Non-polarized light guide-based display system with polarizing beam splitter

Abstract

A light guide-based display system includes a light guide (82). An image projector (50, 50', 52, 58, 60, 62, 64, 130, 150) is coupled to the light guide (82) and includes: at least one active pixel array (70); a polarization beam splitter (PBS) (76); a first retroreflective collimating optics (80a); and a second retroreflective collimating optics (80b). The PBS (76) separates the unpolarized image light from the active pixel array (70) and recombines the reflected polarized images from the retroreflective collimating optics (80a, 80b) to inject the superposition of images as a mixed polarization image into the light guide (82).

Description

Technical Field and Background Technology

[0001] This invention relates to optical systems, and more particularly, to light guide-based display systems for use in applications such as near-eye displays, head-up displays, and augmented reality devices.

[0002] Light guide-based displays typically employ image projectors that inject image light into the light guide. Achieving sufficient brightness can be challenging when using active pixel arrays that produce unpolarized light. This challenge is further exacerbated by the inherent 50% loss of light intensity when using polarized optical components such as polarizing beam splitters. Summary of the Invention

[0003] This invention is a display system based on light guides.

[0004] According to the teachings of embodiments of the present invention, a light guide-based display system is provided, comprising: (a) a light guide formed of a transparent material and having a pair of mutually parallel main surfaces supporting the propagation of image light through internal reflection, the light guide preferably including a set of mutually parallel partially reflective inner surfaces arranged to couple light propagating within the light guide to exit the light guide; and (b) an image projector coupled to the light guide to inject a collimated image into the light guide, the image projector comprising: (i) at least one active pixel array configured to generate unpolarized light corresponding to the image, and (ii) a polarization beam splitter. (PBS) prism, the PBS prism being deployed to receive unpolarized light from an active pixel array, the PBS prism including a PBS surface configured to separate the unpolarized light into a first polarized optical path and a second polarized optical path, (iii) a first retroreflective collimating optics associated with the first polarized optical path, and (iv) a second retroreflective collimating optics associated with the first polarized optical path, wherein retroreflected polarized images received from the first and second retroreflective collimating optics are recombined through the PBS surface to be injected into the light guide in a superimposed manner as a mixed polarized image.

[0005] According to another feature of an embodiment of the invention, the polarization beam splitter prism provides an angle-selective reflective surface that is coplanar or parallel to one of the main surfaces of the light guide. The angle-selective reflective surface is through which at least a portion of the light corresponding to the image before recombination passes, and the angle-selective reflective surface reflects at least a portion of the mixed polarization image before the mixed polarization image reaches the entrance aperture of the light guide.

[0006] According to another feature of an embodiment of the invention, the angle-selective reflective surface is provided by a layer or air gap of a low-refractive-index adhesive, the path of at least one polarization component of the image passes through the angle-selective reflective surface, and at least a portion of the mixed polarized image undergoes internal reflection at the angle-selective reflective surface of the light guide within the PBS prism.

[0007] Another feature of the embodiments of the invention also provides an anti-reflective coating on the surface adjacent to the low-refractive-index adhesive or air gap, for minimizing loss in the optical path passing through the angle-selective reflective surface.

[0008] According to another feature of an embodiment of the invention, the polarizing beam splitter prism includes a first part and a second part, which are attached to mutually parallel main surfaces of the light guide and aligned in a relative relationship.

[0009] According to another feature of an embodiment of the invention, the image projector is one of a plurality of similar image projectors deployed sequentially along the light guide, wherein the first of the image projectors projects an image of a first color, and wherein the second of the image projectors projects an image of a second color different from the first color, wherein the main portion of the PBS prism of the second image projector is attached to the light guide by an adhesive with a refractive index matching covering a dichroic layer, the dichroic layer being transparent to the second color and reflective to the first color.

[0010] Another feature of the embodiments of the present invention also provides a transmission or reflection coupling prism configured to couple a mixed polarization image to an optical guide.

[0011] According to another feature of an embodiment of the invention, a refractive lens is also provided, inserted between the PBS prism and the coupling prism, the refractive lens supplementing the optical power of the first retroreflective collimating optics and the second retroreflective collimating optics to achieve collimation of the mixed polarization image.

[0012] According to another feature of an embodiment of the invention, the light path from the entrance to the PBS prism via the first retroreflective collimating optics and the second retroreflective collimating optics and the coupling prism does not pass through any air gap before entering the light guide.

[0013] According to another feature of an embodiment of the invention, the polarization beam splitter prism is configured such that the first retroreflective collimating optics is tilted relative to the axis of the light guide to guide the mixed polarization image to propagate within the light guide.

[0014] According to another feature of an embodiment of the present invention, at least one active pixel array includes a color micro-LED array.

[0015] According to another feature of an embodiment of the invention, the active pixel array is spaced apart from the surface of the polarizing beam splitter prism, and a field lens is attached to the active pixel array.

[0016] According to another feature of an embodiment of the invention, at least one active pixel array comprises three monochromatic arrays combined on the face of a dichroic X-cube prism to provide unpolarized image light to a polarizing beam splitter prism.

[0017] Another feature of an embodiment of the invention provides a lens inserted between a dichroic X-cube prism and a polarizing beam splitter prism, the lens providing a portion of the collimating power.

[0018] According to another feature of an embodiment of the invention, the light guide further includes a second pair of mutually parallel main surfaces perpendicular to a pair of mutually parallel main surfaces, thereby defining a rectangular cross-section light guide that supports the propagation of light through quadruple internal reflection, and wherein a polarizing beam splitter prism is configured such that a first retroreflective collimating optics is tilted relative to the rectangular cross-section of the light guide to guide a mixed polarization image to propagate within the light guide through quadruple internal reflection.

[0019] According to another feature of an embodiment of the present invention, the optical power of the first and second retroreflective collimating optics is supplemented by refractive optics at the entrance or exit of the polarization beam splitter prism to achieve collimation of the mixed polarization image.

[0020] Another feature of the embodiments of the present invention also provides a depolarizer or other polarization modification element deployed between the PBS prism and the light guide.

[0021] According to the teachings of embodiments of the present invention, a method for projecting an image in a light guide-based display system is also provided, the method comprising: (a) generating unpolarized image light from at least one active pixel array; (b) receiving the unpolarized image light from a polarizing beamsplitter prism; (c) separating the received unpolarized image light into a first polarization component directed toward a first retroreflective collimating optics and a second polarization component directed toward a second retroreflective collimating optics by a PBS surface within the polarizing beamsplitter prism; (d) recombining at least partially collimated polarized images received by reflections of the first and second polarization components from the first and second retroreflective collimating optics, respectively, by a PBS surface within the polarizing beamsplitter prism to generate a superposition of collimated polarized images as a mixed polarized image; and (e) coupling the mixed polarized image to a light guide formed of a transparent material and having a pair of mutually parallel main surfaces, such that the mixed polarized image propagates within the light guide by internal reflection.

[0022] According to another feature of an embodiment of the invention, the optical power of the first and second retroreflective collimating optics is supplemented by at least one refractive lens deployed in the optical path, before or after the PBS prism, such that the mixed polarization image coupled into the light guide is a collimated image.

[0023] According to another feature of an embodiment of the present invention, the first retroreflective collimating optics and the second retroreflective collimating optics have sufficient optical power to collimate the first polarization component and the second polarization component, respectively, such that the mixed polarization image coupled into the light guide is a collimated image. Attached Figure Description

[0024] The invention has been described herein by way of example only with reference to the accompanying drawings, in which:

[0025] Figure 1A and Figure 1B This is a side view of the optical components of a light guide-based display system constructed and operated according to an embodiment of the present invention, showing the optical path from the active pixel array image generator through a polarization beam splitter (PBS) prism and into the light guide, wherein, for ease of understanding, the optical path of the first polarization component is shown. Figure 1A The arrow in the diagram shows the optical path of the second polarization component. Figure 1B The arrows in the image show that the two components are recombine in a superimposed manner to be injected into the optical guide;

[0026] Figure 2A and Figure 2B yes Figure 1A and Figure 1B A simplified schematic side view of the optical system based on the light guide, showing a first architecture and a second architecture for integrating the PBS prism and its associated components with the light guide;

[0027] Figure 2C and Figure 2D They are respectively with Figure 2A and Figure 2B A similar schematic side view illustrates a variant implementation with a non-orthogonal PBS prism geometry;

[0028] Figures 3A to 3D Is with Figure 2A A similar schematic side view shows four different options (with or without corresponding structural modifications) for achieving optical alignment and focus matching between the two optical channels during the assembly of the display system;

[0029] Figure 4This is a side view of the optical components of a light guide-based display system constructed and operated according to another embodiment of the present invention, showing the optical path from an active pixel array image generator through a PBS prism and into the light guide, wherein light is coupled into the light guide via a coupling prism.

[0030] Figures 5A to 5C This is a schematic side view of the optical components of a light guide-based display system constructed and operated according to another embodiment of the present invention, employing a reflected polarization-modified spatial light modulator (SLM) illuminated by light passing through the main surface of the light guide, wherein... Figure 5A The sample optical path through the optical components is shown, and for ease of understanding, Figure 5B and Figure 5C The sample optical paths from the illumination source to the SLM and from the SLM to the light guide are shown respectively;

[0031] Figure 5D Is with Figure 5A A similar schematic side view shows an alternative lighting arrangement;

[0032] Figure 6A and Figure 6B They are respectively with Figure 4 and Figure 2A A similar schematic side view, in which the active pixel array is replaced by an X-cube dichroic combiner that combines image light from three monochromatic active pixel array image sources;

[0033] Figure 6C Is with Figure 6B A similar schematic side view shows a refractive lens added between the X-cube dichroic combiner and the PBS prism, and illustrates the sample light path through the display system;

[0034] Figure 7A This is a schematic front view of a display system constructed and operated according to an embodiment of the present invention, showing its connection with... Figure 2A The image projector arrangement is similar to that of the image projector arrangement, which is extended to a tri-color image projector with side-by-side components of PBS prisms sharing a common internal partition, shown in the context of a two-dimensional optical aperture extended light guide.

[0035] Figure 7B yes Figure 7A A schematic isometric representation of a three-color image projector;

[0036] Figure 7C Is with Figure 7A A similar schematic front view has been modified to project multiple partial images along a non-parallel optical axis;

[0037] Figure 8A and Figure 8B It is shown that... Figure 2A A schematic side view of the alternative structure implementation of the optically equivalent display system;

[0038] Figure 9 This is a schematic side view of a light guide-based display system constructed and operated according to another embodiment of the present invention, wherein the PBS prism is implemented using prism portions attached to the main surface of the light guide in a relative relationship;

[0039] Figure 10 This is a schematic side view illustrating an implementation of a display system employing multiple projectors attached to a common light guide, each projector... Figure 9 Similar to a projector;

[0040] Figure 11A This is a schematic plan view of a group of projectors arranged in a staggered relationship with the parallel optical axis, wherein each projector is... Figure 9 Similar to a projector;

[0041] Figure 11B It is deployed on the optical guide. Figure 11A A schematic front view of a display system with a set of projectors;

[0042] Figure 11C This is a schematic plan view of a group of projectors, where each projector is connected to... Figure 9 Similar to projectors, they are deployed in a relationship that is intersected with non-parallel optical axes;

[0043] Figure 11D It is deployed on the optical guide. Figure 11C A schematic front view of a display system with a set of projectors; and

[0044] Figure 12 This is a schematic isometric view of a display system constructed and operated according to another embodiment of the present invention, used to couple an image into a rectangular cross-section light guide to undergo quadruple internal reflection. Detailed Implementation

[0045] The present invention relates to a light guide-based display system, and more particularly to a system for injecting image light from a projector coupled to a light guide into the light guide.

[0046] The principles and operation of the light guide-based display system according to the present invention can be better understood by referring to the accompanying drawings and description.

[0047] Non-polarized light-guide-based display system using PBS

[0048] Generally speaking, common reference Figures 1A to 4 and Figure 6AAs shown in Figure 11, certain particularly preferred embodiments of the present invention provide a light guide-based display system comprising a light guide 82 formed of a transparent material and having a pair of mutually parallel main surfaces 86, 87 supporting the propagation of image light through internal reflection. An image projector (identified as 50, 50', 52, 58, 60, 62, 64, 130, or 150, respectively) is coupled to the light guide 82 to inject a collimated image into the light guide. The image projector includes: at least one active pixel array 70 configured to generate unpolarized light corresponding to the image; and a polarization beam splitter (PBS) prism (typically composed of several prism portions 75a, 75b, 88) and a PBS surface 76 deployed to receive the unpolarized light from the active pixel array and split it into a first polarized light path and a second polarized light path. The first retroreflective collimating optical device 80a is associated with the first polarization optical path, and the second retroreflective collimating optical device 80b is associated with the second polarization optical path.

[0049] Unpolarized image light from the active pixel array enters the PBS prism, where it is split at the PBS prism by the polarization beam splitter surface 76 into a first polarization component guided along a first polarization path toward the first reflective collimating optics 80a, and a second polarization component guided along a second polarization path toward the second reflective collimating optics 80b. The polarized images reflected back from the first and second reflective collimating optics are recombined at the PBS surface 76 so that they are injected into the light guide 82 as a superimposed mixed polarization image.

[0050] To achieve this particularly compact configuration in which the separation and recombination are performed by a single PBS surface 76, the first and second reflective collimating optics are preferably "backward reflective," meaning that they are each substantially on-axis, i.e., their optical axes are within 10 degrees of the principal rays of the incident and reflected images. Most preferably, the backward reflective optics are on-axis such that the principal rays of both the received and reflected images coincide with the optical axis of the optics.

[0051] Active pixel arrays are typically micro-LED arrays, which can be color micro-LED arrays 70 or monochrome arrays. In some cases, a set of three arrays (designated 70R, 70G, and 70B, respectively) providing red, green, and blue images is used, as illustrated below. Although this specification refers to micro-LED arrays throughout as preferred, non-limiting examples, it should be noted that other active pixel arrays using other technologies (e.g., OLED arrays) also fall within the scope of this specification and claims.

[0052] This arrangement achieves high efficiency and brightness by capturing most of the unpolarized image light emitted by the micro-LED array, while also benefiting from the compactness and structural advantages of the PBS prism-based optics. The first and second reflective collimating optics can have sufficient optical power to achieve collimation, or they can have lower optical power and be supplemented by refractive optics at the entrance or exit of the PBS prism. Using a combination of reflective and refractive optics can be advantageous because they typically introduce opposing optical aberrations that can be designed to cancel each other out.

[0053] PBS-based image projectors can be coupled to a light guide via a coupling prism having an angled coupling surface or via a light guide surface having a reflecting prism on an opposing light guide surface. In these cases, a refractive lens can be inserted before coupling to provide a portion of the collimating power and thus compensate for some aberrations caused by reflective optics.

[0054] Alternatively, the projector can be integrated with the light guide. In this case, the PBS prism can be tilted relative to the light guide axis, such that the combined light exiting the PBS plane is properly tilted relative to the light guide surface to allow the entire image field to propagate within the light guide. The light guide surface preferably divides the PBS prism in two. The PBS prism may include a wedge prism positioned below the light guide surface and bonded to it with a low-refractive-index adhesive, such that the injected image passes through the surface, while the exiting collimated image light undergoes total internal reflection (TIR) ​​at that surface. Anti-reflective coatings on both surfaces near the low-refractive-index adhesive can help minimize losses in the light path across the plane. Another variation for coupling to the light guide separates the PBS prism into two parts, which are aligned and attached to the upper and lower surfaces of the light guide in a relative relationship.

[0055] In the case of using a single, for example, colored micro-LED array, it can be slightly spaced from the surface of the PBS prism, and a field lens can be attached to the array. In some implementations, three monochromatic micro-LED arrays are combined on the surface of a dichroic X-cube prism to provide an input image to the PBS prism. If a lens is inserted between the X-cube prism and the PBS prism, it can provide a portion of the collimating power. These options will be illustrated by the embodiments described below.

[0056] Implementation of optical fiber integrated projector

[0057] Now refer to more specifically Figures 1A to 3DThese figures illustrate a first particularly preferred, but non-limiting, embodiment of the display system of the present invention, employing a projector 50 integrated with a light guide 82. In this context, the term "integrated" refers to a configuration in which a polarization beamsplitter prism provides an angle-selective reflective surface 84 that is coplanar or parallel to the main surface 86 of the light guide. As part of the projector's function, this angle-selective reflective surface 84 is traversed by at least one optical path within the PBS prism, and reflects at least a portion of the mixed polarization image before it is injected into the light guide. Surface 84 is used to reflect a portion of the coupled image to "fill" the entrance aperture of the light guide 82 defined by the image in the plane of the cutoff edge 6a and the main surface 86. In a particularly preferred implementation of the invention, this means that at least one polarization component of the image light passes through the inner surface 84 as part of the optical path defined by the PBS prism, while the collimated image light of the mixed polarization output image is angled to undergo internal reflection at the inner surface 84. Angular selective reflection is preferably achieved by attaching the lower wedge prism portion 88 of the PBS prism via a low-refractive-index adhesive, or in some cases by attaching a second retroreflective collimating optic 80b (see below). Figure 2C and Figure 2D This allows for total internal reflection of image light over an angular range associated with the portion of the field that must be reflected from surface 84. In some cases, where the steepest part of the field is at an angle of incidence below the critical angle of the glass-binder interface, the geometry is designed to ensure that steep rays below the critical angle are incident on surface 84 beyond the edge of the prism portion 88, thus encountering the glass-air boundary with a smaller critical angle. To minimize losses in the light path across the boundary at surface 84, one or both surfaces facing the low-refractive-index adhesive can be provided with an anti-reflective coating. As an addition or alternative to using a low-refractive-index adhesive, angle-selective reflection characteristics can be provided by a suitable multilayer dielectric coating on surface 84. The desired functionality can also be provided by an air gap (with anti-reflective coatings on both surfaces), although implementations without air gaps are generally preferred due to their excellent structural integrity and ease of manufacture.

[0058] The PBS prism is preferably tilted relative to the light guide axis, such that the combined light leaving the PBS plane is at an angle relative to the light guide surface, which is suitable for the entire image field to propagate within the light guide 82 through internal reflections at the main surfaces 86 and 87 of the light guide.

[0059] Figure 1A and Figure 1B The optical paths of S-polarized light and P-polarized light through the system are shown respectively. Solid arrows represent unpolarized light emitted from the color micro-LED array 70. Figure 1AIn the diagram, the dotted-line arrow represents S-polarized light, which is reflected by the PBS surface 76 and converted into circularly polarized light (dashed arrow) by a quarter-wave plate 78a associated with the first reflecting collimating optics 80a. The circularly polarized light is then reflected by the reflecting optics 80a, which may be a doublet or other embedded optics to improve optical quality. The reflected light returns through the quarter-wave plate 78a, becoming P-polarized, and then passes through the PBS surface 76 to enter the light guide 82.

[0060] exist Figure 1B In the diagram, the dashed arrow represents P-polarized light, which passes through the PBS surface 76 and the quarter-wave plate 78b before being reflected by the reflecting optics 80b. The reflected light returns and passes through the quarter-wave plate 78b, becoming S-polarized, and is then reflected by the PBS surface 76 to become S-polarized. Figure 1A The other polarization component shown is co-aligned and combined. The combined beam from the two polarizations enters the light guide 82 directly as a combined polarization image or enters the light guide 82 after reflection from within the surface 84.

[0061] In this embodiment, the inner surface 84 is described as part of the light guide surface 86, which extends into and divides the PBS prism in two, thereby subdividing the PBS prism into a portion 75b between surface 84 and PBS surface 76, and an additional wedge-shaped portion 88 positioned below surface 84 (in the indicated orientation). It should be noted that the PBS prism portion 75b is defined according to its optical function and can be structurally implemented in various ways, adjacent to, separated from, or comprising an extension of the light guide combined with one or more additional components.

[0062] By way of non-restrictive examples, Figure 8A and Figure 8B Alternative structural implementations of a display system with an integrated projector are shown, and a structural solution is proposed in the context of the projector 50 described above, but will also be applicable to various other implementations described below.

[0063] Figure 8A The following implementation is shown, wherein the PBS prism is formed by prism portions 75a, 75b and 88 that structurally correspond to the functional portions of the PBS prism described above, and the PBS prism is coupled to the vertical edge surface of the light guide 82.

[0064] In some embodiments, the light guide 82 may be formed of a material having a lower refractive index (n1) than the PBS prism. This allows total internal reflection (TIR) at the interface of the light guide with air. On the other hand, the PBS prism may be formed of a material with a higher refractive index (n2) to achieve TIR within a desired angular range at its interface with the adhesive layer at surface 84.

[0065] When such an arrangement with n1 < n2 is achieved, the interface between the light guide 82 and the PBS prism (portion 75b) is advantageously perpendicular to the main surface of the light guide and surface 84. This perpendicular orientation ensures proper light transmission without introducing distortion even with the refractive index difference.

[0066] Furthermore, the difference between n1 and n2 can be strategically selected to compensate for the dispersion effects that may occur when the light output from the light guide is coupled at an oblique angle.

[0067] The adhesive layer 222 at the interface between the light guide 82 and the prism portion 75b can advantageously be selected to have a lower refractive index compared to both n1 and n2. This applies whether n1 = n2 or n1 ≠ n2. In the case of n2 = n1, the adhesive 222 can have the same refractive index as the "low refractive index" adhesive used on the inner surface 84, as this minimizes any perturbation to the TIR within the light guide 82 caused by the diffusion (spilling) of the adhesive outside the interface onto the light guide surface. Whenever a projector or a coupling prism is joined to a light guide in the context of a display, using a low refractive index adhesive (i.e., having a refractive index lower than that of any of the adjacent elements) is more generally advantageously applicable and is not limited to the context of the other features of the projector described herein.

[0068] Figure 8A The location designated as 222 in the figure may, in addition to the adhesive layer, accommodate a depolarizer or other polarization modifying element deployed between the PBS prism and the light guide. The polarization modifying element may be a polarization rotator (half-wave plate), a quarter-wave plate, or a birefringent depolarizer having a sufficient thickness relative to the bandwidth of each color to achieve effective depolarization. These components can further enhance the uniformity of the output image.

[0069] To enhance the mechanical strength of the joint between the light guide 82 and the prism portion 75b, plates 224a and / or 224b may be placed at the interface above and / or below the joint. Preferably, a low refractive index adhesive (usually the same as that used at the inner surface 84) is used to join the plates to the structure to avoid disrupting the TIR.

[0070] In embodiments where the light guide 82 is made of a low-refractive-index material such that the available low-refractive-index adhesive does not support TIR within the desired propagation angle range, reflective coatings 226a and / or 226b formed of dielectric or metallic materials can be applied beneath the adhesive layer to maintain high reflectivity within the light guide.

[0071] Turn now Figure 8B This illustrates an alternative construction that avoids potential mechanical weaknesses at the small-area vertical joint between the light guide and the PBS prism. It also circumvents the challenge of assembling a system with precise parallelism between surface 84 and the light guide surface 86. In this case, instead of such a joint, the light guide 82 extends into the prism structure, where the thickness of the light guide 82 is complemented by joining it to the prism portion 75c. In this case, the prism portion constituting the PBS prism and the adhesive used to join portion 75c to the light guide should both be matched to the refractive index of the light guide. The joined combination of the light guide end and the prism portion 75c is then polished at the desired angle to create an optically and functionally equivalent system. Figure 8A The effective prism portion of part 75b. The second prism portion 75a (equivalent to...) Figure 8A The prism portion is placed on top, with the PBS surface 76 deployed at the interface to complete the PBS arrangement. This configuration above the waveguide provides another method for integrating components.

[0072] Although surface 84 is shown here as coplanar with light guide surface 86, surface 84 may alternatively be parallel to light guide surface 86, wherein there is a small step (not shown) between surface 84 and light guide surface 86, which serves as an optical cutoff to prevent light that may be scattered due to defects at the interface between optical elements from entering.

[0073] The PBS surface 76 can be implemented as any suitable type of reflective polarization beamsplitter surface, including but not limited to structured polarizers (e.g., wire grid polarizers) or dielectric polarization beamsplitters. As is known in the art, each option has its own advantages and disadvantages. In each case, the subsequent recombination of the two channels results in high efficiency. The above description involving S-polarization being deflected and P-polarization being transmitted relates to an implementation using a correspondingly oriented dielectric PBS or structured polarizer, which can alternatively be deployed to reverse this function or to separate the channels according to some other desired polarization orientation.

[0074] In this embodiment, if color display is required, the micro-LED array 70 is preferably a color micro-LED array, which may employ effective pixels, each comprising a group of red, green, and blue micro-LEDs, or wherein each pixel cycles sequentially among multiple colors. The micro-LED array is preferably slightly spaced from the PBS prism surface, wherein the field lens 74 is preferably attached to the array, such as... Figure 1A and Figure 1B As shown in the image.

[0075] The reflecting optics 80a and 80b are preferably optically identical to achieve identical images with two polarizations, which can be superimposed in an aligned manner into a single perceived image, the single perceived image having the same content as each individual image. Although functionally described as "reflecting optics," they may each include elements having both reflective and refractive power. Thus, in the implementation shown here, the reflecting optics 80a and 80b are each shown as a doublet lens having refractive power in addition to the reflective lens surface. Using such a doublet lens structure provides additional degrees of freedom to minimize optical aberrations in the system. Many subsequent figures illustrate the reflecting optics more schematically without detail of the internal components; however, it should be noted that the doublet lens implementation is equally relevant and applicable to all embodiments.

[0076] In this non-limiting implementation, the optical power of the reflective optics 80a and 80b is sufficient to collimate the image light from the micro-LED array 70 independently. In other words, the effective focal length of the optics is equal to the optical path length from the optics to the array 70.

[0077] For ease of illustration, the accompanying drawings presented herein and throughout this document focus on the structure of the projector 50 and its coupling with the light guide 82, as these convey the novel features of the light guide-based display system of the present invention. The display system of the present invention is particularly (but not exclusively) suitable for augmented reality displays, such as head-up displays (HUDs) or head-mounted displays (HMDs), and includes many additional components known in the art. These include a support structure for the display, which, in the case of an HMD, may be a housing with a shape factor of eyeglasses or goggles. In such a display, the light guide can achieve one-dimensional or two-dimensional aperture expansion and then couple the image toward the user's eyes, typically using an arrangement of partially reflective tilted surfaces inside the light guide or by a diffraction coupling arrangement. In addition to the components of the light guide-based display system described above, such augmented reality displays may also include: a power supply; a microprocessor; an electronic display driver; and communication components, all depending on the needs of each specific application. These features are well known and will not be described further herein.

[0078] Turn now Figures 2A to 2D These diagrams illustrate the various architectures that can be used to integrate projectors and light guides. Figure 2A The configuration corresponds to Figure 1A and Figure 1B The configuration (simplified by omitting details of the field lens and reflecting optics) is shown, and the following architecture is illustrated, in which the micro-LED array 70 and the first reflecting optics 80a are positioned on one side of surface 84, and the second reflecting optics 80b are positioned on the other side of surface 84 and attached to the wedge prism 88. In this case, one of the polarization channels passes through surface 84 twice. Here and in the remainder of this document, the presence of quarter-wave plates 78a and 78b is assumed to be part of the PBS architecture and will not be explicitly stated or discussed further.

[0079] Figure 2B An alternative architecture for the projector, designated 50', is shown, in which the image generating array 70 is positioned below the light guide (in the indicated orientation) and attached to the wedge prism 88, and the reflecting optics 80a and 80b are both positioned on the surface of the PBS prism above surface 84. In this configuration, all unpolarized image light is introduced from below and passes through surface 84 once. The projector 50' functions substantially the same as the projector 50 described above, except that the direction of the light path from the image generating array 70 to the second reflecting optics 80b is reversed, and the orientation of the PBS surface 76b is flipped relative to the surface 76 of the projector 50.

[0080] Figure 2C This illustrates an alternative implementation using projector 50'', where projector 50'' is... Figure 2A The projector 50 is modified, and can be easily manufactured. The angle of the PBS surface 76c is different from that of the PBS surface 76, thus allowing the active pixel array 70 and the second retroreflective collimating optics 80b to be mounted on a surface parallel to the main surface of the light guide. Here, the wedge prism 88 of the previous implementation is replaced by a planar window 89, or in some cases, there is no window at all. The thickness of the window 89 is chosen to keep the optical path from the active pixel matrix 70 to the first retroreflective collimating optics 80a equal to the optical path to the second retroreflective collimating optics 80b, so that the images have the same size and overlap. In this case, the PBS prism has a non-orthogonal surface, wherein the first retroreflective collimating optics 80a is preferably mounted on a surface with an angle that aligns the optical axis of the optics with the desired angle of the principal ray of the collimated image injected into the light guide (as is common to all integrated embodiments of the invention).

[0081] Figure 2DA similar modification using projector 50''' is shown, which has an active pixel array 70 deployed below the light guide, similar to Figure 2B In this configuration, the PBS surface 76d is oriented such that the active pixel array 70 can be deployed against a flat window 89 adjacent to a surface 84 that maintains total internal reflection (TIR). Other configurations may include field lenses, or there may be no window between the array and surface 84.

[0082] Alignment method

[0083] Turn now Figures 3A to 3D In order to recombine the images returned from two polarization channels into a single projected image without degrading image quality, precise spatial and focal alignment between the two channels must be achieved. Acceptable image quality can be achieved directly when sufficiently low manufacturing tolerances are achievable in both component manufacturing and equipment assembly. However, in some cases, the alignment process is performed during assembly. Figures 3A to 3D Four different options (with or without corresponding structural modifications) are shown for achieving optical alignment and focus matching between two optical channels during the assembly of the display system.

[0084] exist Figure 3A In the figure, optics 80b can be laterally offset (arrow 90a) so that the optical axis of the reflected beam is parallel to the optical axis of 80a (alternately, 80a can be laterally offset), while the relative focus can be equalized by offsetting prism 88 (indicated by arrow 90b). This figure only shows the alignment adjustment in the plane of the figure, but offset 90a also allows for adjustment in the direction of entering the page.

[0085] In practice, all components except the one to be moved for alignment are first joined together, and the interface to be adjusted is provided with uncured adhesive and held in place. The device is arranged such that the output image can be viewed directly or via a camera, and a micro-LED array is actuated to generate a test pattern. Before alignment adjustments, it should be ensured that the unaligned optics 80a generate a correctly focused (collimated) output image, typically by adjusting the spacing between array 70 and the input surface of the PBS prism, as known in the art. Then, prism 88 is moved according to arrow 90b until the second component is also precisely collimated, and then optics 80b is moved according to arrow 90a (including the entry page) until the two components being tested are aligned into a single image. These positions are then fixed by UV curing of the adhesive. Alternatively, these alignment adjustments can be performed automatically by a computerized robotic system under the control of image processing performed on images from a camera monitoring the output image.

[0086] Figure 3B The first reflecting optics 80a and the first PBS prism component 75a are shown modified to join at a surface inclined relative to the optical axis of the optics. Therefore, adjustments in the direction of arrow 90b alter both lateral alignment and axial (focal) offset. Thus, adjusting 90b first is used to adjust the focal point (collimation), and then adjusting 90a can be used to align the optical axis, as before, without affecting the focal point. The actual process is similar to the process described above, where pre-focusing is performed on the image component pointing towards the second reflecting optics 80b.

[0087] Figure 3C It shows the relationship with Figure 3B A similar arrangement, but with the addition of a wedge prism 94 at the interface between the first reflecting optics 80a and the first PBS prism component 75a, introducing additional degrees of freedom. This provides two non-parallel adjustments 90a, 90b in the drawing plane (in addition to the adjustment entering the page), thereby allowing for focus adjustment and lateral alignment at the first reflecting optics 80a.

[0088] exist Figure 3D In this process, the relative focus can be balanced by offsetting the prism portions 75a and 75b relative to each other along the plane of the PBS surface 76 (indicated by arrow 90b). Subsequently, alignment can be achieved by adjusting one or both of the reflective optics 80a and 80b in a plane perpendicular to their respective optical axes (arrow 90a).

[0089] The above are non-limiting examples of available options for achieving such alignment and focus adjustments. More generally, at least two adjustments are required, wherein a first adjustment 90a allows alignment in a plane orthogonal to at least one of the respective optical axes of the reflecting optics, and a second adjustment 90b includes at least one component parallel to one of the optical axes. In some cases, for example in Figure 3C In this process, both adjustments affect both lateral alignment and axial position, requiring simultaneous adjustments of both. In some preferred implementations, for example in... Figure 3A , Figure 3B and Figure 3D In the process, one adjustment is made to be completely orthogonal to the corresponding optical axis, which facilitates the sequential adjustment of the focus, followed by lateral alignment.

[0090] Non-integrated projector implementation

[0091] The above-described implementation of the present invention employs a projector 50 integrated with the light guide 82 to achieve a highly compact configuration. However, in some cases, a differentiated projector architecture may be preferred, which can be optionally used in other applications requiring highly miniaturized projectors. The projector can then be coupled to the light guide using a coupling prism, thereby potentially enabling modularization of the device and simplifying manufacturing and assembly. Figure 4 An example of such an implementation is shown.

[0092] Specifically, Figure 4 A compact projector 52 is shown, operating on the same principle as the projector 50 described above, wherein an active pixel array 70 injects unpolarized light corresponding to the image into a polarization beam splitter (PBS) prism (prism portions 75a, 75b). The image generation array is shown without a field lens, but in other preferred configurations, a field lens may be included. A first reflective collimating optics 80a is associated with a first surface of the PBS prism, and a second reflective collimating optics 80b is associated with a second surface of the PBS prism. Unpolarized image light from the active pixel array enters the PBS prism, where it is split at the PBS prism by a polarization beam splitter surface 76 into a first polarization component directed toward the first reflective collimating optics 80a and a second polarization component directed toward the second reflective collimating optics 80b. The polarized images reflected from the first and second reflective collimating optics are recombined at the PBS surface 76 to generate a mixed polarization projection image. This image is coupled to a light guide 82 via a coupling prism 102. In the example shown here, coupling prism 102 is a transmission coupling prism that presents a coupling surface at an angle, oriented approximately perpendicular to the principal rays of the projected image, which are correctly oriented to propagate within light guide 82. In an alternative embodiment (not shown), the projector may be directly attached to one of the principal surfaces of the light guide, and a reflecting prism may be positioned relative to the other side of the light guide to achieve reflective coupling of the projected image, as is known in the art.

[0093] The use of distinct components for the projector 52 and the coupling prism 102 facilitates the insertion of the refractive lens 100 between them. The refractive lens 100 preferably provides a portion of the collimating optical power, thereby reducing the optical power requirements of the reflective collimating optics 80a and 80b. The use of lower-power reflective optics in combination with the reflective and refractive optical components promotes an optical design with reduced optical aberrations.

[0094] In certain particularly preferred implementations, air space is avoided in the optical path from the point where the image light enters the PBS prism to the point of entry into the light guide. This preferred requirement can be combined with the use of a refractive lens 100 having planar attachment surfaces on both sides. For this purpose, the lens 100 can advantageously be implemented as a doublet lens (as shown) with parallel planar outer surfaces or using a graduated refractive index (“GRIN”) lens. In addition to or instead of the lens 100, other optical components may optionally be included between the projector and the coupling prism. Specifically, these optical components may include polarization rotators (half-wave plates), quarter-wave plates, or birefringent depolarizers with sufficient thickness relative to the bandwidth of each color to achieve effective depolarization. These components can further enhance the uniformity of the output image.

[0095] One advantage of the projector 52 is that it usually does not require the above reference. Figures 3A to 3D The multi-stage alignment process is described. A regular cubic PBS prism can be manufactured with high precision and provides a convenient reference plane for the accurate deployment of components on each face of the cube. Therefore, it is generally feasible to achieve precise alignment of the reflective optics 80a and 80b during manufacturing without an adjustment process. Even if an adjustment process is required, it will typically be limited to a single step of lateral adjustment of one of the reflective optics components on the corresponding plane of the cubic prism. This configuration also allows the projector 52 to rotate about the optical axis of the projected image to any desired angular position to meet image orientation requirements and / or overcome structural constraints.

[0096] Although the descriptions so far have all concerned the use of PBS prisms, the same optical architecture can be achieved, particularly in an implementation where the projector is not integrated with the light guide 82, using a “window PBS” (also known as a “cage-mounted cube beam splitter”), where the PBS surface 76 is a flat plate deployed across a 45-degree diagonal plane (sometimes referred to as the (110) plane, borrowing the Miller index notation) within a cube-shaped open frame. The remaining optical elements are attached to the cage / frame in the same spatial relationship as described so far, and function as described above.

[0097] Color displays employing X-Cube dichroic combiners

[0098] The structure described above uses a single active pixel array to generate a projected image, which can be a monochrome image or a color image generated by a color micro-LED array. However, in some cases, it may be desirable to generate a color image by combining images from several separate monochrome arrays. Figures 6A to 6C This demonstrates how such an implementation is carried out.

[0099] Specifically, according to one aspect of the invention, the active pixel (micro-LED) array image generator of the prior embodiment is replaced by an X-cube dichroic (or “trichroic”) combiner 110, which combines image light from three monochromatic active pixel array image sources. Figure 6A It shows the relationship with Figure 4 The implementation methods corresponding to the implementation methods, Figure 6B It shows the relationship with Figure 2A The implementation methods are the corresponding implementation methods.

[0100] In these embodiments, projectors 58 and 60 employ an X-cube dichroic combiner 110 to combine the optical paths of unpolarized light from panels 70R, 70G, and 70B (as indicated by arrows) into a single unpolarized beam incident on the PBS surface 76. For clarity, only a single central ray from the central pixel of each array is shown; however, each pixel generates a diverging beam, which is combined by the dichroic combiner with the beams from the corresponding pixels of the other two colors and guided into the PBS prism. The beam propagates forward from that point as described above for each corresponding embodiment.

[0101] The structure of this X-cube dichroic combiner is known, and it employs a first diagonal dichroic reflector that reflects one color and transmits the other two colors, and a second diagonal dichroic reflector that reflects a second color and transmits the other two colors. The overall effect is to superimpose light corresponding to the image generated by each array in the array.

[0102] The optical designs of projectors 58 and 60 are essentially similar to those of projectors 50 and 52 described above, modified by adding the length of one side of the X-cube dichroic combiner to the optical path from the active pixel array to the reflective optics. While this might be expected to make the projectors bulkier, this is generally offset by the higher pixel density of the monochrome array compared to the color array which requires multiple micro-LEDs per effective pixel. This allows for a reduction in the overall size of the projector assembly, making the seemingly bulkier structure of projectors 58 and 60 actually more compact than that of projectors 50 and 52.

[0103] One or more refractive lenses may be introduced between each image generation array 70R, 70G and 70B and the X-cube combiner 110 (used as a field lens), and / or between the X-cube combiner 110 and the PBS prism input surface. Figure 6C It shows the relationship with Figure 6BIn a similar implementation, the refractive lens 700 is inserted between the X-cube combiner 110 and the PBS prism input surface. The lens in this location (relatively small in size to the X-cube, optically spaced from the image generation array) serves a dual purpose: modifying the field from the micro-LED array while also contributing optical power to the partial collimation of the image, thereby reducing the optical power required for the reflective optics. The positive field curvature introduced by the refractive element 700 can also help counteract the typically negative field curvature of the reflective collimating optics 80a, 80b, further facilitating efficient optical design to generate high-quality image output.

[0104] While the X-cube configuration is considered particularly advantageous due to its compactness and symmetry, it should be noted that equivalent functionality can be provided using alternative designs with trichroic beam combiners. Another such option is a trichroic beam splitter prism design, best known for its use in 3CCD camera systems. This design avoids the complexity of achieving high-quality cross-dichroic filters.

[0105] Alternative Multi-Array Projector Architecture

[0106] In some preferred embodiments, the image projector may include a set of side-by-side combined image generators with different colors to generate multicolor images from individual monochrome active pixel arrays of different colors. Figure 7A and Figure 7B Such an implementation is shown.

[0107] Figure 7A An embodiment in which a multicolor image is projected onto a two-dimensional optical aperture extension light guide is shown. In this embodiment, the three-color image projector 62 includes a side-by-side assembly of a shared internal partition PBS prism.

[0108] Figure 7B It shows Figure 7A The three-color image projector 62 is implemented in this way. In this embodiment, a single PBS prism with a shared PBS surface 76 is used. The PBS prism may have a single continuous top and bottom prism portion shared by all channels, or may include a separator 96a in one or two prisms to minimize crosstalk between channels. The bottom prism portion 88 may also have a separator 96b. The "separator" is typically an absorbing surface, such as a black coating, applied between the portions before they are joined together. Most preferably, the prism portion 75b closest to the outlet aperture is implemented as a continuous single prism without any internal separators, thereby allowing overlap of outlet apertures for different colors.

[0109] Individually illuminating active pixel arrays 70R, 70G, and 70B transmit image light to the PBS prism. Individual reflective collimating optics 80aR, 80aG, and 80aB reflect and collimate one polarization, respectively, while another set of reflective collimating optics 80bR, 80bG, and 80bB (in...) Figure 7B (See image) The two polarized collimated beams of each color are reflected and collimated separately. The two polarized collimated beams are recombined at 76 on the PBS surface, and the combined polarized image beams from all channels (R, G, B) enter the light guide side-by-side, as shown. Figure 7A As shown in the diagram. Using a single PBS surface 76 minimizes channel misalignment, simplifies integration, and reduces cost. Furthermore, in such a configuration (assuming the separator is not near the output), the outlet apertures can overlap, thus ensuring high coupling efficiency while reducing size.

[0110] Incidentally, Figure 7A A projector 62 is illustrated in the context of a two-dimensional aperture-expanding light guide comprising a first light guide portion 82a. This first light guide portion 82a includes a redirection configuration for gradually redirecting light propagating within the light guide portion 82a in a first direction (as shown to the left) to propagate within the light guide towards a second light guide portion 82b (as shown downwards), while horizontally expanding the effective optical aperture. The second light guide portion 82b includes a coupling configuration that gradually couples the propagation towards the user's eye, while vertically expanding the effective optical aperture. In the schematic, non-limiting example shown here, the redirection configuration is implemented as a first set of partially reflective inner surfaces 212a, and the coupling configuration is implemented as a second set of partially reflective inner surfaces 212b at an angle relative to the main light guide surface. As is known in the art, one or both of these sets of inner reflective elements can be replaced by one or more diffractive optical elements to achieve similar functionality.

[0111] Figure 7CAn embodiment of a projector 64, substantially similar to projector 62, is shown, wherein three pixel arrays and three pairs of reflective collimating optics are combined to use a common PBS prism with a shared PBS surface 76. In this case, the first reflective collimating optics 80a1, 80a2, 80a3 (and the corresponding second reflective collimating optics, not visible in this view) of each channel are offset relative to the corresponding pixel array 70, such that the output beams 216, 218, and 220 are not parallel to each other. In such a configuration, each panel projects a different portion of the horizontal field of view of the final image. The panels can be rotated, tilted, and have off-axis field lenses (not shown) to generate minimal aberrations and distortion for each image portion. In the particularly preferred configuration shown here, the lowest projected image 220 needs to propagate the farthest within the light guide, while the uppermost beam 216 propagates the shortest distance across the light guide. Therefore, as shown in the figure, the size of the light guide portion 82a, including reflector 212a, can be reduced.

[0112] Separate integrated projector implementation method

[0113] The above reference Figures 1A to 2B The described implementation employs an image projector 50 or 50' integrated with the light guide 82 at the edge of the light guide. Figure 9 The variant implementation of this embodiment shown in the figure provides a projector 130 in which the polarizing beam splitter prism is separated into two parts, which are respectively attached to the upper and lower parallel main surfaces of the light guide and aligned in a relative relationship.

[0114] Specifically, such as Figure 9 As shown, in this configuration, the PBS prism is formed by a first prism portion 120a located above the PBS surface 76 (in the orientation shown), a second prism portion 120b located below the PBS surface 76, the thickness of the light guide 82 itself, and a lower prism portion 120c deployed below the light guide (in the orientation shown here). The second prism portion 120b is bonded to the light guide surface 87 by a refractive index-matching adhesive to allow an image from the projector to be injected into the light guide, while the lower prism 120c is bonded to the light guide surface 86 by a low refractive index adhesive to provide angle-selective reflection characteristics of the inner surface 84, thereby providing functionality equivalent to the embodiment described above.

[0115] The optical performance of projector 130 is completely similar to that of projector 50 described above. Unpolarized image light from the active pixel array 70 passes through field lens 74 and enters the upper PBS prism portion 120a. At the upper PBS prism portion 120a, this unpolarized image light is split by polarization beamsplitter surface 76 into a first polarization component directed toward the first reflective collimating optics 80a, and a second polarization component directed toward the second reflective collimating optics 80b, passing through the second prism portion 120b, the thickness of the light guide 82, and the lower prism portion 120c. The polarized images reflected from the first and second reflective collimating optics are recombine at the PBS surface 76 to generate a mixed polarization projection image. This mixed polarization projection image is guided through the second prism portion 120b and the refractive index-matching adhesive at the boundary with the light guide to be coupled into the light guide 82 for propagation within the light guide.

[0116] It should be noted that the configuration of the projector 130 is advantageous for a range of applications, not limited to the parallel processing of unpolarized image sources and / or two orthogonally polarized images. Therefore, in some cases, only the first or second optical path exists, and can be advantageously used, for example, in other respects as described below. Figure 10 and Figures 11A to 11D The configuration discussed is similar to other configurations. In other applications, as shown, dual-polarization optics are used for processing and recombination.

[0117] The ability to deploy the projector 130 on the main surface (i.e., not limited to deployment at the very edge of the light guide) opens up the possibility of deploying projector arrays in various geometric configurations. Reference will now be made to... Figures 10 to 11D Discuss possible deployment examples.

[0118] Turn now Figure 10 In one application, two or more similar image projectors 130 are deployed sequentially along a light guide, with each image projector projecting a monochrome image of a different color. Thus, in the example shown here, the first image projector 130R has an active pixel matrix 70R that generates a red image, the second image projector 130G has an active pixel matrix 70G that generates a green image, and the third image projector 130B has an active pixel matrix 70B that generates a blue image. The three colors of images propagate along the light guide and together generate a color image viewed by the user.

[0119] As before, a low-refractive-index adhesive is used to implement the inner surface 84 of each image projector. This low-refractive-index adhesive maintains internal reflection of the image propagating within the light guide, thus preventing leakage through the continuous projectors at surface 84. Regarding the upper attachment surface, surface 122G must be provided with a dichroic coating that is transparent to green light and reflects blue light, thereby preventing "leakage" of the blue image incident by projector 130B. Similarly, in the sequential deployment shown here, the upper attachment surface 122R must be provided with a dichroic coating that is transparent to red light but reflects both green and blue light. The first upper attachment surface 122B in the row can be implemented using a simple refractive index-matching adhesive without a coating.

[0120] As before, although sequential deployment may seem cumbersome, monochrome projectors can be implemented using display arrays with high pixel density, which can facilitate the miniaturization of components.

[0121] In some cases, instead of a single-row deployment, it can be achieved by using, for example Figure 11A and Figure 11B The staggered configuration shown achieves a more compact arrangement of projectors 130R, 130G, and 130B. In each case, the projector housing is wider than the output aperture, which limits how closely the projectors can be arranged side-by-side in a row. By staggering the projectors, the spacing between apertures used to inject different colors can be brought closer together compared to what is otherwise possible, resulting in a smaller light guide. In the example shown here, the staggering is achieved by positioning the projectors with two adjacent projectors, and a third projector aligned between the two adjacent projectors and positioned behind or in front of the other projectors. In an alternative implementation (not shown), three or more projectors can be staggered in a row, one after the next, with partial overlap. Depending on the size of the aperture through which the introduced image passes and the in-plane angular extension of the projection field, overlap between the propagating image within the light guide and the apertures of other projectors can be avoided, thus preventing interference with the image. Figure 10 The dichroic filter described herein is required. If overlap exists, a relatively simple dichroic coating that separates the two colors is sufficient. Therefore, Figure 11B Functionally similar to the above Figure 7A Similarly, but using three separate projectors: 130R, 130G, and 130B.

[0122] Figure 11C and Figure 11D A similar staggered deployment of multiple projectors 130a, 130b, and 130c is shown, these projectors being oriented with non-parallel projection directions to project different areas of the projected image. This is functionally similar to the aforementioned... Figure 7C Similarly, and as described therein, it allows for a reduction in the size of the first light guide portion 82a.

[0123] Rectangular light guide implementation

[0124] The various implementations discussed so far all involve the injection of an image for propagation within a plate-shaped light guide defined by a pair of mutually parallel main surfaces. However, the same principle can be applied to injecting an image into a light guide with a rectangular cross-section, which supports image propagation through quadruple internal reflection, as will now be referred to. Figure 12 The rectangular cross-section light guide described above is extensively discussed in PCT patent application publication WO 2018 / 065975 A1 and can be used to facilitate the expansion of the optical aperture in the first dimension before injecting an image into a second plate-type light guide.

[0125] See Figure 12 This illustrates the application of the invention to a light guide 83, which, in addition to a first pair of mutually parallel main surfaces 86 and 87, has a second pair of mutually parallel main surfaces 89 and 91 perpendicular to the first pair of mutually parallel main surfaces. This defines a rectangular cross-section light guide that supports light propagation via quadruple internal reflection. A projector 150 is provided to inject an image into the light guide 83. The projector 150 is substantially similar to the projector 50 described above, and is based on a PBS prism having image light injected from an active matrix array 70, which is split into two polarization components by a polarization beamsplitter surface 76 and collimated in two channels by a first reflection collimating optics 80a and a second reflection collimating optics 80b, respectively. The two polarized images are then recombine through the PBS surface 76 to be injected into the light guide 83, which is achieved in part by reflection at the inner surface 84, all of which are similar to the description of the projector 50 above. In this case, the PBS prism is also tilted relative to the axis of the light guide, so that the mixed polarization image leaving the polarization beam splitter prism is tilted relative to the rectangular cross section of the light guide to propagate within the light guide by quadruple internal reflection.

[0126] To more clearly illustrate the PBS tilt, the tilt required for injection into the rectangular light guide is the tilt of the principal ray of the projected image relative to both surface 86 (the rear surface as shown) and surface 89 (the bottom surface as shown). The required tilt of the principal ray relative to surface 86 is determined by... Figures 1A to 2A A similar geometric shape can be used, as seen when viewed from above. Figure 12 What you see. The tilt relative to surface 89 is achieved by the additional upward tilt of the projector's PBS prism, as viewed from the front. Figure 12As you can see, the injected image is trimmed by edges 6a and 6b, which can be staggered as shown, or they can be coplanar.

[0127] In all other respects, Figure 12 The implementation method is structurally and functionally similar to Figure 1A The implementation method is similar and can be fully understood by analogy with the description above.

[0128] Polarization Modified Reflection SLM Implementation

[0129] Final turn Figures 5A to 5D Although the implementations discussed so far involve injecting unpolarized image light from an active pixel array and preferably using a recombination of two polarization channels, certain aspects of the optical architecture described herein can also be advantageously used in the context of polarized image sources, and most notably polarization-modified spatial light modulators (SLMs), such as liquid crystal on silicon (LCOS) display chips. Figures 5A to 5D Such an implementation is shown. Due to... Figures 1A to 4 Due to the structural similarities of various implementations, these implementations are therefore included herein. However, in Figures 5A to 5D In this implementation, the image generation process itself generates a polarized image; therefore, there is no polarization recycling or recombination. Instead, the second optical channel is used for illumination.

[0130] Figures 5A to 5C An implementation based on a single LCOS is shown, wherein Figure 5A A sample ray is shown, illustrating the overall optical path of both the illumination entering LCOS 106 and the reflected image (light modulated by LCOS) entering light guide 82. For clarity, Figure 5B Only the path of the illuminating light is shown. Figure 5C Only the reflected image ray path entering the light guide 82 is shown.

[0131] Illumination is injected into the projector from illumination channel 104, which provides polarized illumination directly or indirectly. This illumination channel may include a light pipe, diffuser, Fresnel lens, dichroic combiner, mirror, laser, or other optical element or source. An illumination inlet aperture is located near the outlet aperture to inject the image into the light guide. The injected light from illumination channel 104 is polarized to be reflected by polarization beam splitter surface 76. The reflected polarized light propagates onto a tilted reflecting lens 108 (see...). Figure 5BThe lens incorporates a waveplate that orthogonally polarizes the reflected light. The orthogonally polarized reflected light passes through the PBS surface 76 to illuminate the LCOS 106. The reflected light from the LCOS is modulated to generate an image, which is then followed... Figure 5C The optical path shown includes reflection at the PBS surface 76, reflection at the reflective collimating optics 80a, collimation and polarization rotation (through a quarter-wave plate), transmission through the PBS surface 76, and coupling into the light guide 82, which includes at least a portion of the light reflected by the inner surface 84. By appropriately selecting the characteristics of the reflective illumination lens 108, the illumination aperture 104 is imaged onto the exit aperture (the entrance of the light guide), thereby reducing light loss.

[0132] Figure 5D An alternative illumination arrangement is shown. In this embodiment, illumination passes through a TIR-supporting surface 84. Light from source 200 (e.g., an LED) is extended by a lens or prism or light tube 201 to be reflected by surface 202 toward LCOS 106. A polarizer is positioned at surface 84 to ensure that only the polarized component to be transmitted through PBS surface 76 enters the PBS prism. This light then illuminates LCOS 106. The remainder of the optical path is the same as described above. Figure 5C The descriptions are the same.

[0133] It will be understood that the above description is intended to be illustrative only, and many other embodiments are possible as defined within the scope of the invention as set forth in the appended claims.

Claims

1. A light guide-based display system, comprising: (a) A light guide formed of a transparent material and having a pair of mutually parallel main surfaces that support the propagation of image light by internal reflection, the light guide including a set of mutually parallel partially reflective inner surfaces that are deployed to couple out light propagating within the light guide to exit the light guide. as well as (b) An image projector coupled to the light guide to inject a collimated image into the light guide, the image projector comprising: (i) At least one active pixel array, said active pixel array being configured to generate unpolarized light corresponding to an image, (ii) A polarizing beam splitter (PBS) prism, the PBS prism being deployed to receive the unpolarized light from the active pixel array, the PBS prism including a PBS surface configured to split the unpolarized light into a first polarized optical path and a second polarized optical path. (iii) A first retroreflective collimating optics, the first retroreflective collimating optics being associated with the first polarization path, and (iv) A second retroreflective collimating optics, which is associated with the first polarization path. The retroreflected polarization images received from the first and second retroreflected collimating optics are recombined through the PBS surface to be injected into the light guide as a superimposed mixed polarization image.

2. The light guide-based display system according to claim 1 or 21, wherein, The polarization beam splitter prism provides an angle-selective reflective surface that is coplanar or parallel to one of the main surfaces of the light guide. The angle-selective reflective surface is through which at least a portion of the light corresponding to the image before recombination passes, and the angle-selective reflective surface reflects at least a portion of the mixed polarization image before the mixed polarization image reaches the entrance aperture of the light guide.

3. The light guide-based display system according to claim 2, wherein, The angle-selective reflective surface is provided by a layer or air gap of a low-refractive-index adhesive, the path of at least one polarization component of the image passes through the angle-selective reflective surface, and at least a portion of the mixed polarized image undergoes internal reflection at the angle-selective reflective surface of the light guide within the PBS prism.

4. The light guide-based display system of claim 3 further includes an anti-reflective coating on a surface adjacent to the low-refractive-index adhesive or air gap for minimizing loss in the light path passing through the angle-selective reflective surface.

5. The light guide-based display system according to any one of claims 1 to 4, wherein, The polarizing beam splitter prism includes a first part and a second part, which are attached to the mutually parallel main surfaces of the light guide and aligned in a relative relationship.

6. The light guide-based display system according to claim 5, wherein, The image projector is one of a plurality of similar image projectors deployed sequentially along the light guide, wherein the first of the image projectors projects an image of a first color, and wherein the second of the image projectors projects an image of a second color different from the first color, wherein the main portion of the PBS prism of the second image projector is attached to the light guide by an adhesive with a refractive index matching covering a dichroic layer, the dichroic layer being transparent to the second color and reflective to the first color.

7. The light guide-based display system of claim 1 further includes a transmission or reflection coupling prism configured to couple the hybrid polarization image to the light guide.

8. The light guide-based display system according to claim 7 further includes a refractive lens inserted between the PBS prism and the coupling prism, the refractive lens supplementing the optical power of the first retroreflective collimating optics and the second retroreflective collimating optics to achieve collimation of the mixed polarization image.

9. The light guide-based display system according to claim 7, wherein, The optical path from the entrance to the PBS prism via the first retroreflective collimating optics and the second retroreflective collimating optics and the coupling prism does not pass through any air gap before entering the light guide.

10. The light guide-based display system according to any one of claims 1, 2, and 7, wherein, The polarization beam splitter prism is configured such that the first retroreflective collimating optics is tilted relative to the axis of the light guide to guide the mixed polarization image to propagate within the light guide.

11. The light guide-based display system according to any one of claims 1, 2, and 7, wherein, The at least one active pixel array includes a color micro-LED array.

12. The light guide-based display system according to any one of claims 1, 2, and 7, wherein, The active pixel array is spaced apart from the surface of the polarizing beam splitter prism, and the field lens is attached to the active pixel array.

13. The light guide-based display system according to any one of claims 1, 2, and 7, wherein, The at least one active pixel array includes three monochromatic arrays combined on the face of a dichroic X-cube prism to provide the unpolarized image light to the polarizing beam splitter prism.

14. The light guide-based display system of claim 13, further comprising a lens inserted between the dichroic X-cube prism and the polarizing beam splitter prism, the lens providing a portion of the collimating power.

15. The light guide-based display system according to any one of claims 1, 2, and 7, wherein, The light guide further includes a second pair of parallel main surfaces perpendicular to the first pair of parallel main surfaces, thereby defining a rectangular cross-section light guide that supports the propagation of light through quadruple internal reflection, and wherein the polarizing beam splitter prism is configured such that the first retroreflective collimating optics is tilted relative to the rectangular cross-section of the light guide to guide the mixed polarization image to propagate within the light guide through quadruple internal reflection.

16. The light guide-based display system according to any one of claims 1, 2, and 7, wherein, The optical power of the first and second retroreflective collimating optics is supplemented by the refractive optics at the entrance or exit of the polarization beam splitter prism to achieve collimation of the mixed polarization image.

17. The light guide-based display system according to any one of claims 1, 2 and 7, further comprising a depolarizer or other polarization modification element disposed between the PBS prism and the light guide.

18. A method for projecting an image in a light guide-based display system, the method comprising: (a) Generating unpolarized image light from at least one active pixel array; (b) The unpolarized image light is received by a polarizing beam splitter prism; (c) The received unpolarized image light is separated into a first polarization component guided toward the first retroreflective collimating optics and a second polarization component guided toward the second retroreflective collimating optics by the PBS surface within the polarization beam splitter prism; (d) The PBS surface within the polarization beam splitter prism recombines at least partially collimated polarization images received by reflections of the first polarization component and the second polarization component from the first and second retroreflective collimating optics, respectively, to generate a superposition of collimated polarization images as a mixed polarization image. as well as (e) The mixed polarization image is coupled to an optical guide formed of a transparent material and having a pair of parallel main surfaces, such that the mixed polarization image propagates within the optical guide by internal reflection.

19. The method according to claim 18, wherein, The optical power of the first and second retroreflective collimating optics is supplemented by at least one refractive lens deployed in the optical path before or after the PBS prism, such that the mixed polarization image coupled to the light guide is a collimated image.

20. The method according to claim 18, wherein, The first and second retroreflective collimating optics have sufficient optical power to collimate the first polarization component and the second polarization component, respectively, so that the mixed polarization image coupled to the light guide is a collimated image.

21. A light guide-based display system, comprising: (a) A light guide formed of a transparent material and having a pair of mutually parallel main surfaces that support the propagation of image light by internal reflection, the light guide including a set of mutually parallel partially reflective inner surfaces that are deployed to couple out light propagating within the light guide to exit the light guide. as well as (b) An image projector coupled to the light guide to inject a collimated image into the light guide, the image projector comprising: (i) At least one active pixel array, said active pixel array being configured to generate unpolarized light corresponding to an image, (ii) A polarizing beam splitter (PBS) prism, the PBS prism being deployed to receive the unpolarized light from the active pixel array, the PBS prism including a PBS surface configured to split the unpolarized light into a first polarized optical path and a second polarized optical path. (iii) A first retroreflective collimating optics, the first retroreflective collimating optics being associated with the first polarization path, and (iv) A second retroreflective collimating optics, which is associated with the first polarization path. The retroreflected polarization images received from the first and second retroreflected collimating optics are recombined through the PBS surface to be injected into the light guide as a superimposed mixed polarization image.

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