WO2022257530A1 - 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
WO2022257530A1
WO2022257530A1 PCT/CN2022/081305 CN2022081305W WO2022257530A1 WO 2022257530 A1 WO2022257530 A1 WO 2022257530A1 CN 2022081305 W CN2022081305 W CN 2022081305W WO 2022257530 A1 WO2022257530 A1 WO 2022257530A1
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pulse
energy
laser
distance measurement
proximity
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PCT/CN2022/081305
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English (en)
French (fr)
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孙恺
向少卿
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上海禾赛科技有限公司
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Priority to KR1020237039253A priority Critical patent/KR20230170761A/ko
Priority to JP2023575486A priority patent/JP2024521950A/ja
Priority to EP22819135.9A priority patent/EP4354175A1/en
Priority to DE112022002066.0T priority patent/DE112022002066T5/de
Publication of WO2022257530A1 publication Critical patent/WO2022257530A1/zh

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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
    • 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
    • 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
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/87—Combinations of systems using electromagnetic waves other than radio 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
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/88—Lidar systems specially adapted for specific applications
    • G01S17/93—Lidar systems specially adapted for specific applications for anti-collision purposes
    • G01S17/931—Lidar systems specially adapted for specific applications for anti-collision purposes of land vehicles
    • 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
    • G01S7/481—Constructional features, e.g. arrangements of optical elements
    • G01S7/4814—Constructional features, e.g. arrangements of optical elements of transmitters alone
    • 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
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K7/00—Modulating pulses with a continuously-variable modulating signal
    • H03K7/08—Duration or width modulation ; Duty cycle modulation
    • 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
    • G01S7/4868—Controlling received signal intensity or exposure of sensor

Definitions

  • the present invention generally relates to the technical field of laser detection, and in particular to a control method of a laser radar and the laser radar.
  • Lidar is usually used for ranging based on the direct time-of-flight method (TOF), that is, by emitting laser pulses with narrow width but high peak power, and measuring the flight time of the laser pulse back and forth between the laser radar and the target for ranging.
  • TOF direct time-of-flight method
  • the measurement principle is based on the measurement of the time-of-flight of the emitted laser pulses. If each laser radar cannot determine whether the received echo pulse is sent by itself, then there is a certain probability that when receiving the echo pulse sent by other radars, it will also It is judged as an echo signal, which leads to an error in the ranging result, that is, crosstalk occurs.
  • the problem of mutual interference between different laser radars has become one of the bottlenecks restricting its development.
  • lasers are divided into four categories: Category 1: Laser radiation must not exceed the threshold of category 1 at the corresponding wavelength and emission duration Laser products; Class 1M: within the wavelength range of 0.3-4 ⁇ m, the energy threshold shall not exceed Class 1 and a smaller measurement aperture shall be adopted; Class 2: laser products whose laser radiation shall not exceed the Class 2 threshold at the corresponding wavelength and emission duration ; Class 2M: In the wavelength range of 0.7-1.4 ⁇ m, the energy threshold shall not exceed Class 2 and shall be evaluated with a smaller measurement aperture or a place farther away from the performance light; Class 3R and 3B: In any wavelength range, it is allowed to exceed Class 1 and Class 2 energy thresholds, but laser products that must not exceed the respective energy thresholds of 3R and 3B; Class 4: Personnel contact with laser products that may exceed the accessible emission limit of Class 3B.
  • Category 1 Laser radiation must not exceed the threshold of category 1 at the corresponding wavelength and emission duration Laser products
  • Class 1M within the wavelength range of 0.3-4 ⁇ m, the energy threshold shall not exceed Class 1 and
  • the wavelength of the laser is set between 0.7-1.4 ⁇ m.
  • the maximum safety for naked eyes is 3R.
  • MPE average MPE max /N
  • the calculated radiation dose MPEAVERAGE of a single pulse is 0.033J/m2. If a continuous pulse is used, the continuous pulse MPETRAIN is 1.962 ⁇ J/m2.
  • the laser wavelength affects the maximum allowable radiation dose of a single pulse; under the same radiation time, when the emitted pulse frequency increases, the maximum allowable radiation dose of continuous pulses increases with The reduction; in the case of the same laser repetition frequency, when the irradiation time increases, the maximum allowable exposure of continuous pulses also decreases; the energy of a single pulse is lower than that of repeated pulses. That is, the maximum allowable irradiation energy of the laser is jointly determined by the wavelength, repetition frequency, irradiation angle and irradiation time.
  • the present invention provides a control method for laser radar, including:
  • S101 Transmit a laser pulse signal according to the pulse code and the current energy allocation strategy, the laser pulse signal includes multiple laser pulses using the pulse code to detect the target;
  • S102 Receive echo information of the plurality of laser pulses reflected by the target.
  • the sum of the energies of the multiple laser pulses is less than a first energy threshold, and the first energy threshold is determined according to the requirement that the total energy of the emitted pulses within a preset time is less than the human eye safety threshold.
  • step S103 further includes:
  • the distance measurement condition is judged according to the echo information of the target object, and when the distance measurement condition is the distance measurement condition, the energy of the distance measurement pulse is increased.
  • step S103 further includes:
  • the energy of the distance measurement pulse is increased, the energy of the proximity measurement pulse is decreased, and the energy of the proximity measurement pulse is greater than a second energy threshold.
  • the telemetry condition includes that the target is located outside the first distance range
  • the second energy threshold is determined according to the detection requirements of the second distance range
  • the second distance range is less than or equal to the The first distance range
  • the energy of the distance measurement pulse is gradually increased at each detection until the sum of the energy of the multiple laser pulses is close to the first An energy threshold.
  • the energy of the distance measurement pulse is increased during the next detection, so that the sum of the energy of the multiple laser pulses is close to the first energy threshold , and the energy of the proximity pulse is close to the second energy threshold.
  • step S103 further includes:
  • the distance measurement pulse and the proximity measurement pulse with energy close to each other are transmitted in the next detection, and the energy of the multiple laser pulses is equal to and approach the first energy threshold.
  • control method further includes:
  • Adjusting the intensity peaks or pulse widths of the multiple laser pulses by adjusting the energy distribution of the multiple laser pulses when the laser radar is emitted next time.
  • control method further includes:
  • the pulse peak value of the multiple laser pulses is increased.
  • control method further includes:
  • the pulse width of the multiple laser pulses is extended/shortened by extending/shortening the emission time of the multiple laser pulses.
  • control method further includes:
  • the present invention also provides a laser radar, including:
  • the emitting unit emits a laser pulse signal according to the pulse code and the current energy allocation strategy, and the laser pulse signal includes a plurality of laser pulses using the pulse code to detect the target;
  • a receiving unit configured to receive echo information reflected by the plurality of laser pulses by the target
  • the control unit is configured to update the energy allocation strategy adopted when the lidar is launched next time according to the echo information of the target.
  • the sum of the energies of the multiple laser pulses is less than a first energy threshold, and the first energy threshold is determined according to the requirement that the total energy of the emitted pulses within a preset time is less than the human eye safety threshold.
  • control unit is further configured to:
  • the distance measurement condition is judged according to the echo information of the target object, and when the distance measurement condition is the distance measurement condition, the energy of the distance measurement pulse is increased.
  • control unit is further configured to:
  • the energy of the distance measurement pulse is increased, the energy of the proximity measurement pulse is decreased, and the energy of the proximity measurement pulse is greater than a second energy threshold.
  • the telemetry condition includes that the target is located outside the first distance range
  • the second energy threshold is determined according to the detection requirements of the second distance range
  • the second distance range is less than or equal to the The first distance range
  • the lidar further includes:
  • the first energy adjustment unit is coupled with the at least one laser and the control unit, and is configured to adjust the driving current/voltage of the at least one laser under the control of the control unit, so as to adjust the laser The pulse peak value of the plurality of laser pulses at the next transmission of the radar.
  • the lidar further includes:
  • the second energy adjustment unit is coupled with the at least one laser and the control unit, and is configured to adjust the emission time of the at least one laser under the control of the control unit, so as to adjust the laser radar The pulse width of the plurality of laser pulses in one shot.
  • a preferred embodiment of the present invention provides a laser radar control method, which emits multiple laser pulses coded at time intervals, and adjusts the energy distribution of the multiple laser pulses in the next emission according to the echo information of the target.
  • the preferred embodiment of the present invention not only takes into account the anti-crosstalk requirements in the short-distance range, but also improves the detection accuracy and detection performance in the long-distance range, and obtains the maximum benefit of laser pulse energy while meeting the safety requirements of human eyes. application.
  • Fig. 1 shows the control method of the lidar according to a preferred embodiment of the present invention
  • Fig. 2 schematically shows the curve of laser eye safety power changing with time
  • Fig. 3 schematically shows the emission pulse sequence and the echo pulse sequence of the lidar
  • Fig. 4 schematically shows the transmitting pulse sequence of the laser radar and the echo pulse sequence received by other radars
  • Figure 5A schematically illustrates the transmission of at least one proximity pulse and at least one telemetry pulse according to a preferred embodiment of the present invention
  • Figure 5B schematically illustrates the transmission of at least one proximity pulse and at least one telemetry pulse according to a preferred embodiment of the present invention
  • Fig. 6 schematically shows the echo situation of at least one proximity pulse and at least one telemetry pulse in different distance ranges according to a preferred embodiment of the present invention
  • Fig. 7A schematically shows transmitting at least one proximity pulse and at least one distance measurement pulse with the same or similar pulse width and different peak powers according to a preferred embodiment of the present invention
  • Fig. 7B schematically shows transmitting at least one proximity pulse and at least one telemetry pulse with the same or similar peak power and different pulse widths according to a preferred embodiment of the present invention
  • Fig. 8 schematically shows a driving circuit of a laser according to a preferred embodiment of the present invention
  • Fig. 9A schematically shows a driving circuit of a laser according to another preferred embodiment of the present invention.
  • FIG. 9B shows the timing changes of each node of the driving circuit in FIG. 9A
  • Fig. 10 schematically shows an energy regulation circuit according to a preferred embodiment of the present invention
  • Fig. 11 schematically shows a laser pulse signal triggered by a switch control signal according to a preferred embodiment of the present invention
  • Fig. 12A schematically shows a double pulse under encoding triggered by a switch control signal according to a preferred embodiment of the present invention
  • Fig. 12B schematically shows a double pulse under another encoding triggered by a switch control signal according to a preferred embodiment of the present invention
  • Fig. 13 schematically shows a lidar according to a preferred embodiment of the present invention.
  • first and second are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features.
  • a feature defined as “first” or “second” may explicitly or implicitly include one or more of said features.
  • “plurality” means two or more, unless otherwise specifically defined.
  • connection should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection.
  • Connected, or integrally connected it can be mechanically connected, or electrically connected, or can communicate with each other; it can be directly connected, or indirectly connected through an intermediary, and it can be the internal communication of two components or the interaction of two components relation.
  • a first feature being “on” or “under” a second feature may include that the first and second features are in direct contact, or may include the first and second features Not in direct contact but through another characteristic contact between them.
  • “on”, “above” and “above” the first feature on the second feature include that the first feature is directly above and obliquely above the second feature, or simply means that the level of the first feature is higher than that of the second feature.
  • "Below”, “below” and “under” the first feature to the second feature include that the first feature is directly above and obliquely above the second feature, or simply means that the first feature has a lower horizontal height than the second feature.
  • the basic idea of the pulse coding scheme is: the laser radar emits laser pulses containing preset code information to detect the target; when receiving the echo, it is identified by the preset code to determine the reflected echo of the detection beam sent by the radar.
  • the pulse encoding can adopt one or more of encoding methods such as time interval encoding, peak intensity encoding, and pulse width encoding.
  • time interval coding multiple laser pulses containing time code information are emitted, preferably, double laser pulses with a preset time interval are emitted, and at the receiving end, according to the time interval of the pulse echo, it is judged whether the echo is the original The reflected echo of the detection beam emitted by the radar.
  • the two laser pulses with a preset time interval may contain the same or different pulse energies, that is, two laser pulses with different energies can be emitted.
  • multiple laser pulses containing peak intensity encoding information are emitted, preferably, three laser pulses with peak intensity having a "high-short-high" variation trend are emitted, and at the receiving end according to the pulse echo
  • the ratio of the peak intensity (the peak intensity of the pulse echo will be attenuated compared with the transmitted pulse, but the ratio is basically unchanged, and a certain tolerance can be set), to determine whether the pulse echo is the reflection of the detection beam emitted by the radar echo.
  • pulse width coding is used to transmit multiple laser pulses containing pulse width coding information.
  • three laser pulses with pulse widths with a "wide-narrow-wide" variation trend are emitted, and at the receiving end according to the pulse echo Pulse width ratio (the echo pulse width will be wider than the transmitted pulse, but the ratio is basically unchanged, and a certain tolerance can be set), to judge whether the pulse echo is the reflected echo of the detection beam sent by the radar.
  • the pulse energy available in one detection needs to be allocated to multiple laser pulses, and the amplitude/pulse width of multiple laser pulses will be affected.
  • the energy obtained by each pulse under the scheme of pulse coding is lower, which reduces the distance measurement performance of the lidar.
  • the preferred embodiment of the present invention provides a laser radar control method, within the scope of meeting the requirements of human eye safety, increase the energy of the distance measurement pulse as much as possible, compress the bottom line of the proximity measurement pulse as much as possible, and make the coded information Laser pulses can have better performance in distance measurement, and at the same time can achieve the effect of anti-crosstalk in near-field measurement.
  • the present invention provides a laser radar control method 10, including step S101, step S102 and step S103.
  • a laser pulse signal is emitted according to the pulse code and the current energy distribution strategy, and the laser pulse signal includes a plurality of laser pulses using the pulse code to detect the target.
  • the pulse coding can adopt one or more of the above-mentioned time interval coding, peak intensity coding, and pulse width coding.
  • the premise of the energy distribution strategy is that the sum of the energy of the transmitted pulses is less than the human eye safety threshold.
  • Fig. 2 schematically shows the graph of the laser power changing with time for human eye safety (may be different because of different wavelengths, repetition frequencies, irradiation angles and irradiation times, both for different types of laser radars, There may be differences in this change curve), since the sum of the time of the transmitted pulses in one detection is much less than 5 ⁇ s, so it only needs to be considered that the energy sum of the transmitted pulses in one detection is less than the human eye safety energy threshold within 5 ⁇ s (for the curve shown in Figure 2 Integrate the eye-safe laser power).
  • Fig. 2 schematically shows the graph of the laser power changing with time for human eye safety (may be different because of different wavelengths, repetition frequencies, irradiation angles and irradiation times, both for different types of laser radars, There may be differences in this change curve), since the sum of the time of the transmitted pulses in one detection is much less than 5 ⁇ s, so it only needs to be considered that the energy sum of the transmitted pulses in one detection is less than the human eye safety
  • FIG. 2 is only a schematic form of the human eye safety power curve corresponding to a laser radar, and the actual human eye safety power conversion may be based on the measurement standards of different dimensions and/or the type and structure of the laser radar , performance and other aspects of the different resulting in different curves.
  • step S102 echo information of the multiple laser pulses reflected by the target is received.
  • the validity of the echo pulse is judged according to whether the echo pulse carries the same encoded information as the transmitted pulse.
  • the echo pulse sequence when the timing of the echo pulse sequence is the same as that of the transmitting pulse sequence, the echo pulse sequence is judged as the echo signal of the transmitting pulse sequence, and the signal is retained. And extract the information carried by the signal.
  • the echo pulse sequence when the timing of the echo pulse sequence is different from the timing of the transmit pulse sequence, the echo pulse sequence is judged to be the echo of the transmit pulse sequence emitted by other laser radars. echo signal and discard the echo pulse train.
  • step S103 according to the echo information of the target, the energy allocation strategy adopted for the next launch of the laser radar is updated.
  • the echo information of the target object judge the distance of the target object and the effectiveness of the echo pulse, and adjust the energy distribution strategy according to the distance of the target object and/or the effectiveness of the echo pulse, so as to meet the requirements of human eye safety. Achieve the best distance measurement performance, and at the same time ensure the anti-interference performance within a certain distance range.
  • each detection pulse is usually kept relatively consistent in ranging capability, that is, multiple laser pulses with similar emission energies are used. Therefore, the small pulses (detection pulses with low energy or power) are often the bottleneck of LiDAR distance measurement performance.
  • the needs of lidar distance measurement and proximity measurement are different.
  • the distance measurement it is necessary to consider the distance measurement capability, and hope to achieve the detection distance as far as possible, which requires the laser pulse to have high energy; at the same time, the probability of crosstalk may be low during the distance measurement.
  • the performance of large pulses detection pulses with high energy or power
  • the probability of crosstalk at short distances increases. Therefore, in practice, it is only necessary to provide anti-crosstalk coding at short distances.
  • the echo information of the target determine the distance range of the current target, or the current ranging conditions of the laser radar, and then according to the target Adjust the energy distribution of the laser pulse according to the distance range/ranging conditions of the object.
  • the sum of the energies of the emitted multiple laser pulses is less than the first energy threshold, wherein the first energy threshold is based on the sum of the energies of the emitted pulses within the preset time
  • the requirement to be less than the eye-safe threshold is determined.
  • the total energy of the laser pulses emitted by the laser radar for multiple detections within a predetermined period of time needs to be less than the human eye safety threshold.
  • the predetermined time period and the corresponding human eye safety threshold are different according to different detection methods and performances of the lidar.
  • the total energy that can be used by the laser radar that adopts the mechanical rotation scanning detection method can be higher, because it will perform rotation scanning during the detection process and will not be fixed in one direction; LiDAR in the detection mode allows less energy because it points in a fixed direction, etc.
  • the predetermined time period is a time interval on the order of microseconds, for example, about 5 ⁇ s.
  • the time required for a lidar detection is tens of nanoseconds to hundreds of nanoseconds. That is, the time for one detection by the lidar is less than a predetermined time period.
  • the sum of the pulse energy available for each detection can be determined, that is, the sum of the energy of multiple laser pulses emitted by a detection can be determined. For example, since the total time of the transmitted pulses in one detection is much less than 5 ⁇ s, it can be directly considered that the total energy of the transmitted pulses in one detection is less than the human eye safety threshold within 5 ⁇ s.
  • the emitted multiple laser pulses include at least one telemetry pulse and at least one proximity pulse, and the at least one telemetry pulse and at least one
  • the sequence of transmitting the proximity pulses is not limited, but the energy/power of the proximity pulses should not be greater than the energy/power of the long-range pulses.
  • the pulse with the greatest energy can be used as the distance-measuring pulse, and the remaining at least two pulses can be used as the proximity pulse, so that the ranging Maximize capacity.
  • a proximity pulse and a telemetry pulse coded at time intervals are transmitted, wherein the sequence of the proximity pulse and the telemetry pulse is not limited.
  • peak intensity and pulse width can also be used for encoding, or a combination of multiple encoding methods in time interval, peak intensity, and pulse width can be used for encoding, all of which are within the protection scope of the present invention .
  • Step S103 of the control method 10 further includes: judging the distance measurement condition according to the echo information of the target object, and increasing the energy of the distance measurement pulse when the distance measurement condition is the distance measurement condition.
  • the radar is currently in the distance measurement condition:
  • the target object is located outside the first distance range. For example, at a distance of 80 meters, the requirements for the performance of the lidar distance measurement are increased at this time, and the requirements for combating crosstalk are reduced.
  • the first distance can be adjusted according to the actual situation and needs.
  • the first distance range is used to indicate an area where better ranging performance can be obtained only based on the telemetry pulse;
  • the echo of the received proximity pulse is weak or no echo of the proximity pulse is received. There may be many reasons at this time, for example, the target is located outside the first distance range, the energy of the proximity pulse is not enough to detect the target, all attenuation or almost all attenuation; the reflectivity of the target is low, and so on.
  • the echoes of both the proximity pulse and the distance pulse can be received by the laser radar; when the target is within a distance of more than 80 meters, LiDAR can only pick up the echoes of the telemetry pulses.
  • the energy of the distance measurement pulse is increased, the energy of the proximity pulse is decreased, and the energy of the proximity pulse is greater than the second energy threshold.
  • the second energy threshold is determined by the basic requirements of the lidar for anti-jamming performance.
  • the sum of the energy of multiple laser pulses must be less than the first energy threshold in one detection as mentioned above, in order to further increase the energy of the distance measuring pulse, it can be achieved by reducing the energy of the proximity measuring pulse.
  • the first distance range for example, 80 meters
  • the requirement for distance measurement performance is increased, and the requirement for anti-crosstalk function is reduced, and the energy of the proximity measurement pulse can be appropriately reduced.
  • the echo of the proximity pulse is weak, or the echo of the proximity pulse is not received, the proximity pulse cannot play a practical role in analyzing the distance of the target object, so the proximity pulse can also be appropriately reduced energy of.
  • the limitation on the proximity pulse energy is determined by the basic anti-crosstalk requirements of the laser radar, that is, when the target returns to within the second distance range (for example, 50 meters), the demand for the anti-crosstalk function of the laser radar increases. The requirements are lowered. In this case, the laser radar is required to still be able to detect and distinguish the reflected echoes of the detection beam emitted by the radar.
  • the telemetry condition includes that the target is located outside the first distance range (for example, 80 meters), and the second energy threshold is determined according to the detection requirements of the second distance range (for example, 50 meters).
  • the first distance range is 80 meters and the second distance range is 50 meters. According to actual detection needs, it is also feasible to set the first distance range to be less than or equal to the first distance range. Yes, these are all within the protection scope of the present invention.
  • the second distance range is the range where the laser radar has a high anti-crosstalk requirement. For example, within the range of 50 meters near the laser radar, the laser radar The emitted echo signal corresponding to the detection beam may be affected by other lidars mounted on the vehicle, or by the lidars mounted on nearby passing vehicles.
  • the first distance range is the range where the laser radar has high requirements for distance measurement performance. For example, within the range of 80 meters away from the laser radar, the distance measurement condition includes analyzing the target object located outside the first distance range according to the echo information. .
  • the energy of the distance measurement pulse is gradually increased at each detection until the sum of the energy of multiple laser pulses is close to the first energy threshold, wherein the energy of the proximity pulse is not lower than the second energy threshold.
  • the first energy threshold is determined according to the human eye safety threshold
  • the second energy threshold is determined according to the basic requirements of the lidar for anti-jamming performance. That is, the energy allocation strategy is switched step by step.
  • the first energy threshold determined according to the human eye safety threshold is 800nJ
  • the second energy threshold determined according to the basic anti-jamming requirements of the lidar is 100nJ.
  • the energy distribution strategy of the dual-pulse detection scheme using time interval coding is shown in the table below.
  • pulse code Telemetry pulse energy Measuring near pulse energy PCode1 300nJ 300nJ PCode2 400nJ 300nJ PCode3 500nJ 300nJ PCode4 600nJ 200nJ PCode5 700nJ 100nJ
  • the default is to use PCode1 for encoding.
  • the energy of the distance measurement pulse is increased by 100nJ, that is, it is switched to PCode2; the distance measurement condition is still determined according to the echo information.
  • the remote condition in the next detection, increase the energy of the long-distance pulse by 100nJ, that is, switch to PCode3.
  • the upper limit of the sum of the double-pulse energy can be set near the first energy threshold and not exceeding the first energy threshold, such as 750nJ); according to the echo information, when the distance measurement condition is still the distance measurement condition, in the next detection, the Increase the energy of the telemetry pulse by 100nJ, and reduce the energy of the proximity pulse by 100nJ at the same time, that is, switch to PCode4; judge that the distance measurement condition is still the telemetry condition according to the echo information, and increase the energy of the distance measurement pulse by 100nJ in the next detection At the same time, reduce the energy of the proximity pulse by 100nJ, that is, switch to PCode5.
  • the energy of the proximity pulse has dropped to the second energy threshold; if the distance measurement condition is still the distance measurement condition according to the echo information, the next time For detection, continue to use PCode5 for detection; if in any detection, if the distance measurement condition is judged to be the proximity condition according to the echo information (that is, there may be a target at a short distance), the code can be switched back to PCode1...
  • the measurement Remote conditions include:
  • the ranging information obtained within the predetermined time is all located outside the first distance range (for example, 80 meters). Analyzing the distance of the target object according to the echo information, the ranging information obtained within a predetermined time indicates that the target object is located outside the first distance range; and/or
  • the echo of the received proximity pulse is weak or no echo of the proximity pulse is received;
  • the radar optical axis faces a specific angle (for example, facing the front of the vehicle).
  • the demand for detection accuracy is increased, and for the front direction, the crosstalk of surrounding vehicles is improved, and the demand for anti-interference is relatively reduced.
  • the energy distribution measurement is adjusted between the proximity pulse and the distance measurement pulse, so as to Optimize probing results.
  • the step size of the step-by-step adjustment can be made larger or smaller. It can even achieve the effect of approximately stepless adjustment, for example, by setting a resistance adjustment module that can be approximately steplessly changed, the stepless adjustment of laser energy can be realized.
  • the energy of the distance measurement pulse is increased during the next detection, so that the energy sum of multiple laser pulses is close to the first energy threshold, and the energy of the proximity pulse The energy approaches a second energy threshold.
  • the "closer” mentioned here is used to indicate the trend of energy adjustment, that is: the sum of the adjusted energies of the multiple laser pulses is closer to the first energy threshold than the sum of the energies before the adjustment, and, The energy of the proximity pulse after adjustment is closer to the second energy threshold than the energy before adjustment.
  • the first energy threshold is determined according to the human eye safety threshold, for example, according to the laser product safety standards of various countries or regions and the type and detection mode of the actual radar product used, the first energy threshold can be calculated; the second energy threshold is based on the laser
  • the basic requirements of radar for anti-jamming performance are determined. That is, a one-time switch is performed for the energy allocation strategy.
  • the first energy threshold determined according to the human eye safety threshold is 800nJ
  • the second energy threshold determined according to the basic anti-jamming requirements of the lidar is 100nJ.
  • the energy allocation strategy of the dual-pulse detection scheme using time interval coding is shown in the table below.
  • pulse code Measuring near pulse energy Telemetry pulse energy PCode6 400nJ 400nJ PCode7 600nJ 200nJ
  • Telemetry conditions include:
  • the ranging information obtained within the predetermined time is all located outside the first distance range (for example, 80 meters); and/or
  • the echo of the received proximity pulse is weak or no echo of the proximity pulse is received;
  • the radar optical axis faces a specific angle (for example, facing the front of the vehicle).
  • the multiple laser pulses include at least one telemetry pulse and at least one proximity pulse
  • step S103 further includes:
  • the proximity conditions include:
  • the ranging information obtained within the predetermined time is all within the second distance range (for example, 50 meters). That is, the distance of the target object is analyzed according to the echo information, and the ranging information obtained within a predetermined time indicates that the target object is located in an area where crosstalk frequently occurs near the laser radar; and/or
  • the distance measurement pulse and the proximity measurement pulse with energy close to each other are transmitted at the next detection, and the energy sum of multiple laser pulses is close to the first energy threshold . Transmits a double pulse sequence coded at time intervals with similar energies to achieve the best short-distance detection performance (anti-crosstalk performance).
  • the first energy threshold determined according to the human eye safety threshold is 800nJ
  • the second energy threshold determined according to the basic anti-jamming requirements of the lidar is 100nJ.
  • the dual-pulse detection scheme using time interval coding, the energy distribution strategy is shown in Table 2 above: currently PCode2 is used for coding, and when the proximity conditions are met, switch to PCode1.
  • control method 10 further includes:
  • Adjust the intensity peak or pulse width of multiple laser pulses by adjusting the energy distribution of multiple laser pulses when the lidar is next fired.
  • the peak intensity and/or pulse width of the laser pulse can be adjusted to achieve the purpose of adjusting energy distribution.
  • the ratio (change trend) of the peak intensity can be kept unchanged, and the energy distribution can be adjusted by adjusting the pulse width.
  • the ratio (change trend) of the pulse width can be kept unchanged, and the energy distribution can be adjusted by adjusting the peak intensity.
  • the proximity pulse and the distance pulse in the same detection can have the same or similar pulse time, but different peak powers (as shown in FIG. 7A ), It is also possible that the pulse peak power is the same or similar, but the pulse time is different (as shown in FIG. 7B ).
  • the pulse peak power is the same or similar, but the pulse time is different (as shown in FIG. 7B ).
  • FIG. 7A preferably, it is applied to a multi-channel mechanical radar, and the detection accuracy is improved through a telemetry pulse with a high peak power, and crosstalk is prevented through a double pulse code.
  • FIG. 7B preferably, it is applied to an area array flash solid-state lidar, and the telemetry pulse with a wider pulse width is used to increase the probability of photon reception, and the double-pulse code is used to prevent crosstalk.
  • the operations required to adjust the peak intensity and/or pulse width are also different.
  • the detection end does not need to be adjusted accordingly when energy adjustment is performed; for example, when peak encoding is used, the initial waveform
  • the pulse width of each pulse is the same and the peak value is different
  • the distribution ratio information used by the detection terminal for verification can be based on The adjustment of energy distribution is updated; similarly, when pulse width encoding is used, the pulse width of each pulse in the initial waveform is different, and the peak value is the same, then when the energy distribution is adjusted, the distribution ratio adopted by the detection end can also be updated accordingly information.
  • the transmitting unit of the laser radar emits a multi-pulse sequence using time interval coding and an energy distribution strategy.
  • this multi-pulse sequence for example, the first laser pulse and the second laser pulse (a telemetry pulse) are included. and a proximity pulse), of course, is not general, and may also include the first laser pulse, the second laser pulse...the Nth laser pulse, and the multiple laser pulses have a time sequence relationship.
  • the above time interval describes the timing relationship of the transmitted pulse sequence.
  • the receiving unit can still determine the reflected echo of the transmitted pulse sequence sent by the radar by verifying the timing relationship between the echo pulse sequence and the transmitted pulse sequence.
  • the transmitting unit of the laser radar transmits a multi-pulse sequence using peak intensity encoding and an energy distribution strategy, wherein the energy distribution strategy includes: reducing the energy of the proximity pulse in the case of conforming to the distance measurement mode , and increase the energy of the telemetry pulse.
  • the multi-pulse sequence includes a distance-measuring pulse and a proximity-measuring pulse.
  • the peak ratio of the distance-measuring pulse and the proximity-measuring pulse is 1.2:1. :1, to determine whether the pulse received is the laser radar to which it belongs.
  • the energy of the proximity pulse is reduced by 50%, and the 50% energy is transferred to the distance measurement pulse.
  • the distance between the distance measurement pulse and the proximity pulse The peak ratio may be 1.7:0.5, that is, 3.4:1, and correspondingly update the peak ratio of the echo pulse judged by the detection end to be 3.4:1.
  • the transmitting end transmits the distance measuring pulse and the proximity measuring pulse according to the new energy distribution ratio measurement, and the detecting end judges whether the received echo is a correct echo pulse according to the new energy distribution ratio.
  • the transmitting unit of the laser radar transmits a multi-pulse sequence using a pulse width encoding and energy allocation strategy.
  • the multi-pulse sequence includes a strong pulse and a weak pulse, and the pulse width ratio of the strong pulse to the weak pulse is 2:1, that is, the pulse width of the strong pulse is twice that of the weak pulse.
  • the detection end determines whether the received pulse is the laser radar to which it belongs.
  • the transmitting end transmits the distance measuring pulse and the proximity measuring pulse according to the new energy distribution ratio measurement, and the detecting end judges whether the received echo is the correct echo pulse according to the new energy distribution ratio.
  • the lidar continues to detect according to the new energy distribution ratio.
  • the current distance measurement information is 46 meters and belongs to the proximity mode
  • the ratio is 1.5:1, so that the pulse codes of the long-range pulse and the near-measuring pulse can be better used to distinguish the pulses emitted by the laser radar.
  • the distance measurement mode can have multiple levels.
  • the distance measurement mode can be divided into medium and long distance (for example, 50-100 meters) and ultra long distance (for example, greater than 100 meters), and the detection end is only in In the mid-range and long-range mode, the judgment is performed according to the new energy distribution ratio.
  • the ultra-long-range mode as long as the echo pulse is received, it is regarded as the echo pulse corresponding to the telemetry pulse.
  • the interference from other lidars or emission sources is already very small and can be ignored, and only the pulses that can be received can be considered. At this point, the detection end can no longer verify the pulse code.
  • part of the proximity pulse when a detection is encoded with one distance measurement pulse and more than two proximity pulses, part of the proximity pulse can be removed, and the energy of this part of the proximity pulse can be allocated to the distance measurement pulse Pulse, and correspondingly adjust the anti-crosstalk judgment conditions adopted by the detection end to make judgments based on the pulse code after the energy is redistributed.
  • the lidar initially uses three-pulse encoding, and the peak ratio of the three pulses pulse1, pulse2, and pulse3 is 1:2:3, of which the largest peak value is the long-range pulse, and the remaining two are near-measuring pulses.
  • the detection end needs to determine that the echo pulse belongs to the laser radar when it receives three echo pulses and the energy ratio of the three echo pulses is 1:2:3.
  • the laser radar determines that it is currently in the distance measurement mode, the energy of the pulse pulse1 with the smallest energy is transferred to the largest pulse pulse3, that is, the laser radar only transmits double-pulse codes with a peak ratio of 2:4, and updates the detection end.
  • the judgment condition is to determine that the echo pulse belongs to the laser radar when receiving two pulses with an energy ratio of 2:4. Conversely, when entering the proximity mode from the distance measurement mode, the transmission and detection are still performed according to the three-pulse encoding with a peak ratio of 1:2:3.
  • a certain tolerance can be set for the energy distribution of the telemetry pulse and the proximity pulse.
  • the transmitting unit adjusts the energy distribution strategy by adjusting the pulse width of multiple laser pulses
  • the receiving unit determines the pulse of the multi-pulse sequence for this detection according to the energy distribution strategy updated by the control unit of the laser radar The preset proportional relationship of the width, and then by verifying the ratio of the echo pulse sequence to the pulse width of the transmitted pulse sequence to determine the reflected echo of the transmitted pulse sequence sent by the radar, a certain tolerance can be set.
  • the energy distribution measurement in the case of distance measurement can only increase the distance energy of the pulse without reducing the energy of the near-measuring pulse.
  • control method 10 further includes: increasing the pulse peak value of the multiple laser pulses by increasing the maximum driving current/voltage of the multiple laser pulses.
  • a voltage-adjustable driving circuit or a laser driving circuit including multiple energy storage circuits can be used to adjust the energy of each pulse.
  • the current on the laser is directly proportional to the driving voltage applied to the laser, and inversely proportional to the resistance of the circuit where the laser is located. Therefore, there are two main ways to adjust the current/voltage on the laser, one is to adjust the driving voltage, and the other is to adjust the resistance.
  • FIG. 8 shows a schematic diagram of an implementation of a circuit structure that can adjust the energy of the emission pulse by adjusting the current on the laser.
  • the current of the laser shown in Figure 8 has the following relationship with the applied voltage and resistance:
  • HVDD1 is the driving voltage applied on the laser
  • Rd is the equivalent resistance of the laser itself
  • Rdson is the total resistance of the PMOS and other devices connected to it. Therefore, there are two main methods for adjusting Imax, one is to adjust the voltage HVDD1, and the other is to adjust the resistance Rdson.
  • a control module On the basis of the above adjustable circuit, a control module is integrated.
  • the control module can switch multiple sets of pulse codes, which can be directly switched based on the above two coding methods, or pulse codes adjusted step by step to generate pulse control signals respectively.
  • pulse control signal to adjust the input voltage HVDD1, or the resistance value Rdson to emit corresponding laser pulses.
  • the timing diagram of the regulating circuit shown in FIG. 9A is shown in FIG. 9B.
  • the current intensity of the laser corresponds to the magnitude of the voltage Vx
  • Vx can be passed through the low voltage Linear regulator (LDO) output V2 to regulate.
  • LDO Linear regulator
  • Vx becomes smaller
  • Vx becomes larger
  • the laser current can be adjusted, that is, the emission pulse can be adjusted.
  • Fig. 10 schematically shows a circuit implementation using an energy storage module.
  • multiple energy storage modules are connected to the power supply module, each energy storage module is connected to a control switch, and the control switch is responsible for controlling the on-off of the energy storage module and the laser emitting unit.
  • the control switch is responsible for controlling the on-off of the energy storage module and the laser emitting unit.
  • the control switch between a certain energy storage module and the laser emitting unit is closed, the charge stored in the energy storage module drives the laser emitting unit to emit light pulses.
  • the unit switches shown in FIG. 10 may be independent of each other, and the control switches are independently controlled by the control unit. At the same moment in time sequence, the control unit may control the control switches to open or close independently.
  • the emitted laser pulse energy is the sum of the energy of several energy storage modules.
  • the detection of distant objects can be realized.
  • the pulse shape transmitted in the sequence can be controlled. For example, at a certain moment, only one control switch is closed, then the pulse intensity transmitted at this moment is 1 unit, and at a subsequent time N control switches are closed, then the pulse intensity transmitted at the corresponding moment is N units.
  • the timing and intensity of the emission pulses can be controlled.
  • multiple laser pulses with the same or similar pulse width and different peak powers are obtained by controlling the emission time of multiple laser pulses.
  • the switch trigger signal (TRIGGER) is triggered at the end of the switch control signal (GATE1, GATE2,..., GATEN), for example, the timing falling edge of the switch control signal (GATE1, GATE2,..., GATEN) shown in the figure triggers the switch trigger signal (TRIGGER ) falling edge; without loss of generality, if the end of the switch trigger signal (TRIGGER) is the rising edge of the timing signal, the rising edge is used as the trigger timing of the switch control signal, so as to ensure that the light emitting process starts after the charging is completed, and After the previous charging and lighting process ends, the next charging-lighting process can start immediately.
  • control method 10 further includes:
  • the driving current/voltage is kept constant, and the pulse width of the multiple laser pulses is extended/shortened by extending/shortening the emission time of the multiple laser pulses. That is, multiple laser pulses with the same or similar peak power and different pulse widths are obtained as shown in FIG. 7B .
  • the specific circuit implementation structure for adjusting the emission time will not be repeated here.
  • the present invention also provides a laser radar 100 including a transmitting unit 110 , a receiving unit 120 and a control unit 130 . in:
  • the emitting unit 110 emits a laser pulse signal, the laser pulse signal includes a plurality of laser pulses coded at time intervals, for detecting the target;
  • the receiving unit 120 is configured to receive echo information of the multiple laser pulses reflected by the target;
  • the control unit 130 is configured to adjust the energy distribution of the plurality of laser pulses when the laser radar emits next time according to the echo information of the target.
  • the sum of the energies of multiple laser pulses is less than a first energy threshold, and the first energy threshold is determined according to the requirement that the total energy of the emitted pulses within a preset time is less than the human eye safety threshold.
  • control unit 130 is further configured to:
  • the distance measurement condition is judged according to the echo information of the target object, and when the distance measurement condition is the distance measurement condition, the energy of the distance measurement pulse is increased.
  • control unit 130 is further configured to:
  • the energy of the distance measurement pulse is increased, and the energy of the proximity pulse is decreased, and the energy of the proximity pulse is greater than the second energy threshold.
  • the second energy threshold is determined according to the detection requirements of the second distance range, and the second distance range is less than or equal to the first distance range .
  • the lidar 100 also includes:
  • the first energy adjustment unit is coupled with the at least one laser and the control unit 130, and is configured to adjust the driving current/voltage of the at least one laser under the control of the control unit 130, so as to adjust the laser radar 100 when it emits the next time Pulse peak of multiple laser pulses.
  • the lidar 100 also includes:
  • the second energy adjustment unit is coupled with the at least one laser and the control unit 130, and is configured to adjust the emission time of the at least one laser under the control of the control unit 130, so as to adjust the laser radar 100 when it emits next time.
  • the pulse width of the laser pulse is coupled with the at least one laser and the control unit 130, and is configured to adjust the emission time of the at least one laser under the control of the control unit 130, so as to adjust the laser radar 100 when it emits next time.
  • the pulse width of the laser pulse is coupled with the at least one laser and the control unit 130, and is configured to adjust the emission time of the at least one laser under the control of the control unit 130, so as to adjust the laser radar 100 when it emits next time.
  • a preferred embodiment of the present invention provides a laser radar control method, which emits multiple laser pulses coded at time intervals, and adjusts the energy distribution of the multiple laser pulses in the next emission according to the echo information of the target.
  • the preferred embodiment of the present invention not only takes into account the anti-crosstalk requirements in the short-distance range, but also improves the detection accuracy and detection performance in the long-distance range, and obtains the maximum benefit of laser pulse energy while meeting the safety requirements of human eyes. application.

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Abstract

一种激光雷达的控制方法，包括：S101：根据脉冲编码以及当前的能量分配策略，发射激光脉冲信号，激光脉冲信号包括采用脉冲编码的多个激光脉冲，用以探测目标物；S102：接收多个激光脉冲被目标物反射的回波信息；和S103：根据目标物的回波信息，更新激光雷达下一次发射时所采用的能量分配策略。既兼顾了近距离范围内的抗串扰需求，又提高了远距离范围内的探测精度和探测性能，在满足人眼安全要求的同时，获得了激光脉冲能量的最大效益的应用。

Description

激光雷达的控制方法及激光雷达 技术领域
本发明大致涉及激光探测技术领域，尤其涉及一种激光雷达的控制方法及激光雷达。
背景技术
激光雷达用于测距通常基于直接飞行时间法(TOF)，也即通过发射宽度窄但峰值功率高的激光脉冲，测量激光脉冲在激光雷达和目标物之间来回的飞行时间进行测距。
在同一测量范围内，同时有多台激光雷达在工作的场景下，例如，在一辆车上安装多台激光雷达时，或者多辆安装有激光雷达的车辆相距较近时，由于激光雷达的测量原理是基于对发射激光脉冲的飞行时间进行测量，如果每台激光雷达无法判别收到的回波脉冲是不是自己发出的，那么有一定概率接收到其他雷达发出的回波脉冲时，也会被判定为回波信号，从而导致测距结果的错误，亦即会发生串扰。多台激光雷达同时工作时，不同激光雷达之间相互干扰的问题成为了制约其发展的瓶颈之一。
目前，采用多脉冲编码的方式对回波信号进行识别，是一种行之有效的激光雷达的抗干扰方案。然而，采用脉冲编码会影响到激光雷达的测远性能。
这是因为，激光雷达每次发射脉冲的能量受到人眼安全要求的范围限制。亦即每次发射脉冲的能量不能无限制地提高，需要低于人眼安全阈值。
比如，在我国，根据《中华人民共和国国家标准激光产品安全第14部分用户指南》，将激光器分为四大类：1类：在相应波长和发射持续时间内，激光辐射不得超过1类阈值的激光产品；1M类：波长在0.3-4μm范围内，能量阈值不得超过1类且采用更小的测量孔径；2类：在相应波长和发射持续时间内，激光辐射不得超过2类阈值的激光产品；2M类：波长在0.7-1.4μm范围内，能量阈值不得超过2类且采用更小的测量孔径或距表现光距离更远的地方评估；3R和3B类：在任何波长范围内，允许超过1类、2类能量阈值，但不得超过3R和3B各自能量阈值的加光产品；4类：人员接触有可能超过3B类可达发射极限的激光产品。
在实际的应用过程中，激光如果直接照射将对人眼，会对人眼产生伤害，因此对于激光器的选择是具有严格要求的。通常，激光器的波长设置在0.7-1.4μm之间，根据《指南》的分类，对于裸眼安全的最大限度为3R类。以波长为905nm为例，假定照射持续时间为t等于10s，脉冲重频率f为8.8kHz，则该时间内的脉冲个数N为8×104个，其对角膜最大允许辐照量MPEMAX为2601.4J/m2。根据公式:MPE average＝MPE max/N,计算得出单个脉冲的辐照量MPEAVERAGE为0.033J/m2。如果采用连续脉冲，得到连续脉冲MPETRAIN为1.962μJ/m2。
此外，根据国际标准，在规定辐照角度的情况下，激光波长影响单脉冲最大允许辐照量；在相同的辐照时间下，当发射的脉冲频率增大时，连续脉冲最大允许照射量随之降低；在激光重频率相同情况下，当辐照时间增大时，连续脉冲最大允许照射量也随之减少；单个脉冲能量比重复脉冲能量低。即，激光最大允许辐照能量是由波长、重频率、辐照角度和辐照时间共同决定的。
在受到上述人眼安全要求制约的情况下，激光雷达每次探测发射的脉冲数量越多，每个脉冲能够被分配到的能量将越少，则其可探测的距离就越近。而若每次探测仅发射单个脉冲，又无法很好的解决防串扰问题，会极大影响激光雷达的点云质量。在采用多脉冲编码技术的背景下，如何兼顾激光雷达的测远能力和人眼安全要求，是本领域亟待解决的技术问题。
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，包括：
S101：根据脉冲编码以及当前的能量分配策略，发射激光脉冲信号，所述激光脉冲信号包括采用所述脉冲编码的多个激光脉冲，用以探测目标物；
S102：接收所述多个激光脉冲被目标物反射的回波信息；和
S103：根据所述目标物的回波信息，更新所述激光雷达下一次发射时所采用的所述能量分配策略。
根据本发明的一个方面，其中所述多个激光脉冲的能量之和小于第一能量阈值,所述第一能量阈值根据预设时间内发射脉冲的总能量小于人眼安全阈值的要求确定。
根据本发明的一个方面，其中所述多个激光脉冲包括至少一个测远脉冲和至少一个测近脉冲，步骤S103进一步包括：
根据所述目标物的回波信息判断测距条件，当测距条件为测远条件时，提高所述测远脉冲的能量。
根据本发明的一个方面，其中步骤S103进一步包括：
当所述测距条件为测远条件时，提高所述测远脉冲的能量，降低所述测近脉冲的能量，且所述测近脉冲的能量大于第二能量阈值。
根据本发明的一个方面，其中所述测远条件包括所述目标物位于第一距离范围以外，所述第二能量阈值根据第二距离范围的探测需求确定，所述第二距离范围小于等于所述第一距离范围。
根据本发明的一个方面，当所述测距条件为测远条件时，在每次探测时逐级提高所述测远脉冲的能量，直到所述多个激光脉冲的能量之和接近所述第一能量阈值。
根据本发明的一个方面，当所述测距条件为测远条件时，在下一次探测时提高所述测远脉冲的能量，使得所述多个激光脉冲的能量之和接近所述第一能量阈值，且所述测近脉冲的能量接近所述第二能量阈值。
根据本发明的一个方面，其中所述多个激光脉冲包括至少一个测远脉冲和至少一个测近脉冲，步骤S103进一步包括：
根据所述目标物的回波信息判断测距条件，当测距条件为测近条件时，降低所述测远脉冲的能量，提高所述测近脉冲的能量，且在同一次发射中所述测近脉冲的能量小于等于所述测远脉冲的能量。
根据本发明的一个方面，当所述测距条件为测近条件时，在下一次探测时发射能量接近的所述测远脉冲和所述测近脉冲，且使得所述多个激光脉冲的能量之和接近所述第一能量阈值。
根据本发明的一个方面，所述控制方法进一步包括：
通过调整所述激光雷达下一次发射时所述多个激光脉冲的能量分配，以调整所述 多个激光脉冲的强度峰值或脉冲宽度。
根据本发明的一个方面，所述控制方法进一步包括：
通过提高所述多个激光脉冲的最大驱动电流/电压，来提升所述多个激光脉冲的脉冲峰值。
根据本发明的一个方面，所述控制方法进一步包括：
保持驱动电流/电压不变，通过延长/缩短所述多个激光脉冲的发射时间，来扩展/缩短所述多个激光脉冲的脉冲宽度。
根据本发明的一个方面，所述控制方法进一步包括：
根据所述多个激光脉冲对应的回波信息计算所述目标物的距离。
本发明还提供一种激光雷达，包括：
发射单元，根据脉冲编码以及当前的能量分配策略，发射激光脉冲信号，所述激光脉冲信号包括采用所述脉冲编码的多个激光脉冲，用以探测目标物；
接收单元，配置成接收所述多个激光脉冲被目标物反射的回波信息；
控制单元，配置成根据所述目标物的回波信息，更新所述激光雷达下一次发射时所采用的所述能量分配策略。
根据本发明的一个方面，其中所述多个激光脉冲的能量之和小于第一能量阈值,所述第一能量阈值根据预设时间内发射脉冲的总能量小于人眼安全阈值的要求确定。
根据本发明的一个方面，其中所述多个激光脉冲包括至少一个测远脉冲和至少一个测近脉冲，所述控制单元进一步被配置成：
根据所述目标物的回波信息判断测距条件，当测距条件为测远条件时，提高所述测远脉冲的能量。
根据本发明的一个方面，其中所述控制单元进一步被配置成：
当所述测距条件为测远条件时，提高所述测远脉冲的能量，降低所述测近脉冲的能量，且所述测近脉冲的能量大于第二能量阈值。
根据本发明的一个方面，其中所述测远条件包括所述目标物位于第一距离范围以外，所述第二能量阈值根据第二距离范围的探测需求确定，所述第二距离范围小于等于所述第一距离范围。
根据本发明的一个方面，其中所述发射单元包括至少一个激光器，所述激光雷达还包括：
第一能量调节单元，与所述至少一个激光器和所述控制单元耦接，并配置成可在所述控制单元的控制下调节所述至少一个激光器的驱动电流/电压，用以调整所述激光雷达下一次发射时所述多个激光脉冲的脉冲峰值。
根据本发明的一个方面，其中所述发射单元包括至少一个激光器，所述激光雷达还包括：
第二能量调节单元，与所述至少一个激光器和所述控制单元耦接，并配置成可在所述控制单元的控制下调节所述至少一个激光器的发射时间，用以调整所述激光雷达下一次发射时所述多个激光脉冲的脉冲宽度。
本发明的优选实施例提供了一种激光雷达的控制方法，发射以时间间隔编码的多个激光脉冲，并根据目标物的回波信息，调整下一次发射时多个激光脉冲的能量分配。本发明的优选实施例既兼顾了近距离范围内的抗串扰需求，又提高了远距离范围内的探测精度和探测性能，在满足人眼安全要求的同时，获得了激光脉冲能量的最大效益的应用。
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2示意性地示出了激光人眼安全功率随时间变化的曲线；
图3示意性地示出了激光雷达的发射脉冲序列及其回波脉冲序列；
图4示意性地示出了激光雷达的发射脉冲序列及接收到的其他雷达的回波脉冲序列；
图5A示意性地示出了根据本发明的一个优选实施例发射至少一个测近脉冲和至少一个测远脉冲；
图5B示意性地示出了根据本发明的一个优选实施例发射至少一个测近脉冲和至 少一个测远脉冲；
图6示意性第示出了根据本发明的一个优选实施例的至少一个测近脉冲与至少一个测远脉冲在不同距离范围内的回波情况；
图7A示意性地示出了根据本发明的一个优选实施例发射脉宽相同或近似、峰值功率不同的至少一个测近脉冲与至少一个测远脉冲；
图7B示意性地示出了根据本发明的一个优选实施例发射峰值功率相同或近似、脉冲宽度不同的至少一个测近脉冲与至少一个测远脉冲；
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器的驱动电路；
图9A示意性地示出了根据本发明的另一个优选实施例的激光器的驱动电路；
图9B示出了图9A的驱动电路各节点的时序变化；
图10示意性地示出了根据本发明的一个优选实施例的能量调节电路；
图11示意性地示出了根据本发明的一个优选实施例的通过开关控制信号触发激光脉冲信号；
图12A示意性地示出了根据本发明的一个优选实施例的通过开关控制信号触发一种编码下的双脉冲；
图12B示意性地示出了根据本发明的一个优选实施例的通过开关控制信号触发另一种编码下的双脉冲；
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。
当前激光雷达通常采用脉冲编码的方案来抗干扰。脉冲编码方案的基本思路是： 激光雷达发射含有预设编码信息的激光脉冲，用以探测目标物；接收回波时通过预设编码进行识别，确定本雷达发出的探测光束的反射回波。
脉冲编码可以采用时间间隔编码、峰值强度编码、脉冲宽度编码等编码方式中的一种或多种。例如，采用时间间隔编码，发射包含时间编码信息的多个激光脉冲，优选地，发射具有预设时间间隔的双激光脉冲，在接收端根据脉冲回波的时间间隔，判断该回波是否是本雷达发出的探测光束的反射回波。而该具有预设时间间隔的两个激光脉冲，所包含的脉冲能量可能相同，也可能不同，即可以发射能量大小不同的双激光脉冲。
又例如，采用峰值强度编码，发射包含峰值强度编码信息的多个激光脉冲，优选地，发射峰值强度具有“高-矮-高”的变化趋势的三激光脉冲，在接收端根据脉冲回波的峰值强度的比值(脉冲回波的峰值强度相较于发射脉冲会有衰减，但比值基本不变，且可以设定一定容差)，判断该脉冲回波是否是本雷达发出的探测光束的反射回波。
又例如，采用脉冲宽度编码，发射包含脉冲宽度编码信息的多个激光脉冲，优选地，发射脉冲宽度具有“宽-窄-宽”的变化趋势的三激光脉冲，在接收端根据脉冲回波的脉宽比值(回波脉宽相较于发射脉冲会有展宽，但比值基本不变，且可以设定一定容差)，判断该脉冲回波是否是本雷达发出的探测光束的反射回波。
然而，如果使用脉冲编码的方案，意味着一次探测内需要发射多个激光脉冲。出于人眼安全的考虑，激光雷达在每次探测内发射脉冲的总能量是受到限制的。
使用脉冲编码的方案，需要将一次探测内可用的脉冲能量分配给多个激光脉冲，多个激光脉冲各自的幅度/脉宽都会受到影响。相比于一次探测内仅发射单脉冲的方案，采用脉冲编码的方案下每个脉冲所能获得的能量要低，从而使激光雷达的测远性能下降。
本发明的优选实施例提供了一种激光雷达的控制方法，在符合人眼安全要求的范围内，尽可能增大测远脉冲的能量，尽可能压缩测近脉冲的底线，使携带编码信息的激光脉冲能够具有更加优秀的测远性能，同时亦能达到近场测量时的防串扰效果。在激光雷达的测远性能与防串扰功能之间进行权衡，以获得对于脉冲能量的最大效益的应用。
根据本发明一个优选实施例，如图1所示，本发明提供一种激光雷达的控制方法10，包括步骤S101、步骤S102和步骤S103。
在步骤S101中，根据脉冲编码及当前的能量分配策略，发射激光脉冲信号，该激光脉冲信号包括采用该脉冲编码的多个激光脉冲，用以探测目标物。该脉冲编码可以采用如上文所述的时间间隔编码、峰值强度编码、脉冲宽度编码中的一种或多种，能量分配策略的前提是发射脉冲的能量总和小于人眼安全阈值。
图2示意性地示出了对于人眼安全的激光功率随时间变化的曲线图(可能因为不同波长、重频率、辐照角度和辐照时间而有所不同，既对于不同类型的激光雷达，该变化曲线可能存在差异)，由于一次探测内发射脉冲的时间总和远小于5μs，因此只需考虑一次探测内发射脉冲的能量总和小于5μs内的人眼安全能量阈值(对图2所示曲线下的人眼安全激光功率进行积分)即可。本领域技术人员可以理解，图2仅为一种激光雷达对应的人眼安全功率曲线的一种示意形式，实际人眼安全功率变换可能根据不同维度的衡量标准和/或激光雷达的种类、结构、性能等方面的不同而产生不同的曲线。
在步骤S102中，接收该多个激光脉冲被目标物反射的回波信息。根据回波脉冲是否携带与发射脉冲相同的编码信息，判断回波脉冲的有效性。
根据本发明的一个实施例，如图3所示，当回波脉冲序列的时序与发射脉冲序列的时序相同时，将该回波脉冲序列判断为发射脉冲序列的回波信号，保留该信号，并提取该信号所携带的信息。
根据本发明的另一个实施例，如图4所示，当回波脉冲序列的时序与发射脉冲序列的时序不相同时，将该回波脉冲序列判断为其它激光雷达发射的发射脉冲序列的回波信号，并丢弃该回波脉冲序列。
本领域技术人员容易理解，根据峰值强度、脉冲宽度进行编码和识别，或结合时间间隔、峰值强度、脉冲宽度中的一种或多种作为编码，同样在本发明的保护范围之内。
在步骤S103中，根据目标物的回波信息，更新激光雷达下一次发射时所采用的能量分配策略。根据目标物的回波信息，判断目标物的距离、回波脉冲的有效性，并根 据目标物的距离和/或回波脉冲的有效性调整能量分配策略，以使得在满足人眼安全要求下达到最佳测远性能，且同时保证一定距离范围内的抗干扰性能。
当采用多脉冲编码的方案时，现有技术中，通常使各个探测脉冲保持相对一致的测距能力，即采用发射能量相近的多个激光脉冲。因此，其中的小脉冲(能量或功率较小的探测脉冲)往往是激光雷达测远性能的瓶颈。
然而实际上，激光雷达测远和测近的需求不同。在测远时，需要考虑测远能力，希望能够达到尽量远的探测距离，这要求测远时的激光脉冲能够具有较高的能量；与此同时，测远时可能发生串扰的概率较低。而在测近时，大脉冲(能量或功率较大的探测脉冲)的表现并不突出，尤其是受到探测器自身饱和因素的影响；而近距离发生串扰的概率增加。因此，在实践中，只需要在近距离时提供防串扰的编码即可，根据目标物的回波信息，判定当前目标物的距离范围，或当前激光雷达所处的测距条件，再根据目标物的距离范围/测距条件，调整激光脉冲的能量分配。
根据本发明的一个优选实施例，控制方法10中，在一次探测的时间内，发射多个激光脉冲的能量总和小于第一能量阈值,其中第一能量阈值根据预设时间内发射脉冲的能量总和小于人眼安全阈值的要求确定。
具体地，根据人眼安全要求，激光雷达在预定时间段内的多次探测所发射的激光脉冲的总能量需要小于人眼安全阈值。其中，该预定时间段以及相应的人眼安全阈值根据激光雷达的探测方式不同、性能的不同而不同。
例如，相同时间内，采用机械旋转式扫描探测方式的激光雷达可使用的总能量可以较高，因为其在探测过程中会进行旋转扫描而不会固定在一个方向上；而采用面阵闪光式探测方式的激光雷达可允许的能量较小，因为其指向固定的方向，等等。
一般地，该预定时间段为微秒级的时间区间，例如，5μs左右。而通常来说，激光雷达的一次探测所需花费的时间在几十纳秒至百纳秒级别。亦即，激光雷达一次探测的时间小于预定时间段。
由于对一个特定激光雷达来说，其一次探测所花的时间是确定，因此可以确定每次探测可用的脉冲能量总和，亦即，可确定一次探测所发射的多个激光脉冲的能量总 和。例如，由于一次探测内发射脉冲的时间总和远小于5μs，因此可以直接考量一次探测内的发射脉冲能量总和小于5μs内的人眼安全阈值。
此外，根据本发明的一个优选实施例，控制方法10中，在一次探测时，发射的多个激光脉冲中包括至少一个测远脉冲和至少一个测近脉冲，该至少一个测远脉冲和至少一个测近脉冲的发射先后顺序不限，但测近脉冲的能量/功率应不大于测远脉冲的能量/功率。
优选地，当存在多个，如大于等于三个，的不同大小的编码脉冲时，可将能量最大的脉冲作为测远脉冲，而将余下的至少两个脉冲作为测近脉冲，以使得测距能力最大化。
根据本发明的一个优选实施例，如图5A、图5B所示，发射以时间间隔编码的一个测近脉冲和一个测远脉冲，其中测近脉冲和测远脉冲的发射先后顺序不限。且除了采用时间间隔编码之外，也可以采用峰值强度、脉冲宽度进行编码，或采用时间间隔、峰值强度、脉冲宽度中的多种编码方式结合进行编码，这些都在本发明的保护范围之内。
为论述方便起见，现以发射时间间隔编码的双脉冲方案为例。控制方法10的步骤S103进一步包括：根据目标物的回波信息判断测距条件，当测距条件为测远条件时，提高测远脉冲的能量。
优选地，当满足以下至少任一项条件时，判定雷达当前处于测远条件：
(1)目标物位于第一距离范围以外。例如80米以外，此时对激光雷达测远性能要求提高，对抗串扰的需求降低。其中，第一距离可根据实际情况和需求进行调整，通常来说，第一距离范围用于指示仅基于测远脉冲即可获得较好测距性能的区域；
和/或
(2)接收到的测近脉冲的回波较弱或没有接收到测近脉冲的回波。此时可能存在多种原因，如目标物位于第一距离范围以外，测近脉冲的能量不足以探测该目标物，全部衰减或几近全部衰减；目标物的反射率低，等等。
如图6所示，当目标物位于小于50米的距离范围之内时，测近脉冲和测远脉冲的回波均能够被激光雷达接收到；当目标物位于大于80米的距离范围时，激光雷达仅能 接收到测远脉冲的回波。
因此，在测远条件下，需要通过在下一次探测提高测远脉冲的能量/功率，来增加激光雷达的远距离探测精度。
根据本发明的一个优选实施例，当测距条件为测远条件时，提高测远脉冲的能量，降低测近脉冲的能量，且测近脉冲的能量大于第二能量阈值。其中第二能量阈值通过该激光雷达对于抗干扰性能的基本需求确定。
由于存在上文所述的一次探测内，多个激光脉冲的能量总和须小于第一能量阈值的限制,为了进一步提高测远脉冲的能量，可以通过降低测近脉冲的能量来实现。在测远条件下，如果目标物位于第一距离范围(例如80米)以外，对于测远性能的要求提高，对于抗串扰功能的需求降低，可以适当降低测近脉冲的能量。和/或，如果测近脉冲的回波较弱，或没有收到测近脉冲的回波，则测近脉冲在解析目标物的距离时无法起到实际作用，因此也可以适当降低测近脉冲的能量。对于测近脉冲能量的限制由激光雷达基本的抗串扰需求确定，即在目标物恢复到第二距离范围(例如50米)以内时，激光雷达的抗串扰功能的需求增加，对于测远性能的要求降低，在此种情况下，要求激光雷达仍然能够探测并分辨本雷达发射的探测光束的反射回波。
根据本发明的一个优选实施例，测远条件包括目标物位于第一距离范围(例如80米)以外，第二能量阈值根据第二距离范围(例如50米)的探测需求确定。本领域技术人员容易理解，优选实施例中第一距离范围为80米、第二距离范围为50米，根据实际探测需要，设定第一距离范围小于等于第一距离范围，该技术方案也是可行的，这些均在本发明的保护范围之内。
对于测近脉冲的能量限制，是在第二距离范围以内仍然可以进行探测，第二距离范围是激光雷达抗串扰需求较高的范围，如在本激光雷达附近50米的范围内，本激光雷达发出的与探测光束对应的回波信号可能受到本车辆搭载的其他激光雷达的影响，也可能受到附近往来车辆上搭载的激光雷达的影响。而第一距离范围是激光雷达对于测远性能要求较高的范围，如在距离本激光雷达80米远的范围内，测远条件包括根据回波信息解析出目标物位于该第一距离范围以外。
根据本发明的一个优选实施例，控制方法10中，当测距条件为测远条件时，在每次探测时逐渐提高测远脉冲的能量，直到多个激光脉冲的能量之和接近第一能量阈值，而其中测近脉冲的能量不低于第二能量阈值。其中第一能量阈值根据人眼安全阈值确定，第二能量阈值根据该激光雷达对于抗干扰性能的基本需求确定。即对于能量分配策略进行逐级切换。
例如，根据人眼安全阈值确定的第一能量阈值为800nJ，根据该激光雷达的基本抗干扰需求确定的第二能量阈值为100nJ。采用时间间隔编码的双脉冲探测方案，能量分配策略如下表所示。
表1
脉冲编码 测远脉冲能量 测近脉冲能量
PCode1 300nJ 300nJ
PCode2 400nJ 300nJ
PCode3 500nJ 300nJ
PCode4 600nJ 200nJ
PCode5 700nJ 100nJ
预设采用PCode1进行编码，根据回波信息判断测距条件为测远条件时，在下一次探测，将测远脉冲的能量提高100nJ，即切换至PCode2；根据回波信息判断测距条件仍为测远条件时，在下一次探测，将测远脉冲的能量提高100nJ，即切换至PCode3，此时双脉冲的能量之和已达到第一能量阈值(在实际探测过程中，基于能耗等其他方面的考虑，可以将双脉冲能量之和的上限设置在第一能量阈值附近且不超过第一能量阈值，如750nJ)；根据回波信息判断测距条件仍为测远条件时，在下一次探测，将测远脉冲的能量提高100nJ，同时将测近脉冲的能量降低100nJ，即切换至PCode4；根据回波信息判断测距条件仍为测远条件时，在下一次探测，将测远脉冲的能量提高100nJ，同时将测近脉冲的能量降低100nJ，即切换至PCode5，此时测近脉冲的能量之已低至第二能量阈值；如根据回波信息判断测距条件仍为测远条件时，在下一次探测，继续采用PCode5进行探测；如在任意一次探测内，根据回波信息判断测距条件为测近条件 时(即近距离可能存在目标物的情况)，可将编码切换回PCode1……其中测远条件包括：
(1)、预定时间内获得的测距信息均位于第一距离范围(例如80米)以外。根据回波信息对目标物的距离进行解析，预定时间内得到的测距信息均表示目标物位于第一距离范围之外；和/或
(2)、接收到的测近脉冲的回波较弱或没有接收到测近脉冲的回波；和/或
(3)、在一些情况下，雷达光轴朝向特定角度时(例如面向车辆行驶的正前方时)。车辆行驶的正前方，对于探测精度的需求提高，且对于正前方方向，周围车辆的串扰状况得到改善，对于抗干扰的需求相对降低。
综上所述，在不超过人眼安全所允许的第一能量阈值的情况下，亦即总能量保持不变的情况下，在测近脉冲和测远脉冲之间调整能量的分配测量，以优化探测结果。
其中，本领域技术人员能够理解，通过对电路进行合理设计，可使得逐级调整的步长更大或更小。甚至可实现近似无级调整的效果，例如，通过设置可近似无级变化的电阻调节模块，实现对于激光器能量的无极调整。
根据本发明的一个优选实施例，当测距条件为测远条件时，在下一次探测时提高测远脉冲的能量，使得多个激光脉冲的能量之和接近第一能量阈值，且测近脉冲的能量接近第二能量阈值。具体地，此处所述“接近”用于表明能量调整的趋势，亦即：该多个激光脉冲的调整之后的能量之和相对于调整之前的能量之和更加靠近第一能量阈值，并且，测近脉冲在调整之后的能量相较于调整之前的能量更加靠近第二能量阈值。
其中第一能量阈值根据人眼安全阈值确定，例如根据各个国家或地区的激光产品安全标准及实际使用雷达产品的类型和探测模式，可计算获得该第一能量阈值；第二能量阈值根据该激光雷达对于抗干扰性能的基本需求确定。即对于能量分配策略进行一次性切换。
例如，根据人眼安全阈值确定的第一能量阈值为800nJ，根据该激光雷达的基本抗干扰需求确定的第二能量阈值为100nJ。采用时间间隔编码的双脉冲探测方案，能量分 配策略如下表所示。
表2
脉冲编码 测近脉冲能量 测远脉冲能量
PCode6 400nJ 400nJ
PCode7 600nJ 200nJ
预设采用如表2中所示的PCode6进行编码，当满足测远条件的时候，切换至PCode7。测远条件包括：
(1)、预定时间内获得的测距信息均位于第一距离范围(例如80米)以外；和/或
(2)、接收到的测近脉冲的回波较弱或没有接收到测近脉冲的回波；和/或
(3)、在一些情况下，雷达光轴朝向特定角度时(例如面向车辆行驶的正前方时)。
根据本发明的一个优选实施例，控制方法10中，多个激光脉冲包括至少一个测远脉冲和至少一个测近脉冲，步骤S103进一步包括：
根据目标物的回波信息判断测距条件，当测距条件为测近条件时，降低测远脉冲的能量，提高测近脉冲的能量，且在同一次发射中测近脉冲的能量小于等于测远脉冲的能量。
其中测近条件包括：
(1)、预定时间内获得的测距信息均位于第二距离范围(例如50米)以内。即根据回波信息对目标物的距离进行解析，预定时间内得到的测距信息均表示目标物位于激光雷达附近串扰情况频发区域之内；和/或
(2)、雷达光轴未朝向该特定角度时(例如面向车辆行驶正前方以外的其他方向时)。对于车辆行驶正前方以外的其他探测方向，存在与周围车辆搭载的激光雷达的相互干扰的情况，应提高测近脉冲的能量，以提高近距离的探测性能。
根据本发明的一个优选实施例，当测距条件为测近条件时，在下一次探测时发射能量接近的测远脉冲和测近脉冲，且使得多个激光脉冲的能量之和接近第一能量阈值。 发射能量相近的以时间间隔编码的双脉冲序列，以使得近距离的探测性能(抗串扰性能)达到最佳。
例如，根据人眼安全阈值确定的第一能量阈值为800nJ，根据该激光雷达的基本抗干扰需求确定的第二能量阈值为100nJ。采用时间间隔编码的双脉冲探测方案，能量分配策略如上文中表2所示：当前采用PCode2进行编码，当满足测近条件的时候，切换至PCode1。
根据本发明的一个优选实施例，控制方法10进一步包括：
通过调整激光雷达下一次发射时多个激光脉冲的能量分配，以调整多个激光脉冲的强度峰值或脉冲宽度。
通常，当该激光雷达采用时间间隔编码时，对于激光脉冲的峰值强度和/或脉冲宽度均可实行调整，以达到调节能量分配的目的。当该激光雷达采用峰值强度进行编码时，可保持峰值强度的比例(变化趋势)不变，通过调整脉冲宽度调节能量分配。当该激光雷达采用脉冲宽度进行编码时，可保持脉冲宽度的比例(变化趋势)不变，通过调整峰值强度调节能量分配。
根据本发明的一个优选实施例，如图7A、图7B所示，同一次探测内的测近脉冲与测远脉冲可以是脉冲时间相同或近似，但峰值功率不同(如图7A所示)，也可以是脉冲峰值功率相同或近似，但脉冲时间不同(如图7B所示)。对于图7A所示的实施例，优选地，应用于多通道机械雷达，通过峰值功率较高的测远脉冲提高探测精度，通过双脉冲编码抗串扰。对于图7B所示的实施例，优选地，应用于面阵闪光固态激光雷达，通过脉冲宽度较宽的测远脉冲提高光子接收概率，通过双脉冲编码抗串扰。
具体地，根据脉冲编码方式的不同，调节峰值强度和/或脉冲宽度时所需采用的操作也不同。例如，当仅采用时间间隔编码时，无需考虑初始波形中各个脉冲的峰值比例或脉宽比例，则在进行能量调节时，无需相应地调节探测端；又例如，当采用峰值编码时，初始波形中各个脉冲的脉宽相同，峰值不同时，在改变能量分配时，需要同时更新各个探测端在验证时所依据的能量分配比例，亦即，探测端所用于进行验证的分配比例的信息可根据能量分配的调节而更新；相似地，当采用脉宽编码时，初始波形中各个脉冲的脉宽不同，峰值相同，则在进行能量分配调节时，也可相应地更新探 测端所采用的分配比例信息。
根据本发明的一个优选实施例，激光雷达的发射单元发射采用时间间隔编码及能量分配策略的多脉冲序列，该多脉冲序列中，例如包含第一激光脉冲和第二激光脉冲(一个测远脉冲和一个测近脉冲)，当然，不是一般性的，也可以包含第一激光脉冲，第二激光脉冲……第N激光脉冲，多个激光脉冲具有时序关系。上述时间间隔表述了发射脉冲序列的时序关系，在调整能量分配策略后，接收单元仍然可以通过验证回波脉冲序列与发射脉冲序列的时序关系来确定本雷达发出的发射脉冲序列的反射回波。
根据本发明的又一个优选实施例，激光雷达的发射单元发射采用峰值强度编码及能量分配策略的多脉冲序列，其中能量分配策略包括：在符合测远模式的情况下，减少测近脉冲的能量，并增加测远脉冲的能量。继续对本实施例的方案进行说明。该多脉冲序列中包括一个测远脉冲和一个测近脉冲，测远脉冲与测近脉冲的峰值比例是1.2:1，相应地，探测端根据连续接收的两个脉冲的峰值能量比是否满足1.2:1，来确定接收到的是否是自身所属激光雷达的脉冲。
随后，当在一次探测中，发现当前属于测远模式，则将测近脉冲的能量减少50％，并将该50％的能量转加至测远脉冲，此时测远脉冲与测近脉冲的峰值比可以为1.7:0.5,亦即3.4:1，并相应地更新探测端判断回波脉冲的峰值比例为3.4:1。随后，发射端根据新的能量分配比例测量来发射测远脉冲与测近脉冲，探测端根据该新的能量分配比例来判定接收到的回波是否为正确的回波脉冲。
根据本发明的又一个优选实施例，激光雷达的发射单元发射采用脉冲宽度编码及能量分配策略的多脉冲序列。该多脉冲序列中包括一个强脉冲和一个弱脉冲，强脉冲与弱脉冲的脉宽比例是2:1，亦即，强脉冲的脉宽是弱脉冲的两倍。相应地，探测端根据连续接收的两个脉冲的脉宽比是否满足2:1，来确定接收到的是否是自身所属激光雷达的脉冲。
随后，当在一次探测中，发现当前属于测远模式，因而减少测近脉冲的能量，提高测远脉冲的能量，使得测远脉冲与测近脉冲的脉宽比例为3:1，并相应地更新探测端判断回波脉冲的脉宽比例为3:1。随后，发射端根据新的能量分配比例测量来发射测远脉冲与测近脉冲，探测端根据该新的能量分配比例来判定接收到的回波是否为正确的 回波脉冲。
随后，激光雷达根据新的能量分配比例继续进行探测。当在又一次探测中发现当前的测距信息为46米，属于测近模式时，减少测远脉冲的能量，同时增加测近脉冲的能量，使得测远脉冲与测近脉冲的脉宽比例变为1.5:1，从而能够更好的利用测远脉冲与测近脉冲的脉冲编码来区分本激光雷达发射的脉冲。
作为一个更优选地方案，测远模式可以具有多种级别，例如，可以将测远模式分为中远程(例如50-100米)和超远程(例如大于100米)，并且，探测端仅在中远程模式下根据新的能量分配比例来执行判断，在超远程时，只要接收到回波脉冲，即认为是与测远脉冲对应的回波脉冲。
亦即在某些探测模式下，例如超远程模式下，其他激光雷达或者发射源的干扰已经极小，可以忽略，而仅考虑所能接收到的脉冲即可。此时，探测端可不再验证脉冲编码。
作为本方案的又一个优选实施例，当一次探测采用一个测远脉冲以及两个以上的测近脉冲进行编码时，可去掉部分测近脉冲，而将该部分测近脉冲的能量分配给测远脉冲，并相应地调节探测端采用的防串扰判定条件，以基于重新分配能量后的脉冲编码进行判断。
例如，激光雷达初始采用三脉冲编码，三个脉冲pulse1、pulse2、pulse3的峰值比例为1:2:3，其中峰值最大的为测远脉冲，其余两个为测近脉冲。同时，探测端需要在接收到三个回波脉冲并且该三个回波脉冲的能量比为1:2:3时确定该回波脉冲属于本激光雷达。在激光雷达确定当前为测远模式时，将能量最小的脉冲pulse1的能量转而分配给最大脉冲pulse3，亦即，激光雷达仅以峰值比例2:4的比例发射双脉冲编码，并更新探测端的判定条件为接受到能量比为2:4的两个脉冲时确定该回波脉冲属于本激光雷达。反之，当从测远模式进入测近模式时，仍按照1:2:3的峰值比例的三脉冲编码的来进行发射和探测。
相似地，当采用更多脉冲来进行编码时，可采用类似的分配方式，进而实现在测远模式下增强测远脉冲的能量，获得更好的测远性能的目的。
更优选地，对于测远脉冲和测近脉冲的能量分配可以设置一定的容差。在调整能 量分配策略后，如果发射单元通过调整多个激光脉冲的脉冲宽度来调整能量分配策略，则接收单元根据激光雷达的控制单元更新的能量分配策略，确定本次探测发射多脉冲序列的脉冲宽度的预设比例关系，再通过验证回波脉冲序列与发射脉冲序列的脉冲宽度的比值来确定本雷达发出的发射脉冲序列的反射回波，其中可以设置一定的容差。
作为一种优选替换方案，在一次探测的总能量有余裕的情况下，亦即，一次探测发射的总能量小于人眼安全阈值时，在测远情况下的能量分配测量可以为仅增加测远脉冲的能量，而不减少测近脉冲的能量。
根据本发明的一个优选实施例，控制方法10进一步包括：通过提高多个激光脉冲的最大驱动电流/电压，来提升多个激光脉冲的脉冲峰值。
电路实现上可以采用多种实现方式，例如，可采用电压可调节的驱动电路或者包含多个储能电路的激光器驱动电路等，来调节各个脉冲的能量。通常来说，激光器上的电流与激光器上施加的驱动电压成正比，与激光器所在电路的电阻成反比。因此，调节激光器上的电流/电压的主要方法有两个，一个是调节驱动电压，一个是调节电阻。
根据本发明的一个优选实施例，图8示意出了一种可通过调节激光器上的电流来调节发射脉冲的能量的电路结构的实现示意图。
其中，图8所示的激光器的电流与施加的电压和电阻呈如下关系：
Imax＝HVDD1/(Rd+Rdson)
其中，HVDD1为激光器上施加的驱动电压，Rd为激光器自身的等效电阻，Rdson为与PMOS及其连接的其他器件的总电阻。因此，调节Imax的主要方法有两个，一个是调节电压HVDD1，一个是调节电阻Rdson。
在上述可调电路的基础上，集成一个控制模块，控制模块可以切换多套脉冲编码，可基于上述两种编码方式直接切换，或逐级调节的脉冲编码，分别生成脉冲控制信号，通过脉冲控制信号，来调节输入电压HVDD1，或者电阻值Rdson，以发射相应的激光脉冲。
根据本发明的一个优选实施例，如图9A所示的调节电路，其时序图如图9B所示，在此实施例中，激光器的电流强度与电压Vx的大小相对应，而Vx可通过低压线性稳压器(LDO)输出的V2来调节。当V2变大时，Vx变小，V2变小时，Vx变大。通 过控制LDO输出相应的V2，即可实现对于激光器电流的调节，亦即实现对于发射脉冲的调节。
根据本发明的一个优选实施例，图10示意出了一种采用储能模块的电路实现方式。如图10所示，多个蓄能模块与电源模块相连接，每个蓄能模块与一个控制开关相连，控制开关负责控制蓄能模块与激光发射单元的通断。当某一蓄能模块与激光发射单元之间的控制开关闭合时，蓄能模块中存储的电荷驱动激光发射单元发射光脉冲。具体地，图10所示的各个单元开关可以是相互独立的，并且控制开关由控制单元分别独立控制，在时序上的同一时刻，控制单元可以控制控制开关独立地打开或者闭合。当同一时刻存在多个控制开关闭合时，发射激光脉冲能量是几个蓄能模块能量的总和。通过在同一时刻同时闭合多个控制开关以发射高能脉冲，可以实现对于远距离物体的探测。通过控制在时序上闭合的控制开关的个数和时间点，可以控制时序上发射的脉冲形状。例如，在某一时刻，只有1个控制开关闭合，那么该时刻发射的脉冲强度为1单位，而在后续时刻N个控制开关闭合，那么对应时刻发射的脉冲强度为N个单位。通过控制单元控制在不同时刻闭合开关的数量，可以控制发射脉冲的时序和强度。
根据本发明的一个优选实施例，如图11所示，通过控制多个激光脉冲的发射时间，来获得脉宽相同或近似，峰值功率不同的多个激光脉冲。开关控制信号(GATE1，GATE2,…，GATEN)结束时触发开关触发信号(TRIGGER)，例如图中所示的开关控制信号(GATE1，GATE2,…，GATEN)的时序下降沿触发开关触发信号(TRIGGER)的下降沿；不失一般性的，如果开关触发信号(TRIGGER)结束是时序信号的上升沿，则将该上升沿作为开关控制信号的触发时机，以保证在充电结束后开始发光过程，并且在前一个充电发光过程结束后，可以立即开始下一个充电-发光过程。在图11所示的实施例中，开关控制信号(GATE1，GATE2,…，GATEN)的时间宽度是相等的，如此保证发射的脉冲序列中各个脉冲宽度基本一致。
图12A、图12B示出了在开关控制信号的触发下，获得前文所述的PCode1和PCode2。
根据本发明的一个优选实施例，控制方法10进一步包括：
保持驱动电流/电压不变，通过延长/缩短多个激光脉冲的发射时间，来扩展/缩短多 个激光脉冲的脉冲宽度。即得到如图7B所示的峰值功率相同或近似，脉冲宽度不同的多个激光脉冲。调整发射时间的具体电路实现结构在此不再赘述。
根据本发明的一个优选实施例，如图13所示，本发明还提供一种激光雷达100，包括发射单元110、接收单元120和控制单元130。其中：
发射单元110发射激光脉冲信号，该激光脉冲信号包括以时间间隔编码的多个激光脉冲，用以探测目标物；
接收单元120配置成接收该多个激光脉冲被目标物反射的回波信息；
控制单元130配置成根据目标物的回波信息，调整激光雷达下一次发射时该多个激光脉冲的能量分配。
根据本发明的一个优选实施例，其中多个激光脉冲的能量之和小于第一能量阈值,该第一能量阈值根据预设时间内发射脉冲的总能量小于人眼安全阈值的要求确定。
根据本发明的一个优选实施例，其中多个激光脉冲包括至少一个测远脉冲和至少一个测近脉冲，控制单元130进一步被配置成：
根据目标物的回波信息判断测距条件，当测距条件为测远条件时，提高测远脉冲的能量。
根据本发明的一个优选实施例，其中控制单元130进一步被配置成：
当测距条件为测远条件时，提高测远脉冲的能量，降低测近脉冲的能量，且测近脉冲的能量大于第二能量阈值。
根据本发明的一个优选实施例，其中测远条件包括目标物位于第一距离范围以外，该第二能量阈值根据第二距离范围的探测需求确定，该第二距离范围小于等于该第一距离范围。
根据本发明的一个优选实施例，其中发射单元110包括至少一个激光器，激光雷达100还包括：
第一能量调节单元，与该至少一个激光器和控制单元130耦接，并配置成可在控制单元130的控制下调节该至少一个激光器的驱动电流/电压，用以调整激光雷达100下一次发射时多个激光脉冲的脉冲峰值。
根据本发明的一个优选实施例，其中发射单元110包括至少一个激光器，激光雷达100还包括：
第二能量调节单元，与该至少一个激光器和控制单元130耦接，并配置成可在控制单元130的控制下调节该至少一个激光器的发射时间，用以调整激光雷达100下一次发射时多个激光脉冲的脉冲宽度。
本发明的优选实施例提供了一种激光雷达的控制方法，发射以时间间隔编码的多个激光脉冲，并根据目标物的回波信息，调整下一次发射时多个激光脉冲的能量分配。本发明的优选实施例既兼顾了近距离范围内的抗串扰需求，又提高了远距离范围内的探测精度和探测性能，在满足人眼安全要求的同时，获得了激光脉冲能量的最大效益的应用。
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 (20)

  1. 一种激光雷达的控制方法，包括：
    S101：根据脉冲编码以及当前的能量分配策略，发射激光脉冲信号，所述激光脉冲信号包括采用所述脉冲编码的多个激光脉冲，用以探测目标物；
    S102：接收所述多个激光脉冲被目标物反射的回波信息；和
    S103：根据所述目标物的回波信息，更新所述激光雷达下一次发射时所采用的所述能量分配策略。
  2. 如权利要求1所述的控制方法，其中所述多个激光脉冲的能量之和小于第一能量阈值,所述第一能量阈值根据预设时间内发射脉冲的总能量小于人眼安全阈值的要求确定。
  3. 如权利要求2所述的控制方法，其中所述多个激光脉冲包括至少一个测远脉冲和至少一个测近脉冲，步骤S103进一步包括：
    根据所述目标物的回波信息判断测距条件，当测距条件为测远条件时，提高所述测远脉冲的能量。
  4. 如权利要求3所述的控制方法，其中步骤S103进一步包括：
    当所述测距条件为测远条件时，提高所述测远脉冲的能量，降低所述测近脉冲的能量，且所述测近脉冲的能量大于第二能量阈值。
  5. 如权利要求4所述的控制方法，其中所述测远条件包括所述目标物位于第一距离范围以外，所述第二能量阈值根据第二距离范围的探测需求确定，所述第二距离范围小于等于所述第一距离范围。
  6. 如权利要求3-5中任一项所述的控制方法，当所述测距条件为测远条件时，在每次探测时逐级提高所述测远脉冲的能量，直到所述多个激光脉冲的能量之和接近所述第一能量阈值。
  7. 如权利要求4或5所述的控制方法，当所述测距条件为测远条件时，在下一次探测时提高所述测远脉冲的能量，使得所述多个激光脉冲的能量之和接近所述第一能量阈值，且所述测近脉冲的能量接近所述第二能量阈值。
  8. 如权利要求2所述的控制方法，其中所述多个激光脉冲包括至少一个测远脉冲和至少一个测近脉冲，步骤S103进一步包括：
    根据所述目标物的回波信息判断测距条件，当测距条件为测近条件时，降低所述测远脉冲的能量，提高所述测近脉冲的能量，且在同一次发射中所述测近脉冲的能量小于等于所述测远脉冲的能量。
  9. 如权利要求8所述的控制方法，当所述测距条件为测近条件时，在下一次探测时发射能量接近的所述测远脉冲和所述测近脉冲，且使得所述多个激光脉冲的能量之和接近所述第一能量阈值。
  10. 如权利要求1-5、8、9中任一项所述的控制方法，进一步包括：
    通过调整所述激光雷达下一次发射时所述多个激光脉冲的能量分配，以调整所述多个激光脉冲的强度峰值或脉冲宽度。
  11. 根据权利要求10所述的控制方法，进一步包括：
    通过提高所述多个激光脉冲的最大驱动电流/电压，来提升所述多个激光脉冲的脉冲峰值。
  12. 根据权利要求10所述的控制方法，进一步包括：
    保持驱动电流/电压不变，通过延长/缩短所述多个激光脉冲的发射时间，来扩展/缩短所述多个激光脉冲的脉冲宽度。
  13. 如权利要求1-5、8、9中任一项所述的控制方法，进一步包括：
    根据所述多个激光脉冲对应的回波信息计算所述目标物的距离。
  14. 一种激光雷达，包括：
    发射单元，根据脉冲编码以及当前的能量分配策略，发射激光脉冲信号，所述激光脉冲信号包括采用所述脉冲编码的多个激光脉冲，用以探测目标物；
    接收单元，配置成接收所述多个激光脉冲被目标物反射的回波信息；
    控制单元，配置成根据所述目标物的回波信息，更新所述激光雷达下一次发射时所采用的所述能量分配策略。
  15. 如权利要求14所述的激光雷达，其中所述多个激光脉冲的能量之和小于第一能量阈值,所述第一能量阈值根据预设时间内发射脉冲的总能量小于人眼安全阈值的要求确定。
  16. 如权利要求15所述的激光雷达，其中所述多个激光脉冲包括至少一个测远脉冲和至少一个测近脉冲，所述控制单元进一步被配置成：
    根据所述目标物的回波信息判断测距条件，当测距条件为测远条件时，提高所述测远脉冲的能量。
  17. 如权利要求16所述的激光雷达，其中所述控制单元进一步被配置成：
    当所述测距条件为测远条件时，提高所述测远脉冲的能量，降低所述测近脉冲的能量，且所述测近脉冲的能量大于第二能量阈值。
  18. 如权利要求17所述的激光雷达，其中所述测远条件包括所述目标物位于第一距离范围以外，所述第二能量阈值根据第二距离范围的探测需求确定，所述第二距离范围小于等于所述第一距离范围。
  19. 如权利要求14-18中任一项所述的激光雷达，其中所述发射单元包括至少一个激光器，所述激光雷达还包括：
    第一能量调节单元，与所述至少一个激光器和所述控制单元耦接，并配置成可在 所述控制单元的控制下调节所述至少一个激光器的驱动电流/电压，用以调整所述激光雷达下一次发射时所述多个激光脉冲的脉冲峰值。
  20. 如权利要求14-18中任一项所述的激光雷达，其中所述发射单元包括至少一个激光器，所述激光雷达还包括：
    第二能量调节单元，与所述至少一个激光器和所述控制单元耦接，并配置成可在所述控制单元的控制下调节所述至少一个激光器的发射时间，用以调整所述激光雷达下一次发射时所述多个激光脉冲的脉冲宽度。
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