Multilayer liquid crystal diffraction gratings for redirecting light with a wide range of incident angles

Abstract

An optical device includes a stack of multiple grating structures, each of which includes multiple sublayers of liquid crystal material. Each sublayer of liquid crystal material includes laterally extending repeating units, each repeating unit being formed by multiple liquid crystal molecules. The repeating units of the liquid crystal layers are laterally offset from each other and define a tilt angle. The grating structures forming the stack have different tilt angles. The grating structures can be configured to redirect light of visible or infrared wavelengths. Advantageously, the different tilt angles of the grating structure stack allow for efficient diffraction of light incident on the grating structures over a wide range of incident angles.

Description

[0001] This application is a divisional application of the patent application filed on November 16, 2017, with application number 201780083634.X and entitled "Multilayer liquid crystal diffraction grating for redirecting light with a wide incident angle range".

[0002] Priority Statement

[0003] This application claims priority to U.S. Provisional Patent Application No. 62 / 424,305, filed November 18, 2016, which is incorporated herein by reference in its entirety.

[0004] Cross-references to related applications

[0005] This application is incorporated in its entirety by reference to each of the following patent applications: U.S. Application No. 14 / 555,585, filed November 27, 2014; U.S. Application No. 14 / 690,401, filed April 18, 2015; U.S. Application No. 14 / 212,961, filed March 14, 2014; and U.S. Application No. 14 / 331,218, filed July 14, 2014. Technical Field

[0006] This disclosure relates to optical devices, including virtual reality and augmented reality imaging and visualization systems. Background Technology

[0007] Modern computing and display technologies have facilitated the development of systems for so-called “virtual reality” or “augmented reality” experiences, in which digitally reproduced images or portions thereof are presented to the user in a way that appears real or is perceived as real. Virtual reality (or “VR”) scenarios typically involve the presentation of digital or virtual image information that is opaque to other actual visual input from the real world; augmented reality (or “AR”) scenarios typically involve the presentation of digital or virtual image information as an enhancement of the visualization of the real world surrounding the user. Mixed reality (or “MR”) scenarios are a type of AR scenario and typically involve virtual objects integrated into and responding to the natural world. For example, in an MR scenario, AR image content can be obscured by real-world objects or perceived as interactive with those objects.

[0008] refer to Figure 1The illustration shows an augmented reality scene 10, in which an AR user sees a real-world park-like setting 20 characterized by people, trees, buildings in the background, and a concrete platform 30. In addition to these items, the AR user also perceives that he "sees" "virtual content" such as a robot statue 40 standing on the real-world platform 30, and a cartoonish avatar 50 flying by, which appears to be an avatar of Bumblebee, even though these elements 40 and 50 do not exist in the real world. Because the human visual perception system is complex, producing AR technology that contributes to a comfortable, natural, and rich presentation of virtual imagery elements along with other virtual or real-world imagery elements is challenging.

[0009] The systems and methods disclosed in this paper address various challenges related to AR and VR technologies. Summary of the Invention

[0010] The systems, methods, and apparatus of this disclosure each have several innovative aspects, none of which alone is responsible for the desired properties of this disclosure.

[0011] The innovative aspect of this application includes an optical device comprising a first polarizing grating structure and a second polarizing grating structure situated above the first polarizing grating structure. The first polarizing grating structure includes: a first plurality of liquid crystal sublayers comprising liquid crystal molecules. The liquid crystal molecules form repeating units having a first period along a horizontal axis. The repeating unit is laterally shifted by a first shift distance compared to a similar repeating unit in an adjacent sublayer of the first plurality of sublayers. The repeating unit shifted by the first shift distance defines a first tilt angle relative to a normal to the horizontal axis, the normal extending along the thickness axis of the first polarizing grating structure. The second polarizing grating structure includes: a second plurality of liquid crystal sublayers comprising liquid crystal molecules, wherein the liquid crystal molecules form repeating units having a second period along the horizontal axis. The repeating unit is laterally shifted by a second shift distance compared to a similar repeating unit in an adjacent sublayer of the plurality of sublayers. The repeating unit shifted by the second shift distance defines a second tilt angle relative to the normal to the horizontal axis. The magnitudes of the first and second tilt angles are different.

[0012] In various embodiments of the optical device, the liquid crystal molecules in each of the plurality of sublayers of the first polarizing grating structure can be twisted at a first twist angle. As shown in the side or top view, the orientation of the liquid crystal molecules can vary laterally in a repeating pattern across each of the sublayers. Each of the repeating units in the plurality of liquid crystal sublayers of the first polarizing grating structure can be formed by a plurality of liquid crystal molecules having similar orientation progressions.

[0013] In various embodiments of the optical device, the repeating units in successive higher levels of the liquid crystal sublayers of the first and second polarization grating structures can be shifted in the same direction. In various embodiments, the liquid crystal molecules in each of the plurality of sublayers of the second polarization grating structure can be twisted at a second twist angle. As shown in the side or top view, the orientation of the liquid crystal molecules can vary laterally in a repeating pattern across each of the sublayers. Each of the repeating units in the plurality of liquid crystal sublayers of the second polarization grating structure can be formed by a plurality of liquid crystal molecules having similar orientation progression. The liquid crystal molecules in the plurality of sublayers can be part of a polymeric liquid crystal material. For example, the liquid crystal molecules in the plurality of sublayers can include diacrylate liquid crystals. In various embodiments, the plurality of sublayers can be doped with a chiral dopant. The liquid crystal molecules can have a tilt angle (θ1) between about -85 degrees and 85 degrees. In various embodiments, the liquid crystal molecules can be configured to diffract at an incident angle (θ) between about -20 degrees and 20 degrees relative to the tilt angle. inc At least 40% of the light beam incident on the polarization grating structure.

[0014] Various embodiments of the optical device may further include a third polarization grating structure situated above the second polarization grating structure. The third polarization grating structure may include a plurality of liquid crystal sublayers, each sublayer comprising liquid crystal molecules forming repeating units with a third period. Compared to a similar repeating unit in an adjacent sublayer of the plurality of sublayers, the repeating unit may be laterally shifted by a third shift distance. The repeating unit that can be shifted by the third shift distance defines a third tilt angle relative to the normal to the transverse axis. The magnitudes of the first, second, and third tilt angles may be different.

[0015] The liquid crystal sublayer of each of the first, second, and third polarization grating structures may have a composition different from the other structures in the first, second, and third polarization grating structures. The first and second polarization grating structures may be located above the waveguide and further include a template layer located above the waveguide and below the first and second polarization grating structures. In various embodiments, the first, second, and third polarization grating structures may be coupling optical elements configured to couple an incident light beam into the waveguide such that the incident light beam propagates through the waveguide via total internal reflection. The first, second, and third polarization grating structures may be coupling optical elements configured to couple an incident light beam propagating through the waveguide via total internal reflection outwards. The first, second, and third polarization grating structures may be orthogonal pupil expanders configured to redirect light propagating through the waveguide via total internal reflection, wherein the redirected light continues to propagate through the waveguide via total internal reflection.

[0016] Various embodiments of the optical device may include an optical modulation device configured to guide light into the waveguide via the first and second polarization grating structures. Various embodiments of the optical device may further include waveguide stacks, each waveguide including the first and second polarization grating structures comprising multiple liquid crystal sublayers with different tilt angles.

[0017] Another innovative aspect of this application is an optical device comprising a first polarization grating structure having a first thickness and a second polarization grating structure situated above the first polarization grating structure. The first polarization grating structure includes a first plurality of liquid crystal sublayers, each sublayer comprising liquid crystal molecules and a chiral dopant. The second polarization grating structure has a second thickness and includes a second plurality of liquid crystal sublayers, each sublayer comprising liquid crystal molecules and a chiral dopant. The thickness of the first and second polarization grating structures, the concentration of the chiral dopant in the first and second polarization grating structures, or at least one of the chiral dopants in the first and second polarization grating structures may be different between the first and second polarization grating structures. The different chiral dopants in the first and second polarization grating structures may have the same chirality.

[0018] In various embodiments of the optical device, the liquid crystal molecules may include chiral nematic liquid crystal molecules. The concentrations of the chiral dopants in the first and second polarization grating structures may differ by about 0.1 wt% or more. The thicknesses of the first and second polarization grating structures may differ by less than about 10 μm.

[0019] Another innovative aspect of this application includes a method for manufacturing an optical device, the method comprising: providing an alignment layer on a substrate; patterning the alignment layer; depositing a first liquid crystal layer on the alignment layer; aligning liquid crystal molecules in the first liquid crystal layer with the alignment layer to form first multilevel repeating liquid crystal molecules defining a first tilt angle; depositing a second liquid crystal layer on the first liquid crystal layer; aligning liquid crystal molecules in the second liquid crystal layer with liquid crystal molecules in an immediately following lower first liquid crystal layer to form second multilevel repeating liquid crystal molecules defining a second tilt angle; wherein the first and second tilt angles are of different magnitudes.

[0020] In various embodiments of the method, patterning the alignment layer may include defining a groove pattern in the alignment layer. Defining a groove pattern in the alignment layer may include nanoimprinting. Patterning the alignment layer may include recording an interference pattern in the alignment layer. Various embodiments of the method may include depositing an additional alignment layer on top of the first liquid crystal layer; and patterning the additional alignment layer.

[0021] Another innovative aspect of this application is a display system comprising: an optical transmission waveguide; and diffractive optical elements having coupling optical elements, exit pupil expanders, or orthogonal pupil expanders formed on the surface of the waveguide. The diffractive optical elements include: a plurality of liquid crystal sublayers comprising liquid crystal molecules. The liquid crystal molecules can form periodic repeating units along a horizontal axis. The repeating unit is laterally shifted by a displacement distance compared to a similar repeating unit in an adjacent sublayer of the plurality of sublayers. The displacement distance defines an angle of inclination relative to a normal extending along the thickness axis of the first polarization grating structure.

[0022] In various embodiments of the display system, the waveguide may be part of a waveguide stack. Each waveguide in the stack may have an associated diffractive optical element comprising a plurality of liquid crystal sublayers, each sublayer comprising liquid crystal molecules. The liquid crystal molecules may form a periodic repeating unit. The repeating unit may be laterally shifted by a distance compared to a similar repeating unit in an adjacent sublayer. This shift distance may define a tilt angle relative to the normal to the horizontal axis.

[0023] Another innovative aspect of the subject matter of this application includes a method for manufacturing an optical device, the method comprising: providing a first liquid crystal layer in contact with a substrate and a first imprinting template, the first imprinting template including a plurality of surface features arranged in a first pattern; and aligning molecules in the first liquid crystal layer with the surface features to form a first multilevel repeating liquid crystal molecule defining a first tilt angle.

[0024] Various embodiments of the method may include polymerizing the molecules in the first liquid crystal layer; removing the first imprint template; depositing a second liquid crystal layer in contact with the first liquid crystal layer; and aligning the molecules in the second liquid crystal layer with the molecules in the first liquid crystal layer.

[0025] In various embodiments, the thickness of the first and second liquid crystal layers, the concentration of the chiral dopant in the first and second liquid crystal layers, or at least one of the chiral dopant in the first and second liquid crystal layers may be different between the first and second liquid crystal layers. The different chiral dopants in the first and second liquid crystal layers have the same directional properties.

[0026] In various embodiments of the method, providing a first liquid crystal layer and a first imprinting template in contact with the substrate includes depositing the first liquid crystal layer on the substrate; and bringing the first liquid crystal layer into contact with the first imprinting template.

[0027] Various embodiments of the method may further include polymerizing the molecules in the first liquid crystal layer; removing the first imprinting template; depositing a second liquid crystal layer in contact with the first liquid crystal layer; contacting the second liquid crystal layer with a second imprinting template; and aligning the molecules in the second liquid crystal layer with the surface feature pattern in the second imprinting template.

[0028] Various embodiments of the method may further include polymerizing molecules in the first liquid crystal layer; removing the first imprinting template; forming a planarization layer on the first liquid crystal layer; depositing a second liquid crystal layer on the planarization layer; contacting the second liquid crystal layer with a second imprinting template; and aligning molecules in the second liquid crystal layer with surface feature patterns in the second imprinting template.

[0029] This article describes various embodiments of optical devices including grating structures and methods for manufacturing the same, such as the examples listed below:

[0030] Example 1: An optical device comprising:

[0031] The first polarization grating structure includes:

[0032] A first plurality of liquid crystal sublayers, comprising liquid crystal molecules, wherein the liquid crystal molecules form repeating units having a first period along a transverse axis, and

[0033] Compared to a similar repeating unit in an adjacent sublayer of the first plurality of sublayers, the repeating unit is laterally shifted by a first shift distance, wherein the repeating unit shifted by the first shift distance defines a first tilt angle relative to a normal to the horizontal axis, the normal extending along the thickness axis of the first polarization grating structure; and

[0034] A second polarization grating structure is located above the first polarization grating structure, and the second polarization grating structure includes:

[0035] The second plurality of liquid crystal sublayers includes liquid crystal molecules, wherein the liquid crystal molecules form repeating units having a second period along the transverse axis, and

[0036] Compared to a similar repeating unit in an adjacent sublayer of the plurality of sublayers, the repeating unit is laterally shifted by a second shift distance, wherein the repeating unit shifted by the second shift distance defines a second tilt angle relative to the normal of the horizontal axis.

[0037] The first and second tilt angles are of different magnitudes.

[0038] Example 2: According to the device of Example 1, the liquid crystal molecules in each of the plurality of sublayers of the first polarizing grating structure are twisted at a first twist angle.

[0039] As shown in the side or top view, the orientation of the liquid crystal molecules varies laterally in a repeating pattern across each of the sublayers, and

[0040] Each of the repeating units in the plurality of liquid crystal sublayers of the first polarization grating structure is formed by a plurality of liquid crystal molecules having similar orientation progression.

[0041] Example 3: According to any one of Examples 1-2, the repeating units in successive higher levels of the liquid crystal sublayers of the first and second polarization grating structures are shifted in the same direction.

[0042] Example 4: According to any one of Examples 1-3, the liquid crystal molecules in each of the plurality of sublayers of the second polarization grating structure are twisted at a second twist angle.

[0043] As shown in the side or top view, the orientation of the liquid crystal molecules varies laterally in a repeating pattern across each of the sublayers.

[0044] Each of the repeating units in the plurality of liquid crystal sublayers of the second polarization grating structure is formed by a plurality of liquid crystal molecules having similar orientation progression.

[0045] Example 5: According to any one of Examples 1-4, the liquid crystal molecules in the plurality of sublayers are part of a polymeric liquid crystal material.

[0046] Example 6: According to any one of Examples 1-5, the liquid crystal molecules in the plurality of sublayers comprise diacrylate liquid crystals.

[0047] Example 7: The device according to any one of Examples 1-6, wherein the plurality of sublayers are doped with chiral dopants.

[0048] Example 8: The device according to any one of Examples 1-7, wherein the liquid crystal molecules have a tilt angle (θ1) between approximately -85 degrees and 85 degrees.

[0049] Example 9: A device according to any one of Examples 1-8, wherein the liquid crystal molecules are configured to diffract at an incident angle (θ) between approximately -20 degrees and 20 degrees relative to the tilt angle. inc At least 40% of the light beam incident on the polarization grating structure.

[0050] Example 10: The device according to any one of Examples 1-9 further includes a third polarization grating structure, the third polarization grating structure being located above the second polarization grating structure, the third polarization grating structure comprising a plurality of liquid crystal sublayers, the liquid crystal sublayers comprising liquid crystal molecules.

[0051] The liquid crystal molecules form repeating units with a third period.

[0052] Compared to a similar repeating unit in an adjacent sublayer among the plurality of sublayers, the repeating unit is laterally shifted by a third shift distance, wherein the repeating unit shifted by the third shift distance defines a third tilt angle relative to the normal to the horizontal axis.

[0053] The first, second, and third tilt angles are different in size.

[0054] Example 11: The device according to Example 10, wherein the liquid crystal sublayer of each of the first, second and third polarization grating structures has a composition different from the other structures in the first, second and third polarization grating structures.

[0055] Example 12: According to any one of Examples 1-11, the first and second polarization grating structures are located on the waveguide and further include:

[0056] A template layer is located above the waveguide and below the first and second polarization grating structures.

[0057] Example 13: The device according to Example 12, wherein the first and second polarization grating structures are coupled optical elements configured to couple an incident light beam into the waveguide such that the incident light beam propagates through the waveguide via total internal reflection.

[0058] Example 14: The device according to Example 13 further includes an optical modulation device configured to guide light into the waveguide via the first and second polarization grating structures.

[0059] Example 15: The device according to any one of Examples 13-14, wherein the first and second polarization grating structures are coupling optical elements configured to couple out incident light beams propagating through the waveguide via total internal reflection.

[0060] Example 16: The device according to any one of Examples 13-15, wherein the first and second polarization grating structures are orthogonal pupil expanders configured to redirect light propagating through the waveguide via total internal reflection, wherein the redirected light continues to propagate through the waveguide via total internal reflection.

[0061] Example 17: The device according to any one of Examples 13-16 further includes a waveguide stack, each waveguide including first and second polarization grating structures, the first and second polarization grating structures including a plurality of liquid crystal sublayers with different tilt angles.

[0062] Example 18: An optical device comprising:

[0063] A first polarization grating structure having a first thickness, the first polarization grating structure comprising:

[0064] The first plurality of liquid crystal sublayers, comprising liquid crystal molecules and chiral dopants; and

[0065] A second polarization grating structure is located above the first polarization grating structure, the second polarization grating structure having a second thickness and comprising:

[0066] The second set of multiple liquid crystal sublayers comprises liquid crystal molecules and chiral dopants.

[0067] At least one of the following is different between the first and second polarization grating structures:

[0068] The thickness of the first and second polarization grating structures;

[0069] The concentration of chiral dopant in the first and second polarization grating structures; or

[0070] The chiral dopants in the first and second polarization grating structures, wherein the different chiral dopants in the first and second polarization grating structures have the same chirality.

[0071] Example 19: The device according to Example 18, wherein the liquid crystal molecule is a chiral nematic liquid crystal molecule.

[0072] Example 20: The device according to any one of Examples 18-19, wherein the concentration of the chiral dopant in the first and second polarization grating structures differs by about 0.1 wt% or more.

[0073] Example 21: According to any one of Examples 18-20, the thickness of the first and second polarization grating structures differs by less than about 10 μm.

[0074] Example 22: A method for manufacturing an optical device, the method comprising:

[0075] An alignment layer is provided on the substrate;

[0076] Pattern the alignment layer;

[0077] A first liquid crystal layer is deposited on the alignment layer;

[0078] Aligning the liquid crystal molecules in the first liquid crystal layer with the alignment layer to form a first multi-level repeating liquid crystal molecule that defines a first tilt angle.

[0079] A second liquid crystal layer is deposited on the first liquid crystal layer;

[0080] Align the liquid crystal molecules in the second liquid crystal layer with the liquid crystal molecules in the immediately following lower first liquid crystal layer to form a second multilevel repeating liquid crystal molecule that defines a second tilt angle.

[0081] The first and second tilt angles are of different sizes.

[0082] Example 23: The method according to Example 22, wherein patterning the alignment layer includes defining a groove pattern in the alignment layer.

[0083] Example 24: The method according to Example 23, wherein the groove pattern defining the alignment layer includes nanoimprinting.

[0084] Example 25: The method according to any one of Examples 22-24, wherein patterning the alignment layer includes recording an interference pattern in the alignment layer.

[0085] Example 26: The method according to any one of Examples 22-25 further includes:

[0086] Deposit an additional alignment layer on top of the first liquid crystal layer; and

[0087] Pattern the additional alignment layer.

[0088] Example 27: A display system comprising:

[0089] Optical transmission waveguide;

[0090] A diffractive optical element, which forms a coupling optical element, an exit pupil expander, or an orthogonal pupil expander on the surface of the waveguide, the diffractive optical element comprising:

[0091] Multiple liquid crystal sublayers, which include liquid crystal molecules,

[0092] The liquid crystal molecules form periodic repeating units along the horizontal axis.

[0093] Compared to a similar repeating unit in an adjacent sublayer of the plurality of sublayers, the repeating unit is laterally shifted by a shift distance, wherein the shift distance defines an angle of inclination relative to the normal of the horizontal axis, which extends along the thickness axis of the first polarization grating structure.

[0094] Example 28: A system according to Example 27, wherein waveguides are part of a waveguide stack, wherein each of the waveguides has an associated diffractive optical element, the diffractive optical element comprising:

[0095] Multiple liquid crystal sublayers, which include liquid crystal molecules,

[0096] The liquid crystal molecules form periodic repeating units, wherein the repeating units are laterally shifted by a shift distance compared to a similar repeating unit in an adjacent sublayer of the plurality of sublayers, wherein the shift distance defines an angle of inclination relative to the normal of the horizontal axis.

[0097] Example 29: A method for manufacturing an optical device, the method comprising:

[0098] A first liquid crystal layer is provided in contact with a substrate and a first imprinting template, the first imprinting template including a plurality of surface features arranged in a first pattern; and

[0099] The molecules in the first liquid crystal layer are aligned with the surface features to form a first multilevel repeating liquid crystal molecule that defines a first tilt angle.

[0100] Example 30: The method described in Example 29 further includes:

[0101] To polymerize the molecules in the first liquid crystal layer;

[0102] Remove the first imprint template;

[0103] A second liquid crystal layer is deposited in contact with the first liquid crystal layer; and

[0104] Align the molecules in the second liquid crystal layer with the molecules in the first liquid crystal layer.

[0105] Example 31: According to the method of Example 30, at least one of the following is different between the first and second liquid crystal layers:

[0106] The thickness of the first and second liquid crystal layers;

[0107] The concentration of chiral dopants in the first and second liquid crystal layers; or

[0108] The chiral dopants in the first and second liquid crystal layers, wherein the different chiral dopants in the first and second liquid crystal layers have the same axial rotation.

[0109] Example 32: The method according to any one of Examples 29-31, wherein providing a first liquid crystal layer in contact with the substrate and the first imprint stencil comprises:

[0110] The first liquid crystal layer is deposited on the substrate; and

[0111] Make the first liquid crystal layer contact the first imprint template.

[0112] Example 33: The method described according to any one of Examples 29-32 further includes:

[0113] To polymerize the molecules in the first liquid crystal layer;

[0114] Remove the first imprint template;

[0115] A second liquid crystal layer is deposited in contact with the first liquid crystal layer;

[0116] Make the second liquid crystal layer contact the second imprinting template; and

[0117] Align the molecules in the second liquid crystal layer with the surface feature pattern in the second imprint template.

[0118] Example 34: The method described according to any one of Examples 29-33 further includes:

[0119] This causes the molecules in the first liquid crystal layer to polymerize;

[0120] Remove the first imprint template;

[0121] A planarization layer is formed on the first liquid crystal layer;

[0122] A second liquid crystal layer is deposited on the planarization layer;

[0123] Make the second liquid crystal layer contact the second imprinting template; and

[0124] Align the molecules in the second liquid crystal layer with the surface feature pattern in the second imprint template.

[0125] Details of one or more embodiments of the subject matter described in this specification are set forth in the accompanying drawings and the following description. Other features, aspects, and advantages will become apparent from the description, drawings, and claims. It should be noted that the relative dimensions in the following drawings may not be drawn to scale. Attached Figure Description

[0126] Figure 1 The user view is shown via an augmented reality (AR) device.

[0127] Figure 2 An example of a wearable display system is shown.

[0128] Figure 3 A conventional display system for simulating three-dimensional images for users is shown.

[0129] Figure 4 An aspect of a method for simulating a 3D image using multiple depth planes is shown.

[0130] Figures 5A-5C The relationship between the radius of curvature and the focal radius is shown.

[0131] Figure 6 An example of waveguide stacking used to output image information to a user is shown.

[0132] Figure 7 An example of an outgoing beam output from a waveguide is shown.

[0133] Figure 8 An example of a stacked waveguide assembly is shown, where each depth plane includes an image formed using multiple different component colors.

[0134] Figure 9A A cross-sectional side view of an example of a stacked waveguide assembly is shown, each stacked waveguide including incoupling optical elements.

[0135] Figure 9B It shows Figure 9A A perspective view of an example of multiple stacked waveguides.

[0136] Figure 9C It shows Figure 9A and 9B A top plan view of an example of multiple stacked waveguides.

[0137] Figure 10A A top perspective view shows an example of a grating structure comprising multiple liquid crystal material sublayers.

[0138] Figure 10B It shows Figure 10A A side view of the grating structure.

[0139] Figure 11 An example of a grating structure comprising multiple liquid crystal material sublayers having laterally offset repeating units of liquid crystal molecules is shown.

[0140] Figure 12A and 12B-1 An example of a stacked grating structure is shown.

[0141] Figure 12B-2 yes Figure 12B-1 An example of a graph showing the tilt angle and thickness of the stack.

[0142] Figure 12C-1 An example of a single liquid crystal polarizing grating structure with a tilt angle is shown. Figure 12C-2 It shows Figure 12C-1 The example shown illustrates the first-order diffraction efficiency of a single liquid crystal polarizing grating structure with a tilt angle for light at different incident angles.

[0143] Figure 12D-1 An example of a stack of two liquid crystal polarization grating structures is shown, each with a different tilt angle. Figure 12D-2 It shows Figure 12D-1 The example shown illustrates the first-order diffraction efficiency of a stack of two liquid crystal polarization grating structures with respect to light at different incident angles, each with a different tilt angle.

[0144] Figures 13A-13E Examples of different structures formed during the process of manufacturing stacked grating structures are shown.

[0145] Figure 14 A stack of grating structures with multiple alignment layers is shown.

[0146] Figures 15A-15D Examples of different structures formed during another process of manufacturing stacked grating structures are shown.

[0147] The same reference numerals and names in the figures denote the same elements. Detailed Implementation

[0148] In some embodiments, diffractive optical elements, such as polarizing gratings, include liquid crystal grating structures (e.g., liquid crystal polarizing gratings) configured to diffract light efficiently (e.g., with a diffraction efficiency greater than or equal to about 40%) over a wide range of incident angles. The liquid crystal grating structure includes a plurality of liquid crystal material sublayers comprising liquid crystal molecules. The orientation of the liquid crystal molecules varies at regular intervals along a transverse axis across the sublayers, thereby forming repeating units with spaced-apart elongated liquid crystal molecules along the transverse axis. The repeating liquid crystal units are laterally offset relative to similar repeating units in adjacent liquid crystal material sublayers, such that the offset repeating units of different sublayers (e.g., adjacent sublayers) define a tilt angle (θ) relative to a normal to the transverse axis, wherein the normal extends parallel to the thickness dimension of the liquid crystal grating structure. Multiple liquid crystal grating structures can be formed in a stack, wherein each liquid crystal grating structure is formed by a plurality of liquid crystal material sublayers. The tilt angle of the sublayer forming each liquid crystal grating structure can have a different magnitude than the tilt angle of the sublayers forming adjacent liquid crystal grating structures in the stack. In some embodiments, the liquid crystal grating structures may have different compositions and / or thicknesses from one another. For example, different liquid crystal grating structures may have different concentrations and / or types of chiral dopants. In some embodiments, at least some of the liquid crystal grating structures may include liquid crystal materials different from those of other liquid crystal grating structures, and the materials used for each structure may be selected to provide a desired tilt angle.

[0149] In some embodiments, the liquid crystal material of each sublayer comprises liquid crystal molecules that are rotated with respect to liquid crystal molecules in other sublayers of the grating structure at a twist angle (Φ). In some embodiments, the twist angle is the relative azimuth angle between the liquid crystal molecules on the uppermost sublayer and the underlying (e.g., directly underlying) liquid crystal molecules on the lowermost sublayer. In some embodiments, the twist angles of the liquid crystal molecules in different liquid crystal grating structures within the liquid crystal grating structure can be different, resulting in different tilt angles with respect to different grating structures. For a given type of liquid crystal molecules, it should be understood that the twist angle can vary based on the presence of chiral dopants in the sublayers and the thickness of the liquid crystal material forming the liquid crystal grating structure (e.g., the total thickness of the sublayers forming a particular liquid crystal grating structure). Therefore, as discussed herein, different twist angle sizes with respect to different liquid crystal grating structures can be achieved by using different compositions and / or different thicknesses of the liquid crystal material forming each of the liquid crystal grating structures.

[0150] In some embodiments, an alignment layer can be used to orient liquid crystal molecules. An alignment layer can be deposited on a substrate and subsequently patterned. A first liquid crystal molecule layer can then be deposited on the alignment layer, allowing the liquid crystal molecules to align with the underlying pattern of the alignment layer. In some embodiments, as discussed herein, this alignment can result in the formation of multiple liquid crystal molecule sublayers having specific tilt angles. The liquid crystal molecules can then be fixed in place. In some embodiments, the liquid crystal molecules can be polymerizable, for example by exposure to an energy source such as UV light, wherein the liquid crystal molecules comprise photoactivated crosslinking chemicals. A second liquid crystal layer can then be deposited, allowing the liquid crystal molecules of this layer to align with the underlying liquid crystal layer, and then the liquid crystal molecules are fixed in place. In some embodiments, additional crystalline layers can be deposited, allowing their constituent liquid crystal molecules to self-align, and then the liquid crystal molecules are fixed in place. As discussed herein, the second and additional liquid crystal layers can have different compositions and / or thicknesses than the first liquid crystal layer, resulting in different tilt angles for each layer.

[0151] It should be understood that in some embodiments, liquid crystal molecules may be polymerizable and, once polymerized, may form a network with other liquid crystal molecules. For example, liquid crystal molecules may connect with other liquid crystal molecules via chemical bonds or linking chemicals. For ease of description, the term "liquid crystal molecule" is suitably used herein to refer to liquid crystal molecules prior to polymerization and to the liquid crystal domains formed by these molecules after polymerization. In some embodiments, once joined together, liquid crystal molecules may form liquid crystal domains having substantially the same orientation and position as before they were joined together.

[0152] Unrestricted by theory, different tilt angles can lead to different peak efficiencies for diffracting different light with different incident angles. By providing a liquid crystal grating structure comprising liquid crystal sublayers with different tilt angles (e.g., by modifying the twist angle of the liquid crystal molecules in the sublayers of the liquid crystal grating to achieve different tilt angles), different peak efficiencies can be combined to achieve a wide incident angle range, for which the stacking of liquid crystal grating structures is highly efficient with respect to diffracted light. Therefore, advantageously, the amount of light redirected by the liquid crystal grating structure can be increased.

[0153] Not limited by theory, in some embodiments, the diffraction angle of incident light is considered to be substantially proportional to (e.g., approximately equal to) the tilt angle (θ). In other words, the angle at which light is diffracted into the waveguide by the coupled optical element can be proportional to (e.g., approximately equal to) the tilt angle (θ). Therefore, the liquid crystal grating structure included in the coupled optical element can be configured to provide the desired tilt angle (θ), such as, for example, in the range of about ±85 degrees, by adjusting the amount and / or type of chiral dopant included in the sublayer, changing the thickness, etc. In some embodiments, the diffractive optical element can be configured to efficiently diffract (e.g., diffraction efficiency greater than or equal to about 40%) light incident at an angle of about ±30 degrees near the Bragg angle.

[0154] Furthermore, it should be understood that changing the grating period (e.g., the period of the individual liquid crystal molecules) can alter the wavelength of light most effectively diffracted by the liquid crystal grating structure. In some embodiments, multiple grating structures with different grating periods can be used to diffract light of different wavelengths. Such grating structures can be stacked vertically and / or arranged at the same vertical height (e.g., spaced laterally apart from each other).

[0155] In some embodiments, diffractive optical elements formed by grating structures can be used as components of a display system. The display system may include a waveguide and an image injection device configured to guide light flow into the waveguide. The diffractive optical element can be used as one or more of coupling-in optical elements, coupling-out optical elements, and optical elements for receiving incident light propagating in the waveguide and for redirecting the incident light such that the redirected light continues to propagate through the waveguide via total internal reflection. Examples of the latter type of optical element include pupil expanders, such as orthogonal pupil expanders (OPEs).

[0156] In some embodiments, diffractive optical elements can be used to couple in, couple out, and / or redirect light propagating within a waveguide. The light can be a single wavelength or a single wavelength range. In some other embodiments, the light can be an optical flow that is part of a multiplexed optical flow comprising multiple optical flows having different optical properties (e.g., each flow may have a different wavelength). For example, the waveguide may include diffractive optical elements that can be configured to selectively redirect an optical flow formed by light having specific optical properties (e.g., a first wavelength) while being substantially transmissive to one or more other optical flows (e.g., having wavelengths different from the first wavelength). In some embodiments, the waveguide is part of a waveguide stack that may include a second waveguide including a coupling optical element configured to selectively steer a second optical flow while transmitting one or more other optical flows. In some embodiments, the coupling diffractive optical element of the waveguide is configured to transmit at least one of the optical flows to the coupling diffractive optical element of the second waveguide.

[0157] Referring now to the accompanying drawings, wherein like reference numerals denote like parts throughout. It should be understood that the embodiments disclosed herein generally include an optical system that includes a display system. In some embodiments, the display system is wearable, which can advantageously provide a more immersive VR or AR experience. For example, a display comprising one or more waveguides (e.g., waveguide stacks) can be configured to be worn and positioned in front of the eyes of a user or viewer. In some embodiments, two waveguide stacks (one waveguide stack for one of the viewer's eyes) can be used to provide different images to each eye.

[0158] Example display system

[0159] Figure 2 An example of a wearable display system 60 is shown. The display system 60 includes a display 70 and various mechanical and electronic modules and systems supporting the functionality of the display 70. The display 70 may be coupled to a frame 80, which may be worn by a user or viewer 90 of the display system and configured to position the display 70 in front of the user 90's eyes. In some embodiments, the display 70 may be considered eyewear. In some embodiments, a speaker 100 is coupled to the frame 80 and configured to be located near the user 90's ear canal (in some embodiments, another speaker (not shown) is located near the user's other ear canal to provide stereo / shape-shifting sound control). In some embodiments, the display system may also include one or more microphones 110 or other devices to detect sound. In some embodiments, the microphones are configured to allow the user to provide input or commands to the system 60 (e.g., voice menu commands, natural language questions, etc.) and / or may allow audio communication with other people (e.g., users of other similar display systems). The microphones may also be configured as peripheral sensors to collect audio data (e.g., sound from the user and / or environment). In some embodiments, the display system may further include a peripheral sensor 120a, which may be detached from the frame 80 and attached to the body of the user 90 (e.g., the user 90's head, torso, limbs, etc.). In some embodiments, the peripheral sensor 120a may be configured to acquire data characterizing the physiological state of the user 90. For example, the sensor 120a may be an electrode.

[0160] Continue to refer to Figure 2The display 70 is operatively coupled to the local data processing and module 140 via a communication link 130 (e.g., via a wired lead or wireless connection). The local data processing and module 140 can be mounted in various configurations, such as being fixedly attached to the frame 80, fixedly attached to a helmet or hat worn by the user, embedded in headphones, or otherwise detachably attached to the user 90 (e.g., in a backpack configuration or a belt-coupled configuration). Similarly, the sensor 120a can be operatively coupled to the local processing and data module 140 via a communication link 120b (e.g., via a wired lead or wireless connection). The local processing and data module 140 may include a hardware processor and digital memory such as non-volatile memory (e.g., flash memory or hard disk drive), both of which can be used for auxiliary processing, caching, and storing data. The data includes: a) data captured from sensors (which may be operatively coupled to frame 80 or otherwise operatively attached to user 90), such as image capture devices (e.g., cameras), microphones, inertial measurement units, accelerometers, compasses, GPS units, radios, gyroscopes, and / or other sensors disclosed herein; and / or b) data acquired and / or processed using remote processing module 150 and / or remote data storage 160 (which includes data related to virtual content), which may be transmitted to display 70 after such processing or retrieval. Local processing and data module 140 may be operatively coupled to remote processing module 150 and remote data storage 160 via communication links 170, 180, such as via wired or wireless communication links, such that these remote modules 150, 160 are operatively coupled to each other and can be used as resources of local processing and data module 140. In some embodiments, the local processing and data module 140 may include one or more of an image capture device, a microphone, an inertial measurement unit, an accelerometer, a compass, a GPS unit, a wireless device, and / or a gyroscope. In some other embodiments, one or more of these sensors may be attached to the frame 80 or may be a separate structure that communicates with the local processing and data module 140 via a wired or wireless communication path.

[0161] Continue to refer to Figure 2In some embodiments, the remote processing module 150 may include one or more processors configured to analyze and process data and / or image information. In some embodiments, the remote data repository 160 may include a digital data storage facility that may be available via the Internet or other network configurations in a "cloud" resource configuration. In some embodiments, the remote data repository 160 may include one or more remote servers that provide information, such as information for generating augmented reality content, to the local processing and data module 140 and / or the remote processing module 150. In some embodiments, all data is stored and all computations are performed in the local processing and data module, thereby allowing for completely autonomous use from the remote module.

[0162] An image can be perceived as “three-dimensional” or “3-D” by providing a slightly different image presentation to each of the viewer’s eyes. Figure 3 A conventional display system for simulating 3D images for a user is illustrated. Two distinct images 190 and 200—one for each eye 210 and 220—are output to the user. Images 190 and 200 are spaced 230 from the eyes 210 and 220 along an optical axis or z-axis parallel to the viewer's line of sight. Images 190 and 200 are flat, and the eyes 210 and 220 can focus on the images by presenting a single adaptive state. Such a 3D display system relies on the human visual system to combine images 190 and 200 to provide a sense of depth and / or scale in the combined image.

[0163] However, it should be understood that the human visual system is more complex and providing a realistic perception of depth is more challenging. For example, many viewers of conventional “3-D” display systems find such systems uncomfortable or completely incapable of perceiving depth. Without being bound by theory, it is believed that viewers of objects may perceive them as “three-dimensional” due to a combination of convergence and adaptation. The convergence and divergence of the two eyes relative to each other (i.e., the rotation of the eyes, causing the pupils to move toward or away from each other to converge the eyes’ line of sight to an object) are closely related to the focusing (or “adaptation”) of the eye’s lens and pupil. Under normal circumstances, changing the focusing of the eye’s lens or adapting the eye to change the focusing when switching from one object to another at a different distance will automatically result in a matching change that converges or diverges to the same distance due to a relationship known as the “accommodation-vergence reflex” and pupil dilation or constriction. Similarly, under normal circumstances, changes in convergence and divergence will trigger matching changes in the adaptation of the lens shape and pupil size. As described in this article, many stereoscopic or “3-D” display systems present a scene to each eye using slightly different presentations (and therefore slightly different images), allowing the human visual system to perceive three-dimensional perspective. However, such systems are uncomfortable for many viewers because, among other things, they simply provide different presentations of the scene, and the eyes view all image information in a single adaptive state, violating the “adaptation-convergence reflex” principle. Display systems that provide a better match between adaptation and convergence can create more realistic and comfortable 3D image simulations, thus contributing to increased wear time and compliance with diagnostic and treatment protocols.

[0164] Figure 4 This illustrates aspects of a method for simulating 3D images using multiple depth planes. (Continue to reference...) Figure 4Objects at different distances along the z-axis from eyes 210 and 220 are adapted by eyes 210 and 220 to infocus those objects. Eyes 210 and 220 adopt specific adaptation states to bring objects at different distances along the z-axis into focus. Thus, a specific adaptation state can be said to be associated with a specific depth plane in depth plane 240, which has an associated focal length such that when the eye is in the adaptation state of that depth plane, an object or part of an object in that depth plane is in focus. In some embodiments, a three-dimensional image can be simulated by providing different renderings of the image to each of eyes 210 and 220, and also by providing different renderings of the image corresponding to each depth plane in the depth plane. Although shown separately for clarity, it should be understood that, for example, the fields of view of eyes 210 and 220 may overlap as the distance along the z-axis increases. Additionally, although shown flat for ease of illustration, it should be understood that the shape of the depth plane may be curved in physical space such that all features in the depth plane are in focus with the eye in a specific adaptation state.

[0165] The distance between the object and the eye (210 or 220) can also change the amount of light scattering from the object, as seen by the eye. Figures 5A-5C The relationship between distance and ray divergence is illustrated. The distance between the object and eye 210 is represented by the order R1, R2, and R3, which decrease in distance. Figures 5A-5C As shown, light rays become more divergent as the distance to the object decreases. As the distance increases, the light rays become more collimated. In other words, it can be said that the light field generated by a point (an object or part of an object) has a spherical wavefront curvature, which is a function of how far that point is from the user's eye. The curvature increases as the distance between the object and the eye 210 decreases. Therefore, the divergence of light rays differs at different depth planes, increasing as the distance between the depth plane and the viewer's eye 210 decreases. While to clearly illustrate... Figures 5A-5C The other figures in this article show only a single eye 210, but it should be understood that the discussion of eye 210 can be applied to both eyes 210 and 220 of the viewer.

[0166] Unrestricted by theory, it is believed that the human eye can typically interpret a finite number of depth planes to provide depth perception. Therefore, by providing the eye with different representations of the image corresponding to each of these finite number of depth planes, a highly reliable simulation of depth perception can be achieved. These different representations can be individually focused by the viewer's eye, thus facilitating depth cues for the user based on eye adaptation and / or on observing different image features located on different, out-of-focus depth planes, where eye adaptation is required to focus on the different image features of the scene located on different depth planes.

[0167] Figure 6 An example of a waveguide stack for outputting image information to a user is shown. The display system 250 includes a waveguide stack or stacked waveguide assembly 260 that can be used to provide three-dimensional perception to the eye / brain using multiple waveguides 270, 280, 290, 300, 310. In some embodiments, the display system 250 is... Figure 2 System 60, of which Figure 6 Some parts of the system 60 are shown schematically in more detail. For example, the waveguide assembly 260 may be... Figure 2 It is part of the display 70. It should be understood that in some embodiments, the display system 250 may be considered a light field display.

[0168] Continue to refer to Figure 6Waveguide assembly 260 may also include a plurality of features 320, 330, 340, 350 located between waveguides. In some embodiments, features 320, 330, 340, 350 may be one or more lenses. Waveguides 270, 280, 290, 300, 310 and / or the plurality of lenses 320, 330, 340, 350 may be configured to send image information to the eye at various levels of wavefront curvature or light divergence. Each waveguide level may be associated with a specific depth plane and may be configured to output image information corresponding to that depth plane. Image injection devices 360, 370, 380, 390, 400 may serve as light sources for the waveguides and may be used to inject image information into waveguides 270, 280, 290, 300, 310, as described herein, wherein each waveguide may be configured to distribute incident light through each respective waveguide for output to the eye 210. Light leaves the output surfaces 410, 420, 430, 440, and 450 of the image injection devices 360, 370, 380, 390, and 400 and is injected into the corresponding input surfaces 460, 470, 480, 490, and 500 of the waveguides 270, 280, 290, 300, and 310. In some embodiments, each of the input surfaces 460, 470, 480, 490, 500 may be an edge of the corresponding waveguide or a portion of the main surface of the corresponding waveguide (i.e., one of the waveguide surfaces directly facing the world 510 or the viewer's eye 210). In some embodiments, a single beam of light (e.g., a collimated beam) may be injected into each waveguide to output the entire field of view of a cloned collimated beam oriented toward the eye 210 at a specific angle (and divergence) corresponding to a depth plane associated with a particular waveguide. In some embodiments, a single image injection device among the image injection devices 360, 370, 380, 390, 400 may be associated with multiple (e.g., three) of the waveguides 182, 184, 186, 188, 190 and inject light into multiple (e.g., three) of the waveguides 270, 280, 290, 300, 310.

[0169] In some embodiments, image injection devices 360, 370, 380, 390, and 400 are discrete displays, each generating image information for injection into corresponding waveguides 270, 280, 290, 300, and 310, respectively. In some other embodiments, image injection devices 360, 370, 380, 390, and 400 are the outputs of a single multiplexed display, which can, for example, deliver image information to each of the image injection devices 360, 370, 380, 390, and 400 via one or more optical guides (such as fiber optic cables). It will be understood that the image information provided by image injection devices 360, 370, 380, 390, and 400 may include light of different wavelengths or colors (e.g., different component colors as discussed herein).

[0170] In some embodiments, light injected into waveguides 270, 280, 290, 300, 310 is provided by a light projector system 520 including an optical module 530, which may include a light emitter, such as a light-emitting diode (LED). Light from the optical module 530 may be directed to an optical modulator 540 and modified via an optical beamsplitter 550 by the optical modulator 540 (e.g., a spatial light modulator). The optical modulator 540 may be configured to change the perceived intensity of light injected into waveguides 270, 280, 290, 300, 310. Examples of spatial light modulators include liquid crystal displays (LCDs), including liquid crystal on silicon (LCOS) displays.

[0171] In some embodiments, the display system 250 may be a scanning fiber optic display comprising one or more scanning fibers configured to project light in various patterns (e.g., raster scanning, spiral scanning, Lissajous patterns, etc.) into one or more waveguides 270, 280, 290, 300, 310 and ultimately into the viewer's eye 210. In some embodiments, the image injection devices 360, 370, 380, 390, 400 may schematically represent a single scanning fiber or a bundle of scanning fibers configured to inject light into one or more waveguides 270, 280, 290, 300, 310. In some other embodiments, the illustrated image injection devices 360, 370, 380, 390, 400 may schematically represent a plurality of scanning fibers or multiple bundles of scanning fibers, each of the plurality of scanning fibers or each of the multiple bundles of scanning fibers being configured to inject light into an associated waveguide among waveguides 270, 280, 290, 300, 310. It should be understood that one or more fibers may be configured to transmit light from optical module 530 to one or more waveguides 270, 280, 290, 300, 310. It should be understood that one or more intermediate optical structures may be provided between one or more scanning fibers and one or more waveguides 270, 280, 290, 300, 310 to, for example, redirect light emitted from the scanning fibers into one or more waveguides 270, 280, 290, 300, 310.

[0172] Controller 560 controls the operation of one or more of the stacked waveguide assemblies 260, including the operation of image injection devices 360, 370, 380, 390, 400, light source 530, and optical modulator 540. In some embodiments, controller 560 is part of local data processing module 140. Controller 560 includes programming (e.g., instructions in a non-transitory medium), such programming, according to any of the various schemes disclosed herein, that regulates the timing and delivery of image information to waveguides 270, 280, 290, 300, 310. In some embodiments, the controller may be a single monolithic device or a distributed system connected via wired or wireless communication channels. In some embodiments, controller 560 may be processing module 140 or 150. Figure 2 () part.

[0173] Continue to refer to Figure 6Waveguides 270, 280, 290, 300, and 310 can be configured to propagate light within each respective waveguide via total internal reflection (TIR). Waveguides 270, 280, 290, 300, and 310 can each be planar or have other shapes (e.g., curved surfaces) having a top primary surface and a bottom primary surface, and an edge extending between these top and bottom primary surfaces. In the illustrated configuration, waveguides 270, 280, 290, 300, and 310 can each include outcoupling optics 570, 580, 590, 600, and 610, which are configured to extract light outside the waveguide by redirecting light propagating within each respective waveguide to the outside of the waveguide, in order to output image information to eye 210. The extracted light can also be referred to as the outcoupling light, and the outcoupling optics light can also be referred to as the light extraction optics. The extracted light beam can be output from the waveguide at the location where the light extraction optics are located, as light propagating in the waveguide illuminates. The coupling optics 570, 580, 590, 600, and 610 may, for example, include gratings with diffractive optical features, as further discussed herein. Although illustrated for ease of description and clarity of illustration as being disposed on the bottom main surface of waveguides 270, 280, 290, 300, and 310, in some embodiments, the coupling optics 570, 580, 590, 600, and 610 may be disposed on the top and / or bottom main surfaces, and / or may be disposed directly within the volume of waveguides 270, 280, 290, 300, and 310, as further discussed herein. In some embodiments, the coupling optics 570, 580, 590, 600, and 610 may be formed in a material layer attached to a transparent substrate to form waveguides 270, 280, 290, 300, and 310. In some other embodiments, waveguides 270, 280, 290, 300, and 310 may be monolithic materials, and coupling optical elements 570, 580, 590, 600, and 610 may be formed on the surface of the monolithic material and / or within the monolithic material.

[0174] Continue to refer to Figure 6As discussed herein, each waveguide 270, 280, 290, 300, 310 is configured to output light to form an image corresponding to a specific depth plane. For example, the waveguide 270 closest to the eye can be configured to transmit collimated light (injected into this waveguide 270) to the eye 210. The collimated light may represent the optical infinity focal plane. The next up-waveguide 280 can be configured to transmit collimated light passing through a first lens 350 (e.g., a negative lens) before it can reach the eye 210; such a first lens 350 can be configured to produce a slightly convex wavefront curvature, such that the eye / brain interprets the light from the next up-waveguide 280 as originating from a first focal plane that is closer to the eye 210 from optical infinity. Similarly, the third uplink waveguide 290 causes its output light to pass through the first lens 350 and the second lens 340 before reaching the eye 210; the combined optical power of the first lens 350 and the second lens 340 can be configured to produce another incremental wavefront curvature so that the eye / brain interprets the light from the third waveguide 290 as coming from a second focal plane that is closer to the person from optical infinity than the light from the next uplink waveguide 280.

[0175] Other waveguide layers 300, 310 and lenses 330, 320 are similarly configured, with the highest waveguide 310 in the stack transmitting its output through all the lenses between it and the eye, representing the aggregate focal power representing the focal plane closest to the person. When viewing / interpreting light from world 510 from the other side of the stacked waveguide assembly 260, a compensation lens layer 620 can be positioned on top of the stack to compensate for the aggregate focal power of the underlying lens stack 320, 330, 340, 350 to compensate for the stacked lenses 320, 330, 340, 350. This configuration provides as many perceptible focal planes as available waveguide / lens pairs. The decoupled optics of the waveguides and the focusing aspects of the lenses can be static (i.e., not dynamic or electrically active). In some alternative embodiments, one or both can be dynamic using electrically active features.

[0176] In some embodiments, two or more of waveguides 270, 280, 290, 300, 310 may have the same associated depth plane. For example, multiple waveguides 270, 280, 290, 300, 310 may be configured to output images set to the same depth plane, or multiple subsets of waveguides 270, 280, 290, 300, 310 may be configured to output images set to the same multiple depth planes, one set for each depth plane. This can provide an advantage in forming tiled images to provide an extended field of view at those depth planes.

[0177] Continue to refer to Figure 6 The coupling optical elements 570, 580, 590, 600, and 610 can be configured to redirect light outside their respective waveguides and output light with appropriate divergence or collimation for a specific depth plane associated with that waveguide. As a result, waveguides with different associated depth planes can have different configurations of coupling optical elements 570, 580, 590, 600, and 610, which output light with different divergence depending on the associated depth plane. In some embodiments, the light extraction optical elements 570, 580, 590, 600, and 610 can be volumetric or surface features that can be configured to output light at a specific angle. For example, the light extraction optical elements 570, 580, 590, 600, and 610 can be volumetric holograms, surface holograms, and / or diffraction gratings. In some embodiments, features 320, 330, 340, and 350 may not be lenses; instead, they may simply be spacers (e.g., coverings and / or structures for forming air gaps).

[0178] In some embodiments, the coupling optical elements 570, 580, 590, 600, and 610 are diffraction features that form a diffraction pattern, or "diffractive optical elements" (also referred to herein as "DOEs"). Preferably, the DOEs have sufficiently low diffraction efficiency that only a portion of the light beam is deflected toward the eye 210 at each intersection of the DOE, while the remainder continues to travel through the waveguide via TIR. The light carrying image information is thus split into multiple associated outgoing beams that exit the waveguide at multiple locations, resulting in a relatively uniform pattern of outgoing emission toward the eye 210 for that particular collimated beam bouncing within the waveguide.

[0179] In some embodiments, one or more DOEs can be switchable between an "on" state where they actively diffract and an "off" state where they do not significantly diffract. For example, a switchable DOE may include a polymer-dispersed liquid crystal layer in which droplets contain diffraction patterns in a host medium, and the refractive index of the droplets may be switched to substantially match the refractive index of the host material (in which case the pattern does not significantly diffract incident light), or the droplets may be switched to a refractive index that does not match the refractive index of the host medium (in which case the pattern actively diffracts incident light).

[0180] In some embodiments, a camera assembly 630 (e.g., a digital camera, including visible light and infrared light cameras) may be provided to capture images of the eye 210 and / or tissues surrounding the eye 210, thereby, for example, detecting user input and / or monitoring the user's physiological state. As used herein, the camera can be any image capture device. In some embodiments, the camera assembly 630 may include an image capture device and a light source to project light (e.g., infrared light) onto the eye, which can then be reflected by the eye and detected by the image capture device. In some embodiments, the camera assembly 630 may be attached to a frame 80 (… Figure 2 It can also be electrically connected to processing modules 140 and / or 150, which can process image information from camera assembly 630 to make various determinations regarding, for example, the user's physiological state, as discussed herein. It should be understood that information regarding the user's physiological state can be used to determine the user's behavioral or emotional state. Examples of such information include the user's movements and / or facial expressions. The collected environmental and / or virtual content data can then be used to triangulate the user's behavioral or emotional state to determine the relationship between the behavioral or emotional state, the physiological state, and the environmental or virtual content data. In some embodiments, a single camera assembly 630 can be used for each eye to monitor each eye separately.

[0181] Now for reference Figure 7 An example of an outgoing beam output from a waveguide is shown. A waveguide is shown, but it should be understood that waveguide assembly 260 ( Figure 6 Other waveguides in the waveguide assembly 260 can function similarly, where the waveguide assembly 260 includes multiple waveguides. Light 640 is injected into waveguide 270 at its input surface 460 and propagates within waveguide 270 via TIR. At the point where light 640 impinges on DOE 570, a portion of the light exits the waveguide as an outgoing beam 650. The outgoing beam 650 is shown as substantially parallel, but as discussed herein, depending on the depth plane associated with waveguide 270, the outgoing beam 650 can also be redirected at an angle (e.g., forming a diverging outgoing beam) to propagate toward eye 210. It should be understood that a substantially parallel outgoing beam can indicate a waveguide including a coupling optics element that couples light out to form an image that appears to be positioned on a depth plane at a considerable distance (e.g., optical infinity) from eye 210. Other waveguides or other coupled optical element groups can output a more divergent outgoing beam pattern, which would require the eye 210 to adapt to a closer distance to focus it on the retina and be interpreted by the brain as light coming from a distance closer to the eye 210 than optical infinity.

[0182] In some embodiments, a panchromatic image can be formed at each depth plane by overlaying images of each component color (e.g., three or more component colors). Figure 8 An example of a stacked waveguide assembly is shown, where each depth plane includes an image formed using multiple different component colors. The illustrated embodiment shows depth planes 240a-240f, but more or fewer depths can also be considered. Each depth plane may have three or more component color images associated with it, including: a first image G of a first color; a second image R of a second color; and a third image B of a third color. Different numbers in the figure represent different depth planes for the diopter (dpt) following the letters G, R, and B. As an example, the number following each of these letters represents the diopter (1 / m), or the inverse distance of the depth plane from the viewer, and each box in the figure represents a separate component color image. In some embodiments, the precise placement of the depth planes with different component colors can be varied to address differences in the eye's focusing on different wavelengths of light. For example, different component color images of a given depth plane can be placed on depth planes corresponding to different distances from the user. Such an arrangement can increase visual sensitivity and user comfort and / or reduce chromatic aberration.

[0183] In some embodiments, light of each component color can be output by a single dedicated waveguide; therefore, each depth plane can have multiple waveguides associated with it. In such embodiments, each box in the figure including the letters G, R, or B can be understood as representing a separate waveguide, and each depth plane can provide three waveguides, where each depth plane provides three component color images. Although for ease of description, the waveguides associated with each depth plane are shown adjacent to each other in the figure, it should be understood that in a physical device, the waveguides can all be arranged as a stack with one waveguide per layer. In some other embodiments, multiple component colors can be output by the same waveguide, such that, for example, each depth plane can provide only a single waveguide.

[0184] Continue to refer to Figure 8 In some embodiments, G is green, R is red, and B is blue. In some other embodiments, other colors associated with light of other wavelengths (including magenta and cyan) may be used in addition to red, green, or blue, or one or more of red, green, or blue may be replaced. In some embodiments, features 320, 330, 340, and 350 may be active or passive optical filters configured to block or selectively transmit light from the surrounding environment to the viewer's eye.

[0185] It should be understood that reference to light of a given color throughout this disclosure will be understood as including light of one or more wavelengths within the wavelength range that a viewer perceives as having that given color. For example, red light may include light of one or more wavelengths in the range of about 620-780 nm, green light may include light of one or more wavelengths in the range of about 492-577 nm, and blue light may include light of one or more wavelengths in the range of about 435-493 nm.

[0186] In some embodiments, the light source 530 ( Figure 6 The display 250 can be configured to emit light at one or more wavelengths (e.g., infrared and / or ultraviolet wavelengths) outside the viewer's visual perception range. Furthermore, the waveguide's coupling-in, coupling-out, and other light redirection structures of the display 250 can be configured to direct the light from the display and towards the user's eye 210, for example, for imaging and / or user stimulation applications.

[0187] Now for reference Figure 9A In some embodiments, it may be necessary to redirect light incident on a waveguide to couple the light into the waveguide. Coupled optics can be used to redirect the light and couple it into its respective waveguide. Figure 9A A cross-sectional side view of an example of multiple stacked waveguides or stacked waveguide groups 660 is shown, each stacked waveguide including coupled optical elements. Each waveguide can be configured to output light of one or more different wavelengths, or light of one or more different wavelength ranges. It should be understood that stack 660 may correspond to stack 260 (…). Figure 6 The stacked waveguide 660 may correspond to a portion of multiple waveguides 270, 280, 290, 300, 310, except that one or more light from image injection devices 360, 370, 380, 390, 400 are injected into the waveguide from the location where the light needs to be redirected for coupling.

[0188] The stacked waveguide assembly 660 shown includes waveguides 670, 680, and 690. Each waveguide includes an associated coupling optics element (which may also be referred to as a light input region on the waveguide), such as coupling optics element 700 disposed on the main surface (e.g., upper main surface) of waveguide 670, coupling optics element 710 disposed on the main surface (e.g., upper main surface) of waveguide 680, and coupling optics element 720 disposed on the main surface (e.g., upper main surface) of waveguide 690. In some embodiments, one or more of the coupling optics elements 700, 710, and 720 may be disposed on the bottom main surface of the respective waveguide 670, 680, and 690 (particularly in the case where one or more coupling optics elements are reflective or deflective optics elements). As shown, coupling optics elements 700, 710, and 720 may be disposed on the upper main surface of their respective waveguides 670, 680, and 690 (or on top of the next lower waveguide), particularly in the case where the coupling optics elements are transmissive or deflective optics elements. In some embodiments, coupling optical elements 700, 710, 720 may be disposed within the body of the respective waveguides 670, 680, 690. In some embodiments, as discussed herein, coupling optical elements 700, 710, 720 are wavelength selective, such that they selectively redirect one or more wavelengths of light while transmitting other wavelengths. Although shown on one side or corner of their respective waveguides 670, 680, 690, it should be understood that in some embodiments, coupling optical elements 700, 710, 720 may be disposed in other regions of their respective waveguides 670, 680, 690.

[0189] As shown, the coupling optical elements 700, 710, and 720 can be laterally offset from each other. In some embodiments, each coupling optical element can be offset such that it receives light while the light does not pass through the other coupling optical element. For example, each coupling optical element 700, 710, and 720 can be configured to receive light from, for example,... Figure 6 The different image injection devices 360, 370, 380, 390 and 400 shown receive light and can be separated from other coupled optical elements 700, 710, 720 (e.g., laterally spaced) so that they substantially do not receive light from other coupled optical elements 700, 710, 720.

[0190] Each waveguide also includes associated light distribution elements, such as light distribution element 730 disposed on the main surface (e.g., top main surface) of waveguide 670, light distribution element 740 disposed on the main surface (e.g., top main surface) of waveguide 680, and light distribution element 750 disposed on the main surface (e.g., top main surface) of waveguide 690. In some other embodiments, light distribution elements 730, 740, and 750 may be disposed on the bottom main surface of associated waveguides 670, 680, and 690, respectively. In some other embodiments, light distribution elements 730, 740, and 750 may be disposed on the top and bottom main surfaces of associated waveguides 670, 680, and 690, respectively; or light distribution elements 730, 740, and 750 may be disposed on different main surfaces of the top and bottom main surfaces of different associated waveguides 670, 680, and 690.

[0191] Waveguides 670, 680, and 690 may be spaced apart and separated by layers of, for example, gaseous, liquid, and / or solid materials. For example, as shown, layer 760a may separate waveguides 670 and 680; and layer 760b may separate waveguides 680 and 690. In some embodiments, layers 760a and 760b are formed of a low-refractive-index material (i.e., a material having a lower refractive index than the material forming the adjacent waveguides in waveguides 670, 680, and 690). Preferably, the refractive index of the material forming layers 760a and 760b is 0.05 or more, or 0.10 or less, smaller than the refractive index of the material forming waveguides 670, 680, and 690. Advantageously, the low-refractive-index layers 760a and 760b may serve as clad layers that promote total internal reflection (TIR) ​​of light passing through waveguides 670, 680, and 690 (e.g., TIR between the top and bottom main surfaces of each waveguide). In some embodiments, layers 760a and 760b are formed of air. Although not shown, it should be understood that the top and bottom of the illustrated waveguide assembly 660 may include adjacent cladding layers.

[0192] Preferably, for ease of manufacturing and other considerations, the materials forming waveguides 670, 680, and 690 are similar or the same, as are the materials forming layers 760a and 760b. In some embodiments, the materials forming waveguides 670, 680, and 690 may be different among one or more waveguides, and / or the materials forming layers 760a and 760b may be different, while still maintaining the various refractive index relationships described above.

[0193] Continue to refer to Figure 9ALight rays 770, 780, and 790 are incident on waveguide assembly 660. It should be understood that light rays 770, 780, and 790 can be transmitted through one or more image injection devices 360, 370, 380, 390, and 400. Figure 6 Injected into waveguides 670, 680, and 690.

[0194] In some embodiments, the light rays 770, 780, and 790 have different properties, such as different wavelengths or different wavelength ranges, which may correspond to different colors. The coupled optical elements 700, 122, and 720 each deflect the incident light so that the light propagates through a corresponding waveguide 670, 680, or 690 via TIR.

[0195] For example, the coupling optical element 700 can be configured to deflect light 770 having a first wavelength or wavelength range. Similarly, transmitted light 780 is incident on and deflected by the coupling optical element 710, which is configured to deflect light having a second wavelength or wavelength range. Likewise, light 790 is deflected by the coupling optical element 720, which is configured to selectively deflect light having a third wavelength or wavelength range.

[0196] Continue to refer to Figure 9A The deflected light rays 770, 780, and 790 are deflected so that they propagate through the corresponding waveguides 670, 680, and 690; that is, the coupling optical elements 700, 710, and 720 of each waveguide deflect the light into the corresponding waveguide 670, 680, and 690 to couple the light into the corresponding waveguide. The light rays 770, 780, and 790 are deflected at a certain angle, which causes the light to propagate via TIR through the corresponding waveguides 670, 680, and 690. The light rays 770, 780, and 790 propagate via TIR through the corresponding waveguides 670, 680, and 690 until they reach the corresponding light distribution elements 730, 740, and 750 of the incident waveguide.

[0197] Now for reference Figure 9B , showed Figure 9A A perspective view of an example of multiple stacked waveguides. As described above, coupled rays 770, 780, and 790 are deflected by coupled optical elements 700, 710, and 720, respectively, and then propagate via TIR within waveguides 670, 680, and 690, respectively. Rays 770, 780, and 790 are then incident on light distribution elements 730, 740, and 750, respectively. Light distribution elements 730, 740, and 750 deflect rays 770, 780, and 790 so that they propagate toward coupled optical elements 800, 810, and 820, respectively.

[0198] In some embodiments, light distribution elements 730, 740, and 750 are orthogonal pupil expanders (OPEs). In some embodiments, the OPE deflects or distributes light to output optics 800, 810, and 820, and also increases the beam or spot size of the light as it propagates to the output optics. In some embodiments, for example, where the beam size already has a desired size, light distribution elements 730, 740, and 750 can be omitted, and input optics 700, 710, and 720 can be configured to directly deflect light to output optics 800, 810, and 820. For example, refer to... Figure 9A The light distribution elements 730, 740, and 750 can be replaced by coupling optical elements 800, 810, and 820, respectively. In some embodiments, the coupling optical elements 800, 810, and 820 are exit pupils (EP) or exit pupil expanders (EPE), which guide light in the viewer's eye 210. Figure 7 It should be understood that the OPE can be configured to increase the size of the eyebox on at least one axis, and the EPE can increase the eyebox on, for example, an axis orthogonal to the axis of the OPE.

[0199] Therefore, refer to Figure 9A and 9BIn some embodiments, waveguide group 660 includes waveguides 670, 680, and 690; coupling optics 700, 710, and 720; light distribution elements (e.g., OPE) 730, 740, and 750; and coupling out optics (e.g., EP) 800, 810, and 820 for each component color. Waveguides 670, 680, and 690 may be stacked, with an air gap / cladding layer between each. The coupling optics 700, 710, and 720 redirect or deflect incident light (using different coupling optics that receive light of different wavelengths) into their respective waveguides. The light then propagates at an angle, resulting in a TIR within the respective waveguides 670, 680, and 690. In the example shown, ray 770 (e.g., blue light) is deflected by the first coupled-in optics 700 and then continues to the waveguide, interacting with the light distribution element (e.g., OPE) 730 in the manner described above, and then with the coupled-out optics (e.g., EPs) 800. Rays 780 and 790 (e.g., green and red light, respectively) will pass through waveguide 670, where ray 780 is incident on coupled-in optics 710 and deflected by coupled-in optics 710. Ray 780 then hops to waveguide 680 via TIR, continues to the light distribution element (e.g., OPE) 740 thereto, and then to the coupled-out optics (e.g., EPs) 810. Finally, ray 790 (e.g., red light) passes through waveguide 690 as incident on the light coupled-in optics 720 of waveguide 690. The light-coupled optical element 720 deflects the light ray 790, causing the light to propagate via TIR to the light distribution element (e.g., OPE) 750, and then via TIR to the output optical element (e.g., EP) 820. The output optical element 820 then finally couples the light ray 790 out to the viewer, who also receives the coupled light from other waveguides 670, 680.

[0200] Figure 9C It shows Figure 9A and 9B A top plan view of an example of multiple stacked waveguides. As shown, waveguides 670, 680, 690 and the associated light distribution elements 730, 740, 750 and associated coupling optics 800, 810, 820 of each waveguide can be vertically aligned. However, as discussed herein, the coupling optics 700, 710, 720 are not vertically aligned; instead, the coupling optics are preferably non-overlapping (e.g., laterally spaced, as seen in the top view). As further discussed herein, this non-overlapping spatial arrangement facilitates the one-to-one injection of light from different sources into different waveguides, thereby allowing a specific light source to be uniquely coupled to a specific waveguide. In some embodiments, an arrangement including non-overlapping, spatially separated coupling optics may be referred to as a shifted pupil system, and the coupling optics within these arrangements may correspond to sub-pupils.

[0201] Example liquid crystal polarization grating

[0202] It should be understood that liquid crystal polarization gratings used for light manipulation can preferably diffract or redirect light at a large angle relative to the grating normal, to, for example, facilitate the coupling of light into a waveguide, allowing the light to propagate through the waveguide via TIR. However, conventional liquid crystal polarization gratings may struggle to achieve both high diffraction efficiency and large-angle light redirection. It has been found that inducing a twist along the thickness of the grating (which may result in the displacement of sublayers of the grating to define a tilt angle) can provide high diffraction efficiency while achieving large-angle diffraction or light redirection. However, the diffraction efficiency of such gratings is highly dependent on the angle of incidence of light on the grating. Advantageously, it has also been found that changing the tilt angle provides high efficiency over a wide range of incident angles. In some embodiments, the range of incident angles for achieving high efficiency can be increased by stacking multiple grating structures together, where each grating structure has a different tilt angle.

[0203] Advantageously, the various diffractive optical elements discussed herein can be grating structures, including liquid crystal grating structures, such as liquid crystal polarization gratings. The grating structure is preferably configured to provide high diffraction efficiency with respect to a wide range of incident angles (e.g., between approximately ±20 degrees near the Bragg angle, between approximately ±30 degrees near the Bragg angle, between approximately ±45 degrees near the Bragg angle, etc.). Therefore, the grating structures described herein can advantageously have low sensitivity to the incident angle of light. The grating structure can be fabricated using various methods, including but not limited to using a patterned alignment layer (which may be located beneath the liquid crystal material) to align the liquid crystal molecules in a layer of polymerizable liquid crystal material.

[0204] In some embodiments, the liquid crystal grating structure can be formed for waveguide stacking 260 ( Figure 6 ) or 660 ( Figures 9A-9C Various waveguide optical redirection elements in ) . For example, such liquid crystal grating structures can be advantageously used to form coupling optical elements 700, 710, 720, light distribution elements 730, 740, 750 and / or coupling out optical elements 800, 810, 820 ( Figures 9A-9C Beyond AR display systems, it should be understood that liquid crystal grating structures can be used in other applications that utilize diffractive optical elements. For example, liquid crystal grating structures can be used to manipulate light in other optical systems, including VR display systems, tablet computer monitors or televisions, lighting signs, imaging systems, etc.

[0205] It should be understood that liquid crystals are partially ordered materials, whose molecules are typically shaped into rods or plates that can be aligned along a certain direction. The orientation and pattern of liquid crystal molecules can be manipulated by using template patterns that interact with the molecules (e.g., through spatial and / or anchoring energy interactions). Furthermore, liquid crystal materials may include chiral dopants and / or reactive mesogens (RMs). Chiral dopants can cause liquid crystal molecules to rotate at a twist angle (Ф) across the thickness of the liquid crystal material, and reactive mesogens can allow the orientation and position of liquid crystal molecules to be fixed through polymerization.

[0206] Figure 10A A top perspective view shows an example of a grating structure 1001 including a first main surface 1002a and a second main surface 1002b. Multiple liquid crystal material sublayers (e.g., sublayers 1004a, 1004b, 1004c, and 1004d) may be included between the first surface 1002a and the second surface 1002b, as shown below. Figure 10B As shown, Figure 10B yes Figure 10A The diagram shows a side view of the structure. Each sublayer can be defined by multiple liquid crystal molecules arranged in a common plane; therefore, each sublayer is only the thickness of a single liquid crystal molecule. The sublayers form an aggregate layer of liquid crystal material with a thickness D, which can be equal to the total thickness of all sublayers. Although four sublayers are shown, it should be understood that the grating structure 1001 may include more or fewer sublayers.

[0207] Continue to refer to Figure 10A The grating structure 1001 has a surface normal 1003 intersecting the first and second surfaces 1002a and 1002b. As described above, in some embodiments, the liquid crystal material may have a twist angle (Ф) defined by the angular rotation between the liquid crystal molecules (e.g., 1005b) of the uppermost sublayer 1004a of the grating structure 1001 and the lower layer liquid crystal molecules (e.g., 1005b') of the lowermost sublayer 1004d of the grating structure 1001. Without being theoretically limited, the interaction between adjacent liquid crystal molecules can cause the orientation of the molecules to vary along the transverse axis (X) across the grating structure 1001 in a regular progression. Therefore, liquid crystal molecules can form repeating units, each of which has a similar liquid crystal orientation progression along the X-axis. Thus, the group of liquid crystal molecules for the repeating units in each of sublayers 1004a-1004d can have a period (Λ) equal to the transverse distance 1006' between two consecutive liquid crystal molecules having the same orientation, as shown in the side and / or top views.

[0208] Refer again Figure 10A and 10BIn some embodiments, the grating structure 1001 may include a chiral nematic liquid crystal material. For example, the plurality of liquid crystal material sublayers may include cholesteric liquid crystal materials. Preferably, the liquid crystal material is polymerizable. As discussed herein, the liquid crystal material may include reactive crystalline molecule (RM), such as liquid crystal diacrylate. Also as discussed herein, the grating structure 1001 preferably includes a chiral dopant that can be used to influence the twist angle Φ of the liquid crystal molecules. Examples of chiral dopant include cholesterol benzoate, cholesterol nonanoate, cholesterol chloride, and cholesterol oley carbonate.

[0209] refer to Figure 10B The diagram shows a single repeating unit for each sublayer 1004a, 1004b, 1004c, and 1004d. The repeating unit 1006 has a period of 1006'. Although the repeating units are shown as perfectly directly perpendicularly aligned for ease of discussion, it should be understood that twisting the liquid crystal molecules across the thickness of the grating structure 1001 can cause the repeating units of different sublayers to be laterally displaced relative to each other.

[0210] refer to Figure 11 In some embodiments, the sublayers 1004a, 1004b, 1004c, and 1004d of the liquid crystal material can be laterally offset relative to each other. This offset allows the grating optical axis passing through the corresponding liquid crystal molecules (i.e., liquid crystal molecules with the same orientation) in each of the multiple sublayers 1004a, 1004b, 1004c, and 1004d to be tilted at an angle θ relative to the normal to the transverse axis X, which can also be the normal to the main surface of the polarization grating structure. Therefore, the sublayers 1004a, 1004b, 1004c, and 1004d form a tilted grating pattern having a grating optical axis tilted at an angle θ relative to the normal to the main surface of the polarization grating structure 1001. In some embodiments, without being limited by theory, when the grating period satisfies the following conditions (1) for wavelength λ, average refractive index n, grating period Λ (corresponding to length 1006') and tilt angle θ of the grating optical axis of the grating structure, such a tilted grating pattern can efficiently diffract incident light perpendicularly.

[0211]

[0212] The following equation (2) can be used to determine the twist angle Ф based on the tilt angle θ of the grating optical axis, the twist angle Ф, the thickness D of the grating structure, and the grating period Λ.

[0213]

[0214] Continue to refer to Figure 11Liquid crystal molecules in multiple sublayers 1004a, 1004b, 1004c, and 1004d can form repeating units. The period of the repeating unit can be equal to the period (Λ) of the liquid crystal molecules. The repeating unit in each of the multiple liquid crystal sublayers can be laterally offset by a displacement distance r relative to the repeating unit in the adjacent sublayer. It should be understood that the tilt angle (θ) can be determined based on the angle formed between the normal to the main surface of the grating structure 1001 and an imaginary line extending between similar points in the repeating liquid crystal units of the directly adjacent sublayers. For example, the imaginary line can be defined by the right-hand edge of the repeating unit, as shown in the figure.

[0215] Unrestricted by theory, when the liquid crystal molecules of the grating structure 1001 are chiral, the anisotropic orientation of the liquid crystal material rotates along the thickness of the polarization grating structure. The amount of rotation (also known as the torsion angle of the liquid crystal material) is determined by the pitch P, which is the distance of a 360-degree rotation of the anisotropic axis of the liquid crystal. In some embodiments, the grating structure 1001 has a uniform and continuous cycloidal anisotropic profile, and the rotation of the anisotropy along the thickness D of the grating structure 1001 results in a lateral displacement (ρ) of the anisotropic profile along the grating direction. This increases the inclination of the grating optical axis relative to the normal of the main surface of the grating structure, such as... Figure 11 As shown. As discussed above with respect to equation (2), the tilt angle θ of sublayers 1004a, 1004b, 1004c, and 1004d depends on the twist angle Ф of the liquid crystal molecules, the thickness D of the grating structure 1001, and the grating period Λ. Therefore, the tilt angle of the grating optical axis can be changed by altering the twist angle of the liquid crystal molecules, the thickness D of the grating structure, and / or the period Λ of the grating structure. With the period and thickness D of the grating structure constant, the tilt angle can be changed by altering the twist angle of the liquid crystal molecules in the grating structure. It should be understood that, furthermore, the twist angle can be changed based on the chiral dopant of the doped grating structure and the thickness D of the grating structure.

[0216] As discussed herein, while grating structures such as grating structure 1001 advantageously provide high diffraction efficiency and large-angle diffraction, these grating structures can only achieve this efficient large-angle diffraction with respect to a limited range of incident angles. Undesirably, light incident on the grating structure outside this limited range of incident angles cannot be effectively diffracted. To increase the large-angle diffraction efficiency with respect to light with different incident angles, multiple liquid crystal grating structures with different tilt angles can be used. Preferably, these grating structures are formed in a stacked configuration.

[0217] This stacking Figure 12A and 12B-1 As shown in the image. Figure 12AAn example of a liquid crystal polarization grating (LCPG) stack 1100a including two liquid crystal polarization grating (LCPG) structures 1110 and 1120 is shown. The first LCPG structure 1110 includes a plurality of liquid crystal sublayers 1104a-1, 1104b-1, 1104c-1, and 1104d-1, which are laterally offset from each other by a distance r1, such that repeating units formed by a plurality of liquid crystal molecules are laterally displaced by a distance ρ1 on a thickness D1, resulting in a tilt angle θ1 relative to the surface normal of the first LCPG structure. The second LCPG structure 1120 is disposed on top of and preferably in direct contact with the first LCPG structure 1110. The second LCPG 1120 structure includes multiple liquid crystal sublayers 1104a-2, 1104b-2, and 1104c-2, which are offset from each other by a distance r2, such that the repeating units formed by multiple liquid crystal molecules are laterally shifted by a distance ρ2 on the thickness D2. This causes the optical axis of the second grating to be tilted at a tilt angle θ2 relative to the surface normal of the second LCPG structure. Preferably, the tilt angles θ1 and θ2 are of different magnitudes.

[0218] Continue to refer to Figure 12A The lateral shift ρ2 of grating structure 1120 can be smaller than the lateral shift ρ1 of grating structure 1110. Therefore, the tilt angle θ2 of grating structure 1120 is smaller than the tilt angle θ1 of grating structure 1110.

[0219] Figure 12B-1 An example of a grating structure is shown, wherein a third LCPG structure 1130 is disposed above a second LCPG structure 1120. The third LCPG structure 1130 may include a plurality of liquid crystal sublayers 1104a-3 and 1104b-3, which are laterally offset relative to each other such that repeating units formed by a plurality of liquid crystal molecules in sublayers 1104a-3 and 1104b-3 are laterally displaced by a distance ρ3 in thickness D3, resulting in a third tilt angle θ3 relative to the surface normal of the third LCPG structure. It should be understood that the lateral displacement ρ3 of the third LCPG structure is greater than the lateral displacement ρ1 of the first LCPG structure. Therefore, the tilt θ3 of the third grating optical axis is greater than the tilt θ1 of the first grating optical axis.

[0220] Figure 12B-2 yes Figure 12B-1 The example shown is a graph depicting the tilt angle and thickness of a stacked grating structure. Without being limited by theory, the tilt angle can be understood as the angle corresponding to the optical axis of the grating, and... Figure 12B-2 The graph shown can be interpreted as illustrating the change in the optical axis across the stack of grating structures.

[0221] The various embodiments of the liquid crystal polarizing grating structure described herein can be configured to diffract various wavelengths in the ultraviolet, visible, and infrared spectral ranges. For example, the grating structure can be configured to diffract incident light having wavelengths in the range of about 300 nm to about 10 μm. In some embodiments, to achieve a high diffraction angle, it may be necessary for the period Λ of the grating structure to be approximately equal to or even smaller than the wavelength of the incident light. Therefore, depending on the wavelength range on which the grating structure is configured to operate, the period Λ of the grating structure can be between about 200 nm and about 100 μm. For example, the period Λ of the grating structure can be between about 200 nm and about 350 nm, between about 330 nm and about 410 nm, between about 370 nm and about 480 nm, between about 450 nm and about 510 nm, between about 500 nm and about 570 nm, between about 550 nm and about 700 nm, between about 650 nm and about 1 μm, between about 980 nm and about 3 μm, between about 1.3 μm and about 3.2 μm, between about 2.3 μm and about 5 μm, between about 5 μm and about 10 μm, between about 5 μm and about 100 μm, or any value within these ranges or subranges. Preferably, in display applications, the grating structure is configured to diffract visible light such that the light propagates away from the grating structure at a wide diffraction angle, such that the wide diffraction angle is, for example, an angle suitable for the TIR within the waveguide on which the grating structure can be formed.

[0222] In some embodiments, the thickness D (e.g., D1, D2, and D3) of the various embodiments of the LCPG structure described herein can range from about 100 nm to about 50 μm. For example, the thickness D of the grating structure can be in the range of about 100 nm to about 350 nm, in the range of about 320 nm to about 510 nm, in the range of about 450 nm to about 600 nm, in the range of about 550 nm to about 800 nm, in the range of about 700 nm to about 1 μm, in the range of about 1 μm to about 5 μm, in the range of about 3 μm to about 10 μm, in the range of about 7.5 μm to about 20 μm, in the range of about 15 μm to about 30 μm, in the range of about 25 μm to about 50 μm, or any value within these ranges or subranges. In some embodiments, the thickness of the stacked grating structures differs by about 0 to 10 μm, including about 0 to 100 nm, about 100 nm to 1 μm, about 1 μm to 2 μm, or about 2 μm to 10 μm.

[0223] In some embodiments, the tilt angle θ of the grating optical axis (e.g., θ1, θ2, and θ3) can be in the range of -85 degrees to about 85 degrees. For example, the tilt angle θ can be in the range of -10 degrees to about 10 degrees, in the range of -20 degrees to about 20 degrees, in the range of -35 degrees to about 35 degrees, in the range of -45 degrees to about 45 degrees, in the range of -50 degrees to about 50 degrees, in the range of -65 degrees to about 65 degrees, in the range of -75 degrees to about 75 degrees, or any value within these ranges or subranges. Preferably, the tilt angle between the stacked grating structures differs by about 0 to ±90 degrees, including about 0 to ±10 degrees, about ±10 degrees to ±20 degrees, about ±20 degrees to ±30 degrees, about ±30 degrees to ±40 degrees, about ±40 degrees to ±50 degrees, about ±50 degrees to ±60 degrees, about ±60 degrees to ±70 degrees, about ±70 degrees to ±80 degrees, or about ±80 degrees to ±90 degrees.

[0224] In some embodiments, the pattern shift distance ρ (e.g., ρ1, ρ2, and ρ3) of the grating pattern across the thickness of the grating structure can be in the range of 1 nm to about 50 μm. For example, the pattern shift distance ρ of the grating structure can vary between about 1 nm and about 20 nm, between about 10 nm and about 50 nm, between about 25 nm and about 125 nm, between about 100 nm and about 350 nm, between about 320 nm and about 510 nm, between about 450 nm and about 600 nm, between about 550 nm and about 800 nm, between about 700 nm and about 1 μm, between about 1 μm and about 5 μm, between about 3 μm and about 10 μm, between about 7.5 μm and about 20 μm, between about 15 μm and about 30 μm, between about 25 μm and about 50 μm, or between any values ​​within these ranges or subranges.

[0225] In some embodiments, all sub-layers in the stacked grating structures can be shifted in the same direction, such as... Figure 10A , 10B As shown in 11, 12A, and 12B-1. For example, the repeating liquid crystal molecule units of each sublayer can be shifted to the same side, for example, to the left or to the right. For example, as Figure 12A and 12B-1 As shown, the optical axes of the different polarization grating stacks are all tilted to the right of the surface normal. Tilting the optical axes of the gratings of different sublayers to the same side can help increase the diffraction efficiency over a wider range of incident angles, as shown in the reference below. Figure 12C-1 , 12C-2 The explanation given by 12D-1 and 12D-2.

[0226] Now for reference Figure 12C-1 ,12C-2 12D-1 and 12D-2, which illustrate the advantageous diffraction efficiency of grating structure stacks with different tilt angles, as disclosed herein. Figure 12C-2 It shows Figure 12C-1 The first-order diffraction efficiency of a single liquid crystal polarization grating structure 1148 is shown. For light incident on the grating structure at an angle parallel to the normal to the main surface of the grating structure (i.e., at an angle of 0 degrees relative to the normal), the diffraction efficiency has a peak. However, the peak efficiency decreases rapidly with changing the incident angle. It has been found, however, that the peak diffraction efficiency can be changed by altering the tilt angle. It should be noted that, as... Figure 12D-2 As shown, Figure 12D-1 The stacking of two liquid crystal polarization grating structures 1150 and 1152 with different tilt angles, as shown, can provide multiple diffraction peaks, thereby effectively expanding the window on which high diffraction efficiency is achieved. Furthermore, the stacked grating structure can increase the diffraction efficiency of light incident at angles far from these peaks. For example, as... Figure 12D-1 and 12D-2 As shown, the grating structure of layer 1150 is tilted at a first tilt angle, which is configured to provide high diffraction efficiency for light with an incident angle of approximately -20 degrees to 0 degrees, and the grating structure of layer 1152 is tilted at a second tilt angle on the same side, which is configured to provide high diffraction efficiency for light with an incident angle of approximately 0 degrees to approximately 20 degrees. Therefore, compared with the structure of layer 1150, the grating structure of layer 1152 is tilted at a second tilt angle on the same side, which is configured to provide high diffraction efficiency for light with an incident angle of approximately 0 degrees to approximately 20 degrees. Figure 12C-1 and 12C-2 Compared to the approximately 20% diffraction efficiency achieved by the single grating structure 1148 shown, the diffraction efficiency of incident light in an angular range of ±20 degrees is increased to approximately 40%.

[0227] Although two liquid crystal polarization grating structures are shown for simplification Figure 12D-1 The illustration shows that, however, in some embodiments, two or more liquid crystal polarization grating structures (each with a different tilt angle and peak diffraction efficiency for light with different incident angles) can be stacked together to form a liquid crystal polarization grating structure stack. In some embodiments, the grating structure stack has a window of at least about 50 degrees, 40 degrees, or 30 degrees (with respect to the incident angle of light) while providing at least about 40% diffraction efficiency. Preferably, the diffraction efficiency is greater than about 50%, 60%, or 75% at the window.

[0228] As discussed herein, a liquid crystal polarization grating structure can be formed on a substrate, which may be a transmission waveguide. In some embodiments, the transmission waveguide may be transmissive to visible wavelengths of light and may be configured to guide the light internally via a TIR. The transmission waveguide may include coupling-in and coupling-out elements comprising a polarization grating structure comprising a plurality of liquid crystal material sublayers, wherein a repeating unit in each liquid crystal sublayer is laterally displaced relative to a corresponding repeating unit in an adjacent liquid crystal sublayer to define a tilt angle θ relative to the normal of the main surface of the polarization grating structure. The coupling-in and coupling-out elements may be disposed on the surface of the waveguide and may be configured to couple incident light into a guided mode of the waveguide or to couple light propagating within the waveguide out. In some other embodiments, the liquid crystal polarization grating structure may be used to redirect light propagating within the waveguide, for example, to change the direction of the light while allowing the light to continue propagating within the waveguide.

[0229] Example methods of manufacturing

[0230] refer to Figures 13A to 13E Examples of methods for fabricating the various liquid crystal polarization grating structures described herein are shown. References Figure 13A A substrate 1205 having an overlying alignment layer 1210 is provided. The substrate 1205 is preferably optically transmissive. Examples of suitable materials for the substrate include glass, quartz, sapphire, indium tin oxide (ITO), or polymeric materials, wherein polymeric materials include polycarbonate, polyacetate, and acrylic acid. In some embodiments, the substrate 1205 is transmissive to visible wavelengths of light.

[0231] In some embodiments, for example, the alignment layer 1210 may be a layer that causes the liquid crystal molecules to exhibit a specific orientation or pattern due to spatial interactions with the liquid crystal molecules and / or the anchoring energy applied to the liquid crystal molecules by the photoalignment layer. Examples of materials for the alignment layer 1210 include resists (e.g., photoresists), polymers, and resins. As examples, the alignment layer 1210 may include polyimide, linearly polarizable photopolymerizable polymer (LPP), azo-containing polymer, coumarin-containing polymer, and cinnamic acid ester-containing polymer. Preferably, the alignment layer 1210 may include a polymerizable liquid crystal material (e.g., a reactive liquid crystal precursor). In some embodiments, the alignment layer may be deposited on the main surface of the substrate, for example, by spin coating or jet deposition. It should be understood that the main surface may be the largest area surface of the substrate or one of a pair of opposing surfaces of similar size (each opposing surface having a larger area than the other surface).

[0232] refer to Figure 13BThe alignment layer 1210 can then be patterned. The pattern can correspond to a desired grating pattern of a liquid crystal polarization grating (e.g., the pattern can be the same as or the opposite of the desired grating pattern). In some embodiments, the alignment layer can contain photoactivated chemicals, and patterning can be accomplished by exposing the alignment layer to light of an appropriate wavelength for activating those chemicals. For example, a polarization interference pattern can be recorded in the alignment layer 1210 by generating two orthogonal circularly polarized beams (e.g., left-handed circularly polarized beam 1212a and right-handed circularly polarized beam 1212b) and directing these beams to the alignment layer, which can be formed of a linearly polarized photopolymerizable polymer material.

[0233] In some other embodiments, nanoimprint lithography can be used to pattern the alignment layer 1210 to create surface-embossed nanostructures within the alignment layer 1210. For example, the alignment layer 1210 may be formed of a resist material that is physically contacted and deformed by reticles that imprint the desired pattern into the alignment layer. In some embodiments, the alignment layer 1210 may then be exposed to light (e.g., UV light) to cure or harden the patterned layer 1210.

[0234] refer to Figure 13C Liquid crystal material layer 1215 can be deposited on patterned alignment layer 1210 and is allowed to self-organize into sublayers, as discussed herein. In some embodiments, the liquid crystal material can be deposited, for example, by spin coating. The liquid material can include polymerizable liquid crystal molecules, such as acrylate liquid crystals. Liquid crystal layer 1215 may also include a chiral dopant. Preferably, the chiral dopant is incorporated into the liquid crystal material prior to deposition on patterned alignment layer 1210. After deposition, the liquid crystal molecules of layer 1215 can be allowed to self-organize, thus forming the various sublayers disclosed herein. In some embodiments, self-organization can be promoted by applying thermal energy. In some embodiments, the liquid crystal molecules of layer 1215 can self-organize under naturally occurring forces over a period of time (e.g., hours or days). In some embodiments, the rate of self-organization of the liquid crystal molecules of layer 1215 can be increased by applying, for example, thermal energy. It should be understood that the thickness of layer 1215 and the characteristics and concentration of the chiral dopant can be selected to provide a specific twist angle for the liquid crystal molecules during self-organization.

[0235] Once self-organization is complete, the orientation and position of the liquid crystal molecules can be fixed, for example, through the polymerization of these molecules. In some embodiments, polymerization is initiated by applying UV light 1217 to the liquid crystal material 1215, such as... Figure 13D As shown.

[0236] like Figure 13E As shown, it can then be repeated Figure 13C-13D The process involves the sequential deposition, self-organization, and polymerization of additional liquid crystal layers. For example, liquid crystal layer 1220 can be deposited directly on and in contact with liquid crystal layer 1215, allowing for self-organization followed by polymerization. An additional liquid crystal layer 1222 can be deposited directly on and in contact with liquid crystal layer 1220, allowing for self-organization followed by polymerization. This sequence can then be repeated with respect to other liquid crystal layers. It should be understood that the thickness and chiral dopant concentration or composition of each of liquid crystal layers 1215, 1220, and 1222 can be different to provide different twist angles and different tilt angles, as discussed herein. It should be understood that once polymerized, liquid crystal layers 1215, 1220, and 1222 can form liquid crystal gratings, such as the liquid crystal gratings 1110, 1120, and 1130 discussed above.

[0237] Advantageously, each lower liquid crystal layer can serve as an alignment layer for the overlying liquid crystal layer that is in direct contact with that lower layer. This provides a simplified manufacturing process and also reduces Fresnel reflections at the interfaces between liquid crystal layers.

[0238] In some other embodiments, an additional alignment layer may be formed on one or more fixed liquid crystal layers before depositing additional liquid crystal layers. (See above regarding...) Figure 13A and 13B The discussion focuses on the deposition and patterning of additional alignment layers. In some embodiments, these additional alignment layers may be patterned with the same pattern as the patterned alignment layer 1210. In some other embodiments, these additional alignment layers may have different patterns than the patterned alignment layer 1210 to provide different light manipulation characteristics to the liquid crystal layer aligned with those additional alignment layers.

[0239] Figure 14 A stack of the resulting liquid crystal grating structures 1215, 1220, and 1222 is shown, wherein an additional patterned alignment layer 1211 is present between liquid crystal grating structures 1215 and 1220. In some other embodiments, the additional alignment layer and liquid crystal layer are processed on separate substrates and then transferred to another substrate by lamination.

[0240] In some embodiments, an imprinting template can be used to align liquid crystal molecules. The imprinting template can then be removed, allowing the formation of a liquid crystal grating structure without an alignment layer. Advantageously, the imprinting template can be used for more than one liquid crystal alignment, thus eliminating the need for patterning alignment layers for individual substrates. In some embodiments, the imprinting template can be an intermediate imprinting template, which is a replica of the main imprinting template, thus avoiding potential damage or contamination of the main imprinting template. Figures 15A to 15DA method for fabricating various liquid crystal polarization grating structures described herein using an imprint template is illustrated. The method involves aligning liquid crystal molecules in a liquid crystal layer based on a pattern of protrusions and recesses on the surface of the imprint template 1513. As described above, the imprint template 1513 can be used in place of the alignment layer 1210 and can have a pattern similar to that provided in the alignment layer 1210. Figure 15A As shown, a liquid crystal material layer 1515 is imprinted using an imprinting template 1513. In some embodiments, layer 1515 is first deposited on substrate 1505, and then layer 1515 is brought into contact with imprinting template 1513, such that a pattern in imprinting template 1513 is imprinted into layer 1515. In some other embodiments, layer 1515 is deposited on input template 1513 and then bonded to substrate 1505. It should be understood that various techniques can be used to deposit the liquid crystal material layer on the substrate, including but not limited to spray deposition or spin-coating deposition.

[0241] Continue to refer to Figure 15A The molecules of the liquid crystal material layer can be aligned (e.g., self-aligned or self-organized) based on the surface features of the imprint template 1513 to produce a liquid crystal polarization grating with the desired grating structure. As discussed herein, self-alignment can be facilitated by subjecting the liquid crystal material to elevated temperatures. After molecular self-alignment of the liquid crystal material and polymerization of the liquid crystal material with the grating structure (e.g., by exposure to UV light), the imprint template is subsequently separated from the liquid crystal layer 1515, as... Figure 15B As shown. It should be understood that removing the embossing template can leave a recessed pattern on the surface of the liquid crystal layer 1515. In some embodiments, the surface may be subjected to a planarization treatment (e.g., chemical and / or mechanical planarization treatment) to form a flat surface. For example, a planarization layer 1525 may be disposed on the patterned liquid crystal layer 1515, such as Figure 15D As shown. The exposed surface of the planarization layer 1525 (e.g., the surface opposite to the adjacent surface of the liquid crystal layer 1515) can be planarized using a planarization template (e.g., a template having a substantially flat surface) through chemical mechanical polishing, self-leveling, etc. In various embodiments, the planarization layer 1525 may comprise an oxide layer having a thickness between about 1 nm and about 100 nm. In various embodiments, the planarization layer 1525 may be configured to serve as an isolation layer. Alternatively, the planarization layer 1525 may be omitted, and the recessed pattern on the surface of the liquid crystal layer 1515 may be retained.

[0242] like Figure 15C and 15DAs shown, additional liquid crystal layers can be sequentially deposited on the polymerized liquid crystal layer 1515. As described above, the surface of the liquid crystal layer 1515 on which the additional layers are deposited can be planarized or a recessed pattern forming an imprinting template can be retained. The recessed pattern can then be filled with an optically transmissive filler (e.g., a planarization layer as described above), or the recessed pattern can simply be retained, and additional liquid crystal layers can be deposited into and over the recesses. It should be understood that each lower liquid crystal layer can be used as a self-aligned template for the overlying liquid crystal layer 1520 or 1522, as disclosed herein and as... Figure 15C As shown.

[0243] In some other embodiments, one or more additional liquid crystal layers can be imprinted using an imprinting template and these liquid crystal layers can be polymerized to achieve the desired alignment of liquid crystal molecules in those one or more additional liquid crystal layers 1520, 1522, or 1530. For example, in Figure 15D In the illustrated embodiment, a second liquid crystal layer 1530 is disposed on the planarization layer 1525 and imprinted by a second imprinting template. In such an embodiment, the second liquid crystal layer 1530 may have an orientation different from that obtained using a lower liquid crystal layer with an alignment layer. For example, different imprinting templates can be used to form a stack of liquid crystal gratings with different tilt angles without using a subsequent alignment layer. In some embodiments, a stack of liquid crystal grating structures 1515, 1520, and 1522 can be formed, wherein each layer is in direct contact with an adjacent layer and has a different tilt angle.

[0244] Various embodiments are envisioned to be implemented in or associated with a variety of applications, such as imaging systems and devices, display systems and devices, spatial light modulators, liquid crystal-based devices, polarizers, waveguides, etc. The structures, devices, and methods described herein are particularly applicable to displays such as wearable displays (e.g., head-mounted displays) that can be used for augmented and / or virtual reality. More generally, the described embodiments can be implemented in any device, apparatus, or system that can be configured to display images, whether moving (e.g., video) or still (e.g., still images), and whether text, graphics, or drawings. However, the described embodiments are envisioned to be included in or associated with a variety of electronic devices, such as, but not limited to: mobile phones, cellular phones enabling multimedia internet, mobile TV receivers, wireless devices, smartphones, etc. Devices, personal digital assistants (PDAs), wireless email receivers, handheld or portable computers, netbooks, notebooks, smartbooks, tablets, printers, copiers, scanners, fax machines, GPS receivers / navigators, cameras, digital media players (e.g., MP3 players), portable video cameras, game consoles, wristwatches, clocks, calculators, television monitors, flat panel displays, electronic reading devices (e.g., e-readers), computer monitors, automatic displays (including odometer and speedometer displays), cockpit controls and / or displays, camera view displays (e.g., displays in rearview cameras in vehicles), electronic photographs, electronic billboards or signs, projectors, building structures, microwave ovens, refrigerators, stereo systems, tape recorders or players, DVD players, CD players, VCRs, radios, portable memory chips, washing machines, dryers, washer / dryers, parking timers, head-mounted displays, and various imaging systems. Therefore, this teaching is not intended to be limited to the embodiments shown only in the accompanying drawings, but has a broad applicability that will be apparent to those skilled in the art.

[0245] Various modifications to the embodiments described in this disclosure will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the spirit or scope of this disclosure. Various changes and equivalents can be made to the described invention without departing from the true spirit and scope of the invention. Furthermore, numerous modifications can be made to adapt particular circumstances, materials, composition of substances, processes, one or more process actions, or one or more steps to one or more objects, spirit, or scope of the invention. All such modifications are intended to fall within the scope of the claims associated with this disclosure.

[0246] The word “exemplary” is used herein specifically to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. Furthermore, those skilled in the art will readily understand that the terms “upper” and “lower,” “above” and “below,” etc., are sometimes used to simplify the description of the drawings and to indicate relative positions corresponding to the orientation of graphics on a suitably oriented page, and may not reflect the orientation of the structures described herein when those structures are implemented.

[0247] Certain features described in the context of separate embodiments in this specification may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented individually or in any suitable sub-combination in multiple embodiments. Furthermore, although features may be described above as functioning in a particular combination, or even initially claimed in this manner, in some cases one or more features in the claimed combination may be removed from that combination, and the claimed combination may involve sub-combinations or variations thereof.

[0248] Similarly, although operations are shown in a specific order in the accompanying drawings, they should not be construed as requiring these operations to be performed in the specific order or sequence shown, nor should they be construed as requiring the execution of all shown operations to achieve the desired result. Furthermore, the drawings may schematically illustrate one or more example processes in the form of flowcharts. However, other operations not shown may be incorporated into the schematically shown example processes. For example, one or more additional operations may be performed before, after, between, or concurrently with any of the shown operations. In some cases, multitasking and parallel processing are advantageous. Moreover, the separation of various system components in the above embodiments should not be construed as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. Additionally, other embodiments are within the scope of the following claims. In some cases, the actions listed in the claims may be performed in a different order and still achieve the desired result.

[0249] This invention includes a method that can be performed using a subject device. The method may include the action of providing such a suitable device. This provision can be performed by an end user. In other words, the "providing" action only requires the end user to obtain, access, approach, locate, set, activate, turn on, or otherwise provide the necessary device in the method. The method described herein may be performed in any logically possible order of the events as well as in the order of the events described.

[0250] Exemplary aspects of the invention, as well as details regarding material selection and manufacturing, have been described above. Further details regarding the invention can be understood in conjunction with the foregoing references to the patents and publications, and what is commonly known or understood by those skilled in the art. The same applies to additional actions that are typically or logically utilized in relation to aspects of the basic method according to the invention.

[0251] Furthermore, although the invention has been described with reference to several examples incorporating various features optionally, the invention is not limited to the invention described or indicated for each variation thereof. Various changes may be made to the described invention without departing from the true spirit and scope thereof, and equivalents may be substituted (whether or not included herein for brevity). Moreover, where a range of values ​​is provided, it should be understood that every intermediate value between the upper and lower limits of the range, as well as any other stated or intermediate value within that range, is included within the scope of the invention.

[0252] Furthermore, it is conceivable that any optional features of the described variations of the invention may be claimed and asserted independently or in combination with any one or more of the features described herein. The use of singular terms includes plural terms that may exist. More specifically, as used herein and in the associated claims, the singular forms “a,” “an,” “the,” and “the” include plural objects unless expressly stated otherwise. In other words, the article “at least one” is permitted in the foregoing description and in the claims associated with this disclosure. It should be further noted that such claims may be drafted to exclude any optional elements. Therefore, this statement is intended as a preliminary basis for the use of exclusive terms such as “solely,” “only,” etc., in conjunction with claim elements or the use of “negative” limitations.

[0253] Without using such exclusive terminology, the term "comprising" in claims associated with this disclosure shall allow the inclusion of any additional elements, regardless of whether a given number of elements are enumerated in such claim or whether the addition of features may be considered to alter the nature of the elements recited in the claim. In addition to the specific definitions herein, all technical and scientific terms used herein shall be given the broadest possible common understanding meaning while preserving the validity of the claims.

[0254] The scope of this invention is not limited to the examples and / or subject matter descriptions provided, but is limited only by the scope of the claims language associated with this disclosure.

Claims

1. A display system, comprising: Optical transmission waveguide; A diffractive optical element, which forms a coupling optical element, an exit pupil expander, or an orthogonal pupil expander on the surface of the waveguide, the diffractive optical element comprising: Multiple liquid crystal sublayers, which include liquid crystal molecules, The liquid crystal molecules form periodic repeating units along the horizontal axis. Compared to a similar repeating unit in an adjacent sublayer of the plurality of sublayers, the repeating unit is laterally shifted by a displacement distance, wherein the displacement distance defines an angle of inclination relative to a normal to the transverse axis, the normal extending along the thickness axis of the diffractive optical element. The plurality of liquid crystal sublayers include a first plurality of liquid crystal sublayers and a second plurality of liquid crystal sublayers. The liquid crystal molecules of the first plurality of liquid crystal sublayers form a first repeating unit with a first period along the horizontal axis, and the liquid crystal molecules of the second plurality of liquid crystal sublayers form a second repeating unit with a second period along the horizontal axis. A first displacement distance between adjacent repeating units of the first plurality of sublayers defines a first tilt angle, and a second displacement distance between adjacent repeating units of the second plurality of sublayers defines a second tilt angle, wherein the first displacement distance is greater than the second displacement distance.

2. The system of claim 1, wherein the waveguides are part of a waveguide stack, wherein each of the waveguides has an associated diffractive optical element, the diffractive optical element comprising: Multiple liquid crystal sublayers, which include liquid crystal molecules, The liquid crystal molecules form periodic repeating units, wherein the repeating units are laterally shifted by a shift distance compared to a similar repeating unit in an adjacent sublayer of the plurality of sublayers, wherein the shift distance defines an angle of inclination relative to the normal of the horizontal axis.

3. A method for manufacturing an optical device, the method comprising: A first liquid crystal layer is provided in contact with a substrate and a first imprinting template, the first imprinting template including a plurality of surface features arranged in a first pattern; as well as The molecules in the first liquid crystal layer are aligned with the surface feature to form a first multi-level repeating liquid crystal molecule that defines a first tilt angle relative to a normal extending along the thickness axis of the first liquid crystal layer. The first multi-level repeating liquid crystal molecule forms a first repeating unit having a first period along the horizontal axis. A first displacement distance between adjacent repeating units of the first liquid crystal layer defines the first tilt angle. A second liquid crystal layer is provided, the second liquid crystal layer having a second tilt angle of a normal extending along the thickness axis of the second liquid crystal molecule layer, the second multi-level repeating liquid crystal molecules forming a second repeating unit having a second period along the horizontal axis, a second displacement distance between adjacent repeating units of the second liquid crystal layer defining the second tilt angle, the first displacement distance being greater than the second displacement distance.

4. The method according to claim 3, further comprising: To polymerize the molecules in the first liquid crystal layer; Remove the first imprint template; A second liquid crystal layer is deposited in contact with the first liquid crystal layer; as well as Align the molecules in the second liquid crystal layer with the molecules in the first liquid crystal layer.

5. The method according to claim 4, wherein the first liquid crystal layer and the second liquid crystal layer are doped with chiral dopants.

6. The method of claim 5, wherein at least one of the following is different between the first liquid crystal layer and the second liquid crystal layer: The thicknesses of the first liquid crystal layer and the second liquid crystal layer; The concentration of chiral dopants in the first and second liquid crystal layers; or The chiral dopants in the first liquid crystal layer and the second liquid crystal layer, wherein the different chiral dopants in the first liquid crystal layer and the second liquid crystal layer have the same chirality.

7. The method of claim 3, wherein providing the first liquid crystal layer in contact with the substrate and the first imprinting template comprises: The first liquid crystal layer is deposited on the substrate; as well as Make the first liquid crystal layer contact the first imprint template.

8. The method according to claim 4, further comprising depositing a third liquid crystal layer on the second liquid crystal layer.

9. The method according to claim 3, further comprising: To polymerize the molecules in the first liquid crystal layer; Remove the first imprint template; A second liquid crystal layer is deposited in contact with the first liquid crystal layer; Make the second liquid crystal layer contact the second imprint template; as well as Align the molecules in the second liquid crystal layer with the surface feature pattern in the second imprint template.

10. The method of claim 3, further comprising: This causes the molecules in the first liquid crystal layer to polymerize; Remove the first imprint template; A planarization layer is formed on the first liquid crystal layer; A second liquid crystal layer is deposited on the planarization layer; Make the second liquid crystal layer contact the second imprint template; as well as Align the molecules in the second liquid crystal layer with the surface feature pattern in the second imprint template.

11. The method according to claim 10, wherein, The planarization layer includes an optical transmission filler.

12. The method according to claim 10, wherein, After the molecules of the second liquid crystal layer are aligned, the molecules of the second liquid crystal layer have an orientation different from that of the molecules of the first liquid crystal layer.

13. An optical device, comprising: A first polarization grating structure having a first thickness, the first polarization grating structure comprising: The first plurality of liquid crystal sublayers, comprising liquid crystal molecules and chiral dopants; and A second polarization grating structure is located above the first polarization grating structure, the second polarization grating structure having a second thickness and comprising: The second set of multiple liquid crystal sublayers comprises liquid crystal molecules and chiral dopants. At least one of the following is different between the first and second polarization grating structures: The thickness of the first and second polarization grating structures; The concentration of chiral dopant in the first and second polarization grating structures; or The chiral dopants in the first and second polarization grating structures, wherein the different chiral dopants in the first and second polarization grating structures have the same chirality. Wherein, the liquid crystal molecules of the first plurality of liquid crystal sublayers form a first repeating unit with a first period along the horizontal axis, and the liquid crystal molecules of the second plurality of liquid crystal sublayers form a second repeating unit with a second period along the horizontal axis. A first shift distance between adjacent repeating units of the first plurality of sublayers defines a first tilt angle, and a second shift distance between adjacent repeating units of the second plurality of sublayers defines a second tilt angle. The first shift distance is greater than the second shift distance.

14. The device according to claim 13, wherein the liquid crystal molecule is a chiral nematic liquid crystal molecule.

15. The device of claim 13, wherein the concentrations of the chiral dopant in the first and second polarization grating structures differ by 0.1 wt% or more.

16. The device of claim 13, wherein the thickness difference between the first and second polarization grating structures is less than 10 μm.

17. The device according to claim 13, wherein, The first plurality of liquid crystal sublayers are laterally shifted by a first set displacement, and the first set displacement is greater than the second set displacement of the second plurality of liquid crystal sublayers.

18. The device according to claim 13, wherein, The repeating units of the liquid crystal sublayers of the first polarization grating structure and the second polarization grating structure are shifted in the same direction at higher levels.

19. The device according to claim 13, wherein, The first tilt angle and the second tilt angle are between -85 degrees and 85 degrees.

20. The device according to claim 13, wherein, The liquid crystal molecules in the plurality of sublayers include liquid crystal diacrylates.

21. The device according to claim 13, wherein, The spacing along the thickness axis between adjacent sub-layers of the first plurality of liquid crystal sub-layers is greater than the spacing along the thickness axis between adjacent sub-layers of the second plurality of liquid crystal sub-layers.

22. The device according to claim 13, wherein, The first polarization grating structure and the second polarization grating structure are on the waveguide.

23. The device according to claim 22, wherein, The first polarization grating structure and the second polarization grating structure are coupled optical elements configured to internally couple an incident beam into the waveguide such that the incident beam propagates through the waveguide via total internal reflection.

24. The device according to claim 23, wherein, The first polarization grating structure and the second polarization grating structure are output coupling optical elements configured to couple an incident beam propagating through the waveguide by total internal reflection.

25. The device according to claim 23, wherein, The first polarization grating structure and the second polarization grating structure are orthogonal pupil expanders configured to redirect light propagating through the waveguide via total internal reflection, wherein the redirected light continues to propagate through the waveguide via total internal reflection.

26. The device according to claim 23, wherein, It also includes waveguide stacks, each waveguide comprising a first polarization grating structure and a second polarization grating structure, which includes multiple liquid crystal sublayers with different tilt angles.

27. The device of claim 13, further comprising a third polarization grating structure above the second polarization grating structure, the third polarization grating structure comprising a third plurality of liquid crystal sublayers, the third plurality of liquid crystal sublayers comprising liquid crystal molecules and chiral dopants, in, The first polarization grating structure, the second polarization grating structure, and the third polarization grating structure differ from each other in at least one of the following ways: The thicknesses of the first polarization grating structure, the second polarization grating structure, and the third polarization grating structure; The concentration of chiral dopant in the first polarization grating structure, the second polarization grating structure, and the third polarization grating structure; or The first polarization grating structure, the second polarization grating structure, and the third polarization grating structure are chiral dopants, wherein the different chiral dopants of the first polarization grating structure and the second polarization grating structure have the same chirality.

28. The device according to claim 27, wherein, The liquid crystal molecules of the third plurality of liquid crystal sublayers form repeating units with a third period, wherein the repeating unit is laterally shifted by a third displacement distance compared to a similar repeating unit of an adjacent sublayer, wherein the repeating unit is shifted by a third displacement distance defining a third tilt angle relative to the normal of the horizontal axis, wherein the first tilt angle, the second tilt angle and the third tilt angle are of different magnitudes.

29. The device according to claim 27, wherein, The liquid crystal sublayer of each of the first polarization grating structure, the second polarization grating structure, and the third polarization grating structure has a different composition from the others in the first polarization grating structure, the second polarization grating structure, and the third polarization grating structure.

30. An optical device, comprising: A stack of waveguides, each waveguide comprising: A first polarization grating structure having a first thickness, the first polarization grating structure comprising: The first plurality of liquid crystal sublayers, comprising liquid crystal molecules and chiral dopants; and A second polarization grating structure is located above the first polarization grating structure. The second polarization grating structure has a second thickness and includes: The second set of multiple liquid crystal sublayers contains liquid crystal molecules and chiral dopants. The first and second polarization grating structures are situated on corresponding waveguides, and the first and second polarization grating structures are coupling optical elements configured to internally couple an incident beam into the corresponding waveguide, such that the incident beam propagates through the waveguide via total internal reflection. The tilt angles of the first and second plurality of liquid crystal sub-layers are different. Wherein, at least one of the following is different between the first and second polarization grating structures: The thickness of the first and second polarization grating structures; The concentration of chiral dopant in the first and second polarization grating structures; or The chiral dopants in the first and second polarization grating structures, wherein the different chiral dopants in the first and second polarization grating structures have the same rotational property.

31. A method for manufacturing an optical device, the method comprising: An alignment layer is provided on the first substrate; Pattern the alignment layer; A first liquid crystal layer is deposited on the alignment layer; The liquid crystal molecules in the first liquid crystal layer are aligned with the alignment layer to form a first plurality of sub-layers. The first plurality of sub-layers include repeating units of liquid crystal molecules arranged periodically along a horizontal axis. Each repeating unit of the first plurality of sub-layers is shifted by a first shift distance in a first shift direction compared to a repeating unit of an adjacent sub-layer, thereby defining a first tilt angle relative to the normal of the horizontal axis. A second liquid crystal layer is deposited on the first liquid crystal layer; The liquid crystal molecules in the second liquid crystal layer are aligned with the liquid crystal molecules in the immediately following lower first liquid crystal layer to form a second plurality of sublayers. The second plurality of sublayers include repeating units of liquid crystal molecules arranged periodically along a horizontal axis. Each repeating unit of the second plurality of sublayers is shifted by a second shift distance in a second shift direction compared to the repeating unit of an adjacent sublayer in the second plurality of sublayers, thereby defining a second tilt angle relative to the normal of the horizontal axis. The first tilt angle and the second tilt angle are different in size. Wherein, the first shift distance and the second shift distance are different. Wherein, the first shift direction and the second shift direction are the same, and Wherein, the first plurality of liquid crystal sub-layers are laterally shifted by a first set displacement, and the first set displacement is different from the second set displacement of the second plurality of liquid crystal sub-layers.

32. The method of claim 31, wherein patterning the alignment layer includes defining a groove pattern in the alignment layer.

33. The method of claim 32, wherein the groove pattern defining the alignment layer comprises nanoimprinting.

34. The method of claim 31, wherein patterning the alignment layer comprises recording an interference pattern in the alignment layer.

35. The method of claim 31, wherein the first liquid crystal layer and the second liquid crystal layer are doped with different concentrations of chiral dopant.

36. The method of claim 31, further comprising polymerizing the first liquid crystal layer prior to depositing the second liquid crystal layer.

37. The method according to claim 31, wherein the first liquid crystal layer and the second liquid crystal layer have different thicknesses.

38. The method of claim 31, further comprising a third liquid crystal layer deposited on the second liquid crystal layer.

39. The method of claim 31, further comprising: Provide a second substrate; An alignment layer is provided on the second substrate; Pattern the alignment layer; A second liquid crystal layer is deposited on the alignment layer; Align the liquid crystal molecules in the second liquid crystal layer with the alignment layer; The alignment layer and the second liquid crystal layer are laminated on the first liquid crystal layer.

40. The method of claim 31, further comprising: An additional alignment layer is deposited on the first liquid crystal layer; and Pattern the additional alignment layer.

41. The method according to claim 40, wherein, Compared to the alignment layer, the additional alignment layer is patterned with a different pattern.

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