Eyepiece for augmented reality display system

Abstract

An eyepiece waveguide for an augmented reality display system may include a transparent substrate, an input coupling grating (ICG) region, a multi-directional pupil expander (MPE) region, and an exit pupil expander (EPE) region. The ICG region may receive an input light beam and couple the input light beam into the substrate as a guided light beam. The MPE region may include a plurality of diffraction features that exhibit periodicity along at least a first periodic axis and a second periodic axis. The MPE region may be positioned to receive the guided light beam from the ICG region and diffract the guided light beam in multiple directions to generate a plurality of diffracted light beams. The EPE region may be positioned to receive one or more diffracted light beams from the MPE region and couple the diffracted light beams out of the transparent substrate as output light beams.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application Serial No. 62 / 599,663, entitled “EYEPIECES FOR AUGMENTED REALITY DISPLAY SYSTEM,” filed on December 15, 2017, and U.S. Provisional Patent Application Serial No. 62 / 608,555, entitled “EYEPIECES FOR AUGMENTED REALITY DISPLAY SYSTEM,” filed on December 20, 2017, and U.S. Provisional Patent Application Serial No. 62 / 620,465, entitled “EYEPIECES FOR AUGMENTED REALITY DISPLAY SYSTEM,” filed on January 22, 2018. Any and all applications that identify a foreign or domestic priority claim above and / or in the Application Data Sheet filed with this application are incorporated herein by reference pursuant to 37 CFR § 1.57. Technical Field

[0003] The present disclosure relates to eyepieces for virtual reality, augmented reality, and mixed reality systems. Background Art

[0004] Modern computing and display technologies have facilitated the development of virtual reality, augmented reality, and mixed reality systems. Virtual reality, or "VR," systems create simulated environments for users to experience. This is achieved by presenting computer-generated image data to the user using a head-mounted display. This image data creates a sensory experience that immerses the user in the simulated environment. Virtual reality scenarios generally involve presenting only computer-generated image data, without including actual real-world image data.

[0005] Augmented reality systems generally use simulated elements to supplement the real-world environment. For example, an augmented reality or "AR" system can provide a user with a view of the surrounding real-world environment through a head-mounted display. However, computer-generated image data can also be presented on the display to augment the real-world environment. Such computer-generated image data can include elements that are contextually relevant to the real-world environment. Such elements can include simulated text, images, objects, etc. Mixed reality or "MR" systems are AR systems that also introduce simulated objects into the real-world environment, but these objects are typically more interactive. The simulated elements can typically be interactive in real time.

[0006] Figure 1An example AR scene 1 is shown in which a user sees a real-world park setting 6, which features people, trees, buildings in the background, and a concrete platform 20. In addition to these items, the user is presented with computer-generated image data. The computer-generated image data may include, for example, a robotic statue 10 standing on the real-world platform 20, and a cartoon-like avatar character 2 flying by, which appears to be an avatar of a bumblebee, even though these elements 2, 10 do not actually exist in the real-world environment. Summary of the Invention

[0007] In some embodiments, an eyepiece waveguide for an augmented reality display system includes: a transparent substrate; an input coupling grating (ICG) region formed on or in the substrate, the ICG region being configured to receive an input light beam and couple the input light beam into the substrate as a guided light beam; a multi-directional pupil expander (MPE) region formed on or in the substrate, the MPE region including a plurality of diffraction features exhibiting periodicity along at least a first periodic axis and a second periodic axis, the MPE region being positioned to receive the guided light beam from the ICG region and diffract the guided light beam in multiple directions to generate a plurality of diffracted light beams; and an exit pupil expander (EPE) region formed on or in the substrate, the EPE region being positioned to receive one or more of the diffracted light beams from the MPE region and couple the diffracted light beams out of the transparent substrate as output light beams.

[0008] In some embodiments, an eyepiece waveguide for an augmented reality display system includes: a light-transmitting substrate; an input coupling grating (ICG) region formed on or in the substrate, the ICG region configured to receive an input beam group and couple the input beam group into the substrate as a guided beam group, the guided beam group being associated with a k-vector group in k-space, the k-vector group being at least partially located in a k-space ring associated with the eyepiece waveguide, the k-space ring corresponding to a region in k-space associated with guided propagation in the eyepiece waveguide; and a multi-directional pupil expander (MPE) region formed on or in the substrate, the MPE region being positioned to transmit light from the I The CG region receives the guided beam group and is configured to diffract the guided beam group to generate a plurality of diffracted beam groups, the plurality of diffracted beam groups being at least three diffracted beam groups, the plurality of diffracted beam groups being associated with a plurality of k-vector groups, the plurality of k-vector groups being at least three k-vector groups, the at least three k-vector groups being at least partially located in the k-space ring and centered at three different angular positions; and an exit pupil expander (EPE) region formed on or in the substrate, the EPE region being positioned to receive one of the plurality of diffracted beam groups from the MPE region and couple the diffracted beam group out of the transparent substrate as an output beam.

[0009] In some embodiments, an eyepiece waveguide for an augmented reality display system includes: an input coupling region for receiving an input light beam associated with an image, the input light beam having an associated pupil; a multi-directional pupil expander (MPE) region configured to expand the pupil in at least three directions; and an exit region for projecting an output light beam associated with the image.

[0010] In some embodiments, an eyepiece waveguide for an augmented reality display system comprises: a light-transmissive substrate; an input coupling grating (ICG) region formed on or in the substrate, the ICG region being configured to: receive an input beam group, the input beam group being associated with a k-vector group in k-space; diffract the input beam group to produce a first guided beam group and a first undiffracted beam group, the first guided beam group corresponding to a translated k-vector subset located within a k-space ring associated with the eyepiece waveguide, and the first undiffracted beam group corresponding to a translated k-vector subset located outside the k-space ring, the k-space ring corresponding to a region in k-space associated with guided propagation in the eyepiece waveguide; diffract the input beam group to produce a separated second guided beam group and a separated second undiffracted beam group, the second guided beam group corresponding to the translated k-vector subset located within the k-space ring, and the first undiffracted beam group corresponding to the translated k-vector subset located outside the k-space ring. two non-diffracted beam groups corresponding to shifted k-vector subsets located outside the k-space ring; a first pupil expander region formed on or in the substrate, the first pupil expander region positioned to receive the first guided beam group from the ICG region and configured to replicate the first guided beam group into a first replicated beam group; a second pupil expander region formed on or in the substrate, the second pupil expander region positioned to receive the second guided beam group from the ICG region and configured to replicate the second guided beam group into a second replicated beam group; and an exit region formed on or in the substrate, the exit region positioned to receive the first replicated beam group and the second replicated beam group, and the exit region configured to couple the first replicated beam group and the second replicated beam group out as output beams, wherein the output beams represent the complete input beam group.

[0011] In some embodiments, an eyepiece waveguide for an augmented reality display system includes: a light-transmissive substrate; an input coupling grating (ICG) region formed on or in the substrate, the ICG region configured to: receive a group of input beams associated with a group of k-vectors forming a field of view (FOV) shape in k-space, the FOV shape having a first dimension in k-space that is greater than a width of a k-space ring associated with the eyepiece waveguide, the k-space ring corresponding to a region in k-space associated with guided propagation in the eyepiece waveguide; and diffract the input beams so as to couple the input beams into the substrate as guided beams and so as to translate the FOV shape into the k-space. The substrate further comprises a first position and a second position in the k-space annulus, wherein at the first position, a portion of the FOV shape is outside the k-space annulus and only a first sub-portion of the FOV shape is within the k-space annulus, and wherein at the second position, a portion of the FOV shape is outside the k-space annulus and only a second sub-portion of the FOV shape is within the k-space annulus; and a plurality of pupil expander regions formed on or in the substrate, the plurality of pupil expander regions being positioned to diffract the guided beam so as to translate the first and second sub-portions of the FOV shape to a third position in the k-space annulus where the complete FOV shape is recombined.

[0012] In some embodiments, an eyepiece waveguide for an augmented reality display system includes: a light-transmitting substrate; an input coupling grating (ICG) region formed on or in the substrate, the ICG region configured to receive an input beam group and couple the input beam group into the substrate as a guided beam group, the input beam group being associated with a k-vector group in k-space, the k-vector group having a first dimension in k-space greater than a width of a k-space ring associated with the eyepiece waveguide, the k-space ring corresponding to a region in k-space associated with guided propagation in the eyepiece waveguide; a plurality of pupil expander regions formed on or in the substrate, the plurality of pupil expander regions positioned to collectively receive the guided beams from the ICG region and diffract the guided beams to produce a replicated beam group; and an exit region formed on or in the substrate, the exit region positioned to receive the replicated beams and couple the replicated beams out of the light-transmitting substrate as an output beam group, the output beam group representing the complete input beam group.

[0013] In some embodiments, an eyepiece waveguide for an augmented reality display system includes: a light-transmitting substrate; an input coupling grating (ICG) region formed on or in the substrate, the ICG region including a diffraction grating configured to diffract an input light beam group corresponding to an input image into a plurality of diffraction orders, the diffraction grating having a period Λ that satisfies wherein n2 is the refractive index of the transparent substrate, n1 is the refractive index of the medium surrounding the transparent substrate, ω is the angular frequency of the input light beam, and c is the speed of light constant; a plurality of pupil expander regions formed on or in the substrate, the plurality of pupil expander regions being positioned to collectively receive light beams from the ICG region and diffract the light beams to generate a set of replica beams; and an exit region formed on or in the substrate, the exit region being positioned to receive the replica beams and couple the replica beams out of the transparent substrate as a set of output beams, the set of output beams representing the complete input image.

[0014] In some embodiments, an eyepiece waveguide for an augmented reality display system includes: a transparent substrate having a first surface and a second surface; a first input coupling grating (ICG) region formed on or in one of the surfaces of the substrate, the first ICG region being configured to receive an input beam and couple the input beam into the substrate as a guided beam; a multi-directional pupil expander (MPE) region formed on or in the first surface of the substrate, the MPE region comprising a plurality of diffraction features exhibiting periodicity along at least a first periodic axis and a second periodic axis, the MPE region being positioned to receive the guided beam from the first ICG region and diffract the guided beam in multiple directions to generate a plurality of diffracted beams; and an exit pupil expander (EPE) region formed on or in the second surface of the substrate, the EPE region overlapping the MPE region, and the EPE region being configured to couple one or more of the diffracted beams out of the transparent substrate as an output beam. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 An augmented reality (AR) view viewed by a user through an AR device is shown.

[0016] Figure 2 An example of a wearable display system is shown.

[0017] Figure 3 A conventional display system for simulating three-dimensional image data for a user is shown.

[0018] Figure 4 Aspects of a method for simulating three-dimensional image data using multiple depth planes are shown.

[0019] Figures 5A to 5C The relationship between the radius of curvature and the focal radius is shown.

[0020] Figure 6 An example of a waveguide stack used in an AR eyepiece to output image information to a user is shown.

[0021] Figures 7A to 7B An example of an outgoing light beam output from a waveguide is shown.

[0022] Figure 8 An example of a stacked waveguide assembly is shown where each depth plane includes an image formed using multiple different component colors.

[0023] Figure 9A A cross-sectional side view of an example of a set of stacked waveguides, each stacked waveguide including an in-coupling optical element, is shown.

[0024] Figure 9B Shown Figure 9A A perspective view of an example of multiple stacked waveguides.

[0025] Figure 9C Shown Figure 9A and 9B A top plan view of an example of multiple stacked waveguides.

[0026] Figure 10 is a perspective view of an example AR eyepiece waveguide stack.

[0027] Figure 11 is a cross-sectional view of a portion of an example eyepiece waveguide stack having an edge seal structure supporting the eyepiece waveguides in a stacked configuration.

[0028] Figure 12A and 12B A top view of the eyepiece waveguide is shown in operation as it projects an image toward the user's eye.

[0029] Figure 13A The k-vector that can be used to represent the propagation direction of a ray or light beam is shown.

[0030] Figure 13B The light rays within the planar waveguide are shown.

[0031] Figure 13C The allowed k-vectors for light with a given angular frequency ω propagating in an unbounded homogeneous medium with refractive index n are shown.

[0032] Figure 13D The allowed k-vectors for light with a given angular frequency ω propagating in a homogeneous planar waveguide medium with refractive index n are shown.

[0033] Figure 13E A ring in k-space corresponding to the k-vector of a light wave that can be guided within a waveguide having a refractive index n2 is shown.

[0034] Figure 13F A k-space diagram and an eyepiece waveguide are shown, illustrating the relationship between a k-vector and the interaction density between a guided light beam corresponding to the k-vector and a diffraction grating formed on or in the waveguide.

[0035] Figure 13G A diffraction grating and some of its associated k-space diffraction grating vectors (G -2 , G -1 , G1, G2) top view.

[0036] Figure 13H A cross-sectional view of a diffraction grating and its effect on the k-vector corresponding to a normally incident ray or beam in k-space is shown.

[0037] Figure 13I Shown Figure 13G A cross-sectional view of a diffraction grating is shown, and its effect on the k-vector in k-space corresponding to an obliquely incident ray or beam.

[0038] Figure 13J is a k-space diagram showing the field of view of the image projected into the AR eyepiece waveguide.

[0039] Figure 13K is a k-space diagram showing the translational displacement of the FOV rectangle in k-space caused by the input coupling grating (ICG) located at the entrance pupil of the eyepiece waveguide.

[0040] Figure 14A An example eyepiece waveguide is shown having an ICG region, an orthogonal pupil expander (OPE) region, and an exit pupil expander (EPE) region.

[0041] Figure 14B Shown Figure 14A K-space manipulation of the eyepiece waveguide shown.

[0042] Figure 14C The optical operation of the OPE regions shown in Figures 14A and 14B is shown.

[0043] Figure 14D Techniques for determining the size and shape of OPE and EPE regions are shown.

[0044] Figure 15A An example embodiment of a waveguide eyepiece is shown in which the OPE region is tilted and positioned so that its lower boundary is parallel to the upper boundary of the EPE region.

[0045] Figure 15B Includes a k-space map showing Figure 15A Operation of the eyepiece waveguide is shown.

[0046] Figure 15C is another k-space diagram showing Figure 15A Operation of the eyepiece waveguide is shown.

[0047] Figure 15D is the input beam and Figure 15A Diagram of the first generation interaction between the OPE regions of the eyepiece waveguide embodiment shown.

[0048] Figure 15E is the input beam and Figure 15A Diagram of the second generation interaction between OPE regions of the eyepiece waveguide embodiment shown.

[0049] Figure 15F is the input beam and Figure 15A Diagram of the third generation interaction between OPE regions of the eyepiece waveguide embodiment shown.

[0050] Figure 15G is a diagram showing how a single input beam from the ICG region is replicated through the OPE region and how the single input beam is redirected to the EPE region as multiple beams.

[0051] Figure 16A An example eyepiece waveguide is shown having a multi-directional pupil expander (MPE) region instead of an OPE region.

[0052] Figure 16B Shows that it can be Figure 16A A portion of an example 2D raster and its associated raster vectors used in the MPE region is shown.

[0053] Figure 16C is a k-space diagram showing Figure 16A K-space manipulation of the MPE region of the eyepiece waveguide is shown.

[0054] Figure 16D is a k-space diagram, which further shows Figure 16A K-space manipulation of the MPE region of the eyepiece waveguide is shown.

[0055] Figure 16E is a k-space diagram showing Figure 16A K-space manipulation of the eyepiece waveguide shown.

[0056] Figure 16F is the input beam and Figure 16A Diagram of the first generation interaction between the MPE regions of the eyepiece waveguide embodiment shown.

[0057] Figure 16G is the input beam and Figure 16A Diagram of the second generation interaction between the MPE regions of the eyepiece waveguide embodiment shown.

[0058] Figure 16H is the input beam and Figure 16A Diagram of the third generation interaction between MPE regions of the eyepiece waveguide embodiment shown.

[0059] Figure 16I is the input beam and Figure 16A Diagram of the fourth generation interaction between MPE regions of the eyepiece waveguide embodiment shown.

[0060] Figure 16J It shows that according to Figure 16A Diagram showing the various paths a light beam of an eyepiece waveguide embodiment can follow through the MPE region and ultimately to the EPE region.

[0061] Figure 16K is a diagram showing how a single input beam from the ICG region is replicated by the MPE region and how the single input beam is redirected to the EPE region as multiple beams.

[0062] Figure 16L is a side-by-side comparison showing the performance of an eyepiece waveguide with an OPE region versus an eyepiece waveguide with an MPE region.

[0063] Figure 16M The performance of the eyepiece waveguide with an MPE region is further shown compared to the performance of other eyepiece waveguides with an OPE region.

[0064] Figure 17A A portion of an example 2D grating and its associated grating vectors that can be used in the MPE region of an eyepiece waveguide are shown.

[0065] Figure 17B is a k-space diagram illustrating the k-space operation of the MPE region of the eyepiece waveguide.

[0066] Figure 17C is a k-space diagram showing the k-space operation of the eyepiece waveguide with the MPE region.

[0067] Figure 17D is a diagram of the first generation interaction between the input beam and the MPE region of the eyepiece waveguide.

[0068] Figure 17E is a diagram of the second-generation interaction between the input beam and the MPE region of the eyepiece waveguide.

[0069] Figure 17Fis a diagram of the third-generation interaction between the input beam and the MPE region of the eyepiece waveguide.

[0070] Figure 17G is a diagram of the fourth-generation interaction between the input beam and the MPE region of the eyepiece waveguide.

[0071] Figure 18A An example eyepiece waveguide is shown having an ICG region, two orthogonal pupil expander regions, and an exit pupil expander region.

[0072] Figure 18B and 18C Shown Figure 18A A top view of the EPE region of the eyepiece waveguide is shown.

[0073] Figure 19 An embodiment of an eyepiece waveguide with an extended field of view is shown.

[0074] Figure 20A An embodiment of an extended FOV eyepiece waveguide having an MPE region overlapping an EPE region is shown.

[0075] Figure 20B Shows that it can be Figure 20A A portion of an example 2D grating and its associated grating vector used in the MPE region of the eyepiece waveguide.

[0076] Figure 20C is a k-space diagram showing Figure 20A K-space manipulation of the ICG region in the eyepiece waveguide.

[0077] Figure 20D is a k-space diagram showing Figure 20A The eyepiece waveguide is part of the k-space operation of the MPE region.

[0078] Figure 20E is a k-space diagram showing Figure 20A The eyepiece waveguide is another part of the MPE region for k-space manipulation.

[0079] Figure 20F Similar to Figure 20E , except that it shows the MPE area Figure 20D Move to 9 o'clock (instead of Figure 20E k-space operation of the FOV rectangle (as shown translated to the 3 o'clock position).

[0080] Figure 20G is a k-space diagram showing Figure 20A K-space manipulation of the EPE region in the eyepiece waveguide.

[0081] Figure 20His the k-space map, which summarizes Figure 20A k-space manipulation of the eyepiece waveguide.

[0082] Figure 20I It shows how the light beam passes through Figure 20A Diagram of the eyepiece waveguide extension shown.

[0083] Figure 20J Shown Figure 20A Figure 3 illustrates how the diffraction efficiency of the MPE region of the eyepiece waveguide can be spatially varied to enhance brightness uniformity in the waveguide.

[0084] Figure 20K Shown Figure 20A Figure 3. How the diffraction efficiency of the EPE region of the eyepiece waveguide in FIG. 5 varies spatially to enhance brightness uniformity in the waveguide.

[0085] Figure 20L Shown Figure 20A An embodiment of an eyepiece waveguide in which includes one or more diffraction mirrors around a peripheral edge of the waveguide.

[0086] Figure 20M Shown is the inclusion Figure 20A Example embodiments of glasses having one or more instances of an eyepiece waveguide.

[0087] Figure 20N Shown is the inclusion Figure 20A Another example embodiment of glasses having one or more instances of an eyepiece waveguide in the eyepiece.

[0088] Figure 21A Another embodiment of an eyepiece waveguide having an MPE region overlapping an EPE region is shown.

[0089] Figure 21B is a k-space diagram showing Figure 20A The eyepiece waveguide in operates on the k-space of a first set of input beams corresponding to a first sub-portion of the FOV of the input image.

[0090] Figure 21C is a k-space diagram showing Figure 21A The eyepiece waveguide in operates on the k-space of a second set of input beams corresponding to a second sub-portion of the FOV of the input image.

[0091] Figure 21D is the k-space map, which summarizes Figure 21A k-space manipulation of the eyepiece waveguide.

[0092] Figure 21E Shown is the inclusion Figure 21A Example embodiments of glasses having one or more instances of an eyepiece waveguide.

[0093] Figure 21F Shown is the corresponding Figure 21E Example FOV of glasses in .

[0094] Figure 21G Shown Figure 21A K-space manipulation of another embodiment of the eyepiece waveguide is shown.

[0095] Figure 22A An embodiment of an eyepiece waveguide that can project a FOV that extends in two directions is shown.

[0096] Figure 22B Shown Figure 22A The opposite side of the eyepiece waveguide is shown.

[0097] Figure 22C Shown Figure 22A k-space manipulation of the ICG region and OPE region in an eyepiece waveguide embodiment.

[0098] Figure 22D Shown Figure 22A K-space manipulation of the MPE region in an eyepiece waveguide embodiment.

[0099] Figure 22E Shown Figure 22A K-space manipulation of the EPE region in an eyepiece waveguide embodiment.

[0100] Figure 23 An example embodiment of an eyepiece waveguide designed to work with a tilted projector is shown. DETAILED DESCRIPTION

[0101] Overview

[0102] This disclosure describes various eyepiece waveguides that can be used in an AR display system to project images into a user's eye. The eyepiece waveguides can be described both in physical terms and using a k-space representation.

[0103] Examples of HMD devices

[0104] Figure 2An example of a wearable display system 60 is shown. The display system 60 includes a display or eyepiece 70, as well as various mechanical and electronic modules and systems that support the functionality of the display 70. The display 70 can be coupled to a frame 80, which can be worn by a display system user 90 and is configured to position the display 70 in front of the user's 90 eyes. In some embodiments, the display 70 can be considered as glasses. In some embodiments, a speaker 100 is coupled to the frame 80 and positioned near the user's 90 ear canal. The display system can also include one or more microphones 110 to detect sound. The microphones 110 can allow the user to provide input or commands to the system 60 (e.g., selection of voice menu commands, natural language questions, etc.) and / or can allow for audio communication with others (e.g., with other users of similar display systems). The microphones 100 can also collect audio data from the user's surroundings (e.g., sounds from the user and / or the environment). In some embodiments, the display system can also include peripheral sensors 120a, which can be detached from the frame 80 and attached to the user's 90 body (e.g., head, torso, limbs, etc.). In some embodiments, the peripheral sensor 120 a may acquire data representative of the physiological state of the user 90 .

[0105] The display 70 is operably coupled to a local data processing module 140 via a communication link 130 (e.g., via a wired lead or a wireless connection). The local data processing module 140 can be mounted in various configurations, such as fixedly attached to the frame 80, fixedly attached to a helmet or hat worn by the user, embedded in headphones, or removably attached to the user 90 (e.g., in a backpack-style configuration or in a belt-coupled configuration). Similarly, the sensor 120a can be operably coupled to the local processing and data module 140 via a communication link 120b (e.g., via a wired lead or a wireless connection). The local processing and data module 140 can include a hardware processor, as well as digital memory, such as non-volatile memory (e.g., flash memory or a hard drive), both of which can be used to assist in processing, caching, and data storage. Such data may include 1) data captured by sensors (which may, for example, be operably 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, radios, gyroscopes, and / or other sensors disclosed herein; and / or 2) data (including data regarding virtual content) acquired and / or processed using remote processing module 150 and / or remote data repository 160, which data may be transmitted to display 70 after being so processed or retrieved. Local processing and data module 140 may be operably coupled to remote processing module 150 and remote data repository 160 via communication links 170, 180 (such as via wired or wireless communication links), such that these remote modules 150, 160 are operably 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 radio, and / or a gyroscope. In some other embodiments, one or more of these sensors may be attached to the frame 80 or may be a separate device that communicates with the local processing and data module 140 via a wired or wireless communication path.

[0106] Remote processing module 150 may include one or more processors that analyze and process data (such as images or audio information). In some embodiments, remote data repository 160 may be a digital data storage facility that is accessible via the Internet or other network 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 used to generate 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 module.

[0107] Perceiving an image as "three-dimensional" or "3D" may be achieved by providing a slightly different image presentation to each eye of the user. Figure 3 A conventional display system for simulating three-dimensional image data for a user is shown. Two different images 190, 200 are output to the user, one for each eye 210, 220. Images 190, 200 are spaced a distance 230 from the eyes 210, 220 along an optical axis or z-axis parallel to the user's line of sight. Images 190, 200 are flat, and the eyes 210, 220 can focus on the images by assuming a single accommodation state. Such 3D display systems rely on the human visual system to combine images 190, 200 to provide a perception of depth and / or scale in the combined image.

[0108] However, the human visual system is complex, and providing a realistic sense of depth is challenging. For example, many users of conventional "3D" display systems find such systems uncomfortable or unable to perceive depth at all. Objects can be perceived as "three-dimensional" due to a combination of vergence and accommodation. The vergence movement of the two eyes relative to each other (e.g., the rotation of the eyes so that the pupils are directed toward or away from each other to converge their respective lines of sight while focusing on an object) is closely related to the focusing (or "accommodation") of the eye lenses. Under normal circumstances, changing the focus of the eye lenses or accommodating the eyes to shift focus from one object to another at a different distance will automatically result in a matching change in vergence to the same distance, based on a relationship known as the "accommodation-vergence reflex" and pupil dilation or contraction. Similarly, under normal circumstances, changes in vergence will trigger matching changes in lens shape and pupil size. As described herein, many stereoscopic or "3D" display systems display a scene to each eye using slightly different presentations (and therefore slightly different images) to enable the human visual system to perceive a three-dimensional perspective. However, such systems can be uncomfortable for some users because they only provide image information in a single accommodation state and react to the "accommodation-vergence reflex." Display systems that provide a better match between accommodation and vergence can result in more realistic and comfortable simulations of three-dimensional image data.

[0109] Figure 4 Aspects of a method for simulating three-dimensional image data using multiple depth planes are shown. Figure 4, eyes 210, 220 adopt different accommodation states to focus on objects at different distances along the z-axis. Thus, a particular accommodation state can be considered to be associated with a particular one of the depth planes 240 shown (having an associated focal length), such that when the eye is in an accommodation state for a particular depth plane, objects or portions of objects in that particular depth plane are in focus. In some embodiments, three-dimensional image data can be simulated by providing a different presentation of an image to each eye 210, 220, and also by providing different presentations of images corresponding to multiple depth planes. Although the respective fields of view of the eyes 210, 220 are shown as separate for clarity of illustration, they can overlap, for example as the distance along the z-axis increases. Furthermore, although the depth planes are shown as flat for ease of illustration, it should be understood that the contours of the depth planes can be curved in physical space so that all features within the depth planes are in focus when the eyes are in a particular accommodation state.

[0110] The distance between an object and eye 210 or 220 may also change the amount of divergence of light from the object viewed by the eye. Figures 5A to 5C The relationship between distance and light divergence is shown in FIG. The distance between the object and the eye 210 is represented by R1, R2 and R3 in descending order of distance. Figures 5A to 5C As shown, as the distance to the object decreases, the light rays become more divergent. As the distance increases, the light rays become more collimated. In other words, the light field generated by a point (an object or a portion of an object) can be considered to have a spherical wavefront curvature that is a function of the distance of that point relative to the user's eye. As the distance between the object and the eye 210 decreases, the curvature increases. Therefore, at different depth planes, the light rays diverge to different degrees, with the divergence increasing as the distance between the depth plane and the user's eye 210 decreases. Although in order to Figures 5A to 5C While only a single eye 210 is shown for clarity in FIG. 1 and other figures herein, it should be understood that the discussion regarding eye 210 may apply to both eyes 210 and 220 of a user.

[0111] Highly convincing perceived depth simulation can be achieved by providing the eye with a different representation of an image corresponding to each of a limited number of depth planes. The different representations can be individually focused by the user's eyes, thereby helping to provide depth cues to the user based on the amount of eye accommodation required to bring different image features of the scene located at different depth planes into focus and / or based on the observation that different image features are located at different depth planes that are out of focus.

[0112] Example of a waveguide stack for AR or MR eyepieces

[0113] Figure 6An example of a waveguide stack for outputting image information to a user in an AR eyepiece is shown. The display system 250 includes a waveguide stack or stacked waveguide assembly 260 that can be used to provide a three-dimensional perception to the eye / brain using multiple waveguides 270, 280, 290, 300, 310. In some embodiments, the display system 250 is Figure 2 System 60, Figure 6 Some parts of the system 60 are shown schematically in more detail. For example, the waveguide assembly 260 may be Figure 2 It will be appreciated that in some embodiments, the display system 250 may be considered a light field display.

[0114] The waveguide assembly 260 may also include a plurality of 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 the plurality of lenses 320, 330, 340, 350 may be configured to deliver image information to the eye at various levels of wavefront curvature or light divergence. Each waveguide level may be associated with a particular depth plane and may be configured to output image information corresponding to that depth plane. The image injection devices 360, 370, 380, 390, 400 may serve as light sources for the waveguides and may be used to inject image information into the waveguides 270, 280, 290, 300, 310. As described herein, each waveguide may be configured to distribute incident light across each respective waveguide for output toward the eye 210. Light exits the output surface 410, 420, 430, 440, 450 of each respective image injection device 360, 370, 380, 390, 400 and is injected into the respective input surface 460, 470, 480, 490, 500 of the respective waveguide 270, 280, 290, 300, 310. In some embodiments, each of the input surfaces 460, 470, 480, 490, 500 can be an edge of the respective waveguide, or can be a portion of a major surface of the respective waveguide (i.e., one of the waveguide surfaces that directly faces the world 510 or the user's eye 210). In some embodiments, a light beam (e.g., a collimated light beam) can be injected into each waveguide and can be replicated (e.g., sampled into sub-beams by diffraction) in the waveguide and then directed to the eye 210 with an optical focal length corresponding to the depth plane associated with that particular waveguide. In some embodiments, a single one of image injection devices 360 , 370 , 380 , 390 , 400 may be associated with multiple (eg, three) of waveguides 270 , 280 , 290 , 300 , 310 and inject light into these waveguides.

[0115] In some embodiments, image injection devices 360, 370, 380, 390, 400 are separate displays that each generate image information for injection into a respective waveguide 270, 280, 290, 300, 310. In some other embodiments, image injection devices 360, 370, 380, 390, 400 are outputs of a single multiplexed display that can transmit image information to each of image injection devices 360, 370, 380, 390, 400 via one or more optical conduits (e.g., fiber optic cables). It will be appreciated that the image information provided by image injection devices 360, 370, 380, 390, 400 can include light of different wavelengths or colors.

[0116] 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). The light from the light module 530 can be directed to a light modulator 540 (e.g., a spatial light modulator) via a beam splitter (BS) 550 and modulated by the light modulator. The light modulator 540 can 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), including liquid crystal on silicon (LCOS) displays, and digital light processing (DLP) displays.

[0117] In some embodiments, the light projector system 520 or one or more components thereof may be attached to the frame 80 ( Figure 2 ). For example, the light projector system 520 can be part of the temple portion of the frame 80 (e.g., the ear stem 82), or can be provided at the edge of the display 70. In some embodiments, the light module 530 can be separated from the BS 550 and / or the light modulator 540.

[0118] In some embodiments, the display system 250 may be a scanning fiber display that includes one or more scanning optical 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 image injection devices 360, 370, 380, 390, 400 shown may schematically represent a single scanning optical fiber or a scanning optical fiber bundle 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 schematically represent a plurality of scanning optical fibers or a plurality of scanning optical fiber bundles, each of which is configured to inject light into an associated waveguide of the waveguides 270, 280, 290, 300, 310. The one or more optical fibers may transmit light from the optical module 530 to the one or more waveguides 270, 280, 290, 300, and 310. Furthermore, one or more intermediate optical structures may be provided between the one or more scanning optical fibers and the one or more waveguides 270, 280, 290, 300, 310 to, for example, redirect light emitted from the scanning optical fibers into the one or more waveguides 270, 280, 290, 300, 310.

[0119] The controller 560 controls the operation of the stacked waveguide assembly 260, including the operation of the image injection devices 360, 370, 380, 390, 400, the light source 530, and the light modulator 540. In some embodiments, the controller 560 is part of the local data processing module 140. The controller 560 includes programming (e.g., instructions in a non-transitory medium) that regulates the timing and provides image information to the waveguides 270, 280, 290, 300, 310. In some embodiments, the controller can be a single integral device or a distributed system connected by wired or wireless communication channels. In some embodiments, the controller 560 can be a processing module 140 or 150 ( Figure 2 ) part.

[0120] The waveguides 270, 280, 290, 300, 310 can be configured to propagate light within each respective waveguide by total internal reflection (TIR). The waveguides 270, 280, 290, 300, 310 can each be planar or have another shape (e.g., curved), having a top major surface and a bottom major surface and an edge extending between these top major surfaces and bottom major surfaces. In the configuration shown, the waveguides 270, 280, 290, 300, 310 can each include an out-coupling optical element 570, 580, 590, 600, 610 that is configured to extract light from the waveguide by redirecting the light to propagate within the respective waveguide and exit from the waveguide to output image information to the eye 210. The extracted light can also be referred to as outcoupled light, and the out-coupling optical element can also be referred to as a light extraction optical element. The extracted light beam can be output from the waveguide at a location where the light propagating in the waveguide impinges on the light extraction optical element. As further discussed herein, the outcoupling optical elements 570, 580, 590, 600, 610 can be, for example, diffractive optical features, including diffraction gratings. Although the outcoupling optical elements 570, 580, 590, 600, 610 are shown as being disposed at the bottom major surface of the waveguides 270, 280, 290, 300, 310, in some embodiments, as further discussed herein, the outcoupling optical elements 570, 580, 590, 600, 610 can be disposed at the top and / or bottom major surfaces and / or can be disposed directly in the volume of the waveguides 270, 280, 290, 300, 310. In some embodiments, the outcoupling optical elements 570, 580, 590, 600, 610 may be formed in a layer of material 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 a single piece of material, and the outcoupling optical elements 570, 580, 590, 600, 610 may be formed on a surface of and / or within the interior of the piece of material.

[0121] Each waveguide 270, 280, 290, 300, 310 can output light to form an image corresponding to a specific depth plane. For example, the waveguide 270 closest to the eye can transmit a collimated light beam to the eye 210. The collimated light beam can represent the focal plane at optical infinity. The next upstream waveguide 280 can output a collimated light beam that is transmitted through a first lens 350 (e.g., a negative lens) before reaching the eye 210. The first lens 350 can add a slightly convex wavefront curvature to the collimated light beam so that the eye / brain interprets the light from this waveguide 280 as originating from the first focal plane, which is closer to the eye 210 from optical infinity. Similarly, the third waveguide 290 transmits its output light through the first lens 350 and the second lens 340 before reaching the eye 210. The combined optical power of the first lens 350 and the second lens 340 can add another increment of wavefront curvature so that the eye / brain interprets light from the third waveguide 290 as originating from a second focal plane that is further inward from optical infinity than the light from the second waveguide 280.

[0122] 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 the lenses between it and the eye to achieve a total optical power that represents the focal plane closest to the person. To compensate for the stack of lenses 320, 330, 340, 350 when viewing / interpreting light from the world 510 on the other side of the stacked waveguide assembly 260, a compensating lens layer 620 can be provided at the top of the stack to compensate for the total optical power of the underlying lens stack 320, 330, 340, 350. This configuration provides as many perceived focal planes as there are available waveguide / lens pairs. Both the outcoupling optics of the waveguide and the focusing aspects of the lens can be static (i.e., not dynamic or electro-active). In some alternative embodiments, one or both of the outcoupling optics of the waveguide and the focusing aspects of the lens can be dynamic using electro-active features.

[0123] 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 a set of images to the same depth plane, or multiple subsets of the waveguides 270, 280, 290, 300, 310 may output a set of images to the same multiple depth planes, one set per depth plane. This may provide advantages for forming tiled images to provide an extended field of view at those depth planes.

[0124] The outcoupling optical elements 570, 580, 590, 600, 610 can be configured to both redirect light out of their respective waveguides and output that light with an appropriate amount of divergence or collimation for a particular depth plane associated with the waveguide. As a result, waveguides with different associated depth planes can have differently configured 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 features or surface features that can be configured to output light at a specific 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, features 320, 330, 340, 350 may not be lenses; instead, they may simply be spacers (eg, cladding and / or structures used to form air gaps).

[0125] In some embodiments, the outcoupling optical elements 570, 580, 590, 600, 610 are diffractive features having a sufficiently low diffraction efficiency that, upon each interaction, only a portion of the power of the light beam is redirected toward the eye 210, while the remainder continues to move through the waveguide via TIR. Thus, the exit pupil of the light module 530 is replicated across the entire waveguide to produce multiple output beams carrying image information from the light source 530, effectively expanding the number of locations where the eye 210 can interpret the replicated light source exit pupil. These diffractive features can also have a diffraction efficiency that is variable across their geometry to improve the uniformity of the light output by the waveguide.

[0126] In some embodiments, one or more diffractive features may be switchable between an "on" state in which they actively diffract and an "off" state in which they do not significantly diffract. For example, a switchable diffractive element may include a polymer dispersed liquid crystal layer in which droplets form a diffraction pattern in a host medium, and the refractive index of the droplets may be switched to substantially match that of the host material (in which case the pattern does not significantly diffract incident light) or to a refractive index that is mismatched with that of the host medium (in which case the pattern actively diffracts incident light).

[0127] In some embodiments, a camera assembly 630 (e.g., a digital camera, including visible light and infrared cameras) may be provided to capture images of the eye 210, portions of the eye 210, or at least a portion of the tissue surrounding the eye 210 to, for example, detect user input, extract biometric information from the eye, estimate and track the gaze direction of the eye, to monitor the physiological state of the user, etc. In some embodiments, the camera assembly 630 may include an image capture device and a light source to project light (e.g., infrared or near-infrared light) into 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 infrared or near-infrared light. In some embodiments, the camera assembly 630 may be attached to the frame 80 ( Figure 2 ) and can be in electrical communication with processing module 140 or 150, which can process image information from camera assembly 630 to make various determinations regarding, for example, the physiological state of the user, the wearer's gaze direction, iris recognition, etc. In some embodiments, one camera assembly 630 can be used for each eye to monitor each eye separately.

[0128] Figure 7A An example of an outgoing beam outputted by a waveguide is shown. One waveguide is shown (in perspective view), but the waveguide assembly 260 ( Figure 6 ) can also function similarly. Light 640 is injected into the waveguide 270 at the input surface 460 of the waveguide 270 and propagates within the waveguide 270 by TIR. Through interaction with the diffraction features, the light emerges from the waveguide as an exit beam 650. The exit beam 650 replicates the exit pupil from the projector device that projects the image into the waveguide. Any of the exit beams 650 includes a sub-portion of the total energy of the input light 640. In a reasonably efficient system, the sum of the energies of all the exit beams 650 is equal to the energy of the input light 640. In Figure 7A , the exit beams 650 are shown as being substantially parallel, but, as discussed herein, may be imparted with a certain amount of focality depending on the depth plane associated with the waveguide 270. A parallel exit beam may be indicative of a waveguide having an outcoupling optical element that couples light out to form an image at a depth plane that appears to be disposed at a large distance (e.g., optical infinity) from the eye 210. Other waveguides or other sets of outcoupling optical elements may output a more divergent exit beam pattern, such as Figure 7B As shown, this will require the eye 210 to adapt to a closer distance so that the more divergent exit beam pattern is focused on the retina and will be interpreted by the brain as light coming from a distance closer to the eye 210 than optical infinity.

[0129] In some embodiments, a full color image can be formed at each depth plane by superimposing images in each of the component colors (eg, three or more component colors such as red, green, and blue). Figure 8 An example of a stacked waveguide assembly is shown, in which each depth plane includes an image formed using multiple different component colors. The illustrated embodiment shows depth planes 240a to 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 of a first color, G; a second image of a second color, R; and a third image of a third color, B. The different depth planes are indicated in the figure by different diopters following the letters G, R, and B. The number following each of these letters indicates the diopters (1 / m), or the inverse of the distance of the depth plane from the user, and each box in the figure represents a separate component color image. In some embodiments, the precise placement of the depth planes for the different component colors can vary to account for differences in the eye's focus on light of different wavelengths. For example, different component color images for a given depth plane can be placed on depth planes corresponding to different distances from the user. Such an arrangement can increase visual acuity and user comfort, or can reduce chromatic aberration.

[0130] In some embodiments, light for each component color can be output by a single dedicated waveguide, and thus, each depth plane can have multiple waveguides associated with it. In such an embodiment, each box in the figure can be understood to represent a separate waveguide, and three waveguides can be provided for each depth plane so that three component color images are displayed for each depth plane. Although for ease of illustration, the waveguides associated with each depth plane are shown as being adjacent to each other in this figure, it should be understood that in a physical device, the waveguides can all be arranged in a stacked form with one waveguide per layer. In some other embodiments, multiple component colors can be output by the same waveguide, so that, for example, only a single waveguide can be provided for each depth plane.

[0131] Continue to refer Figure 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 red, green, or blue, or these other colors 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 light from the surrounding environment or selectively allow light from the surrounding environment to pass to the user's eyes.

[0132] References throughout this disclosure to light of a given color will be understood to include light of one or more wavelengths within a range of wavelengths perceived by a user as light of the given color. For example, red light may include light of one or more wavelengths within a range of approximately 620-780 nm, green light may include light of one or more wavelengths within a range of approximately 492-577 nm, and blue light may include light of one or more wavelengths within a range of approximately 435-493 nm.

[0133] In some embodiments, the light source 530 ( Figure 6 ) can be configured to emit light of one or more wavelengths outside the user's visual perception range (e.g., infrared or ultraviolet wavelengths). Infrared light can include light with wavelengths in the range of 700 nm to 10 μm. In some embodiments, infrared light can include near-infrared light with wavelengths in the range of 700 nm to 1.5 μm. Furthermore, the incoupling, outcoupling, and other light redirecting structures of the waveguide of the display 250 can be configured to direct this light out of the display and toward the user's eye 210, for example, for imaging or user stimulation applications.

[0134] Now refer to Figure 9A In some embodiments, it may be desirable to redirect light impinging on a waveguide in order to couple the light into the waveguide. Incoupling optics may be used to redirect the light and couple the light into its corresponding waveguide. Figure 9A A cross-sectional side view of an example of a stacked waveguide set 660 is shown, wherein each waveguide includes an incoupling optical element. Each waveguide can be configured to output light of one or more different wavelengths, or one or more different wavelength ranges. It should be understood that stack 660 can correspond to stack 260 ( Figure 6 ), the waveguides shown in stack 660 may correspond to portions of multiple waveguides 270, 280, 290, 300, 310, in addition to light from one or more image injection devices 360, 370, 380, 390, 400 being injected into the waveguide from a location or orientation where the light needs to be redirected for coupling in.

[0135] The stacked waveguide set 660 shown includes waveguides 670, 680, and 690. Each waveguide includes an associated coupling-in optical element (which may also be referred to as a light input region on the waveguide), wherein, for example, coupling-in optical element 700 is disposed on a major surface (e.g., an upper major surface) of waveguide 670, coupling-in optical element 710 is disposed on a major surface (e.g., an upper major surface) of waveguide 680, and coupling-in optical element 720 is disposed on a major surface (e.g., an upper major surface) of waveguide 690. In some embodiments, one or more of the coupling-in optical elements 700, 710, 720 may be disposed on the bottom major surface of the respective waveguide 670, 680, 690 (particularly where one or more of the coupling-in optical elements is a reflective optical element). As shown, the coupling-in optical elements 700, 710, 720 may be disposed on the top major surface of their respective waveguides 670, 680, 690 (or the top of the next downstream waveguide), particularly where those coupling-in optical elements are transmissive optical elements. In some embodiments, the incoupling optical elements 700, 710, 720 can be disposed in the body of the respective waveguides 670, 680, 690. In some embodiments, as discussed herein, the incoupling optical elements 700, 710, 720 are wavelength selective such that they selectively redirect light of one or more wavelengths while transmitting light of other wavelengths. Although shown on a side or corner of their respective waveguides 670, 680, 690, it should be understood that in some embodiments, the incoupling optical elements 700, 710, 720 can be disposed in other areas of their respective waveguides 670, 680, 690.

[0136] As shown, the coupling-in optical elements 700, 710, and 720 can be laterally offset from each other. In some embodiments, each coupling-in optical element can be offset so that the coupling-in optical element receives light without transmitting the light through another coupling-in optical element. For example, Figure 6 As shown, each coupling-in optical element 700, 710, 720 can be configured to receive light from a different image injection device 360, 370, 380, 390 and 400, and can be separated from the other coupling-in optical elements 700, 710, 720 (e.g., laterally spaced apart) so that the coupling-in optical element does not substantially receive light from the other coupling-in optical elements in the coupling-in optical elements 700, 710, 720.

[0137] Each waveguide further includes an associated light distribution element, wherein, 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 surface of the associated waveguides 670, 680, 690, respectively. In some other embodiments, light distribution elements 730, 740, 750 may be disposed on both the top major surface and the bottom major surface of the associated waveguides 670, 680, 690, respectively; or light distribution elements 730, 740, 750 may be disposed on different major surfaces of the top major surface and the bottom major surface in different associated waveguides 670, 680, 690, respectively.

[0138] Waveguides 670, 680, 690 may be separated and separated by layers of, for example, gas, liquid, or solid material. For example, as shown, layer 760a may separate waveguide 670 from waveguide 680, and layer 760b may separate waveguide 680 from waveguide 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 an immediately adjacent waveguide among waveguides 670, 680, 690). Preferably, the refractive index of the material forming layers 760a and 760b is at least 0.05, or at least 0.10, less than the refractive index of the material forming waveguides 670, 680, 690. Advantageously, the lower-refractive-index layers 760a and 760b may serve as cladding that promotes TIR of light passing through waveguides 670, 680, 690 (e.g., TIR between the top and bottom major surfaces of each waveguide). In some embodiments, layers 760a, 760b are formed of air. Although not shown, it is understood that the top and bottom portions of the illustrated waveguide set 660 may include immediately adjacent cladding layers.

[0139] Preferably, for ease of manufacturing and other considerations, the materials forming waveguides 670, 680, 690 are similar or identical, and the materials forming layers 760a, 760b are similar or identical. In other embodiments, the materials forming waveguides 670, 680, 690 can be different between one or more waveguides, or the materials forming layers 760a, 760b can be different, while still maintaining the various refractive index relationships described above.

[0140] Continue to refer Figure 9A , light rays 770, 780, 790 are incident on the waveguide group 660. Light rays 770, 780, 790 can be injected into the waveguide group 660 by one or more image injection devices 360, 370, 380, 390, 400 ( Figure 6 ) is injected into waveguides 670, 680, and 690.

[0141] In some embodiments, the light rays 770, 780, 790 have different characteristics (e.g., different wavelengths or different wavelength ranges), which can correspond to different colors. The incoupling optical elements 700, 710, 720 each redirect the incident light so that the light propagates through a corresponding one of the waveguides 670, 680, 690 by TIR.

[0142] For example, the coupling-in optical element 700 can be configured to redirect light 770 having a first wavelength or a first range of wavelengths. Similarly, transmitted light 780 impinges on and is redirected by the coupling-in optical element 710, which is configured to redirect light of a second wavelength or a second range of wavelengths. Similarly, light 790 is redirected by the coupling-in optical element 720, which is configured to selectively redirect light of a third wavelength or a third range of wavelengths.

[0143] Continue to refer Figure 9A , light rays 770, 780, 790 are redirected so that they propagate through the corresponding waveguide 670, 680, 690; that is, the incoupling optical element 700, 710, 720 of each waveguide redirects light into the corresponding waveguide 670, 680, 690 to couple the light into the corresponding waveguide. Light rays 770, 780, 790 are redirected at an angle that causes the light to propagate through the corresponding waveguide 670, 680, 690 by TIR. Light rays 770, 780, 790 propagate through the corresponding waveguide 670, 680, 690 by TIR until they interact with the corresponding light distributing element 730, 740, 750 of the waveguide.

[0144] Now refer to Figure 9B , showing Figure 9A 6. As described above, light rays 770, 780, and 790 are coupled into the in-coupling optical elements 700, 710, and 720, respectively, and then propagate through TIR within the 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, respectively, so that they propagate toward out-coupling optical elements 800, 810, and 820, respectively.

[0145] In some embodiments, the light distributing elements 730, 740, 750 are orthogonal pupil expanders (OPEs). In some embodiments, as light rays 770, 780, 790 propagate to the outcoupling optics, the OPEs redirect the light to the outcoupling optics 800, 810, 820 by sampling the light rays 770, 780, 790 at multiple locations across the light distributing elements 730, 740, 750, and also expand the pupil associated with the light. In some embodiments (e.g., where the exit pupil already has the desired size), the light distributing elements 730, 740, 750 can be omitted, and the incoupling optics 700, 710, 720 can be configured to redirect the light directly to the outcoupling optics 800, 810, 820. For example, referring to Figure 9A , the light distribution elements 730, 740, and 750 can be replaced by outcoupling optical elements 800, 810, and 820, respectively. In some embodiments, the outcoupling optical elements 800, 810, and 820 are exit pupils (EPs) or exit pupil expanders (EPEs) that redirect light out of the waveguide and toward the user's eye 210 ( FIG. 7 ). The OPE can be configured to increase the size of the eye box in at least one axis, and the EPE can be configured to increase the eye box in an axis that intersects (e.g., is orthogonal to) the axis of the OPE.

[0146] Therefore, reference Figure 9A and 9BIn some embodiments, waveguide set 660 includes waveguides 670, 680, and 690; incoupling optics 700, 710, and 720; light distribution elements (e.g., optical power elements) 730, 740, and 750; and outcoupling optics (e.g., optical power elements) 800, 810, and 820, one for each component color. The waveguides 670, 680, and 690 can be stacked with an air gap / cladding layer between each waveguide. The incoupling optics 700, 710, and 720 guide incident light (via different incoupling optics receiving light of different wavelengths) into the corresponding waveguide. The light then propagates at an angle that supports TIR within the corresponding waveguide 670, 680, and 690. Because TIR only occurs within a specific angular range, the angular range over which light rays 770, 780, and 790 propagate is limited. In such examples, the angular range that supports TIR can be considered the angular limit of the field of view that can be displayed by the waveguides 670, 680, and 690. In the example shown, light ray 770 (e.g., blue light) is coupled in by the first in-coupling optic 700 in the manner previously described and then continues to reflect back and forth from the waveguide's surfaces as it travels along the waveguide, where it is gradually sampled by a light distribution element (e.g., OPE) 730 to produce additional replicated light rays, which are directed to an out-coupling optic (e.g., EP) 800. Light rays 780 and 790 (e.g., green and red light, respectively) propagate through waveguide 670, where light ray 780 impinges on and is in-coupled by the in-coupling optic 710. Light ray 780 then propagates along waveguide 680 via TIR, proceeding to its light distribution element (e.g., OPE) 740, and then to an out-coupling optic (e.g., EPE) 810. Finally, light ray 790 (e.g., red light) propagates through waveguides 670, 680 and impinges on the light in-coupling optic 720 of waveguide 690. The in-coupling optical element 720 couples in the light 790, causing the light to propagate through TIR to the light distribution element (e.g., OPE) 750, and then propagate through TIR to the out-coupling optical element (e.g., EPE) 820. The out-coupling optical element 820 then ultimately couples the light 790 out to the user, who also receives out-coupled light from the other waveguides 670 and 680.

[0147] Figure 9C Shown Figure 9A and Figure 9BFIG2 is a top plan view of an example of a plurality of stacked waveguides. As shown, the waveguides 670, 680, 690 and the associated light distribution elements 730, 740, 750 and associated outcoupling optical elements 800, 810, 820 for each waveguide can be vertically aligned. However, as discussed herein, the incoupling optical elements 700, 710, 720 are not vertically aligned; instead, the incoupling optical elements can be non-overlapping (e.g., laterally spaced apart when viewed in a top view). This non-overlapping spatial arrangement can facilitate one-to-one injection of light from different sources into different waveguides, thereby allowing a particular light source to be uniquely optically coupled to a particular waveguide. In some embodiments, arrangements including non-overlapping, spatially separated incoupling optical elements can be referred to as shifted pupil systems, and the incoupling optical elements within these arrangements can correspond to sub-pupils.

[0148] Figure 10 is a perspective view of an example AR eyepiece waveguide stack 1000. The eyepiece waveguide stack 1000 may include a world-side cover window 1002 and an eye-side cover window 1006 to protect one or more eyepiece waveguides 1004 located between the cover windows. In other embodiments, one or both of the cover windows 1002, 1006 may be omitted. As already discussed, the eyepiece waveguides 1004 may be arranged in a stacked 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 secured to an edge seal such as a Figure 11 The eyepiece waveguides 1004 are coupled together with edge seals 1108 as shown so that adjacent eyepiece waveguides 1004 do not directly contact each other.

[0149] Each eyepiece waveguide 1004 can be made of an at least partially transparent substrate material, such as glass, plastic, polycarbonate, sapphire, etc. The selected material can have a refractive index greater than 1.4, for example, greater than 1.6 or greater than 1.8, to facilitate light guidance. The thickness of each eyepiece waveguide substrate can be, for example, 325 microns or less, although other thicknesses can also be used. Each eyepiece waveguide can include one or more incoupling regions, light distribution regions, image expansion regions, and outcoupling regions, which can be composed of diffractive features formed on or in each waveguide substrate 902.

[0150] although Figure 10 , but 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 the head-mounted display system 60, such as Figure 2 Typically, the eyepiece waveguide stack 1000 is supported so that the outcoupling region is directly in front of the user's eye. It should be understood that Figure 10Only the portion of the eyepiece waveguide stack 1000 corresponding to one of the user's eyes is shown. The complete eyepiece may comprise a mirror image of the same structure, with two parts possibly separated by a nose piece.

[0151] 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 a selected depth plane. For example, because the eyepiece waveguide stack 1000 includes six eyepiece waveguides 1004, it can project color image data corresponding to two different depth planes (e.g., consisting of red, green, and blue components): one eyepiece waveguide 1004 per color component per depth plane. Other embodiments may include eyepiece waveguides 1004 for more or fewer color components and / or more or fewer depth planes.

[0152] Figure 11 is a cross-sectional view of a portion of an example eyepiece waveguide stack 1100 having 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 the eyepiece waveguides from each other by an air gap or another material disposed therebetween. Although not shown, the edge seal structure 1108 may extend around the entire perimeter of the stacked waveguide configuration. Figure 11 The spacing between each eyepiece waveguide is 0.027 mm, but other distances are possible.

[0153] 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. (Additionally, the divergence of the light beams output by the eyepiece waveguides 1104 can make the image data appear to originate from a depth plane located at a particular distance.) 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 the six eyepiece waveguides 1104 is shown as being 0.325 mm thick, but other thicknesses are possible.

[0154] Figure 11Also shown are a world-side cover window 1102 and an eye-side cover window 1106. These cover windows can be, for example, 0.330 mm thick. When the thickness of the six eyepiece waveguides 1104, the seven air gaps, the two cover windows 1102, 1106, and the edge seal 1108 are taken into account, the total thickness of the eyepiece waveguide stack 1100 shown is 2.8 mm.

[0155] K-space representation of AR eyepiece waveguide

[0156] Figure 12A and 12B A top view of the eyepiece waveguide 1200 is shown in operation as it projects an image toward a user's eye 210. An image may first be projected from an image plane 1207 toward an 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 a portion of an image pixel) has a corresponding input light beam (e.g., 1202a, 1204a, 1206a) that propagates in a particular direction (e.g., at a particular angle relative to the optical axis of the projection lens 1210) at the entrance pupil 1208. Although shown as rays, the input light beams 1202a, 1204a, 1206a may be collimated beams, e.g., having a diameter of several millimeters or less, when entering the eyepiece waveguide 1200.

[0157] exist Figure 12A and 12B , the middle image point corresponds to input beam 1204a, shown in solid lines. The image point on the right corresponds to input beam 1202a, shown in dashed lines. The image point on the left corresponds to input beam 1206a, shown in dashed-dotted lines. For clarity, only three input beams 1202a, 1204a, and 1206a are shown at the entrance pupil 1208, but a typical input image will include many input beams propagating over a range of angles in the x- and y-directions, corresponding to different image points within the two-dimensional image plane.

[0158] 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 the corresponding image points at the image plane 1207. The eyepiece waveguide 1200 can be designed to couple in the input beams (e.g., 1202a, 1204a, 1206a), replicate them in a distributed manner through space, and guide them to form an exit pupil 1210, which is larger than the entrance pupil 1208 and consists of replicated beams, all of which substantially maintain the correspondence between image points and beam angles. The eyepiece waveguide 1200 can transform a given input beam (e.g., 1202a) propagating at a particular angle into a plurality of replicated beams (e.g., 1202b) that are output across the exit pupil 1210 at angles that are substantially uniquely associated with the particular input beam and its corresponding image point. For example, the replicated output beam corresponding to each input beam can exit the eyepiece waveguide 1200 at substantially the same angle as its corresponding input beam.

[0159] like Figure 12A and 12B As shown, an input beam 1204a corresponding to an intermediate image point at an image plane 1207 is transformed into a set of replicated output beams 1204b, shown in solid lines, aligned with an optical axis perpendicular to the exit pupil 1210 of the eyepiece waveguide 1200. An input beam 1202a corresponding to a right image point at the image plane 1207 is transformed into a set of replicated output beams 1202b, shown in dashed lines, that exit the eyepiece waveguide 1200 at propagation angles such that they appear to originate from a location in the right portion of the user's field of view. Similarly, an input beam 1206a corresponding to a left image point at the image plane 1207 is transformed into a set of replicated output beams 1206b, shown in dashed-dotted lines, that exit the eyepiece waveguide 1200 at propagation angles such that they appear to originate from a location in the left portion of the user's field of view. The greater the range of input beam angles and / or output beam angles, the larger the field of view (FOV) of the eyepiece waveguide 1200.

[0160] For each image, there are multiple sets of replicated output beams (e.g., 1202b, 1204b, 1206b)—one set for each image point—that are output at different angles across the exit pupil 1210. Each output beam (e.g., 1202b, 1204b, 1206b) can be collimated separately. The set of output beams corresponding to a given image point can be formed by aligning the beams along parallel paths (e.g., Figure 12A ) or divergent paths (as shown in Figure 12B In either case, the specific propagation angles of the set of replicated output beams depend on the positions of the corresponding image points at the image plane 1207. Figure 12A The case where each set of output beams (e.g., 1202b, 1204b, 1206b) consists of beams propagating along parallel paths is shown. This results in the image being projected to appear to originate from optical infinity. Figure 12A 1204b, 1206b towards optical infinity on the world side of the eyepiece waveguide 1200 (opposite the side where the user's eye 210 is located). Figure 12B The case where each set of output beams (e.g., 1202b, 1204b, 1206b) consists of beams propagating along diverging paths is shown. This results in the image being projected to appear to originate from a virtual depth plane that is closer than the optical infinity distance. Figure 12B 1200 by a halo extending from the peripheral output beams 1202b, 1204b, 1206b toward a point on the world side of the eyepiece waveguide 1200.

[0161] Again, each set of replicated output beams (e.g., 1202b, 1204b, 1206b) has a propagation angle corresponding to a particular image point at image plane 1207. Figure 12A ), all beams propagate at the same angle. However, in the case of a set of replicated output beams propagating along diverging paths, the individual output beams can propagate at different angles, but these angles are related to each other because they produce a total diverging wavefront that appears to originate from a common point along the axis of the set of beams (see Figure 12B ). It is this axis that defines the propagation angle of the diverging output beam set and corresponds to a specific image point at the image plane 1207.

[0162] The various light beams that enter the eyepiece waveguide 1200, propagate within the eyepiece waveguide, and then exit the eyepiece waveguide can all be described using one or more wave vectors or k-vectors, which describe the propagation direction of the light beam. K-space is an analytical framework that associates k-vectors with geometric points. In k-space, each point in space corresponds to a unique k-vector, which in turn can represent a light beam or ray with a specific propagation direction. This allows input and output light beams with their corresponding propagation angles to be understood as groups of points in k-space (e.g., rectangles). Diffraction features that change the propagation direction of the light beam as it propagates through the eyepiece can be understood as simply shifting the position of a set of k-space points that make up the image in k-space. This new shifted k-space position corresponds to a new set of k-vectors, which in turn represents the new propagation angle of the light beam or ray after interacting with the diffraction feature.

[0163] The operation of an eyepiece waveguide can be understood in such a way that the operation causes a set of points (e.g., points in a k-space rectangle corresponding to the projected image) to move in k-space. This is in contrast to more complex ray tracing diagrams, which are otherwise used to illustrate light beams and their propagation angles. Therefore, k-space is an effective tool for describing the design and operation of an eyepiece waveguide. The following discussion describes a k-space representation of the features and functionality of various AR eyepiece waveguides.

[0164] Figure 13A A k-vector 1302 is shown that can be used to represent the direction of propagation of a light ray or light beam. The k-vector 1302 specifically shown represents a plane wave having a plane wavefront 1304. The k-vector 1302 points in the direction of propagation of the light ray or light beam it represents. The size or length of the k-vector 1302 is defined by the wavenumber k. The dispersion equation ω = ck involves the angular frequency ω of the light, the speed of light c, and the wavenumber k. (In a vacuum, the speed of light is equal to the speed of light constant c. However, in a medium, the speed of light is inversely proportional to the refractive index of the medium. Therefore, in a medium, the equation becomes k = nω / c.) Note that by definition, k = 2π / λ and ω = 2πf, where f is the frequency of the light (e.g., in Hertz). It is obvious from this equation that a light beam with a higher angular frequency ω has a larger wavenumber and therefore has a k-vector of larger size (assuming the same propagation medium). For example, assuming the same propagation medium, a blue light beam has a k-vector of larger size than a red light beam.

[0165] Figure 13B A light ray 1301 corresponding to a k-vector 1302 is shown within a planar waveguide 1300. Waveguide 1300 can represent any waveguide described herein and can be part of an eyepiece for an AR display system. Waveguide 1300 can guide light rays having certain k-vectors via total internal reflection (TIR). For example, Figure 13B As shown, light ray 1301, indicated by k-vector 1302, is directed at an angle to the upper surface of waveguide 1300. If the angle is not too steep (as governed by Snell's law), light ray 1301 will reflect at the upper surface of waveguide 1300 at an angle equal to the angle of incidence and then travel down to the lower surface of waveguide 1300, where it will again reflect back to the upper surface. Light ray 1301 continues to propagate in a guided manner within waveguide 1300, reflecting back and forth between its upper and lower surfaces.

[0166] Figure 13CThe allowed k-vectors for light of a given angular frequency ω propagating in an unbounded homogeneous medium with a refractive index n are shown. The length or size k of the k-vector 1302 shown is equal to the medium's refractive index n multiplied by the light's angular frequency ω divided by the speed of light constant c. For a light ray or beam of light of a given angular frequency ω propagating in a homogeneous medium with a refractive index n, all allowed k-vectors have the same size. For unguided propagation, all propagation directions are allowed. Therefore, the manifold in k-space that defines all allowed k-vectors is a hollow sphere 1306, where the size of the sphere depends on the angular frequency of the light and the refractive index of the medium.

[0167] Figure 13D The allowed k-vectors for light of a given angular frequency ω propagating in a homogeneous planar waveguide medium with a refractive index n are shown. Given that in an unbounded medium, all allowed k-vectors lie on the hollow sphere 1306, to determine the allowed k-vectors in a planar waveguide, we can project the sphere 1306 of allowed k-vectors into a plane (e.g., the xy plane). This can produce a solid disk 1308 in the projected k-space, which represents the k-vectors that can propagate within the planar waveguide. As Figure 13D As shown, the k-vectors that can propagate in a planar waveguide (e.g., waveguide 1300) in the xy plane refer to all k-vectors whose k-vector components in the xy plane are less than or equal to the refractive index n of the medium multiplied by the angular frequency ω of light divided by the speed of light constant c.

[0168] Each point within the solid disk 1308 corresponds to a k-vector for a wave that can propagate in the waveguide (although not all of these k-vectors result in guided propagation within the waveguide, as discussed below with respect to Figure 13E At each point within the solid disk 1308, there are two allowed waves: one wave with a z component that propagates into the page, and one wave with a z component that propagates out of the page. Therefore, the equation Recover the out-of-plane component k of the k vector z , where the chosen sign determines whether the wave propagates into or out of the page. Since all light waves of a given angular frequency ω propagating in a homogeneous medium of refractive index n have the same magnitude k-vector, a light wave having an xy component of a k-vector closer in magnitude to the radius of the solid disk 1308 will have a smaller propagating z-component (resulting in a less steep propagation angle required for TIR, as discussed with respect to Figure 13B(discussed above), whereas a light wave with an xy component of its k-vector closer to the center of solid disk 1308 has a larger propagation z-component (resulting in a steeper propagation angle where TIR is not possible). Hereinafter, all references to k-space refer to projected k-space (unless the context indicates otherwise), where the two-dimensional k-plane corresponds to the waveguide plane; unless the propagation direction between waveguide surfaces is explicitly mentioned, the discussion and figures generally consider only the direction parallel to the waveguide surfaces. Furthermore, when plotting k-space, it is often most convenient to normalize the free-space disk radius to unity, so that the plots are effectively normalized to ω / c.

[0169] Figure 13E A ring 1310 in k-space corresponding to the k-vector of a light wave that can be guided in a waveguide having a refractive index n2 (e.g., n2=1.5) is shown. The waveguide is physically surrounded by a medium (e.g., air) having a smaller refractive index n1 (e.g., n1≈1). As just discussed with respect to Figure 13D As discussed, the k-vectors corresponding to the allowed waves in the planar waveguide medium in the xy plane are all k-vectors whose respective xy components lie within the solid disk 1308 in k-space. The radius of the solid disk 1308 is proportional to the refractive index of the waveguide medium. Therefore, returning to reference Figure 13E , the k-vectors corresponding to light waves that can propagate in a planar waveguide medium with a refractive index of n2 = 1.5 are k-vectors whose respective xy components are located within the large disk 1308a. Meanwhile, the k-vectors corresponding to light waves that can propagate in a surrounding medium with a refractive index of n1 = 1 are k-vectors whose respective xy components are located within the small disk 1308b. All k-vectors whose respective xy components are located within the ring 1310 correspond to light waves that can propagate in the waveguide medium without propagating in the surrounding medium (e.g., air). These light waves are light waves guided in the waveguide medium via total internal reflection, as described with respect to Figure 13B As described. Therefore, light rays or beams can only be guided and propagated within the waveguide of the AR eyepiece if they have a k-vector that lies within the k-space ring 1310. Note that propagating light waves with a k-vector that lies outside the large disk 1308a are prohibited; there are no propagating light waves whose k-vector lies within this region (waves in this region have amplitudes that decay gradually (rather than being constant) along their propagation direction).

[0170] The various AR eyepiece waveguides described herein can couple light by using diffractive features (e.g., diffractive structures) to guide the k-vector of a light beam propagating in free space (e.g., n1≈1) (e.g., from a projector) into a k-space ring 1310 of the eyepiece waveguide. Any light wave whose k-vector lies within the ring 1310 can propagate in a guided manner in the eyepiece waveguide. The width of the ring 1310 determines the range of k-vectors that can be guided within the eyepiece waveguide, and thus the range of propagation angles. Therefore, it is generally believed that the width of the k-space ring 1310 determines the maximum field of view (FOV) that the eyepiece waveguide can project. Since the width of the ring 1310 depends on the radius of the large disk 1308a (which itself depends in part on the refractive index n2 of the eyepiece waveguide medium), one technique for increasing the eyepiece FOV is to use an eyepiece waveguide medium with a larger refractive index (compared to the refractive index of the medium surrounding the eyepiece waveguide). However, there are practical limitations on the refractive index of waveguide media that can be used in AR eyepieces, such as material cost. This, in turn, is believed to place practical limits on the FOV of AR eyepieces. However, as described herein, there are techniques that can be used to overcome these limitations in order to allow for larger FOVs.

[0171] although Figure 13E The radius of the medium-large disk 1308a also depends on the angular frequency ω of the light, and thus the width of the ring 1310 depends on the color of the light, but this does not mean that the FOV supported by the eyepiece waveguide is larger for light with higher angular frequencies, because any given angular range corresponding to the FOV also scales proportionally with the angular frequency.

[0172] Figure 13F Shows something like Figure 13E Figure 1 shows a k-space diagram. The k-space diagram shows a small disk 1308b corresponding to allowed k-vectors in a first medium having a refractive index n1, a large disk 1308a corresponding to allowed k-vectors in a second medium having a refractive index n2 (n2>n1), and a ring 1310 located between the outer boundaries of the small disk 1308a and the large disk 1308b. Although all k-vectors within the width 1342 of the ring 1310 correspond to guided propagation angles, it is possible that fewer k-vectors than are within the width 1342 of the ring 1310 may be satisfactorily used to display an image.

[0173] Figure 13FAlso shown is waveguide 1350, which has two guided beams shown in comparison to each other. The first beam has a first k-vector 1344a near the outer edge of ring 1310. First k-vector 1344a corresponds to a first TIR propagation path 1344b shown in a cross-sectional view of waveguide 1350 having a refractive index of n2 surrounded by air having a refractive index of n1. Also shown is a second beam having a second k-vector 1346a closer to the center of k-space ring 1310. Second k-vector 1346a corresponds to a second TIR propagation path 1346b in waveguide 1350. Waveguide 1350 may include a diffraction grating 1352 located on or within waveguide 1350. When the beam encounters a surface of waveguide 1350 having diffraction grating 1352, an interaction occurs that can send a sample of the beam's energy out of the waveguide while the beam continues to undergo TIR within the waveguide. The angle at which a light beam propagates within the waveguide via TIR determines the density of reflection events, or the number of times per unit length it bounces off the surface of the waveguide 1350 with the diffraction grating 1352. Returning to the example of the beam comparison, a first light beam in a first TIR propagation path 1344b reflects four times from the surface of the waveguide with the diffraction grating 1352, thereby producing four exit pupils 1354 (shown in solid lines) over the length of the diffraction grating 1352, while a second light beam on a second TIR propagation path 1346b reflects ten times from the surface of the waveguide with the diffraction grating 1352 over the same or similar distance, thereby producing ten exit pupils 1356 (shown in dashed lines) over the length of the diffraction grating 1352.

[0174] In practice, it may be desirable to constrain the output beam or exit pupil distance to be equal to or within a preselected range to ensure that the user will see the projected content from any location within the predetermined eye zone. Using this information, the width 1342 of the ring 1310 can be limited to a subset 1344 of k-vectors, to which the above constraints apply, and angles that are too grazing can be disqualified from being included in the design calculations. Depending on the desired performance, diffraction grating design, and other optimization factors, more or fewer angles than the subset 1344 may be acceptable. Similarly, in some embodiments, k-vectors corresponding to propagation angles that are too steep relative to the waveguide surface and provide too much interaction with the diffraction grating 1352 can also be disqualified. In such embodiments, the width 1342 of the ring 1310 can be reduced by effectively moving the boundary of the available angles radially outward from the boundary between the large disk 1308a and the small disk 1308b. The design of any eyepiece waveguide disclosed herein can be adjusted by constraining the width of the k-space ring 1310 in this manner.

[0175] As described above, k-vectors within the ring 1310 that correspond to suboptimal TIR propagation paths may not be used in the eyepiece design calculations. Instead, various techniques described herein may be used to compensate for k-vectors corresponding to TIR propagation paths that have angles that are too grazing, and therefore have a low density of reflection events on the waveguide surface with the diffraction grating. One technique is to use an incoupling grating to direct portions of the field of view (FOV) of the incoming image to two different regions of the k-space ring 1310. In particular, it may be advantageous to direct the incoming image to a first side of the k-space ring 1310, represented by a first set of k-vectors, and to a second side of the k-space ring 1310, represented by a second set of k-vectors, wherein the first and second sides of the k-space ring 1310 are substantially opposite to each other. For example, the first set of k-vectors may correspond to a FOV rectangle of k-vectors on the left side of the ring 1310, and the second set of k-vectors may correspond to a FOV rectangle of k-vectors on the right side of the ring 1310. The left edge of the left FOV rectangle is located near the outer edge of large disk 1308a, corresponding to a near-grazing k-vector angle. Light at this edge will produce a sparse exit pupil. However, the same left edge of the right FOV rectangle, located to the right of ring 1310, is closer to the center of large disk 1308a. Light at the same left edge of the right FOV rectangle will have a high density of exit pupils. Therefore, when the left and right FOV rectangles are reunited and exit the waveguide toward the user's eye to produce an image, a sufficient number of exit pupils are generated in all areas of the field of view.

[0176] Diffractive features such as diffraction gratings can be used to couple light into the eyepiece waveguide, couple it out of the eyepiece waveguide, and / or redirect light within the eyepiece waveguide. In k-space, the effect of a diffraction grating on a ray or beam represented by a particular k-vector is determined by the vectorial addition of the k-vector components in the plane of the diffraction grating and the grating vector. The magnitude and direction of the grating vector depend on the specific characteristics of the diffraction grating. Figure 13G 、 13H and 13I show the operation of the diffraction grating on the k-vector in k-space.

[0177] Figure 13G A top view of the diffraction grating and some associated k-space diffraction grating vectors (G -2 , G -1 , G1, G2). The diffraction grating 1320 is oriented in the xy plane, Figure 13G A view of the grating is shown from the perspective of a ray or beam incident on the grating in the z direction. The diffraction grating 1320 has an associated set of k-space diffraction grating vectors (e.g., G -2 , G -1 , G1, G2). G1 and G -1 The grating vectors correspond to ±1 diffraction orders, while G2 and G-2 The grating vectors correspond to the ±2 diffraction orders, respectively. The grating vectors for the ±1 diffraction orders point in opposite directions (along the periodic axis of the grating) and have equal sizes that are inversely proportional to the period Λ of the diffraction grating 1320. Therefore, a diffraction grating with a smaller spacing has a larger grating vector. The grating vectors for the ±2 diffraction orders also point in opposite directions and have a size that is twice the size of the grating vector for the ±1 diffraction order. Although not shown, there may also be grating vectors for other higher diffraction orders. For example, the size of the grating vector for the ±3 diffraction orders is three times the size of the grating vector for the ±1 diffraction order, and so on. Note that the basic grating vector G1 is determined only by the periodicity (direction and spacing) of the grating, while the composition of the grating (e.g., surface profile, material, layer structure) can affect other properties of the grating, such as diffraction efficiency and diffraction phase. Since all harmonics of the basic grating vector (e.g., G -1 , G2, G -2 ) is only an integer multiple of the basic G1, so all diffraction directions of the grating are determined only by the periodicity of the grating. The function of the diffraction grating 1320 is to add the grating vector to the in-plane component of the k vector corresponding to the incident light ray or beam. This is Figure 13H Shown in.

[0178] Figure 13H A cross-sectional view of a diffraction grating 1320 is shown, along with the effect of the diffraction grating 1320 on a k-vector 1302 in k-space corresponding to a normally incident ray or beam. The diffraction grating 1320 diffracts the incident ray or beam into one or more diffraction orders. The new ray or beam in each of these diffraction orders is represented by a new k-vector (e.g., 1302a-e). These new k-vectors (e.g., 1302a-e) are the product of the in-plane components of the k-vector 1302 and the sum of the components of each grating vector (e.g., G). -2 , G -1 , G1, G2). In the case of a normally incident ray or beam as shown, the k-vector 1302 has no components in the xy plane of the diffraction grating. Therefore, the effect of the diffraction grating 1320 is to produce one or more new diffracted rays or beams whose k-vectors (e.g., 1302a-e) have xy components equal to the corresponding grating vectors. For example, the xy components of the ±1st diffraction order of the incident ray or beam become G1 and G2, respectively. -1 At the same time, the size of the new k vector is constrained to be 2π / ω, so the new k vectors (such as 1302a-e) are all located on the semicircle, as shown in Figure 13HBecause the in-plane components of the incoming k-vector 1302 are added to a grating vector whose length is equal to the basic increment or twice the basic increment, and the size of each resulting k-vector is constrained, the angles between the k-vectors of the various diffraction orders (e.g., 1302a-e) are not equal; rather, the k-vectors (e.g., 1302a-e) become angularly sparser as the diffraction order increases.

[0179] In the case of a diffraction grating formed on or in a planar eyepiece waveguide, the in-plane components of the new k-vectors (e.g., 1302a-e) may be of most interest because the diffracted rays or beams will be guided through the eyepiece waveguide if they lie within the eyepiece waveguide's k-space ring 1310. However, if the in-plane components of the new k-vectors (e.g., 1302a-e) lie within the central disk 1308b, the diffracted rays or beams will exit the eyepiece waveguide.

[0180] Figure 13I A cross-sectional view of a diffraction grating 1320 is shown, and the effect of the diffraction grating 1320 on the k-vector 1302 in k-space corresponding to an oblique incident ray or beam. This effect is similar to that of Figure 13H Specifically, the k-vector of a diffracted ray or beam is the sum of the in-plane component of the incident k-vector and the grating vector (G -2 , G -1 , G1, G2). For the obliquely incident k-vector 1302, the component of the k-vector in the xy plane of the diffraction grating 1320 is non-zero. This component is added to the grating vector to determine the in-plane component of the new k-vector for the diffracted ray or beam. The magnitude of the new k-vector is constrained to be 2π / ω. And again, if the in-plane component of the k-vector for the diffracted ray or beam lies within the k-space ring 1310 of the eyepiece waveguide, the diffracted ray or beam will be guided and propagated through the eyepiece waveguide.

[0181] Figure 13J 1300 is a k-space diagram illustrating the field of view (FOV) of an image projected into an AR eyepiece waveguide (e.g., 1200, 1300). The k-space diagram includes a large disk 1308a that defines the k-vectors of light beams or rays that can propagate within the eyepiece waveguide. The k-space diagram also includes a small disk 1308b that defines the k-vectors of light beams or rays that can propagate within the medium (e.g., air) surrounding the eyepiece waveguide. Additionally, as already discussed, a k-space ring 1310 defines the k-vectors of light beams or rays that can be guided and propagated within the eyepiece waveguide.

[0182] The input beams (e.g., 1202a, 1204a, 1206a) projected into the entrance pupil of the eyepiece waveguide are Figure 12A and 12B. The propagation angle of each input beam is uniquely defined by the spatial position of the corresponding image point within the image plane. The set of input beams has a certain angular spread in both the x-direction and the y-direction. The angular spread in the x-direction can define the horizontal field of view, while the angular spread in the y-direction can define the vertical field of view. Furthermore, the angular spread of the input beams along, for example, the diagonal line between the x-direction and the y-direction can define the diagonal field of view.

[0183] In k-space, the field of view of the input image can be approximated by FOV rectangle 1330. FOV rectangle 1330 contains the set of k-vectors corresponding to the set of input beams. x The dimension of the axis corresponds to the angular spread of the input beam in the x-direction. Specifically, the horizontal width of the FOV rectangle 1330 is where θ x is the total horizontal FOV and n is the refractive index of the incident medium. The FOV rectangle 1330 also has y The dimension of the axis defines the angular spread of the input beam in the y direction. Similarly, the vertical height of the FOV rectangle 1330 is where θ y is the total vertical FOV. Although rectangles are shown to represent the input beam set, in some embodiments, the input beam set can also be such that it corresponds to a different shape in k-space. However, the k-space analysis herein (generally illustrated using FOV rectangles or FOV squares) is also applicable to other shapes in k-space.

[0184] like Figure 13JAs shown, FOV rectangle 1330 is centered on and completely within small disk 1308b. This location of FOV rectangle 1330 corresponds to the k-vectors for either the input beamset (e.g., in a configuration with coaxial or telecentric projection from the image source) or the output beamset propagating generally along the ±z directions (but centered on the z-axis, with all beams—except those perpendicular to the entrance or exit pupil—having some angular deviation relative to the ±z directions). In other words, when FOV rectangle 1330 is within small disk 1308b in the k-space diagram, it can represent the input beams propagating from the image source to the eyepiece waveguide through free space. It can also represent the output beams propagating from the eyepiece waveguide to the user's eye. Each k-space point within FOV rectangle 1330 corresponds to a k-vector representing one of the input beam directions or one of the output beam directions. In order for the input beam, represented by FOV rectangle 1330, to be guided within the eyepiece waveguide, FOV rectangle 1330 must be translated to k-space ring 1310. Conversely, in order for the output beam, represented by FOV rectangle 1330, to exit the eyepiece waveguide, FOV rectangle 1330 must be translated from k-space ring 1310 back to small disk 1308b. To avoid introducing geometric dispersion and chromatic aberration from propagation through the waveguide, the FOV rectangle 1330 of the input beam can be coincident with the FOV rectangle of the output beam; in this configuration, the eyepiece waveguide maintains the beam angle from input to output.

[0185] The following equation describes the achievable FOV in certain eyepiece waveguides:

[0186]

[0187] FOV x =max(θ x,air )-min(θ x,air )

[0188]

[0189] If the FOV is in θ x = 0, the conventional eyepiece waveguide may have the following extreme values:

[0190]

[0191]

[0192]

[0193] max(FOV x ) on angular frequency arises from the dependence of the waveguide refractive index on angular frequency, which can be an important detail in some applications but usually has a relatively small effect.

[0194] Figure 13K is a k-space diagram showing the translational displacement of the FOV rectangle 1330 in k-space caused by an input coupling grating (ICG) located at the entrance pupil of the eyepiece waveguide. The ICG has an associated diffraction grating vector (G -1 , G1), as just mentioned Figures 13G to 13I The ICG diffracts each input beam represented by the FOV rectangle 1330 into a +1 diffraction order and a -1 diffraction order. In k-space, the diffraction of the input beam into the +1 diffraction order is determined by the G1 grating vector in k x The FOV rectangle 1330 is shown as shifted in the direction. Similarly, in k-space, the diffraction of the input beam to the –1 diffraction order is represented by the G -1 Raster vector in -k x The FOV rectangle 1330 is shown as being shifted in the direction.

[0195] for Figure 13K In the particular example shown, the translated FOV rectangle is too large to fit completely within the k-space annulus 1310. This means that the eyepiece waveguide cannot support all input beams in the FOV in a guided propagation mode, whether in the positive or negative diffraction orders, because the angular spread between them is too large. The k-vectors corresponding to points in the translated FOV rectangle that lie outside the large disk 1308a will not be diffracted at all by the ICG, since these k-vectors are not allowed. (In this case, this will also prevent diffraction into the ±2 and higher diffraction orders, since the grating vectors associated with these orders are further away, thus translating the k-vectors further outside the large disk 1308a.) At the same time, if any portion of the translated FOV rectangle remains within the small disk 1308b after translation by the ICG, the beams corresponding to these particular k-vectors will exit the eyepiece waveguide by transmitting through the plane of the eyepiece waveguide because they cannot undergo TIR, and will not be guided through the waveguide.

[0196] One possible modification that can be made to support more input beams in guided mode, represented by the translated FOV rectangle 1330, is to increase the difference between the refractive index of the eyepiece waveguide and the refractive index of the surrounding medium. This would increase the size of the large disk 1308a and / or decrease the size of the small disk 1308b (which could be decreased if the waveguide is not surrounded by air), thereby increasing the size of the k-space annulus 1310.

[0197] Example AR eyepiece waveguide with orthogonal pupil expander

[0198] Figure 14AAn example eyepiece waveguide 1400 is shown having an ICG region 1440, an orthogonal pupil expander (OPE) region 1450, and an exit pupil expander (EPE) region 1460. Figure 14B A k-space diagram is included that illustrates the role in k-space of each of these components of the eyepiece waveguide 1400. The ICG region 1440, OPE region 1450, and EPE region 1460 of the eyepiece waveguide 1400 include various diffractive features that couple an input beam into the eyepiece waveguide for propagation via guided modes, replicate the beam at multiple distributed locations in space, and cause the replicated beams to exit the eyepiece waveguide and be projected toward the user's eye.

[0199] An input light beam corresponding to an input image can be projected into the eyepiece waveguide 1400 from one or more input devices. The input light beam can be incident on an ICG region 1440, which can coincide with an entrance pupil of the eyepiece waveguide 1400. The input device for projecting the input light beam can include, for example, a spatial light modulation projector (located in front of or behind the eyepiece waveguide 1400 relative to the user's face). In some embodiments, the input device can use a liquid crystal display (LCD), liquid crystal on silicon (LCoS), fiber scanning display (FSD) technology, or a scanning microelectromechanical system (MEMS) mirror display, although other devices can also be used. The input light beam from the input device is projected into the eyepiece waveguide 1400 at various propagation angles, generally along the -z direction illustrated, and is incident on the ICG region 1440 from outside the substrate of the eyepiece waveguide.

[0200] The ICG region 1440 includes diffraction features that redirect an input light beam so that it propagates within the eyepiece waveguide 1400 via total internal reflection. In some embodiments, the diffraction features of the ICG region 1440 can form a one-dimensional periodic (1D) diffraction grating composed of many lines that extend vertically in the illustrated y-direction and repeat periodically horizontally along the illustrated x-direction. In some embodiments, the lines can be etched into the front or back surface of the eyepiece waveguide 1400 and / or formed from material deposited on the front or back surface. The period, duty cycle, depth, profile, blaze angle, etc. of the lines can be selected based on the angular frequency ω of the light for which the eyepiece waveguide 1400 is designed, the desired grating diffraction efficiency, and other factors. In some embodiments, the ICG region 1440 is designed to couple the input light primarily into the +1 and -1 diffraction orders. (Diffraction gratings can be designed to reduce or eliminate the 0th diffraction order and higher diffraction orders beyond the first diffraction order. This can be achieved by appropriately adjusting the profile shape of each line. However, in many practical ICGs in AR displays, all higher diffraction orders correspond to k-vectors outside the k-space ring. These higher diffraction orders will be prohibited regardless of non-k-space properties such as grating duty cycle, depth, and profile.) The diffracted beam in one of the ±1 diffraction orders from the ICG region 1440 then propagates roughly along the -x direction toward the OPE region 1450, while the diffracted beam in the other of the ±1 diffraction orders propagates roughly along the +x direction and exits the eyepiece waveguide 1400.

[0201] The OPE region 1450 includes diffraction features that can perform at least two functions: first, they can perform pupil expansion by spatially replicating each input beam at many new positions roughly along the -x direction; and second, they can guide each replicated beam on a path roughly toward the EPE region 1460. In some embodiments, these diffraction features are lines formed on or in the substrate of the eyepiece waveguide 1400. The period, duty cycle, depth, profile, and blaze angle of these lines can be selected based on the angular frequency ω of the light for which the eyepiece waveguide 1400 is designed, the desired grating diffraction efficiency, and other factors. The specific shape of the OPE region 1450 can vary, but can generally be determined based on the fan-out of the light beam from the ICG region 1440 and the size and position of the EPE region 1460. Figure 14D Further discussion on this.

[0202] The diffraction grating of the OPE region 1450 can be designed with relatively low and / or variable diffraction efficiency. These properties can allow the OPE region 1450 to replicate each light beam arriving from the ICG region 1440 and / or to distribute the light energy more evenly in at least one dimension. Because the diffraction efficiency is relatively low, each interaction of the light beam with the grating diffracts only a portion of the power of the light beam, while the remainder continues to propagate in the same direction. (Some parameters that can be used to influence the diffraction efficiency of the grating are the height and width of the line features, or the size of the refractive index difference between the line features and the background medium.) That is, when the light beam interacts with the diffraction grating in the OPE region 1450, a portion of its power will be diffracted toward the EPE region 1460, while the remainder will continue to propagate within the OPE region, thereby encountering the grating again at a different spatial location, at which location another portion of the power of the light beam can be diffracted toward the EPE region 1460, and so on. Because some portions of the power of each beam travel further through the OPE region 1450 than other portions before being diffracted toward the EPE region 1460, there are many copies of the incident beam traveling toward the EPE region from different locations in the -x direction. Thus, in the direction of propagation of the original incident beam through the OPE region 1450, the spatial extent of the copies of the beams is effectively increased, while the intensity of the incident beam is correspondingly decreased, because the light making up the input beam is now split into many copies of the beams.

[0203] The diffraction grating in the OPE region 1450 is oriented obliquely relative to the light beam arriving from the ICG region 1440 so as to diffract the light beam generally toward the EPE region 1460. The specific tilt angle of the diffraction grating in the OPE region 1450 may depend on the layout of the various regions of the eyepiece waveguide 1400 and may be modified later in the Figure 14B This is more clearly seen in the k-space diagram found and discussed in

[14] . In the eyepiece waveguide 1400, the ICG region 1440 is located to the right of the OPE region 1450, while the EPE region 1460 is located below the OPE region. Therefore, to redirect light from the ICG region 1440 to the EPE region 1460, the diffraction grating of the OPE region 1450 can be oriented at approximately 45° relative to the x-axis as illustrated.

[0204] Figure 14C yes Figure 14A and 14B A three-dimensional schematic diagram of the optical operation of the OPE region 1450 is shown. Figure 14CAn ICG region 1440 and an OPE region 1450 are shown, both located on the side of the waveguide closer to the viewer. Since the grating lines are microscopic, they cannot be seen. In this case, a single input beam 1401 is shown, but the image is composed of many such input beams traveling in slightly different directions through the eyepiece waveguide 1400. The input beam 1401 enters the OPE region 1450 from the ICG region 1440. The input beam 1401 then continues to propagate through the eyepiece waveguide 1400 via total internal reflection, repeatedly reflecting back and forth between its surfaces. This is in Figure 14C The zigzag representation in the propagation of each beam illustrated is shown.

[0205] When the input beam 1401 interacts with the diffraction grating formed in the OPE region 1450, part of its power is diffracted toward the EPE region, while another part of its power continues along the same path through the OPE region 1450. As described above, this is partly due to the low diffraction efficiency of the grating. In addition, the beam diffracted toward the EPE region may encounter the grating of the OPE region 1450 again and be diffracted back to the original propagation direction of the input beam 1401. The path of some of these beams is in Figure 14C The effect is that the spatial extent of the light is expanded because the input beam is replicated as it propagates through the OPE region 1450. Figure 14C This is clearly seen in FIG, which shows that the input beam 1401 is replicated into many beams that ultimately travel roughly in the -y direction towards the EPE region.

[0206] Similarly, the EPE region 1460 includes diffractive features that can perform at least two functions: first, they can replicate the light beams in another direction (e.g., a direction approximately orthogonal to the direction in which the OPE region 1450 replicates the light beams); and second, they can diffract each light beam out of the eyepiece waveguide 1400 toward the user's eye. The EPE region 1460 can replicate the light beams in the same manner as the OPE region 1450. That is, as the light beam propagates through the EPE region 1460, it repeatedly interacts with the diffraction grating and part of its power is diffracted into the first diffraction order, thereby being coupled out toward the user's eye. The remaining portion of the beam power is diffracted at the zeroth order and continues to propagate in the same direction within the EPE region 1460 until it interacts with the grating again later. The diffractive optical features of the EPE region 1460 can also impart a degree of optical power to the replicated output light beams so that the replicated output light beams appear to originate from a desired depth plane, as discussed elsewhere herein. This can be achieved by using a lens function to impart curvature to the lines of the diffraction grating in the EPE region 1460.

[0207] Figure 14BThe operation of the eyepiece waveguide 1400 in k-space is shown. Specifically, Figure 14B A k-space diagram (KSD) is included for each component of the eyepiece waveguide 1400, showing the k-space effect of that component. The FOV rectangles in the k-space diagrams and the arrows showing the corresponding directions of light propagation through the eyepiece waveguide have matching shading. The first k-space diagram KSD1 shows a k-space representation of the input beams incident on the ICG region 1440 from the input device. As already discussed, the input beam group can be represented in k-space by the FOV rectangle 1430, which has a k-space representation of the input beams incident on the ICG region 1440. x and k y The dimensions correspond to the angular spread of the input beam in the x and y directions. Each specific point in the FOV rectangle in KSD1 corresponds to a k vector associated with one of the input beams, where k x The component represents the propagation angle of the input beam in the x direction, and k y The component represents the propagation angle of the input beam in the y direction. More precisely, k x = sin(θ x ), where θ x is the angle between the input beam and the yz plane, and k y = sin(θ y ), where θ y is the angle between the input beam and the xz plane. The FOV rectangle in KSD1 is based on the k z The fact that the axis is centered means that the input beams are represented with propagation angles centered about the input beam propagating in the -z direction, so all input beams propagate roughly along the -z direction. (Although not shown here, any of the waveguide displays described herein can also be designed for off-axis FOVs relative to the ±z directions.)

[0208] The second k-space map KSD2 shows the k-space operation of the ICG region 1440. As already discussed, the diffraction grating has an associated grating vector (eg, G1, G2). -1 ). KSD2 shows the G1 grating vector and G -1 Grating vectors, which are equal in magnitude and opposite in direction along the periodic axis of the ICG. The ICG region 1440 diffracts the input beam into ±1 diffraction orders. Moreover, in k-space, this means that the ICG is formed by using the G1 grating vector and the G -1 The grating vectors both translate the FOV rectangle and copy it to two new locations. In the example shown, the ICG is designed to have a period Λ based on the angular frequency ω of the input beam so that the grating vectors G1, G -1 The size of is such that the replicated FOV rectangle is completely placed within the waveguide’s k-space ring. Therefore, all diffracted input beams enter the guided propagation mode.

[0209] In -k x The rectangular replica of the FOV centered at the point on the axis (9 o'clock position within the k-space ring) indicates that the corresponding diffracted beams have propagation angles centered about a beam whose propagation component within the plane of the eyepiece waveguide 1400 is along the -x direction. Therefore, all of these beams propagate roughly toward the OPE region 1450 while reflecting back and forth between the front and back surfaces of the eyepiece waveguide 1400 via TIR. At the same time, the beams with +k x The rectangular copy of the FOV centered at a point on the axis (the 3 o'clock position within the k-space ring) indicates that the corresponding diffracted beams have propagation angles centered about a beam whose propagation component within the plane of the eyepiece waveguide 1400 is along the +x direction. Consequently, all of these beams propagate roughly toward the right edge of the eyepiece waveguide 1400 while reflecting back and forth between the front and back surfaces of the eyepiece waveguide 1400 via TIR. In this particular eyepiece waveguide 1400, these beams would typically be lost and would not meaningfully contribute to projecting an image toward the user's eye.

[0210] KSD2 is not shown as the first-order raster vectors G1, G -1 The ICG will not diffract the beam into these diffraction orders because, in this case, doing so would shift the k-vectors that make up the FOV rectangle outside the perimeter of the k-space disk that defines the allowed k-vectors. Therefore, higher diffraction orders do not appear in this embodiment.

[0211] The third k-space map KSD3 shows the k-space operation of the OPE region 1450. Again, since the OPE region 1450 includes a diffraction grating, it has associated grating vectors (e.g., G1, G2, G3, G4, G5, G6, G7, G8, G9, G10, G11, G12, G13, G14, G15, G16, G17, G18, G19, G20, G21, G32, G19, G21, G33, G1 -1 ), these vectors are equal in magnitude and opposite in direction along the periodic axis of the OPE grating. In this case, the periodic axis of the diffraction grating is at an angle of 45° relative to the x-axis. Therefore, the grating vectors of the OPE diffraction grating (e.g., G1, G2) are -1 ) points relative to k x As shown in KSD3, one of the raster vectors translates the FOV rectangle to a value of –k yThe FOV rectangle is a new position centered at a point on the k-axis (the 6 o'clock position within the k-space annulus). This FOV rectangle copy indicates that the corresponding diffracted beam has a propagation angle centered about a beam whose propagation component within the plane of the eyepiece waveguide 1400 is along the -y direction toward the EPE region 1460. At the same time, the other shown OPE grating vectors place the FOV rectangle at a position outside the perimeter of the k-space disk. However, k-vectors outside of the disk are not allowed, so the OPE diffraction grating will not diffract the beam into that diffraction order. The periodic axis of the diffraction grating in the OPE region 1450 does not have to be exactly 45°. For example, by observing KSD3, it can be seen that the periodic axis can be at an angle slightly greater or less than 45° while still translating the FOV rectangle to the 6 o'clock position, where the FOV rectangle can fit completely within the k-space annulus. This will place the FOV rectangle at the 6 o'clock position, but the FOV rectangle does not have to be along the -k y The axis is centered in the k-space ring.

[0212] In the example shown, the OPE diffraction grating is designed to have a period Λ based on the angular frequency ω of the input beam, so that the grating vectors G1, G -1 One places the replicated FOV rectangle completely within the waveguide's k-space ring at the 6 o'clock position. Thus, all diffracted input beams remain in guided propagation mode. Since the k-space distance from the 9 o'clock position to the 6 o'clock position in the k-space ring (i.e., the translation performed by the OPE grating) is greater than the distance from the k-space map origin to the ring (the translation performed by the ICG), the OPE grating vector must be different in magnitude from the ICG grating vector. In particular, the OPE grating vector is longer than the ICG grating vector, which means that the OPE grating therefore has a shorter period Λ than the ICG grating.

[0213] The fourth k-space map KSD4 shows the k-space operation of the EPE region 1460. Again, since the EPE region 1460 includes a diffraction grating, it has associated grating vectors (eg, G1, G2, G3, G4, G5, G6, G7, G8, G9, G10, G11, G12, G13, G14, G15, G16, G17, G18, G19, G -1 ), these vectors are equal in magnitude and opposite in direction along the periodic axis of the EPE grating. In this case, the periodic axis of the diffraction grating is along the y-axis of the eyepiece waveguide 1400. Therefore, the grating vectors of the EPE diffraction grating (e.g., G1, G2) are equal in magnitude and opposite in direction along the periodic axis of the EPE grating. -1 ) points to ±k ydirection. As shown in KSD4, one of the grating vectors translates the FOV rectangle to a new position centered at the origin of the k-space map. This FOV rectangle copy indicates that the corresponding diffracted light beam has a propagation angle centered on a beam whose propagation component within the plane of the eyepiece waveguide 1400 is directed along the +z direction toward the user's eye. At the same time, the other first-order EPE grating vectors place the FOV rectangle at a position outside the periphery of the k-space disk so that the EPE diffraction grating does not diffract the light beam into that diffraction order. However, one of the second-order EPE grating vectors translates the FOV rectangle to the 12 o'clock position in the k-space annulus. Therefore, the EPE grating can diffract some light into one of the second diffraction orders. The second-order diffraction direction can correspond to a guided propagation direction along the +y direction and is generally an undesirable effect. For example, as described below, when the EPE grating is perturbed to introduce optical power, second-order diffraction can cause visual artifacts, thereby producing flare or smearing in the image presented to the user.

[0214] In the example shown, the EPE diffraction grating is designed to have a period Λ based on the angular frequency ω of the input beam, so that the grating vectors G1, G -1 One places the replicated FOV rectangle completely within the k-space inner disk of the waveguide. Therefore, all beams diffracted by the EPE diffraction grating are no longer in a guided propagation mode and therefore exit the eyepiece waveguide 1400. In addition, because the EPE diffraction grating translates the FOV rectangle back to the origin of the k-space diagram (where the FOV rectangle corresponding to the input beam is located), the output beam has the same propagation angle as its corresponding input beam. In the embodiment shown, the EPE diffraction grating has the same period Λ as the ICG because both diffraction gratings translate the FOV rectangle by the same k-space distance. However, this is not required. If the k-space of the FOV rectangle y The k-space ring with a size smaller than 6 o'clock position y size, the FOV rectangle can have a range of possible 6 o'clock positions, which are located at different k y Thus, for the EPE grating vectors (and hence for the OPE vectors), there are multiple design choices possible to place the FOV rectangle at multiple locations within the k-space annulus and / or near the origin of the k-space map.

[0215] In some embodiments, the lines of the EPE diffraction grating can be slightly bent in order to impart optical power to the output beam exiting the EPE region 1460. For example, the lines of the diffraction grating in the EPE region 1460 can be bent in the plane of the waveguide towards the OPE region to impart negative optical power. This can be used, for example, to cause the output beam to follow a diverging path, such as Figure 12BAs shown. This causes the projected image to appear to be located at a depth plane closer than optical infinity. This particular curvature can be determined by the lens function. In k-space, this means that different spatial regions within the EPE region 1460 have grating vectors pointing in slightly different directions, depending on the curvature of the grating lines in that particular region. In these embodiments, this causes the FOV rectangle to be translated to various different positions centered about the origin of the k-space map. This in turn causes multiple output beam groups corresponding to each translated FOV rectangle to be centered at different propagation angles, which in turn causes the illusion of depth.

[0216] Figure 14D Techniques for determining the size and shape of the OPE region 1450 and the EPE region 1460 are shown. Figure 14D Shown Figure 14A and 14B The same eyepiece waveguide 1400 shown includes an ICG region 1440, an OPE region 1450, and an EPE region 1460. Figure 14D Simplified versions of the k-space diagrams KSD1, KSD2, and KSD3 are also included. Referring to the first k-space diagram KSD1, the four corner k-vectors of the FOV rectangle are the vectors corresponding to the input beams incident on the ICG at the most oblique angles relative to the corners of the image in the input plane (see Figure 12A and 12B Since the propagation angles of these input beams are the most extreme of all the input beams in the field of view, their k-vectors are located at the four corners of the FOV rectangle in k-space.

[0217] Figure 14D The rays defining the four diffracted beams from the ICG region 1440 are shown, corresponding to the four corners of the input image. In particular, the rays near the top of the OPE region 1450 define the diffracted beams corresponding to the input beam incident on the ICG region 1440 at the strictest propagation angle in the direction upward and away from the OPE region (i.e., the k-vector located at the upper right corner of the FOV rectangle). Moreover, the rays near the bottom of the OPE region 1450 define the diffracted beams corresponding to the input beam incident on the ICG region 1450 at the strictest propagation angle in the direction downward and away from the OPE region (i.e., the k-vector located at the lower right corner of the FOV rectangle). These two beams define the fan-out of the diffracted beams from the ICG region 1440. In order to create a replica instance of these two beams and all other beams between them and project them to the user's eyes, the top and bottom boundaries of the OPE region should include the propagation paths of these two beams. The specific propagation paths of these two beams can be determined with reference to the second k-space map KSD2.

[0218] KSD2 shows the k-vector of the resulting light beam diffracted from the ICG region 1440 toward the OPE region 1450. The arrow in KSD2 shows the propagation angle of the light beam corresponding to the k-vector located at the upper right corner of the FOV rectangle.

[0219] The size, shape, and position of the EPE region 1460 can be determined by performing backward ray tracing using the propagation angles that are apparent from the k vectors in the third k-space diagram KSD3. As is apparent from KSD3, the upper left and upper right k vectors of the FOV rectangle define the fan-out of the propagation path that the light beam follows when propagating in the direction from the OPE region 1450 toward the EPE region 1460. By using these propagation angles to trace backward from the part of the EPE region 1460 farthest from the OPE region 1450 (i.e., the lower corner of the EPE region), the starting point in the OPE region of the light that reaches the lower corner of the EPE region at the propagation angle defined by the upper left and upper right k vectors can be determined. The starting points of these light rays can be used to determine the remaining boundaries of the OPE region 1450. For example, in order to guide the light beam from the OPE region 1450 to the lower left corner of the EPE region 1460, the worst-case propagation angle is the propagation angle indicated by the upper right k vector of the FOV rectangle. Therefore, the propagation path with this angle can be used to define the left boundary of the OPE region 1450. Similarly, to guide a beam from the OPE region 1450 to the lower right corner of the EPE region, the worst-case propagation angle is the propagation angle indicated by the k-vector at the upper left corner of the FOV rectangle. Therefore, a propagation path with this angle can be used to define the right boundary of the OPE region 1450.

[0220] like Figure 14D As shown, in the case of the eyepiece waveguide 1400 shown, the EPE region 1460 is located in the -x and -y directions from the ICG region 1440. Moreover, some diffracted beams fan out from the ICG region 1440 along paths in these same directions. To prevent these diffracted beams from entering the EPE region before first propagating through the OPE region 1450, the ICG region 1440 can be positioned far enough away from the EPE region in the +y direction so that the fan-out of the diffracted beams does not intersect the EPE region 1460. This results in a gap between the upper boundary of the EPE region 1460 and a large portion of the lower boundary of the OPE region 1450. In some embodiments, it may be desirable to reduce the size of the eyepiece waveguide by removing or reducing this gap. Figure 15A Example embodiments that achieve these goals are shown.

[0221] Figure 15AAn example embodiment of a waveguide eyepiece 1500 is shown in which the OPE region 1550 is tilted and positioned so that its lower boundary is parallel to the upper boundary of the EPE region 1560. In fact, the OPE region 1550 and the EPE region 1560 may actually share a boundary. According to this embodiment, by reducing or eliminating Figure 14A The gap between the OPE and EPE regions in the eyepiece waveguide embodiment shown can make the size of the waveguide eyepiece 1500 more compact.

[0222] To accommodate the tilted orientation of the OPE region 1550, the ICG region 1540 may be modified such that the fan-out of the diffracted beams from the ICG region is tilted to match the tilted orientation of the OPE region 1550. For example, the grating lines of the ICG region 1540 may be oriented such that no diffracted beams leave the ICG region along a propagation direction having a -y direction component. Alternatively, the ICG region 1540 may be positioned near a shared boundary of the OPE region 1550 and the EPE region 1560, but such that no portion of the ICG region extends beyond the shared boundary in the -y direction. The operation of the ICG region 1540 may be performed at Figure 15B As seen in the k-space diagram shown.

[0223] Figure 15B Includes a k-space map showing Figure 15A The operation of the eyepiece waveguide 1500 is shown. The first k-space diagram KSD1 shows the FOV rectangle corresponding to the input beams projected from a projector located outside the eyepiece waveguide 1500 toward the ICG region 1540. In the embodiment shown, these input beams have a propagation angle centered in the -z direction. Therefore, in k-space, the k-axis at the origin of KSD1 can be represented by z The FOV rectangles centered on the axes represent these input beams.

[0224] The second k-space diagram KSD2 shows the operation of the ICG region 1540 on the input beam. The ICG region 1540 diffracts the input beam and redirects it to the OPE region 1550. In k-space, this corresponds to translating the FOV rectangle using the grating vector associated with the ICG region 1540. In this embodiment, the grating lines in the ICG region 1540 are oriented with periodic axes having components in the +y direction. This means that the grating vector associated with the ICG 1540 is in the +k direction. y There is also a component in the direction of +k. y The magnitude in the direction can be greater than or equal to k yThis means that after being translated by the ICG region 1540, no part of the FOV rectangle extends below the horizontal axis of the k-space map KSD2. This, in turn, means that none of the diffracted beams from the ICG region 1540 have a -k y Therefore, no diffracted beam propagates downward from the ICG region 1540 toward the EPE region 1560. Therefore, no diffracted beam enters the EPE region 1560 before propagating through the OPE region 1550.

[0225] The third k-space diagram, KSD3, illustrates the operation of the OPE region 1550 on the diffracted beam from the ICG region 1540. As shown, the diffraction grating of the OPE region 1550 can be oriented so as to redirect the beam at an angle corresponding to a FOV rectangle translated to a position slightly offset from the 6 o'clock position in the k-space annulus. For example, the angle at which the translated FOV rectangle in KSD3 deviates from the 6 o'clock position in the k-space annulus can be the same as the angle at which the translated FOV rectangle in KSD2 deviates from the 9 o'clock position. In other words, the translated FOV rectangle in KSD3 can be separated by 90° from the translated FOV rectangle in KSD2. However, this particular angular separation is not required; the specific position of each FOV rectangle can depend on the layout of the various regions of the eyepiece waveguide relative to each other.

[0226] Since the translated FOV rectangle in KSD3 is in -k x The light beam from the OPE region 1550 is centered on a k vector having a component in the -x direction, so the light beam from the OPE region 1550 generally propagates toward the EPE region 1560 at an angle having a component in the -x direction. Figure 15A As can be seen, due to this angle, some light beams from the tip 1555 of the OPE region 1550 will not intersect the EPE region 1560. Since the tip 1555 of the OPE region 1550 can contribute a relatively small portion of light to the EPE region 1560, the size advantage of eliminating the upper tip 1555 can outweigh any optical disadvantages. Therefore, in some embodiments, by eliminating the upper tip 1555 of the OPE region 1550, the waveguide eyepiece 1500 can be made even more compact.

[0227] Finally, the fourth k-space map KSD4 shows that the EPE region 1560 has a diffraction grating designed to translate the FOV rectangle back to the origin of the k-space map. Figure 15A The starting position of the FOV rectangle in the KSD4 of the eyepiece waveguide embodiment shown is Figure 14AThe starting position of the FOV rectangle in KSD4 of the eyepiece waveguide embodiment shown is slightly different, and therefore the design of the diffraction grating in the EPE region 1560 is also slightly different. For example, the orientation of the grating lines of the diffraction grating in the EPE region 1560 can be tilted so that the associated grating vector is at +k x direction, so that the OPE region 1550 does not need to extend beyond the left edge of the EPE region 1560 (see Figure 14D discussion and will Figure 14D The position of the upper right corner k vector in KSD3 is the same as Figure 15B ). This results in Figure 15B The FOV rectangle in KSD4 is translated back to the origin of the k-space diagram, which means that the light beam represented by the translated FOV rectangle is coupled out from the eyepiece waveguide 1500 toward the user's eye at the same propagation angle as its corresponding input light beam, which has been described in this document (i.e., the FOV rectangle representing the output light beam is located at the same position in the k-space diagram as the FOV rectangle representing the input light beam).

[0228] Figure 15C is another k-space diagram showing Figure 15A Operation of the eyepiece waveguide 1500 is shown. Figure 15C The k-space map is Figure 15B Moreover, it is shown that the beam propagating through the OPE region 1550 can be moved along approximately -k x The propagation angle in the direction (represented by the FOV rectangle located near the 9 o'clock position of the k-space ring) is approximately the same as that along the -k y The FOV rectangle is located near the 6 o'clock position of the k-space ring. This is shown by the raster vector with a double-headed arrow between the FOV rectangle located near the 9 o'clock position of the k-space ring and the FOV rectangle located near the 6 o'clock position. Figures 15D to 15F This behavior is shown in more detail.

[0229] Figure 15D is the input beam and Figure 15A A diagram of the first generation of interactions between the OPE region 1550 of the eyepiece waveguide embodiment shown. The OPE region 1550 of the eyepiece waveguide 1500 comprises a diffraction grating composed of parallel grating lines that repeat in a periodic direction. The periodic direction determines the direction of the grating vector associated with the diffraction grating. In this case, Figure 15C The double-headed arrows in the raster vectors illustrate the operation of the OPE region 1550 and are along Figures 15D to 15F The periodic direction of the grating lines is shown pointing toward the grating vector.

[0230] Figure 15D An input beam is shown entering the OPE region 1550 from the ICG region 1540. The input beam is shown as traveling along the same axis as that located at Figure 15C 9 o'clock position of the k-space ring of the FOV rectangle or the direction corresponding to the k-vector. As shown in the figure, the first generation interaction between the input beam and the OPE region 1550 produces two diffracted output beams: a portion of the power of the input beam is reflected from the top or bottom surface of the eyepiece waveguide 1500 as output 1 and continues to propagate in the same xy direction as the input beam (i.e., zeroth order diffraction); and a portion of the power of the input beam is diffracted downward into the first order as output 2 (e.g., through the first order grating vector G1 of the OPE region). The output 2 beam is shown as being along the same direction as that located at Figure 15C After this first generation interaction, the output 1 beam and the output 2 beam have different propagation angles, but they both still propagate within the OPE region 1550 and can therefore have other interactions with the OPE region, such as Figure 15E and 15F Although not shown, other input beams entering the OPE region 1550 at different propagation angles will have similar behavior, but with slightly different input and output angles.

[0231] Figure 15E is the input beam and Figure 15A Diagram of the second generation interaction between the OPE regions 1550 of the eyepiece waveguide embodiment shown. The beams associated with the first generation interaction are shown in dashed lines, while the beams associated with the second generation interaction are shown in solid lines. Figure 15E As shown, each output beam Output 1 and Output 2 from the first generation interaction can now undergo an interaction with the OPE region 1550 similar to that which occurred in the first generation. Figure 15D Some portion of the power of the output 1 beam continues to propagate only along the same xy direction (i.e., zeroth order diffraction), while another portion of the power of this beam interacts with the grating and is redirected downward (e.g., through the first-order grating vector G1 of the OPE region). Similarly, Figure 15D Some portion of the power of the output 2 beam continues solely downward toward the EPE region 1560 (i.e., zeroth-order diffraction), while another portion of the power of the beam interacts with the grating and is diffracted generally along the -x direction (i.e., through the negative first-order grating vector G of the OPE region). -1 ) and further continues to propagate into the OPE region 1550 in the same direction as the initial input beam.

[0232] After the second generation of interactions occurs within OPE region 1550, an interference node 1556 exists where the two generated light beams intersect. The optical paths followed by each of these light beams to reach interference node 1556 are substantially the same length. Therefore, light beams exiting interference node 1556 traveling in the same direction may have the same or similar phases and, therefore, may experience constructive or destructive wave interference with each other. This can lead to image artifacts discussed below.

[0233] Figure 15F is the input beam and Figure 15A Diagram of the third generation of interactions between the OPE regions 1550 of the eyepiece waveguide embodiment shown. The beams associated with the first and second generation interactions are shown in dashed lines, while the beams associated with the third generation interactions are shown in solid lines. Figure 15F As shown, each output beam produced by the second generation of interactions can once again undergo similar interactions with the OPE region 1550 as occurred in the previous generations. Some portion of the power of these beams continues to propagate in the same direction (i.e., zeroth order diffraction), while other portions of the power of these beams are redirected: some roughly along the -x direction and some roughly along the -y direction (i.e., through the first-order grating vectors G1 and G2 of the OPE region). -1 ). All beams propagating roughly in the -x direction are located in the Figure 15C The state represented by the FOV rectangle near the 9 o'clock position of the k-space ring in the k-space diagram of FIG; and all light beams propagating roughly along the -y direction are in the state represented by the FOV rectangle near the 6 o'clock position. Figure 15C It can be seen that for the case where the OPE region 1550 is composed of a 1D periodic diffraction grating, for any given input beam, the replica beam corresponding to that input beam only travels along two directions within the OPE region (although these two directions are different for different input beams entering the OPE region with different propagation angles).

[0234] The third generation interaction with the OPE region results in the creation of additional interference nodes 1556 where light beams with the same or similar optical path lengths intersect each other, potentially leading to constructive or destructive wave interference. Each node 1556 acts as a light source emitting towards the EPE region 1560. In the case where the OPE region consists of a diffraction grating with 1D periodicity, the layout of these nodes 1556 forms a uniform lattice pattern, thus resulting in Figure 15G Image artifacts shown.

[0235] Figure 15GFIG16 is a diagram showing how a single input beam 1545 from the ICG region 1540 is replicated through the OPE region 1550 and redirected as multiple beams 1565 to the EPE region 1560. Each replicated beam 1565 shown as propagating toward or in the EPE region 1560 originates from one of the interference nodes 1556. These interference nodes have an ordered distribution and act as a sparse, periodic array of sources. Due to the ordered distribution of the interference nodes 1556, the replicated beams 1565 that illuminate the EPE region are all spaced apart by the same interval, although the beams may have non-monotonically varying intensities. Therefore, the replicated beams 1565 from the OPE region 1550 may illuminate the EPE region 1560 with a relatively sparse, non-uniform distribution. In some embodiments, it may be beneficial if the replicated beams that illuminate the EPE region of the eyepiece waveguide can be more evenly dispersed. FIG16 illustrates such an embodiment.

[0236] Example AR eyepiece waveguide with multi-directional pupil expander

[0237] Figure 16A An example eyepiece waveguide 1600 is shown having a multi-directional pupil expander (MPE) region 1650 instead of an OPE region. At a macroscopic level, the embodiment of the eyepiece waveguide 1600 shown is similar to Figure 15A The eyepiece waveguide 1500 is shown. The input beam is coupled into the eyepiece waveguide 1600 through the ICG region 1640. The diffracted beam from the ICG region 1640 propagates toward and through the MPE region 1650, which replaces the OPE region. Finally, the MPE region 1650 diffracts the beam toward the EPE region 1660, where the beam is coupled out toward the user's eye. The ICG region 1640 and the EPE region 1660 can be designed to be compatible with the user's eye. Figures 15A to 15G 16. The MPE region 1650 functions in the same manner as the corresponding region in the eyepiece waveguide 1500 described above. However, the MPE region 1650 differs from the OPE region 1550 in that the MPE region 1650 diffracts light in more directions. This feature can advantageously reduce the periodic uniformity of the beam distribution in the EPE region 1660, which in turn can result in a more uniform illumination of the EPE region.

[0238] MPE region 1650 is composed of diffraction features that exhibit periodicity in multiple directions. MPE region 1650 can be composed of an array of scattering features arranged in a 2D grid. Each scattering feature can be, for example, a depression or protrusion of any shape. The 2D array of scattering features has associated grating vectors that are derived from the reciprocal grid of the 2D grid. As an example, MPE region 1650 can be a 2D periodic diffraction grating, which is composed of a crossed grating with grating lines that repeat along two or more different periodic directions. This can be achieved by superimposing two 1D gratings with different periodic directions.

[0239] Figure 16B Shows that it can be Figure 16A A portion of an example 2D periodic grating used in an MPE region 1650 is shown, along with its associated grating vectors. The 2D periodic grating 1650 can be a spatial grid of diffraction features whose periodic directions are shown by vectors u and v. Such a 2D periodic grating is associated with grating vectors. The two fundamental grating vectors G and H, corresponding to the periodic directions u and v, are mathematically defined by:

[0240] u=[u x ,u y ]

[0241]

[0242]

[0243]

[0244] Mathematically, vectors u and v define the spatial grid, while G and H correspond to the fundamental dual lattice vectors or reciprocal lattice vectors. Note that G is orthogonal to u and H is orthogonal to v; however, u is not necessarily parallel to H and v is not necessarily parallel to G.

[0245] As an example, a 2D periodic grating can be designed or formed by superimposing two sets of 1D periodic grating lines, such as Figure 16B shown (although a 2D periodic grating may alternatively be formed by placing e.g. Figure 16B The first set of grating lines 1656 may be repeated along a direction of a base grating vector G. The base grating vector G may have a magnitude equal to 2π / a, where a is a period of the first set of grating lines 1656. Figure 16BThe 2D grating shown is also associated with harmonics of the first fundamental grating vector G. These harmonics include -G and higher order harmonics, such as 2G, -2G, etc. A second set of grating lines 1657 can repeat along the direction of the fundamental grating vector H. The fundamental grating vector H can have a magnitude equal to 2π / b, where b is the period of the second set of grating lines 1657. Figure 16B The 2D grating shown is also associated with harmonics of the second fundamental grating vector H. These harmonics include -H and higher order harmonics such as 2H, -2H, etc.

[0246] Any 2D periodic array of diffractive features has associated grating vectors that correspond to the entire reciprocal grid and point in directions determined by integer linear combinations (superpositions) of the basis grating vectors G and H. In the embodiment shown, these superpositions result in Figure 16B Additional raster vectors are shown in . These raster vectors include, for example, -G, -H, H+G, HG, GH, and -(H+G). Typically, these vectors are described by two indices: (±1,0), (0,±1), (±1,±1), (±2,0), etc. Although Figure 16B Only first order grating vectors associated with the 2D diffraction grating and their superpositions are shown, but higher order grating vectors may also be present.

[0247] As discussed elsewhere herein, the k-space operation of a grating on a set of beams that make up an image is to translate the FOV rectangle corresponding to the image using the grating vector associated with the grating. Figure 16C and 16D As shown in Figure 16B Example 2D MPE diffraction grating shown.

[0248] Figure 16C is a k-space diagram showing Figure 16A Figure 1 shows the k-space operation of the MPE region 1650 of the eyepiece waveguide 1600. The k-space diagram includes a shaded FOV rectangle located near the 9 o'clock position of the k-space annulus. This is the location of the FOV rectangle after the ICG region 1640 has coupled the input beam into the eyepiece waveguide 1600 and redirected it to the MPE region 1650. Figure 16C shows how the 2D grating in the MPE region 1650 is used Figure 16BThe grating vectors shown translate the FOV rectangle. Since there are eight grating vectors (G, H, -G, -H, H+G, HG, GH, and -(H+G)), the MPE region 1650 attempts to translate the FOV rectangle to eight possible new k-space locations. Six of these eight possible k-space locations fall outside the perimeter of the k-space map. These locations are shown as unshaded FOV rectangles. Since k-vectors outside the boundaries of the k-space map are not allowed, none of these six grating vectors will cause diffraction. However, there are two grating vectors (i.e., -G and -(H+G)) that cause the FOV rectangle to translate to a new position within the boundaries of the k-space map. One of the positions is located near the 6 o'clock position in the k-space ring, and the other position is located near the 2 o'clock position. Since the k-vectors at these positions are allowed and do cause guided propagation modes, the FOV rectangles at these positions are shaded to indicate that the beam is diffracted into these two states. Therefore, the power of the light beam entering the MPE region 1650 at the propagation angle indicated by the FOV rectangle located near the 9 o'clock position of the k-space ring is partially diffracted into two states indicated by the other two shaded FOV rectangles (i.e., the FOV rectangle located near the 2 o'clock position and the FOV rectangle located near the 6 o'clock position).

[0249] Figure 16D is a k-space diagram, which further shows Figure 16A Figure 10 illustrates the k-space operation of the MPE region 1650 of the eyepiece waveguide 1600. This particular k-space diagram illustrates the operation of the MPE region 1650 on beams in the propagation state indicated by the FOV rectangle located near the 2 o'clock position of the k-space annulus. Again, the 2D diffraction grating in the MPE region 1650 attempts to diffract these beams into diffraction orders specified by its eight associated grating vectors. As shown, six of the grating vectors would translate the FOV rectangle to locations outside the boundaries of the k-space diagram. Therefore, these diffraction orders do not occur. These locations are illustrated by the unshaded FOV rectangles. However, two of the grating vectors (i.e., H and HG) would translate the FOV rectangle to locations within the boundaries of the k-space diagram. These locations are illustrated by the shaded FOV rectangles located near the 9 o'clock position and near the 6 o'clock position of the k-space annulus. Therefore, the 2D diffraction grating in the MPE region 1650 partially diffracts the power of the light beam propagating along the direction indicated by the FOV rectangle located near the 2 o'clock position of the k-space ring into two states indicated by the other two shaded FOV rectangles (i.e., the FOV rectangle located near the 9 o'clock position and the FOV rectangle located near the 6 o'clock position).

[0250] Although not shown, a similar k-space diagram can be drawn to illustrate the k-space manipulation of the MPE region 1650 for beams traveling at propagation angles indicated by the FOV rectangle located near the 6 o'clock position of the k-space annulus. This k-space diagram would show that the 2D periodic diffraction grating in the MPE region 1650 partially diffracts the power of these beams into two states indicated by the two shaded FOV rectangles located near the 9 o'clock position and at the 2 o'clock position of the k-space annulus.

[0251] Figure 16E It shows Figure 16A 16. As already mentioned, the eyepiece waveguide 1600 can receive input beams that propagate generally along the -z direction and are incident on the ICG region 1640 of the waveguide 1600 from an external source. These input beams are composed of k-space beams at the origin of the k-space diagram. z The ICG region 1640 then diffracts the input beams so that they are directed to have a propagation angle centered about a propagation direction corresponding to the center point of the FOV rectangle located near the 9 o'clock position of the k-space ring.

[0252] The guided beams enter MPE region 1650, where they can have multiple interactions. During each generation of interaction, a portion of the power of each beam can be diffracted into the zeroth order and continue to propagate through MPE region 1650 in the same direction. For example, in the first generation of interaction, this zeroth order diffraction corresponds to a portion of the beam's power remaining in the state indicated by the FOV rectangle located near the 9 o'clock position of the k-space ring. Other portions of the beam's power can be diffracted along new directions. Additionally, in the first generation of interaction, this produces corresponding diffracted beams whose diffraction angles are centered about the propagation directions corresponding to the center points of the FOV rectangle located near the 2 o'clock position of the k-space ring and the propagation directions corresponding to the center points of the FOV rectangle located near the 6 o'clock position.

[0253] As long as the beam remains in the MPE region 1650, it can undergo more interactions, each of which causes part of the beam's power to be diffracted into the zeroth order and continue to propagate in the same direction, or to be diffracted in a new direction. This results in multiple spatially distributed diffracted beam groups with diffraction gratings having the following characteristics: Figure 16E The center points of the FOV rectangles in the k-space annulus are shown as the propagation angles centered at each propagation direction. This behavior is indicated by the double-headed arrows between each pair of FOV rectangles in the k-space annulus.

[0254] When any given input beam propagates within the MPE region 1650, it is split into many diffracted beams that can only travel along three allowed directions – one for each direction represented by Figure 16E 1650 . (This is true for any input beam propagating within MPE region 1650. However, the three allowed directions will be slightly different depending on the propagation angle of each initial input beam entering MPE region 1650.) And, because part of the power of any given input beam is diffracted into any of the same three propagation directions after any number of interactions with MPE region 1650, image information is preserved across these interactions.

[0255] There are advantages associated with having three allowed propagation directions for each input beam in the MPE region 1650, as opposed to the two allowed propagation directions in the OPE region 1550. These advantages are discussed further below, but suffice it to say for now that the increased number of propagation directions in the MPE region 1650 can result in a more complex distribution of interference nodes within the MPE region 1650, which in turn can improve the uniformity of illumination in the EPE region 1660.

[0256] It should be understood that Figure 16E k-space manipulation of an example embodiment of an MPE region 1650 is shown. In other embodiments, the MPE region 1650 can be designed such that each input beam can diffract along more than three directions within the MPE region. For example, in some embodiments, the MPE region 1650 can be designed to allow each input beam to diffract along 4 directions, 5 directions, 6 directions, 7 directions, 8 directions, etc. As already discussed, the diffraction features in the MPE region 1650 can be designed to provide grating vectors that copy the FOV rectangle to locations in the k-space annulus corresponding to the selected diffraction directions. Additionally, the diffraction features in the MPE region 1650 can be designed to have a period corresponding to the size of the grating vectors that results in the copies of the FOV rectangle being completely within the k-space annulus (and causing copies of other attempted FOV rectangles to be completely outside the perimeter of the k-space map).

[0257] In some embodiments, the angular separation between each allowed direction of propagation for a given beam within the MPE region 1650 is at least 45 degrees. If the angular separation between any pair of selected directions is less than this amount, the diffraction features in the MPE region 1650 need to be designed to provide grating vectors to perform those angular transformations within the k-space annulus; due to the small angular separation, such grating vectors are relatively short compared to the size of the k-space annulus. This makes it more likely that the superposition of the elementary MPE grating vectors will create a copy of the FOV rectangle that only partially lies within the k-space annulus, which can result in loss of image information (if not performed carefully, as will be discussed further herein). Additionally, if the angular separation between any pair of allowed directions of propagation in the MPE region 1650 becomes too small, the resulting relatively short grating vectors also make it more likely that the grating vector superposition will create a copy of the FOV rectangle that partially lies within the central disk of the k-space map. This would be undesirable because it could result in light being outcoupled from the eyepiece waveguide 1600 toward the user's eye from locations outside the designated MPE region 1660.

[0258] When determining the allowed propagation directions within the MPE region 1650, various design criteria can be followed. For example, the allowed propagation directions can be selected so that one propagation direction corresponds to the direction from the ICG region 1640 to the MPE region 1650. Alternatively, the allowed propagation directions can be selected so that only one propagation direction causes a beam propagating along that direction from a position within the MPE region 1650 to intersect the EPE region 1660. This ensures that the replicated beam corresponding to each input beam enters the EPE region 1660 at the same propagation angle. Additionally, the allowed propagation directions within the MPE region 1650 can be selected so that the FOV rectangles do not overlap. Overlapping FOV rectangles can cause image information from different image points to mix and can result in artifacts.

[0259] Figure 16F is the input beam and Figure 16A Diagram of first generation interactions between MPE regions 1650 of the eyepiece waveguide embodiment shown. Figure 16F An input beam is shown entering the MPE region 1650 from the ICG region 1640. The input beam is shown along a path that is aligned with the MPE region 1650. Figure 16E The 9 o'clock position of the k-space ring is near the center point of the FOV rectangle or the direction corresponding to the k-vector propagation.

[0260] The MPE region 1650 may include many features smaller than 1 μm. In each interaction with the MPE region, an input beam of approximately 1 mm in diameter will be split into 3 beams (same diameter, but with a fraction of the original power of the input beam) that propagate in TIR along 3 different directions. One direction corresponds to the zeroth order diffraction and is the original propagation angle within the waveguide plane. The other two directions depend on the grating vectors G and H of the MPE region 1650. As shown in the figure, the first generation interaction between the input beam and the MPE region 1650 produces three beams: some portion of the power of the input beam is reflected from only the top or bottom surface of the eyepiece waveguide 1600 as output 1 and continues to propagate in the same xy direction as the input beam (i.e., zeroth order diffraction); some portion of the power of the input beam interacts with the 2D grating in the MPE region 1650 and is diffracted downward as output 2; and some portion of the power of the input beam interacts with the grating and is diffracted upward and to the right as output 3. The output 2 beam is shown as being along a line corresponding to that located at Figure 16E 6 o'clock position of the k-space ring in FIG, while the output 3 beam is shown as propagating along a direction corresponding to the center point or k-vector of the FOV rectangle near the 6 o'clock position, while the output 1 beam, the output 2 beam, and the output 3 beam are shown as propagating along a direction corresponding to the center point or k-vector of the FOV rectangle near the 2 o'clock position. After this first generation of interaction, the output 1 beam, the output 2 beam, and the output 3 beam have different propagation angles, but they are still propagating within the MPE region 1650 and can therefore have additional interactions with the MPE region, such as Figures 16G to 16I Although not shown, other input beams entering the MPE region 1650 at different propagation angles will have similar behavior, but with slightly different input and output angles.

[0261] Figure 16G is the input beam and Figure 16A Diagram of the second generation interaction between the MPE regions 1650 of the eyepiece waveguide embodiment shown. The beams associated with the first generation interaction are shown in dashed lines, while the beams associated with the second generation interaction are shown in solid lines. Figure 16G As shown, each of the output beams Output 1, Output 2, and Output 3 from the first generation of interactions may now undergo a similar interaction with the MPE region 1650 as occurred in the previous generation. Figure 16F A certain portion of the power of the output 1 beam continues to propagate only in the same xy direction, while another portion of the power of the beam interacts with the grating and is diffracted along the direction corresponding to the FOV rectangle located near the 6 o'clock position, and yet another portion of the power of the beam interacts with the grating and is diffracted along the direction corresponding to the FOV rectangle located near the 2 o'clock position. Similarly, the power of Figure 16FA certain portion of the power of the output 2 beam continues to propagate only toward the EPE region 1660, while another portion of the power of the beam interacts with the grating and diffracts along the direction indicated by the FOV rectangle located near the 9 o'clock position, and yet another portion of the power of the beam interacts with the grating and diffracts along the direction corresponding to the FOV rectangle located near the 2 o'clock position. In addition, the power from Figure 16F A certain portion of the power of the output 3 beam continues only along the direction indicated by the FOV rectangle located near the 2 o'clock position, while another portion of the power of the beam interacts with the grating and is diffracted along the direction indicated by the FOV rectangle located near the 9 o'clock position, and still another portion of the power of the beam interacts with the grating and is diffracted along the direction corresponding to the FOV rectangle located near the 6 o'clock position.

[0262] Figure 16H is the input beam and Figure 16A Diagram of the third generation of interactions between the MPE regions 1650 of the eyepiece waveguide embodiment shown. The beams associated with the first and second generation interactions are shown in dashed lines, while the beams associated with the third generation interactions are shown in solid lines. Figure 16H As shown, each output beam resulting from the second generation of interactions may again undergo similar interactions with the MPE region 1650 as occurred in the previous generations.

[0263] Figure 16I is the input beam and Figure 16A Figure 1650 shows a diagram of the fourth generation of interactions between the MPE regions 1650 of the eyepiece waveguide embodiment shown. The beams associated with the first, second, and third generation interactions are shown as dashed lines, while the beams associated with the fourth generation interactions are shown as solid lines. After all of these interactions, all of the resulting beams propagate along one of the three directions that are allowed within the MPE region 1650 for any given input beam: the direction corresponding to the FOV rectangle located near the 9 o'clock position; the direction corresponding to the FOV rectangle located near the 2 o'clock position; or the direction corresponding to the FOV rectangle located near the 6 o'clock position of the k-space annulus. Although there are some nodes at which some of these beams can intersect each other while propagating through the MPE region 1650, the locations of these nodes have a greater impact than the k-space annulus. Figures 15D to 15G The OPE region 1550 shown is a more complex distribution. In addition, the light beams may reach each of these nodes via different paths and therefore are not necessarily in phase with each other. Therefore, in the eyepiece waveguide embodiment 1600 that uses the MPE region 1650 instead of the OPE region (such as 1550), image artifacts that may be caused by the orderly distribution of interference nodes can be reduced. This can be achieved in Figure 16J and 16K Seen in.

[0264] Figure 16J is a diagram showing the various paths that light beams can take through the MPE region 1650 and ultimately to the EPE region 1660. There are some paths that include only a single change in direction, while other paths include multiple changes in direction (although some of these longer, more complex paths will naturally carry less energy). Due to the complexity introduced by the presence of another diffraction angle in the MPE region 1650, there are many different spacings between the light beams 1665 that ultimately illuminate the EPE region 1660. Moreover, in fact, any possible spacing between the light beams 1665 can be achieved by a sufficient number of interactions in the MPE region 1650. As Figure 16K As shown, this can result in more uniform illumination of the EPE region 1660.

[0265] Figure 16K 16 is a diagram showing how a single input beam 1645 from an ICG region 1640 is replicated through an MPE region 1650 and redirected as multiple beams 1665 to an EPE region 1660. Each of these beams 1665 originates from a dense grid of nodes. There may still be gaps between some of these replicated beams 1665, but these gaps are typically smaller than those from an OPE region (e.g., Figure 15G The gaps between the replicated beams output by the MPE region 1650 are smaller and less regular. Because there are so many paths toward the EPE region 1660, and all of the paths are located at different positions, the MPE region 1650 provides a complex exit pupil pattern that can illuminate the EPE region 1560 more uniformly.

[0266] Figure 16L FIG2 is a side-by-side comparison showing the performance of an eyepiece waveguide with an OPE region versus an eyepiece waveguide with an MPE region. On the left, eyepiece waveguide 1500 is shown, which includes an OPE region 1550 with a 1D periodic diffraction grating. As already discussed, the OPE region 1550 illuminates the EPE region 1560 with a sparse set of regularly spaced replicated beams. Below the eyepiece waveguide 1500 is a simulated output image. This is the simulated output image that would be projected from the EPE region 1560 of the eyepiece waveguide 1500 in response to an input image composed of pixels all having the same color and brightness.

[0267] on the right, Figure 16LAn eyepiece waveguide 1600 is shown, which includes an MPE region 1650 having a 2D periodic diffraction grating. As can be seen in the figure, the MPE region 1650 more uniformly illuminates the EPE region 1660. Below the eyepiece waveguide 1600 is a simulated output image, which is the result of the same input image used in the simulation of the eyepiece waveguide 1500 on the left. It can be clearly seen from the simulated image on the right that the eyepiece waveguide 1600 using the MPE region 1650 achieves a smoother, more uniform distribution of output light. In contrast, the image on the left, which is the simulated output of the eyepiece waveguide 1500 with the MPE region 1550, has visible high spatial frequency fringes, which are caused by the sparse, ordered set of replicated beams illuminating its EPE region 1560.

[0268] Figure 16M The performance of the eyepiece waveguide with an MPE region is further shown compared to the performance of other eyepiece waveguides with an OPE region. Figure 16M The top row of the figure shows Figure 15A Performance of the eyepiece waveguide 1500 is shown. A horizontal cross-section of the projected image from the eyepiece waveguide shows relatively high spatial frequency variations. Figure 16L This is seen as streaks in the simulated output image shown. Figure 16M The eyepiece waveguide 1500 is shown to have an eyebox efficiency of 1.2%. It also shows the point spread function associated with the eyepiece waveguide. The point spread function shows the output image obtained from the eyepiece waveguide in response to an input image of a single bright spot. This shows that the eyepiece waveguide 1500 is very sharp, as it has only 2.5 to 5 minutes of blur.

[0269] One approach to overcoming high spatial frequency variations in the output image from the eyepiece waveguide 1500 is to introduce some dithering in the OPE region 1550. For example, small variations can be introduced in the orientation angle and / or grating period of the OPE region 1550. This is done in an attempt to disrupt the ordered nature of the interference nodes that may be present in the OPE region 1550. Figure 16M The second and third rows in Figure 1 show the performance of the eyepiece waveguide 1500 with two different types of dither. As can be seen from the horizontal cross-sections of the projected images of these waveguides, high spatial frequency variations are still present. In addition, the point spread functions of these dithered embodiments show a much greater amount of blur—in one case as much as 45 minutes of arc.

[0270] Figure 16MThe bottom row shows the performance of the eyepiece waveguide 1600 with the MPE region 1650. The cross section of the projected image of this waveguide shows much less high spatial frequency variation. Although low frequency spatial variation is still present, this can be corrected by software much more easily than high spatial frequency variation. The eyepiece efficiency of this eyepiece waveguide is slightly lower (at 0.9%) than that of the other eyepiece waveguides. This can be attributed to the fact that the MPE region 1650 is located along the Figure 16E Some input light is redirected in the general direction corresponding to the FOV rectangle located near the 2 o'clock position in the ring of the k-space diagram shown. Due to the macroscopic layout of eyepiece waveguide 1600, light exiting MPE region 1650 in this propagation direction never enters the EPE region and is therefore not projected to the user's eye; instead, this light is lost outside the edge of waveguide 1600. However, this light loss only results in a relatively small reduction in the efficiency of the eyepiece zone. At the same time, the point spread function of eyepiece waveguide 1600 shows that it is very sharp, with only 2.5 to 5 minutes of blur.

[0271] Figures 16A to 16M The eyepiece waveguide 1600 is shown with an MPE region 1650 having three allowed propagation directions for each input beam. However, other embodiments of the MPE region can be designed to allow each input beam to have further more propagation directions. Figures 17A to 17G These figures show an eyepiece waveguide 1700 having the same macroscopic design as the eyepiece waveguide 1600. That is, the eyepiece waveguide 1700 includes an ICG region 1740, an MPE region 1750, and an EPE region 1760, all of which are arranged in the same manner as the eyepiece waveguide 1600. Figure 16A The corresponding regions are arranged in the same manner as shown in eyepiece waveguide 1600. However, eyepiece waveguide 1700 differs in the microscopic design of its MPE region 1750.

[0272] Figure 17A A portion of an example 2D grating and its associated grating vectors that can be used in the MPE region 1750 of the eyepiece waveguide 1700 is shown. The 2D periodic grating 1750 can be a spatial grid of diffraction features whose periodic directions are u and v. As already discussed, such a 2D periodic grating is associated with elementary grating vectors G and H. As an example, the 2D periodic grating 1750 can be designed or formed by superimposing two sets of 1D periodic grating lines (although the 2D periodic grating can alternatively be formed by two sets of 1D periodic grating lines located, for example, at the same time). Figure 17A The first set of grating lines 1756 may be repeated along a direction of a base grating vector G. The base grating vector G may have a magnitude equal to 2π / a, where a is a period of the first set of grating lines 1756. Figure 17BThe 2D grating shown is also associated with harmonics of the first fundamental grating vector G. These harmonics include -G and higher order harmonics, such as 2G, -2G, etc. A second set of grating lines 1757 can repeat along the direction of the fundamental grating vector H. The fundamental grating vector H can have a magnitude equal to 2π / b, where b is the period of the second set of grating lines 1657. Figure 17B The 2D grating shown is also associated with harmonics of a second fundamental grating vector, H. These harmonics include -H and higher order harmonics, such as 2H, -2H, etc. Moreover, as already discussed, any 2D periodic array of diffraction features will have associated grating vectors that point in directions determined by integer linear combinations (superpositions) of the fundamental grating vectors. In this case, these superpositions result in additional grating vectors. These include, for example, -G, -H, H+G, HG, GH, and -(H+G). Although Figure 17A Only first order grating vectors associated with the 2D diffraction grating and their superpositions are shown, but higher order grating vectors may also be present.

[0273] Figure 17B FIG1 is a k-space diagram illustrating the k-space operation of the MPE region 1750 of the eyepiece waveguide 1700. The k-space diagram includes a shaded FOV rectangle located near the 9 o'clock position of the k-space annulus. This is the location of the FOV rectangle after the ICG region 1740 has coupled the input beam into the eyepiece waveguide 1700 and redirected it to the MPE region 1750. Figure 17B shows how the 2D grating in the MPE region 1750 is used Figure 17AThe grating vectors shown translate the FOV rectangle. Since there are eight grating vectors, the MPE region 1750 attempts to translate the FOV rectangle to eight possible new positions in the k-space map. Five of these eight possible positions fall outside the perimeter of the k-space map. These positions are shown as unshaded FOV rectangles. Since k-vectors outside the perimeter of the k-space map are not allowed, none of these five grating vectors will cause diffraction. However, there are three grating vectors (i.e., -H, -G, and -(H+G)) that cause the FOV rectangle to translate to a new position within the boundaries of the k-space map. One of these positions is located near the 6 o'clock position in the k-space ring, another is located near the 12 o'clock position, and the last is located near the 3 o'clock position. Since the k-vectors at these positions are allowed and do cause guided propagation modes, the FOV rectangles at these positions are shaded to indicate that the beam is diffracted into these three states. Therefore, a light beam entering the MPE region 1750 at a propagation angle indicated by the FOV rectangle located near the 9 o'clock position of the k-space ring is diffracted into all states indicated by the other three shaded FOV rectangles (i.e., the FOV rectangle located near the 12 o'clock position, the FOV rectangle located near the 3 o'clock position, and the FOV rectangle located near the 6 o'clock position).

[0274] Although not shown, similar k-space diagrams can be drawn to illustrate the k-space manipulation of the MPE region 1750 for beams traveling at propagation angles indicated by the FOV rectangles located near the 12 o'clock position, near the 3 o'clock position, and near the 6 o'clock position of the k-space annulus. These k-space diagrams would show that the 2D diffraction grating in the MPE region 1750 diffracts these beams into Figure 17B The shaded FOV rectangle in the ring of the k-space map in indicates the total remaining state.

[0275] Figure 17C is a k-space diagram illustrating the k-space operation of the eyepiece waveguide 1700. The eyepiece waveguide 1700 can receive input beams that propagate generally along the -z direction and are incident on the ICG region 1740 of the waveguide 1700 from an external source. These input beams are represented by a k-space diagram at the origin of the k-space diagram. z The ICG region 1740 then diffracts the input beams so that they are directed to have a propagation angle centered about a propagation direction corresponding to the center point of the FOV rectangle located near the 9 o'clock position of the k-space ring.

[0276] The diffracted beams enter MPE region 1750, where they can have multiple interactions. During each generation of interaction, a portion of the power of each beam continues to propagate through MPE region 1750 in the same direction. For example, in the first generation of interaction, this corresponds to the portion of the beam's power remaining in the state indicated by the FOV rectangle located near the 9 o'clock position. Other portions of the beam's power can be diffracted along new directions. In addition, in the first generation of interaction, this produces corresponding diffracted beams whose diffraction angles are centered about the propagation directions corresponding to the center points of the FOV rectangle located near the 12 o'clock position, the center point of the FOV rectangle located near the 3 o'clock position, and the center point of the FOV rectangle located near the 6 o'clock position of the k-space annulus.

[0277] The diffracted beam remaining in the MPE region 1750 after each interaction may undergo further interactions. Each of these further interactions causes a portion of the beam's power to be diffracted in the zeroth order and to continue propagating in the same direction, while a portion of the beam's power is diffracted in a new direction. This results in multiple sets of diffracted beams distributed spatially, with these diffraction gratings having Figure 17C Each propagation direction indicated by the center point of the FOV rectangles in the k-space annulus is represented by a propagation angle centered thereon. This is indicated by the double-headed arrows between each pair of FOV rectangles in the k-space annulus. In other words, a beam propagating in MPE region 1750 can transition from any propagation state represented by one of the FOV rectangles in the k-space annulus to any other of these propagation states.

[0278] When any given input beam propagates within the MPE region 1750, it is split into many diffracted beams that can only travel in four allowed directions – one for each direction represented by Figure 17C (This is true for any input beam propagating within the MPE region 1750. However, the four allowed directions will be slightly different depending on the propagation angle of each initial input beam entering the MPE region 1750.) And, since part of the power of any given input beam is diffracted into the same four propagation directions after any number of interactions with the MPE region 1750, image information is preserved across these interactions. Figures 16A to 16M The increased propagation directions allowed in the MPE region 1750 can lead to a further improvement in the illumination uniformity in the EPE region 1760 compared to the MPE region 1650 described above. Figures 17D to 17G As shown in the figure.

[0279] Figure 17Dis a diagram of the first generation interaction between the input beam and the MPE region 1750 of the eyepiece waveguide 1700. Figure 17D An input beam is shown entering the MPE region 1750 from the ICG region 1740. The input beam is shown along a path that is aligned with the path located at Figure 17C The 9 o'clock position of the k-space ring is near the center point of the FOV rectangle or the direction corresponding to the k-vector propagation.

[0280] The MPE region 1750 can include many features smaller than 1 μm. In each interaction with the MPE region, a beam of approximately 1 mm in diameter will be split into 4 beams (same diameter, but with a fraction of the original power of the input beam) that propagate in TIR along 4 different directions. One direction corresponds to the zeroth order diffraction and is the original angle within the waveguide plane. The other three directions depend on the grating vectors G and H of the MPE region 1750. As shown in the figure, the first generation interaction between the input beam and the MPE region 1750 produces four beams: a portion of the power of the input beam is reflected from only the top or bottom surface of the eyepiece waveguide 1700 as output 1 and continues to propagate along the same xy direction as the input beam (i.e., zeroth order diffraction); a portion of the power of the input beam interacts with the grating and is diffracted downward as output 2; a portion of the power of the input beam interacts with the grating and is diffracted upward as output 3; a portion of the power of the input beam interacts with the grating and is diffracted to the right as output 4. The output 2 beam is shown as being along the same direction as the grating located at Figure 17C , while the Output 3 beam is shown as propagating in a direction corresponding to the center point or k-vector of the FOV rectangle near the 6 o'clock position of the k-space ring in FIG, while the Output 3 beam is shown as propagating in a direction corresponding to the center point or k-vector of the FOV rectangle located near the 12 o'clock position, and the Output 4 beam is shown as propagating in a direction corresponding to the center point or k-vector of the FOV rectangle located near the 3 o'clock position. After this first generation of interaction, the Output 1 beam, the Output 2 beam, the Output 3 beam, and the Output 4 beam have different propagation angles, but they are still propagating within the MPE region 1750 and can therefore undergo additional interactions with the MPE region, as shown in FIG. Figures 17E to 17G Although not shown, other input beams entering the MPE region 1750 at different propagation angles will have similar behavior, but with slightly different input and output angles.

[0281] Figure 17E FIG is a diagram of the second generation interaction between the input beam and the MPE region 1750 of the eyepiece waveguide 1700. The beam associated with the first generation interaction is shown in dashed lines, while the beam associated with the second generation interaction is shown in solid lines. Figure 17DAs shown, each of the output beams Output 1, Output 2, Output 3, and Output 4 of the first generation of interactions may now undergo similar interactions with the MPE region 1750 as occurred in the previous generation. Figure 17D A portion of the power of the output 1 beam continues to propagate only in the same xy direction, while other portions of the power of the beam interact with the grating and are diffracted along directions corresponding to the FOV rectangles located near the 12 o'clock position, near the 3 o'clock position, and near the 6 o'clock position. Similarly, Figure 17D A portion of the power of the output 2 beam continues only toward the EPE region 1760, while the other portion of the power of the beam interacts with the grating and diffracts along the directions indicated by the FOV rectangles located near the 9 o'clock position, near the 12 o'clock position, and near the 3 o'clock position. Figure 17D A portion of the power of the output 3 beam continues only in the direction indicated by the FOV rectangle located near the 12 o'clock position, while other portions of the power of the beam interact with the grating and are diffracted in the directions indicated by the FOV rectangles located near the 3 o'clock position, near the 6 o'clock position, and near the 9 o'clock position. Figure 17D A portion of the power of the output 4 beam continues only in the direction indicated by the FOV rectangle located near the 3 o'clock position, while other portions of the power of the beam interact with the grating and are diffracted along the directions indicated by the FOV rectangles located near the 6 o'clock position, near the 9 o'clock position, and near the 12 o'clock position.

[0282] Figure 17F FIG is a diagram of the third generation interaction between the input beam and the MPE region 1750 of the eyepiece waveguide embodiment 1700. The beams associated with the first and second generation interactions are shown in dashed lines, while the beams associated with the third generation interactions are shown in solid lines. Figure 17F As shown, each output beam resulting from the second generation of interactions may again undergo similar interactions with the MPE region 1750 as occurred in the previous generations.

[0283] Figure 17Gis a diagram of the fourth generation of interactions between an input beam and the MPE region 1750 of the eyepiece waveguide embodiment 1700. The beams associated with the first, second, and third generation interactions are shown as dashed lines, while the beams associated with the fourth generation interactions are shown as solid lines. After all of these interactions, all of the resulting beams propagate along one of the following four allowed propagation directions within the MPE region 1750 for any given input beam: the direction corresponding to the FOV rectangle located near the 9 o'clock position; the direction corresponding to the FOV rectangle located near the 12 o'clock position; the direction corresponding to the FOV rectangle located near the 3 o'clock position; or the direction corresponding to the FOV rectangle located near the 6 o'clock position of the k-space annulus. Although there are nodes where some beams can intersect each other while propagating through the MPE region 1750, the locations of these nodes have a greater impact than Figures 16A to 16M The case of the MPE region 1650 shown is a further more complex distribution. Furthermore, these nodes are further less likely to cause interference between two in-phase beams. Therefore, this MPE region 1750 can result in a further more uniform illumination of the EPE region 1760.

[0284] In summary, the MPE region described in this article has some or all of the following advantages: the MPE region can expand the image pupil in multiple directions at once; the MPE region can produce a dense, non-periodic array of output pupils; the MPE region can reduce interference effects between light paths passing through the waveguide; and the MPE-based eyepiece waveguide can achieve improved brightness uniformity with high image clarity while reducing high-frequency fringes.

[0285] Example AR eyepiece waveguide with multiple distinct regions for replicating the input beam

[0286] Figure 18A An example eyepiece waveguide 1800 is shown having an ICG region 1840, two orthogonal pupil expander (OPE) regions 1850a, 1850b, and an exit pupil expander (EPE) region 1860. Figure 18A Also included is a k-space diagram illustrating the role of each of these components of the eyepiece waveguide 1800 in k-space. The ICG region 1840, OPE regions 1850a, 1850b, and EPE region 1860 of the eyepiece waveguide 1800 include various diffraction features that couple an input beam into the eyepiece waveguide 1800 for propagation through guided modes, replicate the beam in a spatially distributed manner, and cause the replicated beam to exit the eyepiece waveguide and be projected toward the user's eye. In particular, the eyepiece waveguide 1800 includes multiple distinct and / or discontinuous regions for replicating the input beam. The replicated beams from these different regions can be recombined in a common exit pupil region.

[0287] Figure 18AThe eyepiece waveguide 1800 shown is similar to Figure 14A The eyepiece waveguide 1400 is shown, except that the eyepiece waveguide 1800 includes two (instead of one) OPE regions 1850a and 1850b. Recall that the ICG region 1440 in the eyepiece waveguide 1400 diffracts the input beam into +1 and -1 diffraction orders, but the beam in one of these diffraction orders propagates out of the OPE region 1450 and is ultimately lost from the eyepiece waveguide. Therefore, a portion of the light from the input beam is lost. Figure 18A The eyepiece waveguide 1800 shown solves this problem by including two OPE regions 1850a, 1850b, one located on either side of the ICG region 1840. In this way, the eyepiece waveguide 1800 can utilize the +1 and -1 diffraction orders of the ICG 1840.

[0288] The operation of the ICG region 1840 is similar to that of Figure 14A and 14B The operations described in ICG area 1440. Figure 14B The same k-space image KSD1 shown in FIG is also the same as the incident Figure 18A FIG. 18 is an illustration of the FOV rectangle corresponding to the input beam group on the ICG region 1840 in FIG. That is, before the input beam is incident on the ICG region 1840, the FOV rectangle is centered at the origin of the k-space map.

[0289] Figure 18A The k-space diagram KSD2 in FIG. 1 shows the operation of the ICG region 1840 in k-space. Figure 14B As discussed in the corresponding k-space diagram in , the ICG region 1840 is associated with two grating vectors that translate the FOV rectangle to the 3 o'clock position and the 9 o'clock position within the k-space annulus, respectively. The translated FOV rectangle at the 3 o'clock position represents the diffracted beam propagating toward the right OPE region 1850b, while the translated FOV rectangle at the 9 o'clock position represents the diffracted beam propagating toward the left OPE region 1850a.

[0290] The operation of the left OPE region 1850a is also similar to that of Figure 14A and 14B The operation of the OPE region 1450 in FIG. 14 is described in detail in FIG. 14. K-space diagram KSD3a illustrates the k-space operation of the OPE region 1850a on the left and shows that its diffraction grating translates the FOV rectangle from the 9 o'clock position to the 6 o'clock position in the k-space annulus. The FOV rectangle at the 6 o'clock position represents the diffracted beam propagating along the -y direction toward the EPE region 1860.

[0291] The operation of right OPE region 1850b is similar to that of left OPE region 1850a, except that the grating vector associated with right OPE region 1850b is mirrored about the vertical line relative to the grating vector associated with left OPE region 1850a. This is due to the fact that the lines of the diffraction grating in right OPE region 1850b are mirrored about the vertical line relative to the lines of the diffraction grating in left OPE region 1850a. Due to this orientation of the lines of the diffraction grating in right OPE region 1850b, the effect of the grating in k-space is to translate the FOV rectangle from the 3 o'clock position on the k-space annulus to the 6 o'clock position, as shown in k-space diagram KSD3b. The translated FOV rectangles in KSD3a and KSD3b are located at the same position on the k-space annulus at 6 o'clock. Therefore, although the power of each input beam is split into +1 and -1 diffraction orders by the ICG region 1840, and these different diffraction orders travel along different paths through the eyepiece waveguide 1800, they still arrive at the EPE region 1860 at the same propagation angle. This means that the separated diffraction orders of each input beam that travels along different propagation paths through the eyepiece waveguide 1800 ultimately leave the EPE region 1860 at the same angle and therefore represent the same point in the projected image.

[0292] Finally, the operation of the EPE region 1860 is also similar to that of Figure 14A and 14B 1850a and 1850b.

[0293] Figure 18B and 18C Shown Figure 18A A top view of the EPE region 1860 of the eyepiece waveguide 1800 is shown. The EPE region 1860 is supported directly in front of the user's eye 210. As discussed elsewhere herein (see Figure 12A and 12B ), the EPE region 1860 projects multiple sets of replicated output beams, each set of replicated output beams having a propagation angle corresponding to one of the input beams projected into the eyepiece waveguide.

[0294] Figure 18BOne of these groups of replicated output beams is shown. In this particular case, the replicated output beams 1861 exit the EPE region 1860 in a manner that travels from left to right. In other words, the replicated output beams 1861 have a propagation direction with a component in the +x direction. This propagation angle of the replicated output beams 1861 causes some of the output beams to have a greater tendency to intersect the user's eye 210 than other output beams. In particular, due to the central position of the eye 210 and the propagation of the beams from left to right, the replicated output beams 1861 that exit from the left portion of the EPE region 1860 have a greater tendency to intersect the user's eye 210. These beams are shown as solid lines. At the same time, the replicated output beams 1861 that exit from the right portion of the EPE region 1860 have a greater tendency to miss the eye 210. These beams are shown as dashed lines.

[0295] Figure 18B Also included is a k-space diagram KSD5 showing the state of the output beam in k-space after the EPE region has translated the FOV rectangle back to the origin of the diagram. The FOV rectangle is shown as two halves. Each half represents half of the horizontal field of view of the eyepiece waveguide 1800. The shaded right half 1832 of the FOV rectangle is included in the +k x k vectors with components in the direction. These k vectors are related to Figure 18B The k-vectors corresponding to the output beams 1861 of the type shown as propagating from left to right exiting the EPE region 1860 are shown. Although only one set of replicated output beams 1861 are shown as exiting the EPE region 1860, all output beams whose k-vectors are located in the shaded right half 1832 of the FOV rectangle will similarly exit the EPE region with a propagation direction from left to right. Thus, for all output beams whose k-vectors are located in the shaded right half 1832 of the FOV rectangle, those beams exiting from the left side of the EPE region 1860 have a greater tendency to intersect the eye 210 than those exiting from the right side of the EPE region.

[0296] Figure 18C Another set of replicated beams 1862 are shown exiting the EPE region 1860 of the eyepiece waveguide 1800. However, in this case, the replicated output beams 1862 travel from right to left in the EPE region 1860. In other words, the replicated output beams 1862 have a propagation direction with a component in the -x direction. This propagation angle of the replicated output beams 1862 results in observations that are consistent with the observations of the eyepiece waveguide 1800. Figure 18B That is, for output light beams 1862 propagating from right to left, light beams exiting the right portion of the EPE region 1860 (shown as solid lines) have a greater tendency to intersect the eye 210, while those exiting the left portion of the EPE region (shown as dashed lines) have a greater tendency to miss the eye.

[0297] refer to Figure 18C The k-space diagram KSD5 included in FIG. 5 , the output beams whose k-vectors are located in the shaded left half 1831 of the FOV rectangle are those with Figure 18C Output beams are shown as propagating right to left as they exit the EPE region 1860. Although all of the output beams whose k-vectors lie within the shaded left half 1831 of the FOV rectangle have different angles of propagation, they all share the characteristic that beams exiting the right side of the EPE region 1860 have a greater tendency to intersect the eye 210 than output beams exiting the left side of the EPE region.

[0298] from Figure 18B and 18C It can be concluded that, based on the beams that actually enter the user's eye 210, half of the EPE area 1860 contributes primarily to half of the horizontal field of view, while the other half of the EPE area contributes primarily to the other half of the horizontal field of view. Based on this observation, the field of view projected through the eyepiece waveguide can be extended in at least one dimension beyond the range of propagation angles supported by the eyepiece in guided mode because a full FOV rectangle does not have to be projected from every portion of the EPE area 1960. This is in Figure 19 Shown in.

[0299] Example AR eyepiece waveguide with extended field of view

[0300] Figure 19 An embodiment of an eyepiece waveguide 1900 with an extended field of view is shown. The eyepiece waveguide 1900 includes an ICG region 1940, a left OPE region 1950a, a right OPE region 1950b, and an EPE region 1960. At the macro level, Figure 19 The eyepiece waveguide 1900 shown can be used with Figure 18A The eyepiece waveguide 1800 is shown to be identical. However, some of the diffractive features in the eyepiece waveguide 1900 may be designed to have features that allow for an increased field of view in at least one dimension. Figure 19 These features can be clearly understood from the k-space operation of the eyepiece waveguide 1900 shown in the k-space diagram shown.

[0301] Figure 19 The k-space image shown has a Figure 18A The k-space diagram shown is a larger FOV rectangle. This is because Figure 18AThe FOV rectangles in the k-space diagram of are constrained to have no dimension larger than the width of the k-space annulus. This constraint ensures that these FOV rectangles can fit completely within the k-space annulus at any position around the annulus, so all beams represented by the k-vectors in the FOV rectangles can undergo guided propagation within the eyepiece waveguide 1800 while propagating in any direction within the eyepiece plane. However, in Figure 19 In an example embodiment, at least one dimension of the FOV rectangle (e.g., k x In some embodiments, one or more dimensions of the FOV rectangle can be up to 20%, up to 40%, up to 60%, up to 80%, or up to 100% larger than the width of the k-space annulus.

[0302] for Figure 19 In the particular embodiment shown in the k-space diagram of FIG, the horizontal dimension of the FOV rectangle is wider than the k-space annulus. The horizontal dimension of the FOV rectangle corresponds to the horizontal spread of the propagation angle of the input light beam projected into the eyepiece waveguide. Therefore, since the eyepiece waveguide 1900 is shown as being capable of being used with a FOV rectangle having a larger horizontal dimension, this means that the horizontal field of view of the eyepiece waveguide is increased. For the case of an eyepiece waveguide with a refractive index of 1.8 (surrounded by air), Figure 18A The eyepiece waveguide 1800 shown is generally capable of achieving a 45°×45° FOV, while Figure 19 The eyepiece waveguide 1900 shown is capable of achieving a FOV of up to 90°×45°, but certain embodiments of the eyepiece waveguide can be designed to achieve a smaller FOV of approximately 60°×45° to meet typical eyepiece volume design constraints—it may be advantageous to send some portion of the FOV to both sides of the eyepiece waveguide to provide an eyepiece of sufficient size—and to avoid screendoor artifacts caused by sparsely spaced output beams. Although the techniques for extending the field of view of the eyepiece waveguide 1900 are described in the context of an extended horizontal field of view, the same techniques can also be used to extend the vertical field of view of the eyepiece waveguide 1900. Moreover, in later embodiments, similar techniques for extending both the horizontal and vertical fields of view of the eyepiece waveguide are shown.

[0303] By viewing Figure 19 As can be seen from the k-space diagram, although the FOV rectangles shown may not fit completely within the k-space ring when located at certain positions around the ring, they may still fit completely within the ring when located at other positions. For example, if one dimension of the FOV rectangle is larger than the width of the k-space ring, then the FOV rectangle may not fit completely within the ring when it is located on or near the axis of the enlarged size: when the k-space ring is larger than the width of the k-space ring, the FOV rectangle may not fit completely within the ring. x The FOV rectangle whose size is larger than the width of the k-space ring is located at k xWhen the FOV rectangle is at or near the axis (i.e., at or near the 3 o'clock and 9 o'clock positions), the FOV rectangle may not fit completely within the ring; similarly, when k y The FOV rectangle whose size is larger than the width of the k-space ring is located at k y When the FOV rectangle is at or near the opposite axis (i.e., at or near the 12 o'clock and 6 o'clock positions), the FOV rectangle may not fit completely within the ring. However, when such a FOV rectangle is at or near the opposite axis, it may still fit completely within the k-space ring: when k x The FOV rectangle whose size is larger than the width of the k-space ring is located at k y When the k axis is at or near the 12 o'clock and 6 o'clock positions, the FOV rectangle can still fit completely within the ring; similarly, when k y The FOV rectangle whose size is larger than the width of the k-space ring is located at k x When the k-space ring is at or near the axis (i.e., at or near the 3 o'clock and 9 o'clock positions), the FOV rectangle can still fit completely within the ring. This is because there is more area in the azimuthal direction than in the radial direction within the k-space ring to accommodate a larger FOV rectangle.

[0304] The radial dimension of the k-space ring corresponds to the range of propagation angles of the supported guided propagation mode in the direction perpendicular to the waveguide plane (i.e., the thickness direction). This range of propagation angles is limited by Snell's law and the requirements that must be met for TIR to occur. In contrast, the expansion of the k-vector in the azimuthal dimension of the k-space ring corresponds to the expansion of the propagation angle in the in-plane direction of the planar waveguide. Because the expansion of the in-plane propagation angle of the planar waveguide is not limited by the same constraints as the thickness direction, a wider range of beam propagation angles can be supported.

[0305] Furthermore, the expansion of the propagation angle in the thickness direction of the eyepiece waveguide can be transformed into an expansion of the propagation angle in the in-plane direction, and vice versa. When the diffraction grating (or other set of diffraction features) translates the FOV rectangle from one position in the k-space annulus to another position so that the group of beams represented by the FOV rectangle then propagates in the new direction, this can also cause some of the beams that were previously expanded in the thickness direction of the planar waveguide to instead expand in the in-plane direction, and vice versa. This can be seen, for example, when the diffraction grating translates the FOV rectangle from the 9 o'clock position in the k-space annulus to the 6 o'clock position. At the 9 o'clock position, the beams are in the k-space annulus. x The expansion in the direction corresponds to the physical expansion in the thickness direction of the waveguide, since at this location, k x The direction corresponds to the radial direction of the k-space ring. However, at the 6 o'clock position, the beam is in the k x The expansion in the direction corresponds to the physical expansion in the in-plane direction of the waveguide, since at this location, kx The direction corresponds to the azimuthal direction of the k-space ring.

[0306] Using these observations, the FOV of the eyepiece waveguide can be increased by: dividing the FOV rectangle into multiple subsections; using diffractive features to replicate the beams belonging to the multiple subsections of the FOV in a spatially distributed manner; and using the diffractive features to reassemble the multiple subsections of the FOV at the exit pupil of the eyepiece waveguide so that the beams corresponding to each subsection of the FOV have the correct propagation angle to recreate the original image. For example, the diffractive features can be used to translate each subsection of the FOV rectangle to one or more positions in k-space so that they ultimately have the same relative position with respect to the other subsections of the FOV rectangle as in the original image.

[0307] In some embodiments, multiple sub-portions of the FOV may partially overlap with each other (e.g., different pairs of FOV sub-portions may include some of the same input beams), as this may help alleviate constraints on reassembling the full FOV at the exit pupil of the waveguide and may help ensure that all beams are in. For example, in some embodiments, a pair of sub-portions of the input image FOV may overlap by no more than 10%, no more than 20%, no more than 30%, no more than 40%, no more than 50%, or more.

[0308] Figure 19 The k-space map KSD2 in FIG. 1 shows the k-space manipulation of the ICG region 1940 on the input beam projected into the eyepiece waveguide 1900. As discussed elsewhere herein, the input beam projected into the eyepiece waveguide 1900 can be represented by a FOV rectangle centered at the origin of the k-space map KSD2. The ICG region 1940 translates the position of the FOV rectangle in the k-space map based on its associated grating vector. Figure 18A In the case of the ICG region 1840 shown in FIG. 1 , the ICG region is designed so that the associated grating vectors G1 and G -1 has a size equal to the distance from the origin of the k-space map to the midpoint of the k-space ring. This results in the FOV rectangle being centered within the k-space ring. However, Figure 19 The ICG region 1940 shown can be designed to have a larger grating vector. Moreover, as already discussed, the set of input beams projected into the eyepiece waveguide 1900 can have at least one dimension in k-space that is greater than the width of the k-space ring.

[0309] In some embodiments, the ICG region 1940 may be designed so that its grating vectors G1, G -1The expanded FOV rectangle is translated far enough from the origin of the k-space map so that no part of the expanded FOV rectangle lies within the inner disk of the k-space map. To achieve this goal with a FOV rectangle whose horizontal dimension is twice the width of the k-space annulus, the raster vectors G1, G2, and G3 of ICG1940 are -1 The size of needs to be approximately equal to the radius of the outer disk of the k-space map. At the same time, in order to achieve this goal with a FOV rectangle whose horizontal dimension is only slightly larger than the width of the k-space annulus, the grating vectors G1, G2 of the ICG region 1940 are -1 The size of needs to be larger than the distance from the origin of the k-space map to the midpoint of the k-space ring. Mathematically, this means that

[0310]

[0311] This gives

[0312]

[0313] (Note: This formula also applies to other eyepiece waveguide embodiments described herein, such as those shown in Figures 20 to 22 and described below.)

[0314] In other words, this technique for extending the field of view of the eyepiece waveguide 1900 means that the grating vectors G1, G2 of the ICG region 1940 are -1 is designed to be longer than in the embodiment where the field of view is constrained in all dimensions by the range of propagation angles that can fit within the radial dimensions of the k-space annulus of a given eyepiece waveguide. -1 The length of , therefore, means that the spacing of the ICG regions 1940 is smaller than that conventionally used for light with a given angular frequency ω to ensure that all input beams can be diffracted into guided modes.

[0315] Of course, according to Figure 19 In the embodiment shown, the larger FOV rectangle size and the longer raster vectors G1, G -1This results in some portions of the translated FOV rectangle extending beyond the perimeter of the large disk in k-space after being diffracted by the ICG region 1940. Since k-vectors outside of this disk are not allowed, input beams corresponding to these k-vectors are not diffracted by the ICG region 1940. Instead, only input beams corresponding to k-vectors in the shaded portion of the translated FOV rectangle in KSD2 enter the guided propagation mode within the eyepiece waveguide 1900. Input beams that are diffracted into the +1 order by k-vectors located outside the outer disk of the k-space diagram are not allowed to diffract and are therefore lost. Similarly, input beams that are diffracted into the -1 order by k-vectors located outside the outer disk of the k-space diagram are not allowed to diffract and are therefore lost. Fortunately, the beam lost from each of these diffraction orders is not the same beam. This allows the full field of view to be restored at the EPE region 1960. Even though the truncated FOV rectangle at the 3 o'clock position of the k-space map KSD2 and the truncated FOV rectangle at the 9 o'clock position do not include the complete input beam set, the complete input beam set can be restored when these truncated FOV rectangles are properly reorganized at the EPE region 1960.

[0316] K-space diagrams KSD3a and KSD3b illustrate the k-space operation of the diffraction grating in the left OPE region 1950a and the right OPE region 1950b, respectively. Figure 18A As discussed, these OPE regions may include diffraction gratings oriented to translate the FOV rectangles at the 3 and 9 o'clock positions to the 6 o'clock position. Figure 19 In the embodiment shown, in order to achieve this, the orientation of the diffraction gratings in the OPE regions 1950a, 1950b needs to be adjusted. Specifically, since the grating vectors G1, G2 associated with the ICG region 1940 -1 The FOV rectangle may no longer terminate at the midpoint of the k-space ring in the 3 o'clock and 9 o'clock positions, and therefore, the size and direction of the raster vector associated with the OPE region may need to be adjusted to translate the FOV rectangle to a position at the 6 o'clock position (e.g., along the k-space ring). y direction centered in the k-space ring). These adjustments may be achieved by changing the orientation of the grating lines in the OPE regions 1950a, 1950b and / or by changing their grating period Λ, compared to the OPE regions in embodiments without an expanded FOV.

[0317] The right shaded portion of the FOV rectangle in KSD3a represents the first sub-portion of the FOV, while the left shaded portion of the FOV rectangle in KSD3b represents the second sub-portion of the FOV. In the embodiment shown, these FOV sub-portions overlap in the central region of the FOV rectangle.

[0318] k-space diagram KSD3a shows that when the FOV rectangle at the 9 o'clock position is translated to the 6 o'clock position, there are only beams corresponding to the shaded area on the right side of the FOV rectangle. k-space diagram KSD3b shows the same phenomenon, except that the missing beams are beams whose k-vectors are on the opposite side of the FOV rectangle. Finally, k-space diagram KSD4 shows that when the two truncated FOV rectangles are superimposed at the 6 o'clock position of the k-space annulus, the unshaded portion of the FOV rectangle is filled, which means that all of the beams that make up the complete FOV of the input image are now present and can be projected from the eyepiece waveguide 1900 toward the user's eye via the diffraction grating in the EPE region 1960. Similar to Figure 18A In the embodiment shown in FIG4 , EPE region 1960 translates the FOV rectangle back to the origin in k-space map KSD4. Importantly, the two truncated FOV rectangles are translated from the 9 o'clock and 3 o'clock positions to the 6 o'clock position in a manner that maintains the relative positions of the shaded regions within the original FOV rectangle. This ensures that the beams in each subsection of the FOV have the correct propagation angles to reproduce the original image.

[0319] Physically, this means that the eyepiece waveguide 1900 divides the image field of view into multiple parts. Light beams corresponding to each of these parts of the image field of view propagate along different paths through the eyepiece waveguide 1900, where they can be replicated in a spatially distributed manner by different OPE regions 1950a, 1950b. Ultimately, the separated parts of the image field of view are recombined in the EPE region 1960 for projection toward the user's eye.

[0320] In some embodiments, the various diffraction gratings of the eyepiece 1900 may be designed so that there is overlap between the subsets of light beams provided by the various OPE regions 1950a, 1950b to the EPE region 1960. However, in other embodiments, the diffraction gratings may be designed so that each OPE region 1950a, 1950b provides a unique subset of light beams required to completely recreate the input image.

[0321] Example AR eyepiece waveguide with extended field of view and overlapping MPE and EPE regions

[0322] although Figure 19 An embodiment of an eyepiece waveguide with an extended FOV is shown that uses an OPE region to replicate the input beam, but other embodiments may advantageously use an MPE region. Figures 20A to 20L One such example embodiment is shown.

[0323] Figure 20AAn embodiment of an extended FOV eyepiece waveguide 2000 is shown having an MPE region 2050 overlapping an EPE region 2060. The eyepiece waveguide 2000 can achieve an extended field of view that is greater than the range of propagation angles supported by the guided propagation mode in the thickness direction of the waveguide. The eyepiece waveguide 2000 has a first surface 2000a and a second surface 2000b. As discussed further below, different diffraction features can be formed on or in the opposing surfaces 2000a, 2000b of the eyepiece waveguide 2000. The two surfaces 2000a, 2000b of the eyepiece waveguide 2000 are arranged in a manner that allows for the formation of a plurality of diffraction features. Figure 20A 00a and the second surface 2000b are shown as being displaced relative to each other in the xy plane. However, this is merely to facilitate the illustration of the different diffractive features formed on or in each surface; it should be understood that the first surface 2000a and the second surface 2000b are aligned with each other in the xy plane. Additionally, while the MPE region 2050 and the EPE region 2060 are shown as being of the same size and precisely aligned in the xy plane, in other embodiments, they may have slightly different sizes and may be partially misaligned. In some embodiments, the MPE region 2050 and the EPE region 2060 overlap each other by at least 70%, at least 80%, at least 90%, or at least 95%.

[0324] The eyepiece waveguide 2000 includes an ICG region 2040, an MPE region 2050, and an EPE region 2060. The ICG region 2040 receives a set of input light beams from a projector device. As described elsewhere herein, the input light beams can propagate from the projector device generally along the z-direction through free space until they are incident on the ICG region 2040. The ICG region 2040 diffracts these input light beams such that all or at least some of them enter a guided propagation mode within the eyepiece waveguide 2000. The grating lines of the ICG region 2040 can be oriented to guide the diffracted light beams along the -y-direction toward the MPE region 2050.

[0325] The MPE region 2050 may include a plurality of diffraction features that exhibit periodicity along multiple axes. The MPE region 2050 may consist of an array of scattering features arranged in a 2D grid. Individual scattering features may be, for example, depressions or protrusions of any shape. The 2D array of scattering features has associated grating vectors that are derived from the reciprocal grid of the 2D grid. As an example, the MPE region 2050 may be a 2D diffraction grating consisting of a cross grating having grating lines that repeat along two or more periodic directions. The diffraction features that make up the MPE region 2050 may have a relatively low diffraction efficiency (e.g., 10% or less). As discussed herein, this allows a light beam to be replicated in multiple directions in a spatially distributed manner as it propagates through the MPE region 2050.

[0326] Figure 20B A portion of an example 2D grating and its associated grating vectors that can be used in the MPE region 2050 of the eyepiece waveguide 2000 is shown. A crossed grating is shown, but the 2D periodic grating can instead be composed of individual scattering features located, for example, at the intersections of the grating lines shown. The 2D grating has a first set of grating lines 2056 that repeat along a first periodic direction. These grating lines 2050 have associated base grating vectors G that point along the periodic direction of the first set of grating lines 2056 and have a magnitude equal to 2π / a, where a is the period of the first set of grating lines 2056. Figure 20B The 2D grating shown is also associated with harmonics of the first fundamental grating vector G. These harmonics include -G and higher-order harmonics, such as 2G, -2G, and so on. The 2D grating in the MPE region 2050 also has a second set of grating lines 2057 that repeat along a second periodic direction. In some embodiments, the first and second periodic directions are not perpendicular. The second set of grating lines 2057 has an associated fundamental grating vector H that points along the periodic direction of the second set of grating lines and has a magnitude equal to 2π / b, where b is the period of the second set of grating lines 2057. Figure 20B The 2D grating shown is also associated with harmonics of a second fundamental grating vector, H. These harmonics include -H and higher order harmonics, such as 2H, -2H, etc. Finally, any 2D array of diffractive features also has associated grating vectors that point in directions determined by integer linear combinations (superpositions) of the fundamental grating vectors G and H. In the embodiment shown, these superpositions result in the addition of Figure 20B These include, for example, -G, -H, H+G, HG, GH, and -(H+G). Figure 20B Only first order grating vectors associated with the 2D diffraction grating and their superpositions are shown, but higher order grating vectors may also be present.

[0327] Figure 20C : is a k-space diagram KSD1, which shows the k-space operation of the ICG region 2040 of the eyepiece waveguide 2000. The FOV rectangle centered at the origin of KSD1 represents the input beam group projected by the projector device toward the ICG region 2040. The FOV rectangle is in k x The dimension in the direction represents the FOV of the input beam along the x-direction, and the FOV rectangle is in k y The dimension in the direction represents the FOV of the input beam along the y direction. As shown in the figure, in this particular embodiment, the k of the FOV rectangle is x The size is larger than the width of the k-space ring.

[0328] Because according to Figure 20AIn the physical layout of the eyepiece waveguide 2000 shown, the MPE region 2050 is located in the -y direction from the ICG region 2040, so the diffraction grating in the ICG region 2040 can be designed to diffract the input beam along this direction. Figure 20C KSD1 in FIG. 2 shows that the ICG region 2040 translates the FOV rectangle from the origin of the k-space map to the 6 o'clock position in the k-space ring at -k y The FOV rectangle is positioned along the k-space axis. At this particular position, the wider dimension of the FOV rectangle is oriented along the azimuthal direction of the k-space annulus, so that the FOV rectangle fits completely within the annulus. This means that all beams represented by the FOV rectangle enter guided propagation modes within the eyepiece waveguide 2000 and propagate generally along the −y direction toward the MPE region 2050.

[0329] As in the other MPE regions discussed herein (eg, 1650, 1750), MPE region 2050 expands the image pupil in multiple directions by replicating the input beam in a spatially distributed manner as it propagates through it. Figures 20D to 20F 20H and 20H show this behavior of the MPE region 2050 in k-space.

[0330] Figure 20D FIG2 is a k-space diagram KSD2 showing a portion of the k-space operation of the MPE region 2050 of the eyepiece waveguide 2000. The k-space diagram includes a shaded FOV rectangle located at the 6 o'clock position of the k-space annulus. This is the location of the FOV rectangle after the ICG region 2040 has coupled the input beams into the eyepiece waveguide 2000 and diffracted them toward the MPE region 2050. Figure 20D shows how the 2D grating in the MPE region 2050 is used Figure 20B The grating vectors shown translate the FOV rectangle. Since there are eight grating vectors, the MPE region 2050 attempts to translate the FOV rectangle from the 6 o'clock position in the k-space ring to eight possible new positions in the k-space map. Five of these eight possible positions fall completely outside the perimeter of the k-space map. These positions are shown as unshaded FOV rectangles. Since k-vectors outside the perimeter of the k-space map are not allowed, none of these five grating vectors will cause diffraction. However, there are three grating vectors (i.e., G, -H, and GH) that cause the FOV rectangle to translate to a new position that is at least partially within the boundaries of the k-space map. One of the positions is at the 9 o'clock position in the k-space ring, another is at the 12 o'clock position, and the last is at the 3 o'clock position. Since the k-vectors at these positions are allowed and do cause guided propagation modes, the FOV rectangles at these positions are shaded to indicate that the beam is diffracted into these three states.

[0331] In the case of the 9 o'clock and 3 o'clock positions in the k-space ring, the translated FOV rectangle does not fit completely within the ring because their k x The size is larger than the width of the ring. Therefore, the translated FOV rectangle at these locations will be truncated, meaning that beams whose k-vectors fall outside the perimeter of the k-space map will not be guided. This is represented in KSD2 by the unshaded portions of the translated FOV rectangle at the 9 and 3 o'clock positions. This means that the beam groups extending through MPE region 2050 in the +x and -x directions, respectively, will not all include the entire original input beam group. The missing beam group propagating through MPE region 2050 in the +x direction corresponds to beams on the right side of the FOV rectangle, while the missing beam group propagating in the -x direction corresponds to beams on the left side of the FOV rectangle. However, overall, all beams that make up the FOV are still present.

[0332] The shaded portion on the right side of the translated FOV rectangle at the 9 o'clock position represents the first sub-portion of the FOV, while the shaded portion on the left side of the FOV rectangle at the 3 o'clock position represents the second sub-portion of the FOV. In the embodiment shown, these FOV sub-portions overlap in the center region of the FOV rectangle (although overlap is not required).

[0333] As already mentioned, in some embodiments, the first and second periodic axes in the 2D grating of the MPE region 2050 are not orthogonal. This, in turn, means that the basis grating vectors G and H are also non-orthogonal. This can allow the 2D grating in the MPE region 2050 to translate the FOV rectangles at the 3 and 9 o'clock positions so that the centers of these rectangles are outside the midpoint of the k-space ring, while the centers of the FOV rectangles at the 6 and 12 o'clock positions can be located at or near the midpoint of the ring. As a result, the translated FOV rectangles at the 3 and 9 o'clock positions are truncated, resulting in the FOV being divided into first and second sub-portions. This is noteworthy in the illustrated embodiment because dividing the FOV into first and second sub-portions is part of the process of increasing the FOV of the eyepiece waveguide 2000.

[0334] Figure 20E FIG3 is a k-space diagram KSD3 showing another portion of the k-space manipulation of the MPE region 2050 of the eyepiece waveguide 2000. KSD3 includes a partially shaded FOV rectangle located at the 3 o'clock position of the k-space annulus. This is the position of one of the translated FOV rectangles after the first interaction within the MPE region 2050. Figure 20E shows how the 2D grating in the MPE region 2050 is used during subsequent interaction. Figure 20BThe grating vectors shown translate the FOV rectangle. Again, since there are eight grating vectors, the MPE region 2050 attempts to translate the FOV rectangle from the 3 o'clock position in the k-space annulus to eight possible new positions in the k-space map. Five of these eight possible positions again fall outside the perimeter of the k-space map. These positions are represented by the unshaded FOV rectangles. Since k-vectors outside the perimeter of the k-space map are not allowed, none of these five grating vectors will cause diffraction. However, there are three grating vectors (i.e., G, H, and H+G) that cause the FOV rectangle to translate to a new position that is at least partially within the boundaries of the k-space map. One of these positions is at the 9 o'clock position in the k-space annulus, another is at the 12 o'clock position, and the final position is at the 6 o'clock position. Since the k-vectors at these positions are allowed and do cause guided propagation modes, the FOV rectangles at these positions are shaded to indicate that the beam is diffracted into these three states (or the zero-order diffracted beam can remain in the propagation state represented by the FOV rectangle at the 3 o'clock position).

[0335] like Figure 20E As shown, Figure 20D As a result of the first diffraction interaction in the illustrated MPE region 2050, the translated FOV rectangle at the 3 o'clock position of the k-space annulus has been truncated. Consequently, only the truncated FOV rectangle is translated to the 9 o'clock, 12 o'clock, and 6 o'clock positions of the k-space annulus. In the case of the 9 o'clock position, the FOV rectangle is further truncated, meaning that only the beam corresponding to the central shaded portion of this particular translated FOV rectangle is actually diffracted into that state.

[0336] Figure 20F Similar to Figure 20E , except that it shows the MPE area 2050 for Figure 20D Move to 9 o'clock (instead of Figure 20E The operation of the MPE region 2050 on the beam in this state is Figure 20E The mirror image of the operation shown (with respect to k y axis).

[0337] Although not shown, a similar k-space diagram can be drawn to illustrate the k-space manipulation of the MPE region 2050 for beams traveling at propagation angles indicated by the FOV rectangle located at the 12 o'clock position of the k-space annulus. This k-space diagram would show that the 2D diffraction grating in the MPE region 2050 diffracts these beams into Figure 20D 、 20E The states are represented by the FOV rectangles at the 3 o'clock, 6 o'clock, and 9 o'clock positions within the ring of the k-space map in FIG20F.

[0338] like Figures 20D to 20F As shown in the k-space diagram in , when the diffracted beam from the ICG region 2040 reaches the MPE region 2050, many replica beams are formed in a spatially distributed manner. Moreover, all of these replica beams propagate along one of the directions indicated by the FOV rectangles located at the 3 o'clock, 6 o'clock, 9 o'clock, and 12 o'clock positions in the k-space ring. The beam propagating through the MPE region 2050 can experience any number of interactions with the diffraction features of the MPE region, resulting in any number of changes in propagation direction. In this way, the beam is replicated throughout the MPE region 2050 along the x-direction and the y-direction. This is indicated by Figure 20A The arrow in the MPE region 2050 of the eyepiece waveguide 2000 is indicated.

[0339] Because the EPE region 2060 overlaps the MPE region 2050 in the xy plane of the eyepiece waveguide 2000, as the replicated beams propagate through the waveguide, they also interact with the EPE region 2060, reflecting back and forth between the first surface 2000a and the second surface 2000b via total internal reflection. When one of the beams interacts with the EPE region 2060, a portion of its power is diffracted and exits the eyepiece waveguide toward the user's eye, as shown in FIG. Figure 20A As shown by the arrow in the EPE region 2060 of the eyepiece waveguide 2000.

[0340] In some embodiments, the EPE region 2060 includes diffraction gratings whose lines are oriented perpendicularly relative to the lines of the diffraction gratings comprising the ICG region 2040. Examples of this are shown in FIG. Figure 20A , where the ICG region 2040 has grating lines that extend along the x-direction and repeat periodically along the y-direction, while the EPE region 2060 has grating lines that extend along the y-direction and repeat periodically along the x-direction. Advantageously, the grating lines in the EPE region 2060 are oriented perpendicularly relative to the grating lines in the ICG region 2040 because this helps ensure that the light beam interacts with the MPE region 2050 before being coupled out of the eyepiece waveguide 2000 by the EPE region 2060. This behavior is shown in FIG. Figure 20G is shown in k-space.

[0341] Figure 20G is a k-space diagram KSD5, which shows Figure 20A2060 in the eyepiece waveguide 2000. As already discussed, the light beam propagates through the MPE region 2050 in all directions indicated by the FOV rectangles located at the 12 o'clock, 3 o'clock, 6 o'clock, and 9 o'clock positions of the k-space annulus. Moreover, because the EPE region 2060 physically overlaps with the MPE region 2050, the light beam in all of these propagation states contacts the diffraction grating in the EPE region while expanding through the MPE region.

[0342] Since the periodic axes of the diffraction grating in the EPE region 2060 point to ±k x direction, so the raster vector associated with the EPE region also points in the same direction. Figure 20G It shows how the EPE region 2060 attempts to translate the FOV rectangles at the 12 o'clock, 3 o'clock, 6 o'clock, and 9 o'clock positions using these raster vectors. x Oriented in the θ direction, the grating vector associated with the EPE region 2060 can only translate the FOV rectangles located at the 3 o'clock and 6 o'clock positions of the k-space ring back to the origin of the k-space map. Therefore, the EPE region 2060 can only couple out beams in either of these two propagation states; the EPE region will not couple out beams propagating in the states corresponding to the FOV rectangles located at the 12 o'clock and 6 o'clock positions of the k-space ring.

[0343] It is important to note that if the periodic axis of the grating lines in the EPE region 2060 is parallel to, rather than perpendicular to, the periodic axis of the grating lines in the ICG region 2040, then the grating vector associated with the EPE region will point to ±k y direction. This in turn allows the beam to be coupled out of the EPE region in propagation states corresponding to the FOV rectangles located at the 12 o'clock and 6 o'clock positions of the k-space ring. Since the input beam arrives at the MPE / EPE region in a propagation state corresponding to the 6 o'clock position, this means that the beam can be coupled out of the EPE region 2060 before interacting with and expanding through the MPE region 2050, which is generally undesirable. The fact that the periodic axes of the grating lines in the EPE region 2060 are perpendicular to the periodic axes of the grating lines in the ICG region 2040 means that the beam will typically need to undergo at least one direction change within the MPE region before being coupled out, and possibly more. This allows for enhanced expansion of the beam within the MPE region 2050.

[0344] Figure 20H is the k-space diagram KSD6, which summarizes Figure 20A The k-space operation of the eyepiece waveguide 2000 is shown. It is essentially Figures 20C to 20G Overlay of the k-space maps shown. Again, Figure 20H The k-space diagram in FIG shows a FOV rectangle having at least one dimension that is larger than the width of the k-space annulus. In some embodiments, at least one dimension of the FOV rectangle can be up to about twice the width of the k-space annulus. In the embodiment shown, the horizontal dimension of the FOV rectangle is larger than the width of the k-space annulus, but the same technique can also be used to extend the vertical field of view.

[0345] KSD6 includes a FOV rectangle centered at the origin of the diagram. Again, this position of the FOV rectangle can describe the input beam that is projected into the eyepiece waveguide 2000 or the output beam that projects a replica of the waveguide toward the user's eye. In the embodiment shown, the operation of the ICG region 2040 in k-space is to translate the FOV rectangle downward from the center of the k-space diagram to the 6 o'clock position. As shown, the ICG region 2040 can be designed so that one of its raster vectors is along the -k y This causes the diffracted beam to propagate along the -y direction toward the MPE region 2050. Furthermore, the ICG region 2040 can be designed so that the size of its grating vector causes the FOV rectangle to be replicated to a position where the FOV rectangle fits completely within the k-space annulus at the 6 o'clock position. This can be achieved, for example, by designing the ICG region 2040 to have a spacing such that the size of its first-order grating vector is equal to the distance from the origin of the k-space map to the midpoint of the k-space annulus. Since the FOV rectangle at the 6 o'clock position is completely within the k-space annulus, all diffracted beams enter a guided propagation mode.

[0346] As already discussed, the MPE region includes multiple diffraction features that exhibit periodicity along multiple different axes. This means that the MPE region has multiple associated grating vectors that can translate the FOV rectangle from the 6 o'clock position to any of the 9 o'clock, 12 o'clock, and 3 o'clock positions. During further interaction with the MPE region 2050, the FOV rectangle can be translated back and forth between any of the 12 o'clock, 3 o'clock, 6 o'clock, and 9 o'clock positions. This is represented by the double-headed arrows between those propagation states. As Figure 20H As shown, the FOV rectangles at the 3 o'clock and 6 o'clock positions of the k-space annulus are truncated, meaning that not all beams associated with the full FOV are present in each propagation state. However, when those sub-portions of the FOV are considered together, all beams that make up the full FOV are present. Therefore, when the FOV rectangle is ultimately translated from the 3 o'clock or 6 o'clock positions back to the origin of the k-space diagram to couple beams toward the user's eye, all beams necessary to make up the full FOV of the input image are present and projected from the eyepiece waveguide 2000.

[0347] Figure 20I It shows how the light beam passes through Figure 20A FIG2000 is a diagram showing the expansion of the eyepiece waveguide 2000. A guided beam propagating from the ICG region 2040 along the −y direction into the MPE region 2050 is spatially replicated into many beams, some of which travel along the ±y directions (corresponding to the FOV rectangles at the 6 and 12 o'clock positions in the k-space annulus) and some of which travel along the ±x directions (corresponding to the FOV rectangles at the 3 and 9 o'clock positions in the k-space annulus). In this way, the beam is laterally expanded throughout the eyepiece waveguide 2000.

[0348] Figure 20J The figure shows how the diffraction efficiency of the MPE region 2050 in the eyepiece waveguide 2000 is spatially varied to improve brightness uniformity in the waveguide. In the figure, darker shading within the MPE region 2050 indicates higher diffraction efficiency, while lighter shading indicates lower diffraction efficiency. Spatial variation in the diffraction efficiency of the MPE region 2050 can be achieved by introducing spatial variations in grating properties such as grating depth, duty cycle, blaze angle, tilt angle, etc.

[0349] like Figure 20J As shown, brightness uniformity in the waveguide can be improved by designing the portion of the MPE region 2050 closer to the ICG region 2040 to have a higher diffraction efficiency. Since this is the location where the light beam enters the MPE region 2050 from the ICG region 2040, there is more light in this region. Therefore, the diffraction efficiency here can be higher, thereby more effectively diffusing the light to other portions of the MPE region 2050 where there is less light. Additionally or alternatively, multiple ICG regions can be provided at various angular positions around the periphery of the MPE region 2050 to input light at more locations, thereby improving brightness uniformity in the waveguide.

[0350] Brightness uniformity can also be improved by designing the central portion of the MPE region 2050 to have a higher diffraction efficiency along the direction of the light beam propagating from the ICG region 2040 into the MPE region 2050. Again, more light is present in this region of the MPE region 2050 because it is located along the axis of the input light from the ICG region 2040. Since more light is present in this region, the diffraction efficiency can be higher, thereby more effectively spreading the light to other portions of the MPE region 2050.

[0351] Figure 20KFIG200 shows how the diffraction efficiency of the EPE region 2060 in the eyepiece waveguide 2000 varies spatially to enhance brightness uniformity in the waveguide. Darker shading within the EPE region 2060 again indicates higher diffraction efficiency, while lighter shading indicates lower diffraction efficiency. The EPE region 2060 can be designed to have high diffraction efficiency in the peripheral region. The higher diffraction efficiency in the peripheral region of the EPE region 2060 helps to couple light out to the user's eye before it is lost at the edge of the waveguide.

[0352] Figure 20L An embodiment of an eyepiece waveguide 2000 is shown that includes one or more diffraction mirrors 2070 around the peripheral edge of the waveguide. The diffraction mirrors 2070 can receive light that propagates through the MPE / EPE region and exits the edge of the waveguide 2000. The diffraction mirrors can then diffract this light back into the MPE / EPE region so that it can contribute to the projection of an image from the eyepiece waveguide 2000. As already discussed, the MPE region 2050 allows light beams to propagate in four general directions: generally in the x-direction (i.e., as represented by the FOV rectangle at the 3 o'clock position of the k-space annulus); generally in the -x-direction (i.e., as represented by the FOV rectangle at the 9 o'clock position); generally in the y-direction (i.e., as represented by the FOV rectangle at the 12 o'clock position); and generally in the -y-direction (i.e., as represented by the FOV rectangle at the 6 o'clock position). The diffraction mirrors 2070 can be designed to diffract the light beam into one of these same propagation states.

[0353] For example, the diffraction mirror 2070 located on the left side of the eyepiece waveguide 2000 can diffract light beams incident from approximately the -x direction into a propagation state represented by the FOV rectangle located at the 3 o'clock position, so that these light beams travel back approximately along the x direction through the OPE region 2050. Similarly, the diffraction mirror 2070 located at the bottom of the eyepiece waveguide 2010 can diffract light beams incident from approximately the -y direction into a propagation state represented by the FOV rectangle located at the 12 o'clock position, so that these light beams travel back approximately along the y direction through the OPE region 2050.

[0354] Figure 20LThe k-space operation of the bottom diffraction mirror 2070 is shown. As shown in the k-space diagram, the bottom diffraction mirror 2070 can be designed to have a period that is half the grating period in the ICG region 2040. This smaller period allows the length of the associated grating vector of the bottom diffraction mirror to be twice the length of the grating vector of the ICG region 2040. Therefore, the bottom diffraction mirror can translate the FOV rectangle from the 6 o'clock position in the k-space annulus to the 12 o'clock position. Although described with respect to the eyepiece waveguide 2000, the same techniques (i.e., spatial variation of the diffraction efficiency of the OPE, MPE, EPE regions, etc., and the use of diffraction mirrors along the peripheral edges) can also be used for any of the other embodiments described herein.

[0355] Figure 20M An example embodiment of glasses 70 is shown that includes one or more instances of eyepiece waveguides 2000. A first instance of the eyepiece waveguide 2000 is integrated into the left viewing portion of the glasses 70, while a second instance of the eyepiece waveguide 2000 is integrated into the right viewing portion. In the embodiment shown, each waveguide 2000 is approximately 50 x 30 mm. 2 , but many different sizes can also be used. Each waveguide 2000 can be accompanied by a separate projector 2020 that projects an image into the corresponding waveguide. Assuming the eyepiece waveguide is made of a material with a refractive index of 1.8, some embodiments of the eyepiece waveguide 2000 are capable of achieving a FOV of up to 90° × 45°, but some embodiments of the eyepiece waveguide can be designed to achieve a smaller FOV of approximately 60° × 45° to meet typical design constraints of eyebox volume—it can be advantageous to send some portion of the FOV to both sides of the eyepiece waveguide to provide an eyebox of sufficient size—and to avoid screen door artifacts caused by sparsely spaced output beams.

[0356] Figure 20N Another example embodiment of glasses 70 is shown that includes one or more instances of eyepiece waveguide 2000. This embodiment of glasses 70 is similar to Figure 20M In the embodiment shown, only the orientation of the waveguide 2000 and accompanying projector 2020 is rotated 90° toward the temple of the eyeglasses 70. In this configuration, some embodiments of the eyepiece waveguide 2000 are capable of achieving a FOV of up to 45° × 90°, assuming the eyepiece waveguide is made of a material with a refractive index of 1.8, but certain embodiments can be designed to achieve a smaller FOV of approximately 45° × 60° to meet other design constraints.

[0357] Figure 21A Another embodiment of an eyepiece waveguide 2100 is shown having an MPE region 2150 overlapping an EPE region 2160. Figure 20A The eyepiece waveguide 2000 shown, Figure 21AThe eyepiece waveguide 2100 shown can achieve an extended field of view that can be greater than the range of propagation angles supported by the guided propagation mode in the thickness direction of the waveguide. The eyepiece waveguide 2100 has a first surface 2100a and a second surface 2100b. As discussed further below, different diffraction features can be formed on or in the opposing surfaces 2100a, 2100b of the eyepiece waveguide 2100. The two surfaces 2100a, 2100b of the eyepiece waveguide 2100 are arranged in a manner that allows for the viewing angle to be greater than the range of propagation angles supported by the guided propagation mode in the thickness direction of the waveguide. Figure 21A 00a and the second surface 2100b are shown as being displaced relative to each other in the xy plane. However, this is merely to allow the illustration to show the different diffractive features formed on or in each surface; it should be understood that the first surface 2100a and the second surface 2100b are aligned with each other in the xy plane. Additionally, while the MPE region 2150 and the EPE region 2160 are shown as having the same size and being precisely aligned in the xy plane, in other embodiments, they may have slightly different sizes and may be partially misaligned. In some embodiments, the MPE region 2150 and the EPE region 2160 overlap each other by at least 70%, at least 80%, at least 90%, or at least 95%.

[0358] and Figure 20A The eyepiece waveguide 2000 is the same as shown, Figure 21A The eyepiece waveguide 2100 shown includes an MPE region 2150 and an EPE region 2160. Figure 20A The eyepiece waveguide 2000 shown is different. Figure 21A The eyepiece waveguide 2100 shown includes two ICG regions 2140a, 2140b located on opposite sides of the MPE / EPE region, rather than a single ICG region. Each of the ICG regions 2140a, 2140b can have its own associated projector. Each of the two projectors can input a sub-portion of the complete input image FOV into the eyepiece waveguide 2100. Therefore, each of the ICG regions 2140a, 2140b can be used to couple in an input beam corresponding to a sub-portion of the FOV. These sub-portions can then be combined at the exit pupil of the eyepiece waveguide 2100.

[0359] The left ICG region 2140a receives a first set of input beams corresponding to a first sub-portion of the FOV from a first projector device, while the right ICG region 2140b receives a second set of input beams corresponding to a second sub-portion of the FOV from a second projector device. The first and second sub-portions of the FOV may be exclusive or may partially overlap. The first set of input beams may be projected toward the left ICG region 2140a approximately along the -z direction, but centered around an input beam having a propagating component in the -x direction, while the second set of input beams may be projected toward the right ICG region 2140b approximately along the -z direction, but centered around an input beam having a propagating component in the +x direction. The left ICG region 2140a diffracts the first set of input beams so that at least some of the input beams enter a guided mode that propagates along the +x direction, and the right ICG region 2140b diffracts the second set of input beams so that at least some of the input beams enter a guided mode that propagates along the -x direction. In this way, the first and second sets of input light beams corresponding to the first and second sub-portions of the FOV are coupled into the eyepiece waveguide 2100 so that they propagate toward the MPE region 2150 located between the left and right ICG regions 2140a, 2140b.

[0360] Similar to Figure 20A The eyepiece waveguide 2000 shown, Figure 21A The eyepiece waveguide 2100 shown may also include an MPE region 2150 formed on or in the first side 2100a of the waveguide and an overlapping EPE region 2160 formed on or in the second side 2100b of the waveguide. Figure 21A The MPE region 2150 in the eyepiece waveguide 2100 shown may be similar to Figure 20A The MPE region 2050 in the eyepiece waveguide 2000 is shown. That is, the MPE region 2150 may include multiple diffraction features that exhibit periodicity along multiple axes. Similarly, Figure 21A The EPE region 2160 in the eyepiece waveguide 2100 shown may be similar to Figure 20A The EPE region 2060 is shown in the eyepiece waveguide 2000. That is, the EPE region 2160 may include a diffraction grating whose periodic axis is orthogonal to the periodic axes of the two ICG regions 2140a, 2140b. Figure 21A The operation of the MPE region 2150 and the EPE region 2160 in the embodiment can also be similar to Figure 20A The operations of the MPE region 2050 and the EPE region 2060 are as follows: Figures 21B to 21D shown.

[0361] Figure 21B1 is a k-space diagram KSD1, which shows the k-space operation of the eyepiece waveguide 2100 on a first set of input beams corresponding to a first sub-portion of the FOV of the input image. The FOV rectangle centered at the origin of KSD1 represents the beams corresponding to the complete input image FOV that will be projected by the eyepiece waveguide 2100 toward the user's eye. The size of the FOV rectangle as a whole is at most about twice the width of the k-space annulus. Therefore, Figure 21A The eyepiece waveguide 2100 shown is designed to have a similar Figure 19 and Figure 20A However, the first set of input beams projected toward the left ICG region 2140a corresponds only to the shaded sub-portion of the FOV rectangle. Figure 21B As shown, the shaded portion of the FOV rectangle corresponding to the first set of input beams is the left portion of the FOV rectangle. Since the center of the shaded portion of the FOV rectangle is at -k x direction from the origin of the k-space map, so that the first set of input beams from the first projector is not centered on a beam propagating exactly along the -z direction (which would be the case if the shaded part of the FOV rectangle was centered on the origin of the k-space map), but is centered on a tilted beam having a propagating component in the -x direction.

[0362] The left ICG region 2140a can be designed so that its grating vector is along ±k x Directional orientation. The operation of the left ICG region 2140a in k-space is to translate the left shaded portion of the FOV rectangle from the center of the k-space map to the 3 o'clock position in the k-space annulus. This causes the diffracted beam to propagate approximately along the x-direction toward the MPE region 2150. In some embodiments, the left shaded portion of the FOV rectangle may constitute half or more of the FOV rectangle. Moreover, in some embodiments, the left ICG region 2140a can be designed to translate the center of the FOV rectangle to any radial position from the midpoint of the k-space annulus to the outer edge of the annulus. Furthermore, the left ICG region 2140a can be designed so that the size of its grating vector causes the FOV rectangle to be copied to a position at the 3 o'clock position where the shaded portion fits completely within the k-space annulus. This can be achieved, for example, by setting the size of the ICG grating vector to be larger than the distance from the origin of the k-space map to the midpoint of the k-space annulus. Because the shaded portion of the FOV rectangle at the 3 o'clock position is completely within the k-space annulus, the first group of input beams corresponding to the first subsection of the FOV all enter the guided propagation mode. Although the FOV rectangle located at the 3 o'clock position of the k-space ring has a right portion extending beyond the ring, the input beam corresponding to that portion of the FOV rectangle is not necessarily part of the first sub-portion of the FOV provided by its associated projector to the left ICG region 2140a.

[0363] Although the left ICG region 2140a can also diffract a portion of the first set of input beams in the opposite direction (i.e., translating the FOV rectangle to the 9 o'clock position of the k-space annulus), in the embodiment of the eyepiece waveguide 2100 shown, these particular diffracted beams will only exit from the edge of the waveguide.

[0364] The MPE region 2150 includes a plurality of diffraction features having a plurality of periodic axes. In some embodiments, the MPE region 2150 may be similar to that described with respect to Figures 20A to 20M The MPE region 2050 shown and discussed above may have multiple associated raster vectors that may translate the FOV rectangle from the 3 o'clock position of the k-space annulus to any of the 6 o'clock, 9 o'clock, and 12 o'clock positions. Figure 21B As shown, the shaded portion of the FOV rectangle at the 9 o'clock position of the k-space annulus is truncated, meaning that not all beams associated with the first sub-portion of the FOV are necessarily present in this particular propagation state.

[0365] During additional interactions with the MPE region 2150, the FOV rectangle can be translated back and forth between any of the 12 o'clock, 3 o'clock, 6 o'clock, and 9 o'clock positions. This is represented by the double-headed arrows between those propagation states in KSD1. In this way, as described herein, the first set of input beams can be replicated throughout the MPE region 2150 by undergoing multiple interactions with the diffractive features of the MPE region 2150. This is represented by Figure 21A The arrows in the OPE region 2150 of the eyepiece waveguide 2100 are shown.

[0366] Since the EPE region 2160 overlaps the MPE region 2150 in the xy plane of the eyepiece waveguide 2100, as the replica beams diffuse through the waveguide, they also interact with the EPE region 2160, thereby reflecting back and forth between the first surface 2100a and the second surface 2100b via total internal reflection. Whenever one of the replica beams interacts with the EPE region 2160, a portion of its power is diffracted and coupled out toward the user's eye, as shown in FIG. Figure 21A As shown by the arrow in the EPE region 2160 of the eyepiece waveguide 2100.

[0367] In some embodiments, the EPE region 2160 includes diffraction gratings whose lines are oriented perpendicularly relative to the lines of the diffraction gratings that make up the ICG regions 2140a, 2140b. In this particular example, because the ICG regions 2140a, 2140b have grating lines that extend along the y-direction and repeat periodically along the x-direction, the EPE region 2160 has grating lines that extend along the x-direction and repeat periodically along the y-direction. Again, it is advantageous to orient the grating lines in the EPE region 2160 perpendicularly relative to the grating lines in the ICG regions 2140a, 2140b, as this helps ensure that the light beam interacts with the MPE region 2150 before being coupled out of the eyepiece waveguide 2100 by the EPE region 2160.

[0368] Figure 21B Also shown is the k-space manipulation of the EPE region 2160 on a first set of beams corresponding to a first subsection of the FOV. As already discussed, the beams can propagate through the MPE region 2150 in any of the directions indicated by the FOV rectangles located at the 12 o'clock, 3 o'clock, 6 o'clock, and 9 o'clock positions of the k-space annulus. Moreover, since the EPE region 2160 overlaps with the MPE region 2150, beams in any of these propagation states can interact with the EPE region and be coupled out of the eyepiece waveguide 2100. Since the periodic axes of the diffraction grating in the EPE region 2160 are pointed at ±k y direction, and therefore, the raster vectors associated with the EPE region also point in the same direction. Figure 21B FIG2 shows how the EPE region 2160 translates the FOV rectangles at the 12 o'clock and 6 o'clock positions of the k-space ring back to the origin of the k-space map. Therefore, the EPE region 2160 can only couple out beams in either of these two propagation states. Figure 21B As shown, when the FOV rectangle is finally translated back to the center of the k-space map KSD1, all of the first group of light beams constituting the first sub-portion of the FOV exist and are projected toward the user's eyes.

[0369] Figure 21C 2 is a k-space diagram KSD2 illustrating the k-space manipulation of the eyepiece waveguide 2100 on a second set of input beams corresponding to a second sub-portion of the FOV of the input image. Again, the FOV rectangle centered at the origin of KSD2 represents the beams corresponding to the complete input image projected by the eyepiece waveguide 2100 toward the user's eye. However, the second set of input beams projected toward the right ICG region 2140b corresponds only to the shaded sub-portion of the FOV rectangle. Figure 21C As shown, the shaded portion of the FOV rectangle corresponding to the second set of input beams is the right portion of the FOV rectangle. Since the center of the shaded portion of the FOV rectangle is at +k xdirection from the origin of the k-space map, so that the second set of input beams from the second projector is not centered on a beam propagating exactly along the -z direction (which would be the case if the shaded part of the FOV rectangle was centered on the origin of the k-space map), but is centered on a tilted beam having a propagating component in the +x direction.

[0370] In the embodiment shown, the operation of the right ICG region 2140b in k-space is to translate the right shaded portion of the FOV rectangle from the center of the k-space map to the 9 o'clock position. As shown in the figure, the right ICG region 2140b can be designed so that its grating vector is along ±k x direction orientation. This will cause some of the diffracted beams to propagate along the -x direction toward the MPE region 2150. In some embodiments, the shaded portion on the right side of the FOV rectangle may constitute half of the FOV rectangle or more. Moreover, in some embodiments, the right ICG region 2140b may be designed to translate the center of the FOV rectangle to any radial position from the midpoint of the k-space annulus to the outer boundary of the annulus. In addition, the right ICG region 2140b may be designed so that the size of its grating vector causes the FOV rectangle to be copied to a position where the shaded portion fits completely within the 9 o'clock position of the k-space annulus. This can be achieved, for example, by designing the ICG so that the size of its grating vector is greater than the distance from the origin of the k-space map to the midpoint of the k-space annulus. Since the shaded portion of the FOV rectangle at the 9 o'clock position is completely within the k-space annulus, the second group of input beams corresponding to the second sub-portion of the FOV all enter the guided propagation mode. Although the FOV rectangle located at the 9 o'clock position of the k-space ring has a left portion extending outside the ring, the input beam corresponding to that portion of the FOV rectangle is not necessarily part of the second sub-portion of the FOV projected by its associated projector into the right ICG region 2140b.

[0371] Although the right ICG region 2140b can also diffract a portion of the second set of input beams in the opposite direction (i.e., translating the FOV rectangle to the 3 o'clock position of the k-space annulus), in the embodiment of the eyepiece waveguide 2100 shown, these particular diffracted beams will only exit from the edge of the waveguide.

[0372] As already discussed, the MPE region 2150 can have a plurality of associated raster vectors that can translate the FOV rectangle from the 9 o'clock position of the k-space annulus to any of the 6 o'clock, 3 o'clock, and 12 o'clock positions. Figure 21C As shown, the shaded portion of the FOV rectangle at the 3 o'clock position of the k-space annulus is truncated, meaning that not all beams associated with the second sub-portion of the FOV are necessarily present in this particular propagation state.

[0373] During additional interactions with the MPE region 2150, the FOV rectangle can be translated back and forth between any of the 12 o'clock, 3 o'clock, 6 o'clock, and 9 o'clock positions. This is represented by the double-headed arrows between those propagation states in KSD2. In this way, as described herein, the second set of input beams can be replicated throughout the MPE region 2150 by undergoing multiple interactions with the diffractive features of the MPE region 2150. Again, this is represented by Figure 21A The arrows in the OPE region 2150 of the eyepiece waveguide 2100 are shown.

[0374] Figure 21C Also shown is the k-space manipulation of the EPE region 2160 on a second set of beams corresponding to a second subsection of the FOV. As already discussed, the EPE region 2160 translates the FOV rectangles at the 12 o'clock and 6 o'clock positions of the k-space annulus back to the origin of the k-space map. Therefore, the EPE region 2160 can only couple out beams in either of these two propagation states. Figure 21C As shown, when the FOV rectangle is finally translated back to the center of the k-space map KSD2, all of the second group of light beams making up the second sub-portion of the FOV are present and projected toward the user's eyes.

[0375] Figure 21D is the k-space map KSD3, which summarizes Figure 21A The k-space operation of the eyepiece waveguide 2100 is shown. It is essentially Figure 21B and 21C Overlay of the k-space maps shown. Again, Figure 21D The k-space diagram in FIG shows a FOV rectangle having at least one dimension greater than the width of the k-space annulus. In some embodiments, at least one dimension of the FOV rectangle can be at most approximately twice the width of the k-space annulus. In the embodiment shown, the horizontal dimension of the FOV rectangle is greater than the width of the k-space annulus. Although the eyepiece waveguide 2100 is shown as providing an extended horizontal field of view, the same technique can also be used to extend the vertical field of view.

[0376] like Figure 21D As shown, although separate projectors and ICG regions 2140a, 2140b are used to project the first and second sets of input beams into the eyepiece waveguide 2100, all beams required to compose the complete image FOV are present when the various FOV rectangles are translated from the 12 o'clock, 3 o'clock, 6 o'clock, and 9 o'clock positions of the k-space annulus back to the origin of the k-space map and thus coupled out toward the user's eyes. Furthermore, the first and second sub-portions of the FOV are aligned in k-space, with their relative positions relative to each other being the same as in the complete input FOV.

[0377] Figure 21EAn example embodiment of glasses 70 incorporating one or more instances of the eyepiece waveguide 2100 is shown. Figure 21F Shown is the corresponding Figure 21E 70 in FIG. 1 . A first instance of the eyepiece waveguide 2100 is integrated into the left viewing portion of the glasses 70, while a second instance of the eyepiece waveguide 2100 is integrated into the right viewing portion. In the embodiment shown, each eyepiece waveguide 2100 is approximately 50×30 mm. 2 , but many different sizes can also be used. As just discussed, each eyepiece waveguide 2100 can be accompanied by two separate projectors 2120a, 2120b that each project a sub-portion of the FOV into the corresponding waveguide. In some embodiments, the first projector 2120a for each waveguide 2100 can input light on the temple side of the eyepiece waveguide 2100, while the second projector 2120b can input light on the nose side of the eyepiece waveguide. For the case where the eyepiece waveguide is made of a material with a refractive index of n=1.8, each projector 2120a, 2120b can input a sub-portion of the FOV that is 50°×60° or larger, depending on other design constraints such as the size of the eyepiece zone and screen door artifacts. The size of the full FOV is 100°×60° or larger. This is shown as Figure 21F . As shown by the matching shading, in this configuration, the first projector 2120a (temple side) can be used to project the nasal side of the full FOV, and the second projector 2120b (nose side) can be used to project the temple side of the full FOV. Note that the crosshairs show one possible pupil alignment method, but other methods can also be used.

[0378] Alternatively, two instances of the eyepiece waveguide 2100 and glasses 70 can be used together to provide a binocular FOV. For example, each eyepiece waveguide 2100 can project a FOV, as shown in a monocular eyepiece configuration. However, the FOVs projected by the two eyepiece waveguides 2100 can at least partially overlap. Figure 21F The case where the FOVs projected by the two eyepiece waveguides 2100 overlap horizontally by 50°, providing a total binocular FOV of 150° × 60°, is shown. The binocular FOV can be larger if less overlap is provided between the FOVs of the two eyepiece waveguides 2100. As shown by the matching shading, in the binocular FOV configuration, the first projector 2120a (temple-side) can be used to project the middle portion of the binocular FOV, and the second projector 2120b (nose-side) can be used to project the side portions of the binocular FOV.

[0379] Figure 21G Shown Figure 21A Another embodiment of the eyepiece waveguide 2100 is shown for k-space operation. In this embodiment, the size of the FOV rectangle can be in k-space. xand k y The size exceeds the width of the k-space ring. Figure 21G , the darker shaded portion of the FOV rectangle corresponds to the right portion of the FOV, while the lighter shaded portion of the FOV rectangle corresponds to the left portion of the FOV. As already discussed, the left and right ICG regions 2140a, 2140b can be designed with raster vectors that move the FOV rectangle to the 3 o'clock and 9 o'clock positions. The raster vectors of the ICG regions can be sized such that the center of the complete FOV rectangle is displaced to any radial position between, for example, the midpoint of the k-space ring and the outer periphery of the ring. Furthermore, as already discussed, the MPE regions can be designed with raster vectors that move the complete FOV rectangle to the 3 o'clock, 6 o'clock, 9 o'clock, and 12 o'clock positions. However, the raster vectors of the MPE region 2150 can also be sized such that at these positions, the center of the complete FOV rectangle is displaced to any radial position between, for example, the midpoint of the k-space ring and the outer periphery of the ring. Thus, even at the 12 o'clock and 6 o'clock positions, which are located along the axis of the shorter dimension of the FOV rectangle, a portion of the FOV rectangle may extend beyond the perimeter of the k-space annulus, such that some portion of the rectangle is truncated.

[0380] Although the guided beams corresponding to the truncated portions of the FOV rectangle may be lost, all the beams required to make up the complete FOV are still present in the waveguide, taking into account all the propagation states represented by the 3 o'clock, 6 o'clock, 9 o'clock, and 12 o'clock positions. The left FOV (light shaded rectangle) is fully preserved at the 9 o'clock position, while the bottom portion is preserved at the 12 o'clock position and the top portion is preserved at the 6 o'clock position. Similarly, the right FOV (dark shaded rectangle) is fully preserved at the 3 o'clock position, while the bottom portion is preserved at the 12 o'clock position and the top portion is preserved at the 6 o'clock position. Therefore, when the FOV rectangle is translated back to the origin of the k-space map and coupled out towards the user's eyes, all the beams required to make up the complete FOV are present and the complete FOV can be regenerated. The expansion of the FOV rectangle in multiple directions is shown in Figure 2. Figures 22A to 22E Further discussion in.

[0381] Figure 22AAn embodiment of an eyepiece waveguide 2200 is shown that can project a FOV that extends in two directions beyond the range of propagation angles that can be supported in a guided propagation mode in the thickness direction of the eyepiece waveguide. The eyepiece waveguide 2200 includes a left ICG region 2240a disposed between a first pair of top and bottom OPE regions 2250a1, 2250a2. It also includes a right ICG region 2240b disposed between a second pair of top and bottom OPE regions 2250b1, 2250b2. Finally, an MPE region 2250c and an overlapping EPE region 2260 are disposed between the first and second ICG regions 2240a, 2240b and their respective OPE regions. The MPE region 2250c can be disposed on or in the first surface 2200a of the eyepiece waveguide 2200 (e.g., Figure 22A ), and the EPE region 2260 may be disposed on or in the second surface of the waveguide (as shown Figure 22B ). Although the MPE region 2250c and the EPE region 2260 are shown as having the same size and being precisely aligned in the xy plane, in other embodiments, they may have slightly different sizes and may be partially misaligned. In some embodiments, the MPE region 2250c and the EPE region 2260 overlap each other by at least 70%, at least 80%, at least 90%, or at least 95%.

[0382] The functions of the left ICG region 2240a and the first pair of top and bottom OPE regions 2250a1, 2250a2 are similar to those of Figure 19 The functionality shown and described. That is, a projector or other input device projects a set of light beams corresponding to the input image FOV toward the left ICG area 2240a approximately along the -z direction. The left ICG area 2240a has grating lines extending along the x direction and periodically repeated along the y direction. Therefore, the left ICG area 2240a couples the input light beams into +1 diffraction orders and -1 diffraction orders, which propagate approximately along the +y direction toward the upper OPE area 2250a1 and approximately along the -y direction toward the lower OPE area 2250a2. As discussed herein, a first set of upper and lower OPE areas 2250a1, 2250a2 replicate these input light beams and then guide multiple sets of replicated output light beams approximately along the x direction toward the MPE / EPE area.

[0383] The right ICG region 2240b and the second pair of top and bottom OPE regions 2250a1, 2250a2 function in the same manner, but are mirrored about the y-axis. That is, the projector or other input device projects the same set of input beams toward the right ICG region 2240b approximately along the -z direction. The right ICG region 2240b also has grating lines that extend along the x-direction and repeat periodically along the y-direction. Therefore, the right ICG region 2240b also couples the input beams into +1 diffraction orders and -1 diffraction orders, which propagate approximately along the +y direction toward the upper OPE region 2250b1 and approximately along the -y direction toward the lower OPE region 2250b2. The second set of upper and lower OPE regions 2250b1, 2250b2 replicate these input beams and then guide multiple sets of replicated output beams approximately along the -x direction toward the MPE / EPE region.

[0384] Figure 22C Shown Figure 22A k-space operation of the ICG regions 2240a, 2240b and OPE regions 2250a1, 2250a2, 2250b1, 2250b2 in the eyepiece waveguide embodiment 2200 shown. Specifically, Figure 22C The left panel (KSD1a) shows the k-space operation of the left ICG region 2240a and its associated first set of top and bottom OPE regions 2250a1, 2250a2, while Figure 22C The right panel (KSD1b) shows the k-space operation of the right ICG region 2240b and its associated second set of top and bottom OPE regions 2250b1, 2250b2.

[0385] A set of input beams corresponding to the FOV of the input image is projected onto both the left ICG region 2240a and the right ICG region 2240b. This set of input beams is shown in KSD1a and KSD1b as FOV squares centered about the corresponding origins of these k-space maps. Unlike the previously shown enhanced FOV embodiments, which only showed a single dimension of the FOV being larger than the width of the k-space annulus, both dimensions of the FOV square in KSD1a and KSD1b are larger than the width of the k-space annulus. In some embodiments, both dimensions of the FOV square can be at most approximately 2 times the width of the k-space annulus. Although this embodiment is illustrated using FOV squares with equal horizontal and vertical FOVs, this is not required as the horizontal and vertical FOVs do not need to be equal. Assuming the refractive index of the eyepiece waveguide (surrounded by air) is 1.8, Figure 22AThe illustrated embodiment of the eyepiece waveguide 2200 is capable of achieving a FOV of 100°×60° or larger (e.g., 100°×90°), depending on other design constraints such as eyebox size and screen door artifacts.

[0386] In KSD1a, the grating vector associated with the left ICG region 2240a is used to move the grating vectors along the ±k y Similarly, in KSD1b, the grating vector associated with the right ICG region 2240b is used to translate the FOV square along the ±k y The FOV square is translated in the same direction. In both cases, after being coupled into the eyepiece waveguide 2200 by the ICG regions 2240a and 2240b, the input beam is in the propagation state represented by the translated FOV squares located at the 12 o'clock and 6 o'clock positions of the k-space annulus. As shown in both KSD1a and KSD1b, the FOV squares in these positions are truncated because they do not fit completely within the k-space annulus. Only those beams corresponding to the shaded lower portion of the FOV square at the 12 o'clock position enter the guided propagation mode. Simultaneously, only those beams corresponding to the shaded upper portion of the FOV square at the 6 o'clock position enter the guided propagation mode.

[0387] KSD1a also shows the k-space operation of the first set of top and bottom OPE regions 2250a1, 2250a2. These OPE regions include diffraction gratings designed with associated grating vectors that translate the FOV square from the 12 o'clock and 6 o'clock positions to the 3 o'clock position. The beam at the 3 o'clock position propagates roughly along the x-direction toward the MPE / EPE region.

[0388] The beam corresponding to the upper portion of the FOV square at the 3 o'clock position in k-space is provided by the FOV square previously located at the 6 o'clock position, while the beam corresponding to the lower portion of the FOV square at the 3 o'clock position is provided by the FOV square previously located at the 12 o'clock position. However, the FOV square is again too large to fit completely within the k-space annulus at the 3 o'clock position. Therefore, the FOV square is truncated, but this time the beam corresponding to the left shaded portion of the FOV square remains in guided propagation mode, while the beam corresponding to the unshaded right portion of the FOV square falls outside the k-space annulus and is lost.

[0389] The k-space operations of the second set of top and bottom OPE regions 2250b1, 2250b2 are mirrored versions of the k-space operations of the first set of top and bottom OPE regions 2250a1, 2250a2 (with respect to k yaxis). Thus, as shown in KSD1b, the second set of top and bottom OPE regions 2250b1, 2250b2 ultimately produces a truncated FOV square at the 9 o'clock position of the k-space annulus, where the beam corresponding to the right shaded portion of the square propagates in a guided mode toward the MPE / EPE region, while the beam corresponding to the unshaded left portion of the FOV square falls outside the k-space annulus and is lost.

[0390] Figure 22D Shown Figure 22A K-space operation of the MPE region 2250c in the eyepiece waveguide embodiment 2200 is shown. Specifically, Figure 22D The left panel (KSD2a) shows the k-space operation of the MPE region 2250c on the light beams received from the left ICG region 2240a and its associated first set of top and bottom OPE regions 2250a1, 2250a2, while the right panel (KSD2b) shows the k-space operation of the MPE region 2250c on the light beams received from the right ICG region 2240b and its associated second set of top and bottom OPE regions 2250b1, 2250b2.

[0391] The operation of the MPE region 2250c may be similar to that of Figure 20A and 21A 2150 in KSD2a. That is, as already discussed, the MPE region 2250c can be composed of a 2D array of diffraction features that exhibit periodicity in multiple directions. Thus, the MPE region 2250c has multiple associated grating vectors that can translate the FOV square back and forth between the 3 o'clock, 6 o'clock, 9 o'clock, and 12 o'clock positions of the k-space ring. This is represented by the double-headed arrows between those propagation states in KSD2a and KSD2b. In this embodiment, the grating vectors G and H of the MPE region 2250c can be perpendicular to each other because the FOV extends beyond the width of the k-space ring in two dimensions, and thus the center of the FOV square can be along the k-space ring. x and k y The direction is translated to the same radial position of the k-space annulus.

[0392] As already discussed, the beams arriving at MPE region 2250c from the left ICG region 2240a and the first set of top and bottom OPE regions 2250a1 and 2250a2 are in the propagation state represented by the FOV square at the 3 o'clock position of the k-space annulus. In this propagation state, only the beams corresponding to the left shaded portion of the FOV square exist. As shown in KSD2a, when MPE region 2250c diffracts these beams into the propagation state represented by the FOV square at the 12 o'clock position, the FOV square is truncated again, and only the beams corresponding to the lower left shaded portion of the FOV square remain in the guided propagation state. Simultaneously, when MPE region 2250c diffracts the beams from the propagation state represented by the FOV square at the 3 o'clock position into the propagation state represented by the FOV square at the 6 o'clock position, the FOV square is truncated again. Only the beams corresponding to the upper left shaded portion of the FOV square remain in the guided propagation state. Finally, when the FOV square is translated from the 12 o'clock or 6 o'clock position of the k-space ring to the 9 o'clock position, the FOV square is again truncated, and there may not be any beam left in the guided propagation state. This is shown by the unshaded FOV square at the 9 o'clock position in KSD2a.

[0393] KSD2b is KSD2a about k y axis. KSD2b shows the k-space manipulation of the MPE region 2250c on the beams arriving from the right ICG region 2240b and the second set of top and bottom OPE regions 2250b1 and 2250b2. These beams are in the propagation state represented by the FOV square located at the 9 o'clock position of the k-space ring. In this propagation state, only the beams corresponding to the right shaded portion of the FOV square exist. As shown in KSD2b, when the MPE region 2250c diffracts these beams into the propagation state represented by the FOV square located at the 12 o'clock position, the FOV square is truncated again, and only the beams corresponding to the lower right shaded portion of the FOV square remain in the guided propagation state. At the same time, when the MPE region 2250c diffracts the beams from the propagation state represented by the FOV square located at the 9 o'clock position to the propagation state represented by the FOV square located at the 6 o'clock position, the FOV square is also truncated again. Only the beams corresponding to the upper right shaded portion of the FOV square remain in the guided propagation state. Finally, when the FOV square is translated from the 12 o'clock or 6 o'clock position of the k-space ring to the 3 o'clock position, the FOV square is truncated again, and there may not be any beam left in the guided propagation state. This is shown by the unshaded FOV square at the 3 o'clock position in KSD2b.

[0394] In this way, the replicated beams that propagate through the MPE region 2250c are divided into four sub-portions of the FOV: a first sub-portion corresponding to the upper left portion of the FOV square; a second sub-portion corresponding to the upper right portion of the FOV square; a third sub-portion corresponding to the lower left portion of the FOV square; and a fourth sub-portion corresponding to the lower right portion of the FOV square. Any pair of these sub-portions of the complete FOV may partially overlap. In other words, any pair of these sub-portions of the FOV may include beams corresponding to one or more of the same input beams. Alternatively, the sub-portions of the FOV may also be unique, with no overlap. In either case, the sub-portions of the FOV are combined at the exit pupil of the eyepiece waveguide 2200 to regenerate the complete FOV. This is done in Figure 22E Shown in.

[0395] Figure 22E Shown Figure 22A k-space operation of the EPE region 2260 in the eyepiece waveguide embodiment 2200 shown. The function of the EPE region 2260 can be similar to that of the Figure 20A and 21A The functions described for the EPE regions 2060 and 2160 in the eyepiece waveguide 2200 are shown in FIG. As discussed herein, since the EPE region 2260 overlaps the MPE region 2250c, a light beam propagating in the MPE region can also interact with the EPE region and couple out of the eyepiece waveguide 2200. The EPE region 2260 includes a diffraction grating whose periodic axis is aligned with the periodic axes of the left ICG region 2240a and the right ICG region 2240b. In the embodiment shown, the periodic axis of the EPE region 2260 points to ±k y Thus, the EPE region 2260 has associated raster vectors that also point in the same direction and translate the FOV squares at the 12 o'clock and 6 o'clock positions of the k-space ring back to the origin of the k-space map. Figure 22E It is shown that when this happens, the four sub-portions of the FOV are combined to regenerate the complete FOV. All the beams required to compose the complete image FOV are present. Moreover, the four sub-portions of the FOV are aligned in k-space, with the same relative positions relative to each other as in the complete input FOV.

[0396] Eyepiece waveguide designed to work with angled projectors

[0397] Many of the eyepiece waveguide embodiments described herein have been designed to operate with a projector (or other image input device) whose optical axis intersects the ICG area at a perpendicular angle. In such embodiments, the central input beam (corresponding to the center point of the input image) is incident perpendicularly on the ICG area, and the input beams corresponding to the top / bottom and left / right portions of the input image are incident on the ICG area at symmetrical angles. However, in some embodiments, the eyepiece waveguide can be designed to operate with an angled projector (or other image input device). Figure 23 An example of such an embodiment is shown.

[0398] Figure 23 An example embodiment of an eyepiece waveguide 2300 designed to function with an angled projector is shown. The eyepiece waveguide 2300 includes an ICG region 2340, left and right OPE regions 2350a, 2350b, and an EPE region 2360. An input beam from the projector is incident on the ICG region 2340 and coupled into the eyepiece waveguide 2300 in a guided propagation mode. In this embodiment, the projector is oriented at a non-perpendicular angle relative to the ICG region 2340. Thus, a central input beam 2341 from the projector is incident on the ICG region 2340 at an oblique angle (e.g., as Figure 13I This results in a shift of the k-vectors of the input beams in k-space so that they are no longer centered at the origin of the k-space map. Therefore, as discussed below, the optical design of the ICG, OPE, and / or EPE regions and their physical shape may need to be changed (e.g., according to reference Figure 14D ), and the placement of the FOV rectangle within the k-space ring can also be changed.

[0399] The positive and negative diffraction orders from the ICG region 2340 then propagate to the left and right OPE regions 2350a and 2350b, respectively. The OPE region 2350 replicates the input beam in a spatially distributed manner along the horizontal direction and directs these beams to the EPE region 2360. The EPE region 2360 then further replicates the beam in a spatially distributed manner along the vertical direction and couples these beams out toward the user's eyes, as discussed elsewhere herein.

[0400] Figure 23A k-space diagram KSD is included, which illustrates the k-space operation of the eyepiece waveguide 2300. As described elsewhere herein, the FOV rectangle in the center portion of the k-space diagram corresponds to the input beam from the projector and the output beam from the eyepiece waveguide 2300. The FOV rectangles located near the 4 o'clock and 8 o'clock positions in the k-space annulus correspond to the beam propagating from the ICG region 2340 to the OPE region 2350. Finally, the FOV rectangle located at the 6 o'clock position in the k-space annulus corresponds to the beam propagating downward from the OPE region 2350 toward the EPE region 2360.

[0401] Since the projector is angled relative to the ICG region 2340, the FOV rectangle corresponding to the input beam is not centered at the origin of the k-space map. Instead, in the embodiment shown, the FOV rectangle corresponding to the input beam is centered at the origin of the k-space map. y axis, but located at k x This means that none of the input beams have a propagation direction with a component in the +y direction. In other words, the input beam propagates downward from the projector toward the ICG region. The ICG region 2340 then propagates along the ±k x The direction translates the FOV rectangle horizontally into the k-space ring.

[0402] Since all guided beams from the ICG region 2340 do not have a positive k y k-component vector (i.e., the FOV rectangle is located at k xBecause the OPE area 2350 is positioned below the +y axis (below the +y axis), the top edge of the OPE area 2350 can be horizontal, as shown, because there is no need to accommodate beams fanning upward in the +y direction. This feature of the OPE area 2350 is advantageous in some embodiments because it allows for a compact design. However, the horizontal top edge of the OPE area 2350 is made practical by angled image projectors. However, angled image projectors can be associated with some disadvantages. For example, because the eyepiece waveguide 2300 (including, for example, the optical design and / or physical layout of the grating) is designed to receive input light from an upward angle, light from overhead light sources (such as the sun or a ceiling light fixture) can also be coupled into the eyepiece waveguide. This can result in undesirable image characteristics, such as ghost images, artifacts, and reduced contrast superimposed on the displayed virtual content from these light sources. Although it is possible to shield the eyepiece waveguide 2300 from overhead light by including a sun visor to block light from overhead light sources, such a sun visor can be bulky or unsightly. Therefore, an eyepiece waveguide designed to work with a vertical projector is preferred because the need for a visor can be reduced or eliminated. Additionally, for upward or downward angled projector designs, the fact that the output beam also leaves the waveguide at an angle similar to the input beam means that the eyepiece waveguide may need to be tilted relative to the user's central gaze vector and / or may need to be placed above or below the eye (rather than directly in front of the eye).

[0403] Example Embodiments

[0404] In some embodiments, an eyepiece waveguide for an augmented reality display system includes: a transparent substrate; an input coupling grating (ICG) region formed on or in the substrate, the ICG region being configured to receive an input light beam and couple the input light beam into the substrate as a guided light beam; a multi-directional pupil expander (MPE) region formed on or in the substrate, the MPE region including a plurality of diffraction features exhibiting periodicity along at least a first periodic axis and a second periodic axis, the MPE region being positioned to receive the guided light beam from the ICG region and diffract the guided light beam in multiple directions to generate a plurality of diffracted light beams; and an exit pupil expander (EPE) region formed on or in the substrate, the EPE region being positioned to receive one or more of the diffracted light beams from the MPE region and couple the diffracted light beams out of the transparent substrate as output light beams.

[0405] In the previous embodiment, the MPE region may comprise a two-dimensional grid of separate diffractive features.

[0406] In any of the above embodiments, the MPE region may include a cross grating.

[0407] In any of the above embodiments, the MPE region may be configured to generate the diffracted beam by diffracting a portion of the power of the guided beam from the ICG region in at least three directions.

[0408] In any of the above embodiments, one of the three directions may correspond to a zero-order diffraction beam.

[0409] In any of the above embodiments, two or more of the three directions may correspond to first-order diffraction beams.

[0410] In any of the above embodiments, the three directions may be angularly spaced at least 45 degrees apart.

[0411] In any of the above embodiments, the MPE region and the EPE region may not overlap, and only one of the three directions of the diffracted light beam may intersect the EPE region.

[0412] In any of the above embodiments, one of the three directions may correspond to a direction from the ICG area to the MPE area.

[0413] In any of the above embo...

Claims

1. An eyepiece waveguide for an augmented reality display system, the eyepiece waveguide comprising: light-transmitting substrate; an input coupling grating (ICG) region formed on or in the optically transmissive substrate, the ICG region configured to receive a plurality of input beam groups and couple the plurality of input beam groups into the optically transmissive substrate as guided beam groups, the guided beam groups being associated with a group of k-vectors in k-space, the k-vector group being at least partially located within a k-space ring associated with the eyepiece waveguide, the k-space ring corresponding to a region in k-space associated with guided propagation in the eyepiece waveguide; a multi-directional pupil expander (MPE) region formed on or in the optically transmissive substrate, the MPE region comprising a plurality of diffractive features exhibiting periodicity along at least a first periodicity axis and a second periodicity axis, the MPE region positioned to receive the guided beam group from the ICG region and diffract the guided beam group in a plurality of directions to produce at least three diffracted beam groups associated with at least three k-vector groups located at least partially within the k-space annulus at three different angular positions; as well as An exit pupil expander (EPE) region is formed on or in the transparent substrate, and the EPE region is positioned to receive one or more diffracted beams of the at least three diffracted beam groups from the MPE region and couple the diffracted beams out of the transparent substrate as output beams.

2. The eyepiece waveguide of claim 1 , wherein the MPE region comprises a two-dimensional grid of discrete diffractive features.

3. The eyepiece waveguide of claim 1 , wherein the MPE region comprises a crossed grating.

4. The eyepiece waveguide of claim 1 , wherein the MPE region is configured to generate the diffracted beam by diffracting part of the power of the guided beam from the ICG region in at least three directions.

5. The eyepiece waveguide of claim 4 , wherein one of the three directions corresponds to a zeroth-order diffracted beam.

6. The eyepiece waveguide of claim 4 , wherein two or more of the three directions correspond to first-order diffracted beams.

7. The eyepiece waveguide of claim 4, wherein the three directions are angularly separated by at least 45 degrees.

8. The eyepiece waveguide of claim 4, wherein the MPE region and the EPE region do not overlap, and wherein only one of the three directions of the diffracted light beam intersects the EPE region.

9. The eyepiece waveguide of claim 4 , wherein one of the three directions corresponds to a direction from the ICG region to the MPE region.

10. The eyepiece waveguide of claim 4, wherein the MPE region is configured to generate the diffracted beam by diffracting part of the power of the guided beam from the ICG region in at least four directions.

11. The eyepiece waveguide of claim 10, wherein the four directions are angularly spaced at least 45 degrees apart.

12. The eyepiece waveguide of claim 1 , wherein the MPE region is further configured to increase the number of diffracted beams by re-diffracting those of the diffracted beams that are still propagating within the MPE region after being diffracted for the first time in the same multiple directions and at multiple distribution positions.

13. An eyepiece waveguide according to claim 12, wherein only a subset of the diffracted light beams propagate towards the EPE region.

14. The eyepiece waveguide of claim 13, wherein the EPE region is positioned to receive only those of the diffracted light beams that propagate in one of the plurality of directions.

15. The eyepiece waveguide of claim 14, wherein the diffracted light beams propagating toward the EPE region have non-uniform spacing.

16. The eyepiece waveguide of claim 1 , wherein some of the diffraction features of the MPE region have a diffraction efficiency of 10% or less.

17. The eyepiece waveguide of claim 16, wherein the diffraction efficiency of the diffraction features of the MPE region varies spatially.

18. The eyepiece waveguide of claim 1 , wherein the ICG region comprises a one-dimensional periodic grating.

19. The eyepiece waveguide of claim 1 , wherein the one-dimensional periodic grating of the ICG region is a blazed grating.

20. The eyepiece waveguide of claim 1 , wherein the EPE region comprises a one-dimensional periodic grating.

21. An eyepiece waveguide according to claim 20, wherein the one-dimensional periodic grating in the EPE region comprises a plurality of curved lines to impart optical power to the output beam.

22. The eyepiece waveguide of claim 1 , wherein the input beams in the plurality of input beam groups are collimated and have a diameter of 5 mm or less.

23. The eyepiece waveguide of claim 1 , wherein the MPE region and the EPE region do not overlap.

24. The eyepiece waveguide of claim 1 , wherein the light-transmissive substrate is planar.

25. The eyepiece waveguide of claim 1 , wherein the eyepiece waveguide is incorporated into an eyepiece for an augmented reality display system.

26. The eyepiece waveguide of claim 25, wherein the eyepiece is configured to display color images at multiple depth planes.

27. The eyepiece waveguide of claim 1, wherein the set of k-vectors associated with the set of guided beams lies entirely within the k-space annulus.

28. The eyepiece waveguide of claim 1, wherein the at least three k-vector groups associated with the at least three diffracted beam groups are entirely within the k-space ring.

29. The eyepiece waveguide of claim 1, wherein the at least three k-vector groups associated with the at least three diffracted beam groups are angularly separated from each other by at least 45 degrees in the k-space ring.

30. The eyepiece waveguide of claim 1 , wherein the at least three k-vector groups associated with respective diffracted beam groups do not overlap with each other.

31. The eyepiece waveguide of claim 1 , wherein one k-vector group of the at least three k-vector groups associated with the at least three diffracted beam groups is located at an angular position in the k-space ring corresponding to a direction from the ICG region to the MPE region.

32. The eyepiece waveguide of claim 1 , wherein one k-vector group of the at least three k-vector groups associated with the at least three diffracted beam groups is located at an angular position in the k-space ring corresponding to a direction from the MPE region to the EPE region.

33. The eyepiece waveguide of claim 1 , wherein the MPE region is configured to diffract the guided beam group to produce at least four diffracted beam groups associated with at least four k-vector groups located at least partially within the k-space ring at four different angular positions.

34. The eyepiece waveguide of claim 1 , wherein the MPE region is configured to further diffract the diffracted beam as it propagates in the MPE region such that the corresponding k-vector group of the diffracted beam transitions between the three different angular positions in the k-space ring.

35. The eyepiece waveguide of claim 1 , wherein the plurality of input beam groups are associated with input images.

36. The eyepiece waveguide of claim 1 , wherein an input beam in the plurality of input beam groups corresponds to a center of an input image and is perpendicularly incident on the ICG area.

Images