WO2023051482A1 - 激光雷达测距方法和激光雷达系统 - Google Patents

激光雷达测距方法和激光雷达系统 Download PDF

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Publication number
WO2023051482A1
WO2023051482A1 PCT/CN2022/121526 CN2022121526W WO2023051482A1 WO 2023051482 A1 WO2023051482 A1 WO 2023051482A1 CN 2022121526 W CN2022121526 W CN 2022121526W WO 2023051482 A1 WO2023051482 A1 WO 2023051482A1
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distance
laser
receiving
laser beam
receiving system
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PCT/CN2022/121526
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English (en)
French (fr)
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舒博正
夏冰冰
石拓
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北京一径科技有限公司
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/06—Systems determining position data of a target
    • G01S17/08—Systems determining position data of a target for measuring distance only
    • G01S17/10—Systems determining position data of a target for measuring distance only using transmission of interrupted, pulse-modulated waves
    • G01S17/14—Systems determining position data of a target for measuring distance only using transmission of interrupted, pulse-modulated waves wherein a voltage or current pulse is initiated and terminated in accordance with the pulse transmission and echo reception respectively, e.g. using counters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
    • Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

Definitions

  • the present disclosure relates to the technical field of radar, in particular to a laser radar ranging method and a laser radar system.
  • the maximum measurement distance of each scanning point is limited by the resolution of the point cloud, the number of frames, and the total number of lasers.
  • the maximum measurement distance and the resolution of the point cloud is basically inversely proportional to the relationship.
  • a first aspect of the present disclosure provides a lidar ranging method, including:
  • the nth receiving system in the receiving system receives the echo of the n+N*m laser beam emitted by the transmitting system within a receiving window whose time length is greater than the transmitting interval and not greater than N said transmitting intervals, wherein the The transmitting system emits multiple laser beams according to the transmitting interval, the number of the receiving systems is N, N ⁇ 2, n is a positive integer less than or equal to N, and m is a natural number;
  • the nth receiving system determines the ranging result according to the echo receiving result.
  • the receiving viewing angle of the nth receiving system for the n+N*m laser beam is set according to the emitting viewing angle of the n+N*m laser beam, wherein different from the The receiving angle receives the echoes of laser beams with different emitting angles.
  • the determining the ranging result by the nth receiving system according to the echo receiving result includes:
  • the candidate distances that do not satisfy the preset condition are filtered out to obtain a ranging result of the nth receiving system within the receiving window for the n+N*mth laser beam.
  • the determining whether each of the candidate distances satisfies a preset condition includes:
  • the target reflectivity the laser emitted by the laser radar passes through the reflectivity at the stated alternative distance;
  • the candidate distance satisfies the preset condition.
  • the laser parameters of the laser beams at two adjacent emitting points are different;
  • the nth receiving system determines the ranging result according to the echo receiving result, including:
  • the laser parameters of the n+N*m laser beam filtering the n+N*m laser beam received by the nth receiving system within the time window that does not match the laser parameters echo, obtaining the remaining echo received by the nth receiving system;
  • a ranging result for the n+N*mth laser beam is determined according to the remaining echoes received by the nth receiving system.
  • the laser parameters include at least one of the following:
  • the pulse time interval between adjacent pulses in a laser beam is a pulse time interval between adjacent pulses in a laser beam.
  • the start moment of the time window of the nth receiving system for the n+N*mth laser beam is determined according to the emission moment of the n+N*mth laser beam.
  • the second aspect of this embodiment provides a laser radar system, including: a transmitting system and N receiving systems;
  • the emission system is used to emit multiple laser beams according to emission intervals
  • the nth receiving system among the N receiving systems is used to receive the n+N*mth beam transmitted by the transmitting system within a receiving window whose time length is greater than the transmitting interval and not greater than N transmitting intervals
  • the echo of the laser beam where, 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;
  • the nth receiving system is also used to determine the ranging result according to the echo receiving result.
  • FIG. 1 is a schematic diagram of an implementation flow of a lidar ranging method according to an embodiment of the present disclosure.
  • FIG. 2 is a schematic diagram of a specific implementation flow of step S13 in FIG. 1 .
  • FIG. 3 is a schematic diagram of a specific implementation flow of step S22 in FIG. 2 .
  • FIG. 4 is a schematic flowchart of another specific implementation of step S13 in FIG. 3 .
  • FIG. 5 is a schematic diagram of signal reception performed by a traditional lidar system provided by an embodiment of the present disclosure.
  • FIG. 6 is a schematic diagram of signal reception using a laser radar ranging method according to an embodiment of the present disclosure.
  • FIG. 7 is a schematic diagram of overlapping regions in signals of a receiving system according to an embodiment of the disclosure.
  • Fig. 8 is a schematic structural diagram of a laser radar system according to an embodiment of the present disclosure.
  • 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 number of the lidar point cloud is M frames per second, the resolution of the point cloud is L a ⁇ L e , and the total number of lasers is K, then the number of point cloud points that a single laser is responsible for is Therefore, it can be calculated that the measurement time period of each point is at most seconds, so the maximum measurement distance is Among them, L a is the number of points in the upward direction of the scanning point, Le is the number of points in the azimuth direction of the scanning point, and C is the speed of light. It can be seen that when designing a radar system, the maximum measurement distance and the frame number and resolution of the point cloud are basically inversely proportional.
  • embodiments of the present disclosure provide a laser radar ranging method and a laser radar system, which solve the problem in the related art that increasing the number of lasers increases the maximum measurement distance but increases the complexity of system design.
  • Fig. 1 is a flowchart of a lidar ranging method according to some embodiments of the present disclosure.
  • the laser radar ranging method according to the embodiments of the present disclosure can be applied to any laser radar, such as MEMS (Micro-Electro-Mechanical System, micro-electro-mechanical system) scanning, mechanical rotary scanning and other laser radars.
  • MEMS Micro-Electro-Mechanical System, micro-electro-mechanical system
  • mechanical rotary scanning and other laser radars.
  • step S11 the nth receiving system in the receiving system receives the return of the n+N*mth laser beam emitted by the transmitting system within the receiving window whose time length is greater than the transmitting interval and not greater than N said transmitting intervals wave, where N is the number of the receiving systems, N ⁇ 2, n is a positive integer less than or equal to N, m is a natural number, and the transmitting system emits multiple laser beams according to the transmitting interval.
  • the design method of multiple sets of independent receiving systems is used to improve the problem of shortening the maximum measurement distance due to the insufficient measurement time period of a single point during ranging, and at the same time reduce the complexity of lidar design , that is, through a transmitting system, the laser beam is emitted according to the emission cycle according to the laser emission sequence.
  • the transmitting system performs laser scanning on the target, it will emit multiple laser beams to form a point cloud.
  • the laser beams are emitted according to the emission cycle according to the order of the laser emission points, so that the laser radar system does not need to be designed.
  • Multiple launch systems reduce the complexity of radar system design.
  • the emission interval refers to the emission time interval of adjacent laser beams, for example, the emission system emits a laser beam every 0.01 second.
  • the laser emission points can emit light in the order of 1, 2, 3, 4..., as shown in Figures 5 to 7; among them, 1, 2, 3, 4... can be understood as points on the point cloud of the laser radar
  • the number, that is, the point number marked according to the order of light emission, the order of laser emission is directly related to the resolution.
  • Each of the plurality of laser beams according to an embodiment of the present disclosure may be a light pulse.
  • the transmission system may transmit light pulses at transmission intervals.
  • the receiving window whose time length is greater than the transmission interval and not greater than N transmission intervals refers to a time length that is greater than the transmission interval and not greater than N transmission intervals, and within this time length the nth receiving system receives The echoes of the n+N*mth laser beam emitted by the emitting system, where m is the number of this time length.
  • the time length of the receive window may be N transmit intervals.
  • the radar system includes one transmitting system and four receiving systems.
  • the emission points of the emission system are 100, that is, the emission system emits 100 beams of lasers according to the emission interval, and the 4 receiving systems receive the 100 beams of lasers, then for the emission points 1-100, the receiving systems corresponding to each point are respectively Cycle for 1,2,3,4,1,2,3,4 in turn.
  • 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, and the laser at point 3 is received by receiving system A Receiving, the laser light at point 4 is received by the receiving system B, and circulates in turn, that is, the laser light at the adjacent emitting point is received by different receiving systems.
  • the starting moment of the time window for receiving the n+N*m laser beam of the nth receiving system may be determined according to the emission time of the n+N*m laser beam.
  • the start time of the time window may be equal to or earlier than the emission time of the n+N*m laser beam. This ensures that objects at a distance of 0m from the lidar system are successfully measured.
  • the number of transmitting points is not in multiples of the number of receiving systems, when there are not enough N laser beams in the end, it is still based on: the nth receiving system receives the echo of the n+N*m laser beam; , 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 to say, the transmission point is matched with N as the divisor, and different point numbers are allocated to the respective receiving systems for processing according to the difference in the remainder.
  • the radar system includes 6 receiving systems, and the transmitting point of the transmitting system is 100, so for the 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 are received in order.
  • step S12 the nth receiving system determines the ranging result according to the echo receiving result.
  • the radar system may include a transmitting system and N receiving systems, the transmitting system transmits laser beams according to transmitting intervals, and the nth receiving system is greater than the transmitting interval and not greater than N transmitting intervals
  • the receiving window the echo of the n+N*m laser beam emitted by the transmitting system is received, n is a positive integer less than or equal to N, and m is a natural number; then the nth receiving system determines the measured distance from the result.
  • the number of receiving systems is not specifically limited in this embodiment, and it is at least two, so that adjacent laser beams are received by different receiving systems.
  • End-receiver system mapping that is, multiple sets of independent receiving systems are used to independently receive echoes from different points, which can extend the measurement time of each point on the point cloud.
  • the time length of the receiving window of each receiving system can be extended from the traditional equal to the transmission interval to be longer than the transmission interval and not greater than N transmission intervals.
  • a single laser beam can still be detected after being reflected by a distant object, thereby achieving an increase in the maximum measurement distance without changing the resolution of the point cloud and reducing the number of frames, and reducing the radar System design complexity.
  • Figure 5 shows the transmit and receive logic of a conventional imaging lidar. After each point is emitted, the corresponding echo begins to receive processing, and the receiving window continues until the next point's light-emitting moment, and the measurement time is short. For example, the measurement time of receiving window 1 of point cloud 1 in FIG. 5 is less than or at most equal to the emission interval of laser points.
  • the method according to the embodiment of the present disclosure prolongs the measurement time of each point, there may be a time overlap between the measurement start time and end time of each point, so the logic of the control transmission system and the algorithm improvement of the data processing end are needed , to achieve the distance resolution of adjacent points and solve the ranging ambiguity problem caused by time overlap.
  • the two independent receiving systems distinguish and receive the laser light at the transmitting point.
  • the method of odd and even points is used to map different receiving systems for data processing and analysis.
  • A is processed, even points are processed by receiving system B.
  • 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
  • the laser at point 4 is received by receiving system B.
  • the measurement time of each point can be greater than the emission interval of the laser point and not greater than twice the emission interval (because there are two sets of receiving systems A and B). It can be seen that, under the condition that the lighting sequence does not change, by adjusting the distribution of receiving systems at different points, the measurement time of each point can be extended, thereby realizing the extension of the maximum measurement distance.
  • the system may have the problem of distance ambiguity in processing, that is, multiple distances may be measured according to the echoes of each receiving system, as shown in Figure 6, the measurement of point 1 is the responsibility of receiving system A Yes, the measurement of point 2 is the responsibility of receiving system B, but within the measurement time window of point 1, there will be the time when point 2 emits light, that is to say, the measurement time window of point 2 and the measurement of point 1
  • the time windows overlap, and the overlapping area is shown in Figure 7.
  • the receiving overlapping area there will be echoes from point 1 and point 2 at the same time.
  • various methods may be adopted to avoid or differentiate.
  • the receiving viewing angle of the nth receiving system for the n+N*m laser beam is set according to the emitting viewing angle of the n+N*m laser beam, so that the receiving viewing angle can match the emitting viewing angle , so that different receiving viewing angles are suitable for receiving echoes of laser beams with different emitting viewing angles.
  • each receiving system is capable of receiving echoes of corresponding laser beams from different emission viewing angles at different receiving viewing angles.
  • the receiving viewing angles of the corresponding receiving systems are set according to the emitting viewing angles of the laser beams, so that the receiving viewing angles of adjacent receiving systems are different, and then different receiving systems receive the echoes of laser beams with different emitting viewing angles, and then It is possible to reduce the echoes of laser beams received by each receiving system from other emission angles of view.
  • 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 realize the echo of the laser beam at the No. 1 emission point received by receiving system 1 and receiving system 2 Spatial isolation between the echoes of the received laser beams at the No. 2 emission point, so as to realize the echo distinction between No. 1 point and No. 2 point.
  • the receiving angle of view of each receiving system may be set according to parameters such as the number of transmitting points and/or the maximum scanning angle of the transmitting system.
  • the emission angle of each emission point can be determined according to the number of emission points and the maximum scanning angle of the emission system, and then the reflection angle can be determined, and the receiving viewing angle of the receiving system can be further determined.
  • the receiving viewing angle of the corresponding receiving system may also be directly set according to the transmitting angle of each transmitting point.
  • the number of receiving systems can be reduced, thereby reducing the size of the radar system.
  • the nth receiving system determines the ranging result according to the echo receiving result, including:
  • step S21 a corresponding candidate distance is determined according to each echo signal received by the nth receiving system within the time window for the n+N*mth laser beam.
  • the receiving viewing angles of each receiving system may be the same or different, and there is no need to consider the receiving viewing angles of the receiving systems, thereby reducing the design complexity of the receiving systems.
  • the farthest measurement distance is basically inversely proportional to the frame number and resolution of the point cloud.
  • increasing the number of lasers can increase the maximum measurement distance without changing the resolution of the point cloud and reducing the number of frames
  • the solution to increase the number of lasers requires the use of multiple sets of emitting devices including lasers with different wavelengths and simultaneously
  • the receiving end needs to match the transmitting devices of different wavelengths, so it is necessary to design a separate filter to shield lasers of other wavelengths, which has great complexity in system design and difficulty in engineering practice, and has uncontrollable factors.
  • the embodiments of the present disclosure use multiple sets of independent receiving systems to improve the problem that the maximum measurement distance is shortened due to the insufficient ranging time of a single point during ranging, and at the same time, the echo between multiple sets of receiving systems is adopted. Special system design to improve the problem of distance ambiguity.
  • Embodiments of the present disclosure use the relationship between signal strength and distance to distinguish overlapping echo signals in terms of processing algorithms.
  • the echo intensity of the target is inversely proportional to the square of the distance where the target is located, so the overlapping area can be judged by the echo signal received by the receiving system.
  • the nth receiving system may also receive interference echoes other than the n+N*m laser beam.
  • Embodiments of the present disclosure determine the corresponding candidate distance according to each echo signal received by the nth receiving system, and the interference echo can be filtered out according to the candidate distance.
  • the receiving system A receives the echo of the laser beam of the emission point 1 and the echo of the laser beam of the emission point 2 in the overlapping area, and at this time it is necessary to determine the alternative distance R1 of the emission point 1 As well as the candidate distance R2 of the transmitting point 2, determine whether there is an interference echo in the receiving system A according to the candidate distances R1 and R2, so as to make the ranging result of the receiving system A more accurate.
  • the receiving system 2 receives the 2nd transmitting point, the 7th transmitting point, the 12th transmitting point...the 47th transmitting point, the 52nd transmitting point..., such as receiving
  • the receiving system 2 receives the 2nd transmitting point, the 7th transmitting point, the 12th transmitting point...the 47th transmitting point, the 52nd transmitting point..., such as receiving
  • the echo of the laser beam at the 52nd emission point it is possible to also receive the echo of the laser beam at the 48th, 49th, 50th, and 51st emission points.
  • the echo of the laser beam at the transmitting point determines the corresponding candidate distance, and determines whether there is an interference echo in the receiving system 2 according to the corresponding candidate distance, so that the ranging result of the receiving system 2 is more accurate and the distance ambiguity is reduced.
  • echo signals whose signal strength does not meet the condition can be filtered out; it can also be determined according to the distance value of each echo signal in the receiving system, if If the distance value does not meet the distance condition, the corresponding echo signal that does not meet the distance condition will be filtered out; the interference signal can also be filtered out according to the pulse number of the echo signal in the receiving system, the timing information of the received echo signal and other information.
  • step S22 it is determined whether each candidate distance satisfies a preset condition.
  • the candidate distances that do not meet the preset conditions are filtered out to obtain the remaining candidate distances, which are the ranging results in the receiving window of the nth receiving system ; If the alternative distances all meet the preset conditions, no filtering is required, that is, the distances determined by the echo signals of the nth receiving system are all target distances.
  • the interference echo can be discriminated in the receiving overlapping area of point 1 and point 2.
  • the overlapping area belongs to the end of the ranging time window, that is, the long-distance target. Therefore, the echo signal strength should be small.
  • the overlapping area belongs to the front end of the ranging time window, that is, the short-distance target, so the signal strength should be relatively high. Therefore, in this embodiment, by determining whether the candidate distance satisfies the preset condition, the candidate distance that does not meet the preset condition can be filtered out from the nth receiving system, so as to realize the screening of the echo interference signal of the receiving system, and remove The interference echo signal is the candidate distance obtained by removing the interference echo signal.
  • the preset conditions corresponding to each receiving system are different. As shown in Figure 7, 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-range target Target, therefore, the candidate distance determined by each receiving system based on the interference echo is different, some receiving systems may have a large candidate distance, and some receiving systems may have a small candidate distance, such as the overlapping area of point 1
  • the determined candidate distance is relatively large, and the corresponding preset condition is also relatively large. For example, the candidate distance determined by the overlapping area of point 2 is relatively small, and the corresponding preset condition is also relatively small.
  • determining whether each candidate distance satisfies a preset condition includes:
  • step S31 perform the difference calculation between the candidate distance and the distance determined according to the launch interval to obtain the distance difference, and perform the sum operation between the candidate distance and the distance determined according to the launch interval to obtain distance and value.
  • the emission interval can also be said to be the timing information of adjacently emitted laser light, 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, T N is the emission interval between adjacent laser emission moments, C is the speed of light, is the distance determined according to the launch interval.
  • step S32 the first upper limit is determined according to the distance difference and the target reflectivity, and the first lower limit is determined according to the distance sum value and the target reflectivity; wherein, the target reflectivity is: the reflection of the laser emitted by the lidar through the alternative distance Rate.
  • Embodiments of the present disclosure utilize the principle that the distance and target reflectivity can be used to determine the echo signal strength and the distance is inversely proportional to the echo signal strength.
  • the reflectivity of the target can be deduced according to the strength of the echo signal and the alternative distance.
  • the first upper limit and the first lower limit are respectively determined by using the derived target reflectivity and the distance range varied on the basis of the corresponding candidate distance. Specifically, the first upper limit is determined according to the distance difference and target reflectivity, expressed as Where ⁇ r is the reflectivity of the target; the first lower limit is determined according to the distance sum value and the reflectivity of the target, expressed as Where ⁇ r is also the reflectivity of the target.
  • step S33 the second upper limit is determined according to the candidate distance and the maximum reflectivity of the laser, and the second lower limit is determined according to the candidate distance and the minimum reflectivity of the laser.
  • the embodiments of the present disclosure also constrain the signal strength determined by the candidate distance according to 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 in the embodiments of the present disclosure can be understood as reflection intensity or reflectivity intensity.
  • the second upper limit is determined according to the alternative distance and the maximum reflectivity of the laser, expressed as p(R, ⁇ 100 )
  • the second lower limit is determined according to the alternative distance and the minimum reflectivity, expressed as p(R, ⁇ 1 ) , wherein, ⁇ 1 is the minimum reflectivity of the laser, for example, the reflectivity is 1, and ⁇ 100 is the maximum reflectivity of the laser, for example, the reflectivity is 100.
  • step S34 if the signal strength corresponding to the candidate distance is between the first upper limit and the first lower limit, and the signal strength corresponding to the candidate distance is between the second upper limit and the second lower limit, it is determined that the candidate distance satisfies the preset condition.
  • the candidate distance needs to be filtered out to obtain the remaining candidate distance, and the remaining candidate distance is used as the nth receiving system for the first Ranging results within the receiving window of n+N*m laser beams.
  • the alternative distance does not need to be filtered out; if the signal strength obtained according to the alternative distance is not located between the second upper limit and the second lower limit time, it is necessary to filter out the candidate distance to obtain the remaining candidate distance.
  • the alternative distance need not be filtered out; 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 the alternative distance needs to be filtered out, The remaining candidate distance is obtained, and the remaining candidate distance is used as a ranging result of the nth receiving system within the receiving window for the n+N*mth laser beam.
  • the alternative distance determined by the echo that appears in the overlapping area corresponding to point No. 1 is R 1 , that is, according to the receiving system A
  • the candidate distance for the unknown target determined by the interference echo of the receiving system B, the candidate distance determined by the echo appearing in the overlapping area corresponding to point 2 is R 2 , that is, the candidate distance for the unknown target is determined according to the interference echo of the receiving system B Select distance.
  • the reflected signal strength p(R, ⁇ r ) is determined according to the alternative distance and reflectivity, and whether the reflected signal strength p(R, ⁇ r ) is between the first upper limit and the first lower limit is determined. Specifically, the reflected signal strength p(R, ⁇ r ) should satisfy
  • the candidate distance R corresponding to the reflected signal strength p(R, ⁇ r ) is filtered out.
  • filter R 1 out that is, in the receiving system A corresponding to R 1 Echo filtering; or, if the reflected signal strength p(R 2 , ⁇ r ) determined by R 2 and the reflectivity of the corresponding unknown target does not meet the above conditions, then filter R 2 , that is, the receiving system B and R 2 corresponds to echo filtering.
  • the embodiment of the present disclosure determines the candidate distance according to each echo signal through the relationship between the distance and the signal strength, and then filters out the candidate distances that do not meet the preset conditions, the filtering efficiency is better, and the distance repetition phenomenon is improved.
  • the ranging accuracy of the radar system is greatly improved.
  • the laser parameters of the laser beams at two adjacent emission points may be different.
  • the laser parameters refer to various parameters of the laser beam output by the emitting system, such as the number of pulses of the laser beam at a single emission point, the time interval between adjacent pulses, and the like.
  • the nth receiving system determines the ranging result according to the echo receiving result, including:
  • step S41 according to the laser parameters of the n+N*m laser beam, the echo received by the nth receiving system in the time window for the n+N*m laser beam is different from the laser parameters, Obtain the remaining echoes received by the nth receiving system.
  • step S42 the ranging result for the n+N*mth laser beam is determined according to the remaining echoes received by the nth receiving system.
  • the transmitting logic with different laser parameters of the laser beams at two adjacent transmitting points is adopted, so that each receiving system receives the echoes of the laser beams with different transmitting logics, and at the same time according to
  • the laser parameters of the n+N*m laser beam are used to filter out echoes received by the nth receiving system that are different from the laser parameters, and obtain the remaining intensity of the received intensity of the nth receiving system.
  • this embodiment does not limit the specific values of the laser parameters, nor does it limit the number of receiving systems, at least two, as long as the laser parameters of the laser beams at two adjacent emission points are different, different
  • the receiving system can receive the echoes of laser beams with different laser parameters.
  • the interference echo is filtered through the laser parameters, the filtering effect is better, more accurate, the interference between signals is reduced, and the method is easier to implement, thereby reducing the distance as much as possible Repeatedly, the accuracy of ranging results is improved, and the ranging distance is extended at the same time.
  • the laser parameters include at least one of the following: the number of pulses contained in a single laser beam emission, the pulse time interval of adjacent pulses in the laser beam, but not limited to the number of pulses, the code combination method of the pulse time interval .
  • This embodiment can adopt the system of multi-pulse emission, and the light-emitting logic (laser parameters) of adjacent points can adopt the number of pulses contained in different single-shot laser beams, or the pulse time interval of adjacent pulses in different laser beams , or any combination of two, etc.
  • different data processing methods can be used to distinguish targets. For example, for No. 1 emission point, adopt the emission system of two pulses with a pulse interval of N 2 ; for No. 2 emission point, adopt the emission system of three pulses with pulse intervals of N 2 and N 3 , and so on.
  • the two-pulse data processing method can be used for screening
  • the three-pulse data processing method can be used for screening, so as to realize the distinction of adjacent points in the overlapping area, with high precision and weakened
  • the distance ambiguity phenomenon improves the distance measurement accuracy.
  • the embodiments of the present disclosure solve the problem of conflicting maximum measurement distance, point cloud resolution and frame rate in existing lidar systems.
  • the receiving relationship of the receiving system using one transmitting system and multiple receiving systems, prolongs the measurement time, realizes the improvement of the maximum measurement distance, and reduces the design complexity of the system; at the same time, in order to solve the problem of distance ambiguity, the system design has been carried out Processing optimization, by changing the emission logic of the emitted laser beams, there is no need to design multiple emission systems, which reduces the complexity of radar system design, so that adjacent laser beams are received by different receiving systems, weakening the distance ambiguity.
  • Fig. 8 is a block diagram of a laser radar system according to an exemplary embodiment.
  • the system includes: a transmitting system 100 and N receiving systems 200 .
  • the emission system 100 emits laser beams at emission intervals.
  • the nth receiving system 200 receives the echo of the n+N*m laser beam emitted by the transmitting system within a receiving window whose time length is greater than the transmitting interval and not 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; m is a natural number.
  • the nth receiving system 200 determines the ranging result according to the echo receiving result.
  • the receiving angle of view of the n+N*m laser beam of the receiving system 200 is set according to the emission angle of the n+N*m laser beam, wherein different receiving angles of view receive different emission angles of view The echo of the laser beam.
  • the nth receiving system 200 is specifically used for:
  • the candidate distances that do not meet the preset conditions are filtered out to obtain the ranging result of the nth receiving system within the receiving window for the n+N*mth laser beam.
  • the nth receiving system 200 is specifically used for:
  • the target reflectivity the reflectivity of the laser emitted by the laser radar through the alternative distance
  • the candidate distance satisfies the preset condition.
  • the laser parameters of the laser beams at two adjacent emitting points are different; the nth receiving system 200 is specifically used for:
  • the laser parameters of the n+N*m laser beam filter out the echo received by the nth receiving system in the time window for the n+N*m laser beam that is different from the laser parameters, and obtain the nth receiving system received residual echo;
  • the ranging result for the n+N*mth laser beam is determined.
  • the laser parameters include at least one of the following: the number of pulses included in a single emission of the laser beam, and the pulse time interval between adjacent pulses in the laser beam.

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Abstract

公开了一种激光雷达测距方法和激光雷达系统。该方法包括：由接收系统中的第n接收系统在时间长度大于发射间隔且不大于N个发射间隔的接收窗内，接收发射系统发射的第n+N*m束激光光束的回波，其中，发射系统按照发射间隔发射多束激光光束，接收系统的个数为N，N≥2，n为小于或等于N的正整数，m为自然数。该方法还包括由所述第n接收系统根据回波接收结果，确定测距结果。

Description

激光雷达测距方法和激光雷达系统
本申请是以中国申请号为202111141316.9，申请日为2021年9月28日，名称为“激光雷达测距方法和激光雷达系统”的中国专利申请为基础，并主张其优先权，该中国专利申请的公开内容在此作为整体引入本申请中。
技术领域
本公开涉及雷达技术领域，特别是涉及一种激光雷达测距方法和激光雷达系统。
背景技术
在激光雷达体制中，从系统设计层面考虑，每个扫描点的最大测量距离受限于点云的分辨率、帧数和总激光器数量等各方面，其中，最大测量距离与点云的分辨率、帧数基本上是反比的关系。
发明内容
本公开的第一方面提供了一种激光雷达测距方法，包括：
由接收系统中的第n接收系统在时间长度大于发射间隔且不大于N个所述发射间隔的接收窗内，接收发射系统发射的第n+N*m束激光光束的回波，其中，所述发射系统按照所述发射间隔发射多束激光光束，所述接收系统的个数为N，N≥2，n为小于或等于N的正整数，m为自然数；
由第n接收系统根据回波接收结果，确定测距结果。
根据本公开的一些实施例，所述第n接收系统针对第n+N*m束激光光束的接收视角是根据第n+N*m束激光光束的发射视角来设置的，其中，不同所述接收视角接收不同发射视角的激光光束的回波。
根据本公开的一些实施例，所述由第n接收系统根据回波接收结果，确定测距结果，包括：
根据第n接收系统在针对第n+N*m束激光光束的所述时间窗内接收的每个回波信号确定对应的备选距离；
确定每个所述备选距离是否满足预设条件；
将不满足所述预设条件的所述备选距离滤除，得到所述第n接收系统在针对第n+N*m 束激光光束的所述接收窗内的测距结果。
根据本公开的一些实施例，所述确定每个所述备选距离是否满足预设条件，包括：
进行所述备选距离与根据发射间隔所确定的距离之间的差值运算，得到距离差值，进行所述备选距离与根据发射间隔所确定的距离之间的和运算，得到距离和值；
根据所述距离差值和目标反射率确定第一上限，根据所述距离和值和所述目标反射率确定第一下限；其中，所述目标反射率为：所述激光雷达发射的激光经过所述备选距离的反射率；
根据所述备选距离和所述激光的最大反射率确定第二上限，并根据所述备选距离和所述激光的最小反射率确定第二下限；
若所述备选距离对应的信号强度位于所述第一上限和所述第一下限之间，且所述备选距离对应的信号强度位于所述第二上限和所述第二下限之间，确定所述备选距离满足所述预设条件。
根据本公开的一些实施例，相邻两个发射点的激光光束的激光参数不同；
所述由第n接收系统根据回波接收结果，确定测距结果，包括：
根据第n+N*m束激光光束的激光参数，滤除所述第n接收系统在针对第n+N*m束激光光束的所述时间窗内接收到的与所述激光参数不匹配的回波，得到所述第n接收系统接收的剩余回波；
根据所述第n接收系统接收的剩余回波，确定针对第n+N*m束激光光束的测距结果。
根据本公开的一些实施例，所述激光参数包括以下至少之一：
单次发射激光光束包含的脉冲个数；
激光光束中相邻脉冲的脉冲时间间隔。
根据本公开的一些实施例，所述第n接收系统的针对第n+N*m束激光光束的所述时间窗的起始时刻根据第n+N*m束激光的发射时刻确定。
本实施例的第二方面提供了一种激光雷达系统，包括：一个发射系统和N个接收系统；
所述发射系统用于按照发射间隔发射多束激光光束；
所述N个接收系统中的第n接收系统用于在时间长度大于所述发射间隔且不大于N个所述发射间隔的接收窗内，接收所述发射系统发射的第n+N*m束激光光束的回波；其中，N为接收系统的个数，N≥2；n为小于或等于N的正整数；m为自然数；
所述第n接收系统还用于根据回波接收结果，确定测距结果。
附图说明
图1为根据本公开的实施例的一种激光雷达测距方法的实现流程示意图。
图2为图1中步骤S13的具体实现流程示意图。
图3为图2中步骤S22的具体实现流程示意图。
图4为图3中步骤S13的另一种具体实现流程示意图。
图5为本公开实施例提供的传统激光雷达系统进行信号接收的示意图。
图6为采用根据本公开的实施例的激光雷达测距方法进行信号接收的示意图。
图7为根据本公开的实施例的接收系统的信号中重叠区域的示意图。
图8为根据本公开的实施例的一种激光雷达系统的结构示意图。
具体实施方式
这里将详细地对示例性实施例进行说明，其示例表示在附图中。下面的描述涉及附图时，除非另有表示，不同附图中的相同数字表示相同或相似的要素。以下示例性实施例中所描述的实施方式并不代表与本公开相一致的所有实施方式。相反，它们仅是与如所附权利要求书中所详述的、本公开的一些方面相一致的系统和方法的例子。
在进行激光雷达系统设计时，通常激光雷达中每个扫描点的最大测量距离会受限于点云的分辨率、点云的帧数以及总激光器数量。例如，如果激光雷达点云的帧数为M帧/秒，点云的分辨率为L a·L e，总共激光器的数量为K个，那么单个激光器负责的点云点数为
Figure PCTCN2022121526-appb-000001
于是可以算出每个点的测量时间周期最大为
Figure PCTCN2022121526-appb-000002
秒，所以最大测量距离为
Figure PCTCN2022121526-appb-000003
其中，L a为扫描点的仰向点数，L e为扫描点的方位向点数，C为光速。可见，在进行雷达系统设计时，最大测量距离和点云的帧数和分辨率基本上是反比的关系。
在相关技术中，虽然通过增加激光器的个数可以在不改变点云分辨率和不降低帧数的情况下提升最大测量距离，但是也会增加系统设计复杂度，同时给后期点云拼接和标定带来困难。
基于上述原因，本公开的实施例提供了一种激光雷达测距方法和激光雷达系统，解决相关技术中通过增加激光器的个数来提升最大测量距离但会增加系统设计复杂度的问题。
图1是根据本公开的一些实施例的一种激光雷达测距方法的流程图。根据本公开的实 施例的激光雷达测距方法可以适用于任意激光雷达，例如MEMS(Micro-Electro-Mechanical System，微机电系统)扫描、机械旋转式扫描等激光雷达。
在步骤S11中，由接收系统中的第n接收系统在时间长度大于发射间隔且不大于N个所述发射间隔的接收窗内，接收发射系统发射的第n+N*m束激光光束的回波，其中N为所述接收系统的个数，N≥2，n为小于或等于N的正整数，m为自然数，发射系统按照所述发射间隔发射多束激光光束。
根据本公开的实施例采用多套独立接收系统的设计方法，改善在测距时出现因为单个点的测量时间周期不够长而导致最大测量距离缩短的问题，同时降低激光雷达在设计时的复杂度，即通过一个发射系统，根据激光发射顺序，按照发射周期发射激光光束。具体地，发射系统在对目标进行激光扫描时，会发射多个激光光束形成点云，根据本公开的实施例根据激光发射点的顺序，按发射周期发射激光光束，以使激光雷达系统无需设计多个发射系统，降低了雷达系统设计的复杂度。
这里，发射间隔是指相邻激光光束的发射时间间隔，例如发射系统每隔0.01秒发射一束激光。按照发射间隔，激光发射点可以按顺序1,2,3,4……进行发光，如图5至7；其中，1,2,3,4……可以理解为激光雷达的点云上的点号，即按照发光顺序来标注的点号，激光发射顺序和分辨率直接相关。
根据本公开的实施例的多束激光光束中的每束激光光束可以是光脉冲。发射系统可以按照发射间隔发射光脉冲。
这里，时间长度大于所述发射间隔且不大于N个所述发射间隔的接收窗，是指以大于发射间隔且不大于N个发射间隔为一个时间长度，在这个时间长度内第n接收系统接收所述发射系统发射的第n+N*m束激光的回波，m为这个时间长度的个数。在一些实施例中，该接收窗的时间长度可为N个发射间隔。
示例性地，雷达系统包括一个发射系统和4个接收系统。发射系统的发射点为100，即发射系统按照发射间隔发射100束激光，4个接收系统对该100束激光进行接收，那么对1-100号发射点来说，每个点对应的接收系统分别为1,2,3,4,1,2,3,4依次循环。再例如，如图6和7所示，雷达系统包括2个接收系统，1号点的激光被接收系统A接收，2号点的激光被接收系统B接收，3号点的激光被接收系统A接收，4号点的激光被接收系统B接收，依次循环，即相邻发射点的激光被不同的接收系统接收。
这里，第n接收系统的接收第n+N*m束激光的时间窗的起始时刻可以根据第n+N*m束激光的发射时刻确定。例如，为了确保成功接收第n+N*m束激光的回波，则可以将时间窗的起始时刻等于或早于第n+N*m束激光的发射时刻。这样可以确保距离激光雷达系 统0m的物体被成功测量到。
在一些实施例中，若发射点数与接收系统个数不成倍数关系，则在最后不够N个激光光束的时候，依然根据：第n接收系统接收第n+N*m束激光的回波；其中，N为接收系统的个数，N≥2；n为小于或等于N的正整数；m为自然数。也就是说，发射点配套以N为除数，根据余数的不同对不同点号分配各自的接收系统进行处理。例如，雷达系统包括6个接收系统，发射系统的发射点为100，那么对1-100号发射点来说，每个点对应的接收系统分别为1,2,3,4,5,6,1,2,3,4,5,6,……1,2,3,4,5,6,1,2,3,4的顺序进行接收。
在步骤S12中，由第n接收系统根据回波接收结果，确定测距结果。
示例性地，参见图8，雷达系统可以包括一个发射系统和N个接收系统，发射系统按照发射间隔发射激光光束，第n接收系统在大于所述发射间隔且不大于N个所述发射间隔的接收窗内，接收所述发射系统发射的第n+N*m束激光的回波，n为小于或等于N的正整数，m为自然数；然后第n接收系统根据回波接收结果，确定测距结果。应理解，本实施例对接收系统的个数不进行具体的限定，至少为两个，以使相邻激光光束被不同的接收系统接收。
本实施例在不改变发射系统硬件配置(即无需增加发射装置或激光器数量，因此未改变点云分辨率、帧率)的前提下，只对接收端的系统进行多套冗余接收，通过改变发射端-接收端的系统映射，即采用多套独立接收系统进行独立接收不同点的回波，可以实现点云上的每个点测量时间延长。例如，每个接收系统的接收窗的时间长度可以从传统的等于发射间隔延长为大于发射间隔且不大于N个发射间隔。通过延长接收窗的时间长度，单个激光束被较远处的物体反射回后依然能够被检测到，进而实现在不改变点云分辨率和降低帧数的情况下实现提升最大测量距离，降低雷达系统设计复杂度。
图5示出了常规激光成像雷达的发射和接收逻辑。在每个点发射之后，对应的回波开始接收处理，接收窗延续直到下一个点的发光时刻之前，测量时间较短。例如，图5中点云1的接收窗1的测量时间小于或者至多等于激光点的发射间隔。虽然根据本公开的实施例的方法使得每个点的测量时间延长，但各个点之间的测量起始时刻和结束时刻可能会存在时间重叠，因此需要控制发射系统的逻辑和数据处理端的算法改进，来实现相邻点的距离分辨，解决时间重叠引起的测距模糊问题。
示例性地，以两套独立接收系统为例，两套独立接收系统对发射点的激光进行区分接收，例如采用奇偶点的方式来映射不同的接收系统进行数据处理和分析，奇数点采用接收系统A进行处理，偶数点采用接收系统B进行处理。如图6所示，1号点的激光被接收系统A接收，2号点的激光被接收系统B接收，3号点的激光被接收系统A接收，4号点 的激光被接收系统B接收，依次循环，其中每个点的测量时间可以大于激光点的发射间隔且不大于发射间隔的两倍(因为有A和B两套接收系统)。可见，在发光时序不变动的情况下，通过调整不同点的接收系统分配，可以实现延长各个点的测量时间，从而实现最大测量距离的延长。
但是，该系统在处理上可能会出现距离模糊的问题，也就是根据每个接收系统的回波可能会测量出多个距离，如图6所示，1号点的测量是接收系统A来负责的，2号点的测量是接收系统B来负责的，但是1号点的测量时间窗内，会出现2号点发光的时间，也就是说2号点的测量时间窗和1号点的测量时间窗存在重叠，重叠区域如图7所示。在接收重叠区域，会同时存在1号点和2号点的回波。针对这种情况，根据本公开的进一步的实施例可以采取多种方法进行规避或区分。
在一些实施例中，第n接收系统针对第n+N*m束激光光束的接收视角是根据第n+N*m束激光光束的发射视角来设置的，这样接收视角可以与发射视角相匹配，使得不同接收视角适于接收不同发射视角的激光光束的回波。在一些示例中，各接收系统能够以不同接收视角接收不同发射视角的相应激光光束的回波。
根据本公开的实施例根据激光光束的发射视角设置相应接收系统的接收视角，可以使相邻接收系统的接收视角均不相同，进而不同的接收系统接收不同发射视角的激光光束的回波，进而可以减少每个接收系统接收其他发射视角的激光光束的回波。示例性地，雷达系统包括2个接收系统，设置每个接收系统的接收FOV(视场角)的大小和范围，实现接收系统1接收的1号发射点的激光光束的回波和接收系统2接收的2号发射点的激光光束的回波之间的空间隔离，从而实现1号点和2号点的回波区分。这样，尽管1号点和2号点的测量时间窗口存在重叠，但是1号点和2号点的回波不会出现在同一个接收系统上，从而实现了二者的回波区分，改善了距离模糊问题，且方法简单，实现成本低。
在一些实施例中，可以根据发射点数量和/或发射系统最大扫描角度等参数设置每个接收系统的接收视角。例如，根据发射点的数量和发射系统最大扫描角度可以确定出每个发射点的发射角度，进而可以确定反射角度，进一步可以确定接收系统的接收视角。在一些实施例中，还可以直接根据每个发射点的发射角度设置相应接收系统的接收视角。
使用根据本公开的实施例的上述方法，在使不同发射角度的激光光束的回波空间隔离的同时，充分利用空间信息，可将降低接收系统的个数，进而降低雷达系统的尺寸。
在一些实施例中，如图2所示，由第n接收系统根据回波接收结果，确定测距结果，包括：
在步骤S21中，根据第n接收系统在针对第n+N*m束激光光束的时间窗内接收的每个 回波信号确定对应的备选距离。这里，每个接收系统的接收视角可以相同或不同，无需考虑接收系统的接收视角方面，进而降低接收系统的设计复杂度。
在进行雷达系统设计时，最远测量距离和点云的帧数、分辨率基本上是反比的关系。虽然通过增加激光器的个数可以在不改变点云分辨率和降低帧数的情况下实现提升最大测量距离，但增加激光器个数的方案需要使用包括具有不同波长的激光器的多套发射装置并且同时接收端需要对不同波长的发射装置进行匹配处理，因此需要设计单独的滤波片屏蔽其他波长的激光器，这在系统设计上存在较大复杂度和工程实践的难度，具有不可控因素。因此，本公开的实施例采用多套独立接收系统来改善在测距时出现因为单个点的测距时长不够而导致最大测量距离缩短的问题，同时针对多套接收系统之间的回波采用了特殊的系统设计来改善距离模糊的问题。
本公开的实施例利用信号强度和距离的关系在处理算法上对重叠的回波信号进行区分。根据激光雷达方程可以知道，目标的回波强度与目标所在的距离平方成反比，因此可以通过接收系统接收的回波信号进行重叠区域的判别。具体来说，在重叠区域内，第n接收系统接收第n+N*m束激光的回波同时，还可能接收到第n+N*m束激光外的干扰回波。本公开的实施例根据第n接收系统接收的每个回波信号确定对应的备选距离，可以根据备选距离滤除干扰回波。
如图6或7所示，接收系统A在重叠区域中接收到发射点1的激光光束的回波和发射点2的激光光束的回波，此时就需要确定发射点1的备选距离R1以及发射点2的备选距离R2，根据备选距离R1和R2确定接收系统A是否存在干扰回波，以使接收系统A的测距结果更加精准。再例如，发射点为100个，接收系统为5个，接收系统2接收第2发射点、第7发射点、第12发射点……第47发射点、第52发射点……，比如在接收第52个发射点的激光光束的回波的同时，有可能还接收到了48、49、50、51号发射点的激光光束的回波，此时需要根据48、49、50、51、52号发射点的激光光束的回波确定对应的备选距离，根据对应的备选距离确定接收系统2是否存在干扰回波，以使接收系统2的测距结果更加精准，减少距离模糊。在一些实施例中，可以根据接收系统中每个回波信号的信号强度，将信号强度不满足条件的回波信号滤除；还可以根据接收系统中每个回波信号确定的距离值，若距离值不满足距离条件，则将不满足距离条件的对应的回波信号滤除；还可以根据接收系统中回波信号的脉冲数量、接收回波信号的时序信息等信息滤除干扰信号。
在步骤S22中，确定每个备选距离是否满足预设条件。
若多个备选距离中，有不满足预设条件的，则将不满足预设条件的备选距离滤除， 得到剩余的备选距离，即为第n接收系统接收窗内的测距结果；若备选距离均满足预设条件，则不需要滤除，即第n接收系统的回波信号确定的距离均为目标距离。
如图7所示，可以在1号点和2号点的接收重叠区域进行干扰回波的判别，由于对于1号点来说，重叠区域属于测距时间窗的末端，也就是远距离目标，所以回波信号强度应该较小，对2号点来说，重叠区域属于测距时间窗的前端，也就是近距离目标，所以信号强度应该较高。因此，本实施例可以通过确定备选距离是否满足预设条件，从第n接收系统中，滤除不满足预设条件的备选距离，实现对接收系统的回波干扰信号的筛选，并去除干扰回波信号，即去除了干扰回波信号得到的备选距离。
在一些实施例中，每个接收系统对应的预设条件不同。如图7所示，对于1号点来说，重叠区域属于测距时间窗的末端，也就是远距离目标，对2号点来说，重叠区域属于测距时间窗的前端，也就是近距离目标，因此，每个接收系统根据干扰回波确定的备选距离是不同的，有的接收系统的备选距离可能大，有的接收系统的备选距离可能小，例如1号点的重叠区域所确定的备选距离则较大，对应的预设条件也是较大的，例如2号点的重叠区域所确定的备选距离则较小，则对应的预设条件也是较小的。
在一些实施例中，如图3所示，确定每个备选距离是否满足预设条件，包括：
在步骤S31中，进行备选距离与根据发射间隔所确定的距离之间的差值运算，得到距离差值，进行所述备选距离与根据发射间隔所确定的距离之间的和运算，得到距离和值。
这里，发射间隔也可以说是相邻发射的激光的时序信息，如上述实施例中所描述的内容，距离差值可以表示为
Figure PCTCN2022121526-appb-000004
距离和值可以表示为
Figure PCTCN2022121526-appb-000005
其中，R为备选距离，T N为相邻发射的激光发射时刻之间的发射间隔，C为光速，
Figure PCTCN2022121526-appb-000006
为根据发射间隔所确定的距离。
在步骤S32中，根据距离差值和目标反射率确定第一上限，根据距离和值和目标反射率确定第一下限；其中，目标反射率为：激光雷达发射的激光经过该备选距离的反射率。
本公开的实施例利用距离和目标反射率可以用于确定回波信号强度且距离与回波信号强度成反比关系的原理。在接收系统接收到回波信号后，根据回波信号强度和备选距离可以反推出目标反射率。接着，利用推导出的目标反射率和在相应备选距离基础上变动的距离范围分别确定第一上限和第一下限。具体地，根据距离差值和目标反射率确定第一上限，表示为
Figure PCTCN2022121526-appb-000007
其中ρ r为目标反射率；根据距离和值和目标反射率确 定第一下限，表示为
Figure PCTCN2022121526-appb-000008
其中ρ r同样为目标反射率。
在步骤S33中，根据备选距离和激光的最大反射率确定第二上限，并根据备选距离和激光的最小反射率确定第二下限。
本公开的实施例还根据激光的反射率对备选距离所确定的信号强度进行约束，进一步提高备选距离的筛选精度，使接收系统的测距结果更加精准。本公开的实施例中的反射率可以理解为反射强度或反射率强度。具体地，根据备选距离和激光的最大反射率确定第二上限，表示为p(R,ρ 100)，根据备选距离和最小反射率确定第二下限，表示为p(R,ρ 1)，其中，ρ 1为激光的最小反射率，例如反射率为1，ρ 100为激光的最大反射率，例如反射率为100。
在步骤S34中，若备选距离对应的信号强度位于第一上限和第一下限之间，且备选距离对应的信号强度位于第二上限和第二下限之间，确定备选距离满足预设条件。
具体地，若根据备选距离得到的信号强度位于第一上限和第一下限之间，则不需滤除备选距离，即第n接收系统的回波信号确定的距离均为目标距离；若根据备选距离得到的信号强度没有位于第一上限和第一下限之间，则需要滤除该备选距离，得到剩余的备选距离，该剩余的备选距离作为第n接收系统在针对第n+N*m束激光光束的接收窗内的测距结果。
或者，若根据备选距离得到的信号强度位于第二上限和第二下限之间，则不需滤除备选距离，若根据备选距离得到的信号强度没有位于第二上限和第二下限之间，则需要滤除该备选距离，得到剩余的备选距离。
或者，若根据备选距离得到的信号强度位于第一上限和第一下限之间，且备选距离得到的信号强度位于第二上限和第二下限之间，则不需滤除备选距离；若根据备选距离得到的信号强度没有位于第一上限和第一下限之间，且备选距离得到的信号强度没有位于第二上限和第二下限之间，则需要滤除该备选距离，得到剩余的备选距离，该剩余的备选距离作为第n接收系统在针对第n+N*m束激光光束的接收窗内的测距结果。
示例性地，参见图7，假设1号点和2号点的激光发光间隔为T N，1号点对应的出现于重叠区域的回波确定的备选距离为R 1，即根据接收系统A的干扰回波确定的关于未知目标的备选距离，2号点对应的出现于重叠区域的回波确定的备选距离为R 2，即根据接收系统B的干扰回波确定关于未知目标的备选距离。那么对应接收系统A和B来说，具有反射率强度为ρ r(ρ 1<ρ r<ρ 100，其中ρ 1代表反射率为1的物体，ρ 100代表反射率为100的 物体)和所在距离R(备选距离)的目标具有的反射信号强度为p(R,ρ r)。
进一步地，根据备选距离和反射率确定反射信号强度p(R,ρ r)，确定反射信号强度p(R,ρ r)是否位于第一上限和第一下限之间。具体地，反射信号强度p(R,ρ r)应该满足
Figure PCTCN2022121526-appb-000009
若不满足上述条件，则将反射信号强度p(R,ρ r)对应的备选距离R滤除。示例性地，若R 1与对应的未知目标的反射率确定的反射信号强度p(R 1,ρ r)不满足上述条件，则将R 1滤除，即将接收系统A内与R 1对应的回波滤除；或者，若R 2与对应的未知目标的反射率确定的反射信号强度p(R 2,ρ r)不满足上述条件，则将R 2滤除，即将接收系统B内与R 2对应的回波滤除。
本公开的实施例通过距离与信号强度的关系，根据每个回波信号确定备选距离，然后将不满足预设条件的备选距离滤除，滤除效率更好，改善了距离重复现象，大大提高了雷达系统的测距精度。
在一些实施例中，相邻两个发射点的激光光束的激光参数可以不同。
这里，激光参数是指发射系统输出激光光束的各种参数，例如单次发射点的激光光束的脉冲个数和相邻脉冲的时间间隔等等。
进一步的，参见图4，由第n接收系统根据回波接收结果，确定测距结果，包括：
在步骤S41中，根据第n+N*m束激光的激光参数，滤除第n接收系统在针对第n+N*m束激光光束的时间窗内接收到的与激光参数不同的回波，得到第n接收系统接收的剩余回波。
在步骤S42中，根据第n接收系统接收的剩余回波，确定针对第n+N*m束激光光束的测距结果。
本公开的实施例通过对发射系统的控制逻辑改进，采用相邻两个发射点的激光光束的激光参数不同的发射逻辑，使得每个接收系统接收不同发射逻辑的激光光束的回波，同时根据第n+N*m束激光的激光参数，滤除第n接收系统接收到与激光参数不同的回波，得到第n接收系统接收强度的剩余强度。
应理解，本实施例对激光参数的具体值均不进行限定，对接收系统的个数也不进行限定，至少为两个，只要使得相邻两个发射点的激光光束的激光参数不同，不同的接收系统接收不同激光参数的激光光束的回波即可。
上述一些实施例，实现在延长测量时间的同时，通过激光参数滤除干扰回波，滤除效果更好，更加精准，减少了信号之间干扰，且方法更容易实施，进而尽可能减少了距离重复，提高了测距结果的精度，同时延长了测距距离。
在一些实施例中，激光参数包括以下至少之一：单次发射激光光束包含的脉冲个数、激光光束中相邻脉冲的脉冲时间间隔，但不限于脉冲个数、脉冲时间间隔的编码组合方法。
本实施例可以采用多脉冲发射的体制，相邻点的发光逻辑(激光参数)可以采用不同的单次发射激光光束包含的脉冲个数，或采用不同的激光光束中相邻脉冲的脉冲时间间隔，或任意两个结合等。而在不同的接收系统采用不同的数据处理方式，可以对目标进行区分。例如，对于1号发射点来说，采用俩脉冲，脉冲间隔为N 2的发射体制，对于2号发射点来说，采用三脉冲，脉冲间隔为N 2和N 3的发射体制，依次类推，这样针对接收系统A，可以采用俩脉冲数据处理的方式进行筛选，对于接收系统B，可以采用三脉冲数据处理的方式进行筛选，从而实现相邻点在重叠区域的区分，精度高，也削弱了距离模糊现象，提高测距精度。
上述一些实施例，针对重叠区域的回波干扰导致的距离模糊问题，通过发射系统控制逻辑改进的方法，采用多脉冲发射的体制，同时映射不同的接收系统进行数据处理，可以对重叠区域不同点号的回波进行区分，从而实现不同接收系统内不同点号的回波区分。
本公开的实施例解决了现有激光雷达系统中存在的最大测量距离和点云分辨率以及帧率互相矛盾的问题，在不降低点云分辨率和帧率的前提下，通过改进发射系统与接收系统的接收关系，使用一个发射系统，多个接收系统，延长了测量时间，实现最大测量距离的提升，降低了系统的设计复杂度；同时为了解决距离模糊的问题，在系统设计上进行了处理优化，通过改变发射激光光束的发射逻辑，无需设计多个发射系统，降低了雷达系统设计的复杂度，使得相邻激光光束之间被不同的接收系统接收，削弱了距离模糊。
图8是根据一示例性实施例示出的一种激光雷达系统的框图。参照图8，该系统包括：一个发射系统100和N个接收系统200。
发射系统100按照发射间隔发射激光光束。第n接收系统200在时间长度大于发射间隔且不大于N个发射间隔的接收窗内，接收发射系统发射的第n+N*m束激光的回波；其中，N为接收系统的个数，N≥2；n为小于或等于N的正整数；m为自然数。第n接收系统200根据回波接收结果，确定测距结果。
在一些实施例中，接收系统200针对第n+N*m束激光光束的接收视角是根据第n+N*m束激光光束的发射视角来设置的，其中，不同接收视角接收不同发射视角的激光光束的回波。
在一些实施例中，第n接收系统200具体用于：
根据第n接收系统在针对第n+N*m束激光光束的时间窗内接收的每个回波信号确定对应的备选距离；
确定每个备选距离是否满足预设条件；
将不满足预设条件的备选距离滤除，得到第n接收系统在针对第n+N*m束激光光束的接收窗内的测距结果。
在一些实施例中，第n接收系统200具体用于：
进行备选距离与根据发射间隔所确定的距离之间的差值运算，得到距离差值，进行备选距离与根据发射间隔所确定的距离之间的和运算，得到距离和值；
根据距离差值和目标反射率确定第一上限，根据距离和值和目标反射率确定第一下限；其中，目标反射率为：激光雷达发射的激光经过备选距离的反射率；
根据备选距离和激光的最大反射率确定第二上限，并根据备选距离和激光的最小反射率确定第二下限；
若备选距离对应的信号强度位于第一上限和第一下限之间，且备选距离对应的信号强度位于第二上限和第二下限之间，确定备选距离满足预设条件。
在一些实施例中，相邻两个发射点的激光光束的激光参数不同；第n接收系统200具体用于：
根据第n+N*m束激光的激光参数，滤除第n接收系统在针对第n+N*m束激光光束的时间窗内接收到的与激光参数不同的回波，得到第n接收系统接收的剩余回波；
根据第n接收系统接收的剩余回波，确定针对第n+N*m束激光光束的测距结果。
在一些实施例中，激光参数包括以下至少之一：单次发射激光光束包含的脉冲个数、激光光束中相邻脉冲的脉冲时间间隔。
本领域技术人员在考虑说明书及实践这里公开的发明后，将容易想到本公开的其它实施方案。本申请旨在涵盖本公开的任何变型、用途或者适应性变化，这些变型、用途或者适应性变化遵循本公开的一般性原理并包括本公开未公开的本技术领域中的公知常识或惯用技术手段。说明书和实施例仅被视为示例性的，本公开的真正范围由下面的权利要求指出。
应当理解的是，本公开并不局限于上面已经描述并在附图中示出的精确结构，并且 可以在不脱离其范围进行各种修改和改变。本公开的范围仅由所附的权利要求来限制。

Claims (14)

  1. 一种激光雷达测距方法，包括：
    由接收系统中的第n接收系统在时间长度大于发射间隔且不大于N个所述发射间隔的接收窗内，接收发射系统发射的第n+N*m束激光光束的回波，其中，所述发射系统按照所述发射间隔发射多束激光光束，N为所述接收系统的个数，N≥2，n为小于或等于N的正整数，m为自然数；
    由所述第n接收系统根据回波接收结果，确定测距结果。
  2. 根据权利要求1所述的激光雷达测距方法，其中，
    所述第n接收系统针对第n+N*m束激光光束的接收视角是根据第n+N*m束激光光束的发射视角来设置的，其中，不同所述接收视角接收不同发射视角的激光光束的回波。
  3. 根据权利要求1所述的激光雷达测距方法，其中，所述由所述第n接收系统根据回波接收结果，确定测距结果，包括：
    根据第n接收系统在针对第n+N*m束激光光束的所述时间窗内接收的每个回波信号确定对应的备选距离；
    确定每个所述备选距离是否满足预设条件；
    将不满足所述预设条件的所述备选距离滤除，得到所述第n接收系统在针对第n+N*m束激光光束的所述接收窗内的测距结果。
  4. 根据权利要求3所述的激光雷达测距方法，其中所述确定每个所述备选距离是否满足预设条件，包括：
    进行所述备选距离与根据发射间隔所确定的距离之间的差值运算，得到距离差值，进行所述备选距离与根据发射间隔所确定的距离之间的和运算，得到距离和值；
    根据所述距离差值和目标反射率确定第一上限，根据所述距离和值和所述目标反射率确定第一下限；其中，所述目标反射率为：所述激光雷达发射的激光经过所述备选距离的反射率；
    根据所述备选距离和所述激光的最大反射率确定第二上限，并根据所述备选距离和所述激光的最小反射率确定第二下限；
    若所述备选距离对应的信号强度位于所述第一上限和所述第一下限之间，且所述备选距离对应的信号强度位于所述第二上限和所述第二下限之间，确定所述备选距离满足所述预设条件。
  5. 根据权利要求1所述的激光雷达测距方法，其中，
    相邻两个发射点的激光光束的激光参数不同；
    所述由所述第n接收系统根据回波接收结果，确定测距结果，包括：
    根据第n+N*m束激光光束的激光参数，滤除所述第n接收系统在针对第n+N*m束激光光束的所述时间窗内接收到的与所述激光参数不匹配的回波，得到所述第n接收系统接收的剩余回波；以及
    根据所述第n接收系统接收的剩余回波，确定针对第n+N*m束激光光束的测距结果。
  6. 根据权利要求5所述的激光雷达测距方法，其中，所述激光参数包括以下至少之一：
    单次发射激光光束包含的脉冲个数；
    激光光束中相邻脉冲的脉冲时间间隔。
  7. 根据权利要求1所述的激光雷达测距方法，其中，所述第n接收系统的针对第n+N*m束激光光束的所述时间窗的起始时刻根据第n+N*m束激光的发射时刻确定。
  8. 一种激光雷达系统，包括：一个发射系统和N个接收系统，其中：
    所述发射系统用于按照发射间隔发射多束激光光束；
    所述N个接收系统中的第n接收系统用于在时间长度大于所述发射间隔且不大于N个所述发射间隔的接收窗内，接收所述发射系统发射的第n+N*m束激光光束的回波；其中，N为接收系统的个数，N≥2；n为小于或等于N的正整数；m为自然数；
    所述第n接收系统还用于根据回波接收结果，确定测距结果。
  9. 根据权利要求8所述的激光雷达系统，其中，
    所述第n接收系统针对第n+N*m束激光光束的接收视角是根据第n+N*m束激光光束的发射视角来设置的，其中，不同所述接收视角接收不同发射视角的激光光束的回波。
  10. 根据权利要求8所述的激光雷达系统，其中，为了根据回波接收结果，确定测距结果，所述第n接收系统进一步用于：
    根据第n接收系统在针对第n+N*m束激光光束的所述时间窗内接收的每个回波信号确定对应的备选距离；
    确定每个所述备选距离是否满足预设条件；
    将不满足所述预设条件的所述备选距离滤除，得到所述第n接收系统在针对第n+N*m束激光光束的所述接收窗内的测距结果。
  11. 根据权利要求10所述的激光雷达系统，其中，为了根据回波接收结果，确定测 距结果，所述第n接收系统进一步用于：
    进行所述备选距离与根据发射间隔所确定的距离之间的差值运算，得到距离差值，进行所述备选距离与根据发射间隔所确定的距离之间的和运算，得到距离和值；
    根据所述距离差值和目标反射率确定第一上限，根据所述距离和值和所述目标反射率确定第一下限；其中，所述目标反射率为：所述激光雷达发射的激光经过所述备选距离反射回的强度；
    根据所述备选距离和所述激光的最大反射率确定第二上限，并根据所述备选距离和所述激光的最小反射率确定第二下限；
    若所述备选距离对应的信号强度位于所述第一上限和所述第一下限之间，且所述备选距离对应的信号强度位于所述第二上限和所述第二下限之间，确定所述备选距离满足所述预设条件。
  12. 根据权利要求8所述的激光雷达系统，其中，相邻两个发射点的激光光束的激光参数不同；
    为了根据回波接收结果，确定测距结果，所述第n接收系统进一步用于：
    根据第n+N*m束激光光束的激光参数，滤除所述第n接收系统在针对第n+N*m束激光光束的所述时间窗内接收到与所述激光参数不同的回波，得到所述第n接收系统接收的剩余回波；以及
    根据所述第n接收系统接收的剩余回波，确定针对第n+N*m束激光光束的测距结果。
  13. 根据权利要求12所述的激光雷达系统，其中，所述激光参数包括以下至少之一：
    单次发射激光光束包含的脉冲个数；
    激光光束中相邻脉冲的脉冲时间间隔。
  14. 根据权利要求8所述的激光雷达系统，其中，所述第n接收系统的针对第n+N*m束激光光束的所述时间窗的起始时刻根据第n+N*m束激光的发射时刻确定。
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