LIDAR unit with stray light reduction system

Abstract

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

Description

Technical Field

[0001] One or more of the embodiments relate to a sensor system having one or more light absorbing surfaces for reducing stray internal light reflection.

Background Art

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

Summary of the Invention

Problems to be Solved by the Invention

[0003] High sensitivity of a photodetector enables detection of weak signals returned from distant objects, but such sensitivity to optical signals can be vulnerable to high optical noise sensitivity. Accordingly, the proposed systems and methods of the present disclosure provide a solution for reducing optical noise sensitivity in a photodetector device.

Means for Solving the Problems

[0004] In one embodiment, a focal plane assembly (FPA) is provided to have a detector array. The FPA includes a microlens 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 onto the detector array. A mask is disposed on at least an outer portion of the input surface and the output surface. The mask is configured to absorb stray light within the MLA and reduce optical noise.

[0005] In other embodiments, a microlens array (MLA) is provided having an input surface configured to receive light and an output surface arranged along a focal plane and configured to focus the light onto the detector array. A mask is disposed on at least an outer portion of one of the input surface and the output surface. The mask is configured to absorb stray light.

[0006] A focal plane assembly (FPA) includes a detector array; a microlens array (MLA) including an input surface configured to receive light; and an output surface arranged along a focal plane and configured to focus the light onto the detector array, and a mask disposed on at least an outer portion of one of the input surface and the output surface, the mask being configured to absorb stray light within the MLA and reduce optical noise.

[0007] Also, the MLA includes central apertures and outer apertures that extend between the input surface and the output surface, each central aperture being optically aligned with one detector of the detector array.

[0008] Also, the mask includes an opening aligned with the central aperture to limit any vignetting of the light focused onto the detector array.

[0009] Also, the mask is formed of an opaque material and disposed over the outer apertures of the output surface.

[0010] Also, the FPA further includes a coating disposed over the central apertures and the outer apertures of the output surface.

[0011] Also, the mask is formed of an opaque material and disposed over the outer portion of the input surface.

[0012] Further, the FPA of claim 1 further includes a coating disposed on the input surface, the coating being formed of a partially transmissive material.

[0013] Further, the MLA is formed to have a plano-convex profile having a planar surface formed on one of the input surface and the output surface, and a convex optical array formed on the other of the input surface and the output surface.

[0014] On the other hand, the receiver module includes a housing having an aperture configured to receive light and an exit located on the opposite side of the aperture and aligned along the optical axis; at least one lens supported by the housing to focus light and aligned along the optical axis; and the FPA discussed above, wherein the input surface of the MLA is aligned with the at least one lens to receive the light.

[0015] On the other hand, the lidar unit includes a transmitter module having at least one emitter configured to emit light pulses from a vehicle and the receiver discussed above, the housing being configured to receive the light reflected by an object outside the vehicle as a reflected light pulse; the detector array generates an optical signal representing the reflected light pulse with a high signal-to-noise ratio based on the reduced optical noise present in the detector array.

[0016] On the other hand, the microlens array (MLA) includes an input surface configured to receive light; an output surface arranged along the focal plane and configured to focus light onto a detector array; and a mask disposed on at least one external portion of the input surface and the output surface, the mask being configured to absorb stray light.

[0017] Further, the MLA further includes a central hole and an external hole extending between the input surface and the output surface.

[0018] Also, the mask includes an aperture aligned with the central aperture to limit any vignetting of the light focused on the detector array.

[0019] Also, the mask is formed of an opaque material and is disposed over the outer aperture of the output surface.

[0020] Also, the MLA further includes a coating disposed over the central aperture and the outer aperture of the output surface.

[0021] Also, the mask is formed of an opaque material and is disposed over the outer portion of the input surface.

[0022] On the other hand, the lidar unit includes at least one emitter configured to emit light pulses from a vehicle; a housing having an aperture configured to receive light and an exit located on the opposite side of the aperture and aligned along an optical axis; at least one lens supported by the housing to focus light and aligned along the optical axis; a detector array; an optical array as a lens array: an input surface aligned with at least one lens and configured to receive light; and an output surface configured to focus the light on the detector array; and a mask disposed over at least one outer portion of the input surface and the output surface; including a lens array, the mask being configured to absorb stray light within the lens array and reduce optical noise.

[0023] Also, the lidar unit further includes a coating disposed over the input surface, the coating being formed of a partially transmissive material.

[0024] Also, the lidar unit further includes a coating disposed over the output surface, the coating being formed of a partially transmissive material.

[0025] Further, the lens array is formed to have a planar input surface, and each optic of the optic array is formed to have a convex profile.

Brief Description of the Drawings

[0026]

Figure 1

[0027]

Figure 2

[0028]

Figure 3

[0029]

Figure 4A

[0030]

Figure 4B

[0031]

Figure 5A

[0032]

Figure 5B

[0033]

Figure 6A

[0034]

Figure 6B

[0035]

Figure 7

[0036]

Figure 8

[0037]

Figure 9

[0038]

Figure 10

[0039]

Figure 11

[0040] In the drawings, like reference numerals generally denote the same or similar elements. Also, generally, the leftmost digit of a reference numeral identifies the drawing in which the reference numeral is first shown.

DETAILED DESCRIPTION OF THE INVENTION

[0041] As necessary, detailed embodiments are disclosed herein, but it must be understood that the disclosed embodiments are merely exemplary and can be embodied in various alternative forms. The drawings are not necessarily to scale, and some features may be exaggerated or minimized to show details of particular components. Accordingly, the specific structural and functional details disclosed herein should not be construed as limiting, but should be interpreted only as a representative basis for teaching one of ordinary skill in the art how to variously utilize the present disclosure.

[0042] As mentioned herein, exemplary uses of photodetectors are in the fields of light detection and distance measurement applications (e.g., within lidar systems). For example, one of the most desirable attributes of a lidar system is long-range detection that depends on the sensitivity of the photodetector. Long-range detection can be achieved using a very sensitive photodetector. The high sensitivity of the photodetector can detect weak signals returned from objects far away, thus providing a lidar device capable of detecting objects from long distances. However, the sensitivity to optical signals can be correlated with the sensitivity to optical noise. Due to such a correlation, it is preferable for a device that places a photodetector (e.g., a lidar) to reduce the optical noise sensitivity.

[0043] One example of such noise sensitivity can be due to stray light reflection within a photodetector receiver (e.g., a lidar receiver). Specifically, the discrete microlens array used to improve the optical fill factor within the focal plane assembly (FPA) of the receiver can generate total internal reflection, which can cause the die to function as an optical pipe by transmitting stray light to a distance far from the source position. This can cause an optical blooming effect, which is a type of optical noise that can cause particularly sensitive detectors to be temporarily blind to different signals.

[0044] According to one aspect, the disclosed embodiments limit stray light reflections captured within a micro-lens array (MLA), reduce optical blooming (i.e., stray light reflections), and at the same time maintain a high sensitivity level of a photodetector. For example, the aspect of the disclosure provides an MLA having optical characteristics designed to reduce the effect of stray light captured within the MLA. According to one aspect, the MLA may include a masking layer disposed on an input surface, an output surface, or both surfaces of the MLA to reduce the optical noise of the FPA by absorbing stray light. According to one aspect, the masking layer may be further disposed in an outer region, an inner region, or both regions of the input surface and / or the output surface of the MLA.

[0045] The reduction of optical noise inside the FPA can improve the detection of an incident signal (e.g., a returned optical signal) at the detector. According to some aspects described herein, the reduction of optical noise by the disclosed MLA can lead to a reduction / attenuation of the blooming effect at the detector. Such a reduction can significantly improve the detection ability of the detector, especially when an optical signal returned from a highly reflective object (e.g., a road sign (direction sign, yield sign, stop sign, etc.)) containing an embedded reflective material, any other object containing an embedded reflective material, or other highly reflective object is received.

[0046] The disclosed lidar assembly (e.g., lidar unit 200) including the FPA can improve the detection ability and detection accuracy by the reduced noise that affects the signal. Such performance improvement of the lidar provides additional advantages to an autonomous vehicle (AV) such as the AV102 that operates the lidar unit 200. For example, the lidar unit 200 of the AV102 can receive an optical signal reflected by an object showing a high reflectivity (e.g., an object incorporated with a highly reflective substance such as a mirror, glass or a stop sign, and other road signs). In this case, the lidar unit 200 arranged with the disclosed system and method can reduce the blooming effect and attenuate the noise signal generated by the MLA while continuously detecting an object at a far distance. In this exemplification, the lidar device 200 can improve the signal-to-noise ratio (SNR) of the received signal and reduce the vulnerability to the noisy signal while achieving high detection sensitivity before performing a digital signal processing (DSP) application.

[0047] According to one aspect, the performance improvement of the rider unit 200 is further translated into downstream improvements in DSP speed and accuracy. For example, by removing noisy signals, the on-board computer device (e.g., the AV system 104) can utilize even less bandwidth to filter the noise using signal processing techniques. Also, the AV system 104 can utilize even less bandwidth to confirm the detection accuracy of the rider output. Similarly, the AV system 104 can utilize even less bandwidth to compare the detection accuracy of the rider output with other sensor outputs of the detection stack (e.g., radar and camera data). According to one aspect, the rider unit 200 embodying the disclosed embodiments can provide a more accurate output signal to the AV detection, tracking, and prediction stack. For example, improving the accuracy of the data stack received by the AV system 104 can be achieved by the AV system 104 processing damaged detection signals in the rider unit 200 or reducing the latency that may appear for adjusting such signals with other detection signals received at the same time instance (e.g., from a camera or radar system (not shown)). Minimizing the computational cost associated with processing the detection signals can improve the processing capacity of the AV system 104, reduce the latency time, and secure the AV system 104 bandwidth for performing other downstream navigation tasks such as prediction and motion planning operations.

[0048] According to one aspect, the performance improvement of the lidar unit 200 can be further translated into downstream improvement of detection and classification capabilities, thus improving the navigation ability of the AV102. For example, the AV102 can explore geographical locations without being blinded by optical bloom by the lidar unit 200 and can do so in a continuous manner. Due to the reduced bloom effect described herein, the AV102 can also explore geographical locations while detecting and classifying highly reflective objects. The above advantages are merely exemplary, and it can be understood that other advantages for detection, calculation, and downstream application fields such as autonomous driving and navigation can be within the scope of the present disclosure as understood by those of ordinary skill in the art.

[0049] Referring to FIG. 1, a sensor system having one or more light absorbing surfaces is shown by one or more embodiments and is generally referred to by the numeral 100. The sensor system 100 includes a multi-sensor assembly mounted on an autonomous vehicle (AV). The AV102 is included within the 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.

[0050] The sensor system 100 includes an upper sensor assembly 112 and a plurality of side sensor assemblies 114 for monitoring the external environment of the AV 102. The upper sensor assembly 112 is mounted on the roof of the AV 102 and includes a light detection and distance measurement (lidar) unit according to one or more embodiments. The lidar unit includes one or more emitters 116 and one or more detectors 118. The emitter 116 transmits a light pulse 120 from the AV 102. The transmitted light pulse 120 impinges on one or more objects, such as a remote vehicle 122, a pedestrian 124, and a person on a bicycle 126, and is reflected back towards the upper sensor assembly 112 as a reflected light pulse 128. The upper sensor assembly 112 guides the reflected light pulse 128 towards the detector 118, which provides a corresponding optical signal 130 to the controller 106. The controller 106 processes the optical signal 130 to determine the distance of each object 122, 124, 126 relative to the AV 102. The upper sensor assembly 112 includes an absorbing material disposed on one or more surfaces for absorbing stray light to reduce the optical noise incident on the detector 118, thereby increasing the signal-to-noise ratio of the optical signal 130.

[0051] The side sensor assembly 114 includes a camera for monitoring the external environment, such as a visible light spectrum camera, an infrared camera, etc. The upper sensor assembly 112 and the side sensor assembly 114 may each include a lidar unit, one or more cameras and / or a radar unit.

[0052] The AV system 104 can communicate with a remote computing device 132 via a network 134. The remote computing device 132 may include one or more servers for processing one or more processes of the techniques described herein. The remote computing device 132 can also communicate with a database 136 via the network 134.

[0053] Figure 2 shows an exemplary architecture of a lidar unit 200, such as the lidar unit of the upper sensor assembly 112, according to one or more embodiments. The lidar unit 200 includes a base 202 attached to the roof of the AV102, for example, as shown in FIG. 1, to the AV102. The base 202 includes a motor 204 having a shaft 206 extending along a vertical axis A-A. The lidar unit 200 also includes a housing 208 fixed to the shaft 206 and mounted to rotate relative to the base 202 about the axis A-A. The housing 208 includes an opening 210 and a cover or hole 212 fixed within the opening 210. The hole 212 is formed of a light-transparent material. Although a single hole 212 is shown in FIG. 2, the lidar device 200 may include multiple holes 212.

[0054] The lidar unit 200 includes one or more emitters 216 for transmitting light pulses 220 that impinge on one or more objects and are reflected back towards the lidar unit 200 through the hole 212 to the AV102. The lidar unit 200 also includes one or more photodetectors 218 for receiving the reflected light pulses 228 passing through the hole 212. The detector 218 also receives light from an external light source, such as the sun. The emitter 216 and the detector 218 may be stationary, for example, mounted to the base 202, or may be dynamic and mounted to the housing 208. The emitter 216 may include a laser emitter chip or other light-emitting device and may include any number of individual emitters (e.g., 8 emitters, 64 emitters, or 128 emitters). The emitter 216 can transmit light pulses 220 of substantially the same intensity or of varying intensities in various waveforms, such as sine waves, square waves, and sawtooth waves. The lidar device 200 may include one or more optical elements 222 for focusing and directing the light passing through the hole 212. The detector 218 may include a photodetector or an array of photodetectors arranged to receive the reflected light pulses 228. In one or more embodiments, the detector 218 includes a manual imager.

[0055] The rider unit 200 includes a controller 230 having a processor 232 and a memory 234 for controlling various components such as, for example, a motor 204, a transmitter 216, and a detector 218. The controller 230 also analyzes data collected by the detector 218 to measure the characteristics of the received light and generates information about the external environment of the AV102. The controller 230 may be integrated with other controllers, such as the controller 106 of the AV system 104. The rider unit 200 also includes a power unit 236 that receives power from a battery 238 and supplies power to the vehicle motor 204, the transmitter 216, the detector 218, and the controller 230.

[0056] FIG. 3 shows a receiver assembly 300 of the rider unit 200 according to one or more embodiments. The receiver assembly 300 includes a housing 320 that defines a cavity 322 aligned along the optical axis B-B. 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 collimator lens. The lens 334 focuses the reflected light pulse 328 onto the focal plane within the FPA 338.

[0057] Referring to FIGS. 4A - 5B, the FPA 338 supports an array of detectors 318, such as a photodiode array (PDA). The FPA 338 includes a mounting surface, such as a base 340 formed in an elongated shape with a central opening 342. The FPA 338 also includes a circuit board assembly 344 mounted to the base 340 and disposed over the central opening 342. The detector 318 array is mounted to the upper surface 346 of the circuit board assembly 344. The FPA 338 also includes sidewalls 348 that extend laterally from the periphery 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 surround 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 318 array.

[0058] Referring to FIG. 5B, in one or more embodiments, the MLA 356 is formed within a rectangular packing configuration having spherical, refractive, and single-sided lens profiles. In the illustrated embodiment, the MLA 356 is formed within a plano-convex lens profile. The MLA 356 includes a planar input surface 358 that receives the reflected light pulses 328 from the lens 334. The MLA 356 also includes a convex optical array 360 that forms an output surface. The convex optical array 360 is arranged along a focal plane 362. In other embodiments, the MLA 356 includes an optical array formed on the input surface and a planar output surface, or an optical array formed on both the input and output surfaces (not shown).

[0059] The MLA 356 forms a plurality of holes that extend between a planar input surface 358 and an output surface, which includes a central hole 364 and outer holes 366 (shown in FIG. 4B). In one or more embodiments, each convex optic of the convex optic array 360 is associated with a hole, and each detector of the detector array 318 is optically aligned with one of the central holes 364. The central hole 364 and the outer holes 366 are transparent or optically transparent. As depicted by the reflected light pulses 328 shown as solid lines, FIG. 5B shows two central holes 364 that focus the reflected light pulses 328 onto the optically aligned detectors of the detector array 318. As depicted by the reflected light pulses shown as dashed lines, the outer holes 366 scatter the reflected light pulses 328 inside the MLA 356 and around the cavity 350, which can lead to optical noise.

[0060] Referring again to FIG. 3, the receiver assembly 300 may include a sensitive detector 318 for detecting weak signals reflected by distant objects to achieve long distances. However, such a sensitive detector 318 can be vulnerable to optical noise from stray light reflections. The MLA 356, which is used to improve the optical fill factor, functions as an optical pipe by internal reflection and transmits stray light to distances far from the source position. This generally causes optical blooming, generally referred to by the numeral 368 in FIG. 5B, which is a type of optical noise that can cause particularly sensitive detectors to be temporarily blinded to other signals. In one or more embodiments, the receiver assembly 300 includes a water-absorbing coating on non-functional surfaces within the receiver assembly 300. However, such an approach may not be able to reduce the stray light trapped within the circuit board assembly 344 of the MLA 356 or the FPA 338.

[0061] Referring to FIGS. 6A and 7, the FPA is shown by one or more embodiments and is generally represented by the numeral 638. The FPA 638 is similar to the FPA 338 described with reference to FIGS. 4A - 5B. For example, like the FPA 338, the FPA 638 includes a plano - convex shaped MLA 656 that is arranged along a detector 618 array and a planar input surface 658 and a convex optical array 660 that forms an output surface, and has a plurality of holes that extend axially between the planar input surface 658 and the output surface, which includes a central hole 664 and outer holes 666. In one or more embodiments, each convex optic of the convex optical array 660 is associated with a hole, and each detector of the detector 618 array is optically aligned with one of the central holes 664. The central hole 664 is an optically transparent hole that focuses the reflected light pulse 628 onto the detector 618 array. Unlike the outer holes 366 of the FPA 338, the outer holes 666 of the FPA 638 are not optically transparent. Instead, the outer holes 666 are coated with a mask 668 that absorbs stray light, which reduces optical noise. The mask 668 is formed with an opening 669 that is aligned with the central hole 664 (shown in FIG. 6B). The mask 668 that 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 stray light absorption within the MLA 656 without any vignetting or reduction in brightness of the main signal.

[0062] Figures 8-11 show additional embodiments of an FPA that includes one or more surfaces coated with a substance that absorbs stray light. For example, FIG. 8 shows an FPA 838 that includes an MLA 856 that supports an array of detectors 818 and has a partially transmissive or weakly water-absorbent substance disposed on its output surface. The MLA 856 is formed in a plano-convex shape having a planar input surface 858 and a convex optical array 860 that is arranged along a focal plane 862 and forms the output surface. The MLA 856 forms a plurality of holes that extend between the planar input surface 858 and the output surface, which includes a central hole 864 and outer holes 866. In one or more embodiments, each convex optic of the convex optical array 860 is associated with a hole, and each detector of the detector 818 array is optically aligned with one of the central holes 864. The MLA 856 includes a coating 868 disposed on the convex optical array 860 that includes the central hole 864 and the outer holes 866, which partially absorbs stray light to reduce optical noise. The material absorption rate of the coating 868 is between 0.1% and 10%, and the attenuation of the main signal (e.g., the returned optical signal) is minimal because there is only one surface interaction, but the attenuation of the stray light accumulates due to multiple surface interactions. This is a scenario that is possible when total internal reflection of the MLA 856 "traps" the stray light. This implementation emphasizes the difference between the stray light and the main signal, i.e., the number of surface interactions, in order to attenuate the stray light. On one side, the main signal can pass through the MLA 856 and contact the coating 868 only once on its way to the detector 818 and then exit the MLA 856. In contrast, the stray light trapped inside the MLA 856 can continue to reflect off the surface of the MLA 856 to create multiple interactions with the coating 868. In connection with this, the coating 868 can attenuate the stray light with each contact. Thus, it can be understood that multiple contacts with the coating 868 can achieve a higher attenuation rate of the stray light compared to the main signal.

[0063] FIG. 9 shows an FPA 938 including an MLA 956 that supports a detector 918 array and has an opaque material disposed on a portion of its input surface. The MLA 956 is formed in a plano-convex shape having a convex optical array 960 that is arranged along a planar input surface 958 and a focal plane 962 and forms an output surface. The planar input surface 958 includes a central region 974 and an outer region 976. The MLA 956 forms a plurality of holes that extend between the planar input surface 958 and the output surface. In one or more embodiments, each convex optic of the convex optical array 960 is associated with a hole, and each detector of the detector 918 array is optically aligned with a central hole extending from the central region 974. The central region 974 is optically transparent to focus reflected light pulses 928 onto the detector 918 array. 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 absorbed without any vignetting or reduction in brightness of the main signal.

[0064] FIG. 10 shows an FPA 1038 including an MLA 1056 that supports a detector 1018 array and has a partially transmissive material disposed across its input surface. The MLA 1056 is formed in a plano-convex shape having a convex optical array 1060 that is arranged along a planar input surface 1058 and a focal plane 1062 and forms an output surface. The MLA 1056 forms a plurality of holes that extend between the planar input surface 1058 and the output surface. In one or more embodiments, each convex optic of the convex optical array 1060 is associated with a hole. 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 absorption rate of the coating 1078 is selected between 0.1% and 10%. The attenuation of the main signal is small because there is only one surface interaction, but the attenuation of the stray light accumulates due to multiple surface interactions. This is a scenario that is possible when total internal reflection in the MLA 1056 "traps" the stray light. Since the contact frequency with the coating 1078 is quite high, the stray light undergoes a greater attenuation than the main signal.

[0065] FIG. 11 shows an FPA 1138 that includes an MLA 1156 that supports a detector 1118 array and has an opaque mask disposed on external portions of its input and output surfaces and a partially transmissive coating disposed across its input and output surfaces. The MLA 1156 is formed in a plano-convex shape having a planar input surface 1158 and a convex optical array 1160 arranged along a focal plane 1162 and forming an output surface. The MLA 1156 forms a plurality of holes that extend axially between the planar input surface 1158 and the output surface, which include a central hole 1164 and external holes 1166. In one or more embodiments, each convex optic of the convex optical array 1160 is associated with a hole, and each detector of the detector 1118 array is optically aligned with one of the central holes 1164. Similar to FPA 638, the external holes 1166 are coated with a mask 1168 that absorbs stray light, which reduces optical noise. Similar to FPA 838, the central hole 1164 and the external holes 1166 include a coating 1169 that partially absorbs stray light to reduce optical noise. Similar to FPA 938, the planar input surface 1158 includes a central region 1174 and an external region 1176. The external region 1176 is coated with a mask 1178 that absorbs stray light, which reduces optical noise. Similar to FPA 1038, the central region 1174 and the external region 1176 both include a coating 1179 that partially absorbs stray light to reduce all optical noise.

[0066] Aspects of the present disclosure provide an MLA having optical properties designed to reduce the effects of captured stray light. According to some aspects, the MLA may include a masking layer disposed on the input surface, the output surface, or both surfaces to reduce the optical noise of the FPA by absorbing stray light. According to some aspects, as described herein in connection with FIGS. 6-11, the masking layer may be disposed in the outer region, the inner region, or both regions of the input surface and / or the output surface of the MLA. The reduction of optical noise within the FPA can improve the detection of the returned optical signal. Such improved detection can provide additional advantages in downstream applications such as autonomous driving, transportation, mining, building, and construction applications where high-sensitivity detection is preferred.

[0067] The term "vehicle" refers to any mobile transportation means that can carry one or more human passengers and / or cargo and is driven by any form of energy. The term "vehicle" includes, but is not limited to, automobiles, trucks, vans, trains, autonomous vehicles, aircraft, aerial drones, etc. An "autonomous vehicle" (or "AV") is a vehicle equipped with a drive train component that does not require a processor, programming instructions, and a human driver and can be controlled by a processor. An autonomous vehicle may be fully autonomous in that it does not require a human driver for most or all driving conditions and functions, may require a human driver for specific conditions or specific operations, or may be anti-autonomous in that a human driver can override the vehicle's autonomous driving system and control the vehicle. The point to note is that the present solution is described herein in the context of autonomous vehicles. However, the present solution is not limited to autonomous vehicle applications. The present solution may also be used in other applications such as robotic applications, radar system applications, measurement applications, and / or system performance applications.

[0068] Based on the teachings contained in this disclosure, the methods of making and using embodiments of this disclosure using a data processing apparatus, computer system, and / or computer architecture will be apparent to those of ordinary skill in the relevant art. In particular, the embodiments can operate in implementations of software, hardware, and / or operating systems other than those described herein.

[0069] It should be understood that the detailed description section is not intended to be used to interpret the claims rather than any other section. Other sections can present one or more, which are not all of the exemplary embodiments devised by the inventor, and are not intended to limit the content of this disclosure and the appended claims in any way.

[0070] This disclosure describes exemplary embodiments for exemplary fields and application areas, but it should be understood that this disclosure is not limited thereto. Other embodiments and modifications thereto are possible and are within the scope and spirit of this disclosure. For example, and without limiting the generality of this paragraph, the embodiments are not limited to the software, hardware, firmware, and / or entities illustrated in the drawings or described herein. Further, the embodiments (whether or not explicitly described herein) have a utility equivalent to that of the examples described herein in the fields and application areas.

[0071] The embodiments are described herein with the aid of functional building blocks that exemplify the implementation of specified functions and their relationships. The boundaries of such functional building blocks are arbitrarily defined herein for the sake of explanation. Alternative boundaries may be defined as long as the specified functions and relationships (or their equivalents) are appropriately performed. Also, alternative embodiments can perform functional blocks, steps, operations, methods, etc. using an order different from that described herein.

[0072] As used herein, references to "one embodiment," "an embodiment," "exemplary embodiment," or similar phrases indicate that the described embodiment may include a particular feature, structure, or characteristic, but not every embodiment necessarily includes the particular feature, structure, or characteristic. Further, such phrases do not necessarily refer to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it will be within the knowledge of one of ordinary skill in the relevant art to incorporate such feature, structure, or characteristic into other embodiments, whether or not explicitly recited or described herein. Also, some embodiments may be described using the terms "coupled" and "connected" and derivatives thereof. Such terms are not necessarily intended as synonyms for each other. For example, some embodiments may be described using the terms "connected" and / or "coupled" to indicate that two or more elements are in direct physical or electrical contact with each other. The term "coupled," however, can 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 exemplary embodiments described above, but should be defined only by the following claims and equivalents thereof.

[0073] Exemplary embodiments have been described above, but such embodiments are not intended to describe all possible forms of the disclosure. Rather, the words used in the specification are words of description rather than limitation, and it must be understood that various changes can be made without departing from the spirit and scope of the disclosure. Also, the features of various embodiments can be combined to form additional embodiments. The terms "connected" and / or "coupled" can be used to indicate that two or more elements are in direct physical or electrical contact with each other. The term "coupled", however, can also mean that two or more elements do not contact each other directly but still cooperate or interact with each other. The breadth and scope of the present disclosure should not be limited by any of the exemplary embodiments described above and should be defined only by the following claims and claims equivalent thereto.

[0074] Exemplary embodiments have been described above, but such embodiments are not intended to describe all possible forms of the disclosure. Rather, the words used in the specification are words of description rather than limitation, and it must be understood that various changes can be made without departing from the spirit and scope of the disclosure. Also, the features of various embodiments can be combined to form additional embodiments.

Claims

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

2. The MLA of claim 1, wherein the MLA includes a central hole and an outer hole that extend between the input surface and the output surface, and each central hole is optically aligned with one detector of the detector array.

3. The focal plane assembly of claim 2, wherein the mask includes an aperture aligned with the central hole to limit any vignetting of the light focused onto the detector array.

4. The focal plane assembly of claim 2, wherein the mask is formed of an opaque material and is disposed in the outer hole of the output surface.

5. The focal plane assembly of claim 2, further comprising a coating disposed on the central hole and the outer hole of the output surface.

6. The focal plane assembly of claim 1, wherein the mask is formed of an opaque material and is disposed in the outer portion of the output surface.

7. The focal plane assembly of claim 1, further comprising a coating disposed on the input surface - the coating is formed of a partially transmissive material.

8. The focal plane assembly of claim 1, wherein the MLA is formed to have a plano-convex profile having a planar surface formed on one of the input surface and the output surface, and a convex optical array formed on the other of the input surface and the output surface.

9. In a receiver module, a housing having an aperture configured to receive light and an exit located on the opposite side of the aperture and aligned along the optical axis; at least one lens supported by the housing to focus light and aligned along the optical axis; and The receiver module according to claim 1, wherein the input surface of the MLA is aligned with the at least one lens for receiving the light. **Claim 10** In a lidar unit, A transmitter module having at least one emitter configured to emit an optical pulse from a vehicle; The receiver module according to claim 9, wherein the housing is configured to receive the light reflected by an object outside the vehicle as a reflected optical pulse; and The lidar unit, wherein the detector array generates an optical signal indicating the reflected optical pulse with a high signal-to-noise ratio based on the reduced optical noise present in the detector array.

Images