Eyepiece for virtual reality, augmented reality, and mixed reality systems

Abstract

To provide an eyepiece for suitable virtual reality, augmented reality, and mixed reality systems.SOLUTION: An eyepiece waveguide for augmented reality. The eyepiece waveguide may include a transparent substrate with an input coupler region, first and second orthogonal pupil expander (OPE) regions, and an exit pupil expander (EPE) region. The input coupler region can be positioned between the first OPE region and the second OPE region and can split and redirect an input light beam externally incident on the input coupler region into first and second guided light beams propagating inside the substrate, where the first guided beam is directed toward the first OPE region and the second guided beam is directed toward the second OPE region. Each of the first and second OPE regions may split the first and second guide beams into a plurality of replicated spaced apart beams. The EPE region may redirect the replicated beams from both the first and second OPE regions so that they exit the substrate.SELECTED DRAWING: Figure 13A

Description

[Technical Field]

[0001] (Incorporation by reference of any priority application) Any application for which foreign and domestic priority claims are identified in the Application Data Sheet filed with this application is hereby incorporated by reference under 37 CFR 1.57. This application claims priority to U.S. Patent Application No. 62 / 449,524, filed January 23, 2017, entitled "EYEPIECE FOR VIRTUAL, AUGMENTED, OR MIXED REALITY SYSTEMS."

[0002] (Field) The present disclosure relates to eyepieces for virtual reality, augmented reality, and mixed reality systems. [Background technology]

[0003] Description of Related Art Modern computing and display technologies have facilitated the development of virtual reality, augmented reality, and mixed reality systems. Virtual reality or "VR" systems create a simulated environment for a user to experience. This can be done by presenting computer-generated image data to the user through a head-mounted display. This image data creates a sensory experience that immerses the user within the simulated environment. Virtual reality scenarios typically involve the presentation of only computer-generated image data, rather than also including actual real-world image data.

[0004] Augmented reality systems generally supplement real-world environments with simulated elements. For example, an augmented reality or "AR" system may provide a user with a view of the surrounding real-world environment via a head-mounted display. However, computer-generated image data may also be presented on the display to enhance the real-world environment. This computer-generated image data may include elements that are contextually relevant to the real-world environment. Such elements may include simulated text, images, objects, etc. A mixed reality or "MR" system is a type of AR system that also introduces simulated objects into the real-world environment, but these objects typically feature an additional degree of interactivity. The simulated elements can often be interactive in real time.

[0005] 1 depicts an exemplary AR / MR scene 1 in which a user views a real-world park setting 6 featuring people, trees, a building in the background, and a concrete platform 20. In addition to these items, computer-generated image data is also presented to the user. The computer-generated image data may include, for example, a robotic figure 10 standing on the real-world platform 20 and a flying cartoon-like avatar character 2 that appears to be an anthropomorphic bumblebee, although these elements 2, 10 do not actually exist in the real-world environment. Summary of the Invention [Means for solving the problem]

[0006] (summary) In some embodiments, an eyepiece waveguide for a virtual reality, augmented reality, or mixed reality system includes an at least partially transparent substrate; an input coupler region formed on or within the substrate and configured to split and redirect at least one input light beam externally incident on the input coupler region into first and second guided light beams propagating inside the substrate; a first orthogonal pupil expander (OPE) region formed on or within the substrate and configured to split the first guided light beam from the input coupler region into a plurality of parallel, spaced apart light beams; and a first orthogonal pupil expander (OPE) region formed on or within the substrate and configured to split the first guided light beam from the input coupler region into a plurality of parallel, spaced apart light beams. a second OPE region formed on or in the substrate and configured to split the second guided light beam from the input coupler region into a plurality of parallel spaced-apart light beams; and a common exit pupil expander (EPE) region formed on or in the substrate and configured to redirect the light beams from both the first and second OPE regions to exit the substrate, wherein the input coupler region is positioned between the first OPE region and the second OPE region and configured to direct the first guided light beam towards the first OPE region and the second guided light beam towards the second OPE region.

[0007] In some embodiments, the eyepiece waveguide further comprises a first spreader region that receives the light beam from the first OPE region and spreads its distribution so that it reaches a larger portion of the EPE region, and a second spreader region that receives the light beam from the second OPE region and spreads its distribution so that it reaches a larger portion of the EPE region.

[0008] In some embodiments, both the first spreader region and the second spreader region are configured to spread the distribution of the light beam toward the center of the EPE region.

[0009] In some embodiments, the input coupler region comprises a diffractive optical feature for splitting and redirecting the input light beam towards the first and second OPE regions. The diffractive optical feature of the input coupler region may comprise a plurality of lines forming at least one diffraction grating. The diffractive optical feature of the input coupler region may also comprise a plurality of features laid out in a checkerboard pattern. The diffractive optical feature of the input coupler region may also comprise a cross grating.

[0010] In some embodiments, the diffractive optical features of the input coupler region are configured to direct light toward the first and second OPE regions and toward the EPE region without first passing through either of the OPE regions. The present specification also provides, for example, the following items: (Item 1) 1. An eyepiece waveguide for a virtual reality, augmented reality, or mixed reality system, the eyepiece waveguide comprising: a substrate that is at least partially transparent; an input coupler region formed on or within the substrate, the input coupler region configured to split and redirect at least one input light beam externally incident on the input coupler region into first and second guided light beams propagating inside the substrate; a first orthogonal pupil expander (OPE) region formed on or in the substrate, the first OPE region configured to split the first guided light beam from the input coupler region into a plurality of parallel, spaced-apart light beams; and a second OPE region formed on or in the substrate, the second OPE region configured to split the second guided light beam from the input coupler region into a plurality of parallel, spaced-apart light beams; a common exit pupil expander (EPE) region formed on or in said substrate; Equipped with the common EPE region is configured to redirect the light beams from both the first and second OPE regions so that they exit the substrate; The input coupler region is positioned between the first OPE region and the second OPE region, and the input coupler region is configured to direct the first guided light beam toward the first OPE region and direct the second guided light beam toward the second OPE region. (Item 2) Item 1 , an eyepiece waveguide, wherein the substrate is less than 325 microns thick. (Item 3) Item 1 , wherein the substrate comprises glass, plastic, or polycarbonate. (Item 4) Item 1. The eyepiece waveguide of item 1, wherein the eyepiece waveguide is configured to project color components of image data. (Item 5) Item 1. The eyepiece waveguide of item 1, further comprising a projector for directing light towards the input coupler region. (Item 6) Item 1. An eyepiece waveguide as described in item 1, wherein the input coupler region is configured to split the input light beam into +1st order diffracted light that is directed toward the first OPE region and -1st order diffracted light that is directed toward the second OPE region. (Item 7) Item 1. An eyepiece waveguide as described in item 1, wherein the first and second OPE regions are separated by approximately 180° and the EPE region is located at approximately 90° relative to both of the OPE regions. (Item 8) Item 1, wherein the first and second OPE regions are tilted toward the EPE region. (Item 9) 9. The eyepiece waveguide of item 8, wherein the first and second OPE regions are separated by approximately 120° and the EPE region is positioned at approximately 60° relative to both of the OPE regions. (Item 10) Item 1, an eyepiece waveguide, wherein the input coupler region comprises a diffractive optical feature for splitting the input light beam and redirecting it towards the first and second OPE regions. (Item 11) Item 11. An eyepiece waveguide as described in item 10, wherein the diffractive optical feature of the input coupler region comprises a plurality of lines forming at least one diffraction grating. (Item 12) Item 11. An eyepiece waveguide as described in item 10, wherein the diffractive optical feature of the input coupler region comprises a plurality of features laid out in a checkerboard pattern. (Item 13) Item 13. An eyepiece waveguide as described in item 12, wherein the checkerboard pattern comprises a hexagonal checkerboard pattern. (Item 14) Item 11. An eyepiece waveguide as described in item 10, wherein the diffractive optical feature of the input coupler region comprises a cross grating. (Item 15) Item 11. An eyepiece waveguide as described in Item 10, wherein the diffractive optical features of the input coupler region are configured to direct light toward the first and second OPE regions and toward the EPE region without first passing through either of the OPE regions. (Item 16) Item 1. The eyepiece waveguide of item 1, wherein the first and second OPE regions are provided with diffractive optical features for splitting each of the first and second guided light beams into the plurality of parallel, spaced-apart light beams. (Item 17) Item 17. An eyepiece waveguide as described in item 16, wherein the diffractive optical features of the first and second OPE regions comprise a plurality of lines forming a diffraction grating. (Item 18) Item 18. An eyepiece waveguide as described in item 17, wherein the diffraction gratings of the first and second OPE regions are angled to direct the plurality of spaced light beams toward the EPE region. (Item 19) a first spreader region that receives the light beam from the first OPE region and spreads its distribution so that it reaches a larger portion of the EPE region; a second spreader region that receives the light beam from the second OPE region and spreads its distribution so that it reaches a larger portion of the EPE region; Item 1. The eyepiece waveguide of item 1, further comprising: (Item 20) 20. The eyepiece waveguide of item 19, wherein both the first spreader region and the second spreader region are configured to spread the distribution of the light beam toward the center of the EPE region. (Item 21) 20. The eyepiece waveguide of claim 19, wherein the first and second spreader regions comprise diffractive optical features. (Item 22) 22. An eyepiece waveguide as described in item 21, wherein the diffractive optical features of each of the first and second spreader regions comprise a plurality of lines forming a diffraction grating. (Item 23) 23. The eyepiece waveguide of item 22, wherein the diffraction grating of the first spreader region is oriented at approximately 90° relative to the diffraction grating of the first OPE region, and the diffraction grating of the second spreader region is oriented at approximately 90° relative to the diffraction grating of the second OPE region. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 illustrates a user's view of an augmented reality (AR) scene through an AR system. [Figure 2] FIG. 2 illustrates an example of a wearable display system. [Figure 3] FIG. 3 illustrates a conventional display system for simulating a three-dimensional image for a user. [Figure 4] FIG. 4 illustrates aspects of an approach for simulating a three-dimensional image using multiple depth planes. [Figure 5]5A-5C illustrate the relationship between the radius of curvature and the radius of focus. [Figure 6] FIG. 6 illustrates an example of a waveguide stack for outputting image information to a user within an AR eyepiece. [Figure 7] 7A-7B illustrate examples of output beams output by a waveguide. [Figure 8] FIG. 8 illustrates an example of a stacked waveguide assembly, where each depth plane contains an image formed using multiple different component colors. [Figure 9A] FIG. 9A illustrates a cross-sectional side view of an example set of stacked waveguides, each containing an internal coupling optical element. [Figure 9B] FIG. 9B illustrates a perspective view of the multiple stacked waveguide example of FIG. 9A. [Figure 9C] FIG. 9C illustrates a top-down plan view of the multiple stacked waveguide example of FIGS. 9A and 9B. [Figure 10] FIG. 10 is a perspective view of an exemplary AR eyepiece waveguide stack. [Figure 11] FIG. 11 is a cross-sectional view of a portion of an exemplary eyepiece waveguide stack, along with an edge seal structure for supporting the eyepiece waveguides in a stacked configuration. [Figure 12A] 12A and 12B illustrate a top view of the eyepiece waveguide in operation as it projects an image toward a user's eye. [Figure 12B] 12A and 12B illustrate a top view of the eyepiece waveguide in operation as it projects an image toward a user's eye. [Figure 13A] FIG. 13A illustrates a front view of one half of an exemplary eyepiece for a VR / AR / MR system (in the as-worn position). [Figure 13B] FIG. 13B illustrates some of the diffractive optical features of the eyepiece that allow image data projected into the eyepiece at the input coupler region to propagate through the eyepiece and be projected out of the exit pupil expander (EPE) region towards the user's eye. [Figure 13C]FIG. 13C illustrates the optical operation of the orthogonal pupil expander (OPE) region shown in FIG. 9B. [Figure 14A] FIG. 14A illustrates an embodiment of an eyepiece that includes an input coupler region with a crossed grating. [Figure 14B] FIG. 14B is a perspective view of an exemplary embodiment of the input coupler region shown in FIG. 14A consisting of a crossed grating. [Figure 15A] FIG. 15A illustrates an embodiment of an eyepiece with upper and lower OPE regions that are angled toward the EPE region to provide a more compact form factor. [Figure 15B] FIG. 15B illustrates an exemplary embodiment of the diffractive optical features of the input coupler region of the eyepiece shown in FIG. 15A. [Figure 15C] FIG. 15C illustrates an exemplary embodiment of the diffractive optical features of the OPE region of the eyepiece shown in FIG. 15A. DETAILED DESCRIPTION OF THE INVENTION

[0012] (Detailed explanation) (Exemplary HMD Device) The virtual and augmented reality systems disclosed herein can include a display that presents computer-generated image data to a user. In some embodiments, the display system is wearable, which can advantageously provide a more immersive VR or AR experience. FIG. 2 illustrates an example of a wearable display system 60. The display system 60 includes a display or eyepiece 70 and various mechanical and electronic modules and systems to support the functionality of the display 70. The display 70 can be coupled to a frame 80, which is wearable by a display system user 90 and configured to position the display 70 directly in front of the user's 90 eyes. The display 70 can be considered eyewear in some embodiments. In some embodiments, a speaker 100 is coupled to the frame 80 and positioned adjacent to the user's 90 ear canal. The display system can also include one or more microphones 110 to detect sound. Microphone 110 may enable a user to provide input or commands to system 60 (e.g., voice menu command selections, natural language questions, etc.) and / or enable audio communication with other persons (e.g., other users of similar display systems). Microphone 110 may also collect audio data (e.g., sounds from the user and / or the environment) from around the user. In some embodiments, the display system may also include ambient sensors 120a, which may be separate from frame 80 and attached to the body of user 90 (e.g., on the head, torso, limbs, etc.). Ambient sensors 120a, in some embodiments, may acquire data characterizing the physiological state of user 90.

[0013] The display 70 is operably coupled to a local data processing module 140 by a communication link 130, such as a wired lead or wireless connectivity, which may be mounted in a variety of configurations, such as fixedly attached to the frame 80, fixedly attached to a helmet or hat worn by the user, integrated into headphones, or otherwise removably attached to the user 90 (e.g., in a backpack-style configuration or in a belt-type configuration). Similarly, the sensor 120a may be operably coupled to the local processor and data module 140 by a communication link 120b (e.g., a wired lead or wireless connectivity). The local processing and data module 140 may include a hardware processor and digital memory, such as non-volatile memory (e.g., flash memory or a hard disk drive), both of which may be utilized to aid in processing, caching, and storing data. The data may include 1) data captured from sensors (e.g., which may be operatively coupled to frame 80 or otherwise attached to user 90), such as image capture devices (e.g., cameras), microphones, inertial measurement units, accelerometers, compasses, GPS units, wireless devices, gyroscopes, and / or other sensors disclosed herein, and / or 2) data obtained and / or processed using remote processing module 150 and / or remote data repository 160 (including data related to virtual content), possibly for processing or readout and then passing to display 70. Local processing and data module 140 may be operatively coupled to remote processing module 150 and remote data repository 160 by communication links 170, 180, such as via wired or wireless communication links, such that these remote modules 150, 160 are operatively coupled to each other and available as resources to local processing and data module 140. In some embodiments, the local processing and data module 140 may include one or more of an image capture device, a microphone, an inertial measurement unit, an accelerometer, a compass, a GPS unit, a wireless device, and / or a gyroscope.In some other embodiments, one or more of these sensors may be mounted on the frame 80 or may be stand-alone devices that communicate with the local processing and data module 140 by wired or wireless communication paths.

[0014] Remote processing module 150 may include one or more processors for analyzing and processing data such as image and audio information. In some embodiments, remote data repository 160 may be a digital data storage facility, which may be available through the Internet or other networking configuration in a "cloud" resource configuration. In some embodiments, remote data repository 160 may include one or more remote servers that provide information (e.g., information for generating augmented reality content) to local processing and data module 140 and / or remote processing module 150. In other embodiments, all data is stored and all calculations are performed in the local processing and data module, allowing for fully autonomous use from the remote modules.

[0015] The perception of an image as "three-dimensional" or "3-D" can be achieved by providing a slightly different representation of the image to each of a user's eyes. FIG. 3 illustrates a conventional display system for simulating three-dimensional image data for a user. Two different images 190, 200 are output to the user, one for each eye 210, 220. The images 190, 200 are spaced from the eyes 210, 220 by a distance 230 along an optical axis, or z-axis, parallel to the user's line of sight. The images 190, 200 are flat, and the eyes 210, 220 can focus on the images by assuming a single accommodative state. Such a 3-D display system relies on the human visual system to combine the images 190, 200 and provide the perception of depth and / or scale of the combined image.

[0016] However, the human visual system is complex, making it difficult to provide a realistic perception of depth. For example, many users of conventional “3-D” display systems find such systems uncomfortable or may not perceive any sense of depth at all. Objects can be perceived as “three-dimensional” through a combination of vergence and accommodation. Vergence movement of the two eyes relative to each other (e.g., pupil rotation such that the pupils move toward or away from each other, converging the eyes’ respective lines of sight and fixating on an object) is closely linked to the focusing (or “accommodation”) of the eye’s lenses. Under normal conditions, a change in focus of the eye’s lenses or accommodation of the eye to change focus from one object to another at a different distance will automatically produce a matched change in vergence at the same distance, a relationship known as the “accommodation-vergence reflex” and pupil dilation or constriction. Similarly, under normal conditions, changes in vergence will induce matching changes in accommodation of lens shape and pupil size. As described herein, many stereoscopic or "3-D" display systems display a scene using a slightly different representation (and therefore a slightly different image) to each eye so that a three-dimensional view is perceived by the human visual system. However, such systems can be uncomfortable for many users because they simply present image information in a single accommodated state and work against the "accommodation-vergence reflex." Display systems that provide better matching between accommodation and vergence can produce more realistic and comfortable simulations of three-dimensional image data.

[0017] FIG. 4 illustrates aspects of an approach for simulating three-dimensional image data using multiple depth planes. Referring to FIG. 4 , the eyes 210, 220 assume different accommodation states and focus on objects at various distances along the z-axis. Consequently, a particular accommodation state is said to be associated with a particular one of the illustrated depth planes 240 and has an associated focal length, whereby an object or portion of an object at a particular depth plane is in focus when the eye is in an accommodation state relative to that depth plane. In some embodiments, the three-dimensional image data may be simulated by providing different representations of an image for each of the eyes 210, 220, and may also be simulated by providing different representations of an image corresponding to different depth planes. While the fields of view of each of the eyes 210, 220 are shown as distinct for clarity of illustration, it should be understood that they may overlap, for example, as the distance along the z-axis increases. Additionally, for ease of illustration, the depth plane is shown to be flat, but it should be understood that the contours of the depth plane may be curved in physical space so that all features within the depth plane are in focus with the eye in a particular accommodated state.

[0018] The distance between an object and the eye 210 or 220 can also change the amount of divergence of light from that object as viewed by that eye. Figures 5A-5C illustrate the relationship between distance and divergence of light rays. The distance between an object and the eye 210 is represented by decreasing distances R1, R2, and R3. As shown in Figures 5A-5C, light rays become more divergent as the distance to the object decreases. As the distance increases, the light rays become more collimated. In other words, the light field generated by a point (an object or part of an object) can be said to have a spherical wavefront curvature that is a function of the distance the point is from the user's eye. The curvature increases as the distance between the object and the eye 210 decreases. As a result, the divergence of light rays at different depth planes also differs, and the divergence increases as the distance between the depth plane and the user's eye 210 decreases. While only a single eye 210 is illustrated in Figures 5A-5C and other figures herein for clarity of illustration, it should be understood that the discussion regarding eye 210 may apply to both eyes 210 and 220 of a user.

[0019] A highly realistic simulation of perceived depth can be achieved by providing the eyes with different representations of an image corresponding to each of a limited number of depth planes, which can be focused separately by the user's eyes, thereby serving to provide depth cues to the user based on the amount of ocular accommodation required to bring different image features for a scene located on different depth planes into focus and / or based on the observation of different image features on different depth planes that are out of focus.

[0020] (Example of a waveguide stack assembly for an AR or MR eyepiece) FIG. 6 illustrates an example of a waveguide stack for outputting image information to a user within an AR eyepiece. Display system 250 includes a stack of waveguides or stacked waveguide assembly 260 that can be utilized to provide a three-dimensional perception to the eye / brain using multiple waveguides 270, 280, 290, 300, 310. In some embodiments, display system 250 is system 60 of FIG. 2, and FIG. 6 diagrammatically illustrates several portions of system 60 in greater detail. For example, waveguide assembly 260 can be part of display 70 of FIG. 2. It should be understood that display system 250 can be considered a bright field display in some embodiments.

[0021] The waveguide assembly 260 may include multiple features 320, 330, 340, 350 between the waveguides. In some embodiments, the features 320, 330, 340, 350 may be one or more lenses. The waveguides 270, 280, 290, 300, 310 and / or multiple lenses 320, 330, 340, 350 may be configured to transmit image information to the eye with various levels of wavefront curvature or ray divergence. Each waveguide level may be associated with a particular depth plane and configured to output image information corresponding to that depth plane. Image injection devices 360, 370, 380, 390, 400 may act as light sources for the waveguides and may be utilized to inject image information into waveguides 270, 280, 290, 300, 310, each of which may be configured as described herein to distribute incident light across each respective waveguide for output toward eye 210. Light exits each respective output surface 410, 420, 430, 440, 450 of image injection devices 360, 370, 380, 390, 400 and is injected into a corresponding input surface 460, 470, 480, 490, 500 of each respective waveguide 270, 280, 290, 300, 310. In some embodiments, each of the input surfaces 460, 470, 480, 490, 500 may be an edge of the corresponding waveguide or a portion of a major surface of the corresponding waveguide (i.e., one of the waveguide surfaces that directly faces the world 510 or the user's eye 210). In some embodiments, a beam of light (e.g., a collimated beam) may be launched into each waveguide, replicated by refraction within the waveguide, such as by sampling into beamlets, and then directed toward the eye 210 with an amount of refractive power corresponding to the depth plane associated with that particular waveguide. In some embodiments, a single one of the image launch devices 360, 370, 380, 390, 400 may be associated with and launch light into multiple (e.g., three) waveguides 270, 280, 290, 300, 310.

[0022] In some embodiments, each of the image input devices 360, 370, 380, 390, 400 is an individual display that generates image information for input into a corresponding waveguide 270, 280, 290, 300, 310. In some other embodiments, the image input devices 360, 370, 380, 390, 400 are the output of a single multiplexed display that may transmit image information via one or more optical conduits (such as fiber optic cables) to each of the image input devices 360, 370, 380, 390, 400. It should be understood that the image information provided by the image input devices 360, 370, 380, 390, 400 may include light of different wavelengths or colors.

[0023] In some embodiments, the light injected into the waveguides 270, 280, 290, 300, 310 is provided by a light projector system 520, which includes a light module 530, which may include a light source or light emitter, such as a light emitting diode (LED). Light from the light module 530 may be directed through a beam splitter (BS) 550 to and modulated by a light modulator 540 (e.g., a spatial light modulator). The light modulator 540 may spatially and / or temporally vary the perceived intensity of the light injected into the waveguides 270, 280, 290, 300, 310. Examples of spatial light modulators include liquid crystal displays (LCDs) and digital light processing (DLP) displays, including liquid crystal on silicon (LCOS) displays.

[0024] In some embodiments, light projector system 520 or one or more components thereof may be attached to frame 80 (FIG. 2). For example, light projector system 520 may be part of an temple portion (e.g., earpiece 82) of frame 80 or may be located on an edge of display 70. In some embodiments, light module 530 may be separate from BS 550 and / or light modulator 540.

[0025] In some embodiments, the display system 250 may be a scanning fiber display comprising one or more scanning fibers for projecting light in various patterns (e.g., raster scan, spiral scan, Lissajous pattern, etc.) into one or more waveguides 270, 280, 290, 300, 310 and ultimately into the user's eye 210. In some embodiments, the illustrated image injection devices 360, 370, 380, 390, 400 may diagrammatically represent a single scanning fiber or a bundle of scanning fibers configured to inject light into one or more waveguides 270, 280, 290, 300, 310. In some other embodiments, the illustrated image injection devices 360, 370, 380, 390, 400 may diagrammatically represent multiple scanning fibers or multiple bundles of scanning fibers, each configured to inject light into an associated one of the waveguides 270, 280, 290, 300, 310. One or more optical fibers transmit light from the optical module 530 to one or more of the waveguides 270, 280, 290, 300, and 310. Additionally, one or more intervening optical structures may be provided between the scanning fiber or fibers and one or more of the waveguides 270, 280, 290, 300, 310, for example, to redirect light exiting the scanning fiber into one or more of the waveguides 270, 280, 290, 300, 310.

[0026] Controller 560 controls the operation of stacked waveguide assembly 260, including the operation of image input devices 360, 370, 380, 390, 400, light source 530, and light module 540. In some embodiments, controller 560 is part of local data processing module 140. Controller 560 contains programming (e.g., instructions in a non-transitory medium) that coordinates the timing and provision of image information to waveguides 270, 280, 290, 300, 310. In some embodiments, the controller may be a single integrated device or a distributed system connected by wired or wireless communication channels. Controller 564 may, in some embodiments, be part of processing module 140 or 150 (FIG. 2).

[0027] The waveguides 270, 280, 290, 300, 310 may be configured to propagate light within each respective waveguide by total internal reflection (TIR). Each of the waveguides 270, 280, 290, 300, 310 may be planar or have another shape (e.g., curved) with major top and bottom surfaces and edges extending between the major top and bottom surfaces. In the illustrated configuration, each of the waveguides 270, 280, 290, 300, 310 may include an out-coupling optical element 570, 580, 590, 600, 610 configured to extract light out of the waveguide by redirecting light propagating within each respective waveguide and output image information out of the waveguide to the eye 210. The extracted light may also be referred to as out-coupled light, and the optical element that out-couples light may also be referred to as a light extraction optical element. The extracted beam of light may be output by the waveguide at a location where light propagating within the waveguide strikes a light extraction optical element. The outcoupling optical elements 570, 580, 590, 600, 610 may be diffractive optical features including, for example, diffraction gratings as discussed further herein. While the outcoupling optical elements 570, 580, 590, 600, 610 are shown disposed on the bottom major surfaces of the waveguides 270, 280, 290, 300, 310, in some embodiments, they may be disposed on the top and / or bottom major surfaces and / or directly within the volume of the waveguides 270, 280, 290, 300, 310, as discussed further herein. In some embodiments, the outcoupling optical elements 570, 580, 590, 600, 610 may be formed in a layer of material that is attached to a transparent substrate to form the waveguides 270, 280, 290, 300, 310. In some other embodiments, the waveguides 270, 280, 290, 300, 310 may be monolithic material pieces, and the outcoupling optical elements 570, 580, 590, 600, 610 may be formed on and / or within the material pieces.

[0028] Each waveguide 270, 280, 290, 300, 310 may output light to form an image corresponding to a particular depth plane. For example, the waveguide 270 closest to the eye may deliver a collimated beam of light to the eye 210. The collimated beam of light may represent a focal plane at optical infinity. The next upper waveguide 280 may output a collimated beam of light that passes through a first lens 350 (e.g., a negative lens) before reaching the eye 210. The first lens 350 may add a slight convex wavefront curvature to the collimated beam so that the eye / brain interprets the light emerging from that waveguide 280 as emerging from a first focal plane closer inward from optical infinity toward the eye 210. Similarly, the third upper waveguide 290 passes its output light through both the first lens 350 and the second lens 340 before reaching the eye 210. The combined refractive power of the first lens 350 and the second 340 lens may add another incremental amount of wavefront curvature such that the eye / brain interprets the light emerging from the third waveguide 290 as coming from a second focal plane that is closer inward from optical infinity where the light from the second waveguide 280 was.

[0029] The other waveguide layers 300, 310 and lenses 330, 320 are similarly configured, with the highest waveguide 310 in the stack sending its output through all of the lenses between it and the eye due to the aggregate focal power representing the focal plane closest to the person. To compensate for the stack of lenses 320, 330, 340, 350 when viewing / interpreting light originating from the world 510 on the other side of the stacked waveguide assembly 260, a compensatory lens layer 620 may be placed on top of the stack to compensate for the aggregate refractive power of the lower lens stacks 320, 330, 340, 350. Such a configuration provides as many perceived focal planes as there are available waveguide / lens pairs. Both the waveguide outcoupling optical elements and the focusing sides of the lenses may be static (i.e., not dynamic or electro-active). In some alternative embodiments, one or both may be dynamic using electro-active features.

[0030] In some embodiments, two or more of the waveguides 270, 280, 290, 300, 310 may have the same associated depth plane. For example, multiple waveguides 270, 280, 290, 300, 310 may output images set at the same depth plane, or multiple subsets of waveguides 270, 280, 290, 300, 310 may output images set at the same depth planes, one set for each depth plane. This may provide the advantage of forming tiled images and providing an extended field of view at those depth planes.

[0031] The outcoupling optical elements 570, 580, 590, 600, 610 can be configured to both redirect light from their respective waveguides and output this light with the appropriate amount of divergence or collimation for the particular depth plane associated with the waveguide. As a result, waveguides with different associated depth planes can have different configurations of outcoupling optical elements 570, 580, 590, 600, 610 that output light with different amounts of divergence depending on the associated depth plane. In some embodiments, the light extraction optical elements 570, 580, 590, 600, 610 can be volume or surface features that can be configured to output light at a particular angle. For example, the light extraction optical elements 570, 580, 590, 600, 610 can be volume holograms, surface holograms, and / or diffraction gratings. In some embodiments, the features 320, 330, 340, 350 may not be lenses. Rather, they may simply be spacers (eg, cladding layers and / or structures for forming air gaps).

[0032] In some embodiments, the outcoupling optical elements 570, 580, 590, 600, 610 are diffractive features with sufficiently low diffraction efficiency so that only a portion of the light output in the beam is redirected toward the eye 210 with each interaction, with the remainder continuing to travel through the waveguide via TIR. The exit pupil of the optical module 530 is thus replicated across the waveguide, creating multiple output beams carrying image information from the light source 530 and effectively expanding the number of locations where the eye 210 can see the replicated light source exit pupil. These diffractive features also have variable diffraction efficiency across their geometry, which can improve the uniformity of the light output by the waveguide.

[0033] In some embodiments, one or more diffractive features may be switchable between an actively diffracting "on" state and a less diffracting "off" state. For example, a switchable diffractive feature may include a layer of polymer dispersed liquid crystal in which microdroplets form a diffractive pattern in a host medium, and the refractive index of the microdroplets may be switched to substantially match the refractive index of the host material (in which case the pattern does not significantly diffract incident light), or the microdroplets may be switched to a refractive index that does not match that of the host medium (in which case the pattern actively diffracts incident light).

[0034] In some embodiments, a camera assembly 630 (e.g., a digital camera, including a visible light and IR light camera) is provided to capture images of the eye 210, a portion of the eye 210, or at least a portion of the tissue surrounding the eye 210, and may, for example, detect user input, extract biometric information from the eye, estimate and track the eye's gaze direction, monitor the user's physiological condition, etc. In some embodiments, the camera assembly 630 may include an image capture device and a light source for projecting light (e.g., IR or near-IR light) onto the eye, which may then be reflected by the eye and detected by the image capture device. In some embodiments, the light source includes a light-emitting diode (“LED”) that emits IR or near-IR. In some embodiments, the camera assembly 630 may be mounted on the frame 80 ( FIG. 2 ) and may be in electrical communication with a processing module 140 or 150, which may process image information from the camera assembly 630 and make various determinations, for example, regarding the user's physiological condition, the wearer's gaze direction, iris identification, etc. In some embodiments, one camera assembly 630 may be utilized for each eye to monitor each eye separately.

[0035] FIG. 7A illustrates an example of an output beam output by a waveguide. While one waveguide is shown (using a perspective view), other waveguides in waveguide assembly 260 ( FIG. 6 ) can function similarly. Light 640 is launched into waveguide 270 at input surface 460 of waveguide 270 and propagates within waveguide 270 via TIR. Through interaction with diffractive features, the light exits the waveguide as output beam 650. Output beam 650 replicates the exit pupil from a projector device that projects an image into the waveguide. Any one of output beams 650 contains a subportion of the total energy of input light 640. In a perfectly efficient system, the sum of the energies in all output beams 650 would be equal to the energy of input light 640. Although the exit beam 650 is shown in FIG. 7A as being nearly parallel, as discussed herein, a certain amount of refractive power may be imparted depending on the depth plane associated with the waveguide 270. A parallel exit beam may refer to a waveguide with outcoupling optics that outcouples light and forms an image that appears to be set on a depth plane at a long distance (e.g., optical infinity) from the eye 210. Other waveguides or other sets of outcoupling optics may output a more divergent exit beam pattern, as shown in FIG. 7B, which requires the eye 210 to accommodate to a closer distance and focus it on the retina, which would be interpreted by the brain as light from a distance closer to the eye 210 than optical infinity.

[0036] In some embodiments, a full-color image can be formed at each depth plane by overlaying images in each of the component colors (e.g., three or more component colors, such as red, green, and blue). FIG. 8 illustrates an example of a stacked waveguide assembly, with each depth plane containing an image formed using multiple different component colors. The illustrated embodiment shows depth planes 240a-240f, but more or fewer depths are also contemplated. Each depth plane can have three or more component color images associated with it, including a first image in a first color G, a second image in a second color R, and a third image in a third color B. The different depth planes are indicated in the diagram by different diopter powers following the letters G, R, and B. The number following each of these letters indicates the diopter (1 / m), i.e., the inverse of the distance of the depth plane from the user, and each box in the diagram represents an individual component color image. In some embodiments, the exact locations of the depth planes for different component colors may be varied to account for differences in the eye's focusing of different wavelengths of light. For example, different component color images for a given depth plane may be placed on depth planes corresponding to different distances from the user. Such an arrangement may increase visual acuity and user comfort or reduce chromatic aberrations.

[0037] In some embodiments, light for each component color may be output by a single dedicated waveguide, such that each depth plane may have multiple waveguides associated with it. In such embodiments, each box in the diagram may be understood to represent an individual waveguide, and three waveguides may be provided per depth plane to display three component color images per depth plane. While the waveguides associated with each depth plane are shown adjacent to each other in this drawing for ease of illustration, it should be understood that in a physical device, the waveguides may all be arranged in a stack with one waveguide per level. In some other embodiments, multiple component colors may be output by the same waveguide, such that, for example, only a single waveguide may be provided per depth plane.

[0038] 8, in some embodiments, G is green, R is red, and B is blue. In some other embodiments, other colors associated with other wavelengths of light, including yellow, magenta, and cyan, may be used in addition to or may replace one or more of red, green, or blue. In some embodiments, features 320, 330, 340, and 350 may be active or passive optical filters configured to block or selectively pass light from the surrounding environment to the user's eyes.

[0039] References throughout this disclosure to a given color of light should be understood to encompass light of one or more wavelengths within the range of wavelengths of light perceived by a user as that given color. For example, red light may include one or more wavelengths of light within a range of approximately 620-780 nm, green light may include one or more wavelengths of light within a range of approximately 492-577 nm, and blue light may include one or more wavelengths of light within a range of approximately 435-493 nm.

[0040] In some embodiments, the light source 530 (FIG. 6) may be configured to emit light at one or more wavelengths outside the user's range of visual perception, e.g., IR and / or ultraviolet wavelengths. IR light may include light with wavelengths in the range of 700 nm to 10 μm. In some embodiments, IR light may include near-IR light with wavelengths in the range of 700 nm to 1.5 μm. Additionally, the waveguide in-coupling, out-coupling, and other light redirecting structures of the display 250 may be configured to direct and emit this light from the display toward the user's eye 210, for example, for imaging and / or user stimulation applications.

[0041] Referring now to FIG. 9A , in some embodiments, light impinging on a waveguide may need to be redirected to incoupling the light into the waveguide. An incoupling optical element may be used to redirect and incoupling the light into its corresponding waveguide. FIG. 9A illustrates a cross-sectional side view of an example set of stacked waveguides 660, each including an incoupling optical element. Each of the waveguides may be configured to output light of one or more different wavelengths or one or more different wavelength ranges. While stack 660 may correspond to stack 260 ( FIG. 6 ), and the illustrated waveguides of stack 660 may correspond to a portion of multiple waveguides 270, 280, 290, 300, 310, it should be understood that light from one or more of image injection devices 360, 370, 380, 390, 400 is injected into the waveguide from a position or orientation that requires the light to be redirected for incoupling.

[0042] The illustrated stacked waveguide set 660 includes waveguides 670, 680, and 690. Each waveguide includes an associated internal coupling optical element (which may also be referred to as an optical input area on the waveguide), for example, internal coupling optical element 700 is disposed on a major surface (e.g., the upper major surface) of waveguide 670, internal coupling optical element 710 is disposed on a major surface (e.g., the upper major surface) of waveguide 680, and internal coupling optical element 720 is disposed on a major surface (e.g., the upper major surface) of waveguide 690. In some embodiments, one or more of internal coupling optical elements 700, 710, 720 may be disposed on the bottom major surface of the respective waveguides 670, 680, 690 (particularly, the one or more internal coupling optical elements are reflective optical elements). As shown, the internal coupling optical elements 700, 710, 720 may be disposed on the upper major surfaces of their respective waveguides 670, 680, 690 (or on top of the next lower waveguide), and in particular, the internal coupling optical elements are transmissive optical elements. In some embodiments, the internal coupling optical elements 700, 710, 720 may be disposed within the body of the respective waveguides 670, 680, 690. In some embodiments, as discussed herein, the internal coupling optical elements 700, 710, 720 are wavelength selective, such that they selectively redirect one or more wavelengths of light while transmitting other wavelengths of light. While illustrated on one side or corner of their respective waveguides 670, 680, 690, it should be understood that the internal coupling optical elements 700, 710, 720 may be disposed within other areas of their respective waveguides 670, 680, 690 in some embodiments.

[0043] As shown, the in-coupling optical elements 700, 710, 720 may be laterally offset from one another. In some embodiments, each in-coupling optical element may be offset to receive light without that light passing through another in-coupling optical element. For example, each in-coupling optical element 700, 710, 720 may be configured to receive light from a different image input device 360, 370, 380, 390, and 400, as shown in FIG. 6 , and may be separated (e.g., laterally spaced) from the other in-coupling optical elements 700, 710, 720 so as to receive substantially no light from others of the in-coupling optical elements 700, 710, 720.

[0044] Each waveguide also includes an associated light distribution element, for example, light distribution element 730 is disposed on a major surface (e.g., the top major surface) of waveguide 670, light distribution element 740 is disposed on a major surface (e.g., the top major surface) of waveguide 680, and light distribution element 750 is disposed on a major surface (e.g., the top major surface) of waveguide 690. In some other embodiments, light distribution elements 730, 740, 750 may be disposed on the bottom major surfaces of the associated waveguides 670, 680, 690, respectively. In some other embodiments, the light distribution elements 730, 740, 750 may be disposed on both the top and bottom major surfaces of the associated waveguides 670, 680, 690, respectively, or the light distribution elements 730, 740, 750 may be disposed on different ones of the top and bottom major surfaces in different associated waveguides 670, 680, 690, respectively.

[0045] Waveguides 670, 680, 690 may be spaced apart and separated, for example, by gas, liquid, and / or solid layers of material. For example, as shown, layer 760a may separate waveguides 670 and 680, and layer 760b may separate waveguides 680 and 690. In some embodiments, layers 760a and 760b are formed from a low refractive index material (i.e., a material having a lower refractive index than the material forming the immediately adjacent waveguides 670, 680, 690). In some embodiments, the refractive index of the material forming layers 760a, 760b is at least 0.05 or at least 0.10 below the refractive index of the material forming waveguides 670, 680, 690. Advantageously, the lower refractive index layers 760a, 760b may function as cladding layers to promote TIR of light through the waveguides 670, 680, 690 (e.g., TIR between the top and bottom major surfaces of each waveguide). In some embodiments, the layers 760a, 760b are formed from air. Although not shown, it should be understood that the top and bottom of the illustrated waveguide set 660 may include immediately adjacent cladding layers.

[0046] Preferably, for ease of manufacturing and other considerations, the materials forming waveguides 670, 680, 690 are similar or the same, and the materials forming layers 760a, 760b are similar or the same. In other embodiments, the materials forming waveguides 670, 680, 690 may vary between one or more waveguides, or the materials forming layers 760a, 760b may differ while still maintaining the various refractive index relationships discussed above.

[0047] 9A, light rays 770, 780, 790 enter waveguide set 660. Light rays 770, 780, 790 may be injected into waveguides 670, 680, 690 by one or more image injection devices 360, 370, 380, 390, 400 (FIG. 6).

[0048] In some embodiments, the light rays 770, 780, 790 have different properties (e.g., different wavelengths or different wavelength ranges) that may correspond to different colors. Each of the internal coupling optical elements 700, 710, 720 redirects the incident light such that the light propagates through a respective one of the waveguides 670, 680, 690 by TIR.

[0049] For example, in-coupling optical element 700 may be configured to selectively redirect light ray 770 having a first wavelength or range of wavelengths. Similarly, transmitted light ray 780 impinges on and is redirected by in-coupling optical element 710, which is configured to redirect light of a second wavelength or range of wavelengths. Similarly, light ray 790 is redirected by in-coupling optical element 720, which is configured to selectively redirect light of a third wavelength or range of wavelengths.

[0050] 9A , light rays 770, 780, 790 are redirected to propagate through corresponding waveguides 670, 680, 690. That is, each waveguide's incoupling optical element 700, 710, 720 redirects the light into its corresponding waveguide 670, 680, 690, incoupling the light into the corresponding waveguide. Light rays 770, 780, 790 are redirected at an angle that causes the light to propagate through the respective waveguides 670, 680, 690 by TIR. Light rays 770, 780, 790 propagate through the respective waveguides 670, 680, 690 by TIR until they interact with the waveguide's corresponding light distribution element 730, 740, 750.

[0051] 9B, a perspective view of the example multiple stacked waveguides of FIG. 9A is illustrated. As previously described, light rays 770, 780, and 790 are in-coupled by in-coupling optical elements 700, 710, and 720, respectively, and then propagate by TIR within waveguides 670, 680, and 690, respectively. Light rays 770, 780, and 790 then interact with light distribution elements 730, 740, and 750, respectively. Light distribution elements 730, 740, and 750 redirect light rays 770, 780, and 790 so that they propagate toward out-coupling optical elements 800, 810, and 820.

[0052] In some embodiments, the light distribution elements 730, 740, 750 are orthogonal pupil expanders (OPEs). In some embodiments, the OPEs both redirect light to the out-coupling optical elements 800, 810, 820 and expand the pupil associated with this light by sampling light rays 770, 780, 790 at many locations as they traverse the light distribution elements 730, 740, 750 as they propagate to the out-coupling optical elements. In some embodiments (e.g., if the exit pupil is already the desired size), the light distribution elements 730, 740, 750 may be omitted, and the in-coupling optical elements 700, 710, 720 may be configured to redirect light directly to the out-coupling optical elements 800, 810, 820. For example, with reference to FIG. 9A , the light distribution elements 730, 740, 750 may be replaced with the out-coupling optical elements 800, 810, 820, respectively, in some embodiments. In some embodiments, the outcoupling optical element 800, 810, 820 is an exit pupil (EP) or exit pupil expander (EPE) that redirects light out of the waveguide toward the user's eye 210 ( FIG. 7 ). The OPE may be configured to increase the size of the eyebox in at least one axis, and the EPE may be configured to increase the eyebox in an axis that intersects (e.g., is perpendicular to) the axis of the OPE.

[0053] 9A and 9B, in some embodiments, a waveguide set 660 includes, for each component color, waveguides 670, 680, 690, in-coupling optical elements 700, 710, 720, light distribution elements (e.g., OPEs) 730, 740, 750, and out-coupling optical elements (e.g., EPs) 800, 810, 820. The waveguides 670, 680, 690 may be stacked with an air gap / cladding layer between each one. The in-coupling optical elements 700, 710, 720 direct incident light into the corresponding waveguide (with different in-coupling optical elements receiving light of different wavelengths). The light then propagates at an angle that supports TIR within each waveguide 670, 680, 690. Because TIR occurs only for a certain range of angles, the range of propagation angles of light rays 770, 780, and 790 is limited. The range of angles that support TIR can, in such an example, be thought of as the angular limit of the field of view that can be displayed by waveguides 670, 680, and 690. In the example shown, light ray 770 (e.g., blue light) is incoupled by first incoupling optical element 700 in the manner described above, and then continues to reflect back and forth from the surfaces of the waveguide while traveling through it, with light distribution element (e.g., OPE) 730 progressively sampling it and creating additional replica light rays that are directed toward outcoupling optical element (e.g., EPE) 800. Light rays 780 and 790 (e.g., green and red light, respectively) pass through waveguide 670, with light ray 780 impinging on incoupling optical element 710 and thereby being incoupled. Light ray 780 would then propagate through waveguide 680 via TIR to its light distribution element (e.g., OPE) 740 and then to outcoupling optical element (e.g., EPE) 810. Finally, light ray 790 (e.g., red light) passes through waveguides 670, 680 and impinges on incoupling optical element 720 of waveguide 690. Light incoupling optical element 720 incouples light ray 790 such that the light ray propagates via TIR to light distribution element (e.g., OPE) 750 and then via TIR to outcoupling optical element (e.g., EPE) 820. Outcoupling optical element 820 then finally outcouples light ray 790 to the user, who also receives outcoupled light from the other waveguides 670, 680.

[0054] FIG. 9C illustrates a top-down plan view of the example of multiple stacked waveguides of FIGS. 9A and 9B. As shown, the waveguides 670, 680, 690 may be vertically aligned, along with each waveguide's associated light distribution elements 730, 740, 750 and associated out-coupling optical elements 800, 810, 820. However, as discussed herein, the in-coupling optical elements 700, 710, 720 are not vertically aligned. Rather, the in-coupling optical elements may be non-overlapping (e.g., laterally spaced, as seen in the top-down view). This non-overlapping spatial arrangement may facilitate the injection of light from different sources into different waveguides on a one-to-one basis, thereby allowing a particular light source to be uniquely optically coupled to a particular waveguide. In some embodiments, arrays including non-overlapping, spatially separated in-coupling optical elements may be referred to as shifted-pupil systems, and the in-coupling optical elements in these arrays may correspond to sub-pupils.

[0055] FIG. 10 is a perspective view of an exemplary AR eyepiece waveguide stack 1000. The eyepiece waveguide stack 1000 includes a world-side cover window 1002 and an eye-side cover window 1006, which may protect one or more eyepiece waveguides 1004 positioned between the cover windows. In other embodiments, one or both of the cover windows 1002, 1006 may be omitted. As previously discussed, the eyepiece waveguides 1004 may be arranged in a layered configuration. The eyepiece waveguides 1004 may be coupled together, for example, each individual eyepiece waveguide is coupled to one or more adjacent eyepiece waveguides. In some embodiments, the waveguides 1004 may be coupled together with an edge seal (such as edge seal 1108 shown in FIG. 11 ) to prevent adjacent eyepiece waveguides 1004 from directly contacting each other.

[0056] Each of the eyepiece waveguides 1004 can be made from an at least partially transparent substrate material, such as glass, plastic, polycarbonate, sapphire, etc. The selected material may have a refractive index greater than 1.4, e.g., greater than 1.6 or 1.8, to facilitate light guidance. The thickness of each eyepiece waveguide substrate may be, for example, 325 microns or less, although other thicknesses may be used. Each eyepiece waveguide may include one or more internal coupling regions, light dispersion regions, image enhancement regions, and external coupling regions, which may consist of diffractive features formed on or within each waveguide substrate 902.

[0057] Although not shown in FIG. 10 , the eyepiece waveguide stack 1000 may include a physical support structure for supporting it in front of the user's eyes. In some embodiments, the eyepiece waveguide stack 1000 is part of a head-mounted display system 60, as shown in FIG. 2 . Generally, the eyepiece waveguide stack 1000 is supported so that the external coupling region is directly in front of the user's eyes. It should be understood that FIG. 10 illustrates only a portion of the eyepiece waveguide stack 1000 that corresponds to one of the user's eyes. The completed eyepiece may include a mirror image of the same structure, with two halves that may be separated by a nosepiece.

[0058] In some embodiments, the eyepiece waveguide stack 1000 can project color image data from multiple depth planes into the user's eye. The image data displayed by each individual eyepiece waveguide 1004 in the eyepiece 1000 can correspond to a selected color component of the image data for the selected depth plane. For example, the eyepiece waveguide stack 1000 can include six eyepiece waveguides 1004 and thus project color image data (e.g., consisting of red, green, and blue components) corresponding to two different depth planes: one eyepiece waveguide 1004 per color component per depth plane. Other embodiments can include eyepiece waveguides 1004 for more or fewer color components and / or more or fewer depth planes.

[0059] FIG. 11 is a cross-sectional view of a portion of an exemplary eyepiece waveguide stack 1100 with an edge seal structure 1108 for supporting the eyepiece waveguides 1104 in a stacked configuration. The edge seal structure 1108 aligns the eyepiece waveguides 1104 and separates them from each other with an air space or another material disposed between them. Although not shown, the edge seal structure 1108 can extend around the entire periphery of the stacked waveguide configuration. In FIG. 11, the separation between each eyepiece waveguide is 0.027 mm, although other distances are possible.

[0060] In the illustrated embodiment, there are two eyepiece waveguides 1104 designed to display red image data, one for the 3m depth plane and the other for the 1m depth plane. (Again, the divergence of the beams of light output by the eyepiece waveguides 1104 can make the image data appear to originate from depth planes located at particular distances.) Similarly, there are two eyepiece waveguides 1104 designed to display blue image data, one for the 3m depth plane and the other for the 1m depth plane, and two eyepiece waveguides 1104 designed to display green image data, one for the 3m depth plane and the other for the 1m depth plane. Each of these six eyepiece waveguides 1104 is illustrated as being 0.325mm thick, although other thicknesses are possible.

[0061] A world-side cover window 1102 and an eye-side cover window 1106 are also shown in Figure 11. These cover windows can be, for example, 0.330 mm thick. Taking into account the thickness of the six eyepiece waveguides 1104, the seven air gaps, the two cover windows 1102, 1106, and the edge seal 1108, the total thickness of the illustrated eyepiece waveguide stack 1100 is 2.8 mm.

[0062] 12A and 12B illustrate a top view of the eyepiece waveguide 1200 in operation as it projects an image toward a user's eye 210. The image can be initially projected from an image plane 1207 toward the entrance pupil 1208 of the eyepiece waveguide 1200 using a projection lens 1210 or some other projector device. Each image point (e.g., an image pixel or portion of an image pixel) has a corresponding input beam of light (e.g., 1202a, 1204a, 1206a) that propagates in a particular direction at the entrance pupil 1208 (e.g., at a particular angle relative to the optical axis of the projector lens 1210). While illustrated as rays of light, the input beams of light 1202a, 1204a, 1206a can be collimated beams, for example, with diameters of a few millimeters or less, as they enter the eyepiece waveguide 1200.

[0063] 12A and 12B, the central image point corresponds to input beam 1204a, which is illustrated using a solid line. Input beam 1202a, illustrated using a dashed line, corresponds to an image point displaced to one side of the central image point, while input beam 1206a, illustrated using a dashed line, corresponds to an image point displaced to the other side. For clarity of illustration, only three input beams 1202a, 1204a, and 1206a are shown at entrance pupil 1208, but a typical input image will include many input beams, which correspond to different image points. The input beams will propagate at a range of angles relative to the optical axis in both the x- and y-directions.

[0064] There is a unique correspondence between the various propagation angles of the input beams (e.g., 1202a, 1204a, 1206a) at the entrance pupil 1208 and their respective image points at the image plane 1207. The eyepiece waveguide 1200 can be designed to internally combine the input beams (e.g., 1202a, 1204a, 1206a), replicate them through space in a distributed manner, and direct them to form an exit pupil 1210 that is larger than the entrance pupil 1208 and consists of the replicated beams, all while substantially maintaining the correspondence between image points and beam angles. The eyepiece waveguide 1200 can convert a given input beam of light (e.g., 1202a) propagating at a particular angle into many replicated beams (e.g., 1202b) that traverse the exit pupil 1210 and are output at angles that are substantially uniquely related to that particular input beam and its corresponding image point. Thus, the eyepiece waveguide 1200 can perform pupil expansion while maintaining the relative angular relationships of the beams that make up the projected image.

[0065] 12A and 12B, an input beam of light 1204a corresponds to a central image point at image plane 1207 and is transformed into a set of replicated output beams 1204b, shown as solid lines, which are aligned with an optical axis perpendicular to the exit pupil 1210 of eyepiece waveguide 1200. An input beam of light 1202a is transformed into a set of replicated output beams 1202b, shown as dashed lines, which exit eyepiece waveguide 1200 at propagation angles such that they appear to originate from one side of the user's field of view, while an input beam of light 1206a is transformed into a set of replicated output beams 1206b, shown as dashed lines, which exit eyepiece waveguide 1200 at propagation angles such that they appear to originate from the other side of the user's field of view. The greater the range of input and / or output beam angles, the larger the field of view (FOV) of eyepiece waveguide 1200.

[0066] For each image, there is a set of replicated output beams (e.g., 1202b, 1204b, 1206b), i.e., one set of replicated beams per image point, which are output at different angles across the exit pupil 1210. Each of the output beams (e.g., 1202b, 1204b, 1206b) can be collimated. The set of output beams corresponding to a given image point can consist of beams propagating along parallel paths (as shown in FIG. 12A) or diverging paths (as shown in FIG. 12B). In either case, the specific propagation angles of the replicated output beam sets depend on the location of the corresponding image point in the image plane 1207. FIG. 12A illustrates the case where each set of output beams (e.g., 1202b, 1204b, 1206b) consists of beams propagating along parallel paths. This results in an image being projected that appears to originate from optical infinity. This is represented in Figure 12A by the thin lines extending from the peripheral output beams 1202b, 1204b, and 1206b toward optical infinity on the world side of the eyepiece waveguide 1200 (opposite where the user's eye 210 is located). Figure 12B illustrates the case where each set of output beams (e.g., 1202b, 1204b, and 1206b) consists of beams propagating along diverging paths. This results in images being projected that appear to originate from a distance closer than optical infinity. This is represented in Figure 12B by the thin lines extending from the peripheral output beams 1202b, 1204b, and 1206b toward points on the world side of the eyepiece waveguide 1200.

[0067] Again, each set of replicated output beams (e.g., 1202b, 1204b, 1206b) has a propagation angle that corresponds to a specific image point at image plane 1207. In the case of a set of replicated output beams that propagate along parallel paths (see FIG. 12A), the propagation angles of all beams are identical. However, in the case of a set of replicated output beams that propagate along diverging paths, the individual output beams may propagate at different angles, but their angles are related to each other in that they appear to originate from a common point along the axis of the beam set (see FIG. 12B). This axis defines the angle of propagation for the set of diverging output beams, which corresponds to a specific image point at image plane 1207.

[0068] (Exemplary Eyepiece Waveguide) FIG. 13A illustrates a half-front view of an exemplary eyepiece waveguide 1300 for a VR / AR / MR system (in the as-installed position). The eyepiece waveguide 1300 can include an input coupler region 1310, an upper orthogonal pupil expander (OPE) region 1320a, a lower orthogonal pupil expander (OPE) region 1320b, and an exit pupil expander (EPE) region 1330. In some embodiments, the eyepiece waveguide 1300 can include an upper spreader region 1340a and a lower spreader region 1340b. The eyepiece waveguide 1300 is made from a substrate material that is at least partially transparent. For example, the eyepiece waveguide 1300 can be made from a substrate 1302 of glass, plastic, polycarbonate, sapphire, etc. The material selected may have a relatively high refractive index greater than 1, more preferably greater than 1.4 or preferably greater than 1.6, and most preferably greater than 1.8, to facilitate light guiding. The thickness of the substrate 1302 may be, for example, 325 microns or less. Each of the aforementioned regions of the eyepiece waveguide 1300 may be created by forming one or more diffractive structures on or within the eyepiece waveguide substrate 1302. The specific diffractive structures may vary from region to region.

[0069] Although not shown in FIG. 13A , the eyepiece waveguide 1300 may include a physical support structure for supporting the eyepiece waveguide in front of the user's eye. In some embodiments, the eyepiece waveguide 1300 is part of a head-mounted display such as that shown in FIG. 2 . Generally, the eyepiece waveguide 1300 is supported so that the EPE region 1330 is directly in front of the user's eye. It should be understood that FIG. 13A illustrates only one half of the eyepiece waveguide 1300, corresponding to one of the user's eyes. A completed eyepiece waveguide will typically also include a mirror image of the same structure shown in FIG. 13A (e.g., with each input coupler region 1310 facing the temple of the user's head and each EPE region 1330 in front of the user's eye, sometimes separated by a nose pad). The two halves can be part of the same substrate 1302 or separate substrates.

[0070] As shown in FIGS. 10 and 11 , in some embodiments, an eyepiece can include multiple eyepiece waveguides 1300 made from multiple substrates 1302 stacked together (separated by cladding layers). Each substrate 1302 can be as illustrated in FIG. 13A and can be designed as a waveguide for projecting image data into the eye. In some embodiments, the image data displayed by each eyepiece waveguide 1300 in the stack corresponds to a selected color component of the image data corresponding to a selected depth plane. For example, an eyepiece that projects color image data (e.g., consisting of red, green, and blue components) corresponding to three different depth planes can include a total of nine eyepiece waveguides 1300 stacked together: one eyepiece waveguide 1300 for each color component of the image data for each of the three depth planes.

[0071] 13B illustrates some of the diffractive optical features of the eyepiece waveguide 1300 that allow image data projected into the eyepiece waveguide at the input coupler region 1310 to propagate through the eyepiece waveguide and be projected from the EPE region 1330 toward the user's eye. Generally, image data is projected into the eyepiece waveguide 1300 via a beam of light, which travels generally in the z-direction shown (although the amount of angular variation may depend on the FOV of the image data), and impinges on the input coupler region 1310 from outside the substrate 1302. The input coupler region 1310 includes diffractive optical features that redirect the input beam of light so that it propagates inside the substrate 1302 of the eyepiece waveguide 1300 via total internal reflection. In some embodiments, the input coupler region 1310 is located symmetrically between the upper and lower OPE regions 1320. The input coupler region 1310 splits and redirects the input light to both of these OPE regions 1320 .

[0072] The OPE region 1320 includes diffractive optical features that can perform at least two functions: first, they can perform pupil expansion by spatially replicating each input beam of light at many locations along the y-direction to form many spaced parallel beams, and second, they can generally diffract the replicated beams of light on their way toward the EPE region 1330.

[0073] The EPE region 1330 similarly includes diffractive optical features, which can perform at least two functions: first, they can replicate the beam in many locations along another direction (e.g., a direction substantially orthogonal to that in which the beam is replicated by the OPE region 1320); and second, they can diffract the beams of light emanating from the OPE region 1320 so that they exit the substrate 1302 of the eyepiece waveguide 1300 and propagate toward the user's eye. The diffractive optical features of the EPE region 1330 can also impart a degree of refractive power to the exiting beams of light, causing them to appear to originate from a desired depth plane, as discussed elsewhere herein. The eyepiece waveguide 1300 can have the property that the angle of exit at which the light beam is output by the EPE region 1330 is uniquely correlated with the angle of entry of the corresponding input beam at the input coupler region 1310, thereby allowing the eye to faithfully reproduce the input image data.

[0074] The optical operation of the eyepiece waveguide 1300 will now be described in more detail. Initially, image data is projected into the eyepiece waveguide 1300 at the input coupler region 1310 from one or more input devices. The input devices may include, for example, a spatial light modulator projector (located in front of or behind the eyepiece waveguide 1300 relative to the user's face). In some embodiments, the input devices may use liquid crystal display (LCD) technology, liquid crystal on silicon (LCoS) technology, digital light processing (DLP) technology, or fiber scanning display (FSD) technology, although others may also be used. Each input device can project one or more beams of light onto a subportion of the input coupler region 1310. As discussed elsewhere herein, each substrate 1302 can act as a waveguide, directing a given color component for a given depth plane of the image data into the user's eye. A different subportion of the input coupler region 1310 can be used to input image data for each of the multiple stacked eyepiece waveguides 1300 that make up the eyepiece. This can be accomplished by providing appropriate diffractive optical features in the subportion of the input coupler region 1310 devoted to inputting image data for each eyepiece waveguide 1300 into the substrate 1302 of that eyepiece waveguide 1300 (e.g., as shown in FIGS. 9A-9C ). For example, one substrate 1302 may have a diffractive feature provided in the center of its input coupler region 1310, while the other may have a diffractive feature provided at the periphery of its respective input coupler region, e.g., the 3 o'clock or 9 o'clock position. Thus, input image data intended for each eyepiece waveguide 1300 can be aimed by the projector at the corresponding subportion of the input coupler region 1310 so that the correct image data is coupled into the correct substrate 1302 without being coupled into the other substrates.

[0075] The projector may be provided so that an input beam of light approaches the input coupler region 1310 of the substrate 1302 generally along the z-direction shown (although some angular deviation will exist, given that light beams corresponding to different points on the input image will be projected at different angles). The input coupler region 1310 of any given substrate 1302 includes diffractive optical features that redirect the input beam of light propagating within the substrate 1302 of the eyepiece waveguide 1300 at the appropriate angle via total internal reflection. As shown by the close-up 1312, in some embodiments, the diffractive optical features of the input coupler region 1310 may form a diffraction grating consisting of many lines, the lines extending horizontally in the x-direction shown and periodically repeating vertically in the y-direction shown. In some embodiments, the lines may be etched into the substrate 1302 of the eyepiece waveguide 1300 and / or they may be formed from a material deposited on the substrate 1302. For example, an input coupler grating (ICG) may comprise lines etched into the back surface of the substrate (the side opposite where the input light beam enters) and then coated with a sputtered reflective material such as metal. In such an embodiment, the input coupler grating operates in a reflective mode, although other designs may use a transmissive mode. The input coupler grating can be any of several types, including a surface-relief grating, a binary surface-relief structure, a volume holographic optical element (VHOE), a switchable polymer-dispersed liquid crystal grating, etc. The period, duty cycle, depth, profile, etc. of the lines can be selected based on the wavelength of light for which the substrate is designed, the desired diffraction efficiency of the grating, and other factors.

[0076] Input light incident on this input coupler grating is split and redirected both upward in the +y direction toward the upper OPE region 1320a and downward in the -y direction toward the lower OPE region 1320b. Specifically, input light incident on the grating of the input coupler region 1310 is separated into positive and negative diffraction orders, with positive diffraction orders directed upward toward the upper OPE region 1320a and negative diffraction orders directed downward toward the lower OPE region 1320b, or vice versa. In some embodiments, the grating in the input coupler region 1310 is designed to couple input light primarily into the +1 and -1 diffraction orders. (The grating can be designed to reduce or eliminate diffraction orders higher than the 0th and 1st diffraction orders. This can be accomplished, for example, by appropriately shaping the profile of each line.)

[0077] 13A , light beams 1324a and 1324b illustrate paths along which input beams corresponding to the four corners of an input image projected at the 9 o'clock position on input coupler region 1310 are redirected toward upper OPE region 1320a and lower OPE region 1320b, respectively. Similarly, light beams 1326a and 1326b illustrate paths along which input beams corresponding to the four corners of an input image projected at the 3 o'clock position on input coupler region 1310 are redirected toward upper OPE region 1320a and lower OPE region 1320b, respectively.

[0078] The upper OPE region 1320a and the lower OPE region 1320b also include diffractive optical features. In some embodiments, these diffractive optical features are lines formed on or in the substrate 1302 of the eyepiece waveguide 1300. The period, duty cycle, depth, profile, etc. of the lines can be selected based on the wavelength of light for which the substrate is designed, the desired diffraction efficiency of the grating, and other factors. The specific shapes of the OPE regions 1320a, 1320b can vary, but generally can be determined based on what is needed to accommodate beams of light corresponding to the corners of the input image data and all beams of light in between to provide a complete view of the input image data.

[0079] As previously mentioned, one purpose of these diffraction gratings in the OPE regions 1320a, 1320b is to replicate each input light beam at many spatial locations, producing multiple spaced, parallel light beams. This can be accomplished by designing the OPE diffraction gratings to have a relatively low diffraction efficiency (e.g., less than 10%) so that, with each beam-grating interaction, as it reflects back and forth between the front and back surfaces of the substrate 1302 via TIR, the grating redirects only a desired portion of the output light beam (e.g., via first-order diffraction), while the remaining portion continues to propagate in the same direction within the plane of the eyepiece waveguide 1300 (e.g., via zero-order diffraction). (One parameter that can be used to affect the diffraction efficiency of the grating is the etch depth of the lines.) Another purpose of the diffraction gratings in the OPE regions 1320a, 1320b is to guide those replicated light beams along a path generally toward the EPE region 1330. That is, each time a light beam interacts with an OPE diffraction grating, a portion of its output is diffracted toward the EPE region 1330, a remaining portion of its output continues to propagate in the same direction within the OPE region until it interacts with a grating again, another portion of its output is deflected toward the EPE region, etc. In this way, each input light beam is split into multiple parallel light beams that are directed along paths generally toward the EPE region 1330. This is illustrated in FIG.

[0080] The orientation of the OPE grating is generally tilted with respect to the light beams arriving from the input coupler region 1310 to redirect those light beams toward the EPE region 1330. The specific angle of tilt may depend on the layout of the various regions of the eyepiece waveguide 1300. In the eyepiece waveguide embodiment illustrated in FIGS. 13A and 13B , the upper OPE region 1320a extends in the +y-direction, while the lower OPE region 1320b extends in the -y-direction, and they are oriented 180° apart. Meanwhile, the EPE region 1330 is located at 90° with respect to the axes of the OPE regions 1320a, 1320b. Thus, to redirect light from the OPE regions 1320a, 1320b to the EPE region 1330, the gratings in the OPE region may be oriented at approximately + / −45° with respect to the illustrated x-axis. Specifically, as shown by close-up 1322a, the grating in the upper OPE region 1320a may consist of lines oriented at approximately +45° relative to the x-axis, while as shown by close-up 1322b, the grating in the lower OPE region 1320b may consist of lines oriented at approximately −45° relative to the x-axis.

[0081] Figure 13C is a three-dimensional illustration of the optical operation of the OPE region shown in Figure 13B. Figure 13C shows the input coupler region 1310 and upper OPE region 1320a from Figure 13B, both on the side of the substrate 1302 closer to the viewer. The diffractive optical features of the input coupler region 1310 and upper OPE region 1320a are not visible because they are microscopic. In this case, a single input beam 1311 is illustrated, but the image would be composed of many such input beams propagating at slightly different angles through the eyepiece waveguide 1300. The input beam 1311 enters the upper OPE region 1320a from the input coupler region 1310. The input beam 1311 then continues to propagate through the eyepiece waveguide 1300 via total internal reflection, repeatedly reflecting back and forth between its surfaces. This is represented in Figure 13C by the zigzag in the illustrated propagation of each beam.

[0082] When the input beam 1311 interacts with the diffraction grating formed in the upper OPE region 1320a, a portion of its output is diffracted toward the EPE region 1330, while another portion of its output continues along the same path through the upper OPE region 1320a. As already mentioned, this is due, in part, to the relatively low diffraction efficiency of the grating. Furthermore, the beam diffracted toward the EPE region 1330 may re-encounter the grating in the upper OPE region 1320a, and a portion of its output may be diffracted back to the original propagation direction of the input beam 1311, while another portion of its optical power may continue toward the EPE region. The paths of some of these beams are indicated by arrows in FIG. 13C . The effect is that the input beam is replicated in many places as it propagates through the upper OPE region 1320a, expanding the spatial extent of the light. This is evident from FIG. 13C, which shows that input beam 1311 is ultimately replicated into many light beams traveling generally in the x-direction toward EPE region 1330.

[0083] Referring back to FIG. 13B , it is advantageous for the input coupler region 1310 to be located between the two OPE regions. This allows the eyepiece waveguide 1300 to efficiently utilize the light diffracted into positive and negative diffraction orders in the input coupler region 1310, such that one OPE region receives one or more positive diffraction orders from the input coupler region 1310 and the other OPE region receives one or more negative diffraction orders. The light from the positive and negative diffraction orders can then be recombined in the EPE region 1330 and outcoupled into the user's eye. The location of the input coupler region 1310 between the upper and lower OPE regions 1320 a, 1320 b is advantageous in this regard, but it may result in the input coupler region 1310 effectively shadowing a central portion of the EPE region 1330. That is, because the input beam is first directed in the +y or −y direction by the input coupler before being separated into positive and negative diffraction orders and redirected in the +x direction toward the EPE region 1330, less of the light beam may reach the central portion of the EPE region, which is located directly to the left of the input coupler region 1310 in FIGS. 13A and 13B . This may be undesirable because, when the center of the EPE region 1330 is aligned with the user's eye, less of the light beam may ultimately be directed from the central portion of the EPE region 1330 to the user's eye due to the shadowing effect caused by the position of the input coupler region 1310 between the OPE region 1320. As a solution to this, the eyepiece waveguide 1300 may also include upper and lower spreader regions 1340 a, 1340 b. These spreader regions can redirect the light beam from the OPE region to fill the central portion of the EPE region 1330. The upper and lower spreader regions 1340a, 1340b accomplish this task using diffractive features as illustrated in Figure 13B.

[0084] As shown in close-up 1342a, the upper spreader region 1340a can include a diffraction grating whose grating lines are oriented at approximately −45° with respect to the x-axis, which is approximately perpendicular to the grating lines in the nearby upper OPE region 1320a, where the upper spreader region 1340a primarily receives light. Like an OPE grating, the efficiency of the grating in the spreader region can be designed so that only a portion of the power of each light beam is redirected during each interaction with the grating. Due to the orientation of the grating lines in the upper spreader region 1340a, light beams from the upper OPE region 1320a are redirected somewhat in the −y-direction before continuing toward the EPE region 1330 in the +x-direction. Thus, the upper spreader region 1340a helps increase the number of light beams that reach the central portion of the EPE region 1330, despite any shadowing caused by the position of the input coupler region 1310 relative to the EPE region 1330. Similarly, as shown in close-up 1342b, the lower spreader region 1340b can include grating lines formed at approximately +45° relative to the x-axis, which are approximately perpendicular to the grating lines in the nearby lower OPE region 1320b, where the lower spreader region 1340b primarily receives light. The grating lines in the lower spreader region 1340b redirect the light beams from the lower OPE region 1320b somewhat in the +y direction before continuing in the +x direction toward the EPE region 1330. Thus, the lower spreader region 1340b also serves to increase the number of light beams that reach the central portion of the EPE region 1330.

[0085] The light beams from the OPE regions 1320a, 1320b and the spreader regions 1340a, 1340b propagate through the substrate 1302 of the eyepiece waveguide 1300 until they finally reach the EPE region 1330. The EPE region 1330 can include diffractive optical features that redirect the light beams from the eyepiece waveguide 1300 to the user's eye. As shown in the close-up 1332, the diffractive optical features of the EPE region 1330 can be vertical grating lines extending in the y-direction and periodic in the x-direction. Alternatively, as shown in FIG. 14 , the lines of the diffraction grating in the EPE region 1330 can be curved somewhat to impart refractive power to the image data. The period, duty cycle, depth, profile, etc. of the lines can be selected based on the wavelength of light for which the substrate is designed, the desired diffraction efficiency of the grating, and other factors. A portion of each output light beam is redirected from the substrate 1302 of the eyepiece waveguide 1300 as a result of each interaction with the grating in the EPE region 1330. The specific angle at which each output beam exits the EPE region 1330 of the eyepiece waveguide 1300 is determined by the angle of incidence of the corresponding input beam at the input coupler region 1310.

[0086] FIG. 14A illustrates an embodiment of an eyepiece waveguide 1400 that includes an input coupler region 1410 with a cross-diffraction grating. The eyepiece waveguide 1400 is formed from a substrate 1402 and includes the input coupler region 1410, an upper OPE region 1420a, a lower OPE region 1420b, and an EPE region 1430. Unless otherwise noted, the eyepiece waveguide 1400 shown in FIG. 14 can function similarly to the eyepiece waveguide 1300 illustrated in FIGS. 13A-13C. The design of the eyepiece waveguide 1400 represents another way to increase the amount of light directed toward the central portion of the EPE region 1430 (located immediately to the left of the input coupler region 1410) without necessarily using the type of spreader regions 1340a, 1340b discussed with respect to FIGS. 13A-13C.

[0087] The primary difference between the eyepiece waveguide 1400 in FIG. 14A compared to the eyepiece waveguide 1300 in FIGS. 13A-13C is the design of the input coupler region 1410. In the eyepiece waveguide 1300 shown in FIGS. 13A-13C, the input coupler region 1310 was designed to redirect input light primarily only to the upper and lower OPE regions 1320a, 1320b. In contrast, the input coupler region 1410 shown in FIG. 14A is designed to both direct input light to the upper and lower OPE regions 1420a, 1420b and directly to the EPE region 1430. This can be accomplished by using a crossed diffraction grating within the input coupler region 1410.

[0088] FIG. 14B is a perspective view of an example embodiment of the input coupler region 1410 consisting of crossed diffraction gratings. The crossed grating can be thought of as the overlap of two diffraction gratings with different orientations. The first diffraction grating can be formed similarly to that illustrated with respect to FIGS. 13A-13C . That is, it can consist of lines extending in the x-direction and periodically repeated in the y-direction. This first diffraction grating splits the input light into positive and negative diffraction orders, which are directed toward the upper and lower OPE regions 1420 a, 1420 b, respectively. The first diffraction grating can have a first diffraction efficiency for controlling the power fraction of the input light redirected to the OPE regions 1420 a, 1420 b.

[0089] The second diffraction grating can be composed of lines extending in the y-direction and periodically repeated in the x-direction. In other words, the second diffraction grating can be oriented approximately 90° relative to the first diffraction grating. This orientation of the second diffraction grating redirects the input beam of light without first passing through the OPE region toward the EPE region 1430, which in this embodiment is oriented substantially 90° from the direction in which the OPE regions 1420a, 1420b are oriented relative to the input coupler region 1410. (The second diffraction grating can have other orientations in other embodiments, depending on the orientation in which the EPE region 1430 is oriented.) The second diffraction grating can be designed to have a second diffraction efficiency that can differ from that of the first diffraction grating. In some embodiments, the second diffraction grating can be designed to be less efficient than the first diffraction grating. (This can be accomplished, for example, by making the lines of the second diffraction grating shallower than those of the first diffraction grating, as shown in FIG. 14B.) Thus, most of the input light output is redirected by the first diffraction grating toward the upper and lower OPE regions 1420a, 1420b (represented by light beams 1412a, 1412b), while a smaller portion of the input light output is redirected by the second diffraction grating directly toward the EPE region 1430 (represented by light beam 1414). Because the input coupler region 1410 redirects some of the input light output directly to the EPE region 1430 without first passing through the OPE region 1420, the aforementioned shading of the central portion of the EPE region of the input coupler region can be reduced.

[0090] FIG. 15A illustrates an embodiment of an eyepiece waveguide 1500 with upper and lower OPE regions that are angled toward an EPE region 1530 to provide a more compact form factor. The eyepiece waveguide 1500 is formed from a substrate 1502 and includes an input coupler region 1510, an upper OPE region 1520a, a lower OPE region 1520b, and an EPE region 1530. Unless otherwise stated, the eyepiece waveguide 1500 shown in FIG. 15A can function similarly to the eyepiece waveguide 1300 illustrated in FIGS. 13A-13C.

[0091] The primary difference between the eyepiece waveguide 1500 in FIG. 15A compared to the eyepiece waveguide 1300 in FIGS. 13A-13C is that the OPE regions 1520a, 1520b are angled toward the EPE region 1530. In the embodiment shown in FIG. 15A , each OPE region is tilted approximately 30° from the y-axis. Thus, rather than being separated by approximately 180° as in the embodiment illustrated in FIGS. 13A-13B , the upper OPE region 1520a and the lower OPE region 1520b are separated by approximately 120°. While the precise amount of angling of the OPE regions 1520a, 1520b toward the EPE region can vary (e.g., up to 60°), generally, such angling may allow the eyepiece waveguide 1500 to achieve a more compact design. This may be advantageous because it may allow the head-mounted display of a VR / AR / MR system to be made less bulky.

[0092] The design of the diffractive features in the input coupler region 1510 can be varied to match the angle at which the input beam of light is launched into the substrate 1502 of the eyepiece waveguide 1500, corresponding to the orientation at which the OPE regions 1520a, 1520b are positioned relative to the input coupler region 1510. An example embodiment of the diffractive features of the input coupler region 1510 is shown in close-up 1512 in FIG. 15B.

[0093] Figure 15B illustrates an example embodiment of the diffractive optical features of the input coupler region 1510 of the eyepiece waveguide 1500 shown in Figure 15A. In the illustrated embodiment, the input coupler region 1510 has a plurality of diffractive or light-scattering features 1514 (e.g., indentations, protrusions, etc.) laid out in a hexagonal checkerboard pattern 1516. (Note: The dotted lines around each diffractive feature 1514 are intended to illustrate the hexagonal checkerboard pattern 1516 and do not necessarily correspond to any physical structure along the dotted lines.) The hexagonal checkerboard pattern 1516 of diffractive features causes an input beam of light incident on the input coupler region to be launched into the substrate 1502 of the eyepiece waveguide 1500 in multiple directions at 60° intervals. Thus, as shown in FIG. 15A , a first set of input beams is directed toward the upper OPE region 1520a at approximately 60° relative to the x-axis, a second set of input beams is directed toward the lower OPE region 1520b at approximately −60° relative to the x-axis, and a third set of input beams is directed generally along the x-axis directly toward the EPE region 1530. Other mosaic configurations can be used, depending on the shape of the eyepiece waveguide 1500 and the direction from the input coupler region 1510 to the OPE region. The specific shape of the diffractive features 1514 determines the efficiency with which light is redirected in each of these directions. In the illustrated embodiment, each of the diffractive features 1514 is diamond-shaped, although other shapes are possible. Additionally, the diffractive features 1514 can be single-stage or multi-stage.

[0094] In some embodiments, the diffractive features of the input coupler region 1510 are etched into the back surface of the substrate 1502 (opposite the side where the input beam enters the substrate 1502 from the input device). The etched diffractive features on the back surface of the substrate 1502 can then be coated with a reflective material. In this way, the input beam of light enters the front surface of the substrate and is diffracted from the diffractive features on the back surface such that the diffractive features operate in a reflective mode. The upper OPE region 1520a and the lower OPE region 1520b also include diffractive optical features as described above. The diffractive features of the upper OPE region 1520a are illustrated in the enlarged view 1522 in FIG. 15C.

[0095] FIG. 15C illustrates an exemplary embodiment of the diffractive optical features of the OPE region 1520a of the eyepiece waveguide 1500 shown in FIG. 15A. As with the diffractive features of the OPE region in the eyepiece waveguide 1300 shown in FIGS. 13A and 13B, the diffractive features of the OPE regions 1520a, 1520b of the eyepiece waveguide 1500 shown in FIG. 15A are similarly periodically repeating patterns of lines that form a diffraction grating. However, in this case, the angle at which the lines are oriented is still adjusted to account for the tilted orientation of the OPE region 1520a to redirect the beam of light toward the EPE region 1530. Specifically, the lines of the diffraction grating in the upper OPE region 1520a are oriented at approximately +30° with respect to the x-axis. Similarly, the lines of the diffraction grating in the lower OPE region 1520b are oriented at approximately −30° with respect to the x-axis.

[0096] (Additional Considerations) Unless the context clearly requires otherwise, throughout the description and claims, the words "comprise," "comprising," "including," "including," "having," "having," and the like, should be construed in an inclusive sense, i.e., "including but not limited to," as opposed to an exclusive or inclusive sense. The word "coupled," as generally used herein, refers to two or more elements that may be either directly connected or connected via one or more intermediate elements. Similarly, the word "connected," as generally used herein, refers to two or more elements that may be either directly connected or connected via one or more intermediate elements. Depending on the context, "coupled" or "connected" can refer to an optical coupling or optical connection, such as when light is coupled or connected from one optical element to another. Additionally, the words "herein," "above," "below," "described below," "above," and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of this application. Where the context permits, words in the above Detailed Description using the singular or plural form may also include the plural or singular form, respectively. The word "or," when referring to a list of two or more items, is an inclusive (not exclusive) "or," and "or" covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of one or more of the items in the list, and does not exclude other items added to the list. Additionally, the articles "a," "an," and "the," when used in this application and the appended claims, should be construed to mean "one or more" or "at least one," unless otherwise specified.

[0097] As used herein, a phrase referring to "at least one of" a list of items refers to any combination of those items, including single elements. As an example, "at least one of A, B, or C" is intended to cover A, B, C, A and B, A and C, B and C, and A, B, and C. Transitional phrases such as "at least one of X, Y, and Z," unless specifically stated otherwise, are generally understood differently in the context in which they are used to convey that an item, term, etc. may be at least one of X, Y, or Z. Thus, such transitional phrases generally are not intended to suggest that an embodiment requires that at least one of X, at least one of Y, and at least one of Z, respectively, be present.

[0098] Furthermore, it should be understood that conditional statements used herein, such as, among others, "can," "could," "might," "may," "e.g.," "for example," "such as," and the like, unless specifically stated otherwise or understood otherwise within the context as used, are generally intended to convey that certain embodiments include certain features, elements, and / or conditions, while other embodiments do not. Thus, such conditional statements generally are not intended to suggest that features, elements, and / or conditions are in any way required for one or more embodiments, or whether these features, elements, and / or conditions should be included or implemented in any particular embodiment.

[0099] Unless otherwise stated or shown, or apparent to one of ordinary skill in the art from the context, words such as "about," "approximately," and "generally," used in conjunction with a stated value or other descriptor, may be understood to indicate a range of ±20% around the stated value.

[0100] Although certain embodiments have been described, these embodiments are presented by way of example only and are not intended to limit the scope of the present disclosure. Any one feature of the embodiments can be combined with and / or substituted for any other feature of the embodiments. Certain advantages of various embodiments have been described herein. However, not all embodiments necessarily achieve each of these advantages.

[0101] The embodiments have been described in conjunction with the accompanying drawings. However, the figures are not drawn to scale. Distances, angles, etc. are merely illustrative and do not necessarily convey an exact relationship to the actual dimensions and layout of the devices shown.

[0102] The foregoing embodiments have been described in some detail to enable those skilled in the art to make and use the devices, systems, methods, etc. described herein. Various variations are possible. Components, elements, and / or steps may be modified, added, removed, or rearranged. While certain embodiments have been explicitly described, other embodiments will be apparent to those skilled in the art based on this disclosure.

Claims

1. An eyepiece, wherein the eyepiece is A waveguide substrate that is at least partially transparent, An input coupler grid formed on or inside the waveguide substrate between a first orthogonal pupil expander (OPE) region formed on or inside the waveguide substrate and a second OPE region formed on or inside the waveguide substrate, wherein the input coupler grid is configured to split an input light beam incident on the input coupler grid and redirect it to the first OPE region and the second OPE region, and the first and second OPE regions are configured to split the input light beam from the input coupler grid into a plurality of parallel light beams, An exit pupil expander (EPE) region formed on or within the waveguide substrate, wherein the EPE region has diffractive optical features, and the diffractive optical features are configured such that the EPE region diffracts the plurality of parallel light beams and allows them to exit from the waveguide substrate toward the eye of the eyepiece user. An eyepiece equipped with this feature.

2. The eyepiece according to claim 1, wherein the EPE region defines an EPE grid comprising a plurality of curved grid lines, and the curvature of the curved grid lines determines the refractive power of the EPE grid.

3. The eyepiece according to claim 2, wherein the waveguide substrate is configured to output a plurality of output beams such that each of the plurality of output beams corresponds to a different depth plane, and the different depth planes are determined by the refractive power of the EPE grating.

4. The eyepiece according to claim 2, wherein the exit angle for each of the multiple parallel light beams is related to the corresponding angle of entry of the input light beam incident on the input coupler grating.

5. The eyepiece according to claim 1, wherein the waveguide substrate comprises a first waveguide substrate, a second waveguide substrate, and a third waveguide substrate, and each of the first waveguide substrate, the second waveguide substrate, and the third waveguide substrate is at least partially transparent.

6. The eyepiece according to claim 1, wherein the waveguide substrate comprises glass, plastic, polycarbonate, or sapphire.

7. The eyepiece according to claim 1, wherein the waveguide substrate has a refractive index greater than 1.

8. The eyepiece according to claim 7, wherein the refractive index is greater than 1.

4.

9. The eyepiece according to claim 1, wherein the waveguide substrate is less than 325 microns thick.

10. The eyepiece according to claim 1, wherein the first and second OPE regions are oriented at 120° relative to each other, the EPE region is oriented at 60° relative to the first and second OPE regions, and the input coupler grating defines diffractive optical features having a plurality of features arranged in a hexagonal grating pattern to split the input light beam and redirect it toward the first OPE region.

11. The eyepiece according to claim 1, wherein the first and second OPE regions are oriented 180° relative to each other, and the EPE region is oriented 90° with respect to the axes of the first and second OPE regions.

12. The eyepiece according to claim 1, wherein the orientations of the first and second OPE regions are tilted with respect to the input light beam.

13. The eyepiece according to claim 1, wherein the input coupler grating comprises a plurality of grating lines forming at least one diffraction grating.

14. The eyepiece according to claim 1, wherein the input coupler grating includes a cross-diffraction grating.

15. The eyepiece according to claim 1, further comprising a projector configured to guide light toward the input coupler grating.

16. A virtual reality system comprising the eyepiece described in claim 1.

17. An augmented reality system comprising the eyepiece described in claim 1.

18. A mixed reality system comprising the eyepiece described in claim 1.

19. The eyepiece according to claim 1, wherein the first waveguide substrate is configured to project the color components of image data.

20. The eyepiece according to claim 1, wherein the input coupler grating is configured to separate the input light beam into +1st order diffracted light directed toward the first OPE region and -1st order diffracted light directed toward the second OPE region.

21. The eyepiece according to claim 1, wherein the first and second OPE regions are oriented 180° relative to each other, and the EPE region is oriented 90° relative to the first and second OPE regions.

22. The eyepiece according to claim 1, wherein the first and second OPE regions are inclined toward the EPE region.

23. The eyepiece according to claim 22, wherein the first and second OPE regions are oriented 120° relative to each other, and the EPE region is oriented 60° relative to the first and second OPE regions.

24. The eyepiece according to claim 1, wherein the input coupler grating has diffractive optical features for splitting the input light beam and redirecting it toward the first and second OPE regions.

25. The eyepiece according to claim 24, wherein the diffractive optical features of the input coupler grating include a plurality of lines forming at least one diffraction grating.

26. The eyepiece according to claim 24, wherein the diffractive optical features of the input coupler grating include a plurality of features arranged in a grating pattern.

27. The eyepiece according to claim 26, wherein the first and second OPE regions are oriented at 120° relative to each other, the EPE region is oriented at 60° relative to the first and second OPE regions, and the grid pattern comprises a hexagonal grid pattern.

28. The eyepiece according to claim 24, wherein the diffractive optical feature of the input coupler grating includes a cross grating.

29. The eyepiece according to claim 24, wherein the diffractive optical features of the input coupler grating are configured to guide light toward the first and second OPE regions and to guide light toward the EPE region without first passing through either the first or second OPE region.

30. The eyepiece according to claim 1, wherein the first and second OPE regions have diffractive optical features for splitting each of the first and second guided light beams into a plurality of parallel spaced light beams.

31. The eyepiece according to claim 30, wherein the diffractive optical features of the first and second OPE regions include a plurality of lines that form a diffraction grating.

32. The eyepiece according to claim 31, wherein the diffraction gratings in the first and second OPE regions are angled to guide the plurality of spaced-apart light beams toward the EPE region.

33. The first waveguide substrate is A first spreader grating receives the light beam from the first OPE region and spreads its distribution so that it reaches a larger portion of the EPE region, A second spreader grating receives the light beam from the second OPE region and spreads its distribution so that it reaches a larger portion of the EPE region. The eyepiece according to claim 1, further comprising:

34. The eyepiece according to claim 33, wherein both the first spreader grating and the second spreader grating are configured to spread the distribution of the light beam toward the center of the EPE region.

35. The eyepiece according to claim 33, wherein the first and second spreader gratings have diffractive optical properties.

36. The eyepiece according to claim 35, wherein each of the diffractive optical features of the first and second spreader gratings comprises a plurality of lines forming a diffraction grating.

37. The eyepiece according to claim 36, wherein the diffraction grating of the first spreader grating is oriented at 90° with respect to the diffraction grating of the first OPE region, and the diffraction grating of the second spreader grating is oriented at 90° with respect to the diffraction grating of the second OPE region.

Images