Compound light guide optical element

Abstract

Composite light guide optical elements are involved. An optical system (100) for directing an image towards a user for viewing comprises a light guide optical element (LOE) (10) having parallel major external surfaces (11a, 11b) for supporting propagation of an image by internal reflection, a coupling-out arrangement for coupling the image out towards an eye of the user, and a coupling-in aperture. An image projector (114) comprises an image generator (32) for generating an image, collimating optics (31) for collimating the image, and an image conjugate generator (20, 33, 34). The image projector is coupled to the coupling-in aperture to introduce the collimated image and its conjugate image into the LOE before the image is incident on either of the major external surfaces. The image conjugate generator can be a second image generator (33) or can take the form of one or more reflective surfaces (22, 23, 24, 34) that are discontinuous with the major external surfaces of the LOE.

Description

[0001] This application is a divisional application of Chinese patent application No. 202180067344.2, filed on March 30, 2023, entitled "Composite Optical Guide Element". The international filing date of the parent application is October 1, 2021, and the international application number is PCT / IL2021 / 051185, with the earliest priority date being October 1, 2020. Technical Field

[0002] This invention relates to optical systems, and more particularly to optical systems for displaying images to a user. Background Technology

[0003] Various types of displays, and particularly near-eye displays (NEDs), typically employ one or more waveguides in which an image is injected from an image projector to propagate within the waveguide via total internal reflection (TIR) ​​and subsequently coupled toward the observer's eye via one or more coupling elements (e.g., partially reflective inner surfaces ("facets"), diffraction gratings, etc.). Such waveguides are made of a transparent substrate having a pair of parallel principal outer surfaces extending along the length of the waveguide, between which the image and its conjugate are reflected. The image is preferably collimated, and the waveguide is preferably planar. For optimal performance, both the image and its conjugate should completely fill the waveguide, such that illumination corresponding to each pixel of the image and each pixel of the conjugate image exists at every point within the thickness of the waveguide (for the area of ​​the waveguide that contributes to the output image reaching the user's eye).

[0004] Waveguide filling can be achieved by providing a coupling prism with a coupling surface—oriented approximately perpendicular to the principal ray of the injected image—allowing the image to fall on an extension of one surface of the waveguide to generate a conjugate image. However, particularly for implementations injecting the image at a relatively shallow angle relative to the main outer surface (i.e., close to 90 degrees to the surface normal), the length of the coupling region required to fill the waveguide with the conjugate image significantly increases the waveguide size. This is in Figure 2A As shown in the figure, Figure 2A A typical coupling to waveguide 10 is shown. A coupling prism 14, cut from or attached to the waveguide substrate, is used to guide light rays 40, 41 into the waveguide at a shallow angle. As light rays 40, 41 propagate within the waveguide, light ray 41 is reflected from the top surface of the waveguide, thus becoming a conjugate of light ray 40. As can be clearly seen from Figure 1, even with the use of a coupling prism, a relatively large input aperture is required (and therefore a large projector) to produce shallow conjugate light rays within the waveguide.

[0005] Figure 2B An alternative method for filling the waveguide, as shown, involves using a 50% beamsplitter (or “mixer”) 13 approximately at the midpoint inside the waveguide 10. The beamsplitter 13 subdivides the waveguide thickness between the main outer surfaces and extends at least a portion of the path along the length of the waveguide parallel to the outer surfaces. For example... Figure 2A As shown, the beam splitter effectively partially reflects light to generate its conjugate (e.g., ray 41) within the waveguide, and allows for a smaller input aperture and wedge prism 14.

[0006] While the presence of mixer 13 allows for the use of a smaller projector aperture and coupling prism, the mixer itself significantly increases the waveguide size. The minimum length required for mixer 13 can be calculated using the formula... It is expressed as, where w is the width of the waveguide, and This refers to the propagation of the field of view angle (relative to the normal to the LOE master surface). Therefore, the aforementioned minimum length requirement for the mixer necessitates a longer waveguide to accommodate it. Furthermore, the need for parallelism with the waveguide surface necessitates higher precision in the waveguide manufacturing process to include the mixer within it. Summary of the Invention

[0007] This invention is an optical system for guiding an image toward a user for viewing.

[0008] According to the teachings of embodiments of the present invention, an optical system for guiding an image toward a user for viewing is provided, the optical system comprising: (a) a light-guide optical element (LOE) formed of a transparent material and having a first primary outer surface and a second primary outer surface parallel to each other for supporting the propagation of an image by internal reflection at the first primary outer surface and the second primary outer surface, the LOE having an outgoing arrangement for outgoing the image toward the user's eye, the LOE having an incoming aperture; and (b) an image projector comprising: an image generator for generating an image; a collimating optics for collimating the image; and an image conjugate generator coupled to the incoming aperture to introduce the collimated image and its conjugate image into the incoming aperture before the collimated image and the conjugate image are incident on either the first primary outer surface or the second primary outer surface.

[0009] According to another feature of an embodiment of the present invention, the image conjugate generator includes a second image generator.

[0010] According to another feature of an embodiment of the present invention, the image conjugate generator includes at least one reflective surface that is discontinuous with the first primary outer surface and the second primary outer surface.

[0011] According to another feature of an embodiment of the present invention, the image conjugate generator includes at least one reflective surface that is not parallel to the first primary outer surface and the second primary outer surface.

[0012] According to another feature of an embodiment of the invention, the image conjugate generator includes a beam multiplier that includes at least one beam splitter deployed between and parallel to the two reflective surfaces.

[0013] According to another feature of an embodiment of the invention, the beam multiplier includes at least two beam splitters inserted between at least three reflective surfaces.

[0014] According to another feature of an embodiment of the invention, the beam multiplier has an external thickness that is different from the thickness of the LOE.

[0015] According to another feature of an embodiment of the invention, the reflective surface of the beam multiplier is a reflective surface at the interface between the layers of the layered structure, wherein the outer surface of the layered structure is an optical non-functional surface of the beam multiplier.

[0016] According to another feature of an embodiment of the invention, the LOE further includes a coupling reflector disposed at an angle to the first and second main outer surfaces, the coupling reflector being configured to redirect a collimated image to incident on the first main outer surface and to redirect a conjugate image to incident on the second main outer surface.

[0017] According to another feature of an embodiment of the invention, the coupling reflector is deployed at a 45-degree angle to the first and second main outer surfaces.

[0018] According to another feature of an embodiment of the invention, the image conjugate generator includes a reflective surface that passes through an LOE adjacent to the coupled reflector, the portion of the reflective surface passing through the LOE being an angle-selective reflective surface.

[0019] According to another feature of an embodiment of the invention, the angle-selective reflective surface is achieved using an optical adhesive having a refractive index lower than that of the LOE adjacent to the coupled reflector.

[0020] According to the teachings of embodiments of the present invention, a display is provided, comprising: (a) a light guide formed of a transparent material having a pair of mutually parallel principal surfaces for supporting the propagation of image light by internal reflection at the pair of principal surfaces; and (b) an integrated image projector comprising: (i) a polarization beamsplitter (PBS) prism assembly formed of a plurality of transparent prism components and including a tilted polarization beamsplitter surface, the polarization beamsplitter prism assembly providing an exit surface, an image input surface, and an optical interface surface optically coupled to the light guide; (ii) an image generator deployed to introduce an image through the image input surface of the polarization beamsplitter prism assembly; and (iii) a collimating optics assembly including a reflective transparent surface. The optical interface surface includes a mirror and a quarter-wave plate associated therewith, wherein at least a portion of the optical interface surface is implemented as an angle-selective reflective surface, and wherein the polarizing beam splitter prism device is configured to define the optical path of image light from the image generator by transmitting light through the polarizing beam splitter surface and the optical interface surface and being reflected and collimated by the reflecting lens to generate collimated image light, the collimated image light being reflected by the polarizing beam splitter surface toward the light guide, and wherein a first portion of the collimated image light reflected by the polarizing beam splitter surface undergoes reflection at the optical interface surface before passing through the exit surface and entering the light guide, and a second portion of the collimated image light reflected by the polarizing beam splitter surface passes through the exit surface and enters the light guide without undergoing reflection at the optical interface surface.

[0021] According to an aspect of the invention, a beam multiplier is also provided, comprising a stack of transparent plates defining a plurality of parallel interface planes, the plurality of parallel interface planes being provided with a coating defining: (a) a group of N reflectors, wherein N is at least three; and (b) a group of at least N-1 partially reflective beam splitters, each of the beam splitters being inserted between two adjacent reflectors in the group of reflectors. Attached Figure Description

[0022] In this document, the invention is described by way of example only with reference to the accompanying drawings, in which:

[0023] Figure 1A and Figure 1B The diagram is a schematic isometric view of an optical system implemented using a light-guide optical element (LOE) according to the teachings and operation of the present invention, showing a top-down configuration and a side-injection configuration, respectively.

[0024] Figure 2AAs described above, this is a schematic side view illustrating the conventional coupling of an image into a LOE via a coupling prism, as is the prior art.

[0025] Figure 2B As described above, this is a schematic side view illustrating the conventional coupling of an image into a LOE with an integrated beam multiplier, as is existing technology.

[0026] Figure 3 yes Figure 1A and Figure 1B A schematic side view of a portion of the optical system, showing the coupling of image-conjugate image pairs into the LOE;

[0027] Figure 4A yes Figure 1A and Figure 1B A schematic side view of a portion of the optical system, illustrating an alternative implementation of the invention using a beam multiplier;

[0028] Figure 4B yes Figure 4A A magnified schematic diagram of a beam multiplier;

[0029] Figure 5 yes Figure 1A and Figure 1B A schematic side view of a portion of the optical system, illustrating an alternative implementation of the invention using a beam multiplier and an angled coupling reflector;

[0030] Figure 6 It is based on Figure 5 The ray trajectory diagram of the implementation of the present invention shows the ray paths of different parts of the image guided toward the user's eye;

[0031] Figure 7A and Figure 7B It comes from Figure 6 A magnified partial view of the coupling region of the LOE, showing only half the ray path of a single image pixel, which helps to fill the LOE with the corresponding image illumination of that pixel; and

[0032] Figure 8 yes Figure 1A and Figure 1B A schematic side view of a portion of the optical system, illustrating the present invention's alternative implementation using a reflector surface with a thickness extending through the LOE as an angle-selective reflector. Detailed Implementation

[0033] This invention is an optical system for guiding an image toward a user for viewing.

[0034] Some embodiments of the present invention provide an optical system including a light guide optical element (LOE) for achieving optical aperture expansion for use in a head-up display, and most preferably a near-eye display, which may be a virtual reality display or more preferably an augmented reality display.

[0035] exist Figure 1A and Figure 1B The diagram schematically illustrates an exemplary implementation of a near-eye display in the form of an LOE 10, generally designated by reference numeral 100, which employs the teachings of an embodiment of the present invention. The near-eye display 100 employs a compact image projector (or "POD") 114 optically coupled to inject an image into the LOE (interchangeably referred to as a "waveguide," "substrate," or "plate") 10, within which image light is captured in one dimension by internal reflections at a set of mutually parallel, flat outer surfaces.

[0036] Optical aperture expansion within the LOE 10 is achieved through one or more arrangements for progressively redirecting the image illumination direction. These arrangements typically employ a set of partially reflective surfaces (interchangeably referred to as "facets") parallel to each other and tilted relative to the propagation direction of the image light, where each successive facet deflects a portion of the image light in the deflection direction. For one-dimensional aperture expansion, the facets also couple the image light toward the user's eye. In some cases, as shown here, two-dimensional aperture expansion is achieved by employing a first set of facets in region 116 to progressively redirect the image illumination within the LOE, and by capturing / guiding the image illumination through internal reflection. The deflected image illumination then enters a second substrate region 118, which can be implemented as adjacent different substrates or as a continuation of a single substrate, in which a coupling arrangement (e.g., another set of partially reflective facets) progressively couples a portion of the image illumination toward the observer's eye located within an area defined as an eye-motion box (EMB), thereby achieving a second-dimensional optical aperture expansion. As is known in the art, similar functionality can be achieved by using diffractive optical elements (DOEs) to redirect and / or couple image illumination in one or both regions of region 116 and region 118.

[0037] The entire device can be implemented separately for each eye, and preferably, the entire device is supported relative to the user's head, with each LOE 10 facing the corresponding eye. In a particularly preferred option, as shown herein, the support arrangement is implemented as an eyeglass frame for supporting the side 120 of the device relative to the user's ear. Other forms of support arrangements may also be used, including but not limited to headbands, face shields, or devices suspended from a helmet.

[0038] Reference is made herein to the X and Y axes in the accompanying drawings and claims, the X axis being horizontal in the generally extending direction of the first region of the LOE ( Figure 1A ) or vertical ( Figure 1B Extending, the Y-axis extends perpendicularly to the X-axis, that is, in Figure 1A Extending vertically in the middle and Figure 1B Mid-level horizontal extension. In very approximate terms, the first region 116 of the first LOE or LOE 10 can be considered to achieve aperture extension in the X direction, while the second region 118 of the second LOE or LOE 10 achieves aperture extension in the Y direction. The details of the angular extension of the different parts of the field of view will be described more precisely below. It should be noted that, as Figure 1A The orientation shown can be viewed as a "top-down" implementation, in which image illumination entering the main (second region) of the LOE enters from the top edge, while... Figure 1B The orientation shown can be considered a "lateral injection" implementation, in which the axis referred to here as the Y-axis is deployed horizontally. In the remaining figures, similar to... Figure 1A Various features of certain embodiments of the invention are illustrated in the context of a “top-down” orientation. However, it should be recognized that all these features are equally applicable to lateral injection implementations that also fall within the scope of the invention. In some cases, other intermediate orientations are also applicable and, unless explicitly excluded, are included within the scope of the invention. The two-dimensional extension implementation shown herein is merely exemplary, but the invention is also applicable to implementations in which the LOE performs only one-dimensional aperture extension.

[0039] It should be understood that the near-eye display 100 includes various additional components, typically including a controller 122 for actuating the image projector 114, which typically draws power from a small onboard battery (not shown) or some other suitable power source. It should be understood that the controller 122 includes all the necessary electronic components for driving the image projector, such as at least one processor or processing circuitry, all of which are well known in the art.

[0040] This invention relates to an implementation of an image projector 114, which includes an image conjugate generator arranged such that the image projector injects a collimated image and its conjugate image into a LOE 10. Reference will be made below to... Figures 3 to 8 Illustrate various non-restricted examples of image conjugate generators.

[0041] Therefore, refer to Figure 3 The image shown is an enlarged schematic partial view of the optical system of FIG1 used to guide an image toward a user for viewing. The optical system includes an LOE 10, which is formed of a transparent material and has a first main outer surface 11a and a second main outer surface 11b that are parallel to each other to support the propagation of the image through internal reflection at these surfaces. The LOE 10 also has: a coupling arrangement (in region 118 of FIG1, as described above but not shown here) for coupling the image toward the user's eye; and a coupling aperture 15, which in this case is shown as a side edge of the LOE 10.

[0042] Instead of relying on the structure integrated with LOE 10 to generate image conjugate pairs, the image projector 114 according to this aspect of the invention includes an image conjugate generator to generate image conjugate pairs before either the collimated image or the conjugate image is incident on either of the main outer surfaces 11a and 11b of LOE 10.

[0043] Therefore, in Figure 3 In the example shown, the image projector 114 includes: an image generator 32 for generating an image; a collimating optics 31 for collimating the image; and an image conjugate generator, implemented here as a second image generator 33 for generating conjugate images. In the example shown here, image generator 32 and image generator 33 share a common collimating optics 31. The image projector 114 is coupled to an insertion aperture 15 to directly introduce the collimated image and its conjugate image into the LOE 10 before the collimated image or its conjugate image is incident on either of the main outer surfaces 11a and 11b of the LOE 10.

[0044] What will be understood is that the solution is related to Figure 2A and Figure 2B The coupling arrangement forms a clear contrast, in Figure 2A and Figure 2B In the coupled arrangement, the conjugate image is generated within the LOE itself by reflection from the primary outer surface (or the surface of the coupling prism, which is a continuation of these primary outer surfaces and is defined herein as part of the primary outer surface of the LOE).

[0045] Two image generators 32 and 33 are driven to generate an identical image, one of which is inverted, and each field is displayed identically from both fields. During assembly of the device, active alignment is preferably used by mechanical adjustment or, more preferably, by digital correction of the image display position, to move the two images on the image generators such that they are aligned as complementary conjugate images within the LOE. Thus, the LOE is "filled" with the main image and its conjugate extending radially forward from the coupling aperture, without requiring any extension of the LOE.

[0046] In this and all other embodiments of the invention, the image generator can be any type of microdisplay image generator known in the art. Suitable examples include, but are not limited to, spatial light modulators (SLMs), including transmissive SLMs such as LCD displays and reflective SLMs such as LCOS displays, as well as active light generating displays such as OLED displays. A scanning image generator in which a fast scanning laser beam is modulated synchronously with its scanning motion can also be used as an image generator according to the invention.

[0047] As an alternative to the second image generator 33, other implementations of the invention implement the image conjugate generator as at least one reflective surface discontinuous with the main outer surface to generate a conjugate image. (See also...) Figures 4A to 8 Various examples of this implementation method are presented.

[0048] Figure 4A This illustrates an implementation where the image conjugate generator is a beam multiplier or "mixer" structure 20 external to waveguide 10. Figure 4B A particularly preferred implementation of the mixer 20 is shown in more detail, and is itself considered patentable.

[0049] Conceptually, the mixer 20 performs with Figure 2BThe mixer 13 functions similarly, but in this case, it is not part of the waveguide 10, but rather part of the image projector assembly 114. The mixer 20 is positioned between the LOE 10 and the projector unit 30, which contains an image generator and collimating optics. In this case, the projector unit 30 has a single image generator 32 that produces an image, while the mixer 20 generates image conjugate pairs by producing conjugates (rays 41) through partially reflected rays 40. The image pairs are then injected into the waveguide. Because the mixer 20 is outside the waveguide, it can be actively aligned with the waveguide during assembly without imposing manufacturing constraints on the waveguide. The mixer 20 may include multilayer mirrors 22, 24 and a beam splitter 23, as well as an outer surface 21, which does not need to have optical quality and does not need to be coplanar with the LOE outer surface. This greatly simplifies the manufacturing constraints on the structure.

[0050] Regarding the structure of the beam multiplier 20, the beam multiplier of the present invention differs from those described in prior publications in that it contains at least one intermediate high-reflectivity layer, which effectively subdivides the mixer into two independent mixers, one stacked on top of the other. Therefore, the beam multiplier 20 is preferably formed by a stack of transparent plates defining a plurality of parallel interface planes, which are coated to define:

[0051] (a) A group of N reflectors, where N is at least three;

[0052] (b) A group of at least N-1 partial reflective beamsplitters, each of which is inserted between two adjacent reflectors in the group of reflectors.

[0053] In this context, "reflectors" are preferably highly reflective, meaning they reflect at least 85%, more preferably at least 90%, and typically at least 95% of the incident light in the angular range associated with propagation along the LOE. Partially reflective beam splitters are preferably approximately 50% reflectors (50% ± 10%). In applications where the beam multiplier is located outside the user's field of view, a metallic coating can advantageously be used to realize both the reflector and the beam splitter. Where transparency is required for viewing the scene through the beam multiplier, multilayer dielectric coatings are employed, as known in the art, to provide the desired level of reflectivity at large angles while providing relatively high transparency at small (nearly orthogonal) angles.

[0054] The intermediate reflector effectively subdivides the mixer into two (or more) sub-mixers. This reduces the length required for the mixer to utilize the image and its conjugate to fill the waveguide by a factor of two. Figure 4BIn the diagram, the input and output apertures of a mixer 20, as shown by black lines, are illustrated. These apertures do not need to fill the entire width of the mixer. In fact, it may be advantageous to implement all reflectors and beam splitters at the internal interface plane between the transparent plates, while the outer surface of the layered structure is an optically non-functional surface. "Optically non-functional" here refers to a surface that image light cannot reach, or any image light reaching the surface does not subsequently enter the LOE. In such a case, the outer surface does not need to be a polished surface and does not need to be parallel to other elements. Therefore, as... Figure 4A As shown, the outer thickness of the mixer 20 can be varied, typically greater than the thickness of the LOE 10 (i.e., the distance between the first main outer surface 11a and the second main outer surface 11b). The distance between the outermost reflectors 22 should match the LOE thickness, or be slightly larger than the LOE thickness, to fill the LOE.

[0055] Turn now Figures 5 to 8 In some implementations, the use of an external image conjugate generator facilitates the use of folded optical paths, thereby removing volume from the sides of the component. Therefore, according to certain embodiments of the invention, the LOE 20 also includes a coupling reflector 12, which is deployed to be tilted relative to the first and second main outer surfaces to redirect the collimated image to incident on the first main outer surface 11a and the conjugate image to incident on the second main outer surface 11b. The coupling reflector 12 can be implemented within a certain angular range, but most preferably, it is deployed at 45 degrees to the first and second main outer surfaces, thereby effectively folding the optical axis of the image projector by 90 degrees. Unlike some conventional coupling configurations, the reflector 12 is specifically located within the thickness of the LOE 20, such that the reflector 12 can deflect both the main image and its conjugate image toward their respective upward / downward propagation directions.

[0056] Figure 5 One configuration is shown in which the outer mixer 20 is positioned perpendicular to the waveguide. In this case, the 45-degree reflective coupling surface 12 folds the image exiting the mixer into the waveguide. A wedge prism 25 is preferably used to couple the central FOV light into the mixer at an angle perpendicular to the prism surface. Due to the folding, the aperture width of the mixer must be greater than the aperture width of the waveguide. The exact size of the aperture depends on the angular FOV of the displayed light and the folding angle of surface 12. In this example, the width is increased by 66%.

[0057] It should be noted that in this case, mixer 20 is divided into three sub-mixers. Therefore, there is no need to increase the length of the mixer (because as stated above). And after folding, the width (w) increases by 60%. Therefore, the mixer is divided into three sub-mixers by two inner mirror planes 24 between the outer mirror planes 22. A beam splitter 23 is disposed at the center plane of each sub-mixer.

[0058] Figure 6 It shows including Figure 5 The optical path diagram of the entire optical system of the mixer is shown. Three exemplary points (pixels) on the image generator 32 are collimated by lens 31 to exit the projector unit 30 into the coupling wedge prism 25 and then into the mixer 20. The mixer generates a conjugate field such that the entire image and its conjugate are coupled into the waveguide 10 via the coupling reflector 12. In this example, light is coupled out of the waveguide through a set of parallel partially reflective facets 11 to reach the eye motion box (EMB) 200. It should be noted that the example of facet 11 is only a non-limiting example, and other coupling mechanisms such as holograms or dichroic gratings are possible and included within the scope of this document. Finally, it can be seen that although the propagation angles of the different fields may be very shallow, the input aperture between the mixer 25 and the projector unit 30 remains relatively small.

[0059] Figure 7A and Figure 7B An image of propagation within the waveguide is shown. Figure 7A ) and its conjugate ( Figure 7B Two cross-sectional views of ( ). Overlapping Figure 7A and Figure 7B This illustrates how an image and its conjugate can be completely filled into a waveguide. This achieves homogenization of light within the waveguide. It should be noted that this illustration subdivides illumination into "image" and "conjugate" at any point along the LOE, but as light propagates and reflects from the first and second primary outer surfaces of the LOE, the light continuously interchanges between image and conjugate. A particularly preferred aspect of the invention is that illumination entering the coupling aperture of the LOE and reaching the coupling reflector 12 already includes filling the reflector with both the image and the conjugate image, one of which, as shown, points upward to be incident first on the first primary outer surface 11a, while the other, as shown, points downward to be incident first on the second primary outer surface 11b. The designation of which image is the "primary image" and which is the "conjugate image," and which surface is referred to as the "first" or "second" primary outer surface, is arbitrary, and whether the "primary image" generated by the image generator is the image the user wants to view or a reversed version of that image is generally irrelevant, depending only on various design considerations.

[0060] It is important to note that, such as Figure 7BAs shown, some downward-pointing rays reflected from the coupling reflector 12 are incident on the second primary outer surface 11b in the region overlapping with the beam multiplier 20. To maintain TIR in this overlapping region, the device preferably has a small air gap between the elements, or more preferably uses a low-refractive-index adhesive between the components. Particularly for shallow-angle light propagation, the relatively small refractive index difference between the LOE material and the adhesive is sufficient to define the critical angle for maintaining the propagated image illumination via TIR. Alternatively, an angle-selective multilayer dielectric coating can be applied to the region overlapping with the LOE to provide suitable internal reflection characteristics.

[0061] In all the above embodiments employing mixer 20, the mixer, as defined herein, is functionally part of projector 114 because it forms part of the optical system prior to the injection of the image into LOE 10 and does not include any extension of the surface of the LOE. In the actual construction of the product, the mixer is not necessarily integrated with the projector unit 30, which combines the image generator and collimating optics, and in some cases, the mixer can be more conveniently assembled by attaching it to the LOE before placing the projector unit.

[0062] Figure 8 Another feature of certain particularly preferred implementations of the invention is shown. According to this feature, the image conjugate generator includes a reflective surface 34 that extends through the thickness of the LOE 10 adjacent to the coupled reflector 12. The portion 121 of the reflective surface 34 extending through the LOE is implemented as an angle-selective reflective surface to reflect light entering the LOE from the projector 114 before reflection at the reflector 12, while simultaneously (i.e., transmitting light already reflected by the reflector 12 at an angle related to image propagation along the LOE 20). Here, an optical adhesive with a refractive index lower than that of the LOE adjacent to the coupled reflector can also be used to most conveniently implement the angle-selective reflective surface, thereby providing a critical angle between the angle of incidence of light before reflection at the reflector 12 and the angle of incidence of light after reflection at the reflector 12. Other options described above can also be used, such as using an angle-selective multilayer dielectric coating, or including an air gap.

[0063] exist Figure 8In the non-limiting example shown, projector 114 generates a conjugate image using a single extended reflective surface 34 perpendicular to the primary outer surface of the LOE, instead of via an external mixer. A portion of the projected collimated image is directly incident on the coupling reflector 12, corresponding to the primary image deflected upward toward the first primary outer surface 11a. Another portion of the image is reflected from surface 34, thereby generating a conjugate image that is deflected downward toward the second primary outer surface 11b by the coupling reflector 12. The reflective surface region 121 helps to fill the coupling reflector 12 with the conjugate image, while similarly treating the overlapping region 122 to provide angle-selective reflection, thereby avoiding leakage of conjugate image light reflected downward in the overlapping region (as described above).

[0064] Figure 8 Other aspects of the structure of the projector 114 are based on principles employed in conventional reflective SLM image projectors based on polarizing beam splitter prisms. Specifically, the illumination source 40 introduces illumination into a PBS prism 35, where light is reflected towards a reflective SLM 32 such as LCOS, DLP, etc. The reflected image illumination passes through the PBS to a reflective collimating lens 310 associated with a quarter-wave plate (not shown), such that the reflected collimated image is reflected from the PBS towards the LOE coupling aperture. As described above, doubling of the image and its conjugate is achieved by having a portion of the image directly incident on the reflector 12 while the remaining image illumination is first reflected from surface 34. The area of ​​surface 34 below the reflective lens 310 can also advantageously be provided with an angle-selective reflective coating, such as a low-refractive-index adhesive, to achieve TIR at a relevant angle after reflection from the PBS. Other lenses, such as a field lens 313, can be added to improve optical performance.

[0065] In this implementation, it is particularly advantageous that the prism surface 34 is orthogonal to the main surface of the waveguide 10, and the two parallel rays exiting the reflecting lens 310 shown here will be conjugate before entering the waveguide. Furthermore, it can be seen that the desired input direction of illumination from the source 40 is approximately 110 degrees relative to the main surface of the waveguide, which makes it highly ergonomically designed, with slight offsets between components to be integrated on either side of the device, which is well-suited to the shape factor of eyeglass frames.

[0066] The use of a reflective surface 34 that penetrates the thickness of the LOE at region 121, which has angle-selective reflection characteristics, is also applicable to other implementations of the invention described above. For example, if... Figures 5 to 7B One of the reflectors of the beam multiplier 20 is implemented as a surface that passes through the thickness of the LOE 20, which can significantly reduce the optical input and output apertures required for the beam multiplier 20, thus forming a more compact design.

[0067] The present invention can also be implemented through the following embodiments.

[0068] 1. An optical system for guiding an image toward a user for viewing, the optical system comprising:

[0069] (a) A light guide optical element (LOE) formed of a transparent material and having a first primary outer surface and a second primary outer surface that are parallel to each other for supporting the propagation of an image by internal reflection at the first primary outer surface and the second primary outer surface, the light guide optical element having a coupling out arrangement for coupling the image toward the user's eye, and the light guide optical element having a coupling in aperture;

[0070] (b) An image projector comprising: an image generator for generating an image; a collimating optics for collimating the image; and an image conjugate generator coupled to the coupling aperture to introduce the collimated image and its conjugate image into the coupling aperture before the collimated image and its conjugate image are incident on either the first primary outer surface or the second primary outer surface.

[0071] 2. The optical system according to embodiment 1, wherein the image conjugate generator includes a second image generator.

[0072] 3. The optical system according to embodiment 1, wherein the image conjugate generator includes at least one reflective surface that is discontinuous with the first primary outer surface and the second primary outer surface.

[0073] 4. The optical system according to embodiment 1, wherein the image conjugate generator includes at least one reflective surface that is not parallel to the first primary outer surface and the second primary outer surface.

[0074] 5. The optical system according to embodiment 1, wherein the image conjugate generator includes a beam multiplier, the beam multiplier including at least one beam splitter, the at least one beam splitter being deployed between and parallel to the two reflective surfaces.

[0075] 6. The optical system according to embodiment 5, wherein the beam multiplier includes at least two of the beam splitters, the at least two beam splitters being inserted between at least three of the reflective surfaces.

[0076] 7. The optical system according to embodiment 5, wherein the beam multiplier has an external thickness different from the thickness of the light guide optical element.

[0077] 8. The optical system according to embodiment 5, wherein the reflective surface of the beam multiplier is a reflective surface at the interface between the layers of the layered structure, and wherein the outer surface of the layered structure is an optical non-functional surface of the beam multiplier.

[0078] 9. The optical system according to embodiment 1, wherein the light-guiding optical element further includes a coupling reflector disposed obliquely to the first primary outer surface and the second primary outer surface, the coupling reflector being configured to: redirect the collimated image to incident on the first primary outer surface and redirect the conjugate image to incident on the second primary outer surface.

[0079] 10. The optical system according to embodiment 9, wherein the coupling reflector is deployed at a 45-degree angle to the first main outer surface and the second main outer surface.

[0080] 11. The optical system according to embodiment 9, wherein the image conjugate generator includes a reflective surface that passes through the light guide optical element adjacent to the coupled reflector, and the portion of the reflective surface passing through the light guide optical element is an angle-selective reflective surface.

[0081] 12. The optical system according to embodiment 11, wherein the angle-selective reflective surface is implemented using an optical adhesive having a refractive index lower than that of the light-guiding optical element adjacent to the coupled reflector.

[0082] 13. A beam multiplier comprising a stack of transparent plates defining a plurality of parallel interface planes, the plurality of parallel interface planes being provided with a coating defining:

[0083] (a) A group of N reflectors, where N is at least three;

[0084] (b) A set of at least N-1 partial reflective beamsplitters, each of which is inserted between two adjacent reflectors in the set of reflectors.

[0085] It should be understood that the above description is intended to be illustrative only, and many other embodiments are possible within the scope of the invention as defined by the appended claims.

Claims

1. A display, comprising: (a) A light guide formed of a transparent material having a pair of mutually parallel main surfaces for supporting the propagation of image light by internal reflection at the pair of main surfaces; as well as (b) An integrated image projector, said integrated image projector comprising: (i) A polarizing beam splitter (PBS) prism assembly, the PBS prism assembly being formed of a plurality of transparent prism components and including a tilted polarizing beam splitter surface, the polarizing beam splitter prism assembly providing optical bonding to the exit surface, image input surface and optical interface surface of the light guide. (ii) an image generator, the image generator being deployed to introduce an image through the image input surface of the polarization beam splitter prism device, and (iii) A collimating optical device, the collimating optical device comprising a reflecting lens and a quarter-wave plate associated with the optical interface surface, Wherein, at least a portion of the optical interface surface is implemented as an angle-selective reflective surface. Furthermore, the polarizing beam splitter prism device is configured to define the optical path of image light from the image generator by transmitting light through the polarizing beam splitter surface and the optical interface surface, and reflecting and collimating it with the reflecting lens to generate collimated image light, wherein the collimated image light is reflected by the polarizing beam splitter surface toward the light guide. Furthermore, a first portion of the collimated image light reflected from the surface of the polarizing beam splitter undergoes reflection at the optical interface surface before passing through the exit surface and entering the optical guide, and a second portion of the collimated image light reflected from the surface of the polarizing beam splitter passes through the exit surface and enters the optical guide without undergoing reflection at the optical interface surface.

2. The display according to claim 1, wherein, The exit surface of the polarizing beam splitter prism device is optically coupled to one of the main surfaces of the light guide, and wherein both the first and second portions of the collimated image light are incident on an angled coupler within the light guide to couple into the light guide so as to propagate within the light guide via internal reflection at the main surface.

3. The display according to claim 2, wherein, The first portion of the collimated image light undergoes a first internal reflection at the first primary surface of the paired primary surfaces after being reflected by the coupler, and the second portion of the collimated image light undergoes a first internal reflection at the second primary surface of the paired primary surfaces after being reflected by the coupler, the second primary surface being opposite to the first primary surface.

4. The display according to claim 2, wherein, The angle-selective reflective surface extends to meet the angled coupling reflector at one of the main surfaces of the light guide.

5. The display according to claim 1, wherein, The angle-selective reflective surface extends across the thickness of the light guide between the main surfaces.

6. The display according to claim 1, wherein, The angle-selective reflective surface is implemented as an air gap.

7. The display according to claim 1, wherein, The angle-selective reflective surface is achieved using a low-refractive-index adhesive.

8. The display according to claim 1, wherein, The angle-selective reflective surface is implemented as a multilayer dielectric coating.

9. The display according to claim 1, wherein, The image generator is implemented as a reflective spatial light modulator (SLM), and the polarization beamsplitter prism device also provides an illumination injection surface. The display further includes an illumination source deployed to inject illumination via the illumination injection surface so as to illuminate the spatial light modulator via reflection at the polarization beamsplitter surface.

10. A beam multiplier comprising a stack of transparent plates defining a plurality of parallel interface planes, the plurality of parallel interface planes being provided with a coating defining: (a) A group of N reflectors, where N is at least three; (b) A set of at least N-1 partial reflective beamsplitters, each of which is inserted between two adjacent reflectors in the set of N reflectors.

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