Image light guide with compound diffractive optical element and head-mounted display made therefrom

Abstract

An image light guide for conveying image-bearing light includes a substrate operable to propagate an image-bearing light beam along a length thereof. An in-coupling diffractive optic is formed along the substrate and is operable to diffract a portion of the image-bearing light beam from an image source into the substrate in an angularly encoded form. An out-coupling diffractive optic is formed along the substrate at least partially in a plane having an x-axis and a y-axis and is operable to diffract a portion of the image-bearing light beam from the substrate in an angularly decoded form. The out-coupling diffractive optic includes a first plurality of periodic structures and a second plurality of periodic structures operable to diffract the portion of the image-bearing light beam into a plurality of diffracted orders. The first and second pluralities of periodic structures include a plurality of vertices, wherein each adjacent vertex along the x-axis is offset in the y-axis direction.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 049,824, filed July 9, 2020, which is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure generally relates to electronic displays, and more specifically, to displays that utilize image light guides with diffractive optics to transmit image-carrying light to a viewer. Background Technology

[0004] Head-mounted displays (HMDs) and virtual image near-eye displays are being developed for a range of diverse applications, including military, commercial, industrial, firefighting, and entertainment. For many of these applications, it is valuable to create virtual images that can be visually superimposed on real-world images located within the HMD user's field of view. Optical image guides, which can transmit image-carrying light to the viewer in confined spaces, are used to guide the virtual image to the viewer's pupil and enable this superimposition function.

[0005] While conventional image lightguide arrangements have already offered significant reductions in size, weight, and overall cost for near-eye display optics, further improvements are still needed. In some cases, the size of the eyebox is constrained, forcing HMD designs to limit tolerances for movement and device placement. Light can often be unevenly distributed across the field of view, resulting in hotspots, such as higher light levels at the center of the field of view and lower light levels at the edges. Beam management functions within the waveguides—including beam spreading and light distribution capabilities—can increase the size of the waveguides, as well as their manufacturing cost and complexity. Summary of the Invention

[0006] In a first exemplary embodiment, the image light guide for transmitting image-carrying light includes a substrate (602, 702, 802, 902) operable to propagate an image-carrying beam along its length, the substrate including a first surface and a second surface parallel to the first surface. The image light guide for transmitting image-carrying light also includes ingress-coupled diffraction optics (604, 704, 804, 904) formed along the substrate, wherein the ingress-coupled diffraction optics are operable to diffract a portion of the image-carrying beam from the image source (16) into the substrate in an angle-coded manner. Furthermore, the image light guide for transmitting image-carrying light includes outgress-coupled diffraction optics (500, 706, 806, 906) formed along the substrate, wherein the outgress-coupled diffraction optics are at least partially located in a plane having x-axis and y-axis, and are operable to diffract a portion of the image-carrying beam from the substrate in an angle-coded manner. Additionally, the out-coupled diffractive optics includes a first plurality of periodic structures (412, 424, 414) and a second plurality of periodic structures (416, 426, 418), which are operable to diffract a portion of the image-carrying beam into a diffraction order. Furthermore, the first and second plurality of periodic structures include a plurality of vertices (352, 354, 452, 454, 2154), wherein each adjacent vertex along the x-axis is offset in the y-axis direction.

[0007] In a second exemplary embodiment, a method of manufacturing an image light guide for transmitting image-carrying light includes: providing a substrate (602, 702, 802, 902) having a flat surface, wherein a coating is coupled to the flat surface; providing a beam writing system operable to write in a first direction and a second direction, wherein the second direction is perpendicular to the first direction; and providing a diffraction grating layout pattern comprising a plurality of unit cells (310, 410A, 410B). Each unit cell includes a first plurality of linear diffraction features (412, 424, 414) and a second plurality of linear diffraction features (416, 426, 418), wherein one or more intersections of the first and second plurality of linear diffraction features define one or more corresponding vertices (352, 354, 452, 454, 2154), wherein adjacent vertices along the first direction include an offset along the second direction. The method of manufacturing an image light guide for transmitting image-carrying light further includes positioning the substrate in the beam writing system, whereby the beam writing system is operable to write the coating. The method also includes aligning one of the first and second plurality of linear diffraction features parallel to a first direction of the beam writing system, and writing a diffraction grating layout pattern into the coating via the beam writing system. Attached Figure Description

[0008] The accompanying drawings are incorporated herein by reference as part of the specification. The drawings described herein illustrate embodiments of the subject matter currently disclosed and explain selected principles and teachings of this disclosure. However, the drawings do not illustrate all possible implementations of the subject matter currently disclosed and are not intended to limit the scope of this disclosure in any way.

[0009] Figure 1 A simplified cross-sectional view of the image light guide is shown, illustrating the extension of the image-carrying beam along the propagation direction to expand one dimension of the eyebox.

[0010] Figure 2 A perspective view of an image light guide with a steering grating is shown, illustrating the extension of the image-carrying beam perpendicular to the propagation direction to expand the second dimension of the eyebox.

[0011] Figure 3 A schematic plan view of an image light guide having an out-coupled diffractive optics with an alternating grating vector pattern, according to an exemplary embodiment of the presently disclosed subject matter, is shown.

[0012] Figure 4 A schematic diagram of light behavior within an individual diffraction pattern according to an exemplary embodiment of the presently disclosed subject matter is shown.

[0013] Figure 5 A schematic diagram of a composite diffraction pattern according to an exemplary embodiment of the presently disclosed subject matter is shown.

[0014] Figure 6 A schematic plan view of a composite diffraction pattern according to an exemplary embodiment of the presently disclosed subject matter is shown.

[0015] Figure 7 An arrangement of diffraction pattern cells according to an exemplary embodiment of the presently disclosed subject matter is shown.

[0016] Figure 8A Another arrangement of a diffraction pattern cell according to an exemplary embodiment of the presently disclosed subject matter is shown.

[0017] Figure 8B A diffraction pattern cell is shown according to an exemplary embodiment of the subject matter disclosed herein.

[0018] Figure 9A A schematic plan view of a portion of a composite diffraction grating having three overlapping diffraction grating patterns according to an embodiment of the present disclosure is shown.

[0019] Figure 9B A vector diagram showing the summation raster vectors that form a closed triangle is shown.

[0020] Figure 10AA schematic plan view of an image light guide having a composite diffraction grating pattern, operable to extend and output a coupled image-carrying beam, is shown according to an exemplary embodiment of the presently disclosed subject matter.

[0021] Figure 10B A schematic plan view of an image light guide having a composite diffraction grating pattern, operable to extend and output a coupled image-carrying beam, is shown according to an exemplary embodiment of the presently disclosed subject matter.

[0022] Figure 10C It shows that according to Figure 8A The arrangement of diffraction pattern unit cells, wherein the unit cells rotate about the z-axis.

[0023] Figure 10D A schematic plan view of an image light guide having a composite diffraction grating pattern, operable to extend and output a coupled image-carrying beam, is shown according to an exemplary embodiment of the presently disclosed subject matter.

[0024] Figure 10E A vector diagram showing the summation raster vectors that form a closed triangle is shown.

[0025] Figure 11 A schematic plan view of an image light guide having a pupil expansion diffraction optics and an exit pupil diffraction optics, according to an exemplary embodiment of the presently disclosed subject matter, is shown.

[0026] Figure 12 A schematic plan view of an image light guide having a pupil expansion diffraction optics and an exit pupil diffraction optics, according to an exemplary embodiment of the presently disclosed subject matter, is shown.

[0027] Figure 13 An input center ray incident at an angle other than vertical onto the waveguide surface is shown as an exemplary embodiment of the presently disclosed subject matter.

[0028] Figure 14 It shows that according to Figure 13 The image shows a simplified cross-sectional view of the waveguide, illustrating the light rays propagating within it.

[0029] Figure 15 A simplified schematic diagram of a portion of a composite diffractive optical device according to an exemplary embodiment of the presently disclosed subject matter is shown.

[0030] Figure 16 A schematic diagram of a portion of a composite diffraction grating pattern according to an exemplary embodiment of the presently disclosed subject matter is shown, the composite diffraction grating pattern being operable to expand and output a coupled image-carrying beam.

[0031] Figure 17A portion of a composite diffraction grating pattern according to an exemplary embodiment of the presently disclosed subject matter is shown, the composite diffraction grating pattern being operable to expand and output coupled image-carrying beams.

[0032] Figure 18 This is a perspective view of a binocular display system for augmented reality viewing using at least one image light guide, according to an exemplary embodiment of the currently disclosed subject matter. Detailed Implementation

[0033] It should be understood that the invention may take various alternative orientations and sequences of steps unless explicitly indicated otherwise. It should also be understood that the specific components and systems illustrated in the drawings and described in the following specification are merely exemplary embodiments of the inventive concepts defined herein. Therefore, specific dimensions, orientations, or other physical features associated with the disclosed embodiments should not be considered limiting unless explicitly stated otherwise. Furthermore, although they may not be, in this part of this application, the same elements in the various embodiments described herein may generally refer to using the same reference numerals.

[0034] In the context of this document, the terms “first,” “second,” etc., do not necessarily indicate any order, sequence, or priority relationship, but are simply used to more clearly distinguish one element or set of elements from another, unless otherwise indicated.

[0035] In the context of this document, the terms “viewer,” “operator,” “observer,” and “user” are considered equivalent and refer to a person or machine that wears and / or uses a device with an imaging light guide to view an image.

[0036] In this context, the term "set" refers to a non-empty set, as the concept of the aggregation of elements or members of a set is widely understood in elementary mathematics. In this context, unless explicitly stated otherwise, the term "subset" refers to a non-empty proper subset, that is, a subset of a larger set having one or more members. For a set S, a subset can include the entire set S. However, a "proper subset" of set S is strictly contained within set S and excludes at least one member of set S.

[0037] In the context of this document, the terms “coupled,” “coupler,” or “coupled” refer to a connection in the optical device context that allows light to travel from one optical medium or device to another.

[0038] As used herein, the terms “vertices” and “multiple vertices” refer to features of interest that are repeated in a composite diffraction pattern. For example, a vertex may include a region where two or more lines intersect, a diffraction feature comprising a pillar, or a region where two or more unit cells intersect.

[0039] Optical systems such as HMDs can generate virtual image displays. In contrast to methods used to form real images, virtual images are not formed on the display surface. That is, if the display surface is located at the perceived location of the virtual image, no image will be formed on that surface. Virtual image displays offer many inherent advantages for augmented reality presentation. For example, the apparent size of a virtual image is not limited by the size or location of the display surface. Additionally, the source object of a virtual image can be very small; for example, a magnifying glass provides a virtual image of an object. Compared to systems that project real images, a more realistic viewing experience can be provided by forming virtual images that appear to be at a distance. Providing virtual images also eliminates the need for compensating for screen artifacts, which may be necessary when projecting real images.

[0040] Image light guides can display virtual images using image-carrying light from a light source such as a projector. For example, a collimated, angle-coded beam from the projector is coupled into a planar waveguide via an input coupler, such as an in-coupled diffractive optics device, which can be mounted or formed on the surface of the waveguide or embedded within it. Such diffractive optics can be formed as diffraction gratings, holographic optical elements (HOEs), or in other known forms. For example, a diffraction grating can be formed by surface irregularities. After propagating along the waveguide, the diffracted light can be guided back out of the waveguide via a similar output coupler, such as an out-coupled diffractive optics device, which can be arranged to provide pupil expansion along one dimension of the virtual image. Furthermore, a steering grating can be located on / in the waveguide to provide pupil expansion in orthogonal dimensions of the virtual image. The image-carrying light output from the waveguide provides the viewer with an expanded eyebox.

[0041] like Figure 1 As illustrated, the image light guide 10 may include a planar waveguide 22 having planar parallel surfaces. The waveguide 22 includes a transparent substrate S having an outer surface 12 and an inner surface 14 positioned opposite to the outer surface 12. In this example, an input-coupled diffractive optics IDO and an output-coupled diffractive optics ODO are arranged on the inner surface 14, and the input-coupled diffractive optics IDO is a reflective diffraction grating through which the image-carrying light WI is coupled into the planar waveguide 22. However, the input-coupled diffractive optics IDO may alternatively be a transmission diffraction grating, a volume hologram, or other holographic diffraction element, or other types of optical components that provide diffraction for the incoming image-carrying light WI. The input-coupled diffractive optics IDO may be located on either the outer surface 12 or the inner surface 14 of the planar waveguide 22, and may be a combination of transmission and reflection types, depending on the direction in which the image-carrying light WI approaches the planar waveguide 22.

[0042] When used as part of a virtual display system, the in-line diffraction optics (IDO) couples the image-carrying beam WI from a real, virtual, or hybrid image source to the substrate S of the planar waveguide 22. Any real image or image size is first converted into an array of overlapping angle-correlated beams, which encodes different locations within the virtual image for presentation to the IDO. The image-carrying beam WI is diffracted (generally through a first diffraction order) and thus redirected by the IDO into the planar waveguide 22 as the image-carrying beam WG, for further propagation along the planar waveguide 22 via total internal reflection (“TIR”). Although diffracted to a more concentrated range of angle-correlated beams according to the boundaries set by TIR, the image-carrying beam WG retains image information in an encoded form. The out-line diffraction optics (ODO) receive the encoded image-carrying beam WG and diffracts it as the image-carrying beam WO out of the planar waveguide 22 toward the intended position facing the viewer's eye. Generally, the output-coupled diffractive optics (ODO) are designed symmetrically with respect to the input-coupled diffractive optics (IDO) to restore the original angular relationship of the image-carrying beam WI within the output angle-dependent beam of the image-carrying beam WO. However, to add a dimension of overlap between the angle-dependent beams in the so-called eyebox E within which the virtual image can be viewed, the ODO is arranged to encounter the image-carrying beam WG multiple times, with each encounter diffracting only a portion of the image-carrying beam WG. These multiple encounters along the length of the ODO have the effect of amplifying each dimension of the angle-dependent beam of the image-carrying beam WO, thereby extending the dimension of the eyebox E where the beams overlap within it. The extended eyebox E reduces the sensitivity to the viewer's eye position when viewing the virtual image.

[0043] In this example, the out-coupled diffractive optics (ODO) is a transmission-type diffraction grating disposed on the inner surface 14 of the planar waveguide 22. However, like the in-coupled diffractive optics (IDO), the out-coupled diffractive optics (ODO) can be located on the outer surface 12 or the inner surface 14 of the planar waveguide 22, and can be a combination of transmission-type or reflection-type, depending on the direction in which the image-carrying light WG is intended to exit from the planar waveguide 22.

[0044] like Figure 2As illustrated, the image light guide 20 can be arranged to extend the eyebox 74 in two dimensions, namely, along both the x-axis and y-axis of the desired image. To achieve beam extension in the second dimension, the ingress-coupled diffraction optics IDO are oriented to diffract the image-carrying beam WG around a grating vector k0 toward an intermediate steering grating TG, whose grating vector k1 is oriented in reflection mode to diffract the image-carrying beam WG toward the egress-coupled diffraction optics ODO. Only a portion of the image-carrying beam WG is diffracted in each of the multiple encounters with the intermediate steering grating TG, thereby laterally extending the angularly correlated beam of the image-carrying beam WG approaching the egress-coupled diffraction optics ODO. The steering grating TG redirects the image-carrying beam WG to at least approximately aligned with the grating vector k2 of the egress-coupled diffraction optics ODO, for longitudinally extending the angularly correlated beam of the image-carrying beam WG in the second dimension before it exits as the image-carrying beam WO from the planar waveguide 22. The grating vectors, such as the depicted grating vectors k0, k1, k2, extend in a direction normal to the diffraction feature (e.g., groove, line, or scribe) of the diffraction optics, and have a magnitude opposite to the period or pitch d (i.e., the center distance between grooves) of the diffraction optics IDO, TG, ODO.

[0045] like Figure 2 As illustrated, the input-coupled diffractive optics (IDO) receive the input imaging beam WI, which contains an angle-dependent set of beams corresponding to individual pixels or equivalent locations within the image generated by image source 16. Image source 16—operable to generate a full-range angle-coded beam for producing a virtual image—can be, but is not limited to, a physical display with focusing optics, a beam scanner for more direct beam angle setting, or a combination of a one-dimensional physical display used with a scanner. Image light guide 20 outputs an extended set of angle-dependent beams in both dimensions of the image by providing multiple encounters between the imaging beam WG and the intermediate steering grating TG and the output-coupled diffractive optics (ODO) in different orientations. In the original orientation of planar waveguide 22, the intermediate grating TG provides beam extension in the y-axis direction, and the output-coupled diffractive optics (ODO) provides similar beam extension in the x-axis direction. The reflectivity characteristics of the diffractive optical devices IDO, ODO, and TG, along with their respective periods d and the orientation of their respective grating vectors, provide beam extension in two dimensions while preserving the expected relationship between the angle-dependent beams of the image-carrying light WI output from the image light guide 20 as the image-carrying light WO.

[0046] Although the image-carrying light WI input to the image light guide 20 is encoded into different angle-correlated beam sets by the ingress-coupled diffractive optics IDO, the information required for image reconstruction is preserved by taking into account the system effects of the ingress-coupled diffractive optics IDO. The steering grating TG, located in the intermediate position between the ingress-coupled and egress-coupled diffractive optics IDO and ODO, is typically arranged such that it does not cause any significant change in the encoding of the image-carrying light WG. The egress-coupled diffractive optics ODO are typically arranged symmetrically with respect to the ingress-coupled diffractive optics IDO, for example, including sharing diffraction features with the same period. Similarly, the period of the steering grating TG is typically matched to the common period of the ingress-coupled and egress-coupled diffractive optics IDO and ODO. Figure 2 As illustrated, the grating vector k1 of the steering grating TG can be oriented at a 45-degree angle relative to the other grating vectors k0 and k2 (both considered as undirected line segments). However, in one embodiment, the grating vector k1 of the steering grating TG is oriented at a 60-degree angle to the grating vectors k0 and k2 of the ingress and egress diffraction optics IDO and ODO, causing the image-carrying light WG to be oriented 120 degrees. By oriented the grating vector k1 of the intermediate steering grating TG at a 60-degree angle relative to the grating vectors k0 and k2 of the ingress and egress diffraction optics IDO and ODO, the grating vectors k0 and k2 are also oriented at a 60-degree angle relative to each other (again considered as undirected line segments). With the grating vector values ​​based on the common pitch of the steering grating TG and the ingress and egress diffraction optics IDO and ODO, the three grating vectors k0, k1, and k2 (as directed line segments) form an equilateral triangle, and their sum is zero. This avoids asymmetric effects that could introduce unwanted aberrations, including dispersion.

[0047] The image-carrying light WI, diffracted into the planar waveguide 22, is effectively encoded by the ingress-coupled diffractive optics IDO, regardless of whether the ingress-coupled diffractive optics IDO uses a grating, hologram, prism, mirror, or some other mechanism. Any reflection, refraction, and / or diffraction of light occurring at the ingress-coupled diffractive optics IDO must be correspondingly decoded by the egress-coupled diffractive optics ODO to reconstruct the virtual image presented to the viewer. The steering grating TG, placed at an intermediate position between the ingress-coupled and egress-coupled diffractive optics IDO and ODO, is typically designed and oriented so that it does not cause any alteration to the encoded light. The egress-coupled diffractive optics ODO decodes the image-carrying light WG into an angle-dependent beam of its original or desired form, which has been expanded to fill the eyebox 74.

[0048] Regardless of whether any symmetry is maintained between the steering grating TG and the ingress and egress diffractive optics IDO and ODO, or regardless of any changes in the encoding of the angle-dependent beam of the image-carrying light WI along the planar waveguide 22, the steering grating TG and the ingress and egress diffractive optics IDO and ODO are correlated such that the image-carrying light WO output from the planar waveguide 22 retains or otherwise maintains the original or desired form of the image-carrying light WI for generating the desired virtual image.

[0049] The letter "R" indicates the orientation of the virtual image visible to a viewer within eyebox 74. As shown, the orientation of the letter "R" in the represented virtual image matches the orientation of the letter "R" encoded by the imaging light WI. A change in the rotation or angular orientation of the incoming imaging light WI relative to the xy plane about the z-axis causes a corresponding symmetrical change in the rotation or angular orientation of the outgoing light from the outgoing coupled diffraction optics ODO. From the perspective of image orientation, the steering grating TG simply acts as an optical relay, providing an extension of the angle-coded beam of the imaging light WG along one axis of the image (e.g., along the y-axis). The outgoing coupled diffraction optics ODO further extends the angle-coded beam of the imaging light WG along another axis of the image (e.g., along the x-axis) while maintaining the original orientation of the virtual image encoded by the imaging light WI. Figure 2 As illustrated, the steering grating TG can be an inclined or square grating disposed on the front or rear surface of the planar waveguide 22. Alternatively, the steering grating TG can be a blazed grating.

[0050] This disclosure provides an improved image light guide that eliminates the need for a separate steering grating (TG) in the optical path. More specifically, this disclosure particularly provides a waveguide with a diffraction array operable to expand the image-carrying beam in two dimensions and direct the expanded image-carrying beam toward the eyebox for output.

[0051] like Figure 3As illustrated, the image light guide 100 may have an ingress-coupled diffractive optics (IDO) and an egress-coupled diffractive optics (ODO) formed on / in a first surface 102 of the image light guide 100. Alternatively, one or both of the ingress-coupled and egress-coupled diffractive optics IDO and ODO may be formed on / in a second surface of the image light guide 100 positioned opposite the first surface 102. The ingress-coupled diffractive optics IDO has a grating vector k1 extending in the x-axis direction. The egress-coupled diffractive optics ODO includes a diffraction array 104. Multiple component diffractive optical elements or optics 106 are present. In a row of the diffraction array 104, sequential diffractive optical elements 106 have alternating grating vectors k2 and k3. The arrangement of alternating grating vectors k2 and k3 in a portion of the diffraction array 104 is schematically shown in a magnified detail view. The grating vector k2 is offset from the ingress-coupled grating vector k1 and from the x-axis by +60 degrees (or, alternatively, from the y-axis by -30 degrees). The grating vector k3 is offset by -60 degrees from the input coupled grating vector k1 and the x-axis.

[0052] The diffraction array 104 can be considered structurally formed as a union of non-connected, non-overlapping subsets of diffraction elements or optical devices formed on a single surface. From a set theory perspective, this union of subsets forms a "partition". There exists a unique grating vector corresponding to each subset of the partition, and the subsets are distinguished from each other according to the direction of the grating vector. That is, all diffraction optical elements 106 in each subset share a common grating vector. In the spatial arrangement of the diffraction optical elements 106, the diffraction optical elements 106 of at least two subsets alternate with each other such that each diffraction optical element 106 from the subset having grating vector k2 is adjacent to one or more adjacent diffraction optical elements 106 from another subset having grating vector k3. More than two subsets of adjacent diffraction optical elements 106 can be used to form partitions of the diffraction array 104; each subset has a grating vector extending in a different direction from the corresponding grating vector of any other subset.

[0053] Now for reference Figure 4 When light WG incident from the incident-coupled diffractive optics IDO interacts with the diffraction array 104, a portion of the incident light WG is diffracted and guided at an angle to the rest of the diffraction array 104. For example... Figure 4As illustrated, in one embodiment, when the incident light WG interacts with the diffractive optical element 106 having a grating vector k2, a portion of the incident light WG is diffracted and thus deflected by 120° from the original path of the light from the ingress-coupled diffractive optical element IDO. Similarly, when the incident light WG interacts with the diffractive optical element 106 having a grating vector k3, a portion of the incident light WG is diffracted and thus deflected by -120° from the original path of the light from the ingress-coupled diffractive optical element IDO. Another portion of the incident light WG travels through the diffractive optical element 106 to an adjacent diffractive optical element 106 having a different grating vector. When the diffracted and deflected light WG is incident on the diffractive optical element 106 at an angle substantially parallel to its grating vectors k2 and k3, a portion of the light WO is coupled out of the image light guide 100.

[0054] like Figure 5 As illustrated, in one embodiment, the output-coupled diffractive optics (ODO) includes a first diffraction grating having a grating vector k2 and a second diffraction grating having a grating vector k3. The first and second diffraction gratings overlap to create an angular relationship between grating vectors k2 and k3 between 0° and 180°. In one embodiment, the angular relationship between grating vectors k2 and k3 is approximately 60°. When light diffracted and guided by the first diffraction grating is incident on the second diffraction grating at an angle substantially perpendicular to its features (e.g., lines), a portion of the light is coupled out of the image light.

[0055] Continue to refer to Figure 5 In one embodiment, the period d1 of the first diffraction grating is equal to the period d2 of the second diffraction grating. In another embodiment, the period d1 is greater than the period d2. In yet another embodiment, the period d1 is less than the period d2. In still another embodiment, at least one of the first and second diffraction patterns includes linearly frequency-modulated periods d1 and d2 that change in the directions of the grating vectors k2 and k3.

[0056] like Figure 6As illustrated, in one embodiment, the out-coupled diffraction optics (ODO) includes a composite diffraction pattern comprising a first diffraction grating 206A with a grating vector k1, a second diffraction grating 206B with a grating vector k2, and a third diffraction grating 206C with a grating vector k3. The first, second, and third diffraction gratings 206A, 206B, and 206C overlap in the same plane (i.e., on the same surface / in the image light guide). In one embodiment, the period d of each diffraction grating 206A, 206B, and 206C may be the same. In another embodiment, the period d of one or more diffraction gratings 206A, 206B, and 206C may be different. In one embodiment, the period d of one or more diffraction gratings 206A, 206B, and 206C is linearly frequency modulated. As shown, all three grating vectors k1, k2, and k3 are correlated by a 60° angle (when considered as undirected line segments). By basing the raster vector values ​​on a common pitch, three raster vectors k1, k2, and k3 (as directed line segments) can be organized in a vector diagram to form an equilateral triangle and sum to zero. In other arrangements, the raster vectors k1, k2, and k3 can be relatively oriented by different angular quantities.

[0057] Continue to refer to Figure 6 When a composite diffraction pattern is generated using subtractive manufacturing techniques, the remaining material forms diffraction features 208. For example... Figure 6 As illustrated, in one embodiment, the diffraction feature 208 is triangular. However, in other embodiments, the diffraction feature 208 may be a shape such as, but not limited to, a hexagon, which is determined by the distribution of the removed material.

[0058] In one embodiment, diffraction gratings 206A, 206B, and 206C are formed by an arrangement of replicated unit cells 210 located in a two-dimensional lattice. Figure 6 As illustrated, the entire composite diffraction pattern of the out-coupled diffraction optics (ODO) is formed by the replication and continuous arrangement of hexagonal unit cells 210. Adjacent unit cells 210 share vertices within a two-dimensional lattice. Although the grating vectors k1, k2, and k3 are oriented relative to each other at 60°, the unit cells 210 enable the shaping and orientation of diffraction features 208 within the composite diffraction pattern. For example, even if the diffraction feature 208 is shaped as a square, rectangle, circle, or ellipse, the relative orientation and periodicity of the grating vectors k1, k2, and k3 will remain unchanged. The diffraction feature 208 may be defined by material remaining after machining or other subtractive manufacturing processes, or by material removed by machining or other subtractive manufacturing processes. The diffraction feature 208 may be defined by optical properties (such as differences in refractive index) that distinguish the diffraction feature 208 from its surrounding environment.

[0059] like Figure 7As illustrated, in one embodiment, unit cell 310 defines a non-regular hexagon operable to form a composite diffraction pattern. Unit cell 310 includes a first pair of diffraction features 312, 314 having substantially the same length, a second pair of diffraction features 316, 318 having substantially the same length, and a third pair of diffraction features 320, 322 having substantially the same length. The lengths of the first, second, and third pairs of diffraction features are not the same. For example, diffraction features 312, 320, 316 have different lengths. The first, second, and third pairs of diffraction features 312, 320, 318, 314, 322, 316 define the non-regular hexagon of unit cell 310.

[0060] Unit cell 310 also includes a fourth diffraction feature 324, a fifth diffraction feature 326, and a sixth diffraction feature 328. The fourth, fifth, and sixth diffraction features 324, 326, and 328 intersect within the non-regular hexagon of unit cell 310. The first, second, and third pairs of diffraction features 312, 320, 318, 314, 322, and 316, as well as the fourth, fifth, and sixth diffraction features 324, 326, and 328, define six regions 330, 332, 334, 336, 338, and 340.

[0061] The widths of diffraction features 312, 324, and 314 are approximately the same and can be greater than 50 nm. In one embodiment, the widths of diffraction features 312, 324, and 314 are in the range between 200 nm and 600 nm. The widths of diffraction features 316, 326, and 318 are approximately the same and can be greater than 50 nm. In one embodiment, the widths of diffraction features 316, 326, and 318 are in the range between 200 nm and 600 nm. The widths of diffraction features 320, 328, and 322 are approximately the same and can be greater than 50 nm. In one embodiment, the widths of diffraction features 320, 328, and 322 are in the range between 200 nm and 600 nm. The widths of diffraction features 312, 324, and 314, diffraction features 316, 326, and 318, and diffraction features 320, 328, and 322 may not all be the same. Additionally, in one embodiment, the depths of diffraction features 312, 324, 314, 320, 328, 322, 316, 326, and 318 are the same or equal. In another embodiment, the depths of diffraction features 312, 324, 314, 320, 328, 322, 316, 326, and 318 are not the same or equal.

[0062] In one embodiment, the refractive indices of the six regions 330, 332, 334, 336, 338, and 340 are the same or approximately the same. For example, the refractive indices of the six regions 330, 332, 334, 336, 338, and 340 may be equal to or approximately equal to the refractive index of air. The refractive indices of the six regions 330, 332, 334, 336, 338, and 340 are not the same as the refractive indices of the diffraction features 312, 324, 314, 320, 328, 322, 316, 326, and 318. The refractive indices of the diffraction features 312, 324, 314, 320, 328, 322, 316, 326, and 318 may be the same as or approximately the same as each other. The refractive indices of diffraction features 312, 324, 314, 320, 328, 322, 316, 326, and 318 can be approximated to the refractive index of air. In one embodiment, the refractive indices of diffraction features 312, 324, 314, 320, 328, 322, 316, 326, and 318 are in the range of 1.25 to 3.5.

[0063] Continue to refer to Figure 7 In one embodiment, the unit cell 310 includes a y-axis direction (i.e., as shown in the figure). Figure 7 A vertical offset 350 is shown between vertices 352 and 354 in the vertical direction (as illustrated). In one embodiment, the vertical offset 350 has a distance between 10 nm and 100 nm. In another embodiment, the vertical offset 350 is approximately 65 nm. Vertex 352 is at least partially defined by the intersection of diffraction features 318, 320, and 324. Vertex 354 is at least partially defined by the intersection of diffraction features 314, 322, and 326. Figure 9A As illustrated, the vertical offset 350 is a step change from one unit cell 310 to the adjacent unit cell 310. In one embodiment, the vertical offset 350 defines the geometry of the six regions 330, 332, 334, 336, 338, and 340 as scalene triangles instead of equilateral triangles. The shape of the six regions 330, 332, 334, 336, 338, and 340 as scalene triangles allows diffraction of off-axis inputs arranged with central symmetry of the composite diffraction pattern.

[0064] The vertical offset 350 is substantially uniform within the composite diffraction pattern. As described in further detail below, in one embodiment, the uniformity of the vertical offset 350 facilitates the fabrication of the composite diffraction pattern via a digital writing process.

[0065] Still referencing Figure 7In one embodiment, diffraction features 316 and 326 have a pitch of 360, diffraction features 312 and 324 have a pitch of 362, and diffraction features 322 and 328 have a pitch of 364. In one embodiment, the pitches of the diffraction features 360, 362, and 364 are different from each other. The pitches of the diffraction features 360, 362, and 364 can be in the range of 300 nm to 500 nm. In one embodiment, the pitch 360 is approximately 356 nm, and the pitch 362 is in the range of 300 nm to 500 nm. In one embodiment, the pitch 362 is approximately 323 nm. In one embodiment, the pitch 364 is in the range of 300 nm to 500 nm. In another embodiment, the pitch 364 is approximately 305 nm.

[0066] like Figure 8A As illustrated in the figure, in one embodiment, unit cell 410A defines an offset diffraction pattern operable to form a composite diffraction pattern. In unit cell 410A, no diffraction features (e.g., those of the associated incident-coupled diffraction optics IDO) are fabricated. Figure 7 The diffraction features 320, 328, 322 shown are diffraction features parallel to those of unit cell 310. Unit cell 410A includes a first pair of diffraction features 412, 414 having substantially the same length and a second pair of diffraction features 416, 418 having substantially the same length. The lengths of the first and second pairs of diffraction features are not the same. The different lengths of the first and second pairs of diffraction features 412, 414, 416, 418 at least partially define an offset 450 in unit cell 310. In one embodiment, the vertical offset 450 is located between vertices 452 and 454 in the y-axis direction. Vertex 452 is defined by at least a partial intersection of diffraction features 424 and 418. Vertex 454 is defined by at least a partial intersection of diffraction features 426 and 414.

[0067] Unit cell 410A also includes diffraction features 424 and 426 that intersect each other. The first and second pairs of diffraction features 412, 414, 416, 418 and diffraction features 424, 426 define six regions 430, 432, 434, 436, 438, 440. In one embodiment, diffraction features 416, 426 have a pitch 460, and diffraction features 412, 424 have a pitch 462.

[0068] Diffraction features may also be referred to herein as periodic structures. In one embodiment, the periodic structure may be, but is not limited to, a linear diffraction feature, a circular cylinder, or an elliptical cylinder. For example, Figure 16A composite diffraction pattern 2000 with a periodic structure including circular pillars 2002 is shown. The periodic structure 2002 includes an arrangement of unit cells 410 in a periodic grid, thereby forming a two-dimensional periodic lattice structure. The unit cells 410 describe an offset 450, wherein each adjacent periodic structure 2002 along line 472 is offset in the y-axis direction.

[0069] In one embodiment, such as Figure 17 As illustrated, the regular variation defining the periodicity of the composite diffraction pattern is the pattern of the sinusoidal structure 2100. The composite diffraction pattern can have more than three vector components. Therefore, the diffraction orders generated by the composite diffraction pattern are optimized to promote desired performance. The periodicity of the composite diffraction pattern in the y-axis direction is created by the regular or average spacing between rows of continuous grating features 2100 in the y-axis direction. In one embodiment, the rows 2100 of the sinusoidal pattern can be out of phase with their adjacent rows in the y-axis direction. The periodic structure 2100 includes the arrangement of cells 410A and / or cells 410B in a periodic grid, thereby forming a two-dimensional periodic lattice structure. Cell 410B defines a parallelogram, and cell 410A defines an irregular hexagon. Cells 410A and 410B describe an offset 450, wherein each adjacent peak 2102 of the periodic structure 2100 along the x-axis direction is offset in the y-axis direction. In other words, cell 410A defines vertex 2154 at the intersection of two or more cells 410A, and each adjacent vertex along the x-axis includes an offset 450 in the y-axis direction.

[0070] like Figure 10B As illustrated, the vertical offset 450° represents a step change from one unit cell 410A to an adjacent unit cell 410A. Unit cells 410A create a lattice and / or a regular tiling (i.e., tessellation), where three unit cells 410A meet at each internal vertex (i.e., each vertex includes more than two linear diffraction features). Unit cells 410A form a lattice with diagonal rows, each diagonal row having a centerline 470 arranged at a non-zero angle to the grating vector k0 of the in-coupled diffraction optics 704.

[0071] In one embodiment, such as Figure 10C As illustrated, the widths and refractive indices of the first and second pairs of diffraction features 412, 414, 416, 418, and diffraction features 424, 426 are similar to those described in reference cell 310. Although the diffraction features do not respectively separate regions 430, 440 and 434, 436, cell 410A implicitly defines six distinct regions. The diffraction features designed for cell 410A and the composite diffraction pattern formed therefrom, without being parallel to the diffraction features of the associated incident-coupled diffraction optics IDO, are used to prevent undesirable diffraction of specific diffraction orders (i.e., diffraction orders) of the image-carrying light WG.

[0072] In one embodiment, such as Figure 8B As illustrated, unit cell 410B can be defined as a parallelogram. In this embodiment, unit cell 410B includes diffraction features 424 and 426. Vertex 452 is at least partially defined by one end of diffraction feature 424. Vertex 454 is at least partially defined by one end of diffraction feature 426.

[0073] Figure 9A A schematic plan view of a portion of a composite diffraction grating 500 according to the present disclosure is shown. The composite diffraction grating 500 includes repeating unit cells 310 (e.g., ...). Figure 7 As shown in the diagram, this forms three overlapping diffraction gratings. Grating vector k1 extends in the direction normal to diffraction features 316, 326, and 318, grating vector k2 extends in the direction normal to diffraction features 320, 328, and 322, and grating vector k3 extends in the direction normal to diffraction features 312, 324, and 314.

[0074] like Figure 9B As shown, in one embodiment, grating vector k1, grating vector k3, and incident coupling diffraction optical grating vector k0 (see...) Figure 10A The combination of grating vectors k0, k1, and k3 forms a vector diagram that defines a closed triangle and has a value that is essentially zero. In other words, the combination of grating vectors k0, k1, and k3 forms a vector that has essentially no value. Similarly, the combination of grating vectors k1, k2, and k3 forms a vector diagram that defines a closed triangle and has a value that is essentially zero. Therefore, the sum of all grating vectors in the waveguide (e.g., parallel plate waveguide systems 600, 700) is essentially zero. In one embodiment, grating vectors k0, k1, and k3 form a closed scalene triangle. In another embodiment, grating vectors k0, k1, and k3 form a closed equilateral triangle. In yet another embodiment, grating vectors k0, k1, and k3 form a closed isosceles triangle.

[0075] It should be understood that, due to the variability of manufacturing, the specified dimensions can vary depending on the manufacturing method. The figures may show sharp edges and sharp vertices, but in reality, as those skilled in the art know, the manufactured result will have rounded edges and rounded vertices. The sharpness or roundness of the sharp features described in this disclosure will depend at least in part on the manufacturing process. Similarly, where the figures show sharp edges and sharp vertices, the features may be designed to have rounded edges and / or rounded vertices.

[0076] Figure 10AA schematic diagram of a parallel-plate waveguide system 600 is shown, which includes a waveguide 602 (i.e., a substrate) having an input diffraction optics 604 and a pupil-expanding composite diffraction grating 500. The input diffraction optics 604 has a grating vector k0. The pupil-expanding composite diffraction grating 500, in addition to performing pupil expansion, also acts as an output diffraction grating. (See also: Regarding...) Figure 9B In one embodiment, raster vectors k0, k1, and k3 form a closed triangle. Similarly, raster vectors k0, k1, and k2 form a vector diagram of a closed triangle.

[0077] Figure 1 OB shows a schematic diagram of a parallel plate waveguide system 700, which includes a waveguide 702 (i.e., a substrate) having an input diffraction optics 704 and a pupil-expanding composite diffraction grating 706. The input diffraction optics 704 has a grating vector k0. The pupil-expanding composite diffraction grating 706 includes, as shown in the diagram... Figure 8A and 8B The repeating unit cell 410 is shown. The pupil-expanding composite diffraction grating 706 serves as both an exit diffraction grating and a pupil expander. Grating vector k1 extends in directions normal to diffraction features 416, 426, and 418, and grating vector k3 extends in directions normal to diffraction features 412, 424, and 414. In one embodiment, grating vectors k0, k1, and k3 are combined to form a vector diagram that defines closed triangles with essentially zero magnitudes.

[0078] like Figure 10C and 10D As illustrated, in one embodiment, the composite diffraction grating 706 can be rotated in the xy-plane of waveguide 702, such that the first plurality of periodic structures are oriented parallel to the x-axis and the edge of waveguide 702. A vector diagram formed by grating vectors k0, k1, and k3 defines an isosceles triangle. Figure 10D As illustrated, the input center ray WI is set at a complex angle relative to the grating vector k0 of the input-coupled diffractive optical device 704, and the vector diagram formed by the grating vectors k0, k1, k2 / k3 defines an isosceles triangle. Figure 10DIn this configuration, the input coupling diffraction grating vector k0 is tilted downwards in the xy-plane. If the input coupling diffraction grating vector k0 is tilted to the left in the xy-plane, the resulting central image path WI will not be aligned with the input coupling diffraction grating vector k0, thus necessitating an irregular hexagonal (or parallelogram) unit cell 410. If the optical system rotates or the input central ray WI forms a complex angle with respect to the input grating vector k0, then an unequal-sided triangle relationship should exist between the grating vectors k0, k1, and k2 / k3. In one embodiment, the input coupling diffraction grating vector k0 is parallel and aligned with the output coupling diffraction grating vector k1. In another embodiment, the input coupling diffraction grating vector k0 is parallel and aligned with the output coupling diffraction grating vector k3. In yet another embodiment, the input coupling diffraction grating vector k0 is parallel and aligned with the line bisects the output coupling diffraction grating vectors k1 and k3. Figure 13 As illustrated in the figure, when the input center ray 1006 is set at a complex angle relative to the grating vector k0 of the input coupling diffraction optics 1002, it is necessary to independently consider the grating vectors k0, k1, and k3 of the input and output coupling diffraction optics to form a closed unequal-sided triangle vector diagram.

[0079] like Figure 11 As illustrated in the figure, in one embodiment, the parallel plate waveguide system 800 includes a waveguide 802. The waveguide 802 includes an input coupling diffraction optics element 804, a pupil-expanding composite diffraction optics element 806, and an output coupling diffraction optics element 808. The input diffraction optics element 804 has a grating vector k0, and the pupil-expanding composite diffraction optics element 806 includes grating vectors k1, k2, and k3. In one embodiment, the pupil-expanding composite diffraction optics element 806 is defined by a unit cell 310. The output coupling diffraction optics element 808 has a grating vector k4. In one embodiment, the grating vector k0 is equal to the grating vector k4 in both magnitude and direction. In one embodiment, the grating vectors k0, k1, and k3 form a vector diagram describing a closed triangle, as shown in the reference. Figure 9B As stated above. Still refer to Figure 11 In one embodiment, raster vectors k4, k1, and k3 form a vector diagram of a closed triangle. In one embodiment, raster vectors k4, k1, and k3 form an equilateral triangle. In another embodiment, raster vectors k4, k1, and k3 form a scalene triangle. In yet another embodiment, raster vectors k4, k1, and k3 form an isosceles triangle.

[0080] like Figure 12As illustrated in the figure, in one embodiment, the parallel plate waveguide system 900 includes a waveguide 902. Waveguide 902 includes an input coupling diffraction optics 904, a pupil-expanding composite diffraction optics 906, and an output coupling diffraction optics 908. The input diffraction optics 904 has a grating vector k0, and the pupil-expanding composite diffraction optics 906 includes grating vectors k1 and k3. In one embodiment, the pupil-expanding composite diffraction optics 906 is defined by a unit cell 410. The output coupling diffraction optics 908 has a grating vector k4. In one embodiment, the grating vector k0 is equal to the grating vector k4 in both magnitude and direction. In one embodiment, the grating vectors k0, k1, and k3 form a vector diagram describing a closed triangle, as shown in the reference diagram. Figure 9B As stated above. Still refer to Figure 12 In one embodiment, raster vectors k4, k1, and k3 form a vector diagram of a closed triangle. In one embodiment, raster vectors k4, k1, and k3 form an equilateral triangle. In another embodiment, raster vectors k4, k1, and k3 form a scalene triangle. In yet another embodiment, raster vectors k4, k1, and k3 form an isosceles triangle.

[0081] Now for reference Figure 13 The waveguide assembly 1000 includes an ingress-coupled diffractive optics 1002 operable to couple an image-carrying beam into the waveguide 1004. The central ray 1006 of the image-carrying beam describing the input image can be incident on the ingress-coupled diffractive optics 1002 at an angle other than perpendicular to the first surface 1008 of the waveguide 1004. Figure 13 As illustrated in the figure, in one embodiment, the central ray 1006 forms an angle θ with respect to the z-axis. The z-axis is perpendicular to the first surface 1008 of the waveguide. As illustrated by line segment 1010 projected into the xy-plane, the central ray 1006 incident on the in-coupled diffraction optics 1002 forms an angle with the y-axis.

[0082] Figure 14 yes Figure 13 The image shows a side view of the waveguide assembly 1000. A central ray 1006 is shown incident on the in-line coupled diffractive optics 1002. The resulting diffracted ray 1012 propagates through waveguide 1004 to the second surface 1014 of waveguide 1004, where it undergoes total internal reflection (TIR) ​​to become ray 1016. Ray 1016 continues to propagate through waveguide 1004 via TIR. The grating vector k0 of the in-line coupled diffractive optics 1002 is designed (see...). Figure 13This causes the central ray 1006 to be diffracted, resulting in diffracted rays 1012 whose angle is approximately midway between the TIR minimum boundary line 101g and the TIR maximum boundary line 1020. The TIR minimum boundary line 1018 is defined by an angle ξ measured from the z-axis. Angle ξ is the minimum angle at which TIR begins. That is, any ray with an angle greater than angle ξ relative to the z-axis will undergo TIR when it is incident on the waveguide second surface 1014 and the first surface 1008. In one embodiment, angle α is approximately the same as angle β. The TIR maximum boundary line 1020 is the ray path with the maximum angle to the z-axis that will undergo TIR. In other words, only diffracted rays with an angle between the TIR minimum and maximum boundary lines 101g, 1020 will cause the ray to be incident on the composite diffractive optics 500, 706 at least once, possibly through multiple TIR reflections from the first and second surfaces 1008, 1014. The z-axis, the TIR minimum boundary line 101g, the TIR maximum boundary line 1020, and the diffracted ray 1012 are all shown in the same plane. For example... Figure 13-14 As illustrated, when the input center ray 1006 is set at a complex angle relative to the grating vector k0 of the input coupling diffraction optical device 1002, the vector diagram formed by the grating vectors k0, k1, k2 / k3 defines an isosceles triangle.

[0083] In one embodiment, the layout pattern of the diffractive optical elements can be directly formed or written onto and / or into the surface of the mold substrate using, but not limited to, electron beam lithography, ion beam lithography, laser lithography, and / or other digital beam writing methods. In digital beam writing production of the mold substrate, linear diffraction features not parallel to the x-axis and / or y-axis of the beam writer are produced as sawtooth or stepped patterns. As previously discussed... Figure 7 As described, cell 310 includes a vertical offset of 350, and cells 410A and 410B include a vertical offset of 450. The vertical offsets of 350 and 450 are step changes from one cell 310, 410A, 410B to adjacent cells 310, 410A, 410B.

[0084] For digital beam writing, the vertical offsets 350 and 450 need to be uniformly divided into multiples of the height h of the cells 310, 410A, and 410B by discrete values ​​to ensure that the irregular hexagonal cells 310, 410A, and 410B repeat to form a composite diffraction optical pattern. Figure 15 A simplified schematic diagram of a portion of a pupil-expanding composite diffraction grating 706, including repeating unit cells 410B, is shown. Figure 15In the diagram, unit cell 410B is a parallelogram, and the principle is illustrated as follows: vertical offsets 350° and 450° are selected to be multiples of the height of unit cells 310, 410A, and 410B, uniformly divided by discrete values, to create a composite diffraction optical pattern 706 using repeating unit cells 310, 410A, and 410B. For example, as... Figure 15 As illustrated, the cell height h can be four times (4x) the vertical offset of 450°. The cell is the smallest region within a repeating composite diffraction pattern. When cell 410B describes a parallelogram with a vertical offset, the composite diffraction pattern forms a grating vector describing a scalene triangle.

[0085] Digital writing to cells 310, 410A, and 410B allows for better reproducibility than conventional methods used to create diffraction elements. Additionally, digital beam writing facilitates the optimization of diffraction orders. Diffraction orders can be optimized by varying the duty cycle, shape, and depth of diffraction features that can be symmetrically produced via digital writing.

[0086] For example, the orientation mold substrate oriented diffraction features 320, 328, and 322 substantially parallel to the preferred writing direction of the beam writer (parallel to the x-axis or y-axis of the beam writer) oriented the angles of diffraction features 312, 324, and 314 and the angles of diffraction features 316, 326, and 318, such that any errors in the writing process are reflected in each unit cell 310. In other words, the grating vectors of units 310, 410A, and 410B are aligned parallel to the preferred writing direction of the beam writer (parallel to the x-axis or y-axis of the beam writer).

[0087] Figure 18 The perspective view illustrates a display system 60 for three-dimensional (3-D) augmented reality viewing using a pair of image light guides of this disclosure. The display system 60 is shown as an HMD having a left-eye optical system 64L and a corresponding right-eye optical system 64R, the left-eye optical system 64L having an image light guide 140L for the left eye and the corresponding right-eye optical system 64R having an image light guide 140R for the right eye. An image source 16, such as a microprojector or similar device, can be provided, which can be excited to generate a separate image for each eye, formed as a virtual image with the image orientation required for upright image display. The generated images can be a stereoscopic image pair for 3-D viewing. The virtual image formed by the optical system can appear to be superimposed or overlaid on the real-world scene content seen by the viewer through the image light guides. Additional components familiar to those skilled in the art of augmented reality visualization, such as one or more cameras mounted on the frame of the HMD for viewing scene content or for viewer eye tracking, can also be provided. Alternative arrangements are possible, including display devices for providing images to one eye (e.g., a monocular display).

[0088] One or more features of the embodiments described herein can be combined to create additional embodiments not depicted. While various embodiments have been described in detail above, it should be understood that they are presented by way of example and not as limitation. It will be apparent to those skilled in the art that the disclosed subject matter can be embodied in other particular forms, variations, and modifications without departing from the scope, spirit, or essential characteristics of the disclosed subject matter. Therefore, the above embodiments are to be considered illustrative in all respects and not as limiting. The scope of the invention is indicated by the appended claims, and all modifications within the meaning and scope of their equivalents are intended to be included therein.

Claims

1. An image light guide for transmitting image-carrying light, comprising: A substrate operable to propagate an image-carrying beam along its length; An ingress-coupled diffraction optics formed along the substrate, wherein the ingress-coupled diffraction optics is operable to diffract at least a portion of the image-carrying beam from the image source into the substrate in an angle-coded manner; An out-coupled diffraction optics formed along the substrate, wherein the out-coupled diffraction optics is at least partially located in an xy plane having an x-axis and a y-axis, and is operable to diffract a portion of the image beam from the substrate in an angularly decoded manner; The out-coupled diffractive optical device comprises a plurality of unit cells defining a first plurality of periodic structures and a second plurality of periodic structures, the first plurality of periodic structures and the second plurality of periodic structures being operable to diffract a portion of the image-carrying beam into diffraction orders, and The first plurality of periodic structures and the second plurality of periodic structures include a plurality of vertices, two or more unit cells intersect or overlap at the plurality of vertices, wherein each adjacent vertex along the x-axis is offset in the y-axis direction.

2. The image light guide for transmitting image-carrying light according to claim 1, wherein: The incident-coupled diffractive optical device defines a first grating vector; and The out-coupled diffraction optical device defines the second grating vector and the third grating vector.

3. The image light guide for transmitting image-carrying light according to claim 2, wherein the second grating vector is arranged at a first angle relative to the first grating vector, and the third grating vector is arranged at a second angle relative to the first grating vector.

4. The image light guide for transmitting image-carrying light according to claim 2, wherein the first grating vector, the second grating vector, and the third grating vector form an isosceles triangle.

5. The image light guide for transmitting image-carrying light according to claim 1, wherein the central ray of the image-carrying beam from the image source is positioned at a first angle relative to the xy plane and at a second angle relative to the ingress-coupled diffractive optics within the xy plane.

6. The image light guide for transmitting image-carrying light according to claim 1, wherein: The out-coupled diffractive optics are operable to diffract a portion of a first portion of each of the image-carrying beams in a first direction via the incident first plurality of periodic structures, thereby extending the first portion of each of the image-carrying beams in a first dimension, and The out-coupled diffractive optics are operable to diffract a portion of a second portion of each of the image-carrying beams in a second direction via incident on one or more of the second plurality of periodic structures, thereby extending the second portion of each of the image-carrying beams in a second dimension.

7. The image light guide for transmitting image-carrying light according to claim 6, wherein: The out-coupled diffraction optics are operable to diffract a portion of the first portion of each of the image-carrying beams extended in the first dimension out of the substrate via incident on the second plurality of periodic structures, and The out-coupled diffractive optics are operable to diffract a portion of the second portion of each of the image-carrying beams extended in the second dimension out of the substrate via incident on the first plurality of periodic structures.

8. The image light guide for transmitting image-carrying light according to claim 1, wherein the first plurality of periodic structures and the second plurality of periodic structures include overlapping parallel linear diffraction features.

9. The image light guide for transmitting image-carrying light according to claim 8, wherein the input-coupled diffractive optics comprises a plurality of parallel linear diffraction features. The first plurality of periodic structures are oriented at a first angle relative to the plurality of parallel linear diffraction features of the ingress-coupled diffraction optics, and The second plurality of periodic structures are oriented at a second angle relative to the plurality of parallel linear diffraction features of the ingress-coupled diffractive optical device. The first angle is greater than the second angle.

10. The image light guide for transmitting image-carrying light according to claim 1, wherein the input coupling diffraction optics and the output coupling diffraction optics are formed in a first surface of the substrate.

11. The image light guide for transmitting image-carrying light according to claim 1, wherein each of the unit cells defines an irregular hexagon.

12. The image light guide for transmitting image-carrying light according to claim 11, wherein the height of each cell is a multiple of the offset of the vertex.

13. The image light guide for transmitting image-carrying light according to claim 1, wherein the first plurality of periodic structures and the second plurality of periodic structures include portions of a line structure, or The out-coupled diffraction optical device is formed of a volume holographic material.

14. The image light guide for transmitting image-carrying light according to claim 1, wherein the first plurality of periodic structures and the second plurality of periodic structures define a triangular region.

15. The image light guide for transmitting image-carrying light according to claim 14, wherein the triangular domain comprises an isosceles triangle, thereby diffracting the image-carrying beam entering from the image source at an angle not directed toward the in-coupled diffractive optics.

16. The image light guide for transmitting image-carrying light according to claim 1, wherein the out-coupled diffractive optics defines a first grating vector, a second grating vector, and a third grating vector, and wherein the first grating vector, the second grating vector, and the third grating vector create an isosceles triangle vector diagram.

17. The image light guide for transmitting image-carrying light according to claim 16, wherein the third grating vector is defined by a third plurality of periodic structures.

18. A method for manufacturing an image light guide for transmitting image-carrying light, comprising: A substrate having a first surface is provided, wherein a coating is coupled to the first surface; A beam writing system operable to write in a first direction and a second direction, wherein the second direction is perpendicular to the first direction; Provides a diffraction grating pattern comprising multiple unit cells, each unit cell comprising: The first multiple linear diffraction features, and The second set of multiple linear diffraction features, The intersection points of the first plurality of linear diffraction features and the second plurality of linear diffraction features define one or more corresponding vertices. The adjacent vertices along the first direction include an offset along the second direction, wherein the height of each cell is a multiple of the offset of the vertex; The diffraction grating pattern is written into the coating via the beam writing system.

19. An image light guide for transmitting image-carrying light, comprising: A substrate operable to propagate an image-carrying beam along its length; An ingress-coupled diffraction optics formed along the substrate, wherein the ingress-coupled diffraction optics is operable to diffract a portion of the image-carrying beam from the image source into the substrate in an angle-coded manner; An out-coupled diffractive optics formed along the substrate, wherein the out-coupled diffractive optics is at least partially located in a plane having an x-axis and a y-axis, and is operable to diffract a portion of the image-carrying beam from the substrate in an angularly decoded manner; The out-coupled diffractive optics described herein includes a plurality of consecutive periodic structures defining a sinusoidal line operable to diffract a portion of the image-carrying beam into diffraction orders. The plurality of consecutive periodic structures comprise a plurality of peaks, wherein each adjacent peak along the x-axis is offset in the y-axis direction, and The first and second sinusoidal rows of the out-coupled diffraction optical device are out of phase.

Images