Enhanced pupil replication using folded gratings for eyepieces in near-eye displays

Abstract

Embodiments of the present disclosure relate to a near-eye display system with improved exit pupil density. In one embodiment, a waveguide combiner is provided, the waveguide combiner comprising: a first surface; a second surface; an in-coupler located on the first surface, the in-coupler configured to receive a plurality of input beams and to diffract a first subset of the beams and a second subset of the beams into total internal reflections (TIRs) in two opposite directions in K-space; a first folding grating located on the first surface, the first folding grating configured to receive the first subset of beams from the in-coupler at a first region and to diffract the first subset of beams to a second region; a second folding grating located on the first surface, the second folding grating configured to receive the second subset of beams from the in-coupler at a third region and to diffract the second subset of beams to the second region; and a first out coupler, wherein the first out coupler is located on the first surface.

Description

Technical Field

[0001] Embodiments of the present disclosure relate generally to near-eye display systems, and more particularly to near-eye display systems with improved exit pupil density and improved image clarity and uniformity. Background Art

[0002] Virtual reality (VR) is generally considered a computer-generated simulated environment in which the user has a distinct sense of physical presence. VR experiences can be generated in 3D and viewed using a head-mounted display (HMD), such as glasses or other wearable display devices that use near-eye display panels as lenses to display a VR environment that replaces the real environment.

[0003] However, augmented reality (AR) enables an experience where the user still sees their surroundings through the display lenses of glasses or other head-mounted display devices, but also sees images of virtual objects that are generated for display and appear to be part of that environment. AR can include any type of input that enhances or augments the user's experienced environment, such as audio and tactile input, as well as virtual images, graphics, and images. As an emerging technology, augmented reality presents many challenges and design constraints.

[0004] For waveguide combiners in near-eye display systems, it is desirable to increase the exit pupil density arriving at the user's eyebox. Conventional approaches for increasing pupil density include reducing the thickness of the waveguide combiner. This reduction in thickness results in more incoupled light re-encountering the coupler, leading to a loss of image clarity and quality and an increase in uniformity. If the substrate is thicker, choosing a lower pupil density may result in additional high-frequency non-uniformity due to the sparsely replicated pupil reaching the user's eyebox.

[0005] Therefore, there is a need in the art for improved waveguide combiners. Summary of the Invention

[0006] In one embodiment, a waveguide combiner is provided. The waveguide combiner includes: a first surface; a second surface; an in-coupler located on the first surface, the in-coupler configured to receive a plurality of input beams and diffract a first subset of the beams and a second subset of the beams into total internal reflections (TIRs) in two opposite directions in K-space; a first folding grating located on the first surface, the first folding grating configured to receive the first subset of the beams from the in-coupler at a first region in K-space and diffract the first subset of the beams into a second region in K-space by TIR; a second folding grating located on the first surface, the second folding grating configured to receive the second subset of the beams from the in-coupler at a third region in K-space and diffract the second subset of the beams into a second region in K-space by TIR; and a first out-coupler located on the first surface.

[0007] In another embodiment, a waveguide combiner is provided. The waveguide combiner includes: a first surface; a second surface; an in-coupler located on the first surface, the in-coupler configured to receive a plurality of input beams and diffract the plurality of input beams into total internal reflection (TIR); a first replica grating located on the first surface adjacent to and below the in-coupler, the first replica grating configured to receive the plurality of input beams from the in-coupler at a first region in K-space and diffract the plurality of input beams into a second region in K-space by TIR; a second replica grating located on the first surface adjacent to and below the first replica grating; a first out-coupler located on the first surface adjacent to and below the second replica grating; and a second out-coupler located on the second surface.

[0008] In yet another embodiment, a waveguide combiner is provided. The waveguide combiner includes: a first surface; a second surface; an in-coupler located on the first surface, the in-coupler configured to receive a plurality of input beams and diffract a first subset of the beams and a second subset of the beams into total internal reflections (TIRs) in two opposite directions in K-space; a first folding grating located on the first surface, the first folding grating configured to receive the first subset of the beams from the in-coupler at a first region in K-space and diffract the first subset of the beams into a second region in K-space by TIR; a second folding grating located on the first surface, the second folding grating configured to receive the second subset of the beams from the in-coupler at a third region in K-space and diffract the second subset of the beams into a second region in K-space by TIR; an out-coupler located on the first surface, the out-coupler configured to receive the first subset of the beams from the first folding grating and the second subset of the beams from the second folding grating at a second region in K-space, diffract the first subset of the beams into a second region in K-space by TIR. diffracts a first portion of the first subset of the beam and a second subset of the beam into a fourth region in K-space, diffracts a second portion of the first subset of the beam and the second subset of the beam into a fifth region in K-space, outcouples a third portion of the first subset of the beam and the second subset of the beam from a sixth region, and outcouples a fourth portion of the first subset of the beam and the second subset of the beam from a seventh region in K-space, and an expansion grating located on a second surface, the expansion grating being configured to receive the first portion of the first subset of the beam from the first folding grating and the first portion of the second subset of the beam from the second folding grating at the second region in K-space, diffracts the third portion of the first subset of the beam and the second subset of the beam into the sixth region, diffracts the fourth portion of the first subset of the beam and the second subset of the beam into the seventh region in K-space, outcouples the first portion of the first subset of the beam and the second subset of the beam from the fourth region, and outcouples the second portion of the first subset of the beam and the second subset of the beam from the fifth region in K-space. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order that the manner in which the features of the present disclosure described above may be understood in detail, a more particular description of the disclosure, briefly summarized above, may be given by reference to embodiments, some of which are illustrated in the accompanying drawings. It is to be noted, however, that the drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of the scope of the present disclosure, and other equally effective embodiments may be admitted.

[0010] Figure 1 A perspective view of a near-eye display system is shown, according to one or more embodiments of the present disclosure.

[0011] Figure 2 One or more embodiments according to the present disclosure are shown. Figure 1Cross-sectional view of a near-eye display system.

[0012] Figure 3A A top view of a first surface of a first configuration of a waveguide combiner of a near-eye display system is shown according to an embodiment of the present disclosure.

[0013] Figure 3B A bottom view of a second surface of a first configuration of a waveguide combiner of a near-eye display system is shown according to an embodiment of the present disclosure.

[0014] Figure 3C A K-space diagram of a first configuration of a waveguide combiner according to an embodiment of the present disclosure is shown.

[0015] Figure 3D A comparison of pupil replication diagrams for a first configuration according to an embodiment of the present disclosure and a conventional raster-vector architecture is shown.

[0016] Figure 4A A top view of a first surface of a second configuration of a waveguide combiner of a near-eye display system is shown according to an embodiment of the present disclosure.

[0017] Figure 4B A bottom view of a second surface of a second configuration of a waveguide combiner of a near-eye display system is shown according to an embodiment of the present disclosure.

[0018] Figure 4C A K-space diagram illustrating a second configuration of a waveguide combiner according to an embodiment of the present disclosure is shown.

[0019] Figure 5A A top view of a first surface of a third configuration of a waveguide combiner of a near-eye display system is shown according to an embodiment of the present disclosure.

[0020] Figure 5B A bottom view of a second surface of a third configuration of a waveguide combiner of a near-eye display system is shown according to an embodiment of the present disclosure.

[0021] Figure 5C A K-space diagram of a third configuration of a fourth configuration according to an embodiment of the present disclosure is shown.

[0022] Figure 5D A comparison of pupil replication diagrams for a third configuration according to an embodiment of the present disclosure and a conventional raster-vector architecture is shown.

[0023] Figure 6A A top view of a first surface of a fourth configuration of a waveguide combiner of a near-eye display system is shown according to an embodiment of the present disclosure.

[0024] Figure 6BA bottom view of a second surface of a fourth configuration of a waveguide combiner of a near-eye display system is shown according to an embodiment of the present disclosure.

[0025] Figure 6C A K-space diagram illustrating a fourth configuration of a waveguide combiner according to an embodiment of the present disclosure is shown.

[0026] Figure 6D A comparison of pupil replication diagrams for a fourth configuration according to an embodiment of the present disclosure and a conventional raster-vector architecture is shown.

[0027] Figure 7A Shown is a top view of a first surface of a fifth configuration of a waveguide combiner of a near-eye display system according to an embodiment of the present disclosure.

[0028] Figure 7B A bottom view of a second surface of a fifth configuration of a waveguide combiner of a near-eye display system is shown according to an embodiment of the present disclosure.

[0029] Figure 7C A K-space diagram illustrating a fifth configuration of a waveguide combiner according to an embodiment of the present disclosure is shown.

[0030] Figure 8A Shown is a top view of a first surface of a sixth configuration of a waveguide combiner of a near-eye display system according to an embodiment of the present disclosure.

[0031] Figure 8B A bottom view of a second surface of a sixth configuration of a waveguide combiner in a near-eye display system according to an embodiment of the present disclosure is shown.

[0032] Figure 8C A K-space diagram illustrating a sixth configuration of a waveguide combiner according to an embodiment of the present disclosure is shown.

[0033] Figure 8D A comparison of pupil replication diagrams for a sixth configuration according to an embodiment of the present disclosure and a conventional raster-vector architecture is shown.

[0034] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures, it being contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. DETAILED DESCRIPTION

[0035] The embodiments described herein generally relate to near-eye display systems. More specifically, the embodiments described herein relate to near-eye display systems with improved exit pupil density, image clarity, and image uniformity. A diffractive waveguide combiner layer is designed to increase the exit pupil density without substantially reducing the thickness of the waveguide combiner layer. Because the thickness of the waveguide combiner layer is not substantially reduced, in-coupler bounce is avoided. However, because the exit pupil density is also high, high-frequency non-uniformities in the projected image are also avoided, particularly when using lasers.

[0036] Figure 1 A perspective view of a near-eye display system 100 according to one or more embodiments of the present disclosure is shown. The near-eye display system 100 can present media to a user. Examples of media presented by the near-eye display system 100 can include one or more images, videos, and / or audio. In one embodiment that may be combined with other embodiments, the audio can be presented via an external device (e.g., a speaker and / or headphones) that receives audio information from the near-eye display system 100, a console, or both, and presents audio data based on the audio information. The near-eye display system 100 is generally configured to operate as an artificial reality display. In one embodiment that may be combined with other embodiments, the near-eye display system 100 can operate as an augmented reality (AR) display.

[0037] The near-eye display system 100 may include a frame 110 and a display 120. The frame 110 may be coupled to one or more optical elements. The display 120 may be configured to allow a user to view content presented by the near-eye display system 100. In one embodiment, which may be combined with other embodiments, the display 120 may include a waveguide combiner for directing light from one or more images to the user's eyes.

[0038] Figure 2 shows a method according to one or more embodiments Figure 1 FIG2 is a cross-sectional view of a near-eye display system 100. The near-eye display system 100 may include at least one waveguide combiner 210 having a first surface 202 opposite a second surface 204. The waveguide combiner 210 is configured to direct image light, such as display light, to an eyebox 220 defining an eyebox plane and then to an eye 230 of a user. The waveguide combiner 210 may include one or more materials having one or more refractive indices. In one embodiment, which may be combined with other embodiments, the near-eye display system 100 may include one or more optical elements between the waveguide combiner 210 and the eye 230 of the user.

[0039] Embodiments of the present disclosure discuss diffractive waveguide combiner layers with novel grating architectures that utilize additional gratings. For example, a double-folded grating with a unique grating vector or a double-replicated grating with a unique grating vector can be utilized to enhance pupil replication prior to diffusion and outcoupling in subsequent grating regions, such as outcouplers.

[0040] Figure 3A Shown is a top view of the first surface 202 of the first configuration 301 of the waveguide combiner 210 of the near-eye display system 100 according to an embodiment. Figure 3B A bottom view of the second surface 204 of the first configuration 301 of the waveguide combiner 210 of the near-eye display system 100 is shown. The second surface 204 is opposite to the first surface 202.

[0041] The first surface 202 of the first configuration 301 includes an in-coupler 315, a first folded grating 335A, a second folded grating 335B, and a first out-coupler 325A, which are disposed on or above the first surface. The first folded grating 335A is located adjacent to the in-coupler 315. The second folded grating 335B is located adjacent to the in-coupler 315 opposite the first folded grating 335A. The first out-coupler 325A is located adjacent to the in-coupler 315, the first folded grating 335A, and the second folded grating 335B. In one example, the first out-coupler 325A is positioned above the first folded grating 335A and the second folded grating 335B. In another example, the first out-coupler 325A is positioned below the first folded grating 335A and the second folded grating 335B.

[0042] The second surface 204 of the first configuration 301 includes a second outcoupler 325B disposed on or above the second surface. In one embodiment that may be combined with other embodiments described herein, the second surface 204 of the first configuration 301 includes a second outcoupler 325B, a third folded grating 375A, and a fourth folded grating 375B. The third folded grating 375A is adjacent to the fourth folded grating 375B. In one example of an embodiment including the third folded grating 375A and the fourth folded grating 375B, the second outcoupler 325B is positioned above the third folded grating 375A and the fourth folded grating 375B. In another example of an embodiment including the third folded grating 375A and the fourth folded grating 375B, the second outcoupler 325B is positioned below the third folded grating 375A and the fourth folded grating 375B. The incoupler 315 may have a circular geometry or an oval geometry. The first outcoupler 325A and the second outcoupler 325B may have a square geometry or a rectangular geometry.The first folding grating 335A and the second folding grating 335B may have a trapezoidal geometry.

[0043] Figure 3C A k-space diagram 310 is shown for the first configuration 301 of the waveguide combiner 210. The k-space diagram 310 depicts the path of a virtual FOV generated from the microdisplay of the near-eye display system 100. The path of the virtual FOV is the expected image path using the hexagonal lattice structure of the k-space region. In the k-space diagram, the inner circle represents free space, the outer circle represents the substrate, and the space between the outer diameters of the circles represents TIR. In the optical setup, the virtual FOV (light) propagates between the gratings using TIR. As shown in the k-space diagram 310, light from a light source (e.g., the virtual FOV) is incoupled through the incoupler 315 and diffracted as a beam along a path 321A to a first region 320L, corresponding to the direction of light to be propagated to a first folding grating 335A, and a path 321B to a second region 320R, corresponding to the direction of light to be propagated to a second folding grating 335B. L and R represent "left" and "right," respectively. A beam incident on the first folding grating 335A is diffracted along a path 331A to region 330, corresponding to the direction of the light to be propagated to the first outcoupler 325A and the second outcoupler 325B. A beam incident on the second folding grating 335B is diffracted along a path 331B to region 330, corresponding to the direction of the light to be propagated to the first outcoupler 325A and the second outcoupler 325B. The beam incident on the first outcoupler 325A is diffracted by the first outcoupler 325A along a path 341A to region 340R, corresponding to the direction of the light to be propagated to the second outcoupler 325B. The second outcoupler 325B then outcouples the light along a path 351B to the user's eye box 308. The beam incident on the second outcoupler 325B is diffracted by the second outcoupler 325B along a path 341B to region 340L, corresponding to the direction of the light to be propagated to the first outcoupler 325A. The first outcoupler 325A then outcouples the light along path 351A to the user eye box 308.

[0044] The positions of the first and second regions 320L and 320R must be different from the positions of regions 340L and 340R, respectively, to ensure that the new grid of diffraction beam regions corresponding to regions 340L and 340R does not align with the current grid of diffraction beam regions corresponding to the first and second regions 320L and 320R. Furthermore, the placement of the first and second folding gratings 335A and 335B can mitigate situations where the new grid of diffraction beam regions creates a completely new set of exit pupil regions that could potentially reach the user's eyebox and create a "ghost path," potentially resulting in a secondarily shifted copy of the intended virtual content in the user's FOV. In some embodiments, the positions of the first and second regions 320L and 320R and the positions of regions 340L and 340R involve shifting the positions of regions 340L and 340R in k-space such that the shifted region positions are sufficiently distant from the current k-space region positions 320L and 320R (e.g., a distance of at least approximately 0.02k0, where k0 is 2*π / λ and λ is the wavelength of light).

[0045] Figure 3D 3 shows a comparison of pupil replication diagrams for the first configuration 301 and a conventional raster vector architecture 302. The pupil replication diagram represents a FOV angle of approximately (0 degrees, 0 degrees). Figure 3D As shown, each point in the pupil replica diagram represents an exit pupil. The eye box 380 of the waveguide combiner 210 includes a larger number of exit pupils than the eye box 382 of the conventional grating vector architecture 302. The eye box 380 receiving a larger number of exit pupils results in an increased exit pupil density for a waveguide combiner having the same thickness. Figure 3D This allows for a direct comparison of the enhanced pupil replication and improved exit pupil density of the waveguide combiner 210. The increased pupil density of the waveguide combiner 210 is achieved with a substrate having the same thickness as the conventional grating vector architecture 302. For example, the exit pupil density is at least about five times higher than that of a waveguide combiner having the conventional grating vector architecture 302. Therefore, the substrate thickness does not need to be reduced, or can even be increased, while maintaining a high exit pupil density. This mitigates the negative image effects of in-coupler re-bounce while also limiting high-frequency non-uniformity.

[0046] Figure 4A A top view of the first surface 202 of the second configuration 401 of the waveguide combiner 210 of the near-eye display system 100 is shown in accordance with an embodiment. Figure 4B 1. A bottom view of the second surface 204 of the waveguide combiner 210 of the near-eye display system 100 is shown, according to an embodiment. The second surface 204 is opposite to the first surface 202.

[0047] The first surface 202 of the waveguide combiner 210 includes an in-coupler 415, a first two-dimensional out-coupler 425A, a first folded grating 435A, and a second folded grating 435B, which are disposed on or above the first surface. A two-dimensional grating, such as the first two-dimensional out-coupler 425A, includes periodicity in two directions, thereby resulting in diffraction orders in two directions. The first folded grating 435A is located adjacent to the in-coupler 415. The second folded grating 435B is located adjacent to the in-coupler 415, opposite the first folded grating 435A. The first two-dimensional out-coupler 425A is located adjacent to the in-coupler 415, the first folded grating 435A, and the second folded grating 435B. In one example, the first two-dimensional out-coupler 425A is positioned above the first folded grating 435A and the second folded grating 435B. In another example, the first two-dimensional out-coupler 425A is positioned below the first folded grating 435A and the second folded grating 435B.

[0048] In one embodiment, which may be combined with other embodiments described herein, the second surface 204 of the waveguide combiner 210 includes a third folded grating 475A, a fourth folded grating 475B, and a second outcoupler 425B. The second outcoupler 425B can be a one-dimensional or two-dimensional outcoupler. The third folded grating 475A is adjacent to the fourth folded grating 475B. In one example of an embodiment including the third folded grating 475A and the fourth folded grating 475B, the second outcoupler 425B is positioned above the third folded grating 475A and the fourth folded grating 475B. In another example of an embodiment including the third folded grating 475A and the fourth folded grating 475B, the second outcoupler 425B is positioned below the third folded grating 475A and the fourth folded grating 475B. The incoupler 415 can have a circular or oval geometry. The first two-dimensional outcoupler 425A can have a rectangular or square geometry. The first folding grating 435A and the second folding grating 435B may have a trapezoidal geometry.

[0049] Figure 4C A k-space diagram 410 of a second configuration 401 of the waveguide combiner 210 is shown. Figure 4C and Figure 3C420L and a second region 420R. The beam incident on the second folding grating 435B is diffracted along a path 431B to region 430, corresponding to the direction of the light that will propagate to the first two-dimensional outcoupler 425A. The beam incident on the first two-dimensional outcoupler 425A is diffracted along a path 441A to region 440R and a path 441B to region 440L. The first two-dimensional outcoupler 425A then outcouples the light from region 440L along a path 451A and the light from region 440R along a path 451B to the user's eye box 408.

[0050] The positions of the first and second regions 420L and 420R must be different from the positions of regions 440L and 440R, respectively, to ensure that the new grid of diffraction beam regions corresponding to regions 440L and 440R does not align with the current grid of diffraction beam regions corresponding to the first and second regions 420L and 420R. Additionally, the placement of the first and second folding gratings 435A and 435B can mitigate situations where the new grid of diffraction beam regions creates a completely new set of exit pupil regions that could potentially reach the user's eyebox and create a "ghost path," which could result in a secondarily shifted copy of the intended virtual content in the user's FOV. In some embodiments, the positions of the first and second regions 420L and 420R and the positions of regions 440L and 440R involve shifting the positions of regions 440L and 440R in k-space such that the shifted region positions are sufficiently distant from the current k-space region positions 420L and 420R (e.g., a distance of at least approximately 0.02 k0).

[0051] Figure 5A 1. Shown is a top view of the first surface 202 of a third configuration 501 of the waveguide combiner 210 of the near-eye display system 100 according to an embodiment. Figure 5B 1. A bottom view of the second surface 204 of the waveguide combiner 210 of the near-eye display system 100 is shown, according to an embodiment. The second surface 204 is opposite to the first surface 202.

[0052] The first surface 202 of the waveguide combiner 210 includes an in-coupler 515, a first out-coupler 525A, a first folded grating 535A, and a second folded grating 535B. The first folded grating 535A is located adjacent to the in-coupler 515. The second folded grating 535B is located adjacent to the in-coupler 515 opposite the first folded grating 535A. The first out-coupler 525A is located adjacent to the in-coupler 515, the first folded grating 535A, and the second folded grating 535B. In one example, the first out-coupler 525A is positioned above the first folded grating 435A and the second folded grating 435B. In another example, the first out-coupler 525A is positioned below the first folded grating 435A and the second folded grating 435B.

[0053] The second surface 204 of the waveguide combiner 210 includes a two-dimensional extended grating 525B. In one embodiment, which may be combined with other embodiments described herein, the second surface 204 of the waveguide combiner 210 includes the two-dimensional extended grating 525B, a third folded grating 575A, and a fourth folded grating 575B. The third folded grating 575A is adjacent to the fourth folded grating 575B. In one example of an embodiment including the third folded grating 575A and the fourth folded grating 575B, the two-dimensional extended grating 525B is positioned above the third folded grating 575A and the fourth folded grating 575B. In another example of an embodiment including the third folded grating 575A and the fourth folded grating 575B, the two-dimensional extended grating 525B is positioned below the third folded grating 575A and the fourth folded grating 575B. The in-coupler 515 may have a circular geometry or an oval geometry. The first out-coupler 525A and the two-dimensional extended grating 525B may have a square geometry or a rectangular geometry. The first folding grating 535A and the second folding grating 535B may have a trapezoidal geometry.

[0054] Figure 5CA k-space diagram 510 of a third configuration 501 of the waveguide combiner 210 is shown. The k-space diagram 510 depicts the path of a virtual FOV generated by the microdisplay of the near-eye display system 100. The path of the virtual FOV is the expected image path using a rectangular lattice structure of k-space regions. As shown in the k-space diagram 510, light from a light source, such as the virtual FOV, is incoupled through the incoupler 515 and diffracted as a beam along a path 521A to a first region 520L, corresponding to the direction of the light to be propagated to the first folding grating 535A, and a path 521B to a second region 520R, corresponding to the direction of the light to be propagated to the second folding grating 535B. L and R represent "left" and "right," respectively. The beam incident on the first folding grating 535A is diffracted along a path 531A to a region 530, corresponding to the direction of the light to be propagated to the first outcoupler 525A and the two-dimensional expansion grating 525B. The beam incident on the second folding grating 535B is diffracted along a path 531B to region 530, corresponding to the direction of the light to be propagated to the first outcoupler 525A and the two-dimensional expansion grating 525B. The beam incident on the first outcoupler 525A is diffracted by the first outcoupler 525A along a path 551A to region 540L, corresponding to the direction of the light to be propagated to the two-dimensional expansion grating 525B, and along a path 551B to region 540R, corresponding to the direction of the light to be propagated to the two-dimensional expansion grating 525B. The two-dimensional expansion grating 525B then outcouples the light along paths 581A and 581B to the user's eye box 508. The beam incident on the two-dimensional expansion grating 525B is diffracted by the two-dimensional expansion grating along a path 541A to region 560L, corresponding to the direction of the light to be propagated to the first outcoupler 525A, and along a path 541B to region 560R, corresponding to the direction of the light to be propagated to the first outcoupler 525A. The first outcoupler 525A then outcouples the light to the user eye box 508 along paths 571A and 571B.

[0055] The positions of the first and second regions 520L, 520R must be different from the positions of regions 560L and 560R, respectively, to ensure that the new grid of diffraction beam regions corresponding to regions 560L and 560R does not align with the current grid of diffraction beam regions corresponding to the first and second regions 520L, 520R. Additionally, the placement of the first and second folding gratings 535A, 535B can mitigate situations where the new grid of diffraction beam regions creates a completely new set of exit pupil regions that could potentially reach the user's eyebox and create a "ghost path," which could result in a secondarily shifted copy of the intended virtual content in the user's FOV. In some embodiments, the positions of the first and second regions 520L, 520R and the positions of regions 560L and 560R involve shifting the positions of regions 560L and 560R in k-space such that the shifted region positions are sufficiently distant from the current k-space region positions 520L and 520R (e.g., a distance of at least approximately 0.02 k0).

[0056] Figure 5D A comparison of pupil replication diagrams of the third configuration 501 and a conventional raster vector architecture 502 is shown. The pupil replication diagram represents a FOV angle of approximately (0 degrees, 0 degrees). Figure 5D As shown, each point in the pupil replica diagram represents an exit pupil. The eye box 580 of the waveguide combiner 210 includes a larger number of exit pupils than the eye box 582 of the conventional grating vector architecture 502. The eye box 580 receiving a larger number of exit pupils results in an increased exit pupil density for a waveguide combiner having the same thickness. Figure 5D This allows for a direct comparison of the enhanced pupil replication and improved exit pupil density of the waveguide combiner 210. The increased pupil density of the waveguide combiner 210 is achieved with a substrate having the same thickness as the conventional grating vector architecture 502. For example, the exit pupil density is at least about five times higher than that of a waveguide combiner having the conventional grating vector architecture 502. Therefore, the thickness of the substrate does not need to be reduced, or can even be increased, while maintaining a high exit pupil density. This mitigates the negative image effects of in-coupler bounce while also limiting high-frequency non-uniformity.

[0057] Figure 6A Shown is a top view of the first surface 202 of a fourth configuration 601 of the waveguide combiner 210 of the near-eye display system 100 according to an embodiment. Figure 6B 1. A bottom view of the second surface 204 of the waveguide combiner 210 of the near-eye display system 100 is shown, according to an embodiment. The second surface 204 is opposite to the first surface 202.

[0058] The first surface 202 of the waveguide combiner 210 includes an in-coupler 615, a first replica grating 635A, a second replica grating 635B, and a first out-coupler 625A, which are disposed on or above the first surface. From a top view, the first replica grating 635A is located adjacent to or below the in-coupler 615, as shown in FIG. Figure 6A As shown in FIG. 6 , the second replica grating 635B is located adjacent to or below the first replica grating 635A. Figure 6A As shown, the first replica grating 635A and the second replica grating 635B are connected in series. In one example, from a top view, the first outcoupler 625A is located adjacent to or below the second replica grating 635B, as shown in FIG. Figure 6A In another example, the first out-coupler 625A is positioned above the in-coupler 615 .

[0059] The second surface 204 of the waveguide combiner 210 includes a second outcoupler 625B disposed on or above the second surface. In one embodiment that may be combined with other embodiments described herein, the second surface 204 of the waveguide combiner 210 includes the second outcoupler 625B, a third replica grating 675A, and a fourth replica grating 675B. The fourth replica grating 675B is adjacent to or below the third replica grating 675A. In one example of an embodiment including the third replica grating 675A and the fourth replica grating 675B, the second outcoupler 625B is positioned above the third replica grating 675A. In another example of an embodiment including the third replica grating 675A and the fourth replica grating 675B, the second outcoupler 625B is positioned below the fourth replica grating 675B. The incoupler 615 may have a circular or oval geometry. The first outcoupler 625A and the second outcoupler 625B may have a square or rectangular geometry. The first replica grating 635A and the second replica grating 635B may have a square or rectangular geometry.

[0060] Figure 6CA k-space diagram of a fourth configuration 601 of the waveguide combiner 210 is shown. This k-space diagram depicts the path of a virtual FOV generated from the microdisplay of the near-eye display system 100. The path of the virtual FOV is the expected image path using the hexagonal lattice structure of the k-space region. As shown in the k-space diagram, light from a light source, such as the virtual FOV, is incoupled through the incoupler 615 and directed as a beam along path 621 to the first region 620. The beam incident on the first replica grating 635A is diffracted along path 631A to region 630L, corresponding to the direction of the light to be propagated to the first replica grating 635A. There, the beam re-encounters the first replica grating 635A and is diffracted back to the first region 620. The beam diffracted back to the first region 620 encounters the second replica grating 635B and diffracts along path 631B to region 630R, corresponding to the direction of the light to be propagated to the second replica grating 635B. There, the beam is diffracted back to the first region 620. L and R represent "left" and "right," respectively. A beam incident on the first outcoupler 625A, diffracted by the second replica grating 635B back to the first region 620, is diffracted by the first outcoupler 625A along a path 641A to region 640R, corresponding to the direction of the light that will propagate to the second outcoupler 625B. The second outcoupler 625B outcouples the light along a path 651B to the user's eyebox 608. A beam incident on the second outcoupler 625B, diffracted by the second replica grating 635B back to the first region 620, is diffracted by the second outcoupler 625B along a path 641B to region 640L, corresponding to the direction of the light that will propagate to the first outcoupler 625A. The first outcoupler 625A then outcouples the light along a path 651A to the user's eyebox 608.

[0061] The positions of regions 630L and 630R must be different from the positions of regions 640L and 640R, respectively, to ensure that the new grid of diffraction beam regions corresponding to regions 640L and 640R does not align with the current grid of diffraction beam regions corresponding to regions 630L and 630R. Additionally, the placement of the first replica grating 635A and the second replica grating 635B can mitigate situations where the new grid of diffraction beam regions creates a completely new set of exit pupil regions that could potentially reach the user's eyebox and create a "ghost path," which could result in a secondarily shifted copy of the intended virtual content in the user's FOV. In some embodiments, the positions of regions 630L and 630R and the positions of regions 640L and 640R involve shifting the positions of regions 640L and 640R in k-space such that the shifted region positions are sufficiently distant from the current k-space region positions 630L and 630R (e.g., a distance of at least approximately 0.02 k0).

[0062] Figure 6D6 shows a comparison of pupil replication diagrams for the fourth configuration 601 and a conventional raster vector architecture 602. The pupil replication diagram represents a FOV angle of approximately (0 degrees, 0 degrees). Figure 6D As shown, each point in the pupil replica diagram represents an exit pupil. The eye box 680 of the waveguide combiner 210 includes a larger number of exit pupils than the eye box 682 of the conventional grating vector architecture 602. The eye box 680 receives a larger number of exit pupils, resulting in an increased exit pupil density for a waveguide combiner with the same thickness. Figure 6D This allows for a direct comparison of the enhanced pupil replication and exit pupil density of the waveguide combiner 210. The increased pupil density of the waveguide combiner 210 is achieved with a substrate having the same thickness as the conventional grating vector architecture 602. For example, the exit pupil density is at least about five times higher than that of a waveguide combiner having the conventional grating vector architecture 602. Therefore, the thickness of the substrate does not need to be reduced, or can even be increased, while maintaining a high exit pupil density. This mitigates the negative image effects of in-coupler bounce while also limiting high-frequency non-uniformity.

[0063] Figure 7A A top view of a first surface of a fifth configuration 701 of the waveguide combiner 210 of the near-eye display system 100 is shown in accordance with an embodiment. Figure 7B 1. A bottom view of a second surface of a fifth configuration 701 of the waveguide combiner 210 of the near-eye display system 100 is shown, according to an embodiment. The second surface 204 is opposite to the first surface 202.

[0064] The first surface 202 of the waveguide combiner 210 includes an in-coupler 715, a first two-dimensional out-coupler 725A, a first replica grating 735A, and a second replica grating 735B, which are disposed on or above the first surface. A two-dimensional grating, such as the first two-dimensional out-coupler 725A, contains periodicity in two directions, thereby resulting in diffraction orders in two directions. From a top view, the first replica grating 735A is located adjacent to or below the in-coupler 715, as shown in FIG. Figure 7A As shown in FIG. 1 , the second replica grating 735B is located adjacent to or below the first replica grating 735A. Figure 7A As shown, the first replica grating 735A and the second replica grating 735B are connected in series. In one example, from a top view, the first two-dimensional outcoupler 725A is located adjacent to or below the second replica grating 735B, as shown in FIG. Figure 7A In another example, the first two-dimensional outcoupler 725A is positioned above the incoupler 715 .

[0065] In one embodiment, which may be combined with other embodiments described herein, the second surface 204 of the waveguide combiner 210 includes a third replica grating 775A, a fourth replica grating 775B, and a second outcoupler 725B. The second outcoupler 725B can be a one-dimensional or two-dimensional outcoupler. The fourth replica grating 775B is adjacent to or below the third replica grating 775A. In one example of an embodiment including the third replica grating 775A and the fourth replica grating 775B, the second outcoupler 725B is positioned above the third replica grating 775A. In another example of an embodiment including the third replica grating 775A and the fourth replica grating 775B, the second outcoupler 725B is positioned below the fourth replica grating 775B. The incoupler 715 can have a circular or oval geometry. The first two-dimensional outcoupler 725A can have a square or rectangular geometry. The first folded grating 735A and the second folded grating 735B can have a trapezoidal geometry.

[0066] Figure 7C A k-space diagram 710 of a fifth configuration 701 of the waveguide combiner 210 is shown. Figure 7C and Figure 6C Similarly, except that outcoupler 725A is a two-dimensional outcoupler. As shown in K-space diagram 710, light from a light source, such as a virtual FOV, is incoupled through incoupler 715 and diffracted as a beam along path 721 to first region 720. The beam incident on first replica grating 735A is diffracted along path 731A to region 730L, corresponding to the direction of the light to be propagated to first replica grating 735A. There, the beam re-encounters first replica grating 735A and is diffracted back to first region 720. The beam diffracted back to first region 720 by first replica grating 735A encounters second replica grating 735B and diffracts along path 731B to region 730R, corresponding to the direction of the light to be propagated to second replica grating 735B. There, the beam is diffracted back to first region 720. L and R represent "left" and "right," respectively. The beam incident on the first two-dimensional outcoupler 725A, diffracted by the second replica grating 735B back to the first region 720, is diffracted by the first two-dimensional outcoupler 725A along paths 741A and 741B to regions 740R and 740L. The first two-dimensional outcoupler 725A then outcouples the light along paths 751A and 751B to the user's eye box 708.

[0067] The positions of regions 730L and 730R must be different from the positions of regions 740L and 740R, respectively, to ensure that the new grid of diffraction beam regions corresponding to regions 740L and 740R does not align with the current grid of diffraction beam regions corresponding to regions 730L and 730R. Additionally, the placement of the first replica grating 735A and the second replica grating 735B can mitigate situations where the new grid of diffraction beam regions creates a completely new set of exit pupil regions that could potentially reach the user's eyebox and create a "ghost path," which could result in a secondarily shifted copy of the intended virtual content in the user's FOV. In some embodiments, the positions of regions 730L and 730R and the positions of regions 740L and 740R involve shifting the positions of regions 740L and 740R in k-space such that the shifted region positions are sufficiently distant from the current k-space region positions 730L and 730R (e.g., a distance of at least approximately 0.02 k0).

[0068] Figure 8A 1. A top view of the first surface 202 of the waveguide combiner 801 of the near-eye display system 100 is shown according to an embodiment. Figure 8B FIG. 2 shows a bottom view of the second surface 204 of the waveguide combiner 801 of the near-eye display system 100 according to an embodiment. The second surface 204 is opposite to the first surface 202 .

[0069] The first surface 202 of the waveguide combiner 801 includes an in-coupler 815, a first out-coupler 825A, a first replica grating 835A, and a second replica grating 835B. From a top view, the first replica grating 835A is located adjacent to or below the in-coupler 815, as shown in FIG. Figure 8A As shown in FIG. 8 , from a top view, the second replica grating 835B is located adjacent to or below the first replica grating 835A. Figure 8A As shown, the first replica grating 835A and the second replica grating 835B are connected in series. In one example, from a top view, the first outcoupler 825A is located adjacent to or below the second replica grating 835B, as shown in FIG. Figure 8A In another example, the first out-coupler 825A is positioned above the in-coupler 815 .

[0070] The second surface 204 of the waveguide combiner 801 includes a two-dimensional extended grating 845A. In one embodiment, which may be combined with other embodiments described herein, the second surface 204 of the waveguide combiner 801 includes the two-dimensional extended grating 845A, a third replica grating 875A, and a fourth replica grating 875B. The fourth replica grating 875B is located adjacent to or below the third replica grating 875A. In one example of an embodiment including the third replica grating 875A and the fourth replica grating 875B, the two-dimensional extended grating 845A is positioned above the third replica grating 875A. In another example of an embodiment including the third replica grating 875A and the fourth replica grating 875B, the two-dimensional extended grating 845A is positioned below the fourth replica grating 875B. The in-coupler 815 may have a circular or oval geometry. The first out-coupler 825A and the two-dimensional extended grating 845A may have a square or rectangular geometry. The first replica grating 835A and the second replica grating 835B may have a square or rectangular geometry.

[0071] Figure 8CA k-space diagram 810 of waveguide combiner 801 is shown. K-space diagram 810 depicts the path of a virtual FOV generated from a microdisplay of near-eye display system 100. The path of the virtual FOV is the expected image path using a rectangular lattice structure of k-space regions. As shown in k-space diagram 810, light from a light source, such as a virtual FOV, is incoupled through incoupler 815 and diffracted along path 821 to first region 820. The beam incident on first replica grating 835A is diffracted along path 831A to region 830L, corresponding to the direction of light that would propagate to first replica grating 835A, where it re-encounters first replica grating 835A and is diffracted back to first region 820. The beam incident on the second replica grating 835B, diffracted back to the first region 820 by the first replica grating 835A, is diffracted along a path 831B to a region 830R, corresponding to the direction of the light to be propagated to the second replica grating 835B. There, the beam re-encounters the second replica grating 835B and is diffracted back to the first region 820. L and R represent "left" and "right," respectively. The beam incident on the first outcoupler 825A is diffracted by the first outcoupler 825A along a path 851A to a region 840L, corresponding to the direction of the light to be propagated to the two-dimensional expansion grating 845A, and a path 851B to a region 840R, corresponding to the direction of the light to be propagated to the two-dimensional expansion grating 845A. The two-dimensional expansion grating 845A then outcouples the light along paths 871A and 871B to the user's eye box 808. The beam incident on the two-dimensional expansion grating 845A is diffracted by the two-dimensional expansion grating along a path 841A to region 850L, corresponding to the direction of the light to be propagated to the first outcoupler 825A, and a path 841B to region 860R, corresponding to the direction of the light to be propagated to the first outcoupler 825A. The first outcoupler 825A then outcouples the light along paths 861A and 861B to the user's eye box 808.

[0072] The positions of regions 830L and 830R must be different from the positions of regions 850L and 860R, respectively, to ensure that the new grid of diffraction beam regions corresponding to regions 850L and 860R does not align with the current grid of diffraction beam regions corresponding to regions 830L and 830R. Additionally, the placement of the first replica grating 835A and the second replica grating 835B can mitigate situations where the new grid of diffraction beam regions creates a completely new set of exit pupil regions that could potentially reach the user's eyebox and create a "ghost path," which could result in a secondarily shifted copy of the intended virtual content in the user's FOV. In some embodiments, the positions of regions 830L and 830R and the positions of regions 850L and 860R involve shifting the positions of regions 850L and 860R in k-space such that the shifted region positions are sufficiently distant from the current k-space region positions 830L and 830R (e.g., a distance of at least approximately 0.02 k0).

[0073] Figure 8D A comparison of pupil replication diagrams of a waveguide combiner 801 and a conventional grating vector architecture 802 is shown. The pupil replication diagram represents a FOV angle of approximately (0 degrees, 0 degrees). Figure 8D As shown, each point in the pupil replication diagram represents an exit pupil. The eye box 880 of the waveguide combiner 801 includes a larger number of exit pupils than the eye box 882 of the conventional grating vector architecture 802. The eye box 880 receives a larger number of exit pupils, resulting in an increased exit pupil density for a waveguide combiner with the same thickness. Figure 8D This allows for a direct comparison of the enhanced pupil replication and exit pupil density of waveguide combiner 801. The increased pupil density using waveguide combiner 801 is achieved using a substrate having the same thickness as conventional grating vector architecture 802. For example, the exit pupil density is at least about five times higher than that of a waveguide combiner having conventional grating vector architecture 802. Therefore, the thickness of the substrate does not need to be reduced, or can even be increased, while still maintaining a high exit pupil density. This mitigates the negative image effects of in-coupler bounce while also limiting high-frequency non-uniformity.

[0074] The grating vector architecture of each waveguide combiner described herein can be implemented in a practical waveguide combiner. For example, potential variations include changing which surface of the waveguide combiner each grating is located on, altering the geometric boundary shape of the grating region, modifying the grating vector size, and / or using any number of waveguide combiner layers in a stack. In some embodiments, within a single waveguide combiner layer, three display channels (red, green, and blue) can propagate through the same layer and be diffracted from the same grating structure to transmit a virtual image to the user's eyes. In other embodiments, within a three-waveguide layer system, each waveguide combiner layer can be designed to support only a single display color channel. The addition of additional gratings, the grating angles of all gratings, and the spacing of all gratings can be adjusted to achieve a specific set of optical properties.

[0075] Embodiments of near-eye display systems as described herein allow for improvements in exit pupil density, image clarity, and image uniformity by including additional folded gratings. The additional folded grating and replica grating designs on the diffraction waveguide combiner layer are designed to improve exit pupil density without substantially reducing the thickness of the waveguide combiner layer. A waveguide combiner layer that has not had its thickness reduced will experience the benefit of reduced in-coupler bounce. Similarly, embodiments of near-eye display systems with additional folded gratings as described herein allow for reduction of high frequency non-uniformities in the projected image, particularly when using lasers. Reducing high frequency non-uniformities in the projected image can, in turn, improve image clarity and image uniformity.

[0076] While the foregoing is directed to embodiments of the present disclosure, other and further implementations of the disclosure may be devised without departing from the basic scope of the disclosure, the scope of which is to be determined by the claims that follow.

Claims

1. A waveguide combiner, comprising: a first surface; a second surface; an in-coupler located on the first surface and configured to receive a plurality of input beams and diffract a first subset of the beams and a second subset of the beams into total internal reflections (TIRs) in two opposite directions in K-space; a first folding grating located on the first surface and configured to receive the first subset of beams from the incoupler at a first region in K-space and diffract the first subset of beams in TIR to a second region in K-space; a second folding grating located on the first surface and configured to receive the second subset of beams from the incoupler at a third region in K-space and diffract the second subset of beams in TIR to the second region in K-space; as well as A first outcoupler is located on the first surface.

2. The waveguide combiner of claim 1 , wherein the first outcoupler is configured to receive the first subset of beams from the first folding grating and the second subset of beams from the second folding grating at the second region in K-space, diffract a first portion of the first subset of beams and the second subset of beams to a fourth region in K-space, and outcouple a second portion of the first subset of beams and the second subset of beams.

3. The waveguide combiner of claim 2, wherein the first outcoupler is a two-dimensional outcoupler.

4. The waveguide combiner of claim 2 , further comprising a second outcoupler located on the second surface and configured to receive the first subset of beams from the first folding grating and the second subset of beams from the second folding grating at the second region in K-space, diffract the second portion of the first subset of beams and the second subset of beams to a fifth region in K-space, and outcouple the first portion of the first subset of beams and the second subset of beams. 5 . The waveguide combiner of claim 4 , further comprising a third folding grating, wherein the third folding grating is located on the second surface. 6 . The waveguide combiner of claim 5 , further comprising a fourth folded grating located on the second surface.

7. The waveguide combiner of claim 6, wherein the fourth folding grating is located adjacent to the third folding grating, and both the third folding grating and the fourth folding grating are located adjacent to the second outcoupler.

8. A waveguide combiner, comprising: a first surface; a second surface; an in-coupler positioned on the first surface and configured to receive a plurality of input beams and diffract the plurality of input beams into total internal reflections (TIR); a first replica grating located on the first surface adjacent to and below the in-coupler and configured to receive a plurality of input beams from the in-coupler at a first region in K-space and diffract the plurality of input beams in TIR to a second region in K-space; a second replica grating located on the first surface adjacent to and below the first replica grating; a first outcoupler located on the first surface adjacent to or below the second replica grating; as well as A second outcoupler is located on the second surface.

9. The waveguide combiner of claim 8, wherein the first replica grating and the second replica grating are square or rectangular in shape.

10. The waveguide combiner of claim 8, wherein the first outcoupler or the second outcoupler is a two-dimensional outcoupler.

11. The waveguide combiner of claim 8, further comprising a third replica grating, wherein the third replica grating is located on the second surface.

12. The waveguide combiner of claim 11, further comprising a fourth replica grating, the fourth replica grating being located on the second surface.

13. The waveguide combiner of claim 12, wherein the fourth replica grating is located adjacent to and below the third replica grating, and the second outcoupler is located adjacent to and below the fourth replica grating.

14. A waveguide combiner, comprising: a first surface; a second surface; an in-coupler located on the first surface and configured to receive a plurality of input beams and diffract a first subset of the beams and a second subset of the beams into total internal reflections (TIRs) in two opposite directions in K-space; a first folding grating located on the first surface and configured to receive the first subset of beams from the incoupler at a first region in K-space and diffract the first subset of beams in TIR to a second region in K-space; a second folding grating located on the first surface and configured to receive the second subset of beams from the incoupler at a third region in K-space and diffract the second subset of beams in TIR to the second region in K-space; an outcoupler located on the first surface and configured to receive the first subset of beams from the first folding grating and the second subset of beams from the second folding grating at the second region in K-space, diffract a first portion of the first subset of beams and the second subset of beams to a fourth region in K-space, diffract a second portion of the first subset of beams and the second subset of beams to a fifth region in K-space, outcouple a third portion of the first subset of beams and the second subset of beams from a sixth region, and outcouple a fourth portion of the first subset of beams and the second subset of beams from a seventh region in K-space; as well as an expansion grating located on the second surface and configured to receive the first portion of the first subset of beams from the first folding grating and the first portion of the second subset of beams from the second folding grating at the second region in K-space, diffract the third portion of the first subset of beams and the second subset of beams to the sixth region, diffract the fourth portion of the first subset of beams and the second subset of beams to the seventh region in K-space, outcouple the first portion of the first subset of beams and the second subset of beams from the fourth region, and outcouple the second portion of the first subset of beams and the second subset of beams from the fifth region in K-space.

15. The waveguide combiner of claim 14, wherein the in-coupler is circular or oval in shape.

16. The waveguide combiner of claim 14, wherein the first folded grating and the second folded grating are trapezoidal in shape.

17. The waveguide combiner of claim 14, wherein the outcoupler and the extended grating are square or rectangular in shape.

18. The waveguide combiner of claim 14, further comprising a third folding grating located on the second surface.

19. The waveguide combiner of claim 18, further comprising a fourth folding grating located on the second surface.

20. The waveguide combiner of claim 19, wherein the fourth folded grating is located adjacent to the third folded grating, and both the third folded grating and the fourth folded grating are located adjacent to the extended grating.

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