Signal processing method of lidar and lidar

Abstract

The application provides a signal processing method of a laser radar, comprising: S101: emitting a detection pulse; S102: receiving a return pulse through a detection device; S103: acquiring a receiving time of the return pulse and a spot position of the return pulse on the detection device; and S104: determining whether the return pulse corresponds to the detection pulse according to the receiving time and the spot position. The application also provides a laser radar. By using the signal processing method of the application, whether for multi-pulse detection or single-pulse detection, whether the return pulse corresponds to the detection pulse can be effectively determined according to the receiving time and the spot position of the return pulse, in addition, the detection precision can be improved by shortening the time interval of the detection cycle, time resources are saved, and thus more accurate detection results are obtained.

Description

Technical Field

[0001] This disclosure relates to the field of lidar technology, and in particular to a lidar signal processing method and a lidar. Background Technology

[0002] LiDAR (Lidar) is a commonly used ranging sensor widely applied in fields such as autonomous driving, intelligent robots, drones, and military weaponry. It boasts advantages such as long detection range, high resolution, strong anti-interference capabilities, small size, and light weight. LiDAR measures distances to obstacles based on the Time-of-Flight (TOF) method, which involves emitting detection pulses and measuring the round-trip time of the pulses between the lidar and the obstacle. To achieve more accurate detection and scanning, lidar point cloud densities are increasing, requiring the emission of more detection signals within the same time frame. Therefore, multiple channels need to emit light simultaneously and perform parallel measurements.

[0003] There are two main types of existing scanning lidar. One type uses multiple linearly arranged light sources that emit light in rotation. Each laser and detector forms a detection channel, with the light sources emitting light sequentially and the corresponding detectors receiving the data. Scanning is performed in one direction using a scanner or mechanical rotation, thus achieving two-dimensional scanning. The other type uses one or a few lasers and corresponding detectors, employing a two-dimensional scanner for two-dimensional scanning.

[0004] The detection channel refers to the virtual channel formed by the laser and the corresponding detector, not a physical road. After the laser emits a detection beam, the detectors in the same detection channel receive the echoes reflected by obstacles within a certain time window. This time window is the detection window, and its length is typically required to ensure that echoes from obstacles at the maximum detection range of the lidar can return and be received by the detectors. With the increase in the number of lidar lines and the limitation of total detection time, multiple light sources emitting light one by one, and corresponding detectors receiving echoes sequentially within their respective detection windows, would consume excessively long detection times. Therefore, even in a polling architecture, multiple light sources will emit light simultaneously, and multiple detectors will receive data, meaning multiple detection channels will operate in parallel, leading to crosstalk between channels. For lidar based on 2D scanners, because there are only one or a few lasers and detectors, it is easier to receive echoes from the previous detection cycle. If these echoes are misinterpreted as echoes from the current cycle, noise will occur.

[0005] One solution to the crosstalk problem between multiple channels operating in parallel is laser pulse encoding. For example, when emitting dual pulses, different pulse intervals are used between the multiple channels operating in parallel, and the echo signal is decoded to determine whether it is an echo from the current channel. However, multi-pulse encoding requires that the time of a detection window include the pulse width of multiple pulses and the time interval between pulses, making time resources more scarce.

[0006] Especially for coaxial lidar, because the emitted probe light is reflected back to the receiver by internal components, the detector will receive a very strong stray light signal. At this time, it is impossible to distinguish the echo signal, thus creating a blind zone at close range. Multipulse will make the blind zone even larger.

[0007] The content of the background section only discloses the technology known to the inventors and does not necessarily represent the prior art in this field. Summary of the Invention

[0008] In view of one or more existing defects, the present invention provides a signal processing method for lidar, comprising: S101: Transmit a detection pulse; S102: Receive echo pulses through a detection device; S103: Obtain the reception time of the echo pulse and the position of the echo pulse spot on the detection device; and S104: Determine whether the echo pulse corresponds to the detection pulse based on the receiving time and the position of the light spot.

[0009] According to one aspect of the invention, step S104 includes: Based on the position of the light spot, the first flight time of the echo pulse is obtained; The second flight time is obtained based on the time interval between the receiving time and the transmission time of the detection pulse; When the first flight time is close to the second flight time, it is determined that the echo pulse corresponds to the detection pulse.

[0010] According to one aspect of the invention, the step of obtaining the first flight time based on the position of the light spot includes: Determine the offset of the light spot position relative to the reference position; The first flight time is obtained based on the offset.

[0011] According to one aspect of the invention, the step of obtaining the first time of flight of the echo pulse based on the position of the light spot includes: Based on the preset correspondence between flight time and spot position, the first flight time corresponding to the spot position is obtained.

[0012] According to one aspect of the invention, step S104 includes: The second flight time is obtained based on the time interval between the receiving time and the transmission time of the detection pulse; Based on the second flight time, the expected spot position corresponding to the second flight time is obtained; When the position of the light spot is close to the expected position of the light spot, the echo pulse is determined to correspond to the detection pulse.

[0013] According to one aspect of the present invention, the step of obtaining the expected spot position based on the second flight time includes: obtaining the expected spot position corresponding to the second flight time based on a preset correspondence between flight time and spot position.

[0014] According to one aspect of the invention, the correspondence between the preset flight time and the spot position is determined based on one or more of the following factors: The rotation of the lidar causes a shift in the position of the light spot; The position of the light spot caused by the deflection of the scanning device of the lidar is offset; The distance to the obstacle causes the position of the light spot to shift.

[0015] According to one aspect of the present invention, the detection device includes at least one detector, the detector includes a plurality of detection units, and step S103 includes: taking the center position of the plurality of detection units that receive the echo pulse as the spot position.

[0016] According to one aspect of the invention, the center position is calculated based on the geometric centroid of the plurality of detection units.

[0017] According to one aspect of the present invention, the lidar includes at least one laser and at least one detector, wherein the laser emits detection pulses at preset time intervals, the detector receives echo pulses, and the correspondence between each echo pulse and the detection pulse is determined based on the reception time of each echo pulse and the position of the light spot of the echo pulse on the detector.

[0018] According to one aspect of the present invention, the lidar includes a plurality of lasers and a plurality of detectors, wherein each laser forms a detection channel with at least one detector, and the laser determines whether the echo pulse corresponds to the detection pulse based on the reception time of the echo pulse and the position of the light spot of the echo pulse on the detector in the detection channel.

[0019] The present invention also relates to a lidar, comprising: The transmitting device is configured to transmit detection pulses; The detection device is configured to receive echo pulses; The processing device is configured to acquire the reception time of the echo pulse and the position of the light spot of the echo pulse on the detection device, and determine whether the echo pulse corresponds to the detection pulse based on the reception time and the light spot position.

[0020] According to one aspect of the invention, the processing apparatus is configured to: Based on the position of the light spot, the first flight time of the echo pulse is obtained; The second flight time is obtained based on the time interval between the receiving time and the transmission time of the detection pulse; When the first flight time is close to the second flight time, it is determined that the echo pulse corresponds to the detection pulse.

[0021] According to one aspect of the invention, the processing apparatus is configured to: Determine the offset of the light spot position relative to the reference position; The first flight time is obtained based on the offset.

[0022] According to one aspect of the present invention, the processing device is configured to: obtain a first flight time corresponding to the position of the light spot based on a preset correspondence between flight time and light spot position.

[0023] According to one aspect of the invention, the processing apparatus is configured to: The second flight time is obtained based on the time interval between the receiving time and the transmission time of the detection pulse; Based on the second flight time, the expected spot position corresponding to the second flight time is obtained; When the position of the light spot is close to the expected position of the light spot, the echo pulse is determined to correspond to the detection pulse.

[0024] According to one aspect of the present invention, the processing device is configured to: obtain the expected spot position corresponding to the second flight time based on a preset relationship between flight time and spot position.

[0025] According to one aspect of the invention, the correspondence between the preset flight time and the spot position is determined based on one or more of the following factors: The rotation of the lidar causes a shift in the position of the light spot; The position of the light spot generated by the scanner of the lidar is offset; The distance to the obstacle causes the position of the light spot to shift.

[0026] According to one aspect of the invention, the detection device includes at least one detector, the detector includes a plurality of detection units, the detection units include single-photon avalanche diodes, and the processing device is configured to: take the center position of the plurality of detection units of the received echo pulse as the spot position, the center position being calculated based on the geometric centroid of the plurality of detection units.

[0027] According to one aspect of the invention, the transmitting device includes a laser configured to emit detection pulses at preset time intervals; the processing device is configured to determine the correspondence between each echo pulse and the detection pulse based on the reception time of each echo pulse and the spot position of the echo pulse on the detection unit.

[0028] According to one aspect of the invention, the transmitting device includes a plurality of lasers, the detecting device includes a plurality of detectors, each laser forming a detection channel with at least one detector, and the processing device is configured to determine whether the echo pulse corresponds to the detection pulse based on the reception time of the echo pulse and the position of the echo pulse spot on the detector in the detection channel.

[0029] The signal processing method of this invention, based on the reception time of the echo pulse and the position of the light spot, can effectively determine whether the echo pulse corresponds to the detection pulse without reserving pulse encoding time in the detection window, regardless of whether it is multi-pulse detection or single-pulse detection. This saves time resources, accurately identifies the valid echo signal reflected by the obstacle, filters out interference signals, and improves the accuracy of the detection results.

[0030] In a preferred embodiment of the present invention, by shortening the time interval of the detection cycle, detection efficiency is improved, time resources are saved, and crosstalk between channels is reduced. By combining the reception time of the echo pulse and the position of the light spot, more accurate detection results can be obtained for the determination of the echo pulse. Attached Figure Description

[0031] The accompanying drawings, which form part of this disclosure, are used to provide a further understanding of this disclosure. The illustrative embodiments of this disclosure and their descriptions are used to explain this disclosure and do not constitute an undue limitation of this disclosure. In the drawings: Figure 1 A schematic diagram of a lidar according to an embodiment of the present invention is shown; Figure 2 A flowchart of the signal processing method of the lidar of the present invention is shown; Figure 3 A schematic diagram of a lidar detection device according to an embodiment of the present invention is shown; Figure 4The illustration shows the position shift of the laser spot caused by the rotation of the lidar; Figure 5 This schematically illustrates the shift in the position of the light spot caused by the distance to the obstacle; Figure 6A and 6B The process of determining whether an echo pulse corresponds to a probe pulse according to an embodiment of the present invention is illustrated. Figure 7 A schematic diagram of a single-photon avalanche diode is shown; and Figure 8 A schematic diagram of lidar detection using an embodiment of the present invention is shown. Detailed Implementation

[0032] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0033] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0034] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0035] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0036] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0037] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0038] Figure 1 A schematic diagram illustrating the principle of lidar is shown. (For example...) Figure 1 As shown, the lidar 10 includes a transmitting device 11, a detecting device 12, and a processing device 13. A detection pulse L emitted from the transmitting device 11 is incident on an obstacle and undergoes diffuse reflection. The echo pulse L' returns to the detecting device 12, where it is converted into an electrical signal. The processing device 13 calculates the distance to the obstacle based on the time interval between the emission time of the detection pulse L and the reception time of the echo pulse L'. To accurately calculate the obstacle distance, it is necessary to ensure that the echo pulse L' corresponds to the detection pulse L; that is, the echo pulse L' is generated by the reflection of the detection pulse L. If the echo pulse L' used to calculate the obstacle distance does not correspond to the detection pulse L, it will adversely affect the measurement accuracy of the lidar.

[0039] Figure 2 A signal processing method 100 for a lidar according to an embodiment of the present invention is shown, for determining whether an echo pulse corresponds to a detection pulse; Figure 3 A schematic diagram of a lidar detection device 12 according to an embodiment of the present invention is shown. Referring below... Figure 2as well as Figure 1 and Figure 3 Detailed description.

[0040] In step S101, a detection pulse is emitted.

[0041] refer to Figure 1 The transmitting device 11 of the lidar 10 transmits a detection pulse L into the three-dimensional environment surrounding the lidar 10. The detection pulse L can be a single pulse or an encoded multi-pulse sequence. The present invention does not limit the specific form of the detection pulse.

[0042] In step S102, the echo pulse is received by the detection device.

[0043] When the detection pulse L is incident on the obstacle, it undergoes diffuse reflection. The echo pulse L' returns to the lidar and is received by the detection device 12, and converted into an electrical signal.

[0044] In step S103, the receiving time of the echo pulse and the position of the light spot on the detection device are obtained.

[0045] refer to Figure 1 The processing device 13 is coupled to the detection device 12 to acquire the electrical signal generated by the detection device 12. Based on the electrical signal, the processing device 13 determines the reception time of the echo pulse L'. According to a preferred embodiment of the present invention, the processing device 13 uses the moment when the waveform of the electrical signal exceeds a preset threshold as the reception time of the echo pulse L', thereby mitigating or eliminating the influence of ambient light and noise. This preset threshold can be fixed or dynamically adjusted according to the intensity of ambient light.

[0046] like Figure 3 As shown, the detection device 12 includes one or more detectors 120, which typically have a large photosensitive surface for receiving echo pulses L', such as... Figure 3 The area enclosed by the dashed rectangular line ensures that echoes from obstacles in all directions within the lidar's field of view can be received. For a single echo pulse L', it will typically illuminate a localized area of ​​the detector 120, such as... Figure 3 The light spot S, indicated by the dashed circular line, is shown. The photoelectric device located within the area of ​​the light spot S on the photosensitive surface will be triggered by the echo pulse L' and generate an electrical signal. This photoelectric device is, for example, a detector array based on Geiger modes.

[0047] According to a preferred embodiment of the present invention, such as Figure 2 As shown, the detector 120 includes multiple addressable detection units 121, each of which can generate an electrical signal in response to an incident light signal, thereby determining the position of the light spot S based on the detection units 121 that generate electrical signals. Figure 3 As shown, nine detection units 121 (shown in dark boxes) located approximately in the middle of detector 120 generate electrical signal outputs. The area of ​​these nine detection units 121 can be used as the light spot area, and the center position (e.g., geometric centroid) of the multiple detection units 121 that receive the echo pulse can be used as the light spot position.

[0048] In step S104, it is determined whether the echo pulse corresponds to the detection pulse based on the receiving time and the spot position. The inventors of this application have discovered that a certain correspondence can be established between the flight time of the detection pulse and the spot position of the lidar. Based on this correspondence, it is possible to determine whether the echo pulse corresponds to the detection pulse based on the receiving time and the spot position. Various preferred embodiments of the present invention are described below.

[0049] According to a preferred embodiment of the present invention, in step S104, the first flight time of the echo pulse L' can be calculated or estimated based on the spot position obtained in step S103. For lidar, there is a certain correspondence between the flight time of the detection pulse and the spot position. Specifically, a reference position of the spot can be set, and a correspondence can be established between the flight time of the detection pulse and the offset of the spot position relative to the reference position. This correspondence will be described in detail below. In step S104, based on the spot position and the correspondence, the first flight time of the echo pulse L' can be obtained, where the first flight time is the estimated theoretical flight time.

[0050] The actual flight time can be obtained by combining the reception time of the echo pulse L' with the transmission time of the probe pulse L, and this can be used as the second flight time.

[0051] Then, the first flight time can be compared with the second flight time, that is, the theoretical flight time estimated based on the actual spot position can be compared with the actual flight time. When the two are close, it can be determined that the echo pulse L' corresponds to the detection pulse L. According to one embodiment of the present invention, when the absolute value of the difference between the first flight time and the second flight time is less than a preset threshold, the two can be considered to be close. Alternatively, the relative difference between the two can be calculated, for example, by calculating... When the result does not exceed a preset threshold (e.g., 10%, 5%, or 1%), the two are considered to be close. Conversely, if the above calculation result exceeds the preset threshold, and the first flight time differs significantly from the second flight time, it can be determined that the echo pulse L' is not generated by the detection pulse L, and the obstacle distance should not be calculated based on the echo pulse L'.

[0052] Alternatively, in step S104, the actual flight time is obtained as the second flight time based on the time interval between the reception time of the echo pulse L' and the transmission time of the probe pulse L; then, based on the second flight time and the correspondence, the expected spot position corresponding to the second flight time is obtained; then, it is determined whether the actual spot position and the expected spot position are close; when the actual spot position and the expected spot position are close, it is determined that the echo pulse corresponds to the probe pulse.

[0053] The preferred embodiment described above uses a correspondence between the flight time of the probe pulse and the position of the light spot, such as a correspondence between the flight time of the probe pulse and the offset of the light spot position relative to a reference position. This correspondence is typically determined by the type of lidar, its inherent parameters, and some external parameters, including one or more of the following factors: (1) The position shift of the laser spot caused by the rotation of the lidar; (2) The position shift of the light spot caused by the deflection of the scanning device of the lidar; (3) The distance to the obstacle causes the position of the light spot to shift.

[0054] In some embodiments of the present invention, the reference position is the position of the light spot when the flight time is zero. As the flight time increases, one or more factors such as the rotation of the lidar, the deflection of the scanning device, and the distance to obstacles will cause the position of the light spot of the echo pulse on the detector to shift relative to the reference position.

[0055] For mechanical lidar, its optomechanical rotor typically includes multiple lasers and multiple detectors, with at least one laser and at least one detector corresponding to each other to form a detection channel. The optomechanical rotor contains multiple detection channels. The emission direction of the laser in each detection channel corresponds to a field of view or an angle in the vertical direction. Different detection channels correspond to different fields of view or angles in the vertical direction, thus achieving detection within a certain field of view in the vertical direction. On the other hand, the optomechanical rotor rotates around its vertical axis, achieving 360-degree scanning and detection in the horizontal direction, thereby forming a frame of point cloud data for the lidar. For one of the detection channels, during rotation, it emits a detection pulse every certain rotation angle (i.e., the horizontal angular resolution of the lidar, for example, 0.1 degrees). The lidar's detection device receives the echo pulse after diffuse reflection of this detection pulse on an obstacle.

[0056] In mechanical lidar, the optomechanical rotor is constantly rotating during detection, causing an angular shift in the echo pulse. After the detection pulse is emitted, the angular shift of the lidar's detection device varies with different flight times, resulting in different positions where the echo pulse spot falls on the detection device. Furthermore, this shift is positively correlated with the flight time; the longer the flight time, the greater the shift in the spot's position on the detection device.

[0057] The following is for reference. Figure 4 This section details the spot position shift caused by the rotation of the lidar. Ignoring the spot position shift caused by the optical path, it is assumed that after the lidar emits a detection pulse L, the echo pulse L' returns along the original path. Assume that at time t1, the lidar's emitting device 11 emits a detection pulse L, and at this time, the lidar's detection device 12 is in the first position, such as... Figure 4 As shown in POS1. If the distance to the obstacle is 0, i.e., the flight time Tof is 0, then the echo pulse L' will return at time t1, as shown in POS1. Figure 4 As shown, the position of the light spot is as indicated by S1, which can be used as a reference position (the center of the light spot can be used as the position of the light spot). However, in reality, the distance to the obstacle cannot be zero, and the echo pulse L' will return at time t2. From time t1 to time t2, the optomechanical rotor of the lidar, together with the detection device 12 on it, rotates continuously, as shown... Figure 4 As shown by the clockwise arrow R, the detection device 12 rotates from position POS1 to position POS2. Therefore, at time t2, the position of the echo pulse L' on the detection device 12 is as shown by S2. The position S2 deviates from the position S1, and this deviation is denoted as SHIFTa. The direction of the deviation of the spot position on the detector is opposite to the rotation direction of the lidar optomechanical rotor, and the spot position deviation is positively correlated with the Tof time.

[0058] The offset SHIFTa and the flight time Tof satisfy the following relationship: In the formula, ω is the angular velocity of the lidar rotation, f is the focal length of the lens group, and tof is the time of flight. The above relationship represents the correspondence between the flight time of the detection pulse and the position of the light spot. According to the above relationship, once any three of the four parameters of the lidar—angular velocity ω, focal length f, offset SHIFTa, and time of flight tof—are determined, the other parameter can be calculated.

[0059] The above analysis and formulas also apply to lidar scanning via a scanner, including lidar scanning in one-dimensional and two-dimensional directions. In this case, ω is the angular velocity of the scanner rotation.

[0060] A scanner-based lidar includes one or more lasers, each laser and at least one detector forming a detection channel. The lidar includes one or more detection channels; the scanner can be a one-dimensional scanner or a two-dimensional scanner. For a lidar using a one-dimensional scanner, the emission direction of the laser in each detection channel corresponds to a field of view or an angle in the vertical direction. Different detection channels correspond to different fields of view or angles in the vertical direction, thereby achieving detection within a certain field of view in the vertical direction. Alternatively, when the one-dimensional scanner rotates around a vertical axis, it deflects the detection pulses emitted by the laser at different angles in the horizontal direction, thereby achieving scanning and detection within a certain field of view in the horizontal direction. In other embodiments, multiple detection channels are arranged horizontally, meaning different detection channels correspond to different fields of view or angles in the horizontal direction, thus achieving detection within a certain field of view in the horizontal direction. The rotation axis of the one-dimensional scanner is horizontal, deflecting the detection pulses at different angles in the vertical direction, thereby achieving detection within a certain field of view in the vertical direction.

[0061] For lidar employing a two-dimensional scanner, the scanner has two rotating axes at a certain angle, allowing it to reflect the detection pulses emitted by the laser to different angles in two directions, thus achieving two-dimensional scanning. In other embodiments, the two-dimensional scanner includes two one-dimensional scanners, with their rotating axes at a certain angle, also enabling two-dimensional scanning. In some embodiments, the angle is a right angle.

[0062] In some embodiments, the scanner includes at least one of a rotating mirror, a galvanometer, and a tilting mirror.

[0063] In addition, the distance to obstacles also causes a shift in the laser spot position. For lidar with off-axis optical paths, during detection, the detection pulse emitted by the transmitting device and the echo pulse received by the detection device use different optical components. Therefore, the distance between the obstacle and the lidar varies, resulting in different laser spot positions falling on the detection device. This is the laser spot shift caused by the near-far effect of off-axis optical paths. The amount of shift caused by this reason is also related to the flight time. Figure 5 As shown, for obstacle O1, the position of the echo pulse spot on the detection device is S1; for obstacle O2, the position of the echo pulse spot on the detection device is S2. Obstacle O1 is farther from the lidar than obstacle O2, and the position S1 of the echo pulse spot on the detection device is closer to the transmitting device than S2.

[0064] In some embodiments of the present invention, the echo position S0 of the obstacle at the farthest target detection distance of the lidar is used as the reference position, and the offset SHIFTb of the actual spot position (such as spot position S1 and spot position S2) relative to the reference position S0 is calculated. At this time, the offset of the spot position on the detector is inversely correlated with the flight time, that is, as the distance of the obstacle increases, the corresponding flight time increases, and the position of the spot on the detector gradually moves closer to the reference position.

[0065] In some embodiments of the present invention, for lidar with an off-axis optical path, the spot offset SHIFTb caused by the distance of an obstacle satisfies the following relationship with the distance to the obstacle or the flight time: In the formula, D AX The center-to-center distance of an off-axis transceiver system (e.g.) Figure 5 As shown in the figure, L is the distance to the obstacle, and f is the focal length of the transmitting optical component.

[0066] The above describes three common causes of light spot shift. It should be noted that this invention only uses these three causes as examples to illustrate the reasons for light spot shift. In fact, in addition to the three causes mentioned above, there may be other reasons that cause light spot shift, which will not be elaborated here.

[0067] Furthermore, for different types of lidar, spot position shifts may occur due to one or more of the factors mentioned in (1), (2), and (3) above. For example, for mechanical off-axis lidar, spot position shifts may occur due to factors (1) and (3), so SHIFTa and SHIFTb need to be combined when determining the correspondence; for scanner-based off-axis lidar, spot position shifts may occur due to factors (2) and (3); for coaxial lidar, spot position shifts may occur due to factor (2). For a specific lidar, the factors that cause spot position shifts can be determined according to the type of lidar.

[0068] It should be noted that during actual detection, the directions of SHIFTa and SHIFTb may be the same or opposite depending on the direction of radar rotation. That is, the direction of spot offset caused by radar rotation or scanner rotation may be the same or opposite to the direction of spot offset caused by the near-far effect of off-axis system. For scanners such as galvanometers and oscillating mirrors, they may deflect in different directions at different times, resulting in different spot offset directions. It is necessary to add or subtract the two components according to the actual situation to obtain the actual offset, and then obtain the first flight time.

[0069] The following is for reference. Figure 6A and 6BThe process of determining whether an echo pulse corresponds to a detection pulse through embodiments of the present invention is described in detail.

[0070] like Figure 6A As shown, the transmitting device transmits a first detection pulse Pulse1 and a second detection pulse Pulse2, with a time interval of T between them. CH After the first detection pulse Pulse1 and the second detection pulse Pulse2 are emitted, the detection device receives the first echo pulse echo1 and the second echo pulse echo2. The light spots of the echo pulses fall on the detection device, but the correspondence between the first detection pulses Pulse1 and Pulse2 and the first echo pulse echo1 and the second echo pulse echo2 is unknown. For example... Figure 6B As shown, three circles are depicted. The dashed circle S0 on the left represents the reference position of the light spot. The middle circle S1 and the right circle S2 represent the light spots of the first echo pulse (echo1) and the second echo pulse (echo2).

[0071] According to an embodiment of the present invention, the offset of the middle circle S1 relative to the reference position can be determined first. The offset of the spot position of the middle circle relative to the reference position is calculated and denoted as SHIFT1; the offset of the spot position of the right circle S2 relative to the reference position is calculated and denoted as SHIFT2.

[0072] Based on the offsets SHIFT1 and SHIFT2 of the light spot position relative to the reference position, and based on the preset correspondence between the flight time of the lidar and the light spot position, the first flight time TIME1 and TIME2 corresponding to the light spot position are obtained.

[0073] See Figure 6A After the first detection pulse Pulse1 and the second detection pulse Pulse2 are emitted, the detection device receives two echo pulses echo1 and echo2. By combining them in pairs, four time intervals, which are the second flight times, can be calculated as follows: t1 = echo1-pulse1 t2 = echo1-pulse2 t3 = echo2-pulse1 t4 = echo2-pulse2 Compare and match TIME1 and TIME2 with t1, t2, t3, and t4 respectively. Select the time intervals that match TIME1 and TIME2 from t1, t2, t3, and t4, assuming they are t1 and t4 respectively. This determines that the first echo pulse echo1 corresponds to the first probe pulse pulse1, and the time difference between them is the time of flight Tof1; the second echo pulse echo2 corresponds to the second probe pulse pulse2, and the time difference between them is the time of flight Tof2. Figure 6A shown.

[0074] Assuming t2 and t3 match TIME1 and TIME2 respectively, then the second echo pulse echo2 corresponds to the first probe pulse Pulse1, and the first echo pulse echo1 corresponds to the second probe pulse Pulse2. The matching can be either that the two time values ​​are exactly the same, or that the difference between the two time values ​​is less than a preset matching threshold. If t1 and t2 do not match either TIME1 or TIME2, echo1 can be determined to be noise and thus filtered out.

[0075] Alternatively, the second flight time (t1, t2, t3, and t4 as described above) can be calculated first based on the time of the transmitted pulse and the time of the echo pulse. Then, the spot position offset SHIFT (SHIFT-Ⅰ, SHIFT-Ⅱ, SHIFT-Ⅲ, SHIFT-Ⅳ) corresponding to each second flight time can be calculated. By comparing SHIFT-Ⅰ, SHIFT-Ⅱ, SHIFT-Ⅲ, and SHIFT-Ⅳ with SHIFT1 and SHIFT2 respectively, two matching SHIFTs can be found, thereby determining the matching relationship between the transmitted pulse and the echo pulse. This will not be elaborated further here.

[0076] In some embodiments of the present invention, the correspondence between the spot position and the flight time is predetermined. In practical applications, after obtaining the spot position, the correspondence can be looked up to determine the corresponding first flight time; or after obtaining the second flight time, the correspondence can be looked up to determine the spot position corresponding to the second flight time.

[0077] According to a preferred embodiment of the present invention, the detection device of the lidar includes at least one detector, the detector includes multiple detection units, and the detection unit includes a single-photon avalanche diode (SPAD).

[0078] Figure 7The diagram shows the structure of a single-photon avalanche diode (SPAD). A SPAD is a high-sensitivity semiconductor device capable of detecting low-intensity signals (down to a single photon), converting the optical signal into an electrical signal using the photoelectric effect. A reverse bias voltage higher than the breakdown voltage is applied to the SPAD. When the SPAD receives an echo pulse, the echo pulse triggers the SPAD to avalanche and output current. Avalanche current exceeding a threshold will output "1" after passing through a comparator, while avalanche current below the threshold will output "0". This allows the determination of the triggering state of each SPAD. SPADs are used as detection units and connected in parallel to form a detection unit array, constituting... Figure 3 The detector shown is used to transmit a detection pulse. After receiving the echo pulse, the detection device determines the position of the light spot based on the trigger state of each detection unit, i.e., each single-photon avalanche diode (SPAD), on the detector. For example, if the trigger state is "1", the corresponding SPAD emits light; if the trigger state is "0", the corresponding SPAD does not emit light. Thus, a [0 1] image of the SPAD array can be obtained, and the position of the light spot can be determined from the emitting area corresponding to this image.

[0079] It should be noted that, regarding the detection device, the present invention uses a single-photon avalanche diode (SPAD) as the detection unit and a single-photon avalanche diode (SPAD) array as the detector. These are just one embodiment of the present invention and do not constitute a limitation on the present invention.

[0080] The method described above in this invention can be used in both single-channel and multi-channel lidar. It can be used to match the correspondence between multiple detection pulses emitted by a single laser and multiple received echo pulses, or it can be used to match the correspondence between multiple detection pulses emitted by multiple lasers and multiple received echo pulses. For example, for a single laser, detection pulses are emitted at preset time intervals, and the detector receives the echo pulses. Based on the reception time of each echo pulse and the position of the echo pulse spot on the detector, the correspondence between each echo pulse and the detection pulse is determined.

[0081] Using the judgment method of this invention, even single-channel radar can overcome the limitations of Time-of-Flight (TOF). Single-channel radar uses a laser to periodically emit probe light, combined with a scanner for scanning. In this case, the detection window TCH equals the flight time of the echo pulse at the furthest detection range. Typically, after a laser emits probe light, it needs to wait for the detection window before emitting again. However, through the embodiments of this invention, the laser's emission period ΔTCH can be made smaller than the detection window TCH, shortening the time interval of the detection cycle. Within a certain scanning cycle, this increases the point cloud data rate, thereby improving detection efficiency.

[0082] like Figure 8 As shown, during the detection process, the laser emits a first detection pulse (Pulse1) and a second detection pulse (Pulse2) at time intervals of ΔTCH, resulting in a first echo pulse (Echo1) and a second echo pulse (Echo2), where ΔTCH is less than TCH. Although there is a problem of the echo of Pulse1 intersecting with the detection window of Pulse2, the method of determining whether the detection pulse corresponds to the echo pulse using the spot position and the reception time of the echo pulse of this invention can still distinguish the correspondence between the emitted first detection pulse (Pulse1) and second detection pulse (Pulse2) and the first echo pulse (Echo1) and second echo pulse (Echo2), avoiding crosstalk problems. Therefore, high detection accuracy can be obtained while improving the radar data rate.

[0083] The present invention also relates to a lidar 10, such as Figure 1 As shown, the device includes a transmitting device 11, a detecting device 12, and a processing device 13. The transmitting device 11 is configured to transmit a detection pulse L, the detecting device 12 is configured to receive an echo pulse L', and the processing device 13 is configured to acquire the reception time of the echo pulse and the position of the light spot of the echo pulse on the detecting device, and determine whether the echo pulse corresponds to the detection pulse based on the reception time and the light spot position.

[0084] According to a preferred embodiment of the present invention, the processing apparatus is configured to: Based on the position of the light spot, the first flight time of the echo pulse is obtained; The second flight time is obtained based on the time interval between the receiving time and the transmission time of the detection pulse; When the first flight time is close to the second flight time, it is determined that the echo pulse corresponds to the detection pulse.

[0085] According to a preferred embodiment of the present invention, the processing apparatus is configured to: Determine the offset of the light spot position relative to the reference position; The first flight time is obtained based on the offset.

[0086] According to a preferred embodiment of the present invention, the processing device is configured to: obtain a first flight time corresponding to the position of the light spot based on a preset correspondence between flight time and light spot position.

[0087] According to a preferred embodiment of the present invention, the processing apparatus is configured to: The second flight time is obtained based on the time interval between the receiving time and the transmission time of the detection pulse; Based on the second flight time, the expected spot position corresponding to the second flight time is obtained; When the position of the light spot is close to the expected position of the light spot, the echo pulse is determined to correspond to the detection pulse.

[0088] According to a preferred embodiment of the present invention, the processing device is configured to: obtain the expected spot position corresponding to the second flight time based on a preset relationship between flight time and spot position.

[0089] According to a preferred embodiment of the present invention, the preset correspondence between the flight time and the spot position is determined based on one or more of the following factors: The rotation of the lidar causes a shift in the position of the light spot; The position of the light spot generated by the scanner of the lidar is offset; The distance to the obstacle causes the position of the light spot to shift.

[0090] According to a preferred embodiment of the present invention, the detection device includes at least one detector, the detector includes a plurality of detection units, the detection unit includes a single-photon avalanche diode, and the processing device is configured to: take the center position of the plurality of detection units of the received echo pulse as the spot position, the center position being calculated based on the geometric centroid of the plurality of detection units.

[0091] According to a preferred embodiment of the present invention, the transmitting device includes a laser configured to emit detection pulses at preset time intervals; the processing device is configured to determine the correspondence between each echo pulse and the detection pulse based on the reception time of each echo pulse and the spot position of the echo pulse on the detection unit.

[0092] According to a preferred embodiment of the present invention, the transmitting device includes a plurality of lasers, the detecting device includes a plurality of detectors, the lasers respectively form a detection channel with at least one detector, and the processing device is configured to: determine whether the echo pulse corresponds to the detection pulse based on the reception time of the echo pulse and the position of the light spot of the echo pulse on the detector in the detection channel.

[0093] By employing the technical solution of this invention, based on the reception time of the echo pulse and the position of the light spot, regardless of whether it is multi-pulse detection or single-pulse detection, it is not necessary to reserve pulse encoding time in the detection window to effectively determine whether the echo pulse corresponds to the detection pulse. This saves time resources, accurately judges the effective echo signal reflected by the obstacle, filters out interference signals, and improves the accuracy of the detection results.

[0094] According to a preferred embodiment of the present invention, by shortening the time interval of the detection cycle, time resources can be saved, thereby improving detection efficiency, while reducing crosstalk between channels and improving detection accuracy.

[0095] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended 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 make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A signal processing method for a lidar, comprising: S101: Transmit a detection pulse; S102: Receive echo pulses through a detection device; S103: Obtain the reception time of the echo pulse and the position of the light spot of the echo pulse on the detection device; and S104: Determine whether the echo pulse corresponds to the detection pulse based on the receiving time and the position of the light spot; Step S104 includes: Based on the position of the light spot, the first flight time of the echo pulse is obtained; The second flight time is obtained based on the time interval between the receiving time and the transmission time of the detection pulse; When the first flight time is close to the second flight time, it is determined that the echo pulse corresponds to the detection pulse; or Step S104 includes: The second flight time is obtained based on the time interval between the receiving time and the transmission time of the detection pulse; Based on the second flight time, obtain the expected spot position corresponding to the second flight time; When the position of the light spot is close to the expected position of the light spot, the echo pulse is determined to correspond to the detection pulse.

2. The signal processing method according to claim 1, wherein step S104 includes: Based on the position of the light spot, the first flight time of the echo pulse is obtained; The second flight time is obtained based on the time interval between the receiving time and the transmission time of the detection pulse; When the first flight time is close to the second flight time, it is determined that the echo pulse corresponds to the detection pulse; hour, The step of obtaining the first flight time of the echo pulse based on the position of the light spot includes: Determine the offset of the light spot position relative to the reference position; The first flight time is obtained based on the offset.

3. The signal processing method according to claim 1, wherein step S104 includes: Based on the position of the light spot, the first flight time of the echo pulse is obtained; The second flight time is obtained based on the time interval between the receiving time and the transmission time of the detection pulse; When the first flight time is close to the second flight time, it is determined that the echo pulse corresponds to the detection pulse; hour, The step of obtaining the first flight time of the echo pulse based on the position of the light spot includes: Based on the preset correspondence between flight time and spot position, the first flight time corresponding to the spot position is obtained.

4. The signal processing method according to claim 1, wherein step S104 includes: The second flight time is obtained based on the time interval between the receiving time and the transmission time of the detection pulse; Based on the second flight time, obtain the expected spot position corresponding to the second flight time; When the position of the light spot is close to the position of the expected light spot, the echo pulse is determined to correspond to the detection pulse; hour, The step of obtaining the expected spot position corresponding to the second flight time includes: obtaining the expected spot position corresponding to the second flight time based on a preset correspondence between flight time and spot position.

5. The signal processing method according to claim 3 or 4, wherein the preset correspondence between the flight time and the spot position is determined based on one or more of the following factors: The rotation of the lidar causes a shift in the position of the light spot; The position of the light spot caused by the deflection of the scanning device of the lidar is offset; The distance to the obstacle causes the position of the light spot to shift.

6. The signal processing method according to any one of claims 1-4, wherein the detection device comprises at least one detector, the detector comprises a plurality of detection units, and step S103 comprises: The center position of the multiple detection units that receive the echo pulse is taken as the position of the light spot.

7. The signal processing method according to claim 6, wherein the center position is calculated based on the geometric centroid of the plurality of detection units.

8. The signal processing method according to any one of claims 1-4, wherein the lidar includes at least one laser and at least one detector, the laser emits detection pulses at a preset time interval, the detector receives echo pulses, and the correspondence between each echo pulse and the detection pulse is determined according to the reception time of each echo pulse and the position of the light spot of the echo pulse on the detector.

9. The signal processing method according to any one of claims 1-4, wherein the lidar comprises a plurality of lasers and a plurality of detectors, wherein each laser forms a detection channel with at least one detector, and the method determines whether the echo pulse corresponds to the detection pulse based on the reception time of the echo pulse and the position of the light spot of the echo pulse on the detector in the detection channel.

10. A lidar, comprising: The transmitting device is configured to transmit detection pulses; The detection device is configured to receive echo pulses; The processing device is configured to acquire the reception time of the echo pulse and the position of the light spot of the echo pulse on the detection device, and determine whether the echo pulse corresponds to the detection pulse based on the reception time and the light spot position; The processing device is configured as follows: Based on the position of the light spot, the first flight time of the echo pulse is obtained; The second flight time is obtained based on the time interval between the receiving time and the transmission time of the detection pulse; When the first flight time is close to the second flight time, it is determined that the echo pulse corresponds to the detection pulse.

11. The lidar of claim 10, wherein the processing device is configured to: Determine the offset of the light spot position relative to the reference position; The first flight time is obtained based on the offset.

12. The lidar according to claim 10, wherein the processing device is configured to: obtain a first flight time corresponding to the spot position based on a preset correspondence between flight time and spot position.

13. The lidar of claim 10, wherein the processing device is configured to: The second flight time is obtained based on the time interval between the receiving time and the transmission time of the detection pulse; Based on the second flight time, the expected spot position corresponding to the second flight time is obtained; When the position of the light spot is close to the expected position of the light spot, the echo pulse is determined to correspond to the detection pulse.

14. The lidar according to claim 13, wherein the processing device is configured to: obtain the expected spot position corresponding to the second flight time based on a preset relationship between flight time and spot position.

15. The lidar according to claim 12 or 14, wherein the preset correspondence between flight time and spot position is determined based on one or more of the following factors: The rotation of the lidar causes a shift in the position of the light spot; The position of the light spot generated by the scanner of the lidar is offset; The distance to the obstacle causes the position of the light spot to shift.

16. The lidar according to any one of claims 10-14, wherein the detection device comprises at least one detector, the detector comprises a plurality of detection units, the detection unit comprising a single-photon avalanche diode, and the processing device is configured to: take the center position of the plurality of detection units of the received echo pulse as the spot position, the center position being calculated based on the geometric centroid of the plurality of detection units.

17. The lidar according to claim 16, wherein the transmitting device includes a laser, the laser being configured to emit detection pulses at preset time intervals; and the processing device is configured to: determine the correspondence between each echo pulse and the detection pulse based on the reception time of each echo pulse and the spot position of the echo pulse on the detection unit.

18. The lidar according to claim 16, wherein the transmitting device includes a plurality of lasers, the detecting device includes a plurality of detectors, the lasers respectively form a detection channel with at least one detector, and the processing device is configured to: determine whether the echo pulse corresponds to the detection pulse based on the reception time of the echo pulse and the position of the light spot of the echo pulse on the detector in the detection channel.

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