Optical waveguide with aperture diaphragm

Abstract

An optical waveguide is described herein that includes a pair of major surfaces and an aperture configured to receive an input light beam. The waveguide also includes a first set of facets disposed along the first axis, the first set of facets configured to reflect the input light beam along the second axis. The waveguide further comprises an aperture matched with the aperture, and the aperture is configured to block light outside the aperture from entering the optical waveguide. A first dimension of the aperture (and thus the aperture) corresponds to a pitch of the first set of facets, and a second dimension of the aperture (and thus the aperture) corresponds to an aspect of the waveguide corresponding to the second axis. By using the aperture, overexposure of the waveguide and thus non-uniformity in the projected image can be minimized.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 469,577, filed on May 30, 2023. The entire disclosure of U.S. Provisional Application No. 63 / 469,577 is incorporated by reference herein. Background Art

[0003] Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not to be considered prior art merely by virtue of their inclusion in this section.

[0004] The present disclosure generally relates to systems and methods for presenting information to a user, and more particularly, to optical systems and near - eye displays for presenting information to a user.

[0005] In some optical waveguides, a homogenizer (also referred to as a mixer) is disposed between the major surfaces of the waveguide. Such a homogenizer can mix weaker and stronger light rays within the waveguide, which can improve the uniformity of the light. In addition, the homogenizer can allow a smaller entrance pupil and thus allow a smaller projector. Although the homogenizer can provide the above - mentioned benefits, the homogenizer may also introduce non - uniformity if light enters the waveguide beyond the smaller aperture enabled by the mixer. Summary of the Invention

[0006] An optical waveguide having an aperture stop is described herein. The optical waveguide includes a pair of parallel major surfaces and an aperture configured to receive an input beam. The aperture has a first dimension. The optical waveguide further includes a coupling element configured to receive the input beam from the aperture and couple the input beam into the optical waveguide. The optical waveguide further includes a first set of facets disposed between the major surfaces along a first axis and configured to receive the input beam from the coupling element and at least partially reflect the input beam. The optical waveguide further includes an aperture stop configured to block light outside the aperture from entering the optical waveguide. The first dimension corresponds to the pitch of the first set of facets.

[0007] An apparatus is also described herein. The apparatus includes a projector configured to generate an input beam. The apparatus further includes the above - described optical waveguide. It should be noted that the aperture stop of the apparatus can also be on the exit of the display system (e.g., on the outer surface of the projector), rather than on the optical waveguide or as part of the optical waveguide (e.g., at the entrance of the optical waveguide).

[0008] The foregoing summary is illustrative only and is not intended to be limiting in any way. In addition to the above - described illustrative aspects, embodiments, and features, other aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description. In the drawings, like reference numerals indicate the same elements or elements that are functionally similar. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 Examples of systems including an optical waveguide having an aperture stop are shown in accordance with various examples of the present disclosure.

[0010] Figure 2 Examples of optical waveguides including an aperture stop are shown in accordance with various examples of the present disclosure.

[0011] Figure 3 Examples in accordance with various examples of the present disclosure of Figure 2 another view of the optical waveguide.

[0012] Figure 4A Examples in accordance with various examples of the present disclosure of an optical waveguide having a single homogenizer Figure 2 another view.

[0013] Figure 4B Examples in accordance with various examples of the present disclosure of an optical waveguide having two homogenizers Figure 2 another view.

[0014] Figure 5A Examples in accordance with various examples of the present disclosure of over - illumination caused by light outside a first size of the aperture of the incoming optical waveguide.

[0015] Figure 5B Examples in accordance with various examples of the present disclosure of over - illumination caused by light outside a second size of the aperture of the incoming optical waveguide. DETAILED DESCRIPTION

[0016] In the following description, numerous specific details are set forth, such as specific structures, components, materials, dimensions, processing steps, and techniques, in order to provide an understanding of the various embodiments of the present application. However, those of ordinary skill in the art will understand that the various embodiments of the present application may also be practiced without these specific details. In other instances, well - known structures or processing steps have not been described in detail to avoid obscuring the present application.

[0017] Wearable devices such as near - eye displays and / or smart glasses that can be implemented by the systems and methods according to the present disclosure will be described in more detail below. The system can efficiently provide high - quality optical information to a user in various applications.

[0018] Figure 1 FIG. 1 shows a block diagram of an example of an optical system 100 that includes an optical waveguide having an iris aperture. The optical system 100 may include two or more devices or components. The optical system 100 may generally be implemented as a hybrid system that includes various electronic, optical, and electro-optic elements. As will be described in more detail below, the optical system 100 may include a wearable device 102 such as one or more near-eye displays or smart glasses, which may be worn on or around the user's head to convey optical information to one or both of the user's eyes.

[0019] The wearable device 102 may include a controller 104 having a memory 106, where the controller 104 may be configured, for example, to: send electrical signals to and receive electrical signals from various other elements in the optical system 100; execute program instructions stored in the memory 106 to process and provide information; operate the wearable device 102; and interact with other systems external to the wearable device 102. The controller 104 may include a microcontroller, a processor, various discrete components, a programmable logic device, and / or various interface circuits that can access the memory 106, and the memory 106 may be removable, replaceable, programmable, and reprogrammable to update the instructions to the controller 104.

[0020] The wearable device 102 may also include a power management module 108 having a battery 110, where the power management module 108 may be configured to charge, discharge, and monitor the power usage of the battery 110. For example, various elements of the wearable device 102 may receive power from the battery 110, including the controller 104, one or more image projectors 112 (e.g., projection optics or a Projecting Optical Device (POD)), and a graphics engine 114 having one or more digital images 116.

[0021] Each image projector may be configured to: generate a collimated image beam based on the digital image 116. The collimated image beam may be an illuminated representation of a digital image having an image field that is a two-dimensional representation of a digital image based on a single graphic image (e.g., a static image) or a sequence of graphic images (e.g., a moving image). The collimated image beam may be collimated to infinity.

[0022] The wearable device 102 may also include one or more light guiding optical elements 118 (e.g., LOE, also denoted as waveguide WG, waveguide with an aperture aperture), and the one or more light guiding optical elements 118 include a transparent material configured to receive and propagate light, wherein light can enter and exit various outer and inner surfaces of the light guiding optical element 118. For example, the transparent material including the light guiding optical element 118 may include optical glass or other suitable materials, and the other suitable materials are transformed into complex optical structures using processes that may include coating, stacking, slicing, polishing, and shaping the transparent material. For example, the process may include adding partially reflective materials or fully reflective materials (e.g., mirror coatings). Similarly, for example, the process may also include adding partially opaque materials or fully opaque materials (e.g., light blockers for blocking light).

[0023] The graphics engine 114 may be coupled to the image projector 112 and the light guiding optical element 118. The graphics engine 114 may be configured to directly operate the image projector 112 under the guidance of the controller 104. For example, the graphics engine 114 may provide graphics processing of the digital image before the illuminated representation of the digital image is projected by the image projector 112.

[0024] The wearable device 102 may also include a frame 120 (e.g., structure) for supporting and holding one or more elements in the wearable device 102. For example, the frame 120 may support the first image projector 112a and hold it in a position adjacent to the first light guiding optical element 118a. Similarly, the frame 120 may support the second image projector 112b and hold it in a position adjacent to the second light guiding optical element 118b. In this way, the frame 120 may support one or two image projectors 112 and one or two light guiding optical elements 118 and hold them on or around the user's head. References are made herein to the orientation of various elements relative to each other. Such references may also include references to the elements of the wearable device 102 when supported by the frame 120 or with reference to a coordinate system (e.g., X-axis, Y-axis, Z-axis).

[0025] The optical system 100 may also include a host computer 122, which may include a processor 124 configured to read and execute operations based on instructions 126 stored in a computer-readable medium 128. The instructions 126 may include at least some of the instructions provided to the controller 104 and stored in the memory 106. The host computer 122 may communicate with one or more elements of the wearable device 102 via a signal and power bus 130. In this way, the host computer 122 may provide power to charge the battery 110, provide instructions to the controller 104 and various other elements of the wearable device 102 and receive status from the controller 104 and various other elements of the wearable device 102, and provide digital image data to the graphics engine 114.

[0026] Figure 2 An example of an optical waveguide (hereinafter waveguide 200) having an aperture stop is shown. The waveguide 200 may be one of the light guiding optical elements 118. A three-dimensional Cartesian coordinate system (e.g., X-axis, Y-axis, and Z-axis) is shown. For clarity, the same coordinate system is used throughout the text. The coordinate system used may vary (e.g., axes and directions) without departing from the scope of the present disclosure.

[0027] An input beam from one of the image projectors 112 (not shown) enters the waveguide 200 through the aperture 202. In the example shown, the aperture 202 is disposed on a major surface (e.g., one of two major surfaces) of the waveguide 200. In some implementations, the aperture 202 may be disposed on other surfaces or objects (e.g., an input coupling prism).

[0028] Surrounding the aperture 202 is a stop 216. The stop 216 may be configured to block light outside the aperture 202 from entering the waveguide 200.

[0029] The input beam propagates toward a first set of facets 204 via total internal reflection (TIR) between the major surfaces of the waveguide 200. The first set of facets 204 may be perpendicular to or inclined with respect to the outer surface of the waveguide 200 and are configured to at least partially reflect the input beam toward a second set of facets 206. The beam reflected by the first set of facets 204 propagates via TIR between the major surfaces between the first set of facets 204 and the second set of facets 206. The second set of facets 206 may be inclined with respect to the outer surface of the waveguide 200 and are configured to at least partially reflect the beam from the first set of facets 204 (e.g., toward an eye box) out of the waveguide 200. To generate a uniform image, the cross-section of the waveguide 200 may be fully illuminated.

[0030] One or more homogenizers 208 may be present between the first set of facets 204 and the second set of facets 206. In some implementations, the homogenizer 208 may be disposed in the same region as the first set of facets 204 or the second set of facets 206 (e.g., rather than being disposed between the first set of facets 204 and the second set of facets 206).

[0031] The homogenizer 208 can be any type of optical homogenizer configured to provide improved illumination uniformity. For example, the homogenizer 208 can include a partial planar reflector, a partially transmissive surface, or a film (e.g., a partially reflective dielectric coating) added within the waveguide 200 as a semi-reflective surface. The homogenizer 208 can effectively fill in the gaps in the illumination within the waveguide 200 by separating the light beams passing through the waveguide 200.

[0032] The input light beam generally propagates from the coupling element 210 (e.g., a mirror or a prism) parallel to the Y-axis towards the first set of facets 204 (which can be reflected via TIR in the Y-Z plane but generally advances in a direction parallel to the Y-axis). When the input light beam is reflected by the first set of facets 204, the reflected input light beam generally propagates parallel to the X-axis (which can be reflected via TIR in the X-Z plane but generally advances in a direction parallel to the X-axis). When the reflected input light beam is reflected by the second set of facets 206, the light beam generally propagates parallel to the Z-direction (e.g., out of the waveguide 200). Without departing from the scope of the present disclosure, the angles formed by the propagation directions with the axes can be different.

[0033] As used herein, each set of facets or each facet group can include a plurality of mutually parallel and partially reflective optical elements (e.g., facets) spaced apart from each other. Thus, each facet in the corresponding group can be parallel to each other and be set at the same perpendicular angle or tilt angle. In addition, the facets described herein can include angle-selective coatings and can be controlled to have multiple states (e.g., on / off) or be controlled to change the reflectivity and / or transmissivity levels of each facet or a cooperative set of facets in the structure.

[0034] Returning to the aperture 202, the aperture 202 is generally rectangular and has a first dimension 212 and a second dimension 214. The aperture 202 can be surrounded by an aperture stop 216. In addition, the aperture stop 204 has an internal opening that can match the aperture 202. In other words, the aperture stop 216 can have a first internal dimension and a second internal dimension that are aligned / matched with the first dimension 212 and the second dimension 214. In some implementations, the size of the internal opening of the aperture stop 216 can be slightly smaller than the first dimension 212 and the second dimension 214. The external dimensions of the aperture stop 216 can vary without departing from the scope of the present disclosure.

[0035] Figure 3 From Figure 2 Different views illustrate an example of waveguide 200. The illustrated examples are from a similar direction (e.g., from a direction orthogonal to the X-Y plane), but are rotated for clarity.

[0036] In the illustrated example, projection aperture 300 and projection aperture stop 302 are shown. Projection aperture 300 and projection aperture stop 302 are not physically in the shown positions, but are projected from aperture 202 and aperture stop 216 to illustrate the effects of the sizes of aperture 202 and aperture stop 216. The first length 304 of projection aperture 202 in the X direction corresponds to the first dimension 212 of aperture 202.

[0037] The first length 304 and thus the first dimension 212 correspond to the pitch of the first set of facets 204. For example, the first dimension 212 may be linearly related to the pitch of the first set of facets 204. The pitch of the first set of facets 204 may be the distance 306 in the direction orthogonal to the facets between each adjacent pair of facets (e.g., the closest distance between them). The pitch (e.g., distance 306) may be constant between the facets of the first set of facets 204 or may vary between the first set of facets 204. In either case, the first dimension 212 is linearly related to each of one or more pitches within the first set of facets 204.

[0038] Projection aperture stop 302 covers the area outside the first length 304 of projection aperture 300. Similarly, aperture stop 216 blocks light from entering waveguide 200 outside the first dimension 212 of aperture 202 (which is related to length 304).

[0039] Homogenizer 208 and the second set of facets 206 may be on the Figure 3 left side. As described above, the first set of facets 204 may reflect the input light beam received from the coupling element towards the second set of facets 206 at least in part via homogenizer 208.

[0040] Figure 4A and Figure 4B respectively from Figure 2 Different views illustrate examples of waveguide 200 with one or two homogenizers. For example, Figure 4A and Figure 4B are viewed along an axis orthogonal to the X-Z plane.

[0041] Figure 4A or Figure 4B The examples of Figure 3 may be used alone or in combination with the Figure 4AThe waveguide 200 of FIG. 4 comprises a first homogenizer 208a arranged between the two main surfaces 400. In the example shown, the first homogenizer 208a is equidistant between the two main surfaces 400. Figure 4B The waveguide 200 includes a first homogenizer 208a and a second homogenizer 208b. In the example shown, the first homogenizer 208a and the second homogenizer 208b divide the space between the two major surfaces 400 into three equal parts. The configuration of the homogenizer 208 between the major surfaces 402 can be varied without departing from the scope of the present disclosure. In both examples shown, the second set of facets 206 can be on the left side of the homogenizer 208.

[0042] To mitigate possible overexposure of the waveguide 200 along the axis shown (e.g., along the X direction), the second dimension 214 of the aperture 202 is surrounded by a stop 216. Also shown is a projection aperture 300 and a projection stop 302 (although in the same manner as Figure 3 The projected aperture 302 is shown to illustrate the area to be blocked by the aperture 216. The second dimension 214 corresponds to a second length 402 of the projected aperture 300.

[0043] It should be noted that for Figure 4B In the example shown, aperture 216 may not be necessary. A wider aperture in this size can allow the projector to better match the aperture 202, which can eliminate the need for aperture 216.

[0044] Thus, the first dimension 212 is related to the spacing of the first set of facets 204, and the second dimension 214 is related to aspects of the waveguide 200 in the direction of the second set of facets 206 (e.g., in the X direction). These aspects may include one or more of the following: the thickness of the waveguide 200, the positioning of the homogenizer 208, the field of view in the X direction, the angle of the second set of facets 206, or the angle of the coupling element 210. By using the aperture 216 to block light outside the first dimension 212 and the second dimension 214, overexposure may be mitigated.

[0045] Figure 5A and Figure 5B An example of overexposure is shown when aperture 216 is not implemented. Figure 5A The example of 214 shows overexposure due to light entering outside the first dimension 212 . Figure 5B The examples of 2 and 3 show overexposure due to light entering outside the second dimension 214. In either case, stray light 500 (e.g., light outside the corresponding dimension) enters the waveguide 200 and creates an overexposed region 502. The overexposed region 502 corresponds to an area where a desired light beam (e.g., a light beam within the first dimension 212 and the second dimension 214) overlaps with a reflection of the stray light 500.

[0046] In Figure 5A the example of, the stray light 500 is at least partially reflected by the first set of facets 204 to produce an overexposed region 502. In Figure 5B the example of, the stray light 500 interacts with the homogenizer 208 to produce an overexposed region 502 (e.g., by superimposing on the desired beam). In either case, the overexposed region 502 propagates through the waveguide 200 and exits the waveguide 200.

[0047] The aperture 216 can block the stray light 500 from entering the waveguide 200. By doing so, the overexposed region 502 can be alleviated. Thus, more uniform illumination can be achieved.

[0048] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the present invention. As used herein, unless the context clearly dictates otherwise, the singular forms "a", "an" and "the" are also intended to include the plural forms. It will also be understood that when used in this specification, the terms "include", "comprise" and / or "comprising" specify the presence of the 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. In addition, the terms "upper", "upper part", "lower", "lower part", "above", "below", "left", "right", "front", "rear", etc. are intended to be understood in the context of the representations described and shown above, such that the wearable device can have such an orientation with respect to the frame or with respect to the various elements supported by the frame or as shown in the drawings.

[0049] All corresponding structures, materials, acts and equivalents of the means or steps plus function elements (if any) in the appended claims are intended to include any structure, material or act for performing the function in combination with other claimed elements specifically claimed. The description of the present invention has been given for purposes of illustration and description, but is not intended to be exhaustive or to limit the present invention to the disclosed form. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the present invention. The various embodiments are selected and described in order to best illustrate the principles of the present invention and its practical application, and to enable others of ordinary skill in the art to understand the present invention with various modifications suitable for the particular uses contemplated.

[0050] Example

[0051] Example 1: An optical waveguide, comprising: a pair of parallel main surfaces; an aperture configured to receive an input light beam, the aperture having a first dimension; an input coupling element configured to receive the input light beam from the aperture and couple the input light beam into the optical waveguide; a first set of facets disposed between the main surfaces along a first axis and configured to receive the input light beam from the input coupling element and at least partially reflect the input light beam; and an aperture stop matching the aperture and configured to block light outside the aperture from entering the optical waveguide, wherein the first dimension of the aperture corresponds to the pitch of the first set of facets.

[0052] Example 2: The optical waveguide according to Example 1, wherein the aperture has a second dimension corresponding to an aspect of the optical waveguide corresponding to a second axis.

[0053] Example 3: The optical waveguide according to Example 2, wherein: the optical waveguide further comprises a second set of facets disposed between the main surfaces along the second axis; the first set of facets is configured to at least partially reflect the input light beam towards the second set of facets; and the second set of facets is configured to at least partially reflect the light beam from the first set of facets out of the optical waveguide.

[0054] Example 4: The optical waveguide according to Example 3, wherein the optical waveguide further comprises a first homogenizer disposed between the main surfaces and parallel to the main surfaces.

[0055] Example 5: The optical waveguide according to Example 4, wherein the second dimension of the aperture corresponds to the distance between the first homogenizer and one of the main surfaces.

[0056] Example 6: The optical waveguide according to Example 4 or 5, wherein the first homogenizer is disposed in a region between the first set of facets and the second set of facets.

[0057] Example 7: The optical waveguide according to Example 4 or 5, wherein the first homogenizer is disposed in the same region as the first set of facets or the second set of facets.

[0058] Example 8: The optical waveguide according to any one of Examples 4 to 7, wherein the first homogenizer is equidistant from each of the main surfaces.

[0059] Example 9: The optical waveguide according to any one of Examples 4 to 8, wherein the optical waveguide further comprises a second homogenizer disposed between the first homogenizer and one of the surfaces of the main surfaces.

[0060] Example 10: The optical waveguide according to any one of Examples 2 to 9, wherein a second dimension of the aperture is smaller than a first dimension of the aperture.

[0061] Example 11: The optical waveguide according to any of the preceding examples, wherein a spacing of the first set of facets corresponds to a distance along the first axis between adjacent facets of the first set of facets.

[0062] Example 12: The optical waveguide according to any of the preceding examples, wherein the aperture and the aperture stop are disposed on one of the major surfaces.

[0063] Example 13: The optical waveguide according to any of the preceding examples, wherein the aperture stop includes an opening aligned with the aperture.

[0064] Example 14: The optical waveguide according to any of the preceding examples, wherein the coupling element includes a mirror or a prism.

[0065] Example 15: A device, comprising: a projector configured to generate an input beam; and an optical waveguide according to any of the preceding examples.

[0066] Example 16: A device, comprising: an optical waveguide including: a pair of parallel major surfaces; an aperture configured to receive an input beam, the aperture having a first dimension; a coupling element configured to receive the input beam from the aperture and couple the input beam into the optical waveguide; and a first set of facets disposed between the major surfaces along a first axis and configured to receive the input beam from the coupling element and at least partially reflect the input beam, wherein the first dimension corresponds to a spacing of the first set of facets; and a projector configured to generate an input beam, the projector including an aperture stop that matches the aperture of the optical waveguide and is configured to block light outside the aperture of the optical waveguide from entering the optical waveguide.

Claims

1. An optical waveguide, comprising: A pair of parallel main surfaces; An aperture configured to receive an input beam, the aperture having a first dimension; An input coupling element configured to receive the input beam from the aperture and couple the input beam into the optical waveguide; A first set of facets disposed between the main surfaces along a first axis, and the first set of facets being configured to receive the input beam from the input coupling element and at least partially reflect the input beam; And An aperture stop that matches the aperture and is configured to block light outside the aperture from entering the optical waveguide, Wherein the first dimension of the aperture corresponds to the pitch of the first set of facets.

2. The optical waveguide according to claim 1, wherein, The aperture has a second dimension that corresponds to an aspect of the optical waveguide corresponding to a second axis.

3. The optical waveguide according to claim 2, wherein: The optical waveguide further includes a second set of facets disposed between the main surfaces along the second axis; The first set of facets is configured to at least partially reflect the input beam towards the second set of facets; And The second set of facets is configured to at least partially reflect the beam from the first set of facets out of the optical waveguide.

4. The optical waveguide according to claim 3, wherein, The optical waveguide further includes a first homogenizer disposed between the main surfaces and parallel to the main surfaces.

5. The optical waveguide according to claim 4, wherein, The second dimension of the aperture corresponds to the distance between the first homogenizer and one of the main surfaces.

6. The optical waveguide according to claim 4 or 5, wherein The first homogenizer is disposed in a region between the first set of facets and the second set of facets.

7. The optical waveguide according to claim 4 or 5, wherein, The first homogenizer is disposed in the same region as the first set of facets or the second set of facets.

8. The optical waveguide according to any one of claims 4 to 7, wherein, The first homogenizer is equidistant from each of the main surfaces.

9. The optical waveguide according to any one of claims 4 to 8, wherein The optical waveguide further includes a second homogenizer disposed between the first homogenizer and one of the main surfaces.

10. The optical waveguide according to any one of claims 2 to 9, wherein, The second dimension of the aperture is smaller than the first dimension of the aperture.

11. The optical waveguide according to any one of the preceding claims, wherein, The pitch of the first set of facets corresponds to the distance along the first axis between adjacent facets of the first set of facets.

12. The optical waveguide according to any one of the preceding claims, wherein, The aperture and the aperture stop are disposed on one of the main surfaces.

13. The optical waveguide according to any one of the preceding claims, wherein, The aperture stop includes an opening aligned with the aperture.

14. The optical waveguide according to any one of the preceding claims, wherein, The input coupling element includes a mirror or a prism.

15. A device, comprising: A projector configured to generate an input beam; And The optical waveguide according to any one of the preceding claims.

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