Method and system for large field-of-view augmented reality waveguide utilizing unpolarized light

Abstract

An augmented reality optical system includes a source of virtual content and an eyepiece waveguide optically coupled to the source of virtual content. The eyepiece waveguide includes an incoupling diffractive element and an outcoupling diffractive optical element. At least one of the incoupling diffractive element or the outcoupling diffractive optical element comprises a polarization volume grating (PVG).

Description

PATENT Attorney Docket No. 101782-016010WQ-1526294 Client Ref. No.: ML-5013WOMETHOD AND SYSTEM FOR LARGE FIELD-OF-VIEW AUGMENTED REALITY WAVEGUIDE UTILIZING UNPOLARIZED LIGHTCROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority' to U.S. Provisional Patent Application No. 63 / 724,037, filed November 22, 2024 entitled “METHOD AND SYSTEM FOR LARGE FIELD-OF-VIEW AUGMENTED REALITY WAVEGUIDE UTILIZING UNPOLARIZED LIGHT,” the entire contents of which is hereby incorporated by reference for all purposes.BACKGROUND OF THE INVENTION

[0002] Modem computing and display technologies have facilitated the development of systems for so called “virtual reality” or “‘augmented reality” experiences, wherein digitally reproduced images or portions thereof are presented to a viewer in a manner wherein they seem to be, or may be perceived as, real. A virtual reality, or “VR,” scenario typically involves presentation of digital or virtual image information without transparency to other actual real-world visual input; an augmented reality, or “AR,” scenario typically involves presentation of digital or virtual image information as an augmentation to visualization of the actual world around the viewer.

[0003] Referring to FIG. 1, an augmented reality scene 100 is depicted. The user of an AR technology sees a real-world park-like setting 106 featuring people, trees, buildings in the background, and a real-world concrete platform 120. The user also perceives that he / she "sees" "virtual content" such as a robot statue 110 standing upon the real-world concrete platform 120, and a flying cartoon-like avatar character 102 which seems to be a personification of a bumble bee. The robot statue 110 and the flying cartoon-like avatar character 102 are "virtual" in that they do not exist in the real world. Because the human visual perception system is complex, it is challenging to produce AR technology that facilitates a comfortable, natural-feeling, rich presentation of virtual image elements amongst other virtual or real- world imagery elements.1TOWNSEND 80086574 1

[0004] Despite the progress made in these display technologies, there is a need in the art for improved methods and systems related to augmented reality systems, particularly, display systems.SUMMARY OF THE INVENTION

[0005] The present disclosure relates generally to methods and systems related to projection display systems including wearable displays. More particularly, embodiments of the present invention provide improved systems for compact designs of optical imaging devices. In some embodiments, a full color (i.e., supporting all visible colors such as red, green, and blue), single substrate eyepiece waveguide that is suitable for use in an AR system including a micro-light emitting diode (p-LED) projector is provided. In other embodiments, LCDS, DMD, or other projectors can be utilized. The full color, single substrate eyepiece waveguide supports incoupling, propagation by total internal reflection, and outcoupling of virtual content generated using the projector. Although the present invention is described in reference to an AR device, the disclosure is applicable to a variety of applications in computer vision and image display systems.

[0006] According to some embodiments, a large field of view (FOV) hybrid AR waveguide utilizing unpolarized light is provided. As an example, a hybrid AR waveguide design is described that can achieve high-efficiency with an unpolarized light source, while maintaining the full FOV within the visible range. In an embodiment, two pairs of polarization volume gratings (PVGs) are used as ICGs. Transmissive ICGs are optimized for one color group, while reflective ICGs are optimized for another color group. The color groups can be selected from visible wavelengths, for example, red wavelengths making up Color Group 1 and blue and green wavelengths making up Color Group 2, can be complementary in the sense that the color groups do not overlap in wavelength. The output coupler gratings (OCGs) include 2D transmissive surface relief gratings (SRGs) and reflective SRGs, outcoupling the light from transmissive PVG ICG and reflective PVG ICG, respectively.

[0007] Numerous benefits are achieved by way of the present disclosure over conventional techniques. For example, the use of the eyepiece waveguide designs discussed herein for AR displays can have multiple benefits. First, it can successfully pair with an unpolarized light source and have the benefits of high efficiency of liquid crystal PVGs (LCPVGs). Besides,2TOWNSEND 80086574 1separate routes for color-based light path designs can further guarantee the delicate efficiency control and color uniformity across different eyeboxes. Additionally, embodiments of the present invention can enable the FOV of each color to be maintained through the grating grouping. Moreover, the PVG ICG facilitates high input coupling efficiency for unpolarized light and manifests low back-coupling to the eye-side, which can significantly enhance the total waveguide brightness. These and other embodiments of the disclosure, along with many of its advantages and features, are described in more detail in conjunction with the text below and corresponding figures.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Illustrative embodiments of the present invention are described in detail below with reference to the following drawing figures:

[0009] FIG. 1 illustrates a user's view of augmented reality (AR) through an AR device.

[0010] FIG. 2A illustrates a cross-sectional, side view of an example of a set of stacked waveguides that each includes an incoupling optical element.

[0011] FIG. 2B illustrates a perspective view of an example of the one or more stacked waveguides of FIG. 2A.

[0012] FIG. 2C illustrates a top-down, plan view of an example of the one or more stacked waveguides of FIGS. 2A and 2B.

[0013] FIG. 3 is a simplified illustration of an eyepiece waveguide having a combined pupil expander.

[0014] FIG. 4 illustrates an example of wearable display system.

[0015] FIG. 5 show s a perspective view7of a w earable device.

[0016] FIG. 6 is a simplified cross-sectional diagram illustrating a first series of light interactions in a first eyepiece waveguide according to an embodiment of the present invention. In the eyepiece waveguide 610, the combination of 620 and 622 are the combination of two transmissive PVGs that in-couple a first series of light. The working principle is described in FIG. 1 IB. Element 640 is a either a SRG 2D grating, or multi-stack- PVG-based CPE / OPE, for pupil expansion and outcoupling of the first series of light.3TOWNSEND 80086574 1

[0017] FIG. 7 is a simplified cross-sectional diagram illustrating a second series of light interactions in the first eyepiece waveguide according to an embodiment of the present invention. In the eyepiece waveguide 610, the combination of 630 and 632 are the combination of two reflective PVGs that in-couple a second series of light. The working principle is described in FIG. 10C. Element 642 (e.g., an SRG) is either a SRG 2D grating, or multi-stack-PVG-based CPE / OPE, for pupil expansion and outcoupling of the second series of light.

[0018] FIG. 8 is a simplified cross-sectional diagram illustrating a first series of light interactions in a second eyepiece waveguide according to an embodiment of the present invention. In the eyepiece waveguide 810, the combination of 820 and 822 are the combination of two transmissive PVGs that in-couple a first series of light. The working principle is described in FIG. 1 IB. Elements 842 and 850 (e.g., SRGs) can be a onedimensional grating for pupil expansion and outcoupling, respectively, of the first series of light.

[0019] FIG. 9 is a simplified cross-sectional diagram illustrating a second series of light interactions in the second eyepiece waveguide according to an embodiment of the present invention. In the eyepiece waveguide 810, the combination of 830 and 832 are the combination of two reflective PVGs that in-couple a second series of light. The working principle is described in FIG. 10C. Elements 840 and 852 (e.g., SRGs) can be a onedimensional grating for pupil expansion and outcoupling, respectively, of the first series of light.

[0020] FIG. 10A is a simplified diagram illustrating the working principle of reflective PVGs designed for right-hand-polarization (RHP) input that diffracts RHP.

[0021] FIG. 10B is a simplified diagram illustrating the working principle of a combination of reflective PVGs and a customized retarder film. The reflective PVGs is designed for RHP input that diffracts left-hand-polarization (LHP), according to another embodiment of the present invention.

[0022] FIG. 10C is a simplified diagram illustrating the working principle of reflective color-splitting ICGs according to another embodiment of the present invention. The input is unpolarized light and the output is unpolarized light.4TOWNSEND 80086574 1

[0023] FIG. 11 A is a simplified diagram illustrating the working principle of transmissive PVGs designed for RHP.

[0024] FIG. 1 IB is a simplified diagram illustrating the working principle of transmissive color-splitting ICGs according to an embodiment of the present invention. The input is unpolarized light and the output is unpolarized light.

[0025] FIG. 12A is a simplified cross-sectional diagram illustrating a first series of light interactions in a third eyepiece waveguide according to an embodiment of the present invention. In the eyepiece waveguide 1210, Elements 1220 and 1240 are, respectively, a transmissive PVG with its working principle illustrated in FIG. 11 A, while Element 1230 is a reflective PVG operating as illustrated in FIG. 10A. Combining FIG. 12A and FIG. 12B, the unpolarized input light can be outcoupled as RHP light for one or more colors of light.

[0026] FIG. 12B is a simplified cross-sectional diagram illustrating a second series of light interactions in the third eyepiece waveguide according to an embodiment of the present invention. In the eyepiece waveguide 1210, Element 1221 is a structure described in FIG. 10B, Elements 1231 and 1241 are reflective PVGs described in FIG. 10A. Combining FIG. 12A and FIG. 12B, the unpolarized input light can be outcoupled as RHP light for one or more colors of light.

[0027] FIG. 12C. which is another possible variation of FIG. 12A, is a simplified cross- sectional diagram illustrating that the first series of light shares the same out-coupler with the first series of light. In the eyepiece waveguide 1210, Element 1220 is a transmissive PVG with its working principle described in FIG. 11 A. Elements 1230 and 1241 are, respectively, a reflective PVG with its working principle described in FIG. 10A. Combining FIG. 12B and FIG. 12C, the unpolarized input light can be outcoupled as RHP light for one or more colors of light by sharing exit pupil expander (EPE) implemented by Element 1241.

[0028] FIG. 12D, which is another possible variation of FIG. 12B, is a simplified cross- sectional diagram illustrating that the second series of light shares the same out-coupler with the first series of light. In the eyepiece waveguide 1210, Element 1240 is a transmissive PVG with its working principle described in FIG. HA. Elements 1221 and 1231 are, respectively, a reflective PVG with its working principle described in FIG. 10A. Combining FIG. 12A and FIG. 12D, the unpolarized input light can be outcoupled as RHP light for one or more colors of light by sharing Element 1240 as an EPE.5TOWNSEND 80086574 1

[0029] FIG. 13 A is a simplified cross-sectional diagram illustrating a first series of light interactions in an alternative to the third eyepiece waveguide illustrated in FIG. 12A according to an embodiment of the present invention. In the eyepiece waveguide 1310, Elements 1320 and 1340 are, respectively, a transmissive PVG operating as illustrated in FIG. 11A, while Element 1330 is a reflective PVG operating as illustrated in FIG. 10A. Combining FIG. 13A and FIG. 13B, the unpolarized input light can be outcoupled as unpolarized light for one or more colors of light.

[0030] FIG. 13B is a simplified cross-sectional diagram illustrating a second series of light interactions in an alternative to the third eyepiece waveguide illustrated in FIG. 12B according to an embodiment of the present invention. In the eyepiece waveguide 1310, Elements 1321. 1331, and 1341 are, respectively, a reflective PVG operating as illustrated in FIG. 10A. Combining FIG. 13 A and FIG. 13B, the unpolarized input light can be outcoupled as unpolarized light for one or more colors of light.

[0031] FIG. 13C, which is another possible variation of FIG. 13B, is a simplified cross- sectional diagram illustrating a second series of light interactions in an alternative to the third eyepiece waveguide, according to an embodiment of the present invention. In the eyepiece waveguide 1310, Elements 1321, 1331, and 1341 are, respectively, a reflective PVG operating as illustrated in FIG. 10A, while Element 1340 can also be designed to impose halfwave (HW) retardation for the second series of light so that the output polarization changes from RHP to LHP. Combining FIG. 13A and FIG. 13C, the unpolarized input light can be outcoupled as RHP for one or more colors of light.

[0032] FIG. 14A is a simplified cross-sectional diagram illustrating a first series of light interactions in the third eyepiece waveguide according to an embodiment of the present invention, which demonstrates a case of orthogonal polarization of FIG. 12A. In the eyepiece waveguide 1410, Elements 1420 and 1440 are, respectively, a transmissive PVG operating as illustrated in FIG. 11 A. while Element 1430 is a reflective PVG operating as illustrated in FIG. 10A. Combining FIG. 14A and FIG. 14B, the unpolarized input light can be outcoupled as LHP light for one or more colors of light.

[0033] FIG. 14B is a simplified cross-sectional diagram illustrating a second series of light interactions in the third eyepiece waveguide according to an embodiment of the present invention, which demonstrates a case of orthogonal polarization of FIG. 12B. In the eyepiece waveguide 1410, Element 1421 is a structure operating as illustrated in FIG. 10B, Elements6TOWNSEND 80086574 11431 and 1441 are, respectively, a type of PVG similar to that shown in FIG. 10A. Combining FIG. 14A and FIG. 14B, the unpolarized input light can be outcoupled as LHP light for one or more colors of light.

[0034] FIG. 14C is a simplified cross-sectional diagram illustrating a first series of light interactions in the third eyepiece waveguide according to an embodiment of the present invention, which demonstrates a case of orthogonal polarization of FIG. 12C, as well as a variation of FIG. 14A. In the eyepiece waveguide 1410 is a transmissive PVG operating as illustrated in FIG. 11A, while Elements 1430 and 1441 are reflective PVGs operating as illustrated in FIG. 10A. Combining FIG. 14C and FIG. 14B, the unpolarized input light can be outcoupled as LHP light for one or more colors of light by sharing Element 1441 as an EPE.

[0035] FIG. 14D is a simplified cross-sectional diagram illustrating a second series of light interactions in the third eyepiece waveguide according to an embodiment of the present invention, which demonstrates a case of orthogonal polarization of FIG. 12D, as well as a variation of FIG. 14B. In the eyepiece waveguide 1410, Element 1421 is a structure operating as illustrated in FIG. 10B, Elements 1431 and 1441 are, respectively, a type of PVG similar to that illustrated in FIG. 10A. Combining FIG. 14A and FIG. 14D, the unpolarized input light can be outcoupled as LHP light for one or more colors of light by sharing Element 1440 as an EPE.

[0036] FIG. 15 A is a simplified cross-sectional diagram illustrating a first series of light interactions in an alternative to the third eyepiece waveguide illustrated in FIG. 14A according to an embodiment of the present invention, which also demonstrates a case of orthogonal polarization of FIG. 13A. In the eyepiece waveguide 1510, Elements 1520 and 1540 are, respectively, a transmissive PVG operating as illustrated in FIG. 11 A, while Element 1530 is a reflective PVG operating as illustrated in FIG. 10A. Combining FIG. 15A and FIG. 15B, the unpolarized input light can be outcoupled as unpolarized light for one or more colors of light.

[0037] FIG. 15B is a simplified cross-sectional diagram illustrating a second series of light interactions in an alternative to the third eyepiece waveguide illustrated in FIG. 14B according to an embodiment of the present invention, which demonstrates a case of orthogonal polarization of FIG. 13B. In the eyepiece waveguide 1510, Elements 1521. 1531, and 1541 are, respectively, a reflective PVG operating as illustrated in FIG. 10A. Combining7TOWNSEND 80086574 1FIG. 15 A and FIG. 15B, the unpolarized input light can be outcoupled as unpolarized light for one or more colors of light.

[0038] FIG. 15C. which is another possible variation of FIG. 15B, is a simplified cross- sectional diagram illustrating a second series of light interactions in an alternative to the third eyepiece waveguide, according to an embodiment of the present invention. In the eyepiece waveguide 1510, Elements 1521, 1531, and 1541 are, respectively, a reflective PVG operating as illustrated in FIG. 10A. Combining FIG. 15 A and FIG. 15C, 1540 can also be designed to impose half-wave (HW) retardation for the second series of light so that the output polarization changes from LHP to RHP. The unpolarized input light can be outcoupled as polarized light for one or more colors of light.

[0039] FIG. 16A is a simplified cross-sectional diagram illustrating a first series of light interactions in a fourth eyepiece waveguide according to an embodiment of the present invention. The fourth eyepiece waveguide illustrated in FIG. 16A is a variation of that shown in FIG. 12A such that the PVG orthogonal pupil expander (OPE) is at the user side. In the eyepiece waveguide 1610, Elements 1620 and 1640 are, respectively, a transmissive PVG with its working principle described in FIG. 11 A, while 1630 is a reflective PVG with its working principle described in FIG. 10A. Combining FIG. 16A and FIG. 16B, the unpolarized input light can be outcoupled as RHP light for one or more colors of light.

[0040] FIG. 16B is a simplified cross-sectional diagram illustrating a second series of light interactions in the fourth eyepiece waveguide according to an embodiment of the present invention. The fourth eyepiece waveguide illustrated in FIG. 16A is a variation of that shown in FIG. I2B such that the PVG OPE is at the world side. In the eyepiece waveguide 1610, Element 1621 is a structure described in FIG. 10B, Elements 1631 and 1641 are a reflective PVG similar to that illustrated in FIG. 10A. Combining FIG. 16A and FIG. 16B, the unpolarized input light can be outcoupled as RHP light for one or more colors of light.

[0041] FIG. 16C is a simplified cross-sectional diagram illustrating a first series of light interactions in the fourth eyepiece waveguide according to an embodiment of the present invention. The fourth eyepiece waveguide illustrated in FIG. 16C is a variation of that shown in FIG. 12C such that the PVG OPE is at the user side. In the eyepiece waveguide 1610, Element 1620 is a transmissive PVG with its working principle described in FIG. 11A, while 1630 and 1641 are. respectively, a reflective PVG with its working principle described in8TOWNSEND 80086574 1FIG. 10A. Combining FIG. 16B and FIG. 16C, the unpolarized input light can be outcoupled as RHP light for one or more colors of light by sharing Element 1641 as an EPE.

[0042] FIG. 16D is a simplified cross-sectional diagram illustrating a second series of light interactions in the fourth eyepiece waveguide according to an embodiment of the present invention. The fourth eyepiece waveguide illustrated in FIG. 16D is a variation of that shown in FIG. 12B such that Element 1631 (e.g., a PVG OPE) is at the world side. In the ey epiece waveguide 1610, Element 1621 is a structure with its working principle described in FIG. 10B, Elements 1631 and 1640 are, respectively, a reflective PVG with its working principle described in FIG.10A and transmissive PVG with its working principle described in FIG.11 A. Combining FIG. 16A and FIG. 16D, the unpolarized input light can be outcoupled as RHP light for one or more colors of light.

[0043] FIG. 17A is a simplified cross-sectional diagram illustrating a first series of light interactions in an alternative to the fourth eyepiece waveguide illustrated in FIG. 17A according to an embodiment of the present invention. The fourth eyepiece waveguide illustrated in FIG. 17A is a variation of that shown in FIG. 13 A such that the OPE PVG grating is at the user side. In the eyepiece waveguide 1710, Elements 1720 and 1740 are, respectively, a transmissive PVG with its working principle described in FIG. 11 A, while 1730 is a reflective PVG with its working principle described in FIG. 10A. Combining FIG. 17A and FIG. 17B, the unpolarized input light can be outcoupled as unpolarized light for one or more colors of light.

[0044] FIG. 17B is a simplified cross-sectional diagram illustrating a second series of light interactions in an alternative to the fourth eyepiece waveguide illustrated in FIG. 17B according to an embodiment of the present invention. The fourth eyepiece waveguide illustrated in FIG. 17B is a variation of that shown in FIG. 13B such that the OPE PVG grating is at the user side. In the eyepiece waveguide 1710, Element 1721 is a structure with its working principle described in FIG. 10B. Elements 1731 and 1741 are, respectively, a type of PVG similar to that shown in FIG.10A. Combining FIG. 17A and FIG. 17B, the unpolarized input light can be outcoupled as unpolarized light for one or more colors of light.

[0045] FIG. 17C, w hich is another possible variation of FIG. 17B, is a simplified cross- sectional diagram illustrating a second series of light interactions in an alternative to the fourth eyepiece waveguide, according to an embodiment of the present invention. In the eyepiece waveguide 1710, Elements 1721, 1731, and 1741 are, respectively, a reflective PVG9TOWNSEND 80086574 1with its working principle described in FIG. 10A, while Element 1740 can also be designed to impose half-wave (HW) retardation for the second series of light so that the output polarization changes from LHP to RHP. Combining FIG. 17A and FIG. 17C, the unpolarized input light can be outcoupled as RHP for one or more colors of light.

[0046] FIG. 18A is a simplified cross-sectional diagram illustrating a first series of light interactions in a fourth eyepiece waveguide according to an embodiment of the present invention, which demonstrates a case of orthogonal polarization of FIG. 16A. In the eyepiece waveguide 1810, Elements 1820 and 1840 are, respectively, a transmissive PVG with its working principle described in FIG. 11A, while Element 1830 is a reflective PVG with its working principle described in FIG. 10 A. Combining FIG. 18A and FIG. 18B, the unpolarized input light can be outcoupled as LHP light for one or more colors of light.

[0047] FIG. 18B is a simplified cross-sectional diagram illustrating a second series of light interactions in the fourth eyepiece waveguide according to an embodiment of the present invention, which demonstrates a case of orthogonal polarization of FIG. 16B. In the eyepiece waveguide 1810, Element 1821 is a structure with its working principle described in FIG. 10B, Elements 1831 and 1841 are, respectively, a type of PVG similar to that shown in FIG.10A. Combining FIG. 18A and FIG. 18B, the unpolarized input light can be outcoupled as LHP light for one or more colors of light.

[0048] FIG. 18C is a simplified cross-sectional diagram illustrating a first series of light interactions in the fourth eyepiece waveguide according to an embodiment of the present invention, which demonstrates a case of orthogonal polarization of FIG. 16C. In the eyepiece waveguide 1810. Element 1820 is a transmissive PVG with its working principle is described in FIG. 11A, while Elements 1830 and 1841 are, respectively, a reflective PVG with its working principle described in FIG. 10A. Combining FIG. 18B and FIG. 18C, the unpolarized input light can be outcoupled as LHP light for one or more colors of light by sharing Element 1841 as an EPE.

[0049] FIG. 18D is a simplified cross-sectional diagram illustrating a second series of light interactions in the fourth eyepiece waveguide according to an embodiment of the present invention, which demonstrates a case of orthogonal polarization of FIG. 16D. In the eyepiece waveguide 1810, Element 1821 is a structure with its working principle described in FIG. 10B, Elements 1831 and 1840 are, respectively, a reflective PVG with its working principle described in FIG. 10A and transmissive PVG with its working principle described in FIG.10TOWNSEND 80086574 111 A. Combining FIG. 18A and FIG. 18D, the unpolarized input light can be outcoupled as LHP light for one or more colors of light.

[0050] FIG. 19A is a simplified cross-sectional diagram illustrating a first series of light interactions in an alternative to the fourth eyepiece waveguide illustrated in FIG. 18A according to an embodiment of the present invention, which demonstrates a case of orthogonal polarization of FIG. 17A. In the eyepiece waveguide 1910, Elements 1920 and 1940 are, respectively, a transmissive PVG with its working principle described in FIG. 11 A, while Element 1930 is a reflective PVG with its working principle described in FIG. 10 A. Combining FIG. 19A and FIG. 19B, the unpolarized input light can be outcoupled as unpolarized light for one or more colors of light.

[0051] FIG. 19B is a simplified cross-sectional diagram illustrating a second series of light interactions in an alternative to the fourth eyepiece waveguide illustrated in FIG. 18B according to an embodiment of the present invention, which demonstrates a case of orthogonal polarization of FIG. 17B. In the eyepiece waveguide 1910, Element 1921 is a structure with its working principle described in FIG. 10B, Elements 1931 and 1941 are, respectively, a type of PVG similar to that shown in FIG. 10A. Combining FIG. 19A and FIG. 19B, the unpolarized input light can be outcoupled as unpolarized light for one or more colors of light.

[0052] FIG. 19C, which is another possible variation of FIG. 19B, is a simplified cross- sectional diagram illustrating a second series of light interactions in an alternative to the fourth eyepiece waveguide, according to an embodiment of the present invention. In the eyepiece waveguide 1910, Elements 1921. 1931, and 1941 are, respectively, a reflective PVG with its working principle described in FIG. 10 A, while 1940 can also be designed to impose half-wave (HW) retardation for the second series of light so that the output polarization changes from RHP to LHP. Combining FIG. 19A and FIG. 19C, the unpolarized input light can be outcoupled as LHP for one or more colors of light.

[0053] FIG. 20 illustrates a plan view of an eyepiece waveguide and corresponding grating vectors for a first circular polarization according to an embodiment of the present invention.

[0054] FIG. 21 illustrates a plan view of another eyepiece waveguide and corresponding grating vectors for a second circular polarization according to an embodiment of the present invention.11TOWNSEND 80086574 1

[0055] FIG. 22 is a simplified cross-section view of an eyepiece waveguide including a stack with a multilayer LC grating structure according to an embodiment of the present invention.

[0056] FIG. 23 illustrates a perspective view of light propagation in an eyepiece waveguide for a first circular polarization according to an embodiment of the present invention.

[0057] FIG. 24 illustrates a perspective view of light propagation in the eyepiece waveguide of FIG. 23 for a second circular polarization according to an embodiment of the present invention.

[0058] FIG. 25 is a simplified k-space diagram for a conventional eyepiece waveguide.

[0059] FIG. 26A is a simplified cross-sectional diagram of an eyepiece waveguide with a three layer PVG stack according to an embodiment of the present invention.

[0060] FIG. 26B is a simplified k-space diagram for the eyepiece waveguide show n in FIG. 26A according to an embodiment of the present invention.

[0061] FIG. 27 is a simplified cross-sectional diagram of an eyepiece waveguide with dual sided PVGs according to an embodiment of the present invention.

[0062] FIG. 28 is a simplified cross-sectional diagram of an eyepiece w aveguide with a two layer PVG stack according to an embodiment of the present invention.

[0063] FIG. 29 is a simplified cross-sectional diagram of an eyepiece waveguide structure incorporating two substrates and an encapsulation layer according to an embodiment of the present invention.

[0064] FIG. 30 is a simplified block diagram illustrating components of an AR system.DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0065] The inventors have determined that to maintain a large field of view (FOV), surface-relief grating (SRG) based waveguide designs launch color into different light paths. However, the SRG gratings can still suffer from non-uniformity of different polarization, severe back-coupling, and undesired high-order diffraction from the input coupler grating (ICG), which significantly reduces the waveguide efficiency. Besides, due to their high brightness, p-LEDs have become a more attractive ty pe of light source. However, since the p-LED generates mostly unpolarized light, the SRG-based AR waveguide that is mostly12TOWNSEND 80086574 1optimized for either s-polarization, or p-polarization, can be a hurdle for further improvement of the waveguide efficiency. Therefore, embodiments of the present invention provide a eyepiece waveguide structure that can have high output efficiency, a large FOV, and can operate using an unpolarized light source.

[0066] With reference now to FIG. 2A, in some embodiments, light impinging on a waveguide may need to be redirected to incouple that light into the waveguide. An incoupling optical element may be used to redirect and incouple the light into its corresponding waveguide. Although referred to as "incouphng optical element" through the specification, the incouphng optical element need not be an optical element and may be a non-optical element. FIG. 2A illustrates a cross-sectional, side view of an example of a set of stacked waveguides 200 that each includes an incouphng optical element. The waveguides may each be configured to output light of one or more different wavelengths, or one or more different ranges of wavelengths. Light from a projector is injected into the set of stacked waveguides 200 and outcoupled to a user as described more fully below.

[0067] The illustrated set of stacked waveguides 200 includes waveguide 202, waveguide 204, and waveguide 206. Each waveguide includes an associated incouphng optical element (which may also be referred to as a light input area on the waveguide), with, e.g., incouphng optical element 203 disposed on a major surface (e.g., an upper major surface) of waveguide 202, incoupling optical element 205 disposed on a major surface (e.g., an upper major surface) of waveguide 204, and incoupling optical element 207 disposed on a major surface (e.g., an upper major surface) of waveguide 206. In some embodiments, one or more of the incoupling optical elements may be disposed on the bottom major surface of the respective waveguide (particularly where one or more incoupling optical elements are reflective, deflecting optical elements). As illustrated, the incoupling optical element 203, the incoupling optical element 205, and the incouphng optical element 207 may be disposed on the upper major surface of waveguide 202, waveguide 204, and waveguide 206, respectively (or the top of the next lower waveguide), particularly where those incoupling optical elements are transmissive, deflecting optical elements. In some embodiments, the incoupling optical element 203, the incoupling optical element 205, and the incoupling optical element 207 may be disposed in the body of the waveguide 202. waveguide 204, and waveguide 206, respectively. In some embodiments, as discussed herein, the incoupling optical element 203, the incoupling optical element 205, and the incoupling optical element 207 are wavelength- selective, such that they selectively redirect one or more wavelengths of light, while13TOWNSEND 80086574 1transmitting other wavelengths of light. While illustrated on one side or comer of waveguide 202, waveguide 204, and waveguide 206, respectively, it will be appreciated that the incoupling optical element 203, the incoupling optical element 205, and the incoupling optical element 207 may be disposed in other areas of waveguide 202, waveguide 204, and waveguide 206, respectively, in some embodiments.

[0068] As illustrated, the incoupling optical element 203, the incoupling optical element 205, and the incoupling optical element 207 may be laterally offset from one another. In some embodiments, each incoupling optical element may be offset such that it receives light without that light passing through another incoupling optical element. For example, each of the incoupling optical element 203, the incoupling optical element 205, and the incoupling optical element 207 may be configured to receive light from a different projector and may be separated (e.g., laterally spaced apart) from other incoupling optical elements such that it substantially does not receive light from the other ones of the incoupling optical elements.

[0069] Each waveguide also includes associated light distributing elements, with, e.g., light distributing elements 210 disposed on a major surface (e.g., a top major surface) of waveguide 202, light distributing elements 212 disposed on a major surface (e.g., a top major surface) of waveguide 204, and light distributing elements 214 disposed on a major surface (e.g., a top major surface) of waveguide 206. In some other embodiments, the light distributing elements 210, the light distributing elements 212, and the light distributing elements 214 may be disposed on a bottom major surface of associated waveguide 202, waveguide 204, and waveguide 206, respectively. In some other embodiments, the light distributing elements 210, the light distributing elements 212, and the light distributing elements 214 may be disposed on both top and bottom major surfaces of associated waveguide 202, waveguide 204, and waveguide 206, respectively; or the light distributing elements 210, the light distributing elements 212, and the light distributing elements 214 may be disposed on different ones of the top and bottom major surfaces in different associated waveguide 202, waveguide 204, and waveguide 206, respectively.

[0070] Waveguide 202, waveguide 204, and waveguide 206 may be spaced apart and separated by, e.g., gas, liquid, and / or solid layers of material. For example, as illustrated in FIG. 2A, layer 208 may separate waveguide 202 and waveguide 204 and layer 209 may separate waveguide 204 and waveguide 206. In some embodiments, layer 208 and layer 209 are formed of low refractive index materials (that is, materials having a lower refractive index14TOWNSEND 80086574 1than the material forming the immediately adjacent one of waveguide 202, waveguide 204, or waveguide 206). Preferably, the refractive index of the material forming layer 208 and / or layer 209 is 0.05 or more, or 0. 10 or less than the refractive index of the material forming the waveguide 202, the waveguide 204, or the waveguide 206. Advantageously, layer 208 and layer 209 having the lower refractive index may function as cladding layers that facilitate total internal reflection (TIR) of light through the waveguide 202, the waveguide 204, and the waveguide 206 (e.g., TIR between the top and bottom major surfaces of each waveguide). In some embodiments, the layer 208 and the layer 209 are formed of air. While not illustrated, it will be appreciated that the top and bottom of the illustrated set of stacked waveguides 200 may include immediately neighboring cladding layers.

[0071] Preferably, for ease of manufacturing and other considerations, the material forming the waveguide 202, the waveguide 204, and the waveguide 206 are similar or the same, and the material forming the layer 208 and the layer 209 are similar or the same. In some embodiments, the material forming the waveguide 202, the waveguide 204, and the waveguide 206 may be different between one or more waveguides, and / or the material forming the layer 208 and the layer 209 may be different, while still holding to the various refractive index relationships noted above.

[0072] With continued reference to FIG. 2A, light ray 218, light ray 219, and light ray 220 are incident on the set of stacked waveguides 200. It will be appreciated that the light ray 218, the light ray 219, and the light ray 220 may be injected into the waveguide 202, the waveguide 204, and the waveguide 206 by one or more projectors (not shown).

[0073] In some embodiments, light ray 218. the light ray 219. and the light ray 220 have different properties, e.g., different wavelengths or different ranges of wavelengths, which may correspond to different colors. The incoupling optical element 203, the incoupling optical element 205, and the incoupling optical element 207 each deflect the incident light such that the light propagates through a respective one of the waveguide 202. the waveguide 204, or the waveguide 206 by TIR. In some embodiments, the incoupling optical element 203, the incoupling optical element 205, and the incoupling optical element 207 each selectively deflect one or more particular wavelengths of light, while transmitting other wavelengths to an underlying waveguide and associated incoupling optical element.

[0074] For example, incoupling optical element 203 may be configured to deflect light ray 218, which has a first wavelength or range of wavelengths, while transmitting light ray 21915TOWNSEND 80086574 1and light ray 220. which have different second and third wavelengths or ranges of wavelengths, respectively. The light ray 219 transmitted through the waveguide 202 impinges on and is deflected by the incoupling optical element 205, which is configured to deflect light of a second wavelength or range of wavelengths. The light ray 220 is deflected by the incoupling optical element 207, which is configured to selectively deflect light of third wavelength or range of wavelengths.

[0075] With continued reference to FIG. 2A, the light ray 218, the light ray 219, and the light ray 220 are deflected such that they propagate through corresponding waveguide 202, waveguide 204, and waveguide 206, respectively; that is, the incoupling optical element 203, the incoupling optical element 205, and the incoupling optical element 207 of each waveguide deflects the light into the corresponding waveguide 202, waveguide 204, or waveguide 206 to incouple light into that corresponding waveguide. The light ray 218, the light ray 219, and the light ray 220 are deflected at angles that cause the light to propagate through the respective waveguide 202, waveguide 204, and waveguide 206 by TIR. The light ray 218, the light ray 219, and the light ray 220 propagate through the respective waveguide202, waveguide 204, and waveguide 206 by TIR until impinging on the waveguide's corresponding light distributing elements: the light distributing elements 210, the light distributing elements 212, and the light distributing elements 214, where they are outcoupled to provide out-coupled light rays 216.

[0076] With reference now to FIG. 2B, a perspective view of an example of the set of stacked waveguides 200 of FIG. 2A is illustrated. As noted above, the light ray 218, the light ray 219, and the light ray 220 are incoupled and deflected by the incoupling optical element203, the incoupling optical element 205, and the incoupling optical element 207, respectively, and then propagate by TIR within the waveguide 202, the waveguide 204, and the waveguide 206, respectively. The light ray 218. the light ray 219, and the light ray 220 then impinge on the light distributing elements 210, the light distributing elements 212, and the light distributing elements 214, respectively. The light distributing elements 210, the light distributing elements 212, and the light distributing elements 214 deflect the light ray 218, the light ray 219, and the light ray 220 so that they propagate towards the outcoupling optical elements 222, the outcoupling optical elements 224. and the outcoupling optical elements 226, respectively.16TOWNSEND 80086574 1

[0077] In some embodiments, the light distributing elements 210, the light distributing elements 212, and the light distributing elements 214 are orthogonal pupil expanders (OPEs). In some embodiments, the OPEs deflect or distribute light to the outcoupling optical elements 222, the outcoupling optical elements 224, and the outcoupling optical elements 226 and, in some embodiments, may also increase the beam or spot size of this light as it propagates to the outcoupling optical elements. In some embodiments, the light distributing elements 210, the light distributing elements 212, and the light distributing elements 214 may be omitted and the incoupling optical element 203, the incoupling optical element 205, and the incoupling optical element 207 may be configured to deflect light directly to the outcoupling optical elements 222, the outcoupling optical elements 224, and the outcoupling optical elements 226. For example, with reference to FIG. 2A, the light distributing elements 210. the light distributing elements 212, and the light distributing elements 214 may be replaced with the outcoupling optical elements 222, the outcoupling optical elements 224, and the outcoupling optical elements 226, respectively. In some embodiments, the outcoupling optical elements 222. the outcoupling optical elements 224, and the outcoupling optical elements 226 are exit pupils (EPs) or exit pupil expanders (EPEs) that direct light to the eye of the user. It will be appreciated that the OPEs may be configured to increase the dimensions of the eye box in at least one axis and the EPEs may be configured to increase the eye box in an axis crossing, e.g., orthogonal to, the axis of the OPEs. For example, each OPE may be configured to redirect a portion of the light striking the OPE to an EPE of the same waveguide, while allowing the remaining portion of the light to continue to propagate down the waveguide. Upon impinging on the OPE again, another portion of the remaining light is redirected to the EPE, and the remaining portion of that portion continues to propagate further down the waveguide, and so on. Similarly, upon striking the EPE, a portion of the impinging light is directed out of the waveguide towards the user, and a remaining portion of that light continues to propagate through the waveguide until it strikes the EPE again, at which time another portion of the impinging light is directed out of the w aveguide, and so on. Consequently, a single beam of incoupled light may be "replicated" each time a portion of that light is redirected by an OPE or EPE, thereby forming a field of cloned beams of light. In some embodiments, the OPE and / or EPE may be configured to modify a size of the beams of light. In some embodiments, the functionality of the light distributing elements 210, the light distributing elements 212, and the light distributing elements 214 and the outcoupling optical elements 222. the outcoupling optical elements 224, and the outcoupling optical elements 226 are combined in a combined pupil expander as discussed in relation to FIG. 2E.17TOWNSEND 80086574 1

[0078] Accordingly, with reference to FIGS. 2A and 2B, in some embodiments, the set of stacked waveguides 200 includes the waveguide 202, the waveguide 204. and the waveguide 206; the incoupling optical element 203, the incouphng optical element 205, and the incoupling optical element 207; the light distributing elements 210, the light distributing elements 212, and the light distributing elements 214 (e.g., OPEs); and the outcoupling optical elements 222, the outcoupling optical elements 224, and the outcoupling optical elements 226 (e.g., EPs) for each component color. The waveguide 202, the waveguide 204, and the waveguide 206 may be stacked with an air gap / cladding layer between each one. The incouphng optical element 203, the incoupling optical element 205, and the incoupling optical element 207 redirect or deflect incident light (with different incouphng optical elements receiving light of different wavelengths) into its waveguide. The light then propagates at an angle which will result in TIR within the waveguide 202, the waveguide 204, and the waveguide 206, respectively. In the example shown, light ray 218 (e.g., blue light) is deflected by the incoupling optical element 203, and then continues to bounce down the waveguide, interacting with the light distributing element 210 (e.g., OPEs) and then the outcoupling optical element 222 (e.g., EPs), in a manner described earlier. The light ray 219 and the light ray 220 (e.g., green and red light, respectively) will pass through the waveguide 202, with light ray 219 impinging on and being deflected by incoupling optical element 205. The light ray 219 then bounces down the waveguide 204 via TIR, proceeding on to its light distributing element 212 (e.g., OPEs) and then the outcoupling optical element 224 (e.g., EPs). Finally, light ray 220 (e.g., red light) passes through the waveguide 206 to impinge on the incoupling optical element 207 of the waveguide 206. The incoupling optical element 207 deflects the light ray 220 such that the light ray propagates to light distributing element 214 (e.g., OPEs) by TIR, and then to the outcoupling optical element 226 (e.g., EPs) by TIR. The outcoupling optical element 226 then finally out-couples the light ray 220 to the viewer, who also receives the outcoupled light from the other waveguides: the waveguide 202 and the waveguide 204.

[0079] FIG. 2C illustrates a top-down, plan view- of an example of the set of stacked waveguides 200 of FIGS. 2A and 2B. As illustrated, the waveguide 202, the waveguide 204, and the waveguide 206, along with each waveguide's associated light distributing element: the light distributing element 210, light distributing element 212, and light distributing element 214 and the associated outcoupling optical elements: the outcoupling optical elements 222, the outcoupling optical elements 224, and the outcoupling optical elements18TOWNSEND 80086574 1226, may be vertically aligned. However, as discussed herein, the incoupling optical element 203, the incoupling optical element 205, and the incoupling optical element 207 are not vertically aligned; rather, the incoupling optical elements are preferably nonoverlapping (e.g., laterally spaced apart as seen in the top-down or plan view). As discussed further herein, this nonoverlapping spatial arrangement facilitates the injection of light from different resources into different waveguides on a one-to-one basis, thereby allowing a specific light source to be uniquely coupled to a specific waveguide. In some embodiments, arrangements including nonoverlapping spatially separated incoupling optical elements may be referred to as a shifted pupil system, and the incoupling optical elements within these arrangements may correspond to sub pupils.

[0080] FIG. 3 is a simplified illustration of an eyepiece waveguide 310 having a combined pupil expander according to an embodiment of the present invention. In the example illustrated in FIG. 3, the eyepiece 304 utilizes a combined OPE / EPE region in a single-side configuration. Referring to FIG. 3, the eyepiece 304 includes a substrate 320 in which incoupling optical element 322 and a combined OPE / EPE region 324, also referred to as a combined pupil expander (CPE), are provided. Incident light ray 330 is incoupled via the incoupling optical element 322 and outcoupled as output light rays 332 via the combined OPE / EPE region 324.

[0081] The combined OPE / EPE region 324 includes gratings corresponding to both an OPE and an EPE that spatially overlap in the x-direction and the y-direction. In some embodiments, the gratings corresponding to both the OPE and the EPE are located on the same side of a substrate 320 such that either the OPE gratings are superimposed onto the EPE gratings or the EPE gratings are superimposed onto the OPE gratings (or both). In other embodiments, the OPE gratings are located on the opposite side of the substrate 320 from the EPE gratings such that the gratings spatially overlap in the x-direction and the y-direction but are separated from each other in the z-direction (i.e., in different planes). Thus, the combined OPE / EPE region 324 can be implemented in either a single-sided configuration or in a two- sided configuration.

[0082] FIG. 4 illustrates an example of wearable display system 430 into which the various waveguides and related systems disclosed herein may be integrated. With reference to FIG.4, the wearable display system 430 includes a display 432, and various mechanical and electronic modules and systems to support the functioning of the display 432. The display19TOWNSEND 80086574 1432 may be coupled to a frame 434, which is wearable by a user 440 (also referred to as a viewer or a display system user) and which is configured to position the display 432 in front of the eyes of the user 440. The display 432 may be considered eyewear in some embodiments. In some embodiments, a speaker 436 is coupled to the frame 434 and configured to be positioned adjacent to the ear canal of the user 440 (in some embodiments, another speaker, not shown, may optionally be positioned adjacent to the other ear canal of the user to provide stereo / shapeable sound control). The wearable display system 430 may also include one or more microphones or other devices to detect sound. In some embodiments, the microphone is configured to allow the user to provide inputs or commands to the wearable display system 430 (e.g., the selection of voice menu commands, natural language questions), and / or may allow audio communication with other persons (e.g., with other users of similar display systems). The microphone may further be configured as a peripheral sensor to collect audio data (e.g., sounds from the user and / or environment). In some embodiments, the wearable display system 430 may further include one or more outwardly directed environmental sensors configured to detect objects, stimuli, people, animals, locations, or other aspects of the world around the user. For example, environmental sensors may include one or more cameras, which may be located, for example, facing outward so as to capture images similar to at least a portion of an ordinary field of view of the user 440. In some embodiments, the wearable display system may also include a peripheral sensor, which may be separate from the frame 434 and attached to the body of the user 440 (e.g., on the head, torso, an extremity, of the user 440). The peripheral sensor may be configured to acquire data characterizing a physiological state of the user 440 in some embodiments. For example, the sensor may be an electrode.

[0083] The display 432 is operatively coupled by a communications link, such as by a wired lead or wireless connectivity, to a local data processing module which may be mounted in a variety of configurations, such as fixedly attached to the frame 434, fixedly attached to a helmet or hat worn by the user, embedded in headphones, or otherwise removably attached to the user 440 (e.g., in a backpack-style configuration, in a belt-coupling style configuration). Similarly, the sensor may be operatively coupled by a communications link, e.g., a wired lead or wireless connectivity, to the local processor and data module. The local processing and data module may comprise a hardware processor, as well as digital memory, such as nonvolatile memory (e.g., flash memory or hard disk drives), both of which may be utilized to assist in the processing, caching, and storage of data. Optionally, the local processor and data20TOWNSEND 80086574 1module may include one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, and so on. The data may include data a) captured from sensors (which may be, e.g., operatively coupled to the frame 434 or otherwise attached to the user 440), such as image capture devices (such as cameras), microphones, inertial measurement units, accelerometers, compasses, GPS units, radio devices, gyros, and / or other sensors disclosed herein; and / or b) acquired and / or processed using remote processing module 452 and / or remote data repository 454 (including data relating to virtual content), possibly for passage to the display 432 after such processing or retrieval. The local processing and data module may be operatively coupled by communication links 438 such as via wired or wireless communication links, to the remote processing and data module 450, which can include the remote processing module 452, the remote data repository 454, and a battery 460. The remote processing module 452 and the remote data repository 454 can be coupled by communication links 456 and communication links 458 to remote processing and data module 450 such that these remote modules are operatively coupled to each other and available as resources to the remote processing and data module 450. In some embodiments, the remote processing and data module 450 may include one or more of the image capture devices, microphones, inertial measurement units, accelerometers, compasses, GPS units, radio devices, and / or gy ros. In some other embodiments, one or more of these sensors may be attached to the frame 434, or may be standalone structures that communicate with the remote processing and data module 450 by wired or wireless communication pathways.

[0084] With continued reference to FIG. 4, in some embodiments, the remote processing and data module 450 may comprise one or more processors configured to analyze and process data and / or image information, for instance including one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, and so on. In some embodiments, the remote data repository 454 may comprise a digital data storage facility, which may be available through the internet or other networking configuration in a "cloud" resource configuration. In some embodiments, the remote data repository 454 may include one or more remote servers, which provide information, e.g., information for generating augmented reality content, to the local processing and data module and / or the remote processing and data module 450. In some embodiments, all data is stored and all computations are performed in the local processing and data module, allowing fully autonomous use from a remote module. Optionally, an outside system (e.g., a system of one or more processors, one or more computers) that includes CPUs, GPUs, and so on, may21TOWNSEND 80086574 1perform at least a portion of processing (e.g., generating image information, processing data) and provide information to, and receive information from, the illustrated modules, for instance, via wireless or wired connections.

[0085] FIG. 5 shows a perspective view of a wearable device 500 according to an embodiment of the present invention. Wearable device 500 includes a frame 502 configured to support one or more projectors 504 at various positions along an interior-facing surface of frame 502, as illustrated. In some embodiments, projectors 504 can be attached at positions near temples 506. Alternatively, or in addition, another projector could be placed in position 508. Such projectors may, for instance, include or operate in conjunction with one or more liquid cry stal on silicon (LCoS) modules, micro-LED displays, or fiber scanning devices. In some embodiments, light from projectors 504 or projectors disposed in position 508 could be guided into eyepieces 510 for display to eyes of a user. Projectors placed at positions 512 can be somewhat smaller on account of the close proximity this gives the projectors to the waveguide system. The closer proximity can reduce the amount of light lost as the waveguide system guides light from the projectors to eyepiece 510. In some embodiments, the projectors at positions 512 can be utilized in conjunction with projectors 504 or projectors disposed in position 508. While not depicted, in some embodiments, projectors could also be located at positions beneath eyepieces 510. Wearable device 500 is also depicted including sensors 514 and sensors 516. Sensors 514 and sensors 516 can take the form of forwardfacing and lateral-facing optical sensors configured to characterize the real-world environment surrounding wearable device 500.

[0086] Embodiments of the present invention utilize an eye tracking system to determine the eye gaze location of the user and utilize the eye gaze location for image compression processes. Referring to FIG. 5, eye tracking cameras 505 are located on the frame 502 and can be utilized to track the eye gaze location of the user using the wearable device 500. In other embodiments, other eye tracking systems are utilized to determine the eye gaze location and the eye tracking cameras 505 illustrated in FIG. 5 are merely exemplary. As described more fully herein, the image compression processes utilized to compress and decompress virtual content for storage in memory, internal communications, and display, among other functions, can be modified depending on the eye gaze location, for example, portions of an image or video stream corresponding to the eye gaze location can be compressed using a higher quality’ compression process compared to other portions of the image or video stream that are located more distant from the eye gaze location. Since these more distant portions of22TOWNSEND 80086574 1the image or video stream are in the user's peripheral vision, any impact on the user experience resulting from the reduction in compression quality can be less than the benefits achieved in terms of memory and processing efficiency and / or requirements. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

[0087] Some embodiments utilize a single eyepiece waveguide that supports all visible colors. This eyepiece waveguide can be referred to as a full color, single waveguide. In the embodiments illustrated in FIGS. 6-9, the function of the PVGs are applicable to a color band, e.g., a specific color or a specific group of colors.

[0088] One of the hybrid eyepiece waveguide designs discussed herein is based on colorsplitting light paths, each of which transmit one color group from the projector wavelength. The hybrid waveguide designs presented herein involve PVG based ICG and one (or more) PVG / SRG based OPE and EPE as shown in Table 2. For terminology’ convenience, we separate the wavelength range as Color Group 1, and Color Group 2, each of which can include any color combination of one or two colors of RGB and written as (Group 1, Group 2), for example Group 1 = Blue / Green (-400 nm - -600 nm) and Group 2 = Red (-600 nm - -700 nm). Besides, since Group 1 may be presented by a reflective grating path, and Group 2 by a transmissive grating path, the sequence of the grouping can matter. Therefore, the combination of (Group 1, Group 2) can have the following 6 cases shown in Table 1:Table 1

[0089] Although two color Groups are discussed in relation to Table 1, three or more color Groups can be utilized according to embodiments of the present invention.23TOWNSEND 80086574 1

[0090] The elements are listed as follows. The change in the handedness of the polarization is indicated as right hand polarization to left hand polarization (R— >L) or left hand polarization to right hand polarization (L^R) as shown in Table 2.Table 2

[0091] In embodiments that utilize three color Groups, additional transmissive and / or reflective Elements are added corresponding to the additional color Group(s).

[0092] In order to explain embodiments of the present invention, the unpolarized light of RGB has been separated into two main light paths according to the color grouping within the wavelengths of the projector LEDs.

[0093] FIG. 6 is a simplified cross-sectional diagram illustrating a first series of light interactions in a first eyepiece waveguide according to an embodiment of the present invention. As illustrated in FIG. 6. the eyepiece waveguide 610 utilizes both transmissive ICGs and output coupling gratings (OCGs). Unpolarized light of color Group 2 is incident onto Element 620, which is a transmissive PVG. The RHP portion of the unpolarized light is24TOWNSEND 80086574 1diffracted by Element 620 as LHP light and the LHP portion of the unpolarized light is diffracted by Element 622, which is a transmissive PVG, as RHP light. After total internal reflection (TIR) in the eyepiece waveguide 610, the output of Element 620 and Element 622 impinges on Element 640 (e.g., a 2D SRG optimized for color Group 2), diffracts two times, and outcouples from the eyepiece waveguide 610. The dotted lines in FIG. 6 illustrate diffraction of the incident light by Element 640 operating as an orthogonal pupil expander (OPE). In this embodiment, Element 640 is color selective and preferentially diffracts light in the color Group incoupled by Element 620 and Element 622. Similarly, Element 642 is also color selective and has substantially no diffractive interaction with the color Group incoupled by Element 620 and Element 622. As a result, light in the incoupled color Group experiences TIR at Element 642 but is either diffractively expanded in the eyepiece waveguide or diffractively outcoupled when impinging on Element 640. Thus, both Element 640 and Element 642 are 2D diffractive structures (or semi-2D diffractive structures by stacking PVGs with multiple grating vectors) that are color selective in FIG. 6. In a more general case, light could be outcoupled by either or both of Element 640 and Element 642 although this is not illustrated in FIG. 6. Element 630 and Element 632, which are discussed in relation to FIG. 7 are illustrated in FIG. 6 for purposes of clarity.

[0094] FIG. 7 is a simplified cross-sectional diagram illustrating a second series of light interactions in the first eyepiece waveguide according to an embodiment of the present invention. As illustrated in FIG. 7. reflective ICGs and OCGs are utilized in the eyepiece waveguide 610 during this second series of light interactions. Unpolarized light of color Group 1 is incident onto Element 630, which is a reflective PVG. The RHP portion is diffracted by the Element 630 as RHP light and the LHP portion is diffracted by Element 632, which is a reflective PVG, as LHP light. After TIR in the eyepiece waveguide, the output of Element 630 and Element 632 impinges on Element 642 (e.g., a 2D SRG optimized for color Group 1), diffracts two times, and outcouples from the eyepiece waveguide. The polarization behavior illustrated in FIG. 6 and FIG. 7 are just examples and in general the polarization of the diffracted beams could be similar handedness or opposite handedness of the corresponding input circular polarization for either of the transmissive and reflective PVGs, and the order of the gratings acting on RCP and LCP polarizations could be switched. This is true for all figures in this application.

[0095] The dotted lines in FIG. 7 illustrate diffraction of the incident light by Element 642 operating as an orthogonal pupil expander. In this embodiment, Element 642 is color25TOWNSEND 80086574 1selective and preferentially diffracts light in the color Group incoupled by Element 630 and Element 632. Similarly, Element 640 is also color selective and has substantially no diffractive interaction with the color Group incoupled by Element 630 and Element 632. As a result, light in the incoupled color Group (i.e., color Group 1) experiences TIR at Element 640 but is either diffractively expanded in the eyepiece waveguide or diffractively outcoupled when impinging on Element 642. Thus, both Element 640 and Element 642 are 2D diffractive structures (or semi -2D diffractive structures by stacking PVGs with multiple grating vectors) that are color selective in FIG. 7. In a more general case, light could be outcoupled by either or both of Element 642 and Element 640 although this is not illustrated in FIG. 7.

[0096] Thus, the first set of transmissive ICGs, i.e., Element 620 and Element 622, incouple a first color band (i.e., color Group 2) in both polarization states (i.e., Element 620 for LHP and Element 622 for RHP) simultaneously and the second set of reflective ICGs, i.e., Element 630 and Element 632) incouple a second color band (i.e., color Group 1) in both polarization states (i.e., Element 630 for RHP and Element 632 for LHP) simultaneously.

[0097] In embodiments in which PVGs are utilized to implement one or more of the Elements shown in FIGS. 6 and 7, the various Elements can be laminated as discussed more fully in relation to FIGS. 26A, 27, and 28.

[0098] Another two similar configurations, which share some similarities with the configurations illustrated in FIGS. 6 and 7 and use one-dimensional SRGs or PVGs as the OPE and the EPE, are shown in FIGS. 8 and 9, respectively. In contrast with the eyepiece waveguide illustrated in FIGS. 6 and 7, the eyepiece waveguide illustrated in FIGS. 8 and 9 utilizes three sets of ID diffractive structures (ICGs, OPEs, and EPEs) instead of two sets of diffractive structures (ID ICGs, and 2D OCGs) as in FIGS. 6 and 7.

[0099] FIG. 8 is a simplified cross-sectional diagram illustrating a first series of light interactions in a second eyepiece waveguide according to an embodiment of the present invention. Referring to FIG. 8, the eyepiece waveguide 810 utilizes both transmissive ICGs and output coupling gratings (OCGs). Unpolarized light of color Group 2 is incident onto Element 820, which is a transmissive PVG. The RHP portion of the unpolarized light is diffracted by Element 820 as LHP light and the LHP portion of the unpolarized light is diffracted by Element 822, which is a transmissive PVG, as RHP light. After total internal reflection (TIR) in the eyepiece waveguide, the output of Element 820 and Element 82226TOWNSEND 80086574 1impinges on Element 840, which is an OPE, then impinges on Element 850, which is a transmissive EPE, and outcouples from the eyepiece waveguide. Element 830, Element 832. Element 842, and Element 852, which are discussed in relation to FIG. 9 are illustrated in FIG. 8 for purposes of clarity.

[0100] FIG. 9 is a simplified cross-sectional diagram illustrating a second series of light interactions in the second eyepiece waveguide according to an embodiment of the present invention. Referring to FIG. 9, reflective ICGs and OCGs are utilized in the eyepiece waveguide 810 during this second series of light interactions. Unpolarized light of color Group 1 is incident onto Element 830, which is a reflective PVG. The LEIP portion of the unpolarized light is diffracted by the Element 830 as LHP light and the RHP portion of the unpolarized light is diffracted by Element 832, which is a reflective PVG. as RHP light. After TIR in the eyepiece waveguide, the output of Element 830 and Element 832 impinges on Element 842, which is an OPE, then impinges on Element 852, which is a reflective EPE, and outcouples from the eyepiece waveguide.

[0101] To explain the color-splitting ICGs mechanism, as well as some other PVG stacks in the following, the working principle of some basic structures such as reflective PVG and transmissive PVG are listed in FIGS. 10 and 11, as well as some other complicated stacks utilizing both of these structures as building blocks. It should be noted that in the present application, the polarization definition uses the convention that is generally used in atomic physics, in which right-hand circular polarization (RHP) is defined when a photon positive momentum is achieved as it propagates. To be more specific. RHP is defined as clockwise when an observer looks through the light propagation direction.

[0102] FIG. 10A is a simplified diagram illustrating the working principle of a typical reflective PVG. FIG. 10B is a simplified diagram illustrating the working principle of a stack comprising the right-handed chiral PVG and a retarder film according to an embodiment of the present invention. FIG. 10C is a simplified diagram illustrating the working principle of reflective color-splitting ICGs according to an embodiment of the present invention.

[0103] In FIG. 10A, a right-handed chiral reflective PVG 1010 diffracts its RHP incidence light Light a, and outputs as RHP Light o'. When the handedness of PVG chirality becomes left-handed, it works for LHP input in the same manner.

[0104] In FIG. 10B, a stack implemented as a left-handed chiral PVG 1011 in this embodiment comprises PVG 1013 and retarder film 1012. The retarder film 1012 can27TOWNSEND 80086574 1impose directional phase-shift to the lights at oblique angles, changing the polarization of the output rays to orthogonal circular polarization while keeping the input polarization intact. Therefore, when RHP Light b is incident on a left-handed chiral PVG 1011, it diffracts Light b' as LHP, instead of RHP. When the handedness of PVG 1013 changes, it works for the orthogonal circular polarization in the same manner.

[0105] In FIG. 10C, unpolarized light propagates through Element 1014, a reflective PVG operating on RHP, and Element 1015, a reflective PVG operating on LHP. Both of the reflective PVGs are designed to operate at angle range within the FOV at Color Group 1. Unpolarized light of Color Group 1 can be considered to be composed of equal portions of Light c (LHP) and Light d (RHP). Light d is diffracted by Element 1014 as Light d', with its polarization as RHP. Light c transmits through Element 1014 and maintains the polarization as LHP and its propagation direction as Light c', which will be diffracted by Element 1015 as Light c" with its polarization as LHP, and transmit through Element 1014 as Light c'", whose polarization and direction is the same as that of Light c". In practice, Element 1014 and Element 1015 may be separated by a gap as illustrated in FIG. 10C or not be separated by a gap, i.e., in contact, for example, laminated to each other.

[0106] FIG. 1 IA is a simplified diagram illustrating the working principle of a typical transmissive PVG. FIG. 1 IB is a simplified diagram illustrating the working principle of transmissive color-splitting ICGs according to an embodiment of the present invention.

[0107] In FIG. 11 A, a left-handed chiral transmissive PVG 1110 diffracts its RHP incidence light Light e, and outputs as LHP Light e'. When the handedness of PVG chirality becomes right-handed, it works for LHP input in the same manner.

[0108] In FIG. 1 IB, unpolarized light propagates through Element 11 11, a transmissive PVG operating on RHP, and Element 1112, a transmissive PVG operating on LHP. Both of the transmissive PVGs are designed to operate at angle range within the FOV at Color Group 2. Unpolarized light of Color Group 2 can be considered to be composed of equal portions of Light f (LHP) and Light g (RHP). Light g is diffracted by Element 1111 as Light g’ with LHP polarization, and transmitted through Element 1 1 12 maintaining its polarization and direction. Light f transmits through Element 1111 with its polarization and direction unchanged (Light ft), which continues to be diffracted by Element 1112 as Light f" with RHP polarization. Element 1111 and Element 1112 are designed to let f" and g" to propagate along the same direction. In practice. Element 1111 and Element 1112 can be separated by a28TOWNSEND 80086574 1gap or not be separated by a gap. In the example shown in FIG. 1 IB, the polarizations f" and g" are shown to be orthogonal to the input polarizations. Also, the order of elements acting on LHP and RHP polarizations can be switched. Although circular polarization is illustrated in above figures, and described herein, it will be appreciated the elliptically polarized light can be utilized as well. One of ordinary7skill in the art w ould recognize many variations, modifications, and alternatives. In some scenarios, the retardation of Element 1014, Element 1015, Element 1111, and Element 1112 in FIGS. 10C, and 1 IB can be such that they improve the ICG re-bounce loss via polarization manipulation.

[0109] For the design principle of the OPEs and EPEs, they can either be SRGs or PVGs. For SRGs, it can be a two-dimensional or a one-dimensional grating to realize eyebox expansion and outcoupling. Certain types of coating(s) might be put on top of the grating in order to maximize the efficiency of that color group and to minimize stray reflected light. For the PVG-based CPE / OPE, it can be a stack of PVG gratings that includes PVG designed to diffract both RHP and LHP for the corresponding color groups of that element. For example, if Element 640 is a PVG-based CPE / OPE, then it can be a stack of PVG gratings that includes t o individual PVGs diffracting RHP and LHP respectively for Color Group 2.

[0110] As described herein, some embodiments of the present invention utilize a full liquid crystal polarization volume gratings (LCPVGs) waveguide configuration with double-sided gratings. This waveguide design assumes a single input pupil for combined red, green, blue (RGB) operation, and includes one grating group for one circular polarization, while the other grating group is for the orthogonal circular polarization. In this way, the waveguide system can have a separate light path for different polarization states of light. This is a significant benefit for systems with unpolarized light sources such as p-LEDs, which manifest a significant potential to improve the efficiency of the w aveguide system. With the different light paths for different polarization states, a high efficiency waveguide operating on a large FOV can be designed for unpolarized light by fabricating the two grating groups acting on opposite sides of the waveguide. Alternatively, wdth the development of lamination capabilities, these two groups can exist on the same side of the w aveguide as described later.[OHl] Embodiments of the present invention provide an eyepiece waveguide that can handle both polarization states at the same time, receiving unpolarized light as an input and supporting propagation and outcoupling of both polarization states in the eyepiece w aveguide. In order to support incoupling, propagation, and outcoupling of tw o different29TOWNSEND 80086574 1polarization states, the diffractive (e.g., PVG and grating) structures can be specific to one of the two polarization states.

[0112] As described herein, embodiments of the present invention include an eyepiece waveguide that utilizes an unpolarized light source. This eyepiece waveguide design manifests a single input pupil for red, green, blue (RGB) unpolarized light. To be specific, the ICGs, OPEs are respectively composed of a pair of elements that includes liquid crystal polarization volume gratings (LCPVGs) with (or without) some anisotropic retarder film, while the EPEs can be composed of one or a pair of such elements. Such an All-PVG waveguide forms two separate tight paths for the orthogonal circular polarizations that comprise the unpolarized light.

[0113] Some embodiments of the present invention split polarization into different grating groups, and at the output coupling zone, the two polarizations can be combined together. Each of these paths utilizes PVGs or stacks including PVGs that are designed for a specific input polarization. These two paths are designed to have different grating vector triangles in the k-vector plot so that the loss of the FOV in one path can be recovered by another path.

[0114] According to the handedness of the polarization, there are several configurations that can be adopted. Two main configurations of the grating arrangement are shown in FIGS. 12A-12B and FIGS. 13A-13B. In each main configuration, one or more variations are also listed as the following Table 2-1.Table 2-1

[0115] FIG. 12A is a simplified cross-sectional diagram illustrating a first series of light interactions in a third eyepiece waveguide according to an embodiment of the present30TOWNSEND 80086574 1invention. FIG. 12B is a simplified cross-sectional diagram illustrating a second series of light interactions in the third eyepiece waveguide according to an embodiment of the present invention. In FIG. 12A, unpolarized light is incident on the eyepiece waveguide 1210 and one polarization (e.g., RHP) is incoupled using a first transmissive PVG-based ICG (e.g., Element 1220 operating as illustrated in FIG. 11 A) and diffracts as its orthogonal polarization (e.g., LHP). In FIG. 12B, the other polarization (e.g., LHP) is incoupled using a stack of reflective PVG and retarder film (e.g.. Element 1221 operating as illustrated in FIG. 10B) and diffracts as its orthogonal polarization (e.g., RHP). The first transmissive PVG-based ICG incouples all colors (e.g., RGB) in the first polarization state simultaneously and the second transmissive ICG also incouples all colors (e.g., RGB) in the second polarization state simultaneously.

[0116] FIG. 12A illustrates light interactions using a combination of a transmissive PVG- based ICG (e.g.. Element 1220 operating as illustrated in FIG. 11 A), a reflective PVG-based OPE (Element 1230 operating as illustrated in FIG. 10A), and a transmissive PVG-based EPE (Element 1240 operating as illustrated in FIG. 11A). FIG. 12B illustrates light interactions in an eyepiece waveguide 1210 using ICG that comprises a reflective PVG and retarder film (Element 1221 operating as illustrated in FIG. 10B), a reflective PVG-based OPE and EPE (Elements 1231 and 1241 operating as illustrated in FIG. 10 A).

[0117] As illustrated in FIGS. 12A and 12B, unpolarized input light will be separated into RHP and LHP upon entry' into the eyepiece waveguide and the output light corresponding to both RHP and LHP input light will have the same polarization. This is illustrated by the RHP light output from Element 1240, which entered the eyepiece waveguide as RHP as shown in FIG. 12A, and the RHP light output from Element 1241, which enters the eyepiece waveguide as LHP as shown in FIG. 12B.

[0118] FIG. 12D, which is a possible variation of FIG. 12B, is a simplified cross-sectional diagram illustrating a second series of light interactions in the third eyepiece waveguide according to an embodiment of the present invention. FIG. 12C, which is a possible variation of FIG. 12A, which is a simplified cross-sectional diagram illustrating a first series of light interactions in the third eyepiece waveguide according to an embodiment of the present invention. By combining FIGS. 12A and 12D (or FIGS. 12B and 12C). the output light of the first and second series are of the same polarization after diffracting from the OPE and therefore can share one EPE to diffract all the lights.31TOWNSEND 80086574 1

[0119] In the embodiment illustrated in FIGS. 12A, 12B, 12C, and 12D the elements operating on the each polarization are positioned on both sides of the waveguide:RHP: Element 1220 on a first side. Element 1230 on the opposing second side, and Element1240 on the first side: LHP: Element 1221 on the second side, Element 1231 on the opposing first side, and Element1241 on the second side.

[0120] The elements for the eyepiece waveguides illustrated in FIGS. 12A-D and 13A-C are listed in Table 3:Table 3

[0121] To accomplish the incoupling, orthogonal pupil expansion, and outcoupling, two paths for two input polarization are listed in Table 4.32TOWNSEND 80086574 1Table 4

[0122] Referring to FIG. 12A, the RHP portion of the unpolarized light incident onto Element 1220 is diffracted as LHP light, which undergoes TIR as it propagates in the eyepiece waveguide 1210. Upon reflection at the air-substrate interface, the beam polarization in general can change, especially when there are coatings (for example, multilayer dielectric coatings to provide Anti-Reflection behavior for external light) at that interface. In FIGS. 12A-19B the handedness of the circular polarization flips at each of these interactions in TIR. This is only an example and in general, the beams can undergo polarization change at this interface, which impacts the specific arrangement of gratings consequently, and other elements / coatings could be designed to preserve and / or alter these polarization states. In FIG. 12A, the light is LHP when it propagates towards the bottom surface of the eyepiece waveguide 1210 and RHP when it propagates towards the upper surface of the eyepiece waveguide 1210. In this way, the light impinging on Element 1230 is LHP, which diffracts as LHP to realize pupil replication. The light continues to TIR until it reaches Element 1240 and outcouples while changing polarization state from LHP to RHP. Element 1220 operates in transmission mode on RHP input, Element 1240 operates in transmission mode on LHP input, and Element 1230 operates in reflection mode on LHP input. It will be appreciated that the light is effectively polarization scrambled as it bounces through the waveguide. If the OPE (Element 1230) is optimized for LHP, then it can diffract LHP to RHP, but any input light that is RHP will not be diffracted.

[0123] Referring to Element 1220, this element can be a PVG that diffracts all colors simultaneously or can be formed of multiple layers, each operating on a different color band. Additional discussion related to multilayer PVG implementations is provided in relation to33TOWNSEND 80086574 1FIG. 26A. Thus, although Element 1220 is illustrated as a single element, it can be a multilayer stack in order to address both the full color range and the full FOV.

[0124] Since PVGs can be highly directional, one or more of the diffractive elements, e.g.. all of the diffractive elements, can be implemented using PVGs. As an example, if Element 1240 is a PVG, the diffraction that produces outcoupling can diffract more light toward the user as illustrated in comparison with diffraction toward the lower surface of the waveguide. Thus, in some embodiments, all of the diffractive elements are PVGs whereas, in other embodiments, both PVGs and SRGs can be utilized. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

[0125] In FIG. 12B, the light interaction is similar to that illustrated in FIG. 12A, but the polarization conversions are flipped, focusing on the LHP light that is incoupled into the eyepiece waveguide 1210. Referring to FIG. 12B. the LHP ray incident onto Element 1221 is diffracted as RHP, due to its combination of PVG and a retarder film. The light continues to propagate and TIR until it reaches Element 1231 with RHP and diffracts as RHP to realize pupil expansion. The light continues to propagate until it reaches Element 1241 and diffracts as RHP that is outcoupled from the eyepiece waveguide 1210. Element 1221 operates in reflection mode on LHP input and Element 1241 operates in reflection mode on RHP input. Element 1221 changes the handedness of the polarization state and Element 1241 does not change the handedness of the polarization state. Element 1231 operates in reflection mode on RHP input and does not change the handedness of the polarization state.

[0126] In the embodiment illustrated in FIGS. 12A and 12B, the eyepiece waveguide includes three separate diffractive elements for each polarization. For the RHP state. Element 1220 operates as an ICG, Element 1230 operates as an OPE, and Element 1240 operates as an EPE. For the LHP state, Element 1221 operates as an ICG, Element 1231 operates as an OPE, and Element 1241 operates as an EPE. In other embodiments that comprises FIGS. 12A and 12D (or FIGS. 12C and 12B) as listed in Table 2-1, two series of light share only one EPE.

[0127] In some embodiments, an ICG / OPE / EPE design is utilized to implement polarization splitting. However, in other embodiments, an ICG / 2D CPE design can be utilized to implement polarization splitting. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.34TOWNSEND 80086574 1

[0128] Although, in the embodiment illustrated in FIG. 12B, only Element 1221 changes the handedness of the polarization state upon reflection, similar to the operation illustrated in FIG. 10B, while the other elements do not change the handedness of the polarization state upon reflection, this mode of operation is not limited to Element 1221. The other elements, including Element 1230 in FIG. 12A and Element 1231 and / or Element 1341 in FIG. 12B can be implemented so that one or more of these elements change the handedness of the polarization state upon reflection. Moreover, as illustrated in FIG. 13B, some designs utilize only PVGs that do not change the handedness of the polarization state upon reflection. Thus, although a stack comprising PVG and retarder film operating in reflection mode changes the handedness of the polarization state in FIG. 12B, while elements only contain PVGs operating in reflection mode that do not change the handedness of the polarization state. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

[0129] Thus, embodiments of the present invention provide a great deal of design flexibility7in integrating PVGs with / without other anisotropic retarder films that do or do not change the handedness of the polarization state upon reflection, thereby enabling the polarization state to be controlled in a predetermined manner. Although some of the embodiments described below, in a manner similar to the embodiment illustrated in FIG. 12B, utilize only one element comprising PVG and retarder retarder film that changes the handedness of the polarization state upon reflection, while the other PVGs do not change the handedness of the polarization state upon reflection, this ability to modify the polarization control behavior of any of the PVGs described herein also applies to the other embodiments described below. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

[0130] FIG. 13A is a simplified cross-sectional diagram illustrating a first series of light interactions in an alternative to the third eyepiece waveguide illustrated in FIG. 12A according to an embodiment of the present invention. FIG. 13B is a simplified cross- sectional diagram illustrating a second series of light interactions in an alternative to the third eyepiece waveguide illustrated in FIG. 12B according to an embodiment of the present invention. FIG. 13C is a possible variation of FIG. 13B.

[0131] In FIG. 13B, Element 1321 operates in the manner illustrated in FIG. 10A and the handedness of the light incident on Element 1321 does not change upon reflection.Otherwise, the operation of Elements 1320, 1330, 1340, 1331, and 1341 illustrated in FIGS.35TOWNSEND 80086574 113A and 13B are the same as Elements 1220, 1230, 1240, 1231, and 1241 illustrated in FIGS. 12A and 12B.

[0132] In contrast with the operation of Element 1221 illustrated in FIG. 12B, Element 1321 does not change the handedness of the polarization state upon reflection, similar to the operation illustrated in FIG. 10A. As a result, the RHP portion of the unpolarized input light will be incoupled by Element 1320 upon entry into the eyepiece waveguide 1310 and the output light will have different polarization states as illustrated by the RHP light output from Element 1340 as shown in FIG. 13 A. Similarly, the LHP portion of unpolarized light is incoupled by Element 1321, diffracted by the Element 1331 operating as an OPE 1331 and eventually outcoupled by Element 1341 operating as an OPE as LHP as shown in FIG. 13B.

[0133] FIG. 13C is another possible variation of FIG. 13B, in which the LHP portion of unpolarized light has the identical light path shown in FIG. 13B, but can achieve orthogonal polarization after it transmits Element 1340 by gaining half-wave retardation. In this case. Element 1340 can operate as a retarder for the LHP light at the angle range near normal incidence, while it can simultaneously operate as a transmissive PVG for certain oblique incident angle ranges shown in FIG. 13 A. Such dual properties of PVG being either retarder film or diffractive gratings originates in its high angle / wavelength / polarization selectivity, and it can be achieved by fine-tuning the PVG structures (slant angle, or LC birefringence, grating pitch, etc.), as well as the incidence angles.

[0134] FIGS. 14A-14D represent the orthogonal polarization case of FIGS. 12A-12D. FIG. 14A is a simplified cross-sectional diagram illustrating a third series of light interactions in the third eyepiece waveguide according to an embodiment of the present invention. FIG. 14B is a simplified cross-sectional diagram illustrating a fourth series of light interactions in the third eyepiece waveguide according to an embodiment of the present invention. FIG. 14C is a possible variation of FIG. 14A, and FIG. 14D is a possible variation of FIG. 14B. The combination of these embodiments is identical to FIGS. 12A-12D. FIGS. 15A-15C are the orthogonal polarization case of FIGS. 13A-13C. The configuration of different polarization of FIGS. 14A-14D and 15A-15C are listed as following Table 4-1:36TOWNSEND 80086574 1Table 4-1

[0135] For FIGS. 14A and 14B, the elements are listed in Table 5 and grating combinations are in Table 6.Table 537TOWNSEND 80086574 1Table 6

[0136] In FIG. 14 A, the optical path is similar to FIG. 12 A, but the handedness is flipped. The LHP part of the unpolarized light incident onto Element 1420 is diffracted as RHP light, which undergoes TIR as it propagates. In FIG. 14A, the light is RHP when it propagates towards the bottom surface of the ey epiece waveguide 1410 and LHP when it propagates towards the upper surface of the eyepiece waveguide 1410. In this way, the light impinging on Element 1430 is RHP, which diffracts as RHP to realize pupil replication. The light continues to TIR until it reaches Element 1440 and outcouples while changing polarization state from RHP to LHP.

[0137] In FIG. 14B, the optical path is similar to FIG. 13B, but the handedness is flipped. The RHP ray incident onto Element 1421 is diffracted as LHP. The light continues to propagate and TIR until it reaches Element 1431 with LHP and diffracts as LHP to realize pupil expansion. The light continues to propagate until it reaches Element 1441 and diffracts as LHP that is outcoupled from the eyepiece waveguide 1410.

[0138] FIG. 14D is a possible variation of FIG. 14B, which is a simplified cross-sectional diagram illustrating a fourth series of light interactions in the third eyepiece waveguide according to an embodiment of the present invention. FIG. 14C is a possible variation of FIG. 12A, which is a simplified cross-sectional diagram illustrating a third series of light interactions in the third eyepiece waveguide according to an embodiment of the present invention. By combining FIGS. 14A and 14D (or FIGS. 14B and 14C), the output light of the first and second series are of the same polarization after diffracting from the OPE and therefore can share one EPE to diffract all the light.

[0139] FIG. 15A is a simplified cross-sectional diagram illustrating a first series of light interactions in an alternative to the third eyepiece waveguide illustrated in FIG. 14A according to an embodiment of the present invention. FIG. 15B is a simplified cross- sectional diagram illustrating a second series of light interactions in an alternative to the third38TOWNSEND 80086574 1eyepiece waveguide illustrated in FIG. 14B according to an embodiment of the present invention.

[0140] In FIG. 15B, Element 1521 operates in the manner illustrated in FIG. 10A and the handedness of the light incident on Element 1521 does not change upon reflection. Otherwise, the operation of Elements 1520, 1530, 1540, 1531, and 1541 illustrated in FIGS. 15A and 15B are the same as Elements 1420, 1430, 1440, 1431, and 1441 illustrated in FIGS. 14A and 14B.

[0141] FIG. 15C is a possible variation of FIG. 15B, in which the RHP outcoupled by Element 1541 gains half-wave retardation after transmitting Element 1540. This is identical to the explanation of FIG. 13C.

[0142] In contrast with the operation of Element 1421 illustrated in FIG. 14B, Element 1521 does not change the handedness of the polarization state upon reflection, similar to the operation illustrated in FIG. 10A. As a result, unpolarized input light will be incoupled as RHP upon entry into the eyepiece waveguide 1510 and the output light will have different polarization states as illustrated by the LHP light output from Element 1540, which entered the ey epiece waveguide as RHP after transmission though Element 1520 as shown in FIG. 15A, and the RHP light output from Element 1541, which also entered the eyepiece waveguide as RHP as shown in FIG. 15B.

[0143] FIGS. 16A-16D are similar to FIGS. 12A-12D, the only difference being that all the gratings are placed at the same side for the individual light paths. FIG. 16A is a simplified cross-sectional diagram illustrating a first series of light interactions in a fourth eyepiece waveguide according to an embodiment of the present invention. FIG. 16B is a simplified cross-sectional diagram illustrating a second series of light interactions in the fourth eyepiece w aveguide according to an embodiment of the present invention. FIG. 16D is a possible variation of FIG. 16B, which is a simplified cross-sectional diagram illustrating a second series of light interactions in the fourth eyepiece waveguide according to an embodiment of the present invention. FIG. 16C is a possible variation of FIG. 16A, which is a simplified cross-sectional diagram illustrating a first series of light interactions in the fourth eyepiece w aveguide according to an embodiment of the present invention. By combining FIGS. 16A and 16D (or FIGS. 16B and 16C), the output light of the first and second series are of the same polarization after diffracting from the OPE and therefore can share one EPE to diffract all the light.39TOWNSEND 80086574 1

[0144] FIGS. 17A-17C are similar to FIGS. 13A-13C, the only difference being that all gratings are placed at the same side for the individual light paths. The configuration of different polarization of FIGS. 16A-16D and 17A-17C are listed as following Table 6-1 :Table 6-1

[0145] In the embodiment illustrated in FIGS. 16A and 16B, the eyepiece waveguide 1610 utilizes gratings on one side of the eyepiece waveguide for a first circular polarization state and gratings on the other side of the eyepiece waveguide for the second (e.g., orthogonal) circular polarization state. The element list is similar to Table 6-2, and grating combinations are in Table 7.40TOWNSEND 80086574 1Table 6-2Table 7

[0146] In FIG. 16A, the RHP portion of the unpolarized light incident onto Element 1620 diffracts as LHP light, which undergoes TIR as it propagates. Reflection due to diffraction from Element 1630 does not change the handedness of the polarization state. The light is RHP when it propagates towards the upper surface of the eyepiece waveguide 1610. As a result, the light incident on Element 1630 is RHP, which diffracts as RHP in reflection to realize pupil replication. The light continues to TIR until it reaches Element 1640 and outcouples while changing polarization state from LHP to RHP.

[0147] In FIG. 16B, the LHP portion of the unpolarized light incident onto Element 1621 diffracts as RHP light, which undergoes TIR as it propagates. Reflection due to diffraction from Element 1621 changes the handedness of the polarization state. The light has RHP when it propagates towards the upper surface of the eyepiece waveguide and, after TIR, has LHP as it is incident on Element 1631. As a result, the light incident on Element 1631 diffracts as LHP to realize pupil replication. The light continues to TIR until it reaches Element 1641 and diffracts as RHP that is outcoupled from the eyepiece waveguide 1610.41TOWNSEND 80086574 1

[0148] FIG. 17A is a simplified cross-sectional diagram illustrating a first series of light interactions in an alternative to the fourth eyepiece waveguide illustrated in FIG. 17A according to an embodiment of the present invention. FIG. 17B is a simplified cross- sectional diagram illustrating a second series of light interactions in an alternative to the fourth eyepiece waveguide illustrated in FIG. 17B according to an embodiment of the present invention.

[0149] In FIG. 17B, Element 1721 operates in the manner illustrated in FIG. 10A and the handedness of the light incident on Element 1721 does not change upon reflection. Otherwise, the operation of Elements 1720, 1730, 1740, 1731, and 1741 illustrated in FIGS. 17A and 17B are the same as Elements 1620, 1630, 1640, 1631, and 1641 illustrated in FIGS. 16A and 16B.

[0150] In contrast with the operation of Element 1621 illustrated in FIG. 16B, Element 1721 does not change the handedness of the polarization state upon reflection, similar to the operation illustrated in FIG. 10A. As a result, unpolarized input light will be incoupled as LHP upon entry into the eyepiece waveguide 1710 and the output light will have different polarization states as illustrated by the RHP light output from Element 1740, which entered the eyepiece waveguide as LHP after transmission though Element 1720 as shown in FIG. 17A, and the LHP light output from Element 1741, which also entered the eyepiece waveguide as LHP as show n in FIG. 17B. FIG. 17C is a possible variation of FIG. 17B, in which the LHP outcoupled by Element 1741 gains half-wave retardation after transmitting through Element 1740. This is identical to the explanation of FIG. 15C.

[0151] FIGS. 18A-18D are the orthogonal polarization case of FIGS. 16A-16D. FIG. 18A is a simplified cross-sectional diagram illustrating a third series of light interactions in a fourth eyepiece waveguide according to an embodiment of the present invention. FIG. 18B is a simplified cross-sectional diagram illustrating a fourth series of light interactions in the fourth eyepiece waveguide according to an embodiment of the present invention. FIG. 18D is a possible variation of FIG. 18B, which is a simplified cross-sectional diagram illustrating a fourth series of light interactions in the fourth eyepiece waveguide according to an embodiment of the present invention. FIG. 18C is a possible variation of FIG. 18A, which is a simplified cross-sectional diagram illustrating a third series of light interactions in the fourth eyepiece waveguide according to an embodiment of the present invention. By combining FIGS. 18A and 18D (or FIGS. 18B and 18C), the output lights of first and second42TOWNSEND 80086574 1series are of the same polarization after diffracting from the OPE and therefore can share one EPE to diffract all the lights.

[0152] The embodiment illustrated in FIGS. 18 A and 18B is similar to that shown in FIGS. 16A and 16B except the chirality of the PVGs and the handedness of the polarization states are flipped. Like the embodiment show n in FIGS. 16A and 16B, the embodiment illustrated in FIGS. 18A and 18B utilizes gratings on one side of the waveguide for a first circular polarization and the gratings on the other side for the other circular polarization. The elements are in Table 7-1, and grating combinations are in Table 8.Table 7-143TOWNSEND 80086574 1Table 8

[0153] In FIG. 18 A, the LHP portion of the unpolarized light incident onto Element 1820 diffracts as RHP light, which undergoes TIR as it propagates. The light is LHP when it propagates towards the upper surface of the eyepiece waveguide 1810. As a result, the light incident on Element 1830 is LHP, which diffracts as LHP to realize pupil replication. The light continue to TIR until it reaches Element 1840 and outcouples while changing polarization state from RHP to LHP.

[0154] In FIG. 18B, the RHP portion of the unpolarized light incident onto Element 1821 diffracts as LHP light, which undergoes TIR as it propagates. Since each time TIR occurs, the handedness flips, the light is RHP when it propagates towards the lower surface of the eyepiece waveguide 1810 and is incident on Element 1831, which diffracts as RHP to realize pupil replication. The light continues to TIR until it reaches Element 1841 and diffracts as LHP that is outcoupled from the eyepiece waveguide.

[0155] FIG. 19A is a simplified cross-sectional diagram illustrating a first series of light interactions in an alternative to the fourth eyepiece waveguide illustrated in FIG. 18A according to an embodiment of the present invention. FIG. 19B is a simplified cross- sectional diagram illustrating a second series of light interactions in an alternative to the fourth eyepiece waveguide illustrated in FIG. 18B according to an embodiment of the present invention.

[0156] In FIG. 19B, Element 1921 operates in the manner illustrated in FIG. 10A and the handedness of the light incident on Element 1921 does not change upon reflection.Otherwise, the operation of Elements 1920, 1930, 1940, 1931, and 1941 illustrated in FIGS. 19A and 19B are the same as Elements 1820, 1830, 1840, 1831. and 1841 illustrated in FIGS. 18A and 18B.

[0157] In contrast with the operation of Element 1821 illustrated in FIG. 18B, Element 1921 does not change the handedness of the polarization state upon reflection, similar to the44TOWNSEND 80086574 1operation illustrated in FIG. 10A. As a result, unpolarized input light will be incoupled as RHP upon entry into the eyepiece waveguide 1910 and the output light will have different polarization states as illustrated by the LHP light output from Element 1940, which entered the eyepiece waveguide as RHP after transmission though Element 1920 as shown in FIG. 19A, and the RHP light output from Element 1941, which also entered the eyepiece waveguide as RHP as shown in FIG. 19B. FIG. 19C is a possible variation of FIG. 19B, in which the RHP outcoupled by Element 1941 gains half-wave retardation after transmitting Element 1940. This is identical to the explanation of FIG. 17C.

[0158] As discussed herein, the tw o optical paths are designed to have different grating vector triangles in the k-vector plot so that the loss of the FOV in one path can be recovered by another path. To show the k-vector in three dimensions, the embodiments illustrated in FIGS. 16A-19B can be used as an example. In particular, the grating vector orientation is shown in FIG. 20 for one circular polarization and the other circular polarization is shown in FIG. 21.

[0159] FIG. 20 illustrates a plan view of an eyepiece waveguide and corresponding grating vectors for a first circular polarization according to an embodiment of the present invention.

[0160] FIG. 21 illustrates a plan view of the same (or different) eyepiece waveguide in FIG. 20 and corresponding grating vectors for a second circular polarization according to an embodiment of the present invention.

[0161] In FIG. 20, light diffracted into the eyepiece waveguide 2000 by ICG 2010 is diffracted tow ard the OPE 2012, which is positioned to the upper left with respect to ICG 2010. In FIG. 21, light diffracted into the eyepiece waveguide 2100 by ICG 2110 is diffracted toward the OPE 2112, which is positioned to the upper right with respect to ICG 2110. Thus, different layouts can be utilized depending on the particular application. Thus, the PVGs / SRGs can be distributed in the plane of the w aveguide as well as on the same or opposing sides of the waveguide. Light is outcoupled from eyepiece waveguide 2000 by EPE 2014 and light is outcoupled from eyepiece waveguide 2100 by EPE 2114. Eyepiece waveguide s 2000 and 2100 can be the same wav eguide or separate waveguides stacked together.

[0162] Each PVG in the eyepiece waveguide can have several layers with the same or different types of LC material. FIG. 22 is a simplified cross-section view of an eyepiece waveguide 2200 including a stack with a multilayer LC grating structure according to an45TOWNSEND 80086574 1embodiment of the present invention. Each layer, illustrated by first layer 2210, second layer 2212, and third layer 2214. has different chirality, tilt of the LC, grating pitch, and thickness, causing the slant angle to change through the PVG thickness, which allows control of the Bragg diffraction spectral bandwidth and FOV.

[0163] FIG. 23 illustrates a perspective view of light propagation in an eyepiece waveguide for a first circular polarization according to an embodiment of the present invention. FIG. 24 illustrates a perspective view of light propagation in the eyepiece waveguide of FIG. 23 for a second circular polarization according to an embodiment of the present invention.

[0164] In FIG. 23, light having one circular polarization state is incident onto transmissive PVG-ICGs (Element 2310), undergoes pupil expansion at reflective PVG-CPE (Element 2312), and finally is outcoupled from eyepiece waveguide 2300 by transmissive PVG-OPE (Element 2314). In this embodiment, similar to the eyepiece waveguide 1610 shown in FIG. 16A, all of the PVGs are placed on the bottom surface of the eyepiece waveguide 2300.

[0165] In FIG. 24, light having the other circular polarization state is incident onto PVG- ICGs (Element 2410), undergoes pupil expansion at reflective PVG-CPE (Element 2412), and finally is outcoupled from ey epiece waveguide 2300 by reflective PVG-OPE (Element 2414). In conjunction with the PVGs on the top surface of the eyepiece waveguide 2300 illustrated in FIG. 23, all of the PVGs are placed on the bottom surface of the eyepiece waveguide 2300. In this embodiment, similar to the eyepiece waveguide 1610 shown in FIG. 16B, all of the PVGs are placed on the top surface of the eyepiece waveguide 2300.

[0166] It should be noted that these PVG-based eyepiece waveguide designs can be designed for chromatic or achromatic operation. Some configurations can have more than one layer of waveguide, where each layer of the waveguide is designed for one, two, or more colors. Other configurations can only have one layer of waveguide, which is operable for all visible colors. One of ordinary' skill in the art would recognize many variations, modifications, and alternatives.

[0167] FIG. 25 is a simplified k-space diagram for a conventional eyepiece waveguide. In FIG. 25, the refractive index limitations of PVGs are illustrated. The Liquid Crystal (LC) refractive index (m.c is 1.7 while substrate refractive index is 2.0 in example shown) limits the maximum achievable FOV within a diffractive waveguide based on Polarization Volume Gratings (PVGs) that operate on all colors simultaneously. This is illustrated in the46TOWNSEND 80086574 1exemplaty k-space diagram in FIG. 25 that illustrates, for an ICG, OPE, EPE style waveguide, a 30° diagonal FOV for R. G, B color channels.

[0168] FIG. 26A is a simplified cross-sectional diagram of an eyepiece waveguide with a three layer PVG stack according to an embodiment of the present invention. In FIG. 26A, eyepiece waveguide 2600 includes three layers that are illustrated, each layer operating on a different range of colors. Referring to FIG. 26A, layer 2610 corresponds to red wavelengths, layer 2612 corresponds to green wavelengths, and layer 2614 corresponds to blue wavelengths. Each of PVGs can be designed as color selective and provide the functionality of launching at the same angle illustrated in FIG. 26A. As an example, the periodicity of the diffractive structures in each layer can be tailored to the color of interest. As a result, the angle of diffraction is the same for all colors, thereby improving the FOV achieved. Compared to SRGs, PVGs provide a more elegant scheme of multi -launching of different colors by stacking different grating pitch of gratings. FIG. 26A is a cross-section of the waveguide, the ICG, OPE and of each layer can be spatially separated or fully overlapped in surface orthogonal to the screen plane. It is assumed that the cross talk between R, G, and B layers can be reduced or minimized.

[0169] The layers can be laminated so that they are substantially flat with respect to each other. A high refractive index adhesive material 2607, which can be a glue or dielectric, can be used to fdl the gaps between the different layers and elements (e.g., layer 2614, layer 2612, and layer 2610). The refractive index of this material can be at least as high as the refractive index of the LC material and can be as high as 2.0. The height of the PVG stack can be on the order of 1-5 pm. In the illustrated example, the three PVG layers are laminated together with a high refractive index adhesive material 2607 that is index matched to the waveguide layers. Three PVG layers corresponding to one polarization state are illustrated and another set of three PVG layers corresponding to the other polarization state could be laminated to the first set or disposed on the opposing side of the waveguide substrate 2605. In some embodiments, the layer stack includes two blue layers, two green layers, and two red layers making up the stack of six layers laminated a blue-1, blue-2, green-1, green-2, red-1, and red-2. In other embodiments, two stacks on opposing sides of the waveguide substrate 2605 are utilized: set 1: blue-1 (RHP), green-1 (RHP), and red-1 (RHP); set 2: blue-2 (LHP), green-2 (LHP), and red-2 (LHP). Thus, six layers can be utilized, two sets for each polarization with three layers in each set. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.47TOWNSEND 80086574 1

[0170] Embodiments of the present invention provide benefits including a large FOV with low index LC and vastly improved color uniformity (similar to a reflective waveguide). In some embodiments, each grating can have one, two, three, or more layers with each of the layers operating on one of two orthogonal circular polarizations. In FIG. 26A, the PVG includes three layers laminated on one side of the waveguide substrate 2605 and operating on one polarization. Including the PVG on the opposing side of the waveguide substrate 2605, six layers are utilized, i.e., a first set of three gratings operating on three different colors in a first polarization state and a second set of three gratings operating on the three different colors in a second polarization state. In other embodiments, a single layer PVG is provided that diffracts all three colors simultaneously.

[0171] FIG. 26B is a simplified k-space diagram for the eyepiece waveguide shown in FIG. 26A according to an embodiment of the present invention. The example configuration is for ICG, EPE, and OPE periods of 400 nm with grating vectors at 60° with respect to each other, for green center wavelength of 525 nm, with an example LC refractive index (spectral averaged) of n ~ 1.65, supporting a -30° diagonal FOV. The PVG periods in this equilateral configurations for the Blue and Red layers can be ~ 350 nm and ~ 470 nm correspondingly assuming -460 nm and - 620 nm for blue and red channel center wavelengths. The k-space behavior for Blue and Red wavelengths will be identical to that show n in FIG. 26B for green. As shown in FIG. 26B, since each of the PVG layers is tuned to a particular color, a FOV of up to 30° diagonal can be achieved for all three colors, assuming cross talk between the layers is small. In general ICG, OPE, EPE periods for each of the layers could each be in the range of 200-600 nm, with grating vector orientation angles in plane in the range 0°-180°, the average refractive index of LC can be as high as n = 2.0.

[0172] FIG. 27 is a simplified cross-sectional diagram of an eyepiece waveguide 2700 with dual sided PVGs according to an embodiment of the present invention. As discussed in relation to FIG. 26A, cross talk between R, G, and B layers can be reduced or minimized. In FIG. 27, a first PVG layer 2710 formed on substrate 2705 is utilized that operates on two colors (i.e., B, G) and a second PVG layer 2712 formed on the opposing side of substrate 2705 is utilized that operates on the remaining color (i.e., R). As illustrated in FIG. 27, the first PVG layer 2710 operates in transmission to diffract blue and green wavelengths and the second PVG layer 2712 operates in reflection to diffract red wavelengths.48TOWNSEND 80086574 1

[0173] FIG. 28 is a simplified cross-sectional diagram of an eyepiece waveguide 2800 with a two layer PVG stack according to an embodiment of the present invention. As discussed in relation to FIG. 26A, cross talk between R, G, and B layers can be reduced or minimized. As an alternative to the embodiment illustrated in FIG. 27, in FIG. 28, the first PVG layer 2810 that operates on two colors (i.e., B, G) and the second PVG layer 2812 that operates on the remaining color (i.e., R) are laminated on a single side of the waveguide substrate 2805. In this embodiment, both the first PVG layer 2810 and the second PVG layer 2812 operate in reflection to diffract the blue and green wavelengths and the red wavelengths, respectively.

[0174] Similar to the eyepiece waveguide structure illustrated in FIG. 26, eyepiece waveguide 2800 utilizes a high refractive index adhesive material 2807, e.g., a glue or dielectric, to fill the gaps between the first PVG layer 2810 and the second PVG layer 2812. The refractive index of this material can be at least as high as the refractive index of the LC material and can be as high as 2.0.

[0175] FIG. 29 is a simplified cross-sectional diagram of an eyepiece waveguide structure incorporating two substrates and an encapsulation layer according to an embodiment of the present invention. It should be noted that the gratings in FIG. 29 are not limited to PVGs, but they can also be SRGs. As illustrated in FIG. 29, the eyepiece waveguide structure 2900 includes a first substrate 2910 and a second substrate 2920 separated by encapsulation medium 2930. In some embodiments, the encapsulation medium is a high index of refraction adhesive and / or polymer that provides a protective coating for the gratings. Generally, the index of refraction of the encapsulation mediums is higher than the average index of refraction of the gratings. Referring to FIG. 29, light is received from projector 2905, propagates through antireflection (AR) coating 2912, first substrate 2910, and encapsulation medium 2930 and is incident on PVG ICG 2932 formed on surface 2921 of second substrate 2920. After diffraction in reflection from PVG ICG 2932, light propagates through encapsulation medium 2930 and is incident on PVG OPE 2934. After diffraction in reflection from PVG OPE 2934 and TIR in encapsulation medium 2930, light is incident on PVG EPE 2936. An AR coating 2922 is also formed on the second substrate 2920. It should be noted that although OPE and EPE are spatially overlapped in the eyepiece waveguide structure 2900 cross-section shown in FIG. 29, they are indeed spatially separated in surface orthogonal to the screen plane.49TOWNSEND 80086574 1

[0176] In the embodiment illustrated in FIG. 29, EPE 2936 is a dual-sided EPE with gratings formed on both surface 2911 of first substrate 2910 as well as surface 2921 of second substrate 2920. Diffraction from EPE 2936 results in output of virtual content to user 2907.

[0177] Although eyepiece waveguide structure 2900 illustrated in FIG. 29 shares common elements with eyepiece waveguide 2600 illustrated in FIG. 26A, including a substrate, and an encapsulation medium, and gratings disposed in the encapsulation medium, the use of first substrate 2910 and second substrate 2920 in the embodiment illustrated in FIG. 29 enables the use of an EPE that is distributed over two surfaces with the EPE components facing each other and separated by the encapsulation medium. Additionally, the use of two substrates enables the ICG and the OPE to be positioned adjacent either substrate. Moreover, given presence of two substrates, the ICG and / or the OPE can be distributed on both substrates in a manner similar to the EPE.

[0178] In some embodiments, the first substrate 2910 and the second substrate 2920 are made from the same material, whereas in other embodiments, different materials are utilized to fabricate the two substrates. One of ordinary skill in the art would recognize manyvariations, modifications, and alternatives.

[0179] FIG. 30 is a simplified block diagram illustrating components of an AR system according to an embodiment of the present invention. AR system 3000 as illustrated in FIG. 30 may be incorporated into the AR devices as described herein. FIG. 30 provides a schematic illustration of one embodiment of AR system 3000 that can perform some or all of the steps of the methods provided by various embodiments. It should be noted that FIG. 30 is meant only to provide a generalized illustration of various components, any or all of which may be utilized as appropriate. FIG. 30, therefore, broadly illustrates how individual system elements may be implemented in a relati vely separated or relatively more integrated manner.

[0180] AR system 3000 is shown comprising hardware elements that can be electrically coupled via a bus 3005, or may otherwise be in communication, as appropriate. The hardware elements may include one or more processors 3010, including without limitation one or more general-purpose processors and / or one or more special-purpose processors such as digital signal processing chips, graphics acceleration processors, and / or the like; one or more input devices 3030. which can include without limitation a mouse, a keyboard, a camera, and / or the like; and one or more output devices 3040, which can include without50TOWNSEND 80086574 1limitation a display device, a printer, and / or the like. Additionally, AR system 3000 includes an eye tracking system 3070 that can provide the user's eye gaze location to the AR system. Utilizing one or more processors 3010, the eye tracking techniques discussed herein can be implemented.

[0181] AR system 3000 may further include and / or be in communication with storage device(s) 3020 (e.g., one or more non-transitory storage devices), which can comprise, without limitation, local and / or network accessible storage, and / or can include, without limitation, a disk drive, a drive array, an optical storage device, a solid-state storage device, such as a random access memory (RAM), and / or a read-only memory (ROM), which can be programmable, flash- updateable, and / or the like. Such storage devices may be configured to implement any appropriate data stores, including without limitation, various file systems, database structures, and / or the like.

[0182] AR system 3000 might also include a communications subsystem 3050, which can include without limitation a modem, a network card (wireless or wired), an infrared communication device, a wireless communication device, and / or a chipset such as a Bluetooth™ device, an 802.11 device, a WiFi device, a WiMax device, cellular communication facilities, etc., and / or the like. Communications subsystem 3050 may include one or more input and / or output communication interfaces to permit data to be exchanged with a network such as the network described below to name one example, other computer systems, television, and / or any other devices described herein. Depending on the desired functionality and / or other implementation concerns, a portable electronic device or similar device may communicate an image and / or other information via communications subsystem 3050. In other embodiments, a portable electronic device, e.g., the first electronic device, may be incorporated into AR system 3000, e.g., an electronic device as an input device 3030. In some embodiments, AR system 3000 will further comprise a working memory 3060, which can include a RAM or ROM device, as described above.

[0183] AR system 3000 also can include software elements, shown as being currently located within working memory 3060, including an operating system 3062, device drivers, executable libraries, and / or other code, such as one or more application programs 3064, which may comprise computer programs provided by various embodiments, and / or may be designed to implement methods, and / or configure systems, provided by other embodiments, as described herein. Merely by way of example, one or more procedures described with51TOWNSEND 80086574 1respect to the methods discussed above might be implemented as code and / or instructions executable by a computer and / or a processor within a computer; in an aspect, then, such code and / or instructions can be used to configure and / or adapt a general purpose computer or other device to perform one or more operations in accordance with the described methods.

[0184] A set of these instructions and / or code may be stored on a non-transitory computer- readable storage medium, such as storage device(s) 3020 described above. In some cases, the storage medium might be incorporated within a computer system, such as AR system 3000. In other embodiments, the storage medium might be separate from a computer system e.g., a removable medium, such as a compact disc, and / or provided in an installation package, such that the storage medium can be used to program, configure, and / or adapt a general purpose computer with the instructions / code stored thereon. These instructions might take the form of executable code, which is executable by AR system 3000 and / or might take the form of source and / or installable code, which, upon compilation and / or installation on AR system 3000, e.g., using any of a variety of generally available compilers, installation programs, compression / decompression utilities, then takes the form of executable code.

[0185] It will be apparent to those skilled in the art that substantial variations may be made in accordance with specific requirements. For example, customized hardware might also be used, and / or particular elements might be implemented in hardware, software including portable software, such as applets, etc., or both. Further, connection to other computing devices such as network input / output devices may be employed.

[0186] As mentioned above, in one aspect, some embodiments may employ a computer system such as AR system 3000 to perform methods in accordance with various embodiments of the technology. According to a set of embodiments, some or all of the procedures of such methods are performed by AR system 3000 in response to one or more processors 3010 executing one or more sequences of one or more instructions, which might be incorporated into operating system 3062 and / or other code, such as an application program 3064, contained in working memory 3060. Such instructions may be read into working memory 3060 from another computer-readable medium, such as one or more of storage device(s) 3020. Merely by way of example, execution of the sequences of instructions contained in working memory 3060 might cause one or more processors 3010 to perform one or more procedures of the methods described herein. Additionally or alternatively, portions of the methods described herein may be executed through specialized hardware.52TOWNSEND 80086574 1

[0187] The terms machine-readable medium and computer-readable medium, as used herein, refer to any medium that participates in providing data that causes a machine to operate in a specific fashion. In an embodiment implemented using AR system 3000, various computer-readable media might be involved in providing instructions / code to one or more processors 3010 for execution and / or might be used to store and / or carry such instructions / code. In many implementations, a computer-readable medium is a physical and / or tangible storage medium. Such a medium may take the form of a non-volatile media or volatile media. Non-volatile media include, for example, optical and / or magnetic disks, such as storage device(s) 3020. Volatile media include, without limitation, dynamic memory', such as working memory 3060.

[0188] Common forms of physical and / or tangible computer-readable media include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, or any other magnetic medium, a CD-ROM, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, EPROM, a FLASH-EPROM, any other memory' chip or cartridge, or any other medium from which a computer can read instructions and / or code.

[0189] Various forms of computer-readable media may be involved in carrying one or more sequences of one or more instructions to one or more processors 3010 for execution. Merely by way of example, the instructions may initially be carried on a magnetic disk and / or optical disc of a remote computer. A remote computer might load the instructions into its dynamic memory and send the instructions as signals over a transmission medium to be received and / or executed by AR system 3000.

[0190] Communications subsystem 3050 and / or components thereof generally will receive signals, and bus 3005 then might carry' the signals and / or the data, instructions, etc. carried by the signals to working memory 3060, from which one or more processors 3010 retrieves and executes the instructions. The instructions received by working memory 3060 may optionally be stored on storage device(s) 3020, e.g., a non-transitory' storage device, either before or after execution by one or more processors 3010.

[0191] A summary' of the various embodiments of the invention is provided below as a list of examples. As used below, any reference to a series of examples is to be understood as a reference to each of those examples disjunctively (e.g., "Examples 1-4" is to be understood as "Examples 1, 2, 3, or 4").53TOWNSEND 80086574 1

[0192] Example 1 is an augmented reality optical system comprising a source of virtual content and an eyepiece waveguide optically coupled to the source of virtual content, wherein the eyepiece waveguide includes: an incoupling diffractive element; and an outcoupling diffractive optical element, wherein at least one of the incoupling diffractive element or the outcoupling diffractive optical element comprises a polarization volume grating (PVG).

[0193] Example 2 is the augmented reality optical system of example 1 wherein the incoupling diffractive element comprises: a first set of PVGs disposed on a first surface of the eyepiece waveguide and configured to incouple a first color group; and a second set of PVGs disposed on a second surface of the eyepiece waveguide opposing the first surface and configured to incouple a second color group complementary to the first color group.

[0194] Example 3 is the augmented reality optical system of example 2 wherein the first color group and the second color group do not overlap in wavelength.

[0195] Example 4 is the augmented reality optical system of example(s) 1-3 wherein the incoupling diffractive element comprises: a first PVG disposed on a first surface of the eyepiece waveguide and configured to incouple a first polarization state; and a second PVG disposed on a second surface of the eyepiece waveguide opposing the first surface and configured to incouple a second polarization state orthogonal to the first polarization state.

[0196] Example 5 is the augmented reality optical system of example(s) 1-4 wherein the virtual content is unpolarized.

[0197] Example 6 is the augmented reality optical system of example(s) 1-5 wherein both the incoupling diffractive element and the outcoupling diffractive optical element comprise a PVG.

[0198] Example 7 is the augmented reality optical system of example(s) 1-6 wherein the eyepiece waveguide is configured to support incoupling, propagation by total internal reflection, and outcoupling of visible wavelengths ranging from 400 nm to 700 nm.

[0199] Example 8 is the augmented reality' optical system of example(s) 1-7 wherein the eyepiece waveguide is characterized by a field of view of 40° x 40° for the visible wavelengths ranging from 400 nm to 700 nm.

[0200] Example 9 is the augmented reality optical system of example 8 wherein the field of view is 22° x 22°.54TOWNSEND 80086574 1

[0201] Example 10 is the augmented reality optical system of example(s) 1-9 wherein the eyepiece waveguide comprises a single waveguide substrate.

[0202] Example 11 is the augmented reality optical system of example(s) 1-10 wherein the incoupling diffractive element and the outcoupling diffractive optical element are disposed on a same side of the eyepiece waveguide.

[0203] Example 12 is the augmented reality7optical system of example(s) 1-11 further comprising an orthogonal pupil expander diffractive optical element.

[0204] Example 13 is the augmented reality optical system of example 12 wherein the incoupling diffractive element and the outcoupling diffractive optical element are disposed on a same side of the eyepiece waveguide and the orthogonal pupil expander diffractive optical element is disposed on an opposing side of the eyepiece waveguide.

[0205] Example 14 is the augmented reality optical sy stem of example 12 wherein the incoupling diffractive element, the orthogonal pupil expander diffractive optical element, and the outcoupling diffractive optical element are disposed on a same side of the eyepiece waveguide.

[0206] Example 15 is the augmented reality optical system of example(s) 1-14 wherein the source of virtual content comprises a micro-light emitting diode (p-LED) projector.

[0207] Example 16 is the augmented reality optical system of example 15 wherein the incoupling diffractive element is configured to incouple visible wavelengths ranging from 400 nm to 700 nm.

[0208] Example 17 is an augmented reality optical system comprising a projector; and an eyepiece waveguide optically coupled to the projector, wherein the eyepiece waveguide includes: a first substrate; a second substrate; an encapsulation medium disposed between the first substrate and the second substrate; an incoupling diffractive optical element disposed on the first substrate or the second substrate; and an outcoupling diffractive optical element disposed on the first substrate and the second substrate, wherein at least one of the incoupling diffractive optical element or the outcoupling diffractive optical element comprises a polarization volume grating (PVG).55TOWNSEND 80086574 1

[0209] Example 18 is the augmented reality optical system of example 17 further comprising an orthogonal pupil expander diffractive optical element disposed on the first substrate or the second substrate.

[0210] Example 19 is the augmented reality optical system of example 18 wherein the orthogonal pupil expander diffractive optical element is disposed on the first substrate.

[0211] Example 20 is the augmented reality7optical system of example 18 wherein the orthogonal pupil expander diffractive optical element comprises a PVG.

[0212] Example 21 is the augmented reality optical system of example(s) 17-20 wherein both the incoupling diffractive optical element and the outcoupling diffractive optical element comprise PVGs.

[0213] Example 22 is the augmented reality optical system of example(s) 17-21 wherein the projector is configured to output unpolarized light.

[0214] Example 23 is the augmented reality optical system of example(s) 17-22 wherein the eyepiece waveguide is configured to support incoupling, propagation by total internal reflection, and outcoupling of visible wavelengths ranging from 400 nm to 700 nm.

[0215] Example 24 is the augmented reality optical system of example(s) 17-23 wherein the eyepiece waveguide is characterized by a field of view of 40° x 40° for the visible wavelengths ranging from 400 nm to 700 nm.

[0216] Example 25 is the augmented reality optical system of example 24 wherein the field of view is 22° x 22°.

[0217] Example 26 is the augmented reality optical system of example(s) 17-25 wherein the projector comprises micro-light emitting diode (p-LED) projector.

[0218] Example 27 is the augmented reality optical system of example 26 wherein the incoupling diffractive optical element is configured to incouple visible wavelengths ranging from 400 nm to 700 nm.

[0219] In the foregoing specification, the disclosure has been described with reference to specific embodiments thereof. The systems and devices discussed above are examples. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the disclosure. The specification and drawings are. accordingly, to be regarded in an illustrative rather than restrictive sense. Also,56TOWNSEND 80086574 1technology evolves and, thus, many of the elements are examples that do not limit the scope of the disclosure or claims.

[0220] Indeed, it will be appreciated that the systems and methods of the disclosure each have several innovative aspects, no single one of which is solely responsible or required for the desirable attributes disclosed herein. The various features and processes described above may be used independently of one another, or may be combined in various ways. All possible combinations and subcombinations are intended to fall within the scope of this disclosure.

[0221] Certain features that are described in this specification in the context of separate embodiments also may be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment also may be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination may in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. No single feature or group of features is necessary or indispensable to each and every embodiment.

[0222] Having described several example configurations, various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the disclosure. For example, the above elements may be components of a larger system, wherein other rules may take precedence over or otherwise modify the application of the technology. Also, a number of steps may be undertaken before, dunng, or after the above elements are considered. Accordingly, the above description does not bind the scope of the claims.

[0223] It will be appreciated that conditional language used herein, such as, among others, "can," "could," "might," "may," "e.g.," and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and / or steps. Thus, such conditional language is not generally intended to imply that features, elements and / or steps are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and / or steps are included or are to be performed in any particular embodiment.57TOWNSEND 80086574 1

[0224] The terms "comprising," "including," "having," and the like are synonymous and are used inclusively, in an open-ended fashion, and do not exclude additional elements, features, acts, operations, and so forth. Also, the term "or" is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term "or" means one, some, or all of the elements in the list. In addition, the articles "a," "an." and "the" as used in this application and the appended claims are to be construed to mean "one or more" or "at least one" unless specified otherwise. Similarly, while operations may be depicted in the drawings in a particular order, it is to be recognized that such operations need not be performed in the particular order show n or in sequential order, or that all illustrated operations be performed, to achieve desirable results.

[0225] Further, the drawings may schematically depict one more example processes in the form of a flowchart. However, other operations that are not depicted may be incorporated in the example methods and processes that are schematically illustrated. For example, one or more additional operations may be performed before, after, simultaneously, or between any of the illustrated operations. Additionally, the operations may be rearranged or reordered in other embodiments. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems may generally be integrated together in a single software product or packaged into multiple software products. Additionally, other embodiments are within the scope of the following claims. In some cases, the actions recited in the claims may be performed in a different order and still achieve desirable results.

[0226] It is also understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.

[0227] Accordingly, the claims are not intended to be limited to the embodiments shown herein, but are to be accorded the widest scope consistent with this disclosure, the principles and the novel features disclosed herein.58TOWNSEND 80086574 1

Claims

WHAT IS CLAIMED IS:

1. An augmented reality optical system comprising: a source of virtual content; and an eyepiece waveguide optically coupled to the source of virtual content, wherein the eyepiece waveguide includes: an incoupling diffractive element; and an outcoupling diffractive optical element, wherein at least one of the incoupling diffractive element or the outcoupling diffractive optical element comprises a polarization volume grating (PVG).

2. The augmented reality optical system of claim 1 wherein the incoupling diffractive element comprises: a first set of PVGs disposed on a first surface of the eyepiece waveguide and configured to incouple a first color group; and a second set of PVGs disposed on a second surface of the eyepiece waveguide opposing the first surface and configured to incouple a second color group complementary to the first color group.

3. The augmented reality optical system of claim 2 wherein the first color group and the second color group do not overlap in w avelength.

4. The augmented reality optical system of claim 1 wherein the incoupling diffractive element comprises: a first PVG disposed on a first surface of the eyepiece w aveguide and configured to incouple a first polarization state; and a second PVG disposed on a second surface of the eyepiece waveguide opposing the first surface and configured to incouple a second polarization state orthogonal to the first polarization state.

5. The augmented reality optical system of claim 1 wherein the virtual content is unpolarized.

6. The augmented reality optical system of claim 1 wherein both the incoupling diffractive element and the outcoupling diffractive optical element comprise a PVG.59TOWNSEND 80086574 17. The augmented reality optical system of claim 1 wherein the eyepiece waveguide is configured to support incoupling, propagation by total internal reflection, and outcoupling of visible wavelengths ranging from 400 nm to 700 nm.

8. The augmented reality optical system of claim 1 wherein the eyepiece waveguide is characterized by a field of view of 40° x 40° for the visible wavelengths ranging from 400 nm to 700 nm.

9. The augmented reality optical system of claim 8 wherein the field of view is 22° x 22°.

10. The augmented reality optical system of claim 1 wherein the eyepiece waveguide comprises a single waveguide substrate.

11. The augmented reality optical system of claim 1 wherein the incoupling diffractive element and the outcoupling diffractive optical element are disposed on a same side of the eyepiece waveguide.

12. The augmented reality optical system of claim 1 further comprising an orthogonal pupil expander diffractive optical element.

13. The augmented reality optical system of claim 12 wherein the incoupling diffractive element and the outcoupling diffractive optical element are disposed on a same side of the eyepiece waveguide and the orthogonal pupil expander diffractive optical element is disposed on an opposing side of the eyepiece waveguide.

14. The augmented reality optical system of claim 12 wherein the incoupling diffractive element, the orthogonal pupil expander diffractive optical element, and the outcoupling diffractive optical element are disposed on a same side of the eyepiece waveguide.

15. The augmented reality optical system of claim 1 wherein the source of virtual content comprises a micro-light emitting diode (LI-LED) projector.

16. The augmented reality optical system of claim 15 wherein the incoupling diffractive element is configured to incouple visible wavelengths ranging from 400 nm to 700 nm.60TOWNSEND 80086574 117. An augmented reality optical system comprising: a projector; and an eyepiece waveguide optically coupled to the projector, wherein the eyepiece waveguide includes: a first substrate; a second substrate; an encapsulation medium disposed between the first substrate and the second substrate; an incoupling diffractive optical element disposed on the first substrate or the second substrate; and an outcoupling diffractive optical element disposed on the first substrate and the second substrate, wherein at least one of the incoupling diffractive optical element or the outcoupling diffractive optical element comprises a polarization volume grating (PVG).

18. The augmented reality optical system of claim 17 further comprising an orthogonal pupil expander diffractive optical element disposed on the first substrate or the second substrate.

19. The augmented reality optical system of claim 18 wherein the orthogonal pupil expander diffractive optical element is disposed on the first substrate.

20. The augmented reality optical system of claim 18 wherein the orthogonal pupil expander diffractive optical element comprises a PVG.

21. The augmented reality optical system of claim 17 wherein both the incoupling diffractive optical element and the outcoupling diffractive optical element comprise PVGs.

22. The augmented reality optical system of claim 17 wherein the projector is configured to output unpolarized light.

23. The augmented reality optical system of claim 17 wherein the eyepiece waveguide is configured to support incoupling, propagation by total internal reflection, and outcoupling of visible wavelengths ranging from 400 nm to 700 nm.61TOWNSEND 80086574 124. The augmented reality optical system of claim 17 wherein the eyepiece waveguide is characterized by a field of view of 40° x 40° for the visible wavelengths ranging from 400 nm to 700 nm.

25. The augmented reality optical system of claim 24 wherein the field of view is 22° x 22°.

26. The augmented reality optical system of claim 17 wherein the projector comprises micro-light emitting diode (p-LED) projector.

27. The augmented reality optical system of claim 26 wherein the incoupling diffractive optical element is configured to incouple visible wavelengths ranging from 400 nm to 700 nm.62TOWNSEND 80086574 1

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