In-plane mirror folded light guide

Abstract

According to an embodiment, an optical device may include a light guide optical element having front and rear surfaces that are parallel to each other; a reflector configured to receive a plurality of guide image beams and reflect a plurality of reflected guide image beams, wherein the plurality of guide image beams and the plurality of reflected guide image beams propagate within the light guide optical element between the front and rear surfaces; a first aperture expander having a first plurality of partially reflective parallel facets configured to expand the plurality of reflected guide image beams and provide a first plurality of expanded image beams; and a second aperture expander having a second plurality of partially reflective parallel facets configured to expand the first plurality of expanded image beams and provide a second plurality of expanded image beams configured to exit the rear 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 Ser. No. 63 / 393,928, filed July 31, 2022, entitled "In-plane Mirror Folded Lightguide," the disclosure of which is incorporated herein by reference in its entirety. This application also claims the benefit of priority under 35 U.S.C. §119(e) to U.S. patent application Ser. No. 63 / 453,327, filed March 20, 2023, entitled "In-plane Mirror Folded Lightguide," the disclosure of which is incorporated herein by reference in its entirety. [Background technology]

[0002] Unless otherwise stated herein, the material described in this section is not prior art to the claims of this application and no admission of prior art is made by inclusion in this section. This disclosure relates generally 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.

[0003] Wearable optical devices, such as near-eye displays or smart glasses, are often cumbersome to wear, thus limiting their comfort and practicality. Furthermore, some wearable optical devices have limited ability to view the surrounding scene or do not have a wide viewing angle due to obstructions in the field of view caused by the presence of various optical components. Finally, poor placement of the image projector may require the image input point to be located relatively far from the image output coupling area, leading to degradation of image quality due to a longer image path. What is needed is a solution that addresses these and other issues. Summary of the Invention

[0004] According to an embodiment, an optical device is generally described. The optical device may include a light guide optical element having front and back surfaces that are parallel to one another, a reflector configured to receive a plurality of guiding image beams and reflect a plurality of reflected guiding image beams, where the plurality of guiding image beams and the plurality of reflected guiding image beams propagate within the light guide optical element between the front and back surfaces, a first aperture expander having a first plurality of partially reflective parallel facets configured to expand the plurality of reflected guiding image beams to provide a first plurality of expanded image beams, and a second aperture expander having a second plurality of partially reflective parallel facets configured to expand the first plurality of expanded image beams to provide a second plurality of expanded image beams.

[0005] According to this embodiment, the optical device includes: a plurality of guiding image beams having a guiding image beam central axis; a plurality of reflected guiding image beams having a guiding image beam central axis; an angle between the guiding image beam central axis and the reflected guiding image beam central axis being greater than 90°; a reflector disposed perpendicular to the front surface and / or disposed at a peripheral edge of the light guide optical element; the reflector configured to fully reflect the received guiding image beams; an input coupler configured to receive a collimated first image beam from an image projector and output the plurality of guiding image beams; the plurality of guiding image beams propagate within the light guide optical element between the front surface and the rear surface; the input coupler disposed adjacent to one of the front surface and the rear surface and at least partially embedded within the light guide optical element; the input coupler being one of a prism, a diffractive element, a reflective element, or a holographic element.

[0006] According to this embodiment, the optical device is one in which the reflector faces an inner portion of the light guide optical element and can be a mirror disposed adjacent to a peripheral edge of the light guide optical element at a location vertically below the input coupler or vertically above the input coupler. The optical device is one in which the first plurality of partially reflective parallel facets are inclined at a first angle that is one of inclinations with respect to at least one of the front surface and a transverse plane normal to the front surface, and the second plurality of partially reflective parallel facets are inclined at a second angle that is one of inclinations with respect to at least one of the front surface and a transverse plane normal to the front surface. The optical device is one in which at least one of the first plurality of partially reflective parallel facets and the second plurality of partially reflective parallel facets can include an angle-selective coating.

[0007] According to this embodiment, the optical device includes an upper portion of the light guide optical element that can include an optically transparent line-of-sight region, and a second aperture expander that can be disposed vertically below the line-of-sight region. The first aperture expander can be configured to expand the plurality of reflected guided image beams in a first dimension, and the second aperture expander can be configured to expand the first plurality of expanded image beams in a second dimension, the first and second dimensions being substantially orthogonal to one another. The optical device can further include a light cover disposed on a portion of the front surface adjacent the reflector, the light cover being configured to at least one of reduce scattering of the plurality of guided image beams and reduce impingement of ambient light on the reflector. The optical device includes an optical element configured to emit the second plurality of expanded image beams from the rear surface.

[0008] According to an embodiment, an optical system is generally described, the optical system including a light guide optics element having front and rear surfaces that are parallel to one another, an image projector configured to generate a collimated first image beam based on a digital image, where the collimated first image beam is collimated to infinity, an input coupler configured to receive the collimated first image beam and output multiple guided image beams into the light guide optics element, where the multiple guided image beams propagate between the front and rear surfaces, and a reflector configured to receive the multiple guided image beams and reflect multiple reflected guided image beams. the plurality of guided image beams are propagated within the light guide optical element between the front and rear surfaces; a first aperture expander having a first plurality of partially reflective parallel facets configured to expand the plurality of reflected guided image beams in a first dimension to provide the first plurality of expanded image beams; and a second aperture expander having a second plurality of partially reflective parallel facets configured to expand the first plurality of expanded image beams in a second dimension to provide the second plurality of expanded image beams configured to exit the rear surface.

[0009] According to this embodiment, the optical system includes an input coupler disposed adjacent one of the front and rear surfaces and at least partially embedded within the light guide optics, where the input coupler may be one of a prism, a diffractive element, a reflective element, or a holographic element. The optical system may further include a frame configured to support at least a portion of the light guide optics and the image projector, the frame configured to be worn on a portion of a user's head adjacent the user's eyes, an optical engine configured to receive digital images and operate the image projector, and a controller configured to operate the optical engine and the projector. The optical system includes a plurality of guiding image beams having a guiding image beam central axis, a plurality of reflected guiding image beams having a central axis of the reflected guiding image beam, and an angle between the guiding image beam central axis and the reflected guiding image beam central axis may be greater than 90°.

[0010] According to this embodiment, the optical system may include: a reflector that faces an inner portion of the light guide optical element and that is disposed adjacent to a peripheral edge of the light guide optical element, the reflector being configured to fully reflect the received plurality of guided image beams; a first aperture expander that includes a plurality of partially reflective parallel facets that are inclined at an angle that is one of a slope with respect to at least one of a front surface and a transverse plane normal to the front surface, and a vertical to the front surface; and at least one of the first plurality of partially reflective parallel facets and the second plurality of partially reflective parallel facets that include an angle-selective coating. An upper portion of the light guide optical element may include an optically transparent line-of-sight region, and the second aperture expander that is disposed vertically below the line-of-sight region. The optical system may further include a partially planar reflector disposed within the light guide optical element parallel to the front surface, and the light cover may be disposed on a portion of the front surface adjacent the reflector, and the light cover may be configured to at least one of reduce scattering of the plurality of guided image beams and reduce impingement of ambient light on the reflector.

[0011] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description. In the drawings, like reference numbers indicate identical or functionally similar elements. [Brief explanation of the drawings]

[0012] [Figure 1] 1 illustrates a block diagram of an optical system according to various embodiments of the present disclosure. [Figure 2A] 1 illustrates a front plan view of an optical device including a light guide optical element (LOE), according to various embodiments of the present disclosure. [Figure 2B] 2B illustrates a side plan view of the optical device of FIG. 2A according to various examples of the present disclosure. [Figure 3A] 1 illustrates a front plan view of an optical system including a light guide optical element, according to various embodiments of the present disclosure. [Figure 3B] 3B illustrates a side plan view of the optical system of FIG. 3A according to various embodiments of the present disclosure. [Figure 4] 1 illustrates a schematic isometric view of a portion of an aperture expander having partially reflective parallel facets, according to various embodiments of the present disclosure. [Figure 5] 1 illustrates a front plan view of an optical device including a light guide optical element, according to various embodiments of the present disclosure. [Figure 6] 1 illustrates a front plan view of an optical device including a light guide optical element, according to various embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0013] In the following description, numerous specific details are set forth, such as particular structures, components, materials, dimensions, processing steps, and techniques, to provide an understanding of various embodiments of the present application. However, it will be understood by those skilled in the art that various embodiments of the present application may 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.

[0014] As described in more detail below, near-eye displays and / or wearable devices such as smart glasses can be implemented with the systems and methods described in accordance with the present disclosure, which can efficiently provide high-quality optical information to users for a variety of applications.

[0015] 1 illustrates a block diagram of an optical system according to various examples of the present disclosure. Optical system 100 may include two or more devices or components. Optical system 100 may generally be implemented as a hybrid system including various electronic, optical, and electro-optical elements. Optical device 102 may include one or more elements from optical system 100. As described in more detail below, optical system 100 may include one or more near-eye displays or wearable devices 110, such as smart glasses, which may be worn on or around a user's head to transmit optical information to one or more of the user's eyes.

[0016] Wearable device 110 may include a controller 114 having memory 116, which may be configured to, for example, send and receive electrical signals to various other elements in optical system 100, execute program instructions stored in memory 116 to process and provide information to operate wearable device 110, and interact with other systems external to wearable device 110. Controller 114 may include a microcontroller, a processor, various discrete components, programmable logic devices, and / or various interface circuits that may access memory 116, which may be removable, replaceable, programmable, and reprogrammable, to update instructions to controller 114.

[0017] Wearable device 110 may also include a power management module 120 having a battery 122, which may be configured to charge, discharge, and monitor power usage of battery 122. Various elements of wearable device 110 may receive power from battery 122, including, for example, controller 114, one or more image projectors 126 (e.g., projection optical devices, or PODs), and an optical engine 134 having one or more digital images 136.

[0018] The wearable device 110 may also include one or more image projectors 126 configured to each produce a collimated image beam based on a digital image 136. The collimated image beam may be an illuminated representation of a digital image, based on either a single graphical image (e.g., a still image) or a series of graphical images (e.g., moving images), with an image field that is a two-dimensional representation of the digital image. The collimated image beam may be infinitely collimated.

[0019] The wearable device 110 may also include one or more light guide optics 130 (e.g., LOEs, also referred to as waveguide WGs) comprising transparent materials configured to receive and propagate light, which may enter and exit various exterior and interior surfaces of the light guide optics 130. For example, the transparent materials comprising the light guide optics 130 may include optical glass or other suitable materials that are transformed into complex optical structures using processes that may include coating, laminating, slicing, polishing, and shaping the transparent material. The processes may include, for example, the addition of partially reflective or fully reflective materials, such as mirror coatings. Similarly, the processes may also include the addition of partially opaque or fully opaque materials, such as optical covers, to block light, for example.

[0020] Wearable device 110 may also include one or more optical engines 134 coupled to one or more image projectors 126 and light guide optics 130. Optical engine 134 may be configured to operate image projector 126 directly under the direction of controller 114. For example, optical engine 134 may provide graphics processing of the digital image prior to projection of a lighting representation of the digital image by image projector 126.

[0021] The wearable device 110 may also include a frame 138 (e.g., a structure) for supporting and holding one or more elements within the wearable device 110. For example, the frame 138 may support and hold a first image projector 126 in a position adjacent to a first light guide optics element 130. Similarly, the frame 138 may support and hold a second image projector 126 in a position adjacent to a second light guide optics element 130. In this manner, the frame 138 may support and hold one or more pairs of image projector 126 and light guide optics element 130 on or around the user's head. References are made herein with respect to the orientation of various elements relative to one another. Such references may also include references to various elements of the wearable device 110 as supported by the frame 138 or with reference to a three-dimensional (3D) reference (e.g., X, Y, Z axes) as described in the associated drawings.

[0022] Optical system 100 may also include a host computer 170, which may include a processor 174 configured to read and execute operations based on instructions 178 stored on a computer-readable medium 180. The instructions 178 may include at least some instructions provided to controller 114 and stored in memory 116. Host computer 170 may communicate with one or more elements of wearable device 110 via a signal and power bus 188. In this manner, host computer 170 may provide power to charge battery 122, provide instructions to controller 114 and various other elements of wearable device 110, receive status, and provide digital image data to optical engine 134.

[0023] 2A illustrates a front plan view of an optical device including a light guide optic (LOE) according to various embodiments of the disclosure. The optical device 102 may include a light guide optic 130 having an aperture expander 16 disposed at least partially within the light guide optic 130. As described in more detail below, the aperture expander 16 may include a plurality of partially reflective parallel facets 19 (e.g., internal planar surfaces) configured to accept multiple light beams from a first direction and expand the beam width or aperture of the accepted light beams in a second direction, which may be different from the first direction and may be substantially orthogonal to the first direction. In this manner, the aperture expander 16 may be configured to expand the accepted beams in two dimensions.

[0024] The term facet may generally refer to a reflective optical structure having a flat surface. Each facet may include an angle-selective coating that may have an optical axis that deviates from a normal angle to the coating to selectively pass or attenuate illumination having the same or different orientations, respectively. As used herein, an aperture expander may include multiple planar, mutually parallel, partially reflective optical elements (e.g., facets) that are spaced apart from one another and may be included at an angle that may be oblique, for example, relative to at least one major exterior surface of the light guide optical element 130. Thus, each of the facets 19 in the aperture expander 16 may be parallel to one another and disposed at the same oblique angle. The facets described herein may also include angle-selective coatings and may be controlled to have multiple states (e.g., on / off) or to change the level of reflectivity and / or transmittance of each facet or to change the cooperative collection of facets within the structure. The last facet in the structure (e.g., the terminal facet) may be fully mirrored (e.g., not partially mirrored) to reflect the remaining illumination that has passed through the previous facets in the structure. Alternatively, each facet may have the same fractional reflectivity for consistency, reduced complexity, and simplified structure.

[0025] As used herein, this term refers to a tolerance of substantially less than approximately 1 degree, and substantially orthogonal may refer, for example, to two lines or two planes intersecting at an angle that may be visually compared to about 90° but may vary between less than 89.5° and 90.5°. Similarly, substantially vertical may refer, for example, to an angle having a vertical plane of about 90° that may vary between less than 89.5° and 90.5° from the vertical plane. Finally, substantially horizontal (e.g., substantially transverse) may refer to an angle with the horizontal plane at 0° but may vary between less than +0.5° and −0.5° from the horizontal plane, for example. In this way, verticality may be very precise, typically referring to a variation of much less than 1° (e.g., <<1°), less than 0.1°, less than 0.05°, or even less than 0.01° in some embodiments.

[0026] Light guide optics 130 may also include input coupler 14 located at location 15, which may be on, near, or embedded within the peripheral edge of light guide optics 130. Input coupler 14 may be an optical element configured to conduct image illumination to optical element 130. Alternatively, input coupler 14 may be located at any suitable location that can perform as described herein. Thus, the location of input coupler 14 at location 15, as illustrated in FIG. 2B , is not considered limiting. As described more fully below, input coupler 14 may be located on a portion of light guide optics 130, near light guide optics 130, or embedded within light guide optics 130, and may be configured to couple light from image projector 126 into light guide optics 130. For optimal beam propagation, it may be preferable for the entrance angle of the input image beam from image projector 126 to be shallow to promote total internal reflection (TIR) so that the beam can propagate with minimal escape while remaining within light guide optics 130 (e.g., to reduce scattering). Input coupler 14 may be a prism, a diffractive element, a reflective element, or a holographic element. When input coupler 14 is a prism, input coupler 14 may be rotated so that image projector 126 can be worn adjacent to light guide optics 130 in a manner that is less obtrusive to the user. As shown in FIGS. 2A, 2B, and as in the other figures, it may be useful to refer to a three-dimensional (3D) framework of orthogonal axes X, Y, and Z, where X corresponds generally to the horizontal or lateral direction (e.g., side-to-side), Y corresponds generally to the vertical direction (e.g., superior-inferior or up-and-down), and Z corresponds to the medial-lateral direction (e.g., anterior-posterior or medial-lateral) of the plane of FIG. 2A.

[0027] 2B illustrates a side plan view of the optical device of FIG. 2A according to various embodiments of the present disclosure. Light guide optics 130 may include a front surface 11F and a rear surface 11R that may be parallel to one another; for example, ambient illumination from a scene may enter light guide optics 130 primarily at front surface 11F and exit light guide optics 130 at rear surface 11R. Aperture expander 16 may be disposed on, adjacent to, near, or embedded within light guide optics 130, for example, at a location vertically below the normal location of a user's eye 12 when wearable device 110 is in use. In this manner, ambient light may enter light guide optics 130 along an optically clear line of sight 27 region in a manner that directs incident light toward a user's eye 12. As used herein, optically transparent refers to the absence of reflective or deflecting optical structures such that ambient light may pass through a portion of the light guide optical element 130 in an unobstructed manner, e.g., providing the user with an unobstructed view of the environment through the optical structures.

[0028] As mentioned above, aperture expander 16 may include a plurality of partially reflective parallel facets 19 configured to receive a plurality of light beams from a first guide direction and expand the received light beams in a second out-coupling direction 18. Expanded light beams 18 from aperture expander 16 may exit rear surface 11R at an exit angle 17 (e.g., from guided to unguided), for example, directed toward user's eye 12. Alternatively, the center (e.g., vertical midpoint) of aperture expander 16 may be disposed below line-of-sight 27 region, while at least some of aperture expander 16 may extend into line-of-sight 27 region, depending, for example, on exit angle 17 and possibly other factors. In this manner, the upper portion of light guide optical element may include an optically transparent line-of-sight region 27, with the upper portion including, for example, a vertically separated portion above the midpoint of aperture expander 16.

[0029] 3A illustrates a front plan view of an optical system including a light guide optics element according to various embodiments of the present disclosure. The optical device 102 may include a light guide optics element 130 configured to receive a collimated first image beam from an image projector 126, which is fed (e.g., directly injected) into an input portion of an input coupler 14 and coupled at a shallow angle to enter the light guide optics element 130. In practice, the distance between the image projector 126 and the input coupler 14 may be very short. The injected image beam may be collimated for all points in the image, and different points in the image diverge as they are generated by the image projector 126. The collimated image beam from the image projector 126 may be injected into a portion of the light guide optics element 130, resulting in multiple guided image beams 20 propagating and reflecting due to total internal reflection (TIR) within the light guide optics element 130 between the front surface 11F and the parallel rear surface 11R. For simplicity, the multiple stimulating image beams 20 may correspond to multiple different points within the image area of the collimated first image beam and may have a stimulating image beam central axis 21 corresponding to a central ray within the multiple stimulating image beams 20.

[0030] The plurality of guided image beams 20 may continue to expand within the light guide optics 130 and be directed to a reflector 22, which may be disposed at a second location 23, which may be on or near the peripheral edge of the light guide optics 130. Alternatively, the reflector 22 may be located within a portion of the light guide optics 130 away from the peripheral edge. The reflector 22 may, for example, include a mirror facing an interior portion of the light guide optics 130 and may be located vertically below the input coupler 14, as illustrated. The reflector 22 may be formed as a mirror configured to completely reflect the plurality of guided image beams 20. In this manner, the reflector 22 may be configured to substantially reflect all of the impinging image beams within the plurality of guided image beams 20. In other words, the reflector 22 may be substantially opaque to the plurality of guided image beams 20. For example, the reflector 22 may include a coating configured to transmit scene light (e.g., light at different angles) but reflect the guided image beams 20 that reach the reflector 22 within an expected angle. The reflector 22 may be disposed perpendicular to the front and rear surfaces 11F, 11R, which are parallel, so that any angle referenced to the front surface 11F may equivalently be referenced to the rear surface 11R. Alternatively, the reflector 22 may be disposed at an angle relative to the front surface 11F.

[0031] The multiple guiding image beams 20 may be reflected by the reflector 22 as multiple reflected guiding image beams 24 having reflected guiding image beam central axes 30 that may correspond to central rays of the multiple reflected guiding image beams 24 upon leaving the surface of the reflector 22. In this manner, a first beam angle 33 may be formed between the guiding image beam central axis 21 and the reflected guiding image beam central axis 30, and the first beam angle 33 may be greater than 90°. When the first beam angle 33 between the beam central axis 21 and the central axis of the reflected beam 30 is greater than 90°, the multiple guiding image beams 20 and the multiple reflected guiding image beams 24 may bypass other optical elements within the light guide optics 130, providing improved separation and allowing the other optical elements to be larger and with improved light gathering capabilities compared to conventional light guide optics. Alternatively, the first beam angle 33 may be less than 90°. Herein and elsewhere in this disclosure, the reflection of the multiple guiding image beams 20 by reflector 22 to produce the multiple reflected guiding image beams 24 and the continued steering of the reflected image beams by total internal reflection (TIR) within light guide optics 130 may be considered a type of in-plane folding of the multiple guiding image beams 20. The guiding image beam central axis 21, the reflected guiding image beam central axis 30, and the intersection (e.g., two lines and an intersection) between the guiding image beam central axis 21 and the reflected guiding image beam central axis 30 may form a plane about which the image beam is folded. After leaving reflector 22, the multiple reflected guiding image beams 24 may be directed to a first aperture expander 26, which may be at least partially disposed within light guide optics 130.

[0032] The first aperture expander 26 may include a first plurality of partially reflective parallel facets 29 (e.g., a surface or a reflector) that may be configured to receive the plurality of reflected stimulating image beams 24 and expand the plurality of reflected stimulating image beams 24 in a first dimension to produce the first plurality of expanded image beams 28 having an expanded image stimulating beam central axis 32 that may correspond to a central ray of the plurality of expanded image beams 28 as they exit the first aperture expander 26 (e.g., from stimulating to stimulating). In this manner, a second beam angle 34 may be formed between the reflected beam central axis 30 and the first expanded beam central axis 32, where the second beam angle 34 may be less than 90°. Note that the plurality of partially reflective parallel facets 29 may be different from the reflector 22, which may be configured to reflect substantially all of the impinging image beams in the plurality of stimulating image beams 20. The first plurality of partially reflective parallel facets 29 may be tilted at an angle that may be tilted with respect to at least one of the parallel front surface 11F and a transverse plane perpendicular to the front surface 11F (e.g., the XZ plane), or may be tilted with respect to both. Thus, the term tilt applied to the plurality of partially reflective parallel facets may be used with respect to major exterior surfaces, such as the front surface 11F and the parallel rear surface 11R, which, as illustrated, may be aligned with the orthogonal X, Y, and Z axes and perpendicular to each other. This tilting aspect will be more briefly explained with reference to FIG. 4 . In this manner, the first plurality of expanded image beams 28 may achieve greater and more uniform illumination. Alternatively, the first aperture expander 26 may have a plurality of partially reflective parallel facets 29 disposed perpendicular to the front surface 11F. A coating on the plurality of parallel facets of the first aperture expander 26 may most efficiently reflect light at a predetermined angle. According to an embodiment, when the second beam angle 34 is large (e.g., close to 90°), this may enable the creation and use of optimal coatings for the parallel facets 29 in the first aperture expander 26, particularly in situations where, for example, the parallel facets 29 are inclined at an oblique angle and are not perpendicular to the front surface 11F. This may be due to the angular spectrum of the reflected beam being substantially separated from the angular spectrum of the transmitted beam.Furthermore, this may allow the use of polarization insensitive coatings whose Brewster angle may be outside the reflection angle spectrum, which may result in improved performance.

[0033] After leaving the first aperture expander 26, the first plurality of expanded image beams 28 may be directed to the second aperture expander 16 mentioned briefly above. The second aperture expander 16 may be disposed at least partially within the light guide optics 130. The aperture expander 16 may include a second plurality of partially reflective parallel facets 19 configured to receive the first plurality of expanded image beams 28 from the first aperture expander 26 in a first direction and expand the expanded image beams 28 in a second direction, which may be substantially orthogonal to the first direction.

[0034] As will be explained, the first aperture expander 26 may expand the reflected guided image beam 24 in a first dimension (e.g., substantially horizontally or in the X-axis direction) as a first plurality of expanded image beams 28, and then the second aperture expander 16 may expand the first plurality of expanded image beams 28 in a second dimension (e.g., substantially vertically or in the Y-axis direction), and the second plurality of expanded image beams 18 may exit the rear surface 11R, for example, toward the user's eyes 12. In this manner, the first aperture expander 26 and the second aperture expander 16 may cooperate to expand a version of the input beam in two dimensions (2D), thus resulting in a two-dimensional (2D) expansion of the original aperture of the image projector 126.

[0035] The planar shape of first aperture expander 26 corresponds to the smallest size cross-section that can adequately expand reflected guided image beam 24 into the first plurality of expanded image beams, and first aperture expander 26 may contact the adjacent edge of light guide optical element 130 at only one point (e.g., compared to FIG. 5 ). Advantages of this minimum size first aperture expander 26 include minimizing loss of the reflected beam in less beneficial directions, thereby improving the overall efficiency of the waveguide.

[0036] 3B illustrates a side planar view of the optical device of FIG. 3A according to various examples of the present disclosure. FIG. 3B illustrates total internal reflection (TIR) of the first plurality of expanded image beams 28 within light guide optics 130 after leaving first aperture expander 26. In each of the disclosed embodiments, a partial planar reflector 38 may be introduced into light guide optics 130 disposed between front surface 11F and rear surface 11R to provide better light mixing and create more uniform illumination.

[0037] 4 illustrates a schematic isometric view of a portion of an aperture expander having partially reflective parallel facets according to various embodiments of the present disclosure. As described above, the first aperture expander 26 may include a plurality of partially reflective parallel facets 29, and the second aperture expander 16 may include a second plurality of partially reflective parallel facets 19 that may be inclined at an angle that may be oblique with respect to at least one of the front surface 11F and a transverse plane (e.g., the XZ plane) that may be perpendicular to the front surface 11F. As used herein, describing the partially reflective parallel facets as inclined may describe the plane of each of the partially reflective parallel facets being oriented such that the plane of the partially reflective parallel facet is neither parallel nor perpendicular to any of the long axis or mutually parallel major exterior surfaces that describe the light guide optical element 130. In particular, the planes of the example facets 19 and 29 shown in FIG. 4 may be described as being partially inclined with respect to at least two or more of the X-axis, Y-axis, and Z-axis. Alternatively, the plane of the exemplary facet 29 may also be aligned with the corresponding plane XY R , Y.Z. R , or XZ R While illustrated together, each of the partially reflective parallel facets 19 in the second aperture expander 16 may be disposed at an oblique angle that is different from the oblique angle of the partially reflective parallel facets 29 in the first aperture expander 26.

[0038] 5 illustrates a front plan view of an optical device including a light guide optics element according to various embodiments of the present disclosure. The light guide optics element 130 may include a light cover 36 that may be disposed on a portion of the front surface 11F (FIG. 2B) and configured to reduce scattering of the multiple guided image beams 20 from the front surface 11F. In addition, the light cover 36 may also prevent reflections from the scene by the reflector 22 into the user's eye 12. In this manner, the cover 36 may be disposed on a portion of the front surface 11F adjacent to the reflector 22, and the light cover 36 may at least one of reduce scattering of the multiple guided image beams 20 and reduce impingement of ambient light on the reflector 22, which may improve the user's experience.

[0039] 5 illustrates an embodiment of a first aperture expander 26B having a first plurality of partially reflective parallel facets 29B and a second aperture expander 16B having a second plurality of partially reflective parallel facets 16B, where either or both of the first aperture expander 26B and the second aperture expander 16B may have a larger area compared to the corresponding elements of the embodiment shown in FIG. 3A, which may result in improved manufacturability of the light guide optical element 130. As noted, in the drawings, like reference numbers may indicate identical or functionally similar elements. Thus, the first aperture expander 26B may be similar in some respects to, for example, the first aperture expander 26 illustrated in FIG. 3A. In this example, after leaving reflector 22, the multiple reflected guidance image beams 24 may be at least partially disposed within light guide optics 130 and may be directed toward first aperture expander 26B, which may extend across its entire width to the edge of light guide optics 130 (e.g., compared to FIG. 3A ). The multiple reflected guidance image beams 24 may have a reflected image beam central axis 30 corresponding to a central ray within the multiple reflected guidance image beams 24. First aperture expander 26B may be configured to receive the multiple reflected guidance image beams 24 and expand the multiple reflected image beams in a first dimension to produce a first multiple expanded image beams 28B having an expanded image beam central axis 32B that may correspond to a central ray of the multiple expanded image beams 28B upon leaving first aperture expander 26B. In this manner, the third beam angle 34B between the reflected beam central axis 30 and the first expanded beam central axis 32B can be less than 90° but greater than the second beam angle 34 (FIG. 3A). The exemplary first aperture expander 26B shown in FIG. 5 has various advantages, including being easier to manufacture and therefore less costly.

[0040]

[0023] Figure 6 illustrates a front plan view of an optical device including a light guide optical element according to various embodiments of the present disclosure. The optical device 102 illustrated in Figure 6 is similar in some respects to the optical device 102 illustrated in Figure 3A. However, Figure 6 illustrates a different reflector 22C at a different location 23C, as well as a different orientation for the first aperture expander 26C and a different orientation for the second aperture expander 16C, as shown.

[0041] Optical device 102 may include light guide optics 130 configured to receive a collimated first image beam from an image projector that is applied to an input portion of input coupler 14 located at a first location 15 on or near a peripheral edge of light guide optics 130. In this manner, the collimated image beam from image projector 126 is injected into a portion of light guide optics 130, producing multiple guided image beams 20 due to total internal reflection (TIR) between parallel front and rear surfaces 11F, 11R.

[0042] The plurality of guided image beams 20 continue to propagate within the light guide optical element 130 and may be directed to a reflector 22C at a fourth location 23C at or near the peripheral edge of the light guide optical element 130, which may be disposed near or at the peripheral edge of the light guide optical element 130. As such, the reflector 22C may be located proximate to the peripheral edge of the light guide optical element 130 without overlapping the peripheral edge. Again, this is not considered limiting. In this example, the reflector 22C may be a mirror disposed adjacent to the peripheral edge of the light guide optical element 130, facing an interior portion of the light guide optical element 130, at a location 23C that may be perpendicular to the input coupler 14, for example. The reflector 22C may be formed as a mirror configured to completely reflect the plurality of guided image beams 20. The reflector 22C may be disposed perpendicular to the front surface 11F. Alternatively, the reflector 22C may be disposed at an angle relative to the front surface 11F. The multiple stimulating image beams 20 may be reflected by the reflector 22C as multiple reflected stimulating image beams 24C having reflected beam central axes 30C that may correspond to central rays of the multiple reflected stimulating image beams 24C as they leave the surface of the reflector 22C.

[0043] After leaving reflector 22C, the multiple reflected guidance image beams 24C may be directed to a first aperture expander 26C, which may be at least partially disposed within light guide optics 130. The multiple reflected guidance image beams 24C may have a reflected image beam central axis 30C corresponding to a central ray in the multiple reflected guidance image beams 24C. The first aperture expander 26C may include a first plurality of partially reflective parallel facets 29C, which may be configured to receive the multiple reflected guidance image beams 24C and expand the multiple reflected guidance image beams 24C in a first dimension to produce a first plurality of expanded image beams 28C having an expanded image guidance beam central axis 32C, which may correspond to a central ray of the multiple expanded image beams 28C as they leave first aperture expander 26C. 6 may also provide that the fourth beam angle 34C between the reflected beam central axis 30C and the expanded image beam central axis 32C remains large, similar to the configuration illustrated in FIG. 3A, and may provide the same advantages. Similar to the embodiment of optical device 102 shown in FIG. 3A, first aperture expander 26C may have multiple partially reflective parallel facets 29C that may be inclined at an angle that may be oblique with respect to at least one of front surface 11F and a transverse plane perpendicular to front surface 11F (e.g., the XZ plane), or that may be oblique with respect to both.

[0044] After leaving the first aperture expander 26C, the first plurality of expanded image beams 28C may be directed to the second aperture expander 16C mentioned briefly above. The second aperture expander 16C may be disposed at least partially within the light guide optics 130. The aperture expander 16C may include a second plurality of partially reflective parallel facets 19C configured to receive the first plurality of expanded image beams 28C from the first aperture expander in a first direction and expand the expanded image beams 28C in a second direction.

[0045] The first aperture expander 26C may expand the reflected guided image beam 24C in a first dimension, and then the second aperture expander 16C may expand the first plurality of expanded image beams 28C in a second dimension, which may exit the rear surface 11R toward the user's eye 12. Thus, the first aperture expander 26C and the second aperture expander 16C may cooperate to expand a version of the input image beam in two dimensions (2D), thus resulting in, for example, a two-dimensional expansion of the original aperture of the image projector 126.

[0046] 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. It will be further understood that the terms "includes," "comprises," and / or "comprising," as used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Furthermore, the terms "up," "upper," "down," "lower," "above," "below," "left," "right," "front," "rear," and the like are intended to be understood in the context of the representations described and illustrated above, such that the wearable device may have such orientation relative to the frame, or as supported by the frame, or relative to various elements as illustrated in the drawing figures.

[0047] Wherever possible, the corresponding structure, material, acts, and equivalents of all means or steps plus functional elements in the following claims are intended to encompass any structure, material, or acts for performing a function in combination with other claimed elements when specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or to limit the invention to the form disclosed. Many modifications and variations will be apparent to those skilled 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 and practical applications of the invention and to enable those skilled in the art to understand the invention in various embodiments with various modifications suitable for the particular uses contemplated.

Claims

1. 1. An optical device, comprising: a light guide optical element having front and rear surfaces that are parallel to one another; a reflector configured to receive a plurality of stimulating image beams and reflect a plurality of reflected stimulating image beams, the plurality of stimulating image beams and the plurality of reflected stimulating image beams propagating within the light guide optical element between the front surface and the rear surface; a first aperture expander having a first plurality of partially reflective parallel facets configured to expand the plurality of reflected guided image beams and provide a first plurality of expanded image beams; a second aperture expander having a second plurality of partially reflective parallel facets configured to expand the first plurality of expanded image beams and provide a second plurality of expanded image beams.

2. the plurality of stimulating image beams have a stimulating image beam central axis; the plurality of reflected stimulating image beams having a central axis of the reflected stimulating image beam; The optical device of claim 1 , wherein an angle between the central axis of the stimulating image beam and the central axis of the reflected stimulating image beam is greater than 90°.

3. The reflector is disposed perpendicular to the front surface; and disposed on a peripheral edge of the light guide optical element; The optical device of claim 1 , wherein the reflector is configured to completely reflect the received plurality of directed image beams.

4. an input coupler configured to receive a collimated first image beam from an image projector and to output the plurality of guided image beams, the plurality of guided image beams propagating within the light guide optical element between the front surface and the rear surface; the input coupler is disposed adjacent one of the front and rear faces and is at least partially embedded within the light guide optical element; The optical device of claim 1 , wherein the input coupler is one of a prism, a diffractive element, a reflective element, or a holographic element.

5. the reflector faces an interior portion of the light guide optical element; and vertically below the input coupler; and 5. The optical device of claim 4, wherein the mirror is disposed adjacent to a peripheral edge of the light guide optical element at a location that is one of: vertically above the input coupler.

6. the first plurality of partially reflective parallel facets are inclined at a first angle that is one of inclination with respect to at least one of the front surface and a transverse plane normal to the front surface; 10. The optical device of claim 1, wherein the second plurality of partially reflective parallel facets are inclined at a second angle that is one of inclination with respect to at least one of the front surface and a transverse plane perpendicular to the front surface.

7. The optical device of claim 6 , wherein at least one of the first plurality of partially reflective parallel facets and the second plurality of partially reflective parallel facets includes an angle-selective coating.

8. an upper portion of the light guide optical element including an optically transparent line of sight area; The optical device of claim 1 , wherein the second aperture expander is disposed vertically below the line of sight area.

9. 2. The optical device of claim 1, wherein the first aperture expander is configured to expand the plurality of reflected guided image beams in a first dimension, and the second aperture expander is configured to expand the first plurality of expanded image beams in a second dimension, the first dimension and the second dimension being substantially orthogonal to one another.

10. a light cover disposed on a portion of the front surface adjacent the reflector, the light cover comprising: reducing scattering of the plurality of stimulating image beams; and 10. The optical device of claim 1, configured to at least one of: (a) reduce impingement of ambient light on the reflector;

11. The optical device of claim 1 , wherein the second plurality of expanded image beams are configured to exit the rear surface.

12. 1. An optical system comprising: a light guide optical element having front and rear surfaces that are parallel to one another; an image projector configured to generate a collimated first image beam based on a digital image, wherein the collimated first image beam is infinitely collimated; an input coupler configured to receive the collimated first image beam and output a plurality of guided image beams into the light guide optical element, the plurality of guided image beams propagating between the front surface and the rear surface; a reflector configured to receive a plurality of stimulating image beams and reflect a plurality of reflected stimulating image beams, the plurality of stimulating image beams propagating within the light guide optical element between the front surface and the rear surface; a first aperture expander having a first plurality of partially reflective parallel facets configured to expand the plurality of reflected guided image beams in a first dimension to provide a first plurality of expanded image beams; a second aperture expander having a second plurality of partially reflective parallel facets configured to expand the first plurality of expanded image beams in a second dimension and provide a second plurality of expanded image beams configured to exit the rear surface.

13. the input coupler is disposed adjacent one of the front and rear faces and is at least partially embedded within the light guide optical element; The optical system of claim 12 , wherein the input coupler is one of a prism, a diffractive element, a reflective element, or a holographic element.

14. a frame configured to support at least a portion of the light guide optics and an image projector, the frame configured to be worn on a portion of the user's head adjacent the user's eyes; and an optical engine configured to receive the digital image and operate the image projector; The optical system of claim 12 , further comprising: a controller configured to operate the optical engine and the projector.

15. the plurality of stimulating image beams have a stimulating image beam central axis; the plurality of reflected stimulating image beams having a central axis of the reflected stimulating image beam; The optical system of claim 12 , wherein an angle between the central axis of the stimulating image beam and the central axis of the reflected stimulating image beam is greater than 90°.

16. the reflector faces an inner portion of the light guide optical element; vertically below the input coupler; a mirror disposed adjacent a peripheral edge of the light guide optical element, either vertically above the input coupler; The optical system of claim 12 , wherein the reflector is configured to fully reflect the received plurality of directed image beams.

17. the first aperture expander: a slope relative to at least one of the front surface and a transverse plane perpendicular to the front surface; The optical system of claim 12 , comprising a plurality of partially reflective parallel facets inclined at an angle to one of normal and normal to the front surface.

18. 20. The optical system of claim 17, wherein at least one of the first plurality of partially reflective parallel facets and the second plurality of partially reflective parallel facets includes an angle-selective coating.

19. an upper portion of the light guide optical element including an optically transparent line of sight area; The optical system of claim 12 , wherein the second aperture expander is disposed vertically below the line of sight area.

20. a partially planar reflector disposed within the light guide optical element parallel to the front surface; a light cover disposed on a portion of the front surface adjacent the reflector, the light cover comprising: reducing scattering of the plurality of stimulating image beams; and 13. The optical system of claim 12, configured to at least one of: (a) reduce the impingement of ambient light on the reflector;

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