Virtual and Augmented Reality Display System with Emissive Microdisplays

Abstract

To provide a suitable virtual and augmented reality display system.SOLUTION: A wearable display system includes one or more light-emitting microdisplay (e.g., micro-LED display). The microdisplay may be a monochrome or a color microdisplay. The microdisplay may include an optical emitter array. An optical collimator may be utilized for narrowing the angle emission profile of emitted light by the optical emitter. When using a plurality of light-emitting microdisplays, the microdisplays may be located on a different side of an X-cube prism that receives a beam from different microdisplays and outputs the beam from the same plane of a cube. An optical combiner directs light to a projection optical system that outputs light to an ocular lens that relays light to a user's eyes. The ocular lens may output light to the user's eyes by wave front dispersion with different quantity and present virtual contents to the different depth plane.SELECTED DRAWING: Figure 11A

Description

Technical Field

[0001] (Claiming Priority) This application claims the benefit of priority to U.S. Provisional Application No. 62 / 800,363, filed on February 1, 2019, entitled "VIRTUAL AND AUGMENTED REALITY DISPLAY SYSTEMS WITH EMISSIVE MICRO-DISPLAYS"; U.S. Provisional Application No. 62 / 911,018, filed on October 4, 2019, entitled "AUGMENTED AND VIRTUAL REALITY DISPLAY SYSTEMS WITH SHARED DISPLAY FOR LEFT AND RIGHT EYES"; and U.S. Provisional Application No. 62 / 786,199, filed on December 28, 2018, entitled "LOW MOTION-TO-PHOTON LATENCY ARCHITECTURE FOR AUGMENTED AND VIRTUAL REALITY DISPLAY SYSTEMS". The above applications are hereby incorporated by reference in their entirety. (Incorporation by Reference)

[0002] This application incorporates by reference in its entirety each of the following: U.S. Patent Application No. 14 / 555,585, filed November 27, 2014, and published as U.S. Patent Publication No. 2015 / 0205126 on July 23, 2015; U.S. Patent Application No. 14 / 690,401, filed April 18, 2015, and published as U.S. Patent Publication No. 2015 / 0302652 on October 22, 2015; U.S. Patent Application No. 14 / 212,961, filed March 14, 2014, and issued as U.S. Patent No. 9,417,452 on August 16, 2016; U.S. Patent Application No. 14 / 331,218, filed July 14, 2014, and published as U.S. Patent Publication No. 2015 / 0309263 on October 29, 2015; U.S. Patent Application Publication No. 2018 / 0061121, published March 1, 2018; U.S. Patent Application No. 16 / 221,065, filed December 14, 2018; U.S. Patent Application Publication No. 2018 / 0275410, published September 27, 2018; U.S. Provisional Application No. 62 / 786,199, filed December 28, 2018; U.S. Patent Application No. 16 / 221,359, filed December 14, 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. (Technical Field)

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

Background Art

[0004] Modern computing and display technologies have facilitated the development of systems for so-called "virtual reality" or "augmented reality" experiences, in which digitally reproduced images or portions thereof are presented to a user in a manner that appears or can be perceived as being real. Virtual reality, i.e., the "VR" scenario, typically involves the presentation of digital or virtual image information without transparency to other actual real-world visual inputs, and augmented reality, i.e., the "AR" scenario, typically involves the presentation of digital or virtual image information as an augmentation to the visualization of the actual world around the user. Mixed reality or "MR" scenarios are a type of AR scenario that typically involves virtual objects integrated into and responsive to the natural world. For example, an MR scenario may include AR image content that appears to be blocked by or otherwise interact with objects in the real world.

[0005] Referring to FIG. 1, an augmented reality scene 10 is depicted. To a user of AR technology, a real-world park-like setting 20 is visible, featuring people, trees, buildings in the background, and a concrete platform 30. The user also "sees" "virtual content" such as a robot figure 40 standing on the real-world platform 30 and an avatar character 50 in the form of a flying cartoon that appears anthropomorphic like a bumblebee. These elements 50, 40 are "virtual" in that they do not exist in the real world. The human visual perception system is complex, and it is difficult to produce AR technology that facilitates a comfortable, natural, and rich presentation of virtual image elements among other virtual or real-world image elements. SUMMARY OF THE INVENTION MEANS FOR SOLVING THE PROBLEM

[0006] Some embodiments include a head-mounted display system. The display system includes a head-mountable frame, a plurality of emissive microdisplays supported by the frame, and an eyepiece supported by the frame. The emissive microdisplays are configured to output image light. The eyepiece is configured to receive the image light from the emissive microdisplays and direct the image light toward the user's eyes in response to mounting the frame on the user.

[0007] Some other embodiments also include a head-mounted display system. The display system includes an emissive microdisplay comprising an array of light emitters corresponding to pixels, and a waveguide assembly comprising one or more waveguides. The array of light emitters is configured to define an image. Each waveguide of the waveguide assembly comprises an internal coupling optical element configured to internally couple light from the microdisplay into the waveguide, and an external coupling optical element configured to externally couple the internally coupled light out of the waveguide. The waveguide assembly is configured to output the externally coupled light with a variable amount of wavefront divergence corresponding to a plurality of depth planes.

[0008] Some other embodiments also include a head-mounted display system. The display system includes a head-mountable frame, an emissive microdisplay supported by the frame and comprising an array of groups of microemitters, a microlens array proximate to the array of groups of microemitters, and a projection lens structure configured to receive light from the microlens array. Each group of microemitters of the array of groups of microemitters comprises a first microemitter configured to emit light of a first color, a second microemitter configured to emit light of a second color, and a third microemitter configured to emit light of a third color. Each group of microemitters also has an associated microlens encompassing the microemitters of the group of microemitters.

[0009] Some further embodiments include a light-emitting microdisplay system. The microdisplay system includes an array of light emitters comprising lines of light emitters. The light emitters of each line are elongated along an axis intersecting the line and are configured to emit light of the same color. The plurality of lines of light emitters constitute a group of lines. Each line of the group of lines is configured to emit light of a color different from that of at least one other line of the group of lines.

[0010] Some additional examples of embodiments are provided below.

[0011] (Example 1) A head-mounted display system, A head-mountable frame, and A plurality of light-emitting microdisplays supported by the frame, the light-emitting microdisplays being configured to output image light, and An eyepiece lens supported by the frame, the eyepiece lens being configured to receive image light from the light-emitting microdisplay and direct the image light toward the user's eye in response to mounting the frame on the user. A head-mounted display system comprising.

[0012] (Example 2) Further comprising an X-cube prism, each of the light-emitting microdisplays facing a different side of the X-cube prism, the head-mounted display system according to Example 2.

[0013] (Example 3) The output side of the X-cube prism faces the eyepiece lens, the head-mounted display system according to Example 2.

[0014] (Example 4) The light-emitting microdisplay is a head-mounted display system according to any one of Examples 1-3, which is a monochrome microdisplay.

[0015] (Example 5) The light-emitting microdisplay is a head-mounted display system according to any one of Examples 1-4, which includes an array of micro LEDs.

[0016] (Example 6) The head-mounted display system according to any one of Examples 1-3, further includes a plurality of arrays of optical collimators, each microdisplay has an associated array of optical collimators, and each array of optical collimators is configured to capture and reduce the angular emission profile of light from the microdisplay.

[0017] (Example 7) The head-mounted display system according to Example 6, each microdisplay includes an array of light emitters, and each light emitter has an associated optical collimator.

[0018] (Example 8) The head-mounted display system according to any one of Examples 6-7, the optical collimator includes a microlens.

[0019] (Example 9) The head-mounted display system according to any one of Examples 6-7, the optical collimator includes a nanolens.

[0020] (Example 10) The head-mounted display system according to any one of Examples 6-7, the optical collimator includes a reflective well.

[0021] (Example 11) The head-mounted display system according to any one of Examples 6-7, the optical collimator includes a metasurface.

[0022] (Example 12) The optical collimator is a head-mounted display system according to any one of Examples 6-7, comprising a liquid crystal lattice.

[0023] (Example 13) Each microdisplay comprises rows of light emitters, some rows of light emitters emit light of a different color from other rows of light emitters, and the light emitters in each row emit light of the same color. The head-mounted display system according to any one of Examples 1-12.

[0024] (Example 14) The optical collimator is a head-mounted display system according to Example 13, comprising a grating extending along the major axis of the associated row of light emitters.

[0025] (Example 15) Further comprising a waveguide assembly comprising one or more waveguides, each waveguide An internal coupling optical element configured to internally couple light from the microdisplay into the waveguide, An external coupling optical element configured to externally couple the internally coupled light out of the waveguide And a head-mounted display system according to any one of Examples 1-14.

[0026] (Example 16) The waveguide assembly is configured to output externally coupled light with a variable amount of wavefront divergence corresponding to a plurality of depth planes. The head-mounted display system according to Example 15.

[0027] (Example 17) The waveguide assembly includes a plurality of sets of waveguides, each set of waveguides includes a dedicated waveguide for a primary color, and each set of waveguides includes an external coupling 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 according to any one of Embodiments 15-16.

[0028] (Embodiment 18) Further comprising a variable focus lens element, the waveguide assembly is between a first variable focus lens element and a second variable focus lens element. The first variable focus lens element is configured to correct the wavefront divergence of the light output by the waveguide assembly, and the second variable focus lens element is configured to correct the wavefront divergence of the light from the outside world to the second variable focus lens element. The head-mounted display system according to Embodiment 16.

[0029] (Embodiment 19) The waveguide assembly includes a stack of waveguides, and a plurality of light-emitting microdisplays are configured to output light of a plurality of primary colors. The waveguide assembly includes at least one dedicated waveguide for the light of each primary color. The head-mounted display system according to Embodiment 15.

[0030] (Embodiment 20) A plurality of arrays of optical collimators, each microdisplay having an associated array of optical collimators, and An X-cube prism, each light-emitting microdisplay facing a different side of the X-cube prism, and A projection optical system configured to receive light from the X-cube prism and converge the received light toward the waveguide assembly. The head-mounted display system according to any one of Embodiments 15-19. Further comprising

[0031] (Example 21) The internal coupling optical elements of at least two waveguides are laterally offset in the direction of the light propagating to the internal coupling optical elements as seen in a front-on view, at least one of the array of optical collimators is configured to direct light into the corresponding side of the X-cube prism at a non-normal angle to the corresponding side, and the light passing through at least one of the optical collimators converges onto the corresponding internal coupling optical element, while the light passing through the other of the optical collimators converges onto a different internal coupling optical element. The head-mounted display system according to any one of Examples 15-20.

[0032] (Example 22) Further comprising a color filter between two adjacent waveguides of the stack of waveguides, wherein the first of the adjacent waveguides precedes the second of the adjacent waveguides in the optical path extending from the microdisplay, and the color filter is configured to selectively absorb light of a wavelength corresponding to the wavelength of the light that is internally coupled by the internal coupling optical element of the first of the adjacent waveguides. The head-mounted display system according to any one of Examples 15-20.

[0033] (Example 23) a third waveguide following the second of the adjacent waveguides in the optical path, and another color filter configured to selectively absorb light of a wavelength corresponding to the wavelength of the light that is internally coupled by the internal coupling optical element of the second of the adjacent waveguides. Another color filter The head-mounted display system according to Example 22, further comprising.

[0034] (Example 24) The position of the internal coupling optical element of each waveguide of the waveguide assembly overlaps in the direction of the light propagating to the internal coupling optical element as seen in a front-on view. The head-mounted display system according to any one of Examples 15-23.

[0035] (Example 25) The head-mounted display system according to any one of Examples 15-23, further comprising an absorptive color filter on at least some of the major surfaces of the waveguide, wherein the absorptive color filter on the major surface of the waveguide is configured to absorb light of a wavelength that is internally coupled into the corresponding waveguide.

[0036] (Example 26) The internal coupling optical element is configured to couple light into the internally coupled light that generally propagates in the propagation direction through the associated waveguide, and the internal coupling optical element occupies an area having a width parallel to the propagation direction and a length along an axis intersecting the propagation direction, and the length exceeds the width. The head-mounted display system according to any one of Examples 1-25.

[0037] (Example 27) A head-mounted display system, A light-emitting microdisplay comprising an array of light emitters corresponding to pixels, wherein the array of light emitters is configured to define an image, the light-emitting microdisplay, A waveguide assembly comprising one or more waveguides, each waveguide An internal coupling optical element configured to internally couple light from the microdisplay into the waveguide, An external coupling optical element configured to externally couple the internally coupled light out of the waveguide and The waveguide assembly is configured to output the externally coupled light with a variable amount of wavefront divergence corresponding to a plurality of depth planes. The waveguide assembly and a head-mounted display system comprising the same.

[0038] (Example 28) The light-emitting microdisplay of the head-mounted display system according to Example 27 is a micro-LED display.

[0039] (Example 29) The head-mounted display system according to any one of Examples 27-28, further comprising an array of optical collimators in proximity to the array of optical emitters, each optical emitter having an associated optical collimator, each optical collimator configured to receive and focus the light output by the associated optical emitter.

[0040] (Example 30) The head-mounted display system according to Example 29, wherein the optical collimator comprises a microlens.

[0041] (Example 31) The head-mounted display system according to Example 29, wherein the optical collimator comprises a nanolens.

[0042] (Example 32) The head-mounted display system according to Example 29, wherein the optical collimator comprises a reflective well.

[0043] (Example 33) The head-mounted display system according to Example 29, wherein the optical collimator comprises a metasurface.

[0044] (Example 34) The head-mounted display system according to Example 29, wherein the optical collimator comprises a liquid crystal grating.

[0045] (Example 35) The head-mounted display system according to any one of Examples 27-34, further comprising a projection optical system configured to converge the light from the emissive microdisplay onto the internal coupling optical elements of one or more waveguides.

[0046] (Example 36) Individual ones of the optical emitters are configured to emit light of one of a plurality of primary colors, The waveguide assembly comprises a plurality of sets of waveguides, Each set of waveguides includes a dedicated waveguide for each primary color, and each set of waveguides includes an external coupling 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 according to any one of Examples 27-35.

[0047] (Example 37) Further comprising a variable focus lens element, the waveguide assembly is between a first variable focus lens element and a second variable focus lens element. The first variable focus lens element is configured to correct the wavefront divergence of the light output by the waveguide assembly, and the second variable focus lens element is configured to correct the wavefront divergence of the light from the outside world to the second variable focus lens element. The head-mounted display system according to any one of Examples 27-35.

[0048] (Example 38) The waveguide assembly includes a stack of waveguides. The head-mounted display system according to any one of Examples 27-37.

[0049] (Example 39) Further comprising a color filter between two adjacent waveguides of the stack of waveguides. The first of the adjacent waveguides precedes the second of the adjacent waveguides in the optical path extending from the microdisplay. The color filter is configured to be internally coupled by the internal coupling optical element of the first of the adjacent waveguides and is configured to selectively absorb light of a wavelength corresponding to the wavelength of the light. The head-mounted display system according to Example 38.

[0050] (Example 40) A third waveguide following the second of the adjacent waveguides in the optical path, Another color filter, the other color filter being configured to selectively absorb light of a wavelength corresponding to the wavelength of light that is configured to be internally coupled by an internal coupling optical element of a second one of the neighboring waveguides The head-mounted display system according to Example 39, further comprising .

[0051] (Example 41) The head-mounted display system according to Examples 38-40, further comprising an absorptive color filter on at least some of the major surfaces of the waveguide, the absorptive color filter on the major surface of the waveguide being configured to absorb light of a wavelength that is internally coupled into the corresponding waveguide.

[0052] (Example 42) The internal coupling optical element is configured to internally couple light with the internally coupled light that generally propagates in the propagation direction through the 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 being greater than the width, the head-mounted display system according to any one of Examples 27-41.

[0053] (Example 43) A head-mounted display system, A head-mountable frame, A light-emitting microdisplay supported by the frame, the light-emitting microdisplay comprising an array of groups of microemitters, each group of microemitters A first microemitter configured to emit light of a first color, A second microemitter configured to emit light of a second color, A third microemitter configured to emit light of a third color And a light-emitting microdisplay comprising A micro-lens array proximate to an array of groups of micro-emitters, each group of micro-emitters having an associated micro-lens encompassing the micro-emitters of the group of micro-emitters, the micro-lens array, a projection lens structure configured to receive light from the micro-lens array, and a head-mounted display system comprising the same.

[0054] (Example 44) further comprising a waveguide assembly comprising first, second, and third optical internal coupling regions positioned to receive light from the projection lens structure, the projection lens structure being configured to converge light from a first micro-emitter onto the first internal coupling region, light from a second micro-emitter onto the second internal coupling region, and light from a third micro-emitter onto the third internal coupling region, the head-mounted display system according to Example 43.

[0055] (Example 45) the waveguide assembly comprising first, second, and third waveguides each comprising a first, second, and third optical internal coupling region, the head-mounted display system according to Example 44.

[0056] (Example 46) the first, second, and third optical internal coupling regions being laterally offset so as to be visible from the projection lens structure, the head-mounted display system according to any one of Examples 44 - 45.

[0057] (Example 47) the first and second optical internal coupling regions overlapping so as to be visible from the projection lens structure, the head-mounted display system according to any one of Examples 44 - 45.

[0058] (Example 48) The color filter is further provided between the first optical internal coupling region and the second optical internal coupling region, and the color filter is configured to selectively absorb light having a wavelength corresponding to the wavelength of the light configured to be internally coupled by the first internal coupling optical element. The head-mounted display system according to any one of Examples 44-47.

[0059] (Example 49) The second and third optical internal coupling regions overlap as viewed from the projection lens structure, and further include another color filter configured to selectively absorb light having a wavelength corresponding to the wavelength of the light configured to be internally coupled by the second internal coupling optical element. The head-mounted display system according to any one of Examples 44-48.

[0060] (Example 50) The waveguide is further provided with an absorptive color filter on at least some of the main surfaces of the waveguide, and the absorptive color filter on the main surface of the waveguide is configured to absorb light having a wavelength that is internally coupled into the corresponding waveguide. The head-mounted display system according to any one of Examples 44-49.

[0061] (Example 51) The waveguide assembly includes a plurality of sets of waveguides, Each set of waveguides includes one dedicated waveguide for each of the first, second, or third colors, Each set of waveguides includes an external coupling 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 according to any one of Examples 44-50.

[0062] (Example 52) The head-mounted display system according to any one of Examples 44-50, 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 is configured to correct the wavefront divergence of the light output to the user's eye by the waveguide assembly, and the second variable focus lens element is configured to correct the wavefront divergence of the light from the outside to the user's eye.

[0063] (Example 53) The internal coupling optical element is configured to internally couple light to the coupled light that generally propagates in the propagation direction through the associated waveguide. The internal coupling optical element occupies an area having a width parallel to the propagation direction and a length along an axis intersecting the propagation direction, and the length is greater than the width. The head-mounted display system according to any one of Examples 44-52.

[0064] (Example 54) The first color is green, the second color is blue, and the third color is red. The head-mounted display system according to any one of Examples 43-53.

[0065] (Example 55) The light-emitting microdisplay includes an array of micro LEDs. The head-mounted display system according to any one of Examples 43-54.

[0066] (Example 56) The light-emitting microdisplay is one of a plurality of similar microdisplays and further includes an X-cube prism. Each light-emitting microdisplay faces a different side of the X-cube prism. The head-mounted display system according to any one of Examples 43-55.

[0067] (Example 57) The output side of the X-cube prism is configured to output the light from the light-emitting microdisplay into the projection lens structure, the head-mounted display system described in Example 56.

[0068] (Example 58) A light-emitting microdisplay system, comprising an array of light emitters having lines of light emitters, each line of light emitters extends along an axis intersecting the line, each line of light emitters is configured to emit light of the same color, a plurality of lines of light emitters form a group of lines, each line of the group of lines is configured to emit light of a color different from that of at least one other line of the group of lines, A light-emitting microdisplay system.

[0069] (Example 59) Each group of lines comprises a first line of light emitters configured to emit light of a first color, a second line of light emitters configured to emit light of a second color, and a third line of light emitters configured to emit a third color of the light-emitting microdisplay system described in Example 58.

[0070] (Example 60) The first color is green, the second color is blue, and the third color is red, of the light-emitting microdisplay system described in Example 59.

[0071] (Example 61) Further comprising a lens array across the array of light emitters, the lens array is configured to receive the light from the light emitters and reduce the angular emission profile of the received light, of the light-emitting microdisplay system according to any one of Examples 58-59.

[0072] (Example 62) The lens array is a nano lens array including a plurality of diffraction gratings, and the light-emitting microdisplay system according to Example 61.

[0073] (Example 63) The diffraction grating extends along an axis parallel to the line associated with the light emitter, and the light-emitting microdisplay system according to Example 62.

[0074] (Example 64) Each individual diffraction grating extends across the entire line associated with the light emitter, and the light-emitting microdisplay system according to Example 64.

[0075] (Example 65) The diffraction grating includes a line of material in the substrate, and the material forming the line has a refractive index different from that of the material forming the substrate, and the light-emitting microdisplay system according to any one of Examples 62-64.

[0076] (Example 66) The pitch of the lines is 30 to 300 nm, and the light-emitting microdisplay system according to any one of Examples 58-65.

[0077] (Example 67) The depth of the lines is 10 to 1,000 nm, and the light-emitting microdisplay system according to any one of Examples 58-66.

[0078] (Example 68) The depth and pitch of the lines vary between each line of the group of lines, and the light-emitting microdisplay system according to any one of Examples 58-67.

[0079] (Example 69) The refractive index of the material forming the line is 1.5 to 2.5, and the light-emitting microdisplay system according to any one of Examples 58-68.

[0080] (Example 70) The refractive index of the substrate is 1.5 to 2.5, and the light-emitting microdisplay system according to any one of Examples 58-69.

[0081] (Example 71) A projection optical system configured to converge light from the lens array, A waveguide assembly including one or more waveguides, each waveguide An internal coupling optical element configured to internally couple light from the projection optical system into the waveguide, An external coupling optical element configured to externally couple the internally coupled light out of the waveguide and a waveguide assembly including The light-emitting microdisplay system according to any one of Examples 58-70, further including

[0082] (Example 72) The internal coupling optical element of each waveguide is laterally offset with respect to the internal coupling optical elements of other waveguides as viewed from the line of sight of the projection optical system, The different internal coupling optical elements are configured to internally couple different colors of light, The lens array is configured to direct different colors of light along the optical path toward different ones of the internal coupling optical elements, The light-emitting microdisplay system according to Example 71.

[0083] (Example 73) The head-mounted display system according to any one of Examples 71-72, further including a projection optical system configured to converge light from the light-emitting microdisplay onto the internal coupling optical elements of one or more waveguides.

[0084] (Example 74) Individual light emitters are configured to emit light of one of a plurality of primary colors, The waveguide assembly includes a plurality of sets of waveguides, Each set of waveguides includes a dedicated waveguide for each primary color, and each set of waveguides includes an external coupling 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 according to any one of Examples 58-73.

[0085] (Example 75) Further comprising a variable focus lens element, the waveguide assembly is between a first variable focus lens element and a second variable focus lens element, the first variable focus lens element is configured to correct the wavefront divergence of the light output by the waveguide assembly, and the second variable focus lens element is configured to correct the wavefront divergence of the light from the outside world to the second variable focus lens element. The head-mounted display system according to any one of Examples 71-73.

[0086] (Example 76) The waveguide assembly includes a stack of waveguides, Further comprising a color filter between two adjacent waveguides in the stack of waveguides, The first of the adjacent waveguides precedes the second of the adjacent waveguides in the optical path extending from the microdisplay, The color filter is configured to selectively absorb light of a wavelength corresponding to the wavelength of the light that is internally coupled by the internal coupling optical element of the first of the adjacent waveguides. The head-mounted display system according to any one of Examples 71-75.

[0087] (Example 77) A third waveguide following the second of the adjacent waveguides in the optical path, Another color filter, the other color filter being configured to selectively absorb light of a wavelength corresponding to the wavelength of light that is configured to be internally coupled by an internal coupling optical element of a second one of the neighboring waveguides The head-mounted display system according to Example 76, further comprising .

[0088] (Example 78) The head-mounted display system according to any one of Examples 71-77, further comprising an absorptive color filter on at least some of the major surfaces of the waveguide, the absorptive color filter on the major surface of the waveguide being configured to absorb light of a wavelength that is internally coupled into the corresponding waveguide.

[0089] (Example 79) The internal coupling optical element is configured to internally couple light with the internally coupled light that generally propagates in the propagation direction through the 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 being greater than the width, the head-mounted display system according to any one of Examples 71-78. This specification also provides, for example, the following. (Item 1) A head-mounted display system comprising: a head-mountable frame; a plurality of light-emitting microdisplays supported by the frame, the light-emitting microdisplays being configured to output image light; an eyepiece lens supported by the frame, the eyepiece lens being configured to receive image light from the light-emitting microdisplays and direct the image light towards a user's eye in response to mounting the frame on the user. A head-mounted display system comprising the above. (Item 2) The head-mounted display system according to Item 1, further comprising an X-cube prism, wherein each of the light-emitting microdisplays faces a different side of the X-cube prism. (Item 3) The head-mounted display system according to Item 2, wherein an output side of the X-cube prism faces the eyepiece lens. (Item 4) The head-mounted display system according to Item 2, wherein the light-emitting microdisplay is a monochrome microdisplay. (Item 5) The head-mounted display system according to Item 1, wherein the light-emitting microdisplay comprises an array of micro LEDs. (Item 6) The head-mounted display system according to Item 1, further comprising a plurality of arrays of optical collimators, each microdisplay having an associated array of optical collimators, each array of optical collimators being configured to capture and reduce the angular emission profile of light from the microdisplay. (Item 7) The head-mounted display system according to Item 6, wherein each microdisplay comprises an array of light emitters, and each light emitter has an associated optical collimator. (Item 8) The head-mounted display system according to Item 6, wherein the optical collimator comprises a microlens. (Item 9) The head-mounted display system according to Item 6, wherein the optical collimator comprises a nanolens. (Item 10) The head-mounted display system according to Item 6, wherein the optical collimator comprises a reflective well. (Item 11) The head-mounted display system according to Item 6, wherein the optical collimator comprises a metasurface. (Item 12) The head-mounted display system according to item 6, wherein the optical collimator includes a liquid crystal grating. (Item 13) The head-mounted display system according to item 6, wherein each microdisplay includes rows of light emitters, some rows of light emitters emit light of a different color from other rows of light emitters, and the light emitters in each row emit light of the same color. (Item 14) The head-mounted display system according to item 13, wherein the optical collimator includes a grating extending along the major axis of the associated row of light emitters. (Item 15) Further comprising a waveguide assembly including one or more waveguides, each waveguide an internal coupling optical element configured to internally couple light from the microdisplay into the waveguide, and an external coupling optical element configured to externally couple the internally coupled light out of the waveguide The head-mounted display system according to item 1. (Item 16) The head-mounted display system according to item 15, wherein the waveguide assembly is configured to output the externally coupled light with a variable amount of wavefront divergence corresponding to a plurality of depth planes. (Item 17) The head-mounted display system according to item 16, wherein the waveguide assembly includes a plurality of sets of waveguides, each set of waveguides includes dedicated waveguides for primary colors, each set of waveguides includes an external coupling optical element configured to output light with wavefront divergence corresponding to a common depth plane, and different sets of waveguides output light with different amounts of wavefront divergence corresponding to different depth planes. (Item 18) Further comprising a variable focus lens element, the waveguide assembly is between a first variable focus lens element and a second variable focus lens element, the first variable focus lens element is configured to correct the wavefront divergence of the light output by the waveguide assembly, and the second variable focus lens element is configured to correct the wavefront divergence of the light from the outside world to the second variable focus lens element. The head-mounted display system according to item 16. (Item 19) The head-mounted display system according to item 15, wherein the waveguide assembly includes a stack of waveguides, the plurality of light-emitting microdisplays are configured to output light of a plurality of primary colors, and the waveguide assembly includes at least one dedicated waveguide for each primary color of light. (Item 20) A plurality of arrays of optical collimators, each microdisplay having an associated array of optical collimators, and an X-cube prism, each of the light-emitting microdisplays facing a different side of the X-cube prism, and a projection optical system configured to receive light from the X-cube prism and converge the received light toward the waveguide assembly, The head-mounted display system according to item 19, further comprising. (Item 21) The internal coupling optical elements of at least two waveguides are laterally offset in the direction of the light propagating through the internal coupling optical elements as seen in a front-on view, At least one of the arrays of optical collimators is configured to direct light into the corresponding side of the X-cube prism at a non-normal angle to the corresponding side, and the light passing through at least one of the optical collimators converges on a corresponding internal coupling optical element, while the light passing through the other of the optical collimators converges on a different internal coupling optical element. The head-mounted display system according to item 20. (Item 22) Further comprising a color filter between two adjacent waveguides of a stack of waveguides, the first of the adjacent waveguides preceding the second of the adjacent waveguides in the optical path extending from the microdisplay, the color filter being 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. The head-mounted display system according to item 19. (Item 23) A third waveguide following the second of the adjacent waveguides in the optical path, and Another 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 second of the adjacent waveguides, The head-mounted display system according to item 22, further comprising. (Item 24) The position of the internal coupling optical element of each waveguide of the waveguide assembly is the head-mounted display system according to item 19 that overlaps in the direction of the light propagating to the internal coupling optical element as seen in a front view. (Item 25) The head-mounted display system according to item 19, further comprising an absorptive color filter on at least some of the major surfaces of the waveguides, wherein the absorptive color filter on the major surface of the waveguide is configured to absorb light of a wavelength that is internally coupled into the corresponding waveguide. (Item 26) The internal coupling optical element is configured to couple light to internally coupled light that generally propagates in the propagation direction through the associated waveguide, and the internal coupling optical element occupies an area having a width parallel to the propagation direction and a length along an axis intersecting the propagation direction, and the length exceeds the width. The head-mounted display system according to item 1. (Item 27) A head-mounted display system, A light-emitting microdisplay comprising an array of light emitters corresponding to pixels, wherein the array of light emitters is configured to define an image, a light-emitting microdisplay, A waveguide assembly comprising one or more waveguides, each waveguide An internal coupling optical element configured to internally couple light from the microdisplay into the waveguide, An external coupling optical element configured to externally couple the internally coupled light out of the waveguide And The waveguide assembly is configured to output the externally coupled light with a variable amount of wavefront divergence corresponding to a plurality of depth planes. A waveguide assembly Comprising a head-mounted display system. (Item 28) The head-mounted display system according to item 27, wherein the light-emitting microdisplay is a micro-LED display. (Item 29) The head-mounted display system according to item 27, further comprising an array of optical collimators proximate to the array of light emitters, each of the light emitters having an associated optical collimator, and each optical collimator being configured to receive and concentrate the light output by the associated light emitter. (Item 30) The head-mounted display system according to item 29, wherein the optical collimator comprises a microlens. (Item 31) The head-mounted display system according to item 29, wherein the optical collimator includes a nano lens. (Item 32) The head-mounted display system according to item 29, wherein the optical collimator includes a reflective well. (Item 33) The head-mounted display system according to item 29, wherein the optical collimator includes a metasurface. (Item 34) The head-mounted display system according to item 29, wherein the optical collimator includes a liquid crystal lattice. (Item 35) The head-mounted display system according to item 27, further comprising a projection optical system configured to converge the light from the light-emitting microdisplay onto the internal coupling optical element of the one or more waveguides. (Item 36) Each of the light emitters is configured to emit light of one of a plurality of primary colors. The waveguide assembly includes a plurality of sets of waveguides. Each set of waveguides includes a dedicated waveguide for each primary color, and each set of waveguides includes an external coupling 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 according to item 27. (Item 37) The head-mounted display system according to item 27, 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 is configured to correct the wavefront divergence of the light output by the waveguide assembly, and the second variable focus lens element is configured to correct the wavefront divergence of the light from the outside to the second variable focus lens element. (Item 38) The head-mounted display system according to item 27, wherein the waveguide assembly includes a stack of waveguides. (Item 39) The head-mounted display system according to item 38, further comprising a color filter between two adjacent waveguides in the stack of waveguides. The first of the adjacent waveguides precedes the second of the adjacent waveguides in the optical path extending from the microdisplay, and the color filter is configured to selectively absorb light of a wavelength corresponding to the wavelength of the light internally coupled by the internal coupling optical element of the first of the adjacent waveguides. (Item 40) A third waveguide following a second one of the waveguides in the vicinity within the optical path, Another color filter configured to selectively absorb light of a wavelength corresponding to the wavelength of light that is configured to be internally coupled by the internal coupling optical element of the second one of the waveguides in the vicinity, the other color filter The head-mounted display system according to item 39, further comprising. (Item 41) The head-mounted display system according to item 38, further comprising an absorptive color filter on at least some of the major surfaces of the waveguides, the absorptive color filter on the major surface of the waveguide being configured to absorb light of a wavelength that is internally coupled into the corresponding waveguide. (Item 42) The internal coupling optical element is configured to internally couple light with internally coupled light that generally propagates in the propagation direction through the 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 being greater than the width, the head-mounted display system according to item 38. (Item 43) A head-mounted display system, A head-mountable frame, A light-emitting microdisplay supported by the frame, the light-emitting microdisplay comprising an array of groups of microemitters, each group of microemitters A first microemitter configured to emit light of a first color, A second microemitter configured to emit light of a second color, A third microemitter configured to emit light of a third color And a light-emitting microdisplay, A microlens array proximate to the array of groups of microemitters, each group of microemitters having an associated microlens that encompasses the microemitters of the group of microemitters, the microlens array And a projection lens structure configured to receive light from the microlens array The head-mounted display system comprising. (Item 44) The head-mounted display system further comprising a waveguide assembly comprising first, second, and third optical internal coupling regions positioned to receive light from the projection lens structure. The projection lens structure converges the light from the first micro-emitter onto the first internal coupling region, converges the light from the second micro-emitter onto the second internal coupling region, and converges the light from the third micro-emitter onto the third internal coupling region, and is configured as the head-mounted display system according to item 43. (Item 45) The waveguide assembly includes first, second, and third waveguides each having the first, second, and third optical internal coupling regions respectively, and is the head-mounted display system according to item 44. (Item 46) The first, second, and third optical internal coupling regions are laterally offset so as to be visually recognized from the projection lens structure, and is the head-mounted display system according to item 45. (Item 47) The first and second optical internal coupling regions overlap so as to be visually recognized from the projection lens structure, and is the head-mounted display system according to item 45. (Item 48) A color filter is further provided between the first optical internal coupling region and the second optical internal coupling region, and the color filter is configured to selectively absorb light having a wavelength corresponding to the wavelength of the light configured to be internally coupled by the first internal coupling optical element, and is the head-mounted display system according to item 47. (Item 49) The second and third optical internal coupling regions overlap so as to be visually recognized from the projection lens structure, and further includes another color filter configured to selectively absorb light having a wavelength corresponding to the wavelength of the light configured to be internally coupled by the second internal coupling optical element, and is the head-mounted display system according to item 48. (Item 50) An absorptive color filter is further provided on at least some of the major surfaces of the waveguide, and the absorptive color filter on the major surface of the waveguide is configured to absorb light having a wavelength that is internally coupled into the corresponding waveguide, and is the head-mounted display system according to item 45. (Item 51) The waveguide assembly includes a plurality of sets of waveguides, each set of waveguides includes dedicated waveguides, one for each of the first, second, or third colors, and each set of waveguides includes an external coupling 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 according to item 44. (Item 52) Further comprising a variable focus lens element, the waveguide assembly being between a first variable focus lens element and a second variable focus lens element, the first variable focus lens element being configured to correct the wavefront divergence of light output by the waveguide assembly to the user's eye, the second variable focus lens element being configured to correct the wavefront divergence of light from the outside world to the user's eye, the head-mounted display system according to item 44. (Item 53) The internal coupling optical element is configured to couple light with internally coupled light that generally propagates in the 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 being greater than the width, the head-mounted display system according to item 44. (Item 54) The head-mounted display system according to item 43, wherein the first color is green, the second color is blue, and the third color is red. (Item 55) The head-mounted display system according to item 43, wherein the light-emitting microdisplay comprises an array of micro LEDs. (Item 56) The head-mounted display system according to item 43, wherein the light-emitting microdisplay is one of a plurality of similar microdisplays and further comprises an X-cube prism, and each of the light-emitting microdisplays faces a different side of the X-cube prism. (Item 57) The head-mounted display system according to item 56, wherein the output side of the X-cube prism is configured to output light from the light-emitting microdisplay into the projection lens structure. (Item 58) A light-emitting microdisplay system comprising: An array of light emitters comprising a line of light emitters Each light emitter of each line extends along an axis intersecting the line, Each light emitter of each line is configured to emit light of the same color, The plurality of lines of light emitters form a group of lines, Each line of the group of lines is configured to emit light of a different color from at least one other line of the group of lines. ​ Light-emitting microdisplay system. (Item 59) Each group of said lines comprises a first line of light emitters configured to emit light of a first color, a second line of light emitters configured to emit light of a second color, and a third line of light emitters configured to emit a third color The light-emitting microdisplay system according to item 58. (Item 60) The first color is green, the second color is blue, and the third color is red. The light-emitting microdisplay system according to item 59. (Item 61) Further comprising a lens array across the array of light emitters, the lens array being configured to receive light from the light emitters and reduce the angular emission profile of the received light. The light-emitting microdisplay system according to item 58. (Item 62) The lens array is a nano lens array comprising a plurality of diffraction gratings. The light-emitting microdisplay system according to item 61. (Item 63) The diffraction grating extends along an axis parallel to the associated line of the light emitter. The light-emitting microdisplay system according to item 62. (Item 64) Each individual one of the diffraction gratings extends across the entire associated line of the light emitter. The light-emitting microdisplay system according to item 63. (Item 65) The diffraction grating comprises lines of material in the substrate, and the material forming the lines has a refractive index different from that of the material forming the substrate. The light-emitting microdisplay system according to item 61. (Item 66) The pitch of the lines is 30 - 300 nm. The light-emitting microdisplay system according to item 65. (Item 67) The depth of the lines is 10 - 1,000 nm. The light-emitting microdisplay system according to item 65. (Item 68) The depth and pitch of the lines vary between each line of the group of lines. The light-emitting microdisplay system according to item 65. (Item 69) The refractive index of the material forming the lines is 1.5 - 2.5. The light-emitting microdisplay system according to item 65. (Item 70) The refractive index of the substrate is 1.5 - 2.5. The light-emitting microdisplay system according to item 69. (Item 71) A projection optical system configured to converge the light from the lens array A waveguide assembly comprising one or more waveguides, each waveguide comprising: An internal coupling optical element configured to internally couple light from the projection optical system into the waveguide; An external coupling optical element configured to externally couple the internally coupled light out of the waveguide A waveguide assembly; The light-emitting microdisplay system according to item 61, further comprising: (Item 72) The internal coupling optical element of each waveguide is laterally offset with respect to the internal coupling optical element of other waveguides as viewed from the line of sight of the projection optical system; The different internal coupling optical elements are configured to internally couple light of different colors; The lens array is configured to direct light of different colors along an optical path towards different ones of the internal coupling optical elements; The light-emitting microdisplay system according to item 71; (Item 73) The head-mounted display system according to item 71, further comprising a projection optical system configured to converge light from the light-emitting microdisplay onto the internal coupling optical element of the one or more waveguides; (Item 74) Each individual one of the light emitters is configured to emit light of one of a plurality of primary colors; The waveguide assembly comprises a plurality of sets of waveguides; Each set of waveguides comprises a dedicated waveguide for each primary color, and each set of waveguides comprises an external coupling optical element configured to output light with wavefront divergence corresponding to a common depth plane, and different sets of waveguides output light with different amounts of wavefront divergence corresponding to different depth planes; The head-mounted display system according to item 71; (Item 75) The head-mounted display system according to item 71, 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 being configured to correct the wavefront divergence of the light output by the waveguide assembly, and the second variable focus lens element being configured to correct the wavefront divergence of light from the outside world to the second variable focus lens element; (Item 76) The waveguide assembly comprises a stack of waveguides; A color filter is further provided between two adjacent waveguides in the stack of waveguides; The first of the waveguides in the vicinity precedes the second of the waveguides in the vicinity within the optical path extending from the microdisplay. The color filter is 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 waveguides in the vicinity. The head-mounted display system according to item 71. (Item 77) A third waveguide following the second of the waveguides in the vicinity within the optical path. Another color filter, the other color filter being 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 second of the waveguides in the vicinity. The head-mounted display system according to item 76, further comprising. (Item 78) The head-mounted display system according to item 71, further comprising an absorptive color filter on at least some of the major surfaces of the waveguides, the absorptive color filter on the major surface of the waveguide being configured to absorb light of a wavelength internally coupled into the corresponding waveguide. (Item 79) The internal coupling optical element is configured to internally couple light with the internally coupled light that generally propagates in the propagation direction through the 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 being greater than the width. The head-mounted display system according to item 71.

Brief Description of the Drawings

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[0136] An augmented reality (AR) or virtual reality (VR) system may display virtual content to a user or viewer. This content may be displayed, for example, on a head-mounted display as part of eyewear that projects image information onto 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, enabling 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 a user's head or viewer.

[0137] Many head-mounted display systems utilize a transmissive or reflective spatial light modulator to form an image presented to a 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 is provided between the light source and the spatial light modulator to focus light from the light source onto the spatial light modulator. Unfortunately, the light source and associated optics can add bulk and weight to the display system. This added bulk or weight can negatively impact the comfort of the display system and the ability to wear the system over an extended period of time.

[0138] In addition, frame rate limitations of some display systems have been found to cause visual discomfort. Some display systems use a spatial light modulator to form an image. Many spatial light modulators utilize movement of optical elements to modulate the intensity of light output by the spatial light modulator, thereby forming an image. For example, an MEMS-based spatial light modulator can utilize a movable mirror to modulate incident light, while an LCoS-based display can utilize movement of liquid crystal molecules to modulate light. Other AR or VR systems can utilize a scanning fiber display where 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 for the optical fiber, mirror, and liquid crystal molecules to 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.

[0139] Such limitations can cause visual discomfort, for example, due to motion blur and / or a mismatch between the orientation of the user's head and the image being displayed. For example, there may be a latency in detecting the orientation of the user's head and presenting an image that matches 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 an object from a different orientation. Such a mismatch between the orientation of the user's head and the presented image can cause discomfort (e.g., nausea) to the user.

[0140] In addition, a scanned fiber display may present other undesirable optical artifacts due to the small cross-section of the fibers, for example, requiring the use of a high-intensity light source to form an image of a desired apparent brightness. Suitable high-intensity light sources include lasers, which output coherent light. Unfortunately, the use of coherent light can cause optical artifacts.

[0141] Advantageously, a display system that utilizes a light-emitting microdisplay as described herein can enable a low weight and compact form factor, which can also provide a high frame rate and low motion blur. Preferably, the microdisplay is a light-emitting microdisplay, which provides the advantages of high brightness and high pixel density. In some embodiments, the light-emitting microdisplay is a micro-LED display. In some other embodiments, the light-emitting microdisplay is a micro-OLED display. In some embodiments, the light-emitting microdisplay comprises an array of light emitters having a pitch of less than 10 μm, less than 8 μm, less than 6 μm, less than 5 μm, or less than 2 μm, including, for example, from 1 to 5 μm, and an emitter size of 2 μm or less, 1.7 μm or less, or 1.3 μm or less. In some embodiments, the emitter size is within a range having an upper limit of the above sizes and a lower limit of 1 μm. In some embodiments, the ratio of emitter size to pitch is from 1:1 to 1:5, from 1:2 to 1:4, or from 1:2 to 1:3, which can have the advantage of individual control of the emitters and efficient utilization of the light emitted by the eyepiece lens, as further discussed herein.

[0142] In some embodiments, a plurality of light-emitting microdisplays may be utilized to form an image 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 can vary, for example, in wavelength, intensity, polarization, etc. The light-emitting microdisplay outputs the image light to the eyepiece lens, which then relays the light to the user's eye.

[0143] In some embodiments, multiple emissive microdisplays may be positioned on different sides of an optical combiner, such as an X-cube prism or a 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 same face of the cube. The output light may be directed towards a projection optical system configured to converge or focus the image light onto an eyepiece lens.

[0144] In some embodiments, the multiple emissive microdisplays comprise monochrome microdisplays, which are configured to output light of a single primary color. Combining various primary colors forms a full-color image. In some other embodiments, one or more of the emissive microdisplays may have subpixels configured to emit light that is two or more but not all of the primary colors utilized by the display system. For example, a single emissive microdisplay may have subpixels that emit light of the colors blue and green, while a separate emissive microdisplay on a different face of the X-cube may have pixels configured to emit red light. In some embodiments, the multiple microdisplays are each full-color displays comprising pixels formed from multiple subpixels, for example, configured to emit light of different primary colors. Advantageously, combining the light of multiple full-color microdisplays can increase display brightness and dynamic range.

[0145] It should be understood that the emissive microdisplay may comprise an array of light emitters. The light emitters may emit light with a Lambertian angular emission profile. Unfortunately, such an angular emission profile may "waste" light because only a small portion of the emitted light may ultimately be incident on the eyepiece. In some embodiments, an optical collimator may be utilized to narrow the angular emission profile of the light emitted by the light emitter. As used herein, an optical collimator is an optical structure that narrows the angular emission profile of incident light. That is, the optical collimator receives light from an associated light emitter with a relatively wide initial angular emission profile and outputs that light with an angular emission profile that is narrower than the wide initial angular emission profile. In some embodiments, the light rays of the light exiting the optical collimator are transmitted through the collimator and are more parallel than the light rays of the light received by the optical collimator before exiting therefrom. Examples of optical collimators include microlenses, nanolenses, reflective wells, metasurfaces, and liquid crystal gratings. In some embodiments, the optical collimator may be configured to steer light and ultimately converge it onto a light coupling optical element that is laterally offset to a different side. In some embodiments, each light emitter has a dedicated optical collimator. The optical collimator is preferably positioned directly adjacent to or in contact with the light emitter and captures a large proportion of the light emitted by the associated light emitter.

[0146] In some embodiments, a single emissive microdisplay may be utilized to direct light to an eyepiece. For example, the single emissive microdisplay may be a full-color display comprising light emitters that emit light of different primary colors. In some embodiments, the light emitters may form groups localized within a common area, each group comprising light emitters that emit 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 appear as light of different primary colors incident on different internal coupling optical elements of the eyepiece, as discussed herein.

[0147] In some embodiments, the full-color microdisplay may comprise repeating groups of light emitters of the same primary color. For example, the microdisplay may comprise rows of light emitters, with the light emitters of each individual row configured to emit light of the same color. Thus, different rows may emit light of different primary colors. Additionally, the microdisplay may have an associated array of light collimators configured to direct light to a desired location on the eyepiece, such as an associated internal coupling optical element. Advantageously, although the individual light emitters of such a full-color microdisplay may not be positioned to form a high-quality full-color image such that they are directly visible on the microdisplay, the lens array properly steers the light from the light emitters to the eyepiece, which combines the monochrome images formed by the light emitters of different colors, thereby forming a high-quality full-color image.

[0148] In some embodiments, an eyepiece that receives image light from a microdisplay may comprise a waveguide assembly. The area of the waveguide of the waveguide assembly onto which the image light is incident may include an internal coupling optical element that internally couples the incident image light such 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 having an associated internal coupling optical element. The different internal coupling optical elements may be configured to internally couple different colors of light such that different waveguides are configured to propagate different colors of light therein. The waveguide may include an external coupling optical element that externally couples the light propagating therein such that the externally coupled light propagates towards the user's eye. In some other embodiments, the waveguide assembly may include a single waveguide having an associated internal coupling optical element configured to internally couple different primary colors of light.

[0149] In some embodiments, the internal coupling optical element is laterally offset as viewed from the projection optical system. The different internal coupling optical elements may be configured to internally couple different colors of light. Preferably, the different colors of image light follow different paths to the eyepiece and thus impinge on different corresponding internal coupling optical elements.

[0150] In some other embodiments, other types of eyepieces or optical systems for relaying the 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 the image light therein by TIR. As another example, the eyepiece may include a water tank mirror combiner comprising a translucent mirror that performs both directing the image light to the viewer and enabling a view of the surrounding environment.

[0151] In some embodiments, the eyepiece may be configured to selectively output light with different amounts of wavefront divergence to provide virtual content that is perceived to be at different distances from the user across a plurality of virtual depth planes (also simply referred to herein as "depth planes"). For example, the eyepiece may include a plurality of waveguides having external coupling optical elements with different refractive powers for outputting light with different amounts of wavefront divergence, respectively. In some other 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 the refractive power to provide the desired wavefront divergence for a particular virtual content. In some embodiments, as an alternative to or in addition to the waveguide optical structures for providing refractive power, the display system may also include a plurality of lenses that provide, or additionally provide, refractive power.

[0152] In addition to the compact form factor and high frame rate discussed above, the emissive microdisplay according to some embodiments may provide one or more of the following advantages. For example, the microdisplay may provide a significantly small pixel pitch and high pixel density. The microdisplay may also provide high brightness and efficiency. For example, the light emitters of the emissive microdisplay may consume only the power for emitting light when the light emitters are required to provide content at a certain brightness. This is in contrast to other display technologies where the light source may illuminate the entire panel of pixels regardless of whether some of those pixels are dark. Further, the human visual system integrates the received light over time, and the light emitters of the emissive microdisplay, such as micro LEDs, advantageously have a high duty cycle (e.g., the short activation period for the light emitters in the microdisplay to rise from “off” to fully “on” state and correspondingly the short time for the light emitters to fall from the “on” state to the “off” state allows the light emitters to emit light at the on level over a large percentage of each cycle). As a result, the power used to generate an image with a given perceived brightness may be less compared to conventional display technologies with a lower duty cycle. In some embodiments, the duty cycle may be 70% or more, 80% or more, or 90% or more. In some embodiments, the duty cycle may be about 99%. Additionally, as described herein, the microdisplay may facilitate a significantly high frame rate, which may provide advantages including reducing the mismatch between the position of the user's head and the content being displayed.

[0153] Reference is now made to the drawings, wherein like reference numerals refer to like parts throughout. Unless otherwise indicated, the drawings are schematic and are not necessarily drawn to scale.

[0154] FIG. 2 illustrates a conventional display system for simulating a three-dimensional image for a user. It should be understood that the user's eyes are separated, and when looking at a real object in space, each eye has a slightly different view of the object and can form an image of the object at different locations on the retina of each eye. This can be referred to as binocular disparity and can be utilized by the human visual system to provide a perception of depth. The conventional display system simulates binocular disparity by presenting two distinct images 190, 200 with slightly different views of one identical virtual object for each of the eyes 210, 220, corresponding to the views of the virtual object that would be seen by each eye as if the virtual object were a real object at the desired depth. These images provide binocular cues that can be interpreted by the user's visual system to derive a perception of depth.

[0155] Continuing to refer to FIG. 2, the images 190, 200 are separated from the eyes 210, 220 by a distance 230 on the z-axis. The z-axis is parallel to the optical axis of the viewer in a state where the eye is fixating on an object at optical infinity directly in front of the viewer. The images 190, 200 are flat and at a fixed distance from the eyes 210, 220. Based on the slightly different views of the virtual object in the images presented to the eyes 210, 220 respectively, the eyes can necessarily rotate so that the image of the object comes to corresponding points on the respective retinas of the eyes and a single binocular vision is maintained. This rotation can converge the respective lines of sight of the eyes 210, 220 onto a point in the space where the virtual object is perceived to exist. As a result, the provision of a three-dimensional image has conventionally involved manipulating the convergence and divergence movements of the user's eyes 210, 220 and providing binocular cues that are interpreted by the human visual system to provide a perception of depth.

[0156] However, generating realistic and comfortable perceptions of depth is difficult. It should be understood that light from objects at different distances from the eye has wavefronts with different amounts of divergence. FIGS. 3A - 3C illustrate the relationship between distance and the divergence of light rays. The distances between the object and the eye 210 are represented in the order of decreasing distances R1, R2, and R3. As shown in FIGS. 3A - 3C, the light rays diverge more as the distance to the object decreases. Conversely, as the distance increases, the light rays become more collimated. In other words, it can be said that the light field generated by a point (an object or a part of an object) has a spherical wavefront curvature that is a function of the distance the point is away from the user's eye. The curvature increases as the distance between the object and the eye 210 decreases. Only the single eye 210 is illustrated in FIGS. 3A - 3C and various other figures herein for clarity of illustration, but the discussion regarding the eye 210 can be applied to both eyes 210 and 220 of the viewer.

[0157] Continuing to refer to FIGS. 3A - 3C, the light from the object on which the viewer's eye is fixated can have different degrees of wavefront divergence. Due to the different amounts of wavefront divergence, the light can be focused differently by the eye's lens, which in turn may require the lens to take on different shapes to form a focused image on the retina of the eye. If the focused image is not formed on the retina, the resulting retinal blur acts as a cue for accommodation, causing a change in the shape of the eye's lens until the focused image is formed on the retina. For example, the cue for accommodation triggers the relaxation or contraction of the ciliary muscle surrounding the eye's lens, thereby modulating the force applied to the zonular fibers that hold the lens, and thus changing the shape of the eye's lens until the retinal blur of the fixated image is eliminated or minimized, thereby forming a focused image of the fixated object on the retina (e.g., the fovea) of the eye. 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 the fixated object on the retina (e.g., the fovea) of the eye can be referred to as the accommodative state.

[0158] Referring now to FIG. 4A, the representation of the accommodation-convergence / divergence motion response of the human visual system is illustrated. The movement of the eyes to fixate on an object causes the eyes to receive light from the object, and the light forms an image on each of the retinas of the eyes. The presence of retinal blur in the image formed on the retina can provide a cue for accommodation, and the relative location of the image on the retina can provide a cue for convergence / divergence motion. The cue for accommodation results in accommodation occurring and the eye's lens taking on a particular accommodation state that forms a focused image of the object on the eye's retina (e.g., the fovea). On the other hand, the cue for convergence / divergence motion causes convergence / divergence motion (rotation of the eyes) such that the images formed on each retina of each eye are at corresponding retinal points that maintain single binocular vision. At these positions, it can be said that the eyes are in a particular convergence / divergence motion state. Continuing to refer to FIG. 4A, accommodation can be understood to be the process by which the eyes achieve a particular accommodation state, and convergence / divergence motion can be understood to be the process by which the eyes achieve a particular convergence / divergence motion state. As shown in FIG. 4A, the accommodation and convergence / divergence motion states of the eyes can change when the user fixates on another object. For example, the accommodated state can change when the user fixates on a new object at a different depth along the z-axis.

[0159] Although not limited by theory, it is believed that a viewer of an object can perceive the object as "three-dimensional" due to a combination of convergence / divergence motion and accommodation. As described above, the convergence / divergence movement of the two eyes relative to each other (e.g., the rotation of the eyes such that the pupils move towards each other or away from each other, converging the lines of sight of the eyes and fixating on the object) is closely associated with the accommodation of the eye's lens. Under normal conditions, a change in the focus of the eye's lens to change the focus from one object to another object at a different distance will automatically cause a corresponding change in the convergence / divergence motion to the same distance under a relationship known as the "accommodation-convergence / divergence reflex". Similarly, a change in the convergence / divergence motion will, under normal conditions, induce a corresponding change in the shape of the lens.

[0160] Referring now to FIG. 4B, an example of different accommodation and convergence / divergence states of the eyes is illustrated. The pair of eyes 222a fixates on an object at optical infinity, while the pair of eyes 222b fixates on an object 221 at less than optical infinity. It should be noted that the convergence / divergence states of each pair of eyes are different, with the pair of eyes 222a being directed straight, while the pair of eyes 222 converges on the object 221. The accommodation states of the eyes forming each pair of eyes 222a and 222b are also different, as represented by the different shapes of the lenses 210a, 220a.

[0161] Unfortunately, many users of conventional "3-D" display systems find such conventional systems uncomfortable or may not perceive any sense of depth at all due to the inconsistency between the depth adjustment and the convergence / divergence motion state in these displays. As described above, many stereoscopic or "3-D" display systems display a scene by providing slightly different images to each eye. Such systems are uncomfortable for many viewers because they merely provide different presentations of the scene, causing a change in the convergence / divergence motion state of the eyes, but without a corresponding change in the depth adjustment state of those eyes. Rather, the images are presented at a fixed distance from the eyes by the display such that the eyes view all the image information in a single depth adjustment state. Such an arrangement violates the "accommodation-convergence / divergence reflex" by causing a change in the convergence / divergence motion state without a corresponding change in the depth adjustment state. This inconsistency is thought to cause viewer discomfort. A display system that provides better alignment between accommodation and convergence / divergence motion can create a more realistic and comfortable simulation of three-dimensional images.

[0162] Although not limited by theory, the human eye is typically thought to be able to interpret a finite number of depth planes and provide depth perception. As a result, a highly realistic simulation of the perceived depth can be achieved by providing different presentations of images corresponding to each of these limited number of depth planes to the eyes. In some embodiments, the different presentations may provide both a cue for convergence / divergence motion and a corresponding cue for depth adjustment, thereby providing a physiologically correct accommodation-convergence / divergence motion alignment.

[0163] Continuing to refer to FIG. 4B, two depth planes 240 are illustrated, corresponding to different distances in space from the eyes 210, 220. For a given depth plane 240, a convergence / divergence motion cue may be provided by appropriately displaying images of different viewpoints for each of the eyes 210, 220. Additionally, for a given depth plane 240, the light forming the images provided to each eye 210, 220 may have a wavefront divergence corresponding to a light field generated by a point at the distance of that depth plane 240.

[0164] In the illustrated embodiment, the distance along the z-axis of the depth plane 240 containing the point 221 is 1 m. As used herein, the distance or depth along the z-axis may be measured using a zero point located at the exit pupil of the user's eye. Thus, the depth plane 240 located at a depth of 1 m corresponds to a distance 1 m away from the exit pupil of the user's eye on the optical axis of those eyes in a state where the eyes are directed towards optical infinity. As an approximation, the depth or distance along the z-axis is measured from the front of the user's eye (e.g., the surface of the waveguide), and a value related to the distance between the device and the exit pupil of the user's eye may be added. That value is referred to as the pupil distance and may correspond to the distance between the exit pupil of the user's eye and the display worn by the user in front of the eye. In practice, the value for the pupil distance may generally be a normalized value used for all viewers. For example, the pupil distance may be assumed to be 20 mm, and the depth plane at a depth of 1 m may be at a distance of 980 mm in front of the display.

[0165] Referring now to FIGS. 4C and 4D, examples of consistent vergence-accommodation movement distances and inconsistent vergence-accommodation movement distances are illustrated, respectively. As shown in FIG. 4C, the display system may provide an image of the virtual object to each eye 210, 220. The image may cause the eyes 210, 220 to assume a vergence-accommodation state in which the eyes converge on a point 15 on the depth plane 240. Additionally, the image may be formed by light having a wavefront curvature corresponding to the real object in the depth plane 240. As a result, the eyes 210, 220 assume an accommodation state in which the image is focused on their retinas. Thus, the user may perceive the virtual object as being at the point 15 on the depth plane 240.

[0166] It should be understood that the accommodation and vergence-accommodation 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 causes those eyes to assume a particular accommodation state based on the distance of the object. The distance associated with a particular accommodation state may be referred to as the accommodation distance A d Similarly, there exists a particular vergence distance V d associated with a particular vergence-accommodation state or the eyes in a particular position relative to each other. When the accommodation distance and the vergence distance are consistent, the relationship between accommodation and vergence can be said to be physiologically correct. This is regarded as the most comfortable scenario for the viewer.

[0167] However, in a stereoscopic display, the focusing adjustment distance and the convergence / divergence movement distance may not always match. For example, as shown in FIG. 4D, the images displayed on eyes 210, 220 may be displayed with wavefront divergence corresponding to depth plane 240, and eyes 210, 220 may take a specific focusing adjustment state in which points 15a, 15b on that depth plane are in focus. However, the images displayed on eyes 210, 220 may provide a cue for convergence / divergence movement that converges eyes 210, 220 on points 15 that are not located on depth plane 240. As a result, in some embodiments, the focusing adjustment distance corresponds to the distance from the exit pupils of eyes 210, 220 to depth plane 240, while the convergence / divergence movement distance corresponds to a greater distance from the exit pupils of eyes 210, 220 to points 15. The focusing adjustment distance is different from the convergence / divergence movement distance. As a result, there is a focusing adjustment - convergence / divergence movement mismatch. Such a mismatch is considered undesirable and can cause discomfort to the user. The mismatch corresponds to a distance (e.g., V d -A d ) and can be characterized using diopters.

[0168] It should be understood that in some embodiments, as long as the same reference point is used for the focusing adjustment distance and the convergence / divergence movement distance, a reference point other than the exit pupils of eyes 210, 220 may be used to determine the distance for determining the focusing adjustment - convergence / divergence movement mismatch. For example, the distance can be measured from the cornea to the depth plane, from the retina to the depth plane, from the eyepiece (e.g., the waveguide of the display device) to the depth plane, etc.

[0169] Although not limited by theory, it is believed that a user may perceive vergence-accommodation divergence mismatches of up to about 0.25 diopters, up to about 0.33 diopters, and up to about 0.5 diopters as being 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 an image having a vergence-accommodation divergence mismatch of about 0.5 diopters or less to a viewer. In some other embodiments, the vergence-accommodation divergence mismatch of an image provided by the display system is about 0.33 diopters or less. In still other embodiments, the vergence-accommodation divergence mismatch of an image provided by the display system is about 0.25 diopters or less and includes about 0.1 diopters or less.

[0170] FIG. 5 illustrates a side view 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 the user's eye 210. The waveguide 270 may output light 650 with a defined amount of wavefront divergence corresponding to the wavefront divergence of 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. Additionally, the user's other eye would be illustrated as being provided with image information from a similar waveguide.

[0171] In some embodiments, a single waveguide may be configured to output light with a set amount of wavefront divergence corresponding to a single or limited number of depth planes, and / or the waveguide may be configured to output light within a limited range of wavelengths. As a result, in some embodiments, multiple or stacked waveguides may be utilized to provide different amounts of wavefront divergence for different depth planes and / or output light within different ranges of wavelengths. It should be understood that as used herein, a depth plane can be a plane or can follow the contour of a curved surface.

[0172] FIG. 6 illustrates an example of a stack of waveguides for outputting image information to a user. Display system 250 includes a stack or stacked waveguide assembly 260 of waveguides 270, 280, 290, 300, 310 that can be utilized to provide a three-dimensional perception to the eye / brain. It should be understood that in some embodiments, display system 250 may be considered a light field display. Additionally, waveguide assembly 260 may also be referred to as an eyepiece.

[0173] In some embodiments, display system 250 may be configured to provide a substantially continuous cue for convergence / divergence motion and a plurality of discrete cues for depth adjustment. The cue for convergence / divergence motion may be provided by displaying different images to each of the user's eyes, and the cue for depth adjustment may be provided by outputting light that forms an image with a selectable discrete amount of wavefront divergence. In other words, display system 250 may be configured to output light with a variable level of wavefront divergence. In some embodiments, each discrete level of wavefront divergence may correspond to a particular depth plane and may be provided by a particular one of waveguides 270, 280, 290, 300, 310.

[0174] Continuing to refer to FIG. 6, waveguide assembly 260 may also include a plurality of features 320, 330, 340, 350 between the waveguides. In some embodiments, features 320, 330, 340, 350 may be one or more lenses. Waveguides 270, 280, 290, 300, 310 and / or The plurality of 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 may be configured to output image information corresponding to that depth plane. Image input devices 360, 370, 380, 390, 400 may function as light sources for the waveguides and may be utilized to input image information into waveguides 270, 280, 290, 300, 310, and may each be configured to disperse incident light across an individual waveguide to output it toward eye 210, as described herein. Light exits from output surfaces 410, 420, 430, 440, 450 of image input devices 360, 370, 380, 390, 400 and is input into corresponding input surfaces 460, 470, 480, 490, 500 of waveguides 270, 280, 290, 300, 310. In some embodiments, input surfaces 460, 470, 480, 490, 500 may each be an edge of the corresponding waveguide or may be a portion of the major surface of the corresponding waveguide (i.e., one of the waveguide surfaces facing directly toward world 510 or viewer's eye 210). In some embodiments, a single beam of light (e.g., a collimated beam) may be input into each waveguide and output an entire field of cloned collimated beams directed toward eye 210 at a particular angle (and divergence amount) corresponding to a depth plane associated with a particular waveguide. In some embodiments, a single one of image input devices 360, 370, 380, 390, 400 may be associated with and input light into a plurality (e.g., three) of waveguides 270, 280, 290, 300, 310.

[0175] In some embodiments, the image input devices 360, 370, 380, 390, 400 are discrete displays that each generate image information for input into their respective waveguides 270, 280, 290, 300, 310. In some other embodiments, the image input devices 360, 370, 380, 390, 400 are output ends of a single multiplexed display that can send image information to each of the image input devices 360, 370, 380, 390, 400, for example, via one or more optical waveguides (such as optical fiber 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).

[0176] In some embodiments, the light input into waveguides 270, 280, 290, 300, 310 is provided by a light projection system 520, which includes a light module 530, which may include a light emitter such as a light emitting diode (LED). The light from the light module 530 may be directed and modified by a light modulator 540, such as a spatial light modulator, via a beam splitter 550. The light modulator 540 may be configured to vary the perceived intensity of the light input into waveguides 270, 280, 290, 300, 310 and to encode the light with image information. Examples of spatial light modulators include liquid crystal displays (LCDs), including liquid crystal on silicon (LCOS) displays. In some other embodiments, the spatial light modulator may be a MEMS device such as a digital light processing (DLP) device. Image input devices 360, 370, 380, 390, 400 are shown schematically, and in some embodiments, these image input devices may represent different optical paths and locations within a common projection system configured to output light into the associated ones of waveguides 270, 280, 290, 300, 310. In some embodiments, the waveguides of waveguide assembly 260 may function as an ideal lens while relaying the light input into the waveguides to the user's eye. In this concept, the object may be the spatial light modulator 540, and the image may be an image on a depth plane.

[0177] In some embodiments, the display system 250 may be a scanning fiber display comprising one or more scanning fibers configured to project light in various patterns (e.g., raster scan, spiral scan, Lissajous pattern, etc.) into one or more waveguides 270, 280, 290, 300, 310 and ultimately into the viewer's eye 210. In some embodiments, the illustrated image input devices 360, 370, 380, 390, 400 may schematically represent a single scanning fiber or a bundle of scanning fibers configured to input light into one or more waveguides 270, 280, 290, 300, 310. In some other embodiments, the illustrated image input devices 360, 370, 380, 390, 400 may schematically represent a plurality of scanning fibers or a plurality of bundles of scanning fibers, each configured to input 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 the one or more waveguides 270, 280, 290, 300, 310 and may, for example, redirect light exiting the scanning fiber into one or more of the waveguides 270, 280, 290, 300, 310.

[0178] Controller 560 controls the operation of one or more of the stacked waveguide assemblies 260, including the operation of the image input devices 360, 370, 380, 390, 400, the light source 530, and the optical module 540. In some embodiments, controller 560 is part of the local data processing module 140. Controller 560 includes programming (e.g., instructions in a non-transitory medium) that adjusts 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 monolithic device or a distributed system connected by wired or wireless communication channels. Controller 560 may, in some embodiments, also be part of processing module 140 or 150 (FIG. 9E).

[0179] Continuing to refer to FIG. 6, the waveguides 270, 280, 290, 300, 310 may be configured to propagate light within each individual waveguide by total internal reflection (TIR). The waveguides 270, 280, 290, 300, 310 may each be planar, or have another shape (e.g., curved), with a major top surface and a bottom surface and an edge extending between those major top and bottom surfaces. In the illustrated configuration, the waveguides 270, 280, 290, 300, 310 each include external coupling optical elements 570, 580, 590, 600, 610 configured to extract light from the waveguide by redirecting the light propagating within each individual waveguide out of the waveguide and outputting the image information to the eye 210. The extracted light may also be referred to as external coupled light, and the external coupling optical elements may also be referred to as light extraction optical elements. The beam of extracted light may be output by the waveguide at the location where the light propagating within the waveguide impinges on the light extraction optical element. The external coupling optical elements 570, 580, 590, 600, 610 may be gratings, for example, including diffractive optical features as further discussed herein. For ease of explanation and clarity of the drawings, the external coupling optical elements 570, 580, 590, 600, 610 are shown disposed on the bottom major surfaces of the waveguides 270, 280, 290, 300, 310, but in some embodiments, the external coupling optical elements 570, 580, 590, 600, 610 may be disposed on the top and / or bottom major surfaces, and / or directly within the volume of the waveguides 270, 280, 290, 300, 310, as further discussed herein. In some embodiments, the external coupling optical elements 570, 580, 590, 600, 610 may be attached to a transparent substrate and formed within a layer of the material forming the waveguides 270, 280, 290, 300, 310. In some other embodiments, the waveguides 270, 280, 290, 300, 310 may be a monolithic piece of material, and the external coupling optical elements 570, 580, 590, 600, 610 may be formed on and / or within the surface of that piece of material.

[0180] Continuing to refer to FIG. 6, as discussed herein, each of the waveguides 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 (input into such a waveguide 270) to the eye 210. The collimated light may represent an optically infinite focal plane. The next upper waveguide 280 may be configured to deliver collimated light that passes through a first lens 350 (e.g., a negative lens) before reaching the eye 210. Such a first lens 350 may be configured to generate a somewhat convex wavefront curvature such that the eye / brain interprets the light resulting from the next upper waveguide 280 as originating from a first focal plane that is closer inwardly toward the eye 210 from optically infinite. Similarly, the third upper waveguide 290 passes its output light through both the first 350 and second 340 lenses before reaching the eye 210. The combined refractive power of the first 350 and second 340 lenses may be configured to generate another incremental amount of wavefront curvature such that the eye / brain interprets the light resulting from the third waveguide 290 as originating from a second focal plane that is even closer inwardly toward the person from optically infinite than the light from the next upper waveguide 280 was interpreted as originating from.

[0181] The other waveguide layers 300, 310 and lenses 330, 320 are similarly configured, and the top waveguide 310 in the stack sends its output through all of the lenses between it and the eye for the collective focusing power that represents the focal plane closest to the person. When viewing / interpreting light originating from the world 510 on the other side of the stacked waveguide assembly 260, a compensation lens layer 620 may be disposed on top of the stack to compensate for the stack of lenses 320, 330, 340, 350. Such a configuration provides the same number of perceived focal planes as there are available waveguide / lens pairs. Both the external coupling optical elements of the waveguides and the focusing sides of the lenses may be static (i.e., not dynamic or electroactive). In some alternative embodiments, one or both may be dynamic using electroactive features.

[0182] In some embodiments, two or more of the waveguides 270, 280, 290, 300, 310 may have the same associated depth plane. For example, a plurality of waveguides 270, 280, 290, 300, 310 may be configured to output images set to the same depth plane, or a plurality of subsets of waveguides 270, 280, 290, 300, 310 may be configured to output images set to the same plurality of depth planes, with one set per depth plane. This can provide the advantage of forming a tiled image to provide an extended field of view in those depth planes.

[0183] Continuing to refer to FIG. 6, the external coupling optical elements 570, 580, 590, 600, 610 may be configured to redirect light from their respective waveguides for a particular depth plane associated with the waveguide and output the light with an appropriate amount of divergence or collimation. As a result, waveguides having different associated depth planes may have different configurations of the external coupling optical elements 570, 580, 590, 600, 610, which output light with different amounts of divergence depending on the associated depth plane. In some embodiments, the light extraction optical elements 570, 580, 590, 600, 610 may be three-dimensional or surface features configured to output light at a specific angle. For example, the light extraction optical elements 570, 580, 590, 600, 610 may be a volume hologram, a surface hologram, and / or a diffraction grating. In some embodiments, the features 320, 330, 340, 350 may not be lenses. Rather, they may simply be spacers (e.g., a cladding layer and / or structure for forming a void).

[0184] In some embodiments, the external coupling optical elements 570, 580, 590, 600, 610 are diffraction features or “diffractive optical elements” (also referred to herein as “DOEs”) that form a diffraction pattern. Preferably, the DOE has a sufficiently low diffraction efficiency such that only a portion of the light of the beam is deflected towards the eye 210 at each intersection of the DOE, while the remainder continues to travel through the waveguide via TIR. The light carrying the image information is thus split into several associated output beams that exit the waveguide at various locations, resulting in a very uniform pattern of output emission towards the eye 210 with respect to this particular collimated beam that bounces within the waveguide.

[0185] In some embodiments, one or more DOEs may be switchable between an “on” state in which they actively diffract and an “off” state in which they do not significantly diffract. For example, a switchable DOE may comprise a layer of polymer dispersed liquid crystal in which microdroplets have a diffraction 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 the 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 the incident light).

[0186] 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, and, for example, detect user input and / or monitor the user's physiological state. 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 (e.g., infrared light) that projects light into the eye, which light may then be reflected by the eye and detected by the image capture device. In some embodiments, the camera assembly 630 may be attached to a frame or support structure 80 (FIG. 9E) and may communicate electrically with a processing module 140 and / or 150 that may process image information from the camera assembly 630. In some embodiments, one camera assembly 630 may be utilized per eye to monitor each eye separately.

[0187] In some embodiments, the camera assembly 630 may observe the movement of the user, such as the eye movement of the user. As an example, the camera assembly 630 may capture an image of the eye 210 and determine the size, position, and / or orientation of the pupil of the eye 210 (or some other structure of the eye 210). The camera assembly 630 may, if desired, acquire an image (processed by a processing circuitry network of the type described herein) that is used to determine the direction in which the user is looking (e.g., eye pose or line of sight direction). In some embodiments, the camera assembly 630 may include multiple cameras, at least one of which is utilized per eye and may independently determine the eye pose or line of sight direction of each eye separately. In some embodiments, the camera assembly 630 may, in combination with a processing circuitry such as the controller 560 or the local data processing module 140, determine the eye pose or line of sight direction based on a flash (e.g., reflection) of light (e.g., infrared light) reflected from a light source included within the camera assembly 630.

[0188] Referring now to FIG. 7, an embodiment of an output beam output by a waveguide is shown. Although one waveguide is illustrated, it should be understood that other waveguides within the waveguide assembly 260 (FIG. 6) may function similarly, and the waveguide assembly 260 includes a plurality of waveguides. Light 640 is input into the waveguide 270 at the input surface 460 of the waveguide 270 and propagates through the waveguide 270 by TIR. At the point where the light 640 impinges on the DOE 570, a portion of the light exits the waveguide as the output beam 650. The output beam 650 is illustrated as being substantially parallel, but as discussed herein, and depending on the depth plane associated with the waveguide 270, it may be redirected to propagate at an angle (e.g., to form a diverging output beam) to the eye 210. It should be understood that a waveguide with an external coupling optical element that externally couples light to form an image that appears to be set in a depth plane at a long distance (e.g., optical infinity) from the eye 210 may be shown for the substantially parallel output beam. Other waveguides or other sets of external coupling optical elements may output a more diverging output beam pattern, which would require the eye 210 to focus at a closer distance and would be interpreted by the brain as light from a distance closer to the eye 210 than optical infinity.

[0189] In some embodiments, a full-color image may be formed in each depth plane by overlaying the image on each of the primary colors, e.g., three or more primary colors. FIG. 8 illustrates an example of a stacked waveguide assembly, and each depth plane includes an image formed using a plurality of different primary colors. The illustrated embodiment shows depth planes 240a-240f, although more or fewer depths may also be considered. Each depth plane may have three or more primary color images associated therewith, including a first image of a first color G, a second image of a second color R, and a third image of a third color B. Different depth planes are shown in the figure by different numbers related to the diopter (dpt) following the letters G, R, and B. As a mere example, the numbers following each of these letters indicate the diopter (1 / m), i.e., the inverse distance of the depth plane from the viewer, and each box in the figure represents an individual primary color image. In some embodiments, to account for differences in the focusing of light of different wavelengths by the eye, the exact location of the depth planes for different primary colors may vary. For example, the different primary color images for a given depth plane may be placed on a depth plane corresponding to a different distance from the user. Such an arrangement may increase visual acuity and user comfort and / or reduce chromatic aberration.

[0190] In some embodiments, the light of each primary color may be output by a single dedicated waveguide, and as a result, each depth plane may have a plurality of waveguides associated therewith. In such embodiments, each box in the figure, including those containing the letters G, R, or B, may be understood to represent an individual waveguide, and three waveguides may be provided for each depth plane, with three primary color images being provided for each depth plane. The waveguides associated with each depth plane are shown adjacent to each other in this drawing for ease of explanation, but it should be understood that in a physical device, all of the waveguides may be arranged in a stack with one waveguide per level. In some other embodiments, a plurality of primary colors may be output by the same waveguide, e.g., such that only a single waveguide is provided for each depth plane.

[0191] Continuing to refer to FIG. 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 also be used in addition to or in place of one or more of red, green, or blue.

[0192] It is to be understood that references throughout this disclosure to the color of a given light include 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 light of one or more wavelengths within the range of about 620 to 780 nm, green light may include light of one or more wavelengths within the range of about 492 to 577 nm, and blue light may include light of one or more wavelengths within the range of about 435 to 493 nm.

[0193] In some embodiments, the light source 530 (FIG. 6) may be configured to emit light of one or more wavelengths outside the visual perception range of the viewer, such as infrared and / or ultraviolet wavelength light. Additionally, the internal coupling, external coupling, and other light redirection structures of the waveguide of the display 250 may be configured to direct and emit this light from the display toward the user's eye 210, for example, for imaging and / or user stimulation applications.

[0194] Referring now to FIG. 9A, in some embodiments, light that impinges on the waveguide may need to be redirected to internally couple the light into the waveguide. An internal coupling optical element may be used to redirect and internally couple the light into its corresponding waveguide. FIG. 9A illustrates a cross-sectional side view of an example of a stack of a plurality or set 660 of waveguides, each including an internal coupling optical element. Each waveguide may be configured to output light of one or more different wavelengths or one or more different wavelength ranges. Stack 660 may correspond to stack 260 (FIG. 6), and the illustrated waveguides of stack 660 may correspond to a portion of the plurality of waveguides 270, 280, 290, 300, 310, but it should be understood that light from one or more of the image input devices 360, 370, 380, 390, 400 is input into the waveguide from a location that requires the light to be redirected for internal coupling.

[0195] 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 a 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 internal coupling optical elements 700, 710, 720 may be disposed on the bottom major surface of the respective waveguides 670, 680, 690 (in particular, one or more of the internal coupling optical elements are reflective deflecting optical elements). As illustrated, internal coupling optical elements 700, 710, 720 may be disposed on the upper major surface (or the upper portion of the next lower waveguide) of their respective waveguides 670, 680, 690, and in particular, those internal coupling optical elements are transmissive deflecting optical elements. In some embodiments, internal coupling optical elements 700, 710, 720 may be disposed within the body of the respective waveguides 670, 680, 690. In some embodiments, as discussed herein, 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. Although illustrated on one side or corner of their respective waveguides 670, 680, 690, it should be understood that in some embodiments, internal coupling optical elements 700, 710, 720 may be disposed within other areas of their respective waveguides 670, 680, 690.

[0196] As shown, the internally coupled optical elements 700, 710, 720 may be laterally offset from each other in the direction of the light propagating in these internally coupled optical elements, as seen in the illustrated front view. In some embodiments, each internally coupled optical element may be offset so that its light is received without passing through another internally coupled optical element. For example, each of the internally coupled optical elements 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 other internally coupled optical elements 700, 710, 720 so as to substantially not receive light from other ones of the internally coupled optical elements 700, 710, 720.

[0197] Each waveguide also includes an associated light dispersing element. For example, the light dispersing element 730 is disposed on a major surface (e.g., the upper major surface) of the waveguide 670, the light dispersing element 740 is disposed on a major surface (e.g., the upper major surface) of the waveguide 680, and the light dispersing element 750 is disposed on a major surface (e.g., the upper major surface) of the waveguide 690. In some other embodiments, the light dispersing elements 730, 740, 750 may each be disposed on the bottom major surface of the associated waveguides 670, 680, 690. In some other embodiments, the light dispersing elements 730, 740, 750 may each be disposed on both the upper and bottom major surfaces of the associated waveguides 670, 680, 690, or the light dispersing elements 730, 740, 750 may each be disposed on different ones of the upper and bottom major surfaces within different associated waveguides 670, 680, 690.

[0198] Waveguides 670, 680, 690 may be separated and isolated, for example, by a gas, liquid, and / or solid layer 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 immediate waveguides 670, 680, 690). Preferably, the refractive index of the material forming layers 760a, 760b is 0.05 or more or 0.10 or less than 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 (e.g., TIR between the upper and bottom major surfaces of each waveguide) through waveguides 670, 680, 690. In some embodiments, layers 760a, 760b are formed from air. It should be understood that, although not shown, the top and bottom of the illustrated set 660 of waveguides may include an immediate cladding layer.

[0199] Preferably, for ease of manufacture and other considerations, the materials forming waveguides 670, 680, 690 are similar or identical, and the materials forming layers 760a, 760b are similar or identical. In some embodiments, the materials forming waveguides 670, 680, 690 may be different between one or more waveguides and / or the materials forming layers 760a, 760b may still be different while maintaining the various refractive index relationships described above.

[0200] Continuing to refer to FIG. 9A, light rays 770, 780, 790 are incident on the set 660 of waveguides. It should be understood that light rays 770, 780, 790 may be introduced into waveguides 670, 680, 690 by one or more image input devices 360, 370, 380, 390, 400 (FIG. 6).

[0201] In some embodiments, the light rays 770, 780, 790 may have different properties, such as different wavelengths or different wavelength ranges, corresponding to different colors. The internal coupling optical elements 700, 710, 720 each deflect the incident light so that the light propagates through an individual one of the waveguides 670, 680, 690 by TIR. In some embodiments, the internal coupling optical elements 700, 710, 720 each selectively deflect one or more specific wavelengths of light while transmitting other wavelengths to the underlying waveguide and the associated internal coupling optical element.

[0202] For example, the internal coupling optical element 700 may be configured to deflect the light ray 770 having the first wavelength or wavelength range while transmitting the light rays 780 and 790 having different second and third wavelengths or wavelength ranges, respectively. The transmitted light ray 780 impinges on the internal coupling optical element 710 configured to deflect the light of the second wavelength or wavelength range, thereby being deflected. The light ray 790 is deflected by the internal coupling optical element 720 configured to selectively deflect the light of the third wavelength or wavelength range.

[0203] Continuing to refer to FIG. 9A, the deflected light rays 770, 780, 790 are deflected to propagate through the corresponding waveguides 670, 680, 690. That is, the internal coupling optical elements 700, 710, 720 of each waveguide deflect the light into its corresponding waveguide 670, 680, 690 and internally couple 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 individual waveguides 670, 680, 690 by TIR. The light rays 770, 780, 790 propagate through the individual waveguides 670, 680, 690 by TIR until they impinge on the corresponding light dispersion elements 730, 740, 750 of the waveguide.

[0204] Referring now to FIG. 9B, a perspective view of an embodiment of the plurality of stacked waveguides of FIG. 9A is illustrated. As described above, the internally coupled light rays 770, 780, 790 are each deflected by the internally coupled optical elements 700, 710, 720 and then each propagate by TIR within the waveguides 670, 680, 690. The light rays 770, 780, 790 then each impinge on the light dispersing elements 730, 740, 750. The light dispersing elements 730, 740, 750 each deflect the light rays 770, 780, 790 so as to propagate towards the externally coupled optical elements 800, 810, 820.

[0205] In some embodiments, the optical dispersion elements 730, 740, 750 are orthogonal pupil expanders (OPEs). In some embodiments, the OPE deflects or disperses light to the external coupling optical elements 800, 810, 820, and in some embodiments, also increases the beam or spot size of the present light as it propagates to the external coupling optical elements. In some embodiments, the optical dispersion elements 730, 740, 750 may be omitted, and the internal coupling optical elements 700, 710, 720 may be configured to deflect light directly to the external coupling optical elements 800, 810, 820. For example, referring to FIG. 9A, the optical dispersion elements 730, 740, 750 may each be replaced with the external coupling optical elements 800, 810, 820. In some embodiments, the external coupling optical elements 800, 810, 820 are an exit pupil (EP) or an exit pupil expander (EPE) that directs light to the viewer's eye 210 (FIG. 7). It should be understood that the OPE may be configured to increase the size of the eyebox in at least one axis, and the EPE may increase the eyebox in an axis that intersects, for example, is orthogonal to, the axis of the OPE. For example, each OPE may be configured to redirect a portion of the light impinging on the OPE to the EPE of the same waveguide while allowing the remaining portion of the light to continue to propagate along the waveguide. In response to a collision with the OPE, again, another portion of the remaining light is redirected to the EPE, and the remaining portion of that portion continues to propagate further along the waveguide or the like. Similarly, in response to a collision with the EPE, a portion of the colliding light is directed from the waveguide towards the user, and the remaining portion of that light continues to propagate through the waveguide until it impinges again on the EP, at which point another portion of the colliding light is directed from the waveguide, and so on. As a result, a single beam of internally coupled light is "replicated" each time a portion of that light is redirected by the OPE or EPE, thereby forming a beam field of cloned light as shown in FIG. 6. In some embodiments, the OPE and / or EPE may be configured to modify the size of the beam of light.

[0206] Thus, referring to FIGS. 9A and 9B, in some embodiments, the waveguide set 660 includes, for each primary color, waveguides 670, 680, 690, internal coupling optical elements 700, 710, 720, light dispersion elements (e.g., OPE) 730, 740, 750, and external coupling optical elements (e.g., EP) 800, 810, 820. The waveguides 670, 680, 690 may be stacked with a gap / cladding layer between each one. The internal coupling optical elements 700, 710, 720 redirect or deflect the incident light into their respective waveguides (using different internal coupling optical elements that receive light of different wavelengths). The light then propagates at an angle that will result in TIR within the individual waveguides 670, 680, 690. In the illustrated example, the ray 770 (e.g., blue light) is polarized by the first internal coupling optical element 700 in the manner described above and then continues to bounce through the waveguide, interacting with the light dispersion element (e.g., OPE) 730 and then the external coupling optical element (e.g., EP) 800. The rays 780 and 790 (e.g., green and red light, respectively) pass through the waveguide 670, and the ray 780 impinges on the internal coupling optical element 710 and is thereby deflected. The ray 780 then bounces through the waveguide 680 via TIR and will proceed to its light dispersion element (e.g., OPE) 740 and then the external coupling optical element (e.g., EP) 810. Finally, the ray 790 (e.g., red light) passes through the waveguide 690 and impinges on the internal coupling optical element 720 of the waveguide 690. The internal coupling optical element 720 deflects the ray 790 such that the ray propagates by TIR to the light dispersion element (e.g., OPE) 750 and then by TIR to the external coupling optical element (e.g., EP) 820. The external coupling optical element 820 then finally externally couples the ray 790 to the viewer, who also receives the externally coupled light from the other waveguides 670, 680.

[0207] FIG. 9C illustrates a top and bottom plan view of an embodiment of the plurality of stacked waveguides of FIGS. 9A and 9B. This top and bottom view may also be referred to as a front-on view, as seen in the direction of propagation of light towards the internal coupling optical elements 800, 810, 820, i.e., it should be understood that the top and bottom view is a view of the waveguide where the image light is incident normal to the page. As shown, waveguides 670, 680, 690 may be vertically aligned, along with their associated light dispersing elements 730, 740, 750 and associated external coupling optical elements 800, 810, 820. However, as discussed herein, the internal coupling optical elements 700, 710, 720 are not vertically aligned. Rather, the internal coupling optical elements are preferably non-overlapping (e.g., laterally spaced as seen in the top and bottom view). As further discussed herein, this non-overlapping spatial arrangement facilitates the injection of light from different sources into different waveguides on a one-to-one basis, thereby enabling a specific light source to be uniquely coupled to a specific waveguide. In some embodiments, an array comprising non-overlapping spatially separated internal coupling optical elements may be referred to as a shifted pupil system, and the internal coupling optical elements within these arrays may correspond to sub-pupils.

[0208] It should be understood that the spatially overlapping area may have a lateral overlap of 70% or more, 80% or more, or 90% or more of that area, as seen in the top and bottom view. On the other hand, the laterally shifted area may have less than 30%, less than 20%, or less than 10% of that area overlapping, as seen in the top and bottom view. In some embodiments, the laterally shifted area has no overlap.

[0209] FIG. 9D illustrates a top and bottom plan view of another embodiment of a plurality of stacked waveguides. As shown, waveguides 670, 680, 690 may be vertically aligned. However, compared to the configuration of FIG. 9C, separate optical dispersion elements 730, 740, 750 and associated external coupling optical elements 800, 810, 820 are omitted. Instead, the optical dispersion elements and the external coupling optical elements are, in effect, superimposed and occupy the same area as seen in the top and bottom views. In some embodiments, an optical dispersion element (e.g., OPE) may be disposed on one major surface of waveguides 670, 680, 690, and an external coupling optical element (e.g., EPE) may be disposed on the other major surface of those waveguides. Thus, each of waveguides 670, 680, 690 may collectively have superimposed optical dispersion and external coupling optical elements, respectively, referred to as combined OPE / EPEs 1281, 1282, 1283. Further details regarding such combined OPE / EPEs can be found in U.S. Patent Application No. 16 / 221,359, filed on December 14, 2018, the entire disclosure of which is incorporated herein by reference. Internal coupling optical elements 700, 710, 720 internally couple light and direct it, respectively, to combined OPE / EPEs 1281, 1282, 1283. In some embodiments, as shown, internal coupling optical elements 700, 710, 720 may be laterally offset if they have an offset pupil spatial arrangement (e.g., they are laterally separated as seen in the top and bottom views shown). Similar to the configuration of FIG. 9C, this laterally offset spatial arrangement facilitates the injection of light of different wavelengths into different waveguides on a one-to-one basis (e.g., from different light sources).

[0210] FIG. 9E illustrates an embodiment of a wearable display system 60 into which various waveguides and related systems disclosed herein may be integrated. In some embodiments, display system 60 is the system 250 of FIG. 6, which schematically shows some parts of that system 60 in more detail. For example, the waveguide assembly 260 of FIG. 6 may be part of display 70.

[0211] Continuing to refer to FIG. 9E, the display system 60 includes a display 70 and various mechanical and electronic modules and systems for supporting the functions 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 is configured to position the display 70 in front of the user's 90 eyes. In some embodiments, the display 70 may be regarded as eyewear. The display 70 may include one or more waveguides, such as waveguide 270, configured to relay internally coupled image light and output the image light to the user's 90 eyes. In some embodiments, a speaker 100 is coupled to the frame 80 and configured to be positioned adjacent to the user's 90 outer ear canal (in some embodiments, another speaker, not shown, may also optionally be positioned adjacent to the user's other outer ear canal to provide stereo / formable sound control). The display system 60 may also include one or more microphones 110 or other devices for detecting sound. In some embodiments, the microphone is configured to enable the user to provide an input or command to the system 60 (e.g., selection of a voice menu command, natural language question, etc.) and / or enable audio communication with other persons (e.g., other users of a similar display system). The microphone may further be configured as a peripheral sensor to collect audio data (e.g., sound from the user and / or the environment). In some embodiments, the display system 60 may further include one or more outwardly directed environmental sensors 112 configured to detect objects, stimuli, people, animals, locations, or other aspects of the world around the user. For example, the environmental sensor 112 may include one or more cameras, which may be positioned facing outward to capture an image similar to at least a portion of the user's 90 normal field of view. In some embodiments, the display system may also include a peripheral sensor 120a, which is separate from the frame 80 and may be attached to the user's 90 body (e.g., the user's 90 head, torso, limbs, etc.).In some embodiments, the peripheral sensor 120a may be configured to obtain data characterizing the physiological state of the user 90. For example, the sensor 120a may be an electrode.

[0212] Continuing to refer to FIG. 9E, the display 70 is operably coupled to the local data processing module 140 by a communication link 130, such as a wired conductor or wireless connectivity, which may be mounted in various configurations, such as fixedly attached to the frame 80, fixedly attached to a helmet or hat worn by the user, built into headphones, or removably attached to the user 90 in some other manner (e.g., in a backpack configuration, in a belt attachment configuration). Similarly, the sensor 120a may be operably coupled to the local data processing module 140 by a communication link 120b, such as a wired conductor or wireless connectivity. The local processing and data module 140 may include digital memory, such as a hardware processor and non-volatile memory (e.g., flash memory or hard disk drive), both of which may be utilized to assist in the processing, caching, and storage of data. Optionally, the local processing and data module 140 may include one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, etc. The data may include a) data captured from sensors (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., operably coupled to the frame 80 or otherwise attachable to the user 90)), and / or b) potentially, data obtained and / or processed using the remote processing module 150 and / or remote data repository 160 (including data related to virtual content) for passage to the display 70 after processing or retrieval. The local processing and data module 140 may be operably coupled to the remote processing module 150 and the remote data repository 160 by communication links 170, 180, such as via a wired or wireless communication link, such that these remote modules 150, 160 are operably coupled to each other and available as resources to the local processing and data module 140.In some embodiments, the local processing and data module 140 may include one or more of an image capture device, a microphone, an inertial measurement unit, an accelerometer, a compass, a GPS unit, a wireless device, and / or a gyroscope. In some other embodiments, one or more of these sensors may be attached to the frame 80 or may be an independent structure that communicates with the local processing and data module 140 via a wired or wireless communication path.

[0213] Continuing to refer to FIG. 9E, in some embodiments, the remote processing module 150 may comprise one or more processors configured to analyze and process data and / or image information, for example, including one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, etc. In some embodiments, the remote data repository 160 may comprise a digital data storage facility, which may be available through the Internet or other networking configurations in a “cloud” resource configuration. In some embodiments, the remote data repository 160 may include one or more remote servers, which provide information, for example, information for generating virtual content, to the local processing and data module 140 and / or the remote processing module 150. In some embodiments, all data is stored and all calculations are performed in the local processing and data module, enabling 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), for example, providing information to and receiving information from modules 140, 150, 160 via a wireless or wired connection.

[0214] FIG. 10 illustrates an embodiment of a wearable display system with an optical 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 a spatial light modulator (SLM) 930. A lens structure 960 may be used to focus light from the light source 940 onto the SLM 930. A beam splitter (e.g., a polarizing beam splitter (PBS)) 950 reflects light from the light source 940 to the spatial light modulator 930, which reflects and modulates the light. The reflected and modulated light, also referred to as image light, then propagates through the beam splitter 950 to an eyepiece lens 920. A projection optical system 970, which is another lens structure, may be utilized to converge or focus the image light onto the eyepiece lens 920. The eyepiece lens 920 may include one or more waveguides or waveguides that relay the modulated light to the eye 210.

[0215] As described herein, the separate light source 940 and associated lens structure 960 may undesirably add weight and size to the wearable display system. This may reduce the comfort of the display system, particularly for a user wearing the display system for an extended period of time.

[0216] In addition, the light source 940 may consume energy inefficiently in conjunction with the SLM 930. For example, the light source 940 may illuminate the entire SLM 930. The SLM 930 then selectively reflects the light towards the eyepiece lens 920. Thus, not all of the light produced by the light source 940 can be utilized to form an image. A portion of this light, e.g., the light corresponding to dark regions of the image, is not reflected towards the eyepiece lens 920. As a result, the light source 940 uses energy to generate light to illuminate the entire SLM 930, but only a certain percentage of this light may be required to form some images.

[0217] Furthermore, as described herein, in some cases, the SLM930 can modulate light and selectively reflect incident light by using micromirrors or by using liquid crystal molecules that 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 in an LCoS or DLP panel, respectively) to modulate the light from the light source 940. The physical movement required to modulate light and encode the light with image information corresponding to, for example, pixels can occur at a relatively low speed compared to, for example, the ability to turn an LED or OLED “on” or “off”. This relatively low speed movement can limit the frame rate of the display system and can be visible as, for example, motion blur, color breakup, and / or an inconsistent presented image with respect to the user's head pose or a change in that pose.

[0218] Advantageously, a wearable display that utilizes a light-emitting microdisplay as disclosed herein can facilitate a wearable display system having relatively low weight and bulk, high energy efficiency, and high frame rate, with low motion blur and short latency from motion to image rendering. The low blur and short latency from motion to image rendering are further discussed in U.S. Provisional Application No. 62 / 786,199, filed Dec. 28, 2018, the entire disclosure of which is incorporated herein by reference. Additionally, compared to a scanned fiber display, a light-emitting microdisplay can avoid artifacts resulting from the use of a coherent light source.

[0219] Referring now to FIG. 11A, an embodiment of a wearable display system is illustrated with a light projection system 1010 having a plurality of light-emitting 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. A projection optical system 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 light projection system 1010 and the eyepiece 1020 may be supported (e.g., attached) by a frame 80 (FIG. 9E).

[0220] In some embodiments, the microdisplays 1030a, 1030b, 1030c may be monochrome microdisplays, each monochrome microdisplay outputting light of a different primary color and providing a monochrome image. As discussed herein, the monochrome images are combined to form a full-color image.

[0221] In some other embodiments, the microdisplays 1030a, 1030b, 1030c may each be a full-color display configured to output light of all primary colors. For example, the microdisplays 1030a, 1030b, 1030c each include red, green, and blue light emitters. The microdisplays 1030a, 1030b, 1030c may be the same and may display the same image. However, using a plurality of microdisplays may provide the advantage of increasing the brightness and brightness dynamic range of the image by combining light from the plurality of 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.

[0222] The microdisplay may comprise an array of light emitters. Examples of light emitters include organic light emitting diodes (OLEDs) and micro light emitting diodes (microLEDs). It should be understood that OLEDs utilize organic materials to emit light, and microLEDs utilize inorganic materials to emit light. Advantageously, some microLEDs provide higher brightness and higher efficiency (from the perspective of lux / W) than OLEDs. In some embodiments, the microdisplay is preferably a microLED display.

[0223] Continuing to refer to FIG. 11A, the microdisplays 1030a, 1030b, 1030c may each be configured to emit image light 1032a, 1032b, 1032c. When the microdisplay is a monochromatic microdisplay, the image lights 1032a, 1032b, 1032c may each be different primary colors. The optical combiner 1050 receives the image lights 1032a, 1032b, 1032c and effectively combines this light such that the light generally propagates in the same direction, e.g., towards the projection optical system 1070. In some embodiments, the optical combiner 1050 may be a dichroic X-cube prism having a reflective internal surface that redirects the image lights 1032a, 1032b, 1032c to the projection optical system 1070. It should be understood that the projection optical system 1070 may be a lens structure comprising one or more lenses that converge or focus the image light onto the eyepiece lens 1020. The eyepiece lens 1020 then relays the image lights 1032a, 1032b, 1032c to the eye 210.

[0224] In some embodiments, the eyepiece 1020 may include a plurality of stacked waveguides 1020a, 1020b, 1020c, each having an individual 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 the waveguides 1020a, 1020b, 1020c and the internal coupling optical elements 1022a, 1022b, 1022c may correspond to the waveguides 670, 680, 690 and the internal coupling optical elements 700, 710, 720 of FIGS. 9A - 9C, respectively. As viewed from the projection optics 1070, the internal coupling optical elements 1022a, 1022b, 1022c may be laterally offset so that they do not overlap, at least partially, as seen in such figures.

[0225] As shown, the various internally coupled optical elements (e.g., internally coupled optical elements 1022a, 1022b, 1022c) disclosed herein may be disposed on a major surface of an associated waveguide (e.g., waveguides 1020a, 1020b, 1020c, respectively). Additionally, as shown, the major surface on which a given internally coupled optical element is disposed may be the back surface of the waveguide. In such a configuration, the internally coupled optical element may be a reflective light redirecting element, which internally couples light by reflecting the light at an angle that supports TIR through the associated waveguide. In certain other configurations, the internally coupled 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 internally coupled optical element may be a transmissive light redirecting element, which internally couples light by changing the propagation direction of the light as the light is transmitted through the internally coupled optical element. It should be understood that any of the internally coupled optical elements disclosed herein may be either reflective or transmissive internally coupled optical elements.

[0226] Continuing to refer to FIG. 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 internally coupled optical elements 1022a, 1022b, 1022c. If the image light 1032a, 1032b, 1032c includes light of different primary colors, the associated internally coupled optical elements 1022a, 1022b, 1022c may be configured to selectively internally couple light of different wavelengths, respectively, as described above with respect to the internally coupled optical elements 700, 710, 720 of FIGS. 9A-9C, for example.

[0227] Continuing to refer to FIG. 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 in order to impinge on appropriately associated ones of the internal coupling 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 plane of the optical combiner 1050, but the light exits the optical combiner in slightly different directions. For example, the reflective internal surfaces 1052, 1054 of the X-cube prism may each be angled to direct the image light 1032a, 1032b, 1032c along different paths toward the eyepiece lens 1020. As a result, the image light 1032a, 1032b, 1032c may impinge on different associated ones of the internal coupling optical elements 1022a, 1022b, 1022c. In some embodiments, the microdisplays 1030a, 1030b, 1030c may be appropriately angled with respect to the reflective internal surfaces 1052, 1054 of the X-cube prism to provide the desired optical paths to the internal coupling optical elements 1022a, 1022b, 1022c. For example, the surfaces of one or more of the microdisplays 1030a, 1030b, 1030c may be angled to match the surfaces of the optical combiner 1050 such that the image light emitted by the microdisplay impinges on the reflective internal surfaces 1052, 1054 at an appropriate angle and propagates toward the associated internal coupling optical element 1022a, 1022b, or 1022c. In addition to a cube, it should be understood that the optical combiner 1050 may take the form of various other polyhedra. For example, the optical combiner 1050 may be in the shape of a right prism having at least two faces, rather than a square.

[0228] Continuing to refer to FIG. 11A, in some embodiments, the monochromatic microdisplay 1030b that directly faces the output surface 1051 advantageously may 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 monochromatic microdisplay 1030b that faces the output surface 1051 preferably outputs green light such that the green light can proceed directly through the optical combiner 1050 without having to be reflected for output from the optical combiner 1050. However, it will be understood that the green monochromatic microdisplay may face other surfaces of the optical combiner 1050 in some other embodiments.

[0229] As discussed herein, the perception of a full-color image by a user can, in some embodiments, be achieved using time-division multiplexing. For example, different ones of the emissive microdisplays 1030a, 1030b, 1030c can be activated at different times to generate different primary color images. In such embodiments, the different primary color images that form a single full-color image can be sequentially displayed quickly enough such that the human visual system does not perceive that the primary color images are being displayed at different times. That is, all of the different primary color images that form a single full-color image can be displayed within a duration that is short enough such that the user perceives the primary color images as being presented simultaneously rather than being temporally separated. 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 at which the human visual system is unable to distinguish 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. Flicker images with a temporal gap between the images outside of that duration are not combined and the flicker of the images is perceivable. In some embodiments, the duration is 1 / 60 of a second or less, which corresponds to a frame rate of 60 Hz or more. Preferably, the image frames for any individual eye are provided to the user at a frame rate that is equal to or higher than the duration of the user's flicker fusion threshold. For example, the frame rate for each of the left and right eyepieces can be 60 Hz or more, or 120 Hz or more, and as a result, the frame rate provided by the light projection system 1010 can be 120 Hz or more, or 240 Hz or more in some embodiments.

[0230] It should be understood that time division multiplexing can 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 computational resources are available, all the primary color images that form a full-color image may be simultaneously displayed by the microdisplays 1030a, 1030b, 1030c.

[0231] As discussed herein, each of the microdisplays 1030a, 1030b, 1030c may include an array of light emitters. FIG. 11B illustrates an example of an array 1042 of light emitters 1044. When the associated microdisplay is a monochrome microdisplay, all of the light emitters 1044 may be configured to emit light of the same color.

[0232] When 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 embodiments, 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, when 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.

[0233] It will be understood that the light emitters 1044 are shown arranged in a grid pattern for ease of illustration, but 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 the groups of light emitters may vary, and so on.

[0234] Continuing to refer to FIG. 11B, it should be understood that the micro emitter 1044 emits light. In addition, manufacturing constraints such as lithography or other patterning and processing limits and / or electrical considerations may limit the proximity at which neighboring light emitters 1044 are spaced apart. As a result, there may be an area 1045 surrounding the light emitter 1044 where it is not practical to form other light emitters 1044. This area 1045 forms an inter-emitter region between the light emitters 1044. In some embodiments, considering the area 1045, the light emitters have a pitch that is, for example, less than 10 μm, less than 8 μm, less than 6 μm, or less than 5 μm and greater than 1 μm including 1 - 5 μm, and the emitter size is 2 μm or less, 1.7 μm or less, or 1.3 μm or less. In some embodiments, the emitter size is within a range having the upper limit of the above sizes and a lower limit of 1 μm. In some embodiments, the ratio of emitter size to pitch is 1:1 to 1:5, 1:2 to 1:4, or 1:2 to 1:3.

[0235] Assuming some light emitter device architectures and materials, it should be understood that current crowding can reduce the efficiency of the emitter and pixel droop can cause unintentional activation of the pixel (e.g., due to energy directed at one light emitter leaking to neighboring light emitters). As a result, the relatively large area 1045 can, advantageously, reduce current crowding and pixel droop. In some embodiments, the ratio of emitter size to pitch is preferably 1:2 to 1:4 or 1:2 to 1:3.

[0236] However, it should also be understood that a large separation between light emitters (e.g., a small ratio of light emitter pair pitch) can undesirably cause visible gaps or dark regions between the light emitters. In some embodiments, a lens structure such as a light collimator may be utilized to effectively fill these dark regions. For example, a light collimating lens may extend over and around the light emitter 1044 such that the light from the emitter 1044 completely fills the lens. For example, the light collimating lens may have a width larger than the light emitter 1044, and in some embodiments, the width of the collimating lens may be approximately equal to the pitch. As a result, the size of the emitter 1044 is effectively increased such that it extends across the area of the lens, thereby filling part or all of the area 1045. Lens structures such as light collimators are further discussed herein (e.g., in FIGS. 30A and the related discussion).

[0237] As discussed herein, the light emitter 1044 may be an OLED or a micro LED. It should be understood that an OLED may utilize, for example, a layer of organic material disposed between electrodes to emit light. A micro LED may utilize an inorganic material, e.g., a Group III-V material such as GaAs, GaN, and / or GaIn, for light emission. An example of a GaN material includes InGaN, which may be used to form a blue or green light emitter in some embodiments. An example of a GaIn material includes AlGaInP, which may be used to form a red light emitter in some embodiments. In some embodiments, the light emitter 1044 may emit light of an initial color, which may be converted to another desired color using a phosphor material or quantum dots. For example, the light emitter may emit blue light, which excites a phosphor material or quantum dots that convert blue wavelength light to a green or red wavelength.

[0238] Referring now to FIG. 12, another embodiment of a wearable display system with an optical projection system having a plurality of emissive microdisplays 1030a, 1030b, 1030c is illustrated. The illustrated display system is similar to the display system of FIG. 11A, but the optical combiner 1050 has a standard X-cube prism configuration and includes light redirection structures 1080a and 1080c to modify the angle of incidence of light on the reflective surfaces 1052, 1054 of the X-cube prism. It should be understood that the standard X-cube prism configuration will redirect this light at 45° to receive light that is normal to the faces of the X-cube and output it at a normal angle from the lateral faces of the X-cube. However, this would cause the image light 1032a, 1032b, 1032c to impinge on the same internal coupling optical elements of the eyepiece 1020. Light redirection structures 1080a, 1080c may be utilized to provide different paths for the image light 1032a, 1032b, 1032c such that the image light impinges on those associated with the internal coupling optical elements 1022a, 1022b, 1022c of the waveguide assembly.

[0239] In some embodiments, the light redirecting structures 1080a, 1080c may be lens structures. It should be understood that the lens structure may be configured to receive incident light and redirect the incident light at an angle such that the light is reflected from the corresponding ones of the reflective surfaces 1052, 1054 and propagates along the optical path towards the corresponding ones of the internal coupling optical elements 1022a, 1022c. By way of example, the light redirecting structures 1080a, 1080c may comprise microlenses, nanolenses, reflective wells, metasurfaces, and liquid crystal gratings. In some embodiments, the microlenses, nanolenses, reflective wells, metasurfaces, and liquid crystal gratings may be arranged in an array. For example, each light emitter of the microdisplays 1030a, 1030c may be aligned with one microlens. In some embodiments, the microlens or reflective well may be asymmetric and / or the light emitter may be disposed offset from the center with respect to the microlens in order 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 internally coupled into the eyepiece lens 1020. Further details regarding such light redirecting structures 1080a, 1080c are discussed below with respect to FIGS. 24A - 27C.

[0240] Referring now to FIG. 13A, in some embodiments, two or more of the internal coupling optical elements 1022a, 1022b, 1022c may overlap (e.g., as seen in a front view in the direction of light propagation into the internal coupling optical elements 1022a, 1022b, 1022c). FIG. 13A illustrates an example side view of a wearable display system with an optical projection system 1010 having a plurality of light emitting microdisplays 1032a, 1032b, 1032c, and an eyepiece 1020 with overlapping light internal coupling optical elements 1022a, 1022c and a non-overlapping light internal coupling optical element 1022b. As shown, the internal coupling optical elements 1022a, 1022c overlap, while the internal coupling optical element 1022b is laterally offset. In other words, the internal coupling optical elements 1022a, 1022c are directly aligned within the path of the image light 1032a, 1032c, while the image light 1032b follows another path to the eyepiece 1020 such that it is incident on an area of the eyepiece 1020 that is laterally offset from the area where the image light 1032a, 1032c is incident.

[0241] As shown, the differences between the paths for image light 1032b and image lights 1032a, 1032c may be established using light redirection structures 1080a, 1080c. In some embodiments, image light 1032b from the emissive microdisplay 1030b travels directly through the optical combiner 1052. Image light 1032a from the emissive microdisplay 1032a is redirected by the light redirection structure 1080a to reflect from the reflective surface 1054 and propagate outward from the optical combiner 1050 in the same direction as image light 1032c. It should be understood that image light 1032c from the emissive microdisplay 1032c is redirected by the light redirection structure 1080c to reflect from the reflective surface 1052 at an angle such that image light 1032c propagates outward from the optical combiner 1050 in the same direction as image light 1032b. Thus, the redirection of light by the light redirection structures 1080a, 1080c and the angles of the reflective surfaces 1052, 1054 are configured to provide a common path for image lights 1032a, 1032c outward from the optical combiner 1050, and this common path is different from the path of image light 1032b. In some other embodiments, one or both of the light redirection structures 1080a, 1080c may be omitted, and the reflective surfaces 1052, 1054 within the optical combiner 1050 may be configured to reflect image lights 1032a, 1032c in appropriate individual directions so as to propagate in the same direction that is different from the direction of image light 1032b and exit the optical combiner 1050. Thus, after propagating through the projection optics 1070, image lights 1032a, 1032c exit from one exit pupil, while image light 1032b exits from another exit pupil. In this configuration, the light projection system 1010 may be referred to as a two-pupil projection system.

[0242] In some embodiments, the light projection system 1010 may have a single exit pupil and may be referred to as a single pupil projection system. In such embodiments, the light projection system 1010 may be configured to direct the image lights 1032a, 1032b, 1032c onto a single common area of the eyepiece 1020. Such a configuration is illustrated in FIG. 13B, which depicts a wearable display system with a light projection system 1010 having a plurality of light-emitting microdisplays 1030a, 1030b, 1030c configured to direct light onto a single light internal coupling area of the eyepiece 1020. In some embodiments, as further discussed herein, the eyepiece 1020 may include a stack of waveguides having overlapping light internal coupling optical elements. In some other embodiments, the single light internal coupling optical element may be configured to internally couple light of all primary colors into a single waveguide. The display system of FIG. 13B is similar to the display system of FIG. 13A, except for the omission of the light redirection structures 1080a, 1080c and the combined use of the internal coupling optical element 1122a associated with the waveguide 1020a. As shown, the internal coupling optical element 1122a internally couples each of the image lights 1032a, 1032b, 1032c into the waveguide 1020a, which then relays the image light to the eye 210. In some embodiments, the internal coupling optical element 1122a may comprise a diffraction grating. In some embodiments, the internal coupling optical element 1122a is a metasurface and / or a liquid crystal grating.

[0243] As discussed herein, in some embodiments, the emissive microdisplays 1030a, 1030b, 1030c may be monochromatic microdisplays configured to emit light of different colors. In some embodiments, one or more of the emissive microdisplays 1030a, 1030b, 1030c may have a group of light emitters configured to emit light of two or more but not all of the primary colors. For example, a single emissive microdisplay may have a group 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, and separate emissive microdisplays on different faces of the X-cube 1050 may have light emitters configured to emit red light. In some other embodiments, the emissive microdisplays 1030a, 1030b, 1030c may each be a full-color display having all of the primary color light emitters. As described herein, utilizing multiple similar microdisplays may provide advantages for dynamic range and increased display brightness.

[0244] In some embodiments, a single full-color emissive microdisplay may be utilized. FIG. 14 illustrates an example of a wearable display system with a single emissive microdisplay 1030b. The wearable display system of FIG. 14 is similar to the wearable display system of FIG. 14, except that the single emissive microdisplay 1030b is a full-color microdisplay configured to emit all of the primary colors of light. As shown, the microdisplay 1030b emits image light 1032a, 1032b, 1032c of each primary color. In such embodiments, the optical combiner 1050 (FIG. 13B) may be omitted, which may advantageously reduce the weight and size of the wearable display system relative to systems with an optical combiner.

[0245] As discussed above, the internal coupling optical elements of the eyepiece 1020 may take various configurations. Some embodiments of the configuration regarding the eyepiece 1020 are discussed below in relation to FIGS. 15-23C.

[0246] FIG. 15 illustrates side views of embodiments of the eyepiece 1020 having stacks of waveguides 1020a, 1020b, 1020c, each with overlapping internal coupling optical elements 1022a, 1022b, 1022c. It should be understood that the illustrated waveguide stacks may be utilized in place of the single illustrated waveguide 1020a of FIGS. 13B and 14. As discussed herein, the internal coupling optical elements 1022a, 1022b, 1022c are each configured to internally 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 in which image light propagates vertically through the page towards the eyepiece 1020, the internal coupling optical elements 1022a, 1022b, 1022c are aligned perpendicular to each other (e.g., along an axis parallel to the propagation direction of the image light 1032a, 1032b, 1032c) such that they spatially overlap each other as seen in the front-on view in the up-down view (the direction of the image light 1032a, 1032b, 1032c propagating to the internal coupling optical elements).

[0247] Continuing to refer to FIG. 15, as discussed herein, the projection system 1010 (FIGS. 13, 14) is configured to output a first monochromatic image, a second monochromatic image, and a third monochromatic image (e.g., red, green, and blue color images) through a single pupil of the projection system, and the monochromatic images are formed by image lights 1032a, 1032b, 1032c, respectively. The internal coupling optical element 1022c is configured to internally couple the image light 1032c into the waveguide 1020c for the first color image so as to propagate through the waveguide 1020c by multiple total internal reflections at the upper and bottom major surfaces of the waveguide 1020c. The internal coupling optical element 1022b is configured to internally couple the image light 1032b into the waveguide 1020b for the second color image so as to propagate through the waveguide 1020b by multiple total internal reflections at the upper and bottom major surfaces of the waveguide 1020b. The internal coupling optical element 1022a is configured to internally couple the image light 1032a into the waveguide 1020a for the third color image so as to propagate through the waveguide 1020a by multiple total internal reflections at the upper and bottom major surfaces of the waveguide 1020a.

[0248] As discussed herein, the internal coupling optical element 1022c is preferably configured to internally couple substantially all of the incident light 1032c corresponding to the first color image into the associated waveguide 1020c, while allowing substantially all of the incident lights 1032b, 1032a corresponding to the second and third color images, respectively, to be transmitted without being internally coupled. Similarly, the internal coupling optical element 1022b is preferably configured to internally couple substantially all of the incident image light 1032b corresponding to the second color image into the associated waveguide 1020b, while allowing substantially all of the incident light corresponding to the third color image to be transmitted without being internally coupled.

[0249] In practice, it should be understood that various internal coupling optical elements may not have perfect selectivity. For example, a portion of the image light 1032b, 1032a may undesirably be internally coupled into the waveguide 1020c by the internal coupling optical element 1022c, and a portion of the incident image light 1032a may undesirably be internally coupled into the waveguide 1020b by the internal coupling optical element 1022b. Further, a portion of the image light 1032c may be transmitted through the internal coupling optical element 1022c and may be internally coupled into the waveguides 1020b and / or 1020a by the internal coupling optical elements 1020b and / or 1020a, respectively. Similarly, a portion of the image light 1032b may be transmitted through the internal coupling optical element 1022b and may be internally coupled into the waveguide 1020a by the internal coupling optical element 1022a.

[0250] Internally coupling the image light for a color image into an unintended waveguide can cause undesirable optical effects such as, for example, crosstalk and / or ghosting. For example, the unintended internal coupling of the image light 1032c for the first color image into the 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 ghosting. As another example, the unintended internal coupling of the image light 1032b, 1032a for the second or third color image, respectively, into the waveguide 1020c can result in undesirable crosstalk between the first color image, the second color image, and / or the third color image, and / or can cause undesirable ghosting. In some embodiments, these undesirable optical effects can be reduced by providing a color filter (e.g., an absorptive color filter) that can reduce the amount of incident light that is internally coupled into the unintended waveguide.

[0251] FIG. 16 illustrates a side view of an embodiment of a stack of waveguides with color filters to reduce afterglow or crosstalk between waveguides. The eyepiece lens 1020 of FIG. 16 is similar to that of FIG. 15 except for the presence of one or more of the color filters 1024c, 1024b and 1028, 1026. The color filters 1024c, 1024b are each configured to reduce the amount of light that is unintentionally internally coupled into the waveguides 1020b and 1020a, respectively. The color filters 1028, 1026 are each configured to reduce the amount of unintentionally internally coupled image light that propagates through the waveguides 1020b, 1020c, respectively.

[0252] Continuing to refer to FIG. 16, a pair of color filters 1026 disposed on the upper and lower major surfaces of the waveguide 1020c may be configured to absorb the image light 1032a, 1032b that may be unintentionally internally coupled into the waveguide 1020c. In some embodiments, the color filter 1024c disposed between the waveguides 1020c and 1020b is configured to absorb the image light 1032c that is transmitted through the internal coupling optical element 1022c without being internally coupled. A pair of color filters 1028 disposed on the upper and lower major surfaces of the waveguide 1020b are configured to absorb the image light 1032a that is internally coupled into the waveguide 1020b. The color filter 1024b disposed between the waveguides 1020b and 1020a is configured to absorb the image light 1032b that is transmitted through the internal coupling optical element 710.

[0253] 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 filter 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 filter 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, in the TIR bounces 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 their major surfaces, and a portion of that image light is absorbed. Preferably, due to the selective absorption of the image light 1032a, 1032b by the color filters 1026, the propagation of the image light 1032c internally coupled through the waveguide 1020c via TIR is not significantly affected.

[0254] Similarly, a plurality of color filters 1028 may be configured as absorption filters that absorb the internally coupled image light 1032a propagating through the waveguide 1020b by total internal reflection. In the TIR bounces of the image light 1032a from the major surfaces of the waveguide 1020b, the image light 1032a contacts the color filters 1028 on their major surfaces, and a portion of that image light is absorbed. Preferably, the absorption of the image light 1032a is selective and does not affect the propagation of the internally coupled image light 1032b that also propagates through the waveguide 1020b via TIR.

[0255] Continuing to refer to FIG. 16, color filters 1024c and 1024b may also be configured as absorption filters. Color filter 1024c may be substantially transparent to light of the colors of image lights 1032a and 1032b such that image lights 1032a and 1032b are 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. Color filters 1024c and 1024b may be aligned perpendicular to a single pupil of a projector that outputs image lights 1032a, 1032b, and 1032c (in an orientation in which image lights 1032a, 1032b, and 1032c propagate perpendicular to waveguide stack 1020 as shown).

[0256] In some embodiments, 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 unwanted absorption of light (e.g., light of the color of image light 1032a, 1032b propagating through the thickness of waveguides 1020c, 1020b and propagating from the surrounding environment and / or other waveguides through waveguides 1020c, 1020b). Various embodiments of 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 more than 80%, more than 90%, or more than 95% of the incident light having the color of image light 1032a, 1032b and absorb more than 80%, more than 90%, or more than 95% of the incident light having the color of image light 1032a. Similarly, color filter 1024b may be configured to transmit more than 80%, more than 90%, or more than 95% of the incident light having the color of image light 1032a and absorb more than 80%, more than 90%, or more than 95% of the incident light having the color of image light 1032b.

[0257] In some embodiments, color filters 1026, 1028, 1024c, 1024b may comprise a layer of color-selective light-absorbing material deposited on one or both surfaces of waveguides 1020c, 1020b, and / or 1020a. The color-selective light-absorbing material may comprise 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 color-selectively achieved by using these materials to form a sub-wavelength grating (e.g., a grating that does not diffract light). The grating may be made of plasmonics (e.g., gold, silver, and aluminum) or semiconductors (e.g., silicon, amorphous silicon, and germanium).

[0258] Color - selective materials may be deposited on a substrate using various deposition methods. For example, color - selective light - absorbing materials may be deposited on a substrate using jet deposition techniques (e.g., ink - jet deposition). Ink - jet deposition can facilitate the deposition of a thin layer of color - selective light - absorbing material. Ink - jet deposition enables the deposition to be localized on a selected area of the substrate, and thus provides a high degree of control over the thickness and / or composition of the layer of color - selective light - absorbing material, including providing a non - uniform thickness and / or composition across the substrate. In some embodiments, the color - selective light - absorbing material deposited using ink - jet 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 the range / sub - range defined by any of these values). Controlling the thickness of the layer on which the color - selective light - absorbing material is deposited can be advantageous in achieving a color filter with a desired attenuation coefficient. Additionally, layers with different thicknesses may be deposited on different parts of the substrate. In addition, different compositions of the color - selective light - absorbing material may be deposited on different parts of the substrate using ink - jet deposition. Such variations in composition and / or thickness may advantageously allow for location - specific variations in light absorption. For example, in the area of a waveguide where transmission of light from the surroundings (to allow the viewer to see the surrounding environment) is not required, the composition and / or thickness may be selected to provide a high absorption rate or attenuation rate for a selected wavelength of light. Other deposition methods such as coating, spin - coating, spraying, etc. may also be employed to deposit the color - selective light - absorbing material on the substrate.

[0259] FIG. 17 illustrates an example of a top and bottom view of the waveguide assemblies of FIGS. 15 and 16. As shown, the internal coupling optical elements 1022a, 1022b, 1022c are spatially overlapping. Additionally, the waveguides 1020a, 1020b, 1020c may be vertically aligned together with the associated optical dispersion elements 730, 740, 750 and the associated external coupling optical elements 800, 810, 820 of each waveguide. The internal coupling optical elements 1022a, 1022b, 1022c are configured such that the incident image light 1032a, 1032b, 1032c (FIGS. 15 and 16) internally couples into the waveguides 1020a, 1020b, 1020c, respectively, such that the image light propagates towards the associated optical dispersion elements 730, 740, 750 by TIR.

[0260] FIG. 18 illustrates another example of a top and bottom view of the waveguide assemblies of FIGS. 15 and 16. As in FIG. 17, the internal coupling optical elements 1022a, 1022b, 1022c are spatially overlapping and the waveguides 1020a, 1020b, 1020c are vertically aligned. However, instead of the associated optical dispersion elements 730, 740, 750 and the associated external coupling optical elements 800, 810, 820 of each waveguide, there are respectively combined OPE / EPEs 1281, 1282, 1283. The internal coupling optical elements 1022a, 1022b, 1022c are configured such that the incident image light 1032a, 1032b, 1032c (FIGS. 15 and 16) internally couples into the waveguides 1020a, 1020b, 1020c, respectively, such that the image light propagates towards the associated combined OPE / EPEs 1281, 1282, 1283 by TIR.

[0261] Figures 15-18 show overlapping internal combining optical elements for a single pupil configuration of the display system, but it should be understood that the display system may have a two-pupil configuration in some embodiments. In such a configuration where three primary colors are utilized, the image light for two of the colors may have overlapping internal combining optical elements, while the image light for the third color may have laterally displaced internal combining optical elements. For example, the optical combiner 1050 (Figs. 11A, 12, 13A-13B) and / or the light redirecting structures 1080a, 1080c may be configured to direct the image light through the projection optics 1070 such that the image light of two colors is incident directly on the overlapping area of the eyepiece lens 1020, while the image light of another color is incident on an area that is laterally displaced. For example, the reflective surfaces 1052, 1054 (Fig. 11A) may be angled such that the image light of one color follows a common optical path with the image light from the emissive microdisplay 1030b, while the image light of another color follows a different optical path. In some embodiments, rather than having both of the light redirecting structures 1080a, 1080c (Fig. 12), one of these light redirecting structures may be omitted such that only the light from one of the microdisplays 1030a, 1030c is angled to provide a different optical path from the light emitted by the other two microdisplays.

[0262] FIG. 19A illustrates a side view of an embodiment of an eyepiece having a stack of waveguides with several overlapping internal coupling optical elements and several laterally offset internal coupling optical elements. The eyepiece of FIG. 19A is similar to the eyepiece of FIG. 15, except that one of the internal coupling optical elements is laterally offset with respect to the other internal coupling optical elements. In the illustrated orientation of the eyepiece 1020 in which image light propagates vertically following the page towards the eyepiece 1020, the internal coupling optical elements 1022a, 1022c are mutually perpendicularly aligned (e.g., along an axis parallel to the propagation direction of the image light 1032a, 1032c) such that they spatially overlap each other as seen in a front view in the direction of the image light 1032a, 1032c propagating to the internal coupling optical elements 1022a, 1022c. As seen in the same front view (e.g., as seen in the top and bottom views in the illustrated orientation), the internal coupling optical element 1022b is laterally offset with respect to the other internal coupling optical elements 1022a, 1022c. Light for the internal coupling optical element 1022b is output to the eyepiece 1020 through a different exit pupil than the light for the internal coupling optical elements 1022a, 1022c. It should be understood that the illustrated waveguide stack comprising waveguides 1020a, 1020b, 1020c may be utilized instead of the single illustrated waveguide 1020a of FIGS. 13 and 14.

[0263] Continuing to refer to FIG. 19, the internal coupling optical element 1022c is configured to internally couple the image light 1032c into the waveguide 1020c to propagate through the waveguide 1020c by multiple total internal reflections between the upper major surface and the bottom major surface of the waveguide 1020c, the internal coupling optical element 1022b is configured to internally couple the image light 1032b into the waveguide 1020b to propagate through the waveguide 1020b by multiple total internal reflections between the upper major surface and the bottom major surface of the waveguide 1020b, and the internal coupling optical element 1022a is configured to internally couple the image light 1032a into the waveguide 1020a to propagate through the waveguide 1020a by multiple total internal reflections between the upper major surface and the bottom major surface of the waveguide 1020a.

[0264] The internal coupling optical element 1022c is preferably configured to internally couple all incident light 1032c into the associated waveguide 1020c while transmitting all incident light 1032a. On the other hand, the image light 1032b can propagate to the internal coupling optical element 1022b without having to propagate through any other internal coupling optical element. This can be advantageous in some embodiments by allowing light to which the eye is more sensitive to be incident on the desired internal coupling optical element without any losses or distortions associated with propagation through other internal 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. The waveguides 1020a, 1020b, 1020c are shown arranged in a particular order, but it should be understood that in some embodiments, the order of the waveguides 1020a, 1020b, 1020c can be different.

[0265] As discussed herein, it should be understood that the upper internal coupling optical element 1022c of the internal coupling optical element 1022a may not have perfect selectivity. A portion of the image light 1032a may undesirably be internally coupled by the internal coupling optical element 1022c into the waveguide 1020c, and a portion of the image light 1032c may be transmitted through the internal coupling optical element 1022c and then the image light 1032c may impinge on the internal coupling optical element 1020a and be internally coupled into the waveguide 1020a. As discussed herein, such undesirable internal coupling can be visible as ghosting or crosstalk.

[0266] FIG. 19B illustrates a side view of an embodiment of the eyepiece lens of FIG. 19A with a color filter for reducing afterimages or crosstalk between waveguides. In particular, color filters 1024c and / or 1026 are added to the structure shown in FIG. 19A. As shown, internal coupling optical element 1022c may unintentionally internally couple a portion of image light 1032a into waveguide 1020c. Additionally, or alternatively, a portion of image light 1032c may undesirably pass through internal coupling optical element 1022c and then be unintentionally internally coupled by internal coupling optical element 1022a.

[0267] To reduce the unintentional internal coupling of image light 1032a propagating through waveguide 1022c, an absorptive color filter 1026 may be provided on one or both major surfaces of waveguide 1022c. The absorptive color filter 1026 may be configured to absorb light of the color of image light 1032a that is unintentionally internally coupled. As shown, the absorptive color filter 1026 is disposed in the general propagation direction of the image light through waveguide 1020c. Thus, the absorptive color filter 1026 is configured to absorb image light 1032a as the light propagates through waveguide 1020c by TIR and contacts the absorptive color filter 1026 as it reflects from one or both of the major surfaces of waveguide 1020c.

[0268] Continuing to refer to FIG. 19B, an absorptive color filter 1024c may be provided in front of the internally coupled optical element 1022a to reduce the image light 1032c that propagates through the internally coupled optical element 1022c without being internally coupled. The absorptive color filter 1024c is configured to absorb light of the color of the image light 1032c and prevent that light from propagating to the internally coupled optical element 1022a. Although shown between the waveguides 1020c and 1020b, in some other embodiments, the absorptive color filter 1024c may be disposed between the waveguides 1020b and 1020a. It should be understood that further details regarding the composition, formation, and properties of the absorptive color filters 1024c and 1026 are provided in the discussion of FIG. 16.

[0269] Also, in the embodiments illustrated in FIGS. 16 and 19B, one or more of the color filters 1026, 1028, 1024c, and 1024b may be omitted if one or more of the internally coupled optical elements 1022a, 1022b, 1022c are intended to be internally coupled into the associated waveguides 1020a, 1020b, 1022c, respectively, and have sufficiently high selectivity with respect to the color of light.

[0270] FIG. 20A illustrates an example of a top - down view of the eyepiece of FIGS. 19A and 19B. As shown, the internally coupled optical elements 1022a, 1022c spatially overlap, while the internally coupled optical element 1022b is laterally offset. Additionally, the waveguides 1020a, 1020b, 1020c may be vertically aligned with the associated light dispersing elements 730, 740, 750 and the associated external coupling optical elements 800, 810, 820 of each waveguide. The internally coupled optical elements 1022a, 1022b, 1022c are configured to internally couple the incident image lights 1032a, 1032b, 1032c (FIGS. 15 and 16) into the waveguides 1020a, 1020b, 1020c, respectively, such that the image light propagates towards the associated light dispersing elements 730, 740, 750 by TIR.

[0271] FIG. 20B illustrates another embodiment of a top and bottom view of the waveguide assembly of FIGS. 19A and 19B. As in FIG. 20A, the internal coupling optical elements 1022a, 1022c are spatially overlapping, the internal coupling optical elements are laterally offset, and the waveguides 1020a, 1020b, 1020c are vertically aligned. However, instead of the associated optical dispersion elements 730, 740, 750 and the associated external coupling optical elements 800, 810, 820 of each waveguide, there are respectively combined OPE / EPEs 1281, 1282, 1283. The internal coupling optical elements 1022a, 1022b, 1022c are configured to internally couple the incident image light 1032a, 1032b, 1032c (FIGS. 15 and 16) into the waveguides 1020a, 1020b, 1020c respectively such that the image light propagates towards the associated combined OPE / EPEs 1281, 1282, 1283 by TIR.

[0272] Referring now to FIG. 21, it should be understood that unwanted rebounding of internally coupled light can occur within the waveguide. Rebounding occurs when the internally coupled light propagating along the waveguide strikes the internal coupling optical element a second time or at a subsequent time after the initial internal coupling incidence. Rebounding can result in a portion of the internally coupled light being undesirably externally coupled and / or absorbed by the material of the internal coupling optical element. External coupling and / or absorption can undesirably result in a reduction in the overall internal coupling efficiency and / or the uniformity of the internally coupled light.

[0273] FIG. 21 illustrates a side view of an example of a re-bounce within waveguide 1030a. As shown, image light 1032a is internally coupled into waveguide 1030a by internal coupling optical element 1022a. Internal coupling optical element 1022a generally re-directs image light 1032a to propagate through the waveguide in direction 1033. A re-bounce can occur when the internally coupled image light internally reflects or bounces off the major surface of waveguide 1030a opposite internal coupling optical element 1022a and impinges on internal coupling optical element 1022a or undergoes a second bounce (re-bounce). The distance between two neighboring bounces on the same surface of waveguide 1030a is indicated by interval 1034.

[0274] Although not limited by theory, it should be understood that internal coupling optical element 1022a can behave symmetrically. That is, it can re-direct incident light so that the incident light propagates through the waveguide at the TIR angle. However, light incident on the diffractive optical element at the TIR angle (such as in response to a re-bounce, etc.) can also be externally coupled. Additionally, or alternatively, in embodiments where 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 can also involve partial absorption of the incident light because the reflection can involve absorption and emission of light from the material. As a result, external coupling and / or absorption of light can undesirably cause loss of the internally coupled light. Thus, the re-bounced light can incur significant loss compared to light that interacts with internal coupling optical element 1022a only once.

[0275] In some embodiments, the internal coupling element is configured to reduce internal-coupled image light loss due to rebounce. Generally, the rebounce of internally coupled light occurs in the propagation direction 1033 of the internally coupled light towards the end 1023 of the internal coupling optical element 1022a. For example, the light internally coupled at the end of the internal coupling optical element 1022a facing the end 1023 can rebounce if the spacing 1034 for that light is short enough. To avoid such rebounce, 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 rebounce is likely to occur. In some embodiments, the truncation may be a complete truncation of all structures (e.g., metallization and diffraction gratings) of the internal coupling optical element 1022a. In some other embodiments, for example, when the internal coupling optical element 1022a comprises 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 hardly absorbs the rebounced light and / or externally couples the rebounced light with lower efficiency. In some embodiments, the diffraction region of the internal coupling optical element 1022a may have a width shorter than its length perpendicular to the propagation direction 1033 along the propagation direction 1033, and / or the first portion of the image light 1032a is incident on the internal coupling optical element 1022a and the second portion of the light beam is sized and shaped to impinge on the waveguide 1030a without being incident on the internal coupling optical element 1022a. The waveguide 1032a and the optical internal coupling element 1022a are shown separately for clarity, but it should be understood that the rebounce and the discussed strategies for reducing rebounce may be applicable to any of the internal coupling optical elements disclosed herein. Also, it should be understood that the spacing 1034 is related to the thickness of the waveguide 1030a (a larger thickness results in a larger spacing 1034). In some embodiments, the thickness of the individual waveguides may be selected to set the spacing 1034 such that no rebounce occurs.Further details regarding bounce reduction can be found in U.S. Provisional Application No. 62 / 702,707, filed Jul. 24, 2018, the entire disclosure of which is incorporated herein by reference.

[0276] Figures 22A - 23C illustrate examples of top and bottom views of an eyepiece having internally coupled optical elements configured to reduce rebounce. The internally coupled optical elements 1022a, 1022b, 1022c are configured to internally couple light so as to propagate in a propagation direction towards associated light dispersing elements 730, 740, 750 (Figures 22A - 22C) or combined OPE / EPE 1281, 1282, 1283 (Figures 23A - 23C). As shown, the internally coupled optical elements 1022a, 1022b, 1022c may have a shorter dimension along the propagation direction and a longer dimension along the transverse axis. For example, each of the internally coupled optical elements 1022a, 1022b, 1022c may be rectangular in shape with a shorter side along the axis of the propagation direction and a longer side along an orthogonal axis. It should be understood that the internally coupled optical elements 1022a, 1022b, 1022c may have other shapes (e.g., orthogonal, hexagonal, etc.). Additionally, different ones of the internally coupled optical elements 1022a, 1022b, 1022c may have different shapes in some embodiments. Also, preferably, as shown, non - overlapping internally coupled optical elements may be positioned such that they are not in the propagation direction of other internally coupled optical elements. For example, as shown in Figures 22A, 22B, 23A, and 23B, non - overlapping internally coupled optical elements may be arranged along a line along an axis that intersects (e.g., is orthogonal to) the axis of the propagation direction.

[0277] It should be understood that the waveguide assemblies of FIGS. 22A - 22C are similar, except for the overlap of the internally coupled optical elements 1022a, 1022b, 1022c. For example, FIG. 22A illustrates the internally coupled optical elements 1022a, 1022b, 1022c without overlap. FIG. 22B illustrates the overlapping internally coupled optical elements 1022a, 1022c and the non - overlapping internally coupled optical element 1022b. FIG. 22C illustrates the overlap among all the internally coupled optical elements 1022a, 1022b, 1022c.

[0278] The waveguide assemblies of FIGS. 23A - 23C are also similar, except for the overlap of the internally coupled optical elements 1022a, 1022b, 1022c. FIG. 23A illustrates the internally coupled optical elements 1022a, 1022b, 1022c without overlap. FIG. 23B illustrates the overlapping internally coupled optical elements 1022a, 1022c and the non - overlapping internally coupled optical element 1022b. FIG. 22C illustrates the overlap among all the internally coupled optical elements 1022a, 1022b, 1022c.

[0279] Referring now to FIG. 24A, it should be understood that the emissive microdisplay has a high étendue, which presents challenges regarding the efficient utilization of light. As discussed herein, the emissive microdisplay may include a plurality of individual light emitters. Each of these light emitters may have a large - angle emission profile, for example, a Lambertian or near - Lambertian emission profile. Unfortunately, not all of this light may be captured and directed towards the eyepiece of the display system.

[0280] FIG. 24A illustrates an example of the angular emission profile of the light emitted by the individual light emitters 1044 of the emissive microdisplay 1032 and the light captured by the projection optics 1070. The illustrated emissive microdisplay 1032 may correspond to any of the emissive microdisplays disclosed herein, including emissive microdisplays 1032a, 1032b, 1032c. As illustrated, 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 emitter 1044 is significantly larger, and not all of the light emitted by the light emitter 1044 is incident on the projection optics 1070, and necessarily does not enter at an angle at which the light would propagate through and within the projection optics 1070. As a result, a portion of the light emitted by the light emitter 1044 may be undesirably captured and ultimately relayed to the user's eye without forming an image, and thus may be "wasted." This can result in an image that appears darker than would be expected if more of the light output by the light emitter 1040 ultimately reached the user's eye.

[0281] 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 optical system 1070 and increase the size of the numerical aperture of the projection optical system 1070 that captures the light. Additionally, or alternatively, the projection optical system 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 optical system 1070 may utilize lenses sized to capture a desired high percentage of the light emitted by the light emitter 1044. In some embodiments, the projection optical system 1070 may have an extended exit pupil and be configured to emit a light beam having, for example, 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 optical system 1070 may be extended in dimensions corresponding to the extended dimensions of the internal coupling optical elements 1022a, 1022b, 1022c of FIGS. 22A-23C. Without being limited by theory, such extended internal coupling optical elements 1022a, 1022b, 1022c may improve the étendue mismatch between the light-emitting microdisplay and the eyepiece lens 1020 (FIGS. 22A-23C). In some embodiments, the waveguide thickness of the eyepiece lens 1020 (e.g., FIGS. 11A and 12-23C) may be selected to increase the percentage of light effectively captured, for example, by increasing the rebounce interval and thereby reducing rebounce as discussed herein.

[0282] 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 is captured by the projection optics 1070 and relayed to the user's eye, and advantageously, the brightness of the image and the efficiency of the display system can be increased. In some embodiments, the light collimator enables the light collection efficiency of the projection optics (the percentage of the light emitted by the light emitter 1044 that is captured by the projection optics) to reach a value of 80% or more, 85% or more, or 90% or more, including from about 85% to 95% or from 85% to 90%. Additionally, the angular emission profile of the light from the light emitter 1044 can be reduced to 60° or less, 50° or less, or 40° or less (e.g., from 180°). In some embodiments, the reduced angular emission profile may be in the range of about 30° to 60°, 30° to 50°, or 30° to 40°. It should be understood that the light from the light emitter 1044 can create a conical shape, and the light emitter 1044 is at the apex of the cone. The angular emission profile refers to the angle created by the sides of the cone, and the associated light emitter 1044 is at the apex of that angle (as seen in a cross-section taken along a plane extending through the center of the cone and including the cone apex).

[0283] FIG. 24B illustrates an example of narrowing of the angular emission profile using an array of optical collimators. As shown, the emissive microdisplay 1032 includes an array of light emitters 1044, which emit light with an angular emission profile 1046. An array 1300 of optical 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 optical collimator 1302 (one optical collimator 1302 per light emitter 1044). Each optical collimator 1302 redirects the incident light from the associated light emitter 1044 and provides a narrowed angular emission profile 1047. Thus, the relatively large angular emission profile 1046 is narrowed to a smaller angular emission profile 1047.

[0284] In some embodiments, the optical collimators 1302 and the array 1300 may be part of the light redirecting structures 1080a, 180c of FIGS. 12 and 13A. Thus, the optical collimators 1302 may propagate at an appropriate angle into the optical combiner 1050 and narrow the angular emission profile of the light emitters 1044 and redirect the light so as to define a plurality of optical paths and associated plurality of exit pupils. It should be understood that the light may be redirected in a particular direction by appropriately shaping the optical collimators 1302.

[0285] Preferably, the optical collimator 1302 is positioned in close proximity to the optical emitter 1044 and captures a large proportion of the light output by the optical emitter 1044. In some embodiments, a gap may exist between the optical collimator 1302 and the optical emitter 1044. In some other embodiments, the optical collimator 1302 may be in contact with the optical emitter 1044. It should be understood that the angular emission profile 1046 may create a broad cone of light. Preferably, all or most of the cone of light from the optical emitter 1044 is incident on a single associated optical collimator 1302. Thus, in some embodiments, each optical emitter 1044 is smaller (occupies a smaller area) than the light-receiving surface of the associated optical collimator 1302. In some embodiments, each optical emitter 1044 has a width that is smaller than the spacing between adjacent remote optical emitters 1044.

[0286] Advantageously, the optical collimator 1302 can increase the efficiency of light utilization and can also reduce the occurrence of crosstalk between adjacent optical emitters 1044. It should be understood that crosstalk between the optical emitters 1044 can occur when light from a neighboring optical emitter is captured by an optical collimator 1302 not associated with that neighboring optical emitter. That captured light can propagate to the user's eye, thereby providing incorrect image information regarding a given pixel.

[0287] Referring to FIGS. 24A and 24B, the size of the beam of light captured by the projection optical system 1070 can affect the size of the beam of light exiting the projection optical system 1070. As shown in FIG. 24A, without using an optical collimator, the output beam can have a relatively large size 1050. As shown in FIG. 24B, with the optical collimator 1302, the output beam can have a smaller width 1052. Thus, in some embodiments, the optical collimator 1302 may be used to provide a desired beam size for internal coupling within the eyepiece lens. For example, the amount by which the optical collimator 1302 narrows the angular emission profile 1046 may be selected, at least in part, based on the size of the internal coupling optical element within the eyepiece lens to which the light output by the projection optical system 1070 is directed thereagainst.

[0288] It should be understood that the optical collimator 1302 may take various forms. For example, the optical collimator 1302 may be a microlens or a microlenslet in some embodiments. As discussed herein, each microlens preferably has a width that exceeds the width of the associated light emitter 1044. The microlens may be formed from a curved transparent material such as glass or polymer, including resins such as photoresist and epoxy. In some embodiments, the optical collimator 1302 may be a nanolens, such as a diffractive optical grating. In some embodiments, the optical collimator 1302 may be a metasurface and / or a liquid crystal grating. In some embodiments, the optical collimator 1302 may take the form of a reflective well.

[0289] It should be understood that the different optical collimators 1302 may have different dimensions and / or shapes depending on the wavelength or color of the light emitted by the associated light emitter 1044. Thus, for a full-color emissive microdisplay, the array 1300 may include a plurality of optical collimators 1302 with different dimensions and / or shapes depending on the color of the light emitted by the associated light emitter 1044. In an embodiment where the emissive microdisplay is a monochrome microdisplay, the array 1300 may be simplified, and each of the optical collimators 1302 within the array is configured to redirect light of the same color. By using such a monochrome microdisplay, the optical collimators 1302 may be similar across the array 1300 in some embodiments.

[0290] Continuing to refer to FIG. 24B, as discussed herein, the optical 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 optical collimator 1302. In some other embodiments, the optical collimators 1302 may be elongated such that they extend across a plurality of light emitters 1044. For example, in some embodiments, the optical collimator 1302 may be elongated towards the far side of the page and extend in front of a row of a plurality of light emitters 1044. In some other embodiments, a single optical collimator 1302 may extend across a column of light emitters 1044. In yet other embodiments, the optical collimators 1302 may comprise stacked columns and / or rows of lens structures (e.g., nanolens structures, microlens structures, etc.).

[0291] As described above, the optical collimator 1302 may take the form of a reflective well. 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 optical collimator array 1300 may include a substrate 1301 in which a plurality of optical 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 angle emission profile 1046. The reflective wall 1303 of the well of the optical collimator 1302 is tapered and reflects the emitted light so as to be output from the well with a narrower angle emission profile 1047. As shown, the reflective wall 1303 may be tapered such that the cross-sectional size increases with the distance from the light emitter 1044. In some embodiments, the reflective wall 1303 may be curved. For example, side 1303 may have the shape of a compound parabolic concentrator (CPC).

[0292] Referring now to FIG. 25B, an example of a side view of an asymmetric tapered reflective well is illustrated. As discussed herein, for example, as shown in FIGS. 12A-13A, it may be desirable to use the optical 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 as shown in FIG. 25B, the optical collimator 1302 may be asymmetric, and the upper side 1303a forms a different angle (e.g., a larger angle) with the surface of the light emitter 1044 than the lower side 1303b. For example, the angles of the reflective walls 1303a, 1303b with respect to the light emitter 1044 may be different on different sides of the optical collimator 1302 to direct the light in a particular non-normal direction. Thus, as shown, the light exiting the optical 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 upper side 1303a may be different from the taper of the lower side to direct the light in the direction 1048. For example, the upper side 1303a may flare out over a wider range than the lower side 1303b.

[0293] Continuing to refer to FIG. 25, the substrate 1301 may be formed from various materials that have sufficient mechanical integrity to maintain the desired shape of the reflective wall 1303. Examples of suitable materials include metals, plastics, and glass. In some embodiments, the substrate 1301 may be a plate of material. In some embodiments, the substrate 1301 is a continuous, integral piece of material. In some other embodiments, the substrate 1301 may be formed by bonding together two or more pieces of material.

[0294] The reflective wall 1303 may be formed within the substrate 1301 in a variety of ways. For example, the wall 1303 may be machined into the substrate 1301 or, alternatively, material may be removed to define the wall 1303 and thereby form it into the desired shape. In some other embodiments, the wall 1303 may be formed as the substrate 1301 is formed. For example, the wall 1303 may be molded into the substrate 1301 as the substrate 1301 is molded into its desired shape. In some other embodiments, the wall 1303 may be defined by rearrangement of material after formation of the body 2200. For example, the wall 1303 may be defined by an imprint.

[0295] Once the contours of the walls 1303 are formed, they may undergo further processing to form a surface having the desired reflectivity. In some embodiments, the surface of the substrate 1301 itself may be reflective. For example, the body may be formed from a reflective metal. In such cases, the further processing may include smoothing or polishing the inner surface of the wall 1303 to increase its reflectivity. In some other embodiments, the inner 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).

[0296] It should be understood that the location of the light emitter relative to the associated light collimator can affect the direction of the light emitted out of the light collimator. This is illustrated in FIGS. 26A - 26C, which illustrate examples of differences in the optical paths for light emitters at different positions relative to the centerline of the upper associated light collimator. As shown in FIG. 26A, the light - emitting microdisplay 1030 has a plurality of light emitters 1044a, each having an associated light collimator 1302, which promotes the output of light having a narrowed - angle emission profile 1047. The light passes through a projection optical system 1070 (represented as a simple lens for ease of illustration), which converges the light from the various light emitters 1044a onto an area 1402a.

[0297] Continuing to refer to FIG. 26A, in some embodiments, each of the light collimators 1302 may be symmetric and may have a centerline that extends along the axis of symmetry of the light collimator. In the illustrated configuration, the light emitters 1044a are disposed on the respective centerlines of the light collimators 1302.

[0298] Referring now to FIG. 26B, the light emitter 1044b is offset by a distance 1400 from the centerline of its respective light collimator 1302. This offset causes the light from the light emitter 1044b to follow a different path through the light collimator 1302, which outputs the light from the light emitter 1044b with a narrowed - angle emission profile 1047b. The projection optical system 1070 then converges the light from the light emitter 1044b onto an area 1402b, which is offset with respect to the area 1402a onto which the light from the light emitter 1044a converges.

[0299] Referring now to FIG. 26C, a light emitter 1044c offset from both light emitters 1044a and 1044b is illustrated. This offset causes the light from light emitter 1044c to follow a path different from the light from light emitters 1044a and 1044b through the optical collimator 1302. This results in the optical collimator 1302 outputting the light from light emitter 1044c with a narrowed angular emission profile that follows a path different from the light from light emitters 1044a and 1044b to the projection optical system 1070. Ultimately, the projection optical system 1070 converges the light from light emitter 1044c onto area 1402c, which is offset with respect to areas 1402a and 1402b.

[0300] Referring to FIGS. 26A - 26C, the three-fold symmetry axes of each of the light emitters 1044a, 1044b, 1044c may share a common optical collimator 1302. In some embodiments, the 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, the offset areas 1402a, 1402b, 1402c may, in some embodiments, correspond to internal coupling optical elements of a waveguide. For example, the areas 1402a, 1402b, 1402c may respectively correspond to the internal coupling optical elements 1022a, 1022b, 1022c of FIGS. 11A and 12. Thus, the offset orientation of the optical collimator 1302 and the light emitters 1044a, 1044b, 1044c may advantageously provide a simple three-pupil projection system 1010 using a full-color emitting microdisplay.

[0301] As described herein, the optical collimator 1302 may also take the form of a nanolens. FIG. 27 illustrates an example of a side view of an individual light emitter 1044 of the emissive microdisplay 1030 with an upper layer array 1300 of optical collimators 1302 that are nanolenses. As discussed herein, each of the individual light emitters 1044 may have an associated optical collimator 1302. The optical collimator 1302 redirects the light from the light emitter 1044, narrows the large-angle emission profile 1046 of the light emitter 1044, and outputs light with a narrowed angular emission profile 1047.

[0302] Continuing to refer to FIG. 27, in some embodiments, the optical collimator 1302 may be a grating structure. In some embodiments, the optical collimator 1302 may be a grating formed by alternating elongated discrete extensions (e.g., lines) of materials having different refractive indices. For example, the extensions of material 1306 may extend in and out of the page, be formed within the material of the substrate 1308, and thereby be separated. 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, configured to receive from the light emitter 1044 with which the optical collimator 1302 is associated). In some embodiments, the pitch 1304 may be from 30 to 300 nm, the depth of the grating may be from 10 to 1,000 nm, the refractive index of the material forming the substrate 1308 may be from 1.5 to 3.5, and the refractive index of the material forming the grating feature 1306 may be from 1.5 to 2.5 (and different from the refractive index of the material forming the substrate 1308).

[0303] The illustrated grating structure may be formed by various methods. For example, the substrate 1308 may be etched or nanoimprinted to define trenches, and the trenches may be filled with a material having a refractive index different from that of the substrate 1308 to form the grating feature 1306.

[0304] Advantageously, the nanolens array can provide various advantages. For example, the light collection efficiency of the nanolenslets can be large, e.g., 80 - 95%, including 85 - 90%, and is accompanied by an excellent reduction of the angular emission profile, e.g., a reduction to 30 - 40° (from 180°). In addition, low-level crosstalk can be achieved because each of the nanolens collimators 1302 is selected to act on light of a specific color and possibly a specific angle of incidence, while preferably providing a high extinction ratio (with respect to the wavelengths of light of other colors), and can have physical dimensions and properties (e.g., pitch, depth, refractive index of the material forming features 1306 and substrate 1308). In addition, the nanolens array can have a flat profile (e.g., formed on a flat substrate), which can facilitate integration with a microdisplay, which can be a flat panel, and can also facilitate manufacturing and provide high reproducibility and accuracy when forming the nanolens array. For example, highly reproducible groove formation and deposition processes may be used to form each nanolens. Further, these processes allow an ease and reproducibility that exceed what is typically achieved when forming curved lenses with similar variations with respect to variations between the nanolenses of the array.

[0305] Referring now to FIG. 28, a perspective view of an embodiment of a light-emitting microdisplay 1030 is illustrated. It should be understood that the optical collimator array 1300 advantageously enables the light emitted from the microdisplay to be routed as desired. As a result, in some embodiments, the light emitters of a full-color microdisplay may be arranged as desired, for example, for ease of manufacture or implementation within the display device. In some embodiments, the light emitters 1044 may be arranged within rows or columns 1306a, 1306b, 1306c. Each row or column may include light emitters 1044 configured to emit light of the same primary color. In a display where three primary colors are utilized, there may be three groups of rows or columns, which are repeated across the microdisplay 1030. It should be understood 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, and one row or one column is formed by light emitters configured to emit light of a single primary color.

[0306] In some embodiments, some rows or columns may be repeated to increase the number of light emitters of a particular primary color. For example, the light emitters of some primary colors may occupy multiple rows or columns. This may facilitate color balance and / or may be utilized to address differential degradation or reduction in light emission intensity over time.

[0307] Referring to FIGS. 27 and 28, in some embodiments, each light emitter 1044 may have an associated optical collimator 1302. In some other embodiments, each line 1306a, 1306b, 1306c of the plurality of light emitters 1044 may have a single associated optical collimator 1302. The single associated optical collimator 1302 may extend across substantially the entire associated line 1306a, 1306b, or 1306c. In some other embodiments, the associated optical collimator 1302 may be extended and extend across a plurality of light emitters 1044 that form a part of the associated line 1306a, 1306b, or 1306c, and a plurality of similar optical collimators 1302 may be provided along each of the associated lines 1306a, 1306b, 1306c.

[0308] Continuing to refer to FIG. 28, each light emitter 1044 may be extended along a particular axis (e.g., along the y-axis as shown). That is, each light emitter has a length along a particular axis, and the length is longer than the width of the light emitter. In addition, a set of light emitters configured to emit light of the same primary color may be arranged within a line 1306a, 1306b, or 1306c (e.g., a row or column) that extends along an axis (e.g., the x-axis) that intersects (e.g., is orthogonal to) the extension axis of the light emitters 1044. Thus, in some embodiments, the light emitters 1044 of the same primary color form a line 1306a, 1306b, or 1306c of light emitters that extends along a first axis (e.g., the x-axis), and the individual light emitters 1044 within the line are extended along a second axis (e.g., the y-axis).

[0309] In contrast, a full-color microdisplay typically includes sub-pixels of each primary color, where the sub-pixels are arranged in a particular relatively tightly packed spatial orientation within a group, and these groups are understood to be replicated across the array. Each group of sub-pixels may form a pixel within the image. In some cases, the sub-pixels are elongated along an axis, and rows or columns of sub-pixels of the same primary color extend along that same axis. Such an arrangement allows the sub-pixels of each group to be positioned close together, and it should be understood that this can have advantages with respect to image quality and pixel density. However, in the arrangement illustrated in FIG. 28, sub-pixels of different primary colors are relatively far apart due to the elongated shape of the light emitters 1044. That is, the light emitter of line 1306a is relatively far from the light emitter of line 1306c because the elongated shape of the light emitter of line 1306b causes the light emitters 1306a and 1306c to be spaced apart from the light emitters in the vicinity of a given line of light emitters. This can be expected to provide unacceptably poor image quality if the image formed on the surface of the microdisplay 1030 is relayed directly to the user's eye, but the use of the 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 an eyepiece such as the eyepiece 1020 (e.g., FIGS. 11A and 12 - 14) and combined therein.

[0310] Referring to FIGS. 27 and 28, in some embodiments, each of the light emitters 1044 may have an associated optical collimator 1302. In some other embodiments, each line 1306a, 1306b, 1306c of the light emitters 1044 may have a single associated optical collimator 1302. The single associated optical collimator 1302 may extend substantially across the entirety of the associated line 1306a, 1306b, or 1306c. In some other embodiments, the associated optical collimator 1302 may be extended and extend across a plurality of light emitters 1044 that form a part of the associated line 1306a, 1306b, or 1306c, and a plurality of similar optical collimators 1302 may be provided along each of the associated lines 1306a, 1306b, 1306c.

[0311] It should be understood that the optical collimator 1302 may be used to direct light along different optical paths to form a multi-pupil projection system. For example, the optical collimator 1302 may direct light of different primary colors to two or three areas respectively for internal light combining.

[0312] FIG. 29 illustrates an example of a wearable display system with the full-color emissive microdisplay 1030 of FIG. 28 used to form a multi-pupil projection system 1010. In the illustrated embodiment, the full-color emissive microdisplay 1030 emits light of three primary colors to form a three-pupil projection system 1010. The projection system 1010 has three exit pupils, through which image light 1032a, 1032b, 1032c of different primary colors propagate to the light internal combining optical elements 1022a, 1022b, 1022c offset to three sides of the eyepiece 1020 respectively. The eyepiece 1020 then relays the image light 1032a, 1032b, 1032c to the user's eye 210.

[0313] The light-emitting microdisplay 1030 includes an array of light emitters 1044, which may be subdivided into monochromatic light emitters 1044a, 1044b, 1044c, which emit image light 1032a, 1032b, 1032c, respectively. It should be understood that the light emitters 1044 emit image light with a wide-angle 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.

[0314] In addition, the array of light collimators 1300 is configured to redirect the image light (image lights 1032a, 1032b, 1032c) at an angle such that the image light is output to the projection optical system 1070 so that the image light propagates to appropriate internal coupling optical elements 1022a, 1022b, 1022c. For example, the array of light collimators 1300 is preferably configured to direct the image light 1032a to propagate through the projection optical system 1070 and impinge on the internal coupling optical element 1022a, direct the image light 1032b to propagate through the projection optical system 1070 and impinge on the internal coupling optical element 1022b, and direct the image light 1032c to propagate through the projection optical system 1070 and impinge on the internal coupling optical element 1022c.

[0315] The different light emitters 1044 may emit light of different wavelengths and may need to be redirected in different directions to reach the appropriate internal coupling optical elements. Thus, in some embodiments, the light collimators associated with the 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 the light collimators, which vary the physical properties across the array of light collimators 1300. As described herein, the nanolenses may be formed using patterning and deposition processes, which facilitate the formation of structures with different pitches, widths, etc. across the substrate.

[0316] Referring back to FIG. 24A, it should be understood that the illustrated display system shows a single-emitter type 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 it would be expected that the light from the light emitter 1044, after being reflected from the reflective surfaces 1052, 1054, would retain its large-angle emission profile. Thus, the problem regarding the wasted light shown in FIG. 24A also exists when the optical combiner 1050 is utilized.

[0317] Referring now to FIG. 30A, an example of a wearable display system is illustrated that includes a light-emitting type microdisplay and an array of associated 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 additional monochrome microdisplays (not shown) may be provided on different faces of an optional optical combiner 1050 (as shown in FIG. 30C).

[0318] Continuing to refer to FIG. 30A, each microdisplay 1030b includes an array of light emitters 1044 that emit light, each with a wide-angle emission profile (e.g., a Lambertian angle emission profile). Each light emitter 1044 has an associated dedicated light collimator 1302, which effectively narrows the angle emission profile to a narrowed angle emission profile 1047. The light beam 1032b with the narrowed angle emission profile passes through the projection optical system 1070, which projects or converges those light beams onto the internal coupling optical element 1022b. It should be understood that the light beam 1032b has a certain cross-sectional shape and size 1047a. In some embodiments, the internal 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 beam 1032b when the beam 1032b is incident on the internal coupling optical element 1022b. Thus, in some embodiments, the size and shape of the internal coupling optical element 1022b may be selected based on the cross-sectional size and shape of the light beam 1032b when incident on the internal coupling optical element 1022b. In some other embodiments, other factors (re-bounce reduction or angles or fields of view assisted by the internal coupling optical element 1022b) may be utilized to determine the size and shape of the internal coupling optical element 1022b, and the light collimator 1302 is preferably configured (e.g., sized and shaped) to provide a light beam 1032b with a properly sized and shaped cross-section that is fully or substantially fully encompassed by the size and shape of the internal coupling optical element 1022b. In some embodiments, the physical parameters for the light collimator 1302 and the internal coupling optical element 1022b may be mutually modified to provide highly efficient light utilization in conjunction with other desired functionality (e.g., re-bounce reduction, 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 internally combined light then propagates through waveguide 1020b and is externally coupled to the eye 210.

[0319] As shown, the microdisplay 1030b may comprise an array 1042 of light emitters 1044, each surrounded by a non-emitting area 1045 having a total width 1045w. Additionally, the light emitters 1044 have a width W and a pitch P. In an array where the light emitters 1044 are regularly spaced, each light emitter 1044 and the surrounding area 1045 form a unit cell having a width 1045w that may in fact be equal to the pitch P.

[0320] In some embodiments, the optical collimator 1302 is a microlens disposed directly on and surrounding the associated light emitter 1044. In some embodiments, the width of the microlens 1302 is equal to 1045w such that neighboring microlenses 1302 are substantially in contact or directly in contact with each other. It should be understood that the light from the light emitter 1044 fills the associated microlens 1302 and may in fact expand the area encompassed by the light emitter 1044. Advantageously, such a configuration reduces the perceptibility of the area 1045 that would otherwise be non-light-emitting and thus visible to the user as a dark space. However, since the microlens 1302 effectively expands the associated light emitter 1044 such that it extends across the entire area of the microlens 1302, the area 1045 may be masked.

[0321] Continuing to refer to FIG. 30A, the relative sizes of the light emitter 1044 and the optical collimator 1302 may be selected such that the light from the light emitter 1044 fills the associated optical collimator 1302. For example, the light emitter 1044 may be sufficiently spaced so that a microlens collimator 1302 having a desired curvature can be formed extending across individual ones of the light emitters 1044. Additionally, as described above, the size and shape of the internal coupling optical element 1022b are preferably selected to match or exceed the cross-sectional shape and size of the light beam 1032b when it is incident on the internal coupling optical element 1022b. As a result, in some embodiments, the width 1025 of the internal coupling optical element 1022b may be greater than or equal to the width of the microlens 1302 (which may have a width equal to 1045w or P). Preferably, the width 1025 exceeds the width of the microlens 1302 or 1045w or P to account for some divergence of the light beam 1032b. As discussed herein, the width 1025 may also be selected to reduce backscatter and may be shorter than the length of the internal coupling optical element 1022b (orthogonal to the width). In some embodiments, the width 1025 may extend along the same axis as the propagation direction of the internally coupled light 1032b through the waveguide 1020b before being externally coupled for propagation to the eye 210.

[0322] Referring now to FIG. 30B, an example of a light projection system 1010 is illustrated with a plurality of light-emitting microdisplays 1030a, 1030b, 1030c and associated arrays 1300a, 1300b, 1300c of optical collimators. The angular emission profiles of the light emitted by the microdisplays 1030a, 1030b, 1030c are narrowed by the optical collimator arrays 1300a, 1300b, 1300c, thereby facilitating the focusing of a large percentage of the light that is emitted by the projection optical system 1070 after passing through the optical combiner 1050. The projection optical system 1070 then directs the light to an eyepiece, such as the eyepiece 1020 (e.g., FIGS. 11A and 12 - 14) (not shown).

[0323] Figure 30C illustrates an embodiment of a wearable display system with a plurality of light-emitting microdisplays 1030a, 1030b, 1030c, each with an associated array 1300a, 1300b, 1300c of optical collimators. The illustrated display system includes a plurality of microdisplays 1030a, 1030b, 1030c for emitting light with image information. As illustrated, the microdisplays 1030a, 1030b, 1030c may be micro-LED panels. In some embodiments, the microdisplay may be a monochromatic micro-LED panel and is configured to emit different primary colors, respectively. For example, the microdisplay 1030a may be configured to emit light 1032a that is red, the microdisplay 1030b may be configured to emit light 1032b that is green, and the microdisplay 1030c may be configured to emit light 1032c that is blue.

[0324] Each microdisplay 1030a, 1030b, 1030c may have an associated array 1300a, 1300b, 1300c of optical collimators, respectively. The optical collimator narrows the angular emission profile of the light 1032a, 1032b, 1032c from the light emitters of the associated microdisplay. In some embodiments, the individual light emitters have dedicated associated optical collimators (as shown in FIG. 30A).

[0325] Continuing to refer to FIG. 30C, the arrays 1300a, 1300b, 1300c of the optical collimators are between the associated microdisplays 1030a, 1030b, 1030c and the optical combiner 1050, which may be an X-cube. As shown, the optical combiner 1050 has internal reflective surfaces 1052, 1054 to reflect incident light out from the output surface of the optical combiner. In addition to narrowing the angular emission profile of the incident light, the arrays 1300a, 1300c of the optical collimators are configured to redirect light from the associated microdisplays 1030a, 1030c at an angle appropriate for the light to impinge on the internal reflective surfaces 1052, 1054 of the optical combiner 1050 so that the light propagates toward the associated light internal coupling optical elements 1022a, 1022c, respectively. In some embodiments, to redirect light in a particular direction, the arrays 1300a, 1300c of the optical collimators may comprise microlenses or reflective wells, which may be asymmetric and / or the light emitters may be offset from the center with respect to the microlenses or reflective wells as disclosed herein.

[0326] Continuing to refer to FIG. 30C, a projection optical system 1070 (e.g., a projection lens) is disposed on the output surface of the optical combiner 1050 and receives the image light emitted from the optical combiner. The projection optical system 1070 may include a lens configured to converge or focus the image light onto the eyepiece lens 1020. As shown, the eyepiece lens 1020 may include a plurality of waveguides, each configured to internally and externally couple light of a specific color. For example, the waveguide 1020a may be configured to receive red light 1032a from the microdisplay 1030a, the waveguide 1020b may be configured to receive green light 1032b from the microdisplay 1030b, and the waveguide 1020c may be configured to receive blue light 1032c from the microdisplay 1030c. Each of the waveguides 1020a, 1020b, 1020c has associated light internal coupling optical elements 1022a, 1022b, 1022c, respectively, for internally coupling light therein. Additionally, as discussed herein, the waveguides 1020a, 1020b, 1020c may each correspond to the waveguides 670, 680, 690 of FIG. 9B and may each have an associated orthogonal pupil expander (OPE) and an exit pupil expander (EPE), which ultimately externally couple the light 1032a, 1032b, 1032c to the user.

[0327] As discussed herein, a wearable display system incorporating a microdisplay preferably outputs light with different amounts of wavefront divergence and is configured to provide comfortable near - far accommodation - convergence / divergence motion matching for the user. These different amounts of wavefront divergence may be achieved using external coupling optical elements with different refractive powers. As discussed herein, the external coupling optical elements may be present on or within the waveguides of an eyepiece lens, such as the eyepiece lens 1020 (e.g., FIGS. 11A and 12 - 14). In some embodiments, a lens may be utilized to increase the wavefront divergence provided by the external coupling optical element, or in a configuration where the external coupling optical element is configured to output collimated light, it may be used to provide the desired wavefront divergence.

[0328] Figures 31A and 31B illustrate an embodiment of the eyepiece lens 1020 having a lens for varying the wavefront divergence of light to the viewer. FIG. 31A illustrates the eyepiece lens 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 lens. In some other embodiments, the waveguide structure 1032 may be understood to include a plurality of 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.

[0329] 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 to the eye 210 by the waveguide structure 1032. It should be understood that the variable focus optical element 1530 may have a refractive power that can distort the view of the world by the eye 210. 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, if the waveguide structure 1032 has a refractive power, opposite to the net refractive power of the optical element 1530 and the waveguide structure 1032) such that the net refractive power of the variable focus lens elements 1530, 1540 and the waveguide structure 1032 is substantially zero.

[0330] Preferably, the refractive powers of the variable focus lens elements 1530, 1540 may be dynamically modified, for example, by applying an electrical signal thereto. In some embodiments, the variable focus lens elements 1530, 1540 may comprise a transmissive optical element such as a liquid crystal lens, an electroactive lens, a conventional refractive lens with movable elements, a mechanically deformable-based lens, an electrowetting lens, an elastomer lens, or a plurality of fluids with different refractive indices. By modifying the shape, refractive index, or other properties of the variable focus lens element, the wavefront of the 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 an optically transmissive material such as glass, plastic, acrylic, or the like.

[0331] In some embodiments, in addition to or instead of providing a variable amount of wavefront divergence to place virtual content on different depth planes, the variable focus lens elements 1530, 1540 and the waveguide structure 1032 may advantageously provide a net refractive power equal to the user's prescription refractive power for a corrective lens. Accordingly, the eyepiece lens 1020 may serve as a substitute for a lens used to correct refractive errors, including myopia, hyperopia, presbyopia, and spherical aberration. 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 on April 6, 2017, the entire disclosure of which is incorporated herein by reference.

[0332] Referring now to FIG. 31B, in some embodiments, the eyepiece 1020 may include static lens elements rather than variable ones. Similar to FIG. 31B, the waveguide structure 1032 may include a single waveguide (e.g., capable of relaying light of different colors) or multiple waveguides (e.g., each capable of relaying light of a single primary color). Similarly, the waveguide structure 1034 may include a single waveguide (e.g., capable of relaying light of different colors) or multiple waveguides (e.g., each capable of relaying light of a single primary color). One or both of the waveguide structures 1032 and 1034 may have refractive power and may output light with a specific amount of wavefront divergence, or may simply output collimated light.

[0333] Continuing to refer to FIG. 31B, in some embodiments, the eyepiece 1020 may include static lens elements 1532, 1534, 1542. Each of these lens elements is disposed within the path of light from the surrounding environment through the waveguide structures 1032 and 1034 into the eye 210. In addition, the lens element 1532 is between the waveguide structure 1003 2 and the eye 210. The lens element 1532 corrects the wavefront divergence of the light output to the eye 210 by the waveguide structure 1032.

[0334] The lens element 1534 corrects the wavefront divergence of the light output to the eye 210 by the waveguide structure 1034. It should be understood that the light from the waveguide structure 1034 also passes through the lens element 1532. Thus, the wavefront divergence of the light output by the waveguide structure 1034 is corrected by both the lens element 1534 and the lens element 1532 (and the waveguide structure 1032 if the waveguide structure 1003 2 has refractive power). In some embodiments, the lens elements 1532, 1534 and the waveguide structure 1032 provide a specific net refractive power for the light output from the waveguide structure 1034.

[0335] The illustrated embodiments provide two different levels of wavefront divergence, one for the light output from waveguide structure 1032 and a second for the light output by waveguide structure 1034. As a result, virtual objects can be placed on two different depth planes corresponding to different levels of wavefront divergence. In some embodiments, additional levels of wavefront divergence, and thus additional depth planes, may be provided by adding additional lens elements between the additional waveguide structure and eye 210, by adding an additional waveguide structure between lens element 1532 and eye 210. Further levels of wavefront divergence may be added as well, by adding additional waveguide structures and lens elements.

[0336] Continuing to refer to FIG. 31B, it should be understood that lens elements 1532, 1534 and waveguide structures 1032, 1034 provide a net refractive power that can distort the user's view of the world. As a result, lens element 1542 may be used to counteract the refractive power and distortion of ambient light. In some embodiments, the refractive power of lens element 1542 is set to nullify the aggregate refractive power provided by lens elements 1532, 1534 and waveguide structures 1032, 1034. In some other embodiments, the net refractive power of lens element 1542, lens elements 1532, 1534, and waveguide structures 1032, 1034 is equal to the user's prescription refractive power for corrective lenses.

[0337] Referring now to FIGS. 11A - 31B, it should be understood that any of the illustrated components of the wearable display system may be supported on frame 80 (FIG. 9E). Thus, each of these components may effectively be mounted on the user's head 90 as part of the wearable display system.

[0338] Various exemplary embodiments of the present invention are described herein. By way of non-limiting example, these examples are referenced. They are provided to illustrate broader and applicable aspects of the present invention. Various changes may be made to the invention described, and equivalents may be substituted without departing from the true spirit and scope of the invention.

[0339] For example, advantageously, it is utilized with an AR display that provides an image across multiple depth planes, although the virtual content disclosed herein may also be displayed by a system that provides an image on a single depth plane.

[0340] In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process, process act, or step to the purposes, spirit, or scope of the present invention. Further, as will be understood by those skilled in the art, each of the individual variations described and illustrated herein can be readily separated from, or combined with, features of any of the other several embodiments without departing from the scope or spirit of the present invention, and has discrete components and features. All such modifications are intended to be within the scope of the claims associated with this disclosure.

[0341] The present invention includes methods that can be implemented using the devices of the subject matter. The methods may include the act of providing such a suitable device. Such providing may be performed by an end user. In other words, the act of "providing" simply requires that the user act to obtain, access, approach, locate, configure, activate, power on, or otherwise provide the device required in the subject method. The methods recited herein may be performed in any order of the recited logical events and in the recited order of events.

[0342] Exemplary aspects of the invention are described above, along with details regarding materials selection and manufacture. With respect to other details of the invention, these are understood in relation to the patents and publications referenced above and are generally known or understandable by those of ordinary skill in the art. The same may apply with respect to method-based embodiments of the invention from the perspective of additional acts that are commonly or logically employed.

[0343] In addition, the invention has been described with reference to several embodiments that optionally incorporate various features, but the invention is not limited to what is described and indicated as would be considered with respect to each variation of the invention. Various changes may be made to the invention as described, and equivalents (whether listed herein or not for the sake of some brevity) may be substituted without departing from the true spirit and scope of the invention. In addition, when ranges of values are provided, it is to be understood that all intervening values, as well as any other stated value or intervening values within the stated range between the upper and lower limits of that range, are encompassed within the invention.

[0344] Also contemplated is that any optional feature of any variation of the invention described may be described and claimed independently or in combination with any one or more of the features described herein. References to singular items include the possibility that there are multiple identical items 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 the articles enables “at least one” of the items of the subject matter in the above description and the claims associated with this disclosure. Further, note that such claims may be drafted to exclude any optional element. Thus, the text is intended to serve as a precedent for the use of exclusive terminology such as “merely,” “only,” and equivalents, or the use of “negative” limitations, in relation to the recitation of elements of a claim.

[0345] Without using such exclusive terms, the term "comprising" in the claims associated with the present disclosure shall be construed to allow for any additional elements, whether a given number of elements are recited in such claims or the addition of features can be regarded as a transformation of the nature of the elements recited in such claims. Unless specifically defined herein, all technical and scientific terms used herein shall be given the broadest generally understood meaning possible while maintaining the validity of the claims.

Claims

1. A head mounted display system, comprising: an emissive microdisplay comprising an array of light emitters corresponding to pixels, the array of light emitters configured to output image light defining an image; an eyepiece configured to receive the image light from the emissive microdisplay and direct the image light to an eye of a user; an array of light collimators proximate to the array of light emitters, each of the light emitters being associated with and in contact with a light collimator, the light collimator being configured to receive and concentrate the image light output by an associated light emitter, the light collimator comprising a liquid crystal grating; A head mounted display system comprising:

2. The head mounted display system of claim 1 , wherein the emissive micro display is a micro LED display.

3. The head mounted display system of claim 1 , wherein the light collimator comprises a metasurface.

4. The head mounted display system of claim 1 , further comprising projection optics configured to focus light from the emissive microdisplay onto the eyepiece.

5. 2. The head mounted display system of claim 1, wherein each of the light emitters is configured to emit light of one of a plurality of primary colors, the eyepiece comprises a waveguide assembly comprising a plurality of sets of waveguides, each set of waveguides comprising a dedicated waveguide for each primary color, each set of waveguides comprising an external coupling 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.

6. 2. The head mounted display system of claim 1, further comprising first and second variable focus lens elements, the eyepiece comprising a waveguide assembly, the waveguide assembly being between the first and second variable focus lens elements, the first variable focus lens element configured to modify wavefront divergence of light output by the eyepiece toward the eye, and the second variable focus lens element configured to modify wavefront divergence of light from the external world.

7. The eyepiece includes a waveguide assembly having one or more waveguides, each waveguide having: an incoupling optical element configured to incoupling light from the emissive microdisplay into the waveguide; an outcoupling optical element configured to outcouple the incoupling light out of the waveguide; Equipped with The head mounted display system of claim 1 , wherein the waveguide assembly is configured to output the outcoupled light with varying amounts of wavefront divergence corresponding to multiple depth planes.

8. The head mounted display system of claim 7 , wherein the waveguide assembly comprises a stack of waveguides.

9. 9. The head mounted display system of claim 8, further comprising a color filter between two adjacent waveguides of the stack of waveguides, a first of the adjacent waveguides preceding a second of the adjacent waveguides in an optical path extending from the emissive microdisplay, the color filter configured to selectively absorb light of a wavelength corresponding to a wavelength of light configured to be internally coupled by the internal coupling optical element of the first of the adjacent waveguides.

10. a third waveguide following the second of the adjacent waveguides in the optical path; 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; The head mounted display system of claim 9 further comprising:

11. 9. The head mounted display system of claim 8, further comprising absorptive color filters on major surfaces of at least some of the waveguides, the absorptive color filters on the major surfaces of the waveguides configured to absorb light of wavelengths that are internally coupled into the corresponding waveguides.

12. 9. The head mounted display system of claim 8, wherein the internal coupling optical element is configured to internally couple light through an associated waveguide generally with internally coupled light propagating in a propagation direction, 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 being greater than the width.

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