HK40098221A - Image light guide with zoned diffractive optic - Google Patents

Description

Image light guide with zoned diffraction optics

Technical Field

This disclosure relates generally to electronic displays, and more specifically to displays utilizing image light guides with diffractive optics.

Background Technology

Head-mounted displays (HMDs) and virtual imaging near-eye displays are being developed for a diverse range of applications, including military, commercial, industrial, firefighting, and entertainment. For many of these applications, the ability to create virtual images that can be visually overlaid on real-world images within the HMD user's field of vision is valuable. Optical image guides can transmit image-carrying light to the viewer in a narrow space to direct the virtual image to the viewer's pupil and enable the overlay function.

In a conventional image light guide, a collimated beam of light encoded with relative angles from an image source is input-coupled (e.g., by an in-line diffraction optics device) into a planar waveguide. This in-line diffraction optics device can be mounted or formed on the surface of the planar waveguide or embedded within it. After propagating along the waveguide, the diffracted light can be guided back out of the waveguide by an out-of-line diffraction optics device, which can be arranged to provide pupil dilation along one dimension of the virtual image. Additionally, steering optics can be positioned along the waveguide between the in-line and out-of-line diffraction optics devices to provide pupil dilation in orthogonal dimensions of the virtual image. The image-carrying light output from the waveguide provides an enlarged eyebox for the viewer.

It is understandable that there will be advantages for display devices with improved diffraction efficiency, image-carrying light output intensity, and uniformity across the entire output aperture.

Summary of the Invention

The purpose of this disclosure is to advance the field of virtual image rendering, particularly when using compact head-mounted devices and similar imaging apparatuses. According to one aspect of this disclosure, in a first exemplary embodiment, an image light guide for transmitting a virtual image is provided, comprising: a waveguide; an input diffractive optics operable to guide an image-carrying beam into the waveguide; and an output diffractive optics operable to guide the image-carrying beam from the waveguide eyebox. The output diffractive optics has a first region located adjacent to a second region, wherein the first region includes a first set of diffraction features, and the second region includes a second set of diffraction features. The output diffractive optics has a first interface region formed by the first region and the second region. The first interface region includes one or more first sub-regions and one or more second sub-regions, the first sub-regions having the first set of diffraction features, and the second sub-regions having the second set of diffraction features.

Attached Figure Description

The accompanying drawings are incorporated herein by reference as a part of the specification. The drawings described herein illustrate embodiments of the subject matter and illustrate the 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.

Figure 1 is a schematic diagram of a simplified cross-sectional view of an image light guide used to transmit a virtual image using a coupled-out diffractive optics device that provides pupil expansion along one dimension of the virtual image.

Figure 2 is a schematic perspective view of an image light guide used to transmit virtual images using a steering grating in addition to a coupled-out diffractive optics device, which provides pupil expansion along two dimensions of the virtual image.

Figures 3A, 3B, and 3C are respectively a side view, a top view, and a perspective view of an imaging device having an image light guide for forming a virtual image at a focal point at infinity.

Figures 4A, 4B, and 4C are respectively a top view, a side view, and an end view of an image light guide having partitioned diffractive optical devices coupled out, according to exemplary embodiments of the currently disclosed subject matter.

Figures 5A, 5B, and 5C are respectively the top view, side view, and end view of the image light guide with partitioned coupling out diffractive optical devices according to Figure 4A.

Figures 6A and 6B show raster vector diagrams according to exemplary embodiments of the subject matter currently disclosed.

Figures 7A, 7B, and 7C are respectively the top view, side view, and end view of the image light guide with partitioned coupling out diffractive optical devices according to Figure 4A.

Figures 8A, 8B, 8C, and 8D are schematic diagrams illustrating progressive diffraction feature depths according to exemplary embodiments of the currently disclosed subject matter.

Figure 9 is a top view of an image light guide with partitioned coupling out diffractive optical devices according to an exemplary embodiment of the subject matter currently disclosed.

Figure 10 is a top view of an image light guide with partitioned coupling out diffractive optical devices according to an exemplary embodiment of the subject matter currently disclosed.

Figures 11A, 11B, 11C, 11D, and 11E are schematic diagrams of diffraction features according to exemplary embodiments of the currently disclosed subject matter.

Figure 12 shows a schematic diagram of a rectangular unit cell operable to form a repeating pattern of diffraction features within a coupled diffractive optical device, according to an exemplary embodiment of the subject matter currently disclosed.

Figure 13 shows a schematic diagram of a portion of the coupled diffractive optical device, including a unit cell, according to Figure 12.

Figures 14A and 14B show schematic top and side views, respectively, of an image light guide with partitioned diffractive optical devices according to exemplary embodiments of the subject matter currently disclosed.

Figure 15 shows a schematic diagram of the portion of the coupled diffractive optical device according to Figure 14.

Figures 16A and 16B are top and side views, respectively, of an image light guide having partitioned diffractive optical devices coupled out, according to an exemplary embodiment of the subject matter disclosed herein.

Figure 17 shows a schematic diagram of the portion of the coupled diffractive optical device according to Figure 16A.

Figure 18 shows a schematic diagram of a portion of the interface of the three regions of a diffractive optical device coupled out according to an exemplary embodiment of the subject matter currently disclosed.

Figure 19 shows a schematic diagram of a portion of the interface of the three regions of a diffractive optical device coupled out according to an exemplary embodiment of the subject matter currently disclosed.

Figure 20 shows a schematic diagram of a portion of the interface of a region coupled out of a diffractive optical device according to an exemplary embodiment of the subject matter currently disclosed.

Figure 21 shows a schematic diagram of a portion of the interface of a region of a diffractive optical device coupled out according to an exemplary embodiment of the subject matter currently disclosed.

Figure 22 is a perspective view of a binocular display system for augmented reality viewing using at least one near-focus image light guide, according to an exemplary embodiment of the currently disclosed subject matter.

Detailed Implementation

It should be understood that various alternative orientations and sequences of steps may be assumed in this invention unless expressly specified to the contrary. It should also be understood that the specific components and systems illustrated in the drawings and described in the following description are merely exemplary embodiments of the inventive concept defined herein. Therefore, specific dimensions, orientations, or other physical characteristics associated with the disclosed embodiments should not be considered limiting unless otherwise expressly stated. Furthermore, similar elements in the various embodiments described herein may be publicly referred to using similar reference numerals within this section of the application, although this is not always the case.

In the context of this document, the terms “first,” “second,” etc., do not necessarily indicate any ordinal, sequential, or priority relationship, but are merely used to more clearly distinguish one element or set of elements from another, unless otherwise specified.

In the context of this document, the term “exemplary” is intended to indicate “an example of…” and is not intended to imply any preferred or ideal embodiment.

In the context of this document, the terms “viewer,” “operator,” “observer,” and “user” are considered equivalent and refer to a person who views a virtual image transmitted by one of the image guides under consideration, particularly as arranged in an HMD viewing device.

As used herein, the term "excitable" refers to a set of devices or components that perform the indicated function when power is received and optionally when an enable signal is received.

In this text, the term "set" refers to a non-empty set, due to the widespread understanding of the concept of a union of elements or members of a set in elementary mathematics. Unless otherwise explicitly stated, the term "subset" is used in this text to refer to a non-empty proper subset having one or more members, that is, a subset of a larger set. For a set S, a subset may include the entire set S. However, a "proper subset" of a set S is strictly contained within the set S and excludes at least one member of the set S.

In the context of this article, the phrases “optical infinity” and “at infinity” correspond to conventional usage in the field of cameras and imaging, indicating the formation of an image using one or more bundles of substantially collimated light, such that the focal length exceeds at least about 4 meters.

In the context of this document, the term “coupled” or “coupler” in the context of optical devices refers to a connection through which light travels from one optical medium or device to another via an intermediate structure that facilitates the connection.

In this document, the terms “beam expander” and “pupil expander” are considered synonyms and are used interchangeably. These terms are generally used herein to refer to the area of overlap between angle-dependent beams used to transmit virtual images.

As used herein, the term “beam augmentation” is intended to mean the replication of a beam by multiple encounters with an optical element to provide an expansion of the exit pupil in one or more directions. Similarly, as used herein, “augmenting” a beam or a portion of a beam is intended to mean the replication of a beam by multiple encounters with an optical element to provide an expansion of the exit pupil in one or more directions.

Optical systems (such as HMDs) can generate virtual images. Unlike methods used to form real-world images, virtual images are not formed on the display surface. That is, if the display surface is positioned at the perceived location of the virtual image, no image will be formed on that surface. Virtual images offer several 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 for a virtual image can be small; for example, a magnifying glass provides a virtual image of an object. Compared to systems that project real-world images, a more realistic viewing experience can be provided by forming a virtual image that appears at a distance. Providing virtual images also eliminates the need for compensating for screen artifacts, as might be necessary when projecting real-world images.

Image light guides can utilize image-carrying light from a light source (such as a projector) to display virtual images. For example, a collimated, relative angle-coded beam of light from a projector is coupled into a planar waveguide via input coupling (such as coupling into a diffractive optics device), which can be mounted or formed on the surface of the planar waveguide or embedded within it. Such diffractive optics can be formed as a diffraction grating, a holographic optical element (HOE), or otherwise known. For example, a diffraction grating can be formed by surface undulations. After propagation along the waveguide, the diffracted light can be guided back out of the waveguide via output coupling (such as coupling out a diffractive optics device), which can be arranged to provide pupil dilation in at least one direction. Additionally, a steering grating can be positioned on/in the waveguide to provide pupil dilation in at least one other direction. The image-carrying light output from the waveguide provides an enlarged eyebox for the viewer.

As illustrated in Figure 1, 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 the outer surface 12. In this example, an input diffraction optics IDO and an output diffraction optics ODO are arranged on the inner surface 14, and the input diffraction optics IDO is a reflective diffraction grating through which the image-carrying light WI is coupled into the planar waveguide 22. Alternatively, however, the input diffraction optics IDO may be a volume hologram or other holographic diffraction element, or other type of optical component providing diffraction for the incoming image-carrying light WI. The input diffraction optics IDO may be located on the outer surface 12 or the inner surface 14 of the planar waveguide 22, and may be transmissive or reflective depending on the direction in which the image-carrying light WI approaches the planar waveguide 22.

When used as part of a virtual display system, the coupled-in diffractive optics (IDO) couples the image-carrying light WI from a real-world image source to the substrate S of the planar waveguide 22. Any real-world image or image dimension is first converted into an array of overlapping angle-correlated beams, thereby encoding the different pixel positions within the image for presentation to the coupled-in diffractive optics (IDO). The image-carrying light WI is diffracted, and at least a portion of the image-carrying light WI is thus redirected by the coupled-in diffractive optics (IDO) into the planar waveguide 22 as the image-carrying light WG, for further propagation along the planar waveguide 22 via total internal reflection (“TIR”). Although diffracted into a generally more concentrated range of angle-correlated beams to align with the boundaries set by the TIR, the image-carrying light WG stores image information in an encoded form. The coupled-out diffractive optics (ODO) receive the encoded image-carrying light WG and diffracts at least a portion of the image-carrying light WG outward from the planar waveguide 22 toward the intended position of the viewer's eye, as the image-carrying light WO. Generally, the coupled-out diffractive optics (ODO) are designed symmetrically with respect to the coupled-in diffractive optics (IDO) to recover the original angular relationship between the image-carrying light WI and the angle-dependent beams output by the image-carrying light WO. However, to increase the overlap in one direction between the angle-dependent beams in the so-called eyebox E where the virtual image can be seen, the coupled-out diffractive optics (ODO) are arranged to encounter the image-carrying light WG multiple times and diffract only a portion of the image-carrying light WG at each encounter. Multiple encounters along the length of the coupled-out optics in the propagation direction have the effect of expanding one direction of the eyebox where the image-carrying beams overlap. The expanded eyebox E reduces the sensitivity of the viewer's eye to the position used to view the virtual image.

A coupler-out diffractive optics having a refractive index variation along a single direction can expand one direction of the eyebox in the waveguide propagation direction via multiple encounters between the image-carrying beam and the coupler-out diffractive optics, resulting in the replication of the coupled image-carrying beam. Additionally, a coupler-out diffractive optics having a refractive index variation along a second direction can expand the eyebox in a second direction, providing bidirectional expansion of the eyebox. The refractive index variation along the first direction of the coupler-out diffractive optics can be arranged to diffract a portion of the energy of each beam out of the waveguide at each encounter via desired first-order diffraction, while conserving another portion of the beam energy for further propagation in its original direction via zero-order diffraction. The refractive index variation along the second direction of the coupler-out diffractive optics can be arranged to diffract a portion of the energy of each beam at each encounter via desired first-order diffraction in a direction angular to the original propagation direction of the beam, while conserving another portion of the beam energy for further propagation in its original direction via zero-order diffraction.

The coupled-out diffractive optics (ODO) are shown as a transmission-type diffraction grating arranged on the inner surface 14 of the planar waveguide 22. However, similar to the coupled-in diffractive optics (IDO), the coupled-out diffractive optics (ODO) can be located on either the outer surface 12 or the inner surface 14 of the planar waveguide 22, and in combination can be either transmission-type or reflection-type, depending on the direction in which the image-carrying light WG is intended to exit the planar waveguide 22.

As illustrated in Figure 2, the image light guide 20 can be arranged to expand the eyebox 74 in two directions (i.e., along both the x-axis and y-axis of the desired image). To achieve the second dimension of beam expansion, the coupled-in diffractive optics IDO with grating vector k0 is oriented to diffract a portion of the image-carrying light WI towards the intermediate steering grating TG with grating vector k1. The intermediate steering grating TG is oriented to diffract a portion of the image-carrying light WG towards the coupled-out diffractive optics ODO in reflection mode. Each of the angularly correlated beams of the image-carrying light WG adjacent to the coupled-out diffractive optics ODO is laterally expanded by diffracting only a portion of the image-carrying light WG through multiple encounters with the intermediate steering grating TG. The steering grating TG redirects the image-carrying light WG towards the coupled-out diffractive optics ODO to longitudinally expand the angularly correlated beam of the image-carrying light WG in the second dimension before exiting the planar waveguide 22, as the image-carrying light WO. The grating vectors (such as the depicted grating vectors k0, k1, k2) extend in a direction normal to the diffraction features (e.g., grooves, lines, or scribes) of the diffraction optics IDO, TG, and ODO, and have a value that is the reciprocal of the period or pitch d (i.e., the center distance between the grooves) of the diffraction optics IDO, TG, and ODO. The coupled-in diffraction optics IDO, the directional grating TG, and the coupled-out diffraction optics ODO can all have different periods or pitches d.

As illustrated in Figure 2, the coupled-in diffractive optics (IDO) receive the incoming image-carrying light WI, which comprises a set of angle-dependent beams corresponding to individual pixels or equivalent positions within the image generated by the image source 16. The image source 16, operable to generate the full range of angle-coded beams used to produce the virtual image, can be, but is not limited to, a reality display with focusing optics, a beam scanner for more direct beam angle setting, or a combination such as a one-dimensional reality display used with a scanner. The image light guide 20 outputs an expanded set of angle-dependent beams in both dimensions of the image by providing multiple encounters between the image-carrying light WG and the intermediate steering grating TG and the coupled-out diffractive optics (ODO) at different orientations. In the original orientation of the planar waveguide 22, the intermediate grating TG provides beam expansion in the y-axis direction, and the coupled-out diffractive optics (ODO) provides similar beam expansion in the x-axis direction. The reflectivity characteristics and corresponding period d of the diffractive optical devices IDO, ODO, and TG, together with the orientation of their corresponding grating vectors, provide beam extension in two dimensions, while maintaining the expected relationship between the image-carrying light WI output from the image light guide 20 as the image-carrying light WO and the angle-dependent beam.

Although the image-carrying light WI input to the image light guide 20 is coupled into the diffractive optical element IDO and encoded into different sets of angle-dependent beams, the information required for image reconstruction is preserved by taking into account the system effects of the coupled-in diffractive optical element IDO. The steering grating TG, located in an intermediate position between the coupled-in and coupled-out diffractive optical elements IDO and ODO, is typically arranged such that it does not cause any significant changes in the encoding of the image-carrying light WG. The coupled-out diffractive optical element ODO is typically arranged symmetrically with respect to the coupled-in diffractive optical element IDO (e.g., including sharing diffraction features with the same period). Similarly, the period of the steering grating TG is also typically matched to the common period of the coupled-in and coupled-out diffractive optical elements IDO and ODO. As illustrated in Figure 2, the grating vector k1 of the steering grating TG can be oriented at 45 degrees with respect to the other grating vectors k0 and k2 (all as undirected line segments). However, in this embodiment, the grating vector k1 of the steering grating TG is oriented at 60 degrees relative to the grating vectors k0 and k2 of the coupled-in and coupled-out diffractive optical devices IDO and ODO, such that the image-carrying light WG is turned by 120 degrees. By oriented the grating vector k1 of the intermediate steering grating TG at 60 degrees relative to the grating vectors k0 and k2 of the coupled-in and coupled-out diffractive optical devices IDO and ODO, the grating vectors k0 and k2 are also oriented at 60 degrees relative to each other (again considered as undirected line segments). The grating vector values are based on the common pitch of the steering grating TG and the coupled-in and coupled-out diffractive optical devices IDO and ODO. These three grating vectors k0, k1, and k2 (as directed line segments) form an equilateral triangle with a sum of zero vector values. This avoids asymmetric effects that could introduce undesirable chromatic aberrations, including dispersion.

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

Regardless of whether any symmetry is maintained between the steering grating TG and the coupled-in and coupled-out diffractive optics IDO, ODO, or regardless of any change in the encoding of the angle-dependent beam of the image carrier light WI along the planar waveguide 22, the steering grating TG and the coupled-in and coupled-out diffractive optics IDO, ODO are correlated such that the image carrier light WO output from the planar waveguide 22 retains or otherwise maintains the original or desired form of the image carrier light WI used to generate the intended virtual image.

The letter “R” indicates the orientation of the virtual image visible to a viewer whose eyes are positioned 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 image-carrying light WI. A rotation of the incoming image-carrying light WI about the z-axis or a change in the angular orientation of the incoming image-carrying light WI about the x-y plane results in a corresponding symmetrical change in the rotation or angular orientation of the outgoing light from the coupled-out diffractive optics ODO. From the perspective of image orientation, the steering grating TG merely acts as a type of optical repeater, thereby providing an expansion of the angle-encoded beam of the image-carrying light WG along one axis of the image (e.g., along the y-axis). The coupled-out diffractive optics ODO further expands the angle-encoded beam of the image-carrying 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 image-carrying light WI. As illustrated in Figure 2, the steering grating TG can be an inclined or square grating arranged on the front or back surface of the planar waveguide 22. Alternatively, the steering grating TG can be a blazing grating.

In diffractive optics formed as diffraction gratings, increasing the grating depth leads to improved diffraction efficiency. However, the increased diffraction efficiency in the coupled-out diffraction grating can reduce the image-carrying light WO output from the outer regions of the grating, because too much image-carrying light WG is output from the center of the coupled-out diffraction optics, thus creating visual hotspots. Currently disclosed embodiments of image light guides utilize partitioned coupled-out diffraction optics to promote a more uniform distribution of the coupled-out image-carrying light WO with improved diffraction efficiency.

In an embodiment, as illustrated in Figures 3A, 3B, and 3C, the image light guide 100 is operable to transmit a virtual image to an expanded eyebox and present the virtual image at an optical infinity focal point. That is, each of the angle-dependent beams of image-carrying light within the eyebox remains substantially collimated. The image content, generated by the projector 110 and transmitted by the image light guide 100 through coupled-in and coupled-out diffractive optics IDO and ODO, appears to the viewer's eye as a virtual image V1, perfectly positioned at an infinity focal point in front of the image light guide 100. The apparent size of the virtual image within the viewer's field of vision is related to the range of angles through which the angle-dependent beams encode the image. The solid line departing from the coupled-out diffractive optics ODO represents one of the collimated beams of image-carrying light WO, and the dashed line represents the virtual extension of that collimated beam in front of the image light guide 100 corresponding to the pixels of the virtual image emanating from a source located at infinity.

As illustrated in Figures 4A-4C, in one embodiment, the image light guide 200 includes a waveguide 202 having front and back parallel surfaces 204, 206. An input diffractive optics device 210 and an output diffractive optics device 212 are located on the front surface 204 of the waveguide. In one embodiment, the input optics device 210 and the output diffractive optics device 212 are located on the back surface 206 of the waveguide. In another embodiment, the input optics device 210 is located on the front surface 204 of the waveguide, and the output diffractive optics device 212 is located on the back surface 206 of the waveguide.

In this embodiment, the intermediate diffractive optics are optically located between the coupled-in diffractive optics 210 and the coupled-out diffractive optics 212. The intermediate diffractive optics may be a steering grating, and/or the intermediate diffractive optics may enable increased design variance.

The coupled diffractive optics device 212 includes a composite diffraction grating pattern operable to expand and couple an image-carrying light WG as an image-carrying light WO. The composite diffraction grating pattern includes two or more overlapping diffraction patterns, each delimited by a grating vector k. In an embodiment, the composite diffraction grating pattern includes non-overlapping sinusoidal diffraction patterns having three or more vector k components. As illustrated in Figure 4A, in this embodiment, the coupled diffractive optical device 212 includes two or more regions 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, and 229 with diffraction characteristics, wherein the diffraction characteristics of each region 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, and 229 are different from the diffraction characteristics of neighboring regions 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, and 229. As illustrated in Figures 4A-6C, in this embodiment, the coupled diffractive optics 212 includes a first region 214 generally positioned centrally in the y-axis direction. A second region 216 is generally positioned above and adjacent to the first region 212 in the y-axis direction. A third region 218 is generally positioned above and adjacent to the second region 216. A fourth region 220 is generally positioned below and adjacent to the first region 212 in the y-axis direction. A fifth region 222 is generally positioned below and adjacent to the fourth region 220 in the y-axis direction. A sixth region 224 is generally centrally positioned in the y-axis direction and generally positioned to the right of the first region 214 in the x-axis direction. A seventh region 226 is generally positioned to the right of the sixth region 224 along the x-axis direction.

The coupling-out diffractive optics 212 defines the output aperture 230. A portion of the coupling-out diffractive optics 212 positioned outside the output aperture 230 sometimes redirects image-carrying light into the output aperture 230 and can be shaped like a wedge or triangle. The output aperture 230 is shown by a dotted line located outside the coupling-out diffractive optics 212; however, those skilled in the art will appreciate that, for clarity, the figures are presented in this manner, and the output aperture 230 does not extend outside the coupling-out diffractive optics 212.

Referring again to Figure 4A, for visualization purposes, an eyebox 232A (i.e., a head movement box) is shown above the first region 214 from which the diffractive optics 212 is coupled. The eyebox 232A corresponds to the incoming ray of image-carrying light at the center of the field of view (FOV) of the virtual image. The viewer's eye is positioned at a distance from the waveguide 202, which may be referred to as the eye-fit distance. In operation, the viewer's eye can move within the eyebox 232A and still see the pixels corresponding to the incoming ray.

The coupling-in diffraction optics 210 is operable to couple the incoming light of the image-carrying light WI at TIR conditions, thereby propagating the image-carrying light WG towards the coupling-out diffraction optics 212, in which the image-carrying light WO can be coupled out towards the eyebox 232A. As illustrated in Figures 4A-4C, in this embodiment, light corresponding to the center of the field of view (FOV) for the virtual image is coupled into the waveguide 202 via the coupling-in diffraction optics 210. The light is shown to be incident on the coupling-in diffraction optics 210 normally to the waveguide 202; however, the input center light can be incident on the coupling-in diffraction optics 210 at an angle other than perpendicular to the waveguide 202. In the embodiment illustrated in Figures 4A-4C, the first region 214 of the coupling-out diffraction optics 212 is operable to expand the image-carrying light WG in one or more dimensions (i.e., the x-axis and y-axis directions) and couple the image-carrying light WO out in the eyebox 232A.

Viewed from this field of view, the ideal coupling-out grating in this region below eyebox 232A would have a linear grating positioned parallel to the linear grating of the coupling-in grating, serving only one function—coupling the image-carrying light WG. However, to facilitate the expansion of the image-carrying light to create a larger eyebox, the coupling-out grating of the first region 214 includes generally rhomboid stakes, which implicitly define a grating vector k3 parallel to the grating vector k0 of the coupling-in diffractive optics 210. In other words, in the first region 214, the vertical linear grating features are almost completely degraded, making the only evidence of vertical linear grating features the points of the generally rhomboid stakes. The generally rhomboid stakes are row-to-row offset, but still create vertical lines. The diffraction of the image-carrying light WO in eyebox 232A is produced by the periodicity of the diffraction features.

As illustrated in Figures 5A-5C, when the image-carrying light WG corresponds to the portion of the virtual image pointing downwards and to the right of the center of the virtual image, the projection of the eyebox 232B is moved accordingly. If the image-carrying light WG is not redirected (i.e., turned) at the coupled diffractive optics 212, the coupled image-carrying light WO will completely miss the projection of the eyebox 232B. Here, different regions couple the image-carrying light WO from a single pixel or field of view into the same angular range, thereby forming a virtual image. In other words, the image-carrying light from a single virtual pixel is output to the same angle by adjacent regions. For example, as illustrated in Figure 5A, the image-carrying light WG corresponding to the virtual pixel of the eyebox 232B is coupled out at the same angle or angular range in both the first region 214 and the fourth region 220.

In an embodiment, the first region 214 includes a diffraction feature operable to diffract (i.e., deflect) the image-carrying light WG downwards at an angle relative to the direction of travel of the image-carrying light WG in the deflected region. The diffraction feature of the first region 214 is also operable to couple the deflected image-carrying light WG as the image-carrying light WO. As illustrated in Figures 6A and 6B, the diffraction feature of the first region 214 defines two grating vectors k1 and k2, which, combined with the grating vector k0 coupled into the diffractive optics 210, form a vector diagram describing a closed triangle and having substantially zero magnitude. In other words, the combination of grating vectors k0, k1, and k2 forms a vector that has substantially no magnitude. In one embodiment, the grating vectors k0, k1, and k2 form a closed isosceles triangle. In another embodiment, the grating vectors k0, k1, and k2 form a closed scalene triangle. In this way, there will be no scattering or angular errors in the virtual image caused by the diffraction feature of the first region 214. The first region 214 also implicitly defines a fourth grating vector k3 via the arrangement of its diffraction features, which is equivalent to the grating vector k0 coupled into the diffractive optics 210. In this embodiment, these grating vectors k0, k1, k2, and k3 are all necessary in the first diffraction region 214.

As illustrated in Figures 7A-7C, when the image-carrying light WG corresponds to a portion of the virtual image further downwards and to the right of the center of the virtual image, the projection of the eyebox 232C is moved accordingly. When the image-carrying light WG propagates through waveguide 202 to a region in the third region 218, but the light needs to exit from the portion of the coupled diffraction optics 212 in the fourth or fifth regions 220, 222, the third region 218 can be operated to redirect (i.e., deflect) the image-carrying light WG downwards towards the fifth region 222 in the y-axis direction. Any image-carrying light WG directly coupled from the third region 218 (i.e., as from a linear diffraction grating) will miss the viewer's eye. Only one grating vector is needed to redirect or couple the image-carrying light WG from the third and fifth regions 218, 222.

The propagation symmetry stipulates that sometimes, the image-carrying light WG will travel downwards towards the fifth region 222 in the y-axis direction, and needs to be redirected upwards towards the third region 218 in the y-axis direction to be coupled out as the image-carrying light WO. The grating features required to redirect the image-carrying light WG to the third region 218 are the same as those required to couple out the image-carrying light WG redirected from the third region 218. Therefore, only a single grating vector k5 is necessary in the fifth region 222.

The second and fourth regions 216, 220 can operate as transition or intermediate regions for coupling out diffractive optics 212, wherein the grating features in the second and fourth regions 216, 220 are designed as a combination or wrap-around of two adjacent regions. For example, the second region 216 describes a combination of the first and third regions 214, 218. The transition regions 216, 220 facilitate a smoother transition in waveguide 202 and produce a more desirable perspective experience for the image light guide 200; for example, more uniform illumination across the field of view (FOV) of the resulting virtual image. In an embodiment, coupling out diffractive optics 212 includes multiple transition regions in the x-axis and y-axis directions from the center of coupling out diffractive optics 212 to its edges.

As illustrated in Figures 8A-8C, in this embodiment, the depth of the diffraction features in two or more regions 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 229 coupled out of the diffraction optics 212 can vary independently of the region boundary 290 (see Figure 10) defined in the underlying configuration of the diffraction features. The underlying configuration of the diffraction features coupled out of the diffraction optics 212 determines the direction and relative magnitude of the diffraction order, while the depth modulation of the diffraction features serves to modulate the relative efficiency of all current diffraction orders. It is possible to apply a gradient depth independent of the underlying mode of the diffraction features coupled out of the diffraction optics 212.

In the embodiment, as the diffraction features approach the edge of the coupling diffraction optics in the y-axis direction, the depth of the diffraction features in regions 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, and 229 gradually increases. For example, as illustrated in FIG8D, diffraction feature 250 (see FIG9) can gradually vary in the y-axis direction from the center line 280 of the first region 214 to the outer edge of the first region 214 within a depth range of _n1 - _n3 ; diffraction feature 256 (see FIG9) can gradually vary in the y-axis direction from the edge of the first region 214 to the outer edge of the second region 216 within a depth range of _n4 - _n6 ; and diffraction feature 252 (see FIG9) can gradually vary in the y-axis direction from the edge of the second region 216 to the outer edge of the third region 218 within a depth range of _n7 - _n9 . This gradual increase in depth of the diffraction feature is mirrored across the centerline 280 of the first region 214. Figure 8A shows a schematic diagram of a linear grating feature that increases in depth along the y-axis symmetrically across a center plane 282 parallel to the xz plane. Figure 8B shows a schematic diagram of a linear grating feature that increases in depth symmetrically across a center plane 282 parallel to the xz plane in a stepped configuration along the y-axis.

In another embodiment, the depth of the diffraction features in regions 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, and 229 gradually increases as the diffraction features approach the edge of the diffraction optics in the x-axis direction. Figure 8C shows a schematic diagram of a linear grating feature that increases in depth along the x-axis symmetrically across a central plane 284 parallel to the y-z plane. In this embodiment, the depth of the diffraction features in regions 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, and 229 gradually increases as the diffraction features approach the edge of the diffraction optics in both the x-axis and y-axis directions.

As illustrated in Figure 9, in one embodiment, the first region 214 from which the diffractive optics 212 is coupled includes diffraction features 250 describing a composite diffraction pattern. The diffraction features 250 illustrated in Figure 9 are generally rhomboid posts. A schematic diagram of the diffraction features 250 is shown in Figure 11A. In another embodiment, the diffraction features 250 are one or more sinusoidal or wavy features. The diffraction features 252 and 254 of the third and fifth regions 218 and 222 respectively describe linear gratings. Diffraction features 254 and 252 are symmetrical about the center line 280 of the first region 214. Diffraction features 252 and 254 are also positioned at an angle φ relative to the center line 280. A schematic diagram of the diffraction features 252 is shown in Figure 11C, and a schematic diagram of the diffraction features 254 is shown in Figure 11E.

Diffraction feature 256 in region 216 describes a combination of diffraction features 250 and 252. In other words, in an embodiment, diffraction feature 256 is a parallelogram feature. A schematic diagram of diffraction feature 256 is shown in Figure 11B. Similarly, diffraction feature 258 in region 220 describes a combination of diffraction features 250 and 254, such that a rhomboid feature approximates a linear grating. In other words, in an embodiment, diffraction feature 258 is a parallelogram feature. A schematic diagram of diffraction feature 258 is shown in Figure 11D. Diffraction feature 260 in region 224 describes a generally triangular feature approximating a generally linear grating generally positioned parallel to the y-axis. Diffraction feature 262 in region 226 describes a generally vertical linear grating generally positioned parallel to the y-axis.

Figure 12 shows a schematic diagram of rectangular unit cells 300A, 300B, 300C, 300D, and 300E. In an embodiment, the first region 214, the fourth region 220A, 220B, 220C, and the fifth region 222, from which the diffractive optical device 212 is coupled, are formed by an arrangement of unit cells 300A, 300B, 300C, 300D, and 300E located in a two-dimensional lattice. In an embodiment, each unit cell 300A, 300B, 300C, 300D, and 300E includes the minimum repeating diffraction feature within the region. However, the unit cells 300A, 300B, 300C, 300D, and 300E can be of any size, such that the unit cells are repeatable within the region to form their periodic diffraction features. The diffraction features within each region include the arrangement of the unit cells in a periodic grid, thereby forming a two-dimensional periodic lattice structure. The periodic grid is identical for each of the regions 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, and 229 within the coupled diffractive optical device 212. As shown in Figure 13, the portion of the composite diffraction pattern coupled to the diffractive optical device 212 comprises replicates and adjacent arrangements of unit cells 300A, 300B, 300C, 300D, and 300E. Those skilled in the art will recognize that more unit cells 300A, 300B, 300C, 300D, and 300E may exist in the x-axis and/or y-axis directions of each of the first region 214, the fourth regions 220A, 220B, 220C, and the fifth region 222.

In the embodiments, multiple regions exist in the y-axis and/or x-axis directions, transitioning from the center to the edge of the coupled diffractive optical device 212. However, in reality, only a limited number of nanostructures are permitted in the y-axis and/or x-axis directions of the coupled diffractive optical device 212. Therefore, in the embodiments, the number of transition regions in the y-axis and/or x-axis directions from the center to the edge of the coupled diffractive optical device 212 is at least partially a function of the minimum achievable structure and size of the coupled diffractive optical device 212.

In another embodiment, regions 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, and 229 of the coupled diffractive optical device 212 are delineated by gap regions. As illustrated in FIG10, region boundaries 290 are indicated by dotted lines defining regions 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, and 229. Region boundaries 290 can define gap regions between regions 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, and 229.

As illustrated in Figure 10, in this embodiment, the diffraction feature 250 of the first region 214 may include only a single row. In this embodiment, the second region 216 includes sub-regions 216A and 216B, wherein the diffraction feature 256 in region 216B is closer to a linear grating than the diffraction feature 256 in region 216A. The fourth region 220 includes sub-regions 220A and 220B, wherein the diffraction feature 258 in region 220B is closer to a linear grating than the diffraction feature 258 in region 220A.

As illustrated in Figures 14A and 14B, in this embodiment, the image light guide 300 includes a waveguide 302 having front and back parallel surfaces 304 and 306. An input diffraction optics device 310 and an output diffraction optics device 312 are located on the front surface 304 of the waveguide. The output diffraction optics device 312 includes a composite diffraction grating pattern operable to expand and couple out image-carrying light WG as image-carrying light WO. The coupled diffractive optical device 312 includes ten regions 314, 316, 318, 320, 322, 324, 326, 328, 330, and 332 with diffraction characteristics, wherein the diffraction characteristics of each region 314, 316, 318, 320, 322, 324, 326, 328, 330, and 332 are different from the diffraction characteristics in the neighboring regions 314, 316, 318, 320, 322, 324, 326, 328, 330, and 332.

The first region 314 of the coupled diffractive optical element is generally centrally located in the y-axis direction. The second region 316 is generally located above and adjacent to the first region 314 in the y-axis direction. The third region 318 is generally located above and adjacent to the second region 316. The fourth region 320 is generally located above and adjacent to the third region 318. The second region 316 and the third region 318 comprise diffractive optical elements operable as transition regions between the diffraction features of the first region 314 and the fourth region 320. In other words, the second and third regions 316, 318 comprise diffraction features that are a combination or wrap around the first region 314 and the fourth region 310. As illustrated in Figure 15, the second region 316 is more closely similar to the first region 314, and the third region 318 is more closely similar to the fourth region 320.

Fifth region 322 is generally located below and adjacent to first region 314 in the y-axis direction. Sixth region 324 is generally located below and adjacent to fifth region 322 in the y-axis direction. Seventh region 326 is generally located below and adjacent to sixth region 324 in the y-axis direction. Fifth and sixth regions 322, 324 include diffractive optical elements operable as transition regions between the diffraction features of first region 314 and seventh region 326. In other words, fifth and sixth regions 322, 324 include diffraction features as a combination or wrap around first region 314 and seventh region 326. The diffraction features of fifth, sixth, and seventh regions 322, 324, 326 are symmetrical with the diffraction features of second, third, and fourth regions 316, 318, 320 across the centerline of first region 314. However, the shape of the coupled diffractive optical element 312 is not necessarily symmetrical across the centerline of first region 314.

Region 328 is generally centrally located in the y-axis direction and generally located to the right of Region 314 in the x-axis direction. Region 330 is generally centrally located in the y-axis direction and generally located to the right of Region 328 in the x-axis direction. Region 332 is also generally centrally located in the y-axis direction between Region 318 and Region 324, and generally located to the right of Region 330, Region 316, and Region 322 in the x-axis direction. Regions 328 and 330 include diffraction features operable as transition regions between the diffraction features of Region 314 and Region 332. In other words, regions 328 and 330 include diffraction features that are a combination or wrap around Region 314 and Region 332.

Furthermore, the first zone 314, the eighth zone 326, and the ninth zone 330 have generally the same width in the y-axis direction. The combined first zone 314, second zone 316, and fifth zone 322 have a generally the same width in the y-axis direction as the tenth zone 332. In the embodiment, the fourth zone 320, the third zone 318, the sixth zone 324, and the seventh zone 326 have unequal lengths in the y-axis direction.

As illustrated in Figures 16A-16B, in one embodiment, the image light guide 400 includes a waveguide 402 having front and back parallel surfaces 404, 406. An input diffractive optics 410 and an output diffractive optics 412 are located on the front surface 404 of the waveguide. In one embodiment, the input optics 410 and the output diffractive optics 412 are located on the back surface 406 of the waveguide. In another embodiment, the input optics 410 are located on the front surface 404 of the waveguide, and the output diffractive optics 412 are located on the back surface 406 of the waveguide.

In this embodiment, the intermediate diffractive optics are optically located between the coupled-in diffractive optics 410 and the coupled-out diffractive optics 412. The intermediate diffractive optics may be a steering grating, and/or the intermediate diffractive optics may enable increased design variance.

The coupled-out diffraction optics 412 includes a composite diffraction grating pattern operable to expand the image-carrying light WG in two dimensions and couple the image-carrying light WG as the image-carrying light WO. The composite diffraction grating pattern includes two or more overlapping diffraction patterns, each describing a grating vector k. In an embodiment, the composite diffraction grating pattern includes non-overlapping sinusoidal diffraction patterns describing three or more vector k components. As illustrated in Figures 16A and 17, in an embodiment, the coupled-out diffraction optics 412 includes multiple regions 414, 416, 418, 420, 422, 424 of diffraction features, wherein the diffraction features of each region 414, 416, 418, 420, 422, 424 are different from the diffraction features in neighboring regions 414, 416, 418, 420, 422, 424. As illustrated in Figure 16A, in an embodiment, the coupled-out diffraction optics 412 includes a first region 414 generally centrally located in the y-axis direction. The second zone 416 is generally positioned above and adjacent to the first zone 414 along the y-axis. The third zone 418 is generally positioned above and adjacent to the second zone 416. The fourth zone 420 is generally positioned below and adjacent to the first zone 414 along the y-axis. The fifth zone 422 is generally positioned below and adjacent to the fourth zone 420 along the y-axis. The sixth zone 424 is generally positioned in the center along the y-axis and generally positioned to the right of the first zone 414 along the x-axis.

The coupling-in diffraction optics 410 is operable to couple the incoming light of the image-carrying light WI at TIR conditions, thereby propagating the image-carrying light WG toward the coupling-out diffraction optics 412, in which the image-carrying light WO can be coupled out toward the eyebox. In an embodiment, light corresponding to the center of the field of view (FOV) for the virtual image is coupled into the waveguide 402 via the coupling-in diffraction optics 410. The light is shown to be incident on the coupling-in diffraction optics 410 normally to the waveguide 402; however, the input center light can be incident on the coupling-in diffraction optics 410 at an angle other than perpendicular to the waveguide 402. In the embodiment illustrated in Figures 16A-16B, the first region 414 of the coupling-out diffraction optics 412 is operable to expand the image-carrying light WG in one or more dimensions (i.e., the x-axis and y-axis) and couple the image-carrying light WO out in the eyebox.

To facilitate the expansion of the image-carrying light to create a larger eyebox, the coupling-out grating of the first region 414 includes general rhombus-shaped posts 414A, which define grating vectors k1 and k2 and implicitly define a grating vector k3 parallel to the grating vector k0 coupled into the diffractive optics 410. In other words, in the first region 414, the vertical linear grating features are almost completely degraded, such that the only evidence of vertical linear grating features is the point of the general rhombus-shaped post 414A. The general rhombus-shaped posts 414A are row-to-row offset, but still form vertical lines. In the second region 416, the general rhombus-shaped posts 416A are reduced in size relative to the posts 414A in the first region 414. The general rhombus-shaped posts 416A in the second region 416 are connected by linear diffraction features 416B at an angle relative to the grating vector k0 (see Figure 17). In the third region 418, the periodic diffraction features include linear grating features 418A. Linear diffraction feature 418A is generally positioned parallel to linear diffraction feature 416B. The sixth region 424 includes periodic diffraction features 424A that generally comprise three sets of periodic linear features, wherein the first and second sets of linear features intersect each other, and the third set of linear features is arranged perpendicularly through the intersection of the first and second sets of linear features. In an embodiment, the coupled diffractive optics 412 are symmetrical about the longitudinal axis BB, such that the fourth region 420 mirrors the second region 416 and the fifth region 422 mirrors the third region 418.

In an embodiment, as illustrated in FIG18, the diffraction features of regions 414, 416, 418, 420, 422, and 424 are mixed within the interface region. In other words, a portion of one of regions 414, 416, 418, 420, 422, and 424 contains the same grating features as neighboring regions 414, 416, 418, 420, 422, and 424 at the interface region. For example, in an alternating pattern within the first interface region, a general triangular portion 450 of the first region 414 extends into the second region 416, and a general triangular portion 452 of the second region 416 extends into the first region 414. Similarly, in an alternating pattern within the second interface region, a general triangular portion 450 of the first region 414 extends into the sixth region 424, and a general triangular portion 454 of the sixth region 424 extends into the first region 414. In an embodiment, the general triangular portions 450, 452, and 454 may be 400 μm high and 800 μm wide.

In this embodiment, the diffraction features within each region 414, 416, 418, 420, 422, 424 include an arrangement of unit cells 414C, 416C, 418C, 420C, 422C, 424C in a periodic grid, thereby forming a two-dimensional periodic lattice structure coupling out the diffractive optical device 412. In this embodiment, each unit cell 414C, 416C, 418C, 420C, 422C, 424C includes the minimum repeating diffraction feature within the region. However, the unit cells 414C, 416C, 418C, 420C, 422C, 424C can be of any size, such that the unit cells can be repeated within the region to form their periodic diffraction features. The diffraction features within each region include an arrangement of unit cells in a periodic grid, thereby forming a two-dimensional periodic lattice structure. Each triangular portion 450, 452, 454 of adjacent regions 414, 416, 418, 420, 422, 424 may include multiple unit cells. The unit cell 424C of the sixth region 424 shown in Figure 18 is for reference only and is not shown to scale.

In another embodiment, as illustrated in FIG19, the hybrid interface between neighboring regions 414, 416, 418, 420, 422, 424 may include only one unit cell 414C, 416C, 418C, 420C, 422C, 424 extending in an alternating pattern from each of the neighboring regions 414, 416, 418, 420, 422, 424.

As illustrated in Figure 20, in an embodiment, the region interface between the first and second regions 414, 416 comprises a plurality of unit cells 414C, 416C mixed in a pseudo-random arrangement. In an embodiment, the diffraction pattern described by the unit cells within regions 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 229 coupled out of the diffraction optics 212 may include a non-overlapping sinusoidal diffraction pattern describing three or more grating vector k components and/or stakes.

Referring now to FIG. 21, in another embodiment, the interface between the first and second regions 414, 416 includes sub-regions 414S, 416S mixed in a pseudo-random arrangement. Each sub-region 414S includes one or more unit cells 414C, and each sub-region 416S includes one or more unit cells 416C. In one embodiment, each sub-region 414S, 416S includes the same number of unit cells. In another embodiment, sub-regions 414S, 416S may include different numbers of unit cells. The unit cells 416C shown in FIG. 21 are not shown to scale but are for reference only. For example, the interface region between neighboring regions 414, 416, 418, 420, 422, and 424 can be less than 1 mm wide, the sub-regions 414S, 416S, 418S, 420S, 422S, and 424S can be less than 0.15 mm wide, and the unit cells 414C, 416C, 418C, 420C, 422C, and 424C can be 1 μm wide.

As illustrated in Figure 21, in this embodiment, the interface region between the first and second regions 414 and 416 can be divided into a grid of sub-regions 414S and 416S. Those skilled in the art will recognize that the grid shown and described is for illustrative purposes only and is not a physical characteristic of the image light guide 400. In this embodiment, at the center line of the interface region along the vertical axis L1, the sub-regions 414S and 416S of the center row of the interface region alternate with each other sub-region in the x-axis direction. In the y-axis direction, in the rows of sub-regions 414S and 416S below the center row (i.e., adjacent to the center row on the side of the first region 414), every third sub-region is sub-region 416S. In the y-axis direction, in the rows of sub-regions 414S and 416S below the center row, every fourth sub-region is sub-region 416S. In the y-axis direction, in the rows of sub-regions 414S and 416S below the center row, all sub-regions are sub-region 414S. The total area of sub-regions 414S in the interface region increases from the longitudinal center line of the interface region toward the first region 414.

As shown in Figure 21, sub-regions 414S and 416S are similarly arranged to move from the center row towards the second region 416. In the rows of sub-regions 414S and 416S located above the center row in the y-axis direction (i.e., adjacent to the center row on the side of the second region 414), every third sub-region is sub-region 414S. In the rows of sub-regions 414S and 416S located two rows above the center row in the y-axis direction, every fourth sub-region is sub-region 414S. In the rows of sub-regions 414S and 416S located three rows above the center row in the y-axis direction, all sub-regions are sub-region 416S. The total area of sub-regions 416S in the interface region increases from the longitudinal centerline of the interface region towards the second region 416.

In one embodiment, the depth of the diffraction feature within sub-region 416S is different from the depth of the diffraction feature within sub-region 414S. In another embodiment, the depth of the diffraction feature from one sub-region 416S to the next sub-region 416S is different, and the depth of the diffraction feature from one sub-region 414S to the next sub-region 414S is also different.

One advantage of blending the interface to remove abrupt transitions is the reduction in visibility of the transition from one diffraction pattern to another.

The perspective view of Figure 22 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 right-eye optical system 64R having an image light guide 140R for the right eye. An image source 152 (such as a microprojector or similar device) can be provided, which can be excited to generate a separate image for each eye, the separate image being formed as a virtual image with a desired image orientation for upright image display. The generated image can be an image of a stereo pair for 3-D viewing. The virtual image formed by the optical system can be displayed as an overlay or superimposed on real-world scene content seen by a viewer through the image light guides. Additional components familiar to those skilled in the art of augmented reality virtualization, 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. Replaceable arrangements are possible, including display devices for providing images to an eye.

One or more features of the embodiments described herein can be combined to create additional embodiments not depicted. Although various embodiments have been described in detail above, it should be understood that they are presented as examples and not as limitations. It will be apparent to those skilled in the art that the disclosed subject matter can be embodied in other specific forms, variations, and modifications without departing from the scope, spirit, or essential characteristics of the disclosed subject matter. The embodiments described above should therefore be considered illustrative rather than restrictive in all respects. The scope of the invention is indicated by the appended claims, and all changes falling within the meaning and scope of their equivalents are intended to be encompassed therein.

Claims (15)

1. An image optical guide for transmitting virtual images, comprising: waveguide; Coupled into a diffractive optics device, operable to guide an image-carrying beam into the waveguide; and Coupled out diffractive optics, operable to expand the image-carrying beam in two dimensions and guide at least a portion of the image-carrying beam from the waveguide eyebox; The coupled-out diffraction optical device includes: A first region is located adjacent to the second region, wherein the first region includes a first set of diffraction features, and the second region includes a second set of diffraction features; and The first region and the second region form a first interface region, wherein the first interface region includes one or more first sub-regions and one or more second sub-regions, the first sub-regions include the first diffraction feature set, and the second sub-regions include the second diffraction feature set. 2. The image light guide according to claim 1, wherein the first and second sub-regions are arranged in a pseudo-random configuration within the first interface region. 3. The image light guide of claim 1, wherein the first and second sub-regions describe substantially triangular regions, and the first and second sub-regions alternate along one dimension of the first interface region. 4. The image light guide according to claim 1, wherein the first sub-region is mixed with the second sub-region. 5. The image light guide according to claim 1, wherein the total area of the first sub-region in the first interface region increases from the longitudinal center line of the first interface region toward the first region. 6. The image light guide according to claim 5, wherein the total area of the second sub-region in the first interface region increases from the longitudinal center line of the first interface region toward the second region. 7. The image light guide according to claim 1, wherein the coupled diffractive optical device comprises: A third region located adjacent to the first and second regions, wherein the third region includes a third set of diffraction features; and The first region and the third region form a second interface region, wherein the second interface region includes one or more first sub-regions and one or more third sub-regions, and the third sub-region includes the third diffraction feature set. 8. The image light guide according to claim 7, wherein the first and third sub-regions are arranged in a pseudo-random configuration within the second interface region. 9. The image light guide of claim 7, wherein the first and third sub-regions describe substantially triangular regions, and the first and third sub-regions alternate along one dimension of the second interface region. 10. The image light guide according to claim 7, wherein the total area of the first sub-region in the second interface region increases from the longitudinal centerline of the second interface region to the first region. 11. The image light guide according to claim 10, wherein the total area of the third sub-region in the second interface region increases from the longitudinal center line of the second interface region to the third region. 12. The image light guide of claim 7, wherein the coupled diffractive optical device includes a third interface region located between the second region and the third region, wherein the third interface region includes one or more second sub-regions and one or more third sub-regions. 13. The image light guide of claim 12, wherein the second and third sub-regions are arranged in a pseudo-random configuration within the third interface region. 14. The image light guide of claim 12, wherein the second and third sub-regions describe substantially triangular regions, and the second and third sub-regions alternate along one dimension of the third interface region. 15. The image light guide of claim 1, wherein the first and second sub-regions comprise one or more unit cells with periodic diffraction features.