Gradient array-based displays

Abstract

To provide a suitable tilting array based display.SOLUTION: Various embodiments described herein include an optical system for an augmented reality head mounted display eyepiece lens configured to deliver an image to an eye, where the optical system includes optics. The optics is arranged so as to receive light output from a light source. The optics is further arranged relative to a spatial light modulator array such that light received from the light source passes through the optics and illuminates the spatial light modulator array. Light illuminating the spatial light modulator array is redirected back through the optics and coupled into one of a plurality of waveguides through one of a plurality of in-coupling optical elements. At least a portion of the coupled light is emitted from the waveguide by at least one out-coupling optical element and directed to the eye of a user. A viewing optics assembly comprising the spatial light modulator is configured to rotate the spatial light modulator.SELECTED DRAWING: Figure 26A

Description

[Technical Field]

[0001] (Incorporation by reference to any priority application) This application claims the benefit of priority under 35 U.S.C. § 119(e) to U.S. patent application Ser. No. 62 / 641,976, filed March 12, 2018, and entitled "VERY HIGH INDEX EYEPIECE SUBSTRATE-BASED VIEWING OPTICS ASSEMBLY ARCHITECTURES," the disclosure of which is incorporated herein by reference in its entirety.

[0002] The present disclosure relates to a display system having a common optical system for both spatial light modulator illumination and image projection. [Background technology]

[0003] Modern computing and display technology has facilitated the development of systems for so-called "virtual reality" or "augmented reality" experiences, in which digitally reproduced images or portions thereof are presented to a user in a manner that appears, or can be perceived as, real. Virtual reality, or "VR," scenarios typically involve the presentation of digital or virtual image information without transparency to other actual real-world visual input, while augmented reality, or "AR," scenarios typically involve the presentation of digital or virtual image information as an augmentation to the user's visualization of the real world around them. Mixed reality, or "MR," scenarios are a type of AR scenario that typically involve virtual objects integrated into and responsive to the natural world. For example, MR scenarios may include AR image content that appears occluded by or is perceived to otherwise interact with objects in the real world.

[0004] Referring to FIG. 1 , an augmented reality scene 10 is depicted. A user of the AR technology sees a real-world park-like setting 20 featuring people, trees, and buildings in the background, and a concrete platform 30. The user also perceives that they are "seeing" "virtual content," such as a robotic figure 40 standing on the real-world platform 30 and a flying, cartoon-like avatar character 50 that appears to be an anthropomorphic bumblebee. These elements 50, 40 are "virtual" in that they do not exist in the real world. The human visual perception system is complex, making it difficult to create AR technology that facilitates a comfortable, natural-feeling, and rich presentation of virtual image elements among other virtual or real-world image elements.

[0005] The systems and methods disclosed herein address various challenges associated with AR or VR technology.

[0006] Polarizing beam splitters may be used within display systems to direct polarized light to light modulators, which then direct this light to a viewer or user. There is a continuing demand to reduce the size of display systems, and generally, as a result, there is also a demand to reduce the size of display system components, including components that utilize polarizing beam splitters. Summary of the Invention [Means for solving the problem]

[0007] Various embodiments described herein include an optical system for an augmented reality head-mounted display eyepiece configured to deliver an image to an eye, the optical system including an optical system. The optical system is positioned to receive light output from a light source. The optical system is further arranged with respect to a spatial light modulator array such that the light received from the light source passes through the optical system and illuminates the spatial light modulator array. The light illuminating the spatial light modulator array is redirected back through the optical system and coupled into one of a plurality of waveguides through one of a plurality of internal coupling optical elements. At least a portion of the coupled light is ejected from the waveguide by at least one external coupling optical element and directed to a user's eye. The spatial light modulator array is configured to tilt to direct the light into an appropriate one of the internal coupling optical elements.

[0008] Various embodiments of head mounted display systems, such as the embodiments listed below, are described herein that have common optics for both spatial light modulator illumination and image projection.

[0009] Example 1: A head-mounted display system configured to project light to a user's eye and display augmented reality image content within the user's field of view, the system comprising: a frame configured to be supported on a user's head; at least one light source configured to output light; a spatial light modulator array arranged to receive light from the at least one light source; and an eyepiece arranged on the frame, the eyepiece configured to direct light from the spatial light modulator array into the user's eye and display augmented reality image content in the user's field of view, at least a portion of the eyepiece being transparent and positioned in a location in front of the user's eye when the user is wearing the head-mounted display system, the transparent portion transmitting light from a portion of a physical environment in front of the user to the user's eye to provide a view of the portion of the physical environment in front of the user; (a) at least one waveguide; and (b) at least one internal coupling optical element configured to internally couple light from the spatial light modulator array into the at least one waveguide. (c) an eyepiece lens comprising at least one external coupling optical element configured to couple light guided within the waveguide out of the waveguide and direct the light toward a user's eye; and an optical system having refractive power, the optical system positioned to receive light output from a light source and arranged with respect to the spatial light modulator array so that the light received from the light source passes through the optical system and illuminates the spatial light modulator array, the head-mounted display system configured such that the light illuminating the spatial light modulator array is redirected back through the optical system and coupled into at least one waveguide through at least one internal coupling optical element, at least a portion of the coupled light is ejected from the at least one waveguide by the at least one external coupling optical element and directed toward the user's eye, the spatial light modulator array configured to tilt to direct more light from the at least one light source to different ones of the at least one internal coupling optical element at different times.

[0010] Example 2: A head-mounted display system as described in Example 1, wherein at least one waveguide comprises first and second waveguides having respective first and second internal coupling optical elements associated therewith.

[0011] Example 3: A head-mounted display system as described in Example 2, wherein the spatial light modulator array is configured to tilt to direct more light from the at least one light source toward the first internal coupling optical element when the spatial light modulator array is tilted at a first angle, so that more of the light is coupled into the first waveguide by the first internal coupling optical element than into the second waveguide by the second internal coupling optical element.

[0012] Example 4: A head-mounted display system as described in Example 3, wherein the spatial light modulator array is configured to tilt to direct more light from the at least one light source into the second internal coupling optical element when the spatial light modulator array is tilted at a second angle, so that more of the light is coupled into the second waveguide by the second internal coupling optical element than into the first waveguide by the first internal coupling optical element.

[0013] Example 5: A head-mounted display system described in any of Examples 2-4, wherein the first and second waveguides are configured to output light with wavefronts having different amounts of at least one of divergence, convergence, or collimation, as if projected from different distances from the user's eyes.

[0014] Example 6: A head-mounted display system as described in Example 5, wherein the first and second waveguides are configured such that light coupled out from the first waveguide is collimated and light output from the second waveguide is divergent.

[0015] Example 7: A head-mounted display system as described in Example 5, wherein the first and second waveguides are configured such that light coupled out from the first waveguide diverges by a first amount and light coupled out from the second waveguide diverges by a second amount, the second amount being different from the first amount.

[0016] Example 8: A head-mounted display system as described in any of Examples 2-4, wherein the first and second waveguides are configured to output light into different viewing angles to provide an overall larger field of view for the image content presented to the user.

[0017] Example 9: A head-mounted display system as described in any of Examples 2-4, wherein the first and second waveguides have corresponding first and second outcoupling optical elements that are offset laterally relative to each other to provide an increased eyebox for a user to view the image.

[0018] Example 10: A head-mounted display system according to any of the previous examples, wherein the spatial light modulator array comprises a plurality of pixels.

[0019] Example 11: A head-mounted display system as described in Example 10, wherein the plurality of pixels comprises a two-dimensional linear array of pixels including pixels arranged in rows and columns, or a hexagonal close-packed array of pixels.

[0020] Example 12: The head-mounted display system of example 10 or example 11, wherein the plurality of pixels comprises at least 1,000 pixels.

[0021] Example 13: A head-mounted display system as described in any of the above examples, further comprising a rotating stage on which the spatial light modulator array is disposed, the rotating stage having at least one actuator configured to receive a signal and tilt the rotating stage in response to the received signal.

[0022] Example 14: A head-mounted display system as described in any of the above examples, wherein the spatial light modulator array is configured to switch between two states, namely a first state and a second state, and the orientation of the spatial light modulator array is arranged at a first and second angle in the first and second states, respectively.

[0023] Example 15: A head-mounted display system as described in Example 14, wherein the spatial light modulator array tilts at least 7 degrees when changing from the first state to the second state.

[0024] Example 16: A head-mounted display system as described in Example 14, wherein the spatial light modulator array tilts at least 10 degrees when changing from the first state to the second state.

[0025] Example 17: A head-mounted display system as described in Example 14, wherein the spatial light modulator array tilts at an angle of 20 degrees or less when changing from the first state to the second state.

[0026] Example 18: A head-mounted display system as described in Example 14, wherein the spatial light modulator array tilts by an angle of at least 5 degrees to 15 degrees or less in less than 100 milliseconds when changing from the first state to the second state.

[0027] Example 19: A head-mounted display system as described in Example 14, wherein the spatial light modulator array tilts by an angle of at least 10 degrees to 20 degrees or less in less than 100 milliseconds when changing from the first state to the second state.

[0028] Example 20: A head-mounted display system according to any of the preceding examples, wherein the spatial light modulator array comprises a reflective spatial light modulator array.

[0029] Example 21: A head-mounted display system according to any of the previous examples, wherein the spatial light modulator array comprises a liquid crystal spatial light modulator array or a movable micromirror array.

[0030] Example 22: A head-mounted display system described in any of the above examples, wherein the at least one light source comprises at least one light emitter and at least one coupling optical system positioned relative to the at least one light emitter and collecting light output therefrom.

[0031] Example 23: A head-mounted display system as described in Example 22, wherein the coupling optics comprises a compound parabolic concentrator (CPC).

[0032] Example 24: A head-mounted display system according to any of the preceding examples, wherein at least one waveguide comprises a stack of waveguides.

[0033] Example 25: A head-mounted display system as described in Example 24, wherein different waveguides of the stack of waveguides are configured to output light with different individual colors.

[0034] Example 26: A head-mounted display system as described in Example 24 or Example 25, wherein the first, second, and third waveguides of the waveguide stack are configured to output light of first, second, and third colors, respectively, and the first, second, and third colors of light are red, blue, and green light, respectively.

[0035] Example 27: A head-mounted display system described in any of the above examples, wherein at least one waveguide comprises first and second groups of waveguides having respective first and second groups of internal coupling optical elements associated therewith.

[0036] Example 28: A head-mounted display system as described in Example 27, wherein the spatial light modulator array is configured to tilt to direct more light from the at least one light source to at least one of the internal coupling optical elements of the first group of internal coupling optical elements when the spatial light modulator array is tilted at a first angle so that more light from the light source is coupled into one of the waveguides from the first group of waveguides by one of the internal coupling optical elements of the first group of internal coupling optical elements than is coupled into one of the waveguides of the second group of waveguides by the internal coupling optical elements of the second group of internal coupling optical elements.

[0037] Example 29: A head-mounted display system as described in Example 28, wherein the spatial light modulator array is configured to tilt to direct more light from the light source to the internal coupling optical elements of the second group of internal coupling optical elements when the spatial light modulator array is tilted at a second angle, so that more light from the light source is coupled into the waveguides from the second group of waveguides by the internal coupling optical elements of the second group of internal coupling optical elements than is coupled into the waveguides from the first group of waveguides by the internal coupling optical elements of the first group of internal coupling optical elements.

[0038] Example 30: A head-mounted display system as described in Example 27, wherein the at least one light source comprises a first light source, the first group of waveguides comprises a first waveguide, and the first group of internal coupling optical elements comprises a first internal coupling optical element configured to couple light from the first light source into a first waveguide of the first group of waveguides, and the second group of waveguides comprises a first waveguide, and the second group of internal coupling optical elements comprises a first internal coupling optical element configured to couple light from the first light source into a first waveguide of the second group of waveguides.

[0039] Example 31: A head-mounted display system as described in Example 30, wherein the spatial light modulator array is configured to tilt to direct more light from the first light source to the first internal coupling optical element of the first group of internal coupling optical elements when the spatial light modulator array is tilted at a first angle, so that more light from the first light source is coupled into the first waveguide of the first group of waveguides by the first internal coupling optical element of the first group of internal coupling optical elements than is coupled into the first waveguide of the second group of waveguides by the first internal coupling optical element of the second group of internal coupling optical elements.

[0040] Example 32: A head-mounted display system as described in Example 31, wherein the spatial light modulator array is configured to tilt to direct more light from the first light source into the first internal coupling optical element of the second group of internal coupling optical elements when the spatial light modulator array is tilted at a second angle, so that more light from the first light source is coupled into the first waveguide of the second group of waveguides by the first internal coupling optical element of the second group of internal coupling optical elements than is coupled into the first waveguide of the first group of waveguides by the first internal coupling optical element of the first group of internal coupling optical elements.

[0041] Example 33: A head-mounted display system described in any of Examples 27 and 30-32, wherein the at least one light source comprises a second light source, the first group of waveguides comprises a second waveguide, the first group of internal coupling optical elements comprises a second internal coupling optical element configured to couple light from the second light source into a second waveguide of the first group of waveguides, the second group of waveguides comprises a second waveguide, and the second group of internal coupling optical elements comprises a second internal coupling optical element configured to couple light from the second light source into a second waveguide of the second group of waveguides.

[0042] Example 34: A head-mounted display system as described in Example 33, wherein the spatial light modulator array is configured to tilt to direct more light from the second light source to the second internal coupling optical element of the first group of internal coupling optical elements when the spatial light modulator array is tilted at a first angle, so that more light from the second light source is coupled into the second waveguide of the first group of waveguides by the second internal coupling optical element of the first group of internal coupling optical elements than is coupled into the second waveguide of the second group of waveguides by the second internal coupling optical element of the second group of internal coupling optical elements.

[0043] Example 35: A head-mounted display system as described in Example 34, wherein the spatial light modulator array is configured to tilt to direct more light from the second light source into the second internal coupling optical element of the second group of internal coupling optical elements when the spatial light modulator array is tilted at a second angle, so that more light from the second light source is coupled into the second waveguide of the second waveguide by the second internal coupling optical element of the second group of internal coupling optical elements than is coupled into the second waveguide of the first group of waveguides by the second internal coupling optical element of the first group of internal coupling optical elements.

[0044] Example 36: A head-mounted display system described in any of Examples 33-35, wherein the first and second internal coupling optical elements of the first group of internal coupling optical elements are laterally offset relative to each other.

[0045] Example 37: A head-mounted display system as described in Example 36, wherein the first and second internal coupling optical elements of the second group of internal coupling optical elements are laterally offset relative to each other.

[0046] Example 38: A head-mounted display system described in any of Examples 27 and 30-37, wherein the at least one light source comprises a third light source, the first group of waveguides comprises a third waveguide, the first group of internal coupling optical elements comprises a third internal coupling optical element configured to couple light from the third light source into the third waveguide of the first group of waveguides, the second group of waveguides comprises a third waveguide, and the second group of internal coupling optical elements comprises a third internal coupling optical element configured to couple light from the third light source into the third waveguide of the second group of waveguides.

[0047] Example 39: A head-mounted display system as described in Example 38, wherein the spatial light modulator array is configured to tilt to direct more light from the third light source to the third internal coupling optical element of the first group of internal coupling optical elements when the spatial light modulator array is tilted at a first angle, so that more light from the third light source is coupled into the third waveguide of the first group of waveguides by the third internal coupling optical element of the first group of internal coupling optical elements than is coupled into the third waveguide of the second group of waveguides by the third internal coupling optical element of the second group of internal coupling optical elements.

[0048] Example 40: A head-mounted display system as described in Example 39, wherein the spatial light modulator array is configured to tilt to direct more light from the third light source into the third internal coupling optical element of the second group of internal coupling optical elements when the spatial light modulator array is tilted at a second angle, so that more light from the third light source is coupled into the third waveguide of the second group of waveguides by the third internal coupling optical element of the second group of internal coupling optical elements than is coupled into the third waveguide of the first group of waveguides by the third internal coupling optical element of the first group of internal coupling optical elements.

[0049] Example 41: A head-mounted display system described in any of Examples 38-40, wherein the third internal coupling optical element of the first group of internal coupling optical elements is offset laterally relative to the first and second internal coupling optical elements of the first group of internal coupling optical elements.

[0050] Example 42: A head-mounted display system as described in Example 41, wherein the third internal coupling optical element of the second group of internal coupling optical elements is laterally offset relative to the first and second internal coupling optical elements of the second group of internal coupling optical elements.

[0051] Example 43: A head-mounted display system described in any of Examples 27-42, wherein the first group of internal coupling optical elements is laterally offset relative to the second group of internal coupling optical elements.

[0052] Example 44: A head-mounted display system described in any of Examples 38-43, wherein the first, second, and third light sources comprise red, green, and blue light sources, respectively.

[0053] Example 45: A head-mounted display system described in any of Examples 27-42, wherein the first and second groups of waveguides are configured to output light with wavefronts having different amounts of at least one of divergence, convergence, and collimation, as if projected from different distances from the user's eyes.

[0054] Example 46: A head-mounted display system as described in Example 45, wherein the first and second groups of waveguides are configured such that light coupled out from the first group of waveguides is collimated and light output from the second group of waveguides is divergent.

[0055] Example 47: A head-mounted display system as described in Example 45, wherein the first and second groups of waveguides are configured such that light coupled out from the first group of waveguides diverges by a first amount and light coupled out from the second group of waveguides diverges by a second amount, the second amount being different from the first amount.

[0056] Example 48: A head-mounted display system described in any of Examples 27-44, wherein the first and second groups of waveguides are configured to output light into different viewing angles to provide an overall larger field of view for the image content presented to the user.

[0057] Example 49: A head-mounted display system described in any of Examples 27-44, wherein the first and second groups of waveguides have individual external coupling optical elements that are offset laterally relative to each other to provide the user with an increased eyebox for viewing image content.

[0058] Any of the above embodiments or additional embodiments can be combined. In addition, any of the above embodiments or additional embodiments can be integrated with a head-mounted display. In addition, any of the above embodiments or additional embodiments can be implemented with a single depth plane and / or one or more variable depth planes (e.g., one or more elements with variable focusing power that provide accommodation cues that vary over time).

[0059] Details of one or more implementations of the subject matter described herein are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, drawings, and claims. Neither this summary nor the following detailed description purports to define or limit the scope of the inventive subject matter. The present invention provides, for example, the following. (Item 1) 1. A head-mounted display system configured to project light onto a user's eye and display augmented reality image content within the user's field of view, the head-mounted display system comprising: a frame configured to be supported on the user's head; at least one light source configured to output light; a spatial light modulator array positioned to receive light from the at least one light source; an eyepiece disposed on the frame, the eyepiece configured to direct light from the spatial light modulator array into the user's eye and display augmented reality image content in the user's field of view, at least a portion of the eyepiece being transparent and disposed in a location in front of the user's eye when the user wears the head mounted display system, the transparent portion transmitting light from a portion of a physical environment in front of the user to the user's eye to provide a view of the portion of the physical environment in front of the user, the eyepiece comprising: (a) at least one waveguide; (b) at least one incoupling optical element, the at least one incoupling optical element configured to incoupling light from the spatial light modulator array into the at least one waveguide; (c) at least one outcoupling optical element, the at least one outcoupling optical element configured to couple light guided within the waveguide out of the waveguide and direct the light toward an eye of the user; an eyepiece comprising: an optical system having refractive power, the optical system positioned to receive light output from the light source, the optical system aligned with the spatial light modulator array such that light received from the light source passes through the optical system and illuminates the spatial light modulator array; Equipped with the head-mounted display system is configured such that light illuminating the spatial light modulator array is redirected back through the optical system and coupled into the at least one waveguide through the at least one internal coupling optical element, and at least a portion of the coupled light is ejected from the at least one waveguide by the at least one external coupling optical element and directed to an eye of the user; 10. A head-mounted display system, wherein the spatial light modulator array is configured to tilt to direct more light from the at least one light source to different ones of the at least one internal coupling optical element at different times. (Item 2) Item 1, a head-mounted display system, wherein the at least one waveguide comprises a first and a second waveguide, the first and second waveguides having respective first and second internal coupling optical elements associated therewith. (Item 3) 3. The head-mounted display system of claim 2, wherein the spatial light modulator array is configured to tilt to direct more light from the at least one light source toward the first internal coupling optical element when the spatial light modulator array is tilted at a first angle, so that more of the light is coupled into the first waveguide by the first internal coupling optical element than is coupled into the second waveguide by the second internal coupling optical element. (Item 4) 4. The head-mounted display system of claim 3, wherein the spatial light modulator array is configured to tilt to direct more light from the at least one light source into the second internal coupling optical element when the spatial light modulator array is tilted at a second angle, so that more of the light is coupled into the second waveguide by the second internal coupling optical element than is coupled into the first waveguide by the first internal coupling optical element. (Item 5) A head-mounted display system as described in any of items 2-4, wherein the first and second waveguides are configured to output light with wavefronts having different amounts of divergence, convergence, or collimation, as if projected from different distances from the user's eyes. (Item 6) Item 6. A head-mounted display system as described in item 5, wherein the first and second waveguides are configured so that light coupled out from the first waveguide is collimated and light output from the second waveguide is divergent. (Item 7) Item 6. The head-mounted display system of item 5, wherein the first and second waveguides are configured such that light coupled out from the first waveguide diverges by a first amount and light coupled out from the second waveguide diverges by a second amount, the second amount being different from the first amount. (Item 8) A head-mounted display system as described in any of items 2-4, wherein the first and second waveguides are configured to output light into different viewing angles to provide an overall larger field of view for image content presented to a user. (Item 9) A head-mounted display system as described in any of items 2-4, wherein the first and second waveguides have corresponding first and second outcoupling optical elements, and the corresponding first and second outcoupling optical elements are offset laterally relative to each other to provide an increased eyebox for the user to view the image. (Item 10) 10. A head-mounted display system according to any preceding item, wherein the spatial light modulator array comprises a plurality of pixels. (Item 11) Item 11. A head-mounted display system as described in item 10, wherein the plurality of pixels comprises a two-dimensional linear array of pixels including pixels arranged in rows and columns, or a hexagonal close-packed array of pixels. (Item 12) Item 12. The head-mounted display system of item 10 or 11, wherein the plurality of pixels comprises at least 1,000 pixels. (Item 13) 2. A head-mounted display system according to any preceding item, further comprising a rotating stage on which the spatial light modulator array is disposed, the rotating stage having at least one actuator configured to receive a signal and tilt the rotating stage in response to the received signal. (Item 14) A head-mounted display system as described in any of the preceding items, wherein the spatial light modulator array comprises a spatial modulator array configured to switch between two states, i.e., a first state and a second state, and the orientation of the spatial light modulator array is arranged at a first and second angle in the first and second states, respectively. (Item 15) Item 15. The head-mounted display system of item 14, wherein the spatial light modulator array tilts at least 7 degrees when changing from the first state to the second state. (Item 16) Item 15. The head-mounted display system of item 14, wherein the spatial light modulator array tilts at least 10 degrees when changing from the first state to the second state. (Item 17) Item 15. The head-mounted display system of item 14, wherein the spatial light modulator array tilts at an angle of 20 degrees or less when changing from the first state to the second state. (Item 18) Item 15. The head-mounted display system of item 14, wherein the spatial light modulator array tilts by an angle of at least 5 degrees to 15 degrees or less in less than 100 milliseconds when changing from the first state to the second state. (Item 19) Item 15. The head-mounted display system of item 14, wherein the spatial light modulator array tilts by an angle of at least 10 degrees to 20 degrees or less in less than 100 milliseconds when changing from the first state to the second state. (Item 20) 10. A head-mounted display system according to any preceding item, wherein the spatial light modulator array comprises a reflective spatial light modulator array. (Item 21) 10. A head-mounted display system according to any preceding item, wherein the spatial light modulator array comprises a liquid crystal spatial light modulator array or a movable micromirror array. (Item 22) A head-mounted display system according to any of the preceding items, wherein the at least one light source comprises at least one light emitter and at least one coupling optical system positioned relative to the at least one light emitter and collecting light output therefrom. (Item 23) Item 23. The head-mounted display system of item 22, wherein the coupling optics comprises a compound parabolic concentrator (CPC). (Item 24) 10. A head-mounted display system according to any preceding item, wherein the at least one waveguide comprises a stack of waveguides. (Item 25) Item 25. A head-mounted display system as described in item 24, wherein different waveguides of the stack of waveguides are configured to output light with different individual colors. (Item 26) Item 26. A head-mounted display system as described in item 24 or item 25, wherein the first, second, and third waveguides of the waveguide stack are configured to output light of first, second, and third colors, respectively, and the first, second, and third colors of light are red, blue, and green light, respectively. (Item 27) A head-mounted display system as described in any of the preceding items, wherein the at least one waveguide comprises first and second groups of waveguides, the first and second groups of waveguides having respective first and second groups of internal coupling optical elements associated therewith. (Item 28) 28. The head-mounted display system of item 27, wherein the spatial light modulator array is configured to tilt to direct more light from the at least one light source toward at least one of the internal coupling optical elements of the first group of internal coupling optical elements when the spatial light modulator array is tilted at a first angle, so that more light from the light source is coupled into one of the waveguides from the first group of waveguides by one of the internal coupling optical elements of the first group of internal coupling optical elements than is coupled into one of the waveguides in the second group of waveguides by the internal coupling optical elements of the second group of internal coupling optical elements. (Item 29) 29. The head-mounted display system of item 28, wherein the spatial light modulator array is configured to tilt to direct more light from the light source toward the internal coupling optical elements of the second group of internal coupling optical elements when the spatial light modulator array is tilted at a second angle, so that more light from the light source is coupled into the waveguides from the second group of waveguides by the internal coupling optical elements of the second group of internal coupling optical elements than is coupled into the waveguides from the first group of waveguides by the internal coupling optical elements of the first group of internal coupling optical elements. (Item 30) 28. A head-mounted display system as described in Item 27, wherein the at least one light source comprises a first light source, the first group of waveguides comprises a first waveguide, the first group of internal coupling optical elements comprises a first internal coupling optical element configured to couple light from the first light source into a first waveguide of the first group of waveguides, the second group of waveguides comprises a first waveguide, and the second group of internal coupling optical elements comprises a first internal coupling optical element configured to couple light from the first light source into a first waveguide of the second group of waveguides. (Item 31) Item 31. A head-mounted display system as described in Item 30, wherein the spatial light modulator array is configured to tilt to direct more light from the first light source to a first internal coupling optical element of the first group of internal coupling optical elements when the spatial light modulator array is tilted at a first angle so that more light from the first light source is coupled into a first waveguide of the first group of waveguides by a first internal coupling optical element of the first group of internal coupling optical elements than is coupled into a first waveguide of the second group of waveguides by a first internal coupling optical element of the second group of internal coupling optical elements. (Item 32) Item 32. The head-mounted display system of item 31, wherein the spatial light modulator array is configured to tilt to direct more light from the first light source into the first internal coupling optical element of the second group of internal coupling optical elements when the spatial light modulator array is tilted at a second angle so that more light from the first light source is coupled into the first waveguide of the second group of waveguides by the first internal coupling optical element of the second group of internal coupling optical elements than is coupled into the first waveguide of the first group of waveguides by the first internal coupling optical element of the first group of internal coupling optical elements. (Item 33) A head-mounted display system described in any of items 27 and 30-32, wherein the at least one light source comprises a second light source, the first group of waveguides comprises a second waveguide, the first group of internal coupling optical elements comprises a second internal coupling optical element configured to couple light from the second light source into a second waveguide of the first group of waveguides, the second group of waveguides comprises a second waveguide, and the second group of internal coupling optical elements comprises a second internal coupling optical element configured to couple light from the second light source into a second waveguide of the second group of waveguides. (Item 34) Item 34. The head-mounted display system of item 33, wherein the spatial light modulator array is configured to tilt to direct more light from the second light source to the second internal coupling optical element of the first group of internal coupling optical elements when the spatial light modulator array is tilted at a first angle so that more light from the second light source is coupled into the second waveguide of the first group of waveguides by the second internal coupling optical element of the first group of internal coupling optical elements than is coupled into the second waveguide of the second group of waveguides by the second internal coupling optical element of the second group of internal coupling optical elements. (Item 35) Item 35. The head-mounted display system of item 34, wherein the spatial light modulator array is configured to tilt to direct more light from the second light source into the second internal coupling optical element of the second group of internal coupling optical elements when the spatial light modulator array is tilted at a second angle so that more light from the second light source is coupled into the second waveguide of the second waveguide by the second internal coupling optical element of the second group of internal coupling optical elements than is coupled into the second waveguide of the first group of waveguides by the second internal coupling optical element of the first group of internal coupling optical elements. (Item 36) 36. A head-mounted display system according to any of items 33-35, wherein the first and second internal coupling optical elements of the first group of internal coupling optical elements are laterally offset relative to each other. (Item 37) Item 37. A head-mounted display system as described in item 36, wherein the first and second internal coupling optical elements of the second group of internal coupling optical elements are laterally offset relative to each other. (Item 38) A head-mounted display system described in any of items 27 and 30-37, wherein the at least one light source comprises a third light source, the first group of waveguides comprises a third waveguide, the first group of internal coupling optical elements comprises a third internal coupling optical element configured to couple light from the third light source into the third waveguide of the first group of waveguides, the second group of waveguides comprises a third waveguide, and the second group of internal coupling optical elements comprises a third internal coupling optical element configured to couple light from the third light source into the third waveguide of the second group of waveguides. (Item 39) Item 39. The head-mounted display system of item 38, wherein the spatial light modulator array is configured to tilt to direct more light from the third light source to the third internal coupling optical element of the first group of internal coupling optical elements when the spatial light modulator array is tilted at a first angle so that more light from the third light source is coupled into the third waveguide of the first group of waveguides by the third internal coupling optical element of the first group of internal coupling optical elements than is coupled into the third waveguide of the second group of waveguides by the third internal coupling optical element of the second group of internal coupling optical elements. (Item 40) 40. The head-mounted display system of claim 39, wherein the spatial light modulator array is configured to tilt to direct more light from the third light source into the third internal coupling optical element of the second group of internal coupling optical elements when the spatial light modulator array is tilted at a second angle so that more light from the third light source is coupled into the third waveguide of the second group of waveguides by the third internal coupling optical element of the second group of internal coupling optical elements than is coupled into the third waveguide of the first group of waveguides by the third internal coupling optical element of the first group of internal coupling optical elements. (Item 41) A head-mounted display system as described in any of items 38-40, wherein a third internal coupling optical element of the first group of internal coupling optical elements is laterally offset relative to the first and second internal coupling optical elements of the first group of internal coupling optical elements. (Item 42) Item 42. A head-mounted display system as described in Item 41, wherein a third internal coupling optical element of the second group of internal coupling optical elements is laterally offset relative to the first and second internal coupling optical elements of the second group of internal coupling optical elements. (Item 43) 43. A head-mounted display system according to any of items 27-42, wherein the first group of internal coupling optical elements is laterally offset relative to the second group of internal coupling optical elements. (Item 44) 44. A head-mounted display system according to any one of items 38-43, wherein the first, second, and third light sources comprise red, green, and blue light sources, respectively. (Item 45) A head-mounted display system as described in any of items 27-42, wherein the first and second groups of waveguides are configured to output light with wavefronts having different amounts of at least one of divergence, convergence, and collimation, as if projected from different distances from the user's eyes. (Item 46) Item 46. A head-mounted display system as described in Item 45, wherein the first and second groups of waveguides are configured so that light coupled out from the first group of waveguides is collimated and light output from the second group of waveguides is divergent. (Item 47) Item 46. The head-mounted display system of item 45, wherein the first and second groups of waveguides are configured such that light coupled out from the first group of waveguides diverges by a first amount and light coupled out from the second group of waveguides diverges by a second amount, the second amount being different from the first amount. (Item 48) A head-mounted display system as described in any of items 27-44, wherein the first and second groups of waveguides are configured to output light into different viewing angles to provide an overall larger field of view for image content presented to a user. (Item 49) A head-mounted display system as described in any of items 27-44, wherein the first and second groups of waveguides have individual outcoupling optical elements that are offset laterally relative to each other to provide a user with an increased eyebox for viewing image content. [Brief explanation of the drawings]

[0060] [Figure 1] FIG. 1 illustrates a user's view of an augmented reality (AR) device.

[0061] [Figure 2] FIG. 2 illustrates a conventional display system for simulating a three-dimensional image for a user.

[0062] [Figure 3] 3A-3C illustrate the relationship between the radius of curvature and the radius of focus.

[0063] [Figure 4A] Figure 4A illustrates a representation of the accommodation-vergence response of the human visual system.

[0064] [Figure 4B] FIG. 4B illustrates an example of different accommodation and convergence states of a pair of a user's eyes.

[0065] [Figure 4C] FIG. 4C illustrates an example of a top-down view representation of a user viewing content through a display system.

[0066] [Figure 4D] FIG. 4D illustrates another example of a top-down view representation of a user viewing content through a display system.

[0067] [Figure 5] FIG. 5 illustrates aspects of an approach for simulating three-dimensional images by correcting for wavefront divergence.

[0068] [Figure 6] FIG. 6 illustrates an embodiment of a waveguide stack for outputting image information to a user.

[0069] [Figure 7] FIG. 7 illustrates an example of an output beam output by a waveguide.

[0070] [Figure 8] FIG. 8 illustrates an example of a stacked waveguide assembly where each depth plane contains an image formed using multiple different primary colors.

[0071] [Figure 9A] FIG. 9A illustrates a cross-sectional side view of an example of a set of stacked waveguides, each including an internal coupling optical element.

[0072] [Figure 9B] FIG. 9B illustrates a perspective view of one or more stacked waveguide embodiments of FIG. 9A.

[0073] [Figure 9C] FIG. 9C illustrates a top-down plan view of one or more stacked waveguide embodiments of FIGS. 9A and 9B.

[0074] [Figure 9D] FIG. 9D illustrates an example of a wearable display system.

[0075] [Figure 10]FIG. 10 is a side view of a projector assembly including a polarizing beam splitter with a light source that injects light into one side of the beam splitter and projection optics that receive light from the other side of the beam splitter.

[0076] [Figure 11A] 11A is a side view of an augmented reality display system including a light source, a spatial light modulator, an optical system for illuminating the spatial light modulator and projecting an image of the spatial light modulator (SLM), and a waveguide for outputting image information to a user. The system includes an internal coupling optical element for coupling light from the optical system into the waveguide, and an external coupling optical element for coupling light out of the waveguide to the eye.

[0077] [Figure 11B] 11B is a top view of the augmented reality display system shown in FIG. 11A, showing a waveguide with in-coupling and out-coupling optical elements and a light source disposed thereon. The top view also shows an orthogonal pupil expander.

[0078] [Figure 11C] FIG. 11C is a side view of the augmented reality display system of FIG. 11A with a shared polarizer / analyzer and polarization-based spatial light modulator (eg, liquid crystal-on-silicon SLM).

[0079] [Figure 12A] FIG. 12A is a side view of an augmented reality display system including a multicolor light source (e.g., a time-multiplexed RGB LED or laser diode), a spatial light modulator, an optical system for illuminating the spatial light modulator and projecting an image of the spatial light modulator into the eye, and a stack of waveguides, where different waveguides include different color-selective in-coupling and out-coupling optical elements.

[0080] [Figure 12B]FIG. 12B is a side view of the augmented reality display system of FIG. 12A, further including a MEMS (micro-electromechanical) based SLM such as an array of movable mirrors (e.g., digital light processing (DLP™) technology) and a light dump.

[0081] [Figure 12C] FIG. 12C is a top view of a portion of the augmented reality display system of FIG. 12B, illustrating diagrammatically the internal coupling optical elements and the lateral arrangement of one of the light dumps and light sources.

[0082] [Figure 13A] 13A is a perspective view of an augmented reality display system including a stack of waveguides, different waveguides including different in-coupling optical elements, the in-coupling optical elements being laterally displaced relative to one another. One or more light sources, also laterally displaced relative to one another, are positioned to direct light to individual in-coupling optical elements by passing the light through an optical system, reflecting the light off a spatial light modulator, and passing the reflected light back through the optical system.

[0083] [Figure 13B] FIG. 13B is a side view of the embodiment illustrated in FIG. 13A, showing the laterally displaced incoupling optical element, light source, optics, and spatial light modulator.

[0084] [Figure 13C] FIG. 13C is a top view of the augmented reality display system shown in FIGS. 13A and 13B, showing one or more laterally displaced internal coupling optical elements and one or more associated laterally displaced light sources.

[0085] [Figure 14A] FIG. 14A is a side view of an augmented reality display system including a waveguide stack, where different waveguides include different internal coupling optical elements, and the internal coupling optical elements are laterally displaced relative to each other (the lateral displacement occurs in the z-direction in this example).

[0086] [Figure 14B] FIG. 14B is a top view of the display system illustrated in FIG. 14A, showing the incoupling optical elements and light source displaced laterally.

[0087] [Figure 14C] FIG. 14C is an orthogonal side view of the display system illustrated in FIGS. 14A and 14B.

[0088] [Figure 15] 15 is a top view of an augmented reality display system including a set of stacked waveguides, different waveguides including different in-coupling optical elements, the light sources and in-coupling optical elements arranged in an alternative configuration to that shown in FIGS.

[0089] [Figure 16A] FIG. 16A is a side view of an augmented reality display system including groups of inter-coupling optical elements that are laterally displaced relative to one another, each group including one or more color-selective inter-coupling optical elements.

[0090] [Figure 16B] FIG. 16B is a top view of the display system in FIG. 16A.

[0091] [Figure 17] 17 is a side view of an augmented reality display system that includes a waveguide that is split using a reflective surface that can couple light guided in a portion of the waveguide proximate the light source out of that portion of the waveguide and into an optics system toward a spatial light modulator. In this example, the optics system and light source are shown disposed on the same side of the waveguide.

[0092] [Figure 18]18 is a side view of an augmented reality display system including a waveguide for receiving light from a light source and directing the light guided in the waveguide into an optical system toward a spatial light modulator. The display system additionally includes a waveguide for receiving light from the spatial light modulator and passing it again through the optical system. The waveguide includes reflective surfaces for outcoupling light. The waveguide also includes reflective surfaces for incoupling light therein. In this example, the optical system and the light source are shown disposed on the same side of the waveguide.

[0093] [Figure 19] 19 is a side view of an augmented reality display system including an adaptive or variable-focus optical element. A first variable optical element between the waveguide stack and the eye can vary the divergence and collimation of light coupled out of the waveguides and directed toward the eye, varying the depth at which objects appear to be located. A second variable optical element on the other side of the waveguide stack can compensate for the effect of the first optical element on light received from the augmented reality display system and the environment in front of the user. The augmented reality display system may further include prescription lenses to provide ophthalmic corrections, such as refractive corrections for users with myopia, hyperopia, astigmatism, etc.

[0094] [Figure 20A] 20A is a side view of an augmented reality display system including a color filter array, where one or more laterally displaced in-coupling optical elements are located on different waveguides, and the laterally displaced color filters are aligned with the respective in-coupling optical elements.

[0095] [Figure 20B] FIG. 20B shows the augmented reality display system of FIG. 20A with an analyzer positioned between the optical system and the spatial light modulator.

[0096] [Figure 20C]FIG. 20C shows an augmented reality display system similar to that shown in FIGS. 20A and 20B, however, using a deflection-based spatial light modulator, such as a movable micromirror-based spatial light modulator.

[0097] [Figure 20D] FIG. 20D is a top view of a portion of the augmented reality display system as shown in FIG. 20C, diagrammatically illustrating a laterally displaced light source above the color filter array and a corresponding laterally displaced internal coupling optical element.

[0098] [Figure 20E] FIG. 20E illustrates how a deflection-based spatial light modulator for the augmented reality display system of FIG. 20D directs light away from corresponding internal coupling optical elements and onto a mask that surrounds the filters in the filter array.

[0099] [Figure 20F] FIG. 20F is a side view of an augmented reality display system including a cover glass positioned on the user side of the waveguide stack and a light source positioned on the world side of the cover glass.

[0100] [Figure 20G] FIG. 20G is a side view of an augmented reality display system including a cover glass disposed on the world side of a stack of waveguides and a light source disposed on the world side of the cover glass.

[0101] [Figure 21] FIG. 21 is 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 a certain polarization.

[0102] [Figure 22]22 is a side view of one or more light sources propagating light through corresponding light collection optics and one or more apertures. The light may also propagate through a diffuser located proximate to the one or more apertures.

[0103] [Figure 23A] FIG. 23A is a side view of a portion of an augmented reality display system including a light source, an optical system having refractive power, and a waveguide for receiving and outputting image information to a user's eye, the system further including one or more retarders and polarizers configured to reduce reflections from optical surfaces that may be input to the waveguide as a residual image.

[0104] [Figure 23B] FIG. 23B is a side view of a portion of an augmented reality display system as shown in FIG. 23A, with an additional retarder and polarizer configured to reduce reflections that can produce persistence images.

[0105] [Figure 23C] FIG. 23C is a side view of an augmented reality display system as shown in FIGS. 23A and 23B with a reduced retarder and polarizer configured to reduce reflections that can produce persistence images.

[0106] [Figure 24] FIG. 24 is a side view of an augmented reality display system that utilizes a sloped surface, such as a sloped surface on a cover glass, to direct reflections away from the user's eyes, potentially reducing afterimage reflections.

[0107] [Figure 25] FIG. 25 is an embodiment of the system of FIG. 24, in which an angled surface on the cover glass is configured to direct the reflection toward a light dump that absorbs the light.

[0108] [Figure 26A]26A and 26B are side views of an augmented reality display system including an eyepiece comprising a stack of waveguides, each waveguide having a respective in-coupling optical element associated therewith for coupling light into the waveguide. The augmented reality display system further comprises a light source, a tiltable spatial light modulator array, and an optical system for illuminating the spatial light modulator array and directing light reflected from the spatial light modulator array into one of the in-coupling optical elements in response to tilting the spatial light modulator. [Figure 26B] 26A and 26B are side views of an augmented reality display system including an eyepiece comprising a stack of waveguides, each waveguide having a respective in-coupling optical element associated therewith for coupling light into the waveguide. The augmented reality display system further comprises a light source, a tiltable spatial light modulator array, and an optical system for illuminating the spatial light modulator array and directing light reflected from the spatial light modulator array into one of the in-coupling optical elements in response to tilting the spatial light modulator.

[0109] [Figure 26C] Figure 26C is a top view of the display system shown in Figures 26A and 26B, showing internal coupling optical elements arranged in two sets on opposite sides of multiple light sources so that light from the light sources can be directed to one of the sets of internal coupling optical elements depending on the tilt of the spatial light modulator.

[0110] [Figure 26D] FIG. 26D is a side view of an augmented reality display system depicting a first group of waveguides configured to outcouple light, where the light has a first divergence, and a second group of waveguides configured to outcouple light, where the light has a second divergence, the amounts of divergence being different.

[0111] [Figure 27]FIG. 27 is a side view of an augmented reality display system depicting a first group of waveguides configured to couple light out into a first field of view and a second group of waveguides configured to couple light out into a second field of view that is different from the first field of view.

[0112] [Figure 28] FIG. 28 is a side view of an augmented reality display system depicting first and second groups of waveguides with separate outcoupling optical elements, where the outcoupling optical elements for the first group of waveguides are displaced laterally relative to the outcoupling optical elements for the second group of waveguides to increase the eyebox and provide more locations from which the eye can view images.

[0113] [Figure 29A] Figure 29A is a side view of an augmented reality display system including a multi-color light source (e.g., a time-multiplexed RGB LED or laser diode), a stack of waveguides, the different waveguides including different color-selective internal coupling optical elements, a tiltable spatial light modulator array, and an optical system for illuminating the spatial light modulator array and directing light reflected from the spatial light modulator array to one group of color-selective internal coupling optical elements depending on the tilt of the spatial light modulator array.

[0114] [Figure 29B] Figure 29B is a top view of the display system shown in Figure 29A, showing groups of internal coupling optical elements on opposite sides of a multi-color light source, with each group of internal coupling optical elements at the same lateral position (e.g., overlapping each other).

[0115] [Figure 30A]30A is a side view of an augmented reality display system including a multicolor light source (e.g., a time-multiplexed RGB LED or laser diode) and a stack of waveguides, where different waveguides in the stack have respective broadband in-coupling optical elements associated therewith. The display system further includes a tiltable spatial light modulator array and an optical system for illuminating the spatial light modulator array and directing light reflected from the spatial light modulator array into one of the broadband in-coupling optical elements in response to tilting the spatial light modulator array.

[0116] [Figure 30B] FIG. 30B is a top view of the display system illustrated in FIG. 30A, showing broadband in-coupling optical elements on opposite sides of the multi-color light source. DETAILED DESCRIPTION OF THE INVENTION

[0117] Reference is now made to the drawings, wherein like reference numerals refer to like parts throughout. Unless otherwise indicated, the drawings are schematic and are not necessarily drawn to scale.

[0118] FIG. 2 illustrates a conventional display system for simulating a three-dimensional image for a user. It should be understood that when a user's eyes are spaced apart and viewing a real object in space, each eye may have a slightly different view of the object, forming an image of the object at a different location on each eye's retina. This may be referred to as binocular disparity and may be utilized by the human visual system to provide the perception of depth. Conventional display systems simulate binocular disparity by presenting two distinct images 190, 200, one for each eye 210a, 210b, with slightly different views of the same virtual object, corresponding to the view of the virtual object as it would appear by each eye as if the virtual object were a real object at a desired depth. These images provide binocular cues that the user's visual system may interpret to derive the perception of depth.

[0119] Continuing with reference to FIG. 2 , images 190 and 200 are spaced apart from eyes 210a and 210b by a distance 230 on the z-axis. The z-axis is parallel to the user's optical axis when the eyes are fixating on an object at optical infinity directly in front of the user. Images 190 and 200 are flat and at a fixed distance from eyes 210a and 210b. Based on slightly different views of the virtual object in the images presented to eyes 210a and 210b, respectively, the eyes may naturally rotate so that the image of the object falls on a corresponding point on each eye's retina, maintaining single binocular vision. This rotation may cause the gaze of each eye 210a and 210b to converge on a point in space where the virtual object is perceived to reside. As a result, providing three-dimensional images traditionally involves manipulating the convergence and divergence of eyes 210a and 210b and providing binocular cues that the human visual system interprets to provide the perception of depth.

[0120] However, creating a realistic and comfortable perception of depth is challenging. It should be understood that light from an object at different distances from the eye has a wavefront with different amounts of divergence. Figures 3A-3C illustrate the relationship between distance and light ray divergence. The distance between the object and the eye 210 is represented in order of decreasing distances R1, R2, and R3. As shown in Figures 3A-3C, light rays become more divergent as the distance to the object decreases. Conversely, as the distance increases, the light rays become more collimated. In other words, the light field generated by a point (an object or portion of an object) can be said to have a spherical wavefront curvature that is a function of the distance the point is from the user's eye. As the curvature increases, the distance between the object and the eye 210 decreases. While only a single eye 210 is illustrated in Figures 3A-3C and various other figures herein for clarity of illustration, the discussion regarding the eye 210 may apply to both eyes 210a and 210b of the viewer.

[0121] Continuing with reference to Figures 3A-3C, light from an object that a user's eye is fixating may have different wavefront divergences. Due to the different wavefront divergences, the light may be focused differently by the eye's lens, which in turn may require the lens to assume a different shape to form a focused image on the eye's retina. If a focused image is not formed on the retina, the resulting retinal blur acts as an accommodative cue, causing the shape of the eye's lens to change until a focused image is formed on the retina. For example, the accommodative cue may induce relaxation or contraction of the ciliary muscles surrounding the eye's lens, thereby modulating the force applied to the suspensory ligaments that hold the lens in place, thus changing the shape of the eye's lens and forming a focused image of the fixated object on the eye's retina (e.g., the fovea) until retinal blur of the fixated object is eliminated or minimized. The process by which the eye's lens changes shape can be referred to as accommodation, and the shape of the eye's lens required to form a focused image of a fixated object on the eye's retina (e.g., the fovea) can be referred to as the state of accommodation.

[0122] Referring now to Figure 4A, a representation of the accommodation-vergence response of the human visual system is illustrated. Eye movement to fixate an object causes the eye to receive light from the object, which forms an image on each of the eye's retinas. The presence of retinal blur in the image formed on the retina can provide a cue for accommodation, and the relative location of the image on the retina can provide a cue for vergence. Accommodation cues cause accommodation, resulting in the eye's lens adopting a specific accommodation state in which a focused image of the object is formed on the eye's retina (e.g., the fovea). Conversely, vergence cues cause vergence movements (eye rotations) so that the images formed on each retina of each eye are at corresponding retinal points, maintaining single binocular vision. In these positions, the eyes can be said to adopt a specific vergence state. Continuing with reference to FIG. 4A , accommodation can be understood as the process by which the eyes achieve a particular accommodation state, and convergence can be understood as the process by which the eyes achieve a particular convergence state. As shown in FIG. 4A , the accommodation and convergence states of the eyes can change when the user fixates on a different object. For example, the accommodated state can change when the user fixates on a new object at a different depth on the z-axis.

[0123] Without being limited by theory, it is believed that a user of an object may perceive the object as "three-dimensional" due to a combination of convergence and accommodation. As previously discussed, vergence movement of the two eyes relative to one another (e.g., eye rotation such that the pupils move toward or away from one another, converging the eyes' gazes and fixating on an object) is closely linked to accommodation of the eye's lenses. Under normal conditions, changing the shape of the eye's lenses and shifting focus from one object to another at a different distance will automatically produce a matching change in vergence to the same distance, a relationship known as the "accommodation-vergence reflex." Similarly, a change in vergence will induce a matching change in lens shape under normal conditions.

[0124] 4B, an example of different accommodation and convergence states of the eyes is illustrated. Paired eye 222a fixates an object at optical infinity, while paired eye 222b fixates an object 221 at less than optical infinity. Notably, the convergence states of each pair of eyes are different: paired eye 222a points straight ahead, while paired eye 222 converges on object 221. The accommodation states of the eyes forming each pair of eyes 222a and 222b are also different, as represented by the different shapes of lenses 220a, 220b.

[0125] Unfortunately, many users of conventional "3-D" display systems may find such systems uncomfortable or may not perceive any depth perception due to a mismatch between accommodation and convergence states in these displays. As previously mentioned, many stereoscopic or "3-D" display systems display a scene by providing a slightly different image to each eye. Such systems are uncomfortable for many users because, among other things, they simply provide different presentations of a scene, causing changes in the convergence states of the eyes but without corresponding changes in the accommodation states of those eyes. Rather, images are presented by the displays at a fixed distance from the eyes so that the eyes view all image information in a single accommodation state. Such an arrangement counters the "accommodation-vergence-divergence reflex" by causing changes in convergence states without a corresponding change in accommodation state. This mismatch is believed to cause discomfort to the user. Display systems that offer better alignment between accommodation and convergence-divergence movements may create a more realistic and comfortable simulation of three-dimensional images.

[0126] Without being limited by theory, it is believed that the human eye is typically capable of interpreting a finite number of depth planes to provide depth perception. As a result, a highly realistic simulation of perceived depth may be achieved by providing the eye with different presentations of images corresponding to each of these limited number of depth planes. In some embodiments, the different presentations may provide both vergence cues and matching cues for accommodation, thereby providing physiologically correct accommodation-vergence divergence matching.

[0127] 4B , two depth planes 240 are illustrated, corresponding to different distances in space from the eyes 210 a, 210 b. For a given depth plane 240, vergence-divergence cues may be provided by displaying appropriately different perspective images for each eye 210 a, 210 b. Additionally, for a given depth plane 240, the light forming the image provided to each eye 210 a, 210 b may have a wavefront divergence corresponding to the light field generated by a point at the distance of that depth plane 240.

[0128] In the illustrated embodiment, the distance along the z-axis of depth plane 240 containing point 221 is 1 meter. As used herein, distance or depth along the z-axis may be measured with a zero point located at the exit pupil of the user's eye. Thus, depth plane 240 located at a depth of 1 meter corresponds to a distance of 1 meter away from the exit pupil of the user's eye on the optical axis of the eye with the eye pointed toward optical infinity. As an approximation, the depth or distance along the z-axis may be measured from a display (e.g., the surface of a waveguide) in front of the user's eye, and a value related to the distance between the device and the exit pupil of the user's eye may be added. That value may be referred to as pupil distance and may correspond to the distance between the exit pupil of the user's eye and a display worn by the user in front of the eye. In practice, the value related to pupil distance may be a normalized value generally used for all users. For example, pupil distance may be assumed to be 20 mm, and the depth plane at a depth of 1 meter may be at a distance of 980 mm in front of the display.

[0129] 4C and 4D, examples of matched accommodation-vergence-divergence distances and mismatched accommodation-vergence-divergence distances are illustrated, respectively. As illustrated in FIG. 4C, the display system may provide an image of a virtual object to each eye 210a, 210b. The image may cause the eyes 210a, 210b to assume a convergence-divergence state in which the eyes converge on point 15 on the depth plane 240. In addition, the image may be formed by light having a wavefront curvature corresponding to the real object on the depth plane 240. As a result, the eyes 210a, 210b assume an accommodation state in which the image is focused on the retinas of those eyes. Thus, the user may perceive the virtual object as being at point 15 on the depth plane 240.

[0130] It should be understood that the accommodation and convergence states of the eyes 210a, 210b are each associated with a particular distance on the z-axis. For example, an object at a particular distance from the eyes 210a, 210b will cause the eyes to assume a particular accommodation state based on the object's distance. The distance associated with a particular accommodation state may be referred to as the accommodation distance Ad. Similarly, there is a particular convergence distance Vd or position relative to one another associated with the eyes in a particular convergence state. When the accommodation distance and the convergence distance match, the relationship between accommodation and convergence is said to be physiologically correct. This is considered the most comfortable scenario for the user.

[0131] However, in a stereoscopic display, the accommodation distance and the vergence distance may not always match. For example, as illustrated in FIG. 4D , the image displayed to the eyes 210a, 210b may be displayed with a wavefront divergence corresponding to the depth plane 240, and the eyes 210a, 210b may be in a particular accommodation state in which points 15a, 15b on that depth plane are in focus. However, the image displayed to the eyes 210a, 210b may provide a convergence cue that causes the eyes 210a, 210b to converge on point 15 that is not located on the depth plane 240. As a result, in some embodiments, the accommodation distance corresponds to the distance from the exit pupils of the eyes 210a, 210b to the depth plane 240, while the vergence distance corresponds to the greater distance from the exit pupils of the eyes 210a, 210b to point 15. The accommodation distance is different from the vergence distance. As a result, an accommodation-vergence-divergence mismatch exists. Such a mismatch may be considered undesirable and may cause discomfort to the user. It should be understood that the mismatch may correspond to a distance (e.g., Vd-Ad) and be characterized using diopters.

[0132] It should be understood that in some embodiments, reference points other than the exit pupils of the eyes 210 a, 210 b may be used to determine distances for determining accommodation-vergence mismatch, so long as the same reference points are used for accommodation distance and vergence distance. For example, distances may be measured from the cornea to the depth plane, from the retina to the depth plane, from the eyepiece (e.g., a waveguide in a display device) to the depth plane, etc.

[0133] Without being limited by theory, it is believed that a user may still perceive an accommodation-vergence-divergence mismatch of up to about 0.25 diopters, up to about 0.33 diopters, and up to about 0.5 diopters as physiologically correct without the mismatch itself causing significant discomfort. In some embodiments, a display system disclosed herein (e.g., display system 250, FIG. 6 ) presents images to a user having an accommodation-vergence-divergence mismatch of about 0.5 diopters or less. In some other embodiments, the accommodation-vergence-divergence mismatch of images provided by the display system is about 0.33 diopters or less. In still other embodiments, the accommodation-vergence-divergence mismatch of images provided by the display system is about 0.25 diopters or less, including about 0.1 diopters or less.

[0134] FIG. 5 illustrates aspects of an approach for simulating a three-dimensional image by modifying wavefront divergence. The display system includes a waveguide 270 configured to receive light 770 encoded with image information and output the light to a user's eye 210. The waveguide 270 may output light 650 with a defined amount of wavefront divergence corresponding to the wavefront divergence of a light field generated by a point on a desired depth plane 240. In some embodiments, the same amount of wavefront divergence is provided for all objects presented on that depth plane. In addition, the user's other eye will be illustrated as being provided with image information from a similar waveguide.

[0135] In some embodiments, a single waveguide may be configured to output light with a set wavefront divergence corresponding to a single or limited number of depth planes, and / or the waveguide may be configured to output light of a limited range of wavelengths. As a result, in some embodiments, a stack of waveguides may be utilized to provide different wavefront divergences for different depth planes and / or output light of different ranges of wavelengths. As used herein, it should be understood that a depth plane may follow the contour of a planar or curved surface. In some embodiments, for simplicity, the depth plane may advantageously follow the contour of a flat surface.

[0136] 6 illustrates an example of a waveguide stack for outputting image information to a user. Display system 250 includes a stack of waveguides or stacked waveguide assembly 260 that can be utilized to provide three-dimensional perception to the eye / brain using waveguides 270, 280, 290, 300, 310. It should be understood that display system 250 may be considered a light field display in some embodiments. Additionally, waveguide assembly 260 may also be referred to as an eyepiece.

[0137] In some embodiments, display system 250 may be configured to provide a substantially continuous cue for convergence and multiple discrete cues for accommodation. The cues for convergence may be provided by displaying different images to each of the user's eyes, and the cues for accommodation may be provided by outputting light that forms images with selectable discrete amounts of wavefront divergence. In other words, display system 250 may be configured to output light with variable levels of wavefront divergence. In some embodiments, each discrete level of wavefront divergence corresponds to a particular depth plane and may be provided by a particular one of waveguides 270, 280, 290, 300, and 310.

[0138] Continuing with reference to FIG. 6, the waveguide assembly 260 may also include features 320, 330, 340, and 350 between the waveguides. In some embodiments, the features 320, 330, 340, and 350 may be one or more lenses. The waveguides 270, 280, 290, 300, and 310 and / or the features (lenses) 320, 330, 340, and 350 may be configured to transmit image information to the eye with various levels of wavefront curvature or ray divergence. Each waveguide level may be associated with a particular depth plane and configured to output image information corresponding to that depth plane. The image injection devices 360, 370, 380, 390, 400 may act as light sources for the waveguides and may be utilized to inject image information into the waveguides 270, 280, 290, 300, 310, each configured to disperse incident light across each individual waveguide for output toward the eye 210, as described herein. Light exits output surfaces 410, 420, 430, 440, 450 of the image injection devices 360, 370, 380, 390, 400 and is injected into corresponding input surfaces 460, 470, 480, 490, 500 of the waveguides 270, 280, 290, 300, 310. In some embodiments, each input surface 460, 470, 480, 490, 500 may be an edge of the corresponding waveguide or a portion of a major surface of the corresponding waveguide (i.e., one of the waveguide surfaces that directly faces the world 510 or the user's eye 210). In some embodiments, a single beam of light (e.g., a collimated beam) may be launched into each waveguide, outputting a total field of cloned collimated beams directed toward the eye 210 at a particular angle (and divergence) corresponding to the depth plane associated with the particular waveguide. In some embodiments, a single one of the image launch devices 360, 370, 380, 390, 400 may be associated with and launch light into one or more (e.g., three) waveguides 270, 280, 290, 300, 310.

[0139] In some embodiments, each of the image input devices 360, 370, 380, 390, 400 is a discrete display that generates image information for input into a corresponding waveguide 270, 280, 290, 300, 310. In some other embodiments, the image input devices 360, 370, 380, 390, 400 are the output of a single multiplexed display that may, for example, send image information via one or more optical conduits (such as fiber optic cables) to each of the image input devices 360, 370, 380, 390, 400. It should be understood that the image information provided by the image input devices 360, 370, 380, 390, 400 may include light of different wavelengths or colors (e.g., different primary colors as discussed herein).

[0140] In some embodiments, light injected into waveguides 270, 280, 290, 300, 310 is provided by light projector system 520, which includes light module 530, which may include a light emitter such as a light emitting diode (LED). Light from light module 530 may be directed via beam splitter 550 to and modified by light modulator 540, e.g., a spatial light modulator. Light modulator 540 may be configured to change the perceived intensity of the light injected into waveguides 270, 280, 290, 300, 310 and encode the light with image information. Examples of spatial light modulators include liquid crystal displays (LCDs), including liquid crystal on silicon (LCOS) displays. It should be understood that image injection devices 360, 370, 380, 390, 400 are illustrated diagrammatically, and in some embodiments, these image injection devices may represent different light paths and locations within a common projection system configured to output light into associated ones of waveguides 270, 280, 290, 300, 310. In some embodiments, the waveguides of waveguide assembly 260 may function as ideal lenses, relaying light injected into the waveguides to the user's eye. In this concept, the object may be a spatial light modulator 540, and the image may be an image on a depth plane.

[0141] In some embodiments, the display system 250 may be a scanning fiber display comprising one or more scanning fibers configured to project light in various patterns (e.g., raster scan, spiral scan, Lissajous pattern, etc.) into one or more waveguides 270, 280, 290, 300, 310 and ultimately to the user's eye 210. In some embodiments, the illustrated image injection devices 360, 370, 380, 390, 400 may diagrammatically represent a single scanning fiber or a bundle of scanning fibers configured to inject light into one or more waveguides 270, 280, 290, 300, 310. In some other embodiments, the illustrated image injection devices 360, 370, 380, 390, 400 may diagrammatically represent one or more scanning fibers or one or more bundles of scanning fibers, each configured to inject light into an associated one of the waveguides 270, 280, 290, 300, 310. It should be understood that one or more optical fibers may be configured to transmit light from the optical module 530 to one or more waveguides 270, 280, 290, 300, 310. It should be understood that one or more intervening optical structures may be provided between the scanning fiber or fibers and one or more waveguides 270, 280, 290, 300, 310, for example, to redirect light exiting the scanning fiber into one or more waveguides 270, 280, 290, 300, 310.

[0142] Controller 560 controls the operation of one or more of stacked waveguide assemblies 260, including the operation of image input devices 360, 370, 380, 390, 400, light source 530, and light modulator 540. In some embodiments, controller 560 is part of local data processing module 140. Controller 560 contains programming (e.g., instructions in a non-transitory medium) that coordinates the timing and provision of image information to waveguides 270, 280, 290, 300, 310, for example, according to any of the various schemes disclosed herein. In some embodiments, the controller may be a single integrated device or a distributed system connected by a wired or wireless communication channel. Controller 560 may, in some embodiments, be part of processing module 140 or 150 (FIG. 9D).

[0143] 6, the waveguides 270, 280, 290, 300, and 310 may be configured to propagate light within each individual waveguide by total internal reflection (TIR). Each of the waveguides 270, 280, 290, 300, and 310 may be planar or have another shape (e.g., curved), with major top and bottom surfaces and edges extending between the major top and bottom surfaces. In the illustrated configuration, the waveguides 270, 280, 290, 300, and 310 may each include outcoupling optical elements 570, 580, 590, 600, and 610 configured to extract light from the waveguide by redirecting light propagating within each individual waveguide out of the waveguide and outputting image information to the eye 210. Although referred to throughout this specification as an "outcoupling optical element," the outcoupling optical element need not be an optical element and may be a non-optical element. The extracted light may also be referred to as outcoupling light, and the light outcoupling optical element may also be referred to as a light extraction optical element. The extracted beam of light may be output by a waveguide where the light propagating within the waveguide strikes the light extraction optical element. The outcoupling optical elements 570, 580, 590, 600, 610 may be, for example, a grating including diffractive optical features as discussed further herein. Although shown disposed on the bottom major surfaces of the waveguides 270, 280, 290, 300, 310 for ease of explanation and clarity of drawing, in some embodiments the outcoupling optical elements 570, 580, 590, 600, 610 may be disposed on the top and / or bottom major surfaces, and / or may be disposed directly within the volume of the waveguides 270, 280, 290, 300, 310, as discussed further herein. In some embodiments, the outcoupling optical elements 570, 580, 590, 600, 610 may be formed within a layer of material that is attached to a transparent substrate and forms the waveguides 270, 280, 290, 300, 310. In some other embodiments, the waveguides 270, 280, 290, 300, 310 may be a monolithic piece of material and the outcoupling optical elements 570, 580, 590, 600, 610 may be formed on and / or within the piece of material.

[0144] Continuing with reference to FIG. 6 , as discussed herein, each waveguide 270, 280, 290, 300, 310 is configured to output light and form an image corresponding to a particular depth plane. For example, the waveguide 270 closest to the eye may be configured to deliver collimated light (injected into such waveguide 270) to the eye 210. The collimated light may represent an optical infinity focal plane. The next upper waveguide 280 may be configured to send collimated light that passes through a first lens 350 (e.g., a negative lens) before reaching the eye 210. Such first lens 350 may be configured to generate a slight convex wavefront curvature so that the eye / brain interprets light emerging from the next upper waveguide 280 as emerging from a first focal plane closer inward from optical infinity toward the eye 210. Similarly, the third upper waveguide 290 passes its output light through both the first lens 350 and the second lens 340 before reaching the eye 210. The combined refractive power of the first lens 350 and the second lens 340 may be configured to produce another, increasing amount of wavefront curvature such that the eye / brain interprets the light emerging from the third waveguide 290 as originating from a second focal plane that is closer inward from optical infinity towards the person than was the light from the next upper waveguide 280.

[0145] The other waveguide layers 300, 310 and lenses 330, 320 are similarly configured, with the highest waveguide 310 in the stack sending its output through all of the lenses between it and the eye for a collective focal power representing the focal plane closest to the person. To compensate for the stack of lenses 320, 330, 340, 350 when viewing / interpreting light originating from the world 510 on the other side of the stacked waveguide assembly 260, a compensating lens layer 620 may be placed on top of the stack to compensate for the collective power of the lower lens stacks 320, 330, 340, 350. Such a configuration provides as many perceived focal planes as there are available waveguide / lens pairs. Both the waveguide outcoupling optical elements and the focusing sides of the lenses may be static (i.e., not dynamic or electro-active). In some alternative embodiments, one or both may be dynamic using electro-active features.

[0146] In some embodiments, two or more of the waveguides 270, 280, 290, 300, 310 may have the same associated depth plane. For example, multiple waveguides 270, 280, 290, 300, 310 may be configured to output images set at the same depth plane, or multiple subsets of the waveguides 270, 280, 290, 300, 310 may be configured to output images set at the same one or more depth planes, with one set per depth plane. This may provide the advantage of forming tiled images to provide an extended field of view at those depth planes.

[0147] Continuing with reference to FIG. 6 , the outcoupling optical elements 570, 580, 590, 600, 610 may be configured to redirect light from its respective waveguide and output the light with an appropriate amount of divergence or collimation for a particular depth plane associated with that waveguide. As a result, waveguides with different associated depth planes may have different configurations of outcoupling optical elements 570, 580, 590, 600, 610, which output light with different amounts of divergence depending on the associated depth plane. In some embodiments, the light-extraction optical elements 570, 580, 590, 600, 610 may be volume or surface features that can be configured to output light at specific angles. For example, the light-extraction optical elements 570, 580, 590, 600, 610 may be volume holograms, surface holograms, and / or diffraction gratings. In some embodiments, the features 320, 330, 340, 350 may not be lenses. Rather, they may simply be spacers (eg, cladding layers and / or structures for forming air gaps).

[0148] In some embodiments, the outcoupling optical elements 570, 580, 590, 600, 610 are diffractive features or "diffractive optical elements" (also referred to herein as "DOEs") that form a diffraction pattern. Preferably, the DOEs have a sufficiently low diffraction efficiency so that only a portion of the light in the beam is deflected toward the eye 210 at each intersection of the DOE, while the remainder continues traveling through the waveguide via TIR. The light carrying the image information is thus split into several related output beams that exit the waveguide at various locations, resulting in a very uniform pattern of output emission toward the eye 210 for this particular collimated beam bouncing within the waveguide.

[0149] In some embodiments, one or more DOEs may be switchable between an "on" state in which they actively diffract and an "off" state in which they do not significantly diffract. For example, a switchable DOE may comprise a layer of polymer-dispersed liquid crystal in which microdroplets comprise a diffractive pattern in a host medium, and the refractive index of the microdroplets may be switched to substantially match the refractive index of the host material (in which case the pattern does not significantly diffract incident light), or the microdroplets may be switched to a refractive index that does not match that of the host medium (in which case the pattern actively diffracts incident light).

[0150] In some embodiments, a camera assembly 630 (e.g., a digital camera, including a visible light and infrared light camera) may be provided to capture images of the eye 210 and / or tissue surrounding the eye 210, for example, to detect user input and / or monitor the physiological state of the user. As used herein, a camera may be any image capture device. In some embodiments, the camera assembly 630 may include an image capture device and a light source that projects light (e.g., infrared light) onto the eye, which may then be reflected by the eye and detected by the image capture device. In some embodiments, the camera assembly 630 may be mounted on the frame 80 (FIG. 9D) and may be in electrical communication with processing modules 140 and / or 150, which may process image information from the camera assembly 630. In some embodiments, one camera assembly 630 may be utilized per eye, monitoring each eye separately.

[0151] 7, an example of an output beam output by a waveguide is shown. While one waveguide is illustrated, it should be understood that other waveguides in waveguide assembly 260 (FIG. 6) may function similarly, and that waveguide assembly 260 includes multiple waveguides. Light 640 is launched into waveguide 270 at input surface 460 of waveguide 270 and propagates within waveguide 270 by TIR. At the point where light 640 impinges on DOE 570, a portion of the light exits the waveguide as output beam 650. Output beam 650 is illustrated as being approximately parallel, but may be redirected to propagate to eye 210 at an angle (e.g., forming a diverging output beam), as discussed herein and depending on the depth plane associated with waveguide 270. It should be understood that a nearly collimated exit beam may refer to a waveguide with outcoupling optics that outcouples light to form an image that appears to be set at a depth plane at a large distance (e.g., optical infinity) from the eye 210. Other waveguides or other sets of outcoupling optics may output a more divergent exit beam pattern, which would require the eye 210 to accommodate to a closer distance and focus on the retina, and would be interpreted by the brain as light from a distance closer to the eye 210 than optical infinity.

[0152] In some embodiments, a full-color image may be formed at each depth plane by overlaying an image in each of the primary colors, for example, three or more primary colors. FIG. 8 illustrates an example of a stacked waveguide assembly in which each depth plane includes an image formed using multiple different primary colors. The illustrated embodiment shows depth planes 240a-240f, but more or fewer depths are also contemplated. Each depth plane may have three or more primary color images associated with it, including a first image in a first color G, a second image in a second color R, and a third image in a third color B. Different depth planes are indicated in the diagram by different numbers for diopters (dpt) following the letters G, R, and B. By way of example only, the number following each of these letters indicates the diopter (1 / m), i.e., the inverse distance of the depth plane from the user, and each box in the diagram represents an individual primary color image. In some embodiments, the exact locations of the depth planes for the different primary colors may vary to account for differences in the eye's focusing of light of different wavelengths. For example, different primary color images for a given depth plane may be placed on depth planes corresponding to different distances from the user. Such an arrangement may increase visual acuity and user comfort and / or reduce chromatic aberration.

[0153] In some embodiments, light for each primary color may be output by a single dedicated waveguide, such that each depth plane may have multiple waveguides associated with it. In such embodiments, each box in the diagram containing the letter G, R, or B may be understood to represent an individual waveguide, and three waveguides may be provided per depth plane, with three primary color images provided per depth plane. While the waveguides associated with each depth plane are shown adjacent to each other in this drawing for ease of illustration, it should be understood that in a physical device, the waveguides may all be arranged in a stack with one waveguide per level. In some other embodiments, multiple primary colors may be output by the same waveguide, such that, for example, only a single waveguide may be provided per depth plane.

[0154] 8, in some embodiments, G is green, R is red, and B is blue. In some other embodiments, other colors associated with other wavelengths of light, including magenta and cyan, may be used in addition to or replace one or more of red, green, or blue.

[0155] It should be understood that references throughout this disclosure to a given color of light will be understood to encompass light of one or more wavelengths within the range of wavelengths of light that are perceived by a user as being of that given color. For example, red light may include one or more wavelengths of light in the range of about 620-780 nm, green light may include one or more wavelengths of light in the range of about 492-577 nm, and blue light may include one or more wavelengths of light in the range of about 435-493 nm.

[0156] In some embodiments, light source 530 (FIG. 6) may be configured to emit light at one or more wavelengths outside the range of a user's visual perception, e.g., infrared and / or ultraviolet wavelengths. Additionally, waveguide incoupling, outcoupling, and other light redirecting structures of display 250 may be configured to direct and emit this light from the display toward the user's eye 210, e.g., for imaging and / or user stimulation applications.

[0157] Referring now to FIG. 9A , in some embodiments, light impinging on a waveguide may need to be redirected to incoupling the light into the waveguide. An incoupling optical element may be used to redirect and incoupling the light into its corresponding waveguide. While reference is made throughout this specification to an “incoupling optical element,” the incoupling optical element need not be an optical element and may be a non-optical element. FIG. 9A illustrates a cross-sectional side view of an example of a set 660 of stacked waveguides, each including an incoupling optical element. The waveguides may each be configured to output light of one or more different wavelengths or one or more different wavelength ranges. Stack 660 may correspond to stack 260 (FIG. 6), and the illustrated waveguides of stack 660 may correspond to portions of waveguides 270, 280, 290, 300, 310, although it should be understood that light from one or more of image injection devices 360, 370, 380, 390, 400 is injected into the waveguides from a location requiring the light to be redirected for internal coupling.

[0158] The illustrated set 660 of stacked waveguides includes waveguides 670, 680, and 690. Each waveguide includes an associated internal coupling optical element (which may also be referred to as the light input area on the waveguide), for example, internal coupling optical element 700 is disposed on a major surface (e.g., the top major surface) of waveguide 670, internal coupling optical element 710 is disposed on a major surface (e.g., the top major surface) of waveguide 680, and internal coupling optical element 720 is disposed on a major surface (e.g., the top major surface) of waveguide 690. In some embodiments, one or more of internal coupling optical elements 700, 710, 720 may be disposed on the bottom major surface of an individual waveguide 670, 680, 690 (particularly, one or more internal coupling optical elements are reflective polarizing optical elements). As shown, the internal coupling optical elements 700, 710, 720 may be disposed on the upper major surfaces of their respective waveguides 670, 680, 690 (or on top of the next lower waveguide), and in particular, the internal coupling optical elements are transmissive polarizing optical elements. In some embodiments, the internal coupling optical elements 700, 710, 720 may be disposed within the bodies of the respective waveguides 670, 680, 690. In some embodiments, as discussed herein, the internal coupling optical elements 700, 710, 720 are wavelength selective so as to selectively redirect one or more wavelengths of light while transmitting other wavelengths of light. While illustrated on one side or corner of the respective waveguides 670, 680, 690, it should be understood that the internal coupling optical elements 700, 710, 720 may be disposed within other areas of the respective waveguides 670, 680, 690 in some embodiments.

[0159] As shown, the in-coupling optical elements 700, 710, 720 may be laterally offset from one another. In some embodiments, each in-coupling optical element may be offset to receive light without that light passing through another in-coupling optical element. For example, each in-coupling optical element 700, 710, 720 may be configured to receive light from a different image input device 360, 370, 380, 390, and 400, as shown in FIG. 6 , and may be separated (e.g., laterally spaced) from the other in-coupling optical elements 700, 710, 720 so as to receive substantially no light from others of the in-coupling optical elements 700, 710, 720.

[0160] Each waveguide also includes an associated optically dispersive element, for example, optically dispersive element 730 is disposed on a major surface (e.g., the top major surface) of waveguide 670, optically dispersive element 740 is disposed on a major surface (e.g., the top major surface) of waveguide 680, and optically dispersive element 750 is disposed on a major surface (e.g., the top major surface) of waveguide 690. In some other embodiments, optically dispersive elements 730, 740, 750 may be disposed on the bottom major surfaces of the associated waveguides 670, 680, 690, respectively. In some other embodiments, the optically dispersive elements 730, 740, 750 may be disposed on both the top and bottom major surfaces of the associated waveguides 670, 680, 690, respectively, or the optically dispersive elements 730, 740, 750 may be disposed on different ones of the top and bottom major surfaces in different associated waveguides 670, 680, 690, respectively.

[0161] Waveguides 670, 680, 690 may be spaced apart and separated, for example, by gas, liquid, and / or solid layers of material. For example, as shown, layer 760a may separate waveguides 670 and 680, and layer 760b may separate waveguides 680 and 690. In some embodiments, layers 760a and 760b are formed from a low refractive index material (i.e., a material having a lower refractive index than the material forming the immediately adjacent ones of waveguides 670, 680, 690). Preferably, the refractive index of the material forming layers 760a, 760b is 0.05 or greater, or 0.10 or less, relative to the refractive index of the material forming waveguides 670, 680, 690. Advantageously, the lower refractive index layers 760a, 760b may function as cladding layers that promote total internal reflection (TIR) of light through the waveguides 670, 680, 690 (e.g., TIR between the top and bottom major surfaces of each waveguide). In some embodiments, the layers 760a, 760b are formed from air. Although not shown, it should be understood that the top and bottom of the illustrated set of waveguides 660 may include immediate cladding layers.

[0162] Preferably, for ease of manufacturing and other considerations, the materials forming waveguides 670, 680, 690 are similar or the same, and the materials forming layers 760a, 760b are similar or the same. In some embodiments, the materials forming waveguides 670, 680, 690 may vary between one or more waveguides, and / or the materials forming layers 760a, 760b may vary while still maintaining the various refractive index relationships described above.

[0163] 9A, light rays 770, 780, 790 enter the set of waveguides 660. It should be understood that light rays 770, 780, 790 may be injected into the waveguides 670, 680, 690 by one or more image injection devices 360, 370, 380, 390, 400 (FIG. 6).

[0164] In some embodiments, light rays 770, 780, 790 have different properties, e.g., different wavelengths or different wavelength ranges, which may correspond to different colors. Each of the incoupling optical elements 700, 710, 720 deflects incident light such that the light propagates through a respective one of the waveguides 670, 680, 690 by TIR. In some embodiments, each of the incoupling optical elements 700, 710, 720 selectively deflects one or more particular wavelengths of light while transmitting other wavelengths to the underlying waveguide and associated incoupling optical element.

[0165] For example, in-coupling optical element 700 may be configured to deflect light ray 770 having a first wavelength or wavelength range while transmitting light rays 780 and 790 having different second and third wavelengths or wavelength ranges, respectively. Transmitted light ray 780 impinges on and is deflected by in-coupling optical element 710, which is configured to deflect light of the second wavelength or wavelength range. Light ray 790 is deflected by in-coupling optical element 720, which is configured to selectively deflect light of the third wavelength or wavelength range.

[0166] 9A , the deflected light rays 770, 780, 790 are deflected to propagate through the corresponding waveguides 670, 680, 690. That is, the in-coupling optical element 700, 710, 720 of each waveguide deflects the light into its corresponding waveguide 670, 680, 690 and in-couples the light into its corresponding waveguide. The light rays 770, 780, 790 are deflected at an angle that causes the light to propagate through the respective waveguides 670, 680, 690 by TIR. The light rays 770, 780, 790 propagate through the respective waveguides 670, 680, 690 by TIR until they impinge on the waveguide's corresponding optical dispersive element 730, 740, 750.

[0167] 9B, a perspective view of the multiple stacked waveguide embodiment of FIG. 9A is illustrated. As described above, in-coupled light rays 770, 780, 790 are deflected by in-coupling optical elements 700, 710, 720, respectively, and then propagate by TIR within waveguides 670, 680, 690, respectively. Light rays 770, 780, 790 then impinge on optically dispersive elements 730, 740, 750, respectively. Optically dispersive elements 730, 740, 750 deflect light rays 770, 780, 790 to propagate toward out-coupling optical elements 800, 810, 820, respectively.

[0168] In some embodiments, the optically dispersive elements 730, 740, 750 are orthogonal pupil expanders (OPEs). In some embodiments, the OPEs deflect or disperse light into the out-coupling optical elements 800, 810, 820, and in some embodiments may also increase the beam or spot size of this light as it propagates into the out-coupling optical elements. In some embodiments, the optically dispersive elements 730, 740, 750 may be omitted, and the in-coupling optical elements 700, 710, 720 may be configured to deflect light directly into the out-coupling optical elements 800, 810, 820. For example, with reference to FIG. 9A , the optically dispersive elements 730, 740, 750 may be replaced with the out-coupling optical elements 800, 810, 820, respectively. In some embodiments, the outcoupling optical element 800, 810, 820 is an exit pupil (EP) or exit pupil expander (EPE) that directs light toward the eye 210 ( FIG. 7 ). It should be understood that an OPE can be configured to increase the size of the eyebox in at least one axis, and that the EPE may increase the eyebox in an axis that intersects the axis of the OPE, e.g., orthogonal to the axis of the OPE. For example, each OPE may be configured to redirect a portion of the light striking the OPE to an EPE in the same waveguide while allowing the remaining portion of the light to continue propagating down the waveguide. In response to striking the OPE again, another portion of the remaining light is redirected to the EPE, and the remainder of that portion continues to propagate further down the waveguide, etc. Similarly, in response to striking the EPE, a portion of the impinging light is directed out of the waveguide toward the user, and the remaining portion of that light continues to propagate through the waveguide until it again strikes an EP, at which point another portion of the impinging light is directed out of the waveguide, etc. As a result, a single beam of internally coupled light may be "replicated" each time a portion of that light is redirected by an OPE or EPE, thereby forming a cloned beam field of light, as shown in Figure 6. In some embodiments, the OPE and / or EPE may be configured to modify the size of the beam of light.

[0169] 9A and 9B, in some embodiments, a waveguide set 660 includes, for each primary color, waveguides 670, 680, 690, in-coupling optical elements 700, 710, 720, optically dispersive elements (e.g., OPEs) 730, 740, 750, and out-coupling optical elements (e.g., EPs) 800, 810, 820. The waveguides 670, 680, 690 may be stacked with an air gap / cladding layer between each one. The in-coupling optical elements 700, 710, 720 redirect or deflect incident light into that waveguide (with different in-coupling optical elements receiving light of different wavelengths). The light then propagates at an angle that will result in TIR within the individual waveguides 670, 680, 690. In the example shown, light ray 770 (e.g., blue light) is deflected by the first in-coupling optical element 700 in the manner described above, then continues bouncing down the waveguide, interacting with the optically dispersive element (e.g., OPE) 730 and then the out-coupling optical element (e.g., EP) 800. Light rays 780 and 790 (e.g., green and red light, respectively) pass through the waveguide 670, with light ray 780 impinging on and being deflected by the in-coupling optical element 710. Light ray 780 will then, via TIR, bounce down the waveguide 680, to its optically dispersive element (e.g., OPE) 740 and then the out-coupling optical element (e.g., EP) 810. Finally, light ray 790 (e.g., red light) passes through the waveguide 690 and impinges on the optically in-coupling optical element 720 of the waveguide 690. The light in-coupling optical element 720 deflects the light ray 790 so that it propagates by TIR to an optical dispersive element (e.g., OPE) 750 and then by TIR to an out-coupling optical element (e.g., EP) 820. The out-coupling optical element 820 then finally out-couples the light ray 790 to the user, who also receives the out-coupled light from the other waveguides 670, 680.

[0170] FIG. 9C illustrates a top-down plan view of an example of the multiple stacked waveguides of FIGS. 9A and 9B. As shown, waveguides 670, 680, 690 may be vertically aligned, along with each waveguide's associated optically dispersive element 730, 740, 750 and associated out-coupling optical elements 800, 810, 820. However, as discussed herein, the in-coupling optical elements 700, 710, 720 are not vertically aligned. Rather, the in-coupling optical elements are preferably non-overlapping (e.g., laterally spaced apart, as seen in the top-down view). As discussed further herein, this non-overlapping spatial arrangement facilitates the injection of 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, arrays including non-overlapping, spatially separated in-coupling optical elements may be referred to as shifted-pupil systems, and the in-coupling optical elements in these arrays may correspond to sub-pupils.

[0171] 9D illustrates an example of a wearable display system 60 into which the various waveguide and associated systems disclosed herein may be integrated. In some embodiments, the display system 60 is the system 250 of FIG. 6, which diagrammatically illustrates some portions of the system 60 in greater detail. For example, the waveguide assembly 260 of FIG. 6 may be part of the display 70.

[0172] Continuing with reference to FIG. 9D , display system 60 includes display 70 and various mechanical and electronic modules and systems to support the functionality of display 70. Display 70 may be coupled to frame 80, which is wearable by a display system user or user 90 and configured to position display 70 directly in front of the user's 90's eye. Display 70, in some embodiments, may be considered an eyepiece. In some embodiments, speaker 100 is coupled to frame 80 and configured to be positioned adjacent to the user's 90's ear canal (in some embodiments, another speaker, not shown, may optionally be positioned adjacent the user's other ear canal to provide stereo / shapeable sound control). Display system 60 may also include one or more microphones 110 or other devices to detect sound. In some embodiments, the microphones are configured to allow a user to provide input or commands to system 60 (e.g., voice menu command selections, natural language queries, etc.) and / or enable audio communication with other persons (e.g., other users of similar display systems). The microphone may further be configured as an ambient sensor and collect audio data (e.g., sounds from the user and / or the environment). In some embodiments, the display system 60 may further include one or more outwardly directed environmental sensors 112 configured to detect objects, stimuli, people, animals, places, or other aspects of the world around the user. For example, the environmental sensors 112 may include, for example, one or more cameras that may be positioned facing outward to capture images similar to at least a portion of the user 90's normal field of view. In some embodiments, the display system may also include an ambient sensor 120a, which may be separate from the frame 80 and mounted on the user 90's body (e.g., the user's 90's head, torso, limbs, etc.). The ambient sensor 120a, in some embodiments, may be configured to obtain data characterizing the user 90's physiological state. For example, the sensor 120a may be an electrode.

[0173] 9D , display 70 is operably coupled to local data processing module 140 by a communication link 130, such as wired or wireless connectivity, which may be mounted in a variety of configurations, such as fixedly attached to frame 80, fixedly attached to a helmet or hat worn by the user, embedded within headphones, or otherwise removably attached to user 90 (e.g., in a backpack-style configuration, in a belt-linked configuration). Similarly, sensor 120a may be operably coupled to local processor and data module 140 by a communication link 120b, such as wired or wireless connectivity. Local processing and data module 140 may comprise a hardware processor and digital memory, such as non-volatile memory (e.g., flash memory or a hard disk drive), both of which may be utilized to aid in processing, caching, and storing data. Optionally, local processing and data module 140 may include one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, etc. The data may include a) data captured from sensors (such as image capture devices (cameras, etc.), microphones, inertial measurement units, accelerometers, compasses, GPS units, wireless devices, gyroscopes, and / or other sensors disclosed herein (e.g., which may be operatively coupled to frame 80 or otherwise attached to user 90)) and / or b) data obtained and / or processed using remote processing module 150 and / or remote data repository 160 (including data related to virtual content), possibly for passage to display 70 after processing or retrieval. Local processing and data module 140 may be operatively coupled to remote processing module 150 and remote data repository 160 by communication links 170, 180, such as via wired or wireless communication links, such that these remote modules 150, 160 are operatively coupled to each other and available as resources to local processing and data module 140.In some embodiments, local processing and data module 140 may include one or more of an image capture device, a microphone, an inertial measurement unit, an accelerometer, a compass, a GPS unit, a wireless device, and / or a gyroscope. In some other embodiments, one or more of these sensors may be mounted to frame 80 or may be a freestanding structure that communicates with local processing and data module 140 by a wired or wireless communication path.

[0174] 9D , in some embodiments, remote processing module 150 may comprise one or more processors configured to analyze and process data and / or image information, and may include, for example, one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, etc. In some embodiments, remote data repository 160 may comprise digital data storage facilities that may be available through the Internet or other networking configurations in a “cloud” resource configuration. In some embodiments, remote data repository 160 may include one or more remote servers, which provide information, for example, information for generating augmented reality content, to local processing and data module 140 and / or remote processing module 150. In some embodiments, all data is stored and all computations are performed within the local processing and data module, allowing for fully autonomous use from the remote module. Optionally, an external system (e.g., one or more processors, one or more computer systems), including a CPU, GPU, etc., may perform at least a portion of the processing (e.g., generating image information, processing data) and provide information to and receive information from modules 140, 150, 160, e.g., via a wireless or wired connection.

[0175] FIG. 10 is a schematic diagram illustrating a projector assembly 1000 that utilizes a polarizing beam splitter (PBS) 1020 to illuminate a spatial light modulator (SLM) 1030 and redirect light from the SLM 1030 through projection optics 1040 to an eyepiece (not shown). The projector assembly 1000 includes an illumination source 1010, which may include, for example, a light-emitting diode (LED), a laser (e.g., a laser diode), or other types of light sources. This light may be collimated by collimating optics. The illumination source 1010 can emit polarized, unpolarized, or partially polarized light. In the illustrated design, the illumination source 1010 may emit light 1012 polarized to have p-polarization. A first optical element 1015 (e.g., a pre-polarizer) is aligned to pass light with a first polarization (e.g., p-polarization).

[0176] This light is directed to a polarizing beam splitter 1020. Initially, the light passes through interface 1022 (e.g., a polarizing interface) of the PBS 1020, which is configured to transmit light of a first polarization (e.g., p-polarized light). The light then continues and impinges on a spatial light modulator 1030. As shown, the SLM 1030 is a reflective SLM configured to retroreflect and selectively modulate the incident light. The SLM 1030 includes, for example, one or more pixels that can have different states. The light incident on an individual pixel can be modulated based on the state of the pixel. The SLM 1030 can then be driven to modulate the light to provide an image. In this example, the SLM 1030 may be a polarization-based SLM that modulates the polarization of light incident thereon. For example, in the on state, a pixel of the SLM 1030 changes input light from a first polarization state (e.g., a p-polarization state) to a second polarization state (e.g., an s-polarization state), such that a bright state (e.g., a white pixel) is indicated. The second polarization state may be the first polarization state modulated (e.g., rotated) by 90°. In the on state, light having the second polarization state is reflected by the interface 1022 and propagates downstream through the projector optics 1040. In the off state, the SLM 1030 does not change the polarization state of light incident thereon, e.g., does not rotate input light from the first polarization state, such that a dark state (e.g., a black pixel) is indicated. In the off state, light having the first polarization state is transmitted through the interface 1022 and propagates upstream back to the illumination source 1010, rather than to the user's eye.

[0177] After reflecting from the SLM 1030, a portion of the light 1014 (e.g., modulated light) is reflected from interface 1022, exits the PBS 1020, and is directed toward the user's eye. The emitted light passes through projector optics 1040 and is imaged onto an internal coupling grating (ICG) 1050 in the eyepiece (not shown).

[0178] 11A illustrates a system (e.g., an augmented reality display system) 1100A for presenting an image to a user's eye 210 and viewing a world 510, having an alternative configuration to that shown in FIG. 10 . System 1100 includes a light source 1110, a spatial light modulator (SLM) 1140, and a waveguide 1120 arranged such that light from light source 1110 illuminates SLM 1140 and light reflected from SLM 1140 is coupled into waveguide 1120 to be directed toward eye 210. System 1100A includes an optical system 1130 positioned to both illuminate SLM 1140 and project an image of SLM 1140. Light from light source 1110 propagates, for example, in a first direction, through optical system 1130, and onto SLM 1140, thereby illuminating SLM 1140. Light reflected from SLM 1140 propagates again through optics 1130 in a second direction opposite the first direction and is directed into waveguide 1120 where it is coupled in.

[0179] 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, however, the light source 1110 need not be so limited. In some implementations, a polarizer 1115 may be positioned between the light source 1110 and the SLM 1140. As shown, the polarizer 1115 is between the light source 1110 and the waveguide 1120. This polarizer 1115 may also be a light recycler that transmits light of a first polarization and reflects light of a second polarization back to the light source 1110. Such a polarizer 1115 may be, for example, a wire grid polarizer. A coupling optic 1105, such as a non-imaging optical element (e.g., a cone, a compound parabolic concentrator (CPC, lens)), may be positioned relative to the light source 1110 to receive the light output from the light source 1110. The coupling optics 1105 may collect light from the light source 1110 and, in some cases, reduce the divergence of the light emitted from the light source 1110. The coupling optics 1105 may, for example, collimate the light output from the light source 1110. The coupling optics 1105 may collect light that matches the angular spectral field of view of the system 1100A. Thus, the coupling optics 1105 may match the angular spectrum of the light output by the light source 1110 with the field of view of the system 1100A. The coupling optics 1105 may have an asymmetric profile and act asymmetrically on the light emitted from the light source 1110. For example, the coupling optics 1105 may reduce divergence in orthogonal directions (e.g., the x and z directions) by different amounts. Such asymmetry in the coupling optics 1105 may address asymmetries in the light emitted from the light source 1110, which may include, for example, a laser diode that emits light over a wider range of angles in one direction (e.g., x or z) as opposed to an orthogonal direction (e.g., z or x, respectively).

[0180] As discussed above, system 1100A includes optical system 1130 disposed in the optical path between light source 1110 and SLM 1140 and configured to illuminate SLM 1140. Optical system 1130 may include a transmissive optical system that transmits light from light source 1110 to SLM 1140. Optical system 1130 may also be configured to project an image of SLM 1140, or may be formed by SLM 1140 in waveguide 1120. The image may be projected into eye 210. In some designs, optical system 1130 may include one or more lenses or optical elements having refractive power. Optical system 1130 may have, for example, positive refractive power. Optical system 1130 may include one or more refractive optical elements, such as a refractive lens. Other types of optical elements may also potentially be used.

[0181] The SLM 1140 may be reflective and modulate and reflect light therefrom. The SLM 1140 may be a polarization-based SLM configured to modulate polarization. The SLM 1140 may include, for example, a liquid crystal (LC) SLM (e.g., a liquid crystal on silicon (LCOS) SLM). The LC SLM may include, for example, a twisted nematic (TN) liquid crystal. The SLM 1140 may be substantially similar to the SLM 1030 referenced in FIG. 10 . The SLM 1140 may include one or more pixels configured to selectively modulate light incident on the pixel, for example, depending on the state of the pixel. For some types of SLM 1140, the pixel may modulate a beam incident thereon by altering the polarization state, for example, by rotating the polarization (e.g., rotating the orientation of linearly polarized light).

[0182] As discussed above, the SLM 1140 may be an LCOS SLM 1140. In a cross-polarizer configuration, the LCOS SLM 1140 may be nominally white. When a pixel is off (e.g., at 0 voltage), it has a bright state, and when the pixel is on (e.g., at a voltage above a threshold on voltage), it has a dark state. In this cross-polarizer configuration, leakage is minimized when the pixel is on and has a dark state.

[0183] In a parallel polarizer configuration, the LCOS SLM 1140 is nominally black. When a pixel is off (e.g., at 0 voltage), it has a dark state, and when it is on (e.g., at a voltage above the threshold 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 dark state may be (re)optimized using the rub direction and compensator angle. The compensator angle may refer to the angle of the compensator, which may be between the optical system 1130 and the SLM 1140, for example, as illustrated in FIG. 20B.

[0184] The dynamic range and throughput for the parallel polarizer configuration may be different from that of the crossed polarizer configuration. Additionally, the parallel polarizer configuration may be optimized for contrast differently than the crossed polarizer configuration.

[0185] The system 1100A includes a waveguide 1120 for outputting image information to the eye 210. The waveguide 1120 may be substantially similar to the waveguides 270, 280, 290, 300, 310, 670, 680, and 690 discussed above. The waveguide 1120 may include a substantially transparent material having a refractive index sufficient to guide light therethrough. As shown, the waveguide 1120 may include a first side 1121, a second side 1123 opposite the first side 1121, corresponding upper and lower major surfaces, and a peripheral edge. The first and second major surfaces 1121, 1123 may be sufficiently flat so that image information can be retained upon propagating light from the SLM 1140 to the eye 210 such that an image formed by the SLM 1140 can be projected into the eye. The optical system 1130 and the SLM 1140 may be positioned on a first side 1121 of the waveguide 1120. The light source 1110 may 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 system 1130 to the SLM 1140. Thus, the waveguide 1120 may be disposed between the light source 1110 and the optical system 1130. In addition, at least a portion of the waveguide 1120 may extend between the light source 1110 and the optical system 1130, thereby passing light through a portion of the waveguide 1120 to the optical system 1130. Light emitted from the light source 1110 may thus be directed through the waveguide 1120 into and through the optical system 1130 and incident on the SLM 1140. SLM 1140 reflects the light back through optics 1130 into waveguide 1120 .

[0186] The system 1100A also includes an internal coupling optical element 1160 for coupling light from the optical system 1130 into the waveguide 1120. The internal coupling optical element 1160 may be disposed on a major surface (e.g., the upper major surface 1123) of the waveguide 1120. In some designs, the internal coupling optical element 1160 may be disposed on the lower major surface 1121 of the waveguide 1120. In some designs, the internal coupling optical element 1160 may be disposed within the body of the waveguide 1120. Although illustrated on one side or corner of the waveguide 1120, the internal coupling optical element 1160 may be disposed in / on other areas of the waveguide 1120. The internal coupling optical element 1160 may be substantially similar to the internal coupling optical elements 700, 710, 720 described above with reference to FIGS. 9A, 9B, and 9C. The internal coupling optical element 1160 may be a diffractive optical element or a reflector. Other structures may also be used as the in-coupling optical element 1160. The in-coupling optical element 1160 may be configured to direct light incident thereon at a sufficiently large glancing angle (e.g., above a critical angle) relative to the upper and lower major surfaces 1123, 1121 of the waveguide 1120 into the waveguide 1120 so that it is guided therein by total internal reflection. Furthermore, the in-coupling optical element 1160 may be configured to operate on a wide range of wavelengths and thus couple multiple colors of light into the waveguide 1120. For example, the in-coupling optical element 1160 may be configured to couple red, green, and blue light into the waveguide 1120. The light source 1110 may emit red, green, and blue light at different times.

[0187] The system 1100A includes an optically dispersive element 1170 disposed on or within the waveguide 1120. The optically dispersive element 1170 may be substantially similar to the optically dispersive elements 730, 740, and 750 described above with respect to FIG. 9B . For example, the optically dispersive element 1170 may be an orthogonal pupil expander (OPE). The optically dispersive element 1170 may be configured to spread light within the waveguide 1120 by redirecting light propagating in the x-direction, e.g., toward the z-direction illustrated in the top view of FIG. 11B . The optically dispersive element 1170 may thus be configured to increase the dimension of the eyebox along the z-axis (see FIG. 11B ). The optically dispersive element 1170 may include one or more diffractive optical elements configured to diffract light propagating within the waveguide 1120 that is incident on the diffractive optical element, e.g., to redirect the light in a substantially orthogonal direction. Other configurations are also possible.

[0188] 11B, system 1100A may also include an outcoupling optical element 1180 for coupling light out of waveguide 1120 and into eye 210. Outcoupling optical element 1180 may be configured to redirect light propagating within waveguide 1120 by total internal reflection (TIR) at an angle more normal to the upper and / or lower major surfaces 1123, 1121 of waveguide 1120 so that the light is not guided within waveguide 1120. Instead, the light is directed out of waveguide 1120, for example, through lower major surface 1121. Outcoupling optical element 1180 may include one or more diffractive optical elements configured, for example, to diffract light propagating within waveguide 1120 that enters the diffractive optical element, such that the light is redirected out of waveguide 1120, for example. Other configurations are also possible.

[0189] 11B also shows the location of the in-coupling optical element 1160, which is positioned laterally relative to the light-dispersing optical element (e.g., orthogonal pupil expander) 1170 and the out-coupling optical element 1180. FIG. 11B also shows the location of the light source 1110, which is positioned laterally relative to the in-coupling optical element 1160, the light-dispersing optical element (e.g., orthogonal pupil expander) 1170, and the out-coupling optical element 1180.

[0190] In operation, the light source 1110 of the system 1100A emits light through the polarizer 1115 into the coupling optics 1105. This light may therefore be polarized, for example, linearly polarized in a first direction. This polarization may be transmitted through the waveguide 1120, enter the second major surface of the waveguide 1120, and exit the first major surface of the waveguide 1120. This light may propagate through the optics 1130 to the SLM 1140. The optics 1130 quasi-collimates and / or selects the light from the light source 1110 to illuminate the SLM 1140, which may include a polarization-based modulator that modulates the polarization of the light incident thereon, such as by selectively rotating the orientation of the modulator, on a pixel-by-pixel basis, depending on the state of the pixel. For example, a first pixel may be in a first state and rotate the polarization, while a second pixel may be in a second state and not rotate the polarization. Light between the coupling optics 1105 and the optics 1130 may illuminate the SLM 1140 very uniformly. After incident on the SLM 1140, the light is reflected back through the optics 1130. The optics 1130 may be configured to project an image from the SLM 1140 into the waveguide 1120 and ultimately into the eye 210 so that the image is visible to the eye 210. In some designs, the retina of the eye 210 is optically conjugate to the SLM 1140 and / or the image formed by and / or on the SLM 1140. The refractive power of the optics 1130 may facilitate the projection of the image on the SLM 1140 into and onto the retina of the eye 210. In some implementations, refractive power, for example, provided by the outcoupling optics 1180, may assist and / or influence the image ultimately formed within the eye 210. Optical system 1130 acts as a projection lens as light reflected from SLM 1140 travels through the system toward waveguide 1120. The optical system may generally function as a Fourier transform of the image on SLM 1140 to a plane within waveguide 1120 near internal coupling optical element 1160. Together, both passes through optical system 1130 (the first pass from light source 1110 to SLM 1140, and the second pass from SLM 1140 to waveguide 1120) may generally act to image the pupil of coupling optical system 1105.The alignment and orientation of the light source 1110 (and possibly also the coupling optics 1105 and / or polarizer 1115), the optical system 1130, and the SLM 1140 are such that light from the light source 1110 reflected from the SLM 1140 is directed onto the internal coupling optical element 1160. A pupil associated with the coupling optics 1105 may be aligned with the internal coupling optical element 1160. The light may pass through an analyzer 1150 (e.g., a polarizer) in the optical path between the SLM 1140 and the eye 210. As depicted in FIG. 11A , the analyzer (e.g., polarizer) 1150 may be positioned in the optical path between the optical system 1130 and the internal coupling optical element 1160. The analyzer 1150 may be, for example, a linear polarizer having an orientation that transmits light of a first polarization (p-polarized) and blocks light of a second polarization (s-polarized), or vice versa. The analyzer 1150 may be a clean-up polarizer that further blocks polarized light blocked by another polarizer between the SLM 1140 and the analyzer 1150 or within the SLM 1140. The analyzer 1150 may be, for example, a circular polarizer that acts as an isolator and reduces reflections from the waveguide 1120, particularly from the incoupling optical element 1160, back toward the SLM 1140. The analyzer 1150 may include a wire grid polarizer, such as an absorptive wire grid polarizer, such as any of the polarizers disclosed herein. Such a polarizer may provide significant absorption of undesired light and therefore increased contrast. Some such polarizers can be fabricated to include one or more dielectric layers on top of the wires and / or multilayer films. In some implementations, the SLM 1140 may be a liquid crystal on silicon (LCOS) SLM and may include an LC cell and a retarder (e.g., a compensator). In some implementations, the analyzer 1150 may be a compensator intended to provide a more consistent polarization rotation (e.g., 90°) of the SLM 1140 for different angles of incidence and different wavelengths. The compensator may be used to improve the contrast of the display by improving the rotated polarization for light rays incident across a variety of angles and wavelengths.The SLM 1140 may include, for example, a TN LCOS configured to rotate incident light of a first polarization (e.g., s-polarized) to a second polarization (e.g., p-polarized) for a first pixel as the light passes through the analyzer 1150, producing a bright pixel state. Conversely, the SLM 1140 may be configured not to rotate incident light of a first polarization (e.g., s-polarized) to a second polarization (e.g., p-polarized) for a second pixel such that as the light is attenuated or blocked by the analyzer 1150, the reflected light remains at the first polarization, producing a dark pixel state. In such a configuration, the polarizer 1115 closer to the light source 1110 along the optical path may be oriented differently (e.g., orthogonal) with respect to the analyzer 1150 further from the light source 1110 along the optical path. Other, e.g., opposite, configurations are also possible.

[0191] The light is then deflected, e.g., redirected, by the in-coupling optical element 1160 to be guided within the waveguide 1120, where it propagates by TIR. The light then impinges on the optically dispersive element 1170, redirecting the light in another direction (e.g., more toward the z-direction), resulting in an increase in the size of the eyebox along the z-axis, as shown in FIG. 11B. The light is thus deflected toward the out-coupling optical element 1180, which directs the light out of the waveguide 1120 toward the eye 210 (e.g., the user's eye, as shown). The light being out-coupled along the z-direction by different portions of the out-coupling optical element 1180 results in an increase in the size of the eyebox, at least along a direction parallel to the z-axis, as defined in FIG. 11B. Notably, in this configuration, the optical system 1130 is used both to illuminate the SLM 1140 and to project an image onto the in-coupling optical element 1160. Thus, optical system 1130 may function as projection optics, dispersing (e.g., uniformly) light from light source 1110, and may also act as imaging optics, providing an image of SLM 1140 and / or an image formed by SLM 1140 into the eye. System 1100A in FIG. 11A / B may, in some instances, be more compact than system 1000 in FIG. 10 . In some cases, not employing PBS 1020 shown in FIG. 10 may potentially reduce the cost and / or size of the system. Additionally, by not using PBS 1020, the system may be more symmetrical and easier to design by shortening the back focal length of optical system 1130.

[0192] As referenced above, alternative configurations are also possible. Referring to FIG. 11C , for example, in some designs, system 1100C may be configured to pass light having a polarization that is not rotated by SLM 1140. In one implementation, for example, SLM 1140 may be a liquid crystal (LC)-based SLM, including a vertically aligned (VA) LC-on-silicon (LCoS) device. SLM 1140 may have a first pixel in a first state that does not rotate the polarization and a second pixel in a second state that rotates the polarization. In the configuration illustrated in FIG. 11C , a single shared analyzer / polarizer 1155 is utilized. This analyzer 1155 may transmit light of a first polarization (e.g., s-polarized) and attenuate or reduce transmission of a second polarization (e.g., p-polarized). Thus, light (e.g., s-polarized light) incident on a first pixel in a first state that does not rotate the polarization orientation is reflected from the SLM 1140 and passes through the analyzer 1155 to the waveguide 1120. Conversely, light (e.g., s-polarized light) incident on a second pixel in a second state that rotates the polarization orientation is reflected from the SLM 1140 and is attenuated, reduced, or not passed through the analyzer 1155 to the waveguide 1120. This configuration may thereby allow the polarizer 1115 and analyzer 1150 shown in FIG. 11A to be incorporated into a shared optical element, i.e., the analyzer 1155 shown in FIG. 11C, thereby potentially simplifying the system 1100 of FIG. 11A / B by reducing the number of optical components. The analyzer 1155 may be disposed between the waveguide 1120 and the optical system 1130. In other implementations, separate analyzer / polarizer and analyzer / polarizer may be used as shown in system 1100 of Figures 11A / B. Figures 11A and 11B illustrate a polarizer 1115 between the light source 1110 and the waveguide 1120, and an analyzer 1140 between the optical system 1130 and the waveguide 1120.

[0193] Various other configurations may be employed to utilize optical system 1130 for both illuminating SLM 1140 and imaging the image formed by SLM 1140. For example, although FIGS. 11A-11C show a single waveguide 1120, more than one waveguide may be used, such as a stack of waveguides (possibly different waveguides for different colors of light). FIG. 12A illustrates a cross-sectional side view of an example system 1200A including, for example, a stack 1205 including waveguides 1120, 1122, 1124, each including internal coupling optical elements 1260, 1262, 1264. Waveguides 1120, 1122, 1124 may each be configured to output light of one or more different wavelengths or ranges of one or more different wavelengths. Stack 1205 may be substantially similar to stacks 260 and 660 (FIGS. 6 and 9A), and the illustrated waveguides 1120, 1122, 1124 of stack 1205 may correspond to portions of waveguides 670, 680, 690; however, stack 1205 and waveguides 1120, 1122, 1124 need not be so limited. As illustrated in FIG. 12A, internal coupling optical elements 1260, 1262, 1264 may be associated with and included within or on waveguides 1120, 1122, 1124, respectively. Internal coupling optical elements 1260, 1262, 1264 may be color-selective and may divert or redirect certain wavelengths into corresponding waveguides 1120, 1122, 1124 primarily as guided therein. As shown, because the incoupling optical elements 1260, 1262, 1264 are color-selective, the incoupling optical elements 1260, 1262, 1264 do not need to be laterally displaced and may be stacked over one another. Wavelength multiplexing may be employed to couple specific colors into corresponding waveguides. For example, a red incoupling optical element may incoupling red light into a waveguide designated for propagating red light, while not incoupling blue or green light, which is instead coupled into other waveguides by other blue- and green-selective waveguides, respectively.

[0194] In some implementations, the light source 1110 may be a multicolor light source capable of emitting different colored light at different times. For example, the light source 1110 may emit red, green, and blue (RGB) light and may be configured to emit red and negligible amounts of green and blue during a first time period, green and negligible amounts of red and blue during a second time period, and blue and negligible amounts of red and green during a third time period. These cycles can be repeated, and the SLM 1140 can be coordinated to produce a suitable pattern of pixel states for a particular color (red, green, or blue) to provide the appropriate image color components for a given image frame. Different waveguides 1120, 1122, and 1124 of the stack 1205 may each be configured to output light with a different individual color. For example, as depicted in FIG. 12A , the waveguides 1120, 1122, and 1124 may be configured to output blue, green, and red light, respectively. Of course, other colors are possible; for example, the light source 1110 may emit other colors, and the color-selective in-coupling optical elements 1260, 1262, 1264, out-coupling optical elements, etc., may be configured for such other colors. In addition, individual red, green, and blue emitters may be positioned close enough together to effectively function as a single-pupil light source. Red, green, and blue emitters may be combined with lenses and dichroic splitters to form a single red, green, and blue pupil source. Single-pupil multiplexing may be extended beyond or in addition to color selectivity and may include the use of polarization-dependent gratings and polarization switching. These color or polarization gratings can also be used in combination with multiple display pupils to increase the number of layers that can be addressed.

[0195] Different internal coupling optical elements 1260, 1262, 1264 in different waveguides 1120, 1122, 1124 may be disposed over and / or beneath one another and laterally aligned (e.g., in the x and z directions shown in FIG. 12A ), as opposed to being laterally displaced and unaligned with respect to one another. Thus, in some implementations, for example, different internal coupling optical elements 1260, 1262, 1264 may be configured such that light of a first color may be coupled into waveguide 1120 by internal coupling optical element 1260 to be guided therein, and light of a second color different from the first color may pass through internal coupling optical element 1260 to the next internal coupling optical element 1262 and be coupled into waveguide 1122 by internal coupling optical element 1262 to be guided therein. Light of a third color, different from the first and second colors, may pass through in-coupling optical elements 1260 and 1262 to in-coupling optical element 1264 and be coupled into waveguide 1124 to be guided therein. Additionally, in-coupling optical elements 1260, 1262, 1264 may be polarization-selective. For example, different in-coupling optical elements 1260, 1262, 1264 can be configured such that light of a certain polarization is either coupled into the waveguide by the corresponding polarization-selective in-coupling optical element 1260, 1262, 1264 or passes through the in-coupling optical element 1260, 1262, 1264.

[0196] Depending on the configuration, SLM 1140 may include a polarization-based SLM that modulates polarization. System 1200A may include, for example, a polarizer and / or analyzer that modulates the light injected into stack 1205 on a pixel-by-pixel basis depending on the state of the individual pixel (e.g., whether the pixel rotates the polarization orientation). Various aspects of such systems employing polarization-based SLMs are discussed above, and any one of such features may be employed in combination with any other feature described herein. However, other designs are still possible.

[0197] For example, a deflection-based SLM 1140 may be employed. For example, the SLM 1140 may include one or more movable optical elements, such as movable mirrors, that can reflect and / or deflect light along different directions depending on the state of the optical elements. The SLM 1140 may include one or more pixels that include such optical elements, such as micromirrors or reflectors. The SLM 1140 may incorporate, for example, digital light processing (DLP™) technology, which uses a digital micromirror device (DMD). An example of a system 1200B using such a deflection-based SLM 1140 is shown in FIG. 12B. The system 1200B includes the deflection-based SLM 1140 and a light dump 1250. The light dump 1250 may include a light-absorbing material or structure configured to absorb light. The deflection-based SLM 1140 may include one or more movable micromirrors that can be selectively tilted to deflect light in different directions. For example, the deflection-based SLM 1140 may be configured to deflect light from the light source 1110 incident thereon to the in-coupling optics 1260, 1262, 1264 when a given pixel is in a bright state. As discussed above, this light will therefore be coupled by one of the in-coupling optics 1260, 1262, 1264 into one of the respective waveguides 1120, 1122, 1124, depending on, for example, the color of the light, and directed to the eye 210. Conversely, when a given pixel is in a dark state, light from the light source 1110 may be deflected to the light dump 1250, and the light will not be coupled by one of the in-coupling optics 1260, 1262, 1264 into one of the respective waveguides 1120, 1122, 1124 and directed to the eye 210. The light may instead be absorbed by the light-absorbing material that makes up the light dump 1250. In some implementations, the analyzer 1150 may be a polarizer (e.g., a "clean-up" polarizer) used to eliminate unwanted reflections from the incoupling optical elements 1260, 1262, 1264. This polarizer may be useful because the optical system 1130 may include plastic optical elements that have birefringence and may modify the polarization of light.The "clean-up" polarizer may attenuate or remove light having undesired polarizations (e.g., reflections) from being directed onto the waveguides 1120, 1122, 1124. Other types of light conditioning elements may also be disposed between the SLM 1140 and the waveguides 1120, 1122, 1124, such as between the optical system 1130 and the waveguides 1120, 1122, 1124. For example, such light conditioning elements may also include a circular polarizer (i.e., a linear polarizer and a retarder such as a quarter-wave plate). The circular polarizer may again reduce the amount of reflections from the waveguides 1120, 1122, 1124 or the internal coupling optical elements 1260, 1262, 1264 that are incident on and coupled into the waveguides 1120, 1122, 1124. The reflected light may be circularly polarized and may possess the opposite circular polarization to that of the incident light (e.g., upon reflection, right-handed circularly polarized light is converted to left-handed circularly polarized light, or vice versa). A retarder within the circular polarizer may convert the circularly polarized light to linear polarization, such as the orthogonal polarization of the polarizer, which is attenuated, e.g., absorbed, by the linear polarizer within the circular polarizer. Clean-up polarizers may also be used in conjunction with polarization-independent modulators, such as DMDs. As mentioned above, clean-up polarizers may be useful to suppress reflections and / or improve the coupling of light into the internally coupled optical elements 1260, 1262, 1264 with optimal polarization states.

[0198] 12B illustrates a side or cross-sectional view of such a system 1200B, while FIG. 12C shows a top view of the lateral arrangement of the in-coupling optical element 1264, light dump 1250, and light source 1110. The SLM 1140 would be configured to reflect, deflect, and / or direct light from the light source 1110 either to the in-coupling optical element 1264 (and other in-coupling optical elements 1260, 1262) or to a location lateral to the light dump 1250, depending on the state of a particular pixel.

[0199] In some designs, the light dump 1250 may include an energy recovery system. The light dump 1250 may include, for example, an optical energy conversion element configured to convert optical energy into electrical energy. The optical energy conversion element may include, for example, a solar cell. The optical energy conversion element may include, for example, a photovoltaic detector that produces an electrical output when light is incident thereon. The optical energy conversion element may be electrically connected to an electrical component, for example, conductive wires for directing the electrical output to provide power to the system 1200B and / or potentially charge one or more batteries.

[0200] Laterally displaced non-color-selective or broadband or multi-color in-coupling optical elements may be used in certain designs. Figure 13A is a perspective view of a system 1300 including a stack 1305, for example, including waveguides. The stack 1305 may be substantially similar to the stack 1205 referenced in Figure 12A. Each waveguide in the stack 1305 may include an in-coupling optical element 1360, 1362, 1364; however, in contrast to the design shown in Figure 12A, the in-coupling optical elements 1360, 1362, 1364 are laterally displaced relative to one another. 13A, 13B, and 13C, light sources 1110, 1112, 1114 may also be laterally displaced relative to one another and positioned to direct light to respective in-coupling optical elements 1360, 1362, 1364 by passing the light through optics 1130, reflecting the light off SLM 1140, and passing the reflected light back through optics 1130. System 1300 in FIG. 13B is depicted as if light source 1114 is located behind light source 1110 and is therefore not shown in FIG. 13B. Light sources 1110, 1112, 1114 may correspond to in-coupling optical elements 1360, 1362, 1364, respectively. In one design, for example, the light sources 1110, 1112, 1114 and corresponding in-coupling optical elements 1360, 1362, 1364 are positioned approximately equidistant from (symmetrically about) the center of the optical system 1130 along a common (optical) axis. The common (optical) axis may intersect the center of the optical system 1130. In one design, for example, the light sources 1110, 1112, 1114 and corresponding in-coupling optical elements 1360, 1362, 1364 are not positioned equidistant from (symmetrically about) the center of the optical system 1130 along the common (optical) axis.

[0201] The in-coupling optical elements 1360, 1362, 1364 may be configured to couple multiple colors of light into their respective waveguides. Thus, these in-coupling optical elements 1360, 1362, 1364 may be referred to herein as broadband, multicolor, or non-color-selective in-coupling optical elements 1360, 1362, 1364. For example, in some cases, each one of these in-coupling optical elements 1360, 1362, 1364 is configured to in-couple red, green, and blue light into the associated waveguide in which it is included, and such colored light is guided within the waveguide by TIR. Such broadband in-coupling optical elements 1360, 1362, 1364 may operate across a wide range of wavelengths, e.g., within the visible range, or may select a wavelength or wavelength range width, e.g., across the visible range. Thus, such broadband or multicolor or non-color-selective in-coupling optical elements 1360, 1362, 1364 may be configured to redirect light of various different colors (e.g., red, green, and blue) into the waveguide to be guided therein by TIR. Although red, green, and blue (RGB) are referred to herein in connection with light sources, in-coupling optical elements, waveguides, etc., other colors or color systems may also or alternatively be used, such as, but not limited to, magenta, cyan, and yellow (CMY).

[0202] As shown in FIG. 13A, the light sources 1110, 1112, and 1114 are shown above the top waveguide and are displaced relative to one another (e.g., in the x and z directions). Similarly, three internal coupling optical elements 1360, 1362, and 1364 are shown on three individual waveguides and are displaced relative to one another (e.g., in the x, y, and z directions). FIG. 13B is a side view of the system 1300 shown in FIG. 13A, showing the internal coupling optical elements 1360, 1362, and 1364 spatially displaced laterally relative to one another (e.g., in the x and z directions) and some of the light sources 1110, 1112, and 1114 laterally displaced relative to one another (e.g., in the x and z directions). FIG. 13B also shows the optical system 1130 and the SLM 1140.

[0203] 13C is a top view of the augmented reality display system illustrated in FIGS. 13A and 13B , showing the incoupling optical elements 1360, 1362, 1364 and associated light sources 1110, 1112, 1114. In this design, the incoupling optical elements 1360, 1362, 1364 and associated light sources 1110, 1112, 1114 are arranged in a ring-like pattern about a center point of a common (optical) axis. As shown, the light sources 1110, 1112, 1114 and corresponding incoupling optical elements 1360, 1362, 1364 are approximately equidistantly spaced about the center point of the common (optical) axis, however, this need not be the case. In some designs, this center point may correspond to the center of the optical system 1130 along the common (optical) axis and / or a location along the optical axis of the optical system 1130 that intersects with the center of the optical system 1130. Also as a result, the non-color-selective in-coupling optical elements 1360, 1362, 1364 and the light sources 1110, 1112, 1114 are laterally displaced relative to one another (eg, in the x and z directions).

[0204] Other arrangements of lateral mounting are also possible. Figures 14A-14C illustrate an alternative configuration of system 1400 including a waveguide-containing stack 1405, in which the in-coupling optical elements 1360, 1362, 1364 and light sources 1110, 1112, 1114 are laterally displaced relative to one another. Figure 14A is a side view, while Figure 14B is a top view, of system 1400 illustrated in Figure 14A showing the laterally displaced in-coupling optical elements 1360, 1362, 1364 and light sources 1110, 1112, 1114. Figure 14C is an orthogonal side view of system 1400 illustrated in Figures 14A and 14B.

[0205] The side views of Figures 14A and 14C show how the internal coupling optical elements 1360, 1362, 1364 are arranged on separate waveguides within the stack 1405 so that light can be coupled into the corresponding waveguides by the respective laterally displaced internal coupling optical elements 1360, 1362, 1364. The internal coupling optical elements 1360, 1362, 1364 are shown in Figures 14A and 14C as being arranged within the upper major surfaces of the waveguides. However, the internal coupling optical elements 1360, 1362, 1364 could alternatively be arranged on the lower major surfaces of the respective waveguides or within the volume of the waveguides. Various configurations are also possible.

[0206] 14B , the in-coupling optical elements 1360, 1362, 1364 are arranged in rows that are laterally displaced relative to one another along the z-direction, rather than along the x-direction. Similarly, the light sources 1110, 1112, 1114 are also arranged in rows that are laterally displaced relative to one another along the z-direction, rather than along the x-direction. The in-coupling optical elements 1360, 1362, 1364 are laterally displaced in the x-direction relative to the light sources 1110, 1112, 1114.

[0207] Still other configurations are possible. Figure 15 is a top view of a system 1500 showing an alternative configuration of the light sources 1110, 1112, 1114 and the in-coupling optical elements 1360, 1362, 1364. As opposed to having all of the light sources 1110, 1112, 1114 generally on one side (e.g., of a ring-shaped pattern) and all of the in-coupling optical elements 1360, 1362, 1364 generally on one side (i.e., the opposite side), as in Figure 13C, the light sources 1110, 1112, 1114 and the in-coupling optical elements 1360, 1362, 1364 are interspersed or alternating around the circumference of the ring-shaped pattern.

[0208] However, in some implementations, the incoupling optical elements 1360, 1362, 1364 and associated one or more light sources 1110, 1112, 1114 are also arranged in a ring-like pattern centered on a central point. As a result, the light sources 1110, 1112, 1114 and corresponding incoupling optical elements 1360, 1362, 1364 may generally be arranged approximately equidistant from the center. In some designs, this center may correspond to the center of the optical system 1130 and / or a location along the optical axis of the optical system along a common central axis that intersects the center of the optical system 1130. Thus, light from the first light source 1110 may be coupled through the optical system 1130 into the incoupling optical element 1360 transverse to the center or central axis or optical axis of the optical system 1130 (as seen from the top view of FIG. 15 ). Similarly, light from the second light source 1112 may be coupled through the optical system 1130 into the in-coupling optical element 1362 transverse to the center or central axis or optical axis of the optical system 1130. Similarly, light from the third light source 1114 may be coupled through the optical system 1130 into the in-coupling optical element 1364 transverse to the center or central axis or optical axis of the optical system 1130. Also, as a result, the non-color-selective in-coupling optical elements 1360, 1362, 1364 and the light sources 1110, 1112, 1114 are laterally displaced relative to one another (e.g., in the x and z directions). The optical system 1130 may be designed so that the focal point is closer to the stack 1405, such that the sub-pupil locations and the in-coupling optical elements 1360, 1362, 1364 are closer in the y-direction. In this configuration, the incoupling optical elements 1360, 1362, 1364 may be smaller because they are closer to the focal point of the optical system 1130. The light source 1110 may be on the user side of the stack 1405 (e.g., similar to FIGS. 17 and 18), thus reducing the distance or optical path between the light source 1110 and the optical system 1130.

[0209] In various implementations such as those shown in FIGS. 12A-15 above, stacks (e.g., stacks 1205, 1305, 1405) including multiple waveguides (e.g., stack 1205 including waveguides 1120, 1122, 1124, stack 1305 including waveguides (not labeled), and stack 1405 including waveguides (not labeled)) may be included to handle different colors (e.g., red, green, and blue). Different waveguides may be for different colors. Similarly, multiple stacks can be included to provide different optical properties to light coupled out from individual stacks. For example, waveguides 1120, 1122, 1124 of stack 1205 of FIGS. 12A-12B may be configured to output light having optical properties (e.g., refractive power to provide a particular wavefront shape) possibly associated with the apparent depth from which the light appears to emanate. For example, wavefronts with different amounts of divergence, convergence, or collimation may appear as if projected from different distances from the eye 210. Thus, multiple stacks may be included, with different stacks configured so that light outcoupled by the outcoupling optical element has different amounts of convergence, divergence, or collimation and therefore appears to originate from different depths. In some designs, the different stacks may include different lenses, such as diffractive lenses or other diffractive optical elements, to provide different amounts of refractive power to the different stacks. As a result, the different stacks will produce different amounts of convergence, divergence, or collimation, and therefore, light from the different stacks will appear as if associated with different depth planes or objects at different distances from the eye 210.

[0210] FIG. 16A is a side view of a system 1600 including stacks 1605, 1610, and 1620. As illustrated in FIG. 16A, the system 1600 includes three stacks 1605, 1610, and 1620; however, this need not be the case. The system may be conceived with fewer or more stacks. The stacks 1605, 1610, and 1620 each include one or more (e.g., three) waveguides. FIG. 16A also shows groups 1630, 1640, and 1650 of internally coupled optical elements. The first group 1630 is associated with the first stack 1605, the second group 1640 is associated with the second stack 1610, and the third group 1650 is associated with the third stack 1620. The groups 1630, 1640, and 1650 are laterally displaced relative to one another. Each of the groups 1630, 1640, and 1650 includes color-selective in-coupling optical elements configured to in-couple different individual colors, substantially similar to the in-coupling optical elements 1260, 1262, and 1264 of FIG. 12A . As illustrated in FIG. 16A , the in-coupling optical elements within each of the groups 1630, 1640, and 1650 are not laterally displaced relative to one another; however, this need not be the case. The system may be devised in which the in-coupling optical elements within a group are laterally displaced relative to one another. The system 1600 may be configured such that the light out-coupled from each of the stacks 1605, 1610, and 1620 has different amounts of refractive power. For example, the waveguides within the stacks may have out-coupling optical elements or diffractive lenses with a given refractive power. The refractive powers for the different stacks 1605, 1610, and 1615 may differ such that light from one stack may appear to occur at a different depth than light from another stack. The refractive power of one stack, for example, may cause the light from that stack to be collimated, while the refractive power of another stack may cause the light therefrom to be divergent. Divergent light may appear to originate from objects at a close distance from the eye 210, while collimated light may appear to originate from objects at a far distance.Thus, light coupled out of the first stack 1605, the second stack 1610, and the third stack 1620 may have different amounts of convergence, divergence, and / or collimation and thus appear to originate from different depths. In some implementations, light coupled out of one of the stacks may be collimated, while light coupled out by a different stack may diverge. Light coupled out of one of the other stacks may also diverge, but by a different amount.

[0211] As shown in FIG. 16A , light source 1110 may be positioned relative to optics 1130 and SLM 1140 to direct light into group 1630 of in-coupling optical elements, light source 1112 may be positioned relative to optics 1130 and SLM 1140 to direct light into group 1640 of in-coupling optical elements, and light source 1114 may be positioned relative to optics 1130 and SLM 1140 to direct light into group 1650 of in-coupling optical elements. Light sources 1110, 1112, and 1114 may be configured to emit light of different colors at different times. Similarly, light of different individual colors may be coupled into different waveguides within the stack as a result of the color-selective in-coupling optical elements in the manner described above. For example, if blue light is emitted from second light source 1112, optics 1130 and SLM 1140 will direct the blue light to second group 1640 of in-coupling optical elements. The light may pass through a first red in-coupling optical element and a second green in-coupling optical element in the second group 1640 and be redirected by a third blue in-coupling optical element in the second group 1640 into a third waveguide in the second stack 1610. The waveguide in the second stack 1610 may include an out-coupling optical element or other optical element having an optical power (e.g., a diffractive lens) to provide a beam to the eye 210 associated with a particular depth plane or object distance associated with the second stack 1610.

[0212] Figure 16B is a top view of the system 1600 in Figure 16A. Different groups 1630, 1640, 1650 of incoupling optical elements are shown as being laterally displaced relative to one another (e.g., in the x-direction). Similarly, light sources 1110, 1112, 1114 are shown as being laterally displaced relative to one another (e.g., in the x-direction).

[0213] Various different variations on the above-described system are also possible. For example, the location of the light source 1110 relative to the waveguide and optics 1130 may be different. FIG. 17, for example, is a side view of a system 1700 having the light source 1110 in a different location relative to the waveguide 1720 and optics 1130 than shown in FIGS. 11-16B . In addition, FIG. 17 shows a design with the waveguide 1720 split into a first portion 1720 a and a second portion 1720 b. The waveguide 1720 may further include a reflector 1730 configured to couple light guided within the first portion 1720 a proximal to the light source 1110 out of the first portion 1720 a and into the optics 1130 toward the SLM 1140. Additionally or alternatively, system 1700 may include a diffractive outcoupling optical element for outcoupling light in first portion 1720a of waveguide 1720 into optics 1130 toward SLM 1140. This reflector 1730 may be opaque and include an isolator to reduce crosstalk between first portion 1720a and second portion 1720b. Waveguide 1720 has a first side 1721 and a second side 1723 opposite first side 1721, and optics 1130 and SLM 1140 are disposed on first side 1721 such that light from SLM 1140 is directed onto first side 1721. In this example, the light source 1110 is disposed on a first side 1721 of the waveguide 1720 such that light from the light source 1110 is incident on the first side 1721 prior to passing through the optical system 1130 to the SLM 1140. The system 1700 may further include an internal coupling optical element 1710 disposed on or within the first portion 1720a. The internal coupling optical element 1710 may be configured to receive light from the light source 1110 and couple the light into the first portion 1720a. The internal coupling optical element 1710 may include a diffractive optical element or a reflector configured to redirect light incident thereon into the first portion 1720a at an angle such that it is guided therein by TIR.

[0214] The reflector 1730 may be configured to direct light guided within the first portion 1720a out of the first portion 1720a toward the optical system 1130 and the SLM 1140. (As discussed above, in some implementations, a diffractive optical element may additionally or alternatively be used to direct light within the first portion 1720a out of the first portion 1720a toward the optical system 1130 and the SLM 1140.) Thus, the reflector 1730 may be a mirror, a reflective grating, or one or more coatings that reflect light from the waveguide 1720 toward the SLM 1140. The reflector 1730 causes light emitted from the first portion 1720a to pass through the optical system 1130, impinge on the SLM 1140, and then pass again through the optical system 1130 and impinge on the second portion 1720b. As described above, light reflected from SLM 1140 that is transmitted through optical system 1130 may be incident on in-coupling optical element 1160 and redirect light that is guided within second portion 1720b. Light that is guided within second portion 1720b may be out-coupled therefrom by out-coupling optical element 1180 (not shown) and directed toward eye 210.

[0215] As discussed above, the reflector 1730 may be an isolator that reduces crosstalk between the first portion 1720 a and the second portion 1720 b. The reflector 1730 may include an opaque and / or reflective surface. The reflector 1730 may be disposed within the waveguide 1720 and, in some cases, may define the sides of the first portion 1720 a and the second portion 1720 b.

[0216] Instead of having first and second portions 1720a, 1720b of waveguide 1720, separate waveguides may be used. FIG. 18 is a side view of system 1800 including a first waveguide 1822 that receives light from light source 1110 and directs the light guided therein to optical system 1130 and toward SLM 1140. System 1800 additionally includes a second waveguide 1820 that receives light from SLM 1140 after the light has passed through optical system 1130 again. First waveguide 1822 includes in-coupling and out-coupling optical elements 1730a, 1730b, respectively. These in-coupling and out-coupling optical elements 1730a, 1730b may include reflective surfaces oriented to in-coupling and out-coupling light into and out of waveguide 1822. The inward coupling optical element 1730a may, for example, be positioned to receive light from the light source 1110 and may include a reflective surface oriented (e.g., tilted) to direct the light into the waveguide 1822 at an angle such that it is guided therein by TIR. The outward coupling optical element 1730b may, for example, be positioned to direct the light guided in the waveguide 1822 at an angle such that it is exited from the waveguide 1822. The outward coupling optical element 1730b may be positioned such that light redirected out of the waveguide 1822 is directed into the optical system 1130, reflected from the SLM 1140, passes again through the optical system 1130, and is incident on the inward coupling optical element 1730c of the second waveguide 1820.

[0217] The internal coupling optical element 1730c in the second waveguide 1820 may include a reflective surface that may be positioned and oriented (e.g., tilted) to receive light incident thereon from the SLM 1140 and redirect it to be guided within the second waveguide 1820 by TIR. FIG. 18 illustrates the optical system 1130 and the light source 1110 disposed on the same side of the waveguides 1820, 1822. The system 1800 may further include an isolator that reduces crosstalk between the waveguide 1822 and the waveguide 1820. The isolator may include an opaque and / or reflective surface. The isolator may be disposed within or on at least one of the waveguides 1820, 1822.

[0218] Various designs, such as those discussed above, can include additional features or components. FIG. 19, for example, shows a side view of a system 1900 including variable-focus optical elements (or adaptive optical elements) 1910, 1920. The variable-focus optical elements 1910, 1920 may include optical elements configured to be altered to provide variable optical power. The variable-focus optical elements 1910, 1920 may include multiple states, such as a first state and a second state, where in the first state, the variable-focus optical elements 1910, 1920 have a different optical power than when in the second state. For example, the variable-focus optical elements 1910, 1920 may have a negative optical power in the first state and zero optical power in the second state. In some implementations, the variable-focus optical elements 1910, 1920 have a positive optical power in the first state and zero optical power in the second state. In some implementations, the variable-focus optical element 1910, 1920 has a first negative or positive optical power in a first state and a second, different negative or positive optical power in a second state. Some adaptive or variable-focus optical elements 1910, 1920 may have more than two states, potentially providing a continuous distribution of optical powers.

[0219] The variable-focus optical elements 1910, 1920 may comprise lenses (e.g., variable lenses) and may be transmissive. Transmissive or transparent adaptive or variable-focus optical elements 1910, 1920 are shown in FIG. 7. The variable-focus optical elements 1910, 1920 may comprise liquid lenses (e.g., movable membranes and / or electrowetting). The variable-focus lenses may also include liquid crystal lenses, such as switchable liquid crystal lenses, such as switchable liquid crystal polarizing lenses, which may comprise, for example, diffractive lenses. Alverez lenses may also be used. Other types of variable-focus optical elements 1910, 1920 may also potentially be employed. Examples of variable-focus optical elements can be found in U.S. Patent Application No. 62 / 518,539, filed June 12, 2017, and entitled "AUGMENTED REALITY DISPLY HAVING MULTI-ELEMENT ADAPTIVE LENS FOR CHANGING DEPTH PLANES," which is incorporated herein by reference in its entirety. The variable-focus optical elements 1910, 1920 may have an electrical input that receives an electrical signal that controls the amount of optical power exhibited 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, and the like), the variable-focus elements 1910, 1920 may include fixed lenses (e.g., diffractive lenses, refractive lenses, and the like) to generate desired depth planes within the light field.

[0220] A first variable-focus optical element 1910 may be disposed between the stack 1905 and the eye 210. The stack 1905 may include different waveguides for different colors, as discussed above. The first variable-focus optical element 1910 may be configured to introduce different amounts of refractive power, negative and / or positive refractive power. The variable refractive power may be used to vary the divergence and / or collimation of light coupled out of the stack 1905 and to vary the depth at which virtual objects projected by the system 1900 into the eye 210 appear to be located. Thus, a four-dimensional (4D) light field may be created.

[0221] The second variable-focus optical element 1920 is on the opposite side of the stack 1905 from the first variable-focus optical element 1920. The second variable-focus optical element 1920 can therefore compensate for the effect of the first optical element 1910 on light received from the world 510 in front of the system 1900 and the eye 210. Thus, the world view may effectively be unaltered or altered, as desired.

[0222] 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 are discussed above. The eye 210 may have, for example, myopia, hyperopia, and / or astigmatism. The lens 1930 may have a prescription (e.g., refractive power) to reduce refractive errors of the eye 210. The lens 1930 may be spherical and / or cylindrical and may be positive or negative. The lens 1930 may be positioned between the stack 1905 and the eye 210 such that light from both the world 510 and the stack 1905 receives the correction provided by the lens 1930. In some implementations, the lens 1930 may be positioned between the eye 210 and the first variable focus optical element 1910. Other locations for the lens 1930 are also possible. In some embodiments, the prescription lens may be variable, allowing multiple user prescriptions to be implemented.

[0223] In some designs, the system 1900 may include an adjustable dimmer 1940. In some implementations, the adjustable dimmer 1940 may be located on the opposite side (e.g., the world side) of the stack of waveguides 1900 from the eye 210. Thus, the adjustable dimmer 1940 may be located between the stack of waveguides 1900 and the world 510. The adjustable dimmer 1940 may include an optical element that provides variable attenuation of light transmitted therethrough. The adjustable dimmer 1940 may include an electrical input for controlling the level of attenuation. In some cases, the adjustable dimmer 1940 is configured to increase the attenuation when the eye 210 is exposed to bright light, such as when the user goes outdoors. Thus, the system 1900 may include a light sensor for sensing the brightness of ambient light and control electronics for driving the adjustable dimmer 1940 and varying the attenuation based on the light level sensed by the light sensor.

[0224] Different types of adjustable dimmers 1940 may be employed. Such adjustable dimmers 1940 may include variable liquid crystal switches with polarizers, electrochromic materials, photochromic materials, and the like. The adjustable dimmer 1940 may be configured to adjust the amount of light incident and / or transmitted from the world 510 through the stack 1905. The adjustable dimmer 1940, in some cases, can be used to reduce the amount of ambient light passing through the waveguide stack 1900 to the eye 210, which may otherwise provide glare and reduce the user's ability to perceive virtual objects / images projected from the stack 1905 into the eye 210. Such adjustable dimmers 1940 may reduce incoming bright ambient light so as not to wash out the image projected into the eye 210. The contrast of the virtual objects / images presented to the eye 210 may therefore be increased using the adjustable dimmer 1940. In contrast, when ambient light is low, the adjustable dimmer 1940 may be adjusted to reduce attenuation so that objects in the world 510 in front of the user can be more easily seen by the eye 210. The darkening or attenuation may exist across the system or may be localized to one or more portions of the system. For example, multiple localized portions may be darkened or configured to attenuate light from the world 510 in front of the user 210. These localized portions may be separated from each other by portions without such increased darkening or attenuation. In some cases, only one portion may be darkened or generated to provide increased attenuation relative to other portions of the eyepiece. Other components may also be added in different designs. The arrangement of components may also vary. Similarly, one or more components may be excluded from the system.

[0225] An example of another configuration is shown in Figure 20A. Figure 20A shows a side view of a system 2000 including laterally displaced in-coupling optical elements 1360, 1362, 1364 on different waveguides and a color filter array 2030 including laterally displaced color filters 2040, 2042, 2044 aligned with the respective in-coupling optical elements 1360, 1362, 1364. The color filter array 2030 may be disposed on the side of the stack 2005 proximate the eye 210 and the optics 1130. The color filter array 2030 may be between the stack 2005 and the optics 1130. The color filter array 2030 may be disposed in or on a cover glass 2050 located between the stack 2005 and the optics 1130. The color filter array 2030 may include one or more different color filters 2040, 2042, 2044, such as a red color filter, a green color filter, and a blue color filter, disposed laterally relative to one another. The system 2000 includes light sources 1110, 1112, 1114, which are laterally displaced relative to one another. These light sources 1110, 1112, 1114 may include light sources of different colors, such as red, green, and blue light sources. The color filters 2040, 2042, 2044 may be transmissive or transparent filters. In some implementations, the color filters 2040, 2042, 2044 include light-absorbing 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 masks, such as opaque masks, which may reduce the propagation of stray light. The filters in the color filter array 2030 may be used to reduce or eliminate undesirable reflections within the system, such as from the waveguides and / or the internal coupling optical elements 1360, 1362, 1364, so that they do not re-enter the waveguides used for the different colors through the internal coupling optical elements 1360, 1362, 1364 for the different colors.Examples of color filter arrays can be found in U.S. Patent Application No. 15 / 683,412, filed August 22, 2017, entitled "PROJECTOR ARCHITECTURE INCORPORATING ARTIFACT MITIGATION," which is incorporated herein by reference in its entirety, and U.S. Patent Application No. 62 / 592,607, filed November 30, 2017, entitled "PROJECTOR ARCHITECTURE INCORPORATING ARTIFACT MITIGATION," which is incorporated herein by reference in its entirety. The mask may be a black mask or may include a light-absorbing material to reduce stray light propagation and reflection. The light sources 1110, 1112, and 1114 may be positioned relative to the optical system 1130 and the SLM 1140 to internally couple light into corresponding color filters 2040, 2042, and 2044 in the color filter array 2030. For example, the color filter array 2030 may include first, second, and third (e.g., red, green, and blue) color filters 2040, 2042, 2044 positioned to receive light from the first, second, and third light sources 1110, 1112, 1114, respectively. The first, second, and third (e.g., red, green, and blue) color filters 2040, 2042, 2044 may be aligned (e.g., in the x and z directions) with the respective in-coupling optical elements 1360, 1362, 1364. Thus, light from the first light source 1110 will be directed through the first color filter 2040 to the first in-coupling optical element 1360, light from the second light source 1112 will be directed through the second color filter 2042 to the second in-coupling optical element 1362, and light from the third light source 1114 will be directed through the third color filter 2044 to the third in-coupling optical element 1364. In some implementations, the in-coupling optical elements 1360, 1362, 1364 may be color-specific. For example, the first and second in-coupling optical elements 1360, 1362 may be configured to couple light of distinct first and second colors into the first and second waveguides, respectively.Similarly, the first, second, and third internal coupling optical elements 1360, 1362, 1364 may be configured to couple light of the respective first, second, and third colors into the first, second, and third waveguides, respectively. The first internal coupling optical element 1360 may be configured to couple light of the first color rather than the second color (or third color) into the first waveguide. The second internal coupling optical element 1362 may be configured to couple light of the second color rather than the first color (or third color) into the second waveguide. The third internal coupling optical element 1364 may be configured to couple light of the third color rather than the first color or the second color into the second waveguide. In other configurations, the internal coupling optical elements 1360, 1362, 1364 may be broadband. For example, the first internal coupling optical element 1360 may be configured to couple light of the first, second, and third colors into the first waveguide. The second in-coupling optical element 1362 may be configured to couple light of the first, second, and third colors into the second waveguide. The third in-coupling optical element 1364 may be configured to couple light of the first, second, and third colors into the third waveguide. However, the color filters 2040, 2042, 2044 may be color-specific to selectively transmit light of particular colors. For example, the first color filter 2040 may transmit the first color more than the second color (and the third color). The second color filter 2042 may transmit the second color more than the first color (and the third color). The third color filter 2044 may transmit the third color more than the first and second colors. Similarly, the first, second, and third color filters 2040, 2042, 2044 may be color filters that selectively transmit the first, second, and third colors, respectively. Thus, the first, second, and third color filters 2040, 2042, 2044 may be bandpass filters that selectively pass the first, second, and third colors, respectively. In some implementations, the first, second, and third light sources 1110, 1112, 1114 may selectively emit the first, second, and third colors, respectively. For example, the first light source 1110 may emit the first color over the second color (and third color).The second light source 2042 may emit a second color more than the first color (and a third color). The third light source 2044 may transmit a third color more than the first and second colors. The color filters 2040, 2042, 2044 may reduce the amount of stray light inadvertently directed toward a particular internal coupling optical element. In other implementations, one or more of the light sources 1110, 1112, 1114 are broadband light sources. For example, the first light source 1110 may emit a first and second (and possibly a third) color. The second light source 1112 may also emit a first and second (and possibly a third) color. The third light source 1114 may also emit a first and second (and possibly a third) color. Although three filters are shown in FIGS. 20A-20G, more or fewer filters may be included. For example, in some implementations, two filters (rather than three) may be used. Thus, two colors corresponding to the two color filters may be selectively transmitted therein by the filters. In some such implementations, two corresponding in-coupling optical elements may be used and matched with the two filters. In some implementations, the two in-coupling optical elements each selectively couple two colors into two separate waveguides. In some implementations, two light sources may be used instead of three. Other variations and numbers of components may also be used. Also, the color filters 2040, 2042, 2044 may or may not be integrated together in a single array.

[0226] As discussed above, the components and their locations and arrangements can vary. For example, while FIG. 20A shows the analyzer 1150 positioned between the optical system 1130 and the stack 1905, the analyzer 1150 may be located in a different position. FIG. 20B shows the analyzer 1150 positioned between the optical system 1130 and the SLM 1140. In some designs, the analyzer (e.g., polarizer) 1150 may be directly attached to the SLM 1140. For example, the analyzer 1150 may be glued or mechanically coupled to the SLM 1140. For example, the analyzer 1150 may be glued or fixed to the SLM 1140 (e.g., an SLM window) using an adhesive. Thus, while FIG. 20B shows a gap between the analyzer 1150 and the SLM 1140, in some designs, no gap exists between the analyzer 1150 and the SLM 1140. The analyzer 1150 may be mechanically affixed to the SLM 1140 (e.g., using a mechanical fastener), which may or may not include a gap between the analyzer 1150 and the SLM 1140. Birefringence from the optical system 1130 may be eliminated by positioning a polarizer directly on the SLM 1140, as described above. In some implementations, the analyzer 1150, disposed between the optical system 1130 and the internal coupling optical elements 1360, 1362, 1364, may also be included to eliminate polarization of light outward from the optical system 1130 (e.g., as shown by the dashed lines in FIG. 20B ). Additionally, a retarder (not shown), such as a quarter-wave plate, may be included proximate the SLM 1140, e.g., between the optical system 1130 and the SLM 1140. As used herein, a quarter-wave plate may refer to a quarter-wave retarder, regardless of whether the quarter-wave retarder comprises a plate, film, or other structure for providing a quarter-wave phase difference. In FIG. 20B, for example, a retarder (e.g., a quarter-wave plate) may be disposed between the analyzer 1150 and the SLM 1140. The retarder (e.g., a quarter-wave plate) may be used for distorted light beam management. For example, the retarder (e.g., a quarter-wave plate) may compensate for variations caused by differences in wavelength and angle of incidence on the SLM 1140, for example.As discussed above, a compensator may be included to provide more consistent polarization rotation (e.g., 90°) of the SLM 1140 for different angles of incidence and different wavelengths. The compensator may be used to increase the contrast of the display by providing more consistent orthogonal rotation. The compensator may be attached or affixed to the SLM 1140 as described above. For example, glue, cement, or other adhesive may be used. The compensator may also be attached to the SLM 1140 using mechanical fasteners. A gap or no gap may be included between the compensator and the SLM 1140. Other light conditioning optics may also be included, in addition or alternatively, and may be affixed to the SLM 1140 as described above with respect to the analyzer 1150 and / or the compensator.

[0227] In some embodiments, a large angular width (e.g., about 70 degrees) may be used. Angular width may refer, for example, to the angle of light entering the optical system 1130 from the light sources 1110, 1112, 1114 and / or the angle of light exiting the optical system 1130 into the incoupling optical elements 1360, 1362, 1364. In these embodiments, a thinner SLM 1140 may be used. For example, if the SLM 1140 is a liquid crystal (LC) SLM (e.g., a liquid crystal on silicon (LCOS) SLM), the LC layer may be made thinner to accommodate the large angular width.

[0228] The double-pass retardation through the polarizer and analyzer 1150 may need to be half-wave. The polarizer may be between the optical system 1130 and the analyzer 1150. The double-pass retardation 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, traveling in and out of the LCOS SLM 1140 at large angles creates a longer path length for light than traveling in and out of the LCOS SLM 1140 at small angles. The path length is proportional to the thickness of the LCOS SLM 1140. In one embodiment, the LCOS SLM may have a first refractive index and a first thickness. For small angles, the double-pass retardation of an LCOS SLM having a first refractive index and a first thickness may be half-wave. For large angles, the double-pass retardation of an LCOS SLM having a first refractive index and a first thickness may not be half-wave (e.g., may be greater than half-wave). The thickness of the LCOS SLM may vary from a first thickness to a second thickness, and the second thickness may be less than the first thickness. For small angles, the double-pass retardation of an LCOS SLM having a first refractive index and a second thickness may not be half-wave (e.g., may be less than half-wave). For large angles, the double-pass retardation of an LCOS SLM having a first refractive index and a second thickness may be half-wave.

[0229] Also, while Figures 20A and 20B illustrate the use of a polarization-based SLM 1140, other types of SLMs may also be utilized. Figure 20C illustrates the use of a deflection-based SLM 1140, such as a movable micromirror-based SLM. As discussed above, such an SLM 1140 may include digital light processing (DLP™) and digital micromirror device (DMD) technology. As discussed above, the deflection-based SLM 1140 can couple light from one of the light sources 1110, 1112, and 1114 into a respective internal coupling optical element 1360, 1362, and 1364 depending on the state of the pixels of the SLM 1140. In one state, light from the light sources 1110, 1112, and 1114 will be directed to the respective internal coupling optical elements 1360, 1362, and 1364, as illustrated in Figure 20D. In another state, light from the light sources 1110, 1112, 1114 will be directed away from the incoupling optical elements 1360, 1362, 1364, as shown in FIG. 20E. In some implementations, on the other hand, in the off state, a black light-absorbing mask between the color filters 2040, 2042, 2044 in the color filter array 2030 can act as a light dump. As explained above, the color filters 2040, 2042, 2044 may be surrounded and / or separated by a mask, such as a light-absorbing mask (e.g., a black mask). The mask may include a light-absorbing material such that incident light is absorbed more than that reflected therefrom. The mask may also be opaque.

[0230] Other variations are possible. While the light sources are shown as emitters 1110, 1112, 1114 (e.g., LEDs, laser diodes) coupled to coupling optics 1105, such as a non-imaging optical coupling element (e.g., a compound parabolic concentrator (CPC) or cone), other configurations are possible. For example, the coupling optics 1105 (e.g., a CPC) may be tilted relative to the waveguide stack. In some cases, the projector (i.e., the optics 1130 and SLM 1140) may be tilted relative to the eyepiece (e.g., the waveguide stack). In some implementations, the lens optics 1130 is tilted relative to the SLM 1140 to reduce distortions such as keytone distortion. A Schheimplug configuration may be employed to reduce such distortions. Components may be tilted (e.g., the optics 1130 and / or the spatial light modulator 1140) as needed, for example, to fit more conformally around the head and / or face. As described above, the light emitter and / or the coupling optics 1105 may be tilted. In some configurations, the assembly, including the waveguide, may be tilted with the side closer to the eye 210 (e.g., the temple side) closer to the eye 210, increasing the perceived field of view of the binocular system as a whole (at the expense of binocular overlap).

[0231] As discussed above, the components and their locations and arrangements may vary. For example, FIG. 20F is a side view of system 2000F including a cover glass 2050 disposed between stack 2005 and optics 1130. In some designs, light sources 1110, 1112, 1114 may be disposed on the world side of cover glass 2050 and configured to propagate light through cover glass 2050 to optics 1130 and SLM 1140. As shown, cover glass 2050 may extend laterally (e.g., parallel to the x-axis) beyond stack 2005 so that light emitted by light sources 1110, 1112, 1114 enters optics 1130 without passing through a waveguide within stack 2005. While system 2000F depicts a deflection-based SLM 1140, a similar configuration of light sources may also be used with a non-deflection-based SLM, or with or within any other configuration or feature disclosed herein.

[0232] FIG. 20G is a side view of system 2000G, including a cover glass 2060 disposed on the world side of stack 2005 (i.e., opposite the side of stack 2005 proximal to optics 1130). In some designs, light sources 1110, 1112, 1114 may be disposed on the world side of cover glass 2050 and configured to propagate light through cover glass 2050 to optics 1130 and SLM 1140. As shown, cover glass 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 optics 1130 without passing through a waveguide within stack 2005. While 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 or within any other configuration or feature disclosed herein.

[0233] Additionally, as discussed above, configurations that promote light recycling may be employed. FIG. 21 is a partial side view of a system 2100 equipped with a configuration that provides light recycling of light from, for example, a light source 1110. The light source 1110 may be positioned relative to a polarizer 1115 configured to recycle light having an undesired polarization. The polarizer 1115 may include, for example, a wire-grid polarizer that transmits light of a first polarization and retroreflects light of a second, opposite polarization. Thus, light 2110 may be emitted from the light source 1110 and impinge on the polarizer 1115. The polarizer 1115 may transmit light of a first polarization for use by a projector (not shown). For example, an SLM may operate appropriately using light of this first polarization. Light of a second polarization 2120 may be reflected back toward the light source 1110 and recycled. The polarization of light 2120 may be altered with respect to the rotated polarization after reflection from portions (e.g., sidewalls) of a coupling optic (not shown), such as a non-imaging optic like a compound parabolic concentrator (CPC) at various angles. A portion of the light may result with a preferred polarization (e.g., polarization orientation) that may be passed through polarizer 1115. Multiple reflections may change the polarization of the light, causing it to exit with the desired polarization. This recycled light 2130 is then emitted back toward polarizer 1115. Such a configuration may improve efficiency, e.g., energy efficiency, because more of the desired polarization is produced. Additionally or alternatively, a retarder may be used to change the reflected polarization state and recover light.

[0234] FIG. 22 shows another configuration including 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 range of angles. The light collection optics 2210, 2212, 2214 may be used to collect more of that light. The light sources 1110, 1112, 1114 may emit light asymmetrically. For example, light may be emitted over a wider range of angles in one direction (e.g., the x or z direction) rather than in an 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 refractive powers in different, possibly orthogonal directions. The light collection optics 2210, 2212, 2214 may include lenses, such as anamorphic lenses. The light collection optics 2210, 2212, 2214 may also possibly include non-imaging optics. Apertures 2220, 2222, 2224 may also be included. A diffuser 2230 may also be included proximate the apertures 2220, 2222, 2224, for example, when the light sources 1110, 1112, 1114 are lasers, such as laser diodes. Using a diffuser proximate the apertures 2220, 2222, 2224 can make the apertures appear to be at the location of laterally displaced light sources. The apertures 2220, 2222, 2224 may be matched with in-coupling optical elements on the waveguide or with the waveguide via optics and SLM, as discussed above. For example, each aperture 2220, 2222, 2224 may be matched with a separate in-coupling optical element. Similarly, in one implementation, such as that shown in FIG. 16A, each aperture 2220, 2222, 2224 may be matched with a separate group of (e.g., color-selective) in-coupling optical elements.

[0235] A wide range of system variations and configurations are possible. For example, although linearly polarized light is described as propagating through optics 1130 to SLM 1140 and back through the optics to the waveguide stack, in some designs, circularly polarized light may be used instead. For example, circularly polarized light may be directed into optics 1130. A retarder, such as a quarter-wave plate, may be positioned so that the light passes through the retarder prior to being incident on the SLM. The retarder (e.g., a quarter-wave plate) may be positioned between optics 1130 and SLM 1140. In some cases, as described above, the retarder (e.g., a quarter-wave plate) may be affixed to SLM 1140, such as using an adhesive or mechanical fasteners. The retarder (e.g., a quarter-wave plate) may convert linearly polarized light to circularly polarized light after reflection from SLM 1140. Thus, in some implementations, circularly polarized light may again pass through optics 1130 toward the stack. For example, another retarder (e.g., a quarter-wave plate) proximal to the analyzer 1150 may convert circularly polarized light to linearly polarized light that may or may not pass through the analyzer depending on the linear polarization (e.g., orientation). The pixels of the SLM 1140 may have states that can be varied to rotate or not rotate the polarization. Still other configurations are possible.

[0236] 23A is a side view of an augmented reality display system 2300 including a light source 2305, a polarization rotator 2307, an optic (e.g., a lens) 2320 having refractive power, polarizers 2312, 2335 such as linear polarizers (e.g., horizontal or vertical polarizers), retarders 2315, 2330, 2340 such as quarter-wave retarders (e.g., quarter-wave plates), and at least one waveguide 2348 for outputting image information to a user. Such a configuration can be used to illuminate a reflective spatial light modulator (not shown) such that light emitted from the light source 2305 is coupled into the at least one waveguide 2348 to be reflected from the spatial light modulator and directed toward the user's eye. The configuration and placement of these elements, particularly the polarizer and retarder, can reduce or eliminate reflections from optical surfaces in the system, such as surfaces from the optical system 2320, which could otherwise result in a residual image being visible to the user. For example, polarization-selective and / or phase-differential optical elements (e.g., polarizers 2312, 2335 and retarders 2315, 2330, 2340) can be arranged and configured to convert linearly polarized light into circularly polarized light, which changes from left-handed to right-handed or right-handed to left-handed upon reflection from an optical surface. Similarly, polarization-selective and / or phase-differential optical elements (e.g., polarizers 2312, 2335 and retarders 2315, 2330, 2340) can be arranged and configured to convert circularly polarized light into linearly polarized light, which can be attenuated or filtered out by the polarizer (e.g., linear polarizer). A circular polarizer that converts linearly polarized light into circularly polarized light, or vice versa, can be fabricated together with polarization-selective and phase-differential optical elements (e.g., polarizers 2312, 2335 and retarders 2315, 2330, 2340). For example, the circular polarizer may comprise a linear polarizer and a quarter-wave retarder. The circular polarizer can be used to convert linearly polarized light to circularly polarized light having a first state (e.g., handedness) and filter out circularly polarized light having a second state (e.g., handedness) that is different from the first state.For example, a circular polarizer can be used to convert linearly polarized light with a certain orientation to 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 with a certain orientation to right-handed circularly polarized light and filter out left-handed circularly polarized light. Circular polarizers or other configurations of optical elements, including phase differences, that can be used to convert linearly polarized light to and from circularly polarized light and selectively filter linearly polarized light can be used to reduce back-reflection from optical surfaces, as discussed below in connection with Figures 23A and 23B.

[0237] Note that left-handed and right-handed circular polarizations are depicted using clockwise and counterclockwise arrows in Figures 23A and 23B, respectively. Additionally, horizontal and vertical linear polarizations are depicted using horizontal arrows and circular dots, respectively.

[0238] As discussed above, Figure 23A illustrates a configuration of an augmented reality display system 2300 in which polarizers 2312, 2335, such as linear polarizers (e.g., horizontal polarizers), and retarders 2315, 2330, 2340, such as quarter-wave retarders (e.g., quarter-wave plates), are arranged to reduce back-reflection from optical surfaces, such as surfaces of an optical system 2320, in the path of light illuminating and reflecting from a spatial light modulator (not shown). The first polarizer 2312 and the first retarder 2315 are disposed between the light source 2305 and the optical system 2320. The first polarizer 2312 is disposed between the light source 2305 and the first retarder 2315. Similarly, the first retarder 2315 is disposed between the first polarizer 2312 and the optical system 2320.

[0239] As shown, light source 2305 emits light, as represented by ray 2310. In some implementations, ray 2310 may pass through polarization rotator 2307. Rotator 2307 is optional and can be used to rotate the polarization of light from light source 2305, e.g., ray 2310. In various implementations, rotator 2307 can rotate the angle of polarization (e.g., of linearly polarized light). For example, rotator 2307 can rotate the linear polarization of ray 2310 to be transmitted therethrough to an orientation that is aligned with first polarizer 2312. In some implementations, polarization rotator 2307 may, in some cases, comprise a retarder, e.g., a half-wave retarder. The optical axis of the half-wave retarder may be oriented to rotate the polarization of the light from light source 2305 from vertical to horizontal or vice versa. Alternatively, polarization rotator 2307 may be configured to rotate the angle of polarization of linearly polarized light emitted from light source 2305 by a different amount. Polarization rotator 2307 need not be included in the system. For example, in implementations in which light source 2305 emits light having the same polarization as first polarizer 2312, polarization rotator 2307 may be omitted. As shown, light, e.g., ray 2310, passes through polarizer 2312, shown here as a horizontal polarizer. In instances in which the light from light source 2305 is unpolarized, it is transmitted through horizontal polarizer 2312, and the light shown as ray 2310 becomes linearly polarized (e.g., horizontally polarized) after passing through polarizer 2312. While a horizontal linear polarizer is used in this example, it should be understood that the principles taught can also be applied to the use of a vertical linear polarizer. Alternatively, linear polarizers having a different orientation other than vertical or linear may also be used.

[0240] Horizontally polarized light 2310 travels through retarder 2315, shown here as a quarter-wave retarder. This retarder 2315 contains a sufficient phase difference to convert linearly polarized light to circularly polarized light. For example, horizontally polarized light may be converted to left-handed circularly polarized light, as illustrated by the curved (e.g., clockwise oriented) arrow. In this example, the combination of polarizer 2312 and retarder 2315 (e.g., quarter-wave) forms a circular polarizer, referred to herein as a first circular polarizer, that can convert light of a particular linear polarization (e.g., horizontally or vertically polarized light) to a particular circular polarization (e.g., left-handed or right-handed circularly polarized light, or vice versa). The circular polarizer may also block light of a particular circular polarization (e.g., right-handed or left-handed circularly polarized light), depending on the configuration.

[0241] In some implementations, various optical elements have birefringence. In some such cases, retarder 2315 may include an amount of retardation sufficient to convert linearly polarized light to circularly polarized light and need not be a quarter-wave plate. Retardation greater than or less than a quarter wave may be included within retarder 2315, as retardation may be contributed by other optical elements. Similarly, retardation can be distributed among several optical elements. As another example, multiple retarders may be employed to provide the appropriate amount of retardation.

[0242] Circularly polarized light 2310 (here, left-handed circularly polarized light) then passes through optical system 2320. Unwanted reflections may occur at any interface within the system with a medium having a different refractive index, such as an air / material interface. These reflections may be problematic if allowed to enter at least one waveguide 2348 because the reflected light may be directed into a user's eye and form a visible "afterglow" image in the user's eye. For example, in instances where a display uses at least one waveguide 2348 to project a first image into a user's eye, a second, faint replica image displaced (e.g., laterally displaced) relative to the first image may also be seen by the user. Such "afterglow" images formed by reflections from optical surfaces directed into the user's eye may be distracting or otherwise degrade the viewing experience. For example, as illustrated in FIG. 23A , light such as reflected light ray 2325 may reflect off a lens in optical system 2320. This light may be directed toward at least one waveguide 2348, which is configured to direct the light into the user's eye to present an image thereto. However, in this case, the circularly polarized light reverses its handedness. For example, upon reflection from a lens, the direction of the circularly polarized light is changed (e.g., from left-handed to right-handed). The right-handed reflected light ray 2325 then travels through a retarder 2315 and is converted to linearly polarized light having a different (e.g., orthogonal) linear polarization than that transmitted by the polarizer 2312. In this case, for example, light reflected from the optical surface of the lens is converted by the retarder 2315 to vertically linearly polarized light, which is orthogonal to the polarization transmitted by the horizontal linear polarizer 2312. The horizontal linear polarizer 2312 selectively passes horizontally polarized light and filters out vertically polarized light. Thus, the reflected light rays 2325 are attenuated and / or not transmitted by the horizontal linear polarizer 2312 and are prevented from reaching the at least one waveguide 2348, or at least a reduced amount of such reflected light reaches or is coupled into the at least one waveguide 2348, for example, through an internal coupling optical element (e.g., one or more internal coupling gratings).The result would be similar to left-handed circularly polarized light reflected from a different optical surface in optical system 2320 or from another optical surface on a different optical element.

[0243] As shown, the display system 2300 further includes a second retarder 2330 (e.g., a quarter-wave retarder or a quarter-wave plate) and a second polarizer 2335 (e.g., a linear polarizer) disposed between the optical system 2320 and the spatial light modulator (not shown). The second retarder 2330 and the second linear polarizer 2335 may, in some implementations, form a second circular polarizer. The second retarder 2330 is disposed between the optical system 2320 and the second polarizer 2335. Similarly, the second polarizer 2335 is disposed between the second retarder 2330 and the spatial light modulator. Thus, after passing through the optical system 2320, the light beam 2310 may pass through the second retarder 2330 (e.g., a quarter-wave retarder). The second retarder 2330 is configured (e.g., with its optical axis appropriately oriented) so that the light beam 2310 is converted from left-handed circularly polarized light to horizontally linearly polarized light. Similarly, the second retarder 2330 converts the circularly polarized light back to the original linear polarization state output by the first polarizer 2312. As discussed below, this second retarder 2330 and second polarizer 2312 can be useful in reducing "afterglow" images caused by light reflected from the spatial light modulator passing through an optical surface (e.g., on a refractive power optic or lens 2320) as the light travels to the at least one light guide 2348.

[0244] The third retarder 2340 (e.g., a quarter-wave retarder or quarter-wave plate) is disposed between the second polarizer 2335 and the spatial light modulator. Thus, the third retarder 2340 is disposed between the second retarder 2330 and the spatial light modulator. Also, in various implementations, as shown, the second polarizer 2335 is located between the second and third retarders 2330, 2340. As shown, the light ray 2310 becomes linearly polarized in response to passing through the second polarizer 2335; in some implementations, the second retarder 2330 / second polarizer 2335 may convert the light back to the original linear polarization of the first polarizer 2312 (e.g., horizontally polarized). This linear polarization is incident on the third retarder 2340. The third retarder 2340 is configured to convert the light back into circularly polarized light, in some implementations, the same polarization as that output by the first retarder 2315 (e.g., left-handed circular polarization in this example). In some implementations, the spatial light modulator is configured to operate on circularly polarized light. In some implementations, the spatial light modulator is a reflective spatial light modulator that reflects incident circularly polarized light back as circularly polarized light. In some embodiments, the circularly polarized light reflected from the spatial light modulator may have the same handedness (e.g., left-handed circular polarization) as that incident on it, potentially depending on whether the spatial light modulator pixel is in an "on" or "off" state. In some embodiments, the spatial light modulator may reflect circularly polarized light of a different handedness than that incident on it (e.g., right-handed circular polarization), potentially depending on whether the spatial light modulator pixel is in an "on" or "off" state. However, other types of spatial light modulators may also be used.

[0245] FIG. 23A shows light, illustrated as ray 2342, reflected from the spatial light modulator and traveling toward waveguide 2385. The reflected ray 2342 is depicted as left-handed circularly polarized light. Ray 2342 passes through third retarder 2340, which converts the circularly polarized light to linearly polarized light. In this example, the left-handed circularly polarized light is converted to horizontally polarized light. The linearly polarized light is transmitted through second polarizer 2335. In this example, horizontally polarized light passes through second polarizer 2335. The linearly polarized light is incident on second retarder 2330 and converted to circularly polarized light. In this example, the horizontally polarized light is converted to left-handed polarization and transmitted to optical system 2320. Here again, reflections from an optical surface, such as a surface of the optical system 2320 having refractive power, can create a residual image by reflecting light from the spatial light modulator into at least one waveguide 2348 and back to the user's eye. As explained above, unwanted reflections can occur at any interface involving media with different refractive indices, such as an air / material interface. As referenced above, the inclusion of a second retarder and polarizer 2330, 2335 can attenuate these reflections and reduce the likelihood of residual reflections. FIG. 23A, for example, depicts light, illustrated as ray 2346, reflected from an optical surface of the optical system 2320. The act of reflecting from the surface produces reflected ray 2346, which becomes circularly polarized to switch handedness, in this example, from left-handed to right-handed circular polarization. The switched circular polarization is attenuated by the second circular polarizer formed by the second retarder and polarizer 2330, 2335. 23A, for example, reflected circularly polarized light 2346 is incident on the second retarder 2330 and is converted by the second retarder to linearly polarized light having a different, e.g., orthogonal, linear polarization than that selectively transmitted by the second linear polarizer 2335. In this case, for example, right-handed circularly polarized light reflected from an optical surface of the optical system 2320 is converted by the retarder 2330 to vertically linearly polarized light, which is orthogonal to the polarization selectively transmitted by the polarizer 2335. The second polarizer 2335 attenuates or prevents transmission of this linear polarization.In this embodiment, light 2346 is vertically polarized, while second polarizer 2335 is a horizontal polarizer that selectively passes horizontally polarized light and filters out vertically polarized light.

[0246] In contrast, light 2342 passing through optical system 2320 and incident on first retarder 2315 is circularly polarized and has a different handedness than light reflected from an optical surface of optical system 2320. This light 2342 directed towards at least one waveguide 2348 has a polarization (e.g., left-handed polarized) that is converted by first retarder 2315 to linear polarization (e.g., horizontal linear polarization) that is selectively transmitted by first polarizer 2312. In this way, light 2342 reaches at least one waveguide 2348, is coupled into it, and can be directed towards the user's eye.

[0247] In the embodiment shown in FIG. 23A , a first circular polarizer formed by first polarizer 2312 and first retarder 2315 and a second circular polarizer formed by second retarder 2330 and second polarizer 2335 are on opposite sides of optical system 2320, one closer to light source 2305 and one closer to the spatial light modulator, and are used to reduce reflections that can result in “afterimages.” An additional retarder 2340 is included between the second circular polarizer (e.g., second polarizer 2335) and the spatial light modulator to convert the light to circularly polarized light. However, a wide range of variations are possible. For example, only one circular polarizer may be included. Alternatively, additional circular polarizers or other types of polarization optics may be included.

[0248] Figure 23B illustrates a third circular polarizer that can be added to the augmented reality system 2300 as shown in Figure 23A. In particular, Figure 23B depicts the second circular polarizer, including the second polarizer 2335 and the second retarder 2330 and the third retarder 2340, as introduced above, and further depicts a spatial light modulator 2375. This spatial light modulator (SLM) 2375 may include a liquid crystal spatial light modulator (e.g., liquid crystal on silicon or LCOS). In some implementations, the SLM 2375 can be covered with a cover glass 2370.

[0249] 23B also shows a third circular polarizer including a fourth retarder 2345, such as a quarter-wave retarder (e.g., a quarter-wave plate), and a third polarizer 2355, such as a linear polarizer, disposed between 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 between the fourth retarder 2345 and the spatial light modulator 2375. An additional fifth retarder 2360, such as a quarter-wave retarder (e.g., a quarter-wave plate), and a compensator 2365 are disposed between the third circular polarizer including the fourth retarder 2345 and the third polarizer 2355, and the spatial light modulator 2375, more specifically, the cover glass 2370 shown in FIG. The fifth retarder 2360 is between the third polarizer 2355 and the compensator 2365. The compensator 2365 is between the fifth retarder 2360 and the spatial light modulator 2375, or more specifically, the cover glass 2370.

[0250] Figure 23B shows how light from light source 2305 (shown in Figure 23A), for example, light ray 2310, propagates through a second circular polarizer including retarder 2330 and second polarizer 2335 and a third retarder 2340 to a third circular polarizer including fourth retarder 2345 and third polarizer 2355. After passing through the second circular polarizer including second retarder 2330 and second polarizer 2335, light ray 2310 from light source 2305 is incident on the third circular polarizer, specifically, on fourth retarder 2345. Fourth retarder 2345 may convert the circular polarization of light ray 2310 to linear polarization. In the example shown in FIG. 23B, light ray 2310 is circularly polarized (e.g., left-handed circularly polarized) and is converted to linearly polarized (e.g., horizontally polarized) light by fourth retarder 2345. This linearly polarized light travels through third polarizer 2355, which in FIG. 23B includes a horizontal polarizer that selectively transmits horizontally polarized light. This linearly polarized light propagates through fifth retarder 2360, which may include a quarter-wave retarder that converts linearly polarized light to circularly polarized light. In the example shown in FIG. 23B, horizontally polarized light 2310 incident on fifth retarder 2360 is converted to left-handed circularly polarized light. This circularly polarized light is incident on and passes through compensator 2365. Compensator 2365 may include a polarizing element that adjusts the polarization to a desired polarization. Compensator 2365 may be used to offset birefringence of various optical elements within the system. For example, the light may be slightly elliptically polarized due to the retardation contributions of one or more optical elements. In various implementations, the light output from the compensator 2365 is circularly polarized. In the example shown in FIG. 23B, the light output from the compensator 2365 is left-handed circularly polarized. In various implementations, the compensator 2365 may be used to cancel out residual retardation in an SLM, which may comprise, for example, a liquid crystal (e.g., LCOS) SLM cell. The compensator may introduce in-plane retardation and / or out-of-plane retardation. In some implementations, the compensator 2365 may include a combination of optical retarders that, when combined, produce a retardation that can potentially cancel out residual retardation from the SLM (e.g., an LCOS panel).

[0251] In FIG. 23B , after passing through compensator 2365, light is incident on cover glass 2370 and SLM 2375. This light incident on cover glass 2370 and SLM 2375 is depicted as left-handed circularly polarized light. Depending on the type and state of the spatial light modulator, SLM 2375 may reflect circularly polarized light of the same handedness. For example, when a pixel of SLM 2375 is in the “on” state (although this state may be an undriven state in some implementations), SLM 2375 may introduce a quarter-wave phase difference for each pass through SLM 2375. Thus, upon reflection, incident circularly polarized light may remain circularly polarized upon reflection. In various configurations, the handedness may also remain the same. For example, as shown in FIG. 23B , incident left-handed circularly polarized light may remain left-handed circularly polarized upon reflection. The circularly polarized light reflected from the SLM 2375, represented by ray 2342, passes through the cover glass 2370 and the compensator 2365, and may be incident on the fifth retarder 2360, which converts the circularly polarized light to linearly polarized light. In the example shown in FIG. 23B, the circularly polarized light incident on the fifth retarder 2360 is left-handed, and the fifth retarder 2360 converts the circularly polarized light to horizontally polarized light. The third polarizer 2355 may be configured to selectively transmit the polarization of the light output by the fifth retarder 2360. Thus, in the example shown in FIG. 23B, where the light output from the fifth retarder 2360 is horizontally polarized, the third polarizer 2355 selectively transmits horizontally polarized light. The linearly polarized light transmitted by the polarizer 2355 is incident on the fourth retarder 2345 and converted to circularly polarized light. In the example shown in Figure 23B, the circular polarization is left-handed circular polarization. The light can travel through a second circular polarizer comprising a second retarder 2330 and a second polarizer 2335, optics 2320, a first circular polarizer comprising a first polarizer 2312 and a first retarder 2315, as discussed above in connection with Figure 23A, onto at least one waveguide 2348, and into the user's eye.

[0252] However, light reflected from the optical surface may be attenuated by the third circular polarizer, thereby reducing the likelihood that such reflection will reach at least one waveguide 2348 and be directed toward a user's eye, producing an afterglow image. To illustrate, FIG. 23B shows an exemplary light ray 2343 reflected from an optical surface of the third retarder 2340, for example, from the interface between air and the third retarder 2340. 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, circularly polarized light reverses handedness upon reflection. For example, upon reflecting from the surface of the third retarder 2340, the direction of the circularly polarized light is changed (e.g., from left-handed to right-handed). The right-handed reflected light ray 2343 then travels through the fourth retarder 2345 and is converted to a linearly polarized light having a different, e.g., orthogonal, linear polarization than that selectively transmitted by the third polarizer 2355. In this case, for example, light reflected from the optical surface of the third retarder 2340 is converted by the fourth retarder 2345 to a vertically linearly polarized light, which 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 light ray 2343 is attenuated and / or not transmitted by the third polarizer 2355 and is prevented from reaching the at least one waveguide 2348 (e.g., by reflecting off another surface), or at least a reduced amount of such reflected light reaches or is coupled into the at least one waveguide 2348.

[0253] The result can resemble circularly polarized light reflected from a different optical surface. Figure 23B, for example, shows the reflection of incident light ray 2310 from the optical surface of fourth retarder 2345. Reflection 2350 from fourth retarder 2345 switches the handedness of the polarization. For example, incident light ray 2310, depicted as left-handed circularly polarized light, is converted to light ray 2350, shown to have right-handed circular polarization, upon reflection. Reflected light ray 2350 passes through third retarder 2340 and is converted to vertically polarized light. This vertically polarized light is selectively attenuated or filtered out by second polarizer 2335.

[0254] As described above, a pixel of SLM2375 may be in, for example, an “on” state (but in some implementations, an undriven state), in which case light incident on that pixel of SLM2375 is reflected therefrom, coupled into at least one waveguide 2348, and directed toward the user's eye. However, a pixel of SLM2375 may be in an “off” state (but in some implementations, may be driven), in which case light incident on that pixel of SLM2375 is not coupled into at least one waveguide 2348 and directed toward the user's eye. In this “off” state, for example, various implementations of SLM2375 may not introduce a phase difference upon reflection therefrom. Thus, in the embodiment shown in FIG. 23B , circularly polarized light incident on SLM2375 may remain circularly polarized upon reflection from SLM2375. However, the handedness of the circularly polarized light may change upon reflection from SLM2375. For example, light ray 2310 shown in FIG. 23B , which is left-handed circularly polarized light incident on SLM 2375, may be converted to right-handed circularly polarized light upon reflection from SLM 2375. However, this reflected light may be selectively attenuated by third polarizer 2355. For example, right-handed circularly polarized light reflected from SLM 2375 may pass through cover glass 2370, compensator 2365, and fifth retarder 2360. Fifth retarder 2360 may convert the right-handed circularly polarized light to vertically polarized light, which is selectively attenuated by third polarizer 2355, which may include a horizontal polarizer. Thus, in various implementations, fifth retarder 2360 may convert light reflected from pixels of SLM 2375 to linearly polarized light that is orthogonal to the linearly polarized light selectively transmitted by third polarizer 2355 when the pixels of the SLM are in the “off” state. This third polarizer 2355 can therefore selectively attenuate this linearly polarized light, thereby reducing or blocking light from that pixel of SLM 2375 from reaching at least one waveguide 2348 and being directed into the eye.

[0255] Variations in configuration, such as variations in polarization optical elements, are also possible. For example, more or fewer circular polarizers may be included. In various implementations, the third circular polarizer, including, for example, the fourth retarder 2345 and the third polarizer 2355, is omitted as shown in FIG. 23C. In this particular implementation, the fourth retarder 2345, the third polarizer 2355, and the fifth retarder 2360 are not included in the system. FIG. 23C illustrates a design of an augmented reality system 2300 that includes the components illustrated in FIGS. 23A and 23B, except for the fourth retarder 2345, the third polarizer 2355, and the fifth retarder 2360. Note that even with the omission of the third circular polarizer, the augmented reality display system is still configured to reduce persistence images. The second circular polarizer, for example, reduces reflections that would otherwise contribute to persistence images. To illustrate, FIG. 23C depicts light reflected from the third retarder 2340, shown as ray 2380. The act of reflection from the surface of the third retarder 2340 produces reflected ray 2380, which becomes circularly polarized to switch handedness. In this example, the polarization is switched from left-handed to right-handed circularly polarized light. The switched circularly polarized light 2380 then passes through the compensator 2365 and is incident on the cover glass 2370 and SLM 2375. As discussed above, the SLM 2375 may reflect circularly polarized light of the same handedness. Thus, incident right-handed circularly polarized light may remain right-handed upon reflection. This circularly polarized light reflected from the SLM 2375 is represented by ray 2382 and may then pass through the cover glass 2370 and compensator 2365 and be incident 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 polarizer 2335. As shown in Figure 23C, for example, circularly polarized light 2382 reflected from SLM 2375 is incident on the third retarder 2340 and converted by the third retarder 2340 to linearly polarized light having a different, e.g., orthogonal, linear polarization than that selectively transmitted by the second linear polarizer 2335.In this case, for example, right-handed circularly polarized light 2382 is converted by the third retarder 2340 to vertical linear polarization, which is orthogonal to the polarization selectively transmitted by the second polarizer 2335. The second polarizer 2335 attenuates or prevents transmission of this linear polarization.

[0256] Reflections that can contribute to afterglow reflections can also potentially be reduced by tilting optical surfaces within the system. FIG. 24 illustrates an example configuration with tilted optical surfaces to reduce reflections that can produce afterglow reflections. FIG. 24 shows an augmented reality display system 2400 including a light source 2305 emitting light, represented by light rays 2310, which pass through any number of polarizers, retarders, lenses, and / or other optical components as the light travels toward a spatial light modulator (SLM) 2375. Possibly, a first polarizer 2312 and a first retarder 2315 and a lens 2320 forming a first circular polarizer are shown in FIG. 24 for illustrative purposes. 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 persistent images. Thus, in some implementations, the cover glass 2370 can be shaped to direct reflections that can result in persistent images away from the user's eyes. As shown, the cover glass 2370 has surfaces that can be tilted such that they are not parallel to other components or optical surfaces of the system (e.g., the SLM 2375, the first retarder 2315, the first polarizer 2312, the at least one waveguide 2348, etc., or optical surfaces thereof). A major surface of the cover glass 2370 can have a normal that is not aligned with or tilted such that it is not parallel to the optical axis of an optical component therein, such as the augmented reality display system 2400 or the optical system 2320. By being tilted, reflections from the optical surfaces of the cover glass 2370 can be directed away from at least one waveguide 2348 or an internal coupling optical element (e.g., an internal coupling grating or a diffractive optical element) to internally couple 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 depicted, reflected light 2405 is directed back toward light source 2305 and away from at least one waveguide 2348, where such light may ultimately reach the user's eye. In some implementations, reflected light 2405 is directed back toward the light source, and at least a portion can be recycled in light source 2305.

[0257] Although FIG. 24 depicts the cover glass 2370 with a sloped surface, optical surfaces that are sloped to divert reflections away from being coupled into the at least one waveguide 2348 can be included on any component in the system where unwanted reflections are possible. Thus, optical surfaces on other components, such as polarizers, retarders, etc., may be sloped to reduce reflections that are coupled into the at least one waveguide 2348 and into the user's eyes. Variations in the shape and size of the cover glass 2370 or other optical component are also possible. The cover glass 2370 or other optical component may, for example, be thinner. Similarly, the cover glass 2370 or other optical component may have a different aspect ratio (length to thickness) than that shown in FIG. 24 . In some implementations, the cover glass 2370 or other optical component is wedge-shaped. However, other shapes are possible.

[0258] Still other arrangements are possible. Figure 25, for example, illustrates an implementation of an augmented reality display system 2500 similar to system 2400 shown in Figure 24, but further including a light dump 2505 for absorbing light directed thereto. System 2500 includes a cover glass 2370 that is tilted to direct reflection 2510 from the cover glass 2370 toward the light dump 2505 instead of directing it back toward the light source 2305. The light dump 2505 may include a light-absorbing material or structure configured to absorb light. The location of the light dump 2505 can vary depending on the implementation, for example, depending on the angle of the tilted cover glass 2370. As discussed above, this approach can also be applied to other optical surfaces within the system. Additionally, the shapes and sizes of the optical elements may differ.

[0259] A wide range of variations in the augmented reality display are also possible. Variations in the polarization optical elements are also possible. For example, while a horizontal polarizer is used, in some implementations, a vertical polarizer or a combination of horizontal and vertical polarizers is employed. In addition, polarizers characterized by polarization other than vertical or horizontal may be used. Similarly, light shown in the figures need not be horizontally polarized but may be vertically polarized. Similarly, light shown as vertically polarized may be horizontally polarized in different implementations, or vice versa. Linear polarized light with polarization other than vertical or horizontal may also be used.

[0260] Additionally, the retarder may be configured differently. For example, the polarization in the figures need not be left-handed circular polarization but may be right-handed circular polarization, and / or the right-handed polarization may be left-handed circular polarization. Still other variations are possible. Different retarder configurations can be employed to produce left-handed and / or right-handed polarization combinations different from those shown. Also, in some implementations, elliptically polarized light may possibly be used instead of circularly polarized light. Retarder may be employed, for example, to convert elliptically polarized light to linearly polarized light and vice versa. Linear polarizers can be used to filter light and may be used to reduce residual reflections as described herein.

[0261] In some implementations, other types of polarizing elements and configurations are employed. For example, the retarders are not limited to quarter-wave retarders or quarter-wave plates. For example, in some implementations, various optical elements have birefringence. In some such cases, any one or more of the retarders 2315, 2330, 2340 may include an amount of retardation sufficient to convert linearly polarized light to circularly polarized light and need not be a quarter-wave retarder. Retardation greater than or less than a quarter wave may be included within any one or more of the retarders 2315, 2330, 2340, as retardation may be contributed by other optical elements. Similarly, retardation can be distributed among several optical elements. As another example, multiple retarders may be employed to provide the appropriate amount of retardation. Also, as described above, in some implementations, elliptical polarization may potentially be used instead of circular polarization. Retarder may be employed, for example, to convert elliptical polarization to linear polarization and vice versa. A linear polarizer can be used to filter light and may be used to reduce afterglow reflections as described herein.

[0262] Additionally, the optical components may be in the form of optical layers, sheets, and / or films and stacks or one or more layers, sheets, and / or films. Thus, different polarizing elements, different amounts, locations, and arrangements may be used. For example, one or more of the retarders and / or polarizers may comprise a film.

[0263] In some implementations, the spatial light modulator may operate differently, for example, the spatial light modulator may operate on and / or output light other than circularly polarized light.

[0264] In the foregoing specification, the disclosure has been described with reference to specific embodiments thereof. It will be apparent, however, that various modifications and changes can be made therein without departing from the broader spirit and scope of the disclosure. The specification and drawings are, therefore, to be regarded in an illustrative rather than a restrictive sense.

[0265] Indeed, it should be understood that the systems and methods of the present disclosure each have several innovative aspects, no single one of which is solely responsible for or required for the desirable attributes disclosed herein. The various features and processes described above may be used independently of one another or may be combined in various ways. All possible combinations and subcombinations are intended to fall within the scope of the present disclosure.

[0266] Certain features described herein in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, while features may be described above as operative in a combination and may even be initially claimed as such, one or more features from the claimed combination may, in some cases, be deleted from the combination, and the claimed combination may be directed to a subcombination or variation of the subcombination. No single feature or group of features is required or essential to every embodiment.

[0267] Tilting the spatial light modulator As discussed above, various eyepieces used within a head-mounted display may be configured to direct light with different amounts of divergence into the eye, as if originating from objects located at different distances from the user. For example, a first group of waveguides may outcouple light having a first amount of divergence, and a second group of waveguides may outcouple light having a second amount of divergence, where the second amount of divergence is different from (e.g., less than) the first amount of divergence. Similarly, a first group of waveguides may outcouple light having a first amount of divergence, and a second group of waveguides may outcouple collimated light. As a result, an image formed with light from the first group of waveguides may provide visual cues associated with closer objects, while an image formed with light from the second group of waveguides may provide visual cues associated with more distant objects. As discussed above, the waveguides may therefore have optical powers associated with them to provide divergence or collimation. Each group of waveguides may also include multiple waveguides, for example, to present different color components (e.g., red, green, and blue). As discussed herein, a head-mounted display may therefore benefit by being configured to switch between directing light to a first group of waveguides (e.g., having a first refractive power associated therewith to produce an image that appears to arise from a first distance or set of distances) when in a first state, and directing light to a second group of waveguides (e.g., having a second, different refractive power associated therewith to produce an image that appears to arise from a second distance or set of distances) when in a second state. For example, the head-mounted display may switch between a first state configured to provide an image that appears relatively close and a second state configured to provide an image that appears relatively far away.In various configurations disclosed herein, to provide such switching, the augmented reality display system may include a spatial light modulator (SLM) that can be tilted from a first orientation to a second orientation and direct light to either a first group of internal coupling optical elements for the first group of waveguides or a second group of internal coupling optical elements for the second group of waveguides to provide an image thereto.

[0268] One such augmented reality display device is shown in Figures 26A-26D, in which a spatial light modulator (SLM) is configured to tilt between two or more orientations (e.g., first and second orientations) and direct light in different directions to different internal coupling optical elements so as to couple the light into different groups of waveguides.

[0269] Figure 26A shows an augmented reality display system 2600 including a light source 1116, a spatial light modulator array (SLM) 2610, and an optical system 1130 disposed in the optical path therebetween. The light source 1116 emits light that passes through the optical system 1130 and is incident on the SLM 2610. The SLM 2610 is reflective and reflects the light back into the optical system 1130. The augmented reality display system 2600 further includes an eyepiece 2602 that includes a waveguide stack 2605 that includes one or more waveguides 2603. The optical system 1130 is also disposed in the optical path between the SLM 2610 and the waveguide stack 2605. As shown in Figures 26A and 26B, light 1116 from the light source reflected from the SLM 2610 is incident on the waveguide stack 2605.

[0270] Each waveguide stack 2605 may include two or more sets of waveguides 2603 and two or more sets of internal coupling optical elements. For example, Figures 26A and 26B illustrate a first set of waveguides 2607 having a first set of internal coupling optical elements 2614 and a second set of waveguides 2609 having a second set of internal coupling optical elements 2616. In this design, the first set of internal coupling optical elements 2614 includes three internal coupling optical elements, namely, first, second, and third internal coupling optical elements 2650, 2652, and 2654, to internally couple three different colors, such as red, green, and blue, into the three waveguides 2603 in the first set of waveguides 2607. Similarly, the second set of internal coupling optical elements 2616 similarly includes three internal coupling optical elements, namely, first, second, and third internal coupling optical elements 2640, 2642, and 2644, for internally coupling three different colors, such as red, green, and blue, into three waveguides 2603 in the second set of waveguides 2609.

[0271] 26A and 26B, the SLM 2610 is configured to tilt to direct light either into the first set of internal coupling elements 2614 and the first set of waveguides 2607 when in a first state, or into the second set of internal coupling elements 2616 and the second set of waveguides 2609 when in a second state. For example, the SLM 2610 is shown in FIGS. 26A and 26B as rotating about an axis 2615. In some embodiments, the axis 2615 is parallel to the waveguides in the waveguide stack 2605 (e.g., parallel to the z-axis). In particular, the SLM 2610 is shown tilted counterclockwise by an angle θ(+θ) with respect to a plane parallel to the eyepiece 2602 and the waveguide stack 2605 when in the first state, and clockwise by an angle θ(-θ) with respect to a plane parallel to the eyepiece and the waveguide stack when in the second state. In the example illustrated in Figures 26A and 26B, the tilts are in opposite directions and at the same angle θ, but the angles need not be the same.

[0272] In various implementations, the augmented reality display system 2600 may include more than one light source. For example, the set of light sources 1116 may include three light sources 1110, 1112, and 1114, as shown in FIG. 26C, which depicts a front view of the eyepiece 2602 including the waveguide stack 2605. The light sources 1110, 1112, and 1114 may be laterally displaced relative to one another, as illustrated in FIG. 26C. In this example, the set of light sources 1116 includes three light sources 1110, 1112, and 1114, although a greater or lesser number is also possible. The light sources 1110, 1112, and 1114 may each be a different color light source, for example, a red, green, and blue light source. In this design, the light sources 1110, 1112, 1114 are shown to be displaced relative to one another along a direction parallel to the axis 2615 (eg, parallel to the z-axis) about which the SLM 2610 rotates.

[0273] In the embodiment shown in Figures 26A-26C, the SLM 2610 is configured, when in a first or second state, to direct light from light sources 1110, 1112, 1114 in the set of light sources 1116 to internal coupling optical elements 2650, 2652, 2654, 2640, 2642, 2644 in the first or second set of internal coupling optical elements 2614, 2616, respectively, and tilt to internally couple the light into one of the first or second set of waveguides 2607, 2609. 26A illustrates an SLM 2610 tilted at an angle (e.g., +θ) 2612a such that light from the light source 1110 is directed to one of the in-coupling optical elements 2650, 2652, 2654 in the first set of in-coupling optical elements 2614, as opposed to one of the in-coupling optical elements 2640, 2652, 2644 in the second set of in-coupling optical elements 2616. The in-coupling optical element in the first set of in-coupling optical elements 2614 may then couple the light into one of the waveguides 2603 in the first set of waveguides 2607, as opposed to one of the waveguides 2603 in the second set of waveguides 2609. 26B illustrates an SLM 2610 tilted at an angle (e.g., −θ) 2612b such that light from the light source 1116 is directed to one of the internal coupling optical elements 2640, 2642, 2644 in the second set of internal coupling optical elements 2616, as opposed to one of the waveguides 2650, 2652, 2654 in the first set of internal coupling optical elements 2614. The internal coupling optical elements in the second set of internal coupling optical elements 2614 may then direct more light to one of the waveguides 2603 in the second set of waveguides 2609, as opposed to one of the waveguides 2603 in the first set of waveguides 2607.

[0274] In this design, first and second sets of incoupling optical elements 2614, 2616 are arranged on opposite sides of a set of light sources 1116, which may include light sources 1110, 1112, 1114. Thus, when in a first state, the SLM 2610 may tilt toward the first set of incoupling optical elements 2614 on one side of the light sources 1110, 1112, 1114, and when in a second state, it may tilt toward the second set of incoupling optical elements 2616 on the opposite side of the light sources.

[0275] Figure 26D is a side view of the eyepiece 2602 from a different side than shown in Figures 26A and 26B. In Figure 26D, the in-coupling optical elements 2650, 2652, 2654, 2640, 2642, and 2644 and the light sources 1110, 1112, 1114 are laterally displaced relative to one another in the direction of the axis 2615 about which the SLM 2610 is tilted (e.g., the Z direction). In particular, the first, second, and third in-coupling optical elements 2650, 2652, 2654, 2640, 2642, and 2644 (in both the first and second sets of in-coupling elements 2614, 2616) are laterally displaced relative to one another in the direction of the axis about which the SLM 2610 is tilted (e.g., the Z direction). Similarly, the three light sources 1110, 1112, 1114 are displaced laterally relative to one another in the direction of the axis 2615 about which the SLM 2610 is tilted (eg, the Z direction). However, the first, second, and third light sources 1110, 1112, 1114 are aligned (along the Z direction) with the respective ones of the first, second, and third internal coupling optical elements 2650, 2652, 2654, 2640, 2642, and 2644 in the first and second sets of internal coupling optical elements 2614, 2616 when the SLM 2610 is tilted appropriately.

[0276] As discussed above, in some implementations, each set of waveguides 2607, 2609 may be configured to output light with a different amount of divergence, convergence, or collimation. FIG. 26D , for example, shows a first set of waveguides 2607 including a first set of outcoupling optical elements 2666 configured to output light 2665 and diverge a first amount, and a second set of waveguides 2607 including a second set of outcoupling optical elements 2676 configured to output light 2675 and diverge a second amount. In this example, FIG. 26D shows the first amount of divergence as being greater than the second amount of divergence. As discussed above, in some implementations, one of the sets of waveguides 2607, 2609 may be configured to direct collimated light toward a user's eye, while another set of waveguides is configured to direct diverging light toward a user's eye. Thus, in various implementations, a first set of in-coupling optical elements 2614, including in-coupling optical elements 2650, 2652, and 2654, receives and couples light into a first set of waveguides 2607, which outputs light 2665 to form an image that appears to arise from a first distance (e.g., a closer distance), in response to tilting of the SLM 2610, and a second set of in-coupling optical elements 2616, including 2640, 2642, and 2644, receives and couples light into a second set of waveguides 2609, which outputs light 2675 to form an image that appears to arise from a second distance (e.g., a farther distance). Although out-coupling optical elements 2666 and 2676 are referred to above as producing divergence and / or collimation, in some implementations one or more lenses or other optical elements having refractive power may be included to provide divergence and / or collimation. Lenses may be included in some implementations, for example, between the first and second sets of waveguides 2607, 2609 and / or between the second set of waveguides 2609 and the user's eyes. In any such design, the outcoupling optical elements 2666 and 2676 may or may not include optical power or otherwise be configured to diverge and / or collimate the light.

[0277] Other configurations are possible. For example, as illustrated in FIG. 27 , in some implementations, different sets of waveguides 2707, 2709 are configured to provide different fields of view for the virtual image content. In some cases, these fields of view may be summed together to provide a larger field of view for the user. For example, the first set of waveguides 2707 may provide a field of view from 0° to +45°, while the second set of waveguides may provide a field of view from 0° to -45°. The SLM 2610 may switch between directing light to the first and second sets of waveguides 2707, 2709 by tilting the SLM 2610 back and forth to provide an aggregate field of view from -45° to +45°. The SLM 2610 may switch between the first and second sets of waveguides 2707, 2709 at a rate that is fast enough that the user cannot perceive the switching. 27, for example, shows a first set of in-coupling optical elements 2614 including in-coupling optical elements 2650, 2652, and 2654 configured to direct light into a first set of waveguides 2707, and a second set of in-coupling optical elements 2616 including in-coupling optical elements 2640, 2642, and 2644 configured to direct light into a second set of waveguides 2709. First set of waveguides 2707 has a first set of out-coupling optical elements 2766 configured to output light corresponding to virtual image content within a first angular field of view 2782, and second set of waveguides 2709 has a second set of out-coupling optical elements 2776 configured to output light corresponding to virtual image content within a second angular field of view 2784. FIG. 27 shows first angular field of view 2782 being directed in a different direction than second field of view angle 2784. However, in some implementations, portions of each of the first and second field of view angles 2782, 2784 may overlap. However, the overlap may in some implementations be less than 50%, 25%, 10%, 5%, 1%, or any range between any of these values of the field of view provided by the sets of waveguides 2707, 2709. The different fields of view together may provide a field of view for virtual image content that is larger than just one of the fields of view.In some implementations, the angular fields of view from each set of waveguides 2707, 2709 need not overlap or may diverge. Still other variations are possible. For example, three sets of waveguides may provide three different fields of view. The SLM 2610 can switch between providing light to these three sets of waveguides, as discussed above. In some implementations, the total field of view provided by the sets of waveguides is greater than any one of the individual fields of view.

[0278] Other designs are possible. For example, in some implementations, different sets of waveguides 2807, 2809 may provide an increased eyebox. As shown in FIG. 28 , for example, each set of in-coupling optical elements 2614, 2616 may direct light into a separate set of waveguides 2807, 2809 with out-coupling optical elements 1180 that are laterally shifted or offset relative to each other, providing an increased range of possible lateral positions of the user's eyes. 28 particularly shows a first set of in-coupling optical elements 2614 including in-coupling optical elements 2650, 2652, and 2654 that can direct light into a first set of waveguides 2807 with a first set of out-coupling optical elements 2866, and a second set of in-coupling optical elements 2614 including in-coupling optical elements 2640, 2642, and 2644 that can direct light into a second set of waveguides 2809 with a second set of out-coupling optical elements 2876. As discussed above, the SLM 2610 may switch between directing light into the first and second sets of waveguides 2807, 2809 and the first and second sets of out-coupling optical elements 2866, 2876 by tilting back and forth. The first set of out-coupling elements 2866 is laterally offset or displaced from the second set of out-coupling elements 2876. Advantageously, the first and second sets of outcoupling optical elements 2866, 2876 output light from a larger area than just one of the first and second sets of outcoupling optical elements 2866, 2876. The larger area of projection can translate into an increased eyebox for the user to view the image in the display. Thus, the larger area can accommodate variations in the lateral position of the user's eye 210. For example, the user's interpupillary distance may be such that the eye 210 is more or less nasal or temporal relative to the eyepiece 2602. However, the combination of outcoupling optical elements 1180 increases the locations along the lateral direction (e.g., z-direction) where the eye 210 can be positioned and still receive light from the outcoupling optical elements 2866, 2876 and view the virtual image content.The SLM 2610 can switch between the first and second sets of waveguides 2807, 2809, and hence the first and second sets of internal coupling optical elements 2614, 2616, at a rate that is fast enough so that the user cannot perceive the switching, but appears to have a larger eyebox.

[0279] The light sources and internal coupling optical elements may be arranged and / or configured differently. In some embodiments, such as those shown in Figures 29A and 29B, the light source 2910 may be a multicolor light source, capable of emitting different colored light at different times, for example. For example, the light source 2910 may emit three colors and may be configured to emit a first color and negligible amounts of a second and third color in a first time period, a second color and negligible amounts of the first and third colors in a second time period, and a third color and negligible amounts of the first and second colors in a third time period. For example, the light source 2910 may emit red, green, and blue (RGB) light and may be configured to emit red and negligible amounts of green and blue in a first time period, green and negligible amounts of red and blue in a second time period, and blue and negligible amounts of red and green in a third time period. These cycles can be repeated and the SLM 2610 can be coordinated to produce a suitable pattern of pixel states for a particular color (red, green, or blue) to provide the appropriate image color components for a given image frame.

[0280] It should be noted that different waveguides 2990, 2992, 2994, 2930, 2932, and 2934 of waveguide stack 2605 may each be configured to output light with a different respective color. For example, as depicted in FIG. 29A , first, second, and third waveguides 2930, 2932, 2934 in first set of waveguides 2607 associated with respective first, second, and third internal coupling optical elements 2950, 2952, and 2954 may be configured to output first, second, and third colors of light (e.g., blue, green, and red), respectively. Similarly, the first, second, and third waveguides 2990, 2992, 2994 in the second set of waveguides 2609 associated with the respective first, second, and third internal coupling optical elements 2940, 2942, and 2944 may also be configured to output first, second, and third colors of light (e.g., blue, green, and red), respectively. The different internal coupling optical elements 2950, 2952, 2954 in the first set of waveguides 2607, including 2930, 2932, and 2934, may be laterally aligned (e.g., as shown in FIG. 29B ) or positioned above and / or below each other and laterally aligned with respect to each other, such that an optical path extends through each of the internal coupling optical elements in the first set of internal coupling optical elements 2614. Thus, light may propagate along a path and, in some cases, be incident on all three in-coupling optical elements 2950, 2952, 2954 in the first set of in-coupling optical elements 2614. Similarly, the different in-coupling optical elements 2940, 2942, 2944 in the second set of waveguides 2609, including 2990, 2992, and 2994, may also be laterally aligned (e.g., as shown in FIG. 29B ) or positioned above and / or below each other and laterally aligned with respect to each other, such that an optical path extends through each of the in-coupling optical elements in the second set of in-coupling optical elements 2616. Thus, light may propagate along a path and, in some cases, be incident on all three in-coupling optical elements 2940, 2942, 2944 in the second set of in-coupling optical elements 2616.However, the first set of internal coupling optical elements 2614 may be offset laterally from the second set of internal coupling optical elements 2616 so that light can be directed to either the first set or the second set of internal coupling optical elements 2614, 2616 depending on the tilt of the SLM 2610.

[0281] The incoupling optical elements 2950, 2952, 2954, 2940, 2942, 2944 may be color-selective. For example, the first incoupling optical element 2950, 2940 in the first and second sets of incoupling optical elements 2614, 2616 may be configured to incoupling a non-negligible amount of the first color and negligible or less amounts of the second and third colors. Similarly, the second incoupling optical element 2952, 2942 in the first and second sets of incoupling optical elements 2614, 2616 may be configured to incoupling a non-negligible amount of the second color and negligible or less amounts of the first and third colors. Additionally, the third incoupling optical element 2952, 2942 in the first and second sets of incoupling optical elements 2614, 2616 may be configured to incoupling a non-negligible amount of the third color and negligible or less amounts of the first and second colors. Other configurations are possible. For example, different waveguides in the first set of waveguides 2607 can be configured to receive and output different colors than their respective corresponding waveguides in the second set of waveguides 2609, and vice versa. Of course, other colors are also possible; for example, light source 2910 may emit other colors, and color-selective interconnecting optical elements 2950, 2952, 2954, 2940, 2942, 2944 may be configured for such other colors. Additionally, individual red, green, and blue emitters may be positioned close enough together to effectively function as a single-pupil light source. For efficiency, emitters of any color may be combined with beam-conditioning elements, such as reflectors, films, and holograms, to match the angular output of the light source to the displayed field of view. In some implementations, red, green, and blue emitters may be combined with lenses and dichroic splitters to form a single red, green, and blue pupil source. Single-pupil multiplexing may be extended beyond or in addition to color selectivity to include the use of polarization-dependent gratings and polarization switching. These color or polarization gratings can also be used in combination with multiple display pupils to increase the number of layers that can be addressed.

[0282] A wide range of variations are possible. For example, while two waveguide sets 2607, 2609 are discussed above with reference to Figures 26A-29B, more waveguide sets (and therefore more corresponding sets of internal coupling optical elements) may be included. For example, the SLM 2610 may be configured to switch to different states, e.g., tilt at different angles to couple light from a light source into three, four, or more waveguide sets. The SLM 2610 may have three, four, or more states, for example, in which the SLM is tilted at different angles, e.g., θ1, θ2, and θ3, to direct light into first, second, or third sets of internal coupling optical elements of the first, second, or third waveguide sets. Similarly, the waveguide sets may include more or fewer waveguides 2603. For example, each waveguide set may include only two waveguides 2603. Similarly, in such implementations, each set of in-coupling optical elements may include only two in-coupling optical elements. Alternatively, a set of waveguides may include four or more waveguides 2603. In such implementations, a set of in-coupling optical elements may include four or more in-coupling optical elements.

[0283] Figure 30A shows a configuration in which, instead of using more than one waveguide to provide light tuned to create an image that appears to originate from a certain depth, a single waveguide is used to provide such light. In Figure 30A, for example, two such waveguides (referred to as first and second waveguides 3004, 3006) are used for two distinct depths. Each waveguide 3004, 3006 is configured to receive multiple colors of light from a multicolor light source 3010, depending on the tilt state of a tilted spatial light modulator 2610. Laterally displaced, non-color-selective, or broadband in-coupling optical elements 3050, 3040 may, in various implementations, be configured to receive light from the light source 3010 and couple it into the respective first and second waveguides 3004, 3006.

[0284] 30A, for example, is a side view of an augmented reality display system including an eyepiece 2602 that includes a waveguide stack 2605. The waveguide stack 2605 includes first and second waveguides 3004, 3006, each including therewith a respective in-coupling optical element 3050, 3040 and a respective out-coupling optical element 3060, 3070. The in-coupling optical elements 3040 and 3050 may be configured to couple light of multiple colors into their respective waveguides. Thus, these in-coupling optical elements 3050, 3040 may be referred to herein as broadband, multi-color, or non-color-selective in-coupling optical elements because these in-coupling optical elements combine light of different colors. For example, in some implementations, each of these in-coupling optical elements 3050, 3040 is configured to in-couple first, second, and third colors (e.g., red, green, and blue light) into the associated waveguide 3004, 3006, where the in-coupling optical element is included such that the colored light is guided within the waveguide by TIR. Such broadband in-coupling optical elements 3040 and 3050 may operate, for example, across a wide range of wavelengths, for example, within the visible range, or may select a wavelength or wavelength region spread, for example, across the visible range. Thus, such broadband or multicolor or non-color-selective in-coupling optical elements 3040 and 3050 may be configured to redirect light of various different colors (e.g., red, green, and blue) into the waveguide and guide it therein by TIR. Similarly, each of these out-coupling optical elements 3060 and 3070 may include a broadband out-coupling optical element. Such broadband outcoupling optical elements 3060 and 3070 may operate across a wide range of wavelengths, e.g., within the visible range, or may select a wavelength or a spread of wavelength regions, e.g., across the visible range. Thus, such broadband or multicolor or non-color-selective outcoupling optical elements 3060 and 3070 may be configured to redirect light of a variety of different colors (e.g., red, green, and blue) out of the waveguide and into the eye.Although red, green, and blue colors (RGB) are referenced herein in connection with light sources, in-coupling optical elements, out-coupling optical elements, and / or waveguides, other colors or color systems may also or alternatively be used, including, for example, but not limited to, cyan, magenta, and yellow (CMY).

[0285] In some implementations, the augmented reality display system 2600 may include a tilting stage on which the SLM 2610 is disposed. The tilting stage may include at least one actuator capable of tilting the tilting stage. In some implementations, the actuator may be capable of receiving a signal and may tilt the tilting stage in response to the tilt signal.

[0286] As discussed above, in some implementations, the SLM 2610 may be configured to switch between two or more states. Each state of the SLM 2610 may correspond to a different angle. For example, the SLM 2610 may tilt to a first state corresponding to a first angle and to a second state corresponding to a second angle. For example, FIGS. 26A and 26B show a first angle 2612a and a second angle 2612b. In some embodiments, the first angle 2612a and the second angle 2612b may include angles ranging from -45 to +45 degrees, -30 to +30 degrees, -20 to +20 degrees, -10 to +10 degrees, or -5 to +5 degrees, or any range between any of these values. For example, the first and second angles 2612a may be at least ±7 degrees. In another example, the first angle 2612a and the second angle 2612b may include angles of at least 20 degrees. The first and second angles 2612a, 2612b need not be the same. Additionally, the angles 2612a, 2612b need not be of opposite signs, although in some implementations the angles will be of opposite signs with the same or different magnitudes.

[0287] In some embodiments, the SLM 2610 may tilt at a rate fast enough to avoid detection by the eye 210. For example, the SLM 260 may tilt between states (e.g., 5 to 15 degrees or a greater or lesser range) within less than 0.1 seconds, but should not be so limited. In some implementations, the tilt between states may occur within 200 ms to 100 ms, 100 ms to 50 ms, 100 ms to 50 ms, 50 ms to 20 ms, 50 ms to 10 ms, 40 ms to 5 ms, 30 ms to 1 ms, or any range formed by any of these values.

[0288] As discussed above, a wide range of variations are possible. For example, the SLM 2610 may be configured to tilt in different directions. For example, in the embodiment shown in Figures 26A-29B, the SLM is depicted as tilting about an axis 2615 parallel to the z-axis, but the SLM may rotate about a different axis or about one or more axes. The SLM 2610 may, for example, tilt or rotate about an axis 2615 parallel to the x-axis. In such a configuration, the internal coupling optical element may be positioned on opposite sides of the light source corresponding to different positions that are laterally spaced apart along the z-direction (instead of along the x-direction). Other orientations are also possible. For example, the SLM 2610 may rotate about an axis angled at 45° relative to the x and z axes. Similarly, the SLM 2610 may be configured to rotate about an axis 2615 having other angular orientations.

[0289] Various types of light sources may be employed. U.S. Provisional Patent Application No. 62 / 686,474, filed June 18, 2018, and entitled "RGB ILLUMINATOR SYSTEM HAVING CURVED SURFACES," the disclosure of which is incorporated herein by reference in its entirety, discloses several example light source configurations, such as those in Figures 7 and 8. However, other configurations and types of light sources may also be employed.

[0290] For example, such configurations as described herein may be used in conjunction with designs including multiple internal coupling gratings and / or multiple pupil expanders, such as orthogonal pupil expanders. Some examples of eyepiece designs that could potentially be used in conjunction with the configurations described herein are presented in U.S. Patent Application Publication No. 2018 / 0275411, published September 27, 2018, which corresponds to U.S. Patent Application No. 15 / 927,821, filed March 21, 2018, and entitled "Method and System for Waveguide Projection with Wide Field of View," (the disclosure of which is incorporated herein by reference in its entirety). However, other configurations may also be employed.

[0291] In various designs, the spatial light modulator array includes a reflective spatial light modulator array that modulates light reflected therefrom. In some implementations, the spatial light modulator array may include a liquid crystal spatial light modulator array. In some implementations, the spatial light modulator array may include a movable micromirror array, such as a digital micromirror (DMD) array.

[0292] Also, various different eyepiece configurations are possible. For example, in various implementations (such as in FIGS. 26C, 29B, and 30B), the outcoupling optical element 1180 is shown as being separate from the light-dispersive element or orthogonal pupil expander (OPE) 1170, but other configurations are possible. For example, the functionality of the light-dispersive element or orthogonal pupil expander (OPE) 1170 of the outcoupling optical element 1180 can be combined into a single diffractive optical element or grating in some designs. Additionally, any order of waveguides may be included within the waveguide stack. For example, the top waveguide may output red light, or the bottom waveguide may output red light. Alternatively, the top waveguide may output green light, or the bottom waveguide may output green light. Similarly, the top waveguide may output blue light, or the bottom waveguide may output blue light. Any other order is also possible. Other colors may also be used, as discussed above.

[0293] terminology In particular, conditional language used herein, such as "can," "could," "might," "may," "eg," and the like, should be understood to generally convey that certain embodiments include certain features, elements, and / or steps, while other embodiments do not, unless specifically stated otherwise or understood otherwise within the context as used. Thus, such conditional language is not generally intended to agree that features, elements, and / or steps are in any way required for one or more embodiments, or that one or more embodiments necessarily include logic for determining whether those features, elements, and / or steps should be included or performed in any particular embodiment, with or without authorial input or prompting. The terms "comprising," "including," "having," and the like, are synonymous and used inclusively in a non-limiting manner and do not exclude additional elements, features, acts, operations, etc. Also, the term "or," when used to connect lists of elements, is used in its inclusive sense (and not its exclusive sense), such that the term "or" refers to one, some, or all of the elements in the list. Additionally, the articles "a," "an," and "the," as used in this application and the appended claims, shall be interpreted to mean "one or more" or "at least one," unless otherwise specified. Additionally, the articles "a," "an," and "the," as used in this application and the appended claims, shall be interpreted to mean "one or more" or "at least one," unless otherwise specified. Similarly, while operations may be depicted in the figures in a particular order, it should be recognized that such operations need not be performed in the particular order shown, or in sequential order, or that all of the illustrated operations need not be performed, to achieve desirable results. Additionally, the figures may diagrammatically depict one or more example processes in the form of a flowchart.However, other operations not depicted may be incorporated into the exemplary methods and processes diagrammatically illustrated. For example, one or more additional operations may be performed before, after, simultaneously with, or between any of the illustrated operations. In addition, operations may be rearranged or reordered in other embodiments. In certain situations, multitasking and parallel processing may be advantageous. Furthermore, the separation of various system components in the above-described embodiments should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems may generally be integrated together in a single software product or packaged in multiple software products. In addition, other implementations are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results.

[0294] Thus, the claims are not intended to be limited to the embodiments shown herein but are to be accorded the widest scope consistent with the present disclosure, the principles and novel features disclosed herein.

Claims

1. 1. A head-mountable display system configured to project light onto a user's eye and display augmented reality image content within the user's field of view, the display system comprising: at least one light source configured to output light, the at least one light source including at least one multi-color light source configured to: i) output a first portion of light having a first color during a first time period; and ii) output a second portion of light having a second color during a second time period; at least one spatial light modulator arranged to receive the light from the at least one light source and modulate the received light to output modulated light that conveys the augmented reality image content; An eyepiece and A controller; Rotating stage and Equipped with the eyepiece is disposed in an optical path between the at least one light source and the at least one spatial light modulator, such that the light output by the at least one light source passes through the eyepiece toward the at least one spatial light modulator, the at least one spatial light modulator operates in a reflective mode to output the modulated light toward the eyepiece; and the eyepiece is configured to receive the modulated light output by the at least one spatial light modulator and direct the modulated light toward the eye of the user; The eyepiece is at least one waveguide; a plurality of internal coupling optical elements, the plurality of internal coupling optical elements being on or within the at least one waveguide, the plurality of internal coupling optical elements being configured to internally couple the modulated light received from the at least one spatial light modulator into the at least one waveguide to be guided within the at least one waveguide, the plurality of internal coupling optical elements including a first internal coupling optical element and a second internal coupling optical element; at least one outcoupling optical element, the at least one outcoupling optical element being on or within the at least one waveguide, the at least one outcoupling optical element being configured to outcoupling light guided within the at least one waveguide out of the at least one waveguide towards the eye of the user; Equipped with a rotating stage configured to tilt the rotating stage in response to a signal received from the controller, the rotating stage including at least one actuator configured to: i) direct a first portion of the modulated light corresponding to the first portion of light having the first color to the first internal coupling optical element during the first time period; and ii) direct a second portion of the modulated light corresponding to the second portion of light having the second color to the second internal coupling optical element during the second time period.

2. 10. The display system of claim 1, wherein at least a portion of the eyepiece is transparent such that the eyepiece provides a view of a portion of the physical environment while the augmented reality image content is presented.

3. 2. The display system of claim 1, further comprising an optical system having refractive power, the optical system arranged in the optical path between the eyepiece and the at least one spatial light modulator to receive at least a portion of the light output from the at least one light source, and the optical system arranged relative to the at least one spatial light modulator so that the light received from the at least one light source passes through the optical system and illuminates the at least one spatial light modulator.

4. 4. The display system of claim 3, wherein the display system is configured such that light illuminating the at least one spatial light modulator is redirected back through the optical system and coupled into the at least one waveguide through the internal coupling optical element.

5. 10. The display system of claim 1, wherein the at least one waveguide comprises a first waveguide including the first incoupling optical element and a second waveguide including the second incoupling optical element.

6. 6. The display system of claim 5, wherein the rotation stage is configured to tilt to direct more of the modulated light output from the at least one spatial light modulator to the first internal coupling optical element than to the second internal coupling optical element when the at least one spatial light modulator is tilted to a first angle, and wherein the rotation stage is configured to tilt to direct more of the modulated light output from the at least one spatial light modulator to the second internal coupling optical element than to the first internal coupling optical element when the at least one spatial light modulator is tilted to a second angle different from the first angle.

7. 6. The display system of claim 5, wherein the first and second waveguides are configured to output light with wavefronts having different amounts of at least one of divergence, convergence, or collimation, as if projected from different distances from the eye.

8. 6. The display system of claim 5, wherein the first and second waveguides are configured such that light coupled out from the first waveguide is collimated and light coupled out from the second waveguide is divergent.

9. 6. The display system of claim 5, wherein the first and second waveguides are configured such that light coupled out of the first waveguide diverges by a first amount and light coupled out of the second waveguide diverges by a second amount different from the first amount.

10. 6. The display system of claim 5, wherein the first and second waveguides are configured to output light into different viewing angles to widen a field of view for the augmented reality image content presented to the user.

11. 6. The display system of claim 5, wherein the first and second waveguides have corresponding first and second outcoupling optical elements, the corresponding first and second outcoupling optical elements being laterally offset relative to each other to provide an increased eyebox for the user to view the augmented reality image content.

12. 6. The display system of claim 5, wherein the first waveguide is configured to transmit and output the light having the first color and the second waveguide is configured to transmit and output the light having the second color.

13. 2. The display system of claim 1, wherein the rotation stage is configured to switch between a first state in which the at least one spatial light modulator is tilted at a first angle and a second state in which the at least one spatial light modulator is tilted at a second angle different from the first angle.

14. 14. The display system of claim 13, wherein the first angle differs from the second angle by at least 7 degrees.

15. 14. The display system of claim 13, wherein the first angle differs from the second angle by at least 10 degrees.

16. 14. The display system of claim 13, wherein the first angle differs from the second angle by at least 20 degrees.

17. 14. The display system of claim 13, wherein the rotation stage is configured to switch between the first state and the second state in less than 100 milliseconds.

18. the at least one multi-color light source is further configured to output a third portion of light having a third color during a third time period; the plurality of internal coupling optical elements further includes a third internal coupling optical element; 2. The display system of claim 1, wherein the actuator is further configured to tilt the rotating stage to direct a third portion of the modulated light corresponding to the third portion of light having the third color to the third internal coupling optical element during the third time period.

19. the at least one waveguide further includes a third waveguide including the third internal coupling optical element; 20. The display system of claim 18, wherein the third waveguide is configured to transmit and output the light having the third color.

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