HK40113691A - Double-sided waveguide - Google Patents

Description

Double-sided waveguide

Technical Field

This disclosure generally relates to electronic displays, and more particularly to head-mounted near-eye displays that use image light guides with diffractive optics to transmit a beam of light carrying an image to a viewer.

Background Technology

A head-mounted display (HMD) (which can be in the form of binocular glasses or monocular glasses with suspended eyepieces) may include an image source and an image light guide for presenting virtual images to the wearer's eyes. The image light guide may be equipped with in-coupling and out-coupling optics integrated into a transparent waveguide to transmit the virtual image from an offset position of the image source to a position aligned with the wearer's eyes in an angularly encoded manner. The transparent waveguide may also provide an aperture through which the wearer can simultaneously view the real world, particularly to support augmented reality (AR) applications in which virtual images are overlaid on real-world scenes. For many applications, creating virtual images that can be visually superimposed on real-world images located within the HMD user's field of vision holds particular value.

The image source can take several forms (including backlighting, front lighting, or a light-emitting display combined with focusing optics) to convert spatial information into a substantially collimated, angled beam. Alternatively, the image source can be arranged as a beam scanning device to guide light at an angle from a substantially collimated light source. The two dimensions of the image can also be generated separately, for example, through a combination of a linear display and a beam scanning device.

In a conventional image waveguide, a collimated, angle-coded beam from an image source is coupled into a planar waveguide via an input coupling optics device, which can take various forms, including prisms, mirrors, or diffractive optics, to guide the angled beam from the image source into the waveguide. For example, such diffractive optics can be formed as diffraction gratings or holographic optical elements, which can be mounted on the front or back of the planar waveguide, or formed within the waveguide. For instance, a diffraction grating can be formed by surface relief. A portion of the input beam after coupling into the waveguide is sometimes referred to herein as the "input coupling ray."

After propagating along the waveguide, the diffracted light can be guided out of the waveguide by an out-coupled optics, such as an out-coupled diffraction optics, which can be arranged to provide pupil dilation in one or more directions. To maintain a view of the surrounding environment through the waveguide, the out-coupled optics should avoid distorting or otherwise impairing the wearer's view of the real world. As a diffraction optics, the out-coupled optics can be matched with the in-coupled diffraction optics to decode any angular encoding imposed by the in-coupled diffraction optics. Furthermore, the efficiency of the out-coupled diffraction optics can be controlled to support multiple encounters with the angularly correlated beams propagating along the waveguide, thereby effectively amplifying each beam so that the beams diffracted from the waveguide overlap over a larger area in which a virtual image can be seen by the wearer's eye.

Each optical path or channel carrying an image can transmit different information about the image, such as angular relationships and/or color attributes. Diffractive optics forming the optical paths for the beams of the image carrying each primary color (red, green, blue) may require different properties to achieve optimal performance for each color. Although conventional light guide mechanisms have offered significant reductions in the size, weight, and overall cost of display optics, problems remain to be solved. Crosstalk is commonly encountered in double-sided single-panel waveguides. Unlike most optical systems, waveguides do not have a fixed effective input aperture. Typically, the effective input aperture will depend at least on the thickness of the planar waveguide. If the incident coupled light is reflected back (i.e., via total internal reflection bounce) to the incident coupled diffractive optics, the incident coupled light tends to outcouple, resulting in a reduction in the amount (i.e., intensity) of the light entering the image light guide propagating through the waveguide. Because each beam (considered a collimated beam of the image carrying the image corresponding to a single point or field angle in the virtual image) is incident coupled at a different angle, each field angle has a different effective aperture. Therefore, adding a second ingress-coupled diffractive optics to the second surface of the waveguide can reduce the effective input aperture by more than half. The diffraction characteristics of the second ingress-coupled diffractive optics are known to rotate such that the incident light from the second ingress-coupled diffractive optics propagates in a different direction than the light incident on the first surface of the waveguide by the first ingress-coupled diffractive optics. However, to reduce crosstalk, improved separation of the wavelength range optical paths is required, where colors are processed and displayed from incorrect wavelength range optical paths. Crosstalk can cause discrepancies between the color image data and the displayed colors, and can also be the cause of noticeable and unpleasant color shifts across the image field. Therefore, it is understandable that there is a need for improved designs that still provide pupil expansion capability for the imaging lightguide, but allow these devices to be thinner and lighter, without compromising image quality and color balance.

Summary of the Invention

Embodiments of this disclosure provide a waveguide that provides an optical path for at least two wavelength ranges within a single thickness of a substrate, while reducing crosstalk.

According to an aspect of this disclosure, an imaging light guide for transmitting a virtual image is provided, the imaging light guide comprising: a first planar waveguide operable to propagate a beam carrying an image, the first planar waveguide having first and second parallel surfaces; a first ingress coupling diffraction optics formed along or in the first surface, the first ingress coupling diffraction optics including a first plurality of periodic diffraction structures, wherein the first ingress coupling diffraction optics is operable to diffract a first portion of the beam carrying the image into the first planar waveguide in an angle-coded manner, and wherein the first ingress coupling diffraction optics is operable to transmit a second portion of the beam carrying the image; a first egress coupling diffraction optics formed along the waveguide, wherein the first egress coupling diffraction optics is operable to replicate the first portion of the beam carrying the image and guide the replicated first portion of the beam carrying the image from the waveguide in an angle-coded manner; and a second ingress coupling diffraction optics formed along or in the second surface, wherein the second ingress coupling diffraction optics is operable to diffract a second portion of the beam carrying the image into the first planar waveguide in an angle-coded manner. In the first planar waveguide, the second ingress-coupled diffractive optics includes a second plurality of periodic diffractive structures having periodicity different from the first plurality of periodic diffractive structures of the first ingress-coupled diffractive optics. The first ingress-coupled diffractive optics is substantially co-located with the second ingress-coupled diffractive optics. The first intermediate diffractive optics is operable to guide a first portion of the image-carrying beam toward the first egress-coupled optics and position it along the first plane. The second intermediate diffractive optics is operable to guide a second portion of the image-carrying beam toward the first egress-coupled diffractive optics and position it on a second plane. The first intermediate diffractive optics is offset relative to the second intermediate diffractive optics, thereby reducing the interaction between the first portion of the image-carrying beam and the second ingress-coupled diffractive optics and the second intermediate diffractive optics, and reducing the interaction between the second portion of the image-carrying beam and the first ingress-coupled diffractive optics and the first intermediate diffractive optics. The first portion of the image-carrying beam includes a first wavelength range, and the second portion of the image-carrying beam includes a second wavelength range.

In some embodiments, a first portion of the image-carrying beam includes a first wavelength range, and a second portion of the image-carrying beam includes a second wavelength range. In other embodiments, the first portion of the image-carrying beam includes an angularly correlated beam of a first range, and the second portion of the image-carrying beam includes an angularly correlated beam of a second range different from the angularly correlated beam of the first range.

The first planar waveguide may include a second out-coupled diffraction optics aligned with the first out-coupled diffraction optics on a second surface. In one exemplary embodiment, the first and second out-coupled diffraction optics have the same periodic diffraction characteristics. In another exemplary embodiment, the first and second out-coupled diffraction optics include two-dimensional periodic diffraction characteristics operable to replicate a first and second portion of a beam carrying an image, and to guide the replicated image-carrying beam from the waveguide in an angled decoding manner.

In some embodiments, each of the periodic diffraction features of the first and second out-coupled diffraction optics has a periodic axis, and wherein a first set of periodic diffraction features of the first out-coupled diffraction optics along a periodic first axis is emphasized relative to a second set of periodic diffraction features of the first out-coupled diffraction optics.

In another embodiment, the first set of periodic features of the second out-coupled diffraction optics along the periodic second axis is enhanced relative to the second set of periodic diffraction features of the second out-coupled diffraction optics.

In an additional embodiment, the first and second out-coupled diffraction optics each define a grating vector, and wherein at least one grating vector of the first out-coupled diffraction optics is de-emphasized relative to the other grating vectors of the first out-coupled diffraction optics, and wherein at least one grating vector of the second out-coupled diffraction optics is de-emphasized relative to the other grating vectors of the second out-coupled diffraction optics.

In some exemplary embodiments, the first and second portions of the beam carrying the image may interact with the first and second out-coupled diffractive optics on the half-echo.

The second plurality of periodic diffraction structures of the second ingress-coupled diffraction optics can be oriented at approximately 90 degrees relative to the first plurality of periodic diffraction structures of the first ingress-coupled diffraction optics. In another embodiment, the first and second ingress-coupled diffraction optics can each be further represented by an input grating vector, wherein the input grating vector of the first ingress-coupled diffraction optics and the input grating vector of the second ingress-coupled diffraction optics are within 5 degrees of orthogonality. In some embodiments, the first ingress-coupled diffraction optics and the second ingress-coupled diffraction optics are coaxial. Furthermore, in some embodiments, the first ingress-coupled diffraction optics have a different spacing than the second ingress-coupled diffraction optics.

The first image-carrying beam can be a beam of a red image-carrying image with a wavelength in the range of 625 nm to 740 nm, and the second image-carrying beam can be a beam of a blue image-carrying image with a wavelength in the range of 450 nm to 485 nm. The red image-carrying beam can be coupled inward by a second inward-coupled diffraction optics and diffracted at an extreme grazing angle, wherein when the angle reaches 90 degrees, the red image-carrying beam will not propagate within the first image light guide by total internal reflection (“TIR”). The blue image-carrying beam can be coupled inward by a first inward-coupled diffraction optics and diffracted at an angle less than the critical angle, wherein the blue image-carrying beam will not propagate within the first image light guide by TIR.

An imaging light guide may be part of an imaging light guide system and may also include a first beam source carrying an image and a second beam source carrying an image, each beam source generating an image of one of the three primary color bands, such that when combined, a multi-color virtual image is produced.

According to another aspect of the invention, an imaging light guide for transmitting a virtual image includes a first planar waveguide operable to propagate a beam carrying an image, the first planar waveguide having first and second parallel surfaces, a first ingress coupling diffraction optics formed along the first surface, the first ingress coupling diffraction optics including a first plurality of periodic diffraction structures, wherein the first ingress coupling diffraction optics is operable to diffract a first portion of the beam carrying the image into the first planar waveguide in an angled-coded manner, and wherein the first ingress coupling diffraction optics is operable to transmit a second portion of the beam carrying the image, a first egress coupling diffraction optics formed along the waveguide, wherein the first egress coupling diffraction optics is operable to replicate the first and second portions of the beam carrying the image and guide the replicated beam carrying the image from the waveguide in an angled-decoded manner, the second egress coupling diffraction optics being operable to replicate the first and second portions of the beam carrying the image and guide the replicated beam carrying the image from the waveguide in an angled-decoded manner, the second egress coupling diffraction optics being operable to replicate the first and second portions of the beam carrying the image. An ingress-coupled diffractive optics is formed along the second surface, wherein the second ingress-coupled diffractive optics is operable to diffract a second portion of the image-carrying beam into the first planar waveguide in an angle-coded manner, wherein the second ingress-coupled diffractive optics includes a second plurality of periodic diffraction structures having periodicity different from the first plurality of periodic diffraction structures of the first ingress-coupled diffractive optics, wherein the first ingress-coupled diffractive optics is substantially co-located with the second ingress-coupled diffractive optics, a first intermediate diffractive optics operable to guide a first portion of the image-carrying beam toward a first egress-coupled optics and to guide a second portion of the image-carrying beam toward the first egress-coupled diffractive optics and to be located along a first plane, wherein the first portion of the image-carrying beam includes a first wavelength range and the second portion of the image-carrying beam includes a second wavelength range.

According to another aspect of the invention, an imaging light guide for transmitting a virtual image includes a first planar waveguide operable to propagate an image-carrying beam, the first planar waveguide having first and second parallel surfaces, and a first in-line coupling diffraction optics formed along the first surface, the first in-line coupling diffraction optics including a first plurality of periodic diffraction structures, wherein the first in-line coupling diffraction optics is operable to diffract a first portion of the image-carrying beam into the first planar waveguide in an angled encoded form, and wherein the first in-line coupling diffraction optics is operable to transmit a second portion of the first set of image-carrying beams, a first out-coupling diffraction optics formed along the waveguide, wherein the first out-coupling diffraction optics is operable to replicate the first portion of the image-carrying beam and angled decode... A first portion of a beam carrying an image is copied from the waveguide in an angularly encoded form. A second in-coupled diffractive optics is formed along the second surface. The second in-coupled diffractive optics is operable to diffract a second portion of the beam carrying the image into the first planar waveguide in an angularly encoded form. The second in-coupled diffractive optics includes a second plurality of periodic diffraction structures having periodicity different from the first plurality of periodic diffraction structures of the first in-coupled diffractive optics, and a second out-coupled diffractive optics aligned with the first out-coupled diffractive optics on the second surface. The second out-coupled diffractive optics is operable to copy the second set of image-carrying beams and guide the copied second set of image-carrying beams from the waveguide in an angularly decoded form.

Attached Figure Description

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 illustrate 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 1A is a schematic diagram of a portion of a planar waveguide according to an embodiment of the present disclosure, showing an echo and two half-echoes starting at the top surface of the planar waveguide.

Figure 1B is a schematic diagram of a portion of a planar waveguide according to an embodiment of the present disclosure, showing an echo and two half-echoes starting at the bottom surface of the planar waveguide.

Figure 2A is a side view of a double-sided waveguide according to an embodiment of the present disclosure.

Figure 2B is a side view of a double-sided waveguide with multiple image beam sources according to an embodiment of the present disclosure.

Figure 3A is a perspective view of a double-sided waveguide having one or more overlapping diffractive optical elements according to an embodiment of the present disclosure.

Figure 3B is a top view of the double-sided waveguide in Figure 3A.

Figure 3C is a bottom view of the double-sided waveguide of Figure 3A.

Figure 3D is an exploded view of the double-sided waveguide of Figure 3A according to an embodiment of the present disclosure, showing the distribution of diffractive optics for two wavelength range optical paths.

Figure 3E is a schematic diagram of an out-coupled diffractive optical device according to an embodiment of the present disclosure.

Figure 4 is a side view of a double-sided waveguide having an outgoing coupled diffractive optics according to an embodiment of the present disclosure.

Figure 5 is a perspective view illustrating a display system for augmented reality viewing using an imaging light guide according to an embodiment of the present disclosure.

Figure 6 is a perspective view of a double-sided waveguide having one or more overlapping diffractive optical elements according to an embodiment of the present disclosure.

Detailed Implementation

It should be understood that, unless an opposite orientation and sequence of steps are explicitly specified, the invention may employ various alternative orientations and sequences of steps. It should also be understood that the specific assemblies and systems illustrated in the drawings and described in the following specification are merely exemplary embodiments of the inventive concepts defined herein. Therefore, unless explicitly stated otherwise, specific dimensions, orientations, or other physical characteristics associated with the disclosed embodiments are not considered limiting. Furthermore, although they may not be, within this section of this application, similar elements in the various embodiments described herein may generally refer to those having similar reference numerals.

As used herein, unless otherwise stated, the terms “first,” “second,” etc., do not necessarily refer to any ordinal, sequential, or priority relationship, but are used only to more clearly distinguish one element or group of elements from another element or group of elements.

As used herein, the term “exemplary” is intended to refer to “an example of…” and is not intended to imply any preferred or ideal embodiment.

As used herein, the terms “viewer,” “wearer,” “operator,” “observer,” and “user” are equivalent and refer to a person who uses an augmented reality system to wear and view images.

As used herein, the term "group" refers to a non-empty group, as the concept of a set of elements or members of a group is widely understood in elementary mathematics. As used herein, unless otherwise explicitly stated, the term "subgroup" refers to a non-empty proper subgroup, i.e., a subgroup of a larger group having one or more members. For a group S, a subgroup may include the entire group S. However, a "proper subgroup" of group S is strictly contained within group S and excludes at least one member of group S.

As used herein, the terms “wavelength band” and “wavelength range” are equivalent and have their standard connotations as used by those skilled in the art of color imaging, and refer to the range of continuous light wavelengths used to represent multicolor images.

As used herein, the term "coupled" is intended to mean a physical association, connection, relationship, or link between two or more components such that the arrangement of one component affects the spatial arrangement of its coupled components. For mechanical coupling, the two components do not need to be in direct contact, but can be connected through one or more intermediate components. As understood by those skilled in the art, components used for optical coupling allow light energy to be input to or output from an optical device.

As used herein, the term "echo" is intended to refer to a ray propagating through a planar waveguide by total internal reflection ("TIR") that originates at a first surface (e.g., the top or bottom surface) of the planar waveguide and echoes (or reflects) back to the first surface from a second surface opposite the first surface, as shown in Figures 1A and 1B. The echo has a distance "D," as shown in Figures 1A and 1B. The term "half-echo" is intended to refer to half of the echo and having a distance of 1/2D.

As used herein, the term “eyebox expansion” is intended to mean the reproduction of a beam via multiple encounters with an optical element to provide exit pupil expansion in one or more directions.

The HMD is operable to form a virtual color image that can be visually superimposed on a real-world image located in the HMD user's field of vision. An optically transparent parallel-plate waveguide (also known as a planar waveguide) transmits the light carrying the image, generated by the color projector system, to the HMD user. The planar waveguide transmits the image-carrying light in a narrow space to guide the virtual image to the HMD user's pupil, allowing the virtual image to be superimposed on the real-world image located in the HMD user's field of vision.

In an imaging lightguide, a collimated, angle-coded beam from a color image source is coupled to an optically transparent image lightguide assembly via an input-coupled optics device, such as an input-coupled diffractive optics device, which can be mounted or formed on the surface of a parallel-plate planar waveguide or disposed within the waveguide. Such diffractive optics can be formed, but are not limited to, diffraction gratings or holographic optical elements. For example, a diffraction grating can be formed as a surface-embossed grating. After propagation along the planar waveguide, the diffracted color-carrying image light can be guided out of the planar waveguide via a similar output grating, which can be arranged to provide pupil dilation along one or more directions. Furthermore, one or more intermediate diffractive optics devices (e.g., diffraction rotation gratings) can be optically positioned along the waveguide between the input and output optics to provide pupil dilation in one or more directions.

A collimated, angled, image-encoded beam of light emitted from the waveguide overlaps at a distance from the waveguide's interocular space, forming an exit pupil. Within this exit pupil, a virtual image generated by the image source can be viewed. The area of the exit pupil is called the "eyebox," through which the virtual image can be observed at the interocular space.

The input-coupled optics couples light carrying an image from an image source into a substrate of a planar waveguide. Any real image or image size is first converted into an array of overlapping angle-correlated beams encoding different locations within the image, to be presented to the input-coupled optics. At least a portion of the light carrying the image is diffracted and thus redirected by the input-coupled optics into the waveguide as angle-coded light carrying the image, to be used for further propagation along the waveguide via a TIR. Although the beam diffracted to the angle-correlated light carrying the image, consistent with the boundaries set by the TIR, is generally more concentrated, the light carrying the image retains image information in an encoded form. The output-coupled optics receive the encoded light carrying the image and diffract at least a portion of it out of the waveguide as angle-coded light carrying the image toward the eyebox. Typically, the output-coupled optics are designed symmetrically with respect to the input-coupled optics to recover the original angular relationship of the light carrying the image within the angle-correlated beams of the output light carrying the image. However, to increase the one-dimensional overlap of the angle-dependent beams carrying the image within the eyebox, the out-coupled optics are arranged to encounter the image-carrying beam multiple times, diffracting only a portion of the beam at each encounter. These multiple encounters along the length of the out-coupled optics in the propagation direction have the effect of expanding one direction of the eyebox within which the image-carrying beams overlap. This expanded eyebox reduces sensitivity to the viewer's eye position when viewing the virtual image.

An out-coupled diffraction optics with a refractive index variation along a single direction can extend the eyebox in one direction along the waveguide's propagation direction through multiple encounters between the image-carrying beam and the out-coupled diffraction optics. Furthermore, an out-coupled diffraction optics with a refractive index variation along a second direction can extend the eyebox in a second direction, providing bidirectional extension of the eyebox. The refractive index variation along the first direction of the out-coupled diffraction optics can be arranged such that, upon each encounter with the waveguide, a portion of the beam's energy is diffracted out of the waveguide by a desired first-order diffraction, while the remaining portion of the beam's energy is retained for further propagation in its original direction via zero-order diffraction. The refractive index variation along the second direction of the out-coupled diffraction optics can be arranged such that, upon each encounter with each beam, a portion of the beam's energy is diffracted by a desired first-order diffraction in a direction angular to the beam's original propagation direction, while the remaining portion of the beam's energy is retained for further propagation in its original direction via zero-order diffraction.

Unlike methods used to form real images, virtual images are not formed on a 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 images 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. Furthermore, the source object of a virtual image can be small; for example, a magnifying glass provides a virtual image of an object. By forming virtual images that appear to be at a distance, a more realistic viewing experience can be provided compared to systems that project real images. Providing virtual images also eliminates the need for compensating for screen artifacts, which may be necessary when projecting real images.

Imaging light-guide optics form a virtual image that resembles a real object located at a distance and within the observer's field of vision. As is well known to those skilled in the art of imaging, this virtual image is simulated by the divergence of light rays supplied to the eye from the optical system. This optical effect creates a "virtual image" that appears to be at a given location and distance within the observer's field of vision; there is no corresponding "real" object in the field of vision where the rays actually diverge. The ability to form a virtual image that can be combined with real-world image content within the viewer's field of vision distinguishes augmented reality imaging devices from other virtual image devices that do not allow simultaneous viewing of the real world.

A typical planar optical waveguide is a physical structure used to transmit light carrying an image from one region of the waveguide to another. Applications of such image transmission waveguides include head-mounted monocular or binocular display systems.

As shown in Figures 2A and 2B, in one embodiment, the image light guide assembly 10 includes a first planar waveguide 20. The first planar waveguide 20 has a parallel bottom planar surface 12 and a top planar surface 14. The first planar waveguide 20 includes an ingress-coupled diffraction optics 16 located on the bottom planar surface 12. In one embodiment, the ingress-coupled diffraction optics 16 is a surface-embossed diffraction grating. In another embodiment, the ingress-coupled diffraction optics 16 is a holographic diffraction element. In yet another embodiment, the ingress-coupled diffraction optics 16 is a reflective diffraction grating element. The first planar waveguide 20 may also include an intermediate diffraction optics 18, which is oriented to diffract a portion of the image-carrying light input in reflection mode by the ingress-coupled diffraction optics 16 toward the outgress-coupled diffraction optics 22. The intermediate diffraction optics 18 may be referred to herein as a rotating grating. In one embodiment, the rotating grating 18 is a diffraction grating. In another embodiment, the rotating grating 18 is a holographic diffraction element. Rotating grating 18 is operable to expand the exit pupil (provide pupil expansion in one or more directions) via multiple encounters of an image-carrying beam traveling within the first planar waveguide 20 in one or more directions. Out-coupled diffraction optics 22 is operable to diffract a portion of the image-carrying beam propagating within the first planar waveguide 20 out of the first planar waveguide 20. In one embodiment, out-coupled diffraction optics 22 is a diffraction grating. In another embodiment, out-coupled diffraction optics 22 is a holographic diffraction element. In one embodiment, out-coupled diffraction optics 22 comprises a repeating pattern of three overlapping linear periodic diffraction features. These three patterns may be represented by at least three principal grating vectors. In embodiments of out-coupled diffraction optics 22 in which two overlapping patterns of periodic diffraction features exist, a third grating vector is implicitly present but reduced in amplitude, as described in more detail below. Out-coupled diffraction optics 22 may be arranged to provide pupil expansion in one or more directions. For example, a change in refractive index along a single direction can extend one direction of the eyebox by multiple encounters of individual angularly correlated beams along the first planar waveguide 20 with the out-coupled diffractive optics 22 in their propagation direction.

In Figures 2A and 2B, the ingress-coupled diffractive optics 16, 30 and the egress-coupled diffractive optics 22, 34 are shown with diffraction feature profiles of greater depth than the intermediate diffractive optics 18, 32, to increase the clarity of the figures; however, unless otherwise provided herein, the ingress-coupled diffractive optics 16, 30, the egress-coupled diffractive optics 22, 34 and the intermediate diffractive optics 18, 32 may have the same depth or any combination of depths.

Referring again to Figures 2A and 2B, in one embodiment, the first planar waveguide 20 further includes an ingress coupling diffraction optics 30 located on the top planar surface 14. In one embodiment, the ingress coupling diffraction optics 30 is a surface-embossed diffraction grating. In another embodiment, the ingress coupling diffraction optics 30 is a holographic diffraction element. The first planar waveguide 20 may also include an intermediate diffraction optics 32, which is oriented to diffract a portion of the light carrying the image input in reflection mode by the ingress coupling diffraction optics 30 toward the egress coupling diffraction optics 34. The intermediate diffraction optics 32 may be referred to herein as a rotating grating. In one embodiment, the rotating grating 32 is a diffraction grating. In another embodiment, the rotating grating 32 is a holographic diffraction element. The rotating grating 32 is operable to provide pupil dilation in one or more directions. The egress coupling diffraction optics 34 is operable to diffract a portion of the beam of light carrying the image propagating within the first planar waveguide 20 out of the first planar waveguide 20. In one embodiment, the out-coupled diffraction optics 34 is a diffraction grating. In another embodiment, the out-coupled diffraction optics 34 is a holographic diffraction element. In one embodiment, the out-coupled diffraction optics 34 comprises a repeating pattern of three overlapping linear periodic diffraction features. These three patterns can be represented by at least three principal grating vectors. In embodiments of the out-coupled diffraction optics 34 in which two overlapping patterns of periodic diffraction features exist, a third grating vector is implicitly present but reduced in amplitude, as described in more detail below. The out-coupled diffraction optics 34 is arranged to repeatedly encounter the beam carrying the image to provide pupil dilation in one or more directions. For example, due to repeated encounters with the out-coupled diffraction optics 34, a change in refractive index along a single direction can dilate the eyebox in one direction along the propagation direction of the first planar waveguide 20.

As shown in FIG. 2A, the image light guide assembly 10 also includes an image source 100 that generates a light beam 102 carrying an image. In one embodiment, the image source 100 is a microprojector. For example, the image source 100 may be a microprojector that generates two or more primary color bands 104, 106 (e.g., red, green, or blue) of the light beam carrying the image, which includes an image to be presented by the image light guide assembly 10 to a viewer viewing generally along the z-axis. In another embodiment, as shown in FIG. 2B, the image light guide assembly 10 includes a plurality of image sources 110, 112, each generating a light beam 102 carrying the image. For example, the image sources 110, 112 may each be a microprojector, each generating a single primary color band 104, 106 (e.g., red, green, or blue) of light carrying the image. In one embodiment, the three primary color bands are a green band with wavelengths in the range of 500 nm to 565 nm, a red band with wavelengths in the range of 625 nm to 740 nm, and a blue band with wavelengths in the range of 450 nm to 485 nm. In one embodiment, image source 100 generates a beam 104 carrying an image in the red band and a beam 106 carrying an image in the blue band. In another embodiment, image source 100 generates a beam 104 carrying an image in the red band and a beam 106 carrying an image in the green band. In one embodiment, image source 110 generates a beam 104 carrying an image in the red band, and image source 112 generates a beam 106 carrying an image in the blue band. In another embodiment, image source 112 generates a beam 106 carrying an image in the green band.

In an embodiment, image source 100 or image beam source 110, 112 is positioned such that the central ray of the projected image-carrying beam 102 is generally perpendicular to the top surface 14 of the planar waveguide 20. Image source 100 or image source 110, 112 may also be positioned such that the central ray of the projected image-carrying beam 102 is not perpendicular to the top or bottom surfaces 14, 12 of the planar waveguide 20. It should be understood that Figures 2A and 2B do not illustrate every element that may be included in the image light guide assembly 10. For example, the image light guide assembly 10 may include prisms for directional projection of light within eyeglasses, and/or filters such as polarizing filters, as well as other features.

As illustrated in Figures 2A and 2B, in this embodiment, the image-carrying beam 102 passes through the ingress-coupled diffraction optics 30 on the top surface 14 of the waveguide 20, wherein a first portion of the image-carrying beam 102 is diffracted into the first planar waveguide 20 as the ingress-coupled image-carrying beam 50. A second portion of the image-carrying beam 102 passes through the ingress-coupled diffraction optics 16 on the bottom surface 12 of the waveguide 20, and is diffracted into the first planar waveguide 20 as the ingress-coupled image-carrying beam 52. The ingress-coupled image-carrying beams 50 and 52 propagate through the first planar waveguide 20 via total internal reflection (TIR) between the top and bottom planar surfaces 14 and 12. The ingress-coupled image-carrying beams 50 and 52 can be redirected by rotating gratings 32 and 18, respectively, and can be extended in at least one direction. As discussed further below, the image-carrying beam 50 coupled in at least one direction can be extended and guided out of the first planar waveguide 20 by the out-coupled diffractive optics 34 as the image-carrying beam _130R coupled out. The image-carrying beam 52 coupled in at least one direction can be extended and guided out of the first planar waveguide 20 by the out-coupled diffractive optics 22 as the image-carrying beam _130B coupled out.

Figures 3A-3D are views of the planar waveguide 20, where similar numbers correspond to similar elements in Figures 2A and 2B. Figures 3A-3D further show the ingress-coupled diffractive optics 16 and 30 aligned along the z-axis on surfaces 12 and 14, respectively, and each of the diffraction grating features and associated grating vectors. Regarding Figure 3D, this figure is a visually exploded view separating the bottom and top surfaces of the waveguide 20; however, it is intended that only a single waveguide exists in this figure. Each surface of the planar waveguide 20 has a diffraction structure serving at least one of three color bands. Grating vectors are typically designated as k and denoted by subscripts, where they are specific to the set of diffraction features within the optics.

As shown in Figures 3B and 3C, the ingress-coupled optical element 30 on surface 14 has a diffraction feature 80 and a grating vector k1, and the ingress-coupled diffractive optical element 16 on surface 12 has a diffraction feature 82 and a grating vector k2. In one embodiment, the grating vectors k1 and k2 of the ingress-coupled optical elements 30 and 16 are orthogonal to each other within 5 degrees (5°). The ingress-coupled optical element 30 may have a period or spacing ( _d1 ) different from that of the ingress-coupled optical element _16. Furthermore, in one embodiment, the angle between the grating vectors k1 and k2 of the ingress-coupled diffractive optical elements 16 and 30 is 90 degrees (90°). In another configuration, the angle between the grating vectors k1 and k2 of the ingress-coupled diffractive optical elements 16 and 30 is approximately 90 degrees (90°). The planar waveguide 20 may also include an intermediate diffractive optics 32 having diffraction feature 84 and grating vector k3, and an intermediate diffractive optics 18 having diffraction feature 86 and grating vector k4. Furthermore, the planar waveguide 20 may include coupled diffractive optics 34 and 22, each having diffraction feature 88 and grating vectors k5, k6, and k7.

The grating vectors (e.g., the depicted grating vectors k1, k2, k3, k4, k5, k6, and k7) extend in a direction perpendicular to the diffraction features (e.g., grooves, lines, or scribes) of the diffraction optics and have an amplitude opposite to the period or spacing d of the diffraction optics (i.e., the center-to-center distance between diffraction features). In one embodiment, the combination of grating vectors ±k1, ±k3, and ±k5 forms a triangle when placed end-to-end. In another embodiment, the combination of grating vectors ±k2, ±k4, and ±k6 forms a triangle when placed end-to-end. In one embodiment, the triangle is an equilateral triangle. In another embodiment, the triangle is an isosceles triangle. In yet another embodiment, the triangle is a scalene triangle.

As shown in Figures 3A-3D, the planar waveguide 20 may include outgoing coupling diffraction optics 34 and 22, each having a diffraction feature 88 and grating vectors k5, k6, and k7. In an embodiment, the diffraction feature 88 may include two or three sets of linear diffraction features. In one embodiment, each outgoing coupling diffraction optics 34 and 22 includes a first set of linear diffraction features 70, a second set of linear diffraction features 72, and a third set of linear diffraction features 74, each set of 70, 72, and 74 having different grating vectors k5, k6, and k7. For example, as shown in Figures 3A-3D, the first set of periodic diffraction features 70 may be oriented along a periodic first axis, the second set of periodic diffraction features 72 may be oriented along a periodic second axis, and the third set of periodic diffraction features 74 may be oriented along a periodic third axis. In one embodiment, incoming coupling diffraction optics 16 and rotating grating 18 have the same spacing ( _d2 ), and incoming coupling diffraction optics 30 and rotating grating 32 have the same spacing ( _d1 ). In one embodiment, diffraction feature 70 has the same spacing as the input-coupled diffraction optics 30, and diffraction feature 72 has the same spacing as the input-coupled diffraction optics 16 and the rotating grating 18. In another embodiment, diffraction feature 70 of the output-coupled diffraction optics 34, 22 is more enhanced than diffraction feature 72 of the output-coupled diffraction optics 34, 22. For example, diffraction feature 70 may have a greater depth than diffraction feature 72, thereby increasing the diffraction efficiency of diffraction feature 70 relative to diffraction feature 72. Furthermore, in another embodiment, diffraction feature 72 of the output-coupled diffraction optics 34, 22 is more enhanced than diffraction feature 70 of the output-coupled diffraction optics 34, 22. For example, diffraction feature 72 may have a greater depth than diffraction feature 70, thereby increasing the diffraction efficiency of diffraction feature 72 relative to diffraction feature 70. In the embodiment, the out-coupled diffraction optics 22 and 34 each include grating vectors k5, k6, and k7, and at least one of the grating vectors of the out-coupled diffraction optics 22 and 34 is weakened relative to the other grating vectors of the out-coupled diffraction optics 22 and 34. For example, as shown in FIG3E, the out-coupled diffraction optics 22 and 34 include first and second patterns of diffraction features 70 and 72, respectively, having grating vectors k5 and k6, and a third pattern of diffraction feature 74 is inherent, having a third grating vector k7. In this example, the third grating vector k7 is reduced in amplitude relative to grating vectors k5 and k6.

In one embodiment, the in-line coupled diffractive optics 16 and 30 are co-located. That is, in one embodiment, the in-line coupled diffractive optics 16 and 30 are coaxially aligned or approximately aligned along the z-axis.

In one embodiment, the out-coupled diffraction optics 22 and 34 have the same diffraction characteristics, including the same spacing and orientation. In another embodiment, the planar waveguide 20 includes only one out-coupled diffraction optic, as shown in FIG. 4. For example, the planar waveguide 20 may include out-coupled diffraction optics 22 and 34. In embodiments including only one out-coupled diffraction optic 22 and 34, two-dimensional eyebox extension via the out-coupled diffraction optics 22 and 34 is possible. Refractive index changes along at least two directions can extend the second direction of the eyebox and provide bidirectional extension of the eyebox. Refractive index changes along the first direction of the out-coupled diffraction optic can be arranged such that each time the waveguide is encountered, a portion of the energy of each beam is diffracted out of the waveguide by the desired first-order diffraction, while another portion of the beam energy is retained for further propagation in its original direction by zero-order diffraction. The refractive index change along the second direction of the out-coupled diffractive optics can be arranged such that, each time each beam is encountered, a portion of the energy of each beam is diffracted in a direction angular to the original propagation direction of the beam by the desired first-order diffraction, while another portion of the beam energy is reserved for further propagation in its original direction by zero-order diffraction.

In any of the embodiments described herein, the out-coupled diffraction feature 88 may be formed as a two-dimensional structure having at least two different grating vectors k5, k6. In one embodiment, the out-coupled diffraction feature 88 has at least three principal grating vectors k5, k6, k7. In one embodiment, the two-dimensional structure 88 includes a blazed grating. In another embodiment, the two-dimensional structure 88 is described by a generally triangular shape.

Turning again to Figures 2A, 2B, and 3A-3D, in this embodiment, each surface of the planar waveguide 20 has a diffraction structure serving at least one of three wavelengths (or color bands). Therefore, the components on the bottom 12 are primarily used for one or two wavelengths/optical paths, while the components shown on the top 14 are primarily used for wavelengths/optical paths different from those on the bottom 12. However, each of the out-coupled diffractive optics 22, 34 operates in each of the optical paths of the waveguide 20. For example, in Figure 3D, a wavelength-range optical path _CB is provided for blue light (from approximately 450-485 nm); a second wavelength-range optical path _CR is provided for red light (from approximately 610-780 nm). The wavelength-range optical path _CB has diffractive elements 16 and 22 and a rotating grating 18 formed on the rear surface 12 of the planar waveguide 20. The wavelength-range optical path _CR includes an input-coupled diffractive optics 30, an intermediate diffractive optics 32, and an output-coupled diffractive optics 34 arranged along the top surface 14 of waveguide 20, and an output-coupled diffractive optics 22 arranged along the bottom surface 12 of waveguide 20. In an embodiment, the input-coupled diffractive optics 16 and 30 are aligned with each other along a common imaginary axis perpendicular to the parallel bottom and top surfaces 12, 14. Similarly, the output-coupled diffractive optics 22 and 34 are also aligned along a common imaginary axis perpendicular to the parallel top and bottom surfaces 12, 14. The corresponding rotating gratings 18, 32 are not similarly aligned. It should be understood that any of a variety of arrangements of the wavelength-range optical path and its associated bandwidth range can be used. As shown in Figures 2A and 2B, in one embodiment, the image-carrying beam 102 passes through the ingress-coupled diffraction optics 30 on the top surface 14 of the waveguide 20, wherein a first portion of the image-carrying beam 102 within a first wavelength range is diffracted into the first planar waveguide 20 as the ingress-coupled image-carrying beam 50. In one embodiment, the first wavelength range is the red band. A second portion of the image-carrying beam 102 may include a second wavelength range passing through the ingress-coupled diffraction optics 16 on the bottom surface 12 of the waveguide 20, which is diffracted into the first planar waveguide 20 as the ingress-coupled image-carrying beam 52. In one embodiment, the second wavelength range is the blue band.

In one embodiment, the second portion of the image-carrying beam 102 may further include a third wavelength range passing through a second planar waveguide (not shown) having a third ingress-coupled diffractive optics. In one embodiment, the third wavelength range is in the green band. The ingress-coupled image-carrying beams 50, 52 propagate through the first planar waveguide 20 via total internal reflection (TIR) between the top planar surface 14 and the bottom planar surface 12. The ingress-coupled image-carrying beams 50, 52 may be redirected by rotating gratings 32, 18, respectively, and may be extended in at least one direction. The ingress-coupled image-carrying beam 50 may be extended in at least one direction and may be guided out of the first planar waveguide 20 as an outgress-coupled image-carrying beam _130R by an outgress-coupled diffractive optics 34. The ingress-coupled image-carrying beam 52 may be extended in at least one direction and may be guided out of the first planar waveguide 20 as an outgress-coupled image-carrying beam _130B by an outgress-coupled diffractive optics 22.

Typically, when a beam 104 carrying an image, for example in the red wavelength range, is coupled via an ingress-coupled diffraction optics 16 arranged for ingress coupling of a beam 106 carrying an image, for example in the blue wavelength range, the beam 50 carrying the image coupled to the beam 104 carrying the image will be at an extreme grazing angle and will not propagate through the first planar waveguide 20 via TIR. In an embodiment, the diffraction features 80 of the ingress-coupled diffraction optics 30 have a higher spacing than the diffraction features of the ingress-coupled diffraction optics 16, wherein the beam 52 carrying the image does not diffract at an angle greater than the critical angle, which interferes with the propagation of the beam 52 carrying the image through the first planar waveguide via TIR.

Crosstalk between wavelength-range optical paths can be problematic for many types of imaging systems, including arrangements using multiple stacked waveguides, but it is of particular concern for designs using a single waveguide, including double-sided waveguides. One approach to reduce crosstalk is to separate the optical paths within the waveguide as much as possible in terms of angle and distance. Thus, as shown in Figure 3D, the path of the image-carrying light in the wavelength-range optical path _CR is separated from the path of the image-carrying light in the wavelength-range optical path _CB by both angle and distance, so that light “leaking” into the wrong color path does not occur or is negligible. Therefore, as shown in Figures 3B-3C, the multiple periodic diffraction structures 82 of the in-coupled diffraction optics 16 are typically positioned at 90 degrees (90°) relative to the multiple periodic diffraction structures 80 of the in-coupled diffraction optics 30.

While it is necessary to reduce crosstalk at the input coupling diffraction optics 16, 30, surprisingly, this crosstalk can be beneficial in improving the output intensity and uniformity of the image-carrying light 130 across the entire output aperture. As shown in Figures 2A and 2B, the image-carrying beams 50, 52 interact with the output coupling diffraction optics 22, 34 on the "half-echo". For example, the image-carrying beam 50 interacts with the output coupling diffraction optics 22 on the half-echo and is output coupled as the image-carrying beam 130R _(1/2) , increasing the frequency and uniformity of the output coupled image-carrying beams _130R , _130R(1/2) . Furthermore, the image-carrying beam 52 interacts with the output coupling diffraction optics 34 on the half-echo and is output coupled as the image-carrying beam 130B _(1/2) , increasing the frequency and uniformity of the output coupled image-carrying beams _130B , _130B(1/2) .

In an imaging light guide system, light carrying an image at different angular ranges behaves similarly to light carrying an image at different wavelength ranges. The light carrying the image at different angular ranges can be used to provide an increased field of view (i.e., a wide field of view) for the virtual image. For example, as described above, an imaging light guide utilizing two optical paths for light carrying the image in two wavelength ranges can have full width at half maximum (FWHM) over an angular range of +/-15 degrees. Conversely, in embodiments where the wavelength range is the same for both optical paths in the imaging light guide 10, the first optical path can be used to propagate light in an angular range of -30 to 0 degrees, and the second optical path can be used to propagate light in an angular range of 0 to +30 degrees.

In an embodiment, the imaging light guide 10 is operable to provide multiple angular range paths, rather than multiple wavelength range paths. For example, image source 100 can generate an angle-dependent image-carrying beam 104 in the left angular range (e.g., -30 to 0 degrees) and an angle-dependent image-carrying beam 106 in the right angular range (e.g., 0 to +30 degrees). Similarly, image source 110 can generate an angle-dependent image-carrying beam 104 in the left angular range, and image source 112 can generate an angle-dependent image-carrying beam 106 in the right angular range. The imaging light guide 10 described above provides reduced crosstalk via improved separation of angular range paths.

Figure 5 is a perspective view illustrating a display system 60 for three-dimensional (3-D) augmented reality viewing using the imaging light guides of this disclosure. The display system 60 is shown as an HMD having a left-eye optical system 62L with a waveguide 20L for the left eye and a corresponding right-eye optical system 62R with a waveguide 20R for the right eye. An image source 100, such as a microprojector or similar device, can be provided, which can be excited to generate a separate image for each eye. The generated images can be stereoscopic image pairs for 3-D viewing. The virtual image transmitted to the viewer by the optical system can appear to be superimposed or overlaid on the real-world scene content seen by the viewer. Additional components familiar to those skilled in the art of augmented reality visualization, such as one or more imaging devices mounted on the frame of the HMD for viewing scene content or for viewer gaze tracking, can also be provided. In this embodiment, a separate projector is included for each eye.

Referring now to FIG6, in an embodiment, waveguide 20 may be designed with intermediate diffractive optics 18, 32. For example, output coupling diffractive optics 22, 34 may have increased area to increase the incident rate of the image-carrying beam propagating from input coupling diffractive optics 16, 30.

One or more features of the embodiments described herein can be combined to create additional embodiments not depicted. The invention has been described in detail with particular reference to the presently preferred embodiments; however, it will be understood that variations and modifications can be made within the spirit and scope of the invention. Therefore, the embodiments disclosed herein are to be considered illustrative rather than restrictive in all respects. The scope of the invention is indicated by the appended claims, and all variations within the meaning and scope of their equivalents are intended to be included therein.

Claims (20)

1. An imaging optical guide for transmitting virtual images, comprising: A waveguide having first and second parallel surfaces; A first ingress coupling diffraction optics arranged along the first surface, the first ingress coupling diffraction optics including a first plurality of periodic diffraction structures, wherein the first ingress coupling diffraction optics is operable to diffract a first portion of an image-carrying beam into the waveguide in an angle-coded manner, and wherein the first ingress coupling diffraction optics is operable to transmit a second portion of the image-carrying beam. A second ingress coupling diffraction optics arranged along the second surface, the second ingress coupling diffraction optics including a second plurality of periodic diffraction structures having a periodicity different from the first plurality of periodic diffraction structures, wherein the second ingress coupling diffraction optics is operable to diffract the second portion of the image-carrying beam into the waveguide in an angle-coded form; The first ingress coupling diffraction optical device and the second ingress coupling diffraction optical device are arranged coaxially along an imaginary axis perpendicular to the first surface. An out-coupled diffractive optics arranged along the first or second surface, wherein the out-coupled diffractive optics are operable to guide the first and second portions of a beam carrying an image from the waveguide toward the eyebox in an angled decoding manner. The out-coupled diffraction optics wherein the out-coupled diffraction optics defines at least two grating vectors. 2. The imaging light guide according to claim 1, wherein the first portion of the image-carrying light beam includes a first wavelength range, and the second portion of the image-carrying light beam includes a second wavelength range. 3. The imaging light guide according to claim 1, wherein the first portion of the image-carrying beam comprises an angled-correlated beam of a first range, and the second portion of the image-carrying beam comprises an angled-correlated beam of a second range different from the angled-correlated beam of the first range, wherein the first and second portions of the image-carrying beam form a wide field-of-view image. 4. The imaging light guide of claim 1, further comprising: a first intermediate diffractive optics disposed along the first surface and operable to guide the first portion of the image-carrying beam to the out-coupled diffractive optics; and a second intermediate diffractive optics disposed along the second surface and operable to guide the second portion of the image-carrying beam to the out-coupled diffractive optics, wherein preferably, the first intermediate diffractive optics is offset relative to the second intermediate diffractive optics. 5. The imaging waveguide according to claim 1, wherein the out-coupled diffraction optical device is a first out-coupled diffraction optical device, and the first planar waveguide further includes a second out-coupled diffraction optical device located on the first or second surface opposite to the first out-coupled diffraction optical device, wherein the second out-coupled diffraction optical device is aligned with the first out-coupled diffraction optical device. 6. The imaging optical guide according to claim 5, wherein the periodic diffraction characteristics of the first out-coupled diffraction optical device are the same as the periodic diffraction characteristics of the second out-coupled diffraction optical device. 7. The imaging light guide of claim 6, wherein the first and second out-coupled diffractive optics include two-dimensional periodic diffraction features operable to extend the first and second portions of the image-carrying beam and guide the extended image-carrying beam from the waveguide in an angled decoding manner. 8. The imaging light guide of claim 7, wherein the first and second portions of the image-carrying light beam interact with the first and second out-coupled diffractive optics on a half-echo, wherein at least a portion of the first and second portions of the image-carrying light beam out-couples on the half-echo interaction with the first and second out-coupled diffractive optics. 9. The imaging optical guide according to claim 6, wherein each periodic diffraction feature of the first set of periodic diffraction features of the first out-coupled diffraction optical device has a greater depth than each periodic diffraction feature of the second set of periodic diffraction features of the first out-coupled diffraction optical device. 10. The imaging optical guide according to claim 9, wherein each periodic diffraction feature of the first set of periodic features of the second out-coupled diffraction optical device has a greater depth than each periodic diffraction feature of the second set of periodic diffraction features of the second out-coupled diffraction optical device. 11. The imaging light guide of claim 6, wherein the first and second out-coupled diffractive optical devices each have a plurality of grating vectors, and wherein one of the grating vectors in each of the first and second out-coupled diffractive optical devices has an amplitude smaller than that of the other grating vectors. 12. The imaging light guide according to claim 1, wherein the second plurality of periodic diffraction structures of the second ingress-coupled diffraction optics are oriented at approximately 90 degrees relative to the first plurality of periodic diffraction structures of the first ingress-coupled diffraction optics. 13. The imaging light guide according to claim 1, wherein each of the first and second ingress coupling diffraction optical devices is further represented by an input grating vector, and wherein the input grating vector of the first ingress coupling diffraction optical device is orthogonal to the input grating vector of the second ingress coupling diffraction optical device within 5 degrees. 14. The imaging light guide according to claim 1, wherein the first ingress coupling diffraction optical device has a spacing different from that of the second ingress coupling diffraction optical device. 15. The imaging light guide according to claim 1, wherein the imaging light guide is part of a virtual reality imaging system or an augmented reality imaging system. 16. The imaging light guide according to claim 1, wherein the imaging light guide is part of an imaging light guide system, the imaging light guide system comprising a first beam source carrying an image and a second beam source carrying an image, each beam source generating an image of one of the three primary color bands, such that when combined, a multicolor virtual image is generated. 17. An imaging optical guide for transmitting virtual images, comprising: A first planar waveguide, operable to propagate a beam of light carrying an image, the first planar waveguide having first and second parallel surfaces; A first ingress coupling diffraction optics formed along the first surface, the first ingress coupling diffraction optics including a first plurality of periodic diffraction structures, wherein the first ingress coupling diffraction optics is operable to diffract a first portion of the image-carrying beam into the first planar waveguide in an angled encoded form, and wherein the first ingress coupling diffraction optics is operable to transmit a second portion of the image-carrying beam. A first out-coupled diffractive optics formed along the waveguide, wherein the first out-coupled diffractive optics is operable to extend the first portion of the image-carrying beam and guide the extended image-carrying beam from the waveguide in an angled decoding manner; A second ingress-coupled diffraction optics formed along the second surface, wherein the second ingress-coupled diffraction optics is operable to diffract the second portion of the image-carrying beam into the first planar waveguide in an angled encoded form, wherein the second ingress-coupled diffraction optics includes a second plurality of periodic diffraction structures having periodicity different from the first plurality of periodic diffraction structures of the first ingress-coupled diffraction optics. The first ingress coupling diffraction optical device and the second ingress coupling diffraction optical device are essentially co-located; A first intermediate diffraction optics, operable to guide a first portion of the image-carrying beam toward a first output coupling optics and a second portion of the image-carrying beam toward the first output coupling diffraction optics, and positioned along the first plane; and The first portion of the light beam carrying the image includes a first wavelength range, and the second portion of the light beam carrying the image includes a second wavelength range. 18. An imaging optical guide for transmitting virtual images, comprising: A first planar waveguide, operable to propagate a beam of light carrying an image, the first planar waveguide having first and second parallel surfaces; A first ingress coupling diffraction optics formed along the first surface, the first ingress coupling diffraction optics including a first plurality of periodic diffraction structures, wherein the first ingress coupling diffraction optics is operable to diffract a first portion of the image-carrying beam into the first planar waveguide in an angled encoded form, and wherein the first ingress coupling diffraction optics is operable to transmit a second portion of the first set of image-carrying beams; A first out-coupled diffractive optics formed along the waveguide, wherein the first out-coupled diffractive optics is operable to extend the first portion of the image-carrying beam and to guide the extended first portion of the image-carrying beam from the waveguide in an angled decoding manner; A second ingress-coupled diffraction optics formed along the second surface, wherein the second ingress-coupled diffraction optics is operable to diffract a second portion of an image-carrying beam into the first planar waveguide in an angle-coded manner, wherein the second ingress-coupled diffraction optics includes a second plurality of periodic diffraction structures having periodicity different from the first plurality of periodic diffraction structures of the first ingress-coupled diffraction optics; and A second out-coupled diffraction optics aligned with the first out-coupled diffraction optics on the second surface, wherein the second out-coupled diffraction optics is operable to extend the beam of the second set of image-bearing devices and guide the extended beam of the second set of image-bearing devices from the waveguide in an angled decoding manner. 19. The imaging light guide of claim 20, wherein the first group of image-carrying light beams includes a first wavelength range, and the second group of image-carrying light beams includes a second wavelength range. 20. The imaging light guide of claim 21, wherein the first group of image-carrying light beams comprises an angled-correlated beam of a first range, and the second group of image-carrying light beams comprises an angled-correlated beam of a second range different from the angled-correlated beam of the first range.