Optical device with one-way mirror

Abstract

To provide a favorable optical device with a one-way mirror.SOLUTION: In some implementations, an optical device includes a one-way mirror formed by a polarization selective mirror and an absorptive polarizer. The absorptive polarizer has a transmission axis aligned with a transmission axis of the reflective polarizer. The one-way mirror may be provided on the world side of a head-mounted display system. Advantageously, the one-way mirror may reflect light from the world, which provides privacy and may improve the cosmetics of the display. In some implementations, the one-way mirror may include one or more of a depolarizer and a pair of opposing waveplates to improve alignment tolerances and reduce reflections to a viewer. In some implementations, the one-way mirror may form a compact integrated structure with a dimmer for reducing light transmitted to the viewer from the world.SELECTED DRAWING: Figure 2A

Description

[Technical Field]

[0001] (Priority Claim) This application claims priority to U.S. Provisional Application No. 62 / 994,739, filed March 25, 2020, which is incorporated by reference in its entirety for all purposes. (Incorporated by reference)

[0002] This application incorporates by reference the entirety of each of the following: U.S. Patent Publication No. 2018 / 0234675, entitled "Method and System for Display Device with Integrated Polarizer," published on August 16, 2018; U.S. Patent Publication No. 2019 / 0187474A1, entitled "Eyepieces for Augmented Reality Display System," published on June 20, 2019; and U.S. Patent Publication No. 2018 / 0164627, entitled "Diffractive Devices Based on Cholesteric Liquid Crystal," published on June 14, 2018. (Technical field)

[0003] The present disclosure relates to optical devices that include one-way mirrors, such as augmented reality display devices with one-way mirrors. [Background technology]

[0004] Modern computing and display technologies have facilitated the development of systems for so-called "augmented reality" experiences, in which digitally reproduced images, or portions thereof, are presented to a user in a manner that appears or can be perceived as real. Augmented reality or "AR" scenarios typically involve the presentation of digital or virtual image information as an extension to the user's visualization of the real world around them. Mixed reality or "MR" scenarios are a type of AR scenario and typically involve virtual objects integrated into and responsive to the natural world. For example, MR scenarios may include AR image content that appears blocked by or otherwise perceived to interact with objects in the real world.

[0005] Referring to FIG. 1A , an augmented reality scene 10 is depicted in which a user of the AR technology views a real-world park-like setting 20 featuring people, trees, a building in the background, and a concrete platform 30. In addition to these items, the user of the AR technology also perceives as "seeing" "virtual content," such as a robotic figure 40 standing on the real-world platform 30 and a flying, cartoon-like avatar character 50 that appears to be an anthropomorphic bumblebee, although these elements 40, 50 do not exist in the real world. The human visual perception system is complex, making it difficult to produce AR technology that facilitates a comfortable, natural-feeling, and rich presentation of virtual image elements among other virtual or real-world image elements.

[0006] The systems and methods disclosed herein address, among other things, various challenges associated with AR technology. Summary of the Invention [Means for solving the problem]

[0007] In some implementations, the optical device includes a one-way mirror that includes a depolarizer, a polarization-selective mirror oriented to receive light from the depolarizer and having a transmission axis, and an absorptive polarizer oriented to receive light from the polarization-selective mirror and having a transmission axis aligned with the transmission axis of the polarization-selective mirror, the polarization-selective mirror being disposed between the depolarizer and the absorptive polarizer.

[0008] In some other implementations, the optical device includes a one-way mirror that includes a cholesteric liquid crystal reflective polarizer and a circular polarizer configured to receive light that is transmitted through the cholesteric liquid crystal reflective polarizer.

[0009] In yet another implementation, the optical device comprises a one-way mirror dimmer comprising a polarization-selective mirror having a transmission axis, an absorptive polarizer behind the polarization-selective mirror and having a transmission axis aligned with the transmission axis of the polarization-selective mirror, an array of switchable liquid crystal elements behind the absorptive polarizer, and a polarizer behind the array of switchable liquid crystal elements and having a transmission axis aligned with the transmission axis of the absorptive polarizer.

[0010] In some other implementations, the optical device includes a polarization-selective mirror having a transmission axis, an absorbing polarizer having a transmission axis aligned with the transmission axis of the polarization-selective mirror, and one or more retarders between the polarization-selective mirror and the absorbing polarizer.

[0011] Some additional implementation examples are provided below.

[0012] Implementation 1. An optical device, the optical device comprising: a one-way mirror; One-way mirrors are A depolarizer; a polarization-selective mirror oriented to receive light from the depolarizer and having a transmission axis; and an absorptive polarizer oriented to receive light from the polarization-selective mirror and having a transmission axis aligned with the transmission axis of the polarization-selective mirror. Equipped with An optical device in which the polarization-selective mirror is positioned between the depolarizer and the absorptive polarizer.

[0013] Implementation 2. The optical device of Implementation 1, wherein the depolarizer comprises a quarter-wave plate.

[0014] Implementation 3. The optical device of Implementation 2, wherein the quarter-wave plate comprises an achromatic quarter-wave plate.

[0015] Implementation 4. The optical device of Implementation 1, wherein the depolarizer comprises an ultra-retarder.

[0016] Implementation 5. The optical device of Implementation 1, wherein the depolarizer is configured to output circularly polarized light from the received polarized light.

[0017] Implementation 6. The optical device of Implementation 1, wherein the polarization-selective mirror comprises a reflective polarizer.

[0018] Implementation 7. The optical device of Implementation 1, wherein the polarization-selective mirror is in direct contact with the absorptive polarizer.

[0019] Implementation 8. The optical device of Implementation 1, wherein the polarization-selective mirror and the absorptive polarizer are spaced apart.

[0020] Implementation 9. The optical device of Implementation 8, further comprising one or more retarders between the polarization-selective mirror and the absorptive polarizer.

[0021] Implementation 10. The optical device of Implementation 9, wherein the one or more retarders comprise two spaced apart quarter-wave plates.

[0022] Implementation 11. The optical device of Implementation 1, wherein the absorbing polarizer absorbs light having an electric field vector perpendicular to the transmission axis of the absorbing polarizer.

[0023] Implementation 12. The optical device of implementation 1, wherein the reflective polarizer reflects light having an electric field vector perpendicular to the transmission axis of the absorbing polarizer.

[0024] Implementation 13. The optical device of implementation 1, wherein the reflective polarizer comprises a wire grid polarizer.

[0025] Implementation 14. The optical device of Implementation 13, wherein the wire grid polarizer comprises a nanoscale wire pattern with repeating parallel wires.

[0026] Implementation 15. The optical device of Implementation 14, wherein each of the wires of the wire pattern is elongated parallel to the transmission axis of the polarization-selective mirror.

[0027] Implementation 16. The optical device of implementation 1, wherein the reflective polarizer comprises a multilayer polarizer.

[0028] Implementation 17. The optical device of Implementation 16, wherein the multilayer polarizer is configured to reflect incident light of a predetermined wavelength.

[0029] Implementation 18. The optical device of implementation 16, wherein the multilayer polarizer comprises a plurality of polymer films.

[0030] Implementation 19. The optical device of implementation 16, wherein the multilayer polarizer reflects 50% of incident light with an electric field vector perpendicular to the transmission axis of the multilayer polarizer.

[0031] Implementation 20. The optical device of implementation 16, wherein the multilayer polarizer reflects 30% to 40% of incident light with an electric field vector perpendicular to the transmission axis of the multilayer polarizer.

[0032] Implementation 21. The optical device of Implementation 1, wherein the absorptive polarizer is configured to absorb linearly polarized light.

[0033] Implementation 22. Further comprising an active variable dimmer, the active variable dimmer comprising: an array of liquid crystal elements; Polarizer and Equipped with The optical device of implementation 1, wherein the array of liquid crystal elements is between the polarizer and the one-way mirror absorptive polarizer.

[0034] Implementation 23. The optical device is a head-mounted display system, the display system comprising a head-mounted display; The optical device of Implementation 1, wherein the one-way mirror is positioned on the head-mounted display and is opposite the user side of the display.

[0035] Implementation 24. The optical device of Implementation 23, wherein the display comprises an eyepiece comprising a waveguide stack, the waveguide stack comprising a plurality of waveguides each configured to output light to a viewer.

[0036] Implementation 25. The optical device of Implementation 24, wherein each waveguide of the plurality of waveguides is configured to output light with a wavefront divergence that is different from one or more other waveguides of the plurality of waveguides, the different wavefront divergence corresponding to different depth planes.

[0037] Implementation 26. The optical device of implementation 24, wherein each waveguide comprises a diffractive in-coupling optical element and a diffractive out-coupling optical element.

[0038] Implementation 27. An optical device, the optical device comprising a one-way mirror; One-way mirrors are a cholesteric liquid crystal reflective polarizer; a circular polarizer configured to receive light transmitted through the cholesteric liquid crystal reflective polarizer; An optical device comprising:

[0039] Implementation 28. The optical device of implementation 27, wherein the circular polarizer comprises a quarter-wave plate and an absorptive polarizer.

[0040] Implementation 29. The optical device of implementation 28, wherein the absorptive polarizer comprises a linear polarizer.

[0041] Implementation 30. The optical device of implementation 28, wherein the quarter-wave plate retards light in a direction opposite to the light transmitted by the cholesteric liquid crystal reflective polarizer.

[0042] Implementation 31. The optical device of implementation 28, wherein the quarter-wave plate is an achromatic quarter-wave plate.

[0043] Implementation 32. The optical device of implementation 27, wherein the cholesteric liquid crystal reflective polarizer transmits a first circularly polarized light and reflects a second circularly polarized light having an opposite sense to the first circularly polarized light.

[0044] Implementation 33. The optical device of implementation 28, wherein the quarter-wave plate is configured to retard light such that circularly polarized light transmitted through the cholesteric liquid crystal reflective polarizer is converted to linearly polarized light.

[0045] Implementation 34. The optical device of implementation 28, wherein the absorptive polarizer has a transmission axis parallel to the electric field vector of the linearly polarized light.

[0046] Implementation 35. The optical device is a head-mounted display system, the display system comprising a head-mounted display; The optical device described in Implementation 27, wherein the one-way mirror is positioned on the head-mounted display and is positioned on the side opposite the user side of the head-mounted display.

[0047] Implementation 36. The optical device of Implementation 35, wherein the head-mounted display includes an eyepiece having a waveguide stack, the waveguide stack including a plurality of waveguides each configured to output light to a viewer.

[0048] Implementation 37. The optical device of implementation 36, wherein each waveguide is configured to output light with a different amount of wavefront divergence than one or more other waveguides, the different amount of wavefront divergence corresponding to a different depth plane.

[0049] Implementation 38. Further comprising an active variable dimmer, the active variable dimmer comprising: A polarizer; an array of liquid crystal elements; Equipped with 28. The optical device of implementation 27, wherein the array of liquid crystal elements is between the polarizer and the one-way mirror absorptive polarizer.

[0050] Implementation 39. The optical device of Implementation 38, wherein the liquid crystal elements of the array of liquid crystal elements are configured to switch from a transmissive mode to an absorptive mode.

[0051] Implementation 40. An optical device, the optical device comprising a one-way mirror dimmer; One-way mirror dimmers are a polarization selective mirror having a transmission axis; an absorptive polarizer behind the polarization-selective mirror and having a transmission axis aligned with the transmission axis of the polarization-selective mirror; an array of switchable liquid crystal elements behind an absorptive polarizer; a polarizer behind the array of switchable liquid crystal elements, the polarizer having a transmission axis aligned with the transmission axis of the absorbing polarizer; An optical device comprising:

[0052] Implementation 41. The optical device of Implementation 40, further comprising first and second quarter-wave plates between the polarization-selective mirror and the absorptive polarizer.

[0053] Implementation 42. The optical device of Implementation 41, wherein the first achromatic quarter-wave plate and the second achromatic quarter-wave plate are separated by an air gap greater than 1 mm.

[0054] Implementation 43. The optical device of implementation 40, wherein the polarization-selective mirror is a wire grid polarizer.

[0055] Implementation 44. The optical device of implementation 40, wherein the polarization-selective mirror is a multilayer reflective polarizer.

[0056] Implementation 45. The optical device is a head-mounted display system, the display system comprising a head-mounted display; An optical device as described in Implementation 40, wherein the one-way mirror dimmer is positioned on the head-mounted display and is positioned on the side opposite the user side of the head-mounted display.

[0057] Implementation 46. The optical device of Implementation 45, wherein the head-mounted display includes an eyepiece having a waveguide stack, the waveguide stack including a plurality of waveguides each configured to output light to a viewer.

[0058] Implementation 47. The optical device of Implementation 46, wherein each waveguide is configured to output light with a different wavefront divergence than one or more other waveguides, the different wavefront divergence corresponding to a different depth plane.

[0059] Implementation 48. An optical device, comprising: a polarization selective mirror having a transmission axis; an absorptive polarizer having a transmission axis aligned with the transmission axis of the polarization-selective mirror; one or more retarders between the polarization-selective mirror and the absorptive polarizer; An optical device comprising:

[0060] Implementation 49. The optical device of implementation 48, wherein the one or more retarders comprise two spaced apart quarter-wave plates.

[0061] Implementation 50. The optical device of implementation 49, wherein each of the two quarter-wave plates comprises an achromatic quarter-wave plate.

[0062] Implementation 51. The optical device of implementation 49, wherein the two quarter-wave plates are spaced apart by an air gap of 1 mm or more.

[0063] Implementation 52. The optical device is a head-mounted display system, the display system comprising a head-mounted display; The optical device described in Implementation 48, wherein the one-way mirror dimmer is positioned on the head-mounted display and is positioned on the side opposite the user side of the head-mounted display.

[0064] Implementation 53. The optical device of Implementation 52, wherein the head-mounted display includes an eyepiece having a waveguide stack, the waveguide stack including a plurality of waveguides each configured to output light to a viewer.

[0065] Implementation 54. The optical device of Implementation 53, wherein each waveguide is configured to output light with a different wavefront divergence than one or more other waveguides, the different wavefront divergence corresponding to a different depth plane. The present invention provides, for example, the following. (Item 1) an optical device comprising a one-way mirror; The one-way mirror is A depolarizer; a polarization-selective mirror oriented to receive light from the depolarizer and having a transmission axis; an absorptive polarizer oriented to receive light from the polarization-selective mirror and having a transmission axis aligned with the transmission axis of the polarization-selective mirror; Equipped with The polarization-selective mirror is disposed between the depolarizer and the absorptive polarizer. (Item 2) Item 10. The optical device of item 1, wherein the depolarizer comprises a quarter-wave plate. (Item 3) Item 10. The optical device of item 1, wherein the depolarizer comprises an ultra-phase retarder. (Item 4) Item 10. The optical device of item 1, wherein the depolarizer is configured to output circularly polarized light from a received polarization. (Item 5) Item 10. The optical device of item 1, wherein the polarization selective mirror comprises a reflective polarizer. (Item 6) Item 10. The optical device of item 1, wherein the polarization-selective mirror and the absorptive polarizer are spaced apart, and further comprising one or more retarders between the polarization-selective mirror and the absorptive polarizer. (Item 7) 7. The optical device of claim 6, wherein the one or more retarders comprise two spaced apart quarter-wave plates. (Item 8) Item 1, wherein the reflective polarizer comprises a wire grid polarizer. (Item 9) Item 9. The optical device of item 8, wherein the wire grid polarizer comprises a nanoscale wire pattern with repeating parallel wires. (Item 10) Item 10. The optical device of item 9, wherein each of the wires of the wire pattern is elongated parallel to the transmission axis of the polarization selective mirror. (Item 11) Item 10. The optical device of item 1, wherein the reflective polarizer comprises a multilayer polarizer. (Item 12) Item 12. The optical device of item 11, wherein the multilayer polarizer is configured to reflect incident light of a predetermined wavelength. (Item 13) Item 12. The optical device of item 11, wherein the multilayer polarizer comprises a plurality of polymer films. (Item 14) Item 12. The optical device of item 11, wherein the multilayer polarizer reflects 50% or less of incident light with an electric field vector perpendicular to the transmission axis of the multilayer polarizer. (Item 15) Item 12. The optical device of item 11, wherein the multilayer polarizer reflects 30% to 40% of incident light with an electric field vector perpendicular to the transmission axis of the multilayer polarizer. (Item 16) Item 10. The optical device of item 1, wherein the absorptive polarizer is configured to absorb linearly polarized light. (Item 17) The active variable dimmer further comprises: an array of liquid crystal elements; Polarizer and Equipped with Item 1, an optical device according to item 1, wherein the array of liquid crystal elements is between the polarizer of the one-way mirror and the absorptive polarizer. (Item 18) the optical device is a head-mounted display system, the display system comprising a head-mounted display; Item 1, an optical device according to item 1, wherein the one-way mirror is positioned on the head-mounted display and is positioned on the side of the display opposite the user side. (Item 19) the display comprises an eyepiece comprising a waveguide stack; Item 19. The optical device of item 18, wherein the waveguide stack comprises a plurality of waveguides each configured to output light to a viewer. (Item 20) 20. The optical device of item 19, wherein each waveguide of the plurality of waveguides is configured to output light with a different amount of wavefront divergence than one or more other waveguides of the plurality of waveguides, the different amount of wavefront divergence corresponding to a different depth plane. (Item 21) an optical device comprising a one-way mirror; The one-way mirror is a cholesteric liquid crystal reflective polarizer; a circular polarizer configured to receive light transmitted through the cholesteric liquid crystal reflective polarizer; An optical device comprising: (Item 22) Item 22. The optical device of item 21, wherein the circular polarizer comprises a quarter-wave plate and an absorptive polarizer. (Item 23) Item 23. The optical device of item 22, wherein the absorptive polarizer comprises a linear polarizer. (Item 24) Item 23. The optical device of item 22, wherein the quarter wave plate retards light in a direction opposite to that of light transmitted by the cholesteric liquid crystal reflective polarizer. (Item 25) Item 23. The optical device of item 22, wherein the quarter-wave plate is an achromatic quarter-wave plate. (Item 26) Item 22. The optical device of item 21, wherein the cholesteric liquid crystal reflective polarizer transmits a first circularly polarized light and reflects a second circularly polarized light with an opposite sense to the first circularly polarized light. (Item 27) Item 23. The optical device of item 22, wherein the quarter-wave plate is configured to retard light such that circularly polarized light transmitted through the cholesteric liquid crystal reflective polarizer is converted to linearly polarized light. (Item 28) the optical device is a head-mounted display system, the display system comprising a head-mounted display; Item 22. The optical device of item 21, wherein the one-way mirror is positioned on the head-mounted display and is positioned on the side opposite the user side of the head-mounted display. (Item 29) the head mounted display comprises an eyepiece comprising a waveguide stack; Item 29. The optical device of item 28, wherein the waveguide stack comprises a plurality of waveguides each configured to output light to a viewer. (Item 30) each waveguide configured to output light with a different amount of wavefront divergence than one or more other waveguides; 30. The optical device according to item 29, wherein different amounts of wavefront divergence correspond to different depth planes. (Item 31) The active variable dimmer further comprises: A polarizer; an array of liquid crystal elements; Equipped with 22. The optical device of claim 21, wherein the array of liquid crystal elements is between the polarizer and the absorptive polarizer of the one-way mirror. (Item 32) Item 32. The optical device of item 31, wherein the liquid crystal elements of the array of liquid crystal elements are configured to switch from a transmissive mode to an absorptive mode. (Item 33) an optical device, the optical device comprising a one-way mirror dimmer; In the one-way mirror type dimmer, a polarization selective mirror having a transmission axis; an absorbing polarizer behind the polarization-selective mirror and having a transmission axis aligned with the transmission axis of the polarization-selective mirror; an array of switchable liquid crystal elements behind the absorptive polarizer; a polarizer behind the array of switchable liquid crystal elements, the polarizer having a transmission axis aligned with the transmission axis of the absorptive polarizer; An optical device comprising: (Item 34) Item 34. The optical device of item 33, further comprising first and second quarter-wave plates between the polarization-selective mirror and the absorptive polarizer. (Item 35) Item 35. The optical device of item 34, wherein the first achromatic quarter-wave plate and the second achromatic quarter-wave plate are separated by an air gap of greater than 1 mm. (Item 36) Item 34. The optical device of item 33, wherein the polarization selective mirror is a wire grid polarizer. (Item 37) Item 34. The optical device of item 33, wherein the polarization selective mirror is a multilayer reflective polarizer. (Item 38) the optical device is a head-mounted display system, the display system comprising a head-mounted display; Item 34. The optical device of item 33, wherein the one-way mirror dimmer is positioned on the head-mounted display and is positioned on the side opposite the user side of the head-mounted display. (Item 39) the head mounted display comprises an eyepiece comprising a waveguide stack; Item 39. The optical device of item 38, wherein the waveguide stack comprises a plurality of waveguides each configured to output light to a viewer. (Item 40) each waveguide configured to output light with a different amount of wavefront divergence than one or more other waveguides; Item 40. The optical device of item 39, wherein different amounts of wavefront divergence correspond to different depth planes. (Item 41) An optical device, the optical device comprising: a polarization selective mirror having a transmission axis; an absorptive polarizer having a transmission axis aligned with the transmission axis of the polarization-selective mirror; one or more retarders between the polarization-selective mirror and the absorptive polarizer; An optical device comprising: (Item 42) Item 42. The optical device of item 41, wherein the one or more retarders comprise two spaced apart quarter-wave plates. (Item 43) Item 43. The optical device of item 42, wherein each of the two quarter-wave plates comprises an achromatic quarter-wave plate. (Item 44) Item 43. The optical device of item 42, wherein the two quarter-wave plates are spaced apart by an air gap of 1 mm or more. (Item 45) the optical device is a head-mounted display system, the display system comprising a head-mounted display; Item 42. The optical device of item 41, wherein the one-way mirror dimmer is positioned on the head-mounted display and is positioned on the side opposite the user side of the head-mounted display. (Item 46) the head mounted display comprises an eyepiece comprising a waveguide stack; Item 46. The optical device of item 45, wherein the waveguide stack comprises a plurality of waveguides each configured to output light to a viewer. (Item 47) each waveguide configured to output light with a different amount of wavefront divergence than one or more other waveguides; Item 47. The optical device of item 46, wherein different amounts of wavefront divergence correspond to different depth planes. [Brief explanation of the drawings]

[0066] [Figure 1A] FIG. 1A illustrates a user's view of an augmented reality (AR) device through an AR device.

[0067] [Figure 1B] FIG. 1B is a perspective view of an example wearable augmented reality (AR) display system.

[0068] [Figure 2A] 2A and 2B are examples of schematic side views of an optical device having a one-way mirror and a display. [Figure 2B] 2A and 2B are examples of schematic side views of an optical device having a one-way mirror and a display.

[0069] [Figure 2C] FIG. 2C is an example of a schematic side view of an optical device similar to that of FIGS. 2A and 2B in which a one-way mirror forms part of an integrated dimmer.

[0070] [Figure 3A]3A and 3B are schematic side view examples of the one-way mirror and display of FIGS. 2A and 2B, respectively, showing details of the propagation of light through the optical devices of each of FIGS. 2A and 2B. [Figure 3B] 3A and 3B are schematic side view examples of the one-way mirror and display of FIGS. 2A and 2B, respectively, showing details of the propagation of light through the optical devices of each of FIGS. 2A and 2B.

[0071] [Figure 3C] 3C and 3D are examples of schematic side views of an optical device having a one-way mirror with an optical retarder to provide circularly polarized light. [Figure 3D] 3C and 3D are examples of schematic side views of an optical device having a one-way mirror with an optical retarder to provide circularly polarized light.

[0072] [Figure 4A] 4A and 4B are examples of schematic side views of an optical device having a one-way mirror with a reflective circular polarizer. [Figure 4B] 4A and 4B are examples of schematic side views of an optical device having a one-way mirror with a reflective circular polarizer.

[0073] [Figure 4C] FIG. 4C is an example of a schematic side view of an optical device similar to that of FIGS. 4A and 4B with a one-way mirror having an integrated dimmer.

[0074] [Figure 5] FIG. 5 illustrates aspects of an approach for simulating three-dimensional images by correcting for wavefront divergence.

[0075] [Figure 6] FIG. 6 illustrates an example of a waveguide stack for outputting image information to a user.

[0076] [Figure 7]FIG. 7 illustrates an example of an output beam output by a waveguide.

[0077] [Figure 8] FIG. 8 illustrates an example of a stacked eyepiece, where each depth plane contains an image formed using multiple different component colors.

[0078] [Figure 9A] FIG. 9A illustrates a cross-sectional side view of an example set of stacked waveguides, each containing an internal coupling optical element.

[0079] [Figure 9B] FIG. 9B illustrates a perspective view of the multiple stacked waveguide example of FIG. 9A.

[0080] [Figure 9C] FIG. 9C illustrates a top-down plan view of the multiple stacked waveguide example of FIGS. 9A and 9B.

[0081] [Figure 9D] FIG. 9D illustrates a top-down plan view of another example of multiple stacked waveguides.

[0082] [Figure 9E] FIG. 9E illustrates an example of a wearable display system. DETAILED DESCRIPTION OF THE INVENTION

[0083] An augmented reality (AR) system may display virtual content to a user or viewer. This content may be displayed on a head-mounted display, for example, as part of eyewear, which projects image information into the user's eyes. In addition, if the system is an AR system, the display may also transmit light from the surrounding environment to the user's eyes to enable a view of the surrounding environment. As used herein, it should be understood that a "head-mounted" or "head-mountable" display is a display that can be mounted on the user's head or viewer, and may be an eyepiece display.

[0084] When using an AR device, a user can see both the environment surrounding them (i.e., the ambient environment) and the virtual content presented by the display. The display may output image light backward toward the user's eyes to display the virtual content. In addition, some of this image light may be emitted forward toward the ambient environment. For example, the image light may be emitted from the display to the user's eyes using a diffractive optical element, which functions symmetrically and also emits the image light in the opposite direction toward the ambient environment. Thus, individuals within the ambient environment may undesirably view the displayed content or may see output light that negatively affects the aesthetic appeal of the display device. However, maintaining the privacy of this displayed content is particularly difficult with AR devices because AR devices are designed to be transparent to capture light from the ambient environment. Therefore, simply blocking all image light from escaping into the ambient environment is not an option.

[0085] In some implementations, privacy, aesthetics, and mechanical stability and strength can be improved using a one-way mirror. The one-way mirror is partially reflective, whereby light from the surrounding environment is partially reflected back toward the world and partially transmitted to the user. The light reflected toward the surrounding environment can be used to obscure the content of the image light output from the display toward the surrounding environment, while the transmission of light through the one-way mirror allows the user to see the surrounding environment. Thus, privacy and aesthetics can be improved. Additionally, by providing additional structure in front of the display, the mechanical strength of the assembly can be increased, while the one-way mirror can also provide protection for the display.

[0086] In some implementations, the one-way mirror is formed using a polarization-selective mirror in front of a polarizer. As used herein, "front" refers to the relative positions of the two structures; the front side of the structure is the side in which the one-way mirror is configured to reflect light (e.g., toward the surrounding environment), and the "rear" side of the structure is the side in which the one-way mirror is configured to transmit light (e.g., toward the user). For example, for a head-mounted display in which the one-way mirror is configured to reflect light back into the world, the polarization-selective mirror in front of the polarizer is positioned on the world side of the polarizer, and the polarizer is behind the polarization-selective mirror (or on the user side of the polarization-selective mirror). The polarization-selective mirror reflects light of one polarization while transmitting light of another polarization (e.g., to the user's eyes). The one-way mirror may be provided in front of the display. However, image light may also be emitted from the display onto the polarization-selective mirror, which may undesirably reflect light back into the user's eyes, reducing the perceived image quality. Advantageously, a polarizer can be used to change the polarization of light emerging from the display, so that the light is transmitted through the polarization selective mirror.

[0087] However, it will be appreciated that one-way mirrors may face various challenges that can be advantageously addressed by certain implementations disclosed herein. For example, light from the surrounding environment may be polarized (e.g., light from other display devices such as smartphones, watches, televisions, etc.), and depending on the orientation of the one-way mirror relative to the source of that light, the polarized ambient light may not be transmitted through the one-way mirror. As a result, the user may not be able to see parts of the surrounding environment that output polarized light to the viewer (or that are made visible by directing polarized light to the viewer). In some implementations, a depolarizer may be provided in front of the polarization-selective mirror as part of the one-way mirror. In some implementations, the depolarizer randomizes the polarization of the incident light, for example, converting light of one polarization into light of two different polarizations, one of which is reflected by the polarization-selective mirror and one of which is transmitted through the polarization-selective mirror and polarizer, thereby allowing the user to receive the transmitted polarized light and perceive the content provided by the polarized light. It should be appreciated that a depolarizer may be understood to change the polarization of light that is incident on and transmitted through the depolarizer such that any change in the polarization of the incident light is imperceptible to human vision, even when a polarizing element, such as a polarizer, is applied to filter the transmitted light.

[0088] In some implementations, the presence of a polarizer behind the polarization-selective mirror allows for the formation of a compact, integrated structure with additional optical functionality. For example, the polarizer may be used in conjunction with an active variable dimmer, formed using a rear array of liquid crystal elements and an additional rear polarizer. The variable dimmer allows the transmission of light from the ambient environment to be modulated (e.g., to facilitate the presentation of virtual content by a display device by blocking ambient light that may spatially overlap with the virtual content).

[0089] It should be understood that the polarization-selective mirror and polarizer of a one-way mirror are aligned so that light converted by the polarizer (e.g., image light from a display) is transmitted through the one-way mirror toward the surrounding environment, and vice versa. However, proper alignment of the polarization-selective mirror and polarizer can be difficult, for example, in implementations in which the polarization-selective mirror is spaced from the polarizer by a gap (e.g., an air gap of 1 mm or more). Alignment errors between the transmission axes of the polarization-selective mirror and polarizer can lead to undesired reflection of display light from the polarization-selective mirror back to the user, which can degrade the visual quality of the display (e.g., causing duplicated images of the display content with perceptible misalignment between the images). In such cases, because the polarization-selective mirror and polarizer are not directly attached to each other, misalignment can occur during manufacturing and / or over time during the course of using the device. In some implementations, the alignment tolerance between the polarization-selective mirror and polarizer can be increased using optical retarders attached to the polarization-selective mirror and polarizer, respectively. The optical retarders can be configured to convert linearly polarized light to circularly polarized light and can be quarter-wave plates. In some implementations, these retarders can also be designed to operate across the visible wavelength spectrum. A first retarder converts light passing through a polarization-selective mirror to circularly polarized light, which propagates to a second retarder, which converts the circularly polarized light to linearly polarized light for propagation through a polarizer. A similar conversion of linearly polarized light to circularly polarized light and back to linearly polarized light occurs for light traveling in the opposite direction from the display toward the surrounding environment. Preferably, the first retarder is attached to or laminated with the polarization-selective mirror, and the second retarder is attached to or laminated with the polarizer behind the polarization-selective mirror. Because the light propagating between the first and second retarders is circularly polarized, the unidirectional mirror is relatively insensitive to the relative orientation of the first and second retarders, thereby increasing alignment tolerances.Additionally, as discussed herein, the second retarder may advantageously reduce reflection of image light back to the user due to Fresnel reflections from the front surface of the second retarder.

[0090] In some implementations, the polarization-selective mirror can be a cholesteric liquid crystal reflective polarizer. Such polarization-selective mirrors advantageously provide compact one-way mirrors with large alignment tolerances. For example, a cholesteric liquid crystal reflective polarizer can convert linearly polarized light from the ambient environment to circularly polarized light, thereby providing large alignment tolerances with the rear polarizer, as discussed above. This can be achieved without the need for first and second retarders as described above, which can thereby enable the formation of highly compact one-way mirrors. In some other implementations, the polarization-selective mirror can be a wire-grid polarizer, which can comprise an array of nanowires of a metallic material such as aluminum, or a multilayer polarizer, which can comprise alternating layers of anisotropic films such as stretched polymer films.

[0091] It should be understood that implementations disclosed herein may provide one or more advantages, as discussed herein. For example, the one-way mirror may increase the aesthetic appeal of the display system by providing an appearance that more closely resembles eyewear such as sunglasses. Additionally, by providing a separate structure in front of the display, the one-way mirror may increase the mechanical strength of the display, and the one-way mirror may also shield and protect the portion of the display that provides image content to the user. Additionally, the one-way mirror may hide complex functional components in the display, thereby further increasing the aesthetic appeal of the display system. Furthermore, as discussed above, privacy may be increased by reducing the visibility of image light output toward the surrounding environment.

[0092] Reference is now made to the drawings, wherein like reference numerals refer to like parts throughout.

[0093] 1A is a perspective view of an exemplary wearable augmented reality (AR) display system 60 including a display assembly 102 for presenting image light to a user's eyes. The display assembly 102 may include a pair of displays 104, one for each user's eye. The displays 104 may be optical structures that output image light and provide virtual content to the user's eyes. In some other implementations, the displays 104 may simply be different portions of a continuous light output structure (e.g., a single panel with two different portions).

[0094] In some implementations, display 104 may be an optical combiner, at least partially transparent to light incident from the outside world, and also configured to output image light (light having image information for forming virtual content) toward the user's eye. For example, the optical combiner may be an eyepiece that relays the image light to the user's eye. Display 104 may correspond to waveguide 270 or waveguide stack 260 or 660 discussed further herein with respect to FIGS. 5-9D . As discussed further herein, display assembly 102 may include a one-way mirror configured to reflect ambient light while still allowing the user to see the world and allowing light from the display to be transmitted through the one-way mirror away from the user.

[0095] Figures 2A and 2B are example schematic side views of an optical device having a one-way mirror 212 and a display 210. Figure 2A illustrates an example interaction between light from the surrounding environment ("world light") and the one-way mirror 212, with some world light being reflected back into the surrounding environment and some world light being transmitted through the one-way mirror 212 to the eye 214. Figure 2B illustrates an example interaction of light output by the display 210, with some light propagating toward the user's eye 214 and some light propagating through the one-way mirror 212 to the surrounding environment. Figures 3A and 3B are similar to Figures 2A and 2B and further illustrate details regarding the polarization of light propagating through the structure of Figures 2A and 2B.

[0096] Continuing with reference to FIG. 2A , it should be understood that the display 210 may correspond to one of the displays 104 of FIG. 1B . A one-way mirror 212 may be disposed in front of the display 210. The one-way mirror 212 includes a polarization-selective mirror 206 and an absorptive polarizer 208. The one-way mirror 212 may further include a depolarizer 204 in front of the polarization-selective mirror 206, such that the polarization-selective mirror 206 is disposed between the depolarizer 204 and the absorptive polarizer 208. In some implementations, the polarization-selective mirror 206 may include a reflective polarizer, such as a wire-grid polarizer, a multilayer polarizer, or a cholesteric liquid crystal reflective polarizer. In some implementations, the absorptive polarizer 208 may include a crystal-based polarizer, a Polaroid®-based polarizing filter, or a nanoparticle-based polarizer. The absorptive polarizer 208 may be configured to absorb light having a polarization not aligned with the transmission axis of the absorptive polarizer 208.

[0097] 2A illustrates the interaction of light from the outside world 202 (ambient environment) with a one-way mirror 212. World light 202a propagates through a depolarizer 204 to a polarization-selective mirror 206, where a portion 202b of the world light 202a is reflected back into the ambient environment 202. Another portion 202c of the world light 202a propagates through an absorbing polarizer 208 and further through a display 210 to a user's eye 214, thereby enabling the user to see the ambient environment.

[0098] FIG. 3A provides additional details regarding the optical properties of various portions of one-way mirror 212 to facilitate the mirror's optical functionality. It should be understood that depolarizer 204, polarization-selective mirror 206, and absorptive polarizer 208 can each be configured to preferentially transmit light of one polarization and block the transmission of light of another polarization. Thus, it should be understood that depolarizer 204, polarization-selective mirror 206, and absorptive polarizer 208 are each optical structures having a transmission axis, whereby light of a particular polarization and orientation aligned with the transmission axis is transmitted or propagated through the structure, while light of a different polarization may not be transmitted therethrough. For example, in some implementations, light with an electric field vector parallel to the transmission axis may be transmitted, while light with an electric field vector perpendicular to the transmission axis may not be transmitted therethrough. It should be understood that in some implementations, such as when polarization-selective mirror 206 is a wire-grid polarizer, the transmission axis may be perpendicular to the elongation direction of the "wires" forming the wire-grid polarizer. Similar relationships may apply to other polarizers formed from substantially linear rows of material. Preferably, the transmission axis 206a of the polarization-selective mirror 206 is aligned with or substantially parallel to the transmission axis 208a of the absorptive polarizer 208.

[0099] As shown, world light 202a from the surrounding environment 202 may propagate toward polarization-selective mirror 206. As shown in FIG. 3A , world light 202a may include light of linear polarization 202a-1, which has an electric field vector parallel to the transmission axis 206a of polarization-selective mirror 206 and the transmission axis 208a of absorptive polarizer 208. World light 202a may include light of linear polarization 202a-2, which has an electric field vector oriented perpendicular to the transmission axes of polarization-selective mirror 206 and absorptive polarizer 208. When world light 202a reaches polarization-selective mirror 206, light with a perpendicular electric field vector 202b-1 is reflected by polarization-selective mirror 206 as reflected light 202b, while light with a parallel electric field vector 202c-1 is transmitted through polarization-selective mirror 206 as transmitted light 202c. Furthermore, light with electric field vector parallel 202c-1 is also transmitted through the absorptive polarizer 208 because the transmission axes 206a, 208a of the polarization selective mirror 206 and the absorptive polarizer 208 are aligned.

[0100] 3A , as noted above, world light 202a may include light of different polarizations, some of which is reflected and some of which is transmitted through one-way mirror 212. World light 202a may also include polarized light having a single polarization, such as light from an external display (e.g., a computer monitor, a phone display, a watch display, etc.). It should be understood that if this light strikes polarization-selective mirror 206 and is not aligned with transmission axis 206a, all of this polarization may be reflected. As a result, no polarized light may reach eye 212, and the user may not be able to read the external display, which is undesirable.

[0101] Advantageously, a depolarizer 204 may be provided to randomize the polarization of the incident world light 202a. In some implementations, the depolarizer 204 may have a transmission axis 204a aligned with the transmission axis 206a of the polarization-selective mirror 206 and the transmission axis 208a of the absorptive polarizer 208a. In some implementations, the transmission axis 204a of the depolarizer 204 may be understood to indicate that at least a portion of the light output by the depolarizer 204 is light of a polarization aligned with the transmission axis of the polarization-selective mirror 206 such that it is transmitted through the polarization-selective mirror 206. In some implementations, 20-70%, 30-70%, 30-60%, or 40-60% of the polarized world light 202a initially incident on the depolarizer 204 is transmitted through the one-way mirror 212 toward the eye 214.

[0102] In some implementations, the depolarizer 204 may be a quarter-wave plate, such as an achromatic quarter-wave plate (AQWP). In some implementations, the depolarizer 204 may be an ultra-retarder or one or more layers of material with a high retardation value. In some implementations, the depolarizer 204 may be a retarder with a random optical axis orientation. In some implementations, the depolarizer 204 may be configured to convert a portion of the polarized light to circularly polarized light. As illustrated in FIG. 3A, if the world light 202a is polarized (e.g., has one of orientations 202a-1, 202a-2), the depolarizer 204 may convert a portion of the polarized world light 202a to right-handed circularly polarized light 202a-4 and / or left-handed circularly polarized light 202a-3 before reaching the polarization-selective mirror 206. Regardless of whether the light output by depolarizer 204 is randomly, linearly, or circularly polarized, preferably a portion of the light output by depolarizer 204 is of a polarization such that that portion of the light is transmitted through polarization-selective mirror 206. Preferably, in some embodiments, 20-70%, 30-70%, 30-60%, or 40-60% of the light output by depolarizer 204 has a linear component aligned with the transmission axis of polarization-selective mirror 206 so as to be transmitted through polarization-selective mirror 206. In some implementations, light 202b reflected from polarization-selective mirror 206 may have linear polarization 202b-1, and depolarizer 204 may convert this light 202b to circular polarization 202b-2.

[0103] 2B, there is illustrated the transmission of light output from display 210. Preferably, image light 210b is output from display 210 into the user's eye 214. Additionally, display 210 may also output light 210a into the surrounding environment 202.

[0104] 3B , light 210 a emerging from the display 210 includes light 210 a-1 with polarization aligned with the transmission axes 206 a, 208 a of the polarization-selective mirror 206 and the absorptive polarizer 208, and light 210 a-2 with polarization oriented perpendicular to the transmission axes 206 a, 208 a. Light 210 a-1 with polarization aligned with the transmission axis 208 a of the absorptive polarizer 208 is transmitted through the absorptive polarizer 208, while light 210 a-2 with polarization oriented perpendicular to the transmission axis 208 a of the absorptive polarizer 208 is absorbed by the absorptive polarizer 208. Furthermore, this light 210 a preferably transmits through the polarization-selective mirror 206 with substantially no or only a low level of reflection and, therefore, is not reflected back toward the user's eye 214. It should be understood that light reflected back towards the user's eye 214 by the one-way mirror 212 may undesirably adversely affect the user's viewing experience of the image output by the display, as this reflected image light may be time delayed and / or subject to aberrations as a result of being reflected.

[0105] 3B, the depolarizer 204 further converts the image light 210a from the display 210, which is polarized to have a particular polarization 210a-1, to circularly polarized light 210a-2. Without converting the light to circular polarization, eyewear with a linear polarizer (such as polarized sunglasses) viewing the light 210a and 202b may, in some orientations, filter out the reflected light 202b and transmit the image light 210a, thereby allowing the image light to be visible to the wearer of the eyewear. If the polarization-selective mirror 206 converts the reflected light 202a and the light 210a from the display 210 into circularly polarized light 202b-2, 210a-2, a viewer within the ambient environment 202 of the light 202a, 210a with eyewear with a linear polarizer may not have an electric field vector and the viewer may simply see the light 210a from the display 210, thereby the depolarizer 204 further assisting in providing privacy.

[0106] 3A and 3B, in some implementations, as described herein, the polarization-selective mirror 206 may be a wire grid polarizer (WGP) configured to reflect linearly polarized light. By way of example, the WGP may include a nanoscale wire pattern with repeating parallel wires. In some implementations, each of the wires of the wire pattern may be elongated perpendicular to the transmission axis 206a of the polarization-selective mirror 206.

[0107] In some implementations, the polarization-selective mirror 206 may be a multilayer polarizer (MLP). The multilayer polarizer may be configured to reflect incident light of predetermined wavelengths. For example, the predetermined wavelengths may include wavelengths corresponding to different colors. In some implementations, the multilayer polarizer may include multiple polymer thin films extruded and stretched along an axis, which may provide differences in refractive index along the stretch axis and the lateral axis. Advantageously, the multilayer polarizer may enable color customization of the one-way mirror, thereby providing the ability to provide a variety of different color display systems, much like sunglasses that can be offered in different shades. This may improve the aesthetic appeal of the display system. For example, different colors may be provided through the use of a multilayer polarizer that reflects predetermined wavelengths of light (corresponding to desired colors). Additionally, the color point of the world light reaching the user's eye 214 may be determined by an absorptive polarizer 208, which may reflect certain wavelengths of light but be unaffected as transmitted light, and may be configured to modify the color point by preferentially transmitting certain wavelengths of light. Furthermore, it should be understood that the multilayer polarizers may have different reflectivities. Multilayer polarizers can be advantageously configured to provide a tailored amount of privacy based on the amount of reflected light, for example, a multilayer polarizer with a higher reflectivity can be utilized for greater privacy, and a multilayer polarizer with a lower reflectivity can be utilized when privacy requirements are lower.

[0108] Referring now to FIG. 2C , it should be understood that the absorptive polarizer 208 can be advantageously utilized to form other optical structures to provide additional optical functionality. For example, FIG. 2C illustrates a one-way mirror 212 forming an integrated structure with an active variable dimmer 216. The active variable dimmer 216 can have an active variable optical transmittance. The active variable dimmer 216 can include an array of liquid crystal elements 216a disposed between the absorptive polarizer 208 and an additional polarizer 216b of the one-way mirror 212. The array of liquid crystal elements 216a can be electronically controllable, for example, by application of an electrical input (such as an electrical voltage) to transition from an attenuating mode to a transmissive mode. Examples of such arrays of liquid crystal elements are disclosed in U.S. Patent Publication No. 2018 / 0234675, which is incorporated herein by reference in its entirety.

[0109] It should be understood that the active variable dimmer may include an array of liquid crystal elements sandwiched between two polarizers. Advantageously, the absorptive polarizer 208 may replace one of the polarizers of the active variable dimmer. Thus, the array of liquid crystal elements 216a may be sandwiched between the absorptive polarizer 208 and the polarizer 216b. The absorptive polarizer 208 is shared by the one-way mirror 212 and the active variable dimmer 216 to form a single integrated unit, a one-way mirror dimmer, which may conserve component count and reduce the cost and complexity of devices utilizing both a one-way mirror and an active variable dimmer. Additionally, by including the one-way mirror 212 outside the functional element 216 rather than between the active variable dimmer 216 and the display 212, a passive one-way mirror 212, simply comprising an additional passive layer of material, can be simply added to a device including the dimmer 216 and display 210 without significant re-engineering of the underlying dimmer and display 210.

[0110] It should also be understood that in some implementations, the polarization-selective mirror 206 and the absorptive polarizer 208 may contact one another (e.g., be stacked), or they may be spaced apart by a gap (e.g., an air gap). For example, the polarization-selective mirror 206 and the absorptive polarizer 218 may be separated by a gap of 1 mm or more, 2 mm or more, or 3 mm or more (including 1-5 mm, 2-5 mm, and 3-5 mm). Such a gap may exist, for example, in implementations in which the polarization-selective mirror 206 is combined with an existing absorptive polarizer 218 and display 210. For example, the polarization-selective mirror 206 may be attached to the front portion of a frame that holds the absorptive polarizer 218 and display 212 (or the polarization-selective mirror 206 may be attached to the frame, and the absorptive polarizer in the display 212 may be subsequently added to the rear portion of the frame). As discussed herein, the polarization-selective mirror 206 and the absorptive polarizer 218 are preferably oriented with their transmission axes aligned. However, the mechanical attachment of the polarization-selective mirror 206 and the absorptive polarizer 218 to a common frame can introduce alignment errors, for example, during assembly of the display system and / or during use of the display system. For example, over time, there may be deformation of the frame, the display system may be subjected to mechanical stress (e.g., due to being dropped, roughly handled, etc.), and / or one or both of the polarization-selective mirror 206 and the absorptive polarizer 218 may become loose. Undesirably, misalignment between the polarization-selective mirror 206 and the absorptive polarizer 218 can adversely affect the functionality of the one-way mirror 212 because, as discussed herein, the optical functionality of the one-way mirror depends on proper alignment of the transmission axes of the various polarization-sensing structures that form the one-way mirror, including the polarization-selective mirror 206 and the absorptive polarizer 218.

[0111] In some implementations, the alignment tolerance between the polarization-selective mirror 206 and the absorptive polarizer 218 can be increased using an optical structure that converts light to circular polarization within a volume (e.g., a gap) between the polarization-selective mirror 206 and the absorptive polarizer 218.

[0112] FIG. 3C is a schematic side-view example of an optical device having a one-way mirror 212a with optical retarders 218a, 218b for providing circularly polarized light. As indicated by like reference numerals, the one-way mirror 212a has similar features to those of the one-way mirror 212 of FIGS. 2A, 2B, 3A, and 3B, and details regarding these features will not be repeated here. The one-way mirror 212a further includes one or more retarders 218a, 281b between the polarization-selective mirror 206 and the absorptive polarizer 208. Preferably, the one-way mirror 212a includes a pair of opposing retarders 218a, 281b that directly face each other. The retarders 218a, 281b can be quarter-wave plates, such as achromatic quarter-wave plates.

[0113] 3C, linearly polarized world light 202a aligned with the transmission axis of polarization-selective mirror 206 is transmitted through polarization-selective mirror 206 and then propagates through a first of retarders 218a, 218b, which converts world light 202a to circularly polarized world light 218c. Circularly polarized world light 218c propagates through a second of retarders 218, which converts circularly polarized world light 218c back to linearly polarized light with its orientation aligned with the transmission axis 208 of the absorbing polarizer, which then continues to propagate to eye 214 as linearly polarized world light 202c-1.

[0114] In some implementations, the retarder 218a is laminated or bonded to the polarization-selective mirror 206 such that the retarder 218a and the polarization-selective mirror 206 form a continuous, integrated unit. Additionally or alternatively, in some implementations, the retarder 218b is laminated or bonded to the absorptive polarizer 208 such that the retarder 218b and the absorptive polarizer 208 form a continuous, integrated unit. Advantageously, such an integrated structure may enable precise alignment of the retarder 218a or 218b to the polarization-selective mirror 206 or the absorptive polarizer 208 during manufacturing, which may be achieved without requiring the structure to be snapped onto a frame and aligned (e.g., manually snapped onto a frame). Additionally, forming such an integrated unit may promote the long-term durability and mechanical stability of the one-way mirror 212a, thereby reducing the occurrence of misalignment over time.

[0115] Additionally, it should be understood that a potential significant source of misalignment in the one-way mirrors disclosed herein arises from possible misalignment of the transmission axes of the polarization-selective mirror 206 and the absorptive polarizer 208 (particularly when these features are separated by a gap, as discussed herein). Advantageously, by converting world light 202a to circularly polarized light and traversing the gap, the sensitivity of the one-way mirror to misalignment between the polarization-selective mirror 206 and the absorptive polarizer 208 can be reduced and alignment tolerances can be increased. In some embodiments, the use of circularly polarized light effectively makes the one-way mirror relatively insensitive to misalignment between the polarization-selective mirror 206 and the absorptive polarizer 208, and retarder 218b can be utilized to convert the circularly polarized light to linearly polarized light with the appropriate polarization and orientation to align with the transmission axis of the absorptive polarizer 208, allowing the linearly polarized light to be transmitted through the absorptive polarizer 208.

[0116] FIG. 3D illustrates the structure of FIG. 3C, where an example of light propagation from display 210 through one-way mirror 212a is shown. Display 210 outputs image light 210b to user's eye 214 and, incidentally, also outputs light 210a forwardly towards ambient environment 202. As discussed herein, the polarization of image light 210a and the electric field vector of that light are oriented such that a portion of the image light 210a is transmitted through absorptive polarizer 208, while light with an electric field vector not aligned with the transmission axis is absorbed by absorptive polarizer 208. Retarder plate 218b then converts light 210a to circularly polarized light 218d. Retarder plate 218a subsequently converts circularly polarized light 218d to linearly polarized light, which is oriented to pass through polarization selective mirror 206 as image light 210a-1.

[0117] It should be understood that an incidental reflection can occur at the interface between different materials in front of retarder plate 218b, for example, a Fresnel reflection from the interface between polarization selective mirror 206 and retarder plate 218a. In some embodiments, the incidentally reflected light 210ar can pass through retarder plate 218a and be converted to image light of circularly polarized light 218c. Retarder plate 218b then converts the light to linearly polarized image light having a polarization orthogonal to the transmission axis 208a of absorptive polarizer 208. As a result, the linearly polarized image light is absorbed by absorptive polarizer 208. Thus, absorptive polarizer 208 can effectively absorb the reflection 210ar from polarization selective mirror 206, which can improve image quality.

[0118] As discussed herein, in some implementations, the polarization selective mirror can be a reflective circular polarizer such as a cholesteric liquid crystal reflective polarizer. An example of a cholesteric liquid crystal reflective polarizer is disclosed in U.S. Patent Publication No. 2018 / 0164627, titled "Diffractive Devices Based on Cholesteric Liquid Crystal" and published on June 14, 2018, the entire disclosure of which is incorporated herein by reference.

[0119] 4A and 4B are schematic side-view examples of an optical device having a one-way mirror 416 in which the polarization-selective mirror 206 is a reflective circular polarizer. Figure 4A illustrates the propagation of world light 412a through the optical device, and Figure 4B illustrates the propagation of image light 410a through the optical device. In the illustrated example, the one-way mirror 416 includes a reflective circular polarizer 206 in front of a retarder 204, which is in front of an absorptive polarizer 208.

[0120] Referring to FIG. 4A, world light 412a (which may correspond to world light 202a in FIGS. 2A, 3A, and 3C) is received from world 202. World light 412a includes two orthogonal components 412a-1 and 412a-2, which, in some implementations, may represent different electric field vectors (e.g., for light of different linear polarizations). In the illustrated example, reflective circular polarizer 206 may be configured to transmit light of one polarization and reflect light 412b having the opposite linear polarization. The transmitted light may be converted to light having circular polarization 412a-3, which then passes through retarder 207, such as a quarter-wave plate, and then absorbing polarizer 208. Retarder 207 converts world light 412a-3 having circular polarization to light 412a-4 having linear polarization. Preferably, the orientation of the linear polarization 412 a-4 is aligned with the transmission axis 208 a of the absorbing polarizer 208. Thus, world light with linear polarization 412 a-4 is transmitted through the absorbing polarizer 208. World light 412 a with linear polarization 412 a-4 is then transmitted through the display 210 to the user's eye 214. In some embodiments, the retarder 207 may be laminated or glued to the absorbing polarizer 208. Additionally, in some embodiments, the reflective circular polarizer 206 may be spaced apart from the retarder 207. Advantageously, the circular polarization provided by the reflective circular polarizer 206 may increase alignment tolerances, as discussed herein.

[0121] 4B illustrates the propagation of image light from the display 210, showing the image light propagating in one direction to the user's eye 214 and propagating in the opposite direction through a one-way mirror 416 to the outside world 202. The image light 210b output by the display 210 to the eye 214 provides a virtual image to the user's eye 214. As discussed herein, the display 210 may also incidentally output image light 410a toward the world 202. As shown in FIG. 4B, in some implementations, the image light 410a output from the display 210 includes two orthogonal electric field vectors 410a-1, 410a-2, representing light of different linear polarizations. Image light 410a emerging from the display 210 can be polarized such that image light with an electric field vector 410a-2 orthogonal to the transmission axis 208a of the absorbing polarizer 208 is absorbed, while image light with an electric field vector 410a-3 aligned with the transmission axis 208a is transmitted. The retarder 207 then converts the transmitted image light to light with circular polarization 410a-4. The orientation of the transmission axis of the polarization-selective mirror 206 matches the orientation 410a-4 of the image light propagating forward of the retarder 207 and is transmitted through the polarization-selective mirror 206.

[0122] As discussed herein, the polarization-selective mirror 206 may be a cholesteric liquid crystal polarizer (CLCP), which may offer one or more advantages. The cholesteric liquid crystal polarizer 206 may be substantially insensitive to the angular orientation of the incident circularly polarized light and, therefore, may not need to be oriented with a clear transmission axis alignment with the absorbing circular polarizer 408. Furthermore, similar to the one-way mirror 212 with depolarizer 204 of FIG. 3A, the one-way mirror 416 provides reflected light 412b with circular polarization 412b-1 (FIG. 4A) and transmits light with the opposite circular polarization 410a-4 (FIG. 4B). As discussed above in connection with FIG. 3A, by providing circular polarization to the reflected light 412b, other individuals wearing linear polarizers, such as certain sunglasses, can filter out the reflected light 412b and prevent them from seeing the image light 410a escaping into the world 202.

[0123] Additionally, advantageously, the color tone of the one-way mirror 416 can be adjusted by adjusting the composition of the cholesteric liquid crystal within the CLCP. By adjusting the composition, the CLCP can be configured to reflect light of predetermined wavelengths, thereby affecting the external appearance of a display system utilizing the one-way mirror 416. Additionally, although the CLCP transmits little or no light of certain wavelengths, the color point of the world light reaching the eye 214 will not be affected because the user's view of the world is determined by the absorptive polarizer 208, which can be configured to modify the color point by preferentially transmitting light of certain wavelengths. Furthermore, the reflectivity of the CLCP can be adjusted based on the thickness of the CLCP. In some implementations, the CLCP may reflect up to 50% of the world light 412a, e.g., 30-50% or 40-50% of the world light 412a. In some implementations, the CLCP may reflect 20-70%, 30-70%, 30-60%, or 40-60% of the incident world light 412a. By adjusting the amount of light reflected, the CLCP can adjust the level of privacy.

[0124] Referring again to FIG. 4B, it is to be understood that Fresnel reflection can occur with respect to the image light 410a that is incident on the surface of the cholesteric liquid crystal polarizer 206 after passing through the retarder 207. A portion of the image light 410a can be reflected from the cholesteric liquid crystal polarizer 206 as reflected image light 402a having circular polarization 402a-1, and the circular polarization 402a-1 is opposite to the polarization 410a-4 of the image light 410a incident on the cholesteric liquid crystal polarizer 206. The circularly polarized reflected image light 402a can be converted by the retarder 207 into linearly polarized light having linear polarization 402a-2. The linear polarization 402a-2 can be orthogonal to the transmission axis 208a of the absorptive polarizer 208 and can be absorbed by the absorptive polarizer 208. Advantageously, unlike the implementation of FIG. 3C, the one-way mirror 416 of FIGS. 4A and 4B can omit the use of an additional quarter-wave plate while still providing a large alignment tolerance and a low level of reflected image light 402a to the user's eye 214. Additionally, in some implementations, a depolarizer, such as depolarizer 204 (FIGS. 2A-3D), is provided in front of the cholesteric liquid crystal polarizer 206 and can enable the transmission of polarization through the cholesteric liquid crystal polarizer 206 regardless of the orientation of its polarization with respect to the cholesteric liquid crystal polarizer 206.

[0125] FIG. 4C illustrates a side view of an implementation of the one-way mirror 416 of FIGS. 4A and 4B having an active variable optical device 216. The active variable optical device 216 includes an array 216a of liquid crystal elements that is sandwiched between the absorptive polarizer 208 and a polarizer 216b. Thus, the absorptive polarizer 208 advantageously provides the optical functionality for both the one-way mirror 416 and the active variable optical device 216, thereby providing a highly compact structure with multiple optical functionalities, as further discussed herein with respect to FIG. 2C.

[0126] As discussed herein, the displays and one-way mirrors of FIGS. 2A-4C can also be part of an augmented reality display system. Details of some implementations of the augmented reality display system are described below. (Exemplary Augmented Reality Display System)

[0127] FIG. 5 illustrates aspects of an approach for simulating a three-dimensional image by modifying wavefront divergence. The display system includes a waveguide 270 configured to receive light 770 encoded with image information and output the light to a user's eye 214. The waveguide 270, which may also be referred to as an eyepiece, relays image light 772 to the user's eye 214. The waveguide 270 may output light 650 with a defined amount of wavefront divergence corresponding to the wavefront divergence of a bright field generated by a point on a desired depth plane 240. In some implementations, the same amount of wavefront divergence is provided for all objects presented on that depth plane. In addition, it will be illustrated that the user's other eye may be provided with image information from a similar waveguide.

[0128] In some implementations, a single waveguide may be configured to output light with a set wavefront divergence corresponding to a single or limited number of depth planes, and / or a waveguide may be configured to output light of a limited range of wavelengths. As a result, in some implementations, multiple or stacked waveguides may be utilized to provide different wavefront divergences for different depth planes and / or to output light of different ranges of wavelengths. As used herein, it should be understood that a depth plane may be planar or may follow the contours of a curved surface.

[0129] 6 illustrates an example of a waveguide stack for outputting image information to a user. Display system 250 includes a stack of waveguides or stacked waveguide assembly 260 that can be utilized to provide a three-dimensional perception to the eye / brain using multiple waveguides 270, 280, 290, 300, 310. It should be understood that display system 250 can be considered a bright field display in some implementations. Additionally, waveguide assembly 260 can also be referred to as an eyepiece.

[0130] In some implementations, display system 250 may be configured to provide a substantially continuous cue for vergence and multiple separate cues for accommodation. The cues for vergence may be provided by displaying different images to each of the user's eyes, and the cues for accommodation may be provided by outputting light forming images with selectable separate amounts of wavefront divergence. In other words, display system 250 may be configured to output light with variable levels of wavefront divergence. In some implementations, each separate level of wavefront divergence corresponds to a particular depth plane and may be provided by a particular one of waveguides 270, 280, 290, 300, and 310.

[0131] 6, the waveguide assembly 260 may also include multiple features 320, 330, 340, 350 between the waveguides. In some implementations, the features 320, 330, 340, 350 may be one or more lenses.

[0132] The multiple lenses 320, 330, 340, 350 may be configured to transmit image information to the eye with various levels of wavefront curvature or beam divergence. Each waveguide level may be associated with a particular depth plane and configured to output image information corresponding to that depth plane. Image injection devices 360, 370, 380, 390, 400 may act as light sources for the waveguides and may be utilized to inject image information into the waveguides 270, 280, 290, 300, 310, each of which may be configured to distribute incident light to each respective waveguide for output toward the eye 214, as described herein. Light exits output surfaces 410, 420, 430, 440, 450 of image injection devices 360, 370, 380, 390, 400 and is injected into corresponding input surfaces 460, 470, 480, 490, 500 of waveguides 270, 280, 290, 300, 310. In some implementations, each of the input surfaces 460, 470, 480, 490, 500 may be an edge of the corresponding waveguide or may be a portion of a major surface of the corresponding waveguide (i.e., one of the waveguide surfaces that directly faces the world 510 or the viewer's eye 214). In some implementations, a single beam of light (e.g., a collimated beam) may be injected into each waveguide, outputting an entire field of cloned collimated beams directed toward the eye 214 at a particular angle (and divergence) corresponding to the depth plane associated with the particular waveguide. In some implementations, a single one of the image injection devices 360, 370, 380, 390, 400 may be associated with multiple (e.g., three) waveguides 270, 280, 290, 300, 310 and inject light into them.

[0133] In some implementations, image input devices 360, 370, 380, 390, 400 are each separate display structures that generate image information for input into corresponding waveguides 270, 280, 290, 300, 310. In some other embodiments, image input devices 360, 370, 380, 390, 400 are the output ends of a single multiplexed system for outputting image light that may transmit image information to each of image input devices 360, 370, 380, 390, 400, for example, via one or more optical conduits (such as fiber optic cables). It should be understood that the image information provided by image input devices 360, 370, 380, 390, 400 may include light of different wavelengths or colors (e.g., different component colors, as discussed herein).

[0134] In some implementations, the light injected into the waveguides 270, 280, 290, 300, 310 is provided by an optical projection system 520, which includes an optical module 530, which may include a light emitter such as a light-emitting diode (LED). The light from the optical module 530 may be directed and modified by an optical modulator 540, such as a spatial light modulator, via a beam splitter 550. The optical modulator 540 may be configured to vary the perceived intensity of the light injected into the waveguides 270, 280, 290, 300, 310 and encode the light with image information. Examples of spatial light modulators include liquid crystal displays (LCDs), including liquid crystal on silicon (LCOS) displays. In some other embodiments, the spatial light modulator may be a MEMS device, such as a digital light processing (DLP) device. It should be understood that image injection devices 360, 370, 380, 390, 400 are shown diagrammatically and in some implementations these may represent different light paths and locations in a common projection system configured to output light into associated ones of waveguides 270, 280, 290, 300, 310. In some implementations, the waveguides of waveguide assembly 260 may act as ideal lenses, relaying light injected into the waveguides to the user's eye. In this concept, the object may be a spatial light modulator 540 and the image may be an image on a depth plane.

[0135] In some implementations, the display system 250 may be a scanning fiber display comprising one or more scanning fibers configured to project light in various patterns (e.g., raster scan, spiral scan, Lissajous pattern, etc.) into one or more waveguides 270, 280, 290, 300, 310 and ultimately to the viewer's eye 214. In some implementations, the illustrated image injection devices 360, 370, 380, 390, 400 may diagrammatically represent a single scanning fiber or a bundle of scanning fibers configured to inject light into one or more waveguides 270, 280, 290, 300, 310. In some other embodiments, the illustrated image injection devices 360, 370, 380, 390, 400 may diagrammatically represent multiple scanning fibers or multiple bundles of scanning fibers, each configured to inject light into an associated one of the waveguides 270, 280, 290, 300, 310. It should be understood that one or more optical fibers may be configured to transmit light from the optical module 530 to one or more waveguides 270, 280, 290, 300, 310. It should be understood that one or more intervening optical structures may be provided between the scanning fiber or fibers and one or more waveguides 270, 280, 290, 300, 310, for example, to redirect light exiting the scanning fiber into one or more waveguides 270, 280, 290, 300, 310.

[0136] The controller 560 controls the operation of one or more of the stacked waveguide assemblies 260, including the operation of the image input devices 360, 370, 380, 390, 400, the light source 530, and the light modulator 540. In some implementations, the controller 560 is part of the local data processing module 140. The controller 560 includes programming (e.g., instructions in a non-transitory medium) that coordinates the timing and provision of image information to the waveguides 270, 280, 290, 300, 310, for example, according to any of the various schemes disclosed herein. In some implementations, the controller may be a single integrated device or a distributed system connected by a wired or wireless communication channel. In some implementations, the controller 560 may be part of the processing module 140 or 150 (FIG. 9E).

[0137] Continuing with reference to FIG. 6 , waveguides 270, 280, 290, 300, 310 may be configured to propagate light within each respective waveguide by total internal reflection (TIR). Each of waveguides 270, 280, 290, 300, 310 may be planar with major top and bottom surfaces and edges extending between the major top and bottom surfaces, or may have another shape (e.g., curved). In the illustrated configuration, each of waveguides 270, 280, 290, 300, 310 may include outcoupling optical elements 570, 580, 590, 600, 610 configured to extract light from the waveguide by redirecting light propagating within each respective waveguide out of the waveguide and outputting image information to eye 214. The extracted light may also be referred to as outcoupling light, and the outcoupling optical elements may also be referred to as light extraction optical elements. The extracted beam of light may be output by the waveguide where light propagating within the waveguide strikes the light extraction optical element. The outcoupling optical element 570, 580, 590, 600, 610 may be, for example, a grating including diffractive optical features as discussed further herein. While shown disposed on the bottom major surface of the waveguide 270, 280, 290, 300, 310 for ease of explanation and clarity of drawing, in some implementations the outcoupling optical element 570, 580, 590, 600, 610 may be disposed on the top and / or bottom major surfaces and / or directly within the waveguide 270, 280, 290, 300, 310, as discussed further herein. In some implementations, the outcoupling optical elements 570, 580, 590, 600, 610 may be attached to a transparent substrate and formed within a layer of material that forms the waveguides 270, 280, 290, 300, 310. In some other embodiments, the waveguides 270, 280, 290, 300, 310 may be a monolithic piece of material, and the outcoupling optical elements 570, 580, 590, 600, 610 may be formed on and / or within that piece of material.

[0138] Continuing with reference to FIG. 6 , as discussed herein, each waveguide 270, 280, 290, 300, 310 is configured to output light and form an image corresponding to a particular depth plane. For example, the waveguide 270 closest to the eye may be configured to deliver collimated light (injected into such waveguide 270) to the eye 214. The collimated light may represent an optical infinity focal plane. The next upper waveguide 280 may be configured to send collimated light that passes through a first lens 350 (e.g., a negative lens) before reaching the eye 214. Such first lens 350 may be configured to generate a slight convex wavefront curvature such that the eye / brain interprets light emerging from the next upper waveguide 280 as emerging from a first focal plane closer inward from optical infinity toward the eye 214. Similarly, the third upper waveguide 290 passes its output light through both the first lens 350 and the second lens 340 before reaching the eye 214. The combined refractive power of the first lens 350 and the second lens 340 can be configured to produce another, increased amount of wavefront curvature so that the eye / brain interprets the light emerging from the third waveguide 290 as originating from a second focal plane that is closer inward toward the person from optical infinity, which was the light from the next upper waveguide 280.

[0139] The other waveguide layers 300, 310 and lenses 330, 320 are similarly configured, with the highest waveguide 310 in the stack sending its output through all of the lenses between it and the eye for a combined focal power representing the focal plane closest to the person. To compensate for the stack of lenses 320, 330, 340, 350 when viewing / interpreting light originating from the world 510 on the other side of the stacked waveguide assembly 260, a compensating lens layer 620 may be placed on top of the stack to compensate for the combined power of the lower lens stacks 320, 330, 340, 350. Such a configuration provides as many perceived focal planes as there are available waveguide / lens pairs. Both the waveguide outcoupling optical elements and the focusing sides of the lenses may be static (i.e., not dynamic or electro-active). In some alternative embodiments, one or both may be dynamic using electro-active features.

[0140] In some implementations, two or more of the waveguides 270, 280, 290, 300, 310 may have the same associated depth plane. For example, multiple waveguides 270, 280, 290, 300, 310 may be configured to output images set at the same depth plane, or some multiple of the waveguides 270, 280, 290, 300, 310 may be configured to output images set at the same depth planes, one set for each depth plane. This may provide the advantage of forming tiled images to provide an extended field of view at those depth planes.

[0141] Continuing with reference to FIG. 6 , the outcoupling optical elements 570, 580, 590, 600, 610 can be configured to redirect light from their respective waveguides and output this light with an appropriate amount of divergence or collimation for the particular depth plane associated with the waveguide. As a result, waveguides with different associated depth planes can have different configurations of outcoupling optical elements 570, 580, 590, 600, 610, which output light with different amounts of divergence depending on the associated depth plane. In some implementations, the light extraction optical elements 570, 580, 590, 600, 610 can be solid or surface features that can be configured to output light at a particular angle. For example, the light extraction optical elements 570, 580, 590, 600, 610 can be solid holograms, surface holograms, and / or diffraction gratings. In some implementations, the features 320, 330, 340, 350 may not be lenses. Rather, they may simply be spacers (eg, cladding layers and / or structures to form an air gap).

[0142] In some implementations, the outcoupling optical elements 570, 580, 590, 600, 610 are diffractive features or "diffractive optical elements" (also referred to herein as "DOEs") that form a diffraction pattern. Preferably, the DOEs have a sufficiently low diffraction efficiency so that only a portion of the light in the beam is deflected toward the eye 214 with each intersection of the DOE, while the remainder continues traveling through the waveguide via TIR. The light carrying the image information is thus split into several related output beams that exit the waveguide at various locations, resulting in a highly uniform pattern of output emission toward the eye 214 for this particular collimated beam bouncing within the waveguide.

[0143] In some implementations, one or more DOEs may be switchable between an "on" state in which they actively diffract and an "off" state in which they do not diffract much. For example, a switchable DOE may comprise a layer of polymer-dispersed liquid crystal in which microdroplets comprise a diffractive pattern in a host medium, and the refractive index of the microdroplets may be switched to substantially match the refractive index of the host material (in which case the pattern does not diffract incident light much), or the microdroplets may be switched to a refractive index that does not match that of the host medium (in which case the pattern actively diffracts incident light).

[0144] In some implementations, a camera assembly 630 (e.g., a digital camera including a visible light and infrared light camera) may be provided to capture images of the eye 214 and / or tissue surrounding the eye 214 (e.g., to detect user input and / or to monitor the user's physiological state). As used herein, a camera may be any image capture device. In some implementations, the camera assembly 630 may include an image capture device and a light source for projecting light (e.g., infrared light) onto the eye, which may then be reflected by the eye and detected by the image capture device. In some implementations, the camera assembly 630 may be mounted to a frame or support structure 80 ( FIG. 9E ) and may be in electrical communication with processing modules 140 and / or 150, which may process image information from the camera assembly 630. In some implementations, one camera assembly 630 may be utilized for each eye to monitor each eye separately.

[0145] In some implementations, the camera assembly 630 may observe user movements, such as the user's eye movements. By way of example, the camera assembly 630 may capture images of the eye 214 and determine the size, position, and / or orientation of the pupil of the eye 214 (or some other structure of the eye 214). The camera assembly 630 may, as desired, obtain images (processed by processing circuitry of the type described herein) that are used to determine the direction in which the user is looking (e.g., eye pose or gaze direction). In some implementations, the camera assembly 630 may include multiple cameras, at least one of which may be utilized for each eye and independently determine the eye pose or gaze direction of each eye separately. In some implementations, the camera assembly 630, in combination with processing circuitry such as the controller 560 or the local data processing module 140, may determine the eye pose or gaze direction based on flashes (e.g., reflections) of light (e.g., infrared light) reflected from a light source contained within the camera assembly 630.

[0146] 7, an example of an output beam output by a waveguide is shown. While one waveguide is illustrated, it should be understood that other waveguides in waveguide assembly 260 (FIG. 6) may function similarly, and that waveguide assembly 260 includes multiple waveguides. Light 640 is launched into waveguide 270 at input surface 460 of waveguide 270 and propagates within waveguide 270 by TIR. At the point where light 640 impinges on DOE 570, a portion of the light exits the waveguide as output beam 650. Output beam 650 is illustrated as substantially parallel, but, as discussed herein, may be redirected to propagate to eye 214 at an angle (e.g., forming a diverging output beam) depending on the depth plane associated with waveguide 270. It should be understood that a substantially collimated exit beam may refer to a waveguide with outcoupling optics that outcouples light to form an image that appears to be set in a depth plane at a great distance (e.g., optical infinity) from the eye 214. Other waveguides or other sets of outcoupling optics may output a more divergent exit beam pattern, which would require the eye 214 to accommodate to a closer distance and focus on the retina, and would be interpreted by the brain as light from a distance closer to the eye 214 than optical infinity.

[0147] In some implementations, a full-color image can be formed at each depth plane by overlaying images in each of the component colors (e.g., three or more component colors). FIG. 8 illustrates an example of a stacked waveguide assembly, with each depth plane including an image formed using multiple different component colors. The illustrated embodiment shows depth planes 240a-240f, but more or fewer depths are also contemplated. Each depth plane can have three or more component color images associated with it, including a first image in a first color G, a second image in a second color R, and a third image in a third color B. The different depth planes are indicated in the diagram by different numbers for diopters (dpt) following the letters G, R, and B. By way of example only, the number following each of these letters indicates diopters (1 / m), i.e., the reciprocal of the distance of the depth plane from the viewer, and each box in the diagram represents an image of an individual component color. In some implementations, the exact locations of the depth planes for different component colors may vary to account for differences in the eye's focusing of different wavelengths of light. For example, images of different component colors for a given depth plane may be placed on depth planes corresponding to different distances from the user. Such an arrangement may increase visual acuity and user comfort and / or reduce chromatic aberration.

[0148] In some implementations, light for each component color may be output by a single dedicated waveguide, such that each depth plane may have multiple waveguides associated with it. In such embodiments, each box in the diagram containing the letter G, R, or B may be understood to represent an individual waveguide, and three waveguides may be provided per depth plane, with images of three component colors provided per depth plane. While the waveguides associated with each depth plane are shown adjacent to each other in this diagram for ease of illustration, it should be understood that in a physical device, all of the waveguides may be arranged in a stack with one waveguide per level. In some other embodiments, multiple component colors may be output by the same waveguide, such that, for example, only a single waveguide may be provided per depth plane.

[0149] 8, in some implementations, G is green, R is red, and B is blue. In some other embodiments, other colors associated with other wavelengths of light, including magenta and cyan, may be used in addition to or replace one or more of red, green, or blue.

[0150] It should be understood that references throughout this disclosure to a given color of light are understood to encompass light of one or more wavelengths within the range of wavelengths of light perceived by a viewer as that given color. For example, red light may include one or more wavelengths of light within a range of about 620-780 nm, green light may include one or more wavelengths of light within a range of about 492-577 nm, and blue light may include one or more wavelengths of light within a range of about 435-493 nm.

[0151] In some implementations, the light source 530 (FIG. 6) may be configured to emit light at one or more wavelengths outside the viewer's visual perception range, e.g., infrared and / or ultraviolet wavelengths. Additionally, the waveguide in-coupling, out-coupling, and other light redirecting structures of the display 250 may be configured to direct and emit this light from the display toward the user's eye 214, e.g., for imaging and / or user stimulation applications.

[0152] Referring now to FIG. 9A , in some implementations, light impinging on a waveguide may need to be redirected to incoupling the light into the waveguide. An incoupling optical element may be used to redirect and incoupling the light into its corresponding waveguide. FIG. 9A illustrates a cross-sectional side view of an example of a plurality or set of stacked waveguides 660, each including an incoupling optical element. Each of the waveguides may be configured to output light of one or more different wavelengths or one or more different wavelength ranges. While stack 660 may correspond to stack 260 ( FIG. 6 ), and the illustrated waveguides of stack 660 may correspond to a portion of multiple waveguides 270, 280, 290, 300, 310, it should be understood that light from one or more of image injection devices 360, 370, 380, 390, 400 is injected into the waveguide from a location requiring the light to be redirected for incoupling.

[0153] The illustrated set 660 of stacked waveguides includes waveguides 670, 680, and 690. Each waveguide includes an associated internal coupling optical element (which may also be referred to as an optical input area on the waveguide), for example, internal coupling optical element 700 is disposed on a major surface (e.g., the upper major surface) of waveguide 670, internal coupling optical element 710 is disposed on a major surface (e.g., the upper major surface) of waveguide 680, and internal coupling optical element 720 is disposed on a major surface (e.g., the upper major surface) of waveguide 690. In some implementations, one or more of internal coupling optical elements 700, 710, 720 may be disposed on the bottom major surface of the respective waveguides 670, 680, 690 (particularly, one or more of the internal coupling optical elements is a reflective polarizing optical element). As shown, the internal coupling optical elements 700, 710, 720 may be disposed on the upper major surfaces of their respective waveguides 670, 680, 690 (or on top of the next lower waveguide), and in particular, the internal coupling optical elements are transmissive turning optical elements. In some implementations, the internal coupling optical elements 700, 710, 720 may be disposed within the body of the respective waveguides 670, 680, 690. In some implementations, as discussed herein, the internal coupling optical elements 700, 710, 720 are wavelength selective, selectively redirecting one or more wavelengths of light while transmitting other wavelengths of light. While illustrated on one side or corner of their respective waveguides 670, 680, 690, it should be understood that the internal coupling optical elements 700, 710, 720 may be disposed in other areas of their respective waveguides 670, 680, 690 in some implementations.

[0154] As shown, the in-coupling optical elements 700, 710, 720 may be laterally offset from one another in the direction of light propagating through these in-coupling optical elements, as seen in the illustrated front view. In some implementations, each in-coupling optical element may be offset such that it receives light without that light passing through another in-coupling optical element. For example, each in-coupling optical element 700, 710, 720 may be configured to receive light from different image input devices 360, 370, 380, 390, and 400, as shown in FIG. 6 , and may be separated (e.g., laterally spaced) from the other in-coupling optical elements 700, 710, 720 such that it does not receive substantially light from others of the in-coupling optical elements 700, 710, 720.

[0155] Each waveguide also includes an associated light distribution element, for example, light distribution element 730 is disposed on a major surface (e.g., the top major surface) of waveguide 670, light distribution element 740 is disposed on a major surface (e.g., the top major surface) of waveguide 680, and light distribution element 750 is disposed on a major surface (e.g., the top major surface) of waveguide 690. In some other embodiments, light distribution elements 730, 740, 750 may be disposed on the bottom major surfaces of the associated waveguides 670, 680, 690, respectively. In some other embodiments, the light distribution elements 730, 740, 750 may be disposed on both the top and bottom major surfaces of the associated waveguides 670, 680, 690, respectively, or the light distribution elements 730, 740, 750 may be disposed on different ones of the top and bottom major surfaces in different associated waveguides 670, 680, 690, respectively.

[0156] The waveguides 670, 680, 690 may be spaced apart and separated, for example, by gas, liquid, and / or solid layers of material. For example, as shown, layer 760a may separate waveguides 670 and 680, and layer 760b may separate waveguides 680 and 690. In some implementations, layers 760a and 760b are formed from a low-index material (i.e., a material having a lower index of refraction than the material forming the immediately adjacent ones of the waveguides 670, 680, 690). Preferably, the index of refraction of the material forming layers 760a, 760b is 0.05 or 0.10 below the index of refraction of the material forming waveguides 670, 680, 690. Advantageously, the lower refractive index layers 760a, 760b may function as cladding layers to promote total internal reflection (TIR) ​​of light through the waveguides 670, 680, 690 (e.g., TIR between the top and bottom major surfaces of each waveguide). In some implementations, the layers 760a, 760b are formed from air. Although not shown, it should be understood that the top and bottom of the illustrated set of waveguides 660 may include immediate cladding layers.

[0157] Preferably, for ease of manufacturing and other considerations, the materials forming waveguides 670, 680, 690 are similar or the same, and the materials forming layers 760a, 760b are similar or the same. In some implementations, the materials forming waveguides 670, 680, 690 may vary between one or more waveguides, and / or the materials forming layers 760a, 760b may vary while still maintaining the various refractive index relationships discussed above.

[0158] 9A, light rays 770, 780, 790 enter waveguide set 660. It should be understood that light rays 770, 780, 790 may be injected into waveguides 670, 680, 690 by one or more image injection devices 360, 370, 380, 390, 400 (FIG. 6).

[0159] In some implementations, the light rays 770, 780, 790 have different characteristics, such as different wavelengths or different wavelength ranges, that may correspond to different colors. Each of the in-coupling optical elements 700, 710, 720 deflects incident light such that the light propagates through a respective one of the waveguides 670, 680, 690 by TIR. In some implementations, each of the in-coupling optical elements 700, 710, 720 selectively deflects one or more particular wavelengths of light while transmitting other wavelengths to the underlying waveguide and associated in-coupling optical element.

[0160] For example, internal coupling optical element 700 may be configured to deflect light beam 770 having a first wavelength or wavelength range while transmitting light beams 780 and 790 having different second and third wavelengths or wavelength ranges. Transmitted light beam 780 impinges on and is deflected by internal coupling optical element 710, which is configured to deflect light of the second wavelength or wavelength range. Light beam 790 is deflected by internal coupling optical element 720, which is configured to selectively deflect light of the third wavelength or wavelength range.

[0161] 9A , deflected light rays 770, 780, 790 are deflected to propagate through corresponding waveguides 670, 680, 690. That is, each waveguide's in-coupling optical element 700, 710, 720 deflects the light into its corresponding waveguide 670, 680, 690, in-coupling the light into the corresponding waveguide. Light rays 770, 780, 790 are deflected at an angle that causes the light to propagate through the respective waveguides 670, 680, 690 by TIR. Light rays 770, 780, 790 propagate through the respective waveguides 670, 680, 690 by TIR until they impinge on the waveguide's corresponding light distribution element 730, 740, 750.

[0162] 9B, a perspective view of the example multiple stacked waveguides of FIG. 9A is illustrated. As described above, in-coupled light rays 770, 780, 790 are deflected by in-coupling optical elements 700, 710, 720, respectively, and then propagate by TIR within waveguides 670, 680, 690, respectively. Light rays 770, 780, 790 then impinge on light distribution elements 730, 740, 750, respectively. Light distribution elements 730, 740, 750 deflect light rays 770, 780, 790 to propagate toward out-coupling optical elements 800, 810, 820, respectively.

[0163] In some implementations, the light distribution elements 730, 740, 750 are orthogonal pupil expanders (OPEs). In some implementations, the OPEs deflect or distribute light to the out-coupling optical elements 800, 810, 820, and in some implementations, the OPEs may increase the beam or spot size of this light as it propagates to the out-coupling optical elements. In some implementations, the light distribution elements 730, 740, 750 may be omitted, and the in-coupling optical elements 700, 710, 720 may be configured to deflect light directly to the out-coupling optical elements 800, 810, 820. For example, with reference to FIG. 9A , the light distribution elements 730, 740, 750 may be replaced with the out-coupling optical elements 800, 810, 820, respectively. In some implementations, the outcoupling optical elements 800, 810, 820 are exit pupils (EPs) or exit pupil expanders (EPEs) that direct light toward the viewer's eye 214 ( FIG. 7 ). It should be understood that an OPE can be configured to increase the size of the eyebox in at least one axis, and that the EPE can increase the eyebox in an axis that intersects the axis of the OPE, e.g., an orthogonal axis. For example, each OPE can be configured to redirect a portion of the light striking the OPE to the EPE of the same waveguide, while allowing the remaining portion of the light to continue propagating down the waveguide. Again, upon striking the OPE, another portion of the remaining light is redirected to the EPE, and the remainder of that portion continues propagating further down the waveguide, etc. Similarly, upon striking an EPE, a portion of the impinging light is directed out of the waveguide toward the user, and the remainder of that light continues to propagate through the waveguide until it again strikes an OPE, at which point another portion of the impinging light is directed out of the waveguide, etc. As a result, a single beam of internally coupled light may be "replicated" each time a portion of that light is redirected by the OPE or EPE, thereby forming a cloned beam field of light, as shown in FIG. 6. In some implementations, the OPE and / or EPE may be configured to modify the size of the beam of light.

[0164] 9A and 9B, in some implementations, a waveguide set 660 includes, for each component color, waveguides 670, 680, 690, in-coupling optical elements 700, 710, 720, light distribution elements (e.g., OPEs) 730, 740, 750, and out-coupling optical elements (e.g., EPs) 800, 810, 820. The waveguides 670, 680, 690 may be stacked with an air gap / cladding layer between each one. The in-coupling optical elements 700, 710, 720 redirect or deflect incident light into that waveguide (with different in-coupling optical elements receiving light of different wavelengths). The light then propagates at an angle that will result in TIR within each waveguide 670, 680, 690. In the example shown, light ray 770 (e.g., blue light) is deflected by the first in-coupling optical element 700 in the manner described above, then continues bouncing back down the waveguide, interacting with the light distribution element (e.g., OPE) 730 and then the out-coupling optical element (e.g., EP) 800. Light rays 780 and 790 (e.g., green and red light, respectively) pass through the waveguide 670, with light ray 780 impinging on and being deflected by the in-coupling optical element 710. Light ray 780 will then, via TIR, bounce back down the waveguide 680 to its light distribution element (e.g., OPE) 740 and then the out-coupling optical element (e.g., EP) 810. Finally, light ray 790 (e.g., red light) passes through the waveguide 690 and impinges on the light in-coupling optical element 720 of the waveguide 690. The light in-coupling optical element 720 deflects the light ray 790 so that it propagates by TIR to the light distribution element (e.g., OPE) 750 and then by TIR to the out-coupling optical element (e.g., EP) 820. The out-coupling optical element 820 then finally out-couples the light ray 790 to a viewer, who also receives out-coupled light from the other waveguides 670, 680.

[0165] 9A and 9B . It should be understood that this top-down view may also be referred to as a head-on view, as viewed in the direction of light propagation toward the in-coupling optical elements 800, 810, 820; i.e., the top-down view is a view of the waveguides with image light incident perpendicular to the page. As shown, the waveguides 670, 680, 690 may be vertically aligned, along with each waveguide's associated light distribution elements 730, 740, 750 and associated out-coupling optical elements 800, 810, 820. However, as discussed herein, the in-coupling optical elements 700, 710, 720 are not vertically aligned. Rather, the in-coupling optical elements preferably do not overlap (e.g., are laterally spaced apart, as viewed in the top-down view). As discussed further herein, this non-overlapping spatial arrangement facilitates the injection of light from different sources into different waveguides on a one-to-one basis, thereby allowing a particular light source to be uniquely coupled to a particular waveguide. In some implementations, arrangements including non-overlapping, spatially separated in-coupling optical elements may be referred to as shifted pupil systems, and the in-coupling optical elements in these arrangements may correspond to sub-pupils.

[0166] It should be understood that spatially overlapping areas may have lateral overlap of 70% or more, 80% or more, or 90% or more of their area as seen in a top-down view, whereas laterally shifted areas overlap less than 30%, less than 20%, or less than 10% of their area as seen in a top-down view, and in some implementations, laterally shifted areas have no overlap.

[0167] FIG. 9D illustrates a top-down plan view of another example of multiple stacked waveguides. As shown, waveguides 670, 680, 690 may be vertically aligned. However, compared to the configuration of FIG. 9C , the separate light distribution elements 730, 740, 750 and associated outcoupling optical elements 800, 810, 820 are omitted. Instead, the light distribution elements and outcoupling optical elements are effectively superimposed, occupying the same area as seen in a top-down view. In some implementations, the light distribution elements (e.g., OPEs) may be disposed on one major surface of the waveguides 670, 680, 690, and the outcoupling optical elements (e.g., EPEs) may be disposed on the other major surface of the waveguides. Thus, each waveguide 670, 680, 690 may have superimposed light dispersing and out-coupling optical elements, collectively referred to as combined OPE / EPEs 1281, 1282, 1283, respectively. Further details regarding such combined OPE / EPEs may be found in U.S. Patent Publication No. 2019 / 0187474 A1, entitled "Eyepieces for Augmented Reality Display System," published June 20, 2019, the entire disclosure of which is incorporated herein by reference. In-coupling optical elements 700, 710, 720 in-couple and direct light to combined OPE / EPEs 1281, 1282, 1283, respectively. In some implementations, as shown, in-coupling optical elements 700, 710, 720 may be shifted laterally (e.g., they may be spaced laterally, as seen in the illustrated top-down view) to have a shifted pupil spatial arrangement. Similar to the configuration of FIG. 9C, this laterally shifted spatial arrangement facilitates the injection of different wavelengths of light (eg, from different light sources) into different waveguides on a one-to-one basis.

[0168] 9E illustrates an example of a wearable display system 60 in which the various waveguide and associated systems disclosed herein may be integrated. In some implementations, display system 60 is display system 250 of FIG. 6, which diagrammatically shows some portions of system 60 in greater detail. For example, waveguide assembly 260 of FIG. 6 may be part of display assembly 70, which may correspond to display assembly 102 (FIG. 1B).

[0169] Continuing with reference to FIG. 9E , display system 60 includes display assembly 70 and various mechanical and electronic modules and systems to support the functionality of display assembly 70. Display assembly 70 may be coupled to frame 80, which is wearable by a display system user or viewer 90 and configured to position display assembly 70 directly in front of the user's 90's eyes. Display assembly 70, in some implementations, may be considered eyewear. Display assembly 70 may include one or more waveguides, such as waveguide 270, configured to relay internally coupled image light and output the image light to the user's 90's eyes. In some implementations, speaker 1000 is coupled to frame 80 and configured to be positioned adjacent to the user's 90's ear canal (in some implementations, another speaker, not shown, may optionally be positioned adjacent the user's other ear canal to provide stereo / shapeable sound control). Display system 60 may also include one or more microphones 110 or other devices to detect sound. In some implementations, the microphone may be configured to allow a user to provide input or commands to the system 60 (e.g., voice menu command selections, natural language questions, etc.) and / or enable audio communication with other persons (e.g., other users of similar display systems). The microphone may further be configured as an ambient sensor and collect audio data (e.g., sounds from the user and / or the environment). In some implementations, the display system 60 may further include one or more outwardly oriented environmental sensors 112 configured to detect objects, stimuli, people, animals, places, or other aspects of the world around the user. For example, the environmental sensors 112 may include one or more cameras, which may be positioned, for example, facing outward, to capture images similar to at least a portion of the user 90's normal field of view. In some implementations, the display system may also include ambient sensors 120a, which may be separate from the frame 80 and mounted on the user 90's body (e.g., the user's 90's head, torso, limbs, etc.).The ambient sensor 120a, in some implementations, may be configured to obtain data characterizing a physiological state of the user 90. For example, the sensor 120a may be an electrode.

[0170] 9E , display assembly 70 is operably coupled to local data processing module 140 by a communication link 130, such as a wired or wireless connection, which may be mounted in a variety of configurations, such as fixedly attached to frame 80, fixedly attached to a helmet or hat worn by a user, integrated into headphones, or otherwise removably attached to user 90 (e.g., in a backpack-style configuration, in a belt-linked configuration). Similarly, sensor 120 a may be operably coupled to local data processing module 140 by a communication link 120 b, such as a wired or wireless connection. Local processing and data module 140 may include a hardware processor and digital memory, such as non-volatile memory (e.g., flash memory or a hard disk drive), both of which may be utilized to aid in processing, caching, and storing data. Optionally, local processing and data module 140 may include one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, etc. The data may include a) data captured from sensors (such as image capture devices (cameras), microphones, inertial measurement units, accelerometers, compasses, GPS units, wireless devices, gyroscopes, and / or other sensors disclosed herein (e.g., which may be operatively coupled to frame 80 or otherwise attached to user 90)) and / or b) data obtained and / or processed using remote processing module 150 and / or remote data repository 160 (including data related to virtual content), possibly for passage to display assembly 70 after processing or retrieval. Local processing and data module 140 may be operatively coupled to remote processing module 150 and remote data repository 160 by communication links 170, 180, such as via wired or wireless communication links, such that these remote modules 150, 160 are operatively coupled to each other and available as resources to local processing and data module 140.In some implementations, local processing and data module 140 may include one or more of an image capture device, a microphone, an inertial measurement unit, an accelerometer, a compass, a GPS unit, a wireless device, and / or a gyroscope. In some other embodiments, one or more of these sensors may be mounted to frame 80 or may be a freestanding structure that communicates with local processing and data module 140 by a wired or wireless communication path.

[0171] 9E , in some implementations, remote processing module 150 may comprise one or more processors configured to analyze and process data and / or image information, including, for example, one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, etc. In some implementations, remote data repository 160 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 implementations, remote data repository 160 may include one or more remote servers, which provide information, e.g., information for generating virtual content, to local processing and data module 140 and / or remote processing module 150. In some implementations, all data is stored and all computations are performed in the local processing and data module, allowing for fully autonomous use from the remote module. Optionally, an external system (e.g., one or more processors, one or more computer systems) including a CPU, GPU, etc. may perform at least part of the processing (e.g., generating image information, processing data) and provide information to and receive information from modules 140, 150, 160, e.g., via a wireless or wired connection.

[0172] In the foregoing discussion, the invention has been described with reference to specific implementations thereof. It will be apparent, however, that various modifications and changes may be made therein without departing from the broader spirit and scope of the invention. The specification and drawings are, therefore, to be regarded in an illustrative rather than a restrictive sense.

[0173] Indeed, it should be understood that the systems and methods of the present disclosure each have several innovative aspects, no single one of which is solely responsible for 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 the present disclosure.

[0174] Certain features described herein in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, while features may be described above as operative in a combination and may even initially be claimed as such, one or more features from the claimed combination may, in some cases, be deleted from the combination, and the claimed combination may be directed to a subcombination or a variation of the subcombination. No single feature or group of features is required or essential to every embodiment.

[0175] It should be understood that conditional statements used herein, such as "can," "could," "might," "may," "eg," and the like, among others, are generally intended to convey that certain embodiments include certain features, elements, and / or steps, while other embodiments do not, unless specifically stated otherwise or understood otherwise within the context as used. Thus, such conditional statements are generally not 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 determining whether those features, elements, and / or steps are to be included or performed in any particular embodiment, with or without authorial input or prompting. The terms "comprising," "including," "having," and the like, are synonymous and used inclusively in a non-limiting manner and do not exclude additional elements, features, acts, operations, etc. Also, the term "or" is used in its inclusive sense (and not its exclusive sense); thus, for example, when used to connect a list of elements, the term "or" means one, some, or all of the elements in the list. Additionally, as used in this application and the appended claims, the articles "a," "an," and "the" should be interpreted to mean "one or more" or "at least one," unless otherwise specified. Similarly, while operations may be depicted in the figures in a particular order, it should be recognized that such operations need not be performed in the particular order shown, or in sequential order, to achieve desirable results, and that not all depicted operations need be performed. Furthermore, the figures may diagrammatically depict one or more exemplary processes in the form of a flowchart. However, other operations not depicted may also be incorporated within the diagrammatically depicted exemplary methods and processes.For example, one or more additional operations can be performed before, after, simultaneously with, or between any of the illustrated operations. Additionally, operations may be rearranged or reordered in other implementations. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments. Additionally, other implementations are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results.

[0176] Thus, the claims are not intended to be limited to the embodiments shown herein but are to be accorded the widest scope consistent with the present disclosure, the principles and novel features disclosed herein.

Claims

1. An optical device that can be worn on a user's head, the optical device comprising: an eyepiece including at least one waveguide configured to output light conveying virtual content to the user, the at least one waveguide being at least partially transparent to transmit light from an ambient environment proximate the optical device to at least one eye of the user while conveying the virtual content; a one-way mirror configured to obscure the virtual content being output to the user by partially reflecting at least some of the light from the ambient environment back towards the ambient environment, the one-way mirror comprising: a depolarizer including at least one retarder having a random optical axis orientation, such that the depolarizer receives light from the world-side of the optical device and randomizes the polarization of at least a portion of the received light; a polarization-selective mirror oriented to receive light from the depolarizer, the polarization-selective mirror configured to transmit a portion of the received light having a randomized polarization therethrough, the polarization-selective mirror having a transmission axis, and the polarization-selective mirror including a reflective polarizer; and an absorptive polarizer oriented to receive the light transmitted through the polarization-selective mirror, the absorptive polarizer having a transmission axis aligned with the transmission axis of the polarization-selective mirror; a one-way mirror, wherein the polarization-selective mirror is disposed between the depolarizer and the absorptive polarizer; An optical device comprising:

2. The optical device of claim 1, wherein the depolarizer comprises a quarter-wave plate.

3. An optical device as described in claim 1, wherein the depolarizer comprises an ultra-phase retarder.

4. An optical device as described in claim 1, wherein the polarization selective mirror and the absorptive polarizer are spaced apart and further comprising one or more retardation plates between the polarization selective mirror and the absorptive polarizer.

5. The optical device of claim 4, wherein the one or more retardation plates comprise two spaced apart quarter-wave plates.

6. The optical device of claim 1, wherein the reflective polarizer is a reflective circular polarizer.

7. The optical device described in claim 1, wherein the reflective polarizer is a cholesteric liquid crystal reflective circular polarizer.

8. The optical device of claim 1, wherein the reflective polarizer comprises a multilayer polarizer.

9. The optical device described in Claim 8, wherein the multilayer polarizer is configured to reflect incident light of a predetermined wavelength.

10. The optical device described in claim 8, wherein the multilayer polarizer comprises a plurality of polymer films.

11. An optical device as described in claim 8, wherein the multilayer polarizer reflects less than 50% of incident light with an electric field vector perpendicular to the transmission axis of the multilayer polarizer.

12. An optical device as described in claim 8, wherein the multilayer polarizer reflects 30% to 40% of incident light with an electric field vector perpendicular to the transmission axis of the multilayer polarizer.

13. The optical device of claim 1, wherein the absorptive polarizer is configured to absorb linearly polarized light.

14. The optical device of claim 1, wherein the optical device is a head-mounted display system, the display system comprising a head-mounted display, and the one-way mirror is positioned on the world side of the head-mounted display and opposite the user side of the display while the display is worn by the user.

15. The optical device described in claim 14, wherein the at least one waveguide includes a plurality of waveguides, each of the plurality of waveguides configured to output light with a wavefront divergence that is different from one or more other waveguides of the plurality of waveguides, the different wavefront divergence corresponding to different depth planes.

16. The method of claim 1, further comprising an active variable dimmer comprising the absorptive polarizer, an additional polarizer, and an array of liquid crystal elements disposed between the absorptive polarizer and the additional polarizer; 10. The optical device of claim 1, wherein the active variable dimmer is configured to variably dim at least a portion of the light from the world side that is transmitted through the one-way mirror and transmit the dimmed light toward an eye of the user.

17. An optical device as described in claim 1, wherein the one-way mirror is positioned so that the one-way mirror is on the world side of the optical device while the optical device is attached.

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