High-dynamic high-frame-rate signal processing method of long-distance single-photon laser radar

Abstract

The invention discloses a high-dynamic high-frame-rate signal processing method for a long-distance single-photon laser radar, and belongs to the field of laser radar signal processing. The method comprises the following steps: acquiring the newest ranging results of N laser pulses from a single-photon laser radar to output a low-frame-frequency accumulated target average distance and target average speed; obtaining a target distance measurement result of the latest single laser pulse, and calculating a distance threshold range and a predicted distance value based on the target average distance and the target average speed; and determining the number of the target ranging results satisfying the distance threshold range, and determining the high-frame-rate monopulse distance in combination with the predicted distance value. Therefore, according to the scheme, the distance threshold range and the predicted distance value can be calculated through the target average distance and the target average speed accumulated at the low frame frequency, the high-frame-rate monopulse distance can be output in combination with the latest single laser pulse target distance measurement result, high-frame-frequency distance output can be carried out on the high-dynamic target to be measured, and the target distance measurement accuracy is improved. And the high-frame-frequency distance measurement requirement is met.

Description

Technical Field

[0001] This invention relates to the field of lidar signal processing technology, and in particular to a high dynamic range, high frame rate signal processing method for long-range single-photon lidar. Background Technology

[0002] Due to space resource constraints, long-range on-orbit laser ranging radars often employ a design that combines a high-energy pulsed laser with a high-sensitivity single-photon detector. While single-photon detectors offer high sensitivity, they are susceptible to noise interference, exhibiting significant clutter and making signal extraction difficult.

[0003] In particular, in space-based platform applications, the target object moves at high speeds (high dynamic range), reaching speeds of up to kilometers per second in the line-of-sight direction. Simultaneously, based on these requirements, the ranging results output by the lidar must have a high frame rate (>20Hz). Existing long-range single-photon lidar signal processing methods can only handle low-frame-rate signals, suitable for slow-moving targets, but cannot be applied to high-dynamic target scenarios, nor can they output high-frame-rate processed signals.

[0004] Therefore, there is an urgent need to provide a high dynamic range and high frame rate signal processing method for long-range single-photon lidar. Summary of the Invention

[0005] To address the problem that existing long-range single-photon lidar signal processing methods can only process low-frame-rate signals, are suitable for slow-moving targets, and cannot be applied to high-dynamic target scenarios, nor can they output high-frame-rate processed signals, this invention provides a high-dynamic, high-frame-rate signal processing method for long-range single-photon lidar.

[0006] On the one hand, a high dynamic range, high frame rate signal processing method for long-range single-photon lidar is provided, applied to a spaceborne processing platform. The method includes: The latest N laser pulses ranging results are obtained from the single-photon lidar to output the target average distance and target average velocity accumulated at a low frame rate; Obtain the latest target ranging results from a single laser pulse, and calculate the distance threshold range and predicted distance value based on the target's average distance and average velocity. The number of targets in the ranging results that meet the distance threshold range is determined, and the high frame rate single pulse distance is determined in combination with the predicted distance value.

[0007] On the other hand, a high dynamic range, high frame rate signal processing device for a long-range single-photon lidar based on the steps described in any method embodiment of the specification is provided, disposed on a spaceborne processing platform, the device comprising: The low frame rate unit is used to acquire the ranging results of the latest N laser pulses from the single-photon lidar, so as to output the target average distance and target average velocity accumulated at low frame rate. The calculation unit is used to obtain the target ranging result of the latest single laser pulse, and calculate the distance threshold range and predicted distance value based on the target average distance and target average velocity; The high frame rate unit is used to determine the number of targets in the ranging results that meet the distance threshold range, so as to determine the high frame rate single pulse distance in combination with the predicted distance value.

[0008] On the other hand, a computer device is provided, the computer device including a memory and a processor, the memory for storing a computer program, and the processor for executing the computer program stored in the memory to implement the steps of the method described above.

[0009] On the other hand, a computer-readable storage medium is provided, wherein a computer program is stored therein, and when the computer program is executed by a processor, it implements the steps of the method described above.

[0010] On the other hand, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps of the method described above.

[0011] The technical solution provided by this invention can bring at least the following beneficial effects: With a dual-channel architecture, it can simultaneously output low-frame-rate average distance and high-frame-rate transient distance. High-frame-rate (>20Hz) signal processing for long-distance (>200km) and high-speed moving targets (>1km / s) is currently a blank in the international field. By accumulating the target's average distance and average speed at low frame rates, the distance threshold range and predicted distance value can be calculated to output high-frame-rate single-pulse distance. It can output high-frame-rate distance for highly dynamic targets and meet the high-frame-rate distance update speed. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a flowchart of a high dynamic range, high frame rate signal processing method for a long-range single-photon lidar according to an embodiment of the present invention; Figure 2This is a simulated lidar detection result diagram of a target at a range of 210-280km provided by an embodiment of the present invention; Figure 3 This is a comparison diagram of high frame rate single-pulse distance and actual target distance provided by an embodiment of the present invention; Figure 4 This is a graph showing the difference between the high frame rate single-pulse distance and the actual target distance provided by an embodiment of the present invention; Figure 5 This is a structural diagram of a high dynamic range, high frame rate signal processing device for a long-range single-photon lidar according to an embodiment of the present invention; Figure 6 This is a hardware architecture diagram of a computer device provided in an embodiment of the present invention. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0015] The following describes the specific implementation of the above concept.

[0016] Please refer to Figure 1 This invention provides a high dynamic range, high frame rate signal processing method for long-range single-photon lidar, applied to a spaceborne processing platform. The method includes: Step 100: Obtain the latest ranging results of N laser pulses from the single-photon lidar to output the target average distance and target average velocity accumulated at a low frame rate; Step 102: Obtain the target ranging results of the latest single laser pulse, and calculate the distance threshold range and predicted distance value based on the target average distance and target average velocity; Step 104: Determine the number of targets in the ranging results that meet the distance threshold range, and combine the predicted distance value to determine the high frame rate single pulse distance.

[0017] In this embodiment of the invention, the dual-channel architecture can simultaneously output the average distance at a low frame rate and the transient distance at a high frame rate. The high frame rate (>20Hz) signal processing for long-distance (>200km) and high-speed moving targets (>1km / s) is currently a blank in the international field. By accumulating the average distance and average speed of the target at low frame rates, the distance threshold range and predicted distance value can be calculated to output the high frame rate single-pulse distance. This enables high frame rate distance output for highly dynamic targets and meets the high frame rate distance update speed requirements.

[0018] The following description Figure 1 The execution method for each step is shown.

[0019] For step 100: In some implementations, step 100 may include: Use a sliding window to obtain the ranging results of the latest N laser pulses; Using a biphase histogram, the average target distance accumulated at low frame rates is determined from the ranging results of N laser pulses; The average speed of the target is determined using the exponential weighted average method based on the average distance to the target.

[0020] It should be noted that each laser pulse in a single-photon lidar produces multiple ranging results, and the number of these results varies; for example... Figure 2 The image shows the simulated detection results of a lidar at a range of 210-280km. Only the noise level within ±10km is displayed. The laser frequency is 50Hz, and it can be seen that the noise is quite strong, with the signal being submerged in the noise.

[0021] The latest N laser pulse measurement results are selected to form a one-dimensional array arry1. The selection of measurement results uses a sliding window method with a sliding window step size of 1. For example, if the first laser pulse selected for calculation is the 1st to the Nth pulse, then the second laser pulse selected for calculation is the 2nd to the (N+1)th pulse, and so on. The value of N ranges from 50 to 200, such as 50.

[0022] In some implementations, the step "determining the average target distance accumulated at low frame rates from the ranging results of N laser pulses using a biphase histogram" includes: Construct a first histogram and a second histogram; each histogram contains several pre-opened intervals, and the number of laser echoes contained in each pre-opened interval is counted. Obtain the current average velocity of the target, take the minimum ranging result among the ranging results of N laser pulses as the starting distance of the first histogram, determine the step size of the first and second histograms based on the current average velocity of the target, initialize the number of counts corresponding to each pre-open interval, and determine the starting distance of the second histogram based on the starting distance and step size of the first histogram to complete the parameter update; Iterate through each ranging result of N laser pulses, determine the interval in the first and second histograms for each ranging result, and increment the count of the corresponding pre-open interval by 1 for each ranging result that falls into a pre-open interval. Determine the maximum number of counts in the first histogram and the maximum number of counts in the second histogram, respectively; Compare the maximum count in the first histogram with the maximum count in the second histogram, and take the larger value as the target value; If the target value is greater than or equal to the preset threshold, it is determined that there is a target in the radar signal. The average distance of the target value in the pre-open interval of the histogram is calculated as the average target distance accumulated at low frame rates. If the target value is less than the preset threshold, it is determined that there is no target in the radar signal.

[0023] Specifically, two histograms are constructed. The starting distance of the first histogram is hist1_start, the step size is hist1_step, the number of pre-opened intervals is hist1_num, and the count of each interval is hist1_section_cnts. The starting distance of the second histogram is hist2_start, the step size is hist2_step, the number of pre-opened intervals is hist2_num, and the count of each interval is hist2_section_cnts.

[0024] Let the current average velocity of the target be denoted as . The initial target average velocity at the first moment: =2km / s. Related parameters have been updated as follows: ①hist1_start=min(array1), which means the starting distance of the first histogram is the minimum value of array1; ②hist1_step =hist2_step, meaning the step size of the first histogram is equal to the step size of the second histogram, denoted as step, where step = k. k is a coefficient; preferably, k = 3~9, such as 5.

[0025] ③hist1_num=hist2_num, that is, the number of pre-open intervals of the first histogram is equal to the number of pre-open intervals of the second histogram, denoted as num; preferably, num=100~400, such as 100.

[0026] ④hist1_section_cnts=hist1_section_cnts=0, that is, the count of each pre-open interval of the first and second histograms is initialized to 0; ⑤ Histogram Figure 2 The starting distance is: hist2_start = hist1_start + step / 2.

[0027] Iterate through each ranging result data in arry1, determine the interval in the first and second histograms for each data point, and increment the interval count by 1 for each data point that falls into an interval. Determine the maximum value of the count hist1_section_cnts for each interval of the first histogram, hist1_section_cnts_max, and the maximum value of the count hist2_section_cnts for each interval of the second histogram, hist2_section_cnts_max, where hist1_section_cnts and hist2_section_cnts are arrays of length num.

[0028] The larger of hist1_section_cnts_max and hist2_section_cnts_max is selected as the target value. If this target value is greater than or equal to a preset threshold, the radar signal is considered to have a target. The average distance hist_mean of the corresponding interval of the histogram is then determined, which is the average target distance R accumulated at low frame rates. n If the target value is less than a preset threshold, it is considered that there is no target in the radar signal; preferably, threshold = 10~50, such as 20. If it is determined that there is a target in the radar signal, the step of calculating the average speed of the target is executed; otherwise, it is not executed.

[0029] In some implementations, the step "determining the target average speed using an exponentially weighted average method based on the target average distance" includes: Obtain the current average distance to the target and its corresponding time; Calculate the instantaneous target velocity based on the current average target distance and its corresponding time, as well as the average target distance and its corresponding time output at the previous moment; The average velocity of the target is determined based on the instantaneous target velocity and the exponential weighting coefficient.

[0030] In this embodiment, the current average distance R of the target is recorded and output. n and the corresponding time t n , where n is the time sequence number; Based on the current average target distance and its corresponding time, and the average target distance and its corresponding time output at the previous moment, calculate the instantaneous target velocity v. n = (R n -R n-1 ) / (t n -t n-1 ).

[0031] Based on the instantaneous target velocity and the exponential weighting coefficient, the target average velocity is determined: v tn =beta v n + (1-beta) v n-1 Where beta is the exponential weighting coefficient; preferably, beta = 0.5~0.9, such as 0.9.

[0032] When the time index n is greater than or equal to 2, the target average velocity v is used. tn Update the current target average velocity in the next time step. .

[0033] Regarding step 102: In some implementations, step 102 may include: The lower limit of the distance threshold is calculated using the following formula: R low =R n +v tn Delay1 The upper limit of the distance threshold is calculated using the following formula: R up =R n +v tn Delay2 The predicted distance value is calculated using the following formula: R p = R n +v tn N / (2 freq) In the formula, R low R is the lower limit of the distance threshold. n v is the average distance to the target. tn R represents the target average velocity, Delay1 and Delay2 are the corresponding delay coefficients, and R is the average velocity. up R is the upper limit of the distance threshold. p To predict the distance value, N is the number of the latest selected laser pulses, and freq is the laser frequency.

[0034] It should be noted that the target ranging result of the latest single laser pulse acquired in the high frame rate channel is the latest target ranging result of a single pulse, that is, the Nth pulse in the first instance, the (N+1)th pulse in the second instance, and so on. Furthermore, the latest single laser pulse corresponds to multiple target ranging results.

[0035] Preferably, Delay1 = -2 N / (2 freq) ~ 0. Delay2 = 2 N / (2 freq) ~4 N / (2 (freq). In this embodiment, N=50, freq = 50.

[0036] Regarding step 104: In some implementations, step 104 may include: If the target ranging results are all outside the distance threshold range, then the current high frame rate ranging will not output any distance. If only one target ranging result falls within the distance threshold range, then the target ranging result is a high frame rate single-pulse distance output; If multiple target ranging results fall within the distance threshold range, the target ranging result with the smallest absolute difference from the predicted distance value is selected as the high frame rate single pulse distance output.

[0037] In this embodiment, ① if the distance values ​​in the measurement result Dn are all outside the range (R low , R up If the current high frame rate ranging result is invalid, then there will be no distance output.

[0038] ②If the distance value in the measurement result Dn is within the range (R low , R up If there is only one result in the output, then that result is the high frame rate single pulse distance output value R. q The distance measurement result is valid.

[0039] ③ If the distance value in the measurement result Dn is within the range (R low , R up If there are multiple results (more than 2), then the nearest neighbor method is used to select the predicted value R based on the distance. p The distance value with the smallest absolute difference is used as the high frame rate single-pulse distance output value R. q The distance measurement result is valid.

[0040] Finally, the current ranging result is output as follows: Channel 1: average target distance and average target velocity accumulated at low frame rate, and Channel 2: single pulse distance Rq at high frame rate.

[0041] Simulation calculations were performed to verify the effectiveness of this solution, such as... Figure 3 and Figure 4 The figures show a comparison between the high frame rate single-pulse distance of this method and the actual target distance, as well as a difference between the high frame rate single-pulse distance of this method and the actual target distance. It can be seen that the difference (measurement accuracy) between the high frame rate single-pulse distance of this method and the actual target distance is less than 5.5m (3-sigma), which effectively detects highly dynamic targets and is suitable for signal processing of long-range single-photon lidar in highly dynamic, high frame rate scenarios.

[0042] Please refer to Figure 5 This invention provides a high dynamic range, high frame rate signal processing device for long-range single-photon lidar, mounted on a spaceborne processing platform, for implementing the steps of any method embodiment described in the specification. The device includes: The low frame rate unit 501 is used to acquire the ranging results of the latest N laser pulses from the single-photon lidar, so as to output the target average distance and target average velocity accumulated at the low frame rate. The calculation unit 502 is used to obtain the target ranging results of the latest single laser pulse, and calculate the distance threshold range and predicted distance value based on the average target distance and average target velocity; The high frame rate unit 503 is used to determine the number of targets in the ranging results that meet the distance threshold range, so as to combine the predicted distance value to determine the high frame rate single pulse distance.

[0043] It should be noted that the above device embodiments and method embodiments belong to the same concept, and the specific implementation process can be found in the method embodiments, which will not be repeated here.

[0044] Embodiments of this application also provide a computer device, please refer to... Figure 6 The computer device includes a processor and a memory, the memory storing at least one instruction, at least one program, code set or instruction set, the at least one instruction, at least one program, code set or instruction set being loaded and executed by the processor to implement the high dynamic high frame rate signal processing method for long-range single-photon lidar provided in the above-described method embodiments.

[0045] Embodiments of this application also provide a computer-readable storage medium storing at least one instruction, at least one program, code set, or instruction set, wherein the at least one instruction, at least one program, code set, or instruction set is loaded and executed by a processor to implement the high dynamic and high frame rate signal processing method for long-range single-photon lidar provided in the above-described method embodiments.

[0046] Embodiments of this application also provide a computer program product, which includes a computer program. A processor of a computer device reads the computer program from a computer-readable storage medium and executes the computer program, causing the computer device to perform any of the high dynamic range, high frame rate signal processing methods for long-range single-photon lidar described in the above embodiments.

[0047] For ease of description, the above devices or apparatuses are described separately according to their functions, divided into various modules or units. Of course, in implementing this application, the functions of each unit can be implemented in one or more software and / or hardware.

[0048] As can be seen from the above description of the embodiments, those skilled in the art can clearly understand that this application can be implemented by means of software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of this application, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods of various embodiments or some parts of the embodiments of this application.

[0049] Finally, it should be noted that in this document, relational terms such as first, second, third, and fourth are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0050] The above are merely preferred embodiments of this application. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A high dynamic range, high frame rate signal processing method for long-range single-photon lidar, applied to a spaceborne processing platform, characterized in that... include: The latest N laser pulses ranging results are obtained from the single-photon lidar to output the target average distance and target average velocity accumulated at a low frame rate; Obtain the latest target ranging results from a single laser pulse, and calculate the distance threshold range and predicted distance value based on the target's average distance and average velocity. The number of targets in the ranging results that meet the distance threshold range is determined, and the high frame rate single pulse distance is determined in combination with the predicted distance value.

2. The method as described in claim 1, characterized in that, The process of acquiring the latest N laser pulses ranging results from a single-photon lidar to output the cumulative average target distance and average target velocity at a low frame rate includes: Use a sliding window to obtain the ranging results of the latest N laser pulses; Using a biphase histogram, the average target distance accumulated at low frame rates is determined from the ranging results of N laser pulses; Based on the target average distance, the target average speed is determined using the exponential weighted average method.

3. The method as described in claim 2, characterized in that, The method of determining the average target distance accumulated at low frame rates from the ranging results of N laser pulses using a dual-phase histogram includes: Construct a first histogram and a second histogram; each histogram contains several pre-opened intervals, and the number of laser echoes contained in each pre-opened interval is counted. The current average velocity of the target is obtained. The minimum ranging result among the ranging results of N laser pulses is used as the starting distance of the first histogram. The step size of the first histogram and the second histogram is determined based on the current average velocity of the target. The number of counts corresponding to each pre-open interval is initialized. The starting distance of the second histogram is determined based on the starting distance of the first histogram and the step size to complete the parameter update. Iterate through each ranging result of N laser pulses, determine the interval in the first histogram and the second histogram for each ranging result, and increment the count of the corresponding pre-open interval by 1 for each ranging result that falls into a pre-open interval; Determine the maximum count in the first histogram and the maximum count in the second histogram, respectively; Compare the maximum count in the first histogram with the maximum count in the second histogram, and take the larger value as the target value; If the target value is greater than or equal to a preset threshold, it is determined that there is a target in the radar signal, and the average distance of the pre-open interval corresponding to the histogram of the target value is calculated as the average target distance accumulated at low frame rates. If the target value is less than the preset threshold, then it is determined that there is no target in the radar signal.

4. The method as described in claim 2, characterized in that, The step of determining the target average speed using an exponentially weighted average method based on the target average distance includes: Obtain the current average distance to the target and its corresponding time; Calculate the instantaneous target velocity based on the current average target distance and its corresponding time, as well as the target average distance and its corresponding time output at the previous moment; The target average velocity is determined based on the instantaneous target velocity and the exponential weighting coefficient.

5. The method as described in claim 1, characterized in that, The calculation of the distance threshold range and predicted distance value based on the target average distance and target average speed includes: The lower limit of the distance threshold is calculated using the following formula: R low =R n +v tn Delay1 The upper limit of the distance threshold is calculated using the following formula: R up =R n +v tn Delay2 The predicted distance value is calculated using the following formula: R p = R n +v tn N / (2 freq) In the formula, R low R is the lower limit of the distance threshold. n v is the average distance to the target. tn R represents the target average velocity, Delay1 and Delay2 are the corresponding delay coefficients, and R up R is the upper limit of the distance threshold. p To predict the distance value, N is the number of the latest selected laser pulses, and freq is the laser frequency.

6. The method as described in claim 1, characterized in that, Determining the number of targets in the ranging results that satisfy the distance threshold range, and combining this with the predicted distance value to determine the high frame rate single-pulse distance, includes: If the target ranging results are all outside the distance threshold range, then the current high frame rate ranging will not output any distance. If only one of the target ranging results falls within the distance threshold range, then the target ranging result is a high frame rate single-pulse distance output; If multiple target ranging results fall within the distance threshold range, the target ranging result with the smallest absolute value of the difference from the predicted distance value is selected as the high frame rate single pulse distance output.

7. A high dynamic range, high frame rate signal processing device for a long-range single-photon lidar, mounted on a spaceborne processing platform, for implementing the steps of the method described in any one of claims 1-6, characterized in that... include: The low frame rate unit is used to acquire the ranging results of the latest N laser pulses from the single-photon lidar, so as to output the target average distance and target average velocity accumulated at low frame rate. The calculation unit is used to obtain the target ranging result of the latest single laser pulse, and calculate the distance threshold range and predicted distance value based on the target average distance and target average velocity; The high frame rate unit is used to determine the number of targets in the ranging results that meet the distance threshold range, so as to determine the high frame rate single pulse distance in combination with the predicted distance value.

8. A computer device, characterized in that, The computer device includes a memory and a processor. The memory is used to store computer programs, and the processor is used to execute the computer programs stored in the memory to implement the steps of the method according to any one of claims 1-6.

9. A computer-readable storage medium, characterized in that, The storage medium stores a computer program, which, when executed by a processor, implements the steps of the method described in any one of claims 1-6.

10. A computer program product, characterized in that, Includes a computer program, which, when executed by a processor, implements the steps of the method according to any one of claims 1-6.

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