Lidar unit with stray light reduction system

Abstract

Disclosed herein are system and method embodiments for generating a signal having a high signal-to-noise ratio indicative of light received by a lidar unit. For example, the system includes a focal plane assembly (FPA) having a detector array. The FPA includes a microlens array (MLA) having an input surface configured to receive the light, and an array of optics forming an output surface arranged along a focal plane, the output surface configured to focus the light on the detector array. A mask is disposed on an outer portion of at least one of the input surface and the output surface. The mask is configured to absorb stray light and reduce optical noise within the MLA.

Description

Technical Field

[0001] One or more embodiments are directed to a sensor system having one or more light absorbing surfaces for reducing stray internal light reflections. Background Art

[0002] A photodetector is an optoelectronic device that converts incident light or other electromagnetic radiation in the ultraviolet (UV), visible, and infrared spectral regions into an electrical signal. Photodetectors can be used in a wide range of applications including, for example, fiber optic communication systems, process control, environmental sensing, safety and security, and other imaging applications such as light detection and ranging applications. Summary of the invention

[0003] Technical issues

[0004] High photodetector sensitivity can enable detection of weak signals returned from distant objects, however, such sensitivity to optical signals may be susceptible to high optical noise sensitivity. Therefore, the system and method proposed in the present disclosure provide a solution to reduce the optical noise sensitivity in the photodetector device.

[0005] Solutions to the problem

[0006] In one embodiment, a focal plane assembly (FPA) is provided with an array of detectors. The FPA includes a micro-lens array (MLA) having an input surface configured to receive light and an output surface arranged along a focal plane and configured to focus the light on the detector array. A mask is provided on an outer portion of at least one of the input surface and the output surface. The mask is configured to absorb stray light and reduce optical noise within the MLA.

[0007] In another embodiment, a microlens array (MLA) is provided with an input surface configured to receive light and an output surface arranged along a focal plane and configured to focus the light on a detector array. A mask is provided on an outer portion of at least one of the input surface and the output surface. The mask is configured to absorb stray light.

[0008] A focal plane assembly (FPA) includes: a detector array; a microlens array (MLA), the microlens array including an input surface and an output surface, the input surface being configured to receive light, the output surface being arranged along a focal plane and being configured to focus the light on the detector array; and a mask disposed on an outer portion of at least one of the input surface and the output surface, the mask being configured to absorb stray light and reduce optical noise within the MLA.

[0009] Furthermore, the MLA includes outer apertures and a central aperture extending between the input surface and the output surface, and wherein each central aperture is optically aligned with one of the detectors in the detector array.

[0010] Furthermore, the mask comprises openings aligned with the central aperture to limit any vignetting of the light focused on the detector array.

[0011] Furthermore, a mask is formed of an opaque material and is disposed on the outer aperture of the output surface.

[0012] Additionally, the FPA includes a coating disposed on the outer holes and the central hole of the output surface.

[0013] Furthermore, the mask is formed of an opaque material and is disposed on an outer portion of the input surface.

[0014] Additionally, the FPA of claim 1, further comprising a coating disposed on the input surface, wherein the coating is formed of a partially transmissive material.

[0015] Furthermore, the MLA is formed with a plano-convex profile having a planar surface formed at one of an input surface and an output surface, and a convex optical device array formed at the other of the input surface and the output surface.

[0016] Meanwhile, the receiver module includes: a housing having an opening configured to receive light and an outlet opposite to the opening and aligned along an optical axis; at least one lens supported by the housing and aligned along the optical axis to focus the light; and the above-mentioned FPA, wherein the input surface of the MLA is aligned with the at least one lens to receive light.

[0017] At the same time, the lidar unit includes: a transmitter module having at least one transmitter, wherein the at least one transmitter is configured to transmit light pulses away from a vehicle; and the above-mentioned receiver, wherein the shell is configured to receive light reflected from an object outside the vehicle as a reflected light pulse; and wherein the detector array generates a light signal indicative of the reflected light pulse having a high signal-to-noise ratio based on the reduced optical noise present at the detector array.

[0018] Meanwhile, the microlens array (MLA) includes: an input surface configured to receive light; and an output surface arranged along a focal plane and configured to focus the light onto a detector array; and a mask disposed on an outer portion of at least one of the input surface and the output surface, the mask being configured to absorb stray light.

[0019] In addition, the MLA includes an outer hole and a central hole extending between the input surface and the output surface.

[0020] Furthermore, the mask includes openings aligned with the central aperture to limit any vignetting of the light focused on the detector array.

[0021] Furthermore, a mask is formed of an opaque material and is disposed on the outer aperture of the output surface.

[0022] In addition, the MLA includes a coating disposed on the outer holes and the central hole of the output surface.

[0023] Furthermore, the mask is formed of an opaque material and is disposed on an outer portion of the input surface.

[0024] At the same time, the laser radar unit includes: at least one emitter configured to emit light pulses away from the vehicle; a housing having an opening configured to receive light and an outlet opposite to the opening and aligned along the optical axis; at least one lens supported by the housing and aligned along the optical axis to focus light; a detector array; a lens array including: an input surface aligned with at least one lens and configured to receive light; and an optical device array forming an output surface, the output surface being configured to focus light on the detector array; and a mask disposed on an outer portion of at least one of the input surface and the output surface, the mask being configured to absorb stray light and reduce optical noise within the lens array.

[0025] Furthermore, the laser radar unit further comprises a coating disposed on the input surface, wherein the coating is formed of a partially transmissive material.

[0026] Furthermore, the laser radar unit further comprises a coating disposed on the output surface, wherein the coating is formed of a partially transmissive material.

[0027] Furthermore, the lens array is formed with a planar input surface, and wherein each optic in the array of optics is formed with a convex profile. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic diagram of an exemplary autonomous vehicle (AV) system with a light detection and ranging (“lidar”) unit according to aspects of the present disclosure.

[0029] Figure 2is an exemplary architecture of a lidar unit of an AV system according to aspects of the present disclosure.

[0030] Figure 3 is a side view of a photodetector receiver assembly according to aspects of the present disclosure.

[0031] Figure 4A is a front view of a focal plane assembly (FPA) of a photodetector receiver assembly according to aspects of the present disclosure.

[0032] Figure 4B According to aspects of the present disclosure Figure 4A A magnified view of a portion of the FPA showing the microlens assembly.

[0033] Figure 5A is taken along section line VV according to aspects of the present disclosure Figure 4A A three-dimensional cross-sectional view of the FPA.

[0034] Figure 5B According to aspects of the present disclosure Figure 5A A magnified view of a portion of the FPA.

[0035] Fig. 6A According to aspects of the present disclosure Figure 3 Front view of the FPA's receiver assembly.

[0036] Figure 6B According to aspects of the present disclosure Fig. 6A A magnified view of a portion of the FPA.

[0037] Figure 7 According to aspects of the present disclosure, the Fig. 6A Cross-sectional view of an FPA showing the light absorbing surface.

[0038] Figure 8 is a cross-sectional view of an FPA according to another embodiment, showing another light absorbing surface, according to aspects of the present disclosure.

[0039] Fig. 9 is a cross-sectional view of an FPA according to another embodiment, showing another light absorbing surface, according to aspects of the present disclosure.

[0040] Fig.10 is a cross-sectional view of an FPA according to another embodiment, showing another light absorbing surface, according to aspects of the present disclosure.

[0041] Fig.11 is a cross-sectional view of an FPA according to another embodiment showing multiple light absorbing surfaces according to aspects of the present disclosure.

[0042] In the drawings, like reference numbers generally refer to like or similar elements. Additionally, usually, the leftmost digit(s) of a reference number identifies the drawing in which the reference number first appears. DETAILED DESCRIPTION

[0043] As required, detailed embodiments are disclosed herein; however, it should be understood that the disclosed embodiments are merely exemplary and may be embodied in various and alternative forms. The drawings are not necessarily drawn to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, the specific structural and functional details disclosed herein should not be interpreted as limiting, but merely as a representative basis for teaching those skilled in the art to utilize the present disclosure in various ways.

[0044] As mentioned herein, an example use of a photodetector is in light detection and ranging applications (e.g., within a LiDAR system). For example, one of the most desired properties of a LiDAR system is long-range detection, which depends on the sensitivity of the photodetector. Long-range detection can be achieved using very sensitive photodetectors. The high sensitivity of the photodetector can enable detection of weak signals returned from distant objects, and thus, a LiDAR device capable of detecting objects at remote locations is provided. However, sensitivity to optical signals may also be related to sensitivity to optical noise. Due to this correlation, it is desirable to have a device that utilizes a photodetector (e.g., a LiDAR) to reduce sensitivity to optical noise.

[0045] One example of this noise sensitivity can be due to stray light reflections within a photodetector receiver (e.g., a lidar receiver). Specifically, within the focal plane assembly (FPA) of the receiver, a discrete microlens array used to enhance the optical fill factor can produce total internal reflections that can cause the die to act as a light pipe by carrying stray light long distances from the source location. This can result in an optical blooming effect, a type of optical noise that can temporarily blind a detector that is particularly sensitive to other signals.

[0046] According to some aspects, disclosed embodiments limit stray light reflections captured within a microlens array (MLA), thereby maintaining high photodetector sensitivity levels while reducing optical blur (i.e., stray light reflections). For example, aspects of the present disclosure provide an MLA having optical properties designed to reduce the effects of stray light captured within the MLA. According to some aspects, the MLA may include a mask layer placed at an input surface, an output surface, or both an input surface and an output surface of the MLA to reduce optical noise in the FPA by absorbing stray light. According to some aspects, the mask layer may also be placed at an external region, an internal region, or both an external region and an internal region of either the input surface and / or output surface of the MLA.

[0047] Reducing optical noise within the FPA can improve detection of incident signals (e.g., returned light signals) at the detector. According to some aspects described herein, reducing optical noise by the disclosed MLA can result in a reduction / attenuation of blurring effects at the detector. Such reduction can significantly improve the detection capabilities of the detector, particularly when receiving returned light signals from highly reflective objects including embedded reflective material, such as road signs (directional signs, yield signs, stop signs, etc.), any other objects including embedded reflective material, or other highly reflective objects.

[0048] Due to the reduction in noise affecting the signal, a lidar assembly (e.g., lidar unit 200) including the disclosed FPA can improve its detection capabilities and detection accuracy. This performance improvement of the lidar provides further benefits to an autonomous vehicle (AV) (such as AV 102) operating the lidar unit 200. For example, the lidar unit 200 of the AV 102 can receive light signals reflected from objects that exhibit high reflectivity, such as mirrors, glass, or objects embedded with highly reflective materials (such as stop signs and other road signs). In this case, the lidar unit 200 utilizing the disclosed systems and methods can reduce the blurring effect, so that while the noise signal generated at the MLA is attenuated, it is still able to detect objects at long distances. In this example, the lidar unit 200 is able to achieve high detection sensitivity while reducing sensitivity to noise signals and improving the signal-to-noise ratio (SNR) of the received signal before performing digital signal processing (DSP) applications.

[0049] According to some aspects, the performance improvements of the lidar unit 200 are further translated into downstream improvements in DSP speed and accuracy. For example, by eliminating noise signals, the onboard computer device (e.g., the AV system 104) can use less bandwidth to filter out noise using signal processing techniques. In addition, the AV system 104 can use less bandwidth to check the detection accuracy of the lidar output. For the same reason, the AV system 104 can also use less bandwidth to compare the detection accuracy of the lidar output with other sensor outputs in the detection stack (e.g., radar and camera data). According to some aspects, the lidar unit 200 implementing the disclosed embodiment can provide a more accurate output signal fed into the detection, tracking and prediction stack of the AV. For example, improving the accuracy of the data stack received by the AV system 104 can reduce the delay that the AV system 104 may exhibit when processing a damaged detection signal from the lidar unit 200 or when coordinating the signal with other detection signals received at the same time (e.g., from a camera or radar system (not shown)). Minimizing the computational cost associated with processing the detection signals can increase the processing power of the AV system 104 , reduce latency, and free up bandwidth of the AV system 104 to perform other downstream navigation tasks, such as prediction and motion planning tasks.

[0050] According to some aspects, the performance improvements of the lidar unit 200 can be further translated into downstream improvements in detection and classification capabilities, thereby improving the navigation capabilities of the AV 102. For example, the AV 102 may be able to navigate a geographic location without the lidar unit 200 being blinded by optical blur, and do so in a continuous manner. Due to the reduced optical blurring effects described herein, the AV 102 may also navigate a geographic location while being able to detect and classify highly reflective objects. It can be understood that the above benefits are merely exemplary, and as will be appreciated by those skilled in the art, other benefits for detection, computing, and downstream applications (such as autonomous driving and navigation) may fall within the scope of the present disclosure.

[0051] refer to Figure 1 , a sensor system having one or more light absorbing surfaces according to one or more embodiments is shown and generally indicated by the numeral 100. The sensor system 100 includes a plurality of sensor components mounted to an autonomous vehicle (AV) 102 and included in an AV system 104. The AV system 104 also includes: a controller 106; a communication interface 108 for communicating with other systems and devices; and a user interface 110 for communicating with a user.

[0052] The sensor system 100 includes a top sensor assembly 112 and a plurality of side sensor assemblies 114 for monitoring the external environment of the AV 102. The top sensor assembly 112 is mounted to the top of the AV 102 and includes a light detection and ranging (LiDAR) unit according to one or more embodiments. The LiDAR unit includes one or more emitters 116 and one or more detectors 118. The emitters 116 emit light pulses 120 away from the AV 102. The emitted light pulses 120 are incident on one or more objects (e.g., distant vehicles 122, pedestrians 124, and cyclists 126) and are reflected back to the top sensor assembly 112 as reflected light pulses 128. The top sensor assembly 112 directs the reflected light pulses 128 toward the detectors 118, which provide corresponding light signals 130 to the controller 106. The controller 106 processes the light signals 130 to determine the distance of each object 122, 124, 126 relative to the AV 102. The top sensor assembly 112 includes an absorbent material disposed on one or more surfaces for absorbing stray light to reduce optical noise incident on the detector 118 , thereby increasing the signal-to-noise ratio of the optical signal 130 .

[0053] The side sensor assembly 114 includes a camera for monitoring the external environment, such as a visible spectrum camera, an infrared camera, etc. Both the top sensor assembly 112 and the side sensor assembly 114 may include a lidar unit, one or more cameras, and / or a radar unit.

[0054] The AV system 104 can communicate with a remote computing device 132 via a network 134. The remote computing device 132 can include one or more servers for processing one or more processes of the technology described herein. The remote computing device 132 can also communicate with a database 136 via the network 134.

[0055] Figure 2 FIG. 2 shows an exemplary architecture of a lidar unit 200 (such as a lidar unit of the top sensor assembly 112) according to one or more embodiments. The lidar unit 200 includes a base 202 that is mounted to the AV 102, for example, to the top of the AV 102, such as Figure 1 As shown. Base 202 includes a motor 204 having a shaft 206 extending along a vertical axis AA. Lidar unit 200 also includes a housing 208 that is fixed to shaft 206 and mounted to rotate relative to base 202 about axis AA. Housing 208 includes an opening 210 and a cover or hole 212 fixed within opening 210. Hole 212 is formed of a material that is transparent to light. Although Figure 2 A single hole 212 is shown in FIG, but the lidar unit 200 may include multiple holes 212.

[0056] The lidar unit 200 includes one or more emitters 216 for emitting light pulses 220 that pass through the aperture 212 and away from the AV 102, are incident on one or more objects, and are reflected back toward the lidar unit 200. The lidar unit 200 also includes one or more light detectors 218 for receiving reflected light pulses 228 that pass through the aperture 212. The detectors 218 also receive light from an external light source (e.g., the sun). The emitters 216 and detectors 218 can be stationary, such as mounted to the base 202, or dynamic and mounted to the housing 208. The emitters 216 can include a laser emitter chip or other light emitting device, and can include any number of individual emitters (e.g., 8 emitters, 64 emitters, or 128 emitters). The emitters 216 can emit light pulses 220 of substantially the same intensity or varying intensity and having various waveforms (e.g., sine waves, square waves, and sawtooth waves). The lidar unit 200 may include one or more optical elements 222 to focus and direct the light passing through the aperture 212. The detector 218 may include a photodetector or a photodetector array positioned to receive the reflected light pulses 228. In one or more embodiments, the detector 218 includes a passive imager.

[0057] The lidar unit 200 includes a controller 230 having a processor 232 and a memory 234 to control various components (e.g., the motor 204, the emitter 216, and the detector 218). The controller 230 also analyzes data collected by the detector 218 to measure characteristics of the received light and generate information about the environment outside the AV 102. The controller 230 can be integrally formed with another controller (e.g., the controller 106 of the AV system 104). The lidar unit 200 also includes a power unit 236 that receives power from a vehicle battery 238 and supplies power to the motor 204, the emitter 216, the detector 218, and the controller 230.

[0058] Figure 3 A receiver assembly 300 of a lidar unit 200 is shown according to one or more embodiments. The receiver assembly 300 includes a housing 320 that defines a cavity 322 aligned along an optical axis BB. The receiver assembly 300 supports a lens 334 and a focal plane assembly (FPA) 338. In one or more embodiments, the lens 334 is a collimating lens. The lens 334 focuses the reflected light pulses 328 at a focal plane within the FPA 338.

[0059] refer to Figure 4A-Figure 5B, the FPA 338 supports a detector array 318, such as a photodiode array (PDA). The FPA 338 includes a mounting surface, such as a base 340, which is formed into an elongate shape with a central opening 342. The FPA 338 also includes a circuit board assembly 344, which is mounted to the base 340 and disposed on the central opening 342. The detector array 318 is mounted to a top surface 346 of the circuit board assembly 344. The FPA 338 also includes sidewalls 348 that extend laterally from the perimeter of the base 340 to define a cavity 350. The FPA 338 also includes a cover 352 that extends between distal ends 354 of the sidewalls 348 to enclose the cavity 350. The cover 352 is formed of an optically transparent material, such as glass and sapphire, to receive the reflected light pulses 328. The FPA 338 also includes a series of lenses, such as a microlens array (MLA) 356 mounted to the detector array 318.

[0060] refer to Figure 5B , according to one or more embodiments, the MLA 356 is formed in a rectangular packaging configuration having spherical, refractive, and single-sided lens profiles. In the illustrated embodiment, the MLA 356 is formed as a single-sided plano-convex lens profile. The MLA 356 includes a planar input surface 358 that receives reflected light pulses 328 from the lens 334. The MLA 356 also includes a convex optical device array 360 that forms an output surface. The convex optical device array 360 is arranged along a focal plane 362. In other embodiments, the MLA 356 includes an optical device array formed at the input surface and a planar output surface, or an optical device array formed at both the input surface and the output surface (not shown).

[0061] The MLA 356 is formed with a plurality of holes extending between the planar input surface 358 and the output surface, including a central hole 364 and outer holes 366 (in the Figure 4B In one or more embodiments, each convex optic in the convex optic array 360 is associated with an aperture, and each detector in the detector array 318 is optically aligned with one of the central apertures 364. The central aperture 364 and the outer apertures 366 are transparent or optically clear. Figure 5B Two central apertures 364 are shown, each of which focuses reflected light pulses 328 onto an optical alignment detector of detector array 318, as depicted by reflected light pulses 328 shown in solid lines. External apertures 366 scatter reflected light pulses 328 within MLA 356 and around cavity 350, as depicted by reflected light pulses shown in dashed lines, which may result in optical noise.

[0062] Return to reference Figure 3, the receiver assembly 300 may include a sensitive detector 318 to detect weak signals reflected from distant objects, thereby achieving long range. However, such a sensitive detector 318 may be susceptible to optical noise due to stray light reflections. The MLA 356 used to enhance the optical fill factor acts as a light pipe due to internal reflections, thereby carrying stray light long distances from the source location. This causes optical blur, which is Figure 5B This is a type of optical noise that can temporarily blind detectors that are particularly sensitive to other signals, generally indicated by reference numeral 368. In one or more embodiments, the receiver assembly 300 includes an absorptive coating on non-functional surfaces within the receiver assembly 300. However, this approach may not reduce stray light that is captured within the circuit board assembly 344 of the MLA 356 or FPA 338.

[0063] refer to Fig. 6A and Figure 7 , an FPA according to one or more embodiments is shown and generally indicated by reference numeral 638. FPA 638 is similar to reference numeral 638. Figure 4A-Figure 5B 338. For example, similar to FPA 338, FPA 638 includes a detector array 618 and an MLA 656 formed in a plano-convex shape with a planar input surface 658 and a convex optics array 660 arranged along a focal plane 662 and forming an output surface. MLA 656 is formed with a plurality of apertures extending axially between the planar input surface 658 and the output surface, including a central aperture 664 and external apertures 666. In one or more embodiments, each convex optic in the convex optics array 660 is associated with an aperture, and each detector in the detector array 618 is optically aligned with one of the central apertures 664. The central apertures 664 are optically transparent apertures to focus the reflected light pulses 628 onto the detector array 618. Unlike the external apertures 366 of FPA 338, the external apertures 666 of FPA 638 are not optically transparent. In contrast, the outer aperture 666 is coated with a mask 668 that absorbs stray light, which reduces optical noise. The mask 668 is formed with an opening 669 (at Figure 6B 668, which coincides with the focal plane 662, is formed of an opaque or highly absorptive material such as black chrome or a dielectric / metal stack. This configuration maximizes the amount of absorption of stray light within the MLA 656 without any vignetting or brightness reduction of the main signal.

[0064] Figure 8-Figure 11 Other embodiments of FPAs are shown that include one or more surfaces coated with a material that absorbs stray light. For example, Figure 8An FPA 838 is shown supporting a detector array 818 and including an MLA 856 having a partially transmissive or slightly absorbing material disposed on its output surface. The MLA 856 is formed in a plano-convex shape having a planar input surface 858 and a convex optics array 860 arranged along a focal plane 862 and forming an output surface. The MLA 856 is formed with a plurality of apertures extending between the planar input surface 858 and the output surface, including a central aperture 864 and external apertures 866. In one or more embodiments, each convex optic in the convex optics array 860 is associated with an aperture, and each detector in the detector array 818 is optically aligned with one of the central apertures 864. The MLA 856 includes a coating 868 disposed on the convex optics array 860 including the central aperture 864 and the external apertures 866, which partially absorbs stray light to reduce optical noise. The material absorptivity of coating 868 is between 0.1% and 10%, so that the attenuation of the primary signal (e.g., the returned light signal) is small due to only one surface interaction, but the attenuation of stray light is cumulative due to multiple surface interactions. This is a possible scenario in the case where the total internal reflection of MLA 856 "traps" the stray light. This embodiment highlights the difference between stray light and the primary signal, namely, the number of surface interactions to attenuate the stray light. In one aspect, when the primary signal passes through MLA 856 on the way to detector 818, the primary signal can only encounter coating 868 once before leaving MLA 856. In contrast, the stray light trapped within MLA 856 can be continuously reflected by the surface of MLA 856, thereby generating multiple interactions with coating 868. In this regard, coating 868 can attenuate the stray light at each encounter. Therefore, it can be understood that multiple encounters of stray light with coating 868 mean a greater attenuation rate of the stray light compared to the primary signal.

[0065] Fig. 9An FPA 938 is shown that supports a detector array 918 and includes an MLA 956 having an opaque material disposed on a portion of its input surface. The MLA 956 is formed in a plano-convex shape having a planar input surface 958 and a convex optics array 960 arranged along a focal plane 962 and forming an output surface. The planar input surface 958 includes a central region 974 and an outer region 976. The MLA 956 is formed with a plurality of apertures extending between the planar input surface 958 and the output surface. In one or more embodiments, each convex optic in the convex optics array 960 is associated with an aperture, and each detector in the detector array 918 is optically aligned with a central aperture extending from the central region 974. The central region 974 is optically transparent to focus the reflected light pulses 928 on the detector array 918. However, the outer region 976 is coated with a mask 978 that absorbs stray light, which reduces optical noise. Similar to the FPA 638, this configuration maximizes the amount of stray light that is absorbed without any vignetting or brightness reduction of the primary signal.

[0066] Fig.10 An FPA 1038 is shown supporting a detector array 1018 and including an MLA 1056 having a partially transmissive material disposed on its input surface. The MLA 1056 is formed in a plano-convex shape having a planar input surface 1058 and an array of convex optics 1060 arranged along a focal plane 1062 and forming an output surface. The MLA 1056 is formed with a plurality of apertures extending between the planar input surface 1058 and the output surface. In one or more embodiments, each convex optic in the array of convex optics 1060 is associated with an aperture. The planar input surface 1058 includes a central region 1074 and an outer region 1076, both of which include a coating 1078 that partially absorbs stray light to reduce optical noise. The material absorptivity of the coating 1078 is selected between 0.1% and 10%, so that the attenuation of the main signal is small due to only one surface interaction, but the attenuation of the stray light is accumulated due to multiple surface interactions. This is a possible scenario where stray light is "captured" by total internal reflection of the MLA 1056. Since the stray light encounters the coating 1078 at a significantly higher frequency, the stray light experiences a greater degree of attenuation than the primary signal.

[0067] Fig.11An FPA 1138 is shown supporting a detector array 1118 and including an MLA 1156 having an opaque mask disposed on an outer portion of its input and output surfaces, and a partially transmissive coating disposed on its input and output surfaces. The MLA 1156 is formed in a plano-convex shape, having a planar input surface 1158 and an array of convex optics 1160 arranged along a focal plane 1162 and forming an output surface. The MLA 1156 is formed with a plurality of apertures extending axially between the planar input surface 1158 and the output surface, including a central aperture 1164 and external apertures 1166. In one or more embodiments, each convex optic in the array of convex optics 1160 is associated with an aperture, and each detector in the detector array 1118 is optically aligned with one of the central apertures 1164. Similar to the FPA 638, the external apertures 1166 are coated with a mask 1168 that absorbs stray light, which reduces optical noise. Similar to FPA 838, central aperture 1164 and outer aperture 1166 include coating 1169 that partially absorbs stray light to reduce optical noise. Similar to FPA 938, planar input surface 1158 includes central region 1174 and outer region 1176. Outer region 1176 is coated with mask 1178 that absorbs stray light, which reduces optical noise. Similar to FPA 1038, both central region 1174 and outer region 1176 include coating 1179 that partially absorbs stray light to reduce optical noise.

[0068] Various aspects of the present disclosure provide an MLA having optical properties designed to reduce the effects of trapped stray light. According to some aspects, the MLA can include a mask layer placed at an input surface, an output surface, or both the input surface and the output surface to reduce optical noise in the FPA by absorbing stray light. According to some aspects, the mask layer can be placed at an outer region, an inner region, or both the outer region and the inner region of either the input surface and / or the output surface of the MLA, as described herein with respect to FIG. Fig.11 Reducing optical noise inside the FPA can improve detection of the returning light signal. This improved detection can provide additional benefits for downstream applications such as autonomous driving, transportation, mining, building and construction applications, where highly sensitive detection is preferred.

[0069] The term "vehicle" refers to any mobile form of transport that can carry one or more passengers and / or cargo and is powered by any form of energy. The term "vehicle" includes, but is not limited to, cars, trucks, vans, trains, autonomous vehicles, airplanes, aerial drones, etc. "Autonomous driving vehicles" (or "AV") are vehicles with processors, programming instructions, and transmission components that can be controlled by the processor without the need for a human operator. An autonomous driving vehicle can be fully autonomous, i.e., it does not require a human operator for most or all driving conditions and functions; or it can be semi-autonomous, i.e., a human operator may be required under certain conditions or for certain operations, or a human operator can ignore the autonomous driving system of the vehicle and can control the vehicle. It is worth noting that this paper is the present solution described in the context of an autonomous driving vehicle. However, the present solution is not limited to autonomous driving vehicle applications. The present solution can be used for other applications, such as robotic applications, radar system applications, measurement applications, and / or system performance applications.

[0070] Based on the teachings contained in this disclosure, it will be apparent to those skilled in the relevant art how to use data processing devices, computer systems and / or computer architectures to make and use the embodiments of the present disclosure. In particular, the embodiments can be operated using software, hardware and / or operating system implementations other than those described herein.

[0071] It should be understood that the detailed description section, but not any other section, is intended to be used to interpret the claims. The other sections may set forth one or more (but not all) exemplary embodiments contemplated by the inventors, and therefore are not intended to limit the present disclosure or the appended claims in any way.

[0072] Although the present disclosure describes exemplary embodiments of exemplary fields and applications, it should be understood that the present disclosure is not limited thereto. Other embodiments and modifications thereof are possible and fall within the scope and spirit of the present disclosure. For example, and without limiting the generality of this paragraph, the embodiments are not limited to the software, hardware, firmware and / or entities shown in the figures and / or described herein. In addition, the embodiments (whether or not explicitly described herein) have significant practicality for fields and applications outside the examples described herein.

[0073] Embodiments have been described herein by means of functional building blocks that illustrate implementations of specific functions and relationships thereof. For ease of description, the boundaries of these functional building blocks have been arbitrarily defined herein. Alternative boundaries may be defined as long as the specified functions and relationships (or their equivalents) are appropriately performed. In addition, alternative embodiments may perform functional blocks, steps, operations, methods, etc., in an order different from that described herein.

[0074] References to "one embodiment", "embodiment", "example embodiment" or similar phrases herein indicate that the described embodiments may include specific features, structures or characteristics, but each embodiment may not necessarily include the specific features, structures or characteristics. In addition, such phrases do not necessarily refer to the same embodiment. In addition, when describing specific features, structures or characteristics in conjunction with an embodiment, it is within the knowledge of a technician in the relevant field to incorporate such features, structures or characteristics into other embodiments (whether or not explicitly mentioned or described in this article). In addition, some embodiments may be described using the expressions "connection" and "connection" and their derivatives. These terms are not necessarily intended to be synonyms for each other. For example, some embodiments may be described using the terms "connection" and / or "connection" to indicate that two or more elements are in direct physical or electrical contact with each other. However, the term "connection" may also mean that two or more elements are not in direct contact with each other, but still cooperate or interact with each other. The breadth and scope of the present disclosure should not be limited by any of the above-mentioned exemplary embodiments, but should only be defined according to the attached claims and their equivalents.

[0075] Although exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the present disclosure. On the contrary, the words used in the specification are descriptive rather than restrictive terms, and it should be understood that various changes can be made without departing from the spirit and scope of the present disclosure. In addition, the features of various exemplifying embodiments can be combined to form further embodiments. The terms "connect" and / or "couple" can be used to describe embodiments to indicate that two or more elements are in direct physical or electrical contact with each other. However, the term "couple" can also represent that two or more elements are not in direct contact with each other, but still cooperate or interact with each other. The breadth and scope of the present disclosure should not be limited by any of the above-mentioned exemplary embodiments, but should only be defined according to the attached claims and their equivalents.

[0076] Although exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the present disclosure. On the contrary, the words used in the specification are descriptive rather than restrictive, and it should be understood that various changes may be made without departing from the spirit and scope of the present disclosure. In addition, the features of various exemplified embodiments may be combined to form further embodiments.

Claims

1. A focal plane assembly (FPA), comprising: a detector array; A microlens array (MLA) comprising: an input surface configured to receive light; and an output surface disposed along a focal plane and configured to focus light onto the detector array; and A mask is disposed on an outer portion of at least one of the input surface and the output surface, the mask being configured to absorb stray light and reduce optical noise within the MLA.

2. The FPA according to claim 1, wherein: The MLA includes a central aperture and external apertures extending between the input surface and the output surface, and wherein each central aperture is optically aligned with a detector in the detector array.

3. The FPA according to claim 2, wherein: The mask includes openings that are aligned with the central aperture to limit any vignetting of light focused onto the detector array.

4. The FPA according to claim 2, wherein: The mask is formed of an opaque material and is disposed over the outer aperture of the output surface.

5. The FPA of claim 2, further comprising: A coating is disposed on the central hole and the outer holes of the output surface.

6. The FPA of claim 1, wherein: The mask is formed of an opaque material and is disposed on an outer portion of the input surface.

7. The FPA of claim 1, further comprising: A coating is disposed on the input surface, wherein the coating is formed of a partially transmissive material.

8. The FPA of claim 1, wherein: The MLA is formed with a plano-convex profile having a planar surface formed at one of the input surface and the output surface, and a convex optical device array formed at the other of the input surface and the output surface.

9. A receiver module, comprising: a housing having an opening configured to receive light and an outlet opposite the opening and aligned along an optical axis; at least one lens supported by the housing and aligned along the optical axis to focus light; as well as The FPA of claim 1, wherein an input surface of the MLA is aligned with the at least one lens to receive light.

10. A laser radar unit, comprising: A transmitter module having at least one transmitter configured to transmit light pulses away from a vehicle ； The receiver module according to claim 9, wherein The housing is configured to receive light reflected from an object external to the vehicle as a reflected light pulse; as well as Therein, the detector array generates a light signal indicative of the reflected light pulse having a high signal-to-noise ratio based on reduced optical noise present at the detector array.

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