Light guide structure used to transmit images to the user's eyes

Abstract

An optical system provides a two-stage extension of the input optical aperture for a light-guide optics-based display. The first extension is achieved using two different sets of partially parallel reflective surfaces, each set processing a different portion of the entire field of view presented to the eye. In some cases, a single image projector provides image illumination to two sets of facets integrated into the LOE. In other cases, two separate projectors transmit image illumination corresponding to two different portions of the field of view to their respective sets of facets.

Description

Technical Field

[0001] This invention relates to optical systems, and more particularly, to optical systems including light-guide optical elements (LOEs) for achieving optical aperture expansion. Prior Technology

[0002] Many near-eye display systems include a transparent light-guide optics (LOE) or "waveguide" placed in front of the user's eyes, which transmits the image within the LOE via internal reflection and then couples the image out toward the user's eyes via a suitable output coupling mechanism. The output coupling mechanism can be based on an embedded partial reflector or "facet," or it can employ diffractive elements. The following description will primarily concern facet-based coupling arrangements. Summary of the Invention

[0003] The present invention is an optical system for guiding image illumination to an eye-tracking frame for viewing by the user's eyes.

[0004] According to the teachings of embodiments of the present invention, an optical system is provided for guiding image illumination injected into at least one coupling region to an eye-tracking frame for viewing by a user's eye. The optical system includes a light-guiding optical element (LOE) formed of a transparent material, the LOE comprising: (a) a first region comprising a first set of flat, mutually parallel partially reflective surfaces having a first orientation; (b) the first region further comprising a second set of flat, mutually parallel partially reflective surfaces having a second orientation not parallel to the first orientation; and (c) a second region comprising a third set of flat, mutually parallel partially reflective surfaces having a third orientation not parallel to each of the first and second orientations. (d) A set of parallel primary outer surfaces extending across a first region and a second region, such that a first set of partial reflective surfaces, a second set of partial reflective surfaces, and a third set of partial reflective surfaces are all located between the primary outer surfaces, wherein the third set of partial reflective surfaces is at an angle to the primary outer surfaces, such that a portion of the image illumination propagating from the first region to the second region within the LOE via internal reflection at the primary outer surfaces is coupled out of the LOE toward the eye-tracking frame, and wherein each of the first set of partial reflective surfaces and the second set of partial reflective surfaces is oriented such that a portion of the image illumination propagating within the LOE via internal reflection at the primary outer surfaces from at least one coupled region is deflected toward the second region.

[0005] According to another feature of an embodiment of the invention, a first set of partially reflective surfaces deflects a first portion of the image's field of view toward a second region, and a second set of partially reflective surfaces deflects a second portion of the image's field of view toward the second region, the first portion and the second portion of the field of view being combined to provide a larger consecutive combined field of view than each of the first portion and the second portion.

[0006] According to another feature of an embodiment of the invention, each of the first set of partially reflective surfaces and the second set of partially reflective surfaces includes a deflecting surface configured to reflect most of the image illumination incident on the deflecting surface, the deflecting surface being deployed as a first partially reflective surface reached by the image illumination injected into at least one coupling region of each of the first set of partially reflective surfaces and the second set of partially reflective surfaces.

[0007] According to another feature of an embodiment of the present invention, the deflecting surfaces of the first group of partially reflective surfaces and the deflecting surfaces of the second group of partially reflective surfaces intersect at a line.

[0008] According to another feature of an embodiment of the invention, each of the first set of partial reflective surfaces and the second set of partial reflective surfaces includes a filler surface adjacent to the deflecting surface, the filler surface having a length measured parallel to the main outer surface, the length being less than the length of the deflecting surface and less than the length of another partial reflective surface adjacent to the filler surface.

[0009] According to another feature of an embodiment of the present invention, the first group of partially reflective surfaces and the second group of partially reflective surfaces each have a non-uniform spacing between the partially reflective surfaces.

[0010] According to another feature of an embodiment of the invention, each of the partial reflective surfaces of the first group and the second group has a length measured parallel to the main outer surface, and each of the first group and the second group includes a partial reflective surface with different lengths.

[0011] Another feature of an embodiment of the invention is that the coupling region is within the middle third of the size of the LOE.

[0012] According to another feature of an embodiment of the invention, at least one edge of the LOE adjacent to a first region of the LOE is implemented as a mirror surface perpendicular to the main outer surface, and wherein the path of image illumination from the coupled region to a second region of the LOE includes at least one reflection from the mirror surface of at least one edge of the LOE.

[0013] According to another feature of an embodiment of the invention, an image projector is also provided, which is configured to project an image illumination corresponding to a collimated image. The image projector is optically coupled to the LOE at a coupling region so that the image illumination is injected into a first region of the LOE, thereby propagating within the LOE by internal reflection at the main outer surface. The image illumination is injected with an effective optical aperture and an effective propagation direction to be incident on the partial reflective surfaces of both the first set of partial reflective surfaces and the second set of partial reflective surfaces.

[0014] According to another feature of an embodiment of the invention, the size of the first set of partial reflective surfaces perpendicular to the effective propagation direction is larger than the size of the second set of partial reflective surfaces perpendicular to the effective propagation direction.

[0015] According to another feature of an embodiment of the present invention, the angle formed between the partially reflecting surface of the first set of partially reflecting surfaces and the effective propagation direction is smaller than the angle formed between the partially reflecting surface of the second set of partially reflecting surfaces and the effective propagation direction.

[0016] According to another feature of an embodiment of the invention, a first image projector is also provided, configured to project image illumination corresponding to a first portion of a collimated image, the first image projector being optically coupled to the LOE at a first coupling region such that the image illumination is injected into the first region of the LOE, thereby propagating within the LOE through internal reflection at the main outer surface and incident on the partial reflective surfaces of a first set of partial reflective surfaces; and a second image projector configured to project image illumination corresponding to a second portion of a collimated image, the second image projector being optically coupled to the LOE at a second coupling region such that the image illumination is injected into the first region of the LOE, thereby propagating within the LOE through internal reflection at the main outer surface and incident on the partial reflective surfaces of a second set of partial reflective surfaces, wherein the first and second portions of the collimated image are combined at the eye-tracking frame to provide a combined image.

[0017] According to another feature of an embodiment of the present invention, the first set of partially reflective surfaces and the second set of partially reflective surfaces are perpendicular to the main outer surface of the LOE.

[0018] According to another feature of an embodiment of the present invention, the first set of partially reflective surfaces and the second set of partially reflective surfaces are inclined to the main outer surface of the LOE.

[0019] According to the teachings of embodiments of the present invention, an optical system is also provided for transmitting an image to an eye-tracking frame for viewing by a user's eye. The optical system includes: (a) a light-guiding optical element (LOE) formed of a transparent material, the LOE including a set of mutually parallel primary outer surfaces and a set of outwardly coupled, mutually parallel, planar, partially parallel reflective surfaces located between the primary outer surfaces; (b) a first image projector configured to project image illumination corresponding to a first portion of a collimated image from an optical aperture, the image illumination entering the LOE from the optical aperture along a first optical path, propagating within the LOE via internal reflection at the primary outer surfaces, and gradually coupling outward from the LOE toward the eye-tracking frame via the outwardly coupled set of partially reflective surfaces; and (c) a second image projector configured to project image illumination corresponding to a second portion of a collimated image from an optical aperture, the image... Illumination follows a second optical path from the optical aperture into the LOE to propagate within the LOE via internal reflection at the main outer surface and gradually couples out from the LOE toward the eye-tracking frame via a set of outwardly coupled partial reflective surfaces. A first portion and a second portion of the collimated image are combined at the eye-tracking frame to provide a combined image; (d) a first optical extension component comprising a first set of flat, mutually parallel partial reflective surfaces having a first orientation, the first optical extension component being deployed in the first optical path to extend the optical aperture of the first image projector and guide image light toward the set of outwardly coupled partial reflective surfaces; and (e) a second optical extension component comprising a second set of flat, mutually parallel partial reflective surfaces having a second orientation, the second optical extension component being deployed in the second optical path to extend the optical aperture of the second image projector and guide image light toward the set of outwardly coupled partial reflective surfaces.

[0020] According to another feature of an embodiment of the present invention, the first optical extension component and the second optical extension component are external components optically coupled to the LOE, and wherein image illumination from the first image projector and the second image projector is injected into the LOE through the first optical extension component and the second optical extension component, respectively.

[0021] According to another feature of an embodiment of the invention, the first optical extension component and the second optical extension component are each implemented in a thick plate having two main surfaces, wherein one of the main surfaces is optically coupled to a coupling surface associated with the LOE.

[0022] Another feature of an embodiment of the invention is that the coupling surface is at an angle relative to the main outer surface of the LOE.

[0023] According to another feature of an embodiment of the invention, the thick plate of the first optical extension component is optically coupled to a first coupling surface associated with the LOE, and the thick plate of the second optical extension component is optically coupled to a second coupling surface associated with the LOE, wherein the first coupling surface and the second coupling surface are non-coplanar.

[0024] According to another feature of an embodiment of the invention, the coupling surface is coplanar or parallel to one of the main outer surfaces of the LOE, and wherein the LOE includes at least one at least partially reflective coupling surface.

[0025] According to another feature of an embodiment of the present invention, the first set of partially reflective surfaces and the second set of partially reflective surfaces are located within the LOE between the main outer surface of the LOE.

[0026] According to another feature of an embodiment of the present invention, the first set of partially reflective surfaces and the second set of partially reflective surfaces are perpendicular to the main outer surface of the LOE.

[0027] According to another feature of an embodiment of the invention, the first set of partially reflective surfaces and the second set of partially reflective surfaces are inclined relative to the main outer surface of the LOE.

[0028] According to another feature of an embodiment of the present invention, the first optical extension component further includes a third set of partially reflective surfaces that are not parallel to the first set of partially reflective surfaces, the first set of partially reflective surfaces and the third set of partially reflective surfaces extending the optical aperture of the first image projector in opposite directions and guiding the image light toward the outwardly coupled set of partially reflective surfaces.

[0029] According to another feature of an embodiment of the invention, the first image projector has a central optical axis, and wherein the tilt of the third set of partially reflective surfaces relative to the central optical axis is different from the tilt of the first set of partially reflective surfaces relative to the central axis. Simple Explanation of the Diagram

[0030] The invention is described herein by way of example only with reference to the accompanying drawings, in which: Figures 1A and 1B are schematic isometric views of an optical system implemented using a light-guiding optical element (LOE) with a teachable construction and operation according to a first aspect of the invention, showing a top-down construction and a side-injection construction, respectively. Figures 1C and 1D are schematic isometric views of an optical system employing two image projectors for each display, implemented using a light-guiding optical element (LOE) with a teaching construction and operation according to another aspect of the invention, showing a top-down construction and a side-injection construction, respectively; Figure 2 is a schematic plan view of the LOE construction used to realize the optical systems of Figures 1A and 1B; Figures 3 to 7 are schematic enlarged views of the first region of the LOE in Figure 2, showing various geometric elements used to determine the desired spacing and deployment of partial reflective surfaces in the first region of the LOE; Figure 8 is a schematic representation of the alternative implementation of the LOE in Figure 2; Figure 9 is another schematic representation of the LOE in Figure 2, showing the image projector coupled to the LOE via a wedge prism; Figures 10A to 10C are schematic representations of the relative deployment of some reflective surfaces within the LOE of Figure 2, showing asymmetric tilt, symmetrical arrangement, and off-center coupling regions of the surfaces, respectively. Figure 11 illustrates a particularly preferred implementation of the first region of the LOE of Figure 2, which combines the geometric elements presented in Figures 3 through 7 and employs a variable-length facet. Figures 12A and 12B are schematic representations of another variant implementation of the LOE of Figure 2, in which the first group of partial reflective surfaces and the second group of partial reflective surfaces are subdivided between the two segments of the LOE. Figure 13 is a schematic representation of another variant of the LOE of Figure 2 using the surface of an external peripheral mirror; Figure 14A is a schematic isometric view of the LOE construction used to realize the optical systems of Figures 1C and 1D; Figure 14B is a schematic representation of the subdivision of the entire field of view between two image projectors from the optical system of Figure 14A; Figures 15A and 15B are enlarged schematic isometric views of the LOE of the optical system from Figure 14A, showing the implementation methods of orthogonal and oblique partial reflective surfaces for the first optical aperture extension, respectively. Figure 16A is a side view of an alternative implementation of an optical system according to an aspect of the present invention, wherein an aperture expansion component outside the LOE is used to perform the first expansion of the optical aperture; Figures 16B to 16E are views of the optical system of Figure 16A along the viewing directions labeled V1, V2, V3, and V4 of Figure 16A, respectively; Figure 17 is a schematic representation of a dual-image projector element used with the optical systems of Figures 14A to 16E; Figure 18 is an enlarged schematic isometric view of a variant implementation of the LOE from the optical system of Figure 14A, wherein the optical aperture extension component for each image projector employs two sets of partially reflective surfaces; Figures 19A to 19C are isometric views of variations of the optical system of Figure 16A, wherein the optical aperture extender for each image projector employs two sets of partially reflective surfaces, and three options for optically coupling the optical aperture extender to the LOE are shown; Figures 20A to 20C are front, top, and side views, respectively, of another variation of the optical system of Figure 16A, showing the optical coupling of the optical aperture expansion component to the main outer surface of the LOE; Figures 21A to 21C are respectively a top view, a front view, and a side view of an optical aperture expansion component according to a variant implementation of the optical system of Figures 20A to 20C; and Figures 22A to 22C are the side view, top view, and front view of an optical system using the optical aperture expansion components of Figures 21A to 21C, respectively. Implementation

[0031] The present invention is an optical system for guiding image illumination to an eye-tracking frame for viewing by the user's eyes.

[0032] The principles and operation of the optical system according to the present invention can be better understood by referring to the accompanying drawings and description.

[0033] By way of introduction, certain aspects of the present invention relate to an optical system for guiding image illumination to an eye-motion box (EMB) via a light-guiding optical element (LOE) for viewing by a user's eyes. This optical system provides an optical aperture extension for use in a head-up display and most preferably a near-eye display, which may be a virtual reality display, or more preferably an augmented reality display. The optical system preferably provides a two-stage extension of the input optical aperture, wherein the first extension is achieved using two different sets of mutually parallel partially reflective surfaces (“facets”), each set of partially reflective surfaces treating different portions (not identical but preferably overlapping) of the entire field-of-view (FOV) presented to the eye. In a first subset of embodiments (Figures 1A, 1B, and Figures 2 through 13), the optical system employs a single image projector (“POD”) that provides image illumination to two sets of facets integrated into the LOE. In a second subset of embodiments, two separate PODs transmit image illumination corresponding to two different portions (not identical but preferably overlapping) of the FOV to their respective sets of facets. In the latter case, the first extension may take the form of a small set of planar components that are external to the LOE (Figures 16A to 16D and Figures 19A to 22C) or integrated into a portion of the LOE (Figures 1C, 1D, 14A to 15B and 18). These various subsets of non-limiting embodiments will be described separately below.

[0034] The general reference now adopts various embodiments of a facet integrated with a LOE (e.g., Figures 1A to 1D), all of which illustrate an optical system for guiding image illumination injected into at least one coupling region to an eye-tracking frame for viewing by a user's eye. Generally, the optical system includes a light-guide optical element (LOE) 12 formed of a transparent material and including a first region 16 comprising a first set of flat, mutually parallel partially reflective surfaces (facets) having a first orientation and a second set of flat, mutually parallel partially reflective surfaces (facets) having a second orientation not parallel to the first orientation (these facets are not visible in Figures 1A to 1D but will be schematically shown in the figures below). The LOE also includes a second region 18 comprising a third set of flat, mutually parallel partially reflective surfaces (or "facets," also referred to as "coupling surfaces") having a third orientation not parallel to each of the first and second orientations. The LOE is defined by a set of parallel main outer surfaces extending across the first and second regions, such that the first set of partially reflective surfaces, the second set of partially reflective surfaces, and the third set of partially reflective surfaces are all located between the main outer surfaces.

[0035] The third set of partially reflective surfaces is angled to the main outer surface, such that a portion of the image illumination propagating from the first region into the second region within the LOE via internal reflection at the main outer surface is coupled outward from the LOE toward the eye-tracking frame for viewing by the user's eye. Each of the first and second sets of partially reflective surfaces is oriented such that a portion of the image illumination propagating from at least one coupled region within the LOE via internal reflection at the main outer surface is deflected toward the second region.

[0036] Most preferably, each of the first and second sets of facets is responsible for aperture expansion of a different portion of the entire field of view. Specifically, preferably, the first set of partially reflective surfaces deflects a first portion of the image's field of view toward the second region, and the second set of partially reflective surfaces deflects a second portion of the image's field of view toward the second region, the first and second portions of the field of view being combined to provide a continuously combined field of view larger than each of the first and second portions of the FOV. Preferably, the two portions of the FOV generally correspond to the two sides (left and right or top and bottom) of the entire FOV, but have sufficient overlap of central regions to ensure complete and continuous coverage of the central field across the eye-tracking frame, which corresponds to an acceptable range of the observer's pupil position, and the display is designed for this acceptable range.

[0037] An exemplary embodiment of the invention takes the form of a near-eye display, typically designated 10, employing an LOE 12. A compact image projector (or “POD”) 14 is optically coupled to inject an image into the LOE 12 (interchangeably referred to as a “waveguide,” “substrate,” or “slab”), within which image light is captured in one dimension by internal reflection at a flat primary outer surface. Light impacts a first set of partially reflective surfaces and a second set of partially reflective surfaces (interchangeably referred to as “facets”), wherein each set of facets is tilted relative to the propagation direction of the image light, and each successive facet deflects a portion of the image light in a deflection direction, which is also captured / guided within the substrate by internal reflection. These first and second sets of facets are not shown separately in Figures 1A through 1D, but are located in a first region of the LOE designated 16. Partial reflection at the successive facets achieves an optical aperture expansion in the first dimension.

[0038] The first and second sets of partially reflective surfaces located in the first region 16 deflect the image illumination from a first propagation direction captured within the substrate by total internal reflection (TIR) ​​to a second propagation direction also captured within the substrate by TIR. Partial reflection at successive facets achieves optical aperture expansion in the first dimension. In the cases of Figures 1C and 1D, two image projectors 14 are provided for each display, and the image illumination of each projector is expanded by a corresponding set of partially reflective surfaces in the first region 16.

[0039] The deflected image illumination then enters a second substrate region 18, which can be implemented as adjacent different substrates or as a continuation of a single substrate. In the second substrate region 18, a coupling arrangement (another set of partially reflective facets or diffractive optical elements) gradually couples a portion of the image illumination toward the observer's eye located within the area defined as the eye-tracking frame (EMB), thereby achieving a second-dimensional optical aperture expansion. The entire device can be implemented separately for each eye, and preferably, the entire device is supported relative to the user's head, with each LOE 12 facing the user's corresponding eye. In a particularly preferred option shown here, the support arrangement is implemented as an eyeglass frame having sides 20 for supporting the device relative to the user's ears. Other forms of support arrangements can also be used, including but not limited to headbands, visors, or devices suspended from a helmet.

[0040] The X-axis and Y-axis are mentioned in the accompanying drawings and claims. The X-axis extends horizontally (Fig. 1A and Fig. 1C) or vertically (Fig. 1B and Fig. 1D) in the general direction of extension of the first region of the LOE. The Y-axis extends perpendicular to the X-axis, that is, it extends vertically in Fig. 1A and Fig. 1C and horizontally in Fig. 1B and Fig. 1D.

[0041] In very approximate terms, the first region 16 of the first LOE or LOE 12 can be considered to achieve aperture expansion in the X direction, while the second region 18 of the second LOE or LOE 12 achieves aperture expansion in the Y direction. The details of the angular expansion of the different parts of the field of view will be described more precisely below. It should be noted that the orientations shown in Figures 1A and 1C can be considered as a “top-down” implementation, where the image illumination entering the main (second region) of the LOE enters from the top edge, while the orientations shown in Figures 1B and 1D can be considered as a “lateral injection” implementation, where the axis referred to here as the Y-axis is horizontally deployed. In the remaining figures, various features of certain embodiments of the invention will be described in the context of the “top-down” orientations similar to those in Figures 1A and 1C. However, it should be understood that all these features are equally applicable to the lateral injection implementation, which also falls within the scope of the invention. Other intermediate orientations may also be applicable in some cases and are included within the scope of the invention, except where explicitly excluded.

[0042] In a first set of preferred but non-limiting examples of the invention, the aforementioned set of facets is orthogonal to the main outer surface of the substrate. In this case, the injected image and its conjugate, which undergoes internal reflection as it propagates within the first region 16, are deflected and become a conjugate image propagating in the deflection direction. In an alternative set of preferred but non-limiting examples, the first set of partially reflective surfaces and the second set of partially reflective surfaces are at an angle relative to the main outer surface of the LOE. In the latter case, the injected image or its conjugate forms the desired deflected image propagating within the LOE, while other reflections can be minimized, for example, by employing an angle-selective coating on the facets, making the facets relatively transparent to the range of incident angles presented by images from which reflections are not desired.

[0043] Preferably, the POD used in the apparatus of the present invention is configured to generate a collimated image, that is, in the collimated image, the light of each image primitive is a parallel beam collimated to infinity with an angular direction corresponding to the primitive position. Therefore, the image illumination spans the angular range corresponding to the two-dimensional angular field of view.

[0044] Image projector 14 includes at least one light source, typically deployed to illuminate a spatial light modulator such as an LCOS wafer. The spatial light modulator modulates the projection intensity of each pixel of the image, thereby generating the image. Alternatively, the image projector may include a scanning arrangement, typically implemented using a fast scanning mirror, that scans illumination from a laser source across the image plane of the projector while synchronously changing the intensity of the beam on a pixel-by-pixel basis with motion, thereby projecting the desired intensity onto each pixel. In both cases, collimating optics are provided to generate an output projected image collimated up to infinity. As is known in the art, some or all of the above components are typically arranged on the surface of one or more polarizing beam splitter (PBS) cubes or other prism arrangements.

[0045] The optical coupling from image projector 14 to LOE 12 can be achieved by any suitable optical coupling, such as via a coupling prism with an angled input surface, or via a reflective coupling arrangement, via one of the sides and / or main outer surfaces of the LOE. Details of the coupling configuration are not critical to the present invention, and are shown herein as a non-limiting example of a wedge prism 800 applied to one of the main outer surfaces of the LOE.

[0046] It should be understood that the near-eye display 10 includes various additional components, typically including a controller 22 for actuating the image projector 14, which typically draws power from a small onboard battery (not shown) or some other suitable power source. It should be understood that the controller 22 includes all necessary electronic components, such as at least one processor or processing circuitry, to drive the image projector, all of which are well known in the art.

[0047] Reference is made to the commonly assigned PCT patent application publication WO 2020 / 049542 A1 (hereinafter referred to as “'542 publication”), which was not published as of the priority date of this application and is not prior art, but the entire contents of that PCT patent application are incorporated herein by reference as if fully set forth herein. Unless otherwise stated, all features of the invention should be understood as described in the '542 application.

[0048] The first aspect of the invention differs from the construction described in application '542 primarily in that the first region 16 of the LOE here comprises two distinct sets of partially reflective facets, rather than a single set as disclosed in '542. These facets are typically in different (non-parallel) orientations, and each set of partially reflective facets independently guides a different portion of the image field of view toward the second LOE region 18 to couple out toward the eye-tracking frame. Such a construction is implied by two arrows pointing in opposite directions in Figures 1A and 1B, and is schematically illustrated in Figure 2.

[0049] Specifically, in the non-limiting but preferred example of Figure 2, POD 14 injects an image into a first region of LOE 12 near the middle of the LOE size (typically within the middle third). The injected image is then partially reflected by two sets of partially reflective surfaces 161 and 162 to expand the image in opposite directions along the X-axis and to gradually deflect the image from successive facets toward a second region of the LOE, in which the image is gradually coupled toward the eye-tracking frame by another set of tilted partially reflective facets or by diffractive optics for viewing by the observer.

[0050] Preferably, the first facet of each of the first two groups of partially reflective surfaces is a deflecting surface with relatively high reflectivity (alternatively referred to as a "coupled facet") that reflects more than half (and typically at least 80%) of the image illumination incident on the facet. Preferably, subsequent facets in each group have lower reflectivity (typically except for the last facet) and may have gradually increasing reflectivity from facet to facet, such as 25%, 33%, 50%, and 100%, thus tending to compensate for the gradually decreasing illumination intensity reaching the successive facets, thereby providing a relatively uniform intensity output.

[0051] In some implementations, using two sets of small planes that extend the optical aperture in opposite directions from the coupling region near the middle of the LOE size can shorten the optical path length from the projector to the eye-tracking frame, and thus reduce the overall size of the device required to provide a given field of view for the observer compared to the construction of the aforementioned '542 application.

[0052] According to a particularly preferred set of implementations of the invention, the facets are implemented as “partial facets” such that the partial reflective properties exist only within a sub-region of the cross-sectional region of the first region, which includes the “imaging region” of the plane of each facet, and preferably, exclude at least a majority of some or all of the “non-imaging regions” of the facets. This is illustrated by the varying lengths of facets 161 and 162 in FIG. 2. The effective (partially reflective) regions of these facets are preferably extended slightly beyond the minimum required to complete the geometry of EMB image projection to avoid anomalies that may be caused by defects at the coating edges, and in some cases, the facets may be further extended to achieve improved image uniformity due to additional considerations related to integer overlap between facets in the deflection image direction.

[0053] In the case where the first region is formed by a stack of coated plates (which are then cut at an appropriate angle) (as described, for example, in PCT Patent Publication No. WO2007054928A1 and known in the art), selective spatial deployment of the partial reflective surface can be advantageously achieved by forming the stack of plates, wherein the partial reflective coating is located on a first portion of the interface plane between two plates, while a second portion of the interface plane is joined (typically using a refractive index-matching adhesive and without coating) to form an optical continuum between the two plates. The selective application of the partial reflective coating is typically achieved by applying a suitable masking layer prior to the coating process and removing the masking layer at the end of the coating process.

[0054] According to alternative production techniques, stacks of full-area coated plates can be formed and then cut into the desired shape to include the facets. The desired form of the LOE is then achieved by optically bonding this irregular block containing the partially reflective facets to a complementary block of ordinary refractive index-matching glass.

[0055] The optical axis is not actually parallel to the X-axis, but lies in the XZ plane, where the Z component entering the page is chosen such that the entire angular range of the depth dimension of the FOV undergoes total internal reflection at the surface of the main substrate. As described in detail in application '542, the optical axis can also be offset from the X-axis in the Y direction to optimize the LOE design. For simplicity, the graphical representations and descriptions herein will only refer to the in-plane (XY) components of the ray propagation direction, referred to herein as "in-plane components" or "components parallel to the main outer surface of the LOE".

[0056] It should be noted that some reflections from the left side of the field of view are reflected from a small plane near the right side of the LOE in a direction that will not reach the EMB, and are therefore lost. Similarly, some light rays from the right side of the field of view are reflected from a small plane near the left side of the LOE and deflected in a direction that will not reach the EMB, and are therefore lost. Some aspects of the invention utilize these observations to reduce the size of the first LOE (or LOE region) (and thus reduce volume and weight).

[0057] The distance between adjacent facets 161 and 162 depends on the size of the inlet aperture and the field of view (FOV) of the coupling region, and this distance must be designed to properly replicate the inlet aperture uniformly throughout the EMB without any empty areas. As shown in Figure 3, for a given inlet aperture size, a constant spacing between facets 161 or 162 will cause non-uniform illumination and result in bright or dark "stripes." To avoid this, as will be discussed in detail now, geometric considerations should be used to set the distance between adjacent facets to minimize the occurrence of such stripes.

[0058] As shown in Figure 4, the distance between adjacent facets should be chosen to replicate the entrance aperture without any holes or overlaps. As illustrated in Figures 5 and 6, since each facet reflects a subset of the complete field of view (FOV), this distance should be optimized for the relevant subset of the FOV, and it is desirable that this distance vary between adjacent facets. However, changing the distance between adjacent facets only minimizes the effect of bright or dark "stripes" that begin outside the coupling region. As schematically shown in Figure 7, the first dark "stripe" can be minimized by adding an additional facet between the first two facets—which will redirect the light to the dark region.

[0059] Figure 8 illustrates another embodiment of the invention that helps improve the uniformity of the illuminated output image throughout the EMB, comprising a plurality of closely spaced facets. Compared to the facets described above, by reducing the facet spacing in integer increments, any non-uniformity in the image can be better averaged, thereby mitigating image non-uniformity. Furthermore, since it is extremely difficult to design an achromatic high-reflectivity coating with constant uniform reflectivity for a large FOV, it is advantageous to divide the reflectivity of the first facet onto a plurality of facets, as illustrated by the gray facets in Figure 8.

[0060] Light needs to be coupled from the POD into the waveguide. One way to achieve this is by using a wedge placed between the optical axis of the illumination system in the POD and the plane of the waveguide, as shown in Figure 9.

[0061] So far, symmetrical configurations have been discussed and presented, such as those shown in Figure 10A. However, the two small planes 161 and 162 need not be symmetrical, and the FOV treated by each set of small planes can be different. For example, it is generally preferred to place the POD in a position that is not centered relative to the EMB, as shown in Figure 10B. Furthermore, as in Figure 10C, the angular orientation of the small planes in the two regions can be different, either because the size of the FOV illuminated by each part is different (in which case the sizes of the two regions will generally not be the same), or if the azimuth orientation of the small plane in region 18 is not parallel to / perpendicular to the principal axis of the FOV.

[0062] To minimize ghosting and improve efficiency, as mentioned above, it is advantageous to use "partial facets". Figure 11 schematically illustrates an implementation of this concept of the present application.

[0063] Figures 12A and 12B present another embodiment of the invention in which the two sub-parts of facets 161 and 162 are placed one after the other, rather than side-by-side as in all the previous figures. In such an embodiment, the orientations of the facets in facets 161 and 162 can be substantially opposite to each other, such that light will propagate to opposite orientations (right and left in the figures), as shown in Figure 12A, or the orientations of the facets in facets 161 and 162 can be substantially parallel, such that light in both parts propagates in the same general direction, as shown in Figure 12B. In the latter configuration, the coupling region is positioned around the edge of the first region 16, thereby simplifying the structure of the coupling region and minimizing the non-uniformity effect at the central FOV (principal ray). As shown in Figure 10C, the angular orientations of the facets in Figures 12A and 12B do not need to be the same. (Although not explicitly shown, the option of changing the facet angles in the arrangement of Figure 12A is also possible).

[0064] Figure 13 illustrates the following configuration: the surface of the waveguide in the first region 16 is coated with a highly reflective coating, such as a silver coating, and the facet 161 (162) is oriented such that light striking the facet can be reflected to surface 163 (164) and then reflected back into the second region 18, or light striking the facet can be transmitted through the facet 161 (162), reflected away from edge 165 (166), reflected by the facet 161, and redirected into the second region 18. The angular orientation of surfaces 163 to 166 must be very precise, otherwise there will be a large degree of image ghosting.

[0065] Here and elsewhere in this text, it should be noted that the terms “trimming” and “truncation” are used to refer to a reduction in the geometry or dimensions of the final product relative to the theoretical starting point of the implementation, and generally result in different facets having different lengths measured parallel to the main outer surface of the LOE. The term does not imply any physical removal of material or any other particular manufacturing technique. It is not necessary to assume that the LOE will be precisely truncated along the boundaries of the indicated areas, but rather that these areas provide design flexibility, allowing an LOE to be machined with any arbitrary external contour to be considered aesthetically preferred and / or mechanically compatible with additional details desired for the application.

[0066] It should be noted that using the partial facets described above can provide one or more advantages, including improved efficiency and brightness, where the transmission of images from facets farther from the coupling region does not need to pass through so many additional facets before reaching the second LOE region. Furthermore, in some cases, omitting facets in areas unnecessary for image projection can avoid undesirable "ghosting" reflections that could otherwise degrade image quality.

[0067] Turning now to Figures 1C, 1D, and 14A through 22C, another set of embodiments of the invention employs two different image projectors to provide different portions of the entire field of view of the displayed image to the user's eye. Thus, generally speaking, according to this aspect of the invention, the optical system 10 for transmitting an image to the eye-tracking frame for viewing by the user's eye includes a light-guide optical element (LOE) 12 formed of a transparent material, in which a set of outwardly coupled, flat, mutually parallel partially reflective surfaces are disposed between a set of mutually parallel main outer surfaces. A first image projector POD 1 is configured to project an image illumination corresponding to a first portion of a collimated image from an optical aperture, the image illumination following a first optical path from the optical aperture into the LOE to propagate within the LOE via internal reflection at the main outer surfaces and to be gradually coupled outward from the LOE toward the eye-tracking frame via the outwardly coupled set of partially reflective surfaces. The second image projector POD 2 is configured to project an image illumination corresponding to a second portion of the collimated image from the optical aperture. This image illumination follows a second optical path from the optical aperture into the LOE to propagate within the LOE via internal reflection at the main outer surface and is gradually coupled outward from the LOE toward the eye-tracking frame via an outwardly coupled set of partially reflective surfaces. Alternatively, as known in the art, the outwardly coupled set of facets can be replaced by diffractive optical elements for gradually coupling the image illumination toward the EMB. The first and second portions of the collimated image are combined at the eye-tracking frame to provide a combined image.

[0068] A particularly preferred feature of this aspect of the invention is that the optical system further includes a first optical expansion component comprising a first set of flat, mutually parallel partially reflective surfaces having a first orientation, and is deployed in a first optical path to expand the optical aperture of the first image projector and guide image light toward the outwardly coupled set of partially reflective surfaces. Similarly, the optical system includes a second optical expansion component comprising a second set of flat, mutually parallel partially reflective surfaces having a second orientation, and is deployed in a second optical path to expand the optical aperture of the second image projector and guide image light toward the outwardly coupled set of partially reflective surfaces.

[0069] Figure 14B illustrates how the field of view (FOV) is divided between two PODs in a non-limiting implementation of the invention. Each POD illuminates a portion of the FOV, and together they form the entire FOV projected onto the observer's retina. Here, each of the two PODs is responsible for an equal-sized FOV; alternatively, one POD may provide a larger portion of the FOV than the other. As shown, to reduce boundary artifacts, it is generally preferable to include an overlapping region in the FOV between the two PODs.

[0070] According to a first subset of these implementations, as shown in Figures 14A to 15B and Figure 18, a first set of partially reflective surfaces 161 and a second set of partially reflective surfaces 162 are located within the LOE 12 between the main outer surface of the LOE. As in an earlier embodiment, this implementation may employ a first set of partially reflective surfaces 161 and 162 perpendicular to the main outer surface of the LOE, as shown in Figures 14A and 15A. In this case, the injected image and its conjugate undergoing internal reflection as it propagates within the first region 16 are deflected and become a conjugate image propagating in the deflection direction. Alternatively, a first set of partially reflective surfaces 161 and 162 may be used at an angle relative to the main outer surface of the LOE, as shown in Figure 15B. In the latter case, the injected image or its conjugate forms the desired deflected image propagating within the LOE, while other reflections can be minimized, for example, by employing an angle-selective coating on the facet, wherein the angle-selective coating makes the facet relatively transparent to the range of incident angles presented by images from which reflection is not desired. In these implementations, the structural and design elements of each part (e.g., half) of the first region 16 of LOE 12 are generally similar to the structure described in the aforementioned '542 publication.

[0071] Optionally, one or two of the PODs may be provided with two sets of partially reflective surfaces with different orientations, such that one or both portions of the first region 16 of the LOE 12 can be implemented according to the teachings of Figures 2 to 13 above. An example of such an implementation is schematically shown in Figure 18, wherein the first image projector POD 1 injects image illumination via a first optical extension component, which includes a first set of partially reflective surfaces 161 and a third set of mutually parallel partially reflective surfaces 163 that are not parallel to the surfaces 161. The first set of facets 161 and the third set of facets 163 extend the optical aperture of the first image projector POD 1 in opposite directions along the X-axis in a manner similar to that described above, and guide the image illumination toward an outwardly coupled set of partially reflective surfaces 181 in the second region 18 of the LOE 12.

[0072] Preferably, the second image projector POD 2 also injects image illumination via a second optical extension component, which includes a second set of partially reflective surfaces 162 and a fourth set of mutually parallel partially reflective surfaces 164 that are not parallel to the surfaces 162. The second set of facets 162 and the fourth set of facets 164 extend the optical aperture of the second image projector POD 2 in opposite directions along the X-axis in a manner similar to that described above, and guide the image illumination toward an outwardly coupled set of partially reflective surfaces 181 in the second region 18 of LOE 12. As described above with reference to FIG14B, the two portions of image illumination provided by the first and second image projectors are preferably combined in a slightly overlapping manner at the EMB to provide the user with a fully combined FOV.

[0073] When two sets of facets are used for aperture expansion for a single image projector, the arrangement can be symmetrical or asymmetrical relative to the positioning of the input aperture, the tilt of the facets, and any other design elements, and the length of the facets and their reflectivity can vary along the facet sequence, all as discussed above in the context of single image projector implementations.

[0074] An alternative implementation of this aspect of the invention employs a first optical extension component and a second optical extension component, which are external to and optically coupled to the LOE. Examples of such implementations will now be described with reference to Figures 16A to 16D and Figures 19A to 22C. In these non-limiting but preferred examples, image illumination is injected from the first image projector 210 and the second image projector 220 into the LOE 403 via the first optical extension component 203L and the second optical extension component 203R, respectively.

[0075] As can be seen in Figures 16A to 16D, the first optical extension component 203L and the second optical extension component 203R can each advantageously be implemented as a thick plate having two main surfaces, one of which is optically coupled to a coupling surface associated with LOE 403. In the case shown here, integrating the two components into a single thick plate 203 facilitates the manufacture and assembly of the components. Optical coupling from the thick plate 203 to LOE 403 can be achieved via a wedge prism 800 or other suitably shaped coupling prism, thereby providing a coupling surface at an angle relative to the main outer surface of LOE 403. The angle of the coupling surface is chosen to allow image illumination to be directly coupled within a certain angular range propagating through internal reflections at the main outer surface of LOE 403. Direct optical coupling from the thick plate 203 to the angled edge of LOE 403 is also possible, as illustrated in Figure 19A below.

[0076] Although the illustrations in Figures 16A to 16D show the first optical extension member 203L and the second optical extension member 203R as portions of a flat plate 203 attached to a common flat coupling surface, in some particularly preferred but non-limiting examples, separate coupling surfaces at different angles can be used. In such a case, as illustrated in Figure 19C, the plate of the first optical extension member 203L is optically coupled to the first coupling surface 802L associated with LOE 403, and the plate of the second optical extension member 203R is optically coupled to the second coupling surface 802R associated with LOE 403, wherein the first coupling surface 802L and the second coupling surface 802R are not coplanar. Using non-coplanar coupling surfaces can facilitate certain design elements, particularly when attempting to achieve a wide field of view.

[0077] As an alternative to the aforementioned edge coupling, certain other implementations of this aspect of the invention employ coupling from the first optical extension member 203L and the second optical extension member 203R to the image illumination of the LOE 403 via a coupling surface coplanar or parallel to one of the main outer surfaces of the LOE 403. In this case, preferably, the LOE 403 includes at least one at least partially reflective coupling surface. Implementations of this method will be discussed herein with reference to Figures 20A to 22C.

[0078] As in the integrated implementation, the first optical extension member 203L and / or the second optical extension member 203R can also be implemented here using two different sets of partially reflective surfaces to extend the optical aperture for each image projector, as illustrated in the examples of Figures 19A to 22C. Figure 19A schematically shows an example of such an implementation, in which the first image projector POD 1 injects image illumination via the first optical extension member 203L, which includes a first set of partially reflective surfaces 205 and a third set of mutually parallel partially reflective surfaces 207 that are not parallel to the surfaces 205. The first set of facets 205 and the third set of facets 207 extend the optical aperture of the first image projector POD 1 in opposite directions along the X-axis and guide the image illumination toward the coupling interface with the waveguide 403 to propagate within the LOE 403 by internal reflection until it is coupled out toward the EMB by the outward coupling facet 404.

[0079] Preferably, the second image projector POD 2 also injects image illumination via a second optical extension component 203R, which includes a second set of partially reflective surfaces 206 and a fourth set of mutually parallel partially reflective surfaces 208 that are not parallel to the surfaces 206. The second set of facets 206 and the fourth set of facets 208 extend the optical aperture of the second image projector POD 2 in opposite directions along the X-axis and guide the image illumination toward the coupling interface with the waveguide 403 to propagate within the LOE 403 via internal reflection until it is coupled out toward the EMB via the coupling out facet 404. The two portions of image illumination provided by the first and second image projectors are preferably combined at the EMB in a slightly overlapping manner to provide the user with a fully combined FOV, as described above with reference to FIG14B.

[0080] When using two sets of facets for aperture expansion for a single image projector, this arrangement can be symmetrical or asymmetrical relative to the position of the input aperture, the tilt of the facets, and any other design elements. Furthermore, the length of the facets and their reflectivity can vary along the facet sequence, all as discussed above in the context of single image projector implementations. Examples of asymmetrical facet tilt relative to the central optical axis of the first image projector and, in this case, also relative to the second image projector, are shown in Figures 21A and 21B. This allows for optimization of the facet angles of corresponding portions of the field of view associated with the illumination EMB.

[0081] Referring to FIG17, an exemplary implementation of a system 201 for light expansion is shown. This system 201 includes two optical aperture expansion components 203L and 203R, integrated into a single plate-like element 203, for expanding the optical apertures of two image projectors 210 and 220 to be injected into the LOE (not shown in this view). The optical aperture expansion components expand the effective apertures of the two image projectors to be subsequently injected into the LOE for display to the user. In the current figure, the view is from the edge of the optical aperture expansion components. The aperture expansion structure can be symmetrical and can be included on the sides or more generally outside the field of view as mirrors.

[0082] Figure 17 illustrates non-limiting details of possible implementations of the image projectors suitable for use in any and all of the dual POD implementations described herein. In the non-limiting example shown here, a common light source (e.g., LED light source 202) is provided to illuminate the two image projectors, as part of the exemplary light source configuration 200, illuminating two “PODs” (microdisplay projectors), left POD 210 and right POD 220. Note that “left” and “right” are used throughout this specification for convenience and clarity of reference and are not intended to limit, for example, orientation or position. Each POD typically provides approximately half of the original image (the original image is not shown) and provides a left collimated image 204CL and a right collimated image 204CR to the corresponding aperture expansion members 203L and 203R. The two collimated images 204C propagate along the x-axis, expand within the aperture expansion members, and are projected from the aperture expansion members into LOE 403, shown as the main ray left-coupled ray 238L and right-coupled ray 238R. As shown in the other figures, the left-outgoing ray (238L) and the right-outgoing ray (238R) traverse the LOE 403 and are coupled out along the z-axis from the single LOE 403 at the outwardly coupled partial reflective surface 404 as outwardly coupled rays (left outwardly coupled ray 38L and right outwardly coupled ray 38R) in the direction of the user (the user's eye).

[0083] An exemplary light source 200 typically comprises light 202 provided by one or more LEDs or other sources known in the art, and is typically capable of rapidly switching between red, green, and blue illumination to illuminate successive color image separations that together constitute a single “frame” of the image to be projected. The light 202 is typically extended by an extender 205 and can then be split into two beams (shown as left and right dashed lines) by, for example, a polarization-selective reflector (PBS) 206, to propagate via corresponding light tubes (left light tube 207L and right light tube 207R) to the respective left POD 210 and right POD 220.

[0084] Each of the exemplary PODs (left POD 210 and right POD 220) receives a corresponding beam (left beam and right beam), which is traversed by a PBS (left PBS 214, right PBS 224) to impact the display devices (left display device 212 and right display device 222). Images can be obtained directly from a spatial light modulator (SLM) or indirectly by means of a relay lens or fiber optic bundle from each display device (212, 222), where the SLM is, for example, a cathode ray tube (CRT), a liquid crystal display (LCD), a liquid crystal on silicon (LCoS), a digital micromirror device (DMD), an OLED display, a scanning source, or a similar device. As described below with reference to FIG14B, the image from each display device (212, 222) is typically approximately half of the entire image to be displayed. Each half of the image is propagated in PODs (210, 220) via PBSs (left PBS 214, left PBS 216, right PBS 224, and right PBS 226), and collimated by collimators (left collimator 218 and right collimator 228). The collimated images (left collimated image 204CL and right collimated image 204CR) are output from PODs (210, 220) and enter the corresponding aperture expansion components 203L and 203R.

[0085] The exemplary description of light source 200 and PODs (210, 220) is non-limiting. Based on this description, those skilled in the art will be able to implement other light sources and image sources. For example, each POD may use different portions of a single LCOS, and each POD may have its own individual LED.

[0086] Each of the aperture extension components 203L and 203R includes a first region (left first region 54L and right first region 54R) in which corresponding collimated images (left collimated image 204CL and right collimated image 204CR) are coupled into the substrate. Each of the aperture extension components includes a corresponding waveguide (left waveguide 20L and right waveguide 20R), which are also referred to as the "planar substrate" and the "transparent substrate". Each of the waveguides (20L, 20R) includes at least two parallel (main) surfaces, shown in the current figure as a lower (main) surface 26 and an upper (main) surface 26A. Each of the waveguides (20L, 20R) includes a corresponding set of facets (left facet 22L and right facet 22R) between the first two surfaces (26, 26A), which are shown as double lines. Each set of facets (22L, 22R) includes a first facet (left first facet 40AL, right first facet 40AR) on the side of the facet closest to the first region (54L, 54R), where the collimated image (204CL, 204CR) is coupled into the substrate (20L, 20R). Similarly, each set of facets (22L, 22R) includes a last facet (left last facet 40BL, right last facet 40BR) on the far side of the facet from the first region (54L, 54R). As the collimated light (204CL, 204CR) propagates in the sides (203L, 203R) of the corresponding aperture expander, the captured propagating light is gradually coupled out from the aperture expander 203 as the left coupled-out ray 238L and the right coupled-out ray 238R through the partially reflective surfaces of the facets (22R and 22L). The area where light rays decouple from the sides of the aperture expanders (203L, 203R) and enter a single LOE 403 is shown as the corresponding field of view (FOV) (left FOV-L and right FOV-R). This configuration of the aperture expanders allows for the use of highly reflective surfaces or mirrors in certain locations, since these surfaces are not within the user's FOV. For example, the first plane (40AL, 40AR) and the last plane (40BL, 40BR) can be 100% reflective.

[0087] Using two separate PODs to inject different parts of the entire field of view can provide any of the advantages, including but not limited to achieving an enhanced field of view, and allowing the size and weight of the POD to be reduced compared to the size and weight required to provide the entire image with a single POD.

[0088] Each POD will project approximately half of the beam of the image. For example, for a 55.5° (degree) FOV system with an aspect ratio of 16 / 9, a single POD will typically project a beam of 48.44° horizontally and a beam of 27.22° vertically.

[0089] By using the aperture expansion component described above to divide the FOV horizontally, each POD will process a 24.22° × 27.22° FOV. As mentioned above, there is preferably some overlap between the two PODs. If each POD overlaps by 3°, then each POD will project 27.22° × 27.22° degrees, with a 3-degree overlap. The image (picture) can be divided into two display devices (212, 222) in each of the two corresponding PODs (210, 220), with some information shared by both PODs. The concept of dividing into two PODs can be understood more fully by referring to Figures 16A to 16D, which include simulated light trails. It is assumed that each POD has its own SLM (LCOS in this example) and can have its own or a shared lighting system.

[0090] Figures 16B, 16C, 16D, and 16E correspond to the views along the viewing directions V1, VI2, V3, and V4, respectively, as shown in Figure 16A.

[0091] Referring to FIG16C, a schematic diagram of the system 201 from a top angle is shown, in which a single LOE 403 is partially visible below (at an angle) the aperture expander 203. The left POD 210 is shown to provide a left collimated image 204CL to the aperture expander 203L, wherein the rays of the left collimated image 204CL are shown as the left first edge 410L and the left second edge 412L of the image. The rays from the left first edge (410L) and the left second edge (412L) are shown to propagate via the aperture expander 203L and be coupled out as a left-coupled ray 238L into the single LOE 403, which then couples the left-outward coupled ray 38L toward the EMB.

[0092] Similarly, the right POD 220 is shown to provide a right collimated image 204CR to the aperture expansion member 203R, wherein the rays of the right collimated image 204CR are shown as the right first edge 410R and the right second edge 412R of the image. The rays of the right first edge (410R) and the right second edge (412R) are shown to propagate via the aperture expansion member 203R and be coupled out as right outward coupled rays 238R into a single LOE 403, which then couples the right outward coupled rays 38RL toward the EMB.

[0093] The propagating light rays are integrated into the eye position (EMB) represented by a square detector in a single LOE 403.

[0094] Referring to Figure 16E, a schematic diagram of the system 201 from the front view is shown, in which a single LOE 403 is visible below the aperture expander 203. The z-axis "comes out of the page," so outwardly coupled rays (left outwardly coupled ray 38L and right outwardly coupled ray 38R) "come out of the page" toward the user's eye 10, and are not shown in this figure.

[0095] Referring to Figure 16D, a schematic diagram of the system 201 from a top view is shown, where the individual LOE 403 is not visible (below the aperture expander 203). Outwardly coupled rays (left outwardly coupled ray 38L and right outwardly coupled ray 38R) are directed along the z-axis (towards the bottom as shown) toward the EMB and the user's eye 10. In this view, additional beams, the left third beam 414L and the right third beam 414R, are shown, thus illustrating the left and right extremes of the field of view near the center line of the image height.

[0096] Referring to Figure 16A, a schematic diagram of the system 201 from a left side view is shown, where propagation occurs along the y-axis and z-axis. As can be seen from this figure, the shown left first edge 410L and left second edge 412L correspond to the lower and uppermost extremes of the image field of view, but are at the center of the field in the horizontal direction (as clearly visible from Figures 16B and 16C). A wedge 800 is used to connect the aperture expander 203 to the individual LOE 403. The wedge 800 is a non-limiting example of one type of connection that can be used between the aperture expander 203 and the individual LOE 403. Depending on the specific requirements of the implementation, other means and constructions may be used to provide the desired angle and connection.

[0097] Referring to Figure 16B, a schematic diagram of the system 201 is shown at a 45-degree angle from above to the plane (y-axis) of the individual LOE. The individual LOE 403 is visible below the aperture expander 203. The z-axis "comes out of the page," and therefore the outwardly coupled rays (left outwardly coupled ray 38L and right outwardly coupled ray 38R) "come out of the page" towards the user's eye 10, and their positions are indicated in the figure.

[0098] Referring now to Figures 20A to 22C, these figures illustrate an alternative coupling configuration in which the aperture extension member is optically associated with a coupling surface that is coplanar or parallel to one of the main outer surfaces of the LOE 403. In this case, at least one internal reflective surface within the LOE 403 is used to couple image illumination for propagation within the LOE 403 via internal reflection. According to certain particularly preferred implementations, coupling is achieved using a set of mutually parallel partially reflective coupling surfaces. Figures 20A to 20C illustrate an implementation using a single set of partially reflective surfaces for each aperture extension member according to this method, while Figures 21A to 21C illustrate an aperture extension member using two sets of partially reflective surfaces for each image projector, wherein the facet has an asymmetrical tilt relative to the main plane of the device. Figures 22A to 22C illustrate an optical system employing the aperture extension members of Figures 21A to 21C. Using the asymmetrical tilt of the facet can improve the performance and compactness of the system. As seen in this system, although the FOV of the displayed light is very large, the POD required to fill the entire EMB is relatively small.

[0099] It can also have the following configurations: 1. An optical system for directing image illumination injected into at least one coupling region to an eye-tracking frame for viewing by a user's eye, said optical system comprising a light-guiding optical element (LOE) formed of a transparent material, said LOE comprising: (a) A first region comprising a first set of flat, mutually parallel partial reflective surfaces having a first orientation; (b) The first region further includes a second set of flat, mutually parallel reflective surfaces having a second orientation that is not parallel to the first orientation; (c) A second region comprising a third set of flat, mutually parallel partial reflective surfaces having a third orientation, the third orientation being non-parallel to each of the first and second orientations; (d) A set of parallel main outer surfaces extending across the first and second regions, such that the first set of partial reflective surfaces, the second set of partial reflective surfaces, and the third set of partial reflective surfaces are all located between the main outer surfaces. Wherein, the third set of partially reflective surfaces is at an angle to the main outer surface, such that a portion of the image illumination propagating from the first region to the second region through internal reflection at the main outer surface is coupled out from the LOE toward the eye-tracking frame, and wherein each of the first set of partially reflective surfaces and the second set of partially reflective surfaces is oriented such that a portion of the image illumination propagating within the LOE through internal reflection at the main outer surface from the at least one coupled region is deflected toward the second region. 2. The optical system of claim 1, wherein the first set of partially reflective surfaces deflects a first portion of the field of view of the image toward the second region, and the second set of partially reflective surfaces deflects a second portion of the field of view of the image toward the second region, the first and second portions of the field of view being combined to provide a larger consecutive combined field of view than each of the first and second portions. 3. The optical system of claim 1, wherein each of the first set of partial reflective surfaces and the second set of partial reflective surfaces includes a deflecting surface configured to reflect a majority of image illumination incident on the deflecting surface, the deflecting surface being deployed as a first partial reflective surface reached by image illumination injected into the at least one coupling region of each of the first set of partial reflective surfaces and the second set of partial reflective surfaces. 4. The optical system as described in Scheme 3, wherein the deflecting surfaces of the first set of partial reflective surfaces and the deflecting surfaces of the second set of partial reflective surfaces intersect at a line. 5. The optical system of claim 3, wherein each of the first set of partial reflective surfaces and the second set of partial reflective surfaces includes a filler surface adjacent to the deflecting surface, the filler surface having a length measured parallel to the main outer surface, the length being less than the length of the deflecting surface and less than the length of another partial reflective surface adjacent to the filler surface. 6. The optical system of claim 1, wherein the first set of partial reflective surfaces and the second set of partial reflective surfaces each have a non-uniform spacing between the partial reflective surfaces. 7. The optical system of claim 1, wherein each of the partial reflective surfaces of the first set of partial reflective surfaces and the second set of partial reflective surfaces has a length measured parallel to the main outer surface, and each of the first set of partial reflective surfaces and the second set of partial reflective surfaces includes a partial reflective surface with a different length. 8. The optical system as described in Scheme 1, wherein the coupling region is within the middle third of the size of the LOE. 9. The optical system of claim 1, wherein at least one edge of the LOE adjacent to a first region of the LOE is implemented as a mirror surface perpendicular to the main outer surface, and wherein the path of the image illumination from the coupling region to the second region of the LOE includes at least one reflection from the mirror surface of the at least one edge of the LOE. 10. The optical system of claim 1 further includes an image projector configured to project an image illumination corresponding to a collimated image, the image projector being optically coupled to the LOE at the coupling region such that the image illumination is injected into a first region of the LOE, thereby propagating within the LOE via internal reflection at the main outer surface, the image illumination being injected with an effective optical aperture and an effective propagation direction to be incident on the partial reflective surfaces of both the first set of partial reflective surfaces and the second set of partial reflective surfaces. 11. The optical system of claim 10, wherein the size of the first set of partial reflective surfaces perpendicular to the effective propagation direction is larger than the size of the second set of partial reflective surfaces perpendicular to the effective propagation direction. 12. The optical system of claim 10, wherein the angle formed between the partially reflecting surfaces of the first set of partially reflecting surfaces and the effective propagation direction is smaller than the angle formed between the partially reflecting surfaces of the second set of partially reflecting surfaces and the effective propagation direction. 13. The optical system of claim 1 further includes: a first image projector configured to project image illumination corresponding to a first portion of the collimated image, the first image projector being optically coupled to the LOE at a first coupling region such that the image illumination is injected into the first region of the LOE, thereby propagating within the LOE via internal reflection at the main outer surface and incident on the partial reflective surfaces of the first set of partial reflective surfaces; and a second image projector configured to project image illumination corresponding to a second portion of the collimated image, the second image projector being optically coupled to the LOE at a second coupling region such that the image illumination is injected into the first region of the LOE, thereby propagating within the LOE via internal reflection at the main outer surface and incident on the partial reflective surfaces of the second set of partial reflective surfaces, the first and second portions of the collimated image being combined at the eye-tracking frame to provide a combined image. 14. The optical system of claim 1, wherein the first set of partial reflective surfaces and the second set of partial reflective surfaces are perpendicular to the main outer surface of the LOE. 15. The optical system of claim 1, wherein the first set of partial reflective surfaces and the second set of partial reflective surfaces are inclined to the main outer surface of the LOE. 16. An optical system for transmitting images to an eye-tracking frame for viewing by a user's eye, said optical system comprising: (a) A light-guiding optical element (LOE) formed of a transparent material, the LOE comprising a set of mutually parallel main outer surfaces and a set of outwardly coupled, flat, mutually parallel partial reflective surfaces located between the main outer surfaces; (b) A first image projector configured to project an image illumination corresponding to a first portion of a collimated image from an optical aperture, the image illumination entering the LOE from the optical aperture following a first optical path, propagating within the LOE via internal reflection at the main outer surface, and gradually coupling outward from the LOE toward the eye-tracking frame via a set of outwardly coupled partial reflective surfaces; (c) A second image projector configured to project an image illumination corresponding to a second portion of a collimated image from an optical aperture, the image illumination following a second optical path from the optical aperture into the LOE to propagate within the LOE via internal reflection at the main outer surface, and gradually couples out from the LOE toward the eye-tracking frame via a set of outwardly coupled partial reflective surfaces, the first and second portions of the collimated image being combined at the eye-tracking frame to provide a combined image; (d) A first optical expansion component comprising a first set of flat, mutually parallel partially reflective surfaces having a first orientation, the first optical expansion component being deployed in the first optical path to expand the optical aperture of the first image projector and guide image light toward the outwardly coupled set of partially reflective surfaces; and (e) A second optical extension component comprising a second set of flat, mutually parallel partially reflective surfaces having a second orientation, the second optical extension component being deployed in the second optical path to extend the optical aperture of the second image projector and guide image light toward the outwardly coupled set of partially reflective surfaces. 17. The optical system of claim 16, wherein the first optical extension component and the second optical extension component are external components optically coupled to the LOE, and wherein the injection of image illumination from the first image projector and the second image projector into the LOE occurs through the first optical extension component and the second optical extension component, respectively. 18. The optical system of claim 17, wherein the first optical extension component and the second optical extension component are each implemented in a thick plate having two main surfaces, wherein one of the main surfaces is optically coupled to a coupling surface associated with the LOE. 19. The optical system of claim 18, wherein the coupling surface is at an angle relative to the main outer surface of the LOE. 20. The optical system of claim 18, wherein the thick plate of the first optical extension component is optically coupled to a first coupling surface associated with the LOE, and the thick plate of the second optical extension component is optically coupled to a second coupling surface associated with the LOE, the first coupling surface and the second coupling surface being non-coplanar. 21. The optical system of claim 18, wherein the coupling surface is coplanar or parallel to one of the main outer surfaces of the LOE, and wherein the LOE includes at least one at least partially reflective coupling surface. 22. The optical system of claim 16, wherein the first set of partial reflective surfaces and the second set of partial reflective surfaces are located within the LOE between the main outer surface of the LOE. 23. The optical system of claim 22, wherein the first set of partial reflective surfaces and the second set of partial reflective surfaces are perpendicular to the main outer surface of the LOE. 24. The optical system of claim 22, wherein the first set of partial reflective surfaces and the second set of partial reflective surfaces are inclined relative to the main outer surface of the LOE. 25. The optical system of claim 16, wherein the first optical extension component further includes a third set of mutually parallel partially reflective surfaces that are not parallel to the first set of partially reflective surfaces, the first set of partially reflective surfaces and the third set of partially reflective surfaces extending the optical aperture of the first image projector in opposite directions and guiding the image light toward the outwardly coupled set of partially reflective surfaces. 26. The optical system of claim 25, wherein the first image projector has a central optical axis, and wherein the tilt of the third set of partial reflective surfaces relative to the central optical axis is different from the tilt of the first set of partial reflective surfaces relative to the central axis.

[0100] In this example and throughout this document, it should be noted that each set of partially reflective inner surfaces (“facets”) may have uniform or non-uniform spacing and may extend across the entire thickness dimension of the aperture extension component (between the two main parallel outer surfaces) or only across a portion of that thickness dimension.

[0101] All the principles described above can also be applied to a "lateral" construction, in which the image is injected from a POD located laterally outside the viewing area and vertically extended by a first set of facets, and then horizontally extended by a second set of facets to couple into the user's eye. It should be understood that all the above constructions and variations also apply to lateral injection constructions.

[0102] Throughout the foregoing description, the X-axis and Y-axis as shown in the figures have been mentioned, where the X-axis is horizontal or vertical and corresponds to a first dimension of optical aperture extension, and the Y-axis is another principal axis corresponding to a second dimension of extension. In this context, the X and Y axes can be defined relative to the orientation of the device when mounted on the user's head in an orientation typically defined by a support arrangement (e.g., the eyeglass frames of Figures 1A and 1B above). Other terms generally consistent with the definition of the X-axis include: (a) at least one straight line demarcating the eye-tracking frame, which can be used to define a direction parallel to the X-axis; (b) the edges of a rectangular projected image generally parallel to the X and Y axes; and (c) the boundary between the first region 16 and the second region 18 generally extending parallel to the X-axis.

[0103] It should be understood that the above description is intended to be illustrative only, and many other embodiments are possible within the scope of the invention as defined in the appended claims.

[0104] 12,403: Optical systems include light-guiding optical elements (LOE). 16: First Area 18: Second Zone 14,210,220: Image Projector (POD) 10: Near-eye monitors 20: Side 22: Controller 165,166: Edge 203L: First optical expansion component 203R: Second optical extension component 40AL, 40AR: First minor plane 40BL, 40BR: Last small plane 410L: First left edge 412L: Second edge on the left 210: First Image Projector 220: Second image projector 203: Thick plate (aperture expander) 203L, 203R: Side 800: Wedge Prism 802L: First coupling surface 802R: Second coupling surface 205, 206, 207, 26, 26A: Surface 403: Waveguide 404: Small plane 203:Thick plate components 201: System 202: LED Light Source 200: Exemplary Light Source Construction 204CL: Left collimation image 204CR: Right Collimation Image 204C: Two collimation images 238L: Left-coupled ray 238R: Right-coupled ray 206: Polarization-selective reflector 207L: Left light tube 207R: Right light tube 212: Left display device 222: Right display device 214, 216: Left PBS (Multiple polarization beam splitters) 224, 226: Right PBS (Multiple polarization beam splitters) 218: Left Collimator 228: Right Collimator 54L: Left First Area 54R: Right First Area 20L: Left waveguide 20R: Right waveguide 40AL: Left First Minor Plane 40AR: Right First Minor Plane 238L: Left-coupled ray 238R: Right-coupled ray 40AL, 40AR: First minor plane 40BL, 40BR: Last small plane 410L, 410R: Left First Edge 412L, 412R: Second edge on the left 38RL: Coupled Ray 10: Eyes 414L: Third beam from the left 414R: Third beam from the right 800: Wedge-shaped part POD 1: First Image Projector POD 2: Second Image Projector 26,26A: Surface 22L: Left minor plane 22R: Right minor plane 161, 162, 163, 164, 181, 205, 206, 207, 208, 404, 22L, 22R: Reflective surfaces (small facets)

Claims

1. A light guide structure for transmitting an image to a user's eye, the light guide structure comprising: A light-guiding optical element (LOE), formed of a transparent material, has a set of mutually parallel main outer surfaces for supporting light propagation via internal reflection within the LOE at the main outer surfaces. The LOE also includes a set of flat, mutually parallel partial reflective surfaces located outwardly coupled between the main outer surfaces. A first optical extension component includes a first set of flat, mutually parallel partial reflective surfaces with a first orientation. The first optical extension component is deployed to receive first collimated light corresponding to a first portion of an image guided along a first optical path and to extend the effective optical aperture of the first collimated light while guiding the first collimated light to propagate towards the outwardly coupled set of partial reflective surfaces via internal reflection within the LOE, so as to gradually couple out from the LOE via the outwardly coupled set of partial reflective surfaces for viewing by a user's eye. A second optical extension component includes a second set of mutually parallel, flat, partially reflective surfaces with a second orientation. The second optical extension component is deployed to receive a second collimated light corresponding to a second portion of an image guided along a second optical path and to extend the effective optical aperture of the second collimated light. Simultaneously, the second collimated light is guided to propagate through internal reflection within the LOE toward the outwardly coupled set of partially reflective surfaces to gradually couple out of the LOE for viewing by the user's eye. The first and second portions of the image are combined at the eye-tracking frame to provide an output image.

2. The optical guide structure as described in claim 1, wherein, The first optical extension component and the second optical extension component are external components optically coupled to the LOE, and the first optical path and the second optical path pass through the first optical extension component and the second optical extension component, respectively.

3. The optical guide structure as described in claim 2, wherein, The first optical extension component and the second optical extension component are each implemented in a thick plate having two main surfaces, wherein one of the main surfaces is optically coupled to a coupling surface associated with the LOE.

4. The optical guide structure as described in claim 3, wherein, The coupling surface is at an angle relative to the main outer surface of the LOE.

5. The optical guide structure as described in claim 3, wherein, The thick plate of the first optical extension component is optically coupled to a first coupling surface associated with the LOE, and the thick plate of the second optical extension component is optically coupled to a second coupling surface associated with the LOE, wherein the first coupling surface and the second coupling surface are non-coplanar.

6. The optical guide structure as described in claim 3, wherein, The coupling surface is coplanar or parallel to one of the main outer surfaces of the LOE, and wherein the LOE includes at least one coupling surface that is at least partially reflective.

7. The optical guide structure as described in claim 1, wherein, The first set of partially reflective surfaces and the second set of partially reflective surfaces are located within the LOE between the main outer surface of the LOE.

8. The optical guide structure as described in claim 7, wherein, The first set of partially reflective surfaces and the second set of partially reflective surfaces are perpendicular to the main outer surface of the LOE.

9. The optical guide structure as described in claim 7, wherein, The first set of partially reflective surfaces and the second set of partially reflective surfaces are inclined relative to the main outer surface of the LOE.

10. The optical guide structure as described in claim 1, wherein, The first optical extension component further includes a third set of partially reflective surfaces that are parallel to each other and not parallel to the first set of partially reflective surfaces. The first set of partially reflective surfaces and the third set of partially reflective surfaces extend the optical aperture of the first collimated light in opposite directions and guide the light toward the outwardly coupled set of partially reflective surfaces.

11. The optical guide structure as described in claim 10, wherein, The tilt angle of the third set of partially reflective surfaces relative to the first optical path is different from the tilt angle of the first set of partially reflective surfaces relative to the first optical path.

Images