Micro-led multi-emitter / color display microlens array

Abstract

An HMD comprises a head-mountable frame, and a light projection assembly supported by the frame. The light projection assembly comprises a micro-display supported by the frame. The micro-display has a two-dimensional array of pixels. Each of the pixels comprises a group of light emitters configured for emitting image light. The micro-display further comprises projection optics configured for receiving the image light at an entrance pupil from the group of light emitters of each of the array of pixels, and projecting focused image light from an exit pupil. The micro-display further comprises a two-dimensional array of light collimators disposed between the micro-display and the projection optics. A steerable light collimator is further configured for redirecting the emission profiles of the corresponding group of light emitters towards a center of the entrance pupil of the projection optics.

Description

MICRO-LED MULTI-EMITTER / COLOR DISPLAY MICROLENS ARRAYINCORPORATION BY REFERENCE

[0001] This application claims priority to U.S. Provisional Application Ser. No. 63 / 506,550, filed on June 6, 2023, the contents of which are hereby expressly and fully incorporated by reference in its entirety.FIELD OF THE INVENTION

[0002] The present disclosure generally relates to display systems, and more particularly, to extended reality (XR) display systems.BACKGROUND

[0003] Modern computing and display technologies have facilitated the development of head-mounted displays (HMDs) for so called extended reality (XR) experiences that create an environment for a user in which some or all of the environment is generated by presenting digitally reproduced images (e.g., virtual objects) to a user in a manner where they seem to be, or may be perceived as, real. XR HMDs may be useful for many applications, spanning the fields of scientific visualization, medical training, engineering design and prototyping, tele-manipulation and tele-presence, and personal entertainment. An XR HMD may include, e.g., a virtual reality (VR) HMD, an augmented reality (AR) HMD, or a mixed reality (MR) HMD. A VR HMD typically involves the presentation of digital or virtual image information without transparency to other actual real-world visual input. An AR HMD or MR HMD typically involves presentation of virtual objects to a user in relation to real objects of the physical world. In particular, an AR HMD involves the presentation of digital or virtual image information as an augmentation to visualization of the actual world around the user. An MR HMD involves the presentation of AR image content that appears to be blocked by or is otherwise perceived to interact with objects in the real world.

[0004] Many HMDs utilize transmissive or reflective spatial light modulator (SLM) displays to form images that are presented to the user A light source emits light, which is directed to the SLM display, which then modulates the light, which is then directed to the user.Lens structures may be provided between the light source and the SLM display to focus light from the light sources onto the SLM display. Undesirably, the light source and related optics may add bulkiness and weight to the HMD. This bulkiness and weight may adversely impact the comfort of the HMD and the ability to wear the HMD for long durations.

[0005] In addition, the frame rate limitations of some HMDs may cause viewing discomfort. For example, many SLM displays utilize movement of optical elements to modulate the intensity of light output by these SLM displays to form the images. For example, micro-electromechanical systems (MEMs)-based SLM displays may utilize moving mirrors to modulate the incident light, while liquid crystal on silicon (LCoS)-based displays may utilize the movement of liquid crystal molecules to modulate light. Other HMDs may utilize scanning-fiber technology in which the end of an optical fiber physically moves across an area while outputting light. The light outputted by the optical scanning fiber is timed with the position of the end of the fiber, thereby effectively mimicking pixels at different locations to form images.

[0006] The requirement that the optical fibers, mirrors, and liquid crystals physically move limits the speed at which individual pixels may change states and also constrains the frame rate of HMDs utilizing SLM displays or optical scanning fiber displays. Such limitations may cause viewing discomfort due to, for example, motion blur and / or mismatches between the orientation of the user’s head and the displayed image. For example, there may be latency in the detection of the orientation of the user’s head and the presentation of images consistent with that orientation. In the timespan between detecting the orientation and presenting an image to the user, the user’s head may have moved. The present image, however, may correspond to a view of an object from a different orientation. Such mismatch between the orientation of the user’s head and the presented image may cause discomfort in the user (e.g., nausea).

[0007] In addition, scanning-fiber displays may present other undesirable optical artifacts due to, for example, the small cross-section of the fibers, which requires the use of a high- intensity light source to form images of desirable apparent brightness. Suitable high-intensity light sources include lasers, which output coherent light. Undesirably, the use of coherent light may cause optical artifacts.

[0008] Micro-LED displays have been proposed as replacements for the above-noted SLM displays and scanning-fiber displays. Micro-LED displays have various advantages for use in HMDs. As an example, micro-LED displays are emissive. The power consumption of emissive micro-LED displays generally varies with image content, such that dim or sparse content requires less power to display. Since AR and MR environments may often be sparse — since it may generally be desirable for the user to be able to see their surrounding environment — emissive micro-LED displays may have an average power consumption below that of other display technologies that use an SLM to modulate light from a light source. In contrast, other display technologies may utilize substantial power even for dim, sparse, or “all-off” virtual content. As another example, emissive micro-LED displays may offer an exceptionally high frame-rate (which may enable the use of a partial-resolution array) and may provide low levels of visually apparent motion artifacts (for example, motion blur). As another example, emissive micro-LED displays may not require polarization optics of the type required by LCoS displays. Thus, emissive micro-LED displays may avoid the optical losses present in polarization optics.

[0009] Many micro-LED displays may include planar light emitters formed on a substrate, whereas other micro-LED displays may include nano-wire LEDs formed of arrays of vertically extending nanowires (for example, spaced-apart pillars of material) electrically connected to two electrodes, and that emit light upon application of current through the nanowires, as described in U.S. Patent No. 11 ,604,354, which is expressly incorporated herein by reference.

[0010] In some embodiments, one or more micro-LED displays may be utilized and positioned at different sides of an optical combiner, e.g., an X-cube prism or dichroic X- cube. The X-cube prism receives light rays from different micro-LED displays on difference faces of the cube and outputs the light rays from the different micro-LED displays out of another face of the cube. Light rays from all of the different micro-LED displays may be outputted from the same output face of the cube. The outputted lightmay be directed towards projection optics, which is configured to converge or focus the image light onto an eyepiece for viewing by the user of the HMD.

[0011] In some embodiments, each of the micro-LED displays is monochrome, such that it is configured for outputting light of a single component color, which may then be combined by subsequent optics to form a full color image. In other embodiments, one or more of the micro-LED displays may have sub-pixels configured for emitting light of two or more component colors, but not all, component colors. For example, a single micro- LED display located on one face of the optical combiner may have sub-pixels that emit blue and green light, while a separate micro-LED display located on another face of the optical combiner may have pixels that emit red light. In some embodiments, one or more of the micro-LED displays are each full-color displays including, for example, pixels formed of multiple sub-pixels configured to emit light of all the different component colors, including blue, green, and red light. Advantageously, combining the light of multiple fullcolor micro-LED displays may increase display brightness and dynamic range. In other embodiments, a single full color micro-LED display may be utilized, without an optical combiner, to emit light of all of the different color components.

[0012] In some embodiments, the eyepiece that receives the light from the micro-LED displays may include a waveguide assembly that includes one or more waveguides. Each of the waveguides may include an in-coupling optical element that in-couples incident image light, such that the light propagates through the waveguide by total internal reflection (TIR). Each of the waveguides may also include an out-coupling optical element, which out-couples light propagating therein, such that the out-coupled light propagates towards the eye of the user. In some embodiments, the waveguide assembly may include a stack of waveguides, each of which has an associated in-coupling optical element. The stack of waveguides may be configured for selectively outputting light with different amounts of wavefront divergence to provide virtual content at multiple depth planes perceived to be at different distances away from the user. For example, the stack of waveguides may respectively had out-coupling optical elements with different optical power to output light with different amounts of wavefront divergence.

[0013] Because each LED in the micro-LED display may emit light with a larger than desired angular emission profile, such that only a small portion of the emitted light may ultimately be incident on the eyepiece, thereby wasting light. In some embodiments, light collimators (e.g., micro-lenses, nano-lenses, reflective wells, metasurfaces, and liquid crystal gratings) may be utilized to narrow the angular emission profile of light emitted by the LEDs in a micro-LED display. The light collimators are preferably positioned directly adjacent or contacting the LEDs to capture a large proportion of the light emitted by the associated LEDs.

[0014] In one embodiment illustrated in Fig. 1 , light emitted by a particular micro-LED display 1 having an array of LEDs 2a-2e (only one dimension shown) generally propagates in a direction perpendicular to the plane of the micro-LED display 1 towards projection optics 3 (i.e. , telecentric). An array of microlenses 4a-4e (only one dimension shown) may be respectively positioned over the array of LEDs 2a-2e, such that the angular emission profile 5a-5e of the respective LEDs 2a-2e is narrowed. However, despite the fact the angular emission profiles 5a-5e of the LEDs 2a-2e are narrowed, a significant amount of light emitted by the micro-LED display 1 is not received by the entrance pupil of the projection optics 3. That is, as illustrated in Fig. 1 , the amount of light captured from each LED by the entrance pupil of the projection optics 3 decreases as the distance of the LED from the center of the micro-LED display 1 increases (i.e., as the amount of light captured by the entrance pupil of the projection optics 3 decreases as the LED from which the light is emitted approaches the periphery of the micro-LED display 1 ). As such, the entrance pupil of the projection optics 3 must be large enough to capture as much light as possible from the LEDs (e.g., the LEDs 2d-2e) at the peripheries of the micro-LED display 1 , and as a result, the size, complexity, and cost of the HMD in which the micro-LED display 1 is utilized may increase in a commensurate manner. If the pupil of the projection optics 3 is not made large enough, much of the light emitted by the micro- LED display 1 may undesirably be wasted, since it will not be captured and ultimately relayed to the eye of the user to form images. This may result in images that appear darker than would be expected if more of the light outputted by the micro-LED display ultimately reached the eye of the user.

[0015] It would, thus, be desirable to decrease the size of the projection optics that succeeds one or more micro-LED displays, thereby decreasing the size, complexity, and cost of the HMD, while still maximizing the amount of light emitted by the micro-LED displays that is captured by the pupil of the projection optics.SUMMARY

[0016] In accordance with the present inventions, a head-mounted display (HMD) comprises a head-mountable frame and a light projection assembly supported by the frame. The light projection assembly comprises a micro-display having a two-dimensional array of pixels. Each of the pixels comprises a group of light emitters (e.g., light emitting diodes (LEDs)) configured for emitting image light. The projection optics is configured for receiving the image light at an entrance pupil from the group of light emitters of each of the array of pixels, and projecting focused image light from an exit pupil. The light projection assembly further comprises a two-dimensional array of light collimators (e.g., a refractive light collimator or a diffractive light collimator) disposed between the microdisplay and the projection optics. The array of light collimators is configured for narrowing emission profiles of corresponding groups of the light emitters of the respective array of pixels. The HMD further comprises an eyepiece supported by the frame. The eyepiece is configured for receiving the focused image light from the exit pupil of the projection optics, and directing the image light to an eye of a user when the frame is worn by the user. In one embodiment, the group of light emitters of each of the pixels comprises at least two light emitters respectively configured for emitting image light having two different colors. In another embodiment, the group of light emitters of each of the pixels comprises at least three light emitters respectively configured for emitting image light having three different colors. In still another embodiment, the eyepiece comprises a waveguide and an in-coupling optical element configured for in-coupling the focused image light from the exit pupil of the projection optics into the waveguide.

[0017] In accordance with a first aspect of the present inventions, a steerable light collimator of the array of light collimators being further configured for redirecting the emission profiles of the corresponding group of light emitters towards a center of the entrance pupil of the projection optics. In one embodiment, all of the array of lightcollimators are steerable light collimators configured for steering the emission profiles of the corresponding groups of light emitters towards the center of the entrance pupil of the projection optics. In another embodiment, each of the light collimators has a group of distinct collimating phase profiles respectively for the emission profiles of the corresponding group of light emitters. In this case, the group of distinct collimating phase profiles of the steerable light collimator may be configured for redirecting the emission profiles of the corresponding group of light emitters towards the center of the entrance pupil of the projection optics. The group of distinct collimating phase profiles of the steerable light collimator may also be configured for redirecting the emission profiles of the corresponding group of light emitters at different angles relative to an optical axis of the projection optics. In still another embodiment, the array of collimators is further configured for redistributing intensities amongst the corresponding group of light emitters. In yet another embodiment, the array of light collimators is monolithic.

[0018] In yet another embodiment, the array of light collimators respectively comprise groups of dedicated areas respectively disposed over the groups of light emitters of the respective array of pixels. In this case, the array of light collimators may respectively comprises groups of microlenses that respectively correspond to the groups of distinct areas. The group of microlenses of each of the array of light collimators may be superimposed relative to each other. In one embodiment, only a single light emitter of each group of light emitters is functionally associated with a microlens of a corresponding group of microlenses. The group of microlenses of the steerable light collimator may be decentered relative to the corresponding group of the light emitters, such that the emission profiles of the corresponding group of light emitters are redirected towards the center of the entrance pupil of the projection optics. The group of microlenses of the steerable light collimator may also be decentered relative to the corresponding group of the light emitters to different degrees, such that emission profiles of the corresponding group of light emitters are independently redirected towards the center of the entrance pupil of the projection optics. If the group of microlenses of each of the array of light collimators are superimposed relative to each other, steerable light collimator may have a step profile between at least two of the group of microlenses of the steerable lightcollimator, and / or at least one of the at least two microlenses of the steerable light collimator may be shifted along a focal axis a distance relative to another one of the at least two microlenses, and / or at least two of the group of microlenses of the steerable light collimator may have different focal lengths.

[0019] In yet another embodiment, the array of light collimators respectively comprise common areas respectively disposed over the groups of light emitters of the respective array of pixels. In one embodiment, the array of light collimators respectively comprises diffractive optics that respectively correspond to the common areas. For example, the diffractive optics may comprise meta-optics, each of which may comprise an optically transparent base substrate and a nano-structure having a plurality of subwavelength meta-atoms. In another embodiment, each group of light emitters comprises at least two light emitters respectively configured for emitting image light having two different colors. In still another embodiment, the steerable light collimator may be designed, such that the emission profiles of the corresponding group of light emitters are redirected towards the center of the entrance pupil of the projection optics. The steerable light collimator may also be designed, such that emission profiles of the corresponding group of light emitters are independently redirected towards the center of the entrance pupil of the projection optics.

[0020] In accordance with another aspect of the present inventions, the array of light collimators respectively comprising groups of microlenses, each group of microlenses being superimposed relative to each other. Only a single light emitter of each group of light emitters is functionally associated with a microlens of a corresponding group of microlenses. In one embodiment, the array of light collimators is monolithic. In another embodiment, the group of microlenses of at least one of the light collimators is decentered relative to the corresponding group of the light emitters, such that the emission profiles of the corresponding group of light emitters are redirected. For example, the emission profiles of the corresponding group of light emitters may be redirected towards the center of the entrance pupil of the projection optics. In still another embodiment, the group of microlenses of each of the light collimator(s) may be decentered relative to the corresponding group of the light emitters to different degrees, such that emission profilesof the corresponding group of light emitters are independently redirected. Each of the light collimator(s) may have a step profile between at least two of the group of microlenses of the steerable light collimator, and / or at least one of the at least two microlenses of the steerable light collimator may be shifted along a focal axis a distance relative to another one of the at least two microlenses, and / or at least two of the group of microlenses of the steerable light collimator may have different focal lengths.

[0021] In accordance with still another aspect of the present inventions, the array of light collimators is an array of meta-optic light collimators. In one embodiment, the array of meta-optic light collimators is monolithic. In another embodiment, each of the array of meta-optic light collimators comprises an optically transparent base substrate and a nanostructure having a plurality of subwavelength meta-atoms. In still another embodiment, at least one of the array of meta-optic light collimators is designed, such that the emission profiles of the corresponding group of light emitters are redirected towards the center of the entrance pupil of the projection optics. In this case, the meta-optic light collimator(s) may be designed, such that emission profiles of the corresponding group of light emitters are independently redirected towards the center of the entrance pupil of the projection optics.

[0022] Other and further aspects and features of the invention will be evident from reading the following detailed description of the preferred embodiments, which are intended to illustrate, not limit, the invention.BRIEF DESCRIPTION OF DRAWINGS

[0023] The drawings illustrate the design and utility of embodiments of the present invention, in which similar elements are referred to by common reference numerals. In order to better appreciate how the above-recited and other advantages and objects of the present inventions are obtained, a more particular description of the present inventions briefly described above will be rendered by reference to specific embodiments thereof, which are illustrated in the accompanying drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

[0024] Fig. 1 is a prior art plan view of a telecentric projection assembly for use in a headmounted display (HMD);

[0025] Fig. 2 is a plan view of a wearable extended reality (XR) system;

[0026] Fig. 3 is a plan view of one embodiment of a display subsystem having a non- telecentric projection assembly constructed in accordance with one embodiment of the present inventions;

[0027] Fig. 4 is a plan view of another embodiment of a display subsystem having a non- telecentric projection assembly constructed in accordance with one embodiment of the present inventions;

[0028] Fig. 5 is a plan view of an array of pixels of a micro-display for use in either of the non-telecentric projection assemblies illustrated in Figs. 3 or 4;

[0029] Figs. 6A-6D are plan views of different-sized pixels of the micro-display of Fig. 5;

[0030] Fig. 7 is a plan view of one embodiment of a steerable light collimator for use in either of the non-telecentric projection assemblies illustrated in Figs. 3 or 4;

[0031] Fig. 8 is a plan view of one embodiment of a light redirection structure comprising an array of the steerable light collimators of Fig. 7;

[0032] Fig. 9 is a perspective view of one embodiment of a light redirection structure for use in either of the non-telecentric projection assemblies illustrated in Figs. 3 or 4;

[0033] Figs. 10A-10C are perspective view of different sized groups of superimposed microlenses for use in the light redirection structure of Fig. 9;

[0034] Fig. 11 is a perspective view of another embodiment of a light redirection structure for use in either of the non-telecentric projection assemblies illustrated in Figs. 3 or 4;

[0035] Fig. 12 is perspective view of a group of superimposed microlenses for use in the light redirection structure of Fig. 11;

[0036] Fig. 13 is a plan view of a prior art light collimator having a single microlens for narrowing emission profiles of two light emitters of a single pixel;

[0037] Fig. 14A is a depiction of an asymmetrical illumination of the entrance pupil of projection optics by one of the light emitters of Fig. 13;

[0038] Fig. 14B is a depiction of an asymmetrical illumination of the entrance pupil of projection optics by the other one of the light emitters of Fig. 13;

[0039] Fig. 15 is a profile view of one embodiment of a light collimator with superimposed microlenses for use in the light redirection structure of Fig. 11, particularly showing the superimposed microlenses centered relative to corresponding light emitters of a single pixel;

[0040] Fig. 16A is a depiction of a relatively symmetrical illumination of the entrance pupil of projection optics by one of the light emitters of Fig. 15;

[0041] Fig. 16B is a depiction of a relatively symmetrical illumination of the entrance pupil of projection optics by the other one of the light emitters of Fig. 15;

[0042] Fig. 17 is a profile view of the light collimator of Fig. 15, particularly showing the superimposed microlenses decentered relative to corresponding light emitters of an off- center pixel, thereby redirecting the emission profiles of the corresponding light emitters;

[0043] Fig. 18 is a depiction of a symmetrical illumination of the entrance pupil of projection optics by either of the light emitters of Fig. 17;

[0044] Fig. 19 is a profile view of the light collimator of Fig. 15, particularly showing the superimposed microlenses decentered relative to corresponding light emitters of a center pixel, thereby redirecting the emission profiles of the corresponding light emitters;

[0045] Fig. 20 is a profile view of three neighboring ones of the light collimators of Fig. 11 , particularly showing the superimposed microlenses centered relative to corresponding light emitters of a single pixel;

[0046] Fig. 21 is a profile view of three neighboring ones of the light collimators of Fig. 11 , particularly showing the center one of the microlenses decentered relative to a corresponding light emitter, resulting in step profiles between the superimposed microlenses;

[0047] Fig. 22 is a profile view of three neighboring ones of the light collimators of Fig. 11 , particularly showing the microlenses decentered relative to corresponding light emitters of a single pixel, resulting in step profiles between the microlenses;

[0048] Fig. 23 is a profile view of three neighboring ones of the light collimators of Fig. 11 , particularly showing the microlenses decentered relative to corresponding light emitters of a single pixel, and shifted along their focal axes to obviate the need for step profiles between the microlenses;

[0049] Fig. 24 is a profile view of a light collimator of Fig. 11 , particularly showing the superimposed microlenses centered relative to corresponding light emitters of a single pixel, and a step profile formed between the superimposed microlenses, thereby modifying the relative intensities between the corresponding light emitters;

[0050] Fig. 25 is a perspective view of still another embodiment of a light redirection structure for use in either of the non-telecentric projection assemblies illustrated in Figs. 3 or 4;

[0051] Fig. 26 is a profile view of a light collimator with meta-optics for use in the light redirection structure of Fig. 15, particularly showing collimating phase profiles in first positions relative to corresponding light emitters of a single pixel;

[0052] Fig. 27 is an axial view of the collimating phase profiles generated by the light collimator of Fig. 26; and

[0053] Fig. 28 is a profile view of the light collimator of Fig. 26, particularly showing one of the collimating phase profiles in a second position relative to corresponding light emitters of a single pixel.DETAILED DESCRIPTION

[0054] Referring to Fig. 2, a wearable extended reality (XR) system 10 for use by a user 12 generally comprises a head-mounted display (HMD) 14 (e.g., an eyewear device) and a data and processing module 16. The HMD 14 is generally configured for presenting virtual content and audio to the user 12, while the local processing and data module 16 (e.g., a compute pack) is configured for being worn by the user 12 remotely from the head of the user 12 (e.g., on the torso of the user in a backpack-style configuration or on the hip of the user in a belt-coupling style configuration). The data and processing module 16 may assist the XR system 10 in processing, cashing, and storage of data used to present virtual content to the user. For example, the data and processing module 16 may comprise a power-efficient processor or controller, as well as digital memory, such as flash memory, both of which may be utilized to assist in the processing, caching, and storage of data used by the HMD 14 to present virtual content to the user and / or sensor data acquired by the HMD 14. The HMD 14 may be operably coupled to the data and processing module 16 via a wired or wireless connection 18.

[0055] The HMD 14 comprises a head-mountable frame 20, a display subsystem 22 affixed to the head-mountable frame 20, and one or more optional speakers 24 and one or more optional microphones 26 affixed to the head-mountable frame 20. The head- mountable frame 20 may be worn on the head of the user 12, such that a display (described below) of the display subsystem 22 is positioned in front of the eyes of the user 12, the speaker 24 is positioned adjacent the ear canal of the user 12 (optionally, another speaker (not shown) is positioned adjacent the other ear canal of the user 12 to provide for stereo / shapeable sound control), and the microphone 26 is adjacent the face of the user 12. The microphone 26 may be configured for allowing the user 12 to provide inputs or commands to the XR system 10 (e.g., the selection of voice menu commands, natural language questions, etc.) and / or facilitate audio communication with other persons (e.g., with other uses of similar XR systems 10). In some embodiments, the XR system 10 may further comprise one or more outwardly directed environmental sensors 28 affixed to the head-mountable frame 20 for detecting objects, stimuli, people, animals, locations, or other aspects of the world around the user 12. For example, the sensors 28 may comprise one or more cameras, which may be located, e.g., facing outward so as to capture images in the field of view of the user 12.

[0056] The display subsystem 22 is designed to present the eyes of the user 12 with virtual content. To this end, the display subsystem 22 comprises one or more transparent screens (or eyepieces) 30 and one or more light projection assemblies 32 (shown in Fig. 3) that project light onto the eyepiece(s) 30 for presentation of virtual content to the user 12. The eyepiece(s) 30 and projection assembly(ies) 32 are affixed to the head- mountable frame 20. The head-mountable frame 20 is designed to, not only position the eyepiece(s) 30 in front of the eyes of the user 12, but also to position the eyepiece(s) 30 in the field of view of the user 12 between the eyes of the user 12 and an ambient environment, such that direct light from the ambient environment is transmitted through the eyepiece(s) 30 respectively to the eyes of the user 12. Although, in the illustrated embodiment, the display subsystem 22 only has one eyepiece 30 for presentation of monocular virtual content to the user 12, it should be appreciated that the displaysubsystem 22 may comprise two eyepieces that are respectively positioned in front of the eyes of the user 12 for presentation of binocular virtual content to the user 12.

[0057] The XR system 10 may optionally comprise a remote processing module 34 and remote data repository 36 operatively coupled to the data and processing module 16. The remote processing module 34 may comprise one or more relatively powerful processors or controllers configured to analyze and process data and / or image information, while the remote data repository 36 may comprise a relatively large-scale digital data storage facility, which may be available through the internet or other networking configuration in a “cloud” resource configuration. In one embodiment, all data is stored and all computation is performed in the data and processing module 16, allowing fully autonomous use from any remote modules. The data and processing module 16 may be operably coupled to the remote processing module 34 and remote data repository 36 via respective wired or wireless connections 38, 40.

[0058] Referring to Fig. 3, one embodiment of a display subsystem 22a generally comprises a light projection assembly 32a for projecting colored image light, and an eyepiece 30 for relaying the colored image light in the form of virtual content to one or both eyes 44 of the user 12. It should be appreciated that although the display subsystem 22a is illustrated as having only one light projection assembly 32a and one corresponding eyepiece 30, the display subsystem 22a may comprise two light projection assemblies and two corresponding eyepieces.

[0059] The light projection assembly 32a includes a plurality of micro-displays 46’, 46”, 46’” configured for respectively emitting multi-color image light 54’, 54”, 54”’(i.e., image light having at least two color components (e.g., at least two of blue, green, or red), a plurality of light redirecting structures 48’, 48”, 48’” configured for narrowing and redirecting the angular light profiles of an array of individual light emitters (described in further detail below) of the micro-displays 46’, 46”, 46’”, an optical combiner 50 configured for combining the multi-color image light 54’, 54”, 54’” emitted by the micro-displays 46’, 46”, 46’” via the light redirecting structures 48 and outputting full-color image light 54 (i.e. , image light having all three color components (e.g., all three of blue, green, and red), andprojection optics 52 configured for projecting the full-color image light 54 combined by the optical combiner 50 onto the eyepiece 30.

[0060] At least one of the micro-displays 46’, 46”, 46”’ may output non-monochrome image light that includes at least two different color components (e.g., at least two of green, blue, and red components). In one embodiment, at least one of the micro-displays 46’, 46”, 46’” may output non-monochrome light that includes only two color components (e.g., green and blue components), and at least another one of the micro-displays 46’, 46”, 46’” outputs mono-chrome image light (e.g., having a red component). The non- monochrome image light and mono-chrome image light may then be combined in the eyepiece 30 and output to the eye 44 of the user 12 as a full-color image. In another embodiment, each of the micro-displays 46’, 46”, 46’” may output full-color image light (e.g., having green, blue, and red components). Such micro-displays 46’, 46”, 46’” may be identical and may display the same image. However, utilizing multiple full-color microdisplays 46’, 46”, 46’” may provide advantages for increasing the brightness and dynamic range of the brightness of the image by combining the image light from multiple microdisplays to form a single image. An alternative embodiment of a light projection assembly 32b of a display subsystem 22b illustrated in Fig. 4 comprises only one full-color microdisplay 46 that may output full-color image light 54, in which case, the optical combiner 50 may be omitted, thereby advantageously reducing the size, weight, and cost of the HMD 14.

[0061] The light redirecting structures 46’, 46”, 46’” (or light redirecting structure 48) are configured for respectively redirecting the multi-color image light 54’, 54”, 54’” inward towards the center of the pupil of the projection optics 52. In this manner, compared to projection optics utilized in a telecentric architecture (e.g., the projection optics 3 illustrated in Fig. 3), the projection optics 52 can be made smaller without sacrificing its efficiency in capturing the full-color image light 54 from the micro-displays 46’, 46”, 46’” or micro-display 46, especially the portion of the full-color image light 54 contributed by the peripheries of the micro-displays 46’, 46”, 46’” or periphery of the micro-display 46.

[0062] The optical combiner 50 receives the multi-color image light 54’, 54”, 54’” from the micro-displays 46’, 46”, 46’” via the light redirecting structures 48 and effectively combinesthis light, such that the light is outputted from a common side of the optical combiner 50 and propagates generally along the same path toward the projection optics 52. In some embodiments, the optical combiner 50 may be a X-cube prism or a dichroic X-cube prism having reflective internal surfaces 56 that redirect the full-color image light 54 to the projection optics 52.

[0063] The projection optics 52 has an entrance pupil 56 for receiving the full-color image light 54 from the array of light emitters of the micro-displays 46’, 46”, 46”’ illustrated in Fig. 3 (or alternatively, from the array of light emitters of the micro-display 46 illustrated in Fig. 4), and an exit pupil 58 for projecting focused full-color mage light 54 onto the eyepiece 30. The projection optics 52 may be a lens structure including one or more lenses that converge or focus image light onto the eyepiece 30. The projection optics 52 may be formed with high-refractive index materials (e.g., having refractive indices above 1 .5) to facilitate light collection. In some embodiments, the projection optics 52 may have elongated entrance and exit pupils (e.g., oval) to emit light beams having a cross- sectional profile similar to the shapes of the in-coupling optical element of the eyepiece 30. For example, the projection optics 52 may be elongated in a dimension corresponding to the elongated dimension of the in-coupling optical element to improve the etendue mismatch between the micro-displays 46’, 46”, 46’” and the eyepiece 30.

[0064] In the illustrated embodiment, the eyepiece 30 takes the form of a waveguide assembly that comprises one or more waveguides 60 (only one shown) configured for propagating the full-color image light 54 encoded with image information therein by total internal reflection (TIR), an in-coupling optical element 62 affixed to the waveguide 60 for injecting the full-color image light 54 from the projection optics 52 into the waveguide 60, and an out-coupling optical element 64 affixed to the waveguide 60 for extracting colored light 54 out of the waveguide 60 to the eye 44 of the user 12.

[0065] The waveguide 60 may output the full-color image light 54 with a defined amount of wavefront divergence corresponding to the wavefront divergence of a light field produced by a point in a desired depth plane. In some embodiments, the same amount of wavefront divergence is provided for all objects presented on that depth plane. In the case where the eyepiece 30 comprises a single waveguide 60, such waveguide 60 maybe configured for outputting colored light 54 corresponding to a single or limited number of depth planes. In other embodiments, the eyepiece 30 may comprise a stack of waveguides to provide three-dimensional perception to the eye 44.

[0066] The in-coupling optical element 62 is disposed on the planar surface of the waveguide 60, and in the illustrated embodiment, on the rear planar surface of the waveguide 60 (i.e. , furthest from the projection optics 52). In such a configuration, the incoupling optical element 62 may be a reflective light directing element that in-couples the full-color image light 54 by reflecting the light at angles that support TIR through the waveguide 60. In other configurations, the in-coupling optical element 62 may be disposed on the front surface of the waveguide 60 (i.e., closest to the projection optics 52). In such configuration, the in-coupling optical element 62 may be a transmissive light redirecting element that in-couples the full-color image light 54 by changing the direction of propagation of the full-color image light 54 as it is transmitted through the in-coupling optical element 62.

[0067] The out-coupling optical element 64 takes the form of an exit pupil (EP) or exit pupil expander (EPE) disposed on the planar surface of the waveguide 60, and in the illustrated embodiment, on the front planar surface of the waveguide 60 (i.e., closest to the eye 44 of the user 12). In other embodiments, the out-coupling optical element 64 may be disposed directly in the volume of the waveguide 60. In some embodiments, the out-coupling optical element 64 may be formed in a layer of material that is subsequently attached to the waveguide 60. In other embodiments, the out-coupling optical element 64 may be monolithically formed into the planar surface of the waveguide 60. The fullcolor image light 54 may be outputted by the waveguide 60 at locations at which the fullcolor image light 54 propagating through the waveguide 60 strikes the out-coupling optical element 64. The out-coupling optical element 64 may be, e.g., diffractive optical features, such as gratings.

[0068] In an optional embodiment, the eyepiece 30 further comprises light distributing element (not shown) affixed to the waveguide 60 for deflecting the full-color image light 54 propagating through the waveguide 60 from the in-coupling optical element 62 towards the out-coupling optical element 64. The light distributing element may take the form ofan orthogonal pupil expander (OPE) disposed on the planar surface of the waveguide 60, e.g., on one or both of the front surface and rear surface of the waveguide 60 (i.e. , closest to the projection optics 52). In this case, the full-color image light 54 may propagate through the waveguide 60 by TIR until it impinges on the light distributing element, which then distributes the full-color image light 54 to the out-coupling optical element 64.

[0069] It should be appreciated that, although the eyepiece 30 is illustrated in Figs. 3 and 4 as having only a single waveguide 60 with a single in-coupling optical element 62 and a single out-coupling optical element 64, the eyepiece 30 may have a stacked assembly of waveguide, with associated in-coupling optical elements and out-coupling optical elements, as described in U.S. Patent No. 11 ,604,354, which is expressly incorporated herein by reference. In these case, full-color image light 54 from the projection optics 52 may propagate through each of the waveguides or less than the full-colored image light (e.g., monochrome image light or image light with only blue and green components) may propagate through at least one of the waveguides.

[0070] Referring now to Fig. 5, each of the micro-displays 46’, 46”, 46”’ (Fig. 3) or the single micro-display 46 (Fig. 4) has a two-dimensional array of multi-color pixels 66, while each of the light redirecting structures 48’, 48”, 48’” (Fig. 3) or the single light redirecting structure 48 (Fig. 4) has a two-dimensional array of light collimators 70 that correspond to the arrays of pixels 66 of the respective micro-displays 46’, 46”, 46’” or the single microdisplay 46 on a one-to-one basis. The light collimators 70 may take the form of any suitable optical element capable of narrowing and steering emission profiles of light emitters, including, but not limited to, micro-lenses, nano-lenses, reflective wells, metasurfaces, metaoptics, diffractive lenses / structures, and liquid crystal gratings. Although the two-dimensional array of multi-color pixels 66, and correspondingly, the two- dimensional array of light collimators 70, are illustrated in Fig. 5 as being rectangular, it should be appreciated that the two-dimensional array of multi-color pixels 66 and two- dimensional array of light collimators 70 may have any shape, including circular, elliptical, polygonal, etc. Furthermore, the number of multi-color pixels 66 and corresponding light collimators 70 will generally be much greater than that illustrated in Fig. 5 (e.g., 1280 pixel x 420 pixel).

[0071] As illustrated in Figs. 6A-6D, each of the pixels 66 comprises a group of different colored light emitters 68a-68c (such as, e.g., light emitting diodes (LEDs)) for emitting colored image light. The group of colored emitters 68a-68c may represent sub-pixels that are contained within the pixel 66. In one example illustrated in Fig. 6A, a pixel 66a may include two different colored, but equally sized, light emitters (e.g., a blue light emitter 68a and a green light emitter 68b). In another example illustrated in Fig. 6B, a pixel 66b may include three different colored, but equally sized, light emitters (e.g., a blue light emitter 68a, a green light emitter 68b, and a red light emitter 68c). In still another example illustrated in Fig. 6C, a pixel 66c may include two different colored, but equally sized, light emitters (e.g., a blue light emitter 68a and a green light emitter 68b), and a different colored, larger sized, light emitter (e.g., a red light emitter 68c). In this example, the larger size of the light emitter 68c may compensate for the inefficiency of some colors (e.g., red) relative to the other more light efficient colors (e.g., blue and green). In yet another example illustrated in Fig. 6D, a pixel 66d may include two different colored, but equalized sized, light emitters (e.g., a blue light emitter 68a and a green light emitter 68b), and two same colored, and equalized sized, light emitters (e.g., two red light emitters 68c, 68d). In this embodiment, the multiple light emitters 68c of the same color may compensate for the inefficiency of some colors (e.g., red) relative to other more light efficient colors (e.g., blue and green).

[0072] Referring to Fig. 7, for a particular pixel 66, each light collimator 70 is specifically designed to have a group of distinct collimating phase profiles 72 respectively seen by the group of light emitters 68 of that pixel 66. Although only two light emitters 68a, 68b (e.g., as illustrated in Fig. 6A), and thus only two distinct collimating phase profiles 72a, 72b are illustrated, it should be appreciated that a group of light emitters 68 for a particular pixel 66 may include more than two light emitters (e.g., the light emitters 68a-68c illustrated in Figs. 6B-6C or the four light emitters 68a-68d illustrated in Fig. 6D), and thus, the group of distinct collimating phase profiles 72 of the light collimator 70 may correspondingly include more than two distinct collimating phase profiles 72. For example, the group of distinct collimating phase profiles 72 of a light collimator 70 may include three distinct collimating phase profiles respectively for the three light emitters68a-68c illustrated in Figs. 6B-6C or four distinct collimating phase profiles respectively for the four light emitters 68a-68d illustrated in Fig. 6D.

[0073] Each of the collimating phase profiles 72a, 72b of a light collimator 70 is capable of both narrowing, but also independently steering, the emission profiles 74a, 74b, of the respective light emitters 68a, 68b. For example, such steerable light collimator 70 may be designed, such that the collimating phase profile 72a seen by the respective light emitter 68a narrows and redirects the emission profile 74a towards the center of the entrance pupil 56 of the projection optics 52, while the collimating phase profile 72b seen by the respective light emitter 68b likewise narrows and redirects the emission profile 74b towards the center of the entrance pupil 56 of the projection optics 52. Thus, the arrangement illustrated in Fig. 7 non-telecentrically redirects the emission profiles 74a, 74b towards the center of the entrance pupil 56 of the projection optics 52. Notably, due to the lateral separation of the light emitters 68a, 68b with respect to the center of the entrance pupil 56 of the projection optics 52, as well as the different refractive characteristics of the different colors of the light emitted by the light emitters 68a, 68b, the angles at which the emission profiles 74a, 74b of the respective light emitters 68a, 68b are redirected will be different relative to an optical axis 76 of the projection optics 52.

[0074] Furthermore, the angles 78 at which the emission profiles 74a, 74b of the respective light emitters 68a, 68b are redirected between the different pixels 66 will be different from each other relative to an optical axis 76 of the projection optics 52, as illustrated in Fig. 8. For example, the respective angles 78 at which the emission profiles 74a, 74b of the respective light emitters 68a, 68b are redirected by the light redirecting structure 48 towards the center of the entrance pupil 56 of the projection optics 52 will gradually increase from the pixels 66 at the center of the micro-display 46 to the periphery of the micro-display 46. Thus, it is important that each steerable light collimator 70 be capable of being designed to not only independently redirect the emission profiles 74a, 74b of the respective light emitters 68a, 68b of a particular pixel 66 relative to each other, but also to independently redirect the emission profiles 74a, 74b of the respective light emitters 68a, 68b across different pixels 66 relative to each other. It is also noted that, in the illustrated embodiment, the collimating phase profiles 72a, 72b of each steerable lightcollimator 70, as seen by the respective light emitters 68a, 68b of a pixel 66, may be superimposed relative to each other. In this manner, the focal lengths of the respective steerable light collimators 70 may be made as short as possible in order to maximize the light collected by the projection optics 52 (as the same sized fixed area of the microlens 80 covers a larger part of the fixed emission profile 74 of the respective light emitter 68 when placed closer to the light emitter 68, as well as to reduce the size of the light projection assembly.

[0075] Optionally, each light collimator 70 is capable of redistributing intensities amongst the respective group of light emitters 68a, 68b of the respective pixel 66. For example, instead of a 50 / 50 intensity split between the two light emitters 68a, 68b, a light collimator 70 may redistribute some of the energy from one of the light emitters 68a, 68b to the other of the light emitters 68a, 68b, such that the intensity split between light emitters 68a, 68b is unequal (e.g., 60% to the light emitter 68a and 40% to the light emitter 68b). Such redistributions amongst a group of light emitters 68a, 68b may be useful, e.g., if the eyepiece 60 (illustrated in Figs. 3-4) propagates one color of the multi-color image light 54 more efficiently than another color of the multi-color image light 54. For example, if the eyepiece 60 propagates blue light more efficiently than green light, each light collimator 70 may redistribute some of the energy of one of the light emitters 68a, 68b that emit blue light to the other of the light emitters 68a, 68b that emit green light, thereby compensating for the color-specific propagation efficiencies of the eyepiece 60.

[0076] One embodiment of a light redirection structure 48a illustrated in Fig. 9 comprises an array of light collimators 70a, each of which comprises a group of microlenses 80 capable of being respectively positioned over a corresponding group of light emitters 68. Thus, there is a one-to-one correspondence between the microlenses 80 and the light emitters 68, with each light emitter 68 having a dedicated microlens 80, and thereby providing a single distinct collimating phase profile for the corresponding light emitter 68. Thus, each light collimator 70a comprises a group of distinct structures in the form of microlenses 80 that provide a group of distinct collimating phase profiles respectively to the group of light emitters 68 of a pixel 60. For example, the shared structure of the light collimator 48c may provide two distinct collimating phase profiles for two light emitters(e.g., the collimating phase profiles 72a, 72b illustrated in Fig. 7 for the light emitters 68a, 68b illustrated in Fig. 6A), or three distinct collimating phase profiles respectively for three light emitters (e.g., the light emitters 68a-68c illustrated in Figs. 6B-6C), four distinct collimating phase profiles respectively for four light emitters (e.g., the light emitters 68a- 68d illustrated in Fig. 6D), etc.). In the embodiment of the light redirection structure 48a illustrated in Fig. 9, the individual microlenses 80 of any one particular light collimator 70a are identical in size. In the illustrated embodiment, the light redirection structure 48a, and thus each of the collimators 70a, is monolithic.

[0077] One embodiment of a light collimator 70a(1 ) illustrated in Fig. 10A includes a pair of microlenses 80a, 80b capable of being respectively positioning over a pair of light emitters (e.g., the light emitters 68a, 68b illustrated in Fig. 6A). Another embodiment of a light collimator 70a(2) illustrated in Fig. 10B includes a triad of microlenses 80a-80c capable of being respectively positioned over a triad of light emitters (e.g., the light emitters 68a-68c illustrated in Fig. 6B). Still another embodiment of a light collimator 70a(3) illustrated in Fig. 10C includes a quartet of microlenses 80a-80d capable of being respectively positioned over a quartet of light emitters (e.g., the light emitters 68a-68d illustrated in Fig. 6C).

[0078] Another embodiment of a light redirection structure 48b illustrated in Fig. 11 comprises an array of light collimators 70b, each of which comprises a group of microlenses 80 capable of being respectively positioned over a corresponding group of light emitters 68. The light redirection structure 48b is similar to the light redirection structure 48a illustrated in Fig. 9 in that there is a one-to-one correspondence between the microlenses 80 and the light emitters 68, with each light emitter 68 having a dedicated microlens 80, and thereby providing a single distinct collimating phase profile for the corresponding light emitter 68. However, the light redirection structure 48b differs from the light redirection structure 48a illustrated in Fig. 9 in that at least two of the microlenses in the group of lenses 80 have different sizes. For example, in the embodiment illustrated in Fig. 12, the light collimator 70b includes a triad of microlenses 80a-80c capable of being respectively positioned over a triad of light emitters (e.g., the light emitters 68a-68c illustrated in Fig. 6C). The size of the microlens 80c is larger than that of each of themicrolenses 80a, 80b in order to accommodate the larger size of the light emitter 68c relative to the light emitters 68a-68b.

[0079] Significantly, by providing a dedicated microlens 80 for each light emitter 68, the emission profile of each light emitter 68 may be independently redirected or steered towards the center of the entrance pupil 56 of the projection optics 52, as illustrated in Fig. 7, such that the entrance pupil 56 may be homogenously illuminated by light emitter 68, thereby maximizing the amount of light emitted by the light emitter 68 that is captured by the entrance pupil 56 of the projection optics 52. In contrast, if only one microlens, as opposed to a group of microlenses 80 (e.g., as illustrated in Figs. 15, 17, and 19), is provided for each pixel 66, such that each group of light emitters shares a microlens, the entrance pupil 56 of the projection optics 52 would be non-homogenously illuminated by each of the microlenses 80.

[0080] For example, as illustrated in Fig. 13, a prior art light collimator may include a single microlens 80’ positioned over a pair of light emitters 68a, 68b of a pixel 66. The single microlens 80’ is effectively decentered relative to any particular one of the light emitters 68a, 68b, leading to a non-homogenous illumination of the entrance pupil 56 of the projection optics 52 as the maximum intensities of the light emitted by the light emitters 68a, 68b occur at the border of the entrance pupil 56 of the projection optics 52. That is, due to the respective locations of the light emitters 68a, 68b on the opposite sides of the centerline 82 of the single microlens 80’, the emission profiles 74a, 74b of the light emitters 68a, 68b will be angled away from the center of the entrance pupil 56 of the projection optics 52; that is, the light emitted by the respective light emitters 68a, 68b will be aimed at positions that are decentered with respect to the entrance pupil 56 of the projection optics 52. As such, the maximum intensity 84a of the light emitted by the light emitter 68a occurs at the bottom periphery of the entrance pupil 56, as further illustrated in Fig. 14A, while the maximum intensity 84b of the light emitted by the light emitter 68b occurs at the top periphery of the entrance pupil 56, as further illustrated in Fig. 14B. Thus, each of the light emitters 68a, 68b will asymmetrically illuminate the entrance pupil 56 of the projection optics 52, thereby causing significant portions of the light emitted by the respective light emitters 68a, 68b to be cutoff by the entrance pupil 56 and as a result,compromising the efficiencies of both light emitters 68a, 68b. It follows that physically shifting the microlens 80’ to redirect the emission profile of a particular one of the light emitters 68a, 68b towards the center of the entrance pupil 56 in an effort to increase the efficiency of that light emitter would disadvantageously redirect the emission profile of the other one of the light emitters 68a, 68b further away from the center of the entrance pupil 56, and further decreasing the efficiency of that light emitter.

[0081] In contrast, a group of microlens are respectively positioned over a group of light emitters of each pixel, and in one specific embodiment illustrated in Fig. 15, a pair of microlenses 80a, 80b may be respectively positioned over a pair of light emitters 68a, 68b of a pixel 66, leading to a relatively homogenous illumination of the entrance pupil 56 of the projection optics 52. That is, there is a one-to-one correspondence between the light emitters 68 and the microlenses (only a single light emitter 68 of each group of light emitters is functionally associated with a microlens 80 of a corresponding group of microlenses), such that the locations of the light emitters 68a, 68b may be aligned to the centerlines 82a, 82b of the microlenses 80a, 80b. As a result, the emission profiles 74a, 74b of the light emitters 68a, 68b will be directed towards the center of the entrance pupil 56 of the projection optics 52 (assuming that the light emitters 68a, 68b are located at the center of the corresponding one of the micro-displays 46’, 46”, 46’” (shown in Fig. 3) or the micro-display 46 (shown in Fig. 4)); that is, the light emitted by the respective light emitters 68a, 68b will be aimed at positions that are more centered with respect to the entrance pupil 56 of the projection optics 52. As such, the maximum intensity 84a of the light emitted by the light emitter 68a occurs at the center of the entrance pupil 56, as further illustrated in Fig. 16A, while the maximum intensity 84b of the light emitted by the light emitter 68b occurs at the center of the entrance pupil 56, as further illustrated in Fig. 16B. Thus, each of the light emitters 68a, 68b will substantially symmetrically illuminate the entrance pupil 56 of the projection optics 52, thereby causing significant portions of the light emitted by the respective light emitters 68a, 68b to be captured by the entrance pupil 56, and as a result, maximizing the efficiencies of both light emitters 68a, 68b. For example, studies have shown that the efficiencies of each of the light emitters 68a, 68b can be increased from approximately 16% to 28% by respectively positioning themicrolenses 80a, 80b over the light emitters 68a, 68b, as illustrated in Fig. 13, as opposed to positioning the single microlens 80 over the light emitters 68a, 68b, as illustrated in Fig.15.

[0082] As shown in Fig. 15, the microlenses 80a, 80b are superimposed relative to each other, such that , such that the curvatures of the microlenses 80a, 80b cover the entire area of the corresponding pixel 66. In contrast, if two microlenses are instead designed, such that they are not superimposed relative to each other, the sizes of such microlenses 80a, 80b would have to be reduced, such that radius of a single one of the two microlenses becomes so small that its curvature cannot be mathematically defined over the entire area of its half the square pixel area. For example, in the case of a 3pm pixel, the area covering half of that pixel is 1.5pm x 3.0pm. If the pixel consists of two light emitters spaced 1.3pm apart, each microlens would need have a radius of 0.65pm (half of the 1.3pm), so as to not extend into the other microlens. However, with a radius of 0.65pm, such reduced size microlens can only cover a circular area with a diameter of 1 ,3pm, far less than the half pixel area of 1 ,5pm x 3.0pm.

[0083] To manufacture the superimposed microlenses 80a, 80b, the portions of the microlenses 80a, 80b that would impinge on each other are physically removed, such that the adjacent edges of the microlenses 80a, 80b are in physical contact with other. Thus, although the microlenses 80a, 80b may not be physically superimposed relative to each other, the projections of these microlenses 80a, 80b are superimposed relative to each other. Thus, for the purposes of this specification, immediately neighboring microlenses are superimposed relative to each other if the projections of the microlenses (if fully extended with no material removed) are superimposed relative to each other.

[0084] To obtain a single surface of the physical structure of the light collimator that forms the superimposed microlenses 80a, 80b for each pixel 66, the sag of the physical structure can be derived at any point on the pixel 66 as the maximum sag value of the microlenses 80a, 80b, such that only the maximum sag value of the microlenses 80a, 80b contributes to the final shape of the structure of the light collimator. Thus, as illustrated in Fig. 15, the projected portions of the microlenses 80a, 80b that are shown in phantom do not physically exist and do not contribute to the final shape of the structure of the lightcollimator. It should be appreciated that, although only two microlenses 80a, 80b are illustrated In Fig. 15 as being superimposed relative to each other for positioning over the respective light emitters 68a, 68b (corresponding to the microlenses 80a, 80b of a single light collimator 70a(1 ) illustrated in Fig. 10A), more than two microlenses 80a, 80b may be superimposed relative to each other for positioning over more than two light emitters 68a, 68b (corresponding to the microlenses 80a-80c of a single light collimator 70a(2) illustrated in Fig. 10B, or the microlenses 80a-80d of a single light collimator 70a(3) illustrated in Fig. 10C, or the microlenses 80a-80c of a single light collimator 70b illustrated in Fig. 12).

[0085] In the embodiment illustrated in Fig. 15, the microlenses 80a, 80b are centered over the respective light emitters 68a, 68b, such that the emission profiles 74a, 74b of the respective light emitters 68a, 68b are directed perpendicularly to the plane of the microdisplay 46 (i.e. , telecentrically). However, as discussed above with respect to Fig. 7, it is preferred that the emission profiles 74a, 74b of the light emitters 68a, 68b for each of the pixels 66 be non-telecentrically steered towards the center of the entrance pupil 56 of the projection optics 52 (assuming that the center of the micro-display is optically aligned with the center of the entrance pupil 56 of the projection optics 52). Thus, as the distances of the positions of the pixels 66 increase from the center towards the periphery of the microdisplay, the emission profiles 74a, 74b of the respective light emitters 68a, 68b of each pixel 66 (in contrast to the emission profiles 74a, 74b of the respective pixel 66 illustrated in Fig. 15), will need to be redirected at angles towards the center of the entrance pupil 56 of the projection optics 52. Such angles will incrementally and proportionally increase as the position of the respective pixel 66 relative to the center of the micro-display increases.

[0086] In order to redirect the emission profiles 74a, 74b of a respective pixel 66 that is offset from the optical axis 76 of the projection optics 52 a distance d, the pair of microlenses 80a, 80b may be physically shifted relative to the light emitters 68a, 68b, such that the centerlines 82a, 82b of the microlenses 80a, 80b are decentered relative to the respective light emitters 68a, 68b by distances da, db, as illustrated in Fig. 17. The pair of micro-lenses 80a, 80b may not only be collectively shifted relative to the light emitters68a, 68b to account for the different positions of the corresponding pixels 66 relative to the center of the micro-display, but also, due to the one-to-one correspondence between the light emitters 68 and the microlenses 80, may be individually shifted relative to each other within a single pixel 66 (such that the offset distances daand db differ from each other) to account for the slightly different positions of the light emitters 68a, 68b relative to the center of the micro-display, as well as the different refraction / diffraction properties of the different colored light emitted by the respective light emitters 68a, 68b.

[0087] Thus, the emission profiles 74a, 74b of the respective light emitters 68a, 68b may be redirected by the micro-lenses 80a, 80b towards the center of the entrance pupil 56 of the projection optics 52; that is, the light emitted by the respective light emitters 68a, 68b will be aimed at positions that are identically centered with respect to the entrance pupil 56 of the projection optics 52. As such, the maximum intensities 84a, 84b of the light emitted by the light emitter 68a, 68b occur at the identical center of the entrance pupil 56 for both of the light emitters 68a, 68b, as illustrated in Fig. 18. Thus, each of the light emitters 68a, 68b will symmetrically illuminate the entrance pupil 56 of the projection optics 52. Indeed, the pair of micro-lenses 80a, 80b at the center of the micro-display illustrated in Fig. 15 may be physically shifted toward each other, such that the centerlines 82a, 82b of the microlenses 80a, 80b are decentered relative to the respective light emitters 68a, 68b by distances da, db, as illustrated in Fig. 19, thereby achieving the same effect illustrated in Fig. 18.

[0088] As a result of physically decentering the microlenses 80a, 80b relative to the respective light emitters 68a, 68b the intensities of the light emitted by the light emitters 68a, 68b may slightly decrease, but with the advantage that the entrance pupil 56 of the projection optics 52 will be symmetrically illuminated by the steerable light collimators 70, such that the increased amount of light captured by the entrance pupil 56 of the projection optics 52 outweighs the decreased light efficiency due to the relative shift between the microlenses 80a, 80b and the light emitters 68a, 68b. It should be appreciated that the, although the microlenses 80a, 80b have been illustrated and described as being physically shifted relative to the respective light emitters 68a, 68b in one direction on a plane, the microlenses 80a, 80b may be physically shifted relative to the respective lightemitters 68a, 68b in any direction on the plane necessary to redirect the emission profiles 74a, 74b of the respective light emitters 68a, 68b toward the center of the entrance pupil 56 of the projection optics 52.

[0089] Although the microlenses 80a, 80b have been described as being shifted relative to the respective light emitters 68a, 68b of a particular pixel 66 in order to redirect the emission profiles 74a, 74b of the respective light emitters 68a, 68b toward the center of the entrance pupil 56 of the projection optics 52, it should be appreciated that the microlenses 80a, 80b may be shifted relative to respective light emitters 68a, 68b of a particular pixel 66 to independently redirect the emission profiles 74a, 74b of the respective light emitters 68a, 68b towards any region of the entrance pupil 56 of the projection optic 52, e.g., such that different colors may enter different in-coupling elements on the eyepiece 30, as described in U.S. Patent No. 11,604,354, which is expressly incorporated herein by reference.

[0090] Notably, when shifting a pair of microlenses 80a, 80b of a particular pixel 66 relative to pairs of microlenses 80a, 80b of immediately neighboring pixels 66 and / or shifting a pair of microlenses 80a, 80b relative to each other, step profiles may be required to be formed between or within the steerable light collimators 70. For example, with reference to Fig. 20, three pixels 66, each comprises a pair of microlenses 80a, 80b that are physically aligned with the respective pair of light emitters 68a, 68b (i.e., the centerlines 82a, 82b of the microlenses 80a, 80b are aligned with the center of the light emitters 68a, 68b). A transition line 86 is illustrated between neighboring microlenses 80a, 80b to designate the equal areas of the respective microlenses 80a, 80b positioned over their corresponding light emitters 68a, 68b.

[0091] As illustrated in Fig. 21 , when one microlens 80” is physically decentered in one direction relative to its corresponding light emitter 68” (in the illustrated case, vertically downward), while its two immediately neighboring microlenses 80’, 80”’ remain centered relative to their corresponding light emitters 68’, it is desirable (assuming that it is desirable for the intensities of the light emitted by the light emitters 68 be equal) that the transition line 86 between the decentered microlens 80” and the neighboring centered microlens 80’, and the transition line 86 between the decentered microlens 80” and theneighboring centered microlens 80”’ remain in place (i.e., the areas of the microlenses 80’, 80”, 80’” positioned over their corresponding light emitters 68’, 68”, 68’” remain equal), a first step profile 88a will be formed at the transition line 86 between the moved microlens 80” and the microlens 80’, and a second step profile 88b will be formed at the transition line 86 between the moved microlens 80” and the microlens 80’”. The first step profile 88a will cause at least some of the portion of the microlens 80’ that would have otherwise been previously removed if the microlens 80’ were not moved to instead physically exist and contribute to the final shape of the actual structure of the microlens 80’, whereas the second step profile 88b will cause at least some of the portion of the microlens 80’ that would have otherwise physically existed and contributed to the final shape of the actual structure of the microlens 80’ to instead be removed. In this manner, the areas of the microlenses 80’, 80”, 80’” positioned over their corresponding light emitters 68’, 68”, 68’” will remain equal, and the transition lines 86 will remain in place.

[0092] Although the Fig. 21 illustrates only one of the microlenses 80 as being physically decentered from its corresponding light emitter 68 for purposes of illustration, it should be appreciated that every microlens 80 that is off-center from the optical axis 76 of the projection optics 52 (shown in Fig. 17) will preferably be physically decentered from their corresponding light emitters 68, such that microlenses 80 redirect the emission profiles 74 of the corresponding light emitters 68 towards the center of the entrance pupil 56 of the projection optics 52.

[0093] For example, as illustrated in Fig. 22, all of the microlenses 80 may be physically decentered relative to their corresponding light emitters 68 (in this case, each pair of microlenses 80a, 80b are independently decentered vertically downward relative to their corresponding pair of light emitters 68a, 68b by different distances (e.g., by distances da, db, as illustrated in Fig. 17). Because the angles at which the emission profiles 74 of the light emitters 68 are redirected by the corresponding microlenses 80 (shown in Fig. 17) will incrementally increase as the distances between the positions of the light emitters 68 and the optical axis 76 of the projection optics 52 incrementally increases, the microlenses 80 will be decentered relative their corresponding light emitters 68 at different degrees (i.e., the distances that the microlenses 80 will be physically decentered fromtheir corresponding light emitters 68 will likewise incrementally increase (in this case, vertically in the upward direction)), as illustrated in Fig. 22. As a result, the step profiles 88 will be formed at the transition lines 86 will incrementally increase in size (in this case, vertically in the upward direction) as the distances between the positions of the light emitters 68 and the optical axis 76 of the projection optics 52 incrementally increases. Notably, since each of the microlenses 80 is physically decentered from its corresponding light emitter 68 in Fig. 22, the step profile 88 at each transition line 86 will be a composite of the first step profile 88a (shown in Fig. 21) created by the decentered microlens 80 relative to its corresponding light emitter 68 on one side of the transition line 86 (below the respective transition line 86 as illustrated in Fig. 22) and the second step profile 88b (shown in Fig. 21 ) created by the decentered microlens 80 relative to its corresponding light emitter 68 on the other side of the transition line 86 (above the respective transition line 86 as illustrated in Fig. 22).

[0094] Notably, the introduction of step profiles between the microlenses 80 may increase the time and cost of manufacturing the physical structure of the microlenses 80. Alternatively, instead of creating step profiles 88 at the transition lines 86 in response to decentering the microlenses 80 relative to their corresponding light emitters 68, the microlenses 80 may be shifted along the focal axes of the microlenses 80 (i.e. , along the optical axis 76 of the projection optics 52 (shown in Fig. 17)), and in this case horizontally, as illustrated in Fig. 23. The distances that the microlenses 80 are shifted along the optical axis 76 of the projection emitters 68 will incrementally increase (in this case, vertically in the downward direction) as the distances between the positions of the light emitters 68 and the optical axis 76 of the projection optics 52 incrementally increases. Although it is anticipated that shifting the microlenses 80 along the optical axis 76 of the projection optical 72 will slightly decrease the efficiencies of the light emitted by their corresponding light emitters 68, the increased amount of light captured by the entrance pupil 56 of the projection optics 52 outweighs the decreased light efficiency due to the relative shifts along the optical axis 76 of the projection 72 between the microlenses 80a, 80b and the light emitters 68a, 68b.

[0095] In another alternative embodiment, to obviate the need to create step profiles 88 at the transition lines 86 in response to decentering the microlenses 80 relative to their corresponding light emitters 68, the shapes of the microlenses 80 may be changed (perhaps in combination with modifying the focal lengths), with the accompanying result of modifying the focal lengths of the microlenses 80, and slightly decreasing the efficiencies of the light emitted by their corresponding light emitters 68.

[0096] Although in the embodiment illustrated in Fig. 17, it has been described as being desirable to maintain equality between the intensities of the light emitted by a pair of light emitters 68a, 68b when decentering the corresponding pair of microlenses 80a, 80b relative to the pair of light emitters 68a, 68b (essentially maintaining the positions of the transition line 86 between the microlenses 80a, 80b, in some embodiments, it may be desirable for the intensities of the light emitted by the pair of light emitters 68a, 68b to differ from each other, e.g., to compensate for the color-specific propagation efficiencies of the eyepiece 60. In this case, the transition line 86 may be shifted between the microlenses 80a, 80b, as illustrated in Fig. 24 (in this case, downward) such that the light emitted by the light emitter 68a after passing through the microlens 80a has a greater intensity than that of the light emitted by the light emitter 68b after passing through the microlens 80b. A step profile 88 is formed at the transition line 86 between the microlenses 80a, 80b, which will cause at least some of the portion of the microlens 80a that would have otherwise been previously removed if the transition line 86 has not been shifted to instead physically exist and contribute to the final shape of the actual structure of the microlens 80a, and cause at least some of the portion of the microlens 80b that would have otherwise physically existed and contributed to the final shape of the actual structure of the microlens 80b to instead be removed. In this manner, the area of the microlens 80a positioned over its corresponding light emitter 68a will be greater than the area of the microlens 80b positioned over its corresponding light emitter 68b, and the transition line 86 will be shifted towards the microlens 80b. Alternatively, to obviate the need for step profiles 88, the microlenses 80 may be shifted along the optical axis 76 of the projection optics 52 (shown in Fig. 17) in the same manner described above with respect to Fig. 23, or the shapes of the microlenses 80 may be changed.

[0097] As discussed above, the light redirection structures 48a, 48b illustrated in Figs. 9 and 11 respectively comprise arrays of light collimators 70a, 70b positioned over the arrays of pixels 66 (illustrated in Fig. 5), with each of the light collimators 70a, 70b comprising a group of dedicated structures in the form of microlenses 80 that respectively provide a group of distinct collimating phase profiles respectively to the group of light emitters 68 of a pixel 60 (e.g., any of the groups of light emitters 68 illustrated in Figs. 10A-10C and 12). For example, the microlenses 80a, 80b respectively provide two distinct collimating phase profiles 72a, 72b respectively to the light emitters 68a, 68b of a pixel 66.

[0098] In contrast, another embodiment of a light redirection structure 48c illustrated in Fig. 25 comprises an array of light collimators 70c positioned over the arrays of pixels 66 (illustrated in Fig. 5), with the each of the light collimators 70c comprising a shared structure that provides the group of distinct collimating phase profiles respectively to the group of light emitters 68 of a pixel 60 (e.g., any of the groups of light emitters 68 illustrated in Figs. 10A-10C and 12). For example, the shared structure of the light collimator 70c may provide two distinct collimating phase profiles for two light emitters (e.g., the collimating phase profiles 72a, 72b illustrated in Fig. 7 for the light emitters 68a, 68b illustrated in Fig. 6A), or three distinct collimating phase profiles respectively for three light emitters (e.g., the light emitters 68a-68c illustrated in Figs. 6B-6C), four distinct collimating phase profiles respectively for four light emitters (e.g., the light emitters 68a- 68d illustrated in Fig. 6D), etc.). In the illustrated embodiment, the light redirection structure 48c, and thus each of the collimators 70c, is monolithic.

[0099] Each of the collimators 70c is implemented as a diffractive optic, such as a metaoptic, which consists of small meta-atoms that introduce position dependent phase shifts that replicate the collimation behavior of a microlens. In particular, with reference to Fig. 26, each collimator 70c comprises an optically transparent base substrate 90 and a nanostructure 92 having a plurality of meta-atoms 94 (single nano-structure elements, such as, e.g., nanopillars) formed on the surface of the base substrate 90. In an optional embodiment, the light redirection structure 48c can be used with an underlying refractive surface. Each of the meta-atoms 94 is subwavelength structure (i.e. , the size of eachmeta-atom 94 is less than all wavelengths in the visible light spectrum), such that the nano-structure 92 may be dispersion engineered to implement a group of collimating phase profiles (and in this case, two collimating phase profiles 72a, 72b) for a group of light emitters (and in this case, two light emitters 66a, 66b).

[0100] As further illustrated in Fig. 27, collimating phase profiles 72a, 72b (which are basically the combination of a quadratic phase with a linear phase), which are virtually identical and will be superimposed relative to each other, may be seen at two different wavelengths from two different locations 96a, 96b. As such, the emission profiles (not shown) by the light emitters 66a, 66b positioned at these locations 96a, 96b will be focused and redirected towards the entrance pupil 76 of the projection optics 52. In the same manner described above with respect to the light redirecting structures 48a, 48b, the light redirecting structure 48c may provide a relatively homogenous illumination of the entrance pupil 56 of the projection optics 52, as illustrated in Fig. 18 (assuming that the light emitters 68a, 68b are located at the center of the corresponding one of the microdisplays 46’, 46”, 46”’ (shown in Fig. 3) or the micro-display 46 (shown in Fig. 4)), such that each of the light emitters 68a, 68b will substantially symmetrically illuminate the entrance pupil 56 of the projection optics 52, thereby causing significant portions of the light emitted by the respective light emitters 68a, 68b to be captured by the entrance pupil 56, and as a result, maximizing the efficiencies of both light emitters 68a, 68b.

[0101] Although the collimating phase profiles 72a, 72b illustrated in Fig. 26 will cause the emission profiles of light emitters 66a, 66b that are positioned at the locations 96a, 96b to be telecentric in nature, the nano-structure 92 may be dispersion engineered, such that the emission profiles of the light emitters 66a, 66b are independently redirected relative to each other, such that the emission profiles of the light emitters 66a, 66b may be non-telecentric in nature (e.g., as illustrated in Fig. 7). In particular, the nano-structure 92 may be dispersion engineered to create any arbitrary collimating phase profiles for the light emitters 66a, 66b by modifying the radii of the meta-atoms 94, thereby providing the light collimator 70c with steerable capability.

[0102] For example, as illustrated in Fig. 26, three reference combinations of phases A, B, and C of the collimating phase profiles 72a, 72b are illustrated at particular positionson the base substrate 90. The reference combinations of phases A, B, and C represent specific combinations at respective locations of the collimating phase profiles 72a, 72b, which can be related to specific parameters of the meta-atoms 94 (e.g., a specific phase combination is related to a specific nano-pillar height and diameter). As illustrated in Fig. 28, the nano-structure 92 may be designed by modifying the physical characteristics of the meta-atoms 94 (and in this case, the radii of the nano-pillars), such that the collimating phase profile 72a, 72b shift relative to each other. As a result, the reference phase combinations A, B, and C shift to different positions on the base substrate. That is, a shift in the reference phase combinations A, B, and C shift the meta-atoms 94, which are now defined by the specific new combination of phase profiles A, B, and C. Some of the reference combinations may disappear (as the phase combinations that existed before the relative shift between the collimating phase profiles 72a, 72b do not exist anymore) or new reference combinations may appear (as the phase combinations that did not exist prior to the relative shift in the phase profiles 72a, 72b now exist).

[0103] In one design technique, a design library may be generated by first computing all possible (e.g., manufacturable) combinations of meta-atom parameters (e.g., pillar height, diameter, etc.), and from these combinations, deriving a matching of the meta- atom parameters to optical properties as wavelength-dependent transmission and phase shift for all relevant wavelengths (e.g., the wavelengths for blue color and for green color. The design library provides a connection between the combinations of phases and the manufacturing parameters. After the design library is generated, the desired phase profiles for the light emitters 66a, 66b, which preferably emit light at different wavelengths (e.g., blue and green), are defined, and then for each incremental position along the surface of the meta-optic, a combination of the phase profiles are computed. These phase combinations are then matched with the nearest available phase combination from the previously computed design library, and the corresponding meta-atom parameters at each of the incremental positions are used to construct the meta-atoms 94 along the surface of the meta-optic. To steer the emission profile 74 of one or both of the light emitters 66, the shifted phase profile(s) of the light emitter(s) 66 are first defined, the phase combinations for the phase profiles are then matched with the nearest availablephase combination from the previously computed design library, and then the corresponding meta-atom parameters at each of the incremental positions are used to construct the meta-atoms 94 along the surface of the meta-optic.

[0104] Thus, it can be appreciated that, because the nano-structure 92 can be designed in such a manner that multiple light emitters 66 that emit light of different wavelengths perceive different collimating phase profiles, the entire nano-structure 92 can cover the full area of the pixel 66 and present collimating phase profiles that are respectively centered to the light emitters 68 of the pixel 66. Thus, in contrast to the light collimators 70a, 70b of the respective light redirecting structures 48a, 48b illustrated in 9 and 11 , which provide a group of dedicated areas (e.g., the dedicated microlenses 80) that respectively collimate the different colored light emitted by the light emitters 68, the entire area of each light collimator 70c of the light redirecting structure 48c illustrated in Figs. 26 and 28 is common to the light emitters 68 when collimating the different colored light emitted by the light emitters 68, thereby increasing the efficiencies of the light emitters 68. For example, even if it assumed that the nano-structure 92 has a diffraction efficiency of only 85%, the light efficiencies of light emitters 68, when used with the light redirecting structure 48c will be greater than the light efficiencies of the same light emitters 68, when used with either of the light redirecting structures 48a, 48b (e.g., an efficiency of approximately 43% versus an efficiency of approximately 20%).

[0105] Furthermore, the focal length of the light collimator 70c can be selected to be shorter than the light collimators 70a, 70b illustrated in Figs. 9 and 11 (e.g., a focal length of 3pm versus a focal length of 2pm), since the diameters of the microlenses 80 of the light collimators 70a, 70b are limited to the point where its slope reaches 90 degrees, while the light collimator 70c utilizes a quadratic phase profile that can be indefinitely extended while remaining well-defined. Notably, the shorter the focal length of a light collimator 70, the more light emitted by a light emitter 68 will be captured by the entrance pupil 76 of the projection optics 52 (illustrated in Figs. 3 and 4).

[0106] Although particular embodiments of the present inventions have been shown and described, it will be understood that it is not intended to limit the present inventions to the preferred embodiments, and it will be obvious to those skilled in the art that variouschanges and modifications may be made without departing from the spirit and scope of the present inventions. Thus, the present inventions are intended to cover alternatives, modifications, and equivalents, which may be included within the spirit and scope of the present inventions as defined by the claims.

Claims

CLAIMSWhat is claimed is:

1. A head-mounted display (HMD), comprising: a head-mountable frame; a light projection assembly supported by the frame, the light projection assembly comprising; a micro-display having a two-dimensional array of pixels, each of the pixels comprising a group of light emitters configured for emitting image light; projection optics configured for receiving the image light at an entrance pupil from the group of light emitters of each of the array of pixels, and projecting focused image light from an exit pupil; a two-dimensional array of light collimators disposed between the microdisplay and the projection optics, the array of light collimators being configured for narrowing emission profiles of corresponding groups of the light emitters of the respective array of pixels, a steerable light collimator of the array of light collimators being further configured for redirecting the emission profiles of the corresponding group of light emitters towards a center of the entrance pupil of the projection optics; and an eyepiece supported by the frame, the eyepiece configured for receiving the focused image light from the exit pupil of the projection optics, and directing the image light to an eye of a user when the frame is worn by the user.

2. The HMD of claim 1 , wherein all of the array of light collimators are steerable light collimators configured for steering the emission profiles of the corresponding groups of light emitters towards the center of the entrance pupil of the projection optics.

3. The HMD of claim 1 , wherein the group of light emitters of each of the pixels comprises at least two light emitters respectively configured for emitting image light having two different colors.

4. The HMD of claim 1 , wherein the group of light emitters of each of the pixels comprises at least three light emitters respectively configured for emitting image light having three different colors.

5. The HMD of claim 1 , wherein each group of light emitters comprises a group of light emitting diodes (LEDs).

6. The HMD of claim 1 , wherein the eyepiece comprises a waveguide and an incoupling optical element configured for in-coupling the focused image light from the exit pupil of the projection optics into the waveguide.

7. The HMD of claim 1 , wherein the each of the light collimators has a group of distinct collimating phase profiles respectively for the emission profiles of the corresponding group of light emitters.

8. The HMD of claim 7, wherein the group of distinct collimating phase profiles of the steerable light collimator are configured for redirecting the emission profiles of the corresponding group of light emitters towards the center of the entrance pupil of the projection optics.

9. The HMD of claim 8, wherein the group of distinct collimating phase profiles of the steerable light collimator are configured for redirecting the emission profiles of the corresponding group of light emitters at different angles relative to an optical axis of the projection optics.

10. The HMD of claim 1 , wherein each of the array of collimators is further configured for redistributing intensities amongst the corresponding group of light emitters.11 . The HMD of claim 1 , wherein the array of light collimators is monolithic.

12. The HMD of claim 1 , wherein the each of the light collimators is a refractive light collimator.

13. The HMD of claim 1 , wherein each of the light collimators is a diffractive light collimator.

14. The HMD of claim 1 , wherein the array of light collimators respectively comprise groups of dedicated areas respectively disposed over the groups of light emitters of the respective array of pixels.

15. The HMD of claim 14, wherein the array of light collimators respectively comprises groups of microlenses that respectively correspond to the groups of distinct areas.

16. The HMD of claim 15, wherein the group of microlenses of each of the array of light collimators is superimposed relative to each other.

17. The HMD of claim 16, wherein only a single light emitter of each group of light emitters is functionally associated with a microlens of a corresponding group of microlenses.

18. The HMD of claim 16, wherein the group of microlenses of the steerable light collimator are decentered relative to the corresponding group of the light emitters, such that the emission profiles of the corresponding group of light emitters are redirected towards the center of the entrance pupil of the projection optics.

19. The HMD of claim 18, wherein the group of microlenses of the steerable light collimator are decentered relative to the corresponding group of the light emitters to different degrees, such that emission profiles of the corresponding group of light emitters are independently redirected towards the center of the entrance pupil of the projection optics.

20. The HMD of claim 19, wherein the steerable light collimator has a step profile between at least two of the group of microlenses of the steerable light collimator.21 . The HMD of claim 19, wherein at least one of the at least two microlenses of the steerable light collimator is shifted along a focal axis a distance relative to another one of the at least two microlenses.

22. The HMD of claim 19, wherein at least two of the group of microlenses of the steerable light collimator have different focal lengths.

23. The HMD of claim 1 , wherein the array of light collimators respectively comprise common areas respectively disposed over the groups of light emitters of the respective array of pixels.

24. The HMD of claim 23, wherein the array of light collimators respectively comprises diffractive optics that respectively correspond to the common areas.

25. The HMD of claim 24, wherein the diffractive optics are meta-optics.

26. The HMD of claim 24, wherein each of the meta-optics comprises an optically transparent base substrate and a nano-structure having a plurality of subwavelength meta-atoms.

27. The HMD of claim 24, wherein each group of light emitters comprises at least two light emitters respectively configured for emitting image light having two different colors.

28. The HMD of claim 22, wherein the diffractive optic of the steerable light collimator is designed, such that the emission profiles of the corresponding group of light emitters are redirected towards the center of the entrance pupil of the projection optics.

29. The HMD of claim 23, wherein the steerable light collimator is designed, such that emission profiles of the corresponding group of light emitters are independently redirected towards the center of the entrance pupil of the projection optics.

30. A head-mounted display (HMD), comprising: a head-mountable frame; a light projection assembly supported by the frame, the light projection assembly comprising; a micro-display having a two-dimensional array of pixels, each of the pixels comprising a group of light emitters configured for emitting image light; projection optics configured for receiving the image light at an entrance pupil from the group of light emitters of each of the array of pixels, and projecting focused image light from an exit pupil; a two-dimensional array of light collimators disposed between the microdisplay and the projection optics, the array of light collimators being configured for narrowing emission profiles of corresponding groups of the light emitters of the respective array of pixels, the array of light collimators respectively comprising groups of microlenses, such that only a single light emitter of each group of light emitters is functionally associated with a microlens of a corresponding group of microlenses, the microlenses of each group of microlenses being superimposed relative to each other; andan eyepiece supported by the frame, the eyepiece configured for receiving the focused image light from the exit pupil of the projection optics, and directing the image light to an eye of a user when the frame is worn by the user.31 . The HMD of claim 30, wherein the group of light emitters of each of the pixels comprises at least two light emitters respectively configured for emitting image light having two different colors.

32. The HMD of claim 30, wherein the group of light emitters of each of the pixels comprises at least three light emitters respectively configured for emitting image light having three different colors.

33. The HMD of claim 30, wherein each group of light emitters comprises a group of light emitting diodes (LEDs).

34. The HMD of claim 30, wherein the eyepiece comprises a waveguide and an in-coupling optical element configured for in-coupling the focused image light from the exit pupil of the projection optics into the waveguide.

35. The HMD of claim 30, wherein the array of light collimators is monolithic.

36. The HMD of claim 30, wherein the group of microlenses of at least one of the light collimators is decentered relative to the corresponding group of the light emitters, such that the emission profiles of the corresponding group of light emitters are redirected.

37. The HMD of claim 36, wherein the emission profiles of the corresponding group of light emitters are redirected towards the center of the entrance pupil of the projection optics.

38. The HMD of claim 36, wherein the group of microlenses of each of the at least one light collimator is decentered relative to the corresponding group of the light emitters to different degrees, such that emission profiles of the corresponding group of light emitters are independently redirected.

39. The HMD of claim 38, the each at least one light collimator has a step profile between at least two of the group of microlenses of the respective light collimator.

40. The HMD of claim 38, wherein at least one of the at least two microlenses of the each at least one light collimator is shifted along a focal axis a distance relative to another one of the at least two microlenses.41 . The HMD of claim 38, wherein at least two of the group of microlenses of the each at least one light collimator has different focal lengths.

42. A head-mounted display (HMD), comprising: a head-mountable frame; a light projection assembly supported by the frame, the light projection assembly comprising; a micro-display having a two-dimensional array of pixels, each of the pixels comprising a group of light emitters configured for emitting image light; projection optics configured for receiving the image light at an entrance pupil from the group of light emitters of each of the array of pixels, and projecting focused image light from an exit pupil; a two-dimensional array of meta-optic light collimators disposed between the micro-display and the projection optics, the array of meta-optic light collimators being configured for narrowing emission profiles of corresponding groups of the light emitters of the respective array of pixels; and an eyepiece supported by the frame, the eyepiece configured for receiving the focused image light from the exit pupil of the projection optics, and directing the image light to an eye of a user when the frame is worn by the user.

43. The HMD of claim 42, wherein the group of light emitters of each of the pixels comprises at least two light emitters respectively configured for emitting image light having two different colors.

44. The HMD of claim 42, wherein the group of light emitters of each of the pixels comprises at least three light emitters respectively configured for emitting image light having three different colors.

45. The HMD of claim 42, wherein each group of light emitters comprises a group of light emitting diodes (LEDs).

46. The HMD of claim 42, wherein the eyepiece comprises a waveguide and an in-coupling optical element configured for in-coupling the focused multi-color image light from the exit pupil of the projection optics into the waveguide.

47. The HMD of claim 42, wherein the array of meta-optic light collimators is monolithic.

48. The HMD of claim 42, wherein each of the array of meta-optic light collimators comprises an optically transparent base substrate and a nano-structure having a plurality of subwavelength meta-atoms.

49. The HMD of claim 42, wherein at least one of the array of meta-optic light collimators is designed, such that the emission profiles of the corresponding group of light emitters are redirected towards the center of the entrance pupil of the projection optics.

50. The HMD of claim 49, wherein the at least one meta-optic light collimator is designed, such that emission profiles of the corresponding group of light emitters are independently redirected towards the center of the entrance pupil of the projection optics.

Images