Optical element having an embedded beam splitter that overlaps with the coupled output region

Abstract

The optical system includes a light guide optical element (LOE) having a pair of parallel main external surfaces that support the propagation of image illumination within the LOE by internal reflection at the main external surfaces. A plurality of mutually parallel partial reflective surfaces are arranged obliquely to the main external surfaces within the combined output region of the LOE, and combine output at least a portion of the image illumination from the LOE toward the eye movement box. In an embodiment, a planar homogenizer is located inside the LOE, parallel to the main external surfaces, and extends at least partially within the combined output region so as to overlap with a portion, but not all, of the mutually parallel partial reflective surfaces. In another embodiment, the LOE includes a second plurality of mutually parallel partial reflective surfaces, and the homogenizer is alternatively arranged in a relationship that overlaps with the second plurality of mutually parallel partial reflective surfaces.

Description

Technical Field

[0001] Field Cross - Reference to Related Applications This application claims priority to U.S. Provisional Patent Application No. 63 / 470,967, filed on June 4, 2023, the disclosure of which is hereby incorporated by reference in its entirety.

[0002] The present disclosure relates to an optical system, and more particularly, to an optical system including a light - guiding optical element (LOE) for achieving optical aperture expansion.

Background Art

[0003] In the optical arrangements of near - eye displays (NEDs), head - mounted displays (HMDs), and head - up displays (HUDs), a large aperture is required to cover the area where the observer's (i.e., the user's, viewer's) eye is located, generally referred to as the eye movement box or EMB. To implement a compact device, the image projected onto the observer's eye is generated by a small optical image generator (projector) with a small optical aperture. The image from the image projector is transmitted to the eye by an LOE that magnifies (multiplies) the image to generate a large aperture.

[0004] To achieve uniformity of the viewed image, the LOE needs to be uniformly "filled" with the projected image and its conjugate image. This imposes design limitations on the size of the image projector and various other aspects of the optical design.

Summary of the Invention

[0005] The present disclosure provides an optical system having a light - guiding optical element (LOE) for directing image illumination from an image projector towards an eye movement box for viewing by a user's eye.

[0006] An optical system is provided for directing image illumination corresponding to a collimated image to an eye movement box for viewing by the viewer's eye. The optical system comprises a light guide optical element (LOE) formed from a transparent material. The LOE comprises a pair of principal external surfaces, which are parallel to each other to support the propagation of image illumination within the LOE by internal reflection at the principal external surfaces; a coupled output configuration, which is located within the LOE and is configured to coupled output at least a portion of the image illumination toward the eye movement box, and is associated with a coupled output region of the LOE, and includes a plurality of mutually parallel partial reflective surfaces, which are inclined obliquely with respect to the principal external surfaces; and at least one planar beam splitter, which is located within the LOE and parallel to the principal external surfaces, and which extends at least partially into the coupled output region so as to overlap with a portion, but not all, of the mutually parallel partial reflective surfaces.

[0007] Optionally, multiple mutually parallel partial reflective surfaces have a selected deployment angle relative to the main external surface, and the selected deployment angle is chosen from a range of 55 to 70 degrees.

[0008] Optionally, at least one planar beam splitter comprises a single beam splitter that subdivides a plurality of mutually parallel partial reflectors into a first set of partial reflectors and a second set of partial reflectors, wherein the first set of partial reflectors is laterally offset from the second set of partial reflectors.

[0009] Optionally, the optical system further comprises an image projection device for generating image illumination corresponding to a collimated image, the image projection device being optically coupled to the LOE so as to introduce the image illumination into the coupled input region of the LOE so as to propagate within the LOE by internal reflection.

[0010] Optionally, the LOE includes a first LOE region and a second LOE region, the main outer surface extending across the first and second LOE regions, the coupled output region located in the first region of the LOE, the second LOE region including a coupled region having a coupled configuration associated therewith, the coupled configuration including a second plurality of mutually parallel partial reflective surfaces non-parallel to a plurality of mutually parallel partial reflective surfaces of the coupled output configuration, the second plurality of mutually parallel partial reflective surfaces configured to deflect at least a portion of the image illumination propagating within the second LOE region by internal reflection at the main outer surface into the first LOE region by internal reflection from the main outer surface.

[0011] Optionally, the optical system further comprises an image projection device for generating image illumination corresponding to a collimated image, the image projection device being optically coupled to the LOE such that it introduces the image illumination into the coupled input region of the LOE so that it propagates from the coupled input region toward a second LOE region by internal reflection.

[0012] Optionally, the LOE further comprises a first optical retarder and a second optical retarder, each of which is located inside the LOE and parallel to the main outer surface, and a planar beam splitter is sandwiched between the first and second optical retarders.

[0013] Optionally, at least one planar beam splitter includes two or more planar beam splitters that subdivide the thickness of the LOE between the main outer surfaces into three or more layers of equal thickness.

[0014] Optionally, at least one planar beam splitter consists of a single beam splitter that subdivides the thickness of the LOE between the main outer surfaces into two layers of equal thickness, and the image illumination entering one of the two layers corresponds to both the collimated image and the conjugate of the collimated image.

[0015] Furthermore, according to the teaching of embodiments of the present disclosure, an optical system is also provided for directing image illumination corresponding to a collimated image to an eye movement box for viewing by the viewer's eye. The optical system comprises a light guide optical element (LOE) formed from a transparent material. The LOE comprises a first LOE region including a plurality of mutually parallel partial reflective surfaces of a first plurality of planes having a first orientation; a second LOE region including a plurality of mutually parallel partial reflective surfaces of a second plurality of planes having a second orientation nonparallel to the first orientation; and a pair of mutually parallel main external surfaces extending across the first and second LOE regions such that both the plurality of first and second partial reflective surfaces are located between the main external surfaces, wherein the plurality of second partial reflective surfaces direct image illumination propagating within the LOE from the first LOE region to the second LOE region by internal reflection at the main external surfaces. A portion of the first plurality of partial reflectors is inclined obliquely with respect to the main external surface so as to be coupled out toward the eye movement box from the LOE, and the first plurality of partial reflectors are oriented so as to deflect a portion of the image illumination propagating within the LOE by internal reflection at the main external surface toward a second LOE region from the coupled input region of the LOE, and the LOE further comprises at least one planar beam splitter located inside the LOE and parallel to the main external surface, the at least one planar beam splitter located at least partially within the first LOE region so as to overlap with at least some of the partial reflectors of the first plurality of partial reflectors.

[0016] Optionally, at least one planar beam splitter partially extends across a first LOE region such that at least one planar beam splitter overlaps with a portion, but not all, of the first plurality of partial reflectors.

[0017] Optionally, at least one planar beam splitter extends substantially over the entire first LOE region such that at least one planar beam splitter overlaps with all of the partial reflectors of the first plurality of partial reflectors.

[0018] Optionally, at least one planar beam splitter subdivides at least some of the first plurality of partial reflectors into a first set of partial reflectors and a second set of partial reflectors, the first set of partial reflectors being laterally offset from the second set of partial reflectors.

[0019] Optionally, the LOE further comprises a first optical retarder and a second optical retarder, each of which lies within the first LOE region and is parallel to the main outer surface, and at least one planar beam splitter is sandwiched between the first optical retarder and the second optical retarder.

[0020] Optionally, at least one planar beam splitter includes two or more planar beam splitters that subdivide the thickness of the LOE between the main outer surfaces into three or more layers of equal thickness.

[0021] Optionally, at least one planar beam splitter consists of a single beam splitter that subdivides the thickness of the LOE between the main outer surfaces into two layers of equal thickness, and the image illumination entering one of the two layers corresponds to both the collimated image and its conjugate.

[0022] Optionally, the optical system further comprises an image projection device for generating image illumination corresponding to a collimated image, the image projection device being optically coupled to the LOE such that it introduces the image illumination into the coupled input region of the LOE so that it propagates from the coupled input region toward the first LOE region by internal reflection.

[0023] In the context of this document, the term “induced” generally refers to light trapped within a light-transmitting material (e.g., a substrate) by internal reflection at the main outer surface of the light-transmitting material, so that the light trapped within the light-transmitting material propagates through the light-transmitting material in the direction of propagation. Light propagating through a light-transmitting substrate is trapped by internal reflection when this propagating light is incident on the main outer surface of the light-transmitting material at an incident angle within a specific angular range. The internal reflection of trapped light can take the form of total internal reflection, thereby causing propagating light incident on the main outer surface of the light-transmitting material at an angle greater than a critical angle (partially defined by the refractive index of the light-transmitting material and the surrounding medium, e.g., air), to undergo total internal reflection at the main outer surface. Alternatively, the internal reflection of trapped light can be achieved by coatings, such as angle-selective reflective coatings, applied to the main outer surface of the light-transmitting material to achieve reflection of light incident on the main outer surface within a specific angular range.

[0024] Unless otherwise defined herein, all technical and / or scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to whom this disclosure relates. Similar or equivalent methods and materials may be used in carrying out or testing embodiments of this disclosure, but exemplary methods and / or materials are described below. In case of any conflict, the patent specification, including definitions, shall prevail. Furthermore, materials, methods, and examples are illustrative and not necessarily intended to be limiting. [Brief explanation of the drawing]

[0025] Some embodiments of this disclosure are described herein only as examples, with reference to the accompanying drawings. It should be emphasized that the details given, including specific references to the drawings, are for illustrative purposes only and for illustrative purposes of the embodiments of this disclosure. In this regard, the description made in conjunction with the drawings will make it clear to those skilled in the art how embodiments of this disclosure may be carried out.

[0026] Here, turning attention to the drawings, in the drawings, like reference numerals or letters indicate corresponding or like components.

[0027] [Figure 1A] A schematic isometric view of an optical system implemented using a light guiding optical element (LOE) that provides a one-dimensional aperture expansion and can be constructed in accordance with the teachings of the present disclosure. [Figure 1B] A schematic isometric view of an optical system implemented using a light guiding optical element (LOE) that provides a two-dimensional aperture expansion and can be constructed in accordance with the teachings of the present disclosure. [Figure 2A] A schematic side view illustrating an LOE that can be used in the optical system of FIG. 1A, the LOE having a coupling output configuration implemented as a set of major external surfaces and a set of mutually parallel partial reflection inner surfaces that are inclined obliquely with respect to the major external surfaces. [Figure 2B] A schematic side view illustrating an LOE that can be used in the optical system of FIG. 1A, the LOE having a set of major external surfaces and a coupling output configuration implemented as a diffractive optical element located on one of the major external surfaces. [Figure 3A] FIGS. 3A - 3C are respectively a schematic front view, side view, and plan view illustrating an LOE that can be used in the optical system of FIG. 1B, the LOE having a set of major external surfaces and a first region and a second region each including a set of mutually parallel partial reflection inner surfaces, the partial reflection surface of the first region deflecting light into the second region, and the partial reflection surface of the second region deflecting light out of the LOE. [Figure 3B] FIGS. 3A - 3C are respectively a schematic front view, side view, and plan view illustrating an LOE that can be used in the optical system of FIG. 1B, the LOE having a set of major external surfaces and a first region and a second region each including a set of mutually parallel partial reflection inner surfaces, the partial reflection surface of the first region deflecting light into the second region, and the partial reflection surface of the second region deflecting light out of the LOE. [Figure 3C]Figures 3A to 3C are schematic front, side, and top views illustrating a Line of Effect (LOE) that may be used in the optical system of Figure 1B, the LOE comprising a first region and a second region, each comprising a set of main outer surfaces and a set of mutually parallel partial reflective inner surfaces, the partial reflective surfaces of the first region deflecting light into the second region, and the partial reflective surfaces of the second region deflecting light out of the LOE. [Figure 4A] Figures 4A to 4D schematically illustrate the propagation of rising and descending rays through the LOE shown in Figure 2A. [Figure 4B] Figures 4A to 4D schematically illustrate the propagation of rising and descending rays through the LOE shown in Figure 2A. [Figure 4C] Figures 4A to 4D schematically illustrate the propagation of rising and descending rays through the LOE shown in Figure 2A. [Figure 4D] Figures 4A to 4D schematically illustrate the propagation of rising and descending rays through the LOE shown in Figure 2A. [Figure 5A] Figures 5A–5C schematically illustrate an LOE having an internal beam splitter positioned in the central plane of the LOE to subdivide the LOE into two layers of equal thickness, which completely overlap with a set of mutually parallel partial reflecting surfaces, and show the rising rays that initially spread across the entire cross-section of the LOE. [Figure 5B] Figures 5A–5C schematically illustrate an LOE having an internal beam splitter positioned in the central plane of the LOE to subdivide the LOE into two layers of equal thickness, which completely overlap with a set of mutually parallel partial reflecting surfaces, and show the rising rays that initially spread across the entire cross-section of the LOE. [Figure 5C] Figures 5A–5C schematically illustrate an LOE having an internal beam splitter positioned in the central plane of the LOE to subdivide the LOE into two layers of equal thickness, which completely overlap with a set of mutually parallel partial reflecting surfaces, and show the rising rays that initially spread across the entire cross-section of the LOE. [Figure 6]Figures 5A to 5C illustrate a similar LOE (Land of Energy) schematicly, but initially only one of the two layers is filled, and the other layer is initially unlit, showing rising and falling rays. [Figure 7A] Figures 7A and 7B schematically illustrate an LOE according to an embodiment of the present disclosure, which is similar to Figure 6 but includes a cutting beam splitter that partially overlaps with a set of mutually parallel partial reflective surfaces. [Figure 7B] Figures 7A and 7B schematically illustrate an LOE according to an embodiment of the present disclosure, which is similar to Figure 6 but includes a cutting beam splitter that partially overlaps with a set of mutually parallel partial reflective surfaces. [Figure 8A] This is a schematic side view of a beam splitter, similar to Figures 5A-6 in the embodiments of the present disclosure, but comprising a beam splitter that subdivides a set of mutually parallel partial reflective surfaces into two sets of partial reflective surfaces, one of which is laterally offset from the other. [Figure 8B] This is a schematic side view of the LOE, similar to Figure 8A according to the embodiment of the present disclosure, but in which the partial reflective surface is located only on one side of the beam splitter and is more closely spaced apart. [Figure 8C] This is a schematic side view of the LOE, similar to Figure 8A according to an embodiment of the present disclosure, but with the partial reflective surfaces in each set more closely spaced apart. [Figure 9A] This is a schematic side view of a beam splitter, similar to Figures 5A-6 in the embodiment of the present disclosure, but comprising a pair of beam splitters that subdivide the beam splitter into three layers of equal thickness. [Figure 9B] This is a schematic side view of the LOE, similar to Figure 9A, but with the partial reflective surface located in only one of the three layers. [Figure 9C] This is a schematic side view of the LOE, similar to Figures 9A and 9B, but with partial reflective surfaces located in two adjacent layers, where one of the partial reflective surfaces in these two layers is offset laterally relative to the other. [Figure 9D]This is a schematic side view of the LOE, similar to Figure 9A according to an embodiment of the present disclosure, but in which the partial reflective surfaces in the three layers are offset laterally from each other. [Figure 10] This is a schematic side view of the LOE, similar to the LOEs in Figures 7A and 7B, but with a steeper angled partial reflective surface, showing the traces of rays corresponding to the edge and center of the FOV. [Figure 11A] Figures 11A and 11B illustrate an embodiment of the present disclosure, which is similar to the LOE of Figures 3A-3C, but has an internal beam splitter positioned on the central plane of the LOE in a first region and completely overlapping with the partial reflecting surface of the first region, thereby subdividing the LOE into two layers of equal thickness. [Figure 11B] Figures 11A and 11B illustrate an embodiment of the present disclosure, which is similar to the LOE of Figures 3A-3C, but has an internal beam splitter positioned on the central plane of the LOE in a first region and completely overlapping with the partial reflecting surface of the first region, thereby subdividing the LOE into two layers of equal thickness. [Figure 11C] Figure 11C is a schematic plan view of an embodiment of the present disclosure, similar to Figure 11B, but with a cutting beam splitter that partially overlaps with the partial reflective surface of the first region. [Figure 12A] This is a schematic plan view similar to Figure 11B in the embodiment of the present disclosure, but showing a partial reflective surface without lateral offset. [Figure 12B] This is an enlarged view of the region shown as XII in Figure 12A, showing a beam splitter sandwiched between a pair of optical retarders according to an embodiment of the present disclosure. [Figure 13A] Figures 13A to 13E illustrate the steps for manufacturing an LOE, such as the LOE shown in Figures 11A and 11B, according to embodiments of this disclosure. [Figure 13B] Figures 13A to 13E illustrate the steps for manufacturing an LOE, such as the LOE shown in Figures 11A and 11B, according to embodiments of this disclosure. [Figure 13C]Figures 13A to 13E illustrate the steps for manufacturing an LOE, such as the LOE shown in Figures 11A and 11B, according to embodiments of this disclosure. [Figure 13D] Figures 13A to 13E illustrate the steps for manufacturing an LOE, such as the LOE shown in Figures 11A and 11B, according to embodiments of this disclosure. [Figure 13E] Figures 13A to 13E illustrate the steps for manufacturing an LOE, such as the LOE shown in Figures 11A and 11B, according to embodiments of this disclosure. [Figure 14A] Figures 14A to 15F illustrate the steps for fabricating the first area of ​​the LOE, such as the LOE in Figures 12A and 12B, according to embodiments of the present disclosure. [Figure 14B] Figures 14A to 15F illustrate the steps for fabricating the first area of ​​the LOE, such as the LOE in Figures 12A and 12B, according to embodiments of the present disclosure. [Figure 15] Figures 14A to 15F illustrate the steps for fabricating the first area of ​​the LOE, such as the LOE in Figures 12A and 12B, according to embodiments of the present disclosure. [Figure 16A] Figures 16A to 18C illustrate the steps for mass-producing LOEs according to embodiments of the present disclosure, with each LOE being as shown in Figures 11A and 11B. [Figure 16B] Figures 16A to 18C illustrate the steps for mass-producing LOEs according to embodiments of the present disclosure, with each LOE being as shown in Figures 11A and 11B. [Figure 16C] Figures 16A to 18C illustrate the steps for mass-producing LOEs according to embodiments of the present disclosure, with each LOE being as shown in Figures 11A and 11B. [Figure 17A] Figures 16A to 18C illustrate the steps for mass-producing LOEs according to embodiments of the present disclosure, with each LOE being as shown in Figures 11A and 11B. [Figure 17B] Figures 16A to 18C illustrate the steps for mass-producing LOEs according to embodiments of the present disclosure, with each LOE being as shown in Figures 11A and 11B. [Figure 17C] Figures 16A to 18C illustrate the steps for mass-producing LOEs according to embodiments of the present disclosure, with each LOE being as shown in Figures 11A and 11B. [Figure 17D] Figures 16A to 18C illustrate the steps for mass-producing LOEs according to embodiments of the present disclosure, with each LOE being as shown in Figures 11A and 11B. [Figure 17E] Figures 16A to 18C illustrate the steps for mass-producing LOEs according to embodiments of the present disclosure, with each LOE being as shown in Figures 11A and 11B. [Figure 17F] Figures 16A to 18C illustrate the steps for mass-producing LOEs according to embodiments of the present disclosure, with each LOE being as shown in Figures 11A and 11B. [Figure 18A] Figures 16A to 18C illustrate the steps for mass-producing LOEs according to embodiments of the present disclosure, with each LOE being as shown in Figures 11A and 11B. [Figure 18B] Figures 16A to 18C illustrate the steps for mass-producing LOEs according to embodiments of the present disclosure, with each LOE being as shown in Figures 11A and 11B. [Figure 18C] Figures 16A to 18C illustrate the steps for mass-producing LOEs according to embodiments of the present disclosure, with each LOE being as shown in Figures 11A and 11B. [Figure 19A] Figures 19A to 19F illustrate the steps for creating LOEs, such as the LOEs in Figures 5A to 8A and 10, according to embodiments of this disclosure. [Figure 19B] Figures 19A to 19F illustrate the steps for creating LOEs, such as the LOEs in Figures 5A to 8A and 10, according to embodiments of this disclosure. [Figure 19C] Figures 19A to 19F illustrate the steps for creating LOEs, such as the LOEs in Figures 5A to 8A and 10, according to embodiments of this disclosure. [Figure 19D] Figures 19A to 19F illustrate the steps for creating LOEs, such as the LOEs in Figures 5A to 8A and 10, according to embodiments of this disclosure. [Figure 19E] Figures 19A to 19F illustrate the steps for creating LOEs, such as the LOEs in Figures 5A to 8A and 10, according to embodiments of this disclosure. [Figure 19F] Figures 19A to 19F illustrate the steps for creating LOEs, such as the LOEs in Figures 5A to 8A and 10, according to embodiments of this disclosure. [Modes for carrying out the invention]

[0028] In certain embodiments of the present disclosure, an optical system is provided having a light guide optical element (LOE) for achieving optical aperture expansion for the purpose of a head-up display, most preferably a near-eye display, which may be a virtual reality display or more preferably an augmented reality display.

[0029] The principles and operation of the optical system and LOE described herein can be better understood by referring to the drawings accompanying the specification.

[0030] Before describing in detail at least one embodiment of this disclosure, it should be understood that this disclosure is not necessarily limited to its application to the construction details and arrangement of components and / or methods described in the following specification and / or illustrated in the drawings and / or examples. Other embodiments of this disclosure are possible or can be practiced or implemented in various ways.

[0031] Referring here to the drawings, Figure 1A schematically illustrates an exemplary implementation of a device in the form of a near-eye display, generally shown in 1, employing an LOE 100, which may be constructed according to the teachings of embodiments of the present disclosure. The near-eye display 1 employs a miniature image projector (or "POD") 200, which is optically coupled so that an image is incident on an LOE (compatiblely referred to as a "waveguide," "substrate," or "slab") 100, where image light is captured by internal reflections at a set of mutually parallel planar external surfaces. The propagating image light interacts with an optically coupled output configuration located in region 110 of the LOE 100, not illustrated in Figure 1A, which progressively deflects (couples) a portion of the image illumination emanating from the LOE 100 toward the observer's eye located within a region defined as an eye movement box (EMB), thereby achieving a one-dimensional optical aperture expansion. The coupled output configuration can be implemented as a set of partial reflective surfaces (referred to interchangeably as "facets") that are parallel to each other and inclined obliquely to the direction of image light propagation, in which case the direction of image light propagation is also inclined with respect to the external surfaces of the planes parallel to each other, and each consecutive facet deflects a portion of the image light. Alternatively, the optical coupled output configuration can be implemented as a diffractive optical element located on one of the external surfaces of the plane of the LOE100. In the context of this disclosure, an LOE that achieves only single-dimensional aperture expansion is interchangeably referred to as a 1D LOE.

[0032] Figure 1B illustrates another exemplary implementation of Device 1 in which LOE 100, which can be constructed according to the teachings of embodiments of the present invention, performs two-stage and two-dimensional optical aperture expansion. Here, LOE 100 includes a further optical coupling configuration located in a further region 120 of LOE 100 that defines a coupling region, although not illustrated in Figure 1B. The further optical coupling configuration may be implemented as a further set of facets having an orientation oblique to the propagation direction of image light and non-parallel to the orientation of the facets located in region 110, or as a further diffractive optical element. Throughout much of the remainder of the specification, the optical systems and LOEs of the present disclosure will be described in the context of optically coupled output configurations implemented as sets of facets. However, it should be apparent that implementations of coupling configurations using diffractive elements are also applicable.

[0033] Continuing to refer to Figure 1B, the propagating image illumination strikes facets in region 120, and each consecutive facet deflects a portion of the image light in the deflection direction and is also captured / guided by internal reflection within LOE 100. This partial reflection at consecutive facets achieves a first dimension of optical aperture expansion. In a first set of preferred but non-limiting examples of this disclosure, the set of facets in region 120 is orthogonal to the main external surface of the substrate of LOE 100. In this case, both the injected image and its conjugate, which receives internal reflection as it propagates within region 120, are deflected, resulting in a conjugate image that propagates in the deflected direction. In an alternative set of preferred but non-limiting examples, the first set of partial reflection surfaces is angled obliquely with respect to the main external surface of LOE 100. In the latter case, either the injected image or its conjugate forms the desired deflected image propagating within the LOE100, while other reflections can be minimized, for example, by employing angle-selective coatings on the facets that make them relatively transparent for a range of incident angles presented by images where reflection is not desired.

[0034] Next, the deflected image illumination from region 120 enters the other region 110 (i.e., the facets in region 120 combine the image illumination exiting region 120 into the other region 110). The other region 110 may be implemented as an adjacent, distinct substrate or as a continuation of a single substrate. A combined output configuration associated with region 110 (e.g., a facet in region 110) progressively combines a portion of the image illumination toward the observer's eye located within the EMB, thereby achieving a second-dimensional optical aperture expansion. In the context of this disclosure, an LOE that achieves a two-dimensional aperture expansion is interchangeably referred to as a 2D LOE.

[0035] In this specification, the X-axis extending horizontally (Figures 1A and 1B) and the Y-axis extending perpendicularly to it, i.e., vertically in Figure 1B, are referred to in the drawings in the general extension direction of region 110 of LOE 100.

[0036] Very broadly speaking, region 110 of LOE100 can be considered to achieve aperture expansion in the X direction, while region 120 of LOE100 achieves aperture expansion in the Y direction. In the context of this document, region 110 is interchangeably referred to as the "first LOE" or the "second LOE" or the "first LOE region" or the "second LOE region," and region 120 is interchangeably referred to as the "second LOE" or the "first LOE" or the "second LOE region" or the "first LOE region."

[0037] The POD200 used in the devices of this disclosure is preferably configured to generate a collimated image, i.e., in a collimated image, the light to each image pixel is a parallel beam collimated to infinity in the angular direction corresponding to the pixel's position. Thus, the image illumination extends over an angular range corresponding to a two-dimensional field of view. The POD200 includes at least one light source, typically deployed to illuminate a spatial light modulator, such as an LCOS chip. The spatial light modulator modulates the projection intensity of each pixel in the image, thereby generating the image. Alternatively, the image projector may include a scanning configuration, typically implemented using a high-speed scanning mirror, which scans the illumination from the laser light source across the projector's image plane, with the beam intensity changing pixel by pixel in synchronous motion, thereby projecting the desired intensity onto each pixel. In either case, a collimating optical system is provided to generate an output projection image collimated to infinity. Some or all of the above components are typically arranged on the surface of one or more polarized beam splitter (PBS) cubes or other prism configurations, as is well known in the art.

[0038] The optical coupling of the image projector 200 and the LOE 100 can be achieved by any suitable optical coupling, such as via a coupling prism with an obliquely angled input surface or via a reflective coupling configuration, through one of the side edges and / or main external surfaces of the LOE. Details of the internal coupling configuration are not important to the present invention and are schematically shown in further drawings as non-limiting examples of wedge prisms applied to the main external surfaces of the LOE.

[0039] The near-eye display 1 will be understood to include various additional components, typically including a controller for operating an image projector 200, which typically employs power from a small onboard battery (not shown) or several other suitable power sources. The controller will be understood to include all necessary electronic components, such as at least one processor or processing circuit for driving the image projector, as is all known in the art.

[0040] It should be noted that various optical components of the devices disclosed herein form an optical system. Thus, for example, LOEs, coupled output configurations (e.g., facets or diffractive optical elements), image projectors, coupled input prisms, etc., form an optical system. It should be further noted that the entire devices (and optical systems) in Figures 1A and 1B may be mounted individually for each eye, and each LOE 100 is preferably supported against the user's head, facing the user's corresponding eye. In one particularly preferred option illustrated herein, the support configuration is implemented as an eyeglass frame having sides 106 for supporting the device against the user's ears. Other forms of support configurations may also be used, including but not limited to devices suspended from a headband, sun visor, or helmet.

[0041] Now, looking at Figures 2A and 2B, the optical properties of a conventional 1D LOE implementation that may be used in device 1 of Figure 1A are illustrated in more detail. Specifically, Figure 2A shows a more detailed diagram of a light guide optical element (LOE) 100 formed from a transparent (i.e., light-transmitting) material and having a set (pair) of main external surfaces 101, 102 that are parallel to each other. The main portion of the LOE 100 defines a region 110 through which image illumination propagates by internal reflection. The coupled output region 115 includes a coupled output configuration located within region 110 (and in a particular case, the two regions 110 and 115 may be exactly the same) and implemented as a set 111 of plane, parallel partial reflective surfaces ("facets"). The facets 111 are internal to the LOE 100, that is, they are located between the main external surfaces 101, 102 and are inclined obliquely to the main external surfaces 101, 102.

[0042] Figure 2B shows an alternative example in which the coupled output configuration is implemented as a diffractive optical element 112 located on one of the main external surfaces 102.

[0043] In both Figures 2A and 2B, image illumination from the display 210 is collimated by a collimating lens 220 (e.g., the display 210 and lens 220, which form part of the POD 200) and coupled into the LOE 100 through an optical coupling input arrangement (wedge prism 230) that defines the coupling input region of the LOE 100. The coupled input image illumination is then captured into the LOE 100 by internal reflection at the main external surfaces 101, 102. Supplementary, the internal reflection of the captured light can take the form of total internal reflection, thereby, propagating light incident on the main external surfaces 101, 102 at angles greater than a critical angle (partially defined by the refractive index of the light-transmitting material of the LOE and the refractive index of the medium surrounding the LOE, e.g., air) is internally reflected at the main external surfaces. Alternatively, the internal reflection of the captured light can be achieved by a coating, such as an angle-selective reflective coating, applied to the main external surfaces of the LOE to achieve reflection of light incident on the main external surfaces within a specific angular range.

[0044] Image illumination propagating through the LOE100 is schematically represented in Figures 2A and 2B as rays 11a and 11b. Rays 11a and 11b represent descending and ascending rays associated with specific fields of the image, respectively. Rays 11a and 11b propagate within the LOE100 until they reach the combined output configuration (facet 111 in Figure 2A, or diffracting element 112 in Figure 2B) in the combined output region 115, which progressively combines the propagating light from the LOE100 into a combined output so that the propagating light (ray) 13 is redirected toward the EMB3 where the observer's eye 2 is located, thereby achieving a one-dimensional optical aperture expansion.

[0045] Now, looking at Figures 3A-3C, the optical properties of a conventional 2D LOE implementation that may be used in device 1 of Figure 1B are illustrated in more detail. Here, LOE 100 includes two LOE regions 110 and 120, each containing its own set 111 and 121 of mutually parallel partial reflective surfaces (i.e., "facets") of a plane. Specifically, LOE region 110 includes a coupled output region 115 where the set of facets 111 is located, and LOE region 120 includes a coupled region 125 where the set of facets 121 is located. Regions 115 and 125 are interchangeably referred to as "facet" regions. The main external surfaces 101 and 102 extend across the two regions 110 and 120 such that both sets of facets 111 and 121 are located between the main external surfaces 101 and 102. Most preferably, the main external surfaces 101 and 102 are a pair of surfaces that are continuous across the entirety of two regions 110 and 120, although options for decreasing or increasing thickness between regions 110 and 120 are also within the scope of this disclosure. Regions 110 and 120 may be directly juxtaposed so as to intersect at a boundary, and depending on the particular application, the boundary may be a straight boundary or some other form of boundary, or there may be one or more additional LOE regions inserted between those regions to provide various additional optical or mechanical functions. This disclosure is not limited to any particular manufacturing technique, but in certain particular preferred implementations, particularly high-quality main external surfaces are achieved by employing a continuous external plate in which individually formed regions 110 and 120 are sandwiched between them to form a composite LOE structure.

[0046] The facet 121 located in the coupled region 125 has an orientation that is nonparallel to the orientation of the facet 111 (i.e., the set of facets 121 that are parallel to each other are oriented nonparallel to the set of facets 111 that are parallel to each other). Specifically, the facet 121 is oriented such that a portion of the image illumination propagating through the LOE 100 from the coupled input region (coupled prism 230) by internal reflection at the main outer surfaces is deflected out of region 120 toward region 110 (into region 110), thereby achieving a first dimension of optical aperture expansion. In the illustrated embodiment, the facet 121 is perpendicular to the main outer surfaces 101, 102. The facets 111 located in the combined output region 115 and the orientation of facets 111 are such that, due to internal reflections at the main external surfaces 101 and 102, a portion of the image illumination propagating from region 120 to region 110 within the LOE 100 is combined and output from the LOE 100 toward the eye movement box, thereby achieving a second dimension of optical aperture expansion.

[0047] In Figure 3A, the trajectories of image illumination propagating through a particular field are schematically represented as rays 11 and 12. Ray 12 represents the trajectory of illumination propagating through region 120, and ray 11 represents the trajectory of illumination propagating through region 110. Figure 3B shows the descending ray 11a and ascending ray 11b of image illumination (corresponding to trajectory 11) in region 110. Figure 3C shows the descending ray 12a and ascending ray 12b of image illumination (corresponding to trajectory 12) in region 120.

[0048] With respect to the combined output region 115 and combined region 125 of the LOE described herein, these regions are occupied by the combined output configuration and are substantial areas of the LOE 100 that span between sections of the LOE. For example, the combined output region 115 can effectively span the projection of a combined output configuration (e.g., facet 111) in a plane of one of the main external surfaces 102 along the length dimension of the LOE 100 (the X dimension in Figures 2A, 3A, and 3B), and the combined region 125 can effectively span the projection of another combined output configuration (e.g., facet 121) in a plane perpendicular to the main external surface along the height dimension (the Y dimension in Figures 3A and 3C).

[0049] In general, an LOE100 (whether it is the one in Figures 2A and 2B or Figures 3A-3C) needs to provide uniformly distributed image illumination to the human eye across all angles of light propagation (also known as "fields" or "field of view" - FOV) and throughout the entire EMB. To this end, the apertures of each field of view need to be evenly filled with light. In other words, for any angle of illumination corresponding to a pixel in the collimated image, the entire cross-section of the LOE in a plane perpendicular to the main outer surface of the LOE needs to be filled both with the image and its conjugate, so that at every point in the LOE volume, there are rays corresponding to all pixels in both the collimated image and its conjugate. Figures 4A-4C schematically illustrate this concept of aperture filling in the context of a 1D LOE (Figure 2A), but similar principles apply to a 2D LOE (e.g., the LOE in Figures 3A-3C). Figure 4A illustrates the projection of rising rays 11b that completely fill the entire cross-section of LOE 100 at several initial points. As is clear, the rising rays alone produce a striped (i.e., gapped) output image 13, and therefore the intensity detected by the viewer's eye depends on the specific location of the eye within the EMB. Similarly, Figure 4B shows the projection of descending rays 11a that completely fill the entire cross-section of LOE 100 at the same initial point. Figure 4C shows that only the combination of rising rays 11b and descending rays 11a results in a uniform intensity distribution of the output illumination 13.

[0050] Figure 4D shows that the rising rays 11b can be "deployed" by considering their trajectories before they are reflected by the main outer surface 102. As is clear, the condition for aperture filling is equivalent to requiring rays to fill an aperture 15 perpendicular to the main outer surfaces 101, 102 of LOE 100 and having a size of 2h (where h is the thickness of LOE).

[0051] If the "filling" condition is not met, the light projected from the LOE to the eye will not be evenly dispersed. One simple conventional solution to achieve this filling condition is to employ a larger image projector, for example, with an aperture of size 2h, i.e., an aperture that meets the size of aperture 15 in Figure 4D, or a larger coupled input prism. However, neither of these solutions is ideal because it introduces bulk at the input of the LOE, increasing the overall size of the device. Another conventional solution is to embed a beam multiplier inside the LOE in a region different from the coupled output region of the LOE to fill the missing image sections of the injected image illumination. However, this solution is also not ideal because it requires an additional volume in the LOE separate from the coupled output volume in which the beam multiplier is installed, which unfavorably increases the overall size of the LOE.

[0052] Embodiments of the present disclosure provide a solution for aperture filling by providing a beam multiplication region within the LOE that at least partially overlaps with the coupled output region and at least partially extends within the coupled output region. The beam multiplication region includes at least one planar beam splitter (also referred to as a “planar homogenizing element” or simply “homogenizer”) that is embedded within the LOE, parallel to the main outer surface, and overlapping with the facet region (coupled output region) of the LOE. As will be discussed in more detail below, in certain embodiments the planar homogenizing element is located in facet region 115 of a 1D LOE (such as the LOE in Figure 2A) or a 2D LOE (such as the LOEs in Figures 3A-3C), while in other embodiments the planar homogenizing element is located in facet region 125 of a 2D LOE (such as the LOEs in Figures 3A-3C). Furthermore, as will be discussed in more detail below, the beam multiplication region is such that at least a first facet of the region where the planar homogenization element is deployed completely overlaps with the planar homogenization element. In certain embodiments, the beam multiplication region and the coupled output region have the same starting point, and the beam multiplication region is entirely contained within the coupled output region, or vice versa. In other embodiments, the beam multiplication region extends only partially within the coupled output region, so as to partially overlap with the coupled output region. As will become clear from the following description, the deployment of the beam multiplication region within the coupled output region, or in a relationship that at least partially overlaps with the coupled output region, provides a more compact LOE design, resulting in a smaller overall form factor for the device.

[0053] Referring here to Figures 5A-5C, a section of LOE 100 is illustrated by one set of embodiments of the present disclosure. Here, LOE 100 includes a beam multiplication region 135, which includes a planar beam splitter 130 located inside LOE 100 and parallel to the main external surfaces 101, 102 in the central plane of LOE 100, such that the thickness (h) of LOE 100 between the main external surfaces 101, 102 is subdivided into two layers of equal thickness indicated by 151 and 152. The beam multiplication region 135 includes the entire coupled output region 115, thereby the planar homogenization element 130 extends across the entire coupled output region 115 so as to overlap with all of the facets 111 (in this case, the entire projection of facets 111 in a plane parallel to the main external surfaces 101, 102). Therefore, LOE100 includes facets in both layers 151 and 152 on both sides of the planar homogenization element 130.

[0054] The planar homogenization element 130 is partially reflective, preferably with a reflectivity of about 50%, but reflectivity in the range of 20% to 70% may also be preferred. Structurally, the partial reflectivity of the planar homogenization element 130 can be implemented using any suitable partial reflective layer or coating, including but not limited to thin-film optical coatings, metallic coatings, structural partial reflectors (e.g., dot pattern reflectors), multilayer dielectric coatings, and diffraction gratings.

[0055] The structure of LOE100, which has a homogenizer 130 that induces partial reflectance, can completely fill the opening of LOE100 even when the opening to be filled is only size h (thickness of LOE) and not 2h as shown in Figure 4D. This is illustrated in Figures 5A-5C, first showing that the image illumination is coupled within the LOE such that the rising ray 11b (or alternatively the descending ray 11a, or alternatively both the rising and descending rays) extends across the entire cross-section (h) of LOE100. Figure 4A shows what happens with the rising ray 11b entering the upper half-layer 151, and Figure 4B shows what happens with the rising ray 11b entering the lower half-layer 152. As can be seen, when the rising ray 11b enters only one of the layers, the coupled output image illumination 13 is not uniform (i.e., has gaps). Figure 4C shows the overlap of rising rays 11b (spreading across the entire cross-section of LOE 100) in the upper and lower layers 151 and 152, so that the combination of rising rays 11b entering the upper and lower half regions completely fills the aperture of the LOE, resulting in a uniformly combined output image 13 (i.e., no gaps). The same result can be achieved by injecting descending rays 11b into the upper and lower layers. Thus, in the embodiments illustrated in Figures 5A-5C, the cross-section of the LOE is first filled with illumination corresponding to or conjugate to a collimated image (generated by an image projector). In other words, in Figures 5A to 5C, the cross-section of the LOE within the beam multiplication region 135 is filled such that at every point in the cross-section of the LOE there is a ray corresponding to each pixel of the collimated image, or at every point in the cross-section of the LOE there is a ray corresponding to each pixel of the reflected image corresponding to the reflection of the collimated image in a plane parallel to the main external surfaces 101 and 102.

[0056] Similar results can also be achieved by filling only one of the layers 151 with both the collimated image and its conjugate, while the other layer 152 is initially unilluminated, i.e., both the rising rays 11b and the descending rays 11a can be injected into only one of the two layers 151. Figure 6 illustrates such a configuration, where both the rising rays 11b and the descending rays 11a first enter the upper half layer 151 but not the lower half layer 152, thereby filling the aperture of the LOE and resulting in a uniformly combined output image 13. Thus, in the embodiment illustrated in Figure 6, half of the cross-section of the LOE in the beam multiplication region 135 is filled with illumination corresponding to the collimated image and illumination corresponding to the conjugate of the collimated image. In other words, in Figure 6, half of the cross-section of the LOE within the beam multiplication region 135 is filled such that at every point in the cross-section of the LOE there is a ray corresponding to each pixel of the collimated image, and at every point in the cross-section of the LOE there is a ray corresponding to each pixel of the reflected image corresponding to the reflection of the collimated image in a plane parallel to the main external surfaces 101, 102.

[0057] Both configurations in Figures 5A-5C and Figure 6 smoothly fill the LOE 100 with image illumination so that the combined output illumination 13 is uniform. The specific configuration used (i.e., Figures 5A-5C or Figure 6) may depend on the optical design of the image projector and / or the combined input arrangement (prism 230).

[0058] Figures 5A–5C and 6 illustrate an embodiment in which the homogenizer 130 extends across the entire combined output region 115 so as to overlap with all of facet 111, but the homogenizer has been shown to be able to achieve rapid filling of missing image sections within the LOE so that complete filling of the LOE is achieved within a relatively short distance along the length of the homogenizer 130. Thus, according to certain preferred but non-limiting embodiments of the present disclosure, complete filling of the LOE can be achieved using a cleavage homogenizer 130. Figure 7A illustrates an example of such an embodiment in which the homogenizer 130 (and therefore the beam multiplication region 135) extends only partially within the combined output region 115 so as to overlap with a portion, but not all, of facet 111. In the illustrated embodiment, the homogenizer 130 completely overlaps only the first facet 111-1, but not any of the subsequent facets 111. The length of the homogenizer 130 required to achieve this LOE filling is, ideally, less than half the length of one cycle (period) of the shallowest angled rays of light traveling between the upper major outer surface 101 and the lower major outer surface 102 of the LOE 100. This cycle (period) length is schematically illustrated in Figure 7B.

[0059] Supplementary information: The configuration in Figure 7A is similar to that in Figure 6 (i.e., both the ascending ray 11b and descending ray 11a enter the upper half-layer 151 so that the image illumination corresponding to the collimated image and its conjugate enters half of the cross-section of LOE100), but equivalent results can be achieved using the same configuration as in Figures 5A-5C (i.e., the ascending (or descending) ray enters both the upper and lower half-layers so that the image illumination corresponding to the collimated image or its conjugate enters the entire cross-section of LOE100).

[0060] In the embodiments illustrated in Figures 5A–7B, there is no lateral offset between the upper layer 151 and the lower layer 152. However, it should be noted that, as a result of the actual fabrication techniques used to implement such embodiments, some small alignment errors may exist between the facet portions. If these alignment errors lead to small offsets, such as an offset of approximately half a wavelength, then a phase difference will exist between the rising and descending rays that can cause undesirable diffraction artifacts. Therefore, when implementing the embodiments in Figures 5A–7B, the precision of alignment between the facet portions must be very high so that any resulting shifts (offsets) between the facet portions are very small compared to wavelengths. To avoid such stringent requirements regarding offset tolerances, embodiments in which more pronounced lateral offsets (i.e., intentional offsets) exist between the facet portions are contemplated herein. Figure 8A illustrates one such embodiment. Here, the homogenizer 130 separates the facets 111 so as to subdivide the facet 111 into a first set 111a of facets in the upper layer 151 and a second set 111b of facets in the lower layer 152. The two sets of facets 111a and 111b are preferably offset (displaced) laterally from the other by a predetermined lateral offset amount along the direction of propagation of the image illumination (horizontal direction in the figure). The lateral offset amount is typically in the range of 10 to 100 microns, and more typically in the range of 10 to 50 microns, which is ideal when used in combination with a homogenizer to promote mixing and produce a more uniform output image (and avoid diffraction artifacts). In the illustrated embodiment, the homogenizer 130 is positioned in front of the EMB, and therefore, the high transparency that allows viewing of the real world, in addition to the high reflectivity of the homogenizer 130 at lower angles of incidence of the guide image illumination (ideally around 50%, and in practice 20% to 70%), determines the low reflectivity of the homogenizer 130 at lower angles of incidence.

[0061] Figure 8B shows another embodiment in which facet 111 is located in only one of the two layers 151. In this embodiment, facet 111 is more closely spaced than illustrated in the embodiment of Figure 8A in order to achieve uniformity of the combined output image.

[0062] Figure 8C illustrates an embodiment that can be considered a combination of the embodiments of Figures 8A and 8B. Here, the homogenizer 130 subdivides facet 111 into two sets of facets 111a and 111b (similar to Figure 8A), but the spacing between facets within each set is narrower (similar to Figure 8B). This allows for greater (e.g., maximum) lateral displacement between the two sets of facets 111a and 111b, generally resulting in better mixing and a more uniform output image.

[0063] It should be clear that the embodiments illustrated in Figures 8A to 8C can be implemented using a cleavage homogenizer, such as the homogenizer illustrated in Figures 7A and 7B.

[0064] While the embodiments described herein relate to a single homogenizer embedded within the LOE, other embodiments are contemplated herein in which two or more such homogenizers are embedded within the LOE. Figures 9A–9D illustrate one set of embodiments in which a pair of homogenizers 130a and 130b are arranged to subdivide the thickness of the LOE 100 between the main external surfaces 101, 102 into three layers of equal thickness, indicated by 151, 152, and 153. In the embodiment illustrated in Figure 9A, each facet of the set of facets 111 extends adjacently across the three layers 151, 152, and 153. Here, the facets 111 can be spaced close together to form a substantially uniform plane.

[0065] The embodiment illustrated in Figure 9B is similar to the configuration shown in Figure 8B, thereby the facet 111 is located in only one of the layers 151.

[0066] In the embodiment illustrated in Figure 9C, two of the three layers, layers 151 and 153, contain facets. Here, as in Figures 8A and 8C, the homogenizer 130a separates the facets 111 so as to subdivide the facet 111 into a first set 111a of facets in the upper layer 151 and a second set 111b of facets in the intermediate layer 153. Figure 9C shows that the two sets of facets 111a and 111b are offset (displaced) laterally from the other, but embodiments are intended herein in which there is no offset and each facet within the set of facets 111 extends adjacently across the two layers 151 and 153.

[0067] Figure 9D shows a further embodiment in which homogenizers 130a and 130b separate facets 111 so as to subdivide facet 111 into a first set 111a of facets in the upper layer 151, a second set 111b of facets in the intermediate layer 153, and a third set 111c of facets in the lower layer 152. Here, the three sets of facets are offset laterally from each other.

[0068] In the embodiments illustrated in Figures 9B to 9D, the periodicity of the facets is more precise compared to the periodicity of the facets in Figure 9A, which provides a further mechanism for homogenizing the output image illumination.

[0069] In the embodiments shown in Figures 9A to 9D, the reflectance of one homogenizer 130a may be approximately 50%, and the reflectance of the other homogenizer 130b may be approximately 33%.

[0070] As is obviously obvious, the embodiments illustrated in Figures 5A to 9D can be easily extended to the case of n homogenizers, where the thickness of the LOE is subdivided into n+1 layers of equal thickness for an integer value of n greater than 2. In a particular embodiment, the reflectance of the k-th homogenizer may be 1 / (k+1). Also as is obviously obvious, image illumination can be injected into the LOE according to the various configurations considered above to satisfy the requirements of aperture filling. For example, in one configuration, image illumination can be injected such that the rising rays first traverse the entire cross-section of the LOE (i.e., the LOE is first filled with illumination corresponding to the collimated image or its conjugate). As another example, image illumination can be injected such that both the rising and descending rays 11a first enter one of the layers 151 but not the other two layers 152, 153.

[0071] Furthermore, an LOE having a beam multiplication region 135, including one or more parallel beam splitters 130 in a plane that partially or completely overlap with the combined output region 115 (i.e., partially or completely overlap with the facet 111), such as the LOE illustrated in Figures 5A to 9D, has been found to be particularly effective with facets 111 having a steep or shallow deployment angle selected with respect to the main external surfaces 101, 102, preferably a deployment angle selected from the range of 55° to 70°, more preferably a deployment angle in the range of 55° to 65°. The choice of whether to use such a deployment angle for a facet may be a function of whether the facet combines and outputs rising or falling rays, which is a function of the angle at which the image illumination is combined within the LOE region 110. For example, such a deployment angle is particularly suitable for combining and outputting falling rays, while a differently angled facet is more suitable for combining and outputting rising rays.

[0072] The advantages of employing facets at such specific deployment angles in combination with beam multiplication regions that overlap with the facets are schematically illustrated in Figure 10 in the context of non-limiting exemplary deployment angles and beam multiplication region deployments. In the illustrated example, facet 111 has a deployment angle of approximately 60° (i.e., 30° measured with respect to the normals of the main external surfaces 101, 102) as measured with respect to the main external surfaces 101, 102. Furthermore, the beam multiplication region 135 partially overlaps with the combined output region 115 (having 10 facets 111) such that the beam splitter 130 completely overlaps with the first five facets 111, partially overlaps with the sixth facet, and does not overlap with the last four facets 111. Two representative rays 13a and 13a of the output illumination (i.e., the combined output image) reaching the EMB3 where the observer's eye is located are also shown in Figure 10. The combined output ray 13a is at the edge of the FOV, exits the LOE, is deflected from a further-distant facet (in this case, the second facet 111-2) closer to the left edge of the LOE (i.e., closer to the combined input region of the LOE), and then reaches EMB3. The combined output ray 13b, located at or near the center of the FOV, exits the LOE, is deflected from a facet closer to the center (in this case, the sixth facet 111-6 out of a total of 10 facets), and then reaches EMB3. Furthermore, the propagation field period corresponding to ray 13a (represented as a dashed line in the figure) is much shorter than the propagation field period corresponding to ray 13b (represented as a long dashed line in the figure), and the field period is defined as the length along the LOE during which the field travels between continuous interactions with the same major outer surface. This means that, in the case of propagation image illumination of the field corresponding to ray 13a, the aperture is filled immediately after encountering the first one or two facets 111. In the case of field propagation image illumination corresponding to ray 13b, the entire length of the beam splitter 130 is required for aperture filling, which is acceptable because ray 13b reaches EMB3 only after being deflected from facets 111-6 located further along the LOE in the direction of propagation image illumination.

[0073] The embodiments described so far relate to planar homogenization elements internally deployed in a 1D LOE within the combined output region of the LOE. However, embodiments of the present disclosure also relate to internally deploying such homogenization elements in a 2D LOE, such as the LOE illustrated in Figures 3A-3C. For example, in one set of embodiments, the planar homogenization elements may be deployed in the combined output region 115 of a first LOE 110. In a further set of embodiments, the planar homogenization elements may be deployed in a second LOE 120 instead of the first LOE 110. Figures 11A and 11B illustrate an LOE by one such set of embodiments of the present disclosure, in which one or more planar homogenization elements are deployed internally in the LOE within the combined region 125 of the second LOE 120. Here, the beam multiplication region 135 is located in the second region 120 and includes a planar beam splitter 130 positioned inside the LOE 100 and parallel to the main outer surfaces 101, 102 in the central plane of the LOE 100, so as to subdivide the thickness of the LOE 100 between the main outer surfaces 101, 102 into two layers of equal thickness indicated by 120a and 120b. The planar homogenization element 130 subdivides the facets 121 of the coupling region 125 into a first set 121a of facets located on one side of layer 120a and a second set 121b of facets located on the other layer 120b and parallel to facet 121a. Thus, the LOE 100 in Figures 11A and 11B includes facets in both layers 120a and 120b on both sides of the planar homogenization element 130. To maintain high optical resolution, the parallelism between the two sets of facets 121a and 121b needs to be maintained with high precision, typically around 30 arcseconds. In the illustrated embodiment, the two sets of facets 121a and 121b are preferably offset (displaced) laterally from each other by a predetermined lateral offset amount along the direction of propagation of image illumination through the LOE region 120 (the vertical (Y) direction in the figure). The lateral offset amount is typically in the range of 10 to 100 microns.

[0074] As can be seen in Figure 11B, the beam multiplication region 135 extends across the entire coupling region 125, overlapping with all of facets 121a and 121b. However, the beam splitter 130 may be cut to extend only partially within the coupling region 125, as described, for example, with reference to Figures 7A and 7B. Figure 11C shows an example of such an embodiment, where the beam splitter 130 partially overlaps with facets 121a and 121b.

[0075] As is obviously evident, Figures 11B and 11C illustrate an embodiment in which two sets of facets 121a and facet 121b are displaced laterally relative to the other along the displacement direction (e.g., the Y direction), but embodiments without lateral displacement between sets of facets are contemplated herein. The conditions / requirements for such displacement-free embodiments are the same as those considered above in the context of 1D LOE. Furthermore, for the same reasons described above in the context of 1D LOE, in certain embodiments the facets of the coupling region 125 may be deployed at oblique deployment angles (with respect to the direction of image light propagation), selected from deployment angles in the range of 55° to 70°, and more preferably in the range of 55° to 65°.

[0076] In certain situations, it may be preferable for the plane beam splitter 130 to operate in one polarization state, while the facets within the LOE region where the beam multiplication region 135 is located operate in a different polarization state. This is often the case when the propagating light strikes the facets at or near the Brewster angle, making it difficult to design an optical coating that yields the desired reflectivity for one polarization state (e.g., P polarization). In such cases, it may be desirable to rotate the polarization state of the light before it enters the beam splitter 130 and immediately after it exits the beam splitter 130. Figures 12A and 12B illustrate an embodiment of the LOE that achieves such polarization rotation. Here, a pair of optical retarders 131a and 131b (e.g., half-wave plates) are arranged inside the LOE, in layers 120a and 120b respectively, and a beam splitter 130 is sandwiched between the two optical retarders 131a and 131b, parallel to the main external surfaces 101 and 102. The optical retarders 131a and 131b and the beam splitter 130 may be configured as a laminated structure of beam splitter coatings. The optical retarders 131a and 131b rotate the polarization state of the incident light from a first polarization state to a second polarization state orthogonal to the first polarization state. As an example, consider a configuration in which the beam splitter 130 operates with P polarization and the facet operates with S polarization. In such a configuration, the propagating image illumination may be S-polarized, and the polarization state of the propagating illumination is rotated by the first optical retarder 131a to P polarization. A portion of the P-polarized light is transmitted by the beam splitter 130 and reaches the second optical retarder 131b, which rotates the light back to S-polarized light, and is then reflected from one of the main outer surfaces of the LOE and continues to propagate through the LOE. Another portion of the P-polarized light is reflected by the beam splitter 130 and returns through the first optical retarder 131a, which rotates the light back to S-polarized light. The S-polarized light encounters one of the facets (designed to reflect S-polarized light by its optical coating), and thus a portion of the S-polarized light is deflected by the facet. Another portion of the S-polarized light is transmitted by the facet, reflected from the other main outer surface of the LOE and continues to propagate through the LOE.

[0077] It should be obvious that similar techniques for polarization control can be employed in 1D LOE. Therefore, for example, the beam splitter in the embodiment illustrated in Figures 5A-8C can be similarly deployed between a pair of optical retarders.

[0078] Although the embodiments illustrated in Figures 11A-11C show only a single planar beam splitter 130, the beam multiplication region 135 may include two or more such beam splitters to subdivide the thickness of the LOE into three or more layers of equal thickness. In other words, the beam multiplication region 135 may include n homogenizers to subdivide the thickness of the LOE into n+1 layers of equal thickness for an integer value of n greater than 2. In a particular embodiment, the reflectivity of the k-th homogenizer may be 1 / (k+1).

[0079] As described above, including a beam multiplier region that overlaps with the coupled output region 115 (in the case of a 1D or 2D LOE) or the coupled region 125 (in the case of a 2D LOE) provides a more compact LOE design, resulting in a smaller overall device form factor. Various fabrication methods have been developed by the inventors to produce such compact LOEs. In fact, the inventors have found that fabricating such LOEs is inherently difficult and complex, and therefore, the methods for fabricating LOEs disclosed herein are considered to have utility independent of the LOE itself. The following paragraphs describe several methods for fabricating LOEs according to embodiments of the present disclosure. First, a method for fabricating a 2D LOE having a beam splitter embedded in the coupled region 125 of the LOE region 120 is described, followed by a method for fabricating a 1D LOE having a beam splitter embedded in the coupled output region 115. Subsequently, the method for fabricating a 1D LOE may also be applied to a method for fabricating a 2D LOE having one or more beam splitters embedded in a coupled output region 115. The fabrication method of this disclosure includes many steps, including various bonding steps in which one optical element is bonded to another optical element. Throughout this document, the term “bonding” should be understood to mean attaching using an optical adhesive or tack material.

[0080] Referring here to Figures 13A-13E, and in particular to Figure 13A, an optical structure 120a' is obtained in which a set of mutually parallel planar partial reflective surfaces (facets) 121a is embedded. The structure 120a' ultimately becomes layer 120a of the LOE region 120. A homogenizer coating 130', i.e., a partial reflective coating, is applied directly to the optical structure 120a'. The application of the coating 130' to the structure 120a' forms a beam splitter 130. Because the coating 130' is applied to an element containing potentially sensitive embedded elements (facets 121a), the application of the coating may require a special coating process, such as one applied at a relatively low temperature. Alternatively, as shown in Figure 13B, the coating 130' can be applied to a blank plate 122 to form a beam splitter on the plate 122. Next, the plate 122 (having the coating 130') is bonded to the structure 120a', resulting in the coating 130' being applied to the structure 120a' and forming a beam splitter 130 on the element 120a. The blank plate 122 can then be lapped and polished so that the minimum layer of plate 122 remains, typically about 10 microns. The processes in Figures 13A and 13B yield equivalent results.

[0081] Next, as illustrated in Figure 13C, a second optical structure 120b is obtained in which a second set 121b of mutually parallel partial reflective surfaces (facets) of a plane is embedded. Structure 120b' ultimately becomes another layer 120b of the LOE region 120. Structure 120b' is joined onto structure 120a' having a beam splitter 130 (generated via the process of Figure 13A or Figure 13B), generating a region 120 (Figure 13D) having an embedded beam splitter 130 that subdivides region 120 into two layers 120a and 120b, and subdivides the facets within region 120 into two sets of facets 121a and 121b. In certain embodiments, two structures 120a' and 120b' can be joined together such that two sets of facets 121a and 121b are displaced laterally relative to the other, preferably by an offset amount in the range of 10 to 100 microns. The resulting region 120 can then be joined to a region 110 having embedded facets 111 (which may be manufactured separately), as shown in Figure 13E, to form a complete LOE 100.

[0082] Figures 14A-14B and 15A-15F illustrate embodiments for producing an LOE having a homogenizing element 130 sandwiched between a pair of optical retarders embedded in a coupling region 125, for example, the LOE illustrated in Figures 12A and 12B.

[0083] In Figure 14A, a first optical retarder 131a (e.g., a half-wave plate) is bonded to a first optical structure 120a' having facets 121a, and then coated with a partial reflection homogenization coating 130'. Then, as shown in Figure 14B, a second optical structure 120b' having another set of facets 121b is bonded to a second optical retarder 131b (e.g., a half-wave plate), and the bonded structure of the structure 120b' having the retarder 131b is bonded to the bonded structure formed in Figure 13A to form the region 120 illustrated in Figures 12A and 12B.

[0084] Alternatively, Figures 15A–15F illustrate a production process that does not require coating on sensitive embedded elements. As shown in Figure 15A, a homogenizing coating 130' is applied to a blank plate 131a' of birefringent material to form a beam splitter 130 on the plate 131a'. The plate 131a' having the beam splitter 130 is then bonded to a blank plate 133a', as shown in Figure 15B. The birefringent plate 131a' can then be thinned, as shown in Figure 15C, to form the required optical retarder 131a (typically in the range of 1 to 100 microns in thickness). The structure in Figure 15C is then bonded to a structure 120a' having facets 121a, as shown in Figure 15D. The plate 133a' can then be thinned to a minimum thickness, typically in the range of 10 to 100 microns, to form the element 133a, as shown in Figure 15E. Finally, the process is repeated to form an optical structure 120b' having a joined optical retarder 131b (with or without a beam splitter), and the two structures 120a' and 120b' are joined together to produce region 120, as shown in Figure 15F.

[0085] In both methods shown in Figures 14A-14B and 15A-15F, it is advantageous to apply the homogenizer coating 130' to both structures 120a' and 120b' to minimize the mechanical stress caused by the homogenizer, which may distort the final optical region 120. It should also be noted that in both methods shown in Figures 14A-14B and 15A-15F, two optical structures 120a' and 120b' can be joined together such that two sets of facets 121a and 121b are displaced laterally relative to the other, preferably by an offset amount in the range of 10 to 100 microns. When joining optical structures 120a' and 120b' together due to the lateral displacement of the facets, any excess or protruding portions of either optical structure 120a' and / or 120b' can be trimmed and polished.

[0086] To produce large quantities of LOEs at low cost, it is advantageous to employ alternative manufacturing methods, where parts of the process are applied simultaneously to multiple elements. Figures 16A–18C illustrate embodiments of such manufacturing methods. Figures 16A–16C show steps associated with fabricating an optical structure containing multiple substructures, each becoming region 110 in the final 2D LOE product, and Figures 17A–17F show steps associated with fabricating an optical structure containing multiple substructures, each becoming region 120 in the final 2D LOE product.

[0087] As shown in Figure 16A, individual coated plates 301 are joined together and then cut / sliced ​​along parallel cutting planes 303 to form multiple regions 110 (which are precursor 1D LOEs). Each precursor LOE 110 has a pair of parallel main outer surfaces and multiple partial reflection mirrors (facets) 111 located inside the LOE and inclined obliquely with respect to the main outer surfaces. The facets 111 are formed from the coating applied to the plates. Slicing along the cutting planes 303 is done so that the required angular orientation (oblique inclination angle) of the facets 111 is achieved. As shown in Figures 16B and 16C, the multiple precursor 1D LOEs 110 are stacked and joined together to form a bonded stack (optical structure) 1000.

[0088] As shown in Figures 17A and 17B, individual coated plates 401 are sliced ​​along a cross-section 403 (Figure 17A) to form one or more optical structures 2000 (one of which is shown in Figure 17B), which are joined together and have embedded facets 121 (formed from the coating applied to the plates). The structures 2000 are then sliced ​​along a cross-section 413 to extract structures 120a' and 120b' (Figure 17C). The optical structures 120a' and 120b' are then coated directly onto or bonded to a plate coated with homogenizing coating 130', for example, as previously described with reference to Figures 13A-13D. The optical structures 120a' and 120b' can also be bonded to an optical retarder, for example, as previously described with reference to Figures 14A-15F. Individual optical structures 120a' and 120b', each having a coated beam splitter 130 (and optionally an optical retarder), are then stacked (Figure 17D) and joined together to form a new optical structure 2000' (Figure 17E). An alternative structure for optical structure 2000' is shown in Figure 17F. Here, optical structure 2000' can be formed from multiple adjacent pairs of structures 120a' and 120b', where one structure 120b' of each pair does not have a coated homogenizer, and the other structure 120a' of each pair has a coated homogenizer. Such a structure helps to minimize mechanical stress.

[0089] In the process illustrated in Figures 17D and 17F, it should be noted that the optical structure 120a' is staggered relative to the optical structure 120b' and can be joined together with respect to adjacent optical structures 120a' and 120b', such that the two sets of facets 121a and 121b are preferably displaced laterally relative to the other by an offset amount in the range of 10 to 100 microns. Any excess or protruding portions of the optical structure 2000' can be trimmed and polished.

[0090] As shown in Figure 18A, the optical structures 1000 and 2000' are aligned. The alignment is such that the desired orientation between the sets of facets 121 and 111 is achieved. Then, as shown in Figure 18B, the aligned optical structures 1000 and 2000' are joined together to form a composite optical structure 3000.

[0091] Next, as shown in Figure 18C, the optical structure 3000 is sliced ​​along parallel cross-sections 503 to extract individual 2D LOEs 100, and each extracted 2D LOE has two LOE regions 110 and 120, each containing its own set of facets 111 and 121, one of which has an embedded homogenizer 130, which may or may not be sandwiched between a pair of optical retarders. The cross-sections 503 are parallel to the main outer surfaces of the precursor LOEs that form the stack 1000, and the spacing between the cross-sections 503 is preferably such that the homogenizer 130 of each extracted LOE 100 is in the central plane of the extracted 2D LOE. Each extracted LOE can then be optically polished on its main outer surface.

[0092] In the above-described manufacturing method, the coating 130' can be applied to the optical structure (e.g., structures 120a', 120b', plate 131a', etc.) such that the coating 130' extends over the entire surface area of ​​the optical structure, and as a result, when the optical region 120 is formed (e.g., by joining structures 120a' and 120b' together), the beam splitter formed by the coating 130' overlaps with all the facets of the optical region 120 (i.e., the beam splitter extends over the entire joined region including the facets). However, in certain embodiments, the coating 130' can be applied so that it extends over only a portion of the surface area of ​​the optical structure, and as a result, when the optical region 120 is formed, the beam splitter formed by the coating 130' overlaps with only a portion of the facets of the optical region 120 (specifically, the first facet or the first few facets). It should also be noted that the above method can be easily extended to generate a LOE in which two or more beam splitters are embedded in the coupling region 125 of the optical region 120.

[0093] Referring here to Figures 19A-19D, we will describe a method for fabricating a 1D LOE having one or more beam splitters embedded in the coupled output region 115. First, it should be noted that these methods are applicable to generating a standalone 1D LOE, such as those described with reference to Figures 5A-5C, and can also be used in a process to generate a region 110 of a 2D LOE where the coupled region 125 does not contain a beam splitter.

[0094] First, a precursor LOE 110 is obtained using the technique described above, for example with reference to Figure 16A, as illustrated in Figure 19A. The periodicity (distance between facets 111) of LOE 110 is twice that of the final 1D LOE. Next, LOE 110 is cut along a cutting plane 201 (represented as a dashed line in Figure 19B) perpendicular to the main external surfaces 101, 102 of LOE 110, thereby producing two identical LOE 110a and 110b, as shown in Figure 19C. As a result of the specific bifurcation, the angles of facet 111a relative to surfaces 101a, 102a are identical to the angles of facet 111b relative to surfaces 101b, 102b.

[0095] Next, as illustrated in Figure 19D, a homogenizer coating 130', i.e., a partial reflection coating, is applied to one of the primary external surfaces of LOE 110a, 110b. In the illustrated example, coating 130' is applied to the primary external surface 101b of LOE 110b. Coating 130' may be applied to the entire surface 101b so as to completely overlap all of facet 111b, or to a portion of surface 101b so as to overlap only a portion of facet 111b (including the first facet). Figure 19E shows coating 130' after being applied to a portion of surface 101b so as to overlap only a portion of facet 111b (in this example, the first three facets) (represented as a speckled pattern). In certain embodiments, coating 130' may be applied to one of the primary external surfaces 101 of the precursor LOE 110 before LOE 110 is bifurcated. For example, the coating 130' can be applied to all or part of half of the surface 101 before it is divided in half.

[0096] Next, as shown in Figure 19F, the two LOEs 110a and 110b are joined together at the main outer surfaces 102a and 101b, such that the coating 130' / beam splitter 130 is sandwiched between surfaces 102a and 101b. In the figure, the coating 130' / beam splitter 130 completely overlaps with the first three facets of each set of facets 111a and 111b.

[0097] It should be noted that before joining the two LOEs 110a and 110b together, care must be taken to maintain parallelism between facets 111a and 111b. This can be easily achieved by rotating the two surfaces 102a and 101b together until they are parallel to each other. It should also be noted that in the illustrated embodiments, the two LOEs 110a and 110b are joined together such that there is a lateral offset between the two sets of facets 111a and 111b, preferably within the range of 10 to 50 microns. The excess or protruding portions 103a and 103b of LOEs 110a and 110b may be trimmed and polished to form the final 1D LOE product. In certain embodiments, the two LOEs 110a and 110b may be joined together such that there is no lateral offset between facets 111a and 111b.

[0098] In addition, since the final 1D LOE product has a thickness twice that of LOE110a and 110b, it should be noted that the precursor LOE (from which LOE110a and 110b are extracted) can be manufactured to have a thickness half that of the desired final LOE product. Therefore, if the final LOE product will have a desired thickness h, the precursor LOE can have a thickness of h / 2. This can be achieved, for example, by providing an appropriate spacing between the parallel cutting planes used to produce the precursor LOE. Furthermore, since the cutting along plane 201 bisects the precursor LOE, the width of the precursor LOE (measured in a direction perpendicular to plane 201) must be twice the desired width of the final LOE product.

[0099] The method described with reference to Figures 19A-19E is only one example embodiment of a method for producing a 1D LOE with an embedded beam splitter, and other embodiments are contemplated herein. For example, in one further embodiment, a precursor 1D LOE can be obtained and cut along a cutting plane located in the central plane between the outer surfaces 101, 102 and parallel to the outer surfaces 101, 102 to produce two identical LOEs with half the thickness of the final LOE. The beam splitter coating can then be applied to one of the two LOEs, and then the two LOEs can be joined together as described above. In such embodiments, the width and thickness of the precursor LOE may be the same as the desired width and thickness of the final LOE product. However, there is a strict requirement for the parallelism of the cutting planes, as the cutting along the cutting planes will form the main outer surfaces of each of the two LOEs, and its main outer surface must be parallel to the opposite main outer surface in order to support internal reflection. In another embodiment, the final LOE can be produced from two separate precursor LOEs, each having the same width as the final LOE product and half the thickness of the final LOE product. The beam splitter coating can then be applied to one of the two precursor LOEs, and the two LOEs can then be joined together as described above.

[0100] For example, referring to Figures 19A-19F, a 1D LOE produced according to the method described above can also be used in a process to fabricate a large number of 2D LOEs, where beam splitters are deployed in the LOE region 110. For example, multiple 1D LOEs, each having an embedded beam splitter, can be stacked and joined together to produce a joined stack (similar to the optical structure 1000 in Figure 18A, but with embedded beam splitters within the 1D LOE). The optical structure 2000 in Figure 17B can then be joined with a stack of 1D LOEs having embedded beam splitters in a manner similar to that illustrated in Figures 18A and 18B in order to form a composite optical structure. Next, the composite optical structure can be cut along parallel cross-sections (in a manner similar to that illustrated in Figure 18C) to extract 2D LOEs, each extracted 2D LOE having two LOE regions 110 and 120 containing its own sets of facets 111 and 121, one of which of the LOE regions 110 has an embedded homogenizer 130, and the other region 120 does not contain a homogenizer.

[0101] As described herein, an LOE 100 having at least one embedded beam splitter according to an embodiment of the present disclosure can be deployed as part of a device such as the near-eye display shown in Figures 1A and 1B. For example, a 1D LOE having at least one beam splitter embedded in region 110 may be deployed as part of the near-eye display shown in Figure 1A, and a 2D LOE having at least one beam splitter embedded in region 110 or region 120 may be deployed as part of the near-eye display shown in Figure 1B.

[0102] The descriptions of the various embodiments of this disclosure have been presented for illustrative purposes only, and are not intended to be exhaustive or limitful to the embodiments disclosed. Many modifications and variations that do not deviate from the scope and spirit of the embodiments described will be apparent to those skilled in the art. The terminology used herein has been chosen to best describe the principles of the embodiments, their practical application to market-based technologies, or technical improvements, or to enable those not skilled in the art to understand the embodiments disclosed herein.

[0103] As used herein, the singular forms "a," "an," and "the" include plural references unless the context clearly indicates otherwise.

[0104] The term “exemplary” is used herein to mean “serving as an example, illustration, or illustration.” Any embodiment described as “exemplary” should not necessarily be construed as being preferable or advantageous to other embodiments, and / or preclude the incorporation of features from other embodiments.

[0105] For clarity, it is understood that certain features of the Disclosure described in the context of separate embodiments may also be provided in combination in a single embodiment. Conversely, for brevity, various features of the Disclosure described in the context of a single embodiment may also be provided separately, in any preferred partial combination, or as suitable for any other described embodiment of the Disclosure. Certain features described in the context of different embodiments should not be considered essential features of those embodiments unless the embodiments would not function without those elements.

[0106] The attached claims have been drafted without multiple dependencies, solely to comply with the formal requirements of jurisdictions that do not permit such multiple dependencies. It should be noted that all possible combinations of features that would be implied by making the claims multiple dependencies are explicitly assumed and should be considered part of this disclosure.

[0107] While this disclosure has been described in conjunction with specific embodiments thereof, it is obvious that many alternatives, modifications, and variations will be apparent to those skilled in the art. Therefore, it is intended to encompass all such alternatives, modifications, and variations that fall within the spirit and broad scope of the appended claims.

Claims

1. An optical system for directing image illumination corresponding to a collimated image towards an eye movement box for viewing by the viewer's eye, wherein the optical system comprises a light guide optical element (LOE) formed from a transparent material, and the LOE is A pair of main external surfaces, which are parallel to each other to support the propagation of the image illumination within the LOE by internal reflection at the main external surfaces, A coupled output configuration associated with the coupled output region of the LOE and configured to coupled output at least a portion of the image illumination toward the eye movement box, the coupled output configuration being located within the LOE and including a plurality of mutually parallel partial reflective surfaces that are obliquely inclined with respect to the main external surface, An optical system comprising: at least one planar beam splitter located inside the LOE and parallel to the main outer surface, the at least one planar beam splitter extending at least partially into the coupled output region such as overlapping with, but not with, all, of the mutually parallel partial reflecting surfaces.

2. The optical system according to claim 1, wherein the plurality of mutually parallel partial reflective surfaces have a selected deployment angle with respect to the main external surface, and the selected deployment angle is selected from a range of 55 to 70 degrees.

3. The optical system according to claim 1, wherein the at least one planar beam splitter comprises a single beam splitter that subdivides the plurality of mutually parallel partial reflective surfaces into a first set of partial reflective surfaces and a second set of partial reflective surfaces, the first set of partial reflective surfaces being laterally offset from the second set of partial reflective surfaces.

4. The optical system according to claim 1, further comprising an image projection device for generating the image illumination corresponding to the collimated image, wherein the image projection device is optically coupled to the LOE such that the image illumination is introduced into the coupled input region of the LOE so that it propagates within the LOE by internal reflection.

5. The optical system according to claim 1, wherein the LOE includes a first LOE region and a second LOE region, the main external surface extends across the first LOE region and the second LOE region, the coupled output region is located in the first region of the LOE, the second LOE region includes a coupled region having a coupled configuration associated therewith, the coupled configuration includes a second plurality of mutually parallel partial reflective surfaces non-parallel to the plurality of mutually parallel partial reflective surfaces of the coupled output configuration, and the second plurality of mutually parallel partial reflective surfaces are configured to deflect at least a portion of the image illumination propagating within the second LOE region by internal reflection at the main external surface into the first LOE region by internal reflection from the main external surface.

6. The optical system according to claim 5, further comprising an image projection device for generating the image illumination corresponding to the collimated image, wherein the image projection device is optically coupled to the LOE such that the image illumination is introduced into the coupled input region of the LOE so that it propagates from the coupled input region toward the second LOE region by internal reflection.

7. The optical system according to claim 1, wherein the LOE further comprises a first optical retarder and a second optical retarder, each of which is located inside the LOE and parallel to the main outer surface, and the planar beam splitter is sandwiched between the first optical retarder and the second optical retarder.

8. The optical system according to claim 1, wherein the at least one planar beam splitter comprises two or more planar beam splitters that subdivide the thickness of the LOE between the main outer surfaces into three or more layers of equal thickness.

9. The optical system according to claim 1, wherein the at least one planar beam splitter comprises a single beam splitter that subdivides the thickness of the LOE between the main outer surfaces into two layers of equal thickness, and the image illumination entering one of the two layers corresponds to both the collimated image and the conjugate of the collimated image.

10. An optical system for directing image illumination corresponding to a collimated image towards an eye movement box for viewing by the viewer's eye, wherein the optical system comprises a light guide optical element (LOE) formed from a transparent material, and the LOE is A first LOE region including mutually parallel partial reflective surfaces of a first plurality of planes having a first orientation, A second LOE region including a second plurality of mutually parallel partial reflective surfaces of planes having a second orientation nonparallel to the first orientation, A pair of mutually parallel main external surfaces, each extending across the first LOE region and the second LOE region such that both the first plurality of partial reflective surfaces and the second plurality of partial reflective surfaces are located between the main external surfaces, The second plurality of partial reflective surfaces are inclined obliquely with respect to the main external surface such that a portion of the image illumination propagating within the LOE from the first LOE region to the second LOE region by internal reflection at the main external surface is coupled and output toward the eye movement box from the LOE. The first plurality of partial reflective surfaces are oriented such that a portion of the image illumination propagating within the LOE by internal reflection at the main outer surface is deflected toward the second LOE region from the coupled input region of the LOE. An optical system comprising at least one planar beam splitter located inside the LOE and parallel to the main outer surface, wherein the at least one planar beam splitter is at least partially located within the first LOE region such that it overlaps with at least some of the partial reflecting surfaces of the first plurality of partial reflecting surfaces.

11. The optical system according to claim 10, wherein the at least one planar beam splitter partially extends over the first LOE region such that the at least one planar beam splitter overlaps with a portion, but not all, of the first plurality of partial reflectors.

12. The optical system according to claim 10, wherein the at least one planar beam splitter extends substantially over the entire first LOE region such that the at least one planar beam splitter overlaps with all of the first plurality of partial reflectors.

13. The optical system according to claim 10, wherein the at least one planar beam splitter subdivides at least some of the first plurality of partial reflective surfaces into a first set of partial reflective surfaces and a second set of partial reflective surfaces, the first set of partial reflective surfaces being laterally offset from the second set of partial reflective surfaces.

14. The optical system according to claim 10, wherein the LOE further comprises a first optical retarder and a second optical retarder, each of which is located within the first LOE region and parallel to the main outer surface, and the at least one planar beam splitter is sandwiched between the first optical retarder and the second optical retarder.

15. The optical system according to claim 10, wherein the at least one planar beam splitter comprises two or more planar beam splitters that subdivide the thickness of the LOE between the main outer surfaces into three or more layers of equal thickness.

16. The optical system according to claim 10, wherein the at least one planar beam splitter comprises a single beam splitter that subdivides the thickness of the LOE between the main outer surfaces into two layers of equal thickness, and the image illumination entering one of the two layers corresponds to both the collimated image and the conjugate of the collimated image.

17. The optical system according to claim 16, further comprising an image projection device for generating the image illumination corresponding to the collimated image, wherein the image projection device is optically coupled to the LOE such that the image illumination is introduced into the coupled input region of the LOE so that it propagates from the coupled input region toward the first LOE region by internal reflection.

Images