Multiple in-coupler waveguides and methods

Abstract

This disclosure describes techniques and waveguides for efficiently incoupling light of different optical characteristics with multiple incouplers in a waveguide, the waveguide including a first incoupler for incoupling light having a first optical characteristic, a second incoupler for incoupling light having a second optical characteristic, and a first structure at an interface of the second incoupler for reflecting light having the first optical characteristic within the waveguide.

Description

[Background technology]

[0001] In a conventional wearable head-up display (WHUD), light from an image source is coupled into a light guide substrate, commonly called a waveguide, by an input optical coupler, such as an in-coupling grating (i.e., "in-coupler"), which may be formed on the surface of the substrate or embedded within the substrate. Once the light beam is coupled into the waveguide, it is "guided" through the substrate, typically by multiple instances of total internal reflection (TIR), and then directed out of the waveguide by an output optical coupler (i.e., "out-coupler"), which may also take the form of a diffractive optic. The light beams emitted from the waveguide overlap at an eye relief distance from the waveguide, forming an exit pupil within which the virtual image generated by the image source can be viewed. Summary of the Invention

[0002] This disclosure describes embodiments for efficiently incoupling light of different optical properties with multiple incouplers in a waveguide, yet fitting into the space-constrained form factor of a WHUD.

[0003] In one exemplary embodiment, the waveguide includes a first incoupler for incoupling light having a first optical property, a second incoupler for incoupling light having a second optical property, and a first structure at an interface of the second incoupler for reflecting the incoupled light having the first optical property within the waveguide.

[0004] In some embodiments, for the waveguide, the first optical property comprises a first wavelength range and the second optical property comprises a second wavelength range different from the first wavelength range. The first structure comprises, for example, a dichroic mirror. In some embodiments, the dichroic mirror comprises a short-pass dichroic mirror having a cutoff wavelength between the first wavelength range and the second wavelength range.

[0005] In other embodiments, for a waveguide, the first optical property comprises a first polarization state and the second optical property comprises a second polarization state different from the first polarization state. The first structure may comprise, for example, a polarizing beam splitter that reflects light of the first polarization state and transmits light of the second polarization state.

[0006] In another embodiment, for the waveguide, the first optical characteristic comprises a first angle of light incoupled into the waveguide at the first incoupler grating and the second optical characteristic comprises a second angle of light incoupled into the waveguide at the second incoupler grating, the second angle being different from the first angle. The first structure may, for example, comprise a material with a lower refractive index than a material of a waveguide substrate of the waveguide.

[0007] In some embodiments, relative to the waveguide, the second in-coupler is positioned following the first in-coupler in the direction of light propagation towards one or more out-couplers of the waveguide.

[0008] In further embodiments, the waveguide further includes a third incoupler for incoupling light having a third optical property, and a second structure at an interface of the third incoupler for reflecting the incoupled light having the first optical property and the incoupled light having the second optical property within the waveguide. In some embodiments, the first optical property includes a first wavelength range, the second optical property includes a second wavelength range different from the first wavelength range, and the third optical property includes a third wavelength range different from the first and second wavelength ranges. For example, in these embodiments, the first structure includes a first dichroic mirror and the second structure includes a second dichroic mirror. Further, the first dichroic mirror includes a short-pass dichroic mirror having a cutoff wavelength between the first wavelength range and the second optical wavelength range, and the second dichroic mirror includes a second short-pass dichroic mirror having a cutoff wavelength between the third wavelength range and the first and second wavelength ranges. In some embodiments, the third incoupler is positioned subsequent to the first incoupler and the second incoupler in the light propagation direction toward one or more outcouplers of the waveguide.

[0009] In another exemplary embodiment, a method includes incoupling light having a first optical property into a waveguide via a first incoupler, incoupling light having a second optical property into the waveguide via a second incoupler, and reflecting the incoupled light having the first optical property into the waveguide by a first structure at an interface between the second incoupler and a waveguide substrate of the waveguide.

[0010] In some embodiments, the method includes the first optical property having a first wavelength range and the second optical property having a second wavelength range different from the first wavelength range. Further, in some embodiments, the first structure includes a first dichroic mirror having a cutoff wavelength between the first wavelength range and the second wavelength range.

[0011] In some embodiments, the method includes incoupling light having a third optical property into the waveguide via a third incoupler, and reflecting the incoupled light having the first optical property and the incoupled light having the second optical property into the waveguide via a second structure at an interface between the third incoupler and a waveguide substrate of the waveguide. In some embodiments, the method includes the third optical property including a third wavelength range different from the first wavelength range and the second wavelength range, and the second structure including a second dichroic mirror having a cutoff wavelength between the third wavelength range and the first wavelength range and the second wavelength range.

[0012] In some embodiments, the method includes the first optical property having a first polarization state, the second optical property having a second polarization state different from the first polarization state, and the first structure comprising a polarizing beam splitter.

[0013] 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]

[0014] [Figure 1] 1 illustrates an exemplary display system having a support structure housing a projection system configured to project images toward a user's eyes, according to some embodiments. [Figure 2] 2 shows an example block diagram of a projection system that projects light to display an image to a user's eye through a display system, such as the display system of FIG. 1, according to some embodiments. [Figure 3] 3 illustrates an example of light propagation within a waveguide of a projection system, such as the projection system of FIG. 2, according to some embodiments. [Figure 4] 10 illustrates an example of separate in-coupler gratings aligned with each other in the direction of light propagation, according to some embodiments. [Figure 5] 1 illustrates an example of light being outcoupled from a waveguide, according to some embodiments. [Figure 6] 10 illustrates an example of a waveguide in which a dichroic mirror is located at the interface of the second inter-coupler grating and the waveguide substrate, according to some embodiments. [Figure 7] 10 illustrates an example of a waveguide in which a dichroic mirror is located at the interface of a second inter-coupler grating and a waveguide substrate, and at the interface of a third inter-coupler grating and a waveguide substrate, according to some embodiments. [Figure 8] 9 illustrates an alternative view of FIG. 8 according to some embodiments. [Figure 9] 10 illustrates an example of a waveguide in which a polarizing beam splitter is located at the interface of the second inter-coupler grating and the waveguide substrate, according to some embodiments. [Figure 10] 10 illustrates an example of a waveguide in which a low refractive index material is disposed at the interface of the second inter-coupler grating and the waveguide substrate, according to some embodiments. [Figure 11] 1 shows an example of a flowchart illustrating a method for incoupling light into a waveguide, according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0015] Inefficient transmission of received light through a WHUD's waveguide can degrade image quality at the user's eye and generally negatively impact the user experience. For example, inefficiencies in incouplers result from differences in coupling efficiency between different optical properties (e.g., wavelength / color or polarization state) of the input light and collinear red+green+blue (RGB) light that is incoupled into the waveguide and propagates as angularly separated light. Figures 1-11 illustrate techniques for increasing the efficiency of light propagation within the waveguide while still fitting into the space-constrained form factor of a WHUD. This, in turn, improves the image quality provided to the user.

[0016] By way of example, the present disclosure includes a waveguide having multiple in-couplers, each with a grating tuned to incouple light having one of multiple different optical properties (e.g., wavelength ranges / colors or polarization states) into the waveguide. In some cases, multiple in-couplers are arranged one after the other (i.e., one after the other) in the direction of light propagation to occupy less space and better fit the space-constrained form factor of a WHUD. However, in such an arrangement, light in-coupled at one in-coupler may be reflected by the waveguide, resulting in at least a portion of the light being lost (e.g., out-coupled) at a different in-coupler. Using the techniques described herein, this premature out-coupling of light is prevented by selectively placing reflective structures on one or more in-couplers to reflect light having specific optical properties, such as a specified color or polarization state.

[0017] For example, in some embodiments, the waveguide includes two in-couplers. The first in-coupler is a grating configured to incouple red light, and the second in-coupler is a grating configured to incouple blue and green light. The second in-coupler is positioned relative to the first in-coupler in a direction between the first in-coupler and the out-coupler corresponding to the first and second in-couplers. With this arrangement, the in-coupled red light from the first in-coupler potentially interacts with the second in-coupler as the in-coupled red light propagates through the waveguide. Using the techniques described herein, a dichroic mirror having a cutoff wavelength value between the red light range and the blue and green light range is positioned at or near the second in-coupler. Thus, the dichroic mirror reflects the red light and passes the blue and green light. This prevents (or reduces) the loss of red light at the second in-coupler, thereby improving the overall quality of the image provided by the waveguide.

[0018] 1-11 illustrate embodiments of exemplary display systems and techniques for increasing the amount of incoupled light propagated within a waveguide to an outcoupler, as described in more detail below. However, it will be understood that the apparatus and techniques of the present disclosure are not limited to implementation in this particular display system, but instead may be implemented in any of a variety of display systems using the guidelines provided herein.

[0019] FIG. 1 illustrates an exemplary display system 100 having a support structure 102 including an arm 104 housing a laser projection system configured to project images toward a user's eyes, who perceive the projected images displayed on one or both lens elements 108, 110 within a field of view (FOV) area 106 of the display. In the illustrated embodiment, the display system 100 is a wearable head-up display (WHUD), which includes a support structure 102 configured to be worn on a user's head and has the general shape and appearance of eyeglass (e.g., sunglasses) frames. The support structure 102 houses or otherwise includes various components to facilitate the projection of such images toward the user's eyes, such as a laser projector, an optical scanner, and a waveguide. In some embodiments, the support structure 102 further includes various sensors, such as one or more forward-facing cameras, rear-facing cameras, other optical sensors, motion sensors, accelerometers, etc. 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. Additionally, in some embodiments, support structure 102 further includes one or more batteries or other portable power sources for powering the electrical components of display system 100. In some embodiments, some or all of these components of display system 100 are housed completely or partially within the interior volume of support structure 102, such as within arms 104 within region 112 of support structure 102. It should be noted that while an exemplary form factor is shown, in other embodiments, display system 100 may have a different shape and appearance than the eyeglass frames shown in FIG. 1 .

[0020] One or both of lens elements 108, 110 may be used by display system 100 to provide an augmented reality (AR) display in which rendered graphical content is superimposed on or otherwise combined with a real-world view perceived by a user through lens elements 108, 110. For example, laser light used to form a perceptible image or series of images may be projected to a user's eye by a laser projector of display system 100 through a series of optical elements, such as a corresponding lens element, one or more scanning mirrors, and a waveguide formed at least partially within one or more optical relays. Thus, one or both of lens elements 108, 110 may include at least a portion of a waveguide that routes display light received by a waveguide in-coupler to a waveguide out-coupler, which outputs the display light toward the eye of a user of display system 100. In some embodiments, the waveguide includes multiple in-couplers, each tuned to incouple light of one of multiple optical properties into the waveguide to increase the amount of light displayed to a user within the FOV region 106. The multiple in-couplers, in some embodiments, are arranged consecutively along the light propagation path with one or more corresponding out-coupler directions to fit within the spatial dimension of the display system 100. Furthermore, in some embodiments, one or more of the in-couplers include a selectively reflective structure for reflecting light incoupled by one or more other in-couplers so that this light is not prematurely outcoupled before being displayed to a user within the FOV region 106. The display light is modulated and scanned over the user's eye so that the user perceives the display light as an image. Furthermore, each of the lens elements 108, 110 is sufficiently transparent to provide a view of the user's real-world environment so that the user can see through the lens element, with the image appearing superimposed over at least a portion of the real-world environment.

[0021] In some embodiments, the projector is a digital light processing-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 a digital light processor. In some embodiments, the projector includes multiple laser diodes (e.g., red, green, and / or blue laser diodes) and at least one scanning mirror (e.g., two one-dimensional scanning mirrors, which may be microelectromechanical systems (MEMS)-based or piezo-based). The projector 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 operation of the projector. In some embodiments, the controller is communicatively coupled to a processor (not shown) that controls the projector's scan area size and scan area position and generates content displayed on the display system 100. The projector scans light over a variable area of ​​the display system 100, designated by the FOV area 106. The scan region size corresponds to the size of the FOV region 106, and the scan region position corresponds to the area of ​​one of the lens elements 108, 110 where the FOV region 106 is visible to the user. It is generally desirable for a display to have a wide FOV to accommodate light outcoupling over a wide range of angles. Herein, the range of different user eye positions from which the display can be viewed is referred to as the display's eyebox.

[0022] In some embodiments, the projector routes light through first and second scan mirrors, an optical relay disposed between the first and second scan mirrors, and a waveguide disposed at the output of the second scan mirror. In some embodiments, at least a portion of the waveguide outcoupler may overlap the FOV region 106. These aspects are described in further detail below.

[0023] 2 shows a simplified block diagram of a projection system 200 that projects an image directly onto a user's eye via light. Projection system 200 includes an optical engine 202, an optical scanner 204, and a waveguide 205. Optical scanner 204 includes a first scan mirror 206, a second scan mirror 208, and an optical relay 210. Waveguide 205 includes an in-coupler 212 and an out-coupler 214, which, in this example, is optically aligned with a user's eye 216. In some embodiments, projection system 200 is implemented in a wearable head-up display or other display system, such as display system 100 of FIG. 1.

[0024] The optical engine 202 includes one or more light sources configured to generate and output light 218 (e.g., visible light, such as red, blue, and green light, and / or non-visible light, such as infrared light). In some embodiments, the optical engine 202 is coupled to a driver or other controller (not shown) that controls the timing of light emission from the light sources of the optical engine 202 according to instructions received by the controller or driver from a computer processor coupled thereto, and modulates the light 218 so that it is perceived as an image when output to the retina of the user's eye 216.

[0025] For example, during operation of projection system 200, multiple light beams, each having a different wavelength, are output by light sources in optical engine 202, then combined via a beam combiner (not shown), and directed toward a user's eye 216. Optical engine 202 modulates the intensity of each of the light beams so that the combined light reflects off a series of pixels in an image, with the particular intensity of each light beam at any given time contributing to the corresponding color content and amount of brightness of the pixel as represented by the combined light at that time.

[0026] In some embodiments, one or both of scan mirrors 206 and 208 of optical scanner 204 are MEMS mirrors. For example, scan mirror 206 and scan mirror 208 are MEMS mirrors that, when driven by respective actuation voltages, oscillate during active operation of projection system 200, causing scan mirrors 206 and 208 to scan light 218. The oscillation of scan mirror 206 causes light 218 output by optical engine 202 to be scanned across the surface of second scan mirror 208 through optical relay 210. Second scan mirror 208 scans light 218 received from scan mirror 206 toward in-coupler 212 of waveguide 205. In some embodiments, the light directed from scan mirror 208 toward in-coupler 212 of waveguide 205 is separated into light with different optical properties. That is, multiple inputs of light are directed at incoupler 212, with each input of light having one of multiple optical properties (e.g., wavelength range / color) associated with it. In some embodiments, scan mirror 206 oscillates along a first scan axis 219 such that light 218 is scanned only in one dimension (i.e., in a line) across the surface of second scan mirror 208. In some embodiments, scan mirror 208 oscillates or otherwise rotates along a second scan axis 221. In some embodiments, first scan axis 219 is perpendicular to second scan axis 221.

[0027] In some embodiments, in-coupler 212 has a substantially rectangular outline and is configured to receive light 218 and direct light 218 into waveguide 205. In-coupler 212 is defined by a smaller dimension (i.e., width) and a larger orthogonal dimension (i.e., length). In one embodiment, optical relay 210 is a line-scan optical relay that receives light 218 scanned in a first dimension (e.g., the first dimension corresponds to the smaller dimension of in-coupler 212) by first scan mirror 206, routes light 218 to second scan mirror 208, and introduces focusing of light 218 to an exit pupil beyond second scan mirror 208 in the first dimension. As used herein, "exit pupil" in an optical system refers to a location along an optical path where light beams intersect. For example, following reflection from the first scan mirror 206, the possible optical paths of the light 218 initially diverge along the first scan axis, but later, due to the focusing introduced by the optical relay 210, these paths cross the second scan mirror 208 and intersect at an exit pupil. For example, the width (i.e., smallest dimension) of a given exit pupil corresponds approximately to the diameter of the light corresponding to that exit pupil. Thus, the exit pupil can be considered a "virtual aperture." According to various embodiments, the optical relay 210 includes one or more collimation lenses that shape and focus the light 218 onto the second scan mirror 208, or a molded reflective relay that includes two or more spherical, aspherical, parabolic, and / or freeform lenses that shape and direct the light 218 onto the second scan mirror 208. The second scan mirror 208 receives the light 218 and scans the light 218 in a second dimension, which corresponds to the length dimension of the incoupler 212 of the waveguide 205. In some embodiments, the second scan mirror 208 sweeps the light 218 at the exit pupil along a line along the second dimension. In some embodiments, the in-coupler 212 is positioned at or near the sweep line downstream from the second scan mirror 208 such that the second scan mirror 208 scans the light 218 as a line or row on the in-coupler 212.

[0028] In some embodiments, the optical engine 202 includes an edge-emitting laser (EEL) that emits laser light 218 having a substantially elliptical, non-circular cross-section, and the optical relay 210 expands or minimizes the laser light 218 along its semimajor or semiminor axis to circularize the laser light 218 before focusing the laser light 218 on the second scan mirror 208. In some such embodiments, the surface of the mirror plate of the scan mirror 206 is elliptical and non-circular (e.g., similar in shape and size to the cross-sectional area of ​​the laser light 218). In other such embodiments, the surface of the mirror plate of the scan mirror 206 is circular.

[0029] The waveguide 205 of the projection system 200 includes an in-coupler 212 and an out-coupler 214. As used herein, the term "waveguide" will be understood to mean a combiner that transmits light from an in-coupler (such as in-coupler 212) to an out-coupler (such as out-coupler 214) using one or more of total internal reflection (TIR), special filters, and / or reflective surfaces. In some display applications, the light is a collimated image, and the waveguide transmits and replicates the collimated image to the eye. In general, the terms "in-coupler" and "out-coupler" will be understood to refer to any type of optical grating structure, including, but not limited to, a diffraction grating, a hologram, a holographic optical element (e.g., an optical element that uses 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 in-coupler or out-coupler is configured as a transmission grating (e.g., a transmission diffraction grating or a transmission holographic grating), such that the in-coupler or out-coupler transmits light and applies a designed optical function(s) to the light during transmission. In some embodiments, a given in-coupler or out-coupler is a reflective grating (e.g., a reflective diffraction grating or a reflective holographic grating), such that the reflective grating reflects light to the in-coupler or out-coupler and applies a designed optical function(s) to the light during reflection. In this example, laser light 218 received by in-coupler 212 is relayed to out-coupler 214 via waveguide 205 using TIR. Laser light 218 is then output to user's eye 216 via out-coupler 214. As mentioned above, in some embodiments, waveguide 205 has the form factor of glasses and is implemented as part of an eyeglass lens, such as lens 108 or lens 110 ( FIG. 1 ) of a display system using projection system 200.

[0030] In some embodiments, although only one in-coupler 212 is shown in FIG. 2 , the waveguide 205 includes multiple in-couplers 212 to increase the amount of input light in-coupled into the waveguide 205. Each in-coupler is tuned to incouple light of one of multiple optical properties into the waveguide 205, thereby improving the overall coupling efficiency of the projection system 200. The coupling efficiency is the amount of light propagating along the waveguide divided by the amount of input light (also called incident light). Adjustable in-coupler grating parameters include, but are not limited to, grating height, grating period, grating angle, and grating density. Furthermore, each in-coupler may have different grating parameters and therefore may use a different manufacturing process. In some embodiments, the multiple optical properties are multiple wavelength ranges. In other embodiments, the multiple optical properties are multiple polarization states. In some cases, multiple in-couplers are arranged one after the other (i.e., one after the other) in the light propagation direction to occupy less space within the WHUD system. To prevent light incoupled into a previous incoupler from being lost in the subsequent incoupler, reflective structures are placed at the interfaces with the waveguides or integrated into the subsequent incoupler, with reflective qualities selected to prevent light incoupled into the previous incoupler from interacting with (i.e., being outcoupled into) the subsequent incoupler, as described further herein.

[0031] The terms "incoupler" and "incoupler grating" are used correspondingly in this specification and related drawings unless otherwise specified. Thus, descriptions of "first incoupler grating," "second incoupler grating," "third incoupler grating," etc. (e.g., "first grating," "second grating," "third grating") correspond to "first incoupler," "second incoupler," and "third incoupler," respectively, unless otherwise indicated.

[0032] 2 , in some embodiments, additional optical components are included in the optical path between optical engine 202 and scan mirror 206, between scan mirror 206 and optical relay 210, between optical relay 210 and scan mirror 208, between scan mirror 208 and in-coupler 212, between in-coupler 212 and out-coupler 214, and / or between out-coupler 214 and eye 216 (e.g., to shape the laser light for viewing by user's eye 216). In some embodiments, a prism is used to direct light from scan mirror 208 to in-coupler 212 so that the light is coupled into in-coupler 212 at the appropriate angle to facilitate propagation of light within waveguide 205 via TIR. Also, in some embodiments, an exit pupil expander such as a folding grating (e.g., exit pupil expander 304 in FIG. 3, described below) is positioned at an intermediate stage between in-coupler 212 and out-coupler 214 to receive light coupled into waveguide 205 by in-coupler 212, expand the light, and redirect the light toward out-coupler 214, which then couples the laser light out of waveguide 205 (e.g., toward the user's eye 216).

[0033] 3 illustrates an example of light propagation within waveguide 205 of projection system 200 of FIG. 2 , according to some embodiments. As shown, light received via in-coupler 212 scanned along axis 302 is directed into exit pupil expander (EPE) 304 and then routed to out-coupler 214 for output (e.g., toward a user's eye). In some embodiments, exit pupil expander 304 expands one or more dimensions of the eyebox of the WHUD that includes projection system 200 (e.g., relative to what the dimensions of the eyebox of the WHUD would be without exit pupil expander 304). In some embodiments, in-coupler 212 and exit pupil expander 304 each include a respective one-dimensional diffraction grating (i.e., a diffraction grating that extends along one dimension). 3 illustrates a substantially ideal case, where in-coupler 212 directs light straight down in a first direction perpendicular to scan axis 302 (relative to the currently depicted view), and exit pupil expander 304 directs light to the right in a second direction perpendicular to the first direction (relative to the currently depicted view). Although not shown in this example, it should be understood that in some embodiments, the first direction in which in-coupler 212 directs light is not exactly perpendicular, but is slightly or substantially oblique to scan axis 302.

[0034] In some embodiments, where the waveguide 205 includes multiple in-couplers 212, the waveguide 205 also includes multiple corresponding exit pupil expanders 304 and / or out-couplers 214. For example, a first in-coupler directs light through a first exit pupil expander to a first out-coupler, and a second in-coupler directs light through a second exit pupil expander to a second out-coupler. In some embodiments, each of the in-couplers and their corresponding exit pupil expanders and out-couplers is specifically tuned to propagate light of one of multiple optical properties through the waveguide 205 to a user.

[0035] Multiple incouplers may be applied to waveguides positioned adjacent to each other (i.e., laterally adjacent to each other) so that the optical path incoupled by a first incoupler does not intersect with the optical path incoupled by a second or subsequent incoupler. In other words, each incoupler does not follow another incoupler in the light propagation direction toward one or more outcouplers. While this prevents light incoupled by multiple incouplers from directly interacting with each other, such an arrangement requires a thicker substrate and more space to accommodate the waveguides, thereby adversely affecting other system parameters (e.g., optical uniformity and system complexity). Furthermore, in highly space-constrained form factors, such as the WHUD 100 of FIG. 1, there is typically no space available to accommodate such a setup. The technology described herein addresses this issue by arranging the incouplers in line with each other in the light propagation direction. Furthermore, selectively reflective structures are disposed on one or more of the incouplers to reflect light having specified optical properties, such as a specified color or polarization.

[0036] 4 and 5 show a side view portion 400 and a top view 500, respectively, of a portion of a waveguide substrate 405, such as that corresponding to the waveguide 205 of FIG. 2. As shown, the waveguide substrate 405 has multiple in-couplers, including a first in-coupler 412a and a second in-coupler 412b. The first in-coupler 412a receives first input light 502 in a first wavelength range (e.g., corresponding to red light) and incouples the light into the waveguide 405 as first in-coupled light 520. The second in-coupler 412b receives second input light 504 in a second wavelength range (e.g., corresponding to blue and green light) and incouples the light into the waveguide 405 as second in-coupled light 530. Each of the in-couplers 412a and 412b is tuned to receive light in the corresponding wavelength range to increase the coupling efficiency of the waveguide. Furthermore, to reduce the space required to implement a multiple in-coupler setup, the second in-coupler 412b is positioned following the first in-coupler 412a in the light propagation direction 402 toward one or more out-couplers 550. Because the second in-coupler 412b is positioned in the path of the light propagation 402 from the first in-coupler 412a, a portion of the first in-coupled light 520 may potentially interact with and be lost (522) by the second in-coupler 412b, i.e., may be prematurely out-coupled by the second in-coupler 412b. As a result, the amount of the first in-coupled light 512 is reduced at 524 propagating toward the exit pupil expander(s) and out-coupler(s) 550. In other words, the amount of light at 524 is the first in-coupled light 520 reduced by the amount of the lost light 522.

[0037] Thus, as described in more detail below, in some embodiments, a reflective structure is disposed in one or more intercouplers to reflect light having one or more specified optical properties relative to another intercoupler, thereby preventing or reducing the amount of light loss in the intercoupler and improving the image quality provided by the waveguide.

[0038] 6 shows a top view 600 of a portion of a waveguide substrate 605, such as that corresponding to waveguide 205 of FIG. 2, having a first in-coupler 612a and a second in-coupler 612b. The first in-coupler 612a receives first input light 602 in a first wavelength range and incouples the light into the waveguide 605 as first in-coupled light 620. The second in-coupler 612b receives second input light 604 in a second wavelength range and incouples the light into the waveguide 605 as second in-coupled light 634. Each of the in-couplers 612a and 612b is tuned to receive light in a corresponding wavelength range to increase coupling efficiency. Furthermore, to reduce the space required to implement a multiple in-coupler setup, the second in-coupler 612b is positioned following the first in-coupler 612a in the direction of light propagation towards one or more out-couplers 650 (similar to the setup shown in Figures 4-5).

[0039] To prevent outcoupling of the first incoupled light 620 at the second incoupler 612b (i.e., as shown in FIG. 5 ), a reflective structure 614 is disposed at the second incoupler 612b. For example, as shown, the reflective structure 614 is at the interface between the waveguide substrate 605 and the second incoupler 612b. The reflective structure 614 is a dichroic mirror that reflects light in a first wavelength range corresponding to the first incoupled light 620 and transmits light having a second wavelength range corresponding to the input light 604 and the second incoupled light 634. This reflection of the first incoupled light 620 is indicated by 622. In this way, the reflective structure 614 prevents loss of the first incoupled light 620 at the second incoupler 612b. Therefore, an increased amount of the first incoupled light 620 propagates to 632 toward the exit pupil expander(s) and outcoupler(s) 650. In other words, the light at 632 is the same or substantially the same as the first in-coupled light 620 because the reflective structure 614 prevents the first in-coupled light 620 from being out-coupled at 612b, thereby increasing the coupling efficiency and therefore improving the image quality delivered to the user.

[0040] For example, if a first incoupler 612a incouples a first input light 602 having a first wavelength range corresponding to red light and a second incoupler 612b incouples a second input light 604 having a second wavelength range corresponding to blue+green light, a dichroic mirror is used as the reflective structure 614. The dichroic mirror has a cutoff wavelength between red and green light so as to reflect red light and transmit blue+green light. In this manner, the first incoupled light 620 (red light) bypasses the second incoupler 612b by reflecting off the dichroic mirror 614 at 622. While FIG. 6 shows a waveguide with two incouplers 612a and 612b, in some embodiments, the waveguide has three or more incouplers, as shown in FIGS. 7-8. Including more incouplers improves the coupling efficiency of the overall system by allowing each incoupler to be tuned to a finer range of optical properties. 7-8 show three in-couplers, it is understood that the number of in-couplers is scalable to other amounts (e.g., four or more) depending on system performance considerations. For example, a greater number of in-couplers would be utilized if a higher level of FOV multiplexing were implemented or if the in-coupling of light into the waveguides were segmented for other optical and / or performance-related reasons.

[0041] 7 and 8 show a top view 700 and a side view 800, respectively, of a portion of a waveguide substrate 705, such as that corresponding to waveguide 205 in FIG. 2. As shown, the waveguide substrate 705 includes a first in-coupler grating 712a, a second in-coupler grating 712b, and a third in-coupler grating 712c. The first in-coupler 712a receives a first input light 702 in a first wavelength range and incouples the light into the waveguide 705 as a first in-coupled light 720. The second in-coupler 712b receives a second input light 704 in a second wavelength range and incouples the light into the waveguide 705 as a second in-coupled light 730. The third in-coupler 712c receives a third input light 706 in a third wavelength range and incouples the light into the waveguide 705 as a third in-coupled light 740. Each of the in-couplers 712a, 712b, and 712c is tuned to receive light of a corresponding wavelength range to increase the coupling efficiency of the waveguides. Furthermore, to reduce the space required to implement a multiple in-coupler setup, the second in-coupler 712b is positioned following the first in-coupler 712a in the light propagation direction 802 toward one or more out-couplers 750, and the third in-coupler 712c is positioned following the second in-coupler 712b in the light propagation direction 802 toward one or more out-couplers 750.

[0042] To prevent outcoupling of light incoupled at other incouplers, reflective structures 714 and 716 are disposed at the second incoupler 712b and the third incoupler 712c, respectively. For example, to prevent outcoupling of the first incoupled light 720 at the second incoupler 712b, the reflective structure 714 is disposed at the second incoupler 712b. And, to prevent outcoupling of the first incoupled light 720 and the second incoupled light 730 at the third incoupler 712c, the reflective structure 716 is disposed at the third incoupler 712c. As shown, each of the reflective structures 714 and 716 is located at the interface between the waveguide substrate 705 and the respective incoupler 712b or 712c. The reflecting structure 714 is a dichroic mirror that reflects light in a first wavelength range corresponding to the first incoupled light 720 and transmits light in a second wavelength range corresponding to the second input light 704 and the second incoupled light 730. In other words, the dichroic mirror in 714 has a cutoff wavelength value between the first and second wavelength ranges. The reflecting structure 716 is a dichroic mirror that reflects light in a first wavelength range corresponding to the first incoupled light 720 and the second wavelength range corresponding to the second incoupled light 730 and transmits light in a third wavelength range corresponding to the third input light 706 and the third incoupled light 740. In other words, the dichroic mirror in 716 has a cutoff wavelength value between the third wavelength range and the first and second wavelength ranges. Therefore, light incoupled by an incoupler can bypass other incouplers by reflecting off the dichroic mirror.

[0043] The reflection of the first in-coupled light 720 at the second in-coupler 712b is shown at 722. In this manner, the reflecting structure 714 prevents loss of the first in-coupled light 720 at the second in-coupler 712b. Similarly, the reflecting structure 716 reflects the first in-coupled light 720 at 724 and the second in-coupled light 730 at 732. In this manner, the reflecting structure 716 prevents loss of the first in-coupled light 720 and the second in-coupled light 730 at the third in-coupler 712c. Therefore, the amount of the first in-coupled light 720 and the amount of the second in-coupled light 730 increases as they propagate to 726 and 734, respectively. This results in improved image quality delivered to a user.

[0044] 4-8 are described with respect to incouplers tuned to incouple light of different wavelength ranges into a waveguide, it will be understood that in other embodiments, incouplers are tuned to incouple light of different polarization states or other optical properties into a waveguide, examples of these other embodiments are described in more detail below in FIGS.

[0045] FIG. 9 shows a top view 900 of a portion of a waveguide substrate 905, such as that corresponding to the waveguide 205 of FIG. 2, with a first in-coupler 612a and a second in-coupler 912b. The first in-coupler 912a receives a first input light 902 having a first polarization state and in-couples the light into the waveguide 905 as a first in-coupled light 920. The second in-coupler 912b receives a second input light 904 having a second polarization state and in-couples the light into the waveguide 905 as a second in-coupled light 930. In some embodiments, polarization techniques are used to in-couple light, allowing for the use of multiple light sources, for example, of the same color. Each of the in-couplers 912a and 912b is tuned to receive light of a specific polarization state to increase the coupling efficiency of the waveguide. For example, the first polarization state may be S-polarized and the second polarization state may be P-polarized, or vice versa. Furthermore, to reduce the space required to implement a multiple in-coupler setup, the second in-coupler 912b is positioned following the first in-coupler 912a in the direction of light propagation towards one or more out-couplers 950.

[0046] A PBS layer 914 is disposed at the second incoupler 912b to prevent outcoupling of the first incoupled light 920 at the second incoupler 912b. For example, as shown, the PBS layer 914 is at the interface between the waveguide substrate 905 and the second incoupler 912b. The PBS layer 914 reflects light having a first polarization state corresponding to the first incoupler-coupled light 920 and transmits light having a second polarization state corresponding to the input light 904 and the second incoupled light 930. This reflection of the first incoupled light 920 is indicated at 922. Thus, the PBS layer 914 prevents premature outcoupling of the first incoupled light 920 at the second incoupler 912b. Therefore, an increased amount of the first incoupled light 920 propagates 924 toward the exit pupil expander(s) and outcoupler(s) 950, thereby improving the image quality delivered to the user.

[0047] 10 shows a top view 1000 of a portion of a waveguide substrate 1005, such as that corresponding to waveguide 205 of FIG. 2, having a first in-coupler 1012a and a second in-coupler 1012b. The first in-coupler 1012a receives a first input light 1002 and in-couples the light into the waveguide 1005 as a first in-coupled light 1020 having a first in-coupling angle. The second in-coupler 1012b receives a second input light 1004 and in-couples the light into the waveguide 1005 as a second in-coupled light 1030 having a second in-coupling angle. Each of the in-couplers 1012a and 1012b is adjusted to in-couple light into the waveguide at a respective angle. To reduce the space required to implement a multiple in-coupler setup, the second in-coupler 1012b is positioned following the first in-coupler 1012a in the direction of light propagation towards one or more out-couplers 1050.

[0048] To prevent outcoupling of the first incoupled light 1020 at the second incoupler 1012b, a low-index layer 1014 is disposed in the second incoupler 1012b. For example, as shown, the low-index layer 1014 is at the interface between the waveguide substrate 1005 and the second incoupler 1012b. The low-index layer 1014 reflects the first incoupled light 1020 and transmits the input light 1004 and the second incoupled light 1030. Because the angle of the first incoupled light 1020 is steeper than the input light 1004, the first incoupled light 1020 is reflected from the interface formed in the low-index material 1114 and the waveguide substrate 1105 by being within the critical angle defined by the interface by total internal reflection (TIR). For example, the refractive index of the waveguide substrate is n=2.0, and the refractive index of the low-index material 1014 is n=1.4. It is understood that these values ​​are examples, and that the material of the low-index material 1014 is generally selected based on its refractive index being lower than that of the waveguide substrate 1005. This reflection of the first in-coupled light 1020 is shown at 1022. In this way, the low-index layer 1014 prevents loss of the first in-coupled light 1020 at the second in-coupler 1012b. Therefore, an increased amount of the first in-coupled light 1020 propagates at 1024 toward the exit pupil expander(s) and out-coupler(s) 1050, thereby improving the image quality delivered to the user.

[0049] 11 shows a method flowchart 1100 for incoupling light having different optical properties into a waveguide, according to some embodiments. The method includes incoupling light having a first optical property into the waveguide via a first in-coupler, at 1102. The method includes incoupling light having a second optical property into the waveguide via a second in-coupler, at 1104. The method includes reflecting the light having the first optical property within the waveguide by a first structure at an interface between the second in-coupler and a waveguide substrate of the waveguide, at 1106.

[0050] In some embodiments, the method further includes incoupling light having a third optical property into the waveguide via a third incoupler, hi some embodiments, the method further includes reflecting the incoupled light having the first optical property and the incoupled light having the second optical property via a second structure at an interface between the third incoupler and a waveguide substrate of the waveguide.

[0051] In some embodiments, the first, second, and, if applicable, third optical property of the method is a wavelength range, while in other embodiments, the optical property is a polarization state or angle of light incoupled into the waveguide.

[0052] The reflective structures described herein reflect light inside the waveguide. For example, a reflective structure in a second incoupler in a multiple incoupler waveguide reflects light incoupled into the waveguide by the first incoupler. In other words, the reflective structure reflects light that has already been incoupled, so that the light is retained for propagation within the waveguide.

[0053] 1-11, the direction of the incident light, grating features, and propagating light are depicted in the plane of the page for clarity. However, the direction of some or all of the light paths and / or features may be within or outside the plane of the page. Furthermore, the above techniques and systems are applicable to line-scan MEMS relay systems and 2D optical relay systems.

[0054] 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 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.

[0055] 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 coupled to a computer system via a wired or wireless network (e.g., network-accessible storage (NAS)).

[0056] In addition to the above, it should be noted that not all activities or elements described above in the general description are required, and that some of the specific activities or devices may not be required, or that one or more additional activities may be performed, or that one or more additional elements may be included. Furthermore, the order in which the activities 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 appreciate that various modifications and variations 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.

[0057] Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, benefits, advantages, and solutions to problems, as well as 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 set forth in the claims below. It will therefore be apparent that the specific embodiments disclosed above may be altered or modified, and that all such variations are contemplated within the scope of the disclosed subject matter. The protection sought herein is therefore as set forth in the claims below.

Claims

1. A waveguide, a first incoupler for incoupling light having a first optical characteristic; a second incoupler for incoupling light having a second optical characteristic; and a first structure at an interface of the second incoupler for reflecting incoupled light having the first optical property within the waveguide; Including, A waveguide, wherein the second in-coupler is positioned following the first in-coupler in a direction of light propagation towards one or more out-couplers of the waveguide.

2. 2. The waveguide of claim 1, wherein the first optical property comprises a first wavelength range and the second optical property comprises a second wavelength range different from the first wavelength range.

3. The waveguide of claim 2 wherein the first structure comprises a dichroic mirror.

4. 4. The waveguide of claim 3, wherein the dichroic mirror comprises a shortpass dichroic mirror having a cutoff wavelength between the first wavelength range and the second wavelength range.

5. 2. The waveguide of claim 1, wherein the first optical property comprises a first polarization state and the second optical property comprises a second polarization state different from the first polarization state.

6. The waveguide of claim 5 wherein the first structure comprises a polarizing beam splitter.

7. 7. The waveguide of claim 6, wherein the polarizing beam splitter reflects light of the first polarization state and transmits light of the second polarization state.

8. the first optical characteristic comprises a first angle of light incoupled into the waveguide at the first in-coupler, and the second optical characteristic comprises a second angle of light incoupled into the waveguide at the second in-coupler; the second angle is different from the first angle; The waveguide of claim 1 , wherein the first angle is greater than a critical angle at an interface between a waveguide substrate of the waveguide and the first structure.

9. The waveguide of claim 8 , wherein the first structure comprises a material at the interface that has a lower refractive index than a material of the waveguide substrate of the waveguide.

10. a third incoupler for incoupling light of the third optical characteristic; and a second structure at an interface of the third incoupler for reflecting incoupled light having the first optical property and incoupled light having the second optical property within the waveguide; The waveguide of claim 1 further comprising:

11. 11. The waveguide of claim 10, wherein the first optical property comprises a first wavelength range, the second optical property comprises a second wavelength range different from the first wavelength range, and the third optical property comprises a third wavelength range different from the first wavelength range and the second wavelength range.

12. 12. The waveguide of claim 11, wherein the first structure comprises a first dichroic mirror and the second structure comprises a second dichroic mirror.

13. the first dichroic mirror includes a short-pass dichroic mirror having a cutoff wavelength between the first wavelength range and the second wavelength range; 13. The waveguide of claim 12, wherein the second dichroic mirror comprises a second shortpass dichroic mirror having a cutoff wavelength between the third wavelength range and the first and second wavelength ranges.

14. The waveguide of any one of claims 10 to 13, wherein the third in-coupler is arranged subsequent to the first in-coupler and the second in-coupler in a light propagation direction toward one or more out-couplers of the waveguide.

15. incoupling light having a first optical characteristic into the waveguide via a first incoupler; incoupling light having a second optical property into the waveguide via a second incoupler; reflecting the incoupled light having the first optical property in the waveguide by a first structure at an interface between the second incoupler and a waveguide substrate of the waveguide; Including, The method, wherein the second in-coupler is positioned following the first in-coupler in a direction of light propagation towards one or more out-couplers of the waveguide.

16. the first optical characteristic includes a first wavelength range, and the second optical characteristic includes a second wavelength range different from the first wavelength range; 16. The method of claim 15, wherein the first structure includes a first dichroic mirror having a cutoff wavelength between the first wavelength range and the second wavelength range.

17. incoupling light having a third optical property into the waveguide via a third incoupler; reflecting the incoupled light having the first optical property and the incoupled light having the second optical property within the waveguide via a second structure at an interface between the third incoupler and the waveguide substrate of the waveguide; 17. The method of claim 16, further comprising:

18. the third optical characteristic includes a third wavelength range different from the first wavelength range and the second wavelength range; 18. The method of claim 17, wherein the second structure includes a second dichroic mirror having a cutoff wavelength between the third wavelength range and the first and second wavelength ranges.

19. the first optical characteristic comprises a first polarization state, and the second optical characteristic comprises a second polarization state different from the first polarization state; The method of claim 15 , wherein the first structure comprises a polarizing beam splitter.

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