Micro LED Multi-Emitter / Color Display Microlens Array

Abstract

The HMD comprises a head-mountable frame and an optical projection assembly supported by the frame. The optical projection assembly comprises a microdisplay supported by the frame. The microdisplay has a two-dimensional array of pixels. Each pixel contains a group of emitters configured to emit image light. The microdisplay further comprises a projection optical system configured to receive image light from each group of emitters in the array of pixels at the entrance pupil and project the focused image light from the exit pupil. The microdisplay further comprises a two-dimensional array of optical collimators positioned between the microdisplay and the projection optical system. The steerable optical collimators are further configured to redirect the emission profiles of the corresponding groups of emitters toward the center of the entrance pupil of the projection optical system.

Description

Technical Field

[0001] Incorporation by Reference This application claims priority to U.S. Provisional Application No. 63 / 506,550, filed Jun. 6, 2023, the content of which is hereby expressly and fully incorporated herein by reference in its entirety.

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

Background Art

[0003] Background Modern computing and display technologies have facilitated the development of head-mounted displays (HMDs) for so-called extended reality (XR) experiences for users, where some or all of the environment is created by presenting digital reproduced images (e.g., virtual objects) to the user such that they appear as if they were real or can be perceived as real. XR HMDs can be useful for many applications spanning the fields of scientific visualization, medical training, engineering design and prototyping, remote operation and telepresence, and personal entertainment. XR HMDs can include, for example, virtual reality (VR) HMDs, augmented reality (AR) HMDs, or mixed reality (MR) HMDs. VR HMDs typically involve presenting digital or virtual image information that is opaque to other actual real-world visual inputs. AR HMDs or MR HMDs typically involve presenting virtual objects to the user in relation to real-world objects in the physical world. In particular, AR HMDs involve presenting digital or virtual image information as an extension to the visualization of the actual world around the user. MR HMDs involve presenting AR image content that appears to be occluded by real-world objects or is otherwise perceived to interact with real-world objects.

[0004] Many HMDs utilize transmissive or reflective spatial light modulator (SLM) displays to form the image presented to the user. A light source emits light, which is directed towards the SLM display, which then modulates the light, and this light is then directed towards the user. A lens structure is provided between the light source and the SLM display to focus the light from the light source onto the SLM display. Undesirably, the light source and associated optics can add bulk and weight to the HMD. This bulk and weight can negatively impact the comfort of the HMD and its likelihood of being worn for extended periods.

[0005] In addition, frame rate limitations in some HMDs can cause viewing discomfort. For example, many SLM displays use the movement of optical elements to modulate the intensity of light emitted by these SLM displays to form an image. For instance, micro-electromechanical system (MEMs) based SLM displays can modulate incident light using movable mirrors, while liquid crystal on silicon (LCoS) based displays can modulate light using the movement of liquid crystal molecules. Other HMDs may utilize scanning fiber technology, where the end of an optical fiber physically moves across a region while emitting light. The light emitted by the optical scanning fiber can be synchronized with the position and timing of the fiber end, thereby effectively mimicking pixels at different locations to form an image.

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

[0007] In addition, scanning fiber displays may present other undesirable optical artifacts, for example, due to the small cross-section of the fiber, which necessitates the use of a high-intensity light source to form an image of the desired apparent brightness. A suitable high-intensity light source includes a laser that emits coherent light. Undesirably, the use of coherent light can also cause optical artifacts.

[0008] Micro-LED displays have been proposed as an alternative to the SLM and scanning fiber displays mentioned above. Micro-LED displays offer various advantages for use in HMDs. For example, micro-LED displays are emissive. The power consumption of emissive micro-LED displays generally varies depending on the image content, with dark or sparse content requiring less power for display. Because AR and MR environments are often sparse (generally, it is desirable for the user to be able to see the surrounding environment), emissive micro-LED displays can have a lower average power consumption than other display technologies that use SLM to modulate light from a light source. In contrast, other display technologies may utilize considerable power even for dark, sparse, or "all-off" virtual content. As another example, emissive micro-LED displays can offer very high frame rates (which can enable the use of partial resolution arrays) and can offer low levels of visually noticeable motion artifacts (e.g., motion blur). As yet another example, emissive micro-LED displays may not require the type of polarizing optics required for LCoS displays. Thus, emissive micro-LED displays can avoid the light loss present in polarizing optics.

[0009] Many microLED displays may include planar light-emitting elements formed on a substrate, while other microLED displays may include nanowire LEDs formed from an array of vertically extending nanowires (e.g., spaced pillars of material) electrically connected to two electrodes and emitting light upon application of an electric current through the nanowires, as described in U.S. Patent No. 11,604,354 expressly incorporated herein by reference.

[0010] In some embodiments, one or more micro-LED displays may be utilized and positioned on different sides of an optical combiner, such as an X-cube prism or a dichroic X-cube. The X-cube prism receives rays from different micro-LED displays on different faces of the cube and outputs rays from different micro-LED displays from another face of the cube. Rays from all different micro-LED displays may be output from the same output face of the cube. The output light may be directed to a projection optical system configured to focus or concentrate the image light onto an eyepiece for viewing by the user of the HMD.

[0011] In some embodiments, each microLED display is monochromatic and configured to output light of a single constituent color, which can then be combined by a subsequent optical system to form a full-color image. In other embodiments, one or more of the microLED displays may have subpixels configured to emit light of two or more, but not all, constituent colors. For example, a single microLED display positioned on one side of an optical combiner may have subpixels that emit blue and green light, while a separate microLED display positioned on another side of the optical combiner may have pixels that emit red light. In some embodiments, one or more of the microLED displays are full-color displays, each comprising pixels formed from multiple subpixels configured to emit light of all different constituent colors, such as blue, green, and red light. Advantageously, combining the light from multiple full-color microLED displays can increase the brightness and dynamic range of the display. In other embodiments, a single full-color microLED display can be used without an optical combiner to emit light of all different color components.

[0012] In some embodiments, an eyepiece receiving light from a micro-LED display may include a waveguide assembly comprising one or more waveguides. Each waveguide may also have an input coupling optical element that input couples incident image light so that the light propagates through the waveguide by internal total internal reflection (TIR). Each waveguide may also include an output coupling optical element that output couples the light propagating through it so that the output coupled light propagates toward the user's eye. In some embodiments, the waveguide assembly may include a stack of waveguides, each having an associated input coupling optical element. The stack of waveguides may be configured to selectively output light with different amounts of wavefront divergence to provide virtual content in multiple depth planes perceived as being at different distances from the user. For example, the stack of waveguides may each have output coupling optical elements with different optical powers to output light with different amounts of wavefront divergence.

[0013] Each LED in a micro-LED display may emit light with a larger angular emission profile than desired, resulting in only a small portion of the emitted light ultimately entering the eyepiece, thereby wasting light. In some embodiments, optical collimators (e.g., microlenses, nanolenses, reflective wells, metasurfaces, and liquid crystal gratings) can be used to narrow the angular emission profile of the light emitted by the LEDs in the micro-LED display. The optical collimator is preferably positioned directly adjacent to or in contact with the LED to capture the majority of the light emitted by the LED in question.

[0014] In one embodiment shown in Figure 1, light emitted by a particular micro-LED display 1 having an array of LEDs 2a-2e (only one dimension is shown) generally propagates toward the projection optical system 3 in a direction perpendicular to the plane of the micro-LED display 1 (i.e., telecentric). An array of microlenses 4a-4e (only one dimension is shown) can be positioned on the array of LEDs 2a-2e, respectively, such that the angular emission profiles 5a-5e of each LED 2a-2e are narrowed. However, despite the fact that the angular emission profiles 5a-5e of LEDs 2a-2e are narrowed, a considerable amount of light emitted by the micro-LED display 1 is not received by the entrance pupil of the projection optical system 3. That is, as shown in Figure 1, the amount of light captured by the entrance pupil of the projection optical system 3 from each LED decreases as the distance of the LED from the center of the micro-LED display 1 increases (i.e., as the LED emitting light approaches the periphery of the micro-LED display 1, the amount of light captured by the entrance pupil of the projection optical system 3 decreases). Thus, the entrance pupil of the projection optical system 3 must be large enough to capture as much light as possible from the LEDs surrounding the micro-LED display 1 (e.g., LEDs 2d-2e), and as a result, the size, complexity, and cost of the HMD utilizing the micro-LED display 1 can increase accordingly. If the pupil of the projection optical system 3 is not large enough, much of the light emitted by the micro-LED display 1 may be wasted undesirably, as it is not captured and ultimately not relayed to the user's eye to form an image. This can result in an image that appears darker than expected if more of the light output by the micro-LED display ultimately reached the user's eye.

[0015] Therefore, it is desirable to reduce the size of the projection optics following one or more micro-LED displays, while still maximizing the amount of light emitted by the micro-LED displays that is captured by the pupil of the projection optics, thereby reducing the size, complexity, and cost of the HMD. [Overview of the Initiative] [Means for solving the problem]

[0016] overview According to the present invention, a head-mounted display (HMD) comprises a head-mountable frame and an optical projection assembly supported by the frame. The optical projection assembly comprises a microdisplay having a two-dimensional array of pixels. Each pixel includes a group of light emitters (e.g., light-emitting diodes (LEDs)) configured to emit image light. A projection optical system is configured to receive image light from each group of light emitters in the array of pixels at the entrance pupil and project the focused image light from the exit pupil. The optical projection assembly further comprises a two-dimensional array of optical collimators (e.g., refractive or diffractive collimators) placed between the microdisplay and the projection optical system. The array of optical collimators is configured to narrow the emission profile of the corresponding group of light emitters in each array of pixels. The HMD further comprises an eyepiece supported by the frame. The eyepiece receives focused image light from the exit pupil of the projection optical system and is configured to direct the image light towards the user's eye when the frame is worn by the user. In one embodiment, each group of light emitters for each pixel includes at least two light emitters, each configured to emit image light having two different colors. In another embodiment, each group of light emitters for each pixel includes at least three light emitters, each configured to emit image light having three different colors. In yet another embodiment, the eyepiece includes a waveguide and an input coupling optical element configured to input couple focused image light from the exit pupil of a projection optical system to the waveguide.

[0017] According to a first aspect of the present invention, the steerable optical collimators in an array of optical collimators are further configured to redirect the emission profiles of corresponding groups of emitters toward the center of the entrance pupil of the projection optical system. In one embodiment, all of the array of optical collimators are steerable optical collimators configured to steer the emission profiles of corresponding groups of emitters toward the center of the entrance pupil of the projection optical system. In another embodiment, each optical collimator has a separate group of collimated phase profiles of the emission profiles of corresponding groups of emitters. In this case, the separate group of collimated phase profiles of the steerable optical collimator may be configured to redirect the emission profiles of corresponding groups of emitters toward the center of the entrance pupil of the projection optical system. The separate group of collimated phase profiles of the steerable optical collimator may also be configured to redirect the emission profiles of corresponding groups of emitters to different angles with respect to the optical axis of the projection optical system. In yet another embodiment, the array of collimators is further configured to redistribute intensity among corresponding groups of emitters. In yet another embodiment, the array of optical collimators is monolithic.

[0018] In yet another embodiment, the array of optical collimators includes a group of dedicated regions, each positioned above a group of light emitters in each array of pixels. In this case, the array of optical collimators may comprise a group of microlenses, each corresponding to a separate group of regions. Each group of microlenses in the array of optical collimators may overlap one another. In one embodiment, only a single light emitter from each group of light emitters is functionally associated with one microlens from the corresponding group of microlenses. The group of microlenses in a steerable optical collimator may be eccentric with respect to the corresponding group of light emitters such that the emission profile of the corresponding group of light emitters is redirected toward the center of the entrance pupil of the projection optical system. The group of microlenses in a steerable optical collimator may also be eccentric to different degrees with respect to the corresponding group of light emitters such that the emission profile of the corresponding group of light emitters is independently redirected toward the center of the entrance pupil of the projection optical system. When each group of microlenses in an array of optical collimators is superimposed on one another, a steerable optical collimator may have a step profile between at least two of the groups of microlenses of the steerable optical collimator, and / or at least one of the at least two microlenses of the steerable optical collimator may be shifted along the focal axis by a certain distance relative to the other of the at least two microlenses, and / or at least two of the groups of microlenses of the steerable optical collimator may have different focal lengths.

[0019] In yet another embodiment, the array of optical collimators includes a common region positioned above each group of light emitters in each array of pixels. In one embodiment, the array of optical collimators comprises a diffraction optical system corresponding to each common region. For example, the diffraction optical system may include a meta-optical system, each of which may comprise an optically transparent base substrate and a nanostructure having a plurality of subwavelength metaatoms. In another embodiment, each group of light emitters includes at least two light emitters configured to emit image light having two different colors. In yet another embodiment, the steerable optical collimator may be designed so that the emission profiles of corresponding groups of light emitters are redirected toward the center of the entrance pupil of the projection optical system. The steerable optical collimator may also be designed so that the emission profiles of corresponding groups of light emitters are independently redirected toward the center of the entrance pupil of the projection optical system.

[0020] According to another aspect of the present invention, the array of optical collimators comprises groups of microlenses, each of which is superimposed on the others. Only a single emitter in each group of emitters is functionally associated with the microlenses of the corresponding group of microlenses. In one embodiment, the array of optical collimators is monolithic. In another embodiment, at least one group of microlenses in the optical collimator is eccentric with respect to the corresponding group of emitters such that the emission profile of the corresponding group of emitters is redirected. For example, the emission profile of the corresponding group of emitters may be redirected toward the center of the entrance pupil of the projection optical system. In yet another embodiment, each group of microlenses in the optical collimator may be eccentric to different degrees with respect to the corresponding group of emitters such that the emission profile of the corresponding group of emitters is independently redirected. Each of the optical collimators may have a step profile between at least two of the group of microlenses of the steerable optical collimator, and / or at least one of the at least two microlenses of the steerable optical collimator may be shifted along the focal axis by a certain distance relative to the other of the at least two microlenses, and / or at least two of the group of microlenses of the steerable optical collimator may have different focal lengths.

[0021] According to another aspect of the present invention, the array of optical collimators is an array of meta-optical collimators. In one embodiment, the array of meta-optical collimators is monolithic. In another embodiment, each of the array of meta-optical collimators comprises an optically transparent base substrate and a nanostructure having a plurality of sub-wavelength meta-atoms. In yet another embodiment, at least one of the array of meta-optical collimators is designed such that the emission profile of the corresponding group of light emitters is redirected towards the center of the entrance pupil of the projection optical system. In this case, the meta-optical collimator(s) may be designed such that the emission profile of the corresponding group of light emitters is independently redirected towards the center of the entrance pupil of the projection optical system.

[0022] Other and further aspects and features of the present invention will become apparent from the following detailed description of the preferred embodiments, which are intended to illustrate and not to limit the invention.

Brief Description of the Drawings

[0023] Brief Description of the Drawings The drawings illustrate the design and utility of embodiments of the present invention, and like elements are referred to by common reference numerals. To better understand how the above and other advantages and objects of the present invention are obtained, a more specific description of the present invention briefly described above is made by referring to the specific embodiments of the present invention shown in the accompanying drawings. It is understood that these drawings show only typical embodiments of the present invention and should not be considered as limiting its scope, and the present invention is described and explained with additional specificity and detail by using the accompanying drawings.

[0024] [Figure 1] FIG. 1 is a prior art plan view of a telecentric projection assembly for use in a head-mounted display (HMD).

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

[0026] [Figure 3] Figure 3 is a plan view of one embodiment of a display subsystem having a non-telecentric projection assembly configured according to one embodiment of the present invention.

[0027] [Figure 4] Figure 4 is a plan view of another embodiment of a display subsystem having a non-telecentric projection assembly configured according to one embodiment of the present invention.

[0028] [Figure 5] Figure 5 is a plan view of the pixel array of a microdisplay for use in either of the non-telecentric projection assemblies shown in Figure 3 or Figure 4.

[0029] [Figure 6A] Figure 6A is a plan view of the different sized pixels of the microdisplay shown in Figure 5. [Figure 6B] Figure 6B is a plan view of the microdisplay in Figure 5 with pixels of different sizes. [Figure 6C] Figure 6C is a plan view of pixels of different sizes in the microdisplay shown in Figure 5. [Figure 6D] Figure 6D is a plan view of the microdisplay in Figure 5 with pixels of different sizes.

[0030] [Figure 7] Figure 7 is a plan view of one embodiment of a steerable optical collimator for use in either of the non-telecentric projection assemblies shown in Figure 3 or Figure 4.

[0031] [Figure 8] Figure 8 is a plan view of one embodiment of an optical direction reversal structure comprising the steerable optical collimator array shown in Figure 7.

[0032] [Figure 9] Figure 9 is a perspective view of one embodiment of an optical direction reversal structure for use in either the non-telecentric projection assembly shown in Figure 3 or Figure 4.

[0033] [Figure 10A] Figure 10A is a perspective view of groups of different sizes of superimposed microlenses for use in the optical direction reversal structure shown in Figure 9. [Figure 10B] Figure 10B is a perspective view of groups of different sizes of superimposed microlenses for use in the optical direction reversal structure shown in Figure 9. [Figure 10C] Figure 10C is a perspective view of groups of different sizes of superimposed microlenses for use in the optical direction reversal structure shown in Figure 9.

[0034] [Figure 11] Figure 11 is a perspective view of another embodiment of the optical direction reversal structure for use in either of the non-telecentric projection assemblies shown in Figure 3 or Figure 4.

[0035] [Figure 12] Figure 12 is a perspective view of a group of superimposed microlenses for use in the optical direction reversal structure shown in Figure 11.

[0036] [Figure 13] Figure 13 is a plan view of a conventional optical collimator having a single microlens for narrowing the emission profiles of two emitters in a single pixel.

[0037] [Figure 14A] Figure 14A shows the asymmetric illumination of the entrance pupil of the projection optical system by one of the light-emitting elements in Figure 13.

[0038] [Figure 14B] Figure 14B shows the asymmetric illumination of the entrance pupil of the projection optical system by another light-emitting element from Figure 13.

[0039] [Figure 15] Figure 15 is a profile diagram of one embodiment of an optical collimator having superimposed microlenses for use in the optical direction reversal structure of Figure 11, and in particular shows superimposed microlenses centered with respect to the corresponding light emitter of a single pixel.

[0040] [Figure 16A] Figure 16A shows the relatively symmetrical illumination of the entrance pupil of the projection optical system by one of the light-emitting elements in Figure 15.

[0041] [Figure 16B] Figure 16B shows the relatively symmetrical illumination of the entrance pupil of the projection optical system by another of the light-emitting elements in Figure 15.

[0042] [Figure 17] Figure 17 is a profile diagram of the optical collimator in Figure 15, and in particular shows superimposed microlenses that are eccentric with respect to the corresponding emitters of the out-of-center pixels, thereby redirecting the emission profile of the corresponding emitters.

[0043] [Figure 18] Figure 18 shows the symmetrical illumination of the entrance pupil of the projection optical system by one of the light-emitting elements shown in Figure 17.

[0044] [Figure 19] Figure 19 is a profile diagram of the optical collimator in Figure 15, and in particular shows a superimposed microlens that is eccentric with respect to the corresponding emitter of the central pixel, thereby redirecting the emission profile of the corresponding emitter.

[0045] [Figure 20] Figure 20 shows profile diagrams of three adjacent optical collimators from Figure 11, specifically illustrating superimposed microlenses centered on the corresponding single-pixel emitters.

[0046] [Figure 21] Figure 21 shows the profile diagrams of three adjacent optical collimators from Figure 11, in particular showing the central microlens which is eccentric with respect to the corresponding light source, resulting in a step profile between the superimposed microlenses.

[0047] [Figure 22] Figure 22 shows the profile diagrams of three adjacent optical collimators from Figure 11, and in particular, the microlenses that are eccentric with respect to the corresponding light emitter of a single pixel, resulting in a step profile between the microlenses.

[0048] [Figure 23] Figure 23 shows profile diagrams of three adjacent optical collimators from Figure 11, and in particular, shows microlenses that are eccentric with respect to the corresponding single-pixel emitter and shifted along the focal axis to eliminate the need for a step profile between microlenses.

[0049] [Figure 24] Figure 24 is a profile diagram of the optical collimator shown in Figure 11, and in particular shows the superimposed microlenses centered on the corresponding light emitters of a single pixel, and the step profile formed between the superimposed microlenses, which thereby alters the relative intensity between the corresponding light emitters.

[0050] [Figure 25] Figure 25 is a perspective view of yet another embodiment of the optical direction reversal structure for use in either of the non-telecentric projection assemblies shown in Figure 3 or Figure 4.

[0051] [Figure 26] Figure 26 is a profile diagram of an optical collimator with a metaoptics system for use in the optical direction reversal structure of Figure 15, and in particular shows the collimation phase profile at a first position relative to the corresponding light emitter of a single pixel.

[0052] [Figure 27] Figure 27 is an axial view of the collimated phase profile generated by the optical collimator in Figure 26.

[0053] [Figure 28] Figure 28 is a profile diagram of the optical collimator in Figure 26, and in particular shows one of the collimation phase profiles at a second position relative to the corresponding light emitter of a single pixel. [Modes for carrying out the invention]

[0054] Detailed explanation Referring to Figure 2, a wearable extended reality (XR) system 10 for use by user 12 generally comprises a head-mounted display (HMD) 14 (e.g., eyewear device) and a data and processing module 16. The HMD 14 is generally configured to present virtual content and sound to user 12, while the local processing and data module 16 (e.g., compute pack) is configured to be worn by user 12 remotely from user 12's head (e.g., on the user's torso in a backpack-style configuration, or on the user's buttocks in a belt-mounted style configuration). The data and processing module 16 can assist the XR system 10 in processing, caching, and storing data used to present virtual content to the user. For example, the data and processing module 16 may include a power-efficient processor or controller, as well as digital memory such as flash memory, both of which can be used to assist in processing, caching, and storing data used by the HMD 14 to present virtual content and / or sensor data acquired by the HMD 14 to the user. The HMD14 can be operably coupled to the data and processing module 16 via a wired or wireless connection 18.

[0055] The HMD14 comprises a head-mountable frame 20, a display subsystem 22 fixed to the head-mountable frame 20, and one or more optional speakers 24 and one or more optional microphones 26 fixed to the head-mountable frame 20. The head-mountable frame 20 may be mounted on the user 12's head such that the display (described later) of the display subsystem 22 is positioned in front of the user 12's eyes, the speakers 24 are positioned adjacent to the user 12's ear canal (another speaker (not shown) may be positioned adjacent to the user 12's other ear canal to provide stereo / shapeable acoustic control, if necessary), and the microphones 26 are positioned adjacent to the user 12's face. The microphones 26 may be configured to allow the user 12 to provide input or commands to the XR system 10 (e.g., selection of voice menu commands, natural language questions, etc.) and / or to facilitate acoustic communication with other people (e.g., with other uses of a similar XR system 10). In some embodiments, the XR system 10 may further include one or more outward-facing environmental sensors 28 fixed to a 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 include one or more cameras that can be positioned, for example, to face outward to capture images within the user 12's field of view.

[0056] The display subsystem 22 is designed to present virtual content to the eyes of user 12. For this purpose, the display subsystem 22 comprises one or more transparent screens (or eyepieces) 30 and one or more light projection assemblies 32 (shown in Figure 3) that project light onto the eyepiece(s) 30 to present virtual content to user 12. The eyepiece(s) 30 and projection assemblies(s) 32 are fixed to a head-mountable frame 20. The head-mountable frame 20 is designed not only to position the eyepiece(s) 30 in front of user 12's eyes, but also to position the eyepiece(s) 30 within user 12's field of view, between user 12's eyes and the surrounding environment, so that direct light from the surrounding environment is transmitted through the eyepiece(s) 30 to user 12's eyes. In the illustrated embodiment, the display subsystem 22 has only one eyepiece 30 for presenting monocular virtual content to the user 12, but it should be understood that the display subsystem 22 may also have two eyepieces positioned in front of the user 12's eyes for presenting binocular virtual content to the user 12.

[0057] The XR system 10 may optionally include a remote processing module 34 and a remote data repository 36 operably coupled to the data and processing module 16. The remote processing module 34 may include 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 include a relatively large digital data storage facility that may be available via the Internet or other networking configuration in a “cloud” resource configuration. In one embodiment, all data is stored and all calculations are performed within the data and processing module 16, enabling fully autonomous use from any remote module. The data and processing module 16 can be operably coupled to the remote processing module 34 and the remote data repository 36 via their respective wired or wireless connections 38, 40.

[0058] Referring to Figure 3, one embodiment of the display subsystem 22a generally comprises an optical projection assembly 32a for projecting color image light and an eyepiece 30 for relaying the color image light in the form of virtual content to one or both eyes 44 of the user 12. Although the display subsystem 22a is shown as having only one optical projection assembly 32a and one corresponding eyepiece 30, it should be understood that the display subsystem 22a may have two optical projection assemblies and two corresponding eyepieces.

[0059] The optical projection assembly 32a includes a plurality of microdisplays 46', 46'', 46''' each configured to emit multicolor 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 optical redirection structures 48', 48'', 48''' configured to narrow and redirect the angular light profiles of the arrays of individual light emitters of the microdisplays 46', 46'', 46''' (described in more detail below), an optical combiner 50 configured to combine the multicolor image light 54', 54'', 54''' emitted by the microdisplays 46', 46'', 46''' via the optical redirection structures 48 to output full-color image light 54 (i.e., image light having all three color components (e.g., blue, green, and red)), and a projection optical system 52 configured to project the full-color image light 54 combined by the optical combiner 50 onto the eyepiece 30.

[0060] At least one of the microdisplays 46', 46'', 46'''' may output non-monochromatic image light containing 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 microdisplays 46', 46'', 46'''' may output non-monochromatic light containing only two color components (e.g., green and blue components), and at least one other of the microdisplays 46', 46'', 46'''' may output monochromatic image light (e.g., having a red component). The non-monochromatic and monochromatic image light can then be combined within the eyepiece 30 and output as a full-color image to the user's eye 44. In another embodiment, each of the microdisplays 46', 46'', 46'''' may output full-color image light (e.g., having green, blue, and red components). Such microdisplays 46', 46'', 46'''' may be identical and may display the same image. However, utilizing multiple full-color microdisplays 46', 46'', 46''' can offer advantages in increasing image brightness and dynamic range of brightness by combining image light from multiple microdisplays to form a single image. An alternative embodiment of the optical projection assembly 32b of the display subsystem 22b shown in Figure 4 comprises only one full-color microdisplay 46 capable of outputting full-color image light 54, in which case the optical combiner 50 may be omitted, thereby favorably reducing the size, weight, and cost of the HMD 14.

[0061] The light direction reversal structures 46', 46'', 46'''' (or light direction reversal structure 48) are configured to redirect the multicolor image light 54', 54'', 54'''' inward toward the center of the pupil of the projection optical system 52, respectively. In this way, the projection optical system 52 can be made smaller than the projection optical system used in the telecentric architecture (for example, the projection optical system 3 shown in Figure 3) without sacrificing the efficiency of capturing the full-color image light 54 from the microdisplays 46', 46'', 46'''' or the microdisplay 46, particularly the portion of the full-color image light 54 provided by the periphery of the microdisplays 46', 46'', 46'''' or the periphery of the microdisplay 46.

[0062] The optical combiner 50 receives multicolor image light 54', 54'', 54'''' from the microdisplays 46', 46'', 46'''' via the optical redirection structure 48 and effectively combines this light so that it is output from a common side of the optical combiner 50 and propagates along substantially the same path toward the projection optical system 52. In some embodiments, the optical combiner 50 may be an X-cube prism or a dichroic X-cube prism having a reflective inner surface 56 that redirects the full-color image light 54 toward the projection optical system 52.

[0063] The projection optical system 52 has an entrance pupil 56 for receiving full-color image light 54 from the array of light emitters of the microdisplay 46', 46'', 46''' shown in Figure 3 (or alternatively, from the array of light emitters of the microdisplay 46 shown in Figure 4), and an exit pupil 58 for projecting the focused full-color image light 54 onto the eyepiece 30. The projection optical system 52 may also be a lens structure including one or more lenses for focusing or converging the image light onto the eyepiece 30. The projection optical system 52 may be formed of a high refractive index material (e.g., having a refractive index greater than 1.5) to facilitate focusing. In some embodiments, the projection optical system 52 may have elongated entrance and exit pupils (e.g., elliptical) to emit a light beam having a cross-sectional profile similar to the shape of the input coupling optical element of the eyepiece 30. For example, the projection optical system 52 may be elongated to a dimension corresponding to the elongated dimension of the input coupling optical element to improve the etendue mismatch between the microdisplay 46', 46'', 46''' and the eyepiece 30.

[0064] In the illustrated embodiment, the eyepiece 30 takes the form of a waveguide assembly including one or more waveguides 60 (only one shown) configured to propagate full-color image light 54 on which image information is encoded by internal total internal reflection (TIR), an input coupling optical element 62 fixed to the waveguide 60 to inject full-color image light 54 from the projection optical system 52 into the waveguide 60, and an output coupling optical element 64 fixed to the waveguide 60 to extract color light 54 from the waveguide 60 to the eye 44 of the user 12.

[0065] The waveguide 60 can output full-color image light 54 with a predetermined amount of wavefront divergence corresponding to the wavefront divergence of the light field generated 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. If the eyepiece 30 comprises a single waveguide 60, such waveguide 60 may be configured to output color light 54 corresponding to one or a 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 input coupling optical element 62 is positioned on the plane of the waveguide 60, in the illustrated embodiment, on the rear plane of the waveguide 60 (i.e., furthest from the projection optical system 52). In this configuration, the input coupling optical element 62 may be a reflected light inductor that input couples the full-color image light 54 by reflecting light at an angle that supports TIR through the waveguide 60. In other configurations, the input coupling optical element 62 may be positioned on the front of the waveguide 60 (i.e., closest to the projection optical system 52). In this configuration, the input coupling optical element 62 may be a transmitted light direction changer that input couples the full-color image light 54 by changing the propagation direction of the full-color image light 54 as it passes through the input coupling optical element 62.

[0067] The output coupling optical element 64 takes the form of an exit pupil (EP) or exit pupil expander (EPE) positioned in the plane of the waveguide 60, in the illustrated embodiment, in the forward plane of the waveguide 60 (i.e., closest to the user's eye 44). In other embodiments, the output coupling optical element 64 may be directly installed within the volume of the waveguide 60. In some embodiments, the output coupling optical element 64 may be formed in a layer of material subsequently attached to the waveguide 60. In other embodiments, the output coupling optical element 64 may be formed monolithically in the plane of the waveguide 60. The full-color image light 54 propagating through the waveguide 60 may be output by the waveguide 60 at locations where it strikes the output coupling optical element 64. The output coupling optical element 64 may be a diffractive optical mechanism, such as a grating.

[0068] In an optional embodiment, the eyepiece 30 further comprises an optical distribution element (not shown) fixed to the waveguide 60 to deflect the full-color image light 54 propagating from the input coupling optical element 62 through the waveguide 60 toward the output coupling optical element 64. The optical distribution element may take the form of an orthogonal pupil expander (OPE) positioned on the plane of the waveguide 60, for example, on one or both of the front and rear surfaces of the waveguide 60 (i.e., closest to the projection optical system 52). In this case, the full-color image light 54 can propagate through the waveguide 60 by TIR until it collides with the optical distribution element, which then distributes the full-color image light 54 toward the output coupling optical element 64.

[0069] Although the eyepiece 30 is shown in Figures 3 and 4 as having only a single waveguide 60 having a single input coupled optical element 62 and a single output coupled optical element 64, it should be understood that the eyepiece 30 may have a stacked assembly of waveguides having related input coupled optical elements and output coupled optical elements, as described in U.S. Patent No. 11,604,354, which is expressly incorporated herein by reference. In these cases, the full-color image light 54 from the projection optical system 52 may propagate through each of the waveguides, or less than full-color image light (e.g., monochromatic image light or image light having only blue and green components) may propagate through at least one of the waveguides.

[0070] Referring here to Figure 5, each of the microdisplays 46', 46'', 46''' (Figure 3) or a single microdisplay 46 (Figure 4) has a two-dimensional array of multicolor pixels 66, while each of the optical direction reversal structures 48', 48'', 48''' (Figure 3) or a single optical direction reversal structure 48 (Figure 4) has a two-dimensional array of optical collimators 70 that correspond one-to-one with the array of pixels 66 of each microdisplay 46', 46'', 46''' or a single microdisplay 46. The optical collimator 70 may take the form of any suitable optical element that can narrow and steer the emission profile of an emitter, including but not limited to microlenses, nanolenses, reflective wells, metasurfaces, metaoptics, diffractive lenses / structures, and liquid crystal gratings. In Figure 5, the two-dimensional array of multicolor pixels 66 and the corresponding two-dimensional array of optical collimators 70 are shown as rectangular. However, it should be understood that the two-dimensional arrays of multicolor pixels 66 and optical collimators 70 may have any shape, including circular, elliptical, polygonal, etc. Furthermore, the number of multicolor pixels 66 and the corresponding optical collimators 70 is generally much larger than that shown in Figure 5 (e.g., 1280 pixels × 420 pixels).

[0071] As illustrated in Figures 6A to 6D, each of the 66 pixels contains a group of different color emitters 68a to 68c (e.g., light-emitting diodes (LEDs)) for emitting color image light. The group of color emitters 68a to 68c may represent subpixels contained within the pixel 66. In one example shown in Figure 6A, pixel 66a may contain two emitters of equal size but different colors (e.g., a blue emitter 68a and a green emitter 68b). In another example shown in Figure 6B, pixel 66b may contain three emitters of equal size but different colors (e.g., a blue emitter 68a, a green emitter 68b, and a red emitter 68c). In yet another example shown in Figure 6C, pixel 66c may contain two emitters of equal size but different colors (e.g., a blue emitter 68a and a green emitter 68b) and a larger emitter of a different color (e.g., a red emitter 68c). In this example, the larger size of the light emitter 68c can compensate for the inefficiency of some colors (e.g., red) compared to other more luminescently efficient colors (e.g., blue and green). In yet another example shown in Figure 6D, the pixel 66d may include two light emitters of different colors but equal size (e.g., a blue light emitter 68a and a green light emitter 68b) and two light emitters of the same color but equal size (e.g., two red light emitters 68c, 68d). In this embodiment, multiple light emitters 68c of the same color can compensate for the inefficiency of some colors (e.g., red) compared to other more luminescently efficient colors (e.g., blue and green).

[0072] Referring to Figure 7, for a particular pixel 66, each optical collimator 70 is specifically designed to have a distinct group of collimated phase profiles 72, each seen by a group of emitters 68 for that pixel 66. Although only two emitters 68a, 68b (e.g., as shown in Figure 6A), and therefore only two distinct collimated phase profiles 72a, 72b, are shown, the group of emitters 68 for a particular pixel 66 may include more than two emitters (e.g., emitters 68a-68c shown in Figures 6B-6C or four emitters 68a-68d shown in Figure 6D), and therefore, the distinct group of collimated phase profiles 72 of the optical collimator 70 may correspondingly include more than two distinct collimated phase profiles 72. For example, a group of separate collimated phase profiles 72 of the optical collimator 70 may include three separate collimated phase profiles of three light emitters 68a to 68c shown in Figures 6B to 6C, or four separate collimated phase profiles of four light emitters 68a to 68d shown in Figure 6D.

[0073] Each of the collimated phase profiles 72a and 72b of the optical collimator 70 can narrow the emission profiles 74a and 74b of their respective emitters 68a and 68b, but can also be steered independently. For example, such a steerable optical collimator 70 may be designed so that the collimated phase profile 72a seen by each emitter 68a narrows and redirects the emission profile 74a toward the center of the entrance pupil 56 of the projection optical system 52, while similarly, the collimated phase profile 72b seen by each emitter 68b narrows and redirects the emission profile 74b toward the center of the entrance pupil 56 of the projection optical system 52. Thus, the arrangement shown in Figure 7 redirects the emission profiles 74a and 74b non-telecentrically toward the center of the entrance pupil 56 of the projection optical system 52. In particular, due to the lateral separation of the light emitters 68a and 68b with respect to the center of the entrance pupil 56 of the projection optical system 52, and the different refractive properties of the different colors of light emitted by the light emitters 68a and 68b, the angles at which the emission profiles 74a and 74b of each light emitter 68a and 68b are redirected are different with respect to the optical axis 76 of the projection optical system 52.

[0074] Furthermore, the angles 78 at which the emission profiles 74a and 74b of each light emitter 68a and 68b are redirected between different pixels 66 are different from each other with respect to the optical axis 76 of the projection optical system 52, as shown in Figure 8. For example, the angles 78 at which the emission profiles 74a and 74b of each light emitter 68a and 68b are redirected by the optical redirection structure 48 toward the center of the entrance pupil 56 of the projection optical system 52 increase progressively from the pixel 66 at the center of the microdisplay 46 to the periphery of the microdisplay 46. Therefore, it is important that each steerable optical collimator 70 can be designed not only to redirect the emission profiles 74a and 74b of each light emitter 68a and 68b for a particular pixel 66 independently of each other, but also to redirect the emission profiles 74a and 74b of each light emitter 68a and 68b independently across different pixels 66. Furthermore, it should be noted that in the illustrated embodiment, the collimated phase profiles 72a, 72b of each steerable optical collimator 70 may be superimposed on each other, as seen by the respective light emitters 68a, 68b of the pixel 66. In this way, the focal length of each steerable optical collimator 70 can be made as short as possible to maximize the light collected by the projection optics 52 so that the fixed area of ​​the same size of the microlens 80 covers a larger portion of the fixed emission profile 74 of each light emitter 68 when it is positioned close to the light emitter 68, while also reducing the size of the optical projection assembly.

[0075] If necessary, each optical collimator 70 can redistribute intensity among the respective groups of emitters 68a and 68b for each pixel 66. For example, instead of the intensity being split 50 / 50 between the two emitters 68a and 68b, the optical collimator 70 can redistribute some of the energy from one emitter 68a or 68b to the other, such that the divided intensity between the emitters 68a and 68b is no longer equal (e.g., 60% to emitter 68a and 40% to emitter 68b). Such redistribution between groups of emitters 68a and 68b may be useful, for example, when the eyepiece 60 (shown in Figures 3-4) propagates one color of the multicolor image light 54 more efficiently than another color of the multicolor image light 54. For example, if the eyepiece 60 propagates blue light more efficiently than green light, each optical collimator 70 can redistribute a portion of the energy from one of the blue light-emitting emitters 68a, 68b to the other of the green light-emitting emitters 68a, 68b, thereby compensating for the color-specific propagation efficiency of the eyepiece 60.

[0076] One embodiment of the optical direction reversal structure 48a shown in Figure 9 comprises an array of optical collimators 70a, each comprising a group of microlenses 80 that can be positioned on 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 its own dedicated microlens 80, thereby providing a single distinct collimated phase profile to the corresponding light emitter 68. Thus, each optical collimator 70a includes a distinct group of structures in the form of microlenses 80 that each provide a distinct group of collimated phase profiles to a group of light emitters 68 of pixels 60. For example, the shared structure of the optical collimator 48c may provide two separate collimation phase profiles for two emitters (e.g., collimation phase profiles 72a and 72b shown in Figure 7 for emitters 68a and 68b shown in Figure 6A), or three separate collimation phase profiles for three emitters each (e.g., emitters 68a to 68c shown in Figures 6B to 6C), or four separate collimation phase profiles for four emitters each (e.g., emitters 68a to 68d shown in Figure 6D). In the embodiment of the optical direction reversal structure 48a shown in Figure 9, the individual microlenses 80 of any one particular optical collimator 70a are of the same size. In the illustrated embodiment, each of the optical direction reversal structures 48a, and therefore each of the collimators 70a, is monolithic.

[0077] One embodiment of the optical collimator 70a(1) shown in Figure 10A includes a pair of microlenses 80a, 80b that can be positioned on a pair of light emitters (for example, light emitters 68a, 68b shown in Figure 6A). Another embodiment of the optical collimator 70a(2) shown in Figure 10B includes a set of three microlenses 80a to 80c that can be positioned on a set of three light emitters (for example, light emitters 68a to 68c shown in Figure 6B). Another embodiment of the optical collimator 70a(3) shown in Figure 10C includes a set of four microlenses 80a to 80d that can be positioned on a set of four light emitters (for example, light emitters 68a to 68d shown in Figure 6C).

[0078] Another embodiment 48b of the optical direction reversal structure shown in Figure 11 comprises an array of optical collimators 70b, each comprising a group of microlenses 80 that can be positioned on a corresponding group of light emitters 68. The optical direction reversal structure 48b is similar to the optical direction reversal structure 48a shown in Figure 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 its own dedicated microlens 80, thereby providing a single distinct collimated phase profile for the corresponding light emitter 68. The optical direction reversal structure 48b differs from the optical direction reversal structure 48a shown in Figure 9 in that at least two of the microlenses in the group of lenses 80 are of different sizes. For example, in the embodiment shown in Figure 12, the optical collimator 70b includes a set of three microlenses 80a-80c that can be positioned on a set of three light emitters (e.g., light emitters 68a-68c shown in Figure 6C). The size of microlens 80c is larger than the respective sizes of microlenses 80a and 80b in order to accommodate the larger size of light emitter 68c compared to light emitters 68a and 68b.

[0079] Importantly, by providing each light emitter 68 with a dedicated microlens 80, the emission profile of each light emitter 68 can be independently redirected or steered toward the center of the entrance pupil 56 of the projection optical system 52, as shown in Figure 7, and as a result, the entrance pupil 56 can be uniformly illuminated by the light emitters 68, thereby maximizing the amount of light emitted by the light emitters 68 that is captured by the entrance pupil 56 of the projection optical system 52. In contrast, if only one microlens is provided for each pixel 66, as opposed to a group of microlenses 80 (e.g., as shown in Figures 15, 17, and 19) such that each group of light emitters shares a microlens, the entrance pupil 56 of the projection optical system 52 will be uniformly illuminated by each of the microlenses 80.

[0080] For example, as shown in Figure 13, a conventional optical collimator may include a single microlens 80' positioned above a pair of light emitters 68a, 68b of the pixel 66. The single microlens 80' is effectively eccentric with respect to any particular of the light emitters 68a, 68b, and the maximum intensity of the light emitted by the light emitters 68a, 68b occurs at the boundary of the entrance pupil 56 of the projection optical system 52, resulting in heterogeneous illumination of the entrance pupil 56 of the projection optical system 52. That is, due to the respective locations of the light emitters 68a, 68b on either side of the centerline 82 of the single microlens 80', the emission profiles 74a, 74b of the light emitters 68a, 68b are angled outward from the center of the entrance pupil 56 of the projection optical system 52, i.e., the light emitted by each light emitter 68a, 68b is directed to an eccentric position with respect to the entrance pupil 56 of the projection optical system 52. Thus, as further shown in Figure 14A, the maximum intensity 84a of light emitted by the light emitter 68a occurs at the bottom edge of the entrance pupil 56, while as further shown in Figure 14B, the maximum intensity 84b of light emitted by the light emitter 68b occurs at the top edge of the entrance pupil 56. Therefore, each of the light emitters 68a and 68b illuminates the entrance pupil 56 of the projection optical system 52 asymmetrically, thereby blocking a significant portion of the light emitted by each of the light emitters 68a and 68b, and consequently impairing the efficiency of both light emitters 68a and 68b. Consequently, physically shifting the microlens 80' to redirect the emission profile of one of the light emitters 68a and 68b toward the center of the entrance pupil 56 in order to increase the efficiency of the light emitter unfortunately redirects the emission profile of the other light emitter 68a and 68b further outward from the center of the entrance pupil 56, further reducing the efficiency of that light emitter.

[0081] In contrast, groups of microlenses are positioned above each group of light-emitting elements for each pixel, and in one particular embodiment shown in Figure 15, a pair of microlenses 80a, 80b are positioned above a pair of light-emitting elements 68a, 68b for the pixel 66, respectively, which can result in relatively uniform illumination of the entrance pupil 56 of the projection optical system 52. That is, there is a one-to-one correspondence between the light-emitting elements 68 and the microlenses (only a single light-emitting element 68 in each group of light-emitting elements is functionally associated with the microlens 80 in the corresponding group of microlenses), and as a result, the locations of the light-emitting elements 68a, 68b can be aligned with the centerlines 82a, 82b of the microlenses 80a, 80b. As a result, the emission profiles 74a and 74b of the light emitters 68a and 68b are directed towards the center of the entrance pupil 56 of the projection optical system 52 (assuming that the light emitters 68a and 68b are located at the center of the corresponding microdisplays 46', 46'', 46'''' (shown in Figure 3) or microdisplay 46 (shown in Figure 4)), that is, the light emitted by each light emitter 68a and 68b is directed closer to the center of the entrance pupil 56 of the projection optical system 52. Thus, as further shown in Figure 16A, the maximum intensity 84a of the light emitted by light emitter 68a occurs at the center of the entrance pupil 56, while as further shown in Figure 16B, the maximum intensity 84b of the light emitted by light emitter 68b occurs at the center of the entrance pupil 56. Therefore, each of the light emitters 68a and 68b illuminates the entrance pupil 56 of the projection optical system 52 substantially symmetrically, thereby capturing a significant portion of the light emitted by each of the light emitters 68a and 68b by the entrance pupil 56, and as a result, maximizing the efficiency of both light emitters 68a and 68b. For example, the study shows that by positioning microlenses 80a and 80b on the light emitters 68a and 68b, respectively, as shown in Figure 13, in contrast to positioning a single microlens 80 on the light emitters 68a and 68b as shown in Figure 15, the efficiency of each of the light emitters 68a and 68b can be increased from approximately 16% to 28%.

[0082] As shown in Figure 15, microlenses 80a and 80b are superimposed on each other such that their curvature covers the entire area of ​​the corresponding pixel 66. In contrast, if the two microlenses were instead designed not to overlap with each other, the size of such microlenses 80a and 80b may need to be reduced, resulting in a very small radius for one of the two microlenses, making its curvature mathematically undefined across half the area of ​​the square pixel region. For example, for a 3 μm pixel, the area covering half of that pixel is 1.5 μm × 3.0 μm. If the pixel consists of two light-emitting elements spaced 1.3 μm apart, each microlens must have a radius of 0.65 μm (half of 1.3 μm) so as not to extend into the other microlens. However, with a radius of 0.65 μm, such a reduced-size microlens can only cover a circular area with a diameter of 1.3 μm, which is far smaller than half the pixel area of ​​1.5 μm × 3.0 μm.

[0083] To manufacture superimposed microlenses 80a and 80b, portions of the microlenses 80a and 80b that collide with each other are physically removed so that adjacent edges of the microlenses 80a and 80b are in physical contact with each other. Thus, although the microlenses 80a and 80b cannot be physically superimposed on each other, the projections of these microlenses 80a and 80b are superimposed on each other. Therefore, for the purposes of this specification, if the projections of microlenses (if the material is fully extended without removal) are superimposed on each other, then immediately adjacent microlenses are superimposed on each other.

[0084] To obtain a single surface of the physical structure of the optical collimator that forms superimposed microlenses 80a and 80b for each of the 66 pixels, the sag of the physical structure can be derived at any point on the 66 pixels as the maximum sag value of the microlenses 80a and 80b. As a result, only the maximum sag value of the microlenses 80a and 80b contributes to the final shape of the optical collimator structure. Therefore, as shown in Figure 15, the projected portions of the microlenses 80a and 80b, indicated by the dashed lines, do not physically exist and do not contribute to the final shape of the optical collimator structure. In Figure 15, only two microlenses 80a and 80b are shown superimposed on each other in order to position them on the respective light emitters 68a and 68b (corresponding to the microlenses 80a and 80b of the single optical collimator 70a(1) shown in Figure 10A). However, it should be understood that more than two microlenses 80a and 80b may be superimposed on each other in order to position them on more than two light emitters 68a and 68b (corresponding to the microlenses 80a to 80c of the single optical collimator 70a(2) shown in Figure 10B, or the microlenses 80a to 80d of the single optical collimator 70a(3) shown in Figure 10C, or the microlenses 80a to 80c of the single optical collimator 70b shown in Figure 12).

[0085] In the embodiment shown in Figure 15, the microlenses 80a and 80b are centered (i.e., telecentric) on their respective light emitters 68a and 68b so that their emission profiles 74a and 74b are oriented perpendicular to the plane of the microdisplay 46. However, as described above with respect to Figure 7, it is preferable that the emission profiles 74a and 74b of each light emitter 68a and 68b of the pixel 66 are steered non-telecentrically toward the center of the entrance pupil 56 of the projection optical system 52 (assuming the center of the microdisplay is optically aligned with the center of the entrance pupil 56 of the projection optical system 52). Therefore, as the distance of the pixel 66 increases from the center to the periphery of the microdisplay, the emission profiles 74a and 74b of each light emitter 68a and 68b of each pixel 66 (in contrast to the emission profiles 74a and 74b of each pixel 66 shown in Figure 15) need to be angled and reoriented toward the center of the entrance pupil 56 of the projection optical system 52. Such angles increase incrementally and proportionally as the position of each pixel 66 relative to the center of the microdisplay increases.

[0086] To redirect the emission profiles 74a, 74b of each pixel 66, which are offset by a distance d from the optical axis 76 of the projection optical system 52a, the pair of microlenses 80a, 80b are positioned such that the centerlines 82a, 82b of the microlenses 80a, 80b are at a distance d from the respective emitters 68a, 68b, as shown in Figure 17. a d b The pair of microlenses 80a, 80b may be physically shifted relative to the light emitters 68a, 68b so as to be eccentric. Not only can the pair of microlenses 80a, 80b be collectively shifted relative to the light emitters 68a, 68b to account for the different positions of the corresponding pixels 66 relative to the center of the microdisplay, but also to account for the slightly different positions of the light emitters 68a, 68b relative to the center of the microdisplay, and the different refraction / diffraction characteristics of the different colored light emitted by each of the light emitters 68a, 68b (offset distance da and d b They can be shifted independently of each other within a single pixel 66 (so that they are different from each other).

[0087] Therefore, the emission profiles 74a, 74b of each light emitter 68a, 68b may be redirected by the microlenses 80a, 80b toward the center of the entrance pupil 56 of the projection optical system 52, that is, the light emitted by each light emitter 68a, 68b is directed to a position identically centered with respect to the entrance pupil 56 of the projection optical system 52. Thus, as shown in Figure 18, the maximum intensities 84a, 84b of the light emitted by the light emitters 68a, 68b occur at the same center of the entrance pupil 56 for both light emitters 68a, 68b. Therefore, each of the light emitters 68a, 68b illuminates the entrance pupil 56 of the projection optical system 52 symmetrically. In fact, the pair of microlenses 80a, 80b at the center of the microdisplay shown in Figure 15, as shown in Figure 19, have their centerlines 82a, 82b relative to each light emitter 68a, 68b at a distance d a d b They may be physically shifted toward each other so as to be eccentric, thereby achieving the same effect shown in Figure 18.

[0088] As a result of physically eccentricating the microlenses 80a, 80b relative to each emitter 68a, 68b, the intensity of light emitted by the emitters 68a, 68b may be slightly reduced. However, the advantage is that the increased amount of light captured by the entrance pupil 56 of the projection optical system 52, due to the symmetrical illumination of the entrance pupil 56 by the steerable optical collimator 70, outweighs the decrease in optical efficiency caused by the relative shift between the microlenses 80a, 80b and the emitters 68a, 68b. Although the microlenses 80a, 80b are illustrated and described as being physically shifted relative to each emitter 68a, 68b in one direction on the plane, it should be understood that the microlenses 80a, 80b may also be physically shifted relative to each emitter 68a, 68b in any direction on the plane necessary to redirect the emission profiles 74a, 74b of each emitter 68a, 68b toward the center of the entrance pupil 56 of the projection optical system 52.

[0089] While the microlenses 80a, 80b are described as being shifted relative to each emitter 68a, 68b of a particular pixel 66 to redirect the emission profiles 74a, 74b of each emitter 68a, 68b toward the center of the entrance pupil 56 of the projection optical system 52, it should be understood that the microlenses 80a, 80b may also be shifted relative to each emitter 68a, 68b of a particular pixel 66 to independently redirect the emission profiles 74a, 74b of each emitter 68a, 68b toward any region of the entrance pupil 56 of the projection optical system 52, for example, as described in U.S. Patent No. 11,604,354, expressly incorporated herein by reference.

[0090] In particular, when shifting a pair of microlenses 80a, 80b of a particular pixel 66 relative to a pair of microlenses 80a, 80b of an immediately adjacent pixel 66, and / or when shifting a pair of microlenses 80a, 80b relative to one another, a step profile may need to be formed between or within the steerable optical collimator 70. For example, referring to Figure 20, each of the three pixels 66 has 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 centers of the light emitters 68a, 68b). A transition line 86 is shown between adjacent microlenses 80a, 80b to specify the equal area of ​​each microlens 80a, 80b positioned above the corresponding light emitters 68a, 68b.

[0091] As shown in Figure 21, if one microlens 80'' is physically eccentric in one direction (downward in the illustrated case) relative to its corresponding light emitter 68'', while its two immediately adjacent microlenses 80', 80'''' remain centered relative to their corresponding light emitters 68'', it is desirable that the transition lines 86 between the eccentric microlens 80'' and the adjacent centered microlens 80', and between the eccentric microlens 80'' and the adjacent centered microlens 80'''' remain in place (i.e., the areas of the microlenses 80', 80'', 80'' positioned on their corresponding light emitters 68', 68'', 68'''' remain equal), a first step profile 88a is formed on the transition line 86 between the moved microlens 80'' and microlens 80', and a second step profile 88b is formed on the transition line 86 between the moved microlens 80'' and microlens 80''''. The first step profile 88a causes at least a portion of the microlens 80' that would have been previously removed if the microlens 80' had not been moved to physically exist instead and contribute to the final shape of the actual structure of the microlens 80', while the second step profile 88b causes at least a portion of the microlens 80' that would otherwise physically exist and contribute to the final shape of the actual structure of the microlens 80' to be removed instead. In this way, the areas of the microlenses 80', 80'', 80''' positioned on the corresponding light emitters 68', 68'', 68'''' remain equal and the transition line 86 remains in place.

[0092] Although Figure 21 shows, for illustrative purposes, only one of the microlenses 80 being physically eccentric from its corresponding light-emitting body 68, it should be understood that all microlenses 80 (shown in Figure 17) that are off-center from the optical axis 76 of the projection optical system 52 are preferably physically eccentric from their corresponding light-emitting bodies 68 so that the microlenses 80 redirect the emission profile 74 of the corresponding light-emitting body 68 toward the center of the entrance pupil 56 of the projection optical system 52.

[0093] For example, as shown in Figure 22, all microlenses 80 may be physically eccentric with respect to their corresponding light-emitting bodies 68 (in this case, each pair of microlenses 80a, 80b may be at a different distance from their corresponding pair of light-emitting bodies 68a, 68b (for example, as shown in Figure 17, distance d a d bThe microlenses may be independently eccentric vertically downwards. The angle at which the emission profile 74 of the light emitter 68 is redirected by the corresponding microlenses 80 (shown in Figure 17) increases incrementally as the distance between the position of the light emitter 68 and the optical axis 76 of the projection optical system 52 increases incrementally, so the microlenses 80 are eccentric with respect to their corresponding light emitters 68 at different angles, as shown in Figure 22 (i.e., the distance by which the microlenses 80 are physically eccentric from their corresponding light emitters 68 also increases incrementally (in this case, vertically upwards)). As a result, a step profile 88 is formed on the transition line 86, and its size increases incrementally as the distance between the position of the light emitter 68 and the optical axis 76 of the projection optical system 52 increases incrementally (in this case, vertically upwards). In particular, since each of the microlenses 80 is physically eccentric from its corresponding light-emitting element 68 in Figure 22, the step profile 88 at each transition line 86 is a combination of a first step profile 88a (shown in Figure 21) created by a microlens 80 eccentric with respect to the corresponding light-emitting element 68 on one side of the transition line 86 (below each transition line 86, as shown in Figure 22) and a second step profile 88b (shown in Figure 21) created by a microlens 80 eccentric with respect to the corresponding light-emitting element 68 on the other side of the transition line 86 (above each transition line 86, as shown in Figure 22).

[0094] In particular, introducing a step profile between the microlenses 80 could increase the time and cost of manufacturing the physical structure of the microlenses 80. Alternatively, instead of creating a step profile 88 on the transition line 86 in response to the eccentricity of the microlens 80 relative to the corresponding emitter 68, the microlenses 80 may be shifted along the focal axis of the microlens 80 (i.e., along the optical axis 76 of the projection optical system 52 (shown in Figure 17)), in this case horizontally, as shown in Figure 23. The distance by which the microlenses 80 are shifted along the optical axis 76 of the projection emitter 68 increases incrementally as the distance between the position of the emitter 68 and the optical axis 76 of the projection optical system 52 increases incrementally (in this case, vertically downwards). Shifting the microlenses 80 along the optical axis 76 of the projection optical system 72 is expected to slightly reduce the efficiency of the light emitted by their corresponding light emitters 68. However, the increase in the amount of light captured by the entrance pupil 56 of the projection optical system 52 outweighs the reduction in light efficiency due to the relative shift between the microlenses 80a, 80b and the light emitters 68a, 68b along the optical axis 76 of the projection system 72.

[0095] In another alternative embodiment, the shape of the microlenses 80 may be modified (possibly in combination with a change in focal length) to eliminate the need to create a step profile 88 on the transition line 86 in response to the eccentricity of the microlenses 80 relative to their corresponding light emitters 68, thereby changing the focal length of the microlenses 80 and slightly reducing the efficiency of the light emitted by their corresponding light emitters 68.

[0096] In the embodiment shown in Figure 17, when the corresponding pair of microlenses 80a, 80b are eccentric with respect to the pair of light emitters 68a, 68b, it is desirable to maintain equivalence between the intensities of the light emitted by the pair of light emitters 68a, 68b (essentially maintaining the position of the transition line 86 between the microlenses 80a, 80b). However, in some embodiments, it may be desirable for the intensities of the light emitted by the pair of light emitters 68a, 68b to be different from each other, for example, to compensate for the color-specific propagation efficiency of the eyepiece 60. In this case, as shown in Figure 24, the transition line 86 may be shifted between the microlenses 80a, 80b (in this case, downward), and as a result, the light emitted by light emitter 68a after passing through microlens 80a has a greater intensity than the light emitted by light emitter 68b after passing through microlens 80b. A step profile 88 is formed on the transition line 86 between the microlenses 80a and 80b, which otherwise If the transition line 86 is not shifted, at least a portion of the microlens 80a that would have been previously removed will instead physically exist and contribute to the final shape of the actual structure of the microlens 80a, and otherwise at least a portion of the microlens 80b that would have physically existed and contributed to the final shape of the actual structure of the microlens 80b will instead be removed. In this way, the area of ​​the microlens 80a positioned on its corresponding light emitter 68a will be larger than the area of ​​the microlens 80b positioned on its corresponding light emitter 68b, and the transition line 86 will be shifted toward the microlens 80b. Alternatively, to eliminate the need for the step profile 88, the microlens 80 may be shifted along the optical axis 76 of the projection optical system 52 (shown in Figure 17), as described above with reference to Figure 23, or the shape of the microlens 80 may be changed.

[0097] As described above, the optical direction reversal structures 48a and 48b shown in Figures 9 and 11 each comprise arrays of optical collimators 70a and 70b positioned on the array of pixels 66 (as shown in Figure 5), and each of the optical collimators 70a and 70b comprises a group of dedicated structures in the form of microlenses 80, each providing a separate group of collimated phase profiles to a group of light emitters 68 of pixels 60 (for example, any of the groups of light emitters 68 shown in Figures 10A to 10C and Figure 12). For example, the microlenses 80a and 80b each provide two separate collimated phase profiles 72a and 72b to the light emitters 68a and 68b of pixels 66, respectively.

[0098] In contrast, another embodiment of the optical direction reversal structure shown in Figure 25, 48c, comprises an array of optical collimators 70c positioned on an array of pixels 66 (shown in Figure 5), each of which comprises a shared structure that provides a separate group of collimated phase profiles to a group of light emitters 68 of pixels 60 (e.g., any of the groups of light emitters 68 shown in Figures 10A-10C and Figure 12). For example, the shared structure of the optical collimator 70c may provide two separate collimation phase profiles for two emitters (e.g., collimation phase profiles 72a and 72b shown in Figure 7 for emitters 68a and 68b shown in Figure 6A), or three separate collimation phase profiles for three emitters (e.g., emitters 68a to 68c shown in Figures 6B to 6C), or four separate collimation phase profiles for four emitters (e.g., emitters 68a to 68d shown in Figure 6D). In the illustrated embodiment, each of the optical direction changing structures 48c, and therefore the collimator 70c, is monolithic.

[0099] Each collimator 70c is implemented as a diffractive optical system, such as a meta-optical system, consisting of small metaatoms that introduce a position-dependent phase shift that replicates the collimation behavior of a microlens. In particular, referring to Figure 26, each collimator 70c comprises an optically transparent base substrate 90 and a nanostructure 92 having a plurality of metaatoms 94 (e.g., single nanostructure elements such as nanopillars) formed on the surface of the base substrate 90. In an optional embodiment, an optical direction reversal structure 48c may be used in conjunction with a refractive surface. Each of the metaatoms 94 is a subwavelength structure (i.e., the size of each metaatom 94 is smaller than all wavelengths in the visible light spectrum), and as a result, the nanostructure 92 may be dispersively engineered to implement a group of collimated phase profiles (in this case, two collimated phase profiles 72a, 72b) of a group of emitters (in this case, two emitters 66a, 66b).

[0100] As further shown in Figure 27, the collimated phase profiles 72a and 72b (essentially a combination of quadratic phases with linear phases), which are substantially identical and superimposed on each other, can be observed at two different wavelengths from two different locations 96a and 96b. Thus, the emission profiles (not shown) from the emitters 66a and 66b positioned at these locations 96a and 96b are focused and redirected toward the entrance pupil 76 of the projection optical system 52. In the same manner as described above with respect to the light direction reversal structures 48a and 48b, the light direction reversal structure 48c can provide relatively homogeneous illumination of the entrance pupil 56 of the projection optical system 52, as shown in Figure 18 (assuming that the light emitters 68a and 68b are located at the center of the corresponding microdisplays 46', 46'', 46''' (shown in Figure 3) or microdisplay 46 (shown in Figure 4)). As a result, each of the light emitters 68a and 68b illuminates the entrance pupil 56 of the projection optical system 52 substantially symmetrically, thereby capturing a substantial portion of the light emitted by each of the light emitters 68a and 68b in the entrance pupil 56, and consequently maximizing the efficiency of both light emitters 68a and 68b.

[0101] The collimated phase profiles 72a and 72b shown in Figure 26 make the emission profiles of emitters 66a and 66b positioned at locations 96a and 96b essentially telecentric. However, the nanostructure 92 may be dispersion-engineered such that the emission profiles of emitters 66a and 66b are reoriented independently of each other, resulting in the emission profiles of emitters 66a and 66b being essentially non-telecentric (as shown, for example, in Figure 7). In particular, the nanostructure 92 may be dispersion-engineered to create arbitrary collimated phase profiles of emitters 66a and 66b by changing the radius of the metaatom 94, thereby providing steering capability to the optical collimator 70c.

[0102] For example, as shown in Figure 26, three reference combinations of phases A, B, and C of collimated phase profiles 72a, 72b are shown at specific locations on the base substrate 90. The reference combinations of phases A, B, and C represent specific combinations of collimated phase profiles 72a, 72b at their respective locations, which may be related to specific parameters of the metaatom 94 (for example, a specific combination of phases may be related to the height and diameter of a particular nanopillar). As shown in Figure 28, the nanostructure 92 may be designed by modifying the physical properties of the metaatom 94 (and, in this case, the radius of the nanopillar) so that the collimated phase profiles 72a, 72b are shifted relative to each other. As a result, the reference phase combinations A, B, and C are shifted to different locations on the base substrate. That is, the shift of the reference phase combinations A, B, and C shifts the metaatom 94, which is defined here by a specific new combination of phase profiles A, B, and C. Some of the reference combinations may disappear (because the phase combinations that existed before the relative shift between collimated phase profiles 72a and 72b no longer exist), or new reference combinations may appear (because phase combinations that did not exist before the relative shift between phase profiles 72a and 72b now exist).

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

[0104] Therefore, it can be understood that the nanostructure 92 can be designed so that multiple emitters 66 emitting light of different wavelengths perceive different collimation phase profiles, so that the entire nanostructure 92 can cover the entire area of ​​the pixel 66 and present a collimation phase profile centered on the emitter 68 of the pixel 66. Thus, in contrast to the optical collimators 70a and 70b of the respective optical direction reversal structures 48a and 48b shown in 9 and 11, which provide a group of dedicated regions (e.g., dedicated microlenses 80) for collimating different colored light emitted by the emitter 68, the entire area of ​​each optical collimator 70c of the optical direction reversal structure 48c shown in Figures 26 and 28 is common to the emitter 68 when collimating different colored light emitted by the emitter 68, thereby increasing the efficiency of the emitter 68. For example, even assuming that nanostructure 92 has a diffraction efficiency of only 85%, the optical efficiency of the emitter 68 when used with the optical direction reversal structure 48c is higher than the optical efficiency of the same emitter 68 when used with either the optical direction reversal structure 48a or 48b (e.g., approximately 43% efficiency compared to approximately 20% efficiency).

[0105] Furthermore, the focal length of the optical collimator 70c can be selected to be shorter than that of the optical collimators 70a and 70b shown in Figures 9 and 11 (e.g., a focal length of 3 μm versus a focal length of 2 μm). This is because the diameter of the microlens 80 of the optical collimators 70a and 70b is limited to the point where its gradient reaches 90 degrees, while the optical collimator 70c utilizes a second-order phase profile that can be infinitely extended while remaining clearly defined. In particular, the shorter the focal length of the optical collimator 70, the more light emitted by the light emitter 68 is captured by the entrance pupil 76 of the projection optical system 52 (shown in Figures 3 and 4).

[0106] While specific embodiments of the present invention have been shown and described, it will be understood that the invention is not intended to limit itself to preferred embodiments, and it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. Accordingly, the present invention is intended to encompass alternative forms, modifications, and equivalents that may fall within the spirit and scope of the invention as defined by the claims.

Claims

1. A head-mounted display (HMD), Head-mountable frame and A light projection assembly supported by the frame, wherein the light projection assembly is A microdisplay having a two-dimensional array of pixels, wherein each of the pixels includes a group of light-emitting elements configured to emit image light, A projection optical system configured to receive the image light at the entrance pupil from each group of light-emitting elements in the array of pixels, and to project the focused image light from the exit pupil, A two-dimensional array of optical collimators installed between the microdisplay and the projection optical system, wherein the array of optical collimators is configured to narrow the emission profile of the corresponding group of light emitters in each array of pixels, and a steerable optical collimator of the array of optical collimators is further configured to redirect the emission profile of the corresponding group of light emitters toward the center of the entrance pupil of the projection optical system. A light projection assembly comprising, An eyepiece supported by the frame, wherein the eyepiece receives the focused image light from the exit pupil of the projection optical system and is configured to direct the image light towards the user's eye when the frame is worn by the user. A head-mounted display equipped with [specific features / features].

2. The HMD according to claim 1, wherein all of the array of optical collimators are steerable optical collimators configured to steer the emission profiles of corresponding groups of light emitters toward the center of the entrance pupil of the projection optical system.

3. The HMD according to claim 1, wherein each group of light-emitting elements in the pixels comprises at least two light-emitting elements each configured to emit image light having two different colors.

4. The HMD according to claim 1, wherein each group of light-emitting elements in the pixels comprises at least three light-emitting elements, each configured to emit image light having three different colors.

5. The HMD according to claim 1, wherein each group of light-emitting elements includes a group of light-emitting diodes (LEDs).

6. The HMD according to claim 1, wherein the eyepiece comprises a waveguide and an input coupling optical element configured to input couple the focused image light from the exit pupil of the projection optical system to the waveguide.

7. The HMD according to claim 1, wherein each of the optical collimators has a separate group of collimated phase profiles for the emission profiles of the corresponding group of light emitters.

8. The HMD according to claim 7, wherein the separate group of collimated phase profiles of the steerable optical collimator is configured to redirect the emission profiles of the corresponding group of light emitters toward the center of the entrance pupil of the projection optical system.

9. The HMD according to claim 8, wherein the separate group of collimated phase profiles of the steerable optical collimator is configured to redirect the emission profiles of the corresponding group of emitters to different angles with respect to the optical axis of the projection optical system.

10. The HMD according to claim 1, wherein each of the collimator arrays is further configured to redistribute intensity among corresponding groups of light emitters.

11. The HMD according to claim 1, wherein the array of optical collimators is monolithic.

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

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

14. The HMD according to claim 1, wherein the array of optical collimators includes a group of dedicated regions each positioned above the group of light emitters in each array of pixels.

15. The HMD according to claim 14, wherein the array of optical collimators each comprises a group of microlenses corresponding to the separate group of regions.

16. The HMD according to claim 15, wherein each group of the microlenses in the array of optical collimators is superimposed on one another.

17. The HMD according to claim 16, wherein only a single light-emitting element from each group of light-emitting elements is functionally associated with a microlens from a corresponding group of microlenses.

18. The HMD according to claim 16, wherein the group of microlenses of the steerable optical collimator is eccentric with respect to the corresponding group of light emitters such that the emission profile of the corresponding group of light emitters is redirected toward the center of the entrance pupil of the projection optical system.

19. The HMD according to claim 18, wherein the group of microlenses of the steerable optical collimator is eccentric to different degrees with respect to the corresponding group of light emitters such that the emission profiles of the corresponding group of light emitters are independently redirected toward the center of the entrance pupil of the projection optical system.

20. The HMD according to claim 19, wherein the steerable optical collimator has a step profile between at least two of the groups of microlenses of the steerable optical collimator.

21. The HMD according to claim 19, wherein at least one of the at least two microlenses of the steerable optical collimator is shifted by a certain distance along the focal axis relative to the other of the at least two microlenses.

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

23. The HMD according to claim 1, wherein the array of optical collimators includes a common region located above each group of light emitters in each array of pixels.

24. The HMD according to claim 23, wherein each of the optical collimator arrays comprises a diffraction optical system corresponding to the common region.

25. The HMD according to claim 24, wherein the diffraction optical system is a meta-optical system.

26. The HMD according to claim 24, wherein each of the meta-optical systems comprises an optically transparent base substrate and a nanostructure having a plurality of subwavelength metaatoms.

27. The HMD according to claim 24, wherein each group of light emitters comprises at least two light emitters configured to emit image light having two different colors.

28. The HMD according to claim 22, wherein the diffraction optical system of the steerable optical collimator is designed such that the emission profiles of the corresponding groups of the light emitters are redirected toward the center of the entrance pupil of the projection optical system.

29. The HMD according to claim 23, wherein the steerable optical collimator is designed so that the emission profiles of the corresponding groups of the light emitters are independently redirected toward the center of the entrance pupil of the projection optical system.

30. A head-mounted display (HMD), Head-mountable frame and A light projection assembly supported by the frame, wherein the light projection assembly is A microdisplay having a two-dimensional array of pixels, wherein each of the pixels includes a group of light-emitting elements configured to emit image light, A projection optical system configured to receive the image light from each group of light-emitting elements in the array of pixels at the entrance pupil and project the focused image light from the exit pupil, A two-dimensional array of optical collimators installed between the microdisplay and the projection optical system, wherein the array of optical collimators is configured to narrow the emission profile of the corresponding group of light emitters in each array of pixels, and each array of optical collimators includes a group of microlenses, so that as a result only a single light emitter from each group of light emitters is functionally associated with the microlens of the corresponding group of microlenses, and the microlenses of each group of microlenses are superimposed on each other, and A light projection assembly comprising, An eyepiece supported by the frame, wherein the eyepiece receives the focused image light from the exit pupil of the projection optical system and is configured to direct the image light towards the user's eye when the frame is worn by the user. A head-mounted display equipped with [specific features / features].

31. The HMD according to claim 30, wherein each group of light-emitting elements in the pixels comprises at least two light-emitting elements each configured to emit image light having two different colors.

32. The HMD according to claim 30, wherein each group of light-emitting elements in the pixels comprises at least three light-emitting elements, each configured to emit image light having three different colors.

33. The HMD according to claim 30, wherein each group of light-emitting elements includes a group of light-emitting diodes (LEDs).

34. The HMD according to claim 30, wherein the eyepiece comprises a waveguide and an input coupling optical element configured to input couple the focused image light from the exit pupil of the projection optical system to the waveguide.

35. The HMD according to claim 30, wherein the array of optical collimators is monolithic.

36. The HMD according to claim 30, wherein the group of microlenses of at least one of the optical collimators is eccentric with respect to the corresponding group of light emitters such that the emission profile of the corresponding group of light emitters is redirected.

37. The HMD according to claim 36, wherein the emission profiles of the corresponding groups of the light-emitting elements are redirected toward the center of the entrance pupil of the projection optical system.

38. The HMD according to claim 36, wherein each group of the microlenses of the at least one optical collimator is eccentric to a different degree with respect to the corresponding group of the light emitter such that the emission profile of the corresponding group of the light emitter is independently redirected.

39. The HMD according to claim 38, wherein each of the at least one optical collimators has a step profile between at least two of the groups of microlenses of the respective optical collimator.

40. The HMD according to claim 38, wherein at least one of the at least two microlenses of each of the at least one optical collimator is shifted by a certain distance along the focal axis relative to the other of the at least two microlenses.

41. The HMD according to claim 38, wherein at least two of the groups of microlenses in each of the at least one optical collimator have different focal lengths.

42. A head-mounted display (HMD), Head-mountable frame and A light projection assembly supported by the frame, wherein the light projection assembly is A microdisplay having a two-dimensional array of pixels, wherein each of the pixels includes a group of light-emitting elements configured to emit image light, A projection optical system configured to receive the image light at the entrance pupil from each group of light-emitting elements in the array of pixels, and to project the focused image light from the exit pupil, A two-dimensional array of meta-optical collimators installed between the microdisplay and the projection optical system, wherein the array of meta-optical collimators is configured to narrow the emission profile of the corresponding group of light emitters in each array of pixels, and A light projection assembly comprising, An eyepiece supported by the frame, wherein the eyepiece receives the focused image light from the exit pupil of the projection optical system and is configured to direct the image light towards the user's eye when the frame is worn by the user. A head-mounted display equipped with [specific features / features].

43. The HMD according to claim 42, wherein each group of light-emitting elements in the pixels comprises at least two light-emitting elements each configured to emit image light having two different colors.

44. The HMD according to claim 42, wherein each group of light-emitting elements in the pixels comprises at least three light-emitting elements, each configured to emit image light having three different colors.

45. The HMD according to claim 42, wherein each group of light-emitting elements includes a group of light-emitting diodes (LEDs).

46. The HMD according to claim 42, wherein the eyepiece comprises a waveguide and an input coupling optical element configured to input couple the focused multicolor image light from the exit pupil of the projection optical system to the waveguide.

47. The HMD according to claim 42, wherein the array of meta-optical collimators is monolithic.

48. The HMD according to claim 42, wherein each of the arrays of the meta-optical photocollimators comprises an optically transparent base substrate and a nanostructure having a plurality of subwavelength metaatoms.

49. The HMD according to claim 42, wherein at least one of the arrays of meta-optical optical collimators is designed such that the emission profiles of the corresponding groups of the light emitters are redirected toward the center of the entrance pupil of the projection optical system.

50. The HMD according to claim 49, wherein the at least one meta-optical collimator is designed such that the emission profiles of the corresponding groups of the light emitters are independently redirected toward the center of the entrance pupil of the projection optical system.

Images