Two-dimensional pupil expansion in single light guide structures

Abstract

Techniques are described for providing two-dimensional eye movement range and / or pupil extension for flat or curved reflective light guides using a single reflective structure. The input coupling structure receives the display light and directs the display light into the light guide and directs the display light toward the integrated reflective structure. The reflective structure redirects at least a portion of the display light to extend the eye movement range of the light guide in two dimensions. The display light is directed to an output coupler structure for directing the display light out of the light guide toward the extended eye movement range.

Description

BACKGROUND OF THE INVENTION

[0001] The present disclosure generally relates to augmented reality (AR) eye-wearable devices that fuse a view of the real world with a heads-up display overlay. Wearable display devices, including wearable heads-up displays (WHUDs), eye-wearable device displays (EWDs), and head-mounted displays (HMDs) (all 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 visible to a user when the wearable display device is worn on the user's head. One class of optical combiners uses optical waveguides (also referred to as waveguides) to transmit light. Generally, light from a projector of a wearable display device enters an optical waveguide of an optical combiner through an input coupler, propagates along the optical waveguide via total internal reflection (TIR), and exits the optical waveguide through an output coupler. If the pupil of the eye is aligned with one or more exit pupils provided by the output coupler, at least a portion of the light exiting through the output coupler will enter the pupil of the eye, enabling the user to see the virtual image. Since the combiner lens is transparent, the user will also be able to see the real world. SUMMARY OF THE INVENTION

[0002] In one embodiment, the optical waveguide includes: an input coupling structure configured to receive display light and direct the display light into the optical waveguide; a spatially integrated reflective structure configured to expand the eyebox provided by the optical waveguide in two dimensions; and an output coupling structure configured to direct the display light out of the optical waveguide toward the expanded eyebox.

[0003] The two dimensions may be substantially orthogonal.

[0004] The reflective structure includes a plurality of prisms. The plurality of prisms may include two intersecting sets of parallel facets. The two intersecting sets may be substantially orthogonal.

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

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

[0007] The reflective structure may operate as the output coupling structure.

[0008] The reflective structure may be spatially separated from the output coupling structure along a propagation path of the display light through the optical waveguide.

[0009] In an embodiment, the wearable display device includes an optical waveguide.

[0010] In an embodiment, a method includes: guiding display light into an optical waveguide via an input coupler; expanding the eye movement range of the optical waveguide in two dimensions via a spatially integrated reflective structure; and guiding the display light out of the optical waveguide toward the expanded eye movement range via an output coupling structure.

[0011] Expanding the eye movement range of the optical waveguide can include expanding the eye movement range in two substantially orthogonal dimensions.

[0012] Expanding the eye movement range of the optical waveguide via the reflective structure can include expanding the eye movement range via a plurality of prisms. Expanding the eye movement range via a plurality of prisms can include expanding the eye movement range via two or more sets of intersecting parallel faces. The intersecting sets can be substantially orthogonal.

[0013] Expanding the eye movement range of the optical waveguide via the reflective structure can include expanding the eye movement range via a plurality of substantially triangular faces.

[0014] Expanding the eye movement range of the optical waveguide via the reflective structure can include expanding the eye movement range via an interface between a first portion of an optical substrate and a second portion of the optical substrate. The reflective structure can include one or more reflective coatings disposed at the interface.

[0015] The reflective structure can be substantially coincident with the output coupling structure.

[0016] Guiding the display light out of the optical waveguide toward the expanded eye movement range via the output coupling structure can include guiding the display light along a propagation path between the reflective structure and the output coupling structure within the optical waveguide. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present disclosure can be better understood by reference to the accompanying drawings, and numerous features and advantages of the present disclosure will be apparent to those of ordinary skill in the art. Like reference numerals in the different drawings indicate similar or identical items.

[0018] Figure 1 A diagram showing a wearable display device 100 according to some embodiments.

[0019] Figure 2 An example cross-sectional view showing a 1D reflective structure for 1D eye movement range expansion in a single dimension.

[0020] Figure 3 An example cross-sectional view showing another 1D reflective structure for eye movement range expansion in a single dimension.

[0021] Figure 4Shows a 2D reflective structure for two-dimensional eye movement range and / or pupil expansion according to some embodiments.

[0022] Figure 5 Shows a 2D reflective structure for two-dimensional eye movement range and / or pupil expansion according to some embodiments.

[0023] Figure 6 Shows a cross-sectional view and a cross-sectional component view of a reflective structure for eye movement range and / or pupil expansion according to some embodiments.

[0024] Figure 7 Is an operation flowchart showing the operation for providing two-dimensional eye movement range and / or pupil expansion in a reflective light guide using a single reflective structure according to some embodiments. Detailed Description

[0025] Eye-wear device display optical elements intended for all-weather eye-wear devices require efficiency, image quality, thickness, manufacturability, resolution, artifact control, full color, reliability, and a curved appearance that meets the current eye-wear device industry standards. Current light guide architectures are associated with various limitations in terms of optics, aesthetics, manufacturing, thickness, and ophthalmic correction (prescription).

[0026] Wearable display devices for presenting AR content typically employ an optical combiner light guide (also referred to herein as a "light guide") to transmit and magnify display light emitted by a display to a user's eye, while also allowing light from the real-world scene to pass through the light guide to the user's eye, resulting in an image represented by the display light covering the real-world scene from the user's perspective. Generally, the light guide relies on total internal reflection (TIR) to transmit the light received from the display via an input coupling feature located at one end of the light guide to an output coupling feature facing the user's eye located at the other end of the light guide. The output coupling feature is configured to direct the light beam from within the light guide out of the light guide such that the user perceives the projected light beam as an image displayed in the field of view (FOV) region of a display component located in front of the user's eye, and the display component is a lens of an EWD device having a general shape and size such as glasses. The light beam exiting the light guide then overlaps at an eye relief distance from the light guide, thereby forming a "pupil" within which the virtual image generated by the image source can be viewed.

[0027] In an EWD device, a relatively large FOV region and pupil are desired to provide a focused, immersive experience for the user. It is also desirable for the EWD device to be suitable for a variety of users, despite differences in the relative sizes and positions of their respective facial features relative to the EWD components. For example, one design consideration for an EWD device wearable by a wide range of users is the "eye movement range", or such a 3D volume in space: the pupil of the eye must be positioned within this 3D volume in order to meet a set of viewing experience criteria (such as the user being able to see all four edges of a virtual image). The larger the eye movement range, the larger the range of users that the EWD device can accommodate. Additionally, increasing the size of the eye movement range of the EWD generally corresponds to an expansion of the pupil of the EWD.

[0028] Multiple design elements of the EWD device affect the size of the FOV region, pupil, and eye movement range. For example, the configuration of the output coupling features within the output coupling region of the light guide can be configured to provide an expanded FOV while also expanding the pupil and eye movement range. Previous attempts to achieve two-dimensional (2D) eye movement range and / or pupil expansion have involved the combined use of two spatially separated one-dimensional (1D) reflective structures.

[0029] The embodiments described herein provide 2D eye movement range and / or pupil expansion for a planar (flat) or non-planar (curved) reflective light guide through a single structure, which is a periodic reflective structure formed in one or more optical substrates such as an optical combiner. This periodic reflective structure typically has a period on the order of 1 mm; for visible light wavelengths (e.g., wavelengths of approximately 350 nm to 700 nm), the diffraction of such a reflective structure will be minimal (e.g., on the order of 2 arc minutes), which is quite close to the Nyquist resolution of cone cells in the human retina. For the surfaces of the various 2D reflective structures described herein, it is desirable that there be no such diffraction, which are formed between two refractive-index-matched complementary portions of an optical substrate, where one or more reflective coatings are applied at the interface between these portions. Although the resulting reflective surface is intended to be invisible to the user, the reflective coating can cause diffraction effects in smaller-scale optical structures. Additionally, in certain embodiments, the surfaces of the reflective structure are configured such that the spacing (pitch) of such surfaces avoids causing diffraction artifacts while providing sufficient reflection to expand the eye movement range. Additional advantages of such embodiments include a compact footprint, which allows for additional industrial design options for the frame and other components of the incorporating EWD device.

[0030] Figure 1A diagram showing a wearable display device 100 according to some embodiments. In some embodiments, aspects of the wearable display device 100 may be implemented or may implement 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, which allows 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, which allows the second arm 120 to rotate relative to the front frame 130.

[0031] In Figure 1 an example, the wearable display device 100 may be in an unfolded configuration, in which the first arm 110 and the second arm 120 rotate such that the wearable display device 100 can be worn on a user's head, where 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 of the user's head opposite the first side, and the front frame 130 is positioned on the front of the user's head. The first arm 110 and the second arm 120 may rotate towards the front frame 130 until both the first arm 110 and the second arm 120 are substantially parallel to the front frame 130, such that the wearable display device 100 can be in a compact shape that is conveniently adapted to fit in a rectangular, cylindrical, or rectangular housing. Alternatively, the first arm 110 and the second arm 120 may be fixedly mounted to the front frame 130 such that the wearable display device 100 cannot be folded. In the depicted embodiment, the first arm 110 carries an optical engine 111; the second arm 120 carries a power supply 121.

[0032] Generally, an input coupling structure (input coupler) is used to couple light from a projector into an optical waveguide system, and an output coupling structure (output coupler) couples the propagating light out of the optical waveguide and sends an image to the human eye. In Figure 1 this case, the front frame 130 carries an optical waveguide 135 that includes an input coupling structure (input coupler) 131, an output coupling structure (output coupler) 133, and at least one set of conductive current paths that provide an electrical coupling between the power supply 121 and electrical components (such as the optical engine 111) carried by the first arm 110. In other embodiments, such electrical coupling is provided indirectly (such as through a power circuit) or directly from the power supply 121 to each electrical component in the first arm 110.

[0033] The light engine 111 can output display light 190 (simplified for this example) representing AR content or other display content to be viewed by a user. The display light 190 can be redirected by the light guide 135 towards the user's eye 191 such that the user can see the AR content. The display light 190 from the light engine 111 is incident on the input coupler 131 and redirected to travel within the volume of the light guide 135, where the display light 190 is guided through the light guide, such as by total internal reflection (TIR) and / or surface treatments (such as holographic plates or reflective coatings). Subsequently, the display light 190 traveling within the volume of the light guide 135 is incident on the output coupler 133, which redirects the display light 190 out of the light guide 135 and towards the user's eye 191. In the wearable display device 100, the depicted output coupler 133 has an eye-facing surface 136 that is parallel (and possibly coplanar with) the eye-facing surface 137 of the light guide 135. It should be understood that unless otherwise explicitly indicated, the discussions herein apply to embodiments in which the light guide 135 can be planar (flat) or non-planar (curved).

[0034] As used herein, the term carry or similar terms do not necessarily stipulate that one component physically supports another component. For example, it was stated above that the first arm 110 carries the light engine 111. This can mean that the light engine 111 is mounted to or within the first arm 110 such that the first arm 110 physically supports the light engine 111. However, it can also describe a direct or indirect coupling relationship, even when the first arm 110 does not necessarily physically support the light engine 111.

[0035] The wearable display device 100 may include a processor (not shown) communicatively coupled to each of the electrical components in the wearable display device 100, including but not limited to the light engine 111. The processor may be any suitable component that can execute 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. The wearable display device 100 may include a non-transitory processor-readable storage medium that may store processor-readable instructions thereon, which when executed by the processor may cause the processor to perform any number of functions, including causing the light engine 111 to output light 190 representing display content to be viewed by a user, receiving user input, managing a user interface, generating display content to be presented to the user, receiving and managing data from any sensors carried by the wearable display device 100, receiving and processing external data and messages, and any other functions for a given application as appropriate. 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, magnetic hard disks, optical disks, or any combination of these components.

[0036] Figure 2 An example cross-sectional view of a 1D reflection structure 201 for 1D eye movement range extension in a single dimension X is shown. The 1D reflection structure 201 includes a number of substantially triangular configurations 205 formed between boundaries 210 in an optical substrate 299. Each of the substantially triangular configurations 205 includes a face 208. A portion of any incoming light beam interfacing with the 1D reflection structure 201 is reflected by the substantially triangular configurations 205 (and specifically by the face 208), resulting in an extension of the eye movement range formed at least in part by the reflected light beam along dimension X.

[0037] Figure 3 An example cross-sectional view of another 1D reflection structure 301 for 1D eye movement range extension in a single dimension Y is shown, where in the depicted example, the dimension Y is perpendicular to the extension Figure 2is substantially orthogonal to the dimension X along which the eye movement range of the 1D reflective structure 201 extends. In a manner substantially the same as described above for the 1D reflective structure 201, the 1D reflective structure 301 includes a number of substantially triangular configurations 305 formed between boundaries 310 in the optical substrate 399. Each of the substantially triangular configurations 305 includes a face 308. A portion of any incoming beam that interfaces with the 1D reflective structure 301 is reflected by the substantially triangular configurations 305 (and specifically by the face 308), resulting in an expansion of the eye movement range along the dimension Y formed at least in part by the reflected beam.

[0038] Figure 4 A single 2D reflective structure 401 for two-dimensional eye movement range and / or pupil expansion in accordance with some embodiments is shown. The 2D reflective structure 401 includes the reflective aspects of both the 1D reflective structure 201 and the 1D reflective structure 301 such that by spatially integrating these reflective aspects of the 1D reflective structures 201 and 301, the eye movement range of the combined light guide is expanded in two substantially orthogonal dimensions X and Y. As used herein, spatially integrating refers to such a property of the 2D reflective structure 201 that causes the aspect of the 2D reflective structure 401 that expands the eye movement range along the X dimension and the aspect of the 2D reflective structure 401 that expands the eye movement range along the Y dimension to overlap and occupy substantially the same portion of the 2D reflective structure. Specifically, the 2D reflective structure 401 includes a plurality of pyramid structures 405, each pyramid structure having four substantially triangular faces for expanding the eye movement range provided by the beam that interfaces with these pyramid structures (e.g., two faces reflect such a beam to expand the eye movement range along the X dimension and two faces reflect such a beam to expand the eye movement range along a substantially orthogonal Y dimension). In certain embodiments, the reflective structure may redirect the expanded display light towards the output coupler of the light guide; in other embodiments, the reflective structure 401 may operate as the output coupler itself such that the reflective structure 401 substantially simultaneously expands the eye movement range in two dimensions and output couples light towards that eye movement range.

[0039] Figure 5Shows a single 2D reflection structure 501 formed in an optical substrate 599. According to some embodiments, the reflection structure 501 utilizes multiple prisms for two-dimensional eye movement range and / or pupil expansion. In the depicted embodiment, the multiple prisms form multiple reflective surfaces (parallel surfaces 516 and substantially triangular surfaces 518), through which the incoming display light is redirected in multiple dimensions to expand the eye movement range provided by the light guide incorporating the reflection structure 501. However, the reflection structures 401 and 501 are configured differently such that the intersecting prisms of the pyramid structure 405 forming the reflection structure 401 are orthogonal, while the multiple prisms of the surfaces 516 and 518 forming the reflection structure 501 are not orthogonal. Thus, the reflection structure 401 expands the relevant eye movement range in two substantially orthogonal dimensions, while the reflection structure 501 expands the relevant eye movement range in two non-orthogonal dimensions.

[0040] In certain embodiments, the reflection 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 substrate in a manner similar to that described below with respect to Figure 6 to form multiple prisms 505 as an internal reflective interface.

[0041] Figure 6 Shows a cross-sectional component view of a single 2D reflection structure 601 that can operate substantially similarly to the 2D reflection structure 401 of Figure 4 and / or the 2D reflection structure 501 of Figure 5 . In the depicted embodiment, a first optical substrate portion 610 and a second optical substrate portion 620 are coupled at an optical interface 615. The 2D reflection structure 601 is configured to expand the eye movement range of an incorporated light guide (not shown) via the reflectivity provided by one or more optical coatings disposed along the optical interface 615. Due to the shape of the optical interface 615, these optical coatings are used to form internal reflective surfaces 605 that operate in a manner similar to that described above with respect to the pyramid structure 405 and the prisms 505 of Figure 4 and 5 respectively. In this way, the optical interface 615 and more generally the entire 2D reflection structure 601 provide a reflective surface that expands the provided eye movement range in two distinct (and in this example, substantially orthogonal) dimensions. In certain embodiments, the individual reflective surfaces of the 2D reflection structure 601 utilize a coating structure that is related to both angle and wavelength (e.g., a holographic Bragg mirror, an interference coating, a metal coating, or other suitable partially reflective coating structure). If such surfaces are associated with a low reflectivity that is typically 20% or less, they are generally not perceptible to the user.

[0042] In some embodiments, the internal reflective surface of the 2D reflective structure 601 is encapsulated by a combined light guide using two optical substrate portions 610, 620 (such as injection molded, diamond turned, or glass molded optical substrate portions). Each of the two optical substrate portions 610, 620 includes a phase shift such that the opposing surfaces of the optical substrate portions 610, 620 form complementary pairs that are coupled together (e.g., via an index matching adhesive). Display light is injected via an input coupler surface (not shown) bonded at an angle inside the light guide such that the input coupler surface enables TIR of the reflected light within the optical substrate portions 610, 620. In some embodiments, this surface is coated with a partially reflective material that causes such reflections. Then, due to the angle of the input coupler surface and the incoming display light, the display light propagates within the light guide via TIR. In some embodiments, the reflective structure 601 operates as an output coupler such that the display light is simultaneously output coupled and (in two dimensions) expanded. In other embodiments, a separate output coupling structure (output coupler, not shown) is formed at a distance from the reflective structure 601 within the combined light guide.

[0043] Figure 7 is an operational flowchart showing the operation for providing 2D eye movement range and / or pupil expansion in a reflective light guide using a single reflective structure according to some embodiments. The illustrated operation starts at block 705.

[0044] At block 705, display light (e.g., Figure 1 display light 190 of Figure 1 ) is directed into the reflective light guide via an input coupler (e.g.,

[0045] input coupler 131 of Figures 4 to 7 ).

[0046] At block 710, the display light is directed via TIR towards a spatially integrated reflective structure (such as Figures 4 to 7 one of the reflective structures 401, 501, 601, 701 of

[0046] ).

[0046] At block 715, the display light is redirected in two dimensions by the spatially integrated reflective structure, thereby expanding the eye movement range provided by the light guide.

[0047] At block 720, the display light is redirected out of the light guide towards the now expanded eye movement range via an output coupler (e.g., Figure 1 output coupler 133 of ). As described elsewhere herein, in some embodiments, the spatially integrated reflective structure can further operate as an output coupler of the light guide such that the reflective structure simultaneously expands the eye movement range in two dimensions and output couples light towards that eye movement range.

[0048] In some embodiments, certain aspects of the techniques described above may be implemented by one or more processors of a processing system executing software. The software includes one or more sets of executable instructions stored or otherwise tangibly embodied on a non-transitory computer-readable storage medium. The software may include instructions and certain data that, when executed by one or more processors, manipulate the one or more processors to perform one or more aspects of the techniques described above. The non-transitory computer-readable storage medium may include, for example, a disk or optical storage device, a solid-state storage device such as flash memory, a cache, random access memory (RAM), or one or more other non-volatile memory devices, etc. The executable instructions stored on the non-transitory computer-readable storage medium may be in source code, assembly language code, object code, or other instruction formats that are interpretable or otherwise executable by one or more processors.

[0049] 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 disc (CD), digital versatile disc (DVD), Blu-ray disc), magnetic media (e.g., floppy disk, magnetic tape, or magnetic hard drive), volatile memory (e.g., random access memory (RAM) or cache memory), non-volatile memory (e.g., read-only memory (ROM) or flash memory), or microelectromechanical systems (MEMS)-based storage media. The computer-readable storage medium may be embedded in the computing system (e.g., system RAM or ROM), fixedly attached to the computing system (e.g., magnetic hard drive), removably attached to the computing system (e.g., optical disc or universal serial bus (USB)-based flash memory), or coupled to the computer system via a wired or wireless network (e.g., network-attached storage device (NAS)).

[0050] It should be noted that not all activities or elements described above in the general description are required, that a portion of a particular activity or apparatus may not be required, and that one or more additional activities may be performed, or, in addition to those described, additional elements may be included. Further, the order in which activities are listed is not necessarily the order in which they are performed. Additionally, concepts have been described with reference to specific embodiments. However, those of ordinary skill in the art will understand that various modifications and changes may be made without departing from the scope of the present disclosure as set forth in the appended claims. Accordingly, the specification and drawings are to 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.

[0051] Benefits, other advantages, and solutions to problems have been described above with respect to specific embodiments. However, such benefits, advantages, solutions to problems, and any features that may cause any benefit, advantage, or solution to occur or become more pronounced should not be construed as critical, required, or essential features of any or all claims. Moreover, the specific embodiments disclosed above are merely illustrative, 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 this disclosure. The details of the construction or design shown herein are not intended to be limiting other than as set forth in the appended claims. Thus, it is evident that the specific embodiments disclosed above may be altered or modified, and all such variations are considered to be within the scope of the disclosed subject matter. Accordingly, the protection sought herein is as set forth in the appended claims.

Claims

1. A light guide, comprising: an input coupling structure configured to receive display light and guide the display light into the light guide; and a spatially integrated reflection structure configured to extend the eye movement range provided by the light guide in two dimensions.

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

3. The waveguide according to any one of claims 1 or 2, wherein the reflection structure includes a plurality of prisms.

4. The light guide according to claim 3, wherein the plurality of prisms include two intersecting sets of parallel faces.

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

6. The light guide according to any one of claims 1 to 5, wherein the reflection structure includes a plurality of substantially triangular faces.

7. The light guide according to any one of claims 1 to 6, wherein the reflection structure includes an interface between a first portion of the optical substrate and a second portion of the optical substrate.

8. The light guide according to claim 7, wherein the reflection structure includes one or more reflective coatings disposed at the interface.

9. The light guide according to any one of claims 1 to 8, further comprising an output coupling structure configured to direct the display light out of the light guide towards the extended eye movement range.

10. The light guide according to any one of claims 1 to 8, wherein the reflection structure further output-couples the display light from the light guide towards the extended eye movement range.

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

12. A method, comprising: guiding display light into a light guide via an input coupler; and extending the eye movement range of the light guide in two dimensions via a spatially integrated reflection structure of the light guide.

13. The method according to claim 12, wherein extending the eye movement range of the light guide includes extending the eye movement range in two substantially orthogonal dimensions.

14. The method according to any one of claims 12 or 13, wherein extending the eye movement range of the light guide via the reflection structure includes extending the eye movement range via a plurality of prisms.

15. The method according to claim 14, wherein extending the eye movement range via the plurality of prisms includes extending the eye movement range via two intersecting sets of parallel faces.

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

17. The method according to any one of claims 12 to 16, wherein extending the eye movement range of the light guide via the reflection structure includes extending the eye movement range via a plurality of substantially triangular faces.

18. The method according to any one of claims 12 to 17, wherein extending the eye movement range of the light guide via the reflection structure includes extending the eye movement range via an interface between a first portion of the optical substrate and a second portion of the optical substrate.

19. The method according to claim 18, wherein The reflective structure includes one or more reflective coatings disposed at the interface.

20. The method according to any one of claims 12 to 19, further comprising directing the display light out of the light guide towards the extended eye movement range via an output coupling structure.

21. The method according to any one of claims 12 to 19, wherein, directing the display light out of the light guide towards the extended eye movement range includes using the reflective structure to direct the display light out of the light guide towards the extended eye movement range.

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