LiDAR receiving system

Abstract

This application relates to a laser radar receiving system, comprising a receiving optical unit, a wire-grid micropolarizer array, and an avalanche photodiode (APD) detector array. The wire-grid micropolarizer array is configured to pass laser beams that match the detectors in the APD detector array and absorb other laser beams. When a target object reflects a laser beam toward the system, the laser beam sequentially passes through the receiving optical unit and the wire-grid micropolarizer array before reaching the APD detector array. This system significantly improves the resolution of target point cloud images, thereby enhancing the detection accuracy of the laser radar.

Description

Technical Field

[0001] The present application relates to the field of optical technology, and in particular to a laser radar receiving system. Background Art

[0002] With the rapid development of optical and communication technologies, LiDAR technology has also developed rapidly. Because LiDAR can detect target characteristics such as the position and speed of a target by emitting a laser beam and receiving the laser beam reflected from the target, it is widely used in target detection and other fields.

[0003] To obtain higher-resolution target point cloud images, LiDAR's transceiver laser beams have evolved from single beams to high-beam arrays. However, the avalanche photodiode (APD) detector arrays used in high-beam LiDARs are highly integrated, with very small pixel spacing. This easily causes crosstalk between received light signals in different fields of view, resulting in a distorted target point cloud image and reduced LiDAR detection accuracy. Summary of the Invention

[0004] Based on this, it is necessary to provide a laser radar receiving system that can improve the laser radar detection accuracy in response to the above technical problems.

[0005] The laser radar receiving system provided in the embodiment of the present application includes: a receiving end optical unit, a metal wire grid micro-polarizer array and an avalanche photodiode APD detector array;

[0006] The metal wire grid micro-polarizer array is used to pass the laser beams matched with each detector in the APD detector array and absorb other laser beams;

[0007] When the target object reflects the laser beam to the system, the laser beam sequentially passes through the receiving end optical unit and the metal wire grid micro-polarizer array and reaches the APD detector array.

[0008] In one embodiment, the system further comprises a micro-aperture array, the micro-aperture array being disposed on the laser incident side of the metal wire grid micro-polarizer array, the micro-aperture array being a plate-shaped structure having a plurality of light-through holes, and the plurality of light-through holes corresponding one-to-one to the plurality of APD detectors in the APD detector array;

[0009] Wherein, each of the light holes on the micro-aperture array is used to pass the laser light beam corresponding to the field of view of the corresponding APD detector.

[0010] In one embodiment, the system further comprises a microlens collimating array, wherein the microlens collimating array comprises a plurality of lens correction units, and the microlens collimating array is located between the metal wire grid micropolarizer array and the microaperture array.

[0011] In one embodiment, each of the lens correction units corresponds one-to-one to the APD detector.

[0012] In one embodiment, the system further comprises a microlens focusing array, wherein the microlens focusing array comprises a plurality of lens focusing units, and the microlens focusing array is located between the metal wire grid micropolarizer array and the APD detector array.

[0013] In one embodiment, each of the lens focusing units corresponds one-to-one to the APD detector.

[0014] In one embodiment, the APD detector array includes a plurality of APD detector linear arrays, and the plurality of APD detector linear arrays are overlapped in a preset key area.

[0015] In one embodiment, the number of the APD detector arrays is four.

[0016] In one embodiment, the number of APD detectors in each of the APD detector arrays is sixteen.

[0017] In one embodiment, the metal wire grid micro-polarizer array is a metal wire grid micro-polarizer array coated with a narrow-band filter film.

[0018] The above-mentioned laser radar receiving system includes: a receiving end optical unit, a metal wire grid micropolarizer array, and an avalanche photodiode (APD) detector array; the metal wire grid micropolarizer array is used to pass the laser beam that matches each detector in the APD detector array and absorb other laser beams; when the target object reflects the laser beam to the system, the laser beam passes through the receiving end optical unit and the metal wire grid micropolarizer array in sequence and reaches the APD detector array. Because each aperture of the metal wire grid micropolarizer array can pass laser beams with specific polarization angles and absorb other laser beams, it can match the laser beams entering each detector in the APD detector array with the detector, while laser beams that do not match the detector cannot pass through the area of ​​the metal wire grid micropolarizer array corresponding to the detector, thereby avoiding interference between the laser radar's receiving signals and crosstalk between the laser radar's detection pixels, greatly improving the resolution of the target point cloud image, and thus greatly improving the laser radar's detection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1A schematic structural diagram of a laser radar receiving system provided in one embodiment;

[0020] Figure 1a Schematic diagram of the structure of a polarization filter unit in a metal wire grid micro-polarizer array in one embodiment;

[0021] Figure 1b A schematic diagram of the anti-interference process of a polarization filter unit in a metal wire grid micro-polarizer array in one embodiment;

[0022] Figure 1c A schematic diagram of the structure of a metal wire grid micro-polarizer array in one embodiment;

[0023] Figure 2 A schematic structural diagram of a laser radar receiving system provided in another embodiment;

[0024] Figure 2a A schematic diagram of the optical path of a micro-aperture array through a laser beam in one embodiment;

[0025] Figure 3 A schematic structural diagram of a laser radar receiving system provided in yet another embodiment;

[0026] Figure 4 A schematic structural diagram of a laser radar receiving system provided in yet another embodiment;

[0027] Figure 5 A schematic diagram of the arrangement of an APD detector provided in one embodiment.

[0028] Description of reference numerals:

[0029] Receiving system: 200; Receiving end optical unit: 210;

[0030] APD detector array: 220; APD detector linear array: 221;

[0031] APD detector: 221a; Metal wire grid micropolarizer array: 230;

[0032] Micro aperture array: 240; Micro lens collimation array: 250;

[0033] Lens correction unit: 251; Microlens focusing array: 260;

[0034] Lens focusing unit: 261. DETAILED DESCRIPTION

[0035] With the rapid development of LiDAR technology, the laser beams used to transmit and receive LiDARs have evolved from single beams to high beams. However, the APD detector arrays used in high-beam LiDARs are highly integrated, with very small spacing between pixels. This can easily cause crosstalk between the light signals received in each field of view. Furthermore, interference between LiDARs can easily occur, leading to confusion in the target point cloud image and reduced LiDAR detection accuracy. The LiDAR receiving system provided in the embodiments of this application is intended to address the above technical issues.

[0036] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0037] Figure 1 A schematic structural diagram of a laser radar receiving system provided in accordance with an embodiment is shown. The system 200 includes a receiving-end optical unit 210, a wire grid micropolarizer array 230, and an APD detector array 220. The wire grid micropolarizer array 230 is configured to pass laser beams that match the respective detectors in the APD detector array 220 and absorb other laser beams. The wire grid micropolarizer array 230 is configured to pass laser beams that match the respective detectors in the APD detector array 220 and absorb other laser beams. When the laser beam emitted by the laser radar's transmitting system reaches a target object, it is reflected back to the receiving system 200 by the target object and sequentially passes through the receiving-end optical unit 210 and the wire grid micropolarizer array 230 to reach the APD detector array 220.

[0038] Specifically, the laser radar receiving system 200 includes a receiving end optical unit 210, a metal wire grid micro polarizer array 230 and an APD detector array 220. The APD detector array 220 includes multiple APD detectors 221a for receiving laser beams. The metal wire grid micro polarizer array 230 includes multiple polarization filter units, the structure of which can be seen in FIG. Figure 1a As shown, Figure 1a The structure shown is merely an example and does not limit the present application. The laser beam is reflected from the target object, passes through the receiving optical unit 210, then through the wire grid micropolarizer array 230, and reaches the APD detector array 220. The receiving optical unit 210 can reasonably select the focal length and aperture to meet the divergence angle requirements while ensuring the required laser beam aperture, which is not limited in this embodiment.

[0039] The specific process is as follows: the laser beam is emitted through the laser radar's transmitting system, reaches the target object, is reflected by the target object to the receiving system 200, first passes through the receiving end optical unit 210, and then passes through the metal wire grid micropolarizer array 230. It should be noted that the detectors in the above-mentioned APD detector array 220 are set corresponding to the light-clearing apertures of the metal wire grid micropolarizer array 230. Since each light-clearing aperture of the metal wire grid micropolarizer array 230 can pass the laser beam with a specific polarization angle and block the laser beam with other polarization angles, the laser beam enters the APD detector array 220 through the metal wire grid micropolarizer array 230, which enables each detector in the APD detector array 220 to receive the laser beam with a matching polarization angle, while other laser beams that do not match the detector, including laser beams corresponding to the field of view of other detectors, background light, light from other radars, and stray light, cannot pass through the specific area of ​​the metal wire grid micropolarizer array 230 corresponding to the detector, thereby avoiding interference between the laser radar's receiving signals and crosstalk between the detection pixels. For details, please refer to Figure 1b As shown in Figure 1b FIG. 1 is a schematic diagram of the anti-interference process of the metal wire grid micro-polarizer array 230 in one embodiment. Figure 1b In the example, linearly polarized light from other fields of view as interference light, linearly polarized light from the current field of view as signal light, and other non-polarized light, such as background light, pass through the metal wire grid micro-polarizer array 230 together, and thus signal light, 50% of background light, and very little interference light can be obtained. The structural diagram of the metal wire grid micro-polarizer array can be found in Figure 1c shown.

[0040] The laser radar transmitting system provided in this embodiment includes a receiving optical unit, a metal wire grid micropolarizer array, and an avalanche photodiode (APD) detector array; the metal wire grid micropolarizer array is used to pass the laser beam that matches each detector in the APD detector array and absorb other laser beams; when the target object reflects the laser beam to the system, the laser beam passes through the receiving optical unit and the metal wire grid micropolarizer array in sequence and reaches the APD detector array. Because each aperture of the metal wire grid micropolarizer array can pass laser beams with a specific polarization angle and block laser beams with other polarization angles, it can match the laser beams entering each detector in the APD detector array with the detector, while the laser beams that do not match the detector cannot pass through the area of ​​the metal wire grid micropolarizer array corresponding to the detector, thereby avoiding interference between the laser radar's received signals and crosstalk between the laser radar's detection pixels, greatly improving the resolution of the target point cloud image, and thus greatly improving the laser radar's detection accuracy.

[0041] Optionally, based on the above embodiment, the wire grid micro-polarizer array 230 may be a wire grid micro-polarizer array coated with a narrowband filter film. Because the wire grid micro-polarizer array 230 is coated with a narrowband filter film, it provides a better filtering effect, further reducing interference between LiDAR received signals and crosstalk between LiDAR detection pixels, thereby further improving LiDAR detection accuracy.

[0042] Figure 2 This is a schematic diagram of the structure of a laser radar receiving system provided in another embodiment. Figure 1 In addition to the illustrated embodiment, the system may further include a micro-aperture array 240, which is disposed on the laser incident side of the wire-grid micro-polarizer array 230. The micro-aperture array 240 is a plate-like structure having a plurality of apertures, each of which corresponds one-to-one to the plurality of APD detectors 221a in the APD detector array 220. Each aperture in the micro-aperture array 240 is configured to pass a laser beam corresponding to the field of view of a corresponding APD detector 221a.

[0043] Specifically, the above-mentioned system may further include a micro-aperture array 240. The micro-aperture array 240 is a plate-like structure having a plurality of light-through holes, and is arranged on the laser incident side of the metal wire grid micropolarizer array 230. The plurality of light-through holes thereon correspond one-to-one to the plurality of APD detectors 221a in the APD detector array 220. The plurality of light-through holes on the micro-aperture array 240 may be set with specific light-through apertures, light-blocking apertures, and thicknesses, so as to pass the laser beam corresponding to the field of view of its corresponding APD detector 221a, and block the laser beams corresponding to the field of view of other APD detectors 221a. When the incident laser beam enters from the receiving optical system lens 210 and passes through the micro-aperture array 240, since the plurality of light-through holes on the micro-aperture array 240 correspond one-to-one to the plurality of APD detectors 221a in the APD detector array 220, each light-through hole thereon may pass the laser beam corresponding to the field of view of its corresponding APD detector 221a, and block the laser beams corresponding to other fields of view. For details, please refer to Figure 2a As shown, Figure 2a FIG1 is a schematic diagram of the optical path of the laser beam passing through the micro-aperture array 240 in one embodiment, wherein f1 and f2 represent the focal lengths of the receiving optical lens 210 and the micro-lens 250, respectively. Optionally, the plate-like structure may be a metal plate with multiple light holes, or a glass substrate coated with a light-absorbing film and etched with light holes at corresponding positions, which is not limited in this embodiment. Figure 2aAs shown, in this embodiment, because the micro-aperture array is a plate-like structure with multiple light-through holes and is disposed on the laser-incident side of the metal wire-grid micropolarizer array, the multiple light-through holes correspond one-to-one with the multiple APD detectors 221a in the APD detector array. In this embodiment, the multiple light-through holes in the micro-aperture array can pass the laser beams in the field of view corresponding to their corresponding APD detectors while blocking laser beams in other fields of view. This further prevents signal crosstalk between the various detection pixels of the LiDAR, further improves the resolution of the target point cloud image, and thus further enhances the detection accuracy of the LiDAR.

[0044] Figure 3 This is a schematic diagram of the structure of a lidar receiving system provided in yet another embodiment. Optionally, based on the above embodiments, the system may further include a microlens collimating array 250, which includes multiple lens correction units 251 and is located between the wire grid micropolarizer array 230 and the microaperture array 240.

[0045] Specifically, the receiving system 200 may further include a microlens collimating array 250. The microlens collimating array 250 includes a plurality of lens correction units 251. Optionally, each lens correction unit 251 may be an optical lens or a combination of optical lenses, which is not limited in this embodiment. The microlens collimating array 250 is used to correct the direction of incident light and is disposed between the wire grid micropolarizer array 230 and the microaperture array 240. When the laser beam passes through the microaperture array 240 and then through each lens correction unit 251 of the microlens collimating array 250, the direction of the incident laser beam can be corrected, thereby allowing the laser beam to enter the wire grid micropolarizer array 230 in a nearly parallel manner. This allows the wire grid micropolarizer array 230 to filter the polarization state of the received laser beam, thereby improving the anti-interference capability of the laser radar and increasing the incidence rate of the incident laser beam entering the corresponding APD detector, greatly improving energy utilization. At the same time, the metal wire grid micropolarizer array 230 is a micropolarizer array, and the micropolarizer azimuths corresponding to different positions are different, so the polarization states allowed to pass are different, and the micropolarizer azimuths corresponding to adjacent APD detectors are very different, thereby further improving the anti-crosstalk effect.

[0046] Optionally, in the above Figure 3 In the illustrated embodiment, each lens correction unit 251 corresponds to an APD detector 221a. By providing a one-to-one correspondence between each lens correction unit 251 and an APD detector 221a, it is possible to better correct the laser beam for each polarization state, further improving the anti-crosstalk effect of the lidar receiving system.

[0047] Figure 4 A schematic diagram of the structure of a lidar receiving system according to another embodiment. Optionally, based on the above embodiment, receiving system 200 may further include a microlens focusing array 260 , which includes a plurality of lens focusing units 261 . Microlens focusing array 260 is located between wire grid micropolarizer array 230 and APD detector array 220 .

[0048] Specifically, the receiving system 200 may further include a microlens focusing array 260. The microlens focusing array 260 includes a plurality of lens focusing units 261. Optionally, each lens focusing unit 261 may be an optical lens or a combination unit of optical lenses, which is not limited in this embodiment. The microlens focusing array 260 is disposed between the metal wire grid micropolarizer array 230 and the APD detector array 220. When the laser beam passes through the metal wire grid micropolarizer array 230 and then passes through each lens focusing unit 261 of the microlens focusing array 260, the laser beam can be focused, and the focused laser beam can enter the APD detector more, further improving the incidence rate of the incident laser entering the corresponding APD detector, thereby further improving the energy utilization rate.

[0049] Optionally, in the above Figure 4 Based on the illustrated embodiment, each lens focusing unit 261 corresponds to an APD detector 221a on a one-to-one basis. By providing each lens focusing unit 261 with an APD detector 221a on a one-to-one basis, the incident light beam of each APD detector 221a can be focused, further improving energy utilization and thus further enhancing the anti-crosstalk effect of the laser radar receiving system.

[0050] In one embodiment, the APD detector array 220 may include a plurality of APD detector linear arrays 221. Figure 5 As shown, each APD detector array 221 may include multiple APD detectors 221a. Specifically, multiple APD detectors 221a form an APD detector array 221. For example, the number of APD detectors 221a in each APD detector array 221 may be two, four, six, eight or more. Figure 5 In the figure, the number of APD detectors 221a in each APD detector array 221 is eight as an example; a plurality of APD detector arrays 221 form an APD detector array 220. For example, the number of APD detector arrays 221 in each APD detector array 220 can be two, four, six, eight or more. Figure 5In the figure, the number of APD detector lines 221 in each APD detector array 220 is four as an example. This embodiment does not limit the number of APD detectors 221a in each APD detector line 221 and the number of APD detector lines 221 in each APD detector array 220. This embodiment does not limit the number of APD detectors 221a in each APD detector line 221 and the number of APD detector lines 221 in each APD detector array 220. In this embodiment, the APD detector array can be composed of a plurality of APD detector lines, and each APD detector line is composed of a plurality of APD detectors, which can make the arrangement of the APD detectors simpler and faster, and facilitate design and mass production.

[0051] In one embodiment, the multiple APD detector arrays 221 in the APD detector array 220 can also be overlapped in a preset key area, and similarly, the corresponding LD emission arrays 121 are also overlapped in the preset key area. Figure 5 As shown, Figure 5 A schematic diagram of the arrangement of APD detectors provided in one embodiment includes four APD detector arrays 221 - 1 , 221 - 2 , 221 - 3 and 221 - 4 , wherein the APD detector array 221 - 2 and the APD detector array 221 - 3 are overlapped. Figure 5 The number and arrangement of the APD detector arrays 221 and the number and arrangement of the APD detectors 221a are merely examples and do not limit this embodiment. In this embodiment, overlapping multiple APD detector arrays in a predetermined key area can enhance the density of received signals in the key area, further improving the resolution of the target point cloud image in the key area, and thereby improving the detection angular resolution accuracy of the lidar.

[0052] Optionally, based on the above embodiment, the number of APD detector arrays is four, and four APD detector arrays are provided, which can meet the detection requirements of the field of view; optionally, the number of APD detectors 221a in each APD detector array is sixteen, for example, see Figure 5 As shown, each APD detector array includes sixteen APD detectors 221a, that is, a 16×4 array arrangement can be achieved to form a 64-beam laser radar, which meets the detection requirements of sufficient field of view while effectively controlling the cost.

[0053] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0054] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A laser radar receiving system, characterized in that: The system comprises: a receiving end optical unit, a metal wire grid micro-polarizer array and an avalanche photodiode APD detector array; The metal wire grid micro-polarizer array is used to pass the laser beams matched with each detector in the APD detector array and absorb other laser beams; When the target object reflects the laser beam to the system, the laser beam sequentially passes through the receiving end optical unit and the metal wire grid micro-polarizer array to reach the APD detector array; Each detector in the APD detector array is arranged corresponding to each clear aperture of the metal wire grid micropolarizer array; wherein each clear aperture of the metal wire grid micropolarizer array is capable of passing a laser beam with a specific polarization angle and blocking laser beams with other polarization angles; The azimuth angles of the respective clear apertures of the metal wire grid micro-polarizer array are different; The system also includes a microlens focusing array, which includes a plurality of lens focusing units. The microlens focusing array is located between the metal wire grid micropolarizer array and the APD detector array; each of the lens focusing units corresponds to the APD detector one-to-one.

2. The system according to claim 1, wherein: The system further includes a micro-aperture array, which is arranged on the laser incident side of the metal wire grid micro-polarizer array, and the micro-aperture array is a plate-shaped structure having a plurality of light-through holes, and the plurality of light-through holes correspond one-to-one to the plurality of APD detectors in the APD detector array; Wherein, each of the light holes on the micro-aperture array is used to pass the laser light beam corresponding to the field of view of the corresponding APD detector.

3. The system according to claim 2, characterized in that The distance between the micro-aperture array and the receiving end optical unit is equal to the focal length of the receiving end optical unit.

4. The system according to claim 2, wherein: The system further includes a microlens collimating array, which includes a plurality of lens correction units and is located between the metal wire grid micropolarizer array and the micro aperture array.

5. The system according to claim 4, characterized in that The distance between the microlens collimating array and the micro-aperture is equal to the focal length of the microlens.

6. The system according to claim 4, characterized in that Each of the lens correction units corresponds one-to-one to the APD detector.

7. The system according to claim 1, wherein: The APD detector array includes a plurality of APD detector linear arrays, and the plurality of APD detector linear arrays are overlapped in a preset key area.

8. The system according to claim 1, wherein: The metal wire grid micro polarizer array is a metal wire grid micro polarizer array coated with a narrow band filter film.

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