Display device with diffraction grating having reduced polarization sensitivity

Abstract

Blazed diffraction gratings provide optical elements in head-mounted display systems to, for example, couple light into or out of a waveguide. These blazed diffraction gratings can be configured to have reduced polarization sensitivity. For example, such gratings can couple different polarizations of light in or out at similar levels of efficiency. The blazed diffraction gratings and waveguides can be formed in high index substrates such as lithium niobate. In some implementations, the blazed diffraction gratings can include diffractive features having a feature height of 40 nm to 120 nm, such as 80 nm. The diffractive features can be etched into a high index substrate such as lithium niobate.

Description

[0001] Intersection of related applications

[0002] This application claims priority to U.S. Provisional Application No. 62 / 876,205, filed July 19, 2019, entitled “DISPLAY DEVICE HAVING DIFFRACTION GRATINGS WITH REDUCED POLARIZATION SENSITIVITY,” and U.S. Provisional Application No. 62 / 902,328, filed September 18, 2019, entitled “DISPLAY DEVICE HAVING DIFFRACTION GRATINGS WITH REDUCED POLARIZATION SENSITIVITY,” the entire contents of which are incorporated herein by reference.

[0003] By referencing the merging

[0004] This application incorporates the entire contents of each of the following patent applications by reference: U.S. Application No. 14 / 555,585, filed November 27, 2014, published July 23, 2015 as U.S. Publication 2015 / 0205126; U.S. Application No. 14 / 690,401, filed April 18, 2015, published October 22, 2015 as U.S. Publication 2015 / 0302652; U.S. Application No. 14 / 212,961, filed March 14, 2014, now published August 16, 2016 as U.S. Patent 9,417,452; and U.S. Application No. 14 / 331,218, filed July 14, 2014, published October 29, 2015 as U.S. Publication 2015 / 0309263. Technical Field

[0005] This disclosure relates to display systems, and more specifically, to augmented and virtual reality display systems. Background Technology

[0006] Modern computing and display technologies have facilitated the development of systems for so-called "virtual reality" or "augmented reality" experiences, in which digitally reproduced images or portions thereof are presented to the user in a way that looks or can be perceived as real. Virtual reality or "VR" scenarios typically involve the opaque presentation of digital or virtual image information to other actual real-world visual inputs; augmented reality or "AR" scenarios typically involve the presentation of digital or virtual image information as an enhancement to the visualization of the actual world surrounding the user. Mixed reality or "MR" scenarios are a type of AR scenario and typically involve virtual objects integrated into and responding to the natural world. For example, in an MR scenario, AR image content can be occluded by real-world objects or perceived as interacting with real-world objects.

[0007] refer to Figure 1 The illustration shows an augmented reality scene 10, in which an AR user sees a real-world park-like setting 20, characterized by people, trees, buildings in the background, and a concrete platform 30. In addition to these elements, the AR user also perceives that he "sees" "virtual content," such as a robot statue 40 standing on the real-world platform 30, and a cartoonish avatar 50 flying by, which appears to be an avatar of Bumblebee, even though these elements 40 and 50 do not exist in the real world. Due to the complexity of the human visual perception system, producing AR technology that comfortably, naturally, and richly presents virtual image elements from other virtual or real-world image elements is extremely challenging.

[0008] The systems and methods disclosed in this paper address various challenges related to AR and VR technologies. Summary of the Invention

[0009] In one aspect, a head-mounted display system includes: a head-mounted frame; a light projection system configured to output light to provide image content; and a waveguide supported by the frame. The waveguide includes a substrate comprising a material having a refractive index of at least 1.9. The substrate is configured to guide at least a portion of the light from the light projection system coupled into the waveguide. The head-mounted display system further includes: a blazed diffraction grating formed in the substrate or in a layer disposed above the substrate. The blazed diffraction grating has a first diffraction efficiency for a first polarization within an angular range of incident light, and a second diffraction efficiency for a second polarization within the same angular range. The first diffraction efficiency is between one and two times the second diffraction efficiency.

[0010] In another aspect, an optical waveguide includes a substrate comprising a material having a refractive index of at least 1.9. The substrate is configured to guide light coupled into the waveguide via total internal reflection. The optical waveguide further includes a blazed diffraction grating formed in the substrate or in a layer disposed above the substrate. The blazed diffraction grating has a first diffraction efficiency for a first polarization over an angular range of incident light, and a second diffraction efficiency for a second polarization over the same angular range. The first diffraction efficiency is between one and two times the second diffraction efficiency. Attached Figure Description

[0011] Figure 1 This shows the augmented reality (AR) view that the user sees through an AR device.

[0012] Figure 2 A traditional display system for simulating three-dimensional images for users is shown.

[0013] Figures 3A to 3C The relationship between the radius of curvature and the focal radius is shown.

[0014] Figure 4A This illustrates a representation of the adaptation-vergence response of the human visual system.

[0015] Figure 4B Examples of different adaptation and convergence states of a user's two eyes are shown.

[0016] Figure 4C This shows an example of a top-down view of content viewed by a user via a display system.

[0017] Figure 4D This shows another example of a top-down view representation of content viewed by a user via a display system.

[0018] Figure 5 Various aspects of a method for simulating three-dimensional images by modifying wavefront divergence are illustrated.

[0019] Figure 6 An example of waveguide stacking used to output image information to a user is shown.

[0020] Figure 7 An example of an outgoing beam output from a waveguide is shown.

[0021] Figure 8 An example of a stacked waveguide assembly is shown, where each depth plane includes an image formed using multiple different component colors.

[0022] Figure 9AA cross-sectional side view of an example of a set of stacked waveguides, each including an embedded optical element, is shown.

[0023] Figure 9B It shows Figure 9A A perspective view of an example of multiple stacked waveguides.

[0024] Figure 9C It shows Figure 9A and 9B A top plan view of an example of multiple stacked waveguides.

[0025] Figure 9D An example of a wearable display system is shown.

[0026] Figure 10A A cross-sectional view of a portion of a waveguide is schematically shown, which has a diffraction grating disposed thereon, for example, to couple light into the waveguide.

[0027] Figure 10B A cross-sectional view of the waveguide is shown, which shows the waveguide's field of view (FOV) Δα, and the waveguide has a blazed diffraction grating disposed thereon.

[0028] Figure 11A An etching process for forming a waveguide having a single-step blazed diffraction grating disposed thereon is shown.

[0029] Figure 11B This is a scanning electron micrograph of a single-step blazed photoresist grating.

[0030] Figure 11C An etching process for forming a waveguide having a multi-step blazed diffraction grating disposed thereon is shown.

[0031] Figure 11D It is a scanning electron micrograph of a multi-step blazed photoresist grating.

[0032] Figure 11E Cross-sectional side views of two different blaze geometries of a diffraction grating are shown.

[0033] Figure 12A-12F Scanning electron micrographs of various substrates are shown, on which blazed diffraction gratings with different blazed geometries are formed.

[0034] Figure 13 It is a graph showing the ratio of the diffraction efficiency of transverse magnetic (TM) polarized light to the diffraction efficiency of transverse electric (TE) polarized light as a function of the incident angle for various diffraction gratings with different blaze geometries.

[0035] Figure 14This is a graph showing the ratio of the diffraction efficiency of transversely magnetically (TM) polarized light to that of transversely electrically (TE) polarized light as a function of the incident angle for green, blue, and red wavelengths, with respect to the diffraction characteristics of a diffraction grating having a peak height or groove depth of 80 nm.

[0036] Figure 15 It is a graph showing the diffraction efficiency of a diffraction grating with a peak height or groove depth of 80 nm for green, blue, and red wavelengths.

[0037] Figure 16 The coherence uniformity of blazed photoresist diffraction gratings for both unpolarized and linearly polarized inputs is shown.

[0038] Figure 17 The coherence uniformity of a blazed diffraction grating etched in a lithium niobate substrate is shown for both non-polarized and linearly polarized inputs.

[0039] Figure 18 It is a perspective view of a two-dimensional (2D) diffraction grating that includes the blazed diffraction features of a two-dimensional array.

[0040] Figure 18A and 18B These are cross-sectional and planar views of a 2D diffraction grating with blazed diffraction characteristics of a two-dimensional array.

[0041] Figure 19A It is a perspective view of a 2D diffraction grating with blazing diffraction characteristics of a two-dimensional array in two directions.

[0042] Figure 19B The light is shown to be preferentially guided in different directions by a 2D diffraction grating having blazed diffraction features in two directions.

[0043] Figure 20A and 20B This is a schematic diagram of a method for manufacturing a blazed diffraction grating using a master template.

[0044] Figure 21 This is a schematic diagram of a method for manufacturing blazed diffraction gratings using different master templates.

[0045] Throughout the accompanying drawings, reference numerals may be used repeatedly to indicate the correspondence between referenced elements. The drawings are provided to illustrate exemplary embodiments described herein and are not intended to limit the scope of this disclosure. Detailed Implementation

[0046] AR systems can display virtual content to users or viewers while still allowing them to see the world around them. Preferably, the content is displayed on a head-mounted display, for example, as part of glasses, which projects image information onto the user's eyes. Furthermore, the display can also transmit light from the surrounding environment into the user's eyes to allow viewing of the surrounding environment. As used herein, it should be understood that a "head-mounted" or "head-worn" display is a display that can be worn on the head of a viewer or user.

[0047] In some AR systems, virtual / augmented / hybrid displays with a relatively high field of view (FOV) can enhance the viewing experience. The FOV of a display depends on the angle of the waveguide output light from the eyepiece, through which the viewer sees the image projected onto his or her eyes. Waveguides with a relatively high refractive index, such as 2.0 or greater, can provide a relatively high FOV. However, in order to efficiently couple light into a high-refractive-index waveguide, the diffractive optical coupling element should also have a correspondingly high refractive index. To achieve this, among other advantages, some displays for AR systems according to embodiments described herein include waveguides comprising a material with a relatively high refractive index (e.g., greater than or equal to 2.0), on which a corresponding diffraction grating with a correspondingly high refractive index is formed, such as a Li-based oxide. For example, a diffraction grating can be formed directly on a Li-based oxide waveguide by patterning a surface portion of the waveguide formed from the Li-based oxide.

[0048] For example, some high-refractive-index diffractive optical coupling elements, such as those used for coupling into or out of optical elements, exhibit strong polarization dependence. For instance, coupling gratings (ICGs) used to couple light into a waveguide can allow significantly more light of a given polarization than light of another polarization, where the diffractive optical coupling element comprises a high-refractive-index material. For example, these elements can couple light with a TM polarization into the waveguide at approximately three times the rate of light with a TE polarization. Diffractive optical coupling elements with this polarization dependence may have reduced efficiency (due to inefficiency and general rejection of one polarization) and may also produce coherence artifacts and reduce the uniformity of the far-field image formed by the light coupled from the waveguide. To obtain diffractive optical coupling elements that are insensitive to polarization or at least have reduced polarization sensitivity (e.g., coupling light with relatively polarization-independent efficiency), some displays for AR systems according to various embodiments described herein include waveguides with diffractive gratings formed in a blazed geometry. Diffraction gratings can also be formed directly in a waveguide, which may comprise a high refractive index material (e.g., a refractive index having a value in any range between 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 of these values). For example, the diffraction grating can be formed, for instance, in a Li-based oxide such as lithium niobate (LiNbO3) or lithium tantalate (LiTaO3), or in a high refractive index material such as zirconium oxide (ZrO2), titanium dioxide (TiO2), or silicon carbide (SiC), by patterning the high refractive index material in a blazing geometry.

[0049] Reference will now be made to the accompanying drawings, in which the same reference numerals denote the same parts. Unless otherwise indicated, these drawings are schematic and not necessarily drawn to scale.

[0050] Figure 2 A conventional display system for simulating 3D images for a user is illustrated. It will be understood that a user's eyes are spaced apart, and when viewing a real object in space, each eye has a slightly different view of the object, forming an image of the object at a different location on the retina of each eye. This can 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 distinct images 190 and 200 (one image for each eye 210 and 220) that have slightly different views of the same virtual object. These images correspond to the views of the virtual object that will be perceived by each eye as the desired depth. These images provide binocular cues, which the user's visual system can interpret to obtain a sense of depth.

[0051] Continue to refer to Figure 2Images 190 and 200 are spaced 230 from eyes 210 and 220 on the z-axis. The z-axis is parallel to the viewer's optical axis, which is the axis at which the eyes are focused on an object at optical infinity directly in front of the viewer. Images 190 and 200 are flat and maintain 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 respectively, the eyes can naturally rotate so that the image of the object falls on the corresponding point on the retina of each eye, thus maintaining single binocular vision. This rotation allows the gaze of each eye 210 and 220 to converge on the point in space where the virtual object is perceived to exist. Therefore, providing three-dimensional images typically involves providing binocular cues that can manipulate the convergence and divergence of the user's eyes 210 and 220 and are interpreted by the human visual system to provide a sense of depth.

[0052] However, creating a realistic and comfortable sense of depth is challenging. It should be understood that light from objects at different distances from the eye has wavefronts with varying degrees of divergence. Figures 3A to 3C The relationship between distance and light divergence is illustrated. The distances between the object and the eye 210 are represented in descending order of distance: R1, R2, and R3. Figures 3A to 3C As shown, the light rays become more divergent as the distance to the object decreases. Conversely, the light rays become more collimated as the distance increases. In other words, it can be said that the light field generated by a point (the object or part of the object) has a spherical wavefront curvature, which is a function of how far that point is from the user's eye. The curvature increases as the distance between the object and the eye decreases. Although, for clarity... Figures 3A to 3C The other figures in this article show only a single eye 210, but the discussion of eye 210 can be applied to both eyes 210 and 220 of the viewer.

[0053] Continue to refer to Figures 3A to 3CLight from an object being viewed by a viewer's eye can have varying degrees of wavefront divergence. Due to these differences in wavefront divergence, light can be focused differently by the eye's lens, which in turn may require the lens to take on different shapes to form a focused image on the retina. In the absence of a focused image on the retina, the resulting retinal blur acts as an adaptation cue, causing a change in the shape of the eye's lens until a focused image is formed on the retina. For example, an adaptation cue can trigger the relaxation or contraction of the ciliary muscles surrounding the lens, thereby adapting to the forces applied to the suspensory ligaments that hold the lens, thus changing the shape of the eye's lens until the retinal blur of the viewed object is eliminated or minimized, thereby forming a focused image of the viewed object on the retina (e.g., the fovea). The process of the eye's lens changing shape can be called adaptation, and the shape of the eye's lens required to form a focused image of the viewed object on the retina (e.g., the fovea) can be called the adaptation state.

[0054] Now for reference Figure 4A This illustrates a representation of the adaptation-convergence response of the human visual system. Eye movement to gaze at an object causes the eye to receive light from the object, where the light forms an image on each retina of the eye. The presence of retinal blurring in the image formed on the retina provides adaptation cues, and the relative position of the image on the retina provides convergence cues. Adaptation cues cause adaptation to occur, resulting in the eye's lens presenting a specific adaptation state, which forms a focused image of the object on the retina of the eye (e.g., the fovea). On the other hand, convergence cues cause convergence movements (eye rotation) to occur, such that the image formed on each retina of each eye is located at the corresponding retinal point that maintains single binocular vision. At these positions, it can be said that the eye has presented a specific convergence state. Continue to reference Figure 4A Adaptation can be understood as the process by which the eye achieves a specific adaptive state, and convergence and divergence can be understood as the process by which the eye achieves a specific convergence and divergence state. For example... Figure 4A As shown, the eye's adaptation and convergence / divergence states can change if the user gazes at another object. For example, the adaptation state may change if the user gazes at a new object at a different depth on the z-axis.

[0055] Without being bound by theory, it can be considered that the viewer of an object may perceive it as "three-dimensional" due to a combination of convergence and adaptation. As mentioned above, the convergence and divergence movements of the two eyes relative to each other (e.g., eye rotation causing the pupils to move toward or away from each other to converge the gaze on an object) are closely related to the adaptation of the eye's lens. Under normal circumstances, according to a relationship known as the "adaptation-convergence reflex," changing the shape of the eye's lens to shift the focus from one object to another at a different distance will automatically result in a matching convergence and divergence change at the same distance. Similarly, under normal circumstances, changes in convergence and divergence will trigger a matching change in the lens shape.

[0056] Now for reference Figure 4B Examples of different adaptive and convergent states of the eye are shown. One pair of eyes 222a gazes at an object at optical infinity, while another pair of eyes 222b gazes at an object 221 smaller than optical infinity. Notably, the convergent state of each pair of eyes is different, with one pair of eyes 222a looking straight ahead, while the other pair of eyes 222 converges on object 221. The adaptive states of the eyes forming each pair of eyes 222a and 222b are also different, as illustrated by the different shapes of the lenses 210a and 220a.

[0057] Unexpectedly, many users of traditional “3D” display systems find them uncomfortable or even lacking in depth perception due to a mismatch between the adaptation and convergence states in these displays. As mentioned above, many stereoscopic or “3D” display systems present scenes by providing slightly different images to each eye. Such systems are uncomfortable for many viewers because, among other things, they only offer different presentations of the scene and cause changes in the eyes’ convergence states, but the eyes’ adaptation states do not change accordingly. Instead, the image is displayed by a display at a fixed distance relative to the eyes, allowing the eyes to see all the image information in a single adaptation state. This arrangement addresses the “adaptation-convergence reflex” by causing changes in convergence states when the adaptation states do not change in a matching manner. This mismatch is considered to cause viewer discomfort. Display systems that provide a better match between adaptation and convergence can create more realistic and comfortable 3D image simulations.

[0058] Without being bound by theory, it can be assumed that the human eye can typically interpret a finite number of depth planes to provide a sense of depth. Therefore, highly reliable simulations of perceived depth can be achieved by providing the eye with different image representations corresponding to each of these finite number of depth planes. In some embodiments, the different representations can simultaneously provide convergence / disconvergence cues and adaptive cues for matching, thereby providing physiologically correct adaptive-convergence matching.

[0059] Continue to refer to Figure 4BTwo depth planes 240 are shown, corresponding to different spatial distances relative to eyes 210, 220. For a given depth plane 240, convergence and divergence cues can be provided by displaying images with appropriately different perspectives for each eye 210, 220. Furthermore, for a given depth plane 240, the light forming the image provided to each eye 210, 220 can have wavefront divergence corresponding to the light field generated by a point at a distance from that depth plane 240.

[0060] In the illustrated embodiment, the depth plane 240 containing point 221 is 1 meter away along the z-axis. As used herein, the distance or depth along the z-axis can be measured using a zero point located at the user's exit pupil. Therefore, the depth plane 240 at a depth of 1 meter corresponds to a distance of 1 meter from the user's exit pupil on the optical axis of the user's eye, where the eye points to optical infinity. As an approximation, the depth or distance along the z-axis can be measured from a display (e.g., from the surface of a waveguide) in front of the user's eyes, plus the value of the distance between the device and the user's exit pupil. This value can be referred to as the exit pupil distance and corresponds to the distance between the user's exit pupil and the display worn by the user in front of their eyes. In practice, the value of the exit pupil distance can be a standardized value that is universal for all viewers. For example, it can be assumed that the exit pupil distance is 20 mm, and the depth plane at a depth of 1 meter is located at a distance of 980 mm in front of the display.

[0061] Now for reference Figure 4C and 4D Examples of the adaptive-convergence distances for matching and mismatched results are shown below. Figure 4C As shown, the display system can provide images of virtual objects to each eye 210, 220. These images can cause the eyes 210, 220 to enter a convergent state, where the eyes converge on point 15 on the depth plane 240. Furthermore, the image can be formed by light having a wavefront curvature corresponding to the real object at that depth plane 240. As a result, the eyes 210, 220 enter an adaptive state, where the image is focused on the retina of these eyes. Therefore, the user can perceive the virtual object as located at point 15 on the depth plane 240.

[0062] It should be understood that each of the adaptation and convergence / divergence states of eyes 210 and 220 is associated with a specific distance on the z-axis. For example, objects at specific distances from eyes 210 and 220 cause these eyes to exhibit a specific adaptation state based on the distance to the objects. The distance associated with a specific adaptation state can be referred to as the adaptation distance A. d Similarly, there exists a specific aggregation / disaggregation distance V associated with a specific aggregation / disaggregation state. dOr, relative to each other's positions. When the adaptive distance and the convergence / dispersion distance match, it can be said that the relationship between adaptation and convergence / dispersion is physiologically correct. This is considered the most comfortable scenario for the viewer.

[0063] However, in stereoscopic displays, the adaptation distance and convergence distance may not always match. For example, as Figure 4D As shown, the images displayed to eyes 210 and 220 can be displayed with wavefront divergence corresponding to depth plane 240, and eyes 210 and 220 can exhibit a specific adaptation state in which points 15a and 15b on the depth plane are focused. However, the images displayed to eyes 210 and 220 can provide convergence / divergence cues that cause eyes 210 and 220 to converge at point 15, which is not located on depth plane 240. Therefore, in some embodiments, the adaptation distance corresponds to the distance from the exit pupil of eyes 210 and 220 to depth plane 240, while the convergence / divergence distance corresponds to a greater distance from the exit pupil of eyes 210 and 220 to point 15. The adaptation distance is different from the convergence / divergence distance. Therefore, there is an adaptation-convergence / divergence mismatch. This mismatch is considered undesirable and may cause discomfort to the user. It should be understood that the mismatch corresponds to distance (e.g., V). d -A d And it can be characterized using diopter.

[0064] In some embodiments, it should be understood that a reference point other than the exit pupil of the eye 210, 220 can be used to determine the distance for determining the adaptation-convergence mismatch, provided that the same reference point is used for both the adaptation distance and the convergence distance. For example, the distance from the cornea to the depth plane, from the retina to the depth plane, from the eyepiece (e.g., the waveguide of a display device) to the depth plane, etc., can be measured.

[0065] Without being theoretically limited, it is assumed that, provided the adaptation-convergence mismatch itself does not cause significant discomfort, users can still perceive adaptation-convergence mismatches of up to 0.25 diopters, up to 0.33 diopters, and up to approximately 0.5 diopters as physiologically correct. In some embodiments, the display systems disclosed herein (e.g., Figure 6 The display system 250 presents an image to a viewer with an adaptation-convergence mismatch of about 0.5 diopters or less. In some other embodiments, the adaptation-convergence mismatch of the image provided by the display system is about 0.33 diopters or less. In still other embodiments, the adaptation-convergence mismatch of the image provided by the display system is about 0.25 diopters or less, including about 0.1 diopters or less.

[0066] Figure 5Aspects of a method for simulating a three-dimensional image by modifying wavefront divergence are illustrated. The display system includes a waveguide 270 configured to receive light 770 encoded with image information and output the light to a user's eye 210. The waveguide 270 can output light 650 with a 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. Additionally, it will be explained that image information from a similar waveguide can be provided to the user's other eye.

[0067] In some embodiments, a single waveguide may be configured to output light with a predetermined amount of wavefront divergence corresponding to the wavefront divergence of a single depth plane or a finite number of depth planes, and / or the waveguide may be configured to output light within a finite wavelength range. Therefore, in some embodiments, multiple waveguides or waveguide stacks may be used to provide different amounts of wavefront divergence for different depth planes and / or output light within different wavelength ranges. As used herein, it should be understood that a depth plane may be planar or may have a curved profile.

[0068] Figure 6 An example of a waveguide stack for outputting image information to a user is shown. The display system 250 includes a waveguide stack or a stacked waveguide assembly 260, which can be used to provide three-dimensional perception to the eye / brain using multiple waveguides 270, 280, 290, 300, 310. It should be understood that in some embodiments, the display system 250 can be considered a light field display. Furthermore, the waveguide assembly 260 can also be referred to as an eyepiece.

[0069] In some embodiments, the display system 250 may be configured to provide substantially continuous convergence and divergence cues and multiple discrete adaptation cues. Convergence and divergence cues can be provided by displaying different images to each of the user's eyes, and adaptation cues can be provided by outputting light for image formation with selectable discrete amounts of wavefront divergence. In other words, the display system 250 may be configured to output light with variable wavefront divergence levels. In some embodiments, each discrete level of wavefront divergence corresponds to a specific depth plane and may be provided by one of waveguides 270, 280, 290, 300, 310.

[0070] Continue to refer to Figure 6Waveguide assembly 260 may further include multiple features 320, 330, 340, 350 between waveguides. In some embodiments, features 320, 330, 340, 350 may be one or more lenses. Waveguides 270, 280, 290, 300, 310 and / or multiple lenses 320, 330, 340, 350 may be configured to send image information to the eye at various levels of wavefront curvature or light 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 injection devices 360, 370, 380, 390, 400 may serve as light sources for the waveguides and may be used to inject image information into waveguides 270, 280, 290, 300, 310, as described herein, each waveguide may be configured to distribute incident light across each respective waveguide for output toward eye 210. Light exits from the output surfaces 410, 420, 430, 440, and 450 of the image injection devices 360, 370, 380, 390, and 400, and is injected into the corresponding input surfaces 460, 470, 480, 490, and 500 of the waveguides 270, 280, 290, 300, and 310. In some embodiments, each of the input surfaces 460, 470, 480, 490, and 500 may be an edge of the corresponding waveguide or a portion of the main surface of the corresponding waveguide (i.e., one of the waveguide surfaces directly facing 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 to output the entire field of a cloned collimated beam, which is directed to the eye 210 at a specific angle (and divergence) corresponding to a depth plane associated with a particular waveguide. In some embodiments, one of the image injection devices 360, 370, 380, 390, 400 may be associated with multiple (e.g., three) of the waveguides 270, 280, 290, 300, 310 and inject light therein.

[0071] In some embodiments, image injection devices 360, 370, 380, 390, and 400 are discrete displays, each generating image information for injection into a corresponding waveguide 270, 280, 290, 300, and 310. In some other embodiments, image injection devices 360, 370, 380, 390, and 400 are the output of a single multiplexed display, for example, which may transmit image information through one or more optical conduits (e.g., fiber optic cables) to each of the image injection devices 360, 370, 380, 390, and 400. It should be understood that the image information provided by the image injection devices 360, 370, 380, 390, and 400 may include light of different wavelengths or colors (e.g., different component colors as discussed herein).

[0072] In some embodiments, light injected into waveguides 270, 280, 290, 300, 310 is provided by a light projector system 520, which includes an optical module 530. The optical module 530 may include a light emitter, such as a light-emitting diode (LED). Light from the optical module 530 can be directed and modified by an optical modulator 540 (e.g., a spatial light modulator) via a beam splitter 550. The optical modulator 540 can be configured to change the perceived intensity of light injected into waveguides 270, 280, 290, 300, 310 to encode the light with image information. Examples of spatial light modulators include liquid crystal displays (LCDs), including liquid crystal on silicon (LCOS) displays. It should be understood that image injection devices 360, 370, 380, 390, and 400 are shown schematically, and in some embodiments, these image injection devices may represent different optical paths and locations in a common projection system configured to output light into associated waveguides in waveguides 270, 280, 290, 300, and 310. In some embodiments, the waveguide in waveguide assembly 260 may function as an ideal lens while relaying the light injected into the waveguide 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.

[0073] In some embodiments, the display system 250 may be a scanning fiber optic display comprising one or more scanning fibers configured to project light into one or more waveguides 270, 280, 290, 300, 310 in various patterns (e.g., raster scanning, spiral scanning, Lissajous patterns, etc.) and ultimately onto the viewer's eye 210. In some embodiments, the image injection devices 360, 370, 380, 390, 400 shown may schematically represent a single scanning fiber or a bundle of scanning fibers configured to inject light into one or more waveguides 270, 280, 290, 300, 310. In some other embodiments, the illustrated image injection devices 360, 370, 380, 390, 400 may schematically represent multiple scanning fibers or multiple bundles of scanning fibers, each of which is configured to inject light into an associated waveguide in waveguides 270, 280, 290, 300, 310. It should be understood that one or more fibers may be configured to transmit light from optical module 530 to one or more waveguides 270, 280, 290, 300, 310. It should be understood that one or more intermediary optical structures may be provided between one or more scanning fibers and one or more waveguides 270, 280, 290, 300, 310 to, for example, redirect light emanating from the scanning fibers into one or more waveguides 270, 280, 290, 300, 310.

[0074] Controller 560 controls the operation of one or more of the stacked waveguide assemblies 260, including the operation of image injection devices 360, 370, 380, 390, 400, light source 530, and optical modulator 540. In some embodiments, controller 560 is part of local data processing module 140. Controller 560 includes programming (e.g., instructions in a non-transitory medium) that adjusts timing and provides image information to waveguides 270, 280, 290, 300, 310 according to any of the various schemes disclosed herein. In some embodiments, the controller may be a single monolithic device or a distributed system connected via wired or wireless communication channels. In some embodiments, controller 560 may be processing module 140 or 150. Figure 9D () part.

[0075] Continue to refer to Figure 6Waveguides 270, 280, 290, 300, and 310 can be configured to propagate light within each respective waveguide via total internal reflection (TIR). Waveguides 270, 280, 290, 300, and 310 can each be planar or have another shape (e.g., curved), having a top main surface and a bottom main surface, and an edge extending between these top and bottom main surfaces. In the illustrated configuration, waveguides 270, 280, 290, 300, and 310 can each include coupling optical elements 570, 580, 590, 600, and 610, which are configured to extract light from the waveguide by redirecting light, propagating within their respective respective waveguides, and exiting from the waveguides to output image information to eye 210. The extracted light can also be referred to as the coupling light, and the coupling optical element light can also be referred to as the light extraction optical element. The extracted light beam can be emitted from the waveguide at the location of the light extraction optics, where light propagating in the waveguide is directed. As further discussed herein, the coupling optical elements 570, 580, 590, 600, and 610 can be, for example, gratings that include diffractive optical features. Although shown disposed on the bottom main surface of waveguides 270, 280, 290, 300, and 310, for clarity of description and drawing, in some embodiments, as further discussed herein, the coupling optical elements 570, 580, 590, 600, and 610 can be disposed on the top and / or bottom main surfaces, and / or can be disposed directly within the volume of waveguides 270, 280, 290, 300, and 310. In some embodiments, the coupling optical elements 570, 580, 590, 600, and 610 can be formed in a material layer attached to a transparent substrate to form waveguides 270, 280, 290, 300, and 310. In some other embodiments, waveguides 270, 280, 290, 300, and 310 may be monolithic materials, and coupling optical elements 570, 580, 590, 600, and 610 may be formed on the surface and / or inside the monolithic material.

[0076] Continue to refer to Figure 6As discussed herein, each waveguide 270, 280, 290, 300, 310 is configured to output light to form an image corresponding to a specific depth plane. For example, the waveguide 270 closest to the eye can be configured to deliver collimated light (injected into such a waveguide 270) to the eye 210. This collimated light can represent the optical infinity focal plane. The next uplink waveguide 280 can be configured to emit collimated light that travels through a first lens 350 (e.g., a negative lens) before reaching the eye 210; such a first lens 350 can be configured to produce a slightly convex wavefront curvature such that the eye / brain interprets the light from this next uplink waveguide 280 as originating from a first focal plane closer to the eye 210 from optical infinity. Similarly, the third uplink waveguide 290 allows its output light to travel through both the first lens 350 and the second lens 340 before reaching the eye 210; the combined optical power of the first lens 350 and the second lens 340 can be configured to produce another increment in wavefront curvature, such that the eye / brain interprets the light from the third waveguide 290 as coming from a second focal plane that is further closer to the person than the light from the next uplink waveguide 280.

[0077] Other waveguide layers 300, 310 and lenses 330, 320 are similarly configured, with the highest waveguide 310 in the stack transmitting its output through all the lenses between it and the eye to obtain a total focal power representing the focal plane closest to the person. To compensate for the lens stacks 320, 330, 340, 350 when observing / interpreting light from the world 510 on the other side of the stacked waveguide assembly 260, a compensation lens layer 620 can be positioned on top of the stack to compensate for the total focal power of the lens stacks 320, 330, 340, 350 below. This configuration provides as many perceptible focal planes as available waveguide / lens pairs. Both the outgoing optics of the waveguides and the focusing aspects of the lenses can be static (i.e., not dynamic or electrically active). In some alternative embodiments, one or both can be dynamic by using electrically active features.

[0078] In some embodiments, two or more of 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 image sets to the same depth plane, or multiple subsets of waveguides 270, 280, 290, 300, and 310 may be configured to output image sets to the same multiple depth planes, one set per depth plane. This can provide an advantage in forming tiled images to provide an extended field of view at those depth planes.

[0079] Continue to refer to Figure 6The coupling optical elements 570, 580, 590, 600, and 610 can be configured to both redirect light outside their respective waveguides and output the light with appropriate divergence or collimation to a specific depth plane associated with that waveguide. As a result, waveguides with different associated depth planes can have coupling optical elements 570, 580, 590, 600, and 610 with different configurations, and these different configurations output light with different divergence amounts depending on the associated depth plane. In some embodiments, the light extraction optical elements 570, 580, 590, 600, and 610 can be volumetric or surface features that can be configured to output light at a specific angle. For example, the light extraction optical elements 570, 580, 590, 600, and 610 can be volumetric holograms, surface holograms, and / or diffraction gratings. In some embodiments, features 320, 330, 340, and 350 may not be lenses; instead, they may simply be spacers (e.g., cladding and / or structures for forming air gaps).

[0080] In some embodiments, the coupling optical elements 570, 580, 590, 600, and 610 are diffraction features that form a diffraction pattern, or "diffractive optical elements" (also referred to herein as "DOEs"). Preferably, the DOE has a sufficiently low diffraction efficiency such that only a portion of the beam is deflected toward the eye 210 via each intersection point of the DOE, while the remainder continues through the waveguide via the TIR. Thus, the light carrying image information is split into multiple associated outgoing beams that exit the waveguide at multiple locations, and for this particular collimated beam bouncing within the waveguide, the result is a fairly uniform pattern exiting toward the eye 210.

[0081] In some embodiments, one or more DOEs can be switchable between an "on" state in which they actively diffract and a "off" state in which they do not significantly diffract. For example, a switchable DOE may include a polymer-dispersed liquid crystal layer, wherein the droplets comprise diffraction patterns in a host medium, and the refractive index of the droplets may be switched to a refractive index substantially matching that of the host material (in which case the pattern does not significantly diffract incident light) or the droplets may be switched to a refractive index mismatched with that of the host medium (in which case the pattern actively diffracts incident light).

[0082] In some embodiments, a camera assembly 630 (e.g., a digital camera, including visible light and infrared cameras) may be provided to capture images of the eye 210 and / or tissues surrounding the eye 210, for example, to detect user input and / or monitor the user's physiological state. As used herein, the camera can be any image capture device. In some embodiments, the camera assembly 630 may include an image capture device and a light source to project light (e.g., infrared light) onto the eye, which can then be reflected by the eye and detected by the image capture device. In some embodiments, the camera assembly 630 may be attached to a frame 80 (…). Figure 9D It can also be electrically connected to processing module 140 and / or processing module 150, which can process image information from camera assembly 630. In some embodiments, each eye can use one camera assembly 630 to monitor each eye separately.

[0083] Now for reference Figure 7 An example of an outgoing beam output from a waveguide is shown. A waveguide is shown, but it should be understood that waveguide assembly 260 ( Figure 6 Other waveguides in the waveguide assembly 260 can function similarly, where the waveguide assembly 260 includes multiple waveguides. Light 640 is injected into waveguide 270 at its input surface 460 and propagates within waveguide 270 via TIR. At the point where light 640 illuminates DOE 570, a portion of the light is emitted from the waveguide as an outgoing beam 650. The outgoing beams 650 are shown as substantially parallel, but as discussed herein, they can also be redirected to propagate to eye 210 at an angle (e.g., forming a diverging outgoing beam), the angle depending on the depth plane associated with waveguide 270. It should be understood that substantially parallel outgoing beams can indicate a waveguide with coupled optics that couple light to form an image that appears to be positioned at a distance from eye 210 (e.g., optical infinity) on a depth plane. Other waveguides or other sets of coupled optical elements can output a more divergent outgoing beam pattern, which would require the eye 210 to adapt to a closer distance so that the more divergent outgoing beam pattern is focused on the retina and will be interpreted by the brain as light coming from a distance closer to the eye 210 than optical infinity.

[0084] In some embodiments, a panchromatic image can be formed at each depth plane by overlaying images in each of the component colors (e.g., three or more component colors). Figure 8An example of a stacked waveguide assembly is shown, wherein each depth plane includes an image formed using multiple different component colors. The illustrated embodiment shows depth planes 240a-240f, but more or fewer depths are also contemplated. Each depth plane may have three or more component color images associated with it, including: a first image of a first color G; a second image of a second color R; and a third image of a third color B. Different depth planes are represented in the figure by different numbers following the letters G, R, and B, indicating diopter (dpt). By way of example only, the number following each of these letters represents diopter (1 / m), or the reciprocal of the distance of that depth plane from the viewer, and each box in the figure represents a separate component color image. In some embodiments, the precise placement of the depth planes of different component colors can vary to account for differences in the eye's focusing on different wavelengths of light. For example, different component color images of a given depth plane can be placed on depth planes corresponding to different distances from the user. Such an arrangement can increase visual acuity and user comfort, and / or reduce chromatic aberration.

[0085] In some embodiments, light of each component color can be output by a single dedicated waveguide; therefore, each depth plane can have multiple waveguides associated with it. In such embodiments, each box in the figure including the letters G, R, or B can be understood as representing a separate waveguide, and each depth plane can provide three waveguides, wherein each depth plane provides three component color images. Although for ease of description, the waveguides associated with each depth plane are shown as adjacent to each other in this figure, it should be understood that in a physical device, the waveguides can all be arranged in a stacked form of one waveguide per layer. In some other embodiments, multiple component colors can be output by the same waveguide, such that, for example, each depth plane can provide only a single waveguide.

[0086] Continue to refer to Figure 8 In some embodiments, G is green, R is red, and B is blue. In some other embodiments, in addition to red, green, or blue, other colors associated with light of other wavelengths (including magenta and cyan) may be used, or these other colors may replace one or more of red, green, or blue.

[0087] It should be understood that any reference to a given color of light throughout this disclosure will be construed as including light within one or more wavelengths in the wavelength range perceived by a viewer as having that given color. For example, red light may include light within one or more wavelengths in the range of about 620-780 nm, green light may include light within one or more wavelengths in the range of about 492-577 nm, and blue light may include light within one or more wavelengths in the range of about 435-493 nm.

[0088] In some embodiments, the light source 530 ( Figure 6 The display 250 can be configured to emit light of one or more wavelengths outside the viewer's visual perception range, such as infrared and / or ultraviolet wavelengths. Furthermore, the waveguide coupling-in, coupling-out, and other light redirection structures of the display 250 can be configured to direct this light and direct it from the display toward the user's eye 210, for example, for imaging and / or user stimulation applications.

[0089] Now for reference Figure 9A In some embodiments, it may be necessary to redirect light incident on a waveguide to couple the light into the waveguide. Coupled optical elements can be used to redirect the light and couple it into its corresponding waveguide. Figure 9A A cross-sectional side view of an example of multiple stacked waveguides or stacked waveguide groups 660 is shown, each stacked waveguide including coupled optical elements. The waveguides can each be configured to output light of one or more different wavelengths, or light of one or more different wavelength ranges. It should be understood that stack 660 can correspond to stack 260 (…). Figure 6 In addition to light from one or more image injection devices 360, 370, 380, 390, 400 being injected into the waveguide at the location where the light needs to be redirected for coupling, the waveguide shown in the stack 660 may correspond to portions of the plurality of waveguides 270, 280, 290, 300, 310.

[0090] The illustrated stacked waveguide assembly 660 includes waveguides 670, 680, and 690. Each waveguide includes associated coupling optics (which may also be referred to as light input regions on the waveguide), wherein, for example, coupling optics 700 is disposed on the main surface (e.g., the top main surface) of waveguide 670, coupling optics 710 is disposed on the main surface (e.g., the top main surface) of waveguide 680, and coupling optics 720 is disposed on the main surface (e.g., the top main surface) of waveguide 690. In some embodiments, one or more of coupling optics 700, 710, and 720 may be disposed on the bottom main surface of the respective waveguides 670, 680, and 690 (particularly in cases where one or more coupling optics are reflective deflecting optics). As shown, coupling optics 700, 710, and 720 may be disposed on the top main surface of their respective waveguides 670, 680, and 690 (or on top of the next downlink waveguide), particularly in cases where those coupling optics are transmissive deflecting optics. In some embodiments, coupling optical elements 700, 710, 720 may be disposed within the bodies of their respective waveguides 670, 680, 690. In some embodiments, as discussed herein, coupling optical elements 700, 710, 720 are wavelength selective, such that they selectively redirect one or more wavelengths of light while transmitting other wavelengths. Although shown on one side or corner of their respective waveguides 670, 680, 690, it should be understood that in some embodiments, coupling optical elements 700, 710, 720 may be disposed in other regions of their respective waveguides 670, 680, 690.

[0091] As shown in the figure, the coupling optical elements 700, 710, and 720 can be laterally offset from each other. In some embodiments, each coupling optical element can be offset such that the coupling optical element receives light without the light needing to be transmitted through another coupling optical element. For example, as... Figure 6 As shown, each coupled optical element 700, 710, 720 can be configured to receive light from different image injection devices 360, 370, 380, 390 and 400, and can be separated from other coupled optical elements 700, 710, 720 (e.g., laterally spaced) such that the coupled optical element substantially does not receive light from other coupled optical elements among the coupled optical elements 700, 710, 720.

[0092] Each waveguide also includes associated light distribution elements, wherein, for example, light distribution element 730 is disposed on the main surface (e.g., top main surface) of waveguide 670, light distribution element 740 is disposed on the main surface (e.g., top main surface) of waveguide 680, and light distribution element 750 is disposed on the main surface (e.g., top main surface) of waveguide 690. In some other embodiments, light distribution elements 730, 740, and 750 may be disposed on the bottom main surface of associated waveguides 670, 680, and 690, respectively. In some other embodiments, light distribution elements 730, 740, and 750 may be disposed on the top and bottom main surfaces of associated waveguides 670, 680, and 690, respectively; or light distribution elements 730, 740, and 750 may be disposed on different main surfaces of the top and bottom main surfaces of different associated waveguides 670, 680, and 690.

[0093] Waveguides 670, 680, and 690 may be spaced and separated by layers of, for example, gaseous, liquid, and / or solid materials. 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 of a low-refractive-index material (i.e., a material having a lower refractive index than the material forming one of the adjacent waveguides 670, 680, and 690). Preferably, the refractive index of the material forming layers 760a and 760b differs from the refractive index of the material forming waveguides 670, 680, and 690 by 0.05 or greater, or 0.10 or less. Advantageously, the lower refractive index layers 760a and 760b can serve as cladding, which promotes total internal reflection (TIR) ​​of light passing through waveguides 670, 680, and 690 (e.g., TIR between the top and bottom primary surfaces of each waveguide). In some embodiments, layers 760a and 760b are formed of air. Although not shown, it should be understood that the top and bottom of the illustrated waveguide assembly 660 may include adjacent cladding.

[0094] Preferably, for ease of 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 be different among one or more waveguides, and / or the materials forming layers 760a and 760b may be different, while still maintaining the various refractive index relationships described above.

[0095] Continue to refer to Figure 9ALight rays 770, 780, and 790 are incident on waveguide assembly 660. It should be understood that light rays 770, 780, and 790 can be transmitted through one or more image injection devices 360, 370, 380, 390, and 400. Figure 6 Injected into waveguides 670, 680, and 690.

[0096] In some embodiments, the light rays 770, 780, and 790 have different characteristics, for example, different wavelengths or different wavelength ranges corresponding to different colors. Coupled optical elements 700, 710, and 720 each deflect the incident light, causing it to propagate via TIR through a corresponding waveguide 670, 680, and 690. In some embodiments, coupled optical elements 700, 710, and 720 each selectively deflect one or more specific wavelengths of light while transmitting other wavelengths to the underlying waveguide and associated coupled optical element.

[0097] For example, the coupling optical element 700 can be configured to deflect light 770 having a first wavelength or a first wavelength range, while transmitting light 780 having a different second wavelength or a second wavelength range and light 790 having a third wavelength or a third wavelength range, respectively. The transmitted light 780 illuminates and is deflected by the coupling optical element 710, which is configured to deflect light of the second wavelength or a second wavelength range. The light 790 is deflected by the coupling optical element 720, which is configured to selectively deflect light of the third wavelength or a third wavelength range.

[0098] Continue to refer to Figure 9A The deflected light rays 770, 780, and 790 are deflected so that they propagate through their corresponding waveguides 670, 680, and 690; that is, the coupling optical elements 700, 710, and 720 of each waveguide deflect the light into its corresponding waveguide 670, 680, and 690, thus coupling the light into that waveguide. The light rays 770, 780, and 790 are deflected at a certain angle, which allows the light to propagate through the corresponding waveguides 670, 680, and 690 via TIR propagation. The light rays 770, 780, and 790 propagate through the corresponding waveguides 670, 680, and 690 via TIR propagation until they illuminate the corresponding light distribution elements 730, 740, and 750 of the waveguides.

[0099] Now for reference Figure 9B , showed Figure 9AA perspective view of an example of multiple stacked waveguides. As described above, the coupled light rays 770, 780, and 790 are deflected by coupled optical elements 700, 710, and 720, respectively, and then propagate via TIR within waveguides 670, 680, and 690, respectively. The light rays 770, 780, and 790 then illuminate light distribution elements 730, 740, and 750, respectively. The light distribution elements 730, 740, and 750 deflect the light rays 770, 780, and 790, causing them to propagate toward coupled optical elements 800, 810, and 820, respectively.

[0100] In some embodiments, light distribution elements 730, 740, and 750 are orthogonal pupil expanders (OPEs). In some embodiments, the OPE deflects or distributes light to output optics 800, 810, and 820, and in some embodiments, it can also increase the beam or spot size of the light as it propagates toward the output optics. In some embodiments, light distribution elements 730, 740, and 750 may be omitted, and input optics 700, 710, and 720 may be configured to directly deflect light to output optics 800, 810, and 820. For example, see reference. Figure 9A The light distribution elements 730, 740, and 750 can be replaced by coupling optical elements 800, 810, and 820, respectively. In some embodiments, the coupling optical elements 800, 810, and 820 are exit pupils (EP) or exit pupil expanders (EPE), which direct light into the viewer's eye 210. Figure 7 It should be understood that an OPE can be configured to increase the size of the eyebox on at least one axis, and an EPE can increase the eyebox on an axis intersecting (e.g., orthogonal) to the axis of the OPE. For example, each OPE can be configured to redirect a portion of the light arriving at the OPE to the EPE in the same waveguide, while allowing the remaining portion of the light to continue propagating along the waveguide. Upon illuminating the OPE again, another portion of the remaining light is redirected to the EPE, and that remaining portion continues to propagate further along the waveguide, and so on. Similarly, upon reaching the EPE, a portion of the illuminating light is directed toward the user through the waveguide, and the remaining portion of that light continues to propagate through the waveguide until it reaches the EPE again, at which point another portion of the illuminating light is directed through the waveguide, and so on. Thus, whenever a portion of a single beam of coupled light is redirected by an OPE or EPE, that light can be “replicated,” thereby forming a field of cloned beams, such as Figure 6 As shown. In some embodiments, OPE and / or EPE can be configured to modify the size of the beam.

[0101] Therefore, refer to Figure 9A and Figure 9BIn some embodiments, waveguide group 660 includes: waveguides 670, 680, 690; coupling optics 700, 710, 720; light distribution elements (e.g., OPE) 730, 740, 750; and output optics (e.g., EP) 800, 810, 820 for each component color. Waveguides 670, 680, 690 may be stacked with an air gap / cladding between each waveguide. The coupling optics 700, 710, 720 redirect or deflect incident light (where different coupling optics receive light of different wavelengths) into their respective waveguides. The light then propagates at an angle that will result in a TIR within the respective waveguide 670, 680, 690. In the example shown, ray 770 (e.g., blue light) is deflected by the first coupled-in optics 700 and then continues to bounce along the waveguide, interacting with the light distribution element (e.g., OPE) 730 and the coupled-out optics (e.g., EP) 800 in the manner previously described. Rays 780 and 790 (e.g., green and red light, respectively) will propagate through waveguide 670, where ray 780 illuminates and is deflected by coupled-in optics 710. Ray 780 then bounces along waveguide 680 via TIR, proceeds to its light distribution element (e.g., OPE) 740, and then to coupled-out optics (e.g., EP) 810. Finally, ray 790 (e.g., red light) propagates through waveguide 690 and illuminates the light coupled-in optics 720 of waveguide 690. The light-coupled optical element 720 deflects the light ray 790 so that it propagates via TIR to the light distribution element (e.g., OPE) 750, and then via TIR to the output optical element (e.g., EP) 820. The output optical element 820 then finally couples the light ray 790 out to the viewer, who also receives the coupled light from other waveguides 670, 680.

[0102] Figure 9C It shows Figure 9A and Figure 9B A top plan view of an example of multiple stacked waveguides. As shown, waveguides 670, 680, 690 and their associated light distribution elements 730, 740, 750 and associated coupling optics 800, 810, 820 can be vertically aligned. However, as discussed herein, the coupling optics 700, 710, 720 are not vertically aligned; instead, the coupling optics are preferably non-overlapping (e.g., laterally spaced when viewed in a top view). As further discussed herein, this non-overlapping spatial arrangement facilitates the one-to-one injection of light from different resources into different waveguides, thereby allowing a specific light source to be uniquely coupled to a specific waveguide. In some embodiments, arrangements including non-overlapping, spatially separated coupling optics may be referred to as shifted pupil systems, and the coupling optics within these arrangements may correspond to sub-pupils.

[0103] Figure 9D An example of a wearable display system 60 is shown, into which various waveguides and related systems disclosed herein can be integrated. In some embodiments, the display system 60 is Figure 6 System 250, of which Figure 6 Some components of the system 60 are shown schematically in more detail. For example, Figure 6 The waveguide component 260 may be part of the display 70.

[0104] Continue to refer to Figure 9D The display system 60 includes a display 70 and various mechanical and electronic modules and systems supporting the functionality of the display 70. The display 70 may be coupled to a frame 80, which is wearable by a user or viewer 90 of the display system, and the frame 80 is configured to position the display 70 in front of the user 90's eyes. In some embodiments, the display 70 may be considered as eyeglasses. In some embodiments, a speaker 100 is coupled to the frame 80 and configured to be located adjacent to the user 90's ear canal (in some embodiments, another speaker (not shown) may optionally be located adjacent to the user's other ear canal to provide stereo / shape-shifting sound control). The display system 60 may also include one or more microphones 110 or other devices to detect sound. In some embodiments, the microphones are configured to allow the user to provide input or commands to the system 60 (e.g., selection of voice menu commands, natural language questions, etc.), and / or may allow audio communication with other people (e.g., with other users of similar display systems). The microphones may be further configured as peripheral sensors to collect audio data (e.g., sound from the user and / or environment). In some embodiments, the display system may further include a peripheral sensor 120a, which may be detachable from the frame 80 and attached to the body of the user 90 (e.g., on the user 90's head, torso, limbs, etc.). In some embodiments, the peripheral sensor 120a may be configured to acquire data characterizing the physiological state of the user 90. For example, the sensor 120a may be an electrode.

[0105] Continue to refer to Figure 9DThe display 70 is operatively coupled to the local data processing module 140 via a communication link 130 (e.g., via a wired lead or wireless connection). The local data processing module 140 can 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, embedded in headphones, or otherwise removably attached to the user 90 (e.g., in a backpack configuration or a belt-coupled configuration). Similarly, the sensor 120a is operatively coupled to the local processing and data module 140 via a communication link 120b (e.g., via a wired lead or wireless connection). 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 can be used for auxiliary data processing, caching, and storage. Optionally, the local processing and data module 140 may include one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, etc. Data may include a) data captured from sensors (which may be operatively coupled to frame 80 or otherwise attached to user 90, such as image capture devices (e.g., cameras), microphones, inertial measurement units, accelerometers, compasses, GPS units, radios, gyroscopes, and / or other sensors disclosed herein); and / or b) data acquired and / or processed using remote processing module 150 and / or remote data storage 160 (including data relating to virtual content), possibly for transmission to display 70 after such processing or retrieval. Local processing and data module 140 may be operatively coupled to remote processing module 150 and remote data storage 160 via communication links 170, 180, such as via wired or wireless communication links, such that these remote modules 150, 160 are operatively coupled to each other and can be used as a resource for local processing and data module 140. In some embodiments, the local processing and data module 140 may include one or more of an image capture device, a microphone, an inertial measurement unit, an accelerometer, a compass, a GPS unit, a wireless device, and / or a gyroscope. In some other embodiments, one or more of these sensors may be attached to the frame 80, or may be a separate structure that communicates with the local processing and data module 140 via a wired or wireless communication path.

[0106] Continue to refer to Figure 9DIn some embodiments, the remote processing module 150 may include one or more processors configured to analyze and process data and / or image information, such as one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, etc. In some embodiments, the remote data repository 160 may include digital data storage facilities accessible via the Internet or other network configurations in a "cloud" resource configuration. In some embodiments, the remote data repository 160 may include one or more remote servers that provide information, such as information for generating augmented reality content, to the local processing and data module 140 and / or the remote processing module 150. In some embodiments, all data is stored and all computations are performed in the local processing and data module, allowing for completely autonomous use from the remote modules. Optionally, an external system (e.g., one or more processors, a system of one or more computers) including a CPU, GPU, etc., may perform at least a portion of the processing (e.g., generating image information, processing data) and provide and receive information to and from modules 140, 150, 160, for example, via wireless or wired connections.

[0107] Diffraction grating with reduced polarization sensitivity

[0108] Providing users of waveguide-based display systems (e.g., various display systems configured for the aforementioned virtual / augmented / hybrid display applications) with a high-quality, immersive experience depends, among other things, on the various characteristics of the light coupled into and / or coupled out of the waveguide in the eyepiece of the display system. For example, a virtual / augmented / hybrid display with high light coupling and coupling efficiency can enhance the viewing experience by increasing the brightness of the light directed to the user's eyes. As described above, coupling optics such as coupling diffraction gratings can be used to couple light into the waveguide for guidance therein via total internal reflection. Similarly, coupling optics such as coupling out diffraction gratings can be used to couple light guided within the waveguide via total internal reflection out of the waveguide.

[0109] As mentioned above, for example, refer to Figure 6 and Figure 7 The display systems according to the various embodiments described herein may include optical elements, such as coupling-in optics, coupling-out optics, light distribution elements, and / or combinations thereof, and pupil expander-extractor (CPEs), which may include diffraction gratings. As disclosed herein, the CPE may operate as a light distribution element that propagates or distributes light within a waveguide, thereby potentially increasing the beam size and / or eyebox, and as a coupling-out optics element that couples light out of the waveguide.

[0110] For example, as referenced above Figure 7As described, light 640 injected into waveguide 270 at input surface 460 propagates and is guided within waveguide 270 via total internal reflection (TIR). In various embodiments, at the point where light 640 strikes the coupling-out optics 570, a portion of the guided light within the waveguide exits as a sub-beam 650. In some embodiments, any one of optical elements 570, 580, 590, 600, 610, which may include one or more of coupling-in optics, coupling-out optics, light distribution elements, or CPEs, may include or be configured as a diffraction grating.

[0111] To achieve the desired characteristics of coupling light into (or out of) waveguides 270, 280, 290, 300, and 310, the optical elements 570, 580, 590, 600, and 610 configured as diffraction gratings can be formed of suitable materials and have suitable structures for controlling various optical properties, including diffraction characteristics such as diffraction efficiency as a function of polarization. Possible ideal diffraction characteristics may include any one or more of the following, among others: spectral selectivity, angular selectivity, polarization selectivity (or non-selectivity), high spectral bandwidth, high diffraction efficiency, or wide field of view (FOV).

[0112] Some diffraction gratings exhibit strong polarization dependence and may therefore have relatively reduced overall efficiency (due to suppression of one polarization). Such diffraction gratings can also produce coherence artifacts and reduce the uniformity of far-field images. To provide diffraction gratings with reduced polarization sensitivity (e.g., coupling light with relatively polarization-independent efficiency), some displays for AR systems according to embodiments described herein include waveguides in which blazed diffraction gratings are formed. For example, a blazed grating may include diffraction features with a “sawtooth” shape. In some embodiments, the blazed grating can achieve enhanced grating diffraction efficiency for a given diffraction order, while diffraction efficiency is reduced or minimized for other orders. As a result, more light can be directed to a particular given diffraction order compared to any other order in some embodiments.

[0113] Figure 10AA cross-sectional view of a portion of a display device 1000 according to some designs described herein is shown. The display device 1000 includes, for example, a waveguide 1004 and an eyepiece formed on a substrate serving as the waveguide 1004. In the illustrated embodiment, the blazed diffraction grating 1008 is formed in the substrate / waveguide 1004 (planar in this example). The surface of the substrate or waveguide 1004 has a surface topology including diffraction features that collectively form the diffraction grating 1008. The blazed diffraction grating 1008 is configured to diffract light having wavelengths in the visible spectrum, such that light incident thereon is guided within the waveguide 1004 via TIR. The waveguide 1004 may be transparent and may form part of the eyepiece through which a user's eye can view. Such a waveguide 1004 and eyepiece can be included in a head-mounted display such as an augmented reality display. For example, the waveguide 1004 may correspond to, for example, the above-described... Figures 9A-9C One of the waveguides 670, 680, and 690 described. For example, the blazed diffraction grating 1008 can correspond to the above-described waveguides. Figures 9A-9C One of the coupling optical elements 700, 710, and 720 is described. A blazed diffraction grating 1008 configured to couple light into waveguide 1004 may be referred to herein as a coupling grating (ICG). The display device 1000 may additionally include an optical element 1012, which may correspond to, for example, a light distribution element (e.g., Figures 9A-9C One of the light distribution elements 730, 740, 750 shown) or coupling optical elements (e.g., Figures 9A-9C (One of the coupling optical elements 800, 810, and 820 shown).

[0114] In operation, when an incident beam 1016, such as visible light, from a light projection system providing image content, is directed relative to an extended surface or plane of a blazed diffraction grating or substrate / waveguide and / or a surface 1004S of waveguide 1004 (e.g., the main surface of the waveguide on which the grating is formed) (in... Figure 10A When an incident angle α, measured by a plane normal 1002 (extended parallel to the yx plane) perpendicular or orthogonal to the plane normal 1002, is incident on a blazed diffraction grating 1008, the blazed diffraction grating diffracts the incident beam 1016 into a diffraction beam 1024 at least partially at a diffraction angle θ measured relative to the plane normal 1002. When the diffraction beam 1024 is incident at an angle θ exceeding the critical angle θ required for total internal reflection in waveguide 1004... TIRWhen diffracted at a diffraction angle θ, the diffracted beam 1024 typically propagates along a direction parallel to the x-axis and along the length of the waveguide, and is guided within the waveguide 1004 by total internal reflection (TIR). For example, a portion of this light guided within the waveguide 1004 may reach one of the light distribution elements 730, 740, 750 or the coupling optical elements (800, 810, 820). Figures 9A-9C One of them, and then diffracted again.

[0115] As described herein, a beam incident at an angle relative to the plane normal 1002 in a clockwise direction (i.e., to the right of the plane normal 1002), as in the illustrated embodiment, is said to have a negative α (α<0), while a beam incident at an angle relative to the plane normal 1002 in a counterclockwise direction (i.e., to the left of the plane normal) is said to have a positive α (α>0).

[0116] As further described elsewhere in the specification, a suitable combination of high-refractive-index materials and / or the structure of the diffraction grating 1008 can result in a specific range Δα of incident angle α, referred herein as the field of view (FOV) or acceptance angle range. A range Δα can be described by an angular range spanning negative and / or positive values ​​of α, outside of which the diffraction efficiency decreases relative to α = 0 or in some other direction by more than 10%, 25%, more than 50%, or more than 75%, 80%, 90%, 95%, or any value within the range defined by any of these values. In some embodiments, it may be desirable to keep Δα within a range of relatively high and constant diffraction efficiency, for example, in cases where uniform diffracted light intensity is desired within Δα. Therefore, in some embodiments, Δα is associated with the angular bandwidth of the diffraction grating 1008, such that the incident beam 1016 within Δα is efficiently diffracted by the diffraction grating 1008 at a diffraction angle θ relative to the surface normal 1002 (e.g., a direction parallel to the yz plane), where θ exceeds θ TIR This allows the diffracted light to be guided within waveguide 1004 under total internal reflection (TIR). In some embodiments, this angle Δα range may affect the field of view seen by the user. It should be understood that in various embodiments, light can be guided onto the coupling grating (ICG) from either side. For example, light can be guided through the substrate or waveguide 1004 and incident on, for example, a... Figure 10A The reflective coupling grating (ICG) 1008 shown is illustrated. Light can undergo the same effect, for example, being coupled to the substrate or waveguide 1004 via the coupling grating 1008, such that the light is guided within the substrate or waveguide by total internal reflection. The range of the incident angle α (Δα), referred herein as the range of the field of view (FOV) or the angle of acceptance, may be affected by the refractive index of the substrate or waveguide material. For example, in Figure 10AIn the diagram, the reduced angular range (Δα') illustrates the effect of refraction by high-refractive-index materials on light incident on the coupled grating (ICG). However, the angular range (Δα), or FOV, is much larger.

[0117] Figure 10B A cross-sectional view of an exemplary blazed transmission diffraction grating 1008 is shown. The grating 1008 includes grating features having a peak 1003 and a groove 1005. The blazed transmission grating 1008 includes a surface corresponding to a surface 1004S of a substrate or waveguide, having a "sawtooth" shaped pattern as seen in the illustrated cross-section. The patterned "sawtooth" is formed by a first inclined portion 1007 of surface 1004S. Figure 10B In the example shown, the grating 1008 also includes a second (steeper) tilted portion 1009. In the example shown, the first tilted portion 1007 has a shallower inclination than the second tilted portion 1009, which has a steeper inclination. In this example, the first tilted portion 1007 is also wider than the second tilted portion 1009.

[0118] The height H of peak 1003 corresponds to the distance from the bottom of groove 1005 to the top of peak 1003. Therefore, this value can be referred to herein as peak height and / or groove depth, as grating height or grating depth, or as the height of the diffraction feature of a diffraction grating. Figure 10B In the example shown, the bottom of the groove 1005 is formed by the intersection of the first and second inclined portions 1007, 1009 of two adjacent peaks 1003. The first inclined portion 1007 is on one of the adjacent peaks 1003, and the second inclined portion 1009 is on the other adjacent peak. Similarly, the top of the peak 1003 is formed by the intersection of the first and second inclined portions 1007, 1009 at the top of the peak 1003. However, other configurations are also possible. For example, if the bottom of the groove 1005 has a flat base or if the top of the peak 1003 includes a flat platform, then, for example, the first and second inclined portions may not necessarily intersect, as will be discussed below. The blazed diffraction grating 1008 has a line spacing or pitch d, which may be constant in some embodiments. This line spacing or pitch d may, for example, have a spacing of 1 / 2 with a 2 / 3. Figure 10B The vertices of peaks 1003 in a grating 1008 with a similar shape to the one shown are a measure of separation. Similarly, the line spacing or pitch d can be a measure of separation at the deepest point of adjacent grooves 1005. The line spacing or pitch d can be measured from other locations on the grating feature.

[0119] The slope can be relative to the surface of the grating 1008 or the waveguide (e.g., it can extend beyond the surface of the waveguide 1004S of the grating or the waveguide). Figure 10AThe grating is tilted at an angle δ relative to the plane parallel to the waveguide surface 1004S'. This angle δ of the first (gentler) tilted portion 1007 can be referred to herein as the blaze angle.

[0120] like Figure 10B As shown, the blazed diffraction grating 1008 may include grating lines or features with asymmetrical shapes, such as peaks 1003 and / or grooves 1005 with asymmetrical shapes. For example, in Figure 10B In the diffraction grating shown, the diffraction features include a peak 1003 and / or a groove 1005 with an asymmetrical triangular cross-sectional shape. As described above, this asymmetrical shape results in different inclinations and / or widths of the first and second tilted portions 1007, 1009. However, other shapes are also possible.

[0121] In designs with asymmetrical diffraction features, for example, where the slope of the first inclined portion is relatively gentle while the slope of the second inclined portion is steeper, the diffraction feature can be considered to be formed by repeating slopes and steps. This structure may be referred to herein as an inclined step structure. In some embodiments, the second portion may be so steep that it is not inclined; for example, the second portion may be parallel to the normal 1002.

[0122] However, in other embodiments of the "zigzag" pattern, the peaks 1003 and / or the grooves 1005 can be symmetrical. For example, the first and second inclined portions 1007 and 1009 can have the same inclination and the same width.

[0123] Compared to the multi-step structures discussed below, Figure 10B The cross-sectional pattern shown can be referred to as a single-step geometry in this paper. For example, multi-step structures such as... Figure 11D As shown.

[0124] Regardless of whether the diffraction characteristics are asymmetric or symmetric, in some implementations, a plateau or flat portion may be located at the top of peak 1003, as will be discussed below. For example, in Figure 11B and 11D The diagram shows a diffraction grating 1008 that includes diffraction features having a plateau or flat portion at the top of peak 1003.

[0125] Figure 10B An incident beam 1016 is shown, incident on the grating 1008 at an angle α relative to the normal direction 1002. (As mentioned above...) Figure 10AAs discussed, light can pass through the substrate or waveguide 1004 and, in other examples, be incident on the diffraction grating 1008 from the other side. As described above, the normal 1002 is perpendicular to or orthogonal to the extended surface of the blazed diffraction grating 1008 or the plane of the grating or waveguide and / or the surface 1004S of the waveguide 1004 (e.g., the main surface of the waveguide on which the grating is formed or the opposite planar surface 1004S'). Figure 10B In the diagram, light 1016 incident on diffraction grating 1008 is shown diffracted at an angle β relative to the normal direction 1002.

[0126] According to various embodiments, when configured as a coupling optical element or a coupling diffraction grating, the diffraction grating 1008 can diffractically couple light incident on the substrate 1004, which can be a waveguide as described above. If desired, the diffraction grating 1008 can be configured as a coupling optical element, and in such an embodiment, light from the substrate 1004 can be diffractically coupled, which can also be a waveguide as described above.

[0127] refer to Figure 10A and 10BIn some embodiments, substrate 1004 comprises a high refractive index material having a refractive index of at least 1.9. For example, the refractive index may be at least 2.0, at least 2.1, at least 2.2, or at least 2.3, and may not exceed 2.4, 2.5, 2.6, 2.7, or 2.8, or may be within any range formed by any of these values ​​or possibly outside these ranges. In some embodiments, for example, the substrate comprises a Li-based oxide. In the various examples disclosed herein, diffraction features of diffraction grating 1008 may be formed at the surface of substrate 1004. The diffraction features may be formed in substrate 1004, for example in a waveguide, or in a separate layer formed on substrate 1004, for example in a waveguide, and configured to optically communicate with substrate 1004, for example, coupling light into or out of substrate 1004. In the illustrated example, diffraction features of diffraction grating 1008, for example, lines, are formed in substrate 1004, for example, in the surface of the substrate. For example, diffraction features can be etched into a substrate 1004 comprising a high-refractive-index material such as a Li-based oxide. The substrate may, for example, comprise lithium niobate, and the diffraction grating can be formed in the lithium niobate substrate by etching or patterning the surface of the substrate. Other materials with high refractive indices can also be used. For example, other lithium-containing materials, such as lithium oxides (e.g., lithium tantalate (LiTaO3)), can be used as the substrate. Silicon carbide (SiC) is another option for the substrate material. Examples are not limited to this. In other examples, the diffraction features of the diffraction grating 1008 can be formed in a separate layer disposed on the substrate 1004 (e.g., in physical contact). For example, a thin film coating with a thickness of less than 200 nm of zinc oxide (ZnO), silicon nitride (Si3N4), zirconium dioxide (ZrO2), titanium dioxide (TiO2), silicon carbide (SiC), etc., can be disposed on an existing high-refractive-index substrate. The thin film coating can be patterned to form the diffraction features. However, in some embodiments, the diffraction features of the diffraction grating 1008, such as lines, can be formed of a material different from that of the substrate. The substrate can, for example, comprise a high-refractive-index material, such as a Li-based oxide (e.g., lithium niobate, LiNbO3, or lithium tantalate, LiTaO3), however, the diffraction features can be formed of a different material, such as a coating of zinc oxide (ZnO), zirconium dioxide (ZrO2), titanium dioxide (TiO2), silicon carbide (SiC), or other materials described herein. In some embodiments, such other materials formed on the substrate can have a lower refractive index.In some cases, substrate 1004 may comprise a material different from the lithium-based oxide feature 1008, such as a material having a suitable refractive index as described above (including amorphous high-refractive-index glass substrates), for example, a material based on silica glass (e.g., doped silica glass), silicon oxynitride, transition metal oxides (e.g., hafnium oxide, tantalum oxide, zirconium oxide, niobium oxide, aluminum oxide (e.g., sapphire)), plastics, polymers, or other materials that are optically transmissive to visible light.

[0128] However, as described above, in the various embodiments described herein, the diffraction grating 1008 and the substrate 1004 or waveguide both comprise the same material, such as a Li-based oxide. In some embodiments, the diffraction grating 1008 is directly patterned into the substrate 1004, such that the diffraction grating 1008 and the substrate 1004 form a monolithic or single-piece structure. For example, the substrate 1004 includes a waveguide having the diffraction grating 1008 directly formed in the surface of the waveguide or substrate. In these embodiments, a bulk Li-based oxide material can be patterned at the surface 1004S to form the diffraction grating 1008, while the Li-based oxide material beneath the diffraction grating 1008 can form the waveguide. In yet other embodiments, the bulk or substrate 1004 and surface 1004S patterned to form the diffraction grating 1008 comprise different Li-based oxides. For example, the bulk Li-based oxide material patterned in the surface region to form the diffraction grating 1008 can be formed from a first Li-based oxide material, while the Li-based oxide material beneath the diffraction grating 1008 forming the substrate 1004 or substrate region can be formed from a second Li-based oxide material different from the first Li-based oxide material. As described above, in some other embodiments, the diffraction grating 1008 includes different high-refractive-index materials, such as zirconium dioxide (ZrO2), titanium dioxide (TiO2), silicon carbide (SiC), etc., and the material beneath the diffraction grating 1008 forming the substrate 1004 or substrate region can be formed from a second material such as LiTaO3, LiNbO3, etc., and is different from the first material coated as a thin film.

[0129] exist Figure 10A and 10B In the example shown, the diffraction grating 1008 may include a plurality of blazed diffraction grating lines that elongate in a first horizontal direction or the y-direction and repeat periodically in a second horizontal direction or the x-direction. The diffraction grating lines may be, for example, straight and continuous lines extending in the y-direction. However, the embodiments are not limited thereto.

[0130] In some embodiments, the diffraction grating lines may be discontinuous lines, for example, in the y-direction. In other embodiments, the discontinuous lines may form multiple pillars protruding from the surface of the grating substrate. In some embodiments, at least some of the diffraction grating lines may have different widths in the x-direction.

[0131] In the illustrated example, the diffraction grating 1008 has diffraction grating lines with profiles, such as sawtooth profiles, having asymmetrical opposite side surfaces forming different angles relative to the plane of the substrate. However, the embodiments are not limited to this, and in other embodiments, the diffraction grating lines may have symmetrical opposite side surfaces forming similar angles relative to the plane of the substrate.

[0132] According to various embodiments, the diffraction grating 1008 may have a pitch of 250 nm to 350 nm, 300 nm to 400 nm, 250 nm to 450 nm, or any range defined by these values. Other pitches are also possible.

[0133] The diffraction grating 1008 can have a blaze angle of approximately 10 to 70 degrees (flat dimensions) and an anti-blaze angle of 140 to 70 degrees (steep edge), or any value within the range defined by these values. Values ​​outside these ranges are also possible.

[0134] like Figure 11A-11D As shown, blazed diffraction gratings with single-step or multi-step geometries can be formed. Figure 11A-11D In the example shown, a grating is formed by depositing a scintillation photoresist and then etching and patterning the photoresist.

[0135] Figure 11A This illustrates a single-step blazed grating 1106 formed in a substrate 1104, which may be a waveguide 1004. Figure 10A Patternable materials, such as photoresist 1102, can be deposited on a substrate 1104, which may include a waveguide 1004. The patternable material / photoresist 1102 is patterned to have a blazed grating shape. In some embodiments, forming a blazed geometry in the photoresist 1102 may involve imprinting a pattern, such as a single-step "zigzag" pattern, in the photoresist 1102 (e.g., depositing photoresist on substrate 1104 and then imprinting the blazed geometry). The photoresist 1102 may include a mask, such as a hard mask. The patterned photoresist 1102 and substrate 1104 can then be etched to form a blazed pattern in a substrate 1106. Etching the photoresist 1102 and substrate 1104 may involve, for example, dry plasma or chemical etching and / or wet chemical etching. In some embodiments, Figure 11AThe etching shown can etch away material at a relatively constant rate, such that the thickest part of the patterned photoresist results in a relatively small amount of material removal from the substrate, such as negligible or no removal, while the thinnest (or absent) part of the patterned photoresist results in a relatively large amount of material removal from the substrate or etching to the deepest part of the substrate.

[0136] Figure 11B This is a scanning electron microscope image of a blazed photoresist grating 1112, wherein the blazed grating pattern is formed in photoresist 1104, for example, by imprinting photoresist using a patterned master. The diffraction grating 1112 shown has a single-step blazed geometry.

[0137] Figure 11C This illustrates a multi-step blazed grating 1156 formed in a substrate 1154, which may be a waveguide 1004. Figure 10A Patternable materials, such as photoresist 1152, can be deposited on substrate 1154. The patternable material / photoresist 1152 is patterned to have a blazed grating shape. In some embodiments, forming the blazed photoresist 1152 may involve imprinting a pattern, such as a multi-step “zigzag” pattern, in the photoresist 1152 (e.g., depositing the photoresist onto substrate 1154 and then imprinting the blazed geometry). The patterned photoresist 1152 and substrate 1154 can then be etched to form a multi-step blazed substrate 1156. The photoresist 1152 may include a mask, such as a hard mask. The patterned photoresist 1152 and substrate 1154 can then be etched to form a blazed pattern in substrate 1156. Etching the photoresist 1152 and substrate 1154 may involve, for example, dry plasma or chemical etching and / or wet chemical etching. In some embodiments, Figure 11C The etching shown can etch away material at a relatively constant rate, such that the thickest part of the patterned photoresist results in a relatively small amount of material removal from the substrate, for example, negligible or no removal, while the thinnest (or non-existent) part of the shimmering photoresist results in a relatively large amount of material removal from the substrate or etching to the deepest part of the substrate.

[0138] Figure 11D This is a scanning electron micrograph of a blazed photoresist grating 1162, wherein the blazed grating pattern is formed on photoresist 1164, for example, by imprinting the photoresist with a patterned master. The diffraction grating 1162 may have a multi-step blazed geometry. The width of peak 1003 is shown to be approximately 200 nm.

[0139] like Figure 11E As shown, for example, formed in a high refractive index substrate Figure 10A and 10B The blaze geometry of the diffraction grating 1008 can be varied to have different heights and / or blaze angles. In particular, Figure 11E A first diffraction grating 1170 (e.g., geometry 1) having a first shape and a first height (which may be about 80 nm in some embodiments) is shown. Figure 11E A second diffraction grating 1180 (e.g., geometry 2) with a second shape and a second height (which, for some designs, can be lower than the first height and can be approximately 35 nm) is also shown. As will at least combine Figure 13 As discussed, changing the geometry of a blazed diffraction grating can alter its performance characteristics. For example, geometry 1 with a height (or depth) of 80 nm can provide lower polarization sensitivity than geometry 2 with a height (or depth) of 35 nm.

[0140] Figure 12A-12F Scanning electron micrographs (SEMs) of various blazed diffraction gratings formed in a substrate are shown. Figure 12A-12F The substrate and grating shown are merely illustrative examples, and feature dimensions, pitch, angles, and other characteristics can typically be varied to achieve desired performance characteristics.

[0141] Figures 12A-12C A lithium niobate (LiNbO3) substrate with a top surface having the shape of a blazed diffraction grating (e.g., a blazed geometry) is shown. Figure 12A This is a SEM image 1200 of a blazed diffraction grating formed in a lithium niobate (LiNbO3) substrate, where the step height or peak height of the blazed grating is measured to be approximately 31.90 nm. The angle δ of the first (gently flat) tilted surface relative to the substrate plane is approximately 12.1 degrees. (This angle δ may be referred to herein as the blaze angle.) Figure 12B SEM images 1202 of the blazed grating viewed from different angles are shown. Figure 12B The diagram shows a pitch (e.g., the distance between the minimum values ​​of a peak, step, or groove) measured at approximately 331.8 nm. Figure 12C In the SEM image 1204 shown, the blazed grating formed in the lithium niobate (LiNbO3) substrate is shown as having a peak or step height measured at approximately 46.26 nm. The angle δ of the first (gently flat) tilted surface relative to the substrate plane is approximately 19.5 degrees. (This angle δ may be referred to herein as the blaze angle.)

[0142] Figure 12D SEM image 1206 shows a silicon substrate etched therein to form a blazed diffraction grating. Figure 12DIn the example, the height of the blaze diffraction feature, such as the peak height or the depth of the groove, was measured to be approximately 63.80 nm. The peak width was measured to be approximately 167.5 nm. The "steep" angle of the peak, such as the angle of the second steeper slope, was measured to be approximately 53.0 degrees (relative to the extended plane of the substrate). The "flat" angle of the peak, such as the angle δ of the first gentler slope (which may be referred to as the blaze angle), was measured to be approximately 27.9 degrees (relative to the extended plane of the substrate).

[0143] Figure 12E SEM image 1208 shows a silicon substrate etched to form a multi-step blazed diffraction grating therein. Figure 12D In the example, the height of the multi-step scintillation feature, such as the peak height or the groove depth, was measured to be approximately 66.85 nm. The width of the multi-step scintillation feature or peak was measured to be approximately 206.9 nm (e.g., the width does not include any spacing between adjacent multi-step features). The overall “flat” angle of the peak, determined based on the peak height with respect to the distance from the base of the peak to the top of the peak, was measured to be approximately 22.5 degrees (relative to the extended plane of the substrate). The “steep” angle of the peak, such as the angle of the second steeper slope portion, was measured to be approximately 68.8 degrees (relative to the extended plane of the substrate).

[0144] Figure 12F SEM image 1210 of a substrate formed of glass with a refractive index (RI) of 1.8 is shown. A blazed diffraction grating with a step or feature height of approximately 87.09 nm is formed in the imaging substrate.

[0145] Typically, changes such as Figure 10A and 10B The geometry of the blazed diffraction grating 1008 can alter the performance characteristics of the grating. In at least some embodiments, for example, by appropriately adjusting parameters of the grating, such as the grating thickness or the height of the diffraction characteristic, a diffraction grating less sensitive to the polarization of light can be obtained (e.g., a diffractive optical coupling element that couples or decouples light relatively independently of the polarization of the light). A diffraction grating with reduced polarization sensitivity may have higher overall efficiency (e.g., can couple more light than a more polarization-sensitive grating) and may provide a more uniform image for the viewer, since a polarization-sensitive grating may introduce undesirable coherence artifacts and reduce the uniformity of far-field images, such as those produced by the eyepiece of a head-mounted display.

[0146] For example, Figure 13 The polarization sensitivity of various blazed diffraction gratings is shown. In particular, Figure 13The TM / TE coupling grating diffraction efficiency (DE) ratio as a function of the incident angle is shown. The TM / TE ICG DE ratio can, for example, correspond to the coupling efficiency of transversely magnetically (TM) polarized light divided by the coupling efficiency of transversely electrically (TE) polarized light. The incident angle can be the incident angle α, for example, as... Figure 10A and 10B The reference in the text.

[0147] Curve 1300 shows the TM / TE ratio as a function of the incident angle α for a blazed diffraction grating formed in a photoresist disposed on a lithium niobate substrate. As shown in curve 1300, the diffraction grating formed by the blazed photoresist on the lithium niobate substrate can be relatively polarization sensitive; for example, within the incident angle range, the grating's efficiency for TM-polarized light is 3-4 times that for TE-polarized light.

[0148] Curve 1302 illustrates a blazed diffraction grating (e.g., with) a diffraction feature formed in a lithium niobate substrate, having a feature or peak height (or groove depth) H of 35 nm. Figure 11E The TM / TE ratio of the diffraction grating 1180 (geometry 2 shown) as a function of the incident angle α. As shown in curve 1302, the diffraction grating with an etch feature height of 35 nm is less sensitive to polarization than a blazed grating formed in a photoresist layer deposited on a lithium niobate substrate. Over most of the measured incident angle range, the diffraction grating with an etch feature height of 35 nm moderately favors TM-polarized light over TE-polarized light only at a ratio of approximately 1.5 to 2.0 or 2.2 (e.g., the grating thus exhibits moderately reduced polarization sensitivity).

[0149] Curve 1304 illustrates a blazed diffraction grating (e.g., with) a feature or peak height (or groove depth) H of 80 nm, including diffraction features formed in a lithium niobate substrate. Figure 11E The TM / TE ratio of the diffraction grating 1170 (geometry 1 shown) as a function of the incident angle α. As shown in Figure 1304, the diffraction grating with an 80 nm etched diffraction feature height has a TM / TE diffraction efficiency ratio close to 1 over a wide incident angle range (e.g., the grating has reduced polarization sensitivity, e.g., is essentially polarization insensitive).

[0150] Figure 14 The TM / TE diffraction efficiency of a blazed diffraction grating with a feature height of 80 nm formed in a lithium niobate substrate is shown for different colors of light (e.g., green, blue, and red). Figure 14As shown, for green and blue light, the TM / TE diffraction efficiency ratio (of diffraction grating 1170) is close to 1 over a wide incident angle range. Furthermore, for red light, the TM / TE diffraction efficiency ratio is typically around 1.5, increasing to over 2 (but less than 2.5) for certain incident angles.

[0151] Figure 15 The average diffraction efficiency as a function of the incident angle for green, blue, and red light is shown in a blazed diffraction grating formed in lithium niobate with a feature height of 80 nm. For example, the average diffraction efficiency can indicate the efficiency of the diffraction grating for coupled-in (or coupled-out) unpolarized light.

[0152] In addition to a general reduction in efficiency and brightness, some highly polarization-sensitive diffraction gratings may also produce coherent artifacts and reduce the uniformity of the far-field image produced by the eyepiece of a head-mounted display that guides image content to the user's eyes.

[0153] Figure 16 The distribution of light output from an eyepiece is shown. The eyepiece includes an input grating, a light redirection element (orthogonal pupil expander), and an output optics element (outgoing pupil expander). The input grating includes a blazed diffraction grating formed in a photoresist deposited on a lithium niobate substrate for coupling light into the waveguide-based eyepiece. Figure 16 As shown, an eyepiece having a coupled optical element comprising a blazed diffraction grating in a photoresist deposited on a lithium niobate substrate can produce approximately 9.45% coherence uniformity for non-polarized inputs and approximately 11.3% coherence uniformity for linearly polarized inputs. Figure 16 The charts and images were obtained from a 500-micrometer-thick Z-cut lithium niobate substrate, on which a photoresist layer was patterned by imprinting to form a coupling grating. Figure 16 The non-uniformity in far-field image 1600 is illustrated. In this example, the uniformity score is a mathematical value derived by analyzing the pixel values ​​of the image captured over a specific region, and provides an indication of the non-uniformity of the captured values ​​at different sampling spatial frequencies on the image. Lower values ​​indicate a more uniform color distribution across the field of view of the captured or desired image.

[0154] Figure 17 The distribution of light output from an eyepiece is shown. The eyepiece includes an input grating, a light redirection element (orthogonal pupil expander), and an output optics element (outgoing pupil expander). The input grating includes a blazed diffraction grating formed in a lithium niobate substrate for coupling light into the waveguide-based eyepiece. Figure 17As shown, coupled optical elements including a blazed diffraction grating with a characteristic height (peak height or groove depth) of 80 nm formed by etching into a lithium niobate substrate can have improved coherence uniformity, for example, about 8.1% coherence uniformity for unpolarized input and about 8.35% coherence uniformity for linearly polarized input. Figure 17 The charts and images were obtained from a 500-micrometer-thick Z-cut lithium niobate substrate with a blazed diffraction grating etched into the substrate. EPE and OPE were also etched into the substrate. Figure 17 The reduction in inhomogeneity in far-field image 1700 compared to far-field image 1600 is shown.

[0155] Therefore, blazed gratings formed in high-refractive-index substrates such as lithium niobate with specific dimensions (such as thicknesses of approximately 40 to 120, 60 to 100, 70 to 90, or 80 nanometers, or any value within the range of these values) can provide reduced polarization sensitivity.

[0156] Its structure and manufacturing method may differ from those examples specifically described above. For example, a blazed grating can be used as a coupling optical element (e.g., EPE) and / or a light redirection optical element (e.g., OPE). Alternatively, instead of a diffraction grating, other types of diffraction optical elements can be formed in a high-refractive-index substrate. Different high-refractive-index materials can be used, such as lithium tantalate (e.g., LiTaO3) for the waveguide and the diffraction features formed therein. As mentioned above, in some other embodiments, the waveguide and the diffraction features formed therein may include other high-refractive-index materials, such as silicon carbide or high-refractive-index amorphous glass. Furthermore, in some embodiments, the diffraction grating 1008 includes different high-refractive-index materials or coatings, such as zinc oxide (ZnO), silicon nitride (Si3N4), zirconium dioxide (ZrO2), titanium dioxide (TiO2), silicon carbide (SiC), etc., and the material forming the substrate 1004 or substrate region below it may include a second high-refractive-index material, such as LiTaO3, LiNbO3, etc.

[0157] Diffraction grating with diffraction characteristics of a two-dimensional (2D) array

[0158] Various implementations of diffraction gratings with reduced polarization sensitivity can be realized as diffraction features of a one-dimensional (1D) array, such as lines, as described above. For example, Figure 10A A cross-sectional side view of an example device 1000 is shown, illustrating a series of diffraction features 1012, which may have a "serrated" shape with inclined sidewalls and are located in one direction (e.g., a first horizontal direction or...). Figure 10A The diffraction feature 1012 is arranged laterally in one direction (e.g., the first horizontal direction or...). Figure 10A It fluctuates in the x-direction or in one direction (e.g., the second horizontal direction or) Figure 10A The y-direction in the ray elongates, and is therefore called 1D. As another example of 1D diffraction characteristics, Figure 11B A perspective view of a blazed photoresist grating configured as a 1D array is shown. Diffraction feature 1012 ( Figure 10A It can form a series of elongated longitudinal features, for example in one direction (e.g., a second horizontal direction or) Figure 10A A line extending in the y-direction. The elongated longitudinal feature extends along one direction (e.g., a first horizontal direction or...). Figure 10A Arrange in the x-direction and repeat in that direction.

[0159] In some embodiments, the structure array may also be arranged in two directions to form a diffraction feature of a two-dimensional (2D) array. The diffraction feature of the 2D array may include undulations in both directions. In some cases, the undulations may be periodic, while in others, the pitch of the undulations may vary in at least one direction. According to various examples described herein, the diffraction feature has asymmetrical angled or tilted opposing sidewalls. According to various examples described herein, the diffraction feature may be conical. In some embodiments, the diffraction feature may have substantially angled or tilted opposing sidewalls. In some embodiments, the opposing sidewalls may be tilted in the same direction, while in other embodiments, the opposing sidewalls may be tilted in opposite directions. In some other embodiments, the diffraction feature may have opposing sidewalls, one of which is substantially tilted, while the other of the opposing sidewalls is substantially perpendicular or orthogonal to the horizontal axis, or at least none of said sidewalls is tilted. In various examples of 2D diffraction features described herein, the 2D diffraction feature may be formed in or on an underlying substrate that can serve as a waveguide, as described above for various examples of 1D diffraction features. For example, 2D diffraction features can be etched into the underlying substrate or formed by patterning a separate layer thereon. Therefore, in a manner similar to that described above for various 2D diffraction features, 2D diffraction features can be formed from the same or different material as the substrate. Other variations and configurations are possible.

[0160] Figure 18 An example device 3600 is shown with a 2D array of diffraction features 3603 (e.g., diffraction features 3603 are arranged laterally in two dimensions or directions). In this example, the array resembles a grid pattern. The diffraction features 3603 may be referred to as protrusions. The diffraction features have inclined sidewalls that slope in opposite directions. One of the sidewall slopes may have a smaller slope than the other sidewall slope. As a result of this configuration, the diffraction features are shimmering.

[0161] Figure 18 The diffraction features in the example shown are asymmetrical in at least one lateral direction. Figure 18A and 18B Cross-sectional side and top views of the asymmetric diffraction features of the example array are shown, respectively. The 2D diffraction grating includes a blazed diffraction grating. The diffraction features may be tapered in height (e.g., in thickness). Figure 18 In the example shown, the diffraction feature has two opposing inclined sidewalls or facets, one of which is more inclined than the other and inclined in opposite directions, while... Figure 18A and 18B In the example shown, one sidewall is tilted, while the other opposing sidewall is substantially vertical or not tilted, or has a negligible slope on the second sidewall. In both cases, the slope of one of the opposing sidewalls is greater than the slope of the other (if any), making the diffraction feature asymmetrical and scintillation. As a result, the diffraction feature preferentially diffracts light in one direction but not in others. Such a diffraction grating can be useful, for example, as a coupling optics element configured to diffract light received from a projector toward a light distribution element, a coupling optics element, or a combination of a light distribution element and a coupling optics element (e.g., a combined pupil expander-extractor (CPE)). Such a diffraction grating can be used to couple light out to the eye in the opposite direction to the environment or world in front of the user and head-mounted display. In some embodiments, the sidewall tilt angle is less than 30 degrees relative to the horizontal axis on one side and greater than 80 degrees on the other side (e.g., between 80 and 90 degrees). However, other tilts and angles are also possible. In some cases, diffraction features can form serrated structures in 2D arrays (e.g., serrated nanostructures).

[0162] Therefore, in various implementations, symmetrical or asymmetrical diffraction features of a 2D array can be used as blazed diffraction gratings. As mentioned above, the shape of the diffraction grating (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 can direct more light toward other gratings (e.g., EPE, OPE, or CPE) and / or toward the viewer. In some cases, the diffraction features can be faceted to bias the propagation of light in two or more directions (e.g., blazing in multiple directions). For example, Figure 19A An example device 3700 is shown having a diffraction feature 3703 forming a two-dimensional array in or on a substrate 3701. The diffraction feature 3703 has a first sidewall or facet 3703b-1 and a second sidewall or facet 3703b-2 with an incline. Therefore, the diffraction feature is tapered in height (e.g., in thickness). The diffraction feature 3703 can be configured to preferentially guide light in a direction based on the incline angle of the first and second sidewalls or facets 3703b-1, 3703b-2. Figure 19B An example diffraction feature is shown that directs more light in two specific directions (as indicated by two thick solid arrows pointing upwards to the right and downwards to the left). Other examples are possible.

[0163] Therefore, any structure or device described herein, such as a grating structure, may include a 1D grating. Similarly, any structure or device described herein, such as a grating structure, may include a 2D grating. Such a 2D grating propagates light. These gratings may also include blazed gratings. Such blazed gratings may preferentially guide light in certain directions. In some embodiments, a 2D grating (e.g., having a tilted facet on a diffraction feature) preferentially guides light in one direction, while in other embodiments, a 2D grating (e.g., having two different tilted facets on a diffraction feature) preferentially guides light to multiple directions. Likewise, any method or process described herein can be used for a 1D grating. Similarly, any method or process described herein can be used for a 2D grating. These 1D or 2D gratings may be included in or on a substrate and / or waveguide, and may be included in an eyepiece and may be integrated into a head-mounted display as disclosed herein. These gratings can be used as input gratings (e.g., ICG), output gratings (EPE), light distribution gratings (OPE), or a combination of light distribution gratings / output gratings (e.g., CPE).

[0164] Figure 20AAn example method 3800 for forming a blazed grating is illustrated. Method 3800 includes providing a template or main board 3810. If the diffraction features are to be angled, slanted, or tilted, the template 3810 can be patterned to form an angled structure. Various processes, such as etching processes, can be oriented and angled to form such angled structures. Some examples of angled processes, such as angled etching processes, include ion beam milling, angled dry etching, ion etching, GLAD etching, tilting etching, Faraday cage etching, etc. In some embodiments, the choice of material for the template 3810 can facilitate the creation of an angled structure with angled sidewalls in the template. In this example, the angled structure includes angled elongated protrusions (e.g., for a 1D grating) or angled pillars (e.g., for a 2D grating). These angled elongated protrusions or angled pillars may have sidewalls that are tilted in the same direction and, in some cases, substantially parallel. Once the template 3810 is fabricated, a patternable material layer (e.g., polymer, resist, photoresist, etc.) can be deposited on the substrate 3801, and this layer can be imprinted by the template 3810. The template 3810 can be imprinted into a patternable material (e.g., resist material) 3805 on the substrate 3801 to form a mask 3805 for the substrate. In other embodiments, the patternable material can be deposited on the template, and the substrate can contact the template having the patternable material thereon. The template can be removed, and the resist material 3805 and the underlying substrate 3801 can be dry-etched to form a diffraction feature 3803 in the substrate 3801. In various embodiments, dry etching is employed as shown. The etching can be directional. In the example shown, the etching process is non-angular. The resulting diffraction feature 3803 formed in the substrate 3801 (or in the material layer disposed on the substrate 3801) can have certain shapes, for example, it can be shimmering due to the angled features in the mask 3805. In the example shown, the cross-section of the diffraction feature has a trapezoidal or roughly triangular shape with two sloping sides. The two sides are inclined in opposite directions. In the example shown, one side is inclined more than the other, thus forming a blaze structure. This process can be used to form diffraction features in one-dimensional or two-dimensional arrays.

[0165] Figure 20BAnother example method 3850 for forming blazed diffraction features is shown. A mask 3855 and an underlying substrate 3851 can be etched at an angle (e.g., dry etching) to form diffraction features 3853 in the substrate 3851 (or in a material layer disposed on the substrate 3851). In an angled etching process, the direction of the etchant forms an angle of inclination relative to the surface normal direction of the substrate 3851, which may be due to an inclination of the etchant incident angle or an inclination of the surface of the substrate 3851. Some examples 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 include elongated protrusions (e.g., for 1D gratings) or tapered pillars (e.g., for 2D gratings) comprising a trapezoidal or essentially triangular cross-section. These elongated protrusions or tapered pillars may have sidewalls inclined in opposite directions. One sidewall may be more inclined than the other. Applying an angled etching process to these elongated protrusions or conical pillars can create a blazed grating beneath them, in a material such as a substrate or a layer of material disposed on the substrate. Blazed diffraction features with sides inclined in the same direction can be produced. In various embodiments, one side is more inclined than the other. This process can be used to form diffraction gratings in 1D or 2D arrays.

[0166] In various implementations, due to the angled features in the mask (e.g., such as...) Figure 19A (as shown) and / or due to the use of angled processes (e.g., as shown) Figure 20A As shown), the resulting diffraction features can be made to shimmer in two or more directions. Diffraction features or gratings shimmering in two or more directions can be produced by etching twice. In some embodiments, for example, diffraction features or gratings shimmering in two or more directions can be produced by etching with a first mask and then etching again with a second, different mask. In some cases, such as... Figure 21As shown, mask 3905 and substrate 3901 can be etched to form a first sidewall of diffraction feature 3903 in substrate 3901. Alternatively, patterning can be provided to form a second sidewall. In various embodiments, a second mask with different orientations and / or shapes can be used to form the second sidewall. The second mask (e.g., having an angle and / or a different orientation relative to the first sidewall) can be etched, for example, to form the second sidewall. In some embodiments, after forming the first sidewall of diffraction feature 3903, a planarization layer 3907 can be added to the intermediate diffraction feature 3903 and substrate 3901. The planarization layer 3907, the intermediate diffraction feature 3903, and / or substrate 3901 can be patterned and etched (e.g., at an angle relative to the first sidewall) to form the second sidewall. Although the above examples are discussed in the context of patterned substrates, in some embodiments, the above processes can be used to pattern layers formed on a substrate rather than on the substrate. Alternatively, in some embodiments, the above processes can be used to pattern layers formed on a substrate and the substrate itself.

[0167] Furthermore, although example methods 3800, 3850, and 3900 are shown as forming asymmetric diffraction features of a 2D array, the method can also be used to form symmetric diffraction features of a 2D array (with or without angled sidewalls). The method can also be used to form diffraction features of a 1D array. In some cases, the diffraction features in a 1D array can be symmetric, with or without angled sidewalls. In some cases, the diffraction features in a 1D array can be asymmetric, for example, with inclined sidewalls. Therefore, in some cases, blaze diffraction features can be formed.

[0168] Additional Example - Part I

[0169] 1. A head-mounted display system, comprising:

[0170] Headband;

[0171] A light projection system configured to output light to provide image content; and

[0172] A waveguide supported by the frame, the waveguide including a substrate and a blazed diffraction grating formed therein, the substrate comprising a material having a refractive index of at least 1.9, the substrate being configured to guide at least a portion of the light from the light projection system coupled into the waveguide.

[0173] The blazed diffraction grating has a first diffraction efficiency for a first polarization within the angular range of light incident on it, and a second diffraction efficiency for a second polarization within the same angular range of light incident on it, wherein the first diffraction efficiency is between 1 and 2 times the second diffraction efficiency.

[0174] 2. The head-mounted display system according to Example 1, wherein the material having a refractive index of at least 1.9 comprises a lithium-based oxide.

[0175] 3. The head-mounted display system according to Example 1 or 2, wherein the material having a refractive index of at least 1.9 comprises lithium niobate.

[0176] 4. The head-mounted display system according to Example 1 or 2, wherein the material having a refractive index of at least 1.9 comprises lithium tantalate.

[0177] 5. The head-mounted display system according to Example 1, wherein the material having a refractive index of at least 1.9 comprises silicon carbide.

[0178] 6. The head-mounted display system according to Example 1, wherein the material having a refractive index of at least 1.9 comprises zirconium dioxide.

[0179] 7. The head-mounted display system according to Example 1, wherein the material having a refractive index of at least 1.9 comprises titanium dioxide.

[0180] 8. The head-mounted display system according to any of the above examples, wherein the material has a refractive index of at least 2.0 to 2.7.

[0181] 9. The head-mounted display system according to any of the above examples, wherein the material has a refractive index of at least 2.1 to 2.7.

[0182] 10. The head-mounted display system according to any of the above examples, wherein the material has a refractive index of at least 2.2 to 2.7.

[0183] 11. The head-mounted display system according to any of the above examples, wherein the material has a refractive index of at least 2.3 to 2.7.

[0184] 12. The head-mounted display system according to any of the above examples, wherein the material has a refractive index of at least 2.4 to 2.7.

[0185] 13. The head-mounted display system according to any of the above examples, wherein the material has a refractive index of at least 2.5 to 2.7.

[0186] 14. The head-mounted display system according to any of the examples above, wherein the material has a refractive index of at least 2.6 to 2.7.

[0187] 15. The head-mounted display system according to any of the above examples, wherein the blazed diffraction grating includes diffraction features, the diffraction features including peaks spaced apart by grooves.

[0188] 16. The head-mounted display system according to any of the above examples, wherein the blazed diffraction grating includes diffraction features comprising a plurality of straight lines.

[0189] 17. The head-mounted display system according to any of the examples above, wherein the blazed diffraction grating includes diffraction features having a peak height or groove depth of 40 to 120 nm.

[0190] 18. The head-mounted display system according to any of the above examples, wherein the blazed diffraction grating includes diffraction features having a peak height or groove depth of 60 to 100 nm.

[0191] 19. The head-mounted display system according to any of the above examples, wherein the blazed diffraction grating includes diffraction features having a peak height or groove depth of 70 to 90 nm.

[0192] 20. The head-mounted display system according to any of the above examples, wherein the blazed diffraction grating includes diffraction features having a peak height or groove depth of about 80 nm.

[0193] 21. The head-mounted display system according to any of the above examples, wherein the diffraction feature is asymmetric.

[0194] 22. The head-mounted display system according to any of the above examples, wherein the blazed diffraction grating has a pitch of 250 to 350 nm.

[0195] 23. The head-mounted display system according to any of the above examples, wherein the blazed diffraction grating has a pitch of 300 to 450 nm.

[0196] 24. The head-mounted display system according to any of the above examples, wherein the substrate is planar and the blazed diffraction grating has a blazed angle of 10 to 30 degrees relative to the plane of the substrate.

[0197] 25. The head-mounted display system according to any of the above examples, wherein the substrate is planar and the blazed diffraction grating has a blazed angle of 15 to 25 degrees relative to the plane of the substrate.

[0198] 26. The head-mounted display system according to any of the above examples, wherein the substrate is planar and the blazed diffraction grating has a blazed angle of about 19.5 degrees relative to the plane of the substrate.

[0199] 27. The head-mounted display system according to any of the above examples, wherein the first diffraction efficiency is 1 to 1.5 times the second diffraction efficiency.

[0200] 28. The head-mounted display system according to any of the above examples, wherein the first diffraction efficiency is 1 to 1.4 times the second diffraction efficiency.

[0201] 29. The head-mounted display system according to any of the above examples, wherein the first diffraction efficiency is 1 to 1.3 times the second diffraction efficiency.

[0202] 30. The head-mounted display system according to any of the above examples, wherein the first diffraction efficiency is 1 to 1.2 times the second diffraction efficiency.

[0203] 31. The head-mounted display system according to any of the above examples, wherein the first diffraction efficiency is 1 to 1.1 times the second diffraction efficiency.

[0204] 32. The head-mounted display system according to any of the above examples, wherein the angle range is at least 6 degrees.

[0205] 33. The head-mounted display system according to any of the above examples, wherein the angle range is at least 12 degrees.

[0206] 34. The head-mounted display system according to any of the above examples, wherein the angle range is at least 18 degrees.

[0207] 35. The head-mounted display system according to any of the above examples, wherein the angle range is at least 22 degrees.

[0208] 36. The head-mounted display system according to any of the above examples, wherein the angle range is within ±3 degrees relative to the plane of the substrate.

[0209] 37. The head-mounted display system according to any of the above examples, wherein the angle range is within ±6 degrees relative to the plane of the substrate.

[0210] 38. The head-mounted display system according to any of the above examples, wherein the angle range is within ±9 degrees relative to the plane of the substrate.

[0211] 39. The head-mounted display system according to any of the above examples, wherein the angle range is within ±11 degrees relative to the plane of the substrate.

[0212] 40. The head-mounted display system according to any of the above examples, wherein the first polarization and the second polarization include a first linear polarization and a second linear polarization having different polarization angles.

[0213] 41. The head-mounted display system according to any of the above examples, wherein the first polarization and the second polarization include a first linear polarization and a second linear polarization oriented in orthogonal directions.

[0214] 42. The head-mounted display system according to any of the above examples, wherein the first polarization and the second polarization respectively include transverse magnetic polarization and transverse electrical polarization.

[0215] 43. The head-mounted display system according to any of the above examples, wherein the first polarization and the second polarization respectively include transverse electrical polarization and transverse magnetic polarization.

[0216] 44. The head-mounted display system according to any of the above examples, wherein the first diffraction efficiency includes the diffraction efficiency of transversely magnetically polarized light averaged in the visible spectrum, and wherein the second diffraction efficiency includes the diffraction efficiency of transversely electrically polarized light averaged in the visible spectrum.

[0217] 45. The head-mounted display system according to any of the above examples, wherein the first diffraction efficiency includes the diffraction efficiency of transversely electrically polarized light averaged in the visible spectrum, and wherein the second diffraction efficiency includes the diffraction efficiency of transversely magnetically polarized light averaged in the visible spectrum.

[0218] 46. ​​The head-mounted display system according to any of the above examples, wherein the diffraction efficiency of the blazed diffraction grating for a red light wavelength having the first polarization is 1 to 2 times that for the red light wavelength having the second polarization.

[0219] 47. The head-mounted display system according to any of the above examples, wherein the diffraction efficiency of the blazed diffraction grating for a green light wavelength having the first polarization is 1 to 1.5 times that for the green light wavelength having the second polarization.

[0220] 48. The head-mounted display system according to any of the above examples, wherein the diffraction efficiency of the blazed diffraction grating for a blue light wavelength having the first polarization is 0.7 to 1 times that for the blue light wavelength having the second polarization.

[0221] 49. The head-mounted display system according to any of the examples above, wherein the waveguide is included in an eyepiece configured to direct light to the eyes of a user wearing the head-mounted display.

[0222] 50. The head-mounted display system according to Example 49, wherein the eyepiece is disposed on the frame and configured to direct light from the light projection system into the user's eyes to display augmented reality image content in the user's field of view, at least a portion of the eyepiece is transparent and is positioned in front of the user's eyes when the user wears the head-mounted display system, wherein the transparent portion transmits light from a portion of the physical environment in front of the user into the user's eyes to provide a view of said portion of the physical environment in front of the user.

[0223] 51. The head-mounted display system according to Example 49 or 50, wherein the eyepiece includes the at least one waveguide, and the at least one waveguide is transparent to visible light so that the user can view through the waveguide.

[0224] 52. The head-mounted display system according to any of the examples above, wherein the waveguide includes a coupling optical element for coupling light from the light projection system into the waveguide for being guided therein.

[0225] 53. The head-mounted display system according to any of the above examples, wherein the waveguide includes a coupling optical element for coupling light from the light projection system out of the waveguide and directing the light to the user's eyes to present the image content to the viewer.

[0226] 54. The head-mounted display system according to any of the above examples, wherein the blazed diffraction grating includes a coupling grating (ICG) configured to couple light from the light projection system into the waveguide.

[0227] 55. The head-mounted display system according to any of the above examples, wherein the blazed diffraction grating includes a coupling grating EPE configured to couple light from the light projection system, which is guided within the waveguide, out of the waveguide.

[0228] 56. An optical waveguide, comprising:

[0229] A substrate comprising a material having a refractive index of at least 1.9, the substrate being configured to guide light coupled into the waveguide via total internal reflection; and

[0230] A blazed diffraction grating formed in the substrate

[0231] The blazed diffraction grating has a first diffraction efficiency for a first polarization over the angular range of light incident thereon, and a second diffraction efficiency for a second polarization over the same angular range of light incident thereon, wherein the first diffraction efficiency is between 1 and 2 times the second diffraction efficiency.

[0232] 57. The optical waveguide according to Example 56, wherein the material having a refractive index greater than 1.9 comprises a lithium-based oxide.

[0233] 58. The optical waveguide according to Example 56 or 57, wherein the material having a refractive index greater than 1.9 comprises lithium niobate.

[0234] 59. The optical waveguide according to Example 56 or 57, wherein the material having a refractive index greater than 1.9 comprises lithium tantalate.

[0235] 60. The optical waveguide according to Example 56, wherein the material having a refractive index greater than 1.9 comprises silicon carbide.

[0236] 61. The optical waveguide according to Example 56, wherein the material having a refractive index greater than 1.9 comprises zirconium dioxide.

[0237] 62. The optical waveguide according to Example 56, wherein the material having a refractive index greater than 1.9 comprises titanium dioxide.

[0238] 63. The optical waveguide according to any one of Examples 56-62, wherein the blazed diffraction grating includes diffraction features having a peak height or groove depth of 40 to 120 nm.

[0239] 64. The optical waveguide according to any one of Examples 56-63 above, wherein the blazed diffraction grating includes diffraction features having a peak height or groove depth of 60 to 100 nm.

[0240] 65. The optical waveguide according to any one of Examples 56-64, wherein the blazed diffraction grating includes diffraction features having a peak height or groove depth of 70 to 90 nm.

[0241] 66. The optical waveguide according to any one of Examples 56-65, wherein the blazed diffraction grating includes diffraction features having a peak height or groove depth of about 80 nm.

[0242] 67. An optical waveguide according to any one of Examples 56-66, wherein the diffraction feature is asymmetric.

[0243] 68. The head-mounted display system according to any one of Examples 1-55 or the optical waveguide according to Examples 56-67, wherein the blazed diffraction grating comprises diffraction features formed in a one-dimensional 1D array.

[0244] 69. The head-mounted display system according to any one of Examples 1-55 or the optical waveguide according to Examples 56-67, wherein the blazed diffraction grating comprises diffraction features formed in a two-dimensional 2D array.

[0245] 70. A head-mounted display system according to any one of Examples 1-55 or an optical waveguide according to any one of Examples 56-67, wherein the blazed diffraction grating comprises diffraction features formed in a two-dimensional 2D array, the two-dimensional 2D array comprising a square array.

[0246] 71. A head-mounted display system according to any one of Examples 1-55 or an optical waveguide according to any one of Examples 56-67, wherein the blazed diffraction grating comprises diffraction features formed in a two-dimensional 2D array, wherein the blazed diffraction grating comprises a 1D grating.

[0247] 72. A head-mounted display system according to any one of Examples 1-55 or an optical waveguide according to any one of Examples 56-67, wherein the blazed diffraction grating comprises diffraction features formed in a two-dimensional 2D array, wherein the blazed diffraction grating comprises a 2D grating.

[0248] 73. A head-mounted display system according to any one of Examples 1-55 or an optical waveguide according to any one of Examples 56-67, wherein the blazed diffraction grating comprises diffraction features formed in a two-dimensional 2D array, wherein the blazed diffraction grating comprises a 2D grating comprising a square array.

[0249] 74. A head-mounted display system according to any one of Examples 1-55 or an optical waveguide according to any one of Examples 56-67, wherein the blazed diffraction grating is configured to preferentially guide light in at least two directions.

[0250] 75. A head-mounted display system according to any one of Examples 1-55 or an optical waveguide according to any one of Examples 56-67, wherein the blazed diffraction grating blazes in two directions.

[0251] 76. A head-mounted display system according to any one of Examples 1-55 or an optical waveguide according to any one of Examples 56-67, wherein the blazed diffraction grating includes a coupling optical element configured to receive light from an image source and couple the light into the substrate for guidance therein.

[0252] 77. A head-mounted display system according to any one of Examples 1-55 or an optical waveguide according to any one of Examples 56-67, wherein the blazed diffraction grating includes a light distribution optics element configured to receive light from an image source guided in the substrate and to guide the light to a coupling optics element for coupling out from the substrate.

[0253] 78. A head-mounted display system according to any one of Examples 1-55 or an optical waveguide according to any one of Examples 56-67, wherein the blazed diffraction grating includes a light distribution optical element configured to receive light from an image source guided in the substrate and to propagate the light through the waveguide to increase the beam size or eyebox size.

[0254] 79. A head-mounted display system according to any one of Examples 1-55 or an optical waveguide according to any one of Examples 56-67, wherein the blazed diffraction grating includes a coupling optical element configured to receive light from an image source guided in the substrate and to couple the light out of the substrate.

[0255] 80. A head-mounted display system according to any one of Examples 1-55 or an optical waveguide according to any one of Examples 56-67, wherein the blazed diffraction grating comprises a combined light distribution / coupling optics configured to receive light from an image source guided in the substrate, propagate the light in at least two directions, and couple the light out of the substrate.

[0256] 81. A head-mounted display system according to any one of Examples 1-55 or an optical waveguide according to any one of Examples 56-67, wherein the blazed diffraction grating includes a combined pupil expander-extractor configured to receive light from an image source guided in the substrate, propagate the light, and couple the light out of the substrate.

[0257] Additional Examples - Part II

[0258] 1. A head-mounted display system, comprising:

[0259] Headband;

[0260] A light projection system configured to output light to provide image content; and

[0261] A waveguide supported by the frame, the waveguide including a substrate comprising a material having a refractive index of at least 1.9, the substrate being configured to guide at least a portion of the light from the light projection system coupled into the waveguide;

[0262] The layer disposed on the substrate; and

[0263] A blazed diffraction grating formed in the substrate

[0264] The blazed diffraction grating has a first diffraction efficiency for a first polarization within the angular range of light incident on it, and a second diffraction efficiency for a second polarization within the same angular range of light incident on it, wherein the first diffraction efficiency is between 1 and 2 times the second diffraction efficiency.

[0265] 2. The head-mounted display system according to Example 1, wherein the substrate material having a refractive index of at least 1.9 comprises a lithium-based oxide.

[0266] 3. The head-mounted display system according to Example 1 or 2, wherein the material having a refractive index of at least 1.9 comprises lithium niobate.

[0267] 4. The head-mounted display system according to Example 1 or 2, wherein the material having a refractive index of at least 1.9 comprises lithium tantalate.

[0268] 5. The head-mounted display system according to Example 1, wherein the material having a refractive index greater than 1.9 comprises silicon carbide.

[0269] 6. The head-mounted display system according to Example 1, wherein the material having a refractive index greater than 1.9 comprises titanium dioxide.

[0270] 7. The head-mounted display system according to Example 1, wherein the material having a refractive index greater than 1.9 comprises zirconium dioxide.

[0271] 8. The head-mounted display system according to any of the above examples, wherein the layer comprises zinc oxide.

[0272] 9. The head-mounted display system according to any of the above examples, wherein the layer comprises silicon nitride.

[0273] 10. The head-mounted display system according to any of the above examples, wherein the layer comprises zirconium dioxide.

[0274] 11. The head-mounted display system according to any of the above examples, wherein the layer comprises titanium dioxide.

[0275] 12. The head-mounted display system according to any of the above examples, wherein the layer comprises silicon carbide.

[0276] 13. The head-mounted display system according to any of the above examples, wherein the layer has a refractive index lower than that of the substrate.

[0277] 14. The head-mounted display system according to any of the above examples, wherein the substrate material has a refractive index of at least 2.0 to 2.7.

[0278] 15. The head-mounted display system according to any of the above examples, wherein the substrate material has a refractive index of at least 2.1 to 2.7.

[0279] 16. The head-mounted display system according to any of the above examples, wherein the substrate material has a refractive index of at least 2.2 to 2.7.

[0280] 17. The head-mounted display system according to any of the above examples, wherein the substrate material has a refractive index of at least 2.3 to 2.7.

[0281] 18. The head-mounted display system according to any of the above examples, wherein the substrate material has a refractive index of at least 2.3 to 2.4.

[0282] 19. The head-mounted display system according to any of the above examples, wherein the substrate material has a refractive index of at least 2.3 to 2.5.

[0283] 20. The head-mounted display system according to any of the above examples, wherein the substrate material has a refractive index of at least 2.6 to 2.7.

[0284] 21. The head-mounted display system according to any of the above examples, wherein the blazed diffraction grating includes diffraction features, the diffraction features including peaks spaced apart by grooves.

[0285] 22. The head-mounted display system according to any of the above examples, wherein the blazed diffraction grating includes diffraction features comprising a plurality of straight lines.

[0286] 23. The head-mounted display system according to any of the above examples, wherein the blazed diffraction grating includes diffraction features having a peak height or groove depth of 40 to 120 nm.

[0287] 24. The head-mounted display system according to any of the above examples, wherein the blazed diffraction grating includes diffraction features having a peak height or groove depth of 60 to 100 nm.

[0288] 25. The head-mounted display system according to any of the above examples, wherein the blazed diffraction grating includes diffraction features having a peak height or groove depth of 70 to 90 nm.

[0289] 26. The head-mounted display system according to any of the above examples, wherein the blazed diffraction grating includes diffraction features having a peak height or groove depth of about 80 nm.

[0290] 27. The waveguide according to any of the above examples, wherein the diffraction feature is asymmetric.

[0291] 28. The head-mounted display system according to any of the above examples, wherein the blazed diffraction grating has a pitch of 250 to 350 nm.

[0292] 29. The head-mounted display system according to any of the examples above, wherein the blazed diffraction grating has a pitch of 300 to 450 nm.

[0293] 30. The head-mounted display system according to any of the above examples, wherein the substrate is planar and the blazed diffraction grating has a blazed angle of 10 to 30 degrees relative to the plane of the substrate.

[0294] 31. The head-mounted display system according to any of the above examples, wherein the substrate is planar and the blazed diffraction grating has a blazed angle of 15 to 25 degrees relative to the plane of the substrate.

[0295] 32. The head-mounted display system according to any of the above examples, wherein the substrate is planar and the blazed diffraction grating has a blazed angle of about 19.5 degrees relative to the plane of the substrate.

[0296] 33. The head-mounted display system according to any of the above examples, wherein the first diffraction efficiency is 1 to 1.5 times the second diffraction efficiency.

[0297] 34. The head-mounted display system according to any of the above examples, wherein the first diffraction efficiency is 1 to 1.4 times the second diffraction efficiency.

[0298] 35. The head-mounted display system according to any of the above examples, wherein the first diffraction efficiency is 1 to 1.3 times the second diffraction efficiency.

[0299] 36. The head-mounted display system according to any of the above examples, wherein the first diffraction efficiency is 1 to 1.2 times the second diffraction efficiency.

[0300] 37. The head-mounted display system according to any of the above examples, wherein the first diffraction efficiency is 1 to 1.1 times the second diffraction efficiency.

[0301] 38. The head-mounted display system according to any of the above examples, wherein the angle range is at least 6 degrees.

[0302] 39. The head-mounted display system according to any of the above examples, wherein the angle range is at least 12 degrees.

[0303] 40. The head-mounted display system according to any of the above examples, wherein the angle range is at least 18 degrees.

[0304] 41. The head-mounted display system according to any of the above examples, wherein the angle range is at least 22 degrees.

[0305] 42. The head-mounted display system according to any of the above examples, wherein the angle range is within ±3 degrees relative to the plane of the substrate.

[0306] 43. The head-mounted display system according to any of the above examples, wherein the angle range is within ±6 degrees relative to the plane of the substrate.

[0307] 44. The head-mounted display system according to any of the above examples, wherein the angle range is within ±9 degrees relative to the plane of the substrate.

[0308] 45. The head-mounted display system according to any of the above examples, wherein the angle range is within ±11 degrees relative to the plane of the substrate.

[0309] 46. ​​The head-mounted display system according to any of the above examples, wherein the first polarization and the second polarization include a first linear polarization and a second linear polarization having different polarization angles.

[0310] 47. The head-mounted display system according to any of the above examples, wherein the first polarization and the second polarization include a first linear polarization and a second linear polarization oriented in orthogonal directions.

[0311] 48. The head-mounted display system according to any of the above examples, wherein the first polarization and the second polarization direction respectively include transverse magnetic polarization and transverse electrical polarization.

[0312] 49. The head-mounted display system according to any of the above examples, wherein the first polarization and the second polarization direction respectively include transverse electrical polarization and transverse magnetic polarization.

[0313] 50. The head-mounted display system according to any of the above examples, wherein the first diffraction efficiency includes the diffraction efficiency of transversely magnetically polarized light averaged in the visible spectrum, and wherein the second diffraction efficiency includes the diffraction efficiency of transversely electrically polarized light averaged in the visible spectrum.

[0314] 51. The head-mounted display system according to any of the above examples, wherein the first diffraction efficiency includes the diffraction efficiency of transversely electrically polarized light averaged in the visible spectrum, and wherein the second diffraction efficiency includes the diffraction efficiency of transversely magnetically polarized light averaged in the visible spectrum.

[0315] 52. The head-mounted display system according to any of the examples above, wherein the waveguide is included in an eyepiece configured to direct light to the eyes of a user wearing the head-mounted display.

[0316] 53. The head-mounted display system according to Example 52, wherein the eyepiece is disposed on the frame and configured to direct light from the light projection system into the user's eyes to display augmented reality image content in the user's field of view, at least a portion of the eyepiece is transparent and is positioned in front of the user's eyes when the user wears the head-mounted display system, wherein the transparent portion transmits light from a portion of the physical environment in front of the user into the user's eyes to provide a view of said portion of the physical environment in front of the user.

[0317] 54. The head-mounted display system according to Example 52 or 53, wherein the eyepiece includes the at least one waveguide, and the at least one waveguide is transparent to visible light so that the user can view through the waveguide.

[0318] 55. The head-mounted display system according to any of the examples above, wherein the waveguide includes a coupling optical element for coupling light from the light projection system into the waveguide for being guided therein.

[0319] 56. The head-mounted display system according to any of the above examples, wherein the waveguide includes a coupling optical element for coupling light from the light projection system out of the waveguide and directing the light to the user's eyes to present the image content to the viewer.

[0320] 57. The head-mounted display system according to any of the above examples, wherein the blazed diffraction grating includes a coupling grating (ICG) configured to couple light from the light projection system into the waveguide.

[0321] 58. The head-mounted display system according to any of the above examples, wherein the blazed diffraction grating includes a coupling grating EPE configured to couple light from the light projection system, which is guided within the waveguide, out of the waveguide.

[0322] 59. An optical waveguide, comprising:

[0323] A substrate comprising a material having a refractive index of at least 1.9, the substrate being configured to guide light coupled into the waveguide via total internal reflection within the waveguide;

[0324] A layer disposed above the substrate;

[0325] A blazed diffraction grating formed in the substrate

[0326] The blazed diffraction grating has a first diffraction efficiency for a first polarization over the angular range of light incident thereon, and a second diffraction efficiency for a second polarization over the same angular range of light incident thereon, wherein the first diffraction efficiency is between 1 and 2 times the second diffraction efficiency.

[0327] 60. The optical waveguide according to Example 59, wherein the material having a refractive index greater than 1.9 comprises a lithium-based oxide.

[0328] 61. The optical waveguide according to Example 59 or 60, wherein the material having a refractive index greater than 1.9 comprises lithium niobate.

[0329] 62. The optical waveguide according to Example 59 or 60, wherein the material having a refractive index greater than 1.9 comprises lithium tantalate.

[0330] 63. The optical waveguide according to Example 59, wherein the material having a refractive index greater than 1.9 comprises silicon carbide.

[0331] 64. The optical waveguide according to Example 59, wherein the material having a refractive index greater than 1.9 comprises titanium dioxide.

[0332] 65. The optical waveguide according to Example 59, wherein the material having a refractive index greater than 1.9 comprises zirconium dioxide.

[0333] 66. The optical waveguide according to any one of Examples 59-65, wherein the layer comprises zinc oxide.

[0334] 67. The optical waveguide according to any one of Examples 59-66, wherein the layer comprises silicon nitride.

[0335] 68. The optical waveguide according to any one of Examples 59-67, wherein the layer comprises zirconium dioxide.

[0336] 69. The optical waveguide according to any one of Examples 59-68, wherein the layer comprises titanium dioxide.

[0337] 70. The optical waveguide according to any one of Examples 59-69, wherein the layer comprises silicon carbide.

[0338] 71. An optical waveguide according to any one of Examples 59-70, wherein the layer has a refractive index lower than that of the substrate.

[0339] 72. The optical waveguide according to any one of Examples 59-71, wherein the blazed diffraction grating includes diffraction features having a peak height or groove depth of 40 to 120 nm.

[0340] 73. The optical waveguide according to any one of Examples 59-72 above, wherein the blazed diffraction grating includes diffraction features having a peak height or groove depth of 60 to 100 nm.

[0341] 74. The optical waveguide according to any one of Examples 59-73, wherein the blazed diffraction grating includes diffraction features having a peak height or groove depth of 70 to 90 nm.

[0342] 75. The optical waveguide according to any one of Examples 59-74, wherein the blazed diffraction grating includes diffraction features having a peak height or groove depth of about 80 nm.

[0343] 76. The optical waveguide according to any one of Examples 59-75, wherein the diffraction feature is asymmetric.

[0344] 77. The head-mounted display system according to any one of Examples 1-58 or the optical waveguide according to Examples 59-76, wherein the blazed diffraction grating comprises diffraction features formed in a one-dimensional 1D array.

[0345] 78. The head-mounted display system according to any one of Examples 1-58 or the optical waveguide according to Examples 59-76, wherein the blazed diffraction grating comprises diffraction features formed in a two-dimensional 2D array.

[0346] 79. A head-mounted display system according to any one of Examples 1-58 or an optical waveguide according to any one of Examples 59-76, wherein the blazed diffraction grating comprises diffraction features formed in a two-dimensional 2D array, the two-dimensional 2D array comprising a square array.

[0347] 80. A head-mounted display system according to any one of Examples 1-58 or an optical waveguide according to any one of Examples 59-76, wherein the blazed diffraction grating comprises diffraction features formed in a two-dimensional 2D array, wherein the blazed diffraction grating comprises a 1D grating.

[0348] 81. A head-mounted display system according to any one of Examples 1-58 or an optical waveguide according to any one of Examples 59-76, wherein the blazed diffraction grating comprises diffraction features formed in a two-dimensional 2D array, wherein the blazed diffraction grating comprises a 2D grating.

[0349] 82. A head-mounted display system according to any one of Examples 1-58 or an optical waveguide according to any one of Examples 59-76, wherein the blazed diffraction grating comprises diffraction features formed in a two-dimensional 2D array, wherein the blazed diffraction grating comprises a 2D grating comprising a square array.

[0350] 83. The head-mounted display system according to any one of Examples 1-58 or the optical waveguide according to any one of Examples 59-76, wherein the blazed diffraction grating is configured to preferentially guide light in at least two directions.

[0351] 84. A head-mounted display system according to any one of Examples 1-58 or an optical waveguide according to any one of Examples 59-76, wherein the blazed diffraction grating blazes in two directions.

[0352] 85. A head-mounted display system according to any one of Examples 1-58 or an optical waveguide according to any one of Examples 59-76, wherein the blazed diffraction grating includes a coupling optical element configured to receive light from an image source and couple the light into the substrate for guidance therein.

[0353] 86. A head-mounted display system according to any one of Examples 1-58 or an optical waveguide according to any one of Examples 59-76, wherein the blazed diffraction grating includes a light distribution optical element configured to receive light from an image source guided in the substrate and to guide the light to a coupling optical element for coupling out from the substrate.

[0354] 87. A head-mounted display system according to any one of Examples 1-58 or an optical waveguide according to any one of Examples 59-76, wherein the blazed diffraction grating includes a light distribution optics element configured to receive light from an image source guided in the substrate and to propagate the light through the waveguide to increase the beam size or eyebox size.

[0355] 88. A head-mounted display system according to any one of Examples 1-58 or an optical waveguide according to any one of Examples 59-76, wherein the blazed diffraction grating includes a coupling optical element configured to receive light from an image source guided in the substrate and to couple the light out of the substrate.

[0356] 89. A head-mounted display system according to any one of Examples 1-58 or an optical waveguide according to any one of Examples 59-76, wherein the blazed diffraction grating comprises a combined light distribution / coupling optics configured to receive light from an image source guided in the substrate, propagate the light in at least two directions, and couple the light out of the substrate.

[0357] 90. A head-mounted display system according to any one of Examples 1-58 or an optical waveguide according to any one of Examples 59-76, wherein the blazed diffraction grating includes a combined pupil expander-extractor configured to receive light from an image source guided in the substrate, propagate the light, and couple the light out of the substrate.

[0358] Other considerations

[0359] In the foregoing specification, the present invention has been described with reference to specific embodiments thereof. However, it will be apparent that various modifications and alterations can be made to the invention without departing from its broader spirit and scope. Therefore, the specification and drawings should be considered for illustrative purposes and not for limitation.

[0360] In fact, it will be understood that the systems and methods of this disclosure each have several inventive aspects, none of which independently or alone result in or are necessary for the desired properties disclosed herein. The various features and processes described above can be used independently of each other or can be combined in various ways. All possible combinations and sub-combinations are intended to fall within the scope of this disclosure.

[0361] Some features described in the context of separate embodiments in this specification may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented separately or in any suitable sub-combination in multiple embodiments. Furthermore, although features may be described above as functioning in certain combinations, and even initially claimed to be so, one or more features from a claimed combination may be removed from the combination in some cases, and the claimed combination may be for sub-combinations or sub-combinations of variations. No single feature or group of features is necessary or essential to every embodiment.

[0362] It will be understood that, unless explicitly stated otherwise, conditional language used herein, such as “can,” “may,” “should,” “may,” “e.g.,” etc., or otherwise understood in the context, is generally intended to express that certain embodiments include certain features, elements, and / or steps, while other embodiments do not. Therefore, such conditional language is not generally intended to imply that features, elements, and / or steps are necessary in any way for one or more embodiments, or that one or more embodiments necessarily include the ability to determine, with or without author input or prompting, whether such features, elements, and / or steps are included in or will be performed in any particular embodiment. The terms “comprising,” “including,” “having,” etc., are synonyms and are used inclusively in an open-ended manner, and do not exclude additional elements, features, actions, operations, etc. Furthermore, the term “or” is used in its inclusive meaning (rather than its proprietary meaning), and thus, when used, for example, to connect lists of elements, the term “or” means one, some, or all of the elements in the list. Additionally, unless otherwise stated, the articles “a,” “an,” and “described” used in this application and the appended claims should be interpreted as meaning “one or more” or “at least one.” Similarly, although operations may be depicted in the accompanying drawings in a specific order, it should be understood that these operations do not need to be performed in the specific order shown or sequentially, or that all shown operations need to be performed, to achieve the desired result. Furthermore, the drawings may schematically depict one or more example processes in the form of flowcharts. However, other operations not shown may be incorporated into the exemplary methods and processes schematically illustrated. For example, one or more additional operations may be performed before, after, simultaneously with, or between any shown operations. Additionally, in other implementations, operations may be rearranged or reordered. In some cases, multitasking and parallel processing may be advantageous. Furthermore, the separation of various system components in the above embodiments should not be construed as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. Additionally, other embodiments are within the scope of the following claims. In some cases, the actions listed in the claims may be performed in a different order and still achieve the desired result.

[0363] Therefore, the claims are not intended to be limited to the embodiments shown herein, but are given the broadest scope consistent with the disclosure, principles and novel features disclosed herein.

Claims

1. A head-mounted display system, comprising: Headband; A light projection system configured to output light to provide image content; as well as A waveguide supported by the frame, the waveguide including a substrate comprising a material having a refractive index of at least 1.9, the substrate being configured to guide at least a portion of the light from the light projection system coupled into the waveguide; as well as A blazed diffraction grating is formed in the substrate or in a layer disposed on the substrate, wherein the refractive index of the blazed diffraction grating is less than or equal to the refractive index of the substrate; The blazed diffraction grating has a first diffraction efficiency in the visible spectrum for a first polarization within the angular range of the light incident upon it, and a second diffraction efficiency in the visible spectrum for a second polarization within the same angular range of the light incident upon it. The blazed diffraction grating includes diffraction features with a peak height or groove depth of 60 to 100 nm, such that the first diffraction efficiency is between 1 and 1.2 times the second diffraction efficiency within an incident angle range of ±11 degrees relative to the principal plane of the substrate.

2. The head-mounted display system according to claim 1, wherein, The blazed diffraction grating is formed in the substrate and arranged to optically communicate with the substrate.

3. The head-mounted display system according to claim 1, wherein, The blazed diffraction grating is disposed in a layer on the substrate and arranged to optically communicate with the substrate.

4. The head-mounted display system according to claim 1, wherein, The material having a refractive index of at least 1.9 includes lithium-based oxides, silicon carbide, zirconium dioxide, or titanium dioxide.

5. The head-mounted display system according to claim 1, wherein, The blazed diffraction grating is formed in the layer disposed on the substrate, wherein the layer comprises silicon nitride, zirconium dioxide, titanium dioxide or silicon carbide.

6. The head-mounted display system according to claim 1, wherein, The material has a refractive index of at least 2.0 to 2.

7.

7. The head-mounted display system according to claim 1, wherein, The blazed diffraction grating includes diffraction features, which include peaks spaced apart by grooves.

8. The head-mounted display system according to claim 1, wherein, The blazed diffraction grating includes diffraction features, which include multiple straight lines.

9. The head-mounted display system according to claim 1, wherein, The blazed diffraction grating includes diffraction features comprising a plurality of pillars protruding from the surface of the substrate.

10. The head-mounted display system according to claim 1, wherein, The blazed diffraction grating includes diffraction features with a peak height or groove depth of 70 to 90 nm.

11. The head-mounted display system according to claim 1, wherein, The diffraction characteristics are asymmetric.

12. The head-mounted display system according to claim 1, wherein, The blazed diffraction grating has a pitch of 250 to 350 nm.

13. The head-mounted display system according to claim 1, wherein, The blazed diffraction grating has a pitch of 300 to 450 nm.

14. The head-mounted display system according to claim 1, wherein, The substrate is planar, and the blazed diffraction grating has a blazed angle of 10 to 30 degrees relative to the principal plane of the substrate.

15. The head-mounted display system according to claim 1, wherein, The angle range is within ±6 degrees relative to the main plane of the substrate.

16. The head-mounted display system according to claim 1, wherein, The first polarization and the second polarization include a first linear polarization and a second linear polarization with different polarization angles.

17. The head-mounted display system according to claim 1, wherein, The first polarization and the second polarization include a first linear polarization and a second linear polarization oriented in orthogonal directions.

18. The head-mounted display system according to claim 1, wherein, The first polarization includes one of transverse magnetic polarization and transverse electrical polarization, and the second polarization includes the other of the transverse electrical polarization and the transverse magnetic polarization.

19. The head-mounted display system according to claim 1, wherein, The first diffraction efficiency includes the diffraction efficiency of one of the transversely magnetically polarized light and the transversely electrically polarized light averaged on the visible spectrum, and the second diffraction efficiency includes the diffraction efficiency of the other of the transversely magnetically polarized light and the transversely electrically polarized light averaged on the visible spectrum.

20. The head-mounted display system according to claim 1, wherein, The diffraction efficiency of the blazed diffraction grating for red light wavelengths with the first polarization is 1 to 2 times that for the red light wavelengths with the second polarization.

21. The head-mounted display system according to claim 1, wherein, The diffraction efficiency of the blazed diffraction grating for the green light wavelength with the first polarization is 1 to 1.5 times that for the green light wavelength with the second polarization.

22. The head-mounted display system according to claim 1, wherein, The diffraction efficiency of the blazed diffraction grating for the blue light wavelength with the first polarization is 0.7 to 1 times that for the blue light wavelength with the second polarization.

23. The head-mounted display system according to claim 1, wherein, The waveguide is included in the eyepiece, which is configured to direct light to the eyes of the user wearing the head-mounted display.

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