Optical structure, optical aperture multiplier and manufacturing method

Abstract

The present disclosure provides optical structures, optical aperture multipliers, and methods of manufacture. The manufacturing method comprises the following steps: obtaining a transparent plate with a first pair of parallel surfaces, wherein the first pair of parallel surfaces comprise a first surface and a second surface; obtaining a first optical structure having a plurality of faces including a coupling face, the first optical structure including a plurality of sets of mutually parallel partially reflective inner surfaces, where, for each set, the mutually parallel partially reflective inner surfaces of the set are inclined obliquely with respect to the coupling face; optically coupling the transparent plate with the first optical structure such that the second face is in facing relationship with the coupling face, thereby forming a second optical structure; and sheetly cutting out at least one optical aperture multiplier from the second optical structure by cutting the second optical structure along at least two cutting planes substantially perpendicular to the coupling face wherein the at least one partially reflective surface is associated with the second face or inside the transparent plate.

Description

[0001] This application is a divisional application of the Chinese invention patent application filed on February 24, 2022, with international application number PCT / IL2022 / 050216, invention name “Optical aperture multiplier with rectangular waveguide”, and application number 202280008909.4 after entering the Chinese national stage.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority to U.S. Provisional Patent Application No. 63 / 153,433 filed on February 25, 2021 and U.S. Provisional Patent Application No. 63 / 297,299 filed on January 7, 2022, the disclosures of which are incorporated herein by reference in their entirety. Technical Field

[0004] The present invention relates to an optical aperture multiplier, and in particular to an optical aperture multiplier including a rectangular optical waveguide optically coupled to a thin-plate type optical waveguide. Background Art

[0005] Optical devices that provide two-dimensional optical aperture expansion (or multiplication) have been described in various publications by Lumus Ltd. (Israel). In a particular set of such optical devices, the two-dimensional aperture expansion is achieved by two optical waveguides. The first optical waveguide has two pairs of parallel faces forming a rectangular cross-section and has a first set of partially reflective inner surfaces, which are inclined to the elongation direction of the first optical waveguide. A second optical waveguide in the form of a thin plate is optically coupled to the first (rectangular) waveguide and has a pair of parallel main outer faces and a second set of partially reflective inner surfaces inclined to the main outer faces. The optical coupling and the sets of partially reflective inner surfaces cause the image light coupled into the rectangular waveguide to advance along the rectangular waveguide by quadruple internal reflection (at the two pairs of parallel faces), and a certain proportion of the intensity of the image is reflected at the first set of inner surfaces to be coupled into the second waveguide. Then, the image light advances by internal reflection at the main outer faces of the second waveguide, and a certain proportion of the intensity of the image is reflected at the second set of inner surfaces to be coupled out of the second waveguide to be viewed by the viewer's eyes. Summary of the invention

[0006] Various aspects of the present invention provide an optical aperture multiplier having a rectangular waveguide. Some preferred embodiments according to the first aspect of the present invention provide an optical aperture multiplier, each optical aperture multiplier having an optical coupling structure for transmitting image light to a first rectangular optical waveguide optically coupled to a second thin-plate optical waveguide. The rectangular waveguide has two pairs of parallel faces (forming a rectangular cross-section) and is configured to guide light by quadruple internal reflection at the two pairs of parallel faces, and couple the guided light into the second waveguide via a set of partially reflective surfaces inside the rectangular waveguide. The second waveguide has a pair of parallel faces and is configured to guide the coupled light by internal reflection at the pair of parallel faces, and couple the guided light out toward a viewer via a set of partially reflective surfaces inside the second waveguide (or via one or more diffraction elements). In some embodiments, the optical coupling structure is disposed on a portion of the front or back side of the rectangular waveguide, the portion being adjacent to a second region of the interface between the two waveguides, the second region of the interface having optical properties different from those of the first region of the interface. In one set of embodiments, the first region of the interface comprises a reflective coating and the second region is uncoated or comprises a low refractive index material or coating. In another set of embodiments, the first region of the interface is uncoated and the second region is coated with a low refractive index material.

[0007] Some preferred embodiments according to the second aspect of the present invention provide a rectangular waveguide that does not include a set of partially reflective surfaces inside the rectangular waveguide. Instead, optical coupling of light from the rectangular waveguide into a second waveguide is performed by a partially reflective surface associated with and parallel to the lower surface of the rectangular waveguide, which forms an optical coupling (interface) with the second waveguide. In some preferred embodiments, the partially reflective surface is formed by coating the lower surface of the rectangular waveguide with one or more dielectric layers, and the light coupled into the rectangular waveguide is s-polarized relative to the coated lower surface. Using partially reflective surfaces instead of a set of partially reflective surfaces inside the rectangular waveguide can simplify the manufacturing process and reduce the manufacturing cost of the optical aperture multiplier.

[0008] According to the teachings of an embodiment of the present invention, an optical aperture multiplier is provided. The optical aperture multiplier includes: a first optical waveguide and an optical coupling-in structure. The first optical waveguide has a first pair of parallel faces including a first face and a second face and a second pair of parallel faces including a third face and a fourth face, the pair of parallel faces together forming a rectangular cross-section, the first optical waveguide is configured to guide light by quadruple internal reflection at the pair of parallel faces and is associated with an outcoupling structure, the outcoupling structure couples light from the first optical waveguide to a second optical waveguide optically coupled to the first optical waveguide, the first face or the second face is subdivided into first and second regions having different optical properties, respectively. The optical coupling-in structure includes a surface that transmits light into the first waveguide, the surface is disposed to be associated with a portion of the third face or the fourth face adjacent to the second region, so that an edge associated with the surface trims an input collimated image in a first dimension, and a boundary between the first region and the second region trims the input collimated image in a second dimension to produce a trimmed collimated image, and the trimmed collimated image advances through the first optical waveguide by quadruple internal reflection.

[0009] Optionally, a boundary between the first region and the second region together with an image of the boundary presents an apparent input optical aperture when viewed along the optical input axis.

[0010] Optionally, some of the input collimated image is reflected at points on the first face that intersect or overlap an edge.

[0011] Optionally, the edge is a first edge of the surface, and the surface comprises a second edge, the second edge being a common edge with a light incident surface, the light incident surface receiving the input collimated image from the optical image generator.

[0012] Optionally, the edge is parallel to the light incident surface.

[0013] Optionally, the edge is non-parallel to the light incident surface.

[0014] Optionally, the surface receives an input collimated image from an optical image generator and the edge is a first edge of the surface and the surface includes a second edge that is a common edge with a reflective surface that reflects the received input collimated image back to the surface to be trimmed by the edge.

[0015] Optionally, the optical aperture multiplier also includes a second optical waveguide having a third pair of parallel surfaces and configured to guide light by internal reflection at the third pair of parallel surfaces, and the second optical waveguide includes a plurality of partially reflective surfaces between and inclined to the third pair of parallel surfaces, the plurality of partially reflective surfaces coupling light out of the second optical waveguide.

[0016] Optionally, a coating or material is disposed in association with the second face to subdivide the first face into a first region and a second region.

[0017] Optionally, the optical aperture multiplier further comprises an optical substrate comprising a fifth facet and optically coupled to the first optical waveguide at the first facet, and a coating or material is associated with the first facet to subdivide the first facet into the first region and the second region.

[0018] Optionally, the optical out-coupling configuration comprises a plurality of partially reflective surfaces at least partially traversing the first optical waveguide and obliquely inclined to the elongation direction of the first optical waveguide.

[0019] Optionally, the optical out-coupling construction comprises a partially reflective surface associated with the second face.

[0020] According to an embodiment of the teachings of the present invention, an optical aperture multiplier is also provided. The optical aperture multiplier includes: a first optical waveguide, which has a first pair of parallel faces including a first face and a second face and a second pair of parallel faces including a third face and a fourth face, the pair of parallel faces together form a rectangular cross-section, and the partially reflective surface is associated with the second face and is parallel to the second face; an optical coupling structure for coupling polarized light corresponding to an image into the first optical waveguide with an initial propagation direction at a coupling angle inclined to both the first pair of parallel faces and the second pair of parallel faces, and the polarized light is s-polarized relative to the second face; and a second optical waveguide, which has a plurality of faces including a third pair of parallel faces, and the second optical waveguide is The second optical waveguide is optically coupled to the first optical waveguide at an interface between one of the faces and the second face, an optical out-coupling structure is associated with the second optical waveguide, and the optical coupling and the partially reflective surface are configured such that when light corresponding to an image is coupled into the first optical waveguide: the light advances along the first optical waveguide by quadruple internal reflection, wherein a certain proportion of the intensity of the light is transmitted at the partially reflective surface to be coupled into the second optical waveguide; and the light propagates within the second optical waveguide by internal reflection at a third pair of parallel faces, wherein a certain proportion of the intensity of the light propagating within the second optical waveguide is deflected out of the second optical waveguide by the optical out-coupling structure.

[0021] Optionally, at least a majority of the second face comprises one or more dielectric coatings to form a partially reflective surface and to render the partially reflective surface partially reflective to s-polarized light.

[0022] Optionally, the optical aperture multiplier further comprises a wave plate, which is located at the interface and is used to rotate the polarization state of the light to be coupled into the second optical waveguide.

[0023] Optionally, the optical out-coupling structure comprises a plurality of partially reflective surfaces disposed within the second optical waveguide and tilted to the third pair of parallel surfaces.

[0024] Optionally, the optical out-coupling construction comprises a diffractive optical element associated with at least one of the third pair of parallel faces.

[0025] According to an embodiment of the teachings of the present invention, an optical aperture multiplier is also provided. The optical aperture multiplier includes: a first optical waveguide having a first pair of parallel faces including a first face and a second face and a second pair of parallel faces including a third face and a fourth face, the pair of parallel faces together forming a rectangular cross-section, a partially reflective surface associated with the second face and parallel to the second face; and a second optical waveguide having a plurality of faces including the third pair of parallel faces, the second optical waveguide being optically coupled to the first optical waveguide at an interface between one of the faces of the second optical waveguide and the second face, a light redirection arrangement being associated with a first region of the second optical waveguide, and an optical outcoupling structure being associated with a second region of the second optical waveguide, the optical coupling, the partially reflective surface, the light redirection arrangement, and the optical outcoupling structure being The optical waveguide is configured such that when light corresponding to an image is coupled into the first optical waveguide: the light advances along the first optical waveguide by quadruple internal reflection, wherein a certain proportion of the intensity of the light is transmitted at the partially reflective surface to be coupled into the first region of the second optical waveguide; and the light propagates within the first region of the second optical waveguide by internal reflection at a third pair of parallel surfaces, wherein a certain proportion of the intensity of the light is deflected by the light redirection arrangement to be redirected into the second region of the optical waveguide; and the light propagates within the second region of the second optical waveguide by internal reflection at the third pair of parallel surfaces, wherein a certain proportion of the intensity of the light propagating in the second region of the second optical waveguide is deflected out of the second optical waveguide by the optical out-coupling structure.

[0026] Optionally, the optical out-coupling structure includes a plurality of partially reflective surfaces disposed in the second optical waveguide and tilted to the third pair of parallel surfaces.

[0027] Optionally, the optical out-coupling construction comprises a diffractive optical element associated with at least one of the third pair of parallel faces.

[0028] Optionally, the light redirection arrangement comprises a plurality of partially reflective surfaces disposed within the first region of the second optical waveguide and inclined to the additional facet.

[0029] Optionally, the light redirecting arrangement comprises a diffractive optical element associated with one of the faces of the second light waveguide.

[0030] According to an embodiment of the teachings of the present invention, an optical aperture multiplier is also provided. The optical aperture multiplier includes: a first optical waveguide having a first pair of parallel faces including a first face and a second face and a second pair of parallel faces including a third face and a fourth face, the paired parallel faces together forming a rectangular cross section, a partially reflective surface associated with the second face and parallel to the second face; and a second optical waveguide having a third pair of parallel faces including a fifth face and a sixth face, an optical outcoupling structure associated with the second optical waveguide, and the first optical waveguide is optically coupled to the second optical waveguide and tilted relative to the second optical waveguide so that the second face is obliquely tilted to the fifth face, and the optical coupling and the partially reflective surface are configured so that when light corresponding to an image is coupled into the first optical waveguide: the light advances along the first optical waveguide by quadruple internal reflection, wherein a certain proportion of the intensity of the light is transmitted at the partially reflective surface to enter the second optical waveguide; and some of the light entering the second optical waveguide propagates in the second optical waveguide by internal reflection at the third pair of parallel faces, wherein a certain proportion of the intensity of the light propagating in the second optical waveguide is deflected out of the second optical waveguide by the optical outcoupling structure.

[0031] Optionally, the optical aperture multiplier further comprises an intermediate window providing optical coupling between the first optical waveguide and the second optical waveguide, the intermediate window being arranged so that some of the light entering the second optical waveguide transmitted at the partially reflective surface is reflected back to the intermediate window at the fifth face.

[0032] According to an embodiment of the teachings of the present invention, a manufacturing method is also provided, which includes: obtaining a transparent plate having a first pair of parallel surfaces, the first pair of parallel surfaces including a first surface and a second surface; obtaining a first optical structure having multiple surfaces including a coupling surface, the first optical structure including multiple groups of mutually parallel partially reflective inner surfaces, wherein, for each group, the mutually parallel partially reflective inner surfaces in the group are inclined obliquely relative to the coupling surface; optically coupling the transparent plate with the first optical structure so that the second surface is in a facing relationship with the coupling surface, thereby forming a second optical structure; and cutting the second optical structure along at least two cutting planes substantially perpendicular to the coupling surface, thereby cutting out at least one optical aperture multiplier in a sheet form from the second optical structure, wherein at least one partially reflective surface is associated with the second surface or is inside the transparent plate.

[0033] According to an embodiment of the teachings of the present invention, there is also provided an optical structure, which is an intermediate workpiece in the manufacturing process of an optical aperture multiplier, and the optical structure comprises: a first part, the first part having a first pair of parallel surfaces including a first surface and a second surface; and a second part, the second part having a plurality of surfaces including a coupling surface, the second part comprising a plurality of groups of mutually parallel partially reflective inner surfaces, wherein, for each group, the mutually parallel partially reflective inner surfaces in the group are obliquely inclined relative to the coupling surface, wherein at least one partially reflective surface is arranged in association with the second surface, or is inside the first part, and wherein the first part is optically coupled to the second part so that the second surface is in a facing relationship with the coupling surface.

[0034] According to an embodiment of the teachings of the present invention, there is also provided an optical aperture multiplier, the optical aperture multiplier comprising: a first optical waveguide, the first optical waveguide having a first pair of parallel faces including a first face and a second face and a second pair of parallel faces including a third face and a fourth face, the pair of parallel faces together forming a rectangular cross-section, wherein a partially reflective surface is associated with the second face and is parallel to the second face; an optical coupling structure, the optical coupling structure being used to couple polarized light corresponding to an image into the first optical waveguide in an initial propagation direction at a coupling angle inclined to both the first pair of parallel faces and the second pair of parallel faces, the polarized light being s-polarized relative to the second face; and a second optical waveguide, the second optical waveguide having a plurality of faces including a third pair of parallel faces, the second optical waveguide being coupled to the first optical waveguide. The optical coupling of the optical waveguides causes the second optical waveguide to be optically coupled to the first optical waveguide at an interface between one of the plurality of faces of the second optical waveguide and the second face, wherein an optical out-coupling structure is associated with the second optical waveguide, wherein the optical coupling of the second optical waveguide to the first optical waveguide and the partially reflective surface are configured such that: when light corresponding to an image is coupled into the first optical waveguide, the light proceeds along the first optical waveguide by quadruple internal reflection, wherein a certain proportion of the intensity of the light is transmitted at the partially reflective surface to be coupled into the second optical waveguide; and the light propagates in the second optical waveguide by internal reflection at the third pair of parallel faces, wherein a certain proportion of the intensity of the light propagating in the second optical waveguide is deflected out of the second optical waveguide by the optical out-coupling structure.

[0035] According to an embodiment of the teachings of the present invention, there is also provided an optical aperture multiplier, the optical aperture multiplier comprising: a first optical waveguide, the first optical waveguide having a first pair of parallel faces including a first face and a second face and a second pair of parallel faces including a third face and a fourth face, the pairs of parallel faces together forming a rectangular cross-section, wherein a partially reflective surface is associated with the second face and is parallel to the second face; and a second optical waveguide, the second optical waveguide having a third pair of parallel faces including a fifth face and a sixth face, wherein an optical out-coupling structure is associated with the second optical waveguide, and wherein the optical coupling of the first optical waveguide to the second optical waveguide causes the first optical waveguide to be optically coupled to the second optical waveguide and and is inclined relative to the second optical waveguide so that the second face is obliquely inclined to the fifth face, wherein the optical coupling of the first optical waveguide and the second optical waveguide and the partially reflective surface are configured such that: when light corresponding to an image is coupled into the first optical waveguide, the light advances along the first optical waveguide through quadruple internal reflection, wherein a certain proportion of the intensity of light is transmitted at the partially reflective surface to enter the second optical waveguide; and some of the light entering the second optical waveguide is propagated in the second optical waveguide through internal reflection at the third pair of parallel faces, wherein a certain proportion of the intensity of light propagating in the second optical waveguide is deflected out of the second optical waveguide by the optical out-coupling structure.

[0036] Unless otherwise defined herein, all technical and / or scientific terms used herein have the same meaning as those generally understood by those of ordinary skill in the art to which the invention belongs. Although methods and materials similar or equivalent to those described herein can be used in practicing or testing embodiments of the present invention, exemplary methods and / or materials are described below. In the event of a conflict, the patent specification including definitions shall prevail. In addition, materials, methods and examples are illustrative only and are not intended to be necessarily restrictive. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Certain embodiments of the present invention are described herein by way of example only with reference to the accompanying drawings. With specific reference to the accompanying drawings in detail, it is emphasized that the details shown are by way of example and for the purpose of illustrative discussion of embodiments of the present invention. In this regard, the description by way of the accompanying drawings makes it clear to those skilled in the art how to practice embodiments of the present invention.

[0038] Attention is now directed to the drawings, wherein like reference numerals designate corresponding or identical parts. In the drawings:

[0039] Figure 1A and Figure 1Bschematic front and side views, respectively, showing an optical aperture multiplier having a first rectangular optical waveguide having a plurality of partially reflective inner surfaces optically coupled to a second thin-slab type optical waveguide having a plurality of partially reflective inner surfaces in accordance with the teachings of an embodiment of the first aspect of the present invention;

[0040] Figure 1C is with Figure 1B Similar schematic side view, but Figure 1C showing a second optical waveguide without a cover plate disposed on an outer face of a light-transmissive substrate forming the second optical waveguide;

[0041] Figure 2 is a graph of reflectivity as a function of angle of incidence (AOI) at a majority of an interface region between two optical waveguides according to an embodiment of the present invention;

[0042] Figure 3 is an isometric view showing an optical in-coupling configuration that may be used to couple light into a rectangular optical waveguide in accordance with an embodiment of the present invention;

[0043] FIG. 4A to FIG. 4C They are respectively showing the embodiments according to the present invention and Figure 1A and Figure 1B The corresponding optical aperture multiplier and the bottom-up configuration deployed Figure 3 Schematic front view, side view and top view of the optical coupling structure;

[0044] Figure 5 is with Figure 4A Similar schematic front view, Figure 5 shows a variation of the optical coupling configuration according to an embodiment of the present invention;

[0045] Fig. 6A and Figure 6B They are respectively showing the top-down deployment according to an embodiment of the present invention. Figure 3 Schematic front and side views of an optical coupling structure and an optical substrate coupled to a rectangular optical waveguide;

[0046] Fig. 7A and Figure 7B They are respectively Figure 4B and Figure 4C Similar schematic side and top views, Fig. 7A and Figure 7B shows an optical coupling-in configuration deployed as a coupling prism with a coupling reflector according to an embodiment of the present invention;

[0047] Fig. 8A and Figure 8B are schematic front and side views, respectively, showing an optical aperture multiplier having a partially reflective surface disposed in an interface region between two optical waveguides according to an embodiment of the present invention;

[0048] Fig. 9A and Fig. 9B schematic front and side views, respectively, showing an optical aperture multiplier having a first rectangular optical waveguide optically coupled to a second thin-plate type optical waveguide and further coupled to a block of inert material, wherein the partially reflective surface is parallel to and associated with a face of the rectangular optical waveguide optically coupled to the second optical waveguide, and wherein the second optical waveguide has a plurality of partially reflective inner surfaces, according to the teachings of an embodiment of the second aspect of the present invention;

[0049] Fig.10 is a diagram showing an embodiment of the present invention. Fig. 9A Schematic front view of an optical aperture multiplier similar to that of an optical aperture multiplier, but Fig.10 In the optical aperture multiplier, the rectangular optical waveguide is tilted relative to the second optical waveguide;

[0050] Fig.11 is a diagram showing an embodiment of the present invention. Fig. 9A A schematic isometric view of a similar optical aperture multiplier in which the interface region between the two optical waveguides has a material or coating extending along most but not all of the facets that interface between the two optical waveguides to accommodate Figure 3 Deployment of an optical incoupling structure;

[0051] Fig.12 is a diagram showing an embodiment of the present invention. Fig.11 Schematic isometric view of an optical aperture multiplier similar to the optical aperture multiplier shown in Fig.12 In the optical aperture multiplier, a partially reflective surface associated with a coupling surface of a rectangular optical waveguide is divided into a plurality of non-overlapping regions, each region having a different reflectivity;

[0052] Fig.13 yes Fig.12 A graph of example reflectivity of a region at four example angles of incidence (AOI);

[0053] Fig.14 is a schematic side view showing an optical aperture multiplier according to an embodiment of the present invention, wherein the rectangular optical waveguide is tilted relative to the second optical waveguide so that only one of the images coupled out of the rectangular optical waveguide is coupled into the second optical waveguide;

[0054] Fig.15A and Fig. 15B schematic front and side views, respectively, showing an optical aperture multiplier having a first rectangular optical waveguide optically coupled to a second thin-plate type optical waveguide, wherein a partially reflective surface is associated with a face of the rectangular optical waveguide optically coupled to the second optical waveguide, and wherein a cover member is disposed to cover some outer faces of the rectangular optical waveguide, according to the teachings of an embodiment of the second aspect of the present invention;

[0055] Fig.16A and Fig. 16B The deployed in the supra-ocular structure of the left eye and the right eye are shown respectively. Fig.15A and Fig. 15B Optical aperture multiplier;

[0056] Fig.17A and Fig. 17B The deployed in the subocular structure of the left eye and the right eye are shown respectively. Fig.15A and Fig. 15B Optical aperture multiplier;

[0057] Fig.18A and Fig.18B They are respectively shown according to the embodiments of the present invention and Fig.15A and Fig. 15B Schematic front and side views of an optical aperture multiplier similar to that of an optical aperture multiplier, but Fig.18A and Fig.18B The optical aperture multiplier has no cover member but has diffractive incoupling and outcoupling elements;

[0058] Fig.19A and Fig.19B are schematic front and side views, respectively, showing an optical aperture multiplier having a first rectangular optical waveguide optically coupled to a second thin-plate type optical waveguide, wherein a partially reflective surface is associated with a face of the rectangular optical waveguide optically coupled to the second optical waveguide, and wherein the second optical waveguide has a light redirecting arrangement in a first region and a plurality of partially reflective inner surfaces in a second region, according to the teachings of an embodiment in accordance with the present invention;

[0059] Fig. 20A and Fig. 20B They are respectively showing the embodiments according to the present invention and Fig.19A and Fig.19B Schematic front and side views of an optical aperture multiplier similar to the optical aperture multiplier shown, Fig. 20A and Fig. 20B The optical aperture multiplier has diffractive in-coupling and out-coupling elements;

[0060] Fig.21 It is shown Fig.15A Schematic front view of the optical aperture multiplier shown in, Fig.21shows the beams propagating at the far and near ends of a rectangular waveguide;

[0061] Fig. 22 is a graph of the reflectivity of s-polarized light as a function of AOI, which can be used to design FIG. 15A to FIG. 20B a coating of a partially reflective surface at an interface between two optical waveguides of either;

[0062] Fig.23 are schematic isometric views showing different coupling geometries between a rectangular optical waveguide and a thin-slab type optical waveguide according to an embodiment of the present invention; and

[0063] FIG. 24A to FIG. 24F is a schematic isometric view showing a series of steps used in the manufacture of an optical aperture multiplier according to an embodiment of the present invention. DETAILED DESCRIPTION

[0064] Embodiments of various aspects of the present invention provide an optical device in the form of an optical aperture multiplier having a rectangular waveguide.

[0065] The principles and operation of the optical device and method according to the present invention may be better understood with reference to the accompanying drawings attached to the specification. The drawings provide an xyz coordinate system, which is arbitrarily labeled but consistent between the drawings. The xyz coordinate system is used herein to better illustrate the disclosed embodiments by providing a common reference system between the drawings.

[0066] Before describing in detail at least one embodiment of the present invention, it should be understood that the present invention is not necessarily limited in its application to the details of construction and arrangement of components and / or methods set forth in the following description and / or shown in the drawings and / or examples. The present invention is capable of other embodiments and can be practiced or carried out in various ways. Initially, throughout the document, reference is made to directions such as front and back, top and bottom, up and down. These directional references are exemplary only and are used only for ease of presentation and refer to any orientation shown in the drawings. The final optical device can be deployed in any desired orientation.

[0067] Now referring to the accompanying drawings, Figures 1A to 7B An optical aperture multiplier 1 constructed and operative in accordance with an embodiment of the first aspect of the present invention is shown. In general, the optical aperture multiplier 1 (also referred to as an "optical device") comprises: a first optical waveguide 10 having an elongated direction (arbitrarily shown herein as corresponding to the "x-axis"); and an optical coupling-in construction 80 that couples image light 60 (also referred to as a "light beam" or "beam") corresponding to a collimated image into the optical waveguide 10.

[0068] The optical waveguide 10 is formed of a light-transmitting material (light-transmitting substrate) and has a first pair of parallel faces 12a, 12b and a second pair of parallel faces 14a, 14b forming a rectangular cross section (i.e., the first pair of faces and the second pair of faces are orthogonal). The optical waveguide 10 also has an additional pair of faces 16a, 16b (which may or may not be parallel faces). In certain embodiments where the faces 16a, 16b are parallel faces, the faces 16a, 16b may be orthogonal to the first pair of faces 12a, 12b and the second pair of faces 14a, 14b. According to certain embodiments of the present invention, the optical waveguide 10 has a plurality of mutually parallel partially reflective inner surfaces (also referred to as "facets") 18, the facets 18 at least partially passing through the optical waveguide 10 and obliquely inclined to the elongation direction of the optical waveguide 10 (oblique to the faces 12a, 12b). In certain embodiments, the facets 18 are inclined to both the faces 12a, 12b and 14a, 14b. In this document, the terms "face", "outer face" and "external surface" are used interchangeably. As will become apparent, some of these faces are primary faces (also called "primary outer faces" or "primary exterior surfaces").

[0069] In a preferred embodiment, the optical aperture multiplier 1 further comprises a second optical waveguide 20 optically coupled to the optical waveguide 10, the second optical waveguide 20 having a third pair of parallel faces 22a, 22b. Here again, according to certain embodiments of the present invention, a plurality of mutually parallel partially reflective internal surfaces ("facets") 28 at least partially penetrate the optical waveguide 20 and are obliquely inclined to the faces 22a, 22b. The optical waveguide 20 also has two additional pairs of opposite faces 24a, 24b, 26a, 26b, each pair of opposite faces being non-parallel to the faces 22a, 22b, and each pair of opposite faces may or may not be a pair of parallel faces. In certain embodiments, the pairs of faces 22a, 22b, 24a, 24b, 26a, 26b are mutually orthogonal. In certain embodiments, the facets 28 are also obliquely inclined to the face 24a, however, as will be discussed, in other embodiments, the facets 28 may be parallel to the face 24a.

[0070] The optical waveguide 20 is also formed of a light-transmitting material (light-transmitting substrate 19), and is preferably formed of the same material used to form the optical waveguide 10 (so that the two optical waveguides 10, 20 have the same refractive index), but forms a thin-plate type waveguide in which the distance between pairs of faces 24a, 24b, 26a, 26b is at least one order of magnitude larger than the distance between faces 22a, 22b.

[0071] Preferably, the surfaces 16a, 26a are parallel, and the surfaces 16b, 26b are also parallel. In addition, preferably, the surfaces 14a, 22a are parallel, and the surfaces 14b, 22b are also parallel.

[0072] The optical waveguide 20 is optically coupled to the optical waveguide 10 at the interface 40 between the faces 12b, 24a. In other words, the optical coupling between the optical waveguides 10, 20 defines the interface 40 formed between the faces 12b, 24a. A particular feature of certain embodiments of the present invention is that the optical coupling-in formation 80 is disposed in association with a portion of a specific region 46 (and hence the interface 40) of the front face 14a or the back face 14b of the waveguide 20 adjacent to the face 12b, so as to enable the optical waveguide 10 to be filled with the injection aperture of the light beam 60. In the subsequent parts of this disclosure, particular reference is made to the optical coupling-in formation 80. Figure 3 and Figures 4A-6B , the details of deploying the optical in-coupling structure 80 relative to the waveguides 10, 20 will be described in detail.

[0073] The optical coupling between the optical waveguides 10, 20 and the deployment and construction of the partially reflective surfaces 18, 28 and the optical coupling structure 80 are such that when the optical coupling structure 80 couples (injects) the image light 60 into the optical waveguide 10 in an initial propagation direction at a coupling angle that is inclined to the first pair of parallel surfaces 12a, 12b and the second pair of parallel surfaces 14a, 14b, the image advances along the optical waveguide 10 through fourfold internal reflections (images 62a, 62b, 62c, 62d), wherein a certain proportion of the intensity of the image is reflected at the partially reflective surface 18 to be coupled into the optical waveguide 20, and then the image propagates within the optical waveguide 20 through double internal reflections (images 64a, 64b), wherein a certain proportion of the intensity of the image is reflected (deflected) at the partially reflective surface 28 to be guided outward from one of the parallel surfaces 22a to become a visible image 66 seen by the observer's eye 2. Eye 2 is located somewhere within a range of allowed positions specified by an eye-motion box (EMB) 3 (i.e., a generally rectangular shape spaced from the plane of face 22 of optical waveguide 20 from which the pupil of eye 2 will view the projected image).

[0074] The optical waveguide 10 is referred to herein as a two-dimensional (2D) waveguide in the sense that the optical waveguide 10 guides the injected image in two dimensions by reflection between two sets of parallel faces 12a, 12b, 14a, 14b, while the optical waveguide 20 is referred to as a one-dimensional (1D) waveguide or light-guide optical element (LOE) which guides the injected image in one dimension only between a pair of parallel faces 22a, 22b. The light beam 60 (generated by an optical image generator, not shown) is injected into the optical waveguide 10 at a certain angle through the optical coupling structure 80. Therefore, the light is reflected from all four outer faces 12a, 12b, 14a, 14b of the optical waveguide 10 (as shown in FIG. 1 ). Figure 1B14a, 14b) while propagating along the optical waveguide 10. In this process, four conjugate beam vectors 62a, 62b, 62c, 62d are generated, which represent the same image when reflected internally by the surfaces 12a, 12b, 14a, 14b.

[0075] A portion of the guided light beams within the optical waveguide 10 (e.g., 62a and 62b) are reflected downward by the facet 18 through the interface 40 and onto the input coupling surface (face 24a) of the optical waveguide 20. In the optical waveguide 20, these light beams are defined as 64a and 64b. Light beams 64a and 64b are reflected by the outer faces 22a, 22b and become conjugate, i.e., light beam 64a is reflected into 64b, and conversely, light beam 64b is reflected into 64a (e.g., Figure 1B In other words, the light guide 20 guides the image lights 64a, 64b by double internal reflections at the faces 22a, 22b, so that the image lights 64a, 64b travel along the light guide 20 by double internal reflections (images 64a, 64b). The internal reflections within the light guide 20 may be achieved by TIR due to the steep angle at which the facet 18 injects the light beam into the light guide 20, or may be achieved by an optical coating.

[0076] As previously mentioned, the external front and back faces 14a, 14b of the optical waveguide 10 should be parallel to each other and, in this embodiment, to the corresponding external faces 22a, 22b of the optical waveguide 20. Any deviation from parallelism will result in the coupled images 64a and 64b not being exact conjugate images and the image quality will be degraded.

[0077] The facets 28 within the optical waveguide 20 reflect the light beam 64b out of the optical waveguide and toward the eye 2 as a visible image (referred to as the "projected image"). In the illustrated embodiment, the partial reflectivity of the facets 18, 28 is determined by the optical coating (selective reflective coating) on ​​the facets 18, 28.

[0078] Each set of facets 18, 28 is an optical outcoupling formation associated with a corresponding optical waveguide and used to couple propagating light out of the optical waveguide. However, as will be discussed in subsequent portions of the present disclosure, other embodiments are envisioned in which the optical outcoupling formations take other forms. For example, in some embodiments, instead of internal facets 18, the optical outcoupling formation associated with the first optical waveguide 10 can take the form of a partially reflective surface at the interface 40 between the optical waveguides 10, 20, which is parallel to the bottom surface 12b of the waveguide 10. In some embodiments, the optical outcoupling formation associated with the second optical waveguide 20 can take the form of one or more diffractive elements on one or more portions of the faces 22a, 22b.

[0079] The combined reflections from the exterior and interior facets of waveguides 10 and 20 expand the original injection aperture in both the first and second dimensions. Figure 1A The waveguide 20 extends the aperture in a second dimension orthogonal to the plane of the facet 18 (which is approximately along the x dimension). Figure 1A The aperture is expanded in the y dimension in FIG. 1 , but more specifically in the illustrated embodiment along the y' dimension offset from the y axis. Aperture expansion of the waveguide 10 is preferably achieved by filling the waveguide with an image and then coupling the image out of the waveguide via the facets 18 in a continuous manner along the length of the waveguide.

[0080] Note that in many of the embodiments shown herein, the faces 22a, 22b are actually formed as outer faces of cover plates 39a, 39b, which are optically attached to outer faces 27a, 27b of a light-transmissive substrate 19 from which the optical waveguide 20 is formed. The facets 28 typically extend between the outer faces 27a, 27b of the substrates and therefore do not extend between the faces 22a, 22b of the cover plates 39a, 39b. The cover plates 39a, 39b can be used to avoid double reflections, i.e., situations where the image 64a or 64b is reflected twice from the same facet. Specifically, the cover plates 39a, 39b help ensure that after being reflected once by the facet 28, the transmitted portion of the light will propagate above or below the facet and proceed directly to the next facet, resulting in enhanced image uniformity. However, in some embodiments, the cover plates 39a, 39b may not be included and the thickness of the substrate 19 may be adjusted so that the outer faces 27a, 27a of the substrate 19 and the faces 22a, 22b of the waveguide 10 are the same face. Figure 1C An example of an optical aperture multiplier with a thin-plate type optical waveguide 20 without a cover plate is shown in . Unless explicitly stated otherwise, all embodiments of the invention described herein with cover plates 39a, 39b can also be practiced without such cover plates.

[0081] It should also be noted that as the image progresses through the light guide 10, the illumination intensity gradually decreases due to the gradual outcoupling of light by the facets 18. To achieve better uniformity and light efficiency, in some preferred embodiments, the reflectivity of the facets 18 increases along the propagation direction of light through the light guide 10, which provides a gradual increase in the intensity of light coupled into the light guide 20. In the same manner, in some embodiments, the reflectivity of the facets 28 also preferably increases along the propagation direction of light through the light guide 20 to offset the decrease in light intensity caused by the gradual outcoupling of light by the facets 28.

[0082] Incidentally, wherever in this document an image is represented by a beam, it should be noted that the beam is a sample beam of the image, and an image is usually formed by multiple beams with slightly different angles, each corresponding to a point or pixel of the image. Except where specifically referred to as the extremity of an image, the beam shown is usually the centroid of the image.

[0083] Special reference Figure 1A and Figure 1B , the face 12b is subdivided into non-overlapping first and second regions 45, 46 having respective first and second optical properties. The first region 45 occupies most but not all of the face 12b in the elongation direction (i.e., extends along most but not all of 12b), while the second region 46 occupies the remaining minority of the face 12b in the elongation direction (extends along the remaining minority of the face 12b). The region 45 is preferably at least 70% of the face 12b in the elongation direction, however, the specific extension amount in the elongation direction may be based on the optical design specifications of the optical aperture multiplier, in particular the size and deployment position of the optical coupling structure 80, as will be discussed in subsequent sections of the present disclosure. In some cases, the extension amount in the elongation direction may be at least 80% or at least 90%.

[0084] The first optical characteristic is a partially reflective characteristic that maintains an internal reflection condition, such that light reflected from one of the faces 12a, 14a, 14b and incident on the portion of face 12b in region 45 is reflected at face 12b (to continue to propagate through waveguide 10 by internal reflection), and such light deflected by facet 18 toward the portion of face 12b in region 46 is also transmitted by face 12b into waveguide 20. The second optical characteristic is different from the first optical characteristic in that it is a transmissive characteristic, such that light from optical incoupling construction 80 can enter waveguide 10 via transmission through the portion of waveguide 10 adjacent to region 46.

[0085] Furthermore, the optical waveguide 10 is subdivided into a first waveguide region 11 and a second waveguide region 13 by a rectangular cross section P (in the arbitrarily marked coordinate system) in the optical waveguide 10 that is orthogonal to the elongation direction and passes through a boundary 47 between the two regions 45 and 46. The bottom surface of the first waveguide region 11 is the first region 45 of the face 12b (in other words, the first region 45 corresponds to the first waveguide region 11), and the bottom surface of the second waveguide region 13 is the second region 46 of the face 12b (in other words, the second region 46 corresponds to the second waveguide region 13, also referred to as the “coupling region” of the waveguide 10).

[0086] In certain embodiments, the subdivision of face 12b is achieved at least in part by a coating or material 44 disposed in association with a majority of face 12b that extends along a majority, but not all, of face 12b in the direction of elongation. Figure 1B and Figure 1C As shown, the extension of the coating or material 44 in the transverse (or lateral) direction (along the z-axis in the arbitrarily labeled coordinate system) is also preferably along the entire face 12b. A first region 45 of the face 12b is associated with the material or coating 44, while a second region 46 of the face 12b is not associated with the material or coating 44. In addition, since the interface 40 is formed between the faces 12b, 24a, the coating or material 44 is located at the interface 40 and effectively subdivides the interface 40 into two regions corresponding to the above-mentioned two regions 45, 46.

[0087] In certain embodiments, the extension of the material or coating 44 in the direction of elongation along the face 12b is at least 70%, however, the extension in the direction of elongation may be at least 80% or at least 90%.

[0088] Prior to coupling the two waveguides 10, 20 together, a material or coating 44 may be applied to one or both of the faces 12b, 24a such that the material or coating 44 extends along a majority of the face 12b (region 45) and such that the material or coating 44 is absent from a minority 46 of the face 12b (in the illustrated embodiment, the minority 46 is proximate to the faces 16b, 26b).

[0089] In one example, the material or coating 44 is a reflective coating, which may be a selective reflective coating, such as (preferably according to Figure 2 1. The reflective coating 44 is an angularly selective reflective (ASR) coating that reflects only incident light within a specific range of angles of incidence (AOI) and transmits light outside the angle range. The reflectivity of the coating 44 is such that light reflected from one of the faces 12a, 14a, 14b and incident on the face 12b is reflected at the face 12b, and light deflected by the facet 18 toward the face 12b is transmitted by the face 12b into the waveguide 20. Alternatively, the reflective coating may be applied to the face 24b, or the reflective coating may be applied to one or more corresponding portions of the faces 12b, 24a, so that when the optical waveguides 10, 20 are combined or optically coupled together, the resulting reflective coating extends along a majority of the face 12b.

[0090] In another example, a thin film of partially reflective material having selective reflective properties as described above may be applied to a majority of face 12b (alternatively face 24a) in the elongated direction prior to bonding faces 12b, 24a together.

[0091] In yet another example, the material or coating 44 is a partially reflective material in the form of a separate partially reflective surface located between the faces 12b, 24a and extending along a majority of the faces 12b, 24a in the elongated direction. The partially reflective surface can be formed by any thin sheet of material coated with a reflective coating having selective reflective properties as described above.

[0092] In some embodiments, region 46 is formed only by applying material or coating 44 to a majority of face 12b (or face 24a) and blocking material or coating 44 from reaching the remaining minority of face 12b (or face 24a), so that first region 45 is a "coated portion" and second region 46 is an "uncoated portion", whereby the coated portion and the uncoated portion have substantially different optical properties. However, in some preferred embodiments, a low refractive index material or coating (i.e., a material or coating having a refractive index lower than the refractive index of the material used to make the optical waveguide 10, 20) having optical properties different from those of the optical waveguide 10, 20 is associated with the remaining minority of face 12b to extend along the minority of face 12b (region 46). In one example, a thin sheet of low refractive index material is used. The thin sheet can be deposited directly on a minority of one of faces 12b or 24a and then bonded to the other of faces 24a or 12b with a thin adhesive layer, or can be bonded to faces 12b, 24a using a thin adhesive layer. In another example, a thin coating of solid dielectric material. A range of aerogel materials having very low refractive indices (1.1-1.2) and stable mechanical properties have been developed over the years and may be particularly suitable for forming regions 46. In another example, a low refractive index optical glue is deployed at small portions 46 and is also used to help hold the optical waveguides 10, 20 together.

[0093] In some embodiments, region 46 is formed by applying a low refractive index material only to a small portion of surface 12b (or surface 24a) and not applying any coating or material to a majority of surface 12b (or surface 24a), such that first region 45 is an "uncoated portion" and second region 46 is a "coated portion", whereby the coated and uncoated portions have essentially different optical properties.

[0094] In embodiments where the facet 18 is used to couple light out of the waveguide 10 into the waveguide 20, the material or coating 44 may not be necessary, whereby the reflection of the propagating light at the face 12b is by total internal reflection. In such embodiments, the subdivision of the face 12b into two regions may be achieved by applying a low refractive index material to a small portion of the face 12b (or face 24a) and not applying any coating or material to a large portion of the face 12b (or face 24a). In embodiments where the bottom face 12b of the waveguide 10 is implemented as a partial reflector to couple a certain proportion of the intensity of the propagating light out of the waveguide 10 (and into the waveguide 20), the subdivision of the face 12b into the two aforementioned regions is preferably achieved at least in part by applying a coating or material 44 to a large portion of the face 12b (or face 24a). In such embodiments, the coating or material 44 is preferably implemented as a dielectric coating and / or a metallic coating, as will be discussed in the subsequent sections below.

[0095] In order to obtain uniform intensity across the enlarged aperture, the injected beam should be uniform in initial aperture and should "fill" the waveguide. The term "fill" is used in this context to indicate that the light rays corresponding to each point (pixel) in the image are present throughout the cross section of the optical waveguide 10. Conceptually, this property means that if the optical waveguide 10 were to be cut transversely at any point, and if an opaque sheet with a pinhole were placed on the cut end, the pinhole could be placed anywhere throughout the cross section and a complete projected image would result. In fact, for the optical waveguide 10, this would result in the projection of four complete images 62a, 62b, 62c and 62d, of which 62b and 62d are inverted. In order to ensure that the waveguide is filled with the input image 60, the slightly oversized input image should be trimmed to size when entering the waveguide 10. This ensures that the multiplied adjacent apertures do not overlap on the one hand and do not have gaps on the other hand. The shaping of the image 60 is performed by the optical incoupling configuration 80 when the image is injected into the waveguide 10 but before the image 60 is guided within the waveguide 10 by quadruple internal reflection.

[0096] Continuously refer to Figures 1A to 1C , now refer to Figure 3 as well as FIG. 4A to FIG. 4C , Figure 3 as well as FIG. 4A to FIG. 4C 1 and 80 according to an embodiment of the present invention. It should be noted that, in order to simplify the representation, Figure 4A and Figure 4C The facet 28 of the waveguide 20 is not shown. Figure 3, the optical coupling-in structure 80 is generally formed as a coupling prism having a plurality of surfaces (facets), including faces 81, 83, 85, 87, 89. Faces 81 and 83 are joined at a common edge 82, and faces 81 and 85 are joined at a common edge 84. Vertices 86 and 88 are at opposite ends of edge 84, and are formed as vertices of faces 81, 85, 87 and faces 81, 85, 89, respectively.

[0097] Now turn to FIG. 4A to FIG. 4C , the optical coupling configuration 80 is disposed in association with the waveguides 10, 20 such that the optical coupling configuration 80 abuts the second region 46. In particular, the optical coupling configuration 80 is disposed in association with a portion of the face 14a abutting the second region 46. More specifically, the deployment is such that a first portion of the face 81 is associated with a portion of the front face 14a that is located in the second waveguide region 13, and such that a remaining second portion of the face 81 is associated with a portion of the face 22a of the waveguide 20. In the illustrated embodiment, the vertex 88 is aligned with the plane P (i.e., if the plane P were to extend into the waveguide 20, the vertex 88 would be located in the extended plane P).

[0098] Surface 81 is a light-transmitting surface (i.e., light incident surface) through which light from the optical coupling structure 80 enters (i.e., is transmitted to) the waveguide 10 (or waveguide 20), so it is preferred that the refractive index of surface 81 is matched with that of surfaces 14a, 22a to prevent the injected image light from being refracted when entering the waveguide. In some embodiments, a refractive index matching optical glue can be used to provide refractive index matching and bonding between surface 81 and waveguides 10, 20.

[0099] The optical coupling-in construction 80 is constructed and arranged so that all light within the desired angular field of view passes between the boundary 47 and the image of the boundary 47 (which presents the apparent input optical aperture) to enter the waveguide 10 and proceed through the waveguide 10 by quadruple internal reflection. As will be discussed, this arrangement ensures that edge rays of the desired angular field of view entering the waveguide 10 are incident at points along the boundary 47.

[0100] Figure 4A The footprint of the optical incoupling construction 80 in the plane of the faces 14a, 22a is shown, along with the collimated beam groups representing points in the collimated image 60. In the drawings, for clarity, only one ray of each beam group is shown, but the one ray represents one of many parallel rays in the beam group. Solid rays 60A represent beams at one edge of the projected field, while dashed rays 60C represent beams at the other edge of the projected field (these rays 60A, 60C are "edge rays"). Dot-dash rays 60B represent beams at the center of the field (i.e., the centroid of the image).

[0101] In the illustrated configuration, the coupling prism is simplified so that the sides 82, 84 are parallel to each other and so that the side 84 is parallel to the extension direction of the face 83, which is the light incident surface of the prism. The coupling prism is preferably designed so that the light incident face 83 is perpendicular (orthogonal) to the central beam (light 60B) to reduce optical aberrations. In practice, the orientation of the face 83 is set according to the propagation direction of the central light ray 60B (which is based on the position and spatial orientation of the optical image generator).

[0102] The construction and arrangement of the optical coupling-in structure 80 enables the optical coupling-in structure 80 to modify the input image, as will now be referred to. FIG. 4A to FIG. 4C As shown, light rays 60A, 60B, 60C enter the optical coupling structure 80 via face 83 at respective points 91a, 91b, 91c of face 83, then exit the optical coupling structure 80 via face 81, and enter one of the waveguides via respective points 93a, 93b, 93c. In the illustrated configuration, points 93a, 93b are different points on face 14a of rectangular waveguide 10, and point 93c is a point on face 22a of second waveguide 20. In other words, light rays 60A, 60B enter waveguide 10 via different points on face 14a, and light ray 60C enters waveguide 20 via face 22a.

[0103] After light rays 60A, 60B, 60C enter the waveguide at points 93a, 93b, 93c, the light rays are trimmed in a first dimension (vertical dimension) by edge 86 so that the waveguide is uniformly illuminated in the vertical direction (along the y-axis in the figure). Light rays 60A, 60B, 60C are then trimmed in a second dimension (i.e., laterally, along the z-axis in the figure) orthogonal to the first dimension at boundary 47 so that all beams uniformly illuminate the waveguide 10 in the lateral dimension (z-dimension). In particular, light ray 60A is reflected at point 92 (intersecting or overlapping edge 84) at top 12a to a point on boundary 47. Light ray 60B is also reflected from top 12a (at a different point) to a point on boundary 47, and edge ray 60C is transmitted from waveguide 20 via face 12b through a point on boundary 47 into waveguide 10. The trimmed image then advances through waveguide 10 by quadruple internal reflection.

[0104] Conceptually, the boundary 47, together with its image, presents an apparent input optical aperture to the optical waveguide 10 over the entire desired angular field of view when viewed along the light input axis along which the image 60 is introduced. The optical incoupling configuration 80 shapes the input image 60 so that all light within the field of view enters the waveguide 10 through the apparent input optical aperture (i.e., between the boundary 47 and the image of the boundary 47) and proceeds through the waveguide 10 by quadruple internal reflection. Any other light rays that are not shaped by the optical incoupling configuration 80 do not pass through the apparent input optical aperture and therefore do not enter the waveguide 10.

[0105] Note that the optical coupling-in formation 80 is preferably arranged and constructed so that the surface 81 does not overlap with the projection of any facet 28 in a plane parallel to the faces 22a, 22b (the xy plane in the arbitrarily labeled coordinate system). This non-overlapping geometry and orientation helps prevent the light coupled out by one or more facets 28 from being coupled back into the optical coupling-in formation 80, which can redirect the coupled-out light back into the optical waveguide 10.

[0106] Figure 5 FIG. 8 shows a configuration of an optical coupling configuration 80 according to another embodiment of the present invention. Here, edge 86 is not parallel to edge 82 and face 83, and is positioned close to the reflected light reflected from point 92. In addition, vertex 88 is not parallel to edge 82 and face 83. Figure 4A and Figure 4C 8 is aligned with plane P in the xz plane, but extends beyond boundary 47 so that the projection of vertex 88 in the xz plane protrudes into first region 45.

[0107] Figure 5 The construction shown provides advantages over Figures 3 to 4C The advantages of the construction shown are most notably Figures 3 to 4C This allows the face 83 to be positioned closer to the waveguide faces 14a, 22a than would be permitted by the illustrated configuration. This in turn allows the image projector (optical image generator) to be positioned closer to the waveguide 10, thereby enabling the use of a larger optical image generator than would be permitted by the illustrated configuration. Figures 3 to 4C The image projector that should be used in the configuration shown is a smaller image projector. Figures 3 to 4C In the configuration shown, the injected light is trimmed in the vertical dimension by edge 86 and then in the lateral dimension by border 47 .

[0108] FIG. 4A to FIG. 5 The optical coupling configuration shown in FIG. 1 is arranged to accommodate an image projector illuminating the optical coupling configuration from below (a "bottom-up" configuration, such as that most easily Figure 4B However, the optical incoupling configuration may also be arranged to accommodate illumination from above (a "top-down" configuration), such as Fig. 6A and Figure 6B Here, the optical coupling structure is relative to Figure 4A and Figure 4BThe spatial orientation shown in is in an inverted spatial orientation. In this deployment configuration, the face 12a is subdivided into non-overlapping first and second regions 55, 56 having respective first and second optical properties. The first optical property is a reflective property that maintains an internal reflection condition, so that the portion of light in region 55 that is reflected from one of the faces 12b, 14a, 14b and incident on the face 12a is reflected at the face 12a (and thus continues to propagate through the waveguide 10 by internal reflection). The second optical property, which is different from the first optical property, is a transmissive property, so that light from the optical incoupling construction 80 can enter the waveguide 10 via transmission through the portion of the waveguide 10 adjacent to the region 56.

[0109] The first region 55 occupies most but not all of the face 12a in the elongation direction (i.e., extends along most but not all of the face 12a), while the second region 56 occupies the remaining small portion of the face 12a in the elongation direction (extends along the remaining small portion of the face 12a). The region 55 is preferably at least 70% of the face 12a in the elongation direction, however, the specific extension amount in the elongation direction can be based on the optical design specifications of the optical aperture multiplier, in particular the size and deployment position of the optical coupling structure 80, as will be discussed in subsequent parts of the present disclosure. In some cases, the extension amount in the elongation direction can be at least 80% or at least 90%.

[0110] In certain embodiments, the subdivision is achieved by a coating or material 54 that is disposed in association with the face 12a in a manner similar to the coating or material 44. Specifically, the coating or material 54 is disposed in association with a majority of the face 12a, the majority extending along a majority, but not all, of the face 12a in the direction of elongation. The extension of the coating or material 54 is also preferably along the entire face 12a in the transverse (or lateral) direction. The deployment of the coating or material 54 subdivides the face 12a into non-overlapping first regions 55 and second regions 56 having respective first and second optical properties, whereby the first regions 55 of the face 12a are associated with the material or coating 54, and the second regions 56 of the face 12a are not associated with the material or coating 54.

[0111] As described above, the optical waveguide 10 is subdivided into the first waveguide region 11 and the second waveguide region 13 by the rectangular cross section P passing through the boundary 57 between the two regions 55 and 56. The top surface of the first waveguide region 11 is the first region 55 of the face 12a (in other words, the first region 55 corresponds to the first waveguide region 11), and the top surface of the second waveguide region 13 is the second region 56 of the face 12a (in other words, the second region 56 corresponds to the second waveguide region 13).

[0112] Coating or material 54 can be implemented in a variety of ways. In one example, a metal coating is applied to a majority of face 12a. In another example, a low refractive index material or coating (e.g., an aerogel material or a low refractive index optical glue) is applied to a majority of face 12a. Associated with the remaining minority of face 12b to extend along a minority of face 12b (region 46). In other embodiments, material 54 is the material constituting substrate 30 itself, and its refractive index is less than the refractive index of waveguide 10, so that internal reflection at face 12a is maintained.

[0113] exist Fig. 6A and Figure 6B In the illustrated embodiment, a coating or material 54 is located at an interface 50 between the optical waveguide 10 and another optical substrate 30 (also formed of a light-transmitting material). The optical substrate 30 has a pair of faces 32a, 32b (which may be parallel) and a pair of parallel faces 34a, 34b (and may also include an additional pair of faces 36a, 36b), and the waveguide 10 is optically coupled to the substrate 30 at the interface 50 formed between the faces 12a, 32b (i.e., the optical coupling between the waveguide 10 and the substrate 30 defines the interface 50 formed between the faces 12a, 32b). The coating or material 54 may alternatively be applied to a necessary majority of the face 32b.

[0114] and Figure 3 as well as FIG. 4A to FIG. 4C The construction shown is similar to Fig. 6A and Figure 6B The optical coupling configuration shown is disposed in association with the waveguides 10, 20 such that the optical coupling configuration 80 abuts the second region 56. In particular, the optical coupling configuration 80 is disposed in association with a portion of the face 14b abutting the second region 56. More specifically, the deployment is such that a first portion of the face 81 is associated with a portion of the front face 14a in the second waveguide region 13, and such that a remaining second portion of the face 81 is associated with a portion of the face 34a of the substrate 30. Furthermore, in the illustrated embodiment, the vertex 88 is aligned with the plane P (i.e., if the plane P were to extend into the waveguide 20, the vertex 88 would be located in the extended plane P).

[0115] Fig. 6A and Figure 6B The behavior of the rays 60A, 60B, 60C in FIG. 6 is similar to that of the rays 60A, 60B, 60C in FIG. FIG. 4A to FIG. 4C84. Here, ray 60C enters substrate 30 at point 93c on face 34a. After rays 60A, 60B enter waveguide 10 and ray 60C enters the substrate (at points 93a, 93b, 93c), the rays are trimmed by edge 86 so that waveguide 10 is uniformly illuminated in the vertical direction (along the y-axis in the figure). Rays 60A, 60B, 60C are then trimmed laterally (along the z-axis in the figure) at boundary 57 so that all beams uniformly illuminate waveguide 10 in the lateral dimension (z-dimension). In particular, ray 60A is reflected at point 92 on lower face 12b (the point where lower face 12b intersects or overlaps edge 84) to a point on boundary 57. Light 60B is also reflected at (a different point of) lower surface 12b to a point on boundary 57 , and edge ray 60C is transmitted from substrate 30 through face 12a into waveguide 10 through the point on boundary 57 .

[0116] It should be noted that in Fig. 6A and Figure 6B In the top-down structure shown, it is possible to Figure 6B The distance between the optical pattern generator (image projector) and the waveguide 10 is further reduced by polishing the polishing plane 83 (designated by the dashed line 95 in FIG. 1 ) to further reduce the size of the projection optical device. The polishing plane 95 is generally parallel to the face 83 of the coupling prism 80 and passes approximately through the point 93c (i.e., where the light beam 60C enters the substrate 30). As a result, the polished surface 83 can be made substantially flush or coincident with the substrate 30 at the point 93c. In some embodiments, "polishing" can be performed by polishing the coupling prism 80 using a suitable polishing device or tool, or by grinding / cutting the coupling prism 80 using a suitable grinding / cutting device or tool and then polishing the cut surface.

[0117] It should be clear that Figure 5 A reversed variation of the construction shown in FIG. 1 can be constructed in a manner similar to that of reference 1. Fig. 6A and Figure 6B The described approach deploys an embodiment of the optical waveguide 10 having a coating or material 54 at face 12a.

[0118] In addition to transmitting some of the image light into the waveguide 10 via the prism, the substrate 30 may also provide structural and / or bonding support for the optical in-coupling construction, such as by allowing bonding (via an index-matched optical adhesive) between portions of the face 81 and portions of the face 34a. It should also be noted that while the substrate 30 is shown here as having parallel faces 36a, 36b that are coincident and parallel to the faces 16a, 26a and 16b, 26b, the size of the substrate 30 may be reduced such that the substrate is located only in the portion of the waveguide 10 adjacent to the region 56. In such a reduced size embodiment, the face 36a may be located at or just before the vertex 88 of the optical in-coupling construction.

[0119] Although the embodiments of the optical coupling-in configuration described thus far relate to non-limiting embodiments as a coupling prism having a light entrance face 83 that receives light 60 from an optical image generator (disposed in association with the front face 14a), other embodiments are contemplated herein in which the optical coupling-in configuration is operated as a coupling reflector. In such embodiments, the face 83 is a reflective face, and the optical coupling-in configuration 80 is disposed in association with the waveguide 10, 20 (or the waveguide 10 and the substrate 30) such that a portion of the face 81 abuts the second region 46 / 57, and in particular such that a first portion of the face 81 is associated with a portion of the back face 14b that is located in the second waveguide region 13, and such that a remaining second portion of the face 81 is associated with a portion of the face 22b of the waveguide 20 (or the face 34b of the substrate 30).

[0120] The operation principle of the optical coupling-in structure in this reflective embodiment is generally similar to that described above with reference to Figure 3 as well as 4A to 6B The working principle described above has some minor differences. To explain these differences more clearly, Fig. 7A and Figure 7B They are shown respectively Figure 4B and Figure 4C A variation of , in which the optical coupling-in structure is constructed with a reflective surface 83. One difference is that the light enters the prism through surface 81 rather than surface 83 (i.e., surface 81 receives the collimated image from the optical image generator). Another difference is that in 4A to 6B The points 91a, 91b, 91c on face 83 where the light enters the prism are changed to points where the light on face 83 is reflected back to face 81 to be trimmed by edge 84.

[0121] Finally, to accommodate the deployment of an image projector associated with front face 14a, Fig. 7A and Figure 7BThe optical coupling structure 80 is disposed in association with the back side 14b. In particular, the optical coupling structure 80 is disposed in association with a portion of the face 14b adjacent to the second region 46. This deployment configuration of the optical coupling structure on the back side 14b (i.e., away from the user's eyes) provides certain ergonomic advantages. However, it also requires that the optical coupling structure be placed farther from the optical image generator, and thus may require the use of a larger optical coupling structure than the optical image generator. Figure 3 as well as 4A to 6B The transmission prism configuration shown in FIG. 1 should be used with a larger optical image generator.

[0122] Figures 3 to 7B The optical incoupling configurations shown represent a set of solutions according to embodiments of the invention which make it possible to fill the optical waveguide 10 with the injection aperture of the light beam 60 .

[0123] Fig. 8A and Figure 8B Another embodiment of an optical aperture multiplier is shown, in which aperture filling can be achieved or assisted by using a partially reflective surface 94 disposed in the region between the facets 18, 28 of the waveguide. The partially reflective surface 94 is disposed parallel to the faces 14a, 14b, 22a, 22b and preferably at the mid-plane between the faces 14a (or 22a) and 14b (or 22b). In addition, the partially reflective surface 94 is located in the region where the facets 18, 28 do not exist. In this embodiment, the partially reflective surface 94 is actually disposed in the interface region 70 of the interface 40 formed by the light-transmitting material (substrate). The interface region 70 includes three pairs of faces 72a, 72b, 74a, 74b, 76a, 76b, and the faces 74a, 74b, 76a, 76b are pairs of parallel faces that together form a rectangular cross-section. The faces 72a, 72b may also be parallel faces, in which case the three faces 72a, 72b, 74a, 74b, 76a, 76b may be orthogonal to each other. Preferably, faces 74a and 74b are parallel to faces 12a, 24a, 32a and 12b, 24b, 32b, respectively, and faces 76a and 76b are parallel to faces 14a, 22a, 34a and 14b, 22b, 34b, respectively. Similarly, faces 72a and 72b are preferably parallel to faces 16a, 26a, 36a and 16b, 26b, 36b, respectively. In the illustrated embodiment, the material or coating 44 applied to one or both of faces 12b, 24a in the previously described embodiment is applied to one or both of faces 12b, 74a instead. Additionally, a selective reflective coating 78 may be applied to one or both of the faces 24a, 74b to extend along all (or a majority) of the faces 24a, 74b in the elongated direction.

[0124] The construction of the partially reflective surface 94 is such that when the image is coupled out of the waveguide 10, a certain proportion of the intensity of the coupled-out image is reflected at the partially reflective surface 94 before entering the second waveguide 20, thereby ensuring that conjugate beam vectors 64a, 64b are generated and that the conjugate beam vectors 64a, 64b fill the aperture in the waveguide 20.

[0125] Additional discussion of partially reflective surfaces (beam splitter surfaces) deployed parallel to the main surfaces of the waveguide to ensure filling the waveguide aperture can be found in co-owned PCT patent publication WO2021001841A1.

[0126] The embodiments described thus far relate to an optical aperture multiplier employing a rectangular optical waveguide (optical waveguide 10) having an optical outcoupling formation associated therewith, the optical outcoupling formation being implemented as a set of mutually parallel partially reflective surfaces (facets) 18 inside the waveguide 10. However, as mentioned above, other types of outcoupling arrangements for coupling propagating light out of a rectangular waveguide are contemplated, the outcoupling arrangements including optical outcoupling formations in the form of partially reflective surfaces associated with and parallel to the bottom surface of the rectangular waveguide and located at the interface between the two waveguides 10, 20. Examples of implementations of materials or coatings that may be applied at the interface 40 (and extending along all or a majority of the faces 12b, 24a) to form such partially reflective surfaces have been discussed above with respect to the material or coating 44. The following paragraphs describe an optical aperture multiplier according to an embodiment of the second aspect of the present invention, which has a rectangular optical waveguide that does not include any inclined small planes, but instead adopts a partially reflective surface associated with and parallel to the bottom surface of the rectangular waveguide to perform the light outcoupling function.

[0127] With the above in mind, let’s now focus on Fig. 9A and Fig. 9B , Fig. 9A and Fig. 9BThe optical aperture of an embodiment according to the second aspect of the present invention is shown. In the illustrated embodiment, face 12b is associated with a partially reflective surface 96 (at interface 40). The optical coupling between the optical waveguides 10, 20 and the arrangement and construction of the partially reflective surface 96 are such that when the image light 60 is coupled into the optical waveguide 10 with an initial propagation direction at a coupling angle that is inclined to both the first pair of parallel faces 12a, 12b and the second pair of parallel faces 14a, 14b, the image proceeds along the optical waveguide 10 by quadruple internal reflection as previously described (i.e., generating conjugate images 62a, 62b, 62c, 62d), wherein a certain proportion of the intensity of the image (e.g., 62d) is transmitted at the partially reflective surface 96 to be coupled into the optical waveguide 20, and then the light propagates by double internal reflection (images 64a, 64b) within the optical waveguide 20, wherein a certain proportion of the intensity of the image is reflected (deflected) at the partially reflective surface 28 to be directed outward from one of the parallel faces 22a as a visible image 66.

[0128] exist Fig. 9A , two sample image beams 60a, 60b of image 60 are shown entering the optical waveguide 10. Beams 60a, 60b represent a portion of the end of the FOV, corresponding to two sample beams at two extreme angles for the same pixel of the generated image. As previously described, both beams 60a, 60b advance by quadruple internal reflection at faces 12a, 12b, 14a, 14b (i.e., the two beams produce conjugate images 62a, 62b, 62c, 62d), where a certain proportion of the intensity from each beam is transmitted at the partially reflective surface 96 to couple into the optical waveguide 20. The image (64a, 64b) then advances by double internal reflection at faces 22a, 22b of the second waveguide 20, where a certain proportion of the intensity of the image is reflected (deflected) at the partially reflective surface 28 to be directed outward from one of the parallel faces 22a as a visible image 66 (in this case corresponding to the injected beams 60a, 60b arriving at the lower corner of the EMB 3).

[0129] The angled light beam 60 injected into the optical waveguide 10 is arranged to be reflected from all four outer faces 12a, 12b, 14a, 14b of the optical waveguide 10. The light beam should be partially reflected from the bottom face 12b (and / or partially reflective surface 96) at a shallow (grazing) angle and should therefore be partially transmitted from the optical waveguide 10 into the optical waveguide 20 at a steep angle. In other words, a certain proportion of the intensity of the light beam should be transmitted into the waveguide 20 at the face 12b / partially reflective surface 96 / interface 40, and a certain proportion of the intensity of the light beam should be reflected at the face 12b / partially reflective surface 96 / interface 40 to continue through the waveguide 10 by internal reflection. This partial transmission / reflection characteristic can be achieved by disposing a material or coating 44 at the faces 12b, 24a to form the partially reflective surface 96.

[0130] Incidentally, the light beam is injected through an optical coupling structure (not shown), and in this embodiment, the optical coupling structure is implemented as a coupling arrangement that provides side-illuminated injection. FIG. 19A to FIG. 21 and Fig.23 , an example of a coupling configuration providing side illumination will be provided in a subsequent section of this disclosure. To this end, the entire interface 40 may include the aforementioned partially reflective surface 96, i.e., the material or coating 44 may extend along the entire face 12b in the elongated direction. However, it should be noted that other embodiments employing forward / backward injection through the aforementioned optical coupling configuration 80 will also be referred to herein. Figures 11 to 16B Presentation.

[0131] Now return to Fig. 9A and Fig. 9B Because face 12b is actually a partially reflective surface, each time light (e.g., image 62d) strikes face 12b, a certain fraction of the intensity of the light is transmitted through face 12b and into light guide 20, and the remainder of the intensity is reflected at face 12b and continues on through light guide 10. Thus, each transmission / reflection at face 12b reduces the overall intensity of the propagated image, and it may be desirable to reduce the number of reflections (without sacrificing the aperture expansion of the image) to improve light efficiency. Fig.10 The illustrated embodiment shows a method of improving light efficiency in which the optical waveguide 10 is oriented at an angle (i.e., tilted) relative to the optical waveguide 20. In particular, the faces 12a, 12b are tilted obliquely relative to the face 24b. It has been found that tilt angles in the range of 5°-45° are particularly suitable for improving light efficiency without negatively affecting the aperture expansion. In the illustrated embodiment, the elongation direction of the optical waveguide 10 is no longer along the x-axis, but along a direction that is tilted relative to the x-axis by the tilt angle of the faces 12a, 12b relative to the face 24b.

[0132] Now turn to Fig.11 , showing an isometric view of an optical aperture multiplier according to another embodiment of the present invention, which is similar to Fig. 9A The embodiment shown, however, wherein the partially reflective surface 96 extends along most but not all of the face 12b to accommodate Figures 3 to 5 , Fig. 7A and Figure 7B, and the like. In a particularly preferred, but non-limiting implementation, the partially reflective surface 96 is implemented as a selectively reflective coating applied to the face 12b prior to coupling the optical waveguides 10, 20. Here, the partially reflective surface 96 extends (in the elongated direction) along a majority 45 of the face 12b. The coupling-in region 46 (or "uncoated portion") of the face 12b corresponds to the remaining minority of the face 12b (near the sides 16b, 26b). Here, the image light 60a, 60b enters the optical waveguide 10 through the uncoated portion 46. The plane P and the critical boundary 47 separating the two portions 45, 46 are more clearly shown in this isometric view.

[0133] It should be noted that in the embodiments contemplated herein, reference is made to Fig.11 The described embodiments employ Fig. 6A and Figure 6B "Top-down" coupling-in configuration shown. In such an embodiment, the coating or material 54 is deployed to extend along a majority of the face 12a, as described above.

[0134] As previously described, in embodiments where the optical outcoupling configuration of the optical waveguide 10 is implemented as a set of inclined facets 18, it may be preferred to design the facets 18 such that the reflectivity of the facets 18 decreases along the direction of light propagation through the optical waveguide 10 to provide a gradual increase in the intensity of light coupled into the optical waveguide 20. In the same sense, it may be preferred to design the partially reflective surface 96 such that the reflectivity of the partially reflective surface 96 decreases (equivalently, the transmittance increases) along the direction of light propagation through the optical waveguide 10. Fig.12 An embodiment of such an optical aperture multiplier is shown in which the reduction in reflectivity is achieved by dividing the partially reflective surface 96 into a plurality of regions (preferably discrete, non-overlapping regions) 97a, 97b, 97c, 97d, 97e, 97f along the direction of propagation of light through the optical waveguide 10 (which is the elongated direction, i.e., along the x-axis in an arbitrarily labeled xyz coordinate system), wherein the reflectivity of the regions 97a, 97b, 97c, 97d, 97e, 97f decreases along the direction of propagation of light through the optical waveguide 10. In the illustrated embodiment, six discrete regions 97a, 97b, 97c, 97d, 97e, 97f are shown for exemplary purposes, however, it should be understood that any suitable number of regions may be employed. The variation in reflectivity may be provided by a suitable reflective coating applied at face 12b (or in some embodiments, and sometimes less preferred embodiments, at face 24a).

[0135] In order to ensure that a uniform light beam is coupled (from the rectangular waveguide 10) into the optical waveguide 20, the reflective coating forming the partially reflective surface 96 should preferably be designed so that the reflectivity varies across the length of the face 12b in the direction of elongation of the waveguide 10 (and, therefore, across the interface 40). Here, reflectivity refers to the reflection of unpolarized light averaged across at least a large portion of the visible region of the electromagnetic spectrum, wherein the "large portion" preferably covers at least wavelengths in the range of 430-660 nanometers (nm), but may also include wavelengths up to 750 nanometers. The reflective coating should have color-neutral reflection and transmission properties so that the incident light beam does not experience any color change due to reflection at the partially reflective surface 96.

[0136] In certain embodiments, the reflective coating is a multilayer coating designed such that the reflectivity variation across the length of face 12b (i.e., across interface 40) is preferably between 50%-80% (with as low absorption as possible) at an AOI in the range of 35°-55°. In one set of non-limiting implementations, the multilayer coating is formed of a metal (e.g., silver) layer and one or more dielectric coatings, wherein the variation in reflectivity is determined by the thickness of the metal layer. In another set of non-limiting implementations, the multilayer coating is formed of a metal (e.g., silver) layer and one or more dielectric coatings, wherein the variation in reflectivity is determined by adjusting the thickness of each of the metal layer and the dielectric coating by a predetermined factor. In yet another set of non-limiting implementations, the multilayer coating is formed of a plurality of dielectric coatings without any metal layer. When a multilayer coating of only dielectric material is used, the thickness of the boundaries between adjacent layers should preferably be kept as small as possible, which can be achieved using masking methods. As will be discussed in subsequent portions of the present disclosure, particularly preferred embodiments employ a multilayer coating of only dielectric material as part of a polarized light injection scheme.

[0137] It is noteworthy that the use of a multilayer coating having a silver layer having a thickness in the range of 15nm-35nm will typically produce light absorption in the silver layer in the range of about 4%-8%. The number of layers used in the multilayer coating can be relatively small, between 2-7 layers, providing the advantage that the reflectivity and transmittance can be relatively "flat" in the visible light region of the electromagnetic spectrum, thereby achieving color-neutral reflection and transmission of light. It should also be noted that the use of a multilayer coating without any metal layers (i.e., only layers of dielectric material) (i.e., only layers of dielectric material) can provide low absorption, typically less than about 5%. The number of layers required to achieve a desired reflectivity (by varying the layer thickness) in a multilayer coating of only dielectric material generally does not maintain the flatness of the coating, which can result in color-dependent reflection and transmission.

[0138] Fig.13A reflectivity graph of an exemplary multilayer coating across six regions 97a, 97b, 97c, 97d, 97e, 97f at four exemplary AOIs (35°, 42°, 49°, and 55°) is shown. Light incident on the partially reflective surface 96 at a higher AOI (e.g., 55°) leaves the light guide 10 earlier than light incident on the partially reflective surface 96 at a lower AOI. Therefore, region 97a is designed to have a high reflectivity (low transmission) for a lower AOI and a lower reflectivity (higher transmission) for a higher AOI (e.g., 55°). In regions 97b and 97c, the transmission of the higher AOI is gradually reduced, so that light at the higher AOI is not actually transmitted (i.e., is actually completely reflected) in regions 97d, 97e, and 97f. The transmission of light at the second highest AOI (e.g., 49°) starts at the area 97b with the highest transmission, and then gradually decreases in areas 97c and 97d, so that the light at such AOI is not actually transmitted (i.e., actually completely reflected) in areas 97e and 97f. The transmission of light at the second highest AOI or the second lowest AOI (e.g., 42°) starts from the area 97c with the highest transmission, and then gradually decreases in areas 97d and 97e, and so that the light of such AOI is not actually transmitted (i.e., actually completely reflected) in area 97f. The transmission of light at the lowest AOI (e.g., 35°) starts only at the area 97d with the highest transmission, and then gradually decreases in areas 97e and 97f with the lowest transmission, but is still non-zero in 97f.

[0139] In other embodiments, the partially reflective surface 96 is formed by coating the opposite surface 12b with a dielectric coating. The dielectric coating has a low reflectivity for incident light polarized in a first polarization direction (e.g., p-polarized light) and a high reflectivity for incident light polarized in a second polarization direction orthogonal to the first polarization direction (e.g., s-polarized light). When light (e.g., s-polarized light) coupled into the optical waveguide 10 with an initial polarization along the second polarization direction proceeds through the optical waveguide by quadruple internal reflection, the quadruple internal reflection maintains the polarization direction of the propagating light relative to the partially reflective surface 96, so that the s-polarized light is transmitted into the waveguide 10 at the partially reflective surface 96. The design of the coating according to a specific polarization scheme will be described later in the second group of embodiments according to the second aspect of the present invention ( FIG. 15A to FIG. 22 ), and the second group of embodiments will be described in subsequent parts of the present disclosure.

[0140] It is generally noted that in order for the image to fill the aperture of the optical waveguide 20, both the image and its conjugate (i.e., both images 64a and 64b) must be present in the waveguide 20. One way to achieve aperture filling of the lower waveguide 20 is by propagating both the image and its conjugate (i.e., the four conjugate beam vectors 62a, 62b, 62c, 62d) through the waveguide 10, and by coupling both the image and its conjugate (e.g., both 62a and 62b) into the lower waveguide 20. However, if the angular orientation of the faces 12a, 12b, 14a, 14b is such that the faces 12a, 12b are not parallel and / or such that the faces 14a, 14b are not parallel and / or such that one or both of the faces 12a, 12b are not perpendicular to one or both of the faces 14a, 14b, then the image and the conjugate image are angularly offset in opposite directions upon reflection from a non-perpendicular surface. After several reflections from the non-perpendicular surface, the angular offset accumulates. Therefore, even slight manufacturing errors that result in deviations from parallelism or perpendicularity can introduce significant angular differences between the image and the conjugate image, which can cause ghosting and / or reduce optical resolution. Therefore, the manufacturing tolerances for parallelism and perpendicularity are very tight.

[0141] Fig.14 An embodiment is shown in which tight manufacturing tolerances for aperture filling are improved by tilting the optical waveguide 10 relative to the optical waveguide 20 so that only one of the images coupled out of the waveguide 10 (but not both the image and its conjugate) is coupled into the waveguide 20 to be contained within the waveguide 20 and guided. Fig.14In the non-limiting embodiment shown, the desired tilt angle of the waveguide 10 relative to the waveguide 20 matches the angle α of the second waveguide coupling surface (face 24a), which is tilted by α relative to the face 22a. In other words, the waveguide 10 is tilted so that the face 12b is tilted diagonally relative to the face 22a (angle α). This tilt is selected to couple one image (e.g., 62a) from the waveguide 10 and not couple the other image from the waveguide 10, and so that the light of the coupled-in image is reflected at the face 22a and then reflected at the face 22b, thereby producing a conjugate image pair 64a, 64b and filling the aperture in the lower waveguide 20. In a preferred embodiment, an intermediate window 98 formed as a light-transmissive optical element having faces 98a, 98b is disposed between the waveguides 10, 20 to provide optical coupling between the waveguides 10, 20 and prevent ghosting (caused by unwanted reflections at the face 24a). The intermediate window 98 is disposed to protrude beyond the input aperture of the waveguide 20. In the illustrated embodiment, this arrangement is such that the face 98a is parallel to the face 12b and extends beyond the entire face 12b, and the face 98b is parallel to the face 24a and preferably also extends beyond the entire face 12b (and extends across the entire face 24a, close to the entire face 24a, or beyond the entire face 24a). In some embodiments, the intermediate window 98 may be a refractive layer. Some of the image light coupled out of the waveguide 10 passes through the intermediate window 98 and is coupled into the waveguide 20, while some of the image light coupled out of the waveguide 10 passes through the intermediate window 98 but is not coupled into the waveguide 20. In particular, a light beam (solid arrow) that passes through the intermediate window 98 and enters the waveguide 20 and is reflected at the face 22a and then at the face 22b is coupled into the waveguide 20, thereby being guided through the waveguide 20 by (total) internal reflection at the faces 22a, 22b. However, a light beam (dashed arrow) that passes through the intermediate window 98 and enters the waveguide 20 but is reflected back to the intermediate window 98 at the face 22a is not coupled into the waveguide 20. Instead, these light beams reflected back into the intermediate window 98 re-enter the intermediate window 98 via the inclined (slanted) surface 24a and the face 98b, and are preferably coupled out through the edge or side surface of the intermediate window 98. In some embodiments, a light absorber (not shown) may be placed at the outcoupling edge / surface of the transparent window 98 to absorb external light. In some embodiments, the light absorber may be implemented by coating the outcoupling edge / surface of the intermediate window 98 with a light absorbing material. The intermediate window 98 may have any suitable geometry as long as the faces 98a, 98b are parallel to the faces 12b, 24a and protrude beyond the input aperture of the waveguide 20. For example, in another implementation, the intermediate window 98 may take the form of an intermediate wedge, which may also be used to mount the waveguide 10 at a desired tilt angle relative to the waveguide 20.

[0142] A similar effect can be produced by introducing at least one partially reflecting surface parallel to the faces 22a, 22b in the interface between the two waveguides 10, 20 (similar to Fig. 8A and Figure 8B , and as described in PCT Patent Publication WO2021001841A1). Using this coupling method of only one of the images into the waveguide 20 requires a smaller coupling aperture with significantly higher optical efficiency. For FOVs around 50°-60° along the diagonal, the relative reduction in FOV aperture size and the relative improvement in efficiency level can typically reach about 2 times.

[0143] Continue to refer to Figures 1A to 14 , now refer to Fig.15A and Fig. 15B , Fig.15A and Fig. 15B The optical aperture of an embodiment according to the second aspect of the invention is shown. Fig.15A and Fig. 15B The optical aperture multiplier in the illustrated embodiment is similar to that previously described with reference to FIG. 9A to FIG. 14 An optical aperture multiplier is described herein, but with several significant differences.

[0144] first, Fig.15A and Fig. 15B The optical aperture multiplier in FIG. 1 is configured to operate with a coupling prism 100 that introduces the collimated image 60 into the optical waveguide 10 via side illumination. Similar to the optical coupling-in configuration 80 described above, the coupling prism 100 is configured to trim the input image upon entering the waveguide 10. The coupling prism 100 is only Fig.15A , but may take various forms to provide image injection and trimming. Details of the construction and operation of such coupling prisms may be found in various publications of Lummus Ltd. (Israel), including co-owned U.S. Patent No. 10,133,070, the entire contents of which are incorporated herein by reference.

[0145] Another significant difference is that the optical aperture multiplier of the present embodiment has a protective layer 37 located at the upper face 12a, which can provide mechanical protection for the upper side of the optical waveguide 10. For example, the protective layer 37 can protect the upper side (face 12a) of the waveguide 10 from scratches or wear, which may introduce reflections in undesirable directions, thereby causing image quality degradation. In addition, the reflectivity of the face 12a and the partially reflective surface 96 may cause undesirable reflections from the external scene into the eye. Therefore, in order to reduce reflections, it is preferably deployed an opaque cover member 38 ( Fig. 15B) to cover the faces 14a, 14b of the waveguide 10 and the protective layer 37. As shown, the cover 38 has an inverted U shape and includes an upper portion 38c covering the protective layer 37 (and thus covering the face 12a) and a pair of legs 38a, 38b covering the faces 14a, 14b, respectively. The portion of the cover 38 at the end of the legs 38a, 38b may also cover the upper portion of the faces 22a, 22b of the second waveguide 20. A material 41 such as a reflective coating or a low refractive index material layer may be applied between the portion of the legs 38a, 38b and the contact portion of the waveguides 10, 20. The material 41 may also be applied between the portion of the legs 38a, 38b and the side contact portion of the protective layer 37. In some embodiments, the low refractive index material 41 is a low refractive index optical glue, which may also be used to achieve bonding of the cover 38 to the waveguide.

[0146] Another difference is the second optical waveguide 20, which in the illustrated embodiment has faces 24a, 24b, 26a, 26b forming a more generally quadrilateral cross section. Faces 24a and 26a are preferably orthogonal to each other and parallel to faces 12b and 16a, respectively, with face 24a (together with face 12b) defining the interface between the two waveguides 10, 20. Faces 24b and 26b may be orthogonal to each other, or may be at an oblique angle but still close to 90°, and form obtuse and acute angles with the corresponding faces 26a and 24a, respectively. The optical aperture multiplier has an orientation diagonal to the orientation of the output image 66 (coupled out by facet 28), which may provide a compact and aesthetically pleasing design of the optical aperture multiplier, and facilitate various deployment configurations in which the optical waveguide 10 is oriented diagonally relative to the eye, in which the distal end of the waveguide 10 (opposite to the proximal end of the waveguide 10) is deployed above or below the eye. In the context of this document, the proximal end of the waveguide 10 is the end where the image 60 is injected (coupled) into the waveguide 10 . Fig.16A and Fig. 16B An exemplary supra-ocular deployment configuration is shown for left eyes 2L and 2R, in which each eye 2L, 2R has its own optical aperture multiplier 1LA, 1RA. Fig.17A and Fig. 17B An exemplary subocular deployment configuration of a left eye 2L and a right eye 2R is shown, in which each eye 2L, 2R has its own optical aperture multiplier 1LB, 1RB. Each optical aperture multiplier 1RA, 1LA, 1RB, 1LB is configured according to Fig.15A and Fig. 15B The optical aperture multiplier is constructed and operated as shown and provides an outcoupled image (e.g., Fig. 15B 66). It should also be noted that Fig. 16B The right eye optical aperture multiplier 1RA is Fig.15A The optical aperture multiplier shown in FIG. Fig.16AThe left-eye optical aperture multiplier 1LA can be realized by mirroring the optical aperture multiplier 1RA about the y-axis. Fig.17A and Fig. 17B The left eye optical aperture multiplier 1LB and the right eye optical aperture multiplier 1RB of can be similarly realized by appropriately mirroring the optical aperture multipliers 1RA and 1LA about one or more of the three axes. It should be noted that in Fig.17A and Fig. 17B In the under-eye deployment configuration, the distal end of the waveguide 10 is located under the eye, while the middle and proximal ends of the waveguide 10 are located at or above eye level. However, in some non-limiting embodiments, the geometry of one or both of the waveguides 10, 20 can be modified so that the entirety of the rectangular waveguide 10 is deployed under the user's eye.

[0147] Fig.18A and Fig.18B Shown with Fig.15A and Fig. 15B 14b, except that a diffractive element is used to couple light into and out of the optical waveguide 10. In particular, an optical in-coupling formation 110 in the form of a diffractive element (e.g., a diffraction grating) disposed in association with one of the facets 14b is used to couple the image 60 into the optical waveguide 10. The in-coupling diffractive element is shown as being disposed in association with the facet 14b to accommodate the preferred deployment of the optical image generator at the back of the optical aperture multiplier.

[0148] An outcoupling diffractive optical element 29 (e.g., a diffraction grating) is disposed in association with one of the faces 22a and couples light 64a, 64b out of the optical waveguide 20 toward the eye 2. Although the diffractive element is shown as being associated with the face 22a, the diffractive element may also be disposed in association with the face 22b. Fig.18A and Fig.18B A single diffractive element 29 is shown in FIG. 1 , but a plurality of diffractive elements may be employed, each diffractive element being associated with a respective portion of face 22a or face 22b (or respective non-overlapping portions of faces 22a, 22b).

[0149] It should be noted that in embodiments where the optical outcoupling configuration of the optical waveguide 10 is implemented as a set of inclined facets 18, for example in reference Figure 1A and Figure 1BIn the depicted embodiment, the facets 28 of the optical waveguide 20 can be arranged with or without an oblique angle relative to the face 24a (i.e., oblique to the face 24a, or parallel to the face 24a and perpendicular to the face 26a), and still couple out a full FOV image. This is due in part to the fact that the pair of conjugate images (e.g., images 62a and 62b) are deflected into the optical waveguide 20 by the facets 18. However, in embodiments where the optical outcoupling configuration of the optical waveguide 10 is implemented as a partially reflective surface 96 associated with and parallel to the face 12b (e.g., as FIG. 9A to FIG. 12 as well as Fig.14 ), only the downlink beam vector (e.g., image 62d) is coupled into the optical waveguide 20. Therefore, in order to maintain as much of the image FOV as possible, the facet 28 should have a tilt angle relative to the surface 24a (or 24a). In some cases, the tilt angle of the facet 28 may result in an increase in the size and form factor of the optical aperture multiplier, so it may be desirable to use a facet 28 without a tilt angle deployed in a thin-plate type waveguide, combined with the optical waveguide 10 associated with the out-coupling configuration implemented as a partially reflective surface 96, to reduce the size of the optical aperture multiplier.

[0150] Fig.19A and Fig.19B An embodiment of an optical aperture having a rectangular waveguide 10 having a partially reflective surface 96 (rather than a tilted facet) is shown optically coupled to a second optical waveguide 20 having a non-tilted facet 28. The previously described optical coupling configuration 100 is also shown here, which couples the image 60 into the optical waveguide 10.

[0151] In the illustrated embodiment, the optical waveguide 20 is a thin-plate type waveguide and has a pair of parallel faces 22a, 22b and two additional pairs of faces 24a, 24b, 26a, 26b, which are shown as pairs of parallel faces. A light redirection arrangement 120 is associated with a first region 121 of the optical waveguide 20 and is used to redirect (deflect) light coupled into the optical waveguide 20 toward a facet 28 located in a second region 122 of the optical waveguide 20.

[0152] The first region 121 preferably spans the entire length of the optical waveguide 20 between the faces 26a, 26b and occupies an upper portion of the optical waveguide 20, typically the upper 10%-25% of the optical waveguide 20 measured from the face 24a in a direction toward the face 24b (arbitrarily shown here as corresponding to the "y" direction). The second region 122 also preferably spans the entire length of the optical waveguide 20 between the faces 26a, 26b. The two regions 121, 122 may be non-overlapping regions, such that the second region 122 occupies the lower portion of the optical waveguide 20 not occupied by the first region 121. However, in some embodiments, the two regions 121, 122 may partially overlap (along the "y" direction).

[0153] In a preferred embodiment, the light redirection arrangement 120 spans most or all of the length of the light guide 20 between the faces 26a, 26b. In some embodiments, the light redirection arrangement 120 is implemented as a set of mutually parallel partially reflective surfaces (facets) that at least partially traverse the length of the light guide 20 between the faces 26a, 26b (i.e., between the faces 26a, 26b along the x-axis of an arbitrarily labeled xyz coordinate system) and are obliquely inclined to the faces 12b, 24a (preferably at a steep and still acute angle). In other embodiments, the light redirection arrangement can be implemented as one or more diffractive elements associated with one or more of the faces 22a, 22b, 24a, 24b, 26a, 26b of the light guide 20.

[0154] In embodiments where the light redirection arrangement 120 is implemented as a set of facets 120, the facets 120 have a first orientation that is non-parallel to the orientation of the facets 28 (the facets 28 are obliquely inclined to the faces 22a, 22b). In the illustrated embodiment, the two sets of facets 120, 28 do not overlap, but other embodiments are possible in which one or more facets 28 overlap with the facets 120 when projected onto the plane of the faces 22a, 22b (i.e., the xy plane in the figure).

[0155] The construction of the facets 28 and the light redirection arrangement 120 is such that when the partially reflective surface 96 couples an image (images 62a, 62, 62c, 62d) that propagates through the optical waveguide 10 by quadruple internal reflection into the optical waveguide 20, the coupled-in image propagates in a first region 121 of the optical waveguide 20 by internal reflection at the faces 22a, 22b (images 63a, 63b) along a first guiding direction, wherein a certain proportion of the intensity of the image is reflected (deflected) at the light redirection arrangement 120 to be redirected into a second region 122 of the optical waveguide 20 along a second guiding direction, and then propagates in the second region 122 of the optical waveguide 20 by internal reflection at the faces 22a, 22b (images 64a, 64b), wherein a certain proportion of the intensity of the image is reflected (deflected) at the partially reflective surface 28 to be directed outwardly from one of the parallel faces 22a as a visible image 66 to be seen by the eye 2 of the observer. The first guiding direction is generally diagonal to the direction of elongation of the waveguide 10 (i.e., diagonal to the faces 12b, 24a). The second guiding direction is different from the first guiding direction and is preferably perpendicular or nearly perpendicular to the direction of elongation of the waveguide 10 (and faces 12b, 24a), and is preferably parallel or nearly parallel to the faces 26a, 26b.

[0156] Fig. 20A and Fig. 20B Shown with Fig.19A and Fig.19B An embodiment similar to the embodiment shown, except that a diffractive element is used to couple light into the optical waveguide 10 and out of the optical waveguide 20, similar to the reference Fig.18A and Fig.18B In particular, an optical incoupling configuration 110 in the form of a diffractive element (e.g., a diffraction grating) disposed at one of the faces 14b is used to couple the image 60 into the optical waveguide 10. The incoupling diffractive element is shown as being disposed in association with the face 14b to accommodate the preferred deployment of the optical image generator at the back of the optical aperture multiplier.

[0157] An outcoupling diffractive optical element 29 (e.g., a diffraction grating) is disposed in association with a portion of one of the facets 22a located in the second region 122 and couples light 64a, 64b out of the optical waveguide 20 toward the eye 2. Although the diffractive element is shown as being associated with the facet 22a, the diffractive element may also be disposed in association with a portion of the facet 22b in the second region 122. Fig. 20A and Fig. 20B A single diffractive element 29 is shown in FIG. 1 , but a plurality of diffractive elements may be employed, each diffractive element being associated with a respective portion of face 22a or face 22b in the second region 122 (or respective non-overlapping portions of face 22a, 22b).

[0158] In all disclosed embodiments, the light beam 60 corresponds to light from a collimated image generated by an optical image generator. Although not shown in the accompanying drawings, an optical image generator (also referred to as an "image projector") typically includes at least one light source, which is typically a polarized light source, such as a liquid crystal on silicon (LCoS) chip, disposed to illuminate a spatial light modulator. The spatial light modulator modulates the projection intensity of each pixel of the image to generate an image. Alternatively, the image projector may include a scanning arrangement, typically implemented using a fast scanning mirror, that scans the illumination from a laser light source across the image plane of the projector while synchronously changing the intensity of the light beam on a pixel-by-pixel basis with the scanning motion, thereby projecting the desired intensity for each pixel. In both cases, collimating optics are provided to produce an output projection image (i.e., image light 60) that is collimated to infinity. Some or all of the above components of the image projector are typically arranged on the surface of one or more polarizing beam splitters (PBS) cubes or other prism arrangements known in the art. Thus, the collimated light 60 generated by the image projector may be generally polarized and may have an initial polarization relative to one of the faces of the waveguide 10 when injected into the optical waveguide 10. Optical image generators have been described in various publications including, for example, U.S. Patent No. 8,643,948, U.S. Patent Application Publication No. 2019 / 0391408, and U.S. Patent Application Publication No. 2021 / 0072553 to Lummus Ltd. (Israel).

[0159] In certain embodiments where light is coupled into optical waveguide 20 via a partially reflective surface associated with face 12b (e.g., surface 96) rather than via angled facets disposed within waveguide 10, the polarization scheme employed by the optical aperture multiplier is particularly relevant and should be designed to ensure that the injected light propagates through both the 2D and 1D waveguides without degrading image quality.

[0160] In embodiments where a multilayer coating having a metal layer is used to form the partially reflective surface 96, there is some flexibility in the polarization of the image light 60 injected into the waveguide 10. In particular, the metal coating generally provides a suitable partial reflectivity (and therefore a suitable partial transmittance) for p-polarized light, and a high reflectivity for s-polarized light, at a range of operating incident angles to be coupled out by the partially reflective surface 96. Thus, the partially reflective surface 96 (when formed using a metal layer) can effectively couple the p-polarized component of the propagating light out of the waveguide 10 and retain the s-polarized component within the waveguide 10. Thus, any suitable polarization scheme can be used to generate the light beam 60 to be injected into the waveguide 10.

[0161] In one example, the light beam 60 is unpolarized (thus having s-polarization and p-polarization components) relative to the face 12b (i.e., the surface 96), such that a certain proportion of the intensity of the p-polarization component is transmitted out of the waveguide 10 by the partially reflective surface 96, and such that the s-polarization component is reflected by the surface 96. In certain non-limiting embodiments, the optical image generator outputs the light beam 60 as an unpolarized light beam by adopting a special configuration of the light source. In particular, the optical image generator can combine orthogonally polarized laser sources to produce an unpolarized image beam. In another embodiment, the optical image generator outputs a polarized image beam, but a depolarizer is deployed in the optical path between the optical image generator and the input aperture of the waveguide 10, for example before the optical coupling configuration or at the output of the optical coupling configuration. An example of a depolarizer deployment configuration is described in detail in U.S. Patent No. 10,133,070.

[0162] In another example, the light beam 60 can be circularly polarized relative to the face 12b, for example by deploying a linear polarization filter and a quarter wave plate at the output of the optical image generator (or the input of the optical coupling configuration) or alternatively at the output of the optical coupling configuration.

[0163] In yet another example, the light beam 60 may be p-polarized relative to the face 12 b. This may be achieved by using an optical image generator that outputs p-polarized light. However, in a typical configuration, the optical image generator outputs s-polarized light, and thus a wave plate may be disposed at the output end of the optical image generator (or the input end of the optical coupling configuration) or alternatively at the output end of the optical coupling configuration to rotate the polarization of the output light from s-polarization to p-polarization.

[0164] In embodiments where one or more dielectric coatings are used to form partially reflective surface 96, management of the polarization direction of injected light beam 60 relative to face 12b (partially reflective surface 96) is critical to achieve reasonable light efficiency. In such embodiments, the optical image generator is configured to produce polarized image illumination that is s-polarized relative to face 12b. The optical image generator described in U.S. Pat. No. 8,643,948 is an example of an optical image generator that produces s-polarized image light.

[0165] In some embodiments, in order to tailor the reflectivity of the facet 28 to ensure that the facet 28 sufficiently reflects propagating light out of the one-dimensional waveguide, a wave plate (e.g., a half-wave plate) may be deployed at the interface between the two waveguides 10 and 20. Referring again to Fig.15A and Fig. 15BA wave plate 130 for rotating the polarization state of light to be coupled into the optical waveguide 20 is optionally disposed at the interface between the waveguides 10, 20 and associated with the partially reflective surface 96. In particular, the wave plate 130 is located at the interface 40, between the partially reflective surface 96 and the upper surface 24a of the waveguide 20. The wave plate 130 is of particular value when used in conjunction with an embodiment in which the partially reflective surface 96 is formed using a dielectric coating (and the injected light beam 60 is s-polarized relative to the face 12b). In such an embodiment, the illumination coupled out of the waveguide 10 by the surface 96 is s-polarized relative to the surface 96 / face 12b. However, the facet 28 is typically formed using an optical coating having a reflectivity designed for light that is s-polarized relative to the faces 22a, 22b, which are orthogonal to the face 12b. Therefore, the polarization direction of the light coupled out of the waveguide 10 is p-polarized with respect to the faces 22a, 22b. By disposing the wave plate 130 between the waveguides 10 , 20 , the wave plate 130 rotates the polarization direction of the outcoupled light to be s-polarized relative to the faces 22 a , 22 b , which increases the efficiency of the light outcoupled by the facets 28 .

[0166] It should be clear that in FIG. 18A to FIG. 20B In the illustrated embodiment, the wave plate 130 may be disposed in a similar position between the partially reflective surface 96 and the upper face 24 a of the waveguide 20 .

[0167] Reference Fig.21 and Fig. 22 , the following paragraphs describe some design aspects of the dielectric coating that can be used to form the partially reflective surface 96. Initially, the coating should be optimally designed to achieve maximum power (intensity) for a beam propagating at the distal end of the waveguide 20, while at the same time achieving the same power (intensity) for a beam reflected at the proximal end of the waveguide 20. The "distal end" of the waveguide 20 is generally the area of ​​the face 26a that is near the face 24b, and the "proximal end" of the waveguide 20 is generally the area of ​​the face 24b that is near the face 26b. Fig.21 , a light beam propagating at the distal end of the waveguide 20 is shown as a solid arrow and can be traced back through the first waveguide 10 to the light ray 60F at the input end of the optical coupling-in configuration 100. A light beam propagating at the proximal end of the waveguide 20 is shown as a dashed arrow and can be traced back to the light ray 60N at the input end of the optical coupling-in configuration 100.

[0168] For example, if the reflectivity provided by the coating so that the light beam at the distal end leaves the waveguide 20 at a desired angle is denoted by R, the number of reflections within the waveguide 10 is denoted by N, and the transmittance between two reflections is denoted by T, then the power output of the light beam corresponding to the injected light beam 60F at the distal side of the waveguide 20 can be expressed as:

[0169] P=(1-R)(R*T)N .

[0170] Obviously, power P is a multivariable function and can be maximized in a variety of ways, including, for example, by fixing T and N, then maximizing P and determining the value of R that maximizes P. For example, if T = 0.98 and N = 8, then P reaches a maximum value of about 0.0367 when R ≈ 0.88. max Generally speaking, the reflectivity of the coating to the light corresponding to 60N at the entrance of the waveguide 10 should be 1-P max , in P max =0.0367 in this example yields a reflectivity of approximately 0.9633 (96.33%).

[0171] Fig. 22 A graph of the reflectivity of s-polarized light as a function of AOI is shown. As can be seen from the graph, and continuing with this example, in this example P max = 0.0367, the desired reflectivity of about 96.33% is achieved for s-polarized light (in contrast to the sharp drop-off in reflectivity of p-polarized light near the Brewster angle). max =0.0367, injecting a beam that is s-polarized relative to face 12b will achieve optimal and uniform illumination. In such a polarization scheme, and using the above example reflectivities, the reflectivity of partially reflective surface 96 for s-polarized beam 60F will be approximately 88%, and the reflectivity of partially reflective surface 96 for s-polarized beam 60N will be approximately 96.33%.

[0172] Although embodiments according to the second aspect have been described so far in the context of waveguides 10, 20 optically coupled at faces 12b, 24a, other embodiments are possible in which the optical waveguide 10 is arranged such that the optical coupling is between face 12b and a portion of one of the parallel faces 22a, 22b. In such embodiments, face 22a (or 22b) acts as the input coupling surface of the waveguide 20. A simplified isometric representation of such an embodiment is shown in Fig.23 It is shown in Fig.23 Waveguides 10, 20 are shown coupled together at faces 12b, 22a. An intermediate refractive layer 99 is disposed between faces 12b, 22a through which the image coupled out of waveguide 10 passes before being coupled into waveguide 20 through face 22a. A light beam introduced into waveguide 10 should be reflected by the interface with refractive layer 99, and a light beam propagating through waveguide 10 by internal reflection should be coupled out through refractive layer 99 (through facet 18 or partially reflective surface 96) and coupled into waveguide 20 via face 22a. More details of refractive layers can be found in U.S. Pat. No. 10,133,070.

[0173] The following paragraphs describe methods for making an optical aperture multiplier according to an embodiment of the present invention, with particular reference to FIG. 9A to FIG. 12 Various methods of optical aperture multipliers are described.

[0174] like Fig.24A As shown, a plurality of LOEs (i.e., second optical waveguides) 20 are obtained. Each LOE 20 is as described above, for example, with reference to Figure 1A and Figure 1B , and having a pair of main parallel faces 22a, 22b (which may be formed on cover plates 39a, 39b) and a plurality of mutually parallel partially reflective inner surfaces (small faces) inclined to faces 22a, 22b. However, it should be noted that in some embodiments, each LOE 20 may be formed without a cover plate, such as Figure 1C Each LOE 20 also includes two additional pairs of faces 24a, 24b, 26a, 26b (each of which may or may not be a pair of parallel faces), and a plurality of partially reflective interior surfaces (facets) that are inclined to faces 22a, 22b. For clarity, the interior facets of the LOE are not shown. FIG. 24A to FIG. 24F , but the deployment of the internal facets in the LOE can be best understood from the other figures accompanying this specification.

[0175] Techniques suitable for making each LOE 20 are generally known and may be found, for example, in commonly owned prior U.S. Patent No. 8,432,614, referenced herein. FIG. 18A to FIG. 23 described.

[0176] A plurality of LOEs 20 are aligned and then arranged in a stack and bonded together such that the cover plates 39a, 39b of adjacent LOEs are joined together. Fig. 24BThe final combined stack 200 of aligned LOEs 20 is shown, with the stack 200 having three pairs of faces 222a, 222b, 224a, 224b, 226a, 226b. Faces 222a, 222b are a pair of parallel faces, and the other two pairs of faces may or may not be a pair of parallel faces. In certain embodiments, the three pairs of faces of the combined stack 200 are orthogonal (perpendicular) to each other. The alignment of the LOEs 20 is such that the faces 22a, 22b of all the LOEs 20 are parallel to each other (parallel to the xy plane). The face 22a of the LOE at one end of the stack actually forms the face 222a, while the face 22 of the LOE at the other end of the stack forms the face 222b. In an embodiment where each pair of faces 224a, 224b and 226a, 226b is a pair of parallel faces, the alignment of the LOE 20 is further such that the face 24a of the LOE 20 is coplanar (and parallel to the xz plane), and the face 24b of the LOE 20 is coplanar (and parallel to the xz plane), such that the aligned faces 24a and 24b of the LOE 20 form the faces 224a and 224b of the bonded stack 200, respectively (the faces 224a and 224b are parallel to the xz plane), and the face 26a of the LOE 20 is coplanar (and parallel to the yz plane), and the face 26b of the LOE 20 is coplanar (and parallel to the yz plane), such that the aligned faces 26a and 26b of the LOE 20 form the faces 226a and 226b of the bonded stack 200, respectively (the faces 226a and 226b are parallel to the yz plane). In embodiments where each pair of faces 222a, 222b and 224a, 224b is a pair of parallel faces, each of the pairs of faces 222a, 222b and 224a, 224b is orthogonal (perpendicular) to the faces 22a, 22b of each LOE 20 (and therefore to the faces 222a, 222b of the stack 200).

[0177] like Fig.24CAs shown, a coated transparent thick plate 300 with three pairs of faces 312a, 312b, 314a, 314b, 316a, 316b is obtained. Each pair of faces 312a, 312b and 314a, 314b is a pair of parallel faces, and the two pairs of parallel faces 312a, 312b, 314a, 314b (in the yz plane) together form a rectangular cross-section. The pairs of faces 316a, 316b may or may not be a pair of parallel faces. In some embodiments, the lower surface 312b is coated with a selective reflective coating (e.g., a metal coating with or without a dielectric layer) so that the coated face 312b becomes a partially reflective surface. In other embodiments, a thin plate coated with a selective reflective coating is aligned with face 312b and bonded to face 312b. In yet another embodiment, a film of partially reflective material is attached to face 312b. In all such embodiments, the coating or material is disposed on face 312b such that the coating or material extends along the entire width (in the "z" direction) of face 312b. In certain embodiments, the coating or material is disposed on face 312b such that the coating or material extends along the entire length (in the "x" direction) of face 312b. Such embodiments are useful when the final waveguide configuration is to be coupled to an optical incoupling configuration that provides side illumination (e.g., Fig.15A In other embodiments, the coating or material is disposed on face 312b such that the coating or material extends along most but not all of the length of face 312b. Such embodiments are useful when the final waveguide structure will be used with a "bottom-up" optical coupling configuration that provides front / back illumination (e.g., Figures 3 to 5 , Fig. 7A and Figure 7B It is particularly suitable when used together with an optical coupling-in structure.

[0178] In other embodiments, the metal coating is applied so that it extends along the entire width of face 312a (in the "z" direction) and along most (but not all) of the length of face 312a (in the "x" direction). Such embodiments are useful when the final waveguide structure is to be used with a "top-down" optical coupling configuration (e.g., Fig. 6A and Figure 6B It is particularly suitable when used together with an optical coupling structure.

[0179] exist Fig.24D In FIG. 2 , the coated transparent plate 300 is aligned with the bonded stack 200 of aligned LOEs 20 .

[0180] With reference to the arbitrarily labeled xyz coordinate system used in the accompanying drawings, the alignment of the coated transparent plate 300 with the combined stack 200 (in embodiments where each of the transparent plate 300 and the combined stack 200 has three pairs of parallel faces) can be best understood as follows: each of the faces 312a, 312b, 224a, 224b is parallel to the xz plane, each of the faces 214a, 222a is parallel to the xy plane and is preferably coplanar, each of the faces 314b, 222b is parallel to the xy plane and is preferably coplanar, each of the faces 316a, 226a is parallel to the yz plane and is preferably coplanar, and each of the faces 316b, 226b is parallel to the yz plane and is preferably coplanar.

[0181] The combined stack 200 is optically coupled with the coated transparent plate 300 to form an optical block 280, such as Fig.24E As shown, while maintaining the alignment of the coated transparent plate 300 and the combined stack 200 described in the previous paragraph. The combined stack 200 is optically coupled to the coated transparent plate 300 to form an interface 240 between the faces 312b and 224a (i.e., so that the faces 312b, 224a are opposite to each other). The interface 240 includes a coating or material applied or otherwise associated with the face 312b as described above. Alternatively, before the combined stack 200 is optically coupled to the coated transparent plate 300, a material or coating can be applied to the face 224a instead of the face 312b.

[0182] Optionally, face 312a may be coated with a reflective coating, such as a metallic coating, to ensure that upper face 312a and lower face 312b reflect propagating light of the same incident angle. The coating may be applied to face 312a before or after optically coupling coated transparent plate 300 to bonded stack 200.

[0183] like Fig.24E As shown, along at least two parallel cutting planes (by Fig.24E The optical block 280 is cut (indicated by the dashed line 245 in FIG. 1 ) to slice out at least one optical aperture multiplier (a single optical aperture multiplier such as Fig.24F As shown, however, a plurality of such optical aperture multipliers may be sliced ​​out of optical block 280).

[0184] The cutting plane 245 is parallel to the parallel faces 22a, 22b of the consecutive LOEs 20 of the bonded stack 200 and to the faces 314a, 314b of the coated transparent plate 300. Thus, the cutting plane 245 is orthogonal to the faces 312a, 312b of the transparent plate 300.

[0185] Each of the optical aperture multipliers cut out in a sheet shape has a rectangular optical waveguide 10 (2D optical waveguide) optically coupled to the LOE 20 (1D optical waveguide) at the interface 40, and has a coupling surface ( FIG. 9A to FIG. 12 In embodiments where each LOE 20 includes a pair of cover plates 39a, 39b, each cutting plane 245 preferably passes between consecutive (i.e., adjacent) cover plates 39a, 39b. In embodiments where the LOE 20 does not include any cover plates (e.g., Figure 1C In the embodiment of FIG. 2 , each cutting plane 245 is preferably located at a bonding area between adjacent major outer surfaces (faces) of continuous LOE substrates 19 .

[0186] According to the implementation methods including the above embodiments, the following technical solutions are also disclosed:

[0187] (1) An optical aperture multiplier, comprising:

[0188] a first optical waveguide having a first pair of parallel faces including a first face and a second face and a second pair of parallel faces including a third face and a fourth face, the pair of parallel faces together forming a rectangular cross-section, the first optical waveguide being configured to guide light by quadruple internal reflection at the pair of parallel faces and being associated with an outcoupling structure that couples light out of the first optical waveguide to a second optical waveguide optically coupled to the first optical waveguide, wherein the first face or the second face is subdivided into first and second regions having different optical properties, respectively; and

[0189] An optical coupling-in structure comprising a surface that transmits light into the first waveguide, the surface being disposed in association with a portion of the third face or the fourth face adjacent to the second region such that an edge associated with the surface trims an input collimated image in a first dimension and a boundary between the first region and the second region trims the input collimated image in a second dimension to produce a trimmed collimated image that advances through the first optical waveguide by quadruple internal reflection.

[0190] (2) The optical aperture multiplier of (1), wherein a boundary between the first region and the second region together with an image of the boundary presents an apparent input optical aperture when viewed along an optical input axis.

[0191] (3) The optical aperture multiplier according to (1), wherein some of the input collimated image is reflected at points on the first face that intersect or overlap the edge.

[0192] (4) An optical aperture multiplier according to (1), wherein the edge is a first edge of the surface, and wherein the surface includes a second edge, the second edge is a common edge with a light incident surface, and the light incident surface receives the input collimated image from an optical image generator.

[0193] (5) The optical aperture multiplier according to (4), wherein the side is parallel to the light incident surface.

[0194] (6) The optical aperture multiplier according to (4), wherein the side is not parallel to the light incident surface.

[0195] (7) An optical aperture multiplier according to (1), wherein the surface receives the input collimated image from the optical image generator, and wherein the edge is a first edge of the surface, and wherein the surface includes a second edge, which is a common edge with a reflective surface, and the reflective surface reflects the received input collimated image back to the surface to be trimmed by the edge.

[0196] (8) The optical aperture multiplier according to (1), further comprising the second optical waveguide, wherein the second optical waveguide has a third pair of parallel surfaces and is configured to guide light by internal reflection at the third pair of parallel surfaces, and wherein the second optical waveguide comprises a plurality of partially reflective surfaces between and inclined to the third pair of parallel surfaces, the plurality of partially reflective surfaces coupling light out of the second optical waveguide.

[0197] (9) The optical aperture multiplier of (8), wherein a coating or material is disposed in association with the second face to subdivide the first face into the first region and the second region.

[0198] (10) The optical aperture multiplier of (8), further comprising an optical substrate comprising a fifth facet and optically coupled to the first optical waveguide at the first facet, and wherein a coating or material is associated with the first facet to subdivide the first facet into the first region and the second region.

[0199] (11) An optical aperture multiplier according to (1), wherein the optical outcoupling structure includes a plurality of partially reflective surfaces, which at least partially cross the first optical waveguide and are obliquely inclined to the elongation direction of the first optical waveguide.

[0200] (12) An optical aperture multiplier according to (1), wherein the optical outcoupling structure includes a partially reflective surface associated with the second face.

[0201] (13) An optical aperture multiplier, comprising:

[0202] a first optical waveguide having a first pair of parallel faces including a first face and a second face and a second pair of parallel faces including a third face and a fourth face, the pair of parallel faces together forming a rectangular cross-section, wherein the partially reflective surface is associated with and parallel to the second face;

[0203] an optical coupling structure for coupling polarized light corresponding to an image into the first optical waveguide in an initial propagation direction at a coupling angle inclined to both the first pair of parallel planes and the second pair of parallel planes, the polarized light being s-polarized relative to the second plane; and

[0204] a second optical waveguide having a plurality of faces including a third pair of parallel faces, the second optical waveguide being optically coupled to the first optical waveguide at an interface between one of the faces of the second optical waveguide and the second face, wherein an optical outcoupling formation is associated with the second optical waveguide,

[0205] Wherein, the optical coupling and the partially reflective surface are configured such that when light corresponding to the image is coupled into the first optical waveguide: the light advances along the first optical waveguide by quadruple internal reflection, wherein a certain proportion of the intensity of the light is transmitted at the partially reflective surface to be coupled into the second optical waveguide; and the light propagates in the second optical waveguide by internal reflection at the third pair of parallel surfaces, wherein a certain proportion of the intensity of the light propagating in the second optical waveguide is deflected out of the second optical waveguide by the optical out-coupling structure.

[0206] (14) The optical aperture multiplier according to (13), wherein at least a majority of the second face includes one or more dielectric coatings to form the partially reflective surface and to make the partially reflective surface partially reflective to s-polarized light.

[0207] (15) The optical aperture multiplier according to (13), further comprising a wave plate located at the interface and configured to rotate a polarization state of light to be coupled into the second optical waveguide.

[0208] (16) An optical aperture multiplier according to (13), wherein the optical outcoupling structure includes a plurality of partially reflective surfaces disposed in the second optical waveguide and inclined with respect to the third pair of parallel surfaces.

[0209] (17) An optical aperture multiplier according to (13), wherein the optical outcoupling structure includes a diffractive optical element associated with at least one of the third pair of parallel surfaces.

[0210] (18) An optical aperture multiplier, comprising:

[0211] a first optical waveguide having a first pair of parallel faces including a first face and a second face and a second pair of parallel faces including a third face and a fourth face, the pair of parallel faces together forming a rectangular cross-section, wherein the partially reflective surface is associated with and parallel to the second face; and

[0212] a second optical waveguide having a plurality of faces including a third pair of parallel faces, the second optical waveguide being optically coupled to the first optical waveguide at an interface between one of the faces of the second optical waveguide and the second face, wherein a light redirecting arrangement is associated with a first region of the second optical waveguide and an optical out-coupling configuration is associated with a second region of the second optical waveguide,

[0213] Wherein, the optical coupling, the partially reflective surface, the light redirection arrangement and the optical out-coupling structure are configured so that when light corresponding to an image is coupled into the first optical waveguide: the light advances along the first optical waveguide by quadruple internal reflection, wherein a certain proportion of the intensity of the light is transmitted at the partially reflective surface to be coupled into the first region of the second optical waveguide; and the light propagates within the first region of the second optical waveguide by internal reflection at the third pair of parallel surfaces, wherein a certain proportion of the intensity of the light is deflected by the light redirection arrangement to be redirected into the second region of the optical waveguide; and the light propagates within the second region of the second optical waveguide by internal reflection at the third pair of parallel surfaces, wherein a certain proportion of the intensity of the light propagating in the second region of the second optical waveguide is deflected out of the second optical waveguide by the optical out-coupling structure.

[0214] (19) An optical aperture multiplier according to (18), wherein the optical outcoupling structure includes a plurality of partially reflective surfaces disposed in the second optical waveguide and inclined with respect to the third pair of parallel surfaces.

[0215] (20) An optical aperture multiplier according to (18), wherein the optical outcoupling structure includes a diffractive optical element associated with at least one of the third pair of parallel surfaces.

[0216] (21) An optical aperture multiplier according to (18), wherein the light redirection arrangement includes a plurality of partially reflective surfaces disposed within the first region of the second optical waveguide and inclined with respect to the additional facet.

[0217] (22) The optical aperture multiplier of (18), wherein the light redirection arrangement comprises a diffractive optical element associated with one of the faces of the second optical waveguide.

[0218] (23) An optical aperture multiplier, comprising:

[0219] a first optical waveguide having a first pair of parallel faces including a first face and a second face and a second pair of parallel faces including a third face and a fourth face, the pair of parallel faces together forming a rectangular cross-section, wherein the partially reflective surface is associated with and parallel to the second face; and

[0220] a second optical waveguide having a third pair of parallel faces including a fifth face and a sixth face, wherein an optical outcoupling configuration is associated with the second optical waveguide, and wherein the first optical waveguide is optically coupled to the second optical waveguide and is tilted relative to the second optical waveguide such that the second face is obliquely tilted relative to the fifth face,

[0221] Wherein, the optical coupling and the partially reflective surface are configured so that when light corresponding to an image is coupled into the first optical waveguide: the light advances along the first optical waveguide by quadruple internal reflection, wherein a certain proportion of the intensity of the light is transmitted at the partially reflective surface to enter the second optical waveguide; and some of the light entering the second optical waveguide propagates within the second optical waveguide by internal reflection at the third pair of parallel surfaces, wherein a certain proportion of the intensity of the light propagating within the second optical waveguide is deflected out of the second optical waveguide by the optical out-coupling structure.

[0222] (24) The optical aperture multiplier according to (23) also includes an intermediate window, which provides optical coupling between the first optical waveguide and the second optical waveguide, and the intermediate window is arranged so that some of the light entering the second optical waveguide transmitted at the partially reflective surface is reflected back to the intermediate window at the five faces.

[0223] In the above-described manufacturing methods, as will be appreciated by those of ordinary skill in the art, the cutting or slicing of the various optical structures described herein may be performed by any suitable cutting equipment / device / tool. In certain embodiments, some or all surfaces / faces of the optical structures produced in these cutting / slicing steps may be polished. As will be appreciated by those of ordinary skill in the art, the polishing of the faces and surfaces of the various optical structures described herein may be performed by any suitable polishing equipment / device / tool.

[0224] The description of various embodiments of the present disclosure has been presented for illustrative purposes, but it 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 terms used herein are selected to best explain the principles of the embodiments, practical applications, or technical improvements over those existing in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

[0225] As used herein, the singular form "a," "an," and "the" include plural references unless the context clearly dictates otherwise.

[0226] The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any implementation described as “exemplary” is not necessarily to be construed as preferred or advantageous over other implementations and / or to exclude the incorporation of features from other implementations.

[0227] It should be understood that some features of the invention described in the context of separate embodiments for the sake of clarity may also be provided in combination in a single embodiment. Conversely, various features of the invention described in the context of a single embodiment for the sake of brevity may also be provided in any other described embodiment of the invention, either individually or in any suitable subcombination or as desired. Some features described in the context of various embodiments should not be considered essential features of those embodiments, unless the embodiment is inoperable without those elements.

[0228] To the extent that the appended claims are drafted without multiple references, this is done solely to accommodate formal requirements in jurisdictions that do not permit such multiple references. It should be noted that all possible combinations of features implied by making claims multiple references are expressly contemplated and should be considered part of the present invention.

[0229] Although the present invention has been described in conjunction with specific embodiments of the present invention, it is apparent that many substitutions, modifications and variations will be apparent to those skilled in the art. Therefore, the present invention is intended to include all such substitutions, modifications and variations that fall within the spirit and broad scope of the appended claims.

Claims

1. A manufacturing method comprising: Obtaining a transparent plate having a first pair of parallel surfaces, the first pair of parallel surfaces comprising a first surface and a second surface; Obtaining a first optical structure having a plurality of faces including a coupling face, the first optical structure comprising a plurality of groups of mutually parallel partially reflective inner faces, wherein, for each group, the mutually parallel partially reflective inner faces in the group are inclined obliquely relative to the coupling face; optically coupling the transparent plate to the first optical structure so that the second surface is in a facing relationship with the coupling surface, thereby forming a second optical structure; and cutting at least one optical aperture multiplier from the second optical structure in a sheet-like manner by cutting the second optical structure along at least two cutting planes substantially perpendicular to the coupling surface, Therein, at least one partially reflective surface is associated with the second face or is inside the transparent plate.

2. The manufacturing method according to claim 1, wherein: The at least one partially reflective surface is a plurality of partially reflective surfaces inside the transparent plate that are parallel to each other.

3. The manufacturing method according to claim 1, wherein: The at least one partially reflective surface consists of a partially reflective surface associated with the second face.

4. The manufacturing method according to claim 3, further comprising: A selective reflective coating is provided on at least one of the second facet or the coupling facet to form a partially reflective surface associated with the second facet.

5. The manufacturing method according to claim 4, wherein: Providing the selectively reflective coating includes applying the selectively reflective coating to at least a portion of the second face.

6. The manufacturing method according to claim 4, wherein: Providing the selective reflective coating includes applying the selective reflective coating to at least a portion of the coupling face.

7. The manufacturing method according to claim 4, wherein: Providing the selective reflective coating includes applying the selective reflective coating to at least a portion of a thin transparent plate, and bonding the thin transparent plate to the second face or the coupling face.

8. The manufacturing method according to claim 4, wherein: The selective reflective coating includes a metal coating.

9. The manufacturing method according to claim 8, wherein: The metal coating includes at least one dielectric layer.

10. The manufacturing method according to claim 4, wherein: The selectively reflective coating includes a thin film of partially reflective material.

11. The manufacturing method according to claim 4, wherein: The selective reflective coating is a layer of material having a lower refractive index than that of the transparent plate.

12. The manufacturing method according to claim 1, further comprising: A reflective coating is provided to at least a portion of the first face.

13. The manufacturing method according to claim 12, wherein: The reflective coating includes a metallic coating.

14. The manufacturing method according to claim 1, wherein: The first optical structure is formed by a combined stack of light-guiding optical elements LOE, each LOE in the combined stack having a pair of mutually parallel main surfaces and one of the multiple groups of partially reflective inner surfaces, one of the multiple groups of partially reflective inner surfaces being located between the pair of mutually parallel main surfaces and being obliquely inclined relative to the pair of mutually parallel main surfaces.

15. The manufacturing method according to claim 14, wherein: Each of the pair of mutually parallel major surfaces comprises a cover sheet, and wherein each of the at least two cutting planes passes between adjacent cover sheets of consecutive LOEs of a bonded stack of LOEs.

16. The manufacturing method according to claim 1, wherein: Obtaining the first optical structure includes: obtaining a plurality of light-guiding optical elements (LOEs), each of the plurality of LOEs having a pair of mutually parallel main surfaces and one of the plurality of sets of partially reflective inner surfaces, the one of the plurality of sets of partially reflective inner surfaces being located between the pair of mutually parallel main surfaces and being obliquely inclined relative to the pair of mutually parallel main surfaces, and The plurality of LOEs are arranged in a stack, and the plurality of LOEs are bonded together to form a bonded stack of LOEs.

17. The manufacturing method according to claim 1, further comprising: Before the at least one optical aperture multiplier is cut out of the second optical structure in the form of a plate, a protective layer is applied to the first surface.

18. The manufacturing method according to claim 1, further comprising: For the optical aperture multiplier among the at least one optical aperture multiplier cut out in a sheet form from the second optical structure, a protective layer is applied to the upper surface of the optical aperture multiplier, the upper surface being formed by the first face of the transparent plate.

19. An optical structure, the optical structure being an intermediate workpiece in a manufacturing process of an optical aperture multiplier, the optical structure comprising: a first portion having a first pair of parallel faces including a first face and a second face; as well as a second part, the second part having a plurality of surfaces including a coupling surface, the second part comprising a plurality of groups of mutually parallel partially reflecting inner surfaces, wherein, for each group, the mutually parallel partially reflecting inner surfaces in the group are inclined obliquely relative to the coupling surface, wherein at least one partially reflective surface is provided in association with the second face or within the first portion, and The first portion is optically coupled to the second portion such that the second surface is in a facing relationship with the coupling surface.

20. An optical aperture multiplier, comprising: a first optical waveguide having a first pair of parallel faces including a first face and a second face and a second pair of parallel faces including a third face and a fourth face, the pair of parallel faces together forming a rectangular cross-section, wherein the partially reflective surface is associated with and parallel to the second face; an optical coupling structure for coupling polarized light corresponding to an image into the first optical waveguide in an initial propagation direction at a coupling angle inclined to both the first pair of parallel planes and the second pair of parallel planes, the polarized light being s-polarized relative to the second plane; and a second optical waveguide having a plurality of faces including a third pair of parallel faces, the second optical waveguide being optically coupled to the first optical waveguide such that the second optical waveguide is optically coupled to the first optical waveguide at an interface between one of the plurality of faces of the second optical waveguide and the second face, wherein an optical outcoupling formation is associated with the second optical waveguide, The optical coupling of the second optical waveguide to the first optical waveguide and the partially reflective surface are configured such that: when light corresponding to an image is coupled into the first optical waveguide, the light advances along the first optical waveguide by quadruple internal reflection, wherein a certain proportion of the intensity of light is transmitted at the partially reflective surface to be coupled into the second optical waveguide; and the light propagates in the second optical waveguide by internal reflection at the third pair of parallel surfaces, wherein a certain proportion of the intensity of light propagating in the second optical waveguide is deflected out of the second optical waveguide by the optical out-coupling structure.

21. The optical aperture multiplier of claim 20, wherein: At least a majority of the second face includes one or more dielectric coatings to form the partially reflective surface and to render the partially reflective surface partially reflective to s-polarized light.

22. The optical aperture multiplier of claim 20, further comprising a wave plate located at the interface for rotating a polarization state of light to be coupled into the second optical waveguide.

23. The optical aperture multiplier of claim 20, wherein: The optical out-coupling configuration includes a plurality of partially reflective surfaces disposed within the second optical waveguide and tilted relative to the third pair of parallel faces.

24. The optical aperture multiplier of claim 20, wherein: The optical out-coupling configuration includes a diffractive optical element associated with at least one of the third pair of parallel faces.

25. An optical aperture multiplier, comprising: a first optical waveguide having a first pair of parallel faces including a first face and a second face and a second pair of parallel faces including a third face and a fourth face, the pair of parallel faces together forming a rectangular cross-section, wherein a partially reflective surface is associated with and parallel to the second face; and a second optical waveguide having a third pair of parallel faces including a fifth face and a sixth face, wherein an optical outcoupling configuration is associated with the second optical waveguide, and wherein the optical coupling of the first optical waveguide to the second optical waveguide causes the first optical waveguide to be optically coupled to the second optical waveguide and to be tilted relative to the second optical waveguide such that the second face is obliquely tilted relative to the fifth face, The optical coupling between the first optical waveguide and the second optical waveguide and the partially reflective surface are configured such that: when light corresponding to an image is coupled into the first optical waveguide, the light advances along the first optical waveguide by quadruple internal reflection, wherein a certain proportion of the intensity of light is transmitted at the partially reflective surface to enter the second optical waveguide; and some of the light entering the second optical waveguide propagates in the second optical waveguide by internal reflection at the third pair of parallel surfaces, wherein a certain proportion of the intensity of light propagating in the second optical waveguide is deflected out of the second optical waveguide by the optical out-coupling structure.

26. The optical aperture multiplier of claim 25, further comprising an intermediate window providing optical coupling between the first optical waveguide and the second optical waveguide, the intermediate window being disposed so that some of the light entering the second optical waveguide transmitted at the partially reflective surface is reflected back to the intermediate window at the fifth face.

Images