Broadband adaptive lens assembly for augmented reality display

Abstract

To provide a broadband adaptive lens assembly for a suitable augmented reality display.SOLUTION: A display device comprises a waveguide configured to direct light in a lateral direction parallel to an output surface of the waveguide. The waveguide is configured to outcouple the guided light through an output surface. The display device comprises a broadband adaptive lens assembly configured to in-couple and diffract the out-coupled light from the waveguide. The broadband adaptive lens assembly comprises a first waveplate lens comprising a liquid-crystal (LC) layer arranged such that the waveplate lens has a birefringence (Δ n) that varies in a radially outward direction from a 450nm region of the first waveplate lens and is configured to diffract the out-coupled light within a range of wavelengths including at least from the center to the 630nm at diffractive efficiencies greater than 90%. The broadband adaptive lens assembly is configured to be selectively switched between a plurality of states having different optical powers.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of priority to U.S. Provisional Patent Application No. 62 / 577,672, filed October 26, 2017, and entitled "BROADBAND ADAPTIVE LENS ASSEMBLY FOR AUGMENTED REALITY DISPLAY," the contents of which are incorporated herein by reference in their entirety.

[0002] (Incorporated by reference) This application is related to the following patent applications: U.S. Patent Application No. 14 / 555,585, filed November 27, 2014, and published on July 23, 2015, as U.S. Patent Publication No. 2015 / 0205126; U.S. Patent Application No. 14 / 690,401, filed April 18, 2015, and published on October 22, 2015, as U.S. Patent Publication No. 2015 / 0302652; The entirety of U.S. Patent Application No. 14 / 212,961, now U.S. Patent No. 9,417,452, filed March 14, 2014, issued August 16, 2016, and U.S. Patent Application No. 14 / 331,218, filed July 14, 2014, published October 29, 2015 as U.S. Patent Publication No. 2015 / 0309263, are each incorporated by reference.

[0003] The present disclosure relates to display systems, and more particularly to augmented and virtual reality display systems. [Background technology]

[0004] 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 or can be perceived as real. Virtual reality or "VR" scenarios typically involve the presentation of digital or virtual image information without transparency to other actual real-world visual input, while augmented reality or "AR" scenarios typically involve the presentation of digital or virtual image information as an augmentation to the user's visualization of the real world around them. Mixed reality or "MR" scenarios are a type of AR scenario that typically involve virtual objects integrated into and responsive to the natural world. For example, in MR scenarios, AR image content is perceived as appearing occluded by or otherwise interacting with objects in the real world.

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

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

[0007] In one aspect, a display device includes a waveguide configured to guide light in a lateral direction parallel to an output surface of the waveguide. The waveguide is further configured to outcouple the guided light through the output surface. The display device additionally includes a broadband adaptive lens assembly configured to incouple and diffract the outcoupled light from the waveguide through the waveguide. The broadband adaptive lens assembly includes a first waveplate lens having a birefringence (Δn) that varies radially outward from a central region of the first waveplate lens and including a liquid crystal (LC) layer arranged such that the waveplate lens is configured to diffract the outcoupled light within a wavelength range that includes at least 450 nm to 630 nm with a diffraction efficiency greater than 90%. The broadband adaptive lens assembly is configured to be selectively switched between a plurality of states having different refractive powers.

[0008] In another aspect, a broadband adaptive lens assembly for a display device includes a first waveplate lens, the first waveplate lens having a birefringence (Δn) that varies radially outward from a central region of the first waveplate lens, the first waveplate lens comprising a liquid crystal (LC) layer having LC molecules arranged such that the LC molecules are configured to diffract light within a wavelength range extending from 450 nm to 630 nm with a diffraction efficiency greater than 90%. The broadband adaptive lens assembly additionally includes a switchable waveplate configured to be electrically activated and deactivated. The broadband adaptive lens assembly is configured to be selectively switched between at least two lens states, including a first lens state configured to impart a first lens effect according to a first refractive power and modify the polarization of light passing through the broadband adaptive lens assembly, and a second lens state configured to impart a second lens effect according to a second refractive power and preserve the polarization of light passing through the broadband adaptive lens assembly.

[0009] In another aspect, a broadband adaptive lens assembly for a display device includes a first waveplate lens comprising a liquid crystal (LC) layer formed on a substrate. The LC layer has LC molecules arranged such that the first waveplate lens has a birefringence (Δn) that varies radially outward from a central region of the LC layer and is configured to diffract light within a wavelength range spanning at least 450 nm to 630 nm with a diffraction efficiency greater than 90%. Those of the LC molecules closest to the substrate generally have the same orientation direction at a different location at the same radius from the central region. The broadband adaptive lens assembly is configured to be selectively switched between at least two lens states. The first lens state is configured to provide a first lens effect according to a first refractive power and alter the polarization of light passing through the broadband adaptive lens assembly. The second lens state is configured to provide a second lens effect according to a second refractive power and preserve the polarization of light passing through the broadband adaptive lens assembly.

[0010] In another aspect, an integrated broadband adaptive lens assembly for a display device comprises a first electrode, a second electrode, and a liquid crystal (LC) layer stack interposed between the first and second electrodes. The LC layer stack comprises a switchable liquid crystal (LC) layer comprising unpolymerized LC molecules interposed between first and second polymerized LC layers, each comprising polymerized LC molecules. LC molecules in the switchable LC layer adjacent to LC molecules in the first polymerized LC layer are generally stretched in a first direction. LC molecules in the switchable LC layer adjacent to LC molecules in the second polymerized LC layer are generally stretched in a second direction intersecting the first direction. The switchable LC layer comprises LC molecules configured such that under a first voltage condition across the first and second electrodes, the polarization of incident light passing therethrough is preserved, while under a second voltage condition across the first and second electrodes, the polarization of incident light passing therethrough is altered.

[0011] In another aspect, a display device includes a pair of adaptive lens assemblies in an optical path, each of which includes a corresponding switchable waveplate configured to diffract light within a wavelength range including at least 450 nm to 630 nm with a diffraction efficiency greater than 90% and to switch between first and second states to selectively alter the polarization state of light passing therethrough. The adaptive lens assemblies have optical powers with opposite signs.

[0012] In another aspect, an adaptive lens assembly includes one or more waveplate lenses and one or more switchable waveplates aligned within an optical path. Each of the one or more waveplate lenses is configured to diffract outcoupled light within a wavelength range including at least 450 nm to 630 nm with a diffraction efficiency greater than 90%, modify the polarization state of light passing therethrough, and provide a first refractive power for light having a first polarization and a second refractive power for light having a second polarization. Each of the one or more switchable waveplates is selectively switchable between a first state configured to diffract outcoupled light within a wavelength range including at least 450 nm to 630 nm with a diffraction efficiency greater than 90% and to pass light therethrough without modifying the polarization state of the light, and a second state configured to modify the polarization state of light passing therethrough.

[0013] In another aspect, a wearable augmented reality head-mountable display system includes a light modulation system configured to output light and form an image, a head-mountable frame, one or more waveguides attached to the frame and configured to receive light from the light modulation system, and a pair of adaptive lens assemblies, with the one or more waveguides disposed between the adaptive lens assemblies. Each of the adaptive lens assemblies includes one or more waveplate lenses configured to diffract outcoupled light within a wavelength range including at least 450 nm to 630 nm with a diffraction efficiency greater than 90%, provide a first refractive power for light having a first polarization, and provide a second refractive power for light having a second polarization. Each of the adaptive lens assemblies additionally includes one or more switchable waveplates in its optical path, each of the one or more switchable waveplates configured to diffract outcoupled light within a wavelength range including at least 450 nm to 630 nm with a diffraction efficiency greater than 90%, and selectively alter the polarization state of light passing therethrough. The adaptive lens assembly is configured to provide individual optical powers that are adjustable in response to application of individual electrical signals.

[0014] In another aspect, a method for integrating a broadband adaptive lens assembly includes forming a lower stack and an upper stack. The lower stack includes a first electrode layer formed on a first substrate, a first matching layer formed on the first electrode layer, and a first polymerized LC layer on the first matching layer. The upper stack includes a second electrode layer formed on a second substrate, a second matching layer formed on the second electrode layer, and a second polymerized LC layer on the second matching layer. The method additionally includes, after forming the lower and upper stacks, stacking the upper and lower stacks so that the first and second polymerized LC layers face each other, the stacking step including forming spacers to create a gap between the upper and lower stacks. The method additionally includes filling the gap with unpolymerized LC molecules to form a switchable liquid crystal (LC) layer. The step of forming the switchable LC layer includes the steps of self-aligning LC molecules in the switchable LC layer adjacent to LC molecules in the first polymerized LC layer so that they are generally stretched in a first direction, and self-aligning LC molecules in the switchable LC layer adjacent to LC molecules in the second polymerized LC layer so that they are generally stretched in a second direction that intersects the first direction.

[0015] In another aspect, a method for fabricating a broadband waveplate lens assembly includes providing a transparent substrate and forming a matching layer on the transparent substrate. The matching layer is configured to align liquid crystal (LC) molecules formed thereon according to a waveplate lens pattern. The method additionally includes forming an LC layer on the matching layer. LC molecules in the LC layer directly adjacent to the matching layer align according to the waveplate lens pattern, with the LC molecules in the LC layer at a given radius from a central region of the waveplate lens pattern having elongation directions that are generally aligned in the same direction. The LC layer is configured to diffract light within a wavelength range that includes at least 450 nm to 630 nm with a diffraction efficiency greater than 90%. The broadband adaptive lens assembly is configured to be selectively switchable between a plurality of states having different refractive powers.

[0016] In another aspect, a head-mounted display system is configured to project light to a user's eye and display augmented reality image content within the user's field of view. The head-mounted display system includes a frame configured to be supported on the user's head. The display system also includes an eyepiece disposed on the frame. At least a portion of the eyepiece is transparent and positioned in front of the user's eye so that, when the user wears the head-mounted display, the transparent portion transmits light from an environment in front of the user to the user's eye, providing a view of the environment in front of the user. The eyepiece is configured to emit light into the user's eye and display augmented reality image content within the user's field of view. The at least one switchable lens assembly includes a diffractive liquid crystal lens assembly including a twisted nematic switchable lens. The twisted nematic switchable lens includes an active layer of twisted nematic liquid crystal, a first layer of polymerized liquid crystal adjacent to the active layer of twisted nematic liquid crystal, and a second layer of polymerized liquid crystal adjacent to the active layer of twisted nematic liquid crystal. The active layer of twisted nematic liquid crystal is disposed between the first and second layers of polymerized liquid crystal. The nematic switchable lens further comprises first and second electrodes disposed to apply an electric field to the active layer of twisted nematic liquid crystal. The first and second electrodes are on opposite sides of the active layer and the first and second layers of polymerized liquid crystal such that the active layer and the first and second layers of polymerized liquid crystal are disposed between the first and second electrodes. The head-mounted display additionally comprises electronics configured to vary the refractive power of the switchable lens by applying an electrical signal to the electrodes. The at least one switchable lens assembly is configured to transmit light from an environment in front of the user to the user's eyes.

[0017] In another aspect, a head-mounted display system is configured to project light into a user's eye and display augmented reality image content within the user's field of view. The head-mounted display system includes a frame configured to be supported on the user's head. The system also includes an eyepiece disposed on the frame. At least a portion of the eyepiece is transparent and is positioned in front of the user's eye such that, when the user wears the head-mounted display, the transparent portion transmits light from an environment in front of the user to the user's eye to provide a view of the environment in front of the user. The eyepiece is configured to emit light into the user's eye and display augmented reality image content within the user's field of view. The system also includes at least one switchable lens assembly comprising a diffractive liquid crystal lens assembly. The diffractive liquid crystal lens assembly includes an active layer comprising a twisted nematic liquid crystal diffractive lens, first and second retarders comprising polymerized liquid crystals on opposite sides of the active layer, and first and second electrodes positioned to apply an electric field to the twisted nematic liquid crystal active layer, the first and second electrodes on opposite sides of the active layer. The system further includes electronics configured to vary the refractive power of the switchable lenses by applying an electrical signal to the electrodes, and at least one switchable lens configured to transmit light from an environment in front of the user to the user's eye.

[0018] In another aspect, a head-mounted display system is configured to project light onto a user's eye and display augmented reality image content within the user's field of view. The head-mounted display system includes a frame configured to be supported on the user's head. The system also includes an eyepiece disposed on the frame. At least a portion of the eyepiece is transparent and is disposed in front of the user's eye such that, when the user wears the head-mounted display, the transparent portion transmits light from an environment in front of the user to the user's eye, providing a view of the environment in front of the user. The eyepiece is configured to emit light into the user's eye and display augmented reality image content within the user's field of view. The system also includes at least one switchable lens assembly including a plurality of switchable lenses. Each of the switchable lenses has at least two states. The switchable lens assembly has different refractive powers for different states of the plurality of lenses. The switchable lens assembly has different refractive powers for different wavelengths when the plurality of lenses are set to specific states. The system further includes electronics in communication with the switchable lenses and configured to alter the states of the plurality of lenses, the electronics configured to cause different lenses in the plurality of switchable lenses to be in different states for different wavelengths.

[0019] In another aspect, a method of fabricating an eyepiece for augmented reality eyewear configured to direct light into a wearer's eye to present an image to the wearer includes providing a substrate. The method additionally includes forming a first lens region on the substrate, the first lens region comprising a transparent liquid crystal lens having refractive power. The method further includes providing a second region on the substrate that is transparent and has no refractive power.

[0020] In another aspect, a head-mounted display system is configured to project light onto a user's eye and display augmented reality image content within the user's field of view. The head-mounted display system includes a frame configured to be supported on the user's head. The display system also includes an eyepiece disposed on the frame. At least a portion of the eyepiece is transparent and positioned in front of the user's eye so that, when the user wears the head-mounted display, the transparent portion transmits light from an environment in front of the user to the user's eye, providing a view of the environment in front of the user. The eyepiece is configured to emit light into the user's eye and display augmented reality image content within the user's field of view. The display system also includes at least one switchable lens assembly including a plurality of switchable lenses, each of the switchable lenses having at least two states. A variation in the state of the switchable lenses changes the state of the at least one switchable assembly. The switchable lens assembly has different optical powers for different states of the plurality of lenses. The switchable lens assembly has different refractive powers for different wavelengths when the plurality of lenses are set to specific states. The display system further includes electronics in communication with the switchable lenses and configured to alter the states of the plurality of lenses. The display device is configured to emit light of a first color into the user's eye at a first time and light of a second color into the user's eye at a second time to display augmented reality image content in the user's field of view. The electronics are configured to cause at least one of the lenses to be in a different state at the first and second times to provide an image in the first and second colors.

[0021] For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages are described herein. Of course, it is to be understood that not necessarily all such objects or advantages need be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that the invention can be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages without necessarily achieving other objects or advantages.

[0022] All of these embodiments are intended to be within the scope of the invention disclosed herein. These and other embodiments will become readily apparent to those skilled in the art from the following detailed description taken in conjunction with the accompanying figures, and the invention is not limited to any particular disclosed embodiment. The present invention provides, for example, the following. (Item 1) 1. A display device, comprising: a waveguide configured to guide light in a lateral direction parallel to an output surface of the waveguide, the waveguide further configured to outcouple the guided light through the output surface; a broadband adaptive lens assembly configured to incouple and diffract outcoupled light from the waveguide therethrough, the broadband adaptive lens assembly comprising a first waveplate lens, the first waveplate lens comprising a liquid crystal (LC) layer arranged such that the first waveplate lens has birefringence (Δn) that varies in a radial outward direction from a central region of the first waveplate lens and is configured to diffract the outcoupled light within a wavelength range that includes at least 450 nm to 630 nm with a diffraction efficiency greater than 90%; Equipped with A display device wherein the broadband adaptive lens assembly is configured to be selectively switched between a plurality of states having different optical powers. (Item 2) Item 10. The display device of item 1, wherein the Δn of the first wave plate lens increases with increasing wavelength (λ) within the wavelength range. (Item 3) Item 1, a display device according to item 1, wherein the broadband adaptive lens assembly comprises a plurality of liquid crystal layers, each of which comprises liquid crystal molecules that are continuously twisted in the layer normal direction. (Item 4) When the outcoupled light has a polarization, the broadband adaptive lens assembly is configured to be selectively switched between at least two lens states, the at least two lens states comprising: a first lens state configured to converge or diverge outcoupled light from the waveguide according to a first optical power and to modify the polarization of the outcoupled light; a second lens state configured to converge or diverge the outcoupled light from the waveguide according to a second optical power without altering the polarization of the outcoupled light; and 4. The display device according to any one of items 1-3, comprising: (Item 5) Item 5. The display device of item 4, wherein the broadband adaptive lens assembly further comprises a second wave plate lens having a second liquid crystal layer and a switchable wave plate interposed between the first wave plate lens and the second wave plate lens, and the broadband adaptive lens assembly is configured to be selectively switched between the at least two states by electrically activating and deactivating the switchable wave plate. (Item 6) Item 6. The display device of item 5, wherein the switchable waveplate comprises twisted nematic liquid crystal, and wherein electrical activation alters the degree of twist of the twisted nematic liquid crystal across the thickness of the switchable waveplate. (Item 7) 6. The display device of item 5, wherein when the switchable waveplate is activated, it acts as a half-waveplate configured to invert the handedness of circularly polarized light passing therethrough, while when the switchable waveplate is deactivated, it is configured to preserve the handedness of the circularly polarized light passing therethrough. (Item 8) 8. The display device of claim 7, wherein the first and second wave plate lenses are each configured to invert the handedness of the circularly polarized light passing therethrough, and when the switchable wave plate is activated, the first and second wave plate lenses impart refractive powers having opposite signs. (Item 9) 8. The display device of claim 7, wherein the first and second wave plate lenses are each configured to invert the handedness of the circularly polarized light passing therethrough, and when the switchable wave plate is deactivated, the first and second wave plate lenses impart refractive powers having the same sign. (Item 10) 6. The display device of item 5, wherein when the switchable wave plate is deactivated, the broadband adaptive lens assembly has a net refractive power having a magnitude proportional to the sum of the magnitudes of the refractive powers of the first and second wave plate lenses, while when the switchable wave plate is in an activated state, the adaptive lens assembly has a net refractive power having a magnitude proportional to the difference between the magnitudes of the refractive powers of the first and second wave plate lenses. (Item 11) Item 11. The display device of item 10, wherein the first and second wave plate lenses have refractive powers having approximately the same magnitude so that when the switchable wave plate is electrically activated, the net refractive power is approximately zero. (Item 12) Item 5. The display device of item 4, wherein the first wave plate lens is electrically switchable, and the broadband adaptive lens assembly further includes a second wave plate lens that is electrically switchable, the second wave plate lens comprising a second liquid crystal (LC) layer, the second liquid crystal (LC) layer arranged such that the second wave plate lens has birefringence (Δn) that varies in a radial outward direction from a central region of the second wave plate lens and is configured to diffract outcoupled light within the wavelength range with a diffraction efficiency greater than 90%, and the broadband adaptive lens assembly is configured to be selectively switched between the at least two states by switching one or both of the first and second wave plate lenses. (Item 13) Item 13. The display device of item 12, wherein when activated, the first and second switchable wave plates each act as half-wave plates configured to invert the handedness of circularly polarized light passing therethrough, while when deactivated, the first and second switchable wave plates each are configured to preserve the handedness of the circularly polarized light passing therethrough. (Item 14) Item 14. The display device of item 13, wherein the first and second waveplate lenses are each configured to have refractive powers with opposite signs when circularly polarized light passing therethrough has opposite polarizations. (Item 15) Item 15. The display device of item 14, wherein the broadband adaptive lens assembly has a net refractive power having a magnitude proportional to the sum of the magnitudes of the refractive powers of the first and second wave plate lenses, such that for a given polarization of the outcoupled light, the broadband adaptive lens assembly is configured to be selectively switched between four states by selectively activating one or both of the first and second wave plate lenses. (Item 16) 1. A broadband adaptive lens assembly for a display device, comprising: a first waveplate lens, the first waveplate lens comprising a liquid crystal (LC) layer having LC molecules arranged such that the first waveplate lens has birefringence (Δn) that varies in a radial outward direction from a central region of the first waveplate lens and is configured to diffract light within a wavelength range spanning at least 450 nm to 630 nm with a diffraction efficiency greater than 90%; a switchable waveplate, the switchable waveplate configured to be electrically activated and deactivated; Equipped with The broadband adaptive lens assembly is configured to be selectively switched between at least two lens states, the at least two lens states comprising: a first lens state configured to impart a first lens effect according to a first refractive power and to modify polarization of light passing through the broadband adaptive lens assembly; a second lens state configured to provide a second lens effect according to a second refractive power and to preserve polarization of light passing through the broadband adaptive lens assembly; and a wideband adaptive lens assembly including: (Item 17) Item 17. The wideband adaptive lens assembly of item 16, wherein the switchable wave plate is a switchable half-wave plate (HWP) configured to reverse the handedness of circularly polarized light when deactivated, and to preserve the handedness of the circularly polarized light when activated. (Item 18) Item 18. The wideband adaptive lens assembly of item 17, wherein the switchable HWP comprises a twisted nematic liquid crystal (TN LC) switch, the TN LC switch comprising a switchable TN LC layer configured to reverse the polarization of linearly polarized light when electrically deactivated and to preserve the polarization of the linearly polarized light when electrically activated, the switchable TN LC layer comprising a plurality of elongated nematic LC molecules having a twist angle that varies in a layer normal direction of the switchable TN LC layer. (Item 19) Item 19. The wideband adaptive lens assembly of item 18, wherein the switchable TN LC switch comprises a switchable TN LC layer formed between an upper matching layer and a lower matching layer, the upper matching layer configured to align directors of the elongated nematic LC molecules immediately adjacent to the upper matching layer in a first lateral direction, and the lower matching layer configured to align directors of the elongated nematic LC molecules immediately adjacent to the lower matching layer in a second lateral direction intersecting the first lateral direction. (Item 20) 20. The broadband adaptive lens assembly of claim 19, wherein one or both of the upper matching layer and the lower matching layer comprises a polymer layer comprising polyimide or polyamide. (Item 21) 20. The broadband adaptive lens assembly of claim 19, wherein one or both of the upper matching layer and the lower matching layer comprise patterned nanostructures. (Item 22) Item 22. The wideband adaptive lens assembly of item 21, wherein one or both of the upper matching layer and the lower matching layer act as an electrode or electrodes configured to apply an electric field across the switchable TN LC layer. (Item 23) Item 19. The wideband adaptive lens assembly of item 18, wherein the TN LC switch comprises a pair of interlaced first and second electrodes on one side of the switchable TN LC layer, and the TN LC switch is configured to be switched by applying an electric field between the pair of interlaced first and second electrodes. (Item 24) Item 19. The wideband adaptive lens assembly of item 18, wherein the switchable half-wave plate (HWP) comprises the TN LC switch interposed between a pair of wideband quarter-wave plate (QWP) stacks. (Item 25) Item 25. The broadband adaptive lens assembly of item 24, wherein each of the broadband QWP stacks comprises a plurality of directly stacked polymerized TN LC layers. (Item 26) Item 19. The wideband adaptive lens assembly of item 18, wherein the switchable HWP comprises the switchable TN LC layer directly interposed between a pair of one or more polymerized TN LC layers, the polymerized TN LC layer in contact with the switchable TN LC layer serving as a matching layer for aligning stretched nematic LC molecules of the switchable TN LC layer. (Item 27) Item 26. The wideband adaptive lens assembly of item 25, wherein the directly stacked polymerized TN LC layers each have a thickness across which the elongated nematic LC molecules are twisted by a twist angle, and adjacent ones of the directly stacked TN LC layers have different twist angles. (Item 28) Item 17. The wideband adaptive lens assembly of item 16, further comprising a second waveplate lens, the second waveplate lens comprising a second liquid crystal (LC) layer having LC molecules arranged such that the second waveplate lens has birefringence (Δn) that varies in a radial outward direction from a central region of the second waveplate lens and is configured to diffract light within a wavelength range extending from at least 450 nm to 630 nm with a diffraction efficiency greater than 90%, and the switchable waveplate is interposed between the first waveplate lens and the second waveplate lens. (Item 29) 1. A broadband adaptive lens assembly for a display device, comprising: 1. A first waveplate lens comprising a liquid crystal (LC) layer formed on a substrate, the LC layer having LC molecules arranged such that the first waveplate lens has birefringence (Δn) that varies in a radial outward direction from a central region of the LC layer and is configured to diffract light in a wavelength range extending from at least 450 nm to 630 nm with a diffraction efficiency greater than 90%, and those of the LC molecules closest to the substrate generally have the same orientation direction at different locations at the same radius from the central region. Equipped with The broadband adaptive lens assembly is configured to be selectively switched between at least two lens states, the at least two lens states comprising: a first lens state configured to impart a first lens effect according to a first refractive power and to modify polarization of light passing through the broadband adaptive lens assembly; a second lens state configured to provide a second lens effect according to a second refractive power and to preserve polarization of light passing through the broadband adaptive lens assembly; and a wideband adaptive lens assembly including: (Item 30) 30. The wideband adaptive lens assembly of item 29, wherein the LC layer is arranged in a plurality of concentric zones, each of which has a range of radii within which the LC molecules closest to the substrate generally have the same orientation direction. (Item 31) Item 31. The wideband adaptive lens assembly of item 30, wherein those of the LC molecules closest to the substrate have an azimuthal twist angle that varies with radius according to a mathematical function. (Item 32) Item 30. The broadband adaptive lens assembly of item 29, wherein the Δn of the LC layer increases with increasing wavelength within the wavelength range. (Item 33) Item 33. The wideband adaptive lens assembly of item 32, wherein the LC molecules within the same concentric zone generally have the same twist angle at different depths of the LC layer. (Item 34) 30. The broadband adaptive lens assembly of item 29, wherein the first wave plate lens comprises a plurality of LC layers, each of the LC layers comprising LC molecules that are successively twisted in a layer normal direction. (Item 35) Item 35. The wideband adaptive lens assembly of item 34, wherein the LC layers each have a thickness across which the LC molecules are twisted by a twist angle, and the LC layers have different twist angles. (Item 36) Item 35. The wideband adaptive lens assembly of item 34, wherein adjacent ones of the LC layers forming an interface have opposite twist angles. (Item 37) Item 37. The wideband adaptive lens assembly of item 36, wherein the LC molecules of adjacent ones of the LC layer at approximately the same depth from the interface generally have the same orientation. (Item 38) 30. The broadband adaptive lens assembly of item 29, wherein the first wave plate lens is interposed between a pair of transparent electrodes and configured to be electrically activated and deactivated by application of an electrical signal to the transparent electrodes. (Item 39) Item 39. The broadband adaptive lens assembly of item 38, further comprising a first passive waveplate lens having a first refractive power (P1) and a second passive waveplate lens having a second refractive power (P2), wherein the first waveplate lens is in contact with and interposed between the first and second passive waveplate lenses. (Item 40) 40. The broadband adaptive lens assembly of claim 39, wherein the first waveplate lens is configured to have a third refractive power (P3) when deactivated and approximately zero refractive power when activated. (Item 41) Item 41. The broadband adaptive lens assembly of item 40, wherein the first and second passive waveplate lenses are each half-waveplates, and the first waveplate lens is configured to be a half-waveplate when deactivated. (Item 42) 30. The broadband adaptive lens assembly of item 29, wherein the first and second passive waveplate lenses and the first waveplate lens are integrated into a single stack. (Item 43) 1. An integrated broadband adaptive lens assembly for a display, comprising: a first electrode, a second electrode, and a liquid crystal (LC) layer stack interposed between the first electrode and the second electrode; Equipped with The LC layer stack comprises: A switchable liquid crystal (LC) layer comprising unpolymerized LC molecules sandwiched between first and second polymerized LC layers, each of which comprises polymerized LC molecules. Equipped with LC molecules in the switchable LC layer adjacent to LC molecules in the first polymerized LC layer are generally elongated in a first direction; LC molecules in the switchable LC layer adjacent to LC molecules in the second polymerized LC layer are generally elongated in a second direction that is intersecting the first direction; Item 44: The switchable LC layer comprises LC molecules configured such that under a first voltage condition across the first and second electrodes, the polarization of incident light passing therethrough is preserved, while under a second voltage condition across the first and second electrodes, the polarization of incident light passing therethrough is altered. Item 44. The integrated broadband adaptive lens assembly of item 43, wherein the switchable LC layer contacts at least one of the first and second polymerized LC layers. (Item 45) Item 45. The integrated broadband adaptive lens assembly of item 44, wherein the switchable LC layer comprises twisted nematic LC molecules having a net twist angle of about 90 degrees such that under the second voltage condition, the switchable LC layer converts linearly polarized light having a first polarization direction into linearly polarized light having a second polarization direction perpendicular to the first direction. (Item 46) Item 46. The integrated broadband adaptive lens assembly of item 45, wherein the first and second polymerized LC layers each comprise twisted nematic LC molecules and act as quarter wave plates. (Item 47) Item 46. The integrated broadband adaptive lens assembly of item 45, wherein the LC layer stack comprises a plurality of polymerized LC layers formed on opposite sides of the switchable LC layer, each of the polymerized LC layers forming an interface with an adjacent one of the polymerized LC layers, and wherein the LC molecules adjacent the interface in each of the polymerized LC layers are generally elongated in the same direction as the LC molecules adjacent the interface in an adjacent one of the polymerized LC layers. (Item 48) Item 45. The integrated broadband adaptive lens assembly of item 44, wherein the LC molecules of the switchable LC layer and each of the first and second polymerized LC layers are arranged such that the birefringence (Δn) of the LC molecules varies in a radially outward direction from a central region. (Item 49) Item 49. The integrated broadband adaptive lens assembly of item 48, wherein the Δn increases with increasing wavelength (λ) within a wavelength range including at least 450 nm to 630 nm. (Item 50) Item 49. The integrated broadband adaptive lens assembly of item 48, wherein the LC layer stack comprises two switchable LC layers, each comprising twisted nematic LC molecules that are successively twisted in the layer normal direction. (Item 51) Item 51. The integrated broadband adaptive lens assembly of item 50, wherein the twisted nematic LC molecules of the two switchable LC layers are twisted symmetrically with respect to the interface formed between the two switchable LC layers by a net angle of about 60 degrees to 80 degrees. (Item 52) Item 49. The integrated broadband adaptive lens assembly of item 48, wherein the switchable LC layer comprises twisted nematic LC molecules configured such that under the second voltage condition, the switchable LC layer acts as a half-wave plate. (Item 53) Item 49. The integrated broadband adaptive lens assembly of item 48, wherein the first and second polymerized LC layers each comprise twisted nematic LC molecules and act as half-wave plates. (Item 54) 1. A display device, comprising: a pair of adaptive lens assemblies in the optical path, each of the adaptive lens assemblies comprising: a corresponding switchable waveplate configured to diffract light within a wavelength range including at least 450 nm to 630 nm with a diffraction efficiency greater than 90% and to switch between first and second states to selectively alter the polarization state of light passing therethrough; Equipped with A display device wherein the adaptive lens assemblies have refractive powers with opposite signs. (Item 55) Item 55. The display device of item 54, wherein the adaptive lens assemblies each have an individual optical power that is adjustable based on the state of a switchable waveplate of the adaptive lens assembly. (Item 56) Item 56. The display device of item 55, further comprising a controller, configured such that when a first refractive power of a first one of the pair of adaptive lens assemblies is at a first value, a second refractive power of a second one of the pair of adaptive lens assemblies is correspondingly adjusted to a second value so that the net refractive power of the pair of adaptive lens assemblies remains approximately constant. (Item 57) The constant value is approximately 0 m -1 Item 57. The display device according to item 56, (Item 58) each of the adaptive lens assemblies comprising first and second waveplate lenses interposed by a corresponding switchable waveplate of the lens assembly; Item 55. The display device of item 54, wherein each of the waveplate lenses is configured to modify the polarization state of light passing therethrough. (Item 59) Item 55. The display device of item 54, wherein the display device further comprises a waveguide assembly interposed between the pair of adaptive lens assemblies, the waveguide assembly comprising a waveguide configured to externally couple light propagating therethrough into one of the adaptive lens assemblies. (Item 60) Item 60. The display device of item 59, wherein each of the adaptive lens assemblies comprises a plurality of wave plate lenses and a plurality of switchable wave plates, the wave plate lenses and the switchable wave plates being stacked alternately. (Item 61) Item 61. The display device of item 60, wherein different ones of the switchable waveplates and waveplate lenses have different refractive powers. (Item 62) 1. An adaptive lens assembly, comprising: One or more waveplate lenses and one or more switchable waveplates aligned in the optical path Equipped with each of the one or more waveplate lenses is configured to diffract the outcoupled light within a wavelength range including at least 450 nm to 630 nm with a diffraction efficiency greater than 90%, modify the polarization state of light passing therethrough, and provide a first refractive power for light having a first polarization and a second refractive power for light having a second polarization; each of the one or more switchable waveplates is configured to diffract the outcoupled light within a wavelength range that includes at least 450 nm to 630 nm with a diffraction efficiency greater than 90%; a first state, the first state configured to pass the light therethrough without altering the polarization state of the light; a second state, the second state configured to alter the polarization state of the light passing therethrough; and an adaptive lens assembly selectively switchable between: (Item 63) Item 63. The adaptive lens assembly of item 62, wherein one or both of the waveplate lens and the switchable waveplate comprise liquid crystal. (Item 64) Item 63. The adaptive lens assembly of item 62, wherein each of the one or more switchable wave plates in the second state is a half-wave plate configured to invert the handedness of circularly polarized light. (Item 65) Item 63. The adaptive lens assembly of item 62, wherein each of the switchable wave plates is interposed between a pair of the one or more wave plate lenses. (Item 66) Item 66. The adaptive lens assembly of item 65, wherein the adaptive lens assembly comprises a plurality of the wave plate lenses and a plurality of the switchable wave plates, the wave plate lenses and the switchable wave plates being stacked alternately. (Item 67) 1. A wearable augmented reality head-mountable display system, comprising: a light modulation system configured to output light and form an image; A head mountable frame; one or more waveguides, the one or more waveguides mounted to the frame and configured to receive light from the light modulation system; a pair of adaptive lens assemblies, the one or more waveguides being disposed between the adaptive lens assemblies, each of the adaptive lens assemblies comprising: one or more waveplate lenses configured to diffract the outcoupled light in a wavelength range including at least 450 nm to 630 nm with a diffraction efficiency greater than 90%, and to provide a first refractive power for light having a first polarization and a second refractive power for light having a second polarization; one or more switchable waveplates in the optical path, each of the one or more switchable waveplates configured to diffract the outcoupled light within a wavelength range including at least 450 nm to 630 nm with a diffraction efficiency greater than 90% and to selectively alter the polarization state of light passing therethrough; a pair of adaptive lens assemblies configured to provide separate optical powers that are adjustable in response to application of separate electrical signals; 1. A wearable augmented reality head-mountable display system comprising: (Item 68) 1. A method for integrating a broadband adaptive lens assembly, comprising: forming a lower stack, forming a first electrode layer on a first substrate; forming a first matching layer on the first electrode layer; forming a first polymerized LC layer on the first matching layer; and forming an upper stack, forming a second electrode layer on a second substrate; forming a second matching layer on the second electrode; forming a second polymerized LC layer on the second matching layer; and After forming the lower and upper stacks, stacking the upper stack and the lower stack so that the first and second polymerized LC layers face each other, wherein stacking includes forming a spacer to create a gap between the upper and lower stacks; filling the gap with unpolymerized LC molecules to form a switchable liquid crystal (LC) layer; Including, The method of forming the switchable LC layer includes self-aligning LC molecules in the switchable LC layer adjacent to LC molecules in the first polymerized LC layer to be generally elongated in a first direction, and self-aligning LC molecules in the switchable LC layer adjacent to LC molecules in the second polymerized LC layer to be generally elongated in a second direction intersecting the first direction. (Item 69) Item 69. The method of item 68, wherein forming the switchable LC layer comprises configuring LC molecules of the switchable LC layer such that under a first voltage condition across the first and second electrode layers, the polarization of incident light passing therethrough is preserved, while under a second voltage condition across the first and second electrodes, the polarization of the incident light passing therethrough is altered. (Item 70) Item 70. The method of item 69, wherein the switchable LC layer contacts at least one of the first and second polymerized LC layers. (Item 71) 71. The method of claim 70, wherein self-aligning the LC molecules in the switchable LC layer comprises forming twisted nematic LC molecules with a net twist angle of about 90 degrees, such that under the second voltage condition the switchable LC layer converts linearly polarized light having a first polarization direction into linearly polarized light having a second polarization direction perpendicular to the first direction. (Item 72) Item 71. The method of item 70, wherein the first and second polymerized LC layers each comprise twisted nematic LC molecules and act as quarter wave plates. (Item 73) Item 71. The method of item 70, wherein forming the lower stack and forming the upper stack each include forming a plurality of polymerized LC layers, each of the polymerized LC layers forming an interface with an adjacent one of the polymerized LC layers, and wherein LC molecules adjacent the interface in each of the polymerized LC layers are generally elongated in the same direction as LC molecules adjacent the interface of an adjacent one of the polymerized LC layers. (Item 74) Item 71. The method of item 70, wherein the LC molecules of the switchable LC layer and each of the first and second polymerized LC layers are arranged such that the birefringence (Δn) of the LC molecules varies in a radial outward direction from a central region within the switchable LC layer and each of the first and second polymerized LC layers. (Item 75) Item 75. The method according to item 74, wherein the Δn increases with increasing wavelength (λ) within a wavelength range including at least 450 nm to 630 nm. (Item 76) 75. The method of claim 74, wherein the LC layer stack comprises two switchable LC layers, each comprising twisted nematic LC molecules that are successively twisted in the layer normal direction. (Item 77) 77. The method of claim 76, comprising forming two switchable LC layers that are symmetrically twisted about the interface between the two switchable LC layers by a net angle of about 60 to 80 degrees. (Item 78) Item 75. The method of item 74, wherein the switchable LC layer comprises twisted nematic LC molecules configured such that under the second voltage condition the switchable LC layer acts as a half wave plate. (Item 79) Item 75. The method of item 74, wherein the first and second polymerized LC layers each comprise twisted nematic LC molecules and act as half-wave plates. (Item 80) 1. A method of fabricating a broadband waveplate lens assembly, comprising: providing a transparent substrate; forming a matching layer on the transparent substrate, the matching layer configured to align liquid crystal (LC) molecules formed thereon according to a waveplate lens pattern; forming an LC layer on the matching layer, wherein LC molecules of the LC layer directly adjacent to the matching layer align according to the waveplate lens pattern having elongation directions such that LC molecules of the LC layer at a given radius from a central region of the waveplate lens pattern are aligned in generally the same direction; Including, the LC layer is configured to diffract light within a wavelength range that includes at least 450 nm to 630 nm with a diffraction efficiency greater than 90%; The method, wherein the broadband adaptive lens assembly is configured to be selectively switched between a plurality of states having different optical powers. (Item 81) Item 81. The method of item 80, wherein forming the LC layer comprises arranging LC molecules of the LC layer such that birefringence (Δn) of the LC layer increases with increasing wavelength (λ) within a wavelength range including at least 450 nm to 630 nm. (Item 82) Item 81. The method of item 80, further comprising forming a second LC layer on the LC layer, wherein the LC layer and the second LC layer each comprise twisted nematic LC molecules that are continuously twisted in a layer normal direction. (Item 83) Item 83. The method of item 82, wherein the twisted nematic LC molecules of the LC layer and the second LC layer are twisted symmetrically with respect to the interface formed by the LC layer and the second LC layer by a net angle of about 60 degrees to 80 degrees. (Item 84) Item 81. The method of item 80, wherein forming the matching layer includes constructing an optical matching layer by illuminating the matching layer with two light beams having orthogonal polarizations. (Item 85) Item 81. The method of item 80, wherein forming the matching layer includes constructing an optical matching layer by illuminating the matching layer with a light beam that is partially diffracted through a master lens, the master lens comprising LC crystals arranged according to the waveplate lens pattern. (Item 86) Item 81. The method of item 80, wherein forming the matching layer includes forming a nanoimprinted matching layer having nanostructures whose extension direction has the same dependence on radius from the central region of the wave plate lens as the extension direction of LC molecules of the LC layer. (Item 87) Item 87. The method of item 86, wherein forming the matching layer includes forming a plurality of concentric zones, each of the zones having nanostructures elongated in the same direction. (Item 88) the transparent substrate is a sacrificial carrier wafer, and the method further comprises: forming a release layer interposed between the matching layer and the LC layer; attaching a target substrate onto the LC layer; transferring the LC layer to the transparent substrate by separating the LC layer from the release layer; 81. The method according to item 80, comprising: (Item 89) Item 81. The method of item 80, wherein the method includes forming the broadband waveplate lens assembly on a selected portion of the transparent substrate that is smaller than a major surface area of ​​the transparent substrate. (Item 90) Item 89. The method of item 89, wherein forming the LC layer comprises selectively depositing the LC molecules over the selected portion. (Item 91) forming the LC layer blanket depositing an unpolymerized LC layer over the substrate; selectively exposing the unpolymerized LC layer over the selected portion while leaving a portion of the unpolymerized LC layer unpolymerized to form a polymerized LC layer; removing a portion of the unpolymerized LC layer; Item 89. The method of item 89, comprising: (Item 92) Item 90. The method of item 89, wherein forming the matching layer comprises blanket depositing a matching layer over the transparent substrate and selectively configuring the LC molecules over the selected area to align the LC molecules of the LC layer formed thereon according to the waveplate pattern, and forming the LC layer comprises blanket depositing an unpolymerized LC layer over the substrate. (Item 93) Item 90. The method of item 89, wherein forming the alignment layer comprises forming patterned nanostructures over the selected area to align LC molecules of the LC layer formed thereon according to the waveplate pattern, and forming the LC layer comprises blanket depositing an unpolymerized LC layer over the substrate. (Item 94) 1. A head-mounted display system configured to project light onto a user's eye and display augmented reality image content within the user's field of view, the head-mounted display system comprising: a frame configured to be supported on the user's head; an eyepiece disposed on the frame, at least a portion of the eyepiece being transparent and disposed in a location in front of the user's eye such that, when the user wears the head mounted display, the transparent portion transmits light from an environment in front of the user to the user's eye to provide a view of the environment in front of the user, the eyepiece being configured to emit light into the user's eye and display augmented reality image content in the user's field of view; at least one switchable lens assembly, the at least one switchable lens assembly comprising a diffractive liquid crystal lens assembly, the diffractive liquid crystal lens assembly comprising a twisted nematic switchable lens, the twisted nematic switchable lens comprising: an active layer of twisted nematic liquid crystal; a first layer of polymerized liquid crystal adjacent to the twisted nematic liquid crystal active layer; a second layer of polymerized liquid crystal adjacent to the active layer of twisted nematic liquid crystal, the active layer of twisted nematic liquid crystal being disposed between the first and second layers of polymerized liquid crystal; first and second electrodes positioned to apply an electric field to the active layer of twisted nematic liquid crystal, the first and second electrodes being on opposite sides of the active layer and the first and second layers of polymerized liquid crystal such that the active layer and the first and second layers of polymerized liquid crystal are disposed between the first and second electrodes; at least one switchable lens assembly comprising: electronics configured to vary the optical power of the switchable lens by applying an electrical signal to the electrodes; and Equipped with A head-mounted display system, wherein the at least one switchable lens assembly is configured to transmit light from an environment in front of the user to the user's eyes. (Item 95) Item 95. The display device of item 94, wherein the active layer comprises a diffractive lens. (Item 96) Item 96. The display device of any of items 94 or 95, wherein the first and second layers of polymerized liquid crystal comprise a diffractive lens. (Item 97) 97. A display device according to any of items 94-96, wherein the first and second layers of polymerized liquid crystal are alignment layers for the active liquid crystal layer. (Item 98) 98. A display device according to any of items 94-97, further comprising first and second alignment layers, the first and second alignment layers being positioned adjacent to the first and second layers of polymerized liquid crystal, respectively, the first and second alignment layers on respective sides of the first and second layers of polymerized liquid crystal being opposite the active layer. (Item 99) 99. A display device according to any of items 94-98, wherein at least the first electrode comprises interdigitated electrodes. (Item 100) A display device described in any of items 94-99, wherein the at least one switchable lens assembly is configured to transmit light directed into the user's eye and display augmented reality image content in the user's field of view. (Item 101) A display device as described in any of items 94-100, wherein the at least one switchable lens assembly comprises two switchable lens assemblies, one arranged to transmit light directed into the user's eye and display augmented reality image content in the user's field of view, and both configured to transmit light from the environment in front of the user to the user's eye. (Item 102) 1. A head-mounted display system configured to project light onto a user's eye and display augmented reality image content within the user's field of view, the head-mounted display system comprising: a frame configured to be supported on the user's head; an eyepiece disposed on the frame, at least a portion of the eyepiece being transparent and disposed in a location in front of the user's eye such that, when the user wears the head mounted display, the transparent portion transmits light from an environment in front of the user to the user's eye to provide a view of the environment in front of the user; the eyepiece comprising: an eyepiece configured to emit light into the user's eye and display augmented reality image content in the user's field of view; At least one switchable lens assembly comprising a diffractive liquid crystal lens assembly, the diffractive liquid crystal lens assembly comprising: an active layer comprising a twisted nematic liquid crystal diffractive lens; first and second retarders comprising polymerized liquid crystals on opposite sides of the active layer; first and second electrodes positioned to apply an electric field to the twisted nematic liquid crystal active layer, the first and second electrodes being on opposite sides of the active layer; at least one switchable lens assembly comprising: electronics configured to vary the optical power of the switchable lens by applying an electrical signal to the electrodes; and Equipped with 1. A head-mounted display system, wherein the at least one switchable lens is configured to transmit light from an environment in front of the user to the user's eyes. (Item 103) Item 103. The display device of item 102, wherein the first and second retarders on opposite sides of the twisted nematic liquid crystal active layer are adjacent to the twisted nematic liquid crystal active layer. (Item 104) Item 104. The display device of item 102 or 103, wherein the polymerized liquid crystal comprising the first and second retarders is an alignment layer for the active liquid crystal layer. (Item 105) Item 105. A display device according to any one of items 102-104, wherein the first and second retarders are disposed between the first and second electrodes. (Item 106) 106. A display device as described in any of items 102-105, wherein the first and second retarders respectively comprise first and second quarter-wave retarders comprising polymerized liquid crystal. (Item 107) A display device described in any of items 102-106, further comprising first and second matching layers, the first and second matching layers being positioned adjacent to the first and second retarders, respectively, and the first and second matching layers on respective sides of the first and second retarders being opposite the active layer. (Item 108) Item 108. A display device according to any one of items 102-107, wherein at least the first electrode comprises interdigitated electrodes. (Item 109) A display device described in any of items 102-108, wherein the at least one switchable lens assembly is configured to transmit light directed into the user's eye and display augmented reality image content in the user's field of view. (Item 110) A display device described in any of items 102-109, wherein the at least one switchable lens assembly comprises two switchable lens assemblies, one arranged to transmit light directed into the user's eye and display augmented reality image content in the user's field of view, and both configured to transmit light from the environment in front of the user to the user's eye. (Item 111) 1. A head-mounted display system configured to project light onto a user's eye and display augmented reality image content within the user's field of view, the head-mounted display system comprising: a frame configured to be supported on the user's head; an eyepiece disposed on the frame, at least a portion of the eyepiece being transparent and disposed in a location in front of the user's eye such that, when the user wears the head mounted display, the transparent portion transmits light from an environment in front of the user to the user's eye to provide a view of the environment in front of the user, the eyepiece being configured to emit light into the user's eye and display augmented reality image content in the user's field of view; at least one switchable lens assembly comprising a plurality of switchable lenses, each of the switchable lenses having at least two states, the switchable lens assembly having different refractive powers for different states of the plurality of lenses, the switchable lens assembly having different refractive powers for different wavelengths when the plurality of lenses are set to a particular state; electronics that communicate with the switchable lenses and alter the state of the plurality of lenses; and Equipped with The head mounted display system, wherein the electronics are configured to cause different lenses in the plurality of switchable lenses to be in different states for different wavelengths. (Item 112) Item 112. A head-mounted display system as described in Item 111, wherein when the plurality of switchable lenses are set to a first state combination, the lens assembly produces a refractive power for a green wavelength and a refractive power for a different red wavelength, and when the plurality of switchable lenses are set to a second state combination, the lens assembly produces a refractive power for a green wavelength and a refractive power for a different red wavelength. (Item 113) Item 113. A head-mounted display system as described in Item 112, wherein when the plurality of switchable lenses are set to the second state combination, the refractive power for the red wavelength is closer to the refractive power for the green wavelength when the plurality of lenses are set to the first state combination than to the refractive power for the green wavelength when the plurality of lenses are set to the second state combination. (Item 114) Item 114. The head-mounted display system of item 113, wherein the electronics are configured to set the plurality of lenses to the second state for the red wavelength and the first state for the green wavelength for a given refractive power target. (Item 115) 1. A method of fabricating an eyepiece for augmented reality eyewear configured to direct light into a wearer's eye to present an image to the wearer, the method comprising: Providing a substrate; forming a first lens region on the substrate, the first lens region comprising a transparent liquid crystal lens having refractive power; providing a second region on the substrate that is transparent and has no optical power; A method comprising: (Item 116) Item 116. The method of item 115, wherein the first lens region is surrounded by the second transparent region having no lens power. (Item 117) Item 117. The method of item 115 or 116, wherein the second lens region comprises at least 40% of the area of ​​the substrate. (Item 118) Item 117. The method of item 115 or 116, wherein the second lens region comprises at least 30% of the area of ​​the substrate. (Item 119) Item 117. The method of item 115 or 116, wherein the second lens region comprises at least 20% of the area of ​​the substrate. (Item 120) Item 117. The method of item 115 or 116, wherein the second lens region comprises at least 10% of the area of ​​the substrate. (Item 121) 121. The method of any of items 115-120, comprising selectively depositing liquid crystal on the first lens area and not on the second transparent area. (Item 122) 122. The method of any of items 115-121, further comprising depositing a liquid crystal on the substrate. (Item 123) Item 123. The method of item 122, further comprising selectively polymerizing the liquid crystal in the first lens region and not in the second transparent region. (Item 124) Item 124. The method of item 123, further comprising removing unpolymerized liquid crystal from the second transparent region. (Item 125) Item 125. The method of item 124, further comprising providing a lens pattern on the first lens area and not on the second transparent area. (Item 126) Item 126. The method of item 125, further comprising providing a uniform alignment pattern on the second transparent area. (Item 127) Item 127. The method of item 126, further comprising illuminating the second transparent area with uniform linearly polarized light and not illuminating the first lens area. (Item 128) 121. The method of any of items 115-120, comprising nanoimprinting the first lens area and not nanoimprinting the second transparent area with a lens pattern that will provide refractive power when a liquid crystal is deposited thereon and aligned therewith. (Item 129) Item 129. The method of item 128, comprising nanoimprinting the second transparent area with a uniform imprint pattern that will not provide refractive power when liquid crystal is deposited thereon. (Item 130) Item 130. The method of item 129, further comprising depositing liquid crystal on the first lens region and the second transparent region. (Item 131) Item 112. A head-mounted display system as described in Item 111, configured to emit different colored lights into the user's eyes at different times and display the augmented reality image content in the user's field of view. (Item 132) Item 132. The head-mounted display system of item 131, wherein the electronics is configured to cause different lenses in the plurality of switchable lenses to be in different states at different times when the different colored lights are emitted into the user's eyes and the augmented reality image content is displayed in the user's field of view. (Item 133) 1. A head-mounted display system configured to project light onto a user's eye and display augmented reality image content within the user's field of view, the head-mounted display system comprising: a frame configured to be supported on the user's head; an eyepiece disposed on the frame, at least a portion of the eyepiece being transparent and disposed in a location in front of the user's eye such that, when the user wears the head mounted display, the transparent portion transmits light from an environment in front of the user to the user's eye to provide a view of the environment in front of the user, the eyepiece being configured to emit light into the user's eye and display augmented reality image content in the user's field of view; at least one switchable lens assembly comprising a plurality of switchable lenses, each of the switchable lenses having at least two states, wherein a variation in the state of the switchable lenses changes the state of the plurality of switchable lenses and the at least one switchable assembly, the switchable lens assembly having different refractive powers for different states of the plurality of switchable lenses, the switchable lens assembly having different refractive powers for different wavelengths when the plurality of lenses are set to a particular state; electronics that communicate with the switchable lenses and alter the state of the plurality of lenses; Equipped with the display device is configured to emit light of a first color into the eye of the user at a first time and light of a second color into the eye of the user at a second time to display augmented reality image content in the user's field of view; the electronics are configured to cause at least one of the lenses to be in a different state at the first and second times to provide images in the first and second colors. (Item 134) Item 134. The display system of item 133, wherein when the plurality of switchable lenses are set to a first state combination, the lens assembly produces a refractive power for the first color that is different from a refractive power for the second color, and when the plurality of switchable lenses are set to a second state combination, the lens assembly produces a refractive power for the first color that is different from a refractive power for the second color. (Item 135) Item 135. The display system of item 134, wherein when the plurality of switchable lenses are set to the second state combination, the refractive power for the first color is closer to the refractive power of the second color when the plurality of lenses are set to the first state combination than the refractive power for the second color when the plurality of lenses are set to the second state combination. (Item 136) Item 136. The display system of item 135, wherein the electronics are configured to set the plurality of lenses to the second state for the first color and the first state for a second wavelength for a given refractive power target. (Item 137) Item 134. A display system as described in Item 133, wherein when the plurality of switchable lenses are set to a first state combination, the lens assembly produces a refractive power for red that is different from a refractive power for green, and when the plurality of switchable lenses are set to a second state combination, the lens assembly produces a refractive power for red that is different from a refractive power for green. (Item 138) Item 138. The display system of item 137, wherein when the plurality of switchable lenses are set to the second state combination, the refractive power for the red color is closer to the refractive power for the green color when the plurality of lenses are set to the first state combination than to the refractive power for the green color when the plurality of lenses are set to the second state combination. (Item 139) Item 139. The display system of item 138, wherein the electronics are configured to set the plurality of lenses to the second state for the red wavelength and the first state for the green wavelength for a given refractive power target. (Item 140) Item 134. The display system of item 133, wherein the electronics are configured to cause at least one of the lenses to be in a different state at the first and second times to provide images in the first and second colors as if coming from the same depth. (Item 141) 141. The display system of any of items 130-140, wherein the plurality of switchable lenses comprises liquid crystals. (Item 142) 142. The display system of any of items 130-141, wherein the plurality of switchable lenses comprises waveplate lenses comprising a liquid crystal (LC) layer. (Item 143) 143. The display system of any of items 130-142, wherein the electronics are configured to cause at least one of the lenses to be in a different state at the first and second times to provide images in the first and second colors with reduced differences in focus of the images resulting from chromatic aberrations compared to at least one of the lenses being in the same state at the first and second times. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 illustrates a user's view of an augmented reality (AR) device.

[0024] [Figure 2] FIG. 2 illustrates a conventional display system for simulating a three-dimensional image for a user.

[0025] [Figure 3] 3A-3C illustrate the relationship between the radius of curvature and the radius of focus.

[0026] [Figure 4A] Figure 4A illustrates a representation of the accommodation-vergence response of the human visual system.

[0027] [Figure 4B] FIG. 4B illustrates an example of different accommodation and convergence states of a pair of a user's eyes.

[0028] [Figure 4C] FIG. 4C illustrates an example of a top-down view representation of a user viewing content through a display system.

[0029] [Figure 4D] FIG. 4D illustrates another example of a top-down view representation of a user viewing content through a display system.

[0030] [Figure 5] FIG. 5 illustrates aspects of an approach for simulating three-dimensional images by correcting for wavefront divergence.

[0031] [Figure 6] FIG. 6 illustrates an embodiment of a waveguide stack for outputting image information to a user.

[0032] [Figure 7] FIG. 7 illustrates an example of an output beam output by a waveguide.

[0033] [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.

[0034] [Figure 9A] FIG. 9A illustrates a cross-sectional side view of an example of a set of stacked waveguides, each including an internal coupling optical element.

[0035] [Figure 9B] FIG. 9B illustrates a perspective view of the multiple stacked waveguide embodiment of FIG. 9A.

[0036] [Figure 9C] FIG. 9C illustrates a top-down plan view of the multiple stacked waveguide embodiment of FIGS. 9A and 9B.

[0037] [Figure 9D] FIG. 9D illustrates an example of a wearable display system.

[0038] [Figure 10] FIG. 10 illustrates an example of a display system comprising a pair of adaptive lens assemblies.

[0039] [Figure 11] Figure 11A illustrates an example of the display system of Figure 10 displaying virtual content to a user in a virtual depth plane, and Figure 11B illustrates an example of the display system of Figure 10 providing a user with a view of real-world content.

[0040] [Figure 12A] FIG. 12A illustrates an example of a waveplate lens assembly comprising a liquid crystal.

[0041] [Figure 12B] FIG. 12B illustrates an example of a switchable waveplate lens comprising a liquid crystal.

[0042] [Figure 13A] FIG. 13A illustrates a cross-sectional view of an example of a switchable waveplate layer comprising a layer of twisted nematic liquid crystal.

[0043] [Figure 13B]FIG. 13B illustrates an example of a switchable waveplate assembly comprising the switchable waveplate of FIG. 13A interposed between a pair of quarter-waveplates, in operation, the switchable waveplate being activated or deactivated.

[0044] [Figure 13C] FIG. 13C illustrates an example of a quarter wave plate comprising multiple layers of twisted nematic liquid crystal layers.

[0045] [Figure 13D] FIG. 13D illustrates an example of a switchable waveplate assembly comprising the switchable waveplate of FIG. 13A sandwiched between a pair of quarter-waveplates that are integrated into a single stack using an adhesive layer.

[0046] [Figure 13E] FIG. 13E illustrates an example of a switchable waveplate assembly comprising a layer of twisted nematic liquid crystal sandwiched between a pair of quarter-waveplates integrated as a single stack.

[0047] [Figure 13F] FIG. 13F illustrates an example of a switchable waveplate assembly comprising a layer of twisted nematic liquid crystal sandwiched between a pair of quarter-waveplates of FIG. 13C integrated into a single stack.

[0048] [Figure 14A] FIG. 14A illustrates a perspective view of one embodiment of a pair of transparent electrodes for switching layers of liquid crystal.

[0049] [Figure 14B] FIG. 14B illustrates a perspective view of another embodiment of a pair of transparent electrodes for switching layers of liquid crystal.

[0050] [Figure 14C] FIG. 14C illustrates a perspective view of an embodiment of a pair of vertically separated transparent electrodes for switching layers of liquid crystal.

[0051] [Figure 15] Figure 15A illustrates a plan view of an embodiment of a pair of horizontally interlaced transparent electrodes for switching layers of liquid crystal, and Figure 15B illustrates a cross-sectional view of an embodiment of a switchable waveplate assembly including the pair of horizontally interlaced transparent electrodes of Figure 15A.

[0052] [Figure 16A] FIG. 16A illustrates a plan view of an embodiment of a waveplate lens comprising a liquid crystal.

[0053] [Figure 16B] FIG. 16B illustrates a plan view of an embodiment of a waveplate lens comprising a liquid crystal.

[0054] [Figure 16C] FIG. 16C illustrates an example of a waveplate lens that provides different refractive powers, causing light passing through it to diverge or converge, depending on the polarization of the light and the side on which the light is incident.

[0055] [Figure 16D] FIG. 16D illustrates an example of a waveplate lens that provides different refractive powers, causing light passing through it to diverge or converge, depending on the polarization of the light and the side on which the light is incident.

[0056] [Figure 17A] FIG. 17A illustrates an example of an adaptive lens assembly comprising a waveplate lens and a switchable waveplate.

[0057] [Figure 17B] FIG. 17B illustrates an example of the adaptive lens assembly of FIG. 17A in operation with the switchable waveplate activated.

[0058] [Figure 17C] FIG. 17C illustrates an example of the adaptive lens assembly of FIG. 13A in which, in operation, the switchable waveplate is deactivated.

[0059] [Figure 18A] FIG. 18A illustrates an example of a display device comprising a waveguide between a pair of adaptive lens assemblies, each comprising a wave plate lens and a switchable wave plate, when the switchable wave plate is activated in operation.

[0060] [Figure 18B] FIG. 18B illustrates an embodiment of the display device of FIG. 18A in which, in operation, the switchable waveplate is deactivated.

[0061] [Figure 19A] FIG. 19A illustrates a plan view of an exemplary arrangement of liquid crystal molecules closest to a substrate of a broadband waveplate lens comprising liquid crystals.

[0062] [Figure 19B] FIG. 19B illustrates a broadband waveplate lens comprising liquid crystals arranged as illustrated in FIG. 19A that focuses light having a first circular polarization.

[0063] [Figure 19C] FIG. 19C illustrates a broadband waveplate lens comprising liquid crystals arranged as illustrated in FIG. 19A that diverges light having a second circular polarization.

[0064] [Figure 20] Figure 20A illustrates a plan view of an exemplary arrangement of liquid crystal molecules of a broadband waveplate lens comprising multiple layers of twisted nematic liquid crystal, and Figure 20B illustrates a cross-sectional view of an example of a broadband waveplate lens comprising multiple layers of twisted nematic liquid crystal.

[0065] [Figure 21] FIG. 21 illustrates a cross-sectional view of an example of a broadband waveplate lens comprising a layer of liquid crystal that has birefringence that increases with increasing wavelength.

[0066] [Figure 22A] FIG. 22A illustrates a cross-sectional view of an example of a deactivated switchable broadband waveplate lens that diverges and converts the polarization of light having a first circular polarization.

[0067] [Figure 22B] FIG. 22B illustrates a cross-sectional view of an example of a deactivated switchable broadband waveplate lens that focuses and converts the polarization of light having a second circular polarization.

[0068] [Figure 22C] FIG. 22C illustrates a cross-sectional view of an example of an activated switchable broadband waveplate lens that passes circularly polarized light without substantially converging or diverging it while preserving its polarization.

[0069] [Figure 23-1] Figure 23A illustrates an example of a broadband adaptive waveplate lens assembly comprising a pair of broadband switchable waveplate lenses, where both switchable waveplate lenses are deactivated in operation. Figure 23B illustrates the broadband adaptive waveplate lens assembly of Figure 23A, where one of the switchable waveplate lenses is activated in operation.

[0070] [Figure 23-2] Figure 23C illustrates the broadband adaptive waveplate lens assembly of Figure 23A with one of the switchable waveplate lenses activated in operation. Figure 23D illustrates an example of a broadband adaptive waveplate lens assembly comprising a pair of broadband switchable waveplate lenses with both switchable waveplate lenses activated in operation.

[0071] [Figure 24A] FIG. 24A illustrates an example of an integrated broadband adaptive waveplate lens assembly comprising a switchable broadband waveplate lens sandwiched between a pair of active broadband switchable waveplate lenses.

[0072] [Figure 24B] FIG. 24B illustrates the broadband adaptive waveplate lens assembly of FIG. 24A in operation as a broadband half-waveplate lens combination.

[0073] [Figure 24C] FIG. 24C illustrates the broadband adaptive waveplate lens assembly of FIG. 24B with the switchable broadband waveplate activated in operation.

[0074] [Figure 24D] FIG. 24D illustrates the broadband adaptive waveplate lens assembly of FIG. 24B with the switchable broadband waveplate deactivated in operation.

[0075] [Figure 25] 25A and 25B illustrate simulated diffraction efficiency versus wavelength in the visible spectrum for the broadband adaptive waveplate lens assembly of FIG. 24A with the switchable broadband waveplate activated and deactivated, respectively.

[0076] [Figure 26] Figure 26A illustrates the simulated actual versus target net refractive power of an exemplary broadband adaptive waveplate lens assembly comprising three broadband switchable waveplate lenses using a single lens state and multiple lens states for blue wavelengths, Figure 26B illustrates the simulated actual versus target net refractive power of an exemplary broadband adaptive waveplate lens assembly comprising three broadband switchable waveplate lenses using a single lens state and multiple lens states for green wavelengths, and Figure 26C illustrates the simulated actual versus target net refractive power of an exemplary broadband adaptive waveplate lens assembly comprising three broadband switchable waveplate lenses using a single lens state and multiple lens states for red wavelengths.

[0077] [Figure 27] 27A-27C illustrate an exemplary method for fabricating a broadband waveplate or broadband waveplate lens.

[0078] [Figure 28] FIG. 28 illustrates an exemplary method of constructing an alignment layer for aligning liquid crystal molecules in a broadband waveplate or broadband waveplate lens using two-beam exposure.

[0079] [Figure 29] 29A-29B illustrate an exemplary method of using a master lens to construct a broadband waveplate or alignment layer for aligning liquid crystal molecules within a broadband waveplate lens.

[0080] [Figure 30] 30A-30B illustrate an exemplary method of constructing a nanoimprinted alignment layer for aligning liquid crystal molecules in a broadband waveplate or broadband waveplate lens using a master lens and one-beam exposure. FIG. 30C illustrates an exemplary nanoimprinted alignment layer for aligning liquid crystal molecules in a broadband waveplate lens using the exemplary method of FIGS. 30A-30B.

[0081] [Figure 31] 31A-31C illustrate an exemplary method of fabricating a switchable broadband waveplate comprising liquid crystals or a switchable broadband waveplate lens comprising liquid crystals using a gap-filling process.

[0082] [Figure 32-1] 32A-32E illustrate an exemplary method of fabricating a switchable broadband waveplate comprising liquid crystals or a switchable broadband waveplate lens comprising liquid crystals using a layer transfer process. [Figure 32-2] 32A-32E illustrate an exemplary method of fabricating a switchable broadband waveplate comprising liquid crystals or a switchable broadband waveplate lens comprising liquid crystals using a layer transfer process.

[0083] [Figure 33] FIG. 33 illustrates an example of a switchable broadband waveplate comprising liquid crystal or a switchable broadband waveplate lens comprising liquid crystal formed on a portion of a substrate.

[0084] [Figure 34] FIG. 34 illustrates an exemplary method for forming a switchable broadband waveplate with liquid crystal or a switchable broadband waveplate lens with liquid crystal on a portion of a substrate by selective coating.

[0085] [Figure 35] 35A-35C illustrate an exemplary method of forming a switchable broadband waveplate comprising liquid crystal or a switchable broadband waveplate lens comprising liquid crystal on a portion of a substrate by blanket coating and subtractively removing a layer of liquid crystal.

[0086] [Figure 36] 36A-35C illustrate an exemplary method of forming a switchable broadband waveplate comprising liquid crystal or a switchable broadband waveplate lens comprising liquid crystal on a portion of a substrate by using selective optical patterning of an alignment layer.

[0087] [Figure 37] 37A-37B illustrate an exemplary method of forming a switchable broadband waveplate comprising liquid crystal or a switchable broadband waveplate lens comprising liquid crystal on a portion of a substrate by using selective nanoimprinting of an alignment layer.

[0088] Throughout the drawings, reference numbers may be reused to indicate correspondence between referenced elements. The drawings are provided to illustrate example embodiments described herein and are not intended to limit the scope of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0089] The AR system may display virtual content to a user or viewer while still allowing the user to see the world around them. Preferably, this content is displayed on a head-mounted display, for example, as part of eyewear, that projects image information into the user's eyes. In addition, the display may also transmit light from the surrounding environment to the user's eyes, allowing a view of that surrounding environment. As used herein, it should be understood that a "head-mounted" or "head-mountable" display is a display that can be mounted on the viewer's or user's head.

[0090] In some AR systems, the multiple waveguides may be configured to form virtual images at multiple virtual depth planes (also simply referred to herein as "depth planes"). Different waveguides of the multiple waveguides may have different refractive powers and may be formed at different distances from the user's eyes. The display system may also include multiple lenses that provide, or additionally provide, refractive power. The refractive power of the waveguides and / or lenses may provide images at different virtual depth planes. Undesirably, the waveguides and lenses may each increase the overall thickness, weight, and cost of the display.

[0091] Advantageously, in various embodiments described herein, an adaptive lens assembly may be utilized to provide variable optical power, e.g., to modify the wavefront divergence of light propagating through the lens assembly and provide a virtual depth plane at different perceived distances from the user. The adaptive lens assembly may include a pair of waveplate lenses with a switchable waveplate disposed therebetween. The first and second waveplate lenses may each be configured to alter the polarization state of light passing therethrough, and the switchable waveplate may be switchable between multiple states, e.g., a first state that allows light to pass without changing the polarization of the light, and a second state that alters the polarization of the light (e.g., by changing the handedness of the polarization). In some embodiments, one or both of the waveplate lenses may be switchable between these first and second states, and the intervening switchable waveplate may be omitted.

[0092] It should be understood that an adaptive lens assembly may comprise a stack of multiple waveplate lenses and multiple switchable waveplates. For example, an adaptive lens assembly may comprise multiple subassemblies comprising pairs of waveplate lenses with intervening switchable waveplates. In some embodiments, an adaptive lens assembly may include alternating waveplate lenses and switchable waveplates. Advantageously, such an alternating arrangement allows for reduced thickness and weight by having adjacent switchable waveplates share a common waveplate lens. In some embodiments, more than two discrete levels of optical power may be provided by switching the states of various combinations of switchable plates in the stack.

[0093] In some embodiments, the adaptive lens assembly, together with the waveguide assembly, forms a display device and forms images at different virtual depth planes. In various embodiments, the display device includes a pair of adaptive lens assemblies interposed by a waveguide assembly. The waveguide assembly includes a waveguide configured to propagate light (e.g., visible light) therein (e.g., via total internal reflection) and to outcouple the light. For example, the light may be outcoupled along an optical axis direction normal to a major surface of the waveguide. One of the pair of adaptive lens assemblies may be formed on a first side of the waveguide assembly and may be configured to provide variable refractive power, modify the wavefront of the light passing through the adaptive lens assembly, and form images at each of a plurality of virtual depth planes. For example, the adaptive lens assembly may converge or diverge the outcoupled light received from the waveguide assembly. To compensate for modifications of the real-world view due to convergence or divergence of ambient light propagating through the adaptive lens assembly and / or the waveguide assembly, the other of the pair of adaptive lens assemblies is additionally provided on a second side of the waveguide assembly opposite the first side. When the switchable waveplates of each adaptive lens assembly assume corresponding states, the adaptive lens assemblies may have optical powers with opposite signs such that the other of the adaptive lens assemblies corrects distortions caused by the adaptive lens assembly on the first side of the waveguide assembly.

[0094] Advantageously, utilizing a switchable waveplate switchable between two states for a continuously variable adaptive lens having a continuously variable optical element simplifies driving the adaptive lens assembly and reduces the computing power required to determine how to properly activate the adaptive lens assembly for a desired optical power. Additionally, by allowing the adaptive lens assembly to modify the wavefront divergence of light output by the waveguides, the number of waveguides required to provide multiple depth planes is reduced relative to an arrangement in which each waveguide provides a specific amount of wavefront divergence.

[0095] Reference is now made to the drawings, wherein like reference numerals refer to like parts throughout. Unless otherwise indicated, the drawings are schematic and are not necessarily drawn to scale.

[0096] Exemplary Display Systems FIG. 2 illustrates a conventional display system for simulating a three-dimensional image for a user. It should be understood that when a user's eyes are spaced apart and viewing a real object in space, each eye may have a slightly different view of the object, forming an image of the object at a different location on each eye's retina. This may be referred to as binocular disparity and may be utilized by the human visual system to provide the perception of depth. Conventional display systems simulate binocular disparity by presenting two distinct images 190, 200, one for each eye 210, 220, with slightly different views of the same virtual object, corresponding to the view of the virtual object as it would appear by each eye as if the virtual object were a real object at a desired depth. These images provide binocular cues that the user's visual system may interpret to derive the perception of depth.

[0097] Continuing with reference to FIG. 2 , the images 190 and 200 are spaced apart from the eyes 210 and 220 by a distance 230 on the z-axis. The z-axis is parallel to the viewer's optical axis when the viewer's eyes are fixating on an object at optical infinity directly in front of the viewer. The images 190 and 200 are flat and at a fixed distance from the eyes 210 and 220. Based on slightly different views of the virtual object in the images presented to each eye 210 and 220, the eyes may necessarily rotate so that the image of the object falls on a corresponding point on each eye's retina, maintaining single binocular vision. This rotation may cause the gaze of each eye 210 and 220 to converge on a point in space where the virtual object is perceived to reside. As a result, providing three-dimensional images traditionally involves manipulating the convergence and divergence of the user's eyes 210 and 220 and providing binocular cues that the human visual system interprets to provide the perception of depth.

[0098] However, creating a realistic and comfortable perception of depth is challenging. It should be understood that light from an object at different distances from the eye has a wavefront with different amounts of divergence. Figures 3A-3C illustrate the relationship between distance and light ray divergence. The distance between the object and the eye 210 is represented in order of decreasing distances R1, R2, and R3. As shown in Figures 3A-3C, light rays become more divergent as the distance to the object decreases. Conversely, as the distance increases, the light rays become more collimated. In other words, the light field generated by a point (an object or portion of an object) can be said to have a spherical wavefront curvature that is a function of the distance the point is from the user's eye. As the curvature increases, the distance between the object and the eye 210 decreases. While only a single eye 210 is illustrated in Figures 3A-3C and various other figures herein for clarity of illustration, the discussion regarding the eye 210 may apply to both eyes 210 and 220 of the viewer.

[0099] Continuing with reference to Figures 3A-3C, light from an object that a viewer's eye is fixating may have different wavefront divergences. Due to the different wavefront divergences, the light may be focused differently by the eye's lens, which in turn may require the lens to assume a different shape to form a focused image on the eye's retina. If a focused image is not formed on the retina, the resulting retinal blur acts as an accommodative cue, causing the shape of the eye's lens to change until a focused image is formed on the retina. For example, the accommodative cue may induce relaxation or contraction of the ciliary muscles surrounding the eye's lens, thereby modulating the force applied to the suspensory ligaments that hold the lens, thus changing the shape of the eye's lens and thereby forming a focused image of the fixated object on the eye's retina (e.g., the fovea) until retinal blur of the fixated object is eliminated or minimized. The process by which the eye's lens changes shape can be referred to as accommodation, and the shape of the eye's lens required to form a focused image of a fixated object on the eye's retina (e.g., the fovea) can be referred to as the state of accommodation.

[0100] Referring now to Figure 4A, a representation of the accommodation-vergence response of the human visual system is illustrated. Eye movement to fixate an object causes the eye to receive light from the object, which forms an image on each of the eye's retinas. The presence of retinal blur in the image formed on the retina can provide a cue for accommodation, and the relative location of the image on the retina can provide a cue for vergence. Accommodation cues cause accommodation, resulting in the eye's lens adopting a specific accommodation state in which a focused image of the object is formed on the eye's retina (e.g., the fovea). Conversely, vergence cues cause vergence movements (eye rotations) so that the images formed on each retina of each eye are at corresponding retinal points, maintaining single binocular vision. In these positions, the eyes can be said to adopt a specific vergence state. Continuing with reference to FIG. 4A , accommodation can be understood as the process by which the eyes achieve a particular accommodation state, and convergence can be understood as the process by which the eyes achieve a particular convergence state. As shown in FIG. 4A , the accommodation and convergence states of the eyes can change when the user fixates on a different object. For example, the accommodated state can change when the user fixates on a new object at a different depth on the z-axis.

[0101] 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 convergence-divergence and accommodation. As previously mentioned, vergence-divergence movements of the two eyes relative to one another (e.g., eye rotation such that the pupils move toward or away from one another, converging the eyes' lines of sight and fixating on an object) are closely linked to accommodation of the eye's lenses. Under normal conditions, changing the shape of the eye's lenses and shifting focus from one object to another at a different distance will automatically produce a corresponding change in vergence-divergence to the same distance, a relationship known as the "accommodation-divergence reflex." Similarly, a change in vergence-divergence will induce a corresponding change in lens shape under normal conditions.

[0102] 4B, an example of different accommodation and convergence states of the eyes is illustrated. Paired eye 222a fixates an object at optical infinity, while paired eye 222b fixates an object 221 at less than optical infinity. Notably, the convergence states of each pair of eyes are different: paired eye 222a points straight ahead, while paired eye 222 converges on object 221. The accommodation states of the eyes forming each pair of eyes 222a and 222b are also different, as represented by the different shapes of lenses 210a, 220a.

[0103] Unfortunately, many users of conventional "3-D" display systems may find such systems uncomfortable or may not perceive any depth perception due to a mismatch between accommodation and convergence states in these displays. As previously mentioned, many stereoscopic or "3-D" display systems display a scene by providing a slightly different image to each eye. Such systems are uncomfortable for many viewers because, among other things, they simply provide different presentations of a scene, causing changes in the eyes' convergence states without a corresponding change in the eyes' accommodation states. Rather, images are presented by the displays at a fixed distance from the eyes so that the eyes view all image information in a single accommodation state. Such an arrangement counters the "accommodation-vergence-divergence reflex" by causing changes in the convergence states without a corresponding change in the accommodation state. This mismatch is believed to cause viewer discomfort. Display systems that offer better alignment between accommodation and convergence-divergence movements may create a more realistic and comfortable simulation of three-dimensional images.

[0104] 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 may be achieved by providing the eye with different presentations of images corresponding to each of these limited number of depth planes. In some embodiments, the different presentations may provide both vergence cues and matching cues for accommodation, thereby providing physiologically correct accommodation-vergence divergence matching.

[0105] 4B , two depth planes 240 are illustrated, corresponding to different distances in space from the eyes 210, 220. For a given depth plane 240, vergence-divergence cues may be provided by displaying appropriately different perspective images for each eye 210, 220. Additionally, for a given depth plane 240, the light forming the image provided to each eye 210, 220 may have a wavefront divergence corresponding to the light field generated by a point at the distance of that depth plane 240.

[0106] In the illustrated embodiment, the distance along the z-axis of depth plane 240 containing point 221 is 1 meter. As used herein, distance or depth along the z-axis may be measured with a zero point located at the exit pupil of the user's eye. Thus, depth plane 240 located at a depth of 1 meter corresponds to a distance of 1 meter away from the exit pupil of the user's eye on the optical axis of the eye with the eye pointed toward optical infinity. As an approximation, the depth or distance along the z-axis may be measured from a display (e.g., the surface of a waveguide) in front of the user's eye, and a value for the distance between the device and the exit pupil of the user's eye may be added. That value may be referred to as pupil distance and may correspond to the distance between the exit pupil of the user's eye and a display worn by the user in front of the eye. In practice, the value for pupil distance may be a normalized value generally used for all viewers. For example, pupil distance may be assumed to be 20 mm, and the depth plane at a depth of 1 meter may be at a distance of 980 mm in front of the display.

[0107] 4C and 4D, examples of matched accommodation-vergence-divergence distances and mismatched accommodation-vergence-divergence distances are illustrated, respectively. As illustrated in FIG. 4C, the display system may provide an image of a virtual object to each eye 210, 220. The image may cause the eyes 210, 220 to assume a convergence-divergence state in which the eyes converge on point 15 on the depth plane 240. In addition, the image may be formed by light having a wavefront curvature corresponding to the real object on that depth plane 240. As a result, the eyes 210, 220 assume an accommodation state in which the image is focused on the retinas of those eyes. Thus, the user may perceive the virtual object as being at point 15 on the depth plane 240.

[0108] It should be understood that the accommodation and convergence states of the eyes 210, 220 are each associated with a particular distance on the z-axis. For example, an object at a particular distance from the eyes 210, 220 will cause the eyes to assume a particular accommodation state based on the object's distance. The distance associated with a particular accommodation state may be referred to as the accommodation distance Ad. Similarly, there is a particular convergence distance Vd or position relative to one another associated with the eyes in a particular convergence state. When the accommodation distance and the convergence distance match, the relationship between accommodation and convergence is said to be physiologically correct. This is considered the most comfortable scenario for the viewer.

[0109] However, in a stereoscopic display, the accommodation distance and the vergence distance may not always match. For example, as illustrated in FIG. 4D , images displayed to the eyes 210, 220 may be displayed with a wavefront divergence corresponding to the depth plane 240, and the eyes 210, 220 may be in a particular accommodation state in which points 15a, 15b on that depth plane are in focus. However, the images displayed to the eyes 210, 220 may provide convergence cues that cause the eyes 210, 220 to converge on a point 15 that is not located on the depth plane 240. As a result, in some embodiments, the accommodation distance corresponds to the distance from the exit pupils of the eyes 210, 220 to the depth plane 240, while the vergence distance corresponds to the greater distance from the exit pupils of the eyes 210, 220 to point 15. The accommodation distance is different from the vergence distance. As a result, an accommodation-vergence-divergence mismatch exists. Such a mismatch may be considered undesirable and may cause discomfort to the user. It should be understood that the mismatch may correspond to a distance (e.g., Vd-Ad) and be characterized using diopters.

[0110] It should be understood that in some embodiments, a reference point other than the exit pupil of the eye 210, 220 may be used to determine the distance for determining accommodation-vergence mismatch, so long as the same reference point is used for accommodation distance and vergence distance. For example, the distance may be measured from the cornea to the depth plane, from the retina to the depth plane, from the eyepiece (e.g., a waveguide in a display device) to the depth plane, etc.

[0111] Without being limited by theory, it is believed that a user may still perceive an accommodation-vergence-divergence mismatch of up to about 0.25 diopters, up to about 0.33 diopters, and up to about 0.5 diopters as physiologically correct without the mismatch itself causing significant discomfort. In some embodiments, a display system disclosed herein (e.g., display system 250, FIG. 6 ) presents images to a viewer with an accommodation-vergence-divergence mismatch of about 0.5 diopters or less. In some other embodiments, the accommodation-vergence-divergence mismatch of images provided by the display system is about 0.33 diopters or less. In still other embodiments, the accommodation-vergence-divergence mismatch of images provided by the display system is about 0.25 diopters or less, including about 0.1 diopters or less.

[0112] FIG. 5 illustrates aspects of an approach for simulating a three-dimensional image by modifying wavefront divergence. The display system includes a waveguide 270 configured to receive light 770 encoded with image information and output the light to a user's eye 210. The waveguide 270 may output light 650 with a defined amount of wavefront divergence corresponding to the wavefront divergence of a light field generated by a point on a desired depth plane 240. In some embodiments, the same amount of wavefront divergence is provided for all objects presented on that depth plane. In addition, the user's other eye will be illustrated as being provided with image information from a similar waveguide.

[0113] In some embodiments, a single waveguide may be configured to output light with a set wavefront divergence corresponding to a single or limited number of depth planes, and / or the waveguide may be configured to output light of a limited range of wavelengths. As a result, in some embodiments, multiple or stacked waveguides may be utilized to provide different wavefront divergences for different depth planes and / or to output light of different ranges of wavelengths. It should be understood that, as used herein, a depth plane may be a plane or may follow the contour of a curved surface.

[0114] 6 illustrates an example of a waveguide stack for outputting image information to a user. Display system 250 includes a stack of waveguides or stacked waveguide assembly 260 that can be utilized to provide a three-dimensional perception to the eye / brain using multiple waveguides 270, 280, 290, 300, 310. It should be understood that display system 250 may be considered a light field display in some embodiments. Additionally, waveguide assembly 260 may also be referred to as an eyepiece.

[0115] In some embodiments, display system 250 may be configured to provide a substantially continuous cue for convergence and multiple discrete cues for accommodation. The cues for convergence may be provided by displaying different images to each of the user's eyes, and the cues for accommodation may be provided by outputting light that forms images with selectable discrete amounts of wavefront divergence. In other words, display system 250 may be configured to output light with variable levels of wavefront divergence. In some embodiments, each discrete level of wavefront divergence corresponds to a particular depth plane and may be provided by a particular one of waveguides 270, 280, 290, 300, and 310.

[0116] Continuing with reference to FIG. 6 , the waveguide assembly 260 may also include multiple 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 multiple lenses 320, 330, 340, 350 may be configured to transmit image information to the eye using various levels of wavefront curvature or ray divergence. Each waveguide level may be associated with a particular depth plane and configured to output image information corresponding to that depth plane. The image injection devices 360, 370, 380, 390, 400 may act as light sources for the waveguides and may be utilized to inject image information into the waveguides 270, 280, 290, 300, 310, each configured to disperse incident light across each individual waveguide for output toward the eye 210, as described herein. Light exits output surfaces 410, 420, 430, 440, 450 of the image injection devices 360, 370, 380, 390, 400 and is injected into corresponding input surfaces 460, 470, 480, 490, 500 of the waveguides 270, 280, 290, 300, 310. In some embodiments, each input surface 460, 470, 480, 490, 500 may be an edge of the corresponding waveguide or may be a portion of a major surface of the corresponding waveguide (i.e., one of the waveguide surfaces that directly faces the world 510 or the viewer's eye 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.

[0117] In some embodiments, each of the image input devices 360, 370, 380, 390, 400 is a discrete display that generates image information for input into a corresponding waveguide 270, 280, 290, 300, 310. 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).

[0118] In some embodiments, light injected into the waveguides 270, 280, 290, 300, 310 is provided by a light projector system 520, which includes a light module 530, which may include a light emitter such as a light emitting diode (LED). Light from the light module 530 may be directed and modified by a light modulator 540, e.g., a spatial light modulator, via a beam splitter 550. The light modulator 540 may be configured to vary the perceived intensity of the light injected into the waveguides 270, 280, 290, 300, 310 and encode the light with image information. Examples of spatial light modulators include liquid crystal displays (LCDs), including liquid crystal on silicon (LCOS) displays. It should be understood that image injection devices 360, 370, 380, 390, 400 are illustrated diagrammatically, and in some embodiments, these image injection 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. In some embodiments, the waveguides of waveguide assembly 260 may function as ideal lenses, relaying light injected into the waveguides to the user's eye. In this concept, the object may be a spatial light modulator 540, and the image may be an image on a depth plane.

[0119] 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 configured to inject light into an associated one of the waveguides 270, 280, 290, 300, 310. It should be understood that one or more optical fibers may be configured to transmit light from the optical module 530 to one or more waveguides 270, 280, 290, 300, 310. It should be understood that one or more intervening optical structures may be provided between the scanning fiber or fibers and one or more waveguides 270, 280, 290, 300, 310, for example, to redirect light exiting the scanning fiber into one or more waveguides 270, 280, 290, 300, 310.

[0120] Controller 560 controls the operation of one or more of stacked waveguide assemblies 260, including the operation of image input devices 360, 370, 380, 390, 400, light source 530, and light modulator 540. In some embodiments, controller 560 is part of local data processing module 140. Controller 560 contains programming (e.g., instructions in a non-transitory medium) that coordinates the timing and provisioning of image information to 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. Controller 560 may, in some embodiments, be part of processing module 140 or 150 (FIG. 9D).

[0121] Continuing with reference to FIG. 6 , the waveguides 270, 280, 290, 300, and 310 may be configured to propagate light within each individual waveguide by total internal reflection (TIR). Each of the waveguides 270, 280, 290, 300, and 310 may be planar or have another shape (e.g., curved) with major top and bottom surfaces and edges extending between the major top and bottom surfaces. In the illustrated configuration, the waveguides 270, 280, 290, 300, and 310 may each include outcoupling optical elements 570, 580, 590, 600, and 610 configured to extract light from the waveguide by redirecting light propagating within each individual waveguide out of the waveguide and outputting image information to the eye 210. The extracted light may also be referred to as outcoupling light, and the outcoupling optical element light may also be referred to as a light extraction optical element. The extracted beam of light may be output by the waveguide at a location where light propagating within the waveguide strikes the light extraction optical element. The outcoupling optical element 570, 580, 590, 600, 610 may be a grating, for example, including diffractive optical features as discussed further herein. While shown disposed on the bottom major surface of the waveguides 270, 280, 290, 300, 310 for ease of explanation and clarity of the drawings, in some embodiments the outcoupling optical element 570, 580, 590, 600, 610 may be disposed on the top and / or bottom major surfaces and / or directly within the volume of the waveguides 270, 280, 290, 300, 310, as discussed further herein. In some embodiments, the outcoupling optical elements 570, 580, 590, 600, 610 may be formed within a layer of material that is attached to a transparent substrate and forms the waveguides 270, 280, 290, 300, 310. In some other embodiments, the waveguides 270, 280, 290, 300, 310 may be monolithic pieces of material, and the outcoupling optical elements 570, 580, 590, 600, 610 may be formed on a surface of and / or within that piece of material.

[0122] Continuing with reference to FIG. 6 , as discussed herein, each waveguide 270, 280, 290, 300, 310 is configured to output light and form an image corresponding to a particular depth plane. For example, the waveguide 270 closest to the eye may be configured to deliver collimated light (injected into such waveguide 270) to the eye 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 reaching the eye 210. Such first lens 350 may be configured to generate a slight convex wavefront curvature so that the eye / brain interprets light emerging from the next upper waveguide 280 as emerging from a first focal plane closer inward from optical infinity toward the eye 210. Similarly, the third upper waveguide 290 passes its output light through both the first lens 350 and the second lens 340 before reaching the eye 210. The combined refractive power of the first lens 350 and the second lens 340 may be configured to produce another, increasing amount of wavefront curvature such that the eye / brain interprets the light emerging from the third waveguide 290 as originating from a second focal plane that is closer inward from optical infinity towards the person than was the light from the next upper waveguide 280.

[0123] The other waveguide layers 300, 310 and lenses 330, 320 are similarly configured, with the highest waveguide 310 in the stack sending its output through all of the lenses between it and the eye for a collective focal power representing the focal plane closest to the person. To compensate for the stack of lenses 320, 330, 340, 350 when viewing / interpreting light originating from the world 510 on the other side of the stacked waveguide assembly 260, a compensating lens layer 620 may be placed on top of the stack to compensate for the collective power of the lower lens stacks 320, 330, 340, 350. Such a configuration provides as many perceived focal planes as there are available waveguide / lens pairs. Both the waveguide outcoupling optical elements and the focusing sides of the lenses may be static (i.e., not dynamic or electro-active). In some alternative embodiments, one or both may be dynamic using electro-active features.

[0124] 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 waveguides 270, 280, 290, 300, 310 may be configured to output images set at the same depth planes, with one set per depth plane. This may provide the advantage of forming tiled images to provide an extended field of view at those depth planes.

[0125] Continuing with reference to FIG. 6 , the outcoupling optical elements 570, 580, 590, 600, 610 may be configured to redirect light from its respective waveguide and output the light with an appropriate amount of divergence or collimation for a particular depth plane associated with that waveguide. As a result, waveguides with different associated depth planes may have different configurations of outcoupling optical elements 570, 580, 590, 600, 610, which output light with different amounts of divergence depending on the associated depth plane. In some embodiments, the light-extraction optical elements 570, 580, 590, 600, 610 may be volume or surface features, which may be configured to output light at specific angles. 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, features 320, 330, 340, 350 may not be lenses. Rather, they may simply be spacers (e.g., cladding layers and / or structures for forming air gaps).

[0126] 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 output beams that exit the waveguide at various locations, resulting in a fairly uniform pattern of output emission toward the eye 210 for this particular collimated beam bouncing within the waveguide.

[0127] 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 in which microdroplets comprise a diffractive pattern in a host medium, and the refractive index of the microdroplets may be switched to substantially match the refractive index of the host material (in which case the pattern does not 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).

[0128] 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 monitor the physiological state 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. 9D) and may be in electrical communication with processing modules 140 and / or 150, which may process image information from the camera assembly 630. In some embodiments, one camera assembly 630 may be utilized per eye, monitoring each eye separately.

[0129] 7, an example of an output beam output by a waveguide is shown. While one waveguide is illustrated, it should be understood that other waveguides in waveguide assembly 260 (FIG. 6) may function similarly, and that waveguide assembly 260 includes multiple waveguides. Light 640 is launched into waveguide 270 at input surface 460 of waveguide 270 and propagates within waveguide 270 by TIR. At the point where light 640 impinges on DOE 570, a portion of the light exits the waveguide as output beam 650. Output beam 650 is illustrated as being approximately parallel, but may be redirected to propagate to eye 210 at an angle (e.g., divergent output beam formation), as discussed herein, and depending on the depth plane associated with waveguide 270. It should be understood that a nearly 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 waveguides or other sets of 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.

[0130] 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, with each depth plane including an image formed using multiple different primary colors. The illustrated embodiment shows depth planes 240a-240f, but more or fewer depths are also contemplated. Each depth plane may have three or more primary color images associated with it, including a first image in a first color G, a second image in a second color R, and a third image in a third color B. Different depth planes are indicated in the diagram by different numbers for diopters (dpt) following the letters G, R, and B. By way of example only, the number following each of these letters indicates the diopter (1 / m), i.e., the inverse 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 locations of the depth planes for different primary colors may be varied to account for differences in the eye's focusing of light of different wavelengths. 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 aberrations.

[0131] In some embodiments, light for 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 embodiments, each box in the diagram containing the letter G, R, or B may be understood to represent an individual waveguide, and three waveguides may be provided per depth plane, resulting in three primary color images per depth plane. While the waveguides associated with each depth plane are shown adjacent to each other in this drawing for ease of illustration, it should be understood that in a physical device, the waveguides may all 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.

[0132] 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 replace one or more of red, green, or blue.

[0133] It should be understood that references to a given color of light throughout this disclosure will be understood to encompass light of one or more wavelengths within the range of wavelengths of light that are perceived by a viewer to be of that given color. For example, red light may include one or more wavelengths of light within a range of about 620-780 nm, green light may include one or more wavelengths of light within a range of about 492-577 nm, and blue light may include one or more wavelengths of light within a range of about 435-493 nm.

[0134] In some embodiments, light source 530 (FIG. 6) may be configured to emit light at one or more wavelengths outside the range of a viewer's visual perception, e.g., infrared and / or ultraviolet wavelengths. Additionally, the waveguide incoupling, outcoupling, and other light redirecting structures of 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.

[0135] Referring now to FIG. 9A , in some embodiments, light impinging on a waveguide may need to be redirected to incoupling the light into the waveguide. An incoupling optical element may be used to redirect and incoupling the light into its corresponding waveguide. FIG. 9A illustrates a cross-sectional side view of an example of a plurality or set 660 of stacked waveguides, each including an incoupling optical element. The waveguides may each be configured to output light of one or more different wavelengths or one or more different wavelength ranges. Stack 660 may correspond to stack 260 ( FIG. 6 ), and the illustrated waveguides of stack 660 may correspond to a portion of multiple waveguides 270, 280, 290, 300, 310, although it should be understood that light from one or more of image injection devices 360, 370, 380, 390, 400 is injected into the waveguide from a location requiring the light to be redirected for incoupling.

[0136] The illustrated set 660 of stacked waveguides includes waveguides 670, 680, and 690. Each waveguide includes an associated internal coupling optical element (which may also be referred to as the light input area on the waveguide), for example, internal coupling optical element 700 is disposed on a major surface (e.g., the top major surface) of waveguide 670, internal coupling optical element 710 is disposed on a major surface (e.g., the top major surface) of waveguide 680, and internal coupling optical element 720 is disposed on a major surface (e.g., the top major surface) of waveguide 690. In some embodiments, one or more of internal coupling optical elements 700, 710, 720 may be disposed on the bottom major surface of an individual waveguide 670, 680, 690 (particularly, one or more internal coupling optical elements are reflective polarizing optical elements). As shown, the internal coupling optical elements 700, 710, 720 may be disposed on the upper major surface of the respective waveguide 670, 680, 690 (or on top of the next lower waveguide), and in particular, the internal coupling optical elements are transmissive turning optical elements. In some embodiments, the internal coupling optical elements 700, 710, 720 may be disposed within the body of the respective waveguide 670, 680, 690. In some embodiments, as discussed herein, the internal coupling 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. While illustrated on one side or corner of the respective waveguide 670, 680, 690, it should be understood that the internal coupling optical elements 700, 710, 720 may be disposed within other areas of the respective waveguide 670, 680, 690 in some embodiments.

[0137] 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 to receive light without that light passing through another in-coupling optical element. For example, each in-coupling optical element 700, 710, 720 may be configured to receive light from different image input devices 360, 370, 380, 390, and 400, as shown in FIG. 6 , and may be separated (e.g., laterally spaced) from the other in-coupling optical elements 700, 710, 720 so as to receive substantially no light from others of the in-coupling optical elements 700, 710, 720.

[0138] Each waveguide also includes an associated optically dispersive element, for example, optically dispersive element 730 is disposed on a major surface (e.g., the top major surface) of waveguide 670, optically dispersive element 740 is disposed on a major surface (e.g., the top major surface) of waveguide 680, and optically dispersive element 750 is disposed on a major surface (e.g., the top major surface) of waveguide 690. In some other embodiments, optically dispersive elements 730, 740, 750 may be disposed on the bottom major surfaces of associated waveguides 670, 680, 690, respectively. In some other embodiments, optically dispersive elements 730, 740, 750 may be disposed on both the top and bottom major surfaces of associated waveguides 670, 680, 690, respectively, or optically dispersive 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.

[0139] Waveguides 670, 680, 690 may be spaced apart and separated, for example, by gas, liquid, and / or solid layers of material. For example, as shown, layer 760a may separate waveguides 670 and 680, and layer 760b may separate waveguides 680 and 690. In some embodiments, layers 760a and 760b are formed from a low refractive index material (i.e., a material having a lower refractive index than the material forming the immediately adjacent waveguides 670, 680, 690). Preferably, the refractive index of the material forming layers 760a, 760b is 0.05 or greater, or 0.10 or less, relative to the refractive index of the material forming waveguides 670, 680, 690. Advantageously, the lower refractive index layers 760a, 760b may function as cladding layers that 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.

[0140] Preferably, for ease of manufacturing and other considerations, the materials forming waveguides 670, 680, 690 are similar or the same, and the materials forming layers 760a, 760b are similar or the same. In some embodiments, the materials forming waveguides 670, 680, 690 may differ between one or more waveguides, and / or the materials forming layers 760a, 760b may differ while still maintaining the various refractive index relationships discussed above.

[0141] 9A, light rays 770, 780, 790 enter 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).

[0142] In some embodiments, light rays 770, 780, 790 have different properties, 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.

[0143] For example, in-coupling optical element 700 may be configured to selectively deflect light ray 770 having a first wavelength or wavelength range while transmitting light rays 780 and 790 having different second and third wavelengths or wavelength ranges, respectively. Transmitted light ray 780 impinges on and is deflected by in-coupling optical element 710, which is configured to selectively deflect light of the second wavelength or wavelength range. Light ray 790 is deflected by in-coupling optical element 720, which is configured to selectively deflect light of the third wavelength or wavelength range.

[0144] 9A , the deflected light rays 770, 780, 790 are deflected to propagate through the corresponding waveguides 670, 680, 690. That is, the in-coupling optical element 700, 710, 720 of each waveguide deflects the light into its corresponding waveguide 670, 680, 690, in-coupling 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 waveguide's corresponding optical dispersive element 730, 740, 750.

[0145] 9B, a perspective view of the multiple stacked waveguide embodiment of FIG. 9A is illustrated. As previously described, in-coupled light rays 770, 780, 790 are deflected by in-coupling optical elements 700, 710, 720, respectively, and then propagate by TIR within waveguides 670, 680, 690, respectively. Light rays 770, 780, 790 then impinge on optically dispersive elements 730, 740, 750, respectively. Optically dispersive elements 730, 740, 750 deflect light rays 770, 780, 790 to propagate toward out-coupling optical elements 800, 810, 820, respectively.

[0146] In some embodiments, the optically dispersive elements 730, 740, 750 are orthogonal pupil expanders (OPEs). In some embodiments, the OPEs deflect or disperse light into the out-coupling optical elements 800, 810, 820, and in some embodiments, may also increase the beam or spot size of this light as it propagates into the out-coupling optical elements. In some embodiments, the optically dispersive elements 730, 740, 750 may be omitted, and the in-coupling optical elements 700, 710, 720 may be configured to deflect light directly into the out-coupling optical elements 800, 810, 820. For example, with reference to FIG. 9A , the optically dispersive 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 toward the viewer's eye 210 ( FIG. 7 ). It should be understood that an OPE may be configured to increase the size of the eyebox in at least one axis, and that the EPE may increase the eyebox in an axis that intersects the axis of the OPE, e.g., orthogonal to the axis of the OPE. 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, and the remainder of that portion continues to propagate further down the waveguide, etc. Similarly, upon striking the EPE, a portion of the impinging light is directed out of the waveguide toward the user, and the remaining portion of that light continues to propagate through the waveguide until it again strikes an EP, at which point another portion of the impinging light is directed out of the waveguide, etc. As a result, a single beam of internally coupled light may be "replicated" each time a portion of that light is redirected by 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.

[0147] 9A and 9B, in some embodiments, a waveguide set 660 includes, for each primary color, waveguides 670, 680, 690, in-coupling optical elements 700, 710, 720, optically dispersive elements (e.g., OPEs) 730, 740, 750, and out-coupling optical elements (e.g., EPs) 800, 810, 820. The waveguides 670, 680, 690 may be stacked with an air gap / cladding layer between each one. The in-coupling optical elements 700, 710, 720 redirect or deflect incident light into that waveguide (with different in-coupling optical elements receiving light of different wavelengths). The light then propagates at an angle that will result in TIR within the individual waveguides 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 an optically dispersive element (e.g., OPE) 730 and then an out-coupling optical element (e.g., EP) 800. Light rays 780 and 790 (e.g., green and red light, respectively) pass through waveguide 670, with light ray 780 impinging on and being deflected by in-coupling optical element 710. Light ray 780 will then, via TIR, bounce back down waveguide 680 to its optically dispersive element (e.g., OPE) 740 and then to the out-coupling optical element (e.g., EP) 810. Finally, light ray 790 (e.g., red light) passes through waveguide 690 and impinges on the optically in-coupling optical element 720 of waveguide 690. The light in-coupling optical element 720 deflects the light ray 790 so that it propagates by TIR to the light dispersive element (e.g., OPE) 750 and then by TIR to the out-coupling optical element (e.g., EP) 820. The out-coupling optical element 820 then finally out-couples the light ray 790 to a viewer, who also receives out-coupled light from the other waveguides 670, 680.

[0148] FIG. 9C illustrates a top-down plan view of an example of the multiple stacked waveguides of FIGS. 9A and 9B. As shown, waveguides 670, 680, 690 may be vertically aligned, along with each waveguide's associated optically dispersive elements 730, 740, 750 and associated out-coupling optical elements 800, 810, 820. However, as discussed herein, the in-coupling optical elements 700, 710, 720 are not vertically aligned. Rather, the in-coupling optical elements are preferably non-overlapping (e.g., laterally spaced apart, 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 specific light source to be uniquely coupled to a specific waveguide. In some embodiments, arrays including non-overlapping, spatially separated in-coupling optical elements may be referred to as shifted-pupil systems, and the in-coupling optical elements in these arrays may correspond to sub-pupils.

[0149] 9D illustrates an example of a wearable display system 60 into which the various waveguide and associated systems disclosed herein may be integrated. In some embodiments, the display system 60 is the system 250 of FIG. 6, which diagrammatically illustrates some portions of the system 60 in greater detail. For example, the waveguide assembly 260 of FIG. 6 may be part of the display 70.

[0150] Continuing with reference to FIG. 9D , 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 directly in front of the user's 90's eye. The display 70, in some embodiments, may be considered an eyepiece. In some embodiments, a speaker 100 is coupled to frame 80 and configured to be positioned adjacent to the user's 90 ear canal (in some embodiments, another speaker, not shown, may optionally be positioned adjacent the user's other ear canal to provide stereo / shapeable sound control). Display system 60 may also include one or more microphones 110 or other devices to detect sound. In some embodiments, the microphones are configured to allow a user to provide input or commands to system 60 (e.g., voice menu command selections, 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 mounted on the body of the user 90 (e.g., 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.

[0151] 9D , display 70 is operably coupled to 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 frame 80, fixedly attached to a helmet or hat worn by the user, embedded within headphones, or otherwise removably attached to user 90 (e.g., in a backpack-style configuration, in a belt-linked configuration). Similarly, sensor 120a may be operably coupled to local processor and data module 140 by a communication link 120b, such as wired or wireless connectivity. Local processing and data module 140 may comprise a hardware processor and digital memory, such as non-volatile memory (e.g., flash memory or a hard disk drive), both of which may be utilized to aid in processing, caching, and storing data. Optionally, local processing and data module 140 may include one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, etc. The data may include a) data captured from sensors (such as image capture devices (cameras, 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 frame 80 or otherwise attached to user 90)) and / or b) data obtained and / or processed using remote processing module 150 and / or remote data repository 160 (including data related to virtual content), possibly for passage to display 70 after processing or retrieval. Local processing and data module 140 may be operatively coupled to remote processing module 150 and remote data repository 160 by communication links 170, 180, such as via wired or wireless communication links, such that these remote modules 150, 160 are operatively coupled to each other and available as resources to local processing and data module 140.In some embodiments, 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 frame 80 or may be a freestanding structure that communicates with local processing and data module 140 by a wired or wireless communication path.

[0152] 9D , in some embodiments, remote processing module 150 may comprise one or more processors configured to analyze and process data and / or image information, and may include, for example, one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, etc. In some embodiments, remote data repository 160 may comprise digital data storage facilities that 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, for example, 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 computations are performed within the local processing and data module, allowing for fully autonomous use from the remote module. Optionally, an external system (e.g., one or more processors, one or more computer systems), including a CPU, GPU, etc., may perform at least a portion of the processing (e.g., generating image information, processing data) and provide information to and receive information from modules 140, 150, 160, e.g., via a wireless or wired connection.

[0153] Liquid Crystal Materials for Broadband Adaptive Waveplate Lens Assemblies Generally, liquid crystals possess physical properties that may be intermediate between traditional fluids and solids. Liquid crystals are fluid-like in some aspects, but unlike most fluids, the arrangement of molecules within liquid crystals exhibits a structural order. Different types of liquid crystals include thermotropic, lyotropic, and polymeric liquid crystals. The thermotropic liquid crystals disclosed herein can be implemented in a variety of physical states, e.g., phases, including nematic, smectic, chiral nematic, or chiral smectic states / phases.

[0154] As described herein, liquid crystals in a nematic state or phase can have calamitic (rod-shaped) or discotic (disk-shaped) organic molecules that have relatively little positional order but long-range directional order, with their long axes generally parallel. Thus, the organic molecules can flow freely, their center-of-mass positions randomly dispersed as in a liquid, while still maintaining their long-range directional order. In some implementations, liquid crystals in the nematic phase can be uniaxial, i.e., the liquid crystals have one axis that is longer and preferred, and the other two are approximately equal. In some implementations, the liquid crystal molecules align along their long axes. In other implementations, the liquid crystals can be biaxial, i.e., in addition to aligning their long axes, the liquid crystals can also align along their secondary axes.

[0155] As described herein, liquid crystals in a smectic state or phase can have organic molecules that form relatively well-defined layers that can slide over one another. In some implementations, liquid crystals in a smectic phase can be positionally ordered along one direction. In some implementations, the long axes of the molecules can be oriented approximately normal to the plane of the liquid crystal layer, while in other implementations, the long axes of the molecules can be tilted relative to the normal to the plane of the layer.

[0156] Here, and throughout this disclosure, nematic liquid crystals consist of rod-shaped molecules with the long axes of neighboring molecules approximately aligned with one another. To describe this anisotropic structure, a dimensionless unit vector n, called the director, can be used to describe the direction of preferred orientation of the liquid crystal molecules.

[0157] Here, and throughout this disclosure, the azimuthal angle or rotation angle φ is used to describe the angle of rotation of liquid crystal molecules about an axis normal to the layer or major surfaces of the liquid crystal layer, measured in a plane parallel to the major surfaces of the liquid crystal layer or substrate, e.g., the xy plane, and measured between the alignment direction, e.g., the stretch direction or director direction, and a direction parallel to the major surfaces, e.g., the y-direction.

[0158] Here, and throughout this disclosure, when angles, such as rotation angle φ, are referred to as being substantially the same or different between different regions, it should be understood that the average of the angles may be, for example, within about 1%, about 5%, or about 10% of each other, although the average angle may be greater in some cases.

[0159] As described herein, some liquid crystals in the nematic or smectic state can also exhibit a twist in the layer normal direction. Such liquid crystals are referred to as twisted nematic (TN) or twisted smectic (SN) liquid crystals. TN or SN liquid crystals can exhibit molecular twist about an axis perpendicular to the director, with the molecular axis parallel to the director. When the degree of twist is relatively large, the twisted liquid crystal can be referred to as a chiral or cholesteric phase.

[0160] As described herein, TN or SN liquid crystals may be described as having a twist angle or net twist angle (φ), which may refer, for example, to the relative azimuthal rotation between the top and bottom liquid crystal molecules across a defined length, e.g., the thickness of the liquid crystal layer.

[0161] As described herein, "polymerizable liquid crystal" may refer to a liquid crystal material that can be polymerized, for example, photopolymerized in situ, and may also be described herein as a reactive mesogen (RM).

[0162] Liquid crystal molecules, in some embodiments, may be polymerizable and, once polymerized, may form large-scale networks with other liquid crystal molecules. For example, liquid crystal molecules may be linked by chemical bonds or by linking chemical species to other liquid crystal molecules. Once joined together, the liquid crystal molecules may form liquid crystal domains that have substantially the same orientation and location as before they were linked together. The term "liquid crystal molecules," as used herein, may refer to either or both the liquid crystal molecules before polymerization and / or the liquid crystal domains formed by these molecules after polymerization. Once polymerized, the polymerized network may be referred to as a liquid crystal polymer (LCP).

[0163] In some embodiments, prior to polymerization, unpolymerized or polymerizable liquid crystal molecules may have at least limited rotational freedom. These unpolymerized liquid crystal molecules may rotate or tilt, for example, under electrical stimulation, resulting in altered optical properties. For example, by applying an electric field, some liquid crystal layers containing unpolymerized liquid crystal molecules may be switched between one or more states with different diffraction or polarization-altering properties.

[0164] The inventors recognize that the above-described properties of liquid crystals or reactive mesogens (RMs) can be advantageously applied to various components of the broadband switchable waveplates and waveplate lenses disclosed herein. For example, in some unpolymerized RMs, the orientation of the LC molecules can be altered after deposition, for example, by application of an external stimulus, such as an electric field. Based on this recognition, the inventors disclose herein waveplates and waveplate lenses that can be switched between multiple states by application of an external stimulus.

[0165] Additionally, the inventors recognize that, when not polymerized, the orientation of LC molecules at the surface or interface of some LCs or RMs can be matched by controlling the surface or interface on which the LC molecules are formed. For example, a stack of multiple LC layers can be formed, and by controlling the orientation of the LC molecules closest to the surface of an LC layer, the orientation of the immediately adjacent LC in the next LC layer can be controlled to have, for example, the same orientation as the LC molecules closest to the surface in the previous LC layer or the same orientation as the elongated microstructures in the adjacent layer. Additionally, the LC molecules between LC molecules at a surface or interface can be controlled to have a predetermined amount of twist. Based on the recognition of these and other attributes, including birefringence, chirality, and ease of multiple coatings, the inventors disclose herein waveplates and waveplate lenses with tailored optical properties, such as broadband capability with diffraction efficiency, optical power, and polarization, to name a few.

[0166] Display device having a switchable broadband adaptive waveplate lens assembly 6, some display systems, according to embodiments, include a waveguide assembly 260 configured to form images at multiple virtual depth planes. The waveguide assembly 260 includes waveguides 270, 280, 290, 300, 310, each configured to propagate light by total internal reflection (TIR), and includes outcoupling optical elements 570, 580, 590, 600, 610, each configured to redirect light and thereby extract light out of a respective one of the waveguides 270, 280, 290, 300, 310. Each of the waveguides 270, 280, 290, 300, 310 is configured to output light and form an image corresponding to a particular depth plane. The waveguide assembly 260 may also optionally include multiple lenses 320, 330, 340, 350 between the waveguides to provide different refractive powers for forming images at different virtual depth planes.

[0167] In the illustrated embodiment of waveguide assembly 260 in FIG. 6 , the number of depth planes may be directly proportional to the number of waveguides and lenses. However, the inventors recognize various challenges associated with implementing a waveguide assembly configured to display images at multiple depth planes by having a proportional number of waveguides and lenses. For example, a large number of waveguides 270, 280, 290, 300, 310 and a large number of corresponding lenses 320, 330, 340, 350 can undesirably increase the overall thickness, weight, cost, and manufacturing challenges for waveguide assembly 260. For example, when formed from conventional lens materials, such as glass, each of lenses 320, 330, 340, 350 can add several millimeters or tens of millimeters of thickness and corresponding weight to the display. Additionally, a large number of waveguides and lenses can produce optical effects that are undesirable to the user, such as relatively high absorption losses. Thus, in one aspect, the inventors recognize potential advantages for display systems that, in some cases, may generate images at multiple depth planes using fewer waveguides, fewer lenses, thinner and lighter waveguides and lenses, and / or fewer lenses per waveguide.

[0168] Still referring to FIG. 6 , it should be understood that lenses 320, 330, 340, and 350 can be configured to form images at different depth planes by imparting individual optical powers to light from waveguides 310, 300, 290, and 280. In various embodiments, light coupled out from the waveguides can have a polarization, e.g., circular polarization. However, when polarized light coupled out from the waveguides passes through a waveplate lens or waveplate formed from liquid crystals, less than 100% of the coupled light transmitted therethrough can be optically affected, e.g., diffracted, diverged, focused, or otherwise altered in polarization, resulting in some of the coupled light passing optically unaffected. Light passing through a lens in this manner optically unaffected is sometimes referred to as leaked light. The leaked light can be undesirably focused, defocused, or have its polarization altered, or even unaffected, in the downstream optical path. When a significant portion of light passing through a waveplate or waveplate lens constitutes leakage light, a user may experience undesirable effects such as a "lasting image," which is an unintended image or an image visible to a user at an unintended depth plane. The inventors recognize that such leakage light can result, among other causes, from a waveplate lens or waveplate formed from a liquid crystal configured to have a relatively high diffraction efficiency within a relatively narrow wavelength range within the visible spectrum. Accordingly, in another aspect, the inventors recognize a need for a broadband adaptive waveplate lens assembly that can generate images at multiple depth planes over a relatively wide range of wavelengths within the visible spectrum with little undesirable effects resulting from leakage light. To address these and other needs, various embodiments include a broadband adaptive waveplate lens assembly comprising a liquid crystal-based switchable waveplate lens or switchable waveplate configured to provide variable refractive power. Waveplate lenses and waveplates formed from liquid crystals can offer various advantages toward achieving these goals, including thin thickness, light weight, and a high degree of configurability at the molecular level.In various embodiments described herein, a display device is configured to form images at different virtual depth planes using a waveguide assembly configured to direct light in a lateral direction parallel to an output surface of the waveguide and outcouple the light directed through the output surface into one or more broadband adaptive waveplate lens assemblies. In various embodiments, the broadband adaptive waveplate lens assemblies are configured to incouple and diffract the outcoupled light from the waveguide therethrough. The broadband adaptive lens assemblies include a first waveplate lens comprising a liquid crystal (LC) layer arranged such that the waveplate lens has a birefringence (Δn) that varies radially outward from a central region of the first waveplate lens. The resulting waveplate lens can be configured to diffract the outcoupled light within a broadband wavelength range including at least 450 nm to 630 nm with a diffraction efficiency greater than 90%, greater than 95%, or even greater than 99%. In some embodiments, broadband adaptive waveplate lens assemblies according to embodiments are significantly lighter and thinner (a few microns) compared to conventional lenses, and can advantageously provide variable optical power over a broadband wavelength range. Advantageously, such broadband adaptive lens assemblies can reduce the number, thickness, and weight of waveguide assemblies, such as waveguide assembly 260 (FIG. 6), and can reduce or eliminate undesirable effects resulting from leaking light.

[0169] As used herein, optical power (P, also referred to as refractive power, focusing power, or convergence power) refers to the degree to which a lens, mirror, or other optical system converges or diverges light. It is equal to the reciprocal of the focal length of the device: P=1 / f. That is, high optical power corresponds to short focal lengths. The SI unit for optical power is per meter (m -1 ), which is commonly called diopter (D).

[0170] As described herein, a converging lens, which focuses light passing through it, is described as having a positive refractive power, while a diverging lens, which defocuses light passing through it, is described as having a negative refractive power. Without being bound by theory, when light passes through two or more thin lenses that are relatively close to one another, the refractive power of the combined lenses can be approximated as the sum of the refractive powers of the individual lenses. Thus, when light passes through a first lens having a first refractive power P1 and further passes through a second lens having a second refractive power P2, the light can be understood to converge or diverge according to the sum of the refractive powers Pnet = P1 + P2.

[0171] A medium that has a refractive index that depends on the polarization and direction of propagation of light is referred to as birefringent (or double refractive). As explained throughout this specification and understood in the relevant industry, when light has a polarization perpendicular to the optical axis of the birefringent medium, the birefringent medium exhibits a normal refractive index (n o ), and when light has polarization parallel to the optic axis of the birefringent medium, the birefringent medium has an extraordinary refractive index (n e ) and the refractive index of the birefringent medium material is n e -n o The difference between these two is called the birefringence Δn. The phase delay of light in a material medium with birefringence Δn can be expressed as Γ=2πΔnd / λ, where λ is the wavelength of the light and d is the thickness of the medium.

[0172] Generally, optically anisotropic materials, such as liquid crystals, exhibit a positive dispersion of birefringence (Δn), which decreases with increasing wavelength λ of light. Positive dispersion of Δn results in different phase retardations Γ=2πΔnd / λ at different λ. As disclosed herein, anisotropic materials that exhibit a negative dispersion of birefringence (Δn) refer to materials whose birefringence increases with increasing wavelength λ of light.

[0173] As explained above, the wavelength dependence of the diffraction efficiency of a waveplate lens or waveplate can be an important consideration in reducing or minimizing various undesirable optical effects. As explained herein, the diffraction efficiency (η) of a birefringent medium, such as a layer of liquid crystal, is given by η=sin 2 (πΔnd / λ), where Δn is the birefringence, λ is the wavelength, and d is the thickness. Because the phase retardation of light propagating through a diffractive component varies with wavelength as compared to conventional birefringent media, some diffractive components, including waveplate lenses and waveplates, exhibit a relatively narrow range of wavelengths or bandwidths within the visible spectrum over which the diffraction efficiency is sufficiently high. In contrast, waveplate lenses and waveplates, according to embodiments, exhibit a relatively wide range of wavelengths or bandwidths within the visible spectrum over which the diffraction efficiency is sufficiently high for the various applications described herein.

[0174] According to various embodiments, a broadband waveplate lens or waveplate has a normalized bandwidth (Δλ / λ o ), where λ o is a center wavelength within the visible spectrum spanning a wavelength range of about 400 to 800 nm, including one or more of a red spectrum having a wavelength range of about 620 to 780 nm, a green spectrum having a wavelength range of about 492 to 577 nm, and a blue spectrum having a wavelength range of about 435 to 493 nm; and Δλ is a wavelength at which the diffraction efficiency exceeds 70%, 80%, 90%, 95%, 99%, or any value within a range defined by these values. o It is a range of wavelengths centered around

[0175] According to various embodiments, when a waveplate lens or waveplate is described as being a broadband waveplate lens or broadband waveplate, it will be understood to have a representative, instantaneous, average, median, or minimum diffraction efficiency of greater than 70%, 80%, 90%, 95%, 99%, or a percentage within any of these values ​​within at least a portion of the visible spectrum spanning a wavelength range of about 400-800 nm, including one or more of: a red spectrum comprising a range of wavelengths from about 620-780 nm; a green spectrum comprising wavelengths from about 492-577 nm; a blue spectrum within a range of wavelengths from about 435-493 nm; or any wavelength within the visible spectrum from about 400-800 nm, e.g., 400-700 nm, 430-650 nm, or 450-630 nm.

[0176] The relationship η = sin 2 Based on (πΔnd / λ), a broadband waveplate lens or waveplate can have an efficiency for a fixed d when the ratio of Δn / λ has a positive and relatively constant value. As described herein, a medium with a positive ratio value of Δn / λ is said to have negative dispersion. According to embodiments, the broadband waveplate lens or broadband waveplate described herein has negative dispersion, i.e., a birefringence (Δn) that increases with increasing wavelength (λ) within the wavelength range described above.

[0177] According to various embodiments, a broadband waveplate lens or waveplate may be described as having an instantaneous, mean, median, minimum, or maximum value of the ratio Δn / λ that is a positive value within any range of the visible spectrum described above. o and Δλ is a wavelength range within any of the visible spectrum described above, o is the center wavelength within Δλ. According to various embodiments, the high normalized bandwidth Δλ / λ ocan have a value of about 0.3 to 0.7, 0.4 to 0.7, 0.5 to 0.7, 0.6 to 0.7, or any value within a range defined by these values. In addition, the broadband waveplate lens or waveplate has a ratio Δn / λ that is relatively constant within the various wavelength ranges within the visible spectrum described above. For example, the ratio Δn / λ can have a deviation, e.g., standard deviation, from the mean, median, minimum, or maximum value of the ratio Δn / λ that does not exceed 30%, 20%, 10%, 5%, 1%, or a percentage within any of these values.

[0178] As described herein, a "transmissive" or "transparent" structure, e.g., a transparent substrate, may allow at least a portion, e.g., at least 20, 30, 50, 70, or 90%, of incident light to pass therethrough. Thus, a transparent substrate may, in some embodiments, be a glass, sapphire, or polymer substrate. In contrast, a "reflective" structure, e.g., a reflective substrate, may reflect at least a portion, e.g., at least 20, 30, 50, 70, 90%, or more, of incident light therethrough.

[0179] FIG. 10 illustrates an example of a display device 1000, e.g., a wearable display device, including one or more broadband adaptive lens assemblies, e.g., a pair of broadband adaptive lens assemblies 1004, 1008, in an optical path 1016 interposed by a waveguide assembly 1012. As described above, the waveguide assembly includes a waveguide configured to propagate light (e.g., visible light) under total internal reflection and to outcouple the light in an optical axis extending from (e.g., normal to) a light output surface (e.g., a major surface of the waveguide) of the waveguide. The light may, in some embodiments, be outcoupled by a diffraction grating. Each of the broadband adaptive lens assemblies 1004, 1008 may be configured to at least partially transmit the outcoupled light therethrough. In the illustrated embodiment, each of the broadband adaptive lens assemblies may be configured to receive light outcoupled from the waveguide assembly 1012 and converge or diverge the outcoupled light along an optical axis. Each of the broadband adaptive lens assemblies 1004, 1008 comprises a waveplate lens comprising liquid crystals arranged such that the waveplate lens has a birefringence (Δn) that varies radially from a central region of the waveplate lens and increases or decreases with increasing wavelength (λ) within the visible spectrum. The broadband adaptive lens assemblies are configured to be selectively switched between a plurality of states having different refractive powers. When activated (e.g., electrically activated), the broadband adaptive lens assemblies are configured to alter the polarization state of outcoupled light passing therethrough.

[0180] As described herein, an adaptive lens assembly refers to a lens assembly having at least one optical property that can be adjusted, e.g., reversibly activated and deactivated using an external stimulus. Exemplary optical properties that can be reversibly activated and deactivated include refractive power (focal length), phase, polarization, polarization selectivity, transmittance, reflectance, birefringence, and diffractive properties, among other properties. In various embodiments, an adaptive lens assembly is capable of electrically varying the refractive power and polarization state of light passing therethrough.

[0181] In the illustrated embodiment, the pair of wideband adaptive lens assemblies 1004, 1008 are each configured to be selectively switched between at least two states. In a first state, each is configured to pass outcoupled light therethrough without altering its polarization state, while in a second state, each is configured to alter the polarization state of the outcoupled light passing therethrough. For example, in the second state, each wideband adaptive lens assemblies 1004, 1008 reverses the handedness of circularly polarized light, while in the first state, each wideband adaptive lens assemblies 1004, 1008 preserves the handedness of circularly polarized light.

[0182] Still referring to Figure 10, display device 1000 further comprises a waveguide assembly 1012 interposed between the pair of adaptive lens assemblies 1004, 1008. Waveguide assembly 1012 may be similar to waveguide assembly 260, described above with respect to Figure 6, which comprises one or more waveguides similar to one or more of waveguides 270, 280, 290, 300, 310 in Figure 6. For example, as described above with respect to Figures 6 and 7, the waveguides may be configured to propagate light in a lateral direction parallel to the major surfaces of the waveguide under total internal reflection. The waveguides may also be configured to outcouple light, for example, in a direction normal to the major surfaces of the waveguide.

[0183] Still referring to FIG. 10 , a first adaptive lens assembly 1004 of the paired adaptive lens assembly is positioned on a first side of a waveguide assembly 1012, e.g., the side of the world 510 observed by the user, and a second adaptive lens assembly 1008 of the paired lens assembly is positioned on a second side of the waveguide assembly 1012, e.g., the side of the user's eye 210. As described below, the paired adaptive lens assembly as configured provides the user with virtual content from the waveguide assembly 1012 in multiple virtual depth planes along with a view of the real world. In some embodiments, there is little or no distortion due to the presence of the adaptive lens assemblies. The virtual content and views of the real world are provided to the user in response to activation of the first and second adaptive lens assemblies 1004, 1008, as described below with respect to FIGS. 11A and 11B .

[0184] 11A and 11B illustrate examples of display devices 1100A / 1100B, each including an adaptive lens assembly, that, in operation, output image information to a user. Display devices 1100A and 1100B are structurally identical in an unpowered state. Display device 1100A is used herein to describe outputting a virtual image to a user, while display device 1100B is used herein to describe transmitting a real-world image to a user through display device 1100B. Display devices 1100A / 1100B include a pair of switchable lens assemblies 1004, 1008 configured to be electrically activated, for example, by application of a voltage or current. In some embodiments, in a deactivated state, for example, when no voltage or current is applied, first and second switchable lens assemblies 1004, 1008 each have low, e.g., approximately zero, optical power. In some embodiments, in an activated state, e.g., when a voltage or current is applied, the world-side first adaptive lens assembly 1004 may provide a first net refractive power (Pnet1) having a first sign, e.g., positive refractive power, and the user-side second adaptive lens assembly 1008 may provide a second net refractive power (Pnet2) having a second sign, e.g., negative refractive power, when in the activated state.

[0185] 11A illustrates an example of the display system of FIG. 10 displaying virtual content to a user in a virtual depth plane, according to some embodiments. As described above, the waveguide assembly 1012 interposed between the pair of adaptive lens assemblies 1004, 1008 comprises a waveguide configured to receive light containing virtual image information and propagate the light under total internal reflection. The waveguide assembly 1012 is further configured to outcouple the light toward the eye 210, for example, through a diffraction grating. The outcoupled light passes through the second adaptive lens assembly 1008 prior to entering the eye 210. When activated, the second adaptive lens assembly 1008 has a second net refractive power Pnet2, which may have a negative value such that the user sees a virtual image in the virtual depth plane 1104.

[0186] In some embodiments, the second adaptive lens assembly 1008 may be electrically adjusted to adjust the second net refractive power (Pnet2) of the second adaptive lens assembly 1008, thereby adjusting the distance to the virtual depth plane 1104. For example, as a virtual object “moves” closer and farther relative to the eye 210 in virtual three-dimensional space, the second net refractive power Pnet2 of the second adaptive lens assembly 1008 may be correspondingly adjusted such that the virtual depth plane 1104 is adjusted to track the virtual object. Thus, the user may experience relatively little or no accommodation / vergence-divergence mismatch beyond an acceptable threshold. In some embodiments, the magnitude of the distance to the virtual depth plane 1104 may be adjusted in discrete steps, while in some other embodiments, the magnitude of the distance to the virtual depth plane 1104 may be adjusted continuously.

[0187] 11B illustrates an example of the display system of FIG. 10 providing a user with a view of real-world content, according to some embodiments. When the second adaptive lens assembly 1008 is activated to have a second net refractive power (Pnet2) for displaying virtual content in the virtual depth plane 1104, light from the real world passing through the second adaptive lens assembly 1008 may also converge or diverge according to the Pnet2 of the activated second adaptive lens assembly 1008. Thus, objects in the real world may appear out of focus. To mitigate such distortion, according to an embodiment, the first and second adaptive lens assemblies 1004, 1008 may be configured to have refractive powers with opposite signs when activated. In some embodiments, light passing through the first and second adaptive lens assemblies 1004, 1008 converges or diverges according to a combined refractive power having a magnitude that is approximately the difference in magnitude of the first and second net refractive powers Pnet1, Pnet2 of the first and second adaptive lens assemblies 1004, 1008, respectively. In some embodiments, the waveguide assembly 1012 may also have a refractive power, and the adaptive lens assembly 1008 may be configured to account for distortion caused by both the lens assembly 1004 and the waveguide assembly 1012. For example, the refractive power of the adaptive lens assembly 1008 may be of the opposite sign to the sum of the refractive powers of the lens assembly 1004 and the waveguide assembly 1012.

[0188] In some embodiments, the first adaptive lens assembly 1004 is configured to have a first net refractive power Pnet1 that has an opposite sign to Pnet2, but a magnitude that is close to or identical to the magnitude of the second net refractive power Pnet2 of the second adaptive lens assembly 1008. As a result, when both the first and second adaptive lens assemblies 1004, 1008 are activated simultaneously, objects in the real world appear relatively unaffected by the refractive power of the second adaptive lens assembly 1008 that is provided to display virtual content.

[0189] In some embodiments, the first adaptive lens assembly 1004 may be configured, upon activation, to dynamically match the first net refractive power Pnet1 to the second net refractive power Pnet2 of the second adaptive lens assembly 1008. For example, as the second net refractive power Pnet1 of the second switchable lens assembly 1008 is adjusted to track a moving virtual object in virtual three-dimensional space, the first net refractive power Pnet1 of the first adaptive lens assembly 1004 may be dynamically adjusted such that the magnitude of the combined refractive power P=Pnet1+Pnet2 may be kept below a predetermined value. Thus, according to embodiments, an object in the real world may be positioned such that the magnitude of the combined refractive power P=Pnet1+Pnet2 is small, e.g., approximately 0 m -1 By compensating the second net refractive power (Pnet2) of the second adaptive lens assembly 1008, which may have a negative value, with the first net refractive power (Pnet1) of the first adaptive lens assembly 1004 so that the second net refractive power (Pnet2) of the second adaptive lens assembly 1008 remains negative, unacceptable defocusing can be prevented.

[0190] Switchable Waveplates and Switchable Waveplate Lenses for Broadband Adaptive Waveplate Lens Assemblies As discussed above, advantages of forming images at multiple depth planes using fewer waveguides include an overall reduction in the thickness and weight of a display device (e.g., display device 1000 in FIG. 10 ). Accordingly, various embodiments described herein provide adaptive waveplate lens assemblies that are compact and lightweight and provide a variety of optical functionality, such as high bandwidth capabilities and variable optical power. Additionally, various embodiments described herein provide adaptive lens assemblies with relatively low leakage light.

[0191] To provide images at multiple depth planes with high efficiency across a wide range of the visible spectrum, a broadband adaptive lens assembly according to various embodiments includes a waveplate lens (1154A, 1154B in FIGS. 12A and 12B, respectively) comprising liquid crystals arranged such that the waveplate lens has a birefringence (Δn) that varies radially from a central region of the first waveplate lens and increases or decreases with increasing wavelength (λ) within the visible spectrum. As described above, according to various embodiments, the broadband adaptive waveplate lens assembly can be configured to be selectively switched between multiple states with different refractive powers, thereby generating images at multiple depth planes. Selective switching of the broadband lens assembly can, in turn, be implemented by switching the waveplate lens or waveplate included within the broadband adaptive waveplate lens assembly according to embodiments, as discussed herein.

[0192] 12A, in some embodiments, a broadband adaptive lens assembly 1150A is configured to be switched between different optical power states by employing a switchable waveplate 1158 comprising a liquid crystal in the same optical path as a waveplate lens 1154A. The waveplate lens 1154A may be a passive lens, and the broadband adaptive lens assembly 1150A may be selectively switched between different states by electrically activating and deactivating the switchable waveplate 1158.

[0193] 12A , in operation, the waveplate lens 1154A is configured to diverge or converge incident light 1162A, 1162B passing therethrough depending on the polarization of the light, e.g., circular polarization, according to various embodiments. When configured as a half-waveplate (HWP) lens, which may be a passive waveplate lens, the illustrated waveplate lens 1154A is configured to converge a right-handed circularly polarized (RHCP) light beam 1162B incident on the waveplate lens 1154A into a left-handed circularly polarized (LHCP) light beam 1166A. On the other hand, the waveplate lens 1154A is configured to diverge an LHCP light beam 1162A incident on the waveplate lens 1154A into a right-handed circularly polarized (RHCP) light beam 1166B.

[0194] Still referring to FIG. 12A , after being focused or defocused by waveplate lens 1154A, depending on the circular polarization of the light incident thereon, LHCP light beam 1166A or RHCP light beam 1166B is incident on switchable waveplate 1158. The liquid crystal of switchable waveplate 1158 is configured such that, when activated, e.g., electrically activated, the polarization of the circularly polarized light passing therethrough is preserved (not shown). That is, LHCP light beam 1166A and RHCP light beam 1166B pass through switchable waveplate 1158 unaffected. On the other hand, when deactivated, e.g., electrically deactivated, the polarization of the circularly polarized light passing therethrough is altered or converted (as shown). That is, LHCP light beam 1166A is converted to RHCP light beam 1170A, and RHCP light beam 1166B is converted to LHCP light beam 1170B.

[0195] 12B, in some other embodiments, a broadband adaptive lens assembly 1150B is configured to be switched between different optical power states by employing a switchable waveplate lens 1154B comprising a liquid crystal. The adaptive lens assembly 1150B may be selectively switched between different states by electrically activating and deactivating the switchable waveplate lens 1154B.

[0196] In operation, the liquid crystals of the waveplate lens 1154B are configured, according to various embodiments, so that the waveplate lens 1154B diverges or converges incident light 1162A, 1162B passing therethrough depending on its polarization, e.g., circular polarization. When configured as a half-waveplate lens, when deactivated, e.g., electrically deactivated, the illustrated waveplate lens 1154B is configured to converge an RHCP light beam 1162B incident on the waveplate lens 1160B into an LHCP light beam 1166A. Conversely, when deactivated, the waveplate lens 1154B is configured to diverge a left-handed polarized (LHCP) light beam 1162A incident on the waveplate lens 1154B into an RHCP beam 1166B. On the other hand, when activated, e.g., electrically activated, the polarization of the circularly polarized light passing therethrough is preserved or unaffected (not shown), and the LHCP light beam 1162A and RHCP light beam 1162B incident thereon pass through the waveplate lens 1154B substantially without converging or diverging and with their polarization states unaffected. In various embodiments, by configuring the liquid crystals to realign in response to a switching signal, e.g., an electric field, the waveplate lens assemblies 1150A, 1150B may be activated or deactivated to converge or diverge, and convert or preserve the polarization of the circularly polarized light depending on its polarization.

[0197] (Broadband switchable waveplate) As described above, according to various embodiments, a broadband adaptive waveplate lens assembly can be used to generate images at multiple depth planes by selectively switching the broadband waveplate lens assembly between multiple lens states having different refractive powers. As described above, in some embodiments, the broadband adaptive waveplate lens assembly may be configured to be selectively switched between multiple lens states by electrically activating a broadband switchable waveplate included within the broadband adaptive waveplate lens assembly. Embodiments of such broadband switchable waveplates are disclosed below.

[0198] In some embodiments, the broadband switchable waveplate comprises a layer of unpolymerized twisted nematic (TN) liquid crystal (LC) and is configured to be switched in response to application of an electric field across the thickness of the TN LC layer. Without being bound by any theory, switching may be achieved in response to altering the orientation of the unpolymerized LC molecules across the thickness of the TN LC layer.

[0199] 13A-13F, according to various embodiments, a wideband switchable waveplate comprises a layer of twisted nematic (TN) liquid crystal (LC). Figure 13A illustrates a cross-sectional view of an example switchable waveplate comprising a layer of TN LC. The TN LC switchable waveplate 1300A comprises a layer of TN LC 1302 disposed between a pair of transparent substrates 1312. The transparent substrates 1312 each have conductive transparent electrodes 1316, 1320 formed on their inner surfaces.

[0200] The surfaces of the transparent electrodes 1316, 1320 and / or substrate 1312 may be configured such that the TN LC molecules in contact with or directly adjacent to the upper electrode 1316 tend to align with their long axes extending in a first lateral direction, while the TN LC molecules in contact with or directly adjacent to the lower electrode 1320 tend to align with their long axes extending in a second lateral direction that may intersect, e.g., form an approximately 90-degree angle with the first lateral direction. The TN LC molecules between the TN LC molecules directly adjacent to the lower electrode 1320 and the TN LC molecules directly adjacent to the upper electrode 1316 undergo a twist. The illustrated TN LC switchable waveplate 1300A is configured as a broadband waveplate.

[0201] Still referring to FIG. 13A , in operation, in the absence of an electric field across the TN LC layer 1302 (deactivated state), the nematic director of the TN LC molecules undergoes a smooth 90-degree twist across the thickness of the TN LC layer 1302. In this state, incident light 1308 polarized in a first direction (indicated by the double arrow, the same direction as the LC molecules closest to the bottom electrode 1312) is incident on the TN LC layer 1302. The twisted arrangement of the TN LC molecules within the TN LC layer 1302 acts as an optical waveguide, rotating the plane of polarization by a quarter-turn (90 degrees) prior to reaching the top electrode 1316. In this state, the TN LC layer 1302 acts to shift the polarization direction of linearly polarized light passing through it from one linear polarization direction to another. Thus, the transmitted light 1304A is polarized in a second direction opposite to the first direction (the same direction as the LC molecules adjacent to the top electrode 1316).

[0202] On the other hand, when a voltage exceeding the threshold voltage (V>Vth) of the TN LC switchable waveplate 1300A is applied across the electrodes 1316, 1320 (activated state), the TN The TN LC molecules in the LC layer 1306 tend to align with the resulting electric field, and the optical wave-guiding properties of the TN LC layer 1304 described above with respect to the inactivated state are lost. In this state, the TN LC layer 1306 serves to preserve the polarization direction of light passing through it. Thus, the incident light 1308 and the transmitted light 1304B are polarized in the same first direction (the same direction as the LC molecules closest to the bottom electrode 1312).

[0203] Still referring to the activated state, when the voltage or electric field is turned off, the TN LC molecules relax and return to their twisted state, and the TN LC molecules of TN LC layer 1306 in the activated state return to the configuration of the TN LC molecules of TN LC layer 1302 in the deactivated state.

[0204] As explained above, the TN LC switchable waveplate 1300A described above with respect to Figure 13A serves to shift the polarization direction of linearly polarized light. However, various broadband waveplate lens assemblies described herein include a switchable waveplate configured as a switchable half-waveplate for reversing the handedness of circularly polarized light. Accordingly, below with respect to Figures 13B-13D, a switchable waveplate configured as a switchable half-waveplate is described according to an embodiment.

[0205] 13B illustrates a cross-sectional view of a switchable broadband waveplate 1300B configured as a half-waveplate, according to an embodiment. The switchable broadband waveplate 1300B includes the TN LC switchable waveplate 1300A illustrated with respect to FIG. 13A. In addition, to serve as a broadband half-waveplate for circularly polarized light, the switchable broadband waveplate 1300B also includes a pair of achromatic quarter-waveplates (QWPs) 1324, 1326.

[0206] In operation, in the activated state of the switchable broadband waveplate 1300B (upper portion of FIG. 13B ), an input circularly polarized beam 1324 having a first handedness, e.g., a left-handed circularly polarized (LHCP) light beam, passes through the first QWP 1324, which converts the circularly polarized beam 1324 into a first linearly polarized beam 1328 having a first linear polarization. Subsequently, in response to passing through the activated TN LC switchable waveplate 1300A, the first linearly polarized beam 1328 is converted into a second linearly polarized beam 1332 having a second linear polarization. Subsequently, in response to passing through the second QWP 1326, the second linearly polarized beam 1332 is converted into an outgoing circularly polarized beam 1340 having a second handedness opposite to the first handedness, e.g., an RHCP light beam. Thus, when activated, the switchable broadband waveplate 1300B acts as a half-waveplate, reversing the polarization of the circularly polarized beam.

[0207] On the other hand, when the switchable broadband waveplate 1300B is deactivated (lower portion of FIG. 13B ), the polarization of the first linearly polarized beam 1328 is preserved after the incident circularly polarized beam 1324 passes through the first QWP 1324 and subsequently through the deactivated TN LC switchable waveplate 1300A, as described above. Then, in response to passing through the second QWP 1326, the first linearly polarized beam 1328 is converted into an outgoing circularly polarized beam 1340, e.g., an LHCP light beam, having a first handedness. Thus, when deactivated, the broadband waveplate 1300B acts as a transparent medium, which preserves the polarization of the circularly polarized beam.

[0208] In various embodiments described herein, the first and / or second QWPs 1324, 1326 are broadband quarter-wave plates having similar bandwidths compared to the TN LC switchable waveplate 1300A. According to embodiments, the quarter-wave plates 1324, 1326 can be formed using polymerized TN LC layers. To provide broadband capability, the QWPs, according to various embodiments, include multiple TN LC layers. If each TN LC layer were formed on its own substrate, the optical absorption of the resulting broadband quarter-wave plate and / or the resulting stack could be unacceptably thick. Therefore, below, embodiments of QWPs comprising multiple TN LC layers formed on a single substrate are described with respect to efficient integration with the TN LC switchable waveplate 1300A.

[0209] 13C illustrates a cross-sectional view of a broadband QWP 1300C, which can be the first and / or second QWPs 1324, 1326 illustrated above with respect to FIG. 13B, comprising multiple (M) TN LC layers 1302-1, 1302-2, ... 1302-M stacked on a matching layer 1302-0 formed on a substrate 1312. The matching layer 1302-0, as further described elsewhere herein, is configured to induce the elongation direction of LC molecules in the first TN LC layer 1302-1 directly adjacent to the matching layer 1302-0 to be aligned in a first direction. The LC molecules above the LC molecules aligned by the matching layer 1302-0 are successively subjected to a first twist such that the LC molecules in the first TN LC layer 1302-1, which is immediately adjacent to the second TN LC layer 1302-2 and farthest from the matching layer 1302-0, are stretched in a second direction. The alignment of the LC molecules in each subsequent TN LC layer 1302-2 through 1302-M is similar to that of the first TN LC layer 1302-1, except that the LC molecules closest to the previous layer are aligned in the same direction as the topmost LC molecules of the previous layer. For example, the topmost LC molecules in the first TN LC layer 1302-1 and the bottommost LC molecules in the second TN LC layer 1302-2 are aligned in the same second direction. The LC molecules in the second TN LC layer 1302-2 experience a second twist such that the top LC molecules in the second TN LC layer 1302-2 are stretched in a third direction. Such alignment of the LC molecules in a given TN LC layer as a result of alignment of the LC molecules in an adjacent layer in contact with it is sometimes referred to as self-alignment because no intervening alignment layer is interposed therebetween. Thus, in some embodiments, a wideband QWP comprises multiple TN LC layers, with two or more self-aligned TN LC layers each having a non-zero twist.

[0210] In embodiments, the TN LC layer comprises polymerized LC molecules (LCP), formed, for example, using reactive mesogens. As explained above, reactive mesogens are initially low molecular weight LCs that can be aligned by surface and twist to have complex profiles, similar to conventional LCs, but can then be hardened, for example, by photopolymerization, into solid polymer films.

[0211] Figure 13D illustrates a cross-sectional view of an integrated switchable broadband waveplate 1300D in which a TN LC switchable waveplate 1300A similar to that described above with respect to Figure 13A is integrated into a single stack with a pair of broadband QWPs 1324, 1326 similar to that described above with respect to Figure 13C. In the illustrated embodiment, the TN LC switchable waveplate 1300A is integrated into a single stack by attaching a pair of broadband quarter-waveplates 1324, 1326 to opposite sides thereof using adhesive layer 1348.

[0212] FIG. 13E illustrates a cross-sectional view of an integrated switchable broadband waveplate 1300E in which a TN LC switchable waveplate 1300A similar to that described above with respect to FIG. 13A is integrated into a single stack with a pair of broadband quarter-waveplates 1324, 1326 in a manner similar to that described above with respect to FIG. 13D, except that instead of using an adhesive to form the integrated stack, one of the pair of broadband quarter-waveplates 1324, 1326 serves as a substrate onto which the TN LC switchable waveplate 1300A ( FIG. 13A ) can be formed directly. For example, the different layers of the TN LC switchable waveplate 1300A may be formed directly on one or both surfaces of the QWPs 1324, 1326. Advantageously, one or both of the substrates 1312 of the TN LC switchable waveplate 1300A may be omitted. Thus, the TN LC switchable waveplate 1300A is integrated into a compact single stack by forming directly on one of the pair of wideband QWPs 1324, 1326, on top of which the other of the pair of wideband QWPs 1324, 1326 is formed.

[0213] In each of the embodiments illustrated above with respect to Figures 13D and 13E, the broadband QWP can be formed from a liquid crystal-based material, such as quartz and MgF2, or other non-liquid crystal-based materials. Below with respect to Figure 13F, embodiments in which the broadband QWP comprises a liquid crystal are particularly advantageously integrated with a TN LC switchable waveplate in a single stack, serving not only as a QWP but also as a matching layer for the TN LC switchable waveplate.

[0214] Figure 13F illustrates a cross-sectional view of an integrated switchable broadband waveplate 1300F that integrates a TN LC switchable waveplate similar to that described above with respect to Figure 13A. The switchable broadband waveplate 1300F includes a pair of broadband QWPs 1324, 1326 arranged in a manner similar to that described above with respect to Figure 13E, except that instead of broadband QWPs 1324, 1326 as substrates for the TN LC layer 1302, the broadband QWPs 1324, 1326 comprise thin polymerized LC layers formed on respective surfaces of a substrate 1312. The LC molecules of the TN LC layer 1302 are inserted into a gap formed between the opposing surfaces of the broadband QWPs 1324, 1326 by a spacer 1350 that defines the thickness of the TN LC layer 1302. Methods of inserting the LC molecules are further described elsewhere herein. Additionally, the different layers of the TN LC switchable waveplate 1300A and the different layers of the wideband QWPs 1324, 1326 are integrally formed into a single stack. For example, the first wideband QWP 1324 includes a substrate 1312 on which a lower transparent electrode 1316 is formed, followed by a matching layer 1302-0 and multiple TN LC layers 1302-1, 1302-2. Similarly, the second wideband QWP 1326 includes a substrate 1312 on which an upper transparent electrode 1320 is formed, followed by a matching layer 1302-0 and multiple TN LC layers 1302-1, 1302-2.

[0215] 13F, advantageously, the outermost LC molecules of the TN LC layer 1302-2 of the first wideband QWP 1324 facing the gap and the outermost LC molecules of the TN LC layer 1302-2 of the second wideband QWP 1326 facing the gap are arranged to serve as matching layers for the switchable TN LC layer 1302, such that the outermost LC molecules of the TN LC layer 1302 are self-aligned, in a manner similar to that described above with respect to FIG. 13C. Additionally, by integrally stacking the different layers of the TN LC switchable waveplate 1300A and the different layers of the wideband QWPs 1324, 1326, the total thickness of the entire stack can be substantially reduced. For example, mechanically joining a TN LC switchable waveplate 1300A as shown in FIG. 13A and broadband quarter-waveplates 1324, 1326 as shown in FIG. 13C would result in as many as four substrates, whereas the entire stack of switchable broadband waveplate 1300F has only two substrates.

[0216] 13F and various embodiments throughout the specification, the switchable LC layer, e.g., TN LC layer 1302 inserted in the gap, has a thickness of about 1 μm to 50 μm, 1 to 10 μm, 10 to 20 μm, 20 to 30 μm, 30 to 40 μm, 40 to 50 μm, or any range defined by these values. In addition, the passive LC layers, e.g., TN LC layers 1302-1 and 1302-2, can have a thickness of about 0.1 μm to 50 μm, 0.1 to 1 μm, 1 to 10 μm, 10 to 20 μm, 20 to 30 μm, 30 to 40 μm, 40 to 50 μm, or any range defined by these values.

[0217] In various embodiments described herein, a matching layer (e.g., 1302-0 in Figures 13C and 13F) is used to align LC molecules, e.g., align the elongation direction of LC molecules along a particular direction. For example, as described above with respect to Figures 13A-13F, a matching layer can be used to define the director (n), i.e., the local average elongation direction of elongated LC molecules in a given direction. In some other embodiments, the matching layer may be formed from mechanically rubbed organic polymers such as polyimides and polyamides, obliquely deposited inorganic oxides such as SiO2, or long-chain aliphatic siloxanes. In some embodiments, a non-contact matching layer may be formed from an organic polymer using plane-polarized light to create surface anisotropy, which in turn defines the director. For example, the use of cis-trans photoisomerization of azo dyes, which can be directly deposited or dissolved in standard alignment layers (e.g., polyimides) or LC mixtures, can produce alignment effects in the matching layer without rubbing. Non-contact matching layers that use azo chromophores sometimes employ high intensity laser light to induce isomerization of the dye molecules.

[0218] In some other embodiments, the nanostructure pattern can serve as a matching layer for aligning the LC molecules. Advantageously, in some embodiments, the nanostructure pattern is formed as part of the electrode layer, which can improve optical transparency, reduce process steps, and / or further reduce the overall thickness of the broadband waveplate, e.g., as described above with respect to Figures 13A-13F. To this end, Figure 14A illustrates a perspective view of a pattern of nanostructures 1400A, e.g., nanowires, formed on a transparent substrate 1312, that serves the dual functions of a matching layer and an electrode layer, according to an embodiment. The pattern of nanostructures 1400A can be patterned on the substrate 1312, e.g., using lithography or nanoimprinting techniques, as described in detail elsewhere herein. The nanostructures can be formed from a sufficiently thin conductive material that is patterned as elongated metal wires. For example, the conductive material can be gold, silver, copper, aluminum, or ITO, or any suitable conductive material having a thickness and electrical resistivity such that the resulting pattern of nanostructures can simultaneously serve as a matching layer and an electrode layer. In the illustrated embodiment, the pattern of nanostructures 1400A comprises periodic conductive lines 1404A extending in a first direction, e.g., the x-direction, connected to rails 1408A to supply current or voltage to the periodic conductive lines 1404A. In various embodiments, the periodic conductive lines 1404A can have a pitch of 1 μm to 1000 μm, 5 μm to 500 μm, 10 μm to 100 μm, or any value within a range defined by these values. The conductive lines 1404A can have a width of 10 nm to 1 μm, 100 nm to 1000 nm, 100 nm to 500 nm, 200 nm to 300 nm, or any value within a range defined by these values. The periodic conductive lines 1404 can have a thickness of 10 nm to 1 μm, 100 nm to 1000 nm, 100 nm to 500 nm, 400 nm to 500 nm, or any value within the ranges defined by these values.The combination of material, thickness, and width of the periodic conductive lines 1404A can be selected so that the resulting sheet resistance of the periodic conductive lines 1404A is approximately 1 ohm / sq to 100 ohm / sq, 2 ohm / sq to 50 ohm / sq, 5 ohm / sq to 20 ohm / sq, or any value within the range defined by these values, for example, approximately 10 ohm / sq. Additionally, the combination of material and thickness of the conductive lines 1404A can be selected so that the resulting transmittance within the visible spectrum is 80% to 99%, 90% to 99%, 95% to 99%, 97% to 99%, or any value within the range defined by these values, for example, approximately 98%. Other dimensions, configurations, and values ​​are also possible.

[0219] FIG. 14B illustrates a perspective view of a pattern of nanostructures 1400B similar to the pattern of nanostructures 1400A described above with respect to FIG. 14A, except that the pattern of nanostructures 1400B comprises periodic conductive lines 1404B extending in a second direction, e.g., the x-direction, that are connected to rails 1408B for supplying current to the periodic conductive lines 1404B.

[0220] 14C illustrates a perspective view of a pair of electrodes 1400C, according to an embodiment. The pair of electrodes 1400C includes a pattern of nanostructures 1400A ( FIG. 14A ) and a pattern of nanostructures 1400B ( FIG. 14B ) arranged such that periodic conductive lines 1404A and periodic conductive lines 1404B face and cross each other and are separated by gaps 1412 configured to accommodate one or more LC layers, e.g., TN LC layers, disposed therein. Advantageously, it has been found that the patterns of nanostructures 1400A and 1400B can each act as an alignment layer similar to alignment layer 1302-0 described above with respect to Figures 13C and 13F, such that when nematic LC molecules, e.g., reactive mesogens, are formed thereon, the LC molecules directly adjacent to each of the patterns of nanostructures 1400A and 1400B can be aligned with the directors of the nematic LC molecules, e.g., generally aligned in the same direction as the extension direction of the periodic conductive lines 1404A and 1404B. Additionally, the LC molecules between the LC molecules immediately adjacent the periodic conductive lines 1404A, 1404B can be configured to undergo twisting using a twisting agent such that an unpolymerized TN LC layer similar to the TN LC layer 1302 described above with respect to FIG. 13A and a polymerized TN LC layer similar to the TN LC layers 1302-1, 1302-2, ... 1302-M described above with respect to FIG. 13C can be formed.

[0221] Referring back to FIG. 13F, it should be appreciated that in some embodiments, by combining the functionality of the electrodes and matching layers, the pattern of nanostructures 1400A can replace the combination of transparent electrode 1316 and matching layer 1302-0 of broadband QWP 1324, and the pattern of nanostructures 1400B can replace the combination of transparent electrode 1320 and matching layer 1302-0 of broadband QWP 1326, thereby enabling a more compact overall stack.

[0222] Still referring to FIG. 14C, in operation, the alignment of the LC molecules and the corresponding effects on the polarization of light with and without an electric field are similar to those described above with respect to FIG. 13A.

[0223] 15A and 15B illustrate plan and cross-sectional views, respectively, of a TN LC switchable broadband waveplate 1500 according to an embodiment. Unlike the broadband waveplates illustrated above with reference to FIGS. 13A and 13F , which have vertically separated electrodes for switching, the TN LC switchable broadband waveplate includes in-plane laterally separated electrodes for switching. The TN LC switchable broadband waveplate 1500 includes a matching electrode stack 1524 and a matching layer stack 1526. Similarly, as described above with reference to FIG. 13F , LC molecules are inserted into the gap formed by the spacer 1350 between the opposing surfaces of the matching electrode stack 1524 and the matching layer stack 1526. Methods for inserting LC molecules are described elsewhere herein. The matching electrode stack 1524 includes first and second electrodes 1500A, 1500B formed on the upper transparent substrate 1312, and further includes an optional upper matching layer 1302-0. The matching layer stack 1526 includes a lower matching layer 1302-0 formed on a lower transparent substrate 1312.

[0224] 15A, a matching electrode stack 1524 includes first and second electrodes 1500A, 1500B, each including a respective one of first and second periodic conductive lines 1504A, 1504B. The periodic conductive lines 1504A are interdigitated or interlaced with the periodic conductive lines 1504B. The first and second periodic conductive lines 1504A, 1504B are each strapped to rails 1508A, 1508B, respectively, in a manner similar to that described above with respect to the patterned nanostructures 1400A (FIG. 14A), 1400B (FIG. 14B). The material, thickness, width, and pitch of the alternating periodic conductive lines 1504A, 1504B can be similar to those described above with respect to patterned nanostructures 1400A ( FIG. 14A ), 1400B ( FIG. 14B ). However, unlike the paired electrodes 1400C described above with respect to FIG. 14C , which are vertically separated, the periodic conductive lines 1504A alternate with the periodic conductive lines 1504B in a lateral direction, e.g., the y-direction, such that the electric field between the periodic conductive lines 1504A and 1504B is directed in the lateral direction.

[0225] Referring to the cross-sectional view of TN LC switchable cell 1500 in Figure 15B, in a manner similar to that described above with respect to Figure 13F, LC molecules are inserted into the gap formed between opposing surfaces of matching electrode stack 1524 and matching layer stack 1526 so that a TN LC layer (not shown) similar to TN LC layer 1302 (Figure 13A) can be formed. Methods for inserting LC molecules are described elsewhere herein.

[0226] In some embodiments, in a manner similar to that described above with respect to FIG. 14C , the alternating periodic conductive lines 1504A, 1504B in the matching electrode stack 1524 and / or the upper matching layer 1302-0 can serve as a matching layer for the outermost LC molecules of the TN LC layer 1302 formed in the gap 1412, in a manner similar to the matching layer 1316 described above with respect to FIG. 13A and the conductive line 1404B described above with respect to FIG. 14C . When the alternating periodic conductive lines 1504A, 1504B serve as matching layers, in some embodiments, the upper matching layer 1302-0 may be omitted. Similar to the matching layer 1320 described above with respect to FIG. 13A and the conductive line 1404A described above with respect to FIG. 14C , the lower matching layer 1302-0 can serve to match the LC molecules in the gap 1412 directly adjacent thereto.

[0227] Although not shown, in some embodiments, the illustrated TN LC switchable broadband waveplate 1500 can integrate multiple TN LC layers similar to TN LC layers 1302-1, 1302-2, ... 1302-M (Figure 13F, not shown) between the alternating periodic conductive lines 1504A, 1504B and the LC molecules in the gaps 1412 and / or between the lower matching layer 1302-0 and the LC molecules in the gaps 1412, in a manner similar to that described above with respect to Figure 1300F, thereby providing integrated QWP functionality in a manner similar to that described above with respect to Figure 13F.

[0228] 15A and 15B, in operation, in the absence of an electric field, the alternating periodic conductive lines 1504A, 1504B act as matching layers for the LC molecules directly adjacent to the periodic conductive lines 1504A, 1504B such that the LC molecules have directors that generally extend parallel to the periodic conductive lines 1504A, 1504B. In the deactivated state, the switchable broadband waveplate 1500 is configured to invert the polarization of linearly polarized light in a manner similar to that described above with respect to FIG. On the other hand, when an electric field is applied in a lateral direction, e.g., the y-direction, between the periodic conductive lines 1504A and 1504B, the LC molecules between immediately adjacent periodic conductive lines 1504A, 1504B align their elongation direction, e.g., away from parallel, between parallel and perpendicular, or perpendicular to the periodic conductive lines 1504A, 1504B. In an activated state, in a manner similar to that described above with respect to FIG. 13A , the switchable broadband waveplate 1500 is configured to preserve the polarization of linearly polarized light.

[0229] In some embodiments, in addition to combining the functionality of the electrodes and matching layers, the first and second electrodes 1500A, 1500B can replace, for example, the combination of transparent electrodes 1316, 1320 and upper and lower matching layers 1302-0 of the broadband waveplate 1300F (FIG. 13F), thereby allowing for an even more compact overall stack and even more improved transparency due to halving the electrode layers.

[0230] (Liquid crystal based wave plate lens) 12A , to provide images at multiple depth planes with high efficiency across a wide range of the visible spectrum, some broadband adaptive waveplate lens assemblies, according to embodiments, include a switchable waveplate and one or more waveplate lenses, which may be passive or switchable, formed from thin films of birefringent liquid crystals. Below, exemplary waveplate lenses are disclosed that comprise liquid crystals whose orientation in the plane of the waveplate is adapted to focus and / or modify the polarization state of light transmitted therethrough. Below, various embodiments of lenses and waveplates are formed from liquid crystals.

[0231] One example of a liquid crystal-based waveplate lens is illustrated with respect to Figures 16A and 16B.

[0232] 16A and 16B illustrate examples of wave plate lenses 1200A and 1200B, respectively, each comprising a transparent substrate 1204, e.g., a glass substrate, having formed thereon liquid crystal molecules 1208 that are elongated along different elongation directions relative to a direction parallel to an axial direction (e.g., x-direction or y-direction) along a major surface of the substrate 1204. That is, the liquid crystal molecules 1208 are rotated by different rotation angles (φ) about a direction normal (e.g., z-direction) to the major surface of the substrate 1204, where φ is described as the angle between the elongation directions of the liquid crystal molecules relative to a layer normal and a direction parallel to the layer normal (e.g., x-direction or y-direction).

[0233] In the illustrated implementation, the liquid crystal molecules 1208 at a given radius from the central axis C or center of the lens have substantially the same rotation angle (φ). As arranged, the liquid crystal molecules 1208 are configured to focus a collimated beam of light to a point at a certain focal length. Without being bound by any theory, the rotation angle (φ) of the liquid crystal molecules 1208 may be proportional to a power of r, where r is the radial distance from C and has a value of about 1 to 3, e.g., 2. In one implementation, the angle (φ) is + / - k0r 2 / f, where r is the radial distance from C, k0=2π / λ is the wave number of the light to be focused by the diffractive wave plate lens, λ is the wavelength of the light, and f is the focal length of the wave plate lenses 1200A, 1200B. The + and − signs may correspond to the rotation direction of the liquid crystal molecules 1208 relative to the liquid crystal molecules 1208 nearest to the center C of the wave plate lenses 1200A, 1200B.

[0234] It should be understood that the patterns of liquid crystal molecules 1208 in waveplate lenses 1200A and 1200B represent inverted images of each other. That is, one of waveplate lenses 1200A and 1200B can be obtained by rotating the other of waveplate lenses 1200A and 1200B by 180 degrees about an axial direction (e.g., the x-direction or the y-direction). As configured, the focal lengths and refractive powers of waveplate lenses 1200A and 1200B are identical in magnitude but opposite in sign.

[0235] In some implementations, waveplate lenses 1200A and 1200B can each function as a half-waveplate lens. When configured as a half-waveplate lens, waveplate lenses 1200A and 1200B each rotate the plane of linear polarization by an angle 2α relative to the polarization of the input beam, where α is the angle between the input polarization direction and the waveplate axis. For a circularly polarized beam, this change in angle translates into a phase shift and a reversal of polarization handedness. Thus, a ±2α phase shift can be generated in the circularly polarized beam, with the sign of the phase shift depending on the polarization handedness.

[0236] 16C illustrates an example of a waveplate lens that diverges or converges light passing therethrough, depending on the polarization of the light and the side the light is incident on, according to some embodiments. When configured as a half-waveplate lens, the illustrated waveplate lens 1200A may be configured to diverge a right-handed circularly polarized (RHCP) light beam 1212 incident on a first side into a left-handed circularly polarized (LHCP) beam 1216. On the other hand, the waveplate lens 1200A may be configured to converge a RHCP light beam 1220 incident on a second side opposite the first side into a left-handed circularly polarized (LHCP) beam 1224.

[0237] 16D , when configured as a half-wave plate, waveplate lens 1200B may be configured to converge LHCP light beam 1228 incident on a first side into RHCP beam 1232. On the other hand, waveplate lens 1200B may be configured to diverge LHCP light beam 1236 incident on a second side opposite the first side into RHCP beam 1240.

[0238] Therefore, by controlling the rotation angle direction and radial distribution of the liquid crystal 1208, the waveplate lens can be configured to converge or diverge circularly polarized light of either handedness. It should be understood that the refractive power can be increased or decreased based on the relationship between the rotation angles of the liquid crystal. Additionally, in some embodiments, the liquid crystals may be aligned and misaligned by applying an electric field. It should be understood that, in the limit where the refractive power is approximately zero, the waveplate lens can be used as a waveplate, for example, a switchable waveplate.

[0239] (Broadband adaptive waveplate lens assembly including switchable waveplates) As described above with respect to Figure 12A, to provide images at multiple depth planes with high efficiency across a wide range of the visible spectrum, some broadband adaptive waveplate lens assemblies, according to embodiments, include a switchable waveplate and one or more waveplate lenses, which may be passive or switchable, formed from a thin film of birefringent material, such as a liquid crystal. Below, embodiments of broadband adaptive waveplate lens assemblies are disclosed that include a switchable broadband waveplate. For example, the switchable broadband waveplate may be one of the broadband switchable waveplates described above with respect to Figures 13A-13F, 14A-14C, and 15A-15B.

[0240]

[0013] Figure 17A illustrates an example of a broadband adaptive waveplate lens assembly 1700 comprising a waveplate lens, e.g., a passive waveplate lens, and a switchable waveplate, according to some embodiments. The broadband adaptive waveplate lens assembly 1700 may be configured, for example, as any one of the pair of switchable waveplate assemblies 1004, 1008 described above with respect to Figures 10, 11A, and 11B. Figure 17B illustrates the broadband adaptive waveplate lens assembly 1700A when, in operation, the switchable waveplate of the adaptive lens assembly 1700 illustrated in Figure 17A is activated, while Figure 17C illustrates the broadband adaptive waveplate lens assembly 1700B when, in operation, the switchable waveplate of the adaptive lens assembly 1700 illustrated in Figure 17A is deactivated. The adaptive lens assembly 1700 is configured to couple and transmit light outcoupled from the waveguide assembly 1012 (FIGS. 10, 11A, 11B). The adaptive lens assembly 1700 comprises a first wave plate lens (L1 / HWP1) 1704, e.g., a first half-wave plate lens, a second wave plate lens (L2 / HWP2) 1708, e.g., a second half-wave plate lens, and a switchable wave plate (HWP3) 1712, e.g., a switchable half-wave plate.

[0241] In various embodiments, L1 / HWP1 1704 and L2 / HWP2 1708 are configured to act as a lens and a half-wave plate, respectively. As described above with respect to Figures 12A and 12B, when configured as half-wave plates, L1 / HWP1 1704 and L2 / HWP2 1708 are each configured to convert light having circular polarization of a first handedness (first HCP) to light having circular polarization of a second handedness (second HCP). That is, L1 / HWP1 1704 and L2 / HWP2 1708 are each configured to convert light passing therethrough, from light having an LHCP or an RHCP to light having an RHCP or an LHCP, respectively.

[0242] In various embodiments, L1 / HWP1 1704 and L2 / HWP2 1708 are each configured to act as a lens, with a first lens effect or a second lens effect opposite to the first lens effect, for a given polarization. That is, L1 / HWP1 1704 and L2 / HWP2 1708 are each configured to either converge or diverge light passing therethrough. In various embodiments, L1 / HWP1 1704 and L2 / HWP2 1708 may each be configured to have an opposite lens effect depending on the polarization state of the incident light. For example, L1 / HWP1 1704 and L2 / HWP2 1708 may each be configured to focus light incident thereon with a first HCP, while defocusing light incident thereon with a second HCP.

[0243] In some embodiments, L1 / HWP1 1704 and L2 / HWP2 1708 are configured to have the same lens effect for light with a given HCP, i.e., both L1 / HWP1 1704 and L2 / HWP2 1708 may be configured to focus light with an LHCP, focus light with an RHCP, defocus light with an LHCP, or defocus light with an RHCP.

[0244] In some embodiments, L1 / HWP1 1704 and L2 / HWP2 1708 may each comprise liquid crystal molecules that are stretched and rotated such that the liquid crystals at a given radius from the central axis of the respective waveplate lenses 1704, 1708 have the same rotation angle (φ), as described above with respect to FIGS. 12A and 12B . The first and second waveplate lenses 1704, 1708 are each configured to modify the polarization state, e.g., reverse the polarization state, of light passing therethrough. The switchable waveplate 1712 is configured to modify the polarization state, e.g., reverse the polarization state of light passing therethrough, when electrically deactivated, while being configured to substantially pass light without modifying the polarization state of the light passing therethrough, when activated. An electrical signal, e.g., a current signal or a voltage signal, for switching the switchable waveplate 1712 may be provided by a switching circuit 1716 electrically connected thereto.

[0245] In various embodiments, when deactivated, e.g., electrically deactivated using a voltage or current signal provided by switching circuit 1716, HWP3 1712B (FIG. 17C) acts as a half-wave plate. That is, when deactivated, HWP3 1712B (FIG. 17C) acts as a half-wave plate configured to convert light passing therethrough from light having an LHCP or RHCP to light having an RHCP or LHCP, respectively. Thus, when deactivated (FIG. 17C), L1 / HWP1 1704, L2 / HWP2 1708, and HWP3 1712B are each configured to convert light having a first circular polarization (first HCP) to light having a second circular polarization (second HCP).

[0246] In various embodiments, when activated, e.g., electrically activated using a voltage or current signal provided by switching circuitry 1716, e.g., by removing the voltage or current signal, HWP3 1712A (FIG. 17B) acts as a transmission medium for light without affecting polarization or providing any lens effect.

[0247] In some embodiments, the single waveplate lenses 1704 and / or 1708 may function as both waveplate lenses and switchable half-waveplates, and in such embodiments, the dedicated switchable half-waveplate 1712 may be omitted.

[0248] FIG. 17B illustrates an example of the adaptive lens assembly of FIG. 17A with the switchable waveplate activated during operation, according to some embodiments. Adaptive lens assembly 1700A may be activated when switchable waveplate 1712 is activated, e.g., when no current or voltage is applied to switchable waveplate 1712 by switching circuitry 1716. Adaptive lens assembly 1700A may correspond to first adaptive lens assembly 1004 (world-side) or second adaptive lens assembly 1008 (user-side). By way of example only, adaptive lens assembly 1700A will be described as corresponding to first adaptive lens assembly 1004 or second adaptive lens assembly 1008 as part of display device 1000 ( FIG. 10 ) that displays a view of the real world to a user without displaying a virtual image. For example, display device 1000 ( FIG. 10 ) may be used as regular glasses or regular goggles. L1 / HWP1 1704 and L2 / HWP2 1708 may each be configured to exert a first lens effect, e.g., a diverging effect, on light having a first HCP, e.g., an LHCP, passing therethrough. L1 / HWP1 1704 and L2 / HWP2 1708 may also each be configured to exert a second lens effect, e.g., a converging effect, opposite to the first lens effect, on light having an opposing HCP, e.g., an RHCP, passing therethrough.

[0249] In the illustrated embodiment, light beam 1720 may represent a light beam from the world incident on either first adaptive lens assembly 1004 ( FIGS. 11A / B , world side) or second adaptive lens assembly 1008 ( FIGS. 11A / B , user side) while display device 1700A is being used as regular glasses or goggles without displaying virtual content. By way of example only, light beam 1720 having a first HCP, e.g., an LHCP, travels, e.g., in the positive z-direction, until beam 1720 impinges on L1 / HWP1 1704 to be transmitted therethrough. L1 / HWP1 1704 converts light beam 1720 having an LHCP into light beam 1724 having an RHCP. Because L1 / HWP1 1704 is also configured as a lens, L1 / HWP1 1704 also diverges light beam 1720 according to the first optical power P1 of L1 / HWP1 1704.

[0250] Light beam with RHCP 1724 subsequently impinges on HWP3 1712A, which is in an activated state. Because HWP3 1712A is activated, light beam with RHCP 1724 transmits through HWP3 1712A substantially unaffected in terms of polarization or lensing and impinges on L2 / HWP2 1708 as light beam with RHCP 1728A. As described above, when configured as a user-side adaptive lens assembly (e.g., second adaptive lens assembly 1004 in FIG. 10 ), L2 / HWP2 1708, in the illustrated embodiment, is configured similarly to L1 / HWP1 1704, i.e., to convert polarization and diverge light with an LHCP while converging light with an RHCP. Thus, light beam with RHCP 1728A is converted back into light beam with an LHCP 1732. Thus, when HWP3 1712A is activated, L1 / HWP1 1704 and L2 / HWP2 1704 transmit light beams with opposite polarizations such that L1 / HWP1 1704 and L2 / HWP2 1708 exert opposite lens effects on the light passing therethrough. That is, because light beam 1728A incident on L2 / HWP2 1704 has an RHCP, light beam 1732A emerging from L2 / HWP2 1708 is converged according to the second refractive power P2, unlike light beam 1724 emerging from L1 / HWP1 1704, which is diverged according to the first refractive power P1. Light beam 1732A can then be viewed by the eye in response to emission from adaptive lens assembly 1700A in the activated state.

[0251] In some embodiments, when HWP3 1712A is activated, the first refractive power P1 of L1 / HWP1 1704, which may be negative (i.e., divergence), and the second refractive power P2 of L2 / HWP2 1708, which may be positive (i.e., convergence), may have substantially the same or matched magnitudes. In these embodiments, the net refractive power Pnet of the adaptive lens assembly 1700A, which may be approximately −P1 + P2, may be substantially zero due to compensation for the lens effects of L1 / HWP1 1704 and L2 / HWP2 1708. However, embodiments are not so limited, and the first and second refractive powers P1, P2 may have different magnitudes such that the net refractive power Pnet may have a non-zero value. For example, in some embodiments, a non-zero Pnet may be equal to the user's eyeglass prescription, thereby enabling correction of focusing errors (e.g., refractive focusing errors) of the user's eyes.

[0252] In the illustrated embodiment, incident light beam 1720 has an LHCP, but it should be understood that similar results would occur when incident light beam 1720 has an RHCP. That is, when light beam 1720 has an RHCP, light beams 1724 and 1728A have an LHCP, and unlike the illustrated embodiment, light beams 1724 and 1728A are converged relative to light beam 1720. Similarly, L2 / HWP2 1708 diverges light beam 1728A, which is converged by L1 / HWP1 1704, such that the net optical power Pnet may be substantially zero.

[0253] It should be understood that the lensing effect of L1 / HWP1 1704 and L2 / HWP2 1708 and the selectivity of the lensing effect to the polarization state of the incident light beam described above with respect to Figure 17B serve merely as an example, and other configurations are possible. For example, in Figure 17B, L1 / HWP1 1704 and L2 / HWP2 1708 are configured to diverge light with an LHCP while converging light with an RHCP, but in other embodiments, L1 / HWP1 1704 and L2 / HWP2 1708 may be configured to converge light with an LHCP while diverging light with an RHCP.

[0254] In sum, in some embodiments, when HWP3 1712A of adaptive lens assembly 1700A is in an activated state, outgoing light beam 1732A has the same HCP as incident light beam 1720 and can be substantially matched to incident light beam 1720 in terms of lensing due to compensation for lensing between P1 of L1 / HWP1 1704 and P2 of L2 / HWP2 1708. As a result, when the user is not viewing virtual content, their view of the world is relatively unaffected by the presence of the adaptive lens assemblies (1004, 1008 in FIGS. 10, 11A, 11B).

[0255] FIG. 17C illustrates an example of the adaptive lens assembly of FIG. 17A with the switchable waveplate deactivated during operation, according to some embodiments. Adaptive lens assembly 1700B may be deactivated when switchable waveplate 1712B is deactivated, e.g., when a current or voltage is applied to switchable waveplate 1712B by switching circuitry 1716. Adaptive lens assembly 1700B may correspond, for example, to first adaptive lens assembly 1004 (world-side) or second adaptive lens assembly 1008 (user-side). Below, as an example, adaptive lens assembly 1700B will be described as initially configured as user-side second adaptive lens assembly 1008 as part of a display device (e.g., display device 1100A in FIG. 11A ) that outputs a virtual image to a user. Adaptive lens assembly 1700B will then be described as being configured as a world-side first adaptive lens assembly 1004 as part of display device 1100B (FIG. 11B) that outputs a virtual image to a user while simultaneously transmitting a view of the real world, reducing or essentially eliminating distortion of the real-world view resulting from the lensing effect of second adaptive lens assembly 1008.

[0256] When configured as the second adaptive lens assembly 1008 on the user side (FIG. 11A), L1 / HWP1 1704 and L2 / HWP2 1708 may each be configured to diverge light having one of the HCPs, e.g., the LHCP, passing therethrough. L1 / HWP1 1704 and L2 / HWP2 1708 may also each be configured to converge light having the other HCP, e.g., the RHCP, passing therethrough.

[0257] As described above with respect to FIG. 11A , a portion of the light propagating within waveguide assembly 1012 in the x-direction may be redirected or outcoupled in the z-direction, e.g., by total internal reflection. Light that is outcoupled from waveguide assembly 1012 ( FIG. 11A ) may be incident on switchable lens assembly 1700B as a circularly polarized beam 1720 having an LHCP. Light beam 1720 travels, e.g., in the positive z-direction, until light beam 1720 impinges on and is transmitted through L1 / HWP 1704. L1 / HWP 1704 1704 converts light beam with LHCP 1720 into light beam with RHCP 1724. Because L1 / HWP1 1704 is configured to diverge light with LHCP, light beam 1724 is also diverged according to the first optical power P1 of L1 / HWP1 1704.

[0258] Light beam 1724 with RHCP subsequently impinges on HWP3 1712B in its deactivated state. Unlike activated HWP 1712A illustrated above with respect to FIG. 17B , HWP3 1712B is deactivated, so that light beam 1724 with RHCP transmitting through HWP3 1712B is converted to light beam 1728B with LCHP. Light beam 1728B with LHCP subsequently impinges on L2 / HWP2 1708. Unlike light beam 1728A illustrated above with respect to FIG. 17B , light beam 1728B impinging on L2 / HWP2 1708 has an LHCP, so L2 / HWP2 1708 further diverges light beam 1728B into light beam 1732B with RHCP according to the second optical power P2. That is, unlike the activated state of HWP 1712A illustrated with respect to Figure 17B, HWP 1712B is deactivated so that L1 / HWP1 1704 and L2 / HWP1 1704 are configured to transmit light beams having the same polarization LHCP. Thus, unlike L1 / HWP1 1704 and L2 / HWP2 1708 having a compensating effect illustrated with respect to Figure 17B, L1 / HWP1 1704 and L2 / HWP2 1708 in Figure 17C exert an additive lens effect on light passing therethrough. That is, because light beam 1720 incident on L1 / HWP1 and light beam 1728B incident on L2 / HWP2 1704 both have LHCP, light beam 1732B exiting L2 / HWP2 1708 will be diverged in addition to the divergence due to L1 / HWP1 1704. Light beam 1732A may then be seen by the eye upon exiting adaptive lens assembly 1700B in the deactivated state.

[0259] In some embodiments, the first refractive power P1 of L1 / HWP1 1704 and the second refractive power P2 of L2 / HWP2 1708 may both be negative (i.e., diverging) and may have substantially the same or matched magnitudes. In these embodiments, the net refractive power Pnet of the adaptive lens assembly 1700B, which may be approximately P1 + P2, may be substantially twice that of P1 or P2 due to the additive lens effect of the combination of L1 / HWP1 1704 and L2 / HWP2 1708. However, embodiments are not so limited, and the first and second refractive powers P1, P2 may have different magnitudes.

[0260] In the illustrated embodiment, incident light beam 1720 has an LHCP, but it should be understood that similar results would occur when incident light beam 1720 has an RHCP. That is, when light beam 1720 has an RHCP, unlike the illustrated embodiment, resultant light beam 1732B has an LHCP and is focused by L1 / HWP1 1704 and L2 / HWP2 1708 according to a net refractive power Pnet having a magnitude that is approximately the sum of the magnitudes of the first and second refractive powers P1 and P2.

[0261] It should be understood that the lensing effect of L1 / HWP1 1704 and L2 / HWP2 1708 and its dependence on the polarization state of the incident light beam, described above with respect to Figure 17C, serves merely as an example, and other configurations are possible. For example, while in Figure 17B L1 / HWP1 1704 and L2 / HWP2 1708 are configured to diverge light with an LHCP while converging light with an RHCP, in other embodiments L1 / HWP1 1704 and L2 / HWP2 1708 may be configured the other way around, to diverge light with an LHCP while converging light with an RHCP.

[0262] As a result, in some embodiments, when switchable half-wave plate 1712B of adaptive lens assembly 1700B is in a deactivated state, outgoing light beam 1732B has an opposite HCP to incident light beam 1720 and may diverge according to the additive refractive powers P1 of L1 / HWP1 1704 and P2 of L2 / HWP2 1708. As a result, when a user views virtual content, the virtual content is focused into eye 210 according to the net refractive power, whose value is approximately Pnet=P1+P2.

[0263] The above describes adaptive lens assembly 1700B in a deactivated state when configured as user-side second adaptive lens assembly 1008 in display device 1100A described above with respect to FIG. 11A. However, as described above with respect to FIG. 11B, activating second adaptive lens assembly 1008 and displaying virtual content to user's eye 210 without any compensatory effect may result in defocusing or distortion of the real-world view, which may be undesirable. Therefore, it may be desirable to configure world-side first adaptive lens assembly 1004 to at least partially compensate or nullify the lens effect of second adaptive lens assembly 1008 when deactivated to display virtual content.

[0264] Referring back to FIG. 17C , when configured as a world-side first adaptive lens assembly 1004 ( FIG. 11B ) to neutralize the lens effect of a user-side second adaptive lens assembly 1008 ( FIG. 11B ), the components of adaptive lens assembly 1700B may be similarly configured as described above with respect to FIG. 11B . That is, as light transmitted from the world 510 to the eye 210 traverses the first and second adaptive lens assemblies 1004, 1008, they may each be configured as described above with respect to adaptive lens assembly 1700B described with respect to FIG. 17C . In operation, as described above, the polarization of light transmitted from the world through first adaptive lens assembly 1004 is converted from a first polarization state to a second polarization state, e.g., from RHCP to LHCP. Subsequently, the polarization of light transmitted through second adaptive lens assembly 1008 is converted back from the second polarization state to the first polarization state, e.g., from LHCP to RHCP. 11B, light transmitted from the world through the first adaptive lens assembly 1004 experiences a first lens effect, e.g., a converging effect, according to a first net refractive power Pnet1=P1+P2 having a first sign, e.g., a positive sign. Subsequently, light transmitted through the second adaptive lens assembly 1008 experiences a second lens effect, e.g., a diverging effect, opposite to the first lens effect, according to a second net refractive power Pnet2=P1'+P2' having a second sign, e.g., a negative sign, because the light incident on the second adaptive lens assembly 1008 has the opposite polarization to the light incident on the first adaptive lens assembly 1004. When Pnet1 and Pnet2 have substantially similar magnitudes, the overall lens effect, approximated by P=Pnet1+Pnet2, can be substantially zero. As a result, when a user views virtual content and real objects in the surrounding world by activating the second lens assembly 1008, the view of the world is relatively unaffected by the compensation effect of the first lens assembly 1004.

[0265] In various embodiments, when deactivated, the first and second adaptive lens assemblies 1004, 1008 may each provide a net optical power (positive or negative) within the range of approximately ±5.0 diopters to 0 diopters, ±4.0 diopters to 0 diopters, ±3.0 diopters to 0 diopters, ±2.0 diopters to 0 diopters, ±1.0 diopters to 0 diopters (including any range defined by these values, e.g., ±1.5 diopters).

[0266] Display device including an adaptive lens assembly having a switchable half-wave plate and a waveplate lens 10, 11A, and 11B, in which an adaptive lens assembly comprising a waveplate lens and a switchable waveplate, such as adaptive lens assembly 1300 described above with respect to FIGS. 17A-17C, is integrated according to some embodiments. The switchable waveplate may be one of the broadband switchable waveplates described above with respect to FIGS. 13A-13F, 14A-14C, and 15A-15B, for example.

[0267] 18A and 18B illustrate exemplary display devices 1800A / 1800B, each including a waveguide assembly 1012 interposed between a first wideband adaptive waveguide lens assembly 1004 and a second wideband adaptive waveguide lens assembly 1008. Display device 1800A is similar to display devices 1100A / 1100B, described above with respect to FIGS. 11A / 11B, in that the first and second adaptive lens assemblies 1004, 1008 each comprise a first waveplate lens (L1 / HWP1) 1704, e.g., a first half-waveplate lens, a second waveplate lens (L2 / HWP2) 1708, e.g., a second half-waveplate lens, and a switchable waveplate (HWP3) 1712, e.g., a switchable half-waveplate.

[0268] 18A , display device 1800A is described as operating when both first and second adaptive lens assemblies 1004, 1008, described above with respect to FIG. 17A, are activated. First and second adaptive lens assemblies 1004, 1008 may be activated when switchable waveplate 1712 ( FIG. 17A ) is activated, e.g., when no current or voltage is applied to switchable waveplate 1712 by switching circuitry 1816, 1816′. As configured, display device 1800A may be configured to display a real-world view to a user, for example, without displaying a virtual image. For example, display device 1800A may be configured to be used as regular glasses or regular goggles, as described in detail with respect to FIG. 17B. 17A, the first and second adaptive lens assemblies 1004, 1008 each include a first wave plate lens (L1 / HWP1) 1804, e.g., a first half-wave plate lens, a second wave plate lens (L2 / HWP2) 1808, e.g., a second half-wave plate lens, and a switchable wave plate (HWP3) 1812, e.g., a switchable half-wave plate. As described with respect to FIG. 17A, L1 / HWP1 1804 and L2 / HWP2 1808 may each be configured to exert a first lens effect, e.g., a divergence effect, on light having a first HCP, e.g., an LHCP, passing therethrough. Additionally, L1 / HWP1 1804 and L2 / HWP2 1808 may each also be configured to exert a second lens effect, e.g., a focusing effect, opposite to the first lens effect, on light having an opposite HCP, e.g., RHCP, passing therethrough. When deactivated, e.g., electrically deactivated using a voltage or current signal provided by switching circuitry 1816, 1816′, HWP3 1712B (FIG. 17C) acts as a wave plate, e.g., a half-wave plate.As described above with respect to FIG. 17C, when deactivated, HWP3 1712B (FIG. 17C) acts as a half-wave plate configured to convert light passing therethrough from light having an LHCP or RHCP to light having an RHCP or LHCP, respectively. On the other hand, when activated, e.g., electrically by removing the voltage or current signal, e.g., using a voltage or current signal provided by switching circuit 1816, 1816′, HWP3 1712A (FIG. 17B) acts as a transmission medium for light without affecting its polarization. Detailed operating principles of the first and second adaptive lens assemblies 1004, 1008, including L1 / HWP1 1804, L2 / HWP2 1808, and HWP3, 1812A, have been provided above with respect to FIGS. 17A and 17B and will not be described here.

[0269] 17B and 17C, when the first and second adaptive lens assemblies 1004, 1008 are in an activated state, the light beam (e.g., 1732A in FIG. 17B) exiting each of the first and second adaptive lens assemblies 1004, 1008 has the same HCP as the light beam (e.g., 1720 in FIG. 17B) incident thereon. In addition, the incident light beam 1720 and the exiting light beam 1732A can be substantially matched in terms of the magnitude of the lens refractive power to compensate for the net refractive power of the first and second lens assemblies 1004, 1008, as described above with reference to FIG. 13B.

[0270] Figure 18B illustrates an example of the display device of Figure 18A with the switchable waveplates deactivated during operation, according to some embodiments. The first and second adaptive lens assemblies 1004, 1008 activate their respective switchable waveplates 1712 (Figure 17A) by applying a current or voltage to the switchable waveplates 1712, for example, using switching circuitry 1816, 1816'. Below, operation of the display device 1800B is described, which outputs a virtual image to a user with reduced or essentially eliminated distortion resulting from the lensing effect of the adaptive lens assemblies 1004, 1008, while also transmitting light from objects in the real world.

[0271] When displaying a virtual image, a portion of the light propagating within the waveguides in waveguide assembly 1012 in the x-direction may be redirected or outcoupled in the z-direction, as described above with respect to Figures 11A and 17C. Light beam 1720 travels, for example, in the positive z-direction until light beam 1720 impinges on L1 / HWP 1804 of second adaptive lens assembly 1008. Based on the operating principle of second adaptive lens assembly 1008 described above with respect to Figure 17C, when second adaptive lens assembly 1008 is in the inactivated state, the outgoing light beam (e.g., 1732B in Figure 17C) has an opposite HCP to the incoming light beam (e.g., 1720 in Figure 17C) and is diverged according to a second net refractive power Pnet2 to display virtual content in a corresponding virtual depth plane.

[0272] In various embodiments, when deactivated, the first and second adaptive lens assemblies 1004, 1008 may each provide a net optical power (positive or negative) within a range of approximately ±5.0 diopters to 0 diopters, ±4.0 diopters to 0 diopters, ±3.0 diopters to 0 diopters, ±2.0 diopters to 0 diopters, or ±1.0 diopters to 0 diopters (including any range defined by these values, e.g., ±1.5 diopters). In some embodiments, the first adaptive lens assembly 1004 between the waveguide assembly 1012 and the world may have a positive optical power, while the second adaptive lens assembly 1008 between the waveguide assembly 1012 and the user may have a negative optical power, such that the optical powers of the first and second switchable assemblies 1004, 1008 compensate each other when viewing the world.

[0273] 18A and 18B, display device 1800A / 1800B comprises a pair of adaptive lens assemblies 1004, 1008 in an optical path between world 510 and eye 210, each of which comprises a switchable waveplate (e.g., 1712A / 1712B in FIGS. 17A / 17B) configured to alter the polarization state of light passing therethrough when electrically deactivated. When electrically deactivated, the pair of adaptive lens assemblies have net refractive powers (P, P) with opposite signs, such that light passing through the pair of adaptive lens assemblies converges or diverges according to a combined refractive power having a magnitude that is approximately the difference between the magnitudes of the refractive powers of the pair of adaptive lens assemblies. Virtual content can be observed by a user at a certain depth plane according to Pnet2, which may be negative, while the view of the world is relatively unaffected by Pnet2, which is at least partially compensated by Pnet1, which may be positive.

[0274] In some embodiments, the pair of adaptive lens assemblies each have a respective net refractive power (Pnet1, Pnet2) that is electrically adjustable or tunable to one of a plurality of values ​​using switching circuitry 1816, 1816′. As described above, as the image of the virtual object produced by the light outcoupled by the waveguide assembly 1012 moves in 3D, the second net refractive power (Pnet2) of the user-side second adaptive lens assembly 1008 is adjusted to match the changing depth of the virtual depth plane. At the same time, according to embodiments, the first net refractive power (Pnet1) of the first adaptive lens assembly 1004 is correspondingly adjusted using switching circuitry 1816, 1816′ so that the view of the real world is not undesirably defocused or distorted. To address this and other needs, in some embodiments, the display device 1800A / 1800B includes a controller 1804 configured such that when a first net refractive power (Pnet1) of a first one of the pair of adaptive lens assemblies 1004, 1008 is electrically adjusted, a second refractive power (Pnet2) of a second one of the pair of adaptive lens assemblies is correspondingly adjusted so that the combined refractive power (Pnet1+Pnet2) remains substantially constant, e.g., about zero. The controller circuit and switchable waveplate 1812 are configured such that the time to switch between the first and second net refractive powers Pnet, Pnet2, and to adjust the virtual depth plane using the second adaptive lens assembly 1008 and to compensate for the real world view using the first adaptive lens assembly 1004, as described herein, is less than about 100 milliseconds, less than about 50 milliseconds, less than about 10 milliseconds, less than about 5 milliseconds, less than about 1 millisecond, or a value within a range defined by any of these values.

[0275] (Broadband switchable waveplate lens) As described above, according to various embodiments, a broadband adaptive waveplate lens assembly can generate images at multiple depth planes by being selectively switched between multiple states having different refractive powers. In some embodiments described above, the broadband capability of the broadband adaptive waveplate lens assembly can be enabled by one or more broadband passive waveplate lenses (e.g., 1154A in FIG. 12A ) combined with a broadband switchable waveplate (e.g., 1158 in FIG. 12A ). In some other embodiments, the broadband capability of the broadband adaptive waveplate lens assembly can be enabled by a broadband switchable waveplate lens without a broadband switchable waveplate (e.g., 1154B in FIG. 12B ). Below, the structure and configuration of the liquid crystal layer of the broadband switchable waveplate lens and the broadband adaptive lens assembly having the same will be described according to the embodiments.

[0276] 19A illustrates a plan view of a broadband waveplate lens 1900 comprising a layer of LC molecules formed on a transparent substrate, according to various embodiments. The stretching directions of the bottom LC molecules or the LC molecules closest to the substrate and / or the resulting spatial distribution of the local directors of the LC molecules can be distributed according to the pattern of arrows depicted in FIG. 19A. In the illustrated embodiment, the LC molecules closest to the substrate at a given radius from the central region generally have the same stretching direction.

[0277] In some embodiments, the waveplate lens 1900 is a polarization-type Fresnel zone plate (FZP) lens with a radially symmetric and radially modulated birefringence profile. In some embodiments, the elongational orientation or local director of the LC molecules can vary as a function of radius according to a mathematical function. In the illustrated embodiment, the azimuthal angle φ of the local director of the LC molecules can have discrete values ​​in different zones located at different radii from the center of the waveplate lens 1900. For example, φ in the mth zone can be expressed as: [ka] where f is the focal length and r is the distance from the center of the waveplate lens 1900.

[0278] In some other embodiments, the spatial distribution of the stretching directions or local directors of the LC molecules or the local birefringence resulting therefrom may be similar to that described above with respect to Figures 16A and 16B.

[0279] In some embodiments, the local alignment direction, e.g., stretching direction, of the LC molecules above the bottom LC molecule is generally the same as that of the bottom LC molecule closest to the substrate. In some other embodiments, the local alignment direction of the LC molecules above the bottom LC molecule can be generally different from that of the bottom LC molecule closest to the substrate. For example, the local alignment direction of the LC molecules above the bottom LC molecule can be continuously twisted, as described below (e.g., Figures 20A and 20B).

[0280] In operation, in a manner similar to the waveplate lens described above with respect to Figures 16A and 16B, the broadband waveplate lens 1900 has a polarization-selective lens effect, functioning as a convex (or positive) lens (Figure 19B) for incident light 1162B having a first polarization, e.g., right-handed circular polarization (RHCP), and as a concave (or negative) lens (Figure 19C) for incident light 1162A having a second polarization, e.g., left-handed circular polarization (LHCP). In addition, the broadband waveplate lens 1900 converts the polarization of the diffracted light. That is, the incident light 1162B having RHCP is converted by the broadband waveplate lens 1900 to light 1166A having LHCP, as shown in Figure 19B, while the incident light 1162A having LCHP is converted by the waveplate lens 1900 to light 1166B having RHCP, as shown in Figure 19C. The relative proportion of undiffracted leaked light 1904 determines the diffraction efficiency, as explained above.

[0281] The inventors have found that further improvements in the high bandwidth capabilities of the waveplate lens can be achieved, particularly by configuring the twisted alignment of the LC molecules vertically within one or more LC layers (e.g., Figures 20A, 20B) or by employing negative dispersion LC materials (Figure 21), to further reduce undiffracted leakage light 1904 and increase diffraction efficiency, which in turn further reduces undesirable visual effects such as afterimages, as explained below.

[0282] 20A and 20B schematically illustrate a plan view and a cross-sectional view, respectively, of a broadband waveplate lens 2000 comprising multiple crystalline LC layers, according to an embodiment. The illustrated broadband waveplate lens 2000 comprises a stack of two LC layers 2004, 2008 having LC molecules with opposite twist orientations, such that the retardation of light by one of the LC layers 2004, 2008 is compensated by the other of the LC layers 2004, 2008. For illustrative purposes only, FIGS. 20A and 20B depict the relative orientation of the LC molecules, which schematically varies laterally in a particular manner. However, it should be understood that the lateral alignment of the LC molecules across the xy plane at a given depth in the z direction can also have any of the various alignments described above, including those illustrated above with respect to FIGS. 16A and 16B and with respect to FIG. 19A. For example, in some embodiments, the LC molecules closest to the substrate generally have the same local alignment direction, e.g., a local elongation direction or local director, at a given radius from the central region, and / or have an alignment direction that varies as a function of radius in a manner similar to that described above with respect to Figure 19A. In addition, the alignment of LC molecules within a given columnar region within the two LC layers 2004, 2008 can be described as having a nematic director n, which varies as a function of vertical location within the LC layers according to: [ka] where φ is the azimuthal angle of the director n in the xz plane. That is, for a given row of LC molecules having a first sense of twist in one of the LC layers 2004, 2008, the corresponding row of LC molecules in the other of the LC layers 2004, 2008 has the opposite sense of twist. In other words, the LC molecules in the two LC layers 2004, 2008 are mirror images of each other about the interface between the two LC layers 2004, 2008.

[0283] According to an embodiment, reactive mesogens can be employed to create alignment of the LC molecules in the two LC layers 2004, 2008. For example, by suitably configuring the matching layer 1302-0 on the substrate 1312, the bottom-most LC molecules in the first LC layer 2004 closest to the matching layer 1302-0 can be aligned to have a first azimuthal angle.

[0284] The first azimuthal angle can be defined according to the alignment of the elongation direction of the LC molecules, for example, as described above with respect to any of Figures 16A, 16B, and 19A. Additionally, the LC molecules above the bottommost LC molecules in the first LC layer 2004 can be configured to have a first twist by adding a chiral agent to the first LC layer 2004, such that the topmost LC molecules closest to the surface of the first LC layer 2004 have a second azimuthal angle. Then, by suitably configuring the surface region of the first LC layer 2004, the bottommost LC molecules in the second LC layer 2008 closest to the first LC layer 2004 can be aligned to have the second azimuthal angle. Additionally, the LC molecules above the bottom LC molecules in the second LC layer 2008 can be configured to have a second chiral twist by adding a chiral agent to the second LC layer 2008, such that the top LC molecules closest to the surface of the second LC layer 2008 have a third azimuthal angle. In some embodiments, the first and second chiral twists are nearly identical, such that the bottom LC molecules of the first LC layer 2004 and the top LC molecules of the second LC layer 2008 have the same first azimuthal angle.

[0285] In one exemplary configuration, by configuring the LC layers 2004, 2008 to have a suitable thickness, e.g., about 1 μm to 2 μm or about 1.5 μm to 2 μm, e.g., about 1.7 μm, and a suitable chiral twist of about 50 degrees to 90 degrees or about 60 degrees to 80 degrees, e.g., about 70 degrees, a wavelength range of diffraction efficiency greater than 99%, a relative bandwidth Δλ / λ greater than 40%, 50%, or 60%, e.g., about 56%. o can be achieved according to the embodiment.

[0286] As explained above, the diffraction efficiency (η) is given by η=sin 2 (πΔnd / λ), where Δn is birefringence, λ is wavelength, and d is thickness. Generally, optically anisotropic materials exhibit Δn that decreases with increasing λ (referred to herein as a positive dispersion of Δn). However, a positive dispersion of Δn results in a different phase retardation Γ=2πΔnd / λ at different λ. The inventors recognize that by employing an optically anisotropic material that exhibits Δn that increases with increasing λ (referred to herein as having a negative dispersion of Δn), the phase retardation Γ can be kept relatively constant at different λ, and the diffraction efficiency η can be kept relatively high and constant over a relatively wide wavelength range, according to an embodiment.

[0287] 21 illustrates a cross-sectional view of a broadband waveplate lens 2100 comprising a negative dispersion (ND) liquid crystal (LC) layer 2104 formed on a substrate 1312 and a matching layer 1312-0, according to an embodiment. Similar to the broadband waveplate lenses described above with respect to FIGS. 19A and 20A / 20B, to provide a lens effect, the ND LC layer 2104 can be aligned, for example, by suitably aligning the matching layer 1312-0, so that the waveplate lens 2100 has a birefringence (Δn) that varies radially from a central region. Additionally, in some embodiments, the bottom-most LC molecules closest to the substrate 1312 can be aligned to generally have the same alignment direction at a given radius from the central region and generally have an alignment direction that varies as a function of radius, in a manner similar to that described above with respect to FIGS. 16A, 16B, and 19A, for example, using a matching layer 1312-0 suitably configured as discussed elsewhere herein.

[0288] In various embodiments, the negative dispersion (ND) liquid crystal (LC) layer 2104 can have a birefringence (Δn) of a typical, local, average, median, maximum, or minimum value between 0.05 and 0.10, 0.15 and 0.20, 0.20 and 0.25, 0.25 and 0.30, 0.30 and 0.35, 0.35 and 0.40, 0.40 and 0.45, 0.45 and 0.50, 0.50 and 0.55, 0.55 and 0.60, 0.60 and 0.65, 0.65 and 0.70, or a value within a range defined by any of these values. Additionally, the negative dispersion (ND) liquid crystal (LC) layer 2104 can have an intralayer birefringence (Δn) in the range of 0.01 to 0.05, 0.05 to 0.10, 0.15 to 0.20, 0.20 to 0.25, 0.25 to 0.30, 0.30 to 0.35, 0.35 to 0.40, or a value within a range defined by any of these values.

[0289] Still referring to Figure 21, unlike the LC molecules described above with respect to Figures 20A and 20B, the ND LC layer 2104 may be vertically homogeneous. For example, in the ND LC layer 2104, the LC crystals formed above the bottom LC molecules may not be twisted. Instead, in some embodiments, within a given columnar region, the local director n may be substantially constant across the thickness of the ND LC layer 2104. In some other embodiments, within a given columnar region, the local director n may be substantially random across the thickness of the LC layer 2104.

[0290] According to various embodiments, the ND LC layer 2104 may be formed from a material, e.g., a reactive mesogen, having a material property in which Δn increases with increasing wavelength (λ) within at least a portion of the visible spectrum between 400 and 800 nm, including one or more of the range of wavelengths defined by a red spectrum including wavelengths in the range of about 620 to 780 nm, a green spectrum including wavelengths in the range of about 492 to 577 nm, and a blue spectrum including wavelengths in the range of about 435 to 493 nm, or any wavelength within the visible spectrum between about 400 nm and 800 nm, e.g., 400 to 700 nm, 430 to 650 nm, or 450 to 630 nm. In some embodiments, within any of these wavelength ranges, the NCLC layer 2104 has a normal refractive index n o The extraordinary refractive index n is smaller than that of e has a variance of

[0291] In some embodiments, the ND LC layer 2104 comprises a smectic liquid crystal (LC), for example, a smectic LC polymer composite material.

[0292] Advantageously, in some embodiments, the broadband waveplate lens 2100 has a single ND LC layer 2104 that has birefringence, unlike the broadband waveplate lens 2000 described above with respect to Figures 20A and 20B, for example, which has multiple layers.

[0293] In various embodiments of the broadband waveplate lens described above with respect to any one of Figures 16A, 16B, 19A, 20A / 20B, and 21, the LC layer can be configured to be passive or switchable, depending on the embodiment. When configured as a passive lens, the layer of LC molecules can be formed from polymerized LC (LCP), while when configured as a switchable lens, the layer of LC molecules can be formed from unpolymerized LC molecules or reactive mesogens. When configured as a switchable lens, the waveplate lens described above with respect to Figures 16A, 16B, 19A, 20A / 20B, and 21 further comprises transparent electrodes on both sides (e.g., Figure 14C) or the same side (e.g., Figures 15A / 15B) of the layer of LC molecules, in a manner similar to that described above with respect to the various embodiments described above.

[0294] 22A-22C illustrate a switchable broadband waveplate lens 2200, which, in operation, may resemble any of the broadband waveplate lenses described above with respect to any one of FIGS. 16A, 16B, 19A, 20A / 20B, and 21. Figures 22A, 22B, and 22C respectively illustrate a deactivated switchable broadband waveplate lens 2200 with an LHCP light beam incident thereon, a deactivated switchable broadband waveplate lens 2200 with an RHCP light beam incident thereon, and an activated switchable broadband waveplate lens 2200 with an LHCP light beam 1162A or an RHCP light beam 1162B incident thereon.

[0295] 22A, switchable broadband waveplate lens 2200 comprises liquid crystals arranged as described above with respect to any one of Figures 16A, 16B, 19A, 20A / 20B, and 21 and configured to be selectively switched between different lens states by electrically activating and deactivating them. In operation, switchable broadband waveplate lens 2200 is configured to diverge light according to a refractive power -P and converge light according to a refractive power P depending on the polarization, e.g., circular polarization, of incident light 1162A, 1162B, according to various embodiments.

[0296] 22A , when deactivated, switchable broadband waveplate lens 2200 is configured to diverge LHCP light beam 1162A incident thereon into RHCP light beam 1166B according to refractive power −P. Conversely, with reference to FIG. 22B , when deactivated, e.g., electrically deactivated, switchable broadband waveplate lens 2200 is configured to converge RHCP light beam 1162B incident thereon into LHCP light beam 1166A according to refractive power P. On the other hand, with reference to FIG. 22C , when activated, e.g., electrically activated, the polarization of circularly polarized light passing therethrough is preserved (not shown), and RHCP light beam 1162B and LHCP light beam 1162A incident thereon pass through switchable broadband waveplate lens 2200 without substantially converging or diverging (i.e., refractive power P ≈ 0).

[0297] (Broadband adaptive waveplate lens assembly with switchable waveplate lens) As described above with respect to Figures 22A-22C, a switchable broadband waveplate lens, according to embodiments, can be configured to impart a refractive power P or -P depending on the polarization of incident light when deactivated, while imparting substantially no refractive power when activated. The inventors recognize that by combining two or more switchable broadband waveplate lenses, many more lens states can be obtained for displaying virtual images at many different focal depths. Below, a broadband adaptive lens assembly comprising multiple switchable broadband waveplate lenses is described, in which two or more switchable broadband waveplate lenses can be configured to impart a refractive power P or -P depending on the polarization of incident light. n Different refractive power states can be obtained for incident light with a given polarization.

[0298] 23A-23D illustrate a broadband adaptive lens assembly 2300 comprising a first switchable broadband waveplate lens 2204 and a second switchable broadband waveplate lens 2208, each of which may operate in a manner similar to the switchable waveplate lenses described above with respect to FIGS. 22A-22C. The switchable broadband waveplate lenses 2204, 2208 may each be arranged in a manner similar to any of the broadband waveplate lenses described above with respect to any one of FIGS. 16A, 16B, 19A, 20A / 20B, and 21. FIGS. 23A, 23B, 23C, and 23D illustrate state combinations in which the first switchable broadband waveplate lens 2304 / second switchable broadband waveplate lens 2308 are deactivated / deactivated, deactivated / activated, activated / deactivated, and activated / activated, respectively.

[0299] In the illustrated embodiment, the first switchable broadband waveplate lens 2304 is configured in a similar manner to the broadband waveplate lens 2200 described above with respect to FIGS. 22A-22C. That is, when deactivated, the first switchable broadband waveplate lens 2304 is configured to diverge the LHCP light beam 1162A incident thereon into the RHCP beam 1166B according to a refractive power −P1. Additionally, although not shown, when deactivated, the first switchable broadband waveplate lens 2304 is configured to converge the RHCP light beam incident thereon into the LHCP beam according to a refractive power +P1. On the other hand, when activated, the first switchable broadband waveplate lens 2304 is configured to substantially neither converge nor diverge circularly polarized light passing therethrough (i.e., refractive power P1 approximately 0), thereby substantially preserving polarization.

[0300] On the other hand, when the second switchable broadband waveplate lens 2308 is deactivated, it is configured to operate in an opposite manner with respect to the sign of the applied refractive power compared to the broadband waveplate lens 2200 described above with reference to FIGS. 22A-22C. That is, when deactivated, the second switchable broadband waveplate lens 2308 is configured to converge the LHCP light beam 1162A incident thereon into the RHCP beam 1166B according to the refractive power +P2. In addition, although not shown, when deactivated, the second switchable broadband waveplate lens 2308 is configured to diverge the RHCP light beam incident thereon into the LHCP beam according to the refractive power −P2. On the other hand, when activated, the second switchable broadband waveplate lens 2308 is configured to substantially neither converge nor diverge circularly polarized light passing therethrough (i.e., refractive power P2 approximately 0), thereby substantially preserving polarization.

[0301] 23A, the first switchable broadband waveplate lens 2304 is deactivated, causing the LHCP light beam 1162A incident thereon to diverge into the RHCP light beam 1166B according to a refractive power −P1. The second switchable broadband waveplate lens 2208 is then deactivated, causing the RHCP light beam 1166B incident thereon to diverge into the LHCP light beam 1170A according to a refractive power −P2. In essence, the LHCP light beam 1162A incident on the broadband adaptive lens assembly 2300 is diverged into the LHCP light beam 1170A according to a net refractive power of −(P1 + P2).

[0302] 23B, the first switchable broadband waveplate lens 2304 is deactivated, causing the LHCP light beam 1162A incident thereon to diverge into the RHCP light beam 1166B according to a refractive power −P1. The second switchable broadband waveplate lens 2208 is then activated, preserving the polarization of the RHCP light beam 1166B passing therethrough without substantially converging or further diverging. In essence, the LHCP light beam 1162A incident on the broadband adaptive lens assembly 2300 is diverged into the RHCP light beam 1166BA according to a net refractive power of −P1.

[0303] 23C, the first switchable broadband waveplate lens 2304 is activated and preserves the polarization of the LHCP light beam 1162A passing therethrough without substantially converging or diverging. The second switchable broadband waveplate lens 2308 is then deactivated and converges the LHCP light beam 1162A incident thereon into the RHCP light beam 1170B according to the optical power +P2. In effect, the LHCP light beam 1162B incident on the broadband adaptive lens assembly 2300 is converged into the RHCP light beam 1170B according to the net optical power of +P2.

[0304] 23D, the first and second switchable broadband waveplate lenses 2304, 2308 are both activated and preserve the polarization of the LHCP light beam 1162A passing therethrough without substantially converging or diverging. Thus, the LHCP light beam 1162B incident on the broadband adaptive lens assembly 2300 appears substantially unaffected as the LHCP light beam 1162B.

[0305] In summary, as illustrated in Figures 23A-23D, by selectively switching the first and second switchable broadband waveplate lenses 2304, 2308, the broadband adaptive lens assembly 2300 can have four different refractive power states: 0, -P1, +P2, and -(P1+P2), according to an embodiment.

[0306] Additionally, although not shown, in a similar manner, when the incident light is an RHCP light beam, by selectively switching the first and second switchable broadband waveplate lenses 2304, 2308, the broadband adaptive lens assembly 2300 can have four different refractive power states, which will be 0, +P1, -P2, and +(P1+P2).

[0307] Additionally, although not shown, in some embodiments, the second switchable broadband waveplate lens 2308 can be configured to operate in the same manner as the first switchable broadband waveplate lens 2304 in terms of the dependence of the sign of the refractive power on the polarization of the incident light. In these embodiments, for example, when the incident light is an LHCP light beam, the resulting four different refractive power states will be 0, -P1, -P2, and -(P1-P2).

[0308] Additionally, if the second switchable broadband waveplate lens 2308 is configured to operate in the same manner as the first broadband waveplate lens 2304 in terms of the dependence of the sign of the refractive power on the polarization of the incident light when the incident light is an RHCP light beam, the resulting four different refractive power states will be 0, P1, P2, and (P1-P2).

[0309] 23A-23D, the illustrated broadband adaptive lens assembly 2300 is configured to achieve variable refractive power by independently switching the lenses themselves (e.g., first and second switchable broadband waveplate lenses 2304, 2308). However, other embodiments are also possible in which one or both of the first and second switchable broadband waveplate lenses 2204, 2208 may be replaced by a combination of a passive waveplate lens and a switchable waveplate, similar to the combination of passive waveplate lens 1154A and switchable waveplate 1158, as described above with respect to FIG.

[0310] 24A illustrates an integrated broadband adaptive lens assembly 2400 with a switchable layer of LC molecules similar to that described above with respect to any one of FIGS. 19A, 20A / 20B, and 21, according to an embodiment. The integrated broadband adaptive lens assembly 2400 includes a switchable LC layer 2304, which can be similar to that described above with respect to any one of FIGS. 19A, 20A / 20B, and 21, except that the switchable LC layer 2304 is sandwiched between a pair of passive wave plate lens stacks 2308, 2312. Similarly, as described above with respect to FIG. 13F, the LC molecules are inserted into a gap formed between mutually facing surfaces of the passive wave plate lens stacks 2308, 2312 by a spacer 1350, the method of which is described elsewhere herein. The first passive waveplate lens stack 2308 includes a substrate 1312 on which a lower transparent electrode 1316 is formed, followed by a matching layer 2302 and a lower polymerized LC (LCP) layer 2302-1. Similarly, the second passive waveplate lens stack 2312 includes a substrate 1312 on which an upper transparent electrode 1320 is formed, followed by a matching layer 2302 and an upper polymerized LC (LCP) layer 2302-2.

[0311] The first and second passive waveplate lens stacks 2308, 2312, respectively, act as waveplate lenses and matching layers for aligning the LC molecules within the switchable LC layer 2304. Similarly, as described above with respect to Figures 13C and 13F, the LC molecules of the lower LCP layer 2302-1 closest to the gap and the LC molecules of the upper LCP layer 2302-2 closest to the gap are arranged such that the outermost LC molecules of the switchable LC layer 2304 are self-aligned. However, embodiments are not so limited, and in some other embodiments, the outermost LC molecules of the switchable LC layer 2304 may be sufficiently aligned by the upper and / or lower matching layers 2302 such that one of both the first and second LCP layers 2302-1, 2302-2 is omitted.

[0312] 24A and various embodiments throughout the specification, the switchable LC layer, e.g., switchable LC layer 2304 inserted in the gap, has a thickness of about 1 μm to 50 μm, 1 to 10 μm, 10 to 20 μm, 20 to 30 μm, 30 to 40 μm, 40 to 50 μm, or any range value defined by these values. In addition, the passive LC layers, e.g., LCP layers 2302-1, 2302-2, can have a thickness of about 0.1 μm to 50 μm, 0.1 to 1 μm, 1 to 10 μm, 10 to 20 μm, 20 to 30 μm, 30 to 40 μm, 40 to 50 μm, or any range value defined by these values.

[0313] In the illustrated embodiment, LCP layers 2302-1, 2302-2 can each have LC molecules with a net twist angle of 30 to 90 degrees, 40 to 80 degrees, 50 to 70 degrees, or any angle within a range defined by any of these values, for example, about 60 degrees.

[0314] In some embodiments, the switchable LC layer 2304 can be a single layer, similar to the LC layer described above with respect to Figure 21. However, embodiments are not so limited. For example, the switchable LC layer 2204 can include multiple LC layers in a manner similar to that described above with respect to Figures 20A / 20B.

[0315] In operation, the integrated broadband adaptive lens assembly 2400 described herein with reference to FIG. 24A shares several characteristics that may be similar to the switchable waveplate 1300F described above with reference to FIG. 13F. For example, in both embodiments, the switchable waveplate element (switchable TN LC layer 1302 in FIG. 13F and switchable LC layer 2304 in FIG. 24A) is interposed between a pair of passive waveplate elements (TN LC layers 1302-1, 1302-2, polymerized LC (LCP) layers 2302-1, 2302-2 in FIG. 13F). In both embodiments, the switchable waveplate element is configured to change the polarization of light passing therethrough to an orthogonal polarization. Similarly, in both embodiments, the passive waveplate elements are similarly aligned by separate alignment layers such that the passive waveplate elements have a mutually canceling effect when the switchable waveplate element is electrically activated and allows light to pass therethrough without diffracting. On the other hand, the passive waveplate element has a complementary effect when the switchable waveplate element is electrically deactivated and diffracts light passing therethrough. In certain embodiments, when the passive waveplate elements have the same refractive power and when the switchable waveplate element is activated, the net refractive power of the assembly is about zero and the polarization of the light is not altered. On the other hand, when the switchable waveplate element is deactivated, the net refractive power of the assembly is the net sum of the refractive powers of the switchable and passive waveplate elements, which have opposite signs. Below, with reference to Figures 24B-24D, one particular embodiment is described in which the passive waveplate element is a half-waveplate lens and the switchable waveplate element is also a half-waveplate.

[0316] 24B-24D illustrate an integrated broadband adaptive lens assembly 2400 in operation, which may be similar to the adaptive lens assembly described above with respect to FIGS. 17A-17C, except that a switchable half-wave plate in the center is configured as a lens to provide optical power.

[0317]

[0013] Figure 24B illustrates the integrated broadband adaptive lens assembly 2400 described above with respect to Figure 24A in terms of optical functionality. Figure 24C illustrates the integrated broadband adaptive lens assembly 2400A (Figure 24A) when, in operation, the switchable waveplate lens 2304 of the adaptive lens assembly 2400 illustrated in Figure 24B is activated, while Figure 24D illustrates the switchable assembly 2400B when, in operation, the switchable waveplate lens 2304 of the integrated broadband adaptive lens assembly 2400 illustrated in Figure 24B is deactivated. The integrated broadband adaptive lens assembly 2400 is configured to couple and transmit light outcoupled from the waveguide assembly 1012 (Figures 10, 11A, 11B) therethrough. The integrated wideband adaptive lens assembly 2400 comprises a first wave plate lens (L1 / HWP1) 2308 (Figure 24A), e.g., a first half-wave plate lens, corresponding to the passive wave plate lens stack 2308, a second wave plate lens (L2 / HWP2) 2312 (Figure 24A), e.g., a second half-wave plate lens, corresponding to the passive wave plate lens stack 2312, and a switchable half-wave plate (L3 / HWP3) 2304 (Figure 24A) corresponding to the switchable LC layer 2304.

[0318] 24B-24D, L3 / HWP 2304B (FIG. 24D), L1 / HWP1 2308, and L2 / HWP2 2312 in the deactivated state act as passive half-wave plate lenses that provide optical powers P3, P1, and P2, respectively, and are configured to convert the handedness of circularly polarized light passing therethrough from a first handedness (first HCP) to a second handedness (second HCP), while L3 / HWP 2304A (FIG. 24C) in the activated state is configured to preserve the handedness of circularly polarized light passing therethrough.

[0319] Additionally, when deactivated, e.g., electrically using a voltage or current signal provided by switching circuit 1716, L3 / HWP3 2304B (FIG. 24D) acts as a half-wave plate lens having optical power P3. On the other hand, when activated, e.g., by removing a voltage or current signal using switching circuit 1716, L3 / HWP3 2304A (FIG. 24C) acts as a transmission medium for light without affecting polarization or providing any substantial lens effect.

[0320] FIG. 24C illustrates integrated wideband adaptive lens assembly 2400B when L3 / HWP 2304A is activated in operation. Integrated wideband adaptive lens assembly 2400B may correspond to first adaptive lens assembly 1004 ( FIG. 10 , world side) or second adaptive lens assembly 1008 ( FIG. 10 , user side). By way of example only, integrated wideband adaptive lens assembly 2400A will be described as corresponding to first adaptive lens assembly 1004 or second adaptive lens assembly 1008 as part of display device 1000 ( FIG. 10 ) that displays a view of the real world to the user without displaying a virtual image. For example, display device 1000 ( FIG. 10 ) may be used as regular glasses or regular goggles. L1 / HWP1 2308 and L2 / HWP2 2312 may each be configured to exert a first lens effect, e.g., a diverging effect, on light having a first HCP, e.g., an LHCP, passing therethrough. Although not shown, L1 / HWP1 2308 and L2 / HWP2 2312 may also each be configured to exert a second lens effect, e.g., a converging effect, opposite to the first lens effect, on light having an opposite HCP, e.g., an RHCP, passing therethrough.

[0321] In the illustrated embodiment, light beam 1720 may represent a light beam from the world incident on either first adaptive lens assembly 1004 (world side) or second adaptive lens assembly 1008 (user side) while display device 1000 ( FIG. 10 ) is being used as regular glasses or goggles without displaying virtual content. By way of example only, light beam 1720 having a first HCP, e.g., an LHCP, travels in the positive z-direction until, for example, beam 1720 passes through and is transmitted through L1 / HWP 2308, transforming light beam 1720 into light beam 1724 having an RHCP according to a first optical power −P1, diverging light beam 1720.

[0322] Still referring to FIG. 24C , L3 / HWP3 2304A is subsequently activated, such that light beam with RHCP 1724 transmits through L3 / HWP3 2304A substantially unaffected in terms of polarization or lensing and is incident on L2 / HWP2 2312 as light beam with RHCP 1728A. As described above, when configured as an adaptive lens assembly on the user side (e.g., second adaptive lens assembly 1004 in FIG. 10 ), L2 / HWP2 2312 is configured similarly to L1 / HWP1 1704 ( FIG. 17B ), i.e., to convert polarization and diverge light with LHCP while converging light with RHCP. Thus, light beam with RHCP 1728A is converted back into light beam with LHCP 1732A. Thus, when L3 / HWP3 2304A is activated, L1 / HWP1 2308 and L2 / HWP2 2312 transmit light beams having opposite polarizations such that L1 / HWP1 2308 and L2 / HWP2 2312 exert opposite lens effects on the light passing therethrough. That is, because light beam 1728A incident on L2 / HWP2 2312 has an RHCP, light beam 1732A emerging from L2 / HWP2 2312 is converged according to the second refractive power +P2, unlike light beam 1724 emerging from L1 / HWP1 1704, which is diverged according to the first refractive power −P1. Light beam 1732A can then be viewed by the eye in response to emerging from adaptive lens assembly 1700A in the activated state.

[0323] In some embodiments, when L3 / HWP3 2304A is activated, the first refractive power −P1 of L1 / HWP1 2308 and the second refractive power +P2 of L2 / HWP2 2312 may have opposite signs but substantially identical or matched magnitudes. In these embodiments, the net refractive power Pnet of the integrated wideband adaptive lens assembly 2400, which may be approximately −P1 + P2, may be substantially zero so that the viewer's view of the world is substantially unaffected. However, embodiments are not so limited, and the first and second refractive powers −P1, +P2 may have different magnitudes such that the net refractive power Pnet may have a non-zero value. For example, in some embodiments, a non-zero Pnet may be equal to the user's eyeglass prescription, thereby allowing for correction of focusing errors (e.g., refractive focusing errors) of the user's eyes.

[0324] In the illustrated embodiment, incident light beam 1720 has an LHCP, but similar results would be achieved when incident light beam 1720 has an RHCP. That is, when incident light beam 1720 has an RHCP, light beams 1724 and 1728A have an LHCP, and unlike the illustrated embodiment, light beams 1724 and 1728A are converged according to a refractive power +P1. Similarly, light beam 1728A is diverged according to a refractive power −P2, such that the net refractive power Pnet may be +P1−P2, which may be substantially zero.

[0325] It should be understood that the lensing effect of L1 / HWP1 2308 and L2 / HWP2 2312 and the selectivity of the lensing effect for the polarization state of the incident light beam described above with respect to Figure 24C serve only as one example, and other configurations are possible. For example, in Figure 24C, L1 / HWP1 2308 and L2 / HWP2 2312 are configured to diverge light with an LHCP while converging light with an RHCP, but in other embodiments, L1 / HWP1 2308 and L2 / HWP2 2312 may be configured to converge light with an LHCP while diverging light with an RHCP.

[0326] In short, in some embodiments, when L3 / HWP3 2304A is in an activated state, outgoing light beam 1732A has the same HCP as incident light beam 1720 and can be substantially matched to incident light beam 1720 in terms of lensing due to compensation for the lensing between P1 of L1 / HWP1 2308 and P2 of L2 / HWP2 2312. As a result, when the user is not viewing virtual content, their view of the world is relatively unaffected by the presence of the adaptive lens assemblies (1004, 1008 in FIGS. 10, 11A, 11B).

[0327] Figure 24D illustrates an example of the adaptive lens assembly of Figure 24B when, in operation, L3 / HWP3 2304B is deactivated. Integrated wideband adaptive lens assembly 2400B may correspond, for example, to first adaptive lens assembly 1004 (world-side) or second adaptive lens assembly 1008 (user-side). Below, as an example, integrated wideband adaptive lens assembly 2400B will be described as initially configured as user-side second adaptive lens assembly 1008 as part of a display device (e.g., display device 1100A in Figure 11A) that outputs a virtual image to a user. Subsequently, the integrated wideband adaptive lens assembly 2400B will be described as being configured as a world-side first adaptive lens assembly 1004 as part of a display device 1100B (FIG. 11B) that outputs a virtual image to a user while simultaneously transmitting a view of the real world, reducing or essentially eliminating distortion of the real-world view resulting from the lensing effect of the second adaptive lens assembly 1008.

[0328] When configured as the second adaptive lens assembly 1008 on the user side (FIG. 11A), L1 / HWP1 2308 and L2 / HWP2 2312 may each be configured to diverge light having one of the HCPs, e.g., the LHCP, passing therethrough. L1 / HWP1 2308 and L2 / HWP2 2312 may also each be configured to converge light having the other HCP, e.g., the RHCP, passing therethrough.

[0329] 11A , a portion of the light propagating within the waveguide assembly 1012 in the x-direction may be redirected or outcoupled in the z-direction, e.g., by total internal reflection. Light that is outcoupled from the waveguide assembly 1012 ( FIG. 11A ) may be incident on the integrated broadband adaptive lens assembly 2400B as a circularly polarized beam 1720 having an LHCP. The light beam 1720 travels in the positive z-direction until, for example, the light beam 1720 is transmitted through the L1 / HWP 2308 and converted to a light beam 1724 having an RHCP while also diverging in accordance with the first optical power −P1 of the L1 / HWP1 2308.

[0330] Subsequently, L3 / HWP3 2304B is deactivated, so that light beam 1724 with an RHCP transmitted through L3 / HWP3 2304B is converted into light beam 1728B with an LCHP while also diverging or converging according to the third refractive power − / +P3. Light beam 1728B with an LHCP then impinges on L2 / HWP2 2312. Unlike light beam 1728A illustrated above with respect to FIG. 24C , light beam 1728B impinging on L2 / HWP2 2312 has an LHCP, so L2 / HWP2 2312 further diverges light beam 1728B into light beam 1732B with an RHCP according to the second refractive power −P2. Thus, unlike the configuration illustrated with respect to Figure 24C, L1 / HWP1 2308, L2 / HWP2 2312, and L3 / HWP3 2304B in Figure 24D can have an additive lens effect, after which light beam 1732A can be seen by the eye in response to emerging from adaptive lens assembly 1700B in the deactivated state.

[0331] In some embodiments, the first refractive power -P1 of L1 / HWP1 2308 and the second refractive power -P2 of L2 / HWP2 2312 may both be negative (i.e., diverging) and may have substantially the same or matched magnitudes. In addition, the third refractive power -P3 of L3 / HWP3 2304B may also be negative. In these embodiments, the net refractive power Pnet of the integrated wideband adaptive lens assembly 2400B may be approximately −(P1 + P2 + P3). However, embodiments are not so limited, and in some other embodiments, the third refractive power +P3 of L3 / HWP3 2304B may be positive. In these embodiments, the net refractive power Pnet of the integrated wideband adaptive lens assembly 2400B may be approximately −(P1 + P2) + P3. In addition, the first and second refractive powers P1, P2 may have different magnitudes.

[0332] In the illustrated embodiment, the incident light beam 1720 has LHCP, but equivalent results would also be achieved if the incident light beam 1720 had RHCP. That is, if the light beam 1720 had RHCP, as opposed to the illustrated embodiment, the resulting light beam 1732B would have LHCP and could be converged by L1 / HWP1 2308, L2 / HWP2 2312, and L3 / HWP3 2304B according to a net refractive power Pnet = +(P1 + P2 + P3).

[0333] The lens effects of L1 / HWP1 2308, L2 / HWP2 2312, and L3 / HWP 2304B and the dependence of the lens effects on the polarization state of the incident light beam, as described above with respect to FIG. 24D, serve merely as an example, and other configurations are also conceivable. For example, unlike the illustrated embodiment, L1 / HWP1 2308, L2 / HWP2 2312, and deactivated L3 / HWP3 2304B may each be configured to converge light having LHCP while diverging light having RHCP.

[0334] Above, an integrated broadband adaptive lens assembly 2400B in an inactive state was described when configured as a second adaptive lens assembly 1008 on the user side in the display device 1100A described above with respect to FIG. 11A. However, as described above with respect to FIG. 11B, activating the second adaptive lens assembly 1008 without any compensation effects and displaying virtual content to the user's eye 210 can result in a focus shift or distortion of the real-world view, which may not be desirable. Therefore, when the first adaptive lens assembly 1004 on the world side is deactivated to display virtual content, it may be desirable to configure it to at least partially compensate for or nullify the lens effects of the second adaptive lens assembly 1008.

[0335] Referring back to FIG. 24D , when configured as a world-side first adaptive lens assembly 1004 ( FIG. 11B ) to neutralize the lens effect of a user-side second adaptive lens assembly 1008 ( FIG. 11B ), the components of adaptive lens assembly 1700B may be similarly configured as described above with respect to FIG. 11B . That is, as light transmitted from the world 510 to the eye 210 traverses the first and second adaptive lens assemblies 1004, 1008, they may each be configured as described above with respect to the integrated wideband adaptive lens assembly 2400B described with respect to FIG. 24D . In operation, as described above, the polarization of light transmitted from the world through the first adaptive lens assembly 1004 is converted from a first polarization state to a second polarization state, e.g., from RHCP to LHCP. Subsequently, the polarization of light transmitted through the second adaptive lens assembly 1008 is converted back from the second polarization state to the first polarization state, e.g., from LHCP to RHCP. 11B, light transmitted from the world through the first adaptive lens assembly 1004 experiences a first lens effect, e.g., a converging effect, according to a first net refractive power Pnet1=(P1+P2+P3) having a first sign, e.g., a positive sign. Subsequently, light transmitted through the second adaptive lens assembly 1008 experiences a second lens effect, e.g., a diverging effect, opposite to the first lens effect, according to a second net refractive power Pnet2=-(P1'+P2'+P3') having a second sign, e.g., a negative sign, because the light incident on the second adaptive lens assembly 1008 has the opposite polarization to the light incident on the first adaptive lens assembly 1004. When Pnet1 and Pnet2 have substantially similar magnitudes, the overall lens effect, approximated by P=Pnet1+Pnet2, can be substantially zero. As a result, when a user views virtual content and real objects in the surrounding world by activating the second lens assembly 1008, the view of the world is relatively unaffected by the compensation effect of the first lens assembly 1004.

[0336] In various embodiments, when deactivated, the first and second adaptive lens assemblies 1004, 1008 may each provide a net optical power (positive or negative) within the range of approximately ±5.0 diopters to 0 diopters, ±4.0 diopters to 0 diopters, ±3.0 diopters to 0 diopters, ±2.0 diopters to 0 diopters, ±1.0 diopters to 0 diopters (including any range defined by these values, e.g., ±1.5 diopters).

[0337] 25A and 25B are graphs 2500A, 2500B illustrating transmission spectra corresponding to the integrated wideband adaptive lens assembly 2400 (FIGS. 24A / 24B) with L3 / HWP3 2304 deactivated (FIG. 24C) and activated (FIG. 24D), respectively. The simulation corresponds to an integrated wideband adaptive lens assembly 2400 in which L3 / HWP3 2304 comprises a switchable LC layer 2304 formed from a 10 μm thick unpolymerized LC layer (e.g., switchable LC layer 2304 in FIG. 23) and having a Δn of 0.2, while L1 / HWP1 2308 and L2 / HWP2 2312 each comprise polymerized LC layers (e.g., upper and lower polymerized LC (LCP) layers 2302-1, 2303-2 in FIG. 24A) formed from polymerized twisted LC molecules with a twist angle of 60 degrees. As shown in graph 2500A, when L3 / HWP3 2304A is deactivated (FIG. 24C), the diffraction efficiency is high with low leakage (up to about 20%), indicating that incident light is efficiently diffracted by integrated broadband adaptive lens assembly 2400A with virtually no leakage through 400 nm to 800 nm. On the other hand, as shown in graph 2500B, when L3 / H...

Claims

[Claim 1] A display system or method.

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