Light guide integrated image projector for display

Abstract

An image projector integrated with a light guide (10) has a reflective or reflective-refractive (catadioptric) lens (150) disposed on a surface (11) of the light guide itself or on a prismatic surface parallel or coplanar with the surface of the light guide (10). In some cases, a polarizing beam splitter (158) deflects light reflected from the collimating lens to couple collimated image light directly into the light guide (10) to propagate within the light guide. In some cases, a collimating lens (150) is associated with a prism or a surface of the light guide via an internal reflection retention interface (154) such that at least a portion of the image light coupled into the light guide is reflected at the internal reflection retention interface.

Description

[0001] Technical field and background technology of the invention

[0002] The present invention relates to near-eye displays, and in particular, to a light guide integrated image projector for injecting an image into a light guide of an augmented reality display.

[0003] Near-eye augmented reality displays typically employ an image projector to inject a collimated image into a light guide, which delivers the image to the user's eye while allowing simultaneous viewing of the real world through the light guide. The image is coupled out of the light guide toward the user's eye via an outcoupling arrangement, which may be a set of partially reflective angled internal surfaces within the light guide, or a diffractive optical element.

[0004] In order to provide a uniform image, it is generally preferred that the injected image should fill the thickness of the light guide. This requirement, together with the angular field of view (FOV) of the image and the distance of the collimating optics from the light guide entrance aperture, dictates the minimum size of the collimating optics required to collimate the image before injection into the light guide. Summary of the invention

[0005] The present invention is a light guide integrated image projector for injecting an image into a light guide of an augmented reality display.

[0006] According to the teachings of an embodiment of the present invention, a display is provided, comprising: (a) a light guide formed of a transparent material and having a first pair of mutually parallel principal surfaces for supporting propagation of image light by internal reflection at the first pair of principal surfaces; (b) an image generator for generating an image at an image plane; (c) a collimating optical arrangement comprising a reflective lens and an associated quarter-wave phase plate; and (d) a polarizing beam splitter (PBS), wherein the reflective lens is associated with one of the first pair of principal surfaces via an internal reflection maintaining interface, or is associated with a surface of a prism parallel to or coplanar with one of the first pair of principal surfaces, and wherein the PBS is disposed such that image light from the image plane passes through the PBS to be incident on the reflective lens, is collimated by the reflective lens, and is reflected by the PBS to be coupled into propagation within the light guide by internal reflection at the first pair of principal surfaces, with at least a portion of the image light being reflected at the internal reflection maintaining interface.

[0007] According to another feature of an embodiment of the invention, a normal to the PBS forms an angle of less than 45 degrees with a normal to the internal reflection preserving interface.

[0008] According to another feature of an embodiment of the present invention, the PBS is incorporated into a prism optically coupled to a light guide, and wherein the light guide has a thickness dimension in a direction perpendicular to a first pair of major surfaces, and the PBS occupies a thickness of the prism in a direction perpendicular to the first pair of major surfaces that is greater than the thickness dimension of the light guide.

[0009] According to another feature of an embodiment of the present invention, the light guide further comprises a second pair of main surfaces parallel to each other and perpendicular to the first pair of main surfaces, the first pair of main surfaces and the second pair of main surfaces supporting propagation of image light through quadruple internal reflection at the first pair of main surfaces and the second pair of main surfaces.

[0010] According to another feature of an embodiment of the invention, a normal to the PBS is not parallel to both the first pair of major surfaces and the second pair of major surfaces.

[0011] According to another feature of an embodiment of the invention, the reflective lens has an optical axis that is not parallel to both the first pair of major surfaces and the second pair of major surfaces.

[0012] According to another feature of an embodiment of the present invention, the prism includes a first surface parallel or coplanar with one of the first pair of major surfaces and a second surface parallel or coplanar with one of the second pair of major surfaces, the first surface being provided with an internal reflection preserving interface.

[0013] According to another feature of an embodiment of the present invention, the PBS is incorporated into a prism optically coupled to a light guide, and wherein the light guide has a first thickness dimension in a direction perpendicular to a first pair of major surfaces and a second thickness dimension in a direction perpendicular to a second pair of major surfaces, the PBS occupies a thickness of the prism in a direction perpendicular to the first pair of major surfaces that is greater than the first thickness dimension, and occupies a thickness of the prism in a direction perpendicular to the second pair of major surfaces that is greater than the second thickness dimension.

[0014] According to another feature of embodiments of the invention, the internal reflection preserving interface is realized as a layer of a material having a refractive index lower than that of the light guide.

[0015] According to another feature of an embodiment of the invention, the internal reflection preserving interface comprises an air gap.

[0016] According to another feature of an embodiment of the present invention, the internal reflection maintaining interface is implemented as a multilayer dielectric coating that is configured to be substantially transparent to visible light within a first range of incident angles and reflective to visible light within a second range of incident angles, the second range being at a higher angle relative to the normal of the interface than the first range.

[0017] According to another feature of an embodiment of the present invention, there is further provided a light absorbing boundary disposed along at least two edges of the PBS to define an optical aperture for collimating the image.

[0018] According to another feature of an embodiment of the present invention, the PBS is incorporated into a prism optically coupled to the light guide, and the image generator includes an illumination arrangement for directing illumination from an illumination aperture to an image plane through the prism, wherein a first portion of the illumination undergoes an odd number of reflections from the illumination aperture to the image plane, and a second portion of the illumination undergoes an even number of reflections from the illumination aperture to the image plane.

[0019] According to another feature of embodiments of the invention, the light guide is located between the image plane and the reflective lens.

[0020] According to another feature of embodiments of the invention, the PBS is located between the first pair of major surfaces of the light guide.

[0021] According to another feature of an embodiment of the present invention, the collimating optical arrangement is a polarization catadioptric collimating arrangement, wherein the reflective lens has a partially reflective surface, and wherein the image plane is positioned to transmit image light by transmission through the partially reflective surface, the image light being reflected back toward the partially reflective surface.

[0022] According to the teachings of an embodiment of the present invention, a display is also provided, which includes: (a) a light guide formed of a transparent material, having a first major surface and a second major surface parallel to the first major surface, the light guide supporting the propagation of image light through internal reflection at the first major surface and the second major surface; (b) an image generator, which is used to generate an image at an image plane; and (c) a polarization refractive-reflective collimation and coupling arrangement, including: (i) a non-planar partially reflective first reflector associated with the first major surface of the light guide, (ii) a second reflector associated with the second major surface of the light guide and in a facing relationship with the partial reflector, and (iii) a planar third reflector, which is in a facing relationship with the major surface An oblique angle, wherein one of the second reflector and the third reflector is a total reflector, and the other of the second reflector and the third reflector is a polarization selective reflector between the total reflector and the first reflector, the polarization catadioptric collimation and coupling arrangement also includes at least one phase plate, at least one phase plate is between the polarization selective reflector and the first reflector, so that image light from the image plane is partially transmitted through the partially reflecting first reflector acting as a refractive lens, passes through at least a portion of the thickness of the light guide and is reflected at the second reflector, is partially reflected at the partially reflecting first reflector acting as a reflective lens, and is reflected by the third reflector to be coupled in to propagate by internal reflection within the light guide.

[0023] According to another feature of embodiments of the invention, the second reflector is a total reflector, and wherein the third reflector is a polarization selective reflector disposed within the thickness of the light guide.

[0024] According to another feature of embodiments of the invention, the second reflector is a polarization selective reflector and wherein the third reflector is a total reflector associated with a prism outside the thickness of the light guide.

[0025] According to another feature of embodiments of the invention, the second reflector is a planar reflector.

[0026] According to the teachings of an embodiment of the present invention, a projector for a display is also provided, the projector comprising: (a) a reflective spatial light modulator (SLM) for modulating the polarization of light reflected from an image plane; (b) an illumination source that outputs illumination from an illumination aperture; (c) a collimating optical arrangement comprising at least one lens; and (d) a prism containing a polarizing beam splitter (PBS), wherein the PBS is disposed to reflect illumination from the illumination aperture toward the SLM and to enable light corresponding to an image reflected from the SLM to pass through the PBS to the collimating optical arrangement, and wherein a surface of the prism adjacent to the SLM is provided with an internal reflection maintaining interface, and wherein a portion of the illumination from the illumination aperture is reflected at the interface and then reflected from the PBS before being incident on the SLM, such that a first portion of the illumination undergoes an odd number of reflections from the illumination aperture to the SLM, and a second portion of the illumination undergoes an even number of reflections from the illumination aperture to the SLM. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The invention is herein described, by way of example only, with reference to the accompanying drawings, in which:

[0028] Figure 1A is a schematic side view of a light guide integrated projector for injecting images into a light guide of an augmented reality display, constructed and operative in accordance with an embodiment of the present invention, employing a polarization catadioptric collimation arrangement;

[0029] Figure 1B is a schematic side view of a light guide integrated projector for injecting images into a light guide for an augmented reality display, constructed and operative in accordance with an embodiment of the present invention, employing an alternative polarization catadioptric collimation arrangement;

[0030] Figure 1C is similar to Figure 1B Schematic side view of an embodiment of the present invention, showing an implementation using a reflective spatial light modulator for image generation;

[0031] Figure 1D is similar to Figure 1A Schematic side view of a device showing the use of multiple light guide integrated projectors for injecting images of different colors;

[0032] FIG. 2A to FIG. 2Cis a schematic side view of a light guide integrated projector for injecting images into a light guide for an augmented reality display, constructed and operative in accordance with an embodiment of the present invention, employing a reflective collimation arrangement and a polarizing beam splitter located within the light guide, in a prism adjacent to the light guide, and in a prism above the light guide, respectively;

[0033] Figure 2D is similar to Figure 2C Schematic side view of a device showing the use of multiple light guide integrated projectors for injecting images of different colors;

[0034] Figure 2E It is shown Figure 2B A schematic side view of an alternative configuration of a light guide integrated projector;

[0035] Figure 3A is realized with a rectangular light guide Figure 2B an isometric view of the corresponding light guide arrangement;

[0036] Figure 3B is similar to Figure 3A , showing the deployment of a polarizing beam splitter at an oblique angle relative to two axes of a rectangular light guide;

[0037] Figure 3C is similar to Figure 3B , wherein the polarizing beam splitter is replaced by a reflector;

[0038] Figure 3D and Figure 3E Respectively similar to Figure 3B and Figure 3C , wherein the size of the polarizing beam splitter or reflector is reduced to fit within the dimensions of a rectangular light guide;

[0039] Figure 3F is similar to Figure 3A , showing additional components of a projector deployed to generate a tilted optical axis;

[0040] Figure 4A is generally similar to Figure 2B a side view of a light guide integrated projector of FIG. 1 showing an arrangement for flood illumination of a reflective spatial light modulator;

[0041] Figure 4B is similar to Figure 4A , showing a side view of an arrangement of scanning laser illumination of a reflective spatial light modulator;

[0042] Figure 5A and Figure 5B They are similar to Figure 4A Side and isometric views of a light guide integrated projector showing various arrangements for spatial filtering of a projected image;

[0043] Fig. 6A and Figure 6B They are similar to Figure 2B and Figure 2C , showing an option for achieving polarization control of the plane polarization of the image entering the light guide;

[0044] Figure 6C and Fig.6D They are similar to Figure 2B and Figure 2C , showing an option for achieving polarization control of circular polarization of an image entering the light guide;

[0045] Fig. 7A and Figure 7B are side and top views, respectively, of another implementation of a light guide integrated projector for injecting images into a light guide for an augmented reality display, constructed and operative in accordance with an embodiment of the present invention, employing a rectangular light guide and also showing an illumination light path that undergoes total internal reflection;

[0046] Figure 7C is similar to Fig. 7A The view shows the Fig. 7A The light paths corresponding to the additional image points not shown in FIG.

[0047] Fig.7D yes Fig. 7A Isometric view of the light guide integrated projector;.

[0048] Fig. 8A and Figure 8B is a schematic side view illustrating design considerations in an illumination arrangement for a reflective spatial light modulator; and

[0049] Figure 8C is a schematic side view showing a preferred implementation of an illumination arrangement for a reflective spatial light modulator according to another aspect of the present invention. DETAILED DESCRIPTION

[0050] The present invention is a light guide integrated image projector for injecting an image into a light guide of an augmented reality display.

[0051] The principles and operations of a display according to the present invention may be better understood with reference to the drawings and accompanying description.

[0052] By way of introduction, the present invention provides several different configurations in which an image projector is integrated with a light guide in a manner that places at least a portion of the collimating optics particularly close to an aperture of the light guide, thereby providing a particularly compact projector configuration. In some cases, a reflective or catadioptric (catadioptric) lens is disposed on a surface of the light guide itself, while in other cases, the lens is disposed on a prism surface that is parallel or coplanar with the surface of the light guide. In some cases, a polarizing beam splitter (PBS) deflects light reflected from the collimating lens to couple the collimated image light directly into the light guide for propagation within the light guide. In some cases, the collimating lens is associated with a surface of the light guide or a surface of a prism via an internal reflection preserving interface, such that at least a portion of the image light coupled into the light guide is reflected at the internal reflection preserving interface. Examples of each of these features are shown below.

[0053] Referring now to the accompanying drawings, Figures 1A to 1D Several light guide integrated projectors are schematically shown for use in displays employing polarizing catadioptric collimating optics associated with the major surfaces of the light guide.

[0054] In particular, these examples show a light guide 10 formed of a transparent material having parallel first and second major surfaces 11, 12, thereby supporting propagation of image light within the light guide by internal reflection at major surfaces 11, 12. To simplify the presentation, continuation of the light guide and outcoupling arrangements are omitted.

[0055] An image generator generates the image at the image plane, which may be an active matrix image generator 4, a reflective or transmissive spatial light modulator (SLM) such as an LCOS chip 166, a digital light processor or any other desired image generator.

[0056] The apparatus further comprises a polarization catadioptric collimation and incoupling arrangement comprising:

[0057] 1. A lens 150 having a non-planar surface providing a partially reflecting first reflector 152, the base of the lens being associated with the first major surface 11 of the light guide 10;

[0058] 2. a second reflector, which is typically but not necessarily planar, associated with the second major surface 12 of the light guide 10, in facing relationship with the first reflector 152; and

[0059] 3. A planar tertiary reflector that is at an oblique angle to the primary surface.

[0060] One of the second reflector and the third reflector is a total reflector, and the other of the second reflector and the third reflector is a polarization selective reflector between the total reflector and the first reflector. At least one phase plate 156 is interposed between the polarization selective reflector and the first reflector, so that image light from the image plane is partially transmitted through the partially reflective first reflector 152 used as a refractive lens, passes through at least a portion of the thickness of the light guide 10, is reflected at the second reflector, is partially reflected at the partially reflective first reflector 152 used as a reflective lens, and is reflected by the third reflector to be coupled in to propagate by internal reflection within the light guide 10.

[0061] exist Figure 1A and Figure 1D In the case of , the second reflector is a polarization selective reflector 158 and the third reflector is a total reflector 8, which are associated with the prism 9 outside the thickness of the light guide 10. Figure 1B and Figure 1C In the case of , the second reflector is a total reflector 8 and the third reflector is a polarization selective reflector 158. In the case shown here, the polarization selective reflector is disposed within the thickness of the light guide. The latter case can also be achieved by making the total reflector 8 in a plane parallel to the plane of the surface 12 and outside the plane of the surface 12, in which case the polarization selective reflector 158 can also extend beyond the thickness of the light guide, as long as it does not extend beyond the plane of the total reflector.

[0062] In more detail, Figure 1A , an image source 4 (e.g., a micro-LED or OLED) transmits light onto a lens 150. The light passes through a partially transmissive curved surface (first partial reflector) 152 and through an internal reflection preserving interface 154 (e.g., a layer of low refractive index material or an air gap) into the light guide 10. After passing through the light guide, the light beam passes through a wave plate 156 (which may alternatively be located above the interface 154) to be reflected by a polarizer-reflector 158. The reflected light beam passes through the interface 154 to be partially reflected back by the first reflector 152. The reflected light beam passes through the light guide 10 again, and after passing through the wave plate 156 for the second time, the light beam has an orthogonal polarization to pass through the polarizer-reflector 158 and be reflected by the reflector 8. The light beam maintains its polarization and therefore passes through the polarizer-reflector 158 to be guided by the light guide 10. A portion of the light beam incident on the interface 154 undergoes total internal reflection.

[0063] Figure 1B A more compact architecture is shown, in which a polarizer-reflector 158 (also called a polarizing beam splitter (PBS)) is positioned obliquely within the light guide 10. The light beam entering the light guide is linearly polarized (with Figure 1AThe light beam is orthogonally polarized (orthogonal to the light beam entering in the light guide 10) and thus passes through the PBS 158 to be reflected from the reflector 8. The light beam passes through the PBS 158, the interface 154 and the wave plate 156 to be partially reflected back by the first reflector 152. After the second pass through the wave plate 156, the light beam is orthogonally polarized and thus will be reflected by the PBS 158 to be coupled into and guided within the light guide 10.

[0064] Figure 1C Shown with Figure 1B A similar variant is implemented, but using an LCOS image projector. A similar variant can also be based on Figure 1A Light from source 160 (which may be, for example, LED illumination or a scanned laser beam) is reflected by focusing reflective lens 164 onto PBS surface 162 to illuminate LCOS matrix 166. The light modulated by the LCOS passes through PBS 162 and enters lens 150, and then follows the same procedure as above. Figure 1B The same sequence as described in the context of .

[0065] Such as Figure 1A The configuration of can be combined sequentially along the light guide 10 with a dichroic coating adjacent to the wave plate 156, such as Figure 1D , where 190a denotes a dichroic surface. This enables images of different colors to be coupled in sequentially along the light guide.

[0066] Figure 1B and Figure 1C A particularly compact coupling arrangement is illustrated in which a PBS deployed proximate to a reflective lens is used to couple a collimated image into a light guide, and an internal reflection preserving interface enables the image light to be guided at the interface below the reflective lens. This approach is not limited to the catadioptric optical arrangements of these examples, and will be illustrated below with reference to an alternative optical arrangement employing only a reflective lens.

[0067] Now turn to FIG. 2A to FIG. 2E, these show a portion of a display, including: a light guide 10, formed of a transparent material, having a first pair of mutually parallel major surfaces 11, 12 for supporting propagation of image light by internal reflection; and an image generator for generating an image at an image plane 4. The device also includes: a collimating optical arrangement, which includes a reflective lens 150 and an associated quarter-wave phase plate 156; and a polarizing beam splitter (PBS) 158. The reflective lens 150 is associated with one of the major surfaces 12, or with a surface 112 of a prism 161, via an internal reflection preserving interface 154, wherein the surface 112 is parallel or coplanar with the major surface 12, and the internal reflection preserving interface 154 maintains or simulates a total internal reflection (TIR) ​​condition. The PBS 158 is arranged so that the image light from the image plane 4 passes through the PBS 158 to be incident on the reflective lens 150, is collimated by the reflective lens, and is then reflected by the PBS 158 to be coupled in to propagate within the light guide 10 by internal reflection at the major surfaces 11 and the major surfaces 12. At least a portion of the image light is reflected at the internal reflection preserving interface 154 .

[0068] In more detail, Figure 2A An image source 4 (e.g., OLED, Micro LED, or LCOS) is shown, which is arranged to transmit image light through the major surface 11 of the light guide 10, through the PBS 158 (light polarized for transmission, preferably P), through the interface 154, through the quarter wave plate 156, and onto the reflective lens 150. In this case, the outer face of the lens 150 is highly reflective (preferably at least 95%, and typically close to 100%), acting as a reflective collimating lens. The reflected light passes through the quarter wave plate 156 and the interface 154 again. Now with a polarization orthogonal to the originally introduced polarization (preferably S), it is reflected by the PBS 158 to the angular range guided by the light guide 10. The internal reflection preserving interface 154 ensures internal reflection of the angled reflected light, thereby achieving efficient incoupling. The angle of the PBS 158 is selected according to the desired angular range that the image light should propagate within the light guide. The PBS typically forms an angle of less than 45 degrees with the major surface and the internal reflection preserving interface, and in certain preferred implementations, can form an angle of about 25 to 40 degrees with the major surface / interface. When referring herein to an angle between two planes or two surfaces, this may be defined as the angle between the normal to the first surface and the normal to the second surface.

[0069] Figure 2AThe example is particularly compact because the light guide 10 is located between the image plane 4 and the reflective lens 150, and further because the PBS 158 is located between the major surfaces 11 and 12, being completely contained within the thickness of the light guide 10. This compactness may be obtained at the expense of a lack of uniformity, because all of the image fields do not completely "fill" the thickness of the light guide. This can be remedied by using a uniformity enhancing arrangement, such as a "mixer" partial reflector deployed within the light guide parallel to the major surfaces, and most preferably a 50% reflector located at the center plane of the light guide.

[0070] Figure 2B An architecture for more uniformly illuminating the light guide is depicted. To this end, the PBS 158 extends beyond the face of the light guide 10. Structurally, the PBS 158 is here incorporated into a prism 161 optically bonded to the light guide 10. The PBS 158 occupies a thickness of the prism in a direction perpendicular to the major surfaces 11, 12 that is greater than the thickness dimension of the light guide 10 in a direction perpendicular to the major surfaces 11, 12.

[0071] If the light guide 10 is a rectangular cross-section light guide that guides light by reflection at two orthogonal sets of major surfaces, then the PBS 158 should extend beyond two dimensions of the light guide (this will be referred to below). FIG. 3A to FIG. 3C and Figure 3F shown).

[0072] Figure 2C A simplified configuration is shown in which the light guide 10 is included in the path of the projector optics. Here, the PBS prism 163 is placed on top of the light guide 10, and the reflective lens 150 and associated components such as Figure 2A The focal length ratio in such a system is Figure 2B The focal length of the PBS 158 is long, but the integration of such a system is simpler. This configuration can achieve uniform light guide illumination by properly selecting the length of the PBS 158.

[0073] Figure 2D Shown based on Figure 2C A cascade configuration of structures in which image source 4a and image source 4b have different wavelengths (colors) and surface 190a is a dichroic coating.

[0074] Figure 2E Another implementation for integrating a PBS prism onto a light guide 10 is shown. Here, the light guide 10 is polished to create a plane 159. This plane is used as a reference base for a PBS prism 161a. The prism is placed on top to create a plane on which the PBS 158 is deployed, and another prism 161b is added to support the image generator 4. The resulting structure is optically similar to Figure 2B The structures are equivalent.

[0075] Each of the above configurations can be implemented using an LCOS image generator, where Figure 2B and Figure 2E Schematically shown by thick arrow 160, or referring to Figure 1C Shown in more detail, illumination is injected from an illumination source at the side.

[0076] As mentioned previously, aspects of the present invention may be implemented for injecting image light into a "rectangular light guide", i.e., wherein the light guide has a first pair of mutually parallel major surfaces 11, 12 and a second pair of mutually parallel major surfaces 13, 14 perpendicular to the first pair of major surfaces (see Figure 3A ). Such a light guide supports propagation of image light by quadruple internal reflection at the first pair of major surfaces and the second pair of major surfaces. Such a rectangular light guide is often used as an optical aperture expansion in the first dimension in combination with a plate light guide (having only one pair of major surfaces) that transmits the image light to the user's eyes. Suitable configurations for combining a rectangular light guide with a second light guide are disclosed in the applicant's patent publications US10133070 B2 and WO2023 / 131959 A1.

[0077] Image light introduced into a rectangular light guide should be injected in a direction that is tilted relative to the two axes of the light guide. This can be achieved by using a "twisted" tilt of the PBS, where the normal of the PBS is not parallel to the two pairs of major surfaces, and / or by tilting the optical elements so that the reflective lens has an optical axis that is not parallel to the two pairs of major surfaces. These options refer to FIG. 3A to FIG. 3F The rectangular light guide is implemented in the same way as FIG. 2A to FIG. 2E Each of the variations shown in is related.

[0078] Figure 3A Schematically shows Figure 2B Here, surface 158 is within prism 161. This configuration is suitable for the case where light guide 10 is a plate light guide with only two reflective outer surfaces (upper and lower). If used with a rectangular light guide, it can be seen that the normal of the PBS is parallel to the second pair of major surfaces 13, 14. Tilting of the image light can be achieved using appropriate tilting of optical elements (not shown), as will be described in Figure 3F exemplified in .

[0079] Figure 3B Shown is the coupling into a rectangular light guide 10. Here, the PBS surface 158T is tilted in two dimensions, which facilitates the correct tilt of the reflected beam for coupling into to propagate by quadruple reflection and completely fill the light guide 10 with all four images. Figure 3C PBS surface 158M is shown as an external reflector for use similar to Figure 1AAn implementation of an embodiment in which the image light is injected from below (in the orientation shown here).

[0080] exist FIG. 3A to FIG. 3C In an implementation of , the PBS is incorporated into a prism 161 optically bonded to the light guide, and the PBS occupies a certain thickness of the prism that is greater than the thickness of the light guide in both lateral dimensions. This enables the image light to fill the light guide with all the quadruple images. In addition, in order to couple in the light reflected from the PBS to provide all the quadruple images at the entrance of the light guide, the prism 161 is provided with two surfaces that are parallel and most preferably coplanar with two adjacent surfaces of the rectangular light guide, serving as a continuation of these surfaces for coupling purposes.

[0081] can be achieved by Figure 2A and Figure 1A of Figure 3D and Figure 3E The PBS shown achieves a more compact prism size. These configurations do not fill the light guide with the image and all its reflections, but mixer elements may be used to achieve subsequent filling (as mentioned above).

[0082] Figure 3F Detailed description Figure 3A , showing a PBS 158 perpendicular to one of the paired major surfaces of the rectangular light guide. In order to achieve the tilt angle range required to inject image light into the rectangular light guide, the plane of the image generator 4 and the plane of the collimating lens 150 are tilted to generate the tilted major optical axis required for injection into the light guide inlet 170.

[0083] exist FIG. 3A to FIG. 3F In all of the above examples, where the optical axis and / or PBS has an inclination in two directions relative to the light guide axis and the prism axis, the required polarization orientation is dictated by how the propagating beam encounters the PBS and does not correspond to the light guide axis. In some cases, polarization rotation is required before the light enters the light guide. For this purpose, a wave plate or polarizer can be introduced at the entrance 170 of the light guide.

[0084] As mentioned above, all implementations described herein may be implemented with any suitable image generator. Structurally, if the image generator is a micro-LED array deployed at the image plane 4, no additional structure may be required to complete the optical arrangement. The supporting electronic components (power supply, data storage and processing components, controller, etc.) required to operate all implementations are well known to those skilled in the art and are not shown here.

[0085] If the image generator is a reflective spatial light modulator (SLM) such as a Liquid Crystal on Silicon (LCOS) chip, additional optical components are required to direct the illumination (e.g. from an LED or laser) to illuminate the LCOS at the image plane 4. As an example, Figure 4A LED 200 is shown illuminating the LCOS at plane 4. The light from the LED is expanded in a light pipe 202 and, if necessary, introduced into a diffuser 204 at the end of the light pipe. A reflector 206 reflects the light onto the PBS. If necessary, further beam collimation is performed by a Fresnel lens 208 placed just before the PBS.

[0086] exist Figure 4B , laser 220 illuminates a set of scanning mirrors 222A and 222B (one or both driven in a scanning motion by appropriate drive components, not shown), passes through Fresnel lens 208 and illuminates PBS 158 and LCOS 4.

[0087] Another aspect of the invention relates to spatial filtering of image light injected into the light guide. Scattered light within the projector can reduce the contrast of the image, and large beam divergence can reduce resolution due to aberrations. A spatial filter (aperture) can be implemented to block this scattered light and limit the beam numerical aperture (divergence) to a nominal value.

[0088] Figure 5A and Figure 5B Various spatial filtering configurations are shown that can be implemented in any of the implementations described herein. Any combination of filters is also possible. As a non-limiting example, the configuration shown here is a Figure 2C The designs described are exemplified in the context of FIG.

[0089] Figure 5A The entrance to the light guide 10 is shown to include an edge 250 that performs vertical spatial filtering of the light entering the light guide. Preferably, the prismatic surface 252 is provided with an absorptive coating to prevent scattering of light hitting the surface, thereby enhancing the vertical filtering effect.

[0090] In this configuration, beam 254 is the lowest beam reflected into the light guide from surface 256. The reflection is close to edge 258 of reflective lens 150. By making surface 258 an absorber, efficient trimming of the excess beam is achieved.

[0091] In a preferred embodiment, the three groups of light beams (illumination 260, divergence 262, and collimation 264) incident on PBS 158 are incident on the same overlapping area of ​​PBS 158, such as Figure 5AAs shown. Therefore, according to another feature of the present invention, a highly efficient spatial filter (aperture) can be realized on the PBS plane. Arrow 266 shows the opening of the spatial filter, and absorber 268 is placed around the opening. Figure 5B 2 is an isometric view showing the spatial filter in the plane of the PBS also having a lateral width 270, with the absorber 268 located around the opening of the PBS 158. For clarity and simplicity of presentation, Figure 5B The additional portion 252 provided by the illumination arrangement optics and prisms is omitted.

[0092] Figure 5B Another option for spatial filtering in the in-plane direction of the light guide is also shown, which can be used in addition to or in place of the apertures in the plane of the PBS. A transverse aperture 274 can be created at position 250 by eliminating the TIR associated with the beam diverging outside the aperture. Element 272 (only in Figure 5B and for clarity from Figure 5A 272) are attached to surface 256, thereby spatially selectively eliminating TIR on this plane. Light beams impinging on these elements 272 within the light guide 10 will be coupled out and absorbed. The shape of the elements 272 enables the guidance and transmission of image beams that will pass through the lateral aperture 274 and the vertical aperture 250. The elements 272 can be located on the other side (top) or on both sides of the light guide 10. The shape of the elements 272 shown here is a non-limiting example, and elements of shorter or longer shapes, or elements of different shapes can be used. In addition, in some cases, such as when independent projectors are deployed for injecting images of different colors, the elements can be configured to selectively absorb only one color. The shape can also extend beyond the aperture 274 while providing additional image beam guidance.

[0093] FIG. 6A to FIG. 6D Describes FIG. 2A to FIG. 2E Options for polarization management in the configuration described in . As an example, Figure 2B The configuration is Fig. 6A and Figure 6C The basis of Figure 2C yes Figure 6B and Fig.6D In this description, polarization orientation is defined relative to PBS 158, where a double-headed arrow crossing the light beam represents P polarization and a black dot represents S polarization. Circular polarization is represented as a curved arrow, where the same direction is shown for reflected circular polarization for clarity.

[0094] The example shown here shows normal operation of the PBS 158, which optimally reflects S polarization and transmits P polarization. However, it will be appreciated that this is by way of example only, and implementations are not limited to this option, as some polarizers may operate in other orientations (e.g., wire grid polarizers).

[0095] exist Fig. 6A , P-polarized (P-pol) light from LCOS 4 passes through PBS 158 and then through quarter-wave retarder (QW) 156, thereby generating circular polarization. (It should be noted that the terms "retarder", "phase plate" and "wave plate" are used interchangeably herein.) Lens 150 reflects the circular polarization to pass through QW 156 again, thereby generating S-polarized (S-pol) reflected from PBS 158. If it is desired to inject S polarization into light guide 10, no additional elements are required. However, if P polarization is desired, a half-wave retarder (Half-wave-retarder, HW) is implemented on surface 300. If unpolarized light is desired, a birefringent depolarizer can be introduced at this plane.

[0096] Introducing an element at plane 300 may result in scattering at the interface. To ameliorate this problem, a slight enlargement and shifting of prism 161 may be achieved by step 302 so that light scattered from the edge does not enter light guide 10. The surface of prism 161 formed at internal reflection preserving interface 154 must still be parallel to the surface of the light guide because it participates in the incoupling of image light reflected by PBS 158.

[0097] The half-wave retarder may alternatively be implemented on plane 159 or adjacent to (and below) PBS 158. In such a case, the polarization progression is the same as described below for Figure 6B The polarization processes described are equivalent.

[0098] exist Figure 6B , a half-wave phase plate is placed on surface 304, which is part of one of the main light guide surfaces. The P polarization that passes through PBS 158 is rotated to S polarization after 304. The beam polarization is rotated to P polarization after reflecting from 150 and passing through QW 154 twice. After passing through 304 again, the beam is S polarized and is therefore reflected by PBS 158. The third pass through 304 rotates the beam to P polarization as needed when the beam enters the light guide 10. In this configuration, S polarization injection into the light guide 10 is achieved simply by omitting HW from surface 304.

[0099] Figure 6C and Fig.6D An arrangement for injecting circularly polarized light into the light guide 10 is described. Figure 6C154. In the embodiment of the present invention, QW 156B is placed at a certain distance from or adjacent to PBS 158 (and not next to interface 154). The P-polarized divergent image light that passes through PBS 158 and QW 156B is circularly polarized. After reflecting from 150 and passing through QW 156B again, the light is S-polarized and reflected from PBS 158. This reflected light now passes through QW 156B for the third time to generate circularly polarized light injected into light guide 10.

[0100] Alternatively, you can Fig. 6A A QW retarder is implemented in the plane 300 of , to generate circular polarization in the light guide 10. Fig.6D In FIG. 1 , the QW is placed on plane 156C (rather than adjacent to the PBS), but the same Figure 6C Similar polarization management.

[0101] As mentioned above FIG. 3A to FIG. 3F As described, coupling an image into a rectangular light guide requires that the optical axis of the projector be tilted in two axes relative to the light guide axis, thereby initiating a quadruple image propagation within the light guide. FIG. 7A to FIG. 7D Shown as Figure 3F Another particularly preferred implementation of an alternative configuration of . In this implementation, the lens ( Figure 3F The bottom surface of 150) is adjacent to the TIR interface ( Figure 3F 154 in ), thus simplifying integration.

[0102] FIG. 7A to FIG. 7D The configuration in can be used for an illuminated image matrix such as a micro-LED array, but can also be implemented using an illuminated spatial light modulator (SLM) such as an LCOS chip. The example shown here is for an illuminated LCOS, where the illumination portion itself incorporates partial TIR according to another aspect of the invention (as will be described further below). Due to this combination of features, the projector employs a prism including three different surfaces that provide TIR properties.

[0103] Fig. 7A A side view is shown, and Figure 7B A top view of the beam propagation associated with a point in the projection field is shown. The polarization element is not explained in detail in this description, but is self-explanatory to a person skilled in the art.

[0104] like Fig. 7AAs shown, light from source 348 is projected into prism 357a, which together with prism 357b comprises PBS 356. The light source may be an arrangement of one or more LEDs, or may be an exit aperture of a light pipe that homogenizes illumination from one or more LED light sources. A central beam 350a (shown as a dashed line) propagates into PBS 356 and reflects downward through surface 354 onto lens 358 to be reflected by SLM (e.g., LCOS) 360. The reflected beam propagates through lens 358, surface 354, PBS 356, and surface 363 to be reflected by reflective lens 362. The reflected beam passes through surface 363 to be reflected by PBS 356, passes through prism 357b and prism extension 357c to exit aperture 366, which is the entrance to light guide 10. Two further beams associated with the same image point are shown. Light beam 350b (shown as a dashed line) also propagates directly through prism 357a to PBS 356, while light beam 350c (solid line) is first reflected by surface 354 before being incident on PBS 356. Thus, a portion of the illumination undergoes an odd number of reflections between the illumination aperture and the SLM image plane, while another portion of the illumination undergoes an even number of reflections. These odd and even reflections are part of the optical path that images source 348 onto exit aperture 366 (as further described below).

[0105] As described in the previous configuration, some beams (in this case beam 350c) are reflected from surface 363 by TIR onto exit aperture 366, thereby facilitating filling of the light guide aperture. There is no correlation between the rays that experience TIR at surface 354 and the rays that experience TIR at surface 363.

[0106] Figure 7B Central ray 350a and other rays (solid 350d and dashed 350e, both of which follow similar paths as ray 350a) are shown. Ray 350e originates from illumination aperture 348, is incident on PBS 356 (shown from the top as ray 370), reflects from LCOS 360 (ray 372), reflects from top reflective lens 362 (ray 374), reflects from PBS 356 (ray 376), and exits from side surface 378 (shown from the side view). Fig. 7A The light (not visible in the figure) is reflected to the prism extension 357c and enters the light guide 10 through the exit aperture 366.

[0107] The prism configuration provides two surfaces that are parallel or coplanar with the major surfaces of the rectangular light guide to participate in the coupling of all four images required for quadruple propagation into the light guide at the exit aperture 366. The extent to which these surfaces need to be extended depends on the details of the implementation. In the case shown here, surface 378 is provided in part by extended prism 357c and in part by prism portion 357b, as shown in FIG. Figure 7B Another coupling-in surface is provided by the interface 363 and the extension of the interface 363 above the prism 357c, as shown in FIG. Fig. 7A As shown. Fig.7D The overall resulting shape of the projector prism can be best seen in .

[0108] For clarity, Figure 7C shows the beam propagation at different points in the image. The reflections are at different angles, but the principle of the light path is the same Fig. 7A Same as shown in .

[0109] Optimal coupling of light from illumination aperture 348 to exit aperture 366 is achieved if exit aperture 366 is imaged to the plane of illuminator aperture 348 and if surface 354 terminates at the center of this image. In this case, the vertical size of illumination aperture 348 is effectively doubled by reflection at plane 354, so the illumination source can be half the size of the exit aperture (a one-to-one imaging ratio in this example). Figure 7B ), the size of the illumination aperture 348 is equal to twice the width of the image on the exit aperture 366 (based on the need for uniform illumination / filling of the light guide).

[0110] Fig. 7A and Figure 7C The configuration shown in can also be used to advantage to project images into a plate-type (one-dimensional) light guide, where the other dimensions of the prisms allow divergence of the image with respect to the in-plane dimension of the light guide (ie, without surface 378).

[0111] about FIG. 7A to FIG. 7D The described lighting architecture is considered to be inventive in its own right, independent of the additional features disclosed above. To illustrate the distinguishing features of this aspect of the invention, FIG. 8A to FIG. 8C The design considerations for the illumination arrangement for the SLM in the context of other conventional image projectors for near-eye displays are shown, where Figure 8C Corresponding to the preferred implementation of the lighting arrangement.

[0112] Thus, according to this aspect of the invention, a projector for a display includes: a reflective spatial light modulator (SLM) 506 for modulating the polarization of light reflected from an image plane; an illumination source that outputs illumination from an illumination aperture 500B; a collimating optical arrangement that includes at least one lens 508; and a prism that includes a polarizing beam splitter (PBS) 502B. PBS 502B is disposed to reflect illumination from illumination aperture 500B toward SLM 506 and to enable light corresponding to an image reflected from the SLM to pass through the PBS to reach the collimating optical arrangement 508.

[0113] A particular feature of this aspect of the invention is that the surface 512 of the prism adjacent to the SLM 506 is provided with an internal reflection preserving interface, and a portion of the illumination from the illumination aperture 500B is reflected at the interface and then reflected from the PBS before being incident on the SLM. Thus, a first portion of the illumination experiences an odd number of reflections along its path from the illumination aperture 500B to the SLM 506, and a second portion of the illumination experiences an even number of reflections from the illumination aperture 500B to the SLM 506.

[0114] Fig. 8A A simplified architecture of an image projector based on an LCOS image generator using a conventional illumination arrangement is shown to better illustrate the significance of this aspect of the invention. An illumination source 500A projects light onto a first PBS 502A, which reflects the light through a field lens 504A onto an LCOS chip 506. The modulated light is reflected to a collimating reflective lens 508, which reflects the light to a second PBS 507, which reflects the collimated image light to an exit aperture 510. For optimal power efficiency, the plane of the source 500A is imaged onto the aperture plane 510.

[0115] PBS 502A and PBS 507 in this schematic representation may be combined into a single PBS, similar to Fig. 7A The arrangement.

[0116] Figure 8B An attempt to reduce the size of the illumination portion of the projector is shown. Here, the angle of PBS 502B is shallower than 502A. However, this geometric change results in some of the light from source 500A needing to pass through a field lens (dashed arrow) in a way that will turn and distort the light.

[0117] Figure 8C A practical solution according to this aspect of the invention is shown, where field lens 504B is moved onto the top of LCOS 506 and the bottom surface of prism 512 is now used to perform total internal reflection of a portion of the light emitted by source 500B. Additionally, in this configuration, the size of the emitter can be smaller because it is imaged onto output aperture 510 twice (once directly and once by reflection at surface 512).

[0118] The field lens 504 can still be Fig. 8A The implementation shown is on a prismatic surface, in which case an internal reflection preserving interface must be introduced to maintain TIR at plane 512.

[0119] Optionally, a phase element (with continuous distribution or Fresnel type, refractive or reflective) may be introduced on the surface of the emitter 500B to direct the light beam to generate a uniform illumination of the pupil 510. The phase element may steer the light beam from a non-illumination direction (e.g. along the surface 512) to an illumination direction.

[0120] Emitter 500B may be the exit aperture of a light pipe with or without a diffuser, which may be used to mix illumination originating from multiple sources.

[0121] Throughout this document, wherever an "internal reflection preserving interface" is mentioned, the term is generally used to refer to any and all implementations of an interface that maintains or simulates total internal reflection (TIR) ​​properties. Thus, such an interface may be implemented as a layer of material having a refractive index lower than that of the lightguide, or as a structure containing an air gap adjacent to the surface, thereby creating classical conditions for TIR at the interface between a material having a higher refractive index to a material having a lower refractive index (or air). Alternatively, the internal reflection preserving interface may be implemented as a multilayer dielectric coating that is configured to be substantially transparent to visible light within a first range of incident angles and reflective to visible light within a second range of incident angles, the second range having a larger angle to the normal to the interface than the first range, thereby simulating TIR characteristics.

[0122] It will be appreciated that the above description is intended to be exemplary only and that 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 and having a first pair of mutually parallel major surfaces for supporting propagation of image light by internal reflection at the first pair of major surfaces; (b) an image generator, for generating an image at an image plane; (c) a collimating optical arrangement comprising a reflective lens and an associated quarter wave phase plate; as well as (d) Polarization beam splitter (PBS), wherein the reflective lens is associated with one of the first pair of principal surfaces via an internal reflection preserving interface, or with a surface of a prism parallel to or coplanar with one of the first pair of principal surfaces, and wherein the PBS is disposed such that image light from the image plane passes through the PBS to be incident on the reflective lens, is collimated by the reflective lens, and is reflected by the PBS to be coupled into for propagation within the light guide via internal reflection at the first pair of principal surfaces, at least a portion of the image light being reflected at the internal reflection preserving interface.

2. The display according to claim 1, wherein: A normal to the PBS forms an angle of less than 45 degrees with a normal to the internal reflection preserving interface.

3. The display according to claim 1, wherein: The PBS is incorporated into a prism, the prism is optically coupled to the light guide, and wherein the light guide has a thickness dimension in a direction perpendicular to the first pair of major surfaces, and the PBS occupies a thickness of the prism in a direction perpendicular to the first pair of major surfaces that is greater than the thickness dimension of the light guide.

4. The display according to claim 1, wherein: The light guide also includes a second pair of major surfaces that are parallel to each other and perpendicular to the first pair of major surfaces, the first pair of major surfaces and the second pair of major surfaces supporting propagation of image light by quadruple internal reflection at the first pair of major surfaces and the second pair of major surfaces.

5. The display according to claim 4, wherein: A normal to the PBS is non-parallel to both the first pair of major surfaces and the second pair of major surfaces.

6. The display according to claim 4, wherein: The reflective lens has an optical axis that is non-parallel to both the first pair of major surfaces and the second pair of major surfaces.

7. The display according to claim 4, wherein: The prism includes a first surface parallel or coplanar with one of the first pair of major surfaces and a second surface parallel or coplanar with one of the second pair of major surfaces, the first surface being provided with the internal reflection preserving interface.

8. The display according to claim 4, wherein: The PBS is incorporated into a prism optically coupled to the light guide, and wherein the light guide has a first thickness dimension in a direction perpendicular to the first pair of major surfaces and a second thickness dimension in a direction perpendicular to the second pair of major surfaces, the PBS occupies a thickness of the prism in a direction perpendicular to the first pair of major surfaces that is greater than the first thickness dimension, and occupies a thickness of the prism in a direction perpendicular to the second pair of major surfaces that is greater than the second thickness dimension.

9. The display according to claim 1, wherein: The internal reflection preserving interface is realized as a layer of a material having a refractive index lower than the refractive index of the light guide.

10. The display according to claim 1, wherein: The internal reflection preserving interface includes an air gap.

11. The display according to claim 1, wherein: The internal reflection preserving interface is implemented as a multilayer dielectric coating, which is configured to be substantially transparent to visible light within a first range of incident angles and reflective to visible light within a second range of incident angles, wherein the second range is at a higher angle relative to the normal of the interface than the first range.

12. The display of claim 1 further comprising a light absorbing boundary disposed along at least two edges of the PBS to define an optical aperture of the collimated image.

13. The display according to claim 1, wherein: The PBS is incorporated into a prism, the prism being optically coupled to the light guide, the image generator comprising an illumination arrangement for directing illumination from an illumination aperture to the image plane through the prism, wherein a first portion of the illumination undergoes an odd number of reflections from the illumination aperture to the image plane, and a second portion of the illumination undergoes an even number of reflections from the illumination aperture to the image plane.

14. The display according to claim 1, wherein: The light guide is located between the image plane and the reflective lens.

15. The display according to claim 14, wherein: The PBS is located between the first pair of major surfaces of the light guide.

16. The display according to claim 1, wherein: The collimating optical arrangement is a polarizing catadioptric collimating arrangement, wherein the reflective lens has a partially reflective surface, and wherein the image plane is positioned to transmit image light by transmission through the partially reflective lens, the image light being reflected back towards the partially reflective surface.

17. A display comprising: (a) a light guide formed of a transparent material having a first major surface and a second major surface parallel to the first major surface, the light guide supporting propagation of image light by internal reflection at the first major surface and the second major surface; (b) an image generator, for generating an image at an image plane; as well as (c) A polarization catadioptric collimation and coupling arrangement comprising: (i) a non-planar partially reflective first reflector associated with the first major surface of the light guide, (ii) a second reflector associated with the second major surface of the light guide in facing relationship with the partial reflector, and (iii) a planar third reflector, the planar third reflector being at an oblique angle to the major surface, wherein one of the second reflector and the third reflector is a total reflector, and the other of the second reflector and the third reflector is a polarization selective reflector interposed between the total reflector and the first reflector, and the polarization refractive-reflective collimation and coupling arrangement further comprises at least one phase plate interposed between the polarization selective reflector and the first reflector, so that image light from the image plane is partially transmitted through the partially reflective first reflector acting as a refractive lens, passes through at least a portion of the thickness of the light guide and is reflected at the second reflector, is partially reflected at the partially reflective first reflector acting as a reflective lens, and is reflected by the third reflector to be coupled in to propagate by internal reflection within the light guide.

18. The display according to claim 17, wherein: The second reflector is the total reflector, and wherein the third reflector is the polarization selective reflector disposed within the thickness of the light guide.

19. The display according to claim 17, wherein: The second reflector is the polarization selective reflector, and wherein the third reflector is the total reflector associated with a prism outside the thickness of the light guide.

20. The display according to claim 17, wherein: The second reflector is a planar reflector.

21. A projector for a display, the projector comprising: (a) A reflective spatial light modulator (SLM) for modulating the polarization of light reflected from the image plane. (b) an illumination source that outputs illumination from an illumination aperture; (c) a collimating optical arrangement comprising at least one lens; as well as (d) a prism, the prism comprising a polarizing beam splitter (PBS), wherein the PBS is arranged to reflect illumination from the illumination aperture towards the SLM and to enable light corresponding to an image reflected from the SLM to pass through the PBS to reach the collimating optical arrangement, And wherein a surface of the prism adjacent to the SLM is provided with an internal reflection preserving interface, and wherein a portion of the illumination from the illumination aperture is reflected at the interface and then reflected from the PBS before being incident on the SLM, such that a first portion of the illumination undergoes an odd number of reflections from the illumination aperture to the SLM and a second portion of the illumination undergoes an even number of reflections from the illumination aperture to the SLM.

Images