CN121532692A - An optical system with light-guiding optical elements and homogenized arrangement. - Google Patents

Abstract

An optical system having a homogenizing arrangement and a light guide optical element (LOE) having a pair of parallel major outer surfaces supporting propagation of image illumination within the LOE by internal reflection at the outer surfaces. The LOE has a first region with a first coupling configuration and a second region with a second coupling configuration. The homogenization arrangement receives the image illumination from the image projector via the coupling element and injects the image illumination into the LOE such that the image illumination propagates within the LOE by internal reflection. The homogenizing arrangement has a block of transparent material, at least one beam splitter between a pair of faces of the block, and a reflector generally opposite an interface between the LOE and the block, and performs beam multiplication on received image illumination prior to injection of the image illumination into the LOE.

Description

Optical system with light guide optical element and homogenizing arrangement

Cross Reference to Related Applications

The present application claims priority from U.S. provisional patent application No. 63/547,882, filed on day 2023, month 11, and 9, the disclosure of which is incorporated herein by reference in its entirety.

Technical Field

The present disclosure relates to optical systems, and in particular, to optical systems including light guide optical elements (LOEs) for achieving optical aperture expansion.

Background

Optical arrangements for near-eye displays (NED), head-mounted displays (HMD) and head-up displays (HUD) require a large aperture to cover the area where the eyes of the observer (i.e., user, viewer) are located (commonly referred to as an eye-box or EMB). In order to achieve a compact device, the image to be projected into the eye of the observer 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 through the LOE, which expands (multiplies) the image to generate a large aperture.

To achieve uniformity of the viewed image, the LOE should be uniformly "filled" with the projected image and its conjugate image. This places design constraints on the size and various other aspects of the optical design of the image projector.

Disclosure of Invention

The present disclosure provides an optical system having a homogenizing arrangement and a light guide optical element (LOE) for directing image illumination from an image projector to an eye-box for viewing by a user's eye.

According to the teachings of embodiments of the present disclosure, an optical system for directing image illumination corresponding to a collimated image to an eye box for viewing by an eye of a viewer is provided. The optical system includes a homogenizing arrangement configured to receive image illumination from an image projector via a coupling element, and a light guide optical element (LOE) formed of a transparent material. The LOE includes a first LOE region including a first coupling configuration, a second LOE region including a second coupling configuration, and a pair of mutually parallel primary outer surfaces extending across the first and second LOE regions to support propagation of image illumination within the LOE by internal reflection at the primary outer surfaces, the first coupling configuration being configured to deflect a portion of the image illumination propagating within the LOE by internal reflection at the primary outer surfaces from the homogenizing arrangement toward the second LOE region, and the second coupling configuration being configured to couple a portion of the image illumination propagating within the LOE by internal reflection at the primary outer surfaces from the first LOE region to the second LOE region out of the LOE toward the eyebox. The homogenizing arrangement is configured to inject the received image illumination into the LOE such that the image illumination propagates within the LOE by internal reflection at the main outer surface, and the homogenizing arrangement is further configured to perform beam multiplication on the received image illumination prior to injection into the LOE. The homogenization arrangement includes a block of transparent material having a plurality of faces including at least a first face and a pair of major faces parallel to each other, the block of transparent material optically coupled with the first LOE region to define an interface between the LOE and the homogenization arrangement, the interface being generally opposite the first face, a reflective surface associated with the first face, and at least one planar beam splitter located between and parallel to the pair of major faces and extending at least partially between the reflective surface and the interface.

Optionally, the homogenizing arrangement is configured such that image illumination from the image projector is deflected by the coupling element into the block of transparent material to propagate by internal reflection at the main face and is reflected by the reflective surface to continue to propagate by internal reflection at the main face, and each time the image illumination propagating by internal reflection at the main face encounters at least one planar beam splitter, a portion of the image illumination is transmitted by the at least one planar beam splitter and a portion of the image illumination is reflected by the at least one planar beam splitter.

Optionally, the homogenizing arrangement further comprises an optical retarder associated with the reflecting surface.

Optionally, the homogenizing arrangement further comprises an optical retarder between the coupling element and the at least one planar beam splitter.

Optionally, the image illumination from the image projector is in a first polarization state with respect to the coupling element, the coupling element reflects light polarized in the first polarization state with respect to the coupling element and transmits light polarized in a second polarization state perpendicular to the first polarization state with respect to the coupling element, a pair of main faces of the transparent material block supports propagation of the image illumination within the transparent material block by internal reflection at the pair of main faces, and the homogenizing arrangement further comprises an optical retarder associated with the reflective surface, the optical retarder being configured to rotate the polarization state of the image illumination propagated by internal reflection at the main faces.

Optionally, the first coupling arrangement is oriented such that a portion of the light polarized in the first polarization state with respect to the first coupling arrangement is deflected.

Optionally, the reflective surface is parallel to the interface.

Optionally, the reflective surface is perpendicular to the at least one planar beam splitter.

Optionally, the reflective surface is perpendicular to the primary outer surface.

Optionally, the reflective surface is at an oblique angle relative to at least a portion of the interface.

Optionally, the pair of major faces of the block of transparent material supports propagation of image illumination within the block of transparent material by internal reflection at the pair of major faces, and at least one of the reflective surface or the coupling element has an orientation such that the reflective surface reflects the image illumination propagating through the block of transparent material by internal reflection into a deflection direction such that the image illumination is prevented from being deflected by the coupling element.

Optionally, the at least one planar beam splitter is comprised of a single beam splitter subdividing the thickness of the block of transparent material between the pair of major faces into two regions of equal thickness.

Optionally, the at least one planar beam splitter comprises two or more planar beam splitters subdividing the thickness of the block of transparent material between the pair of major faces into three or more layers of equal thickness.

Optionally, a first one of the pair of major surfaces forms a continuation of a first one of the pair of major outer surfaces and a second one of the pair of major surfaces forms a continuation of a second one of the pair of major outer surfaces.

Optionally, the block of transparent material has a refractive index that is less than the refractive index of the transparent material of the LOE.

Alternatively, the block of transparent material and the LOE form a single unitary piece.

Optionally, the block of transparent material extends away from the LOE in an extension direction substantially opposite to a propagation direction of the image illumination through the first LOE region.

Optionally, the block of transparent material is located outside and adjacent to the LOE to distinguish from the LOE.

Optionally, the first coupling configuration comprises mutually parallel partially reflective surfaces having a first plurality of planes of a first orientation, and the second coupling configuration comprises mutually parallel partially reflective surfaces having a second plurality of planes of a second orientation non-parallel to the first orientation.

Optionally, the first coupling configuration comprises a first at least one diffractive element associated with one of the primary outer surfaces, and the second coupling configuration comprises a second at least one diffractive element associated with one of the primary outer surfaces.

There is also provided, in accordance with the teachings of embodiments of the present disclosure, an optical system for directing image illumination corresponding to a collimated image to an eye box for viewing by an eye of a viewer. The optical system includes a homogenizing arrangement configured to receive image illumination from an image projector via a coupling element, and a light guide optical element (LOE) formed of a transparent material. The LOE includes a pair of mutually parallel major outer surfaces that are parallel to support propagation of image illumination within the LOE by internal reflection at the major outer surfaces, and an out-coupling configuration associated with an out-coupling region of the LOE and configured to couple at least a portion of the image illumination out of the LOE toward the eye-box. The homogenizing arrangement is configured to inject the received image illumination into the LOE such that the image illumination propagates within the LOE by internal reflection at the main outer surface, and the homogenizing arrangement is further configured to perform beam multiplication on the received image illumination prior to injection into the LOE. The homogenization arrangement includes a block of transparent material having a plurality of faces including at least a first face and a pair of major faces parallel to each other, the block of transparent material optically coupled to the first LOE region to define an interface between the LOE and the homogenization arrangement, the interface being generally opposite the first face, a reflective surface associated with the first face, and at least one planar beam splitter located between and parallel to the pair of major faces and extending at least partially between the reflective surface and the interface.

Optionally, the LOE comprises a first LOE region and a second LOE region, and the primary outer surface extends across the first LOE region and the second LOE region, the coupling-out region is located in the second LOE region, and the first LOE region comprises a coupling configuration configured to deflect a portion of the image illumination propagating within the LOE by internal reflection at the primary outer surface from the homogenizing arrangement towards the second LOE region, and the coupling-out configuration is configured to couple out the LOE from the first LOE region to the second LOE region towards the eyebox by a portion of the image illumination propagating within the LOE by internal reflection at the primary outer surface.

In the context of this document, the term "directing" generally refers to light captured within a light transmissive material (e.g., a substrate) by internal reflection at a major outer surface of the light transmissive material such that the light captured within the light transmissive material propagates in a propagation direction through the light transmissive material. When the propagating light is incident on the major outer surface of the light-transmitting material at an incident angle within a specific angle range, the light propagating within the light-transmitting substrate is captured by internal reflection. The internal reflection of the trapped light may be in the form of total internal reflection, whereby propagating light incident on the primary outer surface of the light transmissive material at an angle greater than a critical angle (defined in part by the refractive index of the light transmissive material and the refractive index of the medium surrounding the light transmissive material (e.g., air)) is total internal reflected at the primary outer surface. Alternatively, internal reflection of the captured light may be achieved by a coating (e.g., an angle selective reflective coating) applied to the major outer surface of the light transmissive material to achieve reflection of light incident to the major outer surface over a particular range of angles.

Unless defined otherwise herein, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present disclosure, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

Drawings

Some embodiments of the present disclosure are described herein, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is emphasized that the details shown are by way of example and for purposes of illustrative discussion of embodiments of the present disclosure. In this regard, the description taken with the drawings make apparent to those skilled in the art how the embodiments of the present disclosure may be practiced.

Attention is now directed to the drawings in which like reference numerals or characters designate corresponding or similar parts. In the drawings:

FIGS. 1A and 1B are schematic isometric views of an optical system implemented using a light-guiding optical element (LOE) and an external homogenization arrangement, configured and operated in accordance with the teachings of an embodiment of the present disclosure, showing a top-down injection configuration and a lateral injection configuration;

FIGS. 2 and 3 are schematic front and isometric views, respectively, of the LOE and homogenization arrangement from FIG. 1A or FIG. 1B, showing the general traversal of light rays from the coupling element through the homogenization arrangement and then through the LOE, in accordance with an embodiment of the disclosure;

FIG. 4 is a schematic side view of the homogenization arrangement and LOE from FIGS. 2 and 3, showing in more detail the traversal of light from the coupling element through the homogenization arrangement and then through the LOE;

FIG. 5 is a schematic side view similar to FIG. 4, but wherein the homogenization arrangement includes an optical retarder associated with a reflective surface of the homogenization arrangement, in accordance with an embodiment of the disclosure;

FIG. 6 is a schematic side view similar to FIG. 5, but with an optical retarder positioned between a planar beam splitter of a homogenization arrangement and a coupling element of an optical system, in accordance with an embodiment of the disclosure, and

Fig. 7 and 8 are schematic front and isometric views, respectively, of the LOE and homogenization arrangement from fig. 1A or 1B, showing the general traversal of light rays from the coupling element through the homogenization arrangement and then through the LOE, in accordance with another embodiment of the present disclosure.

Detailed Description

Certain embodiments of the present disclosure provide an optical system with a homogenization arrangement for achieving optical aperture expansion and a light guide optical element (LOE) for the purpose of a heads-up display, and most preferably for a near-eye display, which may be a virtual reality display, or more preferably an augmented reality display.

The principles and operation of an optical system and homogenization arrangement and LOE according to the present disclosure may be better understood with reference to the drawings accompanying the specification.

Before explaining at least one embodiment of the disclosure in detail, it is to be understood that the disclosure is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth in the following description and/or illustrated in the drawings and/or examples. The disclosure is capable of other embodiments or of being practiced or of being carried out in various ways.

Referring now to the drawings, fig. 1A and 1B schematically illustrate an exemplary implementation of a device in the form of a near-eye display (generally designated 10) in the form of an LOE 12 in accordance with the teachings of embodiments of the present disclosure. The near-eye display 10 employs a compact image projector (or "POD") 14, which compact image projector 14 is optically coupled to the LOE to provide an image to be injected into the LOE (interchangeably referred to as a "waveguide," "substrate," or "slab") 12, within the LOE 12, image light being captured by internal reflection at a set of planar outer surfaces that are parallel to each other. The propagating image light interacts with a first optical coupling arrangement that deflects a portion of the image light into a deflection direction, also captured/directed within the LOE 12 by internal reflection. This first optical coupling configuration is not shown in fig. 1A and 1B, but is located in a first region of the LOE 12, designated 16. The deflection of the image light by the first optical coupling arrangement achieves an optical aperture expansion in the first dimension.

In one set of preferred but non-limiting implementations, the first optical coupling arrangement is a first set of planar, mutually parallel partially reflective surfaces (interchangeably referred to as "facets") that are inclined obliquely to the direction of propagation of the image light. In a first set of preferred but non-limiting examples of the present disclosure, the above-mentioned set of facets is orthogonal to the major outer surface of the substrate. In this case, both the injected image and its conjugate that undergoes internal reflection as it propagates within the region 16 are deflected and become a conjugate image that propagates in the direction of deflection. In an alternative set of preferred but non-limiting examples, the first set of partially reflective surfaces are at an oblique angle relative to the major outer surface of the LOE. In the latter case, the injected image or conjugate thereof forms the desired deflected image propagating within the LOE, while other reflections can be minimized, for example, by employing an angle selective coating on the facets that renders the facets relatively transparent to the range of angles of incidence exhibited by images that do not require their reflection.

In another set of non-limiting implementations, the first optical coupling configuration is a diffractive optical element associated with one of the major outer surfaces of the LOE 12.

A first optical coupling configuration (e.g., implemented as a first set of facets or diffractive optical elements) deflects the image illumination from a first propagation direction that is captured within the substrate by internal reflection to a second propagation direction that is also captured within the substrate by internal reflection. When implemented as a first set of facets, each successive facet deflects a portion of the image light into a deflection direction.

The deflected image illumination then passes through a second region (designated 18) into the LOE 12, which may be implemented as an adjacent different substrate or as a continuation of a single substrate, wherein a second optical coupling configuration (another set of partially reflective facets or diffractive optical elements) progressively couples out a portion of the image illumination toward the eyes of an observer located within the region defined as an eye-box (EMB), thereby enabling an optical aperture expansion in a second dimension.

The entire device may be implemented separately for each eye and preferably the entire device is supported relative to the user's head with each LOE 12 facing a corresponding eye of the user. In one particularly preferred option as shown herein, the support arrangement is implemented as an eyeglass frame having sides 20 for supporting the device relative to the user's ears. Other forms of support arrangements may also be used including, but not limited to, a headband, a mask, or a device suspended from a helmet.

In this document and in the drawings, reference is made to an X-axis (dimension) that extends horizontally (fig. 1A) or vertically (fig. 1B) in the general direction of extension of the first LOE region 16, and to a Y-axis (dimension) that extends perpendicular to the X-axis, i.e., vertically in fig. 1A and horizontally in fig. 1B.

In very similar terms, the first LOE region 16 (interchangeably referred to as the first LOE or first region of the LOE) may be considered to effect aperture expansion in the X-dimension (in the direction indicated by the X-arrow in the figure) while the second LOE region 18 (interchangeably referred to as the second LOE or second region of the LOE) effects aperture expansion in the Y-dimension (in the direction indicated by the Y-arrow in the figure). It should be noted that the orientation as shown in fig. 1A may be considered a "top-down" implementation in which image illumination into the main portion of the LOE (second region) enters from the top edge, while the orientation shown in fig. 1B may be considered a "lateral injection" implementation in which an axis, referred to herein as the Y-axis, is deployed horizontally. In the remaining figures, various features of certain embodiments of the present invention will be shown in the context of a "top-down" orientation similar to that of fig. 1A. However, it should be understood that all of these features are equally applicable to lateral implantation implementations that also fall within the scope of the invention. In some cases, other intermediate orientations are also suitable and are included within the scope of the present invention unless explicitly excluded.

The image projector 14 employed with the apparatus of the present invention is preferably configured to generate a collimated image in which the light of each image pixel is a collimated beam of light collimated to infinity with an angular orientation corresponding to the pixel location. Thus, the image illumination spans an angular range corresponding to the two-dimensional angular field of view.

Image projector 14 includes at least one light source that is typically disposed to illuminate a spatial light modulator, such as an LCOS chip. The spatial light modulator modulates the projection intensity of each pixel of the image, thereby generating an image. Alternatively, the image projector may comprise a scanning arrangement, typically implemented using a fast scanning mirror, which scans the illumination from the laser light source across the image plane of the projector, while the intensity of the light beam varies in synchronism with the motion on a pixel-by-pixel basis, projecting the desired intensity for each pixel. In both cases, collimation optics are provided to generate an output projection image that is quasi-to infinity. Some or all of the above components are typically disposed on the surface of one or more Polarizing Beam Splitter (PBS) cubes or other prism arrangements known in the art.

The optical coupling of the image projector 14 to the LOE 12 may be achieved by any suitable optical coupling element, such as, for example, via a coupling prism having an angled input surface, or via a reflective coupling arrangement, via one of the major outer surfaces and/or side edges of the LOE. Details of the coupling element (designated 15 in fig. 2-8) will be discussed in the subsequent sections herein.

It will be appreciated that the near-eye display 10 includes various additional components, typically including a controller 22 for actuating the image projector 14, the controller 22 typically employing power from a small on-board battery (not shown) or some other suitable power source. It will be appreciated that the controller 22 includes all the necessary electronic components, such as at least one processor or processing circuitry, for driving the image projector, all of which are well known in the art.

Turning now to fig. 2 and 3, the optical characteristics of an implementation of a near-eye display are shown in more detail. In particular, a more detailed view of a light guide optical element (LOE) 12 formed of a transparent material is shown, the light guide optical element comprising a first region 16 and a second region 18, the first region 16 comprising a first optical coupling configuration implemented as a first set of planar, mutually parallel partially reflective surfaces 17 having a first orientation, the second region 18 comprising a second optical coupling configuration implemented as a set of planar, mutually parallel partially reflective surfaces 19 having a second orientation that is non-parallel to the first orientation. A set of mutually parallel main outer surfaces 24 extends across the first and second regions 16, 18 such that both the first and second sets of partially reflective surfaces 17, 19 are located between the main outer surfaces 24. Most preferably, the set of major outer surfaces 24 is a pair of surfaces that are each continuous across the entirety of the first and second regions 16, 18, but the option of decreasing or increasing the thickness between the first and second regions 16, 18 is within the scope of the invention. Regions 16 and 18 may be juxtaposed immediately so that they contact at a boundary, which may be a straight boundary or some other form of boundary, or there may be one or more additional LOE regions between these regions to provide various additional optical or mechanical functions, depending on the particular application. Although the invention is not limited to any particular manufacturing technique, in certain particularly preferred implementations, a particularly high quality primary exterior surface is achieved by employing a continuous exterior panel with the separately formed regions 16 and 18 sandwiched therebetween to form a composite LOE structure.

The optical properties of the LOE 12 can be understood by back tracking the image illumination path. The second set of partially reflective surfaces 19 (associated with, i.e., located in, the out-coupling region of the LOE) are at an oblique angle to the main outer surface 24 such that a portion of the image illumination propagating within the LOE 12 by internal reflection at the main outer surface from the first region 16 to the second region 18 is coupled out of the LOE towards an eye-box (EMB) 26. The first set of partially reflective surfaces 17 are oriented obliquely to the direction of propagation of the image illumination such that a portion of the image illumination propagating within the LOE 12 by internal reflection at the main outer surface from the incoupling region is deflected towards the second region 18.

The near-eye display is designed to provide the user's eye with a complete field of view of the projected image, at a location within the range of allowed positions specified by EMB 26 (i.e., a shape generally represented as a rectangle, spaced from the plane of the LOE from which the pupil of the eye will view the projected image). To reach the EMB 26, light must be coupled out from the second region 18 towards the EMB 26 by the second set of partially reflective surfaces 19. In order to provide a complete image field of view, each point in the EMB must receive the entire angular range of the image from the LOE.

In fig. 2 and 3, the sample ends of the field of view are shown, corresponding to the samples of the lower left and lower right pixels of the projected image. The light beam (having a width corresponding to the optical aperture of the image projector when coupled into the LOE) is shown as propagating right and up and right and down from the coupling-in region and partially reflecting from a series of partially reflecting surfaces 17. It is noted that for each directed beam, only a subset of facets 17 generate an image for providing reflection of the corresponding pixel in the image viewed by the user, and only sub-areas of those facets contribute to the view of that pixel. It should also be noted that only the in-plane propagation direction of the light during propagation within the LOE is shown here, but the light actually follows a zig-zag path of repeated internal reflection from the two main outer surfaces, and that the image field of view of a whole dimension is encoded by the tilt angle of the light relative to the main outer surfaces corresponding to the pixel position in the Y dimension.

In general, the LOE 12 should provide image illumination to the human eye in a uniform distribution over all propagation angles of light (also referred to as "field" or "field of view" -FOV) and throughout the EMB. For this purpose, the aperture of each field should be uniformly filled with light. In other words, for any illumination angle corresponding to pixels within the collimated image, the entire cross-section of the LOE in a plane perpendicular to the major outer surface of the LOE should be filled with both the image and its reflection (conjugate) such that at any point in the LOE volume there is a ray corresponding to all pixels of both the collimated image and its conjugate. If the "fill" condition is not met, the light projected from the LOE into the eye will not be evenly distributed. One simple conventional solution to achieve this fill condition is to employ a large image projector or a large coupling element (e.g., coupling prism/reflector). However, none of these solutions is ideal because they introduce a considerable volume at the input of the LOE and increase the overall size of the device. Another solution is to embed a beam multiplication (homogenization) arrangement inside the LOE in a region different from the outcoupling region of the LOE (i.e. the region containing the facets 19) to fill the missing image portions of the injected image illumination. However, this solution is also not ideal, as it requires an additional volume in the LOE, separate from the coupling-out volume, within which additional volume the beam multiplier is placed, which disadvantageously increases the overall size of the LOE.

Embodiments of the present disclosure provide a solution for aperture filling to achieve uniformity of image illumination by providing a homogenizing arrangement 30 coupled with the LOE 12 defining a beam multiplication region. As will be discussed further below, the homogenization arrangement 30 is located upstream of the LOE 12 and downstream of the image projector (and coupling element). In certain embodiments, the homogenization arrangement 30 is external to and adjacent to the LOE (e.g., at an edge portion thereof) to distinguish from the LOE (and from the image projector). The output of the homogenization arrangement also defines the coupling-in region of the LOE. The homogenizing arrangement 30 is configured to receive image illumination from the image projector 14 via injection from the coupling element 15 and deflect the received image illumination to inject the image illumination into the LOE 12 such that the image illumination propagates within the LOE 12 by internal reflection at the main outer surface 24. The homogenizing arrangement 30 is also configured to multiply (i.e., perform beam multiplication on) the received image illumination prior to injection into the LOE, all of which will be described in detail below.

In general, the homogenization arrangement 30 includes a block of transparent material 32, a reflective surface 38, and at least one (i.e., one or more) planar beam splitters 39. The block of transparent material 32 extends away from the LOE 12 in a direction of extension generally opposite to the direction of propagation of the image illumination through the first LOE region 16 (in other words, the direction of extension is generally opposite to the X direction) and has a plurality of faces including at least a first (left) face 33 and a pair of major faces 34.

A reflective surface 38 is associated with the first face 33 (at the first face 33). The reflective surface 38 may be, for example, inside the block of transparent material 32, or outside the block of transparent material 32, for example, bonded to the first face 33. In the illustrated embodiment, the multiple faces of the block of transparent material 32 further include upper and lower faces 36, 37 and a second (right) face 35.

The block of transparent material 32 is a light transmissive substrate in which the major faces 34 are mutually parallel faces that support propagation of the image illumination through the block of transparent material 32 by internal reflection at the faces 34.

The block of transparent material 32 is coupled with the LOE 12 to define an interface 40 between the LOE 12 and the homogenization arrangement 30. The interface 40 is generally opposite the first face 33 and thus generally opposite the reflective surface 38. In the illustrated embodiment, the second face 35 of the block of transparent material 32 is coupled with the edge surface 25 of the LOE 12 at the first LOE region 16 to define an interface 40. Here, the interface 40 is located at an upper portion of the LOE 12, corresponding to the edge surface 25 (left side surface in the drawing) of the first region 16. The edge surfaces 25 are joined to the pair of major outer surfaces 24 and may or may not be planar surfaces, which may or may not be perpendicular to the major outer surfaces 24.

Incidentally, in some embodiments, such as the embodiments shown in fig. 2 and 3, the interface 40 is composed of a single continuous planar interface portion. However, in other embodiments, the interface 40 may include two or more planar interface portions. For example, as will be discussed with reference to fig. 7 and 8, the interface 40 may have two planar interface portions that are inclined obliquely with respect to each other. In such an embodiment, the block of transparent material 32 may have an additional pair of faces instead of a single side face 35.

In the non-limiting embodiment shown in fig. 2 and 3, the reflective surface 38 is parallel to the interface 40 (and also perpendicular to the direction of propagation of the image illumination through the first LOE region 16). However, in other embodiments, the reflective surface 38 is at an oblique angle relative to the interface 40 or an oblique angle relative to a vertical portion of the interface.

In certain non-limiting embodiments, a first major surface of the pair of major surfaces 34 forms a continuation of a first major outer surface of the pair of major outer surfaces 24, and a second major surface of the pair of major surfaces 34 forms a continuation of a second major outer surface of the pair of major outer surfaces 24. In embodiments where the major faces 34 form parallel continuations of the major outer surface 24, the reflective surface 38 may be perpendicular to the major outer surface 24. In general, the reflective surface 38 is preferably perpendicular to the main outer surface 24, but may be at any tilt angle between 90 ° (perpendicular) and 20 ° (measured relative to the main outer surface).

One or more planar beam splitters 39 are located between and parallel to the pair of major faces 34 (inside the block of transparent material 32) and extend (at least partially) between the reflective surface 38 and the interface 40. In the present context, at least partial extension of one or more planar beam splitters 39 means that in some embodiments, the beam splitter 39 may terminate at one edge thereof at or immediately adjacent to the reflective surface 38, and at a generally opposite edge thereof at or immediately adjacent to the interface 40. It should be noted, however, that in some embodiments, one or more of the planar beam splitters 39 may terminate short of the interface 40. The one or more planar beam splitters 39 are also preferably parallel to the major outer surfaces 24 of the LOE 12 and in a plane between the major outer surfaces 24. In the non-limiting embodiment shown in fig. 2 and 3, one or more planar beam splitters 39 are perpendicular to the reflective surface 38.

It is noted that although one or more planar beam splitters 39 are shown in fig. 2 and 3 as having a rectangular shape in a plane parallel to face 34 (and major outer surface 24), the beam splitters may be designed in any suitable shape as long as the beam splitters cover the active area into which light propagates through the block of transparent material 32.

The following paragraphs describe the propagation of the image illumination from the coupling element 15 into the homogenizing arrangement 30 and through the homogenizing arrangement 30 to achieve beam multiplication.

An image illumination (schematically represented as ray 50 in the figure) corresponding to the collimated image is generated by the image projector 14 and reaches the coupling element 15, the coupling element 15 defining an entrance pupil and having a specific orientation. Incidentally, it is noted that the orientation of the coupling element 15 in the configuration according to embodiments of the present disclosure is different from the coupling element orientation in a conventional configuration lacking a homogenization arrangement (or a conventional configuration in which a homogenization arrangement is disposed between the two regions 16 and 18). In such conventional configurations, the coupling element is oriented to deflect collimated image illumination (e.g., to the right) from the image projector into the LOE to be captured by internal reflection between the major outer surfaces of the LOE. In contrast, the coupling element 15 in the configuration according to the embodiments of the present disclosure has a substantially opposite orientation. In particular, the coupling element 15 is deployed in a suitable orientation relative to the homogenizing arrangement 30 such that image illumination from the image projector 15 is deflected by the coupling element 15 away from the LOE 12 and into (injected into) the block of transparent material 32 at a suitable angle relative to the face 34 (and relative to the one or more planar beam splitters 39) such that the image illumination propagates through the block of transparent material 32 by internal reflection at the face 34. Thus, image illumination 50 enters (is injected into) the block of transparent material 32 through an entrance pupil defined by the coupling element 15, typically by deflection at the coupling element 15 (e.g., coupling reflector).

With continued reference to fig. 2 and 3, the optical characteristics of the homogenization arrangement 30 may be better understood with reference to fig. 4, which shows a side view of the homogenization arrangement 30 and the LOE 12. The image illumination 50 is deflected by the coupling element 15 away from the LOE 12 and into the block of transparent material 32 to propagate through the block of transparent material 32 toward the reflective surface 38. The propagated image illumination is reflected back toward the LOE 12 by the reflective surface 38 at an appropriate angle to be injected into the LOE 12 and thus captured by internal reflection at the main outer surface 24. The image illumination 50 propagates through the block of transparent material 32 by internal reflection at the main face 34, encountering the planar beam splitter 39 during propagation. Each time image illumination 50 encounters beam splitter 39, a portion of image illumination 50 passes through planar beam splitter 39 (i.e., is transmitted by planar beam splitter 39) and a portion of image illumination 50 is reflected by planar beam splitter 39, thereby effecting beam multiplication.

Fig. 4 shows beam multiplication and injection of a pair of sample rays 50S1 and 50S2 (thick solid arrows) for image illumination 50. The sample light ray 50S1 is injected (deflected, reflected) into the block of transparent material 32 by a coupling element 15 (denoted herein as coupling reflector/mirror). Upon encountering the beam splitter 39 at point P1, a portion of the sample light ray 50S1 is transmitted by the beam splitter 39, and a portion of the sample light ray 50S1 is reflected by the beam splitter 39. The transmitted and reflected portions of the light ray 50S1 are designated as 50T1 (thin solid arrow) and 50R1 (thin broken arrow), respectively. Light ray 50T1 and light ray 50R1 propagate through the block of transparent material 32 by internal reflection at face 34 in a first direction of propagation (right to left in the figure), are reflected by reflective surface 38, and continue to propagate through the block of transparent material 32 by internal reflection at face 34 in a second direction of propagation (left to right in the figure) opposite the first direction. Light ray 50T1 and light ray 50R1 propagate at an angle such that light rays are injected (coupled) into the LOE 12 to be captured by internal reflection at the major outer surface 24. Similar to the light ray 50S1, the sample light ray 50S2 is also injected (deflected, reflected) into the block of transparent material 32 by the coupling element 15. However, in the figure, the sample ray 50S2 is reflected from the upper face 24 before first encountering the beam splitter 39. At point P2, first encountering beam splitter 39, a portion of sample light ray 50S2 is transmitted by beam splitter 39, and a portion of sample light ray 50S2 is reflected by beam splitter 39. The transmitted and reflected portions of light ray 50S2 are designated as 50T2 (thin solid arrow) and 50R2 (thin dashed arrow), respectively. Light ray 50T2 and light ray 50R2 propagate through the block of transparent material 32 by internal reflection at face 34 in a first direction of propagation (right to left in the figure), are reflected by reflective surface 38, and continue to propagate through the block of transparent material 32 by internal reflection at face 34 in a second direction of propagation (left to right in the figure). Light ray 50T2 and light ray 50R2 propagate at an angle such that their light rays are injected (coupled) into the LOE 12 to be captured by internal reflection at the major outer surface 24. It will be appreciated that each time a reflected or transmitted light encounters a beam splitter, a portion of the light is transmitted through the beam splitter and a portion of the light is reflected by the beam splitter. Thus, each of the light rays 50T1, 50T2, 50R1, 50R2 may be further separated via transmission and reflection at the beam splitter.

It should be appreciated that the light propagation described above occurs for all light rays of the beam of light that span the input illumination 50, thereby effecting multiplication of the input beam 50 from the image projector and filling in any missing image portions of the image illumination when injected into the LOE 12.

In certain embodiments, the planar beam splitter 39 consists of a single beam splitter disposed at the midplane of the block of transparent material 32 (between the major faces 34) to subdivide the thickness of the block of transparent material 32 between the major faces 34 into two regions of equal thickness. In such embodiments, the plane in which the beam splitter 39 also lies is also at the mid-plane of the LOE 12 (i.e., the mid-plane between the major outer surfaces 24). It is noted that the embodiments described and illustrated herein can be readily extended to the case of n planar beam splitters that subdivide the thickness of the block of transparent material 32 between the major faces 34 into n+1 layers of equal thickness (integer value n is greater than 2). In certain embodiments, the thThe reflectivity of the individual planar beam splitters may be。

One or more of the planar beam splitters 39 are partially reflective elements, preferably having a reflectivity of about 50%, although reflectivities in the range of 20% to 70% may also be suitable. Structurally, the partial reflectivity of the planar beam splitter may be achieved using any suitable partially 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.

It is noted that the deployment geometry of the homogenizing arrangement 30 and the coupling element 15 may be such that some of the image radiation exiting the homogenizing arrangement 30 may be deflected by the coupling element 15 to deflect away from the LOE 12 or at angles at which the image radiation is not captured within the LOE by internal reflection. Thus, not all light rays of the image illumination may be successfully injected into the LOE 12, resulting in gaps or missing portions of the out-coupled image. Referring now to fig. 5, an embodiment of the present disclosure is shown that addresses this problem of undesired deflection caused by the coupling element 15. Here, the coupling element 15 is realized as a polarization-selective reflective surface (also referred to as a polarizing beam splitter or "PBS"), and the homogenizing arrangement 30 is further provided (e.g. in front of the reflective surface 38) with an optical retarder 42 (here realized as a quarter-wave plate) associated with the reflective surface 38. In the illustrated embodiment, the coupling element 15, which is a PBS, is configured to reflect light polarized in a first polarization state (e.g., S-polarization) with respect to the coupling element 15 and transmit light polarized in a second polarization state (e.g., P-polarization) perpendicular to the first polarization state with respect to the coupling element 15. The image projector may be configured to generate polarized light such that the generated image illumination is polarized in a first polarization state with respect to the coupling element 15. In other implementations, the image projector may be configured to generate unpolarized light, and a polarizing element may be disposed between the output of the image projector and the input to the coupling element 15 such that the generated image illumination is polarized at the input to the coupling element 15.

As an example, and with continued reference to fig. 5, S-polarized image illumination (represented in the figure as sample light ray 50 SP) from the image projector is reflected by the coupling element 15 into the block of transparent material 32. The S-polarized image illumination propagates through the block of transparent material 32 toward the reflective surface 38 by internal reflection at the face 34 in the same or similar manner as described above. Specifically, the propagation of the image illumination therealong through the block of transparent material 32 encounters the planar beam splitter 39, whereupon a portion of the image illumination is transmitted by the planar beam splitter 39 and a portion of the image illumination is reflected by the planar beam splitter 39. The transmissive portions are indicated by solid arrows in the figure, and the reflective portions are indicated by broken arrows in the figure. Before reaching the reflective surface 38, the S-polarized image illumination passes through an optical retarder 42, which optical retarder 42 rotates the polarization of the image illumination such that the illumination is unpolarized (represented in the figure as ray 50 UP). The unpolarized illumination is then reflected by the reflective surface 38 and passed back through the optical retarder 42, the optical retarder 42 again rotating the polarization of the image illumination so that the illumination is P-polarized with respect to the coupling element 15. The P-polarized (second polarization state) image illumination, represented in the figures as rays 50PP, propagates through the block of transparent material 32 by internal reflection at the face 34 and reaches the coupling element 15, and the coupling element 15 transmits the image illumination to inject it into the LOE 12 and propagates between the major outer surfaces 24 by internal reflection.

In order to achieve a suitable deflection of the propagation image illumination from the first region 16 to the second region 18, the first optical coupling arrangement should be designed to deflect the portion of the light in a suitable polarization state with respect to the first coupling arrangement. Preferably, the first optical coupling configuration is oriented with respect to the coupling element 15 such that light polarized with respect to the coupling element 15 in a first polarization state is polarized with respect to the first optical coupling configuration in a second polarization state and light polarized with respect to the coupling element 15 in the second polarization state is polarized with respect to the first optical coupling configuration in the first polarization state. Thus, the first optical coupling configuration is preferably designed and arranged to deflect a portion of light polarized in a first polarization state with respect to the first coupling configuration. As an example, when the first optical coupling configuration is implemented as facet 17, the facet should be designed to partially reflect the image illumination polarized in a first polarization state (e.g. S-polarization) with respect to facet 17. This can be achieved by designing the facets 17 with a suitable optical coating to achieve polarization-selective reflectivity and by arranging the facets 17 such that they are orthogonal to the coupling element 15.

Fig. 6 shows an alternative embodiment of a homogenization arrangement 30 provided with an optical retarder 42. Here, an optical retarder 42, implemented as a quarter-wave plate, is located between the coupling element 15 and the planar beam splitter 39, for example at the interface 40 between the LOE 12 and the homogenization arrangement 30. Deployment of the optical retarder 42 at the interface 40 may be accomplished, for example, by attaching the optical retarder 42 to the edge surface 25 of the LOE 12 or the second face 35 of the block of transparent material 32 (e.g., via optical cement) and then coupling the LOE 12 and the block of transparent material 32 together at the interface 40. In the non-limiting example shown in fig. 6, S-polarized image illumination 50SP from the image projector passes through optical retarder 42 upon entering transparent material block 32 such that the illumination propagating through transparent material block 32 is unpolarized (denoted as 50UP in the figure). The illumination 50UP encounters the planar beam splitter 39 along its propagation through the block of transparent material 32 toward the reflective surface 38 (i.e., right to left), so that a portion of the image illumination is transmitted by the planar beam splitter 39 and a portion of the image illumination is reflected by the planar beam splitter 39. The transmitted and reflected portions of the illumination are indicated in the figure by solid and dashed arrows, respectively. The unpolarized illumination is then reflected by the reflective surface 38 and propagates back toward the LOE 12 (i.e., left to right). Before entering the LOE 12, the illumination passes back through the optical retarder 42, the optical retarder 42 again rotates the polarization of the image illumination so that the illumination is P-polarized with respect to the coupling element 15. The P-polarized image illumination (denoted 50PP in the figure) now injected into the LOE 12 is transmitted by the coupling element 15 and continues to propagate through the LOE 12 by internal reflection between the major outer surfaces 24.

It is noted that although the beam propagation scenario described above with reference to fig. 5 and 6 relates to S-polarized image illumination from an image projector, similar results may be achieved for the case where the image illumination received at the coupling element 15 from the image projector is P-polarized with respect to the coupling element 15. In such a case, coupling element 15 may be implemented as a PBS configured to reflect light that is P-polarized with respect to coupling element 15 and transmit light that is S-polarized with respect to coupling element 15, and facet 17 may be designed to partially reflect light that is P-polarized with respect to facet 17.

Turning now to fig. 7 and 8, another embodiment according to the present disclosure is shown that addresses the problem of gaps in the out-coupled image due to unwanted deflection of the coupling element 15. Here, instead of employing a PBS and an optical retarder, the homogenization arrangement 30 and/or the coupling element 15 are oriented such that undesired deflection of some of the image illumination caused by the coupling element 15 is reduced or completely avoided. In a particularly preferred but non-limiting embodiment, the orientation of the homogenization arrangement 30 may be such that the reflective surface 38 is at an oblique angle relative to at least a portion of the interface 40.

In the illustrated embodiment, the interface 40 is comprised of two interface portions, however, although it is noted that the interface 40 may be a single continuous planar interface portion as shown in fig. 2 and 3. The two interface portions include a vertical interface portion 40v (generally along the Y dimension) with the reflective surface 38 being inclined obliquely with respect to the vertical interface portion 40v, and an inclined interface portion 40o, the inclined interface portion 40o also being inclined obliquely with respect to the vertical portion 40 v. Furthermore, in the illustrated embodiment, the block of transparent material 32 may have, instead of the second face 35, a vertical side face 35v and an inclined side face 35o inclined obliquely with respect to the face 35 v. Interface portion 40v and interface portion 40o may be defined in part by face 35v and face 35o, respectively. In such an embodiment, the interface 40 is still considered to be generally opposite the first face 33 (and the reflective surface 38) because both the constituent portion 40v and the constituent portion 40o are opposite the face 33/reflective surface 38.

The oblique inclination of the reflective surface 38 relative to the interface is such that the image illumination propagating through the block of transparent material 32 is deflected (reflected) by the reflective surface 38 into a deflection direction away from the coupling element 15 (as can be seen in fig. 7 and 8). Such oblique tilting may be achieved by forming the block of transparent material 32 such that the first face 33 is obliquely tilted with respect to the interface 40 or the vertical portion 40v of the interface 40 (i.e., with respect to the second face 35 or the vertical face 35 v) such that the block of transparent material 32 assumes a trapezoidal shape at its major face 34 (and the one or more planar beam splitters 39 assumes a trapezoidal shape in a plane parallel to the face 34 and the major outer surface 24). In other words, the oblique tilting of the reflective surface 38 may be achieved by forming the block of transparent material 32 such that the reflective surface 38 is obliquely tilted with respect to the propagation direction of the image light through the first LOE region 16.

In fig. 7, the deployment angle of the reflective surface 38 relative to the interface 40 is denoted α. It has been found that a deployment angle a in the range of 90 deg. + -45 deg. achieves good beam multiplication performance while deflecting the image illumination to avoid unwanted deflection caused by the coupling element 15.

The deployment configuration of the homogenization arrangement 30 in the embodiment shown in fig. 7 and 8 also allows the positioning of the entrance pupil (coupling element 15) relative to the LOE 12 according to other geometric constraints. For example, in the present embodiment, the coupling element 15 may be disposed closer to the top or upper portion of the first region 16, in association with one of the major surfaces 24.

In addition to or instead of the tilt angle disposition of the reflective surface 38, the coupling element 15 (and/or the image projector) may be disposed in an orientation that avoids undesired deflection of some of the image illumination caused by the coupling element 15. Preferably, in addition to selecting the deployment position of the coupling element 15 relative to the upper portion of the first region 16, the deployment orientation of the coupling element 15 may include appropriately selecting its azimuth angle(Measured relative to the reflective surface 38) and its elevation angle θ (measured relative to the primary outer surface 24). It has been found that at an azimuth angle of + -45 degThe deployment of the coupling element 15 alone or in combination with an elevation angle θ in the range of 20 ° to 70 ° achieves good deflection of the image illumination into the homogenizing arrangement 30 while avoiding unwanted deflection caused by the coupling element 15.

According to some embodiments, the embodiments shown in fig. 7 and 8 may be modified to include an optical retarder (similar to that described with reference to fig. 6) between the coupling element 15 and the beam splitter 39, except that the optical retarder is implemented as a half-wave plate. In such an embodiment, the deployment location of the optical retarder, in combination with the implementation as a half-wave plate, enables the planar beam splitter 39 to operate with illumination of the same polarization state (e.g., S-polarization) in both light directions during propagation of the image illumination through the transparent material block 32.

As discussed above, the embedded beam splitter 39 provides effective beam multiplication of the image illumination 50 prior to injection of the image illumination 50 into the LOE 12. However, although the embedded beam splitter 39 is effective, the homogenizing arrangement 30 itself does introduce additional volume into the near-eye display (optical system) by extending in the direction of extension. Thus, it may be beneficial to reduce the size and geometry of the homogenization arrangement 30, in particular to reduce the length of the beam splitter 39 (measured along the horizontal dimension in fig. 4), thereby reducing the amount of extension in the direction of extension. Certain embodiments of the present disclosure provide a solution for reducing the size and geometry of the homogenization arrangement 30 without sacrificing the efficacy of beam multiplication. According to such an embodiment, the size (length) of the beam splitter 39 may be reduced by forming the block of transparent material 32 from a material having a refractive index that is less than (lower than) the Refractive Index (RI) of the transparent material of the LOE 12. Lowering the RI of the block of transparent material 32 relative to the RI of the LOE reduces the length of the light path through the block of transparent material 32, which thus reduces the required length of the beam splitter 39. Thus, this difference in refractive index enables the homogenizing arrangement 30 to achieve the same or similar beam multiplication effect as in the previously discussed embodiments, but with a shorter beam splitter. In other words, by employing materials of different refractive indices in combination with a shortened beam splitter, the beam splitter may achieve a rapid filling of the missing image portions of the collimated image within a relatively short distance along the length of the beam splitter.

In one set of non-limiting examples, the LOE 12 may be formed of a transparent material having a refractive index of about 1.7 (e.g., SF-5 glass having a refractive index of 1.67), and the block of transparent material 32 may be formed of a material having a refractive index of about 1.5 (e.g., BK 7).

While in some cases it may be advantageous to employ a higher refractive index for the block of transparent material 32, in some implementations it may be more practical to construct the block of transparent material 32 and the LOE 12 from the same material (and thus with the same refractive index). According to some embodiments of such implementations, the block of transparent material 32 may form a continuation of the first LOE region 16 such that the block of transparent material 32 and the LOE 12 form a single unitary piece.

While the embodiments described so far relate to a homogenization arrangement upstream of (e.g., outside of and adjacent to) an LOE that achieves two-dimensional (2D) aperture expansion via two sets of optical coupling configurations (e.g., two sets of facets or two sets of diffractive elements), the homogenization arrangement according to embodiments of the present disclosure is also suitable for use with one-dimensional (1D) LOEs (i.e., LOEs that achieve only a single-dimensional aperture expansion). Such a 1D LOE has a single optical coupling configuration (out-coupling configuration) implemented, for example, as a set of facets that are tilted obliquely with respect to the major outer surfaces of the LOE, or as a diffractive optical arrangement associated with one of the major outer surfaces of the LOE in embodiments where a homogenization arrangement is used with a 1D LOE, the light beam from the image projector's image illumination is multiplied (by the homogenization arrangement) and injected into the LOE, whereupon it propagates by internal reflection at a pair of major outer surfaces of the LOE, and is gradually coupled out of the LOE toward the eyebox by the out-coupling configuration (e.g., tilted facets or diffractive elements).

The description of the various embodiments of the present disclosure has been presented for purposes of illustration, but is not intended to be exhaustive or limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen in order to best explain the principles of the embodiments, the practical application, or the technical improvement of the technology found in the market, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

The word "exemplary" is used herein to mean "serving as an example, instance, or illustration. Any embodiment described as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments and/or to exclude features from other embodiments.

It is appreciated that certain features of the disclosure, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the disclosure that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or in any other described embodiment of the disclosure. Certain features described in the context of various embodiments should not be considered as essential features of such embodiments unless the embodiment is not operable without such elements.

To the extent that the appended claims are written without multiple references, this is done solely to accommodate formal requirements in a jurisdiction in which such multiple references are not permitted. It should be noted that all possible combinations of features implicit by making multiple references to the claims are expressly contemplated and should be considered part of this disclosure.

While the present disclosure has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the present disclosure is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

Claims (22)

1. An optical system for directing image illumination corresponding to a collimated image to an eye-box for viewing by an eye of a viewer, the optical system comprising:

a homogenizing arrangement configured to receive the image illumination from an image projector via a coupling element, and

A lightguide optical element LOE formed from a transparent material, the LOE comprising:

a first LOE region, said first LOE region including a first coupling configuration,

A second LOE region comprising a second coupling configuration, an

A pair of mutually parallel primary outer surfaces extending across the first and second LOE regions to support propagation of the image illumination within the LOE by internal reflection at the primary outer surfaces, wherein the first coupling arrangement is configured to deflect a portion of the image illumination propagating within the LOE by internal reflection at the primary outer surfaces from the homogenizing arrangement towards the second LOE region, and wherein the second coupling arrangement is configured to couple a portion of the image illumination propagating within the LOE by internal reflection at the primary outer surfaces from the first LOE region to the second LOE region out of the LOE towards the eyebox,

Wherein the homogenizing arrangement is configured to inject the received image illumination into the LOE such that the image illumination propagates within the LOE by internal reflection at the main outer surface, and wherein the homogenizing arrangement is further configured to perform beam multiplication on the received image illumination prior to injection into the LOE, the homogenizing arrangement comprising:

a block of transparent material having a plurality of faces including at least a first face and a pair of mutually parallel major faces, the block of transparent material being optically coupled with the first LOE region to define an interface between the LOE and the homogenization arrangement, the interface being generally opposite the first face,

A reflective surface associated with the first face, and

At least one planar beam splitter located between and parallel to the pair of major faces and extending at least partially between the reflective surface and the interface.

2. The optical system of claim 1, wherein the homogenizing arrangement is configured such that the image illumination from the image projector is deflected into the block of transparent material by the coupling element to propagate by internal reflection at the main face and reflected by the reflecting surface to continue to propagate by internal reflection at the main face, wherein a portion of the image illumination is transmitted by the at least one planar beam splitter and a portion of the image illumination is reflected by the at least one planar beam splitter each time the image illumination propagating by internal reflection at the main face encounters the at least one planar beam splitter.

3. The optical system of claim 1, wherein the homogenization arrangement further comprises an optical retarder associated with the reflective surface.

4. The optical system of claim 1, wherein the homogenization arrangement further comprises an optical retarder between the coupling element and the at least one planar beam splitter.

5. The optical system of claim 1, wherein the image illumination from the image projector is in a first polarization state with respect to the coupling element, wherein the coupling element reflects light polarized in a first polarization state with respect to the coupling element and transmits light polarized in a second polarization state perpendicular to the first polarization state with respect to the coupling element, wherein the pair of major faces of the block of transparent material supports propagation of the image illumination within the block of transparent material by internal reflection at the pair of major faces, and wherein the homogenizing arrangement further comprises an optical retarder associated with the reflective surface, the optical retarder configured to rotate a polarization state of the image illumination propagating by internal reflection at the major faces.

6. The optical system of claim 5, wherein the first coupling configuration is oriented such that a portion of light polarized in the first polarization state with respect to the first coupling configuration is deflected.

7. The optical system of claim 1, wherein the reflective surface is parallel to the interface.

8. The optical system of claim 1, wherein the reflective surface is perpendicular to the at least one planar beam splitter.

9. The optical system of claim 1, wherein the reflective surface is perpendicular to the primary outer surface.

10. The optical system of claim 1, wherein the reflective surface is at an oblique angle relative to at least a portion of the interface.

11. The optical system of claim 1, wherein the pair of major faces of the block of transparent material supports propagation of the image illumination within the block of transparent material by internal reflection at the pair of major faces, and wherein at least one of the reflective surface or the coupling element has an orientation such that the reflective surface reflects the image illumination propagating through the block of transparent material by internal reflection into a deflection direction such that the image illumination is prevented from being deflected by the coupling element.

12. The optical system of claim 1, wherein the at least one planar beam splitter consists of a single beam splitter subdividing the thickness of the block of transparent material between the pair of major faces into two regions of equal thickness.

13. The optical system of claim 1, wherein the at least one planar beam splitter comprises two or more planar beam splitters that subdivide a thickness of the block of transparent material between the pair of major faces into three or more layers of equal thickness.

14. The optical system of claim 1, wherein a first major face of the pair of major faces forms a continuation of a first major outer face of the pair of major outer faces, and wherein a second major face of the pair of major faces forms a continuation of a second major outer face of the pair of major outer faces.

15. The optical system of claim 1, wherein the block of transparent material has a refractive index that is less than a refractive index of the transparent material of the LOE.

16. The optical system of claim 1, wherein the block of transparent material and the LOE form a single unitary piece.

17. The optical system of claim 1, wherein the block of transparent material extends away from the LOE in an extension direction that is substantially opposite to a propagation direction of the image illumination through the first LOE region.

18. The optical system of claim 1, wherein the block of transparent material is located outside and adjacent to the LOE to distinguish from the LOE.

19. The optical system of claim 1, wherein the first coupling configuration comprises mutually parallel partially reflective surfaces having a first plurality of planes of a first orientation, and wherein the second coupling configuration comprises mutually parallel partially reflective surfaces having a second plurality of planes of a second orientation that is not parallel to the first orientation.

20. The optical system of claim 1, wherein the first coupling configuration comprises a first at least one diffractive element associated with one of the primary exterior surfaces, and wherein the second coupling configuration comprises a second at least one diffractive element associated with one of the primary exterior surfaces.

21. An optical system for directing image illumination corresponding to a collimated image to an eye-box for viewing by an eye of a viewer, the optical system comprising:

a homogenizing arrangement configured to receive the image illumination from an image projector via a coupling element, and

A lightguide optical element LOE formed from a transparent material, the LOE comprising:

a pair of mutually parallel major outer surfaces that are parallel to support propagation of the image illumination within the LOE by internal reflection at the major outer surfaces, an

An out-coupling configuration associated with an out-coupling region of the LOE and configured to couple at least a portion of the image illumination out of the LOE toward the eye-box,

Wherein the homogenizing arrangement is configured to inject the received image illumination into the LOE such that the image illumination propagates within the LOE by internal reflection at the main outer surface, and wherein the homogenizing arrangement is further configured to perform beam multiplication on the received image illumination prior to injection into the LOE, the homogenizing arrangement comprising:

a block of transparent material having a plurality of faces including at least a first face and a pair of mutually parallel major faces, the block of transparent material being optically coupled with the first LOE region to define an interface between the LOE and the homogenization arrangement, the interface being generally opposite the first face,

A reflective surface associated with the first face, and

At least one planar beam splitter located between and parallel to the pair of major faces and extending at least partially between the reflective surface and the interface.

22. The optical system of claim 21, wherein the LOE comprises a first LOE region and a second LOE region, and the primary outer surface extends across the first LOE region and the second LOE region, wherein the out-coupling region is located in the second LOE region, and wherein the first LOE region comprises a coupling configuration configured to deflect a portion of the image illumination propagating within the LOE by internal reflection at the primary outer surface from the homogenization arrangement toward the second LOE region, and wherein the out-coupling configuration is configured to couple a portion of the image illumination propagating within the LOE by internal reflection at the primary outer surface from the first LOE region to the second LOE region out of the LOE toward the eye chamber.