WO2022134525A1 - 激光雷达的控制方法及激光雷达 - Google Patents

激光雷达的控制方法及激光雷达 Download PDF

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Publication number
WO2022134525A1
WO2022134525A1 PCT/CN2021/104124 CN2021104124W WO2022134525A1 WO 2022134525 A1 WO2022134525 A1 WO 2022134525A1 CN 2021104124 W CN2021104124 W CN 2021104124W WO 2022134525 A1 WO2022134525 A1 WO 2022134525A1
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Prior art keywords
pulse
echo
signal
measurement
detection
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PCT/CN2021/104124
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English (en)
French (fr)
Inventor
黄福威
时从波
叶良琛
向少卿
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上海禾赛科技有限公司
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Publication of WO2022134525A1 publication Critical patent/WO2022134525A1/zh
Priority to US18/209,171 priority Critical patent/US20230375682A1/en

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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
    • 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
    • G01S7/483—Details of pulse systems
    • G01S7/486—Receivers
    • G01S7/487—Extracting wanted echo signals, e.g. pulse detection
    • G01S7/4873—Extracting wanted echo signals, e.g. pulse detection by deriving and controlling a threshold value
    • 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
    • G01S7/483—Details of pulse systems
    • G01S7/484—Transmitters
    • 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
    • G01S7/483—Details of pulse systems
    • G01S7/486—Receivers
    • G01S7/4865—Time delay measurement, e.g. time-of-flight measurement, time of arrival measurement or determining the exact position of a peak
    • 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
    • G01S7/483—Details of pulse systems
    • G01S7/486—Receivers
    • G01S7/487—Extracting wanted echo signals, e.g. pulse detection
    • G01S7/4876—Extracting wanted echo signals, e.g. pulse detection by removing unwanted signals

Definitions

  • the invention relates to the field of laser detection, in particular to a control method of a laser radar and a laser radar.
  • the receiving device can not only receive the echo beam (echo signal) reflected by the laser after passing through the object, but also receive the stray beam reflected by the laser directly to the receiving device through the mask. (stray light signal).
  • the stray light signal belongs to the interference signal. Due to the existence of the stray light signal, the wrong ranging result will be calculated.
  • an encoded double-pulse detection beam is used.
  • the two pulses are the first pulse A and the second pulse B respectively. If the echo signal of the target corresponding to the first pulse A is exactly the same as the stray light of the second pulse B The superposition of signals will cause the lidar to fail to recognize the double-pulse echo beam, resulting in the inability of the lidar to measure the distance or the serious deterioration of the ranging accuracy.
  • the lidar uses a coded double-pulse detection beam, and the echo beam is the corresponding coded double-pulse echo beam.
  • the echo and the second echo) do not overlap with the echo waveforms of the stray light (the first echo of the mask and the second echo of the mask in Figure 1), that is, as shown in Figure 1, the time of the first echo is At the position of t1, the time of the second echo of the mask is at the position of t, and t1 ⁇ t.
  • the decoding module in the lidar can identify the echo signals (ie the first echo and the second echo), Complete the correct decoding of the echo signal;
  • the present invention provides a control method for a laser radar, the control method re-measures the blind area caused by the superposition of the echo signal and the stray light signal generated by the mask, so as to make the laser radar control method.
  • the ranging results are more accurate, and the full coverage of the field of view within the detection range of the lidar is achieved.
  • the control method includes:
  • S101 Transmit a first laser detection pulse sequence, where the first laser detection pulse sequence at least includes a first transmission pulse and a second transmission pulse encoded with a time interval T;
  • step S104 Control the lidar to transmit a second laser detection pulse sequence to perform re-measurement according to the judgment result of step S103.
  • step S103 further includes: determining whether the multiple echo pulse signals are superimposed according to the echo pulse signals that are not superimposed with the mask echo signal among the multiple echo pulse signals.
  • the step S103 further includes: by detecting whether an echo pulse signal exists within a specific time range, judging whether the multiple echo pulse signals are superimposed, wherein the specific time range is: transmitting The time range from (2T- ⁇ t) to (2T+ ⁇ t) after the first emission pulse, wherein the ⁇ t is based on the mask echoes corresponding to the first laser detection pulse sequence and the first laser detection pulse sequence The time interval between is determined.
  • step S103 further includes: if an echo pulse signal exists within the specific time range, then
  • step S104 It is judged whether the echo pulse signal is greater than the first threshold, and when the echo pulse signal is greater than the first threshold, step S104 is performed.
  • step S103 further includes: determining whether the multiple echo pulse signals are superimposed according to the superposition of the mask echo signal and the echo pulse signal.
  • the step S103 further includes: by detecting whether an echo pulse signal exists within a specific time range, judging whether the multiple echo pulse signals are superimposed, wherein the specific time range is: transmitting The time range from (T- ⁇ t) to (T+ ⁇ t) after the first transmit pulse, wherein the ⁇ t is based on the mask echoes corresponding to the first laser detection pulse sequence and the first laser detection pulse sequence The time interval between is determined.
  • step S103 further includes: if an echo pulse signal exists within the specific time range, then
  • step S104 It is determined whether the echo pulse signal within the specific time range is greater than the second threshold, and when the echo pulse signal is greater than the second threshold, step S104 is performed.
  • the second threshold value is obtained according to the average value of the echo intensity of the reticle of the lidar and the first threshold value of the echo pulse signal measured multiple times.
  • step S104 further includes: if the multiple echo pulse signals are superimposed, controlling the lidar to transmit a second laser detection pulse sequence for re-measurement, where the second laser detection pulse sequence includes The third transmit pulse.
  • step S104 further includes: if the multiple echo pulse signals are superimposed, controlling the lidar to transmit a second laser detection pulse sequence for re-measurement, the second laser detection pulse sequence at least A fourth transmit pulse and a fifth transmit pulse encoded by a time interval T', which is different from the time interval T, are included.
  • step S103 further includes:
  • a re-measurement flag signal is set to adjust the priority of transmitting the second laser detection pulse sequence.
  • step S104 further includes:
  • the second laser detection pulse sequence is immediately emitted to perform the re-measurement.
  • step S104 further includes:
  • the laser of the current detection channel emits the second laser detection pulse sequence to perform the re-measurement.
  • control method further includes:
  • the echo pulse signal is sampled and the echo pulse waveform is obtained.
  • step S103 further includes:
  • the sampling signal of the echo pulse signal it is detected whether there is an echo pulse signal within a specific time range.
  • step S103 further includes:
  • the echo pulse waveform it is detected whether there is an echo pulse signal within a specific time range.
  • the step S104 further includes: completing the retest between the completion of the current detection on the current detection channel corresponding to the step S101 and the start of detection on the next detection channel, and the control method further includes:
  • the retest flag signal is reset before the next detection channel starts detection.
  • control method further includes S105: obtaining a retest result.
  • the step 105 further includes:
  • the second laser detection pulse sequence is a single-pulse or multi-pulse sequence
  • signal processing is performed in a single-pulse decoding manner or a multi-pulse decoding manner, respectively, and the re-measurement result is output.
  • the lidar is a coaxial lidar.
  • the present invention also provides a laser radar, comprising:
  • a transmitting unit configured to transmit a first laser detection pulse sequence, the first laser detection pulse sequence at least including a first transmission pulse and a second transmission pulse encoded with a time interval T;
  • a receiving unit configured to receive a plurality of echo pulse signals
  • a retest detection and control unit configured to determine whether the plurality of echo pulse signals are superimposed
  • the emission control unit is configured to control the lidar to transmit a second laser detection pulse sequence to perform re-measurement when the re-measurement detection and control unit determines that the multiple echo pulse signals are superimposed.
  • the retest detection and control unit is further configured to determine whether the multiple echo pulse signals are not superimposed with the mask echo signal according to the echo pulse signals among the multiple echo pulse signals There is superposition.
  • the retest detection and control unit is configured to determine whether the multiple echo pulse signals are superimposed by detecting whether there is an echo pulse signal within a specific time range, wherein the specific time range is: the time range from (2T- ⁇ t) to (2T+ ⁇ t) after the first emission pulse, wherein the ⁇ t is based on the first laser detection pulse sequence and the mask corresponding to the first laser detection pulse sequence The time interval between echoes is determined.
  • the retest detection and control unit is configured to determine whether the echo pulse signal is greater than a first threshold if there is an echo pulse signal within the specific time range, and the emission control unit It is configured to control the lidar to transmit a second laser detection pulse sequence to perform re-measurement when the echo pulse signal is greater than the first threshold.
  • the retest detection and control unit is further configured to: determine whether the multiple echo pulse signals are superimposed according to the superposition of the reticle echo signal and the echo pulse signal.
  • the retest detection and control unit is configured to determine whether the multiple echo pulse signals are superimposed by detecting whether there is an echo pulse signal within a specific time range, wherein the specific time range is: the time range from (T- ⁇ t) to (T+ ⁇ t) after the first emission pulse, wherein the ⁇ t is based on the first laser detection pulse sequence and the mask corresponding to the first laser detection pulse sequence The time interval between echoes is determined.
  • the retest detection and control unit is configured to determine whether the echo pulse signal in the specific time range is greater than a second threshold if there is an echo pulse signal in the specific time range
  • the emission control unit is configured to control the lidar to emit a second laser detection pulse sequence for re-measurement when the echo pulse signal is greater than the second threshold.
  • the second threshold value is obtained according to the average value of the echo intensity of the reticle of the lidar and the first threshold value of the echo pulse signal measured multiple times.
  • the lidar further includes a signal processing unit, and the signal processing unit includes:
  • an analog-to-digital converter drive module configured to sample the echo pulse signal and generate a sampled signal
  • an analog-to-digital converter data processing module configured to perform pulse information extraction on the sampled signal to obtain basic pulse information
  • the pulse processing module is configured to process the basic pulse information and output a ranging result.
  • the transmission control unit includes:
  • an emission control module configured to send a control signal to the emission unit to trigger the emission unit to emit laser detection pulses
  • the timing control module generates a timing control signal and sends the timing control signal to the emission control module.
  • the retest detection and control unit receives the sampling signal generated by the analog-to-digital converter driving module, and detects whether there is an echo pulse signal within a specific time range according to the sampling signal;
  • the re-measurement detection and control unit transmits a re-measurement signal to the emission control module, and the emission control module triggers the emission unit to send the second laser detection pulse sequence according to the re-measurement signal to perform re-measurement.
  • the retest detection and control unit receives the sampling signal generated by the analog-to-digital converter driving module, and detects whether there is an echo pulse signal within a specific time range according to the sampling signal;
  • the re-measurement detection and control unit transmits a re-measurement signal to the timing control module, and the sequence control module obtains an idle time period in the ranging window according to the re-measurement signal for performing the re-measurement.
  • the re-measurement detection and control unit receives the ranging result output by the pulse processing module, and detects whether there is an echo pulse signal within a specific time range according to the ranging result;
  • the re-measurement detection and control unit transmits a re-measurement signal to the emission control module, and the emission control module triggers the emission unit to send the second laser detection pulse sequence according to the re-measurement signal to perform re-measurement.
  • the re-measurement detection and control unit receives the ranging result output by the pulse processing module, and detects whether there is an echo pulse signal within a specific time range according to the ranging result;
  • the re-measurement detection and control unit transmits a re-measurement signal to the timing control module, and the sequence control module obtains an idle time period in the ranging window according to the re-measurement signal for performing the re-measurement.
  • the emission control unit is further configured to: if the multiple echo pulse signals are superimposed, control the lidar to emit a second laser detection pulse sequence for re-measurement, the second laser detection pulse
  • the sequence is a single-pulse or multi-pulse sequence.
  • the signal processing unit is configured to perform signal processing in a single-pulse decoding method or a multi-pulse decoding method according to whether the second laser detection pulse sequence is a single-pulse or multi-pulse sequence, and output a complex signal. test results.
  • a preferred embodiment of the present invention provides a control method for a laser radar, which re-measures the blind area caused by the superposition of the echo signal and the stray light signal generated by the mask, so that the ranging result of the laser radar is more accurate , and achieve full coverage of the field of view within the detection range of the lidar.
  • Fig. 1 schematically shows a waveform in which the detection echo and the mask echo are not superimposed
  • FIG. 2 schematically shows a waveform in which the detection echo and the mask echo are superimposed
  • FIG. 3 schematically shows the waveforms received by the receiving device when the second reticle echoes and the first detection echoes are superimposed
  • FIG. 4 shows a control method of a lidar according to a preferred embodiment of the present invention
  • Fig. 5a schematically shows a situation where the pulse signal is detected in the time range of 2T ⁇ t;
  • Figure 5b schematically shows another situation where the pulse signal is detected in the time range of 2T ⁇ t;
  • Figure 5c schematically shows another situation where the pulse signal is detected in the time range of 2T ⁇ t;
  • Figure 6a schematically shows a situation in which a pulse signal is detected within the time range of T ⁇ t;
  • Figure 6b schematically shows another situation where the pulse signal is detected in the time range of T ⁇ t
  • Figure 6c schematically shows another situation where the pulse signal is detected in the time range of T ⁇ t
  • Fig. 7A schematically shows the waveform received by the receiving device when the single pulse is used for re-measurement
  • FIG. 7B schematically shows the waveform received by the receiving device when the double pulse is used for re-measurement
  • FIG. 8 schematically shows a lidar according to a preferred embodiment of the present invention.
  • FIG. 9 schematically shows a lidar according to a preferred embodiment of the present invention.
  • FIG. 10 schematically shows a lidar according to a preferred embodiment of the present invention.
  • FIG. 11 schematically shows a lidar according to a preferred embodiment of the present invention.
  • FIG. 12 schematically shows a lidar according to a preferred embodiment of the present invention
  • Figure 13 schematically shows a lidar according to a preferred embodiment of the present invention.
  • connection should be understood in a broad sense, for example, it may be a fixed connection or a detachable connection Connection, or integral connection: it can be a mechanical connection, an electrical connection or can communicate with each other; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal communication of two elements or the interaction of two elements relation.
  • connection should be understood in a broad sense, for example, it may be a fixed connection or a detachable connection Connection, or integral connection: it can be a mechanical connection, an electrical connection or can communicate with each other; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal communication of two elements or the interaction of two elements relation.
  • a first feature "on” or “under” a second feature may include direct contact between the first and second features, or may include the first and second features Not directly but through additional features between them.
  • the first feature being “above”, “over” and “above” the second feature includes that the first feature is directly above and diagonally above the second feature, or simply means that the first feature is level higher than the second feature.
  • the first feature “below”, “below” and “beneath” the second feature includes the first feature being directly above and obliquely above the second feature, or simply means that the first feature has a lower level than the second feature.
  • the time interval between the two transmission pulses is T, and the two detection echoes formed after the two transmission pulses are reflected by the target, and the two transmission pulses are respectively reflected by the light
  • the time interval between the two reticle echoes formed by the reticle reflection is also T. Since the speed of light propagation is very fast, it can be considered that the reticle echoes reach the receiving device at the same time as the detection pulse is transmitted, and the second echo of the reticle When the wave and the echo reflected by the first detection pulse are superimposed by the target, the receiving device will receive the waveform as shown in FIG. 3 . As shown in FIG.
  • the time interval between the first echo L21 of the reticle and the second echo L22 of the reticle is T
  • the echo L11 of the first emission pulse reflected by the target and the echo L11 of the second emission pulse reflected by the target The interval time of the waves L12 is also T, and at this time, the second echo L22 of the mask and the echo L11 of the first transmit pulse reflected by the target are superimposed (at a time position approximately equal to T after the first transmit pulse is transmitted). Therefore, how to judge whether there is a scanning blind spot and how to re-test the scanning blind spot when it is determined that there is a blind spot are the technical issues concerned by the present invention.
  • the present invention provides a control method for a laser radar, which is used to re-measure the blind area caused by the superposition of the echo signal and the stray light signal generated by the mask. .
  • the present invention provides a control method 100 for a lidar, including:
  • step S101 a first laser detection pulse sequence is transmitted, and the first laser detection pulse sequence includes a first transmission pulse and a second transmission pulse encoded with a time interval T. That is, a double-pulse sequence encoded with a time interval T is transmitted for detection.
  • a plurality of echo pulse signals are received.
  • a sequence of echo pulses can be received by a photodetector and converted into electrical signals.
  • the echo pulse signal includes a first echo pulse and a second echo pulse corresponding to the first transmit pulse and the second transmit pulse. If there is a target in the detection range, it will receive double echo pulses at the same time interval T.
  • step S103 it is determined whether the multiple echo pulse signals are superimposed.
  • whether the echo pulse signal is superimposed can be determined in various ways, which will be described in detail below. For example, it can be detected by detecting whether there is an echo pulse signal within a specific time range, that is, by detecting whether there is a situation where the echo reflected by the target object and the reticle echo of the transmitted pulse are superimposed.
  • pulse signal step S104 is executed. If no echo pulse signal within a specific time range is detected, after the current detection channel finishes detection, step S101 is re-entered to drive the next detection channel to emit a laser detection pulse sequence.
  • step S104 the lidar is controlled to transmit a second laser detection pulse sequence for re-measurement. For example, when it is determined that at least two echo pulse signals in the multiple echo pulse signals are superimposed (completely or partially overlapped in time), the lidar is controlled to transmit a second laser detection pulse sequence for repeated measurement.
  • step S103 it is determined whether the multiple echo pulse signals are superimposed according to the echo pulse signals that are not superimposed with the mask echo signal among the multiple echo pulse signals , as described below with reference to Figures 5a-5c. According to a preferred embodiment of the present invention, it is determined whether the multiple echo pulse signals are superimposed by detecting whether there is an echo pulse signal within a specific time range, wherein the preset delay time is ⁇ t, and the specific time range is : the time range from (2T- ⁇ t) to (2T+ ⁇ t) after transmitting the first transmit pulse. Wherein step S103 further includes: if an echo pulse signal exists within the specific time range, judging whether the echo pulse signal is greater than a first threshold, and when the echo pulse signal is greater than the first threshold, executing Step S104.
  • ⁇ t is the interval time from the transmission pulse to the echo reflected by the photomask being received by the receiving device, or the link processing time (about 80ns), which can be preset according to the actual measurement results, such as taking the longer of the two A larger value, or the sum of the two, all fall within the protection scope of the present invention.
  • the detected pulse signal is the echo L12 of the second transmitted pulse reflected by the target
  • the echo L11 of the first transmitted pulse reflected by the target is at time T before the second detected echo L12
  • the first detection echo L11 and the second echo L22 of the mask are superimposed, which will affect the decoding.
  • the echo pulse signal L12 that is not superimposed with the mask echo signal among the plurality of echo pulse signals is used to determine whether the plurality of echo pulse signals are superimposed.
  • the first (noise) threshold shown by the dotted line in FIG. 5b
  • step S103 it is determined whether the multiple echo pulse signals are superimposed according to the superposition of the reticle echo signal and the echo pulse signal, as described below with reference to FIGS. 6a-6c .
  • it is determined whether the multiple echo pulse signals are superimposed by detecting whether there is an echo pulse signal within a specific time range, wherein the preset delay time is ⁇ t, and the specific time range is : the time range from (T- ⁇ t) to (T+ ⁇ t) after the first transmit pulse is transmitted.
  • step S103 further includes: if an echo pulse signal exists within the specific time range, judging whether the echo pulse signal within the specific time range is greater than a second threshold, and when the echo pulse signal is greater than the first When there are two thresholds, step S104 is executed.
  • ⁇ t is the time from the transmission pulse to the time when the echo reflected by the reticle is received by the receiving device, or the link processing time, which can be preset according to the actual measurement results, such as taking the larger value of the two, or taking The sum of the two is within the protection scope of the present invention.
  • the detected pulse signal is the second transmission pulse Mask echo L22.
  • the detected pulse signal is the superposition of the second echo of the reticle and the noise signal.
  • the lidar calculates the distance of the target in the normal decoding method, There will be no unsolvable situations.
  • the echo L11 reflected by the target of the first transmitted pulse is superimposed with the second echo L22 of the reticle, which can be identified according to the preset second threshold, which will affect decoding.
  • the superposition of the mask echo signal and the echo pulse signal is used to determine whether the multiple echo pulse signals are superimposed.
  • the second threshold shown by the dotted line in Figs. 6a-6c
  • the second threshold value may be set based on the superposition of the average value of the echo intensity of the reticle measured multiple times and a threshold value (ie, the first threshold value) for identifying the echo signal, wherein based on the multiple measurements
  • the average value of the reticle echo intensity is used to set the threshold to filter the second echo L22 of the reticle, while the first threshold can filter the noise, so that the two are superimposed to filter out the second echo of the reticle within the time range of T ⁇ t.
  • Wave L22 and noise if there is still a pulse signal, the pulse signal is the echo signal L11 of the first transmitted pulse reflected by the target.
  • This method determines whether the pulse signal in the time range is an echo pulse by setting a threshold value related to the echo of the mask, and the accuracy of the determination result is high.
  • the step S103 further includes: when an echo pulse signal is detected within the specific time range, setting a re-measurement marker signal for adjusting the emission of the second laser detection pulse sequence priority.
  • each detection channel of the multi-channel lidar emits light in turn, and the time interval between the current detection channel and the next detection channel can be defined as a ranging window, and the ranging window can be based on the maximum distance of the detected target.
  • transmitting the second laser detection pulse sequence for re-measurement should be completed within the ranging window.
  • One method is to transmit the second laser detection pulse sequence to perform the re-measurement immediately after the laser of the current detection channel finishes transmitting the laser detection pulse sequence according to the re-measurement marker signal.
  • the advantage of this re-measurement method is that the re-measurement can be completed in time, and there will not be a situation where it is too late to send out the second laser detection pulse sequence, and the latter detection channel has already started to emit the laser detection pulse sequence, so that superposition occurs; the second method According to the re-measurement marker signal, before the current ranging window is closed, that is, before the laser of the next detection channel emits the laser detection pulse sequence, the laser of the current detection channel emits the second laser detection pulse sequence to carry out the measurement. retest.
  • the advantage of this re-measurement method is that it will not confuse the reflected echo signal of the long-distance target and the re-measured echo signal, and fully utilize the time interval of successive lighting between adjacent detection channels.
  • the second laser detection pulse sequence includes a third emission pulse, that is, the emission device emits a single pulse beam as a third emission pulse for detection.
  • the second laser detection pulse sequence may also include at least a fourth emission pulse and a fifth emission pulse encoded by a time interval T', where the time interval T' is different from the time interval T.
  • the control method 100 further includes: sampling the echo pulse signal and acquiring the echo pulse waveform.
  • an analog-to-digital converter is used to collect the echo pulse signal and obtain a real-time echo waveform; the echo pulse signal is collected by the analog-to-digital converter to obtain sampling points, and input to the pulse processing module for processing to output a complete waveform.
  • ADC analog-to-digital converter
  • Whether there is an echo pulse signal in a specific time range can be detected in two ways: one is to directly detect the sampling points collected by the analog-to-digital converter, that is, to determine whether there is an echo pulse in a specific time range according to the sampling signal Signal, this method does not need to wait for the output result of the pulse processing module, the detection time is short, and the re-measurement can be carried out in time without reducing the point cloud density of the lidar; the second is to detect the complete waveform output by the pulse processing module.
  • the detection object of the method includes the pulse front time, pulse width and peak value to obtain the distance and reflectivity of the target, and the detection result is more accurate.
  • the step S104 further includes: completing the retest between the completion of the current detection of the current detection channel corresponding to the step S101 and the start of detection of the next detection channel, and the control method 100 further includes: : For each detection channel, before the next detection channel starts detection, reset the retest flag signal.
  • the controller controls the lidar to transmit a second laser detection pulse sequence for re-measurement, and the signal processing unit also determines which algorithm to use to calculate the distance of the target through the value of the re-measurement marker signal, that is, When it is detected that the value of the re-measurement marker signal changes, single-pulse decoding or multi-pulse decoding is used to obtain the distance of the target, which needs to be completed within the same ranging window. Therefore, before the next detection channel starts to detect, the re-measurement should be The flag signal is reset.
  • the method 100 further includes step S105: obtaining a retest result.
  • step S105 according to whether the second laser detection pulse sequence is a single pulse or a multi-pulse sequence, signal processing can be performed in a single-pulse decoding manner or a multi-pulse decoding manner, respectively, and a retest result is output.
  • FIG. 7A shows the waveform received by the receiving device when the single pulse is used for re-measurement.
  • the first echo from the target and the second echo from the mask are superimposed.
  • control the lidar to transmit the third transmit pulse (single pulse) for re-measurement after transmitting the third transmit pulse, the receiving device receives the echo pulse signal P1 from the mask and the re-measurement echo P2 from the target respectively. , and then perform signal processing to output the retest results.
  • FIG. 7B schematically shows the waveforms received by the receiving device when double pulses are used for re-measurement.
  • the first echo from the target and the second echo from the reticle are superimposed.
  • control the lidar to transmit the fourth and fifth transmit pulses (double pulses) for re-measurement, after transmitting the fourth and fifth transmit pulses, the receiving device receives the echo pulse signal P11 from the mask respectively and P12 and the re-measurement echo pulse signals P21 and P22 from the target, and then perform signal processing to output the re-measurement result.
  • the echo pulse signal P11 of the mask Due to the re-measurement of the target at the same distance, the echo pulse signal P11 of the mask is the same as the re-measurement result.
  • the time interval of the echo pulse signal P21 is still t, and the double-transmission pulse encoded by the time interval t' (different from the time interval t) is used in the re-measurement, so the time interval between the echo pulse signals P21 and P22 is re-measured .
  • the time interval between the echo pulse signals P11 and P12 of the mask is t', in Fig. 7B, t' ⁇ t, so the echo pulse signal P21 and the echo pulse signal P12 of the mask will not be re-measured overlay.
  • the control method 100 further includes: according to the re-measurement marker signal, the controller of the lidar performs signal processing by means of single-pulse or multi-pulse decoding, and outputs a re-measurement result. That is, according to the re-measurement marker signal, it is judged whether the re-measurement has been carried out, and which mode is used to carry out the re-measurement. Calculate the distance measurement result. Re-measurement is performed by transmitting a single pulse, and the distance to the target is calculated through the algorithm corresponding to the single-pulse ranging. Compared with the multi-pulse ranging process and solution process, the time is shorter, and the point cloud density of the lidar is correspondingly guaranteed. .
  • the control method 100 provided by the present invention is suitable for coaxial laser radar, that is, there may be a situation in which the detection echo and the mask echo are superimposed.
  • the coaxial optical path uses the same optical path for transmission and reception, part of the emitted light is reflected by the reticle (the reticle usually reflects 5%-10% of the emitted beam) Afterwards, it will return along the original path to be received by the receiving device, while the transmitting optical path and receiving optical path of the paraxial optical path are separated, and a light isolation device is usually set between the two, so the echo of the mask will not interfere with the paraxial lidar. .
  • the re-measurement method provided by the present invention is also applicable to the case of multi-pulse coding. Multiple reticle echoes and detection echoes overlap, and it can be judged separately or comprehensively whether there is a scanning blind spot, and the re-measurement can be carried out according to the judgment result. For example, in the case of three-pulse detection, there may be two scanning blind areas, that is, the second echo of the mask and the echo of the first transmitted pulse reflected by the target, while the third echo of the mask and the second transmitted pulse are reflected by the target. In the case where the echoes reflected by the object are superimposed, in the case that the echo pulse signal exists in the corresponding time range through the threshold value, the scanning blind area is re-measured. These are all within the protection scope of the present invention.
  • the present invention further provides a lidar 10 , including: a transmitting unit 11 , a receiving unit 12 , a re-measurement detection and control unit 13 and an emission control unit 14 .
  • the transmitting unit 11 is configured to transmit a first laser detection pulse sequence, the first laser detection pulse sequence including at least a first transmission pulse and a second transmission pulse encoded with a time interval T.
  • the receiving unit 12 is configured to receive a plurality of echo pulses and convert them into electrical signals, wherein the receiving unit 12 can be an avalanche diode (avalance photon diode, APD), a silicon photon multiplier (SiPM) or a single photon avalanche diode array (single photon avalanche diode array).
  • the echo pulses preferably include first echo pulses and second echo pulses corresponding to the first transmit pulses and the second transmit pulses.
  • the re-measurement detection and control unit 13 is configured to determine whether there is a superposition of the multiple echo pulse signals, for example, by detecting whether there is an echo pulse signal within a specific time range to determine whether there is a superposition.
  • the emission control unit 14 is configured to control the lidar to transmit a second laser detection pulse sequence again to perform a re-measurement when the re-measurement detection and control unit 13 determines that the multiple echo pulse signals are superimposed.
  • the lidar 10 further includes a signal processing unit 15 configured to sample the echo pulse sequence received by the receiving unit 12 and generate a sampled signal; process the echo pulse sequence and output a ranging result.
  • the signal processing unit 15 may include, for example, an analog-to-digital converter ADC, a time-to-digital converter TDC, a digital signal processor DSP, a single-chip microcomputer, a microprocessor MCU, etc. various types of hardware and/or software program codes stored in the memory, which may The analog signal or digital signal generated by the receiving unit 12 is converted into an electrical signal for signal acquisition and processing.
  • the retest detection and control unit 13 is further configured to determine the plurality of echo pulses according to the echo pulse signals that are not superimposed with the mask echo signals among the plurality of echo pulse signals Whether the signals are superimposed.
  • the re-measurement detection and control unit 13 is configured to determine whether there is a superposition of the multiple echo pulse signals by detecting whether there is an echo pulse signal within a specific time range, wherein the preset echo pulse signal exists. Let the delay time be ⁇ t, and the specific time range is: the time range from (2T- ⁇ t) to (2T+ ⁇ t) after the first transmission pulse.
  • the retest detection and control unit 13 is configured to determine whether the echo pulse signal is greater than the first threshold if there is an echo pulse signal within the specific time range, and the emission control unit 14 is configured to When the echo pulse signal is greater than the first threshold, the lidar is controlled to transmit a second laser detection pulse sequence for re-measurement
  • ⁇ t is the interval time from the transmission pulse to the echo reflected by the photomask being received by the receiving device, or the link processing time (about 80ns), which can be preset according to the actual measurement results, such as taking the longer of the two A larger value, or the sum of the two, all fall within the protection scope of the present invention.
  • the detected pulse signal is the echo L11 of the first transmitted pulse reflected by the target , then the echo L12 of the second transmitted pulse reflected by the target is at time T after the first detection echo L11. At this time, there is no superposition of the detection echo signal and the mask echo signal, and the lidar decodes normally The distance of the target object is solved by the method, and there will be no situation where the solution cannot be solved.
  • This detected pulse signal is a noise signal and needs to be filtered by a threshold.
  • the detected pulse signal is the echo L12 of the second transmission pulse reflected by the target, then the echo L11 of the first transmission pulse reflected by the target is at time T before the second detection echo L12, and the first detection The echo L11 and the second echo L22 of the mask are superimposed, which will affect the decoding.
  • the echo pulse signal L12 that is not superimposed with the mask echo signal among the plurality of echo pulse signals is used to determine whether the plurality of echo pulse signals are superimposed.
  • the first (noise) threshold shown by the dotted line in FIG. 5b
  • the retest detection and control unit 13 is further configured to determine whether the multiple echo pulse signals are superimposed according to the superposition of the mask echo signal and the echo pulse signal, as follows As described with reference to Figures 6a-6c. According to another preferred embodiment of the present invention, it is determined whether the multiple echo pulse signals are superimposed by detecting whether there is an echo pulse signal within a specific time range, wherein the preset delay time is ⁇ t, and the specific time The range is: the time range from (T- ⁇ t) to (T+ ⁇ t) after the first transmit pulse.
  • the retest detection and control unit 13 is configured to, if an echo pulse signal exists within the specific time range, determine whether the echo pulse signal within the specific time range is greater than a second threshold, and the emission control unit 14 is configured to When the echo pulse signal is greater than the second threshold, the lidar is controlled to transmit a second laser detection pulse sequence to perform re-measurement.
  • ⁇ t is the time from the transmission pulse to the time when the echo reflected by the reticle is received by the receiving device, or the link processing time, which can be preset according to the actual measurement results, such as taking the larger value of the two, or taking The sum of the two is within the protection scope of the present invention.
  • the detected pulse signal is the mask echo L22 of the second emission pulse, or the detected pulse signal is the mask echo L22 of the second emission pulse.
  • the laser radar can calculate the distance of the target in the normal decoding method, and there will be no situation where it cannot be solved.
  • the echo L11 of the first transmitted pulse reflected by the target is superimposed with the second echo L22 of the reticle, the lidar decoding will be affected.
  • the second threshold value may be set based on the superposition of the average value of the echo intensity of the reticle measured multiple times and a threshold value (ie, the first threshold value) for identifying the echo signal, wherein based on the multiple measurements
  • a threshold value ie, the first threshold value
  • the average value of the reticle echo intensity is used to set the threshold to filter the second echo L22 of the reticle, while the first threshold can filter the noise, so that the two are superimposed to filter out the second echo of the reticle within the time range of T ⁇ t.
  • Wave L22 and noise if there is still a pulse signal, the pulse signal is the echo signal L11 of the first transmitted pulse reflected by the target.
  • the lidar 10 includes a signal processing unit 15, and the signal processing unit 15 further includes:
  • the analog-to-digital converter drive module 151 is configured to sample the echo pulse sequence and generate a sampling signal
  • an analog-to-digital converter data processing module 152 configured to perform pulse information extraction on the sampled signal to obtain basic pulse information
  • the pulse processing module 153 is configured to process the basic pulse information and output a ranging result.
  • the distance measurement result includes the pulse front time, pulse width and peak value to obtain the distance and reflectivity of the target, and the detection result is relatively accurate.
  • the emission control unit 14 of the lidar 10 further includes:
  • the emission control module 141 is configured to send a control signal to the emission unit to trigger the emission unit to emit laser detection pulses;
  • the timing control module 142 generates a timing control signal, and sends the timing control signal to the emission control module.
  • lidar 10 in the lidar 10:
  • the retest detection and control unit 13 receives the sampling signal generated by the analog-to-digital converter driving module 151, and detects whether there is an echo pulse signal within a specific time range according to the sampling signal;
  • the re-measurement detection and control unit 13 transmits a re-measurement marker signal to the emission control module 141, and the emission control module 141 triggers the emission unit 11 to send the third emission pulse to perform re-measurement according to the re-measurement marker signal.
  • the re-measurement detection and control unit 13 judges whether there is an echo pulse signal in a specific time range according to the sampling signal sampled by the analog-to-digital converter driving module 151, and if the echo pulse signal is detected in the specific time range, it sends the signal to the transmitter.
  • the control module 141 transmits a re-measurement marker signal, and according to the re-measurement marker signal, the emission control module 141 immediately transmits the third emission pulse to perform the re-measurement after the laser of the current detection channel finishes emitting the laser detection pulse sequence. Measurement.
  • the laser radar 10 provided by this embodiment has the shortest detection and control path and the fastest speed, and can complete the re-measurement operation within the current ranging window to ensure that the point cloud density will not decrease, but additional priority control signals need to be set.
  • the retest detection and control unit 13 receives the sampling signal generated by the analog-to-digital converter driving module 151, and detects whether there is an echo pulse signal within a specific time range according to the sampling signal;
  • the re-measurement detection and control unit 13 transmits a re-measurement marker signal to the timing control module 142, and the sequence control module 142 obtains an idle time period in the ranging window according to the re-measurement marker signal for performing the re-measurement.
  • the re-measurement detection and control unit 13 judges whether there is an echo pulse signal within a specific time range according to the sampling signal sampled by the analog-to-digital converter driving module 151, and if the echo pulse signal is detected within the specific time range, it will be sent to the time sequence.
  • the control module 142 transmits a re-measurement marker signal, and the timing control module 142 obtains an idle time period in the ranging window according to the re-measurement marker signal, that is, before the laser of the next detection channel emits the laser detection pulse sequence, controls the current detection channel
  • the laser transmits the third transmit pulse to perform the repeat measurement.
  • the detection path of the lidar 10 provided in this embodiment is the shortest, and the control path is compatible with the original sequential logic, and a control signal with a higher priority is not required to trigger the laser to emit light.
  • lidar 10 in the lidar 10:
  • the re-measurement detection and control unit 13 receives the ranging result output by the pulse processing module 153, and detects whether there is an echo pulse signal within a specific time range according to the ranging result;
  • the re-measurement detection and control unit 13 transmits a re-measurement marker signal to the emission control module 141, and the emission control module 141 triggers the emission unit 11 to send the third emission pulse to perform re-measurement according to the re-measurement marker signal.
  • the retest detection and control unit 13 judges whether there is an echo pulse signal within a specific time range according to the complete pulse waveform output by the pulse processing module 153, and if an echo pulse signal is detected within a specific time range, sends the signal to the emission control module 141.
  • a re-measurement marker signal is transmitted, and according to the re-measurement marker signal, the emission control module 141 immediately transmits the third emission pulse to perform the re-measurement after the laser of the current detection channel finishes emitting the laser detection pulse sequence.
  • the laser radar 10 provided in this embodiment has a long detection path and a short control path, so the control requires a longer time.
  • the information after the pulse processing module includes information such as the leading edge time, pulse width, and peak value of the pulse, which can be more accurate. After the detection is completed, it is not necessary to calculate and detect the original analog-to-digital converter data, and false detection is not easy to occur.
  • the re-measurement detection and control unit 13 receives the ranging result output by the pulse processing module 153, and detects whether there is an echo pulse signal within a specific time range according to the ranging result;
  • the re-measurement detection and control unit 13 transmits a re-measurement marker signal to the timing control module 142, and the sequence control module 142 obtains an idle time period in the ranging window according to the re-measurement marker signal for performing the re-measurement.
  • the retest detection and control unit 13 judges whether there is an echo pulse signal within a specific time range according to the complete pulse waveform output by the pulse processing module 153, and if an echo pulse signal is detected within a specific time range, then sends the signal to the timing control module 142. Transmit the re-measurement marker signal, and the timing control module 142 obtains an idle time period in the ranging window according to the re-measurement marker signal, that is, before the laser of the next detection channel emits the laser detection pulse sequence, controls the laser of the current detection channel to emit The third transmit pulse is used to perform the retest.
  • the laser radar 10 provided by this embodiment has the longest detection and control path, and has the best compatibility with the original structure of the laser radar. It does not require additional calculation and control, but has the longest path delay and is suitable for a relatively long ranging window. application scenarios.
  • lidar 10 in the lidar 10:
  • the pulse processing module 153 judges whether the re-measurement has been carried out according to the re-measurement marker signal, and which mode is used to carry out the re-measurement. 153 processing algorithm, the ranging result is calculated by means of single-pulse decoding.
  • the second laser detection pulse sequence may be a single pulse or a multi-pulse sequence
  • the signal processing unit is configured to be a single pulse or a multi-pulse sequence according to the second laser detection pulse sequence, respectively.
  • Single-pulse decoding or multi-pulse decoding is used for signal processing, and the retest results are output.
  • a preferred embodiment of the present invention provides a control method for a laser radar, which re-measures the blind area caused by the superposition of the echo signal and the stray light signal generated by the mask, so that the ranging result of the laser radar is more accurate , and achieve full coverage of the field of view within the detection range of the lidar.

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Abstract

一种激光雷达（10）的控制方法（100）及激光雷达（10），激光雷达（10）的控制方法（100）包括：发射第一激光探测脉冲序列，第一激光探测脉冲序列至少包括以时间间隔T编码的第一发射脉冲和第二发射脉冲（S101）；接收多个回波脉冲信号（L11，L12）（S102）；判断多个回波脉冲信号（L11，L12）是否存在叠加（S103）；根据步骤S103的判断结果来控制激光雷达（10）发射第二激光探测脉冲序列进行复测（S104）。激光雷达（10）的控制方法（100）对回波信号与光罩产生的杂光信号叠加所导致的盲区进行复测，从而使激光雷达（10）的测距结果更加准确，并实现了激光雷达（10）探测范围内的视场全覆盖。

Description

激光雷达的控制方法及激光雷达 技术领域
本发明涉及激光探测领域，尤其涉及一种激光雷达的控制方法及激光雷达。
背景技术
对于使用同轴光路收发系统的激光雷达，接收装置除了接收到激光经过物体后反射回来的回波光束(回波信号)，同时也能接收到激光直接通过光罩反射到接收装置的杂散光束(杂光信号)。对于激光雷达中的计算模块来说，杂光信号属于干扰信号，由于杂光信号的存在，会导致计算出错误的测距结果。
在激光雷达测距时采用编码的双脉冲探测光束，两个脉冲分别是第一脉冲A和第二脉冲B，如果目标物对应第一脉冲A的回波信号正好和第二脉冲B的杂光信号叠加，就会导致激光雷达无法识别出双脉冲回波光束，从而造成激光雷达无法测距或者测距精度严重变差。
如图1所示，在正常测距时，激光雷达采用编码的双脉冲探测光束，则回波光束为对应编码的双脉冲回波光束，当测距的回波波形(图1中的第一回波和第二回波)与杂光的回波波形(图1中的光罩第一回波和光罩第二回波)没有重叠，即如图1所示，第一回波的时间在t1位置处，光罩第二回波的时间在t位置处，且t1≠t，这种情况下激光雷达中解码模块可以识别出回波信号(即第一回波和第二回波)，完成回波信号的正确解码；
但是，当测距回波信号与杂光回波信号发生交叠时，如图2所示，由于第一回波信号叠加了杂光第二回波(图中的光罩第二回波)的信号，即如图1所示，第一回波的时间在t1位置处，光罩第二回波的时间在t位置处，且t1≈t，这种波形在解码模块中无法与第二回波完成匹配，从而无法识别成测距回波信号；最终在点云中表现为：在编码时长t对应的区域附近变成了激光雷达的盲区，即对于距离在(ct/2)附近范围内的目标物无法探测和识别。
背景技术部分的内容仅仅是公开人所知晓的技术，并不当然代表本领域的现有技术。
发明内容
有鉴于现有技术的至少一个缺陷，本发明提供一种激光雷达的控制方法，该控制方法对回波信号与光罩产生的杂光信号叠加所导致的盲区进行复测，从而使激光雷达的测距结果更加准确，并实现了激光雷达探测范围内的视场全覆盖。
该控制方法包括：
S101：发射第一激光探测脉冲序列，所述第一激光探测脉冲序列至少包括以时间间隔T编码的第一发射脉冲和第二发射脉冲；
S102：接收多个回波脉冲信号；
S103：判断所述多个回波脉冲信号是否存在叠加；
S104：根据步骤S103的判断结果来控制所述激光雷达发射第二激光探测脉冲序列进行复测。
根据本发明的一个方面，步骤S103进一步包括：根据所述多个回波脉冲信号中未与光罩回波信号叠加的回波脉冲信号来确定所述多个回波脉冲信号 是否存在叠加。
根据本发明的一个方面，所述步骤S103进一步包括：通过检测在特定时间范围内是否存在回波脉冲信号，判断所述多个回波脉冲信号是否存在叠加，其中所述特定时间范围为：发射所述第一发射脉冲之后(2T-Δt)至(2T+Δt)的时间范围，其中所述Δt根据所述第一激光探测脉冲序列与所述第一激光探测脉冲序列对应的光罩回波之间的时间间隔确定。
根据本发明的一个方面，步骤S103进一步包括：若在所述特定时间范围内存在回波脉冲信号，则
判断所述回波脉冲信号是否大于第一阈值，当所述回波脉冲信号大于所述第一阈值时，执行步骤S104。
根据本发明的一个方面，步骤S103进一步包括：根据光罩回波信号与回波脉冲信号的叠加来确定所述多个回波脉冲信号是否存在叠加。
根据本发明的一个方面，所述步骤S103进一步包括：通过检测在特定时间范围内是否存在回波脉冲信号，判断所述多个回波脉冲信号是否存在叠加，其中所述特定时间范围为：发射所述第一发射脉冲之后(T-Δt)至(T+Δt)的时间范围，其中所述Δt根据所述第一激光探测脉冲序列与所述第一激光探测脉冲序列对应的光罩回波之间的时间间隔确定。
根据本发明的一个方面，步骤S103进一步包括：若在所述特定时间范围内存在回波脉冲信号，则
判断所述特定时间范围内的回波脉冲信号是否大于第二阈值，当所述回波脉冲信号大于所述第二阈值时，执行步骤S104。
根据本发明的一个方面，所述第二阈值根据多次测量所述激光雷达的光罩回波强度的平均值和回波脉冲信号的第一阈值得到。
根据本发明的一个方面，步骤S104进一步包括：若所述多个回波脉冲信号存在叠加，则控制所述激光雷达发射第二激光探测脉冲序列进行复测，所述第二激光探测脉冲序列包括第三发射脉冲。
根据本发明的一个方面，步骤S104进一步包括：若所述多个回波脉冲信号存在叠加，则控制所述激光雷达发射第二激光探测脉冲序列进行复测，所述第二激光探测脉冲序列至少包括时间间隔T’编码的第四发射脉冲和第五发射脉冲，所述时间间隔T’与时间间隔T不同。
根据本发明的一个方面，步骤S103进一步包括：
当在所述特定时间范围内检测到回波脉冲信号时，设置复测标记信号，用于调节发射第二激光探测脉冲序列的优先级。
根据本发明的一个方面，步骤S104进一步包括：
根据所述复测标记信号，在当前探测通道的激光器完成发射所述第一激光探测脉冲序列后，立即发射所述第二激光探测脉冲序列来进行所述复测。
根据本发明的一个方面，步骤S104进一步包括：
根据所述复测标记信号，在下一探测通道的激光器发射所述第一激光探测脉冲序列之前，当前探测通道的激光器发射所述第二激光探测脉冲序列来进行所述复测。
根据本发明的一个方面，所述控制方法还包括：
对所述回波脉冲信号进行采样并获取回波脉冲波形。
根据本发明的一个方面，步骤S103进一步包括：
根据对所述回波脉冲信号的采样信号，检测在特定时间范围内是否存在回波脉冲信号。
根据本发明的一个方面，步骤S103进一步包括：
根据所述回波脉冲波形，检测在特定时间范围内是否存在回波脉冲信号。
根据本发明的一个方面，所述步骤S104还包括：在所述步骤S101对应的当前探测通道完成当前探测与下一探测通道开始探测之间完成所述复测，所述控制方法还包括：
对于每一探测通道，在下一探测通道开始探测之前，对所述复测标记信号进行复位。
根据本发明的一个方面，所述控制方法还包括S105：获取复测结果。
根据本发明的一个方面，所述步骤105还包括：
根据所述第二激光探测脉冲序列为单脉冲或多脉冲序列，分别采用单脉冲解码的方式或多脉冲解码的方式进行信号处理，输出所述复测结果。
根据本发明的一个方面，所述激光雷达为同轴激光雷达。
本发明还提供一种激光雷达，包括：
发射单元，配置成发射第一激光探测脉冲序列，所述第一激光探测脉冲序列至少包括以时间间隔T编码的第一发射脉冲和第二发射脉冲；
接收单元，配置成接收多个回波脉冲信号；
复测检测与控制单元，配置成判断所述多个回波脉冲信号是否存在叠加；和
发射控制单元，配置成当所述复测检测与控制单元确定所述多个回波脉冲信号存在叠加时，控制所述激光雷达发射第二激光探测脉冲序列进行复测。
根据本发明的一个方面，所述复测检测与控制单元进一步配置成根据多个回波脉冲信号中未与光罩回波信号叠加的回波脉冲信号来确定所述多个回波脉冲信号是否存在叠加。
根据本发明的一个方面，所述复测检测与控制单元配置成通过检测在特定时间范围内是否存在回波脉冲信号，判断所述多个回波脉冲信号是否存在叠加，其中所述特定时间范围为：所述第一发射脉冲之后(2T-Δt)至(2T+Δt)的时间范围，其中所述Δt根据所述第一激光探测脉冲序列与所述第一激光探测脉冲序列对应的光罩回波之间的时间间隔确定。
根据本发明的一个方面，所述复测检测与控制单元配置成若在所述特定时间范围内存在回波脉冲信号，则判断所述回波脉冲信号是否大于第一阈值，所述发射控制单元配置成当所述回波脉冲信号大于所述第一阈值时，控制所述激光雷达发射第二激光探测脉冲序列进行复测。
根据本发明的一个方面，所述复测检测与控制单元进一步配置成：根据光罩回波信号与回波脉冲信号的叠加来确定所述多个回波脉冲信号是否存在叠加。
根据本发明的一个方面，所述复测检测与控制单元配置成通过检测在特定时间范围内是否存在回波脉冲信号，判断所述多个回波脉冲信号是否存在叠加，其中所述特定时间范围为：所述第一发射脉冲之后(T-Δt)至(T+Δt)的时间范围，其中所述Δt根据所述第一激光探测脉冲序列与所述第一激光探测脉冲序列对应的光罩回波之间的时间间隔确定。
根据本发明的一个方面，所述复测检测与控制单元配置成若在所述特定时间范围内存在回波脉冲信号，则判断所述特定时间范围内的回波脉冲信号是否大于第二阈值，所述发射控制单元配置成当所述回波脉冲信号大于所述第二阈值时，控制所述激光雷达发射第二激光探测脉冲序列进行复测。
根据本发明的一个方面，所述第二阈值根据多次测量所述激光雷达的光罩回波强度的平均值和回波脉冲信号的第一阈值得到。
根据本发明的一个方面，所述激光雷达还包括信号处理单元，所述信号 处理单元包括：
模数转换器驱动模块，配置成对所述回波脉冲信号进行采样，并生成采样信号；
模数转换器数据处理模块，配置成对所述采样信号进行脉冲信息提取，得到脉冲基本信息；和
脉冲处理模块，配置成对所述脉冲基本信息进行处理，输出测距结果。
根据本发明的一个方面，所述发射控制单元包括：
发射控制模块，配置成向所述发射单元发送控制信号，触发所述发射单元发出激光探测脉冲；
时序控制模块，生成时序控制信号，并将所述时序控制信号发送给所述发射控制模块。
根据本发明的一个方面，所述复测检测与控制单元接收所述模数转换器驱动模块生成的采样信号，并根据所述采样信号检测特定时间范围内是否存在回波脉冲信号；
所述复测检测与控制单元向所述发射控制模块发射复测信号，所述发射控制模块根据所述复测信号触发所述发射单元发出所述第二激光探测脉冲序列进行复测。
根据本发明的一个方面，所述复测检测与控制单元接收所述模数转换器驱动模块生成的采样信号，并根据所述采样信号检测特定时间范围内是否存在回波脉冲信号；
所述复测检测与控制单元向所述时序控制模块发射复测信号，所述时序控制模块根据所述复测信号在测距窗口中获得空闲时间段，用于进行所述复测。
根据本发明的一个方面，所述复测检测与控制单元接收所述脉冲处理模块输出的测距结果，并根据所述测距结果检测特定时间范围内是否存在回波脉冲信号；
所述复测检测与控制单元向所述发射控制模块发射复测信号，所述发射控制模块根据所述复测信号触发所述发射单元发出所述第二激光探测脉冲序列进行复测。
根据本发明的一个方面，所述复测检测与控制单元接收所述脉冲处理模块输出的测距结果，并根据所述测距结果检测特定时间范围内是否存在回波脉冲信号；
所述复测检测与控制单元向所述时序控制模块发射复测信号，所述时序控制模块根据所述复测信号在测距窗口中获得空闲时间段，用于进行所述复测。
根据本发明的一个方面，发射控制单元进一步配置成：若所述多个回波脉冲信号存在叠加，则控制所述激光雷达发射第二激光探测脉冲序列进行复测，所述第二激光探测脉冲序列为单脉冲或多脉冲序列。
根据本发明的一个方面，所述信号处理单元配置成根据所述第二激光探测脉冲序列为单脉冲或多脉冲序列，分别采用单脉冲解码的方式或多脉冲解码的方式进行信号处理，输出复测结果。
本发明的优选实施例提供了一种激光雷达的控制方法，该控制方法对回波信号与光罩产生的杂光信号叠加所导致的盲区进行复测，从而使激光雷达的测距结果更加准确，并实现了激光雷达探测范围内的视场全覆盖。
附图说明
附图用来提供对本发明的进一步理解，并且构成说明书的一部分，与本发明的实施例一起用于解释本发明，并不构成对本发明的限制。在附图中：
图1示意性地示出了探测回波与光罩回波没有发生叠加的波形；
图2示意性地示出了探测回波与光罩回波发生叠加的波形；
图3示意性地示出了在第二光罩回波与第一探测回波发生叠加的情况下，接收装置接收到的波形；
图4示出了根据本发明的一个优选实施例的激光雷达的控制方法；
图5a示意性地示出了在2T±Δt的时间范围内检测到脉冲信号的一种情形；
图5b示意性地示出了在2T±Δt的时间范围内检测到脉冲信号的另一种情形；
图5c示意性地示出了在2T±Δt的时间范围内检测到脉冲信号的另一种情形；
图6a示意性地示出了在T±Δt的时间范围内检测到脉冲信号的一种情形；
图6b示意性地示出了在T±Δt的时间范围内检测到脉冲信号的另一种情形；
图6c示意性地示出了在T±Δt的时间范围内检测到脉冲信号的另一种情形；
图7A示意性示出了采用单脉冲进行复测时接收装置接收到的波形；
图7B示意性示出了采用双脉冲进行复测时接收装置接收到的波形；
图8示意性地示出了根据本发明的一个优选实施例的激光雷达；
图9示意性地示出了根据本发明的一个优选实施例的激光雷达；
图10示意性地示出了根据本发明的一个优选实施例的激光雷达；
图11示意性地示出了根据本发明的一个优选实施例的激光雷达；
图12示意性地示出了根据本发明的一个优选实施例的激光雷达；
图13示意性地示出了根据本发明的一个优选实施例的激光雷达。
具体实施方式
在下文中，仅简单地描述了某些示例性实施例。正如本领域技术人员可认识到的那样，在不脱离本发明的精神或范围的情况下，可通过各种不同方式修改所描述的实施例。因此，附图和描述被认为本质上是示例性的而非限制性的。
在本发明的描述中，需要理解的是，术语"中心"、"纵向"、"横向"、"长度"、"宽度"、"厚度"、"上"、"下"、"前"、"后"、"左"、"右"、"竖直"、"水平"、"顶"、"底"、"内"、"外"、"顺时针"、"逆时针"等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本发明和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本发明的限制。此外，术语"第一"、"第二"仅用于描述目的，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量。由此，限定有"第一"、"第二"的特征可以明示或者隐含地包括一个或者更多个所述特征。在本发明的描述中，"多个"的含义是两个或两个以上，除非另有明确具体的限定。
在本发明的描述中，需要说明的是，除非另有明确的规定和限定，术语"安装"、"相连"、"连接"应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或一体地连接:可以是机械连接，也可以是电连接或可以相互通讯； 可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通或两个元件的相互作用关系。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本发明中的具体含义。
在本发明中，除非另有明确的规定和限定，第一特征在第二特征之"上"或之"下"可以包括第一和第二特征直接接触，也可以包括第一和第二特征不是直接接触而是通过它们之间的另外的特征接触。而且，第一特征在第二特征"之上"、"上方"和"上面"包括第一特征在第二特征正上方和斜上方，或仅仅表示第一特征水平高度高于第二特征。第一特征在第二特征"之下"、"下方"和"下面"包括第一特征在第二特征正上方和斜上方，或仅仅表示第一特征水平高度小于第二特征。
下文的公开提供了许多不同的实施方式或例子用来实现本发明的不同结构。为了简化本发明的公开，下文中对特定例子的部件和设置进行描述。当然，它们仅仅为示例，并且目的不在于限制本发明。此外，本发明可以在不同例子中重复参考数字和/或参考字母，这种重复是为了简化和清楚的目的，其本身不指示所讨论各种实施方式和/或设置之间的关系。此外，本发明提供了的各种特定的工艺和材料的例子，但是本领域普通技术人员可以意识到其他工艺的应用和/或其他材料的使用。
以下结合附图对本发明的实施例进行说明，应当理解，此处所描述的实施例仅用于说明和解释本发明，并不用于限定本发明。
采用编码的双脉冲探测光束的情形下，两个发射脉冲之间的时间间隔为T，并且两个发射脉冲分别被目标物反射后形成的两个探测回波、以及两个发射脉冲分别被光罩反射后形成的两个光罩回波之间的时间间隔也为T，由于光传播的速度非常快，可以认为光罩回波在发射探测脉冲的同时到达接收装置，在光罩第二回波与第一探测脉冲被目标物反射的回波发生叠加的情况下，接收装置会接收到如图3所示的波形。如图3所示，光罩第一回波L21与光罩第二回波L22的时间间隔为T，第一发射脉冲被目标物反射的回波L11与第二发射脉冲被目标物反射的回波L12的间隔时间也为T，且此时光罩第二回波L22与第一发射脉冲被目标物反射的回波L11发生叠加(在约等于发射第一发射脉冲之后T的时间位置处)。因此如何判断是否存在扫描盲区，以及如何在确定存在盲区的情况下对扫描盲区进行复测，是本发明所关注的技术问题。
为了解决回波信号与杂光信号叠加所导致的盲区问题，本发明提供了一种激光雷达的控制方法，用于对回波信号与光罩产生的杂光信号叠加所导致的盲区进行复测。
如图4所示，根据本发明一个优选实施例，本发明提供一种激光雷达的控制方法100，包括：
在步骤S101中，发射第一激光探测脉冲序列，所述第一激光探测脉冲序列包括以时间间隔T编码的第一发射脉冲和第二发射脉冲。即发射以时间间隔T编码的双脉冲序列进行探测。
在步骤S102中，接收多个回波脉冲信号。例如可通过光电探测器接收回波脉冲序列并转换为电信号。所述回波脉冲信号中包括与所述第一发射脉冲和第二发射脉冲对应的第一回波脉冲和第二回波脉冲。如果探测范围内存在目标物，则将收到同样时间间隔为T的双回波脉冲。
在步骤S103中，判断所述多个回波脉冲信号是否存在叠加。本发明中可以通过多种方式来判断是否发生了回波脉冲信号的叠加，下面将详细描述。例如可以通过检测在特定时间范围内是否存在回波脉冲信号，即通过检测是 否存在发射脉冲被目标物反射的回波与光罩回波发生叠加的情况，若检测到特定时间范围内存在回波脉冲信号，则执行步骤S104。若未检测到特定时间范围内的回波脉冲信号，则在当前探测通道结束探测后，重新进入步骤S101，驱动下一探测通道发射激光探测脉冲序列。
在步骤S104中，根据步骤S103的判断结果来控制所述激光雷达发射第二激光探测脉冲序列进行复测。例如当判断出所述多个回波脉冲信号中的至少两个回波脉冲信号存在叠加时(在时间上完全或部分重合)，则控制激光雷达发射第二激光探测脉冲序列进行复测。
根据本发明的一个优选实施例，在步骤S103中，根据所述多个回波脉冲信号中未与光罩回波信号叠加的回波脉冲信号来确定所述多个回波脉冲信号是否存在叠加，如下文参考图5a-5c描述的。根据本发明的一个优选实施例，通过检测在特定时间范围内是否存在回波脉冲信号，判断所述多个回波脉冲信号是否存在叠加，其中预设延迟时间为Δt，所述特定时间范围为：发射所述第一发射脉冲之后(2T-Δt)至(2T+Δt)的时间范围。其中步骤S103进一步包括：若在所述特定时间范围内存在回波脉冲信号，则判断所述回波脉冲信号是否大于第一阈值，当所述回波脉冲信号大于所述第一阈值时，执行步骤S104。
发射第一发射脉冲之后2T时间如果存在回波信号，则可能是第二发射脉冲被目标物反射的回波，如果是第二探测回波，则在发射第一发射脉冲之后的T时间附近存在第一探测回波与光罩第二回波叠加的情况。其中Δt为从发射脉冲到发射脉冲被光罩反射的回波被接收装置接收的间隔时间，或为链路处理时间(80ns左右)，可根据实测结果预先设定，如取两者中的较大值，或取两者之和，这些都在本发明的保护范围之内。
如图5a、图5b和图5c所示，当在2T±Δt的时间范围内检测到脉冲信号时，此时分三种情况：如图5a所示，若检测到的脉冲信号是第一发射脉冲被目标物反射的回波L11，则第二发射脉冲被目标物反射的回波L12在第一探测回波L11之后T时间处，此时不存在探测回波信号与光罩回波信号叠加的情况，激光雷达以正常的解码方式解算出目标物的距离，不会出现无法解算的情形。如图5b所示，若检测到的脉冲信号是噪声信号，可以根据预设的第一阈值进行过滤和识别。如图5c所示，若检测到的脉冲信号是第二发射脉冲被目标物反射的回波L12，则第一发射脉冲被目标物反射的回波L11在第二探测回波L12之前T时间处，此时第一探测回波L11与光罩第二回波L22存在叠加的情况，会影响解码。当在2T±Δt的时间范围内检测是否存在脉冲信号，只需判断该时间范围内的脉冲信号是否为回波脉冲，无需滤除光罩回波，判断方法简单。针对图5c的叠加的情形，采用所述多个回波脉冲信号中未与光罩回波信号叠加的回波脉冲信号L12来确定所述多个回波脉冲信号是否存在叠加。当在2T±Δt的时间范围内存在高于第一(噪声)阈值(如图5b中的虚线所示)的回波脉冲信号L12时，即可确定存在回波脉冲信号的叠加。
根据本发明的另一个实施例，在步骤S103中，根据光罩回波信号与回波脉冲信号的叠加来确定所述多个回波脉冲信号是否存在叠加，如下面参考图6a-6c描述的。根据本发明的一个优选实施例，通过检测在特定时间范围内是否存在回波脉冲信号，判断所述多个回波脉冲信号是否存在叠加，其中预设延迟时间为Δt，所述特定时间范围为：发射所述第一发射脉冲之后(T-Δt)至(T+Δt)的时间范围。其中步骤S103进一步包括：若在所述特定时间范围内存在回波脉冲信号，则判断所述特定时间范围内的回波脉冲信号是 否大于第二阈值，当所述回波脉冲信号大于所述第二阈值时，执行步骤S104。
发射第一发射脉冲之后T时间如存在回波信号，则可能是第一发射脉冲被目标物反射的回波，如果是第一探测回波，则在发射第一发射脉冲之后的T时间左右存在探测回波与光罩回波叠加的情况。其中Δt为从发射脉冲到发射脉冲被光罩反射的回波被接收装置接收的时间，或为链路处理时间，可根据实测结果预先设定，如取两者中的较大值，或取两者之和，这些都在本发明的保护范围之内。
如图6a、图6b和图6c所示，当在T±Δt的时间范围内检测到脉冲信号时，此时分三种情况：如图6a所示，检测到的脉冲信号为第二发射脉冲的光罩回波L22。如图6b所示，该检测到的脉冲信号是光罩第二回波与噪声信号的叠加，图6a和图6b所示的情况下，激光雷达以正常的解码方式解算出目标物的距离，不会出现无法解算的情形。如图6c所示，第一发射脉冲被目标物反射的回波L11与光罩第二回波L22叠加，可以根据预设的第二阈值进行识别，这种情况会影响解码。针对图6c的叠加的情形，采用光罩回波信号与回波脉冲信号的叠加来确定所述多个回波脉冲信号是否存在叠加。如图6c所示，当在T±Δt的时间范围的存在高于第二阈值(如图6a-6c中的虚线所示)的回波脉冲信号L11/L22时，即可确定存在回波脉冲信号的叠加。
根据本发明的一个优选实施例，第二阈值可以基于多次测量光罩回波强度的平均值与用于识别回波信号的阈值(即第一阈值)叠加来设定，其中基于多次测量光罩回波强度的平均值来设定阈值可以过滤光罩第二回波L22，同时第一阈值可以过滤噪声，从而两者叠加来滤除在T±Δt的时间范围内光罩第二回波L22与噪声，如果仍然存在脉冲信号，则该脉冲信号为第一发射脉冲被目标物反射的回波信号L11。此种方法通过设定与光罩回波相关的阈值判断该时间范围内的脉冲信号是否为回波脉冲，判定结果精确度较高。
根据本发明的一个优选实施例，其中步骤S103进一步包括：当在所述特定时间范围内检测到回波脉冲信号时，设置复测标记信号，用于调节发射所述第二激光探测脉冲序列的优先级。
优选地，多通道激光雷达的各个探测通道轮巡发光，可以定义当前探测通道发光后至下一探测通道发光前的时间间隔为一个测距窗口，该测距窗口可以根据探测目标物的最大距离来设定，从而根据测距窗口获取目标物对应的飞行时间，则发射第二激光探测脉冲序列进行复测应在测距窗口内完成。一种方法是根据所述复测标记信号，在当前探测通道的激光器完成发射所述激光探测脉冲序列后，立即发射所述第二激光探测脉冲序列来进行所述复测。这种复测方法的好处是能够及时完成复测，不会出现来不及发出第二激光探测脉冲序列，后一探测通道已经开始发射所述激光探测脉冲序列，从而发生叠加的情形；第二种方法是根据所述复测标记信号，在当前测距窗口关闭前，即在下一探测通道的激光器发射所述激光探测脉冲序列之前，当前探测通道的激光器发射所述第二激光探测脉冲序列来进行所述复测。此种复测方法的好处是不会使远距离的目标物的反射的回波信号和复测回波信号产生混淆，且充分利用了相邻探测通道之间依次发光的时间间隔。优选地，所述第二激光探测脉冲序列包括第三发射脉冲，即发射装置发射单脉冲光束作为第三发射脉冲进行探测。可替换的，所述第二激光探测脉冲序列也可以至少包括时间间隔T’编码的第四发射脉冲和第五发射脉冲，所述时间间隔T’与时间间隔T不同。继续发射双脉冲序列的优点在于既可以抗干扰，又可以确保能够接收到回波信号，这些都在本发明的保护范围之内。根据本发明的一个优选实施例，控制方法100还包括：对所述回波脉冲信号进行采样并获取回波脉 冲波形。优选地，利用模数转换器(ADC)采集回波脉冲信号并获取实时回波波形；通过模数转换器采集回波脉冲信号得到采样点，并输入脉冲处理模块进行处理，输出完整波形。在特定时间范围内是否存在回波脉冲信号，可以通过两种方式进行检测：一是直接检测模数转换器采集得到的采样点，即根据采样信号得出是否在特定时间范围内存在回波脉冲信号，这种方式无需等待脉冲处理模块的输出结果，检测时间较短，可以及时进行复测，不会降低激光雷达的点云密度；二是通过脉冲处理模块输出的完整波形进行检测，此种方式的检测对象包括脉冲前沿时间、脉宽和峰值得到目标物的距离和反射率，检测结果较为准确。
根据本发明的一个优选实施例，其中所述步骤S104还包括：在所述步骤S101对应的当前探测通道完成当前探测与下一探测通道开始探测之间完成所述复测，控制方法100还包括：对于每一探测通道，在下一探测通道开始探测之前，对所述复测标记信号进行复位。通过改变复测标记信号的值，控制器控制激光雷达发射第二激光探测脉冲序列进行复测，信号处理单元亦通过该复测标记信号的值判断采用何种算法解算目标物的距离，即当检测到复测标记信号的值改变，则采用单脉冲解码或多脉冲解码的方式获取目标物的距离，这些需在同一测距窗口内完成，因此在下一探测通道开始探测之前，应对复测标记信号进行复位。
根据本发明的一个实施例，所述方法100还包括步骤S105：获取复测结果。在步骤S105中，可以根据第二激光探测脉冲序列为单脉冲还是多脉冲序列，分别采用单脉冲解码的方式或者多脉冲解码的方式进行信号处理，输出复测结果。
图7A示出了采用单脉冲进行复测时接收装置接收到的波形。如图7A所示，在时间t处，来自目标物的第一回波与光罩第二回波发生了叠加，在此情况下，针对同一目标物(即目标物与激光雷达的距离近似不变)，控制激光雷达发射第三发射脉冲(单脉冲)进行复测，发射第三发射脉冲之后，接收装置分别接收到来自光罩的回波脉冲信号P1和来自目标物的复测回波P2，然后进行信号处理，输出复测结果。
图7B示意性示出了采用双脉冲进行复测时接收装置接收到的波形。如图7B所示，在时间t处，来自目标物的第一回波与光罩第二回波发生了叠加，在此情况下，针对同一目标物(即目标物与激光雷达的距离近似不变)，控制激光雷达发射第四发射脉冲和第五发射脉冲(双脉冲)进行复测，发射第四发射脉冲和第五发射脉冲之后，接收装置分别接收到来自光罩的回波脉冲信号P11和P12以及来自目标物的复测回波脉冲信号P21和P22，然后进行信号处理，输出复测结果，其中由于对同一距离的目标物进行复测，光罩的回波脉冲信号P11与复测回波脉冲信号P21的时间间隔依然为t，而复测时采用了时间间隔t'(与时间间隔t不同)编码的双发射脉冲，则复测回波脉冲信号P21和P22之间的时间间隔、光罩的回波脉冲信号P11和P12之间的时间间隔都为t'，图7B中，t'<t，因此复测回波脉冲信号P21与光罩的回波脉冲信号P12不会发生叠加。
根据本发明的一个优选实施例，控制方法100还包括：根据所述复测标记信号，所述激光雷达的控制器采用单脉冲或多脉冲解码的方式进行信号处理，输出复测结果。即根据复测标记信号判断是否进行了复测，以及采用何种模式进行复测，如采用发射单脉冲的模式进行了复测，则改变信号处理单元的处理算法，通过单脉冲解码对应的算法解算出测距结果。通过发射单脉冲进行复测，并通过对应单脉冲测距的算法解算出目标物的距离，相对多脉 冲的测距过程和解算过程，时间较短，也相应地保证了激光雷达的点云密度。
本发明所提供的控制方法100适用于同轴激光雷达，即可能存在探测回波与光罩回波出现叠加的情形。针对双脉冲或多脉冲编码的激光雷达，因为同轴光路的发射和接收都是利用同一光路，因此发射的光中部分被光罩(光罩通常会反射5％-10％的发射光束)反射后会沿原路返回从而被接收装置接收，而旁轴光路的发射光路和接收光路分离，并且两者之间通常会设置隔光装置，因此光罩回波不会对旁轴激光雷达造成干扰。
本发明所提供的复测方法同样适用于多脉冲编码的情况，多个光罩回波与探测回波存在重合，可分别判断或通过综合判断是否存在扫描盲区，并根据判断结果进行复测。例如，针对三脉冲探测的情况，可能存在两个扫描盲区，即光罩第二回波与第一发射脉冲被目标物反射的回波、同时光罩第三回波与第二发射脉冲被目标物反射的回波叠加的情况，在通过阈值判定相应的时间范围内存在回波脉冲信号的情况下，对所述扫描盲区进行复测。这些均在本发明的保护范围之内。
根据本发明的一个优选实施例，如图8所示，本发明还提供一种激光雷达10，包括：发射单元11、接收单元12、复测检测与控制单元13和发射控制单元14。发射单元11配置成发射第一激光探测脉冲序列，所述第一激光探测脉冲序列至少包括以时间间隔T编码的第一发射脉冲和第二发射脉冲。接收单元12配置成接收多个回波脉冲并转换为电信号，其中接收单元12可以为雪崩二极管(avalance photon diode，APD)、硅光电倍增器(silicon photon multiplier，SiPM)或单光子雪崩二极管阵列(single photon avalanche diode array)。所述回波脉冲中优选包括与所述第一发射脉冲和第二发射脉冲对应的第一回波脉冲和第二回波脉冲。复测检测与控制单元13配置成判断所述多个回波脉冲信号是否存在叠加，例如通过检测在特定时间范围内是否存在回波脉冲信号来判断是否存在叠加。发射控制单元14配置成当所述复测检测与控制单元13确定所述多个回波脉冲信号存在叠加时，控制所述激光雷达再次发射第二激光探测脉冲序列进行复测。优选地，激光雷达10还包括信号处理单元15，配置成对接收单元12接收到回波脉冲序列进行采样，并生成采样信号；对回波脉冲序列进行处理，输出测距结果。信号处理单元15例如可以包括模数转换器ADC、时间数字转换器TDC、数字信号处理器DSP、单片机、微处理器MCU等各种类型的硬件和/或存储在存储器中的软件程序代码，可以将接收单元12产生的模拟信号或数字信号转换为电信号进行信号采集和处理。
根据本发明的一个实施例，所述复测检测与控制单元13进一步配置成根据多个回波脉冲信号中未与光罩回波信号叠加的回波脉冲信号来确定所述多个回波脉冲信号是否存在叠加。根据本发明的一个优选实施例，其中所述复测检测与控制单元13配置成通过检测在特定时间范围内是否存在回波脉冲信号，判断所述多个回波脉冲信号是否存在叠加，其中预设延迟时间为Δt，所述特定时间范围为：所述第一发射脉冲之后(2T-Δt)至(2T+Δt)的时间范围。所述复测检测与控制单元13配置成若在所述特定时间范围内存在回波脉冲信号，则判断所述回波脉冲信号是否大于第一阈值，所述发射控制单元14配置成当所述回波脉冲信号大于所述第一阈值时，控制所述激光雷达发射第二激光探测脉冲序列进行复测
发射第一发射脉冲之后2T时间如存在回波信号，则可能是第二发射脉冲被目标物反射的回波，如果是第二探测回波，则在发射第一发射脉冲之后的T时间左右存在第一探测回波与光罩第二回波叠加的情况。其中Δt为从发射 脉冲到发射脉冲被光罩反射的回波被接收装置接收的间隔时间，或为链路处理时间(80ns左右)，可根据实测结果预先设定，如取两者中的较大值，或取两者之和，这些都在本发明的保护范围之内。
当在2T±Δt的时间范围内检测到脉冲信号时，如图5a、5b和5c所述，此时分三种情况：该检测到的脉冲信号是第一发射脉冲被目标物反射的回波L11，则第二发射脉冲被目标物反射的回波L12在第一探测回波L11之后T时间处，此时不存在探测回波信号与光罩回波信号叠加的情况，激光雷达以正常的解码方式解算出目标物的距离，不会出现无法解算的情形。该检测到的脉冲信号是噪声信号，需要通过阈值进行过滤。该检测到的脉冲信号是第二发射脉冲被目标物反射的回波L12，则第一发射脉冲被目标物反射的回波L11在第二探测回波L12之前T时间处，此时第一探测回波L11与光罩第二回波L22存在叠加的情况，会影响解码。针对图5c的叠加的情形，采用所述多个回波脉冲信号中未与光罩回波信号叠加的回波脉冲信号L12来确定所述多个回波脉冲信号是否存在叠加。当在2T±Δt的时间范围内存在高于第一(噪声)阈值(如图5b中的虚线所示)的回波脉冲信号L12时，即可确定存在回波脉冲信号的叠加。
根据本发明的另一个实施例，所述复测检测与控制单元13进一步配置成根据光罩回波信号与回波脉冲信号的叠加来确定所述多个回波脉冲信号是否存在叠加，如下面参考图6a-6c描述的。根据本发明的又一优选实施例，通过检测在特定时间范围内是否存在回波脉冲信号，判断所述多个回波脉冲信号是否存在叠加，其中，预设延迟时间为Δt，所述特定时间范围为：所述第一发射脉冲之后(T-Δt)至(T+Δt)的时间范围。复测检测与控制单元13配置成若在所述特定时间范围内存在回波脉冲信号，则判断所述特定时间范围内的回波脉冲信号是否大于第二阈值，所述发射控制单元14配置成当所述回波脉冲信号大于所述第二阈值时，控制所述激光雷达发射第二激光探测脉冲序列进行复测。
发射第一发射脉冲之后T时间如存在回波信号，则可能是第一发射脉冲被目标物反射的回波，如果是第一探测回波，则在发射第一发射脉冲之后的T时间左右存在探测回波与光罩回波叠加的情况。其中Δt为从发射脉冲到发射脉冲被光罩反射的回波被接收装置接收的时间，或为链路处理时间，可根据实测结果预先设定，如取两者中的较大值，或取两者之和，这些都在本发明的保护范围之内。
当在T±Δt的时间范围内检测到脉冲信号时，此时分三种情况：该检测到的脉冲信号为第二发射脉冲的光罩回波L22，或该检测到的脉冲信号是光罩第二回波与噪声信号的叠加，上述情况下激光雷达以正常的解码方式解算出目标物的距离，不会出现无法解算的情形。当第一发射脉冲被目标物反射的回波L11与光罩第二回波L22叠加时，会影响激光雷达解码。
根据本发明的一个优选实施例，第二阈值可以基于多次测量光罩回波强度的平均值与用于识别回波信号的阈值(即第一阈值)叠加来设定，其中基于多次测量光罩回波强度的平均值来设定阈值可以过滤光罩第二回波L22，同时第一阈值可以过滤噪声，从而两者叠加来滤除在T±Δt的时间范围内光罩第二回波L22与噪声，如果仍然存在脉冲信号，则该脉冲信号为第一发射脉冲被目标物反射的回波信号L11。
根据本发明的一个优选实施例，如图9所示，激光雷达10包括信号处理单元15，信号处理单元15进一步包括：
模数转换器驱动模块151，配置成对所述回波脉冲序列进行采样，并生 成采样信号；
模数转换器数据处理模块152，配置成对所述采样信号进行脉冲信息提取，得到脉冲基本信息；和
脉冲处理模块153，配置成对所述脉冲基本信息进行处理，输出测距结果。所述测距结果包括脉冲前沿时间、脉宽和峰值得到目标物的距离和反射率，检测结果较为准确。
根据本发明的一个优选实施例，如图9所示，激光雷达10的发射控制单元14进一步包括：
发射控制模块141，配置成向所述发射单元发送控制信号，触发所述发射单元发出激光探测脉冲；
时序控制模块142，生成时序控制信号，并将所述时序控制信号发送给所述发射控制模块。
根据本发明的一个优选实施例，如图10所示，激光雷达10中：
复测检测与控制单元13接收模数转换器驱动模块151生成的采样信号，并根据所述采样信号检测特定时间范围内是否存在回波脉冲信号；
复测检测与控制单元13向发射控制模块141发射复测标记信号，发射控制模块141根据所述复测标记信号触发发射单元11发出所述第三发射脉冲进行复测。
即复测检测与控制单元13根据模数转换器驱动模块151采样得到的采样信号，判断特定时间范围内是否存在回波脉冲信号，如果在特定时间范围内检测到回波脉冲信号，则向发射控制模块141发射复测标记信号，发射控制模块141根据所述复测标记信号，在当前探测通道的激光器完成发射所述激光探测脉冲序列后，立即发射所述第三发射脉冲来进行所述复测。
本实施例所提供的激光雷达10检测与控制路径最短，速度最快，可在本次测距窗口内完成复测操作，保证点云密度不会降低，但是需要额外设置优先级控制信号。
根据本发明的一个优选实施例，如图11所示，激光雷达10中：
复测检测与控制单元13接收模数转换器驱动模块151生成的采样信号，并根据所述采样信号检测特定时间范围内是否存在回波脉冲信号；
复测检测与控制单元13向时序控制模块142发射复测标记信号，时序控制模块142根据所述复测标记信号在测距窗口中获得空闲时间段，用于进行所述复测。
即复测检测与控制单元13根据模数转换器驱动模块151采样得到的采样信号，判断特定时间范围内是否存在回波脉冲信号，如果在特定时间范围内检测到回波脉冲信号，则向时序控制模块142发射复测标记信号，时序控制模块142根据所述复测标记信号在测距窗口中获得空闲时间段，即在下一探测通道的激光器发射所述激光探测脉冲序列之前，控制当前探测通道的激光器发射所述第三发射脉冲来进行所述复测。
本实施例所提供的激光雷达10检测路径最短，控制路径与原时序逻辑保持兼容，不需要优先级更高的控制信号来触发激光器发光。
根据本发明的一个优选实施例，如图12所示，激光雷达10中：
复测检测与控制单元13接收脉冲处理模块153输出的测距结果，并根据所述测距结果检测特定时间范围内是否存在回波脉冲信号；
复测检测与控制单元13向发射控制模块141发射复测标记信号，发射控制模块141根据所述复测标记信号触发发射单元11发出所述第三发射脉冲进行复测。
即复测检测与控制单元13根据脉冲处理模块153输出的完整脉冲波形，判断特定时间范围内是否存在回波脉冲信号，如果在特定时间范围内检测到回波脉冲信号，则向发射控制模块141发射复测标记信号，发射控制模块141根据所述复测标记信号，在当前探测通道的激光器完成发射所述激光探测脉冲序列后，立即发射所述第三发射脉冲来进行所述复测。
本实施例所提供的激光雷达10检测路径长，控制路径短，因此控制所需时间更长，但经过脉冲处理模块后的信息包含脉冲的前沿时间、脉宽、峰值等信息，可更准确地完成检测，不需要对原始模数转换器数据计算与检测，不易出现误检。
根据本发明的一个优选实施例，如图13所示，激光雷达10中：
复测检测与控制单元13接收脉冲处理模块153输出的测距结果，并根据所述测距结果检测特定时间范围内是否存在回波脉冲信号；
复测检测与控制单元13向时序控制模块142发射复测标记信号，时序控制模块142根据所述复测标记信号在测距窗口中获得空闲时间段，用于进行所述复测。
即复测检测与控制单元13根据脉冲处理模块153输出的完整脉冲波形，判断特定时间范围内是否存在回波脉冲信号，如果在特定时间范围内检测到回波脉冲信号，则向时序控制模块142发射复测标记信号，时序控制模块142根据所述复测标记信号在测距窗口中获得空闲时间段，即在下一探测通道的激光器发射所述激光探测脉冲序列之前，控制当前探测通道的激光器发射所述第三发射脉冲来进行所述复测。
本实施例所提供的激光雷达10检测与控制路径最长，对激光雷达原本架构的兼容性最好，不需要额外的计算与控制，但路径延时最长，适用于测距窗口时间较为宽裕的应用场景。
根据本发明的一个优选实施例，激光雷达10中：
根据所述复测标记信号，脉冲处理模块153根据复测标记信号，判断是否进行了复测，以及采用何种模式进行复测，如采用发射单脉冲的方式进行了复测，则脉冲处理模块153的处理算法，通过单脉冲解码的方式计算测距结果。
根据本发明的一个实施例，所述第二激光探测脉冲序列可以为单脉冲或多脉冲序列，所述信号处理单元配置成根据所述第二激光探测脉冲序列为单脉冲或多脉冲序列，分别采用单脉冲解码的方式或多脉冲解码的方式进行信号处理，输出复测结果。
本发明的优选实施例提供了一种激光雷达的控制方法，该控制方法对回波信号与光罩产生的杂光信号叠加所导致的盲区进行复测，从而使激光雷达的测距结果更加准确，并实现了激光雷达探测范围内的视场全覆盖。
最后应说明的是：以上所述仅为本发明的优选实施例而已，并不用于限制本发明，尽管参照前述实施例对本发明进行了详细的说明，对于本领域的技术人员来说，其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分技术特征进行等同替换。凡在本发明的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。

Claims (36)

  1. 一种激光雷达的控制方法，包括：
    S101：发射第一激光探测脉冲序列，所述第一激光探测脉冲序列至少包括以时间间隔T编码的第一发射脉冲和第二发射脉冲；
    S102：接收多个回波脉冲信号；
    S103：判断所述多个回波脉冲信号是否存在叠加；
    S104：根据步骤S103的判断结果来控制所述激光雷达发射第二激光探测脉冲序列进行复测。
  2. 如权利要求1所述的控制方法，其中步骤S103进一步包括：根据所述多个回波脉冲信号中未与光罩回波信号叠加的回波脉冲信号来确定所述多个回波脉冲信号是否存在叠加。
  3. 如权利要2所述的控制方法，其中所述步骤S103进一步包括：通过检测在特定时间范围内是否存在回波脉冲信号，判断所述多个回波脉冲信号是否存在叠加，其中所述特定时间范围为：发射所述第一发射脉冲之后(2T-Δt)至(2T+Δt)的时间范围，其中所述Δt根据所述第一激光探测脉冲序列与所述第一激光探测脉冲序列对应的光罩回波之间的时间间隔确定。
  4. 如权利要求3所述的控制方法，其中步骤S103进一步包括：若在所述特定时间范围内存在回波脉冲信号，则
    判断所述回波脉冲信号是否大于第一阈值，当所述回波脉冲信号大于所述第一阈值时，执行步骤S104。
  5. 如权利要求1所述的控制方法，其中步骤S103进一步包括：根据光罩回波信号与回波脉冲信号的叠加来确定所述多个回波脉冲信号是否存在叠加。
  6. 如权利要求5所述的控制方法，其中所述步骤S103进一步包括：通过检测在特定时间范围内是否存在回波脉冲信号，判断所述多个回波脉冲信号是否存在叠加，其中所述特定时间范围为：发射所述第一发射脉冲之后(T-Δt)至(T+Δt)的时间范围，其中所述Δt根据所述第一激光探测脉冲序列与所述第一激光探测脉冲序列对应的光罩回波之间的时间间隔确定。
  7. 如权利要求5或6所述的控制方法，其中步骤S103进一步包括：若在所述特定时间范围内存在回波脉冲信号，则
    判断所述特定时间范围内的回波脉冲信号是否大于第二阈值，当所述回波脉冲信号大于所述第二阈值时，执行步骤S104。
  8. 如权利要求7所述的控制方法，其中所述第二阈值根据多次测量所述激光雷达的光罩回波强度的平均值和回波脉冲信号的第一阈值得到。
  9. 如权利要求1-6中任一项所述的控制方法，其中步骤S104进一步包括：若所述多个回波脉冲信号存在叠加，则控制所述激光雷达发射第二激光探测脉冲序列进行复测，所述第二激光探测脉冲序列包括第三发射脉冲。
  10. 如权利要求1-6中任一项所述的控制方法，其中步骤S104进一步包括：若所述多个回波脉冲信号存在叠加，则控制所述激光雷达发射第二激光 探测脉冲序列进行复测，所述第二激光探测脉冲序列至少包括时间间隔T’编码的第四发射脉冲和第五发射脉冲，所述时间间隔T’与时间间隔T不同。
  11. 如权利要求1-6中任一项所述的控制方法，其中步骤S103进一步包括：
    当在所述特定时间范围内检测到回波脉冲信号时，设置复测标记信号，用于调节发射第二激光探测脉冲序列的优先级。
  12. 如权利要求11所述的控制方法，其中步骤S104进一步包括：
    根据所述复测标记信号，在当前探测通道的激光器完成发射所述第一激光探测脉冲序列后，立即发射所述第二激光探测脉冲序列来进行所述复测。
  13. 如权利要求11所述的控制方法，其中步骤S104进一步包括：
    根据所述复测标记信号，在下一探测通道的激光器发射所述第一激光探测脉冲序列之前，当前探测通道的激光器发射所述第二激光探测脉冲序列来进行所述复测。
  14. 如权利要求1-6中任一项所述的控制方法，还包括：
    对所述回波脉冲信号进行采样并获取回波脉冲波形。
  15. 如权利要求14所述的控制方法，其中步骤S103进一步包括：
    根据对所述回波脉冲信号的采样信号，检测在特定时间范围内是否存在回波脉冲信号。
  16. 如权利要求14所述的控制方法，其中步骤S103进一步包括：
    根据所述回波脉冲波形，检测在特定时间范围内是否存在回波脉冲信号。
  17. 如权利要求11所述的控制方法，其中所述步骤S104还包括：在所述步骤S101对应的当前探测通道完成当前探测与下一探测通道开始探测之间完成所述复测，所述控制方法还包括：
    对于每一探测通道，在下一探测通道开始探测之前，对所述复测标记信号进行复位。
  18. 如权利要求1-6中任一项所述的控制方法，还包括S105：获取复测结果。
  19. 如权利要求18所述的控制方法，所述步骤105还包括：
    根据所述第二激光探测脉冲序列为单脉冲或多脉冲序列，分别采用单脉冲解码的方式或多脉冲解码的方式进行信号处理，输出所述复测结果。
  20. 如权利要求1-6中任一项所述的控制方法，其中所述激光雷达为同轴激光雷达。
  21. 一种激光雷达，包括：
    发射单元，配置成发射第一激光探测脉冲序列，所述第一激光探测脉冲序列至少包括以时间间隔T编码的第一发射脉冲和第二发射脉冲；
    接收单元，配置成接收多个回波脉冲信号；
    复测检测与控制单元，配置成判断所述多个回波脉冲信号是否存在叠加；和
    发射控制单元，配置成当所述复测检测与控制单元确定所述多个回波脉冲信号存在叠加时，控制所述激光雷达发射第二激光探测脉冲序列进行复测。
  22. 如权利要求21所述的激光雷达，其中所述复测检测与控制单元进一步配置成根据多个回波脉冲信号中未与光罩回波信号叠加的回波脉冲信号来确定所述多个回波脉冲信号是否存在叠加。
  23. 如权利要求22所述的激光雷达，其中所述复测检测与控制单元配置成通过检测在特定时间范围内是否存在回波脉冲信号，判断所述多个回波脉冲信号是否存在叠加，其中所述特定时间范围为：所述第一发射脉冲之后(2T-Δt)至(2T+Δt)的时间范围，其中所述Δt根据所述第一激光探测脉冲序列与所述第一激光探测脉冲序列对应的光罩回波之间的时间间隔确定。
  24. 如权利要求23所述的激光雷达，其中所述复测检测与控制单元配置成若在所述特定时间范围内存在回波脉冲信号，则判断所述回波脉冲信号是否大于第一阈值，所述发射控制单元配置成当所述回波脉冲信号大于所述第一阈值时，控制所述激光雷达发射第二激光探测脉冲序列进行复测。
  25. 如权利要求21所述的激光雷达，其中所述复测检测与控制单元进一步配置成：根据光罩回波信号与回波脉冲信号的叠加来确定所述多个回波脉冲信号是否存在叠加。
  26. 如权利要求25所述的激光雷达，其中所述复测检测与控制单元配置成通过检测在特定时间范围内是否存在回波脉冲信号，判断所述多个回波脉冲信号是否存在叠加，其中所述特定时间范围为：所述第一发射脉冲之后(T-Δt)至(T+Δt)的时间范围，其中所述Δt根据所述第一激光探测脉冲序列与所述第一激光探测脉冲序列对应的光罩回波之间的时间间隔确定。
  27. 如权利要求25或26所述的激光雷达，其中所述复测检测与控制单元配置成若在所述特定时间范围内存在回波脉冲信号，则判断所述特定时间范围内的回波脉冲信号是否大于第二阈值，所述发射控制单元配置成当所述回波脉冲信号大于所述第二阈值时，控制所述激光雷达发射第二激光探测脉冲序列进行复测。
  28. 如权利要求27所述的激光雷达，其中所述第二阈值根据多次测量所述激光雷达的光罩回波强度的平均值和回波脉冲信号的第一阈值得到。
  29. 如权利要求17-22中任一项所述的激光雷达，还包括信号处理单元，所述信号处理单元包括：
    模数转换器驱动模块，配置成对所述回波脉冲信号进行采样，并生成采样信号；
    模数转换器数据处理模块，配置成对所述采样信号进行脉冲信息提取，得到脉冲基本信息；和
    脉冲处理模块，配置成对所述脉冲基本信息进行处理，输出测距结果。
  30. 如权利要求29所述的激光雷达，其中所述发射控制单元包括：
    发射控制模块，配置成向所述发射单元发送控制信号，触发所述发射单元发出激光探测脉冲；
    时序控制模块，生成时序控制信号，并将所述时序控制信号发送给所述发射控制模块。
  31. 如权利要求30所述的激光雷达，其中所述复测检测与控制单元接收所述模数转换器驱动模块生成的采样信号，并根据所述采样信号检测特定时间范围内是否存在回波脉冲信号；
    所述复测检测与控制单元向所述发射控制模块发射复测信号，所述发射控制模块根据所述复测信号触发所述发射单元发出所述第二激光探测脉冲序列进行复测。
  32. 如权利要求30所述的激光雷达，其中
    所述复测检测与控制单元接收所述模数转换器驱动模块生成的采样信号，并根据所述采样信号检测特定时间范围内是否存在回波脉冲信号；
    所述复测检测与控制单元向所述时序控制模块发射复测信号，所述时序控制模块根据所述复测信号在测距窗口中获得空闲时间段，用于进行所述复测。
  33. 如权利要求30所述的激光雷达，其中
    所述复测检测与控制单元接收所述脉冲处理模块输出的测距结果，并根据所述测距结果检测特定时间范围内是否存在回波脉冲信号；
    所述复测检测与控制单元向所述发射控制模块发射复测信号，所述发射控制模块根据所述复测信号触发所述发射单元发出所述第二激光探测脉冲序列进行复测。
  34. 如权利要求30所述的激光雷达，其中
    所述复测检测与控制单元接收所述脉冲处理模块输出的测距结果，并根据所述测距结果检测特定时间范围内是否存在回波脉冲信号；
    所述复测检测与控制单元向所述时序控制模块发射复测信号，所述时序控制模块根据所述复测信号在测距窗口中获得空闲时间段，用于进行所述复测。
  35. 如权利要求30所述的激光雷达，其中发射控制单元进一步配置成：若所述多个回波脉冲信号存在叠加，则控制所述激光雷达发射第二激光探测脉冲序列进行复测，所述第二激光探测脉冲序列为单脉冲或多脉冲序列。
  36. 如权利要求35所述的激光雷达，其中所述信号处理单元配置成根据所述第二激光探测脉冲序列为单脉冲或多脉冲序列，分别采用单脉冲解码的方式或多脉冲解码的方式进行信号处理，输出复测结果。
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