be a high refractive index dielectric such as titanium dioxide (TiO2), zirconium dioxide (ZrO2), Si3N4, ZnO, SiC, ZnTe, GaP, BP, or other materials. In some embodiments, the high refractive index material 1502 may have a refractive index of 1.9 to 3.5. The transparent material may have a refractive index greater than or equal to 2, such as 2.2, 3, 3.5, 4.0, or other high refractive index values, or may be within any range formed by these values. In some embodiments, the material is a high refractive index material (e.g., n is greater than 2) with a low k (e.g., k is less than 0.05), such as silicon carbide (SiC).

[0176] In some embodiments, the transparent layer may comprise multiple sublayers. For example, the sublayers may include two alternating materials. Figure 15 illustrates an exemplary diffraction grating 1500 having alternating layers deposited on a patterned surface 1506 of a substrate. In some implementations, the sublayers form an interference coating or a band-pass filter coating. In some cases, the sublayers comprise a quarter-wave stack.

[0177] In embodiments where the sublayers include alternating materials, the permeable layer may include alternating sublayers of a high refractive index material 1502 and a low refractive index material 1504. For example, the high refractive index material 1502 may be TiO2, or Si3N4, ZnO, ZrO, having a refractive index of 2.2. 2. The material may include materials having a refractive index greater than or equal to 1.9 or 2, such as TiO2, SiC, ZnTe, GaP, or BP. In some embodiments, the high refractive index material 1502 may have a refractive index of 1.9 to 3.5. In addition, in some designs, the low refractive index material 1504 may include materials having a refractive index lower than or equal to 1.9 or 2, such as SiO2 having a refractive index of 1.45, or less than 1.6. In some embodiments, the alternating layers may include a first layer of high refractive index material 1502, a second layer of low refractive index material 1504, and a third layer of high refractive index material 1504.

[0178] In some implementations, the thickness of one or more sublayers within the composite layer may be varied to achieve a desired reflectance within a certain wavelength of light. For example, the transparent layer may include a thin layer of high refractive index material and a thicker layer of low refractive index material. The thickness of one or more sublayers within the transparent layer, such as a layer of low refractive index material, can be adjusted to increase the reflectance of the transparent layer at a certain wavelength. For example, the thickness of one or both sublayers may be λ / 4 times the refractive index of the material, where λ corresponds to a wavelength or range of wavelengths, or other design wavelength, that has increased reflectance. Graph 1501 in Figure 15 illustrates the reflectance as a function of wavelength with respect to an exemplary diffraction grating 1500, and the thickness of the material within the transparent layer is adjusted to provide increased reflectance 1508 within the indicated range.

[0179] In the embodiment shown in Figure 15, a low refractive index material 1504, such as SiO2, is placed between layers of a high refractive index material 1502, such as TiO2, to create a highly reflective surface. By varying the thickness of one or more of the sublayers 1502, 1504, the diffraction grating 1500 can be configured to allow for maximum reflectivity within a certain wavelength, potentially acting as a color filter or providing some degree of color tuning. For example, the layer thickness may be configured to produce ICG diffraction to select wavelengths such as blue at 450 nm over other wavelengths such as red at 650 nm.

[0180] As discussed above, one or more metal layers may be arranged across the permeable layer. For example, as illustrated in Figure 16, the deposition of one or more metal layers onto the permeable layer can be conformal (1602A, 1602B, 1602C) or directional (1604A, 1604B, 1604C, 1606A, 1606B, 1606C). The deposition type can be the same as or different from the deposition type of the permeable layer. Figure 16 illustrates various combinations. For example, the permeable layer may be deposited conformally (1402A), and the metal layer may be deposited conformally (1602A), linearly in a directional manner (1604A), or angled in a directional manner (1606A). In another embodiment, the permeable layer may be deposited linearly in a directional manner (1404A), and the metallic layer may be deposited conformally (1602B), linearly in a directional manner (1604B), or at an angle in a directional manner (1606B). In another embodiment, the permeable layer may be deposited at an angle in a directional manner (1404A), and the metallic layer may be deposited conformally (1602C), linearly in a directional manner (1604C), or at an angle in a directional manner (1606C).

[0181] Conformal deposition (1602A, 1602B, 1602C) may include various deposition techniques for depositing material 1612, which may result in a material layer covering different sides and portions of a transparent layer positioned on a base pattern geometric shape 1410. In some embodiments, directional deposition may include linear deposition (1604A, 1604B, 1604C) such that the material 1610 to be deposited is incident on the transparent layer material 1412 at an angle approximately perpendicular to the plane or horizontal direction or major planar surface of the substrate. In other embodiments, directional deposition may include angled deposition (1606A, 1606B, 1606C) such that the material 1610 to be deposited is incident on the transparent layer material 1412 at an angle 1616 to the plane or horizontal direction or major planar surface of the substrate. For example, the angle 1616 may be selected based on the pattern geometric shape. For example, the diffraction grating may be a blazed diffraction grating having a sawtooth structure. The orientation may be substantially perpendicular to the surface of the sawtooth structure so that the material to be deposited 1610 is deposited more substantially on a portion (or specific sidewall) of the sawtooth structure, as shown in 1605A, 1606B, and 1606C.

[0182] The deposition type and base pattern geometry can influence the thickness and placement of the layers of material 1612 to be deposited. As discussed above with reference to Figure 14, advantageously, controlling the thickness and placement of the layers of material 1612 to be deposited and generating biased or angled deposition profiles can allow for better control over the emission of light from the ICG in a particular direction. As illustrated in Figures 13-15, the pattern geometry may be asymmetric, having straight sidewalls, angled sidewalls, concave or concave sidewalls, multi-tiered sidewalls, other sidewalls, or some combination thereof. In conformal deposition, the thickness of layers 1612 may be substantially equal across different types of pattern geometry (or a large portion of pattern geometry). In directional deposition, the thickness of layers 1412, 1610 across different types of pattern geometry may depend more strongly on the pattern geometry. For example, in the case of a sawtooth geometric shape 1604A, linearly directional deposition may deposit substantially more material on the sawtooth portions with lower inclines than on the sawtooth portions with higher inclines. In another embodiment, in the case of a sawtooth geometric shape 1606A, angled deposition, substantially perpendicular to the planar or horizontal surface or the main planar surface of the substrate, may deposit more material 1612 on the shallowly inclined surface 1420 than on the steeply inclined surface 1422.

[0183] The metal layer may include metals or conductive materials such as aluminum, silver, gold, copper, or alloys thereof. In some designs, the metal used in the metal layer may be selected to quench certain wavelengths of light. For example, gold or copper may be used to quench light below 600 nm.

[0184] The permeable layer is discussed as the first layer on the base pattern, and the metal layer is discussed as the second layer, although the layers may be placed in any preferred order. In addition, or alternatively, one or more layers of additional material may be present between the base pattern, the permeable layer, or the metal layer. In some embodiments, one or more layers may be repeated or alternating. In some embodiments, one or more layers may be partial layers such that the material which may be part of the layer is deposited on a portion of the substrate or base pattern.

[0185] In some embodiments, an interfacial layer may be present between the metal layer and the permeable layer. The interfacial layer can increase the adhesion strength of the metal layer and the environmental reliability of the stack. For example, without an interfacial layer, the metal layer, such as Ag, Au, Cu, or Al metal, may delaminate from the lattice during unfavorable environmental conditions such as heat and humidity. In some embodiments, the interfacial layer may include TiO2 or other layers that can help bond the metal layer to the polymer surface.

[0186] The deposition of a permeable layer, a metallic layer, or any other layer may include physical vapor deposition (PVD). PVD may include sputtering, evaporation, or other forms of physical vapor deposition. In embodiments where conformal deposition is desired, sputtering may be used. In embodiments where directional deposition is desired, evaporation may be used. In addition, or as an alternative, the deposition of a permeable layer, a metallic layer, or any other layer may include chemical vapor deposition (CVD). CVD may include plasma-enhanced low-pressure deposition, atmospheric pressure deposition, atomic layer deposition (ALD), or other forms of chemical vapor deposition. The form of CVD may be used when conformal deposition is desired. Aspects of PVD or CVD may be varied to affect the physical properties of the deposited layer. For example, the deposition thickness bias may be reduced for highly conformal processes, such as those performed atomically, one single layer at a time. In another embodiment, coating quality (e.g., in terms of particle size or density) may be affected by changes in processing temperature and pressure. Coating quality can, in turn, affect the n and k layers and the shape of adjacent layers coated on top of the deposited layer.

[0187] 3. Exemplary waveguide including a diffraction grating with reduced polarization sensitivity Diffraction gratings having reduced polarization sensitivity as described above can be used in the context of AR displays. For example, a waveguide that may be part of an AR display may include diffraction gratings on one or more sides of the waveguide (such as those described with reference to Figures 6 and 7) that can act as internally coupled optical elements and / or optically dispersed elements and / or externally coupled optical elements. Figure 17A illustrates an exemplary waveguide having multiple diffraction gratings, including a reduced polarization sensitivity diffraction grating that can act as an internally coupled optical element. For example, as shown, waveguide 1710 may include one or more internally coupled gratings (ICGs) 1712, 1714 and one or more diffraction gratings 1720, 1722 that perform optical distribution and / or external coupling. In this embodiment, gratings 1720, 1722 may include pupil expander-extractor (CPE) regions that act as both optically dispersed elements and externally coupled gratings. Light 1702 can be injected into one side of waveguide 1710 through a transmissive ICG 1714. The transmissive ICG 1714 can allow light 1702 to pass through waveguide 1710 and diffract light 1706. Light 1706 can propagate along waveguide 1710 toward one or more pupil expander-extractor gratings 1720, 1722. A second reflective ICG 1712, which may be on the opposite side of waveguide 1710, can also be configured to reflect light 1704 into waveguide 1710. The reflected light 1704 can propagate along waveguide 1710 toward one or more pupil expander-extractor gratings 1720, 1722. As an advantage, the inclusion of one or more ICG1712, 1714 may contribute to image uniformity and / or eyebox efficiency, depending on the light source (e.g., LED, micro-LED, laser, polarized source, or unpolarized source).

[0188] The reflective ICG1712 or the transmissive ICG1714 may include a diffraction grating. The diffraction grating of either or both of the reflective ICG1712 or the transmissive ICG1714 may be formed within a layer on the waveguide or substrate, or within the waveguide itself. The diffraction grating may have diffraction features as described above, for example, with reference to Figures 12A-12B and 13A-13J. For example, the diffraction features of the diffraction grating may have various dimensions and symmetric or asymmetric morphologies.

[0189] In some embodiments, the geometric form of the diffraction feature of reflective ICG1712 and / or transmitted ICG1714 can be symmetrical, with straight sidewalls, angled sidewalls, concave or concave sidewalls, multi-stage sidewalls (e.g., see the third column of the first row in Figure 13A), other types of sidewalls, or some combination thereof. In other embodiments, the geometric form can be asymmetrical, with at least one straight sidewall, angled sidewall, concave (e.g., see the third column of the second row in Figure 13A) or concave sidewall, multi-stage sidewalls (e.g., see the second column of the second row in Figure 13A), other types of sidewalls, or some combination thereof. Regardless of whether the diffraction feature is asymmetrical or symmetrical, in some implementations, a flat region or flat portion may be located at the top of the feature (e.g., a peak). The grating may have a height above or below that defined by a height of 100 nm to 600 nm or that range. For example, a grid may have a depth or height measured from the base to the peak in any range defined by 100–300 nm, 300–600 nm, 200–400 nm, 300–500 nm, etc. The grid may have a pitch above or below 290 nm–690 nm or the range defined therein. If the grid is a blazed grid, it may have a blaze angle measured in the same angular direction, for example, 20–85 degrees, 45–80 degrees, or another angle, and an inverse blaze angle, for example, about 70–150 degrees or any value within the range defined by these values. Values ​​outside of any of these ranges are also possible.

[0190] The reflective ICG1712 may include one or more transparent layers 1713 and / or one or more metallic layers 1711. The metallic layers 1711 may be reflective. In some embodiments, one or more transparent layers 1713 may be efficient in diffracting TE polarization in one or more wavelength ranges. For example, one or more transparent layers may be efficient in diffracting TE polarization in the wavelength range associated with red (e.g., about 620–780 nm), the wavelength range associated with green (e.g., about 492–577 nm), or the wavelength range associated with blue (e.g., 435–493 nm). In some embodiments, one or more metallic layers 1711 may be efficient in diffracting TM polarization in one or more wavelength ranges. For example, one or more metallic layers may be efficient in diffracting TM polarization within the wavelength range associated with red (e.g., approximately 620–780 nm), the wavelength range associated with green (e.g., approximately 492–577 nm), or the wavelength range associated with blue (e.g., 435–493 nm). The transparent ICG1714 may include one or more transparent layers 1715 as described above with reference to Figures 14 and 15. In some embodiments, one or more transparent layers may be efficient in diffracting TE polarization within one or more wavelength ranges. For example, one or more transparent layers may be efficient in diffracting TE polarization within the wavelength range associated with red (e.g., approximately 620–780 nm), the wavelength range associated with green (e.g., approximately 492–577 nm), or the wavelength range associated with blue (e.g., 435–493 nm). In some embodiments, one or more transparent layers 1715 may include nonmetallic materials such as dielectric or semiconductor materials, including, but not limited to, ZrO2, TiO2, or SiC. In various implementations, the diffracted light has a first-order diffraction (e.g., +1 or -1). The majority of the diffracted light may occur within the first order.

[0191] Light received from a projector, such as an image projector, may be diffracted by one or more gratings 1712, 1714 at a certain angle or range of angles, such that the light or at least a portion of it is guided in the waveguide, for example, toward a pupil expander-extractor grating, by total internal reflection. The geometric shape of the diffraction features, e.g., asymmetry or blazed, may preferentially direct the light toward the pupil expander-extractor grating, for example. The pupil expander-extractor grating may be configured to externally couple the light from the waveguide to the user's or wearer's eye. In addition, the pupil expander-extractor grating may increase the area (in two dimensions) over which light exits the waveguide. Thus, the pupil expander-extractor grating may potentially increase the eyebox in some implementations. In various designs, the projector outputs unpolarized or circularly polarized light and directs this unpolarized or circularly polarized light toward the ICG for input into the waveguide. Some embodiments of such projectors, which output unpolarized or circularly polarized light to form an image, may include, for example, micro-LED projectors, digital light projectors (DLP), and liquid crystal on silicon (LCOS) based projectors, but others are also possible.

[0192] Figure 17B illustrates an exemplary waveguide having multiple diffraction gratings that can act as internally coupled optical elements. For example, as shown, waveguide 1710 may include one or more internally coupled gratings (ICGs) 1717, 1714 and one or more gratings 1720, 1722 that perform optical distribution and external coupling. Gratings 1720, 1722 may include one or more pupil expander-extractor (CPE) regions that act as both optical dispersion elements and externally coupled gratings. Light 1702 can be introduced into one side of waveguide 1710 through a transmissive ICG 1714. The transmissive ICG 1714 (e.g., with a transmissive grating) can pass the light 1702 into waveguide 1710 and diffract light 1706. The transmissive ICG 1714 may have a TE diffraction efficiency higher than TM efficiency. Light 1706 can propagate along waveguide 1710 toward one or more pupil expander-extractor gratings 1720, 1722. A second reflective ICG 1713 (e.g., the reflective ICG comprises a reflective diffraction grating), in series with the transmissive ICG 1714 (e.g., matched) and possibly on the opposite side of waveguide 1710, can be configured to diffract and reflect light 1704 into waveguide 1710. The second reflective ICG 1717 may operate in reflection mode and may have a TM diffraction efficiency higher than the TE efficiency. The diffracted / reflected light 1704 can propagate along waveguide 1710 toward one or more pupil expander-extractor gratings 1720, 1722. As an advantage, the inclusion of one or more ICG1712, 1717 may, as possible, contribute to some extent to image uniformity (e.g., brightness and / or color) and / or eyebox efficiency, depending on the light source (e.g., LED, micro-LED, laser, polarized, or unpolarized source).

[0193] The transmissive ICG1714 and / or ICG1717 may be equipped with a diffraction grating. The diffraction grating of either or both of the reflective ICG1717 and transmissive ICG1714 may be formed in a layer on the waveguide or within the waveguide or the substrate itself. The diffraction grating may have diffraction features as described above with reference to Figures 12A-12B and 13A-13J. For example, the diffraction features of the diffraction grating may have various dimensions and different geometric forms. See Figure 13A, for example, showing sawtooth (e.g., row 1, column 2 and row 2, column 1), multi-stage (e.g., row 1, column 3 and row 2, column 2), and concave angle (e.g., row 2, column 3 in Figure 13A). As described herein, the diffraction features may be blazed (e.g., see row 2 in Figure 13A) and direct light in a particular direction.

[0194] In some embodiments, the geometric form of the diffraction feature of the transmissive ICG1714 and / or reflective ICG1717 can be symmetric, with straight sidewalls, angled sidewalls, concave or concave sidewalls, multi-stage sidewalls, other types of sidewalls, or some combination thereof. In other embodiments, the geometric form can be asymmetric, with at least one straight sidewall, angled sidewall, concave or concave sidewall, multi-stage sidewalls, other types of sidewalls, or some combination thereof. Regardless of whether the diffraction feature is asymmetric or symmetric, in some implementations, a flat region or flat portion may be located at the top of the feature (e.g., a peak). The grating may have a height above or below that defined by the height and / or depth or range of 100 nm to 600 nm (e.g., 200 to 400 nm, 205 to 350 nm, 210 to 400 nm, 350 to 500 nm, 300 to 600 nm, 400 to 600 nm, 200 to 600 nm, 200 to 500 nm, or any range formed by any of these values). The grating may have a pitch above or below that defined by the pitch or range of 290 nm to 690 nm. If the grating is a blazed grating, it may have a blaze angle measured in the same angular direction, for example, about 20 to 85 degrees, and an inverse blaze angle, for example, about 70 to 150 degrees or any value within the range defined by these values. These angles may represent interior angles measured from the base of the diffraction grating to the corresponding sidewall or surface. Values ​​outside of any of these ranges are also possible.

[0195] The transmissive ICG1714 may include one or more transmissive layers 1715 as described above with reference to Figures 14, 15, and 17A. The reflective ICG1717 may also include one or more metallic layers 1711. In some embodiments, one or more metallic layers 1711 may be effective in constructing a grating that is efficient in diffracting TM polarization in one or more wavelength ranges. For example, the inclusion of one or more metallic layers may provide increased diffraction efficiency of TM polarization in the wavelength range associated with red (e.g., about 620–780 nm), the wavelength range associated with green (e.g., about 492–577 nm), or the wavelength range associated with blue (e.g., 435–493 nm). Other designs of diffraction gratings that are efficient in diffracting TM polarization, or preferentially diffracting TM polarization, are also possible.

[0196] Advantageously, the combination of a transmissive ICG that preferentially diffracts TE light into the waveguide and a reflective ICG that preferentially diffracts TM light into the waveguide and provides efficient diffraction and internal coupling of both TE and TM polarizations. Therefore, this combination of gratings more efficiently diffracts light containing both TE and TM polarizations, such as unpolarized light, and in the case of the ICG, this light can be coupled into the waveguide. As described above, in various designs, the diffracted light occurs within the first order, such as +1 and / or -1 diffraction order.

[0197] Therefore, light received from a projector such as an image projector may be diffracted by one or more gratings 1717, 1714 such that, at a certain angle or within a range of angles, the main light from the projector or at least a portion thereof is diffracted and coupled into the waveguide and guided therein by total internal reflection toward, for example, a pupil expander-extractor grating, a light dispersion element and / or an external coupling optical element. The geometric shape of the diffraction features, e.g., asymmetry or blazed, may preferentially direct the light toward a particular direction, e.g., toward the pupil expander-extractor grating. The pupil expander-extractor grating may be configured to externally couple the light from the waveguide to the user's or wearer's eye. The pupil expander-extractor grating may also increase the area (in two dimensions) through which light exits the waveguide. Thus, the pupil expander-extractor grating can potentially increase the eyebox in some implementations. In various implementations, the projector outputs unpolarized or circularly polarized light and directs this unpolarized or circularly polarized light to the ICG for input into the waveguide. Some embodiments of such projectors or light sources that output unpolarized or circularly polarized light to form an image may include, for example, micro-LEDs and micro-LED projectors, digital light projectors (DLPs), and liquid crystal on silicon (LCOS) based projectors, but others are also possible.

[0198] Figure 17C illustrates another exemplary waveguide configured to increase the efficiency of coupling light into it. The waveguide includes at least one reduced polarization sensitivity diffraction grating which may act as an internal coupling optical element. For example, as shown, waveguide 1710 may include at least one internal coupling grating (ICG) 1730 and external coupling gratings 1720, 1722. The gratings 1720, 1722 may include pupil expander-extractor (CPE) regions which act as both optical dispersion elements and external coupling gratings. For example, light 1702 from a projector comprising one or more light sources (e.g., micro-LEDs, lasers, LEDs) may be introduced into one side of waveguide 1710 through a transmissive ICG 1730 which comprises a transmissive diffraction grating that diffracts at least a portion of the light transmitted through it. The transmissive ICG 1730 allows light 1702 to pass through its grating into the waveguide 1710 and diffracts light 1706 as it propagates through the grating. The transmissive ICG 1730 may be configured to have both high TM and high TE diffraction efficiency. The grating 1730 may be designed to diffract light incident on it within a range of angles in a certain direction, or within a range of angles that are fully internally reflected within the waveguide. Thus, light 1706 may be guided or propagated along the waveguide 1710 toward one or more pupil expander-extractor gratings 1720, 1722. Advantageously, the inclusion of the transmissive ICG 1730 may contribute to image uniformity and / or eyebox efficiency, depending on the source light (e.g., LED, laser, polarized, or unpolarized).

[0199] The transmissive ICG1730 may be equipped with a diffraction grating. The diffraction grating of the transmissive ICG1730 may be formed in a layer on the waveguide or substrate, or within the waveguide or substrate itself, for example, on its surface. The diffraction grating may have diffraction features as described above with reference to Figures 12A-12B and 13A-13J. For example, the diffraction features of the diffraction grating may have various dimensions and geometric forms. For example, the geometric form of the diffraction features can be symmetrical, with straight sidewalls, angled sidewalls, concave or concave sidewalls, multi-stage sidewalls, other types of sidewalls, or some combination thereof. In another embodiment, the geometric form can be asymmetrical, with at least one straight sidewall, angled sidewall, concave or concave sidewall, multi-stage sidewall, other types of sidewalls, or some combination thereof. Examples of concave or sharktail-shaped sidewalls can be found in Figure 13A (e.g., the second row, third column) and the third row of Figure 14. In some implementations, a flat region or portion may be located at the top of the feature (e.g., the peak), regardless of whether the diffraction features are asymmetric or symmetric. The grating may have a height above or below that defined by a height of 100 nm to 600 nm or its range. As described herein, the height may be 100 to 200 nm, 200 to 300 nm, 205 to 310 nm, 210 to 310 nm, 250 to 350 nm, 300 to 400 nm, 400 to 500 nm, 500 to 600 nm, or any range formed by any of these values, or outside of these ranges. The grating may have a pitch above or below that defined by a pitch of 290 nm to 690 nm or its range. If the grating is a blazed grating, it may have a blaze angle measured in the same angular direction, for example, about 20 to 85 degrees, and an inverse blaze angle, for example, about 70 to 150 degrees or any value within the range defined by these values. As described above, these angles may represent interior angles measured from the base of the diffraction grating to the corresponding sidewall or surface. Values ​​outside of these ranges are also possible.

[0200] Light received from a projector such as an image projector (e.g., equipped with micro-LEDs) is diffracted by one or more gratings 1730 and directed at a certain angle or range of angles so that the light, or at least a portion thereof, is guided in the waveguide toward a pupil expander-extractor grating by total internal reflection. The geometric shape of the diffraction features, e.g., asymmetry or blaze, may preferentially direct the light toward the pupil expander-extractor grating, for example. The pupil expander-extractor grating may be configured to externally couple the light from the waveguide to the user's or wearer's eye. In addition, the pupil expander-extractor grating may increase the area (in two dimensions) over which light exits the waveguide. Thus, the pupil expander-extractor grating can potentially increase the eyebox in some implementations. In various implementations, the projector outputs unpolarized or circularly polarized light and directs this unpolarized or circularly polarized light toward the ICG for input into the waveguide. Some embodiments of such projectors, which output unpolarized or circularly polarized light to form an image, may include, for example, micro-LED projectors, digital light projectors (DLP), and liquid crystal on silicon (LCOS) based projectors, but others are also possible.

[0201] The transmissive ICG1730 may include a high refractive index grating configured to be efficient in both TM and TE modes. For example, ICG1730 may have an improved ICG profile and / or material composition to obtain polarization-insensitive and efficient diffraction over a range of light input angles. For example, ICG1730 may have diffraction efficiencies within a range of 40–90 percent (e.g., 50–60%, 60–70%, 70–80%, 80–90%, or any range between these values) or above with respect to the TE mode, and 40–90 percent (e.g., 50–60%, 60–70%, 70–80%, 80–90%, or any range between these values) or above with respect to the TM mode. In some embodiments, ICG1730 may have similar efficiencies in the TE and TM modes. For example, the ICG1730 may have a TM mode efficiency within 5%, 10%, 20%, 25%, or 30% of its TE mode efficiency (or any range between these values). Alternatively, the ICG1730 may have a TE mode diffraction efficiency within 5%, 10%, 20%, 25%, or 30% of its TM mode efficiency (or any range between these values). Therefore, in various implementations, the difference in diffraction efficiency between TE and TM modes may be within 5%, 10%, 20%, 25%, or 30% of the TE mode efficiency (or any range between these values). Other embodiments are also possible. These efficiencies may be average efficiencies over a range of angles (e.g., 5 degrees, 10 degrees, 20 degrees, 30 degrees, 40 degrees, 50 degrees, or any range between these values). Similarly, these efficiencies may be averaged over wavelengths of visible spectrum light, or wavelengths related to specific colors, such as red, blue, or green, or over a plurality of wavelengths. For example, wavelengths output by light sources in a projector, which may include multiple colored light sources, may be considered. As described above, diffraction may occur in a diffraction mode or a plurality of modes, such as a first-order mode with diffraction order +1 and / or -1.

[0202] Figures 17D-1-17D-4 illustrate exemplary tilted ICG profiles and compositions, along with corresponding polarization efficiency graphs, that can be used to achieve polarization insensitivity within internally coupled grids such as ICG1730 shown in Figure 17C. For example, grid 1742 may produce TM and TE efficiency profiles 1741 shown in the graph, grid 1744 may produce TM and TE efficiency profiles 1743 shown in the graph, grid 1746 may produce TM and TE efficiency profiles 1745, and grid 1748 may produce TM and TE efficiency profiles 1747.

[0203] The grating 1742 illustrated in Figure 17D-1 may include a grating having tilted diffraction features with a tilt angle θ. The tilt angle may include angles of 20 to 85 degrees or other angles. These angles may represent internal angles measured from the base of the diffraction grating to the corresponding sidewall or surface. In some embodiments, the duty cycle 1762A of the grating 1742 may be a percentage of the grating pitch. For example, the duty cycle may be 20 to 80 percent of the pitch, for example, 50 percent of the pitch. The height 1764A of the grating may be, for example, 100 to 600 nm (e.g., 100 to 200, 200 to 300, 300 to 400, 400 to 500, 500 to 600 nanometers, or any range between any of these values). Therefore, the height may be greater than 200 nm, 205 nm, 300 nm, 400 nm, 500 nm, 600 nm, or greater than 700 nm or 800 nm, or within any range formed by any of these values. In some embodiments, the grating 1742 may be located on a layer on the waveguide or substrate or within a portion of the waveguide or substrate itself (e.g., etched into the surface of the substrate). In some embodiments, the substrate may be a material having a refractive index less than 1.9, such as a refractive index in the range of 1.65 to 1.75. Similarly, the refractive index of the substrate may, in some implementations, be less than 1.4 to 1.5, 1.5 to 1.6, 1.6 to 1.7, 1.7 to 1.8, and / or less than 1.8 to 1.9, or within any range formed by any of these values. In some embodiments, the grating features may include a material with a refractive index similar to or identical to that of the substrate or waveguide. In the illustrated embodiment, the grid 1742 has diffraction features having a refractive index of 1.75 on a substrate having a refractive index of 1.75. The materials used to form the diffraction features and to constitute the substrate may be the same or different. The diffraction features may be etched into the substrate, or a layer of material having the same or different refractive indices (e.g., higher or lower) may be used for the diffraction features. For example, the substrate may have a lower refractive index than the material forming the diffraction features.In some cases, for example, the substrate has a refractive index of less than 1.9, while the diffraction features have a refractive index greater than 1.9, or greater than 2.0 or 2.1, or greater than 2.2 or 2.4 or 2.6 or 2.7, for example, or within any range formed by any of these values. Values ​​outside these ranges are also possible. In some embodiments, the grid 1742 may be generated using a high refractive index resist and contact imprinting, or by depositing a high refractive index material and etching into the layer of material.

[0204] The TM and TE diffraction efficiency profiles (1750 and 1752, respectively) associated with grating 1742 may substantially match over a range of incident angles, and / or may be more efficient in TE and more efficient in TM at points within a range of incident angles, as shown in graph 1743. In some embodiments, the average diffraction efficiency may be 40% to 60% or 0.4 to 0.6, or at least 0.45, or 0.5, or 0.6, or 0.7, or 0.8, or 0.9, or 0.95, or 0.99 (for example, having an average efficiency within any range formed by at least 45%, 50%, 55%, 60%, 65%, 70%, 80%, 90%, 95%, or 99%) over a range of incident angles such as -10° to 10°, or over a wider or smaller range (e.g., at least 6°, at least 10°, 20°, 25°, 30°, 35°, 40°, or any range between these values). In some embodiments, the diffraction efficiency is at least 0.4 (or at least 0.45 or at least 0.50 or at least 0.55 or at least 0.6 or at least 0.65 or at least 0.7 or at least 0.8 or at least 0.9) on average over an incident angle range of at least 20 degrees of light, or over an incident angle range of at least 10 degrees of light. In some embodiments, the diffraction efficiency is at least 0.4 or 0.5 or 0.6 or 0.7 or at least 0.8 or at least 0.9 on average over an incident angle range of at least 20 degrees of light, or over an incident angle range of at least 10 degrees of light. In some embodiments, the diffraction efficiency is at least 0.4 or 0.5 or 0.6 or 0.7 or at least 0.8 or at least 0.9 on average over an incident angle range of at least 20 degrees of light, or over an incident angle range of at least 10 degrees of light. In some embodiments, the diffraction efficiency is at least 0.4, 0.5, 0.6, 0.7, or 0.8 over an incident angle range of at least 30 degrees of light.In some embodiments, the diffraction efficiency is at least 0.4 or 0.5 or 0.6 or 0.7 or 0.8 over an incident angle range of at least 20 degrees of light. In some embodiments, the diffraction efficiency is at least 0.4 or 0.5 or 0.6 or 0.7 or 0.8 over an incident angle range of at least 10 degrees of light. The diffraction efficiency may be within any range between any of these values ​​over any of these angular ranges, or similarly, possibly over other larger angular ranges. Similarly, as described above, the average diffraction efficiency over a range of wavelengths may be within 30%, 25%, 20%, 15%, 10%, 5%, 2.5%, 1%, or any range formed by any of these values ​​over an angular range such as 3°, 6°, 12°, 18°, 20°, 25°, 30°, 35°, 40°, or any range formed by any of these values. The diffraction efficiency may be higher with respect to the TE mode in some designs, or higher with respect to the TM mode in some designs. In some designs, the diffraction efficiency may be higher with respect to the TE mode at some angles and with respect to the TM mode at other angles.

[0205] The average diffraction efficiency may be increased by using a higher refractive index material (e.g., a material with a refractive index greater than 2) as illustrated in lattice 1744 of Figure 17D-2. Lattice 1744 is similar to that described with reference to Figure 17D-1, but includes a tilted lattice with a geometric shape and features with diffraction characteristics, consisting of a higher refractive index material 1766 such as a 2.2 refractive index material like TiO2 or a 2.6 refractive index material like SiC. The resulting TM and TE efficiency profiles (1750, 1752, respectively) may be approximately matched over a range of incidence angles (e.g., within 30%, 20%, 15%, 10%, 8%, 5%, etc.) and / or, as illustrated in graph 1745, at a point within a range of incidence angles, it may be more efficient in TE and more efficient in TM (or vice versa). In some embodiments, the average diffraction efficiency may have a peak of approximately 80% to 100% or 0.8 to 0.1 over an incident angle range of -10 to 10 degrees. In some embodiments, the average diffraction efficiency is at least 0.5 or 0.6, or 0.7 or 0.8 or 0.9 or 0.95, or any range formed by any of these values, on average over an incident angle range of at least 10, 20, 30, 40, 50, or 60 degrees of light, or any range formed by any of these values. In some embodiments, the diffraction efficiency is at least 0.5 or 0.6, or 0.7 or 0.8 or 0.9 or 0.95, or any range formed by any of these values, on average over an incident angle range of at least 40 degrees of light. In some embodiments, the diffraction efficiency is at least 0.5 or 0.6, or 0.7 or 0.8 or 0.9 or 0.95, or any range formed by any of these values, on average over an incident angle range of at least 30 degrees of light. In some embodiments, the diffraction efficiency is, on average, at least 0.5 or 0.6, or 0.7 or 0.8 or 0.9 or 0.95, or any range formed by any of these values, over an incident angle range of at least 20 degrees of light.In some embodiments, the diffraction efficiency is at least 0.5 or 0.6, or 0.7 or 0.8 or 0.9 or 0.95, or any range formed by any of these values, on average over an incident angle range of at least 10 degrees of light. In some embodiments, the diffraction efficiency is at least 0.5 or 0.6, or 0.7 or 0.8 or 0.9 or 0.95, or any range formed by any of these values, over an incident angle range of at least 30 degrees of light. In some embodiments, the diffraction efficiency is at least 0.5 or 0.6, or 0.7 or 0.8 or 0.9 or 0.95, or any range formed by any of these values, over an incident angle range of at least 20 degrees of light. In some embodiments, the diffraction efficiency is at least 0.5 or 0.6, or 0.7 or 0.8 or 0.9 or 0.95, or any range formed by any of these values, over an incident angle range of at least 10 degrees of light.

[0206] Similar to lattice 1742, lattice 1744, as illustrated in Figure 17D-2, may include a lattice having tilted diffraction features with a tilt angle θ. The tilt angle may include angles of 20 to 85 degrees or other angles. One side or sidewall is a concave sidewall, and the cross-section has a sharkskin shape. The cross-section is a tilted parallelogram shape, but other shapes are also possible. In some embodiments, the duty cycle 1762B of lattice 1744 may be a percentage of the lattice pitch. For example, the duty cycle may be 20 to 80 percent of the pitch, for example, 50 percent of the pitch. The height 1764B of the lattice may be, for example, 100 to 600 nm (e.g., 100 to 300, 200 to 400, 300 to 500, 400 to 600 nanometers, or any range between any of these values). In various implementations, the height or depth is similarly greater than 200 nm, 205 nm, 210 nm, 250 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, or any range between or outside these values. In some embodiments, the grating 1744 may be located on a layer on the waveguide or substrate, or be part of or embedded within the waveguide or substrate itself, for example, by etching into the substrate. In some embodiments, the substrate may contain a material having a refractive index less than 2 or less than 1.9, such as a refractive index of 1.75. In some embodiments, the grating features may contain a material with a refractive index greater than that of the substrate or waveguide. In the illustrated embodiment, the grating 1744 has a refractive index of 1.75 on a substrate and a diffraction feature having a refractive index of 2.2. Values ​​outside these ranges are also possible. In some embodiments, the grating 1744 may be produced using a high refractive index resist and contact imprinting. In some embodiments, the grid 1744 may be generated using angled etching, such as angled directional etching. Materials that etch preferentially in a certain direction may also be employed. Several exemplary etching methods are described in relation to Figures 13H-13J. Other methods may be employed.Figure 13H shows a method for fabricating a blazed (asymmetric) diffraction feature (3803) having a sawtooth pattern with first and second inclined sidewalls inclined in opposite directions. Figure 13I shows a method for fabricating a blazed (asymmetric) diffraction feature (3853) having a "shark tail" shaped cross-section with first and second inclined sidewalls inclined in the same direction. In Figure 13I, the second sidewall is an example of a concave sidewall or surface. Figures 17D-1-17D-4 also show first and second inclined sidewalls having a second sidewall that is concave sidewall or surface and inclined in the same direction. Other types of lattices with other refractive indices and other material compositions are also possible.

[0207] However, contact imprinting as a mode of manufacture may be more advantageous than etching due to its improved efficiency and ease of manufacture. Therefore, it may be desirable to use materials suitable for use in conjunction with the contact imprinting technique for producing ICG. For example, grids 1746 and 1748 contain ICG profiles with a refractive index of 1.65.

[0208] The lattice 1746 includes a tilted lattice with a material having a refractive index of less than 2 or less than 1.9 or 1.8, for example, 1.65, and a coating deposited on the edge of the lattice using a material having a refractive index greater than 1.9 or greater than 2, such as a material with a refractive index of 2.2, like TiO2, or a material with a refractive index of 2.6, like SiC. The resulting TM and TE efficiency profiles (1750, 1752, respectively) approximate or nearly match over a range of incident angles and / or may be more efficient at TE and more efficient at TM at points within a range of incident angles, or on average, as illustrated in Graph 1745. In some embodiments, the average polarization efficiency may have a peak of about 80% to 100% or 0.8 to 0.1 over an incident angle range of -10 to 10 degrees. In some embodiments, the diffraction efficiency is at least 0.8 on average over an incident angle range of at least 30 degrees. In some embodiments, the diffraction efficiency is at least 0.8 on average over an incident angle range of at least 20 degrees of light. In some embodiments, the diffraction efficiency is at least 0.8 on average over an incident angle range of at least 10 degrees of light. In some embodiments, the diffraction efficiency is at least 0.8 over an incident angle range of at least 30 degrees of light. In some embodiments, the diffraction efficiency is at least 0.8 over an incident angle range of at least 20 degrees of light. In some embodiments, the diffraction efficiency is at least 0.8 over an incident angle range of at least 10 degrees of light.

[0209] In some embodiments, the average diffraction efficiency is at least 0.5 or 0.6, or 0.7 or 0.8 or 0.9 or 0.95, or any range formed by any of these values, over an incident angle range of light of at least 3, 6, 10, 12, 18, 20, 30, 40, 50, or 60 degrees, or any range formed by any of these values. In some embodiments, the diffraction efficiency is at least 0.5 or 0.6, or 0.7 or 0.8 or 0.9 or 0.95, or any range formed by any of these values, over an incident angle range of light of at least 40 degrees. In some embodiments, the diffraction efficiency is at least 0.5 or 0.6, or 0.7 or 0.8 or 0.9 or 0.95, or any range formed by any of these values, over an incident angle range of light of at least 30 degrees. In some embodiments, the diffraction efficiency is at least 0.5 or 0.6, or 0.7 or 0.8 or 0.9 or 0.95, or any range formed by any of these values, on average over an incident angle range of at least 20 degrees of light. In some embodiments, the diffraction efficiency is at least 0.5 or 0.6, or 0.7 or 0.8 or 0.9 or 0.95, or any range formed by any of these values, on average over an incident angle range of at least 10 degrees of light. In some embodiments, the diffraction efficiency is at least 0.5 or 0.6, or 0.7 or 0.8 or 0.9 or 0.95, or any range formed by any of these values, on an incident angle range of at least 30 degrees of light. In some embodiments, the diffraction efficiency is at least 0.5 or 0.6, or 0.7 or 0.8 or 0.9 or 0.95, or any range formed by any of these values, on average over an incident angle range of at least 20 degrees of light. In some embodiments, the diffraction efficiency is at least 0.5 or 0.6, or 0.7 or 0.8 or 0.9 or 0.95, or any range formed by any of these values, over an incident angle range of at least 10 degrees of light.

[0210] The lattice 1748 also includes a blazed lattice having a refractive index of less than 2 or less than 1.9 or 1.8, for example, 1.65, and a coating deposited on the edges of the lattice using a material having a refractive index greater than 1.9 or 2, such as a material with a refractive index of 2.2, like TiO2, or a material with a refractive index of 2.6, like SiC. The resulting TM and TE efficiency profiles (1750, 1752, respectively) approximate or nearly match over a range of incident angles and / or may be more efficient at TE and more efficient at TM at a point within a range of incident angles, as illustrated in Graph 1747. In some embodiments, the average polarization efficiency may have a peak of about 80% to 100% or 0.8 to 0.1 over an incident angle range of -10 to 10 degrees. In some embodiments, the diffraction efficiency is at least 0.8 on average over an incident angle range of at least 30 degrees of light. In some embodiments, the diffraction efficiency is at least 0.8 on average over an incident angle range of at least 20 degrees of light. In some embodiments, the diffraction efficiency is at least 0.8 on average over an incident angle range of at least 10 degrees of light. In some embodiments, the diffraction efficiency is at least 0.8 over an incident angle range of at least 30 degrees of light. In some embodiments, the diffraction efficiency is at least 0.8 over an incident angle range of at least 20 degrees of light. In some embodiments, the diffraction efficiency is at least 0.8 over an incident angle range of at least 10 degrees of light.

[0211] In some embodiments, the average diffraction efficiency is at least 0.5 or 0.6, or 0.7 or 0.8 or 0.9 or 0.95, or any range formed by any of these values, over an incident angle range of light of at least 3, 6, 10, 12, 18, 20, 30, 40, 50, or 60 degrees, or any range formed by any of these values. In some embodiments, the diffraction efficiency is at least 0.5 or 0.6, or 0.7 or 0.8 or 0.9 or 0.95, or any range formed by any of these values, over an incident angle range of light of at least 40 degrees. In some embodiments, the diffraction efficiency is at least 0.5 or 0.6, or 0.7 or 0.8 or 0.9 or 0.95, or any range formed by any of these values, over an incident angle range of light of at least 30 degrees. In some embodiments, the diffraction efficiency is at least 0.5 or 0.6, or 0.7 or 0.8 or 0.9 or 0.95, or any range formed by any of these values, on average over an incident angle range of at least 20 degrees of light. In some embodiments, the diffraction efficiency is at least 0.5 or 0.6, or 0.7 or 0.8 or 0.9 or 0.95, or any range formed by any of these values, on average over an incident angle range of at least 10 degrees of light. In some embodiments, the diffraction efficiency is at least 0.5 or 0.6, or 0.7 or 0.8 or 0.9 or 0.95, or any range formed by any of these values, on an incident angle range of at least 30 degrees of light. In some embodiments, the diffraction efficiency is at least 0.5 or 0.6, or 0.7 or 0.8 or 0.9 or 0.95, or any range formed by any of these values, on average over an incident angle range of at least 20 degrees of light. In some embodiments, the diffraction efficiency is at least 0.5 or 0.6, or 0.7 or 0.8 or 0.9 or 0.95, or any range formed by any of these values, over an incident angle range of at least 10 degrees of light.

[0212] In addition, as described above, the average diffraction efficiency over the wavelength range may be 30%, 25%, 20%, 15%, 10%, 5%, 2.5%, 1%, or any range formed by any of these values, over angular ranges such as 3°, 6°, 12°, 18°, 20°, 25°, 30°, 35°, 40°, or any range formed by any of these values. The diffraction efficiency may be higher with respect to the TE mode in some designs, or higher with respect to the TM mode in some designs. In some designs, the diffraction efficiency may be higher with respect to the TE mode at some angles, and higher with respect to the TM mode at other angles. As illustrated in Figures 17D-3 and 17D-4, the ICG, such as grating 1746 or grating 1748, may include tilted or sharktail gratings, blazed gratings, or other geometric shapes. If the grating is a tilted grating such as grating 1746, the grating may have a tilt angle, which may include, but is not limited to, an angle of 20 to 70 degrees or other angles. If the grating is a blazed grating such as grating 1748, the grating may have a blaze angle of approximately 20 to 85 degrees (shallow size) and an inverse blaze angle (steep side) of 70 to 150 degrees or any value within the range defined by these values, measured in the same angular direction. These angles may represent interior angles measured from the base of the diffraction grating to the corresponding sidewall or surface.

[0213] Furthermore, as described above, various methods may be employed to fabricate diffraction features. In some implementations, imprinting can be cost-effectively employed to form diffraction features from a layer of polymer placed on a substrate. An imprint template may come into contact with the polymer layer, which may, in some cases, be cured using UV and / or thermal curing. Several exemplary methods of etching are also described in relation to Figures 13H-13J.

[0214] In addition, high refractive index material deposited on diffraction grating features may be biased, for example using graze-angle deposition, to provide more material to one side of the diffraction grating feature than to the other. Thus, the thickness and / or coverage may be greater on a first sidewall on one side of the diffraction feature than on a second sidewall on the opposite side of the diffraction feature. In some implementations, it is possible that there is almost no coverage on one sidewall. For example, 90% or 95% of the second sidewall may not be covered. In some cases, deposition on a tilted diffraction feature (e.g., directional deposition) may result in a bias such that more or thicker coverage is provided on the first sidewall or side of the diffraction feature, while almost no deposition is made on the second sidewall or side of the diffraction feature. In some cases, the topography of the underlying diffraction features may facilitate passive bias deposition, as illustrated in Figure 14, for example, in the second and third columns of the third row. Possibly, linear or angled directional etching, when used to deposit material onto a diffraction feature having a concave surface or sidewall (the left sidewall in the diffraction feature shown in row 3 of Figure 14), may not provide much coverage on the concave sidewall or surface.

[0215] Referring to the grid 1746, the duty cycle 1778 of the grid 1746 can be a percentage of the grid pitch. For example, the duty cycle may be 20 to 80 percent of the pitch, for example, 50 percent of the pitch. The height 1774 of the grid may be, for example, 10 to 600 nm. In some embodiments, the grid 1746 may be placed on a substrate or waveguide, or may be part of the waveguide itself. In some embodiments, the substrate may be a material having a refractive index of 1.75. In some embodiments, the grid features may include a material with a refractive index different from that of the substrate or waveguide. In the illustrated embodiment, the grid 1746 comprises a diffraction feature 1770 having a refractive index of 1.65 on a substrate having a refractive index of 1.75. Values ​​outside these ranges are also possible. In some embodiments, material 1772 may be deposited on the diffraction feature 1770. Material 1772 may have a higher refractive index than the diffraction feature 1770. For example, material 1772 may have a refractive index of 2.2. Other values ​​are also possible. The thickness 1776 of material 1772 may be approximately 10-600 nm or another value.

[0216] Referring to grid 1748, the width (WT) at the top of the blazed grid feature 1780 may be greater than the width (WB) at the base of the blazed grid 1784. In some embodiments, WT may be variable or zero. In some embodiments, WB may be variable. For example, WB may be wide enough to allow at least partial filling of the bottom width by the high refractive index coating. For example, WB may be wide enough to allow more than 50% of the width to be filled by the high refractive index coating. In some embodiments, the high refractive index coating may be applied using biased deposition such that the coating is preferentially deposited on the first sidewall over the second sidewall (e.g., a concave sidewall, a vertical sidewall, or a more inclined sidewall). Advantageously, in some cases, this biased deposition can improve the overall average TM and TE efficiencies.

[0217] The lattice height 1782 may be, for example, 100 to 600 nm. In some embodiments, the lattice 1748 may be placed on a substrate or waveguide, or may be part of the waveguide itself. In some embodiments, the substrate may be a material having a refractive index of 1.75. In some embodiments, the lattice features may include a material with a refractive index different from that of the substrate or waveguide. In the illustrated embodiment, the lattice 1746 comprises a diffraction feature 1770 having a refractive index of 1.65 on a substrate having a refractive index of 1.75. Values ​​outside these ranges are also possible. In some embodiments, material 1772 may be deposited on the diffraction feature 1770. Material 1772 may have a higher refractive index than the diffraction feature 1770. For example, material 1772 may have a refractive index of 2.2. Other values ​​are also possible. The thickness 1786 of material 1772 may be about 100 to 600 nm or another value. Other values ​​outside these ranges are also possible.

[0218] As discussed above, in some embodiments, the grid 1744 may be produced using a high refractive index resist and contact imprinting. In some embodiments, the grid 1744 may be produced using tilt etching. Other types of grids, with other material compositions having other refractive indices, are also possible.

[0219] Advantageously, gratings such as blazed gratings with a refractive index coating of 2.2, as discussed with reference to grating 1748, may have improved mean diffraction efficiency, polarization insensitivity, and potentially higher manufacturability than other designs. Advantageously, ICGs, as described with reference to Figures 17C and 17D-3-17D-4, can be used in conjunction with non-polarized sources (e.g., micro-LED sources) in a transmissive mode and in a series configuration within a waveguide stack, as described above with reference to Figure 6. This capability may allow eyepieces utilizing ICGs to have increased brightness and / or field of view. For example, a color exceeding one of the incident light may interact with each ICG in each waveguide color in the stack, which may be advantageous over conventional ICGs with high TM efficiency that are opaque and highly reflective and therefore spatially offset, allowing incident light to pass through each waveguide.

[0220] Similar to the waveguides shown in Figures 17A and 17B, a pair of series-matched ICGs or diffraction gratings with increased polarization insensitivity may be included on the opposite side of the waveguide. One of the ICGs may be a transmissive grating, and the other ICG may be a reflective ICG. Thus, light from an image projector can be directed toward a transmissive ICG on the proximal surface of the waveguide. At least a portion of this light will be diffracted by the transmissive ICG and redirected into the waveguide at an angle such that the light is induced in the waveguide by total internal reflection. This light may be, for example, in a first diffraction order. Other light that is not diffracted, for example in the zero order, may continue forward and be incident on a reflective ICG matched with the transmissive ICG. At least a portion of this light incident on the reflective ICG may be diffracted and thereby coupled into the waveguide and induced therein by total internal reflection. Again, in some implementations, the diffracted light corresponds to the first diffraction order of the reflective diffraction grating. In some implementations, a transmissive diffraction grating or ICG, such as those shown in Figures 17D-1, 17D-2, 17D-3, and 17D-4, may be used. As will be discussed, such a grating may have reduced polarization sensitivity and increased diffraction efficiency with respect to both TE and TM modes. Similarly, light not diffracted by the transmissive grating may be incident on the reflective ICG and diffracted into the waveguide at an angle such that at least a portion of the light is induced in the waveguide by total internal reflection. In some implementations, a reflective diffraction grating or ICG, such as those shown in Figure 11B, may be used. As will be discussed, such a grating may have reduced polarization sensitivity and increased diffraction efficiency with respect to both TE and TM modes. Such a series (or matched) array of diffraction gratings or ICGs increases the efficiency of coupling unpolarized light from the projector into the waveguide and eyepiece, and therefore, potentially, can provide increased brightness to the viewer. In addition, the use of two ICGs can help reduce brightness and color non-uniformity.

[0221] Figure 18 illustrates how a transmissive ICG, such as the transmissive ICG 1714 discussed with reference to Figures 17A and 17B, may be configured to reduce reflection and thereby, and possibly, increase the brightness of the light output to the user / viewer by the waveguide. For example, as illustrated in Figure 18, a transmissive ICG 1801 may receive light 1802 through the side of ICG 1801 that is exposed to air. A zero-order reflection of light 1804 may result in an undesirable reflection loss of light 1802, originating from the grating 1801, passing through one or more transmissive layers 1822, diffracting into ICG 1820, and entering the waveguide 1818.

[0222] Reflection loss can be reduced within the first ICG 1714 if the transparent layer 1822 comprises one or more sublayers 1824, 1826, as discussed above. For example, as shown in Figure 18, the transparent ICG 1803 may include a transparent layer 1822 with one or more sublayers. One or more sublayers may include one or more high refractive index sublayers 1826 such as TiO2 and one or more low refractive index sublayers 1824 such as SiO2. In such a configuration, zero-order reflected light 1804 can be reduced. As discussed above, in some implementations, the sublayers 1824, 1826 or additional sublayers may comprise interference coatings such as quarter-wave stacking. In some embodiments, this configuration can also reduce the first-order diffraction of light 1806 within the ICG 1803. However, reducing reflection loss within the ICG, through the substrate towards the second ICG, can improve image quality by, for example, increasing eyebox efficiency and reducing artifacts such as afterimages or coherent artifacts within the waveguide stack.

[0223] In addition, or alternatively, reflection loss may be reduced by including a material 1828 having a refractive index between air and one or more transparent layers 1822 of the first ICG 1714. For example, as shown in Figure 18, the transparent ICG 1805 may include a material 1828 having a refractive index similar to that of the base pattern 1820 of the ICG. For example, material 1828 may have a refractive index in the range of 1.3 to 1.5. Material 1828 may help reduce zero-order reflections 1808. In some embodiments, this configuration may also reduce the first-order diffraction of light 1806 in the ICG 1803. However, the overall reduction of reflection loss may improve image quality, for example, by increased eyebox efficiency and reduction of artifacts such as afterimages or coherent artifacts in the waveguide stack.

[0224] B. Additional Examples Additional Examples - Part I Example 1: A head-mounted display system, A frame that can be mounted on the head, A light projection system configured to emit light and provide image content, A waveguide supported by a frame, comprising a substrate configured to guide at least a portion of the light from the light projection system into the waveguide, A first diffraction grating extending across the substrate, comprising a material different from the substrate, A first layer arranged across the first diffraction grating, The diffraction grating comprises a second layer, which includes a metal, arranged across the first diffraction grating such that the first diffraction efficiency is 1 to 2 times the second diffraction efficiency, and the diffraction grating has a first diffraction efficiency for a first polarization over a range of angles of light incident thereon, and a second diffraction efficiency for a second polarization over a range of angles of light incident thereon, and the first diffraction efficiency is 1 to 2 times the second diffraction efficiency. A head-mounted display system equipped with the following features.

[0225] Example 2: The head-mounted display system according to Example 1, wherein the substrate contains a lithium-based oxide.

[0226] Example 3: The substrate is a head-mounted display system according to Example 1 or 2, comprising lithium niobate.

[0227] Example 4: The head-mounted display system according to Example 1, wherein the substrate contains silicon carbide.

[0228] Example 5: The head-mounted display system according to Example 1, wherein the substrate comprises a material having a refractive index of at least 1.9.

[0229] Example 6: The head-mounted display system according to Example 1, wherein the substrate comprises a material having a refractive index of at least 2.0.

[0230] Example 7: The head-mounted display system according to Example 1, wherein the substrate comprises a material having a refractive index of at least 2.1.

[0231] Example 8: The head-mounted display system according to Example 1, wherein the substrate comprises a material having a refractive index of at least 2.2.

[0232] Example 9: The head-mounted display system according to Example 1, wherein the substrate comprises a material having a refractive index of at least 2.3.

[0233] Example 10: A head-mounted display system according to any of the above examples, wherein the first diffraction grating material comprises a polymer.

[0234] Example 11: A head-mounted display system according to any of the above examples, wherein the first diffraction grating material includes an imprintable material.

[0235] Example 12: The first diffraction grating material has a refractive index of 1.4 to 1.95, and is a head-mounted display system according to any of the above examples.

[0236] Example 13: The first diffractive grating material is a head-mounted display system according to any of the above examples, having a refractive index lower than that of the substrate.

[0237] Example 14: The first diffractive grating is a head-mounted display system according to any of the above examples, comprising a blazed diffractive grating.

[0238] Example 15: The first diffractive grating is a head-mounted display system according to any of the above examples, having diffractive features and comprising peaks separated by grooves therebetween.

[0239] Example 16: The first diffractive grating is a head-mounted display system according to any of the above examples, having diffractive features and comprising a plurality of straight lines.

[0240] Example 17: The diffractive grating is a waveguide according to any of the above examples, having diffractive features and being asymmetric.

[0241] Example 18: The first layer is a head-mounted display system according to any of the above examples, comprising titanium dioxide (TiO2), zirconium dioxide (ZrO2), or silicon carbide (SiC).

[0242] Example 19: The first layer is a head-mounted display system according to any of the above examples, comprising titanium dioxide (TiO2).

[0243] Example 20: The first layer is a head-mounted display system according to any of the above examples, comprising zirconium dioxide (ZrO2).

[0244] Example 21: The first layer is a head-mounted display system according to any of the above examples, comprising silicon carbide (SiC).

[0245] Example 22: A head-mounted display system according to any of the above examples, comprising a plurality of sublayers, the first layer comprising a first higher refractive index material and a second lower refractive index material.

[0246] Example 23: The head-mounted display system according to Example 22, wherein the first higher refractive index material comprises titanium dioxide (TiO2) and the second lower refractive index material comprises silicon dioxide (SiO2).

[0247] Example 24: The head-mounted display system according to Example 22 or 23, wherein the multiple sublayers comprise only two sublayers.

[0248] Example 25: The head-mounted display system according to Example 22 or 23, wherein the multiple sublayers comprise at least four sublayers.

[0249] Example 26: A head-mounted display system according to any of Examples 22-25, wherein multiple sublayers alternate between a first material and a second material.

[0250] Example 27: A head-mounted display system according to any of Examples 22-26, wherein multiple sublayers are provided with interference coatings.

[0251] Example 28: A head-mounted display system according to any of Examples 22-27, comprising multiple sublayers, each comprising a quarter-wave stack.

[0252] Example 29: A head-mounted display system according to any of the above examples, wherein the metal comprises aluminum, silver, gold, or copper.

[0253] Example 30: A head-mounted display system according to any of the above embodiments, comprising first and second linear polarizations having different polarization angles.

[0254] Example 31: The head-mounted display system according to any of the above embodiments, wherein the first and second polarizations are first and second linear polarizations oriented in orthogonal directions.

[0255] Example 32: The head-mounted display system according to any of the above embodiments, wherein the first and second polarizations are transverse magnetic and transverse electric polarizations, respectively.

[0256] Example 33: The head-mounted display system according to any of the above embodiments, wherein the first and second polarizations are transverse electric and transverse magnetic polarizations, respectively.

[0257] Example 34: The head-mounted display system according to any of the above embodiments, wherein the first diffraction efficiency is the diffraction efficiency for transverse magnetic polarization averaged across the visible light spectrum, and the second diffraction efficiency is the diffraction efficiency for transverse electric polarization averaged across the visible light spectrum.

[0258] Example 35: The head-mounted display system according to any of the above embodiments, wherein the first diffraction efficiency is the diffraction efficiency for transverse electric polarization averaged across the visible light spectrum, and the second diffraction efficiency is the diffraction efficiency for transverse magnetic polarization averaged across the visible light spectrum.

[0259] Example 36: The head-mounted display system according to any of the above embodiments, wherein the first diffraction efficiency is 1 to 1.5 times the second diffraction efficiency.

[0260] Example 37: The head-mounted display system according to any of the above embodiments, wherein the first diffraction efficiency is 1 to 1.4 times the second diffraction efficiency.

[0261] Example 38: The head-mounted display system according to any of the above embodiments, wherein the first diffraction efficiency is 1 to 1.3 times the second diffraction efficiency.

[0262] Example 39: A head-mounted display system according to any of the above examples, wherein the first diffraction efficiency is 1 to 1.2 times that of the second diffraction efficiency.

[0263] Example 40: A head-mounted display system according to any of the above examples, wherein the first diffraction efficiency is 1 to 1.1 times that of the second diffraction efficiency.

[0264] Example 41: A head-mounted display system according to any of the above embodiments, wherein the angle range is at least 6 degrees.

[0265] Example 42: A head-mounted display system according to any of the above embodiments, wherein the angle range is at least 12 degrees.

[0266] Example 43: A head-mounted display system according to any of the above embodiments, wherein the angle range is at least 18 degrees.

[0267] Example 44: A head-mounted display system according to any of the above embodiments, wherein the angle range is at least 22 degrees.

[0268] Example 45: A head-mounted display system according to any of the above examples, wherein the angle range is between ±3 degrees with respect to the plane of the substrate.

[0269] Example 46: A head-mounted display system according to any of the above examples, wherein the angle range is between ±6 degrees with respect to the plane of the substrate.

[0270] Example 47: A head-mounted display system according to any of the above examples, wherein the angle range is between ±9 degrees with respect to the plane of the substrate.

[0271] Example 48: A head-mounted display system according to any of the above examples, wherein the angle range is between ±11 degrees with respect to the plane of the substrate.

[0272] Example 49: A head-mounted display system according to any of the above embodiments, wherein the waveguide is contained within an eyepiece and configured to direct light towards the eye of a user wearing the head-mounted display.

[0273] Example 50: The head-mounted display system according to Example 49, wherein the eyepiece is positioned on a frame and configured to direct light from a light projection system into the user's eye and display augmented reality image content in the user's field of view, and at least a portion of the eyepiece is transparent and positioned in front of the user's eye when the user wears the head-mounted display system, and the transparent portion transmits light from a portion of the physical environment in front of the user to the user's eye and provides a view of a portion of the physical environment in front of the user.

[0274] Example 51: The head-mounted display system according to Example 49 or 50, wherein the eyepiece comprises the at least one waveguide, the at least one waveguide being transparent to visible light so that a user can see through the waveguide.

[0275] Example 52: A head-mounted display system according to any of the above embodiments, wherein the waveguide comprises an internal coupling optical element for coupling light from the optical projection system into the waveguide so that it is guided therein.

[0276] Example 53: A head-mounted display system according to any of the above embodiments, wherein the waveguide comprises an external coupling optical element for coupling light from the light projection system out of the waveguide, directing the light towards the user's eyes, and presenting the image content to the viewer.

[0277] Example 54: A head-mounted display system according to any of the above embodiments, wherein the first diffraction grating comprises an externally coupled grating (EPE) configured to externally couple light from the optical projection system induced within the waveguide to the outside of the waveguide.

[0278] Example 55: A head-mounted display system according to any of the above embodiments, wherein the first diffraction grating comprises an internally coupled grating (ICG) configured to internally couple light from the optical projection system into the waveguide.

[0279] Example 56: A head-mounted display system according to any of the above embodiments, wherein the second layer is configured to be positioned across the first layer.

[0280] Example 57: A head-mounted display system according to any of the above embodiments, further comprising a third layer disposed between the first layer and the second layer.

[0281] Example 58: The head-mounted display system according to Example 57, wherein the third layer is configured to help bond the second layer to the first layer.

[0282] Example 59: A second diffraction grating, comprising a material different from the substrate, is arranged across the substrate. A head-mounted display system according to any of the above embodiments, comprising: a second diffraction grating, a fourth layer, which is arranged across the second diffraction grating such that it has a third diffraction efficiency for a first polarization over a range of angles of light incident thereon, wherein the first diffraction grating is arranged across the substrate on a first side of the substrate, and the second diffraction grating is arranged across the substrate on a second side of the substrate, opposite to the first side of the substrate.

[0283] Example 60: A head-mounted display system according to any of the above examples, wherein the first layer is conformally deposited on one or more diffraction features of the first diffraction grating.

[0284] Example 61: A head-mounted display system according to any of the above embodiments, wherein the first layer is deposited directionally at an angle on one or more diffraction features.

[0285] Example 62: The head-mounted display system according to Example 61, wherein the angle includes 75 to 105 degrees with respect to the main planar surface of the substrate.

[0286] Example 63: The head-mounted display system according to Example 61, wherein the angle is 75 to 105 degrees with respect to the surface of one or more diffraction features of the first diffraction grating.

[0287] Example 64: A head-mounted display system according to any of the above examples, wherein the second layer is conformally deposited on one or more diffraction features of the first diffraction grating.

[0288] Example 65: A head-mounted display system according to any of the above embodiments, wherein the second layer is deposited directionally at an angle on one or more diffraction features of the first diffraction grating.

[0289] Example 66: The head-mounted display system according to Example 65, wherein the angle includes 75 to 105 degrees with respect to the main planar surface of the substrate.

[0290] Example 67: The head-mounted display system according to Example 65, wherein the angle is 75 to 105 degrees with respect to the surface of one or more diffraction features of the first diffraction grating.

[0291] Example 68: A head-mounted display system according to any of the above examples, wherein the first diffraction grating is formed in a 1D array and has diffraction features.

[0292] Example 69: A head-mounted display system according to any of Examples 1-68, wherein the first diffraction grating is formed in a 2D array and has diffraction features.

[0293] Example 70: The head-mounted display system according to Example 69, wherein the 2D array comprises a square array.

[0294] Example 71: A head-mounted display according to any of the above examples, wherein the diffraction features are asymmetrical to provide a blazed grating.

[0295] Example 72: A head-mounted display according to any of the above examples, wherein the diffraction feature has a material deposited asymmetrically thereon to provide a blazed lattice.

[0296] Example 73: A head-mounted display according to any of the above embodiments, wherein the first diffraction grating is configured to preferentially direct light in at least two directions.

[0297] Example 74: A head-mounted display according to any of the above embodiments, wherein the first diffraction grating is blazed in two directions.

[0298] Example 75: A head-mounted display system according to any of the above embodiments, wherein the first diffraction grating comprises a one-dimensional grating.

[0299] Example 76: A head-mounted display system according to any of Examples 1-75, wherein the first diffraction grating comprises a two-dimensional grating.

[0300] Example 77: A second diffraction grating, comprising a material different from the substrate, is arranged across the substrate. A second diffraction grating has a third diffraction efficiency for a first polarization over a certain range of angles of light incident on it, and a fourth diffraction efficiency for a second polarization over that range of angles of light incident on it, and a fourth layer arranged across the second diffraction grating. A head-mounted display system according to any of the above embodiments, comprising: a first diffraction grating arranged across the substrate on the first side of the substrate; and a second diffraction grating arranged across the substrate on the second side of the substrate, opposite the first side of the substrate.

[0301] Example 78: A second diffraction grating is formed within the substrate, The second diffraction grating has a fourth layer arranged across it such that it has a third diffraction efficiency for a first polarization over a certain range of angles of light incident thereon, and a fourth diffraction efficiency for a second polarization over that range of angles of light incident thereon. A head-mounted display system according to any of the above embodiments, comprising: a first diffraction grating arranged across the substrate on the first side of the substrate; and a second diffraction grating arranged across the substrate on the second side of the substrate, opposite the first side of the substrate.

[0302] Example 79: A head-mounted display system according to any of the above embodiments, wherein the substrate is configured to guide at least a portion of the light from the light projection system into the waveguide via the second diffraction grating.

[0303] Example 80: A head-mounted display system according to any of the above embodiments, wherein the third diffraction efficiency for the first polarization over a range of angles of light incident thereon exceeds the fourth diffraction efficiency for the second polarization over a range of angles of light incident thereon.

[0304] Example 81: A head-mounted display system according to any of the above embodiments, wherein the third diffraction efficiency is at least six times the fourth diffraction efficiency over the range of the angle.

[0305] Example 82: A head-mounted display system according to any of the above embodiments, wherein the third diffraction efficiency for the first polarization over a range of angles of light incident thereon is less than the fourth diffraction efficiency for the second polarization over a range of angles of light incident thereon.

[0306] Example 83: A head-mounted display system according to any of the above embodiments, wherein the fourth diffraction efficiency is at least six times the third diffraction efficiency over the range of the angle.

[0307] Example 84: A head-mounted display system according to any of the above examples, wherein the fourth layer includes a dielectric.

[0308] Example 85: A head-mounted display system according to any of the above examples, wherein the substrate comprises a material having a refractive index of 2.6 or less.

[0309] Example 86: A head-mounted display system according to any of the above examples, wherein the substrate comprises a material having a refractive index of 2.7 or less.

[0310] Example 87: A head-mounted display system according to any of the above examples, wherein the substrate comprises a material having a refractive index of 2.8 or less.

[0311] Example 88: A head-mounted display system according to any of the above examples, wherein the first layer comprises a dielectric.

[0312] Example 89: A head-mounted display system according to any of the above examples, wherein the first layer comprises a material having a refractive index of 1.9 or greater.

[0313] Example 90: A head-mounted display system according to any of the above examples, wherein the first layer comprises a material having a refractive index of 2.0 or greater.

[0314] Example 91: A head-mounted display system according to any of the above examples, wherein the first layer comprises a material having a refractive index of 2.1 or greater.

[0315] Example 92: A head-mounted display system according to any of the above embodiments, further comprising a plurality of sublayers over the first layer, wherein the plurality of sublayers comprises a first higher refractive index material and a second lower refractive index material.

[0316] Example 93: The head-mounted display system according to Example 92, wherein the first higher refractive index material comprises titanium dioxide (TiO2) and the second lower refractive index material comprises silicon dioxide (SiO2).

[0317] Example 94: The head-mounted display system according to Example 92 or 93, wherein the multiple sublayers comprise only two sublayers.

[0318] Example 95: The head-mounted display system according to Example 92 or 93, wherein the plurality of sublayers comprises at least four sublayers.

[0319] Example 96: A head-mounted display system according to any of Examples 92-95, wherein multiple sublayers alternate between a first material and a second material.

[0320] Example 97: A head-mounted display system according to any of Examples 92-96, wherein multiple sublayers are provided with interference coatings.

[0321] Example 98: A head-mounted display system according to any of Examples 92-97, wherein multiple sublayers comprise a quarter-wave stack.

[0322] Example 99: A head-mounted display system according to any of Examples 92-98, wherein multiple sublayers across the first layer form a band-pass filter.

[0323] Example 100: A head-mounted display system according to any of Examples 92-98, wherein a plurality of sublayers across the first layer form a notch filter.

[0324] Example 101: A head-mounted display system according to any of Examples 92-98, wherein multiple sublayers across the first layer form an anti-reflective (AR) coating.

[0325] Example 102: The head-mounted display system according to any of Examples 92-101, wherein the first lower refractive index material has a refractive index of 1.6 or less.

[0326] Example 103: A head-mounted display system according to any of Examples 92-102, wherein the second higher refractive index material has a refractive index of 1.9 or greater.

[0327] Example 104: A head-mounted display system according to any of Examples 92-103, wherein the first lower refractive index material comprises silicon dioxide.

[0328] Example 105: A head-mounted display system according to any of Examples 92-104, wherein the second higher refractive index material is titanium dioxide.

[0329] Example 106: A head-mounted display system according to any of Examples 92-104, wherein the second higher refractive index material is zirconium dioxide.

[0330] Example 107: A head-mounted display system according to any of Examples 92-104, wherein the second higher refractive index material is zinc oxide.

[0331] Example 108: A head-mounted display system according to any of the above embodiments, wherein the first diffraction grating has an average diffraction efficiency for the first polarization over the range of angles, and the second diffraction efficiency has an average diffraction efficiency for the second polarization over the range of angles.

[0332] Example 109: A head-mounted display system according to any of the above embodiments, wherein the first diffraction efficiency averaged over the range of angles and the second diffraction efficiency averaged over the range of angles have an efficiency of at least 40%.

[0333] Example 110: A head-mounted display system according to any of the above embodiments, wherein the first diffraction efficiency averaged over the range of angles and the second diffraction efficiency averaged over the range of angles have an efficiency of at least 50%.

[0334] Example 111: A head-mounted display system according to any of the above embodiments, wherein the first diffraction efficiency averaged over the range of angles and the second diffraction efficiency averaged over the range of angles have an efficiency of at least 60%.

[0335] Example 112: A head-mounted display system according to any of the above embodiments, wherein the angle range is at least 25 degrees.

[0336] Example 113: A head-mounted display system according to any of the above embodiments, wherein the angle range is at least 30 degrees.

[0337] Example 114: A head-mounted display system according to any of the above embodiments, wherein the angle range is at least 35 degrees.

[0338] Example 115: A head-mounted display system according to any of the above embodiments, wherein the angle range is at least 40 degrees.

[0339] Example 116: A head-mounted display system according to any of the above examples, wherein the angle range is between ±15 degrees with respect to the plane of the substrate.

[0340] Example 117: A head-mounted display system according to any of the above examples, wherein the angle range is between ±18 degrees with respect to the plane of the substrate.

[0341] Example 118: A head-mounted display system according to any of the above examples, wherein the angle range is between ±20 degrees with respect to the plane of the substrate.

[0342] Example 119: A head-mounted display system according to any of the above embodiments, wherein the first diffraction grating comprises first and second side walls and has diffraction features.

[0343] Example 120: The head-mounted display system according to Example 119, wherein the first and second side walls are separated by a flat area.

[0344] Example 121: The head-mounted display system according to Example 119, wherein the first and second sidewalls are joined to form a prominent angle over the diffraction feature.

[0345] Example 122: A head-mounted display system according to any one of Examples 119-121, wherein at least the first side wall is inclined at an angle such that the first side wall is not as steep as the second side wall.

[0346] Example 123: A head-mounted display system according to any one of Examples 119-122, wherein the first side wall is wider than the second side wall.

[0347] Example 124: A head-mounted display system according to any of Examples 119-123, wherein the first sidewall forms an angle of 45° to 85° at the base of the diffraction feature.

[0348] Example 125: A head-mounted display system according to any one of Examples 119-124, wherein the second side wall forms an acute concave angle at the base of the diffraction feature.

[0349] Example 126: The head-mounted display system according to any one of Examples 119-125, wherein the first diffraction grating has shark tail-shaped diffraction features.

[0350] Example 127: A head-mounted display system according to any one of Examples 119-124, wherein the second sidewall forms an obtuse concave angle at the base of the diffraction feature.

[0351] Example 128: The head-mounted display system according to any of Examples 119-124, wherein the second side wall is vertical.

[0352] Example 129: A head-mounted display system according to any one of Examples 119-124 or 127-128, wherein the first diffraction grating has a sawtooth-shaped diffraction feature.

[0353] Example 130: A head-mounted display system according to any of the above embodiments, wherein the first layer comprises a biased deposition.

[0354] Example 131: A head-mounted display system according to any of the above embodiments, wherein the first layer comprises a graze-angle deposition.

[0355] Example 132: A head-mounted display system according to any of Examples 119-131, wherein the first layer is biased to provide more coverage on the first sidewall than on the second sidewall.

[0356] Example 133: A head-mounted display system according to any of Examples 119-132, wherein the first layer covers a proportion of the first sidewall that is greater than the second sidewall.

[0357] Example 134: A head-mounted display system according to any of Examples 119-133, wherein the first layer is biased to provide a thicker covering on the first sidewall than the second sidewall.

[0358] Example 135: A head-mounted display system according to any of Examples 119-134, wherein the first layer provides a covering on the first sidewall that is on average thicker than the second sidewall.

[0359] Example 136: A head-mounted display system according to any of Examples 119-135, wherein the first side wall is completely covered by the second layer.

[0360] Example 137: A head-mounted display system according to any of Examples 119-136, wherein at least a portion of the second side wall is not covered by the first layer.

[0361] Example 138: A head-mounted display system according to any of Examples 119-137, wherein the second side wall includes an area that is not covered by the first layer, more than the area of ​​the first side wall.

[0362] Example 139: A head-mounted display system according to any one of Examples 119-138, wherein the second layer comprises conformal deposition.

[0363] Example 140: A head-mounted display system according to any of Examples 119-139, wherein the first and second side walls are completely covered by the second layer.

[0364] Example 141: A head-mounted display system according to any of Examples 119-140, wherein the second layer is not biased to cover more of the first sidewall than the second sidewall.

[0365] Example 142: A head-mounted display system according to any of Examples 119-141, wherein the second layer does not provide a thicker covering on the first sidewall than the second sidewall.

[0366] Example 143: A head-mounted display system according to any of Examples 119-142, wherein the second layer does not provide a covering on the first sidewall that is on average thicker than the second sidewall.

[0367] Example 144: The head-mounted display system according to any of Examples 119-143, wherein the second side wall is entirely covered by the second layer.

[0368] Example 145: A head-mounted display system according to any of Examples 119-144, wherein the second sidewall does not include an area that is not covered by the second layer, more than the area of ​​the first sidewall.

[0369] Example 146: A head-mounted display system according to any of the above examples, wherein the first diffraction efficiency for the first polarization is within 20% of the second diffraction efficiency for the second polarization.

[0370] Example 147: A head-mounted display system according to any of the above examples, wherein the first diffraction efficiency for the first polarization is within 30% of the second diffraction efficiency for the second polarization.

[0371] Example 148: A head-mounted display system according to any of the above embodiments, wherein the first diffraction grating, on which the first and second layers are formed, comprises a reflective diffraction grating.

[0372] Example 149: A head-mounted display system according to any of the above embodiments, comprising a reflective diffraction grating, the first diffraction grating having the first and second layers formed thereon, configured to diffract reflected light and couple the light into the waveguide so as to be guided therein by total internal reflection.

[0373] Example 150: A head-mounted display system according to any of Examples 1-148, comprising a reflective diffraction grating, wherein the first diffraction grating, on which the first and second layers are formed, is configured to diffract reflected light and couple the light induced in the waveguide out of the waveguide by total internal reflection.

[0374] Example 151: The diffractive feature has a height of 100 to 600 nanometers, and is a head-mounted display system according to any of the above examples.

[0375] Example 152: The diffractive feature has a height of 200 to 600 nanometers, and is a head-mounted display system according to any of the above examples.

[0376] Example 153: The diffractive feature has a height of 300 to 600 nanometers, and is a head-mounted display system according to any of the above examples.

[0377] Example 154: The head-mounted display system according to any of the above examples, wherein the diffraction features have a pitch of 290 nm to 690 nm.

[0378] Example 155: The light projection system is a head-mounted display system according to any of the above embodiments, comprising microLEDs.

[0379] Example 156: The light projection system is a head-mounted display system according to any of the above embodiments, comprising a DLP or LCOS display.

[0380] Example 157: The head-mounted display system according to any of the above examples, wherein the substrate contains nanoparticles.

[0381] Example 158: The head-mounted display system according to any of the above examples, wherein the substrate contains inorganic nanoparticles.

[0382] Example 159: The head-mounted display system according to any of the above examples, wherein the substrate comprises a polymer.

[0383] Additional Examples - Part II Example 1: A head-mounted display system, A frame that can be mounted on the head, A light projection system configured to emit light and provide image content, A waveguide supported by a frame, the waveguide comprising a substrate containing an optically transparent material and a first diffraction grating formed within the substrate, the substrate being A first layer is arranged across the first diffraction grating formed within the substrate, A first diffraction grating has a first diffraction efficiency for a first polarization over a certain range of angles of light incident thereon, and a second diffraction efficiency for a second polarization over the same range of angles of light incident thereon, wherein the first diffraction efficiency is 1 to 2 times that of the second diffraction efficiency, and a second layer containing a metal is disposed over the first diffraction grating formed in the substrate. A waveguide configured to guide at least a portion of the light from the light projection system into the waveguide, A head-mounted display system equipped with the following features.

[0384] Example 2: The head-mounted display system according to Example 1, wherein the optically transparent material constituting the substrate has a refractive index of 1.45 to 2.0.

[0385] Example 3: The head-mounted display system according to Example 1 or 2, wherein the transparent material constituting the substrate includes a polymer.

[0386] Example 4: A head-mounted display system according to any of the above examples, wherein the first layer comprises titanium dioxide (TiO2), zirconium dioxide (ZrO2), or silicon carbide (SiC).

[0387] Example 5: A head-mounted display system according to any of the above embodiments, wherein the first layer comprises a plurality of sub-layers.

[0388] Example 6: The head-mounted display system according to Example 5, comprising a plurality of sublayers, the first layer comprising a first higher refractive index material and a second lower refractive index material.

[0389] Example 7: A head-mounted display system according to Example 5 or 6, wherein the first higher refractive index material comprises titanium dioxide (TiO2) and the second lower refractive index material comprises silicon dioxide (SiO2).

[0390] Example 8: A head-mounted display system according to any of Examples 5-7, wherein the multiple sublayers comprise only two sublayers.

[0391] Example 9: A head-mounted display system according to any one of Examples 5-7, wherein the multiple sublayers comprise at least four sublayers.

[0392] Example 10: A head-mounted display system according to any of Examples 6-9, wherein multiple sublayers alternate between a first material and a second material.

[0393] Example 11: A head-mounted display system according to any of Examples 5-10, wherein multiple sublayers are provided with interference coatings.

[0394] Example 12: A head-mounted display system according to any of Examples 5-11, comprising multiple sublayers, each comprising a quarter-wave stack.

[0395] Example 13: A head-mounted display system according to any of the above examples, wherein the metal comprises aluminum, silver, gold, or copper.

[0396] Example 14: The head-mounted display system according to any of the above embodiments, wherein the first diffraction grating comprises a blazed diffraction grating.

[0397] Example 15: The head-mounted display system according to Example 14, wherein the first diffraction grating has diffraction features, the peaks being spaced apart by grooves between them.

[0398] Example 16: The first diffraction grating is a head-mounted display system according to any of the above embodiments, comprising diffraction features having a plurality of straight lines.

[0399] Example 17: A waveguide according to any of the above examples, wherein the diffraction grating is asymmetric and has diffraction characteristics.

[0400] Example 18: A head-mounted display system according to any of the above embodiments, comprising first and second linear polarizations having different polarization angles.

[0401] Example 19: A head-mounted display system according to any of the above embodiments, comprising first and second linear polarizations oriented in orthogonal directions.

[0402] Example 20: A head-mounted display system according to any of the above examples, wherein the first and second polarization directions are transverse magnetic and transverse electropolarization, respectively.

[0403] Example 21: A head-mounted display system according to any of Examples 1-19, wherein the first and second polarization directions are transverse electric and transverse magnetic polarization, respectively.

[0404] Example 22: A head-mounted display system according to any of Examples 1-19, wherein the first diffraction efficiency comprises a diffraction efficiency for transverse magnetic polarization averaged across the visible light spectrum, and the second diffraction efficiency comprises a diffraction efficiency for transverse electric polarization averaged across the visible light spectrum.

[0405] Example 23: A head-mounted display system according to any of Examples 1-19, wherein the first diffraction efficiency comprises a diffraction efficiency for transverse electric polarization averaged across the visible light spectrum, and the second diffraction efficiency comprises a diffraction efficiency for transverse magnetic polarization averaged across the visible light spectrum.

[0406] Example 24: A head-mounted display system according to any of the above examples, wherein the first diffraction efficiency is 1 to 1.5 times that of the second diffraction efficiency.

[0407] Example 25: A head-mounted display system according to any of the above examples, wherein the first diffraction efficiency is 1 to 1.4 times that of the second diffraction efficiency.

[0408] Example 26: A head-mounted display system according to any of the above examples, wherein the first diffraction efficiency is 1 to 1.3 times that of the second diffraction efficiency.

[0409] Example 27: A head-mounted display system according to any of the above examples, wherein the first diffraction efficiency is 1 to 1.2 times that of the second diffraction efficiency.

[0410] Example 28: A head-mounted display system according to any of the above examples, wherein the first diffraction efficiency is 1 to 1.1 times that of the second diffraction efficiency.

[0411] Example 29: A head-mounted display system according to any of the above embodiments, wherein the angle range is at least 6 degrees.

[0412] Example 30: A head-mounted display system according to any of the above embodiments, wherein the angle range is at least 12 degrees.

[0413] Example 31: A head-mounted display system according to any of the above embodiments, wherein the angle range is at least 18 degrees.

[0414] Example 32: A head-mounted display system according to any of the above embodiments, wherein the angle range is at least 22 degrees.

[0415] Example 33: A head-mounted display system according to any of the above examples, wherein the angle range is between ±3 degrees with respect to the plane of the substrate.

[0416] Example 34: A head-mounted display system according to any of the above examples, wherein the angle range is between ±6 degrees with respect to the plane of the substrate.

[0417] Example 35: A head-mounted display system according to any of the above examples, wherein the angle range is between ±9 degrees with respect to the plane of the substrate.

[0418] Example 36: A head-mounted display system according to any of the above examples, wherein the angle range is between ±11 degrees with respect to the plane of the substrate.

[0419] Example 37: A head-mounted display system according to any of the above embodiments, wherein the waveguide is contained within an eyepiece and configured to direct light towards the eyes of a user wearing the head-mounted display.

[0420] Example 38: The head-mounted display system according to Example 37, wherein the eyepiece is positioned on a frame and configured to direct light from a light projection system into the user's eye and display augmented reality image content in the user's field of view, and at least a portion of the eyepiece is transparent and positioned in front of the user's eye when the user wears the head-mounted display system, and the transparent portion transmits light from a portion of the physical environment in front of the user to the user's eye, providing a view of a portion of the physical environment in front of the user.

[0421] Example 39: The head-mounted display system according to Example 37 or 38, wherein the eyepiece comprises the at least one waveguide, the at least one waveguide being transparent to visible light so that a user can see through the waveguide.

[0422] Example 40: A head-mounted display system according to any of the above embodiments, wherein the waveguide comprises an internal coupling optical element for coupling light from the light projection system into the waveguide so that it is guided therein.

[0423] Example 41: A head-mounted display system according to any of the above embodiments, wherein the waveguide comprises an external coupling optical element for coupling light from the light projection system out of the waveguide, directing the light towards the user's eyes, and presenting the image content to the viewer.

[0424] Example 42: A head-mounted display system according to any of the above embodiments, wherein the first diffraction grating comprises an internally coupled grating (ICG) configured to internally couple light from the optical projection system into the waveguide.

[0425] Example 43: A head-mounted display system according to any of the above embodiments, wherein the first diffraction grating comprises an externally coupled grating (EPE) configured to externally couple light from the optical projection system induced in the waveguide to the outside of the waveguide.

[0426] Example 44: A head-mounted display system according to any of the above embodiments, wherein the second layer is configured to be positioned across the first layer.

[0427] Example 45: A head-mounted display system according to any of the above embodiments, further comprising a third layer disposed between the first layer and the second layer.

[0428] Example 46: The head-mounted display system according to Example 45, wherein the third layer is configured to help bond the second layer to the first layer.

[0429] Example 47: The waveguide comprises a second diffraction grating formed within the substrate, the substrate configured to guide at least a portion of the light from the light projection system into the waveguide via the second diffraction grating, and the head-mounted display system further comprises a fourth layer positioned across the second diffraction grating such that the second diffraction grating has a third diffraction efficiency for a first polarization over a range of angles of light incident thereon. A head-mounted display system according to any of the above embodiments, wherein a first diffraction grating is formed in the substrate on the first side of the substrate, and a second diffraction grating is formed in the substrate on the second side of the substrate, opposite to the first side of the substrate.

[0430] Example 48: A head-mounted display system according to any of the above examples, wherein the first layer is conformally deposited on one or more diffraction features of the first diffraction grating.

[0431] Example 49: A head-mounted display system according to any of the above embodiments, wherein the first layer is deposited directionally at an angle on one or more diffraction features.

[0432] Example 50: The head-mounted display system according to Example 49, wherein the angle includes 75 to 105 degrees with respect to the main planar surface of the substrate.

[0433] Example 51: The head-mounted display system according to Example 49, wherein the angle is 75 to 105 degrees with respect to the surface of one or more diffraction features of the first diffraction grating.

[0434] Example 52: A head-mounted display system according to any of the above examples, wherein the second layer is conformally deposited on one or more diffraction features of the first diffraction grating.

[0435] Example 53: A head-mounted display system according to any of the above examples, wherein the second layer is deposited directionally at an angle on one or more diffraction features of the first diffraction grating.

[0436] Example 54: The head-mounted display system according to Example 53, wherein the angle includes 75 to 105 degrees with respect to the main planar surface of the substrate.

[0437] Example 55: The head-mounted display system according to Example 53, wherein the angle is 75 to 105 degrees with respect to the surface of one or more diffraction features of the first diffraction grating.

[0438] Example 56: A head-mounted display system according to any of the above examples, wherein the first diffraction grating is formed in a 1D array and has diffraction features.

[0439] Example 57: A head-mounted display system according to any of Examples 1-55, wherein the first diffraction grating is formed in a 2D array and has diffraction features.

[0440] Example 58: The head-mounted display system according to Example 57, wherein the 2D array comprises a square array.

[0441] Example 59: A head-mounted display according to any of the above examples, wherein the diffraction features are asymmetrical to provide a blazed grating.

[0442] Example 60: A head-mounted display according to any of the above examples, wherein the diffraction feature has a material deposited asymmetrically thereon to provide a blazed lattice.

[0443] Example 61: A head-mounted display according to any of the above embodiments, wherein the first diffraction grating is configured to preferentially direct light in at least two directions.

[0444] Example 62: A head-mounted display according to any of the above embodiments, wherein the first diffraction grating is blazed in two directions.

[0445] Example 63: A head-mounted display system according to any of the above embodiments, wherein the first diffraction grating comprises a one-dimensional grating.

[0446] Example 64: A head-mounted display system according to any of Examples 1-62, wherein the first diffraction grating comprises a two-dimensional grating.

[0447] Example 65: A second diffraction grating is formed within the substrate, A second diffraction grating has a third diffraction efficiency for a first polarization over a certain range of angles of light incident on it, and a fourth diffraction efficiency for a second polarization over that range of angles of light incident on it, and a fourth layer arranged across the second diffraction grating. A head-mounted display system according to any of the above embodiments, comprising: a first diffraction grating arranged across the substrate on the first side of the substrate; and a second diffraction grating arranged across the substrate on the second side of the substrate, opposite the first side of the substrate.

[0448] Example 66: A second diffraction grating, comprising a material different from the substrate, is arranged across the substrate. A second diffraction grating has a third diffraction efficiency for a first polarization over a certain range of angles of light incident on it, and a fourth diffraction efficiency for a second polarization over that range of angles of light incident on it, and a fourth layer arranged across the second diffraction grating. The head-mounted display system according to any of the above embodiments, further comprising: a first diffraction grating arranged across the substrate on the first side of the substrate; and a second diffraction grating arranged across the substrate on the second side of the substrate, opposite the first side of the substrate.

[0449] Example 67: A head-mounted display system according to any of the above embodiments, wherein the substrate is configured to guide at least a portion of the light from the light projection system into the waveguide via the second diffraction grating.

[0450] Example 68: A head-mounted display system according to any of the above embodiments, wherein the third diffraction efficiency for the first polarization over a certain range of angles of light incident thereon exceeds the fourth diffraction efficiency for the second polarization over that range of angles of light incident thereon.

[0451] Example 69: A head-mounted display system according to any of the above embodiments, wherein the third diffraction efficiency is at least six times the fourth diffraction efficiency over the range of the angle.

[0452] Example 70: A head-mounted display system according to any of the above examples, wherein the third diffraction efficiency for the first polarization over a range of angles of light incident thereon is less than the fourth diffraction efficiency for the second polarization over a range of angles of light incident thereon.

[0453] Example 71: A head-mounted display system according to any of the above embodiments, wherein the fourth diffraction efficiency is at least six times the third diffraction efficiency over the range of the angle.

[0454] Example 72: A head-mounted display system according to any of the above examples, wherein the fourth layer includes a dielectric.

[0455] Example 73: A head-mounted display system according to any of the above examples, wherein the substrate comprises a material having a refractive index of 2.6 or less.

[0456] Example 74: A head-mounted display system according to any of the above examples, wherein the substrate comprises a material having a refractive index of 2.7 or less.

[0457] Example 75: A head-mounted display system according to any of the above examples, wherein the substrate comprises a material having a refractive index of 2.8 or less.

[0458] Example 76: A head-mounted display system according to any of the above examples, wherein the first layer comprises a dielectric.

[0459] Example 77: A head-mounted display system according to any of the above examples, wherein the first layer comprises a material having a refractive index of 1.9 or greater.

[0460] Example 78: A head-mounted display system according to any of the above examples, wherein the first layer comprises a material having a refractive index of 2.0 or greater.

[0461] Example 79: A head-mounted display system according to any of the above examples, wherein the first layer comprises a material having a refractive index of 2.1 or greater.

[0462] Example 80: A head-mounted display system according to any of the above embodiments, further comprising a plurality of sublayers over the first layer, wherein the plurality of sublayers comprises a first higher refractive index material and a second lower refractive index material.

[0463] Example 81: The head-mounted display system according to Example 80, wherein the first higher refractive index material comprises titanium dioxide (TiO2) and the second lower refractive index material comprises silicon dioxide (SiO2).

[0464] Example 82: The head-mounted display system according to Example 80 or 81, wherein the multiple sublayers comprise only two sublayers.

[0465] Example 83: The head-mounted display system according to Example 80 or 81, wherein the plurality of sublayers comprises at least four sublayers.

[0466] Example 84: A head-mounted display system according to any of Examples 80-83, wherein multiple sublayers alternate between a first material and a second material.

[0467] Example 85: A head-mounted display system according to any of Examples 80-84, wherein multiple sublayers are provided with interference coatings.

[0468] Example 86: A head-mounted display system according to any of Examples 80-85, comprising multiple sublayers comprising a quarter-wave stack.

[0469] Example 87: A head-mounted display system according to any of Examples 80-86, wherein multiple sublayers across the first layer form a band-pass filter.

[0470] Example 88: A head-mounted display system according to any of Examples 80-86, wherein a plurality of sublayers across the first layer form a notch filter.

[0471] Example 89: A head-mounted display system according to any of Examples 80-86, wherein a plurality of sublayers across the first layer form an anti-reflective (AR) coating.

[0472] Example 90: A head-mounted display system according to any of Examples 80-89, wherein the first lower refractive index material has a refractive index of 1.6 or less.

[0473] Example 91: A head-mounted display system according to any of Examples 80-90, wherein the second higher refractive index material has a refractive index of 1.9 or greater.

[0474] Example 92: A head-mounted display system according to any of Examples 80-91, wherein the first lower refractive index material comprises silicon dioxide.

[0475] Example 93: A head-mounted display system according to any of Examples 80-92, wherein the second higher refractive index material is titanium dioxide.

[0476] Example 94: A head-mounted display system according to any of Examples 80-92, wherein the second higher refractive index material is zirconium dioxide.

[0477] Example 95: A head-mounted display system according to any of Examples 80-92, wherein the second higher refractive index material is zinc oxide.

[0478] Example 96: A head-mounted display system according to any of the above embodiments, wherein the first diffraction grating has an average diffraction efficiency for the first polarization over the range of angles, and the second diffraction efficiency has an average diffraction efficiency for the second polarization over the range of angles.

[0479] Example 97: A head-mounted display system according to any of the above examples, wherein the first diffraction efficiency averaged over the range of angles and the second diffraction efficiency averaged over the range of angles have an efficiency of at least 40%.

[0480] Example 98: A head-mounted display system according to any of the above examples, wherein the first diffraction efficiency averaged over the range of angles and the second diffraction efficiency averaged over the range of angles have an efficiency of at least 50%.

[0481] Example 99: A head-mounted display system according to any of the above embodiments, wherein the first diffraction efficiency averaged over the range of angles and the second diffraction efficiency averaged over the range of angles have an efficiency of at least 60%.

[0482] Example 100: A head-mounted display system according to any of the above examples, wherein the angle range is at least 25 degrees.

[0483] Example 101: A head-mounted display system according to any of the above embodiments, wherein the angle range is at least 30 degrees.

[0484] Example 102: A head-mounted display system according to any of the above embodiments, wherein the angle range is at least 35 degrees.

[0485] Example 103: A head-mounted display system according to any of the above embodiments, wherein the angle range is at least 40 degrees.

[0486] Example 104: A head-mounted display system according to any of the above examples, wherein the angle range is between ±15 degrees with respect to the plane of the substrate.

[0487] Example 105: A head-mounted display system according to any of the above examples, wherein the angle range is between ±18 degrees with respect to the plane of the substrate.

[0488] Example 106: A head-mounted display system according to any of the above examples, wherein the angle range is between ±20 degrees with respect to the plane of the substrate.

[0489] Example 107: A head-mounted display system according to any of the above embodiments, wherein the first diffraction grating comprises first and second side walls and has diffraction features.

[0490] Example 108: The head-mounted display system according to Example 107, wherein the first and second side walls are separated by a flat area.

[0491] Example 109: The head-mounted display system according to Example 107, wherein the first and second sidewalls are joined to form a prominent angle over the diffraction feature.

[0492] Example 110: A head-mounted display system according to any one of Examples 107-109, wherein at least the first side wall is inclined at an angle such that the first side wall is not as steep as the second side wall.

[0493] Example 111: A head-mounted display system according to any one of Examples 107-110, wherein the first side wall is wider than the second side wall.

[0494] Example 112: A head-mounted display system according to any one of Examples 107-111, wherein the first sidewall forms an angle of 45° to 85° at the base of the diffraction feature.

[0495] Example 113: A head-mounted display system according to any one of Examples 107-112, wherein the second side wall forms an acute concave angle at the base of the diffraction feature.

[0496] Example 114: The head-mounted display system according to any one of Examples 107-113, wherein the first diffraction grating has shark tail-shaped diffraction features.

[0497] Example 115: A head-mounted display system according to any one of Examples 107-112, wherein the second sidewall forms an obtuse concave angle at the base of the diffraction feature.

[0498] Example 116: The head-mounted display system according to any of Examples 107-112, wherein the second side wall is vertical.

[0499] Example 117: A head-mounted display system according to any one of Examples 107-112 or 115-116, wherein the first diffraction grating has a sawtooth-shaped diffraction feature.

[0500] Example 118: A head-mounted display system according to any of the above embodiments, wherein the first layer comprises a biased deposition.

[0501] Example 119: A head-mounted display system according to any of the above embodiments, wherein the first layer comprises a graze-angle deposition.

[0502] Example 120: A head-mounted display system according to any of Examples 107-119, wherein the first layer is biased to provide more coverage on the first sidewall than on the second sidewall.

[0503] Example 121: A head-mounted display system according to any of Examples 107-120, wherein the first layer covers a proportion of the first sidewall that is greater than the second sidewall.

[0504] Example 122: A head-mounted display system according to any of Examples 107-121, wherein the first layer is biased to provide a thicker covering on the first sidewall than the second sidewall.

[0505] Example 123: A head-mounted display system according to any of Examples 107-122, wherein the first layer provides a covering on the first sidewall that is on average thicker than the second sidewall.

[0506] Example 124: The head-mounted display system according to any of Examples 107-123, wherein the first side wall is completely covered by the second layer.

[0507] Example 125: A head-mounted display system according to any of Examples 107-124, wherein at least a portion of the second side wall is not covered by the first layer.

[0508] Example 126: A head-mounted display system according to any of Examples 107-125, wherein the second side wall includes a larger area not covered by the first layer than the first side wall.

[0509] Example 127: A head-mounted display system according to any of Examples 107-126, wherein the second layer comprises conformal deposition.

[0510] Example 128: A head-mounted display system according to any of Examples 107-127, wherein the first and second side walls are completely covered by the second layer.

[0511] Example 129: A head-mounted display system according to any of Examples 107-128, wherein the second layer is not biased to cover more of the first sidewall than the second sidewall.

[0512] Example 130: A head-mounted display system according to any of Examples 107-129, wherein the second layer is not biased to provide a thicker covering on the first sidewall than the second sidewall.

[0513] Example 131: A head-mounted display system according to any of Examples 107-130, wherein the second layer does not provide a covering on the first sidewall that is on average thicker than the second sidewall.

[0514] Example 132: The head-mounted display system according to any of Examples 107-131, wherein the second side wall is entirely covered by the second layer.

[0515] Example 133: A head-mounted display system according to any of Examples 107-132, wherein the second sidewall does not include an area that is not covered by the second layer more than the first sidewall.

[0516] Example 134: A head-mounted display system according to any of the above examples, wherein the first diffraction efficiency for the first polarization is within 20% of the second diffraction efficiency for the second polarization.

[0517] Example 135: A head-mounted display system according to any of the above examples, wherein the first diffraction efficiency for the first polarization is within 30% of the second diffraction efficiency for the second polarization.

[0518] Example 136: A head-mounted display system according to any of the above embodiments, wherein the first diffraction grating, on which the first and second layers are formed, comprises a reflective diffraction grating.

[0519] Example 137: A head-mounted display system according to any of the above embodiments, comprising a reflective diffraction grating, the first diffraction grating having the first and second layers formed thereon, configured to diffract reflected light and couple the light into the waveguide so as to be guided therein by total internal reflection.

[0520] Example 138: The diffractive feature has a height of 100 to 600 nanometers, and is a head-mounted display system according to any of the above examples.

[0521] Example 139: The diffraction feature has a height of 200 to 600 nanometers, and is a head-mounted display system according to any of the above examples.

[0522] Example 140: The diffractive feature has a height of 300 to 600 nanometers, and is a head-mounted display system according to any of the above examples.

[0523] Example 141: The head-mounted display system according to any of the above examples, wherein the diffraction features have a pitch of 290 nm to 690 nm.

[0524] Example 142: The light projection system is a head-mounted display system according to any of the above embodiments, comprising microLEDs.

[0525] Example 143: The light projection system is a head-mounted display system according to any of the above embodiments, comprising a DLP or LCOS display.

[0526] Example 144: The head-mounted display system according to any of the above examples, wherein the substrate contains nanoparticles.

[0527] Example 145: The head-mounted display system according to any of the above examples, wherein the substrate contains inorganic nanoparticles.

[0528] Example 146: The head-mounted display system according to any of the above examples, wherein the substrate comprises a polymer.

[0529] Additional Examples - Part III Example 1: A head-mounted display system, A frame that can be mounted on the head, A light projection system configured to emit light and provide image content, A waveguide supported by a frame, comprising a substrate configured to guide at least a portion of the light from the light projection system into the waveguide, A first diffraction grating comprising a material different from the substrate, A first diffraction grating is arranged across the first diffraction grating such that the first diffraction grating has a first diffraction efficiency for the first polarization of light incident on it over a range of angles, which exceeds a second diffraction efficiency for the second polarization of light incident on it over a range of angles. A second layer is arranged across the first diffraction grating such that the first diffraction grating has a third diffraction efficiency for the second polarization of light incident on it over that range of angles, which exceeds a fourth diffraction efficiency for the first polarization of light incident on it over that range of angles. A head-mounted display system comprising a first diffraction grating and a first and second layer combined, configured to provide a diffraction efficiency of a fifth diffraction efficiency for a first polarization over that range of angles of light incident thereon, and a sixth diffraction efficiency for a second polarization over that range of angles of light incident thereon, wherein the fifth diffraction efficiency is 1 to 2 times the sixth diffraction efficiency, or the sixth diffraction efficiency is 1 to 2 times the fifth diffraction efficiency.

[0530] Example 2: The head-mounted display system according to Example 1, wherein the substrate comprises a lithium-based oxide material.

[0531] Example 3: The head-mounted display system according to Example 1 or 2, wherein the substrate contains lithium niobate material.

[0532] Example 4: The head-mounted display system according to Example 1, wherein the substrate contains silicon carbide material.

[0533] Example 5: The head-mounted display system according to Example 1, wherein the substrate comprises a material having a refractive index of at least 1.9.

[0534] Example 6: The head-mounted display system according to Example 1, wherein the substrate comprises a material having a refractive index of at least 2.0.

[0535] Example 7: The head-mounted display system according to Example 1, wherein the substrate comprises a material having a refractive index of at least 2.1.

[0536] Example 8: The head-mounted display system according to Example 1, wherein the substrate comprises a material having a refractive index of at least 2.2.

[0537] Example 9: The head-mounted display system according to Example 1, wherein the substrate comprises a material having a refractive index of at least 2.3.

[0538] Example 10: A head-mounted display system according to any of the above examples, wherein the first diffraction grating material comprises a polymer.

[0539] Example 11: A head-mounted display system according to any of the above examples, wherein the first diffraction grating material includes an imprintable material.

[0540] Example 12: The first diffraction grating material has a refractive index of 1.4 to 1.95, and is a head-mounted display system according to any of the above examples.

[0541] Example 13: A head-mounted display system according to any of the above examples, wherein the first diffraction grating material has a refractive index lower than that of the substrate.

[0542] Example 14: The head-mounted display system according to any of the above embodiments, wherein the first diffraction grating comprises a blazed diffraction grating.

[0543] Example 15: A head-mounted display system according to any of the above embodiments, wherein the first diffraction grating has diffraction features, the peaks being spaced apart by grooves between them.

[0544] Example 16: The first diffraction grating is a head-mounted display system according to any of the above embodiments, comprising diffraction features having a plurality of straight lines.

[0545] Example 17: The waveguide according to any of the above examples, wherein the diffraction grating has asymmetric diffraction characteristics.

[0546] Example 18: A head-mounted display system according to any of the above examples, wherein the first layer comprises titanium dioxide (TiO2), zirconium dioxide (ZrO2), or silicon carbide (SiC).

[0547] Example 19: A head-mounted display system according to any of the above examples, wherein the first layer comprises titanium dioxide (TiO2).

[0548] Example 20: A head-mounted display system according to any of the above examples, wherein the first layer comprises zirconium dioxide (ZrO2).

[0549] Example 21: A head-mounted display system according to any of the above examples, wherein the first layer comprises silicon carbide (SiC).

[0550] Example 22: A head-mounted display system according to any of the above examples, comprising a plurality of sublayers, the first layer comprising a first higher refractive index material and a second lower refractive index material.

[0551] Example 23: The head-mounted display system according to Example 22, wherein the first higher refractive index material comprises titanium dioxide (TiO2) and the second lower refractive index material comprises silicon dioxide (SiO2).

[0552] Example 24: The head-mounted display system according to Example 22 or 23, wherein the multiple sublayers comprise only two sublayers.

[0553] Example 25: The head-mounted display system according to Example 22 or 23, wherein the multiple sublayers comprise at least four sublayers.

[0554] Example 26: A head-mounted display system according to any of Examples 22-25, wherein multiple sublayers alternate between a first material and a second material.

[0555] Example 27: A head-mounted display system according to any of Examples 22-26, wherein multiple sublayers are provided with interference coatings.

[0556] Example 28: A head-mounted display system according to any of Examples 22-27, comprising multiple sublayers, each comprising a quarter-wave stack.

[0557] Example 29: A head-mounted display system according to any of the above examples, wherein the second layer comprises aluminum, silver, gold, or copper.

[0558] Example 30: A head-mounted display system according to any of the above embodiments, comprising first and second linear polarizations having different polarization angles.

[0559] Example 31: A head-mounted display system according to any of the above embodiments, comprising first and second linear polarizations oriented in orthogonal directions.

[0560] Example 32: A head-mounted display system according to any of the above examples, wherein the first and second polarization directions are transverse magnetic and transverse electropolarization, respectively.

[0561] Example 33: A head-mounted display system according to any of the above embodiments, wherein the first and second polarization directions are transverse electric and transverse magnetic polarization, respectively.

[0562] Example 34: A head-mounted display system according to any of the above examples, wherein the fifth diffraction efficiency comprises a diffraction efficiency for transverse magnetic polarization averaged across the visible light spectrum, and the sixth diffraction efficiency comprises a diffraction efficiency for transverse electric polarization averaged across the visible light spectrum.

[0563] Example 35: A head-mounted display system according to any of the above examples, wherein the fifth diffraction efficiency comprises a diffraction efficiency for transverse electric polarization averaged across the visible light spectrum, and the sixth diffraction efficiency comprises a diffraction efficiency for transverse magnetic polarization averaged across the visible light spectrum.

[0564] Example 36: A head-mounted display system according to any of the above examples, wherein the fifth diffraction efficiency is 1 to 1.5 times that of the sixth diffraction efficiency, or the sixth diffraction efficiency is 1 to 1.5 times that of the fifth diffraction efficiency.

[0565] Example 37: A head-mounted display system according to any of the above examples, wherein the fifth diffraction efficiency is 1 to 1.4 times that of the sixth diffraction efficiency, or the sixth diffraction efficiency is 1 to 1.4 times that of the fifth diffraction efficiency.

[0566] Example 38: A head-mounted display system according to any of the above examples, wherein the fifth diffraction efficiency is 1 to 1.3 times that of the sixth diffraction efficiency, or the sixth diffraction efficiency is 1 to 1.3 times that of the fifth diffraction efficiency.

[0567] Example 39: A head-mounted display system according to any of the above examples, wherein the fifth diffraction efficiency is 1 to 1.2 times that of the sixth diffraction efficiency, or the sixth diffraction efficiency is 1 to 1.2 times that of the fifth diffraction efficiency.

[0568] Example 40: A head-mounted display system according to any of the above examples, wherein the fifth diffraction efficiency is 1 to 1.1 times that of the sixth diffraction efficiency, or the sixth diffraction efficiency is 1 to 1.1 times that of the fifth diffraction efficiency.

[0569] Example 41: A head-mounted display system according to any of the above embodiments, wherein the angle range is at least 6 degrees.

[0570] Example 42: A head-mounted display system according to any of the above embodiments, wherein the angle range is at least 12 degrees.

[0571] Example 43: A head-mounted display system according to any of the above embodiments, wherein the angle range is at least 18 degrees.

[0572] Example 44: A head-mounted display system according to any of the above embodiments, wherein the angle range is at least 22 degrees.

[0573] Example 45: A head-mounted display system according to any of the above examples, wherein the angle range is between ±3 degrees with respect to the plane of the substrate.

[0574] Example 46: A head-mounted display system according to any of the above examples, wherein the angle range is between ±6 degrees with respect to the plane of the substrate.

[0575] Example 47: A head-mounted display system according to any of the above examples, wherein the angle range is between ±9 degrees with respect to the plane of the substrate.

[0576] Example 48: A head-mounted display system according to any of the above examples, wherein the angle range is between ±11 degrees with respect to the plane of the substrate.

[0577] Example 49: A head-mounted display system according to any of the above embodiments, wherein the waveguide is contained within an eyepiece and configured to direct light towards the eye of a user wearing the head-mounted display.

[0578] Example 50: The eyepiece is positioned on a frame and configured to direct light from a light projection system into the user's eye and display augmented reality image content in the user's field of view, wherein at least a portion of the eyepiece is transparent and positioned in front of the user's eye when the user wears the head-mounted display system, the transparent portion allowing light from a portion of the physical environment in front of the user to pass through to the user's eye and provide a view of a portion of the physical environment in front of the user, the head-mounted display system according to Example 49, the eyepiece is included.

[0579] Example 51: The head-mounted display system according to Example 49 or 50, wherein the eyepiece comprises the at least one waveguide, the at least one waveguide being transparent to visible light so that a user can see through the waveguide.

[0580] Example 52: A head-mounted display system according to any of the above embodiments, wherein the waveguide comprises an internal coupling optical element for coupling light from the optical projection system into the waveguide so that it is guided therein.

[0581] Example 53: A head-mounted display system according to any of the above embodiments, wherein the waveguide comprises an external coupling optical element for coupling light from the light projection system out of the waveguide, directing the light towards the user's eyes, and presenting the image content to the viewer.

[0582] Example 54: A head-mounted display system according to any of the above embodiments, wherein the first diffraction grating comprises an externally coupled grating (EPE) configured to externally couple light from the optical projection system induced within the waveguide to the outside of the waveguide.

[0583] Example 55: A head-mounted display system according to any of the above embodiments, wherein the first diffraction grating comprises an internally coupled grating (ICG) configured to internally couple light from the optical projection system into the waveguide.

[0584] Example 56: A head-mounted display system according to any of the above embodiments, wherein the second layer is configured to be positioned across the first layer.

[0585] Example 57: A head-mounted display system according to any of the above embodiments, comprising a third layer disposed between the first layer and the second layer.

[0586] Example 58: The head-mounted display system according to Example 57, wherein the third layer is configured to help bond the second layer to the first layer.

[0587] Example 59: A second diffraction grating, comprising a material different from the substrate, is arranged across the substrate. A second diffraction grating is arranged with a fourth layer positioned over the second diffraction grating such that it has a seventh diffraction efficiency for a first polarization over a range of angles of light incident thereon, A head-mounted display system according to any of the above embodiments, comprising: a first diffraction grating arranged across the substrate on the first side of the substrate; and a second diffraction grating arranged across the substrate on the second side of the substrate, opposite the first side of the substrate.

[0588] Example 60: The head-mounted display system according to Example 1, wherein the first layer is conformally deposited on one or more diffraction features of the first diffraction grating.

[0589] Example 61: The head-mounted display system according to Example 1, wherein the first layer is deposited directionally at an angle on one or more diffraction features.

[0590] Example 62: The head-mounted display system according to Example 61, wherein the angle includes 75 to 105 degrees with respect to the main planar surface of the substrate.

[0591] Example 63: The head-mounted display system according to Example 61, wherein the angle is 75 to 105 degrees with respect to the surface of one or more diffraction features of the first diffraction grating.

[0592] Example 64: The head-mounted display system according to Example 1, wherein the second layer is conformally deposited on one or more diffraction features of the first diffraction grating.

[0593] Example 65: The head-mounted display system according to Example 1, wherein the second layer is deposited directionally at an angle on one or more diffraction features of the first diffraction grating.

[0594] Example 66: The head-mounted display system according to Example 65, wherein the angle includes 75 to 105 degrees with respect to the main planar surface of the substrate.

[0595] Example 67: The head-mounted display system according to Example 65, wherein the angle is 75 to 105 degrees with respect to the surface of one or more diffraction features of the first diffraction grating.

[0596] Example 68: A head-mounted display system according to any of the above examples, wherein the first diffraction grating is formed in a 1D array and has diffraction features.

[0597] Example 69: A head-mounted display system according to any of Examples 1-68, wherein the first diffraction grating is formed in a 2D array and has diffraction features.

[0598] Example 70: The head-mounted display system according to Example 69, wherein the 2D array comprises a square array.

[0599] Example 71: A head-mounted display according to any of the above examples, wherein the diffraction features are asymmetrical to provide a blazed grating.

[0600] Example 72: A head-mounted display according to any of the above examples, wherein the diffraction feature has a material deposited asymmetrically thereon to provide a blazed lattice.

[0601] Example 73: A head-mounted display according to any of the above embodiments, wherein the first diffraction grating is configured to preferentially direct light in at least two directions.

[0602] Example 74: A head-mounted display according to any of the above embodiments, wherein the first diffraction grating is blazed in two directions.

[0603] Example 75: A head-mounted display system according to any of the above embodiments, wherein the first diffraction grating comprises a one-dimensional grating.

[0604] Example 76: A head-mounted display system according to any of Examples 1-75, wherein the first diffraction grating comprises a two-dimensional grating.

[0605] Example 77: The light projection system is a head-mounted display system according to any of the above embodiments, comprising microLEDs.

[0606] Example 78: The light projection system is a head-mounted display system according to any of the above embodiments, comprising a DLP or LCOS display.

[0607] Example 79: The head-mounted display system according to any of the above examples, wherein the substrate contains nanoparticles.

[0608] Example 80: The head-mounted display system according to any of the above examples, wherein the substrate contains inorganic nanoparticles.

[0609] Example 81: The head-mounted display system according to any of the above examples, wherein the substrate comprises a polymer.

[0610] Additional Examples - Part IV Example 1: A head-mounted display system, A frame that can be mounted on the head, A light projection system configured to emit light and provide image content, A waveguide supported by a frame, the waveguide comprising a substrate containing an optically transparent material and a first diffraction grating formed within the substrate, wherein the substrate is configured to guide at least a portion of the light from the light projection system into the waveguide, A first layer, disposed across the first diffraction grating formed within the substrate, is configured to provide a first diffraction efficiency for the first polarization of light incident on it over a range of angles, which together with the first diffraction grating exceeds a second diffraction efficiency for the second polarization over a range of angles of light incident on it, A second layer, disposed across the first diffraction grating formed within the substrate, is configured to provide a third diffraction efficiency for the second polarization of light incident thereon over that range of angles, exceeding a fourth diffraction efficiency for the first polarization of light incident thereon over that range of angles, together with the first diffraction grating; A head-mounted display system comprising, wherein the first diffraction grating, together with first and second layers, is configured to provide a fifth diffraction efficiency for a first polarization over that range of angles of light incident thereon, and a sixth diffraction efficiency for a second polarization over that range of angles of light incident thereon, wherein the fifth diffraction efficiency is 1 to 2 times the sixth diffraction efficiency, or the sixth diffraction efficiency is 1 to 2 times the fifth diffraction efficiency.

[0611] Example 2: The head-mounted display system according to Example 1, wherein the optically transparent material constituting the substrate has a refractive index of 1.45 to 2.0.

[0612] Example 3: The head-mounted display system according to Example 1 or 2, wherein the transparent material constituting the substrate includes a polymer.

[0613] Example 4: A head-mounted display system according to any of the above examples, wherein the first layer comprises titanium dioxide (TiO2), zirconium dioxide (ZrO2), or silicon carbide (SiC).

[0614] Example 5: A head-mounted display system according to any of the above embodiments, wherein the first layer comprises a plurality of sub-layers.

[0615] Example 6: The head-mounted display system according to Example 5, comprising a plurality of sublayers, the first layer comprising a first higher refractive index material and a second lower refractive index material.

[0616] Example 7: A head-mounted display system according to Example 5 or 6, wherein the first higher refractive index material comprises titanium dioxide (TiO2) and the second lower refractive index material comprises silicon dioxide (SiO2).

[0617] Example 8: A head-mounted display system according to any of Examples 5-7, wherein the multiple sublayers comprise only two sublayers.

[0618] Example 9: A head-mounted display system according to any one of Examples 5-7, wherein the multiple sublayers comprise at least four sublayers.

[0619] Example 10: A head-mounted display system according to any of Examples 6-9, wherein multiple sublayers alternate between a first material and a second material.

[0620] Example 11: A head-mounted display system according to any of Examples 5-10, wherein multiple sublayers are provided with interference coatings.

[0621] Example 12: A head-mounted display system according to any of Examples 5-11, comprising multiple sublayers, each comprising a quarter-wave stack.

[0622] Example 13: A head-mounted display system according to any of the above examples, wherein the metal comprises aluminum, silver, gold, or copper.

[0623] Example 14: The head-mounted display system according to any of the above embodiments, wherein the first diffraction grating comprises a blazed diffraction grating.

[0624] Example 15: The head-mounted display system according to Example 14, wherein the first diffraction grating has diffraction features, the peaks being spaced apart by grooves between them.

[0625] Example 16: The first diffraction grating is a head-mounted display system according to any of the above embodiments, comprising diffraction features having a plurality of straight lines.

[0626] Example 17: A waveguide according to any of the above examples, wherein the diffraction grating ...

Claims

1. Waveguide, wherein the waveguide is A substrate configured to propagate light within the waveguide by total internal reflection, One or more internally coupled diffraction gratings (ICGs) formed in or on the substrate, wherein the one or more ICGs are configured to redirect the light to propagate through the substrate, and the one or more ICGs are arranged in or on one surface of the substrate, and incident light is incident on the substrate, and Equipped with, Each of the one or more ICGs is, A diffraction grating pattern containing a material different from the aforementioned substrate, A multilayer coating arranged over at least a portion of the diffraction grating pattern, wherein the multilayer coating is arranged to reduce zero-order light of light reflected from one or more ICGs, and the multilayer coating comprises at least one high refractive index sublayer and at least one low refractive index sublayer. Waveguides, including

2. The waveguide according to claim 1, wherein the diffraction grating pattern comprises an imprintable material.

3. The waveguide according to claim 1, wherein the diffraction grating pattern comprises a polymer.

4. The waveguide according to claim 1, wherein the diffraction grating pattern comprises a material having a refractive index of 1.4 to 1.

95.

5. The waveguide according to claim 1, wherein the diffraction grating pattern comprises a material having a refractive index of 1.3 to 1.

5.

6. The waveguide according to claim 1, wherein the diffraction grating pattern includes a material having a refractive index lower than that of the substrate.

7. The waveguide according to claim 1, wherein the diffraction grating pattern includes a blazed diffraction grating pattern.

8. The waveguide according to claim 1, wherein the substrate comprises a lithium-based oxide.

9. The waveguide according to claim 1, wherein the substrate contains lithium niobate.

10. The waveguide according to claim 1, wherein the substrate contains silicon carbide.

11. The waveguide according to claim 1, wherein the substrate has a refractive index of at least 1.

9.

12. The waveguide according to claim 1, wherein the substrate has a refractive index of at least 2.

0.

13. The waveguide according to claim 1, wherein the substrate has a refractive index of at least 2.

1.

14. The waveguide according to claim 1, wherein the substrate has a refractive index of at least 2.

2.

15. The waveguide according to claim 1, wherein the substrate has a refractive index of at least 2.

3.

16. The waveguide according to claim 1, wherein the at least one high refractive index sublayer comprises a material having a refractive index of 1.95 to 3.

5.

17. The waveguide according to claim 1, wherein the at least one high refractive index sublayer comprises titanium dioxide.

18. The waveguide according to claim 1, wherein the at least one low refractive index sublayer comprises silicon dioxide.

19. The waveguide according to claim 1, wherein the multilayer coating includes an interference coating.

20. The waveguide according to claim 1, wherein the multilayer coating includes a quarter-wave stack.

21. The waveguide according to claim 1, wherein the multilayer coating comprises at least two sublayers.

22. The waveguide according to claim 1, wherein the multilayer coating comprises at least four sublayers.

23. The waveguide according to claim 1, wherein the multilayer coating includes a plurality of sublayers that alternate between a high refractive index sublayer and a low refractive index sublayer.

24. The waveguide according to claim 1, further comprising an additional material arranged across the multilayer coating, wherein the additional material has a refractive index in the range of 1.3 to 1.

5.

25. The waveguide according to claim 1, wherein the multilayer coating is arranged such that the sublayer furthest from the diffraction grating pattern is a low refractive index sublayer.

26. A head-mounted display system, A frame that can be mounted on the head, A light projection system configured to provide image content by outputting light, An eyepiece supported by the frame, wherein the eyepiece is positioned to receive light output by the light projection system, and the eyepiece includes a waveguide as described in any of claims 1 to 25. A head-mounted display system equipped with the following features.

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