Integrated laser package with light intensity monitoring

Abstract

Systems and methods related to optical engines and laser projectors that can be used in wearable head-up displays are described. An optical engine can include a laser diode configured to output a laser beam and disposed in a fully or partially hermetically sealed package package having an exit window. A holographic or surface-relief diffraction grating can be integrated with or disposed on a primary output surface of the exit window of the housing of the optical engine. The diffraction grating can be configured to redirect a portion of the laser light toward one or more photodetectors disposed at or face-to-face with one or more surfaces of the exit window that are not parallel to the primary output surface. The primary output surface of the exit window can be tilted to be non-orthogonal to a primary propagation direction of the emitted laser light.

Description

Background Technology

[0001] A projector is an optical device that projects or illuminates a pattern of light onto another object (e.g., onto the surface of another object, such as onto a projection screen) to display an image or video on that object. A laser projector is a projector whose light source includes at least one laser, wherein the laser is temporarily modulated to provide a laser pattern, which is then spatially distributed over a display area of ​​another object (e.g., a screen or lens) to display an image or video. For better control of the performance of a laser projector, it is sometimes advantageous to monitor the laser output power of the laser projector. For example, accurately monitoring the laser output power of a laser projector will allow the laser projector to control the laser output power to adjust and tune the white point and / or brightness of the display. Summary of the Invention

[0002] In the example, the laser projector includes a photodetector configured to measure light intensity and an optical engine. The optical engine includes a laser source configured to output a beam, an exit window disposed on the optical path of the beam output from the laser source, and a diffraction grating disposed on the main output surface of the exit window, the diffraction grating redirecting a portion of the beam toward the photodetector.

[0003] In some embodiments, the laser projector includes a housing that surrounds the laser source and includes an exit window.

[0004] In some embodiments, the diffraction grating is a holographic diffraction grating.

[0005] In some embodiments, the diffraction grating is a surface-undulation diffraction grating.

[0006] In some embodiments, at least a portion of the diffraction grating that overlaps with the optical path of the light beam has a resonant wavelength corresponding to the wavelength of the light beam.

[0007] In some embodiments, an optical engine is disposed on the surface of a substrate, a photodetector is disposed opposite a sidewall of an exit window of the housing, the sidewall being adjacent to the main output surface and defining a plane perpendicular to the surface of the substrate, and a diffraction grating redirects a portion of the light beam through the sidewall of the exit window toward the photodetector.

[0008] In some embodiments, an optical engine is disposed on a substrate, a photodetector is disposed directly below the exit window and directly below the optical path of the beam, and a diffraction grating redirects a portion of the beam through the bottom surface of the exit window facing the substrate toward the photodetector.

[0009] In some embodiments, the photodetector is embedded in the substrate.

[0010] In some embodiments, an optical engine is disposed on a first side of a substrate, a photodetector is disposed on a second side of the substrate opposite to the first side, and a diffraction grating redirects a portion of the light beam through the bottom surface of the exit window and through a hole extending from the first side to the second side through the substrate toward the photodetector.

[0011] In some embodiments, an optical engine is disposed on a first substrate, and a photodetector is disposed on a second substrate, the second substrate being disposed above the first substrate such that the photodetector is positioned directly above the exit window and the optical path of the beam, and a diffraction grating redirects a portion of the beam through the top surface of the exit window facing the second substrate and away from the first substrate toward the photodetector.

[0012] In some embodiments, the main output surface of the exit window is inclined relative to the main input surface of the exit window, and the light beam is incident on the main input surface of the exit window.

[0013] In the example, the laser projector includes at least one photodetector configured to measure light intensity and an optical engine. The optical engine includes: a plurality of laser sources configured to output multiple beams; a housing surrounding the plurality of laser sources, the housing having exit windows disposed in each optical path of the plurality of beams output by the plurality of laser sources; and a diffraction grating disposed on the main output surface of the exit windows. The diffraction grating redirects a portion of each of the plurality of beams toward the at least one photodetector.

[0014] In some embodiments, the laser projector includes a collimating lens between the exit window and at least one photodetector.

[0015] In some embodiments, the diffraction grating includes a holographic diffraction grating.

[0016] In some embodiments, the diffraction grating includes a surface-undulation diffraction grating.

[0017] In some embodiments, the diffraction grating includes a first portion having a first resonant wavelength corresponding to a first wavelength of a first beam among a plurality of beams. The first portion overlaps with a first optical path of the first beam. The diffraction grating further includes a second portion having a second resonant wavelength corresponding to a second wavelength of a second beam among a plurality of beams. The second portion overlaps with a second optical path of the second beam.

[0018] In some embodiments, an optical engine is disposed on the surface of a substrate, and the at least one photodetector includes a first photodetector disposed opposite a first sidewall of an exit window of the housing, the first sidewall being adjacent to the main output surface and defining a plane perpendicular to the surface of the substrate, and a diffraction grating redirecting at least a first portion of a plurality of beams through the first sidewall of the exit window toward the first photodetector.

[0019] In some embodiments, the at least one photodetector includes a second photodetector disposed opposite a second sidewall of the exit window of the housing, the second sidewall being opposite to a first sidewall, and a diffraction grating redirects at least a second portion of a plurality of beams through the second sidewall of the exit window toward the second photodetector.

[0020] In some embodiments, the optical engine includes a first dichroic filter disposed on a first sidewall of the exit window and a second dichroic filter disposed on a second sidewall of the exit window. The first dichroic filter is configured to transmit light of a first wavelength corresponding to the wavelength of a first beam and reflect light of a second wavelength corresponding to the wavelength of a second beam, and the second dichroic filter is configured to transmit light of the second wavelength and reflect light of the first wavelength.

[0021] In some embodiments, an optical engine is disposed on a substrate, and the at least one photodetector comprises: a first photodetector disposed directly below an exit window and directly below a first optical path of a first beam among a plurality of beams, wherein a diffraction grating redirects a first portion of the first beam through the bottom surface of the exit window facing the substrate toward the first photodetector; and a second photodetector disposed directly below the exit window and directly below a second optical path of a second beam among a plurality of beams, wherein a diffraction grating redirects a second portion of the second beam through the bottom surface of the exit window toward the second photodetector.

[0022] In some embodiments, the first photodetector and the second photodetector are each embedded in the substrate.

[0023] In some embodiments, an optical engine is disposed on a first side of a substrate, and a first photodetector and a second photodetector are each disposed on a second side of the substrate opposite to the first side. A diffraction grating redirects the first portion of a first beam through the bottom surface of an exit window and through a first hole extending from the first side to the second side through the substrate toward the first photodetector. A diffraction grating redirects the second portion of a second first beam through the bottom surface of an exit window and through a second hole extending from the first side to the second side through the substrate toward the second photodetector.

[0024] In some embodiments, an optical engine is disposed on a first substrate, and at least one photodetector is disposed on a second substrate disposed above the first substrate, such that the at least one photodetector is positioned directly above the exit window and directly above at least one optical path of a plurality of light beams, and a diffraction grating redirects at least a portion of at least one of the plurality of light beams through the top surface of the exit window facing the second substrate and away from the first substrate toward the at least one photodetector.

[0025] In some embodiments, the main output surface of the exit window is inclined relative to the main input surface of the exit window, and the light beam is incident on the main input surface of the exit window.

[0026] In the example, the optical engine includes: a laser source configured to output a beam; an exit window disposed in the optical path of the beam output from the laser source, the exit window receiving the beam via a main input surface of the exit window; and a diffraction grating disposed on the main output surface of the exit window, the diffraction grating redirecting a portion of the beam through at least one surface of the exit window extending between the main input surface and the main output surface.

[0027] In some embodiments, the optical engine includes a housing surrounding the laser source and including an exit window.

[0028] In some embodiments, most of the light beam exits from the exit window.

[0029] In some embodiments, the optical engine includes: a photodetector disposed in the optical path of the light beam exiting from the exit window, and a collimating lens between the exit window and the photodetector.

[0030] In some embodiments, the diffraction grating includes a holographic diffraction grating.

[0031] In some embodiments, the diffraction grating includes a surface-undulation diffraction grating.

[0032] In some embodiments, at least a portion of the diffraction grating that overlaps with the optical path of the light beam has a resonant wavelength corresponding to the wavelength of the light beam.

[0033] In some embodiments, an optical engine is disposed on the surface of a substrate, a diffraction grating redirects a portion of the light beam through a first sidewall of an exit window, and the first sidewall extends between a main input surface and a main output surface and defines a plane perpendicular to the surface of the substrate.

[0034] In some embodiments, the diffraction grating further redirects the portion of the beam through a second sidewall of the exit window, and the second sidewall is opposite to the first sidewall relative to the exit window.

[0035] In some embodiments, the laser source is a first laser source, the beam is a first beam, and the optical engine includes: a second laser source configured to output a second beam, a first dichroic filter disposed on a first sidewall of the exit window, and a second dichroic filter disposed on a second sidewall of the exit window. The first dichroic filter is configured to transmit light of a first wavelength corresponding to the wavelength of the first beam and reflect light of a second wavelength corresponding to the wavelength of the second beam, and the second dichroic filter is configured to transmit light of the second wavelength and reflect light of the first wavelength.

[0036] In some embodiments, an optical engine is disposed on the surface of a substrate, and a diffraction grating redirects a portion of the light beam through the bottom surface of an exit window facing the substrate.

[0037] In some embodiments, an optical engine is disposed on the surface of a substrate, and a diffraction grating redirects a portion of the light beam through the top surface of an exit window that extends between the main input surface and the main output surface and faces away from the substrate.

[0038] In some embodiments, the main output surface of the exit window is inclined relative to the main input surface of the exit window, and the light beam is incident on the main input surface of the exit window. Attached Figure Description

[0039] This disclosure can be better understood by referring to the accompanying drawings, and its many features and advantages will be apparent to those skilled in the art. The same reference numerals are used in different drawings to indicate similar or identical items.

[0040] Figure 1 This is a block diagram of a side view of a wearable heads-up display according to some embodiments.

[0041] Figure 2 It is an isometric view of a wearable heads-up display having a laser projector including an optical engine, according to some embodiments.

[0042] Figure 3 This is a block diagram of a top view of a laser projector, which includes discrete pickup components for redirecting a portion of a laser beam toward a photodetector.

[0043] Figure 4 This is a top view block diagram of a laser projector with an optical engine according to some embodiments, the optical engine including an exit window with a holographic diffraction grating.

[0044] Figure 5 This is a top view block diagram of a laser projector with an optical engine according to some embodiments, the optical engine including an exit window with a diffraction grating having a reflective surface undulation.

[0045] Figure 6 This is a top view block diagram of a laser projector with an optical engine according to some embodiments, the optical engine including an exit window with a diffraction grating, wherein a portion of the laser light incident on the diffraction grating is redirected toward photodetectors aligned with two side surfaces of the exit window, through the side surfaces, and through corresponding color filters.

[0046] Figure 7 This is a block diagram of a side view of a laser projector with an optical engine according to some embodiments, the optical engine including an exit window with a diffraction grating, wherein a portion of the laser light incident on the diffraction grating is redirected through the bottom surface of the exit window toward a photodetector embedded thereon in a substrate on which the exit window is disposed.

[0047] Figure 8 This is a block diagram of a side view of a laser projector with an optical engine according to some embodiments. The optical engine includes an exit window with a diffraction grating, wherein a portion of the laser light incident on the diffraction grating is redirected toward a photodetector disposed on a side of the substrate opposite to the exit window, through the bottom surface of the exit window, and through a through-hole in the substrate on which the exit window is disposed.

[0048] Figure 9 This is a block diagram of a side view of a laser projector with an optical engine according to some embodiments, the optical engine including an exit window with a diffraction grating, wherein the exit window is disposed on a first substrate, and wherein a portion of the laser light incident on the diffraction grating is redirected toward a photodetector disposed on a second substrate located above the top surface of the exit window through the top surface of the exit window.

[0049] Figure 10 A perspective view and a side view of an exit window according to an embodiment are shown, the exit window having a main output surface that slopes outward and upward from the bottom surface of the exit window to the top surface of the exit window.

[0050] Figure 11 A perspective view and a side view of an output window according to an embodiment are shown, the output window having a main output surface that slopes outward and downward from the top surface of the output window to the bottom surface of the output window.

[0051] Figure 12 A perspective view and a side view of an output window according to an embodiment are shown, the output window having a main output surface that slopes outward and to the right from the left side surface of the output window to the right side surface of the output window. Detailed Implementation

[0052] This disclosure describes systems and methods for providing a laser projector with a laser-based optical engine and the ability to measure (e.g., monitor) light intensity and / or laser output power. According to various embodiments described herein, the optical engine of the laser projector includes at least one laser source (e.g., a laser diode or multiple laser diodes) which can be enclosed (e.g., partially or completely hermetically sealed) in a housing. The housing may include an optical window (sometimes referred to herein as an "emission window") that may be integrated with or formed on one of its sidewalls or top surface. During active operation of the laser projector, a laser beam output from the laser source can pass through the emission window to exit the housing. The optical engine can support a relatively small substrate area for power monitoring, thereby reducing the overall size of the optical engine. Therefore, the laser projector or optical engine can be flexibly used in a variety of display designs, including wearable head-up displays or other head-mounted displays. In some embodiments, after passing through the emission window, the beam passes through a corresponding collimating lens to a dichroic filter / beam combiner, where beams of different wavelengths are combined. The combined beam can then be directed to one or more scanning elements that project the beam across the display surface of an object—such as a holographic lens for a pair of smart glasses or another type of wearable head-up display. While the various embodiments described herein are provided in the context of wearable head-up displays, it should be understood that the laser projectors and optical engines of this disclosure can alternatively be included in other systems such as projection engines, lidar systems, sensing systems, ranging systems, external cavity laser diodes (e.g., as integrated intensity-stabilized servo systems), etc.

[0053] Monitoring the laser output power of the laser source of the optical engine in a laser projector is typically desirable. This allows for improved control over the quality of the projected image or video and enables the controller or processor of a device including the laser projector to dynamically limit the maximum output power of the optical engine based on real-time or near real-time measurements of the laser output power. For example, laser output power monitoring tends to be particularly important for the design of laser projectors used in wearable head-up displays, given the often limited availability of power and space (e.g., volume) in such wearable devices. Conventional approaches to designing laser projectors with laser output power monitoring capabilities require a relatively large footprint on the laser projector substrate, which can be a printed circuit board (PCB) dedicated to housing photodetectors such as photodiodes, optical components such as pick-off mirrors, and maintaining a clear optical path to the photodetectors. In some instances, this footprint may be as large as the optical engine itself. Therefore, it would be advantageous to reduce the substrate area occupied by the photodetectors and / or optical components (sometimes collectively referred to herein as "laser output power monitoring components") that implement laser output power monitoring of the laser projector's optical engine.

[0054] The systems, apparatus, and techniques described herein can provide a reduction in the substrate area required for laser power output monitoring components, for example, by utilizing an exit window of the housing of an optical engine having, for example, a diffraction grating, which can be disposed in or on the main output surface of the exit window and can redirect (e.g., via diffraction) a portion of the incident light from a laser beam output from a free laser source to one or more photodetectors, which may be photodiodes and can be disposed opposite one or more surfaces of the exit window. According to various embodiments, the exit window includes a diffraction grating that can be disposed or formed on or in the exit window and redirect incident light from the laser source to one or more photodetectors. In some embodiments, one or more photodetectors can be disposed on the top surface of the substrate to receive light redirected by the diffraction grating and output through one or both sidewalls of the exit window. The “sidewall” or “side surface” of the exit window can be defined as a surface of the exit window extending between the main input surface and the main output surface of the exit window, defining a plane that intersects (e.g., is perpendicular to) the surface of the substrate on which the optical engine is disposed. In some embodiments, one or more photodetectors may be disposed below the exit window and fully or partially embedded in the substrate, such that the one or more photodetectors receive light redirected by a diffraction grating and output through the bottom surface of the exit window. In some embodiments, the exit window is disposed on a first side of the substrate, and one or more photodetectors, which may be photodiodes, may be disposed below the exit window on a second side of the substrate opposite to the first side, such that the one or more photodetectors receive light redirected by a diffraction grating and output through the bottom surface of the exit window, the light passing through one or more apertures extending through the entire thickness of the substrate to reach the one or more photodetectors. In some embodiments, one or more photodetectors may be disposed above the exit window on a surface of a second substrate opposite to the surface of the first substrate on which the exit window is disposed, such that the one or more photodetectors receive light redirected by a diffraction grating and output through the top surface of the window.

[0055] While the exit window can typically be rectangular or cubic, it can be advantageous to tilt the main output surface of the exit window (i.e., the surface through which the laser beam output from the laser source passes) so that it is not orthogonal to the corresponding axis (i.e., the corresponding principal axis) along which the laser beam propagates. By tilting the main output surface of the exit window, the feedback of light redirected back to the laser source by the diffraction grating is reduced compared to the feedback of a generally cubic exit window. In some embodiments, the main output surface of the exit window may tilt outward and upward from the bottom surface to the top surface of the exit window. In some embodiments, the main output surface of the exit window may tilt outward and downward from the top surface to the bottom surface of the exit window, wherein the bottom surface faces the surface of the substrate on which the optical engine is disposed, and the top surface faces away from the substrate. In some embodiments, the main output surface of the exit window may tilt outward from a first side surface to a second side surface of the exit window.

[0056] Figure 1 This is an illustrative diagram showing a side view of a wearable heads-up display (WHUD) 100 employing a laser projector 110, which may be a scanning laser projector. For example, the WHUD 100 may be a pair of smart glasses or a virtual reality (VR) headset. The laser projector 110 includes an optical engine 111, which includes a red laser diode (…). Figure 1 Marked with "R" in the middle), green laser diode ( Figure 1 (marked as "G") and blue laser diode ( Figure 1 The laser projector 110 includes a single scanning mirror 112 rotatable about two axes of freedom (labeled "B" in the document) and a single scanning mirror 112 rotatable about two axes of freedom. The single scanning mirror 112 rotatable about two axes of freedom is used herein only as an illustrative example, and those skilled in the art will understand that similar functionality can be achieved using different mirror configurations, such as those in which the two scanning mirrors are each controllably rotatable about a corresponding one of the two orthogonal axes of freedom and sequentially positioned relative to the optical path of the laser 120. The laser 120 output by the laser projector 110 may include any modulation combination of red laser (output by a red laser diode), green laser (output by a green laser diode), and / or blue laser (output by a blue laser diode). The laser 120 reflected from the scanning mirror 112 is incident on a holographic optics element ("HOE") 130 that redirects the laser 120 back to the user's eye 190. Generally, in this disclosure, the term "user" refers to a user of a device containing a laser projector. Figure 1 In the specific context, the term "user" refers to a person who wears or uses the WHUD 100. Those skilled in the art will understand that the WHUD 100 may include features enabling a user to wear it. Figure 1The supporting frame and / or other support / alignment structure of the element depicted (not depicted in) Figure 1 (To reduce confusion), so that when the WHUD 100 is worn on the user's head, at least the HOE 130 is positioned within the field of view of at least one of the user's eyes 190 degrees.

[0057] HOE 130 is substantially optically transparent to ambient light 140 incident from the opposite side of HOE 130 relative to laser 120 (i.e., optically transparent to most wavelengths constituting ambient light 140). Because HOE 130 effectively combines external ambient light 140 and projected laser 120 in the user's field of view, HOE 130 can be referred to as a "combiner" or related variations, such as a "transparent combiner," a "holographic optical combiner," or the like. If the support frame of WHUD 100 ( Figure 1 If a pair of glasses (not shown) has the general shape, appearance, and / or geometry of an eyeglass, then the HOE 130 can be mounted on one or more clear lenses of the WHUD 100 (such as one or more prescription lenses or one or more non-prescription lenses). In some embodiments, the WHUD 100 may include one or more components, such as a computer processor and a camera or other sensors, which together perform eye-tracking functions.

[0058] Typically, it is desirable to monitor the laser output power in laser projector 110 to better control the image or video projected onto HOE 130 (i.e., the display surface) and to limit the maximum output power of WHUD 100. Monitoring the laser output power in a laser projector such as laser projector 110 is typically performed using discrete pickup components to redirect a portion of the laser 120 to an on-chip photodetector. However, this laser output power monitoring method requires a relatively large footprint on the laser projector substrate. To reduce the footprint of the laser output power monitoring components, the exit window of the housing, including some or all of the components of optical engine 111, can be configured to redirect a portion of the laser 120 toward an optical path opposite to and within the optical path of one or more photodetectors placed on the top, bottom, or sidewall of the exit window. For example, the optical engine 111 may include a diffraction grating in or on the exit window of its housing, wherein the diffraction grating redirects a portion of the laser 120 to one or more photodetectors, which may be photodiodes and detect the intensity of the redirected light, from which the laser output power of the optical engine 111 of the laser projector 110 can be derived (e.g., via a computer processor or fixed or programmable logic circuitry of the WHUD 100). Below... Figure 4-9 Various embodiments provide methods for redirecting a portion of a laser using the exit window of an optical engine, such as optical engine 111.

[0059] Figure 2 This is a schematic diagram of a wearable heads-up display (WHUD) 200 with a laser projector 202 according to the system, device, and method of the present invention. The WHUD 200 includes a support structure 204 having the shape and appearance of a pair of glasses worn on a user's head during use. The support structure 204 carries multiple components, including spectacle lenses 206, a transparent combiner 208, the laser projector 202, and a controller or processor 210. In some embodiments, the laser projector 202 may be integrated with… Figure 1 and Figure 4-9 The laser projector 202 may be similar to or the same as one or more of laser projectors 110, 400, 500, 600, 700, 800, or 900. For example, laser projector 202 may include an optical engine, such as optical engine 111, 402, 502, 602, 702, 802, or 902. Laser projector 202 may be communicatively coupled to a controller 210 (e.g., a microprocessor) that controls the operation of projector 202, as described above. Controller 210 may include or may be communicatively coupled to a non-transitory processor-readable storage medium (e.g., memory circuitry such as ROM, RAM, FLASH, EEPROM, memory registers, disk, optical disk, other stored memory), and the controller may execute data and / or instructions from the non-transitory processor-readable storage medium to control the operation of laser projector 202.

[0060] In the operation of WHUD 200, controller 210 controls laser projector 202 to emit laser light. (See above reference.) Figure 1 The laser projector 202, as discussed, generates and transmits light via at least one controllable mirror ( Figure 2 (not shown) will focus the laser beam (e.g., Figure 1 The laser beam 120 is directed to the transparent combiner 208. The combined beam is directed by the transparent combiner 208 into the field of view of the user's eye. The transparent combiner 208 can collimate the combined beam so that the laser spot incident on the user's eye has at least approximately the same size and shape as the spot at the transparent combiner 208. The transparent combiner 208 can be a holographic combiner including at least one holographic optical element.

[0061] The optical engine of the laser projector 202 may include a housing with an exit window, wherein one or more components of the optical engine (e.g., a laser diode for outputting laser light) are disposed within the housing and are completely or partially hermetically sealed by the housing. The exit window may include a diffraction grating integrated into or disposed thereon on a surface of the exit window (e.g., a main output surface through which most of the laser light output by the laser diode exits the housing). A portion of the laser light is redirected by the diffraction grating to one or more photodetectors, which may be photodiodes, and measures the intensity of the redirected portion of the laser light. The controller 110 may be configured to determine the laser output power of the intensity of the redirected portion of the laser light detected by the one or more photodiodes and selectively limit the maximum output power of the laser projector based on the detected laser output power. In some embodiments, the controller 210 may additionally or alternatively be configured to control the projection of images or videos made by the laser projector based at least in part on the detected laser output power. For example, by monitoring the laser output power, the controller 110 can determine the overall brightness intensity and the brightness intensity of each color of the laser beam output by the laser projector 202 in real time or near real time, and the controller 110 can control the overall brightness and color balance of the laser beam output by the laser projector 202 based on the determined brightness intensity.

[0062] Figure 3 A laser projector 300 is illustrated, which uses a pickup assembly 320 to redirect a laser beam toward a photodetector (PD) 310. The laser projector 300 includes an optical engine 302 comprising blue (B), green (G), and red (R) laser sources 312-1, 312-2, and 312-3, which output corresponding laser beams 330. The beams are collimated, combined, and directed to a scanning element 308, which projects the combined laser beam onto a display area of ​​an object, such as a lens of a WHUD, allowing a user to view an image or video represented in the combined laser beam. The beam 330 is directed by a pickup assembly 320 positioned in the optical path between the optical engine 302 and the scanning element 308. The pickup assembly 320 redirects light 332 (sometimes referred to herein as “redirected laser 332”) that is part of the laser beam 330 to the PD 310, which measures the intensity of the redirected laser 332. The measured light intensity is then used to calculate and monitor the laser output power of the optical engine 302. The optical engine 302, scanning element 308, pickup assembly 320 and PD 310 are all disposed on a substrate 301, which may be, for example, a printed circuit board (PCB).

[0063] The area 340 of the substrate 301 surrounding the pickup assembly 320, PD 310, and the optical path between the pickup assembly 320 and PD 310 is typically large (e.g., roughly the same size as the area of ​​the optical engine 302) and occupies space that could otherwise be used to place other components or could be omitted from the laser projector 300 to reduce the total substrate area required by the laser projector 300. The following... Figure 4-9 The technique described in the embodiments does not require picking up component 120, but instead redirects the light through one or more top, bottom or sidewalls of the exit window of the optical engine housing, thereby advantageously reducing the substrate area required for laser output power monitoring.

[0064] Figure 4 An illustrative laser projector 400 is shown, which uses a holographic diffraction grating to redirect light to a photodetector, which may be a photodiode. Specifically, the laser projector 400 includes an optical engine 402, a collimating lens 404, a dichroic filter / combiner 406, one or more scanning elements 408, and a PD 410, all disposed on a substrate 401. The substrate 401 may be, for example, a printed circuit board (PCB).

[0065] Optical engine 402 includes a blue laser source 412-1, a green laser source 412-2, and a red laser source 412-3. Each laser source 412 may include one or more laser diodes. Each laser source 412 may be configured to emit a corresponding laser beam 430 in a narrow band corresponding to the corresponding color (red, green, or blue) indicated for the laser source 412. In some alternative embodiments, a fourth laser source configured to emit light in the infrared (IR) band may be included in optical engine 402.

[0066] The optical engine 402 further includes a housing 403 that completely or partially hermetically seals an internal volume, within which the laser source is disposed. The housing 403 includes an exit window 414 through which a laser beam 430 emitted by the laser source 412 passes during operation of the laser projector 400. In some embodiments, a portion of the substrate 401 forms some or all of the base plate of the housing 403. The sidewalls of the housing 403 and, in some embodiments, the exit window 414 of the housing 403, may be attached to the substrate 401 using, for example, an adhesive, and the adhesive may form a partial or complete hermetically sealed seal between those elements of the housing 403 and the substrate 401. In some alternative embodiments, other bonding and sealing methods may be used to attach and seal the housing 403 to the substrate 404, such as glass welding, glass frit, and anodic bonding. In addition to the exit window 414, the housing 403 may be opaque to block external light from entering the housing 403 and to prevent laser light from escaping from the housing 403 through any other opening. For example, the ceiling, bottom plate, and sidewalls of housing 403 (again, except for exit window 414) may be opaque. In this example, exit window 414 forms all or part of a sidewall of housing 403 and is positioned in the optical path of the laser beam output by laser source 412. In some alternative embodiments, exit window 414 forms part of the top surface of housing 403 (i.e., is positioned opposite to and not perpendicularly aligned with substrate 401), and one or more mirrors (not shown) enclosed in housing 403 reflect light from laser source 412 toward the top surface of housing 403 and through exit window 414. Exit window 414 receives laser beam 430 at the main input surface facing laser source 412 and outputs beam 430 through a main output surface positioned opposite the main input surface.

[0067] After exiting the main output surface of exit window 414, the laser beams 430 are collimated by collimating lens 404, such that each laser beam 430 is aligned with minimal diffusion to be focused onto dichroic filter / combiner 406. In some alternative embodiments, one or more polarizing beam splitters may be used instead of dichroic filter / combiner 406. Dichroic filter / combiner 406 combines the laser beams 430 into a single combined beam and redirects the combined beam to scanning element 408, which projects the combined beam onto a display area of ​​an object, such as a lens of a WHUD, so that the image or video represented in the combined beam can be viewed by the user.

[0068] The exit window 414 includes a holographic diffraction grating 416, sized to allow light 432 (sometimes referred to herein as “redirected laser 432”) as part of the laser beam 430 (e.g., via diffraction) to pass through the sidewalls of the exit window 414 (e.g., the right sidewall, relative to the sidewall). Figure 4 The laser 432 (as depicted in the diagram) is redirected towards PD 410, which is positioned near the right side wall and in some or all of the optical path of the redirected light. PD 410 measures the intensity of the redirected laser 432. The measured light intensity is then provided to a controller or microprocessor coupled to PD 410, which calculates and monitors the laser output power of optical engine 402 and can limit the maximum laser output power of optical engine 402 based on the calculated laser output power.

[0069] A diffraction grating is a periodic structure that can be formed using a variety of methods—such as subtractive methods, additive methods, holography (e.g., polarization holography), or combinations thereof. A given diffraction grating can be oriented in a reflective mode (i.e., a “reflective diffraction grating”) or a transmission mode (i.e., a “transmission diffraction grating”), depending on how the diffraction grating is oriented relative to the incident light. The diffraction grating can be narrowband or broadband, depending on the wavelength and angle of incidence of the light in which it responds. The fabrication method of a given diffraction grating typically depends on the required feature size of the diffraction grating and its integration with other parts of the system and / or the use case of the diffraction grating itself. Some fabrication methods of diffraction gratings involve using semiconductor processes to etch and / or photolithographically define (e.g., via nanoimprint lithography, direct ultraviolet (UV) lithography, grayscale lithography, etc.) a periodic structure of the grating on a substrate. Such gratings are referred to herein as “surface undulation” diffraction gratings. For example, subtractive gratings can be fabricated by etching grooves into a substrate using styluses (e.g., diamond styluses) or other material-dependent semiconductor fabrication techniques. Other methods of fabricating diffraction gratings, such as holography, use multiple coherent light sources interfering on a photosensitive material to define the periodic structure of the grating. Holographic gratings can achieve significantly higher efficiency than other grating types when the incident light satisfies the Bragg condition. For example, the simplest holographic diffraction grating is typically formed by the interference fringe field of two laser beams whose standing wave pattern is exposed to a substrate, which is then processed to form a pattern of lines, typically with a sinusoidal cross section. The substrate in which or on which the diffraction grating is formed can include dielectrics, half-metals, semiconductors, metals, crystals, glasses, organic or inorganic materials, or suitable combinations of these materials.

[0070] Regardless of type, a diffraction grating reflects incident light at an angle that depends on the angle of incidence and the wavelength of the light. In this embodiment, only a small portion of the incident laser beam 430 is reflected by the holographic diffraction grating 416, while the remaining portion of the light exits through the main output surface of the exit window 414. In some embodiments, the holographic diffraction grating 416 is a volume phase holographic grating (VPHG). In some embodiments, the holographic diffraction grating 416 includes a thick-body holographic film (e.g., about 20 to 200 μm thick, with a refractive index modulated to about 0.001 to about 0.1), which operates in reflection mode and provides a narrowband response for each of one or more desired resonant wavelengths, wherein for each resonant wavelength, a separate grating is included in the thick-body holographic film. In some embodiments, the holographic diffraction grating 416 comprises a thin bulk holographic film (e.g., about 1 μm thick, with a refractive index modulated to about 0.001), which operates in either a reflection or transmission mode depending on the variability of the source parameters in wavelength and divergence and the desired sensitivity of these parameters. For each resonant wavelength, a separate grating is included in the bulk holographic film. Although the diffraction elements of the holographic diffraction grating 416 are shown extending in a direction parallel to the principal propagation direction of the laser beam 430, it should be understood that these elements may be tilted relative to the principal propagation direction of the laser beam or may include one or more tilted surfaces, as required to achieve a desired reflection / diffraction direction for a portion of the laser beam.

[0071] In some embodiments, a reflective coating may be applied to one or more of the top, bottom, or left side wall surfaces of the exit window 414 to increase the amount of internal reflection occurring within the exit window 414, which may advantageously increase the amount of light 432 emitted toward the PD 410 through the right side wall of the exit window 414. For example, adding a reflective coating to these surfaces of the exit window 414 may redirect any portion of the light that would otherwise break the total internal reflection (TIR) ​​condition of the diffraction grating 416—which may occur due to a portion of the incident light on the diffraction grating 416 at an angle less than the critical angle of the diffraction grating 416 or due to contact between the exit window 414 and another component (e.g., adhesive, substrate 401, housing 403, etc.).

[0072] In some embodiments, one or more portions of the holographic diffraction grating 416 may be configured to have a corresponding resonant wavelength corresponding to one or more colors of the laser beam 430. For example, a first portion of the holographic diffraction grating 416 in the optical path of the green laser beam 430 may be configured to have a first peak resonant wavelength matching the wavelength of the green laser beam 430 (e.g., between about 510 and 570 nm), a second portion of the holographic diffraction grating 416 in the optical path of the blue laser beam 430 may be configured to have a second peak resonant wavelength matching the wavelength of the blue laser beam 430 (e.g., between about 360 and 480 nm), and a third portion of the holographic diffraction grating 416 in the optical path of the red laser beam 430 may be configured to have a third peak resonant wavelength matching the wavelength of the red laser beam 430 (e.g., between about 650 and 670 nm). By customizing the holographic diffraction grating 416 to be divided along its length into sections each with a different resonant wavelength, each section corresponding in this way to the wavelength of a different one of the laser beams 430, improvements in the responsivity of the PD 410 and a reduction in the path length to the PD 410 can be achieved. For example, by customizing the diffraction grating 416 specifically for each color, the amount of diffracted light reaching the PD 410 can be maximized, or otherwise increased, because diffracting light at the most efficient angle minimizes losses in the optical path. For example, by providing a section of the diffraction grating 416 for a specific color, the number of TIR bounces within the exit window 414 can be reduced, or the laser beam 430 can be better directed to the PD 410, so that all or substantially all of the diffracted light reaches the PD 410.

[0073] In some embodiments, one or more optical elements, such as collimating lens 433, may be disposed between the right side wall of exit window 414 and PD 410 to focus light 432 onto PD 410. In some embodiments, such optical elements may additionally or alternatively include metasurface optics, focusing lenses, or geometric optics printed on the exit surface of the right side wall of exit window 414.

[0074] Figure 5 An illustrative laser projector 500 is shown, which uses a reflective surface-undulating diffraction grating to redirect light to a photodetector, which may be a photodiode. Specifically, the laser projector 500 includes an optical engine 502, a collimating lens 504, a dichroic filter / combiner 506, one or more scanning elements 508, and a PD 510, all of which are disposed on a substrate 501. The substrate 501 may be, for example, a PCB.

[0075] The optical engine 502, housing 503, collimating lens 504, dichroic filter / combiner 506, scanning element 508, PD 510, laser source 512, exit window 514, and laser beam 530 of the laser projector 500 are generally similar to those of the laser projector 500. Figure 4 The corresponding components of the laser projector 400 are identical in all aspects, and for the sake of brevity, some of the descriptions of such components previously described will not be repeated here.

[0076] Laser projector 500 and Figure 4 The difference between the laser projectors 400 is that a surface-undulation diffraction grating 516 is used in or on the exit window 514, instead of a holographic diffraction grating. The reflective surface-undulation diffraction grating 516 comprises a repeating pattern of undulations on a surface (e.g., the main output surface of the exit window 514), wherein incident light is reflected from the surface-undulation diffraction grating at an angle depending on the angle of incidence and the wavelength of the light. In some embodiments, the reflective surface-undulation diffraction grating 516 may be a blazed reflective surface-undulation diffraction grating. In some embodiments, the reflective surface-undulation diffraction grating 516 may comprise a fine-pitch binary grating with a low feature height. In some embodiments, the grating pitch of the reflective surface-undulation diffraction grating 516 is between 320 nm and 440 nm, and the grating height is approximately 2-300 nm.

[0077] The binary grating spacing is selected based on the input wavelength of the laser beam 530 and the refractive index of the exit window 514. For example, for red, green, and blue input wavelengths (e.g., 610-660 nm, 520-550 nm, and 440-470 nm, respectively) and an exit window refractive index of approximately 1.51, the binary grating spacing can be approximately 440 nm, targeting the blue input wavelength at TIR. The grating spacing increases with increasing refractive index of the exit window 514 and decreases with decreasing refractive index. The height of each grating depends on the material used for that grating. For example, for direct etching or nanoimprint lithography of a glass exit window 514 with a refractive index of approximately 1.51, the binary gratings can each have a height of approximately 20 nm to achieve a coupling efficiency of 1% for the blue wavelength and 0.5% for the red wavelength. As another example, for direct etching or nanoimprint lithography of a glass exit window 514 with a refractive index of approximately 1.51, binary gratings can each have a height of approximately 100 nm to achieve a coupling efficiency of 8% for the blue wavelength. As another example, for direct etching or nanoimprint lithography of a glass exit window 514 with a refractive index of approximately 1.51, binary gratings can each have a height of approximately 200 nm to achieve a coupling efficiency of approximately 2% for the blue wavelength and approximately 2% for the red wavelength. It should be noted that in some embodiments, instead of using a reflective surface-undulation diffraction grating, a transmissive surface-undulation diffraction grating with a very low fill factor is used to achieve similar low coupling efficiency, while also breaking the positive and negative symmetry of the grating. In this example, due to the low input wavelength coupling efficiency of the reflective surface-undulation diffraction grating 516, only a small portion of the incident laser beam 530 is reflected by the reflective surface-undulation diffraction grating 516, while the remaining light exits through the main output surface of the exit window 514.

[0078] The dimensions of the reflective surface undulation diffraction grating 516 are designed to pass through the sidewalls (e.g., the right sidewall) of the exit window 514 relative to the surface undulation diffraction grating 516. Figure 5 The orientation depicted herein redirects (e.g., via diffraction) light 532 (sometimes referred to herein as "redirected laser 532"), which is part of laser beam 530, to PD 510, which is positioned near the right sidewall and in the optical path of some or all of the redirected light. PD 510 measures the intensity of the redirected laser 532. The measured light intensity is then provided to a controller or microprocessor coupled to PD 510, which calculates, monitors, and adjusts the laser output power of optical engine 502, and can limit the maximum laser output power of optical engine 502 based on the calculated laser output power of optical engine 502.

[0079] In some embodiments, a reflective coating may be applied to one or more of the top, bottom, or left side wall surfaces of the exit window 514 to increase the amount of internal reflection occurring within the exit window 514, which may advantageously increase the amount of light 532 emitted toward the PD 510 through the right side wall of the exit window 514. For example, adding a reflective coating to these surfaces of the exit window 514 may redirect any portion of the light that would otherwise break the total internal reflection (TIR) ​​condition of the diffraction grating 516—which may occur due to a portion of the incident light on the diffraction grating 516 at an angle less than the critical angle of the diffraction grating 516 or due to contact between the exit window 514 and another component (e.g., adhesive, substrate 501, housing 503, etc.).

[0080] In some embodiments, one or more portions of the reflective surface undulation diffraction grating 516 may be configured to have a corresponding resonant wavelength corresponding to one or more colors of the laser beam 530. For example, a first portion of the reflective surface undulation diffraction grating 516 in the optical path of the green laser beam 530 may be configured to have a first peak resonant wavelength matching the wavelength of the green laser beam 530 (e.g., between about 510 and 570 nm), a second portion of the reflective surface undulation diffraction grating 516 in the optical path of the blue laser beam 530 may be configured to have a second peak resonant wavelength matching the wavelength of the blue laser beam 530 (e.g., between about 360 and 480 nm), and a third portion of the reflective surface undulation diffraction grating 516 in the optical path of the red laser beam 530 may be configured to have a third peak resonant wavelength matching the wavelength of the red laser beam 530 (e.g., between about 650 and 670 nm). By customizing the reflective surface undulation diffraction grating 516 to be divided along its length into sections with different resonant wavelengths, each section corresponding in this way to the wavelength of a different one of the laser beams 530, improvements in the responsivity of the PD 510 and a reduction in the path length to the PD 510 can be achieved. For example, by customizing the reflective surface undulation diffraction grating 516 specifically for each color, the amount of diffracted light reaching the PD 510 can be maximized, or otherwise increased, because diffracting light at the most efficient angle minimizes losses in the optical path. For example, by providing a section of the reflective surface undulation diffraction grating 516 for a specific color, the number of TIR bounces within the exit window 514 can be reduced, or the laser beam 530 can be better directed to the PD 510, so that all or substantially all of the diffracted light reaches the PD 510.

[0081] In some embodiments, one or more optical elements, such as collimating lens 533, may be disposed between the right side wall of exit window 514 and PD 510 to focus light 532 onto PD 510. In some embodiments, such optical elements may additionally or alternatively include metasurface optics or focusing lenses, geometric optics printed on the exit surface of the right side wall of exit window 514.

[0082] Figure 6 An illustrative laser projector 600 is shown, which uses a reflective surface-undulating diffraction grating to redirect light toward two photodetectors, which may be photodiodes. Specifically, the laser projector 600 includes an optical engine 602, a housing 603 with an exit window 614 and a reflective diffraction grating 616, a collimating lens 604, a dichroic filter / combiner 606, one or more scanning elements 608, and two PDs 610 (i.e., left PD 610-1 and right PD 610-2, relative to each other). Figure 6 (As shown in the directions), they are all disposed on substrate 601. Substrate 601 may be, for example, a PCB. It should be noted that although a reflective surface undulation diffraction grating is shown in this example, in other embodiments, another type of diffraction grating, such as a holographic diffraction grating, may alternatively be disposed at the main output surface of the exit window 614.

[0083] The optical engine 602, housing 603, collimating lens 604, dichroic filter / combiner 606, scanning element 608, PD 610, laser source 612, exit window 614, and laser beam 630 of the laser projector 600 are generally similar to those of the laser projector 600. Figure 4 The corresponding components of the laser projector 400 are identical in all respects, and for the sake of brevity, some of the descriptions of such components previously described will not be repeated here.

[0084] Two photodiodes 610-1 and 610-2 are disposed opposite the sidewall of the exit window 614, such that light 632, which is part of the laser beam 630 output by the laser source 612, is redirected to PDs 610-1 and 610-2 through the sidewall of the exit window 614. In this example, the reflection diffraction grating 616 may be a binary diffraction grating, and can redirect the beam to the left and right of the two sidewalls of the exit window 614, thereby redirecting it to the two PDs 610. In this example, dichroic filters 618-1 and 618-2 are disposed on the surfaces of the left and right sidewalls of the exit window 614, respectively. The dichroic filter 618-1 is disposed on the left side wall of the exit window 614 and substantially transmits (e.g., with a transmittance greater than 80%) light in one or more wavelength bands, which together include the wavelength of the blue laser beam 630 output by the blue laser source 612-1 and the wavelength of the green laser beam 630 output by the green laser source 612-2, and substantially reflects (e.g., with a reflectance greater than 80%) light in the following wavelength band: which includes the wavelength of the red laser beam 630 output by the red laser source 612-3. The dichroic filter 618-2 is disposed on the right side wall of the exit window 614 and substantially transmits (e.g., with a transmittance greater than 80%) light in the following wavelength bands: this band includes the wavelength of the red laser beam 630 output by the red laser source 612-3, and substantially reflects (e.g., with a reflectance greater than 80%) light in one or more wavelength bands, which together include the wavelength of the blue laser beam 630 output by the blue laser source 612-1 and the wavelength of the green laser beam 630 output by the green laser source 612-2. In this manner, PD 610-1 primarily receives the reflected portions 632-1 of the green and blue laser beams, while PD 610-2 receives the reflected portion 632-2 of the red laser beam. Therefore, PD 610-1 measures the combined intensity of the blue and green laser beams, while PD 610-2 measures the intensity of the red laser beam. The measured light intensity is then provided to a controller or microprocessor coupled to PDs 610-1 and 610-2. This controller or microprocessor calculates and monitors the laser output power of the optical engine 602 and can limit the maximum laser output power of the optical engine 602 based on the calculated laser output power. For example, when measuring the brightness intensity of various colors of the laser beam 630, the laser source 612 that does not correspond to the color of the light being measured is turned off, while the laser source 612 that corresponds to the color of the light being measured remains on, and the laser projector 600 typically cannot display image data while these measurements are being performed.By providing multiple photodiodes 610 and color filters that allow PD 610-1 to measure blue and green light while PD 610-2 measures red light, the amount of turn-off time required to measure the brightness intensity of the laser beam 630 is advantageously reduced because it is possible to measure the brightness intensity of red and blue or red and green light simultaneously. Furthermore, PD 610-1 can be tuned to respond to the wavelength of the red laser beam, and PD 610-2 can be tuned to respond to the wavelengths of the blue and green laser beams. This allows PD 610 to accurately measure brightness intensity using less received light (e.g., advantageously reducing the portion of beam 630 that needs to be redirected to PD 610) and / or reduces the amount of time required for PD 610 to accurately obtain the corresponding brightness intensity measurement.

[0085] While in this example, the dichroic filter 618 is used to limit the colors of light that can be delivered to a particular PD 610, it should be understood that in alternative embodiments, other types of filters, such as polarizing filters, can be used instead of the dichroic filter 618. As another alternative embodiment, the dichroic filter 618 can be omitted, allowing the PD 610 to receive and measure all detectable wavelengths of light reflected from the reflective surface undulation diffraction grating 616.

[0086] In some embodiments, a reflective coating may be applied to one or more of the top or bottom surfaces of the exit window 614 to increase the amount of internal reflection occurring within the exit window 614, which may advantageously increase the amount of light 632 emitted toward the PD 610 through the sidewall of the exit window 614.

[0087] In some embodiments, one or more portions of the reflective surface undulation diffraction grating 616 may be configured to have a corresponding resonant wavelength corresponding to one or more colors of the laser beam 630. For example, a first portion of the reflective surface undulation diffraction grating 616 in the optical path of the green laser beam 630 may be configured to have a first peak resonant wavelength matching the wavelength of the green laser beam 630 (e.g., between about 510 and 570 nm), a second portion of the reflective surface undulation diffraction grating 616 in the optical path of the blue laser beam 630 may be configured to have a second peak resonant wavelength matching the wavelength of the blue laser beam 630 (e.g., between about 360 and 480 nm), and a third portion of the reflective surface undulation diffraction grating 616 in the optical path of the red laser beam 630 may be configured to have a third peak resonant wavelength matching the wavelength of the red laser beam 630 (e.g., between about 650 and 670 nm). By customizing the reflective surface undulation diffraction grating 616 to be divided along its length into sections each with a different resonant wavelength, each section corresponding in this way to the wavelength of a different one of the laser beams 630, improvements in the responsivity of the PD 610 and a reduction in the path length to the PD 610 can be achieved. For example, by customizing the diffraction grating 616 specifically for each color, the amount of diffracted light reaching the PD 610 can be maximized, or otherwise increased, because diffracting light at the most efficient angle minimizes losses in the optical path. For example, by setting the diffraction grating 616 to have color-specific sections, the number of TIR bounces within the exit window 614 can be reduced, or the laser beam 630 can be better directed to the PD 610, so that all or substantially all of the diffracted light reaches the PD 610.

[0088] In some embodiments, one or more optical elements, such as collimating lenses 633-1 and 633-2, may be disposed between the sidewall of the exit window 614 and the PD 610 to focus light 632 onto the PD 610. In some embodiments, such optical elements may additionally or alternatively include metasurface optics, focusing lenses, or geometric optics printed on the exit surfaces of the left and right sidewalls of the exit window 614.

[0089] Figure 7 An illustrative cross-sectional side view of a laser projector 700 is shown, which uses a reflective surface undulation diffraction grating to redirect light toward a photodetector embedded in a substrate, wherein the photodetector may be a photodiode. The laser projector 700 includes an optical engine 702, a PD 710, a collimating lens 704, a dichroic filter / combiner 706, and one or more scanning elements (not shown) having a housing 703, a laser source 712, and an exit window 714. Although a top view of the laser projector 700 is not provided, it should be understood that the arrangement of the laser projector 700 can be... Figure 5The arrangement of the laser projectors 500 shown is generally similar, except for the placement of the PDs. For simplicity, the details will not be repeated here. Figure 5 The corresponding components in the laser projector 500 Figure 7 Some descriptions of the components.

[0090] In this example, PD 710 is not placed on the surface of substrate 701, but rather embedded in substrate 701 below exit window 714, such that the top surface of PD 701 is substantially flush with the top surface of substrate 701. The reflective surface undulation diffraction grating 716 can be configured to redirect the reflective portion 732 of laser beam 730 downwards toward PD 710 through the bottom plate of exit window 714. In some embodiments, a reflective coating can be applied to one or more of the top surface, left side wall, or right side wall of exit window 714 to increase the amount of light 732 redirected to PD 710. In some embodiments, the bottom surface of exit window 714 can be attached to PD 710 with an adhesive that matches the refractive index of PD 710 and the refractive index of the bottom surface of exit window 714. As described above, in some embodiments, one or more portions of the reflective surface undulation diffraction grating 716 can be configured to have corresponding resonant wavelengths corresponding to one or more colors of laser beam 730. In some embodiments, a plurality of PDs 710 may be disposed on a second side of substrate 701, wherein each PD 710 is disposed directly below and vertically overlaps with the optical path of a distinct laser beam 730. It should be noted that while a reflective surface undulation diffraction grating is shown in this example, in other embodiments, another type of diffraction grating, such as a holographic diffraction grating, may alternatively be disposed at the main output surface of exit window 714.

[0091] By embedding the PD710 in the substrate 701, the occupied area of ​​the laser projector 700 can be relatively reduced compared to embodiments in which the PD is disposed on the surface of the substrate 701, although at the cost of slightly increased manufacturing complexity and limitations (e.g., potentially limiting the size, type, material and / or responsiveness, electrical connection method, and / or applicable substrate type of the PD).

[0092] Figure 8An illustrative cross-sectional side view of a laser projector 800 is shown, which uses a reflective surface undulation diffraction grating to redirect light toward a photodetector disposed on a side of a substrate opposite the side where the optical engine of the laser diode 800 is located. The photodetector may be a photodiode. The laser projector 800 includes an optical engine 802, a photodiode 810, a collimating lens 804, a dichroic filter / combiner 806, and one or more scanning elements (not shown) having a housing 803, a laser source 812, and an exit window 814. Although a top view of the laser projector 800 is not provided, it should be understood that the arrangement of the laser projector 800 can be similar to... Figure 5 The arrangement of the laser projectors 500 shown is generally similar, except for the placement of the PDs. For simplicity, the details will not be repeated here. Figure 5 The corresponding components in the laser projector 500 Figure 8 Some descriptions of the components.

[0093] In this example, PD 810 is not placed on the surface of substrate 801, but is disposed on a second side of substrate 801 opposite to a first side of the substrate containing optical engine 802 and directly below exit window 814. Substrate 801 includes an aperture (e.g., a pass-through) disposed between PD 810 and the bottom surface of exit window 814. A reflective surface undulation diffraction grating 816 can be configured to redirect the reflective portion 832 of laser beam 830 downwards through the bottom plate of exit window 814 and through aperture 801 toward PD 810. In some embodiments, a reflective coating can be applied to one or more of the top surface, left side wall, or right side wall of exit window 814 to increase the amount of light 832 redirected to PD 810. As described above, in some embodiments, one or more portions of reflective surface undulation diffraction grating 816 can be configured to have corresponding resonant wavelengths corresponding to one or more colors of laser beam 830. In some embodiments, a plurality of PDs 810 may be disposed on a second side of substrate 801, wherein each PD 810 is disposed directly below and vertically overlaps with the optical path of a distinct laser beam 830. It should be noted that while a reflective surface undulation diffraction grating is shown in this example, in other embodiments, another type of diffraction grating, such as a holographic diffraction grating, may alternatively be disposed at the main output surface of exit window 814.

[0094] By placing the PD 810 on the opposite side of the substrate 801 and the optical engine 802, the occupied area of ​​the laser projector 800 can be relatively reduced compared to embodiments in which the PD is placed on the same surface of the substrate 801 as the optical engine 802, although at the cost of slightly increased manufacturing complexity and limitations (e.g., potentially limiting the size, type, material and / or responsiveness of the PD, electrical connection method, and / or applicable substrate type).

[0095] Figure 9 An illustrative cross-sectional side view of a laser projector 900 is shown, which uses a reflective diffraction grating to redirect light toward a photodetector disposed on a second substrate located above the substrate where the optical engine of the laser projector 900 is situated. The photodetector may be a photodiode. The laser projector 900 includes a first substrate 901 having an optical engine 902 with a housing 903, a laser source 912, and an exit window 914, a collimating lens 904, a dichroic filter / combiner 906, and one or more scanning elements (not shown), and a second substrate 950 having at least a PD 910 disposed thereon. Although a top view of the laser projector 900 is not provided, it should be understood that the arrangement of the laser projector 900 can be similar to... Figure 5 The arrangement of the laser projectors 500 shown is basically similar, except for the placement of the PD. For simplicity, the details will not be repeated here. Figure 5 The corresponding components in the laser projector Figure 9 Some descriptions of the components.

[0096] In this example, PD 910 is not placed on the surface of the first substrate 901, but is disposed on the second substrate 950 and directly above the exit window 914, which is located above the first substrate 901 in which the optical engine 902 is disposed. A reflective surface undulation diffraction grating 916 can be configured to redirect the reflective portion 932 of the laser beam 930 upwards toward PD 910 through the top surface of the exit window 914. In some embodiments, a reflective coating can be applied to one or more of the bottom surface, left side wall, or right side wall of the exit window 914 to increase the amount of light 932 redirected to PD 910. As described above, in some embodiments, one or more portions of the reflective surface undulation diffraction grating 916 can be configured to have a corresponding resonant wavelength corresponding to one or more colors of the laser beam 930. In some embodiments, a plurality of PDs 910 can be disposed on the second substrate 950, wherein each PD 910 is disposed directly above and vertically overlaps with the optical path of a distinct laser beam 930. It should be noted that although a reflective surface undulation diffraction grating is shown in this example, in other embodiments, another type of diffraction grating, such as a holographic diffraction grating, may alternatively be provided at the main output surface of the exit window 914.

[0097] By placing the PD 910 on the opposite side of the substrate 901 and the optical engine 902, compared to an embodiment in which the PD is placed on the same substrate 901 as the optical engine 902, the footprint of the laser projector 900 on the first substrate 901 can be relatively reduced. Due to less space, material compatibility and electrical connection limitations, a wider variety of PDs can be used for laser output power intensity monitoring, and additional space can be provided for optical components such as collimating or focusing optics (e.g., in the optical path between the PD 910 and the exit window 914), although this arrangement requires the addition of a second substrate 950.

[0098] Although the reflection diffraction grating has already been... Figure 4-9 As provided in the examples, it should be understood that a transmission diffraction grating can be used instead. Figure 4-9 Any of the diffraction gratings 416, 516, 616, 716, 816, and 916, but will be placed on the optical input surface of the corresponding exit window, rather than on the optical output surface.

[0099] It should be understood that Figure 4-9 The shape of any one of the exit windows 414, 514, 614, 714, 814, and 914 is not limited to the shape of a right-angle prism. In some embodiments, the main output surface of the exit window may be inclined, such as... Figure 10-12As shown, this ensures that the plane of the main output surface of the exit window is not orthogonal to the direction of any beam output by the laser diode.

[0100] For example, Figure 10 Perspective view 1000-1 and side view 1000-2 show an exit window 1014 with a main output surface 1022, the main output surface 1022 defining a plane that is not orthogonal to the direction of the beam 1030 output by the laser diode and not parallel to the plane defined by the rear surface 1024, wherein the main output surface 1022 meets the bottom surface of the exit window 1014 at an obtuse angle. That is, the orientation of the exit window 1014 depicted with respect to the side view 1000-2 slopes outward and upward from the bottom surface of the exit window 1014 to the top surface of the exit window 1014. For example, the main output surface 1022 is inclined relative to the main input surface of the exit window 1014. As shown in side view 1000-2, the side surfaces of the exit window 1014 are shaped as right trapezoids. The width W1 of the top surface of the exit window 1014 is greater than the width W2 of the bottom surface of the exit window 1014. In some embodiments, one or more edges where the surfaces of the exit window 1014 intersect may be chamfered or have an arc shape.

[0101] As another example, Figure 11 Perspective view 1100-1 and side view 1100-2 show an exit window 1114 with a main output surface 1122. The main output surface 1122 defines a plane that is not orthogonal to the direction of the beam 1130 output by the laser diode and is not parallel to the plane defined by the rear surface 1124, wherein the main output surface 1122 meets the bottom surface of the exit window 1114 at an acute angle. That is, the orientation of the exit window 1114 depicted with respect to the side view 1100-2 slopes outward and downward from the top surface of the exit window 1114 to the bottom surface of the exit window 1114. For example, the main output surface 1122 is inclined relative to the main input surface of the exit window 1114. As shown in side view 1100-2, the side surfaces of the exit window 1114 are shaped as right trapezoids. The width W3 of the top surface of the exit window 1114 is smaller than the width W4 of the bottom surface of the exit window 1114. In some embodiments, one or more edges at the intersection of the surfaces of the exit window 1114 may be chamfered or have an arc shape.

[0102] As another example, Figure 12Perspective view 1200-1 and top view 1200-2 are shown of an exit window 1214 having a main output surface 1222. The main output surface 1222 defines a plane that is not orthogonal to the direction of the beam 1230 output by the laser diode and is not parallel to the plane defined by the rear surface 1224. The main output surface 1222 meets the first side surface 1226 (i.e., the right side surface, with respect to the orientation depicted in top view 1200-2) of the exit window 1214 at an acute angle and meets the second side surface 1228 (i.e., the left side surface, with respect to the orientation depicted in top view 1200-2) of the exit window 1214 at an obtuse angle. That is, the exit window 1214, with respect to the orientation depicted in top view 1200-2, tilts outward and to the right from the second side surface 1228 towards the first side surface 1226 of the exit window 1214. For example, the main output surface 1222 is inclined relative to the main input surface of the exit window 1214. The length L1 of the side surface 1228 is less than the length L2 of the side surface 1226. In some embodiments, one or more edges at the intersection of the surfaces of the exit window 1214 may be chamfered or have an arc shape.

[0103] As another example, the exit window can maintain a cube shape and can be about [the size of the exit window]. Figure 4-6 The orientation of the exit window shown is (e.g., in the page plane) rotated clockwise or counterclockwise (e.g., about 0.1 to 15 degrees) about an axis extending through the center point of the top and bottom surfaces of the exit window, without rotating the rest of the housing. Additionally or alternatively, the exit window may be rotated about 0.1 to 10 degrees about its long axis. By changing the orientation of the exit window in this way, the main input surface of the exit window (i.e., the surface that first receives the beam from the laser source and is opposite the main output surface) is not orthogonal to the main propagation direction of the beam output from the laser source.

[0104] By arranging the main output surface of the exit window to be non-orthogonal to the main propagation direction of the beam output from the laser source, such as... Figure 10-12 As shown in various examples, the amount of optical feedback entering the optical engine from the laser diode is advantageously reduced. It should be noted that this optical feedback can be caused by the laser diode output beam being redirected by a diffraction grating positioned on or integrated within the exit window.

[0105] Please note that not all activities or elements described in the general description above are necessary, and a particular activity or device may not be required as part of it. Furthermore, in addition to those described, one or more further activities may be performed, or one or more further elements may be included. Moreover, the order in which the activities are listed is not necessarily the order in which they are performed. These concepts have been described with reference to specific embodiments. However, those skilled in the art will understand that various modifications and changes are possible without departing from the scope of this disclosure as set forth in the following claims. Therefore, the specification and drawings are to be considered illustrative rather than restrictive, and all such modifications are intended to be included within the scope of this disclosure.

[0106] The benefits, other advantages, and solutions to the problems have been described above with respect to specific embodiments. However, the benefits, advantages, solutions to the problems, and any features that may lead to or make more apparent any benefit, advantage, or solution should not be construed as critical, necessary, or essential to any or all claims. Furthermore, the specific embodiments disclosed above are merely illustrative, as the disclosed subject matter can be modified and practiced in different but equivalent ways, as will be apparent to those skilled in the art who have benefited from the teachings herein. No limitation is intended to be made on the details of the constructions or designs shown herein other than those described in the appended claims. Therefore, it is apparent that the specific embodiments disclosed above can be altered or modified, and all such variations are considered to be within the scope of the disclosed subject matter. Therefore, the protection sought herein is as set forth in the appended claims.

Claims

1. A laser projector, comprising: At least one photodetector configured to measure light intensity; as well as An optical engine, the optical engine comprising: At least one laser source, said laser source being configured to output a beam; An exit window, disposed in the optical path of the light beam output from the laser source, wherein the exit window receives the light beam via its main input surface; and A diffraction grating is disposed on the main output surface of the exit window, wherein the diffraction grating redirects a portion of the light beam through at least one surface of the exit window extending between the main input surface and the main output surface toward the photodetector.

2. The laser projector according to claim 1, further comprising: The housing surrounds the laser source and includes the emission window.

3. The laser projector according to claim 1, wherein, The diffraction grating is a holographic diffraction grating.

4. The laser projector according to claim 1, wherein, The diffraction grating is a surface-undulation diffraction grating.

5. The laser projector according to claim 1, wherein, At least a portion of the diffraction grating that overlaps with the optical path of the light beam has a resonant wavelength corresponding to the wavelength of the light beam.

6. The laser projector according to any one of claims 1 to 5, wherein, The optical engine is disposed on the surface of the substrate, wherein the photodetector is disposed opposite the sidewall of the exit window, wherein the sidewall is adjacent to the main output surface and defines a plane perpendicular to the surface of the substrate, and wherein the diffraction grating redirects a portion of the light beam through the sidewall of the exit window toward the photodetector.

7. The laser projector according to any one of claims 1 to 5, wherein, The optical engine is disposed on the substrate, the photodetector is disposed directly below the exit window and directly below the optical path of the beam, and the diffraction grating redirects a portion of the beam through the bottom surface of the exit window facing the substrate toward the photodetector.

8. The laser projector according to claim 7, wherein, The photodetector is embedded in the substrate.

9. The laser projector according to claim 7, wherein, The optical engine is disposed on a first side of the substrate, the photodetector is disposed on a second side of the substrate opposite to the first side, and the diffraction grating redirects a portion of the light beam through the bottom surface of the exit window and through a hole extending from the first side to the second side through the substrate toward the photodetector.

10. The laser projector according to any one of claims 1 to 5, wherein, The optical engine is disposed on a first substrate, and the photodetector is disposed on a second substrate, which is disposed above the first substrate such that the photodetector is positioned directly above the exit window and the optical path of the light beam, and the diffraction grating redirects a portion of the light beam through the top surface of the exit window facing the second substrate and away from the first substrate toward the photodetector.

11. The laser projector according to any one of claims 1 to 5, wherein, The main output surface of the exit window is inclined relative to the main input surface of the exit window, wherein the light beam is incident on the main input surface of the exit window.

12. The laser projector according to any one of claims 1 to 5, wherein, The optical engine includes: Multiple laser sources, the multiple laser sources being configured to output multiple beams; A housing surrounding the plurality of laser sources, the housing having the exit window disposed in each optical path of the plurality of beams output by the plurality of laser sources, wherein the diffraction grating redirects a portion of each of the plurality of beams toward the at least one photodetector.

13. The laser projector of claim 12, further comprising a collimating lens between the exit window and the at least one photodetector.

14. The laser projector according to claim 12, wherein, The diffraction grating includes: A first portion, having a first resonant wavelength corresponding to a first wavelength of a first beam among the plurality of beams, wherein the first portion overlaps with a first optical path of the first beam; and The second part has a second resonant wavelength corresponding to the second wavelength of the second beam among the plurality of beams, wherein the second part overlaps with the second optical path of the second beam.

15. The laser projector according to claim 12, wherein, The optical engine is disposed on the surface of the substrate, and the at least one photodetector includes a first photodetector disposed opposite a first sidewall of the exit window of the housing, the first sidewall being adjacent to the main output surface and defining a plane perpendicular to the surface of the substrate, and the diffraction grating redirecting at least a first portion of a first beam of the plurality of beams through the first sidewall of the exit window toward the first photodetector.

16. The laser projector according to claim 15, wherein, The at least one photodetector further includes a second photodetector disposed opposite a second sidewall of the exit window of the housing, the second sidewall being opposite to the first sidewall, and the diffraction grating redirects a second portion of at least a second beam of the plurality of beams through the second sidewall of the exit window toward the second photodetector.

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