Dual active layer waveguide architecture with two or more separate reflective and transmissive ic pupils for visible spectrum

Abstract

An eyepiece waveguide stack includes: a first eyepiece waveguide including a first coupled diffractive optical element and a first combined pupil expander; and a second eyepiece waveguide including a second coupled diffractive optical element and a second combined pupil expander. The second in-coupling diffractive optical element is offset from the first in-coupling diffractive optical element in the lateral direction.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 421,044, filed Oct. 31, 2022, the disclosure of which is hereby incorporated by reference in its entirety for all purposes. Background Art

[0003] Modern computing and display technologies have facilitated the development of systems for so - called “virtual reality” or “augmented reality” experiences, in which digitally reproduced images or portions thereof are presented to a viewer in a manner that they appear real or are perceivable as real. Virtual reality or “VR” scenarios typically involve the presentation of digital or virtual image information with no transparency to other actual real - world visual inputs; augmented reality or “AR” scenarios generally involve the presentation of digital or virtual image information as an enhancement to the visualization of the actual world surrounding the viewer.

[0004] Reference Figure 1 , describes an augmented reality scenario 10. A user of AR technology sees a real - world park - like setting 120 featuring people, trees, buildings in the background, and a concrete platform 130. The user also perceives that he / she “sees” “virtual content”, such as a robotic figure 140 standing on the real - world platform 130, and a cartoon - like avatar character 150 flying by, which appears to be an anthropomorphic representation of a bumblebee. These elements 150, 140 are “virtual” because they do not exist in the real world. Because the human visual perception system is complex, it is challenging to produce AR technologies that facilitate a comfortable, natural - feeling, rich presentation of virtual image elements with other virtual or real - world image elements. Summary of the Invention

[0005] Embodiments of the present invention relate to systems having dual active layers that utilize different thicknesses of each active layer and incorporate split and inline pupil architectures. Additionally, embodiments relate to using diffraction structures with specific spacings between blue and green for blue and green, and between green and red for green and red, in a particular refractive index waveguide.

[0006] According to an embodiment of the present invention, a system is provided that utilizes a dual-active-layer waveguide architecture with a split pupil design and is combined with a projection system used in AR / MR wearable devices. By using waveguides designed with ICG that operate in both reflection and transmission modes, various combinations can be achieved. These combinations can utilize the split pupil design in combination with the waveguide to optimize the diffraction pitch, different waveguide substrate thicknesses, and thickness variation profiles to accommodate a specific range of eyepiece waveguide stack thicknesses and provide optimal RGB-white output for a specific field of view. Additionally, in some embodiments, a diffraction grating pitch for coupling in and out is achieved that is between two of the three colors (e.g., red, green, and blue) used for virtual image creation, including waveguide and projection of the visible color spectrum in the dual-active layer.

[0007] In some eyepiece waveguide designs suitable for augmented reality (AR) applications, separate active layers for specific colors are used in a split pupil configuration to achieve high-performance eyepieces, enabling a large field of view (FoV). The embodiments described herein utilize a dual-active layer while maintaining sufficient optical performance (e.g., efficiency and color uniformity) and providing a simpler, lighter, and thinner stack, characterized by low back rainbow and back reflection, etc., thus providing a thinner wearable device. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 Shows a user's view of AR through an augmented reality (AR) device.

[0009] Figure 2 Shows a conventional display system for simulating three-dimensional images for a user.

[0010] Figures 3A - 3C Shows the relationship between the radius of curvature and the radius of focus.

[0011] Figure 4A Shows a representation of the accommodation-vergence response of the human visual system.

[0012] Figure 4B Shows an example of different accommodation states and vergence states of a user's pair of eyes.

[0013] Figure 4C Shows an example of a representation of a top view of a user viewing content via a display system.

[0014] Figure 4D Shows another example of a representation of a top view of a user viewing content via a display system.

[0015] Figure 5 Shows aspects of a method for simulating three-dimensional images by modifying wavefront divergence.

[0016] Figure 6 Shows an example of a waveguide stack for outputting image information to a user.

[0017] Figure 7 Shows an example of an outgoing light beam output from a waveguide.

[0018] Figure 8 Shows an example of a stacked waveguide assembly, where each depth plane includes an image formed using multiple different component colors.

[0019] Figure 9A Shows a cross-sectional side view of an example of a set of stacked waveguides, where each waveguide includes an optical coupling element.

[0020] Figure 9B Shows Figure 9A A perspective view of an example of one or more stacked waveguides.

[0021] Figure 9C Shows Figure 9A And 9B A top plan view of an example of one or more stacked waveguides.

[0022] Figure 9D Shows an example of a wearable display system.

[0023] Figure 10 Is a side view of a projector assembly that includes a polarization beam splitter, where a light source injects light into one side of the beam splitter and projection optics receive light from the other side of the beam splitter.

[0024] Figure 11A Is a side view of an augmented reality display system that includes a light source, a spatial light modulator, optics for illuminating the spatial light modulator and projecting an image of the spatial light modulator (SLM), and a waveguide for outputting image information to a user. The system includes an optical coupling element for coupling light from the optics into the waveguide and an optical coupling-out element for coupling light out of the waveguide to the eye.

[0025] Figure 11B Is Figure 11A A top view of the augmented reality display system shown in

[0026] Figure 11C Is Figure 11A A side view of the augmented reality display system of

[0027] Figure 11D Shows an example of a waveguide with combined OPE / EPE according to an embodiment of the present invention.

[0028] Figure 12A Is a side view of an augmented reality display system that includes a multicolor light source (e.g., a time-multiplexed RGB LED or a laser diode), a spatial light modulator, optics for illuminating the spatial light modulator and projecting the image of the spatial light modulator onto the eye, and a waveguide stack, where different waveguides include different color-selective coupling-in optical elements and coupling-out optical elements.

[0029] Figure 12B Is Figure 12A A side view of the augmented reality display system of Which further includes a MEMS (microelectromechanical)-based SLM, such as a movable mirror array (e.g., digital light processing

[0030] Figure 12C Is Figure 12B A top view of a portion of the augmented reality display system of

[0031] Figure 13A Is a perspective view of an augmented reality display system that includes a waveguide stack, where different waveguides include different coupling-in optical elements, and where the coupling-in optical elements are laterally shifted relative to each other. One or more light sources that are also laterally shifted relative to each other are arranged to direct light to the corresponding coupling-in optical elements by passing the light through the optics, reflecting the light off the spatial light modulator, and passing the reflected light through the optics again.

[0032] Figure 13B Is Figure 13A A side view of the example shown in

[0033] Figure 13C Is Figure 13A And 13B A top view of the augmented reality display system shown in

[0034] Figure 14A Is a side view of an augmented reality display system that includes a waveguide stack, where different waveguides include different coupling-in optical elements, and where the coupling-in optical elements are laterally shifted relative to each other (in this example, the lateral shift occurs in the z direction).

[0035] Figure 14B Is Figure 14ATop view of the display system shown in [ID], showing the laterally shifted light-coupling optical element and the light source.

[0036] Figure 14C is Figure 14A and 14B Orthogonal side view of the display system shown in [ID].

[0037] Figure 15 is a top view of an augmented reality display system including a stack of waveguides, where different waveguides include different light-coupling optical elements. The light source and the light-coupling optical elements are arranged in a configuration different from the configuration shown in [ID]. Figures 14A - 14C in

[0038] Figure 16A is a side view of an augmented reality display system including groups of light-coupling optical elements that are laterally shifted relative to each other, with each group including one or more color-selective light-coupling optical elements.

[0039] Figure 16B is Figure 16A the top view of the display system in [ID].

[0040] Figure 17 is a side view of an augmented reality display system including a waveguide that is segmented by a reflective surface, which can couple out light guided in a portion of the waveguide near the light source and direct it into an optical device towards a spatial light modulator. In this example, the optical device and the light source are shown to be disposed on the same side of the waveguide.

[0041] Figure 18 is a side view of an augmented reality display system including a waveguide for receiving light from a light source and guiding the light guided in the waveguide into an optical device and towards a spatial light modulator. The display system further includes a waveguide for receiving light that has passed through the optical device again from the spatial light modulator. The waveguide includes a reflective surface to couple out light. The waveguide also includes a reflective surface to couple light into it. In this example, the optical device and the light source are shown to be disposed on the same side of the waveguide.

[0042] Figure 19 is a side view of an augmented reality display system including adaptive optical elements or variable-focus optical elements. A first variable optical element between the waveguide stack and the eye can change the divergence and collimation of the light coupled out from the waveguide and directed towards the eye, to change the depth at which an object appears to be located. A second variable optical element on the opposite side of the waveguide stack can compensate for the effect of the first optical element on the light received from the augmented reality display system and the environment in front of the user. The augmented reality display system further includes prescription lenses to provide ophthalmic correction, such as refractive correction for users with myopia, hyperopia, astigmatism, etc.

[0043] Figure 20AA side view of an augmented reality display system including a color filter array. One or more laterally shifted light-coupling optical elements are located on different waveguides, and the laterally shifted color filters are aligned with corresponding light-coupling optical elements.

[0044] Figure 20B Shows Figure 20A an augmented reality display system in which an analyzer is located between an optical device and a spatial light modulator.

[0045] Figure 20C Shows an augmented reality display system similar to the augmented reality display system shown in Figure 20A and 20B but using a deflection-based spatial light modulator, such as a spatial light modulator based on movable micromirrors.

[0046] Figure 20D Is a top view of a part of an augmented reality display system such as Figure 20C shown in, schematically showing a laterally shifted light source above the color filter array and corresponding laterally shifted light-coupling optical elements.

[0047] Figure 20E Shows how a deflection-based spatial light modulator guides light away from a corresponding light-coupling optical element and to Figure 20D a mask around a filter in a filter array of an augmented reality display system.

[0048] Figure 20F A side view of an augmented reality display system that includes a cover glass disposed on the user side of a waveguide stack and a light source disposed on the world side of the cover glass.

[0049] Figure 20G A side view of an augmented reality display system that includes a cover glass disposed on the world side of a waveguide stack and a light source disposed on the world side of the cover glass.

[0050] Figure 21 A side view of an augmented reality display system that includes a light source equipped with a light recycler configured to recycle light, such as light of one polarization.

[0051] Figure 22 A side view of one or more light sources that propagate light through corresponding light collection optics and one or more apertures. The light can also propagate through a diffuser located near the one or more apertures.

[0052] Figure 23AA side view of a portion of an augmented reality display system that includes a light source, an optical device having a focal power, a waveguide for receiving image information and outputting the image information to a user's eye, wherein the system further includes one or more retarders and polarizers configured to reduce reflections from optical surfaces that may enter the waveguide as ghost images.

[0053] Figure 23B Such as Figure 23A A side view of a portion of an augmented reality display system as shown in

[0054] Figure 23C Such as Figure 23A And 23B A side view of an augmented reality display system as shown in

[0055] Figure 24 A side view of an augmented reality display system that uses an inclined surface (such as an inclined surface on a cover glass) to deflect reflections away from entering the user's eye, thereby potentially reducing ghost reflections.

[0056] Figure 25 Is Figure 24 An embodiment of the system in which the inclined surface on the cover glass is configured to deflect reflections towards a light dump that absorbs light.

[0057] Figure 26A Shows a plan view of an eyepiece waveguide using a dual active layer architecture according to an embodiment of the present invention.

[0058] Figure 26B Shows Figure 26A An exploded view of the eyepiece waveguide shown in

[0059] Figure 26C Shows Figure 26A A cross-sectional view of the eyepiece waveguide shown in

[0060] Figure 27A Shows a plan view of an eyepiece waveguide using a dual active layer architecture according to another embodiment of the present invention.

[0061] Figure 27B Shows Figure 27A An exploded view of the eyepiece waveguide shown in

[0062] Figure 27C Shows Figure 27A A cross-sectional view of the eyepiece waveguide shown in

[0063] Figures 28A - 28CShows a cross-sectional view of a dual-active-layer eyepiece waveguide according to various embodiments of the present invention.

[0064] Figure 29A Shows a plan view of an eyepiece waveguide using a dual-active-layer architecture with split and inline ICG according to an embodiment of the present invention.

[0065] Figure 29B Shows Figure 29A An exploded view of the shown eyepiece waveguide.

[0066] Figure 29C Shows Figure 29A A cross-sectional view of the shown eyepiece waveguide.

[0067] Figure 30A Shows a plan view of an eyepiece waveguide using a dual-active-layer architecture according to an embodiment of the present invention.

[0068] Figure 30B Shows Figure 30A An exploded view of the shown eyepiece waveguide.

[0069] Figure 30C Shows Figure 30A A cross-sectional view of the shown eyepiece waveguide.

[0070] Figure 31A Shows a plan view of an eyepiece waveguide using a dual-active-layer architecture according to another embodiment of the present invention.

[0071] Figure 31B Shows Figure 31A An exploded view of the shown eyepiece waveguide.

[0072] Figure 31C Shows Figure 31A A cross-sectional view of the shown eyepiece waveguide.

[0073] Figure 32A Shows a cross-sectional view of an eyepiece waveguide according to an embodiment of the present invention.

[0074] Figure 32B Shows Figure 32A A plan view of the ICG of the shown eyepiece waveguide.

[0075] Figure 32C Shows an alternative ICG that can be used with Figure 32A The shown eyepiece waveguide. A plan view of the alternative ICG.

[0076] Figure 32D Shows a cross-sectional view of an eyepiece waveguide according to an alternative embodiment of the present invention.

[0077] Figure 32E ShowsFigure 32D Planar view of the ICG of the eyepiece waveguide shown.

[0078] Figure 32F Shows an alternative ICG that can be used with Figure 32D the eyepiece waveguide shown in a planar view.

[0079] Figure 33A Planar view of an eyepiece waveguide with a three-pupil layout according to an embodiment of the present invention.

[0080] Figure 33B Using Figure 33A The cross-sectional view of the eyepiece waveguide shown shows the coupling and propagation of light.

[0081] Figures 33C - 33E Is generated by Figure 33A the field-of-view image produced by the eyepiece waveguide shown.

[0082] Figure 34A Is a spectrogram showing the diffraction pitch used in a dual-active-layer architecture according to an embodiment of the present invention.

[0083] Figure 34B And 34C Is a simplified cross-sectional view of a dual-active-layer architecture according to an embodiment of the present invention.

[0084] Figure 35A Cross-sectional view of an eyepiece waveguide using a dual-active-layer architecture according to an embodiment of the present invention.

[0085] Figures 35B - 35C Shows Figure 35A a plan view of the user-side eyepiece waveguide layer of the eyepiece waveguide shown in

[0086] Figures 35D - 35E Shows Figure 35A a plan view of the world-side eyepiece waveguide layer of the eyepiece waveguide shown in

[0087] Figures 36A - 36F Shows various diffraction grating structures that can be used for an input grating, an orthogonal pupil expansion grating, an output pupil expansion grating, or a combined pupil expansion grating according to an embodiment of the present invention. Detailed Description

[0088] Reference will now be made to the drawings, where like reference numerals always denote like parts. Unless otherwise noted, the drawings are schematic and not necessarily drawn to scale.

[0089] Figure 2A conventional display system for simulating a three-dimensional image for a user is shown. It will be understood that the user's eyes are separated, and when viewing a real object in space, each eye will have a slightly different view of the object, and an image of the object can be formed at different positions on the retina of each eye. This can be referred to as binocular parallax and can be utilized by the human visual system to provide depth perception. The conventional display system simulates binocular parallax by presenting two different images 190, 200 with slightly different views of the same virtual object (one for each eye 210a, 210b), the different views corresponding to the views of the virtual object that each eye would see, the virtual object being a virtual object of a real object located at a desired depth. These images provide binocular cues, where the user's visual system can interpret the binocular cues to obtain depth perception.

[0090] Continuing to refer to Figure 2 , the images 190, 200 are separated from the eyes 210a, 210b by a distance 230 along the z-axis. In the case where their eyes are fixated on an object at optical infinity directly in front of the viewer, the z-axis is parallel to the viewer's optical axis. The images 190, 200 are flat and at a fixed distance from the eyes 210a, 210b. Based on the slightly different views of the virtual object in the images presented to the eyes 210a, 210b respectively, the eyes can naturally rotate so that the images of the object fall on corresponding points on the retina of each eye to maintain a single binocular vision. This rotation can cause the lines of sight of each eye 210a, 210b to converge to a point in the space where the virtual object is perceived to exist. As a result, providing a three-dimensional image generally involves providing binocular cues that can manipulate the convergence of the user's eyes 210a, 210b, and the human visual system interprets the binocular cues to provide depth perception.

[0091] However, generating a realistic and comfortable depth perception is challenging. It will be understood that light from objects at different distances from the eyes has wavefronts with different amounts of divergence. Figures 3A - 3C The relationship between distance and the divergence of light rays is shown. The distances between the objects and the eye 210 are represented by R1, R2, and R3 in decreasing order of distance. As shown in Figures 3A - 3C , as the distance to the object decreases, the light rays become more divergent. Conversely, as the distance increases, the light rays become more collimated. In other words, it can be said that the light field generated by a point (object or part of an object) has a spherical wavefront curvature that is a function of the distance of the point from the user's eyes. The curvature increases as the distance between the object and the eye 210 decreases. Although for clarity of illustration a single eye 210 is shown in Figures 3A - 3C and other figures in this document, the discussion regarding the eye 210 can be applied to both eyes 210a and 210b.

[0092] Continuing to refer Figures 3A - 3C , light from an object that is fixated by a viewer's eyes can have different degrees of wavefront divergence. Due to the different amounts of wavefront divergence, the light can be focused differently by the eye's lens, which in turn may require the lens to assume different shapes to form a focused image on the retina of the eye. In the case where a focused image is not formed on the retina, the resulting retinal blur serves as an accommodation cue that causes a change in the shape of the eye's lens until a focused image is formed on the retina. For example, the accommodation cue can trigger the relaxation or contraction of the ciliary muscles surrounding the eye lens, thereby adjusting the force applied to the zonular ligaments that hold the lens, and thus causing the shape of the eye lens to change until the retinal blur of the fixated object is eliminated or minimized, thereby forming a focused image of the fixated object on the retina of the eye (e.g., the fovea). The process by which the shape of the eye lens changes can be referred to as accommodation, and the shape of the eye lens required to form a focused image of the fixated object on the retina of the eye (e.g., the fovea) can be referred to as the accommodative state.

[0093] Now referring to Figure 4A , a representation of the accommodation-convergence response of the human visual system is shown. Eye movements are made to fixate on an object such that the eyes receive light from the object, where the light forms an image on each retina of the eyes. The presence of retinal blur in the images formed on the retinas can provide an accommodation cue, and the relative positions of the images on the retinas can provide a convergence cue. The accommodation cue causes accommodation to occur, resulting in each of the eye lenses assuming a particular accommodative state that forms a focused image of the object on the retina of the eye (e.g., the fovea). On the other hand, the convergence cue causes a convergence movement (rotation of the eyes) to occur such that the images formed on each retina of each eye are at corresponding retinal points that maintain single binocular vision. At these positions, the eyes can be said to be in a particular convergence state. Continuing to refer Figure 4A , accommodation can be understood as the process by which the eyes achieve a particular accommodative state, and convergence can be understood as the process by which the eyes achieve a particular convergence state. As Figure 4A shown, if the user fixates on another object, the accommodation and convergence states of the eyes can change. For example, if the user fixates on a new object at a different depth along the z-axis, the accommodative state can change.

[0094] Without being limited by theory, it is believed that a viewer of an object can perceive the object as "three-dimensional" due to a combination of convergence and accommodation. As described above, the convergence movement of the two eyes relative to each other (e.g., rotation of the eyes such that the pupils move towards or away from each other to converge the lines of sight of the eyes to fixate on an object) is closely related to the accommodation of the lenses of the eyes. Under normal circumstances, changing the shape of the lens of an eye to change the focus from one object to another object located at a different distance will automatically cause a matching change in convergence to the same distance in a relationship known as the "accommodation-convergence reflex". Similarly, under normal circumstances, a change in convergence will trigger a matching change in the shape of the lens.

[0095] Now referring to Figure 4B , an example of different accommodation and convergence states of the eyes is shown. The pair of eyes 222a is fixated on an object at optical infinity, while the pair of eyes 222b is fixated on an object 221 that is less than optically infinite. It is noteworthy that the convergence states of each pair of eyes are different, where the pair of eyes 222a is directed straight ahead, while the pair of eyes 222 converges on the object 221. The accommodation states of the eyes forming each pair of eyes 222a and 222b are also different, as indicated by the different shapes of the lenses 220a, 220b.

[0096] Unfortunately, many users of traditional "3-D" display systems find these traditional systems uncomfortable or do not perceive a sense of depth at all due to a mismatch between the accommodation and convergence states in these displays. As described above, many stereoscopic or "3-D" display systems display a scene by providing slightly different images to each eye. Such systems are uncomfortable for many viewers because they simply provide different presentations of the scene among other things and cause a change in the convergence state of the eyes, but without a corresponding change in the accommodation state of those eyes. Instead, the images are presented by a display at a fixed distance from the eyes such that the eyes view all the image information in a single accommodation state. This arrangement violates the "accommodation-convergence reflex" by causing a change in the convergence state without a matching change in the accommodation state. This mismatch is believed to cause discomfort to the viewer. A display system that provides a better match between accommodation and convergence can form a more realistic and comfortable three-dimensional image simulation.

[0097] Without being limited by theory, it is believed that the human eye can typically interpret a limited number of depth planes to provide depth perception. Therefore, a highly believable simulation of perceived depth can be achieved by providing different presentations of images corresponding to each of these limited number of depth planes to the eyes. In some embodiments, the different presentations can provide convergence cues and matching accommodation cues, thereby providing a physiologically correct accommodation-convergence match.

[0098] Continuing to refer to Figure 4B, shows two depth planes 240, which correspond to different distances from the eyes 210a, 210b in space. For a given depth plane 240, a vergence cue can be provided by displaying appropriately different perspectives of an image for each eye 210a, 210b. Additionally, for a given depth plane 240, the light forming the images provided to each eye 210a, 210b can have a wavefront divergence corresponding to the light field generated by points at the distance of that depth plane 240.

[0099] In the illustrated embodiment, the depth plane 240 containing the object 221 is at a distance of 1 m along the z-axis. As used herein, the distance or depth along the z-axis can be measured by a zero point located at the exit pupil of the user's eyes. Thus, the depth plane 240 at a depth of 1 m corresponds to a distance of 1 m from the exit pupil of the user's eyes on the optical axis of those eyes pointing to optical infinity. As an approximation, the depth or distance along the z-axis can be measured from a display in front of the user's eyes (e.g., from the surface of a waveguide), plus the value of the distance between the device and the exit pupil of the user's eyes. This value can be referred to as the eye relief and corresponds to the distance between the exit pupil of the user's eyes and the display worn by the user in front of the eyes. In practice, the value of the eye relief can be a standardized value commonly used for all viewers. For example, it can be assumed that the eye relief is 20 mm, and the depth plane at a depth of 1 m can be at a distance of 980 mm in front of the display.

[0100] Now refer to Figure 4C and 4D , which show examples of a matched accommodation-vergence distance and a mismatched accommodation-vergence distance, respectively. As Figure 4C shown, the display system can provide images of virtual objects to each eye 210a, 210b. The images can cause the eyes 210a, 210b to assume a vergence state in which the eyes converge on a point 15 on the depth plane 240. Additionally, the images can be formed by light having a wavefront curvature corresponding to a real object at that depth plane 240. As a result, the eyes 210a, 210b assume an accommodation state in which the images are in focus on the retinas of those eyes. Thus, the user can perceive the virtual object at the point 15 on the depth plane 240.

[0101] It will be understood that each of the accommodation and vergence states of eyes 210a, 210b is associated with a specific distance on the z-axis. For example, an object at a specific distance from eyes 210a, 210b causes those eyes to exhibit a specific accommodation state based on the distance of the object. The distance associated with a specific accommodation state may be referred to as the accommodation distance Ad. Similarly, there is a specific vergence distance Vd associated with the eyes or the positions of the eyes relative to each other in a specific vergence state. When the accommodation distance and the vergence distance match, it can be said that the relationship between accommodation and vergence is physiologically correct. This is considered the most comfortable scenario for the viewer.

[0102] However, in a stereoscopic display, the accommodation distance and the vergence distance may not always match. For example, as Figure 4D shown, the images presented to eyes 210a, 210b may be presented with a wavefront divergence corresponding to depth plane 240, and eyes 210a, 210b may exhibit a specific accommodation state in which points 15a, 15b on that depth plane are in focus. However, the images presented to eyes 210a, 210b may provide vergence cues that cause eyes 210a, 210b to converge at a point 15 that is not located on depth plane 240. As a result, in some embodiments, the accommodation distance corresponds to the distance from the exit pupils of eyes 210a, 210b to depth plane 240, while the vergence distance corresponds to a greater distance from the exit pupils of eyes 210a, 210b to point 15. The accommodation distance is different from the vergence distance. Thus, there is an accommodation-vergence mismatch. This mismatch is considered undesirable and may cause discomfort to the user. It will be understood that this mismatch corresponds to a distance (e.g., VaAd) and can be characterized using diopters.

[0103] In some embodiments, it will be understood that a reference point other than the exit pupils of eyes 210a, 210b can be used to determine the distances for determining the accommodation-vergence mismatch, provided that the same reference point is used for both the accommodation distance and the vergence distance. For example, the distance from the cornea to the depth plane, from the retina to the depth plane, from the eyepiece (e.g., the waveguide of the display device) to the depth plane, etc. can be measured.

[0104] Without being limited by theory, it is believed that a user can still perceive an accommodation-vergence mismatch of up to approximately 0.25 diopters, up to approximately 0.33 diopters, and up to approximately 0.5 diopters as being physiologically correct without significant discomfort caused by the mismatch itself. In some embodiments, the display systems disclosed herein (e.g., Figure 6The display system 250 presents an image to a viewer with an accommodation-convergence mismatch of about 0.5 diopters or less. In some other embodiments, the accommodation-convergence mismatch of the image provided by the display system is about 0.33 diopters or less. In still some other embodiments, the accommodation-convergence mismatch of the image provided by the display system is about 0.25 diopters or less, including about 0.1 diopters or less.

[0105] Figure 5 Aspects of a method of simulating a three-dimensional image by modifying wavefront divergence are shown. The display system includes a waveguide 270 configured to receive light 770 encoded with image information and output the light to a user's eye 210. The waveguide 270 can output light 650 having a limited amount of wavefront divergence corresponding to the wavefront divergence of the light field generated by points on a desired depth plane 240. In some embodiments, the same amount of wavefront divergence is provided for all objects presented on the depth plane. Additionally, it will be described that image information from a similar waveguide can be provided to the user's other eye.

[0106] In some embodiments, a single waveguide can be configured to output light having a set amount of wavefront divergence corresponding to a single or limited number of depth planes and / or the waveguide can be configured to output light within a limited wavelength range. Thus, in some embodiments, a waveguide stack can be utilized to provide different amounts of wavefront divergence for different depth planes and / or output light having different wavelength ranges. As used herein, it will be understood that the contour of a flat or curved surface can be followed at the depth plane. In some embodiments, for simplicity, the depth plane can advantageously follow the contour of a flat surface.

[0107] Figure 6 An example of a waveguide stack for outputting image information to a user is shown. The display system 250 includes a stack of waveguides or a stacked waveguide assembly 260 that can be used to provide a three-dimensional perception to the eye / brain using waveguides 270, 280, 290, 300, 310. It will be understood that in some embodiments, the display system 250 can be considered a light field display. Additionally, the waveguide assembly 260 can also be referred to as an eyepiece.

[0108] In some embodiments, the display system 250 may be configured to provide substantially continuous vergence cues and a plurality of discrete accommodation cues. Vergence cues may be provided by displaying different images to each of the user's eyes, and accommodation cues may be provided by forming the light of the image with a selectable discrete amount of wavefront divergence. In other words, the display system 250 may be configured to output light having a variable level of wavefront divergence. In some embodiments, each discrete level of wavefront divergence corresponds to a particular depth plane and may be provided by a particular one of waveguides 270, 280, 290, 300, 310.

[0109] Continuing to refer Figure 6 , the waveguide assembly 260 may also include features 320, 330, 340, 350 between the waveguides. In some embodiments, the features 320, 330, 340, 350 may be one or more lenses. Waveguides 270, 280, 290, 300, 310 and / or features (e.g., lenses) 320, 330, 340, 350 may be configured to send image information to the eyes with various levels of wavefront curvature or ray divergence. Each waveguide level may be associated with a particular depth plane and may be configured to output image information corresponding to that depth plane. Image injection devices 360, 370, 380, 390, 400 may act 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 corresponding waveguide for output toward the eye 210. Light leaves the output surfaces 410, 420, 430, 440, 450 of the image injection devices 360, 370, 380, 390, 400 and is injected into the corresponding input surfaces 460, 470, 480, 490, 500 of waveguides 270, 280, 290, 300, 310. In some embodiments, each of the input surfaces 460, 470, 480, 490, 500 may be an edge of the corresponding waveguide or may be a portion of the major surface of the corresponding waveguide (i.e., the surface of the waveguide that directly faces the world 510 or the viewer's eye 210). In some embodiments, a single light beam (e.g., a collimated beam) may be injected into each waveguide to output an entire field of cloned collimated beams that are directed toward the eye 210 at a particular angle (and amount of divergence) corresponding to the depth plane associated with the particular waveguide. In some embodiments, a single one of the image injection devices 360, 370, 380, 390, 400 may be associated with one or more (e.g., three) waveguides 270, 280, 290, 300, 310 and inject light into one or more (e.g., three) waveguides 270, 280, 290, 300, 310.

[0110] In some embodiments, the image injection devices 360, 370, 380, 390, 400 are discrete displays, each of which generates image information for injection into the corresponding waveguides 270, 280, 290, 300, 310, respectively. In some other embodiments, the image injection devices 360, 370, 380, 390, 400 are the output ends of a single multiplexed display, and the output ends of the single multiplexed display can convey image information to each of the image injection devices 360, 370, 380, 390, 400 via, for example, one or more optical conduits such as fiber optic cables. It will be understood that the image information provided by the image injection devices 360, 370, 380, 390, 400 can include light of different wavelengths or colors (e.g., different component colors as discussed herein).

[0111] In some embodiments, the light injected into the waveguides 270, 280, 290, 300, 310 is provided by a light projector system 520, which includes a light module 530 that can include a light emitter such as a light-emitting diode (LED). The light from the light module 530 can be directed to a light modulator 540 (e.g., a spatial light modulator) via a beam splitter 550 and modified by the light modulator 540. The light modulator 540 can be configured to change the perceived intensity of the light injected into the waveguides 270, 280, 290, 300, 310 to encode the light with image information. Examples of spatial light modulators include liquid crystal displays (LCDs) that include liquid crystal on silicon (LCOS) displays. It will be understood that the image injection devices 360, 370, 380, 390, 400 are schematically shown, and in some embodiments, these image injection devices can represent different optical paths and positions in a common projection system that is configured to output light into the associated waveguides among the waveguides 270, 280, 290, 300, 310. In some embodiments, the waveguides of the waveguide assembly 260 can act as ideal lenses while relaying the light injected into the waveguides out to the user's eyes. In this concept, the object can be the spatial light modulator 540, and the image can be an image on a depth plane.

[0112] In some embodiments, the display system 250 can be a scanned fiber optic display that includes one or more scanned optical fibers configured to project light into one or more waveguides 270, 280, 290, 300, 310 and ultimately to the viewer's eye 310 in various patterns (e.g., raster scan, helical scan, Lissajous pattern, etc.). In some embodiments, the illustrated image injection devices 360, 370, 380, 390, 400 can schematically represent a single scanned optical fiber or a bundle of scanned optical fibers configured to inject light into one or more of the waveguides 270, 280, 290, 300, 310. In some other embodiments, the illustrated image injection devices 360, 370, 380, 390, 400 can schematically represent one or more scanned optical fibers or one or more bundles of scanned optical fibers, each of which is configured to inject light into an associated one of the waveguides 270, 280, 290, 300, 310. It will be understood that one or more optical fibers can be configured to transmit light from the optical module 530 to one or more of the waveguides 270, 280, 290, 300, 310. It will be understood that one or more intermediate optical structures can be provided between the scanned optical fiber or fibers and one or more of the waveguides 270, 280, 290, 300, 310 to, for example, redirect light exiting the scanned optical fiber into one or more of the waveguides 270, 280, 290, 300, 310.

[0113] The controller 560 controls the operation of one or more of the stacked waveguide assemblies 260, including the operation of the image injection devices 360, 370, 380, 390, 400, the light source 530, and the light modulator 540. In some embodiments, the controller 560 is part of the local data processing module 140. The controller 560 includes programming (e.g., instructions in a non-transitory medium) that regulates the timing and provision of image information to the waveguides 270, 280, 290, 300, 310 according to any of the various schemes disclosed herein, for example. In some embodiments, the controller can be a single integral device or a distributed system connected by wired or wireless communication channels. In some embodiments, the controller 560 can be part of the processing module 140 or 150 ( Figure 9D ).

[0114] Continuing reference Figure 6, waveguides 270, 280, 290, 300, 310 can be configured to enable light to propagate within each respective waveguide by total internal reflection (TIR). Waveguides 270, 280, 290, 300, 310 can each be planar or have another shape (e.g., curved), having a main top surface and a main bottom surface and edges extending between those main top and bottom surfaces. In the illustrated configuration, waveguides 270, 280, 290, 300, 310 can each include outcoupling optical elements 570, 580, 590, 600, 610, which are configured to extract light out of the waveguide by redirecting the light propagating within each respective waveguide out of the waveguide for outputting image information to the eye 210. Although referred to throughout the specification as "outcoupling optical elements", the outcoupling optical elements are not necessarily optical elements and can be non-optical elements. The extracted light can also be referred to as outcoupled light, and the outcoupling optical element light can also be referred to as a light extraction optical element. The extracted light beam can be output by the waveguide at the location where the light propagating in the waveguide impinges on the light extraction optical element. The outcoupling optical elements 570, 580, 590, 600, 610 can be, for example, gratings including diffractive optical features, as further discussed herein. Although illustrated as being disposed at the bottom main surface of waveguides 270, 280, 290, 300, 310 for ease of description and clarity of the drawings, in some embodiments, the outcoupling optical elements 570, 580, 590, 600, 610 can be disposed at the top and / or bottom main surfaces, and / or can be disposed directly within the volume of waveguides 270, 280, 290, 300, 310, as further discussed herein. In some embodiments, the outcoupling optical elements 570, 580, 590, 600, 610 can be formed in a material layer attached to a transparent substrate to form waveguides 270, 280, 290, 300, 310. In some other embodiments, waveguides 270, 280, 290, 300, 310 can be a single-piece material, and the outcoupling optical elements 570, 580, 590, 600, 610 can be formed on and / or within the surface of the piece of material.

[0115] Continue to refer to Figure 6, as discussed herein, each of waveguides 270, 280, 290, 300, 310 is configured to output light to form an image corresponding to a particular depth plane. For example, the waveguide 270 closest to the eye can be configured to deliver collimated light (which is injected into such waveguide 270) to the eye 210. The collimated light can represent an optically infinite focal plane. The next upper waveguide 280 can be configured to send out collimated light that passes through a first lens 350 (e.g., a negative lens) before it can reach the eye 210; such first lens 350 can be configured to produce a slightly convex wavefront curvature such that the eye / brain interprets the light from the next upper waveguide 280 as coming from a first focal plane that is closer inwards towards the eye 210 from the optically infinite. Similarly, the third upper waveguide 290 has its output light pass through the first lens 350 and a second lens 340 before reaching the eye 210; the combined optical power of the first lens 350 and the second lens 340 can be configured to produce another increment of wavefront curvature such that the eye / brain interprets the light from the third waveguide 290 as coming from a second focal plane that is closer inwards towards the person from the optically infinite than the light from the next upper waveguide 280.

[0116] The other waveguide layers 300, 310 and lenses 330, 320 are configured similarly, where the highest waveguide 310 in the stack sends its output through all of the lenses between it and the eye for a total optical power representing the closest focal plane to the person. To compensate for the stack of lenses 320, 330, 340, 350 when viewing / interpreting light from the world 510 on the other side of the stacked waveguide assembly 260, a compensation lens layer 620 can be provided at the top of the stack to compensate for the total optical power of the underlying lens stack 320, 330, 340, 350. Such a configuration provides as many focal planes as there are available waveguide / lens pairings. Both the outcoupling optical elements of the waveguides and the focusing aspects of the lenses can be static (i.e., non-dynamic or electroactive). In some alternative embodiments, one or both of them can be dynamic using electroactive features.

[0117] In some embodiments, two or more of the waveguides 270, 280, 290, 300, 310 can have the same associated depth plane. For example, multiple waveguides 270, 280, 290, 300, 310 can be configured to output a set of images to the same depth plane, or multiple subsets of the waveguides 270, 280, 290, 300, 310 can be configured to output a set of images to the same one or more depth planes, where there is one set of images for each depth plane. This can provide the advantage of forming a stitched image to provide an extended field of view at those depth planes.

[0118] Continuing reference Figure 6, the output optical elements 570, 580, 590, 600, 610 can be configured to redirect light out of their respective waveguides and output the light with an appropriate amount of divergence or collimation for a particular depth plane associated with the waveguide. Thus, waveguides with different associated depth planes can have different configurations of the output optical elements 570, 580, 590, 600, 610, which depend on the associated depth plane to output light with different amounts of divergence. In some embodiments, the light extraction optical elements 570, 580, 590, 600, 610 can be volume or surface features, which can be configured to output light at a specific angle. For example, the light extraction optical elements 570, 580, 590, 600, 610 can be volume holograms, surface holograms, and / or diffraction gratings. In some embodiments, the features 320, 330, 340, 350 can not be lenses; instead, they can simply be spacers (e.g., cladding and / or structures for forming voids).

[0119] In some embodiments, the output optical elements 570, 580, 590, 600, 610 are diffraction features that form a diffraction pattern, or "diffractive optical elements" (also referred to herein as "DOEs"). Preferably, the DOE has a low enough diffraction efficiency such that only a portion of the light beam is deflected away from the eye 210 through each intersection of the DOE, while the remaining portion continues to travel through the waveguide via TIR. The light carrying the image information is thus split into many associated outgoing beams that leave the waveguide at many locations, and the result is a relatively uniform pattern of outgoing emission towards the eye 210 for that particular collimated beam that bounces (rebounce) everywhere within the waveguide.

[0120] In some embodiments, one or more DOEs can be switched between an "on" state in which they actively diffract and an "off" state in which they do not significantly diffract. For example, a switchable DOE can include a polymer dispersed liquid crystal layer, where the microdroplets include a diffraction pattern in a host medium, and the refractive index of the microdroplets can be switched to substantially match the refractive index of the host material (in which case the pattern does not significantly diffract the incident light) or the microdroplets can be switched to a refractive index that does not match the refractive index of the host medium (in which case the pattern actively diffracts the incident light).

[0121] In some embodiments, a camera component 630 (e.g., a digital camera, including visible light and infrared cameras) can be provided to capture images of the eye 210 and / or tissue around the eye 210 to, for example, detect user input and / or monitor the user's physiological state. As used herein, a camera can be any image capture device. In some embodiments, the camera component 630 can include an image capture device and a light source that projects light (e.g., infrared light) toward the eye, which can then be reflected by the eye and detected by the image capture device. In some embodiments, the camera component 630 can be attached to the frame 80( Figure 9D ) and can be in electrical communication with the processing module 140 and / or 150, which can process image information from the camera component 630. In some embodiments, one camera component 630 can be utilized for each eye to monitor each eye separately.

[0122] Now referring to Figure 7 , an example of an output beam exiting the waveguide is shown. One waveguide is shown, but it will be understood that in the case where the waveguide assembly 260 includes multiple waveguides, the other waveguides in the waveguide assembly 260( Figure 6 ) can operate similarly. Light 640 is injected into the waveguide 270 at the input surface 460 of the waveguide 270 and propagates within the waveguide 270 by TIR. At the point where the light 640 is incident on the DOE 570, a portion of the light exits the waveguide as the output beam 650. The output beam 650 is illustrated as being substantially parallel, but as discussed herein, it can also be redirected to propagate at an angle to the eye 210 (e.g., form a diverging output beam), depending on the depth plane associated with the waveguide 270. It will be understood that a substantially parallel output beam can indicate that the waveguide has an outcoupling optical element that outcouples light to form an image that appears to be set in a depth plane at a large distance from the eye 210 (e.g., optical infinity). Other waveguides or other sets of outcoupling optical elements can output a more diverging output beam pattern, which will require the eye 210 to accommodate to a closer distance to focus on the retina and will be interpreted by the brain as light from a distance closer to the eye 210 than optical infinity.

[0123] In some embodiments, a full-color image can be formed at each depth plane by overlapping images of each component color (e.g., three or more component colors).

[0124] Figure 8An example of a stacked waveguide assembly is shown, where each depth plane includes an image formed using a plurality of different component colors. The illustrated embodiment shows depth planes 240a–240f, although more or fewer depths are also contemplated. Each depth plane may have three or more component color images associated therewith, including: a first image of a first color G; a second image of a second color R; and a third image of a third color B. Different depth planes are indicated in the figures by different numbers for diopters (dpt) following the letters G, R, and B. By way of example only, the numbers following each of these letters indicate the diopter (1 / m), or the inverse distance of the depth plane from the viewer, and each box in the figures represents a single component color image. In some embodiments, to account for differences in the focusing of light of different wavelengths by the eye, the exact placement of the depth planes for different component colors may vary. For example, the different component color images for a given depth plane may be placed on depth planes corresponding to different distances from the user. Such an arrangement may increase visual sensitivity and user comfort and / or may reduce chromatic aberration.

[0125] In some embodiments, light of each component color may be output by a single dedicated waveguide, and thus, each depth plane may have a plurality of waveguides associated therewith. In such embodiments, each box in the figures including the letters G, R, or B may be understood to represent a separate waveguide, and three waveguides may be provided per depth plane, where three component color images are provided per depth plane. While the waveguides associated with each depth plane are shown in the figures as being adjacent to each other, it will be understood that in a physical device, the waveguides may all be arranged in a stack, with one waveguide per layer. In some other embodiments, a plurality of component colors may be output by the same waveguide, such that, for example, only a single waveguide may be provided per depth plane.

[0126] Continuing to refer Figure 8 , in some embodiments, G is green, R is red, and B is blue. In some other embodiments, other colors associated with other wavelengths of light (including magenta and cyan) may additionally be used or may replace one or more of red, green, or blue.

[0127] It will be understood that references throughout this disclosure to a given light color will be understood to encompass light of one or more wavelengths within the range of wavelengths of light that are perceived by a viewer as having that given color. For example, red light may include light of one or more wavelengths in the range of approximately 620–780 nm, green light may include light of one or more wavelengths in the range of approximately 492–577 nm, and blue light may include light of one or more wavelengths in the range of approximately 435–493 nm.

[0128] In some embodiments, light source 530 (Figure 6 ) can be configured to emit light of one or more wavelengths outside the viewer's visual perception range, e.g., infrared and / or ultraviolet wavelengths. Additionally, the light coupling, decoupling, and other light redirecting structures of the waveguide of the display 250 can be configured to direct and emit the light towards the eye 210 and outside the display, e.g., for imaging and / or user stimulation applications.

[0129] Now referring to Figure 9A , in some embodiments, light incident on the waveguide may need to be redirected to couple the light into the waveguide. The coupling optical element can be used to redirect and couple the light into its corresponding waveguide. Although referred to throughout the specification as a "coupling optical element", the coupling optical element is not necessarily an optical element and can be a non-optical element. Figure 9A A cross-sectional side view showing an example of a stack of waveguides 660 is shown, where each waveguide includes a coupling optical element. The waveguides can each be configured to output light of one or more different wavelengths or one or more different wavelength ranges. It will be understood that the stack 660 can correspond to the stack 260 ( Figure 6 ), and the waveguides of the illustrated stack 660 can correspond to a portion of the waveguides 270, 280, 290, 300, 310, except that light from one or more of the image injection devices 360, 370, 380, 390, 400 is injected into the waveguide from a location where the desired light redirection for coupling is to occur.

[0130] The illustrated set of stacked waveguides 660 includes waveguides 670, 680, and 690. Each waveguide includes an associated optical input element (which may also be referred to as an optical input region on the waveguide), e.g., an optical input element 700 disposed on the major surface (e.g., the upper major surface) of waveguide 670, an optical input element 710 disposed on the major surface (e.g., the upper major surface) of waveguide 680, and an optical input element 720 disposed on the major surface (e.g., the upper major surface) of waveguide 690. In some embodiments, one or more of the optical input elements 700, 710, 720 may be disposed on the bottom major surface of the respective waveguides 670, 680, 690 (particularly where one or more of the optical input elements are reflective deflecting optical elements). As illustrated, the optical input elements 700, 710, 720 may be disposed on the upper major surface of their respective waveguides 670, 680, 690 (or on top of the next lower waveguide), particularly where those optical input elements are transmissive deflecting optical elements. In some embodiments, the optical input elements 700, 710, 720 may be disposed within the body of the respective waveguides 670, 680, 690. In some embodiments, as discussed herein, the optical input elements 700, 710, 720 are wavelength selective such that they selectively redirect one or more wavelengths of light while transmitting other wavelengths of light. Although illustrated on one side or corner of their respective waveguides 670, 680, 690, it will be understood that in some embodiments, the optical input elements 700, 710, 720 may be disposed in other regions of their respective waveguides 670, 680, 690.

[0131] As illustrated, the optical input elements 700, 710, 720 may be laterally offset from each other. In some embodiments, each optical input element may be offset such that it receives light without the light passing through another optical input element. For example, each of the optical input elements 700, 710, 720 may be configured to receive light from different image injection devices 360, 370, 380, 390, and 400 as shown in Figure 6 and may be separated (e.g., laterally spaced) from the other optical input elements 700, 710, 720 such that it substantially does not receive light from the other optical input elements among the optical input elements 700, 710, 720.

[0132] Each waveguide also includes an associated optical distribution element, e.g., an optical distribution element 730 disposed on the main surface (e.g., the top main surface) of waveguide 670, an optical distribution element 740 disposed on the main surface (e.g., the top main surface) of waveguide 680, and an optical distribution element 750 disposed on the main surface (e.g., the top main surface) of waveguide 690. In some other embodiments, the optical distribution elements 730, 740, 750 may be disposed on the bottom main surfaces of the associated waveguides 670, 680, 690, respectively. In some other embodiments, the optical distribution elements 730, 740, 750 may be disposed on the top and bottom main surfaces of the associated waveguides 670, 680, 690, respectively; or the optical distribution elements 730, 740, 750 may be disposed on different main surfaces of the top and bottom main surfaces in different associated waveguides 670, 680, 690.

[0133] The waveguides 670, 680, 690 may be separated and isolated by, e.g., layers of gas, liquid, and / or solid-state materials. For example, as illustrated, layer 760a may separate waveguides 670 and 680; and layer 760b may separate waveguides 680 and 690. In some embodiments, layers 760a and 760b are formed of a low refractive index material (i.e., a material having a lower refractive index than the material of the directly adjacent waveguides in waveguides 670, 680, 690). Preferably, the refractive index of the material forming layers 760a, 760b is less than the refractive index of the material forming waveguides 670, 680, 690 by 0.05 or more, or 0.10 or less. Advantageously, the lower refractive index layers 760a, 760b may serve as claddings that facilitate total internal reflection (TIR) of light through waveguides 670, 680, 690 (e.g., TIR between the top and bottom main surfaces of each waveguide). In some embodiments, layers 760a, 760b are formed of air. Although not illustrated, it will be understood that the top and bottom of the illustrated waveguide group 660 may include directly adjacent claddings.

[0134] Preferably, for ease of fabrication and other considerations, the materials forming waveguides 670, 680, 690 are similar or the same, and the materials forming layers 760a, 760b are similar or the same. In some embodiments, the materials forming waveguides 670, 680, 690 may be different between one or more waveguides, and / or the materials forming layers 760a, 760b may be different, while still maintaining the various refractive index relationships noted above. A variety of materials can be used to form the waveguides. While glass is a material that can be used to fabricate waveguides, other materials can also be used, including LiNbO3, SiC, ZnS, or similar materials. These materials can be in the form of optically quality single crystal materials, or materials that have optical quality but are not single crystals. In addition, polycrystalline ceramics of similar composition can also be used to form waveguides. As an example, nanocrystalline materials can be used in the fabrication of waveguides.

[0135] Continuing to refer to Figure 9A , light rays 770, 780, 790 are incident on waveguide group 660. It will be understood that light rays 770, 780, 790 can be injected into waveguides 670, 680, 690 through one or more image injection devices 360, 370, 380, 390, 400 ( Figure 6 ).

[0136] In some embodiments, light rays 770, 780, 790 have different characteristics, e.g., different wavelengths or different wavelength ranges corresponding to different colors. Each of the light-coupling optical elements 700, 710, 720 deflects the incident light such that the light propagates through the respective waveguides in waveguides 670, 680, 690 by TIR. In some embodiments, each of the light-coupling optical elements 700, 710, 720 selectively deflects one or more specific wavelengths of light while transmitting other wavelengths to the underlying waveguide and the associated light-coupling optical element.

[0137] For example, the light-coupling optical element 700 can be configured to deflect light ray 770 having a first wavelength or wavelength range while transmitting light rays 780 and 790 having different second and third wavelengths or wavelength ranges, respectively. The transmitted light ray 780 is incident on the light-coupling optical element 710 and is deflected by the light-coupling optical element 710, which is configured to deflect light of the second wavelength or wavelength range. The light ray 790 is deflected by the light-coupling optical element 720, which is configured to selectively deflect light of the third wavelength or wavelength range.

[0138] Continuing to refer to Figure 9A, the deflected light rays 770, 780, 790 are deflected such that they propagate through the corresponding waveguides 670, 680, 690; that is, the light-coupling optical elements 700, 710, 720 of each waveguide deflect light into the corresponding waveguide 670, 680, 690 to couple the light into the corresponding waveguide. The light rays 770, 780, 790 are deflected at an angle such that the light propagates through the respective waveguides 670, 680, 690 by TIR. The light rays 770, 780, 790 propagate by TIR through the respective waveguides 670, 680, 690 until they are incident on the corresponding light distribution elements 730, 740, 750 of the waveguides.

[0139] Now referring to Figure 9B , a perspective view of an example of a stacked waveguide of Figure 9A is shown. As described above, the coupled-in light rays 770, 780, 790 are respectively deflected by the light-coupling optical elements 700, 710, 720 and then propagate through the waveguides 670, 680, 690 by TIR, respectively. The light rays 770, 780, 790 are then respectively incident on the light distribution elements 730, 740, 750. The light distribution elements 730, 740, 750 deflect the light rays 770, 780, 790 such that they propagate respectively towards the light-coupling-out optical elements 800, 810, 820.

[0140] In some embodiments, the light distribution elements 730, 740, 750 are orthogonal pupil expanders (OPEs). In some embodiments, the OPE deflects or distributes the light to the light-coupling-out optical elements 800, 810, 820, and in some embodiments, the beam size or spot size of the light can also be increased as the light propagates to the light-coupling-out optical elements. In some embodiments, the light distribution elements 730, 740, 750 can be omitted and the light-coupling optical elements 700, 710, 720 can be configured to deflect the light directly to the light-coupling-out optical elements 800, 810, 820. For example, referring to Figure 9A , the light distribution elements 730, 740, 750 can be respectively replaced by the light-coupling-out optical elements 800, 810, 820. In some embodiments, the light-coupling-out optical elements 800, 810, 820 are exit pupils (EPs) or exit pupil expanders (EPEs) that guide the light to the viewer's eyes 210 ( Figure 7)。It will be understood that the OPE can be configured to increase the size of the eye box on at least one axis, and the EPE can increase the eye box on an axis that crosses (e.g., is orthogonal to) the axis of the OPE. For example, each OPE can be configured to redirect a portion of the light impinging on the OPE to the EPE of the same waveguide while allowing the remaining portion of the light to continue propagating downward along the waveguide. When the remaining light impinges on the OPE again, another portion of the remaining light is redirected to the EPE, and the remaining portion of that portion continues to propagate further downward along the waveguide, and so on. Similarly, when impinging on the EPE, a portion of the incident light is guided out of the waveguide towards the user, and the remaining portion of the light continues to propagate through the waveguide until it impinges on the EP again, at which time another portion of the incident light is guided out of the waveguide, and so on. Thus, a single beam of coupled-in light can be "copied" each time a portion of the light is redirected by the OPE or the EPE, thereby forming a field of cloned beams, as Figure 6 shown. In some embodiments, the OPE and / or the EPE can be configured to modify the size of the light beam.

[0141] Accordingly, referring to Figure 9A and 9B, in some embodiments, the set of waveguides 660 includes waveguides 670, 680, 690 for each component color; light-coupling optical elements 700, 710, 720; light distribution elements (e.g., OPE) 730, 740, 750; and light-extracting optical elements (e.g., EPE) 800, 810, 820. The waveguides 670, 680, 690 may be stacked with a gap / cladding between each one. The light-coupling optical elements 700, 710, 720 redirect or deflect incident light (wherein different light-coupling optical elements receive light of different wavelengths) into their respective waveguides. The light then propagates at an angle that will result in TIR within the respective waveguides 670, 680, 690. In the example shown, the light ray 770 (e.g., blue light) is deflected by the first light-coupling optical element 700 in the previously described manner and then continues to bounce downward along the waveguide, interacting with the light distribution element (e.g., OPE) 730 and then the light-extracting optical element (e.g., EP) 800. The light rays 780 and 790 (e.g., green light and red light, respectively) will pass through the waveguide 670, wherein the light ray 780 is incident on the light-coupling optical element 710 and is deflected by the light-coupling optical element 710. The light ray 780 then bounces downward along the waveguide 680 via TIR, continues to its light distribution element (e.g., OPE) 740 and then to the light-extracting optical element (e.g., EP) 810. Finally, the light ray 790 (e.g., red light) passes through the waveguide 690 to be incident on the light-coupling optical element 720 of the waveguide 690. The light-coupling optical element 720 deflects the light ray 790 such that the light ray propagates to the light distribution element (e.g., OPE) 750 via TIR and then propagates to the light-extracting optical element (e.g., EP) 820 via TIR. Then, the light-extracting optical element 820 finally extracts the light ray 790 to the viewer, who also receives the extracted light from the other waveguides 670, 680.

[0142] Figure 9C Shows Figure 9A And Figure 9B A top plan view of an example of a stacked waveguide. As illustrated, the waveguides 670, 680, 690 together with the associated light distribution elements 730, 740, 750 and the associated light-extracting optical elements 800, 810, 820 of each waveguide may be vertically aligned. However, as discussed herein, the light-coupling optical elements 700, 710, 720 are not vertically aligned; rather, the light-coupling optical elements are preferably non-overlapping (e.g., laterally spaced apart as seen in the top view). As further discussed herein, this non-overlapping spatial arrangement facilitates injecting light from different sources into different waveguides on a one-to-one basis, thereby allowing a specific light source to be uniquely coupled to a specific waveguide. In some embodiments, an arrangement including non-overlapping spatially separated light-coupling optical elements may be referred to as an offset pupil system, and the light-coupling optical elements within these arrangements may correspond to sub-pupils.

[0143] Figure 9D illustrates an example of a wearable display system 60 into which various waveguides and related systems disclosed herein can be integrated. In some embodiments, the display system 60 is Figure 6 system 250, wherein Figure 6 some components of the system 60 are shown schematically in more detail. For example, Figure 6 the waveguide assembly 260 can be part of the display 70.

[0144] Continuing to refer to Figure 9D , the display system 60 includes a display 70 and various mechanical and electronic modules and systems that support the functions of the display 70. The display 70 can be coupled to a frame 80 that can be worn by a user or viewer 90 of the display system and is configured to position the display 70 in front of the eyes of the user 90. In some embodiments, the display 70 can be considered glasses. In some embodiments, a speaker 100 is coupled to the frame 80 and is configured to be located near the ear canal of the user 90 (in some embodiments, another speaker, not shown, can optionally be located near the other ear canal of the user to provide stereo / plastic sound control). The display system 60 can also include one or more microphones 110 or other devices to detect sound. In some embodiments, the 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 can allow audio communication with other people (e.g., other users of a similar display system). The microphones can also be configured as peripheral sensors to collect audio data (e.g., sounds from the user and / or the environment). In some embodiments, the display system 60 can also include one or more outwardly directed environmental sensors 112 that are configured to detect objects, stimuli, people, animals, locations, or other aspects of the world around the user. For example, the environmental sensors 112 can include one or more cameras that can be positioned, for example, facing outward to capture images similar to at least a portion of the normal field of view of the user 90. In some embodiments, the display system can also include a peripheral sensor 120a that can be separated from the frame 80 and attached to the body of the user 90 (e.g., on the head, torso, limb, etc. of the user 90). In some embodiments, the peripheral sensor 120a can be configured to capture data characterizing the physiological state of the user 90. For example, the sensor 120a can be an electrode.

[0145] Continuing to refer to Figure 9D, the display 70 is operably coupled to the local data processing module 140 via a communication link 130 (such as via a wired lead or a wireless connection). The local data processing module 140 can be installed in various configurations, such as fixedly attached to the frame 80, fixedly attached to a helmet or hat worn by the user, embedded in a headset, or detachably attached to the user 90 (e.g., in a backpack configuration, in a belt-coupled configuration). Similarly, the sensor 120a can be operably coupled to the local processor and data module 140 via a communication link 120b (e.g., a wired lead or a wireless connection). The local processing and data module 140 can include a hardware processor and a digital memory such as a non-volatile memory (e.g., flash memory or a hard disk drive), both of which can be used to assist in processing, caching, and storing data. Optionally, the local processor and data module 140 can include one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, etc. The data can include: a) data captured from sensors (e.g., the sensor can be operably coupled to the frame 80 or otherwise attached to the user 90), such as an image capture device (such as a camera), a microphone, an inertial measurement unit, an accelerometer, a compass, a GPS unit, a radio device, a gyroscope, and / or other sensors disclosed herein; and / or b) data obtained and / or processed using the remote processing module 150 and / or the remote data repository 160 (including data related to virtual content), which can be transmitted to the display 70 after such processing or retrieval. The local processing and data module 140 can be operably coupled to the remote processing module 150 and the remote data repository 160 via communication links 170, 180 (such as via wired or wireless communication links), such that these remote modules 150, 160 are operably coupled to each other and can be used as resources for the local processing and data module 140. In some embodiments, the local processing and data module 140 can include one or more of an image capture device, a microphone, an inertial measurement unit, an accelerometer, a compass, a GPS unit, a radio device, and / or a gyroscope. In some other embodiments, one or more of these sensors can be attached to the frame 80, or can be an independent structure that communicates with the local processing and data module 140 via a wired or wireless communication path.

[0146] Continuing reference Figure 9D, in some embodiments, the remote processing module 150 may include one or more processors configured to analyze and process data and / or image information, such as one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, etc. In some embodiments, the remote data repository 160 may include a digital data storage facility, which may be available via the Internet or other network configurations in a "cloud" resource configuration. In some embodiments, the remote data repository 160 may include one or more remote servers that provide information to the local processing and data module 140 and / or the remote processing module 150, e.g., information for generating augmented reality content. In some embodiments, all data is stored and all computations are performed in the local processing and data module, allowing for fully autonomous use from the remote module. Alternatively, an external system including a CPU, GPU, etc. (e.g., a system having one or more processors, one or more computers) may perform at least a portion of the processing (e.g., generating image information, processing data) and provide information to and receive information from modules 140, 150, 160, e.g., via a wireless or wired connection.

[0147] Figure 10 is a schematic diagram showing the projector assembly 1000, which uses a polarization beam splitter (PBS) 1020 to illuminate a spatial light modulator (SLM) 1030 and redirect light from the SLM 1030 through projection optics 1040 to an eyepiece (not shown). The projector assembly 1000 includes an illumination source 1010, which may include, for example, a light emitting diode (LED), a laser (e.g., a laser diode), or other types of light sources. The light may be collimated by collimating optics. The illumination source 1010 may emit polarized, unpolarized, or partially polarized light. In the illustrated design, the illumination source 1010 may emit polarized light 1012 having p-polarization. The first optical element 1015 (e.g., a pre-polarizer) is aligned to allow light having a first polarization (e.g., p-polarization) to pass through.

[0148] The light is directed to a polarization beam splitter 1020. Initially, the light passes through an interface 1022 (e.g., a polarization interface) of the PBS 1020, which is configured to transmit light of a first polarization (e.g., p-polarization). Thus, the light advances to and impinges on a spatial light modulator 1030. As illustrated, the SLM 1030 is a reflective SLM, which is configured to retroreflect incident light and selectively modulate the light. For example, the SLM 1030 includes one or more pixels that can have different states. The light incident on a corresponding pixel can be modulated based on the state of the pixel. Thus, the SLM 1030 can be driven to modulate the light to provide an image. In this example, the SLM 1030 can be a polarization-based SLM that modulates the polarization of the light incident thereon. For example, in an on state, a pixel of the SLM 1030 changes the input light from a first polarization state (e.g., p-polarization state) to a second polarization state (e.g., s-polarization state), such that a bright state (e.g., a white pixel) is displayed. The second polarization state can be a 90° modulation (e.g., rotation) of the first polarization state. In the on state, the light having the second polarization state is reflected by the interface 1022 and propagates downstream to the projector optics 1040. In an off state, the SLM 1030 does not change the polarization state of the light incident thereon, e.g., does not rotate the input light from the first polarization state, and thus a dark state (e.g., a black pixel) is displayed. In the off state, the light having the first polarization state is transmitted through the interface 1022 and propagates upstream back to the illumination source 1010 instead of the user's eye.

[0149] After reflection from the SLM 1030, a portion of the light 1014 (e.g., the modulated light) is reflected from the interface 1022 and exits the PBS 1020 to be directed to the user's eye. The emitted light passes through the projector optics 1040 and is imaged onto an input coupling grating (ICG) 1050 of an eyepiece (not shown).

[0150] Figure 11A A system (e.g., an augmented reality display system) 1100A is shown for presenting an image to a user's eye 210 and for viewing the world 510, which has Figure 10Configurations different from those shown in the figure. System 1100 includes a light source 1110, a spatial light modulator (SLM) 1140, and a waveguide 1120 (also referred to as an eyepiece waveguide), which are arranged such that light from the light source 1110 irradiates the SLM 1140, and the light reflected from the SLM 1140 is coupled into the waveguide 1120 to be guided to the eye 210. System 1100A includes an optical device 1130, which is arranged to both irradiate the SLM 1140 and project an image of the SLM 1140. Light from the light source 1110 propagates through the optical device 1130 in a first direction, for example, to irradiate the SLM 1140. The light reflected from the SLM 1140 propagates through the optical device 1130 again in a second direction opposite to the first direction and is guided to the waveguide 1120 and coupled therein.

[0151] The light source 1110 may include a light emitting diode (LED), a laser (e.g., a laser diode), or other types of light sources. The light source 1110 may be a polarized light source, although the light source 1110 need not be so limited. In some embodiments, a polarizer 1115 may be positioned between the light source 1110 and the SLM 1140. As illustrated, the polarizer 1115 is located between the light source 1110 and the waveguide 1120. This polarizer 1115 may also be a light recycler, transmitting light of a first polarization and reflecting light of a second polarization back to the light source 1110. Such a polarizer 1115 may be, for example, a wire grid polarizer. A coupling optical device 1105 (such as a non-imaging optical element (e.g., a cone, a compound parabolic concentrator (CPC), a lens)) may be disposed relative to the light source 1110 to receive the light output from the light source 1110. The coupling optical device 1105 may collect the light from the light source 1110 and, in some cases, reduce the divergence of the light emitted from the light source 1110. The coupling optical device 1105 may, for example, collimate the light output from the light source 1110. The coupling optical device 1105 may collect light that matches the angular spectrum field of view of the system 1100A. Thus, the coupling optical device 1105 may match the angular spectrum of the light output by the light source 1110 to the field of view of the system 1100A. The coupling optical device 1105 may have an asymmetric profile to operate the light emitted from the light source 1110 asymmetrically. For example, the coupling optical device 1105 may reduce the divergence to different amounts in orthogonal directions (e.g., the x and z directions). Such an asymmetry in the coupling optical device 1105 may address the asymmetry of the light emitted from the light source 1110, which may include, for example, a laser diode that emits a wider range of light angles in one direction (e.g., x or z) than in the orthogonal direction (e.g., z or x, respectively).

[0152] As discussed above, system 1100A includes optics 1130 configured to illuminate SLM 1140, which is disposed in the optical path between light source 1110 and SLM 1140. Optics 1130 may include transmissive optics that transmit light from light source 1110 to SLM 1140. Optics 1130 may also be configured to project an image of SLM 1140 or an image formed by SLM 1140 into waveguide 1120. The image may be projected into the eye of eye 210. In some designs, optics 1130 may include one or more lenses or optical elements having a focal power. Optics 1130 may, for example, have a positive focal power. Optics 1130 may include one or more refractive optical elements, such as refractive lenses. Other types of optical elements may also be used.

[0153] SLM 1140 may be reflective, modulate, and reflect light therefrom. SLM 1140 may be a polarization-based SLM configured to modulate polarization. SLM 1140 may, for example, include a liquid crystal (LC) SLM (e.g., a liquid crystal on silicon (LCoS) SLM). The LC SLM may, for example, include twisted nematic (TN) liquid crystal. SLM 1140 may be substantially similar to SLM 1030 of reference Figure 10 . SLM 1140 may, for example, include one or more pixels configured to selectively modulate light incident on the pixel depending on the state of the pixel. For some types of SLM 1140, the pixel may modulate the light beam incident thereon, for example, by changing the polarization state (such as rotating the polarization (e.g., rotating the orientation of linearly polarized light)).

[0154] As discussed above, SLM 1140 may be an LCoS SLM 1140. In a cross-polarizer configuration, the LCoS SLM 1140 may be nominally white. When the pixel is off (e.g., 0 volts), it has a bright state, and when the pixel is on (e.g., a voltage higher than the threshold turn-on voltage), it has a dark state. In this cross-polarization configuration, leakage is minimized when the pixel is on and has a dark state.

[0155] In a parallel-polarizer configuration, the LCoS SLM 1140 is nominally black. When the pixel is off (e.g., 0 volts), it has a dark state, and when the pixel is on (e.g., a voltage higher than the threshold turn-on voltage), it has a bright state. In this parallel-polarizer configuration, leakage is minimized when the pixel is off and has a dark state. The rubbing direction and compensator angle may be used to (re)optimize the dark state. The compensator angle may refer to the angle of a compensator that may be located between optics 1130 and SLM 1140, e.g., as shown in Figure 20B as.

[0156] The dynamic range and throughput of a parallel polarizer configuration can be different from that of a crossed polarizer configuration. Additionally, the parallel polarizer configuration can be optimized differently for contrast than the crossed polarizer configuration.

[0157] System 1100A includes a waveguide 1120 for outputting image information to an eye 210. The waveguide 1120 can be substantially similar to the waveguides 270, 280, 290, 300, 310, 670, 680, and 690 discussed above. The waveguide 1120 can include a substantially transparent material having a refractive index sufficient to guide light therein. As illustrated, the waveguide 1120 can include a first side 1121 and a second side 1123 opposite the first side 1121, as well as corresponding upper and lower major surfaces and surrounding edges. The first major surface 1121 and the second major surface 1123 can be sufficiently flat such that image information can be retained as light propagates from the SLM 1140 to the eye 210, such that an image formed by the SLM 1140 can be injected into the eye. The optical device 1130 and the SLM 1140 can be positioned on the first side 1121 of the waveguide 1120. The light source 1110 can be disposed on the second side 1123 such that light from the light source 1110 is incident on the second side 1123 before passing through the waveguide 1120 and through the optical device 1130 to reach the SLM 1140. Thus, the waveguide 1120 can be disposed between the light source 1110 and the optical device 1130. Additionally, at least a portion of the waveguide 1120 can extend between the light source 1110 and the optical device 1130 such that light passes through that portion of the waveguide 1120 to reach the optical device 1130. Thus, light emitted from the light source 1110 can be guided through the waveguide 1120, into the optical device 1130 and through the optical device 1130, and incident on the SLM 1140. The SLM 1140 reflects the light back through the optical device 1130 and to the waveguide 1120.

[0158] System 1100A further includes an input optical element 1160 for coupling light from the optical device 1130 into the waveguide 1120. The input optical element 1160 can be disposed on a major surface (e.g., the upper major surface 1123) of the waveguide 1120. In some designs, the input optical element 1160 can be disposed on the lower major surface 1121 of the waveguide 1120. In some designs, the input optical element 1160 can be disposed within the body of the waveguide 1120. Although the input optical element 1160 is shown on one side or a corner of the waveguide 1120, the input optical element 1160 can be disposed in / on other regions of the waveguide 1120. The input optical element 1160 can be similar to that referenced above Figure 9A 、 9BThe coupling optical elements 700, 710, and 720 described in 9C are substantially similar. The coupling optical element 1160 can be a diffractive optical element or a reflector. Other structures can be used as the coupling optical element 1160. The coupling optical element 1160 can be configured to guide light incident thereon into the waveguide 1120 at a grazing angle (e.g., greater than the critical angle) with respect to the upper major surface 1123 and the lower major surface 1121 of the waveguide 1120 large enough to be guided in the waveguide 1120 by total internal reflection. In addition, the coupling optical element 1160 can operate over a wide wavelength range and can thus be configured to couple light of multiple colors into the waveguide 1120. For example, the coupling optical element 1160 can be configured to couple red, green, and blue light into the waveguide 1120. The light source 1110 can emit red, green, and blue light at different times.

[0159] The system 1100A includes a light distribution element 1170 disposed on or in the waveguide 1120. The light distribution element 1170 can be substantially similar to the light distribution elements 730, 740, and 750 described above with respect to Figure 9B . For example, the light distribution element 1170 can be an ortho-pupil expander (OPE). The light distribution element 1170 can be configured to spread light within the waveguide 1120 by turning light propagating in the x direction, for example, toward the z direction as shown in the top view Figure 11B . Thus, the light distribution element 1170 can be configured to increase the size of the eye box along the z axis; see Figure 11B . For example, the light distribution element 1170 can include one or more diffractive optical elements configured to diffract light incident on the diffractive optical element propagating within the waveguide 1120 so as to redirect the light in a direction, for example, substantially orthogonal. Other configurations are possible.

[0160] As Figure 11B shown, the system 1100 can also include a coupling-out optical element 1180 for coupling light from the waveguide 1120 to the eye 210. The coupling-out optical element 1180 can be configured to redirect light propagating within the waveguide 1120 by total internal reflection (TIR) to an angle more perpendicular to the upper major surface 1123 and / or the lower major surface 1121 of the waveguide 1120 such that the light is not guided within the waveguide 1120. Instead, the light is guided out of the waveguide 1120 through, for example, the lower major surface 1121. The coupling-out optical element 1180 can, for example, include one or more diffractive optical elements configured to diffract light incident on the diffractive optical element propagating within the waveguide 1120 so as to, for example, redirect the light out of the waveguide 1120. Other configurations are possible.

[0161] Figure 11BThe position of the light-incoupling optical element 1160, which is laterally disposed with respect to the light distribution optical element (e.g., an orthogonal pupil expander) 1170 and the light-extracting optical element 1180, is also shown. Figure 11B The position of the light source 1110, which is laterally disposed with respect to the light-incoupling optical element 1160, the light distribution optical element (e.g., an orthogonal pupil expander) 1170, and the light-extracting optical element 1180, is also shown.

[0162] In operation, the light source 1110 of system 1100A emits light into the coupling optics 1105 and through the polarizer 1115. Thus, the light can be polarized, e.g., linearly polarized in a first direction. The polarized light can pass through the waveguide 1120, enter the second major surface of the waveguide 1120 and exit from the first major surface of the waveguide 1120. The light can propagate through the optics 1130 to reach the SLM 1140. The optics 1130 collimates and / or selects the light from the light source 1110 so as to illuminate the SLM 1140, which can include a polarization-based modulator that modulates the polarization of the light incident thereon, such as by selectively rotating the orientation of the modulator pixel-by-pixel depending on the state of the pixel. For example, a first pixel can be in a first state and rotate the polarization, while a second pixel can be in a second state but not rotate the polarization. The light between the coupling optics 1105 and the optics 1130 can illuminate the SLM 1140 rather uniformly. After being incident on the SLM 1140, the light is reflected back through the optics 1130. The optics 1130 can be configured to project the image from the SLM 1140 into the waveguide 1120 and ultimately into the eye 210 such that the image is visible to the eye 210. In some designs, the retina of the eye 210 is the optical conjugate of the SLM 1140 and / or of the image formed by and / or on the SLM 1140. The focal power of the optics 1130 can facilitate projecting the image on the SLM 1140 into the eye 210 and onto the retina of the eye 210. In some embodiments, the optical power provided, e.g., by the decoupling optical element 1180, can contribute to and / or affect the image ultimately formed in the eye 210. As the light reflected from the SLM 1140 travels through the optics towards the waveguide 1120, the optics 1130 acts as a projection lens. The optics can roughly serve as a Fourier transform of the image on the SLM 1140 to a plane in the waveguide 1120 near the coupling optical element 1160. The total of two passes through the optics 1130 (first from the light source 1110 to the SLM 1140 and second from the SLM 1140 to the waveguide 1120) can together roughly image the pupil of the coupling optics 1105. The alignment and orientation of the light source 1110 (and possibly also the coupling optics 1105 and / or the polarizer 1115), the optics 1130, and the SLM 1140 are such that the light from the light source 1110 reflected from the SLM 1140 is directed onto the coupling optical element 1160. The pupil associated with the coupling optics 1105 can be aligned with the coupling optical element 1160. The light can pass through an analyzer 1150 (e.g., a polarizer) in the optical path between the SLM 1140 and the eye 210. As Figure 11AAs shown, an analyzer (e.g., a polarizer) 1150 can be disposed in the optical path between the optical device 1130 and the optical coupling element 1160. The analyzer 1150 can be, for example, a linear polarizer having an orientation that transmits light of a first polarization (p-polarization) and blocks light of a second polarization (s-polarization), and vice versa. The analyzer 1150 can be a clean polarizer and further blocks polarized light blocked by another polarizer between the SLM 1140 and the analyzer 1150 or within the SLM 1140. The analyzer 1150 can be, for example, a circular polarizer that acts as an isolator to reduce reflections that are reflected back from the waveguide 1120 (specifically, the optical coupling element 1160) to the SLM 1140. Like any polarizer disclosed herein, the analyzer 1150 can include a wire grid polarizer, such as an absorptive wire grid polarizer. Such polarizers can significantly absorb unwanted light and thereby increase the contrast. Some such polarizers can be made to include one or more dielectric layers on top of the wires and / or multilayer films. In some embodiments, the SLM 1140 can be a liquid crystal on silicon (LCoS) SLM and can include LC cells and retarders (e.g., compensators). In some embodiments, the analyzer 1150 can be a compensator that is designed to provide a more consistent polarization rotation (e.g., 90°) of the SLM 1140 for different angles of incidence and different wavelengths. The compensator can be used to improve the contrast of the display by improving the rotation of polarized light incident across an angular and wavelength range. The SLM 1140 can include, for example, a TN LCoS that is configured to rotate incident light of a first polarization (e.g., s-polarization) to a second polarization (e.g., p-polarization) for a first pixel to create a bright pixel state when the light will pass through the analyzer 1150. Conversely, the SLM 1140 can be configured not to rotate incident light of the first polarization (e.g., s-polarization) to the second polarization (e.g., p-polarization) for a second pixel such that the reflected light remains in the first polarization to create a dark pixel state when the light will be attenuated or blocked by the analyzer 1150. In such a configuration, the polarizer 1115 closer to the light source 1110 along the optical path can be oriented differently (e.g., orthogonally) from the analyzer 1150 farther from the light source 1110 along the optical path. Other (e.g., opposite) configurations are possible.

[0163] Then, the light is deflected, e.g., redirected by the optical coupling element 1160, so as to be guided in the waveguide 1120, where the light propagates by TIR. Then, the light impinges on the light distribution element 1170, redirecting the light in another direction (e.g., more towards the z-direction), resulting in an increase in the size of the eye box along the z-axis direction, as Figure 11B shown. Thus, the light is redirected towards the optical coupling-out element 1180, which causes the light to be directed out of the waveguide 1120 towards the eye 210 (e.g., the user's eye as shown). The light is coupled out along the z-direction by different portions of the optical coupling-out element 1180, resulting in an eye box size along at leastFigure 11B increases in a direction parallel to the z-axis defined in. It is noted that in this configuration, the optical device 1130 is used both to illuminate the SLM 1140 and to project an image onto the coupled-in optical element 1160. Thus, the optical device 1130 can act as a projection optical device to distribute the light from the light source 1110 (e.g., uniformly), and act as an imaging optical device to provide the image of the SLM 1140 and / or the image formed by the SLM 1140 into the eye. Figure 11A The system 1100A in / B may be more compact than Figure 10 the system 1000 in some cases. In some cases, not using Figure 10 the PBS1020 shown in may reduce the cost and / or size of the system. Additionally, in the absence of the PBS1020, the system can be more symmetric and easier to design by shortening the back focal length of the optical device 1130.

[0164] As described above, alternative configurations are possible. Referring to Figure 11C , for example, in some designs, the system 1100C can be configured to allow light with a polarization that is not rotated by the SLM 1140 to pass through. In one embodiment, for example, the SLM 1140 is a liquid crystal (LC)-based SLM and can include vertically aligned (VA) liquid crystal on silicon (LCoS). The SLM 1140 can have a first pixel in a first state that does not rotate polarization and a second pixel in a second state that rotates polarization. In Figure 11C the configuration shown in, a single shared analyzer / polarizer 1155 is utilized. The analyzer 1155 can transmit light of a first polarization (e.g., s-polarization) and attenuate or reduce the transmission of a second polarization (e.g., p-polarization). Thus, light (e.g., s-polarized light) incident on the first pixel in the first state that does not rotate polarization orientation is reflected from the SLM 1140 and passes through the analyzer 1155 to reach the waveguide 1120. In contrast, light (e.g., s-polarized light) incident on the second pixel in the second state that rotates polarization orientation is reflected from the SLM1140 and is attenuated, reduced, or does not pass through the analyzer 1155 to reach the waveguide 1120. This configuration can thus allow Figure 11A the polarizer 1115 and the analyzer 1150 shown in to be combined into a shared optical element ( Figure 11C the analyzer 1155 shown in), thereby potentially simplifying Figure 11A the system 1100 in / B by reducing the number of optical components. The analyzer 1155 can be disposed between the waveguide 1120 and the optical device 1130. In other embodiments, separate analyzer / polarizers and analyzer / polarizers can be used, such as Figure 11A shown in the system 1100 in / B. Figure 11A and 11BA polarizer 1115 is shown between the light source 1110 and the waveguide 1120, and an analyzer SLM 1140 is shown between the optical device 1130 and the waveguide 1120.

[0165] Figure 11D An example of a waveguide with combined OPE / EPE according to an embodiment of the present invention is shown. Referring to Figure 11D , the waveguide 1190 with the combined OPE / EPE region 1191 includes gratings corresponding to the OPE and EPE that are spatially overlapped in the x and y directions. In some embodiments, the gratings corresponding to the OPE and EPE are located on the same side of the substrate such that the OPE grating is superimposed on the EPE grating, or the EPE grating is superimposed on the OPE grating (or both). In other embodiments, the OPE grating is located on the opposite side of the substrate from the EPE grating such that the gratings are spatially overlapped in the x and y directions but are separated from each other in the z direction (i.e., in different planes). Thus, the combined OPE / EPE region 1191 can be implemented in a single-sided configuration or a double-sided configuration.

[0166] The optical path within the eyepiece waveguide 1190 includes incident light 1194 that is coupled into the eyepiece waveguide 1190 at the ICG 1193. The incident light propagates through total internal reflection in the substrate 1192 towards the combined OPE / EPE 1191. When these light rays encounter the combined OPE / EPE 1191 (also referred to as the combined pupil expander (CPE)), the light diffracts in the +y direction and then diffracts out of the waveguide along the optical path 1195 in the -z direction towards the user's eye. Similarly, the coupled-in light alternatively encounters the combined OPE / EPE 1191 and diffracts in the -y direction and then diffracts out of the waveguide along the optical path 1195 towards the user's eye.

[0167] As described in more detail herein, embodiments of the present invention utilize an eyepiece waveguide having a difference in optical path length, e.g., the thickness of the eyepiece waveguide varies according to the lateral position (i.e., the position in the x-y plane). In some embodiments, the portion of the eyepiece waveguide that forms the ICG is thicker than the portion that forms the CPE. Additionally, in some embodiments, the thickness of the CPE is different, with the portion adjacent to the ICG being thicker than the portion farther from the ICG. In other embodiments, the physical thickness is uniform, but the refractive index varies according to the lateral position, resulting in a variation in the optical path length difference characterizing the eyepiece waveguide according to the lateral position.

[0168] Various other configurations can be employed that utilize the optical device 1130 to illuminate the SLM 1140 and image the image formed by the SLM 1140. For example, although Figures 11A - 11DA single waveguide 1120 is shown, but one or more waveguides may be used, such as a waveguide stack (possibly using different waveguides for different colors of light).

[0169] For example, Figure 12A A cross-sectional side view of an example system 1200A is shown, which includes a stack 1205 that includes waveguides 1120, 1122, 1124, each waveguide including an optical coupling element 1260, 1262, 1264. Waveguides 1120, 1122, 1124 may each be configured to output one or more different wavelengths of light, or one or more different wavelength ranges of light. Stack 1205 may be substantially similar to stacks 260 and 660 ( Figure 6 and 9A ), and the shown waveguides 1120, 1122, 1124 of stack 1205 may correspond to a portion of waveguides 670, 680, 690. However, stack 1205 and waveguides 1120, 1122, 1124 need not be so limited. As Figure 12A shown, optical coupling elements 1260, 1262, 1264 may be associated with, included in, or on waveguides 1120, 1122, 1124, respectively. Optical coupling elements 1260, 1262, 1264 may be color selective and may primarily transfer or redirect certain wavelengths into the corresponding waveguides 1120, 1122, 1124 for guiding therein. As shown, since optical coupling elements 1260, 1262, 1264 are color selective, optical coupling elements 1260, 1262, 1264 do not need to be laterally shifted and may be stacked on top of each other. Wavelength multiplexing may be employed to couple a specific color into the corresponding waveguide. For example, a red optical coupling element may couple red light into a waveguide designated for propagating red light without coupling blue or green light, which is coupled into other waveguides by other blue and green selective waveguides, respectively.

[0170] In some embodiments, the light source 1110 can be a multi-color light source capable of emitting light of different colors at different times. For example, the light source 1110 can emit red, green, and blue (RGB) light and can be configured to emit red light and no more than a negligible amount of green and blue light during a first time period, green light and no more than a negligible amount of red and blue light during a second time period, and blue light and no more than a negligible amount of red and green light during a third time period. These cycles can be repeated, and the SLM 1140 can be coordinated to generate a suitable pixel state pattern for a particular color (red, green, or blue) to provide an appropriate image color component for a given image frame. The different waveguides 1120, 1122, 1124 of the stack 1205 can each be configured to output light having a different corresponding color. For example, as Figure 12A shown, the waveguides 1120, 1122, 1124 can be configured to output blue, green, and red light, respectively. Of course, other colors are possible. For example, the light source 1110 can emit other colors, and the color-selective coupling-in optical elements 1260, 1262, 1264, the coupling-out optical elements, etc. can be configured for such other colors. Additionally, separate red, green, and blue emitters can be positioned close enough to effectively serve as a single pupil light source. The red, green, and blue emitters can be combined with lenses and dichroic beam splitters to form a single red, green, and blue pupil source. The multiplexing of a single pupil can extend beyond or be complementary to color selectivity and can include the use of polarization-sensitive gratings and polarization switches. These color or polarization gratings can also be used in combination with multiple display pupils to increase the number of addressable layers.

[0171] The different coupling-in optical elements 1260, 1262, 1264 in the different waveguides 1120, 1122, 1124 can be arranged above and / or below each other and laterally aligned with respect to each other (e.g., in Figure 12Ain the x- and z-directions shown), rather than being laterally shifted relative to each other and misaligned. Thus, in some embodiments, for example, the different light-coupling optical elements 1260, 1262, 1264 may be configured such that light of a first color may be coupled by the light-coupling optical element 1260 into the waveguide 1120 and guided therein, while light of a second color different from the first color may pass through the light-coupling optical element 1260 to the next light-coupling optical element 1262 and may be coupled by the light-coupling optical element 1262 into the waveguide 1122 and guided therein. Light of a third color different from the first and second colors may pass through the light-coupling optical elements 1260 and 1262 to the light-coupling optical element 1264 and may be coupled into the waveguide 1124 and guided therein. Additionally, the light-coupling optical elements 1260, 1262, 1264 may be polarization selective. For example, the different light-coupling optical elements 1260, 1262, 1264 may be configured such that light of a particular polarization is either coupled into the waveguide by the corresponding polarization-selective light-coupling optical element 1260, 1262, 1264 or passes through the light-coupling optical elements 1260, 1262, 1264.

[0172] Depending on the configuration, the SLM 1140 may include a polarization-based SLM that modulates polarization. The system 1200A may include a polarizer and / or an analyzer to modulate the light injected into the stack 1205 pixel by pixel, for example depending on the state of the respective pixel (e.g., whether the pixel rotates the polarization orientation). Various aspects of such systems employing a polarization-based SLM have been discussed above, and any one of such features may be used in combination with any other features described herein. However, other designs are still possible.

[0173] For example, a deflection-based SLM 1140 may be employed. For example, the SLM 1140 may include one or more movable optical elements, such as movable mirrors, that may reflect and / or deflect light in different directions depending on the state of the optical element. The SLM 1140 may include, for example, one or more pixels that include optical elements such as micromirrors or reflectors. The SLM 1140 may incorporate, for example, digital light processing (DLP TM ) technology using a digital micromirror device (DMD). Figure 12BAn example of a system 1200B using such a deflection-based SLM 1140 is shown. The system 1200B includes a deflection-based SLM 1140 and a light dump 1250. The light dump 1250 may include an absorbing material or structure configured to absorb light. The deflection-based SLM 1140 may include one or more micro-movable mirrors that can be selectively tilted to deflect light in different directions. For example, the deflection-based SLM 1140 can be configured to deflect light from the light source 1110 incident thereon to the coupling optical elements 1260, 1262, 1264 when a given pixel is in the bright state. As discussed above, depending on the color of the light, for example, the light will thus be coupled by one of the coupling optical elements 1260, 1262, 1264 into one of the corresponding waveguides 1120, 1122, 1124 and guided to the eye 210. Conversely, when a given pixel is in the dark state, the light from the light source 1110 can be deflected to the light dump 1250, and the light will not be coupled by one of the coupling optical elements 1260, 1262, 1264 into one of the corresponding waveguides 1120, 1122, 1124 and guided to the eye 210. Instead, the light may be absorbed by the absorbing material including the light dump 1250. In some embodiments, the analyzer 1150 can be a polarizer (e.g., a "cleaning" polarizer) that is used to eliminate unwanted reflections from the coupling optical elements 1260, 1262, 1264. Since the optical device 1130 may include plastic optical elements having birefringence and can change polarization, this polarizer may be useful. The "cleaning" polarizer can attenuate or remove light (e.g., reflections) having unwanted polarization so that it is not guided onto the waveguides 1120, 1122, 1124. Other types of light conditioning elements can be disposed between the SLM 1140 and the waveguides 1120, 1122, 1124, such as between the optical device 1130 and the waveguides 1120, 1122, 1124. For example, such light conditioning elements can also include circular polarizers (i.e., linear polarizers and retarders, such as quarter-wave plates). The circular polarizer can reduce the amount of reflection from the waveguides 1120, 1122, 1124 or the coupling optical elements 1260, 1262, 1264 that is incident again onto the waveguides 1120, 1122, 1124 and coupled therein. The reflected light can be circularly polarized and can have a circular polarization opposite to that of the incident light (e.g., right-handed circularly polarized light is converted into left-handed circularly polarized light upon reflection and vice versa). The retarder in the circular polarizer can convert the circularly polarized light into linearly polarized light, such as linearly polarized light orthogonal to the polarization of the polarizer, which is attenuated (e.g., absorbed) by the linear polarizer in the circular polarizer. The cleaning polarizer can be used with polarization-independent modulators such as DMDs.As described above, the cleaning polarizer can be used to suppress reflections and / or improve the coupling of light into the coupling optical elements 1260, 1262, 1264 in an optimal polarization state.

[0174] Figure 12B A side view or cross-sectional view of the system 1200B is shown, while Figure 12C A top view showing the lateral arrangement of the coupling optical element 1264, the light dump 1250, and the light source 1110 is shown. The SLM 1140 will be configured to reflect, deflect, and / or direct light from the light source 1110 to the lateral positions of the coupling optical element 1264 (and the other coupling optical elements 1260, 1262) or the light dump 1250 depending on the state of the particular pixel.

[0175] In some designs, the light dump 1250 can include an energy harvesting system. The light dump 1250 can include, for example, a light energy conversion element configured to convert light energy into electrical energy. The light energy conversion element can include, for example, a solar cell. The light energy conversion element can include, for example, a photovoltaic detector that generates an electrical output when light is incident thereon. The light energy conversion element can be electrically connected to an electrical component, such as a conductive wire, to conduct the electrical output to provide power for the system 1200B and / or possibly charge one or more batteries.

[0176] In some designs, laterally shifted, non-color selective, or broadband or multi-color coupling optical elements can be used. For example, Figure 13A is a perspective view of a system 1300 including a stack 1305 containing waveguides. The stack 1305 can be substantially similar to the stack 1205 with reference to Figure 12A Each waveguide in the stack 1305 can include coupling optical elements 1360, 1362, 1364. However, contrary to the design shown in Figure 12A , the coupling optical elements 1360, 1362, 1364 are laterally shifted relative to each other. As shown in Figure 13A , 13B and 13C, the light sources 1110, 1112, 1114 are also laterally shifted relative to each other and can be arranged to direct light to the corresponding coupling optical elements 1360, 1362, 1364 by passing the light through the optical device 1130, reflecting the light away from the SLM 1140, and passing the reflected light through the optical device 1130 again. Figure 13B The system 1300 of Figure 13BShown in. The light sources 1110, 1112, 1114 may respectively correspond to the light-coupling optical elements 1360, 1362, 1364. For example, in one design, the light sources 1110, 1112, 1114 and the corresponding light-coupling optical elements 1360, 1362, 1364 are disposed substantially equidistantly (symmetrically) from the center of the optical device 1130 along a common (optical) axis. The common (optical) axis may intersect the center of the optical device 1130. For example, in one design, the light sources 1110, 1112, 1114 and the corresponding light-coupling optical elements 1360, 1362, 1364 are disposed non-equidistantly (asymmetrically) from the center of the optical device 1130 along the common (optical) axis.

[0177] The light-coupling optical elements 1360, 1362, 1364 may be configured to couple light of multiple colors into their respective waveguides. Accordingly, these light-coupling optical elements 1360, 1362, 1364 may herein be referred to as broadband, multi-color, or non-color-selective light-coupling optical elements 1360, 1362, 1364. For example, in some cases, each of these light-coupling optical elements 1360, 1362, 1364 is configured to couple red, green, and blue light into the associated waveguide that includes the light-coupling optical element 1360, 1362, 1364, such that such colored light is guided within the waveguide by TIR. For example, such broadband light-coupling optical elements 1360, 1362, 1364 may operate across a wide wavelength range, such as within the visible light range, or across a selected wavelength or wavelength region within the visible light range. Accordingly, such broadband or multi-color or non-color-selective light-coupling optical elements 1360, 1362, 1364 may be configured to turn light of various different colors (e.g., red, green, and blue) into the waveguide to be guided therein by TIR. Although red, green, blue (RGB) is mentioned herein, such as in relation to light sources, light-coupling optical elements, waveguides, etc., other colors or color systems may alternatively or additionally be used, such as, for example but not limited to, magenta, cyan, yellow (CMY).

[0178] As Figure 13A shown, the light sources 1110, 1112, 1114 are shown above the uppermost waveguide and are displaced relative to each other (e.g., in the x and z directions). Similarly, the three light-coupling optical elements 1360, 1362, 1364 are shown on three respective waveguides and are displaced relative to each other (e.g., in the x, y, and z directions). Figure 13B is Figure 13A a side view of the system 1300 shown in, which shows the light-coupling optical elements 1360, 1362, 1364 that are laterally spatially displaced relative to each other (e.g., in the x and z directions), and some of the light sources 1110, 1112, 1114 that are laterally displaced relative to each other (e.g., in the x and z directions).Figure 13B Optical device 1130 and SLM 1140 are also shown.

[0179] Figure 13C is Figure 13A and 13B is a top view of the augmented reality display system shown in and, which shows the coupling-in optical elements 1360, 1362, 1364 and the associated light sources 1110, 1112, 1114. In this design, the coupling-in optical elements 1360, 1362, 1364 and the associated light sources 1110, 1112, 1114 are arranged in an annular pattern around the center point of the common (optical) axis. As shown, the light sources 1110, 1112, 1114 and the corresponding coupling-in optical elements 1360, 1362, 1364 are arranged approximately equidistantly around the center point of the common (optical) axis. However, this must be the case. In some designs, this center point may correspond to the center of the optical device 1130 along the common (optical) axis that intersects the center of the optical device 1130 and / or the position along the optical axis of the optical device 1130. Similarly, as a result, the non-color-selective coupling-in optical elements 1360, 1362, 1364 and the light sources 1110, 1112, 1114 are laterally displaced relative to each other (e.g., in the x and z directions).

[0180] Other arrangements in a lateral placement are also possible. Figures 14A - 14C shows an alternative configuration of system 1400, which includes a stack 1405 that includes waveguides, where the coupling-in optical elements 1360, 1362, 1364 and the light sources 1110, 1112, 1114 are laterally displaced relative to each other. Figure 14A is a side view, while Figure 14B is Figure 14A is a top view of the system 1400 shown in and, which shows the laterally displaced coupling-in optical elements 1360, 1362, 1364 and the light sources 1110, 1112, 1114. Figure 14C is Figure 14A and 14B are orthogonal side views of the system 1400 shown in and.

[0181] Figure 14A and 14C The side views of and show how the coupling-in optical elements 1360, 1362, 1364 are arranged on individual waveguides within the stack 1405 such that light can be coupled into the corresponding waveguides through the respective laterally displaced coupling-in optical elements 1360, 1362, 1364. Figure 14A and 14CThe input optical elements 1360, 1362, 1364 are shown as being disposed in the upper major surface of the waveguide. However, the input optical elements 1360, 1362, 1364 may alternatively be disposed on the lower major surface of the respective waveguide or in the body of the waveguide. A variety of configurations are possible.

[0182] As Figure 14B shown in the top view of, the input optical elements 1360, 1362, 1364 are arranged in a column, laterally displaced relative to each other in the z direction but not in the x direction. Similarly, the light sources 1110, 1112, 1114 are arranged in a column, also laterally displaced relative to each other in the z direction but not in the x direction. The input optical elements 1360, 1362, 1364 are laterally displaced relative to the light sources 1110, 1112, 1114 in the x direction.

[0183] Other configurations are still possible. Figure 15 is a top view of the system 1500, showing an alternative configuration of the light sources 1110, 1112, 1114 and the input optical elements 1360, 1362, 1364. Compared with Figure 13C in which all the light sources 1110, 1112, 1114 are located substantially on one side (e.g., in an annular pattern) and all the input optical elements 1360, 1362, 1364 are located substantially on one side (i.e., the opposite side), the light sources 1110, 1112, 1114 and the input optical elements 1360, 1362, 1364 are interspersed or alternated along the circumference of the annular pattern.

[0184] However, in some embodiments, the input optical elements 1360, 1362, 1364 and one or more associated light sources 1110, 1112, 1114 are also arranged in an annular pattern around a central point. Thus, the light sources 1110, 1112, 1114 and the corresponding input optical elements 1360, 1362, 1364 can be arranged substantially equidistant from the center. In some designs, this center may correspond to the center of the optical device 1130 along a common central axis intersecting the center of the optical device 1130 and / or the position along the optical axis of the optical device. Thus, light from the first light source 1110 can be coupled via the optical device 1130 across the center or central axis or optical axis of the optical device 1130 into the input optical element 1360 (as from Figure 15as seen in the top view). Similarly, light from the second light source 1112 can be coupled into the input optical element 1362 via the optical device 1130 across the center or central axis or optical axis of the optical device 1130. Similarly, light from the third light source 1114 can be coupled into the input optical element 1364 via the optical device 1130 across the center or central axis or optical axis of the optical device 1130. As a result, the non-color-selective input optical elements 1360, 1362, 1364 and the light sources 1110, 1112, 1114 are laterally displaced relative to each other (e.g., in the x and z directions). The optical device 1130 can be designed such that the focus is more into the stack 1405, such that the positions of the sub-pupils and the input optical elements 1360, 1362, 1364 are closer in their directions. In this configuration, the input optical elements 1360, 1362, 1364 can be smaller because they are closer to the focus of the optical device 1130. The light source 1110 can be located on the user side of the stack 1405 (e.g., similar to Figure 17 and 18 ), and thereby reduce the distance or optical path between the light source 1110 and the optical device 1130.

[0185] In the various embodiments described above, such as Figures 12A - 15 as shown in, stacks including a plurality of waveguides (e.g., stacks 1205, 1305, 1405) (e.g., stack 1205 includes waveguides 1120, 1122, 1124, stack 1305 includes waveguides (not labeled), and stack 1405 includes waveguides (not labeled)) can be included to process different colors (e.g., red, green, and blue). Different waveguides can be used for different colors. Similarly, a plurality of stacks can be included to provide different optical characteristics to the light coupled out from the respective stacks. For example, Figures 12A - 12B the waveguides 1120, 1122, 1124 of the stack 1205 of

[0186] Figure 16A can be configured to output light having optical characteristics (e.g., providing a focal power of a specific wavefront shape) that may be associated with an apparent depth from which the light appears to emanate. For example, wavefronts having different amounts of divergence, convergence, or collimation may appear as if projected from different distances from the eye 210. Accordingly, a plurality of stacks can be included, where different stacks are configured such that the light coupled out by the output optical elements has different amounts of convergence, divergence, or collimation, and thus appears to originate from different depths. In some designs, different stacks can include different lenses, such as diffractive lenses or other diffractive optical elements, to provide different amounts of focal power to the different stacks. Accordingly, different stacks will produce different amounts of convergence, divergence, or collimation, and thus the light from different stacks will appear as if associated with different depth planes or objects at different distances from the eye 210.is a side view of system 1600 including stacks 1605, 1610, 1620. As Figure 16A shown, system 1600 includes three stacks 1605, 1610, 1620; however, this need not be the case. The system can be designed to have fewer or more stacks. Each of stacks 1605, 1610, and 1620 includes one or more (e.g., three) waveguides. Figure 16A Also shown are groups 1630, 1640, 1650 of coupled-in optical elements. The first group 1630 is associated with the first stack 1605, the second group 1640 is associated with the second stack 1610, and the third group 1650 is associated with the third stack 1620. Groups 1630, 1640, 1650 are laterally offset relative to each other. Each of groups 1630, 1640, 1650 includes color-selective coupled-in optical elements configured to couple in different respective colors in substantially the same manner as Figure 12A coupled-in optical elements 1260, 1262, 1264. As Figure 16A shown, the coupled-in optical elements within each of groups 1630, 1640, 1650 are not laterally shifted relative to each other; however, this need not be the case. A system can be designed in which the coupled-in optical elements within a group are laterally shifted relative to each other. System 1600 can be configured such that the light coupled out from each of stacks 1605, 1610, 1620 has a different optical power. For example, the waveguides in a stack can contain coupled-out optical elements or diffractive lenses having a given optical power. The optical powers of different stacks 1605, 1610, 1615 can be different such that the light from one stack may appear to originate from a different depth than the light from another stack. For example, the optical power of one stack can cause the light from that stack to be collimated, while the optical power of another stack can cause the light from that stack to diverge. The diverging light can appear to originate from an object at a relatively close distance from eye 210, while the collimated light can appear to originate from an object at a relatively far distance. Thus, the light coupled out from the first stack 1605, the second stack 1610, and the third stack 1620 can have at least one of different amounts of convergence, divergence, and collimation and can thus appear to originate from different depths. In some embodiments, the light coupled out from one of the stacks can be collimated, while the light coupled out from a different stack can diverge. The light coupled out from one of the other stacks may also diverge, but by a different amount.

[0187] As Figure 16AAs shown, light source 1110 can be positioned relative to optical device 1130 and SLM 1140 to direct light into coupled-in optical element group 1630, light source 1112 can be positioned relative to optical device 1130 and SLM 1140 to direct light into coupled-in optical element group 1640, and light source 1114 can be positioned relative to optical device 1130 and SLM 1140 to direct light into coupled-in optical element group 1650. Light sources 1110, 1112, 1114 can be configured to emit light of different colors at different times. Similarly, light of different respective colors can be coupled into different waveguides within the stack in the manner described above due to color-selective coupling into the optical elements. For example, if blue light is emitted from the second light source 1112, the optical device 1130 and SLM 1140 will direct the blue light to the second group 1640 of coupled-in optical elements. This light can pass through the first red-coupled-in optical element and the second green-coupled-in optical element in the second group 1640 and be redirected by the third blue-coupled-in optical element in the second group 1640 into the third waveguide in the second stack 1610. The waveguides in the second stack 1610 can include out-coupling optical elements or other optical elements with optical power (e.g., diffractive lenses) to provide a light beam to the eye 210 associated with a particular depth plane or object distance associated with the second stack 1610.

[0188] Figure 16B is Figure 16A A top view of the system 1600 in FIG. The coupled-in optical elements of the different groups 1630, 1640, 1650 are shown laterally displaced relative to each other (e.g., in the x direction). Similarly, the light sources 1110, 1112, 1114 are shown laterally displaced relative to each other (e.g., in the x direction).

[0189] Various different variations are possible in the above-described system. For example, the position of the light source 1110 relative to the waveguide and the optical device 1130 can be different. For example, Figure 17 is a side view of the system 1700, which has a light source 1110 in a position different from the position shown in FIGS. 11-16B relative to the waveguide 1720 and the optical device 1130. Additionally, Figure 17A design is shown in which waveguide 1720 is divided into a first portion 1720a and a second portion 1720b. Waveguide 1720 may further include a reflector 1730 configured to couple out light guided in the first portion 1720a near light source 1110 from the first portion 1720a and into optical device 1130 towards SLM 1140. Additionally or alternatively, system 1700 may include a diffractive outcoupling optical element to couple out light in the first portion 1720a of waveguide 1720 and into optical device 1130 towards SLM 1140. Reflector 1730 may be opaque and include an isolator that reduces crosstalk between the first portion 1720a and the second portion 1720b. Waveguide 1720 has a first side 1721 and a second side 1723 opposite the first side 1721, and optical device 1130 and SLM 1140 are disposed on the first side 1721 such that light from SLM 1140 is directed onto the first side 1721. In this example, light source 1110 is disposed on the first side 1721 of waveguide 1720 such that light from light source 1110 is incident on the first side 1721 before passing through optical device 1130 to reach SLM 1140. System 1700 may further include an in-coupling optical element 1710 disposed on or in the first portion 1720a. In-coupling optical element 1710 may be configured to receive light from light source 1110 and couple the light into the first portion 1720a. In-coupling optical element 1710 may include a diffractive optical element or a reflector configured to turn light incident thereon at an angle into the first portion 1720a for guiding therein by TIR.

[0190] Reflector 1730 may be configured to couple out light guided in the first portion 1720a from the first portion 1720a and direct it towards optical device 1130 and SLM 1140 (as discussed above, in some embodiments, a diffractive optical element may additionally or alternatively be used to couple out light in the first portion 1720a from the first portion 1720a and direct it towards optical device 1130 and SLM 1140). Thus, reflector 1730 may be a mirror, a reflective grating, one or more coatings that reflect light from waveguide 1720 towards SLM 1140. Light emitted from the first portion 1720a by reflector 1730 passes through optical device 1130, is incident on SLM 1140, and passes through optical device 1130 again and is incident on the second portion 1720b. As described above, light reflected from SLM 1140 that passes through optical device 1130 may be incident on in-coupling optical element 1160 and turn the light for guiding in the second portion 1720b. Light guided in the second portion 1720b may be coupled out therefrom by an out-coupling optical element 1180 (not shown) and directed to eye 210.

[0191] As discussed above, the reflector 1730 can be an isolator that reduces crosstalk between the first portion 1720a and the second portion 1720b. The reflector 1730 can include an opaque and / or reflective surface. The reflector 1730 can be disposed within the waveguide 1720 and, in some cases, can define the sides of the first portion 1720a and the second portion 1720b.

[0192] Separate waveguides can be used instead of the first and second portions 1720a, 1720b of the waveguide 1720. Figure 18 is a side view of a system 1800 that includes a first waveguide 1822 for receiving light from a light source 1110 and guiding the light therein to an optical device 1130 and toward an SLM 1140. The system 1800 further includes a second waveguide 1820 that receives light from the SLM 1140 after the light has passed through the optical device 1130 again. The first waveguide 1822 includes an input coupling optical element 1730a and an output coupling optical element 1730b, respectively. These input coupling and output coupling optical elements 1730a, 1730b can include reflective surfaces that are oriented to couple light into and out of the waveguide 1822. The input coupling optical element 1730a can include, for example, a reflective surface that is disposed to receive light from the light source 1110 and is oriented (e.g., tilted) to guide the light into the waveguide 1822 at an angle so as to be guided therein by TIR. The output coupling optical element 1730b can include, for example, a reflective surface that is oriented (e.g., tilted) to guide the light guided within the waveguide 1822 at an angle so as to exit the waveguide 1822. The output coupling optical element 1730b can be positioned such that the light exiting the waveguide 1822 is guided into the optical device 1130, reflected from the SLM 1140, passes through the optical device 1130 again, and is incident on the input coupling optical element 1730c of the second waveguide 1820.

[0193] The input coupling optical element 1730c in the second waveguide 1820 can include a reflective surface that can be positioned and oriented (e.g., tilted) to receive and redirect the light incident thereon from the SLM 1140 to be guided in the second waveguide 1820 by TIR. Figure 18 Shows the optical device 1130 and the light source 1110 disposed on the same side of the waveguides 1820, 1822. The system 1800 can further include an isolator to reduce crosstalk between the waveguide 1822 and the waveguide 1820. The isolator can include an opaque and / or reflective surface. The isolator can be disposed in or on at least one of the waveguides 1820, 1822.

[0194] Various designs (such as those discussed above) can include additional features or components. For example,Figure 19 A side view of a system 1900 including variable-focus optical elements (or adaptive optical elements) 1910, 1920 is shown. The variable-focus optical elements 1910, 1920 may include optical elements configured to be variable to provide a variable optical power. The variable-focus optical elements 1910, 1920 may include multiple states, such as a first state and a second state, wherein in the first state, the variable-focus optical elements 1910, 1920 have an optical power different from that in the second state. For example, the variable-focus optical elements 1910, 1920 may have a negative optical power in the first state and a zero optical power in the second state. In some embodiments, the variable-focus optical elements 1910, 1920 have a positive optical power in the first state and a zero optical power in the second state. In some embodiments, the variable-focus optical elements 1910, 1920 have a first negative or positive optical power in the first state and a second different negative or positive optical power in the second state. Some adaptive optical elements or variable-focus optical elements 1910, 1920 may have more than two states and may provide a continuous distribution of optical power.

[0195] The variable-focus optical elements 1910, 1920 may include lenses (e.g., variable-focus lenses) and are transmissive. Figure 7 Transmissive or transparent adaptive optical elements or variable-focus optical elements 1910, 1920 are shown. The variable-focus optical elements 1910, 1920 may include liquid lenses (e.g., movable membranes and / or electro-wetting). The variable-focus lenses may also include liquid crystal lenses, such as switchable liquid crystal lenses, such as switchable liquid crystal polarization lenses, which may include diffractive lenses, for example. Alverez lenses may also be used. Other types of variable-focus optical elements 1910, 1920 may be employed. Examples of variable-focus optical elements can be found in U.S. Application No. 62 / 518,539, filed on June 12, 2017, entitled “AUGMENTED REALITY DISPLAY HAVING MULTI-ELEMENT ADAPTIVE LENS FOR CHANGING DEPTH PLANES”, the entire content of which is incorporated herein by reference. The variable-focus optical elements 1910, 1920 may have an electrical input that receives an electrical signal controlling the amount of optical power presented by the variable-focus optical elements 1910, 1920. The variable-focus optical elements 1910, 1920 may have positive and / or negative optical power. In addition to variable-focus elements (e.g., polarization switches, geometric phase (GP) lenses, fluid lenses, etc.), the variable-focus elements 1910, 1920 may also include fixed lenses (e.g., diffractive lenses, refractive lenses, etc.) to generate the desired depth planes in the light field.

[0196] The first variable-focus optical element 1910 may be disposed between the stack 1905 and the eye 210. As discussed above, the stack 1905 may include different waveguides of different colors. The first variable optical element 1910 may be configured to introduce different amounts of optical power, negative and / or positive optical power. The variable optical power may be used to change the divergence and / or collimation of the light coupled out from the stack 1905 to change the depth at which the virtual object projected by the system 1900 into the eye 210 is located. Thus, a 4-dimensional (4D) light field may be created.

[0197] The second variable-focus optical element 1920 is located on the side of the stack 1905 opposite to the first variable-focus optical element 1920. Thus, the second variable-focus optical element 1920 may compensate for the effect of the first optical element 1910 on the light received from the world 510 in front of the system 1900 and the eye 210. Thus, the world view may effectively remain unchanged or be changed as needed.

[0198] The system 1900 may further include a static or variable prescription or corrective lens 1930. Such a lens 1930 may provide refractive correction for the eye 210. Additionally, if the prescription lens 1930 is a variable lens, it may provide different refractive corrections for multiple users. Variable-focus lenses were discussed above. The eye 210 may, for example, suffer from myopia, hyperopia, and / or astigmatism. The lens 1930 may have a prescription (e.g., optical power) to reduce the refractive error of the eye 210. The lens 1930 may be spherical and / or cylindrical and may be positive or negative. The lens 1930 may be disposed between the stack 1905 and the eye 210 such that light from both the world 510 and the stack 1905 undergoes the correction provided by the lens 1930. In some embodiments, the lens 1930 may be disposed between the eye 210 and the first variable-focus optical element 1910. Other positions of the lens 1930 are possible. In some embodiments, the prescription lens may be variable and allow for multiple user prescriptions to be achieved.

[0199] In some designs, the system 1900 may include an adjustable dimming device 1940. In some embodiments, the adjustable dimming device 1940 may be disposed on the side of the waveguide 1900 stack opposite the eye 210 (e.g., the world side). Thus, the adjustable dimming device 1940 may be disposed between the stack of waveguides 1900 and the world 510. The adjustable dimming device 1940 may include an optical element that provides variable attenuation of the light transmitted therethrough. The adjustable dimming device 1940 may include an electrical input to control the attenuation level. In some cases, the adjustable dimming device 1940 is configured to increase attenuation when the eye 210 is exposed to bright light (such as when the user walks outdoors). Thus, the system 1900 may include a light sensor to sense the brightness of the ambient light and control electronics to drive the adjustable dimming device 1940 to change the attenuation based on the light level sensed by the light sensor.

[0200] Different types of adjustable dimming devices 1940 may be employed. Such adjustable dimming devices 1940 may include variable liquid crystal switches with polarizers, electrochromic materials, photochromic materials, etc. The adjustable dimming device 1940 may be configured to adjust the amount of light entering and / or transmitted through the stack 1905 from the world 510. In some cases, the adjustable dimming device 1940 may be used to reduce the amount of ambient light passing through the waveguide stack 1900 to the eye 210, which otherwise may provide glare and reduce the user's ability to perceive the virtual objects / images injected into the eye 210 from the stack 1905. Such adjustable dimming devices 1940 may reduce the incident bright ambient light so as not to wash out the images projected into the eye 210. Thus, employing the adjustable dimming device 1940 can increase the contrast of the virtual objects / images presented to the eye 210. Conversely, if the ambient light is low, the adjustable dimming device 1940 may be adjusted to reduce the attenuation so that the eye 210 can more easily see the objects in the world 510 in front of the user. The dimming or attenuation may be across the system or local to one or more parts of the system. For example, multiple local parts may be dimmed or set to attenuate the light from the world 510 in front of the user's eye 210. These local parts may be separated from each other by parts without such increased dimming or attenuation. In some cases, only one part is dimmed or causes increased attenuation relative to other parts of the eyepiece. Other components may be added in different designs. The arrangement of the components may also be different. Similarly, one or more components may be excluded from the system.

[0201] Figure 20A An example of another configuration is shown. Figure 20AShows a side view of system 2000, which includes laterally shifted light-coupling optical elements 1360, 1362, 1364 located on different waveguides and a color filter array 2030, and the color filter array 2030 includes laterally shifted color filters 2040, 2042, 2044 aligned with the corresponding light-coupling optical elements 1360, 1362, 1364. The color filter array 2030 may be disposed on a side of stack 2005 closer to the eye 210 and the optical device 1130. The color filter array 2030 may be located between the stack 2005 and the optical device 1130. The color filter array 2030 may be disposed in or on a cover glass 2050 located between the stack 2005 and the optical device 1130. The color filter array 2030 may include one or more different color filters 2040, 2042, 2044 that are laterally disposed relative to each other, such as a red color filter, a green color filter, and a blue color filter. System 2000 includes light sources 1110, 1112, 1114 that are laterally shifted relative to each other. These light sources 1110, 1112, 1114 may include light sources of different colors, such as a red light source, a green light source, and a blue light source. The color filters 2040, 2042, 2044 may be transmissive or transparent filters. In some embodiments, the color filters 2040, 2042, 2044 include absorption filters. However, the color filters 2040, 2042, 2044 may also include reflective filters. The color filters 2040, 2042, 2044 in the color filter array 2030 may be separated and / or surrounded by a mask (such as an opaque mask) that will reduce the propagation of stray light. The color filters in the color filter array 2030 may be used to reduce or eliminate unwanted reflections within the system, such as from the waveguides and / or the light-coupling optical elements 1360, 1362, 1364, to prevent them from re-entering the waveguides for different colors through the light-coupling optical elements 1360, 1362, 1364 for different colors. Examples of color filter arrays can be found in U.S. Application Serial No. 15 / 683,412, titled "PROJECTOR ARCHITECTURE INCORPORATING ARTIFACT MITIGATION", filed on August 22, 2017, the entire content of which is incorporated herein by reference; and U.S. Application No. 62 / 592,607, titled "PROJECTOR ARCHITECTURE INCORPORATING ARTIFACT MITIGATION", filed on November 30, 2017, the entire content of which is incorporated herein by reference. The mask may be a black mask and may include an absorbing material to reduce the propagation and reflection of stray light. The light sources 1110, 1112, 1114 may be disposed relative to the optical device 1130 and the SLM 1140 to couple light into the corresponding color filters 2040, 2042, 2044 in the color filter array 2030.For example, the color filter array 2030 may include first, second, and third (e.g., red, green, and blue) color filters 2040, 2042, 2044 that are arranged to receive light from first, second, and third light sources 1110, 1112, 1114, respectively. The first, second, and third (e.g., red, green, and blue) color filters 2040, 2042, 2044 may be aligned (e.g., in the x and z directions) with corresponding light-coupling optical elements 1360, 1362, 1364. Thus, light from the first light source 1110 will be guided through the first color filter 2040 and reach the first light-coupling optical element 1360, light from the second light source 1112 will be guided through the second color filter 2042 and reach the second light-coupling optical element 1362, and light from the third light source 1114 will be guided through the third color filter 2044 and reach the third light-coupling optical element 1364. In some embodiments, the light-coupling optical elements 1360, 1362, 1364 may be color-specific. For example, the first and second light-coupling optical elements 1360, 1362 may be configured to couple light of corresponding first and second colors into first and second waveguides, respectively. Similarly, the first, second, and third light-coupling optical elements 1360, 1362, 1364 may be configured to couple light of corresponding first, second, and third colors into first, second, and third waveguides, respectively. The first light-coupling optical element 1360 may be configured to couple more light of the first color than the second color (or the third color) into the first waveguide. The second light-coupling optical element 1362 may be configured to couple more light of the second color than the first color (or the third color) into the second waveguide. The third light-coupling optical element 1364 may be configured to couple more light of the third color than the first color or the second color into the second waveguide. In other configurations, the light-coupling optical elements 1360, 1362, 1364 may be broadband. For example, the first light-coupling optical element 1360 may be configured to couple light of the first, second, and third colors into the first waveguide. The second light-coupling optical element 1362 may be configured to couple light of the first, second, and third colors into the second waveguide. The third light-coupling optical element 1364 may be configured to couple light of the first, second, and third colors into the third waveguide. However, the plurality of color filters 2040, 2042, 2044 may be color-specific, selectively transmitting light of a specific color. For example, the first color filter 2040 may transmit more light of the first color than the second color (and the third color). The second color filter 2042 may transmit more light of the second color than the first color (and the third color). The third color filter 2044 may transmit more light of the third color than the first color and the second color. Also, the first, second, and third color filters 2040, 2042, 2044 may be color filters that selectively transmit the first, second, and third colors, respectively.Accordingly, the first, second, and third color filters 2040, 2042, 2044 can be band-pass filters that selectively transmit the first, second, and third colors, respectively. In some embodiments, the first, second, and third light sources 1110, 1112, 1114 can selectively emit the first, second, and third colors, respectively. For example, the first light source 1110 can emit more of the first color than the second color (and the third color). The second light source 2042 can emit more of the second color than the first color (and the third color). The third light source 2044 can transmit more of the third color than the first and second colors. The color filters 2040, 2042, 2044 can reduce the amount of stray light inadvertently directed to a particular coupling optical element. In other embodiments, one or more of the light sources 1110, 1112, 1114 are broadband light sources. For example, the first light source 1110 may emit the first and second (and possibly also the third) colors. The second light source 1112 may also emit the first and second (and possibly also the third) colors. The third light source 1114 may also emit the first and second (and possibly also the third) colors. Although. Figures 20A - 20G Three filters are shown, but more or fewer filters can be included. For example, in some embodiments, two filters (instead of three) can be used. Accordingly, two colors corresponding to the two color filters can be selectively transmitted by the filters. In some such embodiments, two corresponding coupling optical elements can be used and aligned with the two filters. In some embodiments, the two coupling optical elements selectively couple the two colors into two respective waveguides. In some embodiments, two light sources can be used instead of three light sources. Other variations and other numbers of components can be used. Additionally, the color filters 2040, 2042, 2044 can or can not be integrated in a single array.

[0202] As discussed above, the components and their locations and arrangements can vary. For example, although Figure 20A the analyzer 1150 is shown disposed between the optical device 1130 and the stack 1905, the analyzer 1150 can be located at a different position. Figure 20B the analyzer 1150 is shown located between the optical device 1130 and the SLM 1140. In some designs, the analyzer (e.g., polarizer) 1150 can be directly attached to the SLM 1140. For example, the analyzer 1150 can be adhered to or mechanically coupled to the SLM 1140. For example, the analyzer 1150 can be glued, bonded to the SLM 1140 (e.g., to the SLM window) using an adhesive. Accordingly, although Figure 20BThe gap between the analyzer 1150 and the SLM 1140 is shown, but in some designs, there is no gap between the analyzer 1150 and the SLM 1140. The analyzer 1150 can be mechanically fixed (e.g., using a mechanical fixture) to the SLM 1140, and in such cases, there may or may not be a gap between the analyzer 1150 and the SLM 1140. As described above, birefringence from the optical device 1130 can be removed by positioning a polarizer directly on the SLM 1140. In some embodiments, an analyzer 1150 may also be included between the optical device 1130 and the coupled-in optical elements 1360, 1362, 1364 to remove the polarization of the light exiting the optical device 1130 (e.g., as shown by the dashed line in Figure 20B . Additionally, a retarder (not shown), such as a quarter-wave plate, may be included near the SLM 1140, e.g., between the optical device 1130 and the SLM 1140. As used herein, a quarter-wave plate may refer to a quarter-wave retarder, regardless of whether the quarter-wave retarder includes a plate, film, or other structure for providing a quarter-wave delay. For example, in Figure 20B , a retarder (e.g., a quarter-wave plate) may be disposed between the analyzer 1150 and the SLM 1140. The retarder (e.g., a quarter-wave plate) may be used for skew ray management. For example, the retarder (e.g., a quarter-wave plate) can compensate for variations caused by wavelength and angle-of-incidence differences onto the SLM 1140. As discussed above, a compensator may be included and can provide more consistent polarization rotation (e.g., 90°) of the SLM 1140 for different angles of incidence and different wavelengths. The compensator can be used to increase the contrast of the display by providing more consistent orthogonal rotation. The compensator can be attached or fixed to the SLM 1140 as described above. For example, glue, adhesive, or other adhesives can be used. The compensator can also be attached to the SLM 1140 using a mechanical fixture. There may or may not be a gap between the compensator and the SLM 1140. Other light-adjusting optical devices may also be included additionally or alternatively and can be fixed to the SLM 1140, such as those described above with respect to the analyzer 1150 and / or the compensator.

[0203] In some embodiments, a large angle spread (e.g., -70 degrees) can be used. The angle spread can refer to, for example, the angle of light entering the optical device 1130 from the light sources 1110, 1112, 1114, and / or the angle of light exiting the optical device 1130 and entering the coupled-in optical elements 1360, 1362, 1364. In these embodiments, a thinner SLM 1140 can be used. For example, if the SLM 1140 is a liquid crystal (LC) SLM (e.g., a liquid crystal on silicon (LCoS) SLM), the LC layer can be made thinner to accommodate the large angle spread.

[0204] The double-pass delay through the polarizer and analyzer 1150 may need to be a half-wave. The polarizer may be located between the optical device 1130 and the analyzer 1150. The double-pass delay may be a function of the ratio of the refractive index of the LCoS SLM 1140 to the thickness of the LCoS SLM 1140. For a given refractive index of the LCoS SLM 1140 and a given thickness of the LCoS SLM 1140, light entering and exiting the LCoS SLM 1140 at a large angle results in a longer optical path length than light entering and exiting the LCoS SLM 1140 at a small angle. The path length is related to the thickness of the LCoS SLM 1140. In one example, the LCoS SLM may have a first refractive index and a first thickness. For a small angle, the double-pass delay of the LCoS SLM with the first refractive index and the first thickness may be a half-wave. For a large angle, the double-pass delay of the LCoS SLM with the first refractive index and the first thickness may not be a half-wave (e.g., may be greater than a half-wave). The thickness of the LCoS SLM may be changed from the first thickness to a second thickness, where the second thickness is less than the first thickness. For a small angle, the double-pass delay of the LCoS SLM with the first refractive index and the second thickness may not be a half-wave (e.g., may be less than a half-wave). For a large angle, the double-pass delay of the LCoS SLM with the first refractive index and the second thickness may be a half-wave.

[0205] In addition, although Figure 20A and 20B illustrate the use of a polarization-based SLM 1140, other types of SLMs may also be employed. For example, Figure 20C illustrates the use of a deflection-based SLM 1140, such as an SLM based on a movable micromirror. As discussed above, such an SLM 1140 may include digital light processing and digital micromirror device (DMD) technology. As discussed above, the deflection-based SLM 1140 may couple light from one of the light sources 1110, 1112, 1114 to the corresponding light-coupling optical elements 1360, 1362, 1364 depending on the pixel state of the SLM 1140. In one state, as Figure 20D shown, the light from the light sources 1110, 1112, 1114 will be directed to the corresponding light-coupling optical elements 1360, 1362, 1364. In another state, as Figure 20EAs shown, the light from light sources 1110, 1112, 1114 will be guided away from the coupling optical elements 1360, 1362, 1364. In some embodiments, when in the off state, the black absorption mask between the color filters 2040, 2042, 2044 in the color filter array 2030 can be used as a light dump. As described above, the color filters 2040, 2042, 2044 can be surrounded and / or separated by a mask (such as an absorption mask (e.g., a black mask)). The mask can include an absorbing material such that more incident light is absorbed compared to the light reflected therefrom. The mask can also be opaque.

[0206] Other variations are possible. Although the light sources are shown as emitters 1110, 1112, 1114 (such as LEDs, laser diodes) coupled to a coupling optical device 1105 (such as a non-imaging optical coupling element (e.g., a compound parabolic concentrator (CPC) or a cone)), other configurations are possible. For example, the coupling optical device 1105 (e.g., a CPC) can be tilted relative to the waveguide stack. In some cases, the projector (i.e., the optical device 1130 and the SLM 1140) can be tilted relative to the eyepiece (e.g., the waveguide stack). In some embodiments, the lens optical device 1130 is tilted relative to the SLM 1140 to reduce distortion, such as trapezoidal distortion. A Scheimplug configuration can be employed to reduce such distortion. The components (e.g., the optical device 1130 and / or the spatial light modulator 1140) can be tilted as needed, for example, to more conformally fit the head and / or face. As described above, the light emitter and / or the coupling optical device 1105 can be tilted. In some configurations, the component including the waveguide can be tilted such that the side closer to the eye 210 (e.g., the temporal side) is closer to the eye 210 to increase the perceived field of view of the entire binocular system (at the expense of binocular overlap).

[0207] As discussed above, the components and their positions and arrangements can vary. For example, Figure 20F is a side view of system 2000F, which includes a cover glass 2050 disposed between the stack 2005 and the optical device 1130. In some designs, the light sources 1110, 1112, 1114 can be disposed on the world side of the cover glass 2050 and configured to cause light to propagate through the cover glass 2050 to the optical device 1130 and the SLM 1140. As illustrated, the cover glass 2050 can extend laterally (e.g., parallel to the x-axis) beyond the stack 2005 such that the light emitted by the light sources 1110, 1112, 1114 enters the optical device 1130 without passing through the waveguides in the stack 2005. Although system 2000F depicts a deflection-based SLM 1140, a similar configuration of the light source can also be used with a non-deflection-based SLM, or with any other configuration or feature disclosed herein.

[0208] Figure 20G is a side view of system 2000G, which includes a cover glass 2060 disposed on the world side of stack 2005 (i.e., opposite the side of stack 2005 that is closer to optical device 1130). In some designs, light sources 1110, 1112, 1114 may be disposed on the world side of cover glass 2050 and are configured to cause light to propagate through cover glass 2050 to optical device 1130 and SLM 1140. As illustrated, cover glass 2060 may extend laterally (e.g., parallel to the x-axis) beyond stack 2005 such that light emitted by light sources 1110, 1112, 1114 enters optical device 1130 without passing through the waveguides in stack 2005. Although system 2000G depicts a deflection-based SLM 1140, a similar configuration of light sources may also be used with a non-deflection-based SLM, or with any other configuration or feature disclosed herein.

[0209] In addition, as discussed above, configurations that facilitate light recycling may be employed. For example, Figure 21 is a partial side view of system 2100 equipped with a configuration that provides light recycling of light from light source 1110. Light source 1110 may be disposed relative to polarizer 1115, which is configured to recycle light having an unwanted polarization. Polarizer 1115 may include, for example, a wire grid polarizer that transmits light of a first polarization and retro-reflects light of a second, opposite polarization. Thus, light 2110 may be emitted from light source 1110 and impinge on polarizer 1115. Polarizer 1115 may transmit light of the first polarization, which a projector (not shown) is configured to use. For example, an SLM may operate correctly using light of the first polarization. Light of a second polarization 2120 is reflected back to light source 1110 and may be recycled. After reflecting off a portion (e.g., a sidewall) of a coupling optical device (not shown), such as a non-imaging optical device like a compound parabolic concentrator (CPC), at various angles, the polarization of light 2120 may be changed for polarization rotation. Some light having an appropriate polarization (e.g., polarization orientation) may be produced, which may pass through polarizer 1115. Multiple reflections may change the polarization of the light and may cause the light to exit with the desired polarization. The recycled light 2130 is then emitted back to polarizer 1115. Such configurations may improve efficiency, such as energy efficiency, because more of the desired polarization is produced. In addition, as a supplement or alternative, a retarder may be used to change the polarization state of the reflected light and recycle the light.

[0210] Figure 22Another configuration is shown, which includes light sources 1110, 1112, 1114 and corresponding light collection optics 2210, 2212, 2214. The light collection optics 2210, 2212, 2214 may include lenses or other optics to collect light from the light sources 1110, 1112, 1114. The light sources 1110, 1112, 1114 may be laser diodes or other emitters that emit light over a wide angular range. The light collection optics 2210, 2212, 2214 can be used to collect most of the light. The light sources 1110, 1112, 1114 may emit light asymmetrically. For example, the light may be emitted over a wider angular range in one direction (e.g., the x or z direction) than in the orthogonal direction (e.g., the z or x direction). Thus, the light collection optics 2210, 2212, 2214 may be asymmetric. For example, the light collection optics 2210, 2212, 2214 may have different optical powers in different possible orthogonal directions. The light collection optics 2210, 2212, 2214 may include, for example, lenses such as anamorphic lenses. The light collection optics 2210, 2212, 2214 may also include non-imaging optics. Apertures 2220, 2222, 2224 may be included. For example, when the light sources 1110, 1112, 1114 are lasers such as laser diodes, diffusers 2230 may also be included near the apertures 2220, 2222, 2224. Through the diffusers near the apertures 2220, 2222, 2224, the apertures may appear to be located at the position of the laterally shifted light sources. As discussed above, the apertures 2220, 2222, 2224 may be matched to the coupling optics on one waveguide or multiple waveguides via the optics and the SLM. For example, each aperture 2220, 2222, 2224 may be matched to a corresponding coupling optic. Similarly, in some embodiments, such as Figure 16A as shown in, each aperture 2220, 2222, 2224 may be matched to a corresponding set (e.g., color selective) of coupling optics.

[0211] A variety of system variations and configurations are possible. For example, although linearly polarized light is described as propagating through the optical device 1130 to the SLM 1140 and back through the optical device to the waveguide stack, in some designs, circularly polarized light can be used instead. For example, circularly polarized light can be directed into the optical device 1130. A retarder (such as a quarter-wave plate) can be set such that the light passes through the retarder before being incident on the SLM. The retarder (e.g., a quarter-wave plate) can be set between the optical device 1130 and the SLM 1140. In some cases, such as the above, the retarder (e.g., a quarter-wave plate) can be fixed to the SLM 1140, such as using an adhesive or a mechanical clamp. The retarder (e.g., a quarter-wave plate) can convert the linearly polarized light into circularly polarized light after reflection from the SLM 1140. Thus, in some embodiments, the circularly polarized light can pass through the optical device 1130 again towards the stack. For example, another retarder (e.g., a quarter-wave plate) near the analyzer 1150 can convert the circularly polarized light into linearly polarized light, which can pass through or not pass through the analyzer depending on the linear polarization (e.g., orientation). The pixels of the SLM 1140 can have variable states to rotate or not rotate the polarization. Other configurations are possible.

[0212] Figure 23Ais a side view of an augmented reality display system 2300 that includes a light source 2305, a polarization rotator 2307, an optical device (such as a lens) 2320 having a focal power, polarizers 2312, 2335 (such as linear polarizers (e.g., horizontal or vertical polarizers)), retarders 2315, 2330, 2340 (such as quarter-wave retarders (e.g., quarter-wave plates)), and at least one waveguide 2348 for outputting image information to a user. Such a configuration can be used to illuminate a reflective spatial light modulator (not shown) such that light emitted from the light source 2305 is reflected from the spatial light modulator and coupled into the at least one waveguide 2348 to be directed to the user's eye. The configuration and placement of these elements (especially polarizers and retarders) can reduce or eliminate reflections from optical surfaces within the system (such as from the surface of the optical device 2320), which otherwise might cause the user to see ghost images. For example, polarization-selective and / or retardance-based optical elements (such as polarizers 2312, 2335 and retarders 2315, 2330, 2340) can be arranged and configured to convert linearly polarized light into circularly polarized light that changes from left-handed to right-handed or from right-handed to left-handed when reflected from an optical surface. Similarly, such polarization-selective and / or retardance-based optical elements (such as polarizers 2312, 2335 and retarders 2315, 2330, 2340) can be arranged and configured to convert circularly polarized light into linearly polarized light that can be attenuated or filtered by a polarizer (such as a linear polarizer). Polarization-selective and retardance-based such optical elements (such as polarizers 2312, 2335 and retarders 2315, 2330, 2340) can be used to fabricate a circular polarizer that converts linearly polarized light into circularly polarized light and vice versa. For example, a circular polarizer can include a linear polarizer and a quarter-wave retarder. A circular polarizer can be used to convert linearly polarized light into circularly polarized light having a first state (e.g., handedness) and filter out circularly polarized light having a second state (e.g., handedness) different from the first state. For example, a circular polarizer can be used to convert linearly polarized light having a particular orientation into left-handed circularly polarized light and filter out right-handed circularly polarized light. A circular polarizer can also be used to convert linearly polarized light having a particular orientation into right-handed circularly polarized light and filter out left-handed circularly polarized light. As described below in connection with Figure 23A and 23B a circular polarizer or other configurations of optical elements that include retardation and can selectively filter linearly polarized light can be used to reduce back-reflection from optical surfaces, and the retardation can be used to convert linearly polarized light into circularly polarized light and vice versa.

[0213] It is noted that in Figure 23A and 23BIn it, left - hand and right - hand circular polarizations are respectively represented by clockwise and counter - clockwise arrows. In addition, horizontal and vertical linear polarizations are respectively represented by horizontal arrows and dots.

[0214] As discussed above, [[ID= FIG. shows the configuration of the augmented reality display system 2300, where polarizers 2312, 2335 (such as linear polarizers (e.g., horizontal polarizers)) and retarders 2315, 2330, 2340 (such as quarter - wave retarders (e.g., quarter - wave plates)) are arranged to reduce the back - reflection from an optical surface (such as the surface of the optical device 2320 in the path of light that irradiates a spatial light modulator (not shown) and is reflected from the spatial light modulator). The first polarizer 2312 and the first retarder 2315 are disposed between the light source 2305 and the optical device 2320. The first polarizer 2312 is disposed between the light source 2305 and the first retarder 2315. Similarly, the first retarder 2315 is disposed between the first polarizer 2312 and the optical device 2320.

[0215] As illustrated, the light source 2305 emits light represented by light rays 2310. In some embodiments, the light rays 2310 may pass through a polarization rotator 2307. The rotator 2307 is optional and can be used to rotate the polarization of light (e.g., light rays 2310) from the light source 2305. In various embodiments, the rotator 2307 can rotate the angle of polarization (e.g., linear polarization). For example, the rotator 2307 can rotate the linear polarization of the light rays 2310 to an orientation aligned with the first polarizer 2312 so as to pass through it. In some embodiments, the polarization rotator 2307 may include a retarder, for example, in some cases a half - wave retarder. The optical axis of the half - wave retarder can be oriented to rotate the polarization of light from the light source 2305 from vertical to horizontal or vice versa. Alternatively, the polarization rotator 2307 can be configured to rotate the polarization angle of linearly polarized light emitted from the light source 2305 by a different amount. The polarization rotator 2307 does not need to be included in the system. For example, in embodiments where the light source 2305 emits light with the same polarization as the first polarizer 2312, the polarization rotator 2307 can be excluded. As illustrated, the light (e.g., light rays 2310) passes through the polarizer 2312 (shown here as a horizontal polarizer). In the case where the light from the light source 2305 is unpolarized, the light (shown as light rays 2310) transmitted through the horizontal polarizer 2312 is linearly polarized (e.g., horizontally polarized) after passing through the polarizer 2312. Although a horizontal linear polarizer is used in this example, it can be understood that the taught principles are applicable to vertical linear polarizers. Alternatively, linear polarizers with different orientations other than vertical or linear can also be used.

[0216] The horizontally polarized light ray 2310 travels through a retarder 2315, shown here as a quarter-wave retarder. The retarder 2315 can include sufficient retardation to convert linearly polarized light into circularly polarized light. For example, horizontally polarized light can be converted into left-handed circularly polarized light, as indicated by the curved (e.g., clockwise) arrow. In this example, the combination of the polarizer 2312 and the retarder 2315 (e.g., quarter-wave) forms a circular polarizer, referred to here as the first circular polarizer, which can convert light of a particular linear polarization (e.g., horizontal or vertical polarization) into a particular circular polarization (e.g., left-handed or right-handed circular polarization or vice versa). The circular polarizer can also block light of a particular circular polarization (e.g., right-handed or left-handed circular polarization) depending on the configuration.

[0217] In some embodiments, various optical elements have birefringence. In some such cases, the retarder 2315 can include a retardation amount sufficient to convert linearly polarized light into circularly polarized light and need not be a quarter-wave plate. The retarder 2315 can include more or less than a quarter-wave of retardation since the retardation can be contributed by other optical elements. Similarly, the retardation can be distributed among multiple optical elements. As another example, multiple retarders can be employed to provide an appropriate amount of retardation.

[0218] The circularly polarized light ray 2310 (left-handed circularly polarized here) then passes through the optical device 2320. Unwanted reflections can occur at any interface of media having different refractive indices in the system, such as, for example, an air-to-material interface. If these reflections are allowed to enter at least one waveguide 2348, they can be problematic because the reflected light can be directed into the user's eye and form a "ghost" image visible in the user's eye. For example, in a case where a display uses at least one waveguide 2348 to project a first image onto the viewer's eye, the user may also see a second blurred and repeated image that is shifted (e.g., laterally) relative to the first image. Such "ghost" images formed by reflections from optical surfaces that are directed into the user's eye can be distracting or otherwise degrade the viewing experience. For example, as Figure 23AAs shown, light such as reflected light 2325 can be reflected from a lens within the optical device 2320. This light can be directed toward at least one waveguide 2348, which is configured to direct the light to a user's eye to present an image thereto. However, in this case, the circularly polarized light will reverse its handedness. For example, after reflection from the lens, the direction of circular polarization will change (e.g., from left-handed to right-handed). Then, the right-handed reflected light ray 2325 travels through the retarder 2315 and is converted into linearly polarized light that has a different (e.g., orthogonal) linear polarization from the linear polarization transmitted by the polarizer 2312. In this case, for example, the light reflected from the optical surface of the lens is converted by the retarder 2315 into vertically linearly polarized light that is orthogonal to the polarization transmitted by the horizontally linear polarizer 2312. The horizontally linear polarizer 2312 selectively allows horizontally polarized light to pass through and filters out vertically polarized light. Thus, the reflected light ray 2325 is attenuated and / or not transmitted by the horizontally linear polarizer 2312 and is prevented from reaching at least one waveguide 2348, or at least a reduced amount of such reflected light reaches at least one waveguide 2348 or couples therein, e.g., by coupling into an optical element (e.g., one or more coupling gratings). The result will be similar for left-handed circularly polarized light rays reflected from different optical surfaces of the optical device 2320 or other optical surfaces on different optical elements.

[0219] As illustrated, the display system 2300 further includes a second retarder 2330 (e.g., a quarter-wave retarder or quarter-wave plate) and a second polarizer 2335 (e.g., a linear polarizer) disposed between the optical device 2320 and a spatial light modulator (not shown). In some embodiments, the second retarder 2330 and the second linear polarizer 2335 can form a second circular polarizer. The second retarder 2330 is disposed between the optical device 2320 and the second polarizer 2335. Similarly, the second polarizer 2335 is disposed between the second retarder 2330 and the spatial light modulator. Thus, after passing through the optical device 2320, the light ray 2310 can pass through the second retarder 2330 (e.g., a quarter-wave retarder). The second retarder 2330 is configured (e.g., the optical axis is appropriately oriented) such that the light ray 2310 is converted from left-handed circular polarization to horizontally linear polarization. Similarly, the second retarder 2330 converts the circularly polarized light back to the original linearly polarized state output by the first polarizer 2312. As will be discussed below, the second retarder 2330 and the second polarizer 2312 can be used to reduce "ghost" images caused by light reflected from the spatial light modulator that passes through an optical surface (e.g., on an active optical device or lens 2320) as it travels to at least one light guide 2348.

[0220] A third retarder 2340 (e.g., a quarter-wave retarder or a quarter-wave plate) is disposed between the second polarizer 2335 and the spatial light modulator. Thus, the third retarder 2340 is disposed between the second retarder 2330 and the spatial light modulator. Additionally, in various embodiments such as illustrated, the second polarizer 2335 is located between the second and third retarders 2330, 2340. As illustrated, the light ray 2310 is linearly polarized when passing through the second polarizer 2335, and in some embodiments, the second retarder 2330 / second polarizer 2335 may convert the light into the original linear polarization (e.g., horizontal polarization) of the first polarizer 2312. This linearly polarized light is incident on the third retarder 2340. The third retarder 2340 is configured such that the light ray is converted back to circularly polarized light and in some embodiments is converted back to the same polarization as that output by the first retarder 2315 (e.g., left-handed circularly polarized light in this example). In certain embodiments, the spatial light modulator is configured to operate on the circularly polarized light. In some embodiments, the spatial light modulator is a reflective spatial light modulator that reflects the incident circularly polarized light back as circularly polarized light. In some embodiments, the circularly polarized light reflected from the spatial light modulator may have the same handedness (e.g., left-handed circular polarization) as the circularly polarized light incident thereon, which may depend on whether the spatial light modulator pixels are in the "on" or "off" state. In some embodiments, the spatial light modulator may reflect circularly polarized light of a different handedness (e.g., right-handed circular polarization) incident thereon, which may depend on whether the spatial light modulator pixels are in the "on" or "off" state. However, other types of spatial light modulators may also be used.

[0221] Figure 23A Light reflected from the spatial light modulator and traveling toward the waveguide 2385 is shown as the light ray 2342. The reflected light ray 2342 is depicted as left-handed circularly polarized light. The light ray 2342 passes through the third retarder 2340. The third retarder 2340 converts the circularly polarized light into linearly polarized light. In this example, the left-handed circularly polarized light is converted into horizontally polarized light. The linearly polarized light is transmitted through the second polarizer 2335. In this example, the horizontally polarized light passes through the second polarizer 2335. The linearly polarized light is incident on the second retarder 2330 and is converted into circularly polarized light. In this example, the horizontally polarized light is converted into left-handed polarized light and transmitted to the optical device 2320. Similarly, reflections from optical surfaces (such as the surface of the optical device 2320 having a focal power) can produce ghost images by reflecting back from the spatial light modulator to at least one waveguide 2348 and to the user's eye. As described above, unwanted reflections can occur at any interface between media having different refractive indices, such as an air-to-material interface. As described above, the addition of the second retarder and polarizers 2330, 2335 can attenuate these reflections and reduce the likelihood of ghost reflections. For exampleFigure 23A depicts light reflected from the optical surface of the optical device 2320, illustrated as ray 2346. The act of reflection from the surface causes the reflected circularly polarized ray 2346 to switch its handedness, in this example, from left-handed circular polarization to right-handed circular polarization. The second circular polarizer formed by the second retarder and polarizers 2330, 2335 attenuates this switched circularly polarized light. For example, as Figure 23A shown, the reflected circularly polarized light 2346 is incident on the second retarder 2330 and is converted by the second retarder into linearly polarized light that has a different (e.g., orthogonal) linear polarization from the polarization selectively transmitted by the second linear polarizer 2335. In this case, for example, the right-handed circularly polarized light reflected from the optical surface of the optical device 2320 is converted by the retarder 2330 into vertically linearly polarized light that is orthogonal to the polarization selectively transmitted by the polarizer 2335. The second polarizer 2335 attenuates or blocks the transmission of this linearly polarized light. In this example, the light 2346 is vertically polarized, while the second polarizer 2335 is a horizontal polarizer that selectively passes horizontally polarized light and filters out vertically polarized light.

[0222] Conversely, the light 2342 that passes through the optical device 2320 and is incident on the first retarder 2315 is circularly polarized and has a handedness different from that of the light reflected from the optical surface of the optical device 2320. This light 2342 directed towards at least one waveguide 2348 has a polarization (e.g., left-handed polarization) that is converted by the first retarder 2315 into linearly polarized (e.g., horizontally linearly polarized light) that is selectively transmitted by the first polarizer 2312. In this way, the light 2342 can reach and be coupled into at least one waveguide 2348 and be directed to the user's eye.

[0223] In Figure 23A the example shown, the first circular polarizer formed by the first polarizer 2312 and the first retarder 2315 and the second circular polarizer formed by the second retarder 2330 and the second polarizer 2335 are located on opposite sides of the optical device 2320, one closer to the light source 2305 and one closer to the spatial light modulator, to reduce reflections that may cause "ghost images". An additional retarder 2340 is included between the second circular polarizer (e.g., the second polarizer 2335) and the spatial light modulator to convert the light into circularly polarized light. However, a wide range of variations is possible. For example, only one circular polarizer may be included. Alternatively, additional circular polarizers or other types of polarization optical devices may be included.

[0224] Figure 23B shows a third circular polarizer that can be added to an augmented reality system 2300 such as Figure 23A shown. In particular, Figure 23BDepicts a second circular polarizer including a second polarizer 2335 and a second retarder 2330, and a third retarder 2340 as described above, and further depicts a spatial light modulator 2375. The spatial light modulator (SLM) 2375 may include a liquid crystal spatial light modulator (e.g., liquid crystal on silicon or LCoS). In some embodiments, the SLM 2375 may be covered with a cover glass 2370.

[0225] Figure 23B A third circular polarizer is also shown, which includes a fourth retarder 2345 (such as a quarter-wave retarder (e.g., quarter-wave plate)) and a third polarizer 2355 (such as a linear polarizer), which is disposed between the second circular polarizer including the second polarizer 2335 and the second retarder 2330 and the spatial light modulator 2375. The third polarizer 2355 is located between the fourth retarder 2345 and the spatial light modulator 2375. An additional fifth retarder 2360 (such as a quarter-wave retarder (e.g., quarter-wave plate)) and a compensator 2365 are disposed between the third circular polarizer including the fourth retarder 2345 and the third polarizer 2355 and the spatial light modulator 2375 or more specifically between the cover glass 2370 shown in Figure 23B The fifth retarder 2360 is located between the third polarizer 2355 and the compensator 2365. The compensator 2365 is located between the fifth retarder 2360 and the spatial light modulator 2375 or specifically the cover glass 2370.

[0226] Figure 23B Shows how light (e.g., light ray 2310) from a light source 2305 (shown in Figure 23A propagates through the second circular polarizer including the retarder 2330 and the second polarizer 2335 and the third retarder 2340 to reach the third circular polarizer including the fourth retarder 2345 and the third polarizer 2355. The light ray 2310 from the light source 2305 is incident on the third circular polarizer after passing through the second circular polarizer including the second retarder 2330 and the second polarizer 2335, and in particular on the fourth retarder 2345. The fourth retarder 2345 may convert the circularly polarized light of the light ray 2310 into linearly polarized light. In the example shown in Figure 23B the light ray 2310 is circularly polarized (e.g., left-handed circularly polarized) and is converted into linearly polarized light (e.g., horizontally polarized light) by the fourth retarder 2345. This linearly polarized light passes through the third polarizer 2355, which in Figure 23B includes a horizontal polarizer that selectively transmits horizontally polarized light. This linearly polarized light propagates through the fifth retarder 2360, which may include a quarter-wave retarder that converts the linearly polarized light into circularly polarized light. In Figure 23BIn the example shown, the horizontally linearly polarized light ray 2310 incident on the fifth retarder 2360 is converted into left-handed circularly polarized light. This circularly polarized light is incident on the compensator 2365 and passes through the compensator 2365. The compensator 2365 may include a polarization element that adjusts the polarization to the desired polarization. The compensator 2365 can be used to cancel the birefringence of various optical elements in the system. For example, due to the retardation contributions of one or more optical elements, the light may be slightly elliptically polarized. In various embodiments, the light output from the compensator 2365 is circularly polarized light. In Figure 23B the example shown, the light output from the compensator 2365 is left-handed circularly polarized light. In various embodiments, the compensator 2365 can be used to cancel the residual retardation within the SLM, which may include, for example, a liquid crystal (e.g., LCoS) SLM cell. The compensator can introduce in-plane retardation and / or out-of-plane retardation. In some embodiments, the compensator 2365 may include a combination of optical retarders that, when combined, produce a retardation that can potentially cancel the residual retardation from the SLM (e.g., an LCoS panel).

[0227] In Figure 23B this case, the light is incident on the cover glass 2370 and the SLM 2375 after passing through the compensator 2365. The light incident on the cover glass 2370 and the SLM 2375 is depicted as left-handed circularly polarized light. Depending on the type and state of the spatial modulator, the SLM 2375 can reflect circularly polarized light with the same handedness. For example, when the pixels of the SLM 2375 are in the "on" state (although in some embodiments this state may be the undriven state), the SLM 2375 can introduce a quarter-wave retardation each time the light passes through the SLM 2375. Therefore, upon reflection, the incident circularly polarized light can remain circularly polarized. In various configurations, the handedness can also remain unchanged. For example, as Figure 23B shown, the incident left-handed circularly polarized light can remain left-handed circularly polarized upon reflection. This circularly polarized light reflected from the SLM 2375 (represented by the light ray 2342) can pass through the cover glass 2370 and the compensator 2365 and be incident on the fifth retarder 2360, which converts the circularly polarized light into linearly polarized light. In Figure 23B the example shown, the circularly polarized light incident on the fifth retarder 2360 is left-handed, and the fifth retarder 2360 converts this circularly polarized light into horizontally polarized light. The third polarizer 2355 can be configured to selectively transmit the polarization of the light output by the fifth retarder 2360. Therefore, in Figure 23B the example where the light output from the fifth retarder 2360 is horizontally polarized as shown, the third polarizer 2355 selectively transmits the horizontally polarized light. This linearly polarized light transmitted by the polarizer 2355 is incident on the fourth retarder 2345 and is converted into circularly polarized light. In Figure 23BIn the example shown, the circularly polarized light is left-handed circularly polarized light. This light can travel through a second circular polarizer including a second retarder 2330 and a second polarizer 2335, an optical device 2320, and a first circular polarizer including a first polarizer 2312 and a first retarder 2315, reach at least one waveguide 2348 and enter the user's eye, as discussed above in connection with Figure 23A discussed.

[0228] However, the light reflected from the optical surface can be attenuated by a third circular polarizer, thereby reducing the likelihood that such reflections will reach at least one waveguide 2348 and be guided to the user's eye to produce ghost images. For illustration, Figure 23B An example ray 2343 reflected from the optical surface of the third retarder 2340 (e.g., from the interface between air and the third retarder 2340) is shown. As discussed above, reflection can occur at any interface between media with different refractive indices, such as an air-material interface or an interface between different dielectric layers. However, the handedness of circularly polarized light is reversed upon reflection. For example, when reflected from the surface of the third retarder 2340, the direction of circular polarization changes (e.g., from left-handed to right-handed). The right-handed reflected ray 2343 then travels through the fourth retarder 2345 and is converted into linearly polarized light that has a different (e.g., orthogonal) linear polarization from the polarization selectively transmitted by the third polarizer 2355. In this case, for example, the light reflected from the optical surface of the third retarder 2340 is converted by the fourth retarder 2345 into vertically linearly polarized light that is orthogonal to the polarization selectively transmitted by the third polarizer 2355. The third polarizer 2355 selectively passes horizontally polarized light and filters out vertically polarized light. Thus, the reflected ray 2343 is attenuated and / or not transmitted by the third polarizer 2355 and is prevented from reaching at least one waveguide 2348 (e.g., by reflecting off another surface) or at least a reduced amount of such reflected light reaches at least one waveguide 2348 or is coupled therein.

[0229] For circularly polarized light rays reflected from different optical surfaces, the results may be similar. For example, Figure 23B An incident ray 2310 reflected from the optical surface of the fourth retarder 2345 is shown. The handedness of the polarization is switched upon reflection from the fourth retarder 2345. For example, the incident ray 2310 depicted as left-handed circularly polarized is converted into a ray 2350 shown as having right-handed circular polarization upon reflection. The reflected ray 2350 passes through the third retarder 2340 and is converted into vertically polarized light. This vertically polarized light is selectively attenuated or filtered out by the second polarizer 2335.

[0230] As described above, the pixels of the SLM 2375 can be, for example, in an "on" state (although in some embodiments, an undriven state), where light incident on the pixel of the SLM 2375 is reflected therefrom and coupled into at least one waveguide 2348 and directed to the user's eye. However, the pixels of the SLM 2375 can be in an "off" state (which can be a driven state in some embodiments), where light incident on the pixel of the SLM 2375 is not coupled into at least one waveguide 2348 and not coupled into the user's eye. For example, in this "off" state, various embodiments of the SLM 2375 do not introduce a delay when reflected therefrom. Thus, in Figure 23B the example shown in, circularly polarized light incident on the SLM 2375 can remain circularly polarized when reflected from the SLM 2375. However, the handedness of the circularly polarized light can change when reflected from the SLM 2375. For example, Figure 23B the ray 2310 of left-handed circularly polarized light incident on the SLM 2375 shown in can be converted into right-handed circularly polarized light when reflected from the SLM 2375. However, this reflected light can be selectively attenuated by the third polarizer 2355. For example, right-handed circularly polarized light reflected from the SLM 2375 can pass through the cover glass 2370, the compensator 2365, and the fifth retarder 2360. The fifth retarder 2360 can convert the right-handed circularly polarized light into vertically polarized light, which is selectively attenuated by the third polarizer 2355 that can include a horizontal polarizer. Thus, in various embodiments, when the pixel of the SLM is in the "off" state, the fifth retarder 2360 can convert the light reflected from the pixel of the SLM 2375 into a linear polarization orthogonal to the linear polarization selectively transmitted by the third polarizer 2355. Thus, the third polarizer 2355 can selectively attenuate this linearly polarized light, thereby reducing or preventing light from the pixel of the SLM 2375 from reaching at least one waveguide 2348 and being directed to the eye.

[0231] Changes in configuration, such as changes in polarization optics, are possible. For example, more or fewer circular polarizers can be included.

[0232] In various embodiments, for example, as Figure 23C shown in, the third circular polarizer including the fourth retarder 2345 and the third polarizer 2355 is excluded. In this particular embodiment, the fourth retarder 2345, the third polarizer 2355, and the fifth retarder 2360 are not included in the system. Figure 23C shows a design of the augmented reality system 2300, which includes Figure 23A and 23BThe components shown in , but excluding the fourth retarder 2345, the third polarizer 2355, and the fifth retarder 2360. Nevertheless, despite the exclusion of the third circular polarizer, the augmented reality display system is still configured to reduce ghost images. For example, the second circular polarizer reduces reflections that would otherwise cause ghost images. For illustration, Figure 23C depicts light reflected from the third retarder 2340, illustrated as light ray 2380. The act of reflection from the surface of the third retarder 2340 causes the reflected light ray 2380 (which is circularly polarized) to switch its handedness. In this example, the polarization switches from left-handed circular polarization to right-handed circular polarization. The switched circularly polarized light 2380 then passes through the compensator 2365 and impinges on the cover glass 2370 and the SLM 2375. As discussed above, the SLM 2375 can reflect circularly polarized light with the same handedness. Thus, the incident right-handed circularly polarized light can remain right-handed circularly polarized upon reflection. Then, this circularly polarized light reflected from the SLM 2375 (represented by light ray 2382) can pass through the cover glass 2370 and the compensator 2365 and impinge on the third retarder 2340. The switched circularly polarized light 2382 is attenuated by the second circular polarizer, and in particular, by the third retarder 2340 and the polarizer 2335. As Figure 23C shown in , for example, the circularly polarized light 2382 reflected from the SLM 2375 impinges on the third retarder 2340 and is converted by the third retarder 2340 into linearly polarized light having a polarization (e.g., orthogonal) different from the polarization selectively transmitted by the second linear polarizer 2335. In this case, for example, the right-handed circularly polarized light 2382 is converted by the third retarder 2340 into vertically linearly polarized light orthogonal to the polarization selectively transmitted by the second polarizer 2335. The second polarizer 2335 attenuates or blocks the transmission of this linearly polarized light.

[0233] Reflections that can contribute to ghost reflections can also potentially be reduced by tilting the optical surfaces in the system. Figure 24 Shows an example configuration with tilted optical surfaces for reducing reflections that can produce ghost reflections. Figure 24 Shows an augmented reality display system 2400 that includes a light source 2305 that emits light represented by light ray 2310, which passes through any number of polarizers, retarders, lenses, and / or other optical elements as it travels towards the spatial light modulator (SLM) 2375. For illustrative purposes, Figure 24Shown therein are a first polarizer 2312, a first retarder 2315, and a lens 2320 that may form a first circular polarizer. However, additional components may be included, or components may be excluded or arranged or configured differently. In the illustrated example, the SLM 2375 includes a cover glass 2370 therewith. The cover glass 2370 can be a contributor to reflections that produce ghost images. Thus, in some embodiments, the cover glass 2370 can be shaped to direct reflections that may produce ghost images away from the user's eyes. As illustrated, the cover glass 2370 has an inclined surface such that the surface is not parallel to other components or optical surfaces of the system (e.g., the SLM 2375, the first retarder 2315, the first polarizer 2312, at least one waveguide 2348, etc., or their optical surfaces). The major surface of the cover glass 2370 can, for example, have an inclined normal so as not to be aligned or parallel with the optical axis of the augmented reality display system 2400 or optical components therein such as the optic 2320. By being inclined, reflections from the optical surface of the cover glass 2370 can be directed away from at least one waveguide 2348 or an optical coupling element (e.g., a coupling grating or diffractive optical element) for coupling light into at least one waveguide 2348, and reduce the likelihood of reflections from the cover glass 2370 entering at least one waveguide 2348. As illustrated, the reflected light 2405 is directed back to the light source 2305 and away from at least one waveguide 2348, where such light may ultimately reach the user's eyes. In some embodiments, the reflected light 2405 can be directed back to the light source and at least a portion thereof can be recovered at the light source 2305.

[0234] Although Figure 24 the cover glass 2370 with an inclined surface is depicted, an inclined optical surface can be included on any component in the system where unwanted reflections may occur so that the reflections are not coupled into at least one waveguide 2348. Thus, the optical surfaces on other components (such as polarizers, retarders, etc.) can be inclined to reduce reflections that are coupled into at least one waveguide 2348 and the user's eyes. Variations in the shape and size of the cover glass 2370 or other optical components are possible. For example, the cover glass 2370 or other optical components can be thinner. Similarly, the cover glass 2370 or other optical components can have an aspect ratio (ratio of length to thickness) different from that Figure 24 shown. In some embodiments, the cover glass 2370 or other optical components are wedge-shaped. However, other shapes are possible.

[0235] Other arrangements are possible. For example, Figure 25 an embodiment of an augmented reality display system 2500 is shown, which is similar to Figure 24The system 2400 shown in [description], but further includes a light dump 2505 for absorbing the light directed thereto. The system 2500 includes an angled cover glass 2370 to direct the reflection 2510 from the cover glass 2370 to the light dump 2505 rather than back to the light source 2305. The light dump 2505 may include an absorbing material or structure configured to absorb light. The position of the light dump 2505 may vary depending on the implementation, e.g., depending on the angle of the angled cover glass 2370. As discussed above, the method may be applied to other optical surfaces in the system. Additionally, the shape and size of the optical elements may vary.

[0236] A wide range of variations in the augmented reality display are possible. Variations in the polarization optical elements are possible. For example, although a horizontal polarizer is used, in some implementations, a vertical polarizer or a combination of horizontal and vertical polarizers may be employed. Additionally, polarizers characterized by polarization other than vertical or horizontal may be used. Similarly, the light shown in the figures need not be horizontally polarized and may be vertically polarized instead. Likewise, in different implementations, light shown as vertically polarized may be horizontally polarized or vice versa. Linearly polarized light having polarization other than vertical or horizontal may also be used.

[0237] Furthermore, the retarders may be configured differently. For example, the polarized light in the figures need not be left-handed circularly polarized light and may be right-handed circularly polarized light and / or the right-handed polarized light may be left-handed circularly polarized light. Other variations are possible. Different retarder configurations may be employed to produce different combinations of left-handed and / or right-handed polarized light than those shown. Additionally, in some implementations, elliptically polarized light may be used instead of circularly polarized light. For example, a retarder may be employed to convert elliptically polarized light to linearly polarized light and vice versa. Linear polarizers may be used to filter light and may be used to reduce ghost reflections as described herein.

[0238] In some embodiments, other types of polarization elements and their configurations are employed. For example, retarders are not limited to quarter-wave retarders or quarter-wave plates. For instance, in some embodiments, various optical elements are birefringent. In some such cases, any one or more of the retarders 2315, 2330, 2340 can include a retardation amount sufficient to convert linearly polarized light into circularly polarized light and need not be a quarter-wave retarder. Any one or more of the retarders 2315, 2330, 2340 can include more or less than a quarter-wave of retardation since the retardation can be contributed by other optical elements. Similarly, the retardation can be distributed among multiple optical elements. As another example, multiple retarders can be employed to provide an appropriate amount of retardation. Additionally, as described above, in some embodiments, elliptically polarized light may be used instead of circularly polarized light. For example, a retarder can be employed to convert elliptically polarized light into linearly polarized light and vice versa. Linear polarizers can be used to filter light and can be used to reduce ghost reflections as described herein.

[0239] Furthermore, the optical component can be in the form of an optical layer, sheet, and / or film and a stack or one or more layers, sheets, and / or films. Thus, different polarization elements with different amounts, positions, and arrangements can be used. For example, one or more retarders and / or polarizers can include a film.

[0240] In some embodiments, the spatial light modulator can operate differently. For example, the spatial light modulator can operate on light other than circularly polarized light and / or can output light other than circularly polarized light.

[0241] Embodiments of the present invention relate to manufacturable architectures where an eyepiece stack architecture can benefit from using a split ICG pupil design or a combination of an in-line ICG pupil and a split ICG pupil design, thereby expanding the application range of using only in-line ICG. As described herein, a split ICG pupil refers to an ICG pupil where light from a projection system is coupled to two or more diffractive ICG pupils within a stack, and these two or more diffractive ICG pupils do not overlap when looking through the ICG planar shape surface in the input direction of the projection system. As described herein, an in-line ICG pupil refers to an ICG pupil that partially or fully overlaps in the same planar view. The inventors have determined that using split pupils in an LCOS-based projection system can achieve many advantages. For example, blue and green projection images (e.g., images generated using a light-emitting diode (LED) light source) can be projected into a single pupil or two independent pupils in a single eyepiece waveguide layer.

[0242] Figure 26AShows a plan view of an eyepiece waveguide employing a dual - active - layer architecture according to an embodiment of the present invention. As discussed in more detail below, embodiments of the present invention apply the dual - active - layer architecture to the eyepiece waveguide 2600, where two eyepiece waveguide layers are employed. Light of a first wavelength (e.g., a red projected image generated using a red light source (e.g., a red light - emitting diode (LED))) passes through a light - passing aperture on the first eyepiece waveguide layer and is coupled into the second eyepiece waveguide layer using an input - coupling diffraction structure. After being coupled into the second eyepiece waveguide layer, the first wavelength is waveguide - d to an output - coupling diffraction structure optically coupled to the second eyepiece waveguide layer.

[0243] In the examples described herein, the first wavelength is a red wavelength, the second wavelength is a green wavelength, and the third wavelength is a blue wavelength. Thus, the first / red wavelength, the second / green wavelength, and the third / blue wavelength can be used interchangeably. Additionally, in the examples described herein, the input - coupling diffraction structure is an input - coupling grating (ICG) (i.e., the first ICG 2612), and the output - coupling diffraction structure is a combined OPE / EPE pupil expander (CPE). These references will be used in this specification, but it should be understood that other embodiments are also within the scope of the present invention.

[0244] Light of the second and third wavelengths (e.g., a green projected image generated using a green light source (e.g., a green LED) and a blue projected image generated using a blue light source (e.g., a blue LED)) is coupled into the first eyepiece waveguide layer using an input - coupling diffraction structure, which in some embodiments is implemented as the first ICG 2612. After being coupled into the first eyepiece waveguide layer, the second and third wavelengths are waveguide - d to an output - coupling diffraction structure optically coupled to the first eyepiece waveguide layer. Similar to the exemplary use of the red wavelength as the first wavelength, the green wavelength and the blue wavelength will be used as the exemplary second and third wavelengths, respectively.

[0245] Figure 26B Shows Figure 26A An exploded view of the eyepiece waveguide shown in. In the exploded view of this eyepiece waveguide 2600, the first eyepiece waveguide layer 2610 is located on the user side of the eyepiece waveguide 2600, and the second eyepiece waveguide layer 2620 is located on the world side of the eyepiece waveguide 2600. The first eyepiece waveguide layer 2610 includes the first ICG 2612 for coupling in blue and green wavelengths. The second eyepiece waveguide layer 2620 includes the second ICG 2622 for coupling in red wavelength. The first CPE 2614 couples out light from the first eyepiece waveguide layer 2610, and the second CPE 2624 couples out light from the second eyepiece waveguide layer 2620.

[0246] Figure 26C Shows Figure 26A A cross - sectional view of the eyepiece waveguide shown in. As Figure 26CAs shown, the red projection image can be separately coupled into the second eyepiece waveguide layer 2620 after passing through the first eyepiece waveguide layer 2610 (i.e., the blank area 2605 of the first eyepiece waveguide layer), and is incident on the second ICG 2622 of the second eyepiece waveguide layer 2620. After waveguiding in the second eyepiece waveguide layer 2620, the light is coupled out by the second CPE 2624. The red light passing through the blank area 2605 of the first eyepiece waveguide layer 2610 of the first eyepiece waveguide layer 2610 can have a nano-pattern or an anti-reflection coating with a sub-diffraction grating pitch (e.g., <160nm) to reduce the reflection of these red wavelengths. For example, the first eyepiece waveguide layer 2610 can be TADF55W with a refractive index of n = 2.01, and the first eyepiece waveguide layer 2610 can have an ICG grating pattern pitch of approximately 330nm for blue light (455nm) and green light (530nm).

[0247] Referring again to Figure 26C , the green projection image and the blue projection image can be coupled into the first eyepiece waveguide layer 2610 through the first ICG 2612. After waveguiding in the first eyepiece waveguide layer 2610, the light is coupled out by the first CPE 2614.

[0248] For example, the substrates used to fabricate the first eyepiece waveguide layer 2610 and the second eyepiece waveguide layer 2620 can be TADF55W with a refractive index of n = 2.01. The grating pattern pitch of the first ICG 2612 can be approximately 330nm, which can effectively couple in blue light (i.e., 455nm) and green light (i.e., 530nm), and the grating pitch of the second ICG 2622 can be approximately 420nm, which can effectively couple in red light (i.e., 630nm). The dual-active layer architecture of the eyepiece waveguide 2600 can be suitable for supporting a diagonal field of view of 60° or higher.

[0249] Although this eyepiece waveguide is implemented using a bilateral eyepiece waveguide, i.e., having diffraction structures on both sides of the eyepiece waveguide layer, the present invention does not require this, and a unilateral design can also be used. In addition, although Figure 26A a dual-pupil design is shown, this is not necessary, and as described in more detail below, a triple-pupil design is also within the scope of the present invention.

[0250] Figure 27A A plan view of an eyepiece waveguide employing a dual-active layer architecture according to another embodiment of the present invention is shown. Figure 27B Shown is Figure 27A an exploded view of the eyepiece waveguide shown Figure 27C Shown is Figure 27A a cross-sectional view of the eyepiece waveguide shown

[0251] Figures 27A - 27C The dual-active layer architecture employed by the eyepiece waveguide 2700 shown is the same as that ofFigures 26A - 26C The dual active layer architecture employed by the illustrated eyepiece waveguide 2600 has common characteristics and is relevant to Figures 26A - 26C the related discussion can be applied to the eyepiece waveguide 2700 as appropriate. Specifically, Figure 27A the illustrated triple-pupil design is well-suited for use in an LCOS-based projector system.

[0252] Referring to Figure 27A , the eyepiece waveguide 2700 includes an architecture in which a third ICG 2722, a second ICG 2713, and a first ICG 2712 are spatially separated on the plane of the eyepiece waveguide. As shown in the exploded view of Figure 27B , a first eyepiece waveguide layer 2710 is located on the user side of the eyepiece waveguide 2700, and a second eyepiece waveguide layer 2720 is located on the world side of the eyepiece waveguide 2700. The first eyepiece waveguide layer 2710 includes a first ICG 2712 for coupling in the blue wavelength and a second ICG 2713 for coupling in the green wavelength. The second eyepiece waveguide layer 2720 includes a third ICG 2722 for coupling in the red wavelength. A first CPE 2714 couples out light from the first eyepiece waveguide layer 2710, and a second CPE 2724 couples out light from the second eyepiece waveguide layer 2720.

[0253] Referring to Figure 27C , after passing through the first eyepiece waveguide layer 2710, the red projected image is separately coupled to the second eyepiece waveguide layer 2720 to be incident on the third ICG 2722 of the second eyepiece waveguide layer 2720. After waveguiding in the second eyepiece waveguide layer 2720, the light is coupled out by the second CPE 2724. The blue projected image is coupled into the first eyepiece waveguide layer 2710 by the first ICG 2712, and the green projected image is coupled into the first eyepiece waveguide layer 2710 by the second ICG 2713. After waveguiding in the first eyepiece waveguide layer 2710, the light is coupled out by the first CPE 2714.

[0254] As shown in Figure 27C , another difference in the dual active layer architecture discussed herein is the use of a very flat and relatively thick waveguide substrate (e.g., total thickness variation (TTV) < 100 nm) or the use of a tapered-thickness eyepiece waveguide layer, e.g., the ICG side is thicker than the CPE side and the thickness gradually decreases across the entire eyepiece waveguide layer, e.g., the TTV across the entire eyepiece waveguide layer ranges from 300 nm to 800 nm. In the embodiment shown in Figure 27C , as shown in Figure 27CAs shown, blue and green light are coupled into and waveguided in the thicker first eyepiece waveguide layer 2710, and red light is waveguided in the thinner second eyepiece waveguide layer 2720. This architecture also improves the uniformity of the projected RGB image, especially suitable for designs that maintain the eyepiece waveguide stack at a certain (e.g., minimum) thickness for mechanical stiffness while remaining within a specific total stack thickness range suitable for wearable devices. As Figure 27C shown, red light will have the longest bounce spacing, thus creating a virtual image gap where the pupil replicates and spreads internally when the red light exits, resulting in a screen door image artifact. Conversely, coupling and propagating blue light in the thinnest waveguide may cause blue light loss and reduced image sharpness because blue light has the shortest bounce spacing. When red light is coupled into a thinner waveguide, the uniformity artifacts are improved compared to a thicker waveguide, while when blue and green light are coupled into a thicker waveguide, the overall sharpness of the image is improved, and to some extent, the out-coupling efficiency of both colors of light is improved.

[0255] Figures 28A - 28C Cross-sectional views of dual-active-layer eyepiece waveguides according to various embodiments of the present invention are shown. In these figures, two pupil designs are shown where the waveguide layer thicknesses are different, and the thickness of the waveguide layer varies across the entire waveguide layer (i.e., TTV is the same or varies). These embodiments are applicable to the coupling in and out of different colors of light.

[0256] In Figure 28A , the first eyepiece waveguide layer 2810 is thicker than the second eyepiece waveguide layer 2820. Red light is coupled in at the second ICG 2822, and blue and green light are coupled in at the first ICG 2812. In this separated pupil configuration, the first ICG 2812 and the second ICG 2822 are spatially separated in the transverse (i.e., x - y plane). Thus, in some embodiments, the thickness t2 of the second eyepiece waveguide layer 2820 is greater than the thickness t1 of the first eyepiece waveguide layer 2810. This thickness difference can be designed according to the wavelength propagating in the eyepiece waveguide. For example, as Figure 28A shown, the thinner eyepiece waveguide supports red wavelengths, while the thicker eyepiece waveguide supports blue and green wavelengths.

[0257] In Figure 28B , similar to the embodiment shown in Figure 28A , the first eyepiece waveguide layer 2810 is thicker than the second eyepiece waveguide layer 2830. Red light is coupled in at the second ICG 2822, and blue and green light are coupled in at the first ICG 2812. In this separated pupil configuration, the first ICG 2812 and the second ICG 2822 are spatially separated. Similar to Figure 28AUnlike the embodiments shown, the thickness of the second eyepiece waveguide layer 2830 varies, being thicker near the second ICG 2822 than near the CPE 2832. Accordingly, the thickness of one or more of the eyepiece waveguide layers can vary in a lateral plane (i.e., the x-y plane).

[0258] In Figure 28C the first eyepiece waveguide layer 2840 is thicker than the second eyepiece waveguide layer 2830. Red light is coupled in at the second ICG 2822, and blue and green light are coupled in at the first ICG 2812. Compared with the embodiments shown in Figure 28A and 28B the thickness of the first eyepiece waveguide layer 2840 also varies, being thicker near the first ICG 2812 than near the CPE 2842.

[0259] As shown herein, a single ICG pupil can be used, i.e., for in-line ICG, the ICG pupil is located at one position; or multiple ICG pupils can be used, i.e., a split pupil configuration is employed. In the embodiment shown in Figures 28A - 28C a split pupil configuration is employed, in which the second ICG has a spatial offset relative to the first ICG in a lateral plane (i.e., the x-y plane). These split pupil designs can also include a three-pupil design, as described in connection with Figure 27A In addition, the ICG can operate in a reflection mode as described above, or in a transmission mode as described in more detail below. In some embodiments, at least one ICG is transmissive such that light that is not diffracted when passing through the transmissive ICG can be passed to the ICG pupil of the next active layer, enabling this transmitted light to be coupled in and waveguided in the next active layer.

[0260] Figure 29A A plan view of an eyepiece waveguide employing a dual active layer architecture with split and in-line ICGs in accordance with an embodiment of the present invention is shown. Figure 29A The eyepiece waveguide 2900 shown shares common elements with the eyepiece waveguide 2600 shown in Figure 26A and the description provided for Figure 26A can be applied, mutatis mutandis, to Figure 29A .

[0261] Referring to Figures 29A - 29C, light of a first wavelength (e.g., a red wavelength) is coupled into at the second ICG 2922, propagates in the second eyepiece waveguide layer 2920, and is coupled out by the second CPE 2924. Light of the second and third wavelengths (green wavelength and blue wavelength) is coupled into the first eyepiece waveguide layer 2910 using the first ICG 2912. After being coupled into the first eyepiece waveguide layer 2910, the second and third wavelengths (e.g., green light and blue light) are waveguide to the first CPE 2914. In addition, light of the first wavelength (e.g., red light) is coupled into at the transmissive ICG 2913 that is coupled into the second eyepiece waveguide layer 2920.

[0262] Figure 29B shows Figure 29A An exploded view of the eyepiece waveguide shown. In the exploded view of the eyepiece waveguide 2900, the first eyepiece waveguide layer 2910 is located on the user side of the eyepiece waveguide 2900, and the second eyepiece waveguide layer 2920 is located on the world side of the eyepiece waveguide 2900. The first eyepiece waveguide layer 2910 includes the first ICG 2912 for coupling in blue and green wavelengths. The second eyepiece waveguide layer 2920 includes the second ICG 2922 for coupling in the red wavelength. The first CPE 2914 couples out the light from the first eyepiece waveguide layer 2910, and the second CPE 2924 couples out the light from the second eyepiece waveguide layer 2920.

[0263] Figure 29C shows Figure 29A a cross-sectional view of the eyepiece waveguide shown in. As Figure 29C shown, the red projection image can be coupled into the first eyepiece waveguide layer 2910 through the transmissive ICG 2913 respectively, or can be coupled into the second eyepiece waveguide layer 2920 through the second ICG 2922 respectively. Therefore, compared with the blank area of the first eyepiece waveguide layer shown in Figure 26C , the transmissive ICG 2913 will couple the red wavelength into the first eyepiece waveguide layer 2910 in a transmissive mode. The red wavelength not coupled by the transmissive ICG2913 will propagate through the first eyepiece waveguide layer 2910 and be incident on the second ICG 2922 of the second eyepiece waveguide layer 2920. After being waveguide in the first eyepiece waveguide layer 2910 and the second eyepiece waveguide layer 2920, the red wavelength is coupled out by the second CPE 2924 and the first CPE 2914 respectively.

[0264] Referring again to Figure 29C , the green projection image and the blue projection image can be coupled into the first eyepiece waveguide layer 2910 through the first ICG 2912. After being waveguide in the first eyepiece waveguide layer 2910, the light is coupled out by the first CPE 2914.

[0265] Although the reflective ICG implemented as the second ICG 2922 is coupled to the second eyepiece waveguide layer 2920, in other embodiments, an additional reflective ICG may be implemented as a third ICG opposite the transmissive ICG 2913 to couple additional red light into the first eyepiece waveguide layer 2910. This additional reflective ICG may be implemented in place of or in addition to the second ICG 2922. Additionally, an additional transmissive ICG may be implemented on the second eyepiece waveguide layer 2920 opposite the second ICG 2922. Additionally, a transmissive ICG may be implemented on the first eyepiece waveguide layer 2910 opposite the first ICG 2912. Thus, in a dual active layer architecture, both reflective and transmissive ICGs may be used in combination in split pupil designs and single pupil designs. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0266] Figure 30A A plan view of an eyepiece waveguide 3000 employing a dual active layer architecture in accordance with an embodiment of the present invention is shown. In this dual active layer architecture, a split pupil is used in combination with in-line ICGs, where the in-line ICGs may include ICGs operating in a reflective mode and / or a transmissive mode. Figure 30B Shows Figure 30A An exploded view of the shown eyepiece waveguide. Figure 30C Shows Figure 30A A cross-sectional view of the shown eyepiece waveguide.

[0267] Referring Figures 30A - 30C , light of a first wavelength (e.g., a red wavelength) is coupled in at the second ICG 3022, propagates in the second eyepiece waveguide layer 3020, and is coupled out by the second CPE 3024. Light of a second wavelength (e.g., a green wavelength) is coupled into the second eyepiece waveguide layer 3020 using the third ICG 3023. After being coupled into the second eyepiece waveguide layer 3020, the light of the second wavelength (i.e., the green wavelength) is waveguide - directed towards the second CPE 3024.

[0268] Considering the first eyepiece waveguide layer, light of the second wavelength is coupled into the first eyepiece waveguide layer 3010 using the transmissive ICG 3013. After being coupled into the first eyepiece waveguide layer 3010, the light of the second wavelength is waveguide - directed towards the CPE 3014. Additionally, light of a third wavelength (e.g., a blue wavelength) is coupled in at the first ICG 3012 and propagates in the first eyepiece waveguide layer 3010.

[0269] Thus, in the eyepiece waveguide layer that supports the red wavelength (i.e., the second eyepiece waveguide layer in this example) and the eyepiece waveguide layer that supports the blue wavelength (i.e., the first eyepiece waveguide layer in this example), both support light of the green wavelength. Since the green wavelength may be dominant on the nasal side in the eyepiece waveguide layer designed to support the blue wavelength, and may be dominant on the temple side in the eyepiece waveguide layer designed to support the red wavelength, thus, propagating light of the green wavelength in the first eyepiece waveguide layer 3010 and the second eyepiece waveguide layer 3020 will improve image uniformity.

[0270] In some embodiments, an optional transmissive ICG 3015 is utilized such that light can be coupled into the first eyepiece waveguide layer 3010 via the transmissive ICG (e.g., transmissive ICG 3015) and the reflective ICG (e.g., the first ICG 3012). Thus, for a single color coupled into an active layer, light can enter through the transmissive ICG on the projector light input side, propagate through the eyepiece waveguide layer, and then also be coupled by the reflective ICG, thereby guiding the same type of projector light into the eyepiece waveguide layer via transmissive coupling and reflective coupling. Therefore, embodiments of pi can use two ICGs to split light into two different directions in a plane perpendicular to the cross-section shown in Figure 30C In addition, a thicker substrate can use one or more ICGs on either side of the eyepiece waveguide to increase pupil replication and reduce the screen door artifact. Although the optional transmissive ICG 3015 is used in combination with the first eyepiece waveguide layer 3010, a similar transmissive ICG can be used in combination with the second eyepiece waveguide layer 3020. Thus, as Figure 30C shown, embodiments of the present invention can use transmissive and reflective ICGs, which are located at one or more pupil positions and on one or both sides of the corresponding eyepiece waveguide layer. Those skilled in the art can understand many variations, modifications, and alternatives.

[0271] Figure 31A A plan view of an eyepiece waveguide 3100 employing a dual active layer architecture according to another embodiment of the present invention is shown. Figure 31B Shown is Figure 31A An exploded view of the shown eyepiece waveguide. Figure 31C Shown is Figure 31A A cross-sectional view of the shown eyepiece waveguide.

[0272] Refer to Figures 31A - 31C, light of the red wavelength is coupled into by the first ICG 3113, propagates in the first eyepiece waveguide layer 3110, and is coupled out by the CPE 3114. Light of the green wavelength is coupled into the first eyepiece waveguide layer 3110 by the transmissive ICG 3115, and light of the green wavelength is also coupled into the second eyepiece waveguide layer 3120 by the second ICG 3122. After being coupled into the first eyepiece waveguide layer 3110 and the second eyepiece waveguide layer 3120, light of the green wavelength is respectively guided to the CPE 3114 and the CPE 3124. Light of the blue wavelength is coupled into by the third ICG 3123, propagates in the second eyepiece waveguide layer 3120, and is then coupled out by the CPE 3124.

[0273] Therefore, the eyepiece waveguide layer that supports the red wavelength (i.e., the first eyepiece waveguide layer in this example) and the eyepiece waveguide layer that supports the blue wavelength (i.e., the second eyepiece waveguide layer in this example) both support the green wavelength.

[0274] Similar to Figure 30C the optional transmissive ICG 3015 shown in, the optional transmissive ICG 3125 and the optional transmissive ICG 3127 can be used to enable light to be coupled into the second eyepiece waveguide layer 3120 via the transmissive ICG (e.g., the transmissive ICG 3125 and / or the transmissive ICG 3127) and the reflective ICG (e.g., the second ICG 2133 and / or the third ICG 3123). Therefore, as Figure 31C shown, embodiments of the present invention can utilize transmissive and reflective ICGs located at one or more pupil positions and on one or both sides of the corresponding eyepiece waveguide layer. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0275] Therefore, within the scope of the present invention are included a dual-active layer architecture with a split pupil design, and an architecture combined with in-line ICGs, whether or not using ICGs operating in reflection mode and / or transmission mode. Those of ordinary skill in the art will recognize many variations, modifications, and alternatives.

[0276] In addition to the dual active layer architecture using a split pupil (with or without in-line ICG) shown in the above examples, embodiments of the present invention can also specify the size of the ICG pupil based on the proximity of the ICG to the projector and the thickness of the eyepiece waveguide layer to which the eyepiece waveguide layer is coupled. This is because the light generated by the projector (e.g., an LCOS projector) spreads outwards in a conical geometry, and once the light is coupled in through the diffraction structure of the ICG, since the light undergoing total internal reflection can bounce on the opposite surface and bounce back to the ICG grating, the reflected light can then be coupled out through the diffraction of the ICG pupil. These bounced-back lights are lost and cannot reach the CPE, thus reducing the brightness of the virtual image projected from the eyepiece waveguide to the user. For example, for an eyepiece waveguide layer with a thickness of approximately 350 μm, in the direction of the optical axis towards the combiner element, the ICG size with the minimum bounce-back loss for expansion and coupling out will be less than 0.9 mm. Similarly, for a waveguide substrate with a thickness of 500 μm, the ICG size will increase slightly.

[0277] Figure 32A A cross-sectional view of an eyepiece waveguide according to an embodiment of the present invention is shown. In Figure 32A , the light from the projector 3205 is incident on the first eyepiece waveguide layer 3210, which includes a first ICG 3212 that operates in a transmission mode to couple the light into the first eyepiece waveguide layer 3210. The light from the projector 3205 is also incident on the second eyepiece waveguide layer 3220, which includes a second ICG 3222 that operates in a transmission mode to couple the light into the second eyepiece waveguide layer 3220, and a third ICG 3224 that operates in a reflection mode to couple the light into the second eyepiece waveguide layer 3220. As Figure 32A shown, the diameter D of each ICG increases with the distance from the projector 3205.

[0278] Figure 32B A Figure 32A planar view of the ICGs of the eyepiece waveguide shown in Figure 32A is shown. In this layout, the first ICG 3212, the second ICG 3222, and the third ICG 3224 are concentric, and the diameter of each ICG gradually increases as

[0279] Figure 32C A Figure 32A planar view of an alternative ICG that can be used with the eyepiece waveguide shown in

[0280] Figure 32D A cross-sectional view of an eyepiece waveguide according to an alternative embodiment of the present invention is shown. InFigure 32D In this case, the projector 3235 is tilted with respect to the z-axis, so that the light from the projector 3205 is incident on the eyepiece waveguide layer at an angle. Therefore, the ICG will shift to accommodate this tilted light injection. As Figure 32D shown, the light from the projector 3235 is incident on the first eyepiece waveguide layer 3240, which contains the first ICG 3242, which operates in a transmission mode to couple light into the first eyepiece waveguide layer 3240. The light from the projector 3235 is also incident on the second eyepiece waveguide layer 3250, which contains the second ICG 3252, which operates in a transmission mode to couple light into the second eyepiece waveguide layer 3250; and the third ICG 3254, which operates in a reflection mode to couple light into the second eyepiece waveguide layer 3250. As Figure 32D shown, the diameter D of each ICG increases with the distance from the projector 3235. In addition, as the distance from the projector 3235 increases, the displacement position of the ICG along the x-axis becomes more negative.

[0281] Figure 32E shows Figure 32D a plan view of the ICGs of the eyepiece waveguide shown. In this layout, the first ICG 3242, the second ICG 3252, and the third ICG 3254 are displaced along the x-axis, and the diameter of each ICG is as Figure 32D shown to increase.

[0282] Figure 32F shows Figure 32D a plan view of alternative ICGs that can be used with the eyepiece waveguide shown. In this layout, the first ICG 3242', the second ICG 3252', and the third ICG 3254' are aligned at a common y-position, but are also offset along the x-axis in addition to being truncated at the bottom.

[0283] Therefore, embodiments of the present invention can utilize such a design in which, considering the waveguide substrate thickness and the tilt of the projector plane with respect to the ICG waveguide surface plane, the dependence of pupil positioning and ICG size in the overlapping in-line ICG regions can vary.

[0284] Figure 33A shows a plan view of an eyepiece waveguide having a three-pupil layout according to an embodiment of the present invention. In this dual-active layer architecture, the three pupils are used in combination with an LCOS projector, where the individual ICGs operate in a reflection mode for red and blue wavelengths and in both reflection and transmission modes for green wavelengths. As described below, the green wavelength is coupled into the eyepiece waveguide layer designed for the red wavelength, but in other embodiments, the green wavelength can also be coupled into the eyepiece waveguide layer designed for the blue wavelength, either in combination with the coupling in the red eyepiece waveguide layer or instead of the coupling in the red eyepiece waveguide layer.

[0285] Figure 33B Use Figure 33A The cross-sectional view of the eyepiece waveguide shown in FIG. illustrates the light coupling and propagation. Refer to Figure 33A and 33B , the three-pupil layout of the LCOS projector is used together with the dual-active layer architecture. In the cross-sectional view shown in Figure 33B , for clarity, each eyepiece waveguide layer is shown twice, where the blue light interaction is shown in the upper part of the figure, the green light interaction is shown in the middle part of the figure, and the red light interaction is shown in the lower part of the figure. To couple red light into the first eyepiece waveguide layer 3310 (see the lower part of the figure), the red ICG 3321 coupled to the first eyepiece waveguide layer 3310 operates in a reflection mode. Similarly, to couple blue light into the second eyepiece waveguide layer 3320 (see the upper part of the figure), the blue ICG 3324 coupled to the second eyepiece waveguide layer 3320 also operates in a reflection mode.

[0286] Green light (see the middle part of the figure) is first coupled into the first eyepiece waveguide layer 3310 (optimized for red wavelength in some embodiments) by the transmissive ICG 3323 operating in a transmission mode. The green light not coupled by the transmissive ICG 3323 then transmits through the first eyepiece waveguide layer 3310 and is coupled into the second eyepiece waveguide layer 3320 (optimized for blue wavelength in some embodiments) by the green ICG 3322 operating in a reflection mode. In addition to coupling green light, the green ICG 3322 also diffracts the zero-order light (i.e., zero-order diffracted light) back into the first eyepiece waveguide layer 3310, such that the transmissive ICG 3323 coupled to the first eyepiece waveguide layer 3310 couples the zero-order diffracted light in a reflection mode. The light shown by ray 3315 circulates through multiple eyepiece waveguide layers, which can improve the light efficiency of the eyepiece waveguide because the gap between the eyepiece waveguides can be well controlled, for example, within a range of less than 3 μm / cm. Various embodiments of the present invention control the gap by using spacer elements such as glass beads, imprinted posts, dispensed and cured dots, etc. in certain parts of the waveguide, using a well-cured edge adhesive, and increasing the thickness of at least one eyepiece waveguide layer.

[0287] Figures 33C - 33E is Figure 33A the field-of-view image generated by the eyepiece waveguide shown in FIG. In these figures, the field of view is 70° field of view. As shown in Figures 33C - 33E , the dual-active layer architecture described herein provides the required uniformity.

[0288] The selection of the diffraction pitch for the dual-active eyepiece waveguide layer can vary according to the combination of colors propagating in the eyepiece waveguide layer.

[0289] Figure 34AIt is a spectrogram showing the diffraction pitch used in the dual active layer architecture according to an embodiment of the present invention. Figure 34B and Figure 34C is a simplified cross-sectional view of a dual active layer architecture according to an embodiment of the present invention.

[0290] As Figure 34A shown, in the triple active layer architecture, the grating pitch of the blue ICG corresponds to the blue wavelength λ1, and the grating pitch of the red ICG corresponds to the red wavelength λ4. Figure 34C In the dual active layer architecture shown in, the grating pitch can be set to correspond to a color between the blue and red wavelengths. For example, the grating pitch of the first ICG corresponds to the cyan wavelength λ2, and the grating pitch of the second ICG corresponds to the orange wavelength λ3. Alternatively, as Figure 34B shown, combinations of blue - orange or cyan - red and blue - red can be used to achieve RGB virtual image waveguides and projections.

[0291] Therefore, some embodiments use a combination of waveguides designed separately for more specific wavelength ranges to project RGB virtual images. For example, using a dual active layer combination, with a substrate refractive index n = 2.0, for an ICG diffraction pitch of >60°FoV: a) a 330nm pitch optimized for blue and a 420nm pitch optimized for red; b) a 340nm pitch optimized between blue - green and a 390 - 410nm pitch optimized between green - red. Therefore, some embodiments use gratings corresponding to wavelengths (such as λ2 and λ3) between the wavelengths output by the projector (such as λ1 and λ4). Compared to an eyepiece waveguide stack using gratings corresponding to blue (λ1) and red (λ4), the advantage of using an eyepiece waveguide stack with gratings corresponding to cyan (λ2) and orange (λ3) is that the pitch optimized for red can interact with the world light, thus copying the real world image into the user's field of view (FoV) (e.g., rainbow artifacts). Additionally, the larger pitch reduces the transmittance of the blue wavelength spectrum and results in a less "white" and slightly "yellow" visible stack. This may undesirably change the chromatogram of the world image seen by the user through such a waveguide stack. Therefore, as Figure 34B and 34C shown, the dual active layer architecture can consider using diffraction pitches optimized for blue - red, blue - orange, cyan - orange, or cyan - red combinations to achieve waveguides and projections of RGB virtual images.

[0292] Figure 35A Shows a cross-sectional view of an eyepiece waveguide using a dual active layer architecture according to an embodiment of the present invention. Figures 35B - 35C Shows Figure 35A a plan view of the user - side eyepiece waveguide layer of the eyepiece waveguide shown.Figures 35D - 35E shows Figure 35A A plan view of the world-side eyepiece waveguide layer of the illustrated eyepiece waveguide.

[0293] As Figure 35A shown, the first eyepiece waveguide layer 3510 (i.e., the blue eyepiece waveguide layer) includes a transmissive ICG 3512 that operates in a transmissive mode to diffract the green wavelength into the first eyepiece waveguide layer 3510. The transmissive ICG 3512 can be an inclined grating structure with a bilayer structure (e.g., a SiO2 layer covering a TiO2 layer). In some embodiments, the angle of the inclined grating can be a sharp angle or a rounded angle. Additionally, the first eyepiece waveguide layer 3510 includes a first reflective ICG 3514 that is coupled to the world side of the first eyepiece waveguide layer 3510 and operates in a reflective mode to diffract the blue wavelength into the first eyepiece waveguide layer 3510.

[0294] The second eyepiece waveguide layer 3520 (i.e., the red eyepiece waveguide layer) includes two ICGs that operate in a reflective mode: a second reflective ICG 3522 that is coupled to the world side of the second eyepiece waveguide layer 3520 and operates in a reflective mode to diffract the green wavelength into the second eyepiece waveguide layer 3520, and a third reflective ICG 3524 that is coupled to the world side of the second eyepiece waveguide layer 3520 and operates in a reflective mode to diffract the red wavelength into the second eyepiece waveguide layer 3520.

[0295] Since light of a longer wavelength emitted into an eyepiece waveguide designed to propagate light of a shorter wavelength (e.g., emitting 530 nm green light into an eyepiece waveguide with a grating corresponding to 450 nm blue light) can result in stronger out-coupling on the nasal side, while light of a shorter wavelength emitted into an eyepiece waveguide designed to propagate light of a longer wavelength (e.g., emitting 530 nm green light into an eyepiece waveguide with a grating corresponding to 660 nm red light) can result in stronger out-coupling on the temple side, the combination of the transmissive ICG 3512 on the first eyepiece waveguide layer 3510 (i.e., the blue eyepiece waveguide layer) and the second reflective ICG 3522 on the second eyepiece waveguide layer 3520 (i.e., the red eyepiece waveguide layer) can produce uniform out-coupling because the light coupled in by the transmissive ICG 3512 will be more strongly out-coupled on the nasal side, and the light coupled in by the second reflective ICG 3522 will be more strongly out-coupled on the temple side.

[0296] As Figures 35B to 35E shown, the ICG large pupil 3530 includes six parts: a first part 3531, a second part 3532, a third part 3533, a fourth part 3534, a fifth part 3535, and a sixth part 3536. As Figure 35B and 35CAs shown, the transmissive ICG 3512 is located in the sixth part 3536 of the ICG large pupil 3530, and the first reflective ICG 3514 is located in the first part 3531 of the ICG large pupil 3530. As Figure 35D and 35E shown, the second reflective ICG 3522 is located in the sixth part 3536 of the ICG large pupil 3530, and the third reflective ICG 3524 is located in the fifth part 3535 of the ICG large pupil 3530. Figures 35B to 35E By way of example only, the placement of the ICGs can be adjusted as needed to position the ICGs in other parts of the large pupil. For example, the positions of the first reflective ICG 3514 and the third reflective ICG 3524 can be interchanged, with the first reflective ICG 3514 located in the fifth part 3535 and the third reflective ICG 3524 located in the first part 3531. Additionally, the positions of the eyepiece waveguide layers can also be interchanged, with the first eyepiece waveguide layer 3510 located on the user side (i.e., the projector side) of the eyepiece waveguide and the second eyepiece waveguide layer 3520 located on the world side. Further, in some embodiments, the transmissive ICG 3512 is optional, thereby forming an eyepiece waveguide that uses only three reflective ICGs. In other embodiments, the transmissive ICG 3512 in the eyepiece waveguide is replaced by a reflective ICG, and the eyepiece waveguide utilizes four reflective ICGs that are coupled to the world side of the eyepiece waveguide layer. One or more of the ICGs can include a coating to increase their transparency. Those skilled in the art will appreciate many variations, modifications, and alternatives.

[0297] Referring again to Figure 35A , the cover layer 3542 is integrally stacked with the eyepiece waveguide. The cover layer 3542 can include a reflective surface (e.g., at visible wavelengths) that reflects the incident light that has passed through the eyepiece waveguide layer. In this embodiment, the cover layer 3542 reflects the light and effectively recycles the light, thereby improving the efficiency of the eyepiece waveguide stack. In other embodiments, the cover layer 3542 can include an absorptive surface (e.g., at visible wavelengths) that absorbs the light that has passed through the eyepiece waveguide layer. The absorptive surface can avoid unnecessary reflections and ghosting generated by the eyepiece waveguide stack. In Figure 35A the embodiment shown, the cover layer 3542 includes a dual-film coating implemented using a reflective surface 3544 (e.g., a partially reflective surface) and a light-absorbing surface 3546 opposite the reflective surface 3544. In other embodiments, the positions of the reflective surface 3544 and the light-absorbing surface 3546 can be interchanged.

[0298] Figures 36A - 36FShows various diffraction grating structures according to embodiments of the present invention that can be used to couple in gratings, orthogonal pupil expansion gratings, exit pupil expansion gratings, or combined pupil expansion gratings. The diffractive elements (such as gratings) used in the eyepiece waveguide can be (but are not limited to) tilted (as Figure 36A shown), tilted with a coating (as Figure 36B shown), serrated or shark fin shaped (as Figure 36C shown), or having a reflective coating on the tilt (as Figure 36D shown), tilted (as Figure 36E shown), or serrated (as Figure 36F shown, in the context of a multi-layer reflective coating). The coatings can be high refractive index and / or low refractive index dielectric materials that couple with the underlying structure and can improve efficiency compared to an uncoated grating. To achieve directional emission of diffracted light, non-conformal coatings or directional coatings can be used. These coatings can be formed using PVD processes such as sputtering and evaporation, where the nano-geometry supporting the coating can be tilted, shark fin shaped, serrated, etc., as shown. Additionally, the grating can be binary, multi-order, super-geometric, one-dimensional, two-dimensional, three-dimensional structures, deformed hybrid gratings, etc. Thus, the illustrated examples of diffractive grating architectures can be part of a surface relief grating including an eyepiece waveguide structure. Transmissive and / or reflective ICGs can be defined by imprinting polymers or etching into a substrate or coating. On top of the pattern, subsequent dielectric or metal coatings can be formed through a multi-step process, and directional or conformal coating processes can be employed as needed.

[0299] The pattern of the ICG can be defined by a patterned diffractive structure composed of a UV / thermally curable polymer material with a refractive index range of 1.5 to 2.0. The transmissive ICG can utilize a patterned polymer structure with high refractive index and low refractive index dielectric coatings, for example, coatings made of TiO2, ZrO2, SiC, MgF2, SiO2, etc. The reflective ICG can have dielectric coatings and metal coatings, such as Al, Ag, metal alloys, etc. The metal coating can form an opaque or semi-opaque surface. For example, when the coating thickness is greater than 70 nm, the Al coating becomes opaque. Additionally, a transmissive ICG using Al in the coating architecture and operating in a reflective mode can utilize an Al coating with a thickness range of 5 nm to 50 nm. Those of ordinary skill in the art will recognize many variations, modifications, and alternatives.

[0300] The grating structure can exist on one or both sides of the waveguide. Such gratings can be directly imprinted with a low to high refractive index nanoimprint polymer (1.5 - 2.0), or an inorganic pattern can be directly etched onto a high refractive index substrate (e.g., LiNbO3, LiTaO3, SiC, etc.), or onto a high refractive index film on a high refractive index substrate (e.g., TiO2, ZrO2, SiC, Si3N4, etc.), or a high refractive index (with or without a low refractive index) film coating on the imprinted polymer or etched inorganic pattern. The coating can consist of multiple films with different refractive indices, and the final etched geometry can consist of materials with one or more refractive indices in at least one grating or a portion of the CPE. These diffractive elements can be fabricated by an etching process or a high / low refractive index deposition process.

[0301] Since some grating designs diffract more light in the second order than other grating designs, a grating design that balances the first order diffraction and the second order diffraction can be utilized to balance the light not supported by the eyepiece waveguide after the first order diffraction (e.g., the first portion 803) and the light supported by the eyepiece waveguide after the second order diffraction (e.g., the complementary portion 805), thereby providing a uniformly illuminated field of view. For example, the inventors have determined that a blazed grating etched on a lithium niobate LiNbO3 substrate with a double dielectric / metal coating (e.g., a multi-layer stack of aluminum-coated TiO2 and SiO2) can enhance the second order diffraction, thereby providing a higher emission efficiency (also known as diffraction efficiency) in the second order diffraction than in the first order diffraction. Therefore, an appropriate grating / coating design can be utilized to adjust the amount of light coupled into the first order and the second order. Those of ordinary skill in the art will recognize many variations, modifications, and alternatives.

[0302] A variety of materials can be used in the eyepiece waveguide discussed herein. The waveguide substrate for making the eyepiece can be fabricated using materials with various refractive index ranges, such as high refractive index glass (e.g., 1.7 SCHOTT SF5, 1.8 SF6, HOYA dense tantalum flint glass TAFD55 (refractive index of 2.01), TAFD65 (refractive index of 2.06), etc.), and crystal substrates (e.g., lithium tantalate LiTaO3, lithium niobate LiNbO3 (refractive index of 2.25), silicon carbide (refractive index of 2.65), etc.).

[0303] The inorganic and organic materials that make up the film coating, diffractive and sub-diffractive nanostructures, and / or the outer coating on such nanopatterns on the waveguide substrate can include, but are not limited to:

[0304] Inorganic high refractive index materials such as ZrO2, Ta2O5, Si3N4, TiO2, SiC TiO2 (n range from 2.0 to 2.65), and low refractive index materials such as MgF2, SiO2 (n range from 1.36 to 1.45).

[0305] Organic high refractive index material resists (1.6 ≤ n ≤ 2.11) and low refractive index material resists (1.15 ≤ n ≤ 1.6).

[0306] The deposition of such inorganic and organic materials can be accomplished using, but not limited to, the following methods: for inorganic thin films, physical vapor deposition (evaporation, sputtering), chemical vapor deposition (LP PECVD, ALD, AP PECVD, etc.), and for organic materials, coating by spin coating, slot-die coating, microgravure printing, spin coating, atomization (spraying), etc.

[0307] High refractive index coatings can utilize SiC with a refractive index of 2.5 - 2.6, TiO2 with a refractive index of 2.2 - 2.5, ZrO2 with a refractive index of 2.1, Si3N4 and silicon oxynitride with a refractive index of 1.8 - 2.0, SiO2 with a refractive index of 1.45m, MgF2 with a refractive index of 1.38, etc. Thin film coatings can be obtained using physical vapor deposition (PVD) or chemical vapor deposition (CVD) on blank or patterned surfaces. Physical vapor deposition (PVD) is, for example, evaporation or sputtering (with or without ion assistance (e.g., Ar / O2)), and chemical vapor deposition (CVD) is, for example, low pressure PECVD, atmospheric PECVD, ALD, etc. A fluorinated polymer film with a refractive index of 1.31 can also be coated, where poly[4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxolane-co-tetrafluoroethylene] is dissolved in Fluorinert TM FC-40, with a maximum concentration of up to 2% (weight percentage). Low refractive index films (<1.3) can be formulated into single or multi-layer colloidal film compositions using sol-gel technology, and their components are porous SiO2 polymer matrix compositions. Such low refractive index coatings can be applied by, but not limited to, spin coating, spraying / atomization, inkjet, etc.

[0308] Patternable imprintable prepolymer materials can include resin materials such as epoxy vinyl esters. The resin can include vinyl monomers (e.g., methyl methacrylate) and / or difunctional or trifunctional vinyl monomers (e.g., diacrylate, triacrylate, dimethacrylate, etc.), and the monomers can contain or not contain aromatic molecules. The prepolymer material can contain monomers with one or more functional groups (e.g., alkyl, carboxyl, carbonyl, hydroxyl, and / or alkoxy). Sulfur atoms and aromatic groups (both of which have a relatively high polarizability) can be incorporated into these acrylate components to increase the refractive index of the formulation, which is typically between 1.5 and 1.75. In some embodiments, the prepolymer material can include a resin containing cycloaliphatic epoxy resin, which can be cured using ultraviolet light and / or heat. Additionally, the prepolymer material can contain ultraviolet cationic photoinitiators and co-reactants to facilitate efficient ultraviolet curing under ambient conditions.

[0309] Incorporation of inorganic nanoparticles (NPs) such as ZrO2 and TiO2 into such imprintable resin polymers can significantly increase the refractive index up to 2.1. Pure ZrO2 and TiO2 crystals have refractive indices of up to 2.2 and 2.4-2.6 at 532 nm, respectively. For the preparation of optical nanocomposites of acrylate monomers and inorganic NPs, the particle size can be less than 10 nm to avoid excessive Rayleigh scattering. ZrO2 NPs tend to aggregate in the polymer matrix due to their high specific surface area, high polarity, and incompatibility with the cross-linked polymer matrix. This problem can be overcome by surface modification of the NPs. In this technique, the hydrophilic surface of ZrO2 is modified to be compatible with organic matter, thereby enabling the NPs to be homogeneously mixed with the polymer. This modification can be achieved by end-capping agents containing silanes and carboxylic acids. One end of the end-capping agent is bonded to the ZrO2 surface; the other end of the end-capping agent contains a functional group or a non-functional organic part that can participate in acrylate cross-linking. Examples of surface modified sub-10 nm ZrO2 particles include those manufactured by Pixelligent Technologies TM and Cerion Advanced Materials TM These functionalized nanoparticles are typically sold as a homogenous mixture uniformly suspended in a solvent, which can be combined with other base materials to form photoresist formulations with jettable viscosities and higher refractive indices.

[0310] The prepolymer material can be patterned using a template (superstrate, rigid or flexible) where the anti-tones of the optically functional nanostructures (diffractive and sub-diffractive) are in direct contact with the liquid prepolymer. The liquid prepolymer material can be dispensed onto the substrate or surface to be patterned using methods such as (but not limited to) inkjet drop-on-demand or continuous jet systems, slot coating, spin coating, doctor blade coating, micro-gravure coating, screen printing, spraying or atomization. The template is contacted with the liquid, and once the liquid fills the template features, it crosslinks and patterns, so that the prepolymer with the diffractive pattern is in contact with the template (for example, in imprint lithography (e.g., J-FIL TM ), wherein the prepolymer material is dispensed by inkjet) comprises exposing the prepolymer to a laser having a wavelength between 310 nm and 410 nm and an intensity between 0.1 J / cm 2 and 100 J / cm 2 The method may further include heating the prepolymer to a temperature between 40°C and 120°C while exposing the prepolymer to the actinic radiation.

[0311] To enhance the adhesion between the prepolymer material after patterning (template / mold demolding) and curing on the desired surface or substrate, crosslinking silane coupling agents can be used. One end of these coupling agents bears an organic functional group, and the other end bears a hydrolyzable group, which can form durable bonds with different types of organic and inorganic materials. Examples of organic functional groups can be acrylyl, which can crosslink into a patternable polymer material to form the desired optical pattern / shape. Conversely, the template or mold can also be coated with a similar coating, where the acrylyl end is replaced by a fluorinated chain, which can reduce the surface energy and thus act as non-bonding but releasable sites. Vapor deposition is carried out under low pressure, where the coupling agent is delivered in vapor form, with or without an inert gas (such as N2), for example, in the presence of activated -O and / or -OH groups on the surface of the material to be coated. The vapor coating process can deposit a monolayer film as thin as 0.5 nm to 0.7 nm, and the film thickness can be increased according to specific applications.

[0312] Material Considerations for Eyepiece Waveguides

[0313] The waveguide substrate for making an eyepiece can include materials with a certain refractive index range, such as high refractive index glasses, like 1.7 SCHOTT SF5, 1.8 SF6, HOYA dense tantalum flint glass TAFD55 (refractive index of 2.01), TAFD65 (refractive index of 2.06), etc., and crystal substrates, such as lithium tantalate LiTaO3, lithium niobate LiNbO3 (refractive index of 2.25), silicon carbide (refractive index of 2.65), etc. The high refractive index coating can consist of SiC with a refractive index of 2.5 - 2.6, TiO2 with a refractive index of 2.2 - 2.5, ZrO2 with a refractive index of 2.1, Si3N4 and silicon oxynitride with a refractive index of 1.8 - 2.0, SiO2 with a refractive index of 1.45 m, MgF2 with a refractive index of 1.38, etc. The film coating can be achieved on a blank or patterned surface using physical vapor deposition (PVD) or chemical vapor deposition (CVD), physical vapor deposition such as evaporation or sputtering (with or without ion assistance (such as Ar / O2)), and chemical vapor deposition such as low-pressure PECVD, atmospheric PECVD, ALD, etc.

[0314] The patterned imprintable prepolymer material can include a resin material such as epoxy vinyl ester. The resin can include vinyl monomers (e.g., methyl methacrylate) and / or difunctional or trifunctional vinyl monomers (e.g., diacrylate, triacrylate, dimethacrylate, etc.), and the monomers may or may not contain aromatic molecules. The prepolymer material can contain monomers having one or more functional groups (e.g., alkyl, carboxyl, carbonyl, hydroxyl, and / or alkoxy). Sulfur atoms and aromatic groups (both having a high polarizability) can be incorporated into these acrylate components to increase the refractive index of the formulation, which is typically between 1.5 and 1.75. In some embodiments, the prepolymer material can contain a resin containing cycloaliphatic epoxy resin, which can be cured using ultraviolet light and / or heat. Additionally, the prepolymer material can contain an ultraviolet cationic photoinitiator and a co-reactant to facilitate efficient ultraviolet curing under ambient conditions.

[0315] Incorporating inorganic nanoparticles (NPs) (e.g., ZrO2 and TiO2) into such imprintable resin polymers can significantly increase the refractive index, up to 2.1. The refractive indices of pure ZrO2 and TiO2 crystals can reach 2.2 and 2.4 - 2.6, respectively, at 532 nm. For the preparation of optical nanocomposites of acrylate monomers and inorganic nanoparticles, the particle size can be less than 10 nm to avoid excessive Rayleigh scattering. Due to its high specific surface area, high polarity, and incompatibility with the cross-linked polymer matrix, ZrO2 NPs tend to aggregate in the polymer matrix. This problem can be overcome by surface modification of the NPs. In this technique, the hydrophilic surface of ZrO2 is modified to be compatible with organic substances, enabling the NPs to be uniformly mixed with the polymer. Such modification can be achieved by capping agents containing silane and carboxylic acid. One end of the capping agent bonds to the ZrO2 surface; the other end of the capping agent contains a functional group or a non-functional organic moiety that can participate in acrylate cross-linking. Examples of surface-modified sub-10-nm ZrO2 particles include those provided by TM Pixelligent Technologies TM and Cerion Advanced Materials. These functionalized nanoparticles are typically sold in the form of a homogeneous mixture uniformly suspended in a solvent, which can be combined with other base materials to form a photoresist formulation with a jetable viscosity and a higher refractive index.

[0316] For cross-linking and patterning, contacting the prepolymer with a diffraction pattern with a template (e.g., in imprint lithography techniques (e.g., J-FIL TM ), where the prepolymer material is dispensed by inkjet) includes exposing the prepolymer to a wavelength between 310 nm and 410 nm and an intensity between 0.1 J / cm 2 and 100 J / cm 2Under actinic radiation. The method may further include heating the prepolymer to a temperature between 40°C and 120°C while exposing the prepolymer to actinic radiation. Such prepolymer resin can be dispensed onto the desired surface to be patterned before patterning using a template / mold with inverse tone features, using methods such as inkjet drop-on-demand or continuous jetting systems, slot coating, spin coating, knife coating, microgravure coating, screen printing, spraying, or atomization.

[0317] To enhance adhesion, a crosslinking silane coupling agent is used between the patterning of the prepolymer material (template / mold demolding) and curing on the desired surface or substrate. These coupling agents have an organic functional group at one end and a hydrolyzable group at the other end, and can form durable bonds with different types of organic and inorganic materials. Examples of the organic functional group can be acrylyl, which can crosslink into a patternable polymer material to form the desired optical pattern / shape. Conversely, the template or mold can be coated with a similar coating where the acrylyl end is replaced by a fluorinated chain, which can reduce the surface energy and thus act as a non-bonding but releasable site. Vapor deposition is carried out at low pressure, where the coupling agent is delivered in vapor form, with or without an inert gas (such as N2).

[0318] In some embodiments, a reflective surface and / or an absorptive surface (for the visible spectrum) can be provided on the surface of the added overlay layer. This reflective surface and / or absorptive surface can both help to recycle light and improve the efficiency of the stack, and can also absorb light to avoid unnecessary ejection and ghosting in the eyepiece waveguide stack. Figure 25 Embodiments showing the reflective surface (left figure) and the absorptive surface (right figure) are presented. The overlay layer can also have a dual-film coated surface with a partially reflective surface on one side and a light-absorbing surface on the other side.

[0319] The reflective surface can be made of a metal (such as Al, Ag, etc.) or a high refractive index coating (such as TiO2, SiC, etc.), and the coating of these films can be carried out by dry physical or chemical vapor deposition processes or wet coating processes. The absorptive film can be made of suitable dyes and pigments.

[0320] To prepare the thin film, suitable color-absorbing dyes and pigments can be incorporated into the UV / thermal curable prepolymer resin described above. Suitable dyes and pigments include carbon black (particle size range from 5 nm to 500 nm), Rhodamine B, Tartarzine, chemical dyes from Yamada Chemical Co., and SUNFAST pigments from SunChemical (such as Green 36, Blue, Violet 23, etc.).

[0321] A dye or pigment is mixed with a solvent and then with a UV-curable resin to obtain a color-absorbing resin. The solvent can be a volatile solvent such as an alcohol (methanol, ethanol, butanol, etc.) or other less volatile organic solvents such as dimethyl sulfoxide (DMSO), propylene glycol monomethyl ether acetate (PGMEA), toluene, etc. The dye or pigment can be separated or concentrated from the solvent (e.g., using centrifugal evaporation) to obtain an optimal concentration with a crosslinked organic resin (e.g., a UV-curable highly transparent material). The optimal concentration of the dye or pigment can impart desirable optical properties to the color-absorbing film. For example, the higher the concentration of the color-absorbing dye or pigment, the lower the reflectivity of the film.

[0322] Compared with traditional waterborne and solvent-based coatings, UV radiation-curable coatings and adhesives face additional challenges in balancing the acceptable viscosity for a specific application, the target gloss, and the desired film properties (e.g., scratch resistance, hardness, adhesion strength, etc.). Due to solvent evaporation, traditional coatings start to orient and "concentrate" the matting agent during the physical drying of the film. As the volatile compounds evaporate, the applied film begins to shrink. Depending on the volume solids content, the amount of shrinkage can vary between 30% and 60% of the wet film volume. In contrast, 100% UV coatings only shrink by about 10% during a rapid curing cycle, which will result in a significantly lower packing density of the matting agent. To obtain good matting performance, special attention is usually required in the selection of the matting agent particle size and the addition amount (load) as well as the control of the film thickness. Silica-based matting agents effectively reduce gloss by introducing surface roughness and wrinkling. Examples of silica matting agents include those from Evonik:

[0323] Acematt HK400, with a D50 particle size of 6.3 μm

[0324] Acematt OK607, with a D50 particle size of 4.4 μm

[0325] Acematt OK412, with a D50 particle size of 6.3 μm

[0326] Acematt 3600, with a D50 particle size of 5.0 μm

[0327] In addition to the method of surface roughening by inorganic particles, organic components can also be added to enhance internal light scattering, thereby further improving the matting performance. One such component is from Allnex 898 radiation-curable resin. To increase the opacity of coatings and adhesives to visible light, a broadband absorber (e.g., carbon black pigment) can be added in combination with a matting agent to achieve both bulk darkness and a flat surface finish simultaneously. The percentage of pigment added can range from 0.2 wt% to 15 wt%, depending on the curing thickness requirements. To achieve ultra-darkness at a thickness of 10 - 20 microns, for example, 10% of the pigment can be added. To minimize oxygen inhibition and enhance surface curing in air, an oxygen scavenger and a chain transfer agent (e.g., primary, secondary, and tertiary thiols and amines) can be added.

[0328] The eyepiece waveguide designs described herein can be used in augmented reality display systems, such as in combination with Figures 1 to 25 the systems described. Thus, for example, Figure 11A the waveguide 1120 in [reference] and other waveguides implemented as components of an augmented reality display system can be implemented using one or more of the embodiments described herein.

[0329] Example 1 is an eyepiece waveguide stack including: a first eyepiece waveguide including a first input diffraction optical element and a first combined pupil expander; and a second eyepiece waveguide including a second input diffraction optical element and a second combined pupil expander, wherein the second input diffraction optical element is offset from the first input diffraction optical element in the lateral direction.

[0330] Example 2 is the eyepiece waveguide stack of Example 1, wherein the first eyepiece waveguide is operable to couple in light in a first wavelength range; and the second eyepiece waveguide is operable to couple in light in a second wavelength range.

[0331] Example 3 is the eyepiece waveguide stack of Examples 1 - 2, wherein the first wavelength range includes 630 nm, and the second wavelength range includes 530 nm and 455 nm.

[0332] Example 4 is the eyepiece waveguide stack of Examples 1 - 3, wherein the light incident on the first input diffraction optical element passes through the second eyepiece waveguide before impinging on the first input diffraction optical element.

[0333] Example 5 is the eyepiece waveguide stack of Examples 1 - 4, wherein the thickness of the first eyepiece waveguide is different from the thickness of the second eyepiece waveguide.

[0334] Example 6 is the eyepiece waveguide stack of Examples 1 - 5, wherein the second input diffraction optical element includes two laterally offset diffraction structures.

[0335] Example 7 is the eyepiece waveguide stack of Examples 1 - 6, wherein the second input diffraction optical element includes a first diffraction structure operating in a reflection mode and a second diffraction structure operating in a transmission mode.

[0336] Example 8 is the eyepiece waveguide stack described in Examples 1-7, wherein at least one of the first eyepiece waveguide and the second eyepiece waveguide has a thickness that varies in the lateral direction.

[0337] Example 9 is the eyepiece waveguide stack described in Examples 1-8, wherein the normal vector is orthogonal to the eyepiece waveguide stack, and the lateral direction is orthogonal to the normal vector.

[0338] Example 10 is the eyepiece waveguide stack described in Examples 1-0, further comprising a cover layer having a reflective surface.

[0339] Example 11 is the eyepiece waveguide stack described in Examples 1-10, further comprising a cover layer having an absorptive surface.

[0340] Example 12 is the eyepiece waveguide stack described in Examples 1-11, wherein the cover layer further comprises a partially reflective surface and a light absorptive surface opposite the partially reflective surface.

[0341] Example 13 is an augmented reality head-mounted device, comprising: a projector; an eyepiece waveguide stack optically coupled to the projector, wherein the eyepiece waveguide stack comprises: a first eyepiece waveguide including a first input coupling diffractive optical element and a first combined pupil expander; and a second eyepiece waveguide including a second input coupling diffractive optical element and a second combined pupil expander, wherein the second input coupling diffractive optical element is laterally offset from the first input coupling diffractive optical element in the lateral direction.

[0342] Example 14 is the eyepiece waveguide stack described in Example 13, wherein the first eyepiece waveguide is operable to couple in light within a first wavelength range; and the second eyepiece waveguide is operable to couple in light within a second wavelength range.

[0343] Example 15 is the eyepiece waveguide stack described in Examples 13-14, wherein the first wavelength range includes 630 nm, and the second wavelength range includes 530 nm and 455 nm.

[0344] Example 16 is the eyepiece waveguide stack described in Examples 13-15, wherein the light incident on the first input coupling diffractive optical element passes through the second eyepiece waveguide before hitting the first input coupling diffractive optical element.

[0345] Example 17 is the eyepiece waveguide stack described in Examples 13-16, wherein the thickness of the first eyepiece waveguide is different from the thickness of the second eyepiece waveguide.

[0346] Example 18 is the eyepiece waveguide stack described in Examples 13-17, wherein the second input coupling diffractive optical element comprises two laterally offset diffractive structures.

[0347] Example 19 is the eyepiece waveguide stack described in Examples 13-18, wherein the second coupling-in diffractive optical element includes a first diffractive structure operating in a reflection mode and a second diffractive structure operating in a transmission mode.

[0348] Example 20 is the eyepiece waveguide stack described in Examples 13-19, wherein at least one of the first eyepiece waveguide or the second eyepiece waveguide has a thickness that varies in the lateral direction.

[0349] Example 21 is the eyepiece waveguide stack described in Examples 13-20, wherein the normal vector is orthogonal to the eyepiece waveguide stack, and the lateral direction is orthogonal to the normal vector.

[0350] In the foregoing specification, it has been described with reference to specific embodiments of the present disclosure. However, it will be apparent that various modifications and changes can be made thereto without departing from the broader spirit and scope of the present disclosure. Accordingly, the specification and drawings are to be regarded as illustrative rather than restrictive.

[0351] In fact, it will be understood that the systems and methods of the present disclosure each have several innovative aspects, none of which is the sole responsibility or required for the desired attributes 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 the present disclosure.

[0352] Certain features that are described in the context of separate embodiments in this specification can also be implemented in combination in a single embodiment. Conversely, the various features described in the context of a single embodiment can also be implemented separately in multiple embodiments or in any suitable sub-combination. Additionally, although the features may have been described above as acting in certain combinations and even initially claimed as such, in some cases, one or more features in the claimed combination can be excluded from the combination, and the claimed combination can be directed to a sub-combination or a variation of a sub-combination. No single feature or group of features is necessary or indispensable for each embodiment.

[0353] It will be understood that, unless otherwise expressly stated or otherwise understood from the context of use, conditional language used herein, such as "can", "might", "may", "for example", etc., generally is intended to convey that certain embodiments include certain features, elements, and / or steps, while other embodiments do not include these features, elements, and / or steps. Thus, such conditional language generally is not intended to imply that the features, elements, and / or steps are necessary for one or more embodiments in any way, or that one or more embodiments necessarily include logic for determining whether these features, elements, and / or steps are included or are to be performed in any particular embodiment (regardless of whether the author inputs or suggests them). The terms "comprising", "including", "having", etc. are synonyms and are used inclusively in an open-ended manner and do not exclude additional elements, features, acts, operations, etc. Further, the term "or" is used in an inclusive sense (and not an exclusive sense), so that when, for example, used to connect a list of elements, the term "or" means one, some, or all of the elements in the list. Additionally, unless otherwise specified, the articles "a", "an", and "the" used in this application and the appended claims should be construed to mean "one or more" or "at least one". Similarly, although operations may be depicted in a particular order in the figures, it should be recognized that such operations need not be performed in the particular order shown or sequentially, nor all of the operations shown, to achieve the desired result. Further, the figures may schematically depict one or more example processes in the form of a flowchart. However, other operations not depicted may be incorporated into the example methods and processes schematically shown. For example, one or more additional operations may be performed before, after, simultaneously with, or between any of the operations shown. Further, in other embodiments, the operations may be rearranged or reordered. In some cases, multitasking and parallel processing may be advantageous. Additionally, the separation of various system components in the above embodiments should not be understood to require such separation in all embodiments, and it should be understood that the described program components and systems generally may be integrated together in a single software product or packaged into multiple software products. Further, other embodiments are within the scope of the following claims. In some cases, the acts recited in the claims may be performed in a different order and still achieve the desired result.

[0354] Although the present disclosure includes many specific example details, these details should not be construed as limiting the scope of the subject matter or the scope of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments. Certain features described in the context of separate embodiments in the present disclosure may also be implemented in combination in a single embodiment. Conversely, the various features described in the context of a single embodiment may also be implemented separately in multiple embodiments, or in any suitable sub-combination. Additionally, although the features described previously may be described as acting in certain combinations and even initially claimed as such, in some cases, one or more features from the claimed combination may be excluded from the combination, and the claimed combination may be directed to a sub-combination or a variation of a sub-combination.

[0355] Specific embodiments of the subject matter have been described. It will be apparent to those skilled in the art that other embodiments, changes, and permutations of the described embodiments are within the scope of the following claims. Although the operations are described in a specific order in the figures or claims, this should not be construed as requiring that the operations be performed in the specific order or sequence shown, or that all illustrated operations (some operations may be considered optional) be performed to achieve the desired result.

[0356] Accordingly, the example embodiments described above do not define or limit the present disclosure. Other changes, substitutions, and alterations can be made without departing from the spirit and scope of the present disclosure.

[0357] Accordingly, the claims are not intended to be limited to the embodiments shown herein, but rather to the broadest scope consistent with the present disclosure, the principles disclosed herein, and the novel features.

[0358] The examples and embodiments described herein are for illustrative purposes only. Various modifications or changes can be made by those skilled in the art based on this. Such modifications or changes should all be covered within the spirit and scope of this application and the appended claims.

Claims

1. An eyepiece waveguide stack, comprising: A first eyepiece waveguide including a first input diffraction optical element and a first combined pupil expander; and A second eyepiece waveguide including a second input diffraction optical element and a second combined pupil expander, wherein the second input diffraction optical element is laterally offset from the first input diffraction optical element.

2. The eyepiece waveguide stack according to claim 1, wherein, The first eyepiece waveguide is operable to couple in light within a first wavelength range; and The second eyepiece waveguide is operable to couple in light within a second wavelength range.

3. The eyepiece waveguide stack according to claim 2, wherein, The first wavelength range includes 630 nm, and the second wavelength range includes 530 nm and 455 nm.

4. The eyepiece waveguide stack according to claim 1, wherein, Light incident on the first input diffraction optical element passes through the second eyepiece waveguide before impinging on the first input diffraction optical element.

5. The eyepiece waveguide stack according to claim 1, wherein, The thickness of the first eyepiece waveguide is different from the thickness of the second eyepiece waveguide.

6. The eyepiece waveguide stack according to claim 1, wherein, The second input diffraction optical element includes two laterally offset diffraction structures.

7. The eyepiece waveguide stack according to claim 1, wherein, The second input diffraction optical element includes a first diffraction structure operating in a reflection mode and a second diffraction structure operating in a transmission mode.

8. The eyepiece waveguide stack according to claim 1, wherein, At least one of the first eyepiece waveguide or the second eyepiece waveguide has a thickness that varies in the lateral direction.

9. The eyepiece waveguide stack according to claim 1, wherein, The normal vector is orthogonal to the eyepiece waveguide stack, and the lateral direction is orthogonal to the normal vector.

10. The eyepiece waveguide stack according to claim 1, further comprising a cover layer having a reflective surface.

11. The eyepiece waveguide stack according to claim 1, further comprising a cover layer having an absorptive surface.

12. The eyepiece waveguide stack according to claim 10, wherein, The cover layer further includes a partially reflective surface and a light absorbing surface opposite the partially reflective surface.

13. An augmented reality head-mounted device, comprising: A projector; An eyepiece waveguide stack optically coupled to the projector, wherein the eyepiece waveguide stack includes: A first eyepiece waveguide including a first input diffraction optical element and a first combined pupil expander; and A second eyepiece waveguide including a second input diffraction optical element and a second combined pupil expander, wherein the second input diffraction optical element is laterally offset from the first input diffraction optical element in the lateral direction.

14. The eyepiece waveguide stack according to claim 13, wherein, The first eyepiece waveguide is operable to couple in light within a first wavelength range; and The second eyepiece waveguide is operable to couple in light within a second wavelength range.

15. The eyepiece waveguide stack according to claim 14, wherein, The first wavelength range includes 630 nm, while the second wavelength range includes 530 nm and 455 nm.

16. The eyepiece waveguide stack according to claim 13, wherein, Light incident on the first input diffraction optical element passes through the second eyepiece waveguide before impinging on the first input diffraction optical element.

17. The eyepiece waveguide stack according to claim 13, wherein, The thickness of the first eyepiece waveguide is different from the thickness of the second eyepiece waveguide.

18. The eyepiece waveguide stack according to claim 13, wherein, The second input diffraction optical element includes two laterally offset diffraction structures.

19. The eyepiece waveguide stack according to claim 13, wherein, The second input diffraction optical element includes a first diffraction structure operating in a reflection mode and a second diffraction structure operating in a transmission mode.

20. The eyepiece waveguide stack according to claim 13, wherein, At least one of the first eyepiece waveguide or the second eyepiece waveguide has a thickness that varies in the lateral direction.

21. The eyepiece waveguide stack according to claim 13, wherein, The normal vector is orthogonal to the eyepiece waveguide stack, and the lateral direction is orthogonal to the normal vector.

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