Display system having variable optical power reflector - Patents.com

Abstract

To provide a favorable display system with a variable refractive power reflector.SOLUTION: A wearable augmented reality head-mounted display system can be configured to pass light from the world forward of a wearer wearing the head-mounted system into an eye of the wearer. The head-mounted display system can include an optical display that is configured to output light to form an image. The system may include one or more waveguides that are disposed to receive the light from the display. A variable refractive power reflector can be disposed on the forward side of the one or more waveguides. The reflector can be configured to have a refractive power that is adjustable upon application of an electrical signal.SELECTED DRAWING: Figure 10B

Description

[Technical field]

[0001] (Incorporated by reference) This application claims the benefit of priority to U.S. Provisional Patent Application No. 62 / 462,850, filed Feb. 23, 2017, entitled "VARIABLE-FOCUS VIRTUAL IMAGE DEVICES," which is incorporated herein by reference in its entirety. The provisional patent application includes the following sections, both of which are incorporated by reference and form a part of this patent application: 1. Section I: Specification and Drawings for the portion of the application entitled "DISPLAY SYSTEM WITH VARIABLE POWER REFLECTOR". 2. Section II: Specification and Drawings for the portion of the application entitled "VARIABLE-FOCUS VIRTUAL IMAGE DEVICES BASED ON POLARIZATIO CONVERSION."

[0002] Both Sections I and II discuss features associated with variable focus or variable power devices and components of these devices, and both sections equally form part of the disclosure of this application. Thus, the various features, elements, structures, methods, etc. described in Section I can be used with, combined with, incorporated within, or otherwise compatible with the features, elements, structures, methods, etc. described in Section II in any combination. Similarly, the various features, elements, structures, methods, etc. described in Section II can be used with, combined with, incorporated within, or otherwise compatible with the features, elements, structures, methods, etc. described in Section I in any combination.

[0003] This application also incorporates by reference in its entirety each of the following patent applications: U.S. Application No. 14 / 555,585 (filed November 27, 2014), U.S. Application No. 14 / 690,401 (filed April 18, 2015), U.S. Application No. 14 / 212,961 (filed March 14, 2014), and U.S. Application No. 14 / 331,218 (filed July 14, 2014).

[0004] (background) (Field) The present disclosure relates to optical devices, including augmented reality imaging and visualization systems. [Background technology]

[0005] Description of Related Art Modern computing and display technologies have facilitated the development of systems for so-called "virtual reality" or "augmented reality" experiences, in which digitally reproduced images or portions thereof are presented to a user in a manner that appears and may be perceived as being real. Virtual reality or "VR" scenarios typically involve the presentation of digital or virtual image information without transparency to other actual real-world visual inputs, while augmented reality or "AR" scenarios typically involve the presentation of digital or virtual image information as an extension to the visualization of the real world around the user. Mixed reality or "MR" scenarios are a type of AR scenario, typically involving virtual objects that are integrated into and responsive to the natural world. For example, MR scenarios may include AR image content that appears to be blocked by objects in the real world or that is perceived to otherwise interact with objects in the real world.

[0006] Referring to FIG. 1, an augmented reality scene 1 is depicted. A user of the AR technology sees a real-world park-like setting 20 featuring people, trees, buildings in the background, and a concrete platform 30. The user perceives that they are also "seeing" "virtual content," such as a robotic figure 40 standing on the real-world platform 1120 and a flying cartoon-like avatar character 50 that appears to be an anthropomorphic bumblebee. These elements 50, 40 are "virtual" in that they do not exist in the real world. The human visual perception system is complex, and creating AR technology that facilitates a comfortable, natural-feeling, and rich presentation of virtual image elements among other virtual or real-world image elements is challenging.

[0007] The systems and methods disclosed herein address various challenges associated with AR or VR technology. Summary of the Invention [Problem to be solved by the invention]

[0008] (summary) This application includes a discussion of systems and methods that may be employed to provide variable refractive power. Variable focus or variable refractive power devices may find application in certain head mounted display devices that project images as if they originate from different depths. By varying the refractive power of optical elements in the head mounted display device, images presented to the wearer of the head mounted display device appear as if they are located at different distances from the wearer. Variable focus or variable refractive power optical devices can thus be modulated to display different image content as if the image content were mounted in different locations relative to the user. Some variable refractive power elements include reflectors made of movable membranes. Other variable refractive power elements include liquid crystal switchable devices that can switch between refractive power levels using switchable liquid crystal elements. Some variable focus devices described herein utilize the polarization properties of light to facilitate switching from one focus to another. [Means for solving the problem]

[0009] Each of the systems, methods, and devices of the present disclosure has several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein. Various exemplary systems and methods are provided below.

[0010] Embodiment 1: A wearable augmented reality head mounted display system configured to pass light from the world in front of a wearer wearing the head mounted system into the wearer's eyes, the display system comprising: an optical display configured to output light for forming an image; one or more waveguides positioned to receive light from the display; a frame configured to position a waveguide in front of the eye, the one or more waveguides having an anterior side and a posterior side, the posterior side being closer to the eye than the anterior side; and a variable power reflector disposed on the anterior side of the one or more waveguides, the variable power reflector configured to have an adjustable optical power in response to application of an electrical signal; one or more external coupling elements disposed relative to the one or more waveguides; Equipped with A wearable augmented reality head mounted display system, wherein one or more external coupling elements extract light from the one or more waveguides and direct at least a portion of the light propagating in the waveguides to a variable power reflector, where the light is directed back from the variable power reflector, through the waveguides and into the eye, to present an image from the display into the wearer's eye.

[0011] Embodiment 2: The system of embodiment 1, wherein the optical display comprises a scanning fiber display or a liquid crystal display.

[0012] Embodiment 3: A system described in any of embodiments 1-2, wherein the variable power reflector comprises a deformable reflective surface having an adjustable shape.

[0013] Embodiment 4: The system of embodiment 3, wherein the variable power reflector includes at least one electrode for applying an electric field and deforming the reflective surface.

[0014] Embodiment 5: A system according to any of embodiments 1-4, wherein the variable power reflector comprises silicon nitride.

[0015] Embodiment 6: A system described in any of embodiments 1-5, wherein the variable power reflector comprises one or more switchable optical elements configured to switch between two states.

[0016] Embodiment 7: The system of embodiment 6, wherein the two states include two levels of reflection.

[0017] Embodiment 8: The system of embodiment 6 or 7, wherein the two states include two levels of refractive power.

[0018] Embodiment 9: A system according to any of embodiments 6, 7, or 8, wherein the two states comprise two levels of transmission.

[0019] Embodiment 10: A system described in any of embodiments 6-9, wherein one or more switchable optical elements comprise a diffractive optical element.

[0020] Embodiment 11: A system described in any of embodiments 6-10, wherein one or more switchable optical elements comprise a reflective element.

[0021] Embodiment 12: A system described in any of embodiments 6-11, wherein the one or more switchable optical elements comprises a liquid crystal element comprising a liquid crystal.

[0022] Embodiment 13: A system described in any of embodiments 6-12, wherein the one or more switchable optical elements comprise a switchable polarization grating or a switchable polymer dispersed liquid crystal element.

[0023] Embodiment 14: A system described in any of embodiments 1-13, wherein the variable refractive power reflector comprises a stack of switchable optical elements, different ones of the switchable optical elements being associated with different refractive powers such that the stack of switchable optical elements is capable of switching between the different refractive powers.

[0024] Embodiment 15: A system described in any of embodiments 1-14, wherein the variable power reflector is configured to transmit light from the world in front of the wearer while reflecting light from the display.

[0025] Embodiment 16: A system described in any of embodiments 1-15, wherein the variable power reflector includes a wavelength selective filter for transmitting light from the world in front of the wearer while reflecting light from the display.

[0026] Embodiment 17: A system described in any of embodiments 1-16, wherein the variable power reflector has a transmission spectrum including a notch, and light having a wavelength corresponding to the notch is reflected from the variable power reflector more than wavelengths adjacent to the notch.

[0027] Embodiment 18: The system of embodiment 17, wherein the wavelength corresponding to the notch is reflected at least twice as much as light having a wavelength adjacent to the notch.

[0028] Embodiment 19: The system of embodiment 17, wherein the wavelength corresponding to the notch is reflected at least 5 times more than light having a wavelength adjacent to the notch.

[0029] Embodiment 20: A system described in any of embodiments 17-19, wherein the display is provided with a colored light source having a color corresponding to the notch.

[0030] Embodiment 21: The system of embodiment 20, wherein the color of the color light source corresponds to red, green, or blue light.

[0031] Embodiment 22: A system described in any of embodiments 1-21, wherein the variable power reflector includes one or more polarization selective filters for transmitting light from the world in front of the wearer while reflecting light from the display.

[0032] Embodiment 23: A system described in any of embodiments 1-22, wherein one or more external coupling elements are configured to direct more of the light extracted from one or more waveguides to a forward side of the one or more waveguides compared to an opposite side.

[0033] Embodiment 24: A system described in any of embodiments 1-23, wherein the one or more external coupling elements comprise one or more metasurfaces, one or more liquid crystal polarization gratings, one or more volume phase holograms, or any combination thereof.

[0034] Embodiment 25: A system described in any of embodiments 1-24, further comprising electronics in electrical communication with the variable power reflector and driving the variable power reflector, the electronics configured to vary the refractive power to present different image contents as if arising from different depth planes.

[0035] Embodiment 26: The system described in embodiment 25, wherein the electronics is configured to vary the optical power on a frame-by-frame basis.

[0036] Embodiment 27: The system described in embodiment 25, wherein the electronics is configured to vary the refractive power on a pixel-by-pixel basis.

[0037] Embodiment 28: A system described in any of embodiments 1-27, further comprising a light recycling system configured to redirect light extracted from one or more waveguides toward a rear side of the one or more waveguides to a forward side, whereby the light can be incident on the variable power reflector and guided to the wearer's eye.

[0038] Embodiment 29: The system of embodiment 28, wherein the light recycling system comprises one or more polarization control elements or polarization selective elements.

[0039] Embodiment 30: The system of embodiment 28, wherein the light recycling system comprises a polarization selective reflector disposed between one or more waveguides and the eye.

[0040] Embodiment 31: The system of embodiment 30, wherein the light recycling system comprises one or more retarders disposed between the one or more light guides and the polarization selective reflector.

[0041] Embodiment 32: A system described in embodiment 31, wherein one or more retarders disposed between the one or more optical waveguides and the polarizing reflector introduce a net retardation of about half a wave.

[0042] Embodiment 33: A system described in any of embodiments 29-32, wherein the recycling system comprises one or more retarders disposed between the one or more optical waveguides and the variable power reflector.

[0043] Embodiment 34: The system of embodiment 33, wherein one or more retarders disposed between the one or more optical waveguides and the variable power reflector introduce a net phase difference of about a quarter wave.

[0044] Embodiment 35: A display device, comprising: a waveguide configured to propagate visible light in a direction parallel to a major surface of the waveguide and to outcouple visible light in a direction perpendicular to the major surface under total internal reflection; a deformable mirror configured to reflect visible light having a first polarization; Equipped with A display device, wherein the deformable mirror comprises at least one of a notch reflector or one or more cholesteric liquid crystal (CLC) layers, each of the CLC layers comprising a plurality of chiral structures, each of the chiral structures comprising a plurality of liquid crystal molecules extending in a layer depth direction and successively rotated in a first rotation direction, and an arrangement of the liquid crystal molecules of the chiral structures varies periodically in a lateral direction perpendicular to the layer depth direction such that the one or more CLC layers are configured to Bragg-reflect incident light.

[0045] Embodiment 36: A display device as described in embodiment 35, wherein the waveguide is configured to selectively outcouple visible light towards the deformable mirror.

[0046] Embodiment 37: A display device as described in any of embodiments 35 or 36, wherein different ones of the one or more CLC layers are configured to reflect visible light having wavelengths in wavelength ranges corresponding to different ones of red, green, or blue light, while transmitting light having wavelengths outside the wavelength ranges.

[0047] Embodiment 38: A display device described in any of embodiments 35-37, wherein each of the chiral structures of the CLC layer comprises a plurality of liquid crystal molecules extending in the layer depth direction with at least a certain helical pitch, and different ones of one or more CLC layers have different helical pitches.

[0048] Embodiment 39: A display device according to any of embodiments 35-38, wherein different ones of the one or more CLC layers have substantially the same refractive power.

[0049] Embodiment 40: A display device as described in any of embodiments 35-39, comprising a plurality of notch reflectors, each of the notch reflectors configured to reflect visible light having a first polarization, each of the notch reflectors comprising one or more cholesteric liquid crystal (CLC) layers, each of the CLC layers comprising a plurality of chiral structures, each of the chiral structures comprising a plurality of liquid crystal molecules extending in a layer depth direction and successively rotated in a first rotation direction, and an arrangement of the liquid crystal molecules of the chiral structures periodically varying in a lateral direction perpendicular to the layer depth direction such that the one or more CLC layers are configured to Bragg-reflect incident light.

[0050] Embodiment 41: A display device as described in embodiment 40, wherein different ones of the multiple notch reflectors have different refractive powers.

[0051] Embodiment 42: The display device of embodiment 40, further comprising a half-wave plate corresponding to each of the plurality of notch reflectors.

[0052] Embodiment 43: A display device, comprising: a light projector configured to output light for forming an image; a waveguide assembly configured to receive light from a light projector, the waveguide assembly configured to propagate the received light via total internal reflection in a direction parallel to a major surface of the waveguide assembly and to outcouple the received light in a direction perpendicular to the major surface, the waveguide assembly having a rear side positioned closer to a user's eye and a front side positioned opposite the rear side; a deformable mirror configured to reflect a portion of the outcoupled light having a characteristic; A display device, wherein the deformable mirror is disposed on a front side of the waveguide assembly.

[0053] Embodiment 44: A display device as described in embodiment 43, wherein the properties of the portion of the outcoupled light include polarization properties.

[0054] Embodiment 45: A display device according to embodiment 43 or 44, wherein the characteristics of the portion of the outcoupled light include wavelength characteristics.

[0055] Embodiment 46: A display device described in any of embodiments 43-45, wherein the deformable mirror is provided with a polarizing reflector configured to reflect a portion of the outcoupled light having polarization properties.

[0056] Embodiment 47: A display device described in any of embodiments 43-46, wherein the deformable mirror has a notch reflector configured to reflect light within a certain wavelength range.

[0057] Embodiment 48: A display device described in any of embodiments 43-47, further comprising a polarizer disposed on the rear side of the waveguide assembly.

[0058] Embodiment 49: A display device described in any of embodiments 43-48, wherein the deformable mirror comprises one or more cholesteric liquid crystal (CLC) layers, each of the CLC layers comprising a plurality of chiral structures, each of the chiral structures comprising a plurality of liquid crystal molecules extending in a layer depth direction and successively rotated in a first rotation direction, and the arrangement of the liquid crystal molecules of the chiral structures varies periodically in a lateral direction perpendicular to the layer depth direction such that the one or more CLC layers are configured to Bragg-reflect incident light.

[0059] Embodiment 50: A display device described in any of embodiments 43-49, wherein the waveguide assembly comprises one or more liquid crystal layers.

[0060] Embodiment 51: A system described in any of embodiments 6-11, wherein one or more switchable optical elements comprise cholesteric liquid crystals (CLC).

[0061] Embodiment 52: A system described in any of embodiments 1-23, wherein one or more external coupling elements comprise a cholesteric liquid crystal (CLC).

[0062] Embodiment 53: A display device, comprising: a waveguide configured to propagate visible light in a direction parallel to a major surface of the waveguide and to outcouple visible light in a direction perpendicular to the major surface under total internal reflection; a notch reflector configured to reflect visible light having a first polarization; and Equipped with A display device, wherein the notch reflector comprises one or more cholesteric liquid crystal (CLC) layers, each of the CLC layers comprising a plurality of chiral structures, each of the chiral structures comprising a plurality of liquid crystal molecules extending in a layer depth direction and successively rotated in a first rotation direction, and an arrangement of the liquid crystal molecules of the chiral structures varies periodically in a lateral direction perpendicular to the layer depth direction such that the one or more CLC layers are configured to Bragg-reflect incident light.

[0063] Embodiment 54: A display device as described in embodiment 53, wherein the waveguide is configured to selectively outcouple visible light towards the notch reflector.

[0064] Embodiment 55: A display device as described in any of embodiments 53 or 54, wherein the notch reflector comprises a deformable mirror having one or more CLC layers formed thereon.

[0065] Embodiment 56: A display device as described in any of embodiments 53-55, wherein different ones of the one or more CLC layers are configured to reflect visible light having wavelengths in wavelength ranges corresponding to different ones of red, green, or blue light, while transmitting light having wavelengths outside the wavelength range.

[0066] Embodiment 57: A display device described in any of embodiments 53-56, wherein each of the chiral structures of the CLC layer comprises a plurality of liquid crystal molecules extending in the layer depth direction with at least a certain helical pitch, and different ones of one or more CLC layers have different helical pitches.

[0067] Embodiment 58: A display device according to any of embodiments 53-58, wherein different ones of the one or more CLC layers have substantially the same refractive power.

[0068] Embodiment 59: A display device as described in embodiment 53, comprising a plurality of notch reflectors, each of the notch reflectors configured to reflect visible light having a first polarization, each of the notch reflectors comprising one or more cholesteric liquid crystal (CLC) layers, each of the CLC layers comprising a plurality of chiral structures, each of the chiral structures comprising a plurality of liquid crystal molecules extending in a layer depth direction and successively rotated in a first rotation direction, and an arrangement of the liquid crystal molecules of the chiral structures periodically varies in a lateral direction perpendicular to the layer depth direction such that the one or more CLC layers are configured to Bragg-reflect incident light.

[0069] Embodiment 60: A display device as described in embodiment 59, wherein different ones of the multiple notch reflectors have different refractive powers.

[0070] Embodiment 61: A display device as described in embodiment 59 or 60, further comprising a half-wave plate corresponding to each of the multiple notch reflectors. The present specification also provides, for example, the following items: (Item 1) 1. A wearable augmented reality head mounted display system configured to pass light from a world in front of a wearer wearing the head mounted system into an eye of the wearer, the wearable augmented reality head mounted display system comprising: an optical display configured to output light for forming an image; one or more waveguides positioned to receive light from the display; a frame configured to position the waveguide in front of the eye, the one or more waveguides having an anterior side and a posterior side, the posterior side being closer to the eye than the anterior side; and a variable power reflector disposed on the forward side of the one or more waveguides, the variable power reflector configured to have an adjustable power in response to application of an electrical signal; one or more external coupling elements disposed relative to the one or more waveguides; Equipped with A wearable augmented reality head mounted display system, wherein the one or more external coupling elements extract light from the one or more waveguides and direct at least a portion of the light propagating in the waveguides to the variable power reflector, and the light is directed from the variable power reflector back through the waveguide and into the eye, presenting an image from the display into the eye of the wearer. (Item 2) Item 1 , the system comprising: a scanning fiber display or a liquid crystal display. (Item 3) Item 10. The system of item 1, wherein the variable power reflector comprises a deformable reflective surface having an adjustable shape. (Item 4) Item 4. The system of item 3, wherein the variable power reflector includes at least one electrode for applying an electric field to deform the reflective surface. (Item 5) Item 14. The system of item 1, wherein the variable power reflector comprises silicon nitride. (Item 6) Item 10. The system of item 1, wherein the variable power reflector comprises one or more switchable optical elements configured to switch between two states. (Item 7) 7. The system of claim 6, wherein the two states include two levels of reflection. (Item 8) 7. The system of claim 6, wherein the two states include two levels of optical power. (Item 9) 7. The system of claim 6, wherein the two states include two levels of transmission. (Item 10) Item 7. The system of item 6, wherein the one or more switchable optical elements comprise a diffractive optical element. (Item 11) Item 7. The system of item 6, wherein the one or more switchable optical elements comprise a reflective element. (Item 12) Item 7. The system of item 6, wherein the one or more switchable optical elements comprise a liquid crystal element comprising a liquid crystal. (Item 13) Item 7. The system of item 6, wherein the one or more switchable optical elements comprise cholesteric liquid crystals (CLC). (Item 14) 7. The system of claim 6, wherein the one or more switchable optical elements comprise a switchable polarisation grating or a switchable polymer dispersed liquid crystal element. (Item 15) Item 1, the variable power reflector comprising a stack of switchable optical elements, different ones of the switchable optical elements being associated with different optical powers such that the stack of switchable optical elements is capable of switching between the different optical powers. (Item 16) Item 10. The system of item 1, wherein the variable power reflector is configured to transmit light from the world in front of the wearer while reflecting light from the display. (Item 17) Item 10. The system of item 1, wherein the variable power reflector includes a wavelength selective filter for transmitting light from the world in front of the wearer while reflecting light from the display. (Item 18) Item 10. The system of item 1, wherein the variable power reflector has a transmission spectrum that includes a notch, and light having a wavelength corresponding to the notch is reflected from the variable power reflector more than wavelengths adjacent to the notch. (Item 19) Item 19. The system of item 18, wherein a wavelength corresponding to the notch is reflected at least twice as much as light having a wavelength adjacent to the notch. (Item 20) Item 19. The system of item 18, wherein a wavelength corresponding to the notch is reflected at least 5 times more than light having a wavelength adjacent to the notch. (Item 21) Item 19. The system of item 18, wherein the display comprises a colored light source having a color corresponding to the notch wavelength. (Item 22) 22. The system of claim 21, wherein the color of the color light source corresponds to red, green, or blue light. (Item 23) Item 10. The system of item 1, wherein the variable power reflector includes one or more polarization selective filters for transmitting light from the world in front of the wearer while reflecting light from the display. (Item 24) 2. The system of claim 1, wherein the one or more external coupling elements are configured to direct more of the light extracted from the one or more waveguides to a forward side of the one or more waveguides compared to an opposite side. (Item 25) Item 1, wherein the one or more external coupling elements comprise one or more metasurfaces, one or more liquid crystal polarization gratings, one or more volume phase holograms, or any combination thereof. (Item 26) Item 10. The system of item 1, wherein the one or more external coupling elements comprise cholesteric liquid crystals. (Item 27) 28. The system of claim 1, further comprising electronics in electrical communication with and driving the variable power reflector, the electronics configured to vary the optical power to present different image contents as if originating from different depth planes. Item 28. The system of item 27, wherein the electronics are configured to vary the optical power on a frame-by-frame basis. (Item 29) Item 28. The system of item 27, wherein the electronics are configured to vary the optical power on a pixel-by-pixel basis. (Item 30) Item 1, further comprising a light recycling system configured to redirect light extracted from the one or more waveguides toward a rear side of the one or more waveguides toward the forward side, whereby the light can be incident on the variable power reflector and directed to the eye of the wearer. (Item 31) Item 31. The system of item 30, wherein the light recycling system comprises one or more polarization control or polarization selective elements. (Item 32) 31. The system of claim 30, wherein the light recycling system comprises a polarization selective reflector disposed between the one or more waveguides and the eye. (Item 33) Item 33. The system of item 32, wherein the light recycling system comprises one or more retarders disposed between the one or more light guides and the polarization selective reflector. (Item 34) Item 34. The system of item 33, wherein the one or more retarders disposed between the one or more light guides and the polarizing reflector introduce a net retardation of about half a wave. (Item 35) Item 31. The system of item 30, wherein the recycling system comprises one or more retarders disposed between the one or more light guides and the variable power reflector. (Item 36) Item 36. The system of item 35, wherein the one or more retarders disposed between the one or more light guides and the variable power reflector introduce a net retardation of about a quarter wave. (Item 37) A display device, comprising: a waveguide configured to propagate visible light in a direction parallel to a major surface of the waveguide and to outcouple the visible light in a direction perpendicular to the major surface under total internal reflection; a deformable mirror configured to reflect visible light having a first polarization; Equipped with 38. The display device, wherein the deformable mirror comprises at least one of a notch reflector or one or more cholesteric liquid crystal (CLC) layers, each of the CLC layers comprises a plurality of chiral structures, each of the chiral structures comprises a plurality of liquid crystal molecules extending in a layer depth direction, the plurality of liquid crystal molecules being continuously rotated in a first rotation direction, and the alignment of the liquid crystal molecules of the chiral structures varies periodically in a lateral direction perpendicular to the layer depth direction, thereby causing the one or more CLC layers to Bragg-reflect incident light. Item 38. The display device of item 37, wherein the waveguide is configured to selectively outcouple the visible light toward the deformable mirror. (Item 39) Item 38. The display device of item 37, wherein different ones of the one or more CLC layers are configured to reflect visible light having wavelengths in wavelength ranges corresponding to different ones of red, green, or blue light, while transmitting light having wavelengths outside the wavelength ranges. (Item 40) 38. The display device of item 37, wherein each of the chiral structures of the CLC layer comprises a plurality of liquid crystal molecules extending in a layer depth direction with at least a certain helical pitch, and different ones of the one or more CLC layers have different helical pitches. (Item 41) Item 38. The display device of item 37, wherein different ones of the one or more CLC layers have substantially the same refractive power. (Item 42) Item 38. The display device of item 37, wherein the display device comprises a plurality of notch reflectors, each of the notch reflectors configured to reflect visible light having a first polarization, each of the notch reflectors comprising one or more cholesteric liquid crystal (CLC) layers, each of the CLC layers comprising a plurality of chiral structures, each of the chiral structures comprising a plurality of liquid crystal molecules extending in a layer depth direction, the plurality of liquid crystal molecules being continuously rotated in a first rotation direction, and an arrangement of the liquid crystal molecules of the chiral structures periodically varying in a lateral direction perpendicular to the layer depth direction, thereby causing the one or more CLC layers to Bragg-reflect incident light. (Item 43) Item 43. The display device of item 42, wherein different ones of the plurality of notch reflectors have different optical powers. (Item 44) Item 43. The display device of item 42, further comprising a half-wave plate corresponding to each of the plurality of notch reflectors. [Brief description of the drawings]

[0071] [Figure 1] FIG. 1 illustrates a user's view of an augmented reality (AR) device.

[0072] [Diagram 2] FIG. 2 illustrates an example of a wearable display system.

[0073] [Diagram 3] FIG. 3 illustrates a conventional display system for simulating a three-dimensional image for a user.

[0074] [Figure 4] FIG. 4 illustrates aspects of an approach for simulating a three-dimensional image using multiple depth planes.

[0075] [Diagram 5] 5A-5C illustrate the relationship between the radius of curvature and the radius of focus.

[0076] [Figure 6] FIG. 6 illustrates an example of a waveguide stack for outputting image information to a user.

[0077] [Figure 7] FIG. 7 illustrates an example of an output beam output by a waveguide.

[0078] [Figure 8] FIG. 8 illustrates an example of a stacked waveguide assembly where each depth plane contains an image formed using multiple different primary colors.

[0079] [Figure 9A] FIG. 9A illustrates a cross-sectional side view of an example set of stacked waveguides, each containing an internal coupling optical element.

[0080] [Figure 9B] FIG. 9B illustrates a perspective view of the example of multiple stacked waveguides of FIG. 9A.

[0081] [Figure 9C] FIG. 9C illustrates a top-down plan view of the multiple stacked waveguide example of FIGS. 9A and 9B.

[0082] [Figure 10A] FIG. 10A illustrates a wearable augmented reality head mounted display system including a variable refractive power reflector positioned to receive light from a light projector system.

[0083] [Figure 10B] FIG. 10B illustrates the optical projection system of FIG. 10A, where a variable power reflector creates a virtual image as if emanating from an object at infinity.

[0084] [Figure 10C]FIG. 10C illustrates a variable power reflector that is polarization selective and uses the polarization of light to determine what light is reflected and what light is transmitted.

[0085] [Figure 10D] FIG. 10D illustrates an exemplary display device comprising a deformable mirror and a waveguide assembly with a liquid crystal grating.

[0086] [Figure 11] FIG. 11 illustrates a display device including a light recycling system comprising an array of retarders configured to redirect injected light from a waveguide that is outcoupled toward a user's eye to a reflector.

[0087] [Figure 12] FIG. 12 illustrates a variable power reflector that may comprise one or more switchable optical elements, such as a stack or multiple switchable reflective elements.

[0088] [Figure 13] 13A-13C illustrate an exemplary reflective diffractive lens that may be implemented as part of a display device, the reflective diffractive lens being formed from a patterned CLC material that acts as a reflective polarizing mirror.

[0089] [Figure 14] FIG. 14 illustrates an embodiment of a stack having multiple switchable reflective elements or multiple switchable reflective elements. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0090] (Detailed Description) The wearable augmented reality head mounted display system can be configured to pass light from the world in front of a wearer wearing the head mounted system into the wearer's eye. The head mounted display system can include an optical display configured to output light to form an image. The display system can include a frame, the frame including a waveguide in front of the eye, the one or more waveguides having a front side and a rear side, the rear side being closer to the eye than the front side. The system can include one or more waveguides arranged to receive light from the display. A variable power reflector can be arranged on the front side of the one or more waveguides. The reflector can be configured to have an adjustable power in response to application of an electrical signal. The system can further include one or more external coupling elements arranged with respect to the one or more waveguides to extract light from the one or more waveguides. The element can direct at least a portion of the light propagating in the waveguide to the variable power reflector. The light directed from the variable power reflector can be reflected back through the waveguide into the eye to present an image from the display into the wearer's eye.

[0091] The optical display may include a scanning fiber display or a liquid crystal display. In some variations, the variable power reflector includes a deformable reflective surface having an adjustable shape. The variable power reflector may include at least one electrode that applies an electric field to deform the reflective surface. The variable power reflector may include silicon nitride. The variable power reflector may include one or more switchable optical elements configured to switch between two states. The two states may include two levels of reflection, two levels of optical power, and / or two levels of transmission.

[0092] The one or more switchable optical elements may include a diffractive optical element, a reflective element, and / or a liquid crystal element comprising liquid crystals.

[0093] The head mounted display system may include one or more switchable polarization gratings or switchable polymer dispersed liquid crystal elements. The variable power reflector may include a stack of switchable optical elements associated with different optical powers, which can be switched between the different optical powers.

[0094] In some cases, the variable power reflector is configured to transmit light from the world in front of the wearer while reflecting light from the display. The variable power reflector may include a wavelength selective filter that transmits light from the world in front of the wearer while reflecting light from the display. The variable power reflector may have a transmission spectrum that includes a notch such that light having a wavelength corresponding to the notch is reflected from the variable power reflector more than wavelengths adjacent to the notch. The wavelength corresponding to the notch may be reflected at least five times more than light having a wavelength adjacent to the notch.

[0095] The head mounted display may include a colored light source that produces colors that correspond to the notch wavelengths, for example, the colors of the colored light source may correspond to red, green, or blue light.

[0096] The variable power reflector may include a polarization selective filter that transmits light from the world in front of the wearer while reflecting light from the display.

[0097] In some designs, the one or more external coupling elements are configured to direct more of the light extracted from the one or more waveguides to a forward side of the one or more waveguides compared to a reverse side. The one or more external coupling elements may include one or more metasurfaces, one or more liquid crystal polarization gratings, one or more volume phase holograms, or any combination thereof.

[0098] The display system may include electronics in electrical communication with and driving the variable power reflector. The electronics may be configured to vary the power to present different image content as if originating from different depth planes. The electronics may be configured to vary the power on a frame-by-frame or pixel-by-pixel basis.

[0099] The system may include a recycling system. The recycling system may be configured to redirect light extracted from the one or more waveguides toward a rear side of the one or more waveguides toward a forward side such that the light may be incident on a variable power reflector and directed to the wearer's eye. The recycling system may include one or more polarization control elements or polarization selective elements. The recycling system may include a polarization selective reflector disposed between the one or more waveguides and the eye.

[0100] The recycling system can include one or more retarders disposed between the one or more light guides and the polarizing reflector. The one or more retarders disposed between the one or more light guides and the polarizing reflector can be configured to introduce a net retardation of about half a wave.

[0101] In some designs, the recycling system may include one or more retarders disposed between the one or more light guides and the variable power reflector. The one or more retarders disposed between the one or more light guides and the variable power reflector may be configured to introduce a net retardation of about a quarter wave.

[0102] Reference is now made to the drawings, in which like reference numbers refer to like parts throughout.

[0103] FIG. 2 illustrates an example of a wearable display system 60. The display system 60 includes a display 70 and various mechanical and electronic modules and systems to support the functionality of the display 70. The display 70 may be coupled to a frame 80, which is wearable by a display system user or viewer 90 and configured to position the display 70 in front of the user's 90 eye. The display 70 may be considered eyewear in some embodiments. In some embodiments, a speaker 100 is coupled to the frame 80 and configured to be positioned adjacent to the ear canal of the user 90 (in some embodiments, another speaker, not shown, may optionally be positioned adjacent the user's other ear canal to provide stereo / shapeable sound control). The display system may also include one or more microphones 110 or other devices to detect sound. In some embodiments, the microphones may be configured to allow the user to provide input or commands to the system 60 (e.g., voice menu command selection, natural language queries, 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 to collect audio data (e.g., sounds from the user and / or the environment). In some embodiments, the display system may also include an ambient sensor 120a, which may be separate from the frame 80 and attached to the body of the user 90 (e.g., on the head, torso, limbs, etc. of the user 90). The ambient sensor 120a, in some embodiments, may be configured to obtain data characterizing a physiological state of the user 90. For example, the sensor 120a may be an electrode.

[0104] 2, the display 70 is operably coupled to a local data processing module 140 by a communication link 130, such as wired or wireless connectivity, which may be mounted in a variety of configurations, such as fixedly attached to the frame 80, fixedly attached to a helmet or hat worn by the user, built into headphones, or otherwise removably attached to the user 90 (e.g., in a backpack configuration, in a belt-coupled configuration). Similarly, the sensor 120a may be operably coupled to the local processor and data module 140 by a communication link 120b, such as wired or wireless connectivity. The local processing and data module 140 may include a hardware processor and digital memory, such as non-volatile memory (e.g., flash memory or hard disk drive), both of which may be utilized to aid in processing, caching, and storing data. The data includes a) data captured from sensors (such as image capture devices (cameras, etc.), 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 the frame 80 or otherwise attached to the user 90)) and / or b) data acquired and / or processed using the remote processing module 150 and / or remote data repository 160 (including data related to virtual content), possibly for passing to the display 70 after processing or retrieval. The local processing and data module 140 may be operatively coupled to the remote processing module 150 and the remote data repository 160 by communications 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 the local processing and data module 140. In some embodiments, the local processing and data module 140 may include one or more of an image capture device, a microphone, an inertial measurement unit, an accelerometer, a compass, a GPS unit, a wireless device, and / or a gyroscope.In some other embodiments, one or more of these sensors may be mounted on the frame 80, or they may be free-standing structures that communicate with the local processing and data module 140 via wired or wireless communication paths.

[0105] 2, in some embodiments, remote processing module 150 may comprise one or more processors configured to analyze and process data and / or image information. In some embodiments, remote data repository 160 may comprise a digital data storage facility, which may be available through the Internet or other networking configurations in a "cloud" resource configuration. In some embodiments, remote data repository 160 may include one or more remote servers, which provide information, such as information for generating augmented reality content, to local processing and data module 140 and / or remote processing module 150. In some embodiments, all data is stored and all calculations are performed within the local processing and data module, allowing for fully autonomous use from the remote modules.

[0106] Referring now to FIG. 3, the perception of an image as "three-dimensional" or "3-D" may be achieved by providing a slightly different presentation of the image to each eye of a viewer. FIG. 3 illustrates a conventional display system for simulating a three-dimensional image for a user. Two different images 190, 200, one for each eye 210, 220, are output to the user. The images 190, 200 are spaced from the eyes 210, 220 a distance 230 along an optical axis or z-axis parallel to the viewer's line of sight. The images 190, 200 are flat, and the eyes 210, 220 may focus on the images by assuming a single accommodated state. Such a 3-D display system relies on the human visual system to combine the images 190, 200 to provide a perception of depth and / or scale of the combined image.

[0107] However, it should be appreciated that the human visual system is more complex and providing a realistic perception of depth is more difficult. For example, many viewers of conventional "3-D" display systems find such systems uncomfortable or may not perceive any sense of depth at all. Without being limited by theory, it is believed that a viewer of an object may perceive the object as "three-dimensional" due to a combination of vergence and accommodation. Vergence of the two eyes relative to each other (e.g., pupil rotation such that the pupils move toward or away from each other and converge the line of sight of the eyes to fixate on the object) is closely linked to the focusing (or "accommodation") of the eye's lenses and pupils. Under normal conditions, changing the focus of the eye's lenses or accommodating the eye to change focus from one object to another object at a different distance will automatically produce a matching change in vergence to the same distance, in a relationship known as the "accommodation-vergence reflex." Similarly, changes in vergence will induce matching changes in accommodation of lens shape and pupil size under normal conditions. As described herein, many stereoscopic or "3-D" display systems display a scene using a slightly different presentation (and therefore a slightly different image) to each eye so that a three-dimensional perspective is perceived by the human visual system. However, such systems are uncomfortable for many viewers because, among other things, they simply provide different presentations of the scene, but the eyes view the entire image information in a single accommodated state, working against the "accommodation-vergence reflex." Display systems that provide better matching between accommodation and vergence can produce a more realistic and comfortable simulation of a three-dimensional image.

[0108] FIG. 4 illustrates aspects of an approach for simulating a three-dimensional image using multiple depth planes. With reference to FIG. 4, objects at various distances from the eyes 210, 220 on the z-axis are accommodated by the eyes 210, 220 such that the objects are in focus. The eyes 210, 220 assume a particular accommodated state and focus on objects at different distances along the z-axis. As a result, a particular accommodated state may be said to be associated with a particular one of the depth planes 240 having an associated focal length, and an object or part of an object at a particular depth plane is in focus when the eye is in an accommodated state relative to that depth plane. In some embodiments, a three-dimensional image may be simulated by providing a different presentation of an image for each of the eyes 210, 220, and may also be simulated by providing a different presentation of an image corresponding to each of the depth planes. Although shown as separate for clarity of illustration, it should be understood that the fields of view of the eyes 210, 220 may overlap, for example, as the distance along the z-axis increases. Additionally, while shown to be flat for ease of illustration, it should be understood that the contour of the depth plane may be curved in physical space such that all features within the depth plane are in focus with the eye in a particular accommodated state.

[0109] The distance between an object and the eye 210 or 220 may also change the amount of divergence of light from that object as viewed by that eye. Figures 5A-5C illustrate the relationship between distance and divergence of light rays. The distance between the object and the eye 210 is represented in the order of decreasing distances R1, R2, and R3. As shown in Figures 5A-5C, the light rays become more divergent as the distance to the object decreases. As the distance increases, the light rays become more collimated. In other words, the light field generated by a point (an object or part of an object) may be said to have a spherical wavefront curvature that is a function of the distance the point is away from the user's eye. The curvature increases with decreasing distance between the object and the eye 210. As a result, at different depth planes, the divergence of the light rays is also different, and the divergence increases with decreasing distance between the depth plane and the viewer's eye 210. Although only a monocular 210 is illustrated in FIGS. 5A-5C and various other figures herein for clarity of illustration, it should be understood that the discussion regarding eye 210 may apply to both eyes 210 and 220 of a viewer.

[0110] Without being limited by theory, it is believed that the human eye is typically capable of interpreting a finite number of depth planes to provide depth perception. As a result, a highly realistic simulation of perceived depth can be achieved by providing the eye with different presentations of images corresponding to each of these limited number of depth planes. The different presentations can be focused separately by the viewer's eyes, thereby serving to provide depth cues to the user based on ocular accommodation required to focus on different image features for scenes located on different depth planes and / or based on the observation of different image features on different depth planes that are out of focus.

[0111] FIG. 6 illustrates an example of a waveguide stack for outputting image information to a user. The display system 250 includes a stack of waveguides or a stacked waveguide assembly 260 that can be utilized to provide a three-dimensional perception to the eye / brain using multiple waveguides 270, 280, 290, 300, 310. In some embodiments, the display system 250 is the system 60 of FIG. 2, and FIG. 6 illustrates several portions of the system 60 in more detail. For example, the waveguide assembly 260 can be part of the display 70 of FIG. 2. It should be understood that the display system 250 can be considered a bright field display in some embodiments. In addition, the waveguide assembly 260 can also be referred to as an eyepiece.

[0112] Continuing with reference to FIG. 6, the waveguide assembly 260 may also include a number of features 320, 330, 340, 350 between the waveguides. In some embodiments, the features 320, 330, 340, 350 may be one or more lenses. The waveguides 270, 280, 290, 300, 310 and / or the number of lenses 320, 330, 340, 350 may be configured to transmit image information to the eye with various levels of wavefront curvature or light beam divergence. Each waveguide level may be associated with a particular depth plane and may be configured to output image information corresponding to that depth plane. Image input devices 360, 370, 380, 390, 400 may act as light sources for the waveguides and may be utilized to input image information into waveguides 270, 280, 290, 300, 310, each of which may be configured as described herein to distribute incident light across each respective waveguide for output towards the eye 210. Light exits output surfaces 410, 420, 430, 440, 450 of image input devices 360, 370, 380, 390, 400 and is input into corresponding input surfaces 460, 470, 480, 490, 500 of waveguides 270, 280, 290, 300, 310. In some embodiments, each of the input surfaces 460, 470, 480, 490, 500 may be an edge of the corresponding waveguide or may be a portion of the major surface of the corresponding waveguide (i.e., one of the waveguide surfaces that directly faces the world 510 or the viewer's eye 210). In some embodiments, a single beam of light (e.g., a collimated beam) may be launched into each waveguide, outputting a total field of cloned collimated beams that are directed toward the eye 210 at a particular angle (and divergence) corresponding to the depth plane associated with the particular waveguide. In some embodiments, a single one of the image launch devices 360, 370, 380, 390, 400 may be associated with and launch light into multiple (e.g., three) waveguides 270, 280, 290, 300, 310.

[0113] In some embodiments, the image input devices 360, 370, 380, 390, 400 are separate displays that each generate image information for input into a corresponding waveguide 270, 280, 290, 300, 310, respectively. In some other embodiments, the image input devices 360, 370, 380, 390, 400 are the output of a single multiplexed display that may, for example, send image information via one or more optical conduits (such as fiber optic cables) to each of the image input devices 360, 370, 380, 390, 400. It should be understood that the image information provided by the image input devices 360, 370, 380, 390, 400 may include light of different wavelengths or colors (e.g., different primary colors as discussed herein).

[0114] In some embodiments, the light injected into the waveguides 270, 280, 290, 300, 310 is provided by a light projector system 520, which includes a light module 540, which may include a light emitter such as a light emitting diode (LED). Light from the light module 530 may be directed through a beam splitter 550 to and modified by a light modulator 540, e.g., a spatial light modulator. The light modulator 530 may be configured to change the perceived intensity of the light injected into the waveguides 270, 280, 290, 300, 310. Examples of spatial light modulators include liquid crystal displays (LCDs), including liquid crystal on silicon (LCOS) displays. It should be understood that image input devices 360, 370, 380, 390, 400 are illustrated diagrammatically, and in some embodiments these image input devices may represent different light paths and locations within a common projection system configured to output light into associated ones of waveguides 270, 280, 290, 300, 310.

[0115] In some embodiments, 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 210. In some embodiments, the illustrated image injection devices 360, 370, 380, 390, 400 may diagrammatically represent a single scanning fiber or a bundle of scanning fibers configured to inject light into one or more waveguides 270, 280, 290, 300, 310. In some other embodiments, the illustrated image injection devices 360, 370, 380, 390, 400 may diagrammatically represent multiple scanning fibers or multiple bundles of scanning fibers, each of which is 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 can be configured to transmit light from the optical module 530 to one or more of the waveguides 270, 280, 290, 300, 310. It should be understood that one or more intervening optical structures can be provided between the scanning fiber or fibers and one or more of the waveguides 270, 280, 290, 300, 310, for example, to redirect light exiting the scanning fiber into one or more of the waveguides 270, 280, 290, 300, 310.

[0116] 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 module 540. In some embodiments, the controller 560 is part of the local data processing module 140. The controller 560 includes programming (e.g., instructions in a non-transient medium) that coordinates the timing and provisioning of image information to the waveguides 270, 280, 290, 300, 310, for example, according to any of the various schemes disclosed herein. In some embodiments, the controller may be a single integrated device or a distributed system connected by wired or wireless communication channels. The controller 560 may be part of the processing module 140 or 150 (FIG. 2) in some embodiments.

[0117] Continuing with reference to FIG. 6, the waveguides 270, 280, 290, 300, 310 may be configured to propagate light within each respective waveguide by total internal reflection (TIR). Each of the waveguides 270, 280, 290, 300, 310 may be planar 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 the waveguides 270, 280, 290, 300, 310 may include an out-coupling optical element 570, 580, 590, 600, 610 configured to extract light from the waveguide by redirecting light propagating within each respective waveguide out of the waveguide to output image information to the eye 210. The extracted light may also be referred to as out-coupled light, and the out-coupling optical element may also be referred to as a light extraction optical element. The extracted beam of light may be output by the waveguide at the location where the light propagating in the waveguide strikes the light extraction optical element. The out-coupling optical element 570, 580, 590, 600, 610 may be, for example, a grating including diffractive optical features as further discussed herein. Although 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 embodiments, the out-coupling optical element 570, 580, 590, 600, 610 may be disposed on the top and / or bottom major surfaces and / or directly within the volume of the waveguide 270, 280, 290, 300, 310 as further discussed herein. In some embodiments, the outcoupling optical elements 570, 580, 590, 600, 610 may be attached to a transparent substrate and formed within a layer of material forming the waveguide 270, 280, 290, 300, 310. In some other embodiments, the waveguide 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.

[0118] With continued 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 210. 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 it can reach the eye 210. Such a first lens 350 may be configured to generate a slight convex wavefront curvature such that the eye / brain interprets the light originating from the next upper waveguide 280 as originating from a first focal plane closer inward from optical infinity toward the eye 210. Similarly, the third upper waveguide 290 passes its output light through both the first 350 and second 340 lenses before reaching the eye 210. The combined refractive power of the first 350 and second 340 lenses may be configured to produce another incremental amount of wavefront curvature such that the eye / brain interprets the light originating from the third waveguide 290 as originating from a second focal plane closer inward toward the person from optical infinity, which was the light from the next upper waveguide 280.

[0119] 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 an aggregate focal power that represents the focal plane closest to the person. To compensate for the stack of lenses 320, 330, 340, 350 when viewing / interpreting light 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 aggregate power of the lens stacks 320, 330, 340, 350 below. Such a configuration provides as many perceived focal planes as there are waveguide / lens pairs available. Both the outcoupling optical elements of the waveguides and the focusing sides of the lenses may be static (i.e., not dynamic or electroactive). In some alternative embodiments, one or both may be dynamic using electroactive features.

[0120] In some embodiments, two or more of the waveguides 270, 280, 290, 300, 310 may have the same associated depth plane. For example, multiple waveguides 270, 280, 290, 300, 310 may be configured to output images set at the same depth plane, or multiple subsets 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.

[0121] Continuing with reference to FIG. 6, the outcoupling optical elements 570, 580, 590, 600, 610 may be configured to redirect light from their respective waveguides and output this light with an appropriate amount of divergence or collimation for a particular depth plane associated with the waveguide. As a result, waveguides with different associated depth planes may have different configurations of outcoupling optical elements 570, 580, 590, 600, 610 that output light with different amounts of divergence depending on the associated depth plane. In some embodiments, the light extraction optical elements 570, 580, 590, 600, 610 may be volume or surface features that may be configured to output light at a particular angle. For example, the light extraction optical elements 570, 580, 590, 600, 610 may be volume holograms, surface holograms, and / or diffraction gratings. In some embodiments, the features 320, 330, 340, 350 may not be lenses. Rather, they may simply be spacers (eg, cladding layers and / or structures for forming air gaps).

[0122] In some embodiments, 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 210 at 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 exit beams that exit the waveguide at multiple locations, and the result is a fairly uniform pattern of exit emission toward the eye 210 for this particular collimated beam bouncing within the waveguide.

[0123] In some embodiments, 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 significantly diffract. For example, a switchable DOE may comprise a layer of polymer dispersed liquid crystal, where the 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 significantly diffract incident light), or the microdroplets may be switched to a refractive index that does not match that of the host medium (in which case the pattern actively diffracts incident light).

[0124] In some embodiments, a camera assembly 630 (e.g., a digital camera, including visible and infrared light cameras) may be provided to capture images of the eye 210 and / or tissue surrounding the eye 210, for example, to detect user input and / or to monitor a physiological condition of the user. As used herein, a camera may be any image capture device. In some embodiments, the camera assembly 630 may include an image capture device and a light source that projects 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 embodiments, the camera assembly 630 may be mounted on the frame 80 (FIG. 2) and may be in electrical communication with the processing modules 140 and / or 150, which may process image information from the camera assembly 630. In some embodiments, one camera assembly 630 may be utilized for each eye to monitor each eye separately.

[0125] 7, an example of an exit beam output by a waveguide is shown. Although one waveguide is illustrated, it should be understood that other waveguides in the waveguide assembly 260 (FIG. 6) may function similarly and that the waveguide assembly 260 includes multiple waveguides. Light 640 is launched into the waveguide 270 at the input surface 460 of the waveguide 270 and propagates within the waveguide 270 by TIR. At the point where the light 640 impinges on the DOE 570, a portion of the light exits the waveguide as an exit beam 650. The exit beams 650 are illustrated as substantially parallel, but as discussed herein, they may also be redirected to propagate to the eye 210 at an angle (e.g., divergent exit beam formation) depending on the depth plane associated with the 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 at a depth plane at a large distance (e.g., optical infinity) from the eye 210. Other sets of waveguides or other outcoupling optics may output a more divergent exit beam pattern, which would require the eye 210 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 210 than optical infinity.

[0126] In some embodiments, a full color image may be formed at each depth plane by overlaying images in each of the primary colors, for example, three or more primary colors. FIG. 8 illustrates an example of a stacked waveguide assembly, where each depth plane includes an image formed using multiple different primary colors. The illustrated embodiment shows depth planes 240a-240f, but more or less depths are also envisioned. Each depth plane may have three or more primary color images associated with it, including a first image of a first color G, a second image of a second color R, and a third image of a third color B. The different depth planes are indicated in the diagram by different numbers for diopters (dpt) following the letters G, R, and B. By way of example only, the numbers following each of these letters indicate diopters (1 / m), i.e., the inverse of the distance of the depth plane from the viewer, and each box in the diagram represents an individual primary color image. In some embodiments, the exact location of the depth planes for the different primary colors may vary to account for differences in the eye's focusing of different wavelengths of light. For example, different primary color images for a given depth plane may be placed on depth planes corresponding to different distances from the user. Such an arrangement may increase visual acuity and user comfort and / or reduce chromatic aberration.

[0127] In some embodiments, the light of each primary color may be output by a single dedicated waveguide, such that each depth plane may have multiple waveguides associated with it. In such an embodiment, each box in the figure 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 three primary color images provided per depth plane. The waveguides associated with each depth plane are shown adjacent to each other in this drawing for ease of illustration, but 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 primary colors may be output by the same waveguide, such that, for example, only a single waveguide may be provided per depth plane.

[0128] 8, in some embodiments, G is green, R is red, and B is blue. In some other embodiments, other colors associated with other wavelengths of light, including magenta and cyan, may be used in addition to or in place of one or more of the red, green, or blue colors.

[0129] 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 in 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 in the range of about 620-780 nm, green light may include one or more wavelengths of light in the range of about 492-577 nm, and blue light may include one or more wavelengths of light in the range of about 435-493 nm.

[0130] In some embodiments, the light source 530 (FIG. 6) may be configured to emit light at one or more wavelengths outside the range of visual perception of a viewer, 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 210, e.g., for imaging and / or user stimulation applications.

[0131] 9A, in some embodiments, light impinging on a waveguide may need to be redirected to in-couple the light into the waveguide. An in-coupling optical element may be used to redirect and in-couple 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 in-coupling 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. The stack 660 may correspond to the stack 260 (FIG. 6), and the illustrated waveguides of the stack 660 may correspond to a portion of the plurality of waveguides 270, 280, 290, 300, 310, but it should be understood that light from one or more of the image input devices 360, 370, 380, 390, 400 is launched into the waveguide from a position that requires the light to be redirected for in-coupling.

[0132] The illustrated set 660 of stacked waveguides includes waveguides 670, 680, and 690. Each waveguide includes an associated incoupling optical element (which may also be referred to as the light input area on the waveguide), for example, incoupling optical element 700 is disposed on a major surface (e.g., the upper major surface) of waveguide 670, incoupling optical element 710 is disposed on a major surface (e.g., the upper major surface) of waveguide 680, and incoupling optical element 720 is disposed on a major surface (e.g., the upper major surface) of waveguide 690. In some embodiments, one or more of the incoupling optical elements 700, 710, 720 may be disposed on a bottom major surface of the respective waveguide 670, 680, 690 (particularly, one or more of the incoupling optical elements is a reflective polarizing optical element). As shown, the incoupling 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 incoupling optical elements are transmissive polarizing optical elements. In some embodiments, the incoupling optical elements 700, 710, 720 may be disposed within the body of the respective waveguides 670, 680, 690. In some embodiments, as discussed herein, the incoupling optical elements 700, 710, 720 are wavelength selective such that they selectively redirect one or more wavelengths of light while transmitting other wavelengths of light. Although illustrated on one side or corner of their respective waveguides 670, 680, 690, it should be understood that the incoupling optical elements 700, 710, 720 may be disposed within other areas of their respective waveguides 670, 680, 690 in some embodiments.

[0133] As shown, the in-coupling optical elements 700, 710, 720 may be laterally offset from one another. In some embodiments, each in-coupling optical element may be offset such that it receives light that does not pass 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 receives substantially no light from others of the in-coupling optical elements 700, 710, 720.

[0134] Each waveguide also includes an associated light distribution element, for example, light distribution element 730 is disposed on a major surface (e.g., a top major surface) of waveguide 670, light distribution element 740 is disposed on a major surface (e.g., a top major surface) of waveguide 680, and light distribution element 750 is disposed on a major surface (e.g., a 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.

[0135] The waveguides 670, 680, 690 may be spaced apart and separated, for example, by layers of gas, liquid, and / or solid material. For example, as shown, layer 760a may separate waveguides 670 and 680, and layer 760b may separate waveguides 680 and 690. In some embodiments, layers 760a and 760b are formed from a low 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 more greater and 0.10 or more less than the index of refraction of the material forming the waveguides 670, 680, 690. Advantageously, the lower refractive index layers 760a, 760b may act 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 embodiments, 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.

[0136] Preferably, for ease of manufacturing and other considerations, the materials forming the waveguides 670, 680, 690 are similar or identical, and the materials forming the layers 760a, 760b are similar or identical. In some embodiments, the materials forming the waveguides 670, 680, 690 may vary between one or more of the waveguides, and / or the materials forming the layers 760a, 760b may differ while still maintaining the various refractive index relationships discussed above.

[0137] 9A, light rays 770, 780, 790 are incident on the set of waveguides 660. It should be understood that light rays 770, 780, 790 may be injected into the waveguides 670, 680, 690 by one or more image injection devices 360, 370, 380, 390, 400 (FIG. 6).

[0138] In some embodiments, the light beams 770, 780, 790 have different characteristics, e.g., different wavelengths or different wavelength ranges, which may correspond to different colors. Each of the incoupling 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 embodiments, each of the incoupling optical elements 700, 710, 720 selectively deflects one or more particular wavelengths of light while transmitting other wavelengths to the underlying waveguide and associated incoupling optical element.

[0139] For example, incoupling optical element 700 may be configured to selectively deflect light beam 770 having a first wavelength or wavelength range while transmitting light beams 1242 and 1244 having different second and third wavelengths or wavelength ranges, respectively. Transmitted light beam 780 impinges on and is deflected by incoupling optical element 710, which is configured to selectively deflect light of the second wavelength or wavelength range. Light beam 790 is deflected by incoupling optical element 720, which is configured to selectively deflect light of the third wavelength or wavelength range.

[0140] 9A, the deflected light rays 770, 780, 790 are deflected to propagate through the corresponding waveguides 670, 680, 690. That is, the incoupling optical elements 700, 710, 720 of each waveguide deflect the light into its corresponding waveguide 670, 680, 690 and incoupling the light into the corresponding waveguide. The 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. The light rays 770, 780, 790 propagate through the respective waveguides 670, 680, 690 by TIR until they impinge on the corresponding light distribution elements 730, 740, 750 of the waveguides.

[0141]

[0046] Referring now to Figure 9B, a perspective view of the example of multiple stacked waveguides of Figure 9A is illustrated. As previously described, the in-coupled light rays 770, 780, 790 are deflected by the in-coupling optical elements 700, 710, 720, respectively, and then propagate by TIR within the waveguides 670, 680, 690, respectively. The light rays 770, 780, 790 then impinge on the light distribution elements 730, 740, 750, respectively. The light distribution elements 730, 740, 750 deflect the light rays 770, 780, 790 to propagate towards the out-coupling optical elements 800, 810, 820, respectively.

[0142] In some embodiments, the light distribution elements 730, 740, 750 are orthogonal pupil expanders (OPEs). In some embodiments, the OPEs deflect or distribute the light to the out-coupling optical elements 800, 810, 820, and in some embodiments, may increase the beam or spot size of this light as it propagates to the out-coupling optical elements. In some embodiments, the light distribution elements 730, 740, 750 may be omitted and the in-coupling optical elements 700, 710, 720 may be configured to deflect the light directly to the out-coupling optical elements 800, 810, 820. For example, referring to FIG. 9A, the light distribution elements 730, 740, 750 may be replaced with the out-coupling optical elements 800, 810, 820, respectively. In some embodiments, the outcoupling optical elements 800, 810, 820 are exit pupils (EPs) or exit pupil expanders (EPEs) that direct light to the viewer's eye 210 (FIG. 7). It should be understood that the OPEs may be configured to increase the size of the eyebox in at least one axis, and the EPEs may increase the eyebox in an axis that intersects the axis of the OPE, e.g., an orthogonal axis. For example, each OPE may be configured to redirect a portion of the light striking the OPE to an EPE of the same waveguide, while allowing the remaining portion of the light to continue propagating down the waveguide. Upon striking the OPE, again, another portion of the remaining light is redirected to the EPE, which continues to propagate further down the waveguide, etc. Similarly, upon striking the EPE, a portion of the striking light is directed out of the waveguide towards the user, and the remaining portion of the light continues to propagate through the waveguide until it again strikes the EP, at which point another portion of the striking 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 an OPE or EPE, thereby forming a cloned beam field of light, as shown in Figure 6. In some embodiments, the OPE and / or EPE may be configured to modify the size of the beam of light.

[0143] Thus, referring to Figures 9A and 9B, in some embodiments, a set of waveguides 660 includes, for each primary color, a waveguide 670, 680, 690, an in-coupling optical element 700, 710, 720, a light distribution element (e.g., OPE) 730, 740, 750, and an out-coupling optical element (e.g., EP) 800, 810, 820. The waveguides 670, 680, 690 may be stacked with an air gap / cladding layer between each waveguide. The in-coupling optical element 700, 710, 720 redirects or deflects the incoming light into its waveguide (with different in-coupling optical elements receiving different wavelengths of light). The light then propagates at an angle that will result in TIR within the respective 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 incident on the in-coupling optical element 710 and being deflected thereby. Light ray 780 will then bounce back down the waveguide 680, via TIR, 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 beam 790 so that it propagates by TIR to the light distribution element (e.g., OPE) 750 and then to the out-coupling optical element (e.g., EP) 820. The out-coupling optical element 820 then finally out-couples the light beam 790 to a viewer, who also receives the out-coupled light from the other waveguides 670, 680.

[0144] FIG. 9C illustrates a top-down plan view of the example of multiple stacked waveguides of FIGS. 9A and 9B. As shown, the waveguides 670, 680, 690 may be vertically aligned with each waveguide's associated light distribution element 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 spaced apart laterally, as seen 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 embodiments, an array including non-overlapping, spatially separated in-coupling optical elements may be referred to as a shifted pupil system, and the in-coupling optical elements in these arrays may correspond to sub-pupils.

[0145] (variable power reflector) As illustrated in FIG. 10A, the wearable augmented reality head mounted display system 60 may include a variable refractive power reflector (or variable focus reflector) 1032 arranged to receive light from the light projector system 2000, for example, via a waveguide 2700. The variable refractive power reflector 1032 may be configured to have an adjustable refractive power in response to application of an electrical signal. For example, the variable refractive power reflector 1032 shown in FIG. 10A comprises a deformable reflector having a deformable reflective surface (e.g., the surface closest to the waveguide 2700) with an adjustable shape. For example, the shape of the deformable reflector 1032 may be configured to bend to generate different convex shapes corresponding to different refractive powers. The variable refractive power reflector 1032 may comprise, for example, a deformable membrane or other thin member that is flexible and can vary its shape. In some designs, the deformable reflector 1032 is electrically actuated. The deformable reflector may include, for example, at least one electrode 1036 to apply an electric field to deform the reflective surface, in some cases via electrostatic forces or by some other. As illustrated in FIG. 10A, another electrode 1042 is included on the surface of the waveguide 2700. Application of a voltage across the two electrodes 1036 and 1042 may provide such an electric field and thus deform the deformable reflector. With the deformation of the deformable membrane or member, the reflective surface (e.g., the surface closest to the waveguide 2700) may be deformed. As illustrated, the shape may be convex, thus providing a reflective surface with negative optical power. In some examples, the surface closest to the waveguide 2700 may comprise a reflective surface for reflecting light from the optical projection system (display) 2000, although other surfaces associated with the variable optical power reflector may also reflect light from the optical projection system. The variable power reflector 1032 may include multiple layers, including, for example, one or more reflective surfaces that need not be the surface closest to the light guide 2700. The variable power reflector 1032 may be wavelength-selective and / or polarization-selective, such that light having certain wavelengths and / or polarization states is reflected by the variable power reflector 1032, while light having other wavelengths and / or polarization states is transmitted through the variable power reflector 1032.

[0146] The waveguide 2700 may have a front side and a rear side, the rear side being closest (more proximal) to the wearer's eye and the front side being farther (more distal) from the wearer's eye and closer to the world in front of the wearer and the head mounted display system. As shown, the variable power reflector 1032 may be disposed on the front side of the waveguide. The waveguide may include an external coupling element configured to extract light from the waveguide and direct the light towards the front side of the waveguide so that it is incident on the variable power reflector. Because the variable power reflector is disposed on the front side of the waveguide, the variable power reflector is configured to transmit light from the world in front of the wearer such that the head mounted display system may pass light from the world in front of the wearer wearing the head mounted system into the wearer's eye. Despite being transparent to light from the world in front of the wearer, the variable power reflector 1032 is configured to reflect light from the display. As discussed below, in some examples, the variable power reflector may include one or more wavelength selective filters and transmit light from the world in front of the wearer while reflecting light from the optical projection system (display) 2000. Additionally, in some examples, the variable power reflector may include one or more polarization selective filters and transmit light from the world in front of the wearer while reflecting light from the optical projection system (display) 2000.

[0147] As shown, the variable power reflector may deform its shape to diverge light from the display 2000 that is reflected from the variable power reflector. In particular, light from the light source 530 is directed by a beam splitter 550 to an image injection device 4000 that is positioned relative to the spatial light modulator 540 and the waveguide 2700 to couple the spatially modulated light containing the image into the waveguide. This light 1022 may propagate through the waveguide 2700 by total internal reflection (TIR) ​​and be extracted therefrom via one or more out-coupling optical elements (e.g., an exit pupil expander, e.g., with diffractive features). In some configurations, the light from the display 2000 that is injected into the waveguide 2700 may be collimated, such that the collimated light 1022 may exit the waveguide and propagate toward the variable power reflector 1032, as illustrated in FIG. 10A. 10A, the variable power reflector (or variable focus reflector) is deformed to create a convex reflective surface that produces negative refractive power (e.g., produces a virtual image at a distance from the eye 210), thus causing the reflected light rays 1024 to diverge. The reflected light 1024 then enters the individual's (e.g., wearer's) eye 210, and on the other side of the waveguide and deformable mirror may appear to be formed by an object a short distance from the eye. As a result, the image formed by the display may appear to originate from an object relatively close to the wearer.

[0148] In the example shown in FIG. 10A, light exits image input device 4000 and is injected into input surface 4600 of waveguide 2700 on the edge of waveguide 2700. However, in other examples, light may be injected into a corresponding major surface of the waveguide (e.g., one of the waveguide surfaces directly facing world 144 or the viewer's eye 210). See, e.g., FIGS. 9A-9C. In various embodiments, light from image input device 4000 can be polarized prior to being injected into waveguide 2700. For example, light injected into waveguide 2700 can be configured to be linearly polarized along the vertical (or horizontal) direction.

[0149] In some configurations, the one or more outcoupling optical elements 5700 can be configured to direct substantially all of the outcoupled light in a distal direction, away from the viewer's eye, e.g., toward the world. The one or more outcoupling optical elements 5700 can include one or more asymmetric diffraction gratings.

[0150] The variable power reflector 1032 may be positioned to reflect light outcoupled distally from the user's eye 210 back toward the user's eye 210, potentially altering the wavefront of the light reflected therefrom, while the variable power reflector transmits light from the world in front of the wearer to the user's eye without introducing a similar change to the wavefront. For example, the variable power reflector may be configured to have an optical power that acts on light from the display 2000 that is reflected from the variable power reflector, but the variable power reflector may not similarly act on light from the world in front of the wearer that is transmitted therethrough to the eye. In some cases, for example, the thickness of the variable power reflector 1032 may be chosen to be thin enough so as not to significantly alter the optical properties of light passing through the variable power reflector 1032 (e.g., from the world). Advantageously, this may allow light passing through the variable power reflector 1032 from the world to be viewed at an appropriate depth, while controlling the depth at which an image appears to originate from the display 2000. This configuration therefore eliminates the need for any additional lenses to compensate for changes in the radius of curvature or optical power of the variable power reflector due to light from the world in front of the wearer, thus making the system lighter, cheaper, and less complex.

[0151] The reflector 1036 may be made of one or more transparent materials, such as, for example, silicon nitride (SiN). The material at an appropriate thickness may also be sufficiently flexible to be deformed by electrostatic forces, for example, with the application of an electric field. Other methods of deforming the variable optical power reflector may be used. Similarly, other methods of providing variable optical power other than deforming the shape of the reflector may also be employed, as discussed below.

[0152] In some embodiments, the elasticity of the variable optical power reflector 1032 allows for fast time transitions between one or more optical powers. For example, fast transitions from one focal length (e.g., curvature) to another may allow for time multiplexing of different focal planes as seen by a viewer (e.g., eye 210). In some embodiments, the transitions may toggle between two or more focal lengths multiple times per minute.

[0153] As discussed above, in some cases, the curvature of the variable power reflector 1032 is controlled by two or more electrodes. A distal electrode 1036 may be disposed distal to the variable power reflector 1032 as illustrated by FIG. 10A, and a proximal electrode 1042 may be disposed proximal to the reflector 1032 (e.g., disposed on a waveguide 2700 as shown in FIG. 10A), although other electrode configurations are possible. The distal electrode 1036 may be disposed proximal to the variable power reflector 1032. The electrodes 1036, 1042 may be made of a material that may conduct electricity and be transparent to visible light. For example, one or more materials such as indium tin oxide (ITO) may be used for the electrodes 1036, 1042.

[0154] The electrodes may be in electrical communication with electronics configured to drive the variable power reflector. These electronics may be configured to vary the refractive power of the variable power reflector to present different image content as if originating from different depth planes. In some configurations, for example, the controller 560 or other electronics may control the operation of the variable power reflector, in conjunction with one or more of the waveguide 2700 (e.g., the stacked waveguide assembly of FIG. 6) and / or other parts of the light projector system 2000 (e.g., the image input device 4000, the light source 530, the light modulator 540, the camera assembly 630). In some cases, the controller 560 coordinates the timing and provision of image information to the waveguide 2700 and thus the variable power reflector, and the controller 560 also controls the timing or variation of and synchronization between the actuation of the refractive power of the variable power reflector.

[0155] Thus, the variable power reflector (or variable focus reflector) 1032 may have a refractive power that is adjustable and can be electronically controlled. This capability allows the depth plane corresponding to the image coupled out of the waveguide 2700 to be dynamically adjusted. For example, the light coupled out of the waveguide 2700 may be substantially collimated as if the object generating the light were located at an infinite distance (or at least far away) from the viewer. If the desired focal plane corresponding to the variable power reflector (or variable focus reflector) is at some infinite distance, the reflector 1032 may be set to a planar state to leave the wavefront curvature of the reflected light substantially unchanged in this case where collimated light is output from the waveguide. This situation is shown in FIG. 10B. Alternatively, if the desired focal plane is closer to the viewer than infinity, the variable power reflector 1032 may be adjusted (e.g., bent and electrically influenced) to take on the appropriate amount of convex curvature. This mode is shown in FIG. 10A.

[0156] Thus, Figure 10B illustrates the optical projection system 2000 of Figure 10A when the variable power reflector 1032 creates a virtual image as if it were at infinity. The light rays 1022 exit the waveguide 2700 parallel or substantially parallel to each other and propagate towards the variable power reflector 1032. Because the electrodes 1036, 1042 cause the reflector 1032 to have a flat reflective surface, the reflected light rays 1024 are also parallel to each other as they propagate towards the eye 210. In some embodiments, as in Figure 10A, the variable power reflector 1032, the waveguide 2700, and the outcoupling optical element 5700 are configured not to substantially modify the divergence of the light 1024.

[0157] As discussed above, the variable power reflector may be configured to reflect light from the display 2000 while transmitting light from the world in front of the wearer. For example, the variable power reflector may include a wavelength selective filter to transmit light from the world in front of the wearer while reflecting light from the display. In some designs, for example, the variable power reflector 1032 includes one or more wavelength selective filters (e.g., notch filters, bandpass filters) corresponding to one or more colors or combinations of colors. For example, the one or more notch filters may be tuned to reflect light in a range of wavelengths corresponding to green (e.g., a narrow band in the range of 520-560 nm), red (e.g., a narrow band in the range of 635 nm-700 nm), and / or blue (e.g., a narrow band in the range of 450 nm-490 nm), while allowing light to be transmitted through the reflector 1032 at other visible wavelengths. Since it may be advantageous to allow most visible wavelengths of light (e.g., from the "world") to pass through the reflector, one or more wavelength-selective filters can be tuned to reflect only a narrow range of visible wavelengths. For example, the reflector may comprise one or more notch filters each configured to reflect a band of wavelengths encompassing the ranges of about 0.1 nm to 2 nm, about 1 to 5 nm, about 2 nm to 8 nm, about 5 nm to 10 nm, and / or about 10 to 25 nm. Any range formed by any of these values ​​is possible. Other size bands are also possible.

[0158] The narrow band within the visible spectrum where the variable power reflector is reflective may match the color of light emitted by the display 2000. The display may, for example, include one or more light sources (e.g., LEDs or lasers) that emit light of specific colors. The narrow band reflected by the variable power reflector may overlap and / or match the colors and wavelengths emitted by these light sources in the display.

[0159] The spectral transmission of the variable power reflector 1032 reflects light having wavelengths within these narrow bands, while light outside these bands can be transmitted. Thus, much of the ambient visible light from the world in front of the wearer and the head mounted display is transmitted through the variable power reflector. To provide such reflectance characteristics, the variable power reflector can include one or more reflective layers. For example, the variable power reflector can include multiple layers with different spectral reflectances.

[0160] Similarly, the variable power reflector may include one or more polarization selective filters to transmit light from the world in front of the wearer while reflecting light from the display. For example, FIG. 10C illustrates a variable power reflector 1032 that is polarization selective and uses the polarization of the light to determine which light is reflected and which is transmitted. In this example, the variable power reflector is configured to reflect one polarization state and transmit another. In particular, the variable power reflector is configured to reflect one linear polarization state (vertical) and transmit another linear polarization state (horizontal). As shown in FIG. 10C, the light source 530 in the display emits light 1170a with both horizontal and vertical polarization. However, the light 1170b output from the waveguide by the external coupling element is shown as being vertically polarized. The variable power reflector 1032 is configured to reflect the vertically polarized light in this example. As shown, the vertically polarized light 1170b is reflected by the reflector 1032. Light 1170c entering the eye 210 from the display 2000 may therefore be vertically polarized. As discussed above, the variable power reflector may be wavelength selective in addition to being polarization selective.

[0161] In contrast, in the example shown in Figure 10C, light from the world 510 may comprise both vertically and horizontally polarized light. If the variable power reflector 1032 is configured to transmit horizontally polarized light and / or reflect (and / or absorb) vertically polarized light, the horizontally polarized light 1170d may successfully pass (e.g., be transmitted) through the reflector 1032 without the corresponding vertically polarized light. Thus, light 1170e entering the eye 210 from the world in front of the wearer may be horizontally polarized.

[0162] In this way, the variable power reflector can both reflect light from the display 2000 and pass visible light from the world in front of the wearer and the head mounted display. However, other techniques can be employed.

[0163] For example, in some embodiments, the waveguide 2700 can comprise a liquid crystal grating. The liquid crystal grating can comprise a cholesteric liquid crystal (CLC) layer having a plurality of liquid crystal molecules arranged to have a continuous azimuthal twist of the director as a function of position within the film in the layer normal direction or layer depth direction of the liquid crystal layer. As described herein, liquid crystal molecules arranged to have a continuous azimuthal twist are collectively referred to as a chiral structure. As described herein, the angle (φ) of the azimuthal twist or rotation is described as the angle between the directors of the liquid crystal molecules with respect to a direction parallel to the layer normal. Spatially varying the director of the liquid crystal molecules in the chiral structure can be achieved by varying the helical pitch (p) of the directors by 360 degrees, as described above. o The liquid crystal grating can be configured as a diffraction grating, as discussed below.

[0164] Without being bound by any theory, under the Bragg reflection condition, the wavelength (λ) of the incident light can be proportional to the average or representative refractive index (n) and helical pitch (p) of the CLC layer, and under some circumstances can be expressed as satisfying the following condition:

number

[0165] Therefore, by controlling the pitch p of the liquid crystal molecules, different ones of the switchable reflective elements can be tuned to reflect different wavelengths. In addition, the bandwidth of the Bragg reflection wavelength (Δλ) can be proportional to the birefringence Δn (e.g., the difference in refractive index between different polarizations of light) and the helical pitch (p) of the CLC layer, and can be expressed under some circumstances as satisfying the following condition:

number

[0166] FIG. 10D illustrates an implementation of a display device 3000 configured to output image information to a user using a waveguide assembly 2904 and a deformable mirror 3004. The display device 3000 includes a waveguide assembly 2904 that is inserted between a curved or deformable mirror 3004 (so as to have optical power) and an optional clean polarizer 3008. The waveguide assembly 2904 includes a cholesteric liquid crystal grating (CLCG) 2905. The CLCG 2905 can be disposed between the waveguide assembly 2904 and the deformable mirror 3004 in some implementations. The waveguide assembly can include one or more waveguides configured to propagate light via total internal reflection. The eyepiece lens 2904 can be configured to project light asymmetrically, in this example, toward the left (world side) instead of the right (eye side). The eyepiece 2904 may comprise a DOE, metamaterial, hologram, etc. that may preferentially project light in a desired asymmetric direction and / or in a desired polarization state (e.g., linear or circular). Although not shown, the display device 3000 may comprise an image input device similar to the image input device 4000 discussed above with reference to Figures 10A-10C.

[0167] In operation, a portion of the light propagating in the x-direction in one or more waveguides in the waveguide assembly 2904 may be redirected or coupled out in the z-direction as a light beam 3012 having a uniform circular polarization (e.g., RHCP). The waveguide assembly 2904 projects the virtual image light beam 3012 toward the curved or deformable mirror 3004 (away from the user's eye 4). In some embodiments, the deformable mirror 3004 is coated with a polarizing reflective layer (e.g., a multi-layer linear polarizing reflector or a broadband cholesteric liquid crystal circular polarizing reflector) to reflect light having a specified polarization, e.g., light having the same polarization as the out-coupled polarization of the CLCG, allowing light from the real world 1114 to be transmitted toward the eye 4. In some other embodiments, instead of a polarizing reflective layer, the deformable mirror 3004 is coated with a notch or CLC reflective layer that is designed to reflect light within a narrow bandwidth Δλ that matches the virtual image bandwidth of the light outcoupled from the waveguide assembly 2904. In some embodiments, to eliminate any residual image without passing through the deformable mirror, a clean-up polarizer 3008 can be installed as shown in FIG.

[0168] In the various examples shown in FIGS. 10A-10D, a single waveguide 2700 or waveguide assembly 2904 is shown, although a stack of waveguides may be used to output image information to a user (e.g., as shown in FIG. 6). In some designs, different waveguides in the stack may correspond to particular colors (e.g., ranges of wavelengths) and / or depth planes of the display. Similarly, the image input device 4000, the waveguide 2700, the waveguide assembly 2904, and other elements of the assembly may each represent multiple image input devices, waveguides, etc. For example, the image input device 4000 can be separate displays that generate image information for input into the corresponding waveguide 2700. In some cases, the image input device 4000 may include an output end of a single multiplexed display, which may, for example, send image information to the image input device 4000 via one or more optical conduits (e.g., fiber optic cables). The image information provided by image input device 4000 may include light of different wavelengths or colors (e.g., different primary colors and / or sub-colors). Additional information regarding stacked waveguide assemblies, such as those used for waveguide 2700 or waveguide assembly 2904, may be found above in connection with FIG.

[0169] As discussed above, for example, the external coupling element 5700 discussed above with reference to Figures 10A and 10B can be asymmetric, such that the amount of light injected into the waveguide 2700 from the image injection device 4000 that is directed by the external coupling element 5700 toward the front side of the waveguide and the reflector 1032 is greater than the amount of light injected into the waveguide 2700 from the image injection device 4000 that is directed by the external coupling element 5700 toward the rear side of the waveguide 2700 and the user's eye 210. For example, greater than 50% of the light injected into the waveguide 2700 can be directed by the external coupling element 5700 toward the reflector 1032. In various embodiments, the amount of injected light that is directed by the external coupling element toward the reflector 1032 can be greater than 60%, 70%, 80%, 90%, 95%, and / or any other percentage between about 50% and about 99.9%. Embodiments of the external coupling element 5700 that may be configured to diffract light asymmetrically, such that more light is diffracted in one direction than another, may include liquid crystal polarization gratings, volume phase holograms, and / or metasurfaces. As discussed above, light launched into the waveguide 2700 toward the reflector 1032 and directed to the user's eye 210 may have the advantage that the focus is modulated by the reflector 1032 (the wavefront of the light may be changed, for example, so that the light appears to originate from an object at a different depth). Thus, in some cases, it may be beneficial if a majority, e.g., all or substantially all, of the light launched into the waveguide 2700 is directed toward the reflector 1032.

[0170] However, in some embodiments of the display device, a large portion of the light injected from the image injection device 4000 into the waveguide 2700 may not be directed towards the reflector 1032 by the external coupling element 5700. In some such embodiments, a portion of the injected light may be directed towards the user's eye 210. In some such embodiments, a light recycling system, such as a polarization-based light recycling system comprising an array of retarders (e.g., retarder layers), can be used to recycle the light that is directed towards the user's eye 210 by the external coupling element 5700, such that the light is directed and focus modulated towards the reflector 1032 before being incident on the user's eye 210.

[0171] FIG. 11 illustrates an embodiment of a display device including a light recycling system, i.e., a polarization-based light recycling system, comprising an array of retarders configured to redirect injected light from a waveguide to be out-coupled toward the user's eye 210 to the reflector 1032. In various embodiments, the retarder array includes a quarter-wave retarder or quarter-wave plate 1104 configured to convert linearly polarized light to circularly or elliptically polarized light (and vice versa) and disposed between the waveguide 2700 and the reflector 1032, and a half-wave retarder or half-wave plate 1108 configured to shift (e.g., rotate) the polarization direction of the linearly polarized light and disposed between the waveguide 2700 and the user's eye 210. In various embodiments, the quarter-wave plate 1104 and / or the half-wave plate 1108 can be rigid structures. In some embodiments, the quarter-wave plate 1104 and / or the half-wave plate 1108 can be flexible structures (e.g., films). In some cases, one or more elements or layers having a desired net retardation, such as a quarter wavelength net retardation (λ / 4) or half wavelength net retardation (λ / 2), can be used. The display device illustrated in FIG. 11 further includes a polarization selective reflector 1112 disposed between the half wave plate 1108 and the user's eye 210. In various embodiments, the polarization selective reflector 1112 can include a wavelength selective component (e.g., a notch filter) or a reflective liquid crystal device. In various embodiments, the polarization selective reflector 1112 can include a metasurface. An embodiment of the polarization selective reflector 1112 that includes a wavelength selective component, a reflective liquid crystal component, and / or a metasurface can be configured to reflect light that has certain characteristics (e.g., a narrow band of wavelengths and / or a particular polarization state) and transmit light that does not have those certain characteristics.

[0172] Consider a portion of the light launched into the waveguide 2700 that is outcoupled as beam 1172a by the outcoupling optical element 5700 towards the reflector 1032. The beam 1172a is incident on a quarter-wave (λ / 4) plate that converts the polarization state of the beam 1172a from linear to circular / elliptical polarization or vice versa. Thus, the beam 1174a output from the quarter-wave plate 1104 has a circular / elliptical polarization (or vice versa) if the beam 1172a is linearly polarized. The beam 1174a is reflected by the reflector 1032 and undergoes focal modulation, as discussed above with reference to FIGS. 10A and 10B. The focal modulated reflected beam 1174a passes through the quarter-wave plate 1104 and undergoes a polarization shift from circular / elliptical to linear (or vice versa). The polarization state of the beam 1176a output from the quarter-wave plate 1104 is orthogonal to the polarization state of the beam 1172a. When beam 1176a traverses half (λ / 2) waveplate 1108, the direction of polarization is shifted (or rotated). Thus, beam 1178a exiting half waveplate 1108 has a polarization state orthogonal to the polarization state of beam 1176a. The polarization state of beam 1178a is the same as the polarization state of beam 1172a. Polarization-selective reflector 1112 can be configured to transmit light having the polarization state of beam 1178a (or the polarization state of beam 1172a) and can reflect light having a polarization state orthogonal to the polarization state of beam 1178a (or 1172a).

[0173] Consider a portion of the light launched into the waveguide 2700 that is outcoupled as beam 1172b by the outcoupling optical element 5700 towards the user's eye 210. The beam 1172b is incident on the half-wave plate 1108, which shifts (or rotates) the direction of polarization of the beam 1172b. For example, if the beam 1172b is linearly polarized along the vertical direction, the beam 1176b exiting the half-wave plate is linearly polarized along the horizontal direction. As discussed above, the polarization selective reflector 1112 is configured to transmit light having the polarization state of the beam 1172b and reflect light orthogonal to the polarization state of the beam 1172b. Thus, the beam 1176b having a polarization state orthogonal to the polarization state of the beam 1172b is reflected by the polarization selective reflector 1112 towards the reflector 1032. The direction of the polarization state of beam 1176b is shifted (e.g., rotated) as it traverses the half-wave plate 1108. Thus, beam 1178b has the same polarization state as beam 1172b. The polarization state of beam 1178b is converted from linearly polarized to circular / elliptical polarization as it traverses through the quarter-wave plate 1104. Thus, beam 1174b exiting the quarter-wave plate 1104 is circularly / elliptically polarized and is reflected by the reflector 1032. The beam reflected from the reflector 1032 is focally modulated and undergoes a shift in polarization from circular / elliptical to linear polarization as it traverses through the quarter-wave plate 1104. Beam 1180b exiting the quarter-wave plate 1104 has an orthogonal polarization to beam 1178b. For example, if beam 1178b (or beam 1172b) is linearly polarized along the vertical direction, beam 1180b is linearly polarized along the horizontal direction. The direction of the polarization state of beam 1180b is shifted (or rotated) when traversing through the half-wave plate 1108. For example, if beam 1180b is linearly polarized along the horizontal direction, beam 1182b is linearly polarized along the vertical direction. Beam 1182b has the same polarization state as that of beam 1172b. The polarization selective reflector 1112 is configured to transmit the focally modulated beam 1182b towards the user's eye 210.

[0174] As discussed above, the reflector 1032 can be configured to include a coating configured to transmit light outside of the narrow band of (visible) wavelengths while reflecting light within a narrow band of (visible) wavelengths. For example, the reflector 1032 can be configured to reflect light within a narrow range of red, green, and / or blue wavelengths. As another example, the reflector 1032 can be configured to reflect light within a wavelength range of about 5-10 nm around a red central wavelength, e.g., 630 nm. As yet another example, the reflector 1032 can be configured to reflect light within a wavelength range of about 5-10 nm around a green central wavelength, e.g., 550 nm. As another example, the reflector 1032 can be configured to reflect light within a wavelength range of about 5-10 nm around a blue central wavelength, e.g., 470 nm. In various embodiments, the reflector 1032 can be configured to reflect light within a wavelength range of about 5-20 nm around a central wavelength within the visible spectrum. In various designs, these narrow wavelength bands may overlap and / or match the wavelengths emitted by the light sources of the display 2000. The display 2000 may, for example, include multiple color light sources, and the narrow band regions of reflectance of the variable power reflector may match or overlap the colors of the light emitted by the light sources. For example, with respect to the example cited above, the light sources in the display 2000 may emit red light centered at or within 5-10 nm of about 630 nm, green light centered at or within 5-10 nm of about 550 nm, and blue light centered at or within 5-10 nm of about 470 nm. Different designs may have light sources and reflector filters with different spectral characteristics, however, in various cases, the wavelengths emitted by the light sources and the wavelengths reflected by the variable power reflector may overlap or match, while many other visible wavelengths are not reflected and are transmitted through the variable power reflector. If many other visible wavelengths were transmitted, much of the light from the wearer and objects in front of the head mounted display would be visible to the viewer through the head mounted display.

[0175] As discussed above, the variable optical power reflector may comprise a polarization-selective reflector and selectively reflect light from the display 2000 while also transmitting light from the wearer and objects in front of the head mounted display. In some designs, for example, the reflector 1032 may be configured to comprise a polarization-selective reflector configured to reflect light of a particular polarization. For example, the reflector 1032 may be configured to reflect light having a particular polarization state while being transmissive to other polarization states, in some cases many, most, all, or substantially all other polarization states.

[0176] In one design, the variable power reflector may comprise one or more switchable optical elements, such as a stack or a plurality of switchable reflective elements 1232, as depicted in FIG. 12. Such switchable elements may be configured to switch between two states, such as two levels of reflection, e.g., a low level of reflection (0% or higher) or a higher level of reflection. Similarly, the switchable elements may be configured to switch between two levels of transmission, e.g., a low level of transmission (0% or higher) or a higher level of transmission. Such switchable optical elements may comprise, for example, a switchable reflector, a switchable diffractive optical element, such as a switchable reflective grating or a holographic optical element. The switchable optical elements may be configured to switch between two power levels, such as a low power level (0 diopters or higher) and a higher power level. These power levels may be positive or negative and may switch between two positive powers, two negative powers, or a positive and a negative power, or zero and a non-zero power. Such switchable optical elements may comprise, for example, a switchable diffractive optical element, such as a switchable diffractive optical lens.

[0177] In various cases, the one or more switchable optical elements comprise one or more liquid crystal elements comprising liquid crystals, such as switchable polymer dispersed liquid crystal elements. The switchable optical elements may comprise switchable polarization gratings. In one configuration, the variable optical power reflector comprises a stack of switchable optical elements, different ones of which are associated with different optical powers such that the switchable optical elements are capable of switching between different optical powers. These optical powers may be provided by lenses, such as diffractive lenses, for example.

[0178] 12, different ones of the plurality of switchable reflective elements have negative refractive powers (although one or more of the refractive powers may be positive or zero in different designs). For example, the plurality or stack of switchable reflective elements may have a first switchable reflective element having a first negative refractive power, a second switchable reflective element having a second negative refractive power, a third switchable reflective element having a third negative refractive power, ... an nth switchable reflective element having an nth negative refractive power. In one configuration, one of the first, second, third, ... or nth switchable reflective elements may be configured to reflect light that is outcoupled from the waveguide 2700, while the remaining switchable reflective elements may be configured to be transmissive. In this manner, light coupled out of the waveguide 2700 directed away from the user's eye 210 is reflected from a selected one of the first, second, third, ... or nth switchable reflective elements such that it appears to the user to originate from a depth plane. In various embodiments, each of the multiple switchable reflective elements can be configured to reflect a particular wavelength of light such that the particular wavelength of light appears to originate from a particular depth.

[0179] Some display devices comprise a plurality or stack of switchable reflective elements, as described above with respect to Figure 12. Advantageously, each of the switchable reflective elements may comprise liquid crystals, as described elsewhere herein and below, for example with respect to Figures 13A-13C. For example, the switchable reflective elements may be formed from non-polymerizable or polymerizable liquid crystals or reactive mesogens (RM), the configuration of which may be altered by an external stimulus, for example an electric field.

[0180] In some embodiments, the switchable reflective element can comprise a liquid crystal, such as, for example, a cholesteric liquid crystal (CLC) layer, as discussed above. Figures 13A and 13B illustrate an exemplary switchable reflective element 3100A that can be implemented as part of a display device, where the switchable reflective element 3100A is formed from a patterned CLC layer that serves as a reflective polarizing mirror. Figure 13A illustrates the local orientation (arrows) of the liquid crystal directors on top of a binary Fresnel lens pattern. Thus, the switchable reflective element 3100A can be configured to have an adjustable refractive power using an applied electric field. An embodiment of the switchable reflective element 3100A can be used, for example, as an alternative to the deformable mirrors illustrated with respect to Figures 10A-10C and 11.

[0181] 13B, when the switchable reflective element 3100A is illuminated with circularly polarized incident light 3012 having a circular polarization corresponding (e.g., having the same handedness) to the handedness of the CLC chirality (e.g., RHCP), the reflected light 3016 exhibits a lens effect similar to the curved mirror reflector described above. On the other hand, light with the orthogonal polarization (e.g., LHCP) is transmitted without interference. The switchable reflective element 3100A can be configured to have a bandwidth in the range of less than about 10 nm, less than about 25 nm, less than about 50 nm, less than about 100 nm, or some other range.

[0182] FIG. 13C illustrates a switchable reflective element 3100C comprising multiple switchable reflective elements 3100-R, 3100-G, and 3100-B. In the illustrated embodiment, the switchable reflective elements 3100-R, 3100-G, and 3100-B are in a stacked configuration and are configured to reflect light in the range of wavelengths Δλ in the red, green, and blue spectrums, respectively. When the switchable reflective element 3100C is illuminated with circularly polarized incident light 3012 having a circular polarization corresponding to the handedness of the CLC chirality (e.g., RHCP) and a wavelength in the range of wavelengths Δλ in the red, green, and blue spectrums, the reflected light 3016 exhibits a lens effect similar to a curved mirror lens. On the other hand, light with the orthogonal polarization (e.g., LHCP) is transmitted without interference.

[0183] FIG. 14 illustrates an embodiment of a stack or multiple switchable reflective elements 1232 having multiple switchable reflective elements 1404a, 1404b, 1404c, 1408a, 1408b, and 1408c. The reflective elements 1404a-1404c are configured to have a first negative refractive power, and the reflective elements 1408a-1408c are configured to have a second negative refractive power. The reflective elements 1404a and 1408a can be configured to reflect a first range of wavelengths (e.g., about 5-10 nm around red). The reflective elements 1404b and 1408b can be configured to reflect a second range of wavelengths (e.g., about 5-10 nm around green). The reflective elements 1404c and 1408c can be configured to reflect a third range of wavelengths (e.g., about 5-10 nm around blue). Each of the reflective elements 1404a, 1404b, 1404c, 1408a, 1408b, and 1408c is sandwiched between a pair of electrodes 1173. A selected one of the reflective elements 1404a, 1404b, 1404c, 1408a, 1408b, and 1408c can be switched on or off by applying a voltage across the pair of electrodes 1173 that bounds the selected one of the reflective elements 1404a, 1404b, 1404c, 1408a, 1408b, and 1408c.

[0184] In various embodiments, each of the multiple switchable reflective elements in the stack 1232 can comprise, for example, a liquid crystal diffraction grating, a polymer dispersed liquid crystal grating structure, and / or a polarization grating structure. In various embodiments, each of the multiple switchable reflective elements can be switched on or off in a frame sequential manner on a pixel-by-pixel basis. The switchable reflective elements can comprise diffractive optical elements, such as diffractive lenses.

[0185] Additionally, in various embodiments, the stack of reflective elements 1232 can be integrated with a deformable membrane (e.g., a variable power reflector 1032) to provide additional control for adjusting the divergent optical power of the reflective stack.

[0186] 12, image content from an image projection device 1282 (e.g., a spatial light modulator) is launched into a waveguide 2700 via an optical coupling element 2050. In various embodiments, the optical coupling element 2050 can comprise a polarizing beam splitter. Light from the waveguide 2700 is directed towards the reflector 1232 by an external coupling element associated with the waveguide 2700 (e.g., external coupling element 5700). In various embodiments, a light recycling system, such as a polarization-based light recycling system comprising an array of retarders, as discussed above with respect to FIG. 11, can be used in the example display device illustrated in FIG. 12 to redirect any light from the waveguide 2700 that is directed towards the user's eye 210 to the reflector 1232. Light that is outcoupled from the waveguide 2700 and directed to the variable power reflector can be reflected from the variable power reflector by switching one of the reflective elements such that the user's eye 210 receives the light from the display at a particular divergence (or in some cases, no divergence, but rather, collimation) and therefore perceives the light as originating from an object at a particular depth in front of the wearer, such as near or far away from the wearer. Note that light from the surrounding environment (also referred to herein as the world) 510 surrounding the display device is transmitted through the reflector 1232 towards the user's eye 210.

[0187] Although not shown, the waveguide 2700 in Figures 11 and 12 may include a stack of waveguides, as described above with reference to Figure 6. A combination of a waveguide and a stack of variable reflectors 1032 or a stack of switchable reflective elements 1232 may be useful in some cases to provide increased ability to provide a desired depth.

[0188] It should be understood that each of the processes, methods, and algorithms described herein and / or depicted in the figures may be embodied in code modules executed by one or more physical computing systems, hardware computer processors, application-specific circuits, and / or electronic hardware configured to execute specific and particular computer instructions, and thus may be fully or partially automated. For example, a computing system may include a general-purpose computer (e.g., a server) or a special-purpose computer programmed with specific computer instructions, special-purpose circuits, etc. The code modules may be compiled, linked into an executable program, installed in a dynamic link library, or written in an interpreted programming language. In some implementations, certain operations and methods may be performed by circuitry specific to a given function.

[0189] Furthermore, certain implementations of the functionality of the present disclosure may be sufficiently mathematically, computationally, or technically complex that special purpose hardware (utilizing appropriate specialized executable instructions) or one or more physical computing devices may be required to implement the functionality, e.g., due to the amount or complexity of the calculations involved, or to provide results in substantially real-time. For example, a video may contain many frames, each frame may have millions of pixels, and specifically programmed computer hardware is required to process the video data to provide the desired image processing task or application in a commercially reasonable amount of time.

[0190] The code modules or any type of data may be stored on any type of non-transitory computer readable medium, such as physical computer storage devices, including hard drives, solid state memory, random access memory (RAM), read only memory (ROM), optical disks, volatile or non-volatile storage devices, combinations of the same, and the like. In some embodiments, the non-transitory computer readable medium may be part of one or more of the local processing and data module (140), the remote processing module (150), and the remote data repository (160). The methods and modules (or data) may also be transmitted (e.g., as part of a carrier wave or other analog or digital propagating signal) generated on a variety of computer readable transmission media, including wireless-based and wired / cable-based media, and may take a variety of forms (e.g., as part of a single or multiplexed analog signal, or as multiple separate digital packets or frames). The results of the disclosed processes or process steps may be stored persistently or otherwise in any type of non-transitory tangible computer storage device or communicated via a computer readable transmission medium.

[0191] Any process, block, state, step, or functionality in the flow diagrams described herein and / or depicted in the accompanying figures should be understood as potentially representing a code module, segment, or portion of code that includes one or more executable instructions for implementing a specific function (e.g., logical or arithmetic) or step in the process. The various processes, blocks, states, steps, or functionality may be combined, rearranged, added, deleted, modified, or otherwise altered from the illustrative examples provided herein. In some embodiments, additional or different computing systems or code modules may perform some or all of the functionality described herein. The methods and processes described herein are not limited to any particular sequence, and the blocks, steps, or states associated therewith may also be performed in other sequences as appropriate, e.g., serially, in parallel, or in some other manner. Tasks or events may be added to or removed from the disclosed exemplary embodiments. Furthermore, the separation of various system components in the implementations described herein is for illustrative purposes and should not be understood as requiring such separation in all embodiments. It should be understood that the program components, methods, and systems described may generally be integrated together in a single computer product or packaged into multiple computer products.

[0192] In the foregoing specification, the invention has been described with reference to specific embodiments thereof. It will be apparent, however, that various modifications and changes can 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.

[0193] Indeed, it should be understood that each of the systems and methods of the present disclosure has several innovative aspects, none 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.

[0194] 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, although features may be described above as acting in a combination and may even be initially 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 variation of the subcombination. No single feature or group of features is necessary or essential to every embodiment.

[0195] In particular, it should be understood that conditional statements used herein, such as "can," "could," "might," "may," "eg," and the like, 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 suggest 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 or not those features, elements, and / or steps should 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, and the like. The term "or" is also 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. In addition, the articles "a," "an," and "the," as used in this application and the appended claims, should be interpreted to mean "one or more" or "at least one," unless otherwise specified. Similarly, although 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 depicted, or in the sequential order, or that all of the depicted operations need not be performed to achieve desirable results. Additionally, the figures may diagrammatically depict one or more exemplary processes in the form of a flow chart. However, other operations not depicted may also be incorporated within the diagrammatically depicted exemplary methods and processes. For example, one or more additional operations may be performed before, after, simultaneously with, or during any of the depicted operations. In addition, operations may be rearranged or reordered in other embodiments.In some situations, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the program components and systems described may generally be integrated together in a single software product or packaged into multiple software products. Additionally, other implementations are within the scope of the following claims. In some cases, the actions recited in the claims may be performed in a different order and still achieve desirable results.

[0196] Thus, the claims are not intended to be limited to the implementations shown in the specification but are to be accorded the widest scope consistent with the disclosure, the principles and novel features disclosed herein.

Claims

1. A display device, comprising: a waveguide configured to propagate visible light in a direction parallel to a major surface of the waveguide and to outcouple the visible light in a direction perpendicular to the major surface under total internal reflection; a deformable mirror configured to reflect visible light having a first polarization; Equipped with the deformable mirror comprises at least one of one or more notch reflectors or one or more cholesteric liquid crystal (CLC) layers, the one or more notch reflectors configured to reflect light within a wavelength range, each of the CLC layers comprising a plurality of chiral structures, each of the chiral structures comprising a plurality of liquid crystal molecules extending parallel to a layer depth direction and being continuously rotated in a first rotation direction, an arrangement of the liquid crystal molecules of the chiral structures varying periodically in a lateral direction perpendicular to the layer depth direction such that the one or more CLC layers are configured to Bragg-reflect incident light; The waveguide is configured to outcouple the visible light towards the deformable mirror.

2. 2. The display device of claim 1, wherein the deformable mirror comprises one or more CLC layers, different ones of which are configured to reflect visible light having wavelengths in wavelength ranges corresponding to different ones of red, green, or blue light, while transmitting light having wavelengths outside of the wavelength ranges.

3. 2. The display device of claim 1, wherein the deformable mirror comprises one or more CLC layers, each of the chiral structures of the CLC layers comprising a plurality of liquid crystal molecules extending in a layer depth direction at least with a helical pitch, and different ones of the one or more CLC layers having different helical pitches.

4. 10. The display device of claim 1, wherein the deformable mirror comprises one or more CLC layers, different ones of the one or more CLC layers having substantially the same optical power.

5. 2. The display device of claim 1, wherein the deformable mirror comprises one or more notch reflectors, each of the notch reflectors configured to reflect visible light having the first polarization, each of the notch reflectors comprising one or more cholesteric liquid crystal (CLC) layers, each of the CLC layers comprising a plurality of chiral structures, each of the chiral structures comprising a plurality of liquid crystal molecules extending in a layer depth direction and being continuously rotated in a first rotation direction, and an arrangement of the liquid crystal molecules of the chiral structures varies periodically in a lateral direction perpendicular to the layer depth direction such that the one or more CLC layers are configured to Bragg-reflect incident light.

6. 6. The display device of claim 5, wherein different ones of the one or more notch reflectors have different optical powers.

7. 6. The display device of claim 5, further comprising a half-wave plate corresponding to each of the one or more notch reflectors.

8. 10. The display device of claim 1, wherein the waveguide comprises a cholesteric liquid crystal grating configured to outcouple a portion of the visible light propagating within the waveguide toward the deformable mirror.

9. The display device of claim 1 , wherein the deformable mirror is configured to redirect the visible light directed by the waveguide towards the deformable mirror back towards the waveguide.

10. 10. The display device of claim 9, wherein the deformable mirror has a front side and a rear side, the rear side being positioned closer to the waveguide than the front side, and the deformable mirror is configured to allow at least a portion of light transmitted from an external light source positioned on the front side of the deformable mirror to pass through the deformable mirror.

11. 2. The display device of claim 1, further comprising a frame configured to position the waveguide in front of a wearer's eye such that the waveguide has a front side and a rear side, the rear side being positioned closer to the eye than the front side, and the deformable mirror being positioned on the front side and configured to redirect light from the waveguide toward the wearer's eye.

12. 12. The display device of claim 11, further comprising a light projector configured to output the visible light toward the waveguide, the deformable mirror configured to reflect the visible light having the first polarization while transmitting light from an external light source located in front of the deformable mirror.

13. 13. The display device of claim 12, further comprising one or more internal coupling elements positioned relative to the waveguide to redirect the visible light from the light projector into the waveguide.

14. 12. The display device of claim 11, further comprising one or more external coupling elements positioned relative to the waveguide to selectively extract a portion of the visible light propagating within the waveguide and direct the extracted visible light towards the deformable mirror, from which the light is redirected back through the waveguide and into the eye of the wearer.

15. 15. The display device of claim 14, wherein the one or more outcoupling elements comprise a cholesteric liquid crystal grating.

16. A display device, comprising: a waveguide configured to propagate visible light in a direction parallel to a major surface of the waveguide and to outcouple the visible light in a direction perpendicular to the major surface under total internal reflection; a deformable mirror configured to reflect visible light having a first polarization; Equipped with the deformable mirror comprises at least one of one or more notch reflectors or one or more cholesteric liquid crystal (CLC) layers, the one or more notch reflectors configured to reflect light within a wavelength range, each of the CLC layers comprising a plurality of chiral structures, each of the chiral structures comprising a plurality of liquid crystal molecules extending parallel to a layer depth direction and being continuously rotated in a first rotation direction, an arrangement of the liquid crystal molecules of the chiral structures varying periodically in a lateral direction perpendicular to the layer depth direction such that the one or more CLC layers are configured to Bragg-reflect incident light; A display device, wherein the waveguide comprises a cholesteric liquid crystal grating configured to outcouple a portion of the visible light propagating in the waveguide towards the deformable mirror.

17. the deformable mirror comprises the one or more CLC layers; different ones of the one or more CLC layers are configured to reflect visible light having wavelengths in wavelength ranges corresponding to different ones of red, green, or blue light, while transmitting light having wavelengths outside of the wavelength ranges; each of the chiral structures of the CLC layer comprises a plurality of liquid crystal molecules extending in the layer depth direction at least with a helical pitch, different ones of the one or more CLC layers having different helical pitches; or Different ones of the one or more CLC layers have substantially the same refractive power.

17. The display device of claim 16, wherein the at least one of

18. 17. The display device of claim 16, wherein the deformable mirror comprises the one or more notch reflectors, each of the notch reflectors configured to reflect visible light having the first polarization, each of the notch reflectors comprising one or more cholesteric liquid crystal (CLC) layers, each of the CLC layers comprising a plurality of chiral structures, each of the chiral structures comprising a plurality of liquid crystal molecules extending in a layer depth direction and being continuously rotated in a first rotation direction, and an arrangement of the liquid crystal molecules of the chiral structures varies periodically in a lateral direction perpendicular to the layer depth direction such that the one or more CLC layers are configured to Bragg-reflect incident light.

19. 20. The display device of claim 18, wherein different ones of the one or more notch reflectors have different optical powers.

20. 17. The display device of claim 16, wherein the deformable mirror is configured to redirect the visible light directed by the waveguide towards the deformable mirror back towards the waveguide.

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