Compact waveguide system

Abstract

An optical waveguide apparatus may include an in-coupling region for receiving image light traveling in a first direction, an out-coupling region, expander light-guide elements in the in-coupling region, a propagation region between the in-coupling region and the out-coupling region, and supporting light-guide elements in the propagation region. The expander light-guide elements receive the image light, transmit a first portion of the image light in the first direction, and reflect a second portion of the image light in a second direction toward the out-coupling region. The propagation region includes primary sub-regions that receive a light beam of the second portion from the expander light-guide elements, and target sub-regions that do not directly receive a light beam of the second portion from the expander light-guide elements. The supporting light-guide elements direct a light beam of the second portion from the expander light-guide elements to the out-coupling region via the target sub-regions.

Description

COMPACT WAVEGUIDE SYSTEMFIELD

[0001] The present disclosure relates to the field of near-eye display systems, such as head-mounted displays for augmented reality (AR). More specifically, the present disclosure relates to a compact waveguide system designed for near-eye displays (NEDs).BACKGROUND

[0002] Consumer demands for improved human-computer interfaces have led to an increased interest in high-quality image head-mounted displays (HMDs) or near-eye displays (NED), commonly known as smart glasses. These devices can provide augmented reality (AR) or virtual reality (VR) experiences, enhancing the way users interact with digital content and their surrounding environment.

[0003] In recent years, demand is increasing for better image quality, more immersive experiences, and greater comfort when using HMDs. Displays are expected to provide high resolution, vibrant colors, and minimal distortion to create a realistic and enjoyable viewing experience. Additionally, comfort is a significant factor since users often wear these devices for extended periods. Consumers desire lightweight, sleek designs that are less obtrusive and more convenient to wear in various scenarios. Smaller devices also offer improved portability, making them easier to carry and use in different environments. As such, there is a growing demand for higher performing yet smaller and more compact HMDs.

[0004] One principal element in traditional near-eye display systems is the waveguide. In general, a waveguide is a device that guides light from a system image projector to the user's eyes. Waveguides rely on total internal reflection along the major surfaces within the device to propagate light. There are inherent limitations in miniaturizing waveguides, which in turn restricts the miniaturization of head-mounted displays. For example, conventional features that would assist more efficient illumination of the waveguides tend to increase their size. In another example, conventional features that would assist in miniaturization of waveguides tend to reduce image quality or aesthetic appeal of the near-eye display system.Docket No. LMUS22PWO01

[0005] Therefore, there is a demand for innovative compact illuminations systems including compact waveguide systems that would contribute to compactness of the NED.SUMMARY

[0006] An optical waveguide apparatus for a near-eye display may include an incoupling region for receiving image light traveling in a first direction from a light source, an out-coupling region for directing at least a portion of the image light toward an eye-motion box, a set of expander light-guide elements positioned in the in-coupling region, a propagation region positioned between the in-coupling region and the out-coupling region, and a set of supporting light-guide elements positioned in the propagation region. The set of expander light-guide elements may receive the image light from the light source, transmit a first portion of the image light in the first direction, and reflect a second portion of the image light in a second direction toward the out-coupling region. The propagation region may include a primary set of sub-regions that receive a light beam of the second portion of the image light from the set of expander light-guide elements, and a target set of sub-regions that do not directly receive a light beam of the second portion of the image light from the set of expander light-guide elements. The set of supporting light-guide elements may direct a light beam of the second portion of the image light from the expander light-guide elements to the out-coupling region via the target set of sub-regions.

[0007] According to an aspect of the present disclosure, an optical waveguide apparatus for a near-eye display may include an in-coupling region for receiving image light traveling in a first direction from a light source; an out-coupling region for directing at least a portion of the image light toward an eye-motion box; a set of expander light-guide elements positioned in the in-coupling region and configured to receive the image light from the light source, transmit a first portion of the image light in the first direction, and reflect a second portion of the image light in a second direction toward the out-coupling region; a propagation region positioned between the in-coupling region and the out- coupling region, the propagation region including: a primary set of propagation subregions that receive a light beam of the second portion of the image light from the set of expander light-guide elements, and a target set of propagation sub-regions that do not directly receive a light beam of the second portion of the image light from the set ofDocket No. LMUS22PWO01 expander light-guide elements; and a set of supporting light-guide elements positioned in the propagation region and configured to direct a light beam of the second portion of the image light from the set of expander light-guide elements to the out-coupling region via the target set of propagation sub-regions.

[0008] According to an embodiment of any paragraph(s) of this summary, the set of expander light-guide elements are oriented obliquely with respect to the first direction.

[0009] According to an embodiment of any paragraph(s) of this summary, the set of supporting light-guide elements includes a first supporting element and a second supporting element oriented parallel to each other.

[0010] According to an embodiment of any paragraph(s) of this summary, the second supporting element has a reflectivity that is within a range of 1 .0-2.5 times a reflectivity of the first supporting element.

[0011] According to an embodiment of any paragraph(s) of this summary, the first supporting element and the second supporting element are oriented obliquely with respect to the set of expander light-guide elements.

[0012] According to an embodiment of any paragraph(s) of this summary, the first supporting element is configured to receive a first light beam of the second portion of the image light from the set of expander light-guide elements, transmit a first portion of the first light beam in the second direction toward the out-coupling region, and reflect a second portion of the first light beam to the second supporting element; and the second supporting element is configured to receive the second portion of the first light beam from the first supporting element and reflect the second portion of the first light beam to a target sub-region of the target set of propagation sub-regions.

[0013] According to an embodiment of any paragraph(s) of this summary, the first supporting element is configured to reflect the second portion of the first light beam to the second supporting element in a direction that has an anti-parallel component with respect to the first direction.Docket No. LMUS22PWO01

[0014] According to an embodiment of any paragraph(s) of this summary, the set of supporting light-guide elements includes a third supporting element and a fourth supporting element oriented parallel to the set of expander light-guide elements.

[0015] According to an embodiment of any paragraph(s) of this summary, the fourth supporting element has a reflectivity that is within a range of 1 .0-2.5 times the reflectivity of the third supporting element.

[0016] According to an embodiment of any paragraph(s) of this summary, the third supporting element is configured to receive a second light beam of the second portion of the image light from the set of expander light-guide elements, transmit a first portion of the second light beam in the second direction toward the out-coupling region, and reflect a second portion of the second light beam to the fourth supporting element in a direction that has a component in the first direction; and the fourth supporting element is configured to receive the second portion of the second light beam from the third supporting element and reflect the second portion of the second light beam to a target sub-region of the target set of propagation sub-regions.

[0017] According to an embodiment of any paragraph(s) of this summary, the incoupling region and the set of expander light-guide elements are formed in a first substrate; and the in-coupling region receives the image light from a light source disposed externally to the first substrate. According to an embodiment of any paragraph(s) of this summary, the image light is directed to the in-coupling region via a coupling-in mirror.

[0018] According to an embodiment of any paragraph(s) of this summary, the out- coupling region, the propagation region, and the set of supporting light-guide elements are formed in a second substrate optically coupled to the first substrate.

[0019] According to an embodiment of any paragraph(s) of this summary, the second substrate is formed of an inert glass.

[0020] According to an aspect of the present disclosure, a method for generating an image in a near-eye display includes transmitting, by a set of expander light-guide elements positioned in an in-coupling region and configured to receive image light traveling from a light source in a first direction, a portion of the image light in the firstDocket No. LMUS22PWO01 direction; reflecting, by the set of expander light-guide elements, a second portion of the image light in a second direction through a propagation region and toward an out-coupling region, the propagation region including a primary set of propagation sub-regions that receive a light beam of the second portion of the image light from the set of expander light-guide elements and a target set of propagation sub-regions that do not directly receive a light beam of the second portion of the image light from the set of expander light-guide elements; and directing, by a set of supporting light-guide elements, a light beam of the second portion of the image light from the set of expander light-guide elements to the out-coupling region via the target set of propagation sub-regions.

[0021] According to an embodiment of any paragraph(s) of this summary, directing, by the set of supporting light-guide elements, the light beam of the second portion of the image light from the set of expander light-guide elements to the target set of propagation sub-regions includes: transmitting, by the first supporting element in response to receiving a first light beam of the second portion of the image light from the set of expander lightguide elements, a first portion of the first light beam in the second direction toward the out- coupling region, reflecting a second portion of the first light beam to the second supporting element; and reflecting, by the second supporting element in response to receiving the second portion of the first light beam from the first supporting element, the second portion of the first light beam to a target sub-region of the target set of propagation sub-regions.

[0022] According to an embodiment of any paragraph(s) of this summary, reflecting the second portion of the first light beam to the second supporting element includes: reflecting the second portion of the first light beam to the second supporting element in a direction that has an anti-parallel component with respect to the first direction.

[0023] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate various example systems, methods, and so on, that illustrate various example embodiments of aspects of the invention. It will be appreciated that the illustrated element boundaries (e.g., boxes, groups of boxes, or other shapes) in the figures represent one example of the boundaries. One of ordinary skill in the art will appreciate that one element may be designed as multiple elements or that multiple elements may be designed as one element. An element shown as an internal componentDocket No. LMUS22PWO01 of another element may be implemented as an external component and vice versa. Furthermore, elements may not be drawn to scale.BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Fig. 1 illustrates a block diagram of an optical system, in accordance with various examples of the present disclosure.

[0025] Fig. 2 illustrates an example of a near-eye display (NED).

[0026] Fig. 3 shows schematically the concept of a two-dimensional aperture expansion (aperture multiplication) for a NED.

[0027] Fig. 4 shows schematically a comparison between an internal coupling-in mirror configuration and an external coupling in-mirror configuration with a projector in a first position.

[0028] Fig. 5 shows schematically a comparison between an internal coupling-in mirror configuration and an external coupling in-mirror configuration with a projector in a second position.

[0029] Fig. 6 illustrates an example of target sub-regions bypassed by light rays when a projector is positioned in an external coupling-in mirror configuration at the same position as in an internal coupling-mirror configuration.

[0030] Fig. 7 illustrates an example of aspects of the optical waveguide apparatus according to the embodiments of the present disclosure.

[0031] Fig. 8 illustrates an example of a novel optical waveguide apparatus for a NED according to the embodiments of the present disclosure.

[0032] Fig. 9 illustrates examples of waveguide contours in different configurations, according to the embodiments of the present disclosure

[0033] Fig. 10 illustrates an additional novel optical waveguide apparatus for a NED according to the embodiments of the present disclosure.

[0034] Fig. 11 illustrates implementation examples of the optical waveguide apparatus according to the embodiments of the present disclosure.Docket No. LMUS22PWO01

[0035] Fig. 12 illustrates an example of a method for generating an image in a neareye display using the optical waveguide apparatus according to the embodiments of the present disclosure.DETAILED DESCRIPTION

[0036] In the following description, numerous specific details are set forth, such as particular structures, components, materials, dimensions, processing steps and techniques, in order to provide an understanding of the various embodiments of the present application. However, it will be appreciated by one of ordinary skill in the art that the 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 in order to avoid obscuring the present application.

[0037] To be described in more detail below, a wearable device, such as a near eye display and / or smart glasses, can be implemented by a system and method described in accordance with the present disclosure. The system can efficiently provide high quality optical information to a user in various applications.

[0038] For purposes of the present description, the following definitions are provided to clarify certain terminology used herein. Unless expressly stated otherwise, the singular forms of the terms include the plural, and the terms “comprise,” “include,” and “have,” as well as derivatives thereof, are used in an open, non-exclusive sense. The definitions below are intended to clarify terminology employed throughout the following embodiments and figures.

[0039] As used herein, the term “near-eye display” (NED) refers to a display device configured to present visual content proximate to a viewer’s eye, such as in a headmounted display, smart glasses, visor, or other wearable imaging apparatus.

[0040] The term “waveguide” or “waveguide system” denotes an optical element formed of a transparent medium configured to receive, guide, and out-couple image light by total internal reflection between opposing major surfaces. The term encompasses single-layer or multi-layer structures and assemblies that may include reflective, partially reflective, or diffractive optical features. As used herein, ‘image light’ refers to the opticalDocket No. LMUS22PWO01 radiation that carries visual image information from the light source. A ‘beam of the image light’ or ‘light beam’ refers to any portion or bundle of that image light propagating along a defined direction

[0041] The term “substrate” refers to a transparent structural layer, such as glass, polymer, or another optical medium, within which one or more optical elements, e.g., such as light-guide elements, mirrors, coatings, or couplers, are formed, embedded, or applied. In certain embodiments, the substrate may form part or all of the waveguide, and the terms ‘waveguide’ and ‘substrate’ may be used interchangeably when the context clearly indicates an optically transmissive guiding medium.

[0042] The term “light source” refers to any device configured to emit image light, such as a projector, laser, micro-display, or LED array. In certain embodiments, the light source may be external to the waveguide and may direct image light thereto via a coupling-in mirror.

[0043] The term “in-coupling region” designates a portion of the waveguide or substrate configured to receive image light from a light source, such as a projector, and to inject that light into the guiding medium.

[0044] The term “out-coupling region” refers to a portion of the waveguide or substrate configured to direct at least a portion of the guided image light out of the waveguide toward an eye-motion box, which is a three-dimensional spatial region within which a user’s eye pupil may move while still perceiving the displayed image.

[0045] The term “propagation region” means a portion of the waveguide positioned between the in-coupling region and the out-coupling region through which the guided image light travels after injection into the waveguide.

[0046] The term “expander light-guide element” (also referred to as an “expander facet”) denotes a partially reflective or diffractive surface, coating, or structure configured to transmit a first portion of the incident image light and reflect a second portion at an angle that expands the image pupil or aperture. Such elements may be planar, parallel, or obliquely oriented relative to the propagation direction of the image light.

[0047] The term “supporting light-guide element” (also referred to as a “supportingDocket No. LMUS22PWO01 facet”) denotes an optical element disposed within the propagation region and configured to redirect, fold, or otherwise guide a portion of the image light from one region of the waveguide to another, e.g., to illuminate propagation sub-regions that would otherwise be bypassed. Supporting light-guide elements may operate singly or in cooperating pairs to form a periscope-type optical path.

[0048] The phrase “propagation sub-region” refers to a defined portion of the propagation region traversed by guided image light. A “primary set of propagation subregions” directly receives image light from the expander light-guide elements, whereas a “target set of propagation sub-regions” does not directly receive such light without redirection by supporting light-guide elements. The term ‘target set of propagation subregions’ may include one or more target sub-regions, each of which may be referenced individually herein.

[0049] The terms “first direction” and “second direction” identify distinct propagation directions of the image light within the waveguide. The first direction typically corresponds to the direction of image light entering through the in-coupling region, and the second direction corresponds to a deflected direction toward the out-coupling region.

[0050] The term “reflectivity” refers to the fraction of incident optical power reflected by a surface, coating, or element, averaged over the operational angles and wavelengths of the image light. The term “transmissivity” refers to the corresponding fraction of optical power transmitted through the element under the same conditions.

[0051] The term “obliquely oriented” means disposed at a non-parallel, nonperpendicular angle relative to a referenced direction or plane, such as between a supporting light-guide element and an expander light-guide element.

[0052] The phrase “anti-parallel component with respect to the first direction” denotes that a reflected light path includes a component opposite in direction to the first direction while not being strictly opposite, for example a reflection rotated by greater than ninety degrees relative to the first direction.

[0053] The term “coupling-in mirror” refers to a mirror or reflective element, positioned internally or externally to the waveguide substrate, used to redirect image light from aDocket No. LMUS22PWO01 projector or other source into the in-coupling region of the waveguide.

[0054] The phrase “compact waveguide contour” denotes a waveguide geometry having reduced external dimensions, e.g., height, width, or thickness, relative to a conventional configuration, while maintaining the desired optical path, field of view, and luminance uniformity.

[0055] The term “operable connection,” or a connection by which entities are “operably connected,” is one in which signals, physical communications, or logical communications may be sent or received. An operable connection may include a physical interface, an electrical interface, or a data interface, and may include any combination of these or other connection types sufficient to allow operable control. For example, two entities may be operably connected by being able to communicate signals to each other directly or through one or more intermediate entities such as a processor, operating system, logic circuit, or software module. Logical or physical communication channels may be used to create an operable connection.

[0056] To the extent that the term “includes” or “including” is employed in the description or the claims, it is intended to be inclusive in a manner similar to the term “comprising” as that term is interpreted when used as a transitional word in a claim.

[0057] Furthermore, to the extent that the term “or” is employed in the description or the claims (e.g., “A or B”), it is intended to mean “A or B or both,” unless the phrase “only A or B but not both” is expressly used. Thus, the term “or” is used in the inclusive sense and not the exclusive sense. See, Bryan A. Garner, A Dictionary of Modem Legal Usage 624 (2d. Ed. 1995).

[0058] The definitions set forth above are intended to clarify the terminology used throughout the following embodiments. Where alternative or equivalent structures, materials, or orientations are described, such alternatives are regarded as being within the spirit and scope of the disclosure unless specifically excluded. The invention is not limited to the particular examples described, but is intended to encompass variations and modifications apparent to those skilled in the art in view of the following figures and description.Docket No. LMUS22PWO01

[0059] Fig. 1 illustrates a block diagram of an optical system, in accordance with various examples of the present disclosure. Optical system 100 may include two or more devices or components. Optical system 100 may be implemented generally as a hybrid system including various electronic, optical, and electro-optical elements. An optical device 102 may include one or more elements from optical system 100. To be described in more detail below, an optical system 100 may include a wearable device 110, such as one or more near eye displays or smart glasses, which may be worn on or about the head of a user to convey optical information to one or more eyes of a user.

[0060] Wearable device 110 may include a controller 114 with a memory 116 where controller 114 may be configured to send and receive electrical signals to various other elements in optical system 100, to execute program instructions stored in memory 116 in order to process and provide information, to operate wearable device 110, and to interact with other systems outside wearable device 110, for example. 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.

[0061] Wearable device 110 may also include a power management module 120 having a battery 122, where power management module 120 may be configured to charge, discharge, and monitor power usage for battery 122. Various elements of wearable device 110 may receive power from battery 122, including controller 114, image projector 126, and optical engine 134, for example. Wearable device 110 may also include one or more image projectors 126, each configured to produce a collimated image beam based on a digital image 128. The collimated image beam may be an illuminated representation of the digital image having an image field which 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 moving image). The collimated image beam may be collimated to infinity.

[0062] Wearable device 110 may also include one or more waveguides 130 (e.g. , WGs, also denoted as light-guide optical elements LOEs) comprising transparentDocket No. LMUS22PWO01 materials configured to receive and propagate light, where light may enter into and exit through various external and internal surfaces of waveguide 130. For example, the transparent material comprising waveguide 130 may include optical glass or other suitable material that is transformed into complex optical structures using a process that may include coating, stacking, slicing, polishing, and shaping the transparent materials. The process may include the addition of partially reflective or fully reflective materials such as mirror coatings, for example. Similarly, the process may also include the addition of partially opaque or fully opaque materials such as light covers to block light, for example.

[0063] Wearable device 110 may also include one or more optical engines 134 coupled to the one or more image projectors 126 and waveguides 130. Optical engine 134 may be configured to directly operate image projector 126 under the direction of the controller 114. For example, optical engine 134 may provide graphics processing for digital image 128 before projection of an illuminated representation of the digital image by image projector 126.

[0064] Wearable device 110 may also include a frame 138 (e.g., a structure) for supporting and retaining one or more elements in wearable device 110. For example, frame 138 may support and retain a first image projector 126 in position next to a first waveguide 130. Similarly, frame 138 may support and retain a second image projector 126 in position next to a second waveguide 130. In this manner, frame 138 may support and retain one or two image projectors 126 and waveguide 130 pairs on or about the head of a user, for example. References are made herein regarding the orientation of various elements relative to each other, such references may also include reference to various elements of wearable device 110 when supported by frame 138 or in reference to a three- dimensional (3D) reference (e.g., X,Y,Z axes), as described in the relevant drawing figure.

[0065] Optical system 100 may also include a host computer 170 that may include a processor 174 configured to read and execute operations based on instructions 178 stored in a computer-readable medium 180. 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 over a signal and power bus 188. In this manner, host computer 170 may provide power to charge battery 122,Docket No. LMUS22PWO01 provide instructions to and receive status from controller 114, to control various other elements of wearable device 110, and to provide digital image data to optical engine 134.

[0066] An exemplary implementation of a device in the form of a near-eye display according to the teachings of an embodiment of the present invention, generally designated 200, employing a waveguide system 215, is illustrated schematically in Fig. 2. The near-eye display (NED) 200 employs a compact image projector 212 optically coupled so as to inject light beams corresponding to an image (interchangeably referred to as the “light,” “light rays,” the “image,” or the “image light”) into waveguide system (interchangeably referred to as “substrate” or “slab”) 215 within which the image light is trapped in one dimension by internal reflection at a set of mutually-parallel planar external surfaces.

[0067] Optical aperture expansion is achieved within waveguide system 215 by one or more arrangements for progressively redirecting the image light, typically employing a set of partially-reflecting surfaces (interchangeably referred to as “facets” or “elements”) that may be parallel to each other and inclined obliquely to the direction of propagation of the image light, with each successive facet deflecting a proportion of the image light into a deflected direction. As illustrated in Fig. 2, two-dimensional aperture expansion is achieved by employing a first waveguide section 201 that transmits the light along the X direction and a first set of facets in waveguide section 201 to progressively redirect the image light within the waveguide system 215 in the Y direction, also trapped / guided by internal reflection.

[0068] The deflected image light then passes into a second waveguide section 205, which may be implemented as an adjacent distinct substrate or as a continuation of a single substrate, in which a coupling-out arrangement (for example, a further set of partially reflective facets) progressively couples out a portion of the image light in the Z direction towards the eye of an observer located within a section defined as the eyemotion box (EMB), thereby achieving a second dimension of optical aperture expansion. Similar functionality may be obtained using diffractive optical elements (DOEs) for redirecting and / or coupling-out of image light within one or both of waveguide sections 201 and 205.Docket No. LMUS22PWO01

[0069] The overall device may be implemented separately for each eye and is preferably supported relative to the head of a user with each waveguide system 215 facing a corresponding eye of the user. In one embodiment, as illustrated here, a support arrangement is implemented as an eyeglasses frame 218 with sides for supporting the device relative to ears of the user. Other forms of support arrangement may also be used, including but not limited to head bands, visors or devices suspended from helmets.

[0070] Reference is made herein in the drawings and claims to an X axis which extends horizontally (or, in alternative embodiments, vertically), in the general extensional direction of the first section 201 of the waveguide system 215, a Y axis which extends perpendicular thereto, i.e., vertically in Fig. 2 (or, in alternative embodiments, horizontally), and a Z axis which extends perpendicular thereto, i.e., horizontal towards the eye of the user. In very approximate terms, the first waveguide section 201 of waveguide system 215 may be considered to achieve aperture expansion in the X direction while the second waveguide section 205 of waveguide system 215 achieves aperture expansion in the Y direction. The details of the spread of angular directions in which different parts of the field of view propagate will be addressed more precisely below. It should be noted that the orientation as illustrated in Fig. 2 may be regarded as a “top-down” implementation, where the image illumination entering the second waveguide section 205 of the waveguide system 215 enters from the top edge, whereas an alternative orientation may be regarded as a “side-injection” implementation, where the axis referred to here as the Y axis is deployed horizontally.

[0071] Herein, the various features of certain embodiments of the present disclosure may be illustrated in the context of a “top-down” orientation, similar to Fig. 2. However, it should be appreciated that all of those features are equally applicable to side-injection implementations, which also fall within the scope of the invention. In certain cases, other intermediate orientations are also applicable, and are included within the scope of the present invention except where explicitly excluded. The two-dimensional expansion embodiments illustrated here are merely for the sake of example, but the invention is also applicable to embodiments in which only a single dimension of aperture expansion is performed by the waveguide system 215.Docket No. LMUS22PWO01

[0072] It will be appreciated that the near-eye display 200 includes various additional components, typically including a controller 219 for actuating the image projector 212, typically employing electrical power from a small onboard battery (not shown) or some other suitable power source. It will be appreciated that controller 219 includes all necessary electronic components such as at least one processor or processing circuitry to drive the image projector 12. In embodiments, the near-eye display 200 may be implemented using the components of the wearable device 110 described with reference to Fig. 1.

[0073] Large field of view waveguides for NED, such as the waveguide system 215, may require a large surface area that is not always available ergonomically. Fig. 3 shows schematically the concept of a two-dimensional aperture expansion (aperture multiplication) for a NED. Image projector 212 projects collimated light beams representing an image at infinity (two arrows represent the beams of the edge of the image). The light from projector 212 enters waveguide system 215 and propagates while in one dimension being guided by total internal reflection (TIR) and in the other dimension diverging (different beams of different parts of the image diverge). The beams propagate within the waveguide system 215 and specifically first waveguide section 201 (also referred to as a “HLOE” in some cases) by total internal reflection as shown in Fig. 3(a) Top View. The beams impinge on embedded partial reflectors 201a of the first waveguide section 201 as shown in Fig. 3(b) Front View and are redirected toward partial reflectors 205a of the second waveguide section 205 (also referred to as an “LOE” in some cases) that reflect the beams out of the waveguide system 215 and toward the observer or eye-motion box (EMB) 217 as shown in Fig. 3(c) Side View.

[0074] Partial reflectors 201a and 205a multiply the aperture laterally and vertically, respectively. The length, position and spacing of facets 201 a and 205a may vary (shown as same distance for clarity) for achieving an optimal and uniform projected image. Facets 201a and 205a may be perpendicular or oblique relative to external faces of the first waveguide section 201 and the second waveguide section 205, respectively. A waveplate may be introduced between the first waveguide section 201 and the second waveguide section 205 to improve reflectivity. A longitudinal partial reflector (homogenizer) may be introduced before the first waveguide section 201 (for improved light injection) or after theDocket No. LMUS22PWO01 first waveguide section 201 for better image uniformity.

[0075] Solutions for 2D expansion utilizing the aforementioned HLOE and LOE are commercially available from Lumus Ltd. (Israel), and details of such waveguide systems can be found in, for example, commonly owned International Patent Application Publication WO 2020 / 049542 A1 , the entire disclosure of which is incorporated by reference herein.

[0076] In some implementations, the waveguide system 215 of Figs. 2 and 3 may be relatively large, particularly in the height (Y) dimension, which makes corresponding NED 200 relatively large and bulky. NED users, however, seek greater comfort. Comfort is a significant factor since users often wear these devices for extended periods. Consumers desire lightweight, sleek designs that are less obtrusive and more convenient to wear in various scenarios. Smaller devices also offer improved portability, making them easier to carry and use in different environments. As such, there is a growing demand for smaller and more compact NED. Miniaturization of waveguides would allow for smaller, more comfortable NED. However, conventionally, there have been limitations in miniaturizing waveguides, which in turn restricts the miniaturization of NED.

[0077] In some cases, it may be desirable to use an external coupling-in mirror outside the waveguide in place of an internal coupling-in mirror within the waveguide. Such a configuration may be advantageous, for example, when using thinner waveguides, as it may be difficult to arrange an internal coupling-in mirror having a size sufficient for coupling-in all the desired light rays from a light source. However, aspects of the present disclosure relate to the recognition that implementing an external coupling-in mirror outside the waveguide in place of an internal coupling-in mirror within the waveguide can lead to challenges associated with the projector-to-waveguide geometry. In particular, as can be seen in Fig. 4, in comparison to the case in which an internal coupling-in mirror is used to couple light rays into the waveguide 402, when an external coupling-in mirror disposed outside the waveguide 402 is used to couple light rays into the waveguide 402, the folding of the light rays at the external coupling-in mirror necessitates a larger exitpupil distance of the projector 404 used to project the light rays, leading to displacement of the projector 404 with respect to its placement in an internal coupling-in mirrorDocket No. LMUS22PWO01 configuration. That is, conventionally, in order to realize the same light path in the external coupling-in mirror configuration as in the internal coupling-in mirror configuration, the position of the projector 404 must be changed, which often enlarges the required waveguide contour, resulting in a near-eye display with a bulkier form factor.

[0078] Conversely, as can be seen in Fig. 5, positioning the projector 404 in an external coupling-in mirror configuration at the same position as in the internal couplingmirror configuration will cause light rays to couple into the waveguide 402 at a lower height and, as a consequence, bypass the upper optical element (e.g., HLOE facet) regions that would otherwise be illuminated.

[0079] Fig. 6 shows schematically a depiction of the regions bypassed by the light rays when a projector is positioned in an external coupling-in mirror configuration at the same position as in the internal coupling-mirror configuration, as described with respect to Fig. 5. As can be seen in Fig. 6, in comparison to the internal coupling-in mirror configuration in which light rays from each of the light-guide elements 612 (also referred to as a “set of expander light-guide elements” herein) propagate throughout the propagation region 620 to an out-coupling region 630, in the external coupling-in mirror configuration, there arise regions (also referred to as a “target set of propagation sub-regions” herein) 621 that are bypassed (i.e., skipped) by the light rays from the light-guide elements 612. This can result in eye motion box truncation, luminance non-uniformity, contrast reduction, geometric distortion of the image, color non-uniformity, and the like.

[0080] Accordingly, aspects of the present disclosure have been developed in view of these challenges, and relate to an optical waveguide apparatus that allows for the same projector position to be maintained in both internal and external coupling-in mirror configurations relative to the contour of the waveguide. Particularly, as illustrated in Fig. 7, in the optical waveguide apparatus according to the embodiments of the present disclosure, the placement of the set of expander light-guide elements 712 can be adjusted laterally (shifted in the negative x direction of Fig. 7) relative to their position in an internal coupling-in mirror configuration (represented by the dotted lines in Fig. 7) in order to realize the reflected ray pattern associated with an internal coupling-in mirror configuration. In addition, a set of supporting light-guide elements 721 may be provided inDocket No. LMUS22PWO01 the propagation region 720 and configured to direct a light beam reflected from the set of expander light-guide elements 712 to the target set of propagation sub-regions 723. In this way, by using the set of supporting light-guide elements 721 as a ‘periscope’ to direct light rays to the target set of propagation sub-regions 723 that would otherwise have been bypassed, it is possible to enable the use of an external coupling-in mirror configuration that provides the same or similar optical characteristics (e.g., projector placement light path, field-of-view) as an internal coupling-in mirror configuration while maintaining a compact waveguide contour. A detailed description of the optical waveguide apparatus according to the embodiments of the present disclosure will be described below with reference to Figs. 8-11.

[0081] Fig. 8 illustrates an example of a novel optical waveguide apparatus 800 for a NED according to the embodiments of the present disclosure. As illustrated in Fig. 8, the optical waveguide apparatus 800 primarily includes an in-coupling region 810, a propagation region 820, an out-coupling region 830, a set of expander light-guide elements 812, a set of supporting light-guide elements 822, and a set of output elements 845. The in-coupling region 810, propagation region 820, out-coupling region 830, set of expander light-guide elements 812, set of supporting light-guide elements 822, and other components of the optical waveguide apparatus 800 may be formed within a waveguide 850. In embodiments, the waveguide 850 may include one or more individual substrates that are optically coupled to one another. In certain embodiments, the waveguide 850 may be formed within the lens of a NED.

[0082] The in-coupling region 810 is a region (e.g., area, section) of the optical waveguide apparatus 800 for receiving image light L traveling in a first direction from a light source. In embodiments, the in-coupling region 810 may receive the image light L from a light source disposed external to the waveguide 850 via an aperture 805. In certain embodiments, as described herein, the light source may include a projector. In some embodiments, image light from the projector may be directed to the in-coupling region 810 via an external coupling-in mirror disposed outside the waveguide 850. Herein, an example will be described in which the image light L is traveling in a first direction that is generally along the negative y-axis shown in Fig. 8, but it will be understood that the embodiments of the disclosure are not limited herein, and other light injectionDocket No. LMUS22PWO01 configurations are also possible.

[0083] The out-coupling region 830 is a region of the optical waveguide apparatus 800 for directing at least a portion of the image light L toward an eye-motion box. As used herein, an “eye-motion box” denotes the three-dimensional spatial region within which the user’s eye pupil may move while still receiving the displayed image. In embodiments, the out-coupling region 830 may include a set of output elements 845 for coupling the guided image light toward the eye-motion box. In embodiments, the set of output elements 845 may include a set of planar, mutually parallel, partially reflecting surfaces oriented nonparallel to the set of expander light-guide elements 812. For example, the set of output elements 845 may include mirrored facets embedded between the major external surfaces of the optical waveguide apparatus 800, diffractive out-couplers, or coated partial reflectors whose reflectance varies along the array to promote uniform luminance across the eye-motion box. Polarization-selective internal reflectors and / or an interposed retarder may be additionally employed to optimize out-coupling efficiency while maintaining controlled propagation within the waveguide.

[0084] The set of expander light-guide elements 812 are optical elements configured to receive the image light L from the light source, transmit a first portion L1 of the image light L in the first direction, and reflect a second portion L2 of the image light L in a second direction toward the out-coupling region 830. In various embodiments, the expander lightguide elements 812 may include a set of planar, mutually parallel, partially reflective surfaces (“expander facets”) that are positioned in, or adjacent to, the in-coupling region 810. Accordingly, the set of expander light-guide elements 812 may have a reflectivity and a transm ittivity selected to allow the first portion L1 of the image light L to pass through in the first direction (e.g., generally along the negative y-axis shown in Fig. 8), and a reflectivity selected to cause the second portion L2 of the image light L to be reflected in the second direction (generally along the positive x-axis shown in Fig. 8). In embodiments, the set of expander light-guide elements 812 may be oriented obliquely (e.g., at a nonzero angle) with respect to the first direction to facilitate splitting / expansion of the incident beam of the image light L. The angle of orientation of the set of expander light-guide elements 812 is not particularly limited herein, and may be selected to facilitate the desired expansion of the image light L.Docket No. LMUS22PWO01

[0085] During operation, the set of expander light-guide elements 812 may split the incident beam of the image light L1 so that a first portion L1 continues in the first direction (e.g., generally along the negative y-axis in Fig. 8) while a second portion L2 is deflected in the second direction (e.g., generally along the x-axis in Fig. 8) toward the propagation region 820 and subsequently toward the out-coupling region 830, thereby providing beam replication and pupil-expansion. In embodiments, reflectivity-modifying coatings may be provided on individual elements of the set of expander light-guide elements 812 to apportion optical power among multiple deflected beams to approximate a desired luminance distribution at the out-coupling region 830. As examples, the set of expander light-guide elements 812 can be implemented as embedded mirrored facets, diffractive structures, polarization-engineered internal reflectors, or the like. It should be noted that the number of expander light-guide elements 812 is not particularly limited herein, and may be selected in accordance with the size and desired operation of the optical waveguide apparatus 800.

[0086] The propagation region 820 is a region of the optical waveguide apparatus through which the second portion L2 of the image light L deflected by the set of expander light-guide elements 812 travels on its way to the out-coupling region 830, and may be positioned between the in-coupling region 810 and the out-coupling region 830 of the optical waveguide apparatus 800. The propagation region 820 includes a primary set of propagation sub-regions 821 that receive a light beam L2B of the second portion L2 of the image light L from the set of expander light-guide elements 812 and a target set of propagation sub-regions 823 that do not directly receive a light beam L2B of the second portion L2 of the image light L from the set of expander light-guide elements 812. It will be appreciated that the primary set of propagation sub-regions 821 shown in Fig. 8 are not drawn to scale and are intended solely to illustrate direction and / or potential areas within the waveguide 850 in which such propagation may occur. Thus, while shown as extending into the out-coupling region 830, such primary set of propagation sub-regions 821 may be within the propagation region and / or extend into such region 830. That is, the light beams L2B from the set of expander light-guide elements 812 bypass the target set of propagation sub-regions 823 due to the location at which the image light L is coupled into the waveguide 850. More particularly, as described herein, this target set ofDocket No. LMUS22PWO01 propagation sub-regions 823 arise as a result of the second portion L2 of the image light L bypassing (i.e., skipping) the outer (e.g., peripheral) regions of the waveguide 850 due to the use of an external coupling-in mirror located outside of the waveguide 850 while maintaining the projector in the same location that would be used for an internal couplingin mirror arrangement. The number of target sub-regions within the target set of propagation sub-regions 823 is not particularly limited herein, and may be one or more. Here, an example will be described of a case in which the target set of propagation subregions 823 include one target sub-regions.

[0087] As used herein, the phrase “the target set of propagation sub-regions do not directly receive a light beam of the second portion of the image light from the set of expander light-guide elements” denotes that, under nominal operation of the optical waveguide apparatus 800, rays constituting the second portion L2 of the image light L emerging from the set of expander light-guide elements 812 do not propagate along an optical path that, by itself and without redirection (e.g., by the set of supporting light-guide elements 822), couples those rays into the target set of propagation sub-regions 823. That is, the phrase “directly receive” refers to reception along the propagation path established by the set of expander light-guide elements 812 prior to interaction with any structures whose function is to reroute light in other directions. As can be seen in Fig. 8, in embodiments, the primary set of propagation sub-regions 821 may receive the second portion L2 of the image light L directly (e.g., straight from, without passing through any intermittent optical elements) from the set of expander light-guide elements 812, whereas the target set of propagation sub-regions 823 do not receive the second portion L2 of the image light L directly from the set of expander light-guide elements 812, but after redirection by the set of supporting light-guide elements 822.

[0088] The set of supporting light-guide elements 822 are optical elements configured to direct (e.g., reflect, deflect, or otherwise guide) portion of a first light beam L2B1 of the second portion L2 of the image light L from the set of expander light-guide elements 812 to the target set of propagation sub-regions 823. In embodiments, as illustrated in Fig. 8, the set of supporting light-guide elements 822 may include a first supporting element 822a and a second supporting element 822b oriented parallel to each other. As shown in Fig. 8, the first supporting element 822a and the second supporting element 822b may beDocket No. LMUS22PWO01 positioned within a predetermined distance from the furthest upstream expander lightguide element of the set of expander light-guide elements 812 (e.g., proximal to the aperture 805). For example, the predetermined distance may be 10%, 15%, or 25% of the total distance between the top and bottom edges of the waveguide 850 (e.g., where the top and bottom edges are those surfaces opposing each other in the y-direction of Fig. 8).

[0089] As described herein, in operation, the set of supporting light-guide elements 822 may function to establish a periscope-type fold of the light beam so that light is directed into the target set of propagation sub-regions 823 that would otherwise be bypassed by the second portion L2 of the image light L from the set of expander light-guide elements 812. It should be noted that while Fig. 8 illustrates a set of supporting light-guide elements822 including two elements for directing image light to the target set of propagation subregions 823 with two redirection events (e.g., a first redirection from the first supporting element 822a to the second supporting element 822b and a second redirection from the second supporting element 822 to the set of propagation sub-regions 823), the present disclosure is not limited herein, and configurations that incorporate greater or fewer supporting light-guide elements 822 that direct image light to the target set of propagation sub-regions 823 with a greater or fewer number of redirection events are also possible.

[0090] In embodiments, the set of supporting light-guide elements 822 include planar, partially reflective light-guide elements that are oriented obliquely with respect to the set of expander light-guide elements 812 so as to fold the light beam along a controlled path into the target set of propagation sub-regions 823 and subsequently toward the out-coupling region 830. The oblique orientation of the set of supporting light-guide elements 822 with respect to the set of expander light-guide elements 812 enables a compact fold of the image light to illuminate target sub-regions of the target set of propagation sub-regions823 that are located upstream from the expander light-guide elements 812 with respect to the direction of propagation of the image light L (e.g., the first direction, generally along the negative y direction in the figure). As will be described later on herein, in embodiments, the set of supporting light-guide elements 822 may be implemented within a substrate (e.g., a second substrate) adjacent to a primary light-guide segment (e.g., a first substrate) housing the set of expander light-guide elements 812, with an inert glass fill completing the outer contour.Docket No. LMUS22PWO01

[0091] In embodiments, the first supporting element 822a is configured to receive a first light beam L2B1 of the second portion L2 of the image light L from the set of expander light-guide elements 812, transmit a first portion L2B1 a of the first light beam L2B1 in the second direction (e.g., generally along the x-axis in Fig. 8) toward the out-coupling region 830, and reflect a second portion L2B1 b of the first light beam L2B1 to the second supporting element 822b. The second supporting element 822b is configured to receive the reflected second portion L2B1 b from the first supporting element 822a and reflect the second portion L2B1 b of the first light beam L2B1 to a target sub-region of the target set of propagation sub-regions 823. In this way, the set of supporting light-guide elements 822 can direct light to the target set of propagation sub-regions 823 that would otherwise be bypassed by the second portion L2 of the image light L from the set of expander lightguide elements 812, and thereby provide an external coupling-in mirror configuration with the same or similar optical characteristics (e.g., projector placement, light path, field-of- view) as an internal coupling-in mirror configuration while maintaining a compact waveguide contour.

[0092] In embodiments, the second supporting element 822b has a reflectivity that is within a range of 1 .0-2.5 times the reflectivity of the first supporting element 822a. Here, the reflectivity refers to the average reflectance over the image angle of incidence range and spectrum. As an example, in the case that the set of supporting light-guide elements 822 includes two elements (822a, 822b) as shown in Fig. 8, the first supporting element 822a may be configured with a reflectivity of between 40% and 60% and the second supporting element 822b may be configured with a reflectivity of between 72% and 95% or greater. More particularly, the first supporting element 822a may be configured with a reflectivity of 50% (and transmissivity of about 50%) and the second supporting element 822b may be configured with a reflectivity of 95% or greater (and transmissivity of about 0%). That is, the second supporting element 822b may have a reflectivity that is approximately double the reflectivity of the first supporting element 822a. In this way, the optical power redirected by the two redirection events is apportioned to emulate the luminance that would have been produced by the bypassed portion of the target set of propagation sub-regions 823. In embodiments, other reflectivity ratios may be selected to accommodate more than two redirection events, polarization-dependent reflectance, orDocket No. LMUS22PWO01 wavelength-selective coatings used elsewhere in the optical waveguide apparatus 800. For instance, in cases in which more than two supporting light-guide elements are used, the reflectivity of each supporting light-guide element may be similarly adjusted such that the same optical power (e.g., the same luminance) is output to the out-coupling region 830 from each target sub-region of the target set of propagation sub-regions 823. In certain embodiments, the second supporting element 822b may have a reflectivity that is equal to the reflectivity of the first supporting element 822a. Such a configuration may be selected in cases where image uniformity is not required, for example. Here, it should be noted that the transmissivity of the first supporting element 822a and the second supporting element 822b may depend on the mirror material. For example, if made of metal, a transmissivity of approximately 0% may be achieved; if made of dielectric layers the transmissivity may become 1-R, where R is the reflectance of the first supporting element 822a or the second supporting element 822b.

[0093] In embodiments, the first supporting element 822a and the second supporting element 822b may be oriented obliquely with respect to the set of expander light-guide elements 812. Here, the term “obliquely” denotes a non-parallel, non-zero angle orientation between the plane of each of the first supporting element 822a and the second supporting element 822b and the planes of the set of expander light-guide elements 812. This oblique relationship allows the set of supporting light-guide elements 822 to transmit a first portion L2B1 a of the first light beam L2B1 of the second portion L2 of the image light L in the second direction (e.g., generally along the x-axis in Fig. 8) toward the out- coupling region 830, and reflect a second portion L2B1 b of the first light beam L2B1 to the second supporting element 822b.

[0094] In embodiments, as shown in Fig. 8, the first supporting element 822a is configured to reflect the second portion L2B1b of the first light beam L2B1 to the second supporting element 822b in a direction having an anti-parallel component with respect to the first direction (e.g., generally along the negative y-axis in Fig. 8). As used herein, “a direction having an anti-parallel component with respect to the first direction” denotes that the reflected propagation vector includes a component opposite to the first direction while not being strictly opposite; this component is selected to direct the second portion L2B1 b toward the target set of propagation sub-regions 823 before the second supportingDocket No. LMUS22PWO01 element 822b redirects the beam toward the out-coupling region 830. For instance, the first supporting element 822a may reflect the second portion L2B1 b of the first light beam L2B1 to the second supporting element 822b in a direction having an axis that is rotated at an angle of greater than 90 degrees with respect to the first direction. As an example, as shown in Fig. 8, the first supporting element 822a is configured to reflect the second portion L2B1 b of the first light beam L2B1 to the second supporting element 822b in a direction that is generally along the positive y-axis in Fig. 8 (e.g., a direction having an axis rotated by approximately 135 degrees clockwise with respect to the first direction). Put differently, the first supporting element 822a is used to reflect the second portion L2B1 b of the first light beam L2B1 to the second supporting element 822b in a direction that is upstream with respect to the propagation direction of the light L1 from the expander lightguide element 812 from which the first light beam L2B1 was received.

[0095] According to the optical waveguide apparatus 800 illustrated in Fig. 8, by using the set of supporting light-guide elements 822 as a ‘periscope’ to direct light rays to the target set of propagation sub-regions 823 that would otherwise have been bypassed by light from the set of expander elements 812, it is possible to enable the use of an external coupling-in mirror configuration that provides the same or similar optical characteristics (e.g., projector placement, light path, field-of-view) as an internal coupling-in mirror configuration while maintaining a compact waveguide contour.

[0096] Fig. 9 illustrates examples of waveguide contours in different configurations, according to the embodiments of the present disclosure. Particularly, Fig. 9 illustrates a first waveguide contour 910, a second waveguide contour 920, and a comparison view 930 of the first waveguide contour 910 overlaid on the second waveguide contour 920. The first waveguide contour 910 substantially corresponds to the optical waveguide apparatus 800 illustrated in Fig. 8, and includes the set of supporting light-guide elements 822 disposed in the waveguide in a configuration in which light is coupled into the waveguide using an external coupling-in mirror. The second waveguide contour 920 corresponds to a configuration in which light is coupled into the waveguide using an external coupling-in mirror but the set of supporting light-guide elements 822 are not disposed in the waveguide. As a result, the second waveguide contour 920 becomes larger than the first waveguide contour 910 due to the displacement of the projector thatDocket No. LMUS22PWO01 arises in order to realize the appropriate light path, and light from the set of expander lightguide elements 812 bypasses the target set of propagation sub-regions 823.

[0097] The comparison view 930 illustrates the first waveguide contour 910 (represented by the solid lines in the figure) overlaid on the second waveguide contour 920 (represented by the dashed lines in the figure). As can be seen in the comparison view 930, by including the set of supporting light-guide elements 822 to direct light from the set of expander light-guide elements 812 to the target set of propagation sub-regions 823, the desired light path through the waveguide can be realized in the first waveguide contour 910 without displacing the projector, allowing for a more compact contour than that of the second waveguide contour 920. As described herein, the more compact waveguide contour according to the embodiments of the present disclosure can facilitate miniaturization of the associated NED, which in turn allows for greater portability, convenience, and user comfort.

[0098] Fig. 10 illustrates a novel optical waveguide apparatus 1000 for a NED according to the embodiments of the present disclosure. As the structure of the novel optical waveguide apparatus 1000 substantially corresponds to that of the optical waveguide apparatus 800 shown and described with respect to Fig. 8, the same reference numerals will be used for corresponding components and a redundant explanation thereof will be omitted.

[0099] As described herein, the number and position of the set of supporting light lightguide elements is not particularly limited herein, and the set of supporting light-guide elements 822 can be utilized to realize additional contour modification configurations of the optical waveguide apparatus. For instance, in embodiments, aspects of the present disclosure relate to omitting (e.g., removing, reducing) one or more expander light-guide elements from the set of expander light-guide elements 812 according to the optical waveguide apparatus 800 shown and described with respect to Fig. 8. As an example, in embodiments, an expander light-guide element (e.g., the expander light-guide element furthest downstream from the image light L entering the in-coupling region 810 from the aperture 805) may be omitted from the set of expander light-guide elements 812 of the optical waveguide apparatus 800 shown and described with respect to Fig. 8.Docket No. LMUS22PWO01

[0100] As can be seen in Fig. 10, the omission of this expander light-guide element creates a new target sub-region 823n among the target set of propagation sub-regions 823, as this region no longer receives light directly from the removed expander light-guide element. According to the optical waveguide apparatus 1000 shown in Fig. 10, additional supporting elements may be positioned within the waveguide 850 to direct light from the set of expander light-guide elements 812 to the target sub-region 823n. In this way, by omitting one or more expander light-guide elements 812 from the waveguide 850 of the optical waveguide apparatus 800 shown and described with respect to Fig. 8, and providing additional supporting elements to direct light to the target sub-region 823n, it is possible to realize further miniaturization of the waveguide 850 without degrading eyemotion box coverage or luminance uniformity.

[0101] More particularly, as can be seen in Fig. 10, the optical waveguide apparatus 1000 includes a third supporting element 822c and a fourth supporting element 822d positioned within the propagation region 820. Generally, the third supporting element 822c and the fourth supporting element 822d are optical elements configured to direct a second light beam L2B2 of the second portion L2 of the image light L from the set of expander light-guide elements 812 to a target sub-region (e.g., target sub-region 823n) of the target set of propagation sub-regions 823. The target sub-region 823n refers to a particular subregion of target set of propagation sub-regions that does not receive light directly from the set of expander light-guide elements 812. Here, an example of a target sub-region 823n located at the periphery of the waveguide 850 opposite to the aperture 805 will be described.

[0102] In embodiments, the third supporting element 822c and the fourth supporting element 822d may be implemented as planar, partially reflective coatings or embedded mirrored planes situated between the major external surfaces of the waveguide 850, and positioned to receive a second light beam L2B2 from one of the expander light-guide elements of the set of expander light-guide elements 812. As shown in Fig. 10, the third supporting element 822c and the fourth supporting element 822d may be positioned within a predetermined distance from the furthest downstream expander light-guide element of the set of expander light-guide elements 812 (e.g., opposite from the aperture 805). ForDocket No. LMUS22PWO01 example, the predetermined distance may be 10%, 15%, or 25% of the total distance between the top and bottom edges of the waveguide 850.

[0103] In embodiments, the third supporting element 822c and the fourth supporting element 822d may be oriented parallel to the set of expander light-guide elements 812 (in contrast to the first supporting element 822a and the second supporting element 822b that were oriented obliquely with respect to the set of expander light-guide elements 812). As used herein, “oriented parallel” denotes that each planar surface of the third supporting element 822c and the fourth supporting element 822d is substantially parallel to the planes of the expander light-guide elements 812. For instance, the third supporting element 822c and the fourth supporting element 822d may be integrated as additional, laterally displaced members of the same parallel stack as the set of expander light-guide elements 812. This parallel orientation of the third supporting element 822c and the fourth supporting element 822d facilitates guiding light beams from the set of expander lightguide elements 812 to the target sub-region 823n of the target set of propagation subregions 823. Additionally, in certain embodiments, the third supporting element 822c and the fourth supporting element 822d may be implemented as expander light-guide elements 812 that extend from the in-coupling region 810 to the propagation region 820, such that each of the third supporting element 822c and the fourth supporting element 822d include a first section located in the in-coupling region 810 and a second section located in the propagation region 820. In embodiments, the first sections of the third supporting element 822c and the fourth supporting element 822d located in the incoupling region 810 and the second sections of the third supporting element 822c and the fourth supporting element 822d located in the propagation region 920 may have different coatings.

[0104] In embodiments, the third supporting element 822c may be configured to receive a second light beam L2B2 of the second portion L2 of the image light L from the set of expander light-guide elements 812, transmit a first portion L2B2a of the second light beam L2B2 in the second direction (e.g., generally along the x-axis in Fig. 10) toward the out-coupling region 830, and reflect a second portion L2B2b of the second light beam L2B2 to the fourth supporting element 822d in a direction that has a component in the first direction (e.g., generally along the negative y-axis in Fig. 10). The fourth supportingDocket No. LMUS22PWO01 element 822d is configured to receive the reflected second portion L2B2b from the third supporting element 822c and reflect the second portion L2B2b of the second light beam L2B2 to the target sub-region 823n of the target set of propagation sub-regions 823.

[0105] In embodiments, as shown in Fig. 10, the third supporting element 822c is configured to reflect the second portion L2B2b of the second light beam L2B1 to the second supporting element 822b in a direction having a component in the first direction (e.g., generally along the positive y-axis in Fig. 10). As used herein, “a direction having a component in the first direction” denotes any propagation direction for which the projection of its direction vector onto the direction vector of the first direction is positive. For instance, the third supporting element 822c may reflect the second portion L2B2b of the second light beam L2B2 to the fourth supporting element 822d in a direction having an axis that is rotated at an angle of less than 90 degrees with respect to the first direction. As an example, as shown in Fig. 10, the third supporting element 822c is configured to reflect the second portion L2B2b of the second light beam L2B2 to the fourth supporting element 822d in a direction that is generally along the negative y-axis in Fig. 10 (e.g., a direction having an axis rotated by approximately 15 degrees clockwise with respect to the first direction). Put differently, the third supporting element 822c is used to reflect the second portion L2B2b of the second light beam L2B2 to the fourth supporting element 822d in a direction that is downstream with respect to the propagation direction of the light L1 from the expander light-guide element 812 from which the second light beam L2B2 was received.

[0106] As described above with respect to the first supporting element 822a and the second supporting element 822b, in embodiments, the fourth supporting element 822d has a reflectivity that is within a range of 1 .0-2.5 times the reflectivity of the third supporting element 822c. Here, the reflectivity refers to the average reflectance over the image angle of incidence range and spectrum. As an example, the third supporting element 822c may be configured with a reflectivity of between 40% and 60% and the fourth supporting element 822d may be configured with a reflectivity of between 72% and 95% or greater. More particularly, the third supporting element 822c may be configured with a reflectivity of 50% (and transmissivity of about 50%) and the fourth supporting element 822d may be configured with a reflectivity of 95% or greater (and transmissivity ofDocket No. LMUS22PWO01 about 0%). That is, the fourth supporting element 822d may have a reflectivity that is approximately double the reflectivity of the third supporting element 822c. In this way, the optical power redirected by the two redirection events is apportioned to emulate the luminance that would have been produced by the bypassed portion of the target set of propagation sub-regions 823. In embodiments, other reflectivity ratios may be selected to accommodate more than two redirection events, polarization-dependent reflectance, or wavelength-selective coatings used elsewhere in the optical waveguide apparatus 1000. For instance, in cases in which more than two supporting light-guide elements are used, the reflectivity of each supporting light-guide element may be similarly adjusted such that the same optical power (e.g., the same luminance) is output to the out-coupling region 830 from each target sub-region of the target set of propagation sub-regions 823. In certain embodiments, the fourth supporting element 822d may have a reflectivity that is equal to the reflectivity of the third supporting element 822c. Such a configuration may be selected in cases where image uniformity is not required, for example. Here, it should be noted that the transmissivity of the third supporting element 822c and the fourth supporting element 822d may depend on the mirror material. For example, if made of metal, a transmissivity of approximately 0% may be achieved; if made of dielectric layers the transmissivity may become 1-R, where R is the reflectance of the third supporting element 822c or the fourth supporting element 822d.

[0107] By omitting one or more expander light-guide elements that are located downstream from the incident light path, and using the third supporting element 822c and the fourth supporting element 822d to direct image light from the set of expander lightguide elements 812 to a target sub-region 823n of the target set of propagation subregions 823 that does not receive light from the set of expander light-guide elements, the contour of the waveguide 850 can be further reduced while maintaining the same optical output. For example, as shown in Fig. 10, the hashed region 1015 can be removed from the bottom portion of the waveguide (e.g., due to the removal / reduction of the number of expander light-guide elements), thereby further miniaturizing the waveguide contour with respect to the optical waveguide apparatus 800 shown and described with respect to Fig. 8.

[0108] Fig. 11 illustrates implementation examples of the optical waveguideDocket No. LMUS22PWO01 apparatus according to the embodiments of the present disclosure. Particularly, Fig. 11 shows a first implementation example 1110 and a second implementation example 1120. As illustrated in the first implementation example 1110 and the second implementation example 1120, aspects of the disclosure relate to a manufacturing process in which the in- coupling-region 810 and the set of expander light-guide elements 812 are formed in a first substrate 1160, and the set of supporting light-guide elements 822 are formed in a second substrate 1170 optically coupled to the first substrate. Here, the first substrate 1160 and the second substrate 1170 may be bonded glass substrates formed within the lens of a NED. As described herein, the in-coupling region 810 in the first substrate 1160 may receive image light from a light source such as a projector via a coupling-in mirror disposed externally to the first substrate. In embodiments, the second substrate 1170 may be formed of an inert glass. As illustrated in the second implementation example 1120, a portion 1174 of the second substrate 1170 may be removed, modified, or otherwise formed in a desired shape to facilitate subsequent waveguide building process steps.

[0109] Fig. 12 illustrates an example of a method 1200 for generating an image in a near-eye display using the optical waveguide apparatus according to the embodiments of the present disclosure.

[0110] At Step S1210, a set of expander light-guide elements positioned in an incoupling region of the optical waveguide apparatus and configured to receive image light traveling from a light source in a first direction may transmit a first portion of the image light in the first direction.

[0111] At Step 1220, the set of expander light-guide elements may reflect a second portion of the image light in a second direction through a propagation region and toward an out-coupling region of the optical waveguide apparatus. The propagation region may include a primary set of propagation sub-regions that receive a light beam of the second portion of the image light from the set of expander light-guide elements and a target set of propagation sub-regions that do not directly receive a light beam of the second portion of the image light from the set of expander light-guide elements.

[0112] At Step 1230, a set of supporting light-guide elements positioned in the propagation region may direct a light beam of the second portion of the image light fromDocket No. LMUS22PWO01 the set of expander light-guide elements to the target set of propagation sub-regions. In embodiments, directing the light beam of the second portion of the image light from the set of expander light-guide elements to the target set of propagation sub-regions may include transmitting, by a first supporting element of the set of supporting light-guide elements in response to receiving a first light beam of the second portion of the image light from the set of expander light-guide elements, a first portion of the first light beam in the second direction toward the out-coupling region, reflecting a second portion of the first light beam to a second supporting element of the set of supporting light-guide elements; and reflecting, by the second supporting element in response to receiving the second portion of the first light beam from the first supporting element, the second portion of the first light beam to a target sub-region of the target set of propagation sub-regions.

[0113] According to the embodiments of the present disclosure, as described herein, by using a set of supporting light-guide elements as a ‘periscope’ to direct light rays to a target set of propagation sub-regions that would otherwise have been bypassed by light from the set of expander elements, it is possible to enable the use of an external couplingin mirror configuration that provides the same or similar optical characteristics (e.g., projector placement, light path, field-of-view) as an internal coupling-in mirror configuration while maintaining a compact waveguide contour. In turn, the more compact waveguide contour according to the embodiments of the present disclosure can facilitate miniaturization of the associated NED, allowing for greater portability, convenience, and user comfort.

[0114] While example systems, methods, and so on, have been illustrated by describing examples, and while the examples have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit scope to such detail. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the systems, methods, and so on, described herein. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention is not limited to the specific details, the representative apparatus, and illustrative examples shown and described. Thus, this application is intended to embrace alterations, modifications, and variations that fall within the scope of the appended claims. Furthermore, the preceding description is not meant to limit theDocket No. LMUS22PWO01 scope of the invention. Rather, the scope of the invention is to be determined by the appended claims and their equivalents.

Claims

Docket No. LMUS22PWO01CLAIMSWhat is claimed is:1 . An optical waveguide apparatus for a near-eye display, the optical waveguide apparatus comprising: an in-coupling region for receiving image light traveling in a first direction from a light source; an out-coupling region for directing at least a portion of the image light toward an eye-motion box; a set of expander light-guide elements positioned in the in-coupling region and configured to receive the image light from the light source, transmit a first portion of the image light in the first direction, and reflect a second portion of the image light in a second direction toward the out-coupling region; a propagation region positioned between the in-coupling region and the out-coupling region, the propagation region including: a primary set of propagation sub-regions that receive a light beam of the second portion of the image light from the set of expander light-guide elements, and a target set of propagation sub-regions that do not directly receive a light beam of the second portion of the image light from the set of expander light-guide elements; and a set of supporting light-guide elements positioned in the propagation region and configured to direct a light beam of the second portion of the image light from the set of expander light-guide elements to the out-coupling region via the target set of propagation sub-regions.

2. The optical waveguide apparatus according to claim 1 , wherein the set of expander light-guide elements are oriented obliquely with respect to the first direction.Docket No. LMUS22PWO013. The optical waveguide apparatus according to claim 1 , wherein the set of supporting light-guide elements includes a first supporting element and a second supporting element oriented parallel to each other.

4. The optical waveguide apparatus according to claim 3, wherein the second supporting element has a reflectivity that is within a range of 1 .0-2.5 times a reflectivity of the first supporting element.

5. The optical waveguide apparatus according to claim 3, wherein the first supporting element and the second supporting element are oriented obliquely with respect to the set of expander light-guide elements.

6. The optical waveguide apparatus according to claim 3, wherein: the first supporting element is configured to receive a first light beam of the second portion of the image light from the set of expander light-guide elements, transmit a first portion of the first light beam in the second direction toward the out-coupling region, and reflect a second portion of the first light beam to the second supporting element; and the second supporting element is configured to receive the second portion of the first light beam from the first supporting element and reflect the second portion of the first light beam to a target sub-region of the target set of propagation sub-regions.

7. The optical waveguide apparatus according to claim 6, wherein the first supporting element is configured to reflect the second portion of the first light beam to the second supporting element in a direction that has an anti-parallel component with respect to the first direction.Docket No. LMUS22PWO018. The optical waveguide apparatus according to claim 1 , wherein the set of supporting light-guide elements includes a third supporting element and a fourth supporting element oriented parallel to the set of expander light-guide elements.

9. The optical waveguide apparatus according to claim 8, wherein the fourth supporting element has a reflectivity that is within a range of 1.0-2.5 times a reflectivity of the third supporting element.

10. The optical waveguide apparatus according to claim 8, wherein: the third supporting element is configured to receive a second light beam of the second portion of the image light from the set of expander light-guide elements, transmit a first portion of the second light beam in the second direction toward the out-coupling region, and reflect a second portion of the second light beam to the fourth supporting element in a direction that has a component in the first direction; and the fourth supporting element is configured to receive the second portion of the second light beam from the third supporting element and reflect the second portion of the second light beam to a target sub-region of the target set of propagation sub-regions.11 . The optical waveguide apparatus according to claim 1 , wherein: the in-coupling region and the set of expander light-guide elements are formed in a first substrate; and the in-coupling region receives the image light from a light source disposed externally to the first substrate.

12. The optical waveguide apparatus according to claim 11 , wherein the image light is directed to the in-coupling region via a coupling-in mirror.Docket No. LMUS22PWO0113. The optical waveguide apparatus according to claim 11 , wherein the out-coupling region, the propagation region, and the set of supporting light-guide elements are formed in a second substrate optically coupled to the first substrate.

14. The optical waveguide apparatus according to claim 13, wherein the second substrate is formed of an inert glass.

15. A method for generating an image in a near-eye display, the method comprising: transmitting, by a set of expander light-guide elements positioned in an in-coupling region and configured to receive image light traveling from a light source in a first direction, a first portion of the image light in the first direction; reflecting, by the set of expander light-guide elements, a second portion of the image light in a second direction through a propagation region and toward an out-coupling region, the propagation region including a primary set of propagation sub-regions that receive a light beam of the second portion of the image light from the set of expander lightguide elements and a target set of propagation sub-regions that do not directly receive a light beam of the second portion of the image light from the set of expander light-guide elements; and directing, by a set of supporting light-guide elements, a light beam of the second portion of the image light from the set of expander light-guide elements to the out-coupling region via the target set of propagation sub-regions.

16. The method according to claim 15, wherein the set of supporting light-guide elements includes a first supporting element and a second supporting element oriented parallel to each other.

17. The method according to claim 16, wherein the second supporting element has a reflectivity that is within a range of 1 .0-2.5 times a reflectivity of the first supporting element.Docket No. LMUS22PWO0118. The method according to claim 16, wherein the first supporting element and the second supporting element are oriented obliquely with respect to the set of expander lightguide elements.

19. The method according to claim 16, wherein directing, by the set of supporting lightguide elements, the light beam of the second portion of the image light from the set of expander light-guide elements to the target set of propagation sub-regions includes: transmitting, by the first supporting element in response to receiving a first light beam of the second portion of the image light from the set of expander light-guide elements, a first portion of the first light beam in the second direction toward the out- coupling region, reflecting a second portion of the first light beam to the second supporting element; and reflecting, by the second supporting element in response to receiving the second portion of the first light beam from the first supporting element, the second portion of the first light beam to a target sub-region of the target set of propagation sub-regions.

20. The method according to claim 19, wherein reflecting the second portion of the first light beam to the second supporting element includes: reflecting the second portion of the first light beam to the second supporting element in a direction that has an anti-parallel component with respect to the first direction.

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