Apparatus and method for directing light into multiple in-coupler waveguides

Abstract

This disclosure describes techniques and configurations for directing light from an optical engine to one of multiple incouplers of a multiple incoupler waveguide system. For example, this disclosure describes multiple reflective and transmissive elements for selectively directing light to a first incoupler or a second incoupler based on multiple optical properties.

Description

[Background technology]

[0001] In conventional wearable head-up displays (WHUDs), a light beam from an image source is coupled into a light guide substrate, commonly called a waveguide, by an input optical coupling, such as an incoupling diffraction grating (i.e., an in-coupler), which may be formed on the surface of the substrate or embedded within the substrate. Once coupled into the waveguide, the light beam 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 coupling (i.e., an "out-coupler"), which may take the form of a diffractive optical system. The light beam emitted from the waveguide overlaps with the waveguide at an eye-relief distance, forming an exit pupil, within which the virtual image generated by the image source can be viewed. [Overview of the project]

[0002] This disclosure describes a technique and apparatus for selectively directing light to multiple in-couplers based on the optical properties of light, using multiple transmission and reflection elements.

[0003] In one exemplary embodiment, the apparatus includes a waveguide comprising a first in-coupler and a second in-coupler, and a plurality of reflective and transmitting elements that selectively direct light to the first in-coupler or the second in-coupler based on a plurality of optical properties.

[0004] In certain embodiments of the device, a plurality of reflective and transmitting elements separate the light into a portion having a first optical property among a plurality of optical properties and a portion having a second optical property among a plurality of optical properties. In some embodiments, the plurality of reflective and transmitting elements selectively direct the portion of light having the first optical property to a first in-coupler and the portion of light having the second optical property to a second in-coupler.

[0005] In certain embodiments of the device, the multiple optical properties are multiple wavelength ranges, and each in-coupler is tuned to in-couple light from one of the multiple wavelength ranges. In some embodiments, the multiple reflective and transmitting elements include mirrors. In some embodiments, the multiple reflective and transmitting elements include a beam splitter, which is a dichroic beam splitter that separates light into two or more of the multiple wavelength ranges. In certain embodiments, the multiple reflective and transmitting elements include an optical relay element for focusing a first pupil plane associated with a first wavelength range of the multiple wavelength ranges to a first in-coupler, or for focusing a second pupil plane associated with a second wavelength range of the multiple wavelength ranges to a second in-coupler. For example, the optical relay element includes one or more of a lens group, a reflector, a metasurface, a prism assembly having a total internal reflection (TIR) ​​gap with multiple reflective and transmitting elements, or any combination thereof.

[0006] In certain embodiments of the device, the multiple optical properties are multiple polarization states, and each in-coupler is tuned to in-couple light from one of the multiple polarization states. In some embodiments, the multiple reflective and transmitting elements include a polarizing beam splitter and one or more waveplates.

[0007] In certain embodiments of the device, the plurality of reflective and transmitting elements include a plurality of lenses having different focal lengths. In some embodiments, the plurality of reflective and transmitting elements include an optical cleanup filter, which includes a color-selective filter or a polarization-selective filter for removing light having undesirable optical properties from being directed to a first or second in-coupler. In some embodiments, the plurality of reflective and transmitting elements receive light from a single optical engine and selectively direct the received light to a first or second in-coupler.

[0008] In another exemplary embodiment, the apparatus includes a waveguide stack comprising a first waveguide substrate including a first in-coupler and a second waveguide substrate including a second in-coupler offset from the first in-coupler. The apparatus also includes a plurality of reflective and transmitting elements for selectively directing light to the first in-coupler or the second in-coupler based on a plurality of optical properties.

[0009] In a particular embodiment of the device, multiple reflective and transmitting elements direct light of a first optical property among multiple optical properties to a first in-coupler and light of a second optical property among multiple optical properties to a second in-coupler.

[0010] In certain embodiments, the apparatus further includes one or more additional waveguide substrates laminated on a second waveguide substrate, each of which includes an additional in-coupler, each of which is laterally offset from the first in-coupler, the second in-coupler, and each other additional in-coupler. Furthermore, a plurality of reflective and transmitting elements are configured to selectively direct light to each of the one or more additional in-couplers based on a plurality of optical properties.

[0011] In some embodiments of the device, the multiple reflective and transmitting elements include a beam splitter. For example, in a particular embodiment, the beam splitter is a dichroic beam splitter, and the multiple optical properties are multiple distinct wavelength ranges. In this example, the dichroic beam splitter separates light into multiple distinct wavelength ranges for transmission to one of the in-couplers. In another example, in a different embodiment, the beam splitter is a polarizing beam splitter, and the multiple optical properties are multiple distinct polarization states. In this example, the polarizing beam splitter separates light into multiple distinct polarization states for transmission to one of the in-couplers.

[0012] In some embodiments of the device, the multiple reflective and transmissive elements include one or more optical focusing elements for focusing light toward one or more in-couplers.

[0013] Another exemplary embodiment includes a plurality of reflective and transmitting elements that receive input light from a single optical engine, separate the input light into at least two parts of light based on one or more optical properties, and selectively direct each of the at least two parts of light to one of a plurality of in-couplers of a waveguide. In some embodiments, the plurality of reflective and transmitting elements include elements and features described herein.

[0014] This disclosure will be better understood by referring to the accompanying drawings, and many of its features and advantages may become apparent to those skilled in the art. The use of the same reference numeral in different drawings indicates similar or identical items. [Brief explanation of the drawing]

[0015] [Figure 1] The following are exemplary display systems having a support structure that houses a projection system configured to project an image toward the user's eyes, according to several embodiments. [Figure 2] The following are examples of block diagrams of projection systems that project light representing an image onto a user's eye via a display system, such as the display system shown in Figure 1, according to several embodiments. [Figure 3] Examples of optical propagation in a waveguide of a projection system, such as the projection system shown in Figure 2, are shown according to several embodiments. [Figure 4] Examples of enlarged views of waveguide stacks according to several embodiments are shown. [Figure 5] Examples of top and side views of a portion of a waveguide stack and a portion of an optical scanner according to several embodiments are shown. [Figure 6] Examples of top views of a portion of a waveguide stack and a portion of an optical scanner according to several embodiments are shown. [Figure 7] Another example of a top view of a portion of a waveguide stack and a portion of an optical scanner according to several embodiments is shown. [Figure 8]An example of a top view of a portion of a waveguide stack having three waveguides and a portion of an optical scanner according to some embodiments is shown. [Figure 9] An example of a top view of a portion of a waveguide stack and a portion of an optical scanner having a MEMS mirror according to some embodiments is shown. [Figure 10] An example of a zoomed-in view of FIG. 9 according to some embodiments is shown. [Figure 11] An example of a top view of a portion of a waveguide stack and a portion of an optical scanner having an optical focusing element according to some embodiments is shown. [Figure 12] An example of a portion of a waveguide having a plurality of couplers in a common waveguide and a portion of an optical scanner according to some embodiments is shown. [Figure 13] An example of a pupil plane and a plurality of couplers of a waveguide according to some embodiments is shown. [Figure 14] An example of pupil walk at a coupler according to some embodiments is shown. [Figure 15] An example of a lens as a secondary optical relay element of an optical scanner according to some embodiments is shown. [Figure 16] An example of a metasurface as a secondary optical relay element of an optical scanner according to some embodiments is shown. [Figure 17] An example of an optical scanner having a plurality of reflective elements including a mirror, a beam splitter, an air gap, and a plurality of prisms according to some embodiments is shown. [Figure 18] An example of an optical scanner having a plurality of reflective elements including a mirror and a beam splitter according to some embodiments is shown. [Figure 19] An example of separating red light from blue + green light according to some embodiments is shown. [Figure 20] An example of an optical scanner utilizing a plurality of couplers and polarization of a waveguide according to some embodiments is shown. [Figure 21]Another example of an optical scanner utilizing multiple in-couplers and polarization in a waveguide, according to several embodiments, is shown. [Figure 22] Examples of optical scanners including multiple waveguide in-couplers and optical focusing elements are shown according to several embodiments. [Figure 23] Examples of filtering light in a color-selective manner, according to several embodiments, are shown. [Figure 24] Examples of filtering light in a polarization-selective manner according to several embodiments are shown. [Figure 25] Examples of waveguides, optical scanners, and display light sources as optical engines having multiple in-couplers are shown according to several embodiments. [Modes for carrying out the invention]

[0016] In a WHUD, a waveguide with multiple in-couplers offers the advantage of higher in-coupling efficiency because each in-coupler can be tuned to in-couple light with specific optical properties, such as a particular wavelength range. However, multiple in-coupler waveguides typically require a separate projector and / or optical scanner for each in-coupler, and the spatially constrained form factor of a WHUD may not have enough space to accommodate such a configuration. Figures 1-25 illustrate a technique for selectively directing light from a single projector to multiple in-couplers via an optical scanner with multiple transmission and reflection elements based on the optical properties of the light. Thus, the advantage of multiple in-coupler waveguides is that they can be realized in a smaller form factor WHUD, thereby improving the overall user experience.

[0017] In other embodiments, in the case of a waveguide with multiple in-couplers, the first in-coupler is tuned to in-couple light with a first optical characteristic (e.g., a first wavelength range), and the second in-coupler is tuned to in-couple light with a second optical characteristic (e.g., a second wavelength range). In some embodiments, the multiple in-couplers are arranged via a waveguide stack, with each waveguide in the stack having a corresponding in-coupler. In other embodiments, the multiple in-couplers are applied to a common waveguide. In all cases, the optical scanner includes multiple reflective and transmitting elements, such as mirrors, beam splitters, prisms, lenses, waveplates, or metasurfaces, or any combination thereof, which are designed and arranged to selectively direct light having one or more specified optical characteristics to a corresponding in-coupler. Furthermore, the optical scanner equalizes the optical path length of the light directed to each in-coupler (within a margin of difference). Therefore, the pupil plane of each optical path is highly aligned with each in-coupler, effectively in-coupling and increasing the amount of light received through the waveguide. This improves the quality of the image delivered by the waveguide while using a single projector.

[0018] To illustrate further, in some embodiments, the waveguide has two incouplers designated as a first incoupler and a second incoupler. The first incoupler is tuned to incouple red light, and the second incoupler is tuned to incouple blue and green light. Using the techniques described herein, a plurality of reflective and transmitting elements of an optical scanner receive light from a single optical engine (i.e., a projector), direct the red portion of the received light to the first incoupler, and direct the blue and green portions of the received light to the second incoupler. Specifically, the plurality of reflective and transmitting elements include a dichroic mirror that reflects the red portion to the first incoupler and transmits the blue and green portions. The plurality of reflective and transmitting elements further include a mirror that receives the transmitted blue and green portions from the dichroic mirror and reflects the blue and green portions to the second incoupler. Furthermore, the multiple reflective and transmitting elements include additional elements such as lenses and / or prisms to equalize (within a margin of difference) the optical path length of the red light portion directed to the first incoupler and the optical path lengths of the blue and green light portions directed to the second incoupler, so that the pupil plane of each light portion coincides with its respective incoupler. This increases the amount of incoupled light that is effectively propagated within the waveguide.

[0019] Figures 1–25 illustrate embodiments of a display system having optical scanners for directing light to multiple in-couplers, as will be described in more detail below. However, it should be understood that the apparatus and techniques of this disclosure are not limited to implementation in this particular display system, but may instead be implemented in any of the various display systems using the guidelines provided herein.

[0020] Figure 1 shows an exemplary display system 100 having a support structure 102 including an arm 104, which houses a projection system configured to project an image toward the user's eye so that the user perceives the projected image as being displayed within the field of view (FOV) area 106 of the display on one or both of the lens elements 108, 110. In the illustrated embodiment, the display system 100 is a wearable head-up display (WHUD) having a general shape and appearance of a spectacle (e.g., sunglasses) frame, and includes a support structure 102 configured to be worn on the user's head. The support structure 102 includes, or otherwise includes, various components that facilitate the projection of such an image toward the user's eye, such as a projector, an optical scanner, and a waveguide. In some embodiments, the support structure 102 further includes various sensors such as one or more front cameras, a rear camera, 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. Furthermore, in some embodiments, the support structure 102 further includes one or more batteries or other portable power sources for supplying power to the electrical components of the display system 100. In some embodiments, some or all of these components of the display system 100 are contained entirely or partially within the internal volume of the support structure 102, such as within the arms 104 of region 112 of the support structure 102. It should be noted that while exemplary form factors are shown, in other embodiments the display system 100 may have a different shape and appearance from the eyeglass frame shown in Figure 1.

[0021] One or both of the lens elements 108, 110 are used by the display system 100 to provide an augmented reality (AR) display, in which rendered graphic content can be superimposed on a real-world view so as to be perceived by the user through the lens elements 108, 110, or otherwise provided in conjunction with the real-world view. For example, light used to form a perceptible image or series of images may be projected by the projector of the display system 100 to the user's eye via a series of optical elements such as waveguides at least partially formed in the corresponding lens elements, one or more scanning mirrors, and one or more optical relays. Thus, one or both of the lens elements 108, 110 include at least a portion of a waveguide that sends display light received by an in-coupler of the waveguide to an out-coupler of the waveguide, which outputs the display light toward the user's eye of the display system 100. The display light is modulated so that the user perceives the display light as an image and is scanned toward the user's eye. In addition, each of the lens elements 108 and 110 is transparent enough to allow the user to view through the lens element and provide a field of view of the user's real-world environment, so that the image appears superimposed on at least a portion of the real-world environment.

[0022] In some embodiments, the projector is a digital photoprocessing-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 photoprocessors. In some embodiments, the projector includes a plurality of laser diodes (e.g., red laser diodes, green laser diodes, and / or blue laser diodes) and at least one scanning mirror (e.g., two one-dimensional scanning mirrors which may be micro-electromechanical system (MEMS) based or piezoelectric based). The projector is communicatively coupled to a controller and a non-temporary processor-readable storage medium or memory that stores processor-executable instructions and other data that cause the controller to control the operation of the projector when the controller is running. In some embodiments, the controller is communicatively coupled to a processor (not shown) that controls the scanning area size and scanning area position of the projector and generates content to be displayed on the display system 100. The projector scans light over a variable area specified in the FOV area 106 of the display system 100. The scanning area size corresponds to the size of the FOV area 106, and the scanning area position corresponds to one of the lens elements 108, 110 in which the FOV area 106 is visible to the user. Generally, it is desirable for a display to have a wide FOV to accommodate light outcoupling over a wide range of angles. In this specification, the range of eye positions of different users from which the display can be viewed is referred to as the eye box of the display.

[0023] In some embodiments, the projector transmits light through a first scanning mirror, a second scanning mirror, an optical relay positioned between the first and second scanning mirrors, and a waveguide positioned at the output of the second scanning mirror. In some embodiments, an optical scanner including one or more of the first scanning mirror, the second scanning mirror, or the optical relay includes multiple reflective and transmitting elements that selectively direct light to a specific in-coupler of a waveguide having multiple in-couplers based on one of several different optical properties (e.g., wavelength range or polarization state). Multiple in-couplers offer the advantage of higher light in-coupling efficiency, thereby increasing the amount of light propagated through the waveguide to the corresponding out-coupler for out-coupling to the FOV region 106, with at least a portion of the out-coupler (or multiple out-couplers) overlapping with the FOV region 106. Furthermore, the optical scanner allows for multiple in-coupler configurations within the form factor of the support structure 102, as will be described in more detail below.

[0024] Figure 2 shows a simplified block diagram of a projection system 200 that projects an image directly onto the user's eye via light, such as laser light or microdisplay light. The projection system 200 includes an optical engine 202, an optical scanner 204, and a waveguide 205. In some embodiments, the optical scanner 204 includes a first scanning mirror 206, a second scanning mirror 208, and an optical relay 210. The waveguide 205 includes an in-coupler 212 and an out-coupler 214, the out-coupler 214 being optically aligned with the user's eye 216 in this example. In some embodiments, the projection system 200 is implemented in a wearable head-up display or other display system such as the display system 100 in Figure 1.

[0025] In some embodiments, the optical engine 202 (also referred to as the projector) includes one or more light sources configured to generate and output light 218 (e.g., visible laser light such as red, blue, and green laser light, and / or invisible laser light such as infrared laser light). In some embodiments, the optical engine 202 is coupled to a driver or other controller (not shown) and, in accordance with instructions received from a computer processor coupled to it by the controller or driver, controls the timing of light emission from the light sources of the optical engine 202 to modulate the light 218 so that it is perceived as an image when output to the retina of the user's eye 216. In some embodiments, the optical engine 202 includes one or more laser light sources. In other embodiments, the optical engine 202 includes one or more light-emitting diode (LED) light sources, or other types of LED displays (e.g., microLED displays), liquid crystal displays (LCDs), or dot matrix displays (DMDs).

[0026] For example, during the operation of the projection system 200, multiple light beams, each having a different wavelength, are output by the light source of the optical engine 202, then combined via a beam combiner (not shown), and finally directed towards the user's eye 216. The optical engine 202 modulates the intensity of each light beam so that the combined light reflects a set of pixels in the image, with a specific intensity of each light beam at any given time contributing to the corresponding color content and luminance of the pixels represented by the combined light at that time.

[0027] In some embodiments, one or both of the scanning mirrors 206 and 208 of the optical scanner 204 are MEMS mirrors. For example, scanning mirrors 206 and 208 are MEMS mirrors driven by their respective operating voltages and vibrate during the active operation of the projection system 200, causing the scanning mirrors 206 and 208 to scan light 218. The vibration of scanning mirror 206 causes light 218 output by the optical engine 202 to pass through the optical relay 210 and be scanned across the surface of the second scanning mirror 208. The second scanning mirror 208 scans the light 218 received from scanning mirror 206 toward the in-coupler 212 of the waveguide 205. In some embodiments, scanning mirror 206 vibrates along a first scanning axis 219 so that light 218 is scanned only in one dimension (i.e., linearly) across the surface of the second scanning mirror 208. In some embodiments, the scanning mirror 208 vibrates along the second scanning axis 221 or rotates in other ways. In some embodiments, the first scanning axis 219 is perpendicular to the second scanning axis 221.

[0028] In some embodiments, the in-coupler 212 has a substantially rectangular shape and is configured to receive light 218 and direct the light 218 into the waveguide 205. The in-coupler 212 is defined by a smaller dimension (i.e., width) and a larger orthogonal dimension (i.e., length). In one embodiment, the optical relay 210 is a line-scanning optical relay that receives light 218 scanned in a first dimension (e.g., a first dimension corresponding to the smaller dimension of the in-coupler 212) by a first scanning mirror 206, sends the light 218 to a second scanning mirror 208, and introduces convergence of the light 218 in the first dimension to an exit pupil beyond the second scanning mirror 208. Hereinafter, “exit pupil” in an optical system refers to a location along the optical path where light beams intersect. For example, the possible optical paths of light 218 following reflection by the first scanning mirror 206 initially spread along the first scanning axis, but later, these paths intersect at an exit pupil beyond the second scanning mirror 208 due to convergence introduced by the optical relay 210. For example, the width (i.e., minimum dimension) of a given exit pupil approximately corresponds 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 scanning mirror 208, or includes a shaped reflection relay that includes two or more spherical, aspherical, parabolic, and / or free-form surface lenses that shape and direct the light 218 onto the second scanning mirror 208. The second scanning mirror 208 receives light 218 and scans the light 218 in a second dimension, the second dimension corresponding to the length dimension of the in-coupler 212 of the waveguide 205. In some embodiments, the second scanning mirror 208 causes the exit pupil of light 218 to sweep along a line along the second dimension. In some embodiments, the in-coupler 212 is positioned downstream of the second scanning mirror 208 on or near the sweep line so that the second scanning mirror 208 scans the light 218 as a line or row on the in-coupler 212.

[0029] In some embodiments, the optical engine 202 includes an end-emitting laser (EEL) that emits a laser beam 218 having a substantially elliptical, non-circular cross-section, and the optical relay 210 magnifies or minimizes the laser beam 218 along its major and minor radii to circularize the laser beam 218 before it converges onto the second scanning mirror 208. In some such embodiments, the surface of the mirror plate of the scanning mirror 206 is elliptical and non-circular (e.g., similar in shape and size to the cross-sectional area of ​​the laser beam 218). In other such embodiments, the surface of the mirror plate of the scanning mirror 206 is circular.

[0030] The waveguide 205 of the projection system 200 includes an in-coupler 212 and an out-coupler 214. As used herein, the term “waveguide” is understood to mean a combiner that uses one or more of the following: total internal reflection (TIR), dedicated filters, and / or reflective surfaces, to transmit light from an in-coupler (e.g., in-coupler 212) to an out-coupler (e.g., out-coupler 214). In some display applications, the light is a collimated image, and the waveguide transmits and replicates the collimated image to the eye. Generally, the terms “in-coupler” and “out-coupler” are understood to refer to any type of optical grating structure, including but not limited to diffraction gratings, holograms, holographic optical elements (e.g., optical elements using one or more holograms), volume diffraction gratings, volume holograms, surface relief diffraction gratings, and / or surface relief holograms. In some embodiments, a given in-coupler or out-coupler is configured as a transmissive grating (e.g., a transmissive diffraction grating or a transmissive holographic grating) that transmits light through the in-coupler or out-coupler and applies an optical function(s) designed for 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) that reflects light through the in-coupler or out-coupler and applies an optical function(s) designed for the light during reflection. In this example, light 218 received by the in-coupler 212 is relayed to the out-coupler 214 via the waveguide 205 using TIR. The light 218 is then output to the user's eye 216 via the out-coupler 214. As described above, in some embodiments, the waveguide 205 is implemented as part of an eyeglass lens, such as lens 108 or lens 110 (Figure 1) of a display system that has the form factor of eyeglasses and uses a projection system 200.

[0031] In some embodiments, although shown as a single incoupler 212 in Figure 2, the waveguide 205 includes multiple incouplers 212. The multiple incouplers are arranged either in a common waveguide such as waveguide 205, or in a stack of waveguides (multiple waveguides 205 stacked on top of each other) each having an incoupler. In some embodiments, each of the multiple incouplers is tuned to incouple light with specific optical properties to improve the overall incoupling efficiency of the projection system 200. Adjustable incoupler grating parameters include, but are not limited to, grating height, grating spacing, grating angle, and grating density. To effectively implement multiple incoupler waveguides with a single optical engine 202, the optical scanner 204 includes multiple reflective and transmitting elements that separate light 218 based on one or more optical properties and direct each portion of the light to its respective incoupler. Furthermore, the multiple reflective and transmitting elements of the optical scanner are designed and arranged (within a margin of difference) to equalize the optical path lengths of the light directed to each incoupler. The optical path length is understood to be the product of the geometric length of the optical path and the refractive index and geometric shape of the medium through which the light propagates. Optical scanners, which include multiple reflective and transmissive elements, are described in more detail below.

[0032] The terms “incoupler” and “incoupler grate” are used to correspond to each other in this specification and the related drawings unless otherwise specified. Therefore, descriptions such as “first incoupler grate,” “second incoupler grate,” “third incoupler grate,” etc. (for example, “first grate,” “second grate,” “third grate”) correspond to “first incoupler,” “second incoupler,” and “third incoupler,” respectively, unless otherwise indicated.

[0033] Although not shown in the example in Figure 2, in some embodiments, multiple reflective and transmitting elements are included in any of the optical paths (for shaping light so that it is visible to the user's eye 216) between the optical engine 202 and the scanning mirror 206, between the scanning mirror 206 and the optical relay 210, between the optical relay 210 and the scanning mirror 208, between the scanning mirror 208 and the in-coupler 212, between the in-coupler 212 and the out-coupler 214, and / or between the out-coupler 214 and the eye 216. For example, in some embodiments, a prism or prism assembly is used to guide light from the scanning mirror 208 into the corresponding in-coupler 212 so that the light is coupled into the corresponding in-coupler 212 at an appropriate angle to facilitate the propagation of light in the waveguide 205 by TIR. In some embodiments, an exit pupil expander, such as a folding grid (e.g., the exit pupil expander 304 in Figure 3, described later), is positioned at an intermediate stage between the in-coupler 212 and the out-coupler 214 to receive the light coupled into the waveguide 205 by the in-coupler 212, expand the light, and redirect the light toward the out-coupler 214, where the out-coupler 214 then couples the light out of the waveguide 205 (e.g., toward the user's eye 216). In some embodiments, the projection system 200 includes a plurality of exit pupil expanders, each of which optically couples the respective in-coupler of a plurality of in-coupler systems with its respective out-coupler.

[0034] Figure 3 shows examples of light propagation within the waveguide 205 of the projection system 200 of Figure 2, according to several embodiments. It is shown with one in-coupler 212, one exit pupil expander 304, and one out-coupler 214, but this is for clarity, and it will be understood that in some embodiments the waveguide may include multiple instances of each. In such configurations, for example, each in-coupler 212 is tuned to in-coupled light of specific optical properties (e.g., wavelength range or polarization state) to proceed to the corresponding exit pupil expander 304 and the corresponding out-coupler 214. An optical scanner having multiple reflective and transmitting elements receives light, separates the light, and directs each portion of the light to one of the respective in-couplers. As shown, light scanned along axis 302, received through the in-coupler 212, is directed into the exit pupil expander (EPE) 304, and then sent to the out-coupler 214 for output (e.g., towards the user's eye). In some embodiments, the exit pupil expander 304 expands one or more dimensions of the eyebox of the WHUD, including the projection system 200 (e.g., relative to the dimensions of the eyebox of the WHUD without the exit pupil expander 304). In some embodiments, the in-coupler 212 and the exit pupil expander 304 each include their respective one-dimensional diffraction gratings (i.e., diffraction gratings extending along one dimension). In the example of Figure 3, the in-coupler 212 directs all or a substantial portion of the incoming light straight down in a first direction perpendicular to the scanning axis 302 (relative to the currently shown figure), and the exit pupil expander 304 directs it to the right in a second direction perpendicular to the first direction (relative to the currently shown figure). Although not shown in this example, it is understood that in some embodiments, the first direction in which the in-coupler 212 directs the light is not strictly perpendicular to the scanning axis 302, but slightly or substantially oblique.

[0035] Figure 4 shows an enlarged view 400 of a waveguide stack 402 having multiple waveguides 405A, 405B. In some embodiments, the waveguide stack including waveguides 405A, 405B corresponds to waveguide 205 in Figures 2 and 3. Each of the waveguides 405A, 405B in the waveguide stack has in-couplers 412A, 412B, respectively, exit pupil expanders (EPEs) 404A, 404B, respectively, and out-couplers 414A, 414B, respectively. The in-couplers 412A, 412B of the waveguide stack 400 are offset from each other, i.e., they do not completely overlap with respect to each other in the waveguide stack 400. This offset of the in-coupler positions makes it possible to direct light with specific optical properties to each in-coupler that is tuned to in-couple light with those specific optical properties. For example, incoupler 412A is tuned to incouple light in a first wavelength range (e.g., corresponding to red light), and incoupler 412B is tuned to incouple light in a second wavelength range (e.g., corresponding to blue and green light). By tuning incouplers 412A and 412B to incouple light in specific wavelength ranges and include the aforementioned offset, the overall incoupling efficiency of the waveguide stack is increased, thereby increasing the amount of light propagated to the user.

[0036] Figure 5 shows a top view 500 and a side view 550 of a portion of the waveguide stack, including the waveguide stack 402 which includes the first waveguide 405A and the second waveguide 405B. As shown in the figure, the in-coupler 412A of the first waveguide 405A is offset from the in-coupler 412B of the second waveguide 405B. Therefore, light 502 incident on the in-coupler 412A is in-coupled and propagated within the first waveguide 405A, and light 504 incident on the in-coupler 412B is in-coupled and propagated within the second waveguide 405B. Light propagating from in-coupler 412A in the first waveguide 405A is directed to the corresponding EPE 404A, passes through EPE 404A, and reaches the corresponding out-coupler 414A. Light propagating from in-coupler 412B in the second waveguide 405B is directed to the corresponding EPE 404B, passes through EPE 404B, and reaches the corresponding out-coupler 414B. In this figure, out-couplers 414A and 414B are shown to substantially overlap to output light to similar FOVs of the WHUD, but it is understood that other configurations, such as out-couplers dedicated to specific portions of the WHUD's entire FOV, are similarly considered and covered by this disclosure.

[0037] In some embodiments, each of the in-couplers 412A and 412B is tuned to in-couple light with specific optical properties, such as a particular wavelength range or polarization state. For example, light 502 directed to the first in-coupler 412A has a wavelength range corresponding to red light, and light 504 directed to the second in-coupler 412b has wavelength ranges corresponding to blue and green light. Techniques for optical scanners to effectively separate light based on its wavelength range (i.e., color) and direct each portion of the light to its respective in-coupler 412A and 412B are described in detail below. These techniques include the use of beam splitters to separate the light and reflective surfaces(s) to direct portions of the light to the corresponding in-couplers. Furthermore, additional elements such as prisms and / or lenses may, for example, equalize the optical path length of each portion of the light to improve the quality of the image provided to the user.

[0038] Figure 6 shows a portion of a waveguide stack having two waveguides 405A and 405B, and a top view 600 of a portion of an optical scanner having multiple reflective and transmissive elements 620, 622, 634, and 636. In some embodiments, the waveguide stack having waveguides 405A and 405B corresponds to the waveguide stack 402 in Figure 2.

[0039] In some embodiments, the plurality of reflective and transmitting elements 620, 622, 634, 636 include folding mirrors that receive the input light 601, separate the input light 601 into optical portions based on one or more optical properties, and deliver them to the in-coupler 412A of waveguide 405A and the in-coupler 412B of waveguide 404B. For example, the in-coupler 412B is tuned to incouple red light, and the in-coupler 412A is tuned to incouple blue and green light. In this case, the plurality of reflective and transmitting elements include a prism assembly having two prisms 620, 622, a first selective transmitting layer 634 such as a dichroic mirror that transmits blue and green light toward the in-coupler 412A and reflects red light toward the in-coupler 412B, and a reflective surface 636 such as a mirror for reflecting the blue and green light from the selective transmitting layer 634 toward the in-coupler 412A. Furthermore, the multiple reflective and transmitting elements 620, 622, 634, and 636 are configured such that the pupil plane of each separated portion of light coincides with the position of each in-coupler (i.e., in-couplers 412A and 412B) in different planes (i.e., waveguides 405A and 405B). The optical path length satisfies the relationship a+b=c (or falls within a specified margin of the difference in the relationship), in other words, the length of the optical path to the corresponding in-coupler for each separated portion of light is the same. In this example, optical path portion "a" corresponds to the portion from reflective surface 636 to in-coupler 412A, optical path portion "b" corresponds to the portion from selective reflective surface 634 to reflective surface 636, and optical path portion "c" corresponds to the portion from selective reflective surface 634 to in-coupler 412B. In some embodiments, the dimensions and materials of the prisms 620 and 622 are selected to satisfy the optical path length formula described above. For example, the material is selected from one or more types of glass, one or more types of plastic, or any combination thereof. Furthermore, as shown in Figure 6 and subsequent figures, the optical path length is partially based on the thickness of the waveguide substrates 405A and 405B. Thus, the optical scanner shown in Figure 6 effectively guides each portion of the light to its respective in-coupler 412A and 412B while equalizing the optical path length (within the margin of difference).This increases the amount of incoupled light within waveguides 405A and 405B, improving the quality of the image delivered to the user.

[0040] Figure 7 shows a portion of a waveguide stack having two waveguides 405A and 405B, and a top view 700 of a portion of an optical scanner having multiple reflective and transmissive elements 720, 722, 734, and 736. In some embodiments, the waveguide stack having waveguides 405A and 405B corresponds to the waveguide stack 402 in Figure 2.

[0041] Multiple reflective and transmitting elements include a beam splitter 734 positioned between two prism assemblies having two prisms 720, 722. In some embodiments, the beam splitter 734 is a polarizing beam splitter, a dichroic beam splitter (i.e., a dichroic mirror), or a proportional (i.e., 50T / 50R, 90T / 10R, 33T / 67R, 90R / 10T, etc.) beam splitter. Generally, the beam splitter 734 separates the input light into light with two or more optical properties. For example, a dichroic mirror is used to separate the light into light of different wavelengths (i.e., colors) by reflecting red light to the in-coupler 412B, transmitting blue and green light, and then reflecting the blue and green light from a reflective surface 736 such as a mirror to the in-coupler 412A. In some embodiments, the dimensions and materials of the prisms 720, 722 are selected such that they satisfy the optical path length relationship a+b=c (or are within a specified margin of the difference in the relationship), i.e., the length of the optical path each separated portion of light reaches the corresponding in-coupler is the same. In this example, optical path portion "a" corresponds to the portion from the reflecting surface 736 to the in-coupler 412A, optical path portion "b" corresponds to the portion from the beam splitter 734 to the reflecting surface 736, and optical path portion "c" corresponds to the portion from the beam splitter 734 to the in-coupler 412B. For example, the material is selected from one or more types of glass, one or more types of plastic, or any combination thereof. As shown in Figure 7, the light 701 received by the first prism 720 contains "n" optical paths (in this example, n=3), but the multiple reflecting and transmitting elements 720, 722, 734, 736 of the optical scanner have the same optical path length, i.e., a n +b n =c n While maintaining this characteristic, it is still possible to separate the light of each optical property and effectively guide it to its respective incoupler. This increases the amount of light incoupled in the waveguide, improving the quality of the image delivered to the user.

[0042] Figures 4-7 show two waveguides 405A and 405B in a waveguide stack, but in some embodiments the waveguide stack includes three or more waveguides, and the waveguide incouplers are arranged offset from each other so as not to completely overlap. Such configurations are described in more detail in Figure 8. Furthermore, it is understood that the concepts discussed herein can be extended to other quantities, such as four or more waveguides in the waveguide stack, depending on the required level of optical resolution based on optical considerations.

[0043] Figure 8 shows a portion of a waveguide stack having three waveguides 405A, 405B, and 405C, each with its corresponding in-coupler 412A, 412B, and 412C, as well as a top view 800 of a portion of an optical scanner having a plurality of reflective and transmissive elements 820-830. In some embodiments, the plurality of reflective and transmissive elements include a prism assembly having three prisms 820, 822, and 824, two beam splitters 826, and 828, and one reflective surface 830 such as a mirror. The beam splitters 826, and 828 are one or more of the following: polarizing beam splitters, dichroic beam splitters (i.e., dichroic mirrors), or proportional (i.e., 50T / 50R, 90T / 10R, 33T / 67R, 90R / 10T, etc.) beam splitters. Generally, beam splitters 826 and 828 separate the light 801 input into the system into light with three optical properties. For example, when separating light into different wavelength ranges, the first dichroic mirror 826 reflects the light in the first wavelength range (e.g., red) to the in-coupler 412C and transmits the light in the second wavelength range (e.g., green) and the third wavelength range (e.g., blue). The second dichroic mirror 828 reflects the light in the second wavelength range (e.g., green) to the in-coupler 412B and transmits the light in the third wavelength range (e.g., blue), which is then reflected by a reflective surface 830 such as a mirror and reaches the in-coupler 412A. In some embodiments, the dimensions and materials of prisms 820, 822, and 824 are selected such that they satisfy the optical path length relationship a+b+d=c+d=e (or fall within a specified margin of the difference in the relationship), i.e., the length of the optical path to the corresponding incoupler for each separated portion of light is the same. In this example, optical path portion "a" corresponds to the portion from the reflecting surface 830 to the incoupler 412A, optical path portion "b" corresponds to the portion from the beam splitter 828 to the reflecting surface 830, optical path portion "c" corresponds to the portion from the beam splitter 828 to the incoupler 412B, optical path portion "d" corresponds to the portion from the beam splitter 826 to the beam splitter 828, and optical path portion "e" corresponds to the portion from the beam splitter 826 to the incoupler 412C.For example, the materials are selected from one or more types of glass, one or more types of plastic, or any combination thereof. This increases the amount of light incoupled in waveguides 405A, 405B, and 405C, improving the quality of the image delivered to the user.

[0044] The embodiment shown in Figure 8 offers the additional advantage of allowing each incoupler to be more precisely tuned to incouple light with a narrower range of optical properties. For example, when two incouplers are used, each incoupler can be more precisely tuned to incouple light with one of three wavelength ranges instead of just one of two. This improves the coupling efficiency of each incoupler and further improves the coupling efficiency of the entire waveguide, resulting in higher quality images being delivered to the user.

[0045] Figure 9 shows a top view 900 of a block diagram of an optical scanner having an optical relay system, such as the one shown in Figure 2, which has optical focusing elements 912, 914 positioned in the optical path from a scanning MEMS mirror 902 to a plurality of reflective and transmitting elements 720, 722, 734, 736, as shown in Figure 7, for example. In some embodiments, the MEMS mirror 902 corresponds to one of the mirrors 206 or 208 in Figure 2. In some embodiments, the MEMS mirror 902 corresponds to 206, and the plurality of reflective elements 720, 722, 734, 736 are (in this example) included instead of mirror 208 in Figure 2. The optical focusing elements 912, 914 of the optical relay (such as the one corresponding to 210) are lenses that direct light toward the plurality of reflective and transmitting elements 720, 722, 734, 736. Figure 10 shows Figure 1000 zoomed in on a portion of Figure 9. As shown in Figure 10, the optical focusing element 904 is positioned in front of the multiple transmitting and reflecting elements 720, 722, 734, and 736 to direct the light into the first element, i.e., the prism 720 in this example.

[0046] FIG. 11 shows a top view 1000 of a portion of a waveguide stack having two waveguides 405A, 405B and a portion of an optical scanner. In some embodiments, the waveguide stack having waveguides 405A, 405B corresponds to the waveguide stack 402 of FIG. 2. The optical scanner includes a plurality of transmissive and reflective elements 1120, 1122, 1124, 1126 including optical focusing elements 1120, 1122 disposed between a beam splitter 1124 and a reflective surface 1126, and stacked waveguides 405A, 405B. In this embodiment, the two optical focusing elements 1120, 1122 are disposed in the optical path after the beam splitter 1124, the optical focusing element 1120 is disposed between the beam splitter 1124 and the incoupler 412B, and the optical focusing element 1122 is disposed between the beam splitter 1124 and the reflective surface 1126. As shown in FIG. 11, the optical focusing elements 1120, 1122, together with the beam splitter 1124 and the reflective surface 1126, separate the received light 1101 into two portions and direct each portion to coincide with one of the two incouplers 412A, 412B. The dimensions and materials of the optical focusing elements 1120 and 1122 are designed and selected such that the light beams coincide with the respective incouplers 412A, 412B (within a margin of difference). The plurality of transmissive and reflective elements 1120, 1122, 1124, 1126 are arranged and designed such that the relationship of the optical path lengths represented as a n +b n =c n is satisfied (or within a specified margin of difference in the relationship), i.e., the optical path lengths of each portion of the separated light reaching the corresponding incoupler are the same. In this example, the optical path portion "a n " corresponds to the portion from the reflective surface 1126 to the incoupler 412a, the optical path portion "b n " corresponds to the portion from the beam splitter 1124 to the reflective surface 1126, and the optical path portion "c nThe section from beam splitter 1124 to in-coupler 412B corresponds to n=3 in this example (corresponding to three optical paths). For example, the material can be selected from one or more types of glass, one or more types of plastic, or any combination thereof. The configuration shown in Figure 11 improves the coupling efficiency of each in-coupler and the overall coupling efficiency of the waveguide, resulting in more light propagating through waveguides 405A and 405B and delivering a higher quality image to the user.

[0047] Figure 12 shows a top view 1200 of waveguide 1205, such as a portion of waveguide 205 in Figure 2, which has a plurality of in-couplers 1212A, 1212B and a portion of the optical scanner. As shown in Figure 12, the plurality of in-couplers 1212A and 1212B are arranged on a common waveguide substrate 1205. The optical scanner includes a plurality of reflective and transmitting elements 1220-1226, including a beam splitter 1224 and a reflective surface 1226, which receive light 1201 and separate the light 1201 into two parts based on its optical properties and direct each part to its respective in-coupler. However, unlike the waveguide stack in the previous figure, the optical path lengths directed to each incoupler by each portion of the light are not equal; that is, the relationship of the optical paths in this case is a+b≠c, where optical path portion "a" corresponds to the portion from the reflecting surface 1226 to incoupler 1212A, optical path portion "b" corresponds to the portion from the beam splitter 1224 to the reflecting surface 1226, and optical path portion "c" corresponds to the portion from the beam splitter 1224 to incoupler 1212B. Therefore, the pupil plane of the optical relay does not coincide with both incouplers 1212A and 1212B at the same time. This is further illustrated in Figure 13 as an example. As shown in 1300, when the pupil plane of the second portion of the light coincides with the second incoupler (shown in 1302), the pupil plane of the first portion of the light corresponding to the first incoupler extends beyond the first incoupler (shown in 1304). Alternatively, as shown in 1350, when the pupil plane of the first portion of light coincides with the first incoupler (shown in 1352), the pupil plane of the second portion of light corresponding to the second incoupler occurs in front of the second incoupler (shown in 1354). The scenario shown in 1350 results in a pupil walk 1402 at the second incoupler 1354, which is illustrated in more detail in Figure 14, where an arrow 1405 indicates the direction of light propagation. In some embodiments, to minimize double bounce losses, the system typically allows colors with larger bounce intervals (i.e., red light) to have a pupil walk 1402.As will be described in more detail below, in some embodiments, the multiple reflective and transmissive elements include secondary optical relay elements for refocusing the secondary pupil plane to each in-coupler, thereby preventing or reducing pupil walk and improving the quality of the image provided by the waveguide.

[0048] For example, this secondary optical relay element is included in the optical path of light incident on the in-coupler 1212A, as shown in Figures 15 and 16. In some embodiments, the secondary optical relay element is one of a lens group, a reflector, a metasurface, or a combination thereof. Although shown in the optical path to the in-coupler 1212A, in alternative embodiments, the secondary optical relay element is included in the optical path to the in-coupler 1212B to address a scenario shown, for example, 1300. The secondary optical relay element refocuses the light beam, and as a result, the secondary pupil plane is focused on each in-coupler. This improves the quality of the image provided to the user. Furthermore, since multiple in-couplers are arranged on a common waveguide substrate as opposed to a waveguide stack, the thickness of the waveguide components is reduced.

[0049] Figure 15 shows a top view 1500 corresponding to 1350, with a lens 1528 added as a secondary optical relay element to a plurality of reflective and transmitting elements. In some embodiments, the optical scanner also includes a plurality of reflective and transmitting elements 1220-1226, including a beam splitter 1224 and a beam splitter 1224, and a beam splitter 1224, which collectively receive light 1501 and separate the light 1501 into two parts based on its optical properties, directing each part to its respective in-coupler 1212A, 1212B. As shown, the lens 1528 refocuses a portion of the second part of the light beam passing through the beam splitter 1224, so that the secondary pupil plane 1534 coincides with the in-coupler 1212A. The original pupil plane 1354 is also shown. The dimensions and material of the lens 1528 are designed and selected so that the secondary pupil plane 1534 coincides with the in-coupler 1212A. For example, the material is selected from one or more types of glass, one or more types of plastic, or any combination thereof. Thus, pupil walk is minimized or completely avoided.

[0050] Figure 16 shows a top view 1600 of a configuration similar to that shown in Figure 15, but with a metasurface 1628 as a secondary optical relay element instead of the lens 1528 shown in Figure 15. The metasurface 1628 refocuses the light beam directed to the in-coupler 1212A so that the secondary pupil surface 1634 coincides with the in-coupler 1212A. The material and / or design of the metasurface is artificially designed so that the secondary pupil surface 1634 coincides with the in-coupler 1212A. For example, the metasurface consists of a thin film containing a set of elements specifically designed to provide the desired refractive quality. Thus, pupil walk is minimized or completely avoided, and the waveguide improves the quality of the image delivered to the user.

[0051] Figure 17 shows a top view 1700 of a portion of waveguide 1205, such as the one corresponding to waveguide 205 in Figure 2, which has a portion of optical scanner having a plurality of in-couplers 1212A, 1212B and a plurality of transmission and reflection elements 1740, 1742, 1744, 1746, 1748, 1750 according to several embodiments. Similar to Figures 15-16, waveguide 1205 includes a plurality of in-couplers 1212A, 1212B. In this example, an additional prism 1740 and air gap 1742 of the plurality of reflection and transmission elements 1740-1750 solve the pupil walk problem. The optical scanner also includes a prism assembly having prisms 1744 and 1748 in the plurality of reflection and transmission elements, a beam splitter 1746, and a mirror 1750. Multiple reflective and transmitting elements 1740-1750 equalize the optical path lengths (within a margin of difference) of the portions of light directed to in-couplers 1212A and 1212B. That is, the optical path lengths satisfy the relationship a+b=c+d (or fall within a specified margin of difference of the relationship), i.e., the length of the optical path to each separated portion of light arriving at the corresponding in-coupler is the same. In this example, optical path portion "a" corresponds to the portion from mirror 1750 to in-coupler 1212A, optical path portion "b" corresponds to the portion from beam splitter 1746 to mirror 1750, optical path portion "c" corresponds to the portion from beam splitter 1746 to the interface of prism 1744 and air gap 1742, and optical path portion "d" corresponds to the portion from the interface of prism 1744 and air gap 1742 to in-coupler 1212B. Specifically, input light 1701 enters prism 1740. The input angle and prism material are designed and selected so as not to exceed the TIR critical angle at the exit surface / air gap 1742. The light continues until it interacts with beam splitter 1746, positioned between prisms 1744 and 1748. A second portion of the light continues through the beam splitter, reflecting off mirror surface 1750 and heading towards incoupler 1212A, while a first portion of the light reflects off beam splitter 1746, returns towards air gap 1742, and reflects off the interface between prism 1744 and air gap 1742, heading towards incoupler 1212B.In some embodiments, the mirror surface 1750 is a TIR reflecting surface, a metallic mirror, or a dielectric mirror.

[0052] The prism angles shown in 1700 are designed so that the reflected light satisfies the TIR condition and is directed toward each in-coupler, e.g., in-coupler 1212B. Similar to the multiple substrate examples described above, the beam splitter 1746 is a polarizing beam splitter, a dichroic beam splitter (i.e., a dichroic mirror), or a proportional (i.e., 50T / 50R, 90T / 10R, 33T / 67R, 90R / 10T, etc.) beam splitter. For example, a dichroic beam splitter is used to direct light of different wavelengths (i.e., colors) toward in-couplers 1212A and 1212B. The dimensions and / or materials of the multiple reflective and transmitting elements 1740-1750 are selected so that the optical path lengths a, b, c, and d satisfy the equation a+b=c+d (or are within the margin of difference). Therefore, eye movement is minimized or completely avoided, resulting in improved image quality delivered to the user.

[0053] Figure 18 shows a top view 1800 of a portion of waveguide 1205, such as the one corresponding to waveguide 205 in Figure 2, which has multiple in-couplers 1212A, 1212B and a portion of the optical scanner. The optical scanner includes multiple reflective and transmitting elements 1844-1850, including a beam splitter 1846 and a mirror 1850, as well as a prism assembly having prisms 1844, 1846. In some embodiments, the optical scanner shown in Figure 18 is substantially the same as that shown in Figure 17, except that it has a prism 1740 and no air gap 1742. The dimensions and materials of the multiple reflective and transmitting elements 1844-1850 are selected such that the optical path lengths a, b, c, and d satisfy the relationship a+b=c+d (or fall within a specified margin of the difference in the relationship), i.e., the length of the optical path to each portion of separated light reaching the corresponding in-coupler is the same. In this example, optical path section "a" corresponds to the section from mirror 1850 to incoupler 1212A, optical path section "b" corresponds to the section from beam splitter 1846 to mirror 1850, optical path section "c" corresponds to the section from beam splitter 1846 to interface 1860 of prism 1844, and optical path section "d" corresponds to the section from interface 1860 of prism 1844 to incoupler 1212B. Therefore, pupil walk is minimized or completely avoided, resulting in improved image quality delivered to the user.

[0054] Figure 19 shows Figures 1900A to 1900D illustrating an example of separating a red light beam and a blue + green light beam from an incident light 1901. As shown in 1900A, the multiple reflective and transmitting elements of the optical scanner include a TIR prism 1940, an air gap 1942, a dichroic mirror 1934, a mirror surface 1936, and a MEMS structure 1908. The area marked 1912B indicates the region where the blue + green light beam is directed toward its respective incoupler, and the area marked 1912A indicates the region where the red light beam is directed toward its respective incoupler. 1900B shows the separation of the blue + green light beam from the red light beam, 1900C focuses on the path of the red light beam, and 1900D focuses on the path of the blue + green light beam.

[0055] Figure 20 shows a top view of a portion of waveguide 1205, such as waveguide 205 in Figure 2, which has a plurality of in-couplers 1212A and 1212B and a portion of an optical scanner. In this embodiment, the optical scanner includes a plurality of reflective and transmitting elements 2002-2014 that receive input light 2001, separate the input light 2001 into two parts based on polarization technique, and direct each part of the light to one of two in-couplers 1212A, 1212B. For example, in-coupler 1212A is tuned to in-couple light in a first polarization state, and in-coupler 1212B is tuned to in-couple light in a second polarization state. In some embodiments, depending on the system configuration, polarization separation technique is selected over color separation technique to reduce the number or space of components. Depending on the type of coupler, for example, the response of the coupler as a function of polarization versus color, polarization separation technique is selected as opposed to color separation technique.

[0056] The multiple reflective and transmitting elements 2002-2014 include a prism assembly having prisms 2002, 2006, and 2012, a polarizing beam splitter (PBS) 2004, a waveplate 2008, a beam splitter 2010, and a mirror 2014. In some embodiments, the waveplate 2008 is a fractional waveplate, e.g., a quarter waveplate (QWP) or a half waveplate; the mirror 2414 is a TIR reflector, a metallic mirror, or a dielectric mirror; and the beam splitter 2010 is a dichroic beam splitter or a proportional (i.e., 50T / 50R, 90T / 10R, 33T / 67R, 90R / 10T, etc.) beam splitter that separates light.

[0057] For example, P-polarized light 2001 enters prism 2002 and is transmitted through PBS 2004. The light passes through waveplate 2008 and is converted to circular polarization. A portion of the light continues through beam splitter 2010, reflects off mirror surface 2014 and heads toward incoupler 1212A, while the remaining light is reflected from beam splitter 2010 and returns through waveplate 2008. The two passes through waveplate 2008 convert the polarization state from P-polarized to S-polarized. The S-polarized light continues toward PBS 2004, reflects off PBS 2004 and heads toward incoupler 1212B. The dimensions and materials of the multiple reflective and transmitting elements 2002-2014 are selected and designed such that the optical path lengths a, b, c, and d satisfy the relationship a+b=c+d (or fall within a specified margin of the difference in the relationship), i.e., the length of the optical path to each separated portion of the light reaching the corresponding incoupler is the same. In this example, optical path section "a" corresponds to the section from mirror 2014 to in-coupler 1212A, optical path section "b" corresponds to the section from beam splitter 2010 to mirror 2014, optical path section "c" corresponds to the section from beam splitter 2010 to PBS2004, and optical path section "d" corresponds to the section from PBS2004 to in-coupler 1212B. Therefore, the waveguide improves the quality of the image delivered to the user.

[0058] Figure 20 shows that multiple reflective and transmitting elements, such as PBS2004, waveplate 2008, beam splitter 2010, and mirror 2014, are implemented in a structure such as a prism assembly, although in some embodiments the same function is achieved using separate components. In Figure 21, PBS2104, waveplate 2108, beam splitter 2110, and mirror 2114 correspond to similar components in Figure 20, except that they are implemented without the prism assembly shown in Figure 20. In other words, the multiple reflective and transmitting elements 2104, 2108, 2110, and 2114 are separate components designed and positioned such that the optical path lengths a, b, c, and d satisfy the relationship a+b=c+d (or fall within a specified margin of the difference in the relationship), i.e., the length of the optical path to which each separated portion of light reaches the corresponding in-coupler is the same. In this example, optical path portion "a" corresponds to the section from mirror 2114 to in-coupler 1212A, optical path portion "b" corresponds to the section from beam splitter 2110 to mirror 2114, optical path portion "c" corresponds to the section from beam splitter 2110 to PBS2104, and optical path portion "d" corresponds to the section from PBS2104 to in-coupler 1212B. Therefore, multiple reflective and transmitting elements include fewer components than shown in Figure 20, but it is still possible to improve the quality of the image delivered by the waveguide.

[0059] Figure 22 shows a top view of waveguide 1205, such as the one corresponding to waveguide 205 in Figure 2, which has a plurality of in-couplers 1212A and 1212B and a portion of an optical scanner. In this embodiment, the optical scanner includes a plurality of reflective and transmitting elements 2204-2212 that direct light from the scanning MEMS mirror 2202 to one of the two in-couplers 1212A and 1212B by using a plurality of optical lenses 2204, 2210, and 2212 with different magnifications in the optical path to each in-coupler. For example, the focal length of lens 2210 is not equal to the focal length of lens 2212. Thus, the magnification of each optical path of light to each in-coupler 1212A and 1212B is different. This makes it possible to magnify the fixed-diameter spot size in the MEMS mirror 2202 (i.e., limited by the size of the mirror aperture) by different amounts for different wavelength ranges / colors. For example, the system shown in Figure 22 is configured to output a blue spot with a diameter of 1.0 mm and a red spot with a diameter of 1.4 mm. In some embodiments, this feature is also achieved by a secondary optical relay element including additional lenses, reflectors, and / or metasurfaces.

[0060] In any of the above configurations, a potential concern is that undesirable light may reach an unintended incoupler, for example, that red light is directed to an incoupler tuned to incouple blue and green light. In some embodiments, cleanup filters on both sides of the optical path prevent undesirable light from reaching an unintended incoupler. The filters may be either color-selective (dichroic), as shown in Figure 23, or polarization-selective, as shown in Figure 24.

[0061] Figure 23 shows a top view 2300 of an optical scanner that uses optical cleanup filters 2302-2306 to separate incident light 2301. As shown in the figure, dielectric mirror 2302 reflects red light and transmits green light, dielectric mirror 2304 reflects red light and transmits green light, and dielectric mirror 2306 reflects green light and transmits red light. Thus, green light is directed exclusively to an in-coupler via dielectric mirror 2304, and red light is directed exclusively to another in-coupler via dielectric mirror 2306. Although this example demonstrates the separation of green and red light, a similar technique can be used for other colors, such as blue light. In some embodiments, blue light is also transmitted through dielectric mirror 2304 along with green light.

[0062] Figure 24 shows a top view of waveguide 1205, such as waveguide 205 in Figure 2, which has multiple in-couplers 1212A and 1212B and an optical scanner. The optical scanner includes multiple reflective and transmitting elements 2402-2414 that use polarization techniques to direct the light 2401 received by one of the two in-couplers 1212A and 1212B. The multiple reflective and transmitting elements 2402-2414 include a prism assembly of prisms 2402, 2406, and 2412, a PBS 2404, a waveplate 2408, a beam splitter 2410, and a mirror 2414. For example, waveplate 2408 is a fractional waveplate, e.g., QWP; mirror 2414 is a TIR reflector, metallic mirror, or dielectric mirror; and beam splitter 2410 is a dichroic beam splitter or a proportional (i.e., 50T / 50R, 90T / 10R, 33T / 67R, 90R / 10T, etc.) beam splitter. In some embodiments, multiple reflective and transmitting elements 2402-2414 correspond to multiple reflective and transmitting elements 2002-2014 in Figure 20. Waveplate / filter 2440 and waveplate / filter 2442 are also included to change the polarization state of the light coming in for each of the in-couplers 1212A, 1212B. Waveplate / filter 2440, 2442 include one or more QWPs, one or more half-waveplates, or any combination thereof.

[0063] In some embodiments, parallel output at the in-coupler is achieved by angular separation between colors of optical relays by varying the angles of multiple reflective and transmissive elements, such as beam splitters and / or mirrors. In other words, the different types of light input to the multiple reflective and transmissive elements do not all need to be collinear. That is, the optical paths from the multiple reflective elements to the in-coupler are parallel, but the optical paths entering the multiple reflective and transmissive elements are not parallel. For this reason, in some embodiments, no optical components are needed to collinearize the individual color light beams before the MEMS mirror.

[0064] In some embodiments, the separation of light into light with different optical properties for directing it into one of several in-couplers (e.g., in-couplers 1212A, 1212B for a common waveguide, or in-couplers 412A, 412B for a waveguide stack) is performed based on different wavelength ranges / colors of light. For example, red and green light enter the waveguide at the first in-coupler, and blue light enters at the second in-coupler. In another example, blue and green light enter the waveguide at the first in-coupler, while red light enters at the second in-coupler. In yet another example, red and blue light enter the waveguide at the first in-coupler, while green light enters at the second in-coupler.

[0065] The above-described technique for making the optical path length equivalent can be extended to other display light sources such as micro-LEDs, LCDs, and DMDs. This is illustrated in Figure 25 along with the display light source 2552. An optical scanner including an optical relay 2554 having two lenses and a plurality of reflective and transmitting elements 2502-2514 directs light from the display light source 2552 to two in-couplers 1212A and 1212B. The plurality of reflective and transmitting elements 2502-2514 include a prism assembly having three prisms 2502, 2506, and 2512, a PBS 2504, a waveplate 2508, a beam splitter 2510, and a reflective surface 2514 such as a mirror. Thus, the plurality of reflective and transmitting elements direct light to each of the in-couplers, improving the quality of the image delivered by the waveguide.

[0066] Within this disclosure, the margin of difference in optical path length described is in the range of 15% or less, and in some embodiments, 5% or less. In some embodiments, the margin of difference is understood to be a function of the thickness of the waveguide substrate (or waveguide stack), and the optical scanner described herein minimizes the margin of difference in optical path length of the light directed to each in-coupler such that the margin of difference is less than the thickness of the waveguide.

[0067] Referring to Figures 1-25, the direction of incident light, grating features, and propagated light are shown in the plane of the page for clarity. However, some or all directions of the optical path and / or features may be in or outside the plane of the page. Furthermore, the above techniques and systems are applicable to linear scanning MEMS relay systems and 2D optical relay systems.

[0068] In some embodiments, certain aspects of the techniques described above may be implemented by one or more processors of a processing system that executes the software. The software includes one or more sets of executable instructions, which are stored in a non-temporary computer-readable storage medium or otherwise materialized in a tangible form. The software may include instructions and specific data that, when executed by one or more processors, cause one or more processors to execute one or more aspects of the techniques described above. Non-temporary computer-readable storage mediums may include, for example, magnetic or optical disk storage devices, and solid-state storage devices such as flash memory, cache, random access memory (RAM), or a single or multiple non-volatile memory devices. Executable instructions stored in a non-temporary 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.

[0069] Computer-readable storage media may include any storage media, or combinations of storage media, that are accessible by a computer system while in 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 tapes, 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 system (MEMS) based storage media. Computer-readable storage media may be embedded in a computing system (e.g., system RAM or ROM), fixedly mounted to a computing system (e.g., magnetic hard drives), removable mounted to a computing system (e.g., optical disks or Universal Serial Bus (USB) based flash memory), or connected to a computer system via a wired or wireless network (e.g., network-accessible storage (NAS)).

[0070] In addition to those stated above, it should be noted that not all activities or elements described in the general description are required, and that certain activities or parts of 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 does not necessarily indicate the order in which they are performed. Also, concepts are described with reference to specific embodiments. However, those skilled in the art will understand that various modifications and changes can be made without departing from the scope of this disclosure, as described in the claims below. Accordingly, this specification and the drawings should be considered illustrative rather than restrictive, and all such modifications are intended to be within the scope of this disclosure.

[0071] Benefits, other advantages, and solutions to problems have been described above with respect to specific embodiments. However, benefits, advantages, and solutions to problems, as well as any features(if any) that may produce or make more prominent any benefit, advantage, or solution, should not be construed as material, necessary, or essential features of any or all claims. Furthermore, the subject matter of the disclosed invention can be modified and implemented in different but equivalent ways that will be apparent to those skilled in the art who have a benefit of teaching herein; therefore, the specific embodiments disclosed above are merely illustrative. No limitation is intended to any details of configuration or design shown herein other than those described in the claims below. Accordingly, it will be apparent that the specific embodiments disclosed above can be modified or altered, and all such variations are considered to fall within the scope of the subject matter of the disclosed invention. Thus, the protection sought herein is as described in the claims below.

Claims

1. A waveguide substrate including a first in-coupler and a second in-coupler, Multiple reflective and transmitting elements for selectively directing light to the first in-coupler or the second in-coupler based on multiple optical properties, Includes, The plurality of reflective and transmitting elements are arranged to equalize the optical path length of the first portion of light directed to the first in-coupler and the optical path length of the second portion of light directed to the second in-coupler.

2. The apparatus according to claim 1, wherein the plurality of reflective and transmitting elements separate the light into a first portion of the light having a first optical property among the plurality of optical properties and a second portion of the light having a second optical property among the plurality of optical properties, and selectively direct the first portion having the first optical property to the first in-coupler and the second portion having the second optical property to the second in-coupler.

3. The apparatus according to claim 1, wherein the plurality of optical properties are a plurality of wavelength ranges, and each of the first in-coupler and the second in-coupler is adjusted to in-couple light in one of the plurality of wavelength ranges.

4. The apparatus according to claim 3, wherein the plurality of reflective and transmissive elements include mirrors.

5. The apparatus according to claim 3, wherein the plurality of reflective and transmitting elements include a beam splitter, and the beam splitter is a dichroic beam splitter that separates light into two or more of the plurality of wavelength ranges.

6. A waveguide substrate including a first in-coupler and a second in-coupler, Multiple reflective and transmitting elements for selectively directing light to the first in-coupler or the second in-coupler based on multiple optical properties, Includes, The optical path length of the first portion directed from the plurality of reflective and transmissive elements to the first in-coupler is different from the optical path length of the second portion directed from the plurality of reflective and transmissive elements to the second in-coupler. The aforementioned multiple optical properties are in multiple wavelength ranges, The apparatus comprises an optical relay element for focusing a first pupil plane associated with a first wavelength range among the plurality of wavelength ranges onto the first incoupler, or for focusing a second pupil plane associated with a second wavelength range among the plurality of wavelength ranges onto the second incoupler.

7. The apparatus according to claim 6, wherein the optical relay element includes one or more of a lens group, a reflector, a metasurface, a prism assembly having a total internal reflection (TIR) ​​gap with the plurality of reflective and transmitting elements, or any combination thereof.

8. The apparatus according to any one of claims 1 to 7, wherein the plurality of reflective and transmitting elements include a plurality of lenses with different focal lengths.

9. The apparatus according to any one of claims 1 to 2, wherein the plurality of optical properties are a plurality of polarization states, and each of the first in-coupler and the second in-coupler is adjusted to in-couple light in one of the plurality of polarization states.

10. The apparatus according to claim 9, wherein the plurality of reflective and transmitting elements include a polarizing beam splitter and one or more waveplates.

11. The apparatus according to any one of claims 1 to 7, wherein the plurality of reflective and transmitting elements include an optical cleanup filter, which includes a color-selective filter or a polarization-selective filter, to remove light having undesirable optical properties as it is directed towards the first in-coupler or the second in-coupler.

12. The apparatus according to any one of claims 1 to 7, wherein the plurality of reflective and transmitting elements receive light from a single optical engine and selectively direct the received light to the first in-coupler or the second in-coupler.

13. The waveguide stack includes, A first waveguide substrate including a first in-coupler, The invention includes a second waveguide substrate which includes the first in-coupler and an offset second in-coupler, Multiple reflective and transmitting elements for selectively directing light to the first in-coupler or the second in-coupler based on multiple optical properties. It further includes, The plurality of reflective and transmitting elements are arranged to equalize the optical path length of the first portion of light directed to the first in-coupler and the optical path length of the second portion of light directed to the second in-coupler.

14. The apparatus according to claim 13, wherein the plurality of reflective and transmitting elements direct the light of the first optical property among the plurality of optical properties to the first in coupler and the light of the second optical property among the plurality of optical properties to the second in coupler.

15. The waveguide stack is The waveguide stack includes one or more additional waveguide substrates stacked on the second waveguide substrate, each of the one or more additional waveguide substrates includes its own additional in-coupler, each of which is laterally offset from the first in-coupler, the second in-coupler, and each of the other additional in-couplers, and the waveguide stack further includes, The apparatus according to any one of claims 13 to 14, further comprising the plurality of reflective and transmissive elements configured to selectively direct light to each of the additional in-couplers based on the plurality of optical properties.

16. The apparatus according to any one of claims 13 to 14, wherein the plurality of reflective and transmitting elements include a beam splitter.

17. The apparatus according to claim 16, wherein the beam splitter is a dichroic beam splitter, the plurality of optical properties are a plurality of distinct wavelength ranges, and the dichroic beam splitter separates light into the plurality of distinct wavelength ranges for transmission to one of the first in-coupler and the second in-coupler.

18. The apparatus according to claim 16, wherein the beam splitter is a polarizing beam splitter, the plurality of optical properties are a plurality of distinct polarization states, and the polarizing beam splitter separates light into the plurality of distinct polarization states for transmission to one of the first in-coupler and the second in-coupler.

19. The plurality of reflective and transmissive elements are, The apparatus according to any one of claims 13 to 14, comprising one or more optical focusing elements for focusing light toward one or more of the first in-coupler and the second in-coupler.

20. Receiving input light from a single optical engine, Based on one or more optical properties, the input light is separated into at least two optical parts, To selectively direct each of the at least two optical portions to the first or second in-coupler of the waveguide, And A plurality of reflective and transmitting elements are provided to equalize the optical path length of the first portion of light directed to the first in-coupler and the optical path length of the second portion of light directed to the second in-coupler.

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