Hybrid polymer waveguide and method of making same

Abstract

To provide suitable hybrid polymer waveguides and methods for making the same. In some embodiments, a head-mounted augmented reality display system includes one or more hybrid waveguides configured to display images by directing modulated light containing image information into a viewer's eye. Each hybrid waveguide is formed from two or more layers of different materials. A thicker one of the layers is a highly optically transparent "core" layer, while a thinner layer includes a pattern of protrusions and depressions, e.g., forming a diffractive optical element. The pattern may be formed by imprinting. The hybrid waveguide may include additional layers, e.g., forming multiple alternating core layers and thinner patterned layers. Multiple waveguides may be stacked to form an integrated eyepiece, with each waveguide configured to receive and output light of a different primary color.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 62 / 651,507, entitled "HYBRID POLYMER WAVEGUIDE AND METHODS FOR MAKING THE SAME," filed April 2, 2018. The above-mentioned applications are incorporated herein by reference in their entireties.

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

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

[0004] Modern computing and display technologies have facilitated the development of systems for so-called "virtual reality" or "augmented reality" experiences, in which digitally reproduced images or portions thereof are presented to a user in a manner that appears or can be perceived as real. Virtual reality, or "VR," scenarios typically involve the presentation of digital or virtual image information without transparency to other actual real-world visual input, while augmented reality, or "AR," scenarios typically involve the presentation of digital or virtual image information as an augmentation to the user's visualization of the real world around them. Mixed reality, or "MR," scenarios are a type of AR scenario that typically involve virtual objects integrated into and responsive to the natural world. For example, in an MR scenario, AR image content may be perceived as occluded by or otherwise interacting with objects in the real world.

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

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

[0007] In some embodiments, an optical device is provided, the optical device comprising a waveguide, the waveguide comprising an optically transmissive core layer having a major surface opposite the other major surface, and an optically transmissive auxiliary layer on the major surface, the auxiliary layer having a nanophotonic structure, the auxiliary layer being thinner than the core layer and formed from a material different from the material forming the core layer.

[0008] In some other embodiments, an optical system is provided. The optical system comprises a set of stacked, spaced-apart waveguides. At least one of the waveguides comprises an optically transmissive core layer having a major surface opposite the other major surface, and an optically transmissive help layer on the major surface. The help layer comprises a nanophotonic structure. The help layer is thinner than the core layer and is formed from a different material than the material forming the core layer.

[0009] In yet another embodiment, a method for fabricating an optical device is provided. The method includes forming a waveguide. The forming of the waveguide includes providing upper and lower imprint molds, the imprint molds facing each other. A first polymer material is provided between the imprint molds. A second polymer material is provided between the imprint molds over the first polymer material. The second polymer material is in a liquid state. The second polymer material is brought into contact with the upper imprint mold. The first polymer material and the second polymer material are exposed to a hardening process. The first polymer material forms a first layer, and the second polymer material forms a second layer. The upper imprint mold is then removed.

[0010] In addition, various examples of embodiments are provided below.

[0011] (Example 1) An optical device, A waveguide comprising: an optically transmissive core layer having a major surface opposite the other major surface; an optically transmissive helplayer on the major surface, the helplayer having a nanophotonic structure; The auxiliary layer is thinner than the core layer and is formed from a material different from that forming the core layer. comprising a waveguide; Optical devices.

[0012] (Example 2) The optical device of Example 1, wherein the nanophotonic structure comprises an optical lattice.

[0013] (Example 3) The optical device according to any one of Examples 1-2, wherein the core layer and the auxiliary layer are each formed from a polymer or a resin.

[0014] (Example 4) An optical device according to any one of Examples 1-3, wherein the material forming the auxiliary layer has a refractive index that differs from the refractive index of the material forming the core layer by about 0.05 or more.

[0015] (Example 5) The optical device according to any one of Examples 1 to 4, wherein the core layer has a thickness of 100 to 5,000 μm, and the auxiliary layer has a thickness of 0.01 to 5 μm.

[0016] (Example 6) An optical device according to any of Examples 1-5, further comprising an additional auxiliary layer thinner than the core layer and directly adjacent to the other major surface.

[0017] (Example 7) The optical device of Example 6, wherein the additional auxiliary layer comprises an optical grating.

[0018] (Example 8) A waveguide described in any of Examples 1-7, further comprising an additional core layer positioned on the opposite side of the auxiliary layer from the core layer.

[0019] (Example 9) An optical device described in any of Examples 1-8, further comprising multiple core layers alternating with auxiliary layers thinner than the core layers, the auxiliary layers being formed from a different material than the core layers.

[0020] (Example 10) The optical device of Example 9, wherein the core layers are formed from the same material.

[0021] (Example 11) An optical device according to any one of Examples 9-10, wherein the auxiliary layers are formed from the same material.

[0022] (Example 12) An optical device described in any of Examples 9-11, wherein one or more of the auxiliary layers has a different optical grating than one or more other auxiliary layers.

[0023] (Example 13) An optical system, a set of stacked spaced apart waveguides, at least one of the waveguides having: an optically transmissive core layer having a major surface opposite the other major surface; an optically transmissive helplayer on the major surface, the helplayer having a nanophotonic structure; The auxiliary layer is thinner than the core layer and is formed from a material different from that forming the core layer. Optical system.

[0024] (Example 14) The optical system of Example 13, wherein each waveguide is separated by an air gap.

[0025] (Example 15) An optical system described in any of Examples 13-14, wherein each waveguide is spaced apart by one or more spacers disposed between the waveguides.

[0026] (Example 16) An optical system described in any of Examples 13-15, wherein each waveguide comprises a core layer and an auxiliary layer, and one or more spacers are integral with one of the core layer or the auxiliary layer.

[0027] (Example 17) An optical system described in any of Examples 13-16, wherein each waveguide has a core layer and an auxiliary layer, and the core layer of each waveguide is formed from a material different from the core layers of the other waveguides in the set of stacked spaced waveguides.

[0028] (Example 18) The optical system is an augmented reality system, a spatial light modulator configured to provide modulated light containing image information to the waveguide; Each waveguide comprises a plurality of nanophotonic structures, the nanophotonic structures comprising: an internally coupled diffractive optical element configured to direct the modulated light into the waveguide; an outcoupling diffractive optical element configured to extract the incoupling modulated light from the waveguide; and 18. An optical system according to any one of Examples 13-17, comprising:

[0029] (Example 19) An optical system described in Example 18, wherein the spatial light modulator is part of an optical projection system configured to project an image onto an internally coupled diffractive optical element.

[0030] (Example 20) An optical system described in any of Examples 18-19, wherein the spatial light modulator modulates light for a scanning fiber display.

[0031] (Example 21) Further comprising a plurality of sets of stacked spaced apart waveguides, each waveguide having: an optically transmissive core layer having a major surface opposite the other major surface; an optically transmissive helplayer on the major surface, the helplayer having a nanophotonic structure; The auxiliary layer is thinner than the core layer and is formed from a material different from that forming the core layer. The optical system according to any one of Examples 13-20.

[0032] Example 22. A method for making an optical device, comprising: forming a waveguide, the forming of the waveguide comprising: providing upper and lower imprint molds, the imprint molds facing each other; providing a first polymer material between an imprint mold; providing a second polymer material over the first polymer material and between the imprint mold, the second polymer material being in a liquid state; contacting a second polymer material with the upper imprint mold; exposing the first polymeric material and the second polymeric material to a hardening process, wherein the first polymeric material forms a first layer and the second polymeric material forms a second layer; removing the upper imprint mold; including, including the steps method.

[0033] (Example 23) The method described in Example 22, wherein the upper imprint mold comprises a pattern of protrusions and depressions, and the step of contacting the second polymer material with the upper imprint mold transfers the corresponding pattern of protrusions and depressions into the second polymer material.

[0034] (Example 24) The method described in any of Examples 22-23, wherein the lower imprint mold comprises a pattern of protrusions and depressions and the first layer comprises a matching pattern of protrusions and depressions.

[0035] (Example 25) The method of any of Examples 22-24, wherein the first polymeric material is in a liquid state.

[0036] (Example 26) The step of providing a first polymeric material comprises: providing a first polymer material between the lower imprint mold and the additional imprint mold; compressing a first polymer material between the lower imprint mold and the additional imprint mold; hardening the first polymer material between the lower imprint mold and the additional imprint mold; Including, The step of providing upper and lower imprint molds includes: removing the additional imprint mold; placing an upper imprint mold over a first polymer material; The method of any of Examples 22-25, comprising:

[0037] (Example 27) The method described in any of Examples 22-26, wherein exposing the first and second polymeric materials to a hardening process includes exposing the first and second polymeric materials to ultraviolet light.

[0038] Example 28. Depositing a third polymeric material onto the second layer of the second polymeric material; contacting a third polymeric material with the third polymeric material mold; hardening the third polymeric material to form a third layer of the third polymeric material; and removing the third polymeric material mold. The method of any of Examples 22-27, further comprising:

[0039] Example 29: Depositing a fourth polymeric material on the third layer; contacting a fourth polymeric material with the fourth polymeric material mold; hardening the fourth polymeric material to form a fourth layer formed from the fourth polymeric material; removing the fourth polymeric material mold; The method of Example 28, further comprising:

[0040] (Example 30) depositing a fifth polymeric material on the fourth layer; contacting a fifth polymeric material with the fifth polymeric material mold; hardening the fifth polymeric material to form a fifth layer formed from the fifth polymeric material; removing the fifth polymeric material mold; 30. The method of Example 29, further comprising:

[0041] (Example 31) The method of Example 30, wherein the first, third, and fifth polymeric materials are the same material.

[0042] (Example 32) The method of any of Examples 29-31, wherein the second and fourth polymeric materials are the same material.

[0043] (Example 33) The method described in any of Examples 30-32, wherein the first, third, and fifth layers comprise a pattern of protrusions and depressions that form a diffractive optical element.

[0044] Example 34 forming a waveguide comprising alternating layers of polymer material, every other layer comprising a pattern of protrusions and depressions; affixing an additional waveguide to the waveguide, the additional waveguide and the waveguide being separated by a gap; The method of any of Examples 22-33, further comprising: [Brief explanation of the drawings]

[0045] [Figure 1] FIG. 1 illustrates a user's view of an augmented reality (AR) device.

[0046] [Figure 2] FIG. 2 illustrates a conventional display system for simulating a three-dimensional image for a user.

[0047] [Figure 3] 3A-3C illustrate the relationship between the radius of curvature and the radius of focus.

[0048] [Figure 4A] Figure 4A illustrates a representation of the accommodation-vergence response of the human visual system.

[0049] [Figure 4B] FIG. 4B illustrates examples of different accommodation and convergence states of a pair of eyes of a user.

[0050] [Figure 4C] FIG. 4C illustrates an example of a top-down view representation of a user viewing content through a display system.

[0051] [Figure 4D] FIG. 4D illustrates another example of a top-down view representation of a user viewing content through a display system.

[0052] [Figure 5] FIG. 5 illustrates aspects of an approach for simulating three-dimensional images by correcting for wavefront divergence.

[0053] [Figure 6] FIG. 6 illustrates an embodiment of a waveguide stack for outputting image information to a user.

[0054] [Figure 7] FIG. 7 illustrates an example of an output beam output by a waveguide.

[0055] [Figure 8] FIG. 8 illustrates an example of a stacked waveguide assembly in which each depth plane contains an image formed using multiple different primary colors.

[0056] [Figure 9A] FIG. 9A illustrates a cross-sectional side view of an example of a set of stacked waveguides, each including an internal coupling optical element.

[0057] [Figure 9B] FIG. 9B illustrates a perspective view of the multiple stacked waveguide embodiment of FIG. 9A.

[0058] [Figure 9C] FIG. 9C illustrates a top-down plan view of the multiple stacked waveguide embodiment of FIGS. 9A and 9B.

[0059] [Figure 9D] FIG. 9D illustrates an example of a wearable display system.

[0060] [Figure 10] FIG. 10 illustrates an example of a hybrid waveguide with a core layer and an auxiliary layer.

[0061] [Figure 11] FIG. 11 illustrates an example of a hybrid waveguide with a core layer and multiple auxiliary layers.

[0062] [Figure 12] FIG. 12 illustrates an example of a hybrid waveguide with multiple core and auxiliary layers.

[0063] [Figure 13] FIG. 13 illustrates an example of a hybrid waveguide with multiple core layers and multiple auxiliary layers.

[0064] [Figure 14] FIG. 14 illustrates an example of a stack of hybrid waveguides.

[0065] [Figure 15] 15a-15e illustrate a method of forming a hybrid waveguide with a core layer and an auxiliary layer.

[0066] [Figure 16] 16a-16d illustrate another method of forming a hybrid waveguide with a core layer and an assist layer.

[0067] [Figure 17-1]17a-17g illustrate a method of forming a hybrid waveguide with a core layer and multiple auxiliary layers. [Figure 17-2] 17a-17g illustrate a method of forming a hybrid waveguide with a core layer and multiple auxiliary layers.

[0068] [Figure 18] 18a-18d illustrate a method for forming a hybrid waveguide with patterned core and assist layers.

[0069] [Figure 19-1] 19a-19g illustrate a method for forming a hybrid waveguide with an integral spacer. [Figure 19-2] 19a-19g illustrate a method for forming a hybrid waveguide with an integral spacer. DETAILED DESCRIPTION OF THE INVENTION

[0070] Waveguides may be utilized to direct light within display devices, including head-mounted augmented reality display systems. For example, waveguides may be incorporated into eyeglasses, allowing a viewer to view the surrounding environment through the waveguide. Additionally, waveguides may display images by receiving light containing image information and directing the light into the viewer's eye. Received light may be internally coupled into the waveguide using nanophotonic structures, such as diffractive optical elements. The internally coupled light may then be externally coupled out of the waveguide, also using nanophotonic structures, such as diffractive optical elements. The nanophotonic structures may take the form of depressions and protrusions within the waveguide.

[0071] However, it has been found that the requirements for forming nanophotonic structures and supporting their functionality can be in tension with the requirements for forming waveguides with desired properties for propagating light. For example, materials with a high refractive index at the interface where light is outcoupled from the waveguide are beneficial for providing displays with a wide field of view and for providing waveguides with high compactness and highly efficient optical outcoupling and incoupling. In addition, the waveguide is preferably highly transparent and homogeneous to limit optical losses for light propagating therein, and preferably also capable of being formed on a large scale, i.e., to a thickness and area suitable for the waveguide. Unfortunately, it has been found that materials with high transparency and homogeneity and that can be formed on a large scale may not have the desired high refractive index, and conversely, materials with high refractive index may not have the desired high transparency and homogeneity and ease of formation on a large scale for use in forming waveguides.

[0072] Advantageously, in some embodiments, a hybrid waveguide comprises multiple layers of different materials. For example, a hybrid waveguide may include a core layer and an auxiliary layer. Preferably, the core layer is formed from a highly transparent material, and the auxiliary layer is formed from a thinner layer of material in which the nanophotonic structure is provided. In some embodiments, the material forming the core layer is a highly transparent polymer, e.g., having a transparency transmission of greater than 85%, greater than 90%, or greater than 96% in the visible light spectrum across the thickness of the core layer. The material may be a flowable material (e.g., a flowable polymer) that can be flowed onto a surface and subsequently hardened, e.g., by curing. The auxiliary layer may be thinner than the core layer and preferably formed from a different material than the core layer. For example, the core layer may have a thickness of about 100 μm to 1,000 μm, and the auxiliary layer may have a thickness of about 5 nm to about 5,000 nm (0.01 μm to about 5 μm), including about 50 nm to about 5,000 nm. In some embodiments, the auxiliary layer is formed from a polymer (e.g., an organic polymer), an inorganic material, a hybrid organic / inorganic material, or a combination thereof. In some embodiments, for a given thickness, the auxiliary layer may have lower transparency in the visible spectrum and / or less homogeneity (in optical properties such as composition and / or transparency) than the core layer. However, this lower transparency may be ameliorated by the relative thinness of the auxiliary layer compared to the core layer.

[0073] Preferably, the hybrid waveguide is formed from a material with a high refractive index, which can advantageously utilize a core layer within the waveguide to provide a wide field of view for a display device. In some embodiments, the materials forming the core layer and the auxiliary layer may have a refractive index of about 1.65 or greater, about 1.70 or greater, or about 1.80 or greater. Additionally, the auxiliary layer may be formed from a material with a different refractive index than the core layer. It should be understood that a refractive index difference at the interface between the nanophotonic structure and another material can enhance the nanophotonic structure's ability to redirect light. In some embodiments, the nanophotonic structure comprises a depression filled with another material. For example, the other material may be a subsequently formed core layer. In some embodiments, the material forming the auxiliary layer has a refractive index that is about 0.05 or greater, about 0.1 or greater, or about 0.2 or greater than the refractive index of the material filling the depression of the nanophotonic structure. In some embodiments, the material filling the depression of the nanophotonic structure may be the material of the core layer, which is formed after forming the nanophotonic structure in the auxiliary layer. In some embodiments, the material forming the help layer has a refractive index that differs from the refractive index of the material forming the core layer filling the depressions of the nanophotonic structure by about 0.05 or more, about 0.1 or more, or about 0.2 or more. In some embodiments, the refractive index of the material forming the help layer can be higher than that of the core layer filling the depressions, such as about 1.65 or more, about 1.70 or more, or about 1.80 or more. In some other embodiments, the refractive index of the material forming the help layer can be lower than that of the core layer filling the depressions.

[0074] The nanophotonic structures may take the form of repeated lines of material with intervening depressions or open volumes within the helplayer. In some embodiments, the nanophotonic structures have a critical dimension (e.g., the width of the lines of material) that is less than the wavelength of light in the visible spectrum. The nanophotonic structures may be surface-relief features, including diffractive optical elements such as diffraction gratings. In some embodiments, the nanophotonic structures may be metasurfaces. The nanophotonic structures may include features that extend partially or completely through the helplayer. In some embodiments, one or more of the nanophotonic structures may extend into the immediately adjacent core layer. The core layer may provide additional flexibility and form features of desired sizes, depending, for example, on the desired optical functionality. For example, depressions between lines of material in the helplayer may extend into the core layer to form features in the nanophotonic structure with larger aspect ratios than would be possible if those features were formed using only the helplayer.

[0075] Advantageously, the use of layers of different materials as disclosed herein allows the functionality of a layer to be better matched with the materials forming that layer. For example, the core layer may be formed from a homogeneous, highly transparent material. In addition, the material forming the core layer can be easily processed to form thick layers while maintaining the desired homogeneity and transparency. In some embodiments, such materials may be relatively soft or flexible. On the other hand, the auxiliary layer may be formed from a material having a sufficiently large refractive index difference with the core layer to enable the formation of a diffractive optical element with light redirecting capabilities as disclosed. As discussed herein, the refractive index of the material forming the auxiliary layer is preferably different from that of the core layer. In addition, the auxiliary layer material may be mechanically hard and / or robust (e.g., more mechanically hard or robust than the core layer). In some embodiments, a relatively thick core layer may be utilized to provide light propagation with little optical loss, while a relatively thin auxiliary layer with a high refractive index is utilized to form the photonic structure and to mechanically protect and / or reinforce the core layer.

[0076] The provision of separate and auxiliary layers advantageously allows additional functionality to be achieved. For example, in some embodiments, a waveguide may comprise multiple core and / or auxiliary layers. For example, a core layer may have auxiliary layers on both sides of it, e.g., on the top and bottom major surfaces, or two core layers may be provided, one on each side of the auxiliary layer. In still other embodiments, auxiliary layers may be provided alternating with the core layer. The ability to provide multiple auxiliary layers can advantageously provide additional optical functionality. For example, different auxiliary layers may have different nanophotonic structures that can be configured to provide different optical functionality. In some embodiments, the different nanophotonic structures are configured to address shortcomings of other nanophotonic structures such that the aggregate functionality of all of the nanophotonic structures is improved relative to a single structure. For example, some nanophotonic structures, such as optical lattices, may operate over narrower wavelength bands and / or angles of incidence of light. By utilizing multiple nanophotonic structures, each configured to operate at slightly different wavelength bands and / or angles of incidence, the aggregate wavelength band and / or angle of incidence of light acted upon by the waveguide can be increased.

[0077] Reference will now be made to the drawings in which like reference numerals refer to like parts throughout. Unless otherwise indicated, the drawings are schematic and are not necessarily drawn to scale. Exemplary Display Systems

[0078] FIG. 2 illustrates a conventional display system for simulating a three-dimensional image for a user. It should be understood that when a user's eyes are spaced apart and viewing a real object in space, each eye may have a slightly different view of the object, forming an image of the object at a different location on each eye's retina. This may be referred to as binocular disparity and may be utilized by the human visual system to provide the perception of depth. Conventional display systems simulate binocular disparity by presenting two distinct images 190, 200, one for each eye 210, 220, with slightly different views of the same virtual object, corresponding to the view of the virtual object as it would appear by each eye as if the virtual object were a real object at a desired depth. These images provide binocular cues that the user's visual system may interpret to derive the perception of depth.

[0079] Continuing with reference to FIG. 2 , the images 190, 200 are spaced apart from the eyes 210, 220 by a distance 230 on the z-axis. The z-axis is parallel to the optical axis of the viewer when the eyes are fixating on an object at optical infinity directly in front of the viewer. The images 190, 200 are flat and at a fixed distance from the eyes 210, 220. Based on slightly different views of the virtual object in the images presented to each eye 210, 220, the eyes may necessarily rotate so that the image of the object falls on a corresponding point on each eye's retina, maintaining single binocular vision. This rotation may cause the gaze of each eye 210, 220 to converge on a point in space where the virtual object is perceived to reside. As a result, providing three-dimensional images traditionally involves manipulating the convergence and divergence of the user's eyes 210, 220 and providing binocular cues that the human visual system interprets to provide the perception of depth.

[0080] However, creating a realistic and comfortable perception of depth is difficult. It should be understood that light from an object at different distances from the eye has a wavefront with different amounts of divergence. Figures 3A-3C illustrate the relationship between distance and light ray divergence. The distance between the object and the eye 210 is represented in order of decreasing distances R1, R2, and R3. As shown in Figures 3A-3C, light rays become more divergent as the distance to the object decreases. Conversely, as the distance increases, the light rays become more collimated. In other words, the light field generated by a point (an object or part of an object) can be said to have a spherical wavefront curvature that is a function of the distance the point is from the user's eye. The curvature increases with decreasing distance between the object and the eye 210. While only a single eye 210 is illustrated in Figures 3A-3C and other figures herein for clarity of illustration, the discussion regarding the eye 210 can apply to both eyes 210 and 220 of the viewer.

[0081] Continuing with reference to Figures 3A-3C, light from an object that a viewer's eye is fixating may have different wavefront divergences. Due to the different wavefront divergences, the light may be focused differently by the eye's lens, which in turn may require the lens to assume a different shape and form a focused image on the eye's retina. If a focused image is not formed on the retina, the resulting retinal blur acts as an accommodative cue, causing the shape of the eye's lens to change until a focused image is formed on the retina. For example, the accommodative cue may induce relaxation or contraction of the ciliary muscles surrounding the eye's lens, thereby modulating the force applied to the suspensory ligaments that hold the lens in place, thus changing the shape of the eye's lens and forming a focused image of the fixated object on the eye's retina (e.g., the fovea) until retinal blur of the fixated object is eliminated or minimized. The process by which the eye's lens changes shape can be referred to as accommodation, and the shape of the eye's lens required to form a focused image of a fixated object on the eye's retina (e.g., the fovea) can be referred to as the state of accommodation.

[0082] Referring now to Figure 4A, a representation of the accommodation-vergence response of the human visual system is illustrated. Eye movement to fixate an object causes the eye to receive light from the object, which forms an image on each of the eye's retinas. The presence of retinal blur in the image formed on the retina can provide a cue for accommodation, and the relative location of the image on the retina can provide a cue for vergence. The accommodation cue causes accommodation, leading the eye's lens to adopt a specific accommodation state that forms a focused image of the object on the eye's retina (e.g., the fovea). Conversely, the vergence cue causes vergence movement (eye rotation) so that the image formed on each retina of each eye is at the corresponding retinal point, maintaining single binocular vision. In these positions, the eyes can be said to be in a specific vergence state. Continuing with reference to FIG. 4A , accommodation can be understood as the process by which the eyes achieve a particular accommodation state, and convergence can be understood as the process by which the eyes achieve a particular convergence state. As shown in FIG. 4A , the accommodation and convergence states of the eyes can change when the user fixates on a different object. For example, the accommodated state can change when the user fixates on a new object at a different depth on the z-axis.

[0083] Without being limited by theory, it is believed that a viewer of an object may perceive the object as "three-dimensional" due to a combination of convergence and accommodation. As noted above, vergence and divergence movements of the two eyes relative to one another (e.g., eye rotation such that the pupils move toward or away from one another, converging the eyes' gazes, and fixating on an object) are closely linked to accommodation of the eye's lenses. Under normal conditions, changing the shape of the eye's lenses and shifting focus from one object to another at a different distance will automatically produce a corresponding change in vergence and divergence at the same distance, a relationship known as the "accommodation-vergence reflex." Similarly, a change in vergence and divergence will, under normal conditions, induce a corresponding change in lens shape.

[0084] 4B, an example of different accommodation and convergence states of the eyes is illustrated. Pair of eyes 222a fixates an object at optical infinity, while pair of eyes 222b fixates an object 221 at less than optical infinity. Notably, the convergence states of each pair of eyes are different: pair of eyes 222a points straight ahead, while pair of eyes 222 converge on object 221. The accommodation states of the eyes forming each pair of eyes 222a and 222b are also different, as represented by the different shapes of lenses 210a, 220a.

[0085] Unfortunately, many users of conventional "3-D" display systems may find such systems uncomfortable or may not perceive any depth perception due to a mismatch between accommodation and convergence states in these displays. As noted above, many stereoscopic or "3-D" display systems display a scene by providing a slightly different image to each eye. Such systems are uncomfortable for many viewers because, among other things, they simply provide different presentations of a scene, causing changes in the eyes' convergence states without a corresponding change in the eyes' accommodation states. Rather, images are presented by the display at a fixed distance from the eyes so that the eyes view all image information in a single accommodation state. Such an arrangement counters the "accommodation-vergence-divergence reflex" by causing changes in the convergence states without a corresponding change in the accommodation state. This mismatch is believed to cause viewer discomfort. Display systems that provide a better match between accommodation and convergence-divergence movements may produce a more realistic and comfortable simulation of three-dimensional images.

[0086] Without being limited by theory, it is believed that the human eye can typically interpret a finite number of depth planes to provide depth perception. As a result, a highly realistic simulation of perceived depth can be achieved by providing the eye with different presentations of images corresponding to each of these limited number of depth planes. In some embodiments, the different presentations can provide both vergence cues and matching cues for accommodation, thereby providing physiologically correct accommodation-vergence divergence matching.

[0087] 4B , two depth planes 240 are illustrated, corresponding to different distances in space from the eyes 210, 220. For a given depth plane 240, vergence-divergence cues may be provided by displaying appropriately different perspective images for each eye 210, 220. Additionally, for a given depth plane 240, the light forming the image provided to each eye 210, 220 may have a wavefront divergence corresponding to the light field generated by a point at the distance of that depth plane 240.

[0088] In the illustrated embodiment, the distance along the z-axis of depth plane 240 containing point 221 is 1 m. As used herein, distance or depth along the z-axis may be measured with a zero point located at the exit pupil of the user's eye. Thus, depth plane 240 located at a depth of 1 m corresponds to a distance of 1 m away from the exit pupil of the user's eye on the optical axis of the eye with the eye pointed toward optical infinity. As an approximation, the depth or distance along the z-axis may be measured from the display in front of the user's eye (e.g., from the surface of the waveguide) and a value for the distance between the device and the exit pupil of the user's eye may be added. That value may be referred to as pupil distance and corresponds to the distance between the exit pupil of the user's eye and the display worn by the user in front of the eye. In practice, the value for pupil distance may be a normalized value generally used for all viewers. For example, pupil distance may be assumed to be 20 mm, and the depth plane at a depth of 1 m may be at a distance of 980 mm in front of the display.

[0089] 4C and 4D, examples of matched accommodation-vergence-divergence distances and mismatched accommodation-vergence-divergence distances are illustrated, respectively. As illustrated in FIG. 4C, the display system may provide an image of a virtual object to each eye 210, 220. The image may cause the eyes 210, 220 to assume a convergence-divergence state in which the eyes converge on point 15 on the depth plane 240. In addition, the image may be formed by light having a wavefront curvature corresponding to the real object on the depth plane 240. As a result, the eyes 210, 220 assume an accommodation state in which the image is focused on the retinas of the eyes. Therefore, the user may perceive the virtual object as being at point 15 on the depth plane 240.

[0090] It should be understood that the accommodation and convergence states of the eyes 210, 220 are each associated with a particular distance on the z-axis. For example, an object at a particular distance from the eyes 210, 220 will cause those eyes to assume a particular accommodation state based on the distance of the object. The distance associated with a particular accommodation state is referred to as the accommodation distance A. d Similarly, a particular convergence-divergence distance V associated with the eyes in a particular convergence-divergence state or position relative to one another may be referred to as d When the accommodation distance and the convergence distance match, the relationship between accommodation and convergence is physiologically correct. This is considered the most comfortable scenario for the viewer.

[0091] However, in a stereoscopic display, the accommodation distance and the vergence distance may not always coincide. For example, as illustrated in FIG. 4D , the images displayed to the eyes 210, 220 may be displayed with a wavefront divergence corresponding to the depth plane 240, and the eyes 210, 220 may be in a particular accommodation state in which points 15a, 15b on that depth plane are in focus. However, the images displayed to the eyes 210, 220 may provide a convergence cue that causes the eyes 210, 220 to converge on a point 15 that is not located on the depth plane 240. As a result, in some embodiments, the accommodation distance corresponds to the distance from the exit pupils of the eyes 210, 220 to the depth plane 240, while the vergence distance corresponds to the greater distance from the exit pupils of the eyes 210, 220 to point 15. The accommodation distance is different from the vergence distance. As a result, there is an accommodation-vergence-divergence mismatch. Such a mismatch may be considered undesirable and may cause discomfort to the user. The mismatch may be related to distance (e.g., V d -A d ) and can be characterized in terms of diopters.

[0092] It should be understood that in some embodiments, a reference point other than the exit pupil of the eye 210, 220 may be used to determine the distance for determining accommodation-vergence mismatch, so long as the same reference point is used for accommodation distance and vergence distance. For example, the distance may be measured from the cornea to the depth plane, from the retina to the depth plane, from the ocular lens (e.g., a waveguide in a display device) to the depth plane, from the center of rotation of the eye, etc.

[0093] Without being limited by theory, it is believed that a user may still perceive accommodation-vergence-divergence mismatches of up to about 0.25 diopters, up to about 0.33 diopters, and up to about 0.5 diopters as physiologically correct without the mismatch itself causing significant discomfort. In some embodiments, a display system disclosed herein (e.g., display system 250, FIG. 6 ) presents images to a viewer with an accommodation-vergence-divergence mismatch of about 0.5 diopters or less. In some other embodiments, the accommodation-vergence-divergence mismatch of images provided by the display system is about 0.33 diopters or less. In still other embodiments, the accommodation-vergence-divergence mismatch of images provided by the display system is about 0.25 diopters or less, including about 0.1 diopters or less.

[0094] FIG. 5 illustrates aspects of an approach for simulating a three-dimensional image by modifying wavefront divergence. The display system includes a waveguide 270 configured to receive light 770 encoded with image information and output the light to a user's eye 210. The waveguide 270 may output light 650 with a defined amount of wavefront divergence that corresponds to the wavefront divergence of a light field generated by a point on a desired depth plane 240. In some embodiments, the same amount of wavefront divergence is provided for all objects presented on that depth plane. In addition, it will be illustrated that the user's other eye may be provided with image information from a similar waveguide.

[0095] In some embodiments, a single waveguide may be configured to output light with a set wavefront divergence corresponding to a single or limited number of depth planes, and / or the waveguide may be configured to output light in a limited range of wavelengths. As a result, in some embodiments, multiple or stacked waveguides may be utilized to provide different wavefront divergences for different depth planes and / or to output light in different ranges of wavelengths. As used herein, it should be understood that a depth plane may follow the contour of a flat or curved surface. In some embodiments, advantageously, for simplicity, a depth plane may follow the contour of a flat surface.

[0096] 6 illustrates an example of a waveguide stack for outputting image information to a user. Display system 250 includes a stack of waveguides or stacked waveguide assembly 260 that can be utilized to provide a three-dimensional perception to the eye / brain using multiple waveguides 270, 280, 290, 300, 310. It should be understood that display system 250 can be considered a light field display in some embodiments. Additionally, waveguide assembly 260 can also be referred to as an eyepiece.

[0097] In some embodiments, display system 250 may be configured to provide a substantially continuous cue for convergence and multiple discrete cues for accommodation. The cues for convergence may be provided by displaying different images to each of the user's eyes, and the cues for accommodation may be provided by outputting light that forms images with selectable discrete amounts of wavefront divergence. In other words, display system 250 may be configured to output light with variable levels of wavefront divergence. In some embodiments, each discrete level of wavefront divergence corresponds to a particular depth plane and may be provided by a particular one of waveguides 270, 280, 290, 300, and 310.

[0098] Continuing with reference to FIG. 6 , the waveguide assembly 260 may also include multiple features 320, 330, 340, 350 between the waveguides. In some embodiments, the features 320, 330, 340, 350 may be one or more lenses. The waveguides 270, 280, 290, 300, 310 and / or multiple lenses 320, 330, 340, 350 may be configured to transmit image information to the eye using various levels of wavefront curvature or ray divergence. Each waveguide level may be associated with a particular depth plane and configured to output image information corresponding to that depth plane. The image injection devices 360, 370, 380, 390, 400 may function as light sources for the waveguides and may each be utilized to inject image information into the waveguides 270, 280, 290, 300, 310, which may be configured to disperse incident light across each individual waveguide for output toward the eye 210, as described herein. Light exits output surfaces 410, 420, 430, 440, 450 of the image injection devices 360, 370, 380, 390, 400 and is injected into corresponding input surfaces 460, 470, 480, 490, 500 of the waveguides 270, 280, 290, 300, 310. In some embodiments, each input surface 460, 470, 480, 490, 500 may be an edge of the corresponding waveguide or a portion of a major surface of the corresponding waveguide (i.e., one of the waveguide surfaces that directly faces the world 510 or the viewer's eye 210). It should be understood that a major surface of a waveguide corresponds to the surface of the waveguide between which the thickness of the waveguide extends. In some embodiments, a single beam of light (e.g., a collimated beam) may be launched into each waveguide, outputting an entire field of cloned collimated beams directed toward the eye 210 at a particular angle (and divergence) corresponding to the depth plane associated with the particular waveguide. In some embodiments, a single one of the image launch devices 360, 370, 380, 390, 400 may be associated with and launch light into multiple (e.g., three) waveguides 270, 280, 290, 300, 310.

[0099] In some embodiments, image input devices 360, 370, 380, 390, 400 are discrete displays that each generate image information for input into a corresponding waveguide 270, 280, 290, 300, 310. In some other embodiments, image input devices 360, 370, 380, 390, 400 are outputs of a single multiplexed display that may, for example, send image information via one or more optical conduits (such as fiber optic cables) to each of image input devices 360, 370, 380, 390, 400. It should be understood that the image information provided by image input devices 360, 370, 380, 390, 400 may include light of different wavelengths or colors (e.g., different primary colors, as discussed herein).

[0100] In some embodiments, light injected into the waveguides 270, 280, 290, 300, 310 is provided by a light projector system 520 comprising a light module 530, which may include light emitters such as light emitting diodes (LEDs). Light from the light module 530 may be directed via a beam splitter 550 to and modified by a light modulator 540, e.g., a spatial light modulator. The light modulator 540 may be configured to vary the perceived intensity of the light injected into the waveguides 270, 280, 290, 300, 310 and encode the light with image information. Examples of spatial light modulators include liquid crystal displays (LCDs), including liquid crystal on silicon (LCOS) displays. It should be understood that image injection devices 360, 370, 380, 390, 400 are illustrated diagrammatically, and in some embodiments, these image injection devices may represent different light paths and locations within a common projection system configured to output light into associated ones of waveguides 270, 280, 290, 300, 310. In some embodiments, the waveguides of waveguide assembly 260 may function as ideal lenses, relaying light injected into the waveguides to the user's eye. In this concept, the object may be a spatial light modulator 540, and the image may be an image on a depth plane.

[0101] In some embodiments, the display system 250 may be a scanning fiber display comprising one or more scanning fibers configured to project light in various patterns (e.g., raster scan, spiral scan, Lissajous pattern, etc.) into one or more waveguides 270, 280, 290, 300, 310 and ultimately to the viewer's eye 210. In some embodiments, the illustrated image injection devices 360, 370, 380, 390, 400 may diagrammatically represent a single scanning fiber or a bundle of scanning fibers configured to inject light into one or more waveguides 270, 280, 290, 300, 310. In some other embodiments, the illustrated image injection devices 360, 370, 380, 390, 400 may diagrammatically represent multiple scanning fibers or multiple bundles of scanning fibers, each configured to inject light into an associated one of the waveguides 270, 280, 290, 300, 310. It should be understood that one or more optical fibers may be configured to transmit light from the optical module 530 to one or more waveguides 270, 280, 290, 300, 310. It should be understood that one or more intervening optical structures may be provided between the scanning fiber or fibers and one or more waveguides 270, 280, 290, 300, 310, for example, to redirect light exiting the scanning fiber into one or more waveguides 270, 280, 290, 300, 310.

[0102] Controller 560 controls the operation of one or more of stacked waveguide assemblies 260, including the operation of image input devices 360, 370, 380, 390, 400, light source 530, and light module 540. In some embodiments, controller 560 is part of local data processing module 140. Controller 560 contains programming (e.g., instructions in a non-transitory medium) that coordinates the timing and provision of image information to waveguides 270, 280, 290, 300, 310, for example, according to any of the various schemes disclosed herein. In some embodiments, the controller may be a single integrated device or a distributed system connected by a wired or wireless communication channel. Controller 560 may, in some embodiments, be part of processing module 140 or 150 (FIG. 9D).

[0103] Continuing with reference to FIG. 6 , waveguides 270, 280, 290, 300, 310 may be configured to propagate light within each individual waveguide by total internal reflection (TIR). Each of waveguides 270, 280, 290, 300, 310 may be planar or have another shape (e.g., curved) with major top and bottom surfaces and edges extending between the major top and bottom surfaces. In the illustrated configuration, waveguides 270, 280, 290, 300, 310 may each include outcoupling optical elements 570, 580, 590, 600, 610 configured to extract light from the waveguide by redirecting light propagating within each individual waveguide out of the waveguide and outputting image information to eye 210. The extracted light may also be referred to as outcoupling light, and the outcoupling optical elements may also be referred to as light extraction optical elements. The extracted beam of light may be output by the waveguide at a location where light propagating within the waveguide strikes the light extraction optical element. The outcoupling optical element 570, 580, 590, 600, 610 may be, for example, a grating including diffractive optical features as discussed further herein. While shown disposed on the bottom major surface of the waveguides 270, 280, 290, 300, 310 for ease of explanation and clarity of drawing, in some embodiments, the outcoupling optical element 570, 580, 590, 600, 610 may be disposed on the top and / or bottom major surfaces and / or directly within the volume of the waveguides 270, 280, 290, 300, 310, as discussed further herein. In some embodiments, the outcoupling optical elements 570, 580, 590, 600, 610 may be formed within a layer of material attached to a transparent substrate and forming the waveguides 270, 280, 290, 300, 310. In some other embodiments, the waveguides 270, 280, 290, 300, 310 may be monolithic material components, and the outcoupling optical elements 570, 580, 590, 600, 610 may be formed on and / or within the material components.

[0104] Continuing with reference to FIG. 6 , as discussed herein, each waveguide 270, 280, 290, 300, 310 is configured to output light and form an image corresponding to a particular depth plane. For example, the waveguide 270 closest to the eye may be configured to deliver collimated light (injected into such waveguide 270) to the eye 210. The collimated light may represent an optical infinity focal plane. The next upper waveguide 280 may be configured to send collimated light that passes through a first lens 350 (e.g., a negative lens) before reaching the eye 210. Such first lens 350 may be configured to generate a slight convex wavefront curvature so that the eye / brain interprets light emerging from the next upper waveguide 280 as emerging from a first focal plane closer inward from optical infinity toward the eye 210. Similarly, the third upper waveguide 290 passes its output light through both the first lens 350 and the second lens 340 before reaching the eye 210. The combined refractive power of the first lens 350 and the second lens 340 may be configured to produce another, increasing amount of wavefront curvature such that the eye / brain interprets the light emerging from the third upper waveguide 290 as originating from a second focal plane closer inward toward the person from optical infinity, which was the light from the next upper waveguide 280.

[0105] The other waveguide layers 300, 310 and lenses 330, 320 are similarly configured, with the highest waveguide 310 in the stack sending its output through all of the lenses between it and the eye for a collective focal power representing the focal plane closest to the person. To compensate for the stack of lenses 320, 330, 340, 350 when viewing / interpreting light originating from the world 510 on the other side of the stacked waveguide assembly 260, a compensating lens layer 620 may be placed on top of the stack to compensate for the collective power of the lower lens stacks 320, 330, 340, 350. Such a configuration provides as many perceived focal planes as there are available waveguide / lens pairs. Both the outcoupling optical elements of the waveguides and the focusing sides of the lenses may be static (i.e., not dynamic or electro-active). In some alternative embodiments, either or both may be dynamic using electro-active features.

[0106] In some embodiments, two or more of the waveguides 270, 280, 290, 300, 310 may have the same associated depth plane. For example, multiple waveguides 270, 280, 290, 300, 310 may be configured to output images set at the same depth plane, or multiple subsets of waveguides 270, 280, 290, 300, 310 may be configured to output images set at the same depth planes, with one set per depth plane. This may provide advantages for forming tiled images to provide an extended field of view at those depth planes.

[0107] Continuing with reference to FIG. 6 , the outcoupling optical elements 570, 580, 590, 600, 610 may be configured for specific depth planes associated with the waveguides to redirect light out of their respective waveguides and output the light with the appropriate amount of divergence or collimation. As a result, waveguides with different associated depth planes may have different configurations of outcoupling optical elements 570, 580, 590, 600, 610 that output light with different amounts of divergence depending on the associated depth plane. In some embodiments, the light-extracting optical elements 570, 580, 590, 600, 610 may be volume or surface features that may be configured to output light at specific angles. For example, the light-extracting optical elements 570, 580, 590, 600, 610 may be volume holograms, surface holograms, and / or diffraction gratings. In some embodiments, the features 320, 330, 340, 350 may not be lenses. Rather, they may simply be spacers (eg, cladding layers and / or structures for forming air gaps).

[0108] In some embodiments, the outcoupling optical elements 570, 580, 590, 600, 610 are diffractive features or "diffractive optical elements" (also referred to herein as "DOEs") that form a diffraction pattern. Preferably, the DOEs have a sufficiently low diffraction efficiency so that only a portion of the light in the beam is deflected toward the eye 210 at each intersection of the DOE, while the remainder continues traveling through the waveguide via TIR. The light carrying the image information is thus split into several related output beams that exit the waveguide at multiple locations, resulting in a very uniform pattern of output emission toward the eye 210 for this particular collimated beam bouncing within the waveguide.

[0109] In some embodiments, one or more DOEs may be switchable between an "on" state in which they actively diffract and an "off" state in which they do not significantly diffract. For example, a switchable DOE may comprise a layer of polymer-dispersed liquid crystal in which microdroplets comprise a diffractive pattern within a host medium, and the refractive index of the microdroplets may be switched to substantially match the refractive index of the host material (in which case the pattern does not significantly diffract incident light), or the microdroplets may be switched to a refractive index that does not match that of the host medium (in which case the pattern actively diffracts incident light).

[0110] In some embodiments, a camera assembly 630 (e.g., a digital camera, including visible and infrared light cameras) may be provided to capture images of the eye 210 and / or tissue surrounding the eye 210, for example, to detect user input and / or monitor the physiological state of the user. As used herein, a camera may be any image capture device. In some embodiments, the camera assembly 630 may include an image capture device and a light source that projects light (e.g., infrared light) onto the eye, which may then be reflected by the eye and detected by the image capture device. In some embodiments, the camera assembly 630 may be mounted on the frame 80 (FIG. 9D) and may be in electrical communication with processing modules 140 and / or 150, which may process image information from the camera assembly 630. In some embodiments, one camera assembly 630 may be utilized per eye, monitoring each eye separately.

[0111] 7, an example of an output beam output by a waveguide is shown. While one waveguide is illustrated, it should be understood that other waveguides in waveguide assembly 260 (FIG. 6) may function similarly, and that waveguide assembly 260 includes multiple waveguides. Light 640 is launched into waveguide 270 at input surface 460 of waveguide 270 and propagates within waveguide 270 by TIR. At the point where light 640 impinges on DOE 570, a portion of the light exits the waveguide as output beam 650. Although output beams 650 are illustrated as being approximately parallel, as discussed herein, they may also be redirected to propagate to eye 210 at an angle (e.g., forming a diverging output beam) depending on the depth plane associated with waveguide 270. It should be understood that a nearly collimated exit beam may refer to a waveguide with outcoupling optics that outcouples light to form an image that appears to be set on a depth plane at a long distance (e.g., optical infinity) from the eye 210. Other waveguides or other sets of outcoupling optics may output a more divergent exit beam pattern, which would require the eye 210 to accommodate to a closer distance and focus on the retina, and would be interpreted by the brain as light from a distance closer to the eye 210 than optical infinity.

[0112] In some embodiments, a full-color image may be formed at each depth plane by overlaying images in each of the primary colors, for example, three or more primary colors. FIG. 8 illustrates an example of a stacked waveguide assembly in which each depth plane includes an image formed using multiple different primary colors. The illustrated embodiment shows depth planes 240a-240f, but more or fewer depths are also contemplated. Each depth plane may have three or more primary color images associated with it, including a first image in a first color G, a second image in a second color R, and a third image in a third color B. Different depth planes are indicated in the diagram by different numbers for diopters (dpt) following the letters G, R, and B. By way of example only, the number following each of these letters indicates diopters (1 / m), i.e., the inverse distance of the depth plane from the viewer, and each box in the diagram represents an individual primary color image. In some embodiments, the exact placement of the depth planes for different primary colors may be varied to account for differences in the eye's focusing of light of different wavelengths. For example, different primary color images for a given depth plane may be placed on depth planes corresponding to different distances from the user. Such an arrangement may increase visual acuity and user comfort and / or reduce chromatic aberrations.

[0113] In some embodiments, light for each primary color may be output by a single dedicated waveguide, such that each depth plane may have multiple waveguides associated with it. In such embodiments, each box in the diagram containing the letter G, R, or B may be understood to represent an individual waveguide, and three waveguides may be provided per depth plane, with three primary color images provided per depth plane. While the waveguides associated with each depth plane are shown adjacent to each other in this drawing for ease of illustration, it should be understood that in a physical device, the waveguides may all be arranged in a stack with one waveguide per level. In some other embodiments, multiple primary colors may be output by the same waveguide, such that, for example, only a single waveguide may be provided per depth plane.

[0114] 8, in some embodiments, G is green, R is red, and B is blue. In some other embodiments, other colors associated with other wavelengths of light, including magenta and cyan, may be used in addition to or replace one or more of red, green, or blue.

[0115] It should be understood that references throughout this disclosure to a given color of light will be understood to encompass light of one or more wavelengths within the range of wavelengths of light that are perceived by a viewer as being of that given color. For example, red light may include one or more wavelengths of light in the range of about 620-780 nm, green light may include one or more wavelengths of light in the range of about 492-577 nm, and blue light may include one or more wavelengths of light in the range of about 435-493 nm.

[0116] In some embodiments, light source 530 (FIG. 6) may be configured to emit light at one or more wavelengths outside the range of a viewer's visual perception, e.g., infrared and / or ultraviolet wavelengths. Additionally, the waveguide incoupling, outcoupling, and other light redirecting structures of display 250 may be configured to direct and emit this light from the display toward the user's eye 210, e.g., for imaging and / or user stimulation applications.

[0117] Referring now to FIG. 9A , in some embodiments, light impinging on a waveguide may need to be redirected to incoupling the light into the waveguide. An incoupling optical element may be used to redirect and incoupling the light into its corresponding waveguide. FIG. 9A illustrates a cross-sectional side view of an example of a plurality or set 660 of stacked waveguides, each including an incoupling optical element. The waveguides may each be configured to output light of one or more different wavelengths or one or more different wavelength ranges. It should be understood that stack 660 may correspond to stack 260 ( FIG. 6 ), and that the illustrated waveguide of stack 660 may correspond to a portion of multiple waveguides 270, 280, 290, 300, 310, except that light from one or more of image injection devices 360, 370, 380, 390, 400 is injected into the waveguide from a location requiring the light to be redirected for incoupling.

[0118] The illustrated set 660 of stacked waveguides includes waveguides 670, 680, and 690. Each waveguide includes an associated internal coupling optical element (which may also be referred to as the light input area on the waveguide), for example, internal coupling optical element 700 is disposed on a major surface (e.g., the top major surface) of waveguide 670, internal coupling optical element 710 is disposed on a major surface (e.g., the top major surface) of waveguide 680, and internal coupling optical element 720 is disposed on a major surface (e.g., the top major surface) of waveguide 690. In some embodiments, one or more of internal coupling optical elements 700, 710, 720 may be disposed on the bottom major surface of an individual waveguide 670, 680, 690 (particularly if one or more of the internal coupling optical elements is a reflective polarizing optical element). As shown, the internal coupling optical elements 700, 710, 720 may be disposed on the upper major surfaces of the respective waveguides 670, 680, 690 (or on top of the next lower waveguide), particularly if the internal coupling optical elements are transmissive deflecting optical elements. In some embodiments, the internal coupling optical elements 700, 710, 720 may be disposed within the body of the respective waveguides 670, 680, 690. In some embodiments, as discussed herein, the internal coupling optical elements 700, 710, 720 are wavelength selective so as to selectively redirect one or more wavelengths of light while transmitting other wavelengths of light. While illustrated on one side or corner of the respective waveguides 670, 680, 690, it should be understood that the internal coupling optical elements 700, 710, 720 may be disposed within other areas of the respective waveguides 670, 680, 690 in some embodiments.

[0119] As shown, the in-coupling optical elements 700, 710, 720 may be laterally offset from one another. In some embodiments, each in-coupling optical element may be offset to receive light without that light passing through another in-coupling optical element. For example, each in-coupling optical element 700, 710, 720 may be configured to receive light from a different image input device 360, 370, 380, 390, and 400, as shown in FIG. 6 , and may be separated (e.g., laterally spaced) from the other in-coupling optical elements 700, 710, 720 so as to substantially not receive light from others of the in-coupling optical elements 700, 710, 720.

[0120] Each waveguide also includes an associated optically dispersive element, for example, optically dispersive element 730 is disposed on a major surface (e.g., the top major surface) of waveguide 670, optically dispersive element 740 is disposed on a major surface (e.g., the top major surface) of waveguide 680, and optically dispersive element 750 is disposed on a major surface (e.g., the top major surface) of waveguide 690. In some other embodiments, optically dispersive elements 730, 740, 750 may be disposed on the bottom major surfaces of associated waveguides 670, 680, 690, respectively. In some other embodiments, optically dispersive elements 730, 740, 750 may be disposed on both the top and bottom major surfaces of associated waveguides 670, 680, 690, respectively, or optically dispersive elements 730, 740, 750 may be disposed on different ones of the top and bottom major surfaces in different associated waveguides 670, 680, 690, respectively.

[0121] Waveguides 670, 680, 690 may be spaced apart and separated, for example, by gas, liquid, and / or solid layers of material. For example, as shown, layer 760a may separate waveguides 670 and 680, and layer 760b may separate waveguides 680 and 690. In some embodiments, layers 760a and 760b are formed from a low refractive index material (i.e., a material having a lower refractive index than the material forming the immediately adjacent ones of waveguides 670, 680, 690). Preferably, the refractive index of the material forming layers 760a, 760b is 0.05 or more or 0.10 or less than the refractive index of the material forming waveguides 670, 680, 690. Advantageously, the lower refractive index layers 760a, 760b may function as cladding layers to promote total internal reflection (TIR) ​​of light through the waveguides 670, 680, 690 (e.g., TIR between the top and bottom major surfaces of each waveguide). In some embodiments, the layers 760a, 760b are formed from air. Although not shown, it should be understood that the top and bottom of the illustrated set of waveguides 660 may include immediate cladding layers.

[0122] Preferably, for ease of manufacturing and other considerations, the materials forming waveguides 670, 680, 690 are similar or the same, and the materials forming layers 760a, 760b are similar or the same. In some embodiments, the materials forming waveguides 670, 680, 690 may vary between one or more waveguides, and / or the materials forming layers 760a, 760b may vary while still maintaining the various refractive index relationships described above.

[0123] 9A, light rays 770, 780, 790 enter the set of waveguides 660. It should be understood that light rays 770, 780, 790 may be injected into the waveguides 670, 680, 690 by one or more image injection devices 360, 370, 380, 390, 400 (FIG. 6).

[0124] In some embodiments, light rays 770, 780, 790 have different properties, such as different wavelengths or different wavelength ranges, which may correspond to different colors. Each of the incoupling optical elements 700, 710, 720 deflects incident light such that the light propagates through a respective one of the waveguides 670, 680, 690 by TIR. In some embodiments, each of the incoupling optical elements 700, 710, 720 selectively deflects one or more particular wavelengths of light while transmitting other wavelengths to the underlying waveguide and associated incoupling optical element.

[0125] For example, in-coupling optical element 700 may be configured to deflect light ray 770 having a first wavelength or wavelength range while transmitting light rays 780 and 790 having different second and third wavelengths or wavelength ranges, respectively. Transmitted light ray 780 impinges on and is deflected by in-coupling optical element 710, which is configured to deflect light of the second wavelength or wavelength range. Light ray 790 is deflected by in-coupling optical element 720, which is configured to selectively deflect light of the third wavelength or wavelength range.

[0126] 9A , the deflected light rays 770, 780, 790 are deflected to propagate through the corresponding waveguides 670, 680, 690. That is, the in-coupling optical element 700, 710, 720 of each waveguide deflects the light into its corresponding waveguide 670, 680, 690, in-coupling the light into the corresponding waveguide. The light rays 770, 780, 790 are deflected at an angle that causes the light to propagate through the respective waveguides 670, 680, 690 by TIR. The light rays 770, 780, 790 propagate through the respective waveguides 670, 680, 690 by TIR until they impinge on the waveguide's corresponding optical dispersive element 730, 740, 750.

[0127] 9B, a perspective view of the multiple stacked waveguide embodiment of FIG. 9A is illustrated. As described above, in-coupled light rays 770, 780, 790 are deflected by in-coupling optical elements 700, 710, 720, respectively, and then propagate by TIR within waveguides 670, 680, 690, respectively. Light rays 770, 780, 790 then impinge on optically dispersive elements 730, 740, 750, respectively. Optically dispersive elements 730, 740, 750 deflect light rays 770, 780, 790 to propagate toward out-coupling optical elements 800, 810, 820, respectively.

[0128] In some embodiments, the optically dispersive elements 730, 740, 750 are orthogonal pupil expanders (OPEs). In some embodiments, the OPEs deflect or disperse light into the out-coupling optical elements 800, 810, 820, and in some embodiments, may also increase the beam or spot size of this light as it propagates into the out-coupling optical elements. In some embodiments, the optically dispersive elements 730, 740, 750 may be omitted, and the in-coupling optical elements 700, 710, 720 may be configured to deflect light directly into the out-coupling optical elements 800, 810, 820. For example, with reference to FIG. 9A , the optically dispersive elements 730, 740, 750 may be replaced with the out-coupling optical elements 800, 810, 820, respectively. In some embodiments, the outcoupling optical elements 800, 810, 820 are exit pupils (EPs) or exit pupil expanders (EPEs) that direct light into the viewer's eye 210 ( FIG. 7 ). It should be understood that an OPE can be configured to increase the size of the eyebox in at least one axis, and that the EPE can increase the eyebox in an axis that intersects the axis of the OPE, e.g., orthogonal to it. For example, each OPE may be configured to redirect a portion of the light striking the OPE to an EPE in the same waveguide, while allowing the remaining portion of the light to continue propagating down the waveguide. Again, in response to striking the OPE, another portion of the remaining light is redirected to the EPE, which continues to propagate further down the waveguide, and so on. Similarly, in response to striking the EPE, a portion of the impinging light is directed out of the waveguide toward the user, and that remaining portion of the light continues to propagate through the waveguide until it again strikes an EP, at which point another portion of the impinging light is directed out of the waveguide, and so on. As a result, a single beam of internally coupled light may be "replicated" each time a portion of that light is redirected by an OPE or EPE, thereby forming a cloned beam field of light, as shown in Figure 6. In some embodiments, the OPE and / or EPE may be configured to modify the size of the beam of light.

[0129] 9A and 9B, in some embodiments, a waveguide set 660 includes, for each primary color, waveguides 670, 680, 690, in-coupling optical elements 700, 710, 720, optically dispersive elements (e.g., OPEs) 730, 740, 750, and out-coupling optical elements (e.g., EPs) 800, 810, 820. The waveguides 670, 680, 690 may be stacked with an air gap / cladding layer between each one. The in-coupling optical elements 700, 710, 720 redirect or deflect incident light into that waveguide (with different in-coupling optical elements receiving different wavelengths of light). The light then propagates at an angle that will result in TIR within the individual waveguides 670, 680, 690. In the example shown, light ray 770 (e.g., blue light) is deflected by the first in-coupling optical element 700 in the manner previously described, then continues bouncing down the waveguide, interacting with the optically dispersive element (e.g., OPE) 730 and then the out-coupling optical element (e.g., EP) 800. Light rays 780 and 790 (e.g., green and red light, respectively) pass through the waveguide 670, with light ray 780 impinging on and being deflected by the in-coupling optical element 710. Light ray 780 then bounces down the waveguide 680, via TIR, to its optically dispersive element (e.g., OPE) 740 and then the out-coupling optical element (e.g., EP) 810. Finally, light ray 790 (e.g., red light) passes through the waveguide 690 and impinges on the optically in-coupling optical element 720 of the waveguide 690. The light in-coupling optical element 720 deflects the light ray 790 so that it propagates by TIR to the light dispersive element (e.g., OPE) 750 and then by TIR to the out-coupling optical element (e.g., EP) 820. The out-coupling optical element 820 then finally out-couples the light ray 790 to a viewer, who also receives light out-coupled from the other waveguides 670, 680.

[0130] FIG. 9C illustrates a top-down plan view of an example of the multiple stacked waveguides of FIGS. 9A and 9B. As shown, waveguides 670, 680, 690 may be vertically aligned, along with each waveguide's associated optically dispersive element 730, 740, 750 and associated out-coupling optical elements 800, 810, 820. However, as discussed herein, the in-coupling optical elements 700, 710, 720 are not vertically aligned. Rather, the in-coupling optical elements are preferably non-overlapping (e.g., laterally spaced apart, as seen in the top-down view). As discussed further herein, this non-overlapping spatial arrangement facilitates the injection of light from different sources into different waveguides on a one-to-one basis, thereby allowing a specific light source to be uniquely coupled to a specific waveguide. In some embodiments, arrays including non-overlapping, spatially separated in-coupling optical elements may be referred to as shifted-pupil systems, and the in-coupling optical elements in these arrays may correspond to sub-pupils.

[0131] 9D illustrates an example of a wearable display system 60 into which the various waveguide and associated systems disclosed herein may be integrated. In some embodiments, the display system 60 is the system 250 of FIG. 6, which diagrammatically illustrates some portions of the system 60 in greater detail. For example, the waveguide assembly 260 of FIG. 6 may be part of the display 70.

[0132] 9D , display system 60 includes display 70 and various mechanical and electronic modules and systems to support the functionality of display 70. Display 70 may be coupled to a frame 80 that is wearable by a display system user or viewer 90 and configured to position display 70 in front of the user's 90's eye. Display 70, in some embodiments, may be considered an eyepiece. In some embodiments, a speaker 100 is coupled to frame 80 and configured to be positioned adjacent to the user's 90's ear canal (in some embodiments, another speaker, not shown, may optionally be positioned adjacent the user's other ear canal to provide stereo / shapeable sound control). Display system 60 may also include one or more microphones 110 or other devices to detect sound. In some embodiments, the microphones may be configured to allow a user to provide input or commands (e.g., voice menu command selections, natural language queries, etc.) to system 60 and / or enable audio communication with other persons (e.g., other users of similar display systems). The microphone may further be configured as an ambient sensor to collect audio data (e.g., sounds from the user and / or the environment). In some embodiments, the display system 60 may further include one or more outwardly directed environmental sensors 112 configured to detect objects, stimuli, people, animals, places, or other aspects of the world around the user. For example, the environmental sensors 112 may include, for example, one or more cameras that may be positioned facing outward to capture images similar to at least a portion of the user 90's normal field of view. In some embodiments, the display system may also include an ambient sensor 120a that is separate from the frame 80 and that may be attached to the body of the user 90 (e.g., on the user 90's head, torso, limbs, etc.). The ambient sensor 120a, in some embodiments, may be configured to obtain data characterizing the physiological state of the user 90. For example, the sensor 120a may be an electrode.

[0133] 9D , display 70 is operably coupled by a communication link 130, such as wired or wireless connectivity, to a local data processing module 140, which may be mounted in a variety of configurations, such as fixedly attached to frame 80, fixedly attached to a helmet or hat worn by the user, built into headphones, or otherwise removably attached to user 90 (e.g., in a backpack-style configuration, in a belt-linked configuration). Similarly, sensor 120a may be operably coupled to local processor and data module 140 by a communication link 120b, e.g., wired or wireless connectivity. Local processing and data module 140 may comprise a hardware processor and digital memory, such as non-volatile memory (e.g., flash memory or a hard disk drive), both of which may be utilized to aid in processing, caching, and storing data. Optionally, local processor and data module 140 may include one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, etc. The data may include a) data captured from sensors (e.g., which may be operatively coupled to frame 80 or otherwise attached to user 90), such as image capture devices (such as cameras), microphones, inertial measurement units, accelerometers, compasses, GPS units, wireless devices, gyroscopes, and / or other sensors disclosed herein, and / or b) data obtained and / or processed using remote processing module 150 and / or remote data repository 160 (including data related to virtual content), possibly for processing or retrieval and passage to display 70. Local processing and data module 140 may be operatively coupled to remote processing module 150 and remote data repository 160 by communication links 170, 180, such as via wired or wireless communication links, such that these remote modules 150, 160 are operatively coupled to each other and available as resources to local processing and data module 140.In some embodiments, local processing and data module 140 may include one or more of an image capture device, a microphone, an inertial measurement unit, an accelerometer, a compass, a GPS unit, a wireless device, and / or a gyroscope. In some other embodiments, one or more of these sensors may be mounted to frame 80 or may be a stand-alone structure that communicates with local processing and data module 140 by a wired or wireless communication path.

[0134] 9D , in some embodiments, remote processing module 150 may comprise one or more processors configured to analyze and process data and / or image information, including, for example, one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, etc. In some embodiments, remote data repository 160 may comprise a digital data storage facility that may be available through the Internet or other networking configuration in a “cloud” resource configuration. In some embodiments, remote data repository 160 may include one or more remote servers that provide information, for example, information for generating augmented reality content, to local processing and data module 140 and / or remote processing module 150. In some embodiments, all data is stored and all computations are performed within the local processing and data module, allowing for fully autonomous use from the remote module. Optionally, an external system (e.g., one or more processors, one or more computer systems), including a CPU, GPU, etc., may perform at least a portion of the processing (e.g., generating image information, processing data) and provide and receive information to and from modules 140, 150, 160, e.g., via a wireless or wired connection. (Exemplary Hybrid Waveguide Structure)

[0135] 10, an example of a hybrid waveguide with a core layer and an auxiliary layer is illustrated. The hybrid waveguide 1000 includes a relatively thick core layer 1010 having a relatively thin auxiliary layer 1020 disposed thereon, i.e., the core layer 1010 is thicker than the overlying auxiliary layer 1020. In some embodiments, the core layer 1010 may have a thickness of about 50 μm to about 1,000 μm, including about 100 μm to about 1,000 μm, about 300 μm to about 800 μm, about 300 μm to about 500 μm, and about 310 μm to about 450 μm. In some circumstances, the auxiliary layer may have a thickness of about 5 nm to about 5,000 nm (about 0.01 μm to about 5 μm), including about 50 nm to about 5,000 nm, about 10 nm to about 3,000 nm, about 20 nm to about 1,000 nm, about 30 nm to about 400 nm, and about 50 nm to about 300 nm. Preferably, the core layer is sufficiently thick to facilitate the propagation of light across the hybrid waveguide 1000 by total internal reflection, and the auxiliary layer is sufficiently thick to enable the formation of diffractive optical elements therein. For example, the auxiliary layer is preferably at least as thick as the tallest diffractive optical element to be formed therein. In some embodiments, the core layer 1010 directly contacts the auxiliary layer 1020.

[0136] The core layer 1010 and the auxiliary layer 1020 may be formed from different materials. Preferably, the material forming the core layer 1010 is highly transparent to wavelengths of light in the visible spectrum, e.g., 390-700 nm. For example, the core layer 1010 preferably transmits greater than 85%, greater than 90%, or greater than 96% of light in the visible light spectrum across its thickness. In some embodiments, the transparency requirements for the auxiliary layer 1020 per unit volume may be relaxed compared to that of the core layer 1010 due to the auxiliary layer 1020 being thinner than the core layer 1010. For example, the auxiliary layer 1020 may be formed from a material that provides lower transparency in the visible spectrum than the core layer 1010; i.e., for the same material thickness, the auxiliary layer 1020 may transmit less light than the core layer 1010. However, the material forming the auxiliary layer 1020 may have a different refractive index than the material forming the core layer 1010, especially if the material of the core layer 1010 extends into the depressions of the nanophotonic structure formed in the auxiliary layer 1020. In some embodiments, the material forming the auxiliary layer 1020 has a refractive index that differs from the refractive index of the material forming the core layer 1010 by about 0.05 or more, about 0.1 or more, or about 0.2 or more.

[0137] In some embodiments, the core layer 1010 may be formed from a highly transparent polymeric material, such as an organic polymeric material, and the auxiliary layer 1020 may be formed from a different polymeric material (e.g., a different organic or inorganic polymeric material) or a hybrid organic / inorganic material. In some embodiments, examples of high refractive index materials (e.g., having a refractive index higher than 1.65) that can be used in the core layer 1010 include polyimide-based high refractive index resins, halogen-containing (e.g., bromine- or iodine-containing) polymers, phosphorus-containing polymers, thiolene-based polymers, and high refractive index resin materials. Examples of high refractive index resin materials include those commercially available from NTT-AT (Kawasaki-shi, Kanagawa, Japan), such as the high refractive index resins sold under the designations #565 and #566, and those commercially available from Akron Polymer System (Akron, Ohio, USA), such as the high refractive index resins sold under the designations APS-1000, APS2004, APS-4001, and as part of the APS3000 series.

[0138] Examples of low-refractive-index materials (e.g., having a refractive index lower than 1.65), such as materials for the auxiliary layer 1020 in some embodiments, include organic polymer materials, low-refractive-index resins, sol-gel-based hybrid polymers (e.g., TiO, ZrO, and ITO sol-gel materials), polymers doped with nanoparticles (e.g., TiO, ZrO), and active materials (e.g., polymers doped with quantum dots). Examples of low-refractive-index organic polymer materials include those commercially available from Sigma-Aldrich (St. Louis, Missouri, USA), such as polymer materials sold under the names CPS 1040 UV, CPS 1040 UV-A, CPS 1030, CPS 1020 UV, CPS 1040 UV-VIS, CPS 1030 UV-VIS, and CPS 1020 UV-VIS. Examples of low-refractive-index resins include those commercially available from Miwon (Nagase Group, Osaka, Japan).

[0139] Continuing with reference to FIG. 10 , one or more nanophotonic structures 1022, 1024 may be provided within the help layer 1020. The nanophotonic structures 1022, 1024 comprise lines of material and intervening depressions or open volumes. As shown, the nanophotonic structures 1022, 1024 may include features that extend partially or completely through the help layer 1020. In some embodiments, the nanophotonic structures 1024 may extend into the underlying core layer 1010, thereby forming features with higher aspect ratios than would be possible using only the thickness of the help layer 1020. Referring now to FIG. 11 , an example of a hybrid waveguide with a core layer and multiple help layers is illustrated. The illustrated hybrid waveguide 1002 is similar to the hybrid waveguide 1000 of FIG. 10 , except that an additional help layer 1030 is provided on the opposite side of the core layer 1010 from the help layer 1020. As shown, both opposing major surfaces of the core layer 1010 may be in direct contact with one of the auxiliary layers 1020, 1030.

[0140] Additional auxiliary layer 1030 may be similar to auxiliary layer 1020, e.g., preferably formed from a different material than core layer 1010 and preferably having a higher refractive index than core layer 1010. In some embodiments, auxiliary layer 1030 may be formed from the same material as auxiliary layer 1020. In some other embodiments, auxiliary layers 1020 and 1030 may be formed from different materials.

[0141] One or more nanophotonic structures may be provided within the assist layer 1030. In the illustrated example, a single nanophotonic structure 1032 is shown. The nanophotonic structure 1032 may be similar to the nanophotonic structures 1022, 1024 and may take the form of a localized volume of material and intervening depressions or open volumes. The openings may extend partially through the assist layer 1030, as shown. In some other embodiments, the openings defining the nanophotonic structures 1032 may extend completely through the assist layer 1030, and optionally into the underlying core layer 1010. Advantageously, providing nanophotonic structures on opposing surfaces of the core layer 1010 can effectively increase the number of nanophotonic structures across a given area of ​​the core layer 1010, thereby increasing, for example, the amount of light that is outcoupled or incoupled into the waveguide 1004 across that area.

[0142] Referring now to FIG. 12 , an example of a hybrid waveguide with multiple core layers and auxiliary layers is illustrated. The illustrated hybrid waveguide 1004 is similar to the hybrid waveguide 1000 of FIG. 10 , except that an additional core layer 1040 is provided on the opposite side of the auxiliary layer 1020 from the core layer 1010. Each of the opposing major surfaces of the auxiliary layer 1020 may be in direct contact with a corresponding one of the core layers 1010, 1040. As discussed above with respect to FIG. 10 , the auxiliary layer 1020 may include one or more nanophotonic structures 1020, 1024. It should be understood that the additional core layer 1040 increases the overall thickness of the waveguide 1004 relative to the waveguide 1000, thereby promoting lateral propagation of light across the length of the waveguide. Additionally, light propagating laterally through waveguide 1004 may hit the nanophotonic structure twice (e.g., once after reflecting off a major surface of core layer 1040 and once after reflecting off a major surface of core layer 1010), which may increase the efficiency of the nanophotonic structure, for example, for outcoupling light from waveguide 1004.

[0143] As shown, nanophotonic structure 1022 may include multiple depressions in auxiliary layer 1020, which may be filled with the material of overlying additional core layer 1040. The refractive indices of auxiliary layer 1020 and additional core layer 1040 are preferably selected to be different to support the optical functionality of nanophotonic structure 1022. As discussed herein, the refractive indices of auxiliary layer 1020 and additional core layer 1040 differ in some embodiments by about 0.05 or more, about 0.1 or more, or about 0.2 or more. Additionally, in embodiments in which nanophotonic structure 1024 has depressions extending into core layer 1010 and filled with the material of additional core layer 1040, the material of additional core layer 1040 may also have a refractive index different from that of core layer 1010. For example, the refractive indices of the additional core layer 1040 and the core layer 1010 may differ by about 0.05 or more, about 0.1 or more, or about 0.2 or more in such embodiments.

[0144] 13, an example of a hybrid waveguide with multiple core layers and multiple auxiliary layers is illustrated. The illustrated hybrid waveguide 1004 is similar to the hybrid waveguide 1002 of FIG. 11, except that the auxiliary layer 1020 is overlaid by an additional core layer 1040, which is overlaid by a fourth auxiliary layer 1070, which is overlaid by a third core layer 1060, which is overlaid by a third auxiliary layer 1050.

[0145] Auxiliary layers 1030, 1020, 1050, and 1070 may each comprise one or more nanophotonic structures. For example, auxiliary layer 1050 may comprise nanophotonic structures 1052 and 1054, and auxiliary layer 1070 may comprise nanophotonic structure 1072. In some embodiments, the nanophotonic structures may be multilayer structures. For example, nanophotonic structure 1054 is a multilayer structure having a reference layer 1054a, an upper layer 1054b, and a lower layer 1054c. As shown, the material of a given core layer may extend into openings that define nanophotonic structures in the immediately adjacent auxiliary and / or core layers.

[0146] It should be understood that the size, shape, and / or periodicity of the features forming the various nanophotonic structures 1022, 1032, 1052, 1072, 1024, 1054 may vary. For example, the physical dimensions and patterns created by the features may be selected to achieve a desired light redirecting functionality for a given wavelength or color of light. In some embodiments in which hybrid waveguide 1006 includes multiple nanophotonic structures at different levels, the nanophotonic structures at each level may be selected to redirect different wavelengths of light, different angles of incidence, and / or output light toward different directions. Collectively, the different nanophotonic structures may provide a broader bandwidth of response over a wider range of wavelengths, angles of incidence, and / or output directions than a waveguide with a single or more limited number of nanophotonic structures.

[0147] FIG. 14 illustrates an example of a stack of hybrid waveguides. Hybrid waveguide 1000a is stacked over hybrid waveguide 1000b, which is stacked over hybrid waveguide 1000c. Hybrid waveguides 1000a, 1000b, and 1000c may each correspond to one of hybrid waveguides 1000, 1002, 1004, and 1006 (FIGS. 10-13, respectively). In some embodiments, the various hybrid waveguides 1000a, 1000b, and 1000c may be similar to one another or may have different structures. For example, as shown, hybrid waveguides 1000a, 1000b, and 1000c may each be similar to hybrid waveguide 1006 (FIG. 13).

[0148] In some embodiments, the nanophotonic structures in the auxiliary layers of the various hybrid waveguides 1000 a, 1000 b, 1000 c may be different. For example, the nanophotonic structures in each of the hybrid waveguides 1000 a, 1000 b, 1000 c may be configured to redirect light of one color (corresponding to one wavelength or range of wavelengths), while the nanophotonic structures of others of the hybrid waveguides 1000 a, 1000 b, 1000 c may be configured to redirect light of another, different color. In some embodiments, the hybrid waveguides 1000 a, 1000 b, 1000 c may be configured to redirect light with wavelengths corresponding to red, blue, and green, respectively.

[0149] To facilitate stacking and alignment of hybrid waveguides, spacers may be provided between the waveguides. Optionally, at each interface between hybrid waveguides, a spacer may be provided as part of one hybrid waveguide, and a matching opening into which the spacer can fit may be provided in the other hybrid waveguide at that interface. For example, with continued reference to FIG. 14 , hybrid waveguide 1000c may include multiple spacers 1074c, and directly overlapping and interfacing hybrid waveguide 1000b may include multiple openings 1034b into which spacers 1074c can be accommodated on a one-to-one basis. In some embodiments, the spacers and openings may be formed in auxiliary layers. For example, spacers 1074c may be formed in auxiliary layer 1071c, and openings 1034b may be formed in auxiliary layer 1031b. Similarly, spacers 1074b may be formed in auxiliary layer 1071b, and openings 1034a may be formed in auxiliary layer 1031a. In some embodiments, the spacer is sufficiently tall to separate the two hybrid waveguides and form a gap (e.g., an air gap) between each of the hybrid waveguides 1000 a, 1000 b, 1000 c. It should be appreciated that the gap provides a low refractive index that may facilitate light redirection by the nanophotonic structure and propagation through each hybrid waveguide.

[0150] 10-14 , the various materials for the core and auxiliary layers 1010, 1040, 1060, and 1030, 1020, 1050, 1070 are generally as described above with respect to the core layer 1010 and auxiliary layer 1020, respectively, although it should be understood that the specific materials may be the same or different. For example, in some embodiments, the material forming the outer auxiliary layers 1030, 1070 may be selected for hardness and mechanical stability, while these properties may be relaxed with respect to the auxiliary layers 1020, 1050, such that those layers 1020, 1050 may be formed from a less hard and / or mechanically stable material. Each of the illustrated layers may be in direct contact with the immediately adjacent layer. To support the ability of our nanophotonic structure to steer redirected light, the material forming the assist layer preferably has a refractive index that differs from the refractive index of the material forming the immediately adjacent core layer (e.g., a core layer where material from the core layer extends directly into an opening in the nanophotonic structure). Preferably, the refractive indices differ by about 0.05 or more, about 0.1 or more, or about 0.2 or more.

[0151] Any of hybrid waveguides 1000, 1002, 1004, 1006, or combinations thereof, may be utilized as one of the waveguides of waveguide stack 260 (FIG. 6) or 660 (FIGS. 9A-9C), for example, as one of waveguides 270, 280, 290, 300, or 310 (FIG. 6), or 670, 680, or 690 (FIGS. 9A-9C). Additionally, in some embodiments, some of the nanophotonic structures 1022, 1032, 1052, 1072, 1024, 1054 may correspond to the in-coupling optical elements 700, 710, 720 (FIGS. 9A-9C), and other of the nanophotonic structures 1022, 1032, 1052, 1072, 1024, 1054 may correspond to the optically dispersive elements 730, 740, 750 and / or the external coupling optical elements 800, 810, 820 (FIGS. 9A-9C). For example, the nanophotonic structures 1024, 1054 may correspond to the in-coupling optical elements 700, 710, 720, and the nanophotonic structures 1022, 1032, 1052, 1072 may correspond to the optically dispersive elements 730, 740, 750 and / or the external coupling optical elements 800, 810, 820. Exemplary Methods of Fabricating Hybrid Waveguides

[0152] In some embodiments, the core and help layers may be formed using a flowable material without vapor deposition. Additionally, patterns (e.g., patterns defining nanophotonic structures) may be formed during the formation of the core and / or help layers without separate patterning and etching processes. For example, nanophotonic structures may be formed by imprinting, followed by hardening or curing of the imprinted material.

[0153] 15a-15e illustrate a method of forming a hybrid waveguide with a core layer and an assist layer. Referring to FIG. 15a, a pair of molds 1200, 1202 are provided. Mold 1202 includes a pattern of raised features 1232 that may be the negative of the desired nanophotonic structure pattern to be defined in the assist layer to be formed. A mass of material 1230 for forming the assist layer is deposited on mold 1202.

[0154] 15b, molds 1200, 1202 are brought together to compress material 1230, thereby forming help layer 1030. The compressed material 1230 may undergo a curing process (e.g., exposure to ultraviolet light) to harden the material and form solid help layer 1030. As shown, negative pattern 1232 defines nanophotonic structure 1032. It should be understood that additional negative patterns can be provided on mold 1202 to form additional nanophotonic structures as desired.

[0155] Referring to Figure 15c, the molds 1200, 1202 are moved away from each other, and a mass of material 1210 for forming the core layer is deposited onto the assist layer 1030. Referring to Figure 15d, the molds 1200, 1202 are moved closer together to compress the mass of material 1210, thereby forming the core layer 1010. The compressed material 1210 may undergo a curing process (e.g., exposure to ultraviolet light) to harden the material and form the solid core layer 1030. Referring to Figure 15e, the molds 1200, 1202 are moved away from each other, and the core layer 1010 and assist layer 1030 are released from the molds, thereby forming the hybrid waveguide 1000.

[0156] Figures 16a-16d illustrate another method of forming a hybrid waveguide with a core layer and an auxiliary layer. Unlike the method of Figures 15a-15e, the materials forming the core layer and the auxiliary layer are cured together, rather than separately.

[0157] Referring to FIG. 16a, a pair of molds 1200, 1202 are provided, with mold 1202 including a pattern of raised features 1232 for forming a nanophotonic structure pattern in the assist layer to be formed. A mass of material 1230 for forming the assist layer is then deposited on mold 1202. Referring to FIG. 16b, a mass of material 1210 for forming the core layer is deposited on the mass of material 1230 for forming the assist layer. Preferably, the materials forming masses 1230, 1210 are immiscible to prevent intermixing of the materials. Referring to FIG. 16c, molds 1200, 1202 are moved closer together to simultaneously compress the masses of material 1210, 1230, thereby simultaneously forming core layer 1010 and assist layer 1030. The compressed materials 1210, 1230 may undergo a curing process (e.g., by exposure to ultraviolet light) that hardens the materials and forms, respectively, the solid core layer 1010 and the solid auxiliary layer 1030. Referring to Figure 16d, the molds 1200, 1202 are removed and the core layer 1010 and auxiliary layer 1030 are released from the mold to form the hybrid waveguide 1000.

[0158] FIGS. 17a-17g illustrate a method of forming a hybrid waveguide with a core layer and multiple help layers. FIGS. 17a-17d proceed as described above with respect to FIGS. 15a-15d. Referring to FIG. 17e, molds 1200, 1202 are moved apart from one another, and mold 1200 is replaced with another mold 1204. Mold 1204 includes a pattern of protrusions 1222 for defining nanophotonic structures in the additional help layer. An additional mass of material 1220 for forming the additional help layer is deposited on core layer 1010. Referring to FIG. 17f, molds 1204, 1202 are moved closer together to compress the mass of material 1220 and form help layer 1220. It should be understood that the pattern of features 1222 imprints the desired nanophotonic structure 1022 in help layer 1020. The compressed material 1220 may undergo a curing process to harden the material and form the auxiliary layer 1020. Referring to Figure 17g, the molds 1204, 1202 are moved apart and the hybrid waveguide, comprising the core layer 1010 and the auxiliary layers 1030, 1020, is released from the molds.

[0159] 18a-18d illustrate a method of forming a hybrid waveguide with a patterned core layer and assist layer. It should be understood that in some embodiments, the mold in contact with the core layer comprises a patterned surface 1222′ for defining nanophotonic structures within the core layer. The method illustrated in FIGS. 18a-18d proceeds in an identical manner to that described above with respect to FIGS. 16a-16d, except that mold 1200 is replaced with mold 1204′ having a pattern of protrusions 1222′ for patterning features within the core layer. As a result, when molds 1202, 1204′ are brought together to compress the mass of materials 1230, 1210, mold 1204 imprints nanophotonic structures 1022′ within core layer 1010′. The mass of materials 1230, 1210 is hardened to form core layer 1010′ and assist layer 1030. The molds 1202, 1204' are then moved apart and the hybrid waveguide is released. The hybrid waveguide comprises the assist layer 1030 and the core layer 1010' having the nanophotonic structures 1022'.

[0160] In some other embodiments, the mass of material 1230 for forming assist layer 1030 may be compressed using a flat mold, such as mold 1200 (not shown), and cured before depositing the mass of material 1210 onto assist layer 1030. The overlapping mold may then be replaced with mold 1204′ to print nanophotonic structures 1022′ into the mass of material 1210.

[0161] 19a-19d illustrate a method of forming a hybrid waveguide with integrated spacers. The method illustrated in FIGS. 19a-19d is similar to that discussed herein with respect to FIGS. 17a-17d, except that mold 1202′ replaces mold 1202 and includes vertically protruding features for defining an open volume 1034 within the assist layer 1031 to be formed. It should be understood that the open volume is sized, shaped, and positioned to accommodate vertically extending spacers from another waveguide. Referring to FIG. 19e, molds 1200, 1202′ are separated, and mold 1200 is replaced with another mold 1206, which may include a pattern of openings 1274 for defining spacers within the overlapping assist layer. An additional mass of material 1220 for forming the overlapping assist layer is deposited onto core layer 1210. Referring to Figure 17f, the molds 1206, 1202 are moved closer together to compress the mass of material 1220 and form auxiliary layer 1021. The resulting structure is then cured to harden auxiliary layer 1021. Referring to Figure 19g, the molds 1206, 1202 are moved apart and the hybrid waveguide comprising core layer 1210 and auxiliary layers 1071, 1031 is released from the mold, thereby forming a hybrid waveguide having spacers 1074 and openings 1034 for receiving spacers from other waveguides.

[0162] 15a-19g, it should be understood that deposition materials deposited on materials forming other auxiliary or core layers preferably have sufficient wettability to allow the deposited material to maintain contact and possibly diffuse through underlying layers of material. Additionally, it should be understood that additional layers of material can be formed on the illustrated layers of material by depositing a mass of material, compressing the material, and curing the material. Additionally, nanophotonic structures may be formed in these additional layers using an appropriate modality to imprint the nanophotonic structures into the layers prior to curing them.

[0163] In the foregoing specification, the invention has been described with reference to specific embodiments thereof. It will, however, be apparent that various modifications and changes can be made therein without departing from the broader spirit and scope of the invention. The specification and drawings are, therefore, to be regarded in an illustrative rather than a restrictive sense.

[0164] Indeed, it should be understood that the systems and methods of the present disclosure each have several innovative aspects, no single one of which is solely responsible for or required for the desirable attributes disclosed herein. The various features and processes described above may be used independently of one another or may be combined in various ways. All possible combinations and subcombinations are intended to fall within the scope of the present disclosure.

[0165] Certain features described herein in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, while features may be described above as operative in a combination and may even be initially claimed as such, one or more features from the claimed combination may, in some cases, be deleted from the combination, and the claimed combination may be directed to a subcombination or variation of the subcombination. No single feature or group of features is required or essential to every embodiment.

[0166] In particular, conditional statements used herein, such as "can," "could," "might," "may," "eg," and the like, should be understood to generally convey that certain embodiments include certain features, elements, and / or steps, while other embodiments do not, unless specifically stated otherwise or understood otherwise within the context as used. Thus, such conditional statements generally are not intended to imply that features, elements, and / or steps are in any way required for one or more embodiments, or that one or more embodiments necessarily include logic for determining whether those features, elements, and / or steps are to be included or performed in any particular embodiment, with or without authorial input or prompting. The terms "comprising," "including," "having," and the like, are synonymous and used inclusively in a non-limiting manner and do not exclude additional elements, features, acts, operations, etc. Also, the term "or," for example, when used to connect a list of elements, is used in its inclusive sense (and not its exclusive sense), so as to mean one, some, or all of the elements in the list. Additionally, the articles "a," "an," and "the," as used in this application and the appended claims, shall be interpreted to mean "one or more" or "at least one," unless otherwise specified. Similarly, while operations may be depicted in the figures in a particular order, it should be recognized that such operations need not be performed in the particular order shown, or in sequential order, or that all of the illustrated operations need not be performed, to achieve desirable results. Furthermore, the figures may diagrammatically depict one or more exemplary processes in the form of a flowchart. However, other operations not depicted may also be incorporated within the diagrammatically illustrated exemplary methods and processes. For example, one or more additional operations may be performed before, after, concurrently with, or during any of the illustrated operations.Additionally, operations may be rearranged or reordered in other embodiments. In some situations, multitasking and parallel processing may be advantageous. Furthermore, the separation of various system components in the above-described embodiments should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems may generally be integrated together in a single software product or packaged into multiple software products. Additionally, other implementations are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results.

[0167] Thus, the claims are not intended to be limited to the embodiments shown herein but are to be accorded the widest scope consistent with the present disclosure, the principles and novel features disclosed herein. The present specification also provides, for example, the following items: (Item 1) An optical device, the optical device comprising: a waveguide, the waveguide comprising: an optically transmissive core layer having a major surface opposite the other major surface; an optically transmissive sublayer on the major surface, the sublayer having a nanophotonic structure; and Equipped with An optical device, wherein the auxiliary layer is thinner than the core layer and is formed from a material different from the material forming the core layer. (Item 2) Item 1, wherein the nanophotonic structure comprises an optical lattice. (Item 3) Item 2. The optical device of item 1, wherein the core layer and the auxiliary layer are each formed from a polymer or resin. (Item 4) Item 1, wherein the material forming the auxiliary layer has a refractive index that differs from the refractive index of the material forming the core layer by about 0.05 or more. (Item 5) Item 2. The optical device according to item 1, wherein the core layer has a thickness of 100 to 5,000 μm, and the auxiliary layer has a thickness of 0.01 to 5 μm. (Item 6) Item 10. The optical device of item 1, further comprising an additional auxiliary layer thinner than the core layer and directly adjacent to the other major surface. (Item 7) Item 7. The optical device of item 6, wherein the additional auxiliary layer comprises an optical grating. (Item 8) Item 1, the waveguide further comprising an additional core layer disposed on the opposite side of the auxiliary layer from the core layer. (Item 9) Item 1, the optical device further comprising a plurality of core layers alternating with auxiliary layers thinner than the core layers, the auxiliary layers being formed from a different material than the core layers. (Item 10) Item 10. The optical device of item 9, wherein the core layers are formed from the same material. (Item 11) Item 11. The optical device of item 10, wherein the auxiliary layers are formed from the same material. (Item 12) Item 10. The optical device of item 9, wherein one or more of the auxiliary layers comprises a different optical grating than one or more other auxiliary layers. (Item 13) 1. An optical system, comprising: a set of stacked spaced apart waveguides, at least one of the waveguides having: an optically transmissive core layer having a major surface opposite the other major surface; an optically transmissive sublayer on the major surface, the sublayer having a nanophotonic structure; and Equipped with An optical system, wherein the auxiliary layer is thinner than the core layer and is formed from a material different from the material forming the core layer. (Item 14) Item 14. The optical system of item 13, wherein each waveguide is separated by an air gap. (Item 15) Item 14. The optical system of item 13, wherein each waveguide is spaced apart by one or more spacers disposed between the waveguides. (Item 16) Item 16. The optical system of item 15, wherein each of the waveguides comprises a core layer and an auxiliary layer, and the one or more spacers are integral with one of the core layer or auxiliary layer. (Item 17) Item 14. The optical system of item 13, wherein each of the waveguides comprises a core layer and an auxiliary layer, the core layer of each waveguide being formed from a material different from the core layers of the other waveguides in the set of stacked spaced-apart waveguides. (Item 18) the optical system is an augmented reality system; a spatial light modulator configured to provide modulated light containing image information to the waveguide; Each waveguide comprises a plurality of nanophotonic structures, the nanophotonic structures comprising: an internally coupled diffractive optical element configured to direct the modulated light into the waveguide; an outcoupling diffractive optical element configured to extract the incoupling modulated light from the waveguide; and Item 14. The optical system according to item 13, comprising: (Item 19) Item 19. The optical system of item 18, wherein the spatial light modulator is part of an optical projection system configured to project an image onto the internally coupled diffractive optical element. (Item 20) Item 19. The optical system of item 18, wherein the spatial light modulator modulates light for a scanning fiber display. (Item 21) Further comprising a plurality of sets of stacked spaced apart waveguides, each waveguide comprising: an optically transmissive core layer having a major surface opposite the other major surface; an optically transmissive sublayer on the major surface, the sublayer having a nanophotonic structure; and Equipped with Item 14. The optical system of item 13, wherein the auxiliary layer is thinner than the core layer and is formed from a material different from the material forming the core layer. (Item 22) 1. A method for making an optical device, the method comprising: forming a waveguide, the forming of the waveguide comprising: providing upper and lower imprint molds, said imprint molds facing each other; providing a first polymeric material between the imprint mold; providing a second polymeric material over the first polymeric material and between the imprint mold, the second polymeric material being in a liquid state; contacting the second polymeric material with the upper imprint mold; exposing the first polymeric material and the second polymeric material to a hardening process, wherein the first polymeric material forms a first layer and the second polymeric material forms a second layer; removing the upper imprint mold; and A method comprising: (Item 23) Item 23. The method of item 22, wherein the upper imprint mold comprises a pattern of protrusions and depressions, and wherein contacting the second polymer material with the upper imprint mold transfers the corresponding pattern of protrusions and depressions into the second polymer material. (Item 24) Item 23. The method of item 22, wherein the lower imprint mold comprises a pattern of protrusions and depressions and the first layer comprises a matching pattern of protrusions and depressions. (Item 25) 23. The method of claim 22, wherein the first polymeric material is in a liquid state. (Item 26) Providing the first polymeric material includes: providing the first polymeric material between the lower imprint mold and the additional imprint mold; compressing the first polymer material between the lower imprint mold and the additional imprint mold; hardening the first polymer material between the lower imprint mold and the additional imprint mold; Including, Providing upper and lower imprint molds includes: removing the additional imprint mold; disposing the upper imprint mold over the first polymer material; Item 23. The method according to Item 22, comprising: (Item 27) 23. The method of claim 22, wherein exposing the first and second polymeric materials to a hardening process comprises exposing the first and second polymeric materials to ultraviolet light. (Item 28) depositing a third polymeric material over the second layer of second polymeric material; contacting the third polymeric material with a third polymeric material mold; hardening the third polymeric material to form a third layer of the third polymeric material; removing the third polymeric material mold; and 23. The method of claim 22, further comprising: (Item 29) depositing a fourth polymeric material over the third layer; contacting the fourth polymeric material with a fourth polymeric material mold; hardening the fourth polymeric material to form a fourth layer formed from the fourth polymeric material; removing the fourth polymeric material mold; and 29. The method of claim 28, further comprising: (Item 30) depositing a fifth polymeric material over the fourth layer; contacting the fifth polymeric material with a fifth polymeric material mold; hardening the fifth polymeric material to form a fifth layer formed from the fifth polymeric material; removing the fifth polymeric material mold; and 30. The method of claim 29, further comprising: (Item 31) 31. The method of claim 30, wherein the first, third, and fifth polymeric materials are the same material. (Item 32) 32. The method of claim 31, wherein the second and fourth polymeric materials are the same material. (Item 33) Item 32. The method of item 31, wherein the first, third, and fifth layers comprise a pattern of protrusions and depressions that form a diffractive optical element. (Item 34) forming a waveguide comprising alternating layers of polymer material, every other layer comprising a pattern of protrusions and depressions; affixing the additional waveguide to the waveguide, the additional waveguide and the waveguide being separated by a gap; 23. The method of claim 22, further comprising:

Claims

1. An optical device, wherein the optical device is A waveguide is provided, and the waveguide is An optically transparent core layer having a first main surface on the opposite side of a second main surface, A first optically transparent auxiliary layer on the first main surface, wherein the first optically transparent auxiliary layer has a nanophotonic structure comprising a first optical lattice, the first optically transparent auxiliary layer is thinner than the optically transparent core layer, and is formed from a material different from the material forming the optically transparent core layer, A second optically transparent auxiliary layer, wherein the second optically transparent auxiliary layer is thinner than the optically transparent core layer and is directly adjacent to the second main surface, and the second optically transparent auxiliary layer comprises a second optical grating. An optical device equipped with the following features.

2. The optical device according to claim 1, wherein the material forming the optically transparent core layer, the first optically transparent auxiliary layer, and the second optically transparent auxiliary layer has a refractive index of at least 1.

65.

3. The optical device according to claim 1 or 2, wherein the material forming one or both of the first optically transparent auxiliary layer and the second optically transparent auxiliary layer has a refractive index that differs from the refractive index of the material forming the optically transparent core layer by 0.05 or more.

4. The optical device according to any one of claims 1 to 3, wherein the optically transparent core layer is one of a plurality of optically transparent core layers, the plurality of optically transparent core layers are alternated with auxiliary layers that are thinner than the optically transparent core layers, and the auxiliary layers are formed from a material different from the optically transparent core layers.

5. The optical device according to claim 4, wherein one or more of the auxiliary layers comprises an optical grating different from one or more other auxiliary layers.

6. The optical device according to any one of claims 1 to 5, comprising a set of stacked spaced waveguides, wherein the waveguide is one of the set of stacked spaced waveguides.

7. The optical device according to claim 6, wherein each waveguide is separated from another waveguide by an air gap, and the waveguides are preferably separated by one or more spacers placed between the waveguides.

8. The optical device according to claim 6 or 7, wherein each of the waveguides comprises a core layer and at least one auxiliary layer, the one or more spacers are integral with the core layer or one of the at least one auxiliary layer, and the core layer of each waveguide is formed of a different material from the core layer of the other waveguides in the set of spaced waveguides to be stacked.

9. The optical device is an augmented reality display system, The system further includes a spatial light modulator configured to provide modulated light containing image information to the waveguide, Each waveguide comprises multiple nanophotonic structures, and these nanophotonic structures are An internally coupled diffractive optical element configured to direct the modulated light into the waveguide, An externally coupled diffractive optical element configured to extract internally coupled modulated light from the waveguide, Equipped with, The optical device according to any one of claims 6 to 8, wherein the spatial light modulator is configured to provide an image to the internally coupled diffractive optical element.

10. The optical device according to any one of claims 6 to 9, wherein the set of stacked spaced waveguides comprises a plurality of sets of stacked spaced waveguides.

11. The optical device according to claim 1, wherein the first optically transparent auxiliary layer is formed from the same material as the second optically transparent auxiliary layer.

12. The optical device according to claim 1, wherein the first optically transparent auxiliary layer is formed from a material different from the second optically transparent auxiliary layer.

13. The optical device according to claim 1, wherein at least one feature of the first optical grating extends through the first optically transmitted auxiliary layer and extends within the optically transmitted core layer.

14. The optical device according to claim 1, wherein the first optical grating is at least partially aligned with the second optical grating.

15. The optical device according to claim 14, wherein both the first optical grating and the second optical grating are internally coupled optical gratings.

16. The optical device according to claim 14, wherein both the first optical grating and the second optical grating are externally coupled optical gratings.

Images