Switchable diffractive optical element and waveguide containing the same

Abstract

An optical device includes a light source assembly configured to generate image light; and at least one waveguide, the at least one waveguide including an in-coupling element and an out-coupling element, the in-coupling element and the out-coupling element being configured to transmit a plurality of light fields of the image light to an eye box of the optical device via the at least one waveguide in a time-division multiplexed manner. At least one of the in-coupling element or the out-coupling element includes at least one switchable diffraction grating, the switchable diffraction grating including a surface relief grating (SRG) filled with an optical anisotropic material, the optical anisotropic material having a first principal refractive index along a groove direction of the SRG and a second principal refractive index along an in-plane direction perpendicular to the groove direction. One of the first principal refractive index and the second principal refractive index substantially matches the refractive index of the SRG, while the other does not match.

Description

Background Art

[0001] Near-eye displays (NEDs) have been widely used in a variety of applications, such as video playback, gaming, and sports. NEDs have been used to implement virtual reality (VR), augmented reality (AR), or mixed reality (MR). AR or MR head-mounted devices display virtual images that overlap with real-world images or see-through images. Pupil-expanded waveguide display systems with diffractive coupling structures are one of the most promising designs for AR / MR displays, potentially providing a sunglasses / glasses form factor, a moderately large field of view (FOV), high transmittance, and a large eye box. Waveguide display systems typically include a microdisplay, a collimator, and waveguide optics such as a waveguide combiner. A waveguide combiner integrates coupling-in and coupling-out elements, which are typically diffraction gratings, and the corresponding waveguides are called diffraction waveguides. Various diffraction gratings have been integrated into waveguides, such as surface relief gratings obtained by nanofabrication or various types of holographic gratings. Summary of the invention

[0002] One aspect of the present disclosure provides an optical device. The optical device includes a light source assembly configured to generate image light; and at least one waveguide configured to guide the image light to an eye box of the optical device. The at least one waveguide includes an in-coupling element and an out-coupling element, and the in-coupling element and the out-coupling element are configured to transmit multiple light fields of the image light to the eye box of the optical device via the at least one waveguide in a time-division multiplexed manner. At least one of the in-coupling element or the out-coupling element includes at least one switchable diffractive optical element, which includes a surface relief grating (SRG) filled with an optical anisotropic material. The optical anisotropic material has a first principal refractive index along a groove direction of the SRG and a second principal refractive index along an in-plane direction perpendicular to the groove direction. One of the first principal refractive index and the second principal refractive index substantially matches the refractive index of the SRG, while the other does not match the refractive index of the SRG.

[0003] According to some embodiments, an optical device is provided, the optical device comprising: a light source assembly configured to generate image light; and at least one waveguide, the at least one waveguide comprising an in-coupling element and an out-coupling element, the in-coupling element and the out-coupling element being configured to transmit multiple light fields of the image light to an eye box of the optical device via the at least one waveguide in a time-division multiplexed manner, wherein at least one of the in-coupling element and the out-coupling element comprises at least one switchable diffractive optical element, the latter comprising: a surface relief grating (SRG) filled with a switchable optical anisotropic material, the switchable optical anisotropic material having a first principal refractive index along a groove direction of the SRG and a second principal refractive index along an in-plane direction perpendicular to the groove direction, one of the first principal refractive index and the second principal refractive index substantially matching the refractive index of the SRG, while the other does not match the refractive index of the SRG.

[0004] In some embodiments, the light field may correspond to a predetermined portion of a field of view (FOV) of a monochrome image.

[0005] In some embodiments, the light field may correspond to a predetermined portion of a field of view (FOV) of the full-color image.

[0006] In some embodiments, the light field may correspond to a monochrome image of a predetermined color.

[0007] In some embodiments, the switchable optically anisotropic material may include active liquid crystal (LC).

[0008] In some embodiments, the at least one switchable diffractive optical element may be switchable between a diffractive state and a non-diffractive state via an external electric field applied to the at least one switchable diffractive optical element.

[0009] In some embodiments, the SRG may be one of a tilted grating and a non-tilted grating.

[0010] In some embodiments, at least one switchable diffractive optical element may be a one-dimensional diffraction grating.

[0011] In some embodiments, the at least one switchable diffractive optical element may include N switchable diffraction gratings, N is a positive integer and N≥2, and during corresponding time periods, the N switchable diffraction gratings are sequentially configured to be in a diffraction state to transmit corresponding light fields among the multiple light fields, and during a time period, one of the N switchable diffraction gratings is configured to be in a diffraction state to transmit a light field among the multiple light fields, and the remaining switchable diffraction gratings are configured to be in a non-diffraction state.

[0012] In some embodiments, the N switchable diffraction gratings may be arranged to partially overlap each other.

[0013] In some embodiments, N switchable diffraction gratings may be arranged in a stack.

[0014] In some embodiments, the at least one waveguide may include M waveguides arranged in a stack, M is a positive integer and M≥2, each of the M waveguides includes the at least one switchable diffractive optical element, during corresponding time periods, the at least one switchable diffractive optical element included in the corresponding waveguide is sequentially configured to be in a diffractive state to transmit corresponding light fields among the multiple light fields, and during a time period, the at least one switchable diffractive optical element included in one waveguide of the M waveguides is configured to be in a diffractive state to transmit a light field among the multiple light fields, and the at least one switchable diffractive optical element included in the remaining waveguides is configured to be in a non-diffractive state.

[0015] In some embodiments, at least one switchable diffractive optical element included in a corresponding waveguide may include N switchable diffraction gratings, N being a positive integer and N≥2.

[0016] Another aspect of the present disclosure provides a method for an optical device. The method includes: during a first time period, a first coupling grating couples a plurality of first image lights corresponding to a first light field among a plurality of light fields into a first waveguide via diffraction; and a first coupling grating decouples the plurality of first image lights from the first waveguide to an eye box of the optical device via diffraction. The method also includes: during a second time period, a second coupling grating couples a plurality of second image lights corresponding to a second light field among the plurality of light fields into a second waveguide via diffraction; and a second coupling grating decouples the plurality of second image lights from the second waveguide to an eye box of the optical device via the diffraction.

[0017] According to some embodiments, a method for an optical device is provided, comprising: during a first time period, a first coupling grating couples a plurality of first image lights corresponding to a first light field among a plurality of light fields into a first waveguide via diffraction, and a first coupling grating decouples the plurality of first image lights from the first waveguide via the diffraction to an eye box of the optical device; during a second time period, a second coupling grating couples a plurality of second image lights corresponding to a second light field among the plurality of light fields into a second waveguide via diffraction, and a second coupling grating decouples the plurality of second image lights from the second waveguide via the diffraction to an eye box of the optical device.

[0018] In some embodiments, the first light field may correspond to a first portion of a field of view (FOV) of a monochrome image, and the second light field corresponds to a second portion of the FOV of the monochrome image.

[0019] In some embodiments, the first light field may correspond to a first portion of a field of view (FOV) of the panchromatic image, while the second light field corresponds to a second portion of the FOV of the panchromatic image.

[0020] In some embodiments, the first light field may correspond to a monochrome image of a first color, while the second light field corresponds to a monochrome image of a second color.

[0021] In some embodiments, the first and second waveguides may be the same common waveguide, the first and second coupling-in gratings partially overlap and are disposed at a first surface or a second surface of the common waveguide, and the first and second coupling-out gratings partially overlap and are disposed at a first surface or a second surface of the common waveguide.

[0022] In some embodiments, the first and second waveguides may be the same common waveguide, the first and second coupling-in gratings are stacked together and each is disposed at the first surface or the second surface of the common waveguide, and the first and second coupling-out gratings are stacked together and each is disposed at the first surface or the second surface of the common waveguide.

[0023] In some embodiments, the first and second waveguides may be separate waveguides, the first incoupling grating and the first outcoupling grating are both disposed at the first surface or the second surface of the first waveguide, and the second incoupling grating and the second outcoupling grating are both disposed at the first surface or the second surface of the second waveguide.

[0024] In some embodiments, the method may further include: during a third time period, coupling a plurality of third image lights corresponding to a third light field among the plurality of light fields into a third waveguide via diffraction by a third coupling-in grating, and decoupling the plurality of third image lights from the third waveguide to an eye box of the optical device via the diffraction by a third coupling-out grating.

[0025] It will be appreciated that any feature described herein as suitable for incorporation into one or more aspects or embodiments of the present invention is intended to be generalizable across any and all aspects and embodiments of the disclosure.

[0026] Other aspects of the present disclosure may be understood by those skilled in the art based on the specification, claims and drawings of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The following drawings are provided for illustrative purposes in accordance with various disclosed embodiments and are not intended to limit the scope of the present disclosure.

[0028] Figure 1A A schematic diagram showing a near-eye display (NED) according to an embodiment of the present disclosure is shown;

[0029] Figure 1B The embodiment according to the present disclosure is shown Figure 1ACross section of NED in;

[0030] Figure 2A A schematic diagram showing a waveguide display assembly according to an embodiment of the present disclosure is shown;

[0031] Figure 2B A schematic diagram showing a waveguide display assembly according to another embodiment of the present disclosure is shown;

[0032] Figure 3A A schematic diagram showing a grating in a non-diffractive state according to an embodiment of the present disclosure;

[0033] Figure 3B A schematic diagram showing a grating in a diffraction state according to an embodiment of the present disclosure;

[0034] Figure 4A A schematic diagram showing a grating in a diffraction state according to another embodiment of the present disclosure is shown;

[0035] Figure 4B A schematic diagram showing a grating in a non-diffraction state according to another embodiment of the present disclosure is shown;

[0036] Figure 5A A schematic diagram showing a grating in a non-diffraction state according to another embodiment of the present disclosure is shown;

[0037] Figure 5B A schematic diagram showing a grating in a diffraction state according to another embodiment of the present disclosure is shown;

[0038] Fig. 6A A schematic diagram showing a grating in a diffraction state according to another embodiment of the present disclosure is shown;

[0039] Figure 6B A schematic diagram showing a grating in a non-diffraction state according to another embodiment of the present disclosure is shown;

[0040] Figure 7 A schematic diagram showing a switchable diffractive optical element according to another embodiment of the present disclosure;

[0041] FIG. 8A to FIG. 8C A schematic diagram of a switched active grating according to an embodiment of the present disclosure is shown;

[0042] FIG. 9A to FIG. 9B A schematic diagram of a switched active grating according to another embodiment of the present disclosure is shown;

[0043] Fig. 10A A schematic diagram showing a waveguide according to an embodiment of the present disclosure;

[0044] FIG. 10B to FIG. 10D The embodiment according to the present disclosure is shown Fig. 10AAn operating scheme for delivering different portions of a field of view (FOV) in a time-division multiplexed manner of a waveguide in;

[0045] Fig.10E The embodiment according to the present disclosure includes Fig. 10A Schematic diagram of the overlapping configuration of sub-gratings in the waveguide;

[0046] Fig.10F Another embodiment according to the present disclosure includes Fig. 10A Schematic diagram of the overlapping configuration of sub-gratings in the waveguide;

[0047] Fig.11A shows a schematic diagram of a waveguide stack according to an embodiment of the present disclosure;

[0048] FIG. 11B to FIG. 11D The embodiment according to the present disclosure is shown Fig.11A Operational scheme of a waveguide stack in delivering different portions of a FOV in a time-division multiplexed manner;

[0049] Fig. 12A shows a schematic diagram of a waveguide stack according to another embodiment of the present disclosure;

[0050] FIG. 12B to FIG. 12D The embodiment according to the present disclosure is shown Fig. 12A Operation scheme of a waveguide stack in a time-division multiplexed manner to deliver monochrome images of different colors;

[0051] Fig.13 A flow chart showing a method of transmitting an optical device of different portions of a FOV in a time division multiplexed manner according to an embodiment of the present disclosure;

[0052] Fig.14 A flowchart showing a method of an optical device for delivering monochrome images of different colors in a time division multiplexing manner according to another embodiment of the present disclosure; and

[0053] Fig.15 Schematic diagram showing a waveguide delivering different parts of a FOV in a time division multiplexed manner according to another embodiment of the present invention. DETAILED DESCRIPTION

[0054] Hereinafter, embodiments consistent with the present disclosure will be described with reference to the accompanying drawings, which are examples for illustrative purposes only and are not intended to limit the scope of the present disclosure. In the accompanying drawings, shapes and sizes may be exaggerated, distorted or simplified for clarity. Where possible, the same reference numerals are used in all drawings to represent the same or similar parts, and their detailed descriptions may be omitted. In addition, in the present disclosure, the disclosed embodiments and the features of the disclosed embodiments may be combined without conflict. The described embodiments are some but not all embodiments of the present disclosure. Based on the disclosed embodiments, a person of ordinary skill in the art may obtain other embodiments consistent with the present disclosure, all of which are within the scope of the present disclosure.

[0055] The present disclosure provides an optical device. The optical device may include: a light source assembly configured to generate image light; and at least one waveguide configured to guide the image light to an eye box of the optical device. The waveguide may include an incoupling element and an outcoupling element configured to transmit a plurality of light fields corresponding to the image light to the eye box in a time-multiplexed manner via the waveguide. The light field may correspond to a predetermined portion of a field of view (FOV) of a monochrome image, a predetermined portion of the FOV of a full-color image, or a monochrome image of a predetermined color. At least one of the incoupling element or the outcoupling element may include at least one switchable diffractive optical element. The switchable diffractive optical element may include a surface relief grating (SRG) filled with an active optical anisotropic material having a first principal refractive index along a groove direction of the SRG and a second principal refractive index along an in-plane direction perpendicular to the groove direction. One of the first principal refractive index and the second principal refractive index may substantially match the refractive index of the SRG, while the other may not match the refractive index of the SRG. The optically anisotropic material may include an active or reorientable liquid crystal (LC). The switchable diffractive optical element may be switched between a diffractive state and a non-diffractive state due to the reorientation of the LC in an external field (e.g., an electric field, a magnetic field, or light, etc.). The optical device may be a component of a near eye display (NED).

[0056] The optically anisotropic material may be a uniaxially anisotropic material, whose refractive index ellipsoid has axisymmetry with respect to its optical axis. o AN and n e AN is the principal refractive index of a uniaxial anisotropic material. Nematic liquid crystals (LC) (except for some special types, such as bent core shapes) belong to the category of uniaxial anisotropic materials. The refractive index experienced by light propagating in a nematic LC layer can vary between the ordinary refractive index n° AN and the extraordinary refractive index n e ANDepending on the angle α between the light polarization and the optical axis of the optical anisotropic material, the refractive index experienced by light propagating in the nematic LC layer can vary from n° to 0°. AN Change to n e AN .

[0057] The switchable diffractive optical element can be polarization selective, for example, the diffractive optical element can selectively diffract linearly polarized light having a first polarization and transmit linearly polarized light having a second polarization with negligible diffraction. The diffraction efficiency of the linearly polarized light having the first polarization can be controlled by an external field. The diffraction efficiency of the linearly polarized light having the first polarization can be below a predetermined threshold, for example, about 10%, 5%, 1%, 0.5%, 0.1% or 0.05%. In some embodiments, one of the first principal refractive index and the second principal refractive index can be the same as the refractive index of the SRG, and thus, the diffractive optical element can transmit the linearly polarized light having the second polarization without any diffraction.

[0058] Figure 1A A schematic diagram of a near eye display (NED) 100 according to an embodiment of the present disclosure is shown. In some embodiments, the NED 100 may be referred to as a head mounted display (HMD). The NED 100 may present media to a user. Examples of media presented by the NED 100 include one or more images, videos, audio, or some combination thereof. In some embodiments, audio is presented via an external device (e.g., a speaker and / or headphones) that receives audio information from the NED 100, a console (not shown), or both, and audio data is presented based on the audio information. The NED 100 is used as a VR device, an AR device, and / or an MR device, or some combination thereof. In some embodiments, when the NED 100 is used as an AR and / or MR device, portions of the NED 100 and its internal components may be at least partially transparent.

[0059] like Figure 1A As shown, NED 100 may include frame 105 and display 110. Certain devices may be omitted, and other devices or components may be included. Frame 110 may include any suitable type of mounting structure to ensure that display 110 is viewed by the user as the NED. Frame 105 may be coupled to one or more optical elements that together display media to the user. In some embodiments, frame 105 may represent a frame of eyeglasses. Display 110 is configured to enable the user to see content presented by NED 100. As described below in conjunction with Figure 1B As discussed, display 110 may include at least one display component (not shown) for directing image light to the user's eyes. In some embodiments, at least one display component may be a projection system. For purposes of illustration, Figure 1A The projection system is shown to include a projector 135 coupled to the frame 105 .

[0060] Figure 1B According to the embodiment of the present disclosure Figure 1A 1. The display 110 may include at least one waveguide display assembly 115. The waveguide display assembly 115 may include a waveguide or a waveguide stack. The exit pupil 125 may be where the eye 120 is located in the eye box region when the user wears the NED 100. For illustration purposes, Figure 1B A cross section 150 is shown associated with a single eye 120 and a single waveguide display assembly 115, but in an alternative embodiment not shown, Figure 1B Another display assembly separate from the waveguide display assembly 115 shown may provide image light to an eye box located at the exit pupil of the user's other eye.

[0061] As follows in Figure 1B As described in , the waveguide display component 115 can be configured to direct image light to an eye box located at the exit pupil 125 of the eye 120. The waveguide display component 115 can be constructed of one or more materials (e.g., plastic, glass, etc.) having one or more refractive indices that are effective to minimize weight and widen the FOV of the NED 100. In some embodiments, the waveguide display component 115 can be a component of the NED 100 (e.g., the display 110). In some embodiments, the waveguide display component 115 can be part of some other NED or other system that directs display image light to a specific location. Figure 1B As shown, the waveguide display assembly 115 can be used for one eye 120 of the user. The waveguide display assembly 115 for one eye can be separated or partially separated from the waveguide display assembly 115 for the other eye. In some embodiments, a single waveguide display assembly 115 can be used for both eyes 120 of the user.

[0062] In some embodiments, the NED 100 may include one or more optical elements between the waveguide display assembly 115 and the eye 120. The optical elements may be used, for example, to correct aberrations in the image light emitted from the waveguide display assembly 115, to amplify the image light emitted from the waveguide display assembly 115, to make some other optical adjustments to the image light emitted from the waveguide display assembly 115, or some combination thereof. Examples of optical elements may include an aperture, a Fresnel lens, a convex lens, a concave lens, a filter, or any other suitable optical element that affects the image light. In some embodiments, the NED 100 may include an adaptive dimming element 130 that may dynamically adjust the transmittance of a real-world object viewed through the NED 100 to switch the NED 100 between a VR device and an AR device or between a VR device and an MR device. In some embodiments, the adaptive dimming element 130 may be used in an AR and / MR device to mitigate brightness differences between real and virtual objects, accompanying switching between an AR / MR device and a VR device.

[0063] Figure 2A Schematic diagram of a waveguide display assembly 200 according to an embodiment of the present disclosure is shown. The waveguide display assembly 200 can be implemented as a NED for VR, AR or MR applications. Figure 2A As shown, the waveguide display assembly 200 may include a light source assembly 205, a waveguide 210, and a controller 215. The light source assembly 205 may include a light source 220 and an optical system 225. In some embodiments, the light source 220 may be a light source that produces coherent or partially coherent light. The light source 220 may include, for example, a laser diode, a vertical cavity surface emitting laser, and / or a light emitting diode. In some embodiments, the light source 220 may be a display panel, such as a liquid crystal display (LCD) panel, a liquid crystal on silicon (LCoS) display panel, an organic light emitting diode (OLED) display panel, a micro light emitting diode (micro LED) display panel, a digital light processing (DLP) display panel, or some combination thereof. In some embodiments, the light source 220 may be a self-emitting panel, such as an OLED display panel or a micro LED display panel. In some embodiments, the light source 220 may be a display panel illuminated by an external source, such as an LCD panel, an LCoS display panel, or a DLP display panel. Examples of external sources may include lasers, LEDs, OLEDs, or some combination thereof. The optical system 225 may include one or more optical components that adjust the light from the light source 220. Conditioning the light from the light source 220 may include, for example, transmitting, attenuating, expanding, collimating, and / or adjusting the direction according to instructions from the controller 215 .

[0064] The light source assembly 205 may generate image light 230 and output the image light 230 to an incoupling element 235 located at the waveguide 210. The waveguide 210 may expand the image light 230 to the user's eye 265. The waveguide 210 may receive the image light 230 at one or more incoupling elements 235 located at the waveguide 210 and guide the received image light 230 to an outcoupling element 245 located at the waveguide 210, so that the received input image light 230 is decoupled from the waveguide 210 to the eye 265 via the outcoupling element 245. In some embodiments, the incoupling element 235 may couple the image light 230 from the light source assembly 205 into the waveguide 210. The waveguide 210 may include a first surface 210-1 facing the real world and an opposing second surface 210-2 facing the eye 265. In some embodiments, as Figure 2A As shown, the coupling element 235 can be part of the first surface 210-1 of the waveguide 210 or fixed to the first surface 210-1 of the waveguide 210. In some embodiments, the coupling element 235 can be part of the second surface 210-2 of the waveguide 210 or fixed to the second surface 210-2 of the waveguide 210. In some embodiments, the coupling element 235 can include a surface relief grating, a volume hologram, a polarization grating, a polarization volume hologram, a metasurface grating, or other types of diffraction elements, or some combination thereof. In some embodiments, the coupling element 235 can include a diffraction grating, and the pitch of the diffraction grating can be selected so that total internal reflection (TIR) ​​occurs in the waveguide 210 and the image light 230 can propagate inwardly in the waveguide 210 (e.g., by total internal reflection). The coupling element 235 is also referred to as a coupling grating.

[0065] The outcoupling element 245 may be a part of the first surface 210-1 or the second surface 210-2 of the waveguide 210 or may be fixed to the first surface 210-1 or the second surface 210-2 of the waveguide 210. Figure 2A As shown, the outcoupling element 245 can be part of the second surface 210-2 of the waveguide 210 or fixed to the second surface 210-2 of the waveguide 210. In some embodiments, the outcoupling element 245 can be part of the first surface 210-1 of the waveguide 210 or fixed to the first surface 210-1 of the waveguide 210. In some embodiments, the outcoupling element 245 can include a surface relief grating, a volume hologram, a polarization grating, a polarization volume hologram, a metasurface grating, or other types of diffraction elements, or some combination thereof. In some embodiments, the outcoupling element 245 can include a diffraction grating, and the spacing of the diffraction grating can be configured to cause the incident image light 230 to leave the waveguide 210, that is, redirect the image light 230 so that TIR no longer occurs. Such a grating is also referred to as an outcoupling grating.

[0066] The waveguide 210 may be constructed of one or more materials that promote total internal reflection of the image light 230. The waveguide 210 may be constructed of, for example, plastic, glass, and / or polymer. The waveguide 210 may have a relatively small form factor. For example, the waveguide 210 may be approximately 50 mm wide along the x-direction, approximately 30 mm long along the y-direction, and approximately 0.5-1 mm thick along the z-direction. The controller 215 may control the operating scheme of the light source assembly 205. In some embodiments, the waveguide 210 may output the expanded image light 230 to the eye 265 having a large field of view (FOV). For example, the expanded image light 230 may be provided to the eye 265 having a diagonal FOV (expressed in x and y) of 60 degrees and / or greater and / or 150 degrees and / or less. The waveguide 210 may be configured to provide an eye box having a width of 8 mm or greater and / or equal to or less than 50 mm and / or a height of 6 mm or greater and / or equal to or less than 20 mm. Using the waveguide display assembly 200, the physical display and electronics can be moved to the side of the front rigid body and a completely unobstructed view of the real world can be achieved, thus opening up the possibility of true AR.

[0067] In some embodiments, waveguide 210 may include additional gratings that redirect / fold and / or expand the pupil of light source assembly 205. For example, Figure 2B As shown, in the waveguide display assembly 250, the waveguide 210 may further include a guiding element 240 that redirects the received input image light 230 to the outcoupling element 245, so that the received input image light 230 is decoupled from the waveguide 210 via the outcoupling element 245. The guiding element 240 may be a part of the first side 210-1 of the waveguide 210 or fixed to the first side 210-1 of the waveguide 210, and the outcoupling element 245 may be a part of the second side 210-2 of the waveguide 210 or fixed to the second side 210-2 of the waveguide 210, so that the guiding element 240 is arranged opposite to the outcoupling element 245. In some embodiments, the guiding element 240 and the outcoupling element 245 may be similar in structure. In some embodiments, the guiding element 240 may include a surface relief grating, a volume hologram, a polarization grating, a polarization volume hologram, a metasurface grating, or other types of diffraction elements, or some combination thereof. In some embodiments, the guiding element 240 may include a diffraction grating, and in this case, the guiding element 240 is also referred to as a folding grating. In some embodiments, multiple functions (e.g., redirecting / folding and / or expanding the pupil of the light source assembly 205) may be combined into a single grating (e.g., an outcoupling grating).

[0068] refer to FIG. 2A to FIG. 2BIn some embodiments, the waveguide display assembly 200 / 250 may include a plurality of waveguides stacked together, wherein each waveguide 210 is designed to process, for example, some portion of the FOV and / or some portion of the color spectrum of the virtual image. In some embodiments, the waveguide display assembly 200 / 250 may include a plurality of source assemblies 205 and / or a plurality of waveguides 210. Each source assembly 205 may emit a monochromatic image light corresponding to a specific wavelength band of a primary color (e.g., red, green, or blue). A plurality of waveguides 210 may be stacked together to output a multi-color extended image light 230, i.e., a full-color image light 230. In some embodiments, each source assembly 205 may emit a full-color image light corresponding to a different portion of the FOV provided by the waveguide display assembly 200 / 250. In some embodiments, the light source assembly 205 may include a plurality of light sources 220. Each light source 220 may emit a full-color image light. The full-color image light emitted by different light sources 220 may correspond to different portions of the FOV provided by the waveguide display assembly 200 / 250. For example, the light source assembly 205 may include three light sources 220 that emit full-color image light corresponding to the left, middle, and right portions of the FOV, respectively.

[0069] Reference FIG. 2A to FIG. 2B In the waveguide display assembly 200 / 250, at least one of the coupling-in grating 235, the coupling-out grating 245 or the guide grating 235 may include at least one switchable diffractive optical element according to an embodiment of the present disclosure. In some embodiments, the switchable diffractive optical element may be switched between a diffractive state (or an on state) and a non-diffractive state (or an off state) by an external field.

[0070] FIG. 3A to FIG. 3B Schematic diagrams of a grating 300 in a non-diffractive state and a diffractive state, respectively, according to an embodiment of the present disclosure are shown. Figure 3A refer to Figure 3B As shown, the grating 300 may include a surface relief grating (SRG) 305 filled with an optically anisotropic material 315 composed of elongated molecules. The SRG 305 may be a binary non-tilted grating. The molecules 310 of the optically anisotropic material 315 may be arranged in a groove along the groove direction (e.g., FIG. 3A to FIG. 3B The optically anisotropic material 315 may be uniaxial and have a first principal refractive index (eg, n) in the groove direction (eg, y) of the SRG 305. e AN ) and a second principal refractive index (e.g., n) along an in-plane direction (e.g., x direction) perpendicular to the groove direction of the SRG 305. o AN ). The second principal refractive index (e.g., n o AN) can substantially match the refractive index n of SRG 305 g , and the first principal refractive index (e.g., n e AN ) may not match the refractive index n of SRG 305 g .

[0071] The SRG 305 may be fabricated from an organic material such as an amorphous or liquid crystal polymer, a cross-linkable monomer including those having LC properties (reactive mesogens (RMs)), or an inorganic material such as a metal or oxide used to fabricate a metasurface. The material of the SRG 305 may be isotropic or anisotropic. In some embodiments, the SRG 305 may be nanofabricated from a resist material that is transparent or nearly transparent to an EM frequency range such as a visible band. The resist material may be in the form of a thermoplastic, a polymer, an optically transparent photoresist, etc. After shaping or curing, the resist material may provide an orientation of the optically anisotropic material 315 filled into the SRG 305. That is, the SRG 305 may be used as an alignment layer for the optically anisotropic material 315. The SRG 305 may be fabricated from an organic material such as an amorphous or liquid crystal polymer, a cross-linkable monomer including those having LC properties (reactive mesogens (RMs)). The nanofabrication techniques of SRG 305 form various alignment patterns and features (e.g., less than 10 nm) that allow for the creation of alignment patterns of optically anisotropic material 315 with high customizability. For example, optically anisotropic material 315 can be aligned homeotropically or homogeneously or hybridly within the grooves of SRG 305. In some embodiments, molecules 310 of optically anisotropic material 315 can be aligned homeotropically or homogeneously within the grooves of SRG 305 by stretching, light (e.g., photo-alignment), electric field, magnetic field, or any suitable alignment method.

[0072] The optically anisotropic material 315 may include an active material that can be switched by an external field. The active material may include an active or reorientable liquid crystal (LC), or a polymerizable liquid crystal (LC) precursor, or some combination thereof. In some embodiments, the polymerizable LC precursor may include a reactive mesogen (RM) as a polymerizable LC material. In some embodiments, the grating 300 may also include two opposing substrates forming a container for the SRG 305 and the optically anisotropic material 315. In some embodiments, to achieve electrical switching of the grating 300, a transparent electrode, such as an indium tin oxide (ITO) electrode, may be provided for each substrate. In some embodiments, alignment of the optically anisotropic material 315 may be provided by one or more alignment layers different from the SRG 305, wherein the alignment layer may be provided at the substrate. In some embodiments, the thickness of the optically anisotropic material 315 may be the same as the depth d of the SRG 305. In some embodiments, the thickness of the optically anisotropic material 315 may be different than the depth of the SRG 305, wherein the optically anisotropic material 315 disposed above the SRG 105 may be uniform and not contribute to diffraction.

[0073] The grating 300 may be sensitive to incident light that is linearly polarized. Figure 3A As shown in FIG. , for incident light 320 polarized in the in-plane direction (eg, x-direction) perpendicular to the groove direction of SRG 305, due to n° AN With n g , the grating 300 can appear as a substantially optically uniform plate to incident light 320 with negligible diffraction. That is, for incident light 320 polarized in an in-plane direction (e.g., x-direction) perpendicular to the groove direction of the SRG 305, the grating 300 can be in a non-diffracting state. In some embodiments, the second principal refractive index (e.g., n° AN ) can be compared with the refractive index n of SRG 305 g The grating 300 is exactly matched (or may be identical), and therefore, the incident light 320 may be transmitted through without any diffraction. That is, the diffraction effect of the grating 300 may be completely turned off.

[0074] like Figure 3B As shown in FIG. 3 , for incident light 330 polarized in the groove direction (eg, y direction) of SRG 305, due to n e AN With n g The light 330 may experience a periodic modulation of the refractive index in the grating 300 and become diffracted. That is, for incident light 330 polarized in the groove direction of the SRG 305 (e.g., the y direction), the grating 300 may be in a diffractive state. The diffraction efficiency of the light 330 may be determined by the refractive index n provided by the grating 300.m (i.e., n e AN and n g The diffraction efficiency can be controlled by an external field such as an electric field, a magnetic field or light.

[0075] FIG. 4A to FIG. 4B Schematic diagrams of the grating 400 are shown in a diffractive state and a non-diffractive state, respectively. FIG. 4A to FIG. 4B and FIG. 3A to FIG. 3B The similarities between them are no longer repeated, but can explain some of the differences. FIG. 4A to FIG. 4B As shown, molecules 410 of the optically anisotropic material 415 may be arranged in the groove along the groove direction, for example, FIG. 4A to FIG. 4B The optically anisotropic material 415 may have a first principal refractive index (eg, n ) in the groove direction (eg, y direction) of the SRG 405. e AN ) and a second principal refractive index (e.g., n°) in an in-plane direction (e.g., x direction) perpendicular to the groove direction of the SRG 405. AN ). The second principal refractive index (e.g., n° AN ) may not match the refractive index n of SRG 405 g , and the first principal refractive index (e.g., n e AN ) can substantially match the refractive index n of SRG 405 g .

[0076] The grating 400 may be sensitive to incident light that is linearly polarized. Figure 4A As shown, for incident light 420 polarized in the in-plane direction (eg, x-direction) perpendicular to the groove direction of SRG 405, due to n° AN With n g Due to the difference in refractive index between n and n, light 420 may experience periodic modulation of the refractive index in grating 400 and thus be diffracted. That is, for incident light 430 polarized in an in-plane direction (e.g., x-direction) perpendicular to the groove direction of SRG 405, grating 400 may be in a diffraction state. The diffraction efficiency of light 420 may be determined by the refractive index n provided by grating 400. m (i.e., n° AN and n g The difference between them) is determined by modulation.

[0077] like Figure 4B As shown, for incident light 430 polarized in the groove direction (eg, y direction) of SRG 405, due to n e AN and n g, the grating 400 appears as a substantially optically uniform plate to incident light 420 with negligible diffraction. That is, for incident light 430 polarized in the groove direction of the SRG 405 (e.g., the y direction), the grating 400 may be in a non-diffracting state. In some embodiments, the first principal refractive index (e.g., n e AN ) can be compared with the refractive index n of SRG 405 g The grating 400 may be exactly matched (or may be identical thereto), and therefore, the incident light 430 may be transmitted through without any diffraction. That is, the diffraction effect of the grating 400 may be completely turned off.

[0078] FIG. 5A to FIG. 5B Schematic diagrams of the grating 500 are shown in a non-diffractive state and a diffractive state, respectively. FIG. 3A to FIG. 3B and FIG. 5A to FIG. 5B The similarities between are no longer repeated, but can explain some of the differences. FIG. 3A to FIG. 3B The grating 300 in FIG. 5A to FIG. 5B The grating 500 shown in FIG. 5 may include an SRG 505 filled with an optically anisotropic material 515. FIG. 3A to FIG. 3B Different from the binary non-tilted SRG 305 in FIG. 5A to FIG. 5B The SRG 505 in may be a binary tilted grating. FIG. 5A to FIG. 5B The diffraction state and non-diffraction state of the grating 500 can be referred to FIG. 3A to FIG. 3B The diffraction state and non-diffraction state of the grating 300 in FIG. 3 are described in detail without repeating them here.

[0079] FIG. 6A to FIG. 6B Schematic diagrams of the grating 600 are shown in a non-diffractive state and a diffractive state, respectively. FIG. 4A to FIG. 4B and FIG. 6A to FIG. 6B The similarities between are no longer repeated, but can explain some of the differences. FIG. 4A to FIG. 4B The grating 400 in FIG. 6A to FIG. 6B The grating 600 shown in FIG. 6 may include an SRG 605 filled with an optically anisotropic material 615. FIG. 4A to FIG. 4B Different from the binary non-tilted SRG405 in FIG. 6A to FIG. 6B The SRG 605 in may be a binary tilted grating. FIG. 6A to FIG. 6B The diffraction state and non-diffraction state of the grating 600 can be referred to FIG. 4A to FIG. 4B The diffraction state and non-diffraction state of the grating 400 in FIG. 4 are described in detail without repeating them here.

[0080] FIG. 3A to FIG. 6BThe diffractive optical element is shown to be an active grating including an SRG having a periodic rectangular profile, i.e., the cross-sectional profile of the grooves of the SRG has a periodic rectangular shape, which is for illustrative purposes and is not intended to limit the scope of the present disclosure. In some embodiments, the stripes of the grating may be linear, i.e., the grating may be a one-dimensional grating. In some embodiments, the diffractive optical element may include a plurality of SRGs that are patterned and / or stacked. In some embodiments, the cross-sectional profile of the grooves of the SRG may be non-rectangular, such as sinusoidal, triangular, or sawtooth, depending on the application scenario. In some embodiments, the cross-sectional profile of the grooves of the SRG may be non-periodic, and the exemplary diffractive optical element will be in Figure 7 In some embodiments, the diffractive optical element can be configured with or without optical power. The disclosed diffractive optical element can also achieve almost the same optical function as a conventional refractive optical device (such as a lens, a prism or an aspheric surface), but can be smaller and lighter.

[0081] Figure 7 FIG. 4 is a schematic diagram of a switchable diffractive optical element 700 according to another embodiment of the present disclosure. Figure 7 As shown, the diffractive optical element 700 may include an SRG 705 filled with an optical anisotropic material 715. The molecules 710 of the optical anisotropic material 715 may be aligned horizontally or vertically within the grooves, for example, horizontally aligned in the groove direction (for example, the y direction) of the SRG 705. The optical anisotropic material 715 may have a first principal refractive index (for example, an extraordinary refractive index n) in the groove direction (for example, the y direction) of the SRG 705. e AN ) and a second principal refractive index (e.g., ordinary refractive index n°) in an in-plane direction (e.g., x direction) perpendicular to the groove direction. AN ). One of the first principal refractive index and the second principal refractive index may substantially match the refractive index n of the SRG 705. g , and the other may not match the refractive index n of SRG 705 g For the purpose of discussion, in the diffractive optical element 700, the second principal refractive index (eg, n o AN ) can substantially match the refractive index n of SRG 705 g , and the first principal refractive index (eg, n e AN ) may not match the refractive index n of SRG 705 g .

[0082] The cross-sectional profile of the grooves of the SRG 705 may have a non-periodic rectangular profile. In the in-plane direction (eg, x-direction) perpendicular to the groove direction (eg, y-direction) of the SRG 705, the period (w groove +w hill ) can decrease monotonically from the center (c) to the periphery of the SRG 705, and a light focusing effect is achieved by the SRG 705. For the incident light 730 polarized in the groove direction (e.g., y direction) of the SRG 705, due to n e AN and n g Due to the difference in refractive index between the SRG 705 and the SRG 705, the light 730 may experience periodic modulation of the refractive index in the diffractive optical element 700 and be diffracted. By configuring the cross-sectional profile of the grooves of the SRG 705 and the refractive indexes of the optically anisotropic material 715 and the SRG 705, the diffracted light beam 740 may be further focused. That is, the diffractive optical element 700 may function as a cylindrical diffractive lens. The diffractive optical element 700 may also include other elements, such as a substrate, electrodes for electrical switching, an alignment layer, etc., and Figure 7 Only a partial structure of the diffractive optical element 700 is shown.

[0083] The following will be combined with the accompanying FIG. 8A to FIG. 8C and FIG. 9A to FIG. 9B The switching between the diffraction state and the non-diffraction state of an active diffractive optical element (e.g., an active grating) according to an embodiment of the present disclosure is explained. In some embodiments, the active diffractive optical element according to an embodiment of the present disclosure can be switched between the non-diffraction state and the diffraction state by applying an electric field to the active LC material, which is caused by the electric field induced redirection of the LC filled in the SRG. In some embodiments, by applying light to the active LC material, the active diffraction optical element can be switched between the non-diffraction state and the diffraction state due to the light induced redirection of the LC filled in the SRG. In some embodiments, by applying a magnetic field to the active LC material, the active diffraction optical element can be switched between the non-diffraction state and the diffraction state due to the magnetic field induced redirection of the LC filled in the SRG. In addition, in the diffraction state, the diffraction efficiency of the light incident on the active diffraction optical element can be continuously changed by continuously changing the applied electric field or light or magnetic field. That is, the active diffraction optical element can be configured to provide different diffraction efficiencies to the incident light, thereby meeting different application scenarios. In some embodiments, at least one electrode of the active diffractive optical element may include a pixelated electrode. Light incident on the active diffractive optical element may illuminate one or more pixelated electrodes, and the diffraction efficiency of the light may be spatially varied by applying different voltages to different pixelated electrodes. For the purpose of discussion, a grating filled with an active LC is used as an example to explain FIG. 8A to FIG. 8C and FIG. 9A to FIG. 9B Switching of the diffractive optical element disclosed in.

[0084] FIG. 8A to FIG. 8C 8 shows a schematic diagram of a switching diffractive optical element 800 according to an embodiment of the present disclosure. For the purpose of discussion, the diffractive optical element 800 may be a grating 800. FIG. 8A to FIG. 8C As shown, the grating 800 may include an upper substrate and a lower substrate 810 arranged opposite to each other. Each substrate 810 may be provided with a transparent electrode at the inner surface of the substrate 810 for applying an electric field to the grating 800, and the transparent electrode is, for example, an ITO electrode (not shown). The grating 800 may include an SRG 805 bonded to or formed on the lower substrate 810 and an optical anisotropic material 815 filled in the groove of the SRG 805. The optical anisotropic material 815 may include an active anisotropic material, such as an active LC having positive or negative dielectric anisotropy. The optical anisotropic material 815 may have a first principal refractive index (e.g., n in the groove direction (e.g., y direction) of the SRG 805. e AN ) and a second principal refractive index (e.g., n°) in an in-plane direction (e.g., x direction) perpendicular to the groove direction of the SRG 805. AN ).

[0085] For the purpose of discussion, FIG. 8A to FIG. 8C In the embodiment, the optically anisotropic material 815 may include an active LC having positive anisotropy, such as a nematic liquid crystal (NLC). The LC molecules 820 may be horizontally aligned in the groove direction (e.g., the y direction) within the groove. The second principal refractive index (e.g., n° AN ) can basically match the refractive index n of SRG 805 g , and the first principal refractive index (e.g., n e AN ) may not match the refractive index n of SRG 805 g . In Fig. 8A In the voltage-off state shown, for incident light 830 polarized in the groove direction (eg, y direction) of SRG 805, due to n e AN and n g Due to the refractive index difference between the two, light 830 may experience periodic modulation of the refractive index when propagating through the grating 800 and thus be diffracted. That is, for incident light 830 polarized in the groove direction of the SRG 805 (e.g., the y direction), the grating 800 may be in a diffraction state (or a conducting state).

[0086] In some embodiments, in the voltage-off state (or more generally, when the applied voltage is below a threshold voltage to reorient the LC molecules 820), the refractive index n provided by the grating 800 to the light 830 is lower than in the other voltage-on states. m (i.e., n e AN and n g The modulation of the difference between ) can be the largest. Therefore, the diffraction efficiency of light 830 can be the highest. In the voltage-on state, such as Figure 8B As shown, an electric field (e.g., in the z direction) may be generated between two opposing substrates 810. When the applied voltage is gradually increased above a threshold holding voltage, the LC molecules 820 having positive dielectric anisotropy may tend to reorient along the electric field. When the applied voltage is changed, for incident light 830 polarized in the groove direction of the SRG 805 (e.g., in the y direction), the refractive index n provided by the grating 800 is changed. m (i.e., n e AN and n g The modulation of the light 830 (the difference between) can be changed accordingly, which in turn changes the diffraction efficiency provided by the grating 800 to the incident light 830. In addition, in the diffraction state, the diffraction efficiency provided by the grating 800 to the incident light 830 can be continuously adjustable via a continuously changing applied voltage. That is, the grating 800 can provide different diffraction efficiencies to the light 830, thereby meeting different application scenarios. In some embodiments, at least one electrode of the grating 800 may include a plurality of pixelated electrodes. The light 830 can illuminate one or more pixelated electrodes, and the diffraction efficiency of the light 830 can be spatially varied by applying different voltages to different pixelated electrodes.

[0087] In the voltage-on state where the applied voltage is high enough, such as Figure 8C As shown, the LC molecules 820 with positive dielectric anisotropy can be reoriented parallel to the electric field direction (eg, z direction). For incident light 830 polarized in the groove direction of the SRG 805, due to n° AN With n g , the grating 800 may appear as a substantially optically uniform plate for incident light 830. That is, for incident light 830 polarized in the groove direction of the SRG 805, the grating 800 may be in a non-diffracting state (or off state). In some embodiments, the second principal refractive index (e.g., n° AN ) can be compared with the refractive index n of SRG 805 g Exactly matched (or may be identical thereto), therefore, light 830 may be transmitted through grating 800 without any diffraction. That is, for incident light 830, the diffraction effect of grating 800 may be completely turned off.

[0088] FIG. 9A to FIG. 9B FIG. 4 is a schematic diagram of a switching diffractive optical element 900 according to another embodiment of the present disclosure. FIG. 9A to FIG. 9B and FIG. 8A to FIG. 8C The similarities between may not be repetitive, but may explain some of the differences. FIG. 8A to FIG. 8C Unlike the active LC 815 shown with positive dielectric anisotropy filled into the SRG 805, Figures 9A to 9B The SRG 905 in the substrate 910 may be filled with an active LC 915 having a negative dielectric anisotropy. The LC molecules 920 may be arranged in an out-of-plane direction perpendicular to the substrate 910 (e.g., FIG. 9A to FIG. 9B The second principal refractive index of LC 915 (e.g., n°) is vertically aligned in the groove of SRG 905 in the z direction (e.g., n°). AN ) can substantially match the refractive index n of SRG 905 g , and the first principal refractive index of LC 915 (eg, n e AN ) may not match the refractive index n of SRG 905 g .

[0089] In the voltage-off state where the applied voltage is zero (or more generally, the applied voltage is below the threshold voltage that causes the LC molecules 920 to reorient), as shown in FIG. Fig. 9A As shown, LC molecules 920 with negative dielectric anisotropy can be vertically aligned in the grooves, for example, in the z direction. For incident light 930 polarized in the groove direction of the SRG 905 (eg, the y direction), due to n° AN With n g , the grating 900 may appear to be a substantially optically uniform plate of light 930. That is, for light 930 polarized in the direction of the grooves of the SRG 905, the grating 900 may be in a non-diffracting state. In some embodiments, the second principal refractive index of the LC 915 (e.g., n° AN ) can basically match the refractive index n of SRG905 g , and light 930 can be transmitted through grating 800 with negligible diffraction. In some embodiments, the second principal refractive index (e.g., n°) of LC 915 AN ) can be compared with the refractive index n of SRG 905 g The same, therefore, light 930 can be transmitted through without any diffraction. That is, for light 930 polarized in the groove direction of SRG 905, the diffraction effect of grating 900 can be completely turned off.

[0090] When the voltage is on, Fig. 9BAs shown, an electric field may be generated between electrodes at two opposing substrates 910, and LC molecules 920 having negative dielectric anisotropy may be redirected from a vertical (homeotropic) state to a horizontal (planar) state by the electric field. When the applied voltage is high enough, the long axis of the LC molecules 920 may tend to be perpendicular to the electric field direction (e.g., z-direction) of the SRG 905 and parallel to the groove direction (e.g., y-direction) of the SRG 905. Light 930 polarized in the groove direction (e.g., y-direction) of the SRG 905 may experience periodic modulation of the refractive index in the grating 900, and thus due to n e AN With n g That is, for light 930 polarized in the groove direction (e.g., y direction) of SRG 905, grating 900 may be in a diffraction state. FIG. 8A to FIG. 8C and FIG. 9A to FIG. 9B When the grating is in the voltage-off state, the grating can be in a diffractive state or a non-diffractive state. Similarly, when the grating is in the voltage-on state, the grating can be in a diffractive state or a non-diffractive state, depending on the configuration of the grating and the polarization of the incident light.

[0091] Active gratings according to embodiments of the present disclosure can achieve time-division multiplexing of multiple different light fields (e.g., parts of the FOV, images of various colors, etc.) delivered by one or more waveguides. The FOV in a waveguide is typically limited by the angular bandwidth of the grating and the angular confinement of the waveguide, which is primarily determined by the refractive index of the waveguide. One way to extend the FOV is to divide the FOV into several parts and transmit these parts through different gratings or grating groups. In order to avoid crosstalk between gratings, it may be desirable to transmit light fields corresponding to different parts of the FOV in different time frames, for example by using a time-division multiplexing approach. In the following, an exemplary waveguide architecture is explained corresponding to the "symmetric" case where the FOV does not rotate after being translated through the waveguide. This case can also correspond to compensation for light dispersion caused by a separated grating in the waveguide, which can allow a broadband light source to be used as a light source coupled to the waveguide. For example, mutual compensation of dispersion caused by coupling-in and coupling-out gratings can be achieved in a dual-grating waveguide. The mathematical expression describing this state is where k iis the grating vector of the i-th grating, and n is the number of gratings on the path of the light in the waveguide. That is, the vector sum of the grating vectors of the gratings that guide each portion of the light in the waveguide may be substantially equal to zero. Active gratings according to embodiments of the present disclosure may allow the FOV to be extended by time-division multiplexing different portions of the FOV that are divided and delivered by different pairs of active gratings arranged in different ways, such as by tiling gratings at a common waveguide, or by stacking gratings at a common waveguide or at different waveguides. Similar principles may be used to transmit images of different colors.

[0092] Fig. 10A shows a schematic diagram of a waveguide 1000, FIG. 10B to FIG. 10D Shows Fig. 10A The waveguide 1000 in the embodiment transmits different parts of the FOV in a time-division multiplexed manner. The waveguide 1000 may be FIG. 2A to FIG. 2B An embodiment of the waveguide 210 in FIG. Fig. 10A As shown, the waveguide 1000 can be configured to receive image light from the light source assembly 205 via an incoupling grating 1005, and to direct the image light to the eye 265 via an outcoupling grating 1010. At least one of the incoupling grating 1005 and the outcoupling grating 1010 can be any one of the disclosed active gratings. Each of the incoupling grating 1005 and the outcoupling grating 1010 can include a plurality of sub-gratings, wherein adjacent sub-gratings can partially overlap to obtain a continuous FOV. FIG. 10E to FIG. 10F Explanation of exemplary overlapping configurations of sub-gratings.

[0093] Reference Fig. 10A , the sub-gratings of the coupling-in grating 1005 may correspond one-to-one to the sub-gratings of the coupling-out grating 1010. The number of sub-gratings of the corresponding grating may correspond to the number of parts of the divided FOV. The sub-gratings in the coupling-in grating 1005 and the coupling-out grating 1010 may be arranged at the first surface 1000-1 and / or the second surface 1000-2 of the waveguide 1000. The sub-gratings of the coupling-in grating 1005 may be arranged on the same surface or different surfaces of the waveguide 1000. The sub-gratings of the coupling-out grating 1010 may be arranged on the same surface or different surfaces of the waveguide 1000. In some embodiments, the sub-gratings may have a 1D grating pattern to tile the FOV in one dimension. In some embodiments, the sub-gratings may have a 2D grating pattern to tile the FOV in two dimensions.

[0094] For the purpose of discussion, the coupling-in grating 1005 and the coupling-out grating 1010 may be disposed at the second surface 1000_2 and the first surface 1000_1 of the waveguide 1000, respectively, and both the coupling-in grating 1005 and the coupling-out grating 1010 may be the disclosed switchable gratings. The coupling-in grating 1005 may include three sub-gratings: a first coupling-in sub-grating 1005_1, a second coupling-in sub-grating 1005_2, and a third coupling-in sub-grating 1005_3. The coupling-out grating 1010 may include three sub-gratings: a first coupling-out sub-grating 1010_1, a second coupling-out sub-grating 1010_2, and a third coupling-out sub-grating 1010_3, which correspond one-to-one to the first coupling-in sub-grating 1005_1, the second coupling-in sub-grating 1005_2, and the third coupling-in sub-grating 1005_3.

[0095] Light source assembly 205 may emit image light from a light source (e.g., a display) toward incoupling grating 1005. The image light may include light corresponding to different portions of the FOV of the display. Fig. 10A As shown, the angle range included by image light 1020 may correspond to the left portion of the FOV of the display, the angle range included by image light 1030 may correspond to the center portion of the FOV of the display, and the angle range included by image light 1040 may correspond to the right portion of the FOV of the display. In some embodiments, the image light may be linearly polarized light. In some embodiments, the image light may be different from linearly polarized light, and an optical element (e.g., a linear polarizer or a quarter wave plate, etc.) may be arranged between the light source assembly 205 and the waveguide 1000 to convert the image light emitted from the light source assembly 205 into linearly polarized image light to be incident on the incoupling grating 1005.

[0096] The display frame of the display in the light source assembly 205 can be divided into three sub-frames for sequentially transmitting light corresponding to different parts of the FOV of the display, thereby achieving sequential transmission of different parts of the FOV of the display. Fig. 10A and Fig. 10B , the first coupling-in sub-grating 1005_1 and the first coupling-out sub-grating 1010_1 may be switched to a diffraction state (or an on state), and the remaining sub-gratings may all be switched to a non-diffraction state (or an off state). Therefore, the light within the angle range included in the light 1020 may be coupled into the TIR path in the waveguide 1000 via the first coupling-in sub-grating 1005_1, and decoupled from the waveguide 1000 into the angle range included in the light 1020′ via the first coupling-out sub-grating 1010_1 to be viewed by the eye 265, while the light within the angle range included in the light 1030 and the light within the angle range included in the light 1040 may not be coupled into the waveguide 1000. The angle range included in the light 1020′ may correspond to the left portion of the FOV.

[0097] At the second subframe, reference Fig. 10A and Fig. 10C , the second coupling-in sub-grating 1005_2 and the second coupling-out sub-grating 1010_2 may be switched to a diffraction state (or an on state), while the remaining sub-gratings may all be switched to a non-diffraction state (or an off state). Therefore, the light within the angle range surrounded by the light 1030 may be coupled into the TIR path in the waveguide 1000 via the second coupling-in sub-grating 1005_2, and decoupled from the waveguide 1000 into the angle range surrounded by the light 1030' via the second coupling-out sub-grating 1010_2 so as to be viewed by the eye 265, while the light within the angle range surrounded by the light 1020 and the light within the angle range surrounded by the light 1040 may not be coupled into the waveguide 1000. The angle range included in the light 1030' may correspond to the middle part of the FOV.

[0098] At the third subframe, reference Fig. 10A and Fig. 10D , the third coupling-in sub-grating 1005_3 and the third coupling-out sub-grating 1010_3 may be switched to a diffraction state (or an on state), and the remaining sub-gratings may all be switched to a non-diffraction state (or an off state). Therefore, the light within the angle range surrounded by the light 1040 may be coupled into the TIR path in the waveguide 1000 via the third coupling-in sub-grating 1005_3, and decoupled from the waveguide 1000 into the angle range of the light 1040' to be viewed by the eye 265 via the third coupling-out sub-grating 1010_3, while the light within the angle range surrounded by the light 1020 and the light within the angle range surrounded by the light 1030 may not be coupled into the waveguide 1000. The angle range included in the light 1040' may correspond to the right part of the FOV.

[0099] Therefore, by sequentially switching the pair of the first coupling-in sub-grating 1005_1 and the first coupling-out sub-grating 1010_1, the pair of the second coupling-in sub-grating 1005_2 and the second coupling-out sub-grating 1010_2, and the pair of the third coupling-in sub-grating 1005_3 and the third coupling-out sub-grating 1010_3 to the diffraction state, sequential transmission of different parts of the FOV in a common waveguide can be achieved by tiling the FOV. In addition, switching the sub-gratings in different subframes can eliminate crosstalk caused by spatial overlap between adjacent sub-gratings. In some embodiments, the coupling-in grating 1005 and the coupling-out grating 1010 can each include two sub-gratings, which are optimized for sequentially transmitting the right and left parts of the FOV of the display.

[0100] It should be noted that Fig. 10AA single light source assembly 205 emitting image light corresponding to the entire FOV is shown for illustrative purposes and is not intended to limit the scope of the present disclosure. In some embodiments, multiple light source assemblies may be used, each emitting image light corresponding to a portion of the entire FOV provided by the waveguide display assembly. For example, three light source assemblies may be used that emit image light corresponding to the left, middle, and right portions of the entire FOV, respectively. In some embodiments, the emitted image light corresponding to the left and middle portions of the entire FOV may partially overlap, and the image light corresponding to the right and middle portions of the entire FOV may partially overlap, so that a continuous FOV may be introduced into the waveguide from the coupling element 1005.

[0101] It should be noted that Fig. 10A Both the in-coupling grating 1005 and the out-coupling grating 1010 are shown to include a plurality of the disclosed switchable gratings, which is for illustrative purposes and is not intended to limit the scope of the present disclosure. In some embodiments, one of the in-coupling grating 1005 and the out-coupling grating 1010 may include a plurality of the disclosed switchable gratings, while the other may include one or more non-switchable gratings. For example, different portions of the FOV may be introduced into the waveguide from the non-switchable in-coupling grating 1005. The out-coupling grating 1010 may include three out-coupling sub-gratings, and a display frame may include three sub-frames. During each sub-frame, one sub-grating may be switched to a diffraction state to decouple image light corresponding to a predetermined portion of the FOV from the waveguide 1000, while the remaining sub-gratings may be switched to a non-diffraction state to suppress crosstalk.

[0102] FIG. 10E to FIG. 10F Shown included in Fig. 10A Schematic diagram of overlapping configuration of coupling sub-gratings in waveguide 1000 in FIG. In some embodiments, one or more coupling sub-gratings can be arranged on different planes so that adjacent coupling sub-gratings can partially overlap. The space around the coupling sub-gratings can be filled with a refractive index matching material. In one embodiment, as Fig.10E As shown, each coupling sub-grating 1005_1, 1005_2 and 1005_3 can be arranged at different planes so that adjacent coupling sub-gratings can partially overlap. The space around the coupling sub-grating can be filled with a refractive index matching material 1050 so that light reflection can be suppressed in the space. In one embodiment, as Fig.10F As shown, the first coupling sub-grating 1005_1 and the third coupling sub-grating 1005_3 can be arranged at the same plane, and the second coupling sub-grating 1005_2 can be arranged at a different plane, so that adjacent coupling sub-gratings can partially overlap. Fig. 10A The overlapping configuration of the out-coupling sub-gratings in the waveguide 1000 can be similar to the overlapping configuration of the in-coupling sub-gratings, and the details are not repeated here.

[0103] FIG. 11A to FIG. 11D A schematic diagram showing the time division multiplexing of different parts of the FOV transmitted by the waveguide stack. Fig.11A A schematic diagram illustrating a waveguide stack 1100, and FIG. 11B to FIG. 11D illustrate Fig.11A The operation scheme of the stack 1100 in FIG. 1 is used to transmit different parts of the FOV in a time-division multiplexed manner. The waveguide stack 1100 may be FIG. 2A to FIG. 2B An embodiment of the waveguide 210 in FIG. Fig. 10A and Fig.11A The similarities between no longer explain, but can explain some of the differences. Fig.11A As shown, the stack 1100 may include a plurality of waveguides stacked together, for example, three waveguides 1110, 1120, and 1130. Waveguide 1110 may include an in-coupling grating 1112 and an out-coupling grating 1114, waveguide 1120 may include an in-coupling grating 1122 and an out-coupling grating 1124, and waveguide 1130 may include an in-coupling grating 1132 and an out-coupling grating 1134. To ensure that waveguides can occur in each waveguide, the three waveguides 1110, 1120, and 1130 may be separated by an air gap. In some embodiments, the air gaps between the waveguides 1110, 1120, and 1130 may be filled with a material having a refractive index lower than the refractive index of the waveguide (e.g., liquid glue). At least one of the in-coupling grating and the out-coupling grating may include any one of the disclosed switchable gratings. The in-coupling grating and the out-coupling grating may be disposed at the first surface and / or the second surface of each waveguide. For purposes of discussion, in Fig.11A In the stack 1100, all coupling-in gratings and coupling-out gratings may be the disclosed switchable gratings and are arranged at the second surface of the corresponding waveguide.

[0104] Light source assembly 205 may emit image light from a light source (e.g., a display) toward stack 1100, where the image light may include light corresponding to different portions of the FOV of the display. Fig.11A , the angle range included by light 1140 may correspond to the left portion of the FOV of the display, the angle range included by light 1150 may correspond to the middle portion of the FOV of the display, and the angle range included by light 1160 may correspond to the right portion of the FOV of the display. The image light emitted from light source assembly 205 may be linearly polarized light, or may be converted into linearly polarized light by some optical elements disposed between light source assembly 205 and stack 1100.

[0105] The display frame can be divided into three sub-frames for sequentially transmitting light corresponding to different parts of the FOV. Fig.11A and Fig. 11B, the coupling-in grating 1112 and the coupling-out grating 1114 at the waveguide 1110 may be switched to a diffraction state (or an on state), while the coupling-in grating 1122 and the coupling-out grating 1124 at the waveguide 1120 and the coupling-in grating 1132 and the coupling-out grating 1134 at the waveguide 1130 may be switched to a non-diffraction state (or an off state). Therefore, light rays within the angle range included in the light ray 1140 may be coupled into the TIR path in the waveguide 1110 via the coupling-in grating 1112, and decoupled from the waveguide 1110 via the coupling-out grating 1114 to the angle range included in the light ray 1140′ to be viewed by the eye 265, while light rays within the angle range included in the light ray 1150 and light rays within the angle range included in the light ray 1160 may not be coupled into any of the waveguides 1110, 1120, and 1130. The angle range included in the light ray 1140′ may correspond to the left portion of the FOV. That is, the left portion of the FOV may be replicated at the eye box located at the exit pupil of the eye 265 .

[0106] At the second subframe, reference Fig.11A and Fig. 11C , the coupling-in grating 1122 and the coupling-out grating 1124 at the waveguide 1120 can be switched to a diffraction state (or an on state), while the coupling-in grating 1112 and the coupling-out grating 1114 at the waveguide 1110 and the coupling-in grating 1132 and the coupling-out grating 1134 at the waveguide 1130 can all be switched to a non-diffraction state (or an off state). Therefore, the light within the angle range included in the light ray 1150 can be coupled into the TIR path in the waveguide 1120 via the coupling-in grating 1122, and decoupled from the waveguide 1120 via the coupling-out grating 1124 to the angle range included in the light ray 1150' viewed by the eye 265, while the light within the angle range included in the light ray 1140 and the light within the angle range included in the light ray 1160 may not be coupled into any of the waveguides 1110, 1120, and 1130. The angle range included in the light ray 1150' may correspond to the middle portion of the FOV. That is, the middle portion of the FOV may be replicated at the eye box located at the exit pupil of the eye 265 .

[0107] In the third subframe, reference Fig.11A and Fig.11D, the coupling-in grating 1132 and the coupling-out grating 1134 at the waveguide 1130 can be switched to a diffraction state (or an on state), while the coupling-in grating 1112 and the coupling-out grating 1114 at the waveguide 1110 and the coupling-in grating 1122 and the coupling-out grating 1124 at the waveguide 1120 can all be switched to a non-diffraction state (or an off state). Therefore, only the light within the angle range included by the light ray 1160 can be coupled into the TIR path in the waveguide 1130 via the coupling-in grating 1132, and decoupled from the waveguide 1130 into the angle range included by the light ray 1160′ via the coupling-out grating 1134 so as to be viewed by the eye 265, while the light within the angle range included by the light ray 1140 and the light within the angle range included by the light ray 1150 may not be coupled into any of the waveguides 1110, 1120 and 1130. The angular range encompassed by ray 1160' may correspond to the right portion of the FOV. That is, the right portion of the FOV may be replicated at the eye box located at the exit pupil of eye 265.

[0108] Therefore, by sequentially switching the coupling-in grating and the coupling-out grating pairs at the corresponding waveguides in the stack 1100 to the diffraction state, and simultaneously switching the remaining coupling-in gratings and the coupling-out gratings in the stack 1100 to the non-diffraction state, sequential transmission of the left, middle and right parts of the FOV can be achieved. The coupling-in grating and the coupling-out grating in the stack 1100 can be designed so that the left, middle and right parts of the FOV can be transmitted with partial overlap to provide a continuous FOV transmitted by the entire frame. In addition, switching the coupling-in grating and the coupling-out grating pairs at the corresponding waveguides in different subframes can eliminate the crosstalk caused by the spatial overlap between different parts of the FOV. In some embodiments, the FOV can be divided into two parts, such as the left and the right, and the same principle can be used to transmit the two parts of the FOV separately.

[0109] In some embodiments, instead of placing the in-coupling grating and the out-coupling grating at the corresponding waveguides in the stack 1100, as shown in FIG. Fig.15 As shown, the in-coupling gratings 1112, 1122, and 1132 can be stacked and attached to a common (e.g., single) waveguide, and the out-coupling gratings 1114, 1124, and 1134 can be stacked and attached to a common waveguide. Fig.15 A schematic diagram of a waveguide 1500 delivering different portions of a FOV in a time-division multiplexed manner is shown according to another embodiment of the present invention. Fig.11A and Fig.15 The similarities between are no longer repeated, but can explain some of the differences. Fig.15As shown, a plurality of coupling-in gratings 1512, 1522, and 1532 may be disposed at a first surface or a second surface of the waveguide 1500, and a plurality of coupling-out gratings 1514, 1524, and 1534 may be disposed at a first surface or a second surface of the waveguide 1500. The plurality of coupling-in gratings 1512, 1522, and 1532 and the plurality of coupling-out gratings 1514, 1524, and 1534 may be disposed on the same surface or on different surfaces of the waveguide 1500. The operation scheme of the coupling-in gratings 1512, 1522, and 1532 and the coupling-out gratings 1514, 1524, and 1534 for realizing the timed transmission of the left, middle, and right portions of the FOV may be similar to FIG. 11B to FIG. 11D and the details will not be repeated here.

[0110] Fig. 12A A schematic diagram of a waveguide stack 1200 according to another embodiment of the present disclosure is shown, and FIG. 12B to FIG. 12D Shows Fig. 12A The waveguide stack 1200 in FIG. 1 is used to deliver a monochrome image with different colors in a time-division multiplexing manner. The waveguide stack 1200 may be similar to Fig.11A , and the details are not repeated here. The waveguide stack 1100 in FIG. 1200 may receive image light from a plurality of source components (e.g., three source components 1240, 1250, and 1260). Each light source component may emit monochromatic image light of a specific wavelength band corresponding to a primary color (e.g., red, green, or blue). For example, the light source components 1240, 1250, and 1260 may emit monochromatic image light 1245, 1255, and 1265 of a specific wavelength band corresponding to a first primary color (e.g., red), a second primary color (e.g., green), and a third primary color (e.g., blue), respectively. The source components 1240, 1250, and 1260 may be configured to sequentially emit corresponding image light according to instructions from a controller. Each of the image lights emitted from the light source components 1240, 1250, and 1260 may be linearly polarized light or converted into linearly polarized light by some optical elements disposed between the light source component and the stack 1200.

[0111] The waveguide 1210 may include an in-coupling grating 1212 and an out-coupling grating 1214, both designed for a wavelength band corresponding to a first primary color (e.g., red), the waveguide 1220 may include an in-coupling grating 1222 and an out-coupling grating 1224, both designed for a wavelength band corresponding to a second primary color (e.g., green), and the waveguide 1230 may include an in-coupling grating 1232 and an out-coupling grating 1234, both designed for a wavelength band corresponding to a third primary color (e.g., blue). At least one of the in-coupling gratings 1212, 1222, and 1232 and the out-coupling gratings 1214, 1224, and 1234 may include any one of the disclosed polarization-sensitive switchable gratings. For the purpose of discussion, all of the in-coupling gratings 1212, 1222, and 1232 and the out-coupling gratings 1214, 1224, and 1234 may be the disclosed polarization-sensitive switchable gratings.

[0112] The display frame can be divided into three sub-frames for sequentially transmitting image light 1240, 1250 and 1260. In the first sub-frame, reference Fig. 12A and Fig. 12B , image light 1245 (e.g., red light) may be emitted by source component 1240 toward stack 1200, and image lights 1255 (e.g., green light) and 1265 (e.g., blue light) may not be emitted from the corresponding source components. The in-coupling grating 1212 and the out-coupling grating 1214 at waveguide 1210 may be switched to a diffraction state (or an on state), while the in-coupling grating 1222 and the out-coupling grating 1224 at waveguide 1220 and the in-coupling grating 1232 and the out-coupling grating 1234 at waveguide 1230 may all be switched to a non-diffraction state (or an off state). Therefore, image light 1245 (e.g., red light) may be coupled into a TIR path in waveguide 1210 via the in-coupling grating 1212, and decoupled from waveguide 1210 via the out-coupling grating 1214 to become image light 1245' (e.g., red light) to be viewed by eye 265. That is, the eye 265 can see a monochrome image (eg, a red image).

[0113] At the second subframe, reference Fig. 12A and Fig. 12C, image light 1255 (e.g., green light) may be emitted by source component 1250 toward stack 1200, and image lights 1245 (e.g., red light) and 1265 (e.g., blue light) may not be emitted from the corresponding source components. The in-coupling grating 1222 and the out-coupling grating 1224 at waveguide 1220 may be switched to a diffraction state (or an on state), while the in-coupling grating 1212 and the out-coupling grating 1214 at waveguide 1210 and the in-coupling grating 1232 and the out-coupling grating 1234 at waveguide 1230 may all be switched to a non-diffraction state (or an off state). Therefore, image light 1255 (e.g., green light) may be coupled into the TIR path in waveguide 1220 via the in-coupling grating 1222, and decoupled from waveguide 1220 via the out-coupling grating 1224 to become image light 1255′ (e.g., green light) to be viewed by eye 265. That is, a single color image (eg, a green image) may be viewed by eye 265 .

[0114] At the third subframe, reference Fig. 12A and Fig.12D , image light 1265 (e.g., blue light) may be emitted by source component 1260 toward stack 1200, and image lights 1245 (e.g., red light) and 1255 (e.g., green light) may not be emitted from the corresponding source components. The in-coupling grating 1232 and the out-coupling grating 1234 at waveguide 1230 may be switched to a diffraction state (or an on state), while the in-coupling grating 1212 and the out-coupling grating 1214 at waveguide 1210 and the in-coupling grating 1222 and the out-coupling grating 1224 at waveguide 1220 may all be switched to a non-diffraction state (or an off state). Therefore, image light 1265 (e.g., blue light) may be coupled into the TIR path in waveguide 1230 via the in-coupling grating 1232, and decoupled from waveguide 1230 via the out-coupling grating 1234 to become image light 1265′ (e.g., blue light) to be viewed by eye 265. That is, a single color image (eg, a blue image) may be viewed by eye 265 .

[0115] Therefore, by sequentially emitting monochromatic image lights 1245, 1255, and 1265, and sequentially switching the corresponding in-coupling grating and out-coupling grating pairs to the diffraction state, sequential transmission of image lights of different colors (e.g., red, green, blue) can be achieved. That is, sequential transmission of monochromatic images of different colors can be achieved. The final image can be viewed by the eye 265 as a multi-color image. In addition, the time division multiplexing achieved by using the disclosed switchable gratings can eliminate crosstalk in the stack 1200, thereby improving the image performance of the waveguide display assembly including the stack 1200. In some embodiments, the source components 1240, 1250, and 1260 can continue to emit the corresponding image lights even when the corresponding in-coupling grating and out-coupling grating pairs are switched to the non-diffraction state, by which the control can be simplified, however, the power consumption may increase.

[0116] In some embodiments, instead of arranging the in-coupling grating and the out-coupling grating at respective waveguides in the stack 1200, the in-coupling gratings 1212, 1222, and 1232 may be stacked and attached to a common (e.g., single) waveguide, and the out-coupling gratings 1214, 1224, and 1234 may be stacked and attached to a common waveguide, and may refer to FIG. 11A to FIG. 11D A similar structure is described in detail. The stack of coupling-in gratings and the stack of coupling-out gratings can be arranged at the first surface or the second surface of the common waveguide. The operation scheme of the coupling-in gratings 1212, 1222 and 1232 and the coupling-out gratings 1214, 1224 and 1234 for realizing the time-sequential transmission of image lights of different colors can be the same as FIG. 12B to FIG. 12D The details are similar to those shown in , and will not be repeated here.

[0117] Figures 12A to 12D The embodiments in are effective for monochromatic image light. For color images, image light of different colors can be spatially and / or temporally multiplexed. The number of waveguides in the stack can be reduced to two. For separate transmission of colors, one waveguide can be configured for red / green and another for green / blue.

[0118] It should be noted that Fig. 12A In-coupling gratings and out-coupling gratings are shown, each of which is a disclosed switchable grating, which is for illustrative purposes and is not intended to limit the scope of the present disclosure. In some embodiments, each in-coupling grating may be a disclosed switchable grating, and each out-coupling grating may be a non-switchable grating. In some embodiments, each out-coupling grating may be a disclosed switchable grating, and each in-coupling grating may be a non-switchable grating. For example, RGB colors may be introduced from a separate projector through a non-switchable in-coupling grating. A display frame may include three subframes. In each subframe, only the projector emitting one of the RGB colors may be turned on, and the out-coupling grating corresponding to one of the RGB colors may be configured to be in a diffraction state to transmit image light of one of the RGB colors, while the remaining projectors may be turned off, and the remaining out-coupling gratings may be configured to be in a non-diffraction state to suppress crosstalk.

[0119] The present disclosure also provides a method for a waveguide display component to transmit multiple light fields of image light emitted from a light source component in a time-division multiplexed manner. The method may include: during a first time period, a first coupling grating couples a plurality of first image lights corresponding to a first light field in a plurality of light fields into a first waveguide via diffraction; and a first coupling grating decouples the plurality of first image lights from the first waveguide to an eye box of an optical device via diffraction. The method may include: during a second time period, a second coupling grating couples a plurality of second image lights corresponding to a second light field in the plurality of light fields into a second waveguide via diffraction; and a second coupling grating decouples the plurality of second image lights from the second waveguide to an eye box of the optical device via the diffraction. The light field may correspond to a predetermined portion of a field of view (FOV) of a monochrome image, a predetermined portion of a FOV of a full-color image, or a monochrome image of a predetermined color. The method may further include: during a third time period, coupling a plurality of third image lights corresponding to a third light field among the plurality of light fields into a third waveguide via diffraction by a third coupling-in grating; and decoupling the plurality of third image lights from the third waveguide to an eye box of the optical device via the diffraction by a third coupling-out grating.

[0120] For discussion purposes, Fig.13 Flowchart 1300 shows a method for transmitting a waveguide display assembly of different portions of a FOV in a time division multiplexed manner according to an embodiment of the present disclosure. The waveguide display assembly may be FIG. 2A to FIG. 2B Embodiments of the waveguide display components 200 and 250 in FIG. The waveguide display component may include at least one disclosed switchable diffractive optical element.

[0121] like Fig.13 As shown, the method may include: during a first time period, a first coupling element couples a plurality of first light rays emitted from a light source assembly into a first waveguide via diffraction, and a first coupling element decouples the plurality of first light rays from the first waveguide via diffraction into light rays of a first angular range toward an eye box (S1310). The angular range of the plurality of first light rays emitted from the light source assembly may correspond to a first portion of a FOV provided by the light source assembly. The first angular range of light rays decoupled from the first waveguide may correspond to a first portion of a FOV provided by the light source assembly.

[0122] The method may further include: during a second time period, coupling a plurality of second light rays emitted from the light source assembly into the second waveguide via diffraction by a second coupling element, and decoupling the plurality of second light rays from the second waveguide via diffraction into light rays of a second angular range toward the eye box by a second decoupling element (S1320). The angular range of the plurality of second light rays emitted from the light source assembly may correspond to a second portion of the FOV provided by the light source assembly. The second angular range of light rays decoupled from the second waveguide may correspond to a second portion of the FOV provided by the light source assembly.

[0123] In some embodiments, the light source assembly may include a source as a display, and the first time period and the second time period may be the first subframe and the second subframe of the display frame of the display, respectively. In some embodiments, the first waveguide and the second waveguide may be the same waveguide (referred to as a common waveguide), wherein the common waveguide may have a first surface facing the light source assembly and an opposing second surface. In some embodiments, the first and second coupling-in elements may be tiled at the first or second surface of the common waveguide, and the first and second coupling-out elements may be tiled at the first or second surface of the common waveguide. In some embodiments, the first and second coupling-in elements may be stacked and attached to the first or second surface of the common waveguide, and the first and second coupling-out elements may be stacked and attached to the first or second surface of the common waveguide.

[0124] In some embodiments, the first and second waveguides can be separate waveguides separated by a low refractive index material, wherein each waveguide can have a first surface facing the light source assembly and an opposing second surface. The coupling element of the corresponding waveguide can be arranged at the first or second surface of the corresponding waveguide, and the coupling element of the corresponding waveguide can be arranged at the first or second surface of the corresponding waveguide.

[0125] In some embodiments, the method may further include: during a third time period, a third coupling element couples a plurality of third light rays emitted from the light source assembly into a third waveguide via diffraction, and a third coupling element decouples the plurality of third light rays from the third waveguide via diffraction into light rays of a third angular range toward the eye box. The angular range of the plurality of third light rays emitted from the light source assembly may correspond to a third portion of the FOV provided by the light source assembly. The third angular range of light rays decoupled from the third waveguide may correspond to a third portion of the FOV provided by the light source assembly.

[0126] For discussion purposes, Fig.14 A flowchart 1400 is shown of a method for a waveguide display assembly for delivering monochrome images of different colors in a time division multiplexed manner according to an embodiment of the present disclosure. The waveguide display assembly may be FIG. 2A to FIG. 2B Embodiments of the waveguide display components 200 and 250 in FIG. The waveguide display component may include at least one disclosed switchable diffractive optical element.

[0127] like Fig.14 As shown, the method may include: during a first time period, a first coupling element couples the image light of a first color emitted from a first light source assembly into a first waveguide via diffraction, and a first coupling element decouples the image light of the first color from the first waveguide to an eye box via diffraction (S1410). The method may include: during a second time period, a second coupling element couples the image light of a second color emitted from a second light source assembly into a second waveguide via diffraction, and a second coupling element decouples the image light of the second color from the second waveguide to an eye box via diffraction (S1420).

[0128] In some embodiments, the first and second light source assemblies may be separate light source assemblies. Each of the first and second light source assemblies may include a source as a display, and the first time period and the second time period may be the first subframe and the second subframe of the display frame of the display, respectively. In some embodiments, the first and second light source assemblies may be the same common light source assembly, which is controlled to sequentially emit image light of a first color and image light of a second color. In some embodiments, the image light of the first color and the image light of the second color may be monochromatic light corresponding to wavelength bands of different primary colors. The first and second waveguides may be individual waveguides separated by a low refractive index material. Each waveguide may have a first surface facing the light source assembly and an opposing second surface. The coupling-in element of the corresponding waveguide may be disposed at the first or second surface of the corresponding waveguide, and the coupling-out element of the corresponding waveguide may be disposed at the first or second surface of the corresponding waveguide.

[0129] In some embodiments, the method may further include: during a third time period, coupling the image light of a third color emitted from the third light source assembly into the third waveguide via diffraction by a third coupling element, and decoupling the image light of the third color from the third waveguide to the eye box via diffraction by a third decoupling element.

[0130] It should be noted that the disclosed methods for spatial and / or temporal multiplexing of different colors and / or different parts of the FOV based on the disclosed switchable gratings can be combined to deliver full color images with a wide FOV, all within the scope of the present disclosure. For example, Fig.11A The waveguide stack 1100 or Fig.15 The waveguide 1500 in can also be used to transmit a full-color image with a large FOV, where one or more waveguides are configured to deliver a full-color image with different portions of the FOV in a time-division multiplexed manner. To achieve transmission of a full-color image with a large FOV via the waveguide in a time-division multiplexed manner, each of the coupling-in grating and the coupling-out grating in each waveguide can include multiple sub-gratings for delivering different colors (e.g., red, green, and blue) corresponding to different portions of the FOV.

[0131] For example, in order to Fig.11A The waveguide stack 1100 or Fig.15 The waveguide 1500 in the embodiment sequentially delivers full-color image light corresponding to a predetermined portion of the FOV in a time-division multiplexed manner, Fig.11A The coupling gratings 1112, 1122 and 1132 in Fig.15 Each of 1512, 1522, 1532 may include a plurality of switchable coupling sub-gratings, and Fig.11A The outcoupling gratings 1114, 1124 and 1134 or Fig.15 Each of 1514, 1524, 1534 may include a plurality of switchable outcoupling sub-gratings. Fig.11A The coupling gratings 1112, 1122 and 1132 in Fig.15 1512, 1522, 1532 in the embodiment may be coupled into the grating stack, and Fig.11A The outcoupling gratings 1114, 1124 and 1134 or Fig.15 1514, 1524, 1534 in the figure may be an out-coupling grating stack. Assuming that X sub-gratings are designed to transmit the FOV and Y sub-gratings are designed to transmit a monochrome image forming a full-color image (e.g., RGB color), the total number of sub-gratings included in each of the in-coupling and out-coupling grating stacks may be X*Y, where X and Y are positive integers and X≥2 and Y≥2. For example, the number of sub-gratings for transmitting 1 / 3 of the FOV (X=3) may be X*Y. Fig.11A The coupling gratings 1112, 1122 and 1132 in Fig.15 Each of 1512, 1522, 1532 in can be divided into 3 sub-gratings (Y=3) to transmit corresponding parts of the FOV of red, green and blue. For the same purpose, Fig.11A The outcoupling gratings 1114, 1124 and 1134 or Fig.15 1514, 1524, 1534 (for delivering 1 / 3 of the FOV (X=3)) can be divided into 3 sub-gratings (Y=3) to deliver corresponding parts of the FOV in red (R), green (G) and blue (B). The total amount of coupled-in sub-gratings can be equal to the total amount of coupled-out sub-gratings and can be designed as X*Y=3*3=9. In some embodiments, the corresponding sub-gratings from the coupled-in and coupled-out grating stacks can be activated in separate sub-frames (e.g., 9 sub-frames) to suppress crosstalk.

[0132] In each subframe, a pair of switchable in- and out-coupling sub-gratings can be configured to be in a diffraction state to transmit a monochrome image corresponding to a predetermined portion of the FOV to the eye, while the remaining pairs of in- and out-coupling sub-gratings can be configured to be in a non-diffraction state. Therefore, during the entire display frame, monochrome images corresponding to different portions of the FOV can be sequentially sent to the eye in a time-division multiplexed manner. For example, a red monochrome image corresponding to the left portion of the FOV, a green monochrome image corresponding to the left portion of the FOV, a blue monochrome image corresponding to the left portion of the FOV, a red monochrome image corresponding to the middle portion of the FOV, a green monochrome image corresponding to the middle portion of the FOV, a blue monochrome image corresponding to the middle portion of the FOV, a red monochrome image corresponding to the right portion of the FOV, a green monochrome image corresponding to the right portion of the FOV, and a blue monochrome image corresponding to the right portion of the FOV can be sequentially transmitted to the eye in a time-division multiplexed manner. In some embodiments, the number of subframes can be reduced if some of the sub-gratings (e.g., for different colors) in the waveguide stack 1100 or the waveguide 1500 are highly selective so that the crosstalk between them can be ignored.

[0133] Similarly, Fig. 10A The waveguide 1000 in can also be used to transmit a full-color image with a large FOV, wherein the waveguide 1000 is configured to transmit a full-color image with different parts of the FOV in a time-division multiplexed manner. In order to achieve the transmission of a full-color image with a large FOV via the waveguide in a time-division multiplexed manner, each of the coupling-in sub-gratings 1005_1, 1005_2 and 1005_3 can further include a plurality of third coupling-in gratings, and each of the coupling-out sub-gratings 1010_1, 1010_2 and 1010_3 can further include a plurality of third coupling-out gratings for delivering different colors (e.g., red, green and blue). The corresponding third gratings can be stacked or tiled on the surface of the waveguide 1000, and the details thereof are not repeated here. It can be in the same manner as Fig.11A The number of the third coupling-in grating and the third coupling-out grating is determined in the same manner as the number of coupling-in sub-gratings and coupling-out sub-gratings included in the waveguide stack 1100 in FIG. 1 , and the details are not repeated here. The operation scheme of the switchable third coupling-in and coupling-out grating pair in the waveguide 1000 can be similar to Fig.11A The operating scheme of the switchable coupling-in and coupling-out sub-grating pairs in the waveguide stack 1100 is described without repeating the details here.

[0134] In the above discussion, in order to sequentially transmit full-color image light corresponding to a predetermined portion of the FOV in a time-division multiplexed manner, each coupling grating may include three switchable coupling sub-gratings, and each coupling grating may include three switchable coupling sub-gratings, which is for illustrative purposes and is not intended to limit the scope of the present disclosure. In some embodiments, in order to simultaneously multiplex colors and tile the FOV, each coupling grating (sub-grating) may include N coupling sub-gratings (tertiary gratings), and each coupling grating (sub-grating) may include N coupling sub-gratings (tertiary gratings), N is a positive integer and N ≥ 2. In some embodiments, N ≥ 3. That is, the coupling sub-grating (tertiary grating) and the corresponding coupling sub-grating (tertiary grating) may form a pair, and the disclosed waveguide or waveguide stack may include N pairs. During corresponding time periods, corresponding pairs of the N pairs may be sequentially configured to be in a diffraction state to transmit corresponding light fields of a plurality of light fields, and the remaining pairs of the N pairs may be configured to be in a non-diffraction state. The multiple light fields may correspond to different colors of a monochrome image, different portions of the FOV of a monochrome image, or different portions of the FOV of a full-color image.

[0135] Furthermore, the disclosed methods and disclosed waveguide display components for spatial multiplexing and / or time division multiplexing of different colors and / or different portions of the FOV may also be implemented by other switchable gratings, such as active LC-based geometric phase gratings, metasurface / LC gratings, etc., all of which are within the scope of the present disclosure.

[0136] The foregoing description of the embodiments of the present disclosure has been presented for illustrative purposes. It is not intended to be exhaustive or to limit the present disclosure to the precise form disclosed. It will be appreciated by those skilled in the relevant art that many modifications and variations are possible based on the above disclosure.

[0137] Certain parts of this specification describe embodiments of the present disclosure in terms of algorithms and symbolic representations of operations on information. Technicians in the field of data processing typically use these algorithmic descriptions and representations to effectively convey the essence of their work to other technicians in the field. Although these operations are described functionally, computationally, or logically, these operations are understood to be implemented by computer programs or equivalent circuits, microcodes, etc. In addition, without loss of generality, it sometimes proves to be convenient to refer to these operational arrangements as modules. The described operations and their associated modules can be implemented with software, firmware, hardware, or any combination thereof.

[0138] Any steps, operations or processes described herein may be performed or implemented using one or more hardware or software modules, either alone or in combination with other devices. In one embodiment, the software module is implemented using a computer program product that includes a computer-readable medium containing computer program code that can be executed by a computer processor to perform any or all of the steps, operations or processes described.

[0139] Embodiments of the present disclosure may also relate to an apparatus for performing the operations herein. The apparatus may be specially constructed for the desired purpose, and / or it may include a general-purpose computing device selectively activated or reconfigured by a computer program stored in a computer. Such a computer program may be stored in a non-transient, tangible computer-readable storage medium or any type of medium suitable for storing electronic instructions, which may be coupled to a computer system bus. In addition, any computing system mentioned in this specification may include a single processor, or may be an architecture that employs a plurality of processor designs to increase computing power.

[0140] Embodiments of the present disclosure may also relate to products produced by the computing processes described herein. Such products may include information produced by the computing processes, wherein the information is stored on a non-transitory tangible computer-readable storage medium, and may include any embodiment of a computer program product or other data combination described herein.

[0141] Finally, the language used in the specification is selected primarily for readability and instructional purposes, and may not be selected to describe or limit the subject matter of the present invention. Therefore, the scope of the present invention is not intended to be limited by this detailed description, but is intended to be defined by any claims of the present application based thereon. Therefore, the disclosure of the embodiments is intended to illustrate, but not to limit, the scope of the disclosure set forth in the appended claims.

Claims

1. An optical device, comprising: a light source assembly configured to generate image light; as well as a waveguide comprising an incoupling element and an outcoupling element, wherein the incoupling element and the outcoupling element are configured to transmit a plurality of light fields of the image light to an eye box of the optical device via the waveguide in a time-division multiplexed manner, wherein at least one of the coupling-in element or the coupling-out element comprises N switchable diffraction gratings, N is a positive integer and N≧2, wherein the switchable diffraction gratings partially overlap each other at the same surface of the waveguide, and wherein each switchable diffractive optical element comprises: a surface relief grating (SRG) filled with a switchable optical anisotropic material having a first principal refractive index along a groove direction of the SRG and a second principal refractive index along an in-plane direction perpendicular to the groove direction, one of the first principal refractive index and the second principal refractive index substantially matching the refractive index of the SRG and the other mismatching the refractive index of the SRG; and in: During corresponding time periods, the N switchable diffraction gratings are sequentially configured to be in a diffraction state to transmit corresponding light fields of the plurality of light fields, and During a time period, one of the N switchable diffraction gratings is configured to be in the diffraction state to transmit a light field of the plurality of light fields, and the remaining switchable diffraction gratings are configured to be in a non-diffraction state.

2. The optical device of claim 1, wherein the light field corresponds to one or more selected from the group consisting of: i. a predetermined portion of the field of view (FOV) of a monochrome image; ii. a predetermined portion of the field of view (FOV) of the full-color image; iii. Monochrome images of predetermined colors.

3. An optical device according to claim 1 or 2, wherein the switchable optically anisotropic material comprises active liquid crystal (LC).

4. An optical device according to claim 1 or 2, wherein the at least one switchable diffractive optical element is switchable between a diffractive state and a non-diffractive state via an external electric field applied to the at least one switchable diffractive optical element.

5. The optical device according to any one of claims 1 to 2, wherein the SRG is one of a tilted grating and a non-tilted grating.

6. The optical device according to any one of claims 1 to 2, wherein the at least one switchable diffractive optical element is a one-dimensional diffraction grating.

7. An optical device according to any one of claims 1 to 2, wherein: The N switchable diffraction gratings are arranged in a stack.

8. An optical device according to any one of claims 1 to 2, wherein: The waveguide comprises M waveguides arranged in a stack, M is a positive integer and M≥2, each of the M waveguides comprises the at least one switchable diffractive optical element, During corresponding time periods, the at least one switchable diffractive optical element included in the corresponding waveguide is sequentially configured to be in a diffractive state to transmit a corresponding light field of the plurality of light fields, and During a time period, the at least one switchable diffractive optical element included in one waveguide of the M waveguides is configured to be in the diffraction state to transmit the light field of the multiple light fields, and the at least one switchable diffractive optical element included in the remaining waveguides is configured to be in the non-diffraction state.

9. An optical device according to claim 8, wherein: The at least one switchable diffractive optical element included in the corresponding waveguide includes N switchable diffraction gratings, N is a positive integer and N≥2.

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