Extended and Virtual Reality Display Systems with Correlated Internal and External Coupling Optical Regions

Abstract

To provide a suitable augmented and virtual reality display system.SOLUTION: An augmented reality and virtual reality display system and device are configured for efficient use of projected light. In some aspects, a display system includes a light projection system and a head-mounted display configured to project light into the eyes of a user to display virtual image content. The head-mounted display includes at least one waveguide comprising a plurality of in-coupling regions each configured to receive, from the light projection system, light corresponding to a portion of the user's field of view and to in-couple the light into the waveguide, and a plurality of out-coupling regions configured to out-couple the light out of the waveguide to display the virtual content, the out-coupling regions each configured to receive light from different ones of the in-coupling regions. In some implementations, each in-coupling region has one-to-one correspondence with a unique corresponding out-coupling region.SELECTED DRAWING: Figure 14A

Description

Technical Field

[0001] (Cross - Reference to Related Applications) Any application for which a claim of foreign or domestic priority is identified within the application data sheet filed together with this application is incorporated herein by reference under 37 CFR 1.57.

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 029312, filed on May 22, 2020, entitled "METHOD AND SYSTEM FOR DUAL PROJECTOR WAVEGUIDE DISPLAYS WITH WIDE FIELD OF VIEW", and U.S. Provisional Patent Application No. 63 / 050635, filed on July 10, 2020, entitled "AUGMENTED AND VIRTUAL REALITY DISPLAY SYSTEMS WITH CORRELATED IN - COUPLING AND OUT - COUPLING OPTICAL REGIONS FOR EFFICIENT LIGHT UTILIZATION", the contents of which are incorporated herein by reference in their entireties.

[0003] This application incorporates by reference in its entirety each of the following: U.S. Patent Application Publication No. 2018 / 0275410, published on September 27, 2018, titled "DEPTH BASED FOVEATED RENDERING FOR DISPLAY SYSTEMS"; U.S. Patent No. 10,573,042, issued on February 25, 2020, titled "PERIOCULAR TEST FOR MIXED REALITY CALIBRATION"; U.S. Patent Application Publication No. 2019 / 0222830, published on July 18, 2019, titled "DISPLAY SYSTEMS AND METHODS FOR DETERMINING REGISTRATION BETWEEN A DISPLAY AND A USER’S EYES"; U.S. Patent No. 10,296,792, issued on May 21, 2019, titled "IRIS BOUNDARY ESTIMATION USING CORNEA CURVATURE"; U.S. Patent Publication No. 2017 / 0053165, published on February 23, 2017, titled "EYELID SHAPE ESTIMATION USING EYE POSE MEASUREMENT"; U.S. Patent Publication No. 2017 / 0053166, published on February 23, 2017, titled "EYELID SHAPE ESTIMATION"; U.S. Patent Application Publication No. 2019 / 0222830, published on August 8, 2019, titled "EYE CENTER OF ROTATION DETERMINATION, DEPTH PLANE SELECTION,Related to U.S. Patent Application Publication No. 2019 / 0243558, published on January 21, 2021, titled "AND RENDER CAMERA POSITIONING IN DISPLAY SYSTEMS", International Publication No. WO2021 / 01166, published on April 26, 2018, titled "EYE CENTER OF ROTATION DETERMINATION WITH ONE OR MORE EYE TRACKING CAMERAS", U.S. Patent Application Publication No. 2018 / 0113311, published on September 12, 2019, titled "SYSTEM AND METHOD FOR PRESENTING IMAGE CONTENT ON MULIPLE DEPTH PLANES BY PROVIDING MULTIPLE INTRA-PUPIL PARALLAX VIEWS", International Publication No. WO2019 / 173158, published on October 12, 2017, titled "DISPLAY SYSTEM WITH LOW-LATENCY PUPIL TRACKER", U.S. Patent Application Publication No. 2017 / 0293145, published on April 26, 2018, titled "AUGMENTED REALITY SYSTEMS AND METHODS WITH VARIABLE FOCUS LENS ELEMENTS", and U.S. Patent Application Publication No. 2018 / 0113311, published on September 12, 2019, titled "SYSTEM AND METHOD FOR PRESENTING IMAGE CONTENT ON MULIPLE DEPTH PLANES BY PROVIDING MULTIPLE INTRA-PUPIL PARALLAX VIEWS".

[0004] The present disclosure relates to display systems, and more particularly to augmented and virtual reality display systems.

Background Art

[0005] 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 to be, i.e., can be perceived as, 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 surrounding the user. Mixed reality, i.e., the "MR" scenario, is a type of AR scenario that typically involves virtual objects integrated into and responsive to the natural world. For example, in an MR scenario, it may include AR image content that appears to be blocked by or otherwise interact with objects within the real world.

[0006] Referring to FIG. 1, an augmented reality scene 10 is depicted. To the user of AR technology, there is visible a real-world park-like setting 20 featuring people, trees, and buildings in the background, and a concrete platform 30. The user also "sees" "virtual content" such as a robotic 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 honeybee. 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.

[0007] The systems and methods disclosed herein address various challenges related to display technologies, including AR or VR technologies.

Summary of the Invention

Means for Solving the Problems

[0008] Aspects of the present disclosure will now be described in detail with respect to the figures and various embodiments. However, those skilled in the art will understand that other configurations of the devices and methods disclosed herein will still fall within the scope of the present disclosure even if they are not described in as much detail. The aspects of the various configurations discussed are not intended to limit the scope of the present disclosure herein, which is instead defined by the claims that follow this description.

[0009] Various embodiments of a display system are described herein, such as those listed below, which project light onto one or more of a user's eyes and display virtual image content within the user's field of view.

[0010] Example 1: A head-mounted display system configured to project light and display virtual image content, the display system comprising: a light projection system; and a head-mounted display configured to display virtual image content, the head-mounted display including at least one waveguide, the at least one waveguide including a plurality of internal coupling regions, each of the plurality of internal coupling regions being configured to receive light having image information for forming virtual image content from the light projection system and internally couple the light into the waveguide, and a plurality of external coupling regions, each of the plurality of external coupling regions being configured to externally couple light out of the waveguide and display virtual content, each of the plurality of external coupling regions being configured to receive light from a different one of the internal coupling regions.

[0011] Example 2: The display system according to Example 1, wherein each internal coupling region of the plurality of internal coupling regions corresponds to a unique external coupling region of the plurality of external coupling regions and is configured to selectively direct light.

[0012] Example 3: Each internal coupling region is a diffraction grating having at least one of an inclination, a lattice orientation, a lattice structure size, or a lattice pitch selected so as to preferentially externally couple the light internally coupled by the internal coupling region by an external coupling region corresponding to the internal coupling region, the display system according to Example 1 or 2.

[0013] Example 4: The optical coupling region is configured to redirect the incident light from the optical projection system through the waveguide at an angle for total internal reflection along the propagation direction, and further includes an optical dispersion structure configured to redirect a part of the light to propagate along an axis intersecting the propagation direction, the display system according to any one of Examples 1-3.

[0014] Example 5: The optical dispersion structure and the plurality of external coupling regions are disposed on the opposing major surfaces of at least one waveguide, the display system according to any one of Examples 1-4.

[0015] Example 6: The plurality of internal coupling regions include a diffraction grating, the display system according to any one of Examples 1-5.

[0016] Example 7: Each of the plurality of internal coupling regions has a lattice pitch different from that of at least one other internal coupling region of the waveguide, the display system according to any one of Examples 1-6.

[0017] Example 8: The different lattice pitches change the total internal reflection angle at which the light internally coupled in the waveguide undergoes total internal reflection toward the waveguide to the associated external coupling regions of the plurality of external coupling regions, the display system according to any one of Examples 1-7.

[0018] Example 9: Each of the plurality of internal coupling regions has a lattice orientation different from that of at least one other internal coupling region of the waveguide in the plane of the waveguide, the display system according to any one of Examples 1-6.

[0019] Example 10: The display system according to any one of Examples 1-9, wherein different lattice orientations change the angle at which light is coupled into the waveguide so that the light propagates towards the intended external coupling regions of the plurality of external coupling regions.

[0020] Example 11: The display system according to any one of Examples 1-10, wherein each of the plurality of internal coupling regions has an inclination different from at least one other internal coupling region of the waveguide with respect to the plane of the waveguide.

[0021] Example 12: The display system according to any one of Examples 1-11, wherein the internal coupling regions are spaced apart from each other.

[0022] Example 13: The display system according to any one of Examples 1-12, wherein the optical internal coupling regions are arranged in a row around at least one side of the plurality of external coupling regions.

[0023] Example 14: The display system according to any one of Examples 1-13, wherein each of the external coupling regions defines a stripe across the waveguide, and the stripe extends along an axis intersecting the row of internal coupling regions.

[0024] Example 15: The display system according to any one of Examples 1-14, wherein the external coupling regions define a grid pattern across the waveguide.

[0025] Example 16: The display system according to any one of Examples 1-15, wherein each of the plurality of internal coupling regions is arranged to internally couple light, direct the light, and propagate the light in the waveguide along a direction different from at least one other internal coupling region of the waveguide by total internal reflection.

[0026] Example 17: At least one internal coupling region adjacent to the lateral edge of at least one external coupling region is configured to internally couple light along a range of angles symmetrically arranged about an axis biased inwardly, the display system according to any one of Examples 1-16.

[0027] Example 18: At least two of the plurality of internal coupling regions are arranged along at least one different side of at least one of the plurality of external coupling regions, the display system according to any one of Examples 1-17.

[0028] Example 19: The plurality of internal coupling regions comprise an internal coupling optical element surrounding at least one of the plurality of external coupling regions on at least three sides, the display system according to any one of Examples 1-18.

[0029] Example 20: The light projection system comprises a light source and a movable light injector configured to direct image light to individual ones of the internal coupling regions, the display system according to any one of Examples 1-19.

[0030] Example 21: The head-mounted display comprises a plurality of waveguides forming a waveguide stack, each of the waveguides comprising a plurality of internal coupling regions and external coupling regions, and each internal coupling region of the waveguides is laterally displaced as seen in a front view when viewed from the direction of the internal coupling light incident on the internal coupling region, the display system according to any one of Examples 1-20.

[0031] Example 22: The external coupling regions of the same waveguide are configured to output light with the same wavefront divergence, and the external coupling regions of different waveguides are configured to output light with a wavefront divergence amount different from that of at least one other waveguide's external coupling region, and the different wavefront divergence amounts correspond to different depth planes, the display system according to any one of Examples 1-21.

[0032] Example 23: The internal coupling region of each waveguide is configured to internally couple light in a wavelength range corresponding to the same primary color, and the internal coupling regions of some waveguides are configured to internally couple light in a wavelength range corresponding to a primary color different from that of the internal coupling regions of other waveguides. The display system according to any one of Examples 1-212.

[0033] Example 24: The light projection system includes a light source having an array of light emitters, a spatial light modulator configured to modulate light from the light source, and a projection optical system mounted on a frame and configured to direct light from the spatial light modulator to an internal coupling region. The display system is configured to activate a plurality of different light emitters and provide virtual image content on different depth planes. The display system provides a relatively large distance between individual light emitters of the plurality of light emitters to provide virtual image content on a relatively near depth plane, and provides a relatively small distance between individual light emitters of the plurality of light emitters to provide virtual image content on a relatively far depth plane. The display system according to any one of Examples 1-23.

[0034] Example 25: Each of the light emitters of the plurality of light emitters is configured to be sequentially activated at different times, and the display system is configured to synchronize the activation of each light emitter with the display of a disparity-varying non-uniform intra-pupil image. The display system according to any one of Examples 1-24.

[0035] Example 26: The light source is a microdisplay, and the light emitter is a light-emitting diode. The display system according to any one of Examples 1-245.

[0036] Example 27: The display system according to any one of Examples 1-26, further comprising a variable focus lens element on the opposite side of the waveguide.

[0037] Example 28: The optical projection system includes a plurality of projectors, and the projectors of the plurality of projectors are configured to provide image content for a subdivided portion of the FOV of the head-mounted display that is less than the whole, and is the display system according to any one of Examples 1-27.

[0038] Example 29: A display system, comprising: an optical projection system; a head-mounted display configured to project light into a user's eyes and display virtual image content, the head-mounted display including at least one waveguide having a plurality of internal optical coupling regions configured to receive light from the optical projection system and a plurality of external optical coupling regions configured to output light to the user's eyes; and a processing electronic device communicating with the display and an inward-facing imaging system, the processing electronic device including one or more processors and one or more computer storage media, the one or more computer storage media storing instructions that, when executed by the one or more processors, cause the one or more processors to perform operations including determining an external optical coupling region associated with an eye gaze direction of an eye and providing instructions for directing light from the optical projection system to an internal optical coupling region associated with the determined external optical coupling region.

[0039] Example 30: The display system according to Example 29, wherein determining the external optical coupling region includes determining an intersection point of a line of sight of the eye and one of the plurality of external optical coupling regions.

[0040] Example 31: The display system according to Example 29 or 30, wherein the internal optical coupling regions are arranged in a row around at least one side of the plurality of external coupling regions.

[0041] Example 32: The display system according to Example 29, wherein the optical projection system includes at least one light source and at least one movable light injector configured to output image light.

[0042] Example 33: The display system according to any one of Examples 29 to 32, wherein the at least one movable light injector includes a scanning mirror.

[0043] Example 34: The display system according to any one of Examples 29 to 33, wherein the at least one movable light injector includes a scanning fiber injector.

[0044] Example 35: The display system according to any one of Examples 29 to 34, wherein the optical projection system includes at least one light source and at least one spatial light modulator configured to modulate light from the light source.

[0045] Example 36: The head-mounted display is the display system according to any one of Examples 29 to 35, configured to display virtual objects on a plurality of depth planes.

[0046] Example 37: The operation includes projecting a set of intra-pupil images with parallax-induced disparity into the eye and displaying a virtual object on one of the depth planes, according to any one of Examples 29 to 36 of the display system.

[0047] Example 38: The operation includes projecting each of the set of intra-pupil images with parallax-induced disparity within a flicker fusion threshold, according to any one of Examples 29 to 37 of the display system.

[0048] Example 39: The operation includes providing instructions for directing light to a plurality of internal coupling elements within an optical internal coupling region of a plurality of internal coupling regions associated with a determined optical external coupling region, according to any one of Examples 29 to 39 of the display system.

[0049] Example 40: The display system according to any one of Examples 29-39, further comprising at least one variable focus lens element on the user side of at least one waveguide, wherein the first variable focus lens element is configured to modify the projected light and correct the refractive anomaly of the user's eye.

[0050] Example 41: The display system according to any one of Examples 29-40, wherein the operation further includes determining the fixation point of the eye and applying a correction corresponding to the fixation point.

[0051] Example 42: The display system according to any one of Examples 29-41, further comprising an inward-facing imaging system configured to capture one or more images of the user's eye, and the operation includes receiving an image of the user's eye captured by the inward-facing imaging system and identifying the eye pose based on the received image.

[0052] Example 43: The display system according to any one of Examples 29-42, wherein at least one waveguide is one of a plurality of waveguides forming a waveguide stack, and each waveguide includes a plurality of internal coupling regions and external coupling regions, and each internal coupling region of the waveguide is laterally displaced as seen in a front view when viewed from the direction of the internal coupling light incident on the internal coupling region.

[0053] Example 44: The external coupling regions of the same waveguide are configured to output light with the same wavefront divergence, and the external coupling regions of different waveguides are configured to output light with a wavefront divergence amount different from that of at least one other waveguide, and the different wavefront divergence amounts correspond to different depth planes.

[0054] Example 45: The internal coupling region of each waveguide is configured to internally couple light in a wavelength range corresponding to the same primary color, and the internal coupling regions of some waveguides are configured to internally couple light in a wavelength range corresponding to a primary color different from that of the internal coupling regions of other waveguides. The display system according to any one of Examples 29-44.

[0055] Example 46: The light projection system includes a plurality of projectors, and the projectors of the plurality of projectors are configured to provide image content for a subdivided portion of the FOV of the head-mounted display. The display system according to any one of Examples 29-45.

[0056] Example 47: A display system, comprising a light projection system and a head-mounted display configured to project light into a user's eyes and display virtual image content. The head-mounted display includes at least one waveguide, the at least one waveguide including a plurality of optical internal coupling regions configured to receive light from the light projection system and a plurality of optical external coupling regions configured to output light to the user's eyes. A processing electronic device communicating with the display, the processing electronic device including one or more processors and one or more computer storage media, the one or more computer storage media storing instructions that, when executed by one or more processors, cause the one or more processors to determine locations for virtual objects within the user's field of view, identify external coupling regions corresponding to the locations, and provide instructions for directing light from the light projection system to optical internal coupling regions associated with the determined optical external coupling regions.

[0057] Example 48: The display system according to Example 47, wherein identifying the external coupling region includes determining the eye posture of the eye and determining the external coupling region that overlaps with the location to be occupied by the virtual object in the visual field.

[0058] Example 49: The display system according to Example 47 or 48, wherein the operation includes providing movement for the virtual object.

[0059] Example 50: The display system according to any one of Examples 47-49, wherein the operation includes providing over time a temporal change in the visual properties of the virtual object, and the visual properties comprise one or more of color, size, and brightness.

[0060] Example 51: The display system according to any one of Examples 47-50, wherein the light internal coupling region is arranged in a row around at least one side of the plurality of external coupling regions.

[0061] Example 52: The display system according to any one of Examples 47-52, wherein the light projection system includes at least one light source and at least one movable light injector configured to output image light.

[0062] Example 53: The display system according to any one of Examples 47-52, wherein the at least one movable light injector includes a scanning mirror.

[0063] Example 54: The display system according to any one of Examples 47-52, wherein the at least one movable light injector includes a scanning fiber injector.

[0064] Example 55: The display system according to any one of Examples 47-51, wherein the light projection system includes at least one light source and at least one spatial light modulator configured to modulate the light from the light source.

[0065] Example 56: The head-mounted display is the display system according to any one of Examples 47-55, configured to display virtual objects on a plurality of depth planes.

[0066] Example 57: The operation includes projecting a set of intra-pupil images with differential disparity of virtual objects into the eye and displaying the virtual object on one of the depth planes, and is the display system according to any one of Examples 47-56.

[0067] Example 58: The operation includes providing instructions for directing light to a plurality of internal coupling elements within the light internal coupling region of a plurality of internal coupling regions associated with a determined light external coupling region, and is the display system according to any one of Examples 47-56.

[0068] Example 59: Further includes at least one variable focus lens element on the user side of at least one waveguide, and the first variable focus lens element is configured to correct the refractive error of the user's eye by modifying the projected light, and is the display system according to any one of Examples 47-56.

[0069] Example 60: Further includes an inward-facing imaging system configured to capture an image of one or more of the user's eyes, and the operation includes receiving an image of the user's eye captured by the inward-facing imaging system and identifying the eye pose based on the received image, and is the display system according to any one of Examples 47-59.

[0070] Example 61: At least one waveguide is one of a plurality of waveguides forming a waveguide stack, each waveguide includes a plurality of internal coupling regions and external coupling regions, and each internal coupling region of the waveguide is laterally displaced as seen in a front view when viewed from the direction of the internal coupling light incident on the internal coupling region, and is the display system according to any one of Examples 47-60.

[0071] Example 62: The external coupling regions of the same waveguide are configured to output light with the same wavefront divergence, and the external coupling regions of different waveguides are configured to output light with a wavefront divergence amount different from that of at least one other waveguide's external coupling region, and the different wavefront divergence amounts correspond to different depth planes. The display system according to any one of Examples 47-61.

[0072] Example 63: The internal coupling regions of each waveguide are configured to internally couple light in a wavelength range corresponding to the same primary color, and the internal coupling regions of some waveguides are configured to internally couple light in a wavelength range corresponding to a primary color different from that of the internal coupling regions of other waveguides. The display system according to any one of Examples 47-62.

[0073] Example 64: The internal coupling region includes a diffraction grating. The display system according to any one of Examples 47-63.

[0074] Example 65: The external coupling region includes a diffraction grating. The display system according to any one of Examples 47-64.

[0075] Example 66: The light projection system includes a plurality of projectors, and the projectors of the plurality of projectors are configured to provide image content for a portion of the FOV of the head-mounted display that is less than the subdivided portion. The display system according to any one of Examples 47-65.

[0076] Example 67: A head-mounted display system configured to project light and display virtual image content, the display system comprising: a light projection system; and a head-mounted display configured to display virtual image content, the head-mounted display including at least one waveguide, the at least one waveguide having a plurality of internal coupling regions proximate to at least one lateral edge of the at least one waveguide, each waveguide being configured to receive light having image information for forming virtual image content from the light projection system and internally couple the light into the waveguide, the head-mounted display comprising a plurality of internal coupling regions.

[0077] Example 68: The display system according to Example 67, further comprising a plurality of external coupling regions configured to externally couple light out of the waveguide and display virtual content, each of the plurality of external coupling regions being configured to receive light from a different one of the internal coupling regions.

[0078] Example 69: The display system according to Example 67 or 68, wherein at least two of the plurality of internal coupling regions are arranged along different lateral edges of at least one of the plurality of external coupling regions.

[0079] Example 70: The display system according to any one of Examples 67 - 69, wherein the plurality of internal coupling regions surround the plurality of external coupling regions.

[0080] Example 71: The display system according to any one of Examples 67 - 70, wherein each internal coupling region of the plurality of internal coupling regions corresponds to a unique external coupling region of the plurality of external coupling regions and is configured to selectively direct light.

[0081] Example 72: The optical coupling region is configured to redirect incident light from an optical projection system through a waveguide at an angle for total internal reflection and along the propagation direction, and further includes an optical dispersion structure configured to redirect a part of the light to propagate along an axis intersecting the propagation direction. The display system according to any one of Examples 67-71.

[0082] Example 73: The optical dispersion structure and the plurality of external coupling regions are disposed on the opposing major surfaces of at least one waveguide. The display system according to any one of Examples 67-72.

[0083] Example 74: The external coupling region defines a grid pattern across the waveguide. The display system according to any one of Examples 67-73.

[0084] Example 75: The head-mounted display includes a plurality of waveguides forming a waveguide stack. Each waveguide includes a plurality of internal coupling regions and external coupling regions. When viewed from the direction of the internal coupling light incident on the internal coupling region of each waveguide, the internal coupling region of each waveguide is laterally displaced as seen in a front view. The display system according to any one of Examples 67-74.

[0085] Example 76: The external coupling regions of the same waveguide are configured to output light with the same wavefront divergence, and the external coupling regions of different waveguides are configured to output light with a wavefront divergence amount different from that of the external coupling regions of at least one other waveguide. The different wavefront divergence amounts correspond to different depth planes. The display system according to any one of Examples 67-75.

[0086] Example 77: The internal coupling region of each waveguide is configured to internally couple light in a wavelength range corresponding to the same primary color, and the internal coupling regions of some waveguides are configured to internally couple light in a wavelength range corresponding to a primary color different from that of the internal coupling regions of other waveguides. The display system according to any one of Examples 67-76.

[0087] Example 78: A display system according to any one of Examples 67-77, wherein a plurality of internal coupling regions include a diffraction grating.

[0088] Example 79: A display system according to any one of Examples 67-78, wherein each of a plurality of internal coupling regions has a grating pitch different from that of at least one other internal coupling region of the waveguide.

[0089] Example 80: A display system according to any one of Examples 67-79, wherein each of a plurality of internal coupling regions has a grating orientation different from that of at least one other internal coupling region of the waveguide within the plane of the waveguide.

[0090] Example 81: A display system according to any one of Examples 67-80, wherein each of a plurality of internal coupling regions has an inclination different from that of at least one other internal coupling region of the waveguide with respect to the plane of the waveguide.

[0091] Example 82: A display system according to any one of Examples 67-81, wherein the internal coupling regions are spaced apart from each other.

[0092] Example 83: A display system according to any one of Examples 67-82, wherein each of a plurality of internal coupling regions is arranged to internally couple light, direct the light, and propagate it along a direction different from that of at least one other internal coupling region of the waveguide within the waveguide by total internal reflection.

[0093] Example 84: A display system according to any one of Examples 67-83, wherein the light projection system includes at least one light source and at least one movable light injector configured to direct image light to individual ones of the internal coupling regions.

[0094] Example 85: The optical projection system includes at least one light source comprising an array of light emitters, at least one spatial light modulator configured to modulate the light from the light source, and a projection optical system mounted on a frame and configured to direct the light from the spatial light modulator to an internal coupling region. The display system is configured to activate a plurality of different light emitters and provide virtual image content on different depth planes. The display system provides a relatively large distance between individual light emitters of the plurality of light emitters to provide virtual image content on a relatively near depth plane, and provides a relatively small distance between individual light emitters of the plurality of light emitters to provide virtual image content on a relatively far depth plane. The display system according to any one of claims 67 - 84.

[0095] Example 86: Each of the light emitters of the plurality of light emitters is configured to be sequentially activated at different times, and the display system is configured to synchronize the activation of each light emitter with the display of a disparity - different intra - pupil image. The display system according to any one of claims 67 - 86.

[0096] Example 87: The display system according to any one of claims 67 - 86, further comprising a variable - focus lens element on the opposing lateral edges of the waveguide.

[0097] Example 88: The optical projection system includes a plurality of projectors, and the projectors of the plurality of projectors are configured to provide image content for a sub - divided portion of the FOV of a head - mounted display. The display system according to any one of claims 67 - 87.

[0098] Details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will be apparent from the description, drawings, and claims. Neither this description nor the following detailed description purports to limit the scope of the subject matter of the invention. The present invention provides, for example, the following. (Item 1) A head-mounted display system configured to project light and display virtual image content, the display system comprising: A light projection system; A head-mounted display configured to display virtual image content, the head-mounted display including at least one waveguide, the at least one waveguide including: A plurality of internal coupling regions, each of the plurality of internal coupling regions configured to receive light having image information for forming the virtual image content from the light projection system and internally couple the light into the waveguide; A plurality of external coupling regions, each of the plurality of external coupling regions configured to externally couple the light out of the waveguide and display the virtual content, each of the plurality of external coupling regions configured to receive light from a different one of the internal coupling regions; A head-mounted display; A display system. (Item 2) The display system according to item 1, wherein each internal coupling region of the plurality of internal coupling regions corresponds to a unique external coupling region of the plurality of external coupling regions and is configured to selectively direct light. (Item 3) The display system according to item 2, wherein each internal coupling region is a diffraction grating having at least one of an inclination, a grating orientation, a grating structure size, or a grating pitch selected to preferentially externally couple the light internally coupled by the internal coupling region to the external coupling region corresponding to the internal coupling region. (Item 4) The light coupling region is configured to redirect incident light from the light projection system through the waveguide at an angle for total internal reflection along the propagation direction, and further includes a light dispersion structure configured to redirect a part of the light to propagate along an axis intersecting the propagation direction. The display system according to item 1. (Item 5) The display system according to item 4, wherein the light dispersion structure and the plurality of external coupling regions are disposed on opposing major surfaces of the at least one waveguide. (Item 6) The display system according to item 1, wherein the plurality of internal coupling regions include a diffraction grating. (Item 7) The display system according to item 6, wherein each of the plurality of internal coupling regions has a grating pitch different from that of at least one other internal coupling region of the waveguide. (Item 8) The display system according to item 7, wherein the different grating pitches change the total internal reflection angle at which light internally coupled into the waveguide undergoes total internal reflection toward the waveguide, toward the associated external coupling region of the plurality of external coupling regions. (Item 9) The display system according to item 6, wherein each of the plurality of internal coupling regions has a grating orientation different from that of at least one other internal coupling region of the waveguide within the plane of the waveguide. (Item 10) The display system according to item 9, wherein the different grating orientations change the angle at which light is coupled into the waveguide such that the light propagates toward the intended external coupling region of the plurality of external coupling regions. (Item 11) The display system according to item 1, wherein each of the plurality of internal coupling regions has an inclination different from that of at least one other internal coupling region of the waveguide with respect to the plane of the waveguide. (Item 12) The display system according to item 1, wherein the internal coupling regions are spaced apart from each other. (Item 13) The display system according to Item 1, wherein the optical internal coupling region is arranged in a row around at least one side of the plurality of external coupling regions. (Item 14) The display system according to Item 13, wherein each of the external coupling regions defines a stripe across the waveguide, and the stripe extends along an axis intersecting the row of the internal coupling regions. (Item 15) The display system according to Item 1, wherein the external coupling region defines a grid pattern across the waveguide. (Item 16) The display system according to Item 1, wherein each of the plurality of internal coupling regions internally couples light, directs the light, and is arranged to propagate the light in the waveguide along a direction different from that of at least one other internal coupling region of the waveguide by total internal reflection. (Item 17) The display system according to Item 16, wherein at least one internal coupling region proximate to a lateral edge of the at least one external coupling region is configured to internally couple light along a range of angles symmetrically arranged about an inwardly biased axis. (Item 18) The display system according to Item 1, wherein at least two of the plurality of internal coupling regions are arranged along at least one different side of the plurality of external coupling regions. (Item 19) The display system according to Item 18, wherein the plurality of internal coupling regions comprises internal coupling optical elements surrounding at least one of the plurality of external coupling regions on at least three sides. (Item 20) The display system according to Item 1, wherein the light projection system comprises a light source and a movable light injector configured to direct image light to individual ones of the internal coupling regions. (Item 21) The head-mounted display includes a plurality of waveguides forming a waveguide stack, and each of the waveguides includes a plurality of the internal coupling regions and the external coupling regions. When each internal coupling region of the waveguide is viewed from the direction of the internal coupling light incident on the internal coupling region, it is displaced laterally as seen in a front view. The display system according to item 1. (Item 22) The external coupling regions of the same waveguide are configured to output light with the same wavefront divergence. The external coupling regions of different waveguides are configured to output light with a wavefront divergence amount different from that of at least one other waveguide's external coupling region. The different wavefront divergence amounts correspond to different depth planes. The display system according to item 21. (Item 23) The internal coupling region of each waveguide is configured to internally couple light in a wavelength range corresponding to the same primary color. The internal coupling regions of some waveguides are configured to internally couple light in a wavelength range corresponding to a primary color different from that of the internal coupling regions of other waveguides. The display system according to item 21. (Item 24) The light projection system includes a light source having an array of light emitters, a spatial light modulator configured to modulate light from the light source, and a projection optical system mounted on a frame and configured to direct light from the spatial light modulator to the internal coupling region and is provided with The display system is configured to activate a plurality of different ones of the light emitters and provide the virtual image content on different depth planes. The display system provides a relatively large distance between individual light emitters of a plurality of light emitters to provide the virtual image content on a relatively close depth plane, To provide the virtual image content on a relatively far depth plane, providing a relatively small distance between individual light emitters of a plurality of light emitters The display system according to item 1, which is configured to perform the above. (Item 25) Each of the light emitters of the plurality of light emitters is configured to be sequentially activated at different times, and the display system is configured to synchronize the activation of each light emitter with the display of an intra-pupil image having different parallax disparities. The display system according to item 24. (Item 26) The light source is a microdisplay, and the light emitter is a light-emitting diode. The display system according to item 24. (Item 27) The display system according to item 1, further comprising a variable focus lens element on the opposite side of the waveguide. (Item 28) The light projection system includes a plurality of projectors, and the projectors of the plurality of projectors are configured to provide image content for a portion of the FOV of the head-mounted display that is less than the subdivided portion. The display system according to item 1. (Item 29) A display system, A light projection system, A head-mountable display configured to project light into a user's eye and display virtual image content, the head-mountable display comprising: At least one waveguide, A plurality of light internal coupling regions configured to receive light from the light projection system, A plurality of light external coupling regions configured to output light to the user's eye And at least one waveguide comprising A head-mounted display comprising A processing electronic device that communicates with the display and an imaging system facing inward, the processing electronic device comprising one or more processors and one or more computer storage media, the one or more computer storage media storing instructions that, when executed by the one or more processors, cause the one or more processors to determine a light external coupling region associated with the eye posture of the eye, provide instructions for directing light from the light projection system to a light internal coupling region associated with the determined light external coupling region perform operations including, and a processing electronic device A display system comprising. (Item 30) The display system according to item 29, wherein determining the light external coupling region includes determining an intersection point between the line of sight of the eye and one of the plurality of light external coupling regions. (Item 31) The display system according to item 29, wherein the light internal coupling region is arranged in a row around at least one side of the plurality of external coupling regions. (Item 32) The display system according to item 29, wherein the light projection system includes at least one light source and at least one movable light injector configured to output image light. (Item 33) The display system according to item 32, wherein the at least one movable light injector includes a scanning mirror. (Item 34) The display system according to item 32, wherein the at least one movable light injector includes a scanning fiber injector. (Item 35) The display system according to item 29, wherein the light projection system includes at least one light source and at least one spatial light modulator configured to modulate light from the light source. (Item 36) The head-mounted display is the display system according to item 29, configured to display virtual objects on a plurality of depth planes. (Item 37) The operation includes projecting a set of intra-pupil images with parallax disparity into the eye and displaying the virtual object on one of the depth planes, of the display system according to item 36. (Item 38) The operation includes projecting each of the set of intra-pupil images with parallax disparity within a flicker fusion threshold, of the display system according to item 37. (Item 39) The operation includes providing an instruction for directing light to a plurality of internal coupling elements within a light internal coupling region of the plurality of internal coupling regions associated with the determined light external coupling region, of the display system according to item 36. (Item 40) The display system according to item 36 further includes at least one variable focus lens element on the user side of the at least one waveguide, and the first variable focus lens element is configured to correct the projected light and correct refractive abnormalities of the user's eye. (Item 41) The operation further includes determining a fixation point of the eye and applying a correction corresponding to the fixation point, of the display system according to item 40. (Item 42) The display system further includes an inward-facing imaging system configured to capture one or more images of the user's eye, and the operation includes receiving an image of the user's eye captured by the inward-facing imaging system, and identifying the eye pose based on the received image of the display system according to item 29. (Item 43) The at least one waveguide is one of a plurality of waveguides forming a waveguide stack, and each of the waveguides includes a plurality of the internal coupling regions and the external coupling regions. When each internal coupling region of the waveguide is viewed from the direction of the internal coupling light incident on the internal coupling region, it is displaced laterally as seen in a front view plan view. The display system according to item 29. (Item 44) The external coupling regions of the same waveguide are configured to output light with the same wavefront divergence. The external coupling regions of different waveguides are configured to output light with a wavefront divergence amount different from that of the external coupling regions of at least one other waveguide. The different wavefront divergence amounts correspond to different depth planes. The display system according to item 43. (Item 45) The internal coupling region of each waveguide is configured to internally couple light in a wavelength range corresponding to the same primary color. The internal coupling regions of some waveguides are configured to internally couple light in a wavelength range corresponding to a primary color different from that of the internal coupling regions of other waveguides. The display system according to item 43. (Item 46) The light projection system includes a plurality of projectors, and the projectors of the plurality of projectors are configured to provide image content for a subdivided portion of the FOV of the head-mounted display. The display system according to item 29. (Item 47) A display system, A light projection system, and A head-mounted display configured to project light into a user's eyes and display virtual image content, the head-mounted display including At least one waveguide, and A plurality of optical internal coupling regions configured to receive light from the light projection system, and A plurality of optical external coupling regions configured to output light to the eyes of the user and at least one waveguide including A head-mounted display including A processing electronic device that communicates with the display, the processing electronic device comprising one or more processors and one or more computer storage media, the one or more computer storage media storing instructions that, when executed by the one or more processors, cause the one or more processors to Determine a location for a virtual object within the field of view of the user, Identify an external coupling region corresponding to the location, Provide instructions for directing light from the light projection system to an optical internal coupling region associated with the determined optical external coupling region A processing electronic device that performs operations including A display system including (Item 48) Identifying the external coupling region includes Determining the eye posture of the eye, Determining an external coupling region that overlaps the location to be occupied by the virtual object within the field of view The display system according to item 47, including (Item 49) The operation includes providing movement for the virtual object, the display system according to item 47 (Item 50) The operation includes providing over time a temporal change in a visual property of the virtual object, the visual property comprising one or more of color, size, and brightness, the display system according to item 47 (Item 51) The optical internal coupling region is arranged in a row around at least one side of the plurality of external coupling regions, the display system according to item 47 (Item 52) The display system according to item 47, wherein the optical projection system includes at least one light source and at least one movable light injector configured to output image light. (Item 53) The display system according to item 52, wherein the at least one movable light injector includes a scanning mirror. (Item 54) The display system according to item 52, wherein the at least one movable light injector includes a scanning fiber injector. (Item 55) The display system according to item 47, wherein the optical projection system includes at least one light source and at least one spatial light modulator configured to modulate light from the light source. (Item 56) The display system according to item 47, wherein the head-mounted display is configured to display virtual objects on a plurality of depth planes. (Item 57) The display system according to item 56, wherein the operation includes projecting a set of disparity-varying intra-pupillary images of the virtual object into the eye and displaying the virtual object on one of the depth planes. (Item 58) The display system according to item 56, wherein the operation includes providing instructions for directing light to a plurality of internal coupling elements within a light internal coupling region of the plurality of internal coupling regions associated with the determined light external coupling region. (Item 59) The display system according to item 56, further comprising at least one variable focus lens element on the user side of the at least one waveguide, wherein the first variable focus lens element is configured to modify the projected light and correct refractive anomalies of the user's eye. (Item 60) Further comprising an inward-facing imaging system configured to capture one or more images of the user's eye, and the operation is Receiving an image of the user's eye captured by the inward-facing imaging system; Identifying the eye pose based on the received image; The display system according to item 47, comprising: (Item 61) The at least one waveguide is one of a plurality of waveguides forming a waveguide stack, and each of the waveguides includes a plurality of the internal coupling regions and the external coupling regions; When each internal coupling region of the waveguide is viewed from the direction of the internal coupling light incident on the internal coupling region, it is displaced laterally as seen in a front view plan view; The display system according to item 47. (Item 62) The external coupling regions of the same waveguide are configured to output light with the same wavefront divergence; The external coupling regions of different waveguides are configured to output light with a wavefront divergence amount different from that of the external coupling region of at least one other waveguide; The different wavefront divergence amounts correspond to different depth planes; The display system according to item 47. (Item 63) The internal coupling region of each waveguide is configured to internally couple light in a wavelength range corresponding to the same primary color; The internal coupling regions of some waveguides are configured to internally couple light in a wavelength range corresponding to a primary color different from that of the internal coupling regions of other waveguides; The display system according to item 47. (Item 64) The internal coupling region includes a diffraction grating. The display system according to item 47. (Item 65) The external coupling region includes a diffraction grating. The display system according to item 47. (Item 66) The light projection system includes a plurality of projectors, and the projectors of the plurality of projectors are configured to provide image content for a subdivided portion of the FOV of the head-mounted display that is less than the FOV of the head-mounted display, according to the display system of item 46. (Item 67) A head-mounted display system configured to project light and display virtual image content, the display system comprising: A light projection system; and A head-mounted display configured to display virtual image content, the head-mounted display including at least one waveguide, the at least one waveguide including: A plurality of internal coupling regions proximate to at least one lateral edge of the at least one waveguide, each waveguide being configured to receive light having image information for forming the virtual image content from the light projection system and internally couple the light into the waveguide. A head-mounted display comprising; and A display system comprising. (Item 68) A plurality of external coupling regions configured to externally couple the light out of the waveguide and display the virtual content, each of the plurality of external coupling regions being configured to receive light from a different one of the internal coupling regions, according to the display system of item 67. (Item 69) At least two of the plurality of internal coupling regions are arranged along different lateral edges of at least one external coupling region of the plurality of external coupling regions, according to the display system of item 67. (Item 70) The plurality of internal coupling regions surround the plurality of external coupling regions, according to the display system of item 68. (Item 71) The display system according to item 68, wherein each of the plurality of internal coupling regions corresponds to a unique external coupling region of the plurality of external coupling regions and is configured to selectively direct light. (Item 72) The display system according to item 68, wherein the optical coupling region is configured to redirect incident light from the optical projection system through the waveguide at an angle for total internal reflection along the propagation direction, and further includes an optical dispersion structure configured to redirect a part of the light to propagate along an axis intersecting the propagation direction. (Item 73) The display system according to item 72, wherein the optical dispersion structure and the plurality of external coupling regions are disposed on opposing major surfaces of the at least one waveguide. (Item 74) The display system according to item 68, wherein the external coupling region defines a grid pattern across the waveguide. (Item 75) The head-mountable display includes a plurality of waveguides forming a waveguide stack, each of the waveguides including the plurality of internal coupling regions and the external coupling regions. When viewed from the direction of the internal coupling light incident on the internal coupling region of each waveguide, the internal coupling region of each waveguide is displaced laterally as seen in a front view. The display system according to item 68. (Item 76) The external coupling regions of the same waveguide are configured to output light with the same wavefront divergence. The external coupling regions of different waveguides are configured to output light with a wavefront divergence amount different from that of the external coupling regions of at least one other waveguide. The different wavefront divergence amounts correspond to different depth planes. The display system according to item 75. (Item 77) The internal coupling region of each waveguide is configured to internally couple light in a wavelength range corresponding to the same primary color. The internal coupling regions of some waveguides are configured to internally couple light in a wavelength range corresponding to a primary color different from that of the internal coupling regions of other waveguides. The display system according to item 75. (Item 78) The display system according to item 67, wherein the plurality of internal coupling regions include a diffraction grating. (Item 79) The display system according to item 78, wherein each of the plurality of internal coupling regions has a grating pitch different from that of at least one other internal coupling region of the waveguide. (Item 80) The display system according to item 78, wherein each of the plurality of internal coupling regions has a grating orientation different from that of at least one other internal coupling region of the waveguide within the plane of the waveguide. (Item 81) The display system according to item 67, wherein each of the plurality of internal coupling regions has an inclination different from that of at least one other internal coupling region of the waveguide with respect to the plane of the waveguide. (Item 82) The display system according to item 67, wherein the internal coupling regions are spaced apart from each other. (Item 83) The display system according to item 67, wherein each of the plurality of internal coupling regions is arranged to internally couple light, direct the light, and propagate the light along a direction different from that of at least one other internal coupling region of the waveguide within the waveguide by total internal reflection. (Item 84) The display system according to item 67, wherein the light projection system includes at least one light source and at least one movable light injector configured to direct image light to individual ones of the internal coupling regions. (Item 85) The light projection system includes at least one light source including an array of light emitters, at least one spatial light modulator configured to modulate light from the light source, A projection optical system mounted on the frame and configured to direct light from the spatial light modulator to the internal coupling region and comprising The display system is configured to activate a plurality of different light emitters and provide the virtual image content on different depth planes, and the display system To provide the virtual image content on a relatively near depth plane, providing a relatively large distance between individual light emitters of the plurality of light emitters; To provide the virtual image content on a relatively far depth plane, providing a relatively small distance between individual light emitters of the plurality of light emitters The display system according to item 67, which is configured to perform the above. (Item 86) Each of the light emitters of the plurality of light emitters is configured to be sequentially activated at different times, and the display system is configured to synchronize the activation of each light emitter with the display of an intra-pupillary image with different parallax differences. The display system according to item 85. (Item 87) The display system according to item 67, further comprising a variable focus lens element on the opposing lateral edge of the waveguide. (Item 88) The light projection system includes a plurality of projectors, and the projectors of the plurality of projectors are configured to provide image content for a portion of the FOV of the head-mounted display that is less than the subdivided portion. The display system according to item 67.

Brief Description of the Drawings

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[0144] Detailed Description An AR and / or VR system can display virtual content to a user or viewer. For example, the present content may be displayed on a head-mounted display that projects image information onto the user's eyes, for example, as part of eyewear. Additionally, when the present system is an AR system, the display may also transmit light from the surrounding environment through the user's eyes and enable a view of the surrounding environment. As used herein, it should be understood that a "head-mounted" or "head-mountable" display is a display that can be mounted on the head of a viewer or user. Such a display can be understood to form part of a display system.

[0145] In various augmented reality and virtual reality display systems, a waveguide can extend across the eye associated with the user. The waveguide can be configured to output image light with image information for forming an image within the eye. For example, the light can be output using an external coupling element (which may be a grating) that redirects the light out of the waveguide and towards the eye.

[0146] It should be understood that the eye can move relative to the waveguide. To ensure that the eye continues to receive image light even when it moves, the waveguide can output image light with similar image information across the entire expansion of the waveguide's viewing area. This enables the eye to receive image light even when it moves and aligns it with different areas of the waveguide. A portion of the light externally coupled by the external coupling element can be usefully directed into the pupil of the eye where it will enter the eye and form an image, but other light externally coupled by the external coupling element cannot be incident on the pupil of the eye and thus does not contribute to the image seen by the eye. Therefore, energy is used to generate all of the output light, but only a small portion of that light reaches the eye and forms an image. Unfortunately, the light that does not enter the pupil of the eye and the energy used to generate that light are not perceived by the viewer and can thus be considered "wasted" in a sense.

[0147] Advantageously, in some implementations, the display system disclosed herein enables light to be utilized highly efficiently. Instead of outputting light across the entire viewing area of the waveguide, the light is selectively output from regions of the waveguide that are aligned with the eye, thereby increasing the proportion of the output light that enters the pupil of the eye. Preferably, these regions are less than the entire viewing area of the waveguide and, in some implementations, occupy an area that is greater than the area of the average eye pupil, which can result in dividing the viewing area into two or more, three or more, four or more, or nine or more distinct light external coupling regions. Thus, the light is output across the entire viewing area and not wasted, while the output area is large enough to provide the desired field of view and some tolerance for eye movement.

[0148] In some implementations, the external coupling region may have a unique associated or correlated internal coupling region. The internal coupling region receives image light (such as light modulated by a spatial light modulator), and it should be understood that this image light is internally coupled within the waveguide so as to propagate towards the external coupling region to which it is externally coupled and be incident thereon, such that the light propagates towards the external coupling region and then towards the user's eye. In some implementations, optical dispersion features may also be utilized to disperse light from the internal coupling region along the axis and across the desired external coupling region. Since the internal coupling region selectively steers light towards an associated or correlated external coupling region, the external coupling region for outputting light can be selected by directing the light into an associated internal coupling region or a plurality of regions. Advantageously, in addition to energy efficiency, flexibility in the placement of the internal coupling region can be provided by associating a particular internal coupling region with a particular external coupling region. For example, the internal coupling regions may be dispersed in a row across and / or around the circumference of the waveguide, which can have the advantage of providing a shape factor that is thinner than the internal coupling regions that must be localized within the same portion of the waveguide or a wider range of waveguide shapes.

[0149] It should be understood that the display system may include a light projection system configured to selectively direct light into one or more desired internal coupling regions. In some embodiments, the light projection system may include a projector or a plurality of projectors, and / or the projector may, in some implementations, function as a light source. The light projection system may also be referred to as a light input system for inputting light into the internal coupling region. The light projection system may include a single projection device or a plurality of projection devices (such as a light projector). In some implementations, the field of view (FOV) of the display system may be subdivided into a plurality of portions, and each light projection device may be configured to project image content for an associated portion of the full FOV. Thus, in some implementations, each projector provides image content for a subdivided portion of the field of view of the display system. It should be understood that the optics and associated systems for forming the full FOV may be complex and large, especially when the projection system collimates light for input into the waveguide, in order to provide an acceptable image quality. On the other hand, the optics and associated systems for a projector that forms only a portion of the FOV may be simpler, and in some implementations, the overall size of a light projection system having a plurality of light projectors (each providing image content for a portion of the full field of view) may be smaller than the size of a single light projection system that provides image content for the full FOV. Thus, advantageously, the use of a plurality of light projectors may facilitate a smaller form factor than a system with a single light projector for the full field of view.

[0150] In some implementations, the light projection system may include a mechanically actuated structure that physically adjusts the direction of the image light output toward a desired internal coupling region. For example, the light projection system may include one or more switchable mirrors, which may rotate, for example, to direct light from one or more light sources into the desired internal coupling region. In some other implementations, the light projection system may include one or more scanning fibers, which scan across the internal coupling region and are configured to output light when the output end of the scanning fiber is aligned with a location corresponding to the desired internal coupling region.

[0151] In some other implementations, the light projection system may electrically switch the light output onto different internal coupling regions without mechanical actuation. For example, the light projection system may include a plurality of individually activatable light sources arranged to provide a unique light path to the respective corresponding internal coupling regions. As a result, appropriate activation of the light sources may be utilized to direct light into the desired internal coupling region. In some implementations, a spatial light modulator may be provided within the light path between the light source and the internal coupling region to encode the light from the light source with image information and form an image.

[0152] In some implementations, an appropriate external coupling region for outputting light may be selected based on the determination of the orientation of the eye, for example, the orientation of the pupil of the eye. For example, the display system may include an inward-facing camera that images the eye and determines its orientation. In some implementations, the line of sight of the eye may be extrapolated and the intersection of the line of sight and the external coupling region may be determined. The intersecting light external coupling region may be understood as the desired region for receiving the image light to be output to the eye.

[0153] In some implementations, in conjunction with the eye pose, the location of the virtual object to be displayed may be used to select an external coupling region for receiving the image light for output. For example, the virtual object may be understood to be located within a particular portion of the user's field of view that overlaps a particular external coupling region. As a result, that external coupling region may be designated to receive the image light. In some implementations, this external coupling region may also intersect the line of sight of the eye, particularly if the virtual object is an object expected to draw the user's attention (e.g., if the virtual object exhibits temporal changes in visual properties such as movement and / or changes in color, size, brightness, etc.).

[0154] Advantageously, a display system according to some implementations can provide a three-dimensional presentation of a virtual object with a high degree of visual comfort. It should be understood that the user's left and right eyes can be presented with different views of the virtual object to provide a convergence / divergence motion cue and, through stereopsis, provide an impression of depth. Additionally, the display system can be configured to output light with different levels of wavefront divergence to induce an appropriate perspective response for the desired depth. As a result, perspective-convergence / divergence motion matching can be achieved, which can provide a comfortable and realistic visual experience.

[0155] In some implementations, different levels of wavefront divergence may be achieved using a plurality of waveguides that form a stack of waveguides. The external coupling region of each waveguide may include an external coupling feature (e.g., a diffraction grating) configured to externally couple light with a particular amount of wavefront divergence. Thus, a desired amount of wavefront divergence may be selected by directing image light into the internal coupling region of a waveguide having an external coupling region with an external coupling feature configured to output light with the desired amount of wavefront divergence. In some implementations, the internal coupling regions for different waveguides may be laterally displaced as seen in a top plan view. Thus, different waveguides may be selected by directing light into different internal coupling regions. For example, a particular internal coupling region may be associated with a particular waveguide and also a particular external coupling region within that waveguide.

[0156] In some implementations, in addition to or instead of a plurality of waveguides that output light with different amounts of wavefront divergence, one or more variable focus lens elements may be provided to modify the wavefront divergence of light propagating from the waveguide to the eye. In some implementations, the variable focus lens element may be used instead of or in addition to provide refractive aberration correction for light to propagate towards the eye.

[0157] In some other implementations, the light projection system may include an array of discrete light sources that direct light from different angles through the projection optics to provide a binocularly disparate pupil image to approximate different amounts of wavefront divergence. In some implementations, a selectable separation between the discrete light sources may be utilized to modulate the wavefront divergence. For example, a relatively large distance between individual light sources may provide wavefront divergence corresponding to a relatively near depth plane, while a relatively small distance between individual light sources may provide wavefront divergence corresponding to a relatively far depth plane. Image light for the binocularly disparate pupil image may be directed to a suitable internal coupling region as described herein. For example, a mechanically actuated structure such as a scanning mirror or a scanning fiber may be utilized to direct image light for the binocularly disparate pupil image to a suitable internal coupling region.

[0158] Implementations of the present technology may provide various advantages. For example, the implementations disclosed herein advantageously increase the proportion of light produced by the light projection system that is used to form an image perceived by the user while reducing the proportion of light that strikes other parts of the user's eye or face or otherwise contributes to an image perceived by the user, thereby improving display system efficiency. By selectively externally coupling light towards the pupil, such a system may reduce the amount of light energy generated by the light projection system or other display light sources to produce an image of a given brightness in the user's eye. Further, since a greater proportion of the generated light is directed into the eye, the image brightness may be improved. Additionally, less energy is directed towards light generation for a desired brightness, thereby allowing the energy usage to be reallocated for other uses such as for a computational process, which may have advantages such as image rendering, latency reduction, etc.

[0159] Note that internal coupling elements may be referred to herein as input coupling elements, internal coupling gratings (or ICGs), diffractive internal coupling elements, or equivalents. Similarly, external coupling elements may be referred to herein as output coupling elements, diffractive external coupling elements, or equivalents.

[0160] Reference is now made to the drawings, in which like reference numerals refer to like parts throughout. Unless otherwise indicated, the drawings are schematic and are not necessarily drawn to scale. Exemplary display system

[0161] FIG. 2 illustrates a conventional display system for simulating a three-dimensional image for a user. It should be understood that when the user's eyes are separated and 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 may 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 the user's visual system can interpret to derive a perception of depth.

[0162] Continuing to refer to FIG. 2, images 190, 200 are separated from 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 eyes are fixated on an object at optical infinity directly in front of the viewer. Images 190, 200 are flat and at a fixed distance from eyes 210, 220. Based on slightly different views of the virtual object in the images presented to 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 single binocular vision is maintained. This rotation can converge the respective lines of sight of eyes 210, 220 onto a point in the space where the virtual object is perceived to exist. As a result, providing a three-dimensional image has conventionally involved providing binocular cues that can manipulate the convergence / divergence movement of the user's eyes 210, 220 and are interpreted by the human visual system to provide depth perception.

[0163] However, generating a realistic and comfortable perception of depth is difficult. It should be understood that light from objects at different distances from the eyes 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 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 (object or part of an object) has a spherical wavefront curvature that is a function of the distance the point is away from the user's eyes. The curvature increases as the distance between the object and eye 210 decreases. Only the single eye 210 is illustrated in FIGS. 3A-3C and various other figures in this specification for clarity of illustration, but the discussion regarding eye 210 can be applied to both eyes 210 and 220 of the viewer.

[0164] Continuing to refer to FIGS. 3A-3C, light from an object on which a viewer's eye is fixated can have different wavefront divergences. Due to the different amounts of wavefront divergence, the light can be focused differently by the eye's lens, which in turn can require the lens to assume 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 by 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 induces 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 object 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 a fixated object on the retina (e.g., the fovea) of the eye can be referred to as the accommodative state.

[0165] Referring now to FIG. 4A, the representation of the accommodation-convergence / divergence motion response of the human visual system is illustrated. Eye movements to fixate an object cause 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, causing the eye's lens to assume a particular accommodation state that forms a focused image of the object on the retina of the eye (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 the respective retinas 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 as the process by which the eyes achieve a particular accommodation state, and convergence / divergence motion can be understood as 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.

[0166] Without being limited by theory, it is believed that the viewer of an object can perceive the object as "three-dimensional" due to the combination of convergence / divergence motion and accommodation. As described above, the convergence / divergence motion of the two eyes relative to each other (e.g., 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 to fixate on an object) is closely associated with the accommodation of the eye's lens. Under normal conditions, changing the shape 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 convergence / divergence motion to the same distance under a relationship known as the "accommodation-convergence / divergence reflex". Similarly, a change in convergence / divergence motion will induce a corresponding change in the shape of the lens under normal conditions.

[0167] Referring now to FIG. 4B, examples of different accommodation and vergence / divergence motion states of the eyes are 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 vergence / divergence motion states of each pair of eyes are different, with the pair of eyes 222a being directed straight, while the pair of eyes 222 converges onto 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.

[0168] Unfortunately, many users of conventional "3-D" display systems find such conventional systems uncomfortable or perceive no sense of depth due to the mismatch between accommodation and vergence / divergence motion states in these displays. As described above, many stereoscopic or "3-D" display systems display a scene by providing slightly different images to each eye. Such systems are uncomfortable for many viewers because they simply provide different presentations of the scene, causing a change in the vergence / divergence motion state of the eyes, but without a corresponding change in the accommodation 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 accommodation state. Such an arrangement goes against the "accommodation-vergence reflex" by causing a change in the vergence / divergence motion state without a matching change in the accommodation state. This mismatch is thought to cause viewer discomfort. A display system that provides better matching between accommodation and vergence / divergence motion can create a more realistic and comfortable simulation of three-dimensional images.

[0169] 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 eye. In some implementations, the different presentations may provide both cues for convergence / divergence motion and matching cues for accommodation, thereby providing physiologically correct accommodation-convergence / divergence motion matching.

[0170] Continuing to refer to FIG. 4B, two depth planes 240 corresponding to different distances in space from eyes 210, 220 are illustrated. For a given depth plane 240, convergence / divergence motion cues may be provided by appropriately displaying images of different viewpoints for each of eyes 210, 220. Additionally, for a given depth plane 240, the light forming the images provided to each eye 210, 220 may have wavefront divergence corresponding to a light field generated by a point at the distance of that depth plane 240.

[0171] In the illustrated implementation, the distance along the z-axis of depth plane 240 containing 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 may be measured from the front display 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 interpupillary distance and may correspond to the distance between the exit pupil of the user's eye and the front display of the user worn by the user. In practice, the value for the interpupillary distance may generally be a normalized value used for all viewers. For example, the interpupillary 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.

[0172] Referring now to FIGS. 4C and 4D, examples of consistent vergence accommodation - convergence / divergence movement distances and inconsistent vergence accommodation - convergence / divergence 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 convergence / divergence movement state in which the eyes converge on a point 15 on the depth plane 240. In addition, the image may be formed by light having a wavefront curvature corresponding to the real object in the depth plane 240. As a result, the eyes 210, 220 assume an accommodation state in which the image is in focus on the retinas of those eyes. Thus, the user may perceive the virtual object as being at the point 15 on the depth plane 240.

[0173] It should be understood that the accommodation and convergence / divergence movement states of the eyes 210, 220 are each associated with a specific distance on the z - axis. For example, an object at a specific distance from the eyes 210, 220 causes those eyes to assume a specific accommodation state based on the distance of the object. The distance associated with a specific accommodation state may be referred to as the accommodation distance A d Similarly, there exists a specific vergence distance V d associated with a specific convergence / divergence movement 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 convergence / divergence can be said to be physiologically correct. This is considered to be the most comfortable scenario for the viewer.

[0174] However, in a stereoscopic display, the focusing distance and the vergence / accommodation 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 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 vergence / accommodation movement that converges eyes 210, 220 on points 15 that are not located on depth plane 240. As a result, in some implementations, the focusing distance corresponds to the distance from the exit pupils of eyes 210, 220 to depth plane 240, while the vergence distance corresponds to a greater distance from the exit pupils of eyes 210, 220 to point 15. The focusing distance is different from the vergence / accommodation movement distance. As a result, there is a focusing-vergence / accommodation 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.

[0175] It should be understood that in some implementations, as long as the same reference point is used for the focusing distance and the vergence / accommodation 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-vergence / accommodation 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.

[0176] Although not limited by theory, it is believed that a user can perceive a vergence-accommodation disparity 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 disparity itself causing significant discomfort. In some implementations, the display systems disclosed herein (e.g., display system 250, FIG. 6) present an image having a vergence-accommodation disparity of about 0.5 diopters or less to a viewer. In some other implementations, the vergence-accommodation disparity of the image provided by the display system is about 0.33 diopters or less. In yet other implementations, the vergence-accommodation disparity of the image provided by the display system is about 0.25 diopters or less, including about 0.1 diopters or less.

[0177] 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 the light field generated by a point on a desired depth plane 240. In some implementations, 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.

[0178] In some implementations, 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 implementations, multiple or stacked waveguides may be utilized to provide different amounts of wavefront divergence for different depth planes and / or to output light within different ranges of wavelengths. It should be understood that, as used herein, a depth plane may be flat or may follow the contour of a curved surface.

[0179] FIG. 6 illustrates an example of a stack of waveguides for outputting image information to a user. The display system 250 includes a stack or stacked waveguide assembly 260 of waveguides 270, 280, 290, 300, 310 that can be utilized to provide three-dimensional perception to the eye / brain. It should be understood that the display system 250 may be considered a light field display in some implementations. Additionally, the waveguide assembly 260 may also be referred to as an eyepiece.

[0180] In some implementations, the display system 250 may be configured to provide a substantially continuous queue for convergence / divergence movement and a plurality of discrete queues for depth adjustment. The queue for convergence / divergence movement may be provided by displaying different images to each of the user's eyes, and the queue for depth adjustment may be provided by outputting light that forms an image with a selectable discrete amount of wavefront divergence. In other words, the display system 250 may be configured to output light with a variable level of wavefront divergence. In some implementations, 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.

[0181] 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 implementations, 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 with various levels of wavefront curvature or ray divergence. Each waveguide level may be associated with a particular depth plane and may be configured to output image information corresponding to that depth plane. Image 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 towards 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 implementations, 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 towards world 510 or viewer's eye 210). In some implementations, 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 towards eye 210 at a particular angle (and amount of divergence) corresponding to the depth plane associated with the particular waveguide. In some implementations, 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.

[0182] In some implementations, the image input devices 360, 370, 380, 390, 400 are discrete displays, each generating image information for input into their respective waveguides 270, 280, 290, 300, 310. In some other implementations, the image input devices 360, 370, 380, 390, 400 are the output ends of a single multiplexed display that can send image information, for example, via one or more optical waveguides (such as optical fiber cables) to each of the image input devices 360, 370, 380, 390, 400. It should be understood that the image information provided by the image input devices 360, 370, 380, 390, 400 can include light of different wavelengths or colors (e.g., different primary colors as discussed herein).

[0183] In some implementations, the light input into the waveguides 270, 280, 290, 300, 310 is encoded with image information and provided by a light projection system 1010 as further discussed herein. In some implementations, the light projection system 1010 may include one or more emission pixel arrays. Each emission pixel array may include a plurality of light-emitting pixels, which are understood to be configured to emit light of variable intensity and color. The image input devices 360, 370, 380, 390, 400 are schematically illustrated and, in some implementations, 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 the waveguides 270, 280, 290, 300, 310. In some implementations, the waveguides of the 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 pixel array of the light projection device 1010 and the image may be an image on a depth plane.

[0184] 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 and the light projection system 1010. In some implementations, controller 560 is part of 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 implementations, the controller may be a single integrated device or a distributed system connected by wired or wireless communication channels. Controller 560 may be part of processing module 140 or 150 (FIG. 9D) in some implementations.

[0185] 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 their 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 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 the 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 implementations, the external coupling optical elements 570, 580, 590, 600, 610 may be disposed on the top and / or bottom major surfaces, and / or directly disposed within the volume of the waveguides 270, 280, 290, 300, 310, as further discussed herein. In some implementations, 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 implementations, 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 the piece of material.

[0186] 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 originating from the next upper waveguide 280 as originating from a first focal plane that is closer inwardly from the optically infinite towards the eye 210. Similarly, the third upper waveguide 290 passes its output light through both the first lens 350 and the second lens 340 before reaching the eye 210. The combined refractive power of the first lens 350 and the second lens 340 may be configured to generate another incremental amount of wavefront curvature such that the eye / brain interprets the light originating from the third waveguide 290 as originating from a second focal plane that is even closer inwardly from the optically infinite towards the person than the light from the next upper waveguide 280 was.

[0187] 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 converging focusing power representing 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 implementations, one or both may be dynamic using electroactive features.

[0188] In some implementations, 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 the 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 tiled images to provide an extended field of view at those depth planes.

[0189] 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 implementations, 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 volume holograms, surface holograms, and / or diffraction gratings. In some implementations, the features 320, 330, 340, 350 may not be lenses. Rather, they may simply be spacers (e.g., cladding layers and / or structures for forming voids).

[0190] In some implementations, 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.

[0191] In some implementations, one or more diffractive optical elements (DOEs) may be switchable between an “on” state that actively diffracts and an “off” state that does 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 incident light), or the microdroplets may be switched to a refractive index that does not match that of the host medium (in which case the pattern actively diffracts incident light).

[0192] In some implementations, a camera assembly 630 (e.g., a digital camera including visible and infrared cameras) may be provided to capture an image of the eye 210 and / or tissue surrounding the eye 210, e.g., to detect user input and / or monitor the user's physiological state. As used herein, a camera may be any image capture device. In some implementations, 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 is then reflected by the eye and detected by the image capture device. In some implementations, the camera assembly 630 may be attached to the frame 80 (FIG. 9D) and may communicate electrically with a processing module 140 and / or 150 that can process image information from the camera assembly 630. In some implementations, one camera assembly 630 may be utilized per eye to monitor each eye separately.

[0193] 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 within 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 an output beam 650. The output beam 650 is illustrated as being substantially parallel, but as discussed herein, it may also be redirected to propagate to the eye 210 at an angle (e.g., forming a diverging output beam) depending on the depth plane associated with the waveguide 270. 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 divergent 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.

[0194] In some implementations, a full-color image may be formed on 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 in which each depth plane includes an image formed using a plurality of different primary colors. The illustrated implementation 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 illustrated 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 implementations, 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 depth planes corresponding to different distances from the user. Such an arrangement may increase visual acuity and user comfort and / or reduce chromatic aberration. Without being limited by theory, it should be understood that not placing different primary color images at the same physical focus may help compensate for the natural longitudinal chromatic aberration (LCA) of the human eye, which can be important. For example, an eyepiece may help compensate for the eye's LCA by biasing the focus levels of the primary color images such that they are in focus on the retina after being focused by the eye's high LCA optics. In some implementations, the system may have a sparser set of depth planes for one primary color (e.g., 2x blue depth planes) and a denser set of depth planes for another primary color (e.g., 6x green depth planes). Advantageously, this approach may help provide appropriate depth information to the eye while reducing hardware cost and complexity. For example, the eye may prioritize focusing on medium (e.g., "green") wavelengths over short and long wavelengths and thus may not require a uniform set of depth planes across all primary color images.For example, in some implementations, under the assumption that the eye will prioritize medium-wavelength light (e.g., for forming a green primary-color image) when perceiving a depth plane for a full-color image, a waveguide that outputs a primary-color image formed by short or long-wavelength light (e.g., a blue or red primary-color image) may be utilized to form a full-color image on multiple depth planes, while a waveguide that outputs a primary-color image formed by medium-wavelength light (e.g., a green primary-color image) may be used to form a full-color image for only a single depth plane. Thus, there may be a one-to-one correspondence between the number of waveguides for medium-wavelength light and the total number of available depth planes, while the number of waveguides for primary colors of other wavelengths (such as red and / or blue light, etc.) may be less than the total number of available depth planes.

[0195] In some implementations, 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 implementations, each box in the figure containing the letter G, R, or B may be understood to represent an individual waveguide, and three waveguides may be provided for each depth plane for which three primary-color images are provided. The waveguides associated with each depth plane are shown adjacent to each other in this figure 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 implementations, for example, multiple primary colors may be output by the same waveguide such that only a single waveguide is provided for each depth plane.

[0196] Continuing to refer to FIG. 8, in some implementations, G is green, R is red, and B is blue. In some other implementations, other colors associated with other wavelengths of light, including magenta and cyan, may also be used in addition to or instead of one or more of red, green, or blue.

[0197] Throughout this disclosure, any reference to the color of a given light is to be understood to encompass light of one or more wavelengths within the range of wavelengths of the light that is perceived as that given color by a viewer. 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.

[0198] In some implementations, the light projection system 1010 (FIG. 6) may be configured to emit light of one or more wavelengths outside of the viewer's visual perception range, such as infrared and / or ultraviolet wavelengths. Additionally, the internal coupling, external coupling, and other light redirecting structures of the waveguide of the display 250 may be configured to direct and emit this light from the display towards the user's eye 210, for example, for imaging and / or user stimulation applications.

[0199] Referring now to FIG. 9A, in some implementations, the light that impinges on the waveguide may need to be redirected to internally couple the light into the waveguide. Internal coupling optical elements 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 660 of a plurality or set 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 position where the light needs to be redirected for internal coupling.

[0200] The illustrated set 660 of stacked waveguides includes waveguides 670, 680, and 690. Each waveguide includes an associated internal coupling optical element (which may also be referred to as the optical input area on the waveguide). For example, internal coupling optical element 700 is disposed on the major surface (e.g., the upper major surface) of waveguide 670, internal coupling optical element 710 is disposed on the major surface (e.g., the upper major surface) of waveguide 680, and internal coupling optical element 720 is disposed on the major surface (e.g., the upper major surface) of waveguide 690. In some implementations, one or more of the internal coupling optical elements 700, 710, 720 may be disposed on the bottom major surface of the respective waveguides 670, 680, 690 (in particular, one or more of the internal coupling optical elements are reflective deflecting optical elements). As illustrated, the 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. In particular, those internal coupling optical elements are transmissive deflecting optical elements. In some implementations, the internal coupling optical elements 700, 710, 720 may be disposed within the body of the respective waveguides 670, 680, 690. In some implementations, as discussed herein, the internal coupling optical elements 700, 710, 720 are wavelength selective such that they selectively redirect one or more wavelengths of light while transmitting other wavelengths of light. Although illustrated on one side or corner of their respective waveguides 670, 680, 690, it should be understood that in some implementations, the internal coupling optical elements 700, 710, 720 may be disposed within other areas of their respective waveguides 670, 680, 690. It should be understood that the internal coupling optical elements 700, 710, 720 may be understood to be internal coupling regions where each internal coupling element corresponds to an internal coupling region. In some other implementations, as discussed herein, the internal coupling optical element of each waveguide may be subdivided into a plurality of regions respectively.

[0201] As shown, the internally coupled optical elements 700, 710, 720 may be laterally offset from each other. In some implementations, each internally coupled optical element may be offset such that its light is received without passing through another internally coupled optical element. For example, each internally coupled optical element 700, 710, 720 may be configured to receive light from different image input devices 360, 370, 380, 390, and 400, as shown in FIG. 6, and may be separated (e.g., laterally spaced) from other internally coupled optical elements 700, 710, 720 such that it receives substantially no light from the other internally coupled optical elements 700, 710, 720.

[0202] Each waveguide also includes an associated light dispersing element. For example, the light dispersing element 730 is disposed on a major surface (e.g., upper major surface) of the waveguide 670, the light dispersing element 740 is disposed on a major surface (e.g., upper major surface) of the waveguide 680, and the light dispersing element 750 is disposed on a major surface (e.g., upper major surface) of the waveguide 690. In some other implementations, 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 implementations, 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.

[0203] 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 implementations, 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 nearest of 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 facilitate total internal reflection (TIR) of light (e.g., TIR between the upper major surface and the lower major surface of each waveguide) through waveguides 670, 680, 690. In some implementations, layers 760a, 760b are formed from air. It should be understood that although not shown, the upper and lower portions of the illustrated set 660 of waveguides may include the nearest cladding layers.

[0204] Preferably, for ease of manufacturing 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 implementations, 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.

[0205] 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 injected into waveguides 670, 680, 690 by one or more image input devices 360, 370, 380, 390, 400 (FIG. 6).

[0206] In some implementations, the light rays 770, 780, 790 are intended for different waveguides (e.g., waveguides configured to output light with different amounts of wavefront divergence and / or configured to output light having different properties such as different wavelengths or colors, etc.). Thus, in some implementations, the light rays 770, 780, 790 may have different properties, e.g., 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 implementations, 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 associated internal coupling optical elements.

[0207] For example, the internal coupling optical element 700 may be configured to deflect the light ray 770 having a 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 light of the second wavelength or wavelength range, and is thereby deflected. The light ray 790 is deflected by the internal coupling optical element 720 configured to selectively deflect light of the third wavelength or wavelength range.

[0208] 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 its 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 waveguides.

[0209] 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 propagate by TIR within the waveguides 670, 680, 690, respectively. The light rays 770, 780, 790 then each impinge on the light dispersing elements 730, 740, 750. The light dispersing elements 730, 740, 750 deflect the light rays 770, 780, 790 so as to propagate towards the external coupling optical elements 800, 810, 820, respectively.

[0210] In some implementations, the light dispersing elements 730, 740, 750 are orthogonal pupil expanders (OPEs). In some implementations, the OPEs deflect or disperse light to the external coupling optical elements 800, 810, 820, and in some implementations, also increase the beam or spot size of the present light as it propagates to the external coupling optical elements. In some implementations, the light dispersing 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 light dispersing elements 730, 740, 750 may each be replaced by the external coupling optical elements 800, 810, 820. In some implementations, 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 dimensions 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 impinging again on the OPE, 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, etc. Similarly, in response to impinging on the EPE, a portion of the impinging light is directed out of 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 impinging light is directed out of the waveguide, etc. 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 implementations, the OPE and / or EPE may be configured to modify the size of the beam of light.

[0211] Thus, referring to FIGS. 9A and 9B, in some implementations, 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., OPEs) 730, 740, 750, and external coupling optical elements (e.g., EPs) 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 embodiment, the ray 770 (e.g., blue light) is polarized by the first internal coupling optical element 700 in the manner described above, then bounces along the waveguide and interacts with the light dispersion element (e.g., OPE) 730, 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 strikes the internal coupling optical element 710 and is thereby deflected. The ray 780 then bounces along the waveguide 680 via TIR and will proceed to its light dispersion element (e.g., OPE) 740, then the external coupling optical element (e.g., EP) 810. Finally, the ray 790 (e.g., red light) passes through the waveguide 690 and strikes 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, 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.

[0212] FIG. 9C illustrates a top and bottom plan view of an embodiment of the plurality of stacked waveguides of FIGS. 9A and 9B. As shown, waveguides 670, 680, 690 may be vertically aligned, along with their associated optical dispersion 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 views). As further discussed herein, this non-overlapping spatial arrangement facilitates the injection of light from different resources into different waveguides on a one-to-one basis, thereby enabling a particular light source to be uniquely coupled to a particular waveguide. In some implementations, an array that includes non-overlapping spatially separated internal coupling optical elements may be referred to as a pupil-offset system, and the internal coupling optical elements within these arrays may correspond to sub-pupils. It should be understood that the top and bottom views shown are front-on plan views as viewed from the direction of the internal coupling beams of light (e.g., light 770, 780, 790 (FIG. 9B)) incident on internal coupling elements 700, 710, 720, respectively.

[0213] FIG. 9D illustrates an embodiment of a wearable display system 60 in which various waveguides and related systems disclosed herein may be integrated. In some implementations, the display system 60 is the system 250 of FIG. 6, and FIG. 6 schematically shows some parts of that system 60 in more detail. For example, the waveguide assembly 260 of FIG. 6 may be part of the display 70.

[0214] Continuing to refer to FIG. 9D, display system 60 includes a display 70 and various mechanical and electronic modules and systems for supporting the functions of that 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 eyes of the user 90. In some implementations, the display 70 may be regarded as an eyepiece. In some implementations, a speaker 100 is coupled to the frame 80 and configured to be positioned adjacent to the outer ear canal of the user 90 (in some implementations, another speaker, not shown, may also optionally be positioned adjacent to the other outer ear canal of the user to provide stereo / formable sound control). The display system 60 may also include one or more microphones 110 or other devices and may detect sound. In some implementations, 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 to 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 and may collect audio data (e.g., sound from the user and / or the environment). In some implementations, the display system may also include a peripheral sensor 120a, which is separate from the frame 80 and may be attached to the body of the user 90 (e.g., the head, torso, limbs, etc. of the user 90). In some implementations, 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.

[0215] Continuing to refer to FIG. 9D, 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 is fixedly attached to the frame 80, attached to a helmet or hat worn by the user, embedded within headphones, or otherwise removably attached to the user 90 (e.g., in a backpack configuration, in a belt attachment configuration), etc., and may be mounted in various configurations. 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 comprise 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) data obtained and / or processed using the remote processing module 150 and / or remote data repository 160 (including data related to virtual content) for possible 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 are available as resources to the local processing and data module 140.In some implementations, 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 implementations, 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.

[0216] Continuing to refer to FIG. 9D, in some implementations, the remote processing module 150 may include 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 implementations, the remote data repository 160 may include a digital data storage facility, which may be available through the Internet or other networking configurations in a “cloud” resource configuration. In some implementations, the remote data repository 160 may include one or more remote servers that provide information, for example, information for generating augmented reality content to the local processing and data module 140 and / or the remote processing module 150. In some implementations, 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. (Exemplary display system with multiple external coupling regions)

[0217] The display systems described herein (e.g., display system 60, FIG. 9D) may be used to present augmented or virtual reality content (referred to herein as virtual content). To present virtual content, the display system may use one or more external coupling elements that externally couple light from one or more waveguides in a direction such that the light propagates into one or both eyes of a user, such as a wearer of a head-mounted display.

[0218] As shown in FIG. 10A, exemplary external coupling element 830 externally couples light propagating within the waveguide (e.g., by total internal reflection) toward user's eye 1010, as described herein. However, a typical external coupling element may be structured to output light in various directions across the area of the external coupling optical element, in all regions. Thus, a subset of the light externally coupled by external coupling optical element 830 may be usefully directed toward pupil 1012 of user's eye 1010, where it will enter the eye 1010 and form an image. The desirably directed light may be illustrated by exemplary beam 1015, which may extend normal or substantially normal to external coupling element 830 at a location near the center of external coupling element 830 (and may be angled inwardly with respect to a location near the periphery of external coupling element 830). Other light externally coupled by external coupling element 830, which is externally coupled at various angles from the periphery of external coupling element 830 in a direction that does not enter eye 1010 at pupil 1012 or near it, may not contribute to the image formed within eye 1010. Such light that is externally coupled from external coupling optical element 830 but does not enter at or near the pupil may be considered wasted energy. The drawings are schematic and not necessarily to scale, and thus it should be understood that the lateral distance between light beams 115 and 117 may be large relative to the eye 1010 shown.

[0219] Advantageously, some implementations increase the rate of externally coupled light (e.g., externally coupled light that coincides with beam 1015) directed towards the pupil 1012 of the user's eye 1010 and reduce the amount of externally coupled light in other directions (e.g., externally coupled light that coincides with beam 1017) that is not aligned by the eye 1010. For example, such a system can increase the proportion of internally coupled light that ultimately enters the pupil, and thus can reduce the amount of light energy that must be generated by a light projection system or other display light source to produce an image of a given brightness on the user's eye. Various implementations of the present technology provide a system that includes an external coupling element, an internal coupling element, and / or a light projection system configured to selectively direct image light towards the pupil 1012 of the user's eye 1010. Such a system can thereby advantageously increase the proportion of a given amount of light produced by the light projection system that reaches the eye 1010 and forms an image perceived by the user, and can reduce the proportion of light that strikes other parts of the user's eye or face or otherwise contributes to an image perceived by the user, thereby improving the efficiency of the display system disclosed herein.

[0220] As schematically illustrated in FIGS. 10B and 10C, some implementations may include segmentation of the external coupling element 1000 of waveguide 900 into different external coupling regions 1000a, 1000b, 1000c. The different external coupling regions may be configured to externally couple light differently. For example, external coupling region 1000b may direct externally coupled light ray 1015 such that externally coupled light 1017 is output little or not at all from the other external coupling regions 1000a, 1000c. As a result, light 1017 that does not enter the eye and is not perceived by the user is not "wasted" by being output from external coupling regions 1000a, 1000c.

[0221] It should be understood that different external coupling regions can direct the output light at an angle other than normal to the external coupling element 1000. FIG. 10C illustrates exemplary light beam directions 1019 that may be associated with different external coupling regions 1000a, 1000b, 1000c. In some implementations, different external coupling regions may be utilized to externally couple light for different portions of the field of view. For example, the central region 1000b of the external coupling element 1000 may generally desirably externally couple light along a set of angles centered in a direction that generally extends outwardly toward the eye 1010, while the peripheral regions 1000a, 1000c of the external coupling element 1000 may generally be centered in a direction angled inwardly toward the eye 1010 and may desirably externally couple light along a set of angles that enter the pupil of the eye. Thus, in some implementations, the field of view provided by the display system and / or the virtual content available in different portions of the field of view may be varied, as discussed herein, by appropriate selection of the external coupling regions 1000a, 1000b, 1000c, as desired. Advantageously, the ability to select different portions of the field of view (e.g., the portions containing the desired virtual content) promotes high energy utilization efficiency by enabling no light to be emitted from other directions.

[0222] In some implementations, an optical projection system may be utilized to direct light into waveguide 900, and it should be understood that the optical projection system may utilize projection optics to collimate the light for input into that waveguide 900. The image tiling approach disclosed herein advantageously enables the use of discrete light projectors for each or multiple different portions of the field of view, with each projector forming image content for an associated portion of the field of view. It should be understood that collimating the light to provide image content across the entire field of view may require a large and complex projection optical system if a single light projector is utilized. On the other hand, projection optics for providing a relatively small field of view, e.g., a portion of the field of view of a display system, is advantageously simpler and smaller than projection optics for collimating light for a larger field of view. As discussed herein, the use of multiple light projectors may thus occupy a smaller overall volume than the use of a single light projector for the entire field of view.

[0223] FIG. 10D illustrates an exemplary primary light ray 1015 of light that may be externally coupled from a waveguide of an exemplary wearable display system. In some implementations, a single one of the external coupling regions 1000a, 1000b, 1000c may be large enough to generate a desired field of view of the eye 1010. For example, the light ray 1015 that may be externally coupled out from the external coupling region 1000b may be dispersed within an area that includes the visual limit of the eye or may provide an angular range for the light incident on the eye to correspond to the desired field of view.

[0224] Referring now to FIG. 11A, waveguide 900 may have an external coupling element such as external coupling element 1000, which may include an array of diffraction or other optical dispersion structures 1020 that cause diffraction and propagation of light across external coupling element 1000. In some implementations, optical dispersion structure 1020 and external coupling element 1000 may be disposed on the same side of waveguide 900, e.g., on the same major surface of waveguide 900. In such an implementation, the area occupied by external coupling element 1000 may include a structure (e.g., a diffraction structure) that externally couples that light out of the waveguide, and also a structure (e.g., a diffraction structure) that disperses incident light across the waveguide by total internal reflection.

[0225] In some other implementations, in the illustrated top and bottom views, external coupling element 1000 may be understood to be directly below optical dispersion element 1020. In such a configuration, external coupling element 1000 and optical dispersion element 1020 may be disposed on different opposing major surfaces of waveguide 900.

[0226] Continuing to refer to FIG. 11A, when light beam 1025 (e.g., corresponding to image light) impinges on internal coupling element 1005, beam 1025 is internally coupled into waveguide 900 and propagates in the propagation direction along one axis (e.g., a vertical axis) until it strikes optical dispersion structure 1020, which splits a portion of beam 1025 into beamlets 1027, which generally occur in a stepwise manner and may propagate along different axes (e.g., orthogonal or horizontal axes as illustrated). Preferably, internal coupling element 1005 redirects light into waveguide 900 at an angle such that light beam 1025 propagates within the waveguide by total internal reflection. It should be understood that optical dispersion structure 1020 has a sufficiently low light redirection efficiency to allow most of beam 1025 to continue to propagate (e.g., downward along the vertical axis). Thus, beam 1025 may be replicated and substantially fill the entire area of external coupling element 1000. Such an arrangement may provide uniform propagation and high coverage across external coupling element 1000, but may pose difficulties in targeting the propagation of beamlets 1027 for efficient use of light.

[0227] In some implementations, as shown in FIG. 11B, the waveguide 900 may have an external coupling element 1000 that can be segmented into a left region 1000l and a right region 1000r. The left region 1000l may generally include only an optical dispersion structure 1020l configured to cause the propagation of the beamlet 1027l generally to the left and downward. Similarly, the right region 1000r may generally include only an optical dispersion structure 1020r configured to cause the propagation of the beamlet 1027r generally to the right and downward. Thus, each beam 1025 of light entering each region 1000l, 1000r is externally coupled only from the same one of the regions 1000l, 1000r and does not propagate to the other of the regions 1000l, 1000r. This configuration can improve the efficiency of the external coupling element 1000 because the amount of the area of the external coupling element 1000 through which each beam 1025 propagates thereacross is reduced by about half. In various implementations, it should be understood that further segmentation may be implemented to provide an efficient use of the internally coupled light, for example, by including additional segmented regions and / or segmented regions shaped differently. The boundary between the left region 1000l and the right region 1000r may correspond to a physical dividing structure (e.g., an optically opaque and / or absorptive partition) or may simply be an interface between regions of the optical dispersion structures 1020r, 1020l oriented differently.

[0228] FIG. 11C illustrates an exemplary cross-sectional side view of the waveguide of FIG. 11B in an implementation in which the external coupling region and the optical dispersion structure can be on different sides of the waveguide. For example, the external coupling region 1000r may be disposed on a first major surface of the waveguide 900, and the optical dispersion structure 1020r may be disposed on a second opposing major surface of the waveguide 900. In some implementations, as shown, the optical dispersion structure 1020r may be vertically aligned with the external coupling region 1000r and occupy a similar area. As discussed herein, the external coupling region and the optical dispersion structure may be a diffraction structure, such as a diffraction grating, in some implementations.

[0229] Figures 12A and 12B illustrate an exemplary configuration by which the side surfaces of the internal coupling elements can be varied to improve the efficient use of light within the imaging system described herein. In FIGS. 12A and 12B, the waveguide 900 includes a plurality of discrete internal coupling regions.

[0230] In FIG. 12A, the exemplary waveguide 900 includes an external coupling element 1000 that includes regions 1000l, 1000c, and 1000r. Regions 1000l, 1000c, and 1000r may be physically segmented regions of the external coupling element 1000, or may be regions of the external coupling element 1000 that are not physically segmented by any segmentation structure, variation within a light dispersion structure, or other physical structure.

[0231] The exemplary display system further includes corresponding internal coupling elements 1005l, 1005c, 1005r configured to internally couple light incident on the internal coupling elements 1005l, 1005c, 1005r toward the external coupling element 1000. It should be understood that a light dispersion structure such as that shown in FIG. 11C may be disposed on a major surface facing a major surface of the external coupling element 1000 of the waveguide 900. In some other implementations, the light dispersion structure and the light external coupling element 1000 may be on the same major surface.

[0232] Continuing to refer to FIG. 12A, the internal coupling element 1005c internally couples light and directs it towards the central region 1000c of the external coupling element 1000, and it may be desirable for the light to be equally dispersed in both lateral directions. In some implementations, the internal coupling element 1005c may desirably direct the internally coupled light within a certain angular range that is generally symmetrically dispersed about the axis 1025c. Additionally, as shown, the internal coupling elements 1005l and 1005r may internally couple light to the respective regions 1000l, 1000r of the external coupling element 1000, in which case it may be more desirable for the light to be dispersed inwards towards the center of the external coupling element 1000 rather than towards the lateral edges of the external coupling element 1000 (e.g., because light reaching the lateral edges of the external coupling element 1000 may be absorbed, be externally coupled away from the eye, or otherwise not be effectively externally coupled). Thus, the internal coupling elements 1005l and 1005r may desirably direct the internally coupled light within a certain angular range about the inwardly biased axes 1025l, 1025r so as to reduce the amount of light reaching the lateral edges of the external coupling element 1000. In some implementations, the regions 1000l, 1000c, and 1000r may be understood as external coupling regions that define stripes across the waveguide 900, and the stripes extend along an axis that intersects the columns defined by the internal coupling regions 1005l, 1005c, and 1005r.

[0233] In some implementations, such as implementations in which the internal coupling elements 1005l, 1005c, 1005r include diffraction gratings, the internal coupling elements 1005l, 1005c, 1005r may achieve the desired directivity of internal coupling based on the orientation of the internal coupling structure 1007. In the exemplary implementation illustrated in FIG. 12A, the internal coupling structures 1007 of the lateral internal coupling elements 1005l and 1005r are angled or biased in a particular direction with respect to the orientation of the internal coupling structure 1007 of the central internal coupling element 1005c.

[0234] Continuing to refer to FIG. 12A, regions 1000l, 1000c, 1000r and / or associated light dispersion structures 1020 (FIG. 11C) may be separated by optically opaque and / or absorptive partitions that limit the propagation of light between different ones of the correlation regions 1000l, 1000c, 1000r. In some other implementations, partitions are not provided between different regions or their associated light dispersion structures. Rather, light directed into one external coupling region may be allowed to freely propagate to other external coupling regions. Such a configuration nevertheless provides advantages for efficient utilization of light because the internal coupling region directs light primarily to a particular external coupling region such that the entire waveguide receives less light than its external coupling regions.

[0235] FIG. 12B illustrates a further exemplary arrangement of internal coupling elements in conjunction with non-rectangular external coupling element 1000. In the exemplary implementation of FIG. 12B, waveguide 900 includes an even number of internal coupling elements 1005 1 , 1005 2 , 1005 3 , 1005 4 which, in some implementations, may be arranged in a substantially symmetric distribution about the center of external coupling element 1000. Thus, none of internal coupling elements 1005 1 , 1005 2 , 1005 3 , 1005 4 are centered across the central portion of external coupling element 1000, and thus all four internal coupling elements 1005 1 , 1005 2 , 1005 3 , 1005 4 may be configured to have an inward bias. Internal coupling elements 1005 2 and 1005 3 are located more centrally with respect to internal coupling elements 1005 1 and 1005 4 such that internal coupling elements 1005 2 and 1005 3 are 2 and 1005 3The internal coupling element 1005 may have an internal coupling structure 1007 that has less inclination with respect to the internal coupling structure 1007 of the external coupling element 1000 so as to internally couple light to a wider central area of the external coupling element 1000. 1 and 1005 4 The internal coupling structure 1007 may have less inclination with respect to the internal coupling structure 1007 of the external coupling element 1000. The internal coupling element 1005 1 and 1005 4 is located closer to the side edge of the external coupling element 1000, and thus, the light internally coupled by the internal coupling element 1005 1 and 1005 4 has a more inclined internal coupling structure 1007 so that the light has a greater inward bias and is less likely to be incident on the side edge of the external coupling element 1000.

[0236] The implementations illustrated in FIGS. 12A and 12B illustrate a plurality of discrete and spaced internal coupling regions, but the waveguide 900 disclosed herein may also be implemented using one or more internal coupling regions in which continuous portions of individual optical internal coupling elements have differently configured optical redirection structures that define different internal coupling regions. For example, FIG. 13 illustrates a waveguide having internal coupling elements extending along two or more sides of the waveguide, i.e., along the lateral edges. For example, as illustrated, the internal coupling element 1005 may be disposed along a plurality of sides or edges of the waveguide and surround the external coupling element 1000. In some implementations, as illustrated, the internal coupling element 1005 substantially surrounds the external coupling element 1000. The internal coupling element 1005 includes an internal coupling structure 1007 that is arranged to internally couple light and direct the light toward the external coupling element 1000 in a particular desired direction. For example, the internal coupling structure 1007 located near the top of the external coupling element 1000 may generally be arranged to internally couple light downward, the internal coupling structure 1007 located near the bottom of the external coupling element 1000 may generally be arranged to internally couple light upward, and the internal coupling structure 1007 located near the lateral side of the external coupling element 1000 may generally be arranged to internally couple light inwardly toward the center of the external coupling element 1000. It should be understood that different regions of the internal coupling element 1005 having differently configured internal coupling structures 1007 constitute different internal coupling regions.

[0237] In some embodiments, the light input system may be configured to project light towards the internal coupling element 1005. The light input system may include a plurality of projectors, which may have the advantage of simplifying the provision of light into the internal coupling elements on different sides of the waveguide. As discussed herein, the full FOV of the display system may be subdivided into a plurality of portions, and the light input system may include a plurality of projectors configured to provide image content for each associated portion by directing light to different areas of the internal coupling element 1005. Additionally, or alternatively, the projectors may be oriented to direct light to a portion of the internal coupling element 1005 on different sides of the waveguide 900. In some embodiments, the light input system includes a first projector configured to direct light into a portion of the internal coupling element 1005 along the upper edge of the waveguide 900, a second projector configured to direct light into a portion of the internal coupling element 1005 along the right edge of the waveguide 900, a third projector configured to direct light into a portion of the internal coupling element 1005 along the bottom edge of the waveguide 900, and a fourth projector configured to direct light into a portion of the internal coupling element 1005 along the left edge of the waveguide 900. Each projector may be configured to provide image content for a different portion of the external coupling element 1000, as discussed herein, and it should be understood that the different portions are associated with different portions of the internal coupling optical element 1005.

[0238] FIG. 14A illustrates a further exemplary configuration of the waveguide 900 having an internal coupling element for internally coupling light into the external coupling element 1000. The internal coupling element 1005 may include individual internal coupling regions 1005 a1 …1005 d4 and may include. Each internal coupling region 1005 a1 …1005 d4It may be configured to internally couple light that will be externally coupled from the corresponding or correlated external coupling regions a1…d4 of the external coupling element 1000. The external coupling regions a1…d4 may define a grid pattern across the waveguide 900. Each internal coupling region 1005 a1 …1005 d4 The light internally coupled in...1005 may be directed to be externally coupled only from, or primarily from, the corresponding external coupling regions a1…d4 of the external coupling element 1000, based on one or more features such as tilt, grating pitch, grating structure size (e.g., the size of the protrusions on the surface forming the grating), or other characteristics of the individual internal coupling regions 1005 a1 …1005 d4 etc., based on the techniques described above. For example, the internal coupling regions 1005 a2 、1005 b2 、1005 c2 、および1005 d2 may each be different from the others in terms of tilt, grating pitch, grating structure size, or another characteristic such that the light internally coupled in each internal coupling region 1005 a2 、1005 b2 、1005 c2 、1005 d2 is selectively or primarily directed to, and externally coupled by, a particular associated external coupling region. For example, the internal coupling element 1005 a2 may be configured such that the light internally coupled therefrom has an angle of total internal reflection that causes the light to be incident on region a2 within the external coupling element 1000. Similarly, the internal coupling element 1005 b2 may be configured such that the light internally coupled therefrom has a different angle of total internal reflection that causes much of the light to further travel along the external coupling element 1000 and be incident on region b2 within the waveguide 900.

[0239] As discussed herein, the optical input system may direct light to different internal coupling regions 1005 a1 …1005 d4It may be configured to project towards. The light input system may include a plurality of projectors configured to direct light into different internal coupling regions 1005 a1 …1005 d4 The light input system may include a plurality of projectors configured to direct light into one or more internal coupling regions 1005 a1 …1005 d4 of different or overlapping subsets. For example, a first projector may be configured to emit light towards a subset of internal coupling regions closer to the first lateral edge of the waveguide, and a second projector may be configured to emit light towards a subset of internal coupling regions closer to the second lateral edge of the waveguide.

[0240] FIG. 14B is an example of a schematic cross-sectional side view of the waveguide of FIG. 14A, and the cross-section is obtained along plane 14B (FIG. 14A). As shown, the internal coupling regions 1005 a2 、1005 b2 、1005 c2 、1005 d2 may receive the incident light beam 1025, which may be internally coupled and redirected towards the external coupling regions a1, b1, c1, d1 of the external coupling element 1000. It should be understood that the internal coupling regions 1005 a2 、1005 b2 、1005 c2 、1005 d2 、1005 a2 、1005 b2 、1005 c2 、1005 d2 may be configured to internally couple light to propagate through the waveguide 900 by total internal reflection. Additionally, when internally coupling light, the internal coupling regions 1005 a2 、1005 b2 、1005 c2 、1005 d2are deflected by, respectively, internally coupled optical beams 1205 a2 , 1025 b2 , 1025 c2 , 1025 d2 may be provided. The internally coupled optical beams 1205 a2 , 1025 b2 , 1025 c2 , 1025 d2 propagate at an angle such that, by total internal reflection, they subsequently collide, respectively, on corresponding external coupling regions a1, b1, c1, d1. In some implementations, the total internal reflection angle (the angle at which internally coupled light undergoes total internal reflection from the major surface of the waveguide) is selected by appropriately choosing the grating pitch for the internal coupling regions 1005 a2 , 1005 b2 , 1005 c2 , 1005 d2 such that the internally coupled light is deflected and enters the waveguide at the desired total internal reflection angle. In some implementations, the angle for some of the internal coupling regions may be shallower than for other regions).

[0241] In some implementations, the selectivity of the correspondence between a particular internal coupling region and a particular external coupling region can be increased by configuring the external coupling region such that it is most efficient when externally coupling the light received from the internal coupling region to which they are associated. For example, the external coupling region may be configured to most efficiently externally couple the incident light colliding thereon from an angle corresponding to the angle of the internally coupled light propagating from the associated internal coupling region. For example, the external coupling region may most efficiently externally couple the light colliding thereon at the TIR angle provided by the associated internal coupling region, and / or the external coupling region may most efficiently externally couple the light colliding thereon from the lateral direction corresponding to the associated internal coupling region.

[0242] In some implementations, an image tiling approach may be utilized in conjunction with the exemplary configuration of FIG. 14A. In some contexts, it should be understood that virtual content may be displayed only within a portion of the user's field of view. In some implementations, regions a1... d4 may each be associated with a particular portion of the field of view, and the image content to be output by a particular region a1... d4 may correspond to the virtual content for that portion of the field of view. In some cases, an image may span multiple regions a1... d4. Each internal coupling element 1005 a1 …1005 d4 The image light projected thereon may represent a section of the image that will appear in the corresponding regions a1... d4 of the external coupling element 1000. Thus, when individual image sections are projected onto the corresponding internal coupling elements 1005 a1 …1005 d4 the image light for each image section is externally coupled in the corresponding regions a1... d4 of the external coupling element 1000 with an intensity greater than the light from other internal coupling regions 1005 a1 …1005 d4 In some implementations, the image light may be time multiplexed (directed at different times into different internal coupling regions) such that a user viewing the external coupling element 1000 perceives the complete image. When time multiplexed, the image light is preferably provided to each external coupling region at which it is desired to output the image light, within the flicker fusion threshold.

[0243] It should be understood that the waveguide 900 may be one of a plurality of similar waveguides that form a waveguide stack, as illustrated, for example, in FIGS. 11A - 14B. Such a waveguide stack may advantageously be utilized to provide virtual content on multiple depth planes, as discussed herein.

[0244] FIG. 14C illustrates a set 660A of stacked waveguides 670A, 680A, and 690A, each of which may be similar to waveguide 900 (FIGS. 11A - 14B). Each waveguide includes one or more associated internal coupling regions 700A, 700B, 710A, 710B, 720A, and 720B (which may also be referred to as the optical input area on the waveguide and may correspond to the optical internal coupling regions, discussed with reference to FIGS. 12A - 14C). One or more of the internal coupling regions may include one or more internal coupling optical elements and may be configured to direct light into one or more external coupling elements 1000A, 1000B, and 1000C within its associated waveguide. The external coupling elements may be segmented into different regions, as discussed herein. The configuration of the internal coupling regions and the external coupling regions within each of the stacked waveguides may correspond to any of the exemplary waveguide configurations, such as waveguide configurations, disclosed with reference to any one of FIGS. 11A - 14A.

[0245] As shown, the internal coupling optical regions 700A, 700B, 710A, 710B, 720A, and 720B may be laterally offset from each other. In some implementations, each internal coupling optical region may be offset so as to receive light without the light passing through another internal coupling optical region. For example, each of the internal coupling regions 700A, 700B, 710A, 710B, 720A, and 720B may be separated (e.g., laterally spaced) from the other internal coupling optical regions 700A, 700B, 710A, 710B, 720A, and 720B so as to substantially not receive light passing through the other internal coupling optical elements 700A, 700B, 710A, 710B, 720A, and 720B. In some embodiments, one or more of the internal coupling optical regions may share an image input device or may receive light from different image input devices.

[0246] The waveguides may be spaced or separated in a manner similar to the waveguide stack discussed with reference to FIG. 9A. In some implementations, the optical beams 770, 780, 790 are intended for different waveguides (e.g., waveguides configured to output light with different amounts of wavefront divergence and / or configured to output light with different properties such as different wavelengths or colors). Advantageously, different waveguides may be selected by directing light into different internal coupling regions, thereby providing an image light output with different amounts of wavefront divergence. Thus, in some implementations, a particular internal coupling region may be associated with a particular waveguide (for coupling light into that waveguide) and also with a particular external coupling region within that waveguide (for directing the internally coupled light towards the associated external coupling region). (Directing Light to the External Coupling Region)

[0247] The display system may selectively direct light to one or more external coupling regions of the display by identifying a region for outputting image light and directing the image light to that external coupling region. FIG. 15 illustrates an exemplary light directing process 3000 for directing light to an external coupling region of a display.

[0248] Continuing to refer to FIG. 15, in block 3002, the display system may determine a desired location of a virtual object on the display, which may include a waveguide having a viewing area that may include externally coupled elements segmented into a plurality of externally coupled regions. If the display system is an AR or VR system, the system may identify a desired and / or perceived location within the user's 3D environment for displaying the virtual object and determine an associated location within an area of the display. For example, an application of the display system may send instructions to the display system to display a virtual object, such as a butterfly, at a specified location within the user's physical environment. The display system may determine that the specified location corresponds to a projected location of the virtual object on the display, such as the upper right corner of the display. For example, the area of the display that provides image light to form the virtual object may correspond to an expected intersection between the viewing area of the display and an expected path of light from the virtual object to the pupil of the eye.

[0249] The projected location on the display may include the entire area of the display, across which the virtual object may be projected. For example, if the virtual object is a large object, such as a tree, that may occupy a majority of the user's field of view, the desired location may include a large percentage area of the display. In another example, if the virtual object is a small object, such as a butterfly, that will occupy a small portion of the user's field of view, the desired location may include a small percentage area of the display. In another example, the display system may display more than one virtual object. In an embodiment with more than one virtual object, the display system may determine multiple locations, areas, or regions of the display for displaying the virtual objects.

[0250] The representation of virtual objects in 3D space may take into account the user's eye pose, and it should be understood that the area of the display for presenting the virtual objects may change over time as the user's eye pose changes. For example, the location of a virtual object may be anchored to a physical object, and as the user's eye moves relative to the physical object serving as an anchor, the location of the virtual object within the user's field of view may change, which may cause a corresponding change in the area of the display utilized to output the image light. The display system may identify the user's eye pose based on one or more eye-tracking processes as discussed herein. In some implementations, as discussed herein, to provide a perception of virtual objects as being located within the user's 3D environment, the display may output light from positions on an external coupling element associated with that location such that the light propagates from a direction corresponding to that location to the eye.

[0251] In block 3004, the display system may identify one or more external coupling regions associated with the determined location. For example, the display may include a plurality of external coupling regions. One or more determined locations or areas of the display may span and obtain one or more external coupling regions. The display system may identify external coupling regions associated with locations or areas of the display that correlate to one or more displayed virtual objects.

[0252] In block 3006, the display system may send instructions to output light to one or more identified external coupling regions. For example, the display system may send instructions to a controller to project light onto an internal coupling region associated with the identified external coupling region. For example, the internal coupling region may include one or more light redirection structures such as one or more diffraction gratings. The display system may selectively direct light to the internal coupling region using a light input system as discussed with reference to FIGS. 20 - 22.

[0253] In some other implementations, the display system may display different representations of virtual objects according to the user's eye pose. For example, the display system may utilize foveated rendering techniques to reduce the resolution of virtual content and the computational effort involved in displaying the virtual content based on, for example, the distance from the center (e.g., the fixation point) of the user's field of view to the virtual object. For example, the display system may be configured to display a virtual object at a relatively high (e.g., maximum) resolution when the virtual object coincides with the user's eye fixation point and at a relatively low resolution when the virtual object is at the periphery of the user's field of view. Foveated rendering techniques are discussed in U.S. Patent Application Publication No. 2018 / 0275410, published on September 27, 2018, and entitled "DEPTH BASED FOVEATED RENDERING FOR DISPLAY SYSTEMS", the entire disclosure of which is incorporated herein by reference. Example of Region Determination Using Eye Pose Determination

[0254] As discussed above with reference to FIG. 15, the desired location of the display for outputting image light may be determined at least in part based on the user's eye pose. For example, as discussed above, the desired location may correspond to the intersection within the viewing area of the display (e.g., on the waveguide) of the light from the 3D location of the virtual object in the user's environment to the pupil of the user's eye.

[0255] Alternatively, for at least some content (e.g., display system menu items and alerts, or other content not anchored to a location within the physical world), the area of the display for outputting image light may simply be selected based on the user's eye pose. For example, the display system menu may simply be associated with the user's eye pose such that the menu remains within the user's field of view regardless of the eye pose.

[0256] FIG. 16 is an example of a flowchart of an external attachment location determination process 3100 using eye pose. At block 3102, the display system may receive one or more eye images from an imaging system. The imaging system may include an inwardly directed imaging system such as one or more cameras associated with the display of the display system. The imaging system may be configured to image the user's left and / or right eye. As will be described in detail below with reference to FIG. 17A, the eye image may include an image of the eye including one or more features of the eye such as the eyelid, sclera, iris, and pupil.

[0257] At block 3104, the display system may determine the eye pose of the user's eye. For example, the display system may analyze one or more eye images and determine the eye pose. In some embodiments, the eye pose may include the center of rotation of the user's eye, the line of sight direction, other orientations of the user's eye, or some combination thereof. As will be described in detail with reference to FIGS. 17B and 32C, the display system may utilize one or more eye tracking modules to analyze the image and identify the eye pose.

[0258] In block 3106, the display system may determine a region of the display associated with an eye pose for rendering virtual content using the eye pose. For example, the display system may use one or more engines, as described in detail with reference to FIGS. 17B and 32C, to calculate display positions on the display for rendering virtual content at various locations relative to the pupil of the eye, e.g., along a vector that intersects the center of rotation or perspective center of the user's eye. (Exemplary eye image for use in eye tracking)

[0259] FIG. 17A illustrates an image of an eye 3200 with an eyelid 3204, a sclera 3208 (the “white” of the eye), an iris 3212, and a pupil 3216. Curve 3216a indicates the pupil boundary between the pupil 3216 and the iris 3212, and curve 3212a indicates the edge boundary between the iris 3212 and the sclera 3208. The eyelid 3204 includes an upper eyelid 3204a and a lower eyelid 3204b. The eye 3200 is illustrated in a natural rest pose (e.g., both the user's face and line of sight are oriented such that they would be directed towards an object distant from the user's direct front). The natural rest pose of the eye 3200 may be indicated by a natural rest direction 3200, which is a direction orthogonal to the surface of the eye 3200 when in the natural rest pose (e.g., straight out from the plane of the eye 3200 shown in FIG. 17A), and which, in this embodiment, is centered within the pupil 3216.

[0260] As the eye 3200 moves to face different objects, the eye pose will change with respect to the natural rest direction 3200. The current eye pose may be determined with reference to the eye pose direction 3204, which is the direction orthogonal to the surface of the eye (and centered within the pupil 3216), but is oriented towards the object at which the eye is currently directed. Referring to the exemplary coordinate system shown in FIG. 17A, the pose of the eye 3200 can be represented as two angular parameters, both indicating the azimuth deviation and zenith deviation of the eye pose direction 3204 of the eye with respect to the natural rest direction 3200 of the eye. For illustrative purposes, these angular parameters can be represented as θ (azimuth deviation, determined from the base azimuth) and φ (zenith deviation, sometimes also referred to as the polarity deviation). In some implementations, the angular roll of the eye around the eye pose direction 3204 may be included in the determination of the eye pose, and the angular roll may be included in subsequent analysis. In other implementations, other techniques for determining the eye pose, such as pitch, yaw, and optionally, a roll system, may be used.

[0261] Eye images may be obtained from video using any suitable process, such as a video processing algorithm that can extract the image from one or more sequential frames. The pose of the eye may be determined from the eye image using various eye tracking techniques. For example, the eye pose may be determined by considering the lens effect of the cornea on the provided light source. Any suitable eye tracking technique may be used to determine the eye pose. (Example of an eye tracking system)

[0262] FIG. 17B illustrates a schematic diagram of a wearable system 3230 that includes an eye tracking system. The wearable system 3230 may include, in at least some implementations, components located within a head-mounted unit 3232 and components located within a non-head-mounted unit 3234. The non-head-mounted unit 3234 may be, by way of example, a belt-mounted component, a handheld component, a component within a backpack, a remote component, etc. Incorporating some of the components of the wearable system 3230 within the non-head-mounted unit 3234 can help reduce the size, weight, complexity, and cost of the head-mounted unit 3232. In some implementations, some or all of the functionality described as being implemented by one or more components of the head-mounted unit 3232 and / or the non-head-mounted 3234 may be provided using one or more components included anywhere within the wearable system 3230. For example, some or all of the functionality described below and associated with the CPU 3242 of the head-mounted unit 3232 may be provided using the CPU 3246 of the non-head-mounted unit 3234, and vice versa. In some embodiments, some or all of such functionality may be provided using the peripheral devices of the wearable system 3230. Additionally, in some implementations, some or all of such functionality may be provided using one or more cloud computing devices or other remotely located computing devices in a manner similar to that described above with reference to FIG. 9D. Additionally, the wearable system 3230 may correspond to the display system 60 (FIG. 9D), and it should be understood that in some implementations, the head-mounted unit 3232 and the non-head-mounted unit 3234 may correspond to a local data processing module 140 and a remote processing module 150, respectively.

[0263] As shown in FIG. 17B, the wearable system 3230 may include an eye-tracking system that captures an image of the user's eye 3240, including a camera 3270. Optionally, the eye-tracking system may also include light sources 3260a and 3260b (in some implementations, visible light, or in other implementations, non-visible light, such as infrared light, for example, light-emitting diodes “LEDs” that can emit light). The light sources 3260a and 3260b may generate a flash (for example, a reflection from the user's eye that appears in the image of the eye captured by the camera 3270). The positions of the light sources 3260a and 3260b relative to the camera 3270 may be known, and as a result, the position of the flash in the image captured by the camera 3270 may be used when tracking the user's eye (as will be discussed in more detail below). In at least one implementation, there may be one light source 326 and one camera 3270 associated with a single one of the user's eyes 3240. In another implementation, there may be one light source 326 and one camera 3270 associated with both of the user's eyes 3240. In yet another implementation, there may be one or more cameras 3270 and one or more light sources 326 associated with one or each of the user's eyes 3240. As a specific example, there may be two light sources 3260a and 3260b and one or more cameras 3270 associated with each of the user's eyes 3240. As another example, there may be three or more light sources, such as light sources 3260a and 3260b, and one or more cameras 3270 associated with each of the user's eyes 3240. In some implementations described herein, two or more cameras may be employed to image a given eye.

[0264] The eye tracking module 3244 may receive an image from the eye tracking camera 324, analyze the image, and extract various information. As an example, the eye tracking module 3244 may detect the user's eye pose, the three-dimensional position of the user's eyes relative to the eye tracking camera 3270 (and the head-mounted unit 3232), the direction in which one or both of the user's eyes 3240 are focused, the user's vergence / accommodation motion depth (e.g., the depth from the user at which the user is focused), the position of the user's pupils, the position of the user's cornea and / or corneal sphere, one or each rotation center of the user's eyes, and one or each perspective center of the user's eyes, or any combination thereof. The eye tracking module 3244 may extract such information using the techniques described below in connection with FIG. 17C. As shown in FIG. 17B, in some implementations, the eye tracking module 3244 may be a software module implemented using the CPU 3242 within the head-mounted unit 3232.

[0265] One camera 3270 is shown in FIG. 17B as imaging the eye, but in some implementations as discussed herein, multiple cameras may image the eye and be used for measurements such as corneal center and / or rotation center measurement, or alternatively, may be used for eye tracking or other purposes.

[0266] Data from the eye tracking module 3244 may be provided to other components within the wearable system. As an example, such data may be transmitted to components within a non-head-mounted unit 3234, such as the CPU 3246, including software modules for the light field rendering controller 3248 and the alignment observer 3250.

[0267] The rendering controller 3248 may adjust the image to be displayed to the user by the rendering engine 3252 (e.g., a software module within the GPU 3250 that can provide images to the display 220) using the information from the eye tracking module 3244. As an example, the rendering controller 3248 may adjust the image to be displayed to the user based on the user's center of rotation or perspective center. In particular, the rendering controller 3248 may use the information regarding the user's perspective center to simulate the rendering camera (e.g., simulate the collection of images from the user's eye height), and may adjust the image to be displayed to the user based on the simulated rendering camera.

[0268] Sometimes referred to as a "pinhole perspective camera" (or simply, a "perspective camera") or a "virtual pinhole camera" (or simply, a "virtual camera"), a "rendering camera" is potentially a simulated camera for use in rendering virtual image content from a database of objects within a virtual world. The objects can have a location and orientation relative to a user or wearer and potentially relative to real objects within an environment surrounding the user or wearer. In other words, the rendering camera can represent an eye height within a rendering space from where a user or wearer should view 3D virtual content (e.g., virtual objects) within the rendering space. The rendering camera can be managed by a rendering engine and can render a virtual image based on a database of virtual objects to be presented to the eye. The virtual image can be rendered as if captured from the eye height of the user or wearer. For example, the virtual image can be rendered as if captured by a pinhole camera (corresponding to the "rendering camera") having a specific set of intrinsic parameters (e.g., focal length, camera pixel size, principal point coordinates, distortion / aberration parameters, etc.) and a specific set of extrinsic parameters (e.g., translation and rotation components relative to the virtual world). The virtual image is captured from the eye height of such a camera having the position and orientation of the rendering camera (e.g., the extrinsic parameters of the rendering camera). The system is thus capable of defining and / or adjusting the intrinsic and extrinsic rendering camera parameters. For example, the system can define a specific set of extrinsic rendering camera parameters such that the virtual image can be rendered as if captured from the eye height of a camera having a specific location relative to the eye of the user or wearer so as to provide an image that appears to be from the eye height of the user or wearer. The system can later dynamically adjust the extrinsic rendering camera parameters on-the-fly to maintain alignment with that specific location. Similarly, the intrinsic rendering camera parameters can also be defined and dynamically adjusted over time.In some implementations, the image is rendered as if captured from the camera's eye height, having an aperture (e.g., a pinhole) at a specific location relative to the user's or wearer's eye (such as the center of perspective or rotation or any location).

[0269] In some implementations, the system may create or dynamically reposition and / or reorient one rendering camera for the user's left eye and another rendering camera for the user's right eye as the user's eyes are physically separated from each other and thus consistently positioned at different locations. In at least some implementations, virtual content rendered from the eye height of the rendering camera associated with the viewer's left eye may be presented to the user through the left eyepiece of a head-mounted display (e.g., head-mounted unit 3232), and virtual content rendered from the eye height of the rendering camera associated with the user's right eye may be presented to the user through the right eyepiece of such a head-mounted display. Further details regarding the creation, adjustment, and use of the rendering camera in the rendering process are provided in U.S. Patent Application No. 15 / 274,823, entitled "METHODS AND SYSTEMS FOR DETECTING AND COMBINING STRUCTURAL FEATURES IN 3D RECONSTRUCTION", which is hereby expressly incorporated by reference in its entirety for all purposes.

[0270] In some embodiments, one or more modules (or components) of the system 3230 (e.g., the light field rendering controller 3248, the rendering engine 3250, etc.) may determine the position and orientation of a rendering camera within the rendering space based on the position and orientation of the user's head and eyes (e.g., as determined based on head pose and eye tracking data, respectively). That is, the system 3230 effectively maps the position and orientation of the user's head and eyes to specific locations and angular positions within the 3D virtual environment, positions and orients the rendering camera at the specific locations and angular positions within the 3D virtual environment, and may render virtual content for the user as would be captured by the rendering camera. Further details discussing the mapping process between the real world and the virtual world are provided in U.S. Patent Application No. 15 / 296,869, entitled "SELECTING VIRTUAL OBJECTS IN A THREE-DIMENSIONAL SPACE", which is hereby expressly incorporated by reference in its entirety for all purposes. As an example, the rendering controller 3248 may adjust the depth at which an image is displayed by selecting a depth plane (or depth planes) upon which the image is utilized to display the image at any given time. In some implementations, such depth plane switching may be done through the adjustment of one or more intrinsic rendering camera parameters. For example, the light field rendering controller 3248 may adjust the focal length of the rendering camera when performing a depth plane switch or adjustment. As will be described in further detail below, the depth plane may be switched based on the user's determined convergence / divergence motion or fixed depth.

[0271] The alignment observer 3250 may identify whether the head-mounted unit 3232 is properly positioned on the user's head using information from the eye-tracking module 3244. As an example, the eye-tracking module 3244 may provide eye location information such as the position of the center of rotation of the user's eyes, indicating the three-dimensional position of the user's eyes relative to the camera 3270 and the head-mounted unit 3232. The eye-tracking module 3244 may use the location information to determine whether the display 220 is properly aligned within the user's field of view, or whether the head-mounted unit 3232 (or headset) is slipping or otherwise misaligned with the user's eyes. As an example, the alignment observer 3250 may determine whether the head-mounted unit 3232 is slipping from the user's nasal bridge and thus moving the display 220 away from and downward relative to the user's eyes (which may not be desirable), whether the head-mounted unit 3232 is moving above the user's nasal bridge and thus moving the display 220 closer to and above the user's eyes, whether the head-mounted unit 3232 is offset to the left or right relative to the user's nasal bridge, whether the head-mounted unit 3232 is lifted above the user's nasal bridge, or whether the head-mounted unit 3232 is moving away from the desired position or range of positions in these or other ways. Generally, the alignment observer 3250 may be able to determine whether the head-mounted unit 3232, and in particular the display 220, is properly positioned in front of the user's eyes. In other words, the alignment observer 3250 may determine whether the left display within the display system 220 is properly aligned with the user's left eye and whether the right display within the display system 220 is properly aligned with the user's right eye. The alignment observer 3250 may determine whether the head-mounted unit 3232 is properly positioned by determining whether the head-mounted unit 3232 is positioned and oriented within the desired position and / or orientation range relative to the user's eyes.

[0272] In at least some implementations, the alignment observer 3250 may generate user feedback in the form of an alert, message, or other content. Such feedback may be provided to the user to inform the user of any misalignment of the head-mounted unit 3232, along with optional feedback regarding a method for correcting the misalignment (such as a proposal to adjust the head-mounted unit 3232 in a particular manner).

[0273] Exemplary alignment observation and feedback techniques that may be utilized by the alignment observer 3250 are described in U.S. Patent No. 10,573,042, issued on February 25, 2020, entitled "PERIOCULAR TEST FOR MIXED REALITY CALIBRATION," and U.S. Patent Application Publication No. 2019 / 0222830, published on July 18, 2019, entitled "DISPLAY SYSTEMS AND METHODS FOR DETERMINING REGISTRATION BETWEEN A DISPLAY AND A USER’S EYES" (both of which are hereby incorporated by reference in their entireties). (Example of an eye tracking module for eye pose determination)

[0274] A block diagram of an exemplary eye tracking module 614 that can be utilized to determine an eye pose is shown in FIG. 17C. As shown in FIG. 17C, the eye tracking module 614 may include various different sub-modules, may provide various different outputs, and may utilize various available data when tracking a user's eye. By way of example, the eye tracking module 614 may utilize available data including eye tracking incidental and intrinsic properties such as the geometric arrangement of a light source 326 and an eye tracking camera 3270 relative to the head-mounted unit 602, an assumed eye dimension 3304 such as a typical distance of about 4.7 mm between the center of the user's corneal curvature and the average center of rotation of the user's eye or a typical distance between the user's center of rotation and the center of perspective, and user-specific calibration data 3306 such as the interpupillary distance of a particular user. Additional examples of incidental properties, intrinsic properties, and other information that may be employed by the eye tracking module 614 are described in U.S. Patent Application No. 15 / 497,726 (Attorney Docket No. MLEAP.023A7), filed on Apr. 26, 2017, and issued on May 21, 2019, as U.S. Patent No. 10,296,792, entitled "IRIS BOUNDARY ESTIMATION USING CORNEA CURVATURE" (incorporated herein by reference in its entirety).

[0275] The image pre - processing module 3280 may receive an image from an eye camera such as the eye camera 3270 and may perform one or more pre - processing (e.g., adjustment) operations on the received image. As an example, the image pre - processing module 3280 may apply Gaussian blur to the image, may downsample the image to a lower resolution, may apply an unsharp mask, may apply an edge - sharpening algorithm, or may apply other suitable filters that assist in the detection, localization, and labeling of glints, pupils, or other features within the image from the eye camera 3270. The image pre - processing module 3280 may apply a low - pass filter such as an open filter or a morphological filter, which may remove high - frequency noise such as from the pupil boundary 516a (see FIG. 5), thereby removing noise that may interfere with pupil and glint determination. The image pre - processing module 3280 may output the pre - processed image to the pupil identification module 3282 and the glint detection and labeling module 3284.

[0276] The pupil recognition module 3282 may receive the pre - processed images from the image pre - processing module 3280 and may identify the regions of those images that contain the user's pupils. In some implementations, the pupil recognition module 3282 may determine the coordinates of the position of the user's pupil in the eye - tracking image from the camera 3270, or the coordinates of the center or centroid. In at least some implementations, the pupil recognition module 3282 may identify the contour (e.g., the contour of the pupil - iris boundary) in the eye - tracking image, identify the contour moments (e.g., the center of mass), apply the starburst pupil detection and / or Canny edge detection algorithm, exclude outliers based on intensity values, identify sub - pixel boundary points, correct for eye camera distortion (e.g., the distortion in the images captured by the eye camera 3270), apply the random sample consensus (RANSAC) iterative algorithm, fit an ellipse to the boundary in the eye - tracking image, apply a tracking filter to the image, and identify the sub - pixel image coordinates of the centroid of the user's pupil. The pupil recognition module 3282 may output pupil recognition data (which may indicate the regions of the pre - processed image module 3282 identified as showing the user's pupils) to the flash detection and labeling module 3284. The pupil recognition module 3282 may provide the 2D coordinates of the user's pupil (e.g., the 2D coordinates of the centroid of the user's pupil) in each eye - tracking image to the flash detection module 3284. In at least some implementations, the pupil recognition module 3282 may also provide the same type of pupil recognition data to the coordinate system normalization module 3288.

[0277] Pupil detection techniques that may be utilized by the pupil recognition module 3282 are described in U.S. Patent Publication No. 2017 / 0053165, published on February 23, 2017, and U.S. Patent Publication No. 2017 / 0053166, published on February 23, 2017, each of which is incorporated herein by reference in its entirety.

[0278] The flash detection and labeling module 3284 may receive the pre - processed image from module 3280 and the pupil identification data from module 3282. The flash detection module 3284 may use this data to detect and / or identify a flash (e.g., the reflection of light from the light source 326 from the user's eye) within the region of the pre - processed image that indicates the user's pupil. As an example, the flash detection module 3284 may search for bright regions in the eye - tracking image that are within the vicinity of the user's pupil and which are sometimes also referred to herein as "blobs" or local intensity maxima. In at least some implementations, the flash detection module 3284 may scale (e.g., enlarge) the pupil ellipse to include additional flashes. The flash detection module 3284 may filter the flashes by size and / or intensity. The flash detection module 3284 may also determine the 2D position of each flash within the eye - tracking image. In at least some embodiments, the flash detection module 3284 may determine the 2D position of the flash relative to the user's pupil, which may also be referred to as the pupil - flash vector. The flash detection and labeling module 3284 may label the flashes and output the pre - processed image with the labeled flashes to the 3D corneal center estimation module 3286. The flash detection and labeling module 3284 may also inherit data such as the pre - processed image from module 3280 and the pupil identification data from module 3282. In some implementations, the flash detection and labeling module 3284 may determine the light source (e.g., from among the plurality of light sources of the system, including infrared light sources 326a and 326b) that produced each identified flash. In these embodiments, the flash detection and labeling module 3284 may label the flashes with information identifying the associated light source and output the pre - processed image with the labeled flashes to the 3D corneal center estimation module 3286.

[0279] Pupil and flash detection, such as that implemented by modules such as modules 3282 and 3284, may use any suitable technique. As an example, edge detection may be applied to the eye image to identify the flash and pupil. Edge detection may be applied by various edge detectors, edge detection algorithms, or filters. For example, a Canny edge detector may be applied to the image to detect edges such as those within the lines of the image. The edges may include points that correspond to the maxima derivative function and are located along the line. For example, the pupil boundary 516a (see FIG. 5) may be located using a Canny edge detector. Using the determined location of the pupil, various image processing techniques may be used to detect the "pose" of the pupil 116. Determination of the eye pose of an eye image may also be referred to as detection of the eye pose of the eye image. The pose may also be referred to as the line of sight, the direction being faced, or the orientation of the eye. For example, the pupil may be facing left towards an object, and the pose of the pupil may be classified as a left-facing pose. Other methods may also be used to detect the location of the pupil or flash. For example, concentric rings may be located within the eye image using a Canny edge detector. As another example, an integral differential operator may be used to find the corneal limbus boundary of the pupil or iris. For example, a Daugman integral differential operator, a Hough transform, or other iris segmentation techniques may be used to return a curve that estimates the boundary of the pupil or iris.

[0280] The 3D corneal center estimation module 3286 may receive a pre-processed image from modules 3280, 3282, 3284, including the detected flash data and pupil identification data. The 3D corneal center estimation module 3286 may use this data to estimate the 3D position of the user's cornea. In some implementations, the 3D corneal center estimation module 3286 may estimate the center of curvature of the eye's cornea or the 3D position of the user's corneal sphere, e.g., generally, the center of an imaginary sphere having a surface portion that is coextensive with the user's cornea. The 3D corneal center estimation module 3286 may provide data indicating the estimated 3D coordinates of the corneal sphere and / or the user's cornea to the coordinate system normalization module 3288, the optical axis determination module 3292, and / or the light field rendering controller 618. Further details of the operation of the 3D corneal center estimation module 3286 are provided herein in connection with FIGS. 11-16C. Exemplary techniques for estimating the position of eye features such as the cornea or corneal sphere that may be utilized by the 3D corneal center estimation module 3286 and other modules within the wearable system of the present disclosure are discussed in U.S. Patent Application No. 15 / 497,3296, filed Apr. 26, 2017 (Attorney Docket No. MLEAP.023A7), which is incorporated herein by reference in its entirety.

[0281] The coordinate system normalization module 3288 may optionally be included within the eye tracking module 614 (as indicated by its dashed outline). The coordinate system normalization module 3288 may receive data from the 3D corneal center estimation module 3286 indicative of the estimated 3D coordinates of the center of the user's cornea (and / or the center of the user's corneal sphere), and may also receive data from other modules. The coordinate system normalization module 3288 may normalize the eye camera coordinate system, which may help to compensate for slippage of the wearable device (e.g., slippage of a head-mounted component from its normal resting position on the user's head, which may be identified by the alignment observer 620). The coordinate system normalization module 3288 may rotate the coordinate system and align the z-axis of the coordinate system (e.g., the convergence / divergence motion depth axis) with the corneal center (as indicated by the 3D corneal center estimation module 3286), and may translate the camera center (e.g., the origin of the coordinate system) parallel to a predetermined distance such as 30 mm from the corneal center (e.g., the module 3288 may zoom in or out on the eye tracking image depending on whether the eye camera 3270 is determined to be closer or farther than the predetermined distance). By using this normalization process, the eye tracking module 614 may be able to establish consistent orientation and distance within the eye tracking data, relatively independently of variations in the headset positioned on the user's head. The coordinate system normalization module 3288 may provide the 3D coordinates of the center of the cornea (and / or corneal sphere), pupil identification data, and pre-processed eye tracking images to the 3D pupil center locator module 3290.

[0282] The 3D pupil center locator module 3290 may receive data including the 3D coordinates of the center of the user's cornea (and / or corneal sphere), pupil location data, and pre - processed eye - tracking images, in a normalized or non - normalized coordinate system. The 3D pupil center locator module 3290 may analyze such data and determine the 3D coordinates of the user's pupil center in a normalized or non - normalized eye - camera coordinate system. The 3D pupil center locator module 3290 may determine the location of the user's pupil in three dimensions based on the 2D position of the pupil centroid (such as determined by module 3282), the 3D position of the corneal center (such as determined by module 3286), the assumed eye dimensions 3304 such as the size of the typical user's corneal sphere and the typical distance from the corneal center to the pupil center, and the optical properties of the eye such as the refractive index of the cornea (relative to the refractive index of air), or any combination of these. Techniques for estimating the position of eye features such as the pupil, which may be utilized by the 3D pupil center locator module 3290 and other modules within the wearable system of the present disclosure, are discussed in U.S. Patent Application No. 15 / 497,3296, filed on April 26, 2017 (Attorney Docket No. MLEAP.023A7), which is incorporated herein by reference in its entirety.

[0283] The optical axis determination module 3292 may receive data from modules 3286 and 3290 indicating the 3D coordinates of the user's cornea and the user's pupil center. Based on such data, the optical axis determination module 3292 may identify a vector from the position of the corneal center (e.g., from the center of the corneal sphere) to the user's pupil center, which may define the optical axis of the user's eye. As an example, the optical axis determination module 3292 may provide an output defining the user's optical axis to modules 3294, 3298, 3310, and 3312.

[0284] The center of rotation (CoR) estimation module 3294 may receive data from module 3292 that includes parameters of the user's eye's optical axis (e.g., data indicating the direction of the optical axis in a coordinate system with a known relationship to the head-mounted unit 602). For example, the CoR estimation module 3294 may estimate the center of rotation of the user's eye. The center of rotation may indicate the point around which the user's eye rotates when the user's eye rotates left, right, up, and / or down. The eye may not rotate completely around a single point, but assuming a single point may be sufficient. In at least some implementations, the CoR estimation module 3294 may estimate the center of rotation of the eye by moving a specific distance along the optical axis (identified by module 3292) from the center of the pupil (identified by module 3290) or the center of curvature of the cornea (such as identified by module 3286) towards the retina. This specific distance may be the assumed eye dimension 3304. As an example, the specific distance between the center of curvature of the cornea and the CoR may be about 4.7 mm. This distance may be varied for a particular user based on any relevant data including the user's age, gender, visual prescription, other relevant characteristics, etc.

[0285] In at least some implementations, the CoR estimation module 3294 may refine the estimated value of the center of rotation of each of the user's eyes over time. As an example, as time passes, the user may eventually rotate the eye (to look at something else, closer, farther away, or sometimes left, right, up, or down), causing an offset to the optical axis of each of the eyes. The CoR estimation module 3294 may then analyze two (or more) optical axes identified by module 3292 and locate the 3D point of intersection of those optical axes. The CoR estimation module 3294 may then determine that the center of rotation is at that 3D point of intersection. Such techniques may provide an estimated value of the center of rotation with an accuracy that improves over time.

[0286] Various techniques may be employed to increase the accuracy of the CoR estimation module 3294 and the determined CoR positions of the left and right eyes. As an example, the CoR estimation module 3294 may estimate the CoR by finding the average point of the intersections of the optical axes determined over time for various different eye postures. As an additional example, the module 3294 may filter or average over time the estimated CoR positions, may calculate a moving average of the estimated CoR positions over time, and / or may apply a Kalman filter and the known dynamics of the eye and eye tracking system to estimate the CoR position over time. In some implementations, a least squares approach may be taken to determine one or more points of intersection of the optical axes. In such implementations, the system may identify, at a given point in time, the location where the sum of the squared distances to a given set of optical axes is reduced or minimized as the intersection of the optical axes. As a specific example, the module 3294 may calculate a weighted average of the determined intersection of the optical axes and the assumed CoR position (such as 4.7 mm behind the center of curvature of the cornea of the eye) such that as eye tracking data regarding the user is acquired, the determined CoR slowly drifts over time to a somewhat different location within the user's eye from the assumed CoR position, thereby enabling per-user refinement of the CoR position.

[0287] Under ideal conditions, the 3D position of the user's true CoR of the eye with respect to the HMD should change negligibly or by a minimal amount over time as the user moves their eye (e.g., as the user's eye rotates around its center of rotation). In other words, for a given set of eye movements, the 3D position of the user's true CoR (with respect to the HMD) should hypothetically vary no more over time than any other point along the optical axis of the user's eye. Thus, the further a point along the optical axis is from the user's true CoR of the eye, the more variation or dispersion its 3D position will exhibit over time as the user moves their eye. In some implementations, the CoR estimation module 3294 and / or other sub-modules of the eye tracking module 614 may utilize this statistical relationship to improve CoR estimation accuracy. In such implementations, the CoR estimation module 3294 and / or other sub-modules of the eye tracking module 614 may refine the estimated value of the CoR 3D position over time by identifying the variation of its CoR estimates that have low variation (e.g., low dispersion or standard deviation).

[0288] As a first example, in an implementation where the CoR estimation module 3294 estimates the CoR based on the intersection of a plurality of different optical axes (each associated with a user looking in a different direction), the CoR estimation module 3294 may introduce a common offset in each direction of the optical axes (e.g., shift each axis by a uniform amount) and utilize this statistical relationship (the true CoR should have low dispersion) by determining whether the offset optical axes intersect within an intersection that has low variation, e.g., low dispersion or standard deviation. This can help correct for even a small systematic error in calculating the direction of the optical axes and refine the estimated position of the CoR to be closer to the true CoR.

[0289] As a second example, the CoR estimation module 3294 estimates the CoR by moving it a specific distance (e.g., the distance between the center of curvature of the cornea and the CoR, etc.) along the optical axis (or other axis). In an implementation, the system may vary, optimize, adjust, or otherwise regulate a specific distance between the center of curvature of the cornea and the CoR over time in a manner that reduces or minimizes variations, such as the variance and / or standard deviation of the estimated CoR position (e.g., for a large group of eye images captured at different times). For example, the CoR estimation module 3294 initially uses a specific distance value of 4.7 mm (along the optical axis from the center of curvature of the cornea) to obtain an estimated CoR position. However, if the true CoR of a given user's eye can be located 4.9 mm behind the center of curvature of the eye's cornea (along the optical axis), the initial set of CoR position estimates obtained by the CoR estimation module 3294 may exhibit a relatively high amount of variation, such as a variance or standard deviation. In response to the detection of such a relatively high amount of variation (e.g., variance or standard deviation), the CoR estimation module 3294 may search for and identify one or more points along the optical axis that have a lower amount of variation (e.g., variance or standard deviation), and may identify a 4.9 mm distance that has the lowest variation (e.g., variance or standard deviation), and thus may adjust the specific distance value utilized to 4.9 mm.

[0290] The CoR estimation module 3294 may search for an alternative CoR estimate having lower variability (e.g., variance and / or standard deviation) in response to detecting that the current CoR estimate has a relatively high amount of variability (e.g., variance or standard deviation), or may necessarily search for an alternative CoR estimate having lower variability (e.g., variance or standard deviation) after obtaining the initial CoR estimate. In some embodiments, such optimization / regulation may occur gradually over time, while in other embodiments, such optimization / regulation may be performed during an initial user calibration session. In embodiments where such a procedure is performed during the calibration procedure, the CoR estimation module 3294 may not initially adhere to any assumed specific distance, but rather may collect a set of eye-tracking data over time, perform a statistical analysis on the set of eye-tracking data, and based on the statistical analysis, determine a specific distance value that results in a CoR position estimate with the least possible amount of variability (e.g., variance or standard deviation) (e.g., a global minimum).

[0291] The interpupillary distance (IPD) estimation module 3296 may receive data from the CoR estimation module 3294 indicating the estimated 3D positions of the centers of rotation of the user's left and right eyes. The IPD estimation module 3296 may then estimate the user's IPD by measuring the 3D distance between the centers of rotation of the user's left and right eyes. Generally, the distance between the estimated CoR of the user's left eye and the estimated CoR of the user's right eye can be approximately equal to the distance between the user's pupil centers when the user is looking at optical infinity (e.g., the optical axes of the user's eyes are substantially parallel to each other), which is the typical definition of the interpupillary distance (IPD). The user's IPD may be used by various components and modules within the wearable system. As an example, the user's IPD may be provided to the alignment observer 620 and used when assessing the degree to which the wearable device is aligned with the user's eyes (e.g., whether the left and right display lenses are appropriately spaced according to the user's IPD). As another example, the user's IPD may be provided to the convergence / divergence motion depth estimation module 3298 and used when determining the user's convergence / divergence motion depth. The module 3296 may employ various techniques such as those discussed in relation to the CoR estimation module 3294 to increase the accuracy of the estimated IPD. As an example, the IPD estimation module 3294 may apply filtering, averaging over time, weighted averaging including an assumed IPD distance, a Kalman filter, etc. as part of estimating the user's IPD in an accurate manner.

[0292] The convergence-divergence motion depth estimation module 3298 may receive data from various modules and sub-modules within the eye tracking module 614 (as shown in connection with FIG. 17C). In particular, the convergence-divergence motion depth estimation module 3298 may employ data indicative of the estimated 3D position of the pupil center (such as provided by the module 3290 described above), one or more determined parameters of the optical axis (such as provided by the module 3292 described above), the estimated 3D position of the center of rotation (such as provided by the module 3294 described above), the estimated IPD (e.g., the Euclidean distance between the estimated 3D positions of the centers of rotation) (such as provided by the module 3296 described above), and / or one or more determined parameters of the optical and / or visual axis (such as provided by the module 3292 and / or the module 3310 described below). The convergence-divergence motion depth estimation module 3298 may detect or otherwise obtain a measurement of the user's convergence-divergence motion depth, which may be the distance from the user at which the user's eyes are focused. As an example, when the user is looking at an object 3 feet in front of them, the user's left and right eyes have a convergence-divergence motion depth of 3 feet, while when the user is looking at a distant scene (e.g., the optical axes of the user's eyes are substantially parallel to each other such that the distance between the user's pupil centers can be approximately equal to the distance between the centers of rotation of the user's left and right eyes), the user's left and right eyes have a convergence-divergence motion depth of infinity. In some implementations, the convergence-divergence motion depth estimation module 3298 may utilize data indicative of the estimated center of the user's pupil (such as provided by the module 3290) to determine the 3D distance between the estimated centers of the user's pupils. The convergence-divergence motion depth estimation module 3298 may obtain a measurement of the convergence-divergence motion depth by comparing such a determined 3D distance between the pupil centers with the estimated IPD (e.g., the Euclidean distance between the estimated 3D positions of the centers of rotation) (such as shown by the module 3296 described above).In addition to the 3D distance between the pupil center and the estimated IPD, the convergence / divergence motion depth estimation module 3298 may calculate the convergence / divergence motion depth using known, assumed, estimated, and / or determined geometric shapes. As an example, the module 3298 may combine the 3D distances between the pupil center, the estimated IPD, and the 3DCoR position in a triangulation calculation to estimate (e.g., determine) the user's convergence / divergence motion depth. In fact, the evaluation of such a 3D distance between pupil centers determined for the estimated IPD may serve to indicate a measurement of the user's current convergence / divergence motion depth relative to optical infinity. In some embodiments, the convergence / divergence motion depth estimation module 3298 may simply receive or access data indicating the estimated 3D distance between the estimated centers of the user's pupils for the purpose of obtaining such a measurement of the convergence / divergence motion depth. In some implementations, the convergence / divergence motion depth estimation module 3298 may estimate the convergence / divergence motion depth by comparing the user's left and right optical axes. In particular, the convergence / divergence motion depth estimation module 3298 may estimate the convergence / divergence motion depth by locating the distance from the user where the user's left and right optical axes intersect (or where the projections of the user's left and right optical axes on a plane such as a horizontal plane intersect). The module 3298 may utilize the user's IPD in this calculation by setting zero depth to be the depth at which the user's left and right optical axes are separated by the user's IPD. In at least some implementations, the convergence / divergence motion depth estimation module 3298 may determine the convergence / divergence motion depth by triangulating eye tracking data along with known or derived spatial relationships.

[0293] In some implementations, the vergence / accommodation depth estimation module 3298 may estimate the user's vergence / accommodation depth based on the intersection of the user's visual axes (instead of their optical axes), which may provide a more accurate indication of the distance at which the user is focused. In at least some implementations, the eye tracking module 614 may include an optical axis to visual axis mapping module 3310. As will be discussed in more detail in connection with FIG. 10, the user's optical and visual axes are generally not aligned. The visual axis is the axis along which a person is looking, while the optical axis is defined by the person's lens and pupil center and may pass through the center of the person's retina. In particular, the user's visual axis is generally defined by the location of the user's fovea, which is offset from the center of the user's retina, thereby resulting in different optical and visual axes. In at least some of these implementations, the eye tracking module 614 may include an optical axis to visual axis mapping module 3310. The optical axis to visual axis mapping module 3310 may correct for the difference between the user's optical and visual axes and provide information regarding the user's visual axis to other components within the wearable system, such as the vergence / accommodation depth estimation module 3298 and the light field rendering controller 618. In some embodiments, the module 3310 may use an assumed eye dimension 3304 that includes a typical inward (nasal, i.e., towards the user's nose) offset of about 5.2° between the optical and visual axes. In other words, the module 3310 may offset the user's left optical axis 5.2° to the right (nasally) towards the nose and the user's right optical axis 5.2° to the left (nasally) towards the nose to estimate the directions of the user's left and right optical axes. In other embodiments, the module 3310 may utilize user-specific calibration data 3306 when mapping the optical axis (e.g., as shown by the module 3292 described above) to the visual axis. As an additional embodiment, the module 3310 may offset the user's optical axis nasally by 4.0° - 6.5°, 4.5° - 6.0°, 5.0° - 5.4°, etc., or any range formed by any of these values.In some arrays, module 3310 may apply an offset, at least in part, based on characteristics of a particular user, such as their age, gender, visual prescription, or other relevant characteristics, and / or at least in part based on a calibration process for a particular user (e.g., to determine the optical axis - visual axis offset for a particular user). In at least some implementations, module 3310 may also offset the origin of the left and right optical axes and correspond to the user's CoP (as determined by module 3312) instead of the user's CoR.

[0294] Optional perspective center (CoP) estimation module 3312, when provided, may estimate the locations of the user's left and right perspective centers (CoP). The CoP can be a useful location for a wearable system and, in at least some implementations, is the location directly in front of the pupil. In at least some implementations, CoP estimation module 3312 may estimate the locations of the user's left and right perspective centers based on the 3D location of the user's pupil center, the 3D location of the center of curvature of the user's cornea, or such suitable data, or any combination thereof. As an example, the user's CoP can be approximately 5.01 mm in front of the center of curvature of the cornea (e.g., 5.01 mm in the direction from the center of the corneal sphere, towards the user's cornea, and along the optical axis), and can be approximately 2.97 mm behind the outer surface of the user's cornea along the optical or visual axis. The user's perspective center can be directly in front of their pupil center. As an example, the user's CoP can be less than about 2.0 mm from the user's pupil, less than about 1.0 mm from the user's pupil, or less than about 0.5 mm from the user's pupil, or within any range between any of these values. As another example, the perspective center can correspond to a location within the anterior chamber of the eye. As another example, the CoP can be from 1.0 mm to 2.0 mm from the user's pupil, about 1.0 mm, from 0.25 mm to 1.0 mm, from 0.5 mm to 1.0 mm, or from 0.25 mm to 0.5 mm.

[0295] (As the pinhole of the rendering camera and as a potentially desirable position as the anatomical position within the user's eye) The center of perspective described herein can be a position that serves to reduce and / or eliminate undesirable parallax shifts. In particular, the optical system of the user's eye roughly corresponds, respectively, to the user's pupil / iris, lens, and retina, using a pinhole, a lens, and a screen that projects onto the screen and is formed by the pinhole in front of the lens, comparable to a theoretical system. Further, when two point light sources (or objects) at different distances from the user's eye rotate rigidly about the opening of the pinhole (e.g., rotated along a radius of curvature equal to its individual distance from the opening of the pinhole), it may be desirable that there is little or no parallax shift. Thus, the CoP would be expected to be located at the center of the pupil of the eye (and such a CoP could be used in some implementations). However, the human eye includes a cornea that, in addition to the pupil's lens and pinhole, imparts additional refractive power to the light propagating towards the retina. Thus, the anatomical equivalent of the pinhole within the theoretical system described in this paragraph can be the region of the user's eye located between the outer surface of the user's eye's cornea and the center of the user's eye's pupil or iris. For example, the anatomical equivalent of the pinhole can correspond to the region within the anterior chamber of the user's eye. For various reasons discussed herein, it may be desirable to set the CoP to such a position within the anterior chamber of the user's eye.

[0296] As discussed above, the eye tracking module 614 may provide data such as the estimated 3D positions of the left and right eye centers of rotation (CoR), the vergence / accommodation depth, the left and right eye optical axes, the 3D positions of the user's eyes, the 3D positions of the centers of curvature of the user's left and right corneas, the 3D positions of the user's left and right pupil centers, the 3D positions of the user's left and right perspective centers, the user's IPD, etc. to other components such as the light field rendering controller 618 and the alignment observer 620 within the wearable system. The eye tracking module 614 may also include other sub-modules that detect and generate data associated with other aspects of the user's eyes. As an example, the eye tracking module 614 may include a blink detection module that provides a flag or other alert each time the user blinks, and a saccade detection module that provides a flag or other alert each time the user's eyes saccade (e.g., rapidly shift focus to another point).

[0297] Other methods of eye tracking and determination of the center of rotation are also conceivable. Thus, the eye tracking module 614 may vary. In the various implementations of the eye tracking module described below, for example, the estimated value of the center of rotation is determined based on multiple corneal center of curvature values. In some implementations, for example, as discussed with reference to FIGS. 17A - 19, the eye tracking module 614 may potentially estimate the center of rotation of the eye by determining a convergence or intersection from among the surface normal vectors of a surface that is fitted to multiple corneal centers of curvature for different eye postures. Note that one or more features from the eye tracking module 614 described above or anywhere in this specification may be included in other implementations of the eye tracking module.

[0298] Eye tracking techniques are discussed in U.S. Patent Application Publication No. 2019 / 0243558, published on August 8, 2019, titled "EYE CENTER OF ROTATION DETERMINATION, DEPTH PLANE SELECTION, AND RENDER CAMERA POSITIONING IN DISPLAY SYSTEMS", and International Publication No. WO2021 / 01166, published on January 21, 2021, titled "EYE CENTER OF ROTATION DETERMINATION WITH ONE OR MORE EYE TRACKING CAMERAS" (attorney docket number MLEAP.256WO (claiming priority to U.S. Provisional Application No. 62 / 874867, filed on July 16, 2019)) (the entire disclosures of each are incorporated herein by reference). (Exemplary light injection system)

[0299] As discussed above with reference to FIG. 15, the display system may identify one or more external coupling regions for receiving the image light to be output. Additionally, as discussed above, an eye pose may be determined to facilitate the determination of an appropriate external coupling region for the selection of external coupling image light. Once an appropriate external coupling region or regions are determined, the display system may be configured to determine an appropriate routing of the light to the external coupling region or regions. For example, functionally directing light to a particular external coupling region or regions may involve directing the image light into internal coupling regions that are uniquely associated with those external coupling regions.

[0300] FIG. 18 is a flow diagram of an exemplary light directing process 3320 that can be used to direct light to a determined external coupling region of a display. At block 3322, the display system may determine an internal coupling region for directing light toward the display. For example, the internal coupling region may include an internal coupling region associated with a desired rendering location on the display. The desired rendering location may be determined based on a determination process as described with reference to FIG. 16. In some embodiments, the internal coupling region may be an area, group, array, or other combination of internal coupling optical features such as an internal coupling lattice. As illustrated in FIG. 19, the internal coupling region of the display may include an array of internal coupling features arranged along a portion of the display. At block 3322, the display system may determine to direct light to the internal coupling region such that the light is directed to an appropriate associated external coupling region for forming at least a portion of a perceived image on the display.

[0301] In block 3324, the display system may determine an image for display to the user. The image may include a representation of virtual content to be displayed within the user's environment, and the image may include part or all of the virtual content. For example, the display system may receive an indication to display a tree. The display system may determine a representation of the tree for projection onto the determined internal binding region or a part of the tree for projection onto the determined internal binding region. In some embodiments, the display system may split an image or representation of a virtual object that traverses and obtains a plurality of external binding regions of the viewing area of the display. In such a case, to display the full effect of the virtual object, the display system may split the image such that light projected onto a part of the image within a first region of the display contains the part of the image associated with that region during rendering. In some embodiments, the image may contain a portion of the representation of the virtual object that overlaps by an amount to prevent gaps in rendering when displaying a large object across regions of the display.

[0302] In block 3326, the display system may send instructions for directing light to the internal coupling region. As discussed above, the directed light may include image information for forming an image for display from an external coupling region of the display associated with that internal coupling region. The display system may utilize one or more light input systems to direct light to the internal coupling region. For example, as illustrated in FIG. 19, the display system may include a controller 3402, a light input system 3404, a waveguide 3412, and a camera 3408. The controller 3402 may communicate instructions to the light input system 3404 and direct or input light 3410 to a selected internal coupling region such as internal coupling regions 3414A, 3414B, or 3414C on the waveguide 3412. As discussed above with reference to FIGS. 16 - 17C, the display system may determine, for example, based on the user's eye pose, the internal coupling region 3414A, 3414B, 3414C or internal coupling optical elements 3416A, 3416B, 3416C associated with the internal coupling region to which the light should be input. The user's eye pose may be determined by the display system using an image from one or more cameras 3408 configured to image at least one eye of the user. The input light may propagate through one or more waveguides associated with the display towards the associated external coupling regions 3418A, 3418B, 3418C. One or more external coupling optical elements within the external coupling regions 3418A, 3418B, 3418C may output the light towards the user's eye 3406. It should be understood that the internal coupling regions 3414A, 3414B, 3414C may correspond to any of the internal coupling regions identified by reference numerals 1005, 700, 710, and 720 and various subscripts (see, for example, FIGS. 11A and 14B).

[0303] The controller 3402 may include one or more software engines to implement the processes and functions described herein. The software engines may include programmed instructions to implement processes as discussed herein (and illustrated in the flowcharts) to direct the light projection system to project light towards regions of the display. The engines may be executed by one or more hardware processors associated with the display system. The programming instructions may be stored in memory associated with the display system. The programming instructions may be implemented in C, C++, JAVA®, or any other suitable programming language. In some implementations, some or all of the portions of the controller 3402, including the engines, may be implemented within application specific circuitry such as ASICs and FPGAs. Some aspects of the functionality of the controller 3402 may be executed remotely on a server via a network. Thus, the controller 3402 may be implemented using the hardware components (e.g., controller 560, processing module 140, and / or processing module 150) described above with reference to FIGS. 6 and 9D.

[0304] The light projection system may be any suitable system for selectively directing light towards a desired region. For example, as illustrated in FIGS. 20A-20D, the light projection system may include a movable projection mechanism such as a scanning fiber optic projector. In another example, as illustrated in FIGS. 21A-21D, the light projection system may include one or more movable mirrors to direct the light. Additionally or alternatively, the light projection system may utilize one or more stationary projection systems such as those that form images for different internal coupling regions at different locations of an SLM as described in detail with reference to FIG. 22. However, while details of exemplary light projection systems may be discussed, the display system may utilize any number or combination of light projection systems to direct light towards determined internal coupling regions. (Exemplary Mechanically Actuated Optical Input System)

[0305] The optical input system 3404 (FIG. 19) may, in some implementations, take the form of a movable injector system. The movable injector system may include one or more components configured to physically move optical components to direct light to desired locations such as internal coupling regions 3414A, 3414B, 3414C, etc. on waveguide 3412. FIGS. 20A - 20D and 21A - 21B illustrate two exemplary movable injector systems.

[0306] FIGS. 20A - 20D illustrate an implementation of an exemplary movable injector system 3500 that includes at least one scanning fiber injector 3527. It should be understood that the movable injector system 3500 may correspond to the optical input system 3404 (FIG. 19). The scanning fiber injector 3527 may include at least one light emitter 3528 and at least one actuator 3540 that moves fiber 3542. Light 3501 from the end of fiber 3542 may propagate through optical system 3534 towards internal coupling region 3510A' or 3510B' within waveguide 3526'. In some embodiments, as illustrated in FIG. 20A, the optical system 3534 may be a collimating optical system configured to receive light that spreads out from fiber 3542 and collimate the light before it propagates to internal coupling region 3510A' or 3510B'.

[0307] The collimating optical system may take various forms and may include one or more lens structures. In some embodiments, as illustrated in FIG. 20B, the optical system 3534 may include a lenticular lens having a plurality of lenses 3534L’, 3534L’’ (e.g., a lenslet array). Each of the plurality of lenses may be configured to provide collimated light to an associated internal coupling region 3510A’ or 3510B’. In some embodiments, as illustrated in FIG. 20C, the optical system 3534 may include a collimating lens structure 3534C for collimating incident light and a projection lens structure 3534P for propagating the collimated light to the internal coupling region 3510A’ or 3510B’. More generally, it should be understood that the optical system 3534 may include various combinations of lens structures and may perform the function of providing collimated light to a plurality of internal coupling regions such as the internal coupling regions 3510A’ or 3510B’. In some embodiments, as illustrated in FIG. 20D, the projection optical system 3534 may include a collimating lens structure 3534C and a projection lens structure 3534P including a convex lens 3534P’ and a lenticular lens having a plurality of lenses 3534L’, 3534L’’. It should be understood that other combinations of lenses are also contemplated.

[0308] Referring again to FIGS. 20A - 20D, the actuator 3540 may move the fiber 3542 at a known speed along a predetermined path (e.g., a circular path). As a result, the processing module 3638 may be configured to synchronize the propagation of light out of the end of the fiber 3542 with the movement of the fiber 3542 such that the image light propagates out of the fiber 3542 at a desired light output location and is thus synchronized with the image to be displayed.

[0309] In some implementations, the light source 3528 may be replaced with a virtual light source that is formed on the image plane of the light projection system. The light projection system may include an actuator capable of scanning a light beam across an area on the image plane corresponding to the virtual light source. As discussed herein, to mimic the ability to activate the discrete emission area of the light source 3528, the light output by the projection system is synchronized with the movement of the actuator and, at a particular time, outputs light to a desired location on the image plane. Preferably, the rate at which the actuator is capable of scanning a light beam across the image plane is high enough that all desired light output locations on the image plane can be accessed during a time frame in which any given pupil image is displayed therein. For example, during the amount of time that a particular image is displayed, the actuator is preferably capable of scanning a light beam across the area of the image plane corresponding to the virtual 2D light source at least once, preferably a plurality of times.

[0310] Figures 21A and 21B illustrate another exemplary movable input system 3600 that includes at least one scanning mirror system for directing the propagation of light to different locations. The light input system 3626 may include an image source 3628 capable of outputting image light, and mirrors 3630 and 3632 that are moved by actuators 3631 and 3633, respectively. Examples of the image source 3628 include one or more light sources and a spatial light modulator that encodes image information into the light passing from the light source through the spatial light modulator to the mirror 3632.

[0311] As shown, light 3501 may propagate from image source 3628 to mirror 3632, which reflects the light to mirror 3630, which in turn reflects the light propagating through projection optics 3634 toward internal coupling optical regions 3510A' or 3510B' of waveguide 3526'. Mirrors 3630 and 3632 may be part of a biaxial galvanometer, and actuators 3631 and 3633 rotate the mirrors along different axes, e.g., orthogonal axes, thereby enabling the light to be directed to an area defined along two axes of waveguide 3526'. In some implementations, actuators 3631, 3633 may be motors. Projection optics 3634 may be a linear transmission lens such as an F-theta (F-θ or F-tanθ) lens and may be configured to project light onto waveguide 3526' in an internal coupling optical region such as 3510A' or 3510B'. In some implementations, light input system 3626 may also include a collimating lens 3636 to collimate the light emitted by light emitter 3628 before the light reaches mirror 3632. In some embodiments, as shown in FIG. 21A, projection optics 3634 may include various lens structures. In some embodiments, as shown in FIG. 21B, projection optics 3634 may include a convex lens structure 3634P' and a plurality of lenses 3634L', 3634L'' configured to direct collimated light to an associated internal coupling optical region such as 3510A' or 3510B', a lenticular lens.

[0312] Continuing to refer to FIGS. 21A and 21B, the light input system 3626 preferably also includes, or communicates with, a processing module 3638 that controls the output of light from the light emitter 3628 and synchronizes the movement of the actuators 3631, 3633 with the image to be formed. For example, the processing module 3638 may coordinate the movement of the mirrors 3632, 3630 with the emission of light from the image source 3628. In some implementations, the mirrors 3632, 3630 are designed to be reciprocally and continuously rotated or pivoted about an axis on which the mirrors move, by the actuators 3631, 3633. The emission of light (e.g., a pulse of light) by the image source 3628 is timed and adjusted with this movement so that the light is directed to a desired location on the waveguide 3526' at a given instant, and this location and time are also determined based on the image to be displayed (e.g., the internal coupling region coincides temporally with the display of the image for that particular internal coupling region). In some implementations, the emission of light from the image source 3628 is controlled by switching the image source 3628 between an on state and an off state (e.g., by supplying or not supplying power to the light emitter, respectively). In some other implementations, the emission of light from the image source 3628 may be mechanically controlled using a physical switch that selectively enables or blocks the light from reaching the waveguide 3526'.

[0313] In some other implementations, instead of the two mirrors 3632 and 3630, the movable light input system 3600 may include only a single mirror configured to direct light along a single axis. Such a configuration may be utilized, for example, in an array in which internal coupling regions, such as 3510A' or 3510B', are arranged in a row along a single axis.

[0314] Several movable injector techniques are discussed in U.S. Patent Application Publication No. 2018 / 0113311, published on April 26, 2018, and titled "SYSTEM AND METHOD FOR PRESENTING IMAGE CONTENT ON MULIPLE DEPTH PLANES BY PROVIDING MULTIPLE INTRA-PUPIL PARALLAX VIEWS", the entire disclosure of which is incorporated herein by reference. (Exemplary electronically switchable optical output without mechanical actuation)

[0315] The light injection system 3404 may include an injector system in which the location of the output light is electronically switched without mechanical actuation. The stationary injector system may include one or more components configured to selectively emit light to direct the light towards desired locations such as internal coupling regions 3414A, 3414B, 3414C, etc. on the waveguide 3412.

[0316] FIG. 22 illustrates an exemplary stationary input system 3700 that includes a spatial light modulator (SLM) 3736 configured to project light 3501 onto waveguide 3526' toward one or more internal coupling optical regions 3710A', 3710B'. The stationary input system 3700 may include a light emitter 3728 and a spatial light modulator (SLM) 3736. Examples of light emitters 3528 include LEDs and lasers. In some implementations, an optical fiber cable may transmit light from a remotely located light emitter. As shown, light 3501 may propagate from light emitter 3728 to SLM 3736, which modulates the light and propagates it through optical system 3734 toward internal coupling optical region 3710A' or 3710B' within waveguide 3526'. In some implementations, SLM 3736 may be configured to modulate light transmitted through the SLM. In some other implementations, SLM 3736 may be configured to reflect and modulate light. Examples of SLMs include liquid crystal display panels, DLP mirror arrays, LCoS, etc. Optical system 3734 may be a linear transmission lens such as an F-theta (F-θ or F-tanθ) lens and may be configured to focus light onto an internal coupling optical region such as 3710A' or 3710B' on waveguide 3526'. However, other configurations of optical system 3734, such as a lens system including a collimating lens, a lenticular lens, or a combination of other lens structures, are also contemplated.

[0317] The SLM3736 may include a panel display, which may include an array of light emitters such as LEDs or lasers. To select an internal coupling optical region such as 3710A’ or 3710B’ for propagation, the controller 3738 communicates with the light input system 3700 and may activate a pixel, an array, or a group of pixels within the SLM3736 that can be associated with a desired internal coupling optical region or regions. In some implementations, different sections of the SLM may be utilized to form different images for different associated internal coupling regions 3710A’, 3710B’. In some implementations, the size of a group of activated light-emitting pixels on the light source SLM1020 may provide a smaller or larger image. In some other implementations, the size of the light-emitting area on the light source SLM3736 may be modified to control the depth of focus of the display system.

[0318] Some movable inputter techniques are discussed in International Patent Publication No. WO2019 / 173158, published on September 12, 2019, entitled "DISPLAY SYSTEM WITH LOW-LATENCY PUPIL TRACKER", the entire disclosure of which is incorporated herein by reference. (Exemplary depth plane projection)

[0319] Some implementations of the display device, such as those described above, may be configured to adjust the wavefront divergence of light (including light for image information projected from the display system and incident light from objects in the surrounding real world) by adjusting the focal length of a variable focal length lens element included within an augmented reality system. As discussed above, the augmented reality system may include a display device that projects light towards the eyes of a user or viewer (e.g., viewer or user 90 of FIG. 2), which may include a plurality of stacked waveguide (e.g., corresponding to the plurality or set 660 of stacked waveguides of FIGS. 9A and 9B, or corresponding to the stacked waveguide assembly 260 of FIG. 6). In some other implementations, the display device may include only a single waveguide. As a result, although a plurality of waveguides are referenced in various parts of the present disclosure, it should be understood that the plurality of waveguides may be replaced by a single waveguide.

[0320] As discussed herein, the light projected from the waveguide may be used to provide virtual or augmented reality image information to the viewer. The light may be projected such that the user perceives it as originating from one or more different depths or distances from the viewer. The display device may be optically transmissive so that the user can see real-world objects in the surrounding environment through the display device. In some implementations, the waveguide may be configured to have a fixed refractive power. To provide an appearance where the projected light appears to originate from different depths, the waveguide may be configured to output a divergent beam of light, with different amounts of divergence corresponding to different depth planes.

[0321] To provide a virtual object that presents a multi-dimensional sensation, the display system may display an image on a plurality of depth planes. In the case of an array of internal coupling elements, there are several ways to project an image onto a plurality of depth planes. These include a split pupil system as illustrated in FIG. 23, a variable focus lens system as illustrated in FIG. 24, and a system configured to approximate a continuous wavefront using a plurality of intra-pupil images as illustrated in FIGS. 25C and 25D. (Exemplary Split Pupil Depth Plane Projection)

[0322] In some embodiments, the depth plane projection may be accomplished by projecting an image towards internal coupling optical elements within a waveguide stack as described with reference to FIGS. 9A-9C above. In the case of an array of internal coupling regions within a waveguide, the depth plane projection may be accomplished, for example, by having a plurality of internal coupling optical regions for each internal coupling element corresponding to a particular depth plane.

[0323] FIG. 23 illustrates a top and bottom view of an internal coupling region 3800 that may include a plurality of internal coupling optical elements 3810A, 3810B, 3810C. A light emitter (not shown) may emit light of a wavelength corresponding to one of a plurality of colors towards the internal coupling elements 3810A, 3810B, 3810C. The internal coupling optical elements 3810A, 3810B, 3810C may be arranged to be spaced apart in the same manner as the light emitter. For example, the individual ones of the internal coupling optical elements 3810A, 3810B, 3810C may be in the direct optical path of the associated ones of the light emitters. The plurality of internal coupling optical elements such as elements 3810A, 3810B, 3810C, etc. may be arranged within a waveguide stack to provide a multi-depth plane projection for an image projected towards the region 3800 containing the internal coupling optical elements.

[0324] In the illustrated embodiment, there are nine internally coupled optical elements 3810. The nine internally coupled optical elements 3810 may be configured to project a single image having multiple colors on multiple depth planes. The nine internally coupled optical elements 3810 shown, for example, may include three elements configured to emit light of a first color (e.g., red), three elements configured to emit light of a second color (e.g., green), and three elements configured to emit light of a third color (e.g., blue). However, other numbers of internally coupled optical elements with other groupings are also possible. Each grouping may include internally coupled optical elements of different colors (e.g., each grouping may have one internally coupled optical element for a first color, one internally coupled optical element for a second color, and one internally coupled optical element for a third color), and each grouping may be configured to form an image on a specific depth plane. For example, the internally coupled optical elements 3810 may form three groups, with each group projecting an image onto an associated one of three depth planes. However, other numbers, arrangements, and configurations of internally coupled optical elements are also possible, such as six internally coupled optical elements configured to project the light of three primary colors onto two depth planes, twelve internally coupled optical elements configured to project the light of four colors onto three depth planes, etc.

[0325] In some embodiments, the internally coupled region may be configured to project light in multiple colors on multiple depth planes using time multiplexing. For example, the internally coupled element may include multiple internally coupled regions configured to project light on multiple depth planes. One or more light emitters may be coupled to the internally coupled element and project light of a specific color towards the internally coupled optical element at a specific time. If the time between color projections is fast enough, the resulting perceived image may be an image having all the colors projected towards the internally coupled optical element. (Exemplary variable focus lens configuration)

[0326] In some embodiments, the depth plane projection may be performed using a variable focus lens system. FIG. 24 illustrates an exemplary variable focus lens system 3900 that may be used to perform the depth plane projection.

[0327] Referring to FIG. 24, in some implementations, a first variable focus lens element may be provided between the waveguide and the viewer's eye to provide appropriate adjustment to the wavefront of the light output by the waveguide, enabling the light to be properly focused by the viewer's eye. However, this first lens element is also in the path of light propagating from the surrounding environment to the viewer's eye. As a result, the first lens element may modify the wavefront of light from the surrounding environment, thereby causing aberrations in the viewer's view of the world. To correct such aberrations, a second variable focus lens element may be disposed on the opposite side of the first variable focus lens element of the plurality of stacked waveguides, i.e., the second variable focus lens element is between the plurality of stacked waveguides and the surrounding real world and may adjust the wavefront of light from real world objects in the surrounding environment. The second variable focus lens element may be configured to compensate for aberrations caused by the first variable focus lens element. In some implementations, the second variable focus lens may also be configured to compensate for aberrations caused by the waveguide.

[0328] In some implementations, the focal point of the second variable focus lens element may be the inverse or opposite of the focal point of the first variable focus lens element. For example, if the first variable focus lens element has a positive refractive power, then the second variable focus lens element may have a negative refractive power, which may be of a similar magnitude. In some other implementations, the refractive power of the second lens element may be opposite and of a similar magnitude to the combined refractive power of the first lens element and the waveguide to compensate for both the refractive power of the first variable focus lens element and the refractive power of the intervening waveguide.

[0329] In some other implementations, the waveguide may not have a refractive power (e.g., the waveguide may be configured to output collimated light), and the first variable focus lens element may modify the wavefront of the light emitted from the waveguide and may be configured to provide an appropriate amount of divergence so that the image information is interpreted by the viewer as being on a particular depth plane. It should be understood that the appropriate amount of divergence may vary for different viewers because the refractive power for placing the image information on a particular depth plane is adjusted by a particular differential and will take into account the viewer's optical prescription for that depth plane. In such implementations, the waveguide stack between the first variable focus lens element and the second variable focus lens element may simply be formed by a single waveguide.

[0330] It should be understood that the first and second variable focus lens elements may be provided for one of the viewer's eyes, and third and fourth variable focus lens elements, each similar to the first and second variable focus lens elements, may be provided for the viewer's other eye.

[0331] FIG. 24 shows a schematic diagram of an exemplary display system (e.g., an augmented reality display system) having a variable focus lens element and a waveguide stack. It should be understood that the display system 3910 may correspond to the display system 250 (FIG. 6). The first variable focus lens element 3907a and the second variable focus lens element 3907b are disposed on opposite sides of the waveguide stack 3905, and the third variable focus lens element 3908a and the fourth variable focus lens element 3908b are disposed on opposite sides of the waveguide stack 3906.

[0332] The various illustrated waveguides 3905a, 3905b, 3906a, 3906b may have characteristics and / or features similar to those of the individual waveguides 270, 280, 290, 300, 310 of FIG. 6 and / or the waveguides 670, 680, and 690 of FIGS. 9A and 9B. The waveguide stacks 3905, 3906 may have characteristics and / or features similar to those of the stacked waveguide or waveguides of the plurality or set 660 of FIGS. 9A and 9B or the stacked waveguide assembly 260 of FIG. 6. In some implementations, the waveguides 3905a, 3905b, 3906a, 3906b may include optical elements, such as diffractive optical elements, that provide a refractive force, e.g., a fixed refractive force, to the waveguide. For example, one or more than one of these waveguides may have a refractive force in the range of 0 diopters to about 5.0 diopters, about 0.5 diopters to about 4.5 diopters, about 1.0 diopters to about 4.0 diopters, about 1.5 diopters to about 3.5 diopters, about 2.0 diopters to about 3.0 diopters, or any value within or within these ranges or sub-ranges. As another example, in a particular implementation, the waveguides may each have a refractive force of 1.5 diopters.

[0333] As discussed above, light providing image information (e.g., virtual content) from light source 3903 or 3904 may be introduced into waveguide 3905a or 3906a, respectively, such that the light propagates through each of those waveguides by total internal reflection. The propagating light may be projected out of waveguide 3905a (or waveguide 3905b) towards the user's eye 3901 by an external coupling element (e.g., corresponding to external coupling elements 800, 810, 839 of FIGS. 9A and 9B). In some implementations, light sources 3903, 3904 may be fiber scanning devices (FSDs) that utilize movable fibers to create 2D image patterns, as disclosed herein. The FSD may create a 2D image pattern by projecting light in various patterns such as raster scanning, spiral scanning, Lissajous, etc. In some other implementations, light source 3903a (and / or 3903b) may be an image projection system, as also disclosed herein, where, for example, a complete image is projected onto the waveguide. It should be understood that light from light source 3903a (and / or 3903b) may be introduced into waveguide stack 3905 through the edge of the waveguide or through the major surface of the waveguide. If the waveguide stack includes a plurality of waveguides, light sources 3903 and / or 3904 may be configured to introduce light into a plurality of these waveguides, or additional light sources, e.g., one light source per waveguide, may be provided.

[0334] The first variable focus lens element 3907a may be disposed between waveguide stack 3905 and the user's eye 3901, and the second variable focus lens element 3907b may be disposed between waveguide stack 3905 and the real world surrounding the user. It should be understood that eye 3901 may correspond to the viewer's eye 210 of FIG. 6. Similarly, the third variable focus lens element 3908a may be disposed between waveguide stack 3906 and the user's eye 3902, and the second variable focus lens element 3908b may be disposed between waveguide stack 3906 and the real world surrounding the user.

[0335] In some implementations, the first and second variable focus lens elements 3907a and 3907b and the third and fourth variable focus lens elements 3908a and 3908b may be adaptable optical elements. The adaptable optical elements may be dynamically modified, for example, by applying an electrical signal thereto and changing the shape of the wavefront incident thereon. In some implementations, the adaptable optical elements may comprise transmissive optical elements such as dynamic lenses (e.g., liquid crystal lenses, electroactive lenses, conventional refractive lenses with movable elements, mechanically deformable based lenses, electro-wetting lenses, elastomeric lenses, or multiple fluids with different refractive indices). By modifying the shape, refractive index, or other characteristics of the adaptable optical system, the wavefront incident thereon may be changed and, for example, modify the focusing of light by the viewer's eye as described herein.

[0336] In some implementations, the variable focus lens elements 3907a, 3907b, 3908a, 3908b may comprise a layer of liquid crystal that is sandwiched between two substrates. The substrates may comprise, for example, an optically transmissive material such as glass, plastic, acrylic, etc. In some implementations, the substrates may be flat. In some implementations, the substrates may have a curved region such that a portion of the substrate may have a fixed refractive power.

[0337] In some implementations, the refractive power of the variable focus lens elements 3907a, 3907b, 3908a, 3908b may be varied by adjusting, for example, an electrical signal (such as a current and / or voltage) applied to the liquid crystal layer via one or more thin film transistors (TFTs) and / or liquid crystal layers and / or electrodes integrated with the substrate. It should be understood that the orientation of the liquid crystal species within the liquid crystal layer determines the refractive index of the layer. The applied electrical signal sets the orientation of the liquid crystal species, thereby enabling the refractive index of the liquid crystal layer to be varied as desired by modifying the applied electrical signal. In some implementations, the refractive power of the variable focus lens elements 3907a, 3907b, 3908a, 3908b may be varied by about ±5.0 diopters (for example, about -4.0 diopters to +4.0 diopters, about -3.5 diopters to about +3.5 diopters, about -3.0 diopters to about +3.0 diopters, about -2.0 diopters to about +2.0 diopters, about -1.5 diopters to about +1.5 diopters (including values within any of these ranges or sub-ranges)).

[0338] Advantageously, the variable focus lens elements 3907a, 3907b, 3908a, 3908b may have a wide aperture that substantially matches the aperture of the waveguides of their respective associated waveguide stacks 3905, 3906. In some implementations, the aperture of the variable focus lens elements 3907a, 3907b, 3908a, 3908b may be substantially equal to the surface area of the waveguides of the waveguide stacks 3905, 3906 (for example, within about ±39%, about ±15%, or about ±10%). As a result, the area through which the variable focus lens elements 3907a, 3907b, 3908a, 3908b and the waveguide stacks 3905, 2396 transmit light to the associated eyes 3901, 3902 may be substantially equal.

[0339] Continuing to refer to FIG. 24, the first and third variable focus lens elements 3907a, 3908a may each vary their refractive power to adjust the wavefront of light projected from the waveguides of the waveguide stacks 3905, 3906, respectively, and thereby appropriately focus the light onto the retinas of the eyes 3901, 3902, respectively. As described herein, the first and third variable focus lens elements 3907a, 3908a may introduce aberrations into the wavefront of incident light from the object 3909 in the surrounding environment, thereby reducing the optical image quality of the real-world object 3909 as viewed through the first variable focus lens element 3907a. The second and fourth variable focus lens elements 3907b, 3908b may advantageously compensate for aberrations introduced by the first and third variable focus lens elements 3907a, 3908a and any waveguides, respectively, when viewing the object 3909. In some implementations, the second and fourth variable focus lens elements 3907b, 3908b may be configured to provide refractive powers opposite to the refractive powers provided by the first and third variable focus lens elements 3907a, 3908a and the associated waveguide stacks 3905, 3906, respectively. In some implementations, the magnitude of the opposite refractive power is such that, for each of the display systems 3910, eyes 3901, 3902, the net refractive power of the eye is equal to the optical prescription for the eye in the depth plane towards which the eye is converging. The refractive powers provided by the first and second variable focus lens elements 3907a and 3907b may be varied and controlled by an electronic hardware control system 3911. In some implementations, the electronic hardware control system 3911 may correspond to the local processing and data module 140 and / or the remote processing module 150 of FIG. 2.

[0340] In some implementations, the augmented reality display system 3910 may be configured to determine the convergence and divergence movements of the user's eyes. The refractive powers of the first and second variable focus lens elements 3907a, 3907b may be set based on the convergence and divergence movement points of the eyes 3901, 3902. The refractive powers of the third and fourth variable focus lens elements 3908a, 3908b may also be set based on the present convergence and divergence movement points. It should be understood that the convergence and divergence movement point is a point in space where the lines of sight of the eyes 3901, 3902 converge and may correspond to the physiological near and far accommodation targets of those eyes. In some implementations, the distance at which the point is away from the eyes 3901, 3902 may be calculated based on, for example, a known separation amount between the eyes 3901, 3902 and the angles made by each eye. Once that distance is calculated, an appropriate correction for the viewer with respect to that distance may be determined. For example, the display system 3910 may be programmed using one or more optical prescriptions. In some implementations, the optical prescription may be stored in the local processing and data module 140 and / or the remote data repository 160. The distance between the eyes 3901, 3902 and the convergence and divergence movement point may be matched with the appropriate correction for that distance, and the variable focus lens elements 3907a, 3907b, 3908a, 3908b may be adjusted to provide the correction. In some implementations, the eyes 3901, 3902 may have different pre-specified corrections, and as a result, the pair of variable focus lens elements 3907a, 3907b, and 3908a, 3908b may provide different refractive powers.

[0341] Advantageously, the variable focus lens elements 3907a, 3907b, 3908a, 3908b can provide a number of possible corrections since their refractive power can be adjusted as desired, for example, by the application of different voltages. In some implementations, the total number of corrections per eye may be 1, 2, 3, 4, or more. In some implementations, the total number of corrections per eye may be equal to the number of depth planes on which the display system 3910 is configured to display image information. It should be understood that these corrections may correspond to an optical prescription, which may be determined for objects at various distances from the eyes 3901, 3902. For example, four prescriptions may be obtained by determining corrections for refractive anomalies at four progressively greater distances (e.g., near, intermediate near, intermediate far, and far distances) from the eyes 3901, 3902. In some implementations, the number of possible corrections for viewing the image content output by the waveguide stack 3905 may be different from the number of possible corrections for viewing the objects 3909 in the surrounding environment.

[0342] In some implementations, the focus or refractive power of the variable focus lens elements 3907a, 3907b, 3908a, 3908b may be set based on the determined convergence / divergence movements of the user's eyes 3901, 3904, respectively. For example, the refractive powers of the first and second variable focus lens elements 3907a and 3907b may be varied based on the convergence / divergence movement of the user's eye 3901 without specifically referring to the refractive powers of the other lens elements.

[0343] In some implementations, one of the first and second variable focus lens elements 3907a, 3907b or one of the third and fourth variable focus elements 3908a, 3908b may be designated as the master, and the other of the first and second variable focus lens elements 3907a, 3907b or the other of the third and fourth variable focus elements 3908a, 3908b may be designated as the slave. The variable focus lens element designated as the slave may be configured to follow the master variable focus lens element. In some other implementations, the second and fourth variable focus lens elements 3907b, 3908b may be follow-up type with respect to the first and third variable focus lens elements 3907a, 3908a, and the foci of the first and third variable focus lens elements 3907a, 3908a may be set based on the determined convergence / divergence movement points of the user's eyes 3901, 3902. For example, if the waveguide 3905a (and / or the waveguide 3905b) has a refractive power of about 1.5 diopters and the user is converging at 2.0 diopters, the first variable focus lens element 3907a may have a refractive power of +0.5 diopters, and the second variable focus lens element 3907b may have a refractive power of -0.5 diopters.

[0344] The refractive powers of the variable focus lens elements 3907a, 3907b, 3908a, 3908b may be varied in real time, and preferably, may be changed at a rate equal to or higher than the rate at which the human eye changes its focusing state there. Preferably, the first and second variable focus lens elements may change their refractive powers before the human eye changes its focusing state so as not to incur a delay when the user receives an appropriate correction for a given convergence / divergence movement point. In some implementations, the first and second variable focus lens elements may change their refractive powers in less than about 300 ms, less than about 275 ms, or less than about 250 ms. The electronic hardware control system 3911 may drive the variable focus lens elements 3907a, 3907b, 3908a, 3908b so that the refractive powers of the variable focus lens elements 3907a, 3907b, 3908a, 3908b can be varied simultaneously.

[0345] The variable focus lens technique is discussed in U.S. Patent Application Publication No. 2017 / 0293145, published on October 12, 2017, entitled "AUGMENTED REALITY SYSTEMS AND METHODS WITH VARIABLE FOCUS LENS ELEMENTS" (the entire disclosure of which is incorporated herein by reference). Exemplary wavefront approximation using multiple intra-pupil images

[0346] It has been found that continuous wavefronts such as wavefront 4000 in FIG. 25A can be approximated using multiple wavefronts. In some embodiments, depth plane selection can be accomplished by approximating the continuous wavefront at one or more desired depth planes using multiple discrete intra-pupil images directed into the eye within the flicker fusion threshold.

[0347] Referring now to FIG. 25A, the pre-accommodation and post-accommodation states of the eye 210 in response to reception of the continuous input wavefront 4000 are illustrated. Illustration a) shows the pre-accommodation state before the visual system focuses the wavefront 4000 onto the retina 211. Notably, the focus 212 is not on the retina 211. For example, the focus 212 can be in front of the retina 211 as illustrated. Illustration b) shows the post-accommodation state after the human visual system has relaxed the pupil muscle tissue of the viewer's eye 210 and focused the wavefront 4000 onto the retina 211. As illustrated, the focus 212 can be on the retina 211.

[0348] FIG. 25B illustrates the state of the eye 210 before and after focusing adjustment with respect to the reception of the piecewise approximation of the continuous wavefront 4000 of FIG. 25A. Illustration a) of FIG. 25B shows the state of the eye 210 before focusing adjustment, and illustration b) shows the state after focusing adjustment. The approximation may be formed using a plurality of component wavefronts 1010a, 1010b, and 1010c, each associated with a separate light beam. As used herein, the reference numerals 1010a, 1010b, and 1010c may indicate both the light beam and the wavefront associated with that light beam. In some implementations, the component wavefronts 1010a and 1010b may be planar wavefronts such as those formed by a collimated light beam. As shown in illustration b), the wavefront approximation 1010 formed by the component wavefronts 1010a and 1010b is focused by the eye 210 onto the retina 211, with a focal point 212 on the retina 211. Advantageously, the states before and after focusing adjustment are similar to those caused by the continuous wavefront 4000 shown in FIG. 25A.

[0349] It should be understood that the continuous diverging wavefront can be approximated using an optical projection system that outputs a plurality of parallax-differentiated pupil images into the eye. FIG. 25C illustrates an eye that focuses on a diverging wavefront emitted from a finite focal length virtual image provided by a projection system. The system includes a spatial light modulator 4018 and a projection optical system 1020, with a focal length "F" and an external stop. The image may be formed by the spatial light modulator 1018, and the light from the spatial light modulator 4018 containing the image information may be directed through the projection optical system 4020 towards the eye 210. The distance (less than F) between the spatial light modulator 4018 and the projection optical system 4020 may be selected such that the diverging wavefront 4000 is output towards the eye 210. As described above with respect to FIG. 25A, the eye 210 may then focus the wavefront 4000 onto the retina 211.

[0350] Continuing to refer to FIG. 25C, an embodiment of a display system 4001 is illustrated that includes a projection system 4003 for forming the diverging wavefront approximation 4010 of FIG. 25B. The projection system 4003 includes a light source 4026 configured to output light 4010a' and 4010b' to a spatial light modulator 4018 that modulates the light to form images that show slightly different parallax views of the same object or scene. The modulated light, accompanied by image information, then propagates through a relay / projection optical system 4020 and is output into the eye 210 as light beams 4010a and 4010b by the relay / projection optical system 4020. The projection system 4003 may also include a lens structure 4014, which may be configured to convert a spatial difference in the emission of light 4010a' and 4010b' into an angular difference in the propagation of that light to the spatial light modulator 4018. The projection system 4003 further includes a polarization beam splitter 4016 configured to 1) direct light from the light source 4026 to the spatial light modulator 4018 and 2) enable the modulated light from the spatial light modulator 4018 to propagate back through the beam splitter 4016 to the relay / projection optical system 4020. In some implementations, the display system 4001 may include an eye tracking device 4022, such as a camera, configured to monitor the viewer's line of sight. Such monitoring may be used to determine the direction the viewer is looking, which may be used to select appropriate image content for that direction and for eye pose determination, as discussed herein. Preferably, the eye tracking device 4022 tracks both eyes of the viewer, or each eye includes its own associated eye tracking device. As a result, the convergence / divergence movement of both eyes of the viewer can be tracked, and the eye convergence point may be determined to determine the direction and distance the eyes are directed.

[0351] As discussed herein, lights 4010a' and 4010b' may be output by light source 4026 at different times, and spatial light modulator 4018 may form different parallax views using lights 4010a' and 4010b' at different times. It should be understood that the resulting light beams 4010a and 4010b may be introduced into eyes 210 at different times.

[0352] Continuing to refer to FIG. 25C, light source 4026 may be a 2D light source having a plurality of selectively activatable light output locations that are substantially disposed on a plane. In some implementations, the selectively activatable light output locations may be selectively activatable light emitting regions. For example, light source 4026 may be a light emitting diode (LED) array, or a spatial light modulator (e.g., a digital micromirror device such as a digital light processing (DLP) device, an LCOS device, etc.) containing an array of discrete units or light emitters that output light. Examples of LED arrays include organic light emitting diode (OLED) arrays and inorganic light emitting diode (ILED) arrays, each of which may be part of a microdisplay. In some implementations, the individual light emitting diodes and / or light modulators within light source 4026 may constitute a light emitting region. In some other implementations, a group of light emitting diodes and / or light modulators may form a light emitting region. In such implementations, there may be some overlap between the light emitting diodes and / or light modulators of different light emitting regions, but the regions can be considered clearly different because the overlap is not complete.

[0353] In some other implementations, the light source 4026 may be configured to focus light onto the image plane and effectively provide a virtual 2D light source on that image plane. Different locations on the image plane may be considered different light output locations, and those locations may be activated by using an actuated mirror or a fiber scanner to direct light through those locations on the image plane and steering the light from the light emitter. Further details regarding such virtual 2D light sources are provided in the discussions of FIGS. 19 and 20 below.

[0354] In some implementations, an embodiment of the spatial light modulator 4018 includes a liquid crystal on silicon (LCOS) panel. As another example, in some other implementations, the spatial light modulator 4018 may comprise a transmissive liquid crystal panel or a MEMS device such as a DLP.

[0355] Continuing to refer to FIG. 25C, display system 4001 may also include a control system 4024 for determining the timing and type of image content provided by the display system. In some implementations, control system 4024 comprises one or more hardware processors with memory storing a program for controlling display system 4001. For example, system 4024 may be configured to control the activation of the emission regions of light source 4026, the operation of the individual pixel elements of spatial light modulator 4018, and / or the interpretation and reaction of display system 4001 to data received from eye tracking device 4022. Preferably, system 4024 includes a calculation module 4024a configured to receive an input regarding a desired depth plane or wavefront divergence, calculate an appropriate emission region for activation to form a parallax view with an appropriate amount of disparity for the desired depth plane or wavefront divergence. Additionally, calculation module 4024a may be configured to determine the appropriate operation of the pixels of spatial light modulator 4018 and form an image of the desired parallax view. This system 4024 may also include a synchronization module 4024b configured to synchronize the activation of specific emission regions of light source 4026 with the modulation of light by spatial light modulator 4018 and form an image to provide a parallax view corresponding to the activated emission regions. Additionally, system 4024 may include an eye tracking module 4024c that receives input from eye tracking device 4022. For example, eye tracking device 4022 may be a camera configured to image eye 210. Based on the image captured by eye tracking device 4022, eye tracking module 4024c may be configured to determine the orientation of the pupil and extrapolate the line of sight through eye 210. This information may be electronically communicated to calculation module 4024a. Calculation module 4024a may be configured to select image content based on the line of sight or gaze of eye 210 (preferably, also based on the line of sight or gaze of the other eye of the viewer).

[0356] Since the light source 4026 may include an array of off-axis light emitters, the size and shape of the light emitting region formed by the light emitters may be varied, as desired, by activating selected ones of the light emitters. For example, different emission regions may be activated for different parallax views. In one embodiment, the elongated light emitting regions may be horizontally spaced apart, which may be desirable for horizontal parallax-only drive focus adjustment. In another embodiment, the circular light emitting regions may have both horizontal and vertical displacement. In another embodiment, the light emitting regions may have luminance attenuation. In another embodiment, the light emitting regions may overlap. In another embodiment, the light emitting regions may form an array. Thus, the light source 4026 (FIG. 25C) may include binary light emitters (simply turned on and off), and / or light emitters that incorporate grayscale (emit light of selectively variable intensity). In some implementations, the light source 4026 may include elements that switch at a very high rate, including a rate that exceeds the parallax switching rate for the system 4001. For example, the light source 4026 may have a light output element that switches the light output on and off at a rate higher than the rate at which the parallax (intra-pupil) images are switched in an implementation where different intra-pupil images are displayed at different times therein.

[0357] It should be understood that different amounts of wavefront divergence may be approximated by appropriate selection of the physical distances separating the light emitters that are activated to form different intra-pupil images. The light emitters of the light source 4026 may direct light from different angles through the projection optics to approximate different amounts of wavefront divergence and provide a parallax-disparate intra-pupil image. In some implementations, a relatively large distance between individual light sources may provide wavefront divergence corresponding to a relatively near depth plane, while a relatively small distance between individual light sources may provide wavefront divergence corresponding to a relatively far depth plane.

[0358] Referring again to FIG. 25C, in some implementations, the control system 4024 may include two parts, namely, 1) light field generation and 2) decomposed light field optimization. As discussed herein, in order to approximate the wavefront, appropriate images are displayed on the spatial light modulator 4018 for each of the illuminated regions where the light source 4026 is activated. These images are created during the light field generation step, and it should be understood that the 3D scene is rendered from a plurality of slightly offset viewpoints corresponding to slight offsets within the illuminated regions that are activated. For example, to display a 5×5 light field, the 3D scene will be rendered from 25 different viewpoints arranged in a grid pattern 25 times. The location of the viewpoints within the grid pattern corresponds to the location of the illuminated source regions that are activated, and the rendered images will correspond to the images formed by the spatial light modulator.

[0359] It may be desirable to increase the brightness of the images formed by the spatial light modulator 4018. Advantageously, utilizing the light source 4026 comprising an array of light emitters enables the formation of illuminated regions having various shapes and sizes, which may be utilized to increase the brightness. In some implementations, the brightness may be increased by increasing the size of the illuminated regions that are activated without significantly changing the images formed by the spatial light modulator 4018. The calculation module 4024a may be configured to use decomposed light field optimization to determine the size and shape of the illuminated regions that are activated. Module 4024a may be configured to create a series of patterns for display on the spatial light modulator 4018 and on the light source 4026 using a pattern that is configured to utilize the input focus stack to create a desired approximation to the focus stack in a least squares concept. The optimization takes advantage of the fact that small offsets in the viewpoints do not significantly change the images that are perceived, and it is possible to generate an illuminated region pattern that utilizes illumination from a larger area on the light source 4026 while displaying the same image on the spatial light modulator 4018.

[0360] The optimization problem can be formulated as a non-convex optimization problem given below.

Chem.

Chem.

[0361] In some other implementations, the optimization problem can be formulated as a slightly different non-convex optimization problem as given below.

Chem.

[0362] Continuing to refer to FIG. 25C, it should be understood that the flicker fusion threshold of the human visual system imposes a time constraint on the number of images that can be projected into the eye 210 while still being perceived as being projected simultaneously. For example, the processing bandwidth of the control system 4024 and the ability to switch the light modulator of the light source 4026 and the spatial light modulator 4018 can limit the number of images that can be projected into the eye 210 within the duration allowed by the flicker fusion threshold. Given this f...

Claims

1. 1. A display system comprising: A light projection system; 1. A head-mountable display configured to project light into a user's eye and display virtual image content, the head-mountable display comprising at least one waveguide, the at least one waveguide comprising: a plurality of optical in-coupling regions configured to receive light from the optical projection system; a plurality of light out-coupling regions configured to output light to the eye of the user; the plurality of optical outcoupling regions are arranged in a grid pattern across the waveguide; each optical incoupling region of the plurality of optical incoupling regions is associated with a respective one of the plurality of optical outcoupling regions; The light received by each optical incoupling region comprises: directed to and output by a respective optical outcoupling region associated with each of the optical incoupling regions; a head mountable display that is not directed to and output by other light outcoupling regions not associated with each of the light incoupling regions; processing electronics in communication with the head mountable display and the optical projection system; Equipped with The processing electronics includes one or more processors and one or more computer storage media that store instructions that, when executed by the one or more processors, cause the one or more processors to: determining a light outcoupling area associated with an eye posture of the eye; determining a light incoupling region associated with the light outcoupling region associated with the eye posture of the eye; providing instructions for directing light from the light projection system to the determined light in-coupling area associated with the determined light out-coupling area such that the light is received by the determined light in-coupling area and directed to the determined light out-coupling area associated with the eye posture; A display system that performs an operation including:

2. The display system of claim 1 , wherein determining the light outcoupling region comprises determining an intersection of a line of sight of the eye with one of the plurality of light outcoupling regions.

3. The display system of claim 1 , wherein the light in-coupling regions are arranged in a line around at least one side of the plurality of out-coupling regions.

4. The display system of claim 1 , wherein the light projection system comprises at least one light source and at least one movable light launcher configured to output image light.

5. The display system of claim 4 , wherein the at least one movable light launcher comprises a scanning mirror.

6. The display system of claim 4 , wherein the at least one movable light launcher comprises a scanning fiber launcher.

7. 10. The display system of claim 1, wherein the optical projection system comprises at least one light source and at least one spatial light modulator configured to modulate light from the light source.

8. The display system of claim 1 , wherein the head-mountable display is configured to display virtual objects on multiple depth planes.

9. 10. The display system of claim 8, wherein the actions include injecting a set of parallaxly disparate intra-pupillary images of the virtual object into the eye and displaying the virtual object on one of the depth planes.

10. 10. The display system of claim 9, wherein said action includes casting each of said set of parallaxly disparate intrapupillary images within a flicker fusion threshold.

11. The display system of claim 8 , wherein the action includes providing instructions to direct light to a plurality of internal coupling elements within an optical internal coupling region of the plurality of internal coupling regions associated with the determined optical external coupling region.

12. 10. The display system of claim 8, further comprising at least one variable focus lens element on a user side of the at least one waveguide, the at least one variable focus lens element configured to modify the projected light to correct for refractive error of the eye of the user.

13. The display system of claim 12 , wherein the actions further include determining a fixation point of the eye and applying a correction corresponding to the fixation point.

14. and an inwardly facing imaging system configured to capture one or more images of the eye of the user, the operation comprising: receiving an image of the user's eye captured by the inwardly facing imaging system; identifying the eye posture based on the received image; The display system of claim 1 further comprising:

15. the at least one waveguide is one of a plurality of waveguides forming a waveguide stack, each of the waveguides comprising a plurality of the inner and outer coupling regions; 2. The display system of claim 1, wherein the internal coupling regions of each of the waveguides are laterally spaced apart from one another as viewed in a front plan view when viewed from the direction of incident light incident on the internal coupling regions.

16. the outcoupling regions of the same waveguide are configured to output light with the same wavefront divergence; the outcoupling regions of the different waveguides are configured to output light with a different amount of wavefront divergence than the outcoupling regions of the at least one other waveguide; The display system of claim 15 , wherein the different amounts of wavefront divergence correspond to different depth planes.

17. the incoupling region of each waveguide is configured to incoupling light in a range of wavelengths corresponding to a same primary color; 16. The display system of claim 15, wherein the incoupling regions of some waveguides are configured to incouple light in ranges of wavelengths corresponding to different primary colors than the incoupling regions of other waveguides.

18. 2. The display system of claim 1 , wherein the optical projection system comprises a plurality of projectors, each of which is configured to provide image content for at most a subdivided portion of a field of view of the head-mountable display.

19. A display system as described in claim 1, wherein the multiple optical internal coupling regions are laterally spaced apart from each other.

Images