Display system using variable beam expansion of multiple lasers

Abstract

The display system (100) may include a laser projection system (200) having an optical engine (202) and an optical scanner (204). Light output by the optical engine may be directed to a first scanning mirror (206) as two angularly separated laser light beams (1002, 1102). The angularly separated laser light beams typically have different angles of incidence (1010, 1110) on a second scanning mirror (208) of the optical scanner. In the first dimension, different levels of magnification are applied to the beam diameters of each of the angularly separated laser light beams, such that the angularly separated laser light beams have different beam diameters (1012, 1112) upon incidence at the second scanning mirror. The different beam diameters of the angularly separated laser light beams may result in equal or substantially similar incidence areas of each of the angularly separated laser light beams on the second scanning mirror.

Description

Background Art

[0001] Background Some display systems use a projector, which is an optical device that projects or illuminates a pattern of light onto another object (e.g., on the surface of another object such as a projection screen) to display an image or video on or through that other object. In a projector that uses a laser as a light source (i.e., a "laser projector"), each beam of laser light generated by the laser projector is modulated over time to provide a pattern of laser light, and controllable mirrors such as digital micromirrors are commonly used to spatially disperse the modulated pattern of laser light over a two-dimensional area of the other object. The spatial distribution of the modulated pattern of laser light generates an image of this other object.

Summary of the Invention

[0002] This disclosure can be better understood by reference to the accompanying drawings, and many of its features and advantages will become apparent to those skilled in the art. The use of the same reference numerals in different drawings indicates similar or identical items.

Brief Description of the Drawings

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[0004] Detailed Description FIGS. 1-14 illustrate embodiments for compactly arranging a near-eye display system (e.g., a wearable heads-up display (WHUD)) or another display system having a plurality of angularly separated laser inputs to which different beam expansions are applied by different reflecting surfaces of an optical relay. Using the techniques described herein, two or more laser inputs (sometimes referred to herein as "laser light beams") of such a display system are angularly separated from each other, such that these two or more laser light beams are neither parallel nor perpendicular to each other, but instead propagate along non-parallel (i.e., "angularly offset," "angularly separated") optical paths. Due to the angular separation of the two or more laser light beams, the respective angles of incidence of such laser light beams on one or more scanning mirrors of the system's optical scanner are typically different, and as a result, for laser light beams having the same or similar beam diameters, different-sized incident regions of such laser light beams on such scanning mirrors are obtained, which can affect performance and the user experience in a WHUD. To compensate for the differences in the respective angles of incidence and corresponding areas of the incident regions of such angularly separated light beams, different levels of beam expansion (i.e., magnification) are applied to each of the angularly separated laser light beams, such that in some embodiments, the areas of the respective incident regions of the angularly separated laser light beams at a given scanning mirror of the optical scanner are the same or approximately the same.

[0005] For further explanation, in some examples, a laser light beam having an incident area that is significantly larger or smaller than the reflective surface of the scanning mirror is provided onto the scanning mirror. For example, as a result of a portion of the angularly separated laser light beams escaping the reflective surface of the scanning mirror, the brightness of the image projected by the near-eye display system is lost. This applies to any laser light beam of the angularly separated laser light beams that would otherwise have an incident area larger than the reflective surface of the scanning mirror. Magnification level By reducing Magnification level , the brightness of the image can be maintained at a relatively high level. As another example, providing a laser light beam having an incident area smaller than the reflective surface of the scanning mirror results in underutilization of the reflective surface of the scanning mirror and a corresponding reduction in the optical resolution of the near-eye display. By increasing the level of magnification applied to any laser light beam of the angularly separated laser light beams that would otherwise have an incident area smaller than the reflective surface of the scanning mirror, this underutilization of the reflective surface is reduced.

[0006] In some embodiments of the technology disclosed herein, the display system includes a laser projection system that includes an optical engine having at least two tunable laser light sources, two scanning mirrors, an optical relay, and a waveguide. In operation, the at least two tunable laser light sources provide laser light (output as two or more angularly separated laser light beams), the two scanning mirrors receive the laser light in sequence, and each scans the laser light across its respective direction (e.g., the first scanning mirror scans the light along a first dimension and the second scanning mirror scans the light along a second dimension, where the second dimension can be substantially perpendicular to the first dimension). The waveguide includes an input coupler at which the scanned laser light is received from the second scanning mirror. The input coupler redirects the received light through the waveguide, and in some examples, through an intervening exit pupil expander (EPE), towards the output coupler of the waveguide such that the light exits the waveguide (e.g., over the user's eye) for projection.

[0007] In some embodiments of such a display system, two angularly separated laser light beams are output to an optical scanner that includes first and second scanning mirrors and an optical relay (e.g., via an optical engine and a beam combiner). The display system is configured such that a first laser light beam of the two angularly separated laser light beams is incident on the first scanning mirror, and the first scanning mirror scans the first laser light beam along a first scanning dimension onto a first reflective surface of the optical relay. A second laser light beam of the two angularly separated laser light beams is also incident on the first scanning mirror, and the first scanning mirror scans the second laser light beam along the first scanning dimension onto a second reflective surface of the optical relay. The first reflective surface directs the first laser light beam toward a third reflective surface of the optical relay. The second reflective surface directs the second laser light beam toward a fourth reflective surface of the optical relay. The third reflective surface directs the first laser light beam toward the second scanning mirror, and the second scanning mirror scans the first laser light beam across a first region of an input coupler of a waveguide along a second scanning dimension that is at least substantially perpendicular to the first scanning dimension. The fourth reflective surface directs the second laser light beam toward the second scanning mirror, and the second scanning mirror scans the second laser light beam across a second region of the input coupler of the waveguide along the second scanning dimension. In some embodiments, the first region of the input coupler partially overlaps the second region of the input coupler.

[0008] In some embodiments, the first and second reflective surfaces of the optical relay are non-overlapping reflective surfaces of the molded optical relay. In some embodiments, the third and fourth reflective surfaces of the optical relay are non-overlapping surfaces of the molded optical relay. In some embodiments, the first reflective surface expands (in some cases, referred to herein as performing beam expansion or enlargement) the beam diameter of a first laser beam having a first size along a first "non-scanning" dimension that is perpendicular or substantially perpendicular to the scanning dimension and the propagation direction of the first laser beam. In some embodiments, the second reflective surface expands the beam diameter of a second laser beam having a second size along a second non-scanning dimension that is perpendicular or substantially perpendicular to the scanning dimension and the propagation direction of the second laser beam. In some embodiments, the first size is different from the second size. In some embodiments, the first reflective surface has an optical prescription different from the second optical prescription of the second reflective surface, such that different-sized beam expansions are applied to the first laser beam by the first reflective surface and to the second laser beam by the second reflective surface, respectively, along the first and second non-scanning dimensions, respectively.

[0009] Generally, when the incident angle of a given laser beam with respect to a surface (such as that of a scanning mirror) deviates from the normal to that surface, the area of the surface region where the laser beam is incident increases. The surface region where the laser beam is incident is, in some cases, referred to herein as the "incident region". In an example of a laser projection system, if the incident region of a given laser beam and a given scanning mirror is larger than the reflecting surface of the scanning mirror, the portion of the laser beam that does not enter the reflecting surface is not reflected by the scanning mirror (a scenario sometimes referred to as "clipping" or "aperture clipping"), and as a result, the brightness of the image displayed using the laser projection system is lost. In particular, in an embodiment of the laser projection system of the present disclosure that utilizes two or more angularly separated laser beams as inputs, each laser beam will typically have a different incident angle with respect to a second scanning mirror, and as a result, the incident regions on the second scanning mirror will have different sizes. Assuming that each of the laser beams input into the laser projection system initially has the same or substantially the same beam diameter and has a different incident angle with respect to the second scanning mirror, the incident regions of the laser beams with respect to the second scanning mirror will have different sizes if the same level (i.e., magnitude) of beam expansion is applied along each respective non-scanning dimension of each of the laser beams through the reflecting surface of the optical relay, resulting in non-idealities. For example, if at least one of the incident regions of the laser beam exceeds the size of the reflecting surface of the second scanning mirror, undesirably, clipping of the projected image and loss of brightness will result. This loss of brightness can be mitigated by instead applying a reduced level of expansion to any laser beam having an incident region with an area that exceeds (e.g., significantly exceeds) that of the reflecting surface of the second scanning mirror. As another example, if at least one of the laser beams has an incident region on the second scanning mirror that is smaller than (e.g., significantly smaller than) the reflecting surface of the second scanning mirror, the optical resolution of the projected image will undesirably be reduced.This reduction in optical resolution can be mitigated by instead applying a greater level of expansion to any laser light beam having an incident region with an area that is smaller (e.g., significantly smaller) than the reflective surface of the second scanning mirror.

[0010] As confirmed above, by applying different levels of beam expansion to the angularly separated laser light beams of such a laser projection system along their respective non-scanning dimensions (where the different levels of beam expansion are applied, for example, via different reflective surfaces having different optical prescriptions), the size of each respective incident region of the angularly separated laser light beams at the second scanning mirror can be independently selected. For example, by applying different levels of beam expansion to the first and second angularly separated laser light beams along their respective non-scanning dimensions (where the first and second angularly separated laser light beams have the same initial beam diameter and different angles of incidence with respect to the second scanning mirror), the first incident region of the first laser light beam is set to be equal to or approximately equal to the second incident region of the second laser light beam, and in some embodiments, is set to be equal to or approximately equal to the size of the reflective surface of the second scanning mirror.

[0011] According to embodiments of the present disclosure, a laser projection system is provided that includes an optical relay having reflective surfaces with different optical prescriptions, whereby different levels of beam expansion are applied to the angularly separated laser light beams incident on the respective reflective surfaces. In some embodiments, the different levels of beam expansion are applied along the respective non-scanning dimensions of the angularly separated laser light beams such that the angularly separated laser light beams have respective incident regions of similar or the same size with respect to each other, with respect to the reflective surface of the second scanning mirror, or both, at the second scanning mirror.

[0012] Although some embodiments of the present disclosure are described and illustrated with reference to a particular exemplary near-eye display system in the form of a wearable head-up display (WHUD), it should be noted that the apparatus and techniques of the present disclosure are not limited to this particular example, but rather can be implemented in any of a wide variety of display systems using the guidelines provided herein.

[0013] FIG. 1 shows an exemplary display system 100 using a scanning-based optical system according to some embodiments, which includes a support structure 102 having an arm 104 that houses a laser projection system configured to project an image towards a user's eye such that the user perceives the projected image as being displayed within the field of view (FOV) area 106 of the display in one or both of the lens elements 108, 110. In the illustrated embodiment, the display system 100 is a near-eye display system in the form of a WHUD, where the support structure 102 is configured to be worn on the user's head and has the general shape and appearance (i.e., form factor) of a glasses (e.g., sunglasses) frame. The support structure 102 contains or otherwise includes various components for facilitating the projection of such an image towards the user's eye, such as a laser projector, an optical scanner, and waveguides. In some embodiments, the support structure 102 further includes various sensors such as one or more front cameras, rear cameras, other light 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 (trademark) interface, a WiFi interface, etc. Further, in some embodiments, the support structure 102 further includes one or more batteries or other portable power sources for powering the electrical components of the display system 100. In some embodiments, some or all of these components of the display system 100 are fully or partially contained within the internal volume of the support structure 102, such as within the arm 104 within the region 112 of the support structure 102. Although an exemplary form factor is shown, it should be noted that in other embodiments, the display system 100 may have a shape and appearance different from the glasses frame shown in FIG. 1. It should be understood that examples of the term "or" in this specification refer to a non-exclusive definition of "or" unless otherwise stated. For example, in this specification, the phrase "X or Y" means "X, or Y, or both".

[0014] One or both of the lens elements 108, 110 are used by the display system 100 to provide an augmented reality (AR) display. In the AR display, the rendered graphic content can be overlaid on the view of the real world or otherwise combined with the view of the real world when perceived by the user through the lens elements 108, 110. For example, the laser light used to form a perceivable image or series of images can be projected onto the user's eye through a series of optical elements such as a corresponding lens element, one or more scanning mirrors, and a waveguide formed in one or more optical relays by the laser projector of the display system 100. Thus, one or both of the lens elements 108, 110 include at least a portion of the waveguide that routes the display light received by the input coupler of the waveguide to the output coupler of the waveguide, and the output coupler outputs the display light toward the user's eye of the display system 100. The display light is modulated and scanned over the user's eye so that the user perceives the display light as an image. Additionally, each of the lens elements 108, 110 is sufficiently transparent to allow the user to see through the lens element and provide a view of the user's real-world environment such that the image appears overlaid on at least a portion of the real-world environment.

[0015] In some embodiments, the projector is any combination of a digital light processing-based projector, a scanning laser projector, or a tunable light source such as a laser or one or more light emitting diodes (LEDs), and a dynamic reflector mechanism such as one or more dynamic scanners or digital light processors. In some embodiments, the projector includes a plurality of laser diodes (e.g., a red laser diode, a green laser diode, and a blue laser diode), and at least one scanning mirror (e.g., two one-dimensional scanning mirrors that can be based on microelectromechanical systems (MEMS) or piezoelectric). 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 the operation of the projector. In some embodiments, the controller is communicatively coupled to a processor (not shown) that controls the size and location of the scanning area of the projector and generates the content to be displayed in the display system 100. The projector scans light over a variable area designated as the FOV area 106 of the display system 100. The size of the scanning area corresponds to the size of the FOV area 106, and the scanning area location corresponds to an area of one of the lens elements 108, 110 where the FOV area 106 is visible to the user. Generally, it is desirable for the display to have a wide FOV that accommodates the output coupling of light over a wide range of angles. As used herein, the range of positions of the eyes of different users where the display can be viewed is referred to as the eyebox of the display.

[0016] In some embodiments, the projector routes light through a first and a second scanning mirror, an optical relay disposed between the first and second scanning mirrors, and a waveguide disposed at the output of the second scanning mirror. In some embodiments, at least a portion of the output coupler of the waveguide can overlap the FOV area 106. These aspects are described in more detail below.

[0017] Figure 2 shows a schematic block diagram of a laser projection system 200 that directly projects an image onto a user's eye via a laser beam. 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, and the output coupler 214 is optically aligned with the user's eye 216 in this example. In some embodiments, the laser projection system 200 is implemented in a wearable heads-up display such as the display system 100 of FIG. 1 or another display system.

[0018] The optical engine 202 includes one or more laser light sources configured to generate and output laser light 218 (e.g., visible laser light such as red, blue, and green laser light, and in some embodiments, 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 the driver or other controller controls the timing of the emission of laser light from the laser light sources of the optical engine 202 according to instructions received by the coupled computer processor from this controller or driver, modulating the laser light 218 to be perceived as an image when output to the retina of the user's eye 216.

[0019] For example, during operation of the laser projection system 200, a plurality of laser light beams having different wavelengths are output by the laser light sources of the optical engine 202 and then combined via a beam combiner (not shown) before being directed towards the user's eye 216. The optical engine 202 modulates the intensity of each of the laser light beams such that the combined laser light reflects a series of pixels of an image. The specific intensity of each laser light beam at any given point in time contributes to the corresponding color content and amount of brightness of the pixel represented by the combined laser light at that time.

[0020] In some embodiments, one or both of the first and second scanning mirrors 206 and 208 of the optical scanner 204 are MEMS mirrors. For example, the first scanning mirror 206 and the second scanning mirror 208 are MEMS mirrors that are driven by their respective operating voltages to vibrate during the active operation of the laser projection system 200, whereby the first and second scanning mirrors 206 and 208 scan the laser light 218. Due to the vibration of the first scanning mirror 206, the laser light 218 output by the optical engine 202 is scanned through the optical relay 210 and across the surface of the second scanning mirror 208. The second scanning mirror 208 scans the laser light 218 received from the first scanning mirror 206 toward the input coupler 212 of the waveguide 205. In some embodiments, the first scanning mirror 206 vibrates or rotates in some other manner about the first axis 219 such that the laser light 218 is scanned across the surface of the second scanning mirror 208 in only one dimension (i.e., linearly). In some embodiments, the second scanning mirror 208 vibrates or rotates in some other manner about the second axis 221. In some embodiments, the first axis 219 is inclined with respect to the second axis 221.

[0021] In some embodiments, the input coupler 212 has a substantially rectangular outer shape, is configured to receive the laser light 218, and direct the laser light 218 into the waveguide 205. The input coupler 212 is defined by the smaller dimension (i.e., width) and the larger orthogonal dimension (i.e., length). In an embodiment, the optical relay 210 receives the laser light 218 scanned in a first dimension (e.g., the first dimension corresponding to the small dimension of the input coupler 212) by the first scanning mirror 206, routes the laser light 218 to the second scanning mirror 208, and is a line scanning optical relay that causes the laser light 218 to be concentrated (e.g., by collimation) on the exit pupil plane of the optical relay 210 beyond the second scanning mirror 208 in the first dimension. As used herein, "pupil plane" refers to a location along the optical path of the laser light through an optical system where the laser light is concentrated on an aperture along one or more dimensions. For example, the optical relay 210 can be associated with one or more entrance pupil planes located along the optical path of the laser light through the optical system, where the laser light is concentrated on a virtual aperture before entering the optical relay 210. For example, the optical relay 210 can be associated with one or more exit pupil planes located along the optical path of the laser light through the optical system, where the laser light is concentrated on a virtual aperture along one or more dimensions after exiting the optical relay 210. In some embodiments, the entrance pupil plane of the optical relay 210 can be arranged to coincide with the first scanning mirror 206. In some embodiments, the entrance pupil plane of the optical relay 210 can be located at an intermediate location between the first scanning mirror 206 and the optical relay 210. In some embodiments, the exit pupil plane of the optical relay 210 can be arranged to coincide with the second scanning mirror 208. In some embodiments, the exit pupil plane of the optical relay 210 can be arranged to coincide with the input coupler 212.

[0022] In some examples, the laser light is concentrated on a virtual aperture of a first entrance pupil plane along a first dimension (e.g., the laser light is concentrated on a point or line along the z-dimension along the x-y dimension with respect to a Cartesian coordinate system having an x-axis, a y-axis, and a z-axis), and is concentrated on a virtual aperture of a second entrance pupil plane along a second dimension (e.g., the second dimension is substantially perpendicular to the first dimension). Here, the first and second entrance pupil planes differ with respect to location. In some examples, the laser light is concentrated on a virtual aperture of a first exit pupil plane along a first dimension (e.g., the laser light is concentrated on a point or line along the z-dimension along the x-y dimension with respect to a Cartesian coordinate system having an x-axis, a y-axis, and a z-axis), and is concentrated on a virtual aperture of an exit pupil plane along a second dimension (e.g., the second dimension is substantially perpendicular to the first dimension). Here, the first and second exit pupil planes differ with respect to location. In other examples, the laser light is concentrated on a virtual aperture of a single entrance pupil plane along all dimensions (e.g., the laser light is concentrated on the virtual aperture along each of the x, y, and z dimensions), and is concentrated on a virtual aperture of a single exit pupil plane along all dimensions. In this example, the optical engine 202 is shown to output a single beam of laser light 218 towards the first scanning mirror (which itself can be a combination of two or more light beams each having a different polarization or wavelength), but in some embodiments, the optical engine 202 is configured to generate and output two or more laser light beams towards the first scanning mirror, where the two or more laser light beams are angularly separated from each other (i.e., they are "angularly separated laser light beams"). As described above, two or more laser light beams are "angularly separated" when propagating along non-parallel and non-perpendicular optical paths that are inclined with respect to each other (e.g., angularly offset), and in some examples, the angular separation of the optical paths causes the two or more laser light beams to be concentrated to overlap with each other along one or more dimensions (e.g., such overlap corresponds to the virtual aperture of the pupil plane).

[0023] In this example, the possible optical paths of the laser beam 218 are first diffused along the first scanning dimension following reflection by the first scanning mirror 206, but later these optical paths cross at the exit pupil plane beyond the second scanning mirror 208 due to the focusing provided by the optical relay 210. For example, the width (i.e., the smallest dimension) of a given exit pupil plane generally corresponds to the diameter of the laser beam corresponding to that exit pupil plane. Thus, the exit pupil plane can be regarded as a “virtual aperture”. In some embodiments, the exit pupil plane of the optical relay 210 coincides with the input coupler 212. In some embodiments, the entrance pupil plane of the optical relay 210 coincides with the first scanning mirror 206.

[0024] According to various embodiments, the optical relay 210 includes one or more spherical, aspherical, parabolic or free-form lenses that shape and relay the laser beam 218 to the second scanning mirror 208, or a molded reflective relay including two or more optical surfaces including, but not limited to, spherical, aspherical, parabolic or free-form lenses or reflectors (sometimes referred to herein as “reflective surfaces”) that shape and direct the laser beam 218 to the second scanning mirror 208. The second scanning mirror 208 receives the laser beam 218 and scans the laser beam 218 in the second dimension. The second dimension corresponds to the long dimension of the input coupler 212 of the waveguide 205. In some embodiments, the second scanning mirror 208 is arranged such that the exit pupil plane of the laser beam 218 is swept along a line along the second dimension. In some embodiments, the input coupler 212 is positioned in or near the sweep line downstream from the second scanning mirror 208 such that the second scanning mirror 208 scans the laser beam 218 as a column or row across the input coupler 212.

[0025] In some embodiments, the optical engine 202 includes an edge-emitting laser (EEL) that emits a laser beam 218 having a substantially elliptical non-circular cross-section, and the optical relay 210 expands or minimizes the laser beam 218 along one or both of a first direction (e.g., the major axis of the beam profile of the laser beam 218) or a second direction (e.g., the minor axis of the beam profile of the laser beam 218) to reshape (e.g., circularize) the laser beam 218 prior to focusing of the laser beam 218 at the second scanning mirror 208. In some such embodiments, the surface of the mirror plate of the first 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 first scanning mirror 206 is circular.

[0026] 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" means a combiner that transmits light from an input coupler (such as input coupler 212) to an output coupler (such as output coupler 214) using one or more of total internal reflection (TIR), special filters, or reflective surfaces. In some display applications, the light is a collimated image, and the waveguide transmits and duplicates the collimated image to the eye. Generally, the terms "input coupler" and "output coupler" 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, or surface relief holograms. In some embodiments, a given input coupler or output coupler is configured as a transmissive grating (e.g., a transmissive diffraction grating or a transmissive holographic grating) such that the input coupler or output coupler sends light and applies a designed optical function to the light during transmission. In some embodiments, a given input coupler or output coupler is a reflective grating (e.g., a reflective diffraction grating or a reflective holographic grating) such that the input coupler or output coupler reflects light and applies a designed optical function to the light during reflection. In this example, the laser light 218 received at the input coupler 212 is relayed through the waveguide 205 to the output coupler 214 using TIR. Next, the laser light 218 is output to the user's eye 216 through the output coupler 214. As described above, in some embodiments, the waveguide 205 has a glasses form factor and is implemented as part of a glasses lens such as lens elements 108 or 110 (FIG. 1) of a display system that utilizes the laser projection system 200.

[0027] Although not shown in the example of FIG. 2, in some embodiments, additional optical components are included in any of the optical paths between the optical engine 202 and the first scanning mirror 206, between the first scanning mirror 206 and the optical relay 210, between the optical relay 210 and the second scanning mirror 208, between the second scanning mirror 208 and the input coupler 212, between the input coupler 212 and the output coupler 214, or between the output coupler 214 and the eye 216 (e.g., to shape the laser light as seen by the user's eye 216). In some embodiments, a prism is used to steer the light from the second scanning mirror 208 to the input coupler 212 such that the light is coupled to the input coupler 212 at an angle suitable to facilitate the propagation of light in the waveguide 205 by TIR. Also, in some embodiments, an exit pupil expander such as a fold grating (e.g., the exit pupil expander 304 of FIG. 3 described below) is disposed at an intermediate stage between the input coupler 212 and the output coupler 214, receives the light coupled into the waveguide 205 by the input coupler 212, expands the light, redirects the light towards the output coupler 214, where the output coupler 214 then couples the laser light exiting the waveguide 205 (e.g., towards the user's eye 216).

[0028] Figure 3 shows an example of light propagation in waveguide 205 of the laser projection system 200 of FIG. 2 according to some embodiments. As shown, the light received via input coupler 212 and scanned along scanning dimension 302 is directed to exit pupil expander 304 and then routed to output coupler 214 and output (e.g., towards the user's eye). In some embodiments, the exit pupil expander 304 expands one or more dimensions of the eye box of a display system (e.g., display system 100 of FIG. 1, WHUDs 600, 702 of FIGS. 6 and 7) including the laser projection system 200 (e.g., relative to the dimensions of the display's eye box in the absence of the exit pupil expander 304). In some embodiments, input coupler 212 and exit pupil expander 304 each include a respective one-dimensional diffraction grating (i.e., a diffraction grating extending along one dimension) that diffracts the incident light in a particular direction depending on the angle of incidence of the incident light and the structural aspect of the diffraction grating. FIG. 3 shows a substantially ideal case where input coupler 212 directs the light straight down (relative to the currently shown view) in a first direction perpendicular to scanning dimension 302, and exit pupil expander 304 directs the light to the right (relative to the currently shown view) in a second direction perpendicular to the first direction. Although not shown in this example, it should be understood that in some embodiments, the first direction in which input coupler 212 directs the light is not strictly perpendicular to scanning dimension 302 but is slightly or substantially tilted relative thereto.

[0029] Figure 4 shows an exemplary embodiment of a laser projection system 200 in which the optical relay 210 includes a molded reflective relay. As shown, the laser projection system 200 includes a substrate 402 on which a beam combiner 404, a primary lens 406, and a mirror 408 are disposed. According to various embodiments, the substrate 402 is a printed circuit board (PCB) or otherwise another applicable substrate.

[0030] The optical engine 202 comprises a set of one or more laser light sources 410 (e.g., laser diodes), such as the illustrated red laser light source 410-1, green laser light source 410-2, and blue laser light source 410-3. A processor or other controller operates the optical engine 202 to modulate the respective intensity of each laser light source 410 so as to provide the contribution of the corresponding red light, green light, and blue light to the corresponding pixels of the image being generated for display to the user. The primary lens 406 includes a corresponding number of collimation lenses (e.g., three in the case of three laser light sources 410 in the above example), each intervening in the optical path between the respective laser light source 410 of the optical engine 202 and the beam combiner 404. For example, each laser light source 410 outputs laser light of different wavelengths (e.g., corresponding to the respective red, blue, and green wavelengths) that will be combined at the beam combiner 404 through the primary lens 406, and generates the laser light (i.e., the laser light 218 shown in FIG. 2) that will be projected by the laser projection system 200. The beam combiner 404 receives the individual laser light inputs and outputs the combined laser light 218 to the mirror 408, and the mirror 408 redirects the laser light 218 onto the reflecting surface 412 of the first scanning mirror 206. The first scanning mirror 206 scans the laser light 218 into the optical relay 210 along the first scanning dimension.

[0031] In the example of FIG. 4, the optical relay 210 is, for example, a molded reflective relay that can be molded from a solid transparent component (such as glass or an optical plastic such as Zeonex), and its reflective surface is implemented as a mirror coating or a metasurface. In some embodiments, one or more reflective surfaces of the molded reflective relay 1802 reflect light via TIR, and thus do not require a mirror coating or a fabricated metasurface to reflect light. Such molding facilitates incorporating some or all of the optical surfaces of the relay into a single element rather than several separate discrete elements, thus simplifying the manufacture of the laser projection system 200. Further, in some embodiments, the use of a molded structure allows light to propagate through one or more regions of the molded reflective relay 1802 via TIR rather than propagating light through these regions using a mirror coating.

[0032] The optical relay 210 is configured to route the laser light 218 towards the reflective surface 414 of the second scanning mirror 208. The second scanning mirror 208 scans the laser light 218 across an input coupler (such as input coupler 212) of the waveguide 205 along a second scanning dimension. In some embodiments, the second scanning dimension is perpendicular to the plane along which the laser light propagates when passing through the optical relay 210.

[0033] FIG. 5 shows an example of a path that the simultaneously generated laser light output by the optical engine 202 can take through the optical relay 210 in the case where the optical relay 210 is a molded reflective relay. As shown, the optical engine 202 outputs red laser light 218-1, green laser light 218-2, and blue laser light 218-3 toward the beam combiner 404. The beam combiner 404 combines the individual beams of laser light 218-1, 218-2, 218-3 into laser light 218 and redirects the laser light 218 toward the mirror 408. The mirror 408 reflects the laser light 218 onto the first scanning mirror 206. The first scanning mirror 206 scans the laser light 218 into the optical relay 210 along the first scanning dimension 502. The optical relay 210 reflects the laser light 218 from the reflecting surfaces 504, 506, 508, and 510 and then outputs the laser light 218 toward the reflecting surface 414 of the second scanning mirror 208. Next, the second scanning mirror 208 scans the laser light 218 across the input coupler 212 along the second scanning dimension 512. Here, the laser light 218 converges on the input coupler 212 at most or all of the achievable scanning angles of the first scanning mirror 206. In this example, the beam combiner 404 is shown to output a single beam of laser light 218, but it should be understood that in some embodiments, the beam combiner 404 is configured to output two or more angularly separated laser light beams directed onto the first scanning mirror 206.

[0034] FIG. 6 shows a portion of the WHUD 600 including the laser projection system 200 of FIG. 2. In some embodiments, the WHUD 600 represents the display system 100 of FIG. 1. The optical engine 202, the optical scanner 204, the input coupler 212, and a portion of the waveguide 205 are included in the arm 602 of the WHUD 600 in this example.

[0035] The WHUD600 includes an optical combiner lens 604 that includes a first lens 606, a second lens 608, and a waveguide 205, and the waveguide 205 is disposed between the first lens 606 and the second lens 608. The light exiting through the output coupler 214 travels through the second lens 608 (e.g., corresponding to the lens element 110 of the display system 100). In use, the light exiting the second lens 608 enters the pupil of the user's eye 610 wearing the WHUD600, allowing the user to perceive a display image conveyed by the laser light output by the optical engine 202. The optical combiner lens 604 is substantially transparent, allowing light from the real-world scene corresponding to the environment around the WHUD600 to pass through the first lens 606, the second lens 608, and the waveguide 205 and reach the user's eye 610. In this way, when an image or other graphic content output by the laser projection system 200 is projected onto the user's eye 610, it is combined (e.g., overlaid) with the real-world image of the user's environment, providing the user with an AR experience.

[0036] Although not shown in the illustrated example, in some embodiments, additional optical elements are included in any of the optical paths between the optical engine 202 and the input coupler 212, between the input coupler 212 and the output coupler 214, or between the output coupler 214 and the user's eye 610 (e.g., to shape the laser light as seen by the user's eye 610). By way of example, a prism is used to steer the light from the optical scanner 204 to the input coupler 212 so that the light is coupled to the input coupler 212 at an angle suitable for promoting the propagation of light in the waveguide 205 by TIR. Also, in some embodiments, an exit pupil expander such as a folded grating (e.g., exit pupil expander 304) is disposed at an intermediate stage between the input coupler 212 and the output coupler 214, receives the light coupled into the waveguide 205 by the input coupler 212, expands the light, redirects the light towards the output coupler 214, where the output coupler 214 then couples the laser light exiting the waveguide 205 (e.g., towards the user's eye 610).

[0037] Figures 7 and 8 show two different perspective views, namely, partially transparent views 700 (Figure 7) and 800 (Figure 8) of a portion of the WHUD 702 representing the WHUD 600 of Figure 6 or the display system 100 of Figure 1. The WHUD 702 includes an exemplary configuration of the laser projection system 200 of Figures 2, 4, and 5 for an embodiment in which the optical relay 210 is a molded reflective relay. In some embodiments, the WHUD 702 corresponds to the display system 100 of Figure 1, and the portion of the WHUD 702 shown corresponds to the region 112 of the display system 100.

[0038] As shown by view 700 of FIG. 7 and 800 of FIG. 8, the arm 704 of the WHUD 702 houses the optical engine 202, the primary lens 406, and at least a portion of the first scanning mirror 206, the optical relay 210, and the substrate 402. The frame section 706 of the WHUD 702 houses the second scanning mirror 208 and a portion of the first scanning mirror 206, the optical relay 210, and the substrate 402. As shown by view 700 of FIG. 7, the input coupler 212 and the output coupler 214 (not fully shown in the figures of FIGS. 7 and 8) of the waveguide 205 are each either embedded in the lens 708 (e.g., one embodiment of the lens 110 of FIG. 1) or disposed on this lens if not. As described above, the laser light output by the optical engine 202 (e.g., the laser light 218 of FIG. 5) is routed to the input coupler 212 at least via the first scanning mirror 206, the optical relay 210, and the second scanning mirror 208. The first scanning mirror 206 vibrates or otherwise rotates to scan the laser light along the first scanning dimension, and the second scanning mirror 208 vibrates or otherwise rotates to scan the laser light along a second scanning dimension perpendicular to the first scanning dimension. The laser light reflected by the second scanning mirror 208 converges on the line at the input coupler 212. The relay laser light received at the input coupler 212 is routed to the output coupler 214 via the waveguide 205. Next, the laser light received at the output coupler 214 is directed to exit the waveguide 205 (e.g., towards the user's eye of the WHUD 702).

[0039] FIG. 9 shows an exemplary perspective view of a laser projection system 900 (one embodiment of the laser projection system 200 of FIG. 2) that conveys image information for projection using two angularly separated laser light beams. In this example, the perspective view of the laser projection system 900 is provided with respect to a three-dimensional Cartesian coordinate system having x, y, and z axes that are orthogonal to each other, where the perspective view provides a viewpoint looking down the positive z-axis.

[0040] The optical engine 202 includes two or more laser light sources each configured to output a respective different wavelength of laser light toward the beam combiner 404. The beam combiner 404 combines the wavelengths of the laser light output by the optical engine 202 into a first laser light beam 902 and a second laser light beam 904 that are angularly separated from each other (e.g., at an angle of about 0 degrees to about 10 degrees), and outputs the first and second laser light beams 902 and 904 (which may sometimes be referred to herein as the first and second angularly separated laser light beams 902 and 904) toward the first scanning mirror 206. In some embodiments, each of the first laser light beam 902 and the second laser light beam 904 includes a plurality of laser light wavelengths combined via the beam combiner 404 and is thus considered an "aggregated" laser light beam. In this example, only the central rays of the first and second laser light beams 902 and 904 are shown, but it should be understood that the first and second laser light beams 902 and 904 are scanned across their respective scanning regions by the first and second scanning mirrors 206 and 208, and the illustrated central rays are centered within the scanning regions. The first and second laser light beams 902 and 904 converge along the x-y dimension (with respect to the axis shown), overlap at the reflecting surface of the first scanning mirror 206 (e.g., the reflecting surface 412 of FIG. 4) (e.g., an overlap with respect to the z dimension, having the same or substantially the same z coordinate at one or more overlapping points), and the overlapping points correspond to the first entrance pupil plane of the optical relay 210. According to various embodiments, other entrance pupil planes corresponding to the convergence of the first and second laser light beams 902 and 904 onto a virtual aperture along other dimensions or planes (e.g., a dimension or plane substantially perpendicular to the x-y dimension) may be disposed at the same or substantially the same location as the first entrance pupil plane along the optical paths of the first and second laser light beams 902 and 904, or alternatively, may be disposed at other locations along these optical paths. In some embodiments, a first axis 219 about which the first scanning mirror 206 is configured to vibrate is aligned or substantially aligned along the x-y dimension and is perpendicular or substantially perpendicular to the z axis.

[0041] The first scanning mirror 206 scans the first and second laser light beams 902 and 904 into the optical relay 210 along a first scanning dimension (e.g., the scanning dimension 302 in FIG. 3, the first scanning dimension 502 in FIG. 5) corresponding to or substantially corresponding to the x-z dimension that is substantially orthogonal to the x-y dimension. When reflected by the first scanning mirror 206, the optical paths of the first and second laser light beams 902 and 904 diverge again and will be angularly separated along the x-y dimension. In some embodiments, the optical relay 210 expands each of the first and second laser light beams 902 and 904 along one or more dimensions (e.g., circularizes each of the first and second laser light beams 902 and 904). According to various embodiments, different levels (i.e., sizes) of expansion (in some cases, referred to as beam expansion) of the first and second laser light beams 902 and 904 along their respective non-scanning dimensions are applied by the reflecting surface of the optical relay 210. As used herein, two dimensions (e.g., a line, a plane, a direction, etc.) are considered to be "substantially orthogonal" or "substantially perpendicular" to each other when they are orthogonal or perpendicular to each other within about 15 degrees. The optical relay 210 relays the first and second laser light beams 902 and 904 towards the second scanning mirror 208, focuses the first and second laser light beams 902 and 904 along the x-y dimension, and focuses each of the first and second laser light beams 902 and 904 on their respective scanning regions with respect to the z dimension along their respective propagation directions.

[0042] In this example, the first and second laser light beams 902 and 904 are incident on two separate locations of the reflecting surface of the second scanning mirror 208 (e.g., the reflecting surface 414 in FIG. 4) (i.e., the exit pupil plane of the optical relay along the x-y dimension is not disposed on the second scanning mirror 208). However, in some embodiments, the first and second laser light beams 902 and 904 instead are incident on the reflecting surface of the second scanning mirror 208 in an area that is substantially the same as or at least partially overlaps with the area of the reflecting surface of the second scanning mirror 208, and in some such embodiments, it should be understood that the reflecting surface of the second scanning mirror 208 acts as the exit pupil plane of the optical relay 210 along the x-y dimension. As used herein, two areas (e.g., the area of the incident region and the area of the reflecting surface, the areas of two incident regions, etc.) are considered to be "substantially the same" if the first of the two areas is within about 66% to about 133% of the size of the second of the two areas. The second scanning mirror 208 scans the first and second laser light beams 902 and 904 toward the input coupler 212 along the x-y dimension (e.g., the second scanning dimension 512 in FIG. 5).

[0043] In this example, when reflected by the second scanning mirror 208, the first and second laser light beams 902 and 904 converge along the x-y dimension and overlap at the first exit pupil plane of the optical relay 210 in the input coupler 212 (e.g., overlap with respect to the z dimension). However, in embodiments where the exit pupil plane of the optical relay 210 is disposed at or substantially at the reflecting surface of the second scanning mirror 208, the first and second laser light beams 902 and 904 instead diverge along the x-y dimension after being reflected by the second scanning mirror 208 and are incident at respective different locations along the input coupler 212. According to various embodiments, other exit pupil planes corresponding to the convergence of the first and second laser light beams 902 and 904 onto a virtual aperture along other dimensions or planes (e.g., a dimension or plane substantially perpendicular to the x-y dimension such as the z dimension, etc.) may be disposed at the same or substantially the same location as the first exit pupil plane along the optical paths of the first and second laser light beams 902 and 904, or alternatively, may be disposed at other locations along these optical paths. Additionally, the respective scanning regions of the first and second laser light beams 902 and 904 each converge with respect to the z dimension along their respective propagation directions, whereby the second scanning mirror 208 scans each of the first and second laser light beams 902 and 904 along respective substantially one-dimensional paths (e.g., along respective lines or arcs) at the input coupler 212 (e.g., at the first exit pupil plane 908). As used herein, a "substantially one-dimensional" path refers to a path that follows a single straight line or curved line (e.g., an arc).

[0044] In the present example of FIG. 9, the first and second laser light beams 902 and 904 input to the optical scanner 204 are shown to be angularly separated and concentrated along the x-y axis at the first entrance pupil plane at the first scanning mirror 206 and at the first exit pupil plane at the input coupler 212. However, in some alternative embodiments of the laser projection system 900, the first and second laser light beams 902 and 904 are not angularly separated by a substantially non-zero amount and are instead parallel or collinear. In such alternative embodiments, each of the first and second laser light beams 902 and 904 undergoes independent concentration (i.e., of the light of each individual beam, although not necessarily relative to other beams) onto a virtual aperture along the x-y axis at the first entrance pupil plane and the first exit pupil plane.

[0045] FIG. 10 shows an exemplary perspective view 1000 of a portion of a laser projection system (one embodiment of the laser projection system 200 of FIG. 2) in which a laser light beam 1002 (which may sometimes be referred to herein as the "first laser light beam 1002") is incident on a reflecting surface 414 of a second scanning mirror 208 at an angle of incidence 1010, herein represented as θ, with respect to a plane (which may sometimes be referred to herein as the plane of the reflecting surface 414) along which the reflecting surface 414 is oriented. In the present example, the first laser light beam 1002 has a beam diameter 1012 and an angle of incidence 1010 such that the incident region of the first laser light beam 1002 with respect to the second scanning mirror 208 fits entirely within the boundary defined by the reflecting surface 414. That is, all or substantially all of the first laser light beam 1002 is incident on the reflecting surface 414. In some embodiments, the first laser light beam 1002 is an aggregated laser light beam that includes a plurality of laser light wavelengths that were previously combined, for example, using a beam combiner (e.g., the embodiment of the beam combiner 404 of FIGS. 4 and 9).

[0046] In this example, the optical path of the first laser beam 1002 is shown via the central ray 1006, the first boundary ray 1004, and the second boundary ray 1008. For example, the light of the first laser beam 1002 is substantially or completely disposed within the region defined by the first boundary ray 1004 and the second boundary ray 1008 and is centered or substantially centered along the central ray 1006. The shortest distance between the first boundary ray 1004 and the second boundary ray 1008 defines the beam diameter 1012.

[0047] As shown, the second scanning mirror 208 includes a reflective surface 414 having a width 1014. The incident angle 1010 of the first laser beam 1002 on the reflective surface 414 is here defined, with respect to the x-y plane, as the angle θ between the plane of the reflective surface 414 and the central ray 1006 of the first laser beam 1002 when the first laser beam 1002 approaches the reflective surface 414. The beam diameter 1012, the incident angle 1010, and the width 1014 of the reflective surface 414 collectively determine whether the incident region of the first laser beam 1002 on the second scanning mirror 208 is completely located on the reflective surface 414 or whether a portion of the incident region escapes the reflective surface. In some embodiments, the beam diameter 1012 of the first laser beam 1002 is set via the expansion of the first laser beam 1002 applied to the optical relay 210 (e.g., via one or more reflective surfaces having an optical prescription that results in such an expansion).

[0048] The second scanning mirror 208 is shown herein in a particular orientation (i.e., the first orientation), but it should be understood that the reflecting surface 414 of the second scanning mirror 208 vibrates or rotates (e.g., about an axis in the z-dimension such as the second axis 221 shown in FIG. 2) whether or not. In some embodiments, the reflecting surface 414 vibrates or rotates independently of the body portion of the second scanning mirror 208, while in other embodiments, the reflecting surface 414 vibrates or rotates with all or a portion of the body portion of the second scanning mirror 208. Such rotation of the reflecting surface 414 typically changes the size of the incident area of the first laser beam 1002 on the reflecting surface 414 due to the resulting change at the incident angle 1010 (e.g., as the incident angle 1010 approaches perpendicular to the reflecting surface 414, the size of the incident area decreases, and as the incident angle 1010 approaches parallel to the reflecting surface 414, it increases). In some embodiments, the beam diameter 1012 of the first laser beam 1002 is such that the incident area of the first laser beam 1002 on the second scanning mirror 208 is disposed substantially (e.g., with at least about 80% of the first laser beam 1002 incident on the reflecting surface 414) or completely on the reflecting surface 414 over the entire period of vibration or rotation of the reflecting surface 414. That is, the first laser beam 1002 remains substantially or completely incident on the reflecting surface 414 even when the reflecting surface is at the extreme of rotation or vibration during operation. Here, the maximum range over which the scanning mirror rotates or vibrates in a given direction during operation is called the extreme of rotation or vibration in that direction.

[0049] FIG. 11 shows an exemplary perspective view 1100 of a portion of a laser projection system (one embodiment of the laser projection system 200 of FIG. 2) in which a laser light beam 1102 (which may be referred to herein as the "second laser light beam 1102" in some cases) is incident on the reflecting surface 414 of the second scanning mirror 208 at an incident angle 1110, represented herein as φ, with respect to the surface along which the reflecting surface 414 is oriented. In some embodiments, the second laser light beam 1102 is an aggregated laser light beam that includes a plurality of laser light wavelengths previously combined using, for example, a beam combiner (e.g., the embodiment of the beam combiner 404 of FIGS. 4 and 9).

[0050] According to various embodiments, the first laser light beam 1002 and the second laser light beam 1102 of FIG. 10 can be provided together to the second scanning mirror 208 as angularly separated laser light beams. In some embodiments, the incident angle 1110 of the second laser light beam 1102 is away from a state perpendicular to the plane of the reflecting surface 414 as compared to the incident angle 1010 of the first laser light beam 1002. As a result, in the case where the second laser light beam 1102 and the first laser light beam 1002 have the same or similar respective beam diameters, the incident region of the second laser light beam 1102 on the second scanning mirror 208 is larger compared to the incident region of the first laser light beam 1002 on the second scanning mirror 208.

[0051] In the first example, the second laser beam 1102 has a beam diameter 1112 such that, given the angle of incidence 1110, the incident region of the second laser beam 1102 on the second scanning mirror 208 partially crosses the boundary defined by the reflecting surface 414. That is, in the first example, a portion of the second laser beam 1102 escapes the reflecting surface 414 (and thus is not reflected by the reflecting surface 414), resulting in a reduction in the brightness of the image generated by the laser projection system. In some embodiments of the first example, the beam diameter 1112 of the second laser beam 1102 is the same as or substantially the same as the beam diameter 1012 of the first laser beam 1002. In some embodiments of the first example, the beam diameter 1116 is set via the expansion of the second laser beam 1102 applied by the reflecting surface of the optical relay 210.

[0052] In the first example, the optical path of the second laser beam 1102 is shown via the central ray 1106, the first boundary ray 1104, and the second boundary ray 1108. The light of the second laser beam 1102 is substantially or completely disposed within the region defined by the first boundary ray 1104 and the second boundary ray 1108 and is centered or substantially centered along the central ray 1106. The shortest distance between the first boundary ray 1104 and the second boundary ray 1108 defines the beam diameter 1112. As shown, a portion of the light of the second laser beam 1102 near the boundary rays 1104 and 1108 escapes the reflecting surface 414 due to the incident region of the second laser beam 1102 exceeding the width 1114 of the reflecting surface 414.

[0053] In the second example, the second laser light beam 1102 has a beam diameter 1116 that is smaller than the beam diameter 1112 of the first example such that, in terms of the angle of incidence 1110, the incident region of the second laser light beam 1102 on the second scanning mirror 208 fits entirely within the boundary defined by the reflecting surface 414. That is, in the second example, all or substantially all of the second laser light beam 1102 is incident on the reflecting surface 414. In some embodiments of the second example, the beam diameter 1116 of the second laser light beam 1102 is smaller than the beam diameter 1012 of the first laser light beam 1002.

[0054] In some embodiments of the second example, the first laser light beam 1002 and the second laser light beam 1102 are initially generated with matching or substantially matching beam diameters, and different respective levels of expansion are applied to each of the first laser light beam 1002 and the second laser light beam 1102 by the reflecting surface of the optical relay 210, such that as a result, the second laser light beam 1102 has a beam diameter 1116 that is smaller than the beam diameter 1012 of the first laser light beam 1002. In some embodiments of the second example, the beam diameter 1116 is set by the expansion of the second laser light beam 1102 applied by the reflecting surface of the optical relay 210 such that the incident regions of the first laser light beam 1002 and the second laser light beam 1102 are the same size or substantially the same size. By applying different levels of expansion to the first laser light beam 1002 and the second laser light beam 1102 in this way, even if the first laser light beam 1002 and the second laser light beam 1102 are initially generated with the same or substantially similar beam diameters, the beam diameter of the second laser light beam 1102 can be made smaller than the diameter of the first laser light beam 1002 to account for the difference in the angles of incidence 1010 and 1110 and the corresponding difference in the incident regions of the first laser light beam 1002 and the second laser light beam 1102 on the second scanning mirror 208.

[0055] In the second example, the optical path of the second laser beam 1102 is shown via the central ray 1106, the third boundary ray 1118, and the fourth boundary ray 1120. The light of the second laser beam 1102 is substantially or completely disposed within the region defined by the third boundary ray 1118 and the fourth boundary ray 1120 and is centered or substantially centered along the central ray 1106. The shortest distance between the third boundary ray 1118 and the fourth boundary ray 1120 defines the beam diameter 1116. As shown, when the second laser beam 1102 has the beam diameter 1116, all or substantially all of the second laser beam 1102 is incident on the reflecting surface 414.

[0056] In both the first and second examples, the incident angle 1110 of the second laser beam 1102 with respect to the reflecting surface 414 is defined as the angle φ between the plane of the reflecting surface 414 and the central ray 1106 of the second laser beam 1102 when the second laser beam 1102 approaches the reflecting surface 414, with respect to the x - y plane. The beam diameter 1112 or 1116, the incident angle 1110, and the width 1114 of the reflecting surface 414 collectively determine whether the incident region of the second laser beam 1102 with respect to the second scanning mirror 208 is completely located on the reflecting surface 414 or whether a portion of the incident region escapes the reflecting surface.

[0057] Note that the direction of the scanning mirror 208 shown is intended to correspond to the direction of the scanning mirror 208 shown in FIG. 10 (e.g., to facilitate comparison between respective incident angles 1010 and 1110). As described above, rotation of the reflective surface 414 typically changes the size of the incident area of the second laser light beam 1102 on the reflective surface 414 due to the resulting change at the incident angle 1110 (e.g., as the incident angle 1110 approaches perpendicular to the reflective surface 414, the size of the incident area decreases, and as the incident angle 1110 approaches parallel to the reflective surface 414, it increases). In some embodiments, the beam diameter 1116 of the second laser light beam 1102 is such that the incident area of the laser light beam 1102 on the second scanning mirror 208 is disposed substantially (e.g., with 90% or more of the second laser light beam 1102 incident on the reflective surface 414) or completely on the reflective surface 414 over each period of vibration or rotation of the reflective surface 414. That is, the second laser light beam 1102 remains substantially or completely incident on the reflective surface 414 even when the reflective surface is at the extreme values of rotation or vibration during operation.

[0058] FIG. 12 shows an exemplary perspective view 1200 of a portion of a laser projection system (one embodiment of the laser projection system 200 of FIG. 2), where a laser light beam 1202 (sometimes referred to herein as the "first laser light beam 1202" and one embodiment of the first laser light beam 1002 of FIG. 10) travels along the shown optical path following reflection by the reflective surface 412 of the first scanning mirror 206, is incident on the first reflective surface 1204, then on the second reflective surface 1206, and then on the reflective surface 414 of the second scanning mirror 208. The second scanning mirror 208 scans the first laser light beam 1202 along a path (e.g., a line or an arc) in the input coupler 212. The first reflective surface 1204 and the second reflective surface 1206 are reflective surfaces of an optical relay, such as an embodiment of the optical relay 210 of any of FIGS. 2, 4, 5, 7, 8, and 9.

[0059] The first reflecting surface 1204 is configured to focus the first laser beam 1202 on the intermediate pupil plane 1208 with respect to the x-y dimension. Thereafter, the beam width of the first laser beam 1202 expands with respect to the x-y dimension until it hits the second reflecting surface 1206. The second reflecting surface 1206 collimates the first laser beam 1202 and reflects the first laser beam 1202 towards the second scanning mirror 208. According to various embodiments, either or both of the first reflecting surface 1204 and the second reflecting surface 1206 have an optical prescription that effectively expands the first laser beam 1202. That is, due to the expansion caused by either or both of the first reflecting surface 1204 and the second reflecting surface 1206, the first laser beam 1202 will have a larger beam diameter in the first dimension after being reflected by the second reflecting surface 1206 as compared to the beam diameter of the first laser beam 1202 in the first dimension between the first scanning mirror 206 and the first reflecting surface 1204. Here, the beam diameter of the first laser beam 1202 in the "first dimension" refers to the diameter of the first laser beam 1202 along the x-y dimension or along a dimension substantially perpendicular to the scanning dimension of the first scanning mirror 206. The magnitude of the expansion applied to the beam diameter of the first laser beam 1202 in the first dimension by either or both of the first reflecting surface 1204 and the second reflecting surface 1206 is, in some cases, referred to herein as the "first expansion level".

[0060] FIG. 13 shows an exemplary perspective view 1300 of a portion of a laser projection system (one embodiment of the laser projection system 200 of FIG. 2), where a laser light beam 1302 (which may be referred to herein as the "second laser light beam 1302" and is one embodiment of the second laser light beam 1102 of FIG. 11) travels along the shown optical path following reflection by the reflecting surface 412 of the first scanning mirror 206, is incident on a third reflecting surface 1304, then on a fourth reflecting surface 1306, and then on the reflecting surface 414 of the second scanning mirror 208. The second scanning mirror 208 scans the second laser light beam 1302 along a path (e.g., a line or an arc) at the input coupler 212. The third reflecting surface 1304 and the fourth reflecting surface 1306 are, for example, reflecting surfaces of an optical relay such as an embodiment of the optical relay 210 of any of FIGS. 2, 4, 5, 7, 8, and 9.

[0061] The third reflecting surface 1304 is configured to focus the second laser beam 1302 onto the intermediate pupil plane 1308 with respect to the x-y dimensions. Thereafter, the beam width of the second laser beam 1302 expands with respect to the x-y dimensions until it hits the fourth reflecting surface 1306. The fourth reflecting surface 1306 collimates the second laser beam 1302 and reflects the second laser beam 1302 towards the second scanning mirror 208. According to various embodiments, either or both of the third reflecting surface 1304 and the fourth reflecting surface 1306 have an optical prescription that effectively expands the second laser beam 1302. That is, due to the expansion caused by either or both of the third reflecting surface 1304 and the fourth reflecting surface 1306, the second laser beam 1302 has a larger beam diameter in the first dimension after being reflected by the fourth reflecting surface 1306 compared to the beam diameter of the second laser beam 1302 in the first dimension between the first scanning mirror 206 and the third reflecting surface 1304. Here, the beam diameter of the second laser beam 1302 in the "first dimension" refers to the diameter of the second laser beam 1302 along the x-y dimensions or along a dimension substantially perpendicular to the scanning dimension of the first scanning mirror 206. The magnitude of the expansion applied to the beam diameter of the second laser beam 1302 in the first dimension by either or both of the third reflecting surface 1304 and the fourth reflecting surface 1306 is, in some cases, referred to herein as the "second expansion level".

[0062] FIG. 14 shows an exemplary perspective view 1400 of a portion of a laser projection system (one embodiment of the laser projection system 200 of FIG. 2) including embodiments of the first laser beam 1202 and the first and second reflecting surfaces 1204 and 1206 of the example of FIG. 12, and the second laser beam 1302 and the third and fourth reflecting surfaces 1304 and 1306 of the example of FIG. 13. As shown in this example, the first laser beam 1202 and the second laser beam 1302 are angularly separated from each other. It should be noted that the respective optical paths of the first laser beam 1202 and the second laser beam 1302 intersect at various points as shown.

[0063] In this example, the optical relay such as the embodiment of the optical relay 210 of any one of FIGS. 2, 4, 5, 7, 8, and 9 includes reflective surfaces 1204, 1206, 1304, and 1306. In some embodiments, each of the reflective surfaces 1204, 1206, 1304, and 1306 is a separate reflective element such as a mirror, a metasurface, etc. In some embodiments, each of the reflective surfaces 1204, 1206, 1304, and 1306 is included as a surface of a molded reflective relay (e.g., a monolithic molded reflective relay).

[0064] Due to the angular separation of the first laser beam 1202 and the second laser beam 1302, the first laser beam 1202 has a first incident angle (e.g., incident angle 1010 in FIG. 10) on the reflecting surface 414 of the second scanning mirror 208 that is different from the second incident angle (e.g., incident angle 1110 in FIG. 10) of the second laser beam 1302 on the reflecting surface 414. In this example, the first incident angle of the first laser beam 1202 on the reflecting surface 414 is closer to being perpendicular to the plane of the reflecting surface 414 than the second incident angle of the second laser beam 1302, whereby the incident region of the first laser beam 1202 on the second scanning mirror 208 is smaller than the incident region of the second laser beam 1302 if the first laser beam 1202 and the second laser beam 1302 have the same beam diameter when incident on the second scanning mirror 208. To accommodate the difference in the respective incident angles of the first laser beam 1202 and the second laser beam 1302 on the second scanning mirror 208, as shown, the first laser beam 1202 and the second laser beam 1302 initially have similar or matching beam diameters, but a first level of expansion is applied to the beam diameter of the first laser beam 1202 in the first dimension (i.e., the x - y dimension) by one or both of the first reflecting surface 1204 and the second reflecting surface 1206, while a second level of expansion is applied to the beam diameter of the second laser beam 1302 in the first dimension by one or both of the third reflecting surface 1304 and the fourth reflecting surface 1306. For example, the first level of expansion is greater than the second level of expansion, whereby when the first and second beams are incident on the second scanning mirror 208, the beam diameter of the first laser beam 1202 in the first dimension (e.g., a beam diameter of about 1 mm) is larger than the beam diameter of the second laser beam 1202 in the first dimension (e.g., a beam diameter of about 0.9 mm).In some embodiments, the first and second levels of expansion applied to the respective beam diameters of the first laser beam 1202 and the second laser beam 1302 by the respective reflecting surfaces 1204 and 1206, and the reflecting surfaces 1304 and 1306, are such that the respective incident areas of the first laser beam 1202 and the second laser beam 1302 on the second scanning mirror 208 are equal or substantially equal in area, shape, or both, and each is set to fit entirely or substantially within the outer perimeter defined by the reflecting surface 414 of the second scanning mirror 208. By applying different levels of expansion in a first dimension to the respective beam diameters of the first laser beam 1202 and the second laser beam 1302 that are angularly separated, other larger incident areas of the second laser beam 1302 on the second scanning mirror 208 can be accommodated without increasing the size of the reflecting surface 414. This technique can be advantageous, for example, in a laser projector where the size of the reflecting surface (e.g., reflecting surface 414) of the second scanning mirror is a limiting factor and it is not desirable to increase the size of the reflecting surface to accommodate a larger incident area for a wider-angle laser beam (e.g., the second laser beam 1302) of two angularly separated input laser beams.

[0065] The first laser beam 1202 and the second laser beam 1302 are shown in this example to have similar or the same respective initial beam diameters (the "initial beam diameter" in this specification refers to the beam diameter of the first and second laser beams 1202 after reflection at the first scanning mirror 206 and before reflection by the reflecting surfaces 1204 and 1304), but it should be understood that in some embodiments, the first laser beam 1202 and the second laser beam 1302 may instead have different initial beam diameters, at least with respect to the first dimension. In some such embodiments, the first level of expansion applied to the first laser beam 1202 by the reflecting surfaces 1204 and 1206 is different from the second level of expansion applied to the second laser beam 1302 by the reflecting surfaces 1304 and 1306, where the first level of expansion is different from the second level of expansion. The first level of expansion and the second level of expansion are such that, after reflection by the reflecting surfaces 1206 and 1306, the beam diameters of the first laser beam 1202 and the second laser beam 1302 are made such that the respective incident regions of the first laser beam 1202 and the second laser beam 1302 at the second scanning mirror 208 are the same or substantially the same. In some embodiments, given different angles of incidence of the first laser beam 1202 and the second laser beam 1302 at the second scanning mirror 208, the first laser beam 1202 and the second laser beam 1302 can be made to have the same or substantially the same respective shape, area, or both as that of the reflecting surface 414 of the second scanning mirror 208.

[0066] In an alternative embodiment, each of the reflective surfaces 1204, 1206, 1304, and 1306 provides the same level of magnification to the first and second laser light beams 1202 and 1302, and the initial beam diameters of the first and second laser light beams 1202 and 1302 are such that their incident regions at the second scanning mirror 208 are the same or substantially the same, and in some embodiments, are selected to be different (e.g., with respect to a first dimension) such that they have the same area, shape, or both as the reflective surface 414 of the second scanning mirror 208. That is, rather than applying various levels of magnification to the laser light beams 1202 and 1302, the laser light beams 1202 and 1302 are introduced into the optical relay with different initial beam diameters, and the same level of magnification is applied to each of the laser light beams 1202 and 1302 by the reflective surfaces 1204, 1206, 1304, and 1306, such that, given the different angles of incidence of the laser light beams 1202 and 1302 at the second scanning mirror 208, the different initial beam diameters of the laser light beams 1202 and 1302 result in the respective incident regions of the first laser light beam 1202 and the second laser light beam 1302 being the same or substantially the same, and in some embodiments, having the same or substantially the same respective shape, area, or both as that of the reflective surface 414 of the second scanning mirror 208.

[0067] The various embodiments described above are provided in the context of generating and routing laser light through an optical system. However, it should be understood that in addition to or instead of such laser light and corresponding laser light sources, other applicable collimated light sources and corresponding light may be used in conjunction with the described embodiments.

[0068] In the general description, not all of the operations or elements described above are required. There may be cases where a particular operation or a portion of a device is not required, and in addition to those described, one or more additional operations may be performed or elements may be included. Further, the order in which the operations are recited is not necessarily the order in which they are performed. Also, concepts have been 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 the present disclosure as set forth in the following claims. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a limiting sense, and all such changes are intended to be included within the scope of the present disclosure.

[0069] With respect to specific embodiments, benefits, other advantages, and solutions to problems have been described above. However, benefits, advantages, solutions to problems, and any feature that can cause any benefit, advantage, or solution to occur or become more prominent should not be construed as an important, necessary, or essential feature of any or all of the claims. Further, the specific embodiments disclosed above are merely exemplary, since the disclosed subject matter can be modified and implemented in various equivalent manners that will be apparent to those skilled in the art having the benefit of the teachings herein. No limitation to the details of the structures or designs shown herein other than those described in the appended claims is intended. Accordingly, the specific embodiments disclosed above may be modified or varied, and it is clear that all such changes are considered to be within the scope of the disclosed subject matter. Accordingly, the protection sought herein is as set forth in the appended claims.

Claims

1. A laser projection system comprising: an optical relay configured to receive, relay, and apply different levels of magnification to a first laser beam and a second laser beam to generate a first magnified laser beam and a second magnified laser beam; wherein the first laser beam and the second laser beam are angularly separated, and the first magnified laser beam and the second magnified laser beam are scanned within the optical relay; the laser projection system further comprising: a first scanning mirror configured to receive the first magnified laser beam and the second magnified laser beam from the optical relay.

2. The laser projection system according to claim 1, further comprising a second scanning mirror configured to scan the first magnified laser beam and the second magnified laser beam within the optical relay.

3. The optical relay comprises: a first reflecting surface configured to apply a first level of magnification to the first laser beam; and a second reflecting surface configured to apply a second level of magnification to the second laser beam. The laser projection system according to claim 1 or claim 2.

4. The laser projection system according to claim 3, wherein the optical relay is a molded reflective relay, the first reflecting surface is the first reflecting surface of the molded reflective relay, and the second reflecting surface is the second reflecting surface of the molded reflective relay.

5. The first magnified laser beam has a first incident area on the first scanning mirror, the second magnified laser beam has a second incident area on the first scanning mirror, and the first incident area has substantially the same area as the second incident area. The laser projection system according to claim 1 or claim 2.

6. The first scanning mirror is configured to receive the first magnified laser beam at a first incident angle and the second magnified laser beam at a second incident angle, and the first incident angle is different from the second incident angle. The laser projection system according to claim 5.

7. The first incident area and the second incident area are each joined by a reflecting surface of the first scanning mirror. The laser projection system according to claim 5.

8. A near-eye display comprising the laser projection system according to claim 1 or claim 2, a spectacle frame including at least a part of the laser projection system, and further comprising spectacle lenses, wherein the laser projection system is configured to output the first laser beam and the second laser beam through at least a part of the spectacle lenses. A near-eye display.

9. A near-eye display, comprising a laser projection system, the laser projection system comprising: an optical relay configured to receive angularly separated laser beams, apply different levels of magnification to the angularly separated laser beams respectively, and relay the magnified angularly separated laser beams; a scanning mirror configured to receive the magnified angularly separated laser beams from the optical relay and scan the magnified angularly separated laser beams, wherein the magnified angularly separated laser beams have a first magnified laser beam and the second magnified laser beam, and the first magnified laser beam and the second magnified laser beam are scanned within the optical relay. A near-eye display.

10. The angularly separated laser beams include a first laser beam and a second laser beam, and the optical relay comprises: a first reflecting surface configured to apply a first level of magnification to the first laser beam; a second reflecting surface configured to apply a second level of magnification to the second laser beam. The near-eye display according to claim 9.

11. The optical relay is a molded reflective relay, the first reflecting surface is the first reflecting surface of the molded reflective relay, and the second reflecting surface is the second reflecting surface of the molded reflective relay. The near-eye display according to claim 10.

12. The first laser beam has a first incident region on the scanning mirror, the second laser beam has a second incident region on the scanning mirror, and the area of the first incident region is substantially the same as that of the second incident region. The near-eye display according to claim 10.

13. ​ The scanning mirror is configured to receive the first laser beam at a first incident angle and receive the second laser beam at a second incident angle, and the first incident angle is different from the second incident angle. The near-eye display according to claim 12.

14. The first level of magnification causes the first laser beam to have a first beam diameter in a first dimension, and the second level of magnification causes the second laser beam to have a second beam diameter in the first dimension. The first incident region has a first area at least partially defined by the first beam diameter and the first incident angle, and the second incident region has a second area at least partially defined by the second beam diameter and the second incident angle. The near-eye display according to claim 13.

15. The first incident region and the second incident region are each coupled by a reflective surface of the scanning mirror. The near-eye display according to claim 12.

16. A method comprising: Receiving, using an optical relay, angularly separated laser beams from a first scanning mirror; Applying, using the optical relay, different levels of magnification to each of the angularly separated laser beams to generate an expanded angularly separated laser beam; Relaying, using the optical relay, the expanded angularly separated laser beam to a second scanning mirror; The method.

17. Further comprising receiving, using the second scanning mirror, the expanded angularly separated laser beam from the optical relay, The first laser beam of the expanded angularly separated laser beam has a first incident angle and a first incident region with respect to the second scanning mirror, and the second laser beam of the expanded angularly separated laser beam has a second incident angle and a second incident region with respect to the second scanning mirror. The method according to claim 16.

18. Applying, using the optical relay, different levels of magnification to each of the angularly separated laser beams comprises: Applying, using a first reflective surface of the optical relay, a first level of magnification to a first beam diameter of the first laser beam; Applying a second level of expansion to the second beam diameter of the second laser beam using the second reflecting surface of the optical relay; The method according to claim 17, comprising. **Claim 19** The first incident region has a first area at least partially defined by the first beam diameter and the first angle of incidence, and the second incident region has a second area at least partially defined by the second beam diameter and the second angle of incidence, and the first area is substantially the same as the second area. The method according to claim 18. **Claim 20** The method according to claim 17, wherein the first incident region and the second incident region are each coupled by a reflecting surface of the second scanning mirror.

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