Systems and methods for minimizing double bounce in waveguides

Abstract

A system and method for reducing diffraction angle effects such as instances of double bounce effect and bounce separation effect in a laser projection system [200] comprising an optical engine [202] with laser diodes [418] configured to emit light beams of different wavelengths, and beam combiners [224] having reflective surfaces [504] each configured to receive one of the light beams from one of the laser diodes and reflect the received light beam such that an edge of the reflected light beam lies on a common tangent [502] to other light beams reflected from the other reflective surfaces. The laser projection system can be implemented in a head mounted display (HMD) including a waveguide [205] having an input combiner [212] for receiving the combined light beams, the edge of the input combiner corresponding to the tangent where the edges of the multiple light beams are aligned.

Description

[Background technology]

[0001] background In the field of optics, a combiner is an optical device that combines two light sources, for example, ambient light from outside the combiner and light transmitted from a microdisplay that is directed to the combiner via a waveguide. Optical combiners are used in wearable heads up displays (WHUDs), sometimes called head-mounted displays (HMDs) or near-eye displays, to allow a user to see computer-generated content (such as text, images, or video content) overlaid on the user's environment as seen through the WHUD, creating what is known as augmented reality (AR) or mixed reality (MR). Summary of the Invention [Problem to be solved by the invention]

[0002] Transmitting light from the microdisplay to the user's eye within a WHUD typically involves multiple reflections, refractions, diffractions, and / or changes in polarization, which can result in some of the light being redirected out of the waveguide or deviating from its main path along the way, thus effectively "lost" it from its intended destination (i.e., the user's eye). This loss of light can reduce the efficiency of the WHUD and can cause aberrations in the image seen by the user, such as uneven brightness or color.

[0003] 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]

[0004] [Figure 1]FIG. 1 illustrates an exemplary display system including a laser projection system configured to project an image toward a user's eyes, according to some embodiments. [Figure 2] FIG. 2 illustrates a block diagram of the laser projection system of FIG. 1, according to some embodiments. [Figure 3] 3 illustrates an example of light propagation within a waveguide of the laser projection system of FIG. 2 in accordance with some embodiments. [Figure 4] FIG. 3 illustrates an exemplary embodiment of the laser projection system of FIG. 2, where the optical relay includes a shaped reflective relay, according to some embodiments. [Figure 5] FIG. 5 illustrates a portion of the laser projection system of FIG. 4, where the optical engine and beam combiner are configured to tangentially align the beam of laser light, in accordance with some embodiments. [Figure 6] 7A and 7B are diagrams illustrating a partially transparent perspective view of a portion of a WHUD, such as the WHUD of FIG. 6 or the display system of FIG. 1, according to some embodiments. [Figure 7] 5A illustrates a partially transparent perspective view of a portion of a WHUD including an example arrangement of the laser projection system of FIG. 4, according to some embodiments. [Figure 8] 3A-3C illustrate example cross sections of non-concentric coupled light beams provided from an optical engine, such as the optical engine and waveguide of FIG. 2, to a waveguide, according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0005] Detailed Description In a conventional WHUD, light representing visual content from a microdisplay is directed into a waveguide by an input coupler that transmits or reflects light at a specific angle so that the light strikes the waveguide boundary at an angle of incidence greater than the critical angle at which total internal reflection (TIR) ​​occurs. The light then propagates along the waveguide's internal volume via multiple TIRs until it reaches a structure (i.e., an output coupler) designed to direct the light out of the waveguide, typically toward the user's eyes to be viewed as an image or series of images.

[0006] In some cases, the waveguide input coupler is implemented as a diffraction grating disposed on the surface of the waveguide, which diffracts different wavelengths of microdisplay light at different angles. Because these diffraction angles are different, different wavelengths of microdisplay light have different propagation angles within the waveguide, and therefore different distances between TIR bounces within the waveguide. Furthermore, because the diffraction angles of each wavelength of light are different, some light may be lost from the waveguide due to a "double bounce" effect, where light that was transmitted or reflected by the input coupler the first time may enter the input coupler a second time as a result of being reflected from the surface of the waveguide back toward the input coupler. When light enters the input coupler a second time, some of the light is transmitted or reflected (i.e., "lost") from the waveguide, resulting in less light being transmitted through the waveguide to the user's eye than was originally emitted from the microdisplay, potentially reducing the brightness of the image displayed to the user and resulting in a degraded user experience.

[0007] Because each wavelength of light experiences a different diffraction angle, the distance between bounces within the waveguide for each wavelength of light can also vary. The distance between two adjacent bounces (measured from the center of the light beam) is known as the "bounce separation," and the distance between adjacent bounces of different light beams is called the "bounce separation." As the bounce separation and bounce separation between wavelengths of light increase, the color uniformity of the image displayed to the user also decreases. In other words, because light with a relatively short wavelength (e.g., blue light) has a smaller diffraction angle than light with a longer wavelength (e.g., red light), the bounce separation of blue light is smaller than that of red light. This means that blue light experiences more TIR bounces than red light within a given region of the waveguide, and generally, the bounce separation between light beams of blue light is smaller than that of red light. As a result, when blue and red light encounter the output coupler of the waveguide, the blue light experiences more output coupler bounces than the red light, resulting in the blue light exiting the waveguide in more locations than the red light. Thus, the image displayed to the viewer will have a relatively consistent saturation of blue colors throughout the image, but the saturation of red colors will vary in certain areas of the image.

[0008] 1-8 illustrate embodiments of exemplary devices and techniques for reducing diffraction angle effects, such as instances of double bounce and bounce separation effects, in display systems. However, it will be understood that the devices and techniques of the present disclosure are not limited to implementation in the illustrated display systems and instead may be implemented in any of a variety of display systems using the guidelines provided herein. In some embodiments of the exemplary devices, a microdisplay associated with a waveguide uses laser diodes configured to generate light beams of different wavelengths, each light beam having a perimeter proportional to the expected diffraction angle imparted to the particular light beam when incident on the waveguide's input combiner. For example, in some embodiments, a beam combiner associated with the microdisplay's laser diodes includes reflective surfaces positioned such that edges of the emitted circular or elliptical light beams are tangent-aligned and biased at the edges of the input combiner. That is, the light beams are not aligned by the beam combiner based on the centers of the light beams, but rather, the edges of the light beams are aligned to a common edge of the combined light beam output from the beam combiner. Thus, the exemplary devices and techniques reduce instances of double bounce and bounce separation of light beams as they are transmitted within a waveguide.

[0009] FIG. 1 illustrates an example of a 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 such that the user perceives the projected images as being displayed in a field of view (FOV) region 106 of the display in one or both of lens elements 108, 110. In the illustrated embodiment, the display system 100 is a wearable head-up display (WHUD) that includes the support structure 102 configured to be worn on the 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 front-facing cameras, rear-facing cameras, other optical sensors, motion sensors, accelerometers, etc. The support structure 102 can 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 an interior volume of support structure 102, such as within arms 104 of region 112 of support structure 102. Note that while an exemplary form factor is shown, it is understood that display system 100 may have a different shape and appearance than the eyeglass frames shown in FIG.

[0010] One or both of lens elements 108, 110 are used by display system 100 to provide an augmented reality (AR) display in which rendered graphical content can be superimposed on or provided in conjunction with a view of the real world perceived by a user through lens elements 108, 110. For example, laser light used to form a perceptible image or series of images can be projected by a laser projector in display system 100 to a user's eye 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 includes at least a portion of a waveguide that routes display light received by a waveguide input coupler to a waveguide output coupler, which outputs the display light toward the eye of a user of display system 100. The display light is modulated and scanned toward the user's eye such that the user perceives the display light as an image. Additionally, each of the lens elements 108, 110 is sufficiently transparent to allow a user to see through and provide a view of the user's real-world environment such that an image is displayed superimposed on at least a portion of the real-world environment.

[0011] 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 digital light processors. 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 that may be micro-electromechanical system (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 the content displayed on display system 100.

[0012] The projector scans light over a variable area designated as the FOV region 106 of the display system 100. 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 a user. In some embodiments, the projector routes the light through first and second scan mirrors, an optical relay positioned between the first and second scan mirrors, and a waveguide positioned at the output of the second scan mirror. In some embodiments, at least a portion of the output coupler of the waveguide may overlap the FOV region 106.

[0013] To reduce instances of double bounces and bounce separation of the light beams as they are transmitted through the waveguide, in some embodiments, the reflective surfaces of the beam combiners associated with the laser diodes are oriented such that the emitted light beams are tangentially aligned and each laser light beam is aligned with an edge of the input coupler of the waveguide. Examples of these aspects are described in more detail below.

[0014] FIG. 2 illustrates a simplified block diagram of a laser projection system 200 that projects an image directly onto a user's eye via laser light. The laser projection system 200 includes an optical engine 202, an optical scanner 204, and a waveguide 205. 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 input coupler 212 and an output coupler 214; in this example, the output coupler 214 is optically aligned with the user's eye 216. The input coupler 212 of the waveguide 205 includes at least a first edge 220 and a second edge 222. In some embodiments, the laser projection system 200 is implemented in a wearable head-up display or other display system, such as the display system 100 of FIG. 1.

[0015] Optical engine 202 includes one or more laser light sources configured to generate and output light beam 218 (e.g., visible laser light, such as red, blue, and green laser light, and / or non-visible laser light, such as infrared laser light). In some embodiments, optical engine 202 is coupled to a driver or other controller (not shown) that controls the timing of the emission of laser light from the laser light sources of optical engine 202 according to instructions received from a computer processor to which the controller or driver is coupled, to modulate light beam 218 so as to be perceived as an image when output to the retina of a user's eye 216.

[0016] For example, during operation of laser projection system 200, multiple light beams 218, each having a different wavelength, are output by laser light sources of optical engine 202 and then combined via beam combiner 224 into combined light beam 228 before being directed toward user's eye 216. Optical engine 202 modulates the intensity of each of the laser light beams so that the combined laser light reflects off a series of pixels of an image, and the particular intensity of each laser light beam at any given time contributes to the corresponding color content and amount of brightness within the pixel represented by the combined laser light at that time.

[0017] In some embodiments, one or both of the scanning mirrors 206 and 208 of the optical scanner 204 are MEMS mirrors. For example, the scanning mirrors 206 and 208 are MEMS mirrors that are driven to oscillate by respective actuation voltages during active operation of the laser projection system 200, causing the scanning mirrors 206 and 208 to scan the combined light beam 228. The oscillation of the scanning mirror 206 causes the combined light beam 228 output by the beam combiner 224 to be scanned across the surface of the second scanning mirror 208 through the optical relay 210. The second scanning mirror 208 scans the combined light beam 228 received from the scanning mirror 206 toward the input coupler 212 of the waveguide 205. In some embodiments, the scanning mirror 206 oscillates along the first scanning axis 219, such that the combined light beam 228 is scanned in only one dimension (i.e., a line) across the surface of the second scanning mirror 208. In some embodiments, the scan mirror 208 oscillates or rotates along a second scan axis 221 that is perpendicular to the first scan axis.

[0018] In some embodiments, input coupler 212 has a substantially rectangular outer shape and is configured to receive combined light beam 228 and direct combined light beam 228 into waveguide 205. Input coupler 212 is defined by a smaller dimension (i.e., width) and a larger orthogonal dimension (i.e., length). In some embodiments, input coupler 212 has a substantially circular or square shape. In one embodiment, optical relay 210 is a line-scan optical relay that receives combined light beam 228 scanned in a first dimension (e.g., the first dimension corresponding to the smaller dimension of input coupler 212) by a first scanning mirror, routes combined light beam 228 to second scanning mirror 208, and introduces focusing of combined light beam 228 in the first dimension to an exit pupil beyond second scanning mirror 208. According to various embodiments, the optical relay 210 includes one or more collimating lenses that shape and focus the combined light beam 228 onto the second scan mirror 208, or includes a shaped reflective relay that includes two or more spherical, aspherical, parabolic, and / or freeform lenses that shape and direct the combined light beam 228 onto the second scan mirror 208. The second scan mirror 208 receives the combined light beam 228 and scans the combined light beam 228 in a second dimension. The second dimension corresponds to the length dimension of the input coupler 212 of the waveguide 205. In some embodiments, the second scan mirror 208 sweeps the exit pupil of the combined light beam 228 along a line along the second dimension. In some embodiments, the input coupler 212 is positioned at or near the sweep line downstream of the second scan mirror 208 such that the second scan mirror 208 scans the combined light beam 228 as a line or row on the input coupler 212.

[0019] In some embodiments, the optical engine 202 includes edge-emitting laser (EEL) diodes that each emit a light beam 218 having a substantially elliptical, non-circular cross-section, resulting in a combined light beam 228 having an elliptical cross-section. The optical relay 210 expands or minimizes the combined light beam 228 along its semi-major or semi-minor axis to circularize the combined light beam 228 before the combined light beam 228 converges on the second scanning mirror 208. In some embodiments, each EEL diode provides a light beam 218 of a specific wavelength and a collimating lens associated with each EEL diode, such as collimating lens 406 described in more detail with reference to FIG. 4 , configured to collimate the light emitted from the EEL diode to generate a light beam 218 of a specific perimeter. In some embodiments, the perimeter of each light beam 218 is different compared to the light beams 218 emitted by the other EELs to reduce bounce separation. That is, each wavelength of light emitted by an EEL diode is collimated so that its perimeter is different from the perimeter of other wavelengths of light emitted by other EELs in the optical engine 202. Because shorter wavelength light (e.g., blue light at approximately 450 nm) has a smaller diffraction angle than longer wavelength light (e.g., red light at approximately 638 nm), increasing the beam size of the red light minimizes the amount of bounce separation (i.e., the distance between a given bounce and the next closest bounce of light having the same wavelength) in the waveguide 205, thus minimizing degradation of the color uniformity of the image represented by the laser light as it travels through the waveguide. In some embodiments, each collimating lens is positioned relative to a corresponding EEL diode to provide a laser light beam of a particular wavelength with a specific perimeter determined by the distance the collimating lens is positioned from the EEL diode. 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 combined light beam 228). In other such embodiments, the surfaces of the mirror plates of the scanning mirror 206 are circular.

[0020] The waveguide 205 of the laser projection system 200 includes an input coupler 212 and an output coupler 214. As used herein, the term “waveguide” will be understood to mean a coupler that uses one or more of total internal reflection (TIR), special filters, and / or reflective surfaces to transmit light from an input coupler (such as input coupler 212) to an output coupler (such as output coupler 214). 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 “input coupler” and “output 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 input or output coupler is configured as a transmission grating (e.g., a transmission diffraction grating or a transmission holographic grating) that transmits light through the input or output coupler and applies a designed optical function to the light during transmission. In some embodiments, a given input or output coupler is a reflective grating (e.g., a reflective diffraction grating or a reflective holographic grating) that reflects light through the input or output coupler and applies a designed optical function to the light during reflection. In this example, light beam 218 received at input coupler 212 is relayed to output coupler 214 via waveguide 205 using TIR. Light beam 218 is then output via output coupler 214 to user's eye 216. 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 laser projection system 200.

[0021] 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 input coupler 212, between input coupler 212 and output coupler 214, and / or between output coupler 214 and eye 216 (e.g., to shape the laser light so that it is seen by the user's eye 216). In some embodiments, a prism is used to direct the light from scan mirror 208 to input coupler 212 so that the light is coupled into input coupler 212 at the appropriate angle to promote propagation of the light within waveguide 205 by TIR. Also, in some embodiments, an exit pupil expander such as a fold grating (e.g., exit pupil expander 304 in FIG. 3 described below) is positioned intermediate between input coupler 212 and output coupler 214 to receive light coupled into waveguide 205 by input coupler 212, expand the light, and redirect the light toward output coupler 214, where output coupler 214 couples the laser light away from waveguide 205 (e.g., toward user's eye 216).

[0022] 3 is a diagram illustrating an example of light propagation within the waveguide 205 of the laser projection system 200 of FIG. 2, in accordance with some embodiments. As shown, light is received through an input coupler 212 having a first edge 220 and scanned along an axis 302 parallel to the first edge 220. The light is then directed to an exit pupil expander 304 and then routed to an output coupler 214 for output (e.g., toward a user's eye). In some embodiments, the exit pupil expander 304 expands one or more dimensions of the eyebox of a WHUD that includes the laser projection system 200 (e.g., with respect to the dimensions of the eyebox of the WHUD without the exit pupil expander 304). In some embodiments, the input coupler 212 and the exit pupil expander 304 each include a respective one-dimensional diffraction grating (i.e., a diffraction grating extending along one dimension). 3 illustrates a substantially ideal case in which input coupler 212 directs light straight down in a first direction (with respect to the currently shown view) perpendicular to scan axis 302, and exit pupil expander 304 directs light to the right in a second direction (with respect to the currently shown view) perpendicular to the first direction. It should be understood that, although not shown in this example, in some embodiments, the first direction in which input coupler 212 directs light is not exactly perpendicular to scan axis 302, but is slightly or substantially oblique.

[0023] 4 illustrates an exemplary embodiment of a laser projection system 200 in which the optical relay 210 includes a shaped reflective relay. As shown, the laser projection system 200 includes a substrate 402 on which a beam combiner 404, a collimating lens 406, and a mirror 408 are disposed. According to various embodiments, the substrate 402 is a printed circuit board (PCB) or another applicable substrate.

[0024] The optical engine 202 is comprised of a set of one or more laser light sources 418 (e.g., laser diodes), such as the illustrated red laser light diode 418-1, green laser light diode 418-2, and blue laser light diode 418-3, and a processor or other controller operates the optical engine 202 to modulate the respective intensities of each laser diode 418 to provide corresponding red, green, and blue light contributions to corresponding pixels of an image generated for display to a user. Collimating lenses 406 are each inserted in the optical path between each laser diode 418 of the optical engine 202 and the beam combiner 404. For example, each laser light source 418 outputs laser light of a different wavelength (e.g., corresponding to a respective red, blue, or green wavelength) through the collimating lens 406 and combined at the beam combiner 224 to generate the combined light beam 228 projected by the laser projection system 200. The beam combiner 404 receives the individual laser light inputs and outputs a combined laser light beam 228 to a mirror 408, which redirects the combined light beam 228 onto a reflective surface 412 of a scanning mirror 206. The scanning mirror 206 scans the combined light beam 228 across a first scan axis and into an optical relay 210. The optical relay 210 is configured to route the combined light beam 228 towards a reflective surface 414 of the scanning mirror 208. The scanning mirror 208 scans the combined light beam 228 across an input coupler (such as input coupler 212) of the waveguide 205 along a second scan axis that is perpendicular to the first scan axis.

[0025] FIG. 5 illustrates a portion 500 of the laser projection system 200 of FIG. 4 , including the optical engine 202 and an embodiment of the beam combiner 224 configured to align the beams of light 218 on a tangent line 502. Each laser diode 418-1, 418-2, 418-3 (collectively 418) projects a beam of laser light comprised of a range of wavelengths. For example, laser diode 418-1 projects laser light 218-1, laser diode 418-2 projects laser light 218-2, and laser diode 418-3 projects laser light 218-3. For purposes of illustration, each of light beams 218-1, 218-2, and 218-3 (collectively 218) is represented in FIG. 5 by two lines indicating the edges of the light beam in a vertical cross section (i.e., parallel to the direction of propagation of the light beam). The light beam 218 from each laser diode 418 is collimated as it passes through its respective collimating lens 406. The collimating lenses 406 are positioned a distance from the laser diodes based on the desired circumference of the collimated light beam 218 that is then transmitted to the beam combiner 224. For example, placing the collimating lenses 406 closer to their respective laser diodes 418 results in a relatively small ambient light beam 218, while placing the collimating lenses 406 farther from their respective laser diodes 418 results in a larger ambient light beam 218 because the light beam 218 experiences more divergence as it travels a longer distance before intersecting its respective collimating lens 406 (i.e., the circumference of the light beam 218 increases).

[0026] After being collimated by the collimating lenses 406, the light beams 218 are transmitted to a beam combiner 224 that includes at least one reflective surface disposed therein. In some embodiments, the beam combiner 224 includes reflective surfaces 504-1, 504-2, and 504-3 (collectively 504) for receiving the light beams 218 from each of the respective collimating lenses 406. Thus, in the example shown in FIG. 5 , reflective surface 504-1 receives light beam 218-1, reflective surface 504-2 receives light beam 218-2, and reflective surface 504-3 receives light beam 218-3. In some embodiments, the reflective surfaces 504 are disposed in parallel planes within the beam combiner 224, such that the angles at which each of the light beams 218 is reflected from each reflective surface 504 are the same or nearly the same. As a result, the reflected light beams 218 are directed along the same optical path within the beam combiner 224 before emerging from the beam combiner 224 parallel to one another as a combined light beam 228 .

[0027] The spacing between the reflective surfaces 504 in the beam combiner 224 is based on the circumference and shape of each light beam 218 transmitted from each collimating lens 406. The spacing between the reflective surfaces 504 is also based on aligning the incidence points 508-1, 508-2, 508-3 (collectively 508) on each reflective surface along a tangent line 502, where the edge of each light beam 218 transmitted from the associated collimating lens 406 strikes the respective reflective surface 504. For example, the edge of light beam 218-1 strikes reflective surface 504-1 at incidence point 508-1, which is aligned with incidence points 508-2 and 508-3 along the tangent line 502. Thus, the spacing between the reflective surfaces 504 is variable along the z-axis such that the edge of each of the light beams 218-1, 218-2, 218-3 is incident on the respective reflective surface 504 at a respective point of incidence 508 along the tangent line 502. As a result, the edge of the resulting combined light beam 228 is also aligned with the tangent line 502.

[0028] As discussed above, it is desirable to bias the position of each of the light beams 218 in the combined light beam 228 away from concentricity so that the edge of each light beam 218 is aligned on a tangent, such as tangent 502. This alignment is maintained as the combined light beam 228 is directed through the optical scanner 204, so that the combined light beam 228 enters the input coupler 212 with the edges of the light beams 218 of the combined light beam 228 aligned with the edges of the input coupler 212, such as edge 220 shown in FIG. 3 , thus reducing instances of double bounce as the light beams 218 are transmitted through the waveguide.

[0029] Figure 6 is a diagram illustrating a portion of a WHUD 600 that includes the laser projection system 200 of Figure 2. In some embodiments, the WHUD 600 represents the display system 100 of Figure 1. In this example, the optical engine 202, the beam combiner 224, the optical scanner 204, the input coupler 212, and a portion of the waveguide 205 are included in an arm 602 of the WHUD 600.

[0030] The WHUD 600 includes an optical coupling lens 604 including a first lens 606, a second lens 608, and a waveguide 205, with the waveguide 205 disposed between the first lens 606 and the second lens 608. Light exiting the output coupler 214 travels through the second lens 608 (e.g., corresponding to the lens element 110 of the display system 100). During use, the light exiting the second lens 608 enters the pupil of the eye 610 of a user wearing the WHUD 600, causing the user to perceive a displayed image carried by the laser light output by the optical engine 202. Because the optical coupling lens 604 is substantially transparent, light from a real-world scene corresponding to the environment surrounding the WHUD 600 passes through the first lens 606, the second lens 608, and the waveguide 205 to reach the user's eye 610. In this way, images or other graphical content output by the laser projection system 200 are combined (e.g., overlaid) with a real-world view of the user's environment to provide the user with an AR experience.

[0031] Although not shown in the illustrated example, in some embodiments, additional optical elements are included in the optical path either between the optical engine 202 and the input coupler 212, between the input coupler 212 and the output coupler 214, and / or between the output coupler 214 and the user's eye 610 (e.g., to shape the laser light so that it is visible to the user's eye 610). As an example, a prism is used to direct the light from the optical scanner 204 to the input coupler 212 so that the light is coupled into the input coupler 212 at the appropriate angle to promote propagation of the light within the waveguide 205 by TIR. Also, in some embodiments, an exit pupil expander (e.g., exit pupil expander 304), such as a fold grating, is positioned intermediate between input coupler 212 and output coupler 214 to receive light into waveguide 205 by input coupler 212, expand the light, and redirect the light toward output coupler 214, which couples the laser light away from waveguide 205 (e.g., toward the user's eye 610).

[0032] Figure 7 illustrates a partially transparent perspective view of a portion of a WHUD 700, which may represent the WHUD 600 of Figure 6 or the display system 100 of Figure 1. The WHUD 700 includes an example arrangement of the laser projection system 200 of Figures 2 and 4, an embodiment in which the optical relay 210 is a shaped reflective relay. In some embodiments, the WHUD 700 corresponds to the display system 100 of Figure 1, and the illustrated portion of the WHUD 700 corresponds to the region 112 of the display system 100.

[0033] The arm 704 of the WHUD 700 houses the optical engine 202, the beam combiner 224, the collimating lens 406, and at least a portion of the first scan mirror 206. The frame section 706 of the WHUD 700 houses the second scan mirror 208, a portion of the first scan mirror 206, and the optical relay 210. The input coupler 212 and the output coupler 214 of the waveguide 205 are each embedded within or disposed on the lens 708 (e.g., one embodiment of the lens 110 of FIG. 1 ). As described above, the combined light beam 228 output by the optical engine 202 is routed to the input coupler 212 via at least the first scan mirror 206, the optical relay 210, and the second scan mirror 208. The first scanning mirror 206 oscillates or rotates to scan the combined light beam 228 along a first scanning axis, and the second scanning mirror 208 oscillates or rotates to scan the combined light beam 228 along a second scanning axis that is perpendicular to the first scanning axis. The combined laser light 228 reflected by the second scanning mirror 208 converges into a line at the input coupler 212. The combined light beam 228 received at the input coupler 212 is routed to the output coupler 214 via the waveguide 205. The light received at the output coupler 214 is then directed out of the waveguide 205 (e.g., toward the eyes of a user of the WHUD 700).

[0034] To mitigate against degradation of the color uniformity of light guided from the waveguide, it is desirable to minimize instances of double bounces and reduce bounce separation. Therefore, systems such as the WHUDs of FIG. 6 or FIG. 7 include a beam combiner 224 to reduce the likelihood of light encountering the input coupler multiple times by aligning each light beam with an edge of the input coupler in the direction of light propagation within the waveguide, such as the first or second edges 220 and 222 shown in FIG. 2 . By aligning the light beam with the edge of the input coupler, the light beam is guided into the waveguide by the input coupler and then along a path away from the input coupler to reduce the likelihood of the light beam encountering the input coupler multiple times. In some embodiments, the beam combiner 224 includes a reflective surface configured to align each laser light beam emitted by the laser light projector so that the beam abuts the edge of the input coupler to minimize double bounces by laser light beams entering the waveguide through the input coupler.

[0035] FIG. 8 illustrates example cross sections of a combined light beam 228 provided to a waveguide from an optical engine, such as optical engine 202 and waveguide 205 in FIG. 2. In some embodiments, the light beams 218 in the combined light beam 228 are non-concentric and biased to align on a tangent, such as tangent 502 in FIG. 5. Aligning the beams along a tangent reduces the likelihood that the light beams will encounter the waveguide's input coupler again after being directed into the waveguide. Cross sections 9-1 and 9-2 illustrate a circular, non-concentric combined light beam 228 composed of beams of red laser light 218-1, green laser light 218-2, and blue laser light 218-3 having different perimeter lengths. Cross sections 9-3 and 9-4 illustrate a non-concentric combined light beam 228 composed of beams of red laser light 218-1, green laser light 218-2, and blue laser light 218-3 having different major and minor axis lengths. In some embodiments, biasing each of the light beams 218 to be tangent to an edge of the input coupler 212 is achieved by using at least one alignment component configured to adjust the positioning of the laser light beams so that the edges of each of the light beams 218 lie on a common tangent.

[0036] As disclosed herein, a laser projection system includes an optical engine including a plurality of laser diodes configured to emit a plurality of light beams; and a beam combiner having a plurality of reflective surfaces, each reflective surface configured to receive one of the plurality of light beams from one of the plurality of laser diodes and reflect the received light beam such that an edge of the reflected light beam lies on a common tangent to the plurality of light beams reflected from other reflective surfaces of the plurality of reflective surfaces. In one aspect, at least one of the plurality of light beams has a different perimeter compared to at least one other light beam of the plurality of light beams. In another aspect, each of the plurality of laser diodes emits light over a unique wavelength range compared to the other laser diodes. In yet another aspect, the plurality of reflective surfaces are arranged in parallel planes that intersect an optical path within the beam combiner. In yet another aspect, the position of each of the plurality of reflective surfaces within the beam combiner is based on tangent alignment of an edge of each of the plurality of light beams.

[0037] In one aspect, the spacing between each of the plurality of reflective surfaces in the beam combiner is based on aligning an edge of each of the plurality of light beams on a tangent, hi another aspect, the tangent corresponds to an edge of an input coupler of a waveguide associated with the laser projection system.

[0038] In some embodiments, a method includes projecting multiple light beams from the multiple laser diodes in a laser projection system comprising a plurality of laser diodes and a beam combiner having multiple reflective surfaces disposed therein, each of the multiple reflective surfaces positioned to receive a light beam projected from one of the multiple laser diodes, and generating a combined light beam by reflecting the multiple light beams from the multiple reflective surfaces such that edges of each of the multiple light beams are tangentially aligned. In one aspect, at least one of the multiple light beams has a different perimeter compared to at least one other of the multiple light beams. In another aspect, each of the multiple laser diodes emits light over a unique wavelength range compared to the other multiple laser diodes. In yet another aspect, each of the multiple laser diodes emits light over a unique wavelength range compared to the other multiple laser diodes.

[0039] In one aspect, the multiple reflective surfaces are arranged in parallel planes that intersect the optical path in the beam combiner. In another aspect, each of the multiple reflective surfaces in the beam combiner is positioned such that an edge of each of the optical beams reflected by each of the multiple reflective surfaces is aligned on a common tangent to an edge of one of the other multiple optical beams reflected from a different reflective surface of the multiple reflective surfaces. In yet another aspect, the method further includes spacing each of the multiple reflective surfaces in the beam combiner such that an edge of each of the optical beams reflected by each of the multiple reflective surfaces is aligned on a common tangent to an edge of one of the other multiple optical beams reflected from a different reflective surface of the multiple reflective surfaces. In another aspect, the tangent corresponds to an edge of an input coupler of a waveguide associated with the laser projection system.

[0040] In some embodiments, a head-mounted display (HMD) includes a laser projection system including: an optical engine having a plurality of laser diodes configured to emit a plurality of light beams; a beam combiner having a plurality of reflective surfaces and configured to generate a combined light beam by reflecting the plurality of light beams from the plurality of reflective surfaces such that edges of each of the plurality of light beams are aligned tangent to the laser beam; and a waveguide having an input combiner for receiving the combined light beam, an edge of the input combiner corresponding to the tangent to which the edges of the plurality of light beams are aligned. In one aspect, at least one of the plurality of light beams has a different perimeter compared to at least one other of the plurality of light beams. In another aspect, each of the plurality of laser diodes emits light over a unique wavelength range compared to the other laser diodes. In yet another aspect, the plurality of reflective surfaces are arranged in parallel planes that intersect the optical path within the beam combiner. In yet another aspect, the position of each of the plurality of reflective surfaces within the beam combiner and the spacing between each of the plurality of reflective surfaces are based on aligning edges of each of the plurality of light beams tangent to the laser beam.

[0041] It should be noted that not all of the activities or elements described in the general description above are required, that some of the specific activities or devices may not be required, and that one or more additional activities may be performed or elements may be included in addition to those described. 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 recognize that various modifications and changes can be made without departing from the scope of the present disclosure, as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present disclosure.

[0042] Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, benefits, advantages, solutions to problems, and any features by which the benefits, advantages, or solutions occur or become more pronounced should not be construed as critical, necessary, or essential features of any or all claims. Moreover, the specific embodiments disclosed above are merely exemplary, and 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 shown herein, except as set forth in the following claims. It will therefore be apparent that the specific embodiments disclosed above may be altered or modified, and all such variations are considered to be within the scope of the disclosed subject matter. Accordingly, the protection sought herein is as set forth in the following claims.

Claims

1. an optical engine comprising a plurality of laser diodes configured to emit a plurality of light beams; a beam combiner having a plurality of reflective surfaces each configured to receive one of the plurality of light beams from one of the plurality of laser diodes, the plurality of reflective surfaces reflecting the received light beam such that an edge of the reflected light beam lies on a tangent common to the plurality of light beams reflected from other reflective surfaces of the plurality of reflective surfaces; at least one of the plurality of light beams has a different perimeter compared to at least one other light beam of the plurality of light beams; The beam combiner reflects the multiple light beams to an input combiner of a waveguide of the laser projection system.

2. 10. The laser projection system of claim 1, wherein each of the plurality of laser diodes emits light over a unique wavelength range compared to other of the plurality of laser diodes.

3. 10. The laser projection system of claim 1, wherein the plurality of reflective surfaces are arranged in parallel planes that intersect an optical path within the beam combiner.

4. 4. The laser projection system of claim 3, wherein the position of each of the plurality of reflective surfaces within the beam combiner is based on aligning an edge of each of the plurality of light beams on the tangent line.

5. 5. The laser projection system of claim 3 or 4, wherein the spacing between each of the plurality of reflective surfaces in the beam combiner is based on aligning an edge of each of the plurality of light beams on the tangent line.

6. The laser projection system of claim 4 , wherein the tangent corresponds to an edge of an input coupler of a waveguide of the laser projection system.

7. 1. A laser projection system comprising: a plurality of laser diodes; and a beam combiner having a plurality of reflective surfaces disposed therein, each of the plurality of reflective surfaces positioned to receive a light beam projected from one of the plurality of laser diodes; projecting a plurality of light beams from the plurality of laser diodes; generating a combined light beam by reflecting the plurality of light beams from the plurality of reflective surfaces such that edges of each of the plurality of light beams are tangentially aligned; at least one of the plurality of light beams has a different perimeter compared to at least one other light beam of the plurality of light beams; wherein the beam combiner reflects the multiple light beams to an input combiner of a waveguide of the laser projection system.

8. The method of claim 7 , wherein each of the plurality of laser diodes emits light over a unique wavelength range compared to other of the plurality of laser diodes.

9. The method of claim 7 , wherein the plurality of reflective surfaces are arranged in parallel planes that intersect an optical path within the beam combiner.

10. 10. The method of claim 9, wherein each of the plurality of reflective surfaces in the beam combiner is positioned such that an edge of each of the light beams reflected by each of the plurality of reflective surfaces is aligned on the tangent line common to an edge of one of the other of the plurality of light beams reflected from a different one of the plurality of reflective surfaces.

11. 10. The method of claim 9, further comprising spacing each of the plurality of reflective surfaces in the beam combiner such that an edge of each of the light beams reflected by each of the plurality of reflective surfaces is aligned on the tangent line common to an edge of one of the other of the plurality of light beams reflected from a different one of the plurality of reflective surfaces.

12. The method of any one of claims 7 to 11, wherein the tangent corresponds to an edge of an input coupler of a waveguide of the laser projection system.

13. an optical engine comprising a plurality of laser diodes configured to emit a plurality of light beams; a beam combiner having a plurality of reflective surfaces configured to generate a combined light beam by reflecting the plurality of light beams from the plurality of reflective surfaces such that edges of each of the plurality of light beams are tangentially aligned; a laser projection system including: a waveguide having an input coupler for receiving the combined light beam, an edge of the input coupler corresponding to the tangent line with which the edges of the plurality of light beams are aligned; A head mounted display (HMD), wherein at least one of the plurality of light beams has a different perimeter compared to at least one other light beam of the plurality of light beams.

14. The HMD of claim 13 , wherein each of the plurality of laser diodes emits light over a unique wavelength range compared to other of the plurality of laser diodes.

15. The HMD of claim 13 , wherein the plurality of reflective surfaces are arranged in parallel planes that intersect the optical path within the beam combiner.

16. An HMD described in any one of claims 13 to 15, wherein the position of each of the multiple reflective surfaces within the beam combiner and the spacing between each of the multiple reflective surfaces are based on aligning the edges of each of the multiple light beams on the tangent line.

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