Ranging method and ranging device of laser radar and laser radar

Abstract

The invention discloses a range finding method and a range finding device of a laser radar, and the laser radar. According to the invention, in the one-time detection process of the laser radar, the laser radar is controlled to emit a plurality of laser pulses with different emission power levels at the same time; determining effective echoes in the echoes corresponding to the plurality of laser pulses with different transmitting power levels, wherein the effective echoes are echoes which do not enter a saturated state; and outputting the effective echoes and determining the ranging value according to the effective echoes, thereby at least solving the technical problem that in the SPAD laser radar ranging process, in order to meet the ranging capability, the laser pulse power is relatively large, so that quantization errors are generated in near ranging, and the ranging precision of the laser radar is reduced.

Description

A ranging method, ranging device, and lidar for a lidar. Technical Field

[0001] This application relates to the field of lidar ranging, and more specifically, to a lidar ranging method, ranging device, and lidar. Background Technology

[0002] In related technologies, in the field of lidar ranging, when using SPAD receivers as the ranging sensor for lidar, a relatively high laser power is usually required to meet ranging capability requirements. However, this can lead to quantization errors at close range, causing a decrease in the accuracy of close-range measurements. Conversely, if the accuracy requirements at close range are to be met, the lidar ranging capability will be limited.

[0003] Therefore, in a lidar solution using SPAD as the receiver, the ranging accuracy of a medium-to-long-range lidar deteriorates when measuring at close range.

[0004] No effective solutions have yet been proposed in the relevant technologies to address the aforementioned technical problems. Summary of the Invention

[0005] The main objective of this application is to provide a ranging method, ranging device, and lidar for a lidar, in order to solve the technical problem in the prior art where, in order to meet the ranging capability, the laser pulse power is relatively large, which leads to quantization errors in near-field ranging and thus reduces the ranging accuracy of the lidar.

[0006] According to one aspect of this application, a ranging method for a lidar is provided, the method comprising: controlling the lidar to simultaneously emit multiple laser pulses of different emission power levels during a single detection process; determining the effective echo among the echoes corresponding to the multiple laser pulses of different emission power levels, wherein the effective echo is an echo that has not entered a saturation state; outputting the effective echo and determining the ranging value based on the effective echo.

[0007] In an optional embodiment, before controlling the lidar to simultaneously emit multiple laser pulses of different emission power levels during a single detection process, the method further includes: obtaining the minimum and maximum detection range of the lidar, and calibrating the detection process based on the maximum and minimum detection ranges to determine a preset number of laser pulses emitted during the detection process; setting the emission power level corresponding to the preset number of laser pulses, wherein the ranging capability of each emission power level corresponds to a maximum effective detection distance, and the higher the emission power level, the farther the maximum effective detection distance.

[0008] In one optional embodiment, the minimum and maximum detection ranges of the lidar are obtained, and the detection process is calibrated based on the maximum and minimum detection ranges to determine a preset number of laser pulses emitted during the detection process. This includes: S301: Controlling the lidar to emit laser pulses sequentially in descending order of power level; after each pulse emission, detecting whether a quantization error occurs using the received echo; S302: If a quantization error occurs, controlling the lidar to emit a laser pulse corresponding to a lower power level than the current pulse; S303: Receiving the echo corresponding to the lower power level laser pulse, and further determining whether a quantization error has occurred using the echo; S304: Repeating steps S302-S303 until no quantization error exists within the lidar's detection range, and determining the preset number of emitted laser pulses by executing these steps.

[0009] In one optional embodiment, detecting whether a quantization error has occurred by receiving the echo includes: acquiring the echo corresponding to the current laser pulse using a preset reflectivity plate, and determining whether a quantization error exists by whether there is an invalid echo that has not entered a saturation state in the echo, wherein the presence of an invalid echo indicates the presence of a quantization error, and vice versa; controlling the lidar to emit a laser pulse corresponding to a lower emission power level than the current laser pulse includes: determining the maximum distance value at which a quantization error occurs based on the invalid echo, wherein the maximum effective detection distance corresponding to the lower emission power level is the maximum distance value.

[0010] In one optional embodiment, the plurality of different transmission power levels include at least a first power level and a second power level; the maximum effective detection distance L1 corresponding to the first power level is greater than or equal to the maximum detection range L_max of the lidar; the maximum effective detection distance L1 corresponding to the second power level is less than the maximum detection range L_max of the lidar; wherein, the second power level is lower than the first power level, and L1 is based on the maximum distance value corresponding to the quantization error of the lidar after transmitting a laser pulse of the first power level.

[0011] In one optional embodiment, the lidar detector is composed of a SPAD array. Determining the effective echoes among multiple laser pulses of different emission power levels includes: acquiring a photon arrival time histogram corresponding to each echo collected and accumulated by the SPAD array; extracting multiple feature values ​​from each photon arrival time histogram; the feature values ​​include at least: a maximum peak value (A), corresponding to the maximum histogram value in the photon arrival time histogram; a saturation peak value (Max), corresponding to the total pixel value of the receiving channel of the SPAD array; an echo leading edge sampling time point (B), corresponding to the sampling time point when the value in the photon arrival time histogram first exceeds a preset leading edge threshold; and a peak sampling time point (D), corresponding to the sampling time point of the maximum peak value; and determining whether there are effective echoes that have not entered a saturated state in the echoes based on at least one of the maximum peak value (A), saturation peak value (Max), echo leading edge sampling time point (B), and peak sampling time point (D).

[0012] In one optional embodiment, determining whether there is a valid echo that has not entered a saturated state in the echo is based on at least one of the following values: maximum peak value (A), saturation peak value (Max), echo leading edge sampling time point (B), and peak sampling time point (D). This includes: detecting whether the maximum peak value (A) is less than the saturation peak value (Max), and whether the time difference between the peak sampling time point (D) and the echo leading edge sampling time point (B) is greater than a preset threshold; if the maximum peak value (A) is less than the saturation peak value (Max), and the time difference is greater than or equal to the preset threshold, then the echo is determined to be a valid echo that has not entered a saturated state; if the maximum peak value (A) is equal to the saturation peak value (Max), and / or the time difference is greater than or equal to the preset threshold, then the echo is determined to be an invalid echo that has entered a saturated state.

[0013] According to another aspect of this application, a ranging device for a lidar is provided, the device comprising: a first control unit configured to control the lidar to simultaneously emit multiple laser pulses of different emission power levels during a single detection process of the lidar; a first detection unit configured to determine the effective echo among the echoes corresponding to the multiple laser pulses of different emission power levels, wherein the effective echo is an echo that has not entered a saturation state; and an output unit configured to output the effective echo and determine the ranging value based on the effective echo.

[0014] According to another aspect of this application, a lidar is also provided, which includes a lidar ranging device for performing the ranging method of the lidar described above.

[0015] According to another aspect of this application, an apparatus is also provided, the apparatus comprising a lidar of claim 9.

[0016] In this application, by controlling the lidar to simultaneously emit multiple laser pulses of different power levels during a single detection process, determining the effective echo among the echoes corresponding to the multiple laser pulses of different power levels (the effective echo being the echo that has not entered saturation), outputting the effective echo, and determining the ranging value based on the effective echo, this solves the technical problem in related technologies where, in order to meet ranging capabilities, a large laser pulse power leads to quantization errors in near-range ranging, thus reducing the ranging accuracy of the lidar. This achieves the technical effect of improving the overall performance of the lidar. Attached Figure Description

[0017] The accompanying drawings, which are provided to further illustrate this application and form part of this application, are intended to explain this application and do not constitute an undue limitation thereof. In the accompanying drawings: Figure 1 is a flowchart of a ranging method for a lidar provided in this application; Figure 2 is a histogram of photon arrival time with quantization error provided in this application; Figure 3 is a histogram of photon arrival time without quantization error provided in this application; Figure 4 is a schematic diagram of laser pulse power corresponding to the dual-pulse emission embodiment provided in this application; Figure 5 is a schematic diagram of laser pulse power corresponding to the three-pulse emission embodiment provided in this application; Figure 6 is an echo selection logic diagram corresponding to laser pulses emitting two different laser emission powers provided in this application; Figure 7 is an echo selection logic diagram corresponding to laser pulses emitting three different emission powers provided in this application; Figure 8 is a schematic diagram of the peak unsaturated waveform provided in this application; Figure 9 is a schematic diagram of the peak saturated waveform provided in this application; Figure 10 is a schematic diagram of the echo waveform received after emitting two pulses when there is a target at 1m provided in this application; Figure 11 is a schematic diagram of the echo waveform received after emitting three pulses when there is a target at 1m provided in this application; Figure 12 is a schematic diagram of calculating the ranging value based on the half-value start position difference provided in this application; Figure 13 is a structural block diagram of a lidar ranging device provided in an embodiment of this application. Detailed Implementation

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0020] As described in the background section, in related technologies, during the ranging process of SPAD lidar, a relatively high laser pulse power is used to meet ranging requirements, leading to quantization errors in near-range ranging and consequently reducing the ranging accuracy of the lidar. To address this, this application provides a lidar ranging method, a ranging device, and a lidar. The specific details of this application will be described below with reference to the accompanying drawings.

[0021] Quantization error (pile_up): When the echo signal is strong, the detector receives multiple photons at the same time. At this time, the output pulse signal of SPAD will have a count rate error due to the accumulation effect, which will cause a distance measurement error. This error is defined as quantization error.

[0022] Referring to Figure 1, this application embodiment provides a ranging method for a lidar. Figure 1 is a flowchart of a lidar ranging method, which specifically includes the following steps: S101: During a single detection process of the lidar, the lidar is controlled to simultaneously emit multiple laser pulses with different emission power levels; S102: The effective echo among the echoes corresponding to the multiple laser pulses with different emission power levels is determined. The effective echo is the echo that has not entered the saturation state; S103: The effective echo is output and the ranging value is determined based on the effective echo.

[0023] As described above, during a single detection process of the lidar, by controlling the lidar to simultaneously emit two or more laser pulses of different powers, after the receiving device obtains the echo corresponding to each power laser pulse, the echo that has not reached saturation is selected as the effective echo output. Specifically, the lidar emits laser pulses of different powers for different detection distances. By simultaneously emitting laser pulses of different energy intensities in each measurement process, both long-range ranging capability and the problem of decreased ranging accuracy at close ranges due to quantization errors are ensured.

[0024] It's necessary to explain the cause of quantization error. Under strong laser pulses, incident photons continuously trigger the avalanche effect in the SPAD. The resulting photon arrival time histogram exhibits the following characteristics: 1. The "received photon count - time distribution" of the histogram is compressed and distorted; 2. The peak signal intensity (peak_score) fails to reflect the true photon count due to continuous saturation. A schematic diagram of a photon arrival time histogram with quantization error is shown in Figure 2. Figure 3 shows a schematic diagram of a photon arrival time histogram without quantization error.

[0025] As shown in Figure 2, when the target is very close or has high reflectivity, the echo signal is extremely strong. This causes the count to saturate at the front of the histogram (near the emission time) (the peak value exhibits a saturated waveform). In this case, the true peak position may be obscured, and directly taking the maximum value point will introduce errors.

[0026] In an optional embodiment, before controlling the lidar to simultaneously emit multiple laser pulses of different emission power levels during a single detection process, the method further includes: obtaining the minimum and maximum detection range of the lidar, and calibrating the detection process based on the maximum and minimum detection ranges to determine a preset number of laser pulses emitted during the detection process; setting the emission power level corresponding to the preset number of laser pulses, wherein the ranging capability of each emission power level corresponds to a maximum effective detection distance, and the higher the emission power level, the farther the maximum effective detection distance.

[0027] As mentioned above, in the local method provided in this application, the detection process is first calibrated before the lidar starts the specific detection process. Through pre-calibration, the number of laser pulses emitted and the emission power of the pulses are determined.

[0028] Specifically, the calibration process includes the following steps: S301: Control the lidar to emit laser pulses sequentially in descending order of emission power level. After each emission, detect whether a quantization error has occurred by receiving the echo; S302: If a quantization error occurs, control the lidar to emit a laser pulse corresponding to a lower emission power level than the current laser pulse; S303: Receive the echo corresponding to the lower emission power level laser pulse and determine whether a quantization error has occurred by using the echo; S304: Repeat steps S302-S303 until there is no more quantization error within the detection range of the lidar, and determine the preset number of emitted laser pulses by executing the steps.

[0029] Further, detecting whether a quantization error has occurred by receiving the echo includes: acquiring the echo corresponding to the current laser pulse using a preset reflectivity plate, and determining whether a quantization error exists by whether there is an invalid echo that has not entered the saturation state in the echo, wherein the presence of an invalid echo indicates the presence of a quantization error, and vice versa; controlling the lidar to emit a laser pulse corresponding to a lower emission power level than the current laser pulse includes: determining the maximum distance value at which a quantization error occurs by using invalid echoes, and the maximum effective detection distance corresponding to the lower emission power level is the maximum distance value.

[0030] The calibration process described above will be illustrated through a specific embodiment. The design assumes that the minimum measurement range required by the lidar is 0.1m and the maximum range is 30m. Based on this, the number of different power outputs and power intensities that the laser needs to emit are determined: 1) The emission power of the first laser pulse needs to be able to measure a distance of 30m, that is, the maximum effective detection distance of the laser pulse is 30m; 2) By using a 50% reflectivity plate to collect the echo waveform of the first pulse laser power within a certain distance range, quantization error occurs. If the quantization error occurs within 10m, then the quantization error is considered. Therefore, the maximum laser power of the second pulse needs to meet the requirement of a ranging capability of more than 10m, and the second laser pulse is emitted; 3) By using a 50% reflectivity plate, the echo waveform of the second pulse laser power is collected within which distance range quantization error occurs. If there is no quantization error within 0.1-10m, then only the first pulse and the second pulse need to be emitted; 4) If quantization error occurs within 0.1-10m, then the third laser pulse needs to be sent; 5) And so on until the phenomenon of no quantization error is met within the entire ranging range.

[0031] In the specific embodiments described above, the entire detection process is calibrated by emitting laser pulses with different emission powers. In the specific examples above, the number of emitted laser pulses is determined to be 2 or 3 after calibration. See Figures 4 and 5 for details. Figure 4 is a schematic diagram of the laser pulse power corresponding to the dual-pulse emission embodiment. Figure 5 is a schematic diagram of the laser pulse power corresponding to the triple-pulse emission embodiment.

[0032] In an optional embodiment, the plurality of different transmission power levels include at least a first power level and a second power level; the maximum effective detection distance L1 corresponding to the first power level is greater than or equal to the maximum detection range L_max of the lidar; the maximum effective detection distance L1 corresponding to the second power level is less than the maximum detection range L_max of the lidar; wherein, the second power level is lower than the first power level, and L1 is based on the maximum distance value corresponding to the quantization error after the lidar transmits a laser pulse of the first power level. It can be seen from the above specific embodiments that the maximum effective detection distance corresponding to the laser pulse transmitted by the first power level is greater than the maximum effective detection distance corresponding to the second power level; that is, in the definition of this application, first power level > second power level > third power level.

[0033] It should be noted that the calibration process exemplified in this application determines the number of laser emissions as two or three. In specific practical applications, embodiments that emit three or more laser pulses of different power levels are also within the scope of protection of this application, and will not be elaborated here.

[0034] In the ranging method provided in this application, since the number of laser pulses to be emitted and the emission power corresponding to each laser pulse are determined in advance through calibration, in a specific embodiment, echo selection logic corresponding to laser pulses with two different laser emission powers is provided, and the specific selection logic diagram is shown in Figure 6. Echo selection logic corresponding to laser pulses with three different emission powers is also provided, and the specific selection logic diagram is shown in Figure 7.

[0035] In an optional embodiment, the detector of the lidar is composed of a SPAD array. Determining whether there are valid echoes that have not entered a saturation state in the echo includes: acquiring a photon arrival time histogram corresponding to each echo collected and accumulated by the SPAD array; extracting multiple feature values ​​from each photon arrival time histogram; the feature values ​​include at least: maximum peak value (A), corresponding to the maximum histogram value in the photon arrival time histogram; saturation peak value (Pm-ax), corresponding to the total pixel value of the receiving channel of the SPAD array; echo leading edge sampling time point (B), corresponding to the sampling time point when the value in the photon arrival time histogram first exceeds a preset leading edge threshold; peak sampling time point (D), corresponding to the sampling time point of the maximum peak value; and determining whether there are valid echoes that have not entered a saturation state in the echo based on at least one of the maximum peak value (A), saturation peak value (Max), echo leading edge sampling time point (B), and peak sampling time point (D).

[0036] Specifically, the maximum peak value (A), the saturation peak value (Max), the echo leading edge sampling time point (B), and the peak sampling time point (D) are defined. The saturation peak value (Max) is the sum of the SPAD pixels of the received channels (e.g., 9 saturated pixels for a 3*3 SPAD and 252 saturated pixels for a 12*12 SPAD). BIN represents the minimum resolution of the time measurement (usually 1 ns). As shown in Figures 8 and 9, Figure 8 is a schematic diagram of the peak unsaturated waveform provided in this application, and Figure 9 is a schematic diagram of the peak saturated waveform provided in this application.

[0037] Specifically, based on at least one of the following values: maximum peak value (A), saturation peak value (Max), echo leading edge sampling time point (B), and peak sampling time point (D), it is determined whether there is a valid echo that has not entered the saturation state in the echo, including: 1) determining whether the maximum peak value (A) is less than the saturation peak value (Max), and whether the time difference between the peak sampling time point (D) and the echo leading edge sampling time point (B) is greater than a preset threshold; if the maximum peak value (A) is less than the saturation peak value (Max), and the time difference is greater than the preset threshold, then the echo is determined to be a valid echo that has not entered the saturation state; optionally, the preset threshold is 3BIN.

[0038] 2) If the maximum peak value (A) equals the saturation peak value (Max), and / or the time difference is greater than or equal to a preset threshold, then the echo is determined to be an invalid echo that has entered a saturation state. That is, if A=Max, and / or the time difference between DB and DB is ≤3, it indicates that the echo is a saturated echo.

[0039] In a specific example, a target is detected at a distance of 1m. When transmitting two pulses, pulses of different power levels are transmitted according to two sub-detection ranges of 30m and 2m. When transmitting three pulses, pulses of different power levels are transmitted according to three sub-detection ranges of 30m, 10m, and 2m, as shown in Figures 10 and 11. Figure 10 is a schematic diagram of the echo waveforms received after transmitting two pulses when a target is detected at a distance of 1m, as provided in this application. In Figure 10, the echo of the first pulse is a saturated echo waveform, and the echo of the second pulse is an unsaturated waveform. Figure 11 is a schematic diagram of the echo waveforms received after transmitting three pulses when a target is detected at a distance of 1m, as provided in this application. In Figure 11, the echo corresponding to the first pulse is a saturated echo waveform, the echo corresponding to the second pulse is also a saturated echo waveform, and the echo corresponding to the third pulse is an unsaturated echo waveform.

[0040] It should be noted that the quantization process of SPAD (such as the calculation of the start and end positions of the half-value width) relies on linear interpolation (using the difference relationship between adjacent integral values ​​to map the time / position corresponding to the threshold). However, under strong light, relying on linear interpolation has the following drawbacks: 1) The rate of change of the integrated value far exceeds the resolution of the quantization unit (such as the decimal truncation precision of the U12.4 format), resulting in a nonlinear deviation of "actual signal strength - quantization value"; 2) The input parameters (peak_score, min_score) of the half-value calculation threshold (half_Th) deviate from the actual signal characteristics, resulting in a deviation between the threshold itself and the true half-value level.

[0041] The ranging method provided in this application can overcome the above drawbacks, as shown in Figure 12. Figure 12 is a schematic diagram of the ranging value calculated by the half-value start position difference provided in this application. The ranging value is calculated by using the unsaturated echo, which includes: 1) determining the position of the half-value C point of the rising edge of the unsaturated waveform. The echo intensity corresponding to the C point is Half_Th. By using P1≥Half_Th, the T1 time point adjacent to the C point is determined, and the intensity value P0 of the BIN before the C point and the time value T0=(T1-1) corresponding to P0 are used for linear difference fitting.

[0042] 2) The calculation formula is: C=T0+(Half_th-P0) / (P1-P0), and the calculated C is the distance value calculated from the unsaturated waveform.

[0043] From the above description, it can be seen that the embodiments of the present invention achieve the following technical effects: (1) By adding lasers of different energy intensities in each measurement process, the long-distance ranging capability of the lidar is guaranteed.

[0044] (2) While ensuring the long-distance ranging capability of the lidar, it also solves the technical problem of the lidar ranging accuracy deteriorating at close range due to quantization error.

[0045] Corresponding to the methods given in the above method embodiments, this application also provides a corresponding apparatus, which includes a module for executing the corresponding methods in the above method embodiments. This module can be software, hardware, or a combination of software and hardware. It is understood that the technical features described in the above method embodiments are also applicable to the following apparatus embodiments. Therefore, details not described in detail can be found in the above method embodiments, and for brevity, will not be repeated here.

[0046] Figure 13 shows a structural block diagram of the device provided in an embodiment of this application. For ease of explanation, only the parts related to the embodiment of this application are shown. Referring to Figure 13, which is a schematic diagram of a ranging device for a lidar provided in this application, the device may specifically include the following modules: a first control unit, configured to control the lidar to simultaneously emit multiple laser pulses of different emission power levels during a single detection process; a first determining unit, configured to determine the effective echo among the echoes corresponding to the multiple laser pulses of different emission power levels, wherein the effective echo is an echo that has not entered a saturation state; and an output unit, configured to output the effective echo and determine the ranging value based on the effective echo.

[0047] The ranging device for lidar provided in this application emits multiple laser pulses with different emission power levels, i.e., multiple laser pulses with different energy intensities, during each measurement process. This not only ensures the long-range ranging capability of lidar, but also solves the technical problem of maintaining consistent ranging accuracy at close range due to quantization errors. It achieves the technical effect of ensuring the ranging capability of lidar while eliminating quantization errors across the entire range and guaranteeing the accuracy of close-range ranging.

[0048] This application also provides a lidar, which includes a lidar ranging device for performing a lidar ranging method.

[0049] This application also provides an apparatus comprising the lidar provided in this application described above.

[0050] This application also provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it implements the steps in the various method embodiments described above. This application also provides a computer program product that, when run on an electronic device, enables a mobile terminal to implement the steps in the various method embodiments described above. If an integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it implements the steps in the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. A computer-readable medium can include at least: any entity or device capable of carrying computer program code to a photographic device / electronic device, a recording medium, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium. Examples include USB flash drives, external hard drives, magnetic disks, or optical discs. In some jurisdictions, according to legislation and patent practice, computer-readable media cannot be electrical carrier signals or telecommunication signals. In the above embodiments, the descriptions of each embodiment have different focuses; parts not described in detail or in a particular embodiment can be referred to in the relevant descriptions of other embodiments.

[0051] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0052] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0053] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A ranging method for a lidar, characterized in that, The method includes: during a single detection process of the lidar, controlling the lidar to simultaneously emit multiple laser pulses of different emission power levels; determining the effective echo among the echoes corresponding to the multiple laser pulses of different emission power levels, wherein the effective echo is an echo that has not entered a saturation state; outputting the effective echo and determining the ranging value based on the effective echo.

2. The ranging method for lidar according to claim 1, characterized in that, Before controlling the lidar to simultaneously emit multiple laser pulses of different emission power levels during a single detection process, the method further includes: acquiring the minimum and maximum detection range of the lidar, and calibrating the detection process based on the maximum and minimum detection ranges to determine a preset number of laser pulses emitted during the detection process; setting the emission power level corresponding to the preset number of laser pulses, wherein the ranging capability of each emission power level corresponds to a maximum effective detection distance, and the higher the emission power level, the farther the maximum effective detection distance.

3. The ranging method of the lidar according to any one of claims 2, characterized in that, The process involves obtaining the minimum and maximum detection ranges of the lidar, and calibrating the detection process based on these ranges to determine a preset number of laser pulses emitted during the detection process. This includes: S301: Controlling the lidar to emit laser pulses sequentially in descending order of power level, and detecting quantization error by analyzing the received echo after each pulse emission; S302: If a quantization error occurs, controlling the lidar to emit a laser pulse at a lower power level than the current pulse; S303: Receiving the echo from the lower power level laser pulse and further determining whether a quantization error has occurred; S304: Repeating steps S302-S303 until the quantization error no longer exists within the lidar's detection range, and determining the preset number of emitted laser pulses based on these steps.

4. The ranging method for lidar according to claim 3, characterized in that, Detecting whether a quantization error occurs by receiving echoes includes: acquiring the echo corresponding to the current laser pulse using a preset reflectivity plate, and determining whether the quantization error exists by whether there are invalid echoes that have not entered saturation. The presence of invalid echoes indicates the presence of the quantization error, and vice versa. Controlling the lidar to emit a laser pulse with a lower emission power level than the current laser pulse includes: determining the maximum distance value at which the quantization error occurs based on the invalid echoes, where the maximum effective detection distance corresponding to the lower emission power level is the maximum distance value.

5. The ranging method of the lidar according to any one of claims 1 to 4, characterized in that, include: The multiple different transmission power levels include at least a first power level and a second power level; the maximum effective detection distance L1 corresponding to the first power level is greater than or equal to the maximum detection range L_max of the lidar; the maximum effective detection distance L1 corresponding to the second power level is less than the maximum detection range L_max of the lidar; wherein, the second power level is lower than the first power level, and L1 is based on the maximum distance value corresponding to the quantization error after the lidar transmits the laser pulse of the first power level.

6. The ranging method for a lidar according to claim 1, characterized in that, The detector of the lidar is composed of a SPAD array. Determining the effective echoes among the echoes corresponding to multiple laser pulses with different transmission power levels includes: acquiring a photon arrival time histogram corresponding to each echo collected and accumulated by the SPAD array; extracting multiple feature values ​​from each photon arrival time histogram; the feature values ​​include at least: a maximum peak value (A), corresponding to the maximum histogram value in the photon arrival time histogram; a saturation peak value (Max), corresponding to the total pixel value of the receiving channel of the SPAD array; an echo leading edge sampling time point (B), corresponding to the sampling time point when the value in the photon arrival time histogram first exceeds a preset leading edge threshold; and a peak sampling time point (D), corresponding to the sampling time point of the maximum peak value; and determining whether there are any effective echoes in the echoes that have not entered a saturation state based on at least one of the maximum peak value (A), the saturation peak value (Max), the echo leading edge sampling time point (B), and the peak sampling time point (D).

7. The ranging method for a lidar according to claim 6, characterized in that, Determining whether there is a valid echo that has not entered the saturation state in the echo based on at least one of the maximum peak value (A), the saturation peak value (Max), the echo leading edge sampling time point (B), and the peak sampling time point (D) includes: detecting whether the maximum peak value (A) is less than the saturation peak value (Max), and whether the time difference between the peak sampling time point (D) and the echo leading edge sampling time point (B) is greater than a preset threshold; if the maximum peak value (A) is less than the saturation peak value (Max), and the time difference is greater than the preset threshold, then the echo is determined to be a valid echo that has not entered the saturation state; if the maximum peak value (A) is equal to the saturation peak value (Max), and / or the time difference is greater than or equal to the preset threshold, then the echo is determined to be an invalid echo that has entered the saturation state.

8. A ranging device for a lidar system, characterized in that, The device includes: a first control unit configured to control the lidar to simultaneously emit multiple laser pulses of different emission power levels during a single detection process; a first determining unit configured to determine the effective echo among the echoes corresponding to the multiple laser pulses of different emission power levels, wherein the effective echo is an echo that has not entered a saturation state; and an output unit configured to output the effective echo and determine the ranging value based on the effective echo.

9. A lidar, characterized in that, The lidar includes a ranging device for a lidar as described in claim 8, used to perform a ranging method for a lidar as described in any one of claims 1 to 7.

10. A device, characterized in that, The device includes a lidar as described in claim 9.

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