WO2022001219A1 - 光接收装置及激光雷达系统 - Google Patents

光接收装置及激光雷达系统 Download PDF

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Publication number
WO2022001219A1
WO2022001219A1 PCT/CN2021/082359 CN2021082359W WO2022001219A1 WO 2022001219 A1 WO2022001219 A1 WO 2022001219A1 CN 2021082359 W CN2021082359 W CN 2021082359W WO 2022001219 A1 WO2022001219 A1 WO 2022001219A1
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Prior art keywords
light
receiving device
light receiving
homogenizing
pixel
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PCT/CN2021/082359
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English (en)
French (fr)
Inventor
安凯
周熠伦
丁云
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华为技术有限公司
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Priority to EP21833430.8A priority Critical patent/EP4160261A4/en
Publication of WO2022001219A1 publication Critical patent/WO2022001219A1/zh
Priority to US18/147,242 priority patent/US20230139155A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/88—Lidar systems specially adapted for specific applications
    • G01S17/89—Lidar systems specially adapted for specific applications for mapping or imaging
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/481—Constructional features, e.g. arrangements of optical elements
    • G01S7/4817—Constructional features, e.g. arrangements of optical elements relating to scanning
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/481—Constructional features, e.g. arrangements of optical elements
    • G01S7/4816—Constructional features, e.g. arrangements of optical elements of receivers alone
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/4802—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
    • G02B19/0033—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use
    • G02B19/0076—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with a detector
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/09—Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
    • G02B27/0938—Using specific optical elements
    • G02B27/095—Refractive optical elements
    • G02B27/0955—Lenses
    • G02B27/0961—Lens arrays
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/09—Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
    • G02B27/0938—Using specific optical elements
    • G02B27/0994—Fibers, light pipes
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B3/00—Simple or compound lenses
    • G02B3/0006—Arrays
    • G02B3/0037—Arrays characterized by the distribution or form of lenses
    • G02B3/0056—Arrays characterized by the distribution or form of lenses arranged along two different directions in a plane, e.g. honeycomb arrangement of lenses

Definitions

  • the invention relates to the field of light detection, in particular to a light receiving device and a laser radar system.
  • Photodetectors can be used in many fields, for example, they can be used in receiving devices of lidar systems.
  • the working principle of the LiDAR (light detection and ranging, LiDAR) system is to emit a laser beam of a specific frequency to a set area. When the laser encounters an object during flight, it is reflected on its surface, and part of the laser is reflected to the receiving device of the radar. form echoes.
  • the LiDAR receiving device compares the received echo signal with the transmitted signal to obtain the relevant information of the object, such as distance, angle, reflectivity, etc.
  • SiPM Silicon Photomultiplier
  • Avalanche Photo Diode Avalanche Photo Diode
  • SPAD Single Photon Avalanche Diode
  • SiPM Silicon Photomultiplier
  • the silicon photomultiplier SiPM consists of an array of avalanche diodes operating in Geiger mode, including photon counters with multiple pixels.
  • a pixel contains many independent photosensitive units, called cells, and the response signals of the multiple photosensitive units are accumulated and output through a shared output channel.
  • SiPM has the characteristics of high sensitivity, low bias voltage and compact structure.
  • SiPM is used as a light receiving detector
  • the received light signal is collected by the receiving lens, the collected light signal is incident on a small part of the pixels on the SiPM photosensitive surface, resulting in a small dynamic range of the detector and low detection efficiency.
  • Embodiments of the present invention provide a light receiving device and a laser radar system, which increase the dynamic range of the detector and the laser radar system, and improve the detection efficiency.
  • an embodiment of the present invention provides a light receiving device, comprising: a photodetector, and a plurality of uniform light units; wherein the photodetector includes a plurality of pixels, and each pixel includes a plurality of It is used to convert the received optical signal into an electrical signal; each uniform light unit corresponds to at least one pixel of the photodetector, and is used for diffusing the received incident light beam to a plurality of pixels included in the corresponding at least one pixel.
  • the uniform light unit spreads the incident light to multiple pixels, which increases the dynamic range of the entire detector and improves the detection efficiency.
  • the homogenizing unit includes a homogenizing mirror body, and the side wall of the homogenizing mirror body is coated with a reflective film, so that the received light beam is diffused to a plurality of pixels included in at least one pixel of the photodetector.
  • the use of the homogenizing mirror makes the incident light evenly diffused to the light-emitting surface.
  • the length L of the homogenizing mirror body satisfies the condition: L ⁇ d/(2*tan( ⁇ /2)); where d is the length of the short side of the light-passing cross section of the homogenizing lens body, ⁇ is the divergence angle of the beam entering the mirror body.
  • the homogenizing unit further includes a diffusing sheet disposed before the incident surface of the homogenizing mirror body; the diffusing sheet is used to diffuse the received incident light beam and output it to the incident surface of the homogenizing lens body. This further improves the effect of uniform light.
  • the homogenizing unit further includes a microlens, which is arranged on the incident surface of the homogenizing unit; the microlens is used for converging the received incident light beam to the light incident surface of the diffuser or the homogenizing mirror.
  • the use of microlenses enlarges the angle of incidence of the incident light.
  • the components in the homogenizing unit are connected by means of photosensitive adhesive bonding.
  • the use of light glue reduces the energy loss of incident light.
  • the photodetector is a silicon photomultiplier tube SiPM.
  • SiPMs silicon photomultipliers
  • a plurality of light homogenizing units are clamped and fixed by a structural member, which improves the durability of the light receiving device.
  • the dodging unit corresponds to a plurality of pixels
  • the plurality of dodging units are a prism body without isolation inside, forming a row layout, a column layout or a special-shaped layout, so that the application scenarios of the light receiving device are wider.
  • the light-emitting end face of the uniform light unit has the same size as the photosensitive surface in the detector pixel, which reduces the energy loss of incident light.
  • an embodiment of the present invention provides a lidar system, including a light source, a scanner, a receiving lens, the aforementioned light receiving device, and a processor; wherein the light source is used to output a laser beam; the scanner is used to set the Scanning in the area; the receiving lens is used to collect the echo light signal reflected by the object into the light receiving device; the light receiving device is used to convert the echo light signal into an echo electrical signal; the processor is used to analyze the echo electrical signal and control the Light source, scanner, and light receiving device.
  • This lidar system has a large dynamic range and high detection efficiency.
  • an embodiment of the present invention provides a detection method, which is applied to the above-mentioned lidar system, including: outputting a control signal to a light source, driving the light source to output a laser beam; outputting a control signal to a scanner, driving the scanner according to a set Scan in the mode; receive the echo signal output by the light receiving device, process it, and obtain the object information corresponding to the echo.
  • a detection method which is applied to the above-mentioned lidar system, including: outputting a control signal to a light source, driving the light source to output a laser beam; outputting a control signal to a scanner, driving the scanner according to a set Scan in the mode; receive the echo signal output by the light receiving device, process it, and obtain the object information corresponding to the echo.
  • FIG. 1 is a schematic structural diagram of a lidar system according to an embodiment of the present invention
  • FIG. 2 is a schematic diagram of a photosensitive surface of a SiPM detector according to an embodiment of the present invention
  • FIG. 3 is a schematic diagram of the relationship between a uniform light unit and a SiPM detector provided by an embodiment of the present invention
  • FIG. 4 is a schematic diagram of lamination of a uniform light unit and a SiPM detector provided in an embodiment of the present invention
  • FIG. 5 is a schematic structural diagram of a uniform light unit provided by an embodiment of the present invention.
  • FIG. 6 is a schematic diagram of light reflection of a homogenizing mirror body provided by an embodiment of the present invention.
  • FIG. 7 is a schematic diagram of a homogenizing unit provided by an embodiment of the present invention, which is clamped and fixed by a structural member;
  • FIG. 8 is a schematic diagram of a scanning detection method provided by an embodiment of the present invention.
  • FIG. 9 is a schematic diagram of a combination of homogenizing mirror bodies provided by an embodiment of the present invention.
  • FIG. 10 is a schematic perspective view of a cylindrical microlens according to an embodiment of the present invention.
  • FIG. 11 is a schematic diagram of an edge groove existing between photosensitive surfaces of a detector provided by an embodiment of the present invention.
  • FIG. 12 is a schematic structural diagram of the uniform light unit corresponding to FIG. 11 according to an embodiment of the present invention.
  • FIG. 13 is a schematic diagram of an optical path of a light receiving device that does not include a homogenizing mirror provided by an embodiment of the present invention
  • FIG. 14 is a schematic diagram of receiving echo photons corresponding to FIG. 13 according to an embodiment of the present invention.
  • FIG. 15 is a schematic diagram of an optical path of a light receiving device including a homogenizing mirror provided by an embodiment of the present invention.
  • FIG. 16 is a schematic diagram of receiving echo photons corresponding to FIG. 15 according to an embodiment of the present invention.
  • Embodiments of the present invention provide a light receiving device and a laser radar system using the light receiving device.
  • the lidar system 10 includes: a light source 101 , a scanner 102 , a receiving lens 103 , a light receiving device 104 and a processor 105 .
  • the light source 101 is used to output a laser beam.
  • the scanner 102 is used for two-dimensional scanning within a set area.
  • the receiving lens 103 is used for collecting the echo light signal reflected by the object 11 into the light receiving device 104 .
  • the light receiving device 104 is used to convert the echo optical signal into the echo electrical signal.
  • the processor 105 is configured to control the light source 101 , the scanner 102 , and the light receiving device 104 , and analyze the echo electrical signals to obtain the relevant parameters of the object 11 . After the two-dimensional scanning is completed, the processor 105 finally analyzes and obtains a point cloud image.
  • the light receiving device 104 includes a photodetector, which may be a silicon photomultiplier tube SiPM.
  • the SiPM includes a plurality of pixels, which generally form a two-dimensional pixel array, for example, M*N pixels, where M and N are positive integers greater than 1.
  • Each pixel includes a plurality of picture elements, and each picture element is an independent photosensitive unit (cell) for converting the received light signal into an electrical signal.
  • the electrical signals of multiple pixels included in one pixel are accumulated and output through the shared output channel.
  • FIG. 2 An example of a SiPM detector is shown in Figure 2, which includes 6*4 pixels, and each pixel includes 6*6 pixels. If you want to complete a point cloud image of 1440*900 pixels, for a 6*4 pixel SiPM detector, the scanner needs to set 240 angles in the horizontal direction and 225 angles in the vertical direction to scan, and finally form a complete point. Cloud image.
  • the light receiving device 104 further includes a plurality of uniform light units, each of which corresponds to one pixel of the photodetector.
  • the uniform light unit is used for diffusing the received echo light signal to a plurality of picture elements included in a corresponding pixel.
  • the light receiving device includes 6*4 uniform light units (301), and the 24 uniform light units correspond to 6*4 pixels (302) of the photodetector respectively.
  • the light-emitting surface of the uniform light unit is usually attached to the photosensitive surface of the SiPM detector.
  • FIG. 4 is a schematic diagram of the uniform light unit and the SiPM detector being bonded together.
  • the photodetector in the figure includes 3*3 pixels, and there are 9 uniform light units 401, which correspond to the 9 pixels of the SiPM detector 402 one-to-one.
  • a homogenizing unit structure provided by an embodiment of the present invention includes: a microlens 501 , a diffusing sheet 502 , and a homogenizing mirror body 503 .
  • the microlens 501 , the diffuser 502 , and the homogenizing mirror body 503 can be fixedly connected by means of photosensitive adhesive bonding to form a homogenizing unit, as shown on the right side of FIG. 5 .
  • the microlens 501 is used for receiving the echoed incident light beam and condensing the incident light beam onto the diffuser.
  • the microlens can enlarge the receiving numerical aperture, so that the light beam with a larger incident angle can enter the light receiving device.
  • the radius of curvature of the spherical surface of the microlens can be designed to be 1.4mm and the thickness is 1mm, so the receiving numerical aperture is about 0.25.
  • the microlens material can be BK7 glass or the like.
  • the diffusing sheet 502 is used for diffusing the received incident light beam.
  • the light beam entering the diffuser through the microlens is enlarged by the diffuser to spread rapidly in the homogenizer and reduce the length of the homogenizer.
  • the sidewall of the homogenizer 503 is usually coated with a reflective film, so that the light beam passing through the diffuser is further diffused to a plurality of pixels of the corresponding pixels in the photodetector.
  • the homogenizing mirror has a homogenizing effect: the light beam enters the homogenizing mirror, and the side wall of the homogenizing mirror is coated with a reflective film to form a "photon well". , the energy is evenly distributed.
  • the reflective film prevents photons from passing through the lens body to reach adjacent uniform light units, avoiding crosstalk.
  • the light-transmitting cross-section of the dodging mirror body can be a rectangle, usually a square.
  • FIG. 6 is a schematic diagram of light reflection of a homogenizing mirror body.
  • the length of the homogenizing mirror body is L
  • the side length of the cross-sectional square is d.
  • d is generally the same size as the corresponding SiPM detector pixel or slightly larger, so that the light beams all reach the SiPM photosensitive surface.
  • the length L of the homogenizer can be designed according to the following conditions: L ⁇ d/(2*tan( ⁇ /2)).
  • d is the length of the shortest side of the light-transmitting cross section of the mirror body
  • ⁇ is the divergence angle of the light beam when it enters the mirror body.
  • the size of each pixel of the detector is 1mm*1mm
  • the side wall of the homogenizing mirror body can be coated with a reflective film, and the upper and lower end faces, as well as the end faces of the light entrance and exit, can be coated with an anti-reflection coating;
  • the working end face of the microlens can be further polished.
  • the light receiving device may include M*N uniform light units, corresponding to M*N pixels of the photodetector. These homogenizing units can be combined together by some common fastening methods, for example, they can be bonded with photosensitive adhesive.
  • the homogenizing unit can also be fixed by means of structural parts. As shown in FIG. 7 , the 3*3 uniform light units are fixed by a structural member 701, so that the entire light receiving device is not easily deformed, and the detection performance is more stable.
  • each uniform light unit should cover the effective photosensitive surface of the corresponding pixel, and the size of the light-emitting surface is the same as the size of the corresponding pixel, or the same as the size of the effective photosensitive surface of the corresponding pixel.
  • the outlet end is attached to the SiPM photosensitive surface to ensure that the outlet does not leak light.
  • the light-emitting surface of the uniform light unit needs to be aligned with the photosensitive surface of the SiPM detector pixel.
  • One possible assembly method is:
  • Step 1 Laminate the light-emitting end face of the homogenizing unit with the photosensitive surface of the SiPM detector without applying glue;
  • Step 2 Use a thin beam in the working band of the SiPM detector to illuminate the light entrance of any uniform light unit in the light receiving device, monitor the output amplitude of the response signal of the pixel corresponding to the SiPM detector, and adjust the up, down, left, and right of the uniform light unit.
  • the amplitude of the output signal of the SiPM detector is the largest, the position of the uniform light unit is fixed.
  • Step 3 Apply photosensitive adhesive around the bonding part of the uniform light unit and the SiPM detector. After the glue dries, the two are bonded together. In Fig. 7, the position indicated by 702 is the bonding portion of the uniform light unit and the SiPM detector.
  • the beam entrance end face of the light receiving device 104 that is, the incident face 703 of the uniform light unit shown in FIG. 7 , should be placed at the focal plane of the receiving lens 103 to avoid the entrance photon crosstalk occurs.
  • an embodiment of the present invention further provides a scanning detection method for a lidar system, as shown in FIG. 8 , including the following steps.
  • the processor 105 outputs a control signal to the light source 101 to drive the light source to output a laser beam.
  • the output end of the light source 101 may further include an emission lens, which shapes the emitted light beam into a spot light beam, and then enters the scanner 102 .
  • the processor 105 outputs a control signal to the scanner 102, such as information such as a scanning angle, and drives the scanner to scan according to the set mode. In this way, the light beam output by the light source passes through the scanner and is emitted towards the target area.
  • the processor 105 receives the echo signal and processes it to obtain information such as the angle and distance of the object corresponding to the current echo.
  • the light beam output from the scanner 102 is reflected upon encountering an object, and an echo beam is sent to the lidar system.
  • the echo beams are converged by the receiving lens 103 and enter the light receiving device 104. After the beams pass through the uniform light unit, they are irradiated on the photosensitive pixels of the SiPM detector. After photoelectric conversion, the echo electrical signal is output, and the processor receives the echo electrical signal for processing.
  • the processor 105 continues the above process, and scans the target area two-dimensionally, thereby forming a point cloud image of the target area.
  • multiple dodging units can be combined to form row layout, column layout and special-shaped layout.
  • three cube-shaped homogenizing mirror bodies are combined to form a rectangular parallelepiped homogenizing lens body, corresponding to 1*3 pixels of the SiPM detector.
  • the merging method is as follows: three homogenizing mirror bodies with optical path isolation are combined together to form a prism body without internal isolation.
  • the three spherical microlens groups shown in FIG. 9 can also be combined into a cylindrical microlens, as shown in FIG. 10 , which is a perspective view of the cylindrical microlens.
  • Embodiments of the present invention also provide a light receiving device, which is applied to an array SiPM detector with a relatively low pixel fill-factor.
  • edge trenches exist between the photosensitive surfaces of the detector pixels.
  • the size of each pixel of the detector is 1.0mm*1.0mm
  • the size of the photosensitive surface of each pixel is 0.6mm*0.6mm
  • the width of the pixel edge groove (gap) is 0.4mm
  • the fill factor is 60%.
  • the homogenizing unit includes a microlens 1201 , a diffuser 1202 , a homogenizing mirror 1203 , a fixed structure 1204 , and a SiPM detector 1205 . It can be seen from the figure that the size of the light-emitting surface of the homogenizing mirror body is reduced to the same size as the photosensitive surface of the detector, so that all photons received by the light-incident end face can be introduced into the photosensitive surface of the pixel, improving the utilization rate of light energy, which is equivalent to converting Detector fill factor increased from 60% to 100%.
  • Figure 13 is the light path diagram of the light receiving device without the homogenizing mirror body, after the echo light passes through the receiving mirror body 1301, it is focused on the local area of the photosensitive surface of the SiPM detector with 3*3 pixels. Only a small part of each pixel, that is, a small number of pixels, can receive the echo photons.
  • Figure 14 shows a schematic diagram of the corresponding echo photon receiving, and it can be seen that the echo photons are concentrated in the center of 3*3 pixels.
  • a 3*3 homogenizing mirror body 1503 is added in front of the SiPM detector 1502 with 3*3 pixels.
  • the echo light passes through the receiving mirror body 1501, it is focused on the light incident surface of the uniform light mirror body.
  • the echo light rays are evenly distributed on the photosensitive surface of 3*3 pixels, that is, Each pixel in the pixel can receive the echo photons relatively uniformly.
  • Figure 16 shows a schematic diagram of the corresponding echo photon receiving, and it can be seen that the echo photons are relatively evenly distributed on 3*3 pixels.
  • the above-mentioned light receiving device including a homogenizing unit can also be used in products such as security cameras, low-light detection imaging equipment, and the like. Such products need to detect weak light signals, and an array SiPM detector can be used to obtain better images.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Optics & Photonics (AREA)
  • Electromagnetism (AREA)
  • Optical Radar Systems And Details Thereof (AREA)
  • Optical Elements Other Than Lenses (AREA)

Abstract

一种光接收装置，包括：光电探测器（402），以及多个匀光单元（401）；其中：光电探测器（402）包括多个像素，每个像素包括多个像元，像元用于将接收的光信号转换为电信号；每个匀光单元（401）对应光电探测器（402）的至少一个像素，用于将接收的入射光束扩散至对应的至少一个像素包含的多个像元上。这种光接收装置可应用在激光雷达系统中。该装置增大了探测器和激光雷达系统的动态范围，提高了探测效率。

Description

光接收装置及激光雷达系统
本申请要求于2020年6月30日提交中国国家知识产权局、申请号为202010619749.X、申请名称为“光接收装置及激光雷达系统”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明涉及光探测领域，尤其涉及一种光接收装置，以及激光雷达系统。
背景技术
光电探测器可应用于很多领域，例如可应用在激光雷达系统的接收装置中。激光雷达(light detection and ranging,LiDAR)系统的工作原理是，向设定区域发射特定频率的激光束，激光飞行过程中遇到物体，在其表面发生反射，其中部分激光反射到雷达的接收装置形成回波。激光雷达接收装置将收到的回波信号与发射信号进行比较，以获得物体的相关信息，如距离、角度、反射率等。
光电探测器有多种，例如雪崩光电二极管(Avalanche Photo Diode，APD)、单光子雪崩二极管(Single Photon Avalanche Diode，SPAD)、硅光电倍增管(Silicon Photomultiplier，SiPM)等。其中，硅光电倍增管SiPM由工作在盖革模式的雪崩二极管阵列组成，包括多个像素的光子计数器。一个像素内包含有很多个独立感光单元，称为像元(cell)，多个感光单元的响应信号通过共用输出通道进行累加输出。SiPM具有灵敏度高、偏置电压低、结构紧凑等特点。
用SiPM作为光接收探测器时，由于接收的光信号被接收镜头汇聚，汇聚后的光信号入射在SiPM感光面像素的一小部分上，导致探测器的动态范围小，探测效率低。
发明内容
本发明实施例提供一种光接收装置及激光雷达系统，增大了探测器和激光雷达系统的动态范围，提高了探测效率。
第一方面，本发明实施例提供了一种光接收装置，包括：光电探测器，以及多个匀光单元；其中光电探测器包括多个像素，每个像素包括多个像元，像元用于将接收的光信号转换为电信号；每个匀光单元对应光电探测器的至少一个像素，用于将接收的入射光束扩散至对应的至少一个像素包含的多个像元上。匀光单元将入射光扩散到多个像元上，使得整个探测器的动态范围增大，提高了探测效率。
在一个可能的设计中，匀光单元包括匀光镜体，匀光镜体的侧壁镀有反射膜，使接收到的光束扩散至光电探测器的至少一个像素包含的多个像元上。匀光镜体的使用使得入射光能均匀扩散到出光面。
在一个可能的设计中，匀光镜体的长度L满足条件：L≥d/(2*tan(θ/2))；其中，d为匀光镜体通光横截面的短边的长度，θ为光束进入镜体时的发散角。这样的尺寸特性提高了扩散的效果。
在一个可能的设计中，匀光单元还包括扩散片，设置于匀光镜体的入射面之前；扩散片用于将接收到的入射光束扩散输出到匀光镜体的入射面。这样进一步提高了匀光的效果。
在一个可能的设计中，匀光单元还包括微透镜，设置于匀光单元的入射面；微透镜用于将接收的入射光束汇聚到扩散片或匀光镜体的入光面。微透镜的使用扩大了入射光的入射角。
在一个可能的设计中，匀光单元中的各部件之间通过光敏胶粘接的方式连接。光明胶的使用减小了入射光的能量损失。
在一个可能的设计中，光电探测器为硅光电倍增管SiPM。硅光电倍增管SiPM的使用使得探测器具有更高的灵敏度。
在一个可能的设计中，多个匀光单元由结构件箍抱固定，提高了光接收装置的耐用性。
在一个可能的设计中，匀光单元对应多个像素，多个匀光单元为一个内部无隔离的棱镜体，形成行布局、列布局或者异形布局，从而使得光接收装置的应用场景更加广泛。
在一个可能的设计中，匀光单元的出光端面与探测器像素中光敏面尺寸相同，减少了入射光能量损耗。
第二方面，本发明实施例提供了一种激光雷达系统，包括光源、扫描器、接收镜头、前述的光接收装置，以及处理器；其中，光源用于输出激光束；扫描器用于在设定区域内进行扫描；接收镜头用于将物体反射的回波光信号汇聚到光接收装置中；光接收装置用于将回波光信号转换为回波电信号；处理器用于分析回波电信号，并控制光源、扫描器、和光接收装置。这种激光雷达系统动态范围大，探测效率高。
第三方面，本发明实施例提供了一种检测方法，应用于上述激光雷达系统，包括：向光源输出控制信号，驱动光源输出激光光束；向扫描器输出控制信号，驱动扫描器按照设定的模式进行扫描；接收光接收装置输出的回波信号，进行处理，获得回波对应物体信息。这样，增大了检测的动态范围，提高了探测效率。
附图说明
图1为本发明实施例提供的一种激光雷达系统结构示意图；
图2为本发明实施例提供的一种SiPM探测器感光面示意图；
图3为本发明实施例提供的匀光单元与SiPM探测器关系示意图；
图4为本发明实施例提供的匀光单元与SiPM探测器贴合示意图；
图5为本发明实施例提供的匀光单元结构示意图；
图6为本发明实施例提供的匀光镜体的光线反射示意图；
图7为本发明实施例提供的匀光单元由结构件箍抱固定示意图；
图8为本发明实施例提供的一种扫描检测方法的示意图；
图9为本发明实施例提供的匀光镜体合并的示意图；
图10为本发明实施例提供的柱状微透镜的立体示意图；
图11为本发明实施例提供的探测器光敏面之间存在边缘沟槽示意图；
图12为本发明实施例提供的图11对应的匀光单元的结构示意图；
图13为本发明实施例提供的不包括匀光镜体的光接收装置的光路示意图；
图14为本发明实施例提供的图13对应的回波光子接收示意图；
图15为本发明实施例提供的包括匀光镜体的光接收装置的光路示意图；
图16为本发明实施例提供的图15对应的回波光子接收示意图。
具体实施方式
为使本发明的目的、技术方案和优点更加清楚，下面将结合附图对本发明实施方式作进一步地详细描述。
本发明实施例提供一种光接收装置，以及应用该光接收装置的激光雷达系统。如图1所示，激光雷达系统10包括：光源101、扫描器102、接收镜头103、光接收装置104和处理器105组成。
光源101用于输出激光束。
扫描器102用于在设定区域内进行二维扫描。
接收镜头103用于将物体11反射的回波光信号汇聚到光接收装置104中。
光接收装置104用于将回波光信号转换为回波电信号。
处理器105用于控制光源101、扫描器102、光接收装置104，并分析回波电信号获取物体11的相关参数。二维扫描完成后，处理器105最终分析获得点云图像。
光接收装置104包括光电探测器，光电探测器可以是硅光电倍增管SiPM。SiPM包括多个像素，一般组成一个二维的像素阵列，例如M*N个像素，M、N为大于1的正整数。每个像素包括多个像元，每个像元都是一个独立感光单元(cell)，用于将接收的光信号转换为电信号。一个像素内包含的多个像元的电信号通过共用输出通道进行累加输出。
一个SiPM探测器的例子如图2所示，包括6*4个像素，每个像素包括6*6个像元。如果要完成一次1440*900像素的点云图像，对于6*4个像素的SiPM探测器，扫描器需水平方向设定240个角度、垂直方向设定225个角度进行扫描，最终形成完整的点云图像。
光接收装置104还包括多个匀光单元，每个匀光单元对应光电探测器的一个像素。匀光单元用于将接收的回波光信号扩散至对应的一个像素包含的多个像元上。
如图3所示的一个示意图，光接收装置包括6*4个匀光单元(301)，这24个匀光单元分别对应光电探测器的6*4个像素(302)。实际产品中，匀光单元的出光面通常与SiPM探测器的感光面贴合在一起。
图4为匀光单元与SiPM探测器贴合在一起的示意图。为清楚起见，图中的光电探测器包括3*3个像素，匀光单元401有9个，与SiPM探测器402的9个像素一一对应。
本发明实施例提供的一种匀光单元结构如图5所示，包括：微透镜501，扩散片502、匀光镜体503。微透镜501、扩散片502、以及匀光镜体503之间可通过光敏胶粘接的方式固定连接，形成一个匀光单元，如图5右边所示。
微透镜501用于接收回波入射光束，将入射光束汇聚到所述扩散片上。微透镜可以扩大接收数值孔径，让更大入射角的光束能进入光接收装置内。例如，微透镜球面曲率半径可以设计为1.4mm，厚度1mm，则接收数值孔径约为0.25。微透镜材料可以为BK7玻璃等。
扩散片502用于将接收的入射光束扩散。经由微透镜进入扩散片的光束，被扩散片扩大发散角，以便在匀光镜体内快速扩散，减小匀光镜体的长度。
匀光镜体503的侧壁通常镀有反射膜，使经过所述扩散片的光束进一步扩散至对应的光电探测器中像素的多个像元上。匀光镜体具有匀光作用：光束进入匀光镜体内，因匀光镜体侧壁镀反射膜，形成一个“光子井”，光束在井内经多次反射，到达光电探测器SiPM感光面时，能量达到均匀分布。反射膜使光子不能穿透镜体达到相邻匀光单元，避免了串扰发生。
匀光镜体的通光横截面可以是长方形，通常为正方形。图6为匀光镜体的光线反射示意图。图6中匀光镜体的长度为L，横截面正方形的边长为d。d一般与对应的SiPM探测器像素的大小相同或稍大一些，以使光束都达到SiPM感光面。
匀光镜体的长度L可以按照如下条件设计：L≥d/(2*tan(θ/2))。其中，d为镜体通光横截面的最短边的长度，θ为光束进入镜体时的发散角。例如，一个实施例中，探测器每个像素尺寸为1mm*1mm，每个匀光单元的通光面尺寸为1mm*1mm，即d＝1mm。
匀光镜体侧壁可镀反射膜，上下端面，及光出入口端面，可镀增透膜；微透镜、扩散片的通光面均可镀增透膜。微透镜的工作端面还可进一步做抛光处理。
光接收装置可包含M*N个匀光单元，与光电探测器的M*N个像素对应。这些匀光单元可采用一些常用紧固方式组合在一起，例如，可以用光敏胶粘合。
匀光单元也可以采用结构件箍抱固定。如图7所示，3*3个匀光单元由一个结构件701固定，这样整个光接收装置不易变形，检测性能更加稳定。
每个匀光单元的出光面应覆盖对应像素的有效感光面，出光面尺寸与所对应像素尺寸相同，或与对应像素的有效感光面尺寸相同。出口端与SiPM感光面贴合，以确保出口不漏光。
在装配光接收装置时，匀光单元的出光面与SiPM探测器像素的感光面需对准。可能的一种装配方法为：
第一步：将匀光单元的出光端面与SiPM探测器感光面贴合，不涂胶；
第二步：用SiPM探测器工作波段的一细光束，照射光接收装置中任一个匀光单元的入光口，监控SiPM探测器对应像素的响应信号输出幅值，上下左右调整匀光单元的位置，待SiPM探测器输出信号幅值最大时，固定匀光单元的位置。
第三步：在匀光单元与SiPM探测器贴合部的四周涂光敏胶，胶干后两者即粘合在一起。图7中，702所示位置为匀光单元与SiPM探测器的贴合部。
图1所示的激光雷达系统中，光接收装置104的光束入口端面，即如图7所示的匀光单元的入射面703处，应放置在接收镜头103的焦平面处，以避免在入口端发生光子串扰。
应用于图1所示的激光雷达系统，本发明实施例还提供一种激光雷达系统的扫描检测方法，如图8所示，包括如下步骤。
S1，处理器105向光源101输出控制信号，驱动光源输出激光光束。光源101输出端还可以包括一个发射镜头，将发射光束整形为点斑光束，再进入扫描器102。
S2，处理器105向扫描器102输出控制信号，例如扫描角度等信息，驱动扫描器按照设定的模式进行扫描。这样，光源输出的光束经过扫描器，向目标区域发射。
S3，处理器105接收回波信号，进行处理，获得当前回波对应物体的角度、距离等信息。从扫描器102输出的光束遇到物体产生反射，向激光雷达系统发射回波光束。回波光束经过接收镜头103的汇聚，进入光接收装置104，光束经过匀光单元后，照射在SiPM探测器的感光像素上。经过光电转换，输出回波电信号，处理器接收回波电信号进行处理。
处理器105持续上述过程，对目标区域进行二维扫描，从而形成目标区域的点云图像。
在一些实际应用中，可以将多个匀光单元进行合并，形成行布局、列布局以及异形布局。例如，如图9所示，三个正方体的匀光镜体合并形成一个长方体的匀光镜体，对应SiPM探测器的1*3个像素。合并方法为：具有光路隔离的3个匀光镜体合在一起做成一个内部无隔离的棱镜体。进一步，图9所示的3个球形微透镜组还可以合成一个柱状微透镜，如图10所示，为柱状微透镜的立体图。
本发明实施例还提供一种光接收装置，应用于像素填充因子(fill-factor)比较低的阵列SiPM探测器。如图11所示，探测器像素的光敏面之间存在边缘沟槽。图中探测器每个像素尺寸为1.0mm*1.0mm，每个像素光敏面尺寸为0.6mm*0.6mm，像素边缘沟槽(gap)宽度为0.4mm，填充因子为60％。
相应的，匀光单元的结构如图12所示，图中左边为测试图，右边为立体图。匀光单元包括微透镜1201、扩散片1202、匀光镜体1203、固定结构件1204，以及SiPM探测器1205。由图可见，匀光镜体的出光面的尺寸缩小为与探测器光敏面的尺寸相同，这样可以将入光端面接收的光子全部导入到像素光敏面上，提高光能利用率，相当于将探测器填充因子由60％提升至100％。
下面示例性的说明一下本发明实施例的技术效果。如图13所示，为不加匀光镜体的光接收装置的光路图，回波光线经过接收镜体1301后，聚焦在3*3个像素的SiPM探测器感光面的局部范围内。每个像素内只有一小部分，即少部分像元能接收到回波光子。图14所示为相应的回波光子接收示意图，可见回波光子都集中在3*3个像素的中心。
如图15所示，为加了匀光镜体的光接收装置的光路图，3*3像素的SiPM探测器1502感光面前，增加了3*3匀光镜体1503。回波光线经过接收镜体1501后，聚焦在匀光镜体的入光面，经过匀光镜体侧壁的多次反射后，回波光线均匀分布于3*3像素的感光面上，即像素内的每个像元能比较均匀地接收到回波光子。图16所示为相应的回波光子接收示意图，可见回波光子比较均匀地分布在3*3个像素上。
上述包括匀光单元的光接收装置，也可以用于安防相机、微光探测成像设备等产品中。此类产品需要对微弱光信号进行探测，采用阵列SiPM探测器可以获得更好的图像。
尽管在此结合各实施例对本发明进行了描述，然而，在实施所要求保护的本发明过程中，本领域技术人员通过查看所述附图、公开内容、以及所附权利要求书，可理解并实现所述公开实施例的其他变化。在权利要求中，“包括”(comprising)一词不排除其他组成部分或步 骤，“一”或“一个”不排除多个的情况。
尽管结合具体特征及其实施例对本发明进行了描述，显而易见的，可对其进行各种修改和组合。相应地，本说明书和附图仅仅是所附权利要求所界定的本发明的示例性说明，且视为已覆盖本发明范围内的任意和所有修改、变化、组合或等同物。显然，本领域的技术人员可以对本发明进行各种改动和变型而不脱离本发明的范围。这样，倘若本发明的这些修改和变型属于本发明权利要求及其等同技术的范围之内，则本发明也意图包含这些改动和变型在内。

Claims (12)

  1. 一种光接收装置，其特征在于，包括：光电探测器，以及多个匀光单元；其中：
    所述光电探测器包括多个像素，每个像素包括多个像元，所述像元用于将接收的光信号转换为电信号；
    每个所述匀光单元对应所述光电探测器的至少一个像素，用于将接收的入射光束扩散至对应的所述至少一个像素包含的多个像元上。
  2. 如权利要求1所述的光接收装置，其特征在于，所述匀光单元包括匀光镜体；
    所述匀光镜体的侧壁镀有反射膜，使接收到的光束扩散至所述光电探测器的至少一个像素包含的多个像元上。
  3. 如权利要求1所述的光接收装置，其特征在于，所述匀光镜体的长度L满足条件：L≥d/(2*tan(θ/2))；其中，d为匀光镜体通光横截面的短边的长度，θ为光束进入镜体时的发散角。
  4. 如权利要求2或3所述的光接收装置，其特征在于，所述匀光单元还包括扩散片，设置于所述匀光镜体的入射面之前；
    所述扩散片用于将接收到的入射光束扩散输出到所述匀光镜体的入射面。
  5. 如权利要求2-4任一项所述的光接收装置，其特征在于，所述匀光单元还包括微透镜，设置于所述匀光单元的入射面；
    所述微透镜用于将接收的入射光束汇聚到所述扩散片或所述匀光镜体的入光面。
  6. 如权利要求1-5任一项所述的光接收装置，其特征在于，所述匀光单元中的各部件之间通过光敏胶粘接的方式连接。
  7. 如权利要求1-6任一项所述的光接收装置，其特征在于，所述光电探测器为硅光电倍增管SiPM。
  8. 如权利要求1-7任一项所述的光接收装置，其特征在于，所述多个匀光单元由结构件箍抱固定。
  9. 如权利要求1-8任一项所述的光接收装置，其特征在于，所述匀光单元对应多个像素，所述多个匀光单元为一个内部无隔离的棱镜体，形成行布局、列布局或者异形布局。
  10. 如权利要求1-9任一项所述的光接收装置，其特征在于，所述匀光单元的出光端面与探测器像素中光敏面尺寸相同。
  11. 一种激光雷达系统，其特征在于，包括光源、扫描器、接收镜头、如权利要求1-10 所述的光接收装置，以及处理器；其中，
    所述光源用于输出激光束；
    所述扫描器用于在设定区域内进行扫描；
    所述接收镜头用于将物体反射的回波光信号汇聚到所述光接收装置中；
    所述光接收装置用于将回波光信号转换为回波电信号；
    所述处理器用于分析回波电信号，并控制所述光源、扫描器、和光接收装置。
  12. 一种检测方法，应用于如权利要求11所述的激光雷达系统，其特征在于，包括：
    向所述光源输出控制信号，驱动光源输出激光光束；
    向所述扫描器输出控制信号，驱动扫描器按照设定的模式进行扫描；
    接收所述光接收装置输出的回波信号，进行处理，获得回波对应物体信息。
PCT/CN2021/082359 2020-06-30 2021-03-23 光接收装置及激光雷达系统 WO2022001219A1 (zh)

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