Laser radar ranging method and laser radar system

Abstract

The present invention discloses a laser radar ranging method and laser radar system. The method mainly includes: a transmitting system transmits a laser beam according to a transmission interval; the nth receiving system receives the echo of the n+N*mth laser beam emitted by the transmitting system within a receiving window that is greater than the transmission interval and no greater than N transmission intervals; wherein N is the number of receiving systems; n is a positive integer less than or equal to N; m is a natural number; and finally, the ranging result is determined based on the echo reception results of the N receiving systems. The present invention improves the maximum measurement distance without reducing the point cloud resolution and frame rate, thereby reducing the design complexity of the radar system.

Description

Technical Field

[0001] The present invention relates to the field of radar technology, and in particular to a laser radar ranging method and a laser radar system. Background Art

[0002] In the LiDAR system, from the perspective of system design, the maximum measurement distance of each scanning point is limited by various factors such as the point cloud resolution, frame rate, and total number of lasers. Among them, the maximum measurement distance is basically inversely proportional to the point cloud resolution and frame rate. Therefore, there is a contradiction between the maximum measurement distance and the point cloud resolution and frame rate in the LiDAR system.

[0003] In existing technologies, although increasing the number of lasers can increase the maximum measurement distance without changing the point cloud resolution or reducing the frame rate, it will also increase the complexity of system design and bring difficulties to the subsequent point cloud stitching and calibration. Summary of the Invention

[0004] Based on the above reasons, an embodiment of the present invention provides a laser radar ranging method and a laser radar system to solve the problem in the prior art that increasing the maximum measurement distance by increasing the number of lasers will increase the complexity of system design.

[0005] A first aspect of this embodiment provides a laser radar ranging method, including:

[0006] The transmitting system transmits the laser beam according to the transmitting interval;

[0007] The nth receiving system receives the echo of the n+N*mth laser beam emitted by the transmitting system within a receiving window that is greater than the transmitting interval and no greater than N transmitting intervals; wherein N is the number of receiving systems; n is a positive integer less than or equal to N; and m is a natural number;

[0008] A ranging result is determined according to the echo reception results of the N receiving systems.

[0009] Optionally, the receiving angle of the receiving system is set according to the emission angle of the laser beam, wherein different receiving angles receive echoes of laser beams with different emission angles.

[0010] Optionally, determining the ranging result according to the echo reception results of the N receiving systems includes:

[0011] determining a corresponding candidate distance according to each echo signal received by the nth receiving system;

[0012] Determining whether each of the candidate distances meets a preset condition;

[0013] The candidate distances that do not meet the preset conditions are filtered out to obtain the ranging results within the receiving time window of the nth receiving system.

[0014] Optionally, determining whether each candidate distance satisfies a preset condition includes:

[0015] performing a difference operation between the candidate distance and the distance determined according to the transmission interval to obtain a distance difference, and performing a sum operation between the candidate distance and the distance determined according to the transmission interval to obtain a distance sum;

[0016] A first upper limit is determined according to the distance difference and the target reflectivity, and a first lower limit is determined according to the distance sum and the target reflectivity; wherein the target reflectivity is: the reflectivity of the laser emitted by the laser radar passing through the alternative distance;

[0017] determining a second upper limit based on the candidate distance and the maximum reflectivity of the laser, and determining a second lower limit based on the candidate distance and the minimum reflectivity of the laser;

[0018] If the signal strength corresponding to the alternative distance is between the first upper limit and the first lower limit, and the signal strength corresponding to the alternative distance is between the second upper limit and the second lower limit, it is determined that the signal strength corresponding to the alternative distance meets the preset condition.

[0019] Optionally, the laser parameters of the laser beams at two adjacent emission points are different;

[0020] Determining the ranging result according to the echo reception results of the N receiving systems includes:

[0021] filtering out echoes received by the nth receiving system that are different from the laser parameters according to the laser parameters of the n+N*mth laser beam, to obtain remaining echoes received by the nth receiving system;

[0022] A ranging result is determined according to the remaining echoes received by the nth receiving system.

[0023] Optionally, the laser parameters include at least one of the following:

[0024] The number of pulses contained in a single shot laser beam;

[0025] The time interval between successive pulses in a laser beam.

[0026] A second aspect of this embodiment provides a laser radar system, including: a transmitting system and N receiving systems;

[0027] The emission system is used to emit laser beams according to emission intervals;

[0028] The nth receiving system is used to receive the echo of the n+N*mth laser beam emitted by the transmitting system within a receiving window that is greater than the transmitting interval and no greater than N transmitting intervals; wherein N is the number of receiving systems; n is a positive integer less than or equal to N; and m is a natural number;

[0029] The nth receiving system is further configured to determine a ranging result based on an echo reception result.

[0030] Optionally, the receiving angle of the receiving system is set according to the emission angle of the laser beam, wherein different receiving angles receive echoes of laser beams with different emission angles.

[0031] Optionally, the nth receiving system is specifically configured to:

[0032] determining a corresponding candidate distance according to each echo signal received by the nth receiving system;

[0033] Determining whether each of the candidate distances meets a preset condition;

[0034] The candidate distances that do not meet the preset conditions are filtered out to obtain the ranging results within the receiving time window of the nth receiving system.

[0035] Optionally, the nth receiving system is specifically configured to:

[0036] performing a difference operation between the candidate distance and the distance determined according to the transmission interval to obtain a distance difference, and performing a sum operation between the candidate distance and the distance determined according to the transmission interval to obtain a distance sum;

[0037] A first upper limit is determined according to the distance difference and the target reflectivity, and a first lower limit is determined according to the distance sum and the target reflectivity; wherein the target reflectivity is: the intensity of the laser emitted by the laser radar reflected back through the alternative distance;

[0038] determining a second upper limit based on the candidate distance and the maximum reflectivity of the laser, and determining a second lower limit based on the candidate distance and the minimum reflectivity of the laser;

[0039] If the signal strength corresponding to the alternative distance is between the first upper limit and the first lower limit, and the signal strength corresponding to the alternative distance is between the second upper limit and the second lower limit, it is determined that the signal strength corresponding to the alternative distance meets the preset condition.

[0040] Optionally, the laser parameters of the laser beams at two adjacent emission points are different;

[0041] The nth receiving system is specifically used for:

[0042] filtering out echoes received by the nth receiving system that are different from the laser parameters according to the laser parameters of the n+N*mth laser beam, to obtain remaining echoes received by the nth receiving system;

[0043] A ranging result is determined according to the remaining echoes received by the nth receiving system.

[0044] Optionally, the laser parameters include at least one of the following:

[0045] The number of pulses contained in a single shot laser beam;

[0046] The time interval between successive pulses in a laser beam.

[0047] Beneficial effects of the present invention

[0048] In the laser radar ranging method of this embodiment, the transmitting system transmits a laser beam according to a transmitting interval, and the nth receiving system receives the echo of the n+N*mth laser beam emitted by the transmitting system in a receiving window that is greater than the transmitting interval and no greater than N transmitting intervals, thereby extending the measurement time of the ranging. In this way, a single laser beam can still be detected after being reflected back by an object at a farther distance, thereby improving the maximum measurement distance of the laser radar. Moreover, this embodiment does not require an increase in the number of transmitting devices or lasers, that is, without changing the point cloud resolution and frame rate, thereby solving the problem of the contradiction between the maximum measurement distance of the laser radar system and the point cloud resolution and frame rate, thereby improving the maximum measurement distance and reducing the complexity of the system design. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 A schematic diagram of the implementation flow of a laser radar ranging method provided in an embodiment of the present invention.

[0050] Figure 2 for Figure 1 Schematic diagram of the specific implementation process of step S13.

[0051] Figure 3 for Figure 2 Schematic diagram of the specific implementation process of step S22.

[0052] Figure 4 for Figure 3 Another specific implementation flow chart of step S13 is shown in FIG.

[0053] Figure 5 A schematic diagram of signal reception by a conventional lidar system provided in an embodiment of the present invention.

[0054] Figure 6 A schematic diagram of signal reception using the laser radar ranging method provided in an embodiment of the present invention.

[0055] Figure 7 A schematic diagram of overlapping areas in signals of a receiving system provided in an embodiment of the present invention.

[0056] Figure 8 A schematic structural diagram of a lidar system provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0057] Exemplary embodiments will be described in detail herein, examples of which are illustrated in the accompanying drawings. In the following description, when referring to the drawings, like numbers in different figures represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all possible embodiments consistent with the present invention. Rather, they are merely examples of systems and methods consistent with certain aspects of the present invention, as detailed in the appended claims.

[0058] Figure 1 is a flow chart of a laser radar ranging method according to an exemplary embodiment. Figure 1 As shown, the following steps are included.

[0059] In step S11, the emission system emits a laser beam at an emission interval.

[0060] The laser radar ranging method of this embodiment can be applied to any laser radar, such as MEMS (Micro-Electro-Mechanical System) scanning, mechanical rotation scanning and other laser radars.

[0061] When designing a LiDAR system, the maximum measurement distance of each scanning point in the LiDAR is usually limited by the resolution of the point cloud, the number of frames of the point cloud, and the total number of lasers. For example, if the frame rate of the LiDAR point cloud is M frames / second and the resolution of the point cloud is L a ·L e , the total number of lasers is K, then the number of point cloud points that a single laser is responsible for is So we can calculate that the maximum measurement time period of each point is seconds, so the maximum measuring distance is Among them, L a is the number of upward points of the scanning point, L e is the number of scanning points in azimuth, and C is the speed of light. It can be seen that when designing a radar system, the maximum measurement distance and the number of point cloud frames and resolution are generally inversely proportional. Although increasing the number of lasers can increase the maximum measurement distance without changing the point cloud resolution or reducing the frame rate, this also increases the complexity of the system design and brings difficulties to subsequent point cloud stitching and calibration.

[0062] Therefore, this embodiment adopts a design approach of multiple independent receiving systems to avoid the problem of shortened maximum measurement distance due to insufficient ranging time period for a single point during ranging. This also reduces the complexity of LiDAR design. Specifically, a single transmitting system transmits laser beams according to the laser emission sequence and emission cycle. Specifically, when performing laser scanning on a target, the transmitting system emits multiple laser beams to form a point cloud. This embodiment transmits laser beams according to the emission cycle based on the laser emission point sequence. This eliminates the need for multiple transmitting systems for the LiDAR system, reducing the complexity of radar system design.

[0063] Here, the emission interval refers to the time interval between the emission of adjacent laser beams. For example, the emission system emits a laser beam every 0.01 seconds. According to the emission interval, the laser emission points can emit light in the order of 1, 2, 3, 4..., such as Figures 5 to 7 ; Among them, 1, 2, 3, 4... can be understood as the point numbers on the point cloud of the lidar, that is, the point numbers are marked according to the order of light emission. The laser emission order is directly related to the resolution.

[0064] The laser beam in this embodiment may be a light pulse, and the emission system emits the light pulse according to an emission interval.

[0065] In step S12, the nth receiving system receives the echo of the n+N*mth laser beam emitted by the transmitting system within a receiving window that is greater than the transmitting interval and no greater than N of the transmitting intervals; wherein, N is the number of receiving systems; n is a positive integer less than or equal to N; and m is a natural number.

[0066] Here, the receiving window that is greater than the transmission interval but not greater than N of the transmission intervals refers to a time length that is greater than the transmission interval but not greater than N transmission intervals. Within this time length, the nth receiving system receives the echo of the n+N*mth laser beam emitted by the transmitting system, and m is the number of this time length. Optionally, the time length of the receiving window can be N transmission intervals.

[0067] For example, the radar system includes a transmitting system and four receiving systems. The transmitting point of the transmitting system is 100, that is, the transmitting system transmits 100 laser beams according to the transmitting interval, and the four receiving systems receive the 100 laser beams. Then, for the transmitting points 1-100, the receiving systems corresponding to each point are 1, 2, 3, 4, 1, 2, 3, 4 in sequence. For another example, if Figure 6 and 7As shown, the radar system includes two receiving systems. The laser at point 1 is received by receiving system A, the laser at point 2 is received by receiving system B, the laser at point 3 is received by receiving system A, and the laser at point 4 is received by receiving system B. This cycle continues, that is, the lasers at adjacent transmitting points are received by different receiving systems.

[0068] Here, the time window for the nth receiving system to receive the n+N*mth laser beam is determined by the start time of the n+N*mth laser beam. For example, to ensure successful reception of the n+N*mth laser beam's echo, the start time of the time window is set to be equal to or earlier than the required emission time of the n+N*mth laser beam. This ensures that objects 0 meters away from the lidar system can be successfully measured.

[0069] Optionally, if the number of transmitting points is not a multiple of the number of receiving systems, when there are less than N laser beams at the end, the following is still followed: the nth receiving system receives the echo of the n+N*mth laser beam; wherein N is the number of receiving systems, N≥2; n is a positive integer less than or equal to N; m is a natural number, that is, the transmitting point is matched with N as the divisor, and different point numbers are assigned to their respective receiving systems for processing according to the different remainders. For example, the radar system includes 6 receiving systems, and the transmitting system has 100 transmitting points. Then, for transmitting points 1-100, the receiving systems corresponding to each point are 1, 2, 3, 4, 5, 6, 1, 2, 3, 4, 5, 6, ... 1, 2, 3, 4, 5, 6, 1, 2, 3, 4, respectively, and receive in the order of 1, 2, 3, 4, 5, 6, 1, 2, 3, 4.

[0070] In step S13, a ranging result is determined based on the echo reception results of the N receiving systems.

[0071] For example, see Figure 8 The radar system may include a transmitting system and N receiving systems. The transmitting system transmits a laser beam at a transmission interval. The nth receiving system receives the echo of the n+N*mth laser beam emitted by the transmitting system within a receiving window that is greater than the transmission interval but no greater than N transmission intervals, where n is a positive integer less than or equal to N, and m is a natural number. The nth receiving system then determines a ranging result based on the echo reception result. It should be understood that this embodiment does not specifically limit the number of receiving systems, and the number is at least two, so that adjacent laser beams are received by different receiving systems.

[0072] Without changing the hardware configuration of the transmitting system, this embodiment only performs multiple sets of redundant reception on the receiving end system. By changing the system mapping of the receiving end, that is, using multiple sets of independent receiving systems to independently receive echoes from different points, the measurement time of each point on the point cloud can be extended. In this way, a single laser beam can still be detected after being reflected back by a distant object, thereby increasing the maximum measurement distance without changing the point cloud resolution or reducing the frame rate, thereby reducing the complexity of radar system design.

[0073] Furthermore, the original transmission and reception logic of conventional laser imaging radar is as follows Figure 5 As shown, after each point is transmitted, the corresponding echo begins to be received and processed, and the receiving window continues until the next point emits light, resulting in a shorter measurement time. Although the method of this embodiment extends the measurement time, there may be temporal overlap between the start and end times of measurement at each point. Therefore, improvements are needed in the logic controlling the transmission system and the algorithms at the data processing end to achieve distance resolution between adjacent points and resolve the ranging ambiguity caused by temporal overlap.

[0074] For example, two independent receiving systems are used as an example. The two independent receiving systems receive the laser beams from the transmitting points separately. For example, odd and even points are used to map different receiving systems for data processing and analysis. Odd points are processed by receiving system A, and even points are processed by receiving system B. Figure 6 As shown, the laser at point 1 is received by receiving system A, the laser at point 2 is received by receiving system B, the laser at point 3 is received by receiving system A, and the laser at point 4 is received by receiving system B, and so on. That is, without changing the light emission timing, the measurement time of each point is extended by adjusting the distribution of receiving systems at different points, thereby extending the maximum measurement distance.

[0075] However, this system may have the problem of distance ambiguity in processing, that is, multiple distances may be measured based on the echo of each receiving system, such as Figure 6 As shown in the figure, the measurement of point 1 is the responsibility of receiving system A, and the measurement of point 2 is the responsibility of receiving system B. However, within the measurement time window of point 1, there will be a time when point 2 emits light. That is to say, the measurement time window of point 2 overlaps with the measurement time window of point 1. The overlapping area is as follows: Figure 7 In the receiving overlap area, echoes from point 1 and point 2 may coexist. To address this situation, this embodiment can adopt multiple methods to avoid or distinguish them.

[0076] In one embodiment, the receiving angle of the receiving system is set according to the emission angle of the laser beam, wherein different receiving angles receive echoes of laser beams with different emission angles.

[0077] In this embodiment, the receiving angle of the receiving system is set according to the emission angle of the laser beam, so that the receiving angles of adjacent receiving systems are different, and thus different receiving systems receive the echoes of laser beams with different emission angles, thereby preventing each receiving system from receiving the echoes of laser beams with other emission angles. Exemplarily, the radar system includes two receiving systems, and the size and range of the receiving FOV (field of view) of each receiving system are set to achieve spatial isolation between the echo of the laser beam from emission point 1 received by receiving system 1 and the echo of the laser beam from emission point 2 received by receiving system 2, thereby achieving the distinction between the echoes of point 1 and point 2. Although the time overlaps, the echoes of point 1 and point 2 will not appear on the same receiving system, thereby achieving the distinction between the echoes of the two and eliminating the distance ambiguity. The method is simple and has low implementation cost.

[0078] Optionally, this embodiment can set the receiving angle of each receiving system based on parameters such as the number of transmitting points and / or the maximum scanning angle of the transmitting system. For example, the transmission angle of each transmitting point can be determined based on the number of transmitting points and the maximum scanning angle of the transmitting system, and thus the reflection angle can be determined, and further the receiving angle of the receiving system can be determined. This embodiment can also directly set the receiving angle of each receiving system based on the transmission angle of each transmitting point.

[0079] The above embodiment can spatially isolate the echoes of laser beams with different emission angles while making full use of spatial information, thereby reducing the number of receiving systems and further reducing the size of the radar system.

[0080] In one embodiment, Figure 2 As shown, determining the ranging result based on the echo reception results of the N receiving systems includes:

[0081] In step S21, a corresponding candidate distance is determined based on each echo signal received by the nth receiving system. In this embodiment, the receiving angles of each receiving system can be the same or different, and there is no need to consider the receiving angle of the receiving system, thereby reducing the design complexity of the receiving system.

[0082] When designing a radar system, the maximum measurement distance is essentially inversely proportional to the number of point cloud frames and resolution. While increasing the number of lasers can increase the maximum measurement distance without changing the point cloud resolution or reducing the frame rate, using multiple transmitters with different wavelengths and matching the different wavelength transmitters at the receiving end requires designing separate filters to shield lasers of other wavelengths. This introduces significant system complexity and engineering challenges, as well as uncontrollable factors. Therefore, this embodiment employs a design approach with multiple independent receiving systems to avoid the problem of shortened maximum measurement distance due to insufficient ranging timing at a single point during ranging. Furthermore, a special system design approach is employed to address echoes between multiple receiving systems to avoid distance ambiguity.

[0083] This embodiment distinguishes the relationship between signal strength and distance in its processing algorithm. According to the lidar equation, the target's echo intensity is inversely proportional to the square of the target's distance. Therefore, overlapping areas can be identified based on the echo signals received by the receiving system. Specifically, while the nth receiving system receives the echo of the n+N*mth laser beam, it may also receive interference echoes other than the n+N*mth laser beam. This embodiment determines the corresponding candidate distance based on each echo signal received by the nth receiving system, and can filter out interference echoes based on the candidate distance.

[0084] like Figure 6 As shown in Figure 7, receiving system A receives the echo of the laser beam from transmitting point 3 and the echo of the laser beam from transmitting point 2 in the overlapping area. At this time, it is necessary to determine the alternative distance R2 of transmitting point 2 and the alternative distance R3 of transmitting point 3. Based on the alternative distances R2 and R3, it is determined whether receiving system A has an interference echo, so as to make the ranging result of receiving system A more accurate. For another example, there are 100 transmitting points and 5 receiving systems. Receiving system 2 receives transmitting point 2, transmitting point 7, transmitting point 12, transmitting point 47, transmitting point 52, etc. For example, while receiving the echo of the laser beam from transmitting point 52, it is possible that it also receives the echo of the laser beam from transmitting points 48, 49, 50, and 51. In this case, it is necessary to determine the corresponding alternative distance based on the echo of the laser beam from transmitting points 48, 49, 50, 51, and 52. Based on the corresponding alternative distance, it is determined whether receiving system 2 has an interference echo, so as to make the ranging result of receiving system 2 more accurate and avoid distance ambiguity. Optionally, this embodiment can filter out echo signals whose signal strength does not meet the conditions based on the signal strength of each echo signal in the receiving system; it can also filter out the corresponding echo signals that do not meet the distance conditions based on the distance value determined for each echo signal in the receiving system; it can also filter out interference signals based on information such as the number of pulses of the echo signal in the receiving system and the timing information of the received echo signal.

[0085] In step S22, it is determined whether each candidate distance meets a preset condition.

[0086] If any of the multiple alternative distances do not meet the preset conditions, the alternative distances that do not meet the preset conditions will be filtered out to obtain the remaining alternative distances, which are the ranging results within the receiving time window of the nth receiving system; if all the alternative distances meet the preset conditions, they do not need to be filtered out, that is, the distances determined by the echo signals of the nth receiving system are all target distances.

[0087] like Figure 7 As shown, interference echoes can be identified in the overlapping reception area of points 1 and 2. For point 1, the overlapping area is at the end of the ranging time window, indicating a long-distance target, so the echo signal strength should be relatively low. For point 2, the overlapping area is at the front of the ranging time window, indicating a short-distance target, so the signal strength should be relatively high. Therefore, this embodiment can filter out the candidate distances that do not meet the preset conditions from the nth receiving system by determining whether the candidate distances meet the preset conditions, thereby filtering out the echo interference signals of the receiving system and removing the interference echo signals. This is to remove the interference echo signals and obtain the candidate distances.

[0088] Optionally, the preset conditions corresponding to each receiving system are different. Figure 7 As shown, for point 1, the overlapping area belongs to the end of the ranging time window, that is, the long-distance target. For point 2, the overlapping area belongs to the front end of the ranging time window, that is, the short-distance target. Therefore, the alternative distance determined by each receiving system according to the interference echo is different. The alternative distance of some receiving systems may be large, and the alternative distance of some receiving systems may be small. For example, the alternative distance determined by the overlapping area of point 1 is large, and the corresponding preset condition is also large. For example, the alternative distance determined by the overlapping area of point 2 is small, and the corresponding preset condition is also small.

[0089] Optional, such as Figure 3 As shown, the determining whether each candidate distance meets the preset condition includes:

[0090] In step S31, a difference operation is performed between the candidate distance and the distance determined according to the transmission interval to obtain a distance difference value, and a sum operation is performed between the candidate distance and the distance determined according to the transmission interval to obtain a distance sum value.

[0091] Here, the emission interval can also be said to be the timing information of adjacent laser emissions. As described in the above embodiment, the distance difference can be expressed as The distance and value can be expressed as Among them, R is the alternative distance, TN is the emission interval between adjacent laser emission moments, C is the speed of light, is the distance determined based on the emission interval.

[0092] In step S32, a first upper limit is determined based on the distance difference and the target reflectivity, and a first lower limit is determined based on the distance sum and the target reflectivity; wherein the target reflectivity is: the reflectivity of the laser emitted by the laser radar passing through the alternative distance.

[0093] This embodiment determines the echo signal strength based on the distance and the target reflectivity, and the distance and the signal strength are inversely proportional. Specifically, the first upper limit is determined based on the distance difference and the target reflectivity, which is expressed as The first lower limit is determined based on the distance and value and the target reflectivity, which is expressed as

[0094] In step S33 , a second upper limit is determined according to the candidate distance and the maximum reflectivity of the laser, and a second lower limit is determined according to the candidate distance and the minimum reflectivity of the laser.

[0095] This embodiment also constrains the signal strength determined by the candidate distance based on the reflectivity of the laser, further improving the screening accuracy of the candidate distance and making the ranging result of the receiving system more accurate. The reflectivity of this embodiment can be understood as the reflection intensity or reflectivity intensity. Specifically, the second upper limit is determined based on the candidate distance and the maximum reflectivity of the laser, expressed as p(R,ρ 100 ), the second lower limit is determined according to the distance and value and the minimum reflectivity, expressed as p(R,ρ1), where ρ1 is the minimum reflectivity of the laser, for example, the reflectivity is 1, ρ 100 is the maximum reflectivity of the laser, for example, the reflectivity is 100.

[0096] In step S34, if the signal strength corresponding to the alternative distance is between the first upper limit and the first lower limit, and the signal strength corresponding to the alternative distance is between the second upper limit and the second lower limit, it is determined that the signal strength corresponding to the alternative distance meets the preset condition.

[0097] Specifically, if the signal strength obtained according to the alternative distance is between the first upper limit and the first lower limit, there is no need to filter out the alternative distance, that is, the distance determined by the echo signal of the nth receiving system is the target distance; if the signal strength obtained according to the alternative distance is not between the first upper limit and the first lower limit, it is necessary to filter out the alternative distance to obtain the remaining alternative distance, and the remaining alternative distance is used as the ranging result within the receiving time window of the nth receiving system.

[0098] Alternatively, if the signal strength obtained according to the alternative distance is between the second upper limit and the second lower limit, there is no need to filter out the alternative distance; if the signal strength obtained according to the alternative distance is not between the second upper limit and the second lower limit, the alternative distance needs to be filtered out to obtain the remaining alternative distances.

[0099] Alternatively, if the signal strength obtained according to the alternative distance is between the first upper limit and the first lower limit, and the signal strength obtained according to the alternative distance is between the second upper limit and the second lower limit, then there is no need to filter out the alternative distance; if the signal strength obtained according to the alternative distance is not between the first upper limit and the first lower limit, and the signal strength obtained according to the alternative distance is not between the second upper limit and the second lower limit, then it is necessary to filter out the alternative distance to obtain the remaining alternative distance, and the remaining alternative distance is used as the ranging result within the receiving time window of the nth receiving system.

[0100] For example, see Figure 7 , assuming that the laser emitting interval between point 1 and point 2 is T N , the candidate distance determined by the echo appearing in the overlapping area corresponding to point 1 is R1, that is, the candidate distance of the unknown target determined based on the interference echo of receiving system A, and the candidate distance determined by the echo appearing in the overlapping area corresponding to point 2 is R2, that is, the candidate distance of the unknown target determined based on the interference echo of receiving system B. Then for receiving systems A and B, the distance with reflectivity intensity is ρ r (ρ1<ρ r <ρ 100 , where ρ1 represents an object with a reflectivity of 1, ρ 100 The reflected signal strength of the target at distance R (representing an object with a reflectivity of 100) is p(R,ρ r ).

[0101] Furthermore, the reflected signal strength p(R,ρ r ), determine the reflected signal strength p(R,ρ r ) is between the first upper limit and the first lower limit. Specifically, the reflected signal strength p(R,ρ r ) should satisfy

[0102]

[0103] If the above conditions are not met, the reflected signal strength p(R,ρ r ) is filtered out. For example, if R1 and the corresponding unknown target reflectivity determine the reflected signal strength p(R1, ρ r) does not meet the above conditions, then R1 is filtered out, that is, the echo corresponding to R1 in the receiving system A is filtered out; or, if the reflected signal strength p(R2,ρ r ) does not meet the above conditions, R2 is filtered out, that is, the echo corresponding to R2 in the receiving system B is filtered out.

[0104] The above embodiment determines an alternative distance based on the relationship between distance and signal strength according to each echo signal, and then filters out the alternative distances that do not meet the preset conditions. The filtering efficiency is better, the distance duplication phenomenon is avoided, and the ranging accuracy of the radar system is greatly improved.

[0105] In one embodiment, laser parameters of the laser beams at two adjacent emission points are different.

[0106] Here, laser parameters refer to various parameters of the laser beam output by the emission system, such as the number of pulses of the laser beam at the emission point in a single emission and the timing information of adjacent laser beams, etc.

[0107] For further information, see Figure 4 , determining the ranging result according to the echo reception results of the N receiving systems includes:

[0108] In step S41 , based on the laser parameters of the n+N*mth laser beam, echoes received by the nth receiving system that are different from the laser parameters are filtered out to obtain remaining echoes received by the nth receiving system.

[0109] In step S42, a ranging result is determined based on the remaining echoes received by the nth receiving system.

[0110] This embodiment improves the control logic of the transmitting system and adopts a transmitting logic with different laser parameters of the laser beams of two adjacent transmitting points, so that each receiving system receives the echo of the laser beam with different transmitting logic. At the same time, according to the laser parameters of the n+N*mth laser beam, the echo received by the nth receiving system that is different from the laser parameters is filtered out to obtain the remaining intensity of the receiving intensity of the nth receiving system.

[0111] It should be understood that this embodiment does not limit the specific values of the laser parameters, nor does it limit the number of receiving systems, which is at least two. As long as the laser parameters of the laser beams of two adjacent emission points are different, different receiving systems can receive the echoes of laser beams with different laser parameters.

[0112] The above embodiment achieves the purpose of extending the measurement time while filtering out interference callbacks through laser parameters. The filtering effect is better and more accurate, interference between signals is avoided, and the method is easier to implement, thereby eliminating distance duplication as much as possible, improving the accuracy of the ranging results, and extending the ranging distance.

[0113] Optionally, the laser parameters of this embodiment include at least one of the following: the number of pulses contained in a single-shot laser beam, and the pulse time interval between adjacent pulses in the laser beam, but are not limited to the coding combination method of the number of pulses and the pulse time interval.

[0114] This embodiment can employ a multi-pulse emission system. The luminescence logic (laser parameters) of adjacent points can employ different numbers of pulses contained in a single laser beam, or different time intervals between adjacent pulses in a laser beam, or any combination of these two. Different receiving systems employ different data processing methods to distinguish targets. For example, for emission point 1, a two-pulse emission system with a pulse interval of N2 is employed. For emission point 2, a three-pulse emission system with pulse intervals of N2 and N3 is employed. Similarly, for receiving system A, a two-pulse data processing method can be employed for screening, while for receiving system B, a three-pulse data processing method can be employed for screening. This achieves high-precision differentiation of adjacent points in overlapping areas, avoids distance ambiguity, and improves ranging accuracy.

[0115] In the above embodiment, the distance ambiguity problem caused by echo interference in the overlapping area is solved by improving the control logic of the transmitting system, adopting a multi-pulse transmission system, and simultaneously mapping different receiving systems for data processing. It is possible to distinguish the echoes of different point numbers in the overlapping area, thereby realizing the distinction between echoes of different point numbers in different receiving systems.

[0116] This embodiment solves the contradiction between the maximum measurement distance, point cloud resolution and frame rate in existing lidar systems. Without reducing the point cloud resolution and frame rate, by improving the receiving relationship between the transmitting system and the receiving system, one transmitting system and multiple receiving systems are used to extend the measurement time, achieve an increase in the maximum measurement distance, and reduce the design complexity of the system. At the same time, in order to solve the problem of distance ambiguity, processing optimization is carried out in the system design. By changing the emission logic of the emitted laser beam, there is no need to design multiple emission systems, which reduces the complexity of the radar system design, so that adjacent laser beams are received by different receiving systems, avoiding distance ambiguity.

[0117] Figure 8 FIG. 1 is a block diagram of a laser radar system according to an exemplary embodiment. Figure 8 The system includes: a transmitting system 100 and N receiving systems 200.

[0118] Transmitting system 100 transmits a laser beam at a transmission interval. The nth receiving system 200 receives the echo of the n+N*mth laser beam emitted by the transmitting system within a receiving window that is greater than the transmission interval but no greater than N transmission intervals, where N is the number of receiving systems; n is a positive integer less than or equal to N; and m is a natural number. The nth receiving system 200 determines a ranging result based on the echo reception result.

[0119] Optionally, the receiving angle of the receiving system 200 is set according to the emission angle of the laser beam, wherein different receiving angles 200 receive echoes of laser beams with different emission angles.

[0120] Optionally, the nth receiving system 200 is specifically configured to:

[0121] determining a corresponding candidate distance according to each echo signal received by the nth receiving system;

[0122] Determining whether each of the candidate distances meets a preset condition;

[0123] The candidate distances that do not meet the preset conditions are filtered out to obtain the ranging results within the receiving time window of the nth receiving system.

[0124] Optionally, the nth receiving system 200 is specifically configured to:

[0125] performing a difference operation between the candidate distance and the distance determined according to the transmission interval to obtain a distance difference, and performing a sum operation between the candidate distance and the distance determined according to the transmission interval to obtain a distance sum;

[0126] A first upper limit is determined according to the distance difference and the target reflectivity, and a first lower limit is determined according to the distance sum and the target reflectivity; wherein the target reflectivity is: the reflectivity of the laser emitted by the laser radar passing through the alternative distance;

[0127] determining a second upper limit based on the candidate distance and the maximum reflectivity of the laser, and determining a second lower limit based on the candidate distance and the minimum reflectivity of the laser;

[0128] If the signal strength corresponding to the alternative distance is between the first upper limit and the first lower limit, and the signal strength corresponding to the alternative distance is between the second upper limit and the second lower limit, it is determined that the signal strength corresponding to the alternative distance meets the preset condition.

[0129] Optionally, the laser parameters of the laser beams at two adjacent emission points are different; the nth receiving system 200 is specifically configured to:

[0130] filtering out echoes received by the nth receiving system that are different from the laser parameters according to the laser parameters of the n+N*mth laser beam, to obtain remaining echoes received by the nth receiving system;

[0131] A ranging result is determined according to the remaining echoes received by the nth receiving system.

[0132] Optionally, the laser parameters include at least one of the following: the number of pulses contained in a single-shot laser beam, and the pulse time interval between adjacent pulses in the laser beam.

[0133] Other embodiments of the present invention will readily occur to those skilled in the art after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.

[0134] It should be understood that the present invention is not limited to the exact construction described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A laser radar ranging method, characterized in that: include: The transmitting system transmits the laser beam according to the transmitting interval; The nth receiving system receives the echo of the n+N*mth laser beam emitted by the transmitting system within a receiving window that is greater than the transmitting interval and no greater than N transmitting intervals; wherein N is the number of receiving systems, N≥2; n is a positive integer less than or equal to N; and m is a natural number; determining a ranging result based on the echo reception results of the N receiving systems; The determining of the ranging result according to the echo reception results of the N receiving systems includes: determining a corresponding candidate distance according to each echo signal received by the nth receiving system; Determining whether each of the candidate distances meets a preset condition; Filtering out the candidate distances that do not meet the preset conditions to obtain a ranging result within a receiving time window of the nth receiving system; Wherein, determining whether each candidate distance satisfies a preset condition includes: performing a difference operation between the candidate distance and the distance determined according to the transmission interval to obtain a distance difference, and performing a sum operation between the candidate distance and the distance determined according to the transmission interval to obtain a distance sum; A first upper limit is determined according to the distance difference and the target reflectivity, and a first lower limit is determined according to the distance sum and the target reflectivity; wherein the target reflectivity is: the reflectivity of the laser emitted by the laser radar passing through the alternative distance; determining a second upper limit based on the candidate distance and the maximum reflectivity of the laser, and determining a second lower limit based on the candidate distance and the minimum reflectivity of the laser; If the signal strength corresponding to the alternative distance is between the first upper limit and the first lower limit, and the signal strength corresponding to the alternative distance is between the second upper limit and the second lower limit, it is determined that the signal strength corresponding to the alternative distance meets the preset condition.

2. The laser radar ranging method according to claim 1, characterized in that: The receiving angle of the receiving system is set according to the emission angle of the laser beam, wherein different receiving angles receive echoes of laser beams with different emission angles.

3. A laser radar ranging method, characterized in that: include: The emission system emits laser beams according to emission intervals; the laser parameters of the laser beams at two adjacent emission points are different; The nth receiving system receives the echo of the n+N*mth laser beam emitted by the transmitting system within a receiving window that is greater than the transmitting interval and no greater than N transmitting intervals; wherein N is the number of receiving systems, N≥2; n is a positive integer less than or equal to N; and m is a natural number; determining a ranging result based on the echo reception results of the N receiving systems; The determining of the ranging result according to the echo reception results of the N receiving systems includes: filtering out echoes received by the nth receiving system that are different from the laser parameters according to the laser parameters of the n+N*mth laser beam, to obtain remaining echoes received by the nth receiving system; A ranging result is determined according to the remaining echoes received by the nth receiving system.

4. The laser radar ranging method according to claim 3, characterized in that: The laser parameters include at least one of the following: The number of pulses contained in a single shot laser beam; The time interval between successive pulses in a laser beam.

5. The laser radar ranging method according to claim 3, characterized in that: The receiving angle of the receiving system is set according to the emission angle of the laser beam, wherein different receiving angles receive echoes of laser beams with different emission angles.

6. A laser radar system, characterized in that: include: One transmitting system and N receiving systems; The emission system is used to emit laser beams according to emission intervals; The nth receiving system is used to receive the echo of the n+N*mth laser beam emitted by the transmitting system within a receiving window that is greater than the transmitting interval and no greater than N transmitting intervals; wherein N is the number of receiving systems, N≥2; n is a positive integer less than or equal to N; and m is a natural number; The nth receiving system is further configured to determine a ranging result based on the echo reception result; The nth receiving system is specifically used for: determining a corresponding candidate distance according to each echo signal received by the nth receiving system; Determining whether each of the candidate distances meets a preset condition; Filtering out the candidate distances that do not meet the preset conditions to obtain a ranging result within a receiving time window of the nth receiving system; The nth receiving system is specifically used for: performing a difference operation between the candidate distance and the distance determined according to the transmission interval to obtain a distance difference, and performing a sum operation between the candidate distance and the distance determined according to the transmission interval to obtain a distance sum; A first upper limit is determined according to the distance difference and the target reflectivity, and a first lower limit is determined according to the distance sum and the target reflectivity; wherein the target reflectivity is: the intensity of the laser emitted by the laser radar reflected back through the alternative distance; determining a second upper limit based on the candidate distance and the maximum reflectivity of the laser, and determining a second lower limit based on the candidate distance and the minimum reflectivity of the laser; If the signal strength corresponding to the alternative distance is between the first upper limit and the first lower limit, and the signal strength corresponding to the alternative distance is between the second upper limit and the second lower limit, it is determined that the signal strength corresponding to the alternative distance meets the preset condition.

7. The laser radar system according to claim 6, characterized in that The receiving angles of the receiving system are set to be different according to the emission angle of the laser beam, wherein different receiving angles receive echoes of laser beams with different emission angles.

8. A laser radar system, characterized in that: include: One transmitting system and N receiving systems; The emission system is used to emit laser beams according to emission intervals; the laser parameters of the laser beams at two adjacent emission points are different; The nth receiving system is used to receive the echo of the n+N*mth laser beam emitted by the transmitting system within a receiving window that is greater than the transmitting interval and no greater than N transmitting intervals; wherein N is the number of receiving systems, N≥2; n is a positive integer less than or equal to N; and m is a natural number; The nth receiving system is specifically used for: filtering out echoes received by the nth receiving system that are different from the laser parameters according to the laser parameters of the n+N*mth laser beam, to obtain remaining echoes received by the nth receiving system; A ranging result is determined according to the remaining echoes received by the nth receiving system.

9. The laser radar system according to claim 8, characterized in that The laser parameters include at least one of the following: The number of pulses contained in a single shot laser beam; The time interval between successive pulses in a laser beam.

10. The laser radar system according to claim 8, characterized in that The receiving angles of the receiving system are set to be different according to the emission angle of the laser beam, wherein different receiving angles receive echoes of laser beams with different emission angles.

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