Waveguide, optical combiner and eyewear display

Abstract

The waveguide includes a first substrate including an exit pupil expander and a separate second substrate including an output coupler. The first substrate and the second substrate overlap each other and are separated by a partition element. One or more facets direct light from the first substrate to the second substrate after exit pupil expansion so that the output coupler can output-couple the light.

Description

[Background technology]

[0001] In an augmented reality (AR) or mixed reality (MR) eyewear display, light from an image source is coupled into a light guide substrate, commonly referred to as a waveguide or light guide, by an input optical coupler (i.e., an input coupler), which can be formed on the surface of the substrate or disposed within the substrate. Once the light beam is coupled in the waveguide, it is "guided" through the substrate, typically by multiple total internal reflections (TIR), and then directed out of the waveguide by an output optical coupler (i.e., an "output coupler"). In some cases, another optical component known as an exit pupil expander is positioned in the optical path between the input and output couplers to expand the light beam in at least one dimension. The light beams projected from the waveguide by the output coupler overlap at an eye relief distance from the waveguide, forming an exit pupil within which a user of the eyewear display can view a virtual image generated by the image source. Summary of the Invention

[0002] In a first embodiment, the waveguide includes a first substrate including an exit pupil expander, and a second substrate overlying the first substrate, the second substrate including an output coupler.

[0003] In some aspects of the first embodiment, the waveguide includes one or more facets that direct light from the first substrate to the second substrate. In some aspects of the first embodiment, the one or more facets include a reflective facet including a mirror coating. In some aspects of the first embodiment, the one or more facets include a diffraction grating or a holographic grating. In some aspects of the first embodiment, the waveguide includes a partition element between the first substrate and the second substrate. In some aspects of the first embodiment, the partition element has a lower refractive index than the first substrate and the second substrate. In some aspects of the first embodiment, the partition element includes an air gap. In some aspects of the first embodiment, the partition element includes a solid material. In some aspects of the first embodiment, the partition element includes a polarizing beam splitter. In some aspects of the first embodiment, the exit pupil expander expands the light in a first direction, and the output coupler output couples the light from the waveguide in a second direction different from the first direction. In some aspects of the first embodiment, the first direction is orthogonal to the second direction. In some aspects of the first embodiment, the first substrate overlaps the second substrate when viewed from a direction in which the output coupler outcouples light from the waveguide.

[0004] In a second embodiment, the optical combiner includes a first lens layer and a second lens layer, with a waveguide disposed between the first lens layer and the second lens layer. The waveguide includes a first substrate including an exit pupil expander. The waveguide also includes a second substrate overlying the first substrate, with the second substrate including an output coupler.

[0005] In some aspects of the second embodiment, the waveguide includes one or more facets that direct light from the first substrate to the second substrate. In some aspects of the second embodiment, the waveguide includes a partition element disposed between the first substrate and the second substrate. In some aspects of the second embodiment, the partition element has a lower refractive index than the first substrate and the second substrate. In some aspects of the second embodiment, the partition element includes a polarizing beam splitter.

[0006] In a third embodiment, an eyewear display includes one or more lenses that include an optical combiner. The optical combiner includes a waveguide. The waveguide includes a first substrate that includes an exit pupil expander. The waveguide also includes a second substrate overlying the first substrate, the second substrate including an output coupler.

[0007] In some aspects of the third embodiment, the light combiner includes a first lens layer and a second lens layer, and the waveguide is disposed between the first lens layer and the second lens layer. In some aspects of the third embodiment, the waveguide includes one or more facets that direct light from the first substrate to the second substrate, and a partition element between the first substrate and the second substrate. In some aspects of the third embodiment, the partition element has a lower refractive index than the first substrate and the second substrate. In some aspects of the third embodiment, the eyewear display includes a frame that holds the one or more lenses.

[0008] 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]

[0009] [Figure 1] 1 illustrates an exemplary eyewear display, according to some embodiments. [Figure 2] 2 shows an exemplary diagram of a projection system that projects display light representing an image to a user's eye via an eyewear display, such as the eyewear display of FIG. 1, according to some embodiments. [Figure 3] 1 illustrates an example of a portion of an eyewear display with a limited field of view (FOV) area, as specified in this disclosure. [Figure 4] As identified in this disclosure, this illustrates the problem of expanding the FOV area with conventional techniques. [Figure 5]As identified in this disclosure, this illustrates the problem of expanding the FOV area with conventional techniques. [Figure 6] 1 shows a close-up view of a waveguide with an exit pupil expander (EPE) and an output coupler on different substrates according to some embodiments. [Figure 7] 10 illustrates an example of a waveguide with different partition elements disposed between a first substrate with an EPE and a second substrate with an output coupler, according to some embodiments. [Figure 8] 10 illustrates an example of a waveguide with different partition elements disposed between a first substrate with an EPE and a second substrate with an output coupler, according to some embodiments. [Figure 9] 10 illustrates an example of a waveguide with different partition elements disposed between a first substrate with an EPE and a second substrate with an output coupler, according to some embodiments. [Figure 10] 10 illustrates an example of an optical combiner comprising a waveguide, such as that shown in FIGS. 7-9, between two lens layers, according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0010] The lenses of AR / MR eyewear displays with an eyeglass frame form factor typically have a relatively small field of view (FOV) area for projecting images generated by the eyewear display's image source. For example, in this type of conventional eyewear display, the FOV area typically scales approximately 10° x 10° horizontally and vertically. In some cases, it may be advantageous to increase the size of the FOV area so that a user can perceive images across a wider area of ​​the eyewear display's lens. Increasing the FOV area generally involves increasing the size of the output coupler in the waveguide and the size of the corresponding exit pupil expander (EPE). However, due to the limited space available in conventional waveguides, increasing the size of both the EPE and the output coupler in the waveguide using conventional techniques is impractical due to increased interference between the two components. For example, increasing the size of the EPE in the waveguide substrate reduces the space available on the waveguide substrate for enlarging the output coupler. FIGS. 1-10 present a technique for increasing the FOV area of ​​an eyewear display by implementing the EPE and output coupler on separate substrates from the waveguide. Therefore, the EPE and the output coupler can each be expanded without interfering with each other.

[0011] For example, in some embodiments, the waveguide includes an input coupler and EPE in a first substrate and an output coupler in a second substrate. In some embodiments, the first and second substrates are included in a stack of overlapping layers. The waveguide also includes a partition element or layer disposed between the first and second substrates and a set of reflective facets for directing light through or around the partition element from the first substrate to the second substrate. The partition element ensures that light propagating within the EPE of the first substrate does not interfere with light propagating at the output coupler of the second substrate, and vice versa. The set of reflective facets is positioned to direct light from the first substrate to the second substrate so that after passing through the EPE, the light can also pass through the output coupler. In some embodiments, the partition element includes a material having a refractive index lower than the refractive index of the materials of the first and second substrates. By locating the EPE and the output coupler on different overlapping substrates, both the EPE and the output coupler can be expanded within the waveguide without interfering with each other, thus increasing the size of the FOV area of ​​the eyewear display, thereby allowing a user to view the generated image across a wider viewing area of ​​the eyewear display.

[0012] 1-10 illustrate devices and techniques for increasing the FOV area of ​​an eyewear display, thereby increasing the virtual image display area, as described in more detail below. While the disclosed devices and techniques are described with respect to an exemplary display system, it should be understood that the disclosure is not limited to implementation in this particular display system, but may be implemented in any of a variety of display systems using the guidelines provided herein.

[0013] FIG. 1 illustrates an exemplary eyewear display 100 according to various embodiments. The eyewear display 100 (also referred to as a wearable head-up display (WHUD), head-mounted display (HMD), near-eye display, etc.) has a support structure 102 including an arm 104 that houses a microdisplay projection system configured to project an image toward a user's eyes, such that the user perceives the projected image as displayed in a field of view (FOV) area 106 of the display on one or both of lens elements 108, 110. In the illustrated embodiment, the support structure 102 of the eyewear display 100 is configured to be worn on the user's head and has the general shape and appearance (i.e., form factor) of an eyeglass frame. The support structure 102 houses or includes various components to facilitate the projection of such an image toward the user's eyes, such as an image source (also referred to as a light engine, optical engine, projector, etc.), a waveguide (e.g., as shown in FIG. 2 ), etc. In some embodiments, the support structure 102 further includes various sensors, such as one or more front-facing cameras, rear-facing cameras, other light sensors, motion sensors, accelerometers, etc. The support structure 102 may further include one or more radio frequency (RF) interfaces or other wireless interfaces, such as a Bluetooth™ interface, a WiFi interface, etc. In some embodiments, the support structure 102 further includes processing or control circuitry for performing functions of the eyewear display 100, such as eye tracking functions. Additionally, in some embodiments, the support structure 102 includes one or more batteries or other portable power sources for powering the electrical components of the eyewear display 100. In some embodiments, some or all of these components of the eyewear display 100 are housed completely or partially within an interior volume of the support structure 102, such as within arms 104 in a temple region 112 of the support structure 102 or within a nose bridge 114 of the support structure 102.It should be noted that although an exemplary form factor is shown, in other embodiments, the eyewear display 100 may have a different shape and appearance than the eyeglass frame shown in FIG.

[0014] One or both of the lens elements 108, 110 may be used by the eyewear display 100 to provide an AR or MR display in which rendered graphical content is overlaid on or provided in conjunction with a real-world view perceived by a user through the lens elements 108, 110. In some embodiments, one or both of the lens elements 108, 110 include a first lens layer and a second lens layer with a waveguide disposed between the layers. In some embodiments, one or both of the lens elements 108, 110 function as a light combiner that combines ambient light (also referred to as ambient light) from outside the eyewear display 100 with light emitted from an image source of the eyewear display 100. For example, the light used to form a recognizable image or series of images may be projected by the image source of the eyewear display 100 to the user's eye via a series of optical elements, such as a waveguide at least partially formed in the corresponding lens element, one or more scanning mirrors, one or more optical relays, and / or one or more prisms. In some embodiments, multiple image sources are included in the support structure 102. In some cases, the multiple image sources are located in the temple region 112, the nose bridge, or a combination of the two regions (e.g., one image source in the temple region 112 and another image source in the nose bridge region). In some embodiments, the waveguide includes a layer stack comprising a first substrate including an input coupler and an EPE and a second substrate including an output coupler. In some embodiments, a partition element is disposed between the two substrates to ensure that a TIR condition is maintained for light propagating through each of the two substrates. Additionally, a set of facets is included at or near one end of both substrates to direct light (e.g., by reflection) from the first substrate to the second substrate after the light passes through the EPE, thereby directing the light to the output coupler.Thus, one or both of lens elements 108, 110 includes at least a portion of a waveguide that transmits display light received by an input coupler of the waveguide through the EPE of the waveguide to an output coupler, which outputs the display light toward the eye of a user of eyewear display 100. The display light is modulated and projected to the user's eye such that the user perceives the display light as an image within FOV area 106. Additionally, each of lens elements 108, 110 is sufficiently transparent to allow the user to see through the lens element, thereby providing a view of the user's real-world environment, such that the image appears superimposed on at least a portion of the real-world environment.

[0015] In some embodiments, each of the one or more image sources is a matrix-based projector, a scanning laser projector, or any combination of a modulated light source, such as a laser or one or more LEDs, and a dynamic reflector mechanism, such as one or more dynamic scanners or digital light processors. In some embodiments, the image source includes, for example, multiple laser diodes (e.g., red, green, and / or blue laser diodes) and at least one scan mirror (e.g., two one-dimensional scan mirrors that are microelectromechanical systems (MEMS)-based or piezoelectric). The image source is communicatively coupled to a controller and a non-transitory processor-readable storage medium or memory that stores processor-executable instructions and other data that, when executed by the controller, cause the controller to control the operation of the image source. In some embodiments, the controller is communicatively coupled to a processor (not shown) that controls the scan area size and scan area position of the image source and generates content displayed on the eyewear display 100. The image source scans light over a specified FOV area 106, which is a variable area of ​​the eyewear display 100. The scan area size corresponds to the size of the FOV area 106, and the scan area position corresponds to the region of one of the lens elements 108, 110 where the FOV area 106 is visible to the user. Generally, it is desirable for a display to have a wide FOV area to accommodate light outcoupling over a wide angular range. Herein, the range of different user eye positions from which the display can be viewed is referred to as the eyebox of the eyewear display 100.

[0016] The techniques and apparatus described herein increase the FOV area 106 of the waveguide within the form factor limitations imposed by the eyewear display 100. In some embodiments, the waveguide incorporated in one or each of the lens elements 108, 110 is fabricated from a stack of layers including two separate substrate layers. The input coupler and EPE are embedded in or on a first of the two substrate layers, and the output coupler is embedded in or on a second of the two substrate layers. By locating the EPE and output coupler on different substrate layers, each of the EPE and output coupler can be expanded without reducing the space required to potentially expand the other. In this way, the overall FOV area 106 can be increased, thereby increasing the area over which the eyewear display 100 can display images generated by the eyewear display 100 to the user.

[0017] 2 shows a diagram of a projection system 200 that projects display light representing an image onto a user's eye 222 through a waveguide 210 of an eyewear display, such as eyewear display 100 shown in FIG. 1. Projection system 200 includes an image source 202, an optical scanner 220, and waveguide 210. While FIG. 2 shows one image source 202 and corresponding optical scanner 220 for clarity, in some embodiments, multiple image sources 202 and optical scanners 220 are included in projection system 200.

[0018] In some embodiments, image source 202 includes one or more laser light sources configured to generate and output laser light (e.g., visible laser light, such as red, blue, and green laser light, and / or non-visible laser light, such as infrared laser light). In some embodiments, image source 202 is coupled to a controller or driver (not shown), which controls the timing of the emission of display light from the light sources of image source 202 (e.g., according to instructions received by the controller or driver from a computer processor coupled thereto) to modulate display light 218 so as to be perceived as an image when output to the retina of a user's eye 222.

[0019] In some embodiments, optical scanner 220 includes first scan mirror 204, second scan mirror 206, and optical relay 208. In some cases, one or both of scan mirrors 204 and 206 are MEMS mirrors. For example, scan mirror 204 and scan mirror 206 are MEMS mirrors that are driven by respective actuation voltages to oscillate during active operation of laser projection system 200, causing scan mirror 204 and scan mirror 206 to scan display light 218 toward input coupler 212 of waveguide 210.

[0020] The waveguide 210 of the projection system 200 includes an input coupler 212, an EPE 214, and an output coupler 216. As used herein, the term "waveguide" should be understood to mean a combiner that transmits light from an input coupler through an EPE to a corresponding output coupler using total internal reflection (TIR) ​​or a combination of TIR, special filters, and / or reflective surfaces. In a display application, for example, the light represents a collimated image, and the waveguide transmits and replicates the collimated image to the eye. In general, the terms "input coupler," "exit pupil expander (or "EPE" for short)," and "output coupler" should be understood to refer to any type of optical grating structure, including, but not limited to, a diffraction grating, a tilted grating, a blazed grating, a hologram, a holographic optical element (e.g., an optical element using one or more holograms), a volume diffraction grating, a volume hologram, a surface-relief diffraction grating, and / or a surface-relief hologram. In some embodiments, a given input coupler, EPE, or output coupler is configured as a transmission grating that transmits light to the input coupler, EPE, or output coupler and applies a designed optical function(s) to the light during transmission. In some embodiments, a given input coupler, EPE, or output coupler is a reflection grating that reflects light to the input coupler, EPE, or output coupler and applies a designed optical function(s) to the light during reflection. In this example, display light 218 received at input coupler 212 is relayed to EPE 214, which expands the light in one dimension (e.g., into or out of the plane of the page as shown in FIG. 2) and directs the light to output coupler 216 via TIR in waveguide 210. The display light is then output as light 224 (one beam is labeled for clarity) via output coupler 216 to the user's eye 222.

[0021] In some embodiments, the EPE 214 receives light from the input coupler 212 and expands the light in one dimension at the eyebox of an eyewear display (such as that corresponding to eyewear display 100) that houses the projection system 200. In some embodiments, the EPE 214 includes a one-dimensional diffraction grating that expands the light in this manner. After expanding the light in one dimension, the EPE 214 sends the light to the output coupler 216. After receiving the light from the EPE 214, the output coupler 216 expands the light in two dimensions and output-couples light 224 to the user's eye 222. Thus, in some embodiments, the size of the output coupler 216 corresponds to the area over which a user can perceive an image generated by the image source 202. In other words, the size of the output coupler 216 corresponds to the size of the FOV area (such as FOV area 106 shown in FIG. 1 ) of an eyewear display that includes the projection system 200.

[0022] For clarity, FIG. 2 illustrates the optical components of waveguide 210, namely, input coupler 212, EPE 214, and output coupler 216, from right to left, showing the propagation path of light within the waveguide. In some embodiments, the configuration of input coupler 212, EPE 214, and output coupler 216 differs from that shown in FIG. 2. For example, in some embodiments, waveguide 210 comprises a layer stack with input coupler 212 and EPE 214 on a first substrate of the layer stack and output coupler 216 on a second substrate of the layer stack. In some embodiments, waveguide 210 also includes a partition element (not shown in FIG. 2) between the first and second substrates and a reflective facet (not shown in FIG. 2) that directs light from the first substrate to the second substrate.

[0023] FIG. 3 illustrates an example of a portion of an eyewear display 300 having an eyeglass frame form factor with a limited FOV 306, as specified by some embodiments. For example, because the space available in the lens 308 for incorporating a conventional waveguide is limited, the FOV 306 is within a range of approximately 10° by 10° in the horizontal and vertical directions. As shown in FIG. 3 , the waveguide components include an input coupler 312, an EPE 314, and an output coupler 316. In FIG. 3 , the input coupler 312 is located in the temple region of the support structure of the eyewear display 300. The EPE 314 is located partially in the temple region and partially in the lens 308, while the output coupler 316 is located entirely within the lens 308 and corresponds to the FOV area 306. Therefore, increasing the FOV area 306 involves increasing the size of the output coupler 316, which also requires increasing the size of the EPE 314. However, due to the limited space available at lens 308, increasing the size of EPE 314 and output coupler 316 according to conventional techniques is generally not possible due to the problems illustrated in FIGS.

[0024] 4 and 5 illustrate the problems encountered when expanding the FOV area using conventional techniques. FIG. 4 shows an example in which an input coupler 412 is located in the temple region of the support structure. FIG. 5 shows an example in which an input coupler 512 is located in the nose bridge region of the support structure. In either case, a larger output coupler (output coupler 416 in FIG. 4 and output coupler 516 in FIG. 5, respectively) and a larger EPE (EPE 414 in FIG. 4 and EPE 514 in FIG. 5, respectively) are required to provide a wider FOV area for each lens 408, 508. However, as the output coupler and EPE sizes increase, interference 420 and 520 between the two within the waveguide substrate become significant, as shown in FIGS. 4 and 5, respectively. These interferences 420 and 520 result in a conflict between the function of the EPE (i.e., to expand the display light in a first dimension) and the function of the output coupler (i.e., to expand the display light in a second dimension different from the first dimension and output-couple the light to the user). This conflict cannot be resolved by adjusting either the EPE or the output coupler, or both, without compromising the quality of the image delivered to the user. Thus, conventional techniques for increasing the FOV area of ​​a waveguide are significantly limited by the form factor of the lenses and / or eyeglass frames in this type of eyeglass display.

[0025] 6 shows an expanded view of a waveguide 600, according to various embodiments. The waveguide 600 includes a stack of components or layers including a first substrate 602 and a second substrate 604. In some embodiments, the waveguide 600 also includes a partition element 622.

[0026] In some embodiments, the first substrate 602 and the second substrate 604 are made of the same material. For example, in some embodiments, the first substrate 602 and the second substrate 604 are each made of a transparent or translucent material (e.g., plastic, polymer, glass, etc.) with optical properties that enable the functionality of the AR / MR eyewear display. In other embodiments, the first substrate 602 and the second substrate 604 are made of different waveguide materials. The first substrate 602 includes an input coupler 612 and an EPE 614 (such as the input coupler or EPE described in the previous figure), and the second substrate 604 includes an output coupler 616 (such as the output coupler described in the previous figure). As shown, the first substrate 602 and the second substrate 604 overlap each other. For example, the first substrate 602 and the second substrate 604 are included in a stack of components that make up the waveguide 600, which overlap each other in the z-direction, as shown in FIG. 6 . In some embodiments, the term "overlapping" with respect to the first substrate and the second substrate means that at least 50% of the first substrate coincides with the second substrate 604 (or vice versa) along at least one axis (e.g., the z-direction), as shown in FIG. 6 . That is, when viewed from the user side (i.e., from the perspective of the user's eye 222), at least 50% of the second substrate 604 overlaps with the first substrate 602, or when viewed from the world side (i.e., the waveguide opposite the user's eye 222), at least 50% of the first substrate 602 overlaps with the second substrate 604. In some embodiments, the term "overlapping" with respect to the EPE 614 and the output coupler 616 means that each of these optical components (i.e., the EPE and the output coupler) performs its respective optical function (e.g., expanding the light beam along one dimension in the EPE) in a separate but adjacent plane. 6, the EPE 614 expands the light beam in a plane corresponding to the first substrate 602, and the output coupler 616 expands the light beam in a separate but adjacent plane corresponding to the second substrate 604. In some embodiments, to facilitate fabrication of the waveguide 600, the first substrate 602 and the second substrate 604 are entirely or largely coincident with one another.That is, the first and second substrates completely or nearly completely overlap each other, e.g., 90% or more. In some embodiments, the dimensions of the first substrate 602 and the second substrate 604 are essentially the same, and both substrates completely overlap each other, e.g., so that no edges are visible when viewed by a user.

[0027] In some embodiments, the waveguide 600 includes a partition element 622 between the first substrate 602 and the second substrate 604. In some embodiments, the partition element is an air gap (or other gas-filled gap), a low-index material (i.e., a material with a low refractive index compared to the refractive index of the material(s) of the first substrate 602 and the second substrate 604), or a polarizing beam splitter (PBS). In any case, the partition element 622 acts as a barrier to prevent light propagating through the EPE 614 and light propagating through the output coupler 616 from interfering with each other. For example, light from the EPE 614 propagates through the EPE 614 by TIR when entering the partition element 622 from the first substrate 602 side, and light from the output coupler 616 propagates through the output coupler 616 by TIR when entering the partition element 622 from the second substrate 604 side. Thus, in some embodiments, the interface between the first substrate 602 and the partition element 622 and the interface between the second substrate 604 and the partition element 622 enable TIR conditions for light in the first substrate 602 and light in the second substrate 604, respectively.

[0028] In some embodiments, the waveguide 600 also includes a set of facets 632, 634. For example, the first facet 632 is disposed on the first substrate 602, and the second facet 634 is disposed on the second substrate 604. The set of facets 632, 634 directs light from the first substrate 602 to the second substrate 604. For example, after the light passes through the EPE 616 and is expanded in a first dimension / direction (e.g., along the y-dimension in FIG. 6 ), the facet 632 directs the light from the first substrate 602 through or around the partition element 622 to the facet 634. In some embodiments, the partition element 622 includes one or more holes or openings 670 that allow light to pass from the first facet 632 to the second facet 634. In some embodiments, facet 632 is positioned such that light incident thereon violates the TIR condition of first substrate 602, exits first substrate 602, and strikes facet 634. Facet 634 directs light incident thereon by TIR within second substrate 604 to output coupler 616, expanding it in the second dimension / direction (e.g., along the x-dimension in FIG. 6 ) for output coupling to user's eye 222. In some embodiments, the set of facets 632, 634 is any type of reflective surface, such as a mirror or a metal layer. In some embodiments, the set of facets 632, 634 includes facets coated with a mirror coating or facets coated with a Bragg mirror coating. In other embodiments, the set of facets 632, 634 is a diffraction grating or a holographic grating.

[0029] By separating EPE 614 and output coupler 616 on different substrates in this manner, waveguide 600 can extend EPE 614 and output coupler 616 without interfering with each other, thereby increasing the FOV area and allowing an eyewear display including waveguide 600 to provide images generated (e.g., from an image source such as image source 202) over a wider display area.

[0030] In some embodiments, light is sent through the waveguide 600 according to the following path: First, light is coupled at the input coupler 612 and directed by TIR within the first substrate 602 to the EPE 614 as coupled light 642. The EPE 614 expands the display light in a first dimension (e.g., along the y-direction in FIG. 6 ) as EPE light 644 (labeled with a single arrow for clarity). This light propagates within the EPE 614 by TIR through the partition element 622 on one side and the outer surface (near side in FIG. 6 ) of the first substrate 602 on the other side. Upon reaching the first facet 632, the light is directed out of the first substrate 602 as inter-substrate light 646 (labeled with a single dashed arrow for clarity). Inter-substrate light 646 passes through or is directed around partition element 622 and is incident on second facet 634 of second substrate 604. Second facet 634 directs the light incident thereon as second substrate light 648 (labeled with a single arrow for clarity) via TIR through the second substrate outer surface (facing user's eye 222, away from FIG. 6 ) and partition element 622 into the second substrate. Second substrate light 648 is directed to output coupler 616, which expands the light in another dimension / direction and outcouples the light towards user's eye 222 as out-coupled light 650.

[0031] 7-9 illustrate different embodiments of a waveguide, such as waveguide 600, with different types of partition elements disposed between two substrates, according to various embodiments. Light propagation paths within and out of the waveguides in FIGS. 7-9 are indicated by dashed lines. As shown in FIGS. 7-9, the first substrate in each figure (e.g., first substrate 702 in FIG. 7 , first substrate 802 in FIG. 8 , and first substrate 902 in FIG. 9 ) overlaps the second substrate in each figure (e.g., second substrate 704 in FIG. 7 , second substrate 804 in FIG. 8 , and second substrate 904 in FIG. 9 ). In this way, each corresponding EPE and output coupler can be expanded without limiting the size of the other. For example, referring to FIG. 7, the area of ​​EPE 714 is on a different plane in the z direction, allowing it to expand along the x and y dimensions without interfering with the expansion of output coupler 716 along the x and y dimensions. Therefore, the FOV area of ​​an eyewear display with a lens element including waveguide 700 can be increased. This applies equally to the waveguide configurations shown in Figures 8 and 9.

[0032] Referring to FIG. 7 , a waveguide 700 includes a first substrate 702 with an input coupler 712 and an EPE 714. As shown in FIG. 7 , the EPE 714 expands light into and out of the figure, i.e., along the y-direction. The waveguide 700 also includes a second substrate 704 with an output coupler 716. The waveguide 700 further includes a set of facets 732, 734 for directing light from the first substrate 702 to the second substrate 704. The partition element shown in the waveguide 700 is a void 722 (or other gas-filled gap) between the first substrate 702 and the second substrate 704. Thus, light propagates within the first substrate 702 by TIR at an outer surface 742 of the first substrate 702 and an interface 744 between the first substrate 702 and the void 722. Similarly, light propagates within the second substrate 704 due to TIR at an outer surface 746 of the second substrate 704 and an interface 748 between the second substrate 704 and the air gap 722. The light propagating within the second substrate 704 is emitted from the second substrate 704 by the output coupler 716.

[0033] Referring to FIG. 8 , a waveguide 800 includes a first substrate 802 with an input coupler 812 and an EPE 814. As shown in FIG. 8 , the EPE 814 expands light into and out of the plane of the figure, i.e., along the y-direction. The waveguide 800 also includes a second substrate 804 with an output coupler 816. The waveguide 800 further includes a set of facets 832, 834 for directing light from the first substrate 802 to the second substrate 804. The partition element shown in the waveguide 800 is a low-index material 822 between the first substrate 802 and the second substrate 804. The low-index material 822 has a lower refractive index than the materials of the first substrate 802 and the second substrate 804. Thus, light propagates within the first substrate 802 due to TIR at the outer surface 842 of the first substrate 802 and the interface 844 between the first substrate 802 and the low-index material 822. Similarly, light propagates within the second substrate 804 due to TIR at the outer surface 846 of the second substrate 804 and the interface 848 between the second substrate 804 and the low-index material 822. Light propagating within the second substrate 804 is emitted from the second substrate 804 by the output coupler 816.

[0034] Referring to FIG. 9 , a waveguide 900 includes a first substrate 902 with an input coupler 912 and an EPE 914. As shown in FIG. 9 , the EPE expands light into and out of the figure, i.e., along the y-direction. The waveguide also includes a second substrate 904 with an output coupler 916. The waveguide 900 further includes a set of facets 932, 934 for directing light from the first substrate 902 to the second substrate 904. The partition element shown in the waveguide 800 is a polarizing beam splitter (PBS) layer 922 between the first substrate 902 and the second substrate 904. The type of material of the PBS layer 922 is selected to reflect the type of polarization of the light propagating through the waveguide. For example, in some embodiments, the display light emitted from an image source coupled into the waveguide 900 is p-polarized light. Therefore, the PBS layer 922 is configured to reflect light that is in the p-polarized state. In another embodiment, the display light emitted from the image source coupled into the waveguide 900 may be s-polarized. In this case, the PBS layer 922 is configured to reflect light that is in the s-polarized state. In either case, the light propagates through the first substrate 902 by TIR, reflecting off the outer surface 942 of the first substrate 902 and the PBS layer 922 on the opposite side of the first substrate 902. Similarly, the light propagates through the second substrate 904 by TIR, reflecting off the outer surface 946 of the second substrate 904 and the PBS layer 922 on the opposite side of the second substrate 904. The light propagating through the second substrate 904 is emitted from the second substrate 904 by the output coupler 916.

[0035] 10 illustrates an optical combiner 1000 according to various embodiments. For example, the optical combiner 1000 may correspond to one or both of the lens elements 108, 110 of FIG.

[0036] In some embodiments, the light combiner 1000 combines ambient light (also referred to as ambient light) from the world side 1030 with light emitted from an image source (such as image source 202 in FIG. 2 ) so that the user's eye 222 perceives an image from the image source overlaid on the real-world environment. Thus, the light combiner 1000 includes a first lens layer 1010 and a second lens layer 1020 with a waveguide 1015 disposed therebetween. In some embodiments, the first lens layer 1010 and the second lens layer 1020 are transparent or translucent to allow ambient light from the environment to reach the user's eye 222. In some embodiments, the waveguide 1015 corresponds to any one of the waveguides 600, 700, 800, or 900 shown in FIGS. 6-9 , respectively. Thus, the waveguide 1015 of the optical combiner 1000 includes an expanded output coupler, which enables the optical combiner 1000 to display an image over a wider area observed by the user's eye 222.

[0037] It should be noted that not all of the operations or elements described above in the general description are required, that some of the specific operations or devices may not be required, and that one or more additional operations may be performed or elements may be included in addition to those described. Furthermore, the order in which the operations are listed is not necessarily the order in which they are performed. Also, the 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.

[0038] 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 illustrative only, as the disclosed subject matter may be modified and practiced in different but equivalent manners 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 apparent that the specific embodiments disclosed above may be altered or modified, and all such variations are considered within the scope of the disclosed subject matter. Accordingly, the protection sought herein is set forth in the following claims.

Claims

1. a first substrate including an exit pupil expander; a second substrate overlapping the first substrate; one or more reflective facets that direct light expanded by the exit pupil expander from the first substrate to the second substrate; The second substrate includes an output coupler that outputs the light transmitted from the first substrate to the second substrate.

2. The waveguide of claim 1 , wherein the one or more reflective facets include a mirror coating.

3. A first substrate including an exit pupil expander; a second substrate overlapping the first substrate; one or more facets that direct light expanded by the exit pupil expander from the first substrate to the second substrate; the second substrate includes an output coupler that outputs the light transmitted from the first substrate to the second substrate; The one or more facets comprise a diffraction grating or a holographic grating.

4. 4. The waveguide of claim 1 or claim 3, further comprising a partition element between the first substrate and the second substrate.

5. 5. The waveguide of claim 4, wherein the partition element has a lower refractive index than the first substrate and the second substrate.

6. The waveguide of claim 4 , wherein the partition element comprises an air gap.

7. The waveguide of claim 4 , wherein the partition element comprises a solid material.

8. The waveguide of claim 4 , wherein the partition element comprises a polarizing beam splitter.

9. 4. The waveguide of claim 1 or claim 3, wherein the exit pupil expander expands light in a first direction and the output coupler couples light out of the waveguide in a second direction different from the first direction.

10. The waveguide of claim 9 , wherein the first direction is orthogonal to the second direction.

11. 4. The waveguide of claim 1 or claim 3, wherein the first substrate overlaps the second substrate when viewed from a direction in which the output coupler outcouples light from the waveguide.

12. a first lens layer and a second lens layer; An optical combiner comprising: the waveguide of claim 1 or claim 3 disposed between the first lens layer and the second lens layer.

13. The optical combiner of claim 12 , wherein the waveguide includes a partition element disposed between the first substrate and the second substrate.

14. The optical combiner of claim 13 , wherein the partition element has a lower refractive index than the first substrate and the second substrate.

15. The optical combiner of claim 13 , wherein the partition element comprises a polarizing beam splitter.

16. one or more lenses including an optical combiner; An eyewear display, wherein the optical combiner includes the waveguide of claim 1 or claim 3.

17. 17. The eyewear display of claim 16, wherein the light combiner further includes a first lens layer and a second lens layer, and the waveguide is disposed between the first lens layer and the second lens layer.

18. The eyewear display of claim 16 , wherein the waveguide includes a partition element between the first substrate and the second substrate.

19. The eyewear display of claim 18 , wherein the partition element has a lower refractive index than the first substrate and the second substrate.

20. The eyewear display of claim 16 , further comprising a frame that holds the one or more lenses.

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