Optical eyepiece using one-sided patterning of grating couplers.

Abstract

To provide an optical eyepiece using single-sided patterning of grating couplers.SOLUTION: An eyepiece includes a substrate and an in-coupling grating patterned on a single side of the substrate. A first grating coupler is patterned on the single side of the substrate, and has a first grating pattern. The first grating coupler is optically coupled to the in-coupling grating. A second grating coupler is patterned on the single side of the substrate adjacent to the first grating coupler. The second grating coupler has a second grating pattern different from the first grating pattern. The second grating coupler is optically coupled to the in-coupling grating.SELECTED DRAWING: None

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of U.S. Provisional Application No. 62 / 861,646, filed June 14, 2019, which is incorporated by reference in its entirety.

[0002] The present disclosure relates to an optical eyepiece using one-sided patterning of a grating coupler. [Background technology]

[0003] Imprint lithography can be used to fabricate nanometer-scale patterns on a wafer. Imprint lithography creates patterns by mechanical deformation of an imprint resist and subsequent processes. However, eyepieces fabricated using imprint lithography may have a limited field of view. Light must generally travel a long distance to reach the eyepiece's exit pupil expander. As light travels along a long distance, coherent artifacts worsen. Also, double-sided lithography traditionally used to fabricate eyepieces may increase processing complexity and reduce manufacturing yields and throughput. Summary of the Invention [Means for solving the problem]

[0004] Innovative aspects of the subject matter described herein include an optical eyepiece using patterning of grating couplers. The eyepiece includes a substrate and an internal coupling grating patterned on one side of the substrate. A first grating coupler is patterned on the one side of the substrate and has a first grating pattern. The first grating coupler is optically coupled to the internal coupling grating. A second grating coupler is patterned on the one side of the substrate adjacent to the first grating coupler. The second grating coupler has a second grating pattern different from the first grating pattern. The second grating coupler is optically coupled to the internal coupling grating.

[0005] An innovative aspect of the subject matter described herein further includes an eyepiece including an internal coupling grating patterned on one side of a substrate. The internal coupling grating is configured to diffract light received from a projector into a first portion of light and a second portion of light. The first portion has a first orientation with respect to the light received from the projector. The second portion has a second orientation with respect to the light received from the projector. The second orientation is different from the first orientation. A diffraction grating is patterned on one side of the substrate. The diffraction grating is configured to receive the first portion of light and the second portion of light from the internal coupling grating. The first portion of light and the second portion of light are each diffracted. The diffracted first portion of light and the diffracted second portion of light are combined.

[0006] Innovative aspects of the subject matter described herein further include an eyepiece including an internal coupling grating imprinted on one side of a substrate. A grating coupler is imprinted on the one side of the substrate. The grating coupler is optically coupled to the internal coupling grating. The grating coupler includes a plurality of tiles that define an exit pupil expander (EPE) of the eyepiece. Each tile of the plurality of tiles has a first grating pattern. Grating regions are interspersed between the tiles. The grating regions have a second grating pattern that is different from the first grating pattern. The grating regions define an orthogonal pupil expander (OPE) of the eyepiece.

[0007] Innovative aspects of the subject matter described herein further include an eyepiece lens including a substrate having a refractive index above a threshold. An internal coupling grating is patterned on one side of the substrate. Three or more grating couplers are patterned on one side of the substrate. The three or more grating couplers are optically coupled to the internal coupling grating. Each grating coupler of the three or more grating couplers has a different grating pattern.

[0008] Innovative aspects of the subject matter described herein further include an eyepiece including an internal coupling grating patterned on a first side of a substrate having a refractive index above a threshold or on a second side of the substrate. A first grating coupler is patterned on the first side of the substrate. The first grating coupler has a first grating pattern. The first grating coupler is optically coupled to the internal coupling grating. A second grating coupler is patterned on the second side of the substrate. The second grating coupler has a second grating pattern different from the first grating pattern. The second grating coupler is optically coupled to the internal coupling grating.

[0009] Among other benefits and advantages, the embodiments disclosed herein increase the field of view, efficiency, and uniformity of optical eyepieces for virtual reality and augmented reality applications. Each eyepiece can include two or more diffraction gratings patterned on the same side of a substrate. The two or more diffraction gratings can be tiled in layout. The shape, size, density, and distribution of the tiles can be selected to achieve higher optical performance. The embodiments also reduce the amount of Mach-Zehnder interference. The tiles can be as small as hundreds of microns, so far-field virtual image quality is not affected. One-sided manufacturing of the eyepiece increases the user-to-world ratio of the eyepiece. The nano-gratings are blazed or made from high-index materials, such as polymers with a refractive index above 1.6, so that a greater amount of light is directed toward the user's eye. In some embodiments, the gratings are etched in high-index glasses, including TiO2, ZrO2, or ZnO. In some embodiments, the gratings are etched in synthetic high-index substrates, such as LiNbO3, LiTaO3, or SiC. In some embodiments, the grating is etched in a TiO2 thin film coating or other inorganic material to provide additional optical benefits. The layout of the tiles in the grating coupler can be modified to achieve greater uniformity of the far-field virtual image. The clarity of the resulting image is also increased. In some embodiments, the size of each tile can be kept the same while the tile density is reduced from denser to sparser. The eyepiece can thereby be designed to have a preferred diffraction direction. Diffracted light that is directly coupled into the eye of the eyepiece user is reduced while increasing the efficiency of diffraction in other directions. The diffractive nature of the grating can be further improved using protrusion tilts and blazes or multi-step protrusions or recesses. The different design options provided by the embodiments disclosed herein thus provide greater optical efficiency and quality.

[0010] The details of one or more embodiments of the subject matter described herein are set forth in the accompanying drawings and the description below. Other potential features, aspects, and advantages of the subject matter will become apparent from the description, drawings, and claims. The present invention provides, for example, the following: (Item 1) An eyepiece, A substrate; an internal bonding grating patterned on one side of the substrate; a first grating coupler, the first grating coupler being patterned on one side of the substrate, the first grating coupler having a first grating pattern, the first grating coupler being optically coupled to the internal coupling grating; a second grating coupler, the second grating coupler being patterned on one side of the substrate and adjacent to the first grating coupler, the second grating coupler having a second grating pattern different from the first grating pattern, the second grating coupler being optically coupled to the internal coupling grating; An eyepiece comprising: (Item 2) The eyepiece lens of item 1, wherein the first grating coupler comprises a plurality of protrusions, each of the plurality of protrusions having one or more side walls, each of the one or more side walls being oriented at a different angle relative to the substrate. (Item 3) 3. An eyepiece lens as described in item 2, wherein each protrusion of the plurality of protrusions comprises at least two intersecting ridges oriented in two different directions, and the angle between the two different directions is within the range of 55 degrees to 65 degrees. (Item 4) 3. An eyepiece lens as described in item 2, wherein each protrusion of the plurality of protrusions has at least one of a cylindrical shape, an elliptical shape, at least one rectangular surface, at least one circular surface, at least one triangular surface, or at least one polygonal surface. (Item 5) 3. The eyepiece lens of claim 2, wherein the volumetric filling factor of each of the plurality of protrusions measured along the direction of light incident from the internal coupling lattice to the plurality of protrusions is within the range of 10% to 90%. (Item 6) 3. The eyepiece lens according to item 2, wherein the axial pitch of the multiple protrusions is within a range of 300 nm to 450 nm. (Item 7) 3. The eyepiece lens according to item 2, wherein the diagonal pitch of the plurality of protrusions is within a range of 300 nm to 900 nm. (Item 8) 3. The eyepiece lens according to item 2, wherein the height of each of the plurality of protrusions is within a range of 5 nm to 500 nm. (Item 9) 3. The eyepiece lens according to item 2, wherein at least one of the width or length of each of the plurality of protrusions is within a range of 5 nm to 800 nm. (Item 10) 3. An eyepiece lens as described in item 2, wherein a cross section of each of the plurality of protrusions has at least one of a triangular shape, a sawtooth shape, or a staircase shape. (Item 11) 3. An eyepiece lens as described in item 2, wherein each protrusion of the plurality of protrusions comprises a plurality of rectangular parallelepipeds, each rectangular parallelepiped of the plurality of rectangular parallelepipeds having a different height. (Item 12) The eyepiece lens of item 1, wherein the first grating coupler comprises a plurality of recesses, each recess of the plurality of recesses having one or more sidewalls, each sidewall of the one or more sidewalls being oriented at a different angle relative to the substrate. (Item 13) 1. A method for manufacturing an eyepiece lens, the method comprising: Providing a substrate; patterning an internal bonding grating on one side of the substrate; patterning a first grating coupler on one side of the substrate, the first grating coupler being optically coupled to the internal coupling grating and having a first grating pattern; patterning a second grating coupler on one side of the substrate and adjacent to the first grating coupler, the second grating coupler being optically coupled to the internal coupling grating and having a second grating pattern different from the first grating pattern; A method comprising: (Item 14) Item 14. The method of item 13, wherein patterning the first grating coupler comprises patterning a plurality of protrusions on one side of the substrate, each protrusion of the plurality of protrusions having one or more sidewalls, each sidewall of the one or more sidewalls being oriented at a different angle relative to the substrate. (Item 15) Item 15. The method of item 14, wherein patterning the first grating coupler further comprises patterning at least two intersecting ridges oriented in two different directions for each protrusion of the plurality of protrusions, wherein an angle between the two different directions is within a range of 55 degrees to 65 degrees. (Item 16) An eyepiece, an internal coupling grating, the internal coupling grating being patterned on one side of a substrate and configured to diffract light received from a projector into a first portion of the light and a second portion of the light, the first portion having a first orientation with respect to the light received from the projector and the second portion having a second orientation with respect to the light received from the projector, the second orientation being different from the first orientation; a diffraction grating, the diffraction grating being patterned on one side of the substrate; receiving the first portion of the light and the second portion of the light from the internal coupling grating; diffracting the first portion of light and the second portion of light; combining the diffracted first portion of light and the diffracted second portion of light; A diffraction grating configured to An eyepiece comprising: (Item 17) The diffraction grating is a first grating coupler; and a second grating coupler, the first grating coupler configured to direct a diffracted first portion of the light to the second grating coupler, the second grating coupler configured to direct the diffracted first portion of the light to the first grating coupler; 17. An eyepiece lens according to item 16, comprising: (Item 18) Item 18. An eyepiece lens as described in item 17, wherein the first grating combiner defines an orthogonal pupil expander (OPE) of the eyepiece lens and the second grating combiner defines an exit pupil expander (EPE) of the eyepiece lens. (Item 19) Item 18. An eyepiece lens as described in item 17, wherein the first grating coupler comprises a first plurality of ridges oriented in a first direction and the second grating coupler comprises a second plurality of ridges oriented in a second direction. (Item 20) 20. The eyepiece according to item 19, wherein the angle between the first direction and the second direction is within a range of 55 degrees to 65 degrees. [Brief description of the drawings]

[0011] [Figure 1A] FIG. 1A illustrates a side view of an imprint lithography system 100 for forming a relief pattern on a substrate.

[0012] [Figure 1B] FIG. 1B illustrates a side view of a substrate having a patterned layer positioned thereon.

[0013] [Diagram 2]FIG. 2 illustrates a system for fabricating optical waveguides on a substrate.

[0014] [Figure 3A] FIG. 3A illustrates the operating environment of an optical eyepiece.

[0015] [Figure 3B] FIG. 3B illustrates the patterning of an internal coupling grating and a grating coupler in an optical eyepiece.

[0016] [Figure 4] FIG. 4 illustrates the patterning of internal coupling gratings and grating couplers in an optical eyepiece.

[0017] [Figure 5A] FIG. 5A illustrates an interdigitating pattern in an optical eyepiece.

[0018] [Figure 5B] FIG. 5B illustrates a sawtooth grid pattern in an optical eyepiece.

[0019] [Figure 5C] FIG. 5C illustrates a chevron grid pattern in an optical eyepiece.

[0020] [Figure 5D] FIG. 5D illustrates a stencil used in an optical eyepiece.

[0021] [Figure 6A] FIG. 6A illustrates diamond patterned protrusions on a grating coupler in an optical eyepiece.

[0022] [Figure 6B] FIG. 6B illustrates rectangular patterned protrusions on a grating coupler.

[0023] [Figure 6C]FIG. 6C illustrates a protrusion on a grating coupler in an optical eyepiece.

[0024] [Figure 6D] FIG. 6D illustrates sawtooth patterned protrusions on a grating coupler in an optical eyepiece.

[0025] [Figure 7A] FIG. 7A illustrates the patterning of a grating coupler in an optical eyepiece.

[0026] [Figure 7B] FIG. 7B illustrates the patterning of a grating coupler in an optical eyepiece.

[0027] [Figure 8A] FIG. 8A illustrates the patterning of a grating coupler in an optical eyepiece.

[0028] [Figure 8B] FIG. 8B illustrates the patterning of a grating coupler in an optical eyepiece.

[0029] [Figure 9A] FIG. 9A illustrates the patterning of a grating coupler in an optical eyepiece.

[0030] [Figure 9B] FIG. 9B illustrates the patterning of a grating coupler in an optical eyepiece.

[0031] [Figure 10] FIG. 10 illustrates the patterning of a grating coupler in an optical eyepiece.

[0032] [Figure 11A] FIG. 11A illustrates the patterning of a grating coupler in an optical eyepiece.

[0033] [Figure 11B]FIG. 11B illustrates blended patterning of grating couplers in an optical eyepiece.

[0034] [Figure 12] FIG. 12 illustrates the diffraction and coupling of light using a grating coupler in an optical eyepiece. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] This document describes the design and fabrication of an eyepiece using an internal coupling grating and patterning of a grating coupler. The eyepiece can be an optical eyepiece such as used in virtual reality or augmented reality applications. The eyepiece includes a substrate and an internal coupling grating patterned on one side of the substrate. The internal coupling grating receives light from a projector. A first grating coupler is patterned on one side of the substrate. The first grating coupler has a first grating pattern. The first grating coupler is optically coupled to the internal coupling grating. A second grating coupler is patterned on the one side of the substrate adjacent to the first grating coupler. The second grating coupler has a second grating pattern different from the first grating pattern. The second grating coupler is optically coupled to the internal coupling grating.

[0036] Among other benefits and advantages of the embodiments disclosed herein include patterning a diffraction grating on one side of a substrate such that the eyepiece reduces the need for light to travel a longer distance to reach the EPE. The efficiency of light exiting the eyepiece towards the user is improved, coherence artifacts are thereby reduced, and a larger field of view with improved uniformity is achieved within an otherwise small area form factor. Also, processing complexity is reduced by maintaining the relief pattern on one side of the eyepiece, and manufacturing yields and throughput are increased.

[0037] Imprint Lithography System FIG. 1A illustrates an imprint lithography system 100 forming a relief pattern on a substrate 102. The substrate 102 may be coupled to a substrate chuck 104. In some embodiments, the substrate chuck 104 includes a vacuum chuck, a pin-type chuck, a groove-type chuck, an electromagnetic chuck, and / or the like. In some embodiments, the substrate 102 and the substrate chuck 104 are further positioned on an air bearing 106. The air bearing 106 provides motion about the x, y, and / or z axes. In some embodiments, the substrate 102 and the substrate chuck 104 are positioned on a base. The air bearing 106, the substrate 102, and the substrate chuck 104 can also be positioned on a stage 108. In some embodiments, a robotic system 110 positions the substrate 102 on the substrate chuck 104.

[0038] The imprint lithography system 100 further includes an imprint lithography flexible coated resist template 112 that is coupled to one or more rollers 114 depending on design considerations. The rollers 114 provide movement of at least a portion of the flexible coated resist template 112. Such movement may selectively provide different portions of the flexible coated resist template 112 to overlap with the substrate 102. In some embodiments, the flexible coated resist template 112 includes a patterned surface that includes a plurality of features, e.g., spaced apart recesses and protrusions. Other configurations of features are also possible. The patterned surface may define any original pattern that defines the basis of the pattern to be formed on the substrate 102. In some embodiments, the flexible coated resist template 112 is coupled to a template chuck, e.g., a vacuum chuck, a pin-type chuck, a groove-type chuck, or an electromagnetic chuck.

[0039] The imprint lithography system 100 may further include a fluid dispenser 120. The fluid dispenser 120 may be used to deposit a polymerizable material on the substrate 102. The polymerizable material may be positioned on the substrate 102 using techniques such as droplet dispensing, spin coating, dip coating, chemical vapor deposition, physical vapor deposition, thin film deposition, or thick film deposition. In some embodiments, the polymerizable material is positioned on the substrate 102 as a plurality of curable resist droplets.

[0040] A substrate having a patterned layer positioned thereon. 1B illustrates a side view of substrate 102 having patterned layer 150 positioned thereon. With reference to FIGS. 1A and 1B, imprint lithography system 100 may further include an energy source 122 coupled to direct energy (e.g., broadband ultraviolet radiation) toward substrate 102. In some embodiments, rollers 114 and air bearings 106 are configured to position desired portions of flexible coated resist template 112 and substrate 102 in desired orientations. Imprint lithography system 100 may be coordinated by a controller in communication with air bearings 106, rollers 114, fluid dispenser 120, and / or energy source 122, and may operate on a computer readable program stored in memory.

[0041] In some embodiments, the rollers 114, the air bearings 106, or both vary the distance between the flexible coated resist template 112 and the substrate 102 to define a desired volume therebetween to be filled with the polymerizable material. For example, the flexible coated resist template 112 contacts the polymerizable material. After the desired volume is filled with the polymerizable material, the energy source 122 generates energy, for example, broadband ultraviolet radiation, to solidify and / or crosslink the polymerizable material and cause it to conform to the shape of the surface of the substrate 102 and portions of the patterned surface of the flexible coated resist template 122, thus defining a patterned layer 150 on the substrate 102. In some embodiments, the patterned layer 150 includes a residual layer 152 and a plurality of features shown as protrusions 154 and recesses 156.

[0042] System for fabricating optical waveguides on a substrate - Patents.com 2 illustrates a system 200 for fabricating optical waveguides on a substrate. System 200 includes a deposition system 226, a controller 224, a fluid dispenser 120, a laser source 228, and an energy source 122. System 200 is used to fabricate multi-waveguide optical structures that include multiple waveguides that are stacked to block light passing through each waveguide in sequence, and each waveguide may be associated with a different color and a different planar depth.

[0043] The deposition system 226 is configured to deposit an adhesion-promoting layer on a substrate (e.g., 102). The adhesion-promoting layer is intended to improve adhesion of the curable resist droplets to the substrate 102. For example, the adhesion-promoting layer may be applied by spinning a diluted solution onto the substrate 102 and allowing the layer to spin dry.

[0044] The imprint lithography system 200 may be coordinated by a controller 224 in communication with the deposition system 226, the fluid dispenser 120, the laser source 228, and / or the energy source 122, and may operate on a computer-readable program stored in a memory. The controller 224 may be implemented in software or hardware. For example, the controller 224 may be part of a PC, a tablet PC, a smartphone, an Internet of Things (IoT) appliance, or any machine capable of executing instructions that define actions to be taken by that machine.

[0045] The controller 224 may instantiate a gap fiducial in the optical structure being manufactured to monitor the dispensing of the hardenable resist droplets in the optical eyepiece layer. A gap fiducial or fiducial marker is a marker that may be placed in the field of view of the generated optical structure for use as a reference point or measurement. A gap fiducial may be placed in or on a mark or set of marks in the imaging object or optical instrument.

[0046] The controller 224 may overlay a coated resist template (e.g., 112) onto the hardenable resist droplets to contact and pattern the hardenable resist droplets. The coated resist template 112 includes a patterned surface including a plurality of recesses and protrusions. The coated resist template 112 may further include a deep lattice structure or dam configured to prevent the hardenable resist droplets from flowing into the zero RLT regions. The controller 224 may further direct broadband ultraviolet radiation from the energy source 122 to harden the hardenable resist droplets. The controller 224 may further remove the coated resist template 112 and expose the patterned resist, which then conforms to a portion of the patterned surface of the coated resist template 112.

[0047] The controller 224 may etch the grating formed on the optical structure to define the optical eyepiece layer. In some embodiments, the need to dry etch the substrate 102 (e.g., dry etch high index glass or sapphire) is eliminated. In some embodiments, the substrate 102 is partially etched (e.g., a plasma process under atmospheric or low pressure conditions) to remove residual layers and / or transfer patterns into the substrate 102 while maintaining a portion of the residual layers on the surface of the substrate 102.

[0048] The diffraction grating diffracts light traveling through the optical waveguide. The controller 224 may further direct a laser beam from the laser source 228 onto a portion of the adhesion promoting layer to engrave the substrate 102. The controller 224 may engrave the optical eyepiece layer from the substrate 102 by pulsing the laser beam onto a portion of the adhesion promoting layer to generate nano-perforations in the substrate 102. The laser beam is applied to the generated nano-perforations to enlarge the nano-perforations and separate the optical eyepiece layer from the substrate 102. The resist may be removed by laser ablation in some embodiments, but in other embodiments it may simply not be placed under (e.g., by masking) or etched away (e.g., by plasma), or any combination thereof. The controller 224 may further bond the optical eyepiece layer to another optical eyepiece layer imprinted on another substrate to define an optical waveguide.

[0049] The fluid dispenser 120 dispenses a thin layer of imprint resist (e.g., a thermoplastic polymer) in the form of hardenable droplets onto the substrate 102. In some embodiments, the fluid dispenser 120 is configured to dispense the hardenable resist droplets onto an adhesion promoting layer to define a diffraction grating. The adhesion promoting layer is disposed between and in contact with the substrate 102 and the dispensed hardenable resist droplets. The area defining the optical eyepiece layer has an edge, and the edge of the optical eyepiece layer is free of the hardenable resist droplets.

[0050] In some embodiments, the fluid dispenser 120 is configured to dispense the hardenable resist droplets onto the adhesion promoting layer by injecting the hardenable resist droplets onto the adhesion promoting layer at predetermined coordinates and a predetermined frequency. Adjacent droplets of the hardenable resist droplets are made to have a predetermined separation on the adhesion promoting layer. For example, the fluid dispenser 120 may be programmed to indicate areas where resist should or should not be dispensed. A very high resolution resist droplet pattern may be created, including predetermined coordinates for individual resist droplets and a predetermined XY pitch between adjacent droplets. The fluid dispenser 120 operates at a very high frequency dispensing resist droplets while the substrate 102 passes under the inkjet head. Ultra-high resolution and precision (X, Y, volume) are achieved by inkjet dispensing frequency, head voltage, and stage movement control. The curable resist droplets may be dispensed onto the adhesion-promoting layer by moving the inkjet head of the fluid dispenser 120, by moving the substrate across the inkjet head of the fluid dispenser 120, or by moving the inkjet head of the fluid dispenser 120 and the substrate across each other.

[0051] In some embodiments, the fluid dispenser 120 is further configured to maintain a zero RLT region, corresponding to an edge of the optical eyepiece layer that is free of hardenable resist droplets. This configuration increases the optical performance of the optical waveguide by reducing light scattering at the edge of the optical eyepiece layer and reducing the number of particle defects on the zero RLT region of the optical waveguide.

[0052] The laser source 228 provides a laser beam to engrave the substrate 102. In some embodiments, the laser source 228 includes a gain medium, a current carrying mechanism, and an optical feedback mechanism. The gain medium is a material with properties that allow it to amplify light using stimulated emission. Energy may be provided as electrical current or as light at different wavelengths. The laser source 228 may use feedback from an optical cavity to affect properties of the emitted light, such as the polarization, wavelength, and shape of the beam.

[0053] The energy source 122 provides radiation to strengthen (e.g., polymerize or crosslink) the resist droplets, leaving a resist coating on the substrate. In some embodiments, the energy source 122 reduces the wavelength of radiation to achieve higher resolution. For example, the energy source 122 may provide energy at wavelengths in the ultraviolet spectrum or shorter (<400 nm) deep ultraviolet spectrum, etc. In some embodiments, the energy source 122 generates an electron beam to achieve the same results as exposure with light.

[0054] Eyepiece environment using patterning of grating couplers FIG. 3A illustrates the operating environment of an optical eyepiece. The eyepiece shown in FIG. 3A includes a substrate (e.g., substrate 400 illustrated and described below with reference to FIG. 4). The substrate can have a refractive index above a certain threshold. In some embodiments, the refractive index of the substrate is greater than 1.4. The refractive index or refractive index of the substrate is a dimensionless number that describes how fast light propagates through the substrate. The substrate can be made of a high refractive index polymer or glass. In some embodiments, the grating includes a thin layer of a low refractive index material patterned across the high refractive index substrate or etched in a high refractive index glass including TiO2, ZrO2, or ZnO. In some embodiments, the grating is etched in a synthetic high refractive index substrate such as LiNbO3, LiTaO3, or SiC. In some embodiments, the grating is etched in a TiO2 thin film coating or other inorganic material to provide additional optical benefits.

[0055] The eyepiece shown in Figure 3A includes an internal coupling grating 304 patterned on one side of a substrate. The internal coupling grating 304 in Figure 3A is located at the eyebrow of a user using the eyepiece or at the side of the user's head. The internal coupling grating 304 couples rays of light 332 from the source projector 300 into a first grating coupler 308 and a second grating coupler 320 using a combination of total internal reflection and diffraction.

[0056] The internal coupling grating 304 is configured to diffract the light 332 received from the projector 300. The light 332 is diffracted and coupled into a first portion 336 of light and a second portion 312 of light. The first portion 336 has a first orientation with respect to the light 332 received from the projector 300, and the second portion 312 has a second orientation with respect to the light 332 received from the projector 300. The second orientation is different from the first orientation. For example, the first portion 336 can be oriented in a first direction and the second portion 312 can be oriented in a second direction. The internal coupling grating 304 is further configured to direct the first portion 336 to the first grating coupler 308. The internal coupling grating 304 is further configured to direct the second portion 312 to the second grating coupler 320. When the internal coupling grating 304 is located at the user's brow or cheek, the eyepiece is split vertically into a first grating combiner 308 and a second grating combiner 320, as shown in FIG. 3A. The vertical reference frame is in the forehead-to-chin direction of the user of the eyepiece. When the internal coupling grating 304 is located at the user's temple or nostril, the eyepiece can be split horizontally. The horizontal reference frame is in the ear-to-ear direction of the user of the eyepiece.

[0057] The first grating coupler 308 is optically coupled to the internal coupling grating 304 to receive the portion 336 of light diffracted by the internal coupling grating 304. The first grating coupler 308 is patterned on one side of the substrate and has a first grating pattern. The first grating pattern can include ridges, rulings, linear grating sections, protrusions, recesses, or combinations thereof, as illustrated and described in detail below with reference to Figures 6A-D, 7A-B, 8A-B, 9A-B, 10, and 11A-B. The first grating coupler 308 is configured to diffract the first portion 336 of light received from the internal coupling grating 304. The first grating coupler 308 has a periodic structure or pattern that splits and further diffracts the portion 336 of light into several beams traveling in different directions. The different directions of the beams depend on the spacing of the grating and the wavelength of the light such that the grating acts as a dispersive element. The first grating coupler 308 directs the diffracted first portion 340 of the light to the second grating coupler 320. In some embodiments, the first grating coupler 308 defines the OPE of the eyepiece. The OPE uses total internal reflection (TIR) ​​in different directions to spread the diffracted rays of light.

[0058] The second grating coupler 320 is optically coupled to the internal coupling grating 304. In some embodiments, the second grating coupler 320 defines the EPE of the eyepiece. The EPE couples light exiting the OPE towards the user of the eyepiece or towards the world. In some embodiments, the combination of the OPE and EPE working in conjunction is referred to as a combined pupil expander (CPE).

[0059] The second grating coupler 320 is patterned on one side of the substrate and is adjacent to the first grating coupler 308. The second grating coupler 320 has a second grating pattern that is different from the first grating pattern. The second grating pattern can include ridges, rulings, linear grating sections, protrusions, recesses, or combinations thereof, as illustrated and described in detail below with reference to Figures 6A-D, 7A-B, 8A-B, 9A-B, 10, and 11A-B. The second grating coupler 320 is configured to diffract the second portion 312 of the light. The diffracted second portion 316 of the light is directed to the first grating coupler 308. The eyepiece is configured to combine the diffracted first portion 340 and the diffracted second portion 316. The eyepiece is further configured to direct the combined light 324 to the eyeball 328 of a user of the eyepiece. The first grating coupler 308 and the second grating coupler 320 illustrated in FIG. 3A are sometimes referred to as having a split honeycomb pattern or configuration.

[0060] In some embodiments, the internal coupling grating 304 includes a first set of parallel ridges or rulings oriented in a first direction as shown in FIG. 3A. The first set of ridges, rulings, or linear grating segments can be spaced apart by a first pitch distance. The first grating coupler 308 includes a second set of parallel ridges or rulings oriented in a second direction different from the first direction. The second set of ridges, rulings, or linear grating segments can be spaced apart by a second pitch distance. The second grating coupler 320 can include a third set of parallel ridges or rulings oriented in a third direction different from the first and second directions. The third set of ridges, rulings, or linear grating segments can be spaced apart by a third pitch distance. The angle between the second direction and the third direction is in the range of 55 degrees to 65 degrees.

[0061] The path length of the portions of light 336 and 312 shown in FIG. 3A can be designed so that the two portions 336 and 312 are either in phase or out of phase. Similarly, the path length of the portions of light 316 and 340 can be designed so that the two portions 336 and 312 are either in phase or out of phase. The embodiment thus modulates the phase of the light fields of the OPE and EPE. Modulating the phase of the light fields mitigates Mach-Zehnder interference and improves the uniformity of the resulting image. The clarity of the resulting image is also increased. The embodiment illustrated in FIG. 3A also provides increased optical efficiency. In a conventional eyepiece, a large amount of light is diffracted into air, thus reducing efficiency. In contrast, in the eyepiece of FIG. 3A, the portion of light 312 at the second grating coupler does not diffract out of the eyepiece, but instead reaches the first grating coupler 308. Thus, more light is saved and optical efficiency is increased. The eyepiece illustrated in Figure 3A also improves light diffusion in a single layer architecture. By including specific nano-features in the design, the eyepiece can combine two or more wavelengths of light into a single layer, improving image quality.

[0062] Patterning internal coupling gratings and grating couplers in optical eyepieces. FIG. 3B illustrates the patterning of the internal coupling grating 348 and grating couplers 356 and 368 in an optical eyepiece. In other embodiments, the eyepiece includes additional or fewer objects than those described herein. The eyepiece shown in FIG. 3B includes a substrate (e.g., substrate 400 illustrated and described below with reference to FIG. 4) and an internal coupling grating 348 imprinted on one side of the substrate, similar to the internal coupling grating 304 shown in FIG. 3A. A first grating coupler 356 is imprinted on one side of the substrate and is optically coupled to the internal coupling grating 348. The first grating coupler 356 includes a plurality of tiles that define the EPE of the eyepiece. Each tile 352 of the first grating coupler 356 has a first grating pattern. The first grating pattern can include ridges, rulings, linear grating sections, protrusions, recesses, or combinations thereof. The first grating coupler 356 is configured to receive a portion of the light diffracted by the internal coupling grating 348 and further diffract the portion of the light using tiles.

[0063] A second grating coupler (grating region 368) is interspersed between the tiles. The grating region 368 has a second grating pattern (parallel ridges or rulings) that is different from the first grating pattern. The grating region 368 defines the OPE of the eyepiece. In some embodiments, the internal coupling grating 348 includes a first set of parallel ridges as shown in FIG. 3B. The grating region 368 includes a second set of parallel ridges that are orthogonal to the first set of parallel ridges. The grating region 368 is configured to receive another portion of the light diffracted by the internal coupling grating 348 and further diffract another portion of the light. The first grating coupler 356 is configured to thereby reduce the brightness of the light emitted by the central region 364 of the grating region 368. The grating coupler of FIG. 3B receives the light diffracted by the internal coupling grating 348 and diffuses the light emitted by the central region 364 of the grating region 368.

[0064] A single-sided eyepiece, in which the internal coupling grating 348, the first grating coupler 356, and the grating region 368 are imprinted on one side of the substrate, provides a larger field of view and reduced coherent artifacts. Coherent artifacts refer to destructive and constructive interference of diffracted light rays exiting the eyepiece. Such artifacts can cause areas of dark and bright patches in the image projected into the user's field of view. Coherent artifacts can cause reduced image and color uniformity. The embodiments disclosed herein improve image and color uniformity by reducing coherent artifacts. The configuration illustrated in FIG. 3B is sometimes referred to as a tiled snowflake grating pattern or a tiled snowflake grating configuration.

[0065] In some embodiments, the area or size of each tile 352 of the plurality of tiles decreases as the location of the tile 352 changes from the central region 364 of the grating coupler 356 to the boundary 360 of the grating coupler 364. The change in area or size of each tile 352 reduces the brightness of the light emitted by the central region 364. Because the tiles are as small as a few hundred microns, the far-field virtual image quality is not affected. Also, the one-sided nature of the eyepiece increases the user-to-world ratio of the eyepiece. Because the nano-grating is blazed or made from a high index material, such as a polymer with an index of refraction above 1.6, a greater amount of light is directed toward the user's eyeball 328. Additionally, the grating can be etched in high index glasses, including TiO2, ZrO2, or ZnO. In some embodiments, the grating is etched in a synthetic high index substrate, such as LiNbO3, LiTaO3, or SiC. In some embodiments, the grating is etched in a ZrO2, TiO2, or SiC thin film coating.

[0066] In some embodiments, the tiles of the lattice coupler 356 have a rectangular shape. The size of each tile 352 and the length of a side of the tile 352 can vary from the boundary 360 to the central region 364. In some embodiments, the tiles of the lattice coupler 356 have a circular shape. The diameter of each tile 352 can vary from the boundary 360 to the central region 364. In some embodiments, the tiles of the lattice coupler 356 have an elliptical shape. The dimensions of each tile 352 can vary from the boundary 360 to the central region 364. In some embodiments, the tiles of the lattice coupler 356 have a polygonal shape. The polygon can be a regular polygon or a non-regular polygon. For example, the tiles can have a hexagonal shape.

[0067] In some embodiments, each tile 352 of the plurality of tiles shown in FIG. 3B includes a plurality of protrusions, as illustrated and described in detail below with reference to FIGS. 6A-D. The protrusions are sometimes referred to as posts, grating posts, or post gratings. The grating coupler 356 is sometimes referred to as a post grating. Each protrusion of the plurality of protrusions has one or more sidewalls, as illustrated and described below with reference to FIG. 6A. Each sidewall of the one or more sidewalls can be oriented at a different angle relative to the substrate. For example, the slope of each sidewall relative to the substrate can be different. In some embodiments, each protrusion of the plurality of protrusions includes two intersecting ridges oriented in two different directions. The location where the two intersecting ridges meet defines a protrusion.

[0068] Patterning internal coupling gratings and grating couplers in optical eyepieces. FIG. 4 illustrates the patterning of an internal coupling grating 404 and a grating coupler in an optical eyepiece. The eyepiece shown in FIG. 4 includes a substrate 400, which may have a refractive index above a certain threshold. In some embodiments, the refractive index of the substrate is greater than 1.4. The substrate 400 is described in more detail above with reference to FIGS. 1A, 1B, 2, and 3A. The internal coupling grating 404 can be patterned on a first side of the substrate 400, a second side of the substrate 400, or both sides of the substrate 400. A first grating coupler 420 is patterned on the first side of the substrate 400. The first grating coupler 420 has a first grating pattern 408. For example, the first grating pattern 408 can include a periodic array of ridges, rulings, linear grating sections, protrusions, recesses, or combinations thereof. In some embodiments, the first grating coupler 420 includes a first set of ridges oriented in a first direction. The first grating coupler 420 is optically coupled to the in-coupling grating 404 to receive a first portion of the light from the in-coupling grating 404 .

[0069] In some embodiments, the second grating coupler 424 is patterned on a first side of the substrate 400. Both the first grating coupler 420 and the second grating coupler 424 are thus patterned on the same side of the substrate 400. The second grating coupler 424 has a second grating pattern 412 that is different from the first grating pattern 408. For example, the second grating pattern 412 can include a periodic array of ridges, rulings, linear grating sections, protrusions, recesses, or combinations thereof. In some embodiments, the second grating coupler 424 includes a second set of ridges that are oriented in a second direction that is different from the first direction. In some embodiments, the angle between the first direction and the second direction is in the range of 55 degrees to 65 degrees. The second grating coupler 424 is optically coupled to the internal coupling grating 404 such that the second grating coupler 424 is configured to receive a second portion of the light from the internal coupling grating 404.

[0070] In some embodiments, the second grating coupler 424 is patterned on a second side of the substrate 400. The first grating coupler 420 and the second grating coupler 424 are thus patterned on different sides of the substrate 400. The second grating coupler 424 has a second grating pattern 412 that is different from the first grating pattern 408. For example, the second grating pattern 412 can include a periodic array of ridges, rulings, linear grating sections, protrusions, recesses, or combinations thereof. In some embodiments, the second grating coupler 424 includes a second set of ridges that are oriented in a second direction that is different from the first direction. In some embodiments, the angle between the first direction and the second direction is in the range of 55 degrees to 65 degrees. The second grating coupler 424 is optically coupled to the internal coupling grating 404 such that the second grating coupler 424 is configured to receive a second portion of the light from the internal coupling grating 404.

[0071] In some embodiments, the area 416 or region of the first grating coupler 420 overlaps with the area or region of the second grating coupler 424. The overlap area 416 diffracts light into the eye of the user of the eyepiece 328. In some embodiments, the area 416 of the first grating coupler 420 overlaps with the second grating coupler 424 such that the overlap area 416 is configured to diffract a portion of the light into the eye of the user of the eyepiece 328. The overlap area 416 reduces the brightness of the light that is diffracted directly into the eye of the user 328 so that the user does not see a bright central band in the image displayed by the eyepiece. In some embodiments, the size of the area 416 of the first grating coupler is in the range of 10% to 60% of the total area of ​​the first grating coupler 420. In some embodiments, the width 424 of the overlap area 416 (corresponding to the width of the eye box of the eyepiece) is in the range of 5 mm to 20 mm. In some embodiments, the eyebox dimensions are 15 mm horizontally and 18 mm vertically. The vertical frame of reference is in the forehead-to-chin direction of the user of the eyepiece. The horizontal frame of reference is in the ear-to-ear direction of the user of the eyepiece. The eyebox is the area within the eyepiece (EPE / CPE) through which the outgoing light rays are meant to capture the range of movement and positioning of eye 328 within one or more users' fields of view as defined by the eyepiece, where the eyepiece is fixed at a particular distance from the user's eye.

[0072] Grating patterns in optical eyepieces FIG. 5A illustrates an interdigitating pattern 500 in an optical eyepiece. The eyepiece includes a first grating coupler (e.g., the first grating coupler 308 illustrated and described above with reference to FIG. 3A) patterned on one side of a substrate. The first grating coupler has a first grating pattern. For example, the first grating coupler can include a first set of ridges oriented in a first direction, as shown above in FIG. 3A. A second grating coupler (e.g., the second grating coupler 320 illustrated and described above with reference to FIG. 3A) is patterned on one side of the substrate. The second grating coupler has a second pattern that is different from the first pattern. For example, the second grating coupler can include a second set of ridges oriented in a second direction, as shown above in FIG. 3A. 5A, a first grating coupler contacts a second grating coupler to define an interdigitated alternating pattern 500 at the location of contact. The interdigitated alternating pattern 500 diffuses light that would otherwise be diffracted directly into the eye of an eyepiece user 328. In some embodiments, the interdigitated alternating pattern 500 includes a plurality of parallel ridges 504 that are oriented in a particular direction. In other embodiments, the interdigitated alternating pattern 500 includes alternating bands of a first pattern and a second pattern.

[0073] 5B illustrates a sawtooth grid pattern 508 in an optical eyepiece. In the embodiment illustrated in FIG. 5B, an interdigitated alternating pattern is defined to include a plurality of ridges arranged in a sawtooth pattern 508. The sawtooth pattern 508 reduces the brightness of light that is diffracted directly into the user's eye 328. Thus, the user does not see a bright central band in the image displayed by the eyepiece.

[0074] FIG. 5C illustrates a chevron grating pattern 512 in an optical eyepiece. The pattern illustrated in FIG. 5C includes a plurality of ridges arranged in a chevron grating pattern 512. The chevron grating pattern is a V-shaped pattern that includes a substantially equal area or region of a first grating pattern of a first grating coupler (e.g., first grating coupler 308 illustrated and described above with reference to FIG. 3A) and a second grating pattern of a second grating coupler (e.g., second grating coupler 320). The angle between the ridges of the first grating pattern and the ridges of the second grating pattern is within a range of 55 degrees to 65 degrees.

[0075] FIG. 5D illustrates a stencil 516 used in an optical eyepiece. The stencil 516 defines an interdigitated alternating pattern between a first grating coupler 520 and a second grating coupler 524. The first grating coupler 520 is patterned using a first set of parallel ridges 528 oriented in a first direction. The second grating coupler 524 is patterned using a second set of parallel ridges 532 oriented in a second direction different from the first direction. The stencil 516 thereby blends a first boundary of the first grating coupler 520 with a second boundary of the second grating coupler 524.

[0076] In some embodiments, the interdigitating alternating grid pattern in stencil 516 includes a plurality of protrusions 536. Each protrusion is defined by two intersecting ridges, one each from ridges 528 and 532. Each protrusion of the plurality of protrusions 536 can have one or more sidewalls. Each sidewall of the one or more sidewalls can be oriented at a different angle relative to the substrate (e.g., substrate 400 illustrated and described above with reference to FIG. 4). In some embodiments, the plurality of protrusions 536 has a refractive index greater than 1.4.

[0077] Diamond-patterned protrusions in grating couplers. FIG. 6A illustrates diamond patterned protrusions in a grating coupler 600 in an optical eyepiece. The grating couplers 600, 624, 648, and 674 illustrated in FIGS. 6A-D are also sometimes referred to as having a blazed post pattern, a blazed post configuration, a blazed protrusion pattern, or a blazed protrusion configuration. Referring now to FIG. 6A, the grating coupler 600 can be blazed to achieve higher grating efficiency in a given diffraction order. The optical power is thus concentrated in the desired diffraction order, while the residual optical power in other orders is reduced. The shape and pattern of the protrusions of the grating coupler 600 defines the blaze wavelength at which the grating coupler 600 is blazed. The direction in which the optical efficiency is increased is called the blaze angle and is a property of the blazed grating coupler 600. The blaze angle depends on the blaze wavelength and the selected diffraction order.

[0078] The blazed grating coupler 600 can have a specific line spacing or pitch that determines the amount of wavelength division caused by the grating coupler 600. In some embodiments, illustrated and described below with reference to FIG. 6D, the grating coupler can have a triangular or sawtooth cross section that defines a step structure. The steps can be inclined at a blaze angle relative to the grating surface. The blaze angle can be designed to increase the efficiency for a wavelength of light. In some embodiments, the blaze angle is designed so that the diffraction angle and the incidence angle correspond. In some embodiments, a larger blaze angle is selected so that the light strikes the shorter side of the triangular grating lines instead of the longer side. In such embodiments, the grating coupler 600 has a larger line spacing and a higher diffraction order.

[0079] The grating coupler 600 of the eyepiece illustrated in FIG. 6A is patterned on one side of a substrate (e.g., substrate 400 illustrated and described above with reference to FIG. 4) that has a refractive index above a certain threshold. In some embodiments, the refractive index of the substrate is greater than 1.4. The grating coupler 600 is optically coupled to the internal coupling grating of the eyepiece, similar to the above illustration of FIG. 3A. The grating coupler 600 includes multiple protrusions, e.g., protrusion 612. Each protrusion 612 has one or more sidewalls, e.g., sidewall 604. Each sidewall 604 of the one or more sidewalls can be oriented at a different angle relative to the substrate. In some embodiments, the grating coupler 600 illustrated in FIG. 6A is referred to as having a diamond-shaped post pattern or diamond-shaped protrusion configuration.

[0080] In some embodiments, each protrusion 612 of the plurality of protrusions includes at least two intersecting ridge portions oriented in two different directions. The location where the at least two intersecting ridges meet defines the protrusion 612. In some embodiments, each protrusion has a cylindrical shape. In some embodiments, each protrusion of the grating coupler 600 has an elliptical shape. The dimensions of each ellipsoid interact with and diffract the light. In some embodiments, each protrusion has at least one circular surface, for example when the protrusion has a cylindrical shape. In some embodiments, each protrusion 612 has at least one triangular surface 608. In other embodiments, each protrusion 612 has at least one polygonal surface. The polygonal surface can correspond to a regular or irregular polygon.

[0081] In some embodiments, the fill factor (or duty cycle) of the volume of each protrusion 612 as measured along the direction of light incident on the multiple protrusions from the internal coupling lattice is in the range of 10% to 90%. Fill factor refers to the ratio of the volume of the protrusion 612 to the volume of the recess (empty space) between consecutive protrusions. In some embodiments, the pitch of the axes of the protrusions is in the range of 300 nm to 450 nm. Pitch refers to the distance measured from the centroid of a first protrusion to the centroid of an adjacent protrusion located in the same row or column as the first protrusion. The centroid refers to the geometric center of mass of the protrusion. In some embodiments, the diagonal pitch of the protrusions is in the range of 300 nm to 900 nm. Diagonal pitch refers to the distance measured from the centroid of the first protrusion to the centroid of the nearest diagonally neighboring protrusion, i.e., the distance between the centroid of the protrusion in one row and that of the nearest neighboring protrusion in the next row and the next column.

[0082] In some embodiments, the height of the one or more protrusions is in the range of 5 nm to 500 nm. In other embodiments, the width or length of the protrusions is in the range of 5 nm to 800 nm. The protrusions can be fabricated in several shapes. For example, the cross section of the protrusions can have a triangular shape. The multiple protrusions can have a refractive index greater than 1.4. In some embodiments, the grating coupler 600 includes multiple recesses or cavities for diffracting light. Each recess or cavity can have one or more sidewalls, similar to the protrusions as discussed above with reference to FIG. 6A. Each sidewall of the one or more sidewalls can be oriented at a different angle with respect to the substrate.

[0083] Patterned Protrusions on a Grating Coupler FIG. 6B illustrates rectangular patterned protrusions on a grating coupler 624 in an eyepiece. The grating coupler 624 includes multiple protrusions (e.g., protrusion 632). Each protrusion includes multiple rectangular prisms 628. Each rectangular prism can have a different height, length, and depth. Thus, each rectangular prism can have a different volume of grating material. Each protrusion 632 has one or more sidewalls. Each protrusion has at least one rectangular surface. The grating coupler 624 illustrated in FIG. 6B is sometimes referred to as having a stepped sloped strut pattern or stepped sloped protrusion configuration.

[0084] In some embodiments, an eyepiece manufactured using the grating coupler 624 includes a substrate (e.g., substrate 400 illustrated and described above with reference to FIG. 4) and an internal coupling grating imprinted on one side of the substrate. The grating coupler 624 is also imprinted on one side of the substrate and is optically coupled to the internal coupling grating. The grating coupler 624 can include multiple tiles, as illustrated and described above with reference to FIG. 3B, that define the EPE of the eyepiece. Grating regions (e.g., grating region 368) can be interspersed between the tiles to define the OPE of the eyepiece. Each tile of the grating coupler 624 can include multiple cuboids 628, and each cuboid 628 can have a different height. In some embodiments, the height of each cuboid is in the range of 5 nm to 500 nm. In other embodiments, the width or length of each cuboid is in the range of 5 nm to 800 nm. The cross section of each cuboid has a rectangular shape. In some embodiments, the cross section of each protrusion 632 has a step shape.

[0085] FIG. 6C illustrates a protrusion on a grating coupler 648 in an optical eyepiece. The grating coupler 648 may be blazed as described and illustrated above with reference to FIG. 6A. In some embodiments, each protrusion 652 has at least one rectangular surface. For example, the top surface 656 may be rectangular. In some embodiments, each protrusion has at least one circular surface, for example when the protrusion has a cylindrical shape. In some embodiments, each protrusion has at least one triangular surface. In other embodiments, each protrusion has at least one polygonal surface.

[0086] 6D illustrates sawtooth patterned protrusions 678 in a grating coupler 674 in an optical eyepiece. The cross-section of the multiple protrusions has a sawtooth shape. In some embodiments, the portion of the grating coupler 674 illustrated in FIG. 6D may be part of an interdigitating alternating grating pattern that includes multiple ridges or protrusions arranged in a sawtooth grating pattern.

[0087] Patterning of grating couplers FIG. 7A illustrates the patterning of grating couplers in an optical eyepiece. The eyepiece illustrated in FIG. 7A includes an internal coupling grating 724 patterned on one side of a substrate (e.g., substrate 400 illustrated and described above with reference to FIG. 4). The configuration illustrated in FIG. 7A is sometimes referred to as a wing grating configuration or wing grating pattern. In a wing grating configuration, three or more grating couplers are patterned on one side of a substrate. The three or more grating couplers are optically coupled to the internal coupling grating 724. Each grating coupler of the three or more grating couplers has a different grating pattern, as illustrated in FIG. 7A.

[0088] The internal coupling grating 724 is configured to diffract the light received from a projector (e.g., projector 300) into three or more portions of light. Each portion of light has a different orientation relative to the light received from projector 300. The internal coupling grating 724 is further configured to direct a corresponding portion of the light to each grating coupler. Each grating coupler is configured to further diffract the corresponding portion of the light. The eyepiece is configured to combine the three or more diffracted portions of light for transmission to a user's eye (e.g., eye 328).

[0089] The first grating coupler 700 includes a first linear grating section 704 oriented in a first direction. The second grating coupler 712 includes a second linear grating section 716 oriented in a second direction different from the first direction. In some embodiments, the angle between the first direction and the second direction is in the range of 55-65 degrees. At least one grating coupler is located between two other grating couplers in the eyepiece. For example, in FIG. 7A, a third grating coupler 728 having tiles 720 is located between the first grating coupler 700 and the second grating coupler 712. In some embodiments, the width 708 (corresponding to the width of the eyebox of the eyepiece) of the third grating coupler 728 located between the first grating coupler 700 and the second grating coupler 712 is in the range of 5 mm-20 mm. A grating coupler 728, located between two other grating couplers 700 and 712, includes a plurality of tiles 720 having a specific grating pattern. The tiles 720 may include protrusions, cavities or recesses, or ridges. In some embodiments, each tile of the plurality of tiles 720 has a polygonal shape.

[0090] FIG. 7B illustrates a patterning of grating couplers in an optical eyepiece. The eyepiece illustrated in FIG. 7B includes an internal coupling grating 748 and three or more grating couplers, including a first grating coupler 756, a second grating coupler 772, and a third grating coupler 776. The configuration in FIG. 7B is sometimes referred to as a wing grating configuration or a wing grating pattern. In a wing grating configuration or a wing grating pattern, at least one grating coupler is located between two other grating couplers. For example, in FIG. 7B, a third grating coupler 776 including a linear section 752 is located between the first grating coupler 756 and the second grating coupler 772. In some embodiments, the width 764 of the grating coupler including multiple linear grating sections 752 (corresponding to the width of the eyebox of the eyepiece) is in the range of 5 mm to 20 mm.

[0091] The first grating coupler 756 includes a first linear grating section 760 oriented in a first direction. The second grating coupler 772 includes a second linear grating section 768 oriented in a second direction different from the first direction. In some embodiments, the angle between the first direction and the second direction is in the range of 55 degrees to 65 degrees. In some embodiments, as illustrated in FIG. 7B, the pitch spacing of the features of the third two-dimensional (2D) grating coupler 776 can be determined from the pitch spacing defined by the intersections of the features defining the first one-dimensional (1D) grating coupler 756 and the second 1D grating coupler 772. The difference between the pitch spacing of the features of the grating coupler 776 and the pitch spacing of the intersections of the features of the grating couplers 756 and 772 can cause a virtual image shift or virtual image drift that is visible when moving from one grating region to another. Such image drift is undesirable, for example, when there is a change in eye position across the CPE area while viewing the virtual image, or when the interpupillary distance (IPD) for a large population is different. The embodiment illustrated in FIG. 7B reduces image drift for a one-sided full field of view (FOV) waveguide by generating a distortion-free virtual image. The embodiment illustrated with reference to FIGS. 7A and 7B can be implemented to achieve preferential diffraction orders. The preferential diffraction orders reduce the occurrence of a central bright band in the resulting image and increase eyepiece uniformity. The sharpness of the resulting image is also increased.

[0092] Patterning of grating couplers FIG. 8A illustrates the patterning of grating couplers 816 and 820 in an optical eyepiece. The eyepiece illustrated in FIG. 8A includes a substrate (e.g., substrate 400 illustrated and described above with reference to FIG. 4A) and an internal coupling grating 800 imprinted on one side of the substrate. The internal coupling grating 800 includes a first set of parallel ridges. A first grating coupler 816 is imprinted on one side of the substrate and is optically coupled to the internal coupling grating 800. The configuration shown in FIG. 8A is sometimes referred to as a tiled snowflake grating configuration or a tiled snowflake grating pattern. The first grating coupler 816 includes a plurality of tiles 824 that define the EPE of the eyepiece. The tiles 824 have a first grating pattern, e.g., ridges, protrusions, recesses, etc.

[0093] In some embodiments, each tile 824 includes multiple protrusions. Each protrusion has one or more sidewalls. Each sidewall is oriented at a different angle relative to the substrate. In other embodiments, each protrusion includes two intersecting ridges oriented in two different directions. In other embodiments, each tile 824 includes multiple rectangular parallelepipeds. Each rectangular parallelepiped has a different height. In some embodiments, the area of ​​each tile decreases as the location of the tile changes from the central region 812 of the grating coupler 816 to the boundary 804 of the grating coupler 816. The tiles proximate the boundary 804 are smaller in area than the tiles proximate the central region 812.

[0094] A second grating coupler (grating region 820) is interspersed among the tiles 824. The grating region 820 has a second grating pattern that is different from the first grating pattern. The grating region 820 includes a second set of parallel ridges that are orthogonal to the first set of parallel ridges of the internal coupling grating 800. The grating region 820 defines the OPE of the eyepiece. The layout of the tiles 824 can be modified to achieve higher uniformity of the far-field virtual image. Higher uniformity of the far-field virtual image is obtained by varying the shape, size, distribution, and density of the tiles. In some embodiments, the size of each tile can be kept the same while the tile density is reduced from denser to sparser. The distribution of the tiles 824 can be either periodic or random. The clarity of the resulting image is also increased. The different design options provided by the embodiments disclosed herein provide higher optical efficiency and quality.

[0095] In some embodiments, the grating couplers 816 and 820 are configured to receive light diffracted by the internal coupling grating 800. The grating couplers 816 and 820 are configured to reduce the intensity of light emitted by the central region 812 of the grating couplers 816 and 820. In some embodiments, the grating couplers 816 and 820 are configured to diffuse the light emitted by the central region 812.

[0096] Patterning of grating couplers 8B illustrates the patterning of grating couplers 860 and 868 in an optical eyepiece. The eyepiece illustrated in FIG. 8B includes a substrate (e.g., substrate 400 illustrated and described above with reference to FIG. 4) and an internal coupling grating 848 imprinted on one side of the substrate. A first grating coupler 868 is imprinted on one side of the substrate and is optically coupled to the internal coupling grating 848. The first grating coupler 868 includes a plurality of tiles that define the EPE of the eyepiece.

[0097] Each tile 864 has a first grating pattern (e.g., parallel ridges, protrusions, recesses, etc.). In some embodiments, each tile 864 includes a plurality of recesses. Each recess of the plurality of recesses has one or more sidewalls. In some embodiments, the plurality of recesses has a refractive index greater than 1.4. In some embodiments, at least one of the width or length of each recess is in the range of 5 nm to 800 nm. In some embodiments, the cross section of each recess has a triangular, sawtooth, step, or multi-step shape. A second grating coupler (grating region 860) is interspersed between the tiles. The grating region 860 has a second grating pattern that is different from the first grating pattern. The grating region 860 defines the OPE of the eyepiece. As illustrated in FIG. 8B, the area of ​​each tile 864 increases as the location of the tile 864 changes from the first boundary 852 to the second boundary 856 of the grating region 860. The configuration of FIG. 8B is sometimes referred to as a tiled honeycomb lattice configuration or pattern.

[0098] In some embodiments, the internal coupling grating 848 is configured to receive light from a projector (e.g., projector 300 illustrated and described above with reference to FIG. 3A). The internal coupling grating 848 is configured to diffract the light (e.g., light 332 shown in FIG. 3A) into a first portion of light (e.g., portion 336) and a second portion of light (e.g., portion 312). The first portion 336 has a first orientation with respect to the light 332 received from the projector 300. The second portion 312 has a second orientation with respect to the light 332 received from the projector 300. The second orientation is different from the first orientation. A diffraction grating is patterned on one side of the substrate. The diffraction grating is configured to receive the first portion of light 336 and the second portion of light 312 from the internal coupling grating 848. The diffraction grating includes a first grating coupler 868 and a second grating coupler 860. The first grating coupler 868 includes a plurality of tiles (e.g., tiles 864). The second grating coupler 860 includes a grating region 860. The first grating coupler 868 receives the first portion 336 of the light from the internal coupling grating 848. The first grating coupler 868 diffracts the first portion 336 of the light. The first grating coupler 868 directs the diffracted first portion of the light (e.g., portion 340) to the second grating coupler 860. The second grating coupler 860 receives the second portion 312 of the light from the internal coupling grating 848. The second grating coupler 860 further diffracts the second portion 312 of the light. The second grating coupler 860 directs the diffracted second portion of the light (e.g., portion 316) to the first grating coupler 868. The diffraction grating is further configured to combine the diffracted first portion 340 of the light and the diffracted second portion 316 of the light.

[0099] Patterning of grating couplers FIG. 9A illustrates the patterning of a grating coupler 912 in an optical eyepiece. The eyepiece shown in FIG. 9A includes an internal coupling grating 900 and a grating coupler 912. The grating coupler 912 includes a plurality of intersecting linear grating sections. For example, linear grating section 904 intersects with linear grating section 908. The plurality of intersecting linear grating sections are arranged in a hexagonally filled grating pattern. The grating coupler 912 is sometimes referred to as having a thin line one-sided honeycomb grating pattern or configuration. Each polygon defined by the grating coupler 912 defines at least one angle between two linear grating sections (e.g., 904 and 908) that is in the range of 55 degrees to 65 degrees. Each polygon defined by the grating coupler 912 defines at least one other angle between two linear grating sections 904 and 908 that is in the range of 115 degrees to 125 degrees. In some embodiments, the eyepiece shown in Figure 9A further includes a second grating coupler that includes a grating area adjacent to a plurality of linear grating sections of the grating coupler 912. The grating coupler 912 functions similarly to the grating couplers illustrated and described above with reference to Figures 3A, 3B, 4, 7A, 7B, 8A, and 8B.

[0100] FIG. 9B illustrates the patterning of a grating coupler 972 in an optical eyepiece. The eyepiece illustrated in FIG. 9B includes an internal coupling grating 948 and a grating coupler 972 optically coupled to the internal coupling grating 948. The grating coupler 972 includes a plurality of linear grating sections arranged in a honeycomb grating pattern. For example, the grating coupler 972 includes a linear grating section 952. In some embodiments, the eyepiece includes a second grating coupler. The second grating coupler can include a grating area adjacent to the plurality of linear grating sections of the grating coupler 972. The grating coupler 972 is sometimes referred to as having a thin line one sided honeycomb grating pattern or configuration.

[0101] In some embodiments, the grating coupler 972 further comprises a plurality of protrusions. In some embodiments, the pitch 968 of the protrusion axes is in the range of 300 nm to 450 nm. In some embodiments, the diagonal pitch 964 of the plurality of protrusions is in the range of 300 nm to 900 nm. In some embodiments, the grating coupler 972 comprises a first set of protrusions having a first pitch axis 956, and the second grating coupler comprises a second set of protrusions having a second pitch axis 960. In some embodiments, the angle between the first pitch axis 956 and the second pitch axis 960 is about 90 degrees with or without overlap of features in each of the pitch axis directions. In some embodiments, the angle between the first pitch axis 956 and the second pitch axis 960 is in the range of 55 degrees to 65 degrees with or without overlap of features in each of the pitch axis directions. The feature overlap may be about 30% of the length or width of the protrusions.

[0102] Patterning of grating couplers 10 illustrates the patterning of a grating combiner 1008 in an optical eyepiece. The grating combiner 1008 includes a first set of linear grating segments 1000 that define the OPE of the eyepiece. The grating combiner 1008 includes a second set of linear grating segments 1004 that define the EPE of the eyepiece. The second set of linear grating segments 1004 are interleaved with the first set of linear grating segments 1000. The grating combiner 1008 is sometimes referred to as having a snowflake grating pattern or configuration.

[0103] In the eyepiece embodiments illustrated with reference to Figures 9A, 9B, and 10 above, the geometry of the internal coupling grating (e.g., internal coupling grating 900), the OPE (e.g., OPE 1000), and the EPE (e.g., EPE 1004) are adjusted so that the internal coupling grating 900 and the eyepiece have preferential diffraction orders. The portion of light that is directly coupled or diffracted into the user's eye 328 is reduced, thus reducing unwanted artifacts. The eyepiece embodiments illustrated with reference to Figures 9A, 9B, and 10 above therefore prevent the occurrence of a central bright band artifact in the resulting image. The diffractive properties of the OPE and EPE gratings can be further improved using protrusion tilts and blazes or multi-step protrusions or recesses. Patterning grating couplers in optical eyepieces.

[0104] FIG. 11A illustrates the patterning of a grating coupler in an optical eyepiece. The eyepiece illustrated in FIG. 11A includes a substrate (e.g., substrate 400 illustrated and described above with reference to FIG. 4) that has a refractive index above a certain threshold. In some embodiments, the threshold is 1.4. The eyepiece further includes an internal coupling grating 1100 patterned on one side of the substrate. A first grating coupler 1120 is patterned on one side of the substrate. The first grating coupler 1120 is optically coupled to the internal coupling grating 1100 to receive a portion of the light from the internal coupling grating 1100. The first grating coupler 1120 has a first grating pattern 1104.

[0105] A second grating coupler 1124 is also patterned on one side of the substrate. The second grating coupler 1124 is optically coupled to the internal coupling grating 1100. The second grating coupler 1124 is adjacent to the first grating coupler 1120. The second grating coupler 1124 has a second grating pattern 1108 that is different from the first grating pattern 1104. In some embodiments, the first grating coupler 1120 or the first grating pattern 1104 includes a first set of ridges that are oriented in a first direction. The second grating coupler 1124 or the second grating pattern 1108 includes a second set of ridges that are oriented in a second direction as shown in FIG. 11A. In some embodiments, the angle between the first direction and the second direction is in the range of 55 degrees to 65 degrees.

[0106] In some embodiments, the internal coupling grating 1100 includes a first set of parallel ridges oriented in a first direction. The first grating coupler 1120 includes a second set of parallel ridges oriented in a second direction different from the first direction. The second grating coupler 1124 includes a third set of parallel ridges oriented in a third direction different from the first and second directions. In some embodiments, the angle between the second and third directions is in the range of 55 to 65 degrees.

[0107] In some embodiments, the first grating coupler 1120 contacts the second grating coupler 1124. A tile (e.g., tile 1116) patterned using the second grating pattern 1108 is inserted into the first grating coupler 1120. Another tile (e.g., tile 1112) patterned using the first grating pattern 1104 is inserted into the second grating coupler 1124. A tiled pattern (e.g., including tiles 1112 and 1116) is thus defined where the first grating coupler 1120 contacts the second grating coupler 1124. Tile 1112 has the first grating pattern 1104. Tile 1116 has the second grating pattern 1108. In this manner, the tiled regions are configured to diffuse light that is directly coupled into the eyeball 328 of the eyepiece user. The abrupt transition from the left to the right field of view is blurred. Tile size, density, shape, and distribution can be varied to achieve higher virtual image resolution, uniformity, and brightness. The clarity of the resulting image is also increased.

[0108] In some embodiments, the location where the first grating coupler 1120 meets the second grating coupler 1124 includes an interdigitated alternating grating pattern similar to the interdigitated pass pattern 500 illustrated and described above with reference to Figure 5A. In some embodiments, the location where the first grating coupler 1120 meets the second grating coupler 1124 includes a stencil that blends a first boundary of the first grating coupler 1120 with a second boundary of the second grating coupler 1124.

[0109] Blended patterning of grating couplers in optical eyepieces FIG. 11B illustrates blended patterning of grating couplers in an optical eyepiece. The eyepiece illustrated in FIG. 11B includes an internal coupling grating 1168 configured to diffract light received from a projector (e.g., projector 300 illustrated and described above with reference to FIG. 3). The internal coupling grating 1168 diffracts the light into a first portion of light and a second portion of light. A first grating coupler 1160 is optically coupled to the internal coupling grating 1168. The internal coupling grating 1168 is configured to direct the first portion of light to the first grating coupler 1160. The first grating coupler 1160 has a first grating pattern 1148. A second grating coupler 1164 is also optically coupled to the internal coupling grating 1168. The internal coupling grating 1168 is further configured to direct the second portion of light to the second grating coupler 1164. The second grating coupler 1164 has a second grating pattern 1152 that is different from the first grating pattern 1148 .

[0110] A first boundary 1172 of the first grating coupler 1160 blends with a second boundary 1176 of the second grating coupler to define a blended grating area 1156. In some embodiments, the blended grating area 1156 includes an interdigitated alternating pattern of the first grating pattern 1148 and the second grating pattern 1152. In some embodiments, the blended grating area 1156 includes a stencil that blends the first boundary 1172 of the first grating coupler 1160 with the second boundary 1176 of the second grating coupler 1164. In some embodiments, a merged grating area including graded nanofeatures is created to avoid a bright band in the center of the image. The grating features separate into two distinctly different grating patterns from the center of the grating toward each edge.

[0111] Diffraction and coupling of light using grating couplers in optical eyepieces FIG. 12 illustrates the diffraction and coupling of light using a grating coupler in an optical eyepiece. FIG. 12 depicts the manner in which the k-space of light rays allowed to propagate in a waveguide can be viewed. The gratings in FIG. 12 allow the light 1224 to diffract (spread and exit) in a particular direction, so that the angled light is angled to reach the user's field of view.

[0112] The outer circle 1200 corresponds to the angular condition for light to propagate in a high index substrate. The inner circle 1204 represents the condition for light to propagate in air. The annulus between the two concentric circles 1200 and 1204 corresponds to the total internal reflection (TIR) ​​condition for light to propagate in a planar waveguide. The rectangle 1208 represents the field of view in air.

[0113] Additional Embodiments In some embodiments, the eyepiece includes an internal coupling grating patterned on one side of the substrate and configured to diffract light received from the projector into a first portion of light and a second portion of light. The first portion has a first orientation with respect to the light received from the projector and the second portion has a second orientation with respect to the light received from the projector. The second orientation is different from the first orientation. A diffraction grating is patterned on one side of the substrate and configured to receive the first portion of light and the second portion of light from the internal coupling grating. The first portion of light and the second portion of light are diffracted. The diffracted first portion of light and the diffracted second portion of light are combined.

[0114] In some embodiments, the first grating coupler includes a first set of protrusions having a first pitch axis, and the second grating coupler includes a second set of protrusions having a second pitch axis.

[0115] In some embodiments, the angle between the first pitch axis and the second pitch axis is in the range of 55 degrees to 65 degrees.

[0116] In some embodiments, a first region of the first grating coupler overlaps with a second region of the second grating coupler, the overlapped first region and the overlapped second region each having an interdigitated alternating grating pattern.

[0117] In some embodiments, the interdigitated alternating grid pattern is configured to diffuse a third portion of the light, which is diffracted by the eyepiece directly into the eye of a user of the eyepiece.

[0118] In some embodiments, the interdigitated alternating grating pattern includes a stencil that blends a first boundary of a first grating coupler with a second boundary of a second grating coupler.

[0119] In some embodiments, the interdigitating alternating grid pattern includes at least one of a plurality of parallel ridges oriented in a particular direction, a plurality of ridges arranged in a chevron grid pattern, or a plurality of ridges arranged in a sawtooth grid pattern.

[0120] In some embodiments, the interdigitated alternating grid pattern includes a plurality of protrusions, each protrusion of the plurality of protrusions having one or more sidewalls, each sidewall of the one or more sidewalls being oriented at a different angle relative to the substrate.

[0121] In some embodiments, the protrusions have a refractive index greater than 1.4.

[0122] In some embodiments, the first grating coupler includes a tile having a first grating pattern, and the second grating coupler includes a grating area adjacent the tile and having a second grating pattern different from the first grating pattern.

[0123] In some embodiments, the internal coupling grating includes a first set of parallel ridges oriented in a first direction, the first grating coupler includes a second set of parallel ridges oriented in a second direction different from the first direction, and the second grating coupler includes a third set of parallel ridges oriented in a third direction different from the first and second directions.

[0124] In some embodiments, the angle between the second direction and the third direction is in the range of 55 degrees to 65 degrees.

[0125] In some embodiments, the first grating coupler includes a plurality of parallel grating sections oriented in a particular direction and having a first grating pattern, and the second grating coupler includes a grating area adjacent the plurality of parallel grating sections and having a second grating pattern different from the first grating pattern.

[0126] In some embodiments, the first grid coupler includes a plurality of linear grid sections arranged in a honeycomb grid pattern, and the second grid coupler includes a grid area adjacent to the plurality of linear grid sections.

[0127] In some embodiments, the eyepiece includes an internal coupling grating imprinted on one side of the substrate and a grating coupler imprinted on one side of the substrate and optically coupled to the internal coupling grating. The grating coupler includes a plurality of tiles that define an exit pupil expander (EPE) of the eyepiece. Each tile of the plurality of tiles has a first grating pattern. Grating regions are interspersed among the plurality of tiles and have a second grating pattern that is different from the first grating pattern. The grating regions define an orthogonal pupil expander (OPE) of the eyepiece.

[0128] In some embodiments, the grating coupler is configured to receive light diffracted by the internal coupling grating and reduce the intensity of light emitted by a central region of the grating coupler.

[0129] In some embodiments, the grating coupler is configured to receive light diffracted by the internal coupling grating and to diffuse the light emitted by a central region of the grating coupler.

[0130] In some embodiments, each tile of the plurality of tiles includes a plurality of protrusions, each protrusion of the plurality of protrusions having one or more sidewalls, each sidewall of the one or more sidewalls being oriented at a different angle relative to the substrate.

[0131] In some embodiments, each protrusion of the plurality of protrusions includes two intersecting ridges oriented in two different directions.

[0132] In some embodiments, each protrusion of the plurality of protrusions has a cylindrical or elliptical shape.

[0133] In some embodiments, each protrusion of the plurality of protrusions has at least one rectangular, circular, triangular, or polygonal surface.

[0134] In some embodiments, each tile of the plurality of tiles comprises a plurality of cuboids, each cuboid of the plurality of cuboids having a different height.

[0135] In some embodiments, the internal bond lattice includes a first set of parallel ridges and the lattice region includes a second set of parallel ridges orthogonal to the first set of parallel ridges.

[0136] In some embodiments, the area of ​​each tile of the plurality of tiles decreases as the location of the tile changes from the center of the grating coupler to the boundary of the grating coupler.

[0137] In some embodiments, the area of ​​each tile of the plurality of tiles increases as the position of the tile changes from a first boundary of the grating coupler to a second boundary of the grating coupler.

[0138] In some embodiments, each tile of the plurality of tiles has at least one of a rectangular shape, a circular shape, an oval shape, a polygonal shape, or a hexagonal shape.

[0139] In some embodiments, each tile of the plurality of tiles includes a plurality of recesses. Each recess of the plurality of recesses has one or more sidewalls.

[0140] In some embodiments, the plurality of recesses has a refractive index greater than 1.4.

[0141] In some embodiments, at least one of the width or length of each recess of the plurality of recesses is in the range of 5 nm to 800 nm.

[0142] In some embodiments, a cross-section of each recess of the plurality of recesses has a triangular, sawtooth, or step shape.

[0143] In some embodiments, the eyepiece includes a substrate having a refractive index above a threshold and an internal coupling grating patterned on one side of the substrate. Three or more grating couplers are patterned on the one side of the substrate and optically coupled to the internal coupling grating. Each grating coupler of the three or more grating couplers has a different grating pattern.

[0144] In some embodiments, the internal coupling grating is configured to diffract the light received from the projector into three or more portions of light.

[0145] In some embodiments, each of the three or more portions of light has a different orientation relative to the light received from the projector.

[0146] In some embodiments, the internal coupling grating is further configured to direct corresponding portions of the three or more portions of light to each grating coupler of the three or more grating couplers.

[0147] In some embodiments, each grating coupler of the three or more grating couplers is configured to diffract a corresponding portion of the three or more portions of light.

[0148] In some embodiments, the eyepiece is configured to combine three or more diffracted portions of light.

[0149] In some embodiments, at least one grating coupler of the three or more grating couplers is located between two other grating couplers of the three or more grating couplers.

[0150] In some embodiments, a first of the two other grating couplers includes a first linear grating section that is oriented in a first direction.

[0151] In some embodiments, a second of the two other grating couplers includes a second linear grating section that is oriented in a second direction that is different from the first direction.

[0152] In some embodiments, the angle between the first direction and the second direction is in the range of 55 degrees to 65 degrees.

[0153] In some embodiments, at least one grating coupler of the three or more grating couplers includes a plurality of linear grating sections that are oriented in a third direction different from the first direction and different from the second direction.

[0154] In some embodiments, the pitch of at least one grating coupler of the three or more grating couplers is defined by an intersection of a first other grating coupler of the two other grating couplers and a second other grating coupler of the two other grating couplers.

[0155] In some embodiments, the width of at least one grating coupler of the three or more grating couplers is in the range of 5 mm to 20 mm.

[0156] In some embodiments, at least one grating coupler of the three or more grating couplers includes a plurality of tiles.

[0157] In some embodiments, each tile in the set of tiles has a polygonal shape.

[0158] In some embodiments, each tile of the plurality of tiles includes a plurality of protrusions, each protrusion of the plurality of protrusions having one or more sidewalls.

[0159] In some embodiments, the volume fill factor of each of the plurality of protrusions measured along the direction of light incident on the plurality of protrusions from the internal coupling lattice is in the range of 10% to 90%.

[0160] In some embodiments, the pitch of the axes of the multiple protrusions is in the range of 300 nm to 450 nm.

[0161] In some embodiments, the diagonal pitch of the multiple protrusions is within a range of 300 nm to 900 nm.

[0162] In some embodiments, at least one grating coupler of the three or more grating couplers is configured to diffuse a portion of the light received from the internal coupling grating.

[0163] In some embodiments, at least one grating coupler of the three or more grating couplers is configured to reduce an intensity of light emitted by the at least one grating coupler into an eye of a user of the eyepiece.

[0164] In some embodiments, the eyepiece includes an internal coupling grating patterned on at least one of a first side having a refractive index above a threshold or a second side of the substrate. A first grating coupler is patterned on the first side of the substrate and has a first grating pattern. The first grating coupler is optically coupled to the internal coupling grating. A second grating coupler is patterned on the second side of the substrate and has a second grating pattern that is different from the first grating pattern. The second grating coupler is optically coupled to the internal coupling grating.

[0165] In some embodiments, the first grating coupler and the second grating coupler are configured to receive light from the internal coupling grating.

[0166] In some embodiments, the area of ​​the first grating coupler overlaps with the second grating coupler such that the overlapping area is configured to diffract a portion of the light into the eye of a user of the eyepiece.

[0167] In some embodiments, the area is in the range of 10% to 60% of the total area of ​​the first grating coupler.

[0168] In some embodiments, at least one of the first grating coupler or the second grating coupler includes a plurality of protrusions, each protrusion of the plurality of protrusions having one or more sidewalls, each sidewall of the one or more sidewalls being oriented at a different angle relative to the substrate.

[0169] In some embodiments, each protrusion of the plurality of protrusions includes at least two intersecting ridges oriented in two different directions.

[0170] In some embodiments, the volume fill factor of each of the plurality of protrusions measured along the direction of light incident on the plurality of protrusions from the internal coupling lattice is in the range of 10% to 90%.

[0171] In some embodiments, the pitch of the axes of the multiple protrusions is in the range of 300 nm to 450 nm.

[0172] In some embodiments, the diagonal pitch of the multiple protrusions is within a range of 300 nm to 900 nm.

[0173] In some embodiments, the height of each of the plurality of protrusions is in the range of 5 nm to 500 nm.

[0174] In some embodiments, at least one of the width or length of each of the plurality of protrusions is in the range of 5 nm to 800 nm.

[0175] In some embodiments, a cross-section of each protrusion of the plurality of protrusions has a triangular, sawtooth, or step shape.

[0176] In some embodiments, each protrusion of the plurality of protrusions comprises a plurality of rectangular parallelepipeds, each rectangular parallelepiped of the plurality of rectangular parallelepipeds having a different height.

[0177] In some embodiments, the plurality of protrusions has a refractive index greater than 1.4.

[0178] In some embodiments, the first grating coupler includes a tile having a first grating pattern, and the second grating coupler includes a grating area adjacent the tile and having a second grating pattern.

[0179] In some embodiments, the first grating coupler includes a plurality of recesses, each recess of the plurality of recesses having one or more sidewalls, each sidewall of the one or more sidewalls being oriented at a different angle relative to the substrate.

[0180] In some embodiments, the first grating coupler includes a first set of ridges oriented in a first direction, and the second grating coupler includes a second set of ridges oriented in a second direction.

[0181] In some embodiments, the angle between the first direction and the second direction is in the range of 55 degrees to 65 degrees.

[0182] In some embodiments, the first grating coupler includes a first set of protrusions having a first pitch axis, and the second grating coupler includes a second set of protrusions having a second pitch axis.

[0183] In some embodiments, the angle between the first pitch axis and the second pitch axis is in the range of 55 degrees to 65 degrees.

[0184] In the foregoing description, embodiments have been described with reference to numerous specific details that may vary from implementation to implementation. The description and drawings are, therefore, to be regarded in an illustrative sense rather than a restrictive sense.

Claims

1. An eyepiece, the eyepiece comprising: A substrate; an internal coupling grating imprinted on a single surface of the substrate; a grating coupler imprinted on the single surface of the substrate, the grating coupler optically coupled to the internal coupling grating, the grating coupler comprising a plurality of tiles defining an exit pupil expander (EPE) of the eyepiece, each tile of the plurality of tiles comprising a first grating pattern, and grating areas interspersed among the plurality of tiles; An eyepiece comprising:

2. An eyepiece lens as described in claim 1, wherein the grating region has a second grating pattern different from the first grating pattern.

3. The eyepiece of claim 2 , wherein the grid region defines an orthogonal pupil expander (OPE) of the eyepiece.

4. The eyepiece of claim 1 , wherein the grating coupler is configured to receive light diffracted by the internal coupling grating and to reduce the intensity of light emitted by a central region of the grating coupler.

5. The eyepiece of claim 1 , wherein the grating coupler is configured to receive light diffracted by the internal coupling grating and to diffuse light emitted by a central region of the grating coupler.

6. The eyepiece of claim 1 , wherein each tile of the plurality of tiles comprises a plurality of protrusions.

7. The eyepiece of claim 6 , wherein each protrusion of the plurality of protrusions has one or more side walls.

8. The eyepiece of claim 7 , wherein each sidewall of the one or more sidewalls is oriented at a different angle relative to the substrate.

9. The eyepiece of claim 6 , wherein each protrusion of the plurality of protrusions includes two intersecting ridges oriented in two different directions.

10. The eyepiece of claim 6 , wherein each of said protrusions has a cylindrical or elliptical shape.

11. The eyepiece of claim 6, wherein each protrusion of the plurality of protrusions has at least one rectangular surface, a circular surface, a triangular surface, or a polygonal surface.

12. The eyepiece of claim 1 , wherein each tile of the plurality of tiles comprises a plurality of rectangular parallelepipeds.

13. The eyepiece of claim 12 , wherein each of the plurality of rectangular parallelepipeds has a different height.

14. The eyepiece of claim 2 , wherein the internal coupling grating comprises a first set of parallel ridges and the grating region comprises a second set of parallel ridges perpendicular to the first set of parallel ridges.

15. The eyepiece of claim 1 , wherein an area of ​​each tile of the plurality of tiles decreases as the location of the tile changes from a center of the grating combiner to a boundary of the grating combiner.

16. The eyepiece of claim 1 , wherein an area of ​​each tile of the plurality of tiles increases as the position of the tile changes from a first boundary of the grating combiner to a second boundary of the grating combiner.

17. The eyepiece of claim 1 , wherein each tile of the plurality of tiles has at least one of a rectangular shape, a circular shape, an elliptical shape, a polygonal shape, or a hexagonal shape.

18. The eyepiece of claim 1 , wherein each tile of the plurality of tiles comprises a plurality of recesses.

19. 20. The eyepiece of claim 18, wherein the plurality of recesses have a refractive index greater than 1.

4.

20. 19. An eyepiece lens as described in claim 18, wherein at least one of the width or length of each of the plurality of recesses is in the range of 5 nm to 800 nm.

21. 19. An eyepiece lens as described in claim 18, wherein a cross section of each of the plurality of recesses has a triangular shape, a sawtooth shape, or a stepped shape.

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