Embedded Image Pipe

Abstract

The optical device may include a combining assembly configured to receive a collimated image beam and provide a first output image beam and a second output image beam, an image pipe configured to receive the first output image beam at an image pipe input section and provide at least one propagating image beam at an image pipe output section, a first waveguide having a first waveguide back surface and configured to receive the second output image beam and emit a first expanded output image beam from the first waveguide back surface, and a second waveguide having a second waveguide back surface and configured to receive the at least one propagating image beam and emit a second expanded output image beam from the second waveguide back surface.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of priority under 35 U.S.C. § 119(e) to U.S. Patent Application No. 63 / 392,904, filed Jul. 28, 2022, entitled “Embedded Image Pipe,” the entire disclosure of which is hereby incorporated by reference in its entirety.

[0002] Unless otherwise noted herein, the materials described in this section are not prior art to the claims of this application and are not admitted to be prior art by virtue of their inclusion in this section. This disclosure generally relates to systems, devices, and methods for presenting optical information, and more particularly, to head - mounted displays (HMDs) and smart glasses (SGs) having a near - eye display (NED) for presenting optical information to a user.

Background Art

[0003] Conventional wearable optical devices such as head - mounted optical displays and smart glasses having a near - eye display are typically large and often heavy. Such devices may also suffer from performance limitations based on a limited field of view (FoV) and sometimes limited options for injecting images that may require a large input aperture. This can limit the usability of such devices. Further, the electronic components that drive these HMDs and SGs typically consume a significant amount of power, which leads to a low battery life, yet these devices can still provide, for example, unclear, extended images. What is needed are solutions to address these problems.

Summary of the Invention

[0004] According to an example, an optical device is generally described. The optical device includes a coupling assembly configured to receive a collimated image beam and provide a first output image beam and a second output image beam, an image pipe configured to receive the first output image beam at an image pipe input and provide at least one propagating image beam at an image pipe output, a first waveguide having a first waveguide back surface and configured to receive the second output image beam and emit a first expanded output image beam from the first waveguide back surface, and a second waveguide having a second waveguide back surface and configured to receive at least one propagating image beam and emit a second expanded output image beam from the second waveguide back surface.

[0005] According to this example, in the optical device, the coupling assembly further includes a translucent mirror having a first surface of the translucent mirror and a second surface of the translucent mirror opposite to the first surface of the translucent mirror. The first surface of the translucent mirror is configured to receive a collimated image beam and provide a first output image beam reflected from the first surface of the translucent mirror and a second output image beam emitted from the second surface of the translucent mirror. In the optical device, the first waveguide includes a first aperture expander of the first waveguide and a second aperture expander of the first waveguide. The first aperture expander of the first waveguide is configured to expand the second output image beam and provide a first plurality of expanded image beams of the first waveguide directed to the second aperture expander of the first waveguide. The second aperture expander of the first waveguide is configured to expand the first plurality of expanded image beams of the first waveguide and provide a second plurality of expanded image beams of the first waveguide emitted as a first expanded output image beam. The second waveguide includes a mirror configured to receive at least one propagating image beam and provide at least one reflected propagating image beam. The second waveguide further includes a first aperture expander of the second waveguide and a second aperture expander of the second waveguide. The first aperture expander of the second waveguide is configured to expand the at least one reflected propagating image beam and provide a first plurality of expanded image beams of the second waveguide directed to the second aperture expander of the second waveguide. The second aperture expander of the second waveguide is configured to expand the first plurality of expanded image beams of the second waveguide and provide a second plurality of expanded image beams of the second waveguide emitted as a second expanded output image beam. The optical device may further include an image projector configured to provide a collimated image beam based on a digital image. The collimated image beam is infinitely collimated, and the projector includes a liquid crystal on silicon display.

[0006] According to another example, an optical system is generally described. The optical system includes an image projector configured to provide a collimated image beam based on a digital image, a combining assembly configured to receive the collimated image beam and provide a first output image beam and a second output image beam, an image pipe configured to receive the first output image beam at an image pipe input and provide at least one propagating image beam at an image pipe output, a first waveguide having a first waveguide back face and configured to receive the second output image beam and emit a first expanded output image beam from the first waveguide back face, and a second waveguide having a second waveguide back face and configured to receive at least one propagating image beam and emit a second expanded output image beam from the second waveguide back face.

[0007] According to this example, in an optical system, a collimated image beam is collimated to infinity, the projector includes one of a liquid crystal display, a liquid crystal on silicon display, an organic light emitting diode display, a micro light emitting diode display, and a laser display, the image pipe includes at least one of a glass material, an acrylic material, and a polycarbonate material, a portion of the first waveguide is fixed to a portion of the image pipe with a layer of a low refractive index adhesive, the image pipe is an elongated transparent member having a first end and a second end with a rectangular cross section and orthogonal walls, the image pipe is configured to receive at least one input image beam and provide four replicated output image beams based on the at least one input image beam, and is one of them.In an optical system, the coupling assembly includes a translucent mirror having a first surface of the translucent mirror and a second surface of the translucent mirror opposite the first surface of the translucent mirror. The first surface of the translucent mirror is configured to receive a collimated image beam and provide a first output image beam reflected from the first surface of the translucent mirror and a second output image beam emitted from the second surface of the translucent mirror. The first waveguide includes a first aperture expander of the first waveguide and a second aperture expander of the first waveguide. The first aperture expander of the first waveguide is configured to expand the second output image beam and provide a first plurality of expanded image beams of the first waveguide directed to the second aperture expander of the first waveguide. The second aperture expander of the first waveguide is configured to expand the first plurality of expanded image beams of the first waveguide and provide a second plurality of expanded image beams of the first waveguide emitted as a first expanded output image beam. The second waveguide includes a mirror configured to receive at least one propagating image beam and provide at least one reflected propagating image beam. The second waveguide further includes a first aperture expander of the second waveguide and a second aperture expander of the second waveguide. The first aperture expander of the second waveguide is configured to expand the at least one reflected propagating image beam and provide a first plurality of expanded image beams of the second waveguide directed to the second aperture expander of the second waveguide. The second aperture expander of the second waveguide is configured to expand the first plurality of expanded image beams of the second waveguide and provide a second plurality of expanded image beams of the second waveguide emitted as a second expanded output image beam.

[0008] According to this example, in the optical system, the coupling assembly includes a polarization beam splitter having a first side of the polarization beam splitter and a second side of the polarization beam splitter opposite to the first side of the polarization beam splitter. The first side of the polarization beam splitter is configured to receive a collimated image beam, provide a first output image beam from the first side of the polarization beam splitter, and provide a transmitted image beam from the second side of the polarization beam splitter. The optical system further includes a half-wave plate having a first side of the half-wave plate and a second side of the half-wave plate. The first side of the half-wave plate is configured to receive the transmitted image beam and provide a second output image beam from the second side of the half-wave plate. In the optical system, the first waveguide includes a first aperture expander of the first waveguide and a second aperture expander of the first waveguide. The first aperture expander of the first waveguide is configured to expand the second output image beam and provide a first plurality of expanded image beams of the first waveguide directed to the second aperture expander of the first waveguide. The second aperture expander of the first waveguide is configured to expand the first plurality of expanded image beams of the first waveguide and provide a second plurality of expanded image beams of the first waveguide emitted as a first expanded output image beam. The second waveguide includes a first aperture expander of the second waveguide and a second aperture expander of the second waveguide. The first aperture expander of the second waveguide is configured to expand at least one propagated image beam and provide a first plurality of expanded image beams of the second waveguide directed to the second aperture expander of the second waveguide. The second aperture expander of the second waveguide is configured to expand the first plurality of expanded image beams of the second waveguide and provide a second plurality of expanded image beams of the second waveguide emitted as a second expanded output image beam.

[0009] According to this example, in an optical system, the coupling assembly includes an active half-wave plate liquid crystal element configured to receive a collimated image beam and provide a converted image beam, a first side of a polarization beam splitter, and a second side of the polarization beam splitter opposite to the first side of the polarization beam splitter, the polarization beam splitter being configured such that the first side of the polarization beam splitter receives the converted image beam and provides a first output image beam from the first side of the polarization beam splitter and a transmitted image beam from the second side of the polarization beam splitter; a half-wave plate having a first side of the half-wave plate and a second side of the half-wave plate, the half-wave plate being configured to receive the transmitted image beam at the first side of the half-wave plate and provide a second output image beam from the second side of the half-wave plate. The optical system further includes a first waveguide including a first aperture expander of the first waveguide and a second aperture expander of the first waveguide, the first aperture expander of the first waveguide being configured to expand the second output image beam and provide a first plurality of expanded image beams of the first waveguide directed to the second aperture expander of the first waveguide, the second aperture expander of the first waveguide being configured to expand the first plurality of expanded image beams of the first waveguide and provide a second plurality of expanded image beams of the first waveguide emitted as a first expanded output image beam; a second waveguide including a mirror configured to receive at least one propagating image beam and provide at least one reflected propagating image beam, the second waveguide further including a first aperture expander of the second waveguide and a second aperture expander of the second waveguide, the first aperture expander of the second waveguide being configured to expand the at least one reflected propagating image beam and provide a first plurality of expanded image beams of the second waveguide directed to the second aperture expander of the second waveguide, the second aperture expander of the second waveguide being configured to expand the first plurality of expanded image beams of the second waveguide and provide a second plurality of expanded image beams of the second waveguide emitted as a second expanded output image beam.

[0010] According to this example, in the optical system, the first waveguide includes a first aperture expander of the first waveguide and a second aperture expander of the first waveguide. The first aperture expander of the first waveguide is configured to expand a second output image beam and provide a first plurality of expanded image beams of the first waveguide directed to the second aperture expander of the first waveguide. The second aperture expander of the first waveguide is configured to expand the first plurality of expanded image beams of the first waveguide and provide a second plurality of expanded image beams of the first waveguide that are emitted as a first expanded output image beam. The second waveguide includes a first aperture expander of the second waveguide and a second aperture expander of the second waveguide. The first aperture expander of the second waveguide is configured to expand at least one propagating image beam and provide a first plurality of expanded image beams of the second waveguide directed to the second aperture expander of the second waveguide. The second aperture expander of the second waveguide is configured to expand the first plurality of expanded image beams of the second waveguide and provide a second plurality of expanded image beams of the second waveguide that are emitted as a second expanded output image beam.In an optical system, the image pipe is a first image pipe, the first waveguide includes a first waveguide front surface that is opposite to the first waveguide back surface, the optical system further includes a third waveguide having a third waveguide back surface, the third waveguide is configured to receive a second output image beam and emit a third expanded output image beam from the third waveguide back surface, the third waveguide back surface is fixed to the first waveguide front surface, the third waveguide is configured to receive the second output image beam and provide at least one propagated third image beam at a third image pipe output section, a second image pipe configured to provide at least one propagated third image beam, a first aperture expander of the third waveguide configured to expand at least one propagated third image beam and provide a first plurality of expanded image beams of the third waveguide, and a second aperture expander of the third waveguide configured to expand the first plurality of expanded image beams and provide a second plurality of expanded image beams of the third waveguide that are emitted as the third expanded output image beam, wherein the second image pipe is configured to surround at least a portion of the second aperture expander of the third waveguide. The optical system further includes a frame configured to support an image projector, a coupling assembly, an image pipe, a first waveguide, and a second waveguide, and the frame is configured to conceal the image pipe within a portion of the frame.

[0011] According to yet another example, the optical system may include an image projector configured to provide a collimated image beam based on a digital image, a combining assembly configured to receive the collimated image beam and provide a first output image beam and a second output image beam, a first image pipe configured to receive the first output image beam at a first image pipe input and provide at least one first propagating image beam at a first image pipe output, a second image pipe configured to receive the second output image beam at a second image pipe input and provide at least one second propagating image beam at a second image pipe output, a first waveguide having a first waveguide back surface and configured to receive at least one second propagating image beam and emit a first expanded output image beam from the first waveguide back surface, and a second waveguide having a second waveguide back surface and configured to receive at least one first propagating image beam and emit a second expanded output image beam from the second waveguide back surface.

[0012] According to this example, in an optical system, the coupling assembly includes an active half-wave plate liquid crystal element configured to receive a collimated image beam and provide a converted image beam, a first side of a polarization beam splitter, and a second side of the polarization beam splitter opposite to the first side of the polarization beam splitter. The polarization beam splitter is configured such that the first side of the polarization beam splitter receives the converted image beam and provides a second output image beam from the first side of the polarization beam splitter and a transmitted image beam from the second side of the polarization beam splitter. A quarter-wave plate having a first side of the quarter-wave plate and a second side of the quarter-wave plate, the quarter-wave plate being configured to receive the transmitted image beam at the first side of the quarter-wave plate and provide a converted image beam from the second side of the quarter-wave plate. A mirror having a reflective mirror surface configured to receive the converted image beam and provide a reflected image beam, the quarter-wave plate being configured to receive the reflected image beam at the second side of the quarter-wave plate and provide a second converted image beam from the first side of the quarter-wave plate, and the polarization beam splitter being configured to receive the second converted image beam at the second side of the polarization beam splitter and provide a first output image beam.

[0013] According to this example, in the optical system, the first waveguide includes a first mirror configured to receive at least one second propagating image beam and provide at least one reflected second propagating image beam. The first waveguide further includes a first aperture expander of the first waveguide and a second aperture expander of the first waveguide. The first aperture expander of the first waveguide is configured to expand at least one reflected second propagating image beam and provide a first plurality of expanded image beams of the first waveguide directed toward the second aperture expander of the first waveguide. The second aperture expander of the first waveguide is configured to expand the first plurality of expanded image beams of the first waveguide and provide a second plurality of expanded image beams of the first waveguide emitted as a second expanded output image beam. The second waveguide includes a second mirror configured to receive at least one first propagating image beam and provide at least one reflected first propagating image beam. The second waveguide further includes a first aperture expander of the second waveguide and a second aperture expander of the second waveguide. The first aperture expander of the second waveguide is configured to expand at least one reflected first propagating image beam and provide a first plurality of expanded image beams of the second waveguide directed toward the second aperture expander of the second waveguide. The second aperture expander of the second waveguide is configured to expand the first plurality of expanded image beams of the second waveguide and provide a second plurality of expanded image beams of the second waveguide emitted as a second expanded output image beam.In an optical system, a first waveguide includes a first waveguide front face that is opposite to the first waveguide back face. The optical system further includes a third waveguide having a third waveguide back face, configured to receive at least one second propagating image beam and emit a third expanded output image beam from the third waveguide back face, wherein the third waveguide back face is fixed to the first waveguide front face. The third waveguide includes a third image pipe configured to receive at least one second propagating image beam and provide at least one propagated third image beam at a third image pipe output section, a first aperture expander of the third waveguide configured to expand at least one propagated third image beam and provide a first plurality of expanded image beams of the third waveguide, and a second aperture expander of the third waveguide configured to expand the first plurality of expanded image beams and provide a second plurality of expanded image beams of the third waveguide that are emitted as the third expanded output image beam, wherein a second image pipe is configured to surround at least a portion of the second aperture expander of the third waveguide and the second image pipe has a homogenizing layer.

[0014] According to this example, in the optical system, the second waveguide includes a second waveguide front surface that is opposite to the second waveguide back surface, and the optical system includes a first side of a polarization beam splitter and a second side of the polarization beam splitter that is opposite to the first side of the polarization beam splitter, and the polarization beam splitter is configured such that the first side of the polarization beam splitter receives at least one first propagating image beam and provides a second transmitted image beam from the second side of the polarization beam splitter; a half-wave plate having a first side of the half-wave plate and a second side of the half-wave plate, and the half-wave plate is configured to receive the second transmitted image beam on the first side of the half-wave plate and provide a second converted image beam from the second side of the half-wave plate; a fourth waveguide having a fourth waveguide back surface, configured to receive the second converted image beam and emit a fourth expanded output image beam from the fourth waveguide back surface, and the fourth waveguide back surface is fixed to the second waveguide front surface; the fourth waveguide further includes a fourth image pipe configured to receive the second converted image beam and provide at least one propagated fourth image beam at a fourth image pipe output; a first aperture expander of the fourth waveguide configured to expand at least one propagated first image beam and provide a plurality of first expanded image beams of the fourth waveguide; and a second aperture expander of the fourth waveguide configured to expand the plurality of fourth expanded image beams and provide a plurality of second expanded image beams of the fourth waveguide that are emitted as the fourth expanded output image beam, and the fourth image pipe is configured to surround at least a part of the second aperture expander of the fourth waveguide, and the fourth image pipe has a homogenizing layer. The optical system further includes an image projector, a coupling assembly, a first image pipe, a second image pipe, a first waveguide, and a frame configured to support the second waveguide, and the frame is configured to hide the first image pipe and the second image pipe within a part of the frame.

[0015] The foregoing summary is illustrative only and is not intended to be limiting in any way. By referring to the drawings and the following detailed description, additional aspects, embodiments, and features will become apparent in addition to the illustrative aspects, embodiments, and features described above. In the drawings and the description, like reference numbers and / or like element names may indicate the same or functionally similar elements.

Brief Description of the Drawings

[0016]

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DETAILED DESCRIPTION OF THE INVENTION

[0017] In the following description, in order to provide an understanding of various embodiments of the present application, many specific details such as specific structures, components, materials, dimensions, processing steps, and techniques are shown. However, it will be understood by those skilled in the art that various embodiments of the present application can be practiced without these specific details. In other instances, well-known structures or processing steps are not described in detail to avoid obscuring the present application.

[0018] For more detailed description below, wearable devices such as near-eye displays and / or smart glasses can be implemented by the systems and methods described according to the present disclosure. This system can efficiently provide high-quality optical information to users in various applications.

[0019] FIG. 1 illustrates a block diagram of an optical system according to various examples of the present disclosure. The optical system 100 can include two or more devices or components. The optical system 100 can generally be implemented as a hybrid system including various electronic, optical, and electro-optical elements. The optical device 102 can include one or more elements from the optical system 100. For more detailed description below, the optical system 100 can include one or more wearable devices 110 such as near-eye displays configured as smart glasses separately or together, which can be worn on or around the user's head to transmit optical information to one or more of the user's eyes.

[0020] The wearable device 110 may include a controller 114 having a memory 116. The controller 114 may transmit and receive electrical signals to and from various other elements within the optical system 100, execute program instructions stored in the memory 116 to process and provide information, operate the wearable device 110, and may be configured to interact with other systems external to the wearable device 110. The controller 114 may include a microcontroller, a processor, various individual components, a programmable logic device, and / or various interface circuits that can access the memory 116, which may be removable, replaceable, programmable, and reprogrammable, to update the instructions to the controller 114.

[0021] The wearable device 110 may also include a power management module 120 having a battery 122 configured to provide power. The power management module 120 may be configured to monitor the charging, discharging, and power usage of the battery 122. Various elements of the wearable device 110 may receive power and / or control signals, including, for example, the controller 114, the image projector 132, the optical engine 126, and various active elements 138 within one or more coupling assemblies 136. The various coupling assemblies 136 may include one or more cube beam splitters, semi-transparent mirrors, polarizing beam splitters, half-wave plates (e.g., half-wave retardance plates), quarter-wave plates (e.g., to convert linear polarization to circular polarization and vice versa), and the like. The various active elements 138 may include electronically controllable active half-wave plate liquid crystal (AHWP LC) elements and the like.

[0022] The image projector 126 can also be described as a compact image projector, a microdisplay projector, or a projection optical device (POD), and can be configured to generate a collimated image beam based on the digital image 128. The collimated image beam can be infinitely collimated. The collimated image beam can be generated by various projection optical devices including a spatial light modulator (SLM) that provides a two-dimensional (2D) array of pixel elements, and each of the pixel elements is controllable to modulate the characteristics of the light transmitted or reflected by the pixel element, typically polarization. An example of a transmissive light SLM is a liquid crystal display (LCD), and examples of reflective SLMs are liquid crystal on silicon (LCOS) devices or digital light processing (DLP) devices. The image projector 126 can include a liquid crystal display (LCD), a liquid crystal on silicon (LCoS) display, an organic light emitting diode (OLED) display, a micro light emitting diode (Micro-LED) display, and a laser display (LD), among others. The expressions described herein illustrate the emission and propagation of the image beam along the optical path, and it will be understood that this optical path can be folded, reflected, split, and further modulated by various active or passive elements as described below. Thus, the collimated image beam can be an illumination representation of a digital image having an image field that is a two-dimensional representation of the digital image, based on either a single graphical image (e.g., a static image) or a sequence of graphical images (e.g., a video) corresponding to different points within the image field that propagates through various optical elements within the optical system 100. As used herein, the term beam can also be used to refer to a light ray such as an image ray. Generally, a beam can refer to a coherent light ray that can be emitted from a coherent light source such as a laser. As used herein, the terms light ray and beam can be used almost synonymously in some situations.

[0023] The wearable device 110 may also include one or more waveguides 144, such as a light guiding optical element 144 (e.g., LOE), including a transparent material configured to receive, propagate, and emit illumination related to a digital image in proximity to the user's eye for the purpose of communicating information. For example, the transparent material including the waveguide 144 may include an optical glass or other suitable material that can be converted into a composite optical structure or a compound optical structure using a process that may include coating, laminating, slicing, polishing, assembling, and shaping the transparent material. The process may include, for example, adding a partially reflective material or a total reflective material such as a mirror coating and / or a low reflectivity (LRI) adhesive or glue to assemble various elements together. By preparing and assembling the elements using a low reflectivity adhesive, the various elements can be manufactured and tested separately before being assembled, which can reduce costs.

[0024] The optical engine 126 may be operably coupled to the image projector 132, for example, to provide power and control signals and receive status signals. The optical engine 126 may be configured to operate the image projector 132 under the instructions of the controller 114. For example, the optical engine 126 may perform graphic processing to modify the digital image 128 before projection of an illuminated representation of the digital image by the image projector 132. The image projector 132 may be coupled to one or more waveguides 144 by one or more coupling assemblies 136 having one or more active elements and / or passive elements 138. The coupling assembly 136 may include, for example, one or more active elements such as an active half-wave plate liquid crystal (AHWP LC) element, an active half-wave plate, or a spatial light modulator (SLM). The coupling assembly 136 may also include one or more passive elements such as one or more total reflection mirrors, one or more partial reflection (e.g., semi-transparent) mirrors, one or more half-wave plates, one or more quarter-wave plates, and various optical coatings that may be disposed between or on various optical elements.

[0025] The wearable device 110 may also include a frame 148 (e.g., a head-mounted structure) for supporting and holding one or more elements within the wearable device 110. For example, the frame 148 may directly or indirectly support and hold the image projector 126 in a position adjacent to the one or more image pipes 140 and the one or more waveguides 144. In this way, the frame 148 may support and hold, for example, the optical engine 126, the image projector 132, and the one or more waveguides 144 on or around the user's head. References are made herein with respect to the orientation of various elements relative to each other. Such references may also include references to various elements of the wearable device 110 when supported by the frame 148 or with reference to a three-dimensional (3D) reference (e.g., X, Y, Z axes), as may be described in various drawings.

[0026] The optical system 100 may also include a host computer 170 that may include a processor 174 configured to read and execute operations based on pre-programmed instructions 178 stored on a computer-readable medium 180. The instructions 178 may be provided to the controller 114 and may include at least some instructions stored in the memory 116. The host computer 170 may communicate with one or more elements of the wearable device 110 via a signal and power bus 188. In this way, the host computer 170 may provide power for charging the battery 122, provide instructions to the controller 114, receive status from the controller 114, control various other elements of the wearable device 110, and provide digital image data to the optical engine 126.

[0027] FIG. 2 illustrates an end view of an image pipe according to various examples of the present disclosure. As illustrated in an idealized form, the image pipe 140 can be an elongated transparent member having a first end (e.g., the background in FIG. 2) and a second end (e.g., the foreground in FIG. 2) with a rectangular cross-section having orthogonal walls. As a specific example, the image pipe 140 can have a square cross-section having orthogonal walls that can form four outer surfaces. The image pipe 140 can be configured to receive an input image beam (not shown) that can be injected at an angle, for example, by an image projector 126. The image pipe 140 can provide four replicated output image beams 204-210 based on the injected image beam. When light from the injected image propagates along the waveguide 140 while being reflected from all four outer surfaces, four conjugate image beams (e.g., image beam vectors) 202-208 can be generated that represent the same image when internally reflected by the surfaces. A portion or all of one or more outer surfaces of the image pipe 140 can be coated with a partial reflection coating or a total reflection coating or a low refractive index (LRI) adhesive to facilitate the conduction of the injected image beam and reduce losses. The image pipe 140 can include, for example, a glass material, an acrylic material, and / or a polycarbonate material having the same or a different refractive index compared to other elements within the system 100. The image pipe 140 can be attached to or integrated with one or more waveguide elements and can be considered an embedded image pipe, as described more fully below.

[0028] FIGS. 3A-3C illustrate details regarding an optical system according to various examples of the present disclosure. In particular, FIG. 3A illustrates a front plan view of an optical device 302 according to various examples of the present disclosure, FIG. 3B illustrates a side plan view of a portion of the optical device 302, and FIG. 3C illustrates an enlarged view 304 of a portion of the optical device 302. In FIG. 3A and elsewhere, the user's eye 308 and nose 309 can be illustrated to provide a reference for how the optical system 302 can be worn on the user's head and used to provide optical information.

[0029] According to an example, the optical device 302 may include a coupling assembly 320, an image pipe 360, a first waveguide 376, and a second waveguide 388. The coupling assembly 320 may be similar in some respects to the coupling assembly 136 of FIG. 1. The coupling assembly 320 may be configured to receive a collimated image beam 310 (e.g., the "i" image beam) from the projection optical device 132 and provide a first output image beam 312 (e.g., the "j" image beam) and a second output image beam 314 (e.g., the "k" image beam). As used herein, beams i, j, and k may indicate the projection of a beam along an image pipe, for example, at an angle oblique to the side of the image pipe, where the beam may propagate. As shown in various figures, the beams may indicate the projection of the propagation direction of a collimated beam that may be associated with a single field within the field of view. In particular, the coupling assembly 320 may include a passive optical element, such as a cube beam splitter or a semi-transparent mirror 322, having a first side 324 oriented towards the projection optical device 132 and a second side 326 opposite the first side 324 and oriented towards the first waveguide injection region WIR31 of the first waveguide 376. Thus, the collimated image beam 310 may be applied as an input beam to the coupling assembly 320, which may partially reflect a portion of the collimated image beam 310 that is emitted from the coupling assembly 320 as the first output image beam 312, and the semi-transparent mirror 322 may partially transmit a portion of the collimated image beam 310 that is emitted from the coupling assembly 320 as the second output image beam 314.

[0030] The image pipe 360 may be similar in some respects to the image pipe 140 described with reference to FIGS. 1 and 2. The image pipe 360 may be configured to receive a first output image beam 312 at an image pipe input section 362 (e.g., a first end of the image pipe 360) and provide at least one propagated image beam 364 at an image pipe output section 366 (e.g., a second end of the image pipe 360). The first waveguide 376 may have a first waveguide front surface 383 that is parallel to a first waveguide back surface 384. The first waveguide 376 may be configured to receive a second output image beam 314 and emit a first expanded output image beam 386 from the first waveguide back surface 384. As described, terms such as first, second, third, etc. may be assigned to designate different elements and associations, but may be assigned differently or changed depending on the particular example. Similar to the first waveguide 376 in some respects, the second waveguide 388 may have a second waveguide front surface 395 and a second waveguide back surface 396. The second waveguide 388 may be configured to receive at least one propagated image beam 364 from the image pipe 360 and emit a second expanded output image beam 398 from the second waveguide back surface 396.

[0031] The first waveguide 376 (labeled "A") may include a first aperture expander 378 of the first waveguide and a second aperture expander 380 of the first waveguide separated from each other by a first waveguide splitting region 382. The first aperture expander 378 of the first waveguide may include mutually parallel and partially reflective optical elements (e.g., facets) that are spaced apart from each other and inclined at an angle that may be oblique to at least one of the first waveguide front surface 383 and a plane perpendicular to the first waveguide front surface 383 (e.g., the X-Z plane). The first aperture expander 378 of the first waveguide may also include an embedded volume or surface optical diffraction element. Illumination from the second output image beam 314 is received in a first direction (e.g., along the central axis of the first waveguide aperture expander 378) and then reflected in a second direction and propagated as a first plurality of expanded image beams X3A1 of the first waveguide that are directed into the first waveguide 376 toward the second aperture expander 380 of the first waveguide. Thus, the illumination of the second output image beam 314 may be expanded in a first dimension by the spaced-apart facets of the first waveguide aperture expander 378 to provide a first plurality of expanded image beams X3A1. The reflectivity of the first plurality of partially reflective facets within the first aperture expander 378 of the first waveguide may increase in a direction away from the waveguide injection region WIR31, and the first aperture expander 378 of the first waveguide may have a first facet with the lowest reflectivity and may terminate with a final facet (e.g., a terminal facet) that may be highly reflective and may be a total reflection mirror. Alternatively, the reflectivity of the first plurality of partially reflective facets may be constant in a direction away from the waveguide region WIR31 and, separately from this feature, may terminate with a final facet that may or may not be a mirror. A portion of the first waveguide 376 may be fixed to a portion of the image pipe 360 with any of a layer of low refractive index (LRI) adhesive 306, a layer of low refractive index coating, or a thin film coating that ensures total (or nearly total) internal reflection (TIR). Alternatively, the first waveguide 376 may be disposed spaced apart from the image pipe 360 by air. These alternatives may also apply to the various examples disclosed herein.

[0032] Similarly, the second aperture expander 380 of the first waveguide may include mutually parallel and partially reflective optical elements (e.g., facets) that are spaced apart from each other and can be inclined at an angle that can be oblique with respect to at least one of the front surface 383 of the first waveguide and a plane perpendicular to the front surface 383 of the first waveguide (e.g., the X-Z plane). Illumination from the first plurality of expanded image beams X3A1 is received in a second direction and then can be reflected in a third direction toward the back surface 384 of the first waveguide by the second plurality of partially reflective optical elements within the second aperture expander 380 of the first waveguide. Thus, the illumination from the first plurality of expanded image beams X3A1 can be expanded in a second dimension by the spaced-apart facets of the second aperture expander 380 of the first waveguide to provide a second plurality of expanded image beams X3A2. The plurality of expanded image beams X3A1 can be expanded in a second dimension different from the first dimension to provide a second plurality of expanded image beams X3A2. Accordingly, the first aperture expander 378 of the first waveguide and the second aperture expander 380 of the first waveguide can cooperate to provide a two-dimensional (2D) expansion of the illumination of the second output image beam 314 as the first expanded output image beam 386 that can be emitted from the back surface 384 of the first waveguide. Similar to the first aperture expander 378 of the first waveguide, the reflectivity of the second plurality of partially reflective facets within the second aperture expander 380 of the first waveguide can increase in a direction away from the first aperture expander 378 of the first waveguide, and the second aperture expander 380 of the first waveguide can have a first facet with the lowest reflectivity and a final facet (e.g., a terminal facet) that can be a mirror. Alternatively, the reflectivity of the first plurality of partially reflective facets can be constant in a direction away from the first aperture expander 378 of the first waveguide and, separately from this feature, can terminate with a final facet that may or may not be a mirror.

[0033] The second waveguide 388 (labeled "B") may include a first aperture expander 390 of the second waveguide and a second aperture expander 392 of the second waveguide separated from each other by a second waveguide splitting region 394. The second waveguide 388 may also include a mirror 356 configured to receive at least one propagating image beam 364 and provide at least one reflected propagating image beam 365. The first aperture expander 390 of the second waveguide may include mutually parallel and partially reflective optical elements (e.g., facets) that are spaced apart from each other and may be inclined at an angle that may be oblique to at least one of the second waveguide front surface 395 and a plane perpendicular to the second waveguide front surface 395 (e.g., the X-Z plane). The first aperture expander 390 of the second waveguide may also include an embedded volume or surface optical diffraction element. Illumination from the at least one reflected propagating image beam 365 is received in a fourth direction (e.g., along the central axis of the second waveguide aperture expander 390) and then reflected in a fifth direction by a first plurality of partially reflective optical elements within the first aperture expander 390 of the second waveguide and may be directed as a first plurality of expanded image beams X3B1 of the second waveguide towards the second aperture expander 392 of the second waveguide and conducted within the second waveguide 388. Thus, illumination of the at least one reflected propagating image beam 365 may be expanded in a first dimension (e.g., the third dimension) by spaced-apart facets to provide a first plurality of expanded image beams X3B1. The reflectivity of the third plurality of partially reflective facets within the first aperture expander 390 of the second waveguide may increase in a direction away from the second waveguide injection region WIR32, and the first aperture expander 390 of the second waveguide may have an initial facet with the lowest reflectivity and may terminate with a final facet (e.g., a terminal facet) that may be highly reflective or may be a mirror. Alternatively, the reflectivity of the third plurality of partially reflective facets may be constant in a direction away from the waveguide region WIR32 and, separately from this feature, may terminate with a final facet that may or may not be a mirror.

[0034] Likewise, the second aperture expander 392 of the second waveguide may include mutually parallel and partially reflective optical elements (e.g., facets) of a fourth plurality of planes that are spaced apart from each other and may be inclined at an angle that may be oblique to at least one of the second waveguide front surface 395 and a plane perpendicular to the second waveguide front surface 395 (e.g., the X-Z plane). The second aperture expander 392 of the second waveguide may also include an embedded volume or a surface optical diffraction element. Illumination from the third plurality of expanded image beams X3B1 may be received in a fifth direction and then reflected in a sixth direction toward the second waveguide rear surface 396 by the fourth plurality of partially reflective optical elements within the second aperture expander 392 of the second waveguide. Thus, illumination from the third plurality of expanded image beams X3B1 may be expanded in a second dimension (e.g., the fourth dimension) by the spaced-apart facets of the second aperture expander 392 of the second waveguide to provide a second plurality of expanded image beams X3B2. The plurality of expanded image beams X3B1 may be expanded in a second dimension different from the first dimension to provide a second plurality of expanded image beams X3B2. Accordingly, the first aperture expander 390 of the second waveguide and the second aperture expander 392 of the second waveguide may cooperate to provide a two-dimensional (2D) expansion of the illumination of at least one propagated image beam 365 reflected as a second expanded output image beam 398 that may be emitted from the second waveguide rear surface 396. Similar to the first aperture expander 390 of the second waveguide, the reflectivity of the fourth plurality of partially reflective facets within the second aperture expander 392 of the second waveguide may increase in a direction away from the first aperture expander 390 of the second waveguide, and the second aperture expander 392 of the second waveguide may have a first facet with the lowest reflectivity and a final facet (e.g., a terminal facet) that may be highly reflective and may be a mirror. Alternatively, the reflectivity of the fourth plurality of partially reflective facets may be constant in a direction away from the first aperture expander 390 of the second waveguide and may terminate with a final facet that may or may not be a mirror, separate from this feature.

[0035] As described above, the image projector 132 can provide a collimated image beam 310 (e.g., a collimated single field) that can be an illumination representation of a digital image having an image field that is a two-dimensional representation of the digital image. Thus, the image field can have a vertical and / or horizontal extent, as illustrated in FIG. 3A and elsewhere. For example, the first output image beam 312 can propagate through the image pipe 360 into a second waveguide 388 having a vertical extent (labeled "C" and "D"), be reflected by the mirror 356, and then be reflected by the first aperture expander 390 of the second waveguide. Thus, a single pixel on the image can correspond to a collimated beam and a single beam. Accordingly, beams C and D can be horizontally displaced beams having the same orientation (e.g., the lines are parallel), and thus they can be associated with, for example, the same field. The beam expansion described herein may not be related to the expansion of the output image observable by the user. Similarly, the second output image beam 314 can propagate into a first waveguide 376 having a horizontal extent (labeled "C" and "D") and be reflected by the first aperture expander 378 of the first waveguide. Accordingly, the first output image beam 312 and the second output image beam 314 and others can propagate through various optical elements within the optical system 100 as a two-dimensional (2D) image field about the illustrated central axis. In some embodiments, the mirror 356 may not be used.

[0036] According to an example, the first aperture expander 378 of the first waveguide and the first aperture expander 390 of the second waveguide can be oriented parallel to each other. Further, as shown in FIG. 3A, the first aperture expander 390 of the second waveguide can be disposed on the side of the second waveguide 388 closest (e.g., proximal) to the first waveguide 376. Other arrangements are also possible, and the first aperture expander 390 of the second waveguide can be disposed on the side of the second waveguide 388 farthest (e.g., distal) from the first waveguide 376. As briefly mentioned above, the beams depicted in the various drawings can represent projections of the propagation directions of collimated beams associated with a single field within the field of view (FoV). In an actual system, within the first or second waveguide, these beams can be upward and downward beams confined within the waveguide by total internal reflection (TIR). Within the image pipe, the beams can be upward right, upward left, downward right, and downward left.

[0037] Figures 4A-4B illustrate details regarding an optical system according to various examples of the present disclosure. In particular, FIG. 4A illustrates a front plan view of an optical device 402 according to various embodiments of the present disclosure, and FIG. 4B illustrates an enlarged view 404 of a portion of the optical device 402.

[0038] According to an example, the optical device 402 may include a coupling assembly 420, an image pipe 460, a first waveguide 476, and a second waveguide 488. The coupling assembly 420 may be similar to the coupling assembly 136 of FIG. 1 in some respects. The coupling assembly 420 may be configured to receive a collimated image beam 410 (e.g., the "i" image beam) from the projection optical device 132 and provide a first output image beam 412 (e.g., the "j" image beam) and a second output image beam 414 (e.g., the "k" image beam). In particular, the coupling assembly 420 may include a passive optical element such as a polarization beam splitter (PBS) 422 having, for example, a first side 424 oriented toward the projection optical device 132 and a second side 426 opposite the first side 424 and oriented toward the first waveguide injection region WIR41 of the first waveguide 476. Thus, the collimated image beam 410 may be applied as an input beam to the coupling assembly 420, which may partially reflect a portion of the collimated image beam 410 that exits the coupling assembly 420 as the first output image beam 412, and the polarization beam splitter 422 may partially transmit a portion of the collimated image beam 410 that exits the second side 426 of the polarization beam splitter 424 as the transmitted image beam 428.

[0039] The collimated image beam 410 may include polarized illumination. The polarization beam splitter 422 may include a wire grid, crystal, directional polymer, or dielectric material that reflects S-polarization (e.g., vertical) but transmits P-polarization (e.g., parallel), or vice versa. Thus, the polarization beam splitter may receive the collimated image beam 410 and provide a first output beam 412 as an S-polarized image beam and a transmitted image beam 428 as a P-polarized image beam. The combining assembly 420 may also include a half-wave plate (HWP) 430 having a first side 432 of the half-wave plate and a second side 434 of the half-wave plate. The half-wave plate 430 may include a crystal or dielectric material configured to transmit light and retard (e.g., delay) one component of the polarization to correct the polarization without attenuating, deviating, or displacing the incident beam. Thus, the first side 432 of the half-wave plate 430 may receive the transmitted beam 428 and provide a second output image beam 414 from the second side 434 of the half-wave plate 430. In this example, since the transmitted beam 428 is P-polarized by passing through the polarization beam splitter 422 and the second output image beam 414 is converted to S-polarization by passing through the half-wave plate 430, both the first output beam 412 and the second output beam 414 have the same S-polarization.

[0040] The image pipe 460 may be similar in some respects to the image pipe 140 described with reference to FIGS. 1 and 2. The image pipe 460 may be configured to receive a first output image beam 412 at an image pipe input section 462 (e.g., a first end of the image pipe 460) and provide at least one propagated image beam 464 at an image pipe output section 466 (e.g., a second end of the image pipe 460). The first waveguide 476 may have a first waveguide front surface 483 that is parallel to a first waveguide back surface 484. The first waveguide 476 may be configured to receive a second output image beam 414 and emit a first expanded output image beam 486 from the first waveguide back surface 484. Similar to the first waveguide 476 in some respects, the second waveguide 488 may have a second waveguide front surface 495 and a second waveguide back surface 496. The second waveguide 488 may be configured to receive at least one propagated image beam 464 from the image pipe 460 and emit a second expanded output image beam 498 from the second waveguide back surface 396.

[0041] The first waveguide 476 (labeled "A") may include a first aperture expander 478 of the first waveguide and a second aperture expander 480 of the first waveguide separated from each other by a first waveguide splitting region 482. The first aperture expander 478 of the first waveguide may include mutually parallel and partially reflective optical elements (e.g., facets) that are spaced apart from each other and inclined at an angle that may be oblique to at least one of the first waveguide front surface 483 and a plane perpendicular to the first waveguide front surface 483 (e.g., the X-Z plane). Illumination from the second output image beam 414 is received in a first direction (e.g., along the central axis of the first waveguide aperture expander 478) and then reflected in a second direction and propagated within the first waveguide 476 as a first plurality of expanded image beams X4A1 of the first waveguide directed towards the second aperture expander 480 of the first waveguide. Thus, the illumination of the second output image beam 414 may be expanded in a first dimension by the spaced-apart facets of the first waveguide aperture expander 478 to provide the first plurality of expanded image beams X4A1. The reflectivity of the first plurality of partially reflective facets within the first aperture expander 478 of the first waveguide may increase in a direction away from the waveguide injection region WIR41, and the first aperture expander 478 of the first waveguide may have a first facet with the lowest reflectivity and may terminate with a final facet that may be a total reflection mirror. Alternatively, the reflectivity of the first plurality of partially reflective facets may be constant in a direction away from the waveguide region WIR41 and, separately from this feature, may terminate with a final facet that may or may not be a mirror. A portion of the first waveguide 476 may be fixed to a portion of the image pipe 460 having a layer of low refractive index (LRI) adhesive 406.

[0042] Similarly, the second aperture expander 480 of the first waveguide may include mutually parallel and partially reflective optical elements (e.g., facets) that are spaced apart from each other and can be inclined at an angle that may be oblique with respect to at least one of the front surface 483 of the first waveguide and a plane perpendicular to the front surface 483 of the first waveguide (e.g., the X-Z plane). Illumination from the first plurality of expanded image beams X4A1 is received in a second direction and then can be reflected in a third direction toward the back surface 484 of the first waveguide by the second plurality of partially reflective optical elements within the second aperture expander 480 of the first waveguide. In this way, illumination from the first plurality of expanded image beams X4A1 can be expanded in a second dimension by the spaced-apart facets of the second aperture expander 480 of the first waveguide to provide a second plurality of expanded image beams X4A2. The plurality of expanded image beams X4A1 can be expanded in a second dimension different from the first dimension to provide a second plurality of expanded image beams X4A2. Thus, the first aperture expander 478 of the first waveguide and the second aperture expander 480 of the first waveguide can cooperate to provide a two-dimensional (2D) expansion of the illumination of the second output image beam 414 as the first expanded output image beam 486 that can be emitted from the back surface 484 of the first waveguide. Similar to the first aperture expander 478 of the first waveguide, the reflectivity of the second plurality of partially reflective facets within the second aperture expander 480 of the first waveguide can increase in a direction away from the first aperture expander 478 of the first waveguide, and the second aperture expander 480 of the first waveguide can have a first facet with the lowest reflectivity and a final facet that can be a mirror. Alternatively, the reflectivity of the first plurality of partially reflective facets can be constant in a direction away from the first aperture expander 478 of the first waveguide and, separately from this feature, can terminate with a final facet that may or may not be a mirror.

[0043] The second waveguide 488 (labeled "B") may include a first aperture expander 490 of the second waveguide and a second aperture expander 492 of the second waveguide that are separated from each other by a second waveguide splitting region 494. The first aperture expander 490 of the second waveguide may include mutually parallel and partially reflective optical elements (e.g., facets) that are spaced apart from each other and inclined at an angle that may be oblique with respect to at least one of the second waveguide front face 495 and a plane perpendicular to the second waveguide front face 495 (e.g., the X-Z plane). Illumination from at least one propagating image beam 464 is received in a fourth direction (e.g., along the central axis of the second waveguide aperture expander 490), and then reflected in a fifth direction by the first plurality of partially reflective optical elements within the first aperture expander 490 of the second waveguide, and may be conducted into the second waveguide 488 as a first plurality of expanded image beams X4B1 of the second waveguide that are directed toward the second aperture expander 492 of the second waveguide. Thus, the illumination of at least one propagating image beam 464 may be expanded in a first dimension (e.g., the third dimension) by spaced-apart facets to provide a first plurality of expanded image beams X4B1. The reflectivity of the third plurality of partially reflective facets within the first aperture expander 490 of the second waveguide may increase in a direction away from the second waveguide injection region WIR42, and the first aperture expander 490 of the second waveguide may have a first facet with the lowest reflectivity and may terminate with a final facet that may be a mirror. Alternatively, the reflectivity of the third plurality of partially reflective facets may be constant in a direction away from the waveguide region WIR42, and, separately from this feature, may terminate with a final facet that may or may not be a mirror.

[0044] Similarly, the second aperture expander 492 of the second waveguide may include mutually parallel and partially reflective optical elements (e.g., facets) of a fourth plurality of planes that are spaced apart from each other and may be inclined at an angle that may be oblique to at least one of the second waveguide front face 495 and a plane perpendicular to the second waveguide front face 495 (e.g., the X-Z plane). Illumination from the third plurality of expanded image beams X4B1 may be received in a fifth direction and then reflected in a sixth direction toward the second waveguide rear face 496 by the fourth plurality of partially reflective optical elements within the second aperture expander 492 of the second waveguide. Thus, illumination from the third plurality of expanded image beams X4B1 may be expanded in a second dimension (e.g., a fourth dimension) by the spaced-apart facets of the second aperture expander 492 of the second waveguide to provide a second plurality of expanded image beams X4B2. The plurality of expanded image beams X4B1 may be expanded in a second dimension different from the first dimension to provide a second plurality of expanded image beams X4B2. Accordingly, the first aperture expander 490 of the second waveguide and the second aperture expander 492 of the second waveguide may cooperate to provide a two-dimensional (2D) expansion of the illumination of at least one propagated image beam 464 that is reflected as a second expanded output image beam 498 that may be emitted from the second waveguide rear face 496. Similar to the first aperture expander 490 of the second waveguide, the reflectivity of the fourth plurality of partially reflective facets within the second aperture expander 492 of the second waveguide may increase in a direction away from the first aperture expander 490 of the second waveguide, and the second aperture expander 492 of the second waveguide may have a first facet with the lowest reflectivity and a final facet (e.g., a terminal facet) that may be a mirror. Alternatively, the reflectivity of the fourth plurality of partially reflective facets may be constant in a direction away from the first aperture expander 490 of the second waveguide and may terminate with a final facet that may or may not be a mirror, separately from this feature.

[0045] As described above, the image projector 132 may provide a collimated image beam 410 that may be an illumination representation of a digital image having an image field that is a two-dimensional representation of the digital image. Thus, the first output image beam 412 and the second output image beam 414 and others may propagate through various optical elements within the optical system 100 as a two-dimensional (2D) image field around the illustrated central axis.

[0046] According to an example, the first aperture expander 478 of the first waveguide and the first aperture expander 490 of the second waveguide may be oriented perpendicular to each other. Other arrangements are also possible, and the first aperture expander 490 of the second waveguide may be disposed on the side of the second waveguide 488 that is furthest (e.g., distal) from the first waveguide 476. In this case, the second waveguide 488 and various components may be arranged oppositely (e.g., reflected, inverted, or rotated) around the diagonal axis 458. For example, compared to FIG. 3A, the second input aperture 490 may be disposed perpendicular to above or below the diagonal axis 458.

[0047] According to an example, the coupling assembly 420 may also include an active half-wave plate liquid crystal element (AHWP) 448 configured to receive the collimated image beam 410 and provide a converted image beam 450. The active half-wave plate liquid crystal element 448 may be an active optical element controlled by a signal from the controller 114 to selectively change the polarization of at least a portion of the collimated image beam 410, such as changing from S polarization to P polarization when activated, to provide the converted image beam 450. In this example, the first side 424 of the polarization beam splitter 422 may receive the converted image beam 450, provide the first output image beam 412 from the first side 424 of the polarization beam splitter 422, and provide a transmitted beam 428 from the second side 426 of the polarization beam splitter. Thus, the optical device 402 may be practiced with or without the active half-wave plate liquid crystal element 448.

[0048] Figures 5A-5B illustrate details regarding an optical system according to various examples of the present disclosure. In particular, FIG. 5A illustrates a front plan view of an optical device 502 according to various embodiments of the present disclosure, and FIG. 5B illustrates an enlarged view 504 of a portion of the optical device 502.

[0049] According to an example, the optical device 502 may include a coupling assembly 520, an image pipe 560, a first waveguide 576, and a second waveguide 588. The coupling assembly 520 may be similar to the coupling assembly 136 of FIG. 1 in some respects. As mentioned above, similar reference numbers and similar element names may indicate the same or functionally similar elements. For example, the coupling assembly 520 may be similar to the coupling assembly 320 described with reference to FIG. 3A in some respects, and the coupling assembly 520 may be similar to the coupling assembly 420 described with reference to FIG. 4A in some respects. The coupling assembly 520 may be configured to receive a collimated image beam 510 (e.g., the "i" image beam) from the projection optical device 132 and provide a first output image beam 512 (e.g., the "j" image beam) and a second output image beam 514 (e.g., the "k" image beam). In particular, the coupling assembly 520 may include a passive optical element such as a polarization beam splitter (PBS) 522 having, for example, a first side 524 oriented toward the projection optical device 132 and a second side 526 opposite the first side 524 and oriented toward the first waveguide injection region WIR51 of the first waveguide 576. Thus, the collimated image beam 510 may be applied as an input beam to the coupling assembly 520, which may partially reflect a portion of the collimated image beam 510 that exits the coupling assembly 520 as the first output image beam 512. The polarization beam splitter 522 may partially transmit a portion of the collimated image beam 510 that exits the second side 526 of the polarization beam splitter 524 as a transmitted image beam 528. The collimated image beam 510 may include polarized illumination. The polarization beam splitter 522 may include a wire grid, crystal, or dielectric material that reflects S polarization (e.g., vertical) and transmits P polarization (e.g., parallel). Thus, the polarization beam splitter may receive the collimated image beam 510 and provide the first output beam 512 as an S-polarized image beam and the transmitted image beam 528 as a P-polarized image beam.The coupling assembly 520 may also include a half-wave plate (HWP) 530 having a first side 532 and a second side 534 of the half-wave plate. The half-wave plate 530 may include a crystalline or dielectric material configured to transmit light and retard (e.g., delay) one component of polarization to correct the polarization without attenuating, deviating, or displacing the incident beam. Thus, the first side 532 of the half-wave plate 530 may receive the transmitted beam 528 and provide a second output image beam 514 from the second side 534 of the half-wave plate 530. In this example, since the transmitted beam 528 is P-polarized by passing through the polarization beam splitter 522 and the second output image beam 514 is converted to S-polarization by passing through the half-wave plate 530, both the first output beam 512 and the second output beam 514 have the same S-polarization.

[0050] The image pipe 560 may be similar in some respects to the image pipe 140 described with reference to FIGS. 1 and 2. The image pipe 560 may be configured to receive the first output image beam 512 at an image pipe input section 562 (e.g., the first end of the image pipe 560) and provide at least one propagated image beam 564 at an image pipe output section 566 (e.g., the second end of the image pipe 560). The first waveguide 576 may have a first waveguide front surface 583 that is parallel to a first waveguide back surface 584. The first waveguide 576 may be configured to receive the second output image beam 514 and emit a first expanded output image beam 586 from the first waveguide back surface 584. Similar to the first waveguide 576 in some respects, the second waveguide 588 may have a second waveguide front surface 595 and a second waveguide back surface 596. The second waveguide 588 may be configured to receive at least one propagated image beam 564 from the image pipe 560 and emit a second expanded output image beam 598 from the second waveguide back surface 396.

[0051] The first waveguide 576 (labeled "A") may include a first aperture expander 578 of the first waveguide and a second aperture expander 580 of the first waveguide separated from each other by a first waveguide splitting region 582. The first aperture expander 578 of the first waveguide may include optically parallel and partially reflective optical elements (e.g., facets) spaced apart from each other that may be inclined at an angle that may be oblique to at least one of the first waveguide front face 583 and a plane perpendicular to the first waveguide front face 583 (e.g., the X-Z plane). Illumination from the second output image beam 514 is received in a first direction (e.g., along the central axis of the first waveguide aperture expander 578), then reflected in a second direction, and propagated within the first waveguide 576 as a first plurality of expanded image beams X5A1 of the first waveguide directed toward the second aperture expander 580 of the first waveguide. Thus, the illumination of the second output image beam 514 may be expanded in a first dimension by the spaced-apart facets of the first waveguide aperture expander 578 to provide a first plurality of expanded image beams X5A1. The reflectivity of the first plurality of partially reflective facets within the first aperture expander 578 of the first waveguide may increase in a direction away from the waveguide injection region WIR51, and the first aperture expander 578 of the first waveguide may have a first facet with the lowest reflectivity and may terminate with a final facet that may be a total reflection mirror. Alternatively, the reflectivity of the first plurality of partially reflective facets may be constant in a direction away from the waveguide region WIR51 and, separately from this feature, may terminate with a final facet that may or may not be a mirror. A portion of the first waveguide 576 may be fixed to a portion of the image pipe 560 having a layer of low refractive index (LRI) adhesive 506.

[0052] Similarly, the second aperture expander 580 of the first waveguide may include mutually parallel and partially reflective optical elements (e.g., facets) that are spaced apart from each other and can be inclined at an angle that may be oblique to at least one of the first waveguide front surface 583 and a plane perpendicular to the first waveguide front surface 583 (e.g., the X-Z plane). Illumination from the first plurality of expanded image beams X5A1 is received in a second direction and then can be reflected in a third direction toward the back surface 584 of the first waveguide by the second plurality of partially reflective optical elements within the second aperture expander 580 of the first waveguide. In this way, the illumination from the first plurality of expanded image beams X5A1 can be expanded in a second dimension by the spaced-apart facets of the second aperture expander 580 of the first waveguide to provide a second plurality of expanded image beams X5A2. The plurality of expanded image beams X5A1 can be expanded in a second dimension different from the first dimension to provide a second plurality of expanded image beams X5A2. Thus, the first aperture expander 578 of the first waveguide and the second aperture expander 580 of the first waveguide can cooperate to provide a two-dimensional (2D) expansion of the illumination of the second output image beam 514 as the first expanded output image beam 586 that can be emitted from the back surface 584 of the first waveguide. Similar to the first aperture expander 578 of the first waveguide, the reflectivity of the second plurality of partially reflective facets within the second aperture expander 580 of the first waveguide can increase in a direction away from the first aperture expander 578 of the first waveguide, and the second aperture expander 580 of the first waveguide can have an initial facet with the lowest reflectivity and a final facet that can be a mirror. Alternatively, the reflectivity of the first plurality of partially reflective facets can be constant in a direction away from the first aperture expander 578 of the first waveguide and, separately from this feature, can terminate with a final facet that may or may not be a mirror.

[0053] The second waveguide 588 (labeled "B") may include a first aperture expander 590 of the second waveguide and a second aperture expander 592 of the second waveguide separated from each other by a second waveguide splitting region 594. The second waveguide 588 may also include a mirror 556 configured to receive at least one propagating image beam 564 and provide at least one reflected propagating image beam 565. The first aperture expander 590 of the second waveguide may include mutually parallel and partially reflective optical elements (e.g., facets) that are spaced apart and inclined at an angle that may be oblique to at least one of the second waveguide front face 595 and a plane perpendicular to the second waveguide front face 595 (e.g., the X-Z plane). Illumination from the at least one reflected propagating image beam 565 is received in a fourth direction (e.g., along the central axis of the second waveguide aperture expander 590) and then reflected in a fifth direction by a first plurality of partially reflective optical elements within the first aperture expander 590 of the second waveguide and directed to the second aperture expander 592 of the second waveguide and conducted into the second waveguide 588 as a first plurality of expanded image beams X5B1 of the second waveguide. Thus, illumination of the at least one reflected propagating image beam 565 may be expanded in a first dimension (e.g., the third dimension) by spaced-apart facets to provide a first plurality of expanded image beams X5B1. The reflectivity of the third plurality of partially reflective facets within the first aperture expander 590 of the second waveguide may increase in a direction away from the second waveguide injection region WIR52, and the first aperture expander 590 of the second waveguide may have an initial facet with the lowest reflectivity and may terminate with a final facet that may be a mirror. Alternatively, the reflectivity of the third plurality of partially reflective facets may be constant in a direction away from the waveguide region WIR52 and, separately from this feature, may terminate with a final facet that may or may not be a mirror.

[0054] Similarly, second waveguide-second aperture expander 592 may include a fourth plurality of spaced-apart, planar, mutually parallel, partially reflective optical elements (e.g., facets) that may be inclined at an angle that may be oblique with respect to at least one of second waveguide front surface 595 and a plane normal to second waveguide front surface 595 (e.g., the XZ plane). Illumination from the third plurality of expanded image beams X5B1 may be received in a fifth direction and then reflected in a sixth direction by the fourth plurality of partially reflective optical elements in second waveguide-second aperture expander 592 toward second waveguide back surface 596. In this manner, illumination from the third plurality of expanded image beams X5B1 may be expanded in a second dimension (e.g., a fourth dimension) by the spaced-apart facets of second waveguide-second aperture expander 592 to provide the second plurality of expanded image beams X5B2. The plurality of expanded image beams X5B1 may be expanded in a second dimension different from the first dimension to provide a second plurality of expanded image beams X5B2. Thus, the second waveguide first aperture expander 590 and the second waveguide second aperture expander 592 may cooperate to provide a two-dimensional (2D) expansion of the illumination of the reflected at least one propagating image beam 565 as a second expanded output image beam 598, which may be emitted from the second waveguide back surface 596. Similar to the second waveguide first aperture expander 590, the reflectivity of the fourth plurality of partially reflective facets in the second waveguide second aperture expander 592 may increase in a direction away from the second waveguide first aperture expander 590, and the second waveguide second aperture expander 592 may have a first facet with the lowest reflectivity and a final facet (e.g., a terminal facet) which may be a mirror. Alternatively, the reflectivity of the fourth plurality of partially reflective facets may be constant in a direction away from the second waveguide first aperture expander 590 and, independent of this feature, may terminate in a final facet that may or may not be a mirror. As described above, the image projector 132 may provide a collimated image beam 510, which may be an illuminated representation of a digital image having an image field that is a two-dimensional representation of the digital image.Accordingly, the first output image beam 512 and the second output image beam 514 and others can propagate through various optical elements within the optical system 100 as a two-dimensional (2D) image field around the illustrated central axis. A portion of the second waveguide 588 can be fixed to a portion of the image pipe 560 having a layer of low refractive index (LRI) adhesive 516.

[0055] According to an example, the first aperture expander 578 of the first waveguide and the first aperture expander 590 of the second waveguide can be oriented parallel to each other. Other arrangements are also possible, and the first aperture expander 590 of the second waveguide can be disposed on the side of the second waveguide 588 that is farthest (e.g., distal) from the first waveguide 576. In this case, the second waveguide 588 can be disposed oppositely around the vertical axis 546, and for example, compared to FIG. 3A, the second input aperture 590 can be horizontally disposed to the left or right of the second aperture 592 of the second waveguide.

[0056] According to an example, the coupling assembly 520 may also include an active half-wave plate liquid crystal element (AHWP) 548 configured to receive the collimated image beam 510 and provide a converted image beam 550. The active half-wave plate liquid crystal element 548 may be an active optical element controlled by a signal from the controller 114 to selectively change the polarization of at least a portion of the collimated image beam 510, such as changing from S polarization to P polarization when activated, to provide the converted image beam 550. In this example, the first side 524 of the polarization beam splitter 522 may receive the converted image beam 550 and provide a first output image beam 512 from the first side 524 of the polarization beam splitter 522 and a transmitted beam 528 from the second side 526 of the polarization beam splitter. Thus, the optical device 502 may be practiced with or without the active half-wave plate liquid crystal element 548. The coupling assemblies 420 and 520 may include various active or passive optical elements as described. In the systems illustrated in FIGS. 4 and 5, the image may be rotated between the first waveguide and the second waveguide. In a practical system, the image provided by the image projector may be rotated, perhaps to avoid introducing a ghost image that is approximately 50% inverted.

[0057] FIGS. 6A-6B illustrate details regarding an optical system according to various examples of the present disclosure. In particular, FIG. 6A illustrates a front plan view of an optical device 602 according to various embodiments of the present disclosure, and FIG. 6B illustrates an enlarged view 604 of a portion of the optical device 602.

[0058] According to an example, the optical device 602 may include a coupling assembly 620, a first image pipe 660, a second image pipe 668, a first waveguide 676, and a second waveguide 688. The coupling assembly 620 may be similar in some respects to the coupling assembly 136 of FIG. 1. The coupling assembly 620 may be configured to receive a collimated image beam 610 (e.g., the "i" image beam) from the projection optical device 132 and provide a first output image beam 612 (e.g., the "j" image beam) and a second output image beam 614 (e.g., the "k" image beam). The collimated image beam 610 may include polarized illumination. In particular, the coupling assembly 620 may include a passive optical element such as a polarization beam splitter (PBS) 622 having, for example, a first side 624 oriented toward the projection optical device 132 and a second side 626 opposite the first side 624 and oriented away from the projection optical device 132. Thus, the collimated image beam 610 may be applied as an input beam to the coupling assembly 620, which may partially reflect a portion of the collimated image beam 610 that exits the coupling assembly 620 as a first output image beam 612 having S polarization. The polarization beam splitter 622 may partially transmit a portion of the collimated image beam 610 that exits the second side 626 of the polarization beam splitter 624 as a transmitted image beam 628 having P polarization. The polarization beam splitter 622 may include a wire grid, crystal, directional polymer, or dielectric material that reflects S polarization (e.g., vertical) and transmits P polarization (e.g., parallel). Thus, the polarization beam splitter may receive the collimated image beam 610 and provide a first output beam 612 as an S polarization image beam and a transmitted image beam 628 as a P polarization image beam. The coupling assembly 620 may also include a quarter-wave plate 630 having a first side 632 and a second side 634 of the quarter-wave plate. The quarter-wave plate 630 may include a crystal or dielectric material configured to convert linearly polarized light to circularly polarized light and circularly polarized light to linearly polarized light (e.g., S polarization or P polarization).Accordingly, the first side 632 of the quarter-wave plate 630 may receive the transmitted beam 628 at the first side 632 of the quarter-wave plate 630 and provide the first converted image beam 636 at the second side 634 of the quarter-wave plate 630. The combining assembly 630 may also include a mirror 638 disposed adjacent to the second side 634 of the quarter-wave plate, having a total reflection surface 640 configured to receive the first converted beam 636 as a reflected image beam 642 and reflect it. The quarter-wave plate 630 may receive the reflected image beam 642 at the second side 634 of the quarter-wave plate 630 and provide the second converted image beam 644 emitted from the first side 632 of the quarter-wave plate 630. The second side 626 of the polarization beam splitter 622 may receive the second converted image beam 644 and provide the reflected second output beam 614 having S polarization. Thus, the first output beam 612 and the second output beam 614 may have the same S polarization. One technical advantage provided by the series of conversions described above is that they can support passive systems (e.g., systems with passive elements) and symmetric structures, which can facilitate, for example, a simpler design of the eye box position relative to the user's nose.

[0059] The first image pipe 660 and the second image pipe 668 may be similar in some respects to the image pipe 140 described with reference to FIGS. 1 and 2. The first image pipe 660 may be configured to receive the first output image beam 612 at an image pipe input portion 662 (e.g., the first end of the first image pipe 660) and provide at least one first propagated image beam 664 at an image pipe output portion 666 (e.g., the second end of the first image pipe 660). The second image pipe 668 may be configured to receive the second output image beam 614 at a second image pipe input portion 670 (e.g., the first end of the second image pipe 668) and provide at least one second propagated image beam 672 at a second image pipe output portion 674 (e.g., the second end of the second image pipe 668). Thus, the combining assembly 620 can be regarded as integrated or embedded with the first image pipe 660 and the second image pipe 668.

[0060] The first waveguide 676 may have a first waveguide front surface 683 that is parallel to the first waveguide back surface 684. The first waveguide 676 may also include a first mirror 654 configured to receive at least one second propagating image beam 672 and provide at least one second propagating image beam 673 reflected at the first waveguide injection region WIR61. The first waveguide 676 may be configured to receive the at least one reflected second propagating image beam 673 and emit a first extended output image beam 686 from the first waveguide back surface 684. Similar to the first waveguide 676 in some respects, the second waveguide 688 may have a second waveguide front surface 695 and a second waveguide back surface 696. The second waveguide 688 may also include a second mirror 656 configured to receive at least one first propagating image beam 664 and provide at least one first propagating image beam 665 reflected at the second waveguide injection region WIR62. The second waveguide 688 may be configured to receive the at least one reflected first propagating image beam 665 and emit a second extended output image beam 698 from the second waveguide back surface 396.

[0061] The first waveguide 676 (labeled "A") may include a first aperture expander 678 of the first waveguide and a second aperture expander 680 of the first waveguide separated from each other by a first waveguide splitting region 682. The first aperture expander 678 of the first waveguide may include mutually parallel and partially reflective optical elements (e.g., facets) that are spaced apart from each other and inclined at an angle that may be oblique to at least one of the first waveguide front surface 683 and a plane perpendicular to the first waveguide front surface 683 (e.g., the X-Z plane). Illumination from at least one reflected second propagation image beam 673 may be received in a first direction (e.g., along the central axis of the first waveguide aperture expander 678) and then reflected in a second direction and propagated as a first plurality of expanded image beams X6A1 of the first waveguide directed toward the second aperture expander 680 of the first waveguide within the first waveguide 676. Thus, the illumination of at least one reflected second propagation image beam 673 may be expanded in a first dimension by the spaced-apart facets of the first waveguide aperture expander 678 to provide a first plurality of expanded image beams X6A1. The reflectivity of the first plurality of partially reflective facets within the first aperture expander 678 of the first waveguide may increase in a direction away from the waveguide injection region WIR61, and the first aperture expander 678 of the first waveguide may have a first facet with the lowest reflectivity and may terminate with a final facet that may be a total reflection mirror. Alternatively, the reflectivity of the first plurality of partially reflective facets may be constant in a direction away from the waveguide region WIR61 and, separately from this feature, may terminate with a final facet that may or may not be a mirror.

[0062] Similarly, the second aperture expander 680 of the first waveguide may include mutually parallel and partially reflective optical elements (e.g., facets) that are spaced apart from each other and can be tilted at an angle that can be oblique to at least one of the first waveguide front surface 683 and a plane perpendicular to the first waveguide front surface 683 (e.g., the X-Z plane). Illumination from the first plurality of expanded image beams X6A1 is received in a second direction and then can be reflected in a third direction toward the first waveguide rear surface 684 by the second plurality of partially reflective optical elements within the second aperture expander 680 of the first waveguide. Thus, illumination from the first plurality of expanded image beams X6A1 can be expanded in a second dimension by the spaced-apart facets of the second aperture expander 680 of the first waveguide to provide a second plurality of expanded image beams X6A2. The plurality of expanded image beams X6A1 can be expanded in a second dimension different from the first dimension to provide a second plurality of expanded image beams X6A2. Accordingly, the first aperture expander 678 of the first waveguide and the second aperture expander 680 of the first waveguide can cooperate to provide a two-dimensional (2D) expansion of the illumination of at least one reflected second propagation image beam 673 as a first expanded output image beam 686 that can be emitted from the first waveguide rear surface 684. Similar to the first aperture expander 678 of the first waveguide, the reflectivity of the second plurality of partially reflective facets within the second aperture expander 680 of the first waveguide can increase in a direction away from the first aperture expander 678 of the first waveguide, and the second aperture expander 680 of the first waveguide can have a first facet with the lowest reflectivity and a final facet that can be a mirror. Alternatively, the reflectivity of the first plurality of partially reflective facets can be constant in a direction away from the first aperture expander 678 of the first waveguide and, apart from this feature, can terminate with a final facet that may or may not be a mirror.

[0063] The second waveguide 688 (labeled "B") may include a first aperture expander 690 of the second waveguide and a second aperture expander 692 of the second waveguide separated from each other by a second waveguide splitting region 694. The first aperture expander 690 of the second waveguide may include mutually parallel and partially reflective optical elements (e.g., facets) of a third plurality of planes that are spaced apart from each other and may be inclined at an angle that may be oblique to at least one of the second waveguide front surface 695 and a plane perpendicular to the second waveguide front surface 695 (e.g., the X-Z plane). Illumination from at least one propagated image beam 665 that is reflected may be received in a fourth direction (e.g., along the central axis of the second waveguide aperture expander 690), and then reflected in a fifth direction by a first plurality of partially reflective optical elements within the first aperture expander 690 of the second waveguide and directed to the second aperture expander 692 of the second waveguide and may be conducted within the second waveguide 688 as a first plurality of expanded image beams X6B1. Thus, illumination of at least one propagated image beam 665 that is reflected may be expanded in a first dimension (e.g., the third dimension) by spaced-apart facets to provide a first plurality of expanded image beams X6B1. The reflectivity of the third plurality of partially reflective facets within the first aperture expander 690 of the second waveguide may increase in a direction away from the second waveguide injection region WIR62, and the first aperture expander 690 of the second waveguide may have an initial facet with the lowest reflectivity and may terminate with a final facet that may be a mirror. Alternatively, the reflectivity of the third plurality of partially reflective facets may be constant in a direction away from the waveguide region WIR62 and, separately from this feature, may terminate with a final facet that may or may not be a mirror.

[0064] Similarly, the second aperture expander 692 of the second waveguide may include mutually parallel and partially reflective optical elements (e.g., facets) of a fourth plurality of planes that are spaced apart from each other and can be inclined at an angle that can be oblique with respect to at least one of the second waveguide front face 695 and a plane (e.g., the X-Z plane) perpendicular to the second waveguide front face 695. Illumination from the third plurality of expanded image beams X6B1 can be received in a fifth direction and then reflected by the fourth plurality of partially reflective optical elements within the second aperture expander 692 of the second waveguide in a sixth direction toward the second waveguide rear face 696. Thus, the illumination from the third plurality of expanded image beams X6B1 can be expanded in a second dimension (e.g., the fourth dimension) by the spaced-apart facets of the second aperture expander 692 of the second waveguide to provide a second plurality of expanded image beams X6B2. The plurality of expanded image beams X6B1 can be expanded in a second dimension different from the first dimension to provide a second plurality of expanded image beams X6B2. Accordingly, the first aperture expander 690 of the second waveguide and the second aperture expander 692 of the second waveguide can cooperate to provide a two-dimensional (2D) expansion of the illumination of at least one propagated image beam 665 that is reflected as a second expanded output image beam 698 that can be emitted from the second waveguide rear face 696. Similar to the first aperture expander 690 of the second waveguide, the reflectivity of the fourth plurality of partially reflective facets within the second aperture expander 692 of the second waveguide can increase in a direction away from the first aperture expander 690 of the second waveguide, and the second aperture expander 692 of the second waveguide can have a first facet with the lowest reflectivity and a final facet (e.g., a terminal facet) that can be a mirror. Alternatively, the reflectivity of the fourth plurality of partially reflective facets can be constant in a direction away from the first aperture expander 690 of the second waveguide and, separately from this feature, can terminate with a final facet that may or may not be a mirror.

[0065] As described above, the image projector 132 may provide a collimated image beam 610 that may be an illumination representation of a digital image having an image field that is a two-dimensional representation of the digital image. Thus, the first output image beam 612 and the second output image beam 614 and others may propagate through various optical elements within the optical system 100 as a two-dimensional (2D) image field around the illustrated central axis.

[0066] According to an example, the first aperture expander 678 of the first waveguide and the first aperture expander 690 of the second waveguide may be oriented parallel to each other or perpendicular to each other. Other arrangements are also possible, and the first aperture expander 690 of the second waveguide may be disposed on the side of the second waveguide 688 that is furthest (e.g., distal) from the first waveguide 676. In this case, the first waveguide 676 may be disposed oppositely around the diagonal axis 652, and for example, compared to FIG. 4A, the first input aperture 678 may be disposed perpendicular to above or below the diagonal axis 652. Similarly, the second waveguide 688 may be disposed oppositely around the diagonal axis 658, and for example, the second input aperture 690 may be disposed perpendicular to above or below the diagonal axis 658 compared to FIG. 4A. Either the first mirror 654 or the second mirror 656 may include a coating configured to select, for example, two of the four images provided by the associated image pipe. In some examples, the first mirror 654 and / or the second mirror 656 may not be used.

[0067] According to an example, the coupling assembly 620 may also include an active half-wave plate liquid crystal element (AHWP) 648 configured to receive the collimated image beam 610 and provide a converted image beam 650. The active half-wave plate liquid crystal element 648 may be an active optical element controlled by a signal from the controller 114 to selectively change the polarization of at least a portion of the collimated image beam 610, such as changing from S polarization to P polarization when activated, to provide the converted image beam 650. In this example, the first side 624 of the polarization beam splitter 622 may receive the converted image beam 650 and provide a first output image beam 612 from the first side 624 of the polarization beam splitter 622 and a transmitted beam 628 from the second side 626 of the polarization beam splitter. Thus, the optical device 602 may be practiced with or without the active half-wave plate liquid crystal element 648.

[0068] Figures 7A-7C illustrate details regarding an optical system according to various examples of the present disclosure. In particular, FIG. 7A illustrates a front plan view of an optical system 702 according to various embodiments of the present disclosure, FIG. 7B illustrates a first cross-section of the optical system 702 along the X-Z plane identified as cross-section α (alpha), and FIG. 7C illustrates a cross-section of the optical system 702 along the Y-Z plane identified as cross-section β (beta).

[0069] According to an example, the optical device 702 can include an image pipe 760 integrated with a first waveguide 776 (labeled "A"). A portion of the image pipe 760 can be fixed to a portion of the first waveguide 776 using, for example, a low refractive index (LRI) adhesive 706. The first waveguide 776 can have a first waveguide front surface 783 that is parallel to a first waveguide back surface 784. In some examples, the first waveguide 776 can directly receive a collimated image beam 710 ("i" image beam) from the projection optical device 132 at an image pipe input 762 of the image pipe 760. In one example, the first waveguide 776 also receives the collimated image beam 710 and provides a reflected image beam 753 as a first output image beam 712 (e.g., "j" image beam) to the image pipe input 762, and provides a transmitted beam as a second output image beam 714 (e.g., "k" image beam) that can be directed to, for example, another waveguide or other optical element, and can include a first mirror 751 (e.g., a semi-transparent mirror) configured to do so. As described below, the first waveguide 776 can be mounted, for example, to a second waveguide. Similar to the above description, the directly injected image beam 710 or the reflected image beam 753 can propagate within the image pipe 760 as at least one first propagating image beam 764 to an image pipe output 766. Within the image pipe 760, at least one first propagating image beam 764 can be received from a first direction and reflected by a second mirror 755 in a second direction to provide at least one first reflected first propagating image beam 757, which can be further reflected by a third mirror 754 in a third direction (e.g., opposite the first direction) to provide at least one second reflected first propagating image beam 764 at the image pipe output 766, which can be injected into the first waveguide 776 at a waveguide injection region WIR71. The mirror 755 can be oriented to be perpendicular to the front and back surfaces of the waveguide and can be oriented, for example, at an angle of 45° with respect to a side surface of the associated image pipe as compared to the X-axis in the X-Y plane.Thus, the image pipe 760 can have a plurality of segments and mirrors for propagating an image beam around a portion of the first waveguide 776 to the waveguide injection region WIR71 at a distance from the projection optical device 132.

[0070] The first waveguide 776 (labeled "A") can include a first aperture expander 778 of the first waveguide and a second aperture expander 780 of the first waveguide separated from each other by the first waveguide splitting region 782. The first aperture expander 778 of the first waveguide can include mutually parallel and partially reflective optical elements (e.g., facets) that are spaced apart from each other and can be inclined at an angle that can be oblique with respect to at least one of the first waveguide front surface 783 and a plane perpendicular to the first waveguide front surface 783 (e.g., the X-Z plane). Illumination from at least one reflected first propagating image beam 764 is received in a first direction (e.g., along the central axis of the first waveguide aperture expander 778), and then reflected in a second direction and propagated as a first plurality of expanded image beams X7A1 of the first waveguide that can be directed to the second aperture expander 780 of the first waveguide within the first waveguide 776. Thus, the illumination of at least one reflected first propagating image beam 764 can be expanded in a first dimension by the spaced-apart facets of the first waveguide aperture expander 778 to provide a first plurality of expanded image beams X7A1. The reflectivity of the first plurality of partially reflective facets within the first aperture expander 778 of the first waveguide can increase in a direction away from the waveguide injection region WIR71, and the first aperture expander 778 of the first waveguide can have a first facet with the lowest reflectivity and can terminate with a final facet 779 that can be a total reflection mirror. Alternatively, the reflectivity of the first plurality of partially reflective facets can be constant in a direction away from the waveguide region WIR71 and, separately from this feature, can terminate with a final facet 779 that may or may not be a mirror.

[0071] Similarly, the second aperture expander 780 of the first waveguide may include mutually parallel and partially reflective optical elements (e.g., facets) that are spaced apart from each other and can be inclined at an angle that may be oblique to at least one of the front surface 783 of the first waveguide and a plane perpendicular to the front surface 783 of the first waveguide (e.g., the X-Z plane). Illumination from the first plurality of expanded image beams X7A1 is received in a second direction and then can be reflected in a third direction toward the back surface 784 of the first waveguide by the second plurality of partially reflective optical elements within the second aperture expander 780 of the first waveguide. In this way, the illumination from the first plurality of expanded image beams X7A1 can be expanded in a second dimension by the spaced-apart facets of the second aperture expander 780 of the first waveguide to provide a second plurality of expanded image beams X7A2. The plurality of expanded image beams X7A1 can be expanded in a second dimension different from the first dimension to provide a second plurality of expanded image beams X7A2. Thus, the first aperture expander 778 of the first waveguide and the second aperture expander 780 of the first waveguide can cooperate to provide a two-dimensional (2D) expansion of the illumination of at least one first propagated image beam 764 that can be emitted from the back surface 784 of the first waveguide as a first expanded output image beam 786. Similar to the first aperture expander 778 of the first waveguide, the reflectivity of the second plurality of partially reflective facets within the second aperture expander 780 of the first waveguide can increase in a direction away from the first aperture expander 778 of the first waveguide, and the second aperture expander 780 of the first waveguide can have a first facet with the lowest reflectivity and a final facet that can be a mirror. Alternatively, the reflectivity of the first plurality of partially reflective facets can be constant in a direction away from the first aperture expander 778 of the first waveguide and, apart from this feature, can terminate with a final facet that may or may not be a mirror.

[0072] Figures 8A-8C illustrate details regarding an optical system according to various examples of the present disclosure. In particular, FIG. 8A illustrates a front plan view of an optical system 802 according to various embodiments of the present disclosure, FIG. 8B illustrates a first cross-section of the optical system 802 along the X-Z plane identified as cross-section α (alpha), and FIG. 8C illustrates a cross-section of the optical system 802 along the Y-Z plane identified as cross-section β (beta).

[0073] According to an example, the optical device 802 may include an image pipe 860 integrated with a first waveguide 876 (labeled "A"). The optical device 802 may include, for example, a second waveguide 888 (labeled "B") that may be fixed to the back of the first waveguide 876, and / or a portion of the image pipe 860 may be fixed to a portion of the first waveguide 876 using a low refractive index (LRI) adhesive 806. The optical device 802 may also include a coupling assembly 820 that may be disposed at least partially between a portion of the first waveguide 876 and the second waveguide 888. The first waveguide 876 may have a first waveguide front surface 883 that is parallel to the first waveguide back surface 884. The second waveguide 888 may have a second waveguide front surface 895 that is parallel to the second waveguide back surface 896. In some examples, the first waveguide 876 may directly receive a collimated image beam 810 ("i" image beam) from the projection optical device 132 to the image pipe input portion 862 of the image pipe 860 and may be injected at an angle oblique to the first waveguide main surface. In one example, the first waveguide 876 may also include a first mirror 851 configured to receive the collimated image beam 810 and provide a reflected image beam 853 to the image pipe input portion 862. Similar to the above description, the directly injected image beam 810 or the reflected image beam 853 may propagate within the image pipe 860 as at least one first propagating image beam 864 to the image pipe output portion 866. Within the image pipe 860, at least one first propagating image beam 864 may be received from a first direction, reflected by a second mirror 855 in a second direction to provide at least one first reflected first propagating image beam 857, which may be further reflected by a third mirror 854 in a third direction (e.g., opposite to the first direction) to provide at least one second reflected first propagating image beam 864 at the image pipe output portion 866, which may be injected into the first waveguide 876 in the waveguide injection region WIR81.Thus, the image pipe 860 can have a plurality of segments and mirrors for propagating an image beam around a portion of the first waveguide 876 to the waveguide injection region WIR81 at a distance from the projection optical device 132, and can enable injection of an image (e.g., an image beam) from a previously unreached direction, for example.

[0074] The coupling assembly 820 can be disposed between a portion of the second waveguide 888 and a portion of the first waveguide 876, and the collimated image beam 810 can be injected into the back surface 896 of the second waveguide 888. The coupling assembly 820 can include a polarization beam splitter 822 having a first side and a second side. The coupling assembly 820 can also include a half-wave plate 830 having a first side and a second side. The first side of the polarization beam splitter 822 can be disposed adjacent to a portion of the second waveguide 888 and can be configured to receive a portion of the collimated image beam 810 injected into the second waveguide back surface 896. The polarization beam splitter 822 can reflect a portion of the collimated image beam 810 injected into the second waveguide back surface 896 that has S polarization as a first output beam 812 (e.g., a "j" image beam) propagating within the second waveguide 888 and reflected from the second waveguide front surface 895. The polarization beam splitter 822 can transmit a portion of the collimated image beam 810 escaping from the second waveguide front surface 895 having P polarization that is directed to the first side of the half-wave plate 830, which can convert the incident portion of the collimated image beam 810 having P polarization to have S polarization and be injected into the back surface 884 of the first waveguide 876 as a second output beam 814 (e.g., a "k" image beam) propagating within the first waveguide 876 from the second side of the half-wave plate.

[0075] The first waveguide 876 (labeled "A") may include a first aperture expander 878 of the first waveguide and a second aperture expander 880 of the first waveguide separated from each other by a first waveguide splitting region 882. The first aperture expander 878 of the first waveguide may include mutually parallel and partially reflective optical elements (e.g., facets) that are spaced apart from each other and inclined at an angle that may be oblique to at least one of the first waveguide front surface 883 and a plane perpendicular to the first waveguide front surface 883 (e.g., the X-Z plane). Illumination from at least one first propagating image beam 864 that is reflected may be received in a first direction (e.g., along the central axis of the first waveguide aperture expander 878), and then reflected in a second direction and propagated as a first plurality of expanded image beams X8A1 of the first waveguide that may be directed to the second aperture expander 880 of the first waveguide within the first waveguide 876. Thus, the illumination of at least one first propagating image beam 864 that is reflected may be expanded in a first dimension by the spaced-apart facets of the first waveguide aperture expander 878 to provide a first plurality of expanded image beams X8A1. The reflectivity of the first plurality of partially reflective facets within the first aperture expander 878 of the first waveguide may increase in a direction away from the waveguide injection region WIR81, and the first aperture expander 878 of the first waveguide may have a first facet with the lowest reflectivity and may terminate with a final facet 879 that may be a total reflection mirror. Alternatively, the reflectivity of the first plurality of partially reflective facets may be constant in a direction away from the waveguide region WIR81 and, separately from this feature, may terminate with a final facet 879 that may or may not be a mirror.

[0076] Similarly, the second aperture expander 880 of the first waveguide may include optically reflective elements (e.g., facets) that are spaced apart from each other, are parallel to each other, and are partially reflective, and that may be inclined at an angle that may be oblique with respect to at least one of the first waveguide front surface 883 and a plane perpendicular to the first waveguide front surface 883 (e.g., the X-Z plane). Illumination from the first plurality of expanded image beams X8A1 may be received in a second direction and then reflected by the second plurality of partially reflective optical elements within the second aperture expander 880 of the first waveguide in a third direction toward the first waveguide back surface 884. Thus, illumination from the first plurality of expanded image beams X8A1 may be expanded in a second dimension by the spaced-apart facets of the second aperture expander 880 of the first waveguide to provide a second plurality of expanded image beams X8A2. The plurality of expanded image beams X8A1 may be expanded in a second dimension different from the first dimension to provide a second plurality of expanded image beams X8A2. Accordingly, the first aperture expander 878 of the first waveguide and the second aperture expander 880 of the first waveguide may cooperate to provide a two-dimensional (2D) expansion of the illumination of at least one first propagated image beam 864 that may be emitted from the first waveguide back surface 884 as a first expanded output image beam 886. Similar to the first aperture expander 878 of the first waveguide, the reflectivity of the second plurality of partially reflective facets within the second aperture expander 880 of the first waveguide may increase in a direction away from the first aperture expander 878 of the first waveguide, and the second aperture expander 880 of the first waveguide may have an initial facet having the lowest reflectivity and a final facet that may be a mirror. Alternatively, the reflectivity of the first plurality of partially reflective facets may be constant in a direction away from the first aperture expander 878 of the first waveguide and may terminate with a final facet that may or may not be a mirror, separately from this feature.

[0077] The second waveguide 888 (labeled "B") may include a first aperture expander 890 of the second waveguide and a second aperture expander 892 of the second waveguide separated from each other by a second waveguide splitting region 894. The first aperture expander 890 of the second waveguide may include mutually parallel and partially reflective optical elements (e.g., facets) that are spaced apart and inclined at an angle that may be oblique to at least one of the second waveguide front face 895 and a plane perpendicular to the second waveguide front face 895 (e.g., the X-Z plane). Illumination from the first output image beam 812 is received in a fourth direction (e.g., along the central axis of the second waveguide aperture expander 890) and then reflected in a fifth direction by the first plurality of partially reflective optical elements within the first aperture expander 890 of the second waveguide and directed to the second aperture expander 892 of the second waveguide and may be conducted within the second waveguide 888 as a first plurality of expanded image beams X8B1 of the second waveguide. Thus, the illumination of the first output image beam 812 may be expanded in a first dimension (e.g., the third dimension) by the spaced-apart facets to provide a first plurality of expanded image beams X8B1. The reflectivity of the third plurality of partially reflective facets within the first aperture expander 890 of the second waveguide may increase in a direction away from the second waveguide injection region WIR82, and the first aperture expander 890 of the second waveguide may have an initial facet with the lowest reflectivity and may terminate with a final facet that may be a mirror. Alternatively, the reflectivity of the third plurality of partially reflective facets may be constant in a direction away from the waveguide region WIR82 and, apart from this feature, may terminate with a final facet that may or may not be a mirror.

[0078] Similarly, the second aperture expander 892 of the second waveguide may include mutually parallel and partially reflective optical elements (e.g., facets) of a fourth plurality of planes that are spaced apart from each other and may be inclined at an angle that may be oblique with respect to at least one of the second waveguide front surface 895 and a plane perpendicular to the second waveguide front surface 895 (e.g., the X-Z plane). Illumination from the third plurality of expanded image beams X8B1 may be received in a fifth direction and then reflected by the fourth plurality of partially reflective optical elements within the second aperture expander 892 of the second waveguide in a sixth direction toward the second waveguide rear surface 896. Thus, illumination from the third plurality of expanded image beams X8B1 may be expanded in a second dimension (e.g., the fourth dimension) by the spaced-apart facets of the second aperture expander 892 of the second waveguide to provide a second plurality of expanded image beams X8B2. The plurality of expanded image beams X8B1 may be expanded in a second dimension different from the first dimension to provide a second plurality of expanded image beams X8B2. Accordingly, the first aperture expander 890 of the second waveguide and the second aperture expander 892 of the second waveguide may cooperate to provide a two-dimensional (2D) expansion of the illumination of the first output image beam 812 as a second expanded output image beam 898 that may be emitted from the second waveguide rear surface 896. Similar to the first aperture expander 890 of the second waveguide, the reflectivity of the fourth plurality of partially reflective facets within the second aperture expander 892 of the second waveguide may increase in a direction away from the first aperture expander 890 of the second waveguide, and the second aperture expander 892 of the second waveguide may have a first facet with the lowest reflectivity and a final facet (e.g., a terminal facet) that may be a mirror. Alternatively, the reflectivity of the fourth plurality of partially reflective facets may be constant in a direction away from the first aperture expander 890 of the second waveguide and, separately from this feature, may terminate with a final facet that may or may not be a mirror. By way of example, the first aperture expander 878 of the first waveguide and the first aperture expander 890 of the second waveguide may be oriented parallel to each other. Other arrangements are also possible and both the first waveguide 876 and the second waveguide 888 may be rotated.

[0079] As described above, the second waveguide 888 can be configured to receive the first output image beam 812 and emit the second extended output image beam 898 from the back surface 896 of the second waveguide. The first waveguide 876 can be configured to receive the second output image beam 814 and emit the first extended output image beam 886 from the back surface 884 of the first waveguide. It should be noted that the first extended output image beam 886 and the second extended image beam 898 coincide and are separately extended from different directions, and both the first extended output image beam 886 and the second extended image beam 898 can be emitted towards the user's eye to transmit optical information. Therefore, in this configuration, the first waveguide 876 having one embedded image pipe 860 along the overlapping second waveguide 888 can cooperate to effectively double the field of view (FoV) provided by the optical device 802 compared to an example of a single waveguide.

[0080] According to an example, the coupling assembly 820 can also include an active half-wave plate liquid crystal element (AHWP) 848 configured to receive the collimated image beam 810 and provide the converted image beam 850. The active half-wave plate liquid crystal element 848 can be an active optical element controlled by a signal from the controller 114 to selectively change the polarization of at least a portion of the collimated image beam 810, such as changing from S polarization to P polarization when activated, to provide the converted image beam 850. The liquid crystal half-wave plate can be a two-dimensional (2D) array of cells filled with liquid crystals that can twist and align in response to a control voltage. Thus, the active half-wave plate liquid crystal element 848 can provide a variable retardance (e.g., variable delay), for example, by selectively tilting various liquid crystal molecules within the active half-wave plate liquid crystal element 848. The angle of tilt can be rapidly changed on the order of milliseconds. Similar to the other examples described above, the optical device 802 can be practiced with or without the active half-wave plate liquid crystal element 848.

[0081] Figures 9A-9C illustrate details regarding an optical system according to various examples of the present disclosure. In particular, FIG. 9A illustrates a front plan view of an optical system 902 according to various examples of the present disclosure, FIG. 9B illustrates a first cross-sectional view of an image pipe 960 along an X-Z plane illustrating a homogenization layer 963 having a first orientation, and FIG. 9C illustrates a first cross-sectional view of an image pipe 960 along an X-Z plane illustrating a homogenization layer 965 having a second orientation perpendicular to the first orientation.

[0082] According to an example, the optical device 902 can include an image pipe 960 integrated with a first waveguide 976 (labeled "A"). A portion of the image pipe 960 can be fixed to a portion of the first waveguide 976, for example, using a low refractive index (LRI) adhesive 906. The first waveguide 976 can have a first waveguide front 983 that is parallel to a first waveguide back 984. In some examples, the first waveguide 976 can directly receive a collimated image beam 910 ("i" image beam) from a projection optical device 132 (not shown) at an image pipe input 962 of the image pipe 960. Similar to the above description, the directly injected image beam 910 can propagate within the image pipe 960 as at least one first propagating image beam 964 to an image pipe output 966. Within the image pipe 960, at least one first propagating image beam 964 can be received from a first direction, reflected by a mirror 955 in a second direction, and provide at least one reflected propagating image beam 957 at the image pipe output 966, which can be injected into the first waveguide 976 at a waveguide injection region WIR91. Thus, the image pipe 960 can propagate an input image beam to the waveguide injection region WIR91, for example, at a distance from an image source. FIG. 9B illustrates a first cross-sectional view of the image pipe 960 along the X-Z plane illustrating a homogenizing layer 963 having a first orientation, and FIG. 9C illustrates a first cross-sectional view of the image pipe 960 along the X-Z plane illustrating a homogenizing layer 965 having a second orientation perpendicular to the first orientation. The homogenizing layer 963 and / or the homogenizing layer 965 can be formed as a coating layer or film along the length of the image pipe 960 and disposed within the image pipe 960. The homogenizing layer 963 and / or the homogenizing layer 965 can improve the illumination uniformity before expansion, resulting in more uniform illumination and an expanded image.

[0083] The first waveguide 976 (labeled "A") may include a first aperture expander 978 of the first waveguide and a second aperture expander 980 of the first waveguide that are separated from each other by a first waveguide splitting region 982. The first aperture expander 978 of the first waveguide may include mutually parallel and partially reflective optical elements (e.g., facets) that are spaced apart from each other and inclined at an angle that may be oblique to at least one of the first waveguide front surface 983 and a plane perpendicular to the first waveguide front surface 983 (e.g., the X-Z plane). Illumination from at least one reflected first propagation image beam 964 may be received in a first direction (e.g., along the central axis of the first waveguide aperture expander 978), and then reflected in a second direction and propagated as a first plurality of expanded image beams X9A1 of the first waveguide that are directed to the second aperture expander 980 of the first waveguide within the first waveguide 976. Thus, the illumination of at least one reflected first propagation image beam 964 may be expanded in a first dimension by the spaced-apart facets of the first waveguide aperture expander 978 to provide a first plurality of expanded image beams X9A1. The reflectivity of the first plurality of partially reflective facets within the first aperture expander 978 of the first waveguide may increase in a direction away from the waveguide injection region WIR91, and the first aperture expander 978 of the first waveguide may have a first facet with the lowest reflectivity and may terminate with a final facet that may be a total reflection mirror. Alternatively, the reflectivity of the first plurality of partially reflective facets may be constant in a direction away from the waveguide region WIR91 and, separately from this feature, may terminate with a final facet that may or may not be a mirror.

[0084] Similarly, the second aperture expander 980 of the first waveguide may include mutually parallel and partially reflective optical elements (e.g., facets) that are spaced apart from each other and can be tilted at an angle that may be oblique to at least one of the first waveguide front surface 983 and a plane perpendicular to the first waveguide front surface 983 (e.g., the X-Z plane). Illumination from the first plurality of expanded image beams X9A1 is received in a second direction and then can be reflected in a third direction toward the first waveguide back surface 984 by the second plurality of partially reflective optical elements within the second aperture expander 980 of the first waveguide. In this way, the illumination from the first plurality of expanded image beams X9A1 can be expanded in a second dimension by the spaced-apart facets of the second aperture expander 980 of the first waveguide to provide a second plurality of expanded image beams X9A2. The plurality of expanded image beams X9A1 can be expanded in a second dimension different from the first dimension to provide a second plurality of expanded image beams X9A2. Thus, the first aperture expander 978 of the first waveguide and the second aperture expander 980 of the first waveguide can cooperate to provide a two-dimensional (2D) expansion of the illumination of at least one first propagated image beam 964 reflected as a first expanded output image beam 986 that can be emitted from the first waveguide back surface 984. Similar to the first aperture expander 978 of the first waveguide, the reflectivity of the second plurality of partially reflective facets within the second aperture expander 980 of the first waveguide can increase in a direction away from the first aperture expander 978 of the first waveguide, and the second aperture expander 980 of the first waveguide can have a first facet with the lowest reflectivity and a final facet that can be a mirror. Alternatively, the reflectivity of the first plurality of partially reflective facets can be constant in a direction away from the first aperture expander 978 of the first waveguide and, separately from this feature, can terminate with a final facet that may or may not be a mirror. The homogenization layer 963 having the first orientation illustrated in FIG. 9B and the homogenization layer 965 having the second orientation illustrated in FIG. 9C can, in some examples, enable a reduced input aperture.

[0085] Figures 10A - 10H illustrate details regarding various configurations of an optical system according to various examples of the present disclosure. Further, the optical systems illustrated in Figures 7A - 7C, Figures 8A - 8C, and Figures 9A - 9C can be suitably combined with any of the optical systems illustrated in Figures 10A - 10H. Thus, each of the first waveguide and the second waveguide illustrated in Figures 10A - 10H can be implemented as a single waveguide or a dual waveguide, either or both, as described. Also, the orientation of some elements in the various illustrative figures can be modified, exchanged, rotated, reflected, or moved with respect to similar elements in the corresponding illustrative figures while retaining the same function. Each of the features illustrated with the various embodiments is intended to be combinable in any manner consistent with the present disclosure.

[0086] Figure 10A illustrates a front elevation view of an optical system according to various examples of the present disclosure. In particular, Figure 10A illustrates an optical system that may be similar in some respects to the optical systems illustrated in Figures 3A and 4A. Thus, Figure 10B may illustrate an optical system that may be considered a modified version of the optical system illustrated in Figure 10A. In Figure 10A and elsewhere, as described, the user's eyes (1007, 1008) and nose 1009 may be illustrated to provide a reference for how the optical system 1002 may be worn on the user's head and used to provide optical information. For reference, a user right side 1000 and a user left side 1001 may indicate the relative positions of the optical system 1002 and other elements from the user's perspective. The frame 1048 may be configured to support various elements of the optical system 1002, such as a projection optical device (POD), a coupling assembly having various passive and / or active elements, one or more image pipes, a first waveguide, and a second waveguide. The frame 1048 may be configured to hide one or more image pipes or other elements within a portion of the frame. Thus, one or more image pipes may not be visible after the optical system 1002 is assembled. Figure 10C illustrates a front elevation view of an optical system according to various examples of the present disclosure. Similarly, Figure 10D may illustrate an optical system that may be considered a modified version of the optical system illustrated in Figure 10C.

[0087] Similarly, Figure 10E illustrates a front elevation view of an optical system according to various examples of the present disclosure. In particular, Figure 10E illustrates an optical system that may be similar in some respects to the optical system illustrated in Figure 5A. In some respects, Figure 10F may illustrate an optical system that may be considered a modified version of the optical system illustrated in Figure 10E.

[0088] FIG. 10H illustrates a front plan view of an optical system according to various examples of the present disclosure. In particular, FIG. 10H illustrates an optical system that may be similar in some respects to the optical system illustrated in FIG. 6A. FIG. 10G illustrates a front plan view of an optical system according to various examples of the present disclosure. In particular, FIG. 10G illustrates an optical system that may be similar in some respects to a modified version of the optical system illustrated in FIG. 6A. In the example of FIG. 10G, a longer image pipe (e.g., I.P. (image pipe)) may be used relative to the shorter image pipe shown in FIG. 10H. Thus, for example, compared to the corresponding injection points of the image beam illustrated in FIG. 10H or FIG. 6A, the first injection point for the first image beam into the first waveguide may be located further to the right of the user, and the second injection point for the second image beam into the second waveguide may be located further to the left of the user.

[0089] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” and / or “having,” when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0090] The corresponding structures, materials, acts, and equivalents of all means-plus-function or step-plus-function limitations in the claims below, if any, are intended to cover any structure, material, or act for performing the recited function in combination with other claimed elements as specifically claimed. The description of the invention has been presented for purposes of illustration and description but is not intended to be exhaustive or limited to the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The various embodiments were chosen and described in order to best explain the principles of the invention and its practical application and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.

Claims

1. An optical device comprising: a combining assembly configured to receive a collimated image beam and provide a first output image beam and a second output image beam; an image pipe configured to receive the first output image beam at an image pipe input and provide at least one propagating image beam at an image pipe output; a first waveguide having a first waveguide back surface, configured to receive the second output image beam and emit a first expanded output image beam from the first waveguide back surface; a second waveguide having a second waveguide back surface, configured to receive the at least one propagating image beam and emit a second expanded output image beam from the second waveguide back surface; The optical device according to claim 1, comprising:

2. The combining assembly further comprises: a translucent mirror having a first surface of the translucent mirror and a second surface of the translucent mirror opposite to the first surface of the translucent mirror, wherein the first surface of the translucent mirror is configured to receive the collimated image beam, provide the first output image beam reflected from the first surface of the translucent mirror, and provide the second output image beam emitted from the second surface of the translucent mirror. The optical device according to claim 1.

3. The first waveguide comprises a first aperture expander of the first waveguide and a second aperture expander of the first waveguide. The first aperture expander of the first waveguide is configured to expand the second output image beam and provide a first plurality of expanded image beams of the first waveguide directed to the second aperture expander of the first waveguide. The second aperture expander of the first waveguide is configured to expand the first plurality of expanded image beams of the first waveguide and provide a second plurality of expanded image beams of the first waveguide emitted as the first expanded output image beam. The second waveguide includes a mirror configured to receive the at least one propagating image beam and provide a reflected at least one propagating image beam, and the second waveguide further includes a first aperture expander of the second waveguide and a second aperture expander of the second waveguide. The first aperture expander of the second waveguide expands the reflected at least one propagating image beam and is configured to provide a first plurality of expanded image beams of the second waveguide directed toward the second aperture expander of the second waveguide. The second aperture expander of the second waveguide expands the first plurality of expanded image beams of the second waveguide and is configured to provide a second plurality of expanded image beams of the second waveguide emitted as the second expanded output image beam. The optical device according to claim 2.

4. The optical device according to claim 3, further comprising an image projector configured to provide the collimated image beam based on a digital image, wherein the collimated image beam is collimated infinitely, and the projector includes a liquid crystal on silicon display.

5. An optical system, an image projector configured to provide a collimated image beam based on a digital image; a coupling assembly configured to receive the collimated image beam and provide a first output image beam and a second output image beam; an image pipe configured to receive the first output image beam at an image pipe input and provide at least one propagating image beam at an image pipe output; a first waveguide having a first waveguide rear surface, the first waveguide configured to receive the second output image beam and emit a first expanded output image beam from the first waveguide rear surface; a second waveguide having a second waveguide rear surface, the second waveguide configured to receive the at least one propagating image beam and emit a second expanded output image beam from the second waveguide rear surface; comprising an optical system.

6. The collimated image beam is collimated infinitely, the projector includes one of a liquid crystal display, a liquid crystal on silicon display, an organic light emitting diode display, a micro light emitting diode display, and a laser display, The image pipe includes at least one of a glass material, an acrylic material, and a polycarbonate material. A portion of the first waveguide is fixed to a portion of the image pipe with a layer of low refractive index adhesive. The image pipe is an elongated transparent member having a first end and a second end with a rectangular cross-section and orthogonal walls, the image pipe being configured to receive at least one input image beam and provide four replicated output image beams based on the at least one input image beam. The optical system according to claim 5, which is one of the above.

7. The coupling assembly includes a semi-transparent mirror having a first surface of the semi-transparent mirror and a second surface of the semi-transparent mirror opposite the first surface of the semi-transparent mirror, the first surface of the semi-transparent mirror receiving the collimated image beam and providing the first output image beam reflected from the first surface of the semi-transparent mirror and the second output image beam emitted from the second surface of the semi-transparent mirror. The first waveguide includes a first aperture expander of the first waveguide and a second aperture expander of the first waveguide, the first aperture expander of the first waveguide being configured to expand the second output image beam and provide a first plurality of expanded image beams of the first waveguide directed to the second aperture expander of the first waveguide, the second aperture expander of the first waveguide being configured to expand the first plurality of expanded image beams of the first waveguide and provide a second plurality of expanded image beams of the first waveguide emitted as the first expanded output image beam. The second waveguide includes a mirror configured to receive the at least one propagating image beam and provide a reflected at least one propagating image beam, and the second waveguide further includes a first aperture expander of the second waveguide and a second aperture expander of the second waveguide. The first aperture expander of the second waveguide expands the reflected at least one propagating image beam and is configured to provide a first plurality of expanded image beams of the second waveguide directed to the second aperture expander of the second waveguide. The second aperture expander of the second waveguide expands the first plurality of expanded image beams of the second waveguide and is configured to provide a second plurality of expanded image beams of the second waveguide emitted as the second expanded output image beam. The optical system according to claim 5.

8. The coupling assembly is a polarization beam splitter having a first side of the polarization beam splitter and a second side of the polarization beam splitter opposite the first side of the polarization beam splitter. The first side of the polarization beam splitter is configured to receive the collimated image beam, provide the first output image beam from the first side of the polarization beam splitter, and provide a transmitted image beam from the second side of the polarization beam splitter. A polarization beam splitter; is a half-wave plate having a first side of the half-wave plate and a second side of the half-wave plate, and is configured to receive the transmitted image beam on the first side of the half-wave plate and provide the second output image beam from the second side of the half-wave plate. A half-wave plate, and the optical system according to claim 5.

9. The first waveguide includes a first aperture expander of the first waveguide and a second aperture expander of the first waveguide. The first aperture expander of the first waveguide expands the second output image beam and is configured to provide a first plurality of expanded image beams of the first waveguide directed to the second aperture expander of the first waveguide. The second aperture expander of the first waveguide expands the first plurality of expanded image beams of the first waveguide and is configured to provide a second plurality of expanded image beams of the first waveguide emitted as the first expanded output image beam. The second waveguide includes a first aperture expander of the second waveguide and a second aperture expander of the second waveguide. The first aperture expander of the second waveguide expands at least one propagating image beam and is configured to provide a plurality of first expanded image beams of the second waveguide directed to the second aperture expander of the second waveguide. The second aperture expander of the second waveguide expands the plurality of first expanded image beams of the second waveguide and is configured to provide a plurality of second expanded image beams of the second waveguide emitted as the second expanded output image beam. The optical system according to claim 8.

10. The coupling assembly an active half-wave plate liquid crystal element configured to receive the collimated image beam and provide a converted image beam, a polarization beam splitter having a first side of the polarization beam splitter and a second side of the polarization beam splitter opposite to the first side of the polarization beam splitter. The first side of the polarization beam splitter is configured to receive the converted image beam, provide the first output image beam from the first side of the polarization beam splitter, and provide a transmitted image beam from the second side of the polarization beam splitter. A polarization beam splitter, a half-wave plate having a first side of the half-wave plate and a second side of the half-wave plate. The first side of the half-wave plate is configured to receive the transmitted image beam and provide the second output image beam from the second side of the half-wave plate. The optical system according to claim 5, further comprising a half-wave plate.

11. The first waveguide includes a first aperture expander of the first waveguide and a second aperture expander of the first waveguide. The first aperture expander of the first waveguide expands the second output image beam and is configured to provide a plurality of first expanded image beams of the first waveguide directed to the second aperture expander of the first waveguide. The second aperture expander of the first waveguide expands the plurality of first expanded image beams of the first waveguide and is configured to provide a plurality of second expanded image beams of the first waveguide emitted as the first expanded output image beam. The second waveguide includes a mirror configured to receive the at least one propagating image beam and provide a reflected at least one propagating image beam. The second waveguide further includes a first aperture expander of the second waveguide and a second aperture expander of the second waveguide. The first aperture expander of the second waveguide expands the reflected at least one propagating image beam and is configured to provide a first plurality of expanded image beams of the second waveguide directed toward the second aperture expander of the second waveguide. The second aperture expander of the second waveguide expands the first plurality of expanded image beams of the second waveguide and is configured to provide a second plurality of expanded image beams of the second waveguide emitted as the second expanded output image beam. The optical system according to claim 10.

12. The first waveguide includes a first aperture expander of the first waveguide and a second aperture expander of the first waveguide. The first aperture expander of the first waveguide expands the second output image beam and is configured to provide a first plurality of expanded image beams of the first waveguide directed toward the second aperture expander of the first waveguide. The second aperture expander of the first waveguide expands the first plurality of expanded image beams of the first waveguide and is configured to provide a second plurality of expanded image beams of the first waveguide emitted as the first expanded output image beam. The second waveguide includes a first aperture expander of the second waveguide and a second aperture expander of the second waveguide. The first aperture expander of the second waveguide expands at least one propagating image beam and is configured to provide a first plurality of expanded image beams of the second waveguide directed toward the second aperture expander of the second waveguide. The second aperture expander of the second waveguide expands the first plurality of expanded image beams of the second waveguide and is configured to provide a second plurality of expanded image beams of the second waveguide emitted as the second expanded output image beam. The optical system according to claim 10.

13. The image pipe is a first image pipe. The first waveguide includes a front surface of the first waveguide opposite to the back surface of the first waveguide. The optical system Comprising a third waveguide having a third waveguide rear surface, the third waveguide being configured to receive the second output image beam and emit a third expanded output image beam from the third waveguide rear surface, the third waveguide rear surface being fixed to the front surface of the first waveguide, the third waveguide being a second image pipe configured to receive the second output image beam and provide at least one propagated third image beam at a third image pipe output; a first aperture expander of the third waveguide, configured to expand the at least one propagated third image beam and provide a plurality of first expanded image beams of the third waveguide; a second aperture expander of the third waveguide configured to expand the plurality of first expanded image beams and provide a plurality of second expanded image beams of the third waveguide that are emitted as the third expanded output image beam, the second image pipe being configured to surround at least a portion of the second aperture expander of the third waveguide. The optical system according to claim 10.

14. The optical system according to claim 5, further comprising a frame configured to support the image projector, the coupling assembly, the image pipes, the first waveguide, and the second waveguide, the frame being configured to conceal the image pipes within a portion of the frame.

15. An optical system, an image projector configured to provide a collimated image beam based on a digital image; a coupling assembly configured to receive the collimated image beam and provide a first output image beam and a second output image beam; a first image pipe configured to receive the first output image beam at a first image pipe input and provide at least one first propagated image beam at a first image pipe output; a second image pipe configured to receive the second output image beam at a second image pipe input and provide at least one second propagated image beam at a second image pipe output; A first waveguide having a first waveguide back surface, configured to receive at least one second propagating image beam and emit a first expanded output image beam from the first waveguide back surface, a first waveguide; A second waveguide having a second waveguide back surface, configured to receive the at least one first propagating image beam and emit a second expanded output image beam from the second waveguide back surface, a second waveguide; An optical system comprising.

16. The coupling assembly is An active half-wave plate liquid crystal element configured to receive the collimated image beam and provide a converted image beam; A polarization beam splitter having a first side of the polarization beam splitter and a second side of the polarization beam splitter opposite the first side of the polarization beam splitter, wherein the first side of the polarization beam splitter receives the converted image beam and provides the second output image beam from the first side of the polarization beam splitter, and is configured to provide a transmitted image beam from the second side of the polarization beam splitter, a polarization beam splitter; A quarter-wave plate having a first side of the quarter-wave plate and a second side of the quarter-wave plate, configured to receive the transmitted image beam on the first side of the quarter-wave plate and provide a converted image beam from the second side of the quarter-wave plate, a quarter-wave plate; A mirror having a reflective mirror surface configured to receive the converted image beam and provide a reflected image beam, wherein the quarter-wave plate is configured to receive the reflected image beam on the second side of the quarter-wave plate and provide a second converted image beam from the first side of the quarter-wave plate, and the polarization beam splitter is configured to receive the second converted image beam on the second side of the polarization beam splitter and provide the first output image beam, the optical system according to claim 15, comprising a mirror.

17. The first waveguide includes a first mirror configured to receive the at least one second propagating image beam and provide a reflected at least one second propagating image beam. The first waveguide further includes a first aperture expander of the first waveguide and a second aperture expander of the first waveguide. The first aperture expander of the first waveguide expands the reflected at least one second propagating image beam and is configured to provide a first plurality of expanded image beams of the first waveguide directed toward the second aperture expander of the first waveguide. The second aperture expander of the first waveguide expands the first plurality of expanded image beams of the first waveguide and is configured to provide a second plurality of expanded image beams of the first waveguide emitted as the first expanded output image beam. The second waveguide includes a second mirror configured to receive the at least one first propagating image beam and provide a reflected at least one first propagating image beam. The second waveguide further includes a first aperture expander of the second waveguide and a second aperture expander of the second waveguide. The first aperture expander of the second waveguide expands the reflected at least one first propagating image beam and is configured to provide a first plurality of expanded image beams of the second waveguide directed toward the second aperture expander of the second waveguide. The second aperture expander of the second waveguide expands the first plurality of expanded image beams of the second waveguide and is configured to provide a second plurality of expanded image beams of the second waveguide emitted as the second expanded output image beam. The optical system according to claim 16. **Claim 18** The first waveguide includes a first waveguide front surface that is opposite to the back surface of the first waveguide. The optical system further includes a third waveguide having a third waveguide back surface, configured to receive the at least one second propagating image beam and emit a third expanded output image beam from the third waveguide back surface, and the third waveguide back surface is fixed to the first waveguide front surface. The third waveguide configured to receive the at least one second propagated image beam and provide at least one propagated third image beam at a third image pipe output; a first aperture expander of a third waveguide, configured to expand the at least one propagated third image beam and provide a first plurality of expanded image beams of the third waveguide; a second aperture expander of a third waveguide, configured to expand the first plurality of expanded image beams and provide a second plurality of expanded image beams of the third waveguide that are emitted as the third expanded output image beam, wherein the second image pipe is configured to surround at least a portion of the second aperture expander of the third waveguide, and the second image pipe has a homogenizing layer; an optical system according to claim 15 comprising a second aperture expander of the third waveguide. **Claim 19** the second waveguide includes a second waveguide front that is opposite the second waveguide back, and the optical system includes a polarization beam splitter having a first side of the polarization beam splitter and a second side of the polarization beam splitter opposite the first side of the polarization beam splitter, wherein the first side of the polarization beam splitter is configured to receive the at least one first propagated image beam and provide a second transmitted image beam from the second side of the polarization beam splitter; a polarization beam splitter; a half-wave plate having a first side of the half-wave plate and a second side of the half-wave plate, configured to receive the second transmitted image beam at the first side of the half-wave plate and provide a second converted image beam from the second side of the half-wave plate; a half-wave plate; a fourth waveguide having a fourth waveguide back, configured to receive the second converted image beam and emit a fourth expanded output image beam from the fourth waveguide back, wherein the fourth waveguide back is fixed to the second waveguide front; a fourth waveguide further comprising: a fourth image pipe configured to receive the second converted image beam and provide at least one propagated fourth image beam at a fourth image pipe output; A first aperture expander of the fourth waveguide, configured to expand the at least one propagated first image beam and provide a plurality of first expanded image beams of the fourth waveguide. A second aperture expander of the fourth waveguide configured to expand the plurality of fourth expanded image beams and provide a second plurality of expanded image beams of the fourth waveguide that are emitted as the fourth expanded output image beam, wherein the fourth image pipe is configured to surround at least a portion of the second aperture expander of the fourth waveguide, and the fourth image pipe has a homogenizing layer. The optical system according to claim 18, comprising the second aperture expander of the fourth waveguide. **Claim 20** The optical system according to claim 15, further comprising a frame configured to support the image projector, the coupling assembly, the first image pipe, the second image pipe, the first waveguide, and the second waveguide, wherein the frame is configured to conceal the first image pipe and the second image pipe within a portion of the frame.

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