Device comprising a diffractive optical element

Abstract

An apparatus includes a waveguide, an in-coupling element, and an out-coupling element coupled with the waveguide. The waveguide, the in-coupling element, and the out-coupling element are configured to transport a plurality of portions of image light toward an eyebox of the apparatus. At least one of the in-coupling element or the out-coupling element includes a polarization-selective diffractive element. The polarization-selective diffractive element includes a grating including a plurality of microstructures defining a plurality of grooves filled with a passive optically anisotropic material having a first effective refractive index along a groove direction of the grooves and a second effective refractive index along an in-plane direction perpendicular to the groove direction. One of the first effective refractive index or the second effective refractive index substantially matches a refractive index of the microstructures.

Description

TECHNICAL FIELD

[0001] The present invention relates generally to optical devices, and more particularly to a device comprising a diffractive optical element. BACKGROUND

[0002] Near-eye displays (NEDs) have been widely implemented in various applications such as video playing applications, gaming applications, and sports applications. NEDs have been used to present information to users through virtual reality (VR) technology, augmented reality (AR) technology, or mixed reality (MR) technology. AR headsets or MR headsets display virtual images overlaid or superimposed with real-world images or see-through images. Pupil expansion waveguide display systems with diffractive coupling structures are promising designs for AR / MR displays, which can potentially provide a sunglass / glasses form factor, a moderate large field of view (FOV), high transmittance, and a large eyebox. Waveguide display systems include a micro-display, a collimator, and a waveguide optic (e.g., a waveguide combiner). The waveguide combiner integrates in-coupling elements and out-coupling elements, which can be diffractive gratings. Various diffractive gratings can be integrated into the waveguide combiner, such as surface-relief gratings obtained by nano-fabrication or various types of holographic gratings. SUMMARY

[0003] According to an aspect of the present disclosure, there is provided a device comprising a waveguide and in-coupling elements and out-coupling elements coupled with the waveguide; wherein the waveguide, the in-coupling elements, and the out-coupling elements are configured to deliver a plurality of portions of image light towards an eye-box of the device; wherein at least one of the in-coupling elements or the out-coupling elements comprises a polarization-selective diffractive element comprising: a grating comprising a plurality of microstructures defining a plurality of grooves filled with a passive optically anisotropic material having a first effective refractive index along a groove direction of the grooves and a second effective refractive index along an in-plane direction perpendicular to the groove direction, wherein one of the first effective refractive index or the second effective refractive index substantially matches a refractive index of the microstructures.

[0004] In some embodiments, the other one of the first effective refractive index or the second effective refractive index does not match the refractive index of the microstructures.

[0005] In some embodiments, the portion of the image light corresponds to a predetermined portion of a field of view of a single color image or a predetermined portion of a field of view of multiple color images.

[0006] In some embodiments, the portion of the image light corresponds to a single color image of a predetermined color.

[0007] In some embodiments, the passive optically anisotropic material comprises an optically anisotropic polymer.

[0008] In some embodiments, the polarization-selective diffractive element is indirectly switchable between a diffractive state and a non-diffractive state via an external polarization switch coupled to the polarization-selective diffractive element.

[0009] In some embodiments, the grating is a slanted grating or a non-slanted grating.

[0010] In some embodiments, the polarization-selective diffractive element comprises a plurality of gratings, the plurality of gratings being sequentially configured to operate in a diffractive state to deliver a respective one of the plurality of portions of the image light over a plurality of time periods, and at least one of the plurality of gratings being configured to operate in a diffractive state to deliver one of the plurality of portions of the image light and one or more remaining gratings being configured to operate in a non-diffractive state over a time period of the plurality of time periods.

[0011] In some embodiments, the plurality of gratings are arranged to at least partially overlap each other.

[0012] In some embodiments, the plurality of gratings are arranged in a stacked configuration.

[0013] In some embodiments, the polarization-selective diffractive element comprises a plurality of gratings, the plurality of gratings being configured to operate in a diffractive state to deliver a respective one of the plurality of portions of the image light over a same time period; and at least one of an angular spectrum or a wavelength spectrum of the gratings is substantially non-overlapping.

[0014] In some embodiments, the apparatus further comprises a plurality of waveguides arranged in a stacked configuration and a plurality of the polarization-selective diffraction elements coupled to the plurality of waveguides; wherein, in a plurality of time periods, the plurality of polarization-selective diffraction elements are sequentially configured to operate in a diffractive state to deliver respective ones of the plurality of portions of the image light; wherein, in one of the plurality of time periods, the polarization-selective diffraction element coupled to one of the plurality of waveguides is configured to operate in a diffractive state to deliver one of the plurality of portions of the image light, and one or more of the polarization-selective diffraction elements coupled to one or more remaining waveguides is configured to operate in a non-diffractive state.

[0015] In some embodiments, the apparatus further comprises a plurality of waveguides arranged in a stacked configuration and a plurality of the polarization-selective diffraction elements coupled to the plurality of waveguides; wherein, in a plurality of time periods, the plurality of polarization-selective diffraction elements are sequentially configured to operate in a diffractive state to deliver respective ones of the plurality of portions of the image light; wherein, in one of the plurality of time periods, the polarization-selective diffraction element coupled to one of the plurality of waveguides is configured to operate in a diffractive state to deliver one of the plurality of portions of the image light, and one or more of the polarization-selective diffraction elements coupled to one or more remaining waveguides is configured to operate in a non-diffractive state.

[0016] According to another aspect of the present disclosure, a method is provided, the method comprising: configuring at least one of a first polarization-selective in-coupling element or a first polarization-selective out-coupling element coupled to a first waveguide of an apparatus to operate in a diffractive state; directing, by the first polarization-selective in-coupling element, the first waveguide, and the first polarization-selective out-coupling element, a first portion of image light toward an eyebox of the apparatus; configuring at least one of a second polarization-selective in-coupling element or a second polarization-selective out-coupling element coupled to a second waveguide to operate in a diffractive state; and directing, by the second polarization-selective in-coupling element, the second waveguide, and the second polarization-selective out-coupling element, a second portion of the image light toward the eyebox.

[0017] In some embodiments, the first portion of the image light and the second portion of the image light are delivered to the eyebox in a same time period or in different time periods.

[0018] In some embodiments, configuring the at least one of the first polarization-selective in-coupling element or the first polarization-selective out-coupling element to operate in a diffractive state comprises: controlling an operating state of a polarization switch coupled to the at least one of the first polarization-selective in-coupling element or the first polarization-selective out-coupling element.

[0019] In some embodiments, the first portion of the image light corresponds to a first portion of a field of view (“FOV”) of a single color image, a first portion of a field of view of a plurality of color images, or a single color image of a first color; and the second portion of the image light corresponds to a second portion of the field of view (“FOV”) of the single color image, a second portion of the field of view of the plurality of color images, or the single color image of a second color different from the first color.

[0020] In some embodiments, the first waveguide and the second waveguide are a same common waveguide, the first polarization selective in-coupling element and the second polarization selective in-coupling element are configured to at least partially overlap, the first polarization selective out-coupling element and the second polarization selective out-coupling element are configured to at least partially overlap.

[0021] In some embodiments, the first waveguide and the second waveguide are separate waveguides, the first polarization selective in-coupling element and the first polarization selective out-coupling element are coupled to the first waveguide, the second polarization selective in-coupling element and the second polarization selective out-coupling element are coupled to the second waveguide.

[0022] In some embodiments, the method further comprises configuring at least one of a third polarization selective in-coupling element or a third polarization selective out-coupling element coupled to a third waveguide to operate in a diffractive state; and directing, by the third polarization selective in-coupling element, the third waveguide, and the third polarization selective out-coupling element, a third portion of the image light toward the eyebox.

[0023] It will be understood that any of the features described herein which are suitable for incorporation into one or more aspects or embodiments of the present disclosure are intended to be generic throughout the aspects and embodiments of the present disclosure. Other aspects of the present disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the present disclosure. The foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the claims.

[0024] One aspect of the present disclosure provides an apparatus. The apparatus includes a waveguide, an in-coupling element, and an out-coupling element coupled to the waveguide. The waveguide, the in-coupling element, and the out-coupling element are configured to transport a plurality of portions of image light toward an eyebox of the apparatus. At least one of the in-coupling element or the out-coupling element includes a polarization selective diffractive element. The polarization selective diffractive element includes a grating including a plurality of microstructures defining a plurality of grooves filled with a passive optically anisotropic material having a first effective refractive index along a groove direction of the grooves and a second effective refractive index along an in-plane direction perpendicular to the groove direction. One of the first effective refractive index or the second effective refractive index substantially matches a refractive index of the microstructures.

[0025] Another aspect of the disclosure provides a method. The method includes configuring at least one of a first polarization selective in-coupling element or a first polarization selective out-coupling element coupled to a first waveguide of a device to operate in a diffractive state. The method also includes directing a first portion of image light toward an eyebox of the device through the first polarization selective in-coupling element, the first waveguide, and the first polarization selective out-coupling element. The method also includes configuring at least one of a second polarization selective in-coupling element or a second polarization selective out-coupling element coupled to a second waveguide to operate in a diffractive state. The method also includes directing a second portion of the image light toward the eyebox through the second polarization selective in-coupling element, the second waveguide, and the second polarization selective out-coupling element.

[0026] Other aspects of the disclosure will be appreciated by those of skill in the art from consideration of the description, claims, and accompanying drawings of the disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0027] According to various disclosed embodiments, the following drawings are provided for illustrative purposes and are not intended to limit the scope of the disclosure. In the drawings:

[0028] FIG. 1A A schematic diagram of a near-eye display (“NED”) according to an embodiment of the disclosure is shown;

[0029] FIG. 1B A schematic diagram of a waveguide display assembly according to an embodiment of the disclosure is shown; FIG. 1A A cross-sectional view of half of the NED shown in FIG. 1 is shown;

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

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

[0032] FIG. 3A A schematic diagram of a passive grating in a non-diffractive state according to an embodiment of the disclosure is shown;

[0033] FIG. 3B A schematic diagram of a passive grating in a diffractive state according to an embodiment of the disclosure is shown; FIG. 3A A schematic diagram of the passive grating shown in FIG. 2 in a diffractive state is shown;

[0034] FIG. 4A A schematic diagram of a passive grating in a diffractive state according to another embodiment of the disclosure is shown;

[0035] FIG. 4B A schematic diagram of a waveguide display assembly according to another embodiment of the disclosure is shown; FIG. 4Aschematic diagram of a passive grating in a diffractive state as shown in FIG. 1 1 ;

[0036] FIG. 5A schematic diagram of a passive grating in a diffractive state as shown in FIG. 1 1 ;

[0037] FIG. 5B schematic diagram of a passive grating in a diffractive state as shown in FIG. 1 1 ; FIG. 5A schematic diagram of a passive grating in a diffractive state as shown in FIG. 1 1 ;

[0038] FIG. 5C schematic diagram of a passive grating in a diffractive state as shown in FIG. 1 1 ;

[0039] FIG. 5D schematic diagram of a passive grating in a diffractive state as shown in FIG. 1 1 ; FIG. 5C schematic diagram of a passive grating in a diffractive state as shown in FIG. 1 1 ;

[0040] FIG. 6A schematic diagram of a passive grating in a diffractive state as shown in FIG. 1 1 ;

[0041] FIG. 6B schematic diagram of a passive grating in a diffractive state as shown in FIG. 1 1 ;

[0042] FIG. 6C schematic diagram of a passive grating in a diffractive state as shown in FIG. 1 1 ;

[0043] FIG. 6D schematic diagram of a passive grating in a diffractive state as shown in FIG. 1 1 ;

[0044] FIG. 7 schematic diagram of a passive grating in a diffractive state as shown in FIG. 1 1 ;

[0045] FIG. 8A to FIG. 8B schematic diagram of a passive grating in a diffractive state as shown in FIG. 1 1 ;

[0046] FIG. 9A to FIG. 9D schematic diagram of a passive grating in a diffractive state as shown in FIG. 1 1 ;

[0047] FIG. 10A to FIG. 10C schematic diagram of a passive grating in a diffractive state as shown in FIG. 1 1 ;

[0048] FIG. 11A to FIG. 11BAn optical system including a waveguide configured to transport different portions of a field of view ("FOV") in a time-multiplexing manner is shown in accordance with an embodiment of the present disclosure;

[0049] FIG. 12A to FIG. 12C An optical system including a waveguide configured to transport different portions of a FOV in a time-multiplexing manner is shown in accordance with another embodiment of the present disclosure;

[0050] FIG. 12D An optical system including a waveguide configured to transport different portions of a FOV in a time-multiplexing manner is shown in accordance with an embodiment of the present disclosure; FIG. 12A A schematic diagram of an overlapping configuration of in-coupling sub-gratings of a waveguide shown in

[0051] FIG. 12E An optical system including a waveguide configured to transport different portions of a FOV in a time-multiplexing manner is shown in accordance with another embodiment of the present disclosure; FIG. 12A A schematic diagram of an overlapping configuration of in-coupling sub-gratings of a waveguide shown in

[0052] FIG. 13A to FIG. 13B An optical system including a waveguide stack configured to transport different portions of a FOV in a time-multiplexing manner is shown in accordance with an embodiment of the present disclosure;

[0053] FIG. 14A to FIG. 14B An optical system including a waveguide configured to transport different portions of a FOV in a time-multiplexing manner is shown in accordance with another embodiment of the present disclosure;

[0054] FIG. 15A to FIG. 15C An optical system including a waveguide stack configured to transport different portions of a FOV in a time-multiplexing manner is shown in accordance with another embodiment of the present disclosure;

[0055] FIG. 16A to FIG. 16C An optical system including a waveguide configured to transport different portions of a FOV in a time-multiplexing manner is shown in accordance with another embodiment of the present disclosure;

[0056] FIG. 17A A schematic diagram of an optical system including a waveguide stack configured to transport single color images of different colors in accordance with an embodiment of the present disclosure;

[0057] FIG. 17B to FIG. 17D An optical system including a waveguide stack configured to transport single color images of different colors in a time-multiplexing manner is shown in accordance with an embodiment of the present disclosure; FIG. 17A A schematic diagram of an optical system including a waveguide stack configured to transport single color images of different colors in accordance with an embodiment of the present disclosure;

[0058] FIG. 18A flow diagram according to an embodiment of the disclosure is shown, which illustrates a method of guiding a plurality of portions of image light in a time-division multiplexed manner; and

[0059] FIG. 19 A flow diagram according to an embodiment of the disclosure is shown, which illustrates a method of guiding a plurality of portions of image light. DETAILED DESCRIPTION

[0060] Embodiments consistent with the present disclosure will be described with reference to the accompanying drawings, which are for illustration purposes only and are not intended to limit the scope of the present disclosure. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts, and detailed descriptions of these parts can be omitted.

[0061] Further, in the present disclosure, the disclosed embodiments and features of the disclosed embodiments can be combined. The described embodiments are some, but not all, of the many embodiments of the present disclosure. Other embodiments consistent with the present disclosure can be derived from the disclosed embodiments by those skilled in the art based on the present disclosure. For example, modifications, adaptations, permutations, additions, or other variations can be made based on the disclosed embodiments. Such variations are still within the scope of the present disclosure. Accordingly, the present disclosure is not limited to the disclosed embodiments. Rather, the scope of the present disclosure is defined by the appended claims.

[0062] As used herein, the terms "coupled," "coupled to," "coupled with," and like terms can include optical coupling, mechanical coupling, electrical coupling, electromagnetic coupling, or combinations thereof. "Optical coupling" between two optical elements means that the two optical elements are arranged in optical series, and light output from one optical element can be received directly or indirectly by the other optical element. Optical series means the optical positioning of multiple optical elements in a light path such that light output from one optical element can be transmitted, reflected, diffracted, converted, modified, or otherwise processed or manipulated by one or more of the other optical elements. In some embodiments, the order of arrangement of the multiple optical elements can not affect the overall output of the multiple optical elements. Coupling can be direct coupling or indirect coupling (e.g., coupling through intermediate elements).

[0063] The phrase "at least one of A or B" can include all combinations of A and B, for example, only A, only B, or A and B. Likewise, the phrase "at least one of A, B, or C" can include all combinations of A, B, and C, for example only A, only B, only C, A and B, A and C, B and C, or A and B and C. The phrase "A and / or B" can be interpreted to include all combinations of A and B, in a manner similar to the phrase "at least one of A or B." For example, the phrase "A and / or B" can include A and B, for example, only A, only B, or A and B. Likewise, the phrase "A, B, and / or C" has a similar meaning to the phrase "at least one of A, B, or C." For example, the phrase "A, B, and / or C" can include all combinations of A, B, and C, for example only A, only B, only C, A and B, A and C, B and C, or A and B and C.

[0064] When a first element is described as "attached," "provided," "formed," "affixed," "mounted," "fixed," "connected," "joined," "recorded," or "disposed" to a second element, on the second element, at the second element, or at least partially in the second element, the first element can be "attached," "provided," "formed," "affixed," "mounted," "fixed," "connected," "joined," "recorded," or "disposed" to the second element, on the second element, at the second element, or at least partially in the second element using any suitable mechanical or non-mechanical means (e.g., deposition, coating, etching, bonding, gluing, screwing, press-fitting, snap-fitting, clamping, etc.). Moreover, the first element can be in direct contact with the second element, or an intervening element can be present between the first element and the second element. The first element can be disposed on any suitable side of the second element, for example, a left side, a right side, a front side, a back side, a top side, or a bottom side.

[0065] When a first element is shown or described as being positioned or disposed “on” a second element, the term “on” is used merely to indicate an example relative orientation between the first element and the second element. The description can be based on a reference coordinate system shown in the figure, or can be based on a current view or example configuration shown in the figure. For example, a first element can be described as being disposed “on” a second element when describing a view shown in a figure. It will be understood that the term “on” does not necessarily imply that the first element is positioned vertically, in a gravitational direction, above the second element. For example, when an assembly having the first element and the second element is turned 180°, the first element can be positioned “under” the second element (or, the second element can be positioned “on” the first element). Thus, it will be understood that when a figure shows a first element positioned “on” a second element, this configuration is merely an illustrative example. The first element can be disposed or arranged in any suitable orientation relative to the second element (e.g., above or over the second element, below or under the second element, to the left of the second element, to the right of the second element, behind the second element, in front of the second element, etc.).

[0066] In the present disclosure, when a grating structure is described as being disposed (e.g., formed, deposited, coated, etched, recorded, or otherwise disposed) “on” or “at least partially in” a structure, device, or material (e.g., a substrate structure), the term “on” or the phrase “at least partially in” should be broadly interpreted to include various configurations, such as a configuration in which the grating structure is formed on a surface of the structure, device, or material, a configuration in which the grating structure is at least partially formed in or inside the structure, device, or material, a configuration in which the grating structure is recorded, coated, deposited, etched, or printed (or otherwise disposed) on or in the structure, device, or material. In other words, the term “on” or the phrase “at least partially in” can not strictly limit the positional relationship between the grating structure and the structure, device, or material. When a grating structure is referred to as being formed or disposed “at” a structure, device, or material, the term “at” should be broadly interpreted to include various configurations in which the grating structure is “at least partially” formed or disposed “in” or “on” the structure, device, or material, as well as other suitable configurations between the grating structure and the substrate structure, device, or material.

[0067] The wavelength ranges, spectra, or bands mentioned in the present disclosure are for illustrative purposes. The disclosed optical devices, systems, elements, assemblies, and methods can be applied to visible light wavelength ranges, as well as other wavelength ranges, such as ultraviolet (“UV”) wavelength ranges, infrared wavelength ranges, or combinations thereof.

[0068] The term “communicatively coupled” or “communicatively connected” means that the related items are coupled or connected through a communication channel (e.g., a wired or wireless communication channel).

[0069] The linear polarizer selectively transmits first linearly polarized light vibrating in any one direction and selectively blocks second linearly polarized light vibrating in a direction perpendicular to the vibrating direction of the first linearly polarized light. For example, the linear polarizer can be a reflective polarizer (e.g., a dual brightness enhancement film, a lyotropic liquid crystal layer, a wire grid polarizer, a prismatic polarizer, etc.), an absorptive polarizer (e.g., a dichroic polarizer). The linear polarizer can have a light transmission axis and a light absorption axis orthogonal to the light transmission axis in a planar direction. In some embodiments, the polarization efficiency of the linear polarizer can be less than 50%. In some embodiments, the polarization efficiency of the linear polarizer is greater than about 50%, e.g., 60%, 70%, 80%, 90%, or 95%, etc.

[0070] An apparatus, such as an optical apparatus, is provided. The optical apparatus can include a light source assembly configured to generate image light representing a virtual image or a display image. The optical apparatus can also include at least one waveguide configured to direct the image light toward an eyebox of the optical apparatus. The waveguide can be coupled with an in-coupling element and an out-coupling element. The combination of the waveguide, the in-coupling element, and the out-coupling element is configured to transmit multiple portions of the image light toward the eyebox substantially simultaneously within a same time period (e.g., within a same image frame (without dividing into sub-frames)) or in a time-division multiplexed manner (e.g., in sequential image frames or sub-frames). A portion of the image light can correspond to or represent a predetermined portion of a field of view (“FOV”) of a single color image, a predetermined portion of a FOV of a multi-color image (e.g., a panchromatic image), or a single color image of a predetermined color. The term “panchromatic” or “color” refers to a full predetermined range of colors visible to the human eye. For example, panchromatic can include a range of colors that can be generated based on a plurality of primary colors. For example, in some embodiments, the plurality of primary colors can include red, green, and blue. In some embodiments, the plurality of primary colors can include one or more colors in addition to red, green, and blue. A panchromatic image (or image light) can refer to an image (or image light) that substantially includes a full range of colors that can be generated based on primary colors.

[0071] The at least one of the in-coupling element or the out-coupling element can include at least one passive diffractive optical element. The passive diffractive optical element can be polarization dependent or have polarization selectivity. The passive diffractive optical element can selectively diffract incident light having a predetermined polarization and can selectively transmit incident light having a polarization different from (e.g., orthogonal to) the predetermined polarization in a non-diffractive or negligibly diffractive manner. For example, the passive diffractive optical element can operate in a diffractive state to diffract incident light having the predetermined polarization and can operate in a non-diffractive state to transmit incident light having a polarization different from (e.g., orthogonal to) the predetermined polarization in a non-diffractive or negligibly diffractive manner. The passive diffractive optical element can be indirectly switchable between the diffractive state and the non-diffractive state. The term “indirectly switchable” means that the passive diffractive optical element cannot be directly switched between the diffractive state and the non-diffractive state by an external field (e.g., an external electric field applied across the passive diffractive optical element). The passive diffractive optical element can be indirectly switchable between the diffractive state and the non-diffractive state by coupling an external polarization switch or a polarization rotator to the passive diffractive optical element. The polarization of the incident light can be changed or maintained via the external polarization rotator or the polarization switch before the incident light is incident on the passive diffractive optical element. Thus, the external polarization rotator or the polarization switch can control the polarization of the incident light to the passive diffractive optical element, thereby indirectly switching the passive diffractive optical element between the diffractive state and the non-diffractive state.

[0072] In some embodiments, the passive diffractive optical element can be a microstructured (e.g., a structure having a micrometer or nanometer scale dimension) grating, for example, a Surface Relief Grating (“SRG”). The SRG can include a plurality of microstructures (e.g., protrusions) that define a plurality of grooves. The grooves can be at least partially filled with a passive (or non-reorientable) optically anisotropic material. The molecular orientation of the passive (or non-reorientable) optically anisotropic material can not be reorientable by an external field (e.g., an electric field).

[0073] The optically anisotropic material can have a first effective refractive index along a groove direction of the grooves of the microstructured grating (e.g., SRG) and a second effective refractive index along an in-plane direction perpendicular to the groove direction. For example, the groove direction can be a groove length direction. The “in-plane” direction perpendicular to the groove length direction can be a direction along a bottom surface of the groove and perpendicular to the groove length direction. In some embodiments, the in-plane direction perpendicular to the groove length direction can be referred to as an in-plane direction of the periodic microstructures or grooves included in the microstructured grating. In some embodiments, the first effective refractive index can be equal to a first principal refractive index of the optically anisotropic material. In some embodiments, the first effective refractive index can be equal to a component of the first principal refractive index in the groove direction. In some embodiments, the second effective refractive index can be equal to a second principal refractive index of the optically anisotropic material. In some embodiments, the second effective refractive index can be equal to a component of the second principal refractive index in the in-plane direction perpendicular to the groove direction. In some embodiments, the first effective refractive index and the second effective refractive index can be equal to the first principal refractive index and the second principal refractive index, respectively, of the optically anisotropic material. In some embodiments, one of the first effective refractive index and the second effective refractive index can be equal to one of the first principal refractive index and the second principal refractive index of the optically anisotropic material, and the other of the first effective refractive index and the second effective refractive index can not be equal to the first principal refractive index or the second principal refractive index of the optically anisotropic material.

[0074] In some embodiments, one of the first effective refractive index or the second effective refractive index can substantially match a refractive index of the microstructured grating (e.g., SRG), and the other of the first effective refractive index or the second effective refractive index can not match the refractive index of the microstructured grating (e.g., SRG). The refractive index of the microstructured grating (e.g., SRG) can be equal to a refractive index of the microstructures. The optically anisotropic material can include a passive liquid crystal (Liquid Crystal, “LC”). In some embodiments, the optically anisotropic material can include an optically anisotropic polymer polymerized from a polymerizable pre-polymer composition or a polymerizable liquid crystal (“LC”) precursor. In some embodiments, the polymerizable LC precursor can include a reactive mesogen (Reactive Mesogen, “RM”), which is a polymerizable molecule having optical properties similar to those of LC materials. In some embodiments, the optical device can be a component of a near-eye display (Near-eye Display, “NED”).

[0075] The optically anisotropic material can be a uniaxial anisotropic material having an index ellipsoid with axial symmetry with respect to its optical axis, where n o ANand n eANis the ordinary refractive index of the uniaxial anisotropic material. For example, reactive mesogens (“RMs”) belong to the class of uniaxial anisotropic materials. In some embodiments, depending on the angle a between the optical polarization direction of the optically anisotropic material and the optical axis, the refractive index experienced by light propagating in the polymerized RM layer can be able to vary in the range between the ordinary light refractive index n o ANand the extraordinary light refractive index n e AN. For example, when the angle a varies from 90° to 0°, the refractive index experienced by light propagating in the polymerized RM layer can vary from n o ANto n e AN.

[0076] In some embodiments, the passive diffractive optical element can have linear polarization selectivity. For example, the passive diffractive optical element can selectively diffract linearly polarized light having a first polarization and transmit linearly polarized light having a second polarization with negligible or no diffraction. The first polarization and the second polarization can be orthogonal polarizations. Two polarizations are orthogonal when the inner product of two vectors representing the two polarizations is substantially zero. In some embodiments, the diffraction efficiency of the polarized light having the second polarization can be lower than or equal to 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 or the second principal refractive index can be the same as (or can be matched with) the refractive index of the microstructured grating (e.g., SRG). Thus, the passive diffractive optical element can transmit the polarized light having the second polarization with negligible or no diffraction. In some embodiments, the passive diffractive optical element can have circular polarization selectivity or have elliptical polarization selectivity. For example, the passive diffractive optical element can selectively diffract circularly or elliptically polarized light having a first handedness and transmit circularly or elliptically polarized light having a second handedness with negligible or no diffraction. The first handedness and the second handedness can be opposite to each other (e.g., left-handed and right-handed).

[0077] FIG. 1AA schematic diagram of a near-eye display (“NED”) 100 according to an embodiment of the present disclosure is shown. The NED 100 can present media content to a user, such as one or more images, videos, audio, or combinations thereof. In some embodiments, audio can be presented to the user via an external device (e.g., a speaker and / or headphones) that can receive audio information from the NED 100 and / or a console (not shown) and present audio data based on that audio information. The NED 100 can operate as a VR device, an AR device, and / or a MR device, or a combination thereof. In some embodiments, when the NED 100 operates as an AR device and / or a MR device, a portion of the NED 100 can be at least partially transparent, and internal components of the NED 100 can be at least partially visible.

[0078] like FIG. 1A As shown, NED 100 may include a frame 110, a right display system 120R, and a left display system 120L. In some embodiments, FIG. 1A Some of the devices shown may be omitted. In some embodiments, NED 100 may also include FIG. 1A Additional devices or components not shown. Frame 110 may include a suitable type of mounting structure configured to wear the right display system 120R and left display system 120L onto a body part (e.g., head) of a user (e.g., adjacent to the user's eyes). Frame 110 may be coupled to one or more optical elements configured to display media to the user. In some embodiments, frame 110 may represent the frame of eyeglasses. The right display system 120R and left display system 120L may be configured to allow the user to view content presented by NED 100 and / or view images of real-world objects (e.g., the right display system 120R and left display system 120L may each include perspective optics). In some embodiments, the right display system 120R and left display system 120L may include any suitable display component (not shown) configured to generate light (e.g., image light corresponding to a virtual image) and direct the image light toward the user's eyes. In some embodiments, NED 100 may include a projection system. For illustrative purposes, FIG. 1A The projection system is shown to include a projector 135 coupled to a frame 110.

[0079] FIG. 1B According to embodiments of this disclosure FIG. 1A The cross-section 150 of the NED 100 is shown in the image. For illustrative purposes, FIG. 1B A cross-section 150 associated with the left display system 120L is shown. (As shown) FIG. 1BAs shown, left display system 120L can include a waveguide display assembly 115 for eye 160 of the user. Waveguide display assembly 115 can include a waveguide or a stack of waveguides. Exit pupil 165 can be the location where eye 160 is positioned in the eyebox region when the user wears NED 100. For purposes of illustration, FIG. 1B A cross-section 150 associated with a single eye 160 and a single waveguide display assembly 115 is shown. In some embodiments, a waveguide display assembly 115 can be associated with each eye 160 of the user. FIG. 1B Another waveguide display assembly, separate and similar to the waveguide display assembly 115 shown in FIG. 1, can provide image light to an eyebox located at an exit pupil of the other eye of the user.

[0080] Waveguide display assembly 115 can include one or more materials (e.g., plastic, glass, etc.) having one or more indices of refraction. Waveguide display assembly 115 can be effective to minimize weight and to widen a field of view ("FOV") of NED 100. In some embodiments, waveguide display assembly 115 can be a component of NED 100. In some embodiments, waveguide display assembly 115 can be a component of some other NED or other system that directs image light to a particular location. As FIG. 1B As shown, a waveguide display assembly 115 can be provided for one eye 160 of the user. The waveguide display assembly 115 for one eye can be separate or partially separate from the waveguide display assembly for the other eye. In certain embodiments, a single waveguide display assembly 115 can be used for both eyes 160 of the user.

[0081] In some embodiments, NED 100 may include one or more optical elements disposed between waveguide display assembly 115 and eye 160. These optical elements may be configured to, for example, correct aberrations in image light emitted from waveguide display assembly 115, amplify image light emitted from waveguide display assembly 115, or perform another type of optical adjustment of image light emitted from waveguide display assembly 115. Examples of the one or more optical elements may include apertures, Fresnel lenses, convex lenses, concave lenses, filters, any other suitable optical elements affecting image light, or combinations thereof. In some embodiments, waveguide display assembly 115 may include a stack of multiple waveguide displays. In some embodiments, the stacked multiple waveguide displays may include a multicolor display (e.g., a red-green-blue, "RGB") formed by stacking multiple waveguide displays, wherein the respective monochromatic light sources of these waveguide displays are configured to emit light of different colors. For example, the stacked multiple waveguide displays may include a multicolor display (e.g., a multifocal color display) configured to project onto multiple planes. In some embodiments, the stacked waveguide displays may include monochrome displays (e.g., multifocal monochrome displays) configured to project onto multiple planes. In some embodiments, the NED 100 may include an adaptive dimming element 130 that dynamically adjusts the transmittance of real-world objects viewed through the NED 100, thereby allowing the NED 100 to switch between VR and AR devices or between VR and MR devices. In some embodiments, the adaptive dimming element 130 may be used in AR and / or MR devices to mitigate brightness differences between real and virtual objects as switching between AR / MR and VR devices.

[0082] FIG. 2A A 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 in a NED for VR applications, AR applications, and / or MR applications. FIG. 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 a dimming system 225. In some embodiments, the light source 220 may be a light source configured to generate coherent light or partially coherent light.

[0083] In some embodiments, the light source 220 can include, for example, a laser diode, a vertical-cavity surface-emitting laser, a light-emitting diode, or a combination thereof. In some embodiments, the light source 220 can 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 laser display panel, a Micro-electro-mechanical System (“MEMS”) display panel, a Digital Light Processing (“DLP”) display panel, or a combination thereof. In some embodiments, the light source 220 can be a self-emissive panel, such as an OLED display panel or a micro-LED display panel. In some embodiments, the light source 220 can be an externally-illuminated display panel (e.g., an LCD panel, an LCoS display panel, or a DLP display panel). Examples of external sources can include lasers, LEDs, OLEDs, or a combination thereof. The light modulation system 225 can include one or more optical components configured to modulate light from the light source 220. For example, the controller 215 can control the light modulation system 225 to modulate light from the light source 220, which can include, for example, passing through, attenuating, expanding, collimating, and / or adjusting the direction of the light.

[0084] The light source assembly 205 can generate image light 230 and output the image light 230 toward in-coupling elements 235 coupled with a first portion of the waveguide 210. The waveguide 210 can expand and direct the image light 230 toward an eye 265 of a user. The waveguide 210 can receive the image light 230 at one or more in-coupling elements 235 coupled with a first portion of the waveguide 210 and direct the received image light 230 (e.g., by Total Internal Reflection (“TIR”)) toward out-coupling elements 245 coupled with a second portion of the waveguide 210. The first portion and the second portion can be coupled with different portions of the waveguide 210. The out-coupling elements 245 can be configured to out-couple the image light 230 from the waveguide 210 toward the eye 265. In some embodiments, the in-coupling elements 235 can in-couple the image light 230 from the light source assembly 205 into a TIR path inside the waveguide 210. The waveguide 210 can include a first surface or side 210-1 facing a real-world environment and an opposing second surface or side 210-2 facing the eye 265. In some embodiments, as illustrated in FIG. 2A, the waveguide 210 can include a first portion 210-1A and a second portion 210-1B. The first portion 210-1A can be coupled with the in-coupling elements 235 and the second portion 210-1B can be coupled with the out-coupling elements 245.FIG. 2A As shown, the in-coupling element 235 can be disposed at the first surface 210-1 of the waveguide 210. In some embodiments, the in-coupling element 235 can be integrally formed as part of the waveguide 210 at the first surface 210-1. In some embodiments, the in-coupling element 235 can be separately formed and disposed at (e.g., fixed to) the first surface 210-1 of the waveguide 210. In some embodiments, the in-coupling element 235 can be disposed at the second surface 210-2 of the waveguide 210. In some embodiments, the in-coupling element 235 can be integrally formed as part of the waveguide 210 at the second surface 210-2. In some embodiments, the in-coupling element 235 can be separately formed and disposed at (e.g., fixed to) the second surface 210-2 of the waveguide 210. In some embodiments, the in-coupling element 235 can include a surface-relief grating, a volume hologram, a polarization grating, a polarization volume hologram, a metasurface grating, another type of diffractive element, or a combination thereof. In some embodiments, the in-coupling element 235 can include a diffractive grating. The pitch of the diffractive grating can be configured to enable total internal reflection (TIR) of the image light 230 within the waveguide 210. Thus, the image light 230 can propagate inside the waveguide 210 by TIR. The in-coupling element 235 can also be referred to as an in-coupling grating 235.

[0085] The out-coupling element 245 can be disposed at the first surface 210-1 or the second surface 210-2 of the waveguide 210. For example, as shown in FIG. 2A, the out-coupling element 245 can be disposed at the first surface 210-1 of the waveguide 210. In some embodiments, the out-coupling element 245 can be integrally formed as part of the waveguide 210 at the first surface 210-1. In some embodiments, the out-coupling element 245 can be separately formed and disposed at (e.g., fixed to) the first surface 210-1 of the waveguide 210. In some embodiments, the out-coupling element 245 can be disposed at the second surface 210-2 of the waveguide 210. In some embodiments, the out-coupling element 245 can be integrally formed as part of the waveguide 210 at the second surface 210-2. In some embodiments, the out-coupling element 245 can be separately formed and disposed at (e.g., fixed to) the second surface 210-2 of the waveguide 210. In some embodiments, the out-coupling element 245 can include a surface-relief grating, a volume hologram, a polarization grating, a polarization volume hologram, a metasurface grating, another type of diffractive element, or a combination thereof. In some embodiments, the out-coupling element 245 can include a diffractive grating. The pitch of the diffractive grating can be configured to enable TIR of the image light 230 within the waveguide 210. Thus, the image light 230 can propagate inside the waveguide 210 by TIR. The out-coupling element 245 can also be referred to as an out-coupling grating 245. FIG. 2AAs shown, the out-coupling element 245 can be disposed at the second surface 210-2 of the waveguide 210. In some embodiments, the out-coupling element 245 can be integrally formed as part of the waveguide 210, e.g., integrally formed as part of the second surface 210-2 of the waveguide 210. In some embodiments, the out-coupling element 245 can be separately formed and disposed at (e.g., fixed to) the second surface 210-2 of the waveguide 210. In some embodiments, the out-coupling element 245 can be disposed at the first surface 210-1 of the waveguide 210. For example, in some embodiments, the out-coupling element 245 can be integrally formed as part of the waveguide 210 at the first surface 210-1. In some embodiments, the out-coupling element 245 can be separately formed and disposed at (e.g., fixed to) the first surface 210-1 of the waveguide 210. In some embodiments, the out-coupling element 245 can include a surface-relief grating, a volume holographic element, a polarization grating, a polarization volume holographic element, a metasurface grating, another type of diffractive element, or a combination thereof. In some embodiments, the out-coupling element 245 can include a diffractive grating. The pitch of the diffractive grating can be configured such that the incident image light 230 exits the waveguide 210, i.e., redirects the image light 230 such that TIR no longer occurs. In other words, the diffractive grating of the out-coupling element 245 can extract the image light 230 propagating inside the waveguide 210 by TIR out of the waveguide 210 via diffraction as the output light 232. In some embodiments, the out-coupling element 245 can also be referred to as an out-coupling grating 245. The out-coupling element 245 can extract the image light 230 propagating inside the waveguide 210 by TIR out of the waveguide 210 step-wise at different locations of the out-coupling element 245 as the TIR-propagating light is incident on different locations of the out-coupling element 245. Thus, the out-coupling element 245 can replicate the virtual image to expand the effective pupil of the waveguide display assembly 200. In some embodiments, the waveguide 210 can receive light 255 from the real-world environment, can combine the light 255 with the output light 232 (which can be the image light 232), and deliver the combined light towards the eye 265.

[0086] The waveguide 210 can include one or more materials configured to facilitate total internal reflection of the image light 230. For example, the waveguide 210 can include plastic, glass, and / or a polymer. The waveguide 210 can have relatively small form factors. For example, the waveguide 210 can be about 50 mm wide along the x-dimension, about 30 mm long along the y-dimension, and about 0.5 mm to 1 mm thick along the z-dimension.

[0087] The controller 215 can be communicatively coupled with the light source assembly 205 and can control the manner in which the light source assembly 205 operates. In some embodiments, the waveguide 210 can output expanded image light 232 toward the eye 265 with an increased or expanded field of view (“FOV”). For example, the expanded image light 232 can be provided to the eye 265 with a diagonal FOV (in x and y) equal to or greater than 60 degrees and equal to or less than 150 degrees. The waveguide 210 can be configured to provide an eyebox with a width equal to or greater than 8 mm and equal to or less than 50 mm and / or a height equal to or greater than 6 mm and equal to or less than 20 mm. With the waveguide display assembly 200, the physical display and electronics can be moved to the side of the front body of the NED, and a substantially full unobstructed view of the real-world environment can be achieved, which enhances the AR user experience.

[0088] In some embodiments, the waveguide 210 can include additional gratings configured to redirect, fold, and / or expand the pupil of the light source assembly 205. For example, as shown in FIG. 2B, in a waveguide display assembly 250, a guide element 240 can be coupled with the waveguide 210. The guide element 240 can be configured to redirect the received, input image light 230 toward a coupling-out element 245 such that the received, input image light 230 is coupled out of the waveguide 210 via the coupling-out element 245 as the output image light 232. In some embodiments, the guide element 240 and the coupling-out element 245 can be disposed on different sides of the waveguide 210. In some embodiments, the guide element 240 can be disposed on the first surface 210-1 of the waveguide 210. For example, in some embodiments, the guide element 240 can be integrally formed as part of the waveguide 210 on the first surface 210-1. In some embodiments, the guide element 240 can be separately formed and disposed on (e.g., fixed to) the first surface 210-1 of the waveguide 210. In some embodiments, the coupling-out element 245 can be disposed on the second surface 210-2 of the waveguide 210. For example, in some embodiments, the guide element 240 can be integrally formed as part of the waveguide 210 on the second surface 210-2. In some embodiments, the guide element 240 can be separately formed and disposed on (e.g., fixed to) the second surface 210-2 of the waveguide 210. FIG. 2B

[0089] ​In some embodiments, the directing element 240 and the out-coupling element 245 can have similar structures. In some embodiments, the directing element 240 can include a surface-relief grating, a volume holographic element, a polarization grating, a polarization volume holographic element, a metasurface grating, another type of diffractive element, or a combination thereof. In some embodiments, the directing element 240 can include a diffractive grating. The directing element 240 can also be referred to as a folding grating 240 or a directing grating 240. In some embodiments, multiple functions (e.g., redirecting, folding, and / or expanding a pupil of light generated by the light source assembly 205) can be combined into a single grating (e.g., an out-coupling grating).

[0090] Referring to FIG. 2A and FIG. 2B In the waveguide display assembly 200 or 250, a suitable combination of the in-coupling grating 235, the out-coupling grating 245, and / or the directing grating 240 can be configured to sequentially transmit multiple portions of image light provided by the light source assembly 205 in a time-division multiplexing manner. At least one of the in-coupling grating 235, the out-coupling grating 245, or the directing grating 240 according to embodiments of the present disclosure can include at least one passive diffractive optical element. In some embodiments, at least one of the in-coupling grating 235, the out-coupling grating 245, or the directing grating 240 can include one or more sub-gratings. At least one (e.g., each) of these sub-gratings can be an embodiment of the disclosed passive diffractive optical element.

[0091] In some embodiments, a passive diffractive optical element can have polarization selectivity. For example, a passive diffractive optical element can selectively diffract light having a first polarization and transmit light having a second polarization in a diffractively negligible or non-diffractive manner. In some embodiments, the first polarization and the second polarization can be linearly orthogonal polarizations. In some embodiments, the first polarization and the second polarization can be circular polarizations having opposite handedness. In some embodiments, the first polarization and the second polarization can be elliptical polarizations having opposite handedness. A passive diffractive optical element can be a passive element. Via a change in polarization of incident light by an external polarization switch, a passive diffractive optical element can be indirectly switchable between a diffractive state (or an on state) and a non-diffractive state (or an off state). In other words, when a polarization of light incident on a passive diffractive optical element is changed by an external polarization switch, the passive diffractive optical element can switch between operating in a diffractive state or operating in a non-diffractive state depending on the polarization of the incident light.

[0092] Referring to FIG. 2A and FIG. 2B In some embodiments, the waveguide display assembly 200 or 250 can include a combination of the in-coupling grating 235, the out-coupling grating 245, and / or the directing grating 240 in a stacked configuration (e.g., a stacked grating configuration). FIG. 2A and FIG. 2BA plurality of waveguides 210 can be disposed in the waveguide display assembly 200 (not shown in FIG. 2A). At least one (e.g., each) of these waveguides 210 can be configured to handle a portion of the FOV and / or a portion of the color spectrum of a virtual image. Although FIG. 2A And FIG. 2B Although not shown in FIG. 2A, in some embodiments, the waveguide display assembly 200 or 250 can include a plurality of light source assemblies 205 and / or a plurality of waveguides 210. At least one (e.g., each) of these light source assemblies 205 can emit monochromatic image light of a particular waveband corresponding to a primary color (e.g., red, green, or blue). The waveguides 210 can be disposed in a stacked configuration and can be configured to output expanded multi-color image light 232 (e.g., full-color image light). At least one of the one or more waveguides 210 can be a waveguide. In some embodiments, at least one (e.g., each) of these light source assemblies 205 can emit multi-color image light (e.g., full-color image light) corresponding to different portions of the FOV provided by the waveguide display assembly 200 or 250. Although FIG. 2A Although one light source 220 is shown in FIG. 2A, in some embodiments, the light source assembly 205 can include two or more light sources 220. At least one (e.g., each) of these light sources 220 can emit multi-color (e.g., full-color) image light. The multi-color image light (e.g., full-color image light) emitted by different light sources 220 can correspond to different portions of the FOV provided by the waveguide display assembly 200 or 250. For example, the light source assembly 205 can include three light sources 220 configured to respectively emit multi-color image light (e.g., full-color image light) corresponding to left, middle, and right portions of the FOV.

[0093] For the purpose of discussion, a passive diffraction grating is used as an example of the disclosed passive diffractive optical element to explain the polarization selectivity. FIG. 3A And FIG. 3B Schematic diagrams of a passive grating 300 in non-diffractive and diffractive states, respectively, according to embodiments of the present disclosure are shown. As FIG. 3A And FIG. 3BAs shown, the passive grating 300 may include a surface relief grating (“SRG”) 305. The SRG 305 may include a plurality of microstructures 305a, 305b, and 305c (e.g., micrometer- or nanometer-scale protrusions) that define a plurality of grooves 306. The grooves 306 may be at least partially filled with an optically anisotropic material 315. In some embodiments, the microstructures 305a, 305b, and 305c may have the same shape and size. Therefore, the plurality of grooves 306 may have the same shape and size. In some embodiments, the microstructures 305a, 305b, and 305c may have different shapes and sizes. Therefore, the plurality of grooves 306 may have different shapes and sizes. For illustrative purposes, three microstructures 305a, 305b, and 305c are shown. The SRG 305 may include any suitable number of microstructures.

[0094] In some embodiments, the SRG 305 may be a binary non-slanted grating. Each of these microstructures 305a, 305b, and 305c may include vertical walls defining a groove 306. That is, each groove 306 may include two vertical walls and a bottom surface, the vertical walls being perpendicular to the bottom surface. Molecules 310 of the optically anisotropic material 315 may be present within the groove 306 along the groove direction (e.g., the longitudinal direction of the groove), for example, in FIG. 3A and FIG. 3B In the y-direction, it is homogeneously oriented. The optical anisotropic material 315 may be uniaxial and may have a first principal refractive index (e.g., n) in the groove direction (e.g., the y-direction) of SRG 305. e AN It can have a second principal refractive index (e.g., n) in a plane direction perpendicular to the groove direction of SRG305 (e.g., the x-direction, i.e., along the bottom surface of the groove, or the in-plane periodic direction of the microstructure). o AN Second principal refractive index (e.g., n) o AN It can be compared with the refractive index n of SRG 305. g Basic matching, first principal refractive index (e.g., n) e AN It can be compared with the refractive index n of SRG 305. g Mismatch.

[0095] In some embodiments, the SRG 305 can be fabricated based on optically isotropic organic materials (e.g., amorphous polymers). In some embodiments, the SRG 305 can be fabricated based on optically anisotropic organic materials (e.g., liquid crystal polymers). In some embodiments, the SRG 305 can be fabricated based on inorganic materials (e.g., metals or oxides used to fabricate metasurfaces). The materials of the SRG 305 can be isotropic or anisotropic. In some embodiments, the SRG 305 can be nanofabricated from a resist material, which can be substantially transparent to a range of electromagnetic frequencies, e.g., the visible light band. The resist material can be in the form of a thermoplastic, a polymer, an optically clear photoresist, or a combination thereof. After setting or curing, the plurality of parallel grooves 306 can provide an orientation for optically anisotropic materials 315 disposed in the grooves 306 of the SRG 305. That is, the SRG 305 can act as an orientation layer for the optically anisotropic materials 315. In some embodiments, the SRG 305 can be nanofabricated to have various orientation patterns and features (e.g., thicknesses below 10 nm). This process can allow for creating orientation patterns for the optically anisotropic materials 315 with high customizability. For example, the molecules 310 of the optically anisotropic materials 315 can be oriented homeotropically or homogeneously within the grooves 306 of the SRG 305. In some embodiments, the molecules 310 of the optically anisotropic materials 315 can be oriented in a hybrid manner, e.g., some molecules 310 can be oriented homeotropically within the grooves 306 of the SRG 305 and some molecules 310 can be oriented homogeneously within the grooves 306 of the SRG 305. In some embodiments, the molecules 310 of the optically anisotropic materials 315 can be oriented (e.g., homeotropically, homogeneously, or in a hybrid manner) within the grooves 306 of the SRG 305 by suitable orientation methods (e.g., stretching, light (e.g., photo-orientation), electric field, magnetic field, or a combination thereof).

[0096] In some embodiments, the optically anisotropic materials 315 can include passive materials that are not directly switchable by an external field (e.g., an electric field). These passive materials can include passive LCs or non-reorientable LCs, e.g., optically anisotropic polymers polymerized from polymerizable pre-polymer compositions or polymerizable LC precursors. In some embodiments, the polymerizable LC precursors can include RMs that are polymerizable molecules with optical properties similar to those of LC materials. In some embodiments, the optically anisotropic materials 315 can include elongated molecules.

[0097] In some embodiments, the passive grating 300 can include two substrates (e.g., a top substrate 302 and a bottom substrate 304) with a plurality of parallel grooves 306 formed in the top substrate 302 and the bottom substrate 304. In some embodiments, the passive grating 300 can include a single substrate with a plurality of parallel grooves 306 formed in the substrate. FIG. 3AThe two substrates can be disposed opposite each other to form a container for the SRG 305 and the optically anisotropic material 315. In some embodiments, the orientation of the optically anisotropic material 315 can be provided by one or more orientation structures (e.g., orientation layers) in addition to the SRG 305. The orientation structures can be provided at the substrates (e.g., two orientation layers can be provided at the respective opposite surfaces of the two substrates). In some embodiments, the orientation structures provided at each of the two substrates can be configured to provide planar alignment (e.g., an orientation with a pre-tilt angle of zero or a small pre-tilt angle). The orientation structures provided at the two substrates can be configured to provide parallel surface alignment. In some embodiments, the orientation structures provided at the two substrates can be configured to provide hybrid surface alignment. For example, the orientation structure provided at one of the two substrates can be configured to provide planar alignment, and the orientation structure provided at the other of the two substrates can be configured to provide homeotropic alignment.

[0098] In some embodiments, the plurality of grooves 306 can include the same shape with the same depth d. In some embodiments, the thickness (or height) of the optically anisotropic material 315 can be the same as the depth d of the grooves 306 of the SRG 305 (e.g., the optically anisotropic material 315 can be filled to the same level or height as the top surface of the grooves 306). In some embodiments, the thickness of the optically anisotropic material 315 can be different from the depth d of the grooves 306 of the SRG 305. For example, in some embodiments, the optically anisotropic material 315 can be filled above (or higher than) the top surface of the grooves 306 (e.g., the thickness of the optically anisotropic material 315 can be greater than the depth d of the grooves 306). The portion of the optically anisotropic material 315 disposed above (e.g., higher than the depth d) the top surface of the grooves 306 of the SRG 305 can be uniform and can not contribute to diffraction. In some embodiments, the optically anisotropic material 315 can be filled below the top surface of the grooves 306 (e.g., the thickness of the optically anisotropic material 315 can be less than the depth d of the grooves 306). In some embodiments, the substrates can be removed after the passive grating 300 is manufactured.

[0099] The passive grating 300 can be polarization-selective and thus can be indirectly switchable between a diffractive state and a non-diffractive state. For example, the passive grating 300 can be configured to selectively diffract light having a predetermined polarization and to transmit light having a different polarization (e.g., a polarization orthogonal to the predetermined polarization) with negligible or no diffraction. As FIG. 3AAs shown, for incident light 320 polarized in a plane perpendicular to the groove direction (e.g., the y-direction) of the groove 306 of SRG 305, since n o AN and n g The refractive indices of the two components are substantially matched, allowing the passive grating 300 to function as a substantially optically uniform plate for the incident light 320, with negligible or no diffraction. That is, for incident light 320 polarized in a plane perpendicular to the groove direction (e.g., the y-direction) of the groove 306 of the SRG 305, the passive grating 300 can operate in a non-diffractive state. In some embodiments, the second principal refractive index (e.g., n...) is... o AN It can be compared with the refractive index n of SRG 305. g Matching (or identical). Therefore, incident light 320 can be transmitted with negligible or no diffraction. That is, the diffraction effect of grating 300 can be essentially zero.

[0100] like FIG. 3B As shown, for incident light 330 polarized in the groove direction (e.g., the y direction) of SRG 305, since n e AN and n g The refractive index difference between the two allows the incident light 330 to undergo periodic modulation of the refractive index within the grating 300 and to be diffracted. That is, for incident light 330 polarized in the groove direction (e.g., the y-direction) of the SRG 305, the passive grating 300 can operate in a diffraction state. The diffraction efficiency of the incident light 330 can depend on the modulation of the refractive index provided by the passive grating 300. m (that is, n) e AN and n g difference).

[0101] In some embodiments, FIG. 3A and FIG. 3B The SRG 305 shown can be filled with an active optical anisotropic material (e.g., active LC) that can be reoriented when subjected to an external field (e.g., an electric field). An SRG filled with an active optical anisotropic material can serve as an active grating. Similar to the passive grating 300 described above, an active grating can be directly switchable between diffractive and non-diffractive states, or indirectly switchable between diffractive and non-diffractive states. That is, an active grating can be used as an indirectly switchable grating.

[0102] FIG. 4Aand FIG. 4B schematics of the passive grating 400 in a diffractive state and a non-diffractive state, respectively. FIG. 4A and FIG. 4B The passive grating 400 shown in FIG. 4B can include the same or similar elements and structures as those included in the passive grating 300 shown in FIG. 3A. FIG. 3A and FIG. 3B The description of the same or similar elements can refer to the above description in connection with the passive grating 300 shown in FIG. 3A. FIG. 3A and FIG. 3B The passive grating 400 can include an SRG 405, as shown in FIG. 4A. FIG. 4A and FIG. 4B The SRG 405 can include a plurality of microstructures 405a, 405b, and 405c similar to the microstructures 305a, 305b, and 305c described above. The microstructures 405a, 405b, and 405c can bound a plurality of grooves 406, which can be similar to the grooves 306 described above. The molecules 410 of the optically anisotropic material 415 can be oriented in parallel within the grooves 406 along the groove direction (e.g., along the y-direction shown in FIG. 4A). FIG. 4A or FIG. 4B The optically anisotropic material 415 can have a first principal refractive index (e.g., n e AN ) along the groove direction (e.g., the y-direction) of the grooves 406 of the SRG 405, and a second principal refractive index (e.g., n o AN ) along an in-plane direction (e.g., the x-direction, i.e., a direction along the bottom surface of the grooves, or an in-plane periodic direction of the microstructures) perpendicular to the groove length direction of the SRG 405. o AN The second principal refractive index (e.g., n g ) can not match the refractive index n e AN ) of the SRG 405, and the first principal refractive index (e.g., n g ) can substantially match the refractive index n

[0103] The passive grating 400 can be polarization-selective, and thus can be indirectly switchable between the diffractive state and the non-diffractive state. FIG. 4A As shown in FIG. 4B, for an incident light 420 polarized along an in-plane direction (e.g., the x-direction) perpendicular to the groove direction of the grooves 406 of the SRG 405, the light 420 can be diffracted by the passive grating 400 in the diffractive state. o AN and n gDue to the refractive index difference, incident light 420 can undergo periodic modulation of the refractive index in the passive grating 400, and thus be diffracted. That is, for incident light 420 polarized in a plane perpendicular to the groove direction of SRG 405 (e.g., the x-direction), the passive grating 400 can operate in a diffracting state. The diffraction efficiency of the passive grating 400 can depend on the modulation of the refractive index n provided by the passive grating 400. m (that is, n) o AN and n g difference).

[0104] like FIG. 4B As shown, for incident light 430 polarized in the groove direction (e.g., the y direction) of SRG 405, since n e AN With n g The refractive indices of the two components are substantially matched, allowing the passive grating 400 to function as a substantially uniform beam homogenizer for the incident light 430, with negligible or no diffraction. That is, for incident light 430 polarized in the groove direction (e.g., the y-direction) of the SRG 405, the passive grating 400 can operate in a non-diffractive state. In some embodiments, the first principal refractive index (e.g., n...) is... e AN It can be compared with the refractive index n of SRG 405. g The incident light 430 is matched (or can be identical), so it can be transmitted with negligible or no diffraction. That is, the diffraction effect of the passive grating 400 can be essentially zero.

[0105] In some embodiments, FIG. 4A and FIG. 4B The SRG 405 shown can be filled with an active optical anisotropic material (e.g., active LC) that can be reoriented when subjected to an external field, such as an electric field. The SRG filled with active optical anisotropic material can serve as an active grating. Similar to the passive grating 400 described above, this active grating can be directly switchable between diffractive and non-diffractive states, or indirectly switchable between them. That is, the active grating can be used as an indirectly switchable grating.

[0106] FIG. 5A and FIG. 5B The xz-section views of the passive grating 500 in both its non-diffraction and diffraction states are shown. The passive grating 500 may include elements identical or similar to those included in passive gratings 300 or 400. Descriptions of these identical or similar elements can be found above. FIG. 3A to FIG. 4B The presented description. (and) FIG. 3A andFIG. 3B The passive grating 300 shown in FIG. 3B can be similar to the passive grating 300 shown in FIG. 3A, FIG. 5A and FIG. 5B The passive grating 500 shown in FIG. 5B can include an SRG 505 including a plurality of microstructures 505a, 505b, and 505c. The microstructures 505a, 505b, and 505c can define a plurality of grooves 506. These grooves 506 can be at least partially filled with an optically anisotropic material 515. The molecules (e.g., LC molecules) 510 of the optically anisotropic material 515 can be oriented in parallel within the grooves 506 along a groove direction (e.g., along the y direction as shown in FIG. 5B). FIG. 5A and FIG. 5B The passive grating 500 shown in FIG. 5B can be similar to the passive grating 300 shown in FIG. 3A, FIG. 3A and FIG. 3B The passive grating 500 shown in FIG. 5B can be similar to the passive grating 300 shown in FIG. 3A, FIG. 4A and FIG. 4B The passive grating 500 shown in FIG. 5B can be similar to the passive grating 300 shown in FIG. 3A, FIG. 5A and FIG. 5B The SRG 505 shown in FIG. 5B can be a binary slanted grating. That is, as shown in FIG. 5B, each microstructure 505a, 505b, or 505c can form a slant angle β with respect to an in-plane direction (e.g., the x direction, i.e., a direction along the bottom surface of the groove and perpendicular to the groove length direction, or an in-plane periodic direction of the microstructure) perpendicular to the plane of the SRG 505. In some embodiments, the side surface of each groove 506 can be slanted with respect to the bottom surface of the groove 506 at the slant angle β, instead of being perpendicular to the bottom surface as shown in FIG. 5A. FIG. 5A The slant angle β can be referred to as a slant angle of the microstructure or a slant angle of the side surface of the groove. FIG. 3A and FIG. 5A The description of the diffractive state and the non-diffractive state of the passive grating 500 shown in FIG. 5B can refer to those described above in connection with the passive grating 300 shown in FIG. 3A. FIG. 5B and FIG. 3A The passive grating 500 can operate in the non-diffractive state to transmit an incident light 520 polarized in the x direction perpendicular to the groove direction (i.e., the y direction) as shown in FIG. 5B. The passive grating 500 can operate in the diffractive state to diffract an incident light 530 polarized in the groove direction (i.e., the y direction) as shown in FIG. 5B. FIG. 3B The passive grating 500 can operate in the non-diffractive state to transmit an incident light 520 polarized in the x direction perpendicular to the groove direction (i.e., the y direction) as shown in FIG. 5B. The passive grating 500 can operate in the diffractive state to diffract an incident light 530 polarized in the groove direction (i.e., the y direction) as shown in FIG. 5B. FIG. 5A The passive grating 500 can operate in the non-diffractive state to transmit an incident light 520 polarized in the x direction perpendicular to the groove direction (i.e., the y direction) as shown in FIG. 5B. The passive grating 500 can operate in the diffractive state to diffract an incident light 530 polarized in the groove direction (i.e., the y direction) as shown in FIG. 5B. FIG. 5B The passive grating 500 can operate in the non-diffractive state to transmit an incident light 520 polarized in the x direction perpendicular to the groove direction (i.e., the y direction) as shown in FIG. 5B. The passive grating 500 can operate in the diffractive state to diffract an incident light 530 polarized in the groove direction (i.e., the y direction) as shown in FIG. 5B.

[0107] FIG. 5C and FIG. 5D FIGS. 5C and 5D respectively show x-z cross-sectional views of a passive grating 550 in the diffractive state and the non-diffractive state. The passive grating 550 can include the same or similar elements as those included in the passive gratings 300, 400, or 500. The description of these same or similar elements can refer to those described above in connection with the passive grating 300 shown in FIG. 3A. FIG. 3A to FIG. 5BThe description presented. As FIG. 4A and FIG. 4B Passive grating 400 shown in FIG. 5C and FIG. 5D Passive grating 550 shown in FIG. 5A and FIG. 5B may include SRG 555 including a plurality of microstructures 555a, 555b, and 555c, which can be similar to microstructures 505a, 505b, and 505c shown in FIG. 5C and FIG. 5D The plurality of microstructures 555a, 555b, and 555c can define a plurality of grooves 556, which can be similar to grooves 506. Grooves 556 can be at least partially filled with optically anisotropic material 565. Molecules (e.g., LC molecules) 560 of optically anisotropic material 565 can be oriented in parallel within grooves 556 along a groove direction (e.g., along the y-direction as shown in FIG. 4A and FIG. 4B Unlike binary non-tilted SRG 405 in FIG. 5C and FIG. 5D SRG 555 shown in FIG. 5A and FIG. 5B may be a binary tilted grating (similar to tilted grating shown in FIG. 5C and FIG. 5D The description of the diffractive state and the non-diffractive state of passive grating 550 shown in FIG. 4A and FIG. 4B may refer to the description presented above in connection with passive grating 400 shown in FIG. 5C As shown, passive grating 550 can operate in a diffractive state to diffract incident light 520 polarized in the x-direction perpendicular to the groove direction (i.e., the y-direction). As shown, passive grating 550 can operate in a non-diffractive state to transmit incident light 530 polarized in the groove direction (i.e., the y-direction). FIG. 5D

[0108] In some embodiments, FIG. 5A to FIG. 5D SRG 505 and SRG 555 shown in may be filled with an active optically anisotropic material (e.g., an active LC) that can reorient when subjected to an external field, e.g., an electric field. An SRG filled with an active optically anisotropic material can become an active grating. Similar to passive grating 500 and passive grating 550 described above, the active grating can be directly switchable between a diffractive state and a non-diffractive state, or can be indirectly switchable between a diffractive state and a non-diffractive state. That is, the active grating can function as an indirectly switchable grating.

[0109] FIG. 6A and FIG. 6BThe xz-section views of the passive grating 600 in both its non-diffraction and diffraction states are shown. The passive grating 600 may include elements identical or similar to those included in passive gratings 300, 400, 500, or 550. Descriptions of these identical or similar elements can be found in the above combination. FIG. 3A to FIG. 5D The presented description. (and) FIG. 5A and FIG. 5B The passive grating 500 shown in the figure, and FIG. 5C and FIG. 5D Similar to the passive grating 550 shown in the figure, FIG. 6A and FIG. 6B The passive grating 600 shown may include an SRG 605 comprising a plurality of microstructures 605a, 605b, and 605c that define a plurality of grooves 606. Microstructures 605a, 605b, and 605c may be similar to microstructures 505a, 505b, 505c or 555a, 555b, 555c. Grooves 606 may be similar to grooves 506 or 556. The SRG 605 may be a binary tilted grating, wherein microstructures 605a, 605b, and 605c are tilted relative to an in-plane direction (e.g., the x-direction) perpendicular to the groove length direction. In other words, the side surface of each groove 606 forms a tilt angle β relative to the bottom surface of the groove 606. The plurality of grooves 606 may be at least partially filled with an optically anisotropic material 615. Molecules (e.g., LC molecules) 610 of the optically anisotropic material 615 can be tilted within the groove 606. Due to the interaction between the tilted side surface of the groove 606 and the molecules 610, the molecules 610 can be tilted along the tilted side surface of the groove 606. For example, the molecules 610 can form a pretilt angle along the tilted side surface relative to an in-plane direction perpendicular to the length direction of the groove (e.g., the x-direction, i.e., along the bottom surface of the groove and perpendicular to the length direction of the groove, or the in-plane periodic direction of the microstructure). In some embodiments, the pretilt angle of the molecules 610 can be substantially the same as the tilt angle β of the side surface of the groove 606. FIG. 6A As shown, molecules (e.g., LC molecules) 610 can be oriented in the tilt direction 625 of the groove 606 (referred to as the groove tilt direction 625). The tilt direction 625 refers to the tilt direction of the tilted side surface of the groove 606. FIG. 6A In this context, the tilt angle β of SRG 605 can be the angle formed between the groove tilt direction 625 of the groove 606 and an in-plane direction (e.g., the x direction) perpendicular to the groove direction of SRG 605 (e.g., the y-direction). Although in FIG. 5A to FIG. 5D Not shown in the image, but can be found in... FIG. 5A to FIG. 5D The embodiments shown define similar groove tilt directions.

[0110] The optical anisotropic material 615 may be uniaxial and may have a first principal refractive index (e.g., n) in the groove tilt direction 625 of the SRG 605. e AN It can have a second principal refractive index (e.g., n) in a direction perpendicular to the groove tilt direction 625 (e.g., the groove direction of SRG 605 (e.g., the y direction)). o AN First principal refractive index (e.g., n) e AN ) can be decomposed into two components: a first component (e.g., n) in a direction (e.g., x) in a plane perpendicular to the groove direction (e.g., y-direction). e AN-X ), and a second component (e.g., n) in the thickness direction (e.g., z-direction) of SRG 605. e AN-Z First principal refractive index (e.g., n) e AN The first component of ) (e.g., n) e AN-X It can be compared with the refractive index n of SRG 605. g Basic matching, second principal refractive index (e.g., n) o AN It can be compared with the refractive index n of SRG 605. g Mismatch.

[0111] like FIG. 6A As shown, for incident light 620 polarized in a plane perpendicular to the groove direction (e.g., the y-direction) of groove 606, since n e AN-X and n g The refractive indices of the two components are essentially matched, allowing the passive grating 600 to function as a substantially uniform homogenizer for the incident light 620, with negligible or no diffraction. In other words, for incident light 620 polarized in a plane perpendicular to the groove direction (e.g., the y-direction) of the groove 606 of the SRG 605, the passive grating 600 can operate in a non-diffractive state. FIG. 6B As shown, for incident light 630 polarized in the groove direction (e.g., the y direction) of SRG 605, since n o AN With n gThe refractive index difference between the two allows the incident light 630 to undergo periodic modulation of the refractive index within the passive grating 600 and to be diffracted. That is, for incident light 630 polarized in the groove direction (e.g., the y-direction) of the SRG 605, the passive grating 600 can operate in a diffracting state. The diffraction efficiency of light 630 can depend on the modulation of the refractive index n provided by the passive grating 600. m (that is, n) o AN With n g difference).

[0112] FIG. 6C and FIG. 6D The xz-section views of the passive grating 650 in both diffraction and non-diffraction states are shown. The passive grating 650 may include elements identical or similar to those included in passive gratings 300, 400, 500, 550, or 600. Descriptions of these identical or similar elements can be found in the above combination. FIG. 3A to FIG. 6B The presented description. (and) FIG. 6A and FIG. 6B Similar to the passive grating 600 shown in the figure, FIG. 6C and FIG. 6D The passive grating 650 shown may include an SRG 655, which includes a plurality of microstructures 655a, 655b, and 655c defining a plurality of grooves 656. Microstructures 655a, 655b, and 655c may be similar to microstructures 605a, 605b, and 605c. Grooves 656 may be similar to groove 606. The SRG 655 may be a binary tilt grating, which is similar to... FIG. 6A Similar to SRG 605 shown. The groove 656 may be at least partially filled with optically anisotropic material 665. Similar to molecule 610, molecules (e.g., LC molecules) 660 of the optically anisotropic material 665 may be tilted within the groove 656. Due to the interaction between the tilted side surface of the groove 656 and the molecule 660, the molecule 660 may form a pretilt angle along the tilted side surface in a plane direction relative to the direction perpendicular to the length of the groove. The pretilt angle of the molecule 610 may be substantially the same as the tilt angle β of the side surface of the groove 606. That is, with... FIG. 6A Similar to the embodiments shown, molecules (e.g., LC molecules) 660 can be oriented in the tilt direction 675 of the groove 656 (referred to as the groove tilt direction 675).

[0113] The optical anisotropic material 665 may be uniaxial and may have a first principal refractive index (e.g., n) in the groove tilt direction 675 of the SRG 655. e ANIt can have a second principal refractive index (e.g., n) in a direction perpendicular to the groove tilt direction 675 (e.g., the groove direction of SRG 655 (e.g., the y direction)). o AN First principal refractive index (e.g., n) e AN ) can be decomposed into two components: a first component (e.g., n) in a direction (e.g., x) in a plane perpendicular to the groove direction (e.g., y-direction). e AN-X ), and a second component (e.g., n) in the thickness direction (e.g., z-direction) of SRG 655. e AN-Z First principal refractive index (e.g., n) e AN The first component of ) (e.g., n) e AN-X It can be compared with the refractive index n of SRG 655. g Mismatch, second principal refractive index (e.g., n) o AN It can be compared with the refractive index n of SRG 655. g Basic match.

[0114] like FIG. 6C As shown, for incident light 620 polarized in an in-plane direction (e.g., x direction) perpendicular to the groove direction (e.g., y direction) of groove 656, since n e AN-X With n g The refractive index difference between the two allows the incident light 620 to undergo periodic modulation of the refractive index within the passive grating 650 and to be diffracted. That is, for incident light 620 polarized in a plane perpendicular to the length direction of the groove in SRG 655, the passive grating 650 can operate in a diffraction state. The diffraction efficiency of the incident light 620 can depend on the modulation of the refractive index n provided by the passive grating 650. m (that is, n) e AN-X and n g (The difference). For example FIG. 6D As shown, for incident light 630 polarized in the groove direction (e.g., the y direction) of SRG 655, since n o AN-X With n g The refractive indices of the two components are essentially matched, allowing the passive grating 650 to function as a substantially uniform beam homogenizer for the incident light 630, with negligible or no diffraction. In other words, the passive grating 650 can operate in a non-diffractive state for the incident light 630 polarized in the groove direction of the groove 656 of the SRG 655.

[0115] In some embodiments, FIG. 6A to FIG. 6D SRG 605 and SRG 655 shown in FIG. 6B can be filled with an active optically anisotropic material (e.g., an active LC) that can reorient when subjected to an external field, e.g., an electric field. An SRG filled with an active optically anisotropic material can become an active grating. Similar to passive grating 600 and passive grating 650 described above, the active grating can be directly switchable between a diffractive state and a non-diffractive state, or can be indirectly switchable between a diffractive state and a non-diffractive state. That is, the active grating can function as an indirectly switchable grating.

[0116] FIG. 3A to FIG. 6D It is shown that a passive diffractive optical element can be a passive grating including an SRG with a constant periodicity. The periodicity of an SRG can be defined as the distance between two adjacent microstructures (e.g., protrusions). The profile of the grooves of the SRG can have a rectangular shape or a parallelogram shape. That is, the profile of the grooves of the SRG can include a periodic distribution of rectangular shapes or parallelogram shapes. In some embodiments, a passive diffractive optical element can be configured without optical power. In some embodiments, the profile of the grooves of the SRG can include any suitable shape, e.g., any regular shape or irregular shape. For example, depending on the application, the profile of the grooves of the SRG can include a sinusoidal shape, a triangular shape, a trapezoidal shape, or a sawtooth shape. In some embodiments, an SRG (i.e., the microstructures or grooves included in the SRG) can have a varying periodicity, rather than a constant periodicity. An exemplary passive diffractive optical element with an SRG having a varying periodicity is shown in FIG. 6C. In some embodiments, a passive diffractive optical element can be configured with optical power. The disclosed diffractive optical elements can achieve substantially the same optical functionality as conventional refractive optics, e.g., lenses, prisms, or aspheres, in a smaller and lighter configuration. In some embodiments, a passive diffractive optical element can be a one-dimensional grating. In some embodiments, a passive diffractive optical element can be a two-dimensional grating including at least two SRGs that are patterned and / or superimposed. FIG. 7

[0117] FIG. 7 A schematic diagram of a passive diffractive optical element 700 according to another embodiment of the disclosure is shown. As FIG. 7 ​As shown, the passive diffractive optical element 700 can be a passive grating including an SRG 705. The SRG 705 can include a plurality of microstructures 705a-705i. The microstructures can bound a plurality of grooves 706a-706h. The number of microstructures and grooves is for illustrative purposes only. The SRG 705 can include any suitable number of microstructures. The SRG 705 (i.e., the microstructures or grooves of the SRG 705) can have varying periodicity. That is, the grooves 706a-706h can not be identical. For example, the widths of at least two grooves can be different. In some embodiments, a first set of grooves can have a first width (associated with a first periodicity), and a second set of grooves can have a second width (associated with a second periodicity). The second width (and thus the second periodicity) can be different from the first width. The grooves 706a-706h can be at least partially filled with an optically anisotropic material 715. As with the embodiments shown in FIGS. 1-6, the molecules 710 (shown as black rods) of the optically anisotropic material 715 can be oriented parallel within the grooves 706a-706h. For example, in some embodiments, the molecules 710 can be oriented parallel in the groove direction (e.g., the y-direction) of the grooves 706a-706h of the SRG 705. FIG. 3B or FIG. 4A Similar to the embodiments shown in FIGS. 1-6, the molecules 710 (shown as black rods) of the optically anisotropic material 715 can be oriented parallel within the grooves 706a-706h. For example, in some embodiments, the molecules 710 can be oriented parallel in the groove direction (e.g., the y-direction) of the grooves 706a-706h of the SRG 705.

[0118] The optically anisotropic material 715 can have a first principal refractive index (e.g., a very optical refractive index n e AN ) in the groove direction (e.g., the y-direction) of the SRG 705, and can have a second principal refractive index (e.g., a common optical refractive index n o AN ) in a direction (e.g., the x-direction) along a plane perpendicular to the groove direction. One of the first or second principal refractive indices can substantially match the refractive index n g of the SRG 705, and the other of the first or second principal refractive indices can not match the refractive index n g of the SRG 705. For purposes of discussion, in the passive diffractive optical element 700, the second principal refractive index (e.g., n o AN ) of the optically anisotropic material 715 can substantially match the refractive index n g of the SRG 705, and the first principal refractive index (e.g., n e AN ) in the groove direction (e.g., the y-direction) of the SRG 705 can not match the refractive index n g of the SRG 705.

[0119] The cross-sectional profile of the grooves of the SRG 705 can have a non-periodic rectangular profile or shape. As shown, the cross-sectional profile of the grooves 706a-706h can have a non-periodic rectangular profile or shape. As shown, the cross-sectional profile of the grooves 706a-706h can have a non-periodic rectangular profile or shape.FIG. 7 As shown, the width of the groove can be denoted as wl, and the width of the microstructure can be denoted as w2. In a direction (e.g., x-direction, i.e., a direction along the bottom surface of the groove, or an in-plane periodic direction of the microstructure) that is perpendicular to the groove direction (e.g., y-direction) of the SRG 705, the periodicity (wl + w2) of the SRG 705 can monotonically decrease from the center (denoted by “c” in FIG. 7 the middle of the SRG 705 to the periphery (e.g., left and right ends) of the SRG 705, achieving a light focusing effect (or providing a positive optical power) by doing so. For the incident light 730 polarized in the groove direction (e.g., y-direction) of the SRG 705, the refractive index difference between n e AN and n g causes the incident light 730 to experience a refractive index modulation in the passive diffractive optical element 700 and can be diffracted. By configuring the profile of the grooves 706a-706h of the SRG 705 and the refractive indices of the optically anisotropic material 715 and the SRG 705, the diffracted light beams 740 can be further focused. That is, the passive diffractive optical element 700 can function as a cylindrical diffractive lens. In some embodiments, the passive diffractive optical element 700 can also include other elements, such as a substrate, an orientation layer, etc., which can not be shown in FIG. 7 for simplicity. Similar to the grooves shown in FIG. 3A to FIG. 4B , although the varying periodicity configuration shown in FIG. 7 is shown as grooves with side surfaces perpendicular to the bottom surface, it will be understood that the varying periodicity configuration can also be based on the tilted microstructures shown in FIG. 5A to FIG. 6D .

[0120] In some embodiments, the SRG 705 shown in FIG. 7 may be filled with an active optically anisotropic material (e.g., an active LC) that can reorient when subjected to an external field, such as an electric field. The SRG filled with the active optically anisotropic material can become an active grating. Similar to the passive diffractive optical element 700 described above, the active grating can be directly switchable between a diffractive state and a non-diffractive state, or can be indirectly switchable between a diffractive state and a non-diffractive state. That is, the active grating can function as an indirectly switchable grating.

[0121] A passive diffractive optical element according to embodiments of the present disclosure can be indirectly switched between a diffractive state and a non-diffractive state via an external polarization rotator or polarization switch. For the purpose of discussion, a passive binary diffraction grating is used as an example of the disclosed passive diffractive optical element to explain the indirect switching. FIG. 8A and FIG. 8BThe switching configuration shown can be applied to any of the disclosed indirect switchable diffractive optical elements shown in the other figures. FIG. 8A and FIG. 8B A schematic diagram of a system for indirectly switching a passive grating 800 according to an embodiment of the present disclosure is shown. For illustrative purposes, the passive grating 800 may be a single-substrate grating. FIG. 8A and FIG. 8B As shown, the passive grating 800 can have the same characteristics as... FIG. 3A to FIG. 3B The configuration is similar to that of the passive grating 300 shown. For example, the passive grating 800 may include an SRG 805, which includes multiple microstructures 805a, 805b, 805c, etc. The multiple microstructures 805a, 805b, 805c, etc. may be similar to microstructures 305a, 305b, and 305c. The multiple microstructures 805a, 805b, 805c, etc. may define multiple grooves 806, which may be connected to... FIG. 3A Similar to the groove 306 shown. SRG 805 can be disposed on the substrate 810 and can be filled with an optical anisotropic material 815. The optical anisotropic material 815 can be similar to optical anisotropic material 315. Although in FIG. 8A and FIG. 8B The text shows the relationship with... FIG. 3A and FIG. 3B The configuration shown is similar to that of a passive grating used to explain indirect switching, but it will be understood that... FIG. 8A and FIG. 8B The indirect switching shown in the diagram can be similarly applied to... FIG. 4A and FIG. 4B , FIG. 5A and FIG. 5B , FIG. 5C and FIG. 5D , FIG. 6A and FIG. 6B , FIG. 6C and FIG. 6D as well as FIG. 7 The grating shown in the image.

[0122] like FIG. 8A and FIG. 8BAs shown, the polarization switch 820 can be coupled (e.g., optically coupled) to the passive grating 800. The polarization switch 820 can be configured to control the polarization of light incident on the passive grating 800. The polarization switch 820 can be an active element configured to switch the polarization of the incident light between a first polarization and a second polarization different from the first polarization according to an operating state (e.g., a switched state or a non-switched state) of the polarization switch 820. In the switched state, the polarization switch 820 can switch the polarization of the incident light from the first polarization to the second polarization, and vice versa. In the non-switched state, the polarization switch 820 can maintain the polarization of the incident light. In some embodiments, the first polarization and the second polarization can be linear polarizations, and the second polarization can be orthogonal to the first polarization. In some embodiments, the first polarization and the second polarization can be circular or elliptical polarizations, and the first polarization and the second polarization can have different or opposite chirality (e.g., left-handed and right-handed).

[0123] Any suitable polarization switch can be used as the polarization switch 820. In some embodiments, the polarization switch 820 can include an LC-based polarization switch, such as a 90° twist-nematic liquid crystal (TNLC) cell configured to switch the incident light between two orthogonal linear polarizations. The TNLC cell can have a light-incident surface and a light- emergent surface that provides substantially orthogonal orientation directions to the LCs in the TNLC cell. The orientation direction of the light-incident surface of the TNLC cell can be oriented relative to the polarization direction of the linearly polarized incident light (e.g., the first polarization) so as to rotate the polarization of the incident light by about 90° when the TNLC cell is operated in the switched state, or to maintain the polarization of the incident light when the TNLC cell is operated in the non-switched state. In some embodiments, the TNLC cell can be operated in the switched state when an externally applied voltage is below a threshold voltage of the TNLC cell, and can be operated in the non-switched state when the externally applied voltage is high enough to re-orient the LCs along the direction of the electric field.

[0124] In some embodiments, polarization switch 820 can include a switchable half-wave plate (SHWP) having a polarization axis oriented with respect to a polarization direction of the incident light, thereby rotating the incident light from a first polarization to a second polarization when the SHWP is operated in a switched state, and maintaining the first polarization when the SHWP is operated in a non-switched state. The SHWP can be configured to switch the polarization of light between two orthogonal polarizations. For example, the SHWP can switch linearly polarized incident light between two orthogonal polarization directions, and switch circularly polarized incident light between two mutually opposite handednesses. In some embodiments, the SHWP can include an LC layer in which an external electric field (e.g., voltage) can be applied to change the orientation of the LCs in the LC layer, thereby switching the polarization switch 820 between the switched state and the non-switched state. For example, the SHWP can be operated in the switched state when the externally applied voltage is below a threshold voltage of the LCs included in the LC layer. The SHWP can be operated in the non-switched state when the externally applied voltage is high enough to re-orient the LCs along the direction of the electric field.

[0125] For the purpose of discussion, FIG. 8A and FIG. 8B It is shown that polarization switch 820 can include a TNLC cell. The orientation direction of the light-incident surface of the TNLC cell can be oriented parallel to the polarization direction (e.g., y-direction) of incident light 825. As shown, in the voltage-off state, the TNLC cell can be operated in the switched state. The polarization direction of incident light 825 can be rotated by about 90° by the twist structure of the TNLC cell. Thus, the TNLC cell can rotate the polarization of incident light 825 from a first polarization (e.g., polarized in the y-direction shown in FIG. 8A FIG. 8A FIG. 8A That is, incident light 825 having the first polarization can be transmitted toward passive grating 800 as outgoing light 830 having the second polarization. Due to the substantially matching refractive index between n o AN and n g , passive grating 800 can act as a substantial homogenizing plate for light 830. That is, for outgoing light 830 having the second polarization, passive grating 800 can be operated in a non-diffracting state. In some embodiments, the second principal refractive index (e.g., n o AN ) of optically anisotropic material 815 can be substantially matched to the refractive index n g ​​The same (or matched with), thus, the outgoing light 830 can be transmitted through the passive grating 800 in a way that diffraction is negligible or non-existent. That is, the diffraction effect of the passive grating 800 can be substantially zero.

[0126] The twisted structure of the TNLC cell can become untwisted due to an external force (e.g., an external field). Thus, the polarization of the incident light 825 can be maintained. As shown in FIG. 8B , in the voltage-on state, the TNLC cell can be in a non-switching state, and an electric field can be generated between two opposite substrates of the TNLC cell. The LC molecules in the TNLC cell can be reoriented by the electric field, and tend to be parallel to the direction of the electric field when the voltage is high enough. Thus, the twisted structure of the TNLC cell can become untwisted, and the incident light 825 with the first polarization (e.g., polarized in the y direction shown in FIG. 8B ) can be transmitted through the TNLC cell without changing the polarization as the outgoing light 840. That is, the outgoing light 840 incident on the passive grating 800 can also have the first polarization (e.g., polarized in the y direction shown in FIG. 8B ). Due to the refractive index difference between n e AN and n g , the outgoing light 840 can experience a periodic modulation of refractive index in the grating 800, and thus can be diffracted.

[0127] In some embodiments, the polarization switch 820 can include a SHWP. Then, in the non-switching state (e.g., the voltage-on state), the polarization switch 820 can transmit the linearly polarized incident light 825 with the first polarization (e.g., polarized in the y direction shown in FIG. 8A and FIG. 8B without affecting the polarization. Thus, the outgoing light can experience a periodic modulation of refractive index in the passive grating 800, and can be diffracted. In the switching state (e.g., the voltage-off state), the polarization switch 820 can transmit the linearly polarized incident light 825 with the first polarization (e.g., polarized in the y direction shown in FIG. 8A and FIG. 8B ) as the linearly polarized outgoing light with the second polarization (e.g., polarized in the x direction shown in FIG. 8A and FIG. 8B ), which can be transmitted through the passive grating 800 in a way that diffraction is negligible or non-existent.

[0128] Referring to FIG. 8A and FIG. 8BFor incident light 825 polarized in the groove direction (e.g., y direction) of the SRG 805, the passive grating 800 can be switched between the non-diffracting state and the diffracting state by switching the polarization switch 820 between the switching state and the non-switching state. In some embodiments, the incident light 825 can be polarized in a plane perpendicular to the groove direction of the SRG 805 (e.g., x direction). Thus, the passive grating 800 can operate in the diffracting state when the polarization switch 820 is in the switching state, or in the non-diffracting state when the polarization switch 820 is in the non-switching state. The switching time of the TNLC cell can be about 3 to 5 milliseconds (“ms”). In some embodiments, to further increase the switching speed of the passive grating 800, a Ferroelectric Liquid Crystal (“FLC”)-based polarization switch, such as a FLC-based SHWP, can be employed. The switching time can be reduced to the order of microseconds (“ps”), e.g., less than 100 ps. Moreover, by switching the passive grating 800 between the diffracting state and the non-diffracting state via the external polarization switch 820, electrodes that can be included in an active grating can be omitted from the passive grating 800, such that undesirable light absorption and change in refractive index can be significantly suppressed.

[0129] FIG. 9A to FIG. 9D A schematic diagram of a process of fabricating an indirectly switchable diffractive optical element, which can be a passive optical element, is shown in accordance with embodiments of the present disclosure. As shown in FIG. 9A The SRG 905 can be disposed at the substrate 910 (e.g., incorporated into the substrate 910 or formed on the substrate 910). The SRG 905 can include a plurality of microstructures 905a, 905b, 905c, etc. The plurality of microstructures 905a, 905b, 905c, etc. can be similar to the microstructures 305a, 305b, 305c shown in FIG. 3A In some embodiments, although not shown, the microstructures 905a, 905b, 950c, etc. can be tilted microstructures as shown in FIG. 5A to FIG. 6D or FIG. 7 In some embodiments, although not shown, the microstructures 905a, 905b, 950c, etc. can be tilted microstructures as shown in FIG. 9AAs shown, microstructures 905a, 905b, 905c, etc. can define a plurality of grooves 906. Substrate 910 can be transparent and / or reflective in the visible light band (about 380 nm to about 700 nm). In some embodiments, substrate 910 can also be transparent and / or reflective in some or all of the infrared (‘IR’) band (about 700 nm to about 1 mm). Substrate 910 can include organic and / or inorganic materials that are substantially transparent to light in the wavelength ranges listed above. In some embodiments, substrate 910 can be based on a rigid waveguide plate including materials such as glass, plastic, sapphire, etc. In some embodiments, substrate 910 can be based on a flexible or stretchable substrate including materials such as elastomeric materials that can facilitate adjustment of the pitch of SRG 905, thereby enabling the manufactured diffractive optical element to be applied to different incident wavelengths or to steer a light beam.

[0130] In some embodiments, SRG 905 can be fabricated based on organic materials (e.g., polymers, photo-crosslinkable and / or pre-polymerized compositions, reactive mesogens (“RMs”), or combinations thereof). In some embodiments, SRG 905 can be fabricated based on inorganic materials (e.g., inorganic materials used to fabricate metasurfaces). In some embodiments, the material of SRG 905 can be isotropic, e.g., amorphous polymers. In some embodiments, the material of SRG 905 can be anisotropic, e.g., liquid crystal polymers or reactive mesogens (“RMs”). In some embodiments, SRG 905 can be nano-fabricated from a resist material that can be at least partially transparent (e.g., fully transparent or partially transparent) to light in a range of electromagnetic frequencies (e.g., light in the visible light band). The resist material can be in the form of a thermoplastic, a polymer, an optically transparent photoresist, or combinations thereof. In some embodiments, after being set or solidified, the resist material can provide an orientation for optically anisotropic materials disposed in grooves 906 of SRG 905. That is, SRG 905 can act as an orientation layer for optically anisotropic materials disposed in grooves 906 of SRG 905. Various orientation patterns and features (e.g., below 10 nm) of SRG 905 can be formed using nano-fabrication techniques, which allow for the creation of orientation patterns of optically anisotropic materials with high customizability.

[0131] After SRG 905 is disposed at substrate 910 (e.g., incorporated or formed thereon), as FIG. 9BAs shown, an optically anisotropic material 915 can be disposed (e.g., formed or coated) on the SRG 905. The optically anisotropic material 915 can at least partially fill the grooves 906 of the SRG 905. The optically anisotropic material 915 can include a polymerizable prepolymerizable composition or a polymerizable liquid crystal ("LC") precursor. In some embodiments, the polymerizable liquid crystal precursor can include reactive mesocrystalline materials ("RM"), which are polymerizable molecules with optical properties similar to those of the LC material. Due to the orientation pattern provided by the SRG 905, the optically anisotropic material 915 can be oriented in the grooves 906 of the SRG 905 according to the orientation pattern. For example, the molecules of the optically anisotropic material 915 can be oriented vertically, parallelly, or in a mixed manner (e.g., some molecules can be oriented vertically and some other molecules can be oriented parallel) within the grooves 906 of the SRG 905. In some embodiments, the molecules of the optical anisotropic material 915 can be oriented within the groove 906 of the SRG 905 by suitable orientation methods (e.g., stretching, light (e.g., optical orientation), electric field, or combinations thereof). The optical anisotropic material 915 can be oriented to exhibit a first principal refractive index in the groove direction (e.g., the y-direction) and a second principal refractive index in a plane direction perpendicular to the groove direction (e.g., the x-direction). One of the first or second principal refractive indices can substantially match the refractive index of the SRG 905, and the other can not match the refractive index of the SRG 905. The oriented optical anisotropic material 915 can then be polymerized, for example, by thermal polymerization or photopolymerization, to stabilize the orientation or orientation of the molecules of the optical anisotropic material 915. Thus, a passive diffractive optical element that can be indirectly switched via an external polarization rotator can be fabricated.

[0132] In some embodiments, such as FIG. 9B As shown, in the fabricated single-substrate diffractive optical element 930, the thickness of the optical anisotropic material 915 layer can be the same as the depth of the groove 906 of the SRG 905. In some embodiments, such as FIG. 9C As shown, in the fabricated single-substrate diffractive optical element 950, the thickness of the optical anisotropic material 915 layer can be greater than the depth of the groove in the SRG 905. The optical anisotropic material 915 disposed above the top surface of the groove 906 in the SRG 905 can be uniform and may not promote diffraction. In some embodiments, the substrate 910 can be removed after fabrication of the passive diffractive optical element. In some embodiments, such as FIG. 9DAs shown, the manufactured diffractive optical element 970 may include two substrates 910 (e.g., an upper substrate 910 and a lower substrate 910) for support and protection purposes.

[0133] FIG. 10A to FIG. 10C A schematic process for manufacturing a passive diffractive optical element according to another embodiment of this disclosure is shown. (Not repeated here.) FIG. 9A to FIG. 9D and FIG. 10A to FIG. 10C The similarities between the processes shown in the diagram. For example... FIG. 10A As shown, firstly, a substrate 1010 with an upper portion having an alignment layer 1025 and a substrate 1010 with a lower portion having an SRG 1005 can be assembled to form a unit. The SRG 1005 may include multiple microstructures 1005a, 1005b, 1005c, etc., and these microstructures can be... FIG. 3A The form of the microstructure shown in the figure FIG. 5A The form of the tilted microstructure shown in the figure or FIG. 7 The diagram shows a microstructure with a periodic variation. Microstructures 1005a, 1005b, 1005c, etc., can define multiple grooves 1006, which can be... FIG. 3A The form of the groove 306 shown in the figure FIG. 5A The groove 506 shown in the figure is in the form of or FIG. 7 The grooves 706a to 706h are shown in the diagram. For illustrative purposes, the microstructure and grooves are shown as... FIG. 3A The microstructure shown is similar to the groove.

[0134] The alignment layer 1025 can provide a uniform vertical or parallel orientation to the optical anisotropic material to fill the groove 1006 of the SRG 1005 in a next step. For example... FIG. 10B As shown, after the unit is assembled, the optical anisotropic material 1015 can be filled into the groove 1006 of the SRG 1005. The optical anisotropic material 1015 can be used with other materials shown in the figure (e.g., FIG. 9B and FIG. 9Csimilar to the optically anisotropic material 915 shown in FIG. 11B. The optically anisotropic material 1015 can be oriented by the orientation layer 1025 to exhibit a first principal refractive index in the direction of the groove 1006 of the SRG 1005 (e.g., the y-direction) and a second principal refractive index in a direction within the plane perpendicular to the groove direction (e.g., the x-direction). One of the first principal refractive index or the second principal refractive index can substantially match the refractive index of the SRG 1005, and the other of the first principal refractive index or the second principal refractive index can not match the refractive index of the SRG 1005. The oriented optically anisotropic material 1015 can then be polymerized to stabilize the orientation or alignment of the molecules of the optically anisotropic material 1015, so that a passive diffractive optical element can be fabricated. In some embodiments, as shown in FIG. 11C, in the fabricated diffractive optical element 1030, the thickness of the optically anisotropic material 1015 of the layer can be the same as the depth of the groove of the SRG 1005. In some embodiments, as shown in FIG. 11D, in the fabricated diffractive optical element 1050, the thickness of the optically anisotropic material layer 1015 of the layer can be greater than the depth of the groove of the SRG 1005. In some embodiments, the optically anisotropic material 1015 disposed above the top surface of the groove of the SRG 1005 can also be oriented by the orientation layer 1025. FIG. 10B In some embodiments, as shown in FIG. 11C, in the fabricated diffractive optical element 1030, the thickness of the optically anisotropic material 1015 of the layer can be the same as the depth of the groove of the SRG 1005. In some embodiments, as shown in FIG. 11D, in the fabricated diffractive optical element 1050, the thickness of the optically anisotropic material layer 1015 of the layer can be greater than the depth of the groove of the SRG 1005. In some embodiments, the optically anisotropic material 1015 disposed above the top surface of the groove of the SRG 1005 can also be oriented by the orientation layer 1025. FIG. 10C In some embodiments, as shown in FIG. 11C, in the fabricated diffractive optical element 1030, the thickness of the optically anisotropic material 1015 of the layer can be the same as the depth of the groove of the SRG 1005. In some embodiments, as shown in FIG. 11D, in the fabricated diffractive optical element 1050, the thickness of the optically anisotropic material layer 1015 of the layer can be greater than the depth of the groove of the SRG 1005. In some embodiments, the optically anisotropic material 1015 disposed above the top surface of the groove of the SRG 1005 can also be oriented by the orientation layer 1025.

[0135] Indirect switchable gratings (which can be passive gratings in some embodiments) in accordance with embodiments of the present disclosure can enable time-division multiplexing and / or polarization multiplexing of multiple different portions of image light carried by one or more waveguides. The different portions of image light can include, for example, different portions of FOV of a multi-color image / single-color image (e.g., a full-color image), different colors of a single-color image / single-color image, different FOV portions of a single-color image / single-color image, etc. The FOV provided by a waveguide is typically limited by the angular bandwidth of the gratings and the angular limits of the waveguide, which can be determined by the refractive index of the waveguide. One approach to expand the FOV is to divide the FOV into several portions and carry the portions through different gratings or groups of gratings in a time-division multiplexed manner and / or polarization multiplexed manner. To reduce or mitigate crosstalk between the gratings, the portions of image light corresponding to different portions of the FOV can be carried in different time frames, e.g., in a time-division multiplexed manner. Exemplary assemblies or systems configured to carry multiple different portions of image light to an eyebox in a time-division multiplexed manner and / or a polarization multiplexed manner will be described. The following exemplary assemblies or systems can be referred to as “symmetric” configurations in which a pair of in-coupling and out-coupling gratings (or a pair of in-coupling and out-coupling sub-gratings) are configured to carry respective portions of image light to an eyebox. The grating vectors of the in-coupling grating / in-coupling sub-grating and the grating vectors of one of the out-coupling grating / out-coupling sub-grating can satisfy the condition in, The grating vector represents the coupled grating / coupled subgrating. The grating vector represents the output grating / output sub-grating. That is, the vector sum of the grating vectors of the respective portions of image light introduced into the waveguide and those derived from the waveguide can be substantially equal to zero. In a “symmetric” configuration, the FOV can remain unchanged after translation through the waveguide. Indirectly switchable gratings (which may be passive gratings in some embodiments) according to embodiments of this disclosure can be included in the input and / or output gratings to allow the FOV to be extended by time-division multiplexing and / or polarization multiplexing different portions of the FOV. The FOV can be delivered in a time-division manner by indirectly switchable gratings (which may be passive gratings in some embodiments) arranged in different configurations. For example, multiple gratings can be laid out at a common waveguide, or stacked at a common waveguide or different waveguides. A similar principle can be applied to delivering single-color images of different colors.

[0136] FIG. 11A and FIG. 11B An optical system 1100 according to an embodiment of the present disclosure is illustrated. The optical system includes a waveguide 1101 and a plurality of gratings coupled to the waveguide 1101. The waveguide 1101 and the gratings can be configured to deliver different portions of a field of view (FOV) in a time-division multiplexing manner. In some embodiments, the optical system 1100 may also be referred to as a waveguide display system. The waveguide 1101 can be an embodiment of any other waveguide disclosed, such as... FIG. 2A and FIG. 2B Waveguide 210 is shown in the image. FIG. 11A As shown, waveguide 1101 can be configured to receive image light from light source assembly 205 via coupling grating 1105 and direct the image light toward eye 265 via coupling grating 1110. Coupling grating 1105 and coupling grating 1110 can be coupled to waveguide 1101 at different portions of waveguide 1101. At least one of coupling grating 1105 or coupling grating 1110 (e.g., each) can be or may include embodiments of the disclosed indirect switchable grating (which, in some embodiments, may be a passive grating). At least one of coupling grating 1105 or coupling grating 1110 (e.g., each) may include one or more sub-gratings that can overlap each other (e.g., at least partially overlap) to provide a continuous field of view (FOV). For example, sub-gratings can be positioned at different planes of the grating such that adjacent sub-gratings can partially overlap each other. The space surrounding the sub-grating can be at least partially filled with a refractive index-matched material that suppresses light reflection in the space. (See below for reference.) FIG. 12D and FIG. 12E Exemplary overlapping configurations of subgratings are explained.

[0137] Referring to FIG. 11A The in-coupling grating 1105 can include a plurality of sub-gratings 1105a and 1105b (or referred to as, first in-coupling sub-grating 1105a and second in-coupling sub-grating 1105b). The out-coupling grating 1110 can include a plurality of sub-gratings 1110a and 1110b (or referred to as, first out-coupling sub-grating 1110a and second out-coupling sub-grating 1110b). The sub-gratings 1105a and 1105b of the in-coupling grating 1105 can correspond to the sub-gratings 1110a and 1110b of the out-coupling grating 1110 on a one-to-one basis. Any suitable number of sub-gratings can be included in the in-coupling grating 1105. Any suitable number of sub-gratings can be included in the out-coupling grating 1110. The number of sub-gratings included in the respective in-coupling grating 1105 and out-coupling grating 1110 can correspond to the number of portions into which the FOV is divided or partitioned. The sub-gratings included in the in-coupling grating 1105 and the out-coupling grating 1110 can be disposed at the first surface 1101_1 and / or the second surface 1101_2 of the waveguide 1101. The sub-gratings 1105a and 1105b of the in-coupling grating 1105 can be disposed at the same surface or different surfaces of the waveguide 1101. The sub-gratings 1110a and 1110b of the out-coupling grating 1110 can be disposed at the same surface or different surfaces of the waveguide 1101. In some embodiments, the sub-gratings in each of the in-coupling grating 1105 and the out-coupling grating 1110 can be arranged in a one-dimensional grating pattern to lay out the FOV in one dimension.

[0138] For the purpose of discussion, the in-coupling grating 1105 and the out-coupling grating 1110 can be disposed at the second surface 1101_2 of the waveguide 1101, and both the in-coupling grating 1105 and the out-coupling grating 1110 can be embodiments of the disclosed indirect switchable gratings (which can be passive gratings in some embodiments). The first in-coupling sub-grating 1105a and the second in-coupling sub-grating 1105b of the in-coupling grating 1105 can be configured to operate in a diffractive state in response to incident light having two orthogonal polarizations. The first out-coupling sub-grating 1110a and the second out-coupling sub-grating 1110b of the out-coupling grating 1110 can correspond to the first in-coupling sub-grating 1105a and the second in-coupling sub-grating 1105b, respectively. The first out-coupling sub-grating 1110a and the second out-coupling sub-grating 1110b can have the same polarization selectivity as the first in-coupling sub-grating 1105a and the second in-coupling sub-grating 1105b, respectively. The in-coupling sub-grating and the corresponding out-coupling sub-grating can be considered as a sub-grating pair configured to transmit a predetermined portion of the FOV. Each in-coupling sub-grating and out-coupling sub-grating pair can have substantially the same grating period to satisfy the condition

[0139] The light source assembly 205 can emit image light from a light source (e.g., a display) toward the coupling grating 1105. In some embodiments, the image light can be unpolarized image light, and a linear polarizer 1140 can be disposed between the light source assembly 205 and the waveguide 1101 to convert the unpolarized image light into linearly polarized image light with a predetermined polarization. In some embodiments, a polarization rotator or polarization switch 1150 can be disposed between the linear polarizer 1140 and the waveguide 1101. The polarization switch 1150 can be an active element configured to switch the polarization of the received linearly polarized image light from the linear polarizer 1140 between two orthogonal polarizations depending on the operating state of the polarization switch 1150 (e.g., a switched state or a non-switched state). The polarization switch 1150 can be coupled with... FIG. 8A and FIG. 8B It is similar to the polarization switch 820 shown in the figure.

[0140] Image light emitted from the light source assembly 205 may include light rays corresponding to different portions of the display's field of view (FOV). FIG. 11A and FIG. 11B In the illustrated embodiment, the FOV may include two parts: a left part and a right part. For example... FIG. 11A and FIG. 11B As shown, the angular ranges enclosed by ray 1120 and ray 1130 can correspond to the left and right portions of the FOV provided by the image light, respectively. In some embodiments, the display frame can be divided into two consecutive subframes (e.g., a first subframe and a second subframe) for the sequential transmission of light corresponding to different portions of the FOV provided by the image light, thereby achieving sequential transmission of different portions of the FOV in a time-division multiplexing manner.

[0141] For illustrative purposes, the linear polarizer 1140 can convert unpolarized image light emitted from the light source assembly 205 into light with a first polarization (e.g., in...). FIG. 11A The polarization switch 1150 is a linearly polarized image light (polarized in the x-direction as shown in the diagram). When the polarization switch 1150 is in a switching state, the polarization switch 1150 can convert the linearly polarized image light with a first polarization into linearly polarized image light with a second polarization (e.g., polarized in the x-direction). FIG. 11ALinearly polarized image light (polarized in the y-direction as shown in the diagram). When the polarization switch 1150 is in a non-switching state, the polarization switch 1150 can maintain the polarization of the linearly polarized image light having a first polarization. The first coupling sub-grating 1105a and the first coupling sub-grating 1110a can be configured to diffract linearly polarized light having a first polarization and transmit linearly polarized light having a second polarization. The second coupling sub-grating 1105b and the second coupling sub-grating 1110b can be configured to diffract linearly polarized light having a second polarization and transmit linearly polarized light having a first polarization. In some embodiments, the light source assembly 205 can emit linearly polarized light having a first polarization (e.g., polarized in the y-direction). FIG. 11A Polarization in the x-direction shown in the diagram) or a second polarization orthogonal to the first polarization (e.g., in... FIG. 11A The image light is linearly polarized (polarized in the y-direction) as shown in the diagram, and the linear polarizer 1140 can be omitted. The power efficiency of the optical system 1100 can be improved.

[0142] During the first subframe of the display frame, reference FIG. 11A The polarization switch 1150 can be configured to operate in a non-switching state to transmit the received image from the linear polarizer 1140, which has a first polarization (e.g., in a polarization-free manner), without affecting the polarization. FIG. 11A Linearly polarized image light (polarized in the x-direction) is shown in the diagram. Therefore, linearly polarized image light with a first polarization can be diffracted by the first coupling sub-grating 1105a and can be transmitted through the second coupling sub-grating 1105b with negligible or no diffraction. Thus, image light in the angular range surrounded by ray 1120 can be coupled into the TIR path inside waveguide 1101 via the first coupling sub-grating 1105a and can propagate within waveguide 1101 via TIR. Image light propagating within waveguide 1101 can be coupled out of waveguide 1101 via the first coupling sub-grating 1110a into the angular range surrounded by ray 1120', which can be received by the eye 265. Image light in the angular range surrounded by ray 1130 may not be coupled into the TIR path inside waveguide 1101. The angular range surrounded by ray 1120' can correspond to the left side of the FOV.

[0143] During the second subframe of the display frame, reference FIG. 11B The polarization switch 1150 can be configured to operate in a switching state so that the coupling grating 1105 will have a first polarization (e.g., in...). FIG. 11B Linearly polarized image light (polarized in the x-direction shown in the figure) is converted into light with a second polarization (e.g., in the x-direction polarization). FIG. 11Bpolarization of the image light can be diffracted by the second in-coupling sub- grating 1105b and can be transmitted by the first in-coupling sub-grating 1105a in a diffractively negligible or non-diffractive manner. Thus, image light in the angular range encompassed by light ray 1130 can be in-coupled into TIR within the waveguide 1101 via the second in-coupling sub-grating 1105b and out-coupled from the waveguide 1101 via the second out-coupling sub-grating 1110b into the angular range encompassed by light ray 1130’, which can be received by the eye 265. Image light in the angular range encompassed by light ray 1120 can not be in-coupled into TIR within the waveguide 1101. The angular range encompassed by light ray 1130’ can correspond to the right portion of the FOV.

[0144] Thus, by sequentially switching the polarization switch 1150 between the switched and non-switched states in two consecutive sub-frames in a display frame, the two in-coupling sub-grating and out-coupling sub-grating pairs can be switched to the diffractive state in consecutive adjacent sub-frames, respectively. With this configuration, sequential transmission of different portions of the FOV via a common waveguide by tiling the FOV can be achieved. Moreover, the time-division multiplexing scheme enabled by the disclosed indirectly switchable gratings (which can be passive gratings in some embodiments) can eliminate cross-talk between the sub-gratings configured for tiling the FOV.

[0145] Referring back to FIG. 11AIn some embodiments, a pair of polarizers 1160a and 1160b can be disposed on a side of the out-coupling grating 1110 facing the eye 265 to suppress ghost images that can be caused by diffraction of light by sub-grating pairs configured for different portions of the FOV. The polarizers 1160a and 1160b can also be referred to as clean-up polarizers. The polarizers 1160a and 1160b can cover the light exit regions of the first out-coupling sub-grating 1110a and the second out-coupling sub-grating 1110b, respectively. The polarizer 1160a can be configured to transmit linearly polarized image light coupled out of the waveguide 1101 by the first out-coupling sub-grating 1110a and block linearly polarized image light coupled out of the waveguide 1101 by the second out-coupling sub-grating 1110b. The polarizer 1160b can be configured to transmit linearly polarized image light coupled out of the waveguide 1101 by the second out-coupling sub-grating 1110b and block linearly polarized image light coupled out of the waveguide 1101 by the first out-coupling sub-grating 1110a. That is, the polarizers 1160a and 1160b can be oriented to have orthogonal transmission axes. Thus, when image light corresponding to the left portion of the FOV is transmitted via the first in-coupling sub-grating 1105a, the waveguide 1101, and the first out-coupling sub-grating 1110a, ghost images caused by light diffracted by the second in-coupling sub-grating 1105b and / or the second out-coupling sub-grating 1110b configured for the right portion of the FOV can be suppressed. In some embodiments, the polarizers 1160a and 1160b can be omitted.

[0146] Likewise, when image light corresponding to the right portion of the FOV is transmitted via the second in-coupling sub-grating 1105b, the waveguide 1101, and the second out-coupling sub-grating 1110b, ghost images caused by light diffracted by the first in-coupling sub-grating 1105a and / or the first out-coupling sub-grating 1110a configured for the left portion of the FOV can be suppressed. That is, ghost images caused by light diffracted by sub-gratings configured for different portions of the FOV can be suppressed. In some embodiments, a patterned polarizer (rather than two polarizers 1160a and 1160b) can be disposed between the out-coupling grating 1110 and the eye 265 to suppress ghost images that can be caused by diffraction of light by sub-gratings configured for different portions of the FOV. The patterned polarizer can include two regions having different orthogonal transmission axes. The two regions can function in a similar manner as the polarizers 1160a and 1160b, respectively. In some embodiments, the patterned polarizer can be omitted.

[0147] In some embodiments, the polarization switch or polarization rotator 1170 may be disposed on the surface of the coupling grating 1110 facing the eye 265 (or the surface of a pair of polarizers 1160a and 1160b, or the surface of a patterned polarizer). For illustrative purposes, the polarization rotator 1170 is shown separate from the polarizers 1160a and 1160b. The polarization rotator 1170 may be configured to convert the polarization of linearly polarized image light corresponding to a portion (e.g., the left or right portion) of the FOV output from the coupling grating 1110 or the polarizers 1160a and 1160b to orthogonal polarization, such that the image light corresponding to the full FOV may have one polarization instead of two polarizations. For example, the polarization rotator 1170 operating in a switching state may be configured to convert linearly polarized image light having a first polarization to linearly polarized image light having a second polarization. The polarization rotator 1170, operating in a non-switching state, can maintain the polarization of the linearly polarized image light with a second polarization, so that the image light corresponding to the full FOV to be received by the eye 265 can have a second polarization.

[0148] FIG. 11A The diagram illustrates that both the input grating 1105 and the output grating 1110 comprise one or more of the disclosed plurality of indirectly switchable gratings (which may be passive gratings in some embodiments), which are indirectly switchable via an external polarization switch. This configuration is for illustrative purposes and is not intended to limit the scope of this disclosure. In some embodiments, one of the input grating 1105 or the output grating 1110 may include one or more of the disclosed plurality of indirectly switchable gratings (which may be passive gratings in some embodiments), while the other of the input grating 1105 or the output grating 1110 may include one or more non-switchable passive gratings or directly switchable active gratings. For example, different portions of the FOV may be introduced into the waveguide via non-switchable passive input gratings. The output grating 1110 may include two output sub-gratings, which may be indirectly switchable gratings (which may be passive gratings in some embodiments). These two output sub-gratings may be configured to operate in a diffraction state in response to incident image light having two orthogonal polarizations, respectively. A display frame may include two consecutive subframes. During the two consecutive subframes, the coupling grating 1105 may receive image light with orthogonal polarization (e.g., a first polarization and a second polarization) and couple the image light into the waveguide 1101. In at least one of the two consecutive subframes (e.g., each), one of the first coupling subgrating 1110a or the second coupling subgrating 1110b may operate in a diffraction state to couple image light with the corresponding polarization out of the waveguide 1101, and the other of the first coupling subgrating 1110a or the second coupling subgrating 1110b may operate in a non-diffraction state.

[0149] Referring back FIG. 11A And FIG. 11B In some embodiments, the first in-coupling sub-grating 1105a, the second in-coupling sub-grating 1105b, the first out-coupling sub-grating 1110a, and the second out-coupling sub-grating 1110b can be configured to have substantial angular selectivity and polarization selectivity, such that the optical system 1100 can simultaneously deliver different portions of the FOV of the image light emitted from the light source assembly 205 to the eyebox, e.g., in a polarization multiplexed manner, within the same time period (e.g., the same display frame). The display frame can not be divided into multiple sub-frames. For example, the first in-coupling sub-grating 1105a and the first out-coupling sub-grating 1110a can be configured to diffract image light having an angular range corresponding to a first portion (e.g., the left portion) of the FOV and having a first polarization (e.g., polarized in the x-direction as shown in FIG. 11A ), and to transmit image light having an angular range corresponding to a second portion (e.g., the right portion) of the FOV and having a second polarization (e.g., polarized in the y-direction as shown in FIG. 11A ) with negligibly little diffraction. The second in-coupling sub-grating 1105b and the second out-coupling sub-grating 1110b can be configured to diffract image light having an angular range corresponding to the second portion (e.g., the right portion) of the FOV and having the second polarization (e.g., polarized in the y-direction as shown in FIG. 11A ) into the waveguide 1101 via diffraction, and to transmit image light having an angular range corresponding to the first portion (e.g., the left portion) of the FOV and having the first polarization (e.g., polarized in the x-direction as shown in FIG. 11A ) with negligibly little diffraction.

[0150] In some embodiments, the light source assembly 205 can emit unpolarized image light towards the waveguide 1101. The polarizer 1140 and the polarization switch 1150 can be omitted. The unpolarized image light can include a first portion having an angular range corresponding to a first portion of the FOV of the unpolarized image light and a second portion having an angular range corresponding to a second portion of the FOV of the unpolarized image light. Each of the first and second portions of the unpolarized image light can include two components: a first component having a first polarization and a second component having a second polarization. When the unpolarized image light emitted by the light source assembly 205 is incident on the first and second in-coupling sub-gratings 1105a and 1105b simultaneously, image light having an angular range corresponding to the left portion of the FOV (e.g., enclosed by light ray 1120) and having the first polarization (which is the first component of the first portion of the unpolarized image light) can be in-coupled into TIR paths inside the waveguide 1101 via the first in-coupling sub-grating 1105a and out-coupled from the waveguide 1101 via the first out-coupling sub-grating 1110a into an angular range enclosed by light ray 1120’ that can be received by the eye 265. Image light having an angular range corresponding to the right portion of the FOV (e.g., enclosed by light ray 1130) and having the second polarization (which is the second component of the second portion of the unpolarized image light) can be in-coupled into TIR paths inside the waveguide 1101 via the second in-coupling sub-grating 1105b and out-coupled from the waveguide 1101 via the second out-coupling sub-grating 1110b into an angular range enclosed by light ray 1130’ that can be received by the eye 265. At the output side of the waveguide 1101, the angular range enclosed by light ray 1120’ can correspond to the left portion of the FOV and the angular range enclosed by light ray 1130’ can correspond to the right portion of the FOV. Thus, the two portions of the FOV of the unpolarized image light emitted by the light source assembly 205 can be delivered to the eye box simultaneously.

[0151] In some embodiments, the FOV can be divided into three portions, e.g., left, middle, and right portions, which can be delivered to one eye or both eyes by the laid-out in-coupling and out-coupling indirectly switchable gratings (which can be passive gratings in some embodiments). FIGS. 12A-12C An optical system 1200 including a waveguide 1201 configured to deliver different portions of a full FOV in a time-division multiplexing manner is shown according to another embodiment of the present disclosure. The waveguide 1201 can be an embodiment of the waveguide 210 shown in FIGS. 2A and 2B. FIG. 2A and FIG. 2B In some embodiments, the waveguide 1201 can be an embodiment of the waveguide 210 shown in FIGS. 2A and 2B. The embodiments shown in FIGS. 2A and 2B and described above will not be repeated. FIG. 11 A and FIG. 11B In some embodiments, the waveguide 1201 can be an embodiment of the waveguide 210 shown in FIGS. 2A and 2B. The embodiments shown in FIGS. 2A and 2B and described above will not be repeated. FIGS. 12A-12CDescriptions of similar or identical structures and components between embodiments shown in the optical system 1200 are not repeated. The gratings included in the embodiments shown in the optical system 1200 can be any of the disclosed plurality of indirect switchable gratings (which can be passive gratings in some embodiments).

[0152] As FIG. 12AAs shown, waveguide 1201 can be configured to receive image light from light source assembly 205 via in-coupling grating 1205, and can direct the image light toward eye 265 via out-coupling grating 1210. In-coupling grating 1205 and out-coupling grating 1210 can be coupled with waveguide 1201. At least one of in-coupling grating 1205 or out-coupling grating 1210 can be an embodiment of the disclosed indirectly switchable grating (which can be a passive grating in some embodiments). At least one (e.g., each of) in-coupling grating 1205 or out-coupling grating 1210 can include a plurality of sub-gratings configured to transmit a predetermined plurality of portions of FOV, respectively. A corresponding pair of an in-coupling sub-grating and an out-coupling sub-grating can be considered as a sub-grating pair configured to transmit a predetermined portion of FOV. For example, FOV can include three portions: left, middle, and right. Waveguide 1201 can include three sub-grating pairs. At least one (e.g., each of) in-coupling grating 1205 or out-coupling grating 1210 can include three sub-gratings configured to transmit left, middle, and right portions of FOV, respectively. Adjacent portions of FOV can partially overlap to form a continuous FOV at eye 265. For example, the partial overlap of adjacent portions of FOV can be achieved, for example, by having the sub-gratings partially overlap in recording material (e.g., overlapping regions of sub-gratings configured to diffract orthogonally polarized light can be multiplexed). At least one (e.g., each of) of these sub-gratings can be coupled with a polarization switch, which can be configured to indirectly switch at least one (e.g., each of) of these sub-gratings between a diffractive state and a non-diffractive state. Polarization switches 1250a-1250f can be disposed on a side of the corresponding sub-grating from which image light is incident on the sub-grating, thereby controlling the polarization of the image light before it is incident on the corresponding sub-grating. Thus, polarization switches 1250a-1250f can be configured to control the corresponding sub-grating to operate in a diffractive state or a non-diffractive state. In some embodiments, each of polarization switches 1250a-1250f can be configured to have substantially the same size as the corresponding sub-grating. Each of polarization switches 1250a-1250f can be aligned with the corresponding sub-grating. Adjacent in-coupling sub-gratings can partially overlap each other, and adjacent polarization switches corresponding to adjacent in-coupling sub-gratings can partially overlap each other. Adjacent out-coupling sub-gratings can partially overlap each other, and corresponding adjacent polarization switches corresponding to adjacent out-coupling sub-gratings can partially overlap each other. In some embodiments, polarization switches 1250a-1250f can be configured to have substantially the same size.

[0153] In some embodiments, as FIGS. 12A-12CAs shown, the light source assembly 205 can emit unpolarized image light having a predetermined FOV. In some embodiments, a linear polarizer 1240 can be disposed between the light source assembly 205 and the waveguide 1201 to convert the unpolarized image light into linearly polarized image light. In some embodiments, depending on the transmission axis of the linear polarizer 1240, the linearly polarized image light can be configured to have a first polarization (e.g., polarized in the x-direction as shown in FIGS. 12A-12C FIG. 13B) or a second polarization orthogonal to the first polarization (e.g., polarized in the y-direction as shown in FIG. 12A FIG. 13C). The display frame can be divided into three sub-frames. During each corresponding sub-frame, a respective pair of sub-gratings can be sequentially configured to operate in a diffractive state via the corresponding polarization switch to transmit a respective portion of the FOV via the waveguide 1201. During at least one (e.g., each) of the three sub-frames, one of the three pairs of sub-gratings can be configured to operate in a diffractive state to transmit a predetermined portion of the FOV, and the remaining pairs can be configured to operate in a non-diffractive state.

[0154] In some embodiments, the adjacent in-coupling sub-gratings coupled with the waveguide 1201 can be configured to selectively diffract light having orthogonal polarizations (e.g., orthogonal linear polarizations). The adjacent out-coupling sub-gratings coupled with the waveguide 1201 can be configured to selectively diffract light having orthogonal polarizations (e.g., orthogonal linear polarizations). In some embodiments, the pair of sub-gratings configured to transmit a predetermined portion of the FOV can be configured to diffract light having the same first polarization and to transmit light having a second polarization orthogonal to the first polarization in a diffractively negligible manner. In some embodiments, during each sub-frame, a single pair of in-coupling and out-coupling sub-gratings can be configured to operate in a diffractive state, while the remaining pairs can be configured to operate in a non-diffractive state. The three portions of the FOV can be transmitted in a time-sequential manner in three consecutive sub-frames, with crosstalk between adjacent sub-gratings being suppressed. The three portions of the FOV delivered to the eye 265 can have different polarizations.

[0155] For example, during the first sub-frame, with reference to FIG. 12BDuring the first sub-frame, the first in-coupling sub-grating 1205a and the first out-coupling sub-grating 1210a can be indirectly switched to the diffractive state (or ON state) via the respective polarization switches 1250a and 1250d. The remaining sub-gratings can be switched to the non-diffractive state (or OFF state) via the respective polarization switches. As a result, image light located in the angular range encompassed by light ray 1220 can be in-coupled into the TIR path inside the waveguide 1201 via the first in-coupling sub-grating 1205a and out-coupled from the waveguide 1201 via the first out-coupling sub-grating 1210a into the angular range encompassed by light ray 1220’, which can be received by the eye 265. Image light located in the angular range encompassed by light ray 1225 and the angular range encompassed by light ray 1230 can not be in-coupled into the TIR path inside the waveguide 1201. The angular range encompassed by light ray 1220’ can correspond to the left portion of the FOV.

[0156] During the second sub-frame, the reference FIG. 12C , the second in-coupling sub-grating 1205b and the second out-coupling sub-grating 1210b can be indirectly switched to the diffractive state (or ON state) via the polarization switches 1250b and 1250e, respectively. The remaining sub-gratings can be switched to the non-diffractive state (or OFF state) via the respective polarization switches. As a result, image light located in the angular range encompassed by light ray 1225 can be in-coupled into the TIR path in the waveguide 1201 via the second in-coupling sub-grating 1205b and out-coupled from the waveguide 1201 via the second out-coupling sub-grating 1210b into the angular range encompassed by light ray 1225’, which can be received by the eye 265. Image light located in the angular range encompassed by light ray 1220 and the angular range encompassed by light ray 1230 can not be in-coupled into the TIR path inside the waveguide 1201. The angular range encompassed by light ray 1225’ can correspond to the middle portion of the FOV.

[0157] During the third sub-frame, the reference FIGS. 12A-12CThe third in-coupling sub-grating 1205c and the third out-coupling sub-grating 1210c can be indirectly switched to the diffractive state (or the ON state) via the polarization switches 1250c and 1250f, respectively. The remaining sub-gratings can be switched to the non-diffractive state (or the OFF state) via the corresponding polarization switches. Thus, image light located in the angular range encompassed by light ray 1230 can be in-coupled into the TIR path inside the waveguide 1201 via the third in-coupling sub-grating 1205c and out-coupled from the waveguide 1201 into the angular range encompassed by light ray 1230’ via the third out-coupling sub-grating 1210c, which can be received by the eye 265. Image light located in the angular range encompassed by light ray 1220 and the angular range encompassed by light ray 1225 can not be in-coupled into the TIR path inside the waveguide 1201. The angular range encompassed by light ray 1230’ can correspond to the right portion of the FOV.

[0158] Referring back to FIG. 12A, FIGS. 12A-12C In some embodiments, the optical system 1200 can include a polarizer 1260 (e.g., a clean-up polarizer) disposed on the side of the out-coupling grating 1210 facing the eye 265 to reduce or eliminate ghost images. In some embodiments, the polarizer 1260 can be a patterned polarizer with local polarization directions corresponding to the polarization of the respective portions of the FOV delivered by the corresponding pairs of sub-gratings. For example, the polarizer 1260 can be divided into three portions with different transmission axis orientations for different out-coupling sub-gratings. In some embodiments, the polarizer 1260 can be a uniform (e.g., unpatterned) polarizer, and additional polarization switches can be disposed between the polarizer 1260 and the out-coupling grating 1210 to convert the image light coupled out by the out-coupling sub-gratings into image light with the same polarization.

[0159] In some embodiments, adjacent in-coupling sub-gratings coupled with the waveguide 1201 can be configured to selectively diffract light with orthogonal polarizations (e.g., orthogonal linear polarizations), and adjacent out-coupling sub-gratings coupled with the waveguide 1201 can be configured to selectively diffract light with the same polarization. Each out-coupling sub-grating 1210a, 1210c, or 1210c can be controlled by the corresponding polarization switch 1250d, 1250e, or 1250f to operate in the diffractive state during the corresponding sub-frame. The three portions of the FOV delivered to the eye 265 can have substantially the same polarization. The polarizer 1260 can be configured to be a uniform (unpatterned) polarizer to reduce or eliminate ghost images. In some embodiments, the polarizer 1260 can be omitted.

[0160] Although not shown, in some embodiments, the FOV can include a suitable number of portions, e.g., four portions or five portions, etc. The waveguide 1201 can include a suitable number of pairs of sub-gratings (e.g., four pairs or five pairs, etc.) to transmit a suitable number of portions of the FOV. Adjacent portions of the FOV can partially overlap to form a continuous FOV at the eye 265. Accordingly, a display frame can be divided into a suitable number of sub-frames (e.g., four sub-frames or five sub-frames, etc.). During each corresponding sub-frame, a respective pair of sub-gratings can be sequentially configured to operate in a diffractive state via a corresponding polarization switch to transmit a respective portion of the FOV via the waveguide 1201.

[0161] In some embodiments, the light source assembly 205 can emit linearly polarized image light having a first polarization (e.g., polarized in the x-direction shown in FIGS. 12A-12C FIG. 1A) or a second polarization orthogonal to the first polarization (e.g., polarized in the y-direction shown in FIG. 12D FIG. 1A), and the linear polarizer 1240 can be omitted. The power efficiency of the optical system 1200 can be improved.

[0162] FIG. 12E and FIG. 12A FIG. 13 shows a schematic diagram of an overlapping configuration of in-coupling sub-gratings coupled to the waveguide 1201 shown in FIG. 12D FIG. 1A. The in-coupling sub-gratings can include any of the disclosed plurality of indirect switchable gratings (which can be passive gratings in some embodiments). In some embodiments, one or more of the in-coupling sub-gratings can be disposed in different planes such that adjacent in-coupling sub-gratings can partially overlap each other. The space around the in-coupling sub-gratings can be at least partially filled with an index-matching material. In one embodiment, as shown in FIG. 12E FIG. 13A, at least two (e.g., all three) of the in-coupling sub-gratings 1205a, 1205b, and 1205c can be disposed in different planes such that at least two adjacent in-coupling sub-gratings can partially overlap each other. The space around the in-coupling sub-gratings can be at least partially filled with an index-matching material 1270 such that light reflection within the space can be suppressed. In one embodiment, as shown in FIG. 12A FIG. 13B, the first in-coupling sub-grating 1205a and the third in-coupling sub-grating 1205c can be disposed in the same plane, while the second in-coupling sub-grating 1205b can be disposed in a different plane such that adjacent in-coupling sub-gratings can partially overlap each other. The out-coupling sub-gratings coupled to the waveguide 1201 in FIG. 12D FIG. 1A can be similar to the overlapping configuration of the in-coupling sub-gratings shown in FIG. 12E and FIG. 13A FIGS. 13 and 13A-13C.

[0163] FIG. 13B and FIGS. 2A-2BAn optical system 1300 including a waveguide stack 1301 according to an embodiment of the present disclosure is shown. The waveguide stack 1301 is configured to deliver different portions of the field of view (FOV) to the eye-fit frame of the optical system 1300 in a time-division multiplexing manner. The waveguide stack 1301 may include a stack of multiple waveguides, each waveguide being compatible with... FIG. 11 A Waveguide 210 shown in the figure FIG. 12A Waveguide 1101 or shown in the figure FIG. 2A The waveguide 1201 shown is similar. Further details will not be repeated. FIG. 11 A , FIG. 12A , FIG. 13A and FIG. 13A The description of the same or similar structures and / or components between the embodiments shown. FIG. 13A As shown, waveguide stack 1301 may include multiple waveguides stacked together (e.g., two waveguides 1310 and 1320). Other suitable numbers of waveguides may be used, such as three, four, five, etc. Waveguide 1310 may be coupled to an input grating 1312 and an output grating 1314. Waveguide 1320 may be coupled to an input grating 1322 and an output grating 1324. In some embodiments, waveguides 1310 and 1320 may be separated by an air gap for waveguiding within the waveguides. In some embodiments, the air gap between waveguides 1310 and 1320 may be at least partially filled with a material (e.g., liquid adhesive) with a refractive index lower than that of the waveguide. Any grating or sub-grating included in the optical system 1300 may be an embodiment of any of the disclosed plurality of indirectly switchable gratings (which may be passive gratings in some embodiments).

[0164] The image light emitted from the light source assembly 205 may include rays corresponding to the left and right portions of the field of view (FOV). The angular ranges enclosed by ray 1370 and ray 1380 may respectively correspond to the left and right portions of the FOV of the image light. In some embodiments, the display frame of the image light may be divided into two subframes for sequentially transmitting rays corresponding to different portions of the FOV, thereby achieving sequential transmission of the two portions of the FOV in a time-division multiplexing manner.

[0165] At least one of the coupling-in grating or coupling-out grating can be an embodiment of the disclosed indirect switchable grating (in some embodiments, it can be a passive grating). The coupling-in grating or coupling-out grating can be disposed on a first surface and / or a second surface of its respective waveguide. For purposes of discussion, as FIG. 13AAs shown, the in-coupling gratings and out-coupling gratings coupled to the waveguide stack 1301 can be indirectly switchable gratings (which can be passive gratings in some embodiments), and can be disposed at the second surfaces of the respective waveguides. The in-coupling grating 1312 and the in-coupling grating 1322 can be configured to diffract image light having two predetermined orthogonal polarizations, for example, a second polarization (e.g., polarized in the y-direction as shown in FIG. 13A ) and a first polarization (e.g., polarized in the x-direction as shown in FIG. 13A ). The out-coupling grating 1314 and the out-coupling grating 1324 can have the same polarization selectivity as the in-coupling grating 1312 and the in-coupling grating 1322, respectively.

[0166] In some embodiments, the light source assembly 205 can emit unpolarized image light. A linear polarizer 1340 can be disposed between the light source assembly 205 and the waveguide stack 1301 to convert the unpolarized image light into linearly polarized image light having a first polarization (e.g., polarized in the x-direction as shown in FIG. 13A ) or a second polarization orthogonal to the first polarization (e.g., polarized in the y-direction as shown in FIG. 13A ). A polarization rotator or a polarization switch 1350 can be disposed between the linear polarizer 1340 and the waveguide stack 1301. The polarization switch 1350 can be an active element configured to switch the polarization of the received linearly polarized image light from the linear polarizer 1340 between the first polarization and the second polarization according to an operating state (e.g., a switched state or a non-switched state) of the polarization switch 1350. In some embodiments, the light source assembly 205 can emit linearly polarized image light having a first polarization (e.g., polarized in the x-direction as shown in FIG. 13A ) or a second polarization orthogonal to the first polarization (e.g., polarized in the y-direction as shown in FIG. 13A ), and the linear polarizer 1340 can be omitted. The power efficiency of the optical system 1200 can be improved.

[0167] During the first sub-frame, referring to FIG. 13B , the polarization switch 1350 can be configured to operate in a non-switched state to transmit the received linearly polarized image light from the linear polarizer 1340 with the first polarization (e.g., polarized in the x-direction as shown in FIG. 13Apolarized image light having the first polarization can be diffracted by the in-coupling grating 1322 and can be transmitted by the in-coupling grating 1312 in a diffractively negligible or non-diffractive manner. Thus, image light located within the angular range encompassed by light ray 1370 can be in-coupled into TIR within the waveguide 1320 via the in-coupling grating 1322 and out-coupled from the waveguide 1320 via the out-coupling grating 1324 into the angular range encompassed by light ray 1370’, which can be received by the eye 265. Image light located in the angular range encompassed by light ray 1380 can not be in-coupled into TIR within the waveguide 1310. The angular range encompassed by light ray 1370’ can correspond to the left portion of the FOV. That is, the left portion of the FOV can be replicated at an eyebox located at an exit pupil of the eye 265. In some embodiments, a polarizer 1360 can be disposed at a surface of the out-coupling grating 1314 facing the waveguide 1320 to suppress ghost images that can be caused by light diffracted by gratings configured for different portions of the FOV. In some embodiments, the polarizer 1360 can be omitted.

[0168] During the second sub-frame, the reference FIG. 13B polarization switch 1350 can be configured to operate in the switched state to convert linearly polarized image light having the first polarization (e.g., polarized in the x-direction) to linearly polarized image light having the second polarization (e.g., polarized in the y-direction) toward the waveguide stack 1301. Thus, linearly polarized image light having the second polarization can not be diffracted by the in-coupling grating 1322 and can be transmitted by the in-coupling grating 1322 in a diffractively negligible or non-diffractive manner. Thus, image light located within the angular range encompassed by light ray 1380 can be in-coupled into TIR within the waveguide 1310 via the in-coupling grating 1312 and out-coupled from the waveguide 1310 via the out-coupling grating 1314 into the angular range encompassed by light ray 1380’, which can be received by the eye 265. Image light located in the angular range encompassed by light ray 1370 can not be in-coupled into TIR within the waveguide 1320. The angular range encompassed by light ray 1380’ can correspond to the right portion of the FOV. That is, the right portion of the FOV can be replicated at an eyebox located at an exit pupil of the eye 265.

[0169] Referring back to FIG. 13A and FIG. 13BIn some embodiments, the in-coupling grating 1312, the in-coupling grating 1322, the out-coupling grating 1314, and the out-coupling grating 1324 can be configured to have substantial angular selectivity and polarization selectivity, such that the optical system 1300 can be configured to simultaneously deliver different portions of the FOV to the eyebox of the optical system 1300, e.g., in a polarization multiplexed manner, within the same time period (e.g., the same display frame). The display frame can not be divided into sub-frames. For example, the in-coupling grating 1322 and the out-coupling grating 1324 coupled to the waveguide 1320 can be configured to diffract image light having an angular range corresponding to a first portion (e.g., the left portion) of the FOV and having a first polarization (e.g., polarization in the x-direction shown in FIG. 13A and FIG. 13B ). The in-coupling grating 1322, the out-coupling grating 1324, and the waveguide 1320 can be configured to transmit image light having an angular range corresponding to a second portion (e.g., the right portion) of the FOV and having a second polarization (e.g., polarization in the y-direction shown in FIG. 13A and FIG. 13B ) with negligible diffraction. The in-coupling grating 1312 and the out-coupling grating 1314 coupled to the waveguide 1310 can be configured to diffract image light having an angular range corresponding to the second portion (e.g., the right portion) of the FOV and having the second polarization (e.g., polarization in the y-direction shown in FIG. 13A and FIG. 13B ). The in-coupling grating 1312, the out-coupling grating 1314, and the waveguide 1310 can be configured to transmit image light having an angular range corresponding to the first portion (e.g., the left portion) of the FOV and having the first polarization (e.g., polarization in the x-direction shown in FIG. 14A and FIG. 14B ) with negligible diffraction.

[0170] In some embodiments, the light source assembly 205 can emit unpolarized image light toward the waveguide stack 1301. The polarizer 1340 and the polarization switch 1350 can be omitted. The unpolarized image light can include a first portion having an angular range corresponding to a first portion of the FOV of the unpolarized image light and a second portion having an angular range corresponding to a second portion of the FOV of the unpolarized image light. Each of the first and second portions of the unpolarized image light can include two components: a first component having a first polarization and a second component having a second polarization. When the unpolarized image light emitted by the light source assembly 205 is incident on the waveguide stack 1301, image light having an angular range corresponding to the left portion of the FOV (e.g., enclosed by light ray 1370) and having the first polarization, which is the first component of the first portion of the unpolarized image light, can be coupled-in via the in-coupling sub-grating 1322 into a TIR path inside the waveguide 1320 and out-coupled from the waveguide 1320 via the out-coupling sub-grating 1324 into an angular range enclosed by light ray 1370’, which can be received by the eye 265. Image light having an angular range corresponding to the right portion of the FOV (e.g., enclosed by light ray 1380) and having the second polarization, which is the second component of the second portion of the unpolarized image light, can be coupled-in via the in-coupling sub-grating 1312 into a TIR path inside the waveguide 1310 and out-coupled from the waveguide 1310 via the out-coupling sub-grating 1314 into an angular range enclosed by light ray 1380’, which can be received by the eye 265. At the output side of the waveguide stack 1301, the angular range included by light ray 1370’ can correspond to the left portion of the FOV and the angular range enclosed by light ray 1380’ can correspond to the right portion of the FOV. Thus, the two portions of the FOV of the unpolarized image light emitted by the light source assembly 205 can be delivered to the eye box simultaneously.

[0171] In some embodiments, as shown in FIGS. 13A and 13B, the in-coupling gratings and the out-coupling gratings can be stacked and attached to a common (e.g., single) waveguide, rather than being stacked in a waveguide stack. FIG. 14A FIG. 14B FIG. 13A FIG. 13B FIGS. 14A and 14B show an optical system 1400 including a waveguide 1401 configured to deliver different portions of a FOV in a time-division multiplexed manner, according to another embodiment of the disclosure. The description of similar or identical structures and / or components between the embodiments shown in FIGS. 13A and 13B and the embodiments shown in FIGS. 14A and 14B will not be repeated. FIG. 14A FIG. 14B FIG. 14A FIG. 13A FIG. 13B ​​​​​​​As shown, the in-coupling gratings 1412 and 1422 can be superimposed on the first surface or the second surface of the waveguide 1401. The out-coupling gratings 1414 and 1424 can be superimposed on the first surface or the second surface of the waveguide 1401. The in-coupling gratings 1412 and 1422 and the out-coupling gratings 1414 and 1424 can be disposed on the same surface or different surfaces of the waveguide 1401. In some embodiments, the optical system 1400 can be configured to deliver the left and right portions of the FOV in a time-division multiplexing manner. The operation principle of the optical system 1400 including the waveguide 1401 for implementing the time-sequential transmission of the left and right portions of the FOV can be similar to the operation principle described above for the embodiments shown in FIGS. 13A and 13B. FIG. 13A and FIG. 13B The operation principle of the optical system 1400 including the waveguide 1401 for implementing the time-sequential transmission of the left and right portions of the FOV can be similar to the operation principle described above for the embodiments shown in FIGS. 13A and 13B.

[0172] In some embodiments, the light source assembly 205 can emit unpolarized image light toward the waveguide 1401. The polarizer 1440 and the polarization switch 1450 can be omitted. The in-coupling gratings 1412 and 1422 and the out-coupling gratings 1414 and 1424 can be configured to have substantial angular selectivity and polarization selectivity, such that the optical system 1400 can be configured to deliver different portions of the FOV of the unpolarized image light emitted by the light source assembly 205 to the eyebox simultaneously in a polarization-division multiplexing manner. The operation principle of the optical system 1400 including the waveguide 1401 for implementing the simultaneous delivery of the left and right portions of the FOV of the unpolarized image light emitted by the light source assembly 205 to the eyebox can be similar to the operation principle described above for the embodiments shown in FIGS. 14A and 14B. FIGS. 15A-15C and FIG. 2A The operation principle of the optical system 1400 including the waveguide 1401 for implementing the time-sequential transmission of the left and right portions of the FOV can be similar to the operation principle described above for the embodiments shown in FIGS. 13A and 13B.

[0173] FIG. 2B An optical system 1500 including a waveguide stack 1501 to deliver different portions (e.g., three portions) of a FOV in a time-division multiplexing manner is shown according to another embodiment of the present disclosure. The waveguide stack 1501 can be an embodiment of the waveguide 210 shown in FIGS. 21A and 21B. The description of the similar or identical structures and / or components between the embodiments shown in FIGS. 21A and 21B and the embodiments shown in FIGS. 22A and 22B is not repeated again. Any one of the multiple gratings or sub-gratings included in the optical system 1500 can be an embodiment of any one of the disclosed multiple indirectly switchable gratings (which can be passive gratings in some embodiments). FIGS. 15A-15C and FIG. 13A The operation principle of the optical system 1500 including the waveguide stack 1501 for implementing the time-sequential transmission of the different portions of the FOV can be similar to the operation principle described above for the embodiments shown in FIGS. 21A and 21B. FIG. 13B The operation principle of the optical system 1500 including the waveguide stack 1501 for implementing the time-sequential transmission of the different portions of the FOV can be similar to the operation principle described above for the embodiments shown in FIGS. 21A and 21B. FIG. 15A and FIG. 15A The operation principle of the optical system 1500 including the waveguide stack 1501 for implementing the time-sequential transmission of the different portions of the FOV can be similar to the operation principle described above for the embodiments shown in FIGS. 21A and 21B.

[0174] As FIG. 15AAs shown, the waveguide stack 1501 may include three waveguides 1510, 1520, and 1530, configured to transmit the left, middle, and right portions of the field of view (FOV), respectively. At least one of waveguides 1510, 1520, or 1530 (e.g., each) may include a coupling grating and a coupling grating disposed on the same or different surfaces of the waveguide stack 1501. In some embodiments, at least one (e.g., each) coupling grating may be coupled to a polarization switch, allowing the coupling grating to be indirectly switched between a diffractive state and a non-diffractive state via the polarization switch. The polarization switch may be disposed on one side of the corresponding coupling grating, from which image light is incident onto the coupling grating, thereby controlling the polarization of the image light incident onto the corresponding coupling grating. For example, polarization switches 1516, 1526, and 1536 may correspond to coupling gratings 1512, 1522, and 1532, respectively. In some embodiments, at least one of a plurality of coupling gratings (e.g., each) may be coupled to a polarization switch disposed on one side of the corresponding coupling grating from which image light exits. That is, the polarization switch may be disposed on the side of the respective grating facing the eye 265. In some embodiments, at least one of a plurality of coupling gratings (e.g., each) may be coupled to a polarization switch disposed on the side of the corresponding coupling grating from which image light exits, thereby controlling the polarization of the image light exiting the corresponding coupling grating. For example, in FIGS. 15A-15C In the embodiment shown, polarization switches 1528 and 1538 may correspond to coupling gratings 1524 and 1534 respectively, and the polarization switch corresponding to coupling grating 1514 may be omitted.

[0175] The coupling-in grating and coupling-out grating coupled to the waveguide stack 1501 can be configured to diffract image light having the same polarization (e.g., a first polarization) or different polarizations. In some embodiments, the direction of the first polarization can be located at... FIG. 15A The x-direction is shown in the diagram. For the purposes of discussion, in... FIG. 15A In this configuration, the input and output gratings coupled to the waveguide stack 1501 can be configured to diffract image light with the same polarization, for example, a first polarization (e.g., in...). FIG. 15A (Polarization in the x-direction shown). The light source assembly 205 can emit unpolarized image light, and a linear polarizer 1540 can be disposed between the light source assembly 205 and the waveguide stack 1501 to convert the unpolarized image light into light with a predetermined polarization direction (e.g., in...). FIG. 15A The image shown is a linearly polarized image of light or ray (polarized in the x-direction).

[0176] In some embodiments, such as FIG. 15AAs shown, the light source assembly 205 can emit unpolarized image light, and a linear polarizer 1540 can be disposed between the light source assembly 205 and the waveguide stack 1501 to convert the unpolarized image light into linearly polarized image light or light rays having a predetermined polarization direction (e.g., polarized in the x-direction shown in FIG. 1), such as first polarization (e.g., polarized in the x-direction shown in FIG. 15A FIG. 1) or second polarization (e.g., polarized in the y-direction shown in FIG. 15A FIG. 1). In some embodiments, the light source assembly 205 can emit linearly polarized image light having a first polarization (e.g., polarized in the x-direction shown in FIGS. 15A-15C FIG. 1) or a second polarization orthogonal to the first polarization (e.g., polarized in the y-direction shown in FIG. 15A FIG. 1), and the linear polarizer 1540 can be omitted. For example, the light source assembly 205 can be a liquid crystal display, or a laser used in a laser scanning display. The power efficiency of the optical system 1500 can be improved.

[0177] In some embodiments, a display frame can be divided into three sub-frames. In some embodiments, the light source assembly 205 can emit light rays 1570, 1575, and 1580 corresponding to different portions (e.g., left, middle, and right portions) of the FOV in the three sub-frames, respectively. In some embodiments, as shown in FIG. 15B FIG. 1, the light source assembly 205 can emit light rays 1570, 1575, and 1580 corresponding to different portions (e.g., left, middle, and right portions) of the FOV simultaneously during each sub-frame. In some embodiments, in order to deliver a continuous FOV to the eyebox, the angular spectrum of the in-coupling gratings 1512, 1522, and 1532 can slightly overlap with each other, and the angular spectrum of the out-coupling gratings 1514, 1524, and 1534 can slightly overlap with each other.

[0178] Referring to FIG. 15C FIG. 1, during the first sub-frame, the polarization switch 1536 coupled to the in-coupling grating 1532 at the waveguide 1530 can operate in a non-switching state to transmit the light rays 1570 having the first polarization in a manner that does not affect or switch the polarization. Since both the in-coupling grating 1532 and the out-coupling grating 1534 can be configured to diffract image light having the first polarization and to transmit image light having the second polarization in a manner that is negligibly diffractive or non-diffractive, the light rays 1570 having the first polarization can be in-coupled into a TIR path within the waveguide 1530 via the in-coupling grating 1532 and out-coupled from the waveguide 1530 into an angular range encompassed by the light rays 1570’ via the out-coupling grating 1534, which can be received by the eye 265. The angular range encompassed by the light rays 1570’ can correspond to the left portion of the FOV.

[0179] Light rays 1575 and 1580 with the first polarization can not be coupled into the TIR path inside waveguide 1530 via in-coupling grating 1532 and can be transmitted by waveguide 1530 toward waveguide 1520. Polarization switch 1526 coupled to in-coupling grating 1522 at waveguide 1520 can operate in a switching state to convert light rays 1575 and 1580 with the first polarization to light rays with the second polarization. Since in-coupling grating 1522 is configured to diffract image light with the first polarization and to transmit image light with the second polarization with negligible or no diffraction, light rays with the second polarization output from polarization switch 1526 can not be coupled into the TIR path inside waveguide 1520 and can be transmitted through waveguide 1520 toward waveguide 1510.

[0180] Polarization switch 1516 coupled to in-coupling grating 1512 at waveguide 1510 can operate in a non-switching state. Thus, received light rays with the second polarization from waveguide 1520 can maintain the second polarization after being transmitted through polarization switch 1516. Since in-coupling grating 1512 can be configured to diffract image light with the first polarization and to transmit light with the second polarization with negligible or no diffraction, light rays with the second polarization output from polarization switch 1516 can not be coupled into the TIR path inside waveguide 1510 and can be transmitted. Polarization switches 1538, 1528, and 1518 coupled to out-coupling gratings 1534, 1524, and 1514, respectively, can operate in a non-switching state, which can not switch the polarization of image light transmitted through these polarization switches. Thus, during the first sub-frame, light rays 1570 with the first polarization can be directed toward eye 265 via waveguide 1530, through which the left portion of the FOV can be replicated at the eyebox located at the exit pupil of eye 265.

[0181] Reference FIG. 15CDuring the second sub-frame, the polarization switch 1536 coupled to the in-coupling grating 1532 at the waveguide 1530 can operate in the switching state to convert the light rays 1570, 1575, and 1580 having the first polarization to light rays 1570, 1575, and 1580 having the second polarization. The light rays 1570, 1575, and 1580 having the second polarization can not be in-coupled into the TIR paths inside the waveguide 1530. Instead, the light rays 1570, 1575, and 1580 having the second polarization can transmit through the waveguide 1530 towards the waveguide 1520. The polarization switch 1526 coupled to the out-coupling grating 1522 at the waveguide 1520 can operate in the switching state to convert the light rays 1570, 1575, and 1580 having the second polarization to light rays 1570, 1575, and 1580 having the first polarization. The light ray 1575 having the first polarization can be in-coupled into the TIR paths inside the waveguide 1520 via the in-coupling grating 1522 and out-coupled from the waveguide 1520 via the out-coupling grating 1524 as a light ray having the first polarization. The light rays 1570 and 1580 having the first polarization can not be in-coupled into the TIR paths inside the waveguide 1520 via the in-coupling grating 1522 and can transmit through the waveguide 1520.

[0182] On the out-coupling side of the waveguide stack 1501, the polarization switch 1528 coupled to the out-coupling grating 1524 at the waveguide 1520 can operate in the switching state to convert the light ray 1575 having the first polarization output from the out-coupling grating 1524 to a light ray 1575’ having the second polarization towards the waveguide 1530. The light ray 1575’ having the second polarization transmitted from the polarization switch 1528 can not be in-coupled into the TIR paths inside the waveguide 1530. Instead, the light ray 1575’ having the second polarization can directly transmit through the waveguide 1530 towards the polarization switch 1538.

[0183] In some embodiments, the polarization switch 1538 coupled to the out-coupling grating 1534 at the waveguide 1530 can operate in the switching state to convert the light ray 1575’ having the second polarization to a light ray having the first polarization located within an angular range encompassed by the light ray 1575’ that can be received by the eye 265 towards the eye 265. The angular range encompassed by the light ray 1575’ can correspond to the middle portion of the FOV.

[0184] Returning to the coupling side of the reference waveguide stack 1501, the polarization switch 1516, coupled to the coupling grating 1512 at waveguide 1510, can operate in a switching state to convert light rays 1570 and 1580 with first polarization (i.e., light rays 1570 and 1580 with first polarization that are transmitted through waveguide 1520 toward waveguide 1510) that are not coupled into the TIR path inside waveguide 1520 into light rays with second polarization. The light rays 1570 and 1580 with second polarization may not be coupled into the TIR path inside waveguide 1510. Instead, the light rays 1570 and 1580 with second polarization can be transmitted through waveguide 1510. Thus, during the second subframe, the light ray 1575 with first polarization can be directed toward the eye 265 via waveguide 1520, through which the center of the FOV can be replicated at the eye frame located at the exit pupil of the eye 265.

[0185] refer to FIG. 15C During the third subframe, the polarization switch 1536, coupled to the coupling grating 1532 at waveguide 1530, can operate in a switching state to convert light rays 1570, 1575, and 1580 with first polarization into light rays 1570, 1575, and 1580 with second polarization. The light rays 1570, 1575, and 1580 with second polarization may not be coupled into the TIR path inside waveguide 1530. Instead, the light rays 1570, 1575, and 1580 with second polarization can be transmitted through waveguide 1530 toward waveguide 1520.

[0186] exist FIG. 15C In the embodiment shown, the polarization switch 1526, coupled to the coupling grating 1522 at waveguide 1520, can operate in a non-switching state to transmit light rays 1570, 1575, and 1580 with a second polarization in a manner that does not affect or switch the polarization of the light rays. The second-polarized light rays 1570, 1575, and 1580 output from polarization switch 1526 can not be coupled into the TIR path inside waveguide 1520. Instead, the second-polarized light rays 1570, 1575, and 1580 output from polarization switch 1526 can be transmitted through waveguide 1520 toward waveguide 1510.

[0187] exist FIGS. 15A-15CIn the embodiment shown, the polarization switch 1516, coupled to the coupling grating 1512 at waveguide 1510, can operate in a switching state to convert light rays 1570, 1575, and 1580, transmitted from waveguide 1520 and having a second polarization, into light rays having a first polarization. The light ray 1580, output from polarization switch 1516 and having a first polarization, can be coupled into a TIR path within waveguide 1510 via coupling grating 1512 and coupled out of waveguide 1510 via coupling grating 1514 as light ray 1580', having a first polarization. The light rays 1570 and 1575, output from polarization switch 1516 and having a first polarization, can be coupled into a TIR path within waveguide 1510 without coupling via coupling grating 1512 and can be transmitted through waveguide 1510.

[0188] On the output side of the waveguide stack 1501, a polarization switch 1518 coupled to the output grating 1514 at waveguide 1510 can operate in a switching state to convert the light ray 1580' with a first polarization output from the output grating 1514 toward waveguide 1520 into a light ray 1580' with a second polarization. The light ray 1580' with the second polarization output from the polarization switch 1518 can not be coupled into the TIR path inside waveguide 1520. Instead, the light ray 1580' with the second polarization can be transmitted toward waveguide 1530 through waveguide 1520 and output grating 1524.

[0189] exist FIGS. 15A-15C In the illustrated embodiment, the polarization switch 1528, coupled to the coupling grating 1524 at waveguide 1520, can operate in a non-switching state to transmit the second-polarized light ray 1580' transmitted from waveguide 1520 in a manner that does not affect or switch the polarization of the light. The second-polarized light ray 1580' output from polarization switch 1528 may not be coupled into the TIR path inside waveguide 1530. Instead, the second-polarized light ray 1580' can be transmitted toward polarization switch 1538 through waveguide 1530 and coupling grating 1534.

[0190] In some embodiments, the polarization switch 1538 coupled to the out-coupling grating 1534 at the waveguide 1530 can operate in a switching state to convert light rays 1580’ having the second polarization output from the out-coupling grating 1538 to light rays 1580’ having the first polarization towards the eye 265 within an angular range encompassed by the light rays 1580’. The angular range encompassed by the light rays 1580’ can correspond to the right portion of the FOV that can be viewable by the eye 265. Thus, during the third sub-frame, light rays 1580 having the first polarization can be directed towards the eye 265 via the waveguide 1510 through which the right portion of the FOV can be replicated at the eyebox located at the exit pupil of the eye 265. Thus, during a display frame (which includes three sub-frames), sequential transmission of image light corresponding to different portions of the FOV can be achieved and the eye 265 can observe a complete FOV in one polarization (e.g., the first polarization). Furthermore, the time-division multiplexing achieved by the disclosed indirect switchable grating (which can be a passive grating in some embodiments) can eliminate cross-talk in the waveguide stack 1501. Thus, the optical performance of the waveguide display assembly including the waveguide stack 1501 can be enhanced. FIGS. 15A-15C The principles illustrated in FIGS. 15A-15C for splitting the FOV into three portions and delivering the three portions to the eyebox in a time sequence can be extended to splitting the FOV into more than three portions and delivering the more than three portions to the eyebox in a time sequence.

[0191] Referring back to FIGS. 16A-16CIn some embodiments, the angular spectra of the input gratings 1512, 1522, and 1532 can be substantially non-overlapping, thereby minimizing or reducing crosstalk between the input gratings. Therefore, the polarization switches 1516, 1526, and 1536, respectively coupled to the input gratings 1512, 1522, and 1532, can be omitted. In some embodiments, the angular spectra of the output gratings 1514, 1524, and 1534 can be substantially non-overlapping, thereby minimizing or reducing crosstalk between the output gratings. Therefore, the polarization switches 1518, 1528, and 1538, respectively coupled to the output gratings 1514, 1524, and 1534, can be omitted. When the angular spectra of the input gratings 1512, 1522, and 1532 are substantially non-overlapping and the angular spectra of the output gratings 1514, 1524, and 1534 are also substantially non-overlapping, the input gratings 1512, 1522, or 1532 can be configured to couple image light having angular ranges corresponding to the respective portions of the field of view (FOV) into their respective waveguides 1510, 1520, or 1530, and the output gratings 1514, 1524, and 1534 can be configured to couple the coupled image light out of their respective waveguides 1510, 1520, or 1530. Therefore, the optical system 1500 can be configured to simultaneously deliver different portions (e.g., three portions) of the FOV of the image light emitted from the light source assembly 205. In some embodiments, the light source assembly 205 can emit unpolarized image light, and a linear polarizer 1540 can be disposed between the light source assembly 205 and the waveguide stack 1501 to convert the unpolarized image light into light with a predetermined polarization direction (e.g., a first polarization, e.g., in...). FIGS. 16A-16C The image light is linearly polarized in the x-direction, as shown in the diagram. The coupling gratings 1512, 1522, and 1532, and the output gratings 1514, 1524, and 1534 can have the same polarization selectivity; for example, they can diffract image light with a first polarization and transmit image light with a second polarization in a negligible diffraction manner. In some embodiments, the light source assembly 205 can be configured to emit unpolarized image light, and the polarizer 1540 can be omitted. The unpolarized image light can include two orthogonal polarization components. The coupling gratings 1512, 1522, and 1532 can be configured to have different polarization selectivities. Depending on the polarization selectivity of the coupling gratings 1512, 1522, and 1532, one component can be coupled into the corresponding waveguide through the coupling grating, while the other component can be transmitted in a negligible diffraction manner. The polarization selectivity of the output gratings 1514, 1524 and 1534 can be configured such that the output gratings 1514, 1524 and 1534 can couple the corresponding input image light out from the corresponding waveguide.

[0192] Although not shown, in some embodiments, the FOV can include a suitable number of portions, e.g., four portions or five portions, etc. The waveguide stack 1501 can include a suitable number of waveguides (e.g., four waveguides or five waveguides, etc.) coupled with respective in-coupling gratings and out-coupling gratings to transmit a suitable number of portions of the FOV. Adjacent portions of the FOV can partially overlap to form a continuous FOV at the eye 265. Accordingly, a display frame can be divided into a suitable number of sub-frames (e.g., four sub-frames or five sub-frames, etc.). During each sub-frame, respective pairs of gratings can be sequentially configured to operate in a diffractive state via respective polarization switches to transmit respective portions of the FOV via respective waveguides.

[0193] In some embodiments, instead of being disposed at respective waveguides in a waveguide stack, the in-coupling gratings and the out-coupling gratings can be respectively stacked and attached to a common (e.g., single) waveguide, as shown in FIGS. 16A-16C FIGS. 15A-15C An optical system 1600 including a single waveguide 1601 configured to convey different portions of a FOV in a time-division multiplexed manner is shown according to another embodiment of the present disclosure. The description of similar or identical structures and / or components between the embodiments shown in FIG. 16A FIG. 16A is not repeated. Any of the multiple gratings or sub-gratings included in the optical system 1600 can be an embodiment of any of the disclosed multiple indirectly switchable gratings (which can be passive gratings in some embodiments).

[0194] As shown in FIG. 16A , a plurality of in-coupling gratings 1612, 1622, and 1632 can be disposed at the first surface or the second surface of the waveguide 1601. The number of in-coupling gratings is not limited to three and can be any suitable number, e.g., two, four, five, six, etc. A plurality of out-coupling gratings 1614, 1624, and 1634 can be disposed at the first surface or the second surface of the waveguide 1601. The number of out-coupling gratings is not limited to three and can be any suitable number, e.g., two, four, five, six, etc. The plurality of in-coupling gratings 1612, 1622, and 1632 and the plurality of out-coupling gratings 1614, 1624, and 1634 can be disposed at the same surface or different surfaces of the waveguide 1601. As shown in FIGS. 15A-15C , the in-coupling gratings 1612, 1622, and 1632 can be respectively coupled to polarization switches 1616, 1626, and 1636. The number of polarization switches optically coupled with the in-coupling gratings can be the same as the number of in-coupling gratings or can be less than or greater than the number of in-coupling gratings. As shown in FIG. 16A ​​As shown, the out-coupling gratings 1614, 1624, and 1634 can be coupled to the polarization switches 1618, 1628, and 1638, respectively. The number of polarization switches optically coupled to the out-coupling gratings can be the same as the number of out-coupling gratings, or can be less than or greater than the number of out-coupling gratings. The operating principle for sequentially transmitting the left, middle, and right portions of the FOV through the waveguide 1601 in a time-division multiplexing manner, and the operating manner of the light source assembly 205, gratings, and corresponding polarization switches arranged at the waveguide 1601 can be similar to the above-described embodiments. FIG. 17A In some embodiments, the angular spectra of the in-coupling gratings 1612, 1622, and 1632 can substantially overlap with each other (e.g., slightly overlap) so that the continuous FOV can be delivered to the eyebox.

[0195] In some embodiments, the angular spectra of the in-coupling gratings 1612, 1622, and 1632 can substantially not overlap with each other so that the crosstalk between the in-coupling gratings can be minimized or reduced. Accordingly, the polarization switches 1616, 1626, and 1636 coupled to the in-coupling gratings 1612, 1622, and 1632, respectively, can be omitted. In some embodiments, the angular spectra of the out-coupling gratings 1614, 1624, and 1634 can substantially not overlap with each other so that the crosstalk between the out-coupling gratings can be minimized or reduced. Accordingly, the polarization switches 1618, 1628, and 1638 coupled to the out-coupling gratings 1614, 1624, and 1634, respectively, can be omitted. When the angular spectra of the in-coupling gratings 1612, 1622, and 1632 substantially do not overlap with each other and the angular spectra of the out-coupling gratings 1614, 1624, and 1634 substantially do not overlap with each other, the in-coupling gratings 1612, 1622, or 1632 can be configured to in-couple image light having an angular range corresponding to each portion of the FOV into the waveguide 1601, and the out-coupling gratings 1614, 1624, and 1634 can be configured to out-couple the in-coupled image light from the waveguide 1601. Accordingly, the optical system 1600 can be configured to simultaneously deliver different portions (e.g., three portions) of the FOV of the image light emitted from the light source assembly 205. In some embodiments, the light source assembly 205 can emit unpolarized image light, and a linear polarizer 1640 can be disposed between the light source assembly 205 and the waveguide 1601 to convert the unpolarized image light into image light having a predetermined polarization direction (e.g., in the x-direction) before the image light enters the waveguide 1601. FIGS. 17B-17DThe in-coupling gratings 1612, 1622, and 1632 and the out-coupling gratings 1614, 1624, and 1634 can be configured with the same polarization selectivity, e.g., can diffract image light having a first polarization and transmit image light having a second polarization in a diffractively negligible manner. In some embodiments, the light source assembly 205 can be configured to emit unpolarized image light, and the polarizer 1640 can be omitted. The unpolarized image light can include two orthogonal polarization components. The in-coupling gratings 1612, 1622, and 1632 can be configured with different polarization selectivity. Depending on the polarization selectivity of the in-coupling gratings 1612, 1622, and 1632, one component of the unpolarized image light can be coupled into the corresponding waveguide by the in-coupling gratings, while the other component can be transmitted through in a diffractively negligible manner. The polarization selectivity of the out-coupling gratings 1614, 1624, and 1634 can be configured such that the out-coupling gratings 1614, 1624, and 1634 can out-couple the corresponding in-coupled image light from the waveguide 1601.

[0196] Although not shown, in some embodiments, the FOV can include a suitable number of portions, e.g., four portions or five portions, etc. The waveguide 1601 can include a suitable number of grating pairs (e.g., four pairs or five pairs, etc.) to transmit a suitable number of portions of the FOV. Adjacent portions of the FOV can partially overlap to form a continuous FOV at the eye 265. Accordingly, a display frame can be divided into a suitable number of sub-frames (e.g., four sub-frames or five sub-frames, etc.). During respective sub-frames, respective grating pairs can be sequentially configured to operate in a diffractive state via the corresponding polarization switch to transmit respective portions of the FOV via the waveguide 1601.

[0197] FIG. 17A A schematic diagram of an optical system 1700 including a waveguide stack 1701 is shown. FIG. 15A A schematic diagram of an optical system 1700 including a waveguide stack 1701 is shown. FIG. 17A The optical system 1700 shown in FIG. 17A includes a waveguide stack 1701 configured to deliver single-color images of different colors in a time-division multiplexing manner. The waveguide stack 1701 can be similar to the waveguide stack 1501 shown in FIG. 15A. Accordingly, the description of the waveguide stack 1501 can also be applicable to the waveguide stack 1701. In some embodiments, as shown in FIG. 17A, the waveguide stack 1701 can include a first waveguide 1702, a second waveguide 1704, and a third waveguide 1706. The first waveguide 1702 can be configured to transmit a first color image, e.g., a red image. The second waveguide 1704 can be configured to transmit a second color image, e.g., a green image. The third waveguide 1706 can be configured to transmit a third color image, e.g., a blue image. FIG. 2A The waveguide stack 1501 shown in FIG. 15A can be similar to the waveguide stack 1701 shown in FIG. 17A. Accordingly, the description of the waveguide stack 1701 can also be applicable to the waveguide stack 1501. In some embodiments, as shown in FIG. 15A, the waveguide stack 1501 can include a first waveguide 1502, a second waveguide 1504, and a third waveguide 1506. The first waveguide 1502 can be configured to transmit a first color image, e.g., a red image. The second waveguide 1504 can be configured to transmit a second color image, e.g., a green image. The third waveguide 1506 can be configured to transmit a third color image, e.g., a blue image. FIG. 17AAs shown, waveguide stack 1701 can receive image light from one or more light source components (e.g., three light source components 1750, 1760, and 1770). At least one of light source components 1750, 1760, or 1770 (e.g., each) can emit monochromatic image light in a specific band corresponding to a primary color (e.g., red, green, or blue). For example, light source components 1750, 1760, and 1770 can emit monochromatic image light 1755, 1765, and 1775 in specific bands 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. Any of the plurality of gratings or sub-gratings included in optical system 1700 can be an embodiment of any of the disclosed plurality of indirectly switchable gratings (which, in some embodiments, can be passive gratings).

[0198] Light source assemblies 1750, 1760, and 1770 can be controlled by a controller (which can be connected to...) FIG. 17A (Similar to the controller 215 shown) to control the sequential emission of corresponding image lights. In some embodiments, the image light emitted from the light source assemblies 1750, 1760, and 1770 may be unpolarized image light. A linear polarizer 1740 may be disposed between the corresponding light source assembly and the waveguide stack 1701 to convert the unpolarized image light into linearly polarized image light with a predetermined polarization, such as, for example, a first polarization (e.g., in...). FIGS. 17A-17D (Polarization in the x-direction shown). In some embodiments, light source assemblies 1750, 1760, and 1770 may emit linearly polarized image light with a predetermined polarization, and the linear polarizer 1740 may be omitted. In some embodiments, monochromatic image light 1755, 1765, and 1775 in specific bands 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, may be emitted sequentially from a common light source assembly.

[0199] The waveguide 1710 can be coupled with an in-coupling grating 1712 and an out-coupling grating 1714, both of which are configured for a waveband corresponding to a first primary color (e.g., red). The waveguide 1720 can be coupled with an in-coupling grating 1722 and an out-coupling grating 1724, both of which are configured for a waveband corresponding to a second primary color (e.g., green). The waveguide 1730 can be coupled with an in-coupling grating 1732 and an out-coupling grating 1734, both of which are configured for a waveband corresponding to a third primary color (e.g., blue). At least one of the in-coupling gratings 1712, 1722, or 1732 and the out-coupling gratings 1714, 1724, or 1734 can include one or more of the disclosed indirectly switchable gratings (which can be passive gratings in some embodiments). For purposes of discussion, each of the in-coupling gratings 1712, 1722, and 1732 and the out-coupling gratings 1714, 1724, and 1734 includes a disclosed indirectly switchable grating (which can be a passive grating in some embodiments). The in-coupling gratings and the out-coupling gratings coupled to the waveguide stack 1701 can be configured to diffract light having the same predetermined polarization (e.g., a first polarization, polarized in the x-direction shown in FIG. 17A FIG. 1A, for example). For purposes of discussion, in the embodiment shown in FIG. 17A FIG. 1A, the in-coupling gratings and the out-coupling gratings coupled to the waveguide stack 1701 are configured to diffract light having the same predetermined polarization, which is a first polarization (e.g., polarized in the x-direction shown in FIG. 17B

[0200] In some embodiments, at least one (e.g., each) of the in-coupling gratings 1712, 1722, or 1732 can be coupled with a polarization switch. The in-coupling gratings 1712, 1722, and 1732 can be indirectly switched between a diffractive state and a non-diffractive state depending on the polarization of the incident light output from the polarization switch. The polarization switch can be disposed on a side of the corresponding in-coupling grating from which image light is incident on the in-coupling grating, thereby controlling the polarization of the image light incident on the corresponding in-coupling grating. At least one (e.g., each) of the out-coupling gratings 1714, 1724, or 1734 can be coupled with a polarization switch, which can be disposed on a side of the corresponding out-coupling grating from which image light exits the out-coupling grating.

[0201] The display frame can be divided into three sub-frames for sequentially transmitting the image light 1755, 1765, and 1775. During the first sub-frame, reference is made to FIG. 17A and FIG. 17A ​image light 1765 (e.g., green light) and 1775 (e.g., blue light) can not be emitted from the corresponding source assemblies 1760 and 1770. The polarization switch 1736 coupled to the in-coupling grating 1732 at the waveguide 1730 can operate in a non-switching state to transmit the image light 1755 having a first polarization in a manner that does not affect or switch the polarization. Since the in-coupling grating 1732 and the out-coupling grating 1734 can be configured to diffract image light having the first polarization, to transmit image light having a second polarization orthogonal to the first polarization in a diffractively negligible or non-diffractive manner, the image light 1755 having the first polarization can be coupled into the TIR path within the waveguide 1730 via the in-coupling grating 1732. The image light 1755 can be out-coupled from the waveguide 1730 via the out-coupling grating 1734 as image light 1755’ (e.g., red light), which can be received by the eye 265. That is, the eye 265 can perceive a single color image of a first color (e.g., red).

[0202] In FIG. 17C In the illustrated embodiment, the polarization switch 1726 coupled to the in-coupling grating 1722 at the waveguide 1720 can operate in a switching state to convert the image light 1755 having the first polarization to image light having the second polarization. Since the in-coupling grating 1722 can be configured to diffract image light having the first polarization and to transmit image light having the second polarization in a diffractively negligible or non-diffractive manner, the transmitted image light having the second polarization can not be coupled into the TIR path inside the waveguide 1720 and can be transmitted through the waveguide 1720 towards the waveguide 1710. The polarization switch 1716 coupled to the in-coupling grating 1712 at the waveguide 1710 can operate in a non-switching state. Thus, the received image light having the second polarization from the waveguide 1720 can maintain the second polarization after being transmitted through the polarization switch 1716. Since the in-coupling grating 1712 can be configured to diffract image light having the first polarization and to transmit image light having the second polarization in a diffractively negligible or non-diffractive manner, the transmitted image light having the second polarization can not be coupled into the TIR path inside the waveguide 1710 and can be transmitted through the waveguide 1710. The polarization switches 1738, 1728, and 1718 coupled to the out-coupling gratings 1734, 1724, and 1714, respectively, can operate in a non-switching state and can transmit the image light in a manner that does not affect or switch the polarization of the image light. Thus, during the first sub-frame, the image light 1755 (e.g., red light) can be directed towards the eye 265 via the waveguide 1730 and a single color image of a first color (e.g., red) can be reproduced at the eyebox at the exit pupil located at the eye 265.

[0203] Referring toFIG. 17A and FIG. 17C During the second sub-frame, image light 1765 (e.g., green light) can be emitted by light source assembly 1760 toward waveguide stack 1701, and image light 1755 (e.g., red light) and 1775 (e.g., blue light) can not be emitted from corresponding source assemblies 1750 and 1770, respectively. Polarization switch 1736 coupled to in-coupling grating 1732 at waveguide 1730 can operate in a switched state to convert image light 1765 having a first polarization to image light having a second polarization. Image light having the second polarization can not be in-coupled into a TIR path inside waveguide 1730. Instead, image light having the second polarization can be transmitted through waveguide 1730 toward waveguide 1720.

[0204] Polarization switch 1726 coupled to in-coupling grating 1722 at waveguide 1720 can operate in a switched state to convert image light having the second polarization that is output from waveguide 1730 to image light having the first polarization. Image light having the first polarization can be in-coupled into a TIR path inside waveguide 1720 via in-coupling grating 1722 and out-coupled from waveguide 1720 as image light 1765’ having the first polarization via out-coupling grating 1724.

[0205] On the out-coupling side of waveguide stack 1701, polarization switch 1728 coupled to out-coupling grating 1724 at waveguide 1720 can operate in a switched state to convert image light having the first polarization that is output from out-coupling grating 1724 to image light having the second polarization toward waveguide 1730. Image light having the second polarization can not be in-coupled into a TIR path inside waveguide 1730. Instead, image light having the second polarization that is output from polarization switch 1728 can be directly transmitted through waveguide 1730 and out-coupling grating 1734 toward polarization switch 1738. In some embodiments, polarization switch 1738 coupled to out-coupling grating 1734 at waveguide 1730 can operate in a switched state to convert image light having the second polarization that is output from out-coupling grating 1734 to image light having the first polarization toward eye 265. As a result, eye 265 can perceive a single color image of a second color (e.g., green) that is different from a first color (e.g., red).

[0206] Referring back to the in-coupling side of the waveguide stack 1701, the polarization switch 1716 coupled to the in-coupling grating 1712 at the waveguide 1710 can operate in a switching state to convert the image light having the first polarization and not in-coupled into the waveguide 1720 to image light having the second polarization. The image light having the second polarization output from the polarization switch 1716 can not be in-coupled into the TIR path inside the waveguide 1710. Instead, the image light having the second polarization output from the polarization switch 1716 can transmit through the waveguide 1710. Thus, during the second sub-frame, the image light 1765 (e.g., green light) having the first polarization can be directed toward the eye 265 via the waveguide 1720, and a single color image (e.g., a green color image) can be reproduced at the eyebox located at the exit pupil of the eye 265.

[0207] Referring FIG. 16A and FIGS. 17B-17D During the third sub-frame, image light 1775 (e.g., blue light) can be emitted by the light source assembly 1770 toward the waveguide stack 1701, and the image light 1755 (e.g., red light) and 1765 (e.g., green light) can not be emitted from the corresponding source assemblies, respectively. The polarization switch 1736 coupled to the in-coupling grating 1732 at the waveguide 1730 can operate in a switching state to convert the image light 1775 having the first polarization to image light having the second polarization, which can not be in-coupled into the TIR path inside the waveguide 1730. Instead, the image light having the second polarization output from the polarization switch 1736 can transmit through the waveguide 1730 toward the waveguide 1720.

[0208] The polarization switch 1726 coupled to the in-coupling grating 1722 at the waveguide 1720 can operate in a non-switching state to transmit the image light having the second polarization in a manner that does not affect or switch the polarization of the image light. The image light having the second polarization output from the polarization switch 1726 can not be in-coupled into the TIR path inside the waveguide 1720 and can transmit through the waveguide 1720 toward the waveguide 1710.

[0209] The polarization switch 1716 coupled to the in-coupling grating 1712 at the waveguide 1710 can operate in a switching state to convert the image light having the second polarization to image light having the first polarization. The image light having the first polarization can be in-coupled into the TIR path inside the waveguide 1710 via the in-coupling grating 1712 and out-coupled from the waveguide 1710 as image light having the first polarization via the out-coupling grating 1714.

[0210] On the out-coupling side of the waveguide stack 1701, the polarization switch 1718 coupled to the out-coupling grating 1714 at the waveguide 1710 can operate in a switching state to convert the image light having the first polarization to image light having the second polarization toward the waveguide 1720. The image light having the second polarization output from the polarization switch 1718 can not be coupled into the TIR path inside the waveguide 1720. Instead, the image light having the second polarization output from the polarization switch 1718 can be directly transmitted through the waveguide 1720 toward the waveguide 1710.

[0211] The polarization switch 1728 coupled to the out-coupling grating 1724 at the waveguide 1720 can operate in a non-switching state to transmit the image light having the second polarization toward the waveguide 1730 in a manner that does not affect or switch the polarization. The image light having the second polarization output from the polarization switch 1728 can not be coupled into the TIR path inside the waveguide 1730. Instead, the image light having the second polarization output from the polarization switch 1728 can be directly transmitted through the waveguide 1730 toward the polarization switch 1738.

[0212] In some embodiments, the polarization switch 1738 coupled to the out-coupling grating 1734 at the waveguide 1730 can operate in a switching state to convert the image light having the second polarization to image light having the first polarization toward the eye 265, such that the eye 265 can perceive a third monochrome image (e.g., a blue color image). Thus, during the third sub-frame, the image light 1775 having the first polarization (e.g., blue light) can be directed toward the eye 265 via the waveguide 1710, and a monochrome image of a third color (e.g., blue) different from the first color (e.g., red) or the second color (e.g., green) can be replicated at the eye box located at the exit pupil of the eye 265.

[0213] Thus, during a display frame, sequential transmission of image light of different colors (e.g., red, green, blue) can be achieved. That is, sequential transmission of monochrome images of different colors can be achieved. The final image can be perceived by the eye 265 as a multicolor image. In some embodiments, the time-division multiplexing achieved by the disclosed indirect switchable gratings (which can be passive gratings in some embodiments) can reduce or eliminate cross-talk in the waveguide stack 1701. Thus, the optical performance of a waveguide display assembly including the waveguide stack 1701 can be enhanced.

[0214] In some embodiments, at least one (e.g., each) of the light source assemblies 1750, 1760, or 1770 can emit unpolarized monochromatic image light, and at least one (e.g., each) polarizer 1740 can be omitted. The unpolarized image light can be directed toward the incoupling grating 1712, 1722, or 1732. Depending on the polarization selectivity of the incoupling grating 1712, 1722, or 1732, one of the two orthogonal polarization components of the unpolarized image light emitted from the light source assembly 1750, 1760, or 1770 can be incoupled into the waveguide 1710, 1720, or 1730, while the other component can be transmitted through in a diffractively negligible or non-diffractive manner.

[0215] In some embodiments, the wavelength spectra of the out-coupling gratings 1714, 1724, and 1734 can be substantially non-overlapping with each other, such that crosstalk between the out-coupling gratings can be minimized or reduced. Accordingly, the polarization switches 1718, 1728, and 1738 coupled to the out-coupling gratings 1714, 1724, and 1734, respectively, can be omitted. In some embodiments, the wavelength spectra of the in-coupling gratings 1712, 1722, and 1732 can be substantially non-overlapping with each other, such that crosstalk between the in-coupling gratings can be minimized or reduced. Accordingly, the polarization switches 1716, 1726, and 1736 coupled to the in-coupling gratings 1712, 1722, and 1732, respectively, can also be omitted. That is, in some embodiments, the out-coupling gratings 1714, 1724, and 1734 and the in-coupling gratings 1712, 1722, and 1732 can each have a predetermined wavelength selectivity, e.g., the gratings can diffract incident light within a predetermined wavelength band or range and transmit incident light outside the predetermined wavelength band with negligible or no diffraction, such that the corresponding polarization switches coupled to the gratings can be omitted. For example, each of the in-coupling gratings 1712, 1722, and 1732 and the out-coupling gratings 1714, 1724, and 1734 can be fabricated to operate in a Bragg mechanism to have the predetermined wavelength selectivity. In some embodiments, when the out-coupling gratings 1714, 1724, and 1734 and the in-coupling gratings 1712, 1722, and 1732 have substantial wavelength selectivity, the optical system 1700 can be configured to simultaneously deliver single-color images of different colors to the eyebox. In some embodiments, at least one (e.g., each) of the light source assemblies 1750, 1760, or 1770 can emit unpolarized monochromatic image light, and at least one (e.g., each) of the polarizers 1740 can be omitted. The unpolarized image light can be directed toward the in-coupling gratings 1712, 1722, or 1732. Depending on the polarization selectivity of the in-coupling gratings 1712, 1722, or 1732, one of the two orthogonal polarization components of the unpolarized image light emitted from the light source assemblies 1750, 1760, or 1770 can be coupled into the waveguide 1710, 1720, or 1730, while the other component can be transmitted through with negligible or no diffraction. Accordingly, the optical system 1700 can be configured to simultaneously deliver single-color images of a first color (e.g., red), a second color (e.g., green), and a third color (e.g., blue) to the eyebox.

[0216] In some embodiments, instead of being disposed at respective waveguides in the waveguide stack 1701, the in-coupling gratings 1712, 1722, and 1732 can be stacked and attached to a common (e.g., single) waveguide, and the out-coupling gratings 1714, 1724, and 1734 can be stacked and attached to the common waveguide. Similar structures are shown in FIGS. 17A and 17B. FIGS. 17A-17DThe in-coupling gratings and the out-coupling gratings can be arranged in a stack. The stack of in-coupling gratings and the stack of out-coupling gratings can each be arranged at the first surface of the common waveguide, or can each be arranged at the second surface of the common waveguide, or can be arranged at the first surface and the second surface, respectively. The description of the operation scheme for time-sequentially transmitting the image light of different colors for switching the polarization can refer to the above description of the operation scheme for time-sequentially transmitting the image light of different colors for switching the polarization. FIG. 17A The description is presented.

[0217] FIG. 18 The embodiments shown in FIG. 1 can be effective for monochromatic image light. For color image, different colors of image light can be spatially and / or temporally multiplexed. In some embodiments, the number of waveguides in the stack can be reduced to two. For separate transmission of image light of different colors, one waveguide can be configured for red and green, and the other waveguide can be configured for green and blue. FIG. 18 The in-coupling gratings and the out-coupling gratings can be arranged in a stack. The stack of in-coupling gratings and the stack of out-coupling gratings can each be arranged at the first surface of the common waveguide, or can each be arranged at the second surface of the common waveguide, or can be arranged at the first surface and the second surface, respectively. The description of the operation scheme for time-sequentially transmitting the image light of different colors for switching the polarization can refer to the above description of the operation scheme for time-sequentially transmitting the image light of different colors for switching the polarization.

[0218] The present disclosure also provides a method for guiding, by a waveguide display assembly, a plurality of portions of image light emitted from a light source assembly in a time-division multiplexing manner. FIG. 18 A flowchart showing a method 1800 for guiding different portions of image light by a waveguide display assembly in a time-division multiplexing manner according to an embodiment of the present disclosure is shown. As shown in FIG. 18, the method 1800 includes the following steps. FIGS. 2A-2BAs shown, the method 1800 can include configuring at least one of a first in-coupling grating or a first out-coupling grating disposed at a first waveguide of an optical device to operate in a diffractive state for a first time period (step 1810). The method 1800 can also include in-coupling, by the first in-coupling grating, first light into the first waveguide via diffraction for the first time period (step 1820). The first light can correspond to a first portion of image light. The method 1800 can also include out-coupling, by the first out-coupling grating, the first light from the first waveguide toward an eyebox of the optical device via diffraction for the first time period (step 1830). In some embodiments, configuring the at least one of the first in-coupling grating or the first out-coupling grating to operate in the diffractive state can include configuring the at least one of the first in-coupling grating or the first out-coupling grating to operate in the diffractive state by a polarization switch coupled to the at least one of the first in-coupling grating or the first out-coupling grating. A portion of the image light can correspond to a predetermined portion of a field of view (“FOV”) of a single-color image, a predetermined portion of a FOV of a multi-color image (e.g., a panchromatic image), or a single-color image of a predetermined color. In some embodiments, the first portion of the image light can correspond to a first portion of a FOV of a single-color image or a first portion of a FOV of a multi-color image. In some embodiments, the first portion of the image light can correspond to a single-color image of a first color.

[0219] The method 1800 can also include configuring at least one of a second in-coupling grating or a second out-coupling grating disposed at a second waveguide to operate in a diffractive state for a second time period (step 1840). The method 1800 can also include in-coupling, by the second in-coupling grating, second light into the second waveguide via diffraction for the second time period (step 1850). The second light can correspond to a second portion of image light. The method 1800 can also include out-coupling, by the second out-coupling grating, the second light from the second waveguide toward an eyebox of the optical device via diffraction for the second time period (step 1860). In some embodiments, configuring the at least one of the second in-coupling grating or the second out-coupling grating to operate in the diffractive state can include configuring the at least one of the second in-coupling grating or the second out-coupling grating to operate in the diffractive state via a polarization switch coupled to the at least one of the second in-coupling grating or the second out-coupling grating. In some embodiments, the second portion of the image light can correspond to a second portion of a FOV of a single-color image or a second portion of a FOV of a multi-color image (e.g., a panchromatic image). In some embodiments, the second portion of the image light can correspond to a second portion of a FOV of a single-color image or a second portion of a FOV of a multi-color image. In some embodiments, the second portion of the image light can correspond to a single-color image of a second color.

[0220] In some embodiments, the method 1800 can include FIG. 19 additional steps not shown in FIGS. 6A-6C. For example, in some embodiments, the method 1800 can include, during a third time period, configuring at least one of a third in-coupling grating or a third out-coupling grating disposed at a third waveguide to operate in a diffractive state via a polarization switch coupled to the at least one of the third in-coupling grating or the third out-coupling grating. The method 1800 can include, during the third time period, in-coupling, by the third in-coupling grating, third light corresponding to a third portion of the image light into the third waveguide via diffraction. The method 1800 can further include, during the third time period, out-coupling, by the third out-coupling grating, the third light from the third waveguide toward the eyebox of the optical device via diffraction. The waveguide display assembly can be an embodiment of any of the waveguide display assemblies disclosed, such as the waveguide display assembly 200 or 250 shown in FIGS. 6A-6C. The waveguide display assembly can include at least one passive diffractive optical element disclosed as an in-coupling grating or an in-coupling grating. FIG. 11 A

[0221] FIG. 12A ​is a flowchart illustrating a method 1900 for directing portions of image light emitted from a light source assembly through a waveguide display assembly. The method 1900 can include configuring at least one of a first polarization selective in-coupling element or a first polarization selective out-coupling element coupled to a first waveguide of a device to operate in a diffractive state (step 1910). The at least one of the first polarization selective in-coupling element or the first polarization selective out-coupling element can include one or more of the disclosed plurality of indirect switchable gratings. The method 1900 can also include directing a first portion of the image light toward an eyebox of the device through the first polarization selective in-coupling element, the first waveguide, and the first polarization selective out-coupling element (step 1920). The method 1900 can also include configuring at least one of a second polarization selective in-coupling element or a second polarization selective out-coupling element coupled to a second waveguide to operate in a diffractive state (step 1930). The at least one of the second polarization selective in-coupling element or the second polarization selective out-coupling element can include one or more of the disclosed plurality of indirect switchable gratings. The method can also include directing a second portion of the image light toward the eyebox through the second polarization selective in-coupling element, the second waveguide, and the second polarization selective out-coupling element (step 1940). The first portion of the image light and the second portion of the image light can be delivered to the eyebox at the same time period or at different time periods. In some embodiments, configuring the at least one of the first polarization selective in-coupling element or the first polarization selective out-coupling element to operate in the diffractive state can include controlling an operating state of a polarization switch coupled to the at least one of the first polarization selective in-coupling element or the first polarization selective out-coupling element. In some embodiments, the first portion of the image light can correspond to a first portion of a field of view (“FOV”) of a single color image of a single color image, a first portion of a FOV of a single color image of a plurality of color images, or a single color image of a first color. The second portion of the image light can correspond to a second portion of a FOV of a single color image, a second portion of a FOV of a plurality of color images, or a single color image of a second color different from the first color. In some embodiments, the first waveguide and the second waveguide are the same common waveguide, the first polarization selective in-coupling element and the second polarization selective in-coupling element are configured to at least partially overlap, and the first polarization selective out-coupling element and the second polarization selective out-coupling element are configured to at least partially overlap. In some embodiments, the first waveguide and the second waveguide are separate waveguides, the first polarization selective in-coupling element and the first polarization selective out-coupling element are coupled to the first waveguide, and the second polarization selective in-coupling element and the second polarization selective out-coupling element are coupled to the second waveguide. In some embodiments, the method 1900 can include additional steps. For example, the method 1900 can include configuring at least one of a third polarization selective in-coupling element or a third polarization selective out-coupling element coupled to a third waveguide to operate in a diffractive state.Method 1900 may further include: directing a third portion of the image light toward the eye frame via a third polarization-selective input element, a third waveguide, and a third polarization-selective output element.

[0222] The disclosed methods for polarization multiplexing, spatial multiplexing, and / or time-division multiplexing of different colors and / or different portions of the FOV based on the disclosed indirect switchable grating (which in some embodiments may be a passive grating) can be combined to deliver multi-color images (e.g., panchromatic images) with a wide FOV, all of which are within the scope of this disclosure. For example, FIG. 13A Waveguide 1101 in FIG. 14A Waveguide 1201 in FIG. 15A Waveguide stack 1301 in FIG. 16A Waveguide 1401 in FIG. 15A Waveguide stack 1501 or FIG. 16A Waveguide 1601 can also be used to transmit multi-color images (e.g., panchromatic images) with a large field of view (FOV), such as FOV greater than or equal to 60°. One or more waveguides are configured to transmit multi-color images (e.g., panchromatic images) with different portions of the FOV in a time-division multiplexed manner. To achieve the transmission of multi-color images (e.g., panchromatic images) with a large FOV via waveguides in a time-division multiplexed manner, at least one (e.g., each) of the input or output gratings in at least one (e.g., each) waveguide may include multiple sub-gratings for transmitting different colors (e.g., red, green, and blue).

[0223] For example, in order to via FIG. 15A The waveguide stack 1501 shown in the figure or FIG. 16A The waveguide 1601 shown sequentially transmits multiple colors of image light (e.g., full-color image light) corresponding to predetermined portions of the field of view (FOV) in a time-division multiplexing manner. FIG. 15A At least one (e.g., each) of the coupling gratings 1512, 1522 or 1532 shown herein FIG. 16A At least one of the coupling gratings 1612, 1622 or 1632 shown (e.g., each) may include one or more indirect switchable coupling subgratings (in some embodiments, which may be passive subgratings). FIG. 15A At least one (e.g., each) of the coupling gratings 1514, 1524, or 1534 shown herein FIG. 16A At least one of the coupling gratings 1614, 1624 or 1634 shown (e.g., each) may include one or more indirect switchable coupling sub-gratings (in some embodiments, which may be passive sub-gratings). FIG. 15A At least one (e.g., each) of the coupling gratings 1512, 1522 or 1532 shown hereinFIG. 16A At least one (e.g., each) of the in-coupling gratings 1612, 1622, or 1632 shown in FIG. 16A can be an in-coupling grating stack. FIG. 15A At least one (e.g., each) of the out-coupling gratings 1514, 1524, or 1534 shown in FIG. 15A or FIG. 16A At least one (e.g., each) of the out-coupling gratings 1614, 1624, or 1634 shown in FIG. 16A can be an out-coupling grating stack.

[0224] In some embodiments, when X sub-gratings are configured to transport a FOV, and Y sub-gratings are configured to transport a single color image forming a plurality of color images (e.g., RGB colors), the total number of sub-gratings included in at least one (e.g., each) of the in-coupling grating stack or the out-coupling grating stack can be X*Y, where X and Y are positive integers greater than or equal to 2. For example, in some embodiments, 1 / 3 of the FOV (X = 3) is transported by 3 sub-gratings (Y = 3) configured to transport a red color, a green color, and a blue color, respectively. FIG. 12A At least one (e.g., each) of the in-coupling gratings 1512, 1522, or 1532 shown in FIG. 15A or FIG. 12A At least one (e.g., each) of the in-coupling gratings 1612, 1622, or 1632 shown in FIG. 16A can include 3 sub-gratings (Y = 3) to transport respective portions of the FOV in red, green, and blue colors, respectively. Likewise, 1 / 3 of the FOV (X = 3) is transported by 3 sub-gratings (Y = 3) configured to transport a red color, a green color, and a blue color, respectively. FIG. 15A At least one (e.g., each) of the out-coupling gratings 1514, 1524, or 1534 shown in FIG. 15A or FIG. 8A At least one (e.g., each) of the out-coupling gratings 1614, 1624, or 1634 shown in FIG. 16A can include 3 sub-gratings (Y = 3) to transport respective portions of the FOV in red (R), green (G), and blue (B) colors, respectively. The total number of in-coupling sub-gratings can be equal to the total number of out-coupling sub-gratings. In some embodiments, the total number of sub-gratings can satisfy X*Y = 3*3 = 9. In some embodiments, corresponding sub-gratings from the in-coupling grating stack and the out-coupling grating stack can be configured to operate in a diffractive state in separate sub-frames (e.g., 9 sub-frames) to suppress cross-talk.

[0225] In at least one (e.g., each) sub-frame, the indirectly switchable (e.g., passive) in-coupling and out-coupling sub-grating pairs can be configured to operate in a diffractive state to transmit a single color image corresponding to a predetermined portion of the FOV to the eye. The remaining in-coupling and out-coupling sub-grating pairs can be configured to operate in a non-diffractive state. Thus, during the entire display frame, single color images corresponding to different portions of the FOV can be sequentially transmitted to the eye in a time-division multiplexed manner. For example, a red single color image corresponding to the left portion of the FOV, a green single color image corresponding to the left portion of the FOV, a blue single color image corresponding to the left portion of the FOV, a red single color image corresponding to the middle portion of the FOV, a green single color image corresponding to the middle portion of the FOV, a blue single color image corresponding to the middle portion of the FOV, a red single color image corresponding to the right portion of the FOV, a green single color image corresponding to the right portion of the FOV, and a blue single color image corresponding to the right portion of the FOV, can be sequentially transmitted to the eye in a time-division multiplexed manner. The transmission sequence can operate in any suitable order. In some embodiments, when one or more sub-gratings (e.g., for different colors) or waveguides 1601 included in waveguide stack 1501 are highly selective, the number of sub-frames can be reduced such that crosstalk between the sub-gratings can be negligible.

[0226] Likewise, ​ Waveguide 1201 illustrated in FIG. 12 can be configured for transmitting multi-color images (e.g., full color images) having a large FOV. Waveguide 1201 can be configured to deliver multi-color images (e.g., full color images) having different portions of the FOV in a time-division multiplexed manner. To achieve transmission of multi-color images (e.g., full color images) having a large FOV via waveguide 1201 in a time-division multiplexed manner, at least one (e.g., each) of in-coupling sub-gratings 1205a, 1205b, or 1205c can include one or more in-coupling tertiary gratings for delivering different colors (e.g., red, green, and blue). At least one (e.g., each) of out-coupling sub-gratings 1210a, 1210b, or 1210c can include one or more out-coupling tertiary gratings for delivering different colors (e.g., red, green, and blue). The respective tertiary gratings can be stacked or laid at the surface of waveguide 1201 as shown in FIG. 12. The number of in-coupling and out-coupling tertiary gratings can be determined in the same manner as the number of in-coupling and out-coupling sub-gratings coupled to waveguide stack 1501 in FIG. 15. ​ ​ The number of in-coupling and out-coupling tertiary gratings can be determined in the same manner as the number of in-coupling and out-coupling sub-gratings coupled to waveguide stack 1501 in FIG. 15.

[0227] ​In the present disclosure, in some embodiments, to sequentially deliver multiple color image light (e.g., full color image light) corresponding to predetermined portions of a FOV in a time-division multiplexing manner, at least one (e.g., each) in-coupling grating can include three switchable in-coupling sub-gratings, and / or at least one (e.g., each) out-coupling grating can include three switchable out-coupling sub-gratings. The number of switchable in-coupling sub-gratings and the number of switchable out-coupling sub-gratings are for illustration purposes and are not intended to limit the scope of the present disclosure. Any other suitable number of switchable in-coupling sub-gratings and any other suitable number of switchable out-coupling sub-gratings can be used. In some embodiments, to multiplex colors and lay FOVs substantially simultaneously, at least one (e.g., each) in-coupling grating (or sub-grating) can include N in-coupling sub-gratings (or tertiary gratings), and / or at least one (e.g., each) out-coupling grating (or sub-grating) can include N out-coupling sub-gratings (or tertiary gratings), N being a positive integer and N being greater than or equal to 2. In some embodiments, N is greater than or equal to 3. That is, an in-coupling sub-grating (or tertiary grating) and a corresponding out-coupling sub-grating (or tertiary grating) can form a pair. An disclosed waveguide or waveguide stack can include N pairs. In respective time periods, a respective pair of the N pairs can be sequentially configured to operate in a diffractive state to transmit a corresponding portion of the multiple portions of image light, and the remaining pairs of the N pairs can be configured to operate in a non-diffractive state. The multiple portions of image light can correspond to single color images of different colors, different portions of a FOV of a single color image, or different portions of a FOV of multiple color images (e.g., a full color image).

[0228] In some embodiments, when the above waveguide display assembly is used for spatial and / or time-division multiplexing of different colors and / or different portions of a FOV, the polarization of the image light can not change as the image light travels through one or more waveguides. In some embodiments, the polarization of the image light can change as the image light travels through one or more waveguides. In this case, the waveguide display assembly can include a polarization correction anisotropic plate and a clean-up polarizer disposed adjacent to the one or more waveguides to block, reduce, or eliminate undesired (or ghost) images.

[0229] Further, using an indirect switchable grating (which can be a passive grating in some embodiments) as an example, the disclosed methods and waveguide display assemblies for spatially and / or temporally multiplexing different colors and / or different portions of a FOV are described. In some embodiments, the passive, indirect switchable grating can be configured to diffract image light having a predetermined linear polarization and to transmit image light having a different polarization (e.g., a polarization orthogonal to the predetermined linear polarization) with negligible or no diffraction. A polarization switch can be configured to switch the linear polarization of the incident light between two orthogonal linear polarizations before the light is incident on the passive, indirect switchable grating. The indirect switchable grating (which can be a passive grating in some embodiments) is used for illustrative purposes and is not intended to limit the scope of the present disclosure. In some embodiments, the disclosed methods and waveguide display assemblies for spatially and / or temporally multiplexing different colors and / or different portions of a FOV can also be implemented by indirect switchable gratings (which can be passive gratings in some embodiments) that are configured to selectively diffract image light having a polarization other than linear polarization, such as circular or elliptical polarization, all within the scope of the present disclosure. For example, the indirect switchable grating (which can be a passive grating in some embodiments) can include a polarization volume hologram (“PVH”) that can be configured to diffract image light having a circular polarization. In some embodiments, the PVH can diffract circularly polarized light having the same handedness as the helical twist of the PVH and transmit circularly polarized light having a handedness opposite to that of the helical twist of the PVH. A polarization switch can be coupled to the PVH and configured to switch the circular polarization of the incident light between two orthogonal handednesses, thereby controlling the polarization of the light incident on the passive grating. The disclosed methods and waveguide display assemblies for spatially and / or temporally multiplexing different colors and / or different portions of a FOV can also be implemented by other indirect switchable gratings (which can be passive gratings in some embodiments), such as geometric phase gratings based on passive LC, metasurface / LC gratings, etc., all within the scope of the present disclosure. In some embodiments, the passive indirect switchable gratings can be replaced by active and polarization-selective gratings, which can also be indirectly switchable, in the disclosed methods, apparatuses, and systems.

[0230] In the disclosed apparatuses and systems, any polarization switch used to indirectly switch the indirect switchable grating (e.g., a passive grating) can be coupled to ​The polarization switch 820 shown in FIG. 8B is similar. Although not shown in some of the embodiments, it will be understood that in each embodiment including an indirectly switchable grating, a controller similar to the controller 215 can be included to control the polarization switch, thereby indirectly switching the operational state (e.g., diffractive or non-diffractive state) of the indirectly switchable grating.

[0231] The foregoing description of embodiments of the present disclosure has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the present disclosure to the precise form disclosed. Modifications and variations are possible in light of the above

[0232] Some portions of this specification can describe embodiments of the present disclosure in terms of algorithms and symbolic representations of operations on information. Although these operations can be described in functional, computational, or logical terms, it is understood that such operations can be implemented in computer programs or equivalent electrical circuits, microcode, or the like. Additionally, it has also proven convenient at times to refer to these arrangements of operations as modules, because the

[0233] Any of the steps, operations, or processes described herein can be performed or implemented with one or more hardware modules and / or software modules, alone or in combination with other devices. In one embodiment, a software module is implemented with a computer program product comprising a computer-readable medium containing computer program code, which can be executed by a computer processor for performing any or all of the steps, operations, or processes described. In some embodiments, a hardware module can include hardware components such as an apparatus, a system, an optical element, a controller, a circuit, a logic gate, or the like.

[0234] Embodiments of the disclosure can also relate to an apparatus for performing the operations herein. This apparatus can be specially constructed for the required purposes, and / or it can comprise a general-purpose computing device selectively activated or reconfigured by a computer program stored in the computer. Such a computer program can be stored in a non-transitory, tangible computer readable storage medium, or any type of media suitable for storing electronic instructions, which can be coupled to a computer system bus. The non-transitory computer readable storage medium can be any media capable of storing program code, such as a magnetic disk, optical disk, Read-only Memory (ROM), or Random Access Memory (RAM), Electrically Programmable Read Only Memory (EPROM), Electrically Erasable Programmable Read Only Memory (EEPROM), register, hard disk, solid-state disk drive, Smart Media Card (SMC), Secure Digital (SD), Flash card, and the like. Additionally, any of the computing systems described in the specification can include a single processor, or can be an architecture employing multiple processors to realize improved computational performance. The processor can be a Central Processing Unit (CPU), a Graphics Processing Unit (GPU), or any processing device configured to process data and / or perform computations based on data. The processor can include both software components and hardware components. For example, the processor can include hardware components such as an Application-specific Integrated Circuit (ASIC), a Programmable Logic Device (PLD), or a combination thereof. The PLD can be a Complex Programmable Logic Device (CPLD), a Field-programmable Gate Array (FPGA), or the like.

[0235] Embodiments of the present disclosure can also relate to a product produced by a computing process described herein. Such products can include information resulting from computing processes, where the information is stored on a non-transitory, tangible computer-readable storage medium and can include any embodiments of a computer program product or other data combinations described herein.

[0236] Further, when an embodiment is illustrated in the figures, it will be understood that this embodiment can include a plurality of such elements. Likewise, when an embodiment is illustrated in the figures, it will be understood that this embodiment can include only one such element. The number of elements illustrated in the figures is simply for the purposes of illustration and should not be construed as limiting the scope of the embodiments. Further, the embodiments illustrated in the figures are not mutually exclusive and these embodiments can be combined in any suitable manner. For example, elements illustrated in one embodiment but not another embodiment can still be included in the other embodiment.

[0237] Various embodiments have been described to show exemplary implementations. Based on the disclosed embodiments, a person of ordinary skill in the art can make various other changes, modifications, rearrangements, and substitutions without departing from the scope of the present disclosure. Therefore, although the present disclosure has been described in detail with reference to the above embodiments, the present disclosure is not limited to the above embodiments. The present disclosure can be embodied in other equivalent forms without departing from the scope of the present disclosure. The scope of the present disclosure is defined in the appended claims.

Claims

1. An optical device, comprising: waveguide; as well as The input element and the output element are coupled to the waveguide; The waveguide, the coupling element, and the coupling element are configured to deliver multiple portions of the image light to the eye-fitting frame of the optical device. The coupling element includes a polarization-selective diffraction element, which comprises: A grating comprising multiple microstructures defining multiple grooves, the grooves being filled with a passive optical anisotropic material having a first effective refractive index along the groove direction and a second effective refractive index along a plane perpendicular to the groove direction. Wherein, one of the first effective refractive index or the second effective refractive index is matched with the refractive index of the microstructure, and wherein the polarization-selective diffraction element is indirectly switchable between a diffraction state and a non-diffraction state via an external polarization switch coupled to the polarization-selective diffraction element.

2. The optical device according to claim 1, wherein, The other of the first effective refractive index or the second effective refractive index does not match the refractive index of the microstructure.

3. The optical device according to claim 1 or 2, wherein, A portion of the image light corresponds to: (i) a predetermined portion of the field of view of a single-color image or a predetermined portion of the field of view of a multi-color image; or (ii) A single-color image with a predetermined color.

4. The optical device according to claim 1 or 2, wherein, The passive optical anisotropic material includes optical anisotropic polymers.

5. The optical device according to claim 1 or 2, wherein, The grating is either a tilted grating or a non-tilted grating.

6. The optical device according to claim 1 or 2, wherein, The polarization-selective diffraction element includes multiple gratings. During multiple time periods, the plurality of gratings are sequentially configured to operate in a diffraction state to deliver respective portions of the plurality of portions of the image light, and During one of the plurality of time periods, at least one of the plurality of gratings is configured to operate in the diffraction state to deliver a portion of the plurality of portions of the image light, and one or more remaining gratings are configured to operate in a non-diffraction state.

7. The optical device according to claim 6, wherein, The plurality of gratings: (i) arranged to at least partially overlap each other; or (ii) is set to overlay configuration.

8. The optical device according to claim 1 or 2, wherein, The polarization-selective diffraction element includes a plurality of gratings configured to operate in a diffraction state to deliver respective portions of the plurality of portions of the image light within the same time period; and At least one of the angular spectrum or wavelength spectrum of the plurality of gratings does not overlap.

9. The optical device according to claim 1 or 2, further comprising: (i) A plurality of waveguides and a plurality of said polarization-selective diffraction elements, said waveguides being configured in a stacked arrangement, said polarization-selective diffraction elements being coupled to said waveguides. In this configuration, during multiple time periods, the plurality of polarization-selective diffraction elements are sequentially configured to operate in a diffraction state to deliver respective portions of the plurality of image light. During one of the multiple time periods, a polarization-selective diffraction element coupled to one of the plurality of waveguides is configured to operate in the diffraction state to deliver one portion of the plurality of image light, and one or more polarization-selective diffraction elements coupled to one or more remaining waveguides are configured to operate in a non-diffraction state; or (ii) A plurality of waveguides and a plurality of polarization-selective diffraction elements, wherein the plurality of waveguides are configured in a stacked arrangement and the plurality of polarization-selective diffraction elements are coupled to the plurality of waveguides. The plurality of polarization-selective diffraction elements are configured to operate in a diffraction state to deliver respective portions of the plurality of portions of the image light within the same time period; and Wherein, at least one of the angular spectra or wavelength spectra of the plurality of polarization-selective diffraction elements does not overlap.

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