Detection unit of lidar, lidar and detection method thereof

Abstract

The present invention provides a detection unit for a lidar. The detection unit can predict the spot position of the reflected echo on the detector array according to the flight time of the detection beam, and read the electrical signals of some photodetectors corresponding to the spot. A preferred embodiment of the present invention further provides a detection method for predicting the spot position of the reflected echo on the detector array according to the flight time of the detection beam and dynamically adjusting the photosensitive area based on this. Without increasing the receiving field of view, the present invention realizes the full detection of the received light, suppresses the interference of ambient light, and effectively solves the problem of the spot position offset on the focal plane caused by the optical path deformation due to mechanical deformation in the optomechanical structure.

Description

Technical Field

[0001] The present invention generally relates to the technical field of laser detection, and particularly relates to a detection unit with a dynamically adjustable photosensitive surface, a lidar including the detection unit, and a detection method thereof. Background Art

[0002] A lidar system includes a laser emission system and a detection and reception system. The emitted laser is reflected after hitting a target and received by the detection system. By measuring the round-trip time of the laser, the distance between the target and the lidar can be measured (time-of-flight method). When the entire target area is scanned and detected, three-dimensional imaging can ultimately be achieved. As a commonly used ranging sensor, lidar has the advantages of long detection distance, high resolution, strong anti-active interference ability, small size, light weight, etc., and is widely used in fields such as intelligent robots, unmanned aerial vehicles, and driverless vehicles.

[0003] Currently, in the actual application of lidar, due to the non-coaxiality of the emission optical path and the reception optical path, the position of the imaging spot on the detector is different at different reflection distances. For coaxial lidar (such as a scanning galvanometer lidar or a similar field-of-view scanning lidar), during the time-of-flight, due to the slight rotation of the scanning galvanometer during the laser emission and reception processes, the spot will also drift. In addition, due to reasons such as hardware aging, glue deformation, and thermal expansion and contraction of the lidar device, mechanical deformation occurs, which will also cause the position of the spot on the detector to shift. To solve these problems, it is necessary to expand the photosensitive area on the detector to ensure that the spot drift is always within the photosensitive area of the detector.

[0004] However, increasing the photosensitive area of the detector will increase the field of view angle of the reception optical path, increase the ambient light, and reduce the system's ability to suppress ambient light. At the same time, increasing the photosensitive area of the detector will also cause the dark current / dark count to rise, reducing the system's ability to identify small signals.

[0005] Currently, most of the detectors used in lidar are avalanche photodiodes (APDs), and the size of the APD photosensitive surface is determined and cannot be dynamically adjusted.

[0006] The content of the background art section is only the technology known to the applicant and does not necessarily represent the prior art in this field. Summary of the Invention

[0007] In view of at least one defect of the prior art, the present invention provides a detection unit for a lidar, as well as a lidar including the detection unit and a detection method thereof.

[0008] The present invention provides a detection unit for a lidar, comprising:

[0009] A detector array, the detector array including a plurality of individually addressable photodetectors configured to receive an echo of a detection beam emitted by a lidar and reflected by a target object and convert the echo into an electrical signal;

[0010] A control unit, the control unit being coupled to the detector array and configured to predict a spot position of an echo of the detection beam emitted by the lidar and reflected by the target object on the detector array according to a flight time of the detection beam, and read electrical signals of a part of the plurality of photodetectors corresponding to the spot.

[0011] According to one aspect of the present invention, the photodetector includes a single-photon detector, and the detection unit further includes a plurality of address lines respectively corresponding to and connected to the plurality of photodetectors, and the control unit is electrically connected to the plurality of photodetectors through the plurality of address lines to read electrical signals.

[0012] According to one aspect of the present invention, during operation of the lidar, the plurality of photodetectors remain on.

[0013] The present invention also provides a detection unit of a lidar, including:

[0014] A detector array, the detector array including a plurality of individually addressable photodetectors configured to receive an echo of a detection beam emitted by a lidar and reflected by a target object and convert the echo into an electrical signal;

[0015] A control unit, the control unit being coupled to the detector array and configured to predict a spot position of an echo of the detection beam emitted by the lidar and reflected by the target object on the detector array according to a flight time of the detection beam, and only make a part of the plurality of photodetectors corresponding to the spot in an on state and read their electrical signals.

[0016] According to one aspect of the present invention, the detection unit further includes a driving circuit for each photodetector, the driving circuit including a Zener diode, the photodetector being connected to a driving voltage through the Zener diode, the driving circuit further including a switching device coupled across the two ends of the Zener diode, the switching device being coupled to the control unit and controlled by the control unit to conduct and disconnect, wherein when the switching device conducts, the Zener diode is short-circuited and the photodetector is turned on; when the switching device disconnects, the Zener diode is not short-circuited and the photodetector is turned off.

[0017] According to one aspect of the present invention, the photodetector includes a single-photon detector, and the detection unit further includes a plurality of address lines respectively corresponding to and connected to the plurality of photodetectors, and the control unit is electrically connected to the plurality of photodetectors through the plurality of address lines to read electrical signals.

[0018] The present invention also provides a lidar, including the detection unit as described above.

[0019] According to one aspect of the present invention, the lidar further includes:

[0020] A laser configured to emit a laser beam for target detection;

[0021] An emission lens located downstream of the optical path of the laser, configured to receive the laser beam, modulate it, and emit it to the outside of the lidar.

[0022] A receiving lens configured to receive the echo of the laser beam emitted by the laser reflected by the target and converge the echo to the detector array, and the detector array is located on the focal plane of the receiving lens.

[0023] According to one aspect of the present invention, the control unit determines the spot position (xt, yt) of the echo of the detection beam reflected by the target on the detector array according to the following formula:

[0024]

[0025]

[0026] Where (x0, y0) is the spot origin position, which is the spot position of the echo reflected by the target at infinity on the detector array, f is the focal length of the receiving lens, C is the speed of light, t is the flight time calculated from the start of the pulse emitted by the laser, θ is the angle between the laser beam emitted by the laser and the optical axis of the receiving lens, (h x , h y ) are the distance components along the x-axis and y-axis between the emission lens and the receiving lens.

[0027] According to one aspect of the present invention, the lidar further includes:

[0028] A laser configured to emit a laser beam for target detection;

[0029] A field-of-view scanning device configured to reflect the laser beam to the outside of the lidar and receive the echo of the laser beam emitted by the laser reflected by the target;

[0030] A receiving lens configured to converge the echo of the laser beam emitted by the laser reflected by the target to the detector array, and the detector array is located on the focal plane of the receiving lens.

[0031] According to one aspect of the present invention, the control unit determines the spot position (xt, yt) of the echo of the detection beam reflected by the target on the detector array according to the following formula:

[0032] x t = f * tan{2θ x (t)} + x0

[0033] y t = f * tan{2θ y (t)} + y0

[0034] where (x0, y0) is the spot origin position, the spot origin position is the intersection of the optical axis of the receiving lens and the detector array, f is the focal length of the receiving lens, t is the flight time calculated from the start of the pulse emitted by the laser, (θ x (t), θ y (t)) are the angular components of the field of view scanning device rotated in the x - direction and in the y - direction at time t.

[0035] According to one aspect of the present invention, the control unit of the detection unit is configured to obtain the actual projection position of the radar echo on the detector array, calculate the offset (Δx, Δy) between the position obtained according to the formula and the actual projection position, and calculate the average offset according to the offsets Δx and Δy calculated multiple times Use the average offset to correct the spot origin position.

[0036] According to one aspect of the present invention, the lidar includes a plurality of the lasers, and the detector array includes a plurality of independent sub - arrays, and each sub - array corresponds to one of the lasers to form a detection channel.

[0037] According to one aspect of the present invention, the laser is an edge - emitting laser or a vertical - cavity surface - emitting laser.

[0038] The present invention also relates to a detection method of a lidar as described above, including:

[0039] Emit a detection beam to the outside of the lidar;

[0040] Calculate the flight time from the emission of the detection beam;

[0041] Predict the spot position of the echo of the detection beam reflected by the target on the detector array according to the flight time;

[0042] Read the electrical signals of the partial photodetectors corresponding to the light spot among the multiple photodetectors.

[0043] According to one aspect of the present invention, the lidar further includes: a laser configured to emit a laser beam for target detection; a transmitting lens located downstream of the optical path of the laser and configured to receive the laser beam, modulate it and emit it to the outside of the lidar; a receiving lens configured to receive the echo of the laser beam emitted by the laser reflected by the target and converge the echo to the detector array, the detector array being located on the focal plane of the receiving lens. The step of predicting the position of the light spot of the echo of the detection beam reflected by the target on the detector array according to the time of flight includes: determining the light spot position (xt, yt) according to the following formula:

[0044]

[0045]

[0046] where (x0, y0) is the origin position of the light spot, that is, the position of the light spot of the echo reflected by the target when the target is at infinity on the detector array, f is the focal length of the receiving lens, C is the speed of light, t is the time of flight calculated from the start of the pulse emitted by the laser, θ is the angle between the laser beam emitted by the laser and the optical axis of the receiving lens, and (h x , h y ) are the distance components along the x-axis and y-axis between the transmitting lens and the receiving lens.

[0047] According to one aspect of the present invention, the lidar further includes: a laser configured to emit a laser beam for target detection; a field of view scanning device configured to reflect the laser beam to the outside of the lidar and receive the echo of the laser beam emitted by the laser reflected by the target; a receiving lens configured to converge the echo of the laser beam emitted by the laser reflected by the target to the detector array, the detector array being located on the focal plane of the receiving lens. The step of predicting the position of the light spot of the echo of the detection beam reflected by the target on the detector array according to the time of flight includes: determining the light spot position (xt, yt) according to the following formula:

[0048] x t = f * tan{2θ x (t)} + x0

[0049] y t = f * tan{2θ y (t)} + y0

[0050] Where (x0, y0) is the position of the light spot origin, and the position of the light spot origin is the intersection of the optical axis of the receiving lens and the detector array. f is the focal length of the receiving lens, t is the flight time calculated from the start of the pulse emitted by the laser, and (θ x (t), θ y (t)) are the angular components of the field of view scanning device rotated in the x - direction and in the y - direction at time t.

[0051] According to one aspect of the present invention, the detection method further includes:

[0052] Obtain the actual projection position of the radar echo on the detector array;

[0053] Calculate the offset (Δx, Δy) between the position obtained according to the formula and the actual projection position;

[0054] Calculate the average offset according to the offsets Δx and Δy calculated multiple times

[0055] Use the average offset to correct the position of the light spot origin.

[0056] According to one aspect of the present invention, the lidar includes a plurality of the lasers, the detector array includes a plurality of independent sub - arrays, each sub - array corresponds to one of the lasers. After one of the lasers emits a laser beam, read the electrical signals of the photodetectors in one sub - array corresponding to the laser.

[0057] The present invention also relates to a detection method of a lidar as described above, including:

[0058] Emit a detection beam outside the lidar;

[0059] Calculate the flight time starting from the emission of the detection beam;

[0060] Predict the light spot position of the echo reflected by the target of the detection beam on the detector array according to the flight time;

[0061] Control only the part of the plurality of photodetectors corresponding to the light spot to be in the on - state and read their electrical signals.

[0062] According to one aspect of the present invention, the lidar further includes: a laser configured to emit a laser beam for target detection; a transmitting lens located downstream of the optical path of the laser, configured to receive the laser beam, modulate it, and emit it to the outside of the lidar; a receiving lens configured to receive the echo of the laser beam emitted by the laser reflected by the target and converge the echo to the detector array, the detector array being located on the focal plane of the receiving lens. The step of predicting the spot position of the echo of the detection beam reflected by the target on the detector array according to the time of flight includes: determining the spot position (xt, yt) according to the following formula:

[0063]

[0064]

[0065] where (x0, y0) is the spot origin position, which is the spot position of the echo reflected by the target at infinity on the detector array, f is the focal length of the receiving lens, C is the speed of light, t is the time of flight calculated from the start of the pulse emitted by the laser, θ is the angle between the laser beam emitted by the laser and the optical axis of the receiving lens, and (h x , h y ) are the distance components along the x-axis and y-axis between the transmitting lens and the receiving lens.

[0066] According to one aspect of the present invention, the lidar further includes: a laser configured to emit a laser beam for target detection; a field of view scanning device configured to reflect the laser beam to the outside of the lidar and receive the echo of the laser beam emitted by the laser reflected by the target; a receiving lens configured to converge the echo of the laser beam emitted by the laser reflected by the target to the detector array, the detector array being located on the focal plane of the receiving lens. The step of predicting the spot position of the echo of the detection beam reflected by the target on the detector array according to the time of flight includes: determining the spot position (xt, yt) according to the following formula:

[0067] x t = f * tan{2θ x (t)} + x0

[0068] y t = f * tan{2θ y (t)} + y0

[0069] where (x0, y0) is the position of the origin of the light spot, and the position of the origin of the light spot is the intersection of the optical axis of the receiving lens and the detector array. f is the focal length of the receiving lens, t is the flight time calculated from the start of the pulse emitted by the laser, and (θ x (t), θ y (t)) are the angular components of the field-of-view scanning device rotated in the x-direction and the y-direction at time t.

[0070] According to one aspect of the present invention, the detection method further includes:

[0071] Obtaining the actual projection position of the radar echo on the detector array;

[0072] Calculating the offset (Δx, Δy) between the position obtained according to the formula and the actual projection position;

[0073] Calculating the average offset according to the offsets Δx and Δy calculated multiple times

[0074] Using the average offset to correct the position of the origin of the light spot.

[0075] According to one aspect of the present invention, the lidar includes a plurality of the lasers, the detector array includes a plurality of independent sub-arrays, each sub-array corresponds to one of the lasers, and after one of the lasers emits a laser beam, the electrical signals of the photodetectors in one sub-array corresponding to the laser are read.

[0076] A preferred embodiment of the present invention provides a detection unit of a lidar. The detection unit can predict the position of the light spot of the reflected echo on the detector array according to the flight time of the detection beam, and read the electrical signals of some photodetectors corresponding to the light spot. A preferred embodiment of the present invention also provides a detection method for predicting the position of the light spot of the reflected echo on the detector array according to the flight time of the detection beam and dynamically adjusting the photosensitive area accordingly. Without increasing the receiving field of view, the present invention realizes the full detection of the received light, suppresses the interference of ambient light, and effectively solves the problem of the offset of the light spot position on the focal plane caused by the deformation of the optical path due to mechanical deformation in the optomechanical structure. Description of the Drawings

[0077] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation to the present invention. In the drawings:

[0078] Figure 1 Shows the structure diagram of a single-photon avalanche diode array;

[0079] Figure 2 Schematically shows the light spot position on the detector array and the photosensitive area determined by the light spot position;

[0080] Figure 3 Schematically shows the detection unit of a lidar whose photosensitive area can be dynamically adjusted;

[0081] Figure 4 Shows the detector array of a lidar according to another embodiment of the present invention;

[0082] Figure 5 Shows the drive circuit for each photodetector according to an embodiment of the present invention;

[0083] Figure 6 Shows a schematic diagram of the light spot sizes generated by two targets at different distances (near and far) from the lidar on the detector array of the lidar;

[0084] Figure 7 Schematically shows the optical path diagram and light spot offset of a paraxial lidar according to a preferred embodiment of the present invention;

[0085] Figure 8 Schematically shows the optical path diagram and light spot offset of a paraxial lidar according to a preferred embodiment of the present invention;

[0086] Figure 9 Schematically shows the optical path diagram and light spot offset of a scanning galvanometer lidar according to a preferred embodiment of the present invention;

[0087] Figure 10 Shows a laser detection method for predicting the light spot position according to the flight time;

[0088] Figure 11 Shows a laser detection method for predicting the light spot position according to the flight time. Detailed implementation manners

[0089] In the following, only some exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present invention. Therefore, the drawings and the description are considered to be exemplary in nature rather than restrictive.

[0090] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation on the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of the said features. In the description of the present invention, "a plurality of" means two or more unless otherwise specifically defined.

[0091] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "mounted", "connected", and "coupled" shall be construed broadly. For example, it may be a fixed connection, a detachable connection, or an integral connection: it may be a mechanical connection, an electrical connection, or a connection that allows mutual communication; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0092] In the present invention, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes that the first feature is directly above and obliquely above the second feature, or simply means that the horizontal height of the first feature is higher than that of the second feature. The first feature being "below", "beneath" and "underneath" the second feature includes that the first feature is directly below and obliquely below the second feature, or simply means that the horizontal height of the first feature is lower than that of the second feature.

[0093] The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. To simplify the disclosure of the present invention, components and settings of specific examples are described below. Of course, they are only examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numerals and / or reference letters in different examples. Such repetition is for the purpose of simplification and clarity and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0094] Embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the embodiments described herein are only for the purpose of illustrating and explaining the present invention and are not intended to limit the present invention.

[0095] Figure 1 A schematic diagram of the detection unit 10 of a lidar according to an embodiment of the present invention is shown and will be described in detail below with reference to the accompanying drawings. As Figure 1 shown, the detection unit 10 includes a detector array 100 and a control unit 200. The detector array 100 includes a plurality of micro-units, Figure 1 wherein the dotted part in the figure encloses a micro-unit. Each micro-unit includes a photodetector 101 for converting the echo of the detection beam emitted by the lidar reflected by the target into an electrical signal. The photodetector is, for example, an avalanche photodiode (SPAD) with single-photon detection ability. The following will be described taking the SPAD as an example. When there is no light illumination, the reverse current of the SPAD is extremely weak; when at least one photon is incident on the SPAD, the reverse current increases rapidly in an avalanche manner. The avalanche current generated needs to be quenched in time to prepare for the detection of the next photon. In the passive quenching mode of the SPAD, as Figure 1 shown in the figure, the SPAD needs to work together with a quenching resistor 103. When the SPAD generates a current due to light illumination, the current generates a voltage division on the quenching resistor 103, thereby reducing the bias voltage of the diode below the reverse breakdown voltage value to prevent further avalanche. An address line 102 is led out from each SPAD, so that it can be individually addressed. The control unit 200 of the lidar is connected to a plurality of SPADs 101 through the plurality of address lines 102 and can selectively read the electrical signals on some of the SPADs 101. For simplicity, Figure 1 only three address lines 102 are schematically shown connected to the control unit 200 in the figure.

[0096] As Figure 2 shown, the echo of the detection beam emitted by the lidar reflected by the target forms a light spot 202 on the detector array 100. Figure 2The shaded area 203 in [the figure] covers the light spot 202. Therefore, the control unit of the lidar can accurately detect the echo of the lidar by only reading the electrical signals of the corresponding part of the SPAD 101 in this area 203, without having to read the electrical signals output by the entire detector array 100, which is equivalent to reducing the effective photosensitive area of the detection unit, can effectively suppress the influence of ambient light, reduce dark current / dark count, and improve the small-signal recognition ability of the system. The size of the shaded area 203 is basically the same as the size of the light spot 202, which improves the ability of the system to suppress ambient light.

[0097] Figure 3 Schematically shows a schematic diagram of dynamically adjusting the photosensitive area according to the time of flight.

[0098] As Figure 1 shown, the control unit 200 is coupled to the detector array 100. According to an embodiment of the present invention, the control unit 200 is configured to predict the spot position of the echo reflected by the target object of the detection beam emitted by the lidar on the detector array 100 according to the time of flight t of the detection beam, so as to only read the output electrical signals of the photodetectors corresponding to the predicted spot position. The following will be described in detail with reference to Figure 3 Details. Figure 3 The solid coil in [the figure] schematically shows the initially preset received spot position 302, that is, the position where the laser returning from infinity is focused on the detector array, and the dark area shows the initially preset photosensitive surface 303, and the photosensitive surface 303 can cover the original spot position 302; after the time of flight t, the spot position has shifted, and the shift amount can be calculated according to the calculations in the following text. The dashed coil schematically shows the predicted shifted received spot 304, and the light area shows the adjusted photosensitive surface 305, and the photosensitive surface 305 can cover the received spot 304.

[0099] According to an embodiment of the present invention, during the operation of the lidar, the plurality of photodetectors 101 are all kept in the on state. By updating the addresses of the part of the photodetectors 101 that need to be read in the detection unit, that is, reading the electrical signals of the part of the photodetectors 101 corresponding to the adjusted photosensitive surface 305, the position of the effective photosensitive surface can be dynamically adjusted, so as to ensure that the optical signals can be all effectively received, and there is no need to read the electrical signals of the photodetectors 101 outside the effective photosensitive surface, which improves the ability of the system to suppress ambient light.

[0100] Figure 4 Shows the detector array 100' of the lidar according to another embodiment of the present invention, which can be used to replace Figures 1 - 3 the detector array 100 in [the figure]. The following will be described in detail with reference to the accompanying drawings, focusing on the differences from the detector array 100. Additionally, if there is no contrary description,Figures 1 - 3 The features of the detector array 100 in can be used for Figure 4 the detector array 100' shown. As Figure 4 shown, the detector array 100' includes a plurality of photodetectors 101, which are arranged in an array and can be individually addressed, the same as in Figures 1 - 3 the embodiment shown. Figures 1 - 3 In all the photodetectors 101 are always in the on state (the microcell bias voltage is higher than the reverse breakdown voltage), and the control unit only reads the electrical signals of some of the SPADs 101. Figure 4 In the embodiment, the control unit 200 (see Figure 1 ) is coupled to the detector array 100' and is configured to predict the spot position of the echo reflected by the target of the detection beam emitted by the lidar on the detector array according to the flight time of the detection beam, different from Figures 1 - 3 the said embodiment in that Figure 4 in the embodiment, the control unit 200 only enables some of the photodetectors 101 corresponding to the spot on the detector array 100 to be in the on state and reads their electrical signals. While the other photodetectors 101 are in the off state (the microcell bias voltage is lower than the reverse breakdown voltage), and the off state means no response whether or not there is photon irradiation. Figure 4 In, the photodetectors at the middle position of the photodetector array, such as the photodetectors marked by the dashed box, are shown in a different color from the surrounding photodetectors, indicating that they are in the on state and can sense the echo of the lidar; while the surrounding photodetectors are in the off state and cannot sense the echo of the lidar.

[0101] For this reason, according to a preferred embodiment of the present invention, in addition to including a plurality of address lines for connecting to the photodetectors to read electrical signals, the control unit 200 further includes a plurality of enable lines, which are respectively coupled to the photodetectors 101 for controlling the on and off of the photodetectors 101 (the quenching method is not shown in the figure for simplicity), which will be described in detail below.

[0102] Figure 5 shows a drive circuit for each photodetector 101 according to an embodiment of the present invention. As Figure 5 shown, the drive circuit includes a Zener diode 104 and a switching device 105. Wherein the photodetector 101 is connected to the drive voltage V through the Zener diode 104 op, a switching device 105 is coupled across the two ends of the Zener diode 104, and its conduction and cutoff can be controlled by the control unit 200. For example, the control unit 200 can be coupled to the control terminal of the switching device 105, so as to control the conduction or cutoff of the switching device 105 and control whether the Zener diode is short-circuited. For example, when the switching device 105 is conducting, the Zener diode 104 is short-circuited, and the photodetector 101 is directly coupled to the drive voltage V op , so that the photodetector 101 is turned on; when the switching device 105 is off, the Zener diode 104 is not short-circuited, and the voltage across the photodetector is V op minus V zener (V zener is the Zener voltage across the Zener diode), which is lower than the reverse breakdown voltage V BR of the photodetector 101, so the photodetector 101 is turned off. According to an embodiment of the present invention, the Zener voltage V zener of the Zener diode ≥ V ov (where V ov is the overbias voltage of the photodetector 101), the drive voltage V op = V ov + V BR , and it satisfies V op - V zener ≤ V BR . Since the above-mentioned devices are all semiconductor devices, in principle, they can be made into integrated circuits. In this way, integrated on each photodetector, the function of enabling the photodetector to be quickly turned on and off can be realized.

[0103] According to an embodiment of the present invention, the switching device may include a field effect transistor FET, whose gate serves as the control terminal and is connected to the control unit 200 through an enable line; its source and drain are respectively connected to the two ends of the Zener diode. Alternatively, the switching device may also include a bipolar junction transistor BJT. According to an embodiment of the present invention, the photodetector is a single photon detector.

[0104] The inventors have found that as the distance changes, the spot size also changes to a certain extent. The size of the received spot is related to the size of the transmitted spot, the size of the receiving lens, the focal length, and the distance. The closer the target is, the larger the spot size. When the target is far from the lidar, the change in spot size is small. Generally, within a few meters close to the lidar, the spot size will change significantly, and the specific values can be given according to optical simulations. Therefore, according to an embodiment of the present invention, when predicting the received spot 304 based on the time of flight, in addition to calculating the position of the center of the received spot 304, the size of the received spot 304 can also be calculated. For example, the longer the time of flight, the smaller the received spot 304; conversely, the shorter the time of flight, the larger the received spot 304, so that the area of the photosensitive surface 305 can be adjusted appropriately. Refer to Figure 6 Detailed description. Figure 6 Two targets at different distances from the lidar are shown in Figure 6 as the first target OB1 and the second target OB2, where the first target OB1 is farther from the lidar. Generally, the farther the target is from the lidar, the closer the focusing position of the returned echo after being focused by the receiving mirror is to the focal plane of the lidar. The photodetectors are all arranged on the focal plane of the receiving mirror, so the spot irradiated by the echo on the photodetector array is smaller. Therefore, as

[0105] According to a preferred embodiment of the present invention, as shown in Figure 3 , the size of the set photosensitive surface can be variable and adjusted dynamically according to the distance of the target. For example, for a farther target, a smaller photosensitive surface is set, that is, the electrical signals of a smaller number of photodetectors are read or the electrical signals of a smaller number of photodetectors are turned on and read; for a closer target, a larger photosensitive surface is set, that is, the electrical signals of a larger number of photodetectors are read or the electrical signals of a smaller number of photodetectors are turned on and read, and the size of the photosensitive area is close to the size of the received spot. Alternatively, Figure 3 the size of the photosensitive surface set in can be fixed, for example, the spot size of the target returning to the focal plane at infinity can be used as a reference. At this time, for the target at a short distance, the intensity of the returned echo is large. At this time, reading the electrical signals of the photodetectors in a part of the actually irradiated spot will not affect the measurement. Or alternatively, photosensitive surfaces of different sizes are set for different target distance ranges. For example, when the target is more than 5 meters away from the lidar, the control unit selects the first photosensitive surface size, such as the spot size of the target returning to the focal plane at infinity. When the target is less than 5 meters away from the lidar, the control unit selects the second photosensitive surface size, such as the spot size of the target returning to the focal plane at 5m.

[0106] The present invention also relates to a lidar, which includes the detection unit 10 described above, and will be described in detail below with reference to Figure 7 the following.

[0107] According to a preferred embodiment of the present invention, as Figure 7 shown, the lidar 40 includes a laser 401, a transmitting lens 402, a receiving lens 405, and the detection unit 10 described above (the detection unit 10 includes a detector array 100 and a control unit 200). The laser 401 can emit a laser beam 403 for target detection; the transmitting lens 402 is located downstream of the optical path of the laser 401 and is configured to receive the laser beam 403, collimate it and then emit it to the outside of the lidar for detecting the target 404; the receiving lens 405 is configured to receive the echo 406 of the laser beam 403 emitted by the laser reflected by the target 404 and converge the echo to the detector array 100, and the detector array 100 is located on the focal plane of the receiving lens 405.

[0108] Figure 7 shows a case where a paraxial optical path is adopted and the emitted laser beam 403 is parallel to the optical axis 407 of the receiving lens 405. At different reflection distances, the offset of the laser imaging spot from the origin o of the receiving spot on the focal plane is a, where a is a function of the flight time t. The focal length of the receiving lens 405 is f. When the emitted laser beam 403 is parallel to the optical axis 407 of the receiving lens, the axial distance between the emitted laser beam 403 and the receiving lens 405 is h (i.e., the distance of the paraxial optical axis is h), and the flight distance d≈C*t / 2. Assuming that the distance between the transmitting lens 402 and the target 404 is d1 and the distance between the target 404 and the receiving lens 405 is d2, the following relational expression holds:

[0109] (Since h<<d1, it can be considered that d1≈d2, and d1≈C*t / 2,

[0110] where C is the speed of light).

[0111] To simplify the description process, hereinafter, the coordinates of the center of the spot (i.e., Figure 3 the center coordinates of the circular spot shown in Figure 3 ) are used to characterize the spot position. The X-Y coordinate system for describing the spot position is shown in Figure 3 . Define the coordinates of the laser 408 returned from infinity focused on the focal plane as the origin o (x0, y0) of the receiving spot of this channel, as shown in Figure 3 ; when the emitted laser beam 403 is parallel to the receiving optical axis 407, the position of the spot on the focal plane is (x t , y t) and the flight time should satisfy the following formula:

[0112]

[0113]

[0114] In the above formula, the focal length f of the receiving lens, the speed of light C, and h x and h y (h x and h y are the components of the paraxial optical axis distance h in the x-axis and y-axis directions) are all constants, and t is the flight time calculated from the start of the pulse emitted by the laser. It can be seen that as the flight time t increases, the light spot approaches the origin o(x0, y0).

[0115] From the relationship between the above light spot coordinates and the flight time, it can be seen that the theoretically appearing position of the light spot can be calculated in real time according to the time the laser has flown, and selected with reference to the setting of the above-mentioned photosensitive area size (the size of the photosensitive surface), so as to plan the reading address of the detector array in real time, enabling the detection unit composed of the detector array to dynamically and quickly adjust the position of the photosensitive area, realizing the detection of the received light, and at the same time suppressing the interference of ambient light.

[0116] In another embodiment of the present invention, the theoretically appearing position of the light spot can be calculated in real time according to the time the laser has flown, and selected with reference to the setting of the above-mentioned photosensitive area size (the size of the photosensitive surface), so as to plan in real time that some detectors are in the on state and read signals, enabling the detection unit composed of the detector array to dynamically and quickly adjust the position of the photosensitive area, realizing the detection of the received light, and at the same time suppressing the interference of ambient light.

[0117] Figure 7 shows the case where the emitted laser beam 403 is parallel to the optical axis 407 of the receiving lens 405, Figure 8 shows a more general case. As Figure 8 shown, for a lidar with a paraxial optical path, usually there is an angle θ between the emitted laser beam 403 and the optical axis 407 of the receiving lens 405. The following refers to Figure 8 to describe the calculation of the position of the incident light spot under normal circumstances. In Figure 8 , o′ is the convergence position of the echo returned when the target is at infinity at the focal plane of the receiving lens 405 under the angle θ, and a is the offset of the actual light spot convergence position relative to o′, which is also a function of the flight time t.

[0118] It can be known through geometric relations that Figure 8 the two shaded triangular regions in are similar, so the following relational expression holds: After sorting out, there is:

[0119] Since h << d1, it can be considered that d1 ≈ d2 ≈ C * t / 2. Substituting this into the above equation gives:

[0120]

[0121] The more general case is that the emitted laser beam 403 is not parallel to the optical axis 407 of the receiving lens. Parallelism is just a special case of this model, i.e., θ = 0. Similarly, the position (x t , y t ) of the light spot on the focal plane and the flight time should satisfy the following formula:

[0122]

[0123]

[0124] In the above equation, h x and h y are the components of the distance h of the paraxial optical axis on the x-axis and y-axis. Using the above equations, the position of the light spot at various angles can be predicted, so that the photosensitive surface can be adjusted in real time according to the change of the position of the received light spot.

[0125] Figure 7 and Figure 8 show the calculation and prediction of the position of the light spot in the lidar with a paraxial optical path. Figure 9 An embodiment of a lidar with a coaxial optical path is shown.

[0126] According to another preferred embodiment of the present invention, as Figure 9 shown, the lidar includes: a laser 601, a field-of-view scanning device 602, and a receiving lens 606. The laser 601 is configured to emit a laser beam 603 for target detection. The laser beam 603 is incident on a beam splitter 608 (or a coupler). The beam splitter 608 is, for example, a semi-transmissive and semi-reflective film, which reflects part of the laser beam 603 onto the field-of-view scanning device 602. The field-of-view scanning device 602 can rotate around its rotation axis oo, for example, rotate in the Figure 9 plane of the paper, so as to reflect the incident laser beam 603 in different directions outside the lidar for detecting the target 604. The laser beam 603 undergoes diffuse reflection on the target 604, and part of the echo 605 returns to the field-of-view scanning device 602. The field-of-view scanning device 602 reflects the echo 605 onto the beam splitter 608. The echo transmitted through the beam splitter 608 is converged to the detector array 100 by the receiving lens 606. The detector array 100 is located on the focal plane of the receiving lens 606.

[0127] The field of view scanning device includes a galvanometer or a pendulum mirror. Taking the galvanometer as an example of the field of view scanning device, it can be realized that at the moment of laser emission, the optical axis 607 of the receiving lens 606 and the emission light ray 603 are parallel or even overlapping, so that the receiving field of view and the emission field of view can be kept consistent.

[0128] However, since the galvanometer realizes the field of view scanning by rotating rapidly, after the flight time t, when the echo generated by the emitted laser beam 603 is received again, the galvanometer has rotated a certain angle θ(t). In this way, the included angle between the received light ray 605 passing through the receiving lens 606 and the optical axis 607 of the receiving lens is 2θ(t) (this is because the normal deflects by θ(t)).

[0129] In this way, on the detection unit 100, the offset of the light spot is:

[0130] a(t) = f * tan{2θ(t)}

[0131] Define the intersection point of the optical axis 607 of the receiving lens on the focal plane as the light spot origin (x0, y0). The coordinates (x t , y t ) of the light spot on the focal plane and the flight time satisfy the following formula:

[0132] x t = f * tan{2θ x (t)} + x0

[0133] y t = f * tan{2θ y (t)} + y0

[0134] In the above formula, θ x (t) and θ y (t) are the components of θ(t). θ(t) is related to the vibration speed of the galvanometer. With the above formula of θ(t), the position of the light spot can be accurately predicted, so as to adjust the effective photosensitive surface of the detector array in real time.

[0135] In the above discussion, whether it is a lidar with a paraxial optical path or a lidar based on a scanning field of view, the position of the light spot on the detection unit can be calculated according to the flight time. During the actual operation, due to reasons such as mechanical aging and deformation, glue deformation, and thermal expansion and contraction, the light spot origin (x0, y0) may shift, which will cause the theoretically calculated light spot position (x t , y t ) to be inconsistent with the coordinates (x′, y′) of the actual light spot on the detection unit. In this case, it is preferably necessary to make a correction.

[0136] To solve the problem of the spot origin offset caused by mechanical deformation, after detecting the actual spot position each time, the offset can be calculated to obtain the difference between the theoretically calculated spot position (x t , y t ) and the coordinates (x′, y′) of the actual spot on the detection unit. The calculation formula is as follows:

[0137] Δx = x′ - x t

[0138] Δy = y′ - y t

[0139] Since the mechanical deformation process is relatively slow, in order to measure the offset more accurately and increase the robustness of the system, the offset can be measured for a long time to give a more accurate result in a statistical sense For example, take the average value of 1000 offsets.

[0140] After obtaining the accurate spot origin offset , replace the original spot origin coordinates (x0, y0) with the corrected new spot origin coordinates for more accurate calculation of the spot position according to the time of flight in the follow-up.

[0141] According to a preferred embodiment of the present invention, the laser of the transmitting end may include multiple edge-emitting lasers or vertical-cavity surface-emitting lasers. The detector array may include multiple independent sub-arrays located on the focal plane of the receiving lens, and each sub-array corresponds to one of the lasers to form a detection channel. Alternatively, a large photodetector array is provided on the focal plane of the receiving lens, and different regions correspond to different lasers to form a detection channel.

[0142] The present invention also relates to a method 700 for laser detection using the lidar 40 provided by the present invention, as Figure 10 shown, and the specific steps are as follows:

[0143] Step S701: Transmit a detection beam to the outside of the lidar;

[0144] Step S702: Calculate the time of flight starting from the emission of the detection beam;

[0145] Step S703: Predict the spot position of the echo reflected by the target object of the detection beam on the detector array according to the time of flight;

[0146] Step S704: Read the electrical signals of some photodetectors corresponding to the spot among multiple photodetectors.

[0147] Among them, in step S703, the method for predicting the spot position based on the flight time is determined by the structure of the lidar. For off-axis lidars and scanning galvanometer lidars, the formulas for calculating the spot position have been given in the embodiments above and will not be elaborated here. For the spot origin offset caused by reasons such as mechanical aging deformation, glue deformation, and thermal expansion and contraction, the correction method has also been given above and will not be elaborated here either.

[0148] Figure 10 The detection method shown is also applicable to multi-channel lidars. The lidar includes multiple lasers, and the detector array includes multiple independent sub-arrays. Each sub-array corresponds to one of the lasers. After one of the lasers emits a laser beam, the electrical signals of the photodetectors in one sub-array corresponding to the laser are read.

[0149] The present invention also relates to a method 800 for laser detection using the lidar 40 provided by the present invention, as Figure 11 shown. The specific steps are as follows:

[0150] Step S801: Emit a detection beam outside the lidar;

[0151] Step S802: Calculate the flight time starting from the emission of the detection beam;

[0152] Step S803: Predict the spot position on the detector array of the echo reflected by the target object of the detection beam based on the flight time;

[0153] Step S804: Control only the part of the multiple photodetectors corresponding to the spot to be in the on state and read their electrical signals.

[0154] Among them, in step S803, the method for predicting the spot position based on the flight time is determined by the structure of the lidar. For off-axis lidars and scanning galvanometer lidars, the formulas for calculating the spot position have been given in the embodiments above and will not be elaborated here. For the spot origin offset caused by reasons such as mechanical aging deformation, glue deformation, and thermal expansion and contraction, the correction method has also been given above and will not be elaborated here either.

[0155] Among them, in step S804, the method for controlling only the part of the multiple photodetectors corresponding to the spot to be in the on state has been given in the embodiments above and will not be elaborated here.

[0156] A preferred embodiment of the present invention provides a detection unit of a lidar capable of dynamically adjusting a photosensitive area, and a method for calculating the position of a light spot according to the flight time under different lidar structures. The preferred embodiment of the present invention also provides a method for laser detection by dynamically adjusting a photosensitive surface. Without increasing the receiving field of view, all detections of received light are achieved, interference of ambient light is suppressed, and the problem of light path deformation caused by mechanical deformation in an optomechanical structure, resulting in the offset of the light spot position on the focal plane, is effectively solved.

[0157] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A detection unit of a lidar, comprising: A detector array, the detector array including a plurality of individually addressable photodetectors configured to receive an echo of a detection beam emitted by the lidar reflected by a target and convert the echo into an electrical signal; A control unit, the control unit being coupled to the detector array and configured to predict a spot position of an echo of the detection beam reflected by a target on the detector array according to a flight time of the detection beam emitted by the lidar, and only enable a part of the plurality of photodetectors corresponding to the spot to be in an on state and read their electrical signals; A drive circuit for each photodetector, the drive circuit including a Zener diode, the photodetector being connected to a drive voltage through the Zener diode, the drive circuit further including a switching device coupled across the Zener diode, the switching device being coupled to the control unit and controlled by the control unit to be turned on and off, wherein when the switching device is turned on, the Zener diode is short-circuited and the photodetector is turned on; when the switching device is turned off, the Zener diode is not short-circuited and the photodetector is turned off.

2. The detection unit according to claim 1, wherein the photodetector includes a single-photon detector, the detection unit further including a plurality of address lines respectively corresponding to and connected to the plurality of photodetectors, and the control unit is electrically connected to the plurality of photodetectors through the plurality of address lines to read electrical signals.

3. A lidar, comprising the detection unit according to claim 1 or 2.

4. The lidar according to claim 3, further comprising: A laser configured to emit a laser beam for target detection; A transmitting lens, the transmitting lens being located downstream of the optical path of the laser and configured to receive the laser beam, modulate it and emit it to the outside of the lidar; A receiving lens configured to receive an echo of the laser beam emitted by the laser reflected by a target and converge the echo to the detector array, the detector array being located on the focal plane of the receiving lens.

5. The lidar according to claim 4, wherein the control unit determines the spot position (x t , y t ) of the echo reflected by the target object of the detection beam on the detector array according to the following formula: ； wherein ( , ) is the origin position of the light spot, and the origin position of the light spot is the light spot position on the detector array of the echo reflected when the target object is at infinity. is the focal length of the receiving lens. is the speed of light. is the flight time calculated from the start of the pulse emitted by the laser. is the angle between the laser beam emitted by the laser and the optical axis of the receiving lens. ( , ) are the distance components along the x-axis and y-axis between the transmitting lens and the receiving lens.

6. The lidar according to claim 3, further comprising: A laser configured to emit a laser beam for target detection; A field of view scanning device configured to reflect the laser beam to the outside of the lidar and receive an echo of the laser beam emitted by the laser reflected by a target; A receiving lens configured to converge an echo of the laser beam emitted by the laser reflected by a target to the detector array, the detector array being located on the focal plane of the receiving lens.

7. The lidar according to claim 6, wherein the control unit determines the spot position (x t , y t ) of the echo reflected by the target object of the detection beam on the detector array according to the following formula: ； ； wherein ( , ) is the position of the light spot origin, and the position of the light spot origin is the intersection of the optical axis of the receiving lens and the detector array, is the focal length of the receiving lens, is the flight time calculated from the start of the pulse emitted by the laser, ( , ) are the angular components rotated by the field of view scanning device in the time in the x-direction and the y-direction.

8. The lidar according to claim 5 or 7, wherein the control unit of the detection unit is configured to obtain the actual projection position of the radar echo on the detector array, and calculate the offset between the position obtained according to the formula and the actual projection position ( , ), and calculate the average offset according to the offsets calculated multiple times ( , ), and correct the spot origin position by using the average offset. ( , ) 9. The lidar according to any one of claims 4-7, wherein the lidar includes a plurality of the lasers, the detector array includes a plurality of independent sub-arrays, and each sub-array corresponds to one of the lasers to form a detection channel.

10. The lidar according to any one of claims 4-7, wherein the laser is an edge-emitting laser or a vertical-cavity surface-emitting laser.

11. A detection method of a lidar as claimed in claim 3, comprising: Emitting a detection beam outside the lidar; Calculating the flight time starting from the emission of the detection beam; Predicting the spot position of the echo reflected by the target object of the detection beam on the detector array according to the flight time; Reading the electrical signals of some of the photodetectors corresponding to the spot among the multiple photodetectors.

12. The detection method according to claim 11, wherein the lidar further comprises: A laser configured to emit a laser beam for object detection; a transmitting lens located downstream of the optical path of the laser and configured to receive the laser beam, modulate it and emit it outside the lidar; a receiving lens configured to receive the echo of the laser beam emitted by the laser reflected by an object and converge the echo to the detector array, the detector array being located on the focal plane of the receiving lens, the step of predicting the spot position of the echo of the detection beam reflected by the object on the detector array according to the time of flight includes: determining the spot position (x t , y t ) according to the following formula: ； Wherein ( , ) is the position of the light spot origin, and the position of the light spot origin is the position of the light spot of the echo reflected when the target is at infinity on the detector array. is the focal length of the receiving lens. is the speed of light. is the flight time calculated from the start of the pulse emitted by the laser. is the angle between the laser beam emitted by the laser and the optical axis of the receiving lens. ( , ) are the distance components along the x-axis and y-axis between the transmitting lens and the receiving lens.

13. The detection method according to claim 11, wherein the lidar further comprises: A laser configured to emit a laser beam for target object detection; A field of view scanning device configured to reflect the laser beam outside the lidar and receive the echo of the laser beam emitted by the laser being reflected by the target; a receiving lens configured to converge the echo of the laser beam emitted by the laser being reflected by the target to the detector array, the detector array being located on the focal plane of the receiving lens, and the step of predicting the spot position of the echo of the detection beam being reflected by the target on the detector array according to the time of flight includes: determining the spot position (x t , y t ) according to the following formula: ； wherein ( , ) is the position of the light spot origin, and the position of the light spot origin is the intersection of the optical axis of the receiving lens and the detector array, is the focal length of the receiving lens, is the flight time calculated from the start of the pulse emitted by the laser, ( , ) are the angular components rotated by the field of view scanning device in the x - direction and in the y - direction at time.

14. The detection method as claimed in claim 12 or 13, further comprising: Obtaining the actual projection position of the radar echo on the detector array; Calculate the offset between the position obtained according to the formula and the actual projection position ( , ); Based on the offsets calculated multiple times , calculate the average offset ( , ); Correcting the spot origin position by using the average offset.

15. A detection method of a lidar as claimed in any one of claims 11-13, wherein the lidar comprises a plurality of the lasers, the detector array comprises a plurality of independent sub-arrays, each sub-array corresponds to one of the lasers, and after one of the lasers emits a laser beam, the electrical signals of the photodetectors in a sub-array corresponding to the laser are read.

16. A detection method of a lidar as claimed in claim 3, comprising: Emitting a detection beam outside the lidar; Calculating the flight time starting from the emission of the detection beam; Predicting the spot position of the echo reflected by the target object of the detection beam on the detector array according to the flight time; Controlling only some of the photodetectors corresponding to the spot among the multiple photodetectors to be in an on state and reading their electrical signals.

17. The detection method according to claim 16, wherein the lidar further comprises: A laser configured to emit a laser beam for target detection; a transmitting lens located downstream of the optical path of the laser and configured to receive the laser beam, modulate it, and emit it outside the lidar; a receiving lens configured to receive the echo of the laser beam emitted by the laser reflected by the target and converge the echo to the detector array, the detector array being located on the focal plane of the receiving lens. The step of predicting the spot position of the echo of the detection beam reflected by the target on the detector array according to the time of flight includes: determining the spot position (x t , y t ) according to the following formula: ； ； wherein ( , ) is the position of the light spot origin, and the position of the light spot origin is the position of the light spot of the echo reflected when the target object is at infinity on the detector array. is the focal length of the receiving lens. is the speed of light. is the flight time calculated from the start of the pulse emitted by the laser. is the angle between the laser beam emitted by the laser and the optical axis of the receiving lens. ( , ) are the distance components along the x-axis and y-axis between the transmitting lens and the receiving lens.

18. The detection method according to claim 16, wherein the lidar further comprises: A laser configured to emit a laser beam for target object detection; A field of view scanning device, the field of view scanning device being configured to reflect the laser beam outside the lidar and receive the echo of the laser beam emitted by the laser being reflected by the target; a receiving lens, the receiving lens being configured to converge the echo of the laser beam emitted by the laser being reflected by the target to the detector array, the detector array being located on the focal plane of the receiving lens, the step of predicting the spot position of the echo of the detection beam being reflected by the target on the detector array according to the time of flight includes: determining the spot position (x t , y t ) according to the following formula: ； wherein ( , ) is the position of the light spot origin, and the position of the light spot origin is the intersection of the optical axis of the receiving lens and the detector array, is the focal length of the receiving lens, is the flight time calculated from the start of the pulse emitted by the laser, ( , ) are the angular components by which the field of view scanning device rotates in the x-direction and in the y-direction at time .

19. The detection method as claimed in claim 17 or 18, further comprising: Obtaining the actual projection position of the radar echo on the detector array; Calculate the offset between the position obtained according to the formula and the actual projection position ( , ); Based on the offsets calculated multiple times , calculate the average offset ( , ); Correcting the spot origin position by using the average offset.

20. A detection method of a lidar as claimed in any one of claims 16-18, wherein the lidar comprises a plurality of lasers, the detector array comprises a plurality of independent sub-arrays, each sub-array corresponds to one of the lasers, and after one of the lasers emits a laser beam, the electrical signals of the photodetectors in a sub-array corresponding to the laser are read.

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