Two-dimensional pupil dilation in a single light guide structure

Abstract

Techniques are described for providing a two-dimensional eyebox and / or pupil dilation in a flat or curved reflective light guide using a single reflective structure. An in-coupling structure receives display light and directs the display light into the light guide and to an integrated reflective structure. The reflective structure redirects at least a portion of the display light to expand the eyebox of the light guide in two dimensions. The display light is directed to an out-coupler structure for directing the display light from the light guide toward the expanded eyebox.

Description

[Background technology]

[0001] The present disclosure generally relates to augmented reality (AR) eyewear that blends real-world views with head-up display overlays. Wearable display devices, including wearable head-up displays (WHUDs), eyewear display (EWD) devices, and head-mounted display (HMD) devices (all of these terms may be used interchangeably herein), are wearable electronic devices that combine the real world and virtual images via one or more optical combiners, such as one or more integrated combiner lenses, to provide a virtual display that a user can view when the wearable display device is worn on the user's head. Some optical combiners transmit light using light guides (also called waveguides). Generally, light from a projector in a wearable display device enters the light combiner's light guide through an in-coupler, propagates along the light guide via total internal reflection (TIR), and exits the light guide through an out-coupler. When the eye's pupil is aligned with one or more exit pupils provided by the outcoupler, at least a portion of the light exiting the outcoupler enters the eye's pupil, thereby allowing the user to see the virtual image. Because the combiner lens is transparent, the user can also see the real world. Summary of the Invention

[0002] In an embodiment, the light guide comprises an in-coupling structure for receiving display light and directing the display light into the light guide, a spatially integrated reflective structure for extending the eyebox provided by the light guide in two dimensions, and an out-coupling structure for directing the display light from the light guide towards the extended eyebox.

[0003] The two dimensions may be substantially orthogonal.

[0004] The reflective structure comprises a plurality of prisms, which may include two intersecting sets of parallel facets, and the two intersecting sets may be substantially orthogonal.

[0005] The reflective structure may include a plurality of substantially triangular facets.

[0006] The reflective structure may include an interface between the first portion of the optical substrate and the second portion of the optical substrate. The reflective structure may include one or more reflective coatings disposed on the interface.

[0007] The reflective structure may function as an outcoupling structure.

[0008] The reflective structure may be spatially separated from the outcoupling structure along the path that the display light propagates through the light guide.

[0009] In an embodiment, the wearable display device includes a light guide.

[0010] In an embodiment, the method includes directing display light into a light guide via an in-coupler, expanding an eyebox of the light guide in two dimensions via a spatially integrated reflective structure, and directing the display light from the light guide towards the expanded eyebox via an out-coupling structure.

[0011] Expanding the eyebox of the light guide may include expanding the eyebox in two substantially orthogonal dimensions.

[0012] Expanding the eyebox of the light guide via the reflective structure may include expanding the eyebox via a plurality of prisms. Expanding the eyebox via a plurality of prisms may include expanding the eyebox via two or more intersecting sets of parallel facets, where the intersecting sets may be substantially orthogonal.

[0013] Expanding the eyebox of the light guide via the reflective structure may include expanding the eyebox via a plurality of substantially triangular facets.

[0014] Expanding the eyebox of the light guide via the reflective structure can include expanding the eyebox via an interface between the first portion of the optical substrate and the second portion of the optical substrate. The reflective structure can include one or more reflective coatings disposed on the interface.

[0015] The reflecting structure may be substantially coincident with the outcoupling structure.

[0016] Directing the display light from the light guide towards the extended eyebox via the outcoupling structure may include directing the display light along a propagation path between the reflective structure and the outcoupling structure within the light guide.

[0017] The present disclosure may be better understood, and its numerous features and advantages made apparent to those skilled in the art by referencing the accompanying drawings, in which: The use of the same reference symbols in different drawings indicates similar or identical items. [Brief explanation of the drawings]

[0018] [Figure 1] 1 shows a diagram of a wearable display device 100 according to some embodiments. [Figure 2] 1 illustrates an exemplary cross-sectional view of a one-dimensional (1D) reflective structure used in 1D eyebox expansion in one dimension. [Figure 3] 10A-10C show exemplary cross-sectional views of other 1D reflective structures for use in eyebox expansion in one dimension. [Figure 4] 1 illustrates 2D reflective structures used for two-dimensional eyebox and / or pupil dilation, according to some embodiments. [Figure 5] 1 illustrates 2D reflective structures used for two-dimensional eyebox and / or pupil dilation, according to some embodiments. [Figure 6]1A-1C show cross-sectional and transverse partial structural views of reflective structures used in the eyebox and / or pupil dilation, according to some embodiments. [Figure 7] FIG. 10 is an operational flow diagram illustrating operations for providing a 2D eyebox and / or pupil dilation in a reflective light guide using a single reflective structure, according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0019] Eyewear display optics for all-day wear eyewear require efficiency, image quality, thickness, manufacturability, resolution, artifact-free, full color, reliability, and the curved appearance that is standard in today's eyewear industry. Current light guide architectures come with various constraints related to optics, aesthetics, manufacturing, thickness, and vision correction (prescription lenses).

[0020] Wearable display devices that present AR content typically use a light combiner light guide (also referred to herein as a "light guide") to transmit and magnify display light emitted by the display to the user's eyes, while also allowing light from the real-world scene to reach the user's eyes through the light guide. This allows the image represented by the display light to be superimposed on the real-world scene from the user's perspective. Typically, the light guide relies on total internal reflection (TIR) ​​to transmit light received from the display through an in-coupling feature at one end of the light guide to an out-coupling feature at the other end of the light guide that faces the user's eyes. The out-coupling feature is configured to direct light beams from within the light guide out of the light guide, and the user perceives the projected light beams as images displayed in the field of view (FOV) region of a display component positioned in front of the user's eyes, such as the lenses of an EWD device that have the general shape and size of eyeglasses. The light beams emitted from the light guide then overlap at an eye relief distance from the light guide, forming a "pupil" within which the virtual image generated by the image source can be viewed.

[0021] A relatively large FOV region and pupil are desirable in an EWD device to provide a user with a focused, immersive experience. It is also desirable for an EWD device to be adaptable to a variety of users, each with different relative sizes and locations of facial features relative to the EWD components. For example, one consideration in designing an EWD device that can be worn by a wide range of users is the "eyebox," i.e., the three-dimensional region in space where the eye pupils should be located to satisfy a set of viewing experience criteria (e.g., allowing the user to see all four edges of a virtual image). The larger the eyebox, the greater the range of users the EWD device can accommodate. Furthermore, increasing the size of an EWD's eyebox generally corresponds to dilating the EWD's pupils.

[0022] Many design elements of an EWD device contribute to the size of the FOV region, pupil, and eyebox. For example, the configuration of outcoupling features within the outcoupling region of the light guide can be configured to provide an expanded FOV while also expanding the pupil and eyebox. Previous attempts to achieve two-dimensional (2D) eyebox and / or pupil expansion have involved utilizing two spatially separated one-dimensional (1D) reflective structures in combination.

[0023] The embodiments described herein provide 2D eyebox and / or pupil dilation for planar (flat) or non-planar (curved) reflective light guides using a single structure, such as a periodic reflective structure, formed on one or more optical substrates of an optical combiner. Such periodic reflective structures typically have a period on the order of 1 mm. For visible light wavelengths (e.g., wavelengths between approximately 350 and 700 nm), diffraction from such reflective structures is minimal (e.g., on the order of 2 arc minutes), which roughly approximates the Nyquist resolution of the cones in the human retina. This lack of diffraction is desirable for the facets of the various 2D reflective structures described herein, which are formed between two complementary portions of refractive index-matched optical substrates with one or more reflective coatings applied to the interface between these portions. While the resulting reflective facets are intended to be invisible to the user, the reflective coatings can cause diffractive effects in smaller-scale optical structures. Furthermore, in certain embodiments, the facets of the described reflective structures are configured such that the spacing (pitch) of such facets provides sufficient reflection to expand the eyebox while avoiding introducing diffraction artifacts. Additional benefits of such embodiments include a compact footprint that can broaden industrial design options for the frame and other components of embedded EWD devices.

[0024] 1 shows a diagram of a wearable display device 100 according to some embodiments. In some embodiments, the wearable display device 100 may implement or be implemented by aspects of the wearable display device 100. For example, the wearable display device 100 may include a first arm 110, a second arm 120, and a front frame 130. The first arm 110 may be coupled to the front frame 130 by a hinge 119, allowing the first arm 110 to rotate relative to the front frame 130. The second arm 120 may be coupled to the front frame 130 by a hinge 129, allowing the second arm 120 to rotate relative to the front frame 130.

[0025] In the example of FIG. 1 , the wearable display device 100 may be in an unfolded configuration, with the first arm 110 and the second arm 120 positioned to rotate and fit onto a user's head. The first arm 110 is positioned on a first side of the user's head, the second arm 120 is positioned on a second side opposite the first side of the user's head, and the front frame 130 is positioned in front of the user's head. The first arm 110 and the second arm 120 can rotate toward the front frame 130 until both the first arm 110 and the second arm 120 are approximately parallel to the front frame 130, allowing the wearable display device 100 to assume a convenient, compact shape that can fit into a rectangular, cylindrical, or oval case. Alternatively, the first arm 110 and the second arm 120 may be fixedly attached to the front frame 130, preventing the wearable display device 100 from being foldable. In the illustrated embodiment, the first arm 110 carries a light engine 111 and the second arm 120 carries a power source 121 .

[0026] Generally, an in-coupling structure (incoupler) is used to couple light from a projector into a light guide system, and an out-coupling structure (out-coupler) is used to extract light propagating through the light guide and send an image to the human eye. In FIG. 1 , the front frame 130 carries an in-coupling structure (incoupler) 131, an out-coupling structure (out-coupler) 133, and a light guide 135 including at least one set of conductive current paths, thereby providing electrical coupling between the power source 121 and the electrical components (such as the light engine 111) carried on the first arm 110. In other embodiments, such electrical coupling is provided indirectly, such as via a power supply circuit, or directly from the power source 121 to each electrical component of the first arm 110.

[0027] The light engine 111 can output display light 190 (simplified in this example) representing AR content or other display content to be viewed by a user. The display light 190 can be redirected by a light guide 135 toward a user's eye 191 so that the user can view the AR content. The display light 190 from the light engine 111 hits an in-coupler 131 and is redirected to travel through the interior space of the light guide 135, where it is guided through the light guide by, for example, total internal reflection (TIR) ​​and / or surface treatments such as holograms or reflective coatings. The display light 190 traveling within the light guide 135 then hits an out-coupler 133, which redirects the display light 190 from the light guide 135 toward the user's eye 191. In the wearable display device 100, the out-coupler 133 is shown having an eye-facing surface 136 that is parallel to (and possibly coplanar with) an eye-facing surface 137 of the light guide 135. It should be noted that unless expressly stated, the discussion herein also applies to embodiments in which the light guide 135 can be either planar (flat) or non-planar (curved).

[0028] As used herein, the terms "carry," "carries," or similar terms do not necessarily mean that one component physically supports another component. For example, first arm 110 is described above as carrying light engine 111. This may mean that light engine 111 is attached to or within first arm 110, such that first arm 110 physically supports light engine 111. However, a direct or indirect coupling relationship may also be expressed even when first arm 110 does not necessarily physically support light engine 111.

[0029] Wearable display device 100 may include a processor (not shown) communicatively coupled to each of the electrical components of wearable display device 100, including, but not limited to, light engine 111. The processor may be any suitable component capable of executing instructions or logic, including, but not limited to, a microcontroller, a microprocessor, a multi-core processor, an integrated circuit, an ASIC, an FPGA, a programmable logic device, or any suitable combination of these components. Wearable display device 100 may include a processor-readable non-transitory storage medium on which processor-readable instructions may be stored that, when executed by the processor, cause the processor to perform any number of functions, including causing light engine 111 to output light 190 representing display content viewed by a user, receiving user input, managing a user interface, generating display content to be presented to a user, receiving and managing data from any sensors carried by wearable display device 100, receiving and processing external data and messages, and any other functions suitable for a given application. The non-transitory processor-readable storage medium may be any suitable component that can store instructions, logic, or programs, including, but not limited to, non-volatile or volatile memory, read-only memory (ROM), random access memory (RAM), flash memory, registers, a magnetic hard disk, an optical disk, or any combination of these components.

[0030] 2 shows an exemplary cross-sectional view of a one-dimensional (1D) reflective structure 201 used to expand a 1D eyebox in one dimension, X. The 1D reflective structure 201 includes a number of substantially triangular formations 205 formed between boundaries 210 in an optical substrate 299. Each of the substantially triangular formations 205 includes a facet 208. A portion of any incident light beam that couples with the 1D reflective structure 201 is reflected from the substantially triangular formations 205 (and, in particular, from the facets 208), resulting in the eyebox, formed at least in part by the reflected light beam, being expanded along the X dimension.

[0031] 3 shows an exemplary cross-sectional view of another 1D reflective structure 301 used for 1D eyebox expansion in one dimension Y, which in the illustrated example is substantially orthogonal to the dimension X along which the eyebox of 1D reflective structure 201 of FIG. 2 is expanded. In substantially the same manner as described above with respect to 1D reflective structure 201, 1D reflective structure 301 includes a number of substantially triangular formations 305 formed between boundaries 310 of optical substrate 399. Each of substantially triangular formations 305 includes facets 308. A portion of any incident light beam that couples with 1D reflective structure 301 is reflected from substantially triangular formations 305 (and, in particular, from facets 308), resulting in an expansion of the eyebox formed at least in part by the reflected light beam along the Y dimension.

[0032] 4 illustrates a single 2D reflective structure 401 used for two-dimensional eyebox and / or pupil dilation, according to some embodiments. 2D reflective structure 401 includes reflective properties of both 1D reflective structure 201 and 1D reflective structure 301, and spatially integrates these reflective aspects of 1D reflective structures 201 and 301, thereby expanding the eyebox of an incorporated light guide in two substantially orthogonal dimensions, X and Y. As used herein, spatially integrating refers to the property of 2D reflective structure 201 that aspects of 2D reflective structure 401 that expand the resulting eyebox along the X dimension overlap and occupy substantially the same portions of 2D reflective structure 401 as aspects that expand the resulting eyebox along the Y dimension. In particular, the 2D reflective structure 401 includes a plurality of pyramidal structures 405, each having four substantially triangular facets for expanding an eyebox provided by a light beam interacting with the pyramidal structure (e.g., two facets reflect such light beam to expand the eyebox along the X dimension and two facets reflect such light beam to expand the eyebox along the substantially orthogonal Y dimension). In certain embodiments, the reflective structures may redirect the expanded display light toward an out-coupler of the light guide. In other embodiments, the reflective structure 401 can operate as an out-coupler itself, such that the reflective structure 401 expands the eyebox in two dimensions and substantially simultaneously out-couples light toward the eyebox.

[0033] FIG. 5 illustrates a single 2D reflective structure 501 formed on an optical substrate 599. The reflective structure 501 utilizes multiple prisms for two-dimensional eyebox and / or pupil dilation, according to some embodiments. In the illustrated embodiment, the multiple prisms form various reflective facets (parallel facet 516 and substantially triangular facet 518) that redirect incident display light in multiple dimensions, thereby expanding the eyebox provided by a light guide incorporating the reflective structure 501. However, the reflective structures 401 and 501 are configured differently such that, while the intersecting prisms that form the pyramidal structure 405 of the reflective structure 401 are orthogonal, the multiple prisms that form the facets 516 and 518 of the reflective structure 501 are not orthogonal. Thus, the reflective structure 401 expands the associated eyebox in two substantially orthogonal dimensions, while the reflective structure 501 expands the associated eyebox in two non-orthogonal dimensions.

[0034] In certain embodiments, the reflective structure 501 is encapsulated as a reflective interface between separately formed complementary portions of one or more optical substrates. In such embodiments, one or more reflective coatings are applied to the interface between the complementary portions of the optical substrates that form the plurality of prisms 505 as an internally reflective interface in the same manner as described below with respect to FIG.

[0035] FIG. 6 shows a partial lateral block diagram of a single 2D reflective structure 601, which may operate substantially similarly to 2D reflective structure 401 of FIG. 4 and / or 2D reflective structure 501 of FIG. 5. In the depicted embodiment, a first optical substrate portion 610 and a second optical substrate portion 620 are joined at an optical interface 615. 2D reflective structure 601 is configured to expand the eyebox of an incorporated light guide (not shown) through reflectivity provided by one or more optical coatings disposed along optical interface 615. Due to the shape of optical interface 615, these optical coatings function to form internal reflective facets 605, which function in a manner similar to that described above with respect to pyramidal structure 405 and prism 505 of FIGS. 4 and 5, respectively. In this manner, optical interface 615, and more generally, the entire 2D reflective structure 601, provides a reflective surface that expands the provided eyebox in two separate (and, in this example, substantially orthogonal) dimensions. In certain embodiments, the individual reflective facets of 2D reflective structure 601 utilize both angle and wavelength dependent coating structures (e.g., holographic Bragg mirrors, interference coatings, metallic coatings, or other suitable partially reflective coating structures). Such facets, with their low reflectivity, typically 20% or less, generally cannot be detected by a user.

[0036] In certain embodiments, the internal reflective facets of the 2D reflective structure 601 are sealed by an integrated light guide using two optical substrate portions 610, 620 (e.g., injection-molded, diamond-turned, or glass-molded optical substrate portions). Each of the two optical substrate portions 610, 620 includes a phase offset, which causes the opposing facets of the optical substrate portions 610, 620 to form a complementary pair and are bonded to each other (e.g., by an index-matching adhesive). Display light is introduced through an incoupler facet (not shown), which is bonded at an angle to the interior of the light guide, allowing the reflected light to undergo TIR within the optical substrate portions 610, 620. In certain embodiments, this facet is coated with a partially reflective material, which causes reflection. The display light then propagates within the light guide via TIR, depending on the angle of the incoupler facet and the angle of the incident display light. In some embodiments, the reflective structure 601 functions as an outcoupler, simultaneously outcoupling and expanding the display light (in two dimensions). In other embodiments, a separate outcoupling structure (outcoupler, not shown) is formed at some distance from the reflecting structure 601 within the light guide in which it is incorporated.

[0037] 7 is an operational flow diagram illustrating operations for providing 2D eyebox and / or pupil dilation in a reflective light guide using a single reflective structure, according to some embodiments. The illustrated operations begin at block 705.

[0038] At block 705, display light (eg, display light 190 in FIG. 1) is directed into a reflective light guide via an in-coupler (eg, in-coupler 131 in FIG. 1).

[0039] At block 710, display light is directed via TIR towards a spatially integrated reflective structure (such as one of reflective structures 401, 501, 601, 701 of Figures 4-7, respectively).

[0040] In block 715, the display light is redirected along two dimensions by spatially integrated reflective structures, thereby expanding the eyebox provided by the light guide.

[0041] At block 720, the display light is redirected out of the light guide toward the expanded eyebox via an outcoupler (e.g., outcoupler 133 in FIG. 1 ). As noted elsewhere herein, in certain embodiments, the spatially integrated reflective structure can further operate as an outcoupler for the light guide, whereby the reflective structure outcouples light toward the eyebox while simultaneously expanding the eyebox in two dimensions.

[0042] In some embodiments, certain aspects of the techniques described above may be performed by one or more processors of a processing system executing software. The software includes one or more sets of executable instructions stored on, or otherwise tangibly embodied in, a non-transitory computer-readable storage medium. The software may include instructions and specific data that, when executed by, one or more processors, operate the one or more processors to perform one or more aspects of the techniques described above. Non-transitory computer-readable storage media may include, for example, magnetic or optical disk storage devices, solid-state storage devices such as flash memory, cache, random access memory (RAM), or other single or multiple non-volatile memory devices, and the like. The executable instructions stored on the non-transitory computer-readable storage medium may be source code, assembly language code, object code, or other instruction formats that are interpreted or otherwise executable by one or more processors.

[0043] A computer-readable storage medium may include any storage medium, or combination of storage media, that is accessible by a computer system during use to provide instructions and / or data to the computer system. Such storage media may include, but are not limited to, optical media (e.g., compact discs (CDs), digital versatile discs (DVDs), Blu-ray discs), magnetic media (e.g., floppy disks, magnetic tape, or magnetic hard drives), volatile memory (e.g., random access memory (RAM) or cache), non-volatile memory (e.g., read-only memory (ROM) or flash memory), or microelectromechanical systems (MEMS)-based storage media. A computer-readable storage medium may be incorporated into a computing system (e.g., system RAM or ROM), fixedly attached to a computing system (e.g., a magnetic hard drive), removably attached to a computing system (e.g., an optical disk or universal serial bus (USB)-based flash memory), or connected to a computer system via a wired or wireless network (e.g., network-accessible storage (NAS)).

[0044] It should be noted that not all of the operations or elements described above in the general description are required, and that some of the particular operations or devices may not be required, and one or more additional operations may be performed or elements may be included in addition to those described above. Furthermore, the order in which activities are listed is not necessarily the order in which they are performed. Also, concepts have been described with reference to specific embodiments. However, those skilled in the art will recognize that various modifications and changes can be made without departing from the scope of the present disclosure, as set forth in the claims below. Accordingly, the specification and drawings should be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present disclosure.

[0045] Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, any feature or features that may cause or make more pronounced any benefit, advantage, or solution should not be construed as critical, necessary, or essential features of any or all claims. Moreover, the specific embodiments disclosed above are exemplary only, as the disclosed subject matter may be modified and practiced in different but equivalent manners that will be apparent to those skilled in the art having the benefit of the teachings herein. No limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified, and all such variations are considered within the scope of the disclosed subject matter. The protection sought herein is therefore set forth in the following claims.

Claims

1. 1. A light guide comprising: an incoupling structure for receiving display light and directing the display light into the light guide; a spatially integrated reflective structure for extending the eyebox provided by said light guide in two dimensions.

2. The light guide of claim 1 , wherein the two dimensions are substantially orthogonal.

3. The light guide of claim 1 or 2, wherein the reflective structures comprise a plurality of prisms.

4. The light guide of claim 3 , wherein the plurality of prisms comprises two intersecting sets of parallel facets.

5. The light guide of claim 4 , wherein the two intersecting sets are substantially orthogonal.

6. The light guide of any preceding claim, wherein the reflective structure comprises a plurality of substantially triangular facets.

7. The light guide of any preceding claim, wherein the reflective structure comprises an interface between a first portion of the optical substrate and a second portion of the optical substrate.

8. The light guide of claim 7 , wherein the reflective structure comprises one or more reflective coatings disposed on the interface surfaces.

9. The light guide of any preceding claim, further comprising an outcoupling structure for directing the display light from the light guide towards the extended eyebox.

10. The light guide of any one of claims 1 to 8, wherein the reflective structure further outcouples the display light from the light guide towards the extended eyebox.

11. A wearable display device comprising a light guide according to any one of claims 1 to 10.

12. 1. A method comprising: guiding display light into a light guide via an in-coupler; and extending the eyebox of the light guide in two dimensions via spatially integrated reflective structures of the light guide.

13. The method of claim 12 , wherein expanding the eyebox of the light guide comprises expanding the eyebox in two substantially orthogonal dimensions.

14. 14. The method of claim 12 or 13, wherein expanding the eyebox of the light guide via the reflective structure comprises expanding the eyebox via a plurality of prisms.

15. 15. The method of claim 14, wherein expanding the eyebox through the plurality of prisms comprises expanding the eyebox through two intersecting sets of parallel facets.

16. The method of claim 15 , wherein the two intersecting sets are substantially orthogonal.

17. 17. The method of any one of claims 12 to 16, wherein expanding the eyebox of the light guide via the reflective structure comprises expanding the eyebox via a plurality of substantially triangular facets.

18. 18. The method of any one of claims 12 to 17, wherein expanding the eyebox of the light guide via the reflective structure comprises expanding the eyebox via an interface between a first portion of an optical substrate and a second portion of an optical substrate.

19. The method of claim 18 , wherein the reflective structure comprises one or more reflective coatings disposed on the interface.

20. The method of any one of claims 12 to 19, further comprising directing the display light from the light guide towards the extended eyebox via an outcoupling structure.

21. 20. The method of any one of claims 12 to 19, wherein directing the display light from the light guide to the extended eyebox comprises using the reflective structure to direct the display light from the light guide to the extended eyebox.

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