Wearable Display System with Nanowire LED Microdisplays

Abstract

A wearable display system is provided that includes a nanowire LED microdisplay. [Solution] A wearable display system includes one or more nanowire LED microdisplays. The nanowire microLED displays may be monochrome or full color. The nanowire LEDs forming the array may advantageously have a narrow-angle emission profile and high light output. When multiple nanowire LED microdisplays are utilized, the microdisplays may be positioned on different sides of an optical combiner, e.g., an X-cube prism, that receives light from different microdisplays and outputs the light from the same face of the cube. The optical combiner directs the light to projection optics, which outputs the light to an eyepiece that relays the light to the user's eye.

Description

[Technical Field]

[0001] (Priority Claim) This application claims priority to U.S. Provisional Patent Application No. 63 / 005132, entitled "WEARABLE DISPLAY SYSTEMS WITH NANOWIRE LED MICRODISPLAYS," filed April 3, 2020, which is incorporated herein by reference in its entirety. (Incorporated by reference)

[0002] This application incorporates by reference in its entirety U.S. Patent Application No. 16 / 221,359, filed December 14, 2018, U.S. Provisional Application No. 62 / 786,199, filed December 28, 2018, U.S. Provisional Application No. 62 / 702,707, filed July 24, 2018, and U.S. Patent Application No. 15 / 481,255, filed April 6, 2017.

[0003] The present disclosure relates to display systems, and more particularly to augmented and virtual reality display systems. [Background technology]

[0004] 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 blocked by or is perceived to otherwise interact with objects in the real world.

[0005] Referring to FIG. 1 , an AR scene 10 is depicted. A user of the AR technology sees a real-world park-like setting 20 featuring people, trees, a building 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 produce AR technology that facilitates a comfortable, natural-feeling, and rich presentation of virtual image elements among other virtual or real-world image elements. Summary of the Invention [Means for solving the problem]

[0006] In some embodiments, a head-mounted display system is provided, the head-mounted display system including a head-mountable frame, a nanowire microLED display supported by the frame, and an eyepiece supported by the frame, the nanowire LED microdisplay configured to output image light, and the eyepiece configured to receive the image light from the nanowire LED microdisplay and direct the image light to an eye of the user in response to mounting the frame on a user.

[0007] In some other embodiments, a head-mounted display system is provided. The head-mounted display system includes a waveguide assembly including one or more waveguides and an image projection system including an array of nanowire microLEDs. The image projection system is configured to project an image onto the waveguide assembly. Each waveguide of the waveguide assembly includes an in-coupling optical element configured to in-couple light from the image projection system into the waveguide and an out-coupling optical element configured to out-couple the in-coupled light out of the waveguide. The waveguide assembly is configured to output the out-coupled light with variable wavefront divergence corresponding to multiple depth planes.

[0008] Additional examples of embodiments are listed below.

[0009] Example 1. A head mounted display system, comprising: A head mountable frame; a nanowire micro LED display supported by a frame, the nanowire micro LED display configured to output image light; an eyepiece supported by the frame, the eyepiece configured to receive image light from the nanowire LED microdisplay and direct the image light to the user's eye in response to placing the frame on a user; A head-mounted display system comprising:

[0010] Example 2. The nanowire LED microdisplay is one of a plurality of nanowire LED microdisplays, further comprising an X-cube prism; Each nanowire microLED display faces a different side of the X-cube prism. the eyepiece comprises an internal coupling optical element; The output side of the X-cube prism faces the optical incoupling element; 10 is a head-mounted display system according to Example 1.

[0011] Example 3. The head-mounted display system of Example 2, wherein the nanowire LED microdisplay is a monochrome nanowire LED microdisplay.

[0012] Example 4. The head-mounted display system of Example 3, wherein the reflective surfaces of the X-cube prism are configured to confine light from different monochrome nanowire LED microdisplays onto different areas of the eyepiece.

[0013] Example 5. A head-mounted display system as described in Example 4, wherein the eyepiece comprises a plurality of internal coupling optical elements having a spatial arrangement that provides distinctly different light paths from the X-cube prism to the internal coupling optical elements, the spatial arrangement of areas corresponding to the spatial arrangement of the internal coupling optical elements.

[0014] Example 6. An eyepiece comprising a plurality of waveguides forming a waveguide stack, each waveguide of the waveguide stack comprising: an incoupling optical element configured to incoupling light from the nanowire LED microdisplay into the waveguide; an outcoupling optical element configured to outcouple the incoupled light out of the waveguide; 10. The head-mounted display system of claim 1, comprising:

[0015] Example 7. The head-mounted display system of example 6, wherein the waveguide stack comprises a plurality of sets of waveguides, each set of waveguides comprising a dedicated waveguide for a primary color.

[0016] Example 8. The head-mounted display system of Example 1, further comprising a variable focus lens element, the waveguide comprising a diffractive optical in-coupling and out-coupling optical element, the first variable focus lens element configured to modify the wavefront divergence of light output by the waveguide, and the second variable focus lens element configured to modify the wavefront divergence of light from the external world propagating through the second variable focus lens element.

[0017] Example 9. The head-mounted display system of Example 1, further comprising a color filter between two adjacent waveguides of the waveguide stack of the eyepiece, a first of the adjacent waveguides preceding a second of the adjacent waveguides in an optical path extending from the microdisplay, the color filter configured to selectively absorb light of a wavelength corresponding to a wavelength of light configured to be internally coupled by an internal coupling optical element of the first of the adjacent waveguides.

[0018] Example 10. a third waveguide adjacent to the second of the adjacent waveguides in the optical path; another color filter configured to selectively absorb light of wavelengths corresponding to the wavelengths of light configured to be incoupled by an incoupling optical element of a second one of the adjacent waveguides; 10. The head-mounted display system of Example 9, further comprising:

[0019] Example 11. The head-mounted display system of Example 1, wherein the nanowire LED microdisplay comprises a spaced apart array of monochrome nanowire microLEDs on a common substrate backplane.

[0020] Example 12. An eyepiece lens comprising a plurality of waveguides; the waveguides form a waveguide stack; each waveguide comprising an internal coupling optical element; As seen in the top and bottom views, the spatial arrangement of the incoupling optical elements comprises different incoupling optical elements of different waveguides localized at different spaced locations; The spatial arrangement of the array of monochrome nanowire microLEDs matches the spatial arrangement of the internal coupling optical elements; 12. The head-mounted display system of Example 11.

[0021] Example 13. The head-mounted display system of Example 1, wherein the nanowire LED microdisplay comprises an array of nanowire microLEDs, some of the nanowire microLEDs configured to emit light of a different primary color than others of the array of nanowire microLEDs.

[0022] Example 14. A head-mounted display system, a waveguide assembly comprising one or more waveguides; an image projection system comprising an array of nanowire microLEDs, the image projection system configured to project an image onto the waveguide assembly; each waveguide of the waveguide assembly comprising: an incoupling optical element configured to incoupling light from the image projection system into the waveguide; an outcoupling optical element configured to outcouple the incoupled light out of the waveguide; wherein the waveguide assembly is configured to output the outcoupled light with variable wavefront divergence corresponding to a plurality of depth planes.

[0023] Example 15. The head-mounted display system of Example 14, wherein each of the nanowire microLEDs has an angular emission profile of less than 50°.

[0024] Example 16. The head mounted display system of Example 15, wherein the angular emission profile is 30-45°.

[0025] Example 17. The head-mounted display system of Example 14, further comprising projection optics configured to focus light from the nanowire LED microdisplay onto one or more waveguide intercoupling optical elements.

[0026] Example 18. Each of the light emitters is configured to emit light of one of a plurality of primary colors; The waveguide assembly comprises a set of a plurality of waveguides; each set of waveguides comprising a dedicated waveguide for each primary color, each set of waveguides comprising an outcoupling optical element configured to output light with wavefront divergence corresponding to a common depth plane, different sets of waveguides output light with different amounts of wavefront divergence corresponding to different depth planes; The head-mounted display system of Example 14.

[0027] Example 19. A head-mounted display system as described in Example 14, further comprising a variable focus lens element, wherein the waveguide assembly is between the first variable focus lens element and the second variable focus lens element, wherein the first variable focus lens element is configured to modify the wavefront divergence of light output by the waveguide assembly, and the second variable focus lens element is configured to modify the wavefront divergence of light from the outside world to the second variable focus lens element.

[0028] Example 20. The head-mounted display system of example 14, wherein the waveguide assembly comprises a stack of waveguides.

[0029] Example 21. The head-mounted display system of claim 14, further comprising light-absorbing color filters on major surfaces of at least some of the waveguides, the light-absorbing color filters on the major surfaces of the waveguides being configured to absorb light of wavelengths internally coupled into the corresponding waveguides, and the waveguides being arranged in a stack.

[0030] Example 22. A head-mounted display system as described in claim 14, wherein the waveguide assembly comprises a stack of waveguides, and the internal coupling optical elements are configured to internally couple light, the internally coupled light generally propagating through the associated waveguides in a propagation direction, and the internal coupling optical elements occupy an area having a width parallel to the propagation direction and a length along an axis intersecting the propagation direction, the length being greater than the width. The present invention provides, for example, the following items. (Item 1) 1. A head-mounted display system, comprising: A head mountable frame; a nanowire micro LED display supported by the frame, the nanowire micro LED display configured to output image light; an eyepiece supported by the frame, the eyepiece configured to receive the image light from the nanowire LED microdisplay and direct the image light to an eye of the user in response to placing the frame on the user; A head-mounted display system comprising: (Item 2) the nanowire LED microdisplay is one of a plurality of nanowire LED microdisplays; further comprising an X-cube prism; each of the nanowire micro LED displays faces a different side of the X-cube prism; the eyepiece comprises an internal coupling optical element; an output side of the X-cube prism facing the light in-coupling element; Item 1. A head-mounted display system according to item 1. (Item 3) Item 3. The head-mounted display system of item 2, wherein the nanowire LED microdisplay is a monochrome nanowire LED microdisplay. (Item 4) Item 4. The head-mounted display system of item 3, wherein the reflective surfaces of the X-cube prism are configured to localize light from different monochrome nanowire LED microdisplays onto different areas of the eyepiece. (Item 5) Item 5. A head-mounted display system as described in item 4, wherein the eyepiece comprises a plurality of internal coupling optical elements having a spatial arrangement that provides distinctly different light paths from the X-cube prism to the internal coupling optical elements, and the spatial arrangement of the areas corresponds to the spatial arrangement of the internal coupling optical elements. (Item 6) The eyepiece comprises a plurality of waveguides forming a waveguide stack, each waveguide of the waveguide stack having: an incoupling optical element configured to incoupling light from the nanowire LED microdisplay into the waveguide; an outcoupling optical element configured to outcouple the incoupling light out of the waveguide; Item 1. A head-mounted display system comprising: (Item 7) 7. The head-mounted display system of item 6, wherein the waveguide stack comprises a plurality of sets of waveguides, each set of waveguides comprising a dedicated waveguide for a primary color. (Item 8) Item 1. A head-mounted display system as described in item 1, further comprising a variable focus lens element, wherein a waveguide comprising diffractive optical in-coupling and out-coupling optical elements is located between a first variable focus lens element and a second variable focus lens element, the first variable focus lens element being configured to modify wavefront divergence of light output by the waveguide, and the second variable focus lens element being configured to modify wavefront divergence of light from the external world propagating through the second variable focus lens element. (Item 9) Item 1. A head-mounted display system as described in item 1, further comprising a color filter between two adjacent waveguides of the waveguide stack of the eyepiece, a first of the adjacent waveguides preceding a second of the adjacent waveguides in an optical path extending from the microdisplay, the color filter configured to selectively absorb light of a wavelength corresponding to the wavelength of light configured to be internally coupled by an internal coupling optical element of the first of the adjacent waveguides. (Item 10) a third waveguide in the optical path that follows the second of the adjacent waveguides; another color filter configured to selectively absorb light of wavelengths corresponding to wavelengths of light configured to be incoupled by the incoupling optical element of a second one of the adjacent waveguides; Item 10. The head-mounted display system of item 9, further comprising: (Item 11) Item 1, a head-mounted display system, wherein the nanowire LED microdisplay comprises a spaced array of monochrome nanowire microLEDs on a common substrate backplane. (Item 12) the eyepiece comprises a plurality of waveguides; the waveguides form a waveguide stack; each waveguide comprising an internal coupling optical element; As seen in the top and bottom views, the spatial arrangement of the incoupling optical elements comprises different incoupling optical elements of different waveguides confined to different spaced apart locations; the spatial arrangement of the array of monochrome nanowire microLEDs matches the spatial arrangement of the internal coupling optical elements; Item 12. A head-mounted display system according to item 11. (Item 13) Item 1. The head-mounted display system of item 1, wherein the nanowire LED microdisplay comprises an array of nanowire microLEDs, some of which are configured to emit light of a different primary color than others of the array of nanowire microLEDs. (Item 14) 1. A head-mounted display system, comprising: a waveguide assembly comprising one or more waveguides; an image projection system comprising an array of nanowire microLEDs, the image projection system configured to project an image onto the waveguide assembly; Equipped with Each waveguide of the waveguide assembly comprises: an incoupling optical element configured to incoupling light from the image projection system into the waveguide; an outcoupling optical element configured to outcouple the incoupling light out of the waveguide; Equipped with The head-mounted display system, wherein the waveguide assembly is configured to output the outcoupled light with variable wavefront divergence corresponding to multiple depth planes. (Item 15) Item 15. The head-mounted display system of item 14, wherein each of the nanowire micro-LEDs has an angular emission profile of less than 50°. (Item 16) Item 15. The head-mounted display system of item 14, further comprising a projection optical system configured to focus light from the nanowire LED microdisplay onto the one or more waveguide internal coupling optical elements. (Item 17) each of the light emitters is configured to emit light of one of a plurality of primary colors; the waveguide assembly comprises a set of a plurality of waveguides; each set of waveguides comprising a dedicated waveguide for each primary color, each set of waveguides comprising an outcoupling optical element configured to output light with a wavefront divergence corresponding to a common depth plane, different sets of waveguides output light with different amounts of wavefront divergence corresponding to different depth planes; Item 15. A head-mounted display system according to item 14. (Item 18) Item 15. The head-mounted display system of item 14, further comprising a variable focus lens element, wherein the waveguide assembly is between a first variable focus lens element and a second variable focus lens element, the first variable focus lens element configured to modify wavefront divergence of light output by the waveguide assembly, and the second variable focus lens element configured to modify wavefront divergence of light from the outside world to the second variable focus lens element. (Item 19) Item 15. A head-mounted display system as described in item 14, further comprising light-absorbing color filters on major surfaces of at least some of the waveguides, the light-absorbing color filters on the major surfaces of the waveguides being configured to absorb light of wavelengths internally coupled into the corresponding waveguides, and the waveguides being arranged in a stack. (Item 20) Item 15. A head-mounted display system as described in Item 14, wherein the waveguide assembly comprises a stack of waveguides, the internal coupling optical elements are configured to internally couple light, the internally coupled light generally propagating through associated waveguides in a propagation direction, the internal coupling optical elements occupying an area having a width parallel to the propagation direction and a length along an axis intersecting the propagation direction, the length being greater than the width. [Brief explanation of the drawings]

[0031] [Figure 1] FIG. 1 illustrates a user's view of an augmented reality (AR) device.

[0032] [Figure 2] FIG. 2 illustrates a conventional display system for simulating a three-dimensional image for a user.

[0033] [Figure 3] 3A-3C illustrate the relationship between the radius of curvature and the radius of focus.

[0034] [Figure 4A] Figure 4A illustrates the representation of the accommodation-vergence-divergence motor response of the human visual system.

[0035] [Figure 4B] FIG. 4B illustrates an example of different accommodation and convergence states of a pair of a user's eyes.

[0036] [Figure 4C] FIG. 4C illustrates an example of a top-down representation of a user viewing content through a display system.

[0037] [Figure 4D] FIG. 4D illustrates another example of a top-down view representation of a user viewing content through a display system.

[0038] [Figure 5] FIG. 5 illustrates aspects of an approach for simulating three-dimensional images by correcting for wavefront divergence.

[0039] [Figure 6] FIG. 6 illustrates an embodiment of a waveguide stack for outputting image information to a user.

[0040] [Figure 7] FIG. 7 illustrates an example of an output beam output by a waveguide.

[0041] [Figure 8] FIG. 8 illustrates an example of a stacked eyepiece, where each depth plane contains an image formed using multiple different primary colors.

[0042] [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.

[0043] [Figure 9B] FIG. 9B illustrates a perspective view of the multiple stacked waveguide embodiment of FIG. 9A.

[0044] [Figure 9C] FIG. 9C illustrates a top-down plan view of the multiple stacked waveguide embodiment of FIGS. 9A and 9B.

[0045] [Figure 9D] FIG. 9D illustrates a top-down plan view of another embodiment of multiple stacked waveguides.

[0046] [Figure 9E] FIG. 9E illustrates a top-down plan view of another embodiment of an internal coupling optical element configuration.

[0047] [Figure 9F]FIG. 9F illustrates an example of a wearable display system.

[0048] [Figure 10] FIG. 10 illustrates an example of a wearable display system with a light projection system having a spatial light modulator and a separate light source.

[0049] [Figure 11A] FIG. 11A illustrates an example of a wearable display system with a light projection system having multiple nanowire LED microdisplays.

[0050] [Figure 11B] FIG. 11B illustrates a top-down plan view of an embodiment of a nanowire LED microdisplay with an array of light emitters.

[0051] [Figure 11C] FIG. 11C illustrates a cross-sectional side view of the nanowire LED microdisplay embodiment of FIG. 11B formed from a nanowire LED array.

[0052] [Figure 12] FIG. 12 illustrates another example of a wearable display system with a light projection system having multiple nanowire LED microdisplays and associated light redirecting structures.

[0053] [Figure 13A] FIG. 13A illustrates an example of a side view of a wearable display system with an optical projection system having multiple nanowire LED microdisplays and an eyepiece having a waveguide with overlapping, laterally shifted, optical incoupling optical elements.

[0054] [Figure 13B]FIG. 13B illustrates another example of a wearable display system with a light projection system having multiple nanowire LED microdisplays configured to direct light to a single light intercoupling area of ​​an eyepiece.

[0055] [Figure 14] FIG. 14 illustrates an example of a wearable display system with a single nanowire LED microdisplay.

[0056] [Figure 15] FIG. 15 illustrates a side view of an example eyepiece having a stack of waveguides with overlapping interconnecting optical elements.

[0057] [Figure 16] FIG. 16 illustrates a side view of an example of a stack of waveguides with color filters to reduce ghosting or crosstalk between the waveguides.

[0058] [Figure 17] FIG. 17 illustrates an example of a top-down view of the eyepiece of FIGS.

[0059] [Figure 18] FIG. 18 illustrates another embodiment of a top-down view of the eyepiece of FIGS.

[0060] [Figure 19A] FIG. 19A illustrates a side view of an example eyepiece having a stack of waveguides with overlapping, laterally offset, internal coupling optical elements.

[0061] [Figure 19B] FIG. 19B illustrates a side view of an embodiment of the eyepiece of FIG. 19A with a color filter to reduce ghosting or crosstalk between waveguides.

[0062] [Figure 20A]FIG. 20A illustrates an example of a top-down view of the eyepiece of FIGS. 19A and 19B.

[0063] [Figure 20B] FIG. 20B illustrates another example of a top-down view of the eyepiece of FIGS. 19A and 19B.

[0064] [Figure 21] FIG. 21 illustrates a side view of an embodiment of rebouncing in a waveguide.

[0065] [Figure 22A] 22A-22C illustrate examples of top and bottom views of an eyepiece having an internal coupling optical element configured to reduce re-bounce. [Figure 22B] 22A-22C illustrate examples of top and bottom views of an eyepiece having an internal coupling optical element configured to reduce re-bounce. [Figure 22C] 22A-22C illustrate examples of top and bottom views of an eyepiece having an internal coupling optical element configured to reduce re-bounce.

[0066] [Figure 23A] 23A-23C illustrate additional examples of top and bottom views of eyepieces having internal coupling optical elements configured to reduce re-bounce. [Figure 23B] 23A-23C illustrate additional examples of top and bottom views of eyepieces having internal coupling optical elements configured to reduce re-bounce. [Figure 23C] 23A-23C illustrate additional examples of top and bottom views of eyepieces having internal coupling optical elements configured to reduce re-bounce.

[0067] [Figure 24A] FIG. 24A illustrates an example of the angular emission profile of light emitted by individual light emitters of a nanowire LED microdisplay and captured by projection optics.

[0068] [Figure 24B] FIG. 24B illustrates an example of narrowing the angular emission profile using an array of optical collimators.

[0069] [Figure 25A] FIG. 25A illustrates an example of a side view of an array of tapered reflective wells for directing light into projection optics.

[0070] [Figure 25B] FIG. 25B illustrates an example of a side view of an asymmetric tapered reflective well.

[0071] [Figure 26] 26A-26C illustrate examples of differences in light paths for light emitters at different positions relative to the centerline of the superstrate lens.

[0072] [Figure 27] FIG. 27 illustrates an example of a side view of an individual light emitter of a nanowire LED microdisplay with an overlying nanolens array.

[0073] [Figure 28] FIG. 28 is a perspective view of the nanowire LED microdisplay embodiment of FIG.

[0074] [Figure 29] FIG. 29 illustrates an example of a wearable display system involving the full-color nanowire LED microdisplay of FIG.

[0075] [Figure 30A] FIG. 30A illustrates an example of a wearable display system with a nanowire LED microdisplay and an associated array of light collimators.

[0076] [Figure 30B] FIG. 30B illustrates an example of an optical projection system with multiple nanowire LED microdisplays, each with an associated array of optical collimators.

[0077] [Figure 30C] FIG. 30C illustrates an example of a wearable display system with multiple nanowire LED microdisplays, each with an associated array of optical collimators.

[0078] [Figure 31] 31A and 31B illustrate an example of a waveguide assembly having a variable focus element for varying the wavefront divergence of the light relative to the viewer.

[0079] [Figure 32A] FIG. 32A illustrates an example of a wearable display system having a light projection system that directs light of different primary colors into an eyepiece and combines the different colored light without using an optical combiner.

[0080] [Figure 32B] FIG. 32B illustrates another example of a wearable display system having a light projection system that directs light of different primary colors into the eyepieces and combines the different colored light without using an optical combiner. DETAILED DESCRIPTION OF THE INVENTION

[0081] Detailed Description An augmented reality (AR) or virtual reality (VR) system may display virtual content to a user or viewer. This content may be displayed on a head-mounted display, for example, as part of eyewear, that projects image information to the user's eyes. Additionally, if the system is an AR system, the display may also transmit light from the surrounding environment to the user's eyes, allowing a view of the surrounding environment. As used herein, it should be understood that a "head-mounted" or "head-mountable" display is a display that can be mounted on the head of a user or viewer.

[0082] Many head-mounted display systems utilize transmissive or reflective spatial light modulators to form the images presented to the user. A light source emits light, which is directed to the spatial light modulator, which then modulates the light, which is then directed to the user. A lens structure may be provided between the light source and the spatial light modulator to focus the light from the light source onto the spatial light modulator. Undesirably, the light source and associated optics may add bulk and weight to the display system. This bulk or weight may adversely affect the comfort of the head-mounted display system and the ability to wear the head-mounted display system for extended periods of time.

[0083] In addition, the frame rate limitations of some head-mounted display systems can cause viewing discomfort. Some head-mounted display systems use spatial light modulators to form images. Many spatial light modulators utilize the movement of optical elements to modulate the intensity of light output by the spatial light modulator, thereby forming an image. For example, MEMS-based spatial light modulators may utilize movable mirrors to modulate incident light, while LCoS-based displays may utilize the movement of liquid crystal molecules to modulate light. Other AR or VR systems may utilize scanning fiber displays, in which the end of an optical fiber physically moves across an area while outputting light. The light output by the optical fiber is timed with the position of the end of the fiber, thereby effectively mimicking pixels in different locations, thereby forming an image. The requirement that the optical fiber, mirror, and liquid crystal molecules physically move limits the speed at which individual pixels can change state using these optical elements and also constrains the frame rate of the display.

[0084] Such limitations may cause viewing discomfort, for example, due to motion blur and / or a mismatch between the user's head orientation and the displayed image. For example, there may be latency between detecting the user's head orientation and presenting an image consistent with that orientation. During the time period between detecting the orientation and presenting the image to the user, the user's head may be moving. However, the presented image may correspond to a view of the object from a different orientation. Such a mismatch between the user's head orientation and the presented image may cause discomfort (e.g., nausea) to the user.

[0085] Additionally, scanning fiber displays may exhibit other undesirable optical artifacts due to, for example, the small cross-section of the fiber, which requires the use of a high-intensity light source to form an image of desired apparent brightness. Suitable high-intensity light sources include lasers, which output coherent light. Undesirably, the use of coherent light can result in optical artifacts.

[0086] MicroLED displays have been proposed as a replacement for the spatial light modulators and scanning fiber displays described above. MicroLED displays have various advantages for use in head-mounted display systems. As an example, microLED displays are emissive. The power consumption of emissive microdisplays generally varies with image content, such that dark or sparse content generally requires less power to display. Because AR environments are generally often sparse because it may be desirable for the user to be able to see their surroundings, emissive microdisplays may have average power consumption that is lower than that of other display technologies that use spatial light modulators to modulate light from a light source. In contrast, other display technologies may utilize substantial power even for dark, sparse, or "all-off" virtual content. As another example, emissive microdisplays may provide significantly higher frame rates (which may enable the use of sub-resolution arrays) and lower levels of visually apparent motion artifacts (e.g., motion blur). As another example, emissive microdisplays may not require polarization optics of the type required by LCoS displays, and thus may avoid the optical losses present in polarization optics.

[0087] Many micro LED displays include a planar light emitter formed on a substrate. Notably, the light emitter may have a Lambertian reflective light emission profile and may emit light across the surface area of ​​the light emitter. Such micro LED displays may have drawbacks in some configurations. For example, in some cases, optics may be utilized to narrow the light emission profile, allowing more of the emitted light to be directed toward the user, thereby providing greater energy efficiency. Such optics may add complexity and expense to display systems utilizing micro LED displays. Additionally, due to manufacturing and electrical considerations, reductions in the size of the light emitter may be constrained, making reductions in light emitter size (and associated increases in pixel density and resolution) difficult. For example, some micro LED-based micro displays may enable pixel pitches of about 2 to about 3 microns. Even with such pixel pitches, to provide the desired number of pixels, micro LED displays may still be undesirably large for use in wearable display systems, particularly because a goal for such systems may be to have a form factor and size similar to that of eyeglasses. Additionally, the brightness of a light emitter may be limited by its ability to withstand high current densities.

[0088] Various embodiments described herein utilize nanowire LED microdisplays, which offer the benefits of microLED displays in general while providing additional advantages related to one or more of light directionality, brightness, high scalability for increased pixel density, improved color accuracy (e.g., by providing high levels of red light), and high manufacturing throughput. For example, nanowire microLED displays can maintain electrical-to-optical conversion efficiency down to micron-sized pixels, which is an advantage over planar microLED designs, where efficiency can drop off sharply below, for example, 10-20 microns. As a result, highly efficient and significantly higher-resolution nanowire LED arrays can be formed. Furthermore, nanowire LEDs can provide built-in emission profile directionality and steering, which can be selected based on the physical design and composition of the nanowire LED. This can simplify the system architecture and manufacturing of display systems utilizing nanowire LEDs, as additional optics for directionality and steering can be avoided. Furthermore, in some embodiments, by omitting additional optics for directionality and steering, nanowire LED arrays can be populated with nanowire LEDs without the constraints of designing and grouping nanowires to interface with additional optics. As a result, higher nanowire density, and therefore light output, can be achieved without changing the size of the microdisplay. The use of a microdisplay with a nanowire microLED array enables a highly compact form factor viewing optical assembly (VOA) for AR and VR wearable display systems. In some embodiments, the VOA may include a nanowire LED microdisplay and an eyepiece for relaying light from the microLED display to the user's eye. Advantageously, such display systems can deliver high brightness over a wide field of view, with high image quality metrics and color uniformity, in a power-efficient manner.

[0089] It should be understood that nanowire LEDs may be formed from an array of vertically extending nanowires (e.g., spaced-apart pillars of material) electrically connected to two electrodes. The nanowires emit light in response to the application of current through them. In some embodiments, the nanowires may be considered diodes, with P and N sections.

[0090] Nanowires can also be considered three-dimensional LED devices, with a larger light-emitting surface area than typical planar LEDs. For example, a 1 μm×1 μm planar LED has a 1 μm 2 The active emitter areas are, as an example, 1 μm high and 100 nm diameter, respectively. 2 A group of 25 nanowires grown within an area of ​​25 × (π × 0.1 × 1) = 8 μm 2 , which is eight times the light-emitting area of ​​a planar LED. This increase in the surface area-to-volume ratio for the LED "pixel" can improve the light output of nanowire LEDs. This improvement can enable nanowire LED pixels to maintain high brightness output even for very fine pixel pitch operation. In some embodiments, the nature of the emitted light (wavelength, external quantum efficiency, directionality) can also be tailored by selection of nanowire parameters such as, but not limited to, materials and dopants, dimensions, geometry, structure, refractive index, etc. For example, the geometry, size, and spacing of the nanowires can be selected to provide a desired directionality to the light emission profile.

[0091] Additionally, nanowires may be grouped together to form pixels. For example, a common contact or electrode may be used to connect one or more nanowires to form a pixel or discrete light emitter. Because each nanowire may have a diameter of, for example, 100 nm to several hundred nanometers, the pixel size and pitch may be determined by the size of the common electrode for each group of nanowires. For example, nanowires may be grouped into pixels defined by an electrical contact shared by the N and P portions of a group of nanowire diodes. Thus, the pixel size and pitch may be significantly reduced based on the size of the electrode. As a result, pixels with micron or submicron pitch may be achieved. In some embodiments, the pixel pitch is 2 μm or less, 1 μm or less, or 800 nm or less. In some embodiments, the pixel pitch may be within the range of 200 nm to 2 μm, 200 nm to 1 μm, or 200 to 800 nm. As described herein, pixel pitch may refer to the distance between similar points on immediately adjacent light emitters along a particular axis (e.g., a lateral axis), with a different axis having its own pixel pitch. For example, in some embodiments, light emitters may be spaced closer together along a first axis than along a second axis (e.g., an orthogonal axis).

[0092] Additionally, the various physical properties of nanowire LEDs can advantageously provide exceptional light-emitting properties. For example, nanowire LEDs can be formed with low mismatch dislocations, which can withstand higher current density values ​​than planar LEDs, thereby enabling higher levels of light output. Additionally, it should be understood that nanowire LEDs that emit red light can be formed by heavy indium doping of Ga nanowires. However, such doping can result in crystal lattice mismatch, which reduces the light-emitting efficiency of such nanowire LEDs. Because the nanowires can be sparsely dispersed across the substrate, a low level of accumulated crystal lattice mismatch (e.g., mismatch between the InN and GaN-based portions of the nanowire) can occur, which can be advantageous for forming red LEDs. The low level of lattice mismatch provides the LED with high light output efficiency. As a result, a high level of red light output can be achieved, which can be advantageous for forming displays with high color accuracy.

[0093] Additionally, nanowire LEDs may be formed using semiconductor fabrication processes to form the nanowires and associated electrodes, with indium doping utilized to provide the desired electronic bandgap tuning, for example, for the desired color light output. Furthermore, forming nanowire LEDs on a semiconductor substrate allows for process compatibility with CMOS backplanes (e.g., via wafer-to-wafer or flip-chip bonding). It should be appreciated that semiconductor fabrication processes can provide high throughput for high-yield manufacturing results.

[0094] In some embodiments, one or more nanowire LED microdisplays may be utilized to form images for a head-mounted display system. The light containing the image information for forming these images may be referred to as image light. It should be understood that the image light may vary in, for example, wavelength, intensity, polarization, etc. The nanowire LED microdisplay outputs the image light toward an eyepiece, which then relays the light to the user's eye.

[0095] In some embodiments, one or more nanowire LED microdisplays may be utilized and positioned on different sides of an optical combiner, such as an X-cube prism or dichroic X-cube. The X-cube prism receives light rays from different microdisplays on different faces of the cube and outputs the light rays from the different microdisplays out another face of the cube. The light rays from all of the different microdisplays may be output from the same output face of the cube. The output light may be directed toward projection optics configured to converge or focus the image light onto an eyepiece.

[0096] In some embodiments, one or more nanowire LED microdisplays include a monochrome microdisplay configured to output light of a single primary color. Combining the various primary colors forms a full-color image. In other embodiments, one or more of the nanowire LED microdisplays may have subpixels configured to emit light of two or more, but not all, of the primary colors utilized by the display system. For example, a single nanowire LED microdisplay may have subpixels that emit blue and green light, while a separate nanowire LED microdisplay on a different face of the X-cube may have a pixel configured to emit red light. In some embodiments, one or more microdisplays are full-color displays, each including a pixel formed from multiple subpixels configured to emit light of, for example, different primary colors. Advantageously, combining the light of multiple full-color microdisplays may increase display brightness and dynamic range.

[0097] It should be understood that a nanowire LED microdisplay may include an array of light emitters. Preferably, as discussed herein, the composition and geometry, size, and spacing of the nanowires forming the nanowire LED are selected to provide a desired light emission profile with a desired angular expansion.

[0098] Nevertheless, in some embodiments, nanowire LEDs may emit light with a larger-than-desired angular emission profile. Unfortunately, such an angular emission profile can result in "wasted" light, as only a small portion of the emitted light may ultimately be incident on the eyepiece. In some embodiments, a light collimator may be utilized to narrow the angular emission profile of light emitted by a nanowire LED light emitter. As used herein, a light collimator is an optical structure that narrows the angular emission profile of incident light. That is, a light collimator receives light from an associated light emitter with a relatively wide initial angular emission profile and outputs the light with an angular emission profile that is narrower than the wide initial angular emission profile. In some embodiments, the rays of light exiting the light collimator are more parallel than the rays of light received by the light collimator before being transmitted through and exiting the collimator. Examples of light collimators include microlenses, nanolenses, reflective wells, metasurfaces, and liquid crystal gratings. In some embodiments, the light collimators may be configured to steer and ultimately focus the light onto different laterally offset light combining optical elements. In some embodiments, each light emitter has a dedicated light collimator. The light collimator is preferably positioned directly adjacent to or in contact with the light emitter and captures a large percentage of the light emitted by the associated light emitter.

[0099] In some embodiments, a single nanowire LED microdisplay may be utilized to output light to the eyepiece. For example, a single nanowire LED microdisplay may be a full-color display including light emitters that emit different primary colors of light. In some embodiments, the light emitters may form localized groups within a common area, with each group including a light emitter that emits light of each primary color. In such embodiments, each group of light emitters may share a common microlens. Advantageously, light of different colors from different light emitters follows different paths through the microlens, which may manifest as light of different primary colors incident on different internal coupling optical elements of the eyepiece, as discussed herein.

[0100] In some embodiments, a full-color microdisplay may include repeating groups of light emitters of the same primary color. For example, the microdisplay may include rows of light emitters, with the light emitters in each individual row configured to emit light of the same color. Thus, different rows may emit light of different primary colors. In addition, the microdisplay may have an associated array of light collimators configured to direct light to desired locations on the eyepiece, e.g., to associated internal coupling optical elements. Advantageously, although the individual light emitters of such a full-color microdisplay may not be positioned to form a high-quality full-color image as viewed directly on the microdisplay, the lens array appropriately steers light from the light emitters to the eyepiece, which combines the monochrome images formed by the different color light emitters, thereby forming a high-quality full-color image.

[0101] In some embodiments, an eyepiece lens that receives image light from a nanowire LED microdisplay may include a waveguide assembly. The area of ​​the waveguide of the waveguide assembly onto which the image light is incident may include an in-coupling optical element that in-couples the incident image light so that the light propagates through the waveguide by total internal reflection (TIR). In some embodiments, the waveguide assembly may include a stack of waveguides, each with an associated in-coupling optical element. Different in-coupling optical elements may be configured to in-couple light of different colors, such that different waveguides may be configured to propagate light of different colors therein. A waveguide may include an out-coupling optical element that out-couples light propagating therein so that the out-coupled light propagates toward the user's eye. In some embodiments, the waveguide assembly may include a single waveguide with an associated in-coupling optical element configured to in-couple light of multiple different primary colors.

[0102] In some embodiments, the in-coupling optical elements are offset laterally as viewed by the projection optics. Different in-coupling optical elements may be configured to in-couple light of different colors. Preferably, image light of different colors follows different paths to the eyepiece and therefore impinges on different corresponding in-coupling optical elements.

[0103] In some embodiments, other types of eyepieces or optics for relaying image light to the user's eye may be utilized. For example, as discussed herein, the eyepiece may include one or more waveguides that propagate image light therein by TIR. As another example, the eyepiece may include a basin mirror combiner that includes a semi-transparent mirror that both directs image light to the viewer and allows a view of the surrounding environment.

[0104] In some embodiments, the eyepiece may be configured to selectively output light with different amounts of wavefront divergence to provide one or more virtual depth planes (also referred to herein simply as “depth planes”) with virtual content perceived to be at different distances away from the user. For example, the eyepiece may include one or more waveguides each having an outcoupling optical element with different refractive power for outputting light with different amounts of wavefront divergence. In some embodiments, a variable-focus element may be provided between the eyepiece and the user's eye. The variable-focus element may be configured to dynamically change refractive power to provide a desired wavefront divergence for particular virtual content. In some embodiments, as an alternative to, or in addition to, a waveguide optical structure to provide refractive power, the display system may also include one or more lenses that provide, or in addition to, refractive power.

[0105] Reference is now made to the drawings in which like reference numerals refer to like parts throughout. Unless otherwise indicated, the drawings are schematic and are not necessarily drawn to scale.

[0106] 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 210, 220, 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.

[0107] Continuing with reference to FIG. 2 , images 190 and 200 are spaced apart from eyes 210 and 220 by a distance 230 on the z-axis. The z-axis is parallel to the optical axis of the viewer when the eye is fixating on an object at optical infinity directly in front of the viewer. Images 190 and 200 are flat and at a fixed distance from eyes 210 and 220. Based on slightly different views of the virtual object in the images presented to eyes 210 and 220, respectively, the eyes may necessarily 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 210 and 220 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 the user's eyes 210 and 220 and providing binocular cues that the human visual system interprets to provide the perception of depth.

[0108] 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 the 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, 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. The curvature increases as 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 210 and 220 of the viewer.

[0109] Continuing with reference to Figures 3A-3C, light from an object that a viewer'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 trigger 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.

[0110] 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.

[0111] Without being limited by theory, it is believed that a viewer of an object may perceive the object as "three-dimensional" due to a combination of vergence and accommodation. As described above, vergence movements 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' lines of sight and fixating on an object) are closely linked to accommodation of the eye's lenses. Under normal conditions, a change in focus of the eye's lenses to change focus from one object to another at a different distance will automatically produce a corresponding change in vergence to the same distance, a relationship known as the "accommodation-vergence reflex." Similarly, a change in vergence will induce a corresponding change in lens shape under normal conditions.

[0112] 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 210a, 220a.

[0113] 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 described above, 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 viewers because, among other things, they simply provide different presentations of a scene, causing changes in the eyes' convergence states without corresponding changes in the eyes' accommodation states. Rather, images are presented by the display 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 the convergence states without a corresponding change in the accommodation state. This mismatch is believed to cause viewer discomfort. Display systems that provide better alignment between accommodation and convergence-divergence movements may create a more realistic and comfortable simulation of three-dimensional images.

[0114] 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.

[0115] 4B , two depth planes 240 are illustrated, corresponding to different distances in space from the eyes 210, 220. For a given depth plane 240, vergence-divergence cues may be provided by displaying appropriately different perspective images for each eye 210, 220. Additionally, for a given depth plane 240, the light forming the image provided to each eye 210, 220 may have a wavefront divergence corresponding to the light field generated by a point at the distance of that depth plane 240.

[0116] 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 those eyes when those eyes are 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 for 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 for pupil distance may be a normalized value generally used for all viewers. 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.

[0117] 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 210, 220. The image may cause the eyes 210, 220 to assume a convergence-divergence state in which the eyes converge on point 15 on the depth plane 240. In addition, the image may be formed by light having a wavefront curvature corresponding to the real object on that depth plane 240. As a result, the eyes 210, 220 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.

[0118] It should be understood that the accommodation and convergence states of the eyes 210, 220 are each associated with a particular distance on the z-axis. For example, an object at a particular distance from the eyes 210, 220 will cause those eyes to assume a particular accommodation state based on the distance of the object. The distance associated with a particular accommodation state is referred to as the accommodation distance A. d Similarly, a particular convergence distance V associated with the eyes in a particular convergence state or position relative to one another may be referred to as d However, if the accommodation distance and the convergence distance are consistent, the relationship between accommodation and convergence can be said to be physiologically correct. This is considered the most comfortable scenario for the viewer.

[0119] However, in a stereoscopic display, the accommodation distance and the vergence distance may not always be aligned. For example, as illustrated in FIG. 4D , images displayed to the eyes 210, 220 may be displayed with a wavefront divergence corresponding to the depth plane 240, and the eyes 210, 220 may be in a particular accommodation state in which points 15a, 15b on that depth plane are in focus. However, the images displayed to the eyes 210, 220 may provide convergence cues that cause the eyes 210, 220 to converge on a 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 210, 220 to the depth plane 240, while the vergence distance corresponds to the greater distance from the exit pupils of the eyes 210, 220 to point 15. The accommodation distance is different from the vergence distance. As a result, there is an accommodation-vergence-divergence mismatch. Such a mismatch is considered undesirable and can cause discomfort to the user. The mismatch can be caused by distance (e.g., V d -A d ) and can be characterized in terms of diopters.

[0120] It should be understood that in some embodiments, a reference point other than the exit pupil of the eye 210, 220 may be used to determine the distance for determining accommodation-vergence mismatch, so long as the same reference point is used for accommodation distance and vergence distance. For example, the distance 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.

[0121] 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 a viewer with 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.

[0122] 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.

[0123] 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, multiple or stacked waveguides may be utilized to provide different wavefront divergences for different depth planes and / or to output light of different ranges of wavelengths. As used herein, it should be understood that a depth plane may be planar or may follow the contour of a curved surface.

[0124] 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 a three-dimensional perception to the eye / brain using multiple 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.

[0125] 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.

[0126] Continuing with reference to FIG. 6 , the waveguide assembly 260 may also include multiple features 320, 330, 340, 350 between the waveguides. In some embodiments, the features 320, 330, 340, 350 may be one or more lenses. The waveguides 270, 280, 290, 300, 310 and / or multiple lenses 320, 330, 340, 350 may be configured to transmit image information to the eye using 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 distribute 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 viewer's eye 210). In some embodiments, a single beam of light (e.g., a collimated beam) may be launched into each waveguide, outputting an entire 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 multiple (e.g., three) waveguides 270, 280, 290, 300, 310.

[0127] 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 send image information to each of the image input devices 360, 370, 380, 390, 400 via, for example, one or more optical conduits (such as fiber optic cables). It should be understood that the image information provided by the image input devices 360, 370, 380, 390, 400 may include light of different wavelengths or colors (e.g., different primary colors, as discussed herein).

[0128] In some embodiments, light injected into the waveguides 270, 280, 290, 300, 310 is provided by an optical projection system 520, which includes an optical module 530, which may include a light emitter such as a light emitting diode (LED). Light from the optical module 530 may be directed and modified by an optical modulator 540, e.g., a spatial light modulator, via a beam splitter 550. The optical modulator 540 may be configured to vary the perceived intensity of the light injected into the 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.

[0129] In some embodiments, the display system 250 may be a scanning fiber display including 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 viewer'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 multiple scanning fibers or multiple 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.

[0130] 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. 9F).

[0131] Continuing with reference to FIG. 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. The extracted light may also be referred to as outcoupled light, and the outcoupling optical elements may also be referred to as light extraction optical elements. The extracted beam of light may be output by the waveguide at a location where light propagating within the waveguide strikes the light extraction optical element. The outcoupling optical element 570, 580, 590, 600, 610 may be, for example, a grating including diffractive optical features as discussed further herein. While shown disposed on the bottom major surface of the waveguides 270, 280, 290, 300, 310 for ease of explanation and clarity of drawing, in some embodiments, the outcoupling optical element 570, 580, 590, 600, 610 may be disposed on the top and / or bottom major surfaces and / or 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 that piece of material.

[0132] 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 closer inward toward the person from optical infinity, which was the light from the next upper waveguide 280.

[0133] 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.

[0134] 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 multiple 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.

[0135] Continuing with reference to FIG. 6 , the outcoupling optical elements 570, 580, 590, 600, 610 may be configured to redirect light from their respective waveguides and output the light with an appropriate amount of divergence or collimation for the particular depth plane associated with the 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-extracting 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-extracting optical elements 570, 580, 590, 600, 610 may be volume holograms, surface holograms, and / or diffraction gratings. In some embodiments, features 320, 330, 340, 350 may not be lenses. Rather, they may simply be spacers (e.g., cladding layers and / or structures to form air gaps).

[0136] 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.

[0137] 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 include a layer of polymer-dispersed liquid crystal in which microdroplets contain 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).

[0138] In some embodiments, a camera assembly 630 (e.g., a digital camera, including visible and infrared light cameras) 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 to a frame or support structure 80 ( FIG. 9F ) 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.

[0139] 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 substantially 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 great 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.

[0140] 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, with each depth plane including 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. The 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 viewer, and each box in the diagram represents an individual primary color image. In some embodiments, the exact locations of the depth planes for different primary colors may be varied 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 aberrations.

[0141] 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, resulting in three primary color images 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.

[0142] 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.

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

[0144] In some embodiments, light source 530 (FIG. 6) may be configured to emit light at one or more wavelengths outside the range of a viewer's visual perception, e.g., infrared and / or ultraviolet wavelengths. Additionally, the 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.

[0145] 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. FIG. 9A illustrates a cross-sectional side view of an example of a plurality or 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 a portion of multiple 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 waveguide from a location requiring the light to be redirected for incoupling.

[0146] 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 upper major surface) of waveguide 670, internal coupling optical element 710 is disposed on a major surface (e.g., the upper major surface) of waveguide 680, and internal coupling optical element 720 is disposed on a major surface (e.g., the upper major surface) of waveguide 690. In some embodiments, one or more of the internal coupling optical elements 700, 710, 720 may be disposed on the bottom major surface of the respective waveguides 670, 680, 690 (particularly, one or more of the internal coupling optical elements is a reflective polarizing optical element). As shown, the internal coupling optical elements 700, 710, 720 may be disposed on the upper major surface of the respective waveguide 670, 680, 690 (or on top of the next lower waveguide), and in particular, the internal coupling optical elements are transmissive turning optical elements. In some embodiments, the internal coupling optical elements 700, 710, 720 may be disposed within the body of the respective waveguide 670, 680, 690. In some embodiments, as discussed herein, the internal coupling optical elements 700, 710, 720 are wavelength selective, such that they selectively redirect one or more wavelengths of light while transmitting other wavelengths of light. While illustrated on one side or corner of the respective waveguide 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 waveguide 670, 680, 690 in some embodiments.

[0147] As shown, the in-coupling optical elements 700, 710, 720 may be laterally offset from one another, as seen in the illustrated head-on view, in the direction of light propagating through these in-coupling optical elements. 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 different image input devices 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 substantially not receive light from others of the in-coupling optical elements 700, 710, 720.

[0148] 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 associated waveguides 670, 680, 690, respectively. In some other embodiments, optically dispersive elements 730, 740, 750 may be disposed on both the top and bottom major surfaces of associated waveguides 670, 680, 690, respectively, or 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.

[0149] The 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 the waveguides 670, 680, 690). Preferably, the refractive index of the material forming layers 760a, 760b is 0.05 or more or 0.10 below 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.

[0150] Preferably, for ease of manufacturing and other considerations, the materials forming waveguides 670, 680, 690 are similar or the same, and the materials forming layers 760a, 760b are similar or the same. In some embodiments, the materials forming waveguides 670, 680, 690 may differ between one or more waveguides, and / or the materials forming layers 760a, 760b may differ while still maintaining the various refractive index relationships discussed above.

[0151] 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).

[0152] 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.

[0153] 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.

[0154] 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, in-coupling the light into the 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.

[0155] 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.

[0156] 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 elements 800, 810, 820 are exit pupils (EPs) or exit pupil expanders (EPEs) that direct light toward the viewer's eye 210 ( FIG. 7 ). It should be understood that an OPE may 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 of the same waveguide, while allowing the remaining portion of the light to continue propagating down the waveguide. Upon 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, upon 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.

[0157] 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 different wavelengths of light). 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 the light dispersive element (e.g., OPE) 750 and then by TIR to the out-coupling optical element (e.g., EP) 820. The out-coupling optical element 820 then finally out-couples the light ray 790 to a viewer, who also receives the out-coupled light from the other waveguides 670, 680.

[0158] FIG. 9C illustrates a top-down plan view of the multiple stacked waveguide embodiment of FIGS. 9A and 9B. It should be understood that this top-down view may also be referred to as a head-on view, as viewed in the direction of light propagation toward the in-coupling optical elements 800, 810, 820; i.e., the top-down view is a view of the waveguides with image light incident normal to the page. As shown, the 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, arrangements 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 arrangements may correspond to sub-pupils.

[0159] It should be understood that spatially overlapping areas may have lateral overlap of 70% or more, 80% or more, or 90% or more of their areas, as seen in the top and bottom views. On the other hand, laterally shifted areas may have less than 30% overlap, less than 20% overlap, or less than 10% overlap of their areas, as seen in the top and bottom views. In some embodiments, laterally shifted areas have no overlap.

[0160] FIG. 9D illustrates a top-down plan view of another example of multiple stacked waveguides. As shown, the waveguides 670, 680, and 690 may be vertically aligned. However, compared to the configuration of FIG. 9C , the separate optically dispersive elements 730, 740, and 750 and associated outcoupling optical elements 800, 810, and 820 are omitted. Instead, the optically dispersive elements and outcoupling optical elements are effectively superimposed, occupying the same area, as seen in the top-down view. In some embodiments, an optically dispersive element (e.g., an OPE) may be disposed on one major surface of the waveguides 670, 680, and 690, and an outcoupling optical element (e.g., an EPE) may be disposed on the other major surface of those waveguides. Thus, each waveguide 670, 680, and 690 may have superimposed optically dispersive and outcoupling optical elements, collectively referred to as combined OPE / EPEs 1281, 1282, and 1283, respectively. Further details regarding such combined OPE / EPEs can be found in U.S. Patent Application No. 16 / 221,359, filed December 14, 2018, the entire disclosure of which is incorporated herein by reference. Internal coupling optical elements 700, 710, and 720 internally couple and direct light to combined OPE / EPEs 1281, 1282, and 1283, respectively. In some embodiments, as shown, internal coupling optical elements 700, 710, and 720 may be laterally offset (e.g., they are laterally spaced apart, as seen in the top-down views shown) and have a shifted pupil spatial arrangement. Similar to the configuration of FIG. 9C , this laterally offset spatial arrangement facilitates the injection of light of different wavelengths into different waveguides (e.g., from different light sources) on a one-to-one basis.

[0161] 9E illustrates a top-down plan view of another example configuration for the incoupling optical elements 700, 710, 720. As shown, the incoupling optical elements 700, 710, 720 may be offset such that they are spaced apart in a triangular configuration when viewed from a top-down view. It should be understood that in this configuration, the spatial arrangement of the incoupling optical elements 700, 710, 720 may match the spatial arrangement of one or more nanowire LED arrays 1030a, 1030b, 1030c. In some embodiments, these nanowire LED arrays 1030a, 1030b, 1030c may be formed on a common substrate or backplane 1093. In some embodiments, the nanowire LED arrays 1030a, 1030b, 1030c may each be configured to emit light of a different primary color (e.g., red, green, and blue).

[0162] 9F 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 shows some portions of the system 60 in more detail. For example, the waveguide assembly 260 of FIG. 6 may be part of the display 70.

[0163] 9F , display system 60 includes a display 70 and various mechanical and electronic modules and systems to support the functionality of the display 70. The display 70 may be coupled to a frame 80, which is wearable by a display system user or viewer 90 and configured to position the display 70 directly in front of the user's 90 eyes. The display 70, in some embodiments, may be considered eyewear. In some embodiments, a speaker 100 is coupled to frame 80 and configured to be positioned adjacent to the user's 90 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, 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, environmental sensors 112 may include one or more cameras, which may be positioned, for example, facing outward, to capture images similar to at least a portion of user 90's normal field of view. In some embodiments, display system also may include ambient sensor 120a, which may be separate from frame 80 and mounted on user 90's body (e.g., user 90's head, torso, limbs, etc.). Ambient sensor 120a, in some embodiments, may be configured to obtain data characterizing user 90's physiological state.For example, the sensor 120a may be an electrode.

[0164] 9F , 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, integrated into headphones, or otherwise removably attached to user 90 (e.g., in a backpack-style configuration, in a belt-linked configuration). Similarly, sensor 120 a may be operably coupled to local data processing module 140 by a communication link 120 b, such as wired or wireless connectivity. Local processing and data module 140 may include a hardware processor and digital memory, such as non-volatile memory (e.g., flash memory or a hard disk drive), both of which may be 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 (such as cameras), 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 processing or retrieval and subsequent passage to display 70. 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 on frame 80 or may be a freestanding structure that communicates with local processing and data module 140 by a wired or wireless communication path.

[0165] 9F , in some embodiments, remote processing module 150 may include one or more processors configured to analyze and process data and / or image information, including, for example, one or more central processing units (CPUs), graphics processing units (GPUs), special-purpose processing hardware, etc. In some embodiments, remote data repository 160 may include a digital data storage facility, which may be available through the Internet or other networking configuration in a “cloud” resource configuration. In some embodiments, remote data repository 160 may include one or more remote servers, which provide information, e.g., information for generating virtual 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 in 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.

[0166] FIG. 10 illustrates an example of a wearable display system with a light projection system 910 having a spatial light modulator 930 and a separate light source 940. The light source 940 may include one or more light emitters and illuminate the spatial light modulator (SLM) 930. A lens structure 960 may be used to focus the light from the light source 940 onto the SLM 930. A beam splitter (e.g., a polarizing beam splitter (PBS)) 950 reflects the light from the light source 940 onto the spatial light modulator 930, which reflects and modulates the light. The reflected modulated light, also referred to as image light, then propagates through the beam splitter 950 to the eyepiece 920. Another lens structure, projection optics 970, may be utilized to converge or focus the image light onto the eyepiece 920. The eyepiece 920 may include one or more waveguides or waveguides that relay the modulated light to the eye 210.

[0167] As described herein, a separate light source 940 and associated lens structure 960 may undesirably add weight and size to a wearable display system, which may reduce the comfort of the display system, especially for a user wearing the display system for extended periods of time.

[0168] Additionally, light source 940, in conjunction with SLM 930, may consume energy inefficiently. For example, light source 940 may illuminate the entire SLM 930. SLM 930 then selectively reflects the light toward eyepiece 920. Thus, not all of the light produced by light source 940 may be used to form an image. Some of this light, for example, light corresponding to dark areas of the image, is not reflected back to eyepiece 920. As a result, light source 940 utilizes energy to generate light to illuminate the entire SLM 930, but only a certain percentage of this light may be needed to form some images.

[0169] Furthermore, as described herein, in some cases, the SLM 930 may modulate light using micromirrors to selectively reflect incident light or using liquid crystal molecules to modify the amount of light reflected from an underlying mirror. As a result, such devices require physical movement of optical elements (e.g., micromirrors or liquid crystal molecules, respectively) to modulate light from the light source 940. The physical movement required to modulate light and encode it with image information, e.g., corresponding to a pixel, may occur relatively slowly compared to, for example, the ability to turn an LED or OLED “on” or “off.” This relatively slow movement may limit the frame rate of the display system and may be visible, for example, as motion blur, color breakup, and / or a presented image that is misaligned with the user's head pose or changes in that pose.

[0170] Advantageously, wearable displays utilizing nanowire LED microdisplays as disclosed herein may facilitate wearable display systems with relatively low weight and bulk, high energy efficiency, and high frame rates, with low motion blur and low latency from motion to image rendering. Low blur and low latency from motion to image rendering are further discussed in U.S. Provisional Application No. 62 / 786,199, filed December 28, 2018, the entire disclosure of which is incorporated herein by reference. Additionally, compared to scanning fiber displays, nanowire LED microdisplays may avoid artifacts caused by the use of coherent light sources.

[0171] 11A, an example of a wearable display system is illustrated with an optical projection system 1010 having multiple nanowire LED microdisplays 1030a, 1030b, 1030c. Light from the microdisplays 1030a, 1030b, 1030c is combined by an optical combiner 1050 and directed toward an eyepiece 1020, which relays the light to the user's eye 210. Projection optics 1070 may be provided between the optical combiner 1050 and the eyepiece 1020. In some embodiments, the eyepiece 1020 may be a waveguide assembly including one or more waveguides. In some embodiments, the optical projection system 1010 and the eyepiece 1020 may be supported (e.g., mounted) on a frame 80 (FIG. 9F).

[0172] In some embodiments, the microdisplays 1030a, 1030b, 1030c may be monochrome microdisplays, each outputting light of a different primary color to provide a monochrome image that is combined to form a full-color image, as discussed herein.

[0173] In some other embodiments, the microdisplays 1030a, 1030b, and 1030c may each be a full-color display configured to output light of all primary colors. For example, the microdisplays 1030a, 1030b, and 1030c each include red, green, and blue light emitters. The microdisplays 1030a, 1030b, and 1030c may be identical and may display the same image. However, utilizing multiple microdisplays may provide advantages for increasing the brightness and brightness dynamic range of the image by combining light from the multiple microdisplays to form a single image. In some embodiments, two or more (e.g., three) microdisplays may be utilized, and the optical combiner 1050 is configured to combine light from all of these microdisplays.

[0174] 11A , the microdisplays 1030a, 1030b, and 1030c may be configured to emit image light 1032a, 1032b, and 1032c, respectively. If the microdisplays are monochrome microdisplays, the image light 1032a, 1032b, and 1032c may each be a different primary color. The optical combiner 1050 receives the image light 1032a, 1032b, and 1032c and effectively combines the light so that the light generally propagates in the same direction, e.g., toward the projection optics 1070. In some embodiments, the optical combiner 1050 may be a dichroic X-cube prism having reflective interior surfaces that redirect the image light 1032a, 1032b, and 1032c to the projection optics 1070. It should be understood that the projection optics 1070 may be a lens structure including one or more lenses that converge or focus the image light onto the eyepiece 1020. The eyepiece 1020 then relays the image light 1032a, 1032b, 1032c to the eye 210.

[0175] In some embodiments, the eyepiece 1020 may include multiple stacked waveguides 1020a, 1020b, 1020c, each with a separate internal coupling optical element 1022a, 1022b, 1022c. In some embodiments, the number of waveguides is proportional to the number of primary colors provided by the microdisplays 1030a, 1030b, 1030c. For example, if there are three primary colors, the number of waveguides in the eyepiece 1020 may include a set of three waveguides or multiple sets of three waveguides each. In some embodiments, each set may output light with a wavefront divergence corresponding to a particular depth plane, as discussed herein. It should be understood that waveguides 1020a, 1020b, 1020c and in-coupling optical elements 1022a, 1022b, 1022c may correspond to waveguides 670, 680, 690 and in-coupling optical elements 700, 710, 720, respectively, of Figures 9A-9C. As viewed from the projection optics 1070, in-coupling optical elements 1022a, 1022b, 1022c may be offset laterally such that they, at least in part, do not overlap as seen in such views.

[0176] As shown, the various internal coupling optical elements disclosed herein (e.g., internal coupling optical elements 1022a, 1022b, 1022c) may be disposed on a major surface of an associated waveguide (e.g., waveguides 1020a, 1020b, 1020c, respectively). In addition, and as also shown, the major surface on which a given internal coupling optical element is disposed may be the back surface of the waveguide. In such a configuration, the internal coupling optical element may be a reflective light redirecting element, which internally couples light through the associated waveguide by reflecting the light at an angle that supports TIR. In certain other configurations, the internal coupling optical element may be disposed on the front surface of the waveguide (closer to the projection optics 1070 than the back surface). In such a configuration, the internal coupling optical element may be a transmissive light redirecting element, which internally couples light by changing the propagation direction of the light as it is transmitted through the internal coupling optical element. It should be understood that any of the incoupling optical elements disclosed herein may be reflective or transmissive incoupling optical elements.

[0177] 11A , image light 1032a, 1032b, 1032c from different ones of the microdisplays 1030a, 1030b, 1030c may follow different paths to the eyepiece 1020 such that they impinge on different ones of the incoupling optical elements 1022a, 1022b, 1022c. If the image light 1032a, 1032b, 1032c includes light of different primary colors, the associated incoupling optical elements 1022a, 1022b, 1022c may be configured to selectively incoupling light of different wavelengths, for example, as described above with respect to the incoupling optical elements 700, 710, 720 of FIGS. 9A-9C .

[0178] 11A , the optical combiner 1050 may be configured to redirect the image light 1032a, 1032b, 1032c emitted by the microdisplays 1030a, 1030b, 1030c so that the image light propagates along different optical paths to impinge on the appropriate associated one of the internal combining optical elements 1022a, 1022b, 1022c. Thus, the optical combiner 1050 combines the image light 1032a, 1032b, 1032c in the sense that the image light is output from a common face of the optical combiner 1050, but the light exits the optical combiner in slightly different directions. For example, the reflective interior surfaces 1052, 1054 of the X-cube prism may each be angled to direct the image light 1032a, 1032b, 1032c along different paths to the eyepiece 1020. As a result, the image light 1032a, 1032b, 1032c may be incident on different associated ones of the in-coupling optical elements 1022a, 1022b, 1022c. In some embodiments, the microdisplays 1030a, 1030b, 1030c may be appropriately angled relative to the reflective interior surfaces 1052, 1054 of the X-cube prism to provide the desired light path to the in-coupling optical elements 1022a, 1022b, 1022c. For example, a face of one or more of the microdisplays 1030a, 1030b, 1030c may be angled to match a face of the optical combiner 1050 so that image light emitted by the microdisplay is incident at the appropriate angle on the reflective interior surfaces 1052, 1054 and propagates toward the associated in-coupling optical element 1022a, 1022b, or 1022c. In some embodiments, as discussed herein, microwire LEDs may be advantageously engineered to provide directional light output. For each microdisplay 1030a, 1030b, 1030c, a dominant direction of light output may be selected to propagate light along an appropriate optical path from each of these microdisplays to a corresponding one of the incoupling optical elements 1022a, 1022b, and 1022c.It should be understood that in addition to a cube, optical combiner 1050 may take the form of various other polyhedrons. For example, optical combiner 1050 may be in the shape of a right-angled prism having at least two faces rather than a square.

[0179] 11A , in some embodiments, the monochrome microdisplay 1030b directly facing the output surface 1051 may advantageously output green light. It should be understood that the reflective surfaces 1052, 1054 may have optical losses when reflecting light from the microdisplay. Additionally, the human eye is most sensitive to the color green. As a result, the monochrome microdisplay 1030b facing the output surface 1051 preferably outputs green light so that the green light can travel directly through the optical combiner 1050 without having to be reflected to be output from the optical combiner 1050. However, it will be understood that the green monochrome microdisplay may face another surface of the optical combiner 1050 in some other embodiments.

[0180] As discussed herein, the perception of a full-color image by a user can be achieved in some embodiments using time-division multiplexing. For example, different ones of the nanowire LED microdisplays 1030a, 1030b, 1030c can be activated at different times to generate different primary color images. In such embodiments, the different primary color images forming a single full-color image can be displayed sequentially quickly enough that the human visual system does not perceive the primary color images as being displayed at different times. That is, the different primary color images forming the single full-color image can all be displayed within a duration short enough that the user perceives the primary color images as being presented simultaneously, rather than being separated in time. For example, it should be understood that the human visual system can have a flicker fusion threshold. The flicker fusion threshold can be understood as the duration beyond which the human visual system is unable to distinguish between images presented at different times. Images presented within that duration are fused, or combined, and as a result, can be perceived by the user as being presented simultaneously. Flickering images with a temporal gap between images outside that duration will not combine, and image flicker will be perceptible. In some embodiments, the duration is 1 / 60 seconds or less, which corresponds to a frame rate of 60 Hz or greater. Preferably, image frames for any individual eye are provided to the user at a frame rate equal to or greater than the duration of the user's flicker fusion threshold. For example, the frame rate per left or right eyepiece may be 60 Hz or greater, or 120 Hz or greater, resulting in a frame rate provided by the optical projection system 1010 that may be 120 Hz or greater, or 240 Hz or greater, in some embodiments. It should be appreciated that time-division multiplexing may advantageously reduce the computational load on a processor (e.g., a graphics processor) utilized to form the displayed image.In some other embodiments, such as when sufficient computing resources are available, all primary color images forming a full color image may be displayed simultaneously by the microdisplays 1030a, 1030b, 1030c.

[0181] As discussed herein, each of the microdisplays 1030a, 1030b, 1030c may include an array of nanowire LED light emitters for forming an image. Figure 11B illustrates an example of an array 1042 of light emitters 1044. If the associated microdisplay is a monochrome microdisplay, the light emitters 1044 may all be configured to emit light of the same color.

[0182] If the associated microdisplay is a full-color microdisplay, different ones of the light emitters 1044 may be configured to emit light of different colors. In such an embodiment, the light emitters 1044 may be considered subpixels and may be arranged in groups, with each group having at least one light emitter configured to emit light of each primary color. For example, if the primary colors are red, green, and blue, each group may have at least one red subpixel, at least one green subpixel, and at least one blue subpixel.

[0183] Although the light emitters 1044 are shown arranged in a grid pattern for ease of illustration, it will be understood that the light emitters 1044 may have other regularly repeating spatial arrangements. For example, the number of light emitters of different primary colors may vary, the size of the light emitters may vary, the shape of the light emitters and / or the shape created by a group of light emitters may vary, etc.

[0184] FIG. 11C illustrates a cross-sectional side view of the nanowire LED array 1042 of FIG. 11B. In some embodiments, the nanowire LED array 1042 may include one or more nanowires 1094, which may be light-emitting diode elements. In some embodiments, the nanowire array may be a uniform array of nanowires 1094. By way of example, the nanowires 1094 may have a height of 10-10,000 nm, 100-1,000 nm, 500-1,000 nm, or 700-1,000 nm, and a width of 10-1,000 nm, including, for example, 200 nm or less, or 100 nm or less, and greater than 10 nm. In some embodiments, the nanowires 1094 may be cylindrical, and the width may correspond to the diameter of the nanowire. The nanowires 1094 may be grouped into pixels, defined by electrical contacts 1095 shared by each group of nanowires 1094. It should be understood that each group of nanowires 1094 forming a pixel may share a second electrical contact (not shown). Each pixel, which may include a group of nanowires, may be an individual light emitter 1044.

[0185] Continuing with reference to FIG. 11C , the nanowire LED may utilize inorganic materials, e.g., III-V materials such as GaAs, GaN, and / or GaIn, and may reside on a substrate 1093, which may be a backplane containing various electronic devices, such as CMOS devices, for controlling the operation of the nanowire LED. An example of a GaN material includes InGaN, which in some embodiments may be used to form blue or green light emitters. While various embodiments may utilize other materials, GaN may advantageously be used to generate the entire visible spectrum by simply controlling the In doping concentration to obtain the desired electronic bandgap tuning, resulting in emission of light at the desired wavelength. Thus, the nanowires may be monochrome, with each grouping made to emit the same color, or different pixels may be made to emit light of different colors by using different doping levels for the different pixels. As a result, blue, green, and red emitters may all be formed on a single GaN semiconductor, thereby simplifying fabrication and increasing manufacturing throughput. Additionally, GaN and InGaN may be grown on standard semiconductor materials such as silicon, which allows integration with associated microelectronic circuitry (CMOS Si backplane) to drive the nanowire LED pixels.

[0186] Examples of GaIn materials include AlGaInP, which may be used to form red light emitters in some embodiments.

[0187] Referring now to FIG. 12 , another example of a wearable display system is illustrated, which includes a light projection system having multiple nanowire LED microdisplays 1030 a, 1030 b, and 1030 c. The illustrated display system is similar to that of FIG. 11A , except that the optical combiner 1050 has a standard X-cube prism configuration and includes light redirecting structures 1080 a and 1080 c to modify the angle of incidence of light onto the reflective surfaces 1052 and 1054 of the X-cube prism. It should be understood that a standard X-cube prism configuration would receive light normal to the faces of the X-cube and redirect this light at 45° so that it exits the lateral faces of the X-cube at a normal angle. However, this would cause the image light 1032 a, 1032 b, and 1032 c to be incident on the same internal coupling optical element of the eyepiece 1020. Light redirecting structures 1080a, 1080c may be utilized to provide different paths for the image light 1032a, 1032b, 1032c so that the image light is incident on associated ones of the internal coupling optical elements 1022a, 1022b, 1022c of the waveguide assembly.

[0188] In some embodiments, the light redirecting structures 1080a, 1080c may be lens structures. It should be understood that the lens structures may be configured to receive incident light and redirect the incident light at an angle such that the light reflects off a corresponding one of the reflective surfaces 1052, 1054 and propagates along the optical path toward a corresponding one of the internal coupling optical elements 1022a, 1022c. As an example, the light redirecting structures 1080a, 1080c may include microlenses, nanolenses, reflective wells, metasurfaces, and liquid crystal gratings. In some embodiments, the microlenses, nanolenses, reflective wells, metasurfaces, and liquid crystal gratings may be organized in an array. For example, each light emitter of the microdisplays 1030a, 1030c may be matched with one microlens. In some embodiments, the microlenses or reflective wells may be asymmetric and / or the light emitters may be positioned off-center relative to the microlenses to redirect light in a particular direction. Additionally, in some embodiments, the light redirecting structures 1080a, 1080c may be collimators, which narrow the angular emission profile of the associated light emitter and ultimately increase the amount of light in-coupled into the eyepiece 1020. Further details regarding such light redirecting structures 1080a, 1080c are discussed below with respect to Figures 24A-27C.

[0189] 12 , in some embodiments, one or both of the light redirecting structures 1080 a, 1080 c may be omitted, and the nanowire LEDs of the nanowire LED microdisplays 1030 a, 1030 b, 1030 c may be configured to emit light with a desired directionality and propagate along a light path to the associated incoupling optical elements 1022 a, 1022 b, 1022 c. As discussed herein, the nanowire LEDs may be engineered with a selected directionality, which may be non-normal to the light output surface of the associated microdisplay. Thus, in some embodiments, the physical design and composition of each nanowire LED of the nanowire LED microdisplays 1030 a, 1030 b, 1030 c may be selected to provide light output in different directions, as shown.

[0190] 13A , in some embodiments, two or more of the in-coupling optical elements 1022 a, 1022 b, 1022 c may overlap (e.g., as seen in a head-on view in the direction of light propagation into the in-coupling optical elements 1022 a, 1022 b, 1022 c). FIG. 13A illustrates an example of a side view of a wearable display system with an optical projection system 1010 having multiple nanowire LED microdisplays 1032 a, 1032 b, 1032 c and an eyepiece 1020 with overlapping optical in-coupling optical elements 1022 a, 1022 c and a non-overlapping optical in-coupling optical element 1022 b. As shown, the in-coupling optical elements 1022 a, 1022 c overlap, while the in-coupling optical element 1022 b is laterally offset. In other words, the internal coupling optical elements 1022a, 1022c are aligned directly within the paths of the image lights 1032a, 1032c, while the image light 1032b follows a different path to the eyepiece 1020 so that it is incident on an area of ​​the eyepiece 1020 that is laterally shifted relative to the area on which the image lights 1032a, 1032c are incident.

[0191] As shown, a distinction between the paths for image light 1032b and image light 1032a, 1032c may be established using light redirecting structures 1080a, 1080c. In some embodiments, image light 1032b from nanowire LED microdisplay 1030b travels directly through optical combiner 1052. Image light 1032a from nanowire LED microdisplay 1032a is redirected by light redirecting structure 1080a to reflect from reflective surface 1054 and out of optical combiner 1050 propagating in the same direction as image light 1032c. It should be appreciated that image light 1032c from nanowire LED microdisplay 1032c is redirected by light redirecting structure 1080c to reflect from reflective surface 1052 at an angle such that image light 1032c out of optical combiner 1050 propagating in the same direction as image light 1032b. Thus, the redirection of light by light redirecting structures 1080a, 1080c and the angles of reflective surfaces 1052, 1054 are configured to provide a common path for image light 1032a, 1032c out of optical combiner 1050, which common path is different from the path of image light 1032b. In some other embodiments, one or both of light redirecting structures 1080a, 1080c may be omitted, and reflective surfaces 1052, 1054 within optical combiner 1050 may be configured to reflect image light 1032a, 1032c in appropriate individual directions so that it exits optical combiner 1050 and propagates in the same direction, different from the direction of image light 1032b. Thus, after propagating through projection optics 1070, image light 1032a, 1032c emerges from one exit pupil, while image light 1032b emerges from another exit pupil. In this configuration, optical projection system 1010 may be referred to as a two-pupil projection system.

[0192] In some embodiments, the optical projection system 1010 may have a single output pupil and may be referred to as a single-pupil projection system. In such embodiments, the optical projection system 1010 may be configured to direct image light 1032a, 1032b, 1032c onto a single common area of ​​the eyepiece 1020. Such a configuration is shown in FIG. 13B, which illustrates a wearable display system with the optical projection system 1010 having multiple nanowire LED microdisplays 1030a, 1030b, 1030c configured to direct light to a single optical in-coupling area of ​​the eyepiece 1020. In some embodiments, as discussed further herein, the eyepiece 1020 may include a stack of waveguides with overlapping optical in-coupling optical elements. In some other embodiments, a single optical in-coupling optical element may be configured to in-couple light of all primary colors into a single waveguide. In some embodiments, the single waveguide may be formed from an optically transparent high-index material, such as silicon carbide (SiC).

[0193] The display system of Figure 13B is similar to the display system of Figure 13A, except for the omission of light redirecting structures 1080a, 1080c and the use of waveguide 1020a associated with in-coupling optical element 1122a. As shown, in-coupling optical element 1122a in-couples each of image lights 1032a, 1032b, 1032c into waveguide 1020a, which then relays the image light to eye 210. In some embodiments, in-coupling optical element 1122a may include a diffraction grating. In some embodiments, in-coupling optical element 1122a is a metasurface and / or a liquid crystal grating.

[0194] In some other embodiments, the waveguide 1020a may include two or more spaced-apart in-coupling optical elements, each configured to in-couple light of a different wavelength range (e.g., different color). It should be understood that the spaced-apart in-coupling optical elements may be spatially separated as seen in a top-down plan view (as viewed head-on in the direction of light impinging on the waveguide 1020a). For example, waveguide 1020a may include internal coupling optical elements 1022a, 1022b, and 1022c on that single waveguide (e.g., arranged but spatially separated on the same waveguide 1020a, as shown in FIG. 11A (side view) or FIG. 9C or 9D (top and bottom views)), where the internal coupling optical elements are spatially separated such that different colors of image light from optical projection system 1010 uniquely impinge on associated ones of internal coupling optical elements 1022a, 1022b, and 1022c. In some embodiments, two spatially separated internal coupling optical elements may be utilized, at least one of the internal coupling optical elements configured to internally couple multiple different colors of light. For example, in such an arrangement, the internal coupling optical elements may be arranged similarly to internal coupling elements 1022a, 1022b of FIG. 13A (side view), but spatially separated on the same waveguide 1020a.

[0195] As discussed herein, in some embodiments, the nanowire LED microdisplays 1030a, 1030b, 1030c may be monochrome microdisplays configured to emit light of different colors. In some embodiments, one or more of the nanowire LED microdisplays 1030a, 1030b, 1030c may have groups of light emitters configured to emit light of two or more, but not all, primary colors. For example, a single nanowire LED microdisplay may have groups of light emitters with at least one light emitter per group configured to emit blue light and at least one light emitter per group configured to emit green light, while separate nanowire LED microdisplays on different faces of the X-cube 1050 may have light emitters configured to emit red light. In some other embodiments, the nanowire LED microdisplays 1030a, 1030b, 1030c may each be a full-color display having light emitters of all primary colors, respectively. As described herein, utilizing multiple similar microdisplays can provide advantages for dynamic range and increased display brightness.

[0196] In some embodiments, a single full-color nanowire LED microdisplay may be utilized. FIG. 14 illustrates an example of a wearable display system with a single nanowire LED microdisplay 1030b. The wearable display system of FIG. 14 is similar to the wearable display systems of FIGS. 13A and 13B, except that the single nanowire LED microdisplay 1030b is a full-color microdisplay configured to emit light of all primary colors. As shown, the microdisplay 1030b emits image light 1032a, 1032b, 1032c for each primary color. In such an embodiment, the optical combiner 1050 (FIG. 13B) may be omitted, which may advantageously reduce the weight and size of the wearable display system relative to a system with an optical combiner.

[0197] As discussed above, the internal coupling optical elements of the eyepiece 1020 may take on a variety of configurations. Some example configurations for the eyepiece 1020 are discussed below in connection with Figures 15-23C.

[0198] Figure 15 illustrates a side view of an example eyepiece 1020 having a stack of waveguides 1020a, 1020b, 1020c with overlapping in-coupling optical elements 1022a, 1022b, 1022c, respectively. It should be understood that the illustrated waveguide stack may be utilized in place of the single illustrated waveguide 1020a of Figures 13B and 14. As discussed herein, the in-coupling optical elements 1022a, 1022b, 1022c are each configured to in-couple light having a specific color (e.g., light of a particular wavelength or range of wavelengths). In the illustrated orientation of the eyepiece 1020, where the image light propagates vertically down the page toward the eyepiece 1020, the internal coupling optical elements 1022a, 1022b, 1022c are aligned vertically with each other (e.g., along an axis parallel to the propagation direction of the image light 1032a, 1032b, 1032c) so that they spatially overlap each other, as seen in the top-down view (a head-on view in the direction of the image light 1032a, 1032b, 1032c propagating into the internal coupling optical elements).

[0199] Continuing with reference to FIG. 15, as discussed herein, the projection system 1010 (FIGS. 13, 14) is configured to output a first monochrome color image, a second monochrome color image, and a third monochrome color image (e.g., red, green, and blue color images) through a single pupil of the projection system, the monochrome images being formed by image light 1032a, 1032b, and 1032c, respectively. The internal coupling optical element 1022c is configured to internally couple image light 1032c into the waveguide 1020c for a first color image to propagate through the waveguide 1020c by multiple total internal reflections at the top and bottom major surfaces of the waveguide 1020c, the internal coupling optical element 1022b is configured to internally couple image light 1032b into the waveguide 1020b for a second color image to propagate through the waveguide 1020b by multiple total internal reflections at the top and bottom major surfaces of the waveguide 1020b, and the internal coupling optical element 1022a is configured to internally couple image light 1032a into the waveguide 1020a for a third color image to propagate through the waveguide 1020a by multiple total internal reflections at the top and bottom major surfaces of the waveguide 1020a.

[0200] As discussed herein, the in-coupling optical element 1022c is preferably configured to in-couple substantially all incident light 1032c corresponding to the first color image into the associated waveguide 1020c, while allowing substantially all incident light 1032b, 1032a corresponding to the second and third color images, respectively, to be transmitted without being in-coupled. Similarly, the in-coupling optical element 1022b is preferably configured to in-couple substantially all incident image light 1032b corresponding to the second color image into the associated waveguide 1020b, while allowing substantially all incident light corresponding to the third color image to be transmitted without being in-coupling.

[0201] It should be understood that in practice, the various in-coupling optical elements may not have perfect selectivity. For example, some of the image light 1032b, 1032a may be undesirably in-coupled into waveguide 1020c by in-coupling optical element 1022c, and some of the incident image light 1032a may be undesirably in-coupled into waveguide 1020b by in-coupling optical element 1022b. Furthermore, some of the image light 1032c may be transmitted through in-coupling optical element 1022c and in-coupled into waveguides 1020b and / or 1020a by in-coupling optical elements 1020b and / or 1020a, respectively. Similarly, some of the image light 1032b may be transmitted through in-coupling optical element 1022b and in-coupled into waveguide 1020a by in-coupling optical element 1022a.

[0202] Coupling image light for a color image into an unintended waveguide can result in undesirable optical effects, such as crosstalk and / or afterimages. For example, coupling image light 1032c for a first color image into unintended waveguides 1020b and / or 1020a can result in undesirable crosstalk between the first color image, the second color image, and / or the third color image, and / or can result in undesirable afterimages. As another example, coupling image light 1032b, 1032a for the second or third color image, respectively, into unintended waveguides 1020c can result in undesirable crosstalk between the first color image, the second color image, and / or the third color image, and / or can result in undesirable afterimages. In some embodiments, these undesirable optical effects can be mitigated by providing a color filter (e.g., a light-absorbing color filter) that can reduce the amount of incident light that is in-coupled into the waveguide where it is not intended.

[0203] FIG. 16 illustrates a side view of an example of a stack of waveguides with color filters to reduce image retention or crosstalk between the waveguides. The eyepiece 1020 of FIG. 16 is similar to that of FIG. 15 except for the presence of one or more color filters 1024c, 1024b, and 1028, 1026. Color filters 1024c, 1024b are configured to reduce the amount of light that is unintentionally incoupled into waveguides 1020b and 1020a, respectively. Color filters 1028, 1026 are configured to reduce the amount of unintentionally incoupled image light propagating through waveguides 1020b, 1020c, respectively.

[0204] 16 , a pair of color filters 1026 disposed on the upper and lower major surfaces of waveguide 1020c may be configured to absorb image light 1032a, 1032b that may be unintentionally incoupled into waveguide 1020c. In some embodiments, color filter 1024c disposed between waveguides 1020c and 1020b is configured to absorb image light 1032c that is not incoupled but is transmitted through incoupling optical element 1022c. A pair of color filters 1028 disposed on the upper and lower major surfaces of waveguide 1020b is configured to absorb image light 1032a that is incoupling into waveguide 1020b. Color filter 1024b disposed between waveguides 1020b and 1020a is configured to absorb image light 1032b that is transmitted through incoupling optical element 710.

[0205] In some embodiments, the color filters 1026 on each major surface of the waveguide 1020c are similar and configured to absorb light of both wavelengths of the image light 1032a, 1032b. In some other embodiments, the color filters 1026 on one major surface of the waveguide 1020c may be configured to absorb light of the color of the image light 1032a, and the color filters on the other major surface may be configured to absorb light of the color of the image light 1032b. In either arrangement, the color filters 1026 may be configured to selectively absorb the image light 1032a, 1032b propagating through the waveguide 1020c by total internal reflection. For example, upon TIR bounce of the image light 1032a, 1032b from the major surfaces of the waveguide 1020c, the image light 1032a, 1032b contacts the color filters 1026 on those major surfaces, and a portion of that image light is absorbed. Preferably, due to the selective absorption of image light 1032a, 1032b by color filter 1026, the propagation of image light 1032c incoupled via TIR through waveguide 1020c is not significantly affected.

[0206] Similarly, the plurality of color filters 1028 may be configured as absorption filters that absorb the incoupled image light 1032a propagating through the waveguide 1020b by total internal reflection. Upon TIR bouncing of the image light 1032a from the major surfaces of the waveguide 1020b, the image light 1032a contacts the color filters 1028 on those major surfaces, and a portion of the image light is absorbed. Preferably, the absorption of the image light 1032a is selective and does not affect the propagation of the incoupled image light 1032b, which also propagates via TIR through the waveguide 1020b.

[0207] 16 , color filters 1024c and 1024b may also be configured as light-absorbing filters. Color filter 1024c may be substantially transparent to light of the color of image light 1032a, 1032b, such that image light 1032a, 1032b is transmitted through color filter 1024c with little or no attenuation, while light of the color of image light 1032c is selectively absorbed. Similarly, color filter 1024b may be substantially transparent to light of the color of image light 1032a, such that incident image light 1032a is transmitted through color filter 1024b with little or no attenuation, while light of the color of image light 1032b is selectively absorbed. Color filter 1024c may be disposed on a major surface (e.g., the upper major surface) of waveguide 1020b, as shown in FIG. 16 . Alternatively, color filter 1024c may be disposed on a separate substrate positioned between waveguides 1020c and 1020b. Similarly, color filter 1024b may be disposed on a major surface (e.g., the upper major surface) of waveguide 1020a. Alternatively, color filter 1024b may be disposed on a separate substrate positioned between waveguides 1020b and 1020a. It should be understood that color filters 1024c and 1024b may be vertically aligned with a single pupil of the projector that outputs image light 1032a, 1032b, 1032c (in an orientation where image light 1032a, 1032b, 1032c propagates perpendicular to waveguide stack 1020, as shown).

[0208] In some embodiments, the color filters 1026 and 1028 may have a single-pass attenuation coefficient of less than about 10% (e.g., less than or equal to about 5%, less than or equal to about 2%, and greater than about 1%) to avoid significant undesirable absorption of light propagating through the thickness of the waveguides 1020c, 1020b (e.g., light of the color of the image light 1032a, 1032b propagating from the surrounding environment and / or other waveguides through the waveguides 1020c, 1020b). Various embodiments of the color filters 1024c and 1024b may be configured to have a low attenuation coefficient for wavelengths to be transmitted and a high attenuation coefficient for wavelengths to be absorbed. For example, in some embodiments, color filter 1024c may be configured to transmit greater than 80%, greater than 90%, or greater than 95% of incident light having the color of image light 1032a, 1032b and absorb greater than 80%, greater than 90%, or greater than 95% of incident light having the color of image light 1032a. Similarly, color filter 1024b may be configured to transmit greater than 80%, greater than 90%, or greater than 95% of incident light having the color of image light 1032a and absorb greater than 80%, greater than 90%, or greater than 95% of incident light having the color of image light 1032b.

[0209] In some embodiments, color filters 1026, 1028, 1024c, 1024b may include a layer of color-selective light-absorbing material deposited on one or both surfaces of waveguides 1020c, 1020b, and / or 1020a. Color-selective light-absorbing materials may include dyes, inks, or other light-absorbing materials such as metals, semiconductors, and dielectrics. In some embodiments, the light absorption of materials such as metals, semiconductors, and dielectrics may be made color-selective by utilizing these materials to form subwavelength gratings (e.g., gratings that do not diffract light). Gratings may be made from plasmonics (e.g., gold, silver, and aluminum) or semiconductors (e.g., silicon, amorphous silicon, and germanium).

[0210] The color-selective material may be deposited on a substrate using various deposition methods. For example, the color-selective light-absorbing material may be deposited on a substrate using jet deposition techniques (e.g., inkjet deposition). Inkjet deposition can facilitate the deposition of thin layers of color-selective light-absorbing material. Because inkjet deposition allows deposition to be localized onto selected areas of the substrate, inkjet deposition offers a high degree of control over the thickness and composition of the layer of color-selective light-absorbing material, including providing non-uniform thicknesses and / or compositions across the substrate. In some embodiments, the color-selective light-absorbing material deposited using inkjet deposition may have a thickness of about 10 nm to about 1 micron (e.g., about 10 nm to about 50 nm, about 25 nm to about 75 nm, about 40 nm to about 100 nm, about 80 nm to about 300 nm, about 200 nm to about 500 nm, about 400 nm to about 800 nm, about 500 nm to about 1 micron, or any value within a range / subrange defined by any of these values). Controlling the thickness of the deposited layer of color-selectively absorbing material can be advantageous in achieving a color filter with a desired attenuation coefficient. Furthermore, layers with different thicknesses may be deposited on different portions of the substrate. Additionally, different compositions of color-selectively absorbing material may be deposited on different portions of the substrate using inkjet deposition. Such variations in composition and / or thickness can advantageously allow for location-specific variations in absorptivity. For example, in areas of the waveguide where transmission of light from the surroundings is not required (to allow the viewer to see the surrounding environment), the composition and / or thickness may be selected to provide high absorptivity or attenuation of selected wavelengths of light. Other deposition methods, such as coating, spin-coating, spraying, etc., may also be employed to deposit color-selectively absorbing material on the substrate.

[0211] Figure 17 illustrates a top-down view example of the waveguide assembly of Figures 15 and 16. As shown, the in-coupling optical elements 1022a, 1022b, 1022c spatially overlap. Additionally, the waveguides 1020a, 1020b, 1020c may be vertically aligned with each waveguide's associated optically dispersive element 730, 740, 750 and associated external coupling optical element 800, 810, 820. The in-coupling optical elements 1022a, 1022b, 1022c are configured to in-couple incident image light 1032a, 1032b, 1032c (Figures 15 and 16), respectively, into the waveguides 1020a, 1020b, 1020c, respectively, such that the image light propagates toward the associated optically dispersive element 730, 740, 750 by TIR.

[0212] Figure 18 illustrates another embodiment of a top-down view of the waveguide assembly of Figures 15 and 16. As in Figure 17, in-coupling optical elements 1022a, 1022b, 1022c spatially overlap, and waveguides 1020a, 1020b, 1020c are vertically aligned. However, in place of each waveguide's associated optically dispersive element 730, 740, 750 and associated out-coupling optical element 800, 810, 820, there is a combined OPE / EPE 1281, 1282, 1283, respectively. The internal coupling optical elements 1022a, 1022b, 1022c are configured to internally couple the incident image light 1032a, 1032b, 1032c (Figures 15 and 16) into the waveguides 1020a, 1020b, 1020c, respectively, so that the image light propagates by TIR towards the associated combined OPE / EPE 1281, 1282, 1283.

[0213] While Figures 15-18 show overlapping in-coupling optical elements for a single-pupil configuration of the display system, it should be understood that the display system may have a two-pupil configuration in some embodiments. In such configurations where three primary colors are utilized, image light for two colors may have overlapping in-coupling optical elements, while image light for a third color may have a laterally shifted in-coupling optical element. For example, the optical combiner 1050 (Figures 11A, 12, 13A-13B) and / or light redirecting structures 1080a, 1080c may be configured to direct image light through the projection optics 1070 such that image light for two colors is incident directly onto the overlapping area of ​​the eyepiece 1020, while another color of image light is incident onto a laterally shifted area. For example, reflective surfaces 1052, 1054 (FIG. 11A) may be angled so that image light of one color follows a common light path with image light from nanowire LED microdisplay 1030b, while image light of another color follows a different light path. In some embodiments, rather than having both light redirecting structures 1080a, 1080c (FIG. 12), one of these light redirecting structures may be omitted so that only light from one of microdisplays 1030a, 1030c is angled to provide a different light path from light emitted by the other two microdisplays.

[0214] Figure 19A illustrates a side view of an example eyepiece having a stack of waveguides with some overlapping in-coupling optical elements and some laterally offset in-coupling optical elements. The eyepiece of Figure 19A is similar to the eyepiece of Figure 15, but one of the in-coupling optical elements is laterally offset relative to the other in-coupling optical element. In the illustrated orientation of the eyepiece 1020, where image light propagates vertically down the page toward the eyepiece 1020, the in-coupling optical elements 1022a, 1022c are vertically aligned with each other so that they spatially overlap each other (e.g., along an axis parallel to the propagation direction of the image light 1032a, 1032c), as seen in a head-on view in the direction of image light 1032a, 1032c propagating through the in-coupling optical elements 1022a, 1022b, 1022c. As seen in the same head-on view (e.g., as seen in a top-down view in the illustrated orientation), the in-coupling optical element 1022b is laterally offset relative to the other in-coupling optical elements 1022a, 1022c. Light for the in-coupling optical element 1022b is output to the eyepiece 1020 through a different exit pupil than light for the in-coupling optical elements 1022a, 1022c. It should be understood that the illustrated waveguide stack, including waveguides 1020a, 1020b, 1020c, may be utilized in place of the single illustrated waveguide 1020a of FIGS. 13A, 13B, and 14.

[0215] Continuing to refer to FIG. 19A , internal coupling optical element 1022c is configured to internally couple image light 1032c into waveguide 1020c by multiple total internal reflections between the top and bottom major surfaces of waveguide 1020c to propagate through waveguide 1020c, internal coupling optical element 1022b is configured to internally couple image light 1032b into waveguide 1020b by multiple total internal reflections between the top and bottom major surfaces of waveguide 1020b to propagate through waveguide 1020b, and internal coupling optical element 1022a is configured to internally couple image light 1032a into waveguide 1020a by multiple total internal reflections between the top and bottom major surfaces of waveguide 1020a to propagate through waveguide 1020a.

[0216] The in-coupling optical element 1022c is preferably configured to in-couple all incident light 1032c into the associated waveguide 1020c while transmitting all incident light 1032a. On the other hand, the image light 1032b may propagate to the in-coupling optical element 1022b without having to propagate through any other in-coupling optical elements. This may be advantageous in some embodiments by allowing light to which the eye is more sensitive to be incident on the desired in-coupling optical element without any loss or distortion associated with propagation through other in-coupling optical elements. Without being limited by theory, in some embodiments, the image light 1032b is green light to which the human eye is more sensitive. While the waveguides 1020a, 1020b, and 1020c are illustrated as being arranged in a particular order, it should be understood that in some embodiments, the order of the waveguides 1020a, 1020b, and 1020c may be different.

[0217] As discussed herein, it should be understood that the in-coupling optical element 1022c above the in-coupling optical element 1022a may not have perfect selectivity. Some of the image light 1032a may be undesirably in-coupled into the waveguide 1020c by the in-coupling optical element 1022c, and some of the image light 1032c may be transmitted through the in-coupling optical element 1022c, after which the image light 1032c may strike the in-coupling optical element 1020a and be in-coupled into the waveguide 1020a. As discussed herein, such undesirable in-coupling may be visible as afterglow or crosstalk.

[0218] FIG. 19B illustrates a side view of an example of the eyepiece of FIG. 19A with color filters to reduce image retention or crosstalk between waveguides. In particular, color filters 1024c and / or 1026 are added to the structure shown in FIG. 19A. As shown, in-coupling optical element 1022c may unintentionally in-couple a portion of image light 1032a into waveguide 1020c. Additionally, or alternatively, a portion of image light 1032c may undesirably be transmitted through in-coupling optical element 1022c and then unintentionally in-coupled by in-coupling optical element 1022a.

[0219] To mitigate unintentional in-coupling of image light 1032a propagating through the waveguide 1022c, an absorbing color filter 1026 may be provided on one or both major surfaces of the waveguide 1022c. The absorbing color filter 1026 may be configured to absorb light of the color of the image light 1032a that is unintentionally in-coupled. As shown, the absorbing color filter 1026 is positioned in the general direction of propagation of the image light through the waveguide 1020c. Thus, the absorbing color filter 1026 is configured to absorb image light 1032a as that light propagates through the waveguide 1020c by TIR and contacts the absorbing color filter 1026 as it reflects off one or both major surfaces of the waveguide 1020c.

[0220] 19B , an absorbing color filter 1024c may be provided in front of the in-coupling optical element 1022a to attenuate image light 1032c that propagates through the in-coupling optical element 1022c without being in-coupling. The absorbing color filter 1024c is configured to absorb light of the color of the image light 1032c and prevent that light from propagating to the in-coupling optical element 1022a. While illustrated between waveguides 1020c and 1020b, in some other embodiments, the absorbing color filter 1024c may be positioned between waveguides 1020b and 1020a. It should be understood that further details regarding the composition, formation, and properties of the absorbing color filters 1024c and 1026 are provided in the discussion of FIG. 16 .

[0221] It should also be understood that in the embodiments illustrated in Figures 16 and 19B, one or more of the color filters 1026, 1028, 1024c, and 1024b may be omitted if one or more of the internal coupling optical elements 1022a, 1022b, 1022c have sufficiently high selectivity with respect to the color of light intended to be internally coupled into the associated waveguides 1020a, 1020b, 1022c, respectively.

[0222] 20A illustrates an example of a top-down view of the eyepiece of FIGS. 19A and 19B. As shown, the in-coupling optical elements 1022a, 1022c are spatially overlapping, while the in-coupling optical element 1022b is laterally offset. Additionally, the waveguides 1020a, 1020b, 1020c may be vertically aligned, along with each waveguide's associated optically dispersive element 730, 740, 750 and associated out-coupling optical element 800, 810, 820. The internal coupling optical elements 1022a, 1022b, 1022c are configured to internally couple the incident image light 1032a, 1032b, 1032c (Figures 15 and 16) into the waveguides 1020a, 1020b, 1020c, respectively, so that the image light propagates by TIR towards the associated optical dispersion elements 730, 740, 750.

[0223] Figure 20B illustrates another embodiment of a top-down view of the waveguide assembly of Figures 19A and 19B. As in Figure 20A, the in-coupling optical elements 1022a, 1022c are spatially overlapping, the in-coupling optical elements are laterally offset, and the waveguides 1020a, 1020b, 1020c are vertically aligned. However, in place of each waveguide's associated optically dispersive element 730, 740, 750 and associated out-coupling optical element 800, 810, 820, there is a combined OPE / EPE 1281, 1282, 1283, respectively. The internal coupling optical elements 1022a, 1022b, 1022c are configured to internally couple the incident image light 1032a, 1032b, 1032c (Figures 15 and 16) into the waveguides 1020a, 1020b, 1020c, respectively, so that the image light propagates by TIR towards the associated combined OPE / EPE 1281, 1282, 1283.

[0224] 21 , it should be understood that rebouncing of incoupling light can undesirably occur within a waveguide. Rebouncing occurs when incoupling light propagating along a waveguide strikes an incoupling optical element a second or subsequent time after the initial incoupling incident. Rebouncing can result in some of the incoupling light being undesirably outcoupling and / or absorbed by the material of the incoupling optical element. The outcoupling and / or absorption can undesirably reduce the overall incoupling efficiency and / or the uniformity of the incoupling light.

[0225] FIG. 21 illustrates a side view of an example of rebouncing within a waveguide 1030a. As shown, image light 1032a is incoupling into the waveguide 1030a by an incoupling optical element 1022a. The incoupling optical element 1022a redirects the image light 1032a to propagate through the waveguide generally in direction 1033. Rebouncing can occur when the incoupling image light internally reflects or bounces off a major surface of the waveguide 1030a opposite the incoupling optical element 1022a and impinges on the incoupling optical element 1022a or undergoes a second bounce (rebounce). The distance between two nearby bounces on the same surface of the waveguide 1030a is indicated by spacing 1034.

[0226] Without being limited by theory, it should be understood that the internal coupling optical element 1022a may behave symmetrically. That is, it may redirect incident light so that it propagates through the waveguide at a TIR angle. However, light incident on the diffractive optical element at a TIR angle (such as upon rebounce) may also be outcoupled. Additionally or alternatively, in embodiments in which the internal coupling optical element 1022a is coated with a reflective material, it should be understood that reflection of light from a layer of material, such as metal, may also involve partial absorption of the incident light, since reflection may involve absorption and emission of light from the material. As a result, outcoupling and / or absorption of light may undesirably cause loss of incoupled light. Thus, the rebounced light may suffer significant loss compared to light that interacts with the internal coupling optical element 1022a only once.

[0227] In some embodiments, the internal coupling element is configured to mitigate incoupling image light loss due to rebouncing. Generally, rebouncing of incoupling light occurs in the propagation direction 1033 of the incoupling light toward the end 1023 of the internal coupling optical element 1022a. For example, light internally coupled at the end of the internal coupling optical element 1022a opposite the end 1023 may rebounce if the spacing 1034 for that light is sufficiently short. To avoid such rebouncing, in some embodiments, the internal coupling optical element 1022a is truncated at the propagation direction end 1023 to reduce the width 1022w of the internal coupling optical element 1022a along which rebouncing is likely to occur. In some embodiments, the truncation may be complete truncation of all structures (e.g., metallization and diffraction grating) of the internal coupling optical element 1022a. In some other embodiments, for example, if the internal coupling optical element 1022a includes a metallized diffraction grating, a portion of the internal coupling optical element 1022a at the propagation direction end 1023 may not be metallized, such that the propagation direction end 1023 of the internal coupling optical element 1022a absorbs less of the re-bounced light and / or outcouples it with less efficiency. In some embodiments, the diffractive region of the internal coupling optical element 1022a may have a width along the propagation direction 1033 that is shorter than its length perpendicular to the propagation direction 1033, and / or may be sized and shaped such that a first portion of the image light 1032a is incident on the internal coupling optical element 1022a and a second portion of the beam of light impinges on the waveguide 1030a without being incident on the internal coupling optical element 1022a. While the waveguide 1032a and the optical in-coupling optical element 1022a are shown alone for clarity, it should be understood that rebouncing and the discussed strategies for reducing rebouncing may be applied to any of the in-coupling optical elements disclosed herein. It should also be understood that the spacing 1034 is proportional to the thickness of the waveguide 1030a (greater thickness results in greater spacing 1034). In some embodiments, the thickness of the individual waveguides may be selected to set the spacing 1034 such that rebouncing does not occur.Further details regarding rebounce mitigation can be found in U.S. Provisional Application No. 62 / 702,707, filed July 24, 2018, the entire disclosure of which is incorporated herein by reference.

[0228] 22A-23C illustrate examples of top-down views of eyepieces having internal coupling optical elements configured to reduce rebounce. The internal coupling optical elements 1022a, 1022b, 1022c are configured to internally couple light to propagate in a propagation direction toward an associated optically dispersive element 730, 740, 750 (FIGS. 22A-22C) or a combined OPE / EPE 1281, 1282, 1283 (FIGS. 23A-23C). As shown, the internal coupling optical elements 1022a, 1022b, 1022c may have a shorter dimension along the propagation direction and a longer dimension along a horizontal axis. For example, the internal coupling optical elements 1022a, 1022b, 1022c may each be rectangular in shape with a shorter side along the propagation axis and a longer side along an orthogonal axis. It should be understood that the in-coupling optical elements 1022a, 1022b, 1022c may have other shapes (e.g., orthogonal, hexagonal, etc.). Additionally, different ones of the in-coupling optical elements 1022a, 1022b, 1022c may have different shapes in some embodiments. Also, preferably, as shown, non-overlapping in-coupling optical elements may be positioned such that they are not in the propagation direction of other in-coupling optical elements. For example, as shown in Figures 22A, 22B, 23A, and 23B, the non-overlapping in-coupling optical elements may be arranged in lines along an axis that intersects (e.g., orthogonal to) the axis of the propagation direction.

[0229] It should be understood that the waveguide assemblies of Figures 22A-22C are similar except for the overlap of the in-coupling optical elements 1022a, 1022b, 1022c. For example, Figure 22A illustrates in-coupling optical elements 1022a, 1022b, 1022c without overlap. Figure 22B illustrates overlapping in-coupling optical elements 1022a, 1022c and non-overlapping in-coupling optical element 1022b. Figure 22C illustrates overlap between all in-coupling optical elements 1022a, 1022b, 1022c.

[0230] The waveguide assemblies of Figures 23A-23C are also similar, except for the overlap of the in-coupling optical elements 1022a, 1022b, and 1022c. Figure 23A illustrates in-coupling optical elements 1022a, 1022b, and 1022c without overlap. Figure 23B illustrates overlapping in-coupling optical elements 1022a, 1022c and non-overlapping in-coupling optical element 1022b. Figure 23C illustrates overlap between all in-coupling optical elements 1022a, 1022b, and 1022c.

[0231] 24A, it should be understood that nanowire LED microdisplays have a high etendue, which presents challenges for efficient light utilization. As discussed herein, nanowire LED microdisplays may include multiple individual light emitters. Each of these light emitters may have a large-angle emission profile, e.g., a Lambertian or near-Lambertian emission profile. Undesirably, not all of this light may be captured and directed into the eyepiece of the display system.

[0232] Advantageously, as discussed herein, nanowire LEDs may have angular emission profiles that are narrower than those of planar LEDs, for example, due to their periodic array structure, which behaves as a photonic crystal material. Thus, nanowire LEDs may have light output with higher directionality compared to typical planar micro-LEDs. In some embodiments, the directionality may be independent of pixel pitch and may be tailored by adjusting nanowire micro-LED parameters such as, but not limited to, nanowire material, dopants, dimensions, and refractive index. As a result, as discussed herein, nanowire LED microdisplays may advantageously omit optics for steering light emitted from the nanowire LEDs. The absence of such optics may have benefits for simplifying the display system and increasing light output, as discussed herein. Nevertheless, in some embodiments, it may be desirable to further manipulate the angular emission profile and / or the direction of the output light.

[0233] In some embodiments, various optical structures may be utilized to further narrow the angular spread of light emitted by the nanowire LEDs. Figure 24A illustrates, in exaggerated form, an example of the angular emission profile of light emitted by individual light emitters 1044 of a nanowire LED microdisplay 1032 and light captured by projection optics 1070. The nanowire LED microdisplay 1032 shown may correspond to any of the emissive LED microdisplays disclosed herein, including nanowire LED microdisplays 1032a, 1032b, and 1032c. As shown, the projection optics 1070 may be sized to capture light having an angular emission profile 1046. However, the angular emission profile 1046 within the light emitters 1044 may be significantly larger, and not all of the light emitted by the light emitters 1044 may be incident on the projection optics 1070 or necessarily at an angle at which the light may propagate into and through the projection optics 1070. As a result, some of the light emitted by the light emitter 1044 may be undesirably captured and ultimately relayed to the user's eye and "wasted" because it does not form an image. This may result in an image appearing darker than would be expected if more of the light output by the light emitter 1040 ultimately reached the user's eye.

[0234] In some embodiments, one strategy for capturing more of the light emitted by the light emitter 1040 is to increase the size of the projection optics 1070 and increase the size of the numerical aperture of the projection optics 1070 that captures the light. Additionally or alternatively, the projection optics 1070 may also be formed of a high refractive index material (e.g., having a refractive index greater than 1.5), which may also facilitate light collection. In some embodiments, the projection optics 1070 may utilize a lens sized to capture a desired high percentage of the light emitted by the light emitter 1044. In some embodiments, the projection optics 1070 may have an elongated exit pupil and be configured to emit a light beam having a cross-sectional profile similar to the shape of the internal coupling optical elements 1022a, 1022b, 1022c of FIGS. 22A-23C . For example, the projection optics 1070 may be elongated in a dimension corresponding to the elongated dimension of the internal coupling optical elements 1022a, 1022b, 1022c of FIGS. 22A-23C . Without being limited by theory, such extended incoupling optical elements 1022a, 1022b, 1022c may improve the etendue mismatch between the nanowire LED microdisplay and the eyepiece 1020 (FIGS. 22A-23C). In some embodiments, the waveguide thickness of the eyepiece 1020 (e.g., FIGS. 11A and 12-23C) may be selected to increase the percentage of light that is effectively captured by reducing rebounces, for example, by increasing the rebounce spacing as discussed herein.

[0235] In some embodiments, one or more light collimators may be utilized to reduce or narrow the angular emission profile of light from the light emitter 1044. As a result, more of the light emitted by the light emitter 1044 may be captured by the projection optics 1070 and relayed to the user's eye, which may advantageously increase the brightness of the image and the efficiency of the display system. In some embodiments, the light collimators may enable the collection efficiency of the projection optics (the percentage of light emitted by the light emitter 1044 that is captured by the projection optics) to reach values ​​of 80% or greater, 85% or greater, or 90% or greater, including approximately 85-95% or 85-90%. Additionally, the angular emission profile of light from the light emitter 1044 may be reduced to 50° or less, 40° or less, or 30° or less. In some embodiments, the reduced angular emission profile may be within a range of approximately 30-60°, 30-50°, or 30-40°. It should be understood that the light from the light emitter 1044 may create a cone shape, with the light emitter 1044 at the apex of the cone. The angular emission profile refers to the angle created by the sides of the cone, with the associated light emitter 1044 at the apex of that angle (as viewed in cross section, taken along a plane extending through the center of the cone and including the cone apex).

[0236] 24B illustrates an example of narrowing an angular emission profile using an array of light collimators. As shown, a nanowire LED microdisplay 1032 includes an array of light emitters 1044, which emit light with an angular emission profile 1046. An array 1300 of light collimators 1302 is disposed in front of the light emitters 1044. In some embodiments, each light emitter 1044 is matched one-to-one with an associated light collimator 1302 (one light collimator 1302 per light emitter 1044). Each light collimator 1302 redirects incident light from the associated light emitter 1044 to provide a narrowed angular emission profile 1047. Thus, a relatively large angular emission profile 1046 is narrowed to a smaller angular emission profile 1047.

[0237] In some embodiments, the light collimator 1302 and array 1300 may be part of the light redirecting structures 1080a, 180c of Figures 12 and 13A. Thus, the light collimator 1302 may narrow the angular emission profile of the light emitter 1044 and redirect the light so that it propagates at an appropriate angle into the optical combiner 1050 and defines multiple light paths and associated multiple exit pupils. It should be understood that light may be redirected in a particular direction by appropriately shaping the light collimator 1302.

[0238] Preferably, the light collimators 1302 are positioned in close proximity to the light emitters 1044 to capture a large proportion of the light output by the light emitters 1044. In some embodiments, a gap may exist between the light collimators 1302 and the light emitters 1044. In some other embodiments, the light collimators 1302 may contact the light emitters 1044. It should be understood that the angular emission profile 1046 may produce a wide cone of light. Preferably, all or a majority of the cone of light from the light emitters 1044 is incident on a single associated light collimator 1302. Thus, in some embodiments, each light emitter 1044 is smaller (occupies a smaller area) than the light-receiving surface of the associated light collimator 1302. In some embodiments, each light emitter 1044 has a width that is smaller than the spacing between neighboring, distant light emitters 1044.

[0239] Advantageously, the light collimator 1302 may increase the efficiency of light utilization and may also reduce the occurrence of crosstalk between nearby light emitters 1044. It should be understood that crosstalk between light emitters 1044 may occur when light from nearby light emitters is captured by a light collimator 1302 that is not associated with the nearby light emitter. That captured light may propagate to a user's eye, thereby providing erroneous image information for a given pixel.

[0240] 24A and 24B, the size of the beam of light captured by the projection optics 1070 can affect the size of the beam of light exiting the projection optics 1070. As shown in FIG. 24A, without the use of an optical collimator, the exit beam can have a relatively large width 1050. As shown in FIG. 24B, with the optical collimator 1302, the exit beam can have a smaller width 1052. Thus, in some embodiments, the optical collimator 1302 can be used to provide a desired beam size for incoupling into the eyepiece. For example, the amount by which the optical collimator 1302 narrows the angular emission profile 1046 can be selected based, at least in part, on the size of the incoupling optical element in the eyepiece to which the light output by the projection optics 1070 is directed.

[0241] It should be understood that the light collimator 1302 may take a variety of forms. For example, the light collimator 1302 may be a microlens or lenslet in some embodiments. As discussed herein, each microlens preferably has a width greater than the width of the associated light emitter 1044. The microlenses may be formed from curved transparent materials such as glass or polymers, including resins such as photoresist and epoxy. In some embodiments, the light collimator 1302 may be a nanolens, e.g., a diffractive optical grating. In some embodiments, the light collimator 1302 may be a metasurface and / or a liquid crystal grating. In some embodiments, the light collimator 1302 may take the form of a reflective well.

[0242] It should be understood that different light collimators 1302 may have different dimensions and / or shapes depending on the wavelength or color of light emitted by the associated light emitter 1044. Thus, for a full-color nanowire LED microdisplay, the array 1300 may include multiple light collimators 1302 with different dimensions and / or shapes depending on the color of light emitted by the associated light emitter 1044. In embodiments in which the nanowire LED microdisplay is a monochrome microdisplay, the array 1300 may be simplified, with each of the light collimators 1302 in the array configured to redirect light of the same color. With such monochrome microdisplays, the light collimators 1302 may be similar across the array 1300 in some embodiments.

[0243] 24B , as discussed herein, the light collimators 1302 may have a one-to-one association with the light emitters 1044. For example, each light emitter 1044 may have a discrete associated light collimator 1302. In some other embodiments, the light collimators 1302 may be elongated such that they extend across multiple light emitters 1044. For example, in some embodiments, the light collimator 1302 may be elongated across the page and extend in front of a row of multiple light emitters 1044. In some other embodiments, a single light collimator 1302 may extend across a column of light emitters 1044. In still other embodiments, the light collimator 1302 may include stacked columns and / or rows of lens structures (e.g., nanolens structures, microlens structures, etc.).

[0244] As mentioned above, the light collimators 1302 may take the form of reflective wells. FIG. 25A illustrates an example of a side view of an array of tapered reflective wells for directing light to a projection optical system. As shown, the light collimator array 1300 may include a substrate 1301 within which a plurality of light collimators 1302 in the form of reflective wells may be formed. Each well may include at least one light emitter 1044, which may emit light with a Lambertian angular emission profile 1046. The reflective walls 1303 of the wells of the light collimators 1302 are tapered to reflect the emitted light so that it exits the well with a narrower angular emission profile 1047. As shown, the reflective walls 1303 may be tapered such that their cross-sectional size increases with distance from the light emitter 1044. In some embodiments, the reflective walls 1303 may be curved. For example, side 1303 may have the shape of a compound parabolic concentrator (CPC).

[0245] 25B , an example of a side view of an asymmetric tapered reflective well is illustrated. As discussed herein, for example, as illustrated in FIGS. 12-13A , it may be desirable to utilize a light collimator 1302 to steer light in a particular direction that is not normal to the surface of the light emitter 1044. In some embodiments, as viewed in the side view illustrated in FIG. 25B , the light collimator 1302 may be asymmetric, with the top side 1303 a forming a different angle (e.g., a larger angle) with the surface of the light emitter 1044 and the bottom side 1303 b. For example, the angles of the reflective walls 1303 a, 1303 b relative to the light emitter 1044 may be different on different sides of the light collimator 1302 to direct light in a particular non-normal direction. Thus, as illustrated, light exiting the light collimator 1302 may generally propagate in a direction 1048 that is not normal to the surface of the light emitter 1044. In some other embodiments, the taper of the top side 1303a may be different than the taper of the bottom side to direct light in direction 1048. For example, the top side 1303a may flare out more than the bottom side 1303b.

[0246] 25B, substrate 1301 may be formed from a variety of materials that have sufficient mechanical integrity to maintain the desired shape of reflective wall 1303. Examples of suitable materials include metal, plastic, and glass. In some embodiments, substrate 1301 may be a plate of material. In some embodiments, substrate 1301 is a continuous, unitary piece of material. In some other embodiments, substrate 1301 may be formed by joining two or more pieces of material together.

[0247] The reflective walls 1303 may be formed in the substrate 1301 by a variety of methods. For example, the walls 1303 may be formed into the desired shape by machining or otherwise removing material from the substrate 1301 to define the walls 1303. In some other embodiments, the walls 1303 may be formed as the substrate 1301 is formed. For example, the walls 1303 may be molded into the substrate 1301 as the substrate 1301 is shaped into its desired shape. In some other embodiments, the walls 1303 may be defined by rearrangement of material after the formation of the body 2200. For example, the walls 1303 may be defined by imprinting.

[0248] Once the contours of the walls 1303 are formed, they may undergo further processing to form a surface with the desired degree of reflectivity. In some embodiments, the surface of the substrate 1301 itself may be reflective, for example, the body is formed from a reflective metal. In such cases, further processing may include smoothing or polishing the interior surface of the walls 1303 to increase its reflectivity. In some other embodiments, the interior surface of the reflector 2110 may be lined with a reflective coating, for example, by a vapor deposition process. For example, the reflective layer may be formed by physical vapor deposition (PVD) or chemical vapor deposition (CVD).

[0249] It should be understood that the location of a light emitter relative to its associated light collimator can affect the direction of light emitted from the light collimator. This is illustrated, for example, in Figures 26A-26C, which illustrate examples of differences in light paths for light emitters at different locations relative to the centerline of the associated light collimator on the upper layer. As shown in Figure 26A, the nanowire LED microdisplay 30 has multiple light emitters 1044a, each with an associated light collimator 1302, which promotes the output of light having a narrowed angular emission profile 1047. The light passes through projection optics 1070 (represented as a simple lens for ease of illustration), which focuses the light from the various light emitters 1044a onto an area 1402a.

[0250] 26A , in some embodiments, the optical collimators 1302 may each be symmetrical and have a centerline that extends along the axis of symmetry of the optical collimator. In the illustrated configuration, the optical emitter 1044 a is positioned on the centerline of each of the optical collimators 1302.

[0251] 26B, light emitter 1044b is offset from the centerline of its respective light collimator 1302 by a distance 1400. This offset causes light from light emitter 1044b to follow a different path through light collimator 1302, which outputs light from light emitter 1044b with a narrowed angular emission profile 1047b. Projection optics 1070 then focuses the light from light emitter 1044b onto area 1402b, which is offset relative to area 1402a onto which the light from light emitter 1044a focuses.

[0252] 26C, light emitter 1044c is illustrated as being offset from both light emitters 1044a and 1044b. This offset causes light from light emitter 1044c to follow a different path through light collimator 1302 than light from light emitters 1044a and 1044b. This causes light collimator 1302 to output light from light emitter 1044c with a narrowed angular emission profile that follows a different path than light from light emitters 1044a and 1044b to projection optics 1070. Ultimately, projection optics 1070 focuses the light from light emitter 1044c onto area 1402c, which is offset relative to areas 1402a and 1402b.

[0253] 26A-26C, each three-fold symmetry axis of light emitters 1044a, 1044b, 1044c may share a common light collimator 1302. In some embodiments, microdisplay 1030 may be a full-color microdisplay, and each light emitter 1044a, 1044b, 1044c may be configured to emit light of a different primary color. Advantageously, offset areas 1402a, 1402b, 1402c may correspond to waveguide incoupling optical elements in some embodiments. For example, areas 1402a, 1402b, 1402c may correspond to incoupling optical elements 1022a, 1022b, 1022c of FIGS. 11A and 12, respectively. Thus, the offset orientation of the light collimator 1302 and light emitters 1044a, 1044b, 1044c can advantageously provide a simple three-pupil projection system 1010 using a full-color nanowire LED microdisplay.

[0254] As described herein, the light collimators 1302 may also take the form of nanolenses. Figure 27 illustrates an example of a side view of an individual light emitter 1044 of a nanowire LED microdisplay 1030 with an overlying array 1300 of light collimators 1302, which are nanolenses. As discussed herein, each individual one of the light emitters 1044 may have an associated light collimator 1302. The light collimators 1302 redirect light from the light emitters 1044, narrowing the large-angle emission profile 1046 of the light emitters 1044 and outputting light with a narrowed angular emission profile 1047.

[0255] 27 , in some embodiments, the light collimator 1302 may be a grating structure. In some embodiments, the light collimator 1302 may be a grating formed by alternating elongated discrete extensions (e.g., lines) of material having different refractive indices. For example, the extensions of material 1306 may extend into and out of the page and may be formed within and separated by the material of the substrate 1308. In some embodiments, the elongated extensions of material 1306 may have a sub-wavelength width and pitch (e.g., a width and pitch smaller than the wavelength of light that the light collimator 1302 is configured to receive from the associated light emitter 1044). In some embodiments, the pitch 1304 may be 30-300 nm, the grating depth may be 10-1,000 nm, the refractive index of the material forming the substrate 1308 may be 1.5-3.5, and the refractive index of the material forming the grating features 1306 may be 1.5-2.5 (and different from the refractive index of the material forming the substrate 1308).

[0256] The grating structures shown may be formed by a variety of methods. For example, the substrate 1308 may be etched or nanoimprinted to define grooves, which may be filled with a material of a different refractive index than the substrate 1308 to form the grating features 1306.

[0257] Advantageously, nanolens arrays may offer various benefits. For example, the light collection efficiency of the nanolenslets may be as high as 80-95%, including 85-90%, with excellent reduction in angular emission profile, e.g., down to 30-40° (from 180°). In addition, low levels of crosstalk may be achieved because each of the nanolens light collimators 1302 may have physical dimensions and properties (e.g., pitch, depth, refractive index of the material forming the features 1306 and substrate 1308) selected to act on light of a particular color and potentially a particular angle of incidence, while preferably providing a high extinction ratio (with respect to wavelengths of light of other colors). In addition, the nanolens array may have a flat profile (e.g., formed on a flat substrate), which may facilitate integration with microdisplays, which may be flat panels, and may also facilitate manufacturing and provide high reproducibility and precision in forming the nanolens array. For example, highly reproducible groove formation and deposition processes may be used to form each nanolens. Furthermore, these processes allow for greater ease and reproducibility in terms of variation between nanolenses in an array than is typically achieved when forming curved lenses with similar variations.

[0258] Referring now to FIG. 28 , a perspective view of an example nanowire LED microdisplay 1030 is illustrated. It should be appreciated that the light collimator array 1300 advantageously allows light emitted from the microdisplay to be routed as desired. As a result, in some embodiments, the light emitters of a full-color microdisplay can be organized as desired, for example, for ease of manufacturing or implementation within a display device. In some embodiments, the light emitters 1044 may be arranged in rows or columns 1306 a, 1306 b, 1306 c. Each row or column may include light emitters 1044 configured to emit light of the same primary color. In a display in which three primary colors are utilized, there may be three groups of rows or columns that are repeated across the microdisplay 1030. It should be appreciated that if more primary colors are utilized, each repeating group may have that number of rows or columns. For example, if four primary colors are utilized, each group may have four rows or four columns, with one row or one column formed by light emitters configured to emit light of a single primary color.

[0259] In some embodiments, some rows or columns may be repeated to increase the number of light emitters of a particular primary color. For example, some primary color light emitters may occupy multiple rows or columns. This may promote color balancing and / or may be utilized to address differential degradation or reduction in light emission intensity over time.

[0260] 28 , each light emitter 1044 may be elongated along a particular axis (e.g., along the y-axis as shown). That is, each light emitter has a length along the particular axis, the length being greater than the width of the light emitter. Additionally, a set of light emitters configured to emit light of the same primary color may be arranged in a line 1306 a, 1306 b, or 1306 c (e.g., row or column) extending along an axis (e.g., the x-axis) that intersects (e.g., orthogonal to) the elongation axis of the light emitter 1044. Thus, in some embodiments, light emitters 1044 of the same primary color form a line 1306 a, 1306 b, or 1306 c of light emitters, where the line extends along a first axis (e.g., the x-axis) and the individual light emitters 1044 within the line are elongated along a second axis (e.g., the y-axis).

[0261] In contrast, it should be understood that a full-color microdisplay typically includes a subpixel for each primary color, arranged in a particular, relatively closely packed spatial orientation in groups, and these groups are reproduced across the array. Each group of subpixels may form a pixel in an image. In some cases, the subpixels are elongated along an axis, with rows or columns of subpixels of the same primary color extending along that same axis. It should be understood that such an arrangement allows the subpixels of each group to be located closely together, which can have advantages in terms of image quality and pixel density. However, in the illustrated arrangement of FIG. 28 , the subpixels of different primary colors are relatively far apart due to the elongated shape of the light emitter 1044. That is, the light emitters in line 1306a are relatively far away from the light emitters in line 1306c because the elongated shape of the light emitters in line 1306b causes light emitters 1306a and 1306c to be spaced apart more than neighboring light emitters in a given line of light emitters. While this would be expected to provide unacceptably poor image quality if the image formed on the surface of microdisplay 1030 were relayed directly to a user's eye, the use of light collimator array 1300 advantageously allows light of different colors to be routed as desired to form a high-quality image. For example, light of each primary color may be used to form a separate monochrome image, which is then routed to and combined in an eyepiece, such as eyepiece 1020 (e.g., FIGS. 11A and 12-14).

[0262] 27 and 28 , in some embodiments, each light emitter 1044 may have an associated light collimator 1302. In some other embodiments, each line 1306 a, 1306 b, 1306 c of multiple light emitters 1044 may have a single associated light collimator 1302. That single associated light collimator 1302 may extend across substantially the entire associated line 1306 a, 1306 b, or 1306 c. In some other embodiments, the associated light collimator 1302 may be elongated and extend across multiple light emitters 1044 that form part of the associated line 1306 a, 1306 b, or 1306 c, and multiple similar light collimators 1302 may be provided along each of the associated lines 1306 a, 1306 b, 1306 c.

[0263] It should be understood that the light collimator 1302 may be utilized to direct light along different light paths to form a multi-pupil projection system. For example, the light collimator 1302 may direct light of different primary colors to two or three areas, respectively, for light incoupling.

[0264] Figure 29 illustrates an example of a wearable display system with the full-color nanowire LED microdisplay 1030 of Figure 28 used to form a multi-pupil projection system 1010. In the illustrated embodiment, the full-color nanowire LED microdisplay 1030 emits light of three primary colors, forming a three-pupil projection system 1010. The projection system 1010 has three exit pupils through which image light 1032a, 1032b, and 1032c of different primary colors propagate to three laterally shifted light in-coupling optical elements 1022a, 1022b, and 1022c of the eyepiece 1020, respectively. The eyepiece 1020 then relays the image light 1032a, 1032b, and 1032c to the user's eye 210.

[0265] The emissive microdisplay 1030 includes an array of light emitters 1044, which may be subdivided into monochrome light emitters 1044a, 1044b, and 1044c, which emit image light 1032a, 1032b, and 1032c, respectively. It should be understood that the light emitters 1044 emit image light with a wide angular emission profile 1046. The image light propagates through an array of light collimators 1300, which reduces the angular emission profile to a narrowed angular emission profile 1047.

[0266] Additionally, the array of light collimators 1300 is configured to redirect the image light (image light 1032a, 1032b, 1032c) so that the image light is incident on the projection optics 1070 at an angle that causes the projection optics 1070 to output the image light so that the image light propagates to the appropriate in-coupling optical element 1022a, 1022b, 1022c. For example, the array of light collimators 1300 is preferably configured to direct image light 1032a to propagate through the projection optics 1070 and incident on the in-coupling optical element 1022a, direct image light 1032b to propagate through the projection optics 1070 and incident on the in-coupling optical element 1022b, and direct image light 1032c to propagate through the projection optics 1070 and incident on the in-coupling optical element 1022c.

[0267] Because different light emitters 1044 may emit light of different wavelengths and may need to be redirected in different directions to reach the appropriate interconnecting optical element, in some embodiments, the light collimators associated with different light emitters 1044 may have different physical parameters (e.g., different pitches, different widths, etc.). Advantageously, the use of flat nanolenses as light collimators facilitates the formation of light collimators with varying physical properties across the array of light collimators 1300. As described herein, nanolenses may be formed using patterning and deposition processes, which facilitate the formation of structures with different pitches, widths, etc. across the substrate.

[0268] Referring again to FIG. 24A, it should be understood that the illustrated display system shows a single-nanowire LED microdisplay and omits the optical combiner 1050 (FIGS. 11A and 12-13B). In embodiments utilizing the optical combiner 1050, the reflective surfaces 1052, 1054 (FIGS. 11A, 12-13B, and 30B) within the optical combiner 1050 are preferably specular reflectors, and light from the light emitter 1044 would be expected to retain its large-angle emission profile after reflecting from the reflective surfaces 1052, 1054. Thus, the issues with wasted light shown in FIG. 24A are present when the optical combiner 1050 is utilized as well.

[0269] Referring now to FIG. 30A, an example of a wearable display system is illustrated with a nanowire LED microdisplay and an associated array of light collimators. FIG. 30A shows additional details regarding the interaction between the light emitter 1044, the light collimator 1302, and the internal coupling optical elements of the eyepiece 1020. The display system includes a microdisplay 1030b, which in some embodiments may be a full-color microdisplay. In some other embodiments, the microdisplay 1030b may be a monochrome microdisplay, and an additional monochrome microdisplay (not shown) may be provided on a different side of the optional optical combiner 1050 (as shown in FIG. 30C).

[0270] Continuing with reference to FIG. 30A , the microdisplay 1030b includes an array of light emitters 1044, each emitting light with a wide angular emission profile (e.g., a Lambertian angular emission profile). Each light emitter 1044 has an associated dedicated light collimator 1302, which effectively narrows the angular emission profile to a narrowed angular emission profile 1047. The light beams 1032b with the narrowed angular emission profile pass through projection optics 1070, which projects or focuses the light beams onto an in-coupling optical element 1022b. It should be understood that the light beams 1032b have a cross-sectional shape and size 1047a. In some embodiments, the in-coupling optical element 1022b has a size and shape that substantially matches or is larger than the cross-sectional shape and size of the light beams 1032b when the beams 1032b are incident on the in-coupling optical element 1022b. Thus, in some embodiments, the size and shape of the in-coupling optical element 1022b may be selected based on the cross-sectional size and shape of the light beam 1032b as it impinges on the in-coupling optical element 1022b. In some other embodiments, other factors (e.g., rebounce mitigation or the angle or field of view assisted by the in-coupling optical element 1022b) may be utilized to determine the size and shape of the in-coupling optical element 1022b, and the light collimator 1302 may be configured (e.g., sized and shaped) to provide the light beam 1032b with an appropriately sized and shaped cross-section that is preferably completely or nearly completely encompassed by the size and shape of the in-coupling optical element 1022b. In some embodiments, the physical parameters for the light collimator 1302 and the in-coupling optical element 1022b may be modified relative to one another to provide highly efficient light utilization in conjunction with other desired functionality (e.g., rebounce mitigation, assistance for a desired field of view, etc.). Advantageously, the above-described light collimation provided by the light collimator 1302 and the matching of the cross-sectional size and shape of the light beam 1032b with the size and shape of the internal coupling optical element 1022b enable the internal coupling optical element 1022b to capture a large percentage of the incident light beam 1032b.The incoupled light then propagates through waveguide 1020 b and is outcoupled to eye 210 .

[0271] In some embodiments, the light collimator 1302 is a microlens that is positioned directly over and surrounds the associated light emitter 1044. In some embodiments, adjacent microlenses 1302 are in near or direct contact with one another. It should be appreciated that light from the light emitter 1044 may fill the associated microlens 1302, effectively expanding the area encompassed by the light emitter 1044. Advantageously, such a configuration reduces the perception of areas that do not emit light, which may otherwise be visible to a user as dark space. However, because the microlens 1302 effectively expands the associated light emitter 1044 to extend across the entire area of ​​the microlens 1302, the areas that do not emit light may be masked.

[0272] 30A , the relative sizes of the light emitters 1044 and the light collimators 1302 may be selected so that light from the light emitters 1044 fills the associated light collimators 1302. For example, the light emitters 1044 may be spaced apart sufficiently so that microlens collimators 1302 having a desired curvature can be formed extending across each of the light emitters 1044. Additionally, as noted above, the size and shape of the internal coupling optical element 1022b is preferably selected to match or exceed the cross-sectional shape and size of the light beam 1032b as it impinges on that internal coupling optical element 1022b. As a result, in some embodiments, the width 1025 of the internal coupling optical element 1022b is equal to or greater than the width of the microlens 1302. Preferably, the width 1025 exceeds the width of the microlens 1302 to allow for some divergence of the light beam 1032b. As discussed herein, the width 1025 may also be selected to mitigate re-bouncing and may be shorter than the length (orthogonal to the width) of the in-coupling optical element 1022b. In some embodiments, the width 1025 may extend along the same axis as the propagation direction of the in-coupled light 1032b through the waveguide 1020b before being out-coupled for propagation to the eye 210.

[0273] 30B, an example of an optical projection system 1010 is illustrated with multiple nanowire LED microdisplays 1030a, 1030b, 1030c and associated arrays of optical collimators 1300a, 1300b, 1300c, respectively. The angular emission profile of light emitted by the microdisplays 1030a, 1030b, 1030c is narrowed by the optical collimator arrays 1300a, 1300b, 1300c, thereby facilitating collection of a large percentage of the emitted light by projection optics 1070 after the light propagates through optical combiner 1050. Projection optics 1070 then directs the light to an eyepiece, such as eyepiece 1020 (e.g., FIGS. 11A and 12-14) (not shown).

[0274] FIG. 30C illustrates an example of a wearable display system with multiple nanowire LED microdisplays 1030a, 1030b, and 1030c, each with an associated array 1300a, 1300b, and 1300c of light collimators, respectively. The illustrated display system includes multiple microdisplays 1030a, 1030b, and 1030c for emitting light bearing image information. As shown, the microdisplays 1030a, 1030b, and 1030c may be microLED panels. In some embodiments, the microdisplays may be monochrome microLED panels, each configured to emit a different primary color. For example, microdisplay 1030a may be configured to emit light 1032a that is red, microdisplay 1030b may be configured to emit light 1032b that is green, and microdisplay 1030c may be configured to emit light 1032c that is blue.

[0275] Each microdisplay 1030a, 1030b, 1030c may have an associated array 1300a, 1300b, 1300c of light collimators, respectively. The light collimators narrow the angular emission profile of light 1032a, 1032b, 1032c from the light emitters of the associated microdisplay. In some embodiments, each light emitter has its own associated light collimator (as shown in FIG. 30A).

[0276] 30C , arrays of light collimators 1300a, 1300b, 1300c are located between associated microdisplays 1030a, 1030b, 1030c and optical combiner 1050, which may be an X-cube. As shown, optical combiner 1050 has internal reflective surfaces 1052, 1054 to reflect incident light out of the output face of the optical combiner. In addition to narrowing the angular emission profile of the incident light, arrays of light collimators 1300a, 1300c may be configured to redirect light from associated microdisplays 1030a, 1030c such that the light strikes the internal reflective surfaces 1052, 1054 of optical combiner 1050 at the appropriate angle for propagation toward associated optical in-coupling optical elements 1022a, 1022c, respectively. In some embodiments, to redirect light in a particular direction, the array of light collimators 1300a, 1300c may include microlenses or reflective wells, which may be asymmetric and / or the light emitters may be positioned off-center relative to the microlenses or reflective wells as disclosed herein.

[0277] 30C , projection optics 1070 (e.g., a projection lens) is disposed at the output face of optical combiner 1050 and receives the image light exiting the optical combiner. Projection optics 1070 may include a lens configured to converge or focus the image light onto eyepiece 1020. As shown, eyepiece 1020 may include multiple waveguides, each configured to in-couple and out-couple light of a particular color. For example, waveguide 1020a may be configured to receive red light 1032a from microdisplay 1030a, waveguide 1020b may be configured to receive green light 1032b from microdisplay 1030b, and waveguide 1020c may be configured to receive blue light 1032c from microdisplay 1030c. Each waveguide 1020a, 1020b, 1020c has an associated light incoupling optical element 1022a, 1022b, 1022c, respectively, for incoupling light therein. Additionally, as discussed herein, waveguides 1020a, 1020b, 1020c may correspond to waveguides 670, 680, 690, respectively, of Figure 9B and may each have an associated orthogonal pupil expander (OPE) and exit pupil expander (EPE), which ultimately outcouples light 1032a, 1032b, 1032c to a user.

[0278] As discussed herein, wearable display systems incorporating microdisplays are preferably configured to output light with different amounts of wavefront divergence to provide a comfortable accommodation-vergence-divergence match for the user. These different amounts of wavefront divergence may be achieved using outcoupling optics with different optical powers. As discussed herein, the outcoupling optics may be present on or within the waveguide of an eyepiece, such as eyepiece 1020 (e.g., FIGS. 11A and 12-14). In some embodiments, lenses may be utilized to increase the wavefront divergence provided by the outcoupling optics, or may be used to provide the desired wavefront divergence in configurations where the outcoupling optics is configured to output collimated light.

[0279] 31A and 31B illustrate examples of an eyepiece 1020 having a lens for varying the wavefront divergence of light to the viewer. FIG. 31A illustrates the eyepiece 1020 having a waveguide structure 1032. In some embodiments, as discussed herein, light of all primary colors may be internally coupled into a single waveguide such that the waveguide structure 1032 includes only a single waveguide. This advantageously provides a compact eyepiece. In some other embodiments, the waveguide structure 1032 may be understood to include multiple waveguides (e.g., waveguides 1032a, 1032b, 1032c of FIGS. 11A and 12-13A), each configured to relay light of a single primary color to the user's eye.

[0280] In some embodiments, variable-focus lens elements 1530, 1540 may be disposed on both sides of the waveguide structure 1032. The variable-focus lens elements 1530, 1540 may be in the path of image light from the waveguide structure 1032 to the eye 210 and also in the path of light from the surrounding environment through the waveguide structure 1032 to the eye 210. The variable-focus optical element 1530 may modulate the wavefront divergence of the image light output by the waveguide structure 1032 to the eye 210. It should be understood that the variable-focus optical element 1530 may have optical power that may distort the eye 210's view of the world. As a result, in some embodiments, a second variable-focus optical element 1540 may be provided on the world-side of the waveguide structure 1032. The second variable-focus optical element 1540 may provide a refractive power opposite to that of the variable-focus optical element 1530 (or opposite to the net refractive power of the optical element 1530 and the waveguide structure 1032, if the waveguide structure 1032 has a refractive power), so that the net refractive power of the variable-focus lens elements 1530, 1540 and the waveguide structure 1032 is substantially zero.

[0281] Preferably, the refractive power of the variable-focus lens elements 1530, 1540 may be dynamically altered, for example, by applying an electrical signal thereto. In some embodiments, the variable-focus lens elements 1530, 1540 may comprise transmissive optical elements such as dynamic lenses (e.g., liquid crystal lenses, electro-active lenses, conventional refractive lenses with movable elements, mechanical deformation-based lenses, electrowetting lenses, elastomeric lenses, or multiple fluids with different refractive indices). By altering the shape, refractive index, or other properties of the variable-focus lens elements, the wavefront of incident light may be changed. In some embodiments, the variable-focus lens elements 1530, 1540 may comprise a layer of liquid crystal sandwiched between two substrates. The substrates may comprise optically transmissive materials such as glass, plastic, acrylic, etc.

[0282] In some embodiments, in addition to or as an alternative to providing variable amounts of wavefront divergence to place virtual content on different depth planes, the variable-focus lens elements 1530, 1540 and waveguide structure 1032 may advantageously provide a net refractive power equal to the user's prescription refractive power for corrective lenses. Thus, the eyepiece 1020 may serve as a substitute for lenses used to correct refractive errors, including myopia, hyperopia, presbyopia, and astigmatism. Further details regarding the use of variable-focus lens elements as substitutes for corrective lenses may be found in U.S. Patent Application No. 15 / 481,255, filed April 6, 2017, the entire disclosure of which is incorporated herein by reference.

[0283] Referring now to FIG. 31B, in some embodiments, the eyepiece 1020 may include static lens elements rather than variable lenses. Similar to FIG. 31B, the waveguide structure 1032 may include a single waveguide (e.g., which may relay light of different colors) or multiple waveguides (e.g., which may each relay light of a single primary color). Similarly, the waveguide structure 1034 may include a single waveguide (e.g., which may relay light of different colors) or multiple waveguides (e.g., which may each relay light of a single primary color). One or both of the waveguide structures 1032, 1034 may have optical power and may output light with a particular amount of wavefront divergence, or may simply output collimated light.

[0284] 31B , the eyepiece 1020 may, in some embodiments, include static lens elements 1532, 1534, 1542. These lens elements are positioned in the path of light from the surrounding environment through the waveguide structures 1032, 1034, respectively, and into the eye 210. In addition, the lens element 1532 is between the waveguide structure 1032 and the eye 210. The lens element 1532 modifies the wavefront divergence of the light output by the waveguide structure 1032 to the eye 210.

[0285] Lens element 1534 modifies the wavefront divergence of light output by waveguide structure 1034 to eye 210. It should be understood that light from waveguide structure 1034 also passes through lens element 1532. Thus, the wavefront divergence of light output by waveguide structure 1034 is modified by both lens element 1534 and lens element 1532 (and waveguide structure 1032, if waveguide structure 1032 has refractive power). In some embodiments, lens elements 1532, 1534 and waveguide structure 1032 provide a particular net refractive power for light output from waveguide structure 1034.

[0286] The illustrated embodiment provides two different levels of wavefront divergence, one for light output from waveguide structure 1032 and a second for light output by waveguide structure 1034. As a result, a virtual object may be placed on two different depth planes corresponding to the different levels of wavefront divergence. In some embodiments, additional levels of wavefront divergence, and therefore additional depth planes, may be provided by adding an additional waveguide structure between lens element 1532 and eye 210, along with additional lens elements between the waveguide structure and eye 210. Additional levels of wavefront divergence may likewise be added by adding additional waveguide structures and lens elements.

[0287] 31B , it should be understood that the lens elements 1532, 1534 and the waveguide structures 1032, 1034 provide a net refractive power that may distort the user's view of the world. As a result, the lens element 1542 may be used to counteract the refractive power and distortion of ambient light. In some embodiments, the refractive power of the lens element 1542 is set to neutralize the aggregate refractive power provided by the lens elements 1532, 1534 and the waveguide structures 1032, 1034. In some other embodiments, the net refractive power of the lens element 1542, the lens elements 1532, 1534, and the waveguide structures 1032, 1034 is equal to the user's prescribed refractive power for corrective lenses.

[0288] In some embodiments, as illustrated in Figures 32A-32B, even when different microdisplays are utilized to generate light of different primary colors, the optical combiner may be omitted from projection system 1500. For example, microdisplays 1030a-1030c may each route light to the eyepiece 1020 through a dedicated associated one of projection optics 1070a-1070c. As shown, microdisplay 1030a has associated projection optics 1070a that focuses light onto associated incoupling optics 1022a, microdisplay 1030b has associated projection optics 1070b that focuses light onto associated incoupling optics 1022b, and microdisplay 1030c has associated projection optics 1070c that focuses light onto associated incoupling optics 1022c.

[0289] It should be understood that in embodiments in which the optical combiner 1500 is not used, several illustrative advantages may be achieved. As an example, when the intervening optical combiner 1500 is omitted, improved light collection may occur because the microdisplays 1030a-1030c may be located closer to the projection optics 1070a-1070c. As a result, higher light utilization efficiency and image brightness may be achieved. Additionally, optical aberrations (such as crosstalk) and inefficiencies (due to the requirement for a large acceptance angle and inefficiencies in reflecting light) associated with light propagation through the X-cube may be advantageously avoided. As another example, the projection system 1500 may be simplified and tuned to specific primary color light. For example, the optical system design for each individual projection optics 1070a-1070c may be separately calibrated for each primary color light generated by the microdisplays 1030a-1030c. In this manner, projection system 1500 may avoid the need for achromatization of the projection optics.

[0290] As another exemplary advantage, as illustrated in FIG. 32A , light from each of the projection optics 1070a-1070c can advantageously be more uniquely focused onto its respective associated internal coupling element 1022a-1022c. The embodiment of FIGS. 32A-32B allows for more precise focusing of each primary color onto its respective internal coupling element 1022a-1022c. The projection optics 1070a-1070c for each primary color may be configured to precisely focus the light onto its respective internal coupling element 1022a-1022c. In some embodiments, this precise focusing can improve image quality by providing a clearly focused image of each primary color.

[0291] 32A illustrates an example of an optical projection system 1500 without an optical combiner (e.g., the optical combiner 1050 described above). In the example shown, three microdisplays 1030a-1030c provide light (e.g., primary color light) to individual projection optics 1070a-1070c. Light from each microdisplay 1030a-1030c may be routed through projection optics 1070a-1070c and focused onto individual internal coupling elements 1022a-1022c included within the eyepiece 1020. It should be understood that each microdisplay 1030a-1030c may be of a distinctly different structure, with each microdisplay including an array of nanowire LEDs formed on a different backplane.

[0292] 32B illustrates another example of a wearable display system having a light projection system without an optical combiner. In some embodiments, the microdisplays 1030a-1030c may form a single integrated unit, e.g., the microdisplays 1030a-1030c are mounted on a single backplane 1093. In some embodiments, the backplane 1093 may be a silicon backplane, which may include electrical components for the microdisplays 1030a-1030c and may include various electronic devices, such as CMOS devices for controlling the nanowire LEDs of the microdisplays 1030a-1030c.

[0293] 32A and 32B, it should be understood that the illustrated eyepiece 1020 may, in some embodiments, be formed from a single waveguide rather than three waveguides. In such embodiments, the single waveguide may support in-coupling, in-propagation, and out-coupling of multiple colors (e.g., two or three colors). The single waveguide may include each of the in-coupling optical elements 1022a, 1022b, 1022c in different locations that are aligned with the light output of the associated individual microdisplays 1030a, 1030b, 1030c. As discussed herein, in some embodiments, the single waveguide may be formed from an optically transparent high refractive index material (e.g., silicon carbide).

[0294] Various exemplary embodiments of the present invention are described herein. Reference is made to these examples in a non-limiting sense. They are provided to illustrate the broader and more applicable aspects of the present invention. Various modifications may be made to the invention described, and equivalents may be substituted without departing from the true spirit and scope of the invention.

[0295] For example, while advantageously utilized with AR displays that provide images across multiple depth planes, the virtual content disclosed herein may also be displayed by systems that provide images on a single depth plane. In addition, the display systems herein may also function as virtual reality displays in which light from the surrounding environment is not transmitted through the eyepieces.

[0296] As another example, it should also be understood that each of the illustrated eyepieces 1020 with multiple waveguides may also simply include only a single waveguide. In some embodiments, the single waveguide may be formed from an optically transparent high refractive index material, such as silicon carbide (SiC). The single waveguide may include a single internal coupling optical element, for example, to internally couple light of multiple different primary colors. In other embodiments, the single waveguide may include multiple spatially separated internal coupling optical elements, each configured to internally couple light of a different primary color. In some other embodiments, at least one of the internal coupling optical elements may be configured to internally couple light of multiple different primary colors.

[0297] In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process, process acts, or steps to the objective, spirit, or scope of the present invention. Moreover, as will be understood by those skilled in the art, each of the individual variations described and illustrated herein has discrete components and features that can be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present invention. All such modifications are intended to be within the scope of the claims associated with this disclosure.

[0298] The present invention includes methods that may be implemented using the subject devices. The methods may include the act of providing such a suitable device. Such provisioning may be performed by an end user. In other words, the act of "providing" merely requires the user to obtain, access, approach, locate, configure, activate, power on, or otherwise act to provide the device required in the subject methods. The methods recited herein may occur in any order of the recited events and the recited sequence of events that is logically possible.

[0299] Exemplary aspects of the invention have been described above, along with details regarding material selection and manufacturing. As for other details of the invention, these may be understood in connection with the above-referenced patents and publications and are generally known or may be understood by those skilled in the art. The same may be true with respect to method-based aspects of the invention in terms of additional acts as commonly or logically adopted.

[0300] Additionally, while the present invention has been described with reference to several embodiments, optionally incorporating various features, the present invention is not limited to those described and indicated as being contemplated with respect to each variation of the invention. Various modifications may be made to the invention as described, and equivalents (whether recited herein or not included for purposes of brevity to some extent) may be substituted without departing from the true spirit and scope of the invention. Additionally, when a range of values ​​is provided, it is understood that all intervening values ​​between the upper and lower limits of that range, and any other stated value or intervening value within the stated range, are encompassed within the invention.

[0301] It is also contemplated that any optional features of the described inventive variations may be set forth and claimed independently or in combination with any one or more of the features described herein. Reference to a singular item includes the possibility that multiple identical items are present. More specifically, as used in this specification and the claims associated herewith, the singular forms "a," "an," "said," and "the" include plural references unless specifically stated otherwise. In other words, the use of articles allows for "at least one" of the items of the present subject matter in the above description and in the claims associated with this disclosure. It should be further noted that such claims may be drafted to exclude any optional element. Accordingly, this language is intended to serve as a predicate for the use of exclusive terminology such as "solely," "only," and the like in connection with the recitation of claim elements, or the use of a "negative" limitation. Without using such exclusive language, the term "comprising" in the claims associated with this disclosure is intended to allow for the inclusion of any additional elements, regardless of whether a given number of elements are recited in such claims or whether the addition of a feature can be considered as a transformation of the nature of the elements recited in such claims.

[0302] 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. A head-mounted display system, comprising: A head mountable frame; a full-color nanowire LED microdisplay supported by the head-mountable frame, the full-color nanowire LED microdisplay comprising a plurality of nanowire light emitters configured to output image light in a plurality of primary colors; an eyepiece supported by the head-mountable frame, the eyepiece configured to receive the image light from the full-color nanowire LED microdisplay and direct the image light to an eye of the user during operation of the head-mounted display system by a user, the eyepiece comprising one or more sets of waveguides forming a waveguide stack, each set of waveguides comprising a dedicated waveguide for a primary color of the plurality of primary colors, each waveguide of the waveguide stack comprising: an incoupling optical element configured to incoupling light from the full-color nanowire LED microdisplay into the waveguide; an outcoupling optical element configured to outcouple the incoupling light out of the waveguide; an eyepiece comprising: a projection optical system; a plurality of optical collimators configured to redirect the image light output from the plurality of nanowire light emitters such that the image light is incident on the projection optics at an angle that causes the projection optics to output the image light in each primary color so that the image light propagates to an appropriate interconnecting optical element of the dedicated waveguide for that primary color; A head-mounted display system comprising:

2. A head-mounted display system as described in claim 1, further comprising a first variable focus lens element and a second variable focus lens element, wherein the waveguide stack is between the first variable focus lens element and the second variable focus lens element, the first variable focus lens element configured to modify the wavefront divergence of light output by the waveguide, and the second variable focus lens element configured to modify the wavefront divergence of light from the outside world propagating through the second variable focus lens element.

3. A head-mounted display system as described in claim 1, further comprising a color filter between two adjacent waveguides of the waveguide stack of the eyepiece, a first of the adjacent waveguides preceding a second of the adjacent waveguides in an optical path extending from the full-color nanowire LED microdisplay, the color filter configured to selectively absorb light of a wavelength corresponding to the wavelength of light configured to be internally coupled by the internal coupling optical element of the first of the adjacent waveguides.

4. within the optical path, a third waveguide subsequent to the second of the adjacent waveguides; another color filter configured to selectively absorb light of wavelengths corresponding to wavelengths of light configured to be incoupled by the incoupling optical element of the second one of the neighboring waveguides; The head mounted display system of claim 3 further comprising:

5. A head-mounted display system as described in claim 1, further comprising light-absorbing color filters on major surfaces of at least some of the waveguides of the waveguide stack, the light-absorbing color filters on the major surfaces of the waveguides being configured to absorb light of wavelengths internally coupled into the corresponding waveguides.

6. A head-mounted display system as described in claim 1, wherein the waveguide stack is configured to output the externally coupled light with variable wavefront divergence corresponding to multiple depth planes.

7. A head-mounted display system as described in claim 1, wherein each of the multiple nanowire light emitters of the full-color nanowire LED microdisplay has an angular emission profile of less than 50° through the use of the multiple light collimators.

8. A head-mounted display system as described in claim 1, wherein the eyepiece lens has a set of multiple different waveguides that output light with different wavefront divergences corresponding to different depth planes.

9. A head-mounted display system as described in claim 1, wherein the internal coupling optical element is configured to internally couple light, the internally coupled light generally propagating in a propagation direction through an associated waveguide, the internal coupling optical element occupying an area having a width parallel to the propagation direction and a length along an axis intersecting the propagation direction, the length exceeding the width.

10. A head-mounted display system as described in claim 1, wherein light emitted from the multiple nanowire light emitters of the full-color nanowire LED microdisplay having different wavelengths is redirected in different directions by the projection optical system.

11. The head-mounted display system of claim 1 , wherein the plurality of nanowire light emitters of the full-color nanowire LED microdisplay are subdivided into monochrome light emitters.

12. A head-mounted display system as described in claim 1, wherein the multiple nanowire light emitters of the full-color nanowire LED microdisplay emit the image light with a relatively wide angular emission profile, and the multiple light collimators, in addition to redirecting the image light, reduce the angular emission profile of the image light.

13. A head-mounted display system as described in claim 1, wherein the full-color nanowire LED microdisplay emits light of three primary colors and, in combination with the projection optical system and the multiple optical collimators, forms a three-pupil projection system.

14. A head-mounted display system as described in claim 1, wherein the plurality of optical collimators form an array of optical collimators associated with the plurality of nanowire optical emitters of the full-color nanowire LED microdisplay.

15. A head-mounted display system as described in claim 14, wherein the plurality of optical collimators have different physical parameters across the array.

16. A head-mounted display system as described in claim 15, wherein the plurality of optical collimators comprise flat nanolenses.

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